畢業(yè)設(shè)計(jì)（外文翻譯）題目：標(biāo)準(zhǔn)篩振篩機(jī)的總體及夾緊裝置的設(shè)計(jì)系別專(zhuān)業(yè)名稱(chēng)機(jī)械設(shè)計(jì)制造及其自動(dòng)化班級(jí)學(xué)號(hào)學(xué)生姓名指導(dǎo)教師二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