振动筛外文翻译资料--外文翻译.doc -- 5 元

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COALPREPARATIONTABLE714.EffectofGeometryandConcentrationofFeedSolidsonthroughputfora1/6in,diamhydrocyclonecleaning1/4inVaryingthedistancebetweenthebottomofthevortexfinderandthehydrocycloneconebottom.Forexample,thewashedcoalashcanbereducedbydecreasingthediameterofthevortexfinder,decreasingthelengthofthevortexfinder,orincreasingthediameteroftheunderfloworifice.IncreasingfeedSolidscontentincreasesthespecificgravityofseparationand,therefore,washedcoalyieldandash,whichindicatestheimportanceofmaintainingaconstantfeedsolidscontenttopreservewashedcoalquality.Capacityisinfluencedbycyclonegeometry,i.e.,thesizesoftheoverflow,underflow,andinletopenings,andbyfeedsolidscontent.TheeffectsoftheseparametersisgiveninTable714.Increasinginletpressureisasimplemethodofincreasingcapacitywithoutchanginghydrocyclonegeometry,andwashedyieldandasharenotsignificantlyaffected.However,thepenaltyisincreasedpumpingcost,anddegradationofthecoal.FlowsheetsSoonafterthehydrocyclonewasdeveloped,itbecameevidentthatperformancewasinferiortonearlyallothercleaningdevices.Consequently,inanefforttoimproveperformance,threetwostagecircuits,showninFig.764,weredeveloped.Intheearliesttwostagecircuit,calledtwostagerelearnorTSR,therefusefromaprimaryhydrocycloneissimplyrelearnedinasecondaryhydrocyclone,Theoverflowsfromthetwohydrocyclonesarerecombinedasthewashedcoalproduct,andtheunderflowsfromthesecondaryhydroclonecontainsthefinalrefuse.Inmorerecentinstallations,oneoftheproductsfromthesecondaryhydrocycloneisrecirculatedtothefeedoftheprimaryhydrocyclone.Inthetwostageoverflowrecirculationcircuit,TSOR,theprimaryorfirststagehydrocycloneisadjustedtoproduceanacceptablecleancoalandthesecondaryhydrocycloneisadjustedtoproducearefuseessentiallyfreeofmisplacedcoal.Theoverflowfromthesecondaryhydrocyclone,whichcontainsthemisplacedcoalintheunderflowsoftheprimaryhydrocyclone,isreturnedtothefeedoftheprimaryhydrocycloneforreprocessing.Inthetwostageunderflowrecirculationcircuit,TSUR,andtheoverflowisrelearnedinthesecondaryhydrocyclone.Theunderflowfromthesecondaryhydrocloneisrecalculatedtothefeedoftheprimaryhydrocyclone.Theoverflowfromthesecondaryhydrocyclonecontainsthewashedcoal.Eachofthesecircuitshasadvantagesthatdependuponthesizeandspecificgravitycompositionsofthefeed,aswellastherequiredwashedcoalquality.TheTSORcircuitismoreeffectiveinrecoveringwashedcoalwhereastheTSURcircuitismoreeffectiveinrejectingheavyimpurity.TheTSRcircuitismosteffectivewhenthespecificgravityofseparationofthetwohydrocyclonesissimilar.Conversely,theperformanceofTSORandTSURisimprovedbydivergingthespecificgravityofseparationofthetwocyclones.Atthepresenttime,theTSORisthemostcommoncircuit.AvariationoftheTSRcircuithasbeenproposedwherebyunderflowfromtheprimarycycloneisrelearnedonaconcentratingtableratherthanasecondaryhydrocyclone.Someplantsusingjigstocleanthecoarsecoalutilizehydrocyclonestoimproveperformanceonthefinersizes.Onemethodistorelearntheunderflowofthewashedcoalscreen,commonlythe1/4in.material,withhydrocyclones.Anothermethodistoscreentherawcoalataboutthissizeandcleantheundersizewithhydrocyclones.Hydrocycloneshavebeenusedaheadofdensemediumcyclonestoremovesomeofthelowspecificgravitycoalandtherebyreducetheamountofmaterialsenttothedensemediumplant.Thehydrocyclonesareadjustedtoseparateataspecificgravityofabout1.35to1.40.Theadvantageisthatthecapacityofthedensemediumcycloneplantcanbesmaller,thusreducingcapitalandoperatingcosts.HydrocyclonePerformanceAsmentionedpreviously,thequalityofthewashedcoalandrefuseproductscanberegulatedbychangingthediametersoftheoverflowandunderfloworifices.Howeverfromaperformancestandpoint,aratioofoverflowdiametertounderflowdiameterinarangeofabout1.7to2givesthebestresults.Performanceatlowerratiosisinferior.Also,thesolidscontentinthefeedtoprimaryandsecondaryhydrocyclonesshouldrangefrom8to15byweight.Outsidethisrange,eitheraboveorbelow,performanceisadverselyaffected.SeparationsobtainedinasinglehydrocycloneandtwostagecircuitsTSRareshownbythedistributioncurvesinFig.765.Thesharpnessofseparationofthetwostagecircuitissignificantlysuperiortothatofasinglehydrocyclone.Also,thesharpnessofseparationofthetwostagecircuitisnotnearlyassharpastheseparationscharacteristicofadensemediumcyclone.Itfollowsthenthathydrocyclonesarenot