Polysius Roller Mills. For grinding

4Advantages of Polysius roller millsat a glance:x High operating reliability and availability, as well aseasy system handling, due to the fact that grinding, dryingand separation all take place in a single compact unit.x Consistently high product quality with minimumenergy requirement, due to the integrated high-efficiencyseparator.x Housing contours of mill and separator optimallydesigned to transport finish-ground material quickly andreliably to the separator and reduce material circulationswhich disturb the grinding process.x Additional reduction of the energy requirement due tothe external material circulation.x Very low pressure drop in the grinding system due tooptimisation of the gas velocity and gas distribution bythe adjustable nozzle ring.x Optimum feed material pull-in conditions and grindingefficiency due to the double groove grinding table.x Constant economy of operation due to infinitely variablepressure adjustment of the hydraulic system.x Overall ease of maintenance due to the large doors, whichare simple and safe to handle, and to the dismountingdevices, with which the grinding rollers and table liner segmentscan be replaced quickly and without any problem.x Outstandingly economic mill housing wear protection dueto requirement-specific selection of materials.x Use of economically optimum grinding element qualities– chrome chilled casting, hardfacing, ceramic materials.Assembly ofa roller mill forgranulated blastfurnace slaggrinding in China.

6The details decide...when it is loaded with materialafter an emergency stoppage,and allows quick emptyingand positioning of the mill formaintenance work.Hydraulic cylinderof the roller mill.Adjustable nozzle ringThe gas required fortransporting and dryingthe material inside the millflows through the nozzlering.The gas distribution andvelocity can be optimallyadjusted to suit the requiredmaterial loading or dryingcapacity, thus minimisingthe specific gas flow rateand the pressure dropin the grinding system.Hydraulic systemThe grinding force is appliedto each roller pair unit by twohydraulic cylinders. Infinitelyvariable pressure control automaticallyadjusts the grindingforce to the current operatingconditions of the mill.This ensures constant economyof operation over the entirethroughput range (i.e. evenunder partial-load conditions).When the mill is starting andstopping, the grinding forceis reduced by lowering thehydraulic pressure. Eachhydraulic cylinder is connectedto a piston accumulator whichabsorbs the grinding shocks.DriveThe roller mill drive consistsof the motor and a planetarygear unit that was speciallydesigned for roller mills. Thisgear unit is equipped with ahydrodynamic axial thrust bearingwith partial or full hydrostaticlubrication, which acceptsthe grinding forces and transmitsthem directly into the foundationof the unit.An auxiliary drive ensures easystarting up of the mill, evenTo allow the grinding of differentmaterials and finenesses,a variable-speed motor or aspeed-change gear unit adaptsthe grinding speed to therequired product characteristicsand product fineness.HousingThe housing is fitted with specialseals to prevent the inleakageof false air. Easy-to-opendoors facilitate maintenance ofthe mill.Special dismounting devicesensure straightforward turningaroundor replacement of thegrinding rollers through themaintenance doors.The housing contour designguarantees an optimum materialdistribution, quick collectionof the ground material and reliableconveyance of the finishedmaterial to the separator.The design also promotes theformation of a stable grindingbed and greatly reduces theinternal circulation of material,so that the mill can also beoperated efficiently and stablyat high product finenesses.External material circulationThe gas velocity in the nozzlering can be specifically minimised,so that a large portionof ground material is not entrainedby the hot gas streambut falls through the nozzle ringonto a discharge ring rotatingwith the grinding table. Thismaterial is then returned via adischarge chute and bucket

...theavailability and operating economy.7Stages in theassembly of a roller millin Australia.Heatedmaterialfeed systemof a rollermill.View intothe interiorof the millduringassembly.elevator to the grinding table or is conveyedto the high-efficiency separator.The discharge ring is of modular designand made of highly wear-resistant elementsfor long service lives and simplemaintenance.The energy saving mechanical conveyanceby bucket elevator reduces thepneumatic conveying of material in thegrinding compartment itself. This has theeffect of lowering the pressure drop, minimisingthe energy requirement and makingthe mill operation much smoother.Another advantage is that the bucket elevatorfacilitates emptying the roller millfor maintenance purposes.SEPOL ® high-efficiency separatorFor separating the ground material intofinished product and oversize, Polysiusroller mills include a SEPOL ® dynamichigh-efficiency separator, which can beadjusted in accordance with variousparameters. Due to its excellent selectivity,this separator drastically reduces thespecific power requirement for the grindingprocess.designed to suit the mill feed material areintegral parts of the grinding system.Both the coarse feed valve and the chutecan (if necessary) be indirectly heatedin order to ensure reliable operation evenin the case of high material moisturecontents.Wear protectionSpecial materials, adapted to the abrasivenessof the material to be ground, areused for the roller tyres and the grindingtrack, while special linings are installed inthe mill housing and separator.These ensure effective wear protectionand thus increase the service life and theoperating economy.Material feed systemTo ensure efficient feeding of the materialand to act as an airlock, a rotary feederfor coarse material and an inlet chuteGrindingtablegear unit.Coarsefeedvalve.

8Polysius roller mills......for raw material grinding.Roller mills from Polysiusefficiently grind all raw materialsfor the clinker manufacturingprocess – ranging fromsoft to very hard, from dryand fine to very moist and sticky and fromslightly abrasive to extremely abrasive.This grinding system includesa feed belt conveyor to themill (equipped with crossbeltmagnetic separator and metaldetector), the diverter gate forfast removal of tramp metal,the coarse feed valve (optionallyof heatable design) and thefeed chute.øCBThe external material circulationand the adjustable nozzlering minimise the pressuredrop of the mill and the energyrequirement of the mill systemfan.In addition to the plant layout,design details such as grindingelement qualities, the wearprotection and the separatorversion are optimally suited tothe raw material grindingrequirements.The parameters determined bythe specific feed material, such asenergy requirement, operatingbehaviour and wear characteristics,are established by meansof the Atrol test mill and used asa design basis for the mill size,drive power, separator size, wearprotection concept and grindingelement quality.ABasic design data.Type RM27/1330/15 33/16 36/18 38/19 41/20 43/21 46/23 48/24 51/26 54/27 57/28 60/29 66/29Installed powerThroughput(Raw material of averagegrindability, 12 % R 0.09 mm)ABCkWtphmmmmmm580 750 950 1190 1360 1650 1850 2190 2440 2840 3270 3750 4260 480090 115 150 185 210 255 285 340 380 440 500 580 660 7405700 6600 7300 8100 8400 8800 9100 9300 9700 10000 10700 11100 12000 1330010000 11000 12000 13000 14000 15500 16200 17000 17500 18000 19000 22000 25000 280004000 4300 4800 5200 5700 6000 6600 7000 7500 7900 8400 9000 9300 10200

...for granulated blast furnace slag grinding.9Energy-efficient grinding of granulatedblast furnace slag (GBFS) – fine-grained,usually very moist and also abrasive –to an extraordinarily high finished productfineness ... a specially demanding application.An important feature of thePolysius granulated blast furnaceslag grinding system is agenerously dimensioned externalmaterial circuit, in whichthe circulating material passesthrough a magnetic drum separatorwhich removes the liberatedfine iron from the process.The finished material is collectedin a bag filter, in order toprotect the downstream systemfan from abrasive blast furnaceslag dust.A hot gas producer installed fordrying the granulated blast furnaceslag heats not only themill, but also the coarse feedvalve in the new material feedsystem, the feed chute and therecirculating bucket elevator.Chemicalanalysis of the granulated blastfurnace slag provides informationon the wear rate of thegrinding elements and is thusthe basis for selection of thewear protection material.Magnetic drumseparator for fineiron removal.The mill is designed on thebasis of the Zeisel test, whichrequires only 3 kg of granulatedblast furnace slag butshows an excellent correlationto industrial operating results.Compound steelWear protection plateNiHard 4Ceramic mortar with anchoring steel meshBAWear protection forgranulated blastfurnace slag andclinker grinding.Type RMS30/1533/16 36/18 38/19 41/20 43/21 46/23 48/24 51/26 54/27 57/28 60/29 66/29Installed powerThroughput(GBFS of average grindability,4500 cm 2 /g acc. to Blaine)ABkWtphmmmm700 900 1200 1380 1660 1800 2040 2370 2800 3000 3500 4000 445022 28 37 43 52 56 64 74 88 94 110 124 1396600 7300 8100 8400 8800 9100 9300 9700 10000 10700 11100 12000 1330011000 12000 13000 14000 15500 16200 17000 17500 18000 19000 22000 25000 28000

10...for clinker grinding.Clinker – with and withoutadditives and intergrindingmaterials – can be ground flexiblyand energy-efficiently in thePolysius roller mill to all typesof highest quality cement.Selectivity [%]Apart from the simple systemmanagement, the main argumentsin favour of using aroller mill for clinker grindingare:The outstanding selectivity of the SEPOL ® -RMC separator is oneof the factors responsible for the plant efficiency.The diagram shows an unclassified portion of only 5 % and aseparator efficiency topping 90 % in the relevant grain size range.1009080706050Separation curve40Efficiency curve30Reduced separation curve201001 10 100 1000Grain size [µm]x Highly economic operationThe electrical energy requirementis only about 60 % that of a tube mill system.Due to the extraordinarily low wear rates, theservice lives of the grinding elements are enormouslyhigh (in the case of OPC grinding, thegrinding elements achieve lifetimes of above20,000 hours - without any marked changes incontour and thus with consistently high grindingefficiency).x Efficient grinding and dryingFor composite cement production, the roller millpermits the simultaneous grinding and drying oflarge amounts of moist additives. For drying theadditives and for specifically directed dewateringof the sulphate bearer, the mill can be heatedwith hot gas from a hot gas producer or withexhaust air from the clinker cooler.x High flexibilityThe short turnaround timespermit a very rapid changeoverto different product types.x High product qualityThe quality of the produced cements is comparablewith that of tube mill products and in somecases is even better.ABType RMC30/1533/16 36/18 38/19 41/20 43/21 46/23 48/24 51/26 54/27 57/28 60/29 66/29Installed powerThroughput(CEM of average grindability,3000 cm 2 /g acc. to Blaine)ABkWtphmmmm502 649 857 984 1183 1276 1465 1698 2006 2147 2507 2834 318833 43 56 65 78 84 96 111 132 141 165 186 2096600 7300 8100 8400 8800 9100 9300 9700 10000 10700 11100 12000 1330011000 12000 13000 14000 15500 16200 17000 17500 18000 19000 22000 25000 28000

...for coal and petcoke grinding.11Coal, petroleum coke andsimilar solid fuels can beground to the product finenessrequired for the combustionprocess while observingall safety-engineering requirements.This grinding system isdesigned to ensure effectivegrinding, drying and separationof solid fuels such as coal andpetcoke as well as safe handlingof the ignitable and explosivepowdery products.øCBThe grinding plant thereforeincorporates comprehensivesafety features including apressure shock resistant coarsefeed valve for mill feeding,pressure shock resistant rollermill and separator up to8 bar, pressure relief stacksbefore and after the mill, dustcollection filter with explosionvents, quick-closing dampersbefore and after the filter andsystem fan and a return airduct equipped with controldamper for temperature andgas flow control. Further safety-relevantplant componentsare the temperature and CO 2monitoring system and a CO 2inertisation system.The mill interior is designedto largely prevent fuel depositswhich could be a source ofspontaneous combustion.There is no external materialcirculation. Tramp metal isremoved via special dischargesystems.In the case of known fueltypes, the plant is dimensionedon the basis of the HardgroveIndex and the chemical analysis(ash). In extreme cases andin the case of unknown fuelgrades, it is good policy toadditionally conduct a pilottest.Ideally, the grinding plant isoperated with an inert atmosphere(O 2 ≤ 12%). However, itis also possible to use hot airor flue gas with higher oxygencontents - provided that certainvalues for the hot gas temperatureand volatiles content of thefuel are not exceeded.AType RMK8/411/5.5 13/6.5 15/7.5 17/8 19/921/10 23/11 25/12 27/13 30/15 33/16 36/18Installed powerThroughput(Hard coal, 50° Hardgrove, 12 % R 0.09 mm)ABCkWtphmmmmmm30 65 100 140 190 250 320 410 500 610 790 1000 12502.2 5.0 7.5 10.0 14.5 19.5 25 31 38,5 47 61 77 962250 2750 3500 4350 3200 4450 5000 5650 5900 6200 6700 7500 85002500 3500 4800 5000 5800 8000 8300 8700 9400 11000 12500 14500 170001150 1800 2200 2350 3000 3100 3200 3750 4200 4700 4900 5400 6000