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1、ChapterTenSafetyandEnvironmentalProtectionRiskAnalysisoftheunit1.Howtoevaluateriskofunit?Answer:Generally,theriskofpetrochemicalunitisevaluatedbyhazardofrawmaterial,amountofhazardmaterialinunit,processconditions,processcomplex,operationmode,controlmethod.Rawmaterialofcokingunitisresid
2、ue,withprocesscharacteristicsofhightemperatureandhighsulfur.Therefore,mainriskisfirehazardandpoisondamage.2.Whatisoilflashpoint?Whatissignificanceonflashpointanalysis?Answer:Underspecifictestingconditions,whenoilisheating,flashpointistheminimumtemperatureatwhichinstantflashingishappen
3、edwhilemixtureofsteamfromheatedoilandaircontactingwithfire.Basedondifferentmeasuringmethodandinstrument,therearetwomeasuringmethods,suchasopencupmethodandclosedcupmethod.Theformerisusedtomeasureheavyoil,andthelatterisapplicableforbothlightoilandheavyoil.Generally,thelowerpetroleumfrac
4、tionboilingpointis,theloweritsflashpointis.Forexample,flashpointofgasolineis-30~-40℃;flashpointofdieseloilis26~50℃;andflashpointoflubeoilis130~325℃.Ifheavyoil(lubeoil)ismixedwiththeoilwithlowboilingpoint(gasolineordissolvent),theflashpointwillbedecreasedsignificantly.Therefore,evennes
5、softheoil(whetheritismixedwithcomponentwithlowboilingpoint)couldbejudgedbyflashpoint.Risklevelofoilisclassifiedbyitsflashpoint.Forexample,theoilwithflashpointat45℃andaboveiscalledascombustibles,andtheoilwithflashpointat45℃andbelowiscalledasflammables.Thereisarelationshipbetweenflashpo
6、intandchemicalcompositionoftheoil,i.e.theoilwithmuchwaxyhydrocarbonhasahighflashpoint,buttheequivalentoilwithcyclichydrocarbon-aromaticbaseincludingmuchcolloidhasalowflashpoint.3.Whatisrangeofexplosion?Howtocalculateit?Answer:Notallmixtureofoilvaporandaircouldbeflashedandexploded.Esse
7、ntialconditionofflashisthatconcentrationofhydrocarbonoroilvaporinmixtureshouldbewithinacertainlimit.Ifitislowerthanthislimit,oilvaporisnotenough;ifhigherthanthislimit,airwillbenotenoughforflash.Therefore,thisconcentrationrangeiscalledasrangeofexplosion,andthelowerlimitofconcentrationi
8、scall