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Tadipatri's Big Sixer

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The first six-roller Loesche mill for grinding cement raw material was successfully put into operation in July 2008 (see Figure 1). The grinding plant is part of the new production line in the Tadipatri works of the second largest cement manufacturer in India, Grasim Industries Ltd, Mumbai and its subsidiary UltraTech Cement Ltd. Around 16,000t of cement raw material must be ground every day to supply the new kiln which has a cement clinker capacity of 10,000tpd.

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Tadipatri's Big Sixer

  1. 1. RAW MATERIAL GRINDINGI Tadipatri’s big sixerby M Keyssner, Loesche The first six-roller Loesche mill for grinding cement raw material wasGmbH, Germany & successfully put into operation in July 2008 (see Figure 1). The grindingPS Mazumdar, UltraTech plant is part of the new production line in the Tadipatri works of theCement Ltd, India second largest cement manufacturer in India, Grasim Industries Ltd, Mumbai and its subsidiary UltraTech Cement Ltd. Around 16,000t of cement raw material must be ground every day to supply the new kiln which has a cement clinker capacity of 10,000tpd.I n 2005, Loesche GmbH undertook consistent development of the The design of mill model LM 63.4 this LM 63.4, consisting of grinding roller modular system, designed and in the mid-1990s, which had an and rocker arm, was already around 90t.patented by the company in the 1960s arrangement of four grinding rollers The dynamic forces resulting from the(see Figure 2), to keep up with the on a grinding track of f6.3m, was movement of this mass during millingincreasing demands of the cement the next logical step according to operations essentially have an impact onindustry for ever-larger production units. company philosophy. This facilitated the the mill structure, on the mill gearboxIn this way, Loesche can provide mill achievement of a nominal throughput that supports the grinding table anddimensions which are adapted to cope of 800tph, based on a medium hardness on the mill foundation. This challengewith the throughputs of modern kilns. of cement raw material and a product required a rigid design to ensure the A significant aspect of this development fineness of 15 per cent R0.09. longevity of the Loesche mill.was the limitation of the dynamic forces The weight of one roller module from The decisive step for achievinggenerated during grinding operations bythe upwards and downwards movementof the grinding rollers, which can becompared to a car tyre on an unevenroad, so that the known operationalsafety associated with Loesche mills couldstill be guaranteed at larger mill sizeswith nominal throughputs of more than1000tph. The smooth production start ofthe largest Loesche mill ever builthas confirmed the correctness of thisdevelopment direction. The six-rollerLoesche mill of type LM 69.6 has anoutside grinding track diameter of 6.9m. The constant demand for highermill throughput has been the essentialchallenge for Loesche through its 100+year history. Only two-roller mills werebuilt during the first decades of thecompany’s existence. The introduction ofthe roller module system over 30 yearsago resulted in new flexibility for milldesign. A different number of grindingrollers with the same dimension can bearranged around the central grindingtable depending on the mill capacity.Pedestals providing individual bearing andsupport for the grinding rollers permittedthe design of mills with two, three andfour grinding rollers. There is no need foran additional supporting frame to brace Figure 1: LM 69.6 Tadipatri cement worksthe rollers to each other inside the mill. JANUARY 2009 ICR 39
  2. 2. RAW MATERIAL GRINDINGFigure 2: Loesche roller module The handling of components during replacement or servicing work is simplified owing to reduced individual weights. The required mill foundation mass is also clearly reduced owing to the lower individual roller weight compared to a four- or three-roller mill with equivalent throughput (see Figure 5). As of today, orders have already been taken for over 15 of these new six-roller Loesche mills. Commissioning of the LM 69.6 in the Tadipatri cement works took place as expected. After adjusting of the machine settings and stabilisation the guaranteed throughput was achieved in less than 50 operating hours (see Figure 6). The guaranteed throughput is related to the grindability of the cement raw material used in the plant. Grindability tests in the Loesche Technical Center during the project planning phase in 2006 had revealed that the grindabilityFigure 3: LM 69.6 – assembly at site from Tadipatri is very low and at only approximately 50 per cent compared to other raw materials and consequently requires a high specific grinding power of approximately 11.5kWh/t (see Figure 7). As can be seen from this diagram, the cement raw material from Tadipatri represents a clear exception to raw materials otherwise used. It was necessary to pay special attention to this feature when sizing and designing the Loesche mill and additionally to ensure that both the required comminution force and the smoothness of running of the mill lie within known empirical values. This enables the dynamic forces to the affected components and the mill foundations resulting from the grinding process to adjust to within the specified limit values. Unacceptable forces are thereby avoided.yet greater performance units was to to install roller modules Figure 4: four-roller modeincrease the number of grinding rollers, that had already been of LM 69.6 for partial load conditions andwhich makes it possible to control the in operation in the four- six-roller mode for fulldynamic forces resulting from the grinding roller arrangement. This operationoperation. This option was chosen instead excluded the risks to theof increasing the size of the rollers, which operational reliabilitywould also have caused an increase in the of the grinding plantroller mass. The Loesche modular system associated with the failurecould be regarded as the crucial element of newly developed sizesin this scale-up. of grinding roller. Similarly, Recourse was made to the experiences the six-roller arrangementfrom the transfer from two-rollers to permits greater partial loadthree or from three-rollers to four, when operation of the mill, inincreasing the number of rollers to six which two or four rollers(see Figure 3). Additional advantages of may be swung outthis concept resulted from the possibility (see Figure 4).40 ICR JANUARY 2009
  3. 3. RAW MATERIAL GRINDINGFigure 5: comparison of roller sizes Furthermore, Loesche mills will also be installed in the new production lines of all three works of Grasim Industries Ltd and its subsidiary UltraTech Cement Ltd to grind coal/petcoke to fire the rotary kilns and for finish grinding of the cement. The Loesche coal mill, type LM 43.4D, with an outside grinding track diameter of 4.3m, a motor power of 1600kW and Figure 6: start-up of LM 69.6 at Tadipatri plant cement works in the Rajasthan a nominal capacity based on hard coal province in India. For reasons grindability and a fineness of 15 per cent 100% of better grindability of the R0.09 of approximately 200tph are the cement raw material, only largest vertical roller mills in the world for Mill throughput 75% one Model LM 69.6 Loesche coal pulverisation. The LM 43.4Ds coal mill will be installed in the Kot mills are already producing the required 50% Putli works for the rotary kiln coal dust in both the Tadipatri works and capacity of 10,000tpd, which the Aditya works. The commissioning of 25% is currently being assembled. these likewise newly developed Loesche An identically constructed mills, in which a four-roller arrangement 0% version with two cement raw was realised for the first time, also 0 50 100 material mills was chosen for took place without any problems and Operating hours the new cement line in the completely satisfied the expectations of operator and manufacturer.Figure 7: range of grindability of cement raw materials worldwide 2 In each of the three works, two Loesche mills, type LM 53.3+3 CS, will be installed for finish grinding of various types of good ==> 1.5 cement. They have a grinding table of f5.3m, the patented Loesche grinding Grindability system, consisting of three pairs of 1 preparation and comminution rollers each and a motor capacity of 4000kW. These <== poor vertical mills are still in the construction phase. 0.5 A decisive factor when the contract was 0 awarded was the ‘unification concept’ 0 2 4 6 8 10 12 14 16 18 applied by Loesche to the mills for cement Power consumption - mill [kWh/t] raw material and cement grinding. Here identical components such as grinding The values represented in Table 1 rollers, rocker arms for transmissionindicate the throughput of the mill, Aditya works. The first LM 69.6 was also of the spring force onto the rollers,the fineness of the raw meal and the successfully put into operation in these roller bearings and main componentsnecessary specific power consumption. works in September 2008. The guaranteed of the hydro-pneumatic suspensionAll guaranteed values were achieved. throughput of 550tph was achieved after spring systems such as cylinders andFurther optimisations to boost the energy just 20 operating hours. accumulators were used in the millsefficiency of the grinding plant areplanned in close cooperation with thecustomer. Table 1: operational data of LM 69.6 To be able to grind the required mass ofapproximately 16,000tpd of raw material Plant Tadipatrifor the rotary kiln with a capacity of LM 69.6 Guaranteed Achieved10,000tpd clinker, two LM 69.6 Loeschemills will be installed in parallel in the full Mill throughput (tph) 420 430expansion stage of the new line and will Fineness 20 17-21produce at least 840tph of raw mix. The %R0.09 %R0.09second mill is currently under construction Feed moisture (%) <7 <2(see Figures 8 and 9). Product moisture (%) <1 – Grasim Industries Ltd ordered further Specific power consumption (kWh/t) 25.84 22Loesche mills of type LM 69.6 in 2006 for (mill, fan, classifier, aux) (mill motor and fan only)the extension of the Aditya and Kot Putli JANUARY 2009 ICR 41
  4. 4. RAW MATERIAL GRINDING Figure 8: LM 69.6 under erectionand facilitate improved spares inventoryand supply because these parts areinterchangeable. All in all, the new cement lines ofthe three works used 54 identical rollermodules (see Figure 2) installed in the fiveLM 69.6 and eight LM 53.3+3 CS Loeschemills.ConclusionThe successful commissioning of the firstsix-roller Loesche mills has justified theselected development concept, in whichthe grinding capacities of Loesche millswere boosted by increasing the number ofrollers rather than the roller size/mass. Theuse of roller modules tested in practicein four-roller mills made it possible torule out potential development risk todynamically loaded components. Themodules so far installed in the largest six-roller Loesche mills are only medium-sized.Other module sizes, right through to thelargest from the LM 63.4, are availableand have been in use for years in thecomminution of cement raw material.This means that further increases inperformance can also be realised in thefuture insofar as these are demanded bythe industry. ____________________ IFigure 9: mill table of LM 69.6 arriving at site (in upside down position for safe transportation)42 ICR JANUARY 2009

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