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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.
