Fixed Roof Gas-Oil Tank Explosion.docx

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1、ExplosionandFireinGas-OilFixedRoofStorageTank(Anoninherentlysaferdesign)YigalRieZelProcessSafetyManagement,consultantAshdod,ISRAEL77409Email：yriezeltrendline.co.ilAbstractOnNovember2nd,1997anexplosionoffixedroofgas-oiltanklocatedinthetankfarmofAshdodOilRefinerycausedlossoflifeofOneSampleMan,Fireintw

2、oadjacenttankslocatedinthesamedike.Duringthefire,whichlastedlessthan3hours,therewasabigpublicconcernaboutnecessityforemergencyevacuationfrom2neighborhoodsettlements.Emergencyoperationsoftherefineryandexternalforceswereveryeffectiveandwithin3hoursfiresinbothtanksandthedikewereputdownwithoutanyadditio

3、naldamagetoothertanksorequipmentinthetankfarm.Thesourcefirewasaheavytopphasepoolfire.Theinvestigationpointedoutthatthesourceofexplosivemixtureinthetankwashydrogenthatpenetratedwiththegas-oiltothetankasaresultofnon-completegas-oilstrippingwithhydrogenattheexitofgas-oilhydrotreatingunit.Thesourceofign

4、itionwaselectrostaticsparkinitiatedbysyntheticrope(insteadofcottonone)usedwiththesamplingdeviceinordertogetsamplesoutofthetank.Aftertheaccident,unfortunatelytoolate,itwasfoundthatsimilarscenariowasreportedabout15yearsbeforebutwasnotdigestedwidelyenoughthroughaccidentdatabases.1. INTRODUCTIONThereisn

5、odoubtthatstoragetanksofanoilrefinerybelongtoacategoryofinherentrisksystems.Theironlypurposeistostorehazardousmaterials.Butwoulditbesafeenoughtostoregas-oilordiesel-oilinanatmosphericfixedrooftankevenifthetemperatureofthestoredhydrocarbonsislowerthanitsflashpoint?Inthemorningof2ndNovember1997agas-oi

6、ltankcontaining15000cumofgas-oilexplodedandinitiatedabigfirestartingontoplayeraspoolfire.Thefirewascontainedwithinthedikeoftwoadjacenttanks.Averytallsmokeclouddispersedtowardsnortheast(thecenterofthecountry)andwithoutharminganysettlementwanderedunderverylowwindvelocityabout40kmuntilitvanished.Invest

7、igationstartedimmediatelybutalmostsametimecameinfirstquestionfromanexperiencedsafetyadviserofafamousrefiningcorporateabroad,askingforinformationinordertodigestthelessonlearnt.Themainquestionwas:,InPlatt,sOilgramNewsofNovember1997itwasindicatedthatadieseltankexplodedintheAshdodrefinery.Undernormalcir

8、cumstancesitisvirtualimpossibletohaveanexplosioninadieseltank.,.Therealityshowedthatthepossibilityforsuchexplosionisthere.Thethoroughinvestigationaimingtoidentifymainlytherootcausesfocusedonhydrogencontaminationinthegas-oil.Someweaknessesinthesystemcontributedtotheaccidentandilluminatedfewbasicsthat

9、shouldalwaysbekeptinmindandapplied.Itisbettertobrainstormaheadthaninvestigatelater.Inherentlysaferalternativesshouldalwaysbesought.Widedistributionofaccidentdataandlessonslearntcanservemorethanmutualaidbetweenmembersofthesocietydealingwithhazardousmaterials.ComprehensiveschemesofProcessSafetyManagem

10、entsystemsapplicationsarerecommendedforuseevennotyetrequiredbyregulatorsorauthorities.Anequallyimportantlessonwasexpressedbyafamousinternationalsafetyconsultancyservicescompany:OilRefineriesLtd.s,emergencyresponsetotheexplosionappearstohavebeenextremelygoodandfollowedtextbookprocedureonhowtodealwith

11、suchasituation”.2. THEGAS-OILPRODUCTIONSYSTEMINASHDODREFINERY.TheAshdodCrudeOilRefineryisasimpletypeplantanditsgas-oilcourseofproductionfromthedistillationinthemaincrudetowertillthefinishedproductsstoragetanksisviaunitsoffairlylowcomplexityfactor.Inthemaincrudeoildistillationtowerseveraltypesofcrude

12、oilsormixturesofsome,areseparatedtothemainrawproductslike:gas,naphtha,kerosene,lightatmosphericgas-oil(LAGO),heavyatmosphericgas-oil(HAGO)andatmosphericbottoms(fuel-oil).TheLAGOisstripped(aswellasthekerosene)inasteamstrippingtowerinthecrudeunitinordertoreducecontentoflightmaterialsandincreaseitsflas

13、hpoint.TheLAGO,HAGOandanothervacuumgas-oilareroutedtoHydrogenCatalyticDesulfurisingunitsortodirectblendingintheproductsgas-oiltanksinthetankfarm.Theactivityisdependentonthesulfurcontentinthecrudeoilandthelevelofsulfurrequiredinthedifferentgas-oilproductsformarketing.Thereisalsoanoptiontorunthekerose

14、neHDS(hydrogendesulfurisingunit)withgas-oileitherinparallelorassparetothegas-oilHDS.ThetwoHDSunitsincludeastrippingsectionineachofthem.ThesesectionswerestartedasReboilingHeatersStrippersandinordertosaveenergyadaptedtosteaminjectionstripping.Asaconsequenceofturbidityprobleminthestrippedgas-oilitwasde

15、cidedabout20yearsagotoreplacethesteamwithhydrogenasthestrippingmaterialonlyintheGas-OilHDSunitThehydrogenwasthereandcheap,theturbidityproblemdisappearedandtherewerealreadyfewexamplesforapplyingthisprocessinsomeotherindustries.IntheKeroseneHDSunitthestrippingremainedwithsteamandonlyafterabout15yearso

16、fexperiencewithhydrogenintheGas-OilHDSandwhentherewasahigherneedtooperatethisunitalsoongas-oilthechangewasmadeandhydrogenreplacedsteamasstrippingmaterialintheKeroseneunit.Thegas-oilproductsfromthetwoHDSunitsandthosestreamsbypassingtheHDSunitsareroutedandblendedtoonspec,productsinthetankfarmwhichispartoftherefinery.Thetanksareregularatmosphericfixedconerooftankswithopenventtotheair.OnFriday02:30operationdepartmentstartedfillingtank401.