煤矿火灾控制的最近发展和实践外文文献翻译.docx
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煤矿火灾控制的最近发展和实践外文文献翻译.docx
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煤矿火灾控制的最近发展和实践外文文献翻译
英文原文
RecentDevelopmentsandPracticestoControlFireinUndergoundCoalMines
S.K.Ray*andR.P.Singh,CentralMiningResearchInstitute,BarwaRoad,
Dhanbad,Jharkhand826001,India
Abstract:
Coalminefirescauseseriousthreattothepropertyandhumanlives.Out-breakoffiremaybedealtwithadvancedfiresuppressiontechniqueslikeInfusionofinertgasesorliquidnitrogen,DynamicBalancingofpressure,Reversalofunder-groundmineventilation,Applicationofnitrogenfoam,InertisationofGoaf,Watermistetc.Thepaperaddressesallthosecontroltechniquesindetail.Successstoryofcontrollingfiresincoalminesofdifferentpartsoftheworldarereported.ResultsofarecentlycompletedScience&Technology(S&T)projectwithregardtovariousfiresuppressiontechniqueslikeInfusionofliquidnitrogen,Injectionofhighpressurehighstabilitynitrogenfoam,andWatermistonopenfirearealsodiscussed.
Keywords:
coalminefire,reversalofundergroundmineventilation,nitrogenfoam,inertisationofgoaf&watermist
1.Introduction`
Sinceinception,miningisconsideredasamosthazardousanddangerousofpeacetimeactivities.Anoutbreakoffireintheundergroundworkingsofamineposesadirectthreatfromthefireitself.Further,aninvisibleandimmediatethreatfromcarbonmonoxidepoisoningandanexplosion,particularlyingassycoalminesisalsothere.Itaffectstobothpersonsworkingundergroundatthetimeoftheoutbreakandtothoseinvolvedinthesubsequentrescueandfirefighting.Ithampersthecoalproductionandsometimeslossofcoalwinningmachinery.
Firesincoalminesmaybecategorisedintotwogroupsviz.,
(a)firesresultingfromspontaneouscombustionofcoal
(b)openfires,whichareaccidentalinnature,causedasaresultofignitionofcombustiblematerials.
Incoalmines,firesaregenerallycausedduetoseveralreasonsviz.,sluggishventilation,highpressuredifferenceacrossintakeandreturnairways,looseandfallencoalinthegoafarea,electricity,mechanicalfriction,blasting,welding,explosionsandillicitdistillationofliquor.
2.MineFireModelGallery
Tounderstandthecomplexdynamicphenomenonofopenfires(firesthatoccurinmineairwaysusuallycommencefromasinglepointofignition)andtostudytheeffectivenessofvariousfiresuppressiontechniquesviz.,liquidnitrogen,highpressurehighstabilitynitrogenfoamandwatermist,recentlyCentralMiningResearchInstitute,Dhanbad,IndiahasdesignedandconstructedaMineFireModelGallery.Themodelgalleryis65.5mlong;archinshapewithabaseof2.4mandcrownheightof2.7m.Thecrosssectionofthegalleryis5.86m2.Thegalleryisdividedintofiringandnon-firingzones.Anexhausttypeaxialflowfanhavingacapacitytodealwith25m3/s.ofairquantityat50-mmwgpressurehasbeeninstalledatitsend.Thegalleryisprovidedwithtwoslidingdoorsforquicksealingofthefireandarollingshutterforregulationofdesiredairflow.AnisometricviewofminefiremodelgalleryisshowninFigure1.
Itisequippedwithastate-of-the-artcomputeraidedon-linetelemonitoringsystem.Thesystemconsistsof130sensors(98temperature,25gas,3pressure,2heatflux,1eachvelocityandSuspendedParticulateMatter(SPM)concentrationsensor)andinstrumentswithdatalogger,computer,computerperipheraletc.forcontinuousmonitoringofvariousfireparameterslikegasconcentration(O2,CO2,CO,CH4&H2),airvelocity,pressureacrossfirezoneandfanpressure,temperature,heatflux,dustandparticulatematterconcentrationinsidethegallery.
Figure1Isometricviewofminefiremodelgallery
DetailsoftheconstructionofthegalleryanditsinstrumentationsystemhavebeendescribedelsewhereIntheexperimentsinnersideofthefiringzoneofthegallerywhichis22minlength(firingzonestartsfrom10.5mfromtheentryofthegallery)waslinedwithathinlayerofcoalslabs,8–10cmthick,broughtfromDobranaseamofNewKendaColliery.Fixingofcoalslabswereeffectedwithamixtureofairsettingcementandliquidbinder.Ineachsetofexperimentsabout18–20tonsofcoalswereused.
Thepaperaddressesalltheabovecontrolmeasuresthathavebeenappliedallovertheworld.ResultsofexperimentationonopenfiresinMineFireModelGalleryarealsodiscussed.
3.FghtingMineFires
3.1HighPressureFoam
Useoffoamplugshasbeensuccessfulinfightingminefiresinroadwayswheredirectattackwithwaterisnotpossible.USBMstudiesrevealsthatthewatercontentofthefoamshouldnotbelessthan0.20kg/m3otherwisethefoamisnotcapableofcontrollingthefire.Withsufficientventilatingforces(around8cmwg)properlygeneratedfoammaybetransportedover300m.Foamdoesnotappeartobeeffectiveagainstdeepseated,rapidlyadvancing,buriedordeadendfires.
InIndia,suppressionofspontaneousheatingbyhighpressurehighstabilityfoamisanewandeffectivemethod.However,themethodhasbeenwidelyusedinCzechminesincontrollingspontaneousheatingoftheminedoutareasoflongwallpanels.
Thefoamisproducedbyhighpressurefoamgeneratorunderthepressureof10foaminggas.Theproducedfoamistransportedbypipelinesorfirehosestothefirearea.Inertgas(N2,CO2),compressedairoracombinationofbothisusedasfoaminggas.Thefoamgeneratorconsistsoftwoindependentunitsnamelypumpingunitandfoamgeneratingunit.Thefoamisproducedfromamixtureconsistingofwaterand5%foamingagent.Thismixtureispumpedbyapumpingunitintoafoam-generatingunitwherethefoamisproduced.Atthesametimeinertgas(N2)issuppliedtothefoam-generatingunitataminimumpressureof0.2MPa,mixedwithfoamingmixturesprayedfromnozzlesandthenpassesthroughafinemeshinstalledinsidethefoamgenerationunit.Attheoutletofthefoamingunitafireresistanthosepipeofsuitablediameterisattachedbywhichthefoamistransportedtotheplaceofinfusion.AschematicdiagramforHPHSnitrogenfoamgenerationsystemisshowninFigure3.
Thefoamhelpsincontrollingthespontaneousheatinginfollowingmanner.
Reducingairleakagethroughminedoutarea
Reducingtemperature
Reducingtherateofsorptionofoxygenbythecoalasthefoamformsathin
protectivefilmoverthecoal.
PumpingUnit
400V,50Hz
5%mixtureFireHoseFoamtoFire
AffectedArea
ofwater&
foamingagentFoamGeneratingUnit
Figure3Setupforinjectionofhigh-pressurehighstabilitynitrogen
HighpressurenitrogenfoamhasrecentlybeenusedinAW1longwallpanelof1&2InclinemineofJhanjraproject,ECLwithveryencouragingresults.Inthisminefoamwasinjectedinthelongwallgoafthroughboreholes.AtrolleymountedPSAtypenitrogengeneratorhavingacapacityof300Nm3/h.wasused.Highpressurehighstabilitynitrogenfoam(HPHS)ischeap(onekgoffoamingagentcapableofproducing2m3offoamcostingabout2.1$)andhaslongselflife.TheHPHSnitrogenfoamatarateof200m3/hhasbeenappliedduringexperimentationinCMRIMineFireModelGallerytocontrolopenfire.Thefollowingpointsareworthmentioning.
Ithasbeenobservedfromtheresultsthattherewassubstantialreductionintemperature.Theaveragevalueofthisreductionintemperaturehasbeenfoundtobe207°Cperhour.
AfterinfusionoffoaminopenfireconditiontheconcentrationofalltheProductsofCombustion(POC)likeCO2,CO,CH4andH2hasdecreased,indicatingtheretardationofcombustionprocess.
Oninfusionoffoam,reductionofgenerationrateofCO2andCOisestimatedas80%and85%,respectively.
High-pressurehighstabilitynitrogenfoamtechnologyprovedtobepromisingtocontrolopenfires.However,200-m3/hinfusionratewasfoundinadequatetosuppressthefirecompletely.
3.2.WaterMist
Watercanbeusedinmineseitherintheformofsprayormist.McPherson(1993)mentionedthatonceafirehasbeenprogressedtoafuelrichconditionthereislittlechanceofextinguishingwithoutsealingoffthefire.Hedoes,however,suggestthatameansavailabletogaincontrolofthefirebytheapplicationofwaterasanaturalscalefog.
‘‘Watermist’’referstofinewaterspraysinwhich99%ofthevolumeofthesprayisindropletswithdiameterlessthan1,000l.Watermistfiresuppressionsystems(WMFSSs)arereadilyavailable,simpleindesignandconstruction,easytomaintain,effectualinsuppressingvariousfires,non-toxic,andcheaperthanotherfamiliarfiresuppressingsystemwithnoharmfulenvironmentalimpact.
Whileappliedinfireareas,itcleanstheairbydissolvingsolubletoxicgasesproducedduringcombustion,washingdownsmokeandsuppressingdust,andthusimprovesvisibilityaswell.Unlikemanyotherfirefightingsystems,WMFSSscanbesafelyusedinmannedareasandfoundtobeeffectiveinopencondition.Furthermore,waterconsumptioninWMFSSsisfarlessthanthatinwaterflushing,sprayingorsprinklingsystems.Onaccountoftheseadvantages,muchstudyhasbeencarriedoutinrecentyearstodevelopappropriateWMFSSstocontrolvarioustypesandsizeoffires.
Asurveycarriedoutin1996indicatedthatnearly50agenciesaroundtheworldwereinvolvedintheresearchanddevelopmentofWMFSSs,rangingfromtheoreticalinvestigationsintoextinguishingmechanismsandcomputermodelingtothedevelopment,patentingandmanufacturingofwatermistgeneratingequipment.WatermistisbeingevaluatedforthesuppressionoffiresindieselfuelstorageareasinundergroundminesatNationalInstituteforOccupationalSafetyandHealth(NIOSH),Pittsburgh.Watermisthasshownapositiveimpacttocontrolafuel-richductfire[30]whenaseriesofexperimentsonwatermistwascarriedoutina30cmsquare,9mlon
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