World Cement - April 2021 by PalladianPublications

April 2021

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CONTENTS 03 Comment 05 News REGIONAL REPORT: CHINA 10 Everything In Moderation Wang Lan, China Building Materials Academy, discusses the installation and operation of a moderate temperature SCR Reactor for ChangXing Southern Cement Company. GRINDING & MILLING 18 Back To The Grind: World Cement Q&A World Cement interviewed some of the leading equipment suppliers for their thoughts on the topic of grinding & milling. Read on to hear from: FLSmidth, Gebr. Pfeiffer, Loesche, and thyssenkrupp Industrial Solutions AG. EXPLOSION PREVENTION & PROTECTION 29 Fire Away Emre Ergun, IEP Technologies, outlines the preventative and protective measures the company put in place to help a Turkish cement manufacturer mitigate the combustion risks associated with alternative fuels. PYROPROCESSING 35 Claying It All On The Line Luiz Felipe de Pinho and Roberto Campos, Dynamis, discuss the company’s role in the design and supply of equipment for Cementos Argos’ Rio Claro calcined clay activation plant and explain how clay activation technology could allow for a more sustainable and competitive method of cement production.

39 Making Grate Strides Valentina Bordei and Viktor Penner, thyssenkrupp, show how an improved static grate design could enhance cement plant performance with a more stable operation, higher equipment availability, lower fuel consumption, and increased clinker production. 43 Paying Attention To Prevention Paweł Kędzior, Havec Engineering Co., outlines how Hot Kiln Alignment can be employed by cement producers as an effective method of preventive maintenance.

REFRACTORIES 47 A Platform For Improvement Jeff Mirisola, Bricking Solutions, outlines how suspended platforms could help cement producers increase efficiency for vertical vessel maintenance. 52 The Value Of Veneering Refratechnik Cement GmbH discusses the applications of a new concrete veneering technology including its use in emergency kiln lining repair. 56 A Lifetime Achievement Daniel Hansted-Martin, HASLE Refractories, explains how Lafarge Canada’s Exshaw Cement Plant has reduced abrasion and chemical challenges and tripled the lifetime of the refractory lining in the facility’s Riser Duct using a precast Modular Lining. WASTE HEAT RECOVERY 61 No Time To Waste Sabrina Santarossa, Turboden, explains how waste heat recovery technology could help cement plants to reach their sustainability goals, while increasing efficiency and reducing production costs. SAMPLING & ANALYSIS 65 Reaping The Rewards Paul Iverson, SABIA, outlines the optimisation techniques set to enable cement producers to get the most value out of their PGNAA systems and realise the benefits of bulk material analysis technology. PROCESS EFFICIENCY & OPTIMISATION 69 That’s The Ticket! Scott Dugan, Command Alkon, explains how companies can streamline business processes and the operational tasks necessary to ticket and scale cement, enabling drivers to check-in, load, and ticket trucks without interruption.

ON THE COVER Axians Industrial Applications & Services GmbH is owned 100% by VED IT GmbH, as a corporate holding of the ICT companies of VINCI in Germany. The company’s core business involves the development and distribution of process-oriented logistics solutions for the raw material industry worldwide, mainly in the fields of yard management, automation and digitisation, and in particular, using the self-developed VAS® solution for dispatch automation, including all related services, hardware and software components. Product announcement: IAS Suite 2021… further information is soon to be released at www.axians-ias.com.

April 2021

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SUBSCRIPTIONS Annual subscription (published monthly): £160 UK including postage/£175 (e245) overseas (postage airmail)/US$280 USA/Canada (postage airmail). Two year subscription (published monthly): £256 UK including postage/£280 (e392) overseas (postage airmail)/US$448 USA/Canada (postage airmail). Claims for non receipt of issues must be made within 4 months of publication of the issue or they will not be honoured without charge. Applicable only to USA and Canada: WORLD CEMENT (ISSN No: 0263-6050, USPS No: 020-996) is published monthly by Palladian Publications, GBR and is distributed in the USA by Asendia USA, 17B S Middlesex Ave, Monroe NJ 08831. Periodicals postage paid New Brunswick, NJ and additional mailing offices. POSTMASTER: send address changes to World Cement, 701C Ashland Ave, Folcroft PA 19032 Copyright © Palladian Publications Ltd 2021. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owner. All views expressed in this journal are those of the respective contributors and are not necessarily the opinions of the publisher, neither do the publishers endorse any of the claims made in the articles or the advertisements. Uncaptioned images courtesy of Adobe Stock. Printed in the UK. Palladian Publications Ltd 15 South Street, Farnham, Surrey GU9 7QU, UK Tel +44 (0)1252 718999 Fax +44 (0)1252 718992 Email: mail@worldcement.com Website: www.worldcement.com

April 2021 World Cement

DAVID BIZLEY, EDITOR

pring has finally sprung. The trees are lined with blossom, daffodils and tulips have sprouted from seemingly every spare patch of earth, bumblebees are bumbling, I’m buying up hay fever medication, and it’s just a few more days until Easter (and a four-day Bank Holiday weekend for those of us in the UK). But it’s not just the flowers that are opening up. Spurred on by declining case numbers and the success of the vaccine rollout (so far…), the UK is gradually rolling back pandemic restrictions once more. On the day that I write this, in England two households (in groups of up to six people) are once again allowed to meet outdoors (albeit with social distancing), weddings (attended by six people) are back on, and outdoor sports facilities, such as tennis courts and golf courses are reopening. We aren’t out of the woods yet; case numbers are rising elsewhere, and with the risk posed by novel variants of the virus, nowhere is completely safe until everyone has been vaccinated, but there is finally some steady light at the end of the tunnel and we now have the tools to fight back. That means that it’s once again time to think about how we want the world to be when life returns to ‘normal’ in the not too distant future. For example, the sudden change in lifestyles imposed by the pandemic has accelerated the trend towards remote working and left many businesses with decisions as to how much they support it once restrictions are lifted. The other big factor is the environment. Although industrial activity has recovered somewhat since, the initial lockdowns in 2020 provided, for the first time, a live ‘before & after’ snapshot of what the world would be like with fewer emissions, less vehicle traffic, noise, and other ‘side effects’ of our industrialised societies. The stories of wildlife reclaiming quiet streets and news of the drop in emissions were heart-warming and a sign that making ‘green’ choices really did have an impact. That’s why it’s more important than ever that you attend EnivroTech 2021, the interactive online conference hosted by World Cement that focuses on what the cement industry can do to reduce its environmental impact. Set over two days (20 & 21 April), EnviroTech 2021 will feature technical presentations packed with actionable business insights from industry leaders, such as LafargeHolcim, FLSmidth, Votorantim Cimentos, Beumer Group, thyssenkrupp Industrial Solutions and many more. In addition to presentations, we’ll also be running live Q&As so you can put your questions directly to the experts. And if that wasn’t enough, we’ll also be hosting a virtual exhibition, so you can interact with company representatives and check out the latest products, projects and services on offer from a range of leading companies. Simply head over to: www.worldcement.com/envirotech2021 to register, free of charge. I look forward to seeing you there.

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NEWS Axians IAS completes ‘unique’ project with HeidelbergCement “An exceptionally good cooperation and an outstandingly good result.” Those were Alexander Müller’s closing words when HeidelbergCement AG put its new Logistic Portal into operation. Alexander is the responsible and leading IAS team member for the entire VAS® roll out project for the Heidelberg Sand and Gravel works in Germany. Together with the senior HC staff member in charge, the entire roll out team put together a unique project. Especially in times of COVID 19, the launch of a powerful and centralised logistics solution meant a well thought out and planned execution of the project was necessary. The initial logistics portal created specifically for HeidelbergCement AG went live back in 2015. The project team at that time had created an unprecedented online tool that revolutionised the entire ordering process in the bulk materials industry. The project offered several advantages for customers. With the further development of the portal and the new challenges the project team had to face in 2020, they outperformed their former performance many times over. The team had to deal with three areas in particular: f Optimisation of automation processes especially for sand and gravel for shorter gate to gate times. f Development and implementation of a special ‘all in one’ mask for faster manual handling of trucks. f Development and implementation of a wheel loader application for the online and off-line case. One of the top priorities in the project was to integrate the three challenges mentioned above into the software solution in the best possible way. Another priority was the harmonious integration, successful synchronisation and synergy utilisation of the two divisions, cement and aggregates. This was achieved by means of a VAS template.

April 2021 World Cement

Due to restrictions on handling in 2020, the project team had to deal thoroughly with the following challenge: “How can we take all sand and gravel plants into operation without being on site whilst guaranteeing that everything runs well at the end?” As part of the further digitisation and optimisation of HeidelbergCement AG, an integrated material flow management system will be introduced to achieve significant savings in logistics costs throughout the group. Based on the existing development process, HeidebergCement AG was able to provide remote access, which enabled all plants to go live smoothly. Various plants worldwide in the cement, aggregates (sand & gravel) and cement business areas are currently being equipped with the VAS solution from Axians IAS GmbH.

UltraTech chooses AUMUND India as equipment supplier for ‘Project Spring’ expansion UltraTech has chosen AUMUND India to supply a comprehensive equipment package comprising 22 chain bucket elevators, 46 belt bucket elevators, six pan conveyors and 11 Samson® material feeders for its ‘Project Spring’ expansion. The order is one of the largest to date for AUMUND India. The expansion project includes three integrated cement production units, each with capacities of up to 10 000 tpd. For these kiln lines, AUMUND India will supply the critical clinker cooler extraction conveyors, well known for their reliability and availability, as well as the transfer conveyors to the clinker silos. In addition to the clinker production lines in Madhya Pradesh, Rajasthan and Chhattisgarh, six cement grinding plants in various locations in India are part of the capacity expansion plans. The order won by AUMUND India includes raw material handling bucket elevators, critical kiln feed bucket elevators with heights up to 157 m, and roller press recirculation bucket elevators with capacities up to 2200 tph, as well as clinker and cement handling bucket elevators of various sizes. At the end of 2020, UltraTech decided to increase its current consolidated production

NEWS DIARY Hannover Messe - Digital Edition 12 – 16 April, 2021 Hannover, Germany www.hannovermesse.de

20 – 21 April, 2021 An interactive online conference focusing on reducing the cement industry’s environmental footprint. For more information, or to register for free, head over to: www.worldcement.com/ envirotech2021

IEEE-IAS/PCA Cement Conference 2021 24 – 28 May, 2021 www.cementconference.org

16 – 17 June, 2021 www.worldcement.com/ optimisation2021

BULKEX21 12 – 13 October, 2021 Chesford Grange, Warwickshire, UK secretary@mhea.co.uk www.mhea.co.uk

capacity of 116.8 million tpy by 12.8 million tpy with a mix of brownfield and greenfield expansions in the eastern, central and northern parts of India. The completion of these capacity additions will further reinforce the position of UltraTech as the third largest cement producer in the world outside of China.

Starlinger bags fit the national standard for cement packaging in China As China is modernising its cement production, the government has also set up a national standard, defining types and specifications of bags used for packaging cement. One of the three bag types permitted in the Chinese Standard GB/T 9774-2020 ‘Sacks for Packing Cement’, which was officially released in October 2020, are block bottom valve bags made of woven polypropylene tape fabric. This type of bag was invented in 1995 by the Austrian engineering company Starlinger & Co. GmbH and patented under the brand name AD*STAR. With the AD*STAR bag, Starlinger, specialised in machinery for woven plastic packaging, created a sustainable and efficient packaging solution for cement and all kinds of dry bulk goods. The idea behind it was to combine the advantages of a paper bag – its brick shape and suitability for automatic handling – with the tightness and flexibility of a PE film bag, and the strength and resistance of a woven PP bag. The result: A laminated one-layer block bottom valve bag made of stretched and woven polypropylene tapes. The main assets of AD*STAR bags are their extremely low breakage rate and excellent protection against moisture. Especially in countries like China, transport and storage of cement in bags is widespread and involves a lot of transhipping and long-term storage. Loss of cement due to bag rupture or hardening in humid conditions is a big issue. Packaging cement in AD*STAR bags offers substantial savings potential in this respect: low breakage rates and good moisture protection mean that significantly less cement is lost in the logistic chain. Consequently, not only environmental pollution is reduced, but also less cement needs to be produced to replace these losses, which in turn saves CO2 emissions. An independent Life Cycle Analysis carried out in 2015 showed that due to these characteristics, AD*STAR cement bags have lower global warming potential than multi-layer paper cement bags and are currently the most environmentally friendly packaging for cement. AD*STAR bags are produced on Starlinger ad*starKON block bottom conversion lines and are available in a wide range of sizes. The company’s focus on research and development ensures that AD*STAR bags and AD*STAR production technologies are continuously improved and adapted to the needs of the market. Technological advancements and new product features such as easy-open closure or handles for carrying make the bags even more versatile and usable in different applications.

World Cement April 2021

NEWS Currently, around 15.7 billion AD*STAR sacks are produced each year on more than 550 Starlinger conversion lines installed on five continents. The new Chinese Standard for cement packaging applies to cement bags holding up to 50 kg and lists the above mentioned laminated woven plastic bags (made of one layer of laminated plastic fabric or with additional paper liner), paper bags (three-layer, three-layer with PE liner, four-layer bags), as well as paper-plastic composite bags (paper bags with plastic liner) as possible packaging options. All three types of bags must be designed as block bottom valve bags. The standard specifies the dimensions as well as physical and mechanical requirements of the cement bags. Regarding break resistance, for example, a cement bag has to survive a drop from a 1 m height a minimum of six times before it breaks. Furthermore, printing and marking, general bag appearance, testing methods, and rules for quality inspection during bag manufacture are established in the standard. It also stipulates that each bag must be provided with a certificate before selling. By recommending woven polypropylene block bottom bags in the new National Standard, the Chinese government has adopted a future-oriented approach that aims for more sustainability in the cement industry. It curbs unnecessary loss of cement during production, transport and storage, reduces environmental impacts, improves working conditions for operators on the cement filling lines, and generally makes the handling of cement in 50kg or smaller units more efficient. It also means that the formerly widely used sewn woven plastic bags which were irregular in shape, often leaking, and problematic for automatic filling and handling, will no longer be permitted as cement packaging in China. Cement companies are given a transition period until 31 March 2022 to adapt to the new standard. Due to this time limit, Starlinger’s AD*STAR conversion lines are currently high in demand in China. The company expects to deliver and install machines for an additional production capacity of more than 2 billion AD*STAR bags on the Chinese market in 2021 and 2022. 8

IKN makes progress on Kiln Line No. 8 for Märker Cement New projects always begin with a first step. When looking at the construction site at Märker Cement, the first series of steps is already quite visible. Both the solid concrete basis for the preheater and the first kiln pier have almost reached their full heights. Foundation works for the cooler building are in progress, showing the future footprint. The new kiln line No. 8 is being built right next to the existing production line which it will replace after commissioning. The start of this important project directly in the heart of Germany and during the difficult COVID-19 times shows the commitment of Märker Cement towards the plant, its employees, and the region.

Cimprogetti receives orders for multiple lime hydration plants Italy-based engineering firm, Cimprogetti, which supplies vertical kilns for the calcination of limestone and dolomite and complete quicklime hydration units, has received several orders for hydration plants. Rheinkalk, a subsidiary of Belgium’s Lhoist, has placed an order to Cimprogetti for two hydration plants with a 10 tph nominal capacity for its lime plants at Regensburg (Walhalla plant) and Efringen-Kirchen (Istein plant). The Walhalla Plant features a CIM-HYDRAX-4G hydrator mod, the fourth generation of Cimprogetti hydrator, with a customised filter. The Istein Plant features instead the CIM-HYDRAX-4G MAX hydrator mod, with an independent premixing stage. The hydration plants have been ordered as part of a renovation programme. Cimprogetti also received an order from a leading Chinese Group for a 10 tph hydrating plant featuring the 5-shaft hydrator Cim-Hyrdax-TG-600. The calcium hydroxide will be used as absorbent for the FGD device located in Haimen Port area (Jiangsu Province). The use of Ca(OH)2 sorbent allows for a reduction in the concentration of acid gases in different industrial sectors; average of 15 – 30% for HCl, 50 – 90% for SO2 and 80% for HF in certain process conditions (temperature and pressure). World Cement April 2021

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Wang Lan, China Building Materials Academy, discusses the installation and operation of a moderate temperature SCR Reactor for ChangXing Southern Cement Company.

EVERYTHING IN

MODERATION T

he high temperatures in rotary cement kilns result predominately in the formation of NOx. Without emissions control measures, the NOx concentrations in the flue gas of rotary kilns are in the range of 800 to 1800 mg/m3. In China, there are about 1650 cement production lines, producing around 2.4 billion t of cement and 1.55 billion t of clinker in 2020. Calculated with the emission

coefficient of 1.80 kg/t clinker, the yield of NOx is about 2.8 million t from the cement industry. This emission source is ranked third largest after the electrical power and transportation sectors in China. NOx is a severe air pollutant, and can lead to the formation of acid rain while also causing harm to human health. DeNOx is a top priority mission for the sustainable development of the cement industry.

China’s Cement Industry Emission Standard of Air Pollutants (GB4815-2013) set up limitation values for NOx emissions at 320 mg/m3 and 400 mg/m3 from cement kilns in different areas. However, several local governments have issued more stringent requirements, outlining that NOx emissions from cement kilns must be below 50 mg/m3 and NH3 slip below 5 mg/m3 if ammonia is used as reducing agent. The best available technologies for DeNOx operations include primary measures and secondary measures. The former are based on the principle of reducing the excess oxygen levels and the peak flame temperature in cement kilns, for example by using a low nitrogen burner and staged combustion. However, the DeNOx efficiency of the primary measures cannot exceed 50% without interfering with cement kiln operation. The latter includes SNCR (selective non catalytic reduction) and SCR (selective catalytic reduction)

technologies, and they often use ammonia or other nitrogen-containing compounds with the chemical reaction: NH3 + NOx → N2 + H2O. Usually, DeNOx efficiency of SNCR is controlled at 60%, otherwise it could lead to more NH3 slip, e.g. high emissions of unreacted ammonia. Compared to SNCR, SCR can achieve DeNOx efficiency of up to 95% and it cause less NH3 slip, as the NH3 to NOx molar ratio can be controlled as 1:1. In order to limit NOx emissions to a low level of 50 mg/m3, the use of the SCR technique is necessary.

Development of a moderate temperature SCR technique

The key setup of the SCR technique involves a SCR reactor, which is a high tower with several layers of catalyst modules installed inside. Flue gas from the cement kiln mixed with injected ammonia is drawn into the reactor, where NH3 reacts with NOx quickly when passing through the channels of the Table 1. The parameters of the flue gas from the waste heat boiler. catalyst element (Figure 1). The temperature No. Item Data Unit Note of flue gas exiting 1 Flue gas 380 000 m3/hr 710 000 (WC) the top of the preheater is <4 % 2 O2 about 320ºC, 3 Temperature 200 - 220 ºC and the dust 4 SO2 < 300 mg/m3 O2 10% content of the flue gas is about O2 10% 5 NOx < 300 mg/m3 120 g/m3. When 3 O2 10% 6 Dust < 60 g/m exiting the waste 7 Moisture 4 % heat boiler, the temperature of the flue gas is reduced to about 200ºC, and the dust content is reduced to about 60 g/m3. The SCR reactors can be placed before the waste heat boiler (‘high temperature Figure 1. NH3 reacts with NOx quickly in the SCR reactor. configuration’) or after the waste heat boiler (‘moderate temperature configuration’). The ‘high temperature configuration’ can also be classified as a ‘high dust’ layout or a Figure 2. The layout of a moderate temperature SCR reactor. 12

World Cement April 2021

‘low dust’ layout. The ‘high dust’ layout has little effect on the efficiency of the waste heat boiler, but has a high impact on the service life of catalyst material and on the DeNOx efficiency of the SCR reactor. The ‘low dust’ layout requires a dust collector installed in front of the SCR reactor to lower the dust content of the flue gas to about 55 g/m3. This not only reduces the efficiency of the waste heat boiler significantly, but also complicates the SCR reactor system and increases the potential stoppage of the entire system. ‘Moderate temperature configuration’ refers to the SCR reactor being arranged between the high temperature fan and the raw material mill system, as shown in Figure 2. It has the advantages of both ‘high temperature’ layouts. This SCR reactor has no effect on the efficiency of the waste heat boiler. Due to the natural separation in the waste heat boiler, the presence of dust in the flue gas decreases from 120 g/m3 to 60 g/m3 before the flue gas enters the SCR reactor. Moderate temperatures will also result in a smaller volume of flue gas, thus allowing for smaller dimensions of the reactor, and in turn for lower construction investment and lower costs of the SCR reactor system. In order to develop moderate temperature SCR techniques, research has been

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Figure 3. The semi-scale SCR reactor. conducted into the raising of DeNOx activity of the traditional SCR catalyst. Some strong absorptive materials have been added to the catalyst to reinforce its adsorption of NH3 and NOx. Trace transition metals, such as W2O5, have been added to the catalyst to promote its moderate temperature activity. After that, a semi-scale SCR reactor is installed with 3+1 catalyst for the examination of the function of the newly developed catalyst materials, as shown in Figure 3. In this semi-scale

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SCR reactor, each layer of catalyst has only one catalyst module. Flue gas of 10 000 m3/h from the cement kiln is drawn into the reactor and its

temperature and the dust content are 200ºC and 60 g/m3, respectively. The NOx concentration in the flue gas from the cement kiln has been detected as up to 300 mg/m3, and due to the unreacted ammonia of SNCR in kiln system, its NH3 content has also been tested up to 120 mg/m3. In this case, a certain amount of ammonia has been added and injected into the SCR reactor to maintain the molar ratio of NH3 to NOx of 1:1. The semi-scale SCR reactor has been in operation for nearly two years, with DeNOx efficiency up to 90%. Figure 4. The design of a moderate temperature SCR reactor. This research work has confirmed the feasibility of the moderate Table 2. Major equipment and setup of the SCR reactor. temperature SCR technique. No.

Equipment and setup

Reducing agent

Note

The initial storage tank of ammonia for SNCR was used and two new ammonia pumps were added. A new set of meters were added 2

Meter/jetting

Catalyst

Dust blowing

Compressor

and modules to control the dosage of ammonia were delivered. A new ammonia evaporator with 125% capacity was added. Four catalyst layers were installed, and a fifth layer was added as a backup. Rake teeth blowers and acoustic soot blowers with compressed air were used. Two new compressors were added, with one in operation and one on standby.

Connected ducts and pipes

New baffles were set up for original ducts and pipes.

Dust delivery

A screw feeder to star feeder was added below the dust bucket.

Electrical & controlling

Connections were made to the central control room and DCS system.

Application of the moderate temperature SCR technique ChangXing Southern Cement Company is located in the Zhejiang Province, Changxing county. The company owns a 6300 tpd cement clinker production line with a rotary kiln of Ф4.8 x 72 m, a TDF precalciner and a waste heat boiler. A breakdown of the flue gas from the waste heat boiler is listed in Table 1. The production line has been added with the SNCR system, using up 350 l/hr of ammonia (20% concentration), and reducing NOx emissions to about 280 mg/m3. Considering the stringent upcoming requirements to lower the emissions of NOx to less than World Cement April 2021

50 mg/m3 and NH3 slip to less than 5 mg/m3, the cement company decided to make use of SCR techniques – the moderate temperature configuration was chosen for the plant design. The designed SCR reactor (Figure 4) was placed after the waste heat boiler, with a section area of 64 m2, height of 34 m, and the whole tower of 350 t. Inside the SCR reactor, 4+1 catalyst layers were installed, and each layer has 48 modules. The whole volume of the catalyst used is about 200 m3. Around and above each catalyst layer, acoustic soot blowers and rack teeth blowers were fitted to avoid the accumulation of the dust on the catalyst layer and to help convey the dust to a hopper at the bottom of the reactor. CFD simulation analysis was conducted for the design of connected pipes to the reactor in order to optimise their arrangements. Deflectors were set up in suitable positions inside the pipes in order to improve the uniformity of the flue gas and to prevent the creation of deviant dust currents, as deviant dust currents may cause severe abrasion of the catalyst materials and block up the cells of the catalyst. The SCR reactor was equipped with meters and gauges to detect and measure the pressures, temperatures and compositions of the flue gas, and to send all this data to the newly added DCS system for remote monitoring and daily start-stop of the reactor. The SCR reactor was attached to the ammonia injection system and can perform DeNOx by itself. It can also utilise NH3 slip from the SNCR system to perform DeNOx. The economy of both operation methods is under review based on the DeNOx efficiency, the consumption of ammonia, the NH3 slip and the power consumption of the entire system. Major equipment and setups of the SCR reactor are listed in Table 2. The construction duration of the SCR reactor (Figure 5) took around 100 days and the kiln was shut down for a week to integrate the SCR reactor. Since then, it has been in steady operation alongside the kiln for nearly one year. The results of the long-term operation indicate that when operating with SNCR, the consumption of ammonia is 2.2 kg/t-clinker with NOx emissions of less than 40 mg/m3 and NH3 slip of less than 5 mg/m3; whereas when operating by SCR itself, the consumption of ammonia is 2.0 kg/t-clinker, with NOx emission less than 30 mg/m3 and NH3 slip less than 5 mg/m3. The pressure drops of the SCR reactor and entire SCR system are 320 Pa and 1100 Pa, respectively, and the power consumption of the entire SCR system is about 3 kWh/t-clinker, fully meeting the requirements of the plant design proposed by ChangXing Southern Cement Company. April 2021 World Cement

Figure 5. The moderate temperature SCR reactor tower.

Conclusions Controlling NOx emissions is one of the most important tasks for the cement industry to deal with, and achieving low emissions of less than 50 mg/m3 is the top priority of China’s cement industry for the near future. DeNOx techniques, such as low NOx burners, staged combustion and SNCR can reduce NOx emissions to a certain extent, but SCR carries out DeNOx operations much more efficiently. Compared to ‘high temperature configuration’, the ‘moderate temperature configuration’ technique offers some obvious advantages, such as low investment, low operation cost, and long-term steady operation. After nearly one year of operation of the full-scale ‘moderate temperature configuration’ the SCR reactor for ChangXing Southern Cement Company has confirmed its technical feasibility and low operation cost. This technique is imperative for China’s cement plants to realise their NOx ultra-low emissions and green development goals.

About the author Wang Lan is a professor at China Building Materials Academy, Chair of China Cement Engineering Technology Committee, and consultant for China Cement Association. The principal areas of research in which the author has worked are energy saving and emissions reduction of cement production, especially flue gas DeNOx with SCR technology. 15

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GRIND WORLD CEMENT GRINDING Q&A

World Cement interviewed some of the leading equipment suppliers for their thoughts on the topic of grinding & milling. Read on to hear from: FLSmidth, Gebr. Pfeiffer, Loesche, and thyssenkrupp Industrial Solutions AG. 1) What do you see as the main challenges facing the grinding operations of cement manufacturers today? How can these be resolved? FLSmidth There are several challenges facing grinding operations in cement plants. First, enabling the use of new and different feed materials and/or making different cement products as part of sustainability initiatives creates operational challenges. Naturally, operating parameters

have to be adapted to the new materials – and sometimes there is more than one, or materials that have frequently changing properties. In addition to SCMs, there are alternative fuels and the impact they can have on clinker grindability and quality. Then there’s the challenge of whether or not existing equipment can cope with new materials without driving maintenance costs out of control. The need to manage operating and maintenance costs is a general challenge facing cement manufacturers independent of sustainability factors.

The first means of addressing these challenges is careful equipment selection. Whether evaluating the installation of a new mill or a system upgrade, it is critical to balance immediate needs with the likely impact of carbon reduction and sustainability initiatives in the near future. Small adjustments to sizing parameters with minimal effect on cost can have a significant impact on the flexibility to adapt to a broader range of materials. The second is the use of digital technology. Solutions focused on operations such as quality control or process control systems streamline the use of varying feed materials to minimise potential negative quality impacts and smooth operating conditions. Online condition monitoring services (CMS) enable predictive maintenance. This significantly improves system reliability in general and, more importantly, contributes to protecting equipment from mechanical failures and unexpected downtime while optimising for material changes. Gebr. Pfeiffer There are three main challenges: Sustainability, efficiency and digitisation. These are intrinsically linked. Sustainability has come to the forefront, quite rightly so, because our clients strive to (and are required to) improve their environmental performance and energy use. Efficiency is important for sustainability, as well as for the reduction of production costs. Digitisation feeds into the ease of use of the mill, as well as its process efficiency and, hence, sustainability. Our consistent product development is oriented towards the needs of our clients. Some achievements include: a 10% increase in power density of the current MVR series; increased specific dust load after the mill, which leads to a reduced gas volume flow in the plant; and lower plant fan power consumption. The separation efficiency of our classifiers has also been further increased. Of course, we are not only looking at the mill itself, but also at the complete grinding plant. Thus, pressure losses have also been reduced in our compact grinding plants by further optimising the ducting. These are just a few examples of activities that save further energy and thus also resources in general, since fewer raw materials have to be used, which only underlines the fluid relationship between efficiency and sustainability. Loesche The cement industry has gained ever-greater public interest due to its high CO2 emissions. At the same time, the availability of supplementary cementitious materials with comparatively low CO2 footprint (such as fly ash and slag), which have so far been used for cement production, has dropped significantly, especially in Europe. Calcined clay is attributed to have the potential to fill this gap to some extent. The optimal pre-treatment and grinding of

calcined clay will be an important task for the years to come. There are also the first plants grinding inert materials like granite. This of course places much greater demands on the grinding mills. Inert materials are more abrasive, and the cement mixture must be ground to a higher fineness to achieve satisfying product qualities, like good strength development. This results in an increase of requirements regarding the variability and flexibility of the grinding systems, in addition to the existing demands of best possible energy efficiency and availability. Vertical roller mills (VRMs) show good results in all areas and are known as the grinding system with the best product variability. There are grinding plants producing six different mixtures on one single Loesche vertical roller mill. thyssenkrupp Industrial Solutions AG Over the years cement manufacturers have extended their product portfolios by offering larger portions of additive cements, containing, besides clinker, a bigger share of ground limestone, slag, pozzolana or fly ash. The continuous reduction of clinker is also increasingly required in order to reduce the industry’s CO2 footprint. As a consequence, the fineness of cements with high additive content needs to be increased in order to maintain comparable cement properties. Hence, within cement grinding plant projects, companies’ aims range from achieving larger and larger throughputs to finer and finer products. The combination of different cement grinding systems is the key to coping with the challenges of grinding different types of cements. The Cement Technologies business unit of thyssenkrupp Industrial Solutions AG (tkIS) offers state-of-the-art grinding systems as well as common ball-mill grinding plants to serve specific customer needs: f High-pressure grinding roll polycom®: This machine has the lowest possible specific power consumption, which reduces total energy costs and the CO2 output. Especially, in conjunction with a ball-mill, the combi grinding system is an attractive solution regarding OPEX and CAPEX. No water spraying system is needed, but the machine offers a lower drying capacity than other grinding systems. f The vertical roller mill quadropol® incorporates a compact plant layout and is often used for moist raw materials. Due to its flexibility in grinding different cement raw materials and the fact that high throughputs can be realised, these grinding circuits are popular with customers, even though they require big gear boxes and a re-welding of the grinding rolls from time to time. f The polysius® booster mill is an agitated bead mill and is advantageous for producing high

World Cement April 2021

fineness cements. This fine grinder was recently introduced to the cement market. It is also an attractive solution for upgrade projects at existing cement works. As cement producers are under constant pressure to reduce OPEX too, it is also important to ensure the right cement quality by using the best available laboratory equipment. Therefore, tkIS has developed different polab® systems, which work in conjunction with XRF, XRD and laser granulometry. The newest development is the calorimeter polabCal®, which serves with immediate reactivity data of clinker and cement on pace together with regular process control data. It is now possible to adjust reactivity during production, which helps cement manufacturers to reduce their OPEX.

2) What factors should be considered by cement manufacturers when making the choice between different types of mill? FLSmidth When choosing a new mill there are several key considerations: f Capital investment. The total equipment cost for a ball mill remains lower than a VRM. However, the VRM with integrated separator has a more compact footprint, which provides civil/structural cost savings compared to the ball mill. This is particularly relevant in markets with high construction labour costs. f Feed materials. The physical characteristics of the materials being ground – e.g. abrasiveness or fineness – affects which mill is chosen. In addition, if frequent changes to the material characteristics are expected, that also needs to be considered. For most situations VRMs have an advantage with regard to material properties because they have more operating variables that can be adjusted. However, when material is too fine to make a stable grinding bed in a VRM, a ball mill is the more practical solution. If multiple products are being made in one mill, VRMs are the best option due to the short retention times, which allow a faster transition from one product to another. VRMs are also the preference for feed materials with high moisture content. f Maintenance. With a high emphasis on capacity utilisation and Overall Equipment Efficiency (OEE), it is of the utmost importance that the machines are easy to maintain with low maintenance time. With heavy emphasis on ease of maintenance in the past decades, the perceived maintenance burden of VRMs has been significantly reduced. f Energy efficiency and long-term total operating cost. VRMs consume 30 – 50% less power than ball mills, which can amount to millions 22

of dollars/euros per year. More importantly, the broader sustainability impacts have to be considered. These assets last 40 – 50 years. With the cement industry targeting net zero carbon emissions over the next 30 years, installing any equipment that is not in line with this means either the investment life will be shortened, or manufacturers will have to overcompensate later. Gebr. Pfeiffer Compared to other grinding systems, VRMs are characterised by lower maintenance and operating costs. This has been supported by cement producers and has led to vertical roller mills being a core component of modern cement plants today. There, they are used, for example, for grinding raw material, coal, pet coke, cement, blast furnace slag, limestone and pozzolana. The extremely short material dwell time also makes vertical roller mills much more flexible than ball mills when it comes to changing the proportion of the feed material or the fineness of the products. By changing the process parameters during operation, the mill is adjusted very quickly for each product mixture to achieve optimised performance. The Pfeiffer MVR vertical mill can be associated with the term ‘active redundancy’. The grinding rollers of the mill are actively redundant so production continues even if two of the up to six grinding rollers are swung out for maintenance. If the mill is equipped with a MultiDrive®, even individual rollers can be removed from operation. This is unique because here, as in other gearbox systems, in the MultiDrive, motors and gearboxes form several autonomous units. Each of these units can be removed from the system individually. So, it does not matter which component is under maintenance; the mill continues to operate. Numerous results from the field also show that the MVR vertical roller mill in particular is characterised by smooth running. This is due to its design and can therefore be seen across the product range. This low vibration level further increases the availability of Pfeiffer grinding plants and also enables trouble-free production of ultra-fine products. For example, a CEM I with a specific surface of 5500 cm2/g (acc. to Blaine) is being produced in a MVR vertical roller mill in Brazil. These high-strength cements allow for a reduced proportion of cement in the concrete or significantly smaller concrete parts, while maintaining the same loading capacity. Ultra-fine products are also produced with MVR mills for other industries. For example, limestone powder finer than 20 µm is also produced in a plant in Germany with such a vertical mill. Loesche Vertical Roller Mills for cement raw material, coal and cement are superior to ball mill grinding in World Cement April 2021

every respect. At comparable investment costs, the OPEX costs are decisive in the selection of the grinding system. Savings in electrical energy consumption of VRMs are in the order of 40% and VRMs are also significantly cheaper in terms of wear and maintenance costs. The trend is clearly toward cements with the lowest possible clinker content and greater flexibility, as the market demands an ever-increasing number of different cement types. The best suitable grinding system needs to allow product changes as quickly as possible and with minimal hassle. These preconditions are easily achieved when using a VRM system for cement grinding. The Loesche VRM system ensures that production can be quickly changed from simple OPC cement to composite cements, from low Blaine values to high Blaine values – an impossible task for ball mills. thyssenkrupp Industrial Solutions AG The right choice for a cement grinding system depends on individual customer requirements, which are always related to specific site conditions and to their local markets to be served, for instance, the type and number of different cements to be ground and individual product quality characterised by compressive strength (early and final), setting time, workability, water demand, and product fineness. Furthermore, the material compositions as well as the feed material properties (grindability, wear rate, moisture content) and other operational aspects like total specific power consumption of the grinding plant, product flexibility and maximum envisaged throughput rates have a big influence on the process design. It is important that cement manufacturers carry out an analysis of the incurred CAPEX and OPEX costs as well as consumables, spares, maintenance and labour costs, before making a decision regarding which cement grinding system should be installed.

3) What steps can be taken to ensure high separator performance? FLSmidth Performance comes down to the inherent design of the separator and the condition of its internal parts. The mechanical dimensions and geometry of the separator parts are all critical in achieving good separation efficiency. Separator designs are validated using engineering tools like CFD. This helps to ensure proper mixing of gas and material streams and maintain the velocity profiles as mentioned earlier. In addition, the developing use of different feed components as part of sustainability efforts increases the potential range over which separators need to work. To ensure performance under these conditions, installing drives with higher power and April 2021 World Cement

a wider range of operating speeds increases the flexibility of the mill system. It is equally important to maintain the mechanical reliability of a separator to sustain performance over the long term. This means balancing the mechanical dimensions with their influence on the wear rate of critical components. Internal velocities – and therefore wear rates – must be within a manageable range. If the critical internal parts, such as air seal or static guide vanes, wear too quickly they will immediately degrade separator performance. Of course, wear is a part of the comminution and separation process. Eventually, parts wear. It is important to replace them in a timely fashion. This is aided by making maintenance faster and easier through design features such as easy access, appropriate inspection and maintenance doors, and the possibility to replace specific wear prone parts alone. And in cases where material is more abrasive, additional wear protection or use of advanced materials can extend component life for the full production schedule. Gebr. Pfeiffer Through the installation of a high efficiency classifier, the differences in particle size distribution (PSD) between ball mill and vertical roller mill are neglectable. In a vertical roller mill, the PSD can be adjusted by different parameters: for example, by increasing the working pressure, the quantity of fines can be increased. By decreasing the volume flow, the PSD becomes wider. The design principle of the classifiers is always the same irrespective of their sizes. However, the sealing of the gap between the separating rotor and classifier housing can be adapted to suit the envisaged product fineness and oversize product required. The standard design for a ‘normal’ product fineness, as required in the cement industry for example, is a defined annular gap between the upper flange of the separating rotor and three-part wear ring on the classifier housing. Depending on the classifier size, the precise adjustment of the axial and radial gap dimensions is carried out while setting up and commissioning the grinding plant. When doing high fineness classification, seal air is directed onto this annular gap as an additional means to avoid any oversize in the finished product. This seal air feature is used mainly when grinding materials like limestone to very high fineness such as less than 0.1% residue on 20 µm. In some applications, the production of coarser product fractions can be lucrative in addition to the fine end product. By providing a variable speed grit discharge screw conveyor it is possible to simultaneously produce e.g. fine limestone meal as well as grits of sizes up to 1 mm. Such a grinding plant with a Pfeiffer vertical mill and high efficiency classifier of the type SLS is operational in Poland. The fine material, which is the main product, is 23

separated from the gas flow in a bag filter and stored in silos. The discharged classifier grits are separated at 0.1 mm in a downstream Pfeiffer distribution table separator of the type SUV for screening in a three-deck screening machine at 0.4 mm, 0.8 mm and 1.2 mm. These products are then stored in separate silos. Any off-size from the screening and separating stages that is classified as undesirable for marketing reasons can be returned to the mill so that no material has to be discarded. The infinitely variable control of the screw conveyor speed allows a production ranging from 0 to 55% of classifier grits of a defined grain size. Using two-phase CFD, the direction of flow in the separator, the differential pressure and separation efficiency can be optimised very well.

distribution though pipes, filters, and cyclones, which also reduces wear. f Additional steps: It is important to supply enough separation air. By reducing the cage area of the separator, the air velocity and thus the energy for the separation process is increased. The equilibrium of forces such as the drag force created by air velocity, and gravity force created by the rotation speed of cage, have to be maintained. In the case of very fine product, the use of bag filter discharge is recommended instead of cyclones.

Loesche We see three main steps: f Modern simulation and test methods as well as the consideration of practical experience from hundreds of successful customer projects over decades enable the permanent procedural enhancement of separator performance. f Continuous mechanical and design ameliorations make it possible to optimise investment, operation and maintenance costs and to achieve a higher durability of the machines. f Matching of the separator-mill-unit with other components of the grinding plant has the following effects: a compact design reduces investment costs and a higher efficiency of further plant and production processes decreases the operational costs.

FLSmidth Modular grinding systems are most commonly used for small capacity grinding stations and new grinding lines to achieve small capacity increases, typically up to 500 000 tpy. The biggest advantages are in the construction or installation cost savings. Truly modular grinding systems, where the plant equipment is preinstalled in structural elements with all utilities (air, water) and electrical wiring done ‘in the shop’ before shipping to site, can be installed in much less time than traditional plants. The shorter installation time also means a faster journey to production, which can be critical in meeting the needs of rapidly developing markets. Modular grinding systems also have the potential to be relocated from one site to another more easily than conventional installations. While this is typically a secondary consideration, there are some circumstances where it has particular benefits, for example in regions where multiple small isolated markets are expected to develop over a period of several years.

thyssenkrupp Industrial Solutions AG f Adjustable guide vanes can be used to increase the energy level of separation: The design of the new guide vanes has been optimised for best flow pattern, and minimised wear, and enables the operator to adjust the separating gap between the edge of the guide vane and the outer edge of the rotor in a specific range. The separator performance is increased due to the better dispersion of agglomerates within the flow pattern outside the cage rotor. f By installing a swirl breaker, pressure drop can be decreased: A dynamic separator needs swirl to generate centrifugal force. The rotation of the air in the separator rotor shows a flow profile in the form of a vortex. However, as soon as the fines have passed the rotor blades, the swirl inside the cage loses its procedural benefit. The swirl breakers slow down the rotational vortex, ensuring flow alignment, and lower tangential speeds. There is the same angular velocity at every point of the radius. This causes an even distribution of the outflowing air and a more even

4) What advantages do modular grinding systems offer over more conventional set-ups?

Gebr. Pfeiffer We can only speak for our own ready2grind system which has proven itself in the field worldwide. It has fewer options than a traditional mill but can still offer efficiency, sustainability and reliability. This range was developed in response to market demand. After the financial crisis of the late 2000s, there was a realisation that there was severe clinker overcapacity across the industry. At the same time, there were still several markets with relatively weak infrastructure that were natural homes for small grinding plants of 20 tph. Now these too have moved to larger capacities to save on capital expenditure as much as possible, albeit in a lower ‘capacity window.’ The ready2grind 1800 produces 22 – 34 tph, the ready2grind 2500 produces 52 – 79 tph and the ready2grind 3000 producess 59 – 90 tph. These grinding plants are well suited for remote areas or for instances where cement production needs to

World Cement April 2021

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be very close to the cement consumer, even if the infrastructure is challenging. There needs to be a high degree of prefabrication built in at the design stage so that units can be installed. Using the ready2grind range, we have worked with clients that are not traditional cement producers but rather traders and construction companies. For them, the speed with which the project can be completed is often very important. This is another driver towards a modular, pre-fabricated approach. A further advantage of these systems is that the containerised plant components can be transported and installed more easily. Our references demonstrate that we have also implemented our clients’ requirements well in the field of modular systems.

layout, and procurement packages. The modular plant offers a very competitive solution with a low EPC price, short delivery time, easy installation and low maintenance. Modular grinding plants are allowing customers and even newcomers a fast entry into cement markets. Beside the low CAPEX with shorter payback periods, the modular concept bears low technical or financial risks for customers. Modularisation also facilitates the dismantling and re-erection of the grinding plant elsewhere, if commercial or market conditions change. The polysius modular grinding plant ensures the quality and reliability of all equipment and maximises the performance of the plant, producing a high cement quality.

Loesche Loesche has created a modular system for complete grinding plants for all cement mill sizes available from the LM 24.2 CS to the LM 72.4+4 CS. This modular concept enables a fast and still very flexible design of the grinding terminal. For example, the product storage capacity can be individually adapted to the needs of the customer. The grinding plant can be adjusted optimally to all topographical areas. Most of the modules for smaller terminals contain completely pre-assembled container systems which, depending on their use, can also be used in larger mills. Particular focus was placed on quick assembly and good maintenance options, so that access to all maintenance points is given. The decreased installation and engineering times reduce the overall time schedule. Therefore, the grinding terminals can go into production sooner in comparison to a plant not using a modular design. This modular concept is suitable for grinding terminals in greenfield as well as brownfield projects. The advantage of the reduced overall project times and the earlier start of production also come into play here.

5) What role do you see for digital technologies, such as process automation solutions, in the grinding sector?

thyssenkrupp Industrial Solutions AG For years, the cement market has been volatile and with regard to grinding plants, there has been an increasing demand for fast installations, (semi-) mobile solutions and for closing white spots. The market is still driven by a decreasing CAPEX trend, new entrants, higher competition and less engineering capacities at clients’ project engineering teams. All these market drivers are met by the concept of modular grinding plants. This concept is ideal for capturing markets of up to 500 000 tpy, is suitable for greenfield or brownfield projects and offers several advantages compared to a conventional tailor-made grinding system. It is based on a stripped-down concept, which focuses on the core needs of the operation with optimised costs and less engineering, is fully standardised and incorporates pre-engineered equipment, plant

FLSmidth Integration of digital technology is already a proven part of grinding solutions. FLSmidth has offered advanced control through ECS/ProcessExpert® for 20 years. Today, it has been proven to increase overall system performance, lower power consumption, and maintain better quality control (lower standard deviation). Those same benefits apply particularly well to the development of ‘green cements’ with a lower clinker factor. Taking advantage of IOT capability, the ‘newest’ digital offerings are in advanced, predictive maintenance or online condition monitoring services (CMS). These services have been offered for critical components such as gear reducers for many years. Allowing suppliers to monitor the mechanical condition of these critical parts of the mill system helps to prevent unplanned and costly stoppages or breakdowns that result in significant lost production and revenue. The latest condition monitoring services integrate process operating variables and mechanical sensor readings, along with the use of advanced predictive modelling based on large data sets that inform when adjustments are needed to mechanical settings or identify when maintenance of critical parts will be needed. The result is improvement in overall performance from equipment optimisation, but more significantly reduced maintenance cost from better planning and less interrupted production time. Another aspect of digital technology that has been highlighted during the COVID crisis is the increased ability to provide remote services. Availability of historic operating data and long-term monitoring of critical KPIs make it much easier and faster to provide troubleshooting and operating support to plants, independent of location. There are also cost savings from the elimination of travel and on-site

World Cement April 2021

service costs for issues that can easily be resolved remotely, saving the budget allocation for more complex (and often more costly) issues. Gebr. Pfeiffer Digital technologies in cement grinding are not the future, they are the present. We have followed the Industry 4.0 trend since it became a feature of the sector. It drives our clients and so it drives us. We offer several digital products, one of which is GPlink, which saves sensor data for data analysis and enables 24/7 access to data from mobile devices around the world. When transmitted to the company’s service team, a solid basis for support and rapid, targeted assistance is given. GPlink forms the basis for all other digital products. The modular GPpro is the logical continuation of digitalisation. GPpro enables, for example, an advanced maintenance system, with maintenance according to actual need and not according to fixed intervals. The system also includes additional sensors and offers modules for data analysis, reports, optimisation with the help of artificial intelligence (AI) and many other resource-saving optimisations such as dynamic water injection. The topic of AI is particularly exciting because the benefits are clear. A skilled human operator can certainly set several operating parameters and overlook the interaction of these. With the help of artificial intelligence, any number of parameters can be examined and the ideal setting values for an application can be determined. There is enormous potential here and the first results with an industrial mill have been very promising. Digitisation is progressing and we are following this path. There is also a lot of movement in this area and Gebr. Pfeiffer attaches great importance to this topic. Loesche For the plant operator, maintaining international but also regional competitiveness is crucial. Therefore, the comminution technology must be permanently optimised in terms of efficiency, performance, and energy consumption. The systems required for this increase in complexity with the growing demands on, for example, mixed cements in terms of water requirements and strength. Loesche has long been committed to developing solutions and machines that are as environmentally friendly and resource-saving as possible. Digital technologies are absolutely necessary in order to achieve these goals more quickly and to be able to consistently develop the goals further. At Loesche, we do not limit ourselves to computerisation and connectivity, but apply self-learning software for process optimisation that provides forecast data and operating settings in real time in order to operate the grinding technology at the limits of its physical possibilities – stably and reliably. In conjunction with

April 2021 World Cement

diagnostic systems and service platforms for spare parts procurement, this results in the possibility of implementing condition-oriented maintenance and servicing strategies. A holistic picture emerges to support plant operation. thyssenkrupp Industrial Solutions AG Digitalisation is the connecting element between the process know-how of the suppliers, and the needs of the cement producers. Suppliers can benefit from accessing the data for process and machine optimisation and cement producers can achieve higher outputs, less energy consumption and higher plant availability with more reliable plant operation. Today, this is possible as grinding plants are equipped with sensors to control the process and the plant equipment. The data from these sensors is collected and can be displayed on the dashboard in the control room for interactive real-time insights. The KPIs of the grinding plant can be visualised and by identifying anomalies, characteristic patterns and operational conditions, the plant operator can gain a more transparent view about the performance of the grinding plant. By installing an artificial neural network together with optimisation algorithms, recommendations on plant operation can be provided to the operator. The intelligent model advises optimal set-points for process parameters in order to maximise targets for throughput and energy consumption, enabling the operator to enhance the plant efficiency and reduce the operating costs. In addition, remote assistance services by tkIS in combination with predictive maintenance or root cause analysis offer the possibility of increasing the availability of all machines from the grinding plant. A proper and timely supply of spare parts can be organised and maintenance work can be planned better in order to maximise plant availability.

6) Looking to the future – what do you see as the next steps in terms of grinding technology? What advances can we expect to see over the coming years? FLSmidth Grinding technology has reached a stable point in the lifecycle curve. Incremental improvements are most likely to account for advancements for the near future. These will be in the areas of: f Wear materials and metallurgy that allow for longer lasting and smaller/lighter component weights. f Integration of digital technology to push the limits of efficiency and performance higher, while implementing predictive maintenance to streamline costs for labour, and parts supply and inventory.

f Continued optimisation of the production of blended and high Blaine cements and the introduction of new high-performance cements that use a wide range of SCM to replace clinker. This includes advancement of separator designs to achieve finer product residues at higher capacity than are possible today. More significant advancements will likely come over the long term, as research into energy consumption and grinding mechanisms is developed into new applications. Gebr. Pfeiffer Sustainability will be one of the central challenges, because cement production is responsible for 8% of global carbon emissions which is why dependency on fossil fuels must be reduced. Therefore, the use of modern and highly efficient technologies with low electrical energy requirements is indispensable, especially in the cement industry. Around 60% of the carbon dioxide emissions in cement plants are released during the limestone calcination process. As carbon is produced here as a by-product of a chemical reaction, this carbon dioxide emission cannot be reduced by alternative fuels or a higher efficiency of the calcining plants. The obvious solution is therefore to reduce emissions by using clinker substitutes or a higher proportion of additives, as this simply means that less clinker has to be produced and the clinker factor can be reduced tremendously. The MVR is a versatile system for many feed material applications and can be adjusted easily for all different kinds of clinker replacement materials. With features like a heated rotary lock for moist feed materials or when feeding dry and fine materials, an additional feeding point at the classifier housing the MVR mill is prepared for a wide range of clinker replacement materials. Our task as a grinding plant manufacturer is to provide the appropriate solutions for the changing challenges of the industry in order to reduce the carbon footprint in cement plants, protect our environment and at the same time give our customers a competitive advantage. Gebr. Pfeiffer continues to put innovation into practice and subjects its efficient mills and the associated processes to consistent, continuous improvement processes. Our MVR mills have a high power density and produce cements of the broadest range of material compositions. Their comparatively low energy consumption saves resources which is good for the environment and the wallet. This is complemented by a wide range of digital products and services. Loesche A disruptive grinding technology for mass products like in the cement industry is not in sight. In fact, the

already established grinding systems (VRMs, HPGR and ball mills) will still be present on the market, with the energy efficient mills having an advantage. However, the trend towards high-throughput grinding plants, as experienced in the last two decades, will come to a halt. In contrast, the demand for smaller modular grinding terminals with manageable investment costs and fast production starts will further increase. Due to the market situation, the cement industry will put a stronger focus on the modernisation and optimisation of existing plants. Optimisation of grinding plants will also be possible by means of increasingly well-functioning self-learning expert systems using potentials for productivity improvement. Digitalisation acts as a driver for technical innovations and is a touchstone for the innovative strength of leading manufacturers in plant engineering. thyssenkrupp Industrial Solutions AG Along with increasing demand for pre-cast concrete, other high early-strength cement types, and low clinker cement, there will be a demand for finer grinding. One solution to achieve the necessary cement quality – and partially also to compensate for loss of capacity due to a higher fineness – is the polysius booster mill, a horizontal agitated bead mill. Rotating discs with mounted grinding tools rotate at high speed inside a fixed shell, stirring the small balls (beads) and creating a ‘cloud’ of beads and material. This mill, established for decades in wet processes, has been jointly further developed by companies Netzsch and thyssenkrupp Industrial Solutions AG to be applied in dry processes for very fine grinding of cementitious materials. The modular, compact and highly energy-efficient system can be integrated into an existing grinding plant. Results from a first reference, and from trials in a small-scale pilot plant, show that the clinker content of new cement compositions can be reduced significantly while maintaining previous – especially early – strength values. In other trials, ultra-fine cements were produced, achieving comparable quality even at lower fineness values. In terms of quality, another add-on to the solution, and to grinding plants in general, is a calorimeter, recently introduced by thyssenkrupp Industrial Solutions AG. Instead of only using fineness or residue values as indications for quality, this solution measures heat from the early hydration process, allowing for an accurate prediction of the final quality within minutes. It has been tested and proven as beneficial in several plants, showing potential for faster cement quality control in the future. Finally, in combination with process optimisations and the application of digital products at cement grinding plants, the polysius booster mill offers production opportunities for cement manufacturers worldwide.

World Cement April 2021

Emre Ergun, IEP Technologies, outlines the preventative and protective measures the company put in place to help a Turkish cement manufacturer mitigate the combustion risks associated with alternative fuels.

he use of refuse derived fuel (RDF) is becoming increasingly common in heavy industries and power plants where it is viewed as a more sustainable alternative to fossil fuels. RDF is typically a solid fuel, produced from industrial, municipal or commercial waste, which after screening and separation is shredded or pelletised in order to provide a suitable alternative fuel.

One such example of RDF usage is within the cement industry, where it is used to fire kilns. However, in spite of the environmental and cost advantages achieved, systems for preparing and transporting this type of fuel are exposed to the dangers of industrial fires and explosions. Careful planning and design therefore are vital in plants where RDF is used.

Industrial fires and explosions can occur in many manufacturing processes when fine particulates, dispersed in air, are subjected to an ignition source within a contained environment – for example a duct, vessel, or collector. Ignition can be generated by many different factors,

Various types of raw material used for the preparation of refuse derived fuel.

Various types of raw material used for preparation of Refuse Derived Fuel (left) and Refuse Derived Fuel material storage area (right).

including hot surfaces, burning embers, flames, welding, spontaneous combustion, friction or uncontrolled electrostatic discharges. These ignition sources can be minimised or eliminated by a combination of effective engineering controls, safety management and operator awareness, but in many cases, the explosion risk is ever present and therefore techniques to mitigate the potentially catastrophic effects must be employed. It was against this backdrop that a major cement manufacturer located in the western part of Turkey recently made a multi-million euro investment in a system to allow the use of alternative, RDF and related Tyre Derived Fuel (TDF) in its process to reduce its operating costs and improve its carbon footprint. In order to achieve the maximum benefits from the company’s reduction targets, the system consisted of several elements, including an RDF preparation plant and semi-closed material storage warehouse, as well as RDF and TDF transportation systems. Another key consideration for the company was the flexibility of producing its own RDF as well as utilising third party supplied TDF and RDF within its process. The RDF preparation process included the following items: material acceptance pit, front-end loader fed open top primary shredder, metal separation, air-material separation, and a connected secondary shredder where all material transport between processes was to be carried out using closed conveyors. Additionally, an externally located dust collector was to be used for dedusting of the process. RDF fuel prepared at the plant was then to be kept in a storage warehouse where the material was to be fed to the cement kiln using a series of conveyors and chutes.

The challenge

Broken shredder knives – a potential ignition source inside primary and secondary shredders. 30

At the outset, the company’s Operations and Health and Safety Group decided to only use solid wastes such as shredded tyres, paper/packaging wastes, oil/solvent contaminated textiles, dried sludge, and plastic as its alternative fuel source. Due to their variability, the explosibility and ignitability hazards of these materials are not well known and are difficult to quantify. A data and literature review conducted on the various materials that can potentially be introduced to the system indicated that such material may become easy to ignite, especially if mixed with solvent wastes. Furthermore, explosion risks are also created by fibres and dusts suspended inside the enclosed process equipment such as shredder enclosures and chutes. Additional risks from the unintentional inclusion of discarded aerosol cans to the shredding system were identified; these could World Cement April 2021

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create deflagration or flash fires, which could in turn trigger secondary ignitions or deflagrations inside connected equipment. Another potential hazard identified by the company was that the prepared RDF material may have a tendency to self-heat and ignite spontaneously, potentially instigating fires inside the conveying system. Other potential ignition sources such as broken shredder knives, electrostatic ignition sources due to conveyor movement, frictional ignition sources, mechanical sparks, hot particulates and embers were also determined as possible

scenarios inside the RDF preparation plant as well as the RDF/TDF transfer system. After the company conducted a comprehensive risk assessment, they concluded that explosion/fire prevention and explosion protection measures would be necessary to minimise the fire and explosion risks within their RDF and TDF handling processes. In order to meet strict safety standards and local regulations, they looked for potential specialist vendors of ATEX certified systems that would be reliable and robust for use in such harsh environments. ATEX is the umbrella name given to two European Union Directives for controlling explosive atmospheres, and IEP Technologies was eventually selected to provide a complete explosion prevention and protection solution. IEP Technologies has over 60 years of expertise in explosion protection and offers leading solutions to a worldwide client base, assisting with all stages of the selection process, from materials testing, active and passive explosion protection systems, spark detection and extinguishing, and ongoing service and support.

Shredder explosion protection and prevention system. Spark detection and extinguishment on the shredder inlet and outlet chutes are shown. Explosion suppressors (red cylinders) providing explosion isolation can also be seen. The shredder explosion relief vent is located on the opposite end (not shown).

The solution

After an initial site visit to study the process conditions, equipment layout and risk reduction targets, IEP Technologies’ Table 1. The specific protection solutions recommended for the alternative fuel Engineering Team processing and transport systems. designed and proposed Process Protection recommendation both explosion protection and prevention systems Explosion suppression on the primary shredder outlet volume to meet the identified and explosion isolation on the primary shredder outlet conveyor. Explosion protection for primary and company objectives secondary shredders with the goal of and requirements, while minimising explosion propagation to Explosion venting on the secondary shredder and explosion connected equipment. offering a highly reliable isolation via suppressant barriers on the inlet and outlet conveyors feeding the shredder. ATEX certified solution. The specific protection solutions recommended by System consists of: IEP Technologies for the alternative fuel processing Triple IR flame detection and extinguishment on the RDF/TDF acceptance pit to detect and extinguish any flash fires inside and transport systems are the pit due to aerosol can fires or material fires inside the summarised in Table 1. transfer pit. The explosion protection Spark/hot particle/flame detection and system installed on extinguishment on the shredder systems. Hot particle/spark detection and extinguishment on the primary the RDF preparation shredder discharge chute. process included explosion detection Hot particle/spark detection and extinguishment on the using IEP Technologies’ secondary shredder feed and discharge chutes. ATEX certified SmartDS and IR (Infra-Red) flame Spark detection and extinguishment on the dedusting duct. detectors along with E-HRD suppressors, Detectors located on the drop chutes to detect sparks, hot Spark/hot particle detection and particles or embers inside the high flow conveyor system. The designed to provide extinguishment on RDF/TDF transfer system consists of detection and extinguishment on various high speed detection conveyors. drop chutes over five different protection zones. of incipient explosions

World Cement April 2021

coupled with a high degree of false-alarm immunity. Additionally, IEP Technologies’ explosion relief vent panels were used on the secondary shredder feed chute volume with a vent duct directing the products of any explosion to a safe location outside. SmartDS explosion detection technology uses a ‘rate of rise’ principle to determine explosion pressure at a very early stage, able to differentiate between normal process pressure fluctuations and deflagration events. When used together with the IR flame detection, SmartDS reduces suppressor isolation distances while increasing overall detection reliability. The detection and suppression systems are linked back to an EX8000 controller which provides monitoring and control to each process/zone and a comprehensive event log. The Spark Detection and Extinguishment System utilised a patented ATEXON V300EX spark/hot particle detection system which is a wide spectrum flush mounted detector along with extra wide field of view. This detection system is mounted without the need for welding flanges and is flush mounted on the surface of ATEXON V300EX detectors mounted on the the equipment. The V300EX Spark Detector has dedusting duct. full 180° viewing angle which makes it possible to cover the whole cross-sectional area of the protection zone. Another important requirement in RDF handling processes is the ability to detect not only sparks but also hot particles. If the temperature of the particle is less than 500ºC it does not emit visible radiation and is not considered to be a ‘spark’. However, RDF/TDF transportation system/acceptance pit. Triple IR (IR3) flame these hot particles are detectors are located on opposite corners looking inside the pit while viable ignition sources for extinguishers located on the two sides provide wide angle coverage. biomass and RDF transfer systems – for example, where thick material layers exist in the conveyers and silos. IEP Technologies therefore utilised its V300EX detector, which has the ability to detect hot particles with temperatures as low as 300ºC. The high-pressure extinguishing systems installed in the process are activated by fast response solenoids with spring loaded nozzle mechanisms operating at pressures of 7 – 9 bar. The nozzle systems used in the design Sample layout of the detectors on the material acceptance pit and on are specific for high speed dedusting pipe. April 2021 World Cement

dust transportation ducts and transfer chutes between belt conveyors. Due to the minimal protrusion into the duct, they avoid wear from abrasion, while the high-pressure water spray prevents product from clogging the nozzle. The extinguishing system also monitors the water temperature, water flow and ball-valve position, increasing overall system reliability. When a single spark is detected, the extinguisher is actuated for roughly one second to extinguish the hot particle or ember without stopping the process, however if multiple consecutive sparks are detected within a short period, the system engages the extinguishment function while also activating alarm relays to shut down the process.

Conclusion

Typical spark detection and extinguishment locations on a chute for most reliable operation.

As the global cement industry continues to use more and more RDF/TDF type alternative fuels, the risks from explosions and fires will continue to increase unless suitable preventative and/or protective measures are employed. As illustrated in this article, thorough study of the process, equipment and conditions as well as appropriate hazard assessments are required in order to identify all high-risk areas before deciding on the most appropriate protection measures to take. Having on-site reviews prior to decision making, as well as providing necessary engineering and onsite support during installation is crucial in successful implementation of an explosion protection and prevention solutions. Following on from initial installation and commissioning, annual site visits are planned for customer training and periodic system maintenance of both spark detection and explosion protection systems by IEP Technologies’ Field Service Team in Turkey. With both systems now up and running, the company’s Operations Manager praised IEP’s technical team for their involvement and competence during every stage of the project from start to finish.

About the author

RDF conveyor discharge chute spark/hot particle detection and extinguishment. 34

Emre Ergun is the Managing Director of IEP Technologies Turkey. He has 20 years of experience in the industrial explosion protection field with focus on product development, R&D, application engineering, standards development and business development. He holds a BS in Chemical Engineering from Middle East Technical University, Ankara, an MS in Engineering Management from Northeastern University Graduate School of Engineering, Boston, and an MA and MBA from Babson College, F.W. Olin Graduate School of Business. Emre is a certified safety auditor by the National Association of Safety Professionals, NASP. World Cement April 2021

Luiz Felipe de Pinho and Roberto Campos, Dynamis, discuss the company’s role in the design and supply of equipment for Cementos Argos’ Rio Claro calcined clay activation plant and explain how clay activation technology could allow for a more sustainable and competitive method of cement production.

CLAYING IT ALL ON THE LINE ver the years, companies have been searching for business models that can bind together both development and sustainability. New environmental regulations and commitments to society have driven companies to lower their carbon footprint and minimise the usage of fossil fuels and electric power. On the other hand, in a more global and competitive world, markets force companies to lower their prices and cut production costs.

A solution for sustainability

D-Gasifier attached to the kiln hood.

In the cement industry, one of the best solutions for increasing both sustainability and competitiveness is to substitute clinker with pozzolanic-like materials, such as artificial pozzolan, natural pozzolan, fly ash and blast furnace slag. However, the application of these materials may be limited by important factors. Natural pozzolan availability is restricted to geographic regions with volcanic soils, while slag demands high electricity consumption for drying/grinding, and fly ash availability is decreasing rapidly due to the phasing out of coal power plants, making this material more expensive and increasingly unavailable. On the other hand, there is a large availability of clay with thermal activation capacity worldwide, allowing cement producers to industrially manufacture a very high-quality material without the necessity of raw grinding, whilst having control over its production capacity and clay properties. Artificial pozzolan therefore has great potential for supplementary cementitious material.

Real applications with artificial pozzolan Colour comparison between calcined clay with and without colour control and a colour comparison between regular cement and cement blended with calcined clays.

D-HotGas hot gas generator connected to the Flash Dryer (left). D-Gasifier Combustion Chamber of the hot gas generator and its BMS system (right). 36

Artificial pozzolan is produced by an increasing number of cement manufacturers, and Dynamis is playing a major role in this field with the design and equipment supply for several clay activation plants, such as Cementos Argos’ Rio Claro 1500 tpd line, the largest calcined clay kiln in the world. In April 2019, Cementos Argos’ new calcined clay production plant started its operation. Located at the Rio Claro site in Colombia, this line was designed using the D-Pozzolan® technology, to take on challenges such as the production of high-grade pozzolan, starting from low-grade clay, and a decommissioned kiln. Other than the pyroprocessing, Dynamis took part in project World Cement April 2021

development activities in close partnership with Argos. These activities started with initial laboratory tests, that developed into an engineering project and culminated in the equipment supply and technical assistance during erection and start-up. The most impressive aspect of this plant is its colour changing technology. It is interesting to see the reddish clay being fed in to the dryer, changing its colour inside the rotary kiln and finally leaving the cooler as grey calcined clay. This is part of the D-Pozzolan technology, a complete solution carefully designed by Dynamis to meet the specific needs of the clay calcination process. The grey colour of the calcined clay allows high substitution rates and important reductions in the clinker to cement ratio, as well as a reduction in cost and also in the CO2 footprint of the cement produced. The quarry is connected to the industrial plant by trucks. The raw clay received at the plant is processed by deagglomerators which are responsible for obtaining the ideal clay grain sizes for the D-FDryer (Dynamis’ flash drying system). Inside the dryer, the solid particles are dragged by the hot gas stream, making it possible to achieve high heat and mass transfer coefficients in a relatively small space and with a small footprint. The preheated and dried material dragged by the gas stream is separated from the flue gases by a set of cyclones. The hot gas for material drying comes from the kiln and is complemented by the D-HotGas, the Dynamis hot gas generator designed for 100% coal or petcoke. It is important to have the optimum gas flow in the drying system to enable clay particles to drag. Furthermore, the hot gas generator complements the thermal load for material drying. The dry clay collected by the cyclones is fed to the rotary kiln. At the feeding chute, the clay is mixed with coal particles of controlled grain sizes, which act as a reducing agent inside the kiln. The rotary drums (kiln and cooler) used in this project came from deactivated units and were adapted by Dynamis. This utilisation of decommissioned equipment was a premise established by Argos. Dynamis D-Pozzolan technology, with the application of a D-Gasifier that operates with solid fuel (coal or petcoke), provides solid control over temperature and oxygen content throughout the kiln, which are fundamental conditions for obtaining thermally activated clay, for assuring its colour change and for achieving the desired quality. The product from the kiln is forwarded to a rotary cooler. As for the kiln and the dryer,

it is important that material cooling is carried out in a controlled atmosphere so that the grey colour achieved in the previous stages does not reverse. Thus, the airflow for cooling is minimised. Lifters installed inside the cooler maximise the heat exchange coefficients between the air and the material. However, the cooling process must be complemented with water. Dynamis installed water channels over the cooler, promoting the formation of a water film on the shell. Thus, the low temperature of the calcined clay at the cooler outlet is achieved through the airflow inside the

rotary drum and the flow of water outside the cooler shell. Finally, if any unexpected conditions occur and the calcined clay temperature exceeds the maximum set value, emergency lances spray water inside the cooler.

Summary Dynamis is constantly searching and investing in improvements in calcined clay production technology. There are many opportunities for innovation, such as the flash technologies for clay drying and calcining developed by Dynamis. Argos’ Rio Claro line appears as an important landmark in the development of clay activation technology and of a more sustainable and competitive method of cement production.

About the author Luiz Felipe de Pinho is the CEO of Dynamis. He earned his Bachelor’s Degree in Mechanical Engineering at the University of Sao Paulo in 1995. Luiz has over 25 years of professional experience in cement and lime, mining, metallurgy, chemical, agribusiness, and food industries.

View of the water channels above the rotary cooler.

Roberto Campos is an engineer at Dynamis, and holds a Bachelor’s Degree in Mechanical Engineering from the University of Sao Paulo.

MAKING GRATE STRIDES Valentina Bordei and Viktor Penner, thyssenkrupp, show how an improved static grate design could enhance cement plant performance with a more stable operation, higher equipment availability, lower fuel consumption, and increased clinker production.

he static grate plays an important role in the overall cooler performance, influencing key performance indicators such as equipment availability and the overall energy efficiency of the kiln line. From its first introduction decades ago, its design has evolved to accommodate the knowledge gained from practical experience. The newest polysius® double inclined static grate is the result of R&D efforts and feedback from hundreds of coolers in operation. Its main features include minimal operation disturbances and maximum heat recovery.

Static grate function and design

result of an interplay between material chemistry, burning conditions in the kiln and insufficient/slow cooling on the static grate, and they can seriously disturb the operation of the plant. The new design of the polysius static grate addresses all of these issues. The geometry of the static grate was adapted to improve the lateral distribution of the clinker and the penetration of air in the clinker layer. By narrowing the horseshoe and extending the static grate length, the new design helps distribute the material more evenly over the grate width. It has been observed, especially in wider coolers, A poorly performing static grate not only that air can shortcut through the lateral fields of increases operating costs, it can also lead to a the static grate, where the clinker layer is more reduction in equipment availability. Phenomena shallow, resulting in an insufficient aeration of like red river formation and snowmen are the the central field. This leads to inhomogeneous cooling and reduced heat recuperation. The increased length of the new design also ensures that the residence time is sufficient to allow for vigorous heat exchange between the solids and air. The inclination of the static grate was also changed to reduce the height of the clinker dead layer. A certain so-called ‘dead layer’ of cold, stationary clinker is necessary in order to protect the aeration plates from heat damage and extend their operating life. If the dead layer is too thick, it can cause unnecessary flow resistance, reducing the effective aeration to the incoming hot clinker. This aeration is crucial to stop phenomena like red river from forming. The new static grate Figure 1. A section of the new static grate outside the has two sections: an initial section manufacturing workshop, ready for shipment to the with a steeper inclination, and installation site. The grate was delivered in two fully a shorter one with the standard assembled longitudinal sections. inclination angle. Together, they ensure that the aeration plates are continuously covered by a protective layer of cold clinker, but without an excessive pressure drop. The grate is also equipped with the latest design in aeration elements with a well proven spillage-free labyrinth design. The plates also have a very low pressure drop and are made of temperature-resistant steel. The static grate fulfils several key functions: f Quick initial cooling in order to ‘freeze’ the clinker phases and stabilise the alite content (C3S), therefore ensuring high product quality. f Enhancing the heat recovery to the kiln and calciner and reducing the fuel consumption of the kiln line. f Spreading the material falling from the kiln uniformly over the width of the cooler grate to allow a homogeneous cooling result.

The first installation: BinhPhouc cement plant – Vicem Hatien 1 Company, Vietnam Figure 2. After mechanical installation, the refractory of the static grate was renewed to correspond to the new grate geometry. 40

The polysius plant consisting of a polysius kiln, double-stranded DOPOL preheater and REPOL cooler was commissioned in 2008 World Cement April 2021

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with a design capacity of 5500 tpd. Before the upgrade, the kiln line was operating with a remarkable clinker production capacity of ~6200 tpd, but with an increased heat consumption. A closer investigation coupled with a kiln audit performed by thyssenkrupp specialists from Vietnam and Germany helped to identify the root cause of the issue, and suggested opportunities for improvement. It was determined that the relatively low recuperation efficiency of the cooler was the main culprit for the increased heat consumption. The plant burns local anthracite coal with a low volatile matter content, which requires high temperatures (above 900°C) for ignition and complete combustion. Therefore, a high tertiary air temperature is required to improve burnout and significantly reduce fuel consumption. Furthermore, the plant was suffering from reduced plant productivity due to red river formations with a negative impact towards clinker quality as well as equipment availability. Since the overall mechanical condition, as well as the original hydraulic system of the REPOL cooler were still in a very good condition, a complete cooler conversion did not make economic sense. thyssenkrupp set its focus on boosting the efficiency of the recuperation zone with a small and fast, but at the same time, highly effective upgrade of the static grate. This is where the newly developed polysius static grate was introduced.

The upgrade The upgrade of the static grate was realised within ten days, during the normal yearly maintenance shutdown of the kiln. Besides removing the old grate and installing the new one, a few additional adjustments were required. Due to the increased length of the new static grate, the first three rows of the REPOL moving grate needed to be removed. Underneath, the discharge hoppers for the inlet section were sealed off as they were not required anymore, thanks to the new spillage-free aeration elements. The aeration chamber compartments were also adjusted in size to fit the new high pressure process fans. Finally, after the mechanical installation was complete, the refractory was renewed in the conversion area to fit the new horseshoe design, including the temperature resistant shock blower nozzles (Figure 2). The improvement in operation was obvious immediately after restarting the kiln line. After a smooth commissioning, an increase in the tertiary air temperature of more than 100°C was measured, which allowed the calciner to reach the optimum temperature level required for the combustion of the anthracite coal fuel. As expected, the red rivers in the 42

cooler had disappeared. A process expert from the Hanoi office stayed on site after commissioning to support the customer to maximise the plant performance. Because of the higher recuperation efficiency, new set points for the operation of the kiln system needed to be worked out. For the cooler, the control loops and the overall aeration profile were adapted to the new operating point. The flame shape was modified using the easily adjustable nozzles of the existing polflame VN to enhance combustion in the sintering zone. A shorter, more compact flame leads to better burnout with difficult fuels. While the poor cooling on the static grate had in the past led to repeated formation of red rivers, limiting the overall clinker bed height to 500 – 600 mm, with the new improved cooling in the inlet section, it was possible to raise the clinker bed height on the moving grate up to 800 mm. The resulting increase in residence time led in turn to a decrease in the clinker end temperature below 80°C (significantly below 65°C+ ambient). The benefits of the upgrade and process optimisation carried over to the preheater tower as well. While the secondary and tertiary air temperatures increased, the preheater exhaust temperature and volume flow decreased, providing more capacity for the ID fan. This in turn allowed the kiln system to run with an increased and stable clinker production capacity of around 6300 tpd.

Conclusion Overall the result of this upgrade was a success. The return on investment for the customer is manifold: A more stable operation, higher equipment availability, lower fuel consumption, and higher clinker production. In this case, what is good for the wallet also benefits the environment, since the reduced fossil fuel consumption and improved energy efficiency simultaneously reduces CO2 emissions. thyssenkrupp will also support the environmentally-conscious customer on their journey to further reduce the environmental footprint of the plant.

About the authors Valentina Bordei is a Process Engineer with five years of experience in the cement industry. She has been working in different capacities for thyssenkrupp, including the research and development of new emissions reduction technologies. Currently she is the Product Manager for the clinker cooler polytrack® and the polflame® burner. Viktor Penner is a Mechanical Engineer with more than 10 years of experience in the cement industry. He has been working in different capacities for thyssenkrupp, including project engineering for pyroprocessing in Germany. Currently he is the Head of Sales, responsible for Pyro Technology in South-East-Asia. World Cement April 2021

Paweł Kędzior, Havec Engineering Co., outlines how Hot Kiln Alignment can be employed by cement producers as an effective method of preventive maintenance.

PAYING ATTENTION

TO PREVENTION O ne of the main goals of any cement plant is to ensure the continuity of production and maximise profits by minimising costs. To achieve this goal, it is necessary to keep production equipment in perfect condition throughout its entire service life. A Preventive Maintenance Strategy helps with this aim. Its main role is to detect the causes of potential problems long before malfunction. When existing problems are visually obvious, it is often too late. Preventive maintenance with the use of analytical tools can help eliminate the causes of damage.

The heart of every cement plant is the rotary kiln. Maintaining its proper condition is extremely difficult and becomes one of the main challenges involved in ensuring the continuity of production. 99% of all problems related to the operation of the kiln are linked to: f Misalignment of the kiln axis f Axial balance f Kiln shell crank f Kiln shell ovality All of these problems are diagnosable using Hot Kiln Alignment.

A new approach The rotary kiln is one of the most demanding pieces of equipment from a maintenance and operation point of view. It is a kind of a dynamic reactor, with many parameters affecting it chemically, mechanically and electrically at the same time. Cement producers have to act dynamically, like the kiln itself, in order to prevent changes in the above-mentioned conditions from affecting its main components, such as: tyres, rollers, shell, brick lining, bearings etc. Cement producers must therefore rely on their actions to maximise the lifetime of the kiln and achieve the desired working conditions. To achieve a realistic view of the kiln’s operation conditions, the following possible inspection methods can be used: f Surveying (use of advanced technology, knowledge, experience, accurate and advanced equipment) f Vibration analysis f Thermography f Defectoscopy f Mechanical analysis Highly accurate measuring equipment. As a part of a Preventive Maintenance Strategy, periodic alignment of the rotary kiln helps to locate and eliminate operational problems at a very early stage. Instead of costly repairs or damage, with the help of precision measurements and analysis, it is possible to precisely identify and eliminate the causes of kiln damage. If only outcomes are being dealt with, it is highly probable that problems will re-appear and that damages will multiply. Experiencing unplanned kiln stoppage, frequent replacement of kiln components, and excessive wear, is a product of an incorrect maintenance strategy. A clearer and more focused picture of real equipment conditions is needed. The main purpose of Hot Kiln Alignment is to conduct mechanical inspection and to specify activities (adjustments, exchanges, repairs, modifications, etc.) which should be performed to attain and maintain high effectiveness of the rotary kiln’s operation.

Misalignment of kiln axis Precise measurements of kiln axis and roller position.

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Preventive maintenance routine. 44

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Achieving the correct alignment of the kiln axis is particularly important from a load distribution point of view. Deviation of the kiln axis from its optimal shape has a negative impact on supports, tyres and the kiln shell. The axis of the kiln is not constant during operation, especially in a vertical plane. Changes in ŹŹŹŹ temperature distribution on the kiln shell, can cause the axis position to be unstable and this change in position World Cement April 2021

causes different load distribution on rollers and support roller bearings. It is important therefore to maintain the correct kiln shell temperature during operation. Correct kiln axis geometry is responsible for the even distribution of weight, coating, brick lining, and the components for all the supports. Alignment of the kiln in a vertical plane ensures proper load on each individual support, but alignment in the horizontal plane ensures equal distribution on left and right rollers. Consequently, any changes in the geometry of the kiln axis over time cause changes in the load distribution and thereby changes the longitudinal bending stress distribution in the kiln shell. Such load changes are closely related to the kiln stiffness (the relation between the diameter, shell thickness and distance between support etc.) and may involve a risk of failure or reduced service life of the kiln components. Frequent checks of the kiln axis position are recommended as an integral part of the kiln maintenance. To properly assess the impact of the axis geometry on the kiln operation, a detailed knowledge of the mechanical stiffness of the kiln shell and the current status of components on the supports is needed. The mechanical condition of the kiln must be carefully examined. In addition, the position of kiln axis must be measured during normal operation in hot conditions. With the help of Hot Kiln Alignment procedures, determining the optimal kiln axis alignment can allow problems to be located and eliminated. Through frequent monitoring of this parameter, even with very small adjustment steps, significant kiln operation improvements can be observed and kept under control.

temperature of the bearing. Additionally, the incorrect geometrical position of the rollers causes a loss of contact between running surfaces of tyres and rollers so that wear of these surfaces increases. Axial forces generated by incorrect rollers skewing and inclination is transferred directly to the other components. Often the damage or premature mechanical wear appears on the sides of tyre and stop-block surfaces. In the same way, the axial forces are directly transmitted to the thrust roller resulting in faster component wear. Incorrect kiln balance (e.g., a kiln operating in one axial position for too long) also causes accelerated and uneven mechanical wear, both for the running surfaces of support rollers and kiln drive components (pinion and girth gear). With the help of the Hot Kiln Alignment procedures, all axial force generators can be easily determined. By knowing the actual geometrical position and mechanical conditions of components, plant maintenance crew can achieve optimum kiln balance and minimise the wear of critical components.

Kiln shell ovality Ovality is a parameter which describes how well a kiln shell is able to support the refractory. Rotary kiln refractory brick linings depend on the principal of the continuous arch to stay in place. Naturally any forces acting on that arch, such as flexing of the kiln shell, will act to weaken the mechanical stability of the arch.

Axial balance The axial balance of the kiln is dependent on many factors, including: geometrical position of support rollers, both in horizontal (skew of rollers) and vertical planes (inclinations), mechanical wear of running surfaces of tyres and rollers, and hydraulic thrust unit efficiency. Each of these elements generates an axial force, acting on the kiln in a particular direction and with a specified value. In an ideal situation, both the support rollers and tyre surfaces should be cylindrical and their axes parallel to the main kiln axis. In practice, however, especially after many years of operation of each individual component, such a situation is extremely rare. The running surfaces wear out and the axes of the support rollers experience a geometrical deviation, causing further damage to the rotary kiln components. Exceeded tolerances of rollers skewing and rapid wear of support roller bearings (in particular thrust blocks), where increased axial force creates higher pressure, results in an increase in April 2021 World Cement

Comprehensive inspection of the rotary kiln.

Correct alignment improves brick lining lifetime. 45

It is not uncommon, therefore, for refractory to fall out a short time after installation if excessive flexing of the kiln shell exists. Ovality measurement is a method for determining how much a kiln shell flexes. Ovality measurement and analysis is a description of mechanical stability of the refractory. All kiln operators need to be aware of the behaviour of their kiln under its various conditions. Cyclical measurements provide a history of conditions which can be used to analyse very important refractory problems. Excessive ovality will damage the refractory lining, typically, with scattered ‘spallings’ and single brick fall-outs among otherwise undamaged areas.

Kiln shell crank If the kiln cross-section centreline does not coincide with its axis of rotation, the kiln is said to have a crank, which in fact means that the support loads change cyclically during the rotation of the kiln. Crank in the shell is very dangerous because it can be accompanied by rotating extra loads. Additionally, crank is invisible until contact between the tyre and support roller, eventually, ceases. Kiln shell crank can by described by two parameters linked together – local deformation and radial run-out (eccentricity). Local deformation of the kiln shell is the shape deviation from circularity and has a negative effect on brick lining inside the kiln, shortening its lifetime. It is essential from a maintenance point of view to monitor the lining condition at every kiln renovation stoppage. When the loss of lining is observed repeatedly in the same place, a shell segment replacement should be taken into consideration. Kiln shell radial run-out has a negative impact on most kiln components e.g., too much or uneven pressure on shafts of rollers, running surfaces of tyres and rollers, radial run-out of inlet or outlet sealing, root clearance values changing at the girth gear station, increased axial tyre thrust (excessive mechanical wear of tyre side surface and stop-blocks), and uneven load distribution between tyres and rollers as a result of ‘wobbling’ etc. Therefore, it is extremely important to control this parameter through the continuous monitoring of temperature around the shell

circumference (especially shell segments located close to tyres) and conduct the correct procedures during heating (e.g., after kiln stoppage), and cooling of the kiln.

Exchange of key components Knowledge of the real mechanical status of the rotary kiln allows kiln operators to facilitate the planning process of key component exchange. A comprehensive inspection of the kiln will highlight priority repair actions. Such information is crucial when forming and planning budgets. Hot Kiln Alignment measurements and analysis can help identify wear levels for almost all of the important kiln components and allow operators to make the decision to replace, repair or re-design.

The importance of alignment Kilns change over time in a way that cannot be easily predicted. The limits of proper operation are so low, that even if the kiln is working well it needs to be monitored. Statistical research based on operational mechanical wear factors shows that Hot Kiln Alignment intervals should be set to two years, and this is calculated and estimated for a kiln that has no obvious operational and mechanical problems. Hot Kiln Alignment is not only a measurement. It is, above all, a comprehensive mechanical inspection, and produces very advanced analyses, allowing even the most complex problems to be observed within the operation of the rotary kiln. It is also a perfect diagnostic tool allowing for detailed planning of activities, repairs and replacements during a yearly overhaul. Hot Kiln Alignment provides plant personnel with invaluable knowledge about the conditions of the equipment. This type of condition monitoring tool is an investment, preventing unplanned stoppages of the kiln or the need for renovation or replacement jobs. Potential problems can be detected at a very early stage and removed at a minimal cost – this is the Preventive Maintenance Strategy.

About the author

Supervision over roller adjustment. 46

Paweł Kędzior is the CEO of HAVEC Engineering, a company providing international services focused on rotary kilns for maintenance and operation. Paweł is an engineer with much experience in mechanical, technological, and engineering sectors and has an MSc. diploma in surveying sciences in the field of Industrial Precision Measurements. Paweł is also a designer of innovative early-warning monitoring systems dedicated to rotary equipment for the industrial sector, and mechanical challenges in rotary kiln maintenance. World Cement April 2021

A PLATFORM FOR

IMPROVE IMPROVEM MENT IMPROVEMENT Jeff Mirisola, Bricking Solutions, outlines how suspended platforms could help cement producers increase efficiency for vertical vessel maintenance.

t is time to upgrade maintenance practices for vertical vessels. Like any form of routine maintenance, inspecting, removing and replacing refractory in pre-calciners, cyclones, lime kilns, ISAMELT furnaces and other vertical vessels places a costly burden on facilities in terms of downtime and lost productivity. One of the main reasons for this is that the traditional solution for accessing vertical surfaces – scaffolding – severely limits efficiency. It also increases safety risks for employees.

Cement and processing facilities are taking action to reclaim maintenance productivity and safety by investing in custom-manufactured suspended platforms for vertical vessel operations. These systems feature a lightweight, heavy-duty metal platform that is erected inside the vessel and raised or lowered using manual or electric hoists for hassle-free maintenance and relining applications. Suspended platforms offer a number of benefits over scaffolding systems, starting with effectively eliminating the protracted set up times that dominate scaffolding-based maintenance schedules. This article will explain how these customised systems can boost productivity and safety throughout the maintenance process.

Setup The amount of time scaffolding systems take to erect is their biggest deterrent and the greatest drain on maintenance productivity. This is due in part to the sheer complexity of the operation, which includes

Cement and processing facilities are reclaiming maintenance productivity and safety with custom-manufactured suspended platforms for vertical vessel operations.

juggling a variety of pipes, hardware, boards and other materials to create the structure. Erection times vary based on vessel size and configuration, but even with an experienced crew, scaffolding can take several shifts all the way up to an entire week to construct, putting significant stress on maintenance budgets and timelines. To simplify the process and decrease set up times, suspended platforms offer a modular design and pin-together construction. This greatly reduces the number of components and tools required for erection and allows crews to complete setup in as little as two hours. Modular components manufactured from high-strength 6061-T6 aluminium provide the same strength as steel at a third of the weight. Also, because vertical vessels often feature small access points, manufacturers limit the size of modular components. The resulting pieces are easy to manoeuvre, weighing 18 kg (40 lbs) or less, and fit through a 560 mm (22 in.) diameter access hole. This provides a lighter, more easily maneuverable solution than scaffolding’s heavy wooden planks and steel pipes, some of which are up to 4.3 m (14 ft) long. Additionally, pin connections allow for fast assembly and improve platform strength over welded connections by allowing for some flexibility while the platform is being raised or lowered. Welded joints are rigid, which increases stress on risers at platform joints. Pin-together joints are a better solution to help maintain safety and stability when dealing with varying speeds from the climbing hoists. It is worth noting that suspended platforms require some site preparations. This can increase set up times initially – sometimes up to a full shift for complicated systems. But in the long run, a suspended platform can save facilities significant time and effort with each use, leading to significant ROI potential – while scaffolding remains cumbersome every time. A cement facility, for example, was able to eliminate five days of double shifts when installing a drip tube in a cyclone with the suspended platform, saving an estimated US$15 000/hr in downtime. Initial commissioning for the platform took eight hours, but subsequent productivity meant the facility saw ROI after using the platform twice. In another example, a copper plant replaced the scaffold system for its smelter with a suspended platform. This increased not only productivity, but safety as well. Overall, the plant was able to save 320 man-hours per shutdown with the new system.

Room to move Suspended platform systems feature a lightweight, heavy-duty metal platform that is erected inside the vessel and raised or lowered using manual or electric hoists for hassle-free maintenance and relining applications. 48

Even after the platform is assembled, the productivity benefits continue to add up. In terms of surface area, ease of use and access to the work area, suspended platforms rise above scaffolding. With scaffolding, tools and materials need to be hoisted up to working height a little at a time, often manually. This is a slow process with a heavy World Cement April 2021

physical toll. It also limits productivity by restricting supply lines for materials, such as refractory brick, gunning equipment or other necessities. A suspended platform, on the other hand, can easily transport up to 2722 kg (6000 lbs) up and down, and the open design provides ample space for personnel, tools and materials. This allows several workers to operate in the same area comfortably, as well as having everything they need close at hand for efficient maintenance. Crews simply load all necessary materials at the start of the shift while the platform is positioned at the vessel’s access point. When more brick or other supplies are required, the crew lowers the platform, loads the necessary materials, then easily returns to height. This saves considerable time and energy and can increase productivity by limiting the number of trips up and down. The platform also provides more room and easier positioning for equipment such as gunning machines for shotcrete applications. Crews simply set up the machine directly on the platform and maneuver the entire system up and down, eliminating downtime from repositioning while maintaining an ideal distance from the vessel surface for proper adhesion. Using a suspended platform for this application also eliminates the physical toll and risk to crews from heavy hoses hanging from the scaffolding. Additionally, the open platform and electric hoist system allow for infinitely variable height, resulting in access for inspection, removal and replacement of refractory materials. Scaffolding is inherently rigid. It has to be to create a sturdy base of operations. However, this rigidity restricts crew access to the burn surface. Pipes inhibit visual inspection and make it difficult to work on the area directly behind them. The scaffolding structure can also obstruct small flaws, causing them to be overlooked. Additionally, crews must squat down or reach up high when working on surfaces in between 8 ft scaffolding stories. Suspended platforms provide crews with 360º access at a comfortable working height, regardless of the task at hand. To optimise accessibility and productivity for a particular facility, industry-leading manufacturers also customise designs to fit vessels up to 6.7 m (22 ft) in diameter, so crews can get directly against the burn surface without risk of falling. This allows crews to inspect every inch, catching even the small flaws that could lead to bigger problems down the line if overlooked, for more thorough inspection and more productive maintenance. Additionally, some suspended platforms allow crews to adjust the size of the platform by up to 1 m while suspended by changing the outer panels. This results in better accessibility and easy transition between different widths of a vessel such as a cyclone.

Ergonomics for better economics Having a platform, rather than a narrow scaffold, increases worker safety.

Your project, our solution We deliver customised solutions for operators and investors of cement plants throughout the world. Intercem is the competent and experienced partner for planning, detail engineering, project handling of greenﬁeld projects and the conversion/modernisation of production systems. Our 3-level system makes it possible for us to offer both used and modernised products, to compile new solutions made from used and new components or to create completely new systems.

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With a suspended platform, crews enjoy 360º access at a comfortable working height, regardless of the task at hand.

Suspended platforms offer design and pin-together construction that allows crews to complete setup in as little as two hours.

Falls continue to rank number one in workplace injury reports, and refractory repair is not immune to tragic accidents. Recent US Bureau of Labour Statistics data identified 338 fatal falls to the lower level among 1038 total construction fatalities for the year. That same year, falls on the same level or to lower levels amounted to US$17.1 billion – 29.2% – of the nearly US$60 billion spent by employers on serious, non-fatal workplace injuries. A suspended platform replaces narrow wooden catwalks with an aluminium surface that spans the entire vessel, eliminating the risk of falls or dropped objects. It also eliminates the need for workers to climb up and down carrying small tools and the need to haul materials and larger equipment up to height, hand over hand, resulting in a much safer jobsite. There are long-term safety benefits that go beyond this, as well. From setup through all aspects of refractory maintenance, a suspended platform puts less physical strain on employees. The lightweight, modular components are less cumbersome than long poles and heavy wooden planks. Easy access to materials and tools reduces the risk of repetitive motion injuries as well as minor cuts, bruises or scrapes that come with manually moving refractory materials. Being able to position the platform at the ideal working height for the job at hand limits bending or reaching, providing an ergonomic solution instead. All of these small but significant safety benefits lead to long-term savings in the form of compensation claims and insurance premiums from workers.

View from the top Making the switch to a suspended platform requires some initial planning, but positive returns are almost immediate. Facilities that have made the switch save tens of thousands of dollars with each maintenance cycle, providing a return on investment in one or two uses. The key is working with a reputable manufacturer that can provide a customised platform that fits a facility’s needs and vessels perfectly. Working together, these partners can revolutionise refractory maintenance in vertical vessels.

About the author

A cement facility eliminated five days of double shifts installing a drip tube in a cyclone with the suspended platform, saving an estimated US$15 000/hr in downtime. 50

Jeff Mirisola is the Technical Sales Manager for Bricking Solutions, a leader in kiln refractory installation solutions. Jeff is a Mechanical Designer and certified SolidWorks expert with more than 20 years of manufacturing experience and seven years of industry experience. World Cement April 2021

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Refratechnik Cement GmbH discusses the applications of a new concrete veneering technology including its use in emergency kiln lining repair.

THE VALUE OF

VENEERING

ime is money. This applies to every manufacturing industry. The production of cement clinker and lime is a complex system with many pitfalls where the three main components must be brought into harmony: the kiln system, the raw meal and the refractory material. Any small disturbance of one component can have a major impact on the whole system. If the kiln does not run smoothly, the risk of the refractory material being damaged in a short time increases. If the composition of the raw meal varies, this can result not only in the production of inaccurate clinker or lime, but also damage to the refractory lining. Once the refractory material is affected, it loses its protective effect and the kiln shell can overheat and

become deformed, with significant costs occurring as a result. Costs for refractory material only make up a minor part of the operating costs, but they form the basis for a running kiln and thus for a properly used production capacity. It is even more frustrating when refractory damage occurs only shortly before the planned overhaul. Bringing forward a planned pause in production is rarely possible. The fuel tanks have not been run empty and neither refractory material nor installation personnel are on site. In this situation, a fast repair for a short bridging to the planned shutdown of the kiln is needed. Refratechnik Cement offers a cold repair technique that allows refractory damage to be fixed fast and easily: the veneering technology.

Thermochemically resistant as well as flexible, refractory concretes are applied to the worn lining in a fast gunning process that allows a quick restart of the kiln. Short downtimes and a less complex installation keep the costs low compared to the installation of new monolithic products or classic new brick laying instead.

What are the possibilities of veneering?

How is veneering used? Veneering is a fast method of gaining lining thickness in a worn section to reach an upcoming overhaul. The installation of veneering is possible using the casting, wet gunning, or dry gunning process. However, primarily the dry gunning method is most effective and offers easy handling and short processing time. The equipment for dry gunning is available in many plants and allows the veneering concrete to be transported over long distances to all static areas and in the rotary kiln. Aluminosilicate concretes of the system Al2O3-SiO2 e.g. REFRAMULLITE 60 EDG Z AR are used in the static areas and the calcining zone of the rotary kiln. For a non-basic veneering lining an average service life of 12 months in the calcining zone was realised. In the areas of the rotary kiln that are subject to increased thermal and thermochemical stress, basic concretes with a thermal expansion coefficient very similar to that of basic bricks are recommended, e.g. REFRA-MgO 90 SG or REFRA-MgO 82 SG. Dozens of plants have successfully installed basic veneering concretes. The installation mainly took place between the upper and lower transition zone

There are various possible applications for veneering. The repair of small hot spots is as possible as the repair of the complete lining in full circumference (Figures 1 & 2). Lost bricks can be replaced entirely, or, in the case of insufficient lining thickness after brick spalling phenomena, veneering concrete can be installed on top. This can be useful if the kiln shuts down prematurely a few weeks before the scheduled overhaul. The time remaining to the planned shutdown and the size of the area to be repaired play a key role in deciding whether veneering is suitable. The plant operator can decide between a more durable, but initially also more time-consuming and expensive brick laying repair or a faster and cheaper veneering solution. In addition to emergency repair, veneering also offers other areas of application (Figure 3). The use of a protective layer when the rotary kiln is restarted, so-called ‘heat-up protection’, established itself as a suitable solution. Lining that has already seen a campaign or a certain period of production is often infiltrated with various salts and has lost its flexibility, making it particularly susceptible to thermomechanical loads. In this case, the application of a heat-up protection reduces the thermal gradient and allows a smoother temperature rise in the lining until a protective coating has formed. Figures 1 & 2. Insights into practice: Veneering of a hot spot Brick head spalling can thus be (Figure 1 – left) and a protective layer in full circumference reduced, especially during the (Figure 2 – right), both kilns have a diameter > 5.00 m. critical heating up phase. Veneering can also be used to easily adjust the height compensation between an old and new lining and prevents abrasion or blockages caused by the raw meal passing through. Specially shaped bricks, conical parts of the rotary kiln for example, can also benefit from veneering, as their production is often associated with long delivery times. A timely gunning of veneering can significantly extend their life span and reduce warehouse costs for Figure 3. Examples of veneering linings in the rotary kiln for storing these special shapes for a cement clinker production. long period. April 2021 World Cement

where the individual targets regarding an improved lifetime were met, increasing from several weeks up to months.

Does the coating have to be removed? Depending on the kiln area where a repair is necessary, the removal of the coating is always a key question in terms of safety and the duration of the downtime. The more coating to be removed, the longer the kiln downtime. What does this mean for the veneering process? All areas of the kiln that are accessed by the installation personnel must be safe: either the coating has to be removed or common appropriate safety precautions, such as a protective cage, tunnel or scaffolding, must be taken. The lining itself, to which the veneering concrete is to be applied, must always be free of coating. New as well as old veneering layers have to be treated like coating in terms of safety, the same protective measures must be taken. Before the veneering installation starts, the residual thickness of the bricks must be determined. The veneering thickness is usually 30 to 120 mm; up to this thickness no additional anchoring is necessary in most cases. Formwork is not required. Before installation, the area must be cleaned using suitable methods (sweeping, vacuuming, blowing off, etc.). Smooth refractory surfaces can be roughened by sandblasting. Dust, loose clinker, loose adhesions and brick heads as well as layer-like spalling material must be removed to achieve the best possible surface. For veneered linings no specific drying and heat-up are necessary. The kiln can be put back into operation in line with the standard heating up procedure. The exact installation instructions have to be discussed in each case individually and depend on the refractory concrete used, the installation method, the type of damage, and the surface of the lining. Appropriate processing guidelines have been drawn up by Refratechnik Cement in close cooperation with international customers and installation companies considering work and installation safety as well as the best possible interlocking between the existing worn lining and the gunned veneering material.

A veneering lining in static areas of a cement plant is usually more durable and less demanding. In dynamic areas of the rotary kiln, however, numerous factors influence the adhesion and thus the durability. The gunning process of the veneering material onto a worn, rough surface does not initially present a significant challenge. Nevertheless, it is important to achieve a very good form closure and bonding strength between the old refractory lining and the veneered refractory concrete in all parts of the rotary kiln. Wear factors of the old lining different for each zone play a significant role for the quality of adhesion (Figure 4). Besides an insufficiently cleaned surface and loose layers, especially high alkali chloride, alkali carbonate and alkali sulfate/sulfide salt loads in the area of the worn surface can have an impact on the interlocking. Refratechnik Cement’s veneering concretes are specially designed and developed to meet these requirements. They are characterised by a safe gunning behaviour, rapid hardening even at low processing temperatures, high adhesion without anchoring and a very good interlocking with the worn surface. In most cases, these well-balanced settings and properties contribute to optimised application behaviour and thus also support the cement plant operator in extending the service life of the refractory lining until the planned shutdown.

Providing a solution Due to the quick installation period, veneering enables a quick return to production and thus low production losses. Although veneering is not a substitute for new brick laying, it is a small, inexpensive, and, above all, effective repair measure that can reduce follow-up costs when used in a targeted manner. This is an answer to unplanned kiln stops. To ensure the full benefit of the veneering concept strategic stocks at Refratechnik Cement’s production unit and strategic warehouses are already established. Furthermore, the company is working on optimising refractory linings in all areas of the plant, for example, by preparing basic refractory concretes especially for use in static areas in order to withstand the increasing thermal and thermochemical loads and to reduce alkali-based wear.

Authors Figure 4. From the safety zone to the lower transition zone: Illustration of the contact/worn surface area between an existing refractory lining and the gunned veneering layer. Wear factors different for each kiln zone can have an impact on the interlocking. 54

Dr. Kathrin Weber Kai Beimdiek Dr. Ulrich Zielinski Ansgar Schnell Carlos Matus World Cement April 2021

...but we care about you.

www.refra.com

Daniel Hansted-Martin, HASLE Refractories, explains how Lafarge Canada’s Exshaw Cement Plant has reduced abrasion and chemical challenges and tripled the lifetime of the refractory lining in the facility’s Riser Duct using a precast Modular Lining.

et in pristine surroundings at the foot of the Canadian Rocky Mountains, Lafarge’s modernised cement plant showcases environmental and economic efficiency. Built in 1906, as ‘the Western Canadian Cement & Coal Company’, the Lafarge Exshaw Cement Plant is Canada’s biggest cement factory with a capacity of 2.4 million tpy. Over the years, the plant has had six lines in operation, however, today only line K#5 and K#6 are being operated. Each has a production capacity of 2200 tpd and 4200 tpd, respectively. Lafarge Exshaw operates on 100% natural gas and is working towards using low

carbon alternative fuels in the future. Its updated facilities operate the latest cement production technology. As a member of LafargeHolcim, the plant is continually seeking solutions to operate more efficiently and sustainably.

Solving short lining lifetime in the Riser Duct Responding to Western Canada’s significant cement demands, Lafarge Exshaw seeks to increase capacity and minimise stoppages. However, in 2017, the plant faced abrasion and chemical challenges in its refractory lining in Riser Duct K#6. The lifetime of the company’s

A LIFETIME ACHIEVEMENT

existing refractory lining was no more than six to 12 months. Needing a long-life, sustainable alternative, Plant Manager, Kate Strachan, contacted HASLE Refractories with a recommendation from another cement plant within the LafargeHolcim Group, which was already using HASLE’s precast Modular Lining. “We needed to achieve a significantly longer lifetime”, said Kate. “When the Modular Lining was already showing excellent performance at another plant within the group, we didn’t hesitate to install it here at our Canadian plant.” Upon receiving the technical drawings from Lafarge Exshaw, HASLE’s team of

engineers designed a tailor-made solution for line K#6, based on the standard precast element design. Detailed drawings of all 138 m2 of the riser duct were made, and once they were approved by Lafarge Exshaw, the installation was scheduled for mid-March to mid-April 2018. To ensure that the optimal installation technique is used, a team of HASLE supervisors always participates on site whenever the precast Modular Lining is installed – in this case, they had the pleasure of cooperating with the Canadian installation company, Alliance, who undertook the installation at Lafarge Exshaw.

A worthwhile recommendation By September of 2020, the precast Modular Lining installation had been in operation for more than two and a half years. The Lafarge Exshaw Cement Plant has achieved an excellent lining lifetime in its riser duct, with no re-linings or repairs needed to keep it running. This has lowered its use of natural resources per produced unit and resulted in an overall more stable production. When Lafarge Exshaw implements the use of low carbon alternative fuels in the future, the precast Modular Lining will remain a beneficial lining choice for the riser duct, as its low, open porosity and smooth impact surface makes it highly resistant to alkali attack and build-up – even in extremely hostile environments. “Currently, the precast Modular Lining has achieved a lifetime of +30 months”, said Plant Manager, Kate Strachan, and adds, “We estimate it will have an additional lifetime of up to 24 months, so we are very satisfied with it. It certainly proved to be a worthwhile recommendation.” Although HASLE’s pre-cast Modular Lining has been installed at more than 100 plants worldwide, this instance was the first in which the company supplied the lining to a Canadian company; the future might

Earlier refractory lining in K#6 riser duct with a lifetime of only 6 – 12 months.

Steel rails are welded onto the casing and HASLE’s console lining is installed with mortar between the elements. It is now ready for installation of the precast Modular Lining elements. 58

hold more precast Modular Lining installations for the North American country, whose cement industry in the year of the installation generated around CA$10.5 billion in revenue.

The design The HASLE precast Modular Lining was designed almost 20 years ago. The goal was to create a hot face refractory lining for the critical areas of high temperature industries, which was durable and resistant to abrasion, chemical attack and coating, resulting in a significantly longer lifetime than the existing alternatives on the market. Since its creation, it has stood the test of time and can last twice or even three times as long as a traditional cast lining, and sometimes even longer. Whereas traditional in-situ cast solutions typically have an open porosity of 18 – 20% or more, HASLE’s precast Modular Lining was designed to have a low open porosity of only 8 – 10%. This quality is achieved through a combination of selecting raw materials with an optimal corn distribution curve and adding only a very small amount of water (as little as 4.5%) when mixing the castable. The result is a refractory lining which has a longer lifetime, is abrasion- and alkali-resistant, and even when installed in plants operating on 100% RDFs, build-up is almost eliminated. With the precast Modular Lining, it is also possible to achieve a lining thickness as low as 185 mm. This is often less than the thickness of a traditional cast lining, and presents two options; the plant can either decide to go for a reduction in heat loss by applying more back-up lining, or it can decide to increase the cross sectional volume, which will give additional space in the given area. In many cases, an increased production capacity has been achieved by removing a process bottle neck though the installation of the precast Modular Lining, thus increasing the volume of the given area. In order to secure the highest quality of the Modular Lining elements, all elements are cast and pre-fired under strictly controlled conditions in HASLE’s plant in Denmark. Casting the elements at the plant using specialised equipment such as vibration tables, special moulds and dry-out ovens and employing skilled workers secures a strong focus on each step of the casting process and ensures a consistent optimal quality. The process includes dry mixing for 60 seconds, adding water, wet mixing for 4 – 5 minutes., casting it into the moulds and covering the elements in plastic immediately after. The elements are then left to cure for 24 hours and are subsequently pre-fired for five days up to a peak temperature of 500ºC. All these steps are carefully monitored in order to secure the highest possible consistent quality of all pre-cast elements. However, even in this carefully monitored production environment, small deviations in quality can occur, and therefore each World Cement April 2021

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Sustainable Strength through Innovation

element is both visually inspected and subjected to a strict quality control procedure prior to leaving the production facility.

Installation Installing the precast Modular Lining is both fast and easy. Due to a smart element design combining steel anchors with a tongue-and-groove system, the installation of the pre-cast Modular Lining often takes about 50% less time than the installation of a traditional in-situ cast solution. Once preparations are completed, the time required for a typical lining is 80 min/m2, depending on the condition of the area to be lined i.e. number of air blasters, inspection holes, manholes etc. After the welding of the rails and steel plates holding the elements, the console elements are easily installed. Upon these, the square modular elements (250 x 250 mm) with a tongue and grove system are installed. The precast elements weigh only about 15 – 16 kg each, so no special lifting equipment is required. All elements are pre-fired at HASLE’s production facility in Denmark, so no dry out of the lining is required, which allows for a faster restart of production. To ensure the successful

completion of each individual installation project, HASLE Refractories always supplies approximately 5% more elements than needed, and if a surplus of elements remains after completed installation, these can be stored and kept for many years as there is no limited shelf life. Compared to the limited shelf life of castables, this is another valuable advantage.

Applications Now, the precast Modular Lining at Lafarge Exshaw has been in operation for +36 months, and the cement plant is looking into the possibilities of the use of the precast Modular Lining in other areas of their production. Depending on the lifetime achieved from traditional castable or brick linings, there are many other areas in which the precast Modular Lining could be applied. HASLE’s Modular Lining has shown good performance when installed in a variety of applications throughout the world, i.e. feed pipes, coolers, cooler bull noses, smoke chambers, cyclone roofs as well as cyclone bull noses. All areas are lined with the same type of elements and can also be adapted for curved and cylindrical structures. As long as there is a steel casing the rails can be welded to, the precast Modular Lining can be applied, and has even been installed in a number of boilers and incineration plants.

A sustainability perspective

Precast elements are installed on the steel rails, on top of the console elements, with vermiculite back-up insulation between the rails. Ceramic fibres are installed between every four elements (every 1 m) to allow thermal expansion. Now, the system is only missing the pouring of the insulating castable behind the pre-cast lining.

Driven by climate policies and a desire to run a sustainable production, more and more cement plants are implementing sustainability goals. To reach these goals, efficiency improvements are necessary and using HASLE’s precast Modular Lining could be a step towards running a more sustainable operation. Not only does it require less material per installation to create a HASLE precast Modular Lining compared to an in-situ castable solution, but the Modular Lining also has the potential to last longer. Consequently, plants can lower their use of natural resources per produced unit, as using the Modular Lining reduces the number of re-linings and repairs needed. Contrary to a stocked monolithic castable, which can become unfit for use over time, HASLE’s precast Modular Lining has an unlimited shelf-life, thus reducing material waste. The lining offers tangible efficiency improvements that companies in high temperature industries can make on their journey to becoming more sustainable.

About the author

After 1.5 years of operation, HASLE’s logo embedded on the elements is still visible. 60

Daniel Hansted-Martin is Regional Sales Manager at HASLE Refractories. Daniel holds a Bachelor’s Degree in International Management and services the European and North American cement markets. He has extensive theoretical and practical experience from on-site installations, and an in-depth understanding of refractory challenges and solutions. World Cement April 2021

NO TIME TO WASTE

Sabrina Santarossa, Turboden, u urboden, e recovery eat explains how waste heat technology could help cement u ustainability plants to reach their sustainability g efficiency goals, while increasing o costs. on and reducing production

aste heat recovery (WHR) is a proven and widely used technology for boosting the overall efficiency of the cement sector with minimal impact on existing facilities. It allows profit to be generated by valorising a waste heat source, and reducing the specific production cost by decreasing energy demand, thereby improving sustainability. Furthermore, the Levelised Cost Of Energy (LCOE) can reach very low values using waste heat recovery, assuring a low cost and constant source of green energy for at least 25 years. The cement industry is being called upon to make its processes more environmentally-friendly. With the goal of reaching carbon neutrality by 2050, Europe is setting an ambitious target and encouraging the move towards a more sustainable industry.

For the cement sector, generating 7 – 8% of global greenhouse gas emissions, the pressure to become carbon neutral is even greater. In addition, as the COVID-19 outbreak has slowed construction in many countries, cement companies that prioritise sustainability even during this difficult period are likely to emerge as the winners in the next cycle.

The conversion of waste heat into useful power represents a viable and profitable solution to hit these targets. In this framework, Organic Rankine Cycle (ORC) technology represents a feasible option for recovering the heat still available in the hot gases of the pre-heater and clinker cooler and to turn them into clean power. Turboden is an ORC supplier with 40 years’ experience in different fields of applications, with 400 ORC units sold worldwide for a total installed capacity of about 700 MWe. ORC has several advantages compared to steam technology, in particular for electric power less than 15 – 20 MWe. With its high level of automation, good partial load behaviour, and low operation and maintenance costs, ORC is highly suitable for WHR plants, as it allows cement producers to focus on their core business while helping to reduce production costs. Additionally, ORC does not consume any water, thus offering a sustainable option for countries in which it is a scarce resource.

Heat recovery systems in the cement process

ORC technology recovers the heat available in the hot gases of the pre-heater and clinker cooler and turns them into clean electric power.

ORC is highly digitalised and self-operating; remote monitoring control has been an important feature during the COVID-19 pandemic. 62

In the cement production process, there are two main hot gas streams where sensible heat can be recovered and transformed into electricity that usually is consumed by the plant itself. The heat contained in the clinker cooler and pre-heater gas hot streams is transferred to the ORC unit through an intermediate fluid or directly to the organic fluid. Technical features of the two heat recovery exchangers are different due to the different characteristics of the exhaust gas, in particular the high dust content (20 – 100 g/Nm3) and the type of dust (abrasive on clinker cooler gas and soft and sticky on pre-heater gas). The heat recovery exchangers are installed in bypass mode to the main gas duct line to prevent the heat recovery plant having any influence on the main production process. In the ORC, the organic fluid is heated up and vaporised in the pre-heater and evaporator due to the external heat source (gas or thermal oil). Organic vapour expands into the turbine connected to an electric generator producing electric power. After the expansion in the turbine, organic vapour is firstly cooled down in the regenerator and is then condensed in the air condenser. Once again in the liquid form, the organic fluid is pumped into the regenerator and then into the pre-heater, thus closing the thermodynamic cycle. One of the main advantages of ORC compared to steam is its low OPEX during the lifetime of the WHR plant. ORC does not require any major overhaul, or dedicated personnel, nor does it consume any water or require water treatment or related chemicals. In addition, ORC has shown good efficiency, even at partial load, and World Cement April 2021

WHR system availability higher than 98% assures that electricity produced over the year is maximised. ORC is highly digitalised and self-operating, and remote monitoring control has been an important feature during COVID-19 times. In many cement plants, environmental benefits are not limited to the electricity produced by the WHR plant which translates into several tons of CO2 emissions avoided per year. There are further benefits related to electricity savings on the fans of air to air cooling systems often installed on clinker cooler gas lines before a bag filter, as these may not be used when the WHR plant is working. Additionally, the use of the quenching tower to cool pre-heater gas (if any) will not be necessary and the water normally consumed in it will be saved, thus contributing to a greener cement production. Turboden has been installing ORCs for the cement industry since 2010. The first plant was for Italcementi in Morocco, then other international groups such as LafargeHolcim in Romania and Switzerland, CRH in Slovakia and Switzerland, HeidelbergCement in Romania and Cementi Rossi in Italy, followed. WHR size was in the range of 2 to 5 MWe. In recent years, Turboden has installed one 7 MWe ORC and one 8 MWe ORC in Turkey (Çimko and Sonmez cement plants) and despite the COVID-19 outbreak, a new contract for a 7 MWe ORC for Secil group, Portugal, was

signed in 2020, underlining the importance of becoming more efficient in these difficult times. The economic feasibility of a WHR system, since there is no cost of fuel, is mainly related to: f Cost of electricity: With a cost above €60/MWh (US$70 /MWh) the economic feasibility of WHR systems is appealing. f Investment cost (CAPEX): this depends on specific site conditions such as the size of the plant, standards to be followed, type of cooling system, cost of the local workforce, etc.

Despite the COVID-19 outbreak, a new contract for a 7 MWe ORC for Secil Group, Portugal, was signed in 2020, underlining the importance of becoming more efficient in these difficult times.

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Typical values range from about €1500/MW installed up to €2500 – 3000/MW. f Operating and maintenance costs (OPEX): This is mainly related to the specific site workforce cost, however when dealing with

Several tons of CO2 emissions can be avoided per year thanks to a WHR system.

ORC, OPEX is very low, about 1% of CAPEX per year. f Kiln working hours per year: To reach a good level of economic feasibility, the kiln should work for at least 6000 hrs/year. With 60/MWh and 7500 hrs/year, IRR (10 years) is above 17 – 26%, which is much higher than the typical cement industry WACC (Weighted Average Cost of Capital). WHR potential is still huge and remains widely untapped. Some studies identify a potential of more than 2000 MWe to be installed in WHR at cement plants, which corresponds to more than 7 million t of CO2 emissions avoided per year. Sometimes barriers that are slowing down the implementation of WHR plants, even in regions with medium-high price of electricity, are related to restrictions in CAPEX, need for off-balance sheet investments and other financing or investing limitations. Cement producers are encouraged to stay financially focused on their core production process through the different financial and investing solutions that allow them to benefit from the advantages of a lower electricity bill obtained with a WHR system. Different alternatives are also available from a financial point of view: BOT, BOO scheme; low cost financing form International institutions like IFC – International Financing Corporation (World Bank group) and EBRD – European Bank for Reconstruction and Development; and the export credit scheme supported by Italian ECA.

Conclusion Waste heat recovery is a great opportunity for cement plants to reach their goals to be more sustainable while increasing efficiency and reducing production costs. ORC technology is a well-proven solution suitable for industrial customers and companies interested in investing in these projects. Good economic feasibility can be achieved whilst moving towards a greener industry.

About the author

ORC technology is a well-proven solution to boost the overall efficiency of the cement sector. 64

Sabrina Santarossa is a Chemical Engineer with international experience in sales and business development in energy efficiency and renewable energy. Sabrina has worked at Turboden since 2008. She is now a Sales Manager for Industrial Heat Recovery with focus on sustainable projects in the cement, glass and steel production process. She supports potential customers to find the optimised configuration for each project with a consistent attitude to delivering high value customised solutions supported by a solid academic background. In her free time she enjoys reading, sport and travelling. World Cement April 2021

the rewards REAPING

Paul Iverson, SABIA, outlines the optimisation techniques set to enable cement producers to get the most value out of their PGNAA systems and realise the benefits of bulk material analysis technology.

rompt Gamma Neutron Activation Analysis (PGNAA) is a powerful analytical technology that has been used at cement plants worldwide to substantially improve quality control. Continuous improvements of PGNAA equipment have enabled better compensation for highly variable manufacturing processes

than ever before. However, it is important to remember that PGNAA remains bound by the laws of physics and is not a ‘plug-and-play’ technology. The following guidelines help optimise the performance of PGNAA in a cement process but are all not necessarily required to realise the benefits of this bulk material analysis technology.

PGNAA optimisation in general Analyser configuration Cement producers should ensure a proper equipment configuration to meet their site-specific performance needs. PGNAA performance is largely determined by the quantity/size/type of gamma-ray detectors, the neutron source strength, the mass flow through the analyser, and the calibrated oxide ranges. When procuring a PGNAA analyser, cement producers should make sure the specifications for the analyser are appropriate for the application. In a cement raw mix control application where good precision is required, producers should not use a single detector analyser with only 20 micrograms of californium-252 (Cf-252) neutron source loading. A two-detector analyser configuration with at least 40 micrograms of Cf-252 should be used. Neutron source The cross-belt PGNAA industry-standard neutron source is californium-252; it is the safest neutron source for PGNAA due to the relatively low average energy of the Cf-252 neutrons. Low energy neutrons are readily shielded so adjacent periodic maintenance can be performed without safety concerns, with no need for a secure standoff zone or other complex mechanical radiation safety protection protocols. Californium-252 source also has no risk of failure or unscheduled downtime due to a predictable 2.645-year source half-life. Analyser location Selecting where to locate the analyser is critical, as the stream of percent-composition data the analyser continuously outputs must be

actionable for the process control decisions made. An analyser installed before a stockpile will output material composition data that can be used to optimally segregate, stack and pre-blend sections the stockpile while also making quarry grade decisions, whereas an analyser located after a stockpile will output data only after pile reclamation, far too late in the process to be actionable with quarry, blending and stacking decisions. Belt composition The conveyor belt should not contain steel cords or chlorine. Because PGNAA measures iron and chlorine with great sensitivity, when present in the belt, these elements produce high background counts that must be compensated for with on-site analyser calibration. Large conveyor belts used in quarry and stockpile applications frequently contain steel cord reinforcements. Conveyor belts with fire-resistant coatings typically contain chlorine. Gamma signals from these elements produce noise that must be calibrated out. Belt loading It is important to keep the mass flow passing through the analyser as constant as possible. The variation of the depth of material on the belt should be minimised, with the aim of maintaining around 12 to 13 cm (about 5 in.) of material depth; if possible, avoid belt loading below 40 kg/m. 100 kg/m belt loading is typically considered optimal. While modern PGNAA systems utilise various methods to compensate for low belt loading and mass-flow variations, maintaining a consistent material flow with minimal bed-depth variation will produce the most stable PGNAA results. Top size While PGNAA is not affected by the size of rocks on the conveyor belt, it is not desirable to have only large chunks of material without smaller pieces to fill in empty spaces on the belt. As much as possible, cement producers should avoid belt loading with large voids in the material flow. It should be ensured that crushers are operating properly, and locating the analyser after a secondary crusher should be considered.

SABIA X1-LiNX analyser for pre-blend stockpile management. 66

Layering PGNAA continuously sees all bulk material passing through the analyser and results are optimised if bulk material layers are mixed before the analyser. This is straightforward to achieve at most sites by locating the World Cement April 2021

analyser after a conveyor transfer point. It is typical for analysers used for raw mix control to see layered materials on the belt, but PGNAA will always achieve the best results when material layering is minimised. Weight input Ideally the belt-loading weight input to the analyser comes from a well-calibrated belt scale measuring a mass flow (t/hr) representative of the analyser location. Alternatively, feed rates for materials added on the belt can be summed together for a representative mass flow of the analyser location. When starting a PGNAA project, the type of weight signal to be provided for the analyser should be considered and planned for accordingly. Will the weight signal be from an analogue 4-20 mA cable, a digital output from a programmable logic controller, or summed feed rate values from a distributed control system? Calibration ranges The most accurate PGNAA results can be achieved using narrow ranges of analyte concentrations for calibration, but it is important to calibrate for the full typical operating range of analyte concentrations the analyser will see. For some applications it is desirable to use multiple narrow-range analyser calibrations to cover a wide concentration range for a single analyte. Working with a PGNAA supplier on the site-specific calibration plan is recommended. Representative sampling Dynamic tuning and performance verification of the PGNAA system is best when comparative sampling is coordinated with the PGNAA data points to ensure lab samples are representative of what has passed through the analyser. For optimal dynamic tuning, use an automated mechanical sampler to gather high-frequency samples and build composite samples for lab analysis. In quarry/stockpile applications, cement producers can back-calculate from mill samples to derive representative pile compositions. Working with the PGNAA supplier on a site-specific calibration plan in advance of installation is recommended. Buy-in A successful PGNAA installation requires buy-in, communication, and coordination by many parties. Be sure at the outset that plant operators, owners, and PGNAA suppliers share the same expectations. An ‘Analyser Champion’ who will ensure operational success should be assigned. A management sponsor for resource needs should also be established April 2021 World Cement

and IT staff should be prepared early on for system integrations. It is additionally a good idea for lab managers to be taught how the PGNAA system works in conjunction with the lab, and for a unified control strategy to be coordinated with operations to meet clearly defined process goals. A site with buy-in from everyone involved is well positioned to optimise PGNAA performance. Software Online bulk material measurements with PGNAA produce a great deal of useful information. Appropriate software should be used to get the most out of PGNAA data. Stockpile monitoring software can tag composition data by layer, time, and tonnage as a pile is built, including automated alerts when a deviation from quality targets is detected. An entire pile is represented by a tag group for reclamation. Raw mix control software uses PGNAA and lab results to automate raw material feeders to maintain preset quality targets with minimal variations. PGNAA specific software should be used to maximise the value of data.

PGNAA optimisation for raw mix control automation Analyser location The analyser is installed just before the raw mill and outputs continuous analysis data used to make rapid automated feeder adjustments. If instead the analyser is located after the raw mill, then the control loop will be less effective as all feeder adjustments will be delayed by the material residence time in the mill. When selecting where to install a raw mix control analyser it is important to minimise closed-loop control delays. Belt loading Using a conveyor transfer point, raw material layers can be mixed before the analyser. The material depth on the conveyor can be kept consistent using a variable frequency drive (VFD). If needed, consider reducing the belt speed to produce a minimum 40 kg/m belt loading for a strong PGNAA signal. It is common for raw mix analysers to see layered material with frequent bed depth variations or less than 40 kg/m on smaller belts, but these conditions are not optimal. Uniform layering If a process does not allow for a transfer point to mix layers before analysis, then it is key that each feeder adds material at a consistent rate, spread evenly across the conveyor belt. Perform routine feeder maintenance to prevent 67

clumping and plugging feeders. Designate the order of feeders to avoid two separate layers of wet clay on the belt. Even if there is a transfer point to mix materials, efforts should be made to spread additives evenly across the belt by using deflection plates where necessary. Quarry quality A consistent limestone feed allows for tighter calibrated ranges and relatively small feeder adjustments to meet quality targets. Pre-blending minimises limestone variations. It is important to plan in advance for times when a raw mix automation system will see significant changes in limestone quality. Consider using multiple calibrations or multiple product profiles for different limestone seams. Additive consistency Every raw mix automation system is configured for the site-specific additives in the raw mix. The more consistent raw material additives are, the greater the success that can be achieved in meeting quality targets with PGNAA. Additive compositions should not be changed without making corresponding changes to the PGNAA software. If additive qualities often vary greatly, consider establishing multiple product profiles to switch between depending on the quality of additives at any given time. Oxide isolation To the extent that it is possible, cement producers should try to utilise raw materials so that there is a single material source for each major oxide in the raw mix. Doing so will make quality control easier than trying to maintain consistent oxide targets using multiple material sources for a given oxide.

Avoid rogue materials No additional materials should be added between the Raw Mix Analyser and the downstream mechanical sampling point after the raw mill. Care should be taken to ensure that composite samples for lab analysis are representative of the same material seen by the PGNAA analyser before the mill. Kiln dust It is best to recycle kiln dust back into the homogenisation silo when possible. Avoid adding kiln dust into the middle of the control circuit as it will not be detected by the PGNAA system. Additionally, kiln dust should not be added back into the kiln as this can make clinker samples less representative of the control circuit. Sample collection Fine tune the PGNAA calibration dynamically by collecting high-frequently mechanical samples to build one-hour composites that are highly representative of the bulk material flowing through the analyser. Care should be taken to synchronise lab XRF data and online PGNAA data so they represent the same time periods. Factor in mill residence times for synchronisation. XRF accuracy Ensure lab XRF results are accurate by using fused beads, avoiding sample contamination, and by taking great care to synchronise the timing of gathered samples and online bulk material analysis. Perform calibration checks and routine maintenance on lab XRF equipment per the advice of a selected XRF service provider.

Conclusions The optimisation topics mentioned in this article will allow cement producers to get the most value out of their PGNAA systems. While some plants do not have the ability to apply all PGNAA optimisation techniques, they should implement as many as possible to maximise process quality control.

About the author

SABIA X1-LiNX analyser for raw mix control, during initial static calibrations with reference standards on an empty belt. 68

Paul Iverson has spent the past 8+ years focused on PGNAA solutions for the cement industry and is Director of Operations at SABIA Inc. He works closely with the founder of Gamma Metrics which first commercialised PGNAA in the 1980s. This PGNAA focus has instilled a robust understanding of the nuances associated with online bulk material analysis also including coal, gold, iron, nickel, phosphate, and other bulk materials. World Cement April 2021

That’s the TICKET!! TICKET Scott Dugan, Command Alkon, explains how companies can streamline business processes and the operational tasks necessary to ticket and scale cement, enabling drivers to check-in, load, and ticket trucks without interruption.

igital innovations and intelligent networks offer tremendous opportunity to supercharge efficiencies in the cement industry. New technologies have the strength to create powerful connections between physical and digital systems. Many cement players know the benefits of implementing digital solutions, but few have seen its full power or taken advantage of its full potential. Cement operations can realise incredible results through digital technologies that enable employees to manage the business from quote through to collection – enabling dispatchers, field workers, and customers to communicate directly with each other, while adding accountability and tracking that can be seen from the office. Apex from Command Alkon streamlines business processes and operational tasks necessary to ticket and scale cement, enabling drivers to check-in, load, and ticket trucks without interruption.

Rush hour to rapid flow Apex can expedite the ticketing process by ensuring all information about an order is in the system from the start, so that the truck driver knows exactly what is being picked up and where it needs to go as soon as they pull on-site. These point-of-sale modules interface directly with the sale, dispatch, transportation management, and back-office modules for quoting, invoicing, receivables, inventory, reporting, and business intelligence. When order information is entered into the system from the get-go, that data flows through the entire ticketing process and throughout the entire enterprise so that everyone is in the loop.

Seeing as cement is such a pricey product, accurate loading is crucial. Site-automation technologies work in tandem with Apex to deliver improvements in loading accuracy, speed, efficiency, and safety, and integrating Apex directly with the site PLCs and loading system can ensure that the right material is in the right truck and reduce the risk of lost loads. Utilising Apex point-of-sale and back office modules in conjunction with site-automation technologies typically presents the opportunity to cut down 35% of time in the yard. The system cuts down verbal communication once the truck pulls on to a site

The Apex Express Reader works in conjunction with the Auto ID module to automate the ticketing process with this ‘swipe only’ device for vehicle identification.

The All-Terrain Kiosk provides a touch screen interface for load assignment, driver selection, and load confirmation. 70

because the loads are already in the system and a truck is already assigned to those loads. Automating the process keeps the driver in the safety of the cab of the truck the entire time they are in the yard, promoting safety while streamlining throughput. The system also has the ability to interface with the loading system and receive feedback that permits them to prevent the truck from being loaded unless certain safety measures are in place.

Boosting speed and efficiency Apex’s Auto ID module uses Radio Frequency (RF) devices or License Plate Recognition for vehicle identification and assignments. The Apex Express Reader works in conjunction with the Auto ID module to automate the ticketing process with a ‘swipe only’ device for vehicle identification. The Apex All-Terrain Kiosk (ATK) supports the Auto ID module to further automate the driver check-in process. The ATK provides a touch screen interface for load assignment, driver selection, and load confirmation. This automation piece is intended to increase the speed and accuracy of the load processing without the addition of scale personnel. The Automated License Plate Recognition (ALPR) uses a combination of camera and Auto ID technology to identify and process a vehicle entering the site and/or scale in seconds. Scale Watcher is the next generation of hardware and software to provide photo and video verification of a truck’s weighing process. This is an integrated photo verification tool that overlays ticket information onto a photo of a truck on the scale. This image is then saved in a PDF, HTML or other image-friendly format by ticket number. The ticket number provides easy retrieval of the image to email to customers. The tool also provides proof of vehicle pickup without signatures. With Scale Watcher, an optional gate/valve anti-theft module alerts authorised personnel of potential theft of materials. The anti-theft module sends an email alert to one or more designated addresses whenever the gate/valve is opened and closed on a loading system and a ticket is not printed. The gate/valve anti-theft module is not reliant upon the scale or software to function and will work after hours when the plant is shut down. The scale sensing feature will also send an alert if: f A truck has left the scale, but no ticket was generated. f The tare weight is above the set threshold. f The gross weight from the scale does not match that printed on the ticket. f The weight on the scale exceeds the truck GVW (Gross Vehicle Weight). f The ticketing system loses connection with the scale indicator. New functionality also supports bagged cement, providing the ability to cross-check that the load World Cement April 2021

is accurate. If a certain number of bags are ordered and the truck comes over the scale, the system has the ability to check that the right number of bags are loaded based on a certain configurable threshold. If the truck comes over the scale and weighs more than the given threshold, the system can flag that load and the truck will not be allowed to receive a ticket unless someone manually overrides it. Finally, the Remote Printer Enclosure enables drivers to pick up their scale ticket after weighing without getting out of the truck. Combined with a movable swing arm option, the enclosure is installed at cab height immediately following the outbound scale and rotates easily out of the way if bumped. Apex can also integrate with TrackIt, Command Alkon’s truck tracking and telematics system. Utilising a telematics system provides full visibility of the truck throughout the entire delivery process. The system can provide statuses for when the truck arrives at the plant to be loaded and when the truck is in the loading area so that it is easy to determine the difference in the time during check-in to loading, when the truck leaves the loading area, when the truck is ticketed, and then all the way to the delivery site. The result is the ability to improve customer service by improving insight into what is really going on.

implementation process as seamless as possible. The implementation caused no interruption in the company’s operations, and Apex has allowed it to universalise its process across the entire enterprise and have better insight into what is happening in real time from all parts of the organisation. Now that the company has the back-office modules in place with the loadout and scale ticketing, it is using the Apex system with each local plant to manage orders. The system has helped them go from a 15-day close at the end of the month to a three-day close because all the invoices are contained within one platform. The company is now able to manage demand and keep trucks moving, and since implementation, it has maintained a record-setting year. The company also claims that Apex’s modularity is a big factor in this success.

Conclusion Having one point of reference for information on the product from the time it is ordered, out the door, and billed, and streamlining check in and loadout processes, eliminates tedious manual tasks and allows companies to handle the orders that customers need each day.

About the author Site automation in action The back office is an integral part of any organisation, and a significant percentage of customer dissatisfaction can be traced to back office inefficiencies, which has the potential to greatly impact the operation’s profitability. The lack of insight into back-office activities costs many companies significant amounts of money each year. Not having a system in place to manage and optimise productivity can present some serious implications on customer service and business reputation. One of Command Alkon’s Apex customers built a custom application for their back-office processes in 2001. In 2018, the company decided to add the Apex sales and back office modules for quoting, invoicing, receivables, inventory, reporting, and business intelligence because it had expanded its services and had undergone some substantial growth. The company’s in-house system no longer had the power to handle its volume of work. The company’s employees responded positively to the addition of the back-office modules because the interface is familiar, and it is very similar to the way that their custom application works. The system is also highly customisable, so the company was able to easily tailor the solution to work the way that made the most sense for the business and for its people. Because this particular company had been an Apex user for more than two decades prior to adding back office modules, they already had a firm relationship with Command Alkon. This helped in making the April 2021 World Cement

Scott Dugan joined Command Alkon in 2005. He has performed roles in customer support, implementations, project management, product management, technical sales, and is currently the Director of Operations for Bulk Materials Products. His degree in management information systems and prior experience in information technology brings technical expertise to the Bulk Materials industry.

Apex’s rugged Remote Printer Enclosure keeps drivers in the cab, out of harm’s way, and gets vehicles on the road quicker. 71

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