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MARCH 2017
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MARCH 2017
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Editorial Director Dr Robert McCaffrey
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Welcome to the March 2017 issue of Global Cement Magazine, the world’s most widelyread cement magazine, which contains the usual up-to-date industry news, technical articles and features. This issue contains the second part of Xavier d’Hubert’s report on burners for the cement sector, with contributions from all of the major players from Page 10 onwards. We also look at the lime sector (Page 24), roller press maintenance (Page 20) and plant efficiency (Page 29). There is also a review of the 11th Global CemFuels Conference & Exhibition, which took place successfully in Barcelona, Spain in February 2017. Read our review of the event from Page 34 onwards. Our country focus in this issue switches to Brazil, the scene of a major downturn in cement demand in recent years. Over-reliance on oil and mineral exports, coupled with political instability at home and the wider ‘global economic malaise’ have led to a staggering decline in production in the country, from 72.1Mt in 2014 to 57.2Mt in 2016. This is still a very significant market in global terms, albeit one that has had to adjust to a harsh new reality. And it could get worse for Brazil in 2017, with the President of the national cement association stating recently that the situation facing the sector was ‘the worst in the industry’s history.’ Read the whole report from Page 50 onwards. In the global cement news this month we see a variation in fortunes for the big cement producers around the world. Cemex has reported a slight improvement in performance for 2016, with a 6% improvement in underlying profits, albeit with regional variations. US-based Eagle Materials also reported improvements in its finances for the nine months to December 2016. Over in Europe, it appears that the fortunes of Italian producers may finally be picking up. Both Buzzi Unicem and Cementir reported moderate improvements in their 2016 results and HeidelbergCement reported in its results that it had benefitted from the new assets that it picked up when it acquired Italcementi. Meanwhile in Spain, Cementos Portland Valderrivas highlights the continuing malaise in that country, with a swing to a massive loss in 2016. We await to see how the results of LafargeHolcim and others fit in.
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GLOBAL CEMENT CONTENTS
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Global Cement articles 10 Latest burner profiles
10
Combustion consultant Xavier d’Hubert looks at the latest designs of the major cement kiln burner manufacturers, with contributions from KHD, FCT, FLSmidth, Unitherm, Polysius (tkIS), Dynamis, Fives-Pillard, A TEC and Rockteq.
20 An introduction to roller press maintenance
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Serdar Esendemir outlines ways to limit abrasion and effectively maintain roller presses, based on experience with Mardin Çimento’s four roller presses used for cement production.
24 Lime contract round-up We present a range of recently-completed and ongoing projects from around the global lime sector.
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29 Improving efficiency at an Egyptian cement plant Cement efficiency specialist Osama Aly Ahmed describes a case-study in which an Egyptian cement plant was able to monitor and improve its overall energy efficiency using a number of measures.
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34 11th Global CemFuels 2017 - Reviewed Robert McCaffrey reviews the 11th Global CemFuels Conference & Exhibition, which took place successfully in February 2017 in Barcelona, Spain.
38 Product and Contract News Plant project for thyssenkrupp Industrial Solutions in Algeria; Belgian order for Gebr. Pfeiffer; Loesche lands Bangladesh deal.
European cement 40 European cement news
34
Changes to EU ETS approved; HeidelbergCement results boosted by Italcementi; CPV records massive loss.
Cement in the Americas 47 American cement news
38 6
Global Cement Magazine March 2017
Cemex offer for Trinidad Cement accepted; Argos launches Honduran plant; Cemex sees improvement.
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GLOBAL CEMENT CONTENTS
50 Brazil: Still finding the bottom of the curve... Once the epitome of the rapidly-rising BRIC group, Brazil’s economy and cement sector have taken a massive knock since 2008.Here we look at the country’s cement producers, recent production and consumption trends, recent news events and sector outlook.
Asian cement 57 Asian cement news
40 47
Vietnamese exports fall; Production slows in India; Taiwan Cement chairman dies after fall.
Middle East and African cement 60 Middle East and African cement news CBMI hands over plants in Algeria and Nigeria; Lafarge faces probe by French government over alleged ISIS dealings in Syria; Wind farm for Mombassa Cement.
Regulars and comment 63 Global Cement prices
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Cement prices from around the world: Subscribers to Global Cement Magazine receive additional information.
64 Subscription form for Global Cement Magazine Use this form to subscribe to Global Cement Magazine, or subscribe online at www.GlobalCement.com.
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65 The Last Word This issue: How many bird species are there at your cement plant? Join the Global Cement Bird Watch!
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66 Advertiser Index & Forthcoming issue features A list of advertisers and editorial preview for next two issues.
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GLOBAL CEMENT: BURNERS
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Xavier D’Hubert, Combustion Consultant
Latest burner profiles In this article each cement burner OEM was given the opportunity to present the main features of its burners as well as provide insight into design concepts and their evolution. The emphasis is on the latest offering of each OEM, even though several still sell burners from previous generations. As not all OEMs responded, the excersise has been completed using information found in the available literature. For more information on the evolution of burner design trends, see the February 2017 issue of Global Cement Magazine.
T
his article will present information from burner OEMs regarding the following burners:
• KHD Pyrojet; • FCT Turbujet; • Unitherm MAS; • Polysius (tkIS) Polflame; • Dynamis D-Flame; • FLSmidth Jetflex; • Fives-Pillard Novaflam; • A TEC-Greco Flexiflame; • Burners from Rockteq International. Each entry comprises text from the OEM unless stated otherwise, followed by the author’s comments. They are in no particular order. Companies that offer kiln burners for lime or mineral applications are not represented. Nor are cement companies that design their own burners, for example Lafarge (prior to the LafargeHolcim merger) and Buzzi Unicem, as those burners are rooted in some of the OEMs’ designs.
KHD Pyrojet Below: Traditional KHD design with standard cooling tube. Below right: New design with cooling tube.
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KHD has supplied kiln burners for more than 100 years. The modern burner systems from KHD started with the high-pressure gas burner without primary air in 1979. This burner featured a relatively small number of independent nozzles, from which the gas emerges at a supersonic velocity. This creates a strong
Global CementMagazine March 2017
suction effect on the surrounding secondary air and hence mixes the air and fuel efficiently. The single-nozzle design was then applied on coal-fired burners. Prior to 1979, coal burners mainly used swirl air for flame stabilisation and axial air through an annular gap for additional shaping at the outer circumference. This outer axial air gap created a layer of cold air around the fuel cone, which delayed the mixture of fuel and swirl air. The introduction of a nozzle ring for axial air, or ‘jet air,’ greatly improved the combustion: The jet air entrains the secondary air with high-velocity jets and mixes it in a more efficient manner, with the fuel cone in the centre. This is the KHD Pyrojet burner. However, environmental focus in the 1980s revealed that, due to the high flame temperature and the availability of oxygen and nitrogen at the base of the flame, the burner gave rise to high levels of NOx. To moderate these emissions, the amount of jet air was reduced and the pressure increased. In 2000 the nozzle tip was simplified, leading to the current, all-welded design, with a more compact tip. At the same time, KHD introduced the cooling tube to the Pyrojet burner. The cooling tube carries the refractory of the burner and protects the support tube that bears the static load of the burner. It enables a fast exchange of the refractory in case of failures, while the emergency cooling air protects the burner support tube from further damage. The required cooling air demand is 1.5% of the total combustion air. While 10-15 years ago, burners often featured many central channels and pipes for various alternative fuels, both operational results and CFD studies showed that burners should not be unnecessarily large. With intelligent mixes of fuels or slide assemblies that can be exchanged during operation to adapt to different fuel scenarios, the diameter of the burner can be reduced to a reasonable minimum. The advantages of easier burner adjustment and generally better com-
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GLOBAL CEMENT: BURNERS
bustion should be balanced against the trade-off of higher NOx emissions, an increased electrical energy demand for primary air fan/blower and, of course, the reduced cooler efficiency, as the cold primary air reduces the use of secondary air. Today’s ever-changing fuel scenarios require a flexible burner design concept. KHD offers an adjustable swirl system for a better distribution of solid alternative fuels, which are injected through the central pipe. Xavier d’Hubert (Xd’H): The KHD Pyrojet is one of the best known burners in the cement industry. KHD had attempted to follow the trend of adjust able primary air jets with the Pyrostream burner but this design has not been developed futher as the mechanical adjustment is costly and requires more maintenance. A burner that could incorporate all the novelties and features of all competitors would not result in a good overall solution.
FCT Turbujet FCT is an Australian combustion specialist. Its approach to cement kiln burners focuses greatly on scale modelling and CFD simulation. The Turbujet™ is a high momentum kiln burner that provides a very firm and steady flame that can be designed to fit every kiln situation. Primary air slots provide effective jets that result in better mixing of the secondary air into the flame. The swirl air channel is located on the inside of the petcoke/coal channel in order to provide better dispersion of the fuel cloud. This configuration provides an intense mixing of the pulverised coal, resulting in an ignition point close to the burner that makes it possible to burn low volatility fuels. The flame shape is controlled by a single valve that balances the total amount of primary air between the axial and swirl air channels. The amount of primary air is controlled by a variable frequency drive. Most FCT burners have their configuration specifically optimised for the individual kiln using CFD modelling. Parameters used include: Amount and pressure of primary air; Positioning of the burner into the kiln; Best thermal profile; Fuel injection velocities, and other parameters. For solid alternative fuels, FCT has developed the Lofting Air™ system
in order to improve the trajectory of particles into the kiln. This avoids unburned particles falling to the clinker bed and associated problems with localised reducing conditions and brown clinker. The amount and pressure of the air, as well as the angle, is customdesigned depending on the specific characteristics of the alternative fuel, including its particle size, shape, lower heating value, composition and other relevant parameters, as well as the specifics of the kiln. Typical values for used for the Turbujet™ cement kiln burner are: Primary air pressure: 250–700mbar; Primary air rate: 6–10 %; Axial burner momentum: 6–14N/MW; Coal velocity: 26-32m/s; Solid alternative fuel velocity: 35-45m/s. Where NOx needs to be kept at a minimum, higher primary air pressure (up to 700mbar) is used to minimise the quantity of primary air while keeping flame recirculation. FCT burners typically provide early ignition of fuel (close to the burner tip) which has been shown to reduce peak flame temperature and produce less NOx. Other measures can include segmentally variable primary air, leading to variations in fuel/air proportions within the flame, or water sprays that reduce peak flame temperature. FCT has addressed the main wear and maintenance problems on the burner with a coal channel that has protection from either ceramic tiles or a hard wearing steel, such as ‘Duraplate’ or similar. Alternative fuel pipes are made from specially-hardened steel to protect against wear.
Left: An FCT Turbujet burner in the workshop.
Xd’H: Clients appear to be more and more reluctant to pay for specific studies (CFD and modeling). Therefore burners have to have features that allow the operator flexibility in fuels mix, load, NOx control, flame shape and intensity.
Unitherm MAS Unitherm has been a burner company for 60 years and, at the start, offered early versions of the then standard three-channel burners. In the 1990s the company invented the Mono Air System (MAS) burner. At the time it was the only burner that offered a combined axial and radial primary air channel that
Left: A modern Unitherm MAS burner.
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GLOBAL CEMENT: BURNERS
Right: A Polflame and separate injection pipe in a German cement plant.
ends in adjustable (angle-wise) flexible jets. This was a fairly revolutionary concept that demonstrates how sound design and marketable ideas can go together. One of the arguments for the MAS design is that a single adjustable air stream is more efficient and effective than mixing two different streams. It is more efficient as there is no energy loss in the mixing of the two air streams and is more effective as the large angle variation of the primary air exit jets strongly shape the flame. The shape can be easily reproduced using a simple crank with a scale of 0-10 that is mounted at the cold end of the burner. Because of this efficiency, lower primary air pressure (and exit velocity) can be used, avoiding the need for high pressure blowers. Also a single primary air channel reduces the diameter of the burner, an important point for good combustion. While initially kiln engineers worried about moving parts inside a burner, the flexible hoses and the rings used to vary the angles of injection have proven to be remarkably sturdy and smooth to operate. The mechanism rarely has to be repaired. The MAS burner offers several optional features such as a disconnectable outer-pipe tip; a pneumodeflector© for lifting solid alternative fuel particles up into the flame, and a focus on the ejection angle of the coal stream (convergent or divergent) to help control NOx emissions. Xd’H: The notion of ‘effective momentum’ was first brought to the market by Unitherm. Even with a large adjusting capability, some operations end-up with an extreme setting.
Polysius (tkIS) Polflame The industrial culture of the more than 150 year old Polysius AG now continues under the new name thyssenkrupp Industrial Solutions (tkIS) OU Cement Technologies. Over the years Polflame burners were developed to cope with new requirements, first for direct firing of the kiln using mill exhaust gas containing coal dust, then indirect firing systems and today, the wide variety of alternative fuels.
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Global CementMagazine March 2017
In the 1990’s fuels that were difficult to ignite, such as anthracite and petcoke, began to be used. Polysius therefore began to find a new burner technology, leading to the development of the Polflame VN burner. The concept of adjustable ejection angle with moving nozzles allows for the setting of the flame characteristics depending on the burnout of the coal or solid alternative fuel. Alternative fuels substitution and stricter emission limits are the drivers for the ongoing development of the burner, which is designed to fulfil such requirements as high clinker quality, smooth kiln operation, (e.g. kiln inlet temperature control), and a high flexibility with regard to the fuel mix. However, the burner is not the only means of feeding the sintering zone with fuel. In several cases separate fuel injection pipes are used. The reason is that alternative fuels can only be injected when the temperature level in the system is high enough and the complete burnout is assured. That is why the kiln, after ignition, is usually started with a ‘traditional’ fuel, such as lignite. For the start-up the burner nearly reaches 100% of its capacity. After reaching the necessary temperature level the standard fuel is reduced depending on the alternative fuel substitution rate, which means that the burner must have a very high degree of flexibility. Constant high alternative fuel use may lead to extremely large burners as the air velocity is limited at the burner tip and more than one extra alternative fuel channel is needed. This is the reason that tkIS recommends having a certain amount, for example up to 50%, of the solid alternative fuels injected through the burner and installing separate injection pipes for the remainder. This means that burners can stay at a reasonable diameter. Injected above the main burner, the poorer grade solid alternative fuel gets more time to dry out, will have a greater chance of dispersing and better burning and will not drop on the clinker bed. The challenge at present and in the near future remains limits to gaseous emissions. Furthermore suppliers are requested to design the burner without knowing the fuel that might be used after a new plant was completed. Despite this, the sintering zone length and temperature must still be controlled carefully. Xd’H: With its coal channel located inside or outside the primary air (or both) true flexibility can be achieved. As a full cement engineering provider tkIS takes a larger view and goes in the direction opposite to mainstream thinking. Clients may have to be convinced - for many years they have heard the message that all fuels must go through the burner!
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GLOBAL CEMENT: BURNERS FLSmidth Jetflex®
Right: Dynamis D-Flame burner.
Dynamis
Right: An FLSmidth Jetflex burner at the CRH Rohožník plant in Slovakia.
Dynamis was founded in 2003 by Eng. Guilherme who studied and worked with professor Clemente Greco from Brazil. At that time it offering consulting services but is now an engineering and project company as well as a supplier of customised equipment. The Multichannel D-Flame burner is designed with both axial and radial primary air channels, which are fixed. It has 18 orifices for the injection of external and tangential primary air. Some operational improvements include: 1) Finer C3S crystals; 2) The ability to use high sulphur fuels without fouling; 3) Stable kiln operation, and; 4) Increased refractory lifespan. For Dynamis, maximising secondary air entrainment is a very important concept, followed by minimising primary air injection. With respect to momentum, Dynamis uses the concept of kinetic energy, with a bigger emphasis on the speed than mass flow to design burner tips. When designing a burner, calculations of such values as flame impulse, turbulence index and swirl number are important to match the design with the fuels, secondary air temperature, kiln diameter and other parameters. These complement the geometrical design characteristics of the burner tip, including the respective locations of air and fuels injection, number and size of air jets and so forth. Dynamis has published several articles about its studies in the optimum number of primary air axial jets. The findings indicate that fewer jets, down to a certain minimum value, are more effective than a large number of jets.
The Jetflex burner is a good illustration of the development of a new burner to satisfy the changes imposed by the market. In a similar way that Pillard developed its Rotaflam® burner back in the late 1980s to match the requirements of low-NOx burners, or the way that Greco developed the Flexiflame® in the early 2000s to handle the high momentum ‘fad’ of the decade, the Jetflex®, the successor to the well-known Duoflex™, is geared to the ever increasing alternative fuel substitution rate, especially the use of solid alternative fuel in the main burner. Several new ideas were incorporated into the design of this burner and many more were assessed during development. The intensive use of CFD and modeling is a characteristic of the development of new burners in the 21st Century. The new ideas include: Rectangular flat shaped primary air nozzles that are either fixed or that can be adjusted in orientation in order to shape the flame; A common and adjustable (in and out the main body of the burner) centre pipe for solid fuels, which gives the fuel the possibility to expand prior to coming into contact with the combustion air (for a higher retention time). Central air (with or without swirl air) has an important role for cooling and flue gas internal recirculation. The prime benefit is that the burner has a smaller diameter, leading to closer proximity of the primary air and solid alterantive fuels and better mixing and burning. Another novel approach for high solid alternative fuel substitution is to mix it with the solid fossil fuel, (which represents a small fraction of the heat input), though a common pipe located in the centre of the burner. As is the trend in the market, the Jetflex® comes with various option, such as the primary air jets being fixed or orientable, and the possible inclusion (or not) of a swirl air channel.
Xd’H: Dynamis demonstrates how a newer company with fewer references can design a good burner of a simpler design but yet one that is still very effective. It has focused on key burner tip geometry to optimise a wellknown design.
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GLOBAL CEMENT: BURNERS Xd’H: This represents quite an innovative design. Still a new burner, the main features such as flat nozzles and the deceleration and expansion chamber for solid alternative fuels will have to be further demonstrated. It is interesting to see the many differences there are between the previous Duoflex and the Jetflex, which demonstrates the capacity of suppliers to challenge themselves to offer the right burner for the prevailing market requirements.
Fives Pillard Novaflam Fives Pillard has, for a long time, been the only independent cement kiln burner supplier, having led the way with the conventional ‘three-channel’ burners and then the well-known Rotaflam® burner. This was the first to depart for the traditional axial airsolid fossil fuel-swirl air channel arrangement and the beginning of the evolution of burners to lead or follow market needs. For about eight years Pillard has been offering the Novaflam, which incorporates many ideas in one burner. Several variants have since either been added or tested ‘on the drawing board.’ CFD results clearly demonstrated that it would be possible to design the Novaflam burner as a ‘mono’ air channel with two separate, controllable primary air outlets at the burner tip. The axial and swirl air help to achieve a sharp, low diameter flame, that is well controlled by the high air velocity in the axial air at the periphery of the flame. It has a good capability to repeat flame shapes. Crosssections are fixed to avoid the negative impacts of kiln temperature variation on tip shape that are caused by thermal expansion. The key feature is a single primary air inlet and double primary air outlet (axial and radial)
Left: Fives Pillard Novaflam burner.
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GLOBAL CEMENT: BURNERS
Right: A Greco Flexiflame being installed.
with the swirl injection at a progressive angle. Using a crank at the back end of the burner, the radial tip can be moved back and forth to adjust the flame width while the primary air pressure is adjusted to vary the burner impulse using a valve. Xd’H: The Novaflam has the largest market share. As with the FLSmidth Jetflex, the Novaflam shows the ability of burner suppliers to re-invent themselves and adjust previous features in order to stay close to the competition and the needs of cement plants. On the other hand Pillard emphasises larger amount of axial air but stays with having many and small air injection slots.
A TEC-Greco Flexiflame
Right: A burner from Rockteq.
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Xd’H: Here we again see a burner supplier that is capable of more than one offering, with concepts that would have been rejected years ago, in order to best match a given cement plant’s requirements. The impact that adjusting one air channel has on the other two, when using a single primary air fan, may be viewed as difficult by some operators.
The Greco burner company became well known in the 1990s thanks to its founder Prof. Clement Greco who travelled around the world promoting his burner Rockteq International concepts such as the ‘all concentric design.’ However at the time the company was offering engineering The Rockteq burner is a classical multi-primary air only, having its clients manufacture the burners channel burner with coal sandwiched between axial from Greco’s supplied drawings. The company later primary air and radial primary air. became a full OEM. The features of the burners are: Concentric supply The main principles of the Flexiflame burner of all fuels and primary air. The primary air (axial air, are the fact that it has no moving parts and three swirl air and central air) is supplied by three separate main primary air channels, axial, radial/swirl, and concentric ring channels and is measured and effecdispersion, with the fossil solid fuel channel being tively regulated by adjustable flaps. The triple supply located between the axial and swirl channels and the of the air allows an optimum set up of the flame dispersion channel. shape. By means of the good mixture of air/oxygen The benefits are to offer a robust and flexible and fuels a short turbulent flame will be achieved. burner, with the relative amount of primary air beThe high exit velocity of the primary air at the tween the swirl and the dispersion channels offering burner tip (Venturi effect) guarantees a good inadjustment between lower NOx (more swirl) and terference of the secondary air, approximately 85% of the whole combustion air, and a high external higher solid alternative fuel (more dispersion). recirculation, which improves the flame shape and The Flexiflame is capable of a larger turn-down. reduces the heat load in the kiln outlet area. Thus the Sometimes plants anticipate an increase in producfire-resistant wear of the kiln lining is also reduced. tion output but don’t want to have an oversized burner initially. The burner has the ability to plug (and later unplug) some of the air slots to allow for the Axial air optimum amount of primary air flow Coal, meat/bone meal + complementary air – in relation to the stoichiometric Tangential air requirement – over a large burner + natural gas Liquid fuel + output capacity. Compressed air Central air A recent variation is the Flexiflame Ecopro® burner which injects Solid fuel solid alternative fuels into the flame Ignition burner root through a ring channel. This reSwirl air quires careful preparation (grinding) of the solid alternative fuels.
Global CementMagazine March 2017
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GLOBAL CEMENT: BURNERS Good combustion of the coal is achieved by mixing oxygen into the flame core, due to the position of the coal pipe located between axial and swirl air. Therefore coal as supporting fuel for the solid secondary fuels guarantees a hot and short flame. Central air and swirl air generate an optimum internal recirculation, with a correspondingly high residence time for the combustion of solid secondary fuels. Furthermore, by internal recirculation of the combustion gases the spontaneous formation of NOx decreases. Xd’H: The Rockteq burner design has its roots in the Greco design, down to keeping the square axial air jets that were Greco’s signature in the late 1990s, with the idea of having everything concentrically arranged around the axis of the burner. For instance, even the liquid fuel lances are split into four to keep to the letter of that principle. A regional player with good manufacturing quality, it offers a strong focus on the central air, with jets instead of a perforated plate, which is a feature of burners where axial primary air injection is achieved by small jets / open channels, in order to achieve internal recirculation around the root of the flame. This offers greater flame adjustment capability for the very experienced operator.
Conclusions There are several key parameters that must be kept in mind when selecting a new rotary kiln burner, as well as some questions to ask. These include: • Size, shape (round, square, rectangular, twin), number and locations of the primary air jets (either just axial or a combination of axial and swirl) as to their effectiveness, especially for multi-fuel burners; • The effectiveness of the various built-in features of the burners designed to ensure good dispersion of the solid alternative fuels (mostly ‘fluff ’ type) when exiting the burner in order to ensure complete combustion while in suspension.
• Should multi-channel burners be equipped with one fan/blower per channel for easier control of the respective primary air flows? As well, there may be some considerations that are not currently taken on board as ‘mainstream’ burner features by the major manufacturers. These could include such features such as O2 injection to boost alternative fuel burning or H2O injection to control NOx. These are installed on several burners but are usually upgrades conducted with compromise, instead of being inherent options at the design stage; Operational aggravations with burners will always exist, including the premature failure of the outer concrete protection, the (lack of) effectiveness of air canons to remove the so call ‘rhino horn’, the need to change burner tips during commissioning to find the proper swirl angle, or excessive wear of the spacers inside the coal channel. One can also see that EPC companies have now designed burners that stand comparison with the ones from the burner specialists
More conclusions Despite the research conducted towards these two articles and my 30-plus years of experience in the cement sector, I am unsatisfied with a conclusion that is limited to simply a list of important technical factors. I have found that a lot of cement companies, either at the plant or HQ level, have their list of preferred suppliers, either published or implicit. Such lists don’t evolve much with time, if at all, and are often the result of past choices usually based on the OEM’s past market share. I hope that my research, in which I have presented a large variety of designs, will assist all of those involved in buying and operating new kiln burners in the cement sector. Plants should decide first which category of burners fit their own philosophy of operation and needs. They should then approach all suppliers that they think can deliver the desired result. Otherwise a complete and fair comparison between the different designs will be very difficult.
• Effectiveness of the so-called central / cooling / recirculation air channel;
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Contents
GLOBAL CEMENT: GRINDING
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Serdar Esendemir, Mardin Çimento
An introduction to roller press maintenance The welding of rollers, the costs of roller tyres, bearings and housings, unexpected downtime and other costs of maintenance are all important in cement plants that use roller presses. Here, Serdar Esendemir outlines ways to limit abrasion and effectively maintain roller presses, based on experience with Mardin Çimento’s four roller presses used for cement production.
Rollers
Adaptability of installation feature
Required crushing capacity, grain size, abrasiveness, temperature of material are important design criteria for determining various parameters of the rollers used in roller presses, including rotation speeds, diameters, widths and working pressures. From these, loads and energy values are calculated. During periods of high sales intensity, some cement plants can operate at full or even higher than 100% capacity and roller maintenance can take a back seat. In such cases, abrasion reaches the buffer layer by removing the hard layer. Faster abrasion and breakage then occurs in the rollers. Moreover, cracks can occur in the roller shaft. The roller then becomes unusable and may have to be scrapped. However, by careful coordination of the production and maintenance departments, synergies in maintenance and inspection works can (and must) be captured. A method should be developed for this purpose. First, the roller must be checked at each relevant period and, if necessary, welding repairs must be carried out. Appropriate welding must take place before abrasions reach the buffer layer. Not reaching the buffer layer means that abrasive materials are always in contact with hard surfaces, leading to controlled wear and protection of the rollers.
It is not adequate simply to protect the rollers by welding via the appropriate methods at convenient times. Rollers are designed with some installation values according to criteria given by the plant at the design stage. Installation values must be registered and saved. These include the size and structural features of the feed material, gap between rollers (for both loaded and unloaded operation) and commissioning, operation, safety and grinding pressures. Sometimes, in order to reach higher capacity, the gap interval is reduced and/or operating pressure is increased. Under such circumstances, undesirable results can occur due to sudden shocks and unbalanced loads, if the installation values are not first applied. This subject should be examined as a trio of: 1: Production rate, 2: Energy Costs; 3: Wear expenses. Plants can change the design values of the roller press to increase production in some cases. However, they must take into consideration potential problems that might occur in the rollers, including the high cost of potentially catastrophic failures. It is always a risky decision and machines should be operated according to the design values.
Motor
Gravity Feeder
Aux. Drive Frame Right - Figure 1: Roller press schematic.
Gear Reducer
Cooling Water Distributor
Oil cooler Hydraulic cylinder
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Inspection Door
Bearing Accumulator
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20-25mm
20-25mm
Mechanical stress σ max
σ max Fixed roller
Left - Figure 2: The maximum mechanical stress occurs within 20-25mm of the roller surface.
Mechanical stress
Sliding roller
Template The template is derived according to the diameter and width of roller and it should be kept. Welding is controlled by the template. Generally, these templates are provided by the machine manufacturers. It is necessary to protect the templates.
Operation of metal detectors and separators There should be a metal separator and metal detector on the belt conveyor that feeds the roller press. This equipment should be operated at the original sensitivity. Otherwise, pieces of metal that are included in the feed material can reach the rollers. The metal could leave an indent in the roller surface or even break it.
Final layer welding profile There are several kinds of welding profile for the final layer, including rhombic, sergeant, hexadur, straight line profile with circumferential linear pattern at 2025cm intervals, plus many more. Different kinds of profile may give different results. The distance between profiles must be kept short and equal. Straight line profile is most commonly used because of its quick and easy weldability
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should not be used together. If there is even a few millimetres difference in the diameter of the rollers, the larger roller will abrade the smaller roller.
Control Rollers should be checked every day if serious wear problems or high maintenance costs are expected. Abrasion should be repaired before it reaches the buffer layer by providing penetration with the appropriate welding method.
Welding companies A very important subject is welding companies and welders. Factory employees, who are responsible for this field, should give a higher level of importance to this issue. Worn rollers that have been sent for repair should be controlled before welding, during surface cleaning, during lathing, at the end of lathing and during welding.
Welding method Just as a surgical operation should not be done without anaesthesia for the patient, a successful welding operation should not be done without annealing.
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after abrasion. After abrasion of the profile surface, appropriate technical profile welding will extend the life of the rollers.
Mutual rollers Rollers that are bought from different companies
Below - Figures 3-7: 3: Straight line pattern with circumferential lines every 20-25cm. 4: Rhombic profile. 5: Sergeant profile. 6: Hexadur profile. 7: Zig-zag (weave) profile.
Therefore, pre-tempering, the temperature of the tempering during welding and tensionrelieving annealing are all very critical. Prior to the welding the specified surface temperature must be reached homogeneously across the surface of the roller.
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GLOBAL CEMENT: GRINDING Mardin Çimento’s roller presses Mardin Çimento has four cement roller presses. Three (numbers 1-3) have diameters of 1000mm and widths of 930mm. Cement mill number 4 has rollers with diameters of 1400m and widths of 800mm.
Welding procedures on site 1. One of the most important points to consider is that the underside of the zone to be welded must not be empty. The zone to be welded must be checked, cleaned, tempered and welded correctly. In a mill system that has just stopped, it is often the case that the temperature required for welding is already met due to the residual heat from operation. Rollers can be used many times without any fault by using this method of maintenance. 2. The local conditions surrounding the broken part should be thoroughly checked. If there is a gap around this, it should be broken. Otherwise, breaks may occur on the roller surface during subsequent operation after welding. 3. Welding chassis must be connected near the area that requires welding. 4. If there is a revision stop and a lot of abrasion on the buffer side of the roller, surface of the rollers should be abraded and welded by heating. If it is done without heating and penetration is not ensured, it is possible that parts may break. The carbon electrode method is commonly used for abrasion but it has some risks. Local grinding can also be used. It is a new method and is less risky. 5. Penetration of the roller shaft is the most sensitive issue.
Welding procedures in the workshop 1. The worn surface of the roller is lathed. This process continues until the cracked surface finishes. In some cases, cutting tools are broken so the rollers are annealed until 100°C before lathing and it is stripped with carbon or special electrodes. As mentioned above the grinding and lathing method is recommended, instead of carbon electrodes.
2. An ultrasonic crack test is performed after lathing is complete. If the result is satisfactory, welding is allowed. If there are still cracks, lathing should continue until reaching a surface without cracks. During the crack test, weighing and welding approvals, factory technical personnel are required. 3. After obtaining suitability for welding, preannealing is performed by heating to 200-250°C. The rate of temperature increase should not exceed 30°C/hr, although this may vary depending on the diameter of the roller. 4. After annealing, buffer welding is completed. 5. After buffer welding, tension-relieving annealing takes place. The temperature of the roller is increased to 550-600°C at a rate of not more than 30°C/hr. The tension-relieving annealing process should continue at this temperature for a minimum of 10hr. The temperature is then reduced to 200-250°C. Again, the temperature difference of the roller will not exceed 30°C/hr. 6. Hardfacing welding and profile filling are then completed. 7. Final measurement controls should then take place. Polyester slings must be used during transportation to protect the roller bearing surface parts.
Summary The procedures described above may vary in different application areas and sectors. However, it is always best to gain experience in person. Each factory must set up its own control criteria as above for rollers and must monitor welding, electrodes, contractors, abrasions and many other parameters.
Right - Figure 8: A cracked roller due to incorrect annealing. Far right - Figure 9: The result of penetration is breakdown of the hard surface weld and wear on the buffer layer.
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Cimprogetti Srl - A. Grellier - 02.2017
Flex Reversy Lime kiln
A proven operational excellence Simple design and high productivity combined with minimal CAPEX investment; Improved flexibility combined with minimal maintenance; Totally integrated automation and process control driven to an environmental friendly design.
limestone size from 20 to 150 mm
assial symmetrical design Bespoke design to ensure uniform limestone loading into the shafts together with even fuel distribution.
To optimize the quarry yield reducing quarry operation for achieving higher lime quality.
modularized assembly Bespoke design for work-shop preassembled structural, mechanical and electrical modules aimed to minimised site-erection activities with significant benefits in terms of time and cost.
simpler kiln shell design Outstanding R&D investments focused to achieve an “user friendly” design with reduced CAPEX and improvement of kiln performances.
W W W . C I M P R O G E T T I . C O M Cimprogetti Srl - Via Pasubio, 5 - 24044 Dalmine (Italy) ph.+39 035 4550 111 - fax +39 035 4550 335 - email:
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GLOBAL CEMENT: LIME
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Global Cement staff
Lime project round-up Here, Global Cement Magazine rounds up some of the latest projects from around the global lime sector...
Cimprogetti Malaysia: RCI Lime Sdn Bhd has awarded to Cimprogetti a contract for the upgrade of the software and hardware of the Control System (HMI) concerning its kilns No. 4 and No. 5 and hydration plant No. 1. RCI Lime, a prominent Cimprogetti customer since 2001, has developed, at its Ipoh site, a complete lime production plant featuring four Twin shaft vertical kilns of its Twin-D and Flex Reversy designs for a total nominal production of 1500t/day quicklime, as well as two hydration and classification units. The largest use of lime is in steel manufacturing, as a flux to remove impurities such as silica, phosphorus and sulphur.
India: Chemical & Mineral Industries Pvt. Ltd. (CMI), of Jodhpur, Rajasthan, India, has sucessfully operated a 300t/day Twin-D lime kiln from Cimprogetti since 2014. In 2016 the company was put into the ‘Limca Book of Records 2016’ for installing India’s first petcoke fired Twin-D lime kiln. The Cimprogetti twin shaft regenerative (TSR) kiln is a two-shaft vertical kin which uses the
Right: Two of RCI Lime’s four Cimprogetti lime kilns.
Right: A Cimprogetti Flex Reversy 9 lime kiln of the type to be supplied by the company to clients in Algeria, Iran and the US.
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Algeria: In May 2016 an important contract was signed by Cimprogetti Srl together with Bedeschi SpA for the supply, on an engineering and procurement (EP) basis, of a complete plant for the production of lime for the steel industry. The supply features the engineering and equipment for two Flex Reversy 9 type lime kilns with a capacity in excess of 400t/day each. They will be natural gas fired and will be supplied complete with upstream and downstream handling systems. The client, Algerian Qatar Steel (AQS), is a participation between Sider Co. & National Investment Fund (Algeria) and Qatar Steel International (Qatar). Bedeschi SpA, a well-known Italian company that specialises in the construction and design of large plants for the brick industry, cement sector and port logistics, will provide the facilities and equipment for the materials handling system.
Iran: Cimprogetti has been awarded a contract by Middle East Mines Renovation & Development Company (MEMRADCO), a subsidiary of Middle East Mines and Minerals Holding Company (MIDHCO), which specialises in iron ore, copper and coal. Through a consortium partnership, GMI Projects Hamburg GmbH will act as project coordinator for all technical aspects of the engineering, procurement and construction (EPC) project. The engineering delivery, already underway, is the first step in the supply of three Flex Reversy 9 type natural gas fired lime kilns, each with a nominal quicklime and dolomite capacity of 400t/day. They will be installed at Butia, Kerman Region. The supply also includes material handling systems and a bagging plant.
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regenerative process for lime calcinations with high fuel-efficiency and very low emissions. The quicklime produced is of high reactivity, high brightness, high purity and consistent quality. India: In October 2016 Cimprogetti conducted a fuel conversion project at Jindal Steel & Power’s Angul site. Two existing RD-12 model lime kilns, of 500t/day capacity each, were converted to burn mixed gas, a mixture of coke oven gas and blast furnace gas. The project confirms the commitment of Cimprogetti in assisting the clients which operate in the steel field to utilise low value fuels, particularly the tail gas recovered from the steel process, thus allowing significant cost savings.
Confidential clients A confidential client has recently ordered a Cim-Microsep separator for one of its European facilities. A separate client in North America has awarded Cimprogetti a contract for the supply of a Flex Reversy 4 lime kiln with a capacity in excess of 200t/day. Elsewhere, a producer of high calcium and dolomitic lime, limestone and derived products has awarded Cimprogetti a contract for the design and supply of a CIM-HYDRAX-4G MAX model hydrator for one of its European facilities. This new order confirms the renewed confidence of this prominent customer towards Cimprogetti technology. Over the past six years, Cimprogetti has been entrusted with the provision of equipment and plants featuring the fuel conversion of three PFR kilns, a 20t/hr CIMHYDRAX-4G model hydrator, a high-efficiency CIM-MICROSEP 200 HS separator, a highefficiency CIM-MICROSEP 300 HS separator and a tubular grinding mill.
Cimprogetti celebrates half a Century
Above: CMI launched India’s first petcoke-fired Twin-D lime kiln in 2014.
In 2017 the Italian lime kiln manufacturer Cimprogetti Srl celebrates half a century of activity. As part of its celebrations it has relaunched its logo and a presents a new tagline ‘the green edge of lime technologies.’ The company explains that ‘Green’ reflects Cimprogetti’s attention to the environment and its growing sensitivity to the environmental performance of its plants. It is engaged in research and development to find alternative fuels, technical and engineering solutions arrangements and flexible synergies with the goals of reducing the consumption of virgin resources and environmental emissions, energy consumption and sustainable development. ‘Edge’ refers to the fact that Cimprogetti says it is on ‘the cutting edge’ with respect to the high quality and performance of its plants. ‘Technologies’ refers to the fact that Cimprogetti is, ‘the aggregate of the latest lime technologies.’ In its 50th year the company has further identified three routes to success. 1. Consolidating its heritage in terms of its social and human capital, its intellectual and technological know-how and through new investments; 2. Increasing knowledge and technologies, in the light of the new horizons that Industry 4.0 is tracking, and; 3. Converting this aim into technical solutions and in a change of mindset to increase the integration of supply chain processes for the benefit of the customer.
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GLOBAL CEMENT: LIME
Right: The SIC HPK lime kiln installed for Carrieres et Chaux du Mali in Mali.
Far right: Micronising mill installed by SIC for Zao ‘Izvestnyac’ in Russia.
Società Impianti Calce (SIC) 2000 years since the Roman achitect and encyclopedist Vitruvius first laid down the implementation criteria for lime production, Società Impianti Calce (SIC) continues the trend of Italian technology in lime plant manufacturing. Here it outlines some recently completed projects, outlining its problem solving approach and bespoke solutions tailored to different clients. Right: The Santa Rosa Lime CBK kiln has recently undergone a wholesale renovation by SIC.
Completed projects Mali: SIC recently completed the testing and commissioning of a single shaft HPK lime kiln for Carrieres et Chaux du Mali. Located in Sema Falcadiè, near Bamako, the kiln uses heavy fuel oil to produce 100t/day of quicklime, primarily for the gold mines in the area. Russia: In November 2016 SIC completed the commissioning and running test of a micronisation plant in Karachay, Russia for Zao ‘Izvestnyac.’ The plant receives limestone of diameter
