Quartz (SiO 2 ) 50µm Calcite (CaCO 3 ) 20µm Aluminum oxide (Al 2 O 3 ) 5µm. Iron oxide (Fe 2 O 3 ) 20µm. Dolomite 20µm (CaCO 3 MgCO 3 ) - PDF

Quartz (SiO 2 ) 50µm Calcite (CaCO 3 ) 20µm Aluminum oxide (Al 2 O 3 ) 5µm Iron oxide (Fe 2 O 3 ) 20µm Dolomite 20µm (CaCO 3 gco 3 ) Chalk (CaCO 3 ) 2µm Hydromagnesite + Calcite 5µm Hydromagnesite + Calcite

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Quartz (SiO 2 ) 50µm Calcite (CaCO 3 ) 20µm Aluminum oxide (Al 2 O 3 ) 5µm Iron oxide (Fe 2 O 3 ) 20µm Dolomite 20µm (CaCO 3 gco 3 ) Chalk (CaCO 3 ) 2µm Hydromagnesite + Calcite 5µm Hydromagnesite + Calcite 2µm Clay 30µm Air-cooled blast furnace slag 1µm Iron oxide, Titanium 30µm oxide and Orthoclase Air-cooled blast 5µm furnace slag 154_Loesche-mills for cement raw material_en Pictures originated at the electron microscope laboratory of Bauhaus-Universität Weimar 12/2015 LOESCHE-ILLS FOR CEENT RAW ATERIAL Loesche technology always a step ahead Cement raw material has been almost exclusively ground in roller mills (vertical air-swept grinding mills) since the second half of the 20th century. Loesche was and is the pioneer of this technology. Hundreds of Loesche mills have been used in the cement industry across the world to the present day. They operate with two, three, four and six rollers The first spring-loaded air-swept grinding mill in the world, constructed by the original company Curt v. Grueber aschinenbau-anstalt, Teltow near Berlin, is launched onto the market under the name Loesche mill and has 2 grinding rollers. It already has all the essential features of modern air-swept vertical grinding mills built today. Even the first Loesche mills had an integrated dynamic classifier. Several examples of this are deployed in Klingenberg, Europe s first coal dust-fired large-scale power plant in Berlin for coal grinding with a raw coal rate of approx. 12 t/h Loesche mills are increasingly also used worldwide for limestone and cement raw material Loesche mills have already been sold for coal, phosphate and cement raw material The largest Loesche mill at this time is an L 16 with two steel spring-loaded rollers, a grinding track diameter of 1,600 mm and product throughput of 22 t/h The company in Teltow is nationalised; the company is newly established under the name Loesche KG in Düsseldorf (West Germany) Loesche mills supplied in the sizes L 16 to L 20 in modern welded construction with two steel spring-loaded rollers and product throughputs up to approx. 55 t/h Development of 2-roller Loesche mills in the sizes L 22 to L 28 with the world novelty of a hydropneumatic spring assembly system for product throughputs up to 140 t/h. Loesche mill Type L 46.4, Lengerich, Germany, 1971 Introduction of a modular system in mill construction: creation of replacement groups of components such as rollers, rocker arm and hydropneumatic spring for constructing mills with 2, 3 and optionally 4 rollers of the same size. The first L 30.4 and L roller mills are sold and have product throughputs of 178 t/h and 215 t/h Sale of L 36.4 und L 43.4 mills with product throughputs of 260 t/h and 425 t/h Sale of the first L 50.4 with a throughput of 490 t/h Sale of the first L 63.4 with a throughput of 800 t/h Sale of the first 6-roller Loesche mills L 60.6 with a throughput of 740 t/h mills Type L 69.4 and L 69.6 with product throughputs of up to 1200 t/h are sold. In the 1930s Loesche mills are used to grind cement raw material for the first time. The major breakthrough came at the start of the 1960s when rotary kilns with heat exchangers (dry process) are introduced. The following Loesche technological features make the deployment of these mills so successful in the cement industry: Loesche mill Type L 45.4 roller mill, Elmadag, Turkey, 1995 Low specific energy consumption Low pressure loss through large crosssectional flow areas in Loesche mills inimal sound emissions so that no sound insulation measures are required Rapid reaction to fluctuating raw material qualities Rapid readjustment to different product qualities Use of the kiln exhaust gases for dry grinding and as a transport medium for the final product to dust separators Loesche mill Type L 63.4, Hereke, Turkey, Benefits to customers and customer satisfaction Quality and reliability right from the start are the globally recognised benefits to be derived from Loesche grinding plants. As early as 1928, when the first Loesche mill came onto the market, the grinding principle of the vertical roller grinding mill, with a driven grinding track and spring-loaded rollers was shown to be particularly energy-efficient and reduced the use of natural resources. These advantages of Loesche mills will become ever more important in the light of increasing plant size and the obligation to make more careful use of primary energy. oreover, the high product throughputs of Loesche mills (up to 1,300 t/h for cement raw material and already 350 t/h for cement clinker and granulated blast furnace slag) result in considerably reduced investment costs compared to two smaller grinding plants. Our competence is founded on the following key features: Tailor-made plant concepts from planning to commissioning, based on our own experience combined with customer wishes Individual problem solutions through optimised process technology Rational solutions with simultaneous planning of cement clinker/granulated blast furnace slag mills and raw meal mills through the use of exchangeable components for all models of mill, extending to the use of identical gear drives Close cooperation with suppliers of rotary kilns in line with customer wishes Loesche is a competent partner for its customers from the initial sale to customer service and from punctual project planning to the handing over of the plant. Our maxim is Every Loesche grinding mill must be a reference mill! Customer service: plant optimisation and advice in the case of further technical developments Long-term delivery capability when supplying spare parts Certification in accordance with EN ISO 9001: Loesche mill Type L 60.4, Ras Al-Khaimah, United Arab Emirates, Grinding table of an L 69 in the foundry Transport to the port Shipment for further processing Assembly of the lower part of the mill Assembly of the grinding table ill with classifier under construction 5 Working principle, construction and function of Loesche mills Working principle The material to be ground is crushed between the rotating grinding track and the individually guided grinding rollers. Grinding is carried out primarily through the application of compressive force. A small amount of shear force supports the displacement of crystalline layers in the raw material. This effect occurs through conical rollers whose axes are inclined at 15 compared to the horizontal grinding track. As already demonstrated through comparative studies in the 1930s, this permits ideal fine grinding and at the same time ensures minimum wear. A higher specific grinding pressure is applied compared to coal grinding and a lower specific grinding pressure is applied compared to the fine grinding of clinker and granulated blast furnace slag. Hot gases are added in the dry-grinding process to evaporate material moisture. Use is predominantly made of the exhaust gases from the rotary kilns, the heat exchanger or the cement clinker cooler. If none of these sources are available or the heat content of these exhaust gases is insufficient, Loesche s own hot gas generators are deployed. In the classifier above the grinding chamber the ground product is separated from the grit which then falls back onto the grinding track for renewed grinding. Construction The familiar basic principle of the modular system patented in 1970 is applied to Loesche mills with two, three, four and six rollers. The rollers together with their lever systems, hydropneumatic springs and hydraulic control systems make up a functional unit. Large or small modules with a different number of rollers (between two and six) can be deployed in the same mill sizes (grinding table diameter). This makes it possible to customise the product to meet specific customer requirements. The following features characterise Loesche technology: The support and precise guiding of the rocker arm roller system with its roller bearings takes place in a pedestal with integrated spring system. Hydropneumatic spring loading of the roller rocker arm unit with integrated mechanism to lift the rollers serves as an aid for the mills when starting up with a filled grinding track. The rollers are connected in pairs to a common hydraulic unit (except in the case of 3-roller mills). An almost parallel grinding gap is maintained between the grinding rollers and the grinding plates during the entire service life of the grinding parts. 6 Loesche mill Type L 69.6, Idhan, United Arab Emirates, 2009 Gas spring system Rocker arm in working position Hydraulic cylinder View of the grinding chamber of an L 69.6 Rollers of an L 69.6 ill gearbox 7 ill function The cement raw material is fed via a rotary feeder 1 and falls via the chute 2 onto the centre of the grinding bed 3. Free ferrous foreign objects are separated out from the feed material magnetically before reaching the rotary feeder 1 and removed via a diverter gate. A metal detector operates in a similar way and ensures the separation of non-magnetic metal parts. The material to be ground moves on the grinding track towards the edge of the grinding table under the effect of centrifugal force and in this way passes under the hydropneumatically spring-loaded grinding rollers 4.The material that has been drawn in is ground in the material bed in the gap between the rollers and grinding track. The rollers 4 are displaced upwards as they roll over the material bed 5. As a result the functional unit consisting of rocker arm 6, spring rod and pistons from the hydraulic cylinder 7 is moved. The piston displaces the hydraulic oil from the cylinder into the gas-filled bladder accumulator unit. Nitrogen-filled rubber bladders in the accumulator units are compressed and act as gas springs. The gas springs can be set to be harder or softer by selecting the gas pressure in relation to the hydraulic operating pressure, depending on the fracture behaviour of the material to be ground. The ground material is subjected to centrifugal force and rotates outwards and over the edge of the grinding table. In the area of the louvredam ring 8 which surrounds the grinding table 3 the stream of hot gas 9 directed upwards captures the mixture of ground material and material as yet not completely ground and conveys this to the classifier 10. Depending on settings of the classifier 10 it rejects coarse materials. This falls into the internal grit return cone 11 and then onto the grinding table 3 for re-grinding. The ground material passes from the classifier and is conveyed from the Loesche mill with the gas stream 12. The mill is driven by an electric motor 13 via a flexible coupling 14 and the mill gearbox via an output flange 15. A segmental thrust bearing in the top of the gearbox absorbs the grinding forces. The grinding rollers 4 are hydraulically lifted from the grinding track before the mill motor is started. The mill can then not only be started empty but also partially filled with a low starting torque. etallic contact of grinding parts on an empty or loaded mill is prevented by automatic lifting of rollers via a grinding bed depth control. A so-called auxiliary drive for starting up a filled mill at low revolutions is not required! Servicing Worn grinding parts, roller tyres and grinding track segments can be simply and quickly replaced. The rollers are retracted from the grinding chamber into a vertical position using a retracting cylinder. Complete rollers, roller tyres and grinding plates are then made accessible to hoisting devices. When grinding cement raw material the metallic particles usually cause uniform wear throughout their entire service life so that the mill throughput only declines when mill parts are completely worn. Partial wear may occur if, for reasons of cement chemistry, free quartz sand needs to be used as concrete aggregate. This can be offset by targeted hard facing in the mill. Loesche has the required know-how for in-situ welding using appropriate welding equipment. Foreign matter and small amounts of coarse material fall through the louvre ring 8 into the ring channel 16 as reject material. Scrapers 17 connected to the grinding table transport foreign matter into the reject hopper 18. Cement raw material usually has differing degrees of moisture content when extracted from the quarry. As soon as the ground material leaves the grindin g table in the area above the louvre ring 8, the water contained in the working material evaporates sponta neously upon intimate contact with the hot gas stream. Therefore the required mill outlet temperature of the dust/gas mix of approx. 80 to 110 C is already achieved in the grinding chamber. 9 ill selection sizing models dimensions drives Dimensioning parameters The following standard parameters are decisive for dimensioning Loesche cement raw material mills: GRINDING PRESSURE This lies between the minimum value for solid fuels and the maximum value for cement clinker/granulated blast furnace slag. ATERIAL OISTURE The Loesche mill can process material with moisture of up to 25%. Drives An electric motor serves as the drive. It drives a planetary gearbox using a torsionally flexible coupling. The drive shaft lies horizontally, the vertically mounted flanged output shaft rotates in a horizontal plane. The gearbox contains a segmental thrust bearing that accommodates the grinding force at the top of the housing. Loesche mill gearboxes are developed in cooperation between Loesche GmbH and reputable gearbox manufacturers. The dynamic safety factors are suitably chosen for the application. Decades of experience operating Loesche mills determine the design of the (mill) gearbox and their peripherical equipment, bearing in mind all climatic conditions. PRODUCT FINENESS The fineness of the final product is between 6% and 30% R 0.09 mm, depending on the composition of the raw material. DRIVE PERFORANCE The specific energy consumption in the grinding test is decisive for gearbox and motor sizing. odels ill sizes are identified according to the outer effective diameter of the grinding track in decimetres [dm]. odern gearboxes today are constructed in a modular manner in the same way as Loesche mills. Torque split ensures a reduction in the rotating masses and simultaneous multiple use of machine construction elements in gearboxes with different sizes and performance. A lubrication unit ensures that adequate oil is supplied to the gear teeth, the shaft bearings and the segmental thrust bearing. Filters and cooling equipment condition the oil. Electrical and hydraulic instruments that are monitored in the customer s PLC guarantee safe operation. The identification is followed by a digit, separated by a full stop. This specifies the number of rollers operated in the mill. The modular construction principle of gearboxes permits further increases in performance in line with the current state of the art without the need to develop a new construction concept. The number and size of rollers is geared to the required product throughput in conjunction with the Loesche performance factor as well as the product which is influenced by factors of grindability, moisture and fineness. The required gas stream is decisive for the housing dimensioning of mill and classifier. The Loesche cement and raw meal mills are constructed in a modular fashion. odules are understood as units comprising rollers, rocker arms and roller-related spring components with their pedestal. This is arranged from between 2 and 6 times around a grinding table as required. The Loesche mill does not require a motor with increased starting torque. Since the rollers are raised hydraulically, the breakaway torque for the filled mill only comprises 40% of the full load torque. This starting torque can be achieved by a standard motor without a problem. The installed motor power is sized according to the energy requirements of the mill. This is established in the test plant using a grinding test. The next suitable commercially available motor is selected and recommended to the customer. Dimensions The coordinates of the grinding table diameter and number of rollers can be read off from the following table. The x-coordinate indicates which product throughputs can be generated using the respective mills. The width of the fields is a measurement of the output factor (see above). The dimensions H, A and D in turn describe the height of mills with classifier, the footprint diameters and the overall space required, taking a service area (for replacing grinding parts) into consideration. 10 L for Raw aterial and inerals Product rate [tph] as function of the L size A [m] H [m] L 75.6 ~9,600 kw L 70.5 ~7,000 kw L 69.6 ~6,900 kw L 60.6 ~5,300 kw L 56,6 ~4,400 kw L 56.4 ~4,200 kw L 53.6 ~3,600 kw L 48.4 ~3,100 kw L 46.4 ~2,600 kw L 45.4 ~2,000 kw L 41.4 ~1,900 kw L 38.4 ~1,750 kw L 35.4 ~1,600 kw L 38.3 L 31.3 ~1,400 kw ~1,200 kw Fineness Fine Coarse H [m] L 31.2 L 24.2 L 21.2 ~700 kw ~600 kw ~450 kw Difficult Grindability Easy A [m] L 19.2 ~335 kw L 15.2 ~200 kw L 12.2 ~112 kw Product throughput [tph] 11 Raw materials for grinding Cement raw material; deposits Cement raw material is principally a compound made of limestone and argillaceous rock, which undergoes mechanical and thermal treatment to create cement clinker. The geological formation, material composition and water content influence the grinding dryness and energy requirements. The raw materials are classified according to their origin into natural mineral raw materials and synthetic mineral materials that are by-products or waste products from other branches of industry deploying raw materials. The suitability of natural and synthetic mineral raw materials for manufacturing binding agents is primarily determined by their chemical composition. The following fields are chiefly used for the provision of the most important components: For a good and fast reaction during the firing process it is more favourable to use those materials whose composition is by nature closer to the desired chemical compound. Carbonate fields, consisting for example of shell limestone, white Jura, chalk etc. Silicate aluminate deposits, consisting for example of sandstone and argillaceous rock, magmatic and metamorphic rocks etc. The compositions of raw material compounds used in practice can be most easily represented using the table from LABAHN & KOHLHAAS (1982). Chemical composition of cement raw material; ignition loss-free. [LABAHN & KOHLHAAS, 1982] INERAL OXIDE min. and max. mass[%] LIESTONE CaO SILICATE SiO CLAY Al 2 O FERRIC OXIDE Fe 2 O AGNESIU OXIDE go 5.0 POTASSIU OXIDE/ SODIU OXIDE K2O; Na2O 2.0 SULPHUR TRIOXIDE SO 3 According to Labahn & Kohlhaas the following terms are common for the raw materials used arranged with diminishing CaCO 3 content: Cement raw materials require a CaCO 3 content of between 74 and 79 %. The desired raw material composition is rarely found in a natural raw material. Pure limestone 95. % CaCO 3 arly limestone % CaCO 3 Lime marl % CaCO 3 arl % CaCO 3 Argillaceous marl % CaCO 3 For this reason materials containing SiO2 and ferric oxide as well as fluorites must be used as correcting materials to precisely adjust the required raw material compounds and to improve sintering. Some of these grinding materials additives are highly abrasive and lead to the disproportionate wear of grinding parts, areas of machines and in ducts through high speeds of gas-solid mixtures. Loesche takes suitable protective measures against wear when materials of this nature are used. arly clay % CaCO 3 Clay 5. % CaCO 3 13 The homogeneity and fineness of the cement raw meal also plays an important role in the downstream sintering process in addition to the correct chemical composition of the raw meal mixture. There are high demands with respect to the permitted residual moisture in the ground product. The residual moisture (max. 0.5 %) must be just as homogeneous as the distributed chemical componen
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