煤矿火灾控制的最近发展和实践外文文献翻译.docx

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