World Cement August 2021 by PalladianPublications

August 2021

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CONTENTS 03 Comment 05 News REGIONAL REPORT: LATIN AMERICA 10 Latin America: Looking Ahead World Cement Editor, David Bizley, analyses some of the leading economies in Latin America and reviews the state of their cement and construction sectors after a year of COVID-19. GRINDING & MILLING 15 Ready To Upgrade Kaushik Ghosh, Dr.-Ing. Thomas Hanstein, and Dr.-Ing Jörg Oligmüller, Maschinenfabrik Köppern GmbH & Co., outline how existing grinding plants could be made more productive and energy efficient through the use of high pressure grinding rollers. PYROPROCESSING 20 Life In LEILAC Daniel Rennie, Calix, explains how new technology is helping plants capture emissions directly from the precalciner, paving the way towards scalable CO2 capture for the cement industry.

DIGITALISATION & INDUSTRY 4.0 42 Industry 4.0, Smart Plants And Sustainability Max Tschurtschenthaler and Sanjit Shewale, ABB Process Industries, explain how digital applications, together with cloud and edge computing, can help manufacturers optimise performance, paving the way for smart, sustainable cement plants. WELDING 47 Warding Off Wear Dr. Venugopal Thota and Marc Landragin, Welding Alloys, explain how advanced hardfacing alloys can enhance wear resistance and extend the life of cement grinding components. 51 Stacked Up Gregory Shane Boston, S.B. Southern Welding, describes the process of manufacturing and installing a cement kiln stack. MAINTENANCE 54 Keeping An Eye On The Kiln Jacob Becker Ryttergaard, FLSmidth, explores the vast potential offered by digitally-based, people-powered services such as online condition monitoring.

27 Taking The Heat Off Hans-Jorgen Nielsen, LV INTERNATIONAL, introduces a new concept for the design of a pyro system which enables the specific heat consumption of a cement kiln to be reduced, in order to achieve rates below 600 kcal/kg of clinker.

58 Splitting Opinions Ian Breeze, Bowman International, explores the latest developments in split roller bearing design and the related maintenance advantages.

32 Reducing Reaction Time Karsten Brink Floor, FLO2R, reviews the factors that plants need to consider when looking to prevent explosions from occurring in the cement pyro process.

62 Sharing The Secrets To Success World Cement spoke to Thomas Serr of Kalenborn International as the company celebrates its 100th Anniversary and shares the secrets to its longevity and success.

SAMPLING & ANALYSIS 37 Put To The Test Oskar Cylkowski and Hans-Heinrich Reuter, TESTING Bluhm & Feuerherdt GmbH, outline the optimised laboratory testing processes of cement and mortar that allow human error to be significantly reduced and testing quality and quantity to be maintained.

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August 2021

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2021

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August 2021 World Cement

DAVID BIZLEY, EDITOR

he 2020 Tokyo Olympics are finally underway after having been postponed for a year – a first in the history of the modern event. With the complications caused by the pandemic and a recent survey showing that a staggering 83% of Japanese people wanted the event postponed (again) or just cancelled outright, there was reason to suspect that the games wouldn’t be going ahead at all. However, with the decision eventually made to press on, the First and Second World Wars remain the only two events to have ever caused the modern Olympics to be cancelled. Though the games are going ahead, things aren’t exactly business as usual. In happier, pre-pandemic times, the Japanese government had hoped to welcome 1 million spectators over the course of the games. However, with concerns over rising case numbers in Japan (resulting in a state of emergency being declared in Tokyo), there will be no crowds of cheering onlookers at any of the Olympic venues as spectators have been banned – another unfortunate first for the event. The International Olympic Committee (IOC) even made the decision to limit accreditation to only those who have “essential and operational roles” at the games, ruling out athletes from bringing their partners and families for the occasion. This news will be particularly disappointing for Japanese taxpayers who funded the construction of new facilities, such as The Japan National Stadium, built to be the centrepiece of the games. Constructed on the site of the previous national stadium, and designed using timber sourced from across Japan’s 47 prefectures, the stadium cost US$1.43 billion to construct and is designed to hold a fixed capacity of 68 000 people. Another venue constructed specifically for the 2020 games is the Tokyo Aquatics Center. Rising four floors high (with a fifth below ground), the venue covers an area of 65 500 m2 and required 50 000 m3 of concrete in its construction. However, there is a silver lining to this cloud in that another unusual aspect of this Olympics is the large number of existing venues that have been retrofitted and upgraded, rather than being demolished and replaced. Indeed, three of the facilities being retrofitted were originally built for Japan’s last Olympics back in 1964. Whilst it’s a shame that these venues will be largely empty throughout the games, the theme of re-use and retrofitting is certainly one positive aspect that we can acknowledge and apply elsewhere – even the medals were made with precious metals recovered from recycled electronics. It’s going to require a similar attitude towards innovation and the avoidance of waste across industry for global climate and emissions goals to be met, and it’s exciting to see the cement sector making efforts to reduce its environmental impact. Perhaps the message we should take from the Tokyo Olympics is to continue, despite adversity, and make the right decisions for the environment. 3

NEWS HeidelbergCement signs ‘Business Ambition for 1.5˚C’ HeidelbergCement has signed the Business Ambition for 1.5˚C Commitment, a global initiative led by the SBTi in partnership with the UN Global Compact and the ‘We Mean Business’ coalition, aimed at limiting global warming to 1.5˚C and achieving net zero carbon emissions by 2050 at the latest. With this signature, HeidelbergCement joins the global ‘Race To Zero’ campaign, which aims to build positive momentum for the transition to a decarbonised economy ahead of the 26th UN Climate Change Conference of the Parties in November 2021. “As one of the world’s leading building materials producers, we are continuously increasing our efforts in the global fight against climate change,” says Dr. Dominik von Achten, Chairman of the Managing Board of HeidelbergCement. “We are working on all levels to reach climate neutrality – within our operations as well as through associations and initiatives such as the ‘Race To Zero’ campaign. Every effort brings us closer to our goal.” To substantiate the path to 2050 with concrete, scientifically validated targets and measures, HeidelbergCement will intensify its collaboration with the Science Based Targets initiative and global partners. The company has already committed itself to lower its scope 1 emissions to below 500 kg of CO2 per t of cementitious material by 2030, a reduction of 33% compared to 1990. HeidelbergCement’s scope 2 emissions are to be reduced by 65% by 2030 compared to 2016. To also significantly reduce the supply and transport-related scope 3 emissions, HeidelbergCement collaborates with partners along the entire value chain. The company aims to be carbon neutral by 2050 at the latest.

Votorantim Cimentos starts operations at new site in Pecém Votorantim Cimentos, a building materials and sustainable solutions company, has announced the start of operation of a new production line at its cement site in the Pecém Industrial and Port Complex, in the state of Ceará, Brazil. As a result of this expansion, the unit now has a production capacity of approximately 1 million tpy of cement – equivalent to the amount needed to build 40 soccer stadiums. The volume produced in the new site will enhance the supply of the metropolitan area of Fortaleza. August 2021 World Cement

Votorantim Cimentos invested approximately R$200 million in the project, which was constructed over three years and, in line with the company’s sustainability strategy, prioritised energy efficiency and industrial automation by incorporating state-of-the-art equipment. During construction and start of operation, the unit generated more than 600 direct and indirect jobs. “This new Votorantim Cimentos site in Pecém and the increase in its production capacity demonstrate the company’s confidence in our state. This project will help boost our economy by creating jobs and income for our people. We have been working day and night to attract new investments to Ceará and, as a result, drive the creation of new jobs for our population,” said Ceará Governor, Camilo Santana. “The Pecém expansion project fills us with pride and satisfaction for its technical quality and its contribution to the state’s social, economic and environmental development. Through this investment, we are enhancing our performance and presence in the strategic and important market that is Ceará. Our new and more modern and efficient plant will enable us to increase our production and distribution capacity and the quality of our service to our customers in the region,” said Marcelo Castelli, Global CEO of Votorantim Cimentos. Votorantim Cimentos’ new production line in Pecém will manufacture Poty cement. Several studies were carried out to ensure that the product would offer more protection against sea air as an added advantage. “We are offering to our customers a product that, in addition to its recognised quality and performance, incorporates improvements to meet the needs of different types of construction projects, from foundation to finish. We are very happy to improve our processes to offer products that meet the specific needs of the Ceará market, in addition to having less environmental impact,” said Hugo Armelin, Director of Sales and Marketing at Votorantim Cimentos. The new production line in Pecém includes a new cement mill that consumes less electricity. The vertical equipment reduces the kilowatt per hour consumption by 30% compared to the horizontal mill. Another sustainable technology incorporated into the new mill is a closed refrigeration circuit that reduces the production of effluents. This system reuses water to cool the equipment, providing a 90% reduction in the consumption of water resources. 5

NEWS DIARY CEMENTTECH 2021 08 – 10 September, 2021 Jiangxi, China Joannalong@ccpitbm.org www.cementtech.org/eng/dj.asp

CEMBUREAU: Cementing Europe’s Future 12 October, 2021 Brussels, Belgium j.meaden@cembureau.eu www.cembureau.eu/events

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

09 – 10 November, 2021 Online Conference www.worldcement.com/wct2021

SOLIDS & RECYCLINGTECHNIK Dortmund 16 – 17 February, 2022 Dortmund, Germany www.solids-dortmund.de

Holcim shares new Group identity Holcim has recently launched its new Group identity uniting all its market brands behind its purpose to build progress for people and the planet. At the forefront of green building solutions, Holcim is committed to playing an essential role to accelerate our world’s transition to a net zero and inclusive future. Jan Jenisch, Chief Executive Officer at Holcim, says: “Today marks a milestone for our company in our transformation to become the global leader in innovative and sustainable solutions. Our world is changing in many ways, with population growth, urbanisation and the climate challenge. We are determined to play our part to accelerate low-carbon and circular construction so that we build a net zero future and raise living standards for everyone. Our new Group identity sends a signal to the world that we are fully committed to building progress for people and the planet.” Holcim is home to some of the world’s most trusted brands in its sector including ACC, Aggregate Industries, Ambuja Cements, Firestone Building Products, Geocycle, Holcim and Lafarge. All market brands are retaining their respective market identities and names. With its new identity launch, Holcim is reinforcing its focus on making cities greener and infrastructure smarter to improve living standards around the world, with the world’s broadest range of low carbon building materials.

Lafarge Zementwerke GmbH in Retznei, Austria, orders BEUMER solution for handling of alternative fuels For an economical and sustainable operation, the Austrian plant Retznei of Lafarge Zementwerke GmbH relies on alternative fuels and raw materials to ignite the new calciner. In order to transport, store and dose the kiln-ready material efficiently, the manufacturer awarded BEUMER Group to develop an individual single-source solution. The core of this system solution is a U-shape conveyor: the conveying system ensures an environmentally safe, dust-free and low-energy transport of the pre-processed waste. “Cement has been produced in Retznei since 1908,” says Franz Wratschko of Lafarge Zementwerke, who is an Investment Manager at the Retznei plant. If, at that time, the first owner of the plant, the Ehrenhausener Portlandzementwerke, had a yearly production reaching between 4000 and 4500 wagons, as stated in an old report, nowadays the yearly production is approximately 625 000 t. Lafarge Zementwerke places particular value on high-quality products, but also on a sustainable, energy-efficient and environmentally friendly manufacturing. In order to reduce greenhouse gas emissions and lower production costs, the company focused more on the use of alternative fuels for firing the new calciner. Instead of coal and oil, only pre-processed and selected recyclable materials of the waste disposal are fed into the kiln. This is already a low calorie material with a calorific value of approximately 14 000 kilojoules per kg, which represents a practical, cost-effective and environmentally friendly alternative to the conventional deposition and combustion process. World Cement August 2021

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NEWS “However, the thermal exploitation of these materials in cement plants offers further advantages,” explains Franz Wratschko. “The temperatures of approximately 2200 to 2400˚C prevailing in the rotary kiln make sure that the organic pollutants are completely destroyed. During the combustion process, ashes are completely eliminated, and the combustion residues are incorporated in the cement clinker.” The manufacturer commissioned BEUMER Group to install a conveyor line, which feeds the material into the calciner at a capacity of 15 tph. In order to support producers of cement in the alternative fuels and raw materials field (AFR), BEUMER Group has set up its own business segment dedicated to AFR systems. The system provider is able to supply and install the whole chain from the acceptance and unloading of the delivery vehicle, up to the storing, conveying and feeding process of the solid alternative fuels for the specific user. The customer receives everything from one source. The alternative fuels and raw materials have to fulfil specific quality requirements. Only pre-processed waste with a minimum calorific value of 22 000 kilojoules per kg and correspondingly low heavy-metal contents may for example be used. The material is supplied by Geocycle. The waste disposal service provider is part of the LafargeHolcim Group and pre-processes construction and mineral production waste for the clinker production in the recycling centre of Retznei. The kiln-ready material is supplied by Geocycle in moving-floor trailers. The hydraulically controlled moving floor moves the load outwards on the conveying system. “All conveying systems supplied and the accompanying equipment are intertwined to ensure steady fuel feeding,” explains Jan Tuma. “We have installed our unloading station BG OptiBulk”. “A chain belt conveyor with a length of 15 m and a belt width of 2.8 m conveys the material to this unloading station on a height of 6.6 m. The BG OptiBulk is equipped with a special housing, which protects the environment from dust escape and the material from environmental stress. This station enables the unloading of to 150 m3 of fuel per hour,” says the BEUMER expert. The material, which is delivered by trucks, falls from the unloading station into the BG OptiFeed screw weigh feeder in a container of 20 m3. A conveying system transports 8

further combustible material of the waste disposal service provider Geocycle to a second BG OptiFeed in a container of 50 m3. “In order to enable a continuous controlled feeding of the material, we have installed one BG OptiFeed for each material flow,” explains Jan Tuma. The screw conveyors with weighing cells are suitable for completely different materials – ideal for the continuous feeding of alternative fuel or raw materials. Since the screw conveyors are positioned on the weighing cells, it can always be seen how much material is extracted. The feeding speed to the following conveying elements amounts to up to 15 tph. The system is dimensioned for bulk densities reaching between 0.08 and 0.15 t/m3, the regulation ratio is 1:20 and the maximum feeding accuracy between 1 – 2%. In addition, the completely closed screw weigh feeder is protected against dust. “Thus we can feed the downstream U-shaped conveyor with up to 15 tpy of material,” says Jan Tuma. The U-shape Conveyor is the key component of the entire system. “We evaluated and considered different variants of mechanical conveying systems,” reports the BEUMER expert. “Finally we decided on this conveying solution. U-shape conveyors can be simply integrated and are also suitable for long distances and rough terrain as well as horizontal and vertical curves. The material conveyed is protected against external influences such as wind, rain or snow and the environment against possible material loss. This conveying solution is suitable for coarse but also for very fine material. The system in Retznei has a diameter of 250 mm, a conveying length of 253 m and navigates at a speed of one metre per second a height of 32 m with a maximum inclination of more than 20˚.” The U-shape Conveyor transfers the material to a double discharge screw conveyor of the BG OptiLock constructions series. The airlock of this system solution protects the pyroprocess from the infiltrated air from outside, which can arise in the combustion process. The BG OptiLock is also equipped with weighing cells. Therefore, the owner always has an overview of the actual material load. The discharge screw conveyor transfers the bulk material continuously on a screw conveyor, which feeds the calciner. As the material can catch fire, the system provider has designed all supplied systems according to the ATEX directive for the zones 21 and 22. World Cement August 2021

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Latin America:

LOOKING AHEAD

World Cement Editor, David Bizley, analyses some of the leading economies in Latin America and reviews the state of their cement and construction sectors after a year of COVID-19.

atin America has been the region hardest hit by COVID-19 pandemic. The crisis caused growth in the region to contract sharply, and has taken an enormous social and economic toll on the population, adding further strain to countries that had already been struggling with several years of sluggish performance and even social unrest in some cases. Earlier this year, The Financial Times reported that the region’s economic output by the end of 2021 would likely still be

4.8% lower than pre-pandemic levels, with Carlos Felipe Jaramillo, World Bank head for Latin America and the Caribbean, forecasting 2023 as being the earliest date for a full recovery. Jaramillo was quoted as saying: “2020 was a disastrous year […] and we’re very concerned for what that means for poverty and inequality. 2021 should be better but it will only be a very gradual recovery, I don’t think we’re expecting anywhere a quick bounceback.” A more recent forecast from S&P Global casts a more optimistic light on

the situation, particularly in 2021 with growth of 5.9% predicted for the region’s major economies. However, this is still somewhat overshadowed by long term obstacles, such as monetary policy normalisation, fiscal tightening, and less predictable policy actions that look to hinder growth in 2022 and beyond. Exactly how the economies of Latin America deal with the difficult recovery process and manage vaccine rollouts will determine the outlook for this region for years to come.

Brazil At the time of the pandemic arriving in Brazil, the country was still recovering from the impact of a 2014 –16 recession, which has seen economic growth restricted to rates of less than 2% over recent years. The World Bank reports that the country now faces an unprecedented and ongoing health and economic challenge with the pandemic reaching its highest peak so far in March of this year – marking a stark contrast with trends seen across much of the rest of the world. To limit the impact of the virus on the most vulnerable, the government put support programmes in place valued at US$156.8 billion or roughly 11.4% of GDP. The World Bank believes that this stimulus is responsible for a relatively moderate contraction in GDP of 4.1% for the year. A successful vaccine rollout and recovery is expected to push growth to 3% in 2021, but this outcome remains uncertain. Regarding cement, sales figures released by Brazil’s National Cement Industry Union (SNIC) for May of this year show a growth of 14% year-on-year with a total sales volume of 5.5 million t. For the period of January – May 2021, overall sales marked a 19.3% increase on last year’s figures. Though positive, these figures are inflated by comparison with a very weak sales period in the previous year. According to the SNIC, the main driver of growth in the sector continues to be real estate developments, especially in recent months, as very few projects were suspended in May. Other areas supporting growth include commercial renovations. In its ‘Preliminary Results for May 2021’, the SNIC notes that: “Even with a crisis plaguing several segments of the economy, the real estate market is experiencing its best moment since 2014. With the drop in interest rates at the lowest level in history, simplification, reduction of bureaucracy and new credit lines have made the purchase of real estate more attractive.” Whilst the SNIC maintains that the medium-to-long-term outlook for the Brazilian cement sector is broadly positive, there are still hurdles to overcome, including cuts to infrastructure programmes, currency devaluation, unemployment, and rising costs. Looking at the near-term future, Paulo Camillo Penna, SNIC President, stated: “The number of launches below what is necessary imposes caution for the future, as the stocks of works are decreasing. It is essential to diversify the sources of demand for cement for the sustainability of the [sector]. If, on the one hand, we have the continuity of real estate reforms, the maintenance of the pace of works and the recent infrastructure auctions, on the other hand, the high unemployment rates, the uncertainty regarding structural reforms and an approaching water crisis are the great threats to be surpassed.” 12

The last year or so has seen some manoeuvring amongst major European players operating in the country. In October of 2020, CRH announced that it had sold its Brazilian cement business to a joint venture for US$218 million as part of the company’s ongoing withdrawal from emerging markets. The sale was made to Companhai Nacional de Cimento (CNC), which is jointly owned by Buzzi Unicem (50%) and Grupo Ricardo Brennand (50%). CRH’s assets in Brazil consisted of three full-cycle cement plants – located in Matozinhos, Arcos (Minas Gerais) and in Cantagalo (Rio de Janeiro) – and two grinding facilities – located in Santa Luzia and Arcos (Minas Gerais). In April of this year, LafargeHolcim announced that it was exploring the sale of its Brazilian unit, with an estimated value of US$1.5 billion. Similar to CRH, under the leadership of CEO Jan Jenisch, LafargeHolcim has been selling off assets that do not contribute significantly to core operations. According to the SNIC, LafargeHolcim has 12 facilities in operation in Brazil.

Argentina Argentina is one of South America’s largest economies, with a GDP of approximately US$400 billion. Despite this, and vast natural agricultural and energy resources, historical economic volatility left the country vulnerable to the impacts of the pandemic. The World Bank reports that 2020 saw the country suffer a 9.9% decline in GDP – the largest retraction since 2002. As might be expected, sectors such as hotels and restaurants suffered significantly, marking a 49.2% decline in 2020. Like many other countries, Argentina’s government put emergency measures in place to provide protection for the most vulnerable, and supported businesses shuttered by pandemic restrictions. However, significant economic imbalances continue to cause problems for the Argentinian economy, with annual inflation reaching 36% in 2020 and some forecasts expecting it to reach as high as 50% in 2021. Argentina’s construction sector was also badly hit by the pandemic and resultant restrictions. Recently released data showed a year-on-year contraction of 50.2% in Q2 of 2020. Dariana Tani, Economist at GlobalData, commented on the situation: “The significant decline in construction output in the second quarter of the year reflects the deepening economic consequences of the pandemic and the containment measures imposed by the Argentine Government to limit the spread of the virus. The data is also consistent with projections of a sharp contraction in the sector in 2020 and slow recovery in the next four years.” According to GlobalData’s recent quarterly construction update, the forecast for Argentina’s construction industry has been revised downwards World Cement August 2021

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with output now expected to contract by 23.5% in 2020 overall and by 5.4% in 2021, marking a further decline from the already gloomy previous projections of -16% and -5% respectively. Indeed, there is little optimism for the medium term, as Tani adds: “While activity is expected to gradually recover in the coming months as the government continues to push forward its reopening plan to kickstart the economy, the level of output will not be sufficient to pull the construction sector out of recession next year. Risks of a second wave of COVID-19 infections, as well as difficulties to access finance for projects, will continue to hinder investment in critical sectors such infrastructure, residential and energy and utilities.” Unsurprisingly, with the downturn in construction, the cement sector also suffered. The Asociación de Fabricantes de Cemento Portland (AFCP), the official representative body for the Argentinian cement industry, reported that sales in May 2020 dropped 32.8% year-on-year, falling to 648 543 t, with sales in the Buenos Aires area dropping by as much as 79.9%. Figures for 2021, however, are looking more promising with production in June of this year reaching 961 340 t, up from 797 794 t a year prior. Also in June of this year, Loma Negra ignited the kiln on its new 2.7 million tpy line at the L’Amali cement plant, located just south of the city of Olavarría. Costs for the construction of the new line came to US$350 million. At the opening ceremony, CEO Sergio Faifman commented: “This is a milestone in the history of Loma Negra. I would like to thank everyone who was working on the site, workers, Sinoma and contractors. We have had and gone through economic and social difficulties and it is thanks to the efforts of all that we are here today. With effort and commitment, dedication and teamwork, you can go a long way.”

Colombia With a track record of what the World Bank describes as “prudent macroeconomic and fiscal management, anchored on an inflation targeting regime, a flexible exchange rate, and a rule-based fiscal framework”, the Colombian economy experienced a period of uninterrupted growth since 2000, with poverty rates halving in the last decade. However, after growth accelerated to 3.3% in 2019, the global pandemic brought an abrupt end to the good news and resulted in the country’s worst recession in almost half a century. In order to combat the effects of the pandemic, the government announced a fiscal support package worth COP3 trillion (equivalent to approximately 3% of the country’s 2019 GDP). This package provided additional support for the health system and social programmes for vulnerable groups. Despite these efforts, the economy still contracted by 6.8% in 2020. However, provided that the vaccine 14

programme proceeds without trouble, Colombia is expected to return to growth in 2021 – 2022. Reuters reports that the Colombian construction sector contracted by 27.7% in 2020 as it suffered under pandemic restrictions and adverse economic conditions. It comes as no surprise then that the Colombian Chamber of Construction (Camacol) has announced that the construction sector was poised to lead the country’s economic recovery; according to Camacol President, Sandra Forero, the sector “must move from selling to building, because that’s where we’re going to achieve our higher objective of reactivating the economy.” There are also some positive signs coming from the country’s cement sector. According to DANE, Colombia’s national statistics office, May 2021 saw production levels climb to 880 400 t, representing a 13.1% year-on-year increase. While this is certainly a step in the right direction, when compared to May 2019’s figures, the 2021 data still represents a 22.7% decline in output. Despite this, new projects are still being undertaken, with the Cementos Argos port expansion project in Cartagena due to begin operations in the third quarter of this year, allowing the company to export up to 2.5 million tpy of cement and clinker, to new markets in the USA such as Houston and the South East, Puerto Rico and the Caribbean. This project is located in the industrial zone of the Cartagena bay in Colombia, and comprises an investment of close to US$40 million, which includes in its scope a new pier of 152 m long by 18 m wide, from which it will be able to serve vessels of up to 60 000 t dead weight and provide a loading rate of 1200 tph. The new terminal is connected through a 170 m long access walkway, which has a tripper band system and a state-of-the-art shiploader. It will be integrated into the existing cement plant and will be connected by means of a 1 km long pipe conveyor. A complementary system of conveyors will allow the connection with two existing clinker silos of 40 000 t each, while an alternate system will allow the connection of the existing export cement silos with a total storage capacity of 57 000 t.

Summary Whilst the whole world has been impacted by the pandemic, the situation in Latin America has been particularly difficult. The health crisis has, in some cases, compounded pre-existing social and economic issues, scuppered growth, and muddied the outlook for the whole region. However, figures for 2021 appear to show that the turn-around is underway and that things are improving – growth is returning and industries are picking up steam. As with other regions, the success of the vaccine rollout will be key to ensuring that this return to growth is maintained and that Latin America can look forward to a prosperous future. World Cement August 2021

GRADE Kaushik Ghosh, Dr.-Ing. Thomas Hanstein, and Dr.-Ing Jörg Oligmüller, Maschinenfabrik Köppern GmbH & Co., outline how existing grinding plants could be made more productive and energy efficient through the use of high pressure grinding rollers.

igh pressure grinding rollers (HPGRs) have been operating in the cement industry for more than 35 years for the comminution of burned, highly abrasive clinker, granulated ground blast furnace slag (GGBS) and limestone. HPGRs build up a particle bed by feeding material from a filled hopper into the gap between

two counter-rotating rollers. The moveable roller is hydraulically pressed against the material bed and the fixed roller. Within the particle bed, compression and shear forces cause mechanical interactions of the individual drawn in particles responding with fracture or crack initiation.1,2 Due to the high pressure acting in the gap, the feed material is densified to an agglomerate (flake).

Figure 1. Typical HPGR grinding circuit as pregrinder or flake recycling system.

Figure 2. Conversion of flake recycling circuit to semi finish grinding with combination separator from Köppern (KOESEP®).

Using this indirect crushing operation in HPGRs results in a significantly lower specific energy consumption compared to other conventional methods for comminution such as ball mills or vertical mills.3,4 In the past, HPGRs were supplied as pregrinders with or without flake- or edge-recycle systems. Savings of up to 20% of specific energy were noticed compared to closed circuit ball mills. As a pregrinder, the fresh feed is fed to the HPGR and the output from the HPGR is directly forwarded to the ball mill without any separation. A step forward was made when the discharge of the HPGR, especially the edge tailings, were re-circulated to the HPGR. By recycling the flakes, energy consumption was reduced, but still cannot be compared to the modern semi finish or finish grinding systems using HPGRs. As energy costs are becoming an increasingly major part of the total cost of cement production, upgrades of older grinding systems are being explored worldwide. An additional benefit of saving energy is saving CO2. Brownfield projects are known to be more profitable due to comparable low investment cost and quicker ROI. In most cases, a combined separator is installed, which not only breaks the flakes but can also separate fine materials from coarse materials. The major bottleneck is a lack of space for the installation of a combined separator.

Upgrading a grinding circuit with combined separator

Figure 3. Typical arrangement of choke feed system. 16

In 2015 Maschinenfabrik Köppern GmbH & Co. KG successfully upgraded a HPGR with flake recycling grinding system to a semi finish grinding system, as shown in Figure 2. The equipment within the green boundary was pre-existing equipment and the dotted lines indicate the flow of material before upgradation. Since the installation of the KOESEP® separator which includes two separation stages in only one housing, the HPGR output is now fed to the static part for deagglomeration and coarse separation. Coarse rejects of the static stage, so-called ‘coarse grits’, are discharged and fed back to the HPGR for regrinding. Finer materials enter the dynamic stage. Particles that are rejected by the rotating cage are discharged as ‘fine grits’ for regrinding in the ball mill or in both ball mill and HPGR. The ball mill’s discharge material is directly fed onto a dispersion plate in the dynamic stage. All material of defined product fineness passes the rotating cage and is discharged together with the separation air. Thanks to this upgrade, the customer achieved an increase in production capacity of World Cement August 2021

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approximately 20% and approximately 13% savings in specific energy. The major advantages of this combined separator are: f Compact design, which reduces necessary building height. f Only one separating air circuit (including fan, cyclones, filter) is necessary. f Low pressure drop compared to other separator technologies, which directly influences the size of the fan.

Upgrading the existing HPGR with a choke feeding system Lack of space is not a major constraint when upgrading the HPGR. Older HPGRs are equipped with earlier technologies that could be easily replaced at low investment costs compared to an upgrade of the entire plant. With such an upgrade, plant operators gain more control over the machine and process, resulting in higher stability of the grinding process. It is a well known fact that HPGR operation is very stable when a column of material is present above the rollers, commonly known as ‘choke feeding’ (Figure 3). Feeding to the rollers is achieved by a so-called gravity feeder which is mounted directly above the rollers and fixed to the top part of the HPGR frame (Figure 4). Material is fed to the feed bin by a belt conveyor with an axis which is perpendicular to the axis of

Figure 4. Köppern gravity feeder.

the HPGR rollers. A magnetic separator and metal detector are installed on this belt. In case of metal detection, a diverter gate is activated and material is bypassed. Depending upon the capacity of the HPGR and the feed material characteristics, the feed bin should be accordingly designed. Special emphasis needs to be considered for proper flow of material inside the bin. The feed bin is mounted on load cells and should be interlocked with the fresh material dosing system. A slide gate is mounted directly below the feed bin. If the feed arrangement does not match the behaviour of special feed materials, then the HPGR is operated with a starvation feed that could lead to: f High levels of vibration. f Unstable process and torque fluctuations. f Lower or no working gap, therefore higher bed pressures leading to higher wear of roller surfaces and damage to other machine parts such as bearings, gearboxes, etc. Köppern’s patented gravity feeder system consists of two adjustable vertical walls and long-life cheek plates with spring loaded thrust bolts (Figure 4). The sidewalls are adjustable depending upon the fineness of the feed material so as to provide a column of material above the rollers. The distance between the sidewalls and the roller top remains constant at different opening positions of the sidewall. A higher gap will lead to material bypass from the roller top. Köppern recommends that material is equally distributed between the fixed and floating roller for central feeding. In case of uneven material distribution (coarse and fines) between the fixed and floating roller, it is also possible to adjust the side walls accordingly so as to evenly distribute the power drawn by the two main motors. Long life lateral cheek plates are pressed towards the sides of the rollers, providing effective sealing from the side so as to avoid material bypass and thereby production losses. In addition to the production losses, cheek plate leakages could lead to concavity of the roller and skew operation. The bottom of the cheek plate i.e. the wear protection, is made using powder metallurgy techniques, similar to Köppern’s Hexadur® rollers. Köppern’s cheek plates have provided a lifetime of more than five years in high abrasive conditions.

Hydraulic pressurising systems

Figure 5. Skew control logic with Köppern’s valve technology. 18

Process problems often persist due to improper material feeding or closed loop hydraulic systems. Older plants are forced to operate with different materials due to market demand or in order to reduce the plant’s CO2 footprint, however the addition of limestone, slag, trass, etc. as cement binders may not have been considered when the plant was commissioned. Operating pressures must be optimised to achieve the required output from the HPGR. Operating at World Cement August 2021

higher pressures does not necessarily lead to higher output, but can lead to increased wear of the rollers or damage of other machine parts. Besides this, fluctuating pressure levels often have a negative impact on the output of the press. Conventional closed loop hydraulic systems consisting of intermittently operating pump and solenoid valves are found to be inefficient for HPGR grinding operations. Köppern supplies open loop hydraulic systems consisting of continuous duty pumps, a valve technology that maintains the operator set pressure with a fluctuation of ± 3 bar only. Effective skew control can be achieved by use of such valves and individual pumps for the drive and non-drive end of the rollers. In order for a smoother movement of the floating roller, Köppern’s hydraulic system consists of bigger accumulators. In Figure 5, measured working gaps are indicated with S1 and S2. As soon as the working gap difference exceeds a pre-set level, the skew control logic gives different set points (SP1/SP2) to the valves to regulate the pressure accordingly. This means at the bigger gap side, pressure will be increased and at the lower gap side, pressure will simultaneously decreased. Köppern’s hydraulic system consists of pendulum pistons with heavy duty seals. The following outlines the common problems faced by hydraulic cylinders with cylindrical pistons: f Transfer of load vertically through seals therefore regular damage of seals leading to oil leakages, pressure losses and increased unforeseen downtime for maintenance. f Does not facilitate skew operations and therefore leads to seal damage. With a pendulum piston, complete force is transmitted directly onto the cylinder body and then onto the press frame. This also facilitates skew movement and seals are not stressed, hence longer life of the seals and the pistons.

Upgrading the roller surface The upgrading of HPGRs with Hexadur has been successfully tested in many plants around the world. Although comminution with HPGRs keeps the contact between feed material and roller surface to a minimum, the crushing tools still wear out. This reduces availability and generates significant costs for regeneration or replacement of the tools. Thus, Köppern’s powder metallurgically manufactured Hexadur tyres target the combination of high service lifetimes, sufficiently high throughputs over the complete lifetime, and low operating costs. Improvements in the intake behaviour as well as the establishment of an autogenious wear protection layer contribute to an overall cost reduction. Since 1996 Köppern has been supplying Hexadur rollers for Köppern HPGRs and also to customers operating presses of other makes. Typical wear August 2021 World Cement

Figure 6. Photo of the non Köppern HPGR after being upgraded with Köppern equipment. rates for clinker grinding applications are around 1.3 to 2.5 mm for every 10 000 hours of operation. A typical Hexadur tyre is supplied with a wear thickness of 17 mm at minimum. Therefore, an average lifetime between 40 000 to 50 000 hours can be achieved by cement manufacturers around the world.

Conclusion Older plants can be made more productive and cost-effective through simple modifications using separators. A much simpler and even cheaper method is through upgrading the HPGR itself, which is already an energy efficient machine. All mentioned possibilities for refurbishment are not only possible for Köppern HPGRs, but also for HPGRs supplied by other companies. In 2015/2016 a customer from Thailand (Figure 6) upgraded its third-party manufactured HPGR with a Hexadur Köppern feeding system including feed bin and gravity feeder and hydraulics, and has already achieved a 9% increase in hourly production and a 14% decrease in sp. energy consumption of kWH/t. This resulted in a total saving of approximately €1.5 million over the period of five years after calculation of ROI. Minor modifications to the grinding circuit or in the roller press could result in a large impact on energy and costs resulting in lower CO2 input for cement production.

References 1. SCHÖNERT, K., ‘Energetische Aspekte des Zerkleinerns spröder Stoffe’, ZKG 32, 1, 1 - 9, (1979). 2. SCHÖNERT, K., KNOBLOCH, O., ‘Mahlen von Zement in der Gutbett-Walzenmühle’, ZKG 37,11, 563 - 568, (1984). 3. KELLERWESSEL, H., ‘Betriebsergebnisse von Hochdruck-Rollenpressen’, Aufbereitungstechnik 27 10, 555 - 559, (1986). 4. ROSEMANN, H., ELLERBROCK, H., G., ‘Mahltechnik für die Zementherstellung – Entwicklung, Stand und Ausblick’, ZKG-International 51, 2, 51 - 62, (1998). 19

Daniel Rennie, Calix, explains how new technology is helping plants capture emissions directly from the precalciner, paving the way towards scalable CO2 capture for the cement industry.

he adoption of the Paris Agreement, ratified by 175 countries, provided the clear objective of keeping a global temperature rise of well below 2˚C above pre-industrial levels and to pursue efforts to limit the temperature increase even further to below 1.5˚C. In support of those ambitions, the challenging goal of reaching carbon neutrality by 2050 has been set. These commitments are being made at a variety of levels. 127 countries, 823 cities, 101 regions, and 1541 companies have committed to decarbonising their activities by 2050 (New Climate Institute 2021). These commitments are being matched in the cement industry. The Climate Ambition articulated by the members of the Global Cement and Concrete Association, and 2050 Roadmap by Cembureau, and the corresponding wave of individual corporate commitments, all have ambitions for neutrality by 2050. This is not an easy commitment to reach for the cement or lime industry, which is responsible for 8% of global CO2 emissions. Cement and lime provide vital services to society, with essential products that are low cost and very efficiently produced. Since 1990, major efforts have been made to reduce emissions, including improvements to energy efficiency, use of alternative and waste fuels and clinker substitution. However, complete decarbonisation of this industrial sector is far harder than many others, as most CO2 emissions are released directly and unavoidably from the processing of the limestone. These ‘process emissions’ are in addition to the CO2 released from the combustion of fuels used to power the process (representing around two-thirds of a plant’s total emissions, depending on the fuel used).

Capturing unavoidable carbon

Figure 1. One configuration of Calix’s Direct Separation Technology.

To reach the corporate emissions reductions targets by 2050, these unavoidable process emissions must be addressed. The most effective means is to capture the CO2, and ensure that it does not reach the atmosphere. Called Carbon Capture Use and Storage (CCUS), this general approach to decarbonisation has been used for decades in the hydrocarbon processing and recovery industries, further developed for the power sector. This will need to be applied to the majority of cement and lime plants due to these process emissions (Cembureau 2050 Carbon Neutrality Roadmap). As noted by the 2018 IPCC report, CCS plays a major role in decarbonising the industry sector in the context of 1.5˚C and 2˚C pathways, especially in industries with higher process emissions, such as cement. Capturing carbon from industrial and power generation plants has not yet been widely adopted due to the efficiency and cost penalties of traditional capture technologies, and a lack of meaningful (and universally applied) cost implications for emitting CO2. However, changes are very rapidly being seen. Globally, 61 carbon pricing initiatives have been introduced covering 22% of all emissions (World Bank Group, 2021). The European Emissions Trading System (EU ETS), the largest carbon market in the world, reached a price of €56 per t of CO2 in 2021. The current collective objective facing industry and government (creating incentives) is threefold: to maintain economic prosperity, meet cement and lime market demand, and do so while dramatically lowering CO2 emissions.

Carbon capture

Figure 2. The completed LEILAC1 Pilot. 22

The majority of initiatives to capture carbon are based, or adapted, from processes and techniques developed for the energy and chemical sectors, and are all based on separating gases. For 60 years, solvents, such as amines, have been used to strip CO2 from gases (particularly in refineries and natural gas processing plants), and a lot of work has been recently undertaken to apply them to the cement sector at an increasingly lower cost. Sorbents (including calcium looping), membranes, and enhancements are being actively developed to reduce the volumes and/or energy required to separate CO2 from flue gases. Other approaches, such as oxyfuel, separate gases in air, rather than at the stack. All of these approaches must be developed as quickly as possible. A new capture approach is being introduced. Calix’s new process of ‘indirect calcination’ focuses solely on the cement, lime and magnesia sectors, ensuring that the relatively pure, World Cement August 2021

unavoidable, CO2 released from the limestone itself in the precalciner is not contaminated by either air or flue gases.

Capturing CO2 in precalciners

The LEILAC (Low Emissions Intensity Lime And Cement) projects are developing this new technology, aimed at enabling the cement and lime industries to capture unavoidable CO2 emissions emitted from the raw limestone. The Calix process works within a normal cement plant’s process. It is based on indirect calcination, by heating the limestone via a special steel reactor within the precalciner. This unique system enables pure CO2 to be captured as it is released from the limestone, as the furnace exhaust gases are kept separate. Calcining raw meal by indirect heating (LEILAC) or by direct-heating (conventional calciner) can be done in principle with the same specific energy. The process does not involve any additional processes or chemicals, and simply involves a novel ‘precalciner’ design (or new kiln, in the case of a lime plant). This type of precalciner aims to use any type of fuel or heat source. This helps to achieve a very efficient zero-emissions cement kiln, when using biomass rich fuels, green electricity, or hydrogen. If alternative fuels, biomass, or conventional fuels are used, any of the previously mentioned conventional carbon capture techniques can be applied to capture the combustion (heating) emissions. There would be synergies to such a combination, as the lowered energy requirements and capital of such a combined system would result in the most efficient means of achieving ‘negative emissions’ cement plants.

The LEILAC projects Supported by the European Union, the LEILAC projects are applying this new type of precalciner. Applying the technology to the cement industry carries a large number of risks – and to quickly and effectively apply this technology, the European-Australian collaboration LEILAC projects include consortiums of some of the world’s largest cement and lime companies, as well as leading research and environmental institutions. The LEILAC1 project involved the construction of a pilot plant at the HeidelbergCement plant in Lixhe, Belgium. Extensive research, development and engineering was necessary to design and construct the first-of-a-kind pilot – involving the dedicated, flexible, and professional inputs from all the project’s partners, particularly the industrial users HeidelbergCement, Lhoist Solvay and CEMEX. This has enabled the construction of the pilot to be on time and on budget in 2019. Additionally, studies examining integration of the plant in different configurations, and confirmation

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Figures 3. An impression of a retrofit LEILAC module alongside an existing precalciner. Multiple modules (arranged flexibly, including vertically) can be used for a 100% retrofit.

Figure 4. LEILAC1 pilot, sitting to the right of the precalciner at Lixhe.

Figure 5. Example of a Process Flow for a complete retrofit. 24

of the sustainability of the process, and outreach activities have also been conducted by the other parties (TNO, Imperial College, PSE, Quantis and the Carbon Trust). Several challenges were faced in getting the system to run, particularly the burners, feed and conveying systems. These are gradually being overcome, and the system is increasingly stable. Within the current configuration, CBR’s Lixhe cement meal has been processed at up to 8 tph and briefly at 10 tph. Extents of calcination are seen at 85%. Lhoist’s Hermalle limestone has been calcined at 70 – 78%. Meal for LEILAC2 (Hannover) has been processed at up to 8 tph, with consistent calcination at 91% at 5 tph. Calix reactors have obtained 98+% calcination results on pure limestone, using an optimised particle size distribution (PSD). In all runs, separation of CO2 was undertaken (95% purity) directly from the reactor and before any clean up steps, with no air ingress or loss of containment. A number of steps are currently being considered in order to improve the throughput and calcination rates. These include improvements to the natural gas burners used, enabling the furnace to reach its design capacity; the installation of a three-stage cyclone pre-heat unit, currently underway, aims to increase the usable length of the reactor for calcination, further improving throughput and calcination rates and reflecting integration with a host plant. The lime cooler is being removed, and a simpler return system is installed, to improve throughput rates. There are several process configurations also being tested to improve per-tube throughput and calcination rates. Outside of such optimisation, the project has successfully demonstrated that both limestone and raw meal can be processed, that the CO2 is successfully separated, and that (disaggregated from the World Cement August 2021

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entire system) the energy penalty for indirect calcination (LEILAC) is not higher than direct (conventional) calcination. Other major findings are that there has been no build-up of material on the reactor’s wall, that the reactor (despite the numerous runs) is exhibiting no significant negative operational deterioration, that there have been no negative impacts on the host plant, and no impact on clinker production, and that the pilot is safe and easy to operate, with no safety incidents. Calix’s thanks go to all the staff at Lixhe, service providers, and consortium members tirelessly working despite the massive challenges arising from the pandemic.

LEILAC2: Towards process integration A follow-on project – LEILAC2 – has just started, having been awarded €16 million of funding by the EU Horizon 2020 programme with additional industry contributions. HeidelbergCement has kindly agreed to closely integrate the demonstration plant into their operational plant in Hannover, Germany. LEILAC2 will build a demonstration plant that aims to separate around 100 000 tpy of CO2, in a scalable module. The consortium, comprising Calix, HeidelbergCement, Cimpor, Lhoist, CEMEX, IKN, Certh, Polimi, BGR, GSB, Engie Laborelec, and Port of Rotterdam aims to also demonstrate the overall efficiency of the technology, as the reactor will be integrated into the kiln line in a kind of second preheater string configuration, where the calcined material is directly fed to the existing rotary kiln and the impact on clinker quality as well as the energy-efficiency can be demonstrated. The demonstration plant will also aim to show the applicability of less carbon intensive heat sources for the required calcination heat, i.e. the use of electricity and alternative (biomass rich) fuels. Earlier this year, the LEILAC2 Consortium endorsed the pre-FEED study. The criteria for passing this study were: That the demonstration plant’s design is technically viable; fulfilment of the operational objectives of the overall project; the plant’s design poses low integration risks for the main plant; it is within the cost constraints including CAPEX and OPEX of the budget. The LEILAC2 plant is a first-of-a-kind retrofit. The CAPEX is expected to be around €16 million. Further design work and testing is required, but should the design function as planned, current estimates suggest the LEILAC2 may separate CO2 at a cost of around €10/t CO2 extra OPEX (above the host plant’s operating costs). This excludes compression costs and CAPEX retrofit depreciation costs (including foundations, installation, structure), etc., which 26

are expected to be in the region of an additional €10 – 15/t CO2 (compression costs will change greatly depending on what happens to the CO2). Therefore, total costs of this first-of-a-kind LEILAC carbon capture plant are expected to be in the region of €20 – 25/t CO2.

Full scale LEILAC precalciner The intention with LEILAC2 is to start forming a robust, replicable module that can be simply scaled to capture 100% of a cement plant’s process emissions (at any scale). The LEILAC2 project is the first attempt at retrofitting the technology to a plant. At full scale, the LEILAC process conditions (and costs) will be improved from the current LEILAC2 projection through the following of steps in a future implementation, including: The use of the kiln gases; using the heat from the CO2; enhanced preheat; the use of unprocessed RDF (reducing capture costs to €4/t CO2); locating the reactors closer to the tower; skin loss reduction through module placement; increasing the levels of insulation. A full scale retrofit, depending upon the site in question and capital required to recover and utilise the heat, is expected to be close to BAT efficiency. On a greenfield site, when this type of precalciner is part of the planned installation, there is the opportunity for simpler integration and minimal additional capital costs, as a large proportion of the technology’s costs are for foundations, structure, and installation.

A sustainable solution using precalciners Every possible decarbonisation option needs to be urgently developed and deployed. In order to reach the required emission reductions by 2050, carbon capture will need to be applied to a vast majority of cement and lime kilns, and every technology option developed. Once tested and scaled up, the LEILAC technology should provide an option for reducing the costs of carbon capture and accelerate the deployment in both the cement and lime industries using this new type of precalciner, enabling society to continue to benefit from these vital products without negatively impacting the environment.

About the author Daniel Rennie is General Manager – Cement Decarbonisation for Calix, and has coordinated the LEILAC projects since their conception. Prior to joining Calix, Daniel helped establish the Global CCS Institute in Europe and managed the EC’s European CCS Demonstration Project Network. He has previously worked in the electricity industry. World Cement August 2021

Hans-Jorgen Nielsen, LV INTERNATIONAL, introduces a new concept for the design of a pyro system which enables the specific heat consumption of a cement kiln to be reduced, in order to achieve rates below 600 kcal/kg of clinker. his article provides a theoretical estimation of how it could be possible to achieve less than 600 kcal/kg of clinker in a conventional kiln producing clinker for cement, with only marginal additional investment compared to the conventional design used today. In some cases where there is a need for drying in the raw mill in existing plants, a modification can be made, saving

50 – 100 kcal/kg of clinker in the kiln system, while still gathering a similar amount of hot gas from the preheater for drying in the raw mill.

Heat balance of the pyro process based on conventional design Over decades, a great effort has been made to reduce the specific heat consumption for making clinker in the cement process.

By introducing a six-stage preheater instead of a four-stage preheater, and with the introduction of a high efficiency clinker cooler, where the standard cooler loss has been reduced from 140 kcal/kg to 100 kcal/kg using the latest cooler design, it has been possible to obtain heat consumptions of below 680 kcal/kg of clinker based on normal raw materials. There are reported cases with lower heat consumptions, but these have not been backed up with a proper heat balance, and have not mentioned the composition of the clinker and the type of fuel. Using a standard composition of clinker with C3S around 60 and a heat of reaction of 410 kcal/kg and coal with heat value of 6500 kcal/kg, together with a standard Table 1. The heat balance for four stage, five stage and six stage preheaters. 4 stages

5 stages

6 stages

Kcal/kg of clinker

720 – 730

700 – 705

680 – 690

Ncum/kg clinker in exhaust gas

1.30

1.28

1.27

T of exhaust gas

350

300

260

Table 2. The heat balance for four stage, six stage and eight stage preheaters. 4 stages

6 stages

8 stages

Kcal/kg of clinker

691

656

613

Ncum/kg clinker in exhaust gas

1.25

1.21

1.16

T of exhaust gas

422

338

260

Figure 1. Total configuration. 28

cooler loss of 100 kcal/kg, the heat balance with the most important figures mentioned is shown in Table 1 for four stage, five stage and six stage preheaters. It is normal to use the exhaust gases to dry the raw material and the coal, so there is normally little benefit in the overall economy of reducing the temperature in the exhaust gases much below 250˚C. Even if the raw materials are dry and do not require a high temperature to dry, it is not feasible to increase the number of stages beyond six, as any savings in heat consumption will be marginal and will not give a net payback for the additional power consumption of the ID Fan from the increased pressure drop of an additional stage. Instead of trying to make the heat consumption of the kiln system more efficient, the trend has been to recover power from the heat of the exhaust gases and the excess air from the clinker cooler through the introduction of waste heat recovery (WHR) systems, but for small plants as well as for some countries where the cost of electricity is not high, this is not feasible because of the heavy investment in WHR technology.

Recovering heat from excess air from the clinker cooler An analysis has been carried out regarding how to utilise the waste heat from the clinker cooler, assuming the preheater has been adapted to accommodate the number of stages feasible for drying raw materials. The excess air from the clinker cooler is divided into two fractions. One fraction is 1.2 kg of air per kg of clinker at a temperature of approximately 380˚C, and another part of 0.5 kg air per kg of clinker is taken from the outlet of the clinker cooler at a temperature of approximately 130˚C. The 0.5 kg is recirculated into front cooling air fans beyond the air for the fixed inlet, giving the combustion air from the cooler to the kiln and calciner, and reducing the standard cooler loss by approximately 12 kcal/kg of clinker, whereas the mid air of 1.2 kg/kg of clinker is used to preheat the raw meal as kiln feed before going into the preheater, which will be increased from 70˚C to 220˚C, if the system is used to preheat the kiln feed. The values for total cooling air to the clinker cooler and the standard cooler losses are figures used for calculation, and they are taken on the conservative World Cement August 2021

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Table 3. With the new system, it is possible to adapt the preheater from four to five stages. 4 stages

5 stages

Heat consumption

727

678

Cooler loss in excess gas

104

Ncum/kg of clinker in exh. gas

1.35

1.26

Temperature of exhaust gas

374

366

Figure 2. Rearranged preheater cyclone layout.

side of what some suppliers of clinker coolers claim. The total configuration is shown in Figure 1. A heat balance from the system where the 0.5 kg cooling air/kg of clinker is recirculated into the clinker cooler, and where the kiln feed has been heated up from 70˚C to 220˚C by the excess air from the middle of the clinker cooler is shown in Table 2. The heat transferred into the kiln feed by heating the material from 70˚C to 220˚C is approximately 48 kcal/kg of clinker, which can all be recovered in the heat consumption of the kiln, if the number of stages is adjusted to maintain the temperature of the exhaust gases from the preheater, so the overall reduction of the heat consumption will be approximately 52 kcal/kg, as the amount of exhaust gases from the preheater will be reduced by approximately 0.05 Ncum/kg of clinker, contributing to a reduction of the heat consumption of 4 kcal/kg of clinker, whereas there will be an additional loss from the radiation of two cyclones of 8 kcal/kg of clinker. By rearranging the preheater cyclones as shown in Figure 2, where the advantage is that the building height is lessened and that the riser ducts gets better heat transfer, there is an additional gain in the heat consumption of 5 – 10 kcal/kg of clinker. By installing double material refractory with an insulating layer moulded onto the wear resistant bricks at the kiln inlet, which will lower the kiln shell temperature to around 100˚C corresponding to a reduction in heat consumption of 5 kcal/kg of clinker, a heat consumption below 600 kcal/kg of clinker is possible if the raw material can be dried by the exhaust gases at a temperature of 260˚C.

Overall power consumption of fans Figure 3. Converted system flowsheet. 30

With the increased pressure drop of the eight stages World Cement August 2021

against the lower temperature, as well as the lower Ncum/kg of clinker, and the additional air to the clinker cooler, an additional power consumption of approximately 1.2 kwh/t of clinker is calculated for the ID Fan. This amount is partly offset by a saving of 0.4 kwh/t in the bag house fan for the kiln/raw mill. The power consumption in the fan to lift the kiln feed in the air stream at a velocity of 14 m/s is similar to the power consumption of a bucket elevator, so there will not be additional power consumption in the kiln feed, and overall additional power consumption would be less than 0.8 kwh/t of clinker in the ID Fan against a saving of more than 50 kcal/kg of clinker. This is without considering the lower power consumed for the grinding of less coal, because of the lower heat consumption, and the lower installation and maintenance of the kiln feed system, where a high bucket elevator is avoided.

Case study 1 Previously it had been common to split the feed to the preheater between three and four stages to increase the temperature when there was a need for additional drying. This was done against an increased fuel consumption. With the new system, it is possible to adapt the preheater from four to five stages, increase the drying in the raw mill from the exit gases and at the same time benefit from a saving in heat consumption of 50 kcal/kg. As can be seen, the total amount of heat for drying in the raw mill and coal mill is almost maintained at a reduced heat consumption of 49 kcal/kg by adding a sixth stage and heating up the kiln feed by the cooler exhaust air, cooler gases can still be used to heat the kiln feed to 220˚C for drying.

Case study 2 It is possible to convert wet process kilns to pyro systems with a calciner and a two stage preheater where the moisture content in the slurry is reduced by filter press. The cake is fed to a dryer crusher, where hot gas from a two stage preheater is used to dry the material before being fed to the preheater of the kiln. A heat balance for such a system shows a heat consumption of between 890 – 900 kcal with an exhaust gas temperature of 610˚C. If the system to heat up the kiln feed to 220˚C is used, the heat consumption will be reduced by 35 kcal/kg to 860 kcal/kg and the temperature will be increased to 640˚C which will allow higher moisture in the feed to the drying crusher. Also, if the hot gas from the excess air from the clinker cooler after heating up the kiln feed is used, combined with the hot August 2021 World Cement

exhaust gas from the preheater, it will allow a third stage to be added into the preheater, resulting in a heat consumption of 760 kcal/kg of clinker, or a reduction of 100 kcal/kg of clinker. A flow sheet is shown in Figure 3.

Investment cost Compared to the investment cost of a traditional six stage preheater in which cooler gas is dedusted separately, the investment costs of the new system are considerably lower, as it involves no separate dedusting of the cooler gases apart from the dedusting of the 0.5 kg of air recirculated back into the cooling fans. As well as this, the arrangement of the preheater cyclones as shown in Figure 2 will not increase the height of the preheater tower for an eight-stage preheater compared to a six-stage preheater. In cases where the drying in the raw mill and the coal mill is limited by the low temperature of the exhaust gases, the modification of the system to preheat the kiln feed and add additional cyclones offers a great opportunity to reduce production costs through the lower heat consumption.

Conclusion A new concept for the design of a pyro system has been introduced, where it will be possible to reach below 600 kcal/kg of clinker without additional investment compared to conventional kiln systems. The design offers a viable alternative to save heat consumption in the kiln by utilising the excess air from the clinker cooler to heat up the kiln feed and save fuel in the pyro system, avoiding the need for investment in an expensive waste heat recovery system. The design could be considered a breakthrough in the work to obtain lower heat consumption in kiln systems, and it is expected that the concept will be adopted within the near future.

About the author Hans-Jorgen Nielsen graduated from university with an MSc in Chemical Engineering and was employed at FLSmidth from 1975 to 1987 in the process/commissioning department. From 1988 to 1990, Hans-Jorgen worked as the Area Sales Manager for East Asia, where he was an instrumental force behind the first 10 000 tpd plant supplied by FLSmidth in Thailand. Since 1990, he has been operating his private engineering company LV Technology and LV-International in Thailand, where the most famous product is the LV Classifier for Vertical Roller Mills, of which more than 600 have been supplied. 31

Karsten Brink Floor, FLO2R, reviews the factors that plants need to consider when looking to prevent explosions from occurring in the cement pyro process.

ealing with fire and explosion prevention at a cement plant is a complex task where many areas can potentially present a risk. This article will focus on preventing explosions in the pyro process of the kiln and preheater system including the bag or electrostatic filter, using gas analysis as a tool to provide an early warning of a potentially explosive condition.

Explosions in the pyro system of a cement kiln Explosions in the kiln and preheater pyro system are, fortunately, not very common but they do occur. Indeed, whilst the occurrence of explosions might be rare, the danger in the event of an explosion is great with potential loss of life, severe equipment damage and loss of production. The primary cause of pyro process explosions is the combustibles used when producing cement. In modern cement production the type of combustible used is more or less anything that can burn plus the more traditional fuels such as oil, coal, and gas. Common for all of these combustibles is that if burned with too

little access to oxygen, they can produce explosive gases such as CO and CH4. The minimum concentration at which it becomes possible for a gas (at ambient temperature) to explode is known as the Lower Explosion Level (LEL). Some examples are: f LEL CO: 12.5 Vol% f LEL CH4: 5 Vol% In order for an explosion to occur, the gas concentration needs to be high enough and it needs a source of ignition. However, the LEL concentrations mentioned above are based on normal ambient conditions. The LEL will decrease if temperature or pressure is higher. Typical temperatures in the pyro process will be much higher even as the gas leaves the stack. As can be seen, the concentration (especially for CO) needs to be quite high before it becomes explosive, which most likely explains why explosions in the pyro process are not very common. However, the pyro process of a cement kiln contains large volumes of process gas, so if an explosion does occur, the released energy is potentially enormous.

How to prevent explosions in a pyro system Cement plants rely on several methods of reducing the risk of explosions. Commonly used methods include: Process knowledge; plant design and safe operational strategies; systems for safe fuel delivery and handling; automated surveillance systems; and interlocks with start-up and shut-down procedures. Knowing the characteristics of the fuel in use together with a fuel analysis to confirm the burning values and process impact has always been important. With today’s increased use of waste materials or Refuse-Derived Fuel (RDF) this has become even more critical and difficult. A given quality of any particular RDF can be hard to get consistently and rarely comes in a form that is homogenous either in terms of chemical make-up or physical size. With the increased use of various fuel sources an impact on the process stability can be seen in many cases. This can be caused by many things, but if the combustibles introduced to the pyro process are not burning under uniform conditions, pockets of un-combusted material can form on the kiln bed or at combustible feed locations, causing rapid and frequent spikes in CO and increased recirculation of volatile components due to reduced oxygen conditions. The use of various fuel sources can increase the number of times that upsetting conditions and instability in the pyro process occur. Upsetting conditions in a kiln can cause reduced production through-put and high concentrations of explosive gases. Plant operators should therefore be very aware of this when utilising a mix of combustibles. When the pyro process is being fed with a combustible or several combustibles of choice in a way that is as safe as possible, the next line of defence is surveillance of the process. The surveillance system fundamentally depends on access to instrumentation in the field and the quality

and availability of the instrumentation. Primary kiln control and avoidance of explosive concentrations of CO or CH4 will be controlled by gas analysis instrumentation. At a cement plant, the best practice is to have, as a minimum, a capable kiln inlet gas analysis system together with a preheater exit gas analysis system (the compulsory Continuous Emissions Monitoring System or CEMS are not included here as it is not part of the pyro process control and safety system). The kiln inlet gas analysis system will typically be measuring some combination of O2, CO, NO, CH4 and more often also SO2 and CO2. The kiln inlet system is primarily a process control measurement and is used to operate the kiln system in a way that optimises the throughput of clinker. That is, of course, not to say that the kiln inlet analysis system takes no part in securing a safe production environment. By analysing and controlling the O2 and CO content, potentially dangerous production situations can be avoided. Additionally, SO2 analysis will provide trend curves for the recirculation of volatiles in the kiln and the potential for build-up of material. The combustion process in the kiln inlet is however not complete and CO will always be present at some level all the way up through kiln, calciners and cyclones. It would therefore be premature to base fuel feed and other safety measure interlockings on the analysis results from the kiln inlet alone. The combustion process will be completed as it gets to the preheater exit. This means that a preheater gas analysis will have an advantage when it comes to representing the final concentration of CO compared to the potential for an explosion. The downside of this location is that the position is far downstream from the origin of the CO and is thereby late in its analysis result. However, since the preheater exit location is, gas sample-wise, much easier to handle than the kiln inlet, it is a more reliable measuring point with a high run factor, thus making it ideal for safety surveillance instrumentation. Safety interlocking against high levels of explosives on a cement pyro system is therefore best applied at this location.

How fast is a process change in the CO concentration?

Figure 1. Fast gas analysis with a response time of 5 sec. has been developed for explosion prevention in the cement industry. 34

Since a preheater exit analysis system is placed late in the pyro process, it is important to study the speed with which CO can be formed in the pyro process. Over the last four years CO process data has been collected from various plant visits, and helpful process managers have provided the following guidance as to how fast CO spikes can develop over time in the cement pyro process: f Plants with low CO spikes: 0.07 Vol%/sec. f Plants with average CO spikes: 0.18 Vol%/sec. f Plants with high CO spikes: 0.37 Vol%/sec. World Cement August 2021

The above data is highly dependent on a range of factors, including: plant design, fuel used, kiln operation, equipment failure, etc. The fastest pike of 0.37 Vol%/sec. was seen in connection with a fuel feeding system failure. Most plants will at some point see a CO spike develop with a speed of 0.18 Vol%/sec. or higher. This means that it will take only approximately 5 sec. for the CO concentration to reach a level of 1 Vol%. As this data is highly process/plant dependent individual evaluations must be made. This can best be done if the plant has access to historical data with a fine enough resolution time (3 sec.). Otherwise, a data collection with a resolution of CO of no more than 3 sec. can be used. When evaluating this data, it is important that it is collected over some time, typically 1 – 2 months, including as many upsetting conditions as possible to get a valid result.

CO gas analysis performance When the CO spike average is known, the preheater exit gas analysis system performance must be documented with respect to availability and quality. Availability at the preheater exit location is typically very good and is often +98%. The quality of the gas analysis system must be evaluated on several parameters. The two most important parameters when it comes to gas analysis safety

measurements are accuracy and response time. The typical accuracy and repeatability of a preheater gas analysis system is around 2% of full range. An accuracy of around 2% is more than sufficient to be used in connection with safety measurements. The response time of an installed preheater exit gas analysis system can vary significantly. Typically, gas analysis systems seen in the industry have a response time of 30 – 40 sec., with some even up to one minute. If an extractive analysis system is used based on a one probe configuration the response time must take additional time needed for the probe to blow back into account.

What gas analysis response time is safe? Various international and national standards provide the foundation for safe cement plant operations and explosion prevention. In most countries, fire inspectors visit production facilities regularly to make sure the legislation and relevant standards are followed, helping cement plant owners to operate safely. Internationally, the most commonly enforced standard is IEC 60079, Explosive Atmospheres (equivalent to UL 60079 and BS 60079). In the US, it is covered by the NFPA 69 Standard on Explosion Prevention Systems. While the relevant standards vary in content and definitions, one definition

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remains common for all – the Critical Safety Factor (CSF) of 25% of a given LEL for a gas. To be in compliance with the explosion prevention standards, the pyro process must never exceed the CSF for a given gas. Some examples of maximum limits for safe operation are given below: f Max allowed process CO concentration: LEL of 12.5 Vol% CO x 25% = 3.13 Vol% CO max. f Max allowed process CH4 concentration: LEL of 5 Vol% CH4 x 25% = 1.25 Vol% CH4 max. With a typical CO development speed of 0.22 Vol%/sec. it will take 3.13 Vol% CO/0.18 Vol% = 17.4 sec. for the process to potentially reach the max limit for CO gas in the process. For a gas analysis system to provide any analysis relevant for use in safety interlocking it must be able to analyse faster than 17.4 sec. Most installed preheater exit gas analysis systems have a response time longer than 17.4 sec. The response time of a gas analysis system will depend on the type of analysis system used. The industry standard at the preheater outlet is based on extractive gas analysis. The extractive gas analysis system collects a continuous sample from the process and sends it through a gas conditioning unit before it enters the analyser. The sample hose, gas conditioning unit and analyser all contain a volume. It is the time it takes to replace this volume that gives the response time of an extractive gas analysis system. An alternative technology is in situ gas analysers. The high dust load in the preheater exit (+25 g/m3) limits to use of very fast in situ analysers such as laser-based analyser units.

Many plants use a safety interlocking limit of around 1 Vol%. The chart in Figure 2 enables operators to evaluate the required response time needed by a safety analysis system. Here it can be seen (green lines) that an analysis system must have a maximum response time of 11.5 sec. in order to follow the standards for explosion prevention. For plant operators struggling with frequent CO spikes above 1Vol%, the question is how fast an analysis system has to be in order to raise a safe interlocking level to e.g., 2Vol% CO. It can be seen in Figure 2 (purple lines) that a response time faster than 5.75 sec. is required in order to follow the standards for explosion prevention.

Conclusion The interlocking of explosive gases based on a interlocking limit for CO of 1% has to be carried out by a gas analysis system with a response time of less than 11.5 sec. in order to comply with explosion prevention standards. Many cement plants are unaware as to the actual response time of their preheater exit gas analysis system, thus leaving the safety question open. The first step, therefore, will be to measure the actual response time of the preheater exit system and compare to the required time (Figure 2) in order to ensure safety. In the event that the existing preheater analysis system is not capable of providing the required response time, measures such as replacing the gas analysis system for a faster version must be evaluated.

Figure 2. The chart shows the correlation between a wanted interlocking level for CO and the required analyser response time in a process with CO spike development speed at 0.18 Vol%/sec.

World Cement August 2021

Oskar Cylkowski and Hans-Heinrich Reuter, TESTING Bluhm & Feuerherdt GmbH, outline the optimised laboratory testing processes of cement and mortar that allow human error to be significantly reduced and testing quality and quantity to be maintained. ement products are subject to exact quality control, which is crucial for current quality standards. In addition to workability, the relevant criteria are strength and especially durability in varied stress and climate scenarios. Since cement and mortar usually have a maximum particle size of no more than 4 mm, tests are largely modelled on cement tests

according to EN 196, but with all necessary specific extensions. These investigations should be conducted with automatic and calibrated equipment to minimise human influence and to ensure reproducibility of test results. In addition to stationary laboratories, fully-equipped 20 ft and 40 ft high cube container laboratories are very popular for physical tests.

Mortar mixing and sample preparation

and the crucial reproducibility in the laboratory is ensured. However, in order to allow absolute reproducibility, a mixer with free programming and automatic sand and water supply is recommended. Through this, human error in the preparation of mortar can be largely eliminated. As per the request of an internationally known cement group, the TESTING Bluhm & Feuerherdt company of Berlin has now developed a world-first mixer which has an extremely fine torque load cell and can reproduce the desired consistency with paddle resistance. The samples are usually produced in three-gang prism moulds measuring 40.1 x 40 x 160 mm for subsequent pressure and bending tests. Nickel-plated moulds are clearly advisable, since with such forms no rust can develop and lasting durable service is guaranteed. The moulds have numbered webs and, where appropriate, bores for measuring suppositories when testing changes in length. The measuring accuracy of the moulds, their angularity as well as their steel hardness fulfils the strictest requirements. With relatively small test specimens, inaccuracies can lead to large variations in the subsequent measurement results. For further tests, there are also six-gang moulds (10 x 40 Conceptual drawing of a mobile laboratory. x 160 mm or 20 x 20 x160 mm) as well as eight-shaped moulds for the tensile strength of mortar specimens. However, other dimensions in cube shape are also possible. This is somewhat determined by the used grain size of the added aggregate, or simply according to standard specifications such as edge lengths of 50 mm, 70.7 mm or 100 mm. Nevertheless, the strength of test specimens of varying dimensions cannot be Mortar mixer with water flow and dust extraction (left) and directly compared. For this mortar mixer with high sensitivity load cell (right). purpose, a so-called ‘form factor’ must be consulted, which as a rule must be empirically ascertained. The compression of the prism moulds occurs on the shock table or on the state-of-the-art vibrating table with quick clamping device according to a predetermined Exterior (left) and interior (right) view of a mobile laboratory. amplitude and time setting. The cement samples are prepared in standardised mortar mixers. This is necessary and important because the mixing time, mixing intensity and mixing speed has considerable influence on consistency, workability and many other features. In a modern mortar mixer there is the possibility of a defined and specially adapted gap width between the mixing tool and the mixing bowl. The mixer can work at a fast (285 r/min) as well as a slow (140 r/min) mixing speed according to the different standards. The standard mixing bowl has a capacity of 5 l. Furthermore, using a mixer that offers time and speed programming is strongly recommended. Then, the mixed programme is fully automated

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The cubes can be compacted with variations according to standards.

Sample storage As a rule, there are three different storage types for mortar samples: f Wet storage. f Damp storage: i.e. above 90% relative humidity, pursuant to EN or in case of 95% humidity pursuant to ASTM. f Dry storage. The temperature and methods of sample storage are crucial in terms of strength development. Again, test results from varied storage methods or temperatures are not to be directly compared with one another. Very often the duration and type of storage is specified, or there is a time-mixed storage method, e.g. 24 hour moisture storage may

be carried out, and then 28-day storage in water basins until testing. It is generally applicable to assume the 28-day strength from the cement test as 100% strength. In testing the early strength after one day, three days or seven days, corresponding strength reductions will be experienced. For damp storage of mortar prisms there are electronically controlled humidity cabinets for up to 48 three-gang moulds, as well as moist storage worktables for up to 36 three-gang moulds. In wet storage where heating and cooling are available, two-story water baths have proven to be successful, with each water storage unit holding up to 500 standing prisms according to size. Prisms can also be arranged lying in special-purpose baskets of stainless steel. The storage temperature is usually 20˚C in European countries and is often adjusted to be higher in hot countries by standard, for example, in Singapore, storage temperature is around 27˚C.

Physical testing

Nickel plated mould (left) and six gang mould (right).

Vibrating table (left) and humidity storage cabinet (right).

Waterbath for standing mortar specimen (left) and mortar strength testing machine (right). 40

Mortar strength testing In modern mortar laboratories, strength testing is carried out on calibrated servo hydraulic machines with load cells, servo valves and digital controllers with a peak picker in accordance with the variable loading rate. The machines come with testing room protection according to CE regulations, in the form of self-locking, transparent polycarbonate testing room doors and casing. The machines are accurate according to EN ISO 7500-1, class. 1. Modern testing machines have an optional PC interface for control and processing of the measurement results for analysis by means of special testing software. A further advantage of the servo-hydraulic systems is that a 3000 kN test frame for concrete cube or cylinder testing can be linked to the control system economically, without further hydraulics or controls. Flexural tests The bending test on prisms of 40.1 x 40 x 160 mm is carried out by means of automatic flexure testing machines. The testing instrument for the centre point bending test is preinstalled in the machine. A second possibility is a bending device, which World Cement August 2021

is put between the two round compression plates of a compression testing machine. Compression tests The compressive strength test is carried out on the two halves of a broken prism. The applied pressure area here is 40 x 40 mm (EN). However, compressed surfaces of 40 x 62.5 (GOST) or cubes of 50 x 50 mm (ASTM) and 70.7 x 70.7 (BS) are also possible. As a rule, these pressure surfaces can be achieved through appropriately mounted pressure plates or compression devices. The compression testing machines for mortar usually have a maximal compression strength of 250 kN, but with modern high-performance mortars, a machine can apply 600 kN or more. E-Modulus (Young’s modulus) A very important characteristic factor of the mortar is the modulus of elasticity. With modern equipment, the elastic deformation respective to force applied can be recorded and hence the material behaviour can be described in detail. The advantage is that it is possible to determine the elastic range of the material accurately and thus can provide more detailed characteristic values for the load capacity without plastic deformation.

cell according to Blaine Dyckerhoff and with double measuring cell performance. The same devices can also be supplied fully automatic with PC and suitable evaluation software. Workability and consistency One of the most important methods used is the flow table, according to Hägermann. Here, the spreading behaviour of a mortar cone is tested by means of an impact on a flow table. This can be automated on a device with electric drive and the automatic number of blow strokes takes place over the prescribed time period. Further important tests for dry mortar For the maturing heat, calorimeters are available, e.g. the Langavant calorimeter and the solution calorimeter. The air content of mortars is determined as 0.75 l or 1 l by the air entrainment meter.

Conclusion This new approach to a state-of-the-art cement and mortar laboratory allows automatic computerised testing procedures, evaluations and archives. Automatic devices have largely supplanted manual devices and test values are calibrated and have above all become reproducible. The influence of human error has been significantly reduced and the testing process in the laboratory has been optimised, addressing testing quality and quantity.

Tensile strength/tensile bond strength Classic tensile strength on eight-shaped moulds (ASTM) can be integrated likewise into the servo hydraulic testing machine, as all current systems have double-acting testing cylinders available. For most manufacturers, the tensile bond strength of their products is of interest. The tensile bond strength device with a maximum pulling force of 20 kN rips a defined circular area of 50 mm diameter off an under surface with a servo-controlled and adjustable load speed with an accuracy of 1% error margin. This method is applied particularly for coatings. The devices E-Modulus (left) and bond strength tester (right). are also calibrated. Determination of fineness of a surface according to Blaine The Blaine method is usually used to measure the fineness of dusts and powders. Here the results are given in cm2/g via an air-flow process through a defined powder bed. In addition to traditional manual devices, there is also a semi-automatic electronic Blaine base unit with a small measuring cell, alternatively with a large measuring August 2021 World Cement

Haegermann flow table (left) and air entrainment meter (right). 41

Max Tschurtschenthaler and Sanjit Shewale, ABB Process Industries, explain how digital applications, together with cloud and edge computing, can help manufacturers optimise performance, paving the way for smart, sustainable cement plants. ement manufacturing remains an energy intensive and emissions-heavy process, with the industry as a whole responsible for up to 9% of global carbon dioxide emissions. Sustainability, specifically reducing energy usage and greenhouse gas emissions, is therefore a key driver for cement producers as they strive to decarbonise plant operations and adhere to the goals of the 2015 Paris Agreement, while at the same time optimising processes and profitability. Using carbon capture utilisation and storage, fuel switching and thermal efficiency, and reducing the ratio of clinker to cement will help the industry achieve its goal of zero emissions by around 2040, or even sooner. Operators must also be cognisant that sustainability is a priority for the next generation of talent, and

that genuine environmental innovation is needed in order to address the skills gap. The digital revolution has a key role to play in this transition. Like all process industries, the cement sector cannot afford to lose the early adopter advantage when it comes to digital technologies and big data. Innovations like artificial intelligence (AI) and industrial analytics offer unprecedented visibility across the entire value chain, boosting throughput, availability and end product quality. Digital advanced process control (APC), for example, can help manufacturers reduce the electrical energy and manufacturing costs associated with grinding circuits. APC solutions control, stabilise and optimise processes such as coal, raw material and finished cement grinding, helping plants lower energy consumption and hit sustainability targets, while maintaining output standards.

AI and advanced process control A holistic approach to digital strategy is important. This involves transforming the process so that discrete or siloed functions are instead connected using internet of things (IoT) technologies, and then are automated. It is then possible to optimise these autonomous operations and for management functions to take place largely without human intervention within a secure environment. The key to successful digitalisation is, of course, data, collected from connected equipment and processes or using soft sensor models. Plant operators can use APC and advanced analytics models deduced from first principles or process data to predict or estimate process performance, even without reliable measurement data – for example, when real-world measurement would be too expensive – or to increase the frequency of data input and provide back-up for unreliable measurements. Analytics models include graphical (first principles), linear regression, non-linear regression, principal component analysis, artificial neural networks, and support vector machines. Here, advanced

analytics really comes into its own, allowing users to test various models and select the one with either the best fit or performance statistic.

How AI informs the Blaine process The Blaine process measures the specific surface area or the fineness of the cement, which is then given a Blaine number based on its quality. This number is important because process adjustments are made based on it, and infrequent sampling may impact both production and product quality. At present, in the majority of cases, the Blaine process takes place in a laboratory at a frequency of every one to two hours. However, this manual approach has significant limitations in that, despite being used for process control, it does not provide real time insight into the measurement process. Applying AI in the form of predictive quality analytics makes it possible to accurately forecast cement quality in real time at any point in the process, allowing plant operators to improve quality, stabilise industrial operations, and reduce variability, as well as avoid additional OPEX to hit quality targets.

The application of soft sensors

ABB Ability™ Genix industrial analytics and AI suite.

Soft sensors have established themselves as a viable alternative to traditional methods of acquiring data on critical process variables, process monitoring, and other tasks related to process control. In the context of the Blaine process, soft sensors have evolved to the point where they now employ data-driven machine learning algorithms to predict

Many key questions can be answered through data analytics. 44

World Cement August 2021

Blaine at specific production intervals using an array of relevant parameters including fresh feed, separator speed, grinding pressure, and mill DP. This can be accomplished by following these steps: f Collect historical data from control system for model training (production parameters and lab data). f Data cleansing (for e.g. removal of data during mill stoppages etc.). f Create a fully-automatic regression training model selecting best fit from the library of models. f Deploy the model and test the model accuracy using the real time online data. f Automatic data pull and retraining of the model if the accuracy is not met. f Predicted Blaine output is used for further control. The resulting prediction model transforms the cement quality process Blaine from an output process parameter to an input parameter, thus increasing the benefits from adaptive remodelling and tuning. For example, Blaine is unable to provide continuous real time measurements and is liable to provide infrequent sampling. Adopting this new soft sensor methodology enables plant operators to make more informed decisions based on relevant data in order to improve the efficiency of the process. The evolution of advanced analytics means that machine learning models are now more accessible and user-friendly. This, combined with proven domain knowledge, allows users to leverage the true power of machine learning (ML) algorithms to perform a multitude of tasks, from data cleansing and anomaly removal, to analysing the correlation of parameters and efficient interpretation of results. Partnering with a trusted technology provider such as ABB, which has a track record of domain knowledge and know-how around electrification and process control, is key to the successful application of leading-edge innovations such as soft sensors, advanced analytics and ML. Having served the cement industry for more than a century, ABB’s extensive portfolio of analytical and process modelling tools are designed to improve operational performance and energy efficiency.

Industrial analytics and AI suite At present, less than 20% of the data taken by distributed control systems (DCS) from operational technology (OT)

devices, networks and silos is used by companies, and only a fraction of that is analysed to improve business. With the emergence of new digital technologies, ML models can provide productivity improvements in addition to APC solutions, helping industrial plants to monitor and optimise their systems and related assets based on how they react to triggers such as age or operating condition. The ABB Ability™ Genix platform harnesses the power of digitalisation to improve operational excellence, process performance, asset integrity and performance, sustainability and energy efficiency. Sitting in-between the DCS and upper-level business functions, ABB Ability Genix helps cement industry clients to unlock value from OT, IT and engineering data by contextualising and integrating information from multiple systems spanning units, plants and even the entire enterprise ecosystem. The solution then applies AI and analytics to provide actionable insights that add business value. ABB Ability Genix’s 40+ preconfigured asset models can be customised, or have custom templates added, with rule-based models based on pre-decided thresholds. Alternatively, AI/ML

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models are trained with relevant datasets to provide prescriptive analytics. ABB Ability Genix then presents data on a variety of key parameters – emissions monitoring, system anomalies and asset alarms, for example – in customisable dashboards that are intuitive, highly visual and user-friendly. When talking about digital solutions, it is the additional ‘horsepower’ provided by advanced data analytics and artificial intelligence (AI) that is the real gamechanger. Cement plants may not be ready to transition to the cloud, but still want to take advantage of the additional computing ‘horsepower’ provided by data analytics and AI. ABB recognises this fact, and takes a phased approach based upon each individual client embarking on its personal digital journey. Securing the connection between the cloud, control systems and smart devices, the solution allows the edge to ingest data. ABB can apply an asset management solution to condition monitoring at the edge, as well as advanced analytics, for instance. When the client is ready to transition to the cloud, Genix simply makes the data available for cloud applications.

Optimising operations in India ABB was approached by one of Asia’s largest manufacturers of grey cement, ready mix concrete and white cement. The customer has 19 integrated plants, one clinkerisation plant, 25 grinding units and seven bulk terminals. With operations spanning five countries – Bahrain, Bangladesh, India, Sri Lanka and the United Arab Emirates – the client needed to optimise production and operating efficiency. Working together with ABB domain experts, the company used maintenance-oriented algorithms that alerted the client to the potential failure of a particular part or electronic device, allowing it to perform predictive rather than reactive maintenance. This, combined with a range of other digital solutions, including ABB Ability Expert Optimizer and ABB Ability Collaborative Operations, meant the customer was able to:

f f f f f

Increase quality by up to 15%. Reduce operating costs by 3 – 5%. Achieve ROI in eight months. Increase life cycle of assets. Increase productivity.

As assets such as conveyor belts are added to the operation, thickness and wear-rate monitoring, temperature monitoring and slip monitoring applications can also be included in the asset model. In this way, manufacturers can fully utilise the power of digitalisation to reduce energy usage and emissions, paving the way for the smart, sustainable and profitable cement plants of the future.

About the authors Max Tschurtschenthaler joined ABB as a commissioning engineer in 1998. He has worked various cement and mining industries roles at ABB since 2004, including Project Manager for Large Projects and Sales and Regional Manager for South East Asia and Australia. Max has led the Global Cement Industry Segment for ABB’s Process Industries since 2019. He holds a BsC in Electrical Engineering and Digital Signal Processing from the Eastern Switzerland University of Applied Sciences. Sanjit Shewale joined ABB in 2020 as the Head of Digital for Process Industries. He has more than 20 years of experience in the advanced industrial software space across many different verticals, including discrete. Most recently, he was with Honeywell’s Connected Plant & Advanced Solutions and Danaher’s Product Identification business. Sanjit holds a Chemical Engineering degree from McMaster University and a Management Sciences degree from University of Waterloo. At ABB his focus is on digital strategy and sustainability. He writes about ways to accelerate the shift to carbon-free and energy-efficient operation, autonomous systems, remote management, asset performance and more.

The benefits realised from advanced analytics and AI. 46

World Cement August 2021

Dr. Venugopal Thota and Marc Landragin, Welding Alloys, explain how advanced hardfacing alloys can enhance wear resistance and extend the life of cement grinding components.

ertical roller mills (VRMs) are successfully utilised for grinding raw materials in cement manufacturing plants. This technology was developed several decades ago, and has been predominantly used for grinding raw materials. Over the past ten years, VRM technology has been enhanced and it has

been adopted for grinding cement. VRMs offer significant advantages over other comminution technologies. One of the key concerns in any grinding operation is the wear of grinding components such as the rollers and table. The wear of grinding components results in the shutdown of operations to restore the rollers and table back to their original design profile.

Although the wear of grinding components is unavoidable, their operational life can be extended through the application of advanced alloys for hardfacing and rebuilding. The VRM is a piece of grinding equipment which combines the features of grinding as well as classification. As the name indicates, a VRM is a vertical machine with rollers mounted on a table. The table rotates using an electric motor and the materials are fed on the table. A gap is maintained between the rolls and table. Due to the centrifugal force on the table, materials are ground into finer particles below the rolls. This phenomenon results in comminution of large particles into smaller particles and at the same time, causes high stress abrasion on the rolls and table. The material to be ground is compacted between the roll and table and is broken into many pieces. Wear on the surface of the roll and table manifests in the form of chipping, gouging and detachment of any hard particles or deformation. In these circumstances, the hard facing solution adopted should be an optimised balance between yield strength, ductility, and hardness.

material contained 14.6% silica and total wear was 9.3 g/t. It is important to note that the typical free silica content in cement production operations is approximately 2.5%. For each 1.0% of silica over this percentage, wear rate can increase by 25%. Due to the high silica content used, the plant was experiencing problems with high abrasion of grinding components in its VRM. This particular VRM is one of the latest designs with six rolls and 8700 kW installed power. Welding Alloys has studied various options for hardfacing alloys. Iron base hardfacing alloys with more than 20% alloying additions are commonly used for the hardfacing of VRM rolls. The hardfacing alloys typically consist of an austenitic matrix dispersed with various carbides such as chromium carbide, niobium carbide, vanadium carbide, tungsten carbide, etc. In some of the alloy designs, other elements such as carbon, boron, nickel, molybdenum, etc. are added. The materials studied for the present application are listed in Table 1. Various combinations of hardfacing alloys from M1 to M5 resulted in 45 mm of excessive wear of grinding components in three months. Case study However, the cement plant had hoped that the Welding Alloys has recently worked with a hardfacing should last for at least six months of prominent cement plant at which the feed raw operation. When the combination of hardfacing alloys M6 and M7 Table 1. Typical chemistry (weight %) of hardfacing alloys are applied using an automatic studied in current application. welding process, the rolls and table can last for more than six C Cr Nb V Mo B W Others Fe months. M1 > 5.0 > 24.0 < 3.0 Balance After six months, the applied solution (M6 & M7) has resulted M2 > 5.0 > 24.0 + + < 3.0 Balance in 45 mm maximum wear on M3 > 5.0 > 24.0 + < 3.0 Balance roller tyre segments (equivalent M4 > 5.0 > 24.0 + + + < 3.0 Balance to ≤ 0.5 g/t) and 30 mm maximum wear on grinding M5 > 5.0 > 20.0 + + + < 3.0 Balance table (equivalent to ≤ 0.9 g/t). M6 > 5.0 > 20.0 + < 3.0 Balance The selection of appropriate high-quality hardfacing alloys M7 > 5.0 > 20.0 + + + + < 3.0 Balance and the appropriate application - No intentional addition technologies are key factors for + Added to the alloy. success. Hardfacing alloy (M6) is a product for severe abrasion resistance application. The deposit contains a tough matrix and complex chromium and vanadium carbides. The matrix does not contain boron and the hardness of Figure 1. Grinding components after six months of use. 48

World Cement August 2021

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the deposit is up to 66 HRC. The hardness of a typical vanadium carbide is about 2900 HV. Vanadium carbide is 45% harder than a niobium carbide. Further, as seen in Figure 2, the vanadium carbides are relatively small and near spherical, homogeneously distributed in the matrix. This resulted in further increased abrasion resistance of the deposit. Hardfacing alloy, M7 is another product for severe abrasion resistance applications. The deposit contains a tough matrix and high concentration complex carbides of chromium, niobium, vanadium, molybdenum and tungsten. The hardness of the alloy is up to 66 HRC. As seen in Figure 3, the high concentration of complex carbides results in a weld deposit with superior abrasion resistance. It is also worth noting that in the present study, the alloys containing boron such as M2, M4 and M5 did not perform well. Boron results in the formation of hard and brittle borides as well as boron carbides. These borides and carbides have high hardness but could not

Figure 2. Microstructure of hardfacing alloy (M6).

resist any impact. The lack of impact resistance results in spalling or fragmentation of the hardfacing alloy. The hardfacing alloy M6, containing significant amounts of vanadium carbides, works exceptionally well in high pressure and high abrasion conditions. The homogeneous distribution of vanadium carbide in a tough matrix results in a larger interfacial area between matrix and carbides. This larger interfacial area is extremely helpful for uniform distribution of load all along the hardfacing alloy. This makes the alloy resistant to spalling and impact, and thus prolongs the life of the components. This is due to the combined benefits of complex carbides. However, this alloy is to be applied in a limited thickness.

Evaluating operations It is important that the efficiency of VRM operations is evaluated on the basis of Total Cost of Ownership (TCO). The TCO approach considers not only the cost of hardfacing but also the cost of production loss and all other associated costs that are spent on the mill, which include but are not limited to electricity cost, reduced efficiency due to rapid degradation of grinding components profile, etc. The choice of a low performance hardfacing alloy may meet immediate requirements, however this may result in frequent shutdown of the plant and increase the number of hardfacing interventions. It is also important to note that welding or hardfacing processes introduce heat into the base material of the rolls. This results in the change in microstructure of the base materials. In order to achieve a longer life of roller tyres, the number of hardfacing interventions are to be minimised. This is achieved by using high performance hardfacing alloys such as M6 and M7.

About the authors

Figure 3. Microstructure of hardfacing alloy (M7). 50

Dr. Venugopal Thota is currently Managing Director of a welding and hardfacing company operating in several countries, as well as a prominent metallurgist and business strategist. Dr. Venugopal has developed several flux and metal cored welding consumables for hardfacing and cladding applications. In his early career, Dr. Venugopal was a faculty member at the School of Engineering, Monash University, Malaysia. World Cement August 2021

Gregory Shane Boston, S.B. Southern Welding, describes the process of manufacturing and installing a cement kiln stack.

ince the beginning of the 20th Century, the use of cement has become increasingly popular and it is becoming a strategic product for the economic growth of any country. In 2003 alone, world cement production reached 1.86 billion tpy. Between them, China, Japan and the United States are responsible for about 51% of worldwide production. Cement is obtained through a mixture of compounds that react in the cement kiln at high temperatures

(between 1400 – 1500˚C) to form calcium silicates, aluminates and ferrites, the main constituents of clinker. The kiln is heated by the combustion of different types of fuels. These fuels generate reactions and gases at high temperatures, and these temperatures correlate with the rate of metal corrosion. This corrosion affects industrial chimneys or stacks built to release gases resulting from combustion, or from a chemical reaction (‘tail gases’), into the atmosphere for their dispersion in the ambient air.

The corrosion rate of a metal doubles for every 10˚C increase in temperature. Therefore, if the corrosion rate measured in thousandths of an inch per year at 30˚C is 10 mpy, then at 40˚C it is expected to be 20 mpy and at 50˚C 40 mpy. S.B. Southern Welding recently had the opportunity to be part of a major project to manufacture and install an industrial chimney 13 ft 6 in. in diameter and over 388 ft high, for a clinker production system. S.B. Southern Welding has been in the custom fabrication business for over 20 years. The company specialises in components required in cement and other

industrial applications. The company handles all fabrication projects from buckets to the fabrication of stacks and anything in between, and welds and fabricates all types and grades of material, including mild steel, aluminium, stainless steel, wear resistant steel, and more. It also provides turnkey services from initial conception through to final commissioning. Using experienced and certified welders and fabricators allows strict dimensional requirements and customer deadlines to be more easily met. The company is a certified fabrication shop that can conform to a wide range of codes including: AWS D1.1, AWS D1.6, and AISC 360. S.B. Southern Welding facilities are equipped with all the necessary plate rolls, structural rolls, turning rolls, plasma tables, brake presses, and band saws needed to work on most fabrication products in house. Their facilities comply with all required OSHA and MSHA safety requirements.

Case study

Field activities during the installation process.

Fabrication of stack sections in S.B. Southern Welding’s shop. 52

S.B. Southern Welding recently completed a turnkey stack project for one of its customers. The stack was 13 ft 6 in. in diameter, 388 ft tall, and was fabricated in sections of approximately 48 ft and delivered on site for the crews to install. The base material for this project was all 316 stainless steels. Southern Welding’s engineering team worked closely with the customer to design and fabricate the stack to minimise the downtime needed for installation, as well as develop a product that would last substantially longer than the previous stack. Multiple site visits were made to verify dimensions and locate any possible interferences or issues that could arise during the demo and installation process. Upon completion of engineering, the company’s purchasing team negotiated with mills and distributors to get competitive pricing and lead times on all materials. Lead times for this project were negotiated from four months to 12 weeks to satisfy the customer’s downtime requirements. This project was fabricated in strict accordance with AWS D1.6 code. Weld procedures were created for each process and position. All welders required were then certified to each procedure. S.B. Southern Welding can provide all documentation of its weld certifications and procedures, at its customers’ request. Before, throughout, and at completion, S.B. Southern Welding provided a Certified Welding Inspector and a Quality Control Manager to satisfy both the customer’s requirements, and AWS code requirements. The company performed all processing of raw material, fit up, and welding of the complete stack. All loading and transportation to the job site was completed safely and without error. This job was performed in five main stages: World Cement August 2021

f f f f f

Technical design and planning. Fabrication. Removal of current stack. Installation of new stack. Commissioning.

Each stage of this project is important and represents a fundamental part of completing the project safely, efficiently and on time. Technical design and planning The design stage included planning activities in the field, selection of cranes, equipment, and trained personnel to perform the job. This stage also included the selection of materials and welding supplies, in addition to contemplating the activities of interpretation of the client’s specifications and creation of drawings for manufacturing and installation.

for each project. The sequence for removing sections, wind bracing, ports and interconnecting ducts is critical in maintaining the integrity of worn segments during the demo process. Before erection begins, the foundation must be inspected. In most cases, with care, the existing grout base is undisturbed. This provides a level base and saves the customer the time and expense of foundation rework. After each segment of new duct is set in place, the elevation is checked according to approved drawings and each segment is checked for level. As the erection continues, key measurements are continentally being checked for proper alignment and correct elevations of the ducts, ports, wind bracing and platforms. All segments are connected either by welding or bolting following applicable codes.

About the author Fabrication During the manufacturing process, it is important to contemplate and setup the layout required for the manufacturing of parts in the shop, as well as to establish a manufacturing sequence and the welding procedure to be used. Removal of current stack and installation of the new stack The demo of the existing stack or duct can be the most challenging and critical task of the entire project. Typically, these process components are far beyond useful life and require a great deal of detailed planning to ensure the successful removal of these often-deteriorated sections. S. B Southern Welding has designed and engineered devices that have proven to be safe and efficient for removing each segment. Before a removal plan can be established it is crucial to completely understand the existing condition of the segments to be removed. This can be done several ways and will determine the methods for removal based on segment condition. S.B. Southern Welding has a team of highly skilled experts with proven experience on the planning and execution of process duct/stack removal (as large as 14 ft in diameter and in excess of 400 ft in elevation). The entire project was carefully planned with the project owner, supplier and crane services. From the placement of the crane to the staging of new and old segments, the plan ensures consistent flow for removal through the installation sequence and is different

Gregory Shane Boston began his career at Texas Industries, Inc. in 1990, working in an entry-level operating position. He soon obtained the position of Maintenance Manager, leading a team of more than 30 employees. In September 2006 he decided to form his own company: SB Southern Welding LLC.

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Jacob Becker Ryttergaard, FLSmidth, explores the vast potential offered by digitally-based, people-powered services such as online condition monitoring. hen looking at the future of cement manufacturing, there is huge potential to increase efficiency and reduce environmental impact through digitalisation. From an operational perspective, it enables processes to be streamlined by automating controls that would previously have been manual, removing the potential for human error and making calculations much more quickly than people ever could. And when it comes to maintenance, those quick calculations, combined with expert insight, enable the early warning signs of potential failure to be identified. Armed with that information, plant operators can act at the right time, eliminating the occurrence of unplanned downtime.

Digitalisation, then, holds the power to both increase operational efficiencies and enable a predictive maintenance schedule that extends equipment life and reduces costs. But how can that power be harnessed in a real plant setting?

Monitoring kiln health Let’s say, for example, that suddenly cracks are noticed in the kiln tyres. Everyone panics – this is a problem that needs to be dealt with urgently. But the next maintenance shutdown is not due for another nine months. Can the operator afford to take the risk, and wait and see how far they can push it? Or should they be thinking about a more immediate shutdown, with all the associated costs? Without all the data, it is impossible to calculate the risk. But with the right data, the problem could have been avoided altogether. And that is where digital solutions like online condition monitoring services come in.

FLSmidth offers online condition monitoring services across the plant. For the kiln, these services enable plant operators to continuously gather data that was not previously available, and use it – in combination with the continuing support provided by the company’s kiln specialists – to keep a close eye on kiln health, including kiln components that would typically only be inspected every 2 – 3 years. This means, for example, that unusual kiln overload would be detected long before the tyre cracks. The problem could be resolved before it becomes urgent, saving both the cost of unscheduled downtime and all the stress that goes along with it.

Data that informs

The act of gathering data is not new, of course. The kiln is likely already equipped with certain sensors, monitoring the bearings, hydraulic thrust device and kiln drive, and the plant is probably already using a control platform to operate the kiln. The issue is how the data is used. In all likelihood, most of it is What is being monitored? looked at in isolation, and some of it is not looked at very often at all. This presents a risk that key indicators of wear will be The list below comprises all the kiln components missed, along with the root causes that that can be monitored with the online condition could go on to become major kiln failures. monitoring services, though it should be noted that By adding new sensors, it is possible to the actual provision depends on the service package also monitor kiln crank, kiln shell ovality, chosen and the specific equipment to be monitored. kiln drive vibration and axial balance – all on a 24/7/365 basis. This provides most Bearing monitoring of the measurements that would be gained f Identify overload from a Hot Kiln Alignment (HKA), meaning f Identify improper lubrication that all the data needed to schedule the f Analysis of bearing temperature trend HKA and maintenance activities when they f Root cause analysis on hot bearings are needed most is already available. Hydraulic thrust device monitoring f Kiln axial floating and cycles Expertise that empowers f Kiln axial load Data without insight is no good to anyone. f Health of hydraulic system The data needs to be collected, analysed Kiln drive monitoring and reported back in a way that is f Kiln drive power consumption meaningful and actionable – which is why f Kiln drive vibration FLSmidth’s online condition monitoring f Detection of gear issues services are digitally-enabled, but also f Detection of facet formation people-powered. All of the sensors are f Protection of planetary gear collecting data all the time, and feeding it to FLSmidth’s cloud application, which Axial balance is designed to detect any abnormal f Monitor thrust bearings temperatures events or ‘behaviour’. If anything out of f Monitor thrust direction of individual supporting the ordinary shows up, an alarm is sent roller to a 24/7 Global Remote Service Centre f Full overview of axial balance where the data is analysed by kiln experts. f Kiln crank These are people with plant and process f Kiln shell ovality experience, who can decide the context of an alarm and recommend what action Plus, with ECS/CemScanner™ integration (if the plant might need to take in order applicable), it is also possible to detect refractory to solve whatever problem has arisen. failure and the early signs of hot spots. These recommendations are put into a

World Cement August 2021

report for the plant to act on, and these case reports are in addition to the regular condition reports that come as part of the online condition monitoring services package.

Case study: How condition monitoring saved a kiln in Egypt A customer in Egypt had been having some issues with their kiln for a while. With the condition monitoring system, FLSmidth was able to identify that the kiln axial floating was unstable, and this was causing pump cycles as low as five minutes. Using this data, experts worked with the plant on a root cause analysis, which suggested a hydraulic leak was to blame for the instability – the result of a defective valve. This kind of defect would have been virtually impossible to identify without the condition monitoring system and would ultimately have resulted in downtime, and potentially even failure. In this instance online condition monitoring services saved substantial costs and allowed the plant to replace the valve in a stress-free, timely and cost-efficient manner.

No matter where you are

problem. In between planned on-site services, which will always be needed to maintain a kiln correctly, many problems can be solved without sending anyone to the site. This reduces the cost of services, not to mention the environmental impact of all those air-miles.

Decisions that drive efficiency The major benefit of all this information is the ability to be more strategic about maintenance. No more running to failure (unless it makes sense to do so). No more nasty surprises. Instead, maintenance can be planned in such a way that best suits the production schedule, budget, and the urgency of the repair work. This not only reduces the cost of downtime, but also the duration – enabling productivity to be optimised and remain competitive. It also reduces the pressure of downtime because the nature of the problem is already known and preparations can be made accordingly. At its core, managing a maintenance schedule based on data about the current kiln condition enables operators to: f Extend the life of rotating parts. f Improve the life of lining and kiln shell. f Avoid kiln shell constriction and reduce stress. f Avoid girth gear breakdown. f Identify alignment issues. f Stabilise bearing temperatures. f Reduce power consumption.

While on-site services remain an important and necessary provision, the benefits of remote services have really shown themselves over the past 12 months as the world has faced the challenges associated with the COVID-19 pandemic. By coupling on-site tools – such as these condition monitoring sensors or when helmet-mounted cameras are used – together The more efficiently a kiln runs, the more with remote capabilities via the 24/7 Global sustainable the operation. This demonstrates Remote Service Centre, FLSmidth has been the potential of digitally-enabled, able to continue to serve its customers, share people-powered services. its expertise and help with a wide range of projects, from commissioning new kilns to repairing older machines. Even as travel restrictions ease, these remote services will continue to be important to customers who recognise the benefits: Remote services guarantee a quick response, since FLSmidth’s service centre is manned 24/7 and the company is able to monitor continuously – which means action can be taken more FLSmidth’s online condition monitoring services are digitally-enabled, quickly, resulting in a but also people-powered. faster resolution to a August 2021 World Cement

Ian Breeze, Bowman International, explores the latest developments in split roller bearing design and the related maintenance advantages.

ollowing a period of intense innovation using state-of-the-art 3D printing, the humble split roller bearing can now outperform other split roller bearings and solid bearings for high-load applications. Alongside this increased performance comes impressive maintenance benefits too, creating a real shift towards specifying split roller bearings in cement industry applications that have long relied on conventional solid bearing products. In very simple terms, a bearing is a mechanical device that either guides or confines the motion of the moving parts in a machine. In doing so, the bearing reduces friction amongst components, improving the rate of wear and extending the working life of the equipment. Split roller bearings, in particular, are renowned for their ability to improve efficiency, saving time during installation, inspection, and maintenance, particularly in applications where access to the shaft is limited. Yet, despite being a stalwart of the manufacturing industry, split bearing design has remained relatively unchanged since they were first introduced in the early 1900s. The pressures of modern manufacturing, not least the introduction of more automation and increasingly complex machinery, has meant that bearing designs have been forced to evolve and innovate to reduce maintenance time and handle higher loads, in particular the ability to handle both radial and axial loads.

Reducing maintenance through correct specification One of the most common causes of bearing failure is incorrect specification. Innovation continually shapes the components used in industry, so keeping abreast of key changes can help engineers to specify more suitable bearings as and when they become available. This is especially important when specifying bearings for high-load environments because if the wrong bearing is used, it may not carry the required load effectively, leading to damage and potential failure. There are two main types of load. Radial load refers to the loads acting at right angles to the shaft, and axial loads are applied parallel to the shaft in both directions. While many

bearings are designed to handle either axial or radial loads, high-load applications in heavy side industrial applications often require a combination of the two – a requirement that, due to limitations in manufacturing, has been left largely unmet. To best serve the needs of high-load applications that have both types of forces in play, many bearing manufacturers and OEMs will use a combination approach, using a pair of bearings to accommodate the load in each direction. The shortcomings of this method mean more space requirements within the machinery, increasing its overall footprint on the factory floor, as well as potential complications with both assembly and access for ongoing maintenance. While there is an increasing number of bearings on the market that are designed to handle both radial and axial loads, they work by inclining the radial elements to give some axial capacity. In doing so, they trade off radial capacity for axial, a solution that limits the axial load capacity, limiting application usage or putting the bearings at risk of failure. Both radial and axial load specifications directly relate to the strength and rigidity of the bearings, shaft, and overall machinery. Exceeding these specifications in an application with a high axial load may result in damage to the bearing and have a different impact on efficiency. In fact, studies suggest that exceeding either radial or axial load specifications by 10% may reduce the lifespan of the components by about 1000 hours, as well as running the very real risk of unplanned downtime. For applications with a high axial load, these solutions are far from ideal.

More effective load management and maintenance

Split roller bearings.

Bowman advanced split roller bearing. 60

Recent innovations in the manufacture of split roller bearings, and the use of additive manufacturing to create more complex component geometries, are allowing bearing manufacturers to accommodate axial or multidirectional loads as a primary consideration, extending system life and reducing downtime. With no need to invest in expensive tooling, or set up traditional manufacturing production lines, it is possible to experiment with design features in a way that simply was not possible previously. For Bowman, the technology has facilitated the creation of a bearing that offers a substantial increase in axial and radial load capacity, as well as increased durability, functionality and turnaround time. In a standard split roller bearing design, the rollers run against the outer race lips and clamp rings on the inner race assembly of the bearing, creating stress, friction, and a lower tolerance for axial loads. Using engineering-grade 3D-printed Nylon-11 and the latest printing technology, the company has been able to create a bearing design that removes World Cement August 2021

the axial locating lips from the bearing outer race. This means that the radial roller length, as well as the actual number of rollers, can be increased, giving a higher load capacity and an approximate increase of x5 radial L10 life.

Increasing axial capacity By adding axial roller and cage assemblies to their design, Bowman has overcome the issue of reductions in axial load by using three sets of rolling elements to allow independent handling of the radial and bidirectional axial loads. The design incorporates the usual benefits of a split bearing system, including bearing changes of up to ten times faster than solid bearings, while increasing the radial capacity by 25 – 75% and the axial capacity by 1000% compared to standard solutions. In the UK, downtime costs manufacturers £180 billion per year; this is arguably the biggest contributor to production and profitability losses. With bearings critical to the efficiency and operability of industrial machinery, investing in the right component for the job is a simple yet effective way of minimising the likelihood of unexpected downtime. For this reason, due consideration should be given to ensuring that bearings meet type and load capacity requirements, while also taking into account all important lifecycle costs and ease of installation and maintenance.

Ease of maintenance Reducing downtime is an important driver in any industry, especially those with restricted system access, mission critical operational parameters or high levels of customer demand to meet. It can be tempting to skip regular maintenance or cut corners to get equipment back up and running quickly, but this will only lead to further failures. Selecting bearings that offer easy installation and maintenance processes can keep downtime to a minimum and performance optimised. Choosing split bearings over solid bearings for example can save time during installation and maintenance because they are assembled radially around the shaft. This eliminates the need to disconnect the coupling and move other equipment, such as motors, gearboxes or pumps out of the way to access the shaft, making installation up to ten times faster. The Bowman Advanced Split Roller Bearing uses the rollers to lock the two cage halves together, eradicating the use of small and easy-to-lose clips and other locking components. Further enhancing the performance of this split roller bearing is a triple labyrinth seal which not only offers a tighter seal than other split bearings, but also reduces the need for costly removal, machining or replacement of worn shafts. When a shaft becomes worn, engineers can simply fit a new extended seal covering the August 2021 World Cement

undamaged part of the shaft, without compromising performance and without the need for extended downtime. These particular split roller bearings are even dimensionally interchangeable meaning they can be retrofitted directly into existing bearing housings and maintenance engineers can quickly and cost-effectively improve radial and axial load capacities. For highly corrosive environments such as those involved in cement production, selecting the right bearing can significantly reduce maintenance and downtime. It is always tempting to simply re-specify the split roller or solid bearings that have been used for many years, but keeping up to speed on bearing innovation, and following the trend towards advanced split roller bearings can lead to real time, cost and performance benefits.

About the author Ian Breeze is an Aeronautical Engineer with over 25 years’ experience in engineering. With an aerodynamic background in automotive design, Ian went on to work as an applications and service engineer for SKF Cooper, before joining Bowman International Limited, firstly as an application engineer before progressing to his current Technical Director role. Applying the latest technologies, Ian has designed and developed the Bowman Split Roller Bearing range of products, and now oversees this project based at the company’s Birmingham UK facility.

Radially split assembly. 61

SHARING THE

SECRETS TO SUCCESS

World Cement spoke to Thomas Serr of Kalenborn International as the company celebrates its 100th Anniversary and shares the secrets to its longevity and success.

World Cement (WCT): Kalenborn International is celebrating its 100th Anniversary this year. What would you say were the key moments in the company’s history? Thomas Serr (TS): In the 1920s, cast basalt was developed as a material and processed into the first products, e.g. insulators for the Paris subway system. From 1935 onwards, Kalenborn succeeded in acquiring customers from the coal mining and metallurgical industries. Over time, Kalenborn cast basalt Abresist gained importance as industrial wear protection. In the 1960s, sales were expanded to the United States, India and Australia. With the foundation of the Abresist Corporation in Urbana (Indiana) in 1977, an assembly plant for the American market was established. A stronger sales force and a staff of technical advisors were also put in place. The company’s expertise in the production of cast basalt as a mineral material has since been extended to other materials. Metallic and ceramic materials, but also engineering plastics and compounds, now form a wide range of wear-resistant products. Internationalisation began in 1996 with the acquisition and founding of factories in Poland, Canada, Brazil, Hungary, The Philippines and France. The Vietnam operation was also recently founded. This global network of companies brings together all its services under the Kalenborn brand name, providing a high level of brand consistency.

WCT: What is the secret behind the company’s success and longevity? TS: What began in 1921 as Schmelzbasalt AG has become an internationally successful wear protection company a century later. We have only achieved this by consistently aligning our products and solutions to the requirements of the market. Today, we offer

a complete range of wear-resistant materials, which we produce in our own factories and whose service life we are constantly working to improve with our technical laboratory. With 12 companies worldwide and 25 representatives on five continents, we are able to be close to customers wherever they are. All Kalenborn companies offer the complete product range. This starts with wear-resistant materials, continues with wear-resistant plant and pipe systems, and extends to assembly and service.

WCT: The challenges facing industry today are very different from 100 years ago – what would you say were the greatest challenges faced by cement manufacturers in the 21st Century? TS: The German cement industry for example has invested more than half a billion euros in recent years to make the manufacturing

One of the largest global producers of building materials relied on Kalenborn solutions at a California cement plant to solve problems of premature wear and clogging on a pneumatic conveyance line for alternative fuel. Kalenborn supplied around 250 ft of 8 in. pipe, using a combination of Abresist linings on straight runs, Kalocer on all elbows and follower spools for extra wear-resistance, plus Kalmetall for the T-Injector on the feed end. In addition, Kalenborn modified the design by increasing the radius of the elbows, thereby significantly reducing the wear rate and pneumatic energy required to move the RDF. By combining optimal wear protection products and custom solutions, Kalenborn was able to significantly extend service life and improve operational efficiency at the customer’s plant.

process future-proof. The industry’s efforts are particularly concerned with reducing emissions of Carbon Dioxide (CO2), Nitrogen (NOx) and Mercury (Hg). With the use of alternative fuels, the industry improves CO2 performance, but for climate neutrality, new technologies are needed to reuse or enrich the captured CO2 in the cement plant. The constant start-up and shut-down of the plants with high emissions of CO2 during repairs due to wear must be avoided.

WCT: What is your vision for the future? TS: 100 years of Kalenborn – that means 100 years always on the move. This anniversary fills us at Kalenborn with joy and pride and is an incentive for the future. We will hopefully also be able to face the changing times over the next 100 years. We want to continue to focus on new products, new markets and new customers while acting sustainably along the entire value chain. We want to continue to invest in the qualifications of our employees and give them a high degree of self-determination in their work. They are the basis of our success.

WCT: How is Kalenborn helping cement manufacturers meet these challenges?

About the author

TS: We are also facing up to the challenges of sustainability. We act sustainably across the entire value chain. We use natural materials for the cement industry such as basalt and ceramics, which are regenerable. We recycle materials and use special processes for lining pipes and bends so that customers can reuse products. Our wear protection extends the operating life of the plants and conserves our customers’ resources. We improve the CO2 balance.

Thomas Serr is Head of Marketing and Communications at Kalenborn International. He is responsible for the development, coordination and implementation of internal and external communication as well as marketing strategies. After studying business administration with focus on marketing and management in Berlin, he acquired in-depth knowledge of marketing and corporate communications in longstanding leadership positions as Head of Marketing in producing industrial enterprises.

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World Cement August 2021

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