振动筛外文翻译资料--外文翻译.doc

毕业设计（外文翻译）题目：标准筛振筛机的总体及夹紧装置的设计系别专业名称机械设计制造及其自动化班级学号学生姓名指导教师二O一一年三月COALPREPARATIONTABLE7-14.EffectofGeometryandConcentrationofFeedSolidsonthroughputfora1/6-in,diamhydrocyclonecleaning1/4-inVaryingthedistancebetweenthebottomofthevortexfinderandthehydrocycloneconebottom.Forexample,thewashedcoalashcanbereducedbydecreasingthediameterofthevortexfinder,decreasingthelengthofthevortexfinder,orincreasingthediameteroftheunderfloworifice.Increasingfeed-Solidscontentincreasesthespecificgravityofseparationand,therefore,washedcoalyieldandash,whichindicatestheimportanceofmaintainingaconstantfeed-solidscontenttopreservewashedcoalquality.Capacityisinfluencedbycyclonegeometry,i.e.,thesizesoftheoverflow,underflow,andinletopenings,andbyfeed-solidscontent.TheeffectsoftheseparametersisgiveninTable7-14.Increasinginletpressureisasimplemethodofincreasingcapacitywithoutchanginghydrocyclonegeometry,andwashedyieldandasharenotsignificantlyaffected.However,thepenaltyisincreasedpumpingcost,anddegradationofthecoal.FlowsheetsSoonafterthehydrocyclonewasdeveloped,itbecameevidentthatperformancewasinferiortonearlyallothercleaningdevices.Consequently,inanefforttoimproveperformance,threetwostagecircuits,showninFig.764,weredeveloped.Intheearliesttwo-stagecircuit,calledtwo-stagerelearnorTSR,therefusefromaprimaryhydrocycloneissimplyrelearnedinasecondaryhydrocyclone,Theoverflowsfromthetwohydrocyclonesarerecombinedasthewashedcoalproduct,andtheunderflowsfromthesecondaryhydroclonecontainsthefinalrefuse.Inmorerecentinstallations,oneoftheproductsfromthesecondaryhydrocycloneisrecirculatedtothefeedoftheprimaryhydrocyclone.Inthetwo-stageoverflowrecirculationcircuit,TSOR,theprimaryorfirst-stagehydrocycloneisadjustedtoproduceanacceptablecleancoalandthesecondaryhydrocycloneisadjustedtoproducearefuseessentiallyfreeofmisplacedcoal.Theoverflowfromthesecondaryhydrocyclone,whichcontainsthemisplacedcoalintheunderflowsoftheprimaryhydrocyclone,isreturnedtothefeedoftheprimaryhydrocycloneforreprocessing.Inthetwo-stageunderflowrecirculationcircuit,TSUR,andtheoverflowisrelearnedinthesecondaryhydrocyclone.Theunderflowfromthesecondaryhydrocloneisrecalculatedtothefeedoftheprimaryhydrocyclone.Theoverflowfromthesecondaryhydrocyclonecontainsthewashedcoal.Eachofthesecircuitshasadvantagesthatdependuponthesizeandspecificgravitycompositionsofthefeed,aswellastherequiredwashedcoalquality.TheTSORcircuitismoreeffectiveinrecoveringwashedcoalwhereastheTSURcircuitismoreeffectiveinrejectingheavyimpurity.TheTSRcircuitismosteffectivewhenthespecificgravityofseparationofthetwohydrocyclonesissimilar.Conversely,theperformanceofTSORandTSURisimprovedbydivergingthespecificgravityofseparationofthetwocyclones.Atthepresenttime,theTSORisthemostcommoncircuit.AvariationoftheTSRcircuithasbeenproposedwherebyunderflowfromtheprimarycycloneisrelearnedonaconcentratingtableratherthanasecondaryhydrocyclone.Someplantsusingjigstocleanthecoarsecoalutilizehydrocyclonestoimproveperformanceonthefinersizes.Onemethodistorelearntheunderflowofthewashedcoalscreen,commonlythe1/4-in.material,withhydrocyclones.Anothermethodistoscreentherawcoalataboutthissizeandcleantheundersizewithhydrocyclones.Hydrocycloneshavebeenusedaheadofdense-mediumcyclonestoremovesomeofthelowspecificgravitycoalandtherebyreducetheamountofmaterialsenttothedense-mediumplant.Thehydrocyclonesareadjustedtoseparateataspecificgravityofabout1.35to1.40.Theadvantageisthatthecapacityofthedense-mediumcycloneplantcanbesmaller,thusreducingcapitalandoperatingcosts.HydrocyclonePerformanceAsmentionedpreviously,thequalityofthewashedcoalandrefuseproductscanberegulatedbychangingthediametersoftheoverflowandunderfloworifices.Howeverfromaperformancestandpoint,aratioofoverflowdiametertounderflowdiameterinarangeofabout1.7to2givesthebestresults.Performanceatlowerratiosisinferior.Also,thesolidscontentinthefeedtoprimaryandsecondaryhydrocyclonesshouldrangefrom8to15%(byweight).Outsidethisrange,eitheraboveorbelow,performanceisadverselyaffected.Separationsobtainedinasinglehydrocycloneandtwo-stagecircuits(TSR)areshownbythedistributioncurvesinFig.7-65.Thesharpnessofseparationofthetwo-stagec