机械专业英文文献翻译Word文档格式.docx

机械专业英文文献翻译Word文档格式.docx

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HighProductivity—AQuestionofShearerLoaderCuttingSequences

K.Nienhaus,A.K.Bayer&

H.Haut,AachenUniversityofTechnology,GER

1Abstract

Recently,thefocusinundergroundlongwallcoalmininghasbeenonincreasingtheinstalledmotorpowerofshearerloadersandarmouredfaceconveyors（AFC）,moresophisticatedsupportcontrolsystemsandlongerfacelength,inordertoreducecostsandachievehigherproductivity.Theseeffortshaveresultedinhigheroutputandpreviouslyunseenfaceadvancerates.Thetrendtowards“biggerandbetter”equipmentandlayoutschemes,however,israpidlynearingthelimitationsoftechnicalandeconomicalfeasibility.Torealisefurtherproductivityincreases,organisationalchangesoflongwallminingprocedureslooksliketheonlyreasonableanswer.Thebenefitsofopti-misedshearerloadercuttingsequences,leadingtobetterperformance,arediscussedinthispaper.

2Introductions

Traditionally,inundergroundlongwallminingoperations,shearerloadersproducecoalusingeitheroneofthefollowingcuttingsequences:

uni-directionalorbi-directionalcycles.Besidesthesepre-dominantmethods,alternativeminingcycleshavealsobeendevelopedandsuccessfullyappliedinundergroundhardcoalminesallovertheworld.Thehalf-webcuttingcyclease.g.utilizedinRAGCoalInternational’sTwentymileMineinColorado,USA,andthe“Opti-Cycle”ofMatla’sSouthAfricanshortwalloperationmustbementionedinthiscontext.Othermineshavealsotestedsimilarbutmodifiedcuttingcyclesresultinginimprovedoutput,e.g.improvementsintermsofproductiv-ityincreasesofupto40%arethoughtpossible。

Whereasthementionedminesareapplyingthealternativecuttingmethodsaccordingtotheirspe-cificconditions,–e.g.seamheightorequipmentused,–thispaperlookssystematicallyatthediffer-entmethodsfromageneralisedpointofview.Adetaileddescriptionoftheminingcycleforeachcuttingtechnique,includingtheillustrationofproductiveandnon-productivecycletimes,willbefollowedbyabriefpresentationoftheperformedproductioncapacitycalculationandasummaryofthetechnicalrestrictionsofeachsystem.Standardisedequipmentclassesfordifferentseamheightsaredefined,afterthemostsuitableandmostproductiveminingequipmentforeachclassarese-lected.BesidesthetechnicalparametersoftheshearerloaderandtheAFC,thelengthofthelong-wallfaceandthespecificcuttingenergyofthecoalarethemainvariablesforeachheightclassinthemodel.Asaresultofthecapacitycalculations,thedifferentshearercuttingmethodscanbegraphicallycomparedinastandardisedwayshowingtheproductivityofeachmethod.Duetothegeneralchar-acterofthemodel,potentialoptimisations（resultingfromchangesinthecuttingcycleandthebenefitsintermsofhigherproductivityoftheminingoperation）canbederived.

3State-of-the-artofshearerloadercuttingsequences

Thequestion“Whyaredifferentcuttingsequencesappliedinlongwallmining?

”hastobean-swered,beforediscussingthesignificantcharacteristicsintermsofoperationalprocedures.Themajorconstraintsandreasonsfororagainstaspecialcuttingmethodaretheseamheightandhard-nessofthecoal,thegeotechnicalparametersofthecoalseamandthegeologicalsettingofthemineinfluencingthecavingpropertiesaswellasthesubsidenceandespeciallythelengthofthelongwallface.Foreachminingenvironmenttheapplicationofeithersequenceresultsindifferentproductionratesandconsequentlyadvanceratesoftheface.ThecoalflowontotheAFCisanotherpointthatvariesliketheloadsontheshearerloader,especiallytherangingarmsandthestressesandthewearonthepicks.Athoroughanalysisisnecessarytochoosethebest-suitedminingcycle;

therefore,generalsolutionsdonotguaranteeoptimalefficiencyandproductivity.

Acategorizationofshearerloadercuttingsequencesisrealisedbyfourmajorparameters.Firstly,onecanseparatebetweenminingmethods,whichminecoalintwodirections–meaningfromtheheadtothetailgateandonthereturnrunaswell–orinonedirectiononly.Secondly,thewaytheminingsequencedealswiththesituationatthefaceends,toadvancefacelineafterextract-ingtheequivalentofacuttingweb,isacharacteristicparameterforeachseparatemethod.Thenec-essarytraveldistancewhilesumpingvariesbetweenthesequences,asdoesthetimeneededtoper-formthistask,too.Anotheraspectdefiningthesequencesistheproportionofthewebcuttingcoalperrun.Whereastraditionallythefullwebwasused,theintroductionofmodernAFCandroofsup-portautomationcontrolsystemsallowsforefficientoperationsusinghalfwebmethods.Theforthparameteridentifyingstateoftheartshearerloadercuttingsequencesistheopeningcreatedperrun.Otherthanthepartialorhalf-openingmethodlikethoseusedinMatla’s“Opti-Cycle”,thecuttingheightisequaltothecompleteseamheightincludingpartingsandsofthangingorfootwallmaterial.

Bi-directionalcuttingsequence

Thebi-directionalcuttingsequence,depictedinFigure1a,ischaracterisedbytwosumpingopera-tionsatthefaceendsinacompletecycle,whichisaccomplishedduringboththeforwardandreturntrip.Thewholelongwallfaceadvanceseachcompletecycleattheequivalentoftwowebdistancesbythecompletionofeachcycle.Theleadingdrumoftheshearercutstheupperpartoftheseamwhilethereardrumcutsthebottomcoalandcleansthefloorcoal.Themaindisadvantagesofthiscuttingmethodarethoughttobetheunproductivetimeresultingfromthefaceendactivitiesandthecomplexoperation.Therefore,thetrendinrecentyearswastoincreasefacelengthtoreducetherelativeimpactofsumpinginfavouroflongerproductiontime.

Uni-directionalcuttingsequence

Incontrasttothebi-directionalmethod,theshearerloadercutsthecoalinonesingledirectionwheninuni-directionalmode.Onthereturntrip,thefloorcoalisloadedandtheflooritselfcleaned.Theshearerhaulagespeedsonthereturntripsarerestrictedonlybytheoperators’movementthroughthelongwallface,orthehaulagemotorsinafullyautomatedoperation.Thesumpingprocedurestartsinneartheheadgate,asshowninFigure1b.Thelowmachineutilisationbecauseofcuttingjustonewebpercycleisthemaindisadvantageoftheuni-directionalcuttingsequence.Besidesthecoalflowcanbequiteirregulardependingonthepositionoftheshearerinthecycle.

Halfwebcuttingsequence

Themainbenefitofhalfwebcuttingsequencesisthereductionofunproductivetimesintheminingcycle,whichresultsinhighmachineutilisation.Thisisachievedbycuttingonlyahalfwebinmidfacewithbi-directionalgatesequencesasshowninFigure2a.Thefullwebisminedatthefaceends,withlowerspeedsallowingfastersheareroperationinbothdirectionsinmidseam.Besidetherealisationofhigherhaulagespeeds,thecoalflowontheAFCismorebalancedforshearerloadertripsinbothdirections.

Half-/partial-openingcuttingsequence

Theadvantageofthehalf-or,moreprecisely,partial-openingcuttingsequenceisthefactthatthefaceisextractedintwopasses.Figure2bshowsthattheupperandmiddlepartoftheseamiscutduringthepasstowardsthetailgate.Whereasthelastpartofthistripfortheequivalentofama-chinelengththeleadingdrumisraisedtocuttherooftoallowtheroofsupporttobeadvanced.Onthereturntripthebottomcoalisminedwiththeadvantageofafreefaceandasmallerproportionoftheleadingdrumcuttingcoal;

consequentlyleadingtolessrestrictionsofthehaulagespeedduetothespecificcuttingenergyofthematerial.Theshearersumpsinmidseamneartheheadgatetothefullwebwithoutinvokingunproductivecycletime.Likeforthetripthetailgatetheleadingdrumhastobeloweredamachinelengthaheadofthemaingate.

4Productioncapacitycalculations

Atheoreticalcomparisonoftheproductivitybetweendifferentminingmethodsingeneral,orinthiscasebetweendifferentshearerloadercuttingcycles,isalwaysbasedonnumerousassumptionsandtechnicalandgeologicalrestrictions.Asaresult,thisproductioncapacitycalculationdoesnotclaimtoofferexactresults,althoughitdoesindicateproductivitytrendsandcertainparametersforeachanalysedmethod.

Themodelworkswithso-calledheightclassesvaryingtheseamthicknessesbetween2mand5minstepsof50cm.Equipmentisassignedtoeachclass,havingbeenselectedbylookingatthebest-suitedtechnicalpropertiesavailableonthemarket[4].Apartfromthedefinedequipment,itisassumedthattheseamisflatandnoundulationsorgeologicalfaultsoccur.Inthemodel,theventilationandtheroofsupportsystemrepresentnorestrictionstotheproduction.Sincetheaimofthismodelistoshowwaystofurtherincreasesinlongwallproductivity,thecalculationisbasedonafullyautomatedsystemwithnomanualoperatorsrequiredattheface.ThehaulagespeedofthesheareristhereforeonlyrestrictedbytheAFCcapacity,thecuttingmotorsandthehaulagemotorsrespectively.

Thevariableparametersinthiscomparisonofthefourcuttingsequencesare,（besidesseamthick-ness）thespecificcuttingenergyofthecoaltobecutandthelengthofthelongwallface.Theformervaryingbetween0.2and0.4kWh/m³

thelatterbetween100mand400min50mintervals.The100mshortwallsweredeliberatelyselected,sincetheyarecomingmoreintofocusforvariousreasons.Geotechnicalaspects,likee.g.thecavingabilityofthehangingwallandfaults,restrictlong-wallpanelsinmanyplacestomaximumfacelengthsof150morless