雙語-飼料加工工藝學

1CollegeofAnimalScienceInnerMongoliaAgriculturalUniversityFeedManufacturingTechnology23Introduction

In1810,Germanscientist,Thaer,developedthefirstfeedingstandard.Germanscientist,HennebergandStohmann,devisetheproximateanalysissystemthatbrokefeedintosixcomponents:moisture,ash,crudeprotein,etherextract,crudefiberandnitrogen-freeextract.In1944,theNationalResearchCouncil(NRC)developedaseriesoffeedingstandardsforlivestockandpoultrythatareroutinelyupdatedandaretherecognizedbenchmarksforfeedformulationtoday.4Thefirstopportunityfortheformulafeedindustrytobeservicearoseinthelate1800s.Blatchford'siscreditedwithbeingthefirstfeedmanufacturingfirmintheUnitedStates.E.T.&H.K.wastheoldestfamilyfeedfirmofferinggroundgrainin1813inUS.Waukeganwasthefirsttomakeacalffeedin1875inUS.Otherfeedfirmsthatdatetheirbeginningbackmorethan100to150yearsago.Chinastartstoproducefeedfromthe1900s.5ChinaAnnualFeedProductionCapacity（億噸)6ClassificationofFeedProductionin2012（萬噸)

7ClassificationandDefinition

CompoundFeedCompoundfeedsarefeedstuffsthatareblendedfromvariousrawmaterialsandadditives.Theseblendsareformulatedaccordingtothespecificrequirementsofthetargetanimal.Theyaremanufacturedbyfeedproducersasmealtype,pelletsorcrumbles.ConcentratedFeedConcentratedfeedsarealsocalledasproteinsupplements,whicharefeedstuffsthatareblendmainlyfromprotein,vitamin,mineralsandadditivesbutwithoutenergysources.PremixPremixesarecomplexblendsofingredientsfromvitamins,minerals,aminoacidsandotheradditives8AdvantagesofFeedManufacturing

ProductionofasuitablecompoundfeedAnexampleisthesimplemixingofdifferentingredientstoproduceacompoundfeedthatfitsthespecificneedofananimal.IncreasednutritivevalueofthenutrientsinthefeedAnexampleistheheattreatmentofdietsforswinetoimprovedigestionofstarchduetogelatinisation(solubilisation)ofthestarch.IncreasedfeedintakeAnexampleisthepelletingoffeedsthatincreasesdensityandmakesuptakebytheanimaleasier.9BetterhygienicqualityAnexampleistheheattreatmenttoabove81

CtokilloffSalmonella.(沙門氏菌)EliminationofunwantedcomponentsAnexampleistheheattreatmentofsoybeanstodestroytrypsininhibitors.（胰蛋白酶抑制劑）ImprovedtechnicalpropertiesAnexampleispelletingthatreducesvolumeandriskofseparationandimprovesflowability.

10ImpactfactorsonFeedManufacturing

11ChapterOne

RawMaterialsReceivingandCleaning12

LectureOne:CharactersofRawMaterials

ThegrindingcomponentsThesematerialsincludedcereals,oilseeds,cakesandmeals,accountingfor70-80%oftotalrawmaterials,suchascorn,wheat,soybeanmeal(豆粕),rapeseedcake(菜籽餅),etc.Grainandanimalby-productsBy-productusedinfeedpantaremainlyrice-bran,wheat-bran,fishmeals,andsomeby-productfromslaughterhouse.InorganicMaterialsandVitaminsSuchascalciumcarbonate(CaCO3),sodiumchloride(NaCl),calciumphosphate(Ca3(PO4)2),VitaminA,D,E,KandBgroups.13LiquidsThecommonusedliquidmaterialsbyfeedplantsaremolasses(糖蜜)andfat.Exceptthat,aminoacid(氨基酸)andVitaminBgrouparealsoadoptedinliquidforms.MedicinesandAdditivesPreviously,antibioticswerewidelyacceptedbyfeedplants,butnowitwasprohibitedoverall.Otheradditives,suchasflavouring

(香味劑),preservative(防腐劑）notcommonexistinfeedproduction.

14PhysicalCharacterofRawMaterials

Flowability(散落性)Abilityofmaterialspreadaroundinthefreestate,similartotheliquidflowproperties.Fines:10μm～2.0mmParticles:>2.0mmFrictionCoefficient(摩擦系數)Theratiooftheforcethatmaintainscontactbetweenanobjectandasurfaceandthefrictionalforcethatresiststhemotionoftheobject.Higherfrictioncoefficient,easierfeeddelivery.15Auto-segregation(自動分級)Duringtheprocessoftransportationandhandling,duetothedifferentofdensity,bulkandsurfacecharacteristics,particlessegregatefromtherestgroups.Auto-segregationresultinanegativeeffectonfeeddelivery.Commonly,particleswithhighbulkdensity“float”onthesurfacebutlightparticleseasilypileupthebottoms,whichcauseauto-segregation,especiallylongdistancetransmission.16Density

Densitydefinedinaqualitativemannerasthemeasureoftherelative"heaviness"ofobjectswithaconstantvolume.Thedensityisusedtodecidethestoragecapacityduringthedesignofthefeedplants.ClassificationDensity（Kg/M2）MinimumMaximumCapacity

Corn玉米750830750Barley大麥455600500Wheat小麥660800750Soy大豆725760750Sorghum高粱751780760HulledRice糙米70080075017Adsorbability(吸附性)Adsorption,whichisageneraltermintroducedbyJ.W.Mcbain,includesselectivetransfertothesurfaceand/orintothebulkofasolidorliquid.Infeedscience,adsorptionabilityreferstothecharacterofrawfeedmaterialsabsorbothersubstancetotheirsurface.Influencefactorsofadsorbability1、externalform(fine,particles)2、surfacecharacteristics(smooth,coarse)18

Hygroscopicity

(吸濕性)Thepropertypossessedbyfeedparticlesofabsorbingordischargingmoistureaccordingtocircumstances,suchassodiumchloride(NaCl),sulphate(硫酸鹽),cholinechloride(氯化膽堿，ＶB),fishmeals,etc.

Materialswithhighhygroscopicityexertthenegativeeffectonfeedproduction,bywhichcausemildew(霉變),agglomeration

(結塊),aswellasinfluencethefeedstorageandquality.19

ThermalStabilityThermalstabilityindicatethepropertyofheatresistanceunderthermaltreatmentprocess.SomesubstancesuchasVitaminBgroupsandaminoacidsareeasilyoxidizedbyhightemperature.Thermaltreatmentcauseinactivationofsomeharmfulmatterssuchasantitrypsin(抗胰蛋白酶)insoybean,sinigrin

(芥子甙)inrapeseedandeliminatemicrobes.20Toxicity

Somesubstance,mainlymicroelementsandmedicines,havethepoisonouseffectondomesticanimals.Forexample,lead(鉛)，arsenic

(砷)arethecrucialmineralsonanimalgrowthbutoverdosenotonlypoisontheanimalsbutalsocontaminatetheenvironment.21Staticelectricity(靜電)Theitemthatrubsofftheouterlayeroftheatomcausesomeoftheextraelectrons,givingitaslightlynegativecharge.Thisbuilt-upelectricchargeiscalledasstaticelectricity.Thesparkcausedbystaticelectricityisoneofthemostdangeroussourcesduringthefeedproductionprocess,whichcouldbring“explosion”ofthefeedlot.22LectureTwo:Receiving

Receivingincludesnotonlytheactualreceiptandplacementofingredientsbutalsothescheduling,weightverification,initialinspection,sampling,andqualitycontrolofeachingredient.Generally,thereceivingcapacityis3-5timesofproductioncapacitytomeettheprocesslinerunningstable.Theingredientsreceivedmaybegroupedasfollows:１、Unprocessedgrains２、Softfeedingredients３、Heavymaterials４、Microingredients５、Liquids23SolidIngredientsReceivingIngredientscarriedbybulktruckortrainsareweightedanddumpedintoreceivingpit(糧坑)tostorageforfurthertransfer.24１、train２、bulktruck３、beltconveyor４、bucketelevators５、sieving６、magneticselection７、weighing８、storage９、screwconveyorSolidIngredientsReceiving25LiquidIngredientReceiving1、tanktruck2、receivingpump3、molassestank4、heatingsystem5、deliverypump26CharacteristicsofMolassespHis5.5HascorrosiveeffectonstoragetankwhenitcontainwaterToavoidoxidation,installingventilationsystemonthetopoftankHeatingsysteminsidetanktodecreaseitsviscosityHeatingtemperaturenomorethan48℃

27CharacteristicsofFatHavehighcorrosiveeffectonstoragetankduetotheoxidationprocesswhenwatercontentincreasefrom0.5to3%Thicknessoftanknotlessthan3mmBeforetransferring,heatingtemperatureis75～80℃28LectureThree:IngredientsCleaning

ObjectiveTheobjectiveofcleaningisnotonlytocleanouttheimpuritiesbutalsotoprotectmachines,whichiscausedbytheferricsubstanceblendinginthemassiveingredients.

Requirement

1、beforereceivingprocess,ingredientfromanimalorigin,mineralsandvitaminshavenoneedtoclean.

2、massivematerialsandliquidingredients,suchasgrains,molassesandfatmustbecleanedbeforemovingintothefactory.29CleaningMethodsScreening(篩選)

mud,sandandotherimpuritiessuchasstrawsarecarriedawaybysievesCleaningbynaturemagnetorelectromagnettoremoveimpuritiescontainingironCleaningbyDraftAspirating

(吸風除塵)

accordingtodifferentsuspendingcharacter,

finesanddustsarepumpedoutfromingredientsbyairflow.30Screening(篩選)

Accordingtodifferentparticlesizes,preselectionisconductedthroughdifferentsizesofparticlesintheparticulatematerialsandseparatedasminussieves(篩下物andplussieves(篩上物).MainApparatus1、Endlessscreenprecleaner

（網帶初清篩）2、Cylinderprecleaner

（圓筒初清篩）31EndlessScreenPrecleaner1、Import

原料進口2、Belt

網帶3、Settingchamber

沉降室4、Exportofgranules

原料出口5、Exportofimpurities雜質出口32BeltImport33CylinderPrecleanergranulesimport進料口Helix

螺旋片Sievingchamber

篩筒Electromotor

電動機Conveyingsystem

傳動裝置Screening

篩片Supporting

機架3435MagneticSeparationMagneticseparationprovideeffectivemeansremovingferrouschipsandmetalparticlesfromlooselypacked,freeflowingmaterialsthroughmagneticforce.Magneticseparationinstrumentscommonlyusedinfeedmillarepermanentmagneticseparatorandelectromagneticseparator.36Import(進料口)

2.Cylinder(外筒)

3.Magnet(磁鐵)

4.Gateofcylinder(外筒門)5.Export(出口)

6.Encloser(外罩)

7.8.Magnet37ElectromagneticSeparatorMagneticforcecausedbyelectricityseparateferrouschipsandmetalparticlesfromthemixture.Whenrawmaterialsenterbygravitywithinthematrixandastherotorrotates,theyareseparatedfromaferrouspartwhichisretainedinthematrices,andanon-ferrous,non-magnetizedpartbythemagneticfieldandpassesbetweenthem.38LectureFour:FeedstockTransportationUnderthereceivinghopper,itisplacedaconveyorthatmaybescrewordragtype.Whentheingredienttobereceivedisgrainortheproductiseasytoflowallowingforlittlecontamination,thenascrewconveyorischosenforunloadingingredients.Dragconveyorsareoftenchoseniftheingredientmustbehandedmoregentlyand/orcontinuouscleaningoftheequipmentisnecessary.39BeltConveyors

(膠帶輸送機)Thebeltconveyorsystemsarewidelyusedinfeedmanufacturingindustry.Theyareextensivelyusedtotransportfeedingredientsandotherbulksolids(散裝固體)overlongdistances.Beltconveyorcanbedefinedsimplyasendlessstrapofflexiblematerialstretchedbetweentwodrumsandsupportedatintervalsonrollers.Thereareseveraltypesofbeltconveyors.Themainfeaturesinfluencingthechoiceofchoosingthebeltconveyortypeare:40PropertyofBeltConveyorsHighworkreliabilityLowmaterialdamageLowresidualsLowpriceLowenergyinputDifficulttosealandcausetoraisedust41Idler:惰輪Drivingmotor:動力輪42ScrewConveyor

OperationPrincipleHorizontalscrewconveyorhastheadvantagesofsealedoperation,simplestructure.screwconveyorsuitableforconveyingpowdery,granularandsmallbulkmaterialshorizontallyoraslope.Featureofscrewconveyor１、compactstructure２、small-sectionalarea３、lightweight４、goodsealproperty43Featureofscrewconveyor5、hightransportationefficiency6、smarttechnologylayout7、convenientinstallation8、dismountandmoveaswellas9、safeoperation10、dischargematerialsatdifferentstations4445BucketElevators

Insituationswheretheliftingofbulksolidsisinvolved,thebucketelevatorsarethemostsimple,efficientandreliablepieceoftheequipmentthatcouldbeused.Constructionofbucketelevatorsvariesfromthemanufacturertoanotherandspecificdesignfeaturesofbuckets,operatingspeedandthefeedanddischargearrangements.46FeatureofBucketElevatorsEndlessbeltofchainsorothermaterialasatractionelementtowhichareattachedaseriesofcarryingbucketsAsingleordoublecasing(外筒)whichservestoenclosethemovingbucketsAheadattheupperendoftheelevatorwhichincludesabeltlifter(pulley)orchainwheeltoturnthetractionelementandasuitabledischargechute(卸料槽)Aboot(底座)

atthelowerendwhichincludesabeltpulley(皮帶輪)orchainwheel(滑輪),atensiondevice(張力裝置)Buckets(cups,料斗)InspectiondoorSensorsformotiontrackingVentilationorfilterSource:FeedManufacturingTechnologyIV,p.174-1784748PneumaticConveying

Whentheneedforavoidanceofcontaminationisrequiredapneumaticsystemhastobeinstalledwithaseparatetubeforeachingredienttobeunloaded.Thepneumaticsystemmaybepositiveornegativepressureandcombinationofboth.Powerunitstopushorpulltheproductthroughthetubecomesfromastandalongpowerunitoperatedbythefeedplantormorecommonlyisprovidedbythetransportingvehicle.Disadvantageofpneumaticsystemisthatitisexpensivetooperate,havefrequentbreakdownandisusedonlyinafewingredientssuchasmineralswherecontaminationmustbezero.Source:FeedManufacturingTechnologyIV,p.174-17849Lecture5:FeedStorageFromthefeedmanufacturingpointofviewthestoringofingredientsatthefeedplantbecomesthemostimportantquestiontobeanswered.Thevariety(number)ofingredientsthatareneededforproducingfeed,itsphysicalcharacteristics,minimumormaximumthatmustbekeptonhand,flow-abilityofingredientconcerns,sanitationandcontaminationconcerns,etc.Feedingredientswhicharedrybeforeprocessingshouldbekeptdryandcoolandusedonafirst-in,first-outbasis.Asageneralrulethemoisturepercentageshouldbelessthan13%particularlyinhumidand/ortropicalareas.50Liquidingredientssuchastallow,aminoacids,andmolassesshouldbestoredinaccordancewithmanufacturers’recommendedprocedurestoprotectfreshness.Fatsandoilsmayneedtobeheatedforeaseofhandlingand/orhaveantioxidantsadded(topreventlipidperoxidation

(過氧化)andcontroloff-flavors

(異味))tomaintainquality.Aquaticanimalsareparticularlysensitivetolowlevelsof,forexamplefumigants(熏蒸劑),andforthatreasongreatcaremustbetakeninthechoice.51Ifthecompanywishestoprocessrawmaterials，therearetwomethodsoflayingoutaplant.Thefirstiscalledthepre-grindmill,wheretherawmaterialsareprocessedbymillingorgrindingandthenconveyedtostoragebinsorsilospriorblending.Thesecondmethodisthepost-grindmill,inwhichtherawmaterialsarestoredintheirunprocessedstate,weighedintherequiredproportions,pre-blendedandthenground.Inmanycountries,themostpopulararrangementtodayistousethepost-grindmillasitismoreflexible,particularlyifarangeofproductsaretobemanufactured.52StorageInstrumentsSilo(筒倉)Forbulkstoragethemostcommontypeissilooratankforliquids.Atypicalfeedformulacouldhavefrom10to30differentingredientswhethertheyareinverylargeamount(macroingredients)orintheamountslessthenkilo(microingredients).53AccessoriesofSiloAgitators:designedtohelpingredientflowFilter:locatedonthetopofthesiloforrelievingpressureandpreventingdustLevelindicators:designedtoprovideinformationoncapacityofbinattimeoffillingoremptyingThermometerprobes:giveatemperatureprofileofthestoredingredientVibratorsorotherdevicestohelptheflowofhangedmaterialVibratorLevelindicator54PropertiesofSiloHighcapacity

(倉容大)Lowconstructionspace

(占地面積小)Easymechanizedoperation

(易于機械化操作)Lowlaborintensity

(勞動強度小)Highconstructioncost

(建造成本高)55WarehouseWhenafeedplantmustdepositlargeamountoffinishingfeedduetothelogisticsoragriculturalpolicies,morethen10.000tonsatonetime,thenthewarehouseorflatstorageistheidealsolution.

Propertiesofwarehouse

1.Lowconstructioncost2.Suitableforstorageofmash(粉料)andfinishedproducts.3.Highlaborintensity4.Difficulttomechanizedoperation56Chapter２：Grinding

Lecture1:IntroductionIn19thcentury,theintroductionofmodernagriculturalpracticesallovertheworld,theeaseoftransportandinternationaltradeandincreaseddemandforanimalproductsturnedcerealsintoapotentialfeedsource.Paralleltothis,technologytoprocesscerealsandotherfeedingredientsintofeedemerged.Onofthefirsttechnologiestoemergewasgrinding.IntheUSwhereprogressoccurredrapidly,thefirstmillwhichsoldgroundgrainforfeedisreportedtohaveoperatedfrom1803.However,mostfeedmillscameintooperationinthelasthalfofthe19thcenturyandinthefirsthalfofthe20thcentury.57Themainanimalspeciestobefedcommercialconcentratefeedswhereinfacthorsesandcattle.Itwassoonrecognizedthatparticlereductionwasnecessaryfortheanimalstotakefullbenefitofthecereals.Thus,themainmotivationforgrindinginthefirstplacewasprobablytoincreasethesurfaceareaandthusimprovedigestion.Withmoreingredientsbecomingavailable,combinedwithmoreknowledgeondifferentnutrientsandtheproportioninthefeed,mixingbecamemoresophisticated.Thisfurtherincreasedtheneedforgrinding,sincegrindingimprovesmixabilityofingredients.58Anotherdrivetowardsafinerandmoresophisticatedgrindingwasthepelletingtechnologythatbecamecommonplacetowardsthesecondhalfofthe20thcentury.Afinegrindingincreasesthesurfaceareaofparticles,andthuscontributestoanimprovedbindingabilitybetweenparticles,andthusimprovespelletdurability.Eveniffeedisbeingpresentedfortheanimalasamashfeed,afinegrindingmaybedesiredtoassureahomogenousparticledistributionandthuslessriskforsegregationoffeedmaterialthroughtransportationandstorage.Anothermotivationforgrindingistoeliminategerminationabilityinseeds.Thisisparticularlytruewhentheseedsmaycontainweedseedsthatshouldnotbespreadthroughfaeces.59SummaryincreasingthesurfaceandthusimprovedigestionincreasingsurfaceandthusimprovethebindingabilitybetweenparticlesimprovingmixabilityofingredientsEliminationofgerminationabilityincreasingparticlehomogeneity60Requirementofoptimalgrindingprocess

havingverywideparticlesizerangeofincomingmaterialthegrindingshouldresultinauniformparticlesizereductiontheparticlesizedistributionshouldbepredictabletherangeinparticlesizeforaspecifictypeofequipmentshouldbewidethecapacityoftheequipmentshouldbehightheenergyconsumptionshouldbelowmaintenancecostshouldbelowinvestmentcostshouldbelowtheoperationshouldbeeasytheimpactonworkingenvironmentshouldbesmalltemperatureincreaseshouldbesmall61OptimumParticleSizeforDifferentAnimalsPiglet

(仔豬)

1、afterweaning0-14days,300micron(μm)

2、afterweaning15days,500micronFinishingPig

(育肥豬):

500-600micronSow(母豬):

400-500micronBroilers(肉仔雞):700-900micronLayinghen(蛋雞)：1000micron62TypeofGrindingEquipmentsAnumberofdifferenttechnologiesexistforgrinding.However,onlyafewarecommonlyfoundinfeedfactories.Themostcommontypeofgrinderisthehammermill,whichhasbeenreportedtoexistsincebefore1895intheUS.Anothersomewhatlessfrequentlyusedtypeofmillistherollermill,althoughtheuseofthistypeofmillappearstobeontherise.Discmillsandpinmillsarelesscommonlyusedmills,butwhicharesometimesusedforspecificfeedgrindingoperations.63HammerMill錘片粉碎機646566DifferentTypesofScreens67DifferentTypesofHammer

68OperationTheoryHammermillsarethemostcommontouseforparticlereductioninthefeedindustry.Hammermillsaccomplishsizereductionbyimpactingaslowmovingtarget,suchasacerealgrain,witharapidlymovinghammer(alsocalledknifes).Thehammersarerectangularmetalplates,eitherhardenedornothardened,whichareattachedtotherotatingshaftwithabolt.Thehammersareusuallyattachedtotheaxisinseveralrows(4to8arecommonlyobserved),whichcoversthefullwidthofthehammermillchamber,andwithhammersspreadalongthewidth.69Thethicknessofthehammersandthenumberofhammerswillvarydependingonwidthofthegrindingchamber,butthehammerareawillusuallycoverupto50%ofthegrindingchamberwidth.Thefeedtobegroundhaslittleornomomentumasitfallsintothegrindingchamber(lowkineticenergy),whereasthehammertipistravellingataminimumof4880m/min(81m/sec)andperhapsinexcessof7015m/min(117m/sec)(highkineticenergy).70

Thegrindingcanbedescribedasasimplethree-stepoperation,wherematerialisfedintothemill’schamber,typicallybygravity,andstruckbygangedhammers(rectangularpiecesofhardenedsteel)whichareattachedtoashaftandwhichrotatesathighspeedinsidethechamber.Thematerialiscrushedorshatteredbytherepeatedhammerimpacts,collisionswiththewallsofthegrindingchamber,aswellasparticleonparticleimpacts.Thereafter,materialthatistoolargetopassthesieveopeningisretainedforfurthergrindingwhilesomeoftheproperlysizedmaterialswillpassthrough.71Theairassistsystemischaracterizedbyafanthatsucksairthroughthehammermillinthesamedirectionasthefeed.Theairthenfollowstheconveyorunderthegrindingandistransportedthroughacyclonewherecoarsefeedmaterialisseparatedfromtheair.Thereafter,theairgoesthroughfilterbeforebeingdischargedintotheoutsideair.１、Surgebin

緩沖倉２、Hammermill

錘片粉碎機３、Hopper

料斗４、９、Airseal

關風５、Screwconveyor

螺旋運輸器６、DustEnclosure

吸風罩７、Fan

風機８、Clothebagdeduster

布袋除塵器10、Buckelevator

斗式提升機72DisadvantagesofHammerMillThedisadvantagesarethatthegrindingresultsinagreatrangeofparticlesizes,withalotofparticlesbeingverysmall.Theabilitytocontrolthegrindingprocessisalsolimited.Italsohasahighenergyconsumptionandthustemperatureincreaseduringgrindingmaybeanissue.Inaddition,thehammermillisnoisyandproducesdust.73FactorsaffectinggrindingcapacityandgrindingresultThedifferentcerealswillhavedifferenteffectongrindingcapacityinahammermill.Asaruleofthumb,barleygrindsmuchfasterthanoats,wheatgrindsfasterthatbarley,andcorngrindsfasterthanwheat.Somedataindicatethatgrindingcapacitydoubleswhenbarleyisgroundinsteadofoats,whenwheatisgroundinsteadofbarley,andwhenmaizeisgroundinsteadofwheat.Moisturecontentalsohasaneffectonefficiencyofgrinding.Asaruleofthumb,aonepercentageincreaseinmoisturecontentwillincreasethepowerconsumptionwith7percent.74Screenperforationshasalargeinfluenceongrindingresult.Thetablebelowshowstherelationshipbetweenscreendiameterandgrindingcapacityforoatsandwheat.Screenperforation(mm)Grindingcapacityinkg/kWhOATSWHEAT1,520,072,02,034,089,02,541,0116,03,046,5150,53,560,5175,04,075,6190,04,585,0213,55,094,0235,05,5103,0255,06,0111,0274,06,5119,0292,075RollerMill

輥式粉碎機76RollermillsRollermillsarenotascommonlyusedashammermills,butduetotheiradvantageswhenitcomestoenergyconsumption,noise,lackofheatincreaseandthusmoisturelossanduniformityofparticlesizeofmilledproduct,theyshoulddefinitelybeconsidered.Rollermillshastwoormorepairofrollswhichcrushthematerialasitpassesbetweenthecounter-rotatingrolls77Themaingrindingprincipleisthuscompression,andduetothis,friableandbrittlematerialismostsuitableforrollermillgrinding.Thepairofrollsmayrotateatequalorunequalspeed.Iftheytravelatunequalspeed,shearingmayalsoberesponsibleforparticlereduction.Intherollermill,itisextremelyimportantforgrindingefficiencyandgrindingresultthatthematerialtobegroundisdeliveredinanevenflowandwithmaterialdeliveredalongthewholewidthoftherolls.Eachpairofrollsisplacedsuchthatonerollismountedinafixedposition,whiletheothercanbemovedclosedtoorfurtherawayfromthefixedroll.Thisdistancewillbethemajoradjustmentfactorforextentofgrindingintherollermill.78Therollsare23to30cmindiameterwithalengthtodiametermaximumaslargeas4:1,andaregrooved.79ContrastbetweenRollerMillandHammerMillThemainadvantageofrollermillsisthattheyareenergyefficient.Reportedfiguresarea30to50percentimprovementinthroughputperkWhwhengrindingcerealstotypicalsizesusedinthefeedindustry,comparedtohammermills.Rollermillsgiveauniformparticlesizereduction,andtheyarebeneficialfortheworkingenvironmentduetolittlenoiseanddustgeneration.Theuniformparticledistributionisparticularlybeneficialinthattheamountofveryfinedustymaterialislowcomparedtothehammermill.Thisalsoexplainsthelowdustgenerationwitharollermill.80Particledistributionismoreevenofrollermillcomparingwithhammermill.HMmeanshammermill,andRMmeansrollermill.HM3HM6RM3RM6RM9Particledistribution(g/kg):<0.2mm1439