Safetygram-18安全程序-18VIP专享VIP免费

Safetygram-18安全程序-18CarbonDioxide二氧化碳General概述Carbondioxideisnonflammable,colorless,andodorlessinthegaseousandliquidstates.Thegasisapproximatelyoneandone-halftimesasheavyasair.Carbondioxideisaminorbutimportantconstituentoftheatmosphere,averagingabout0.03%or300ppmbyvolume.Sincedrycarbondioxideisarelativelyinertgas,specialmaterialsofconstructionarenotrequired.Intheeventmoistureispresentinhighconcentrations,carbonicacidmaybeformedandmaterialsresistanttothisacidshouldbeused.Highflowratesorrapiddepressurizationofasystemcancausetemperaturesapproachingthesublimationpoint(-109.3F[-78.5C])tobeattainedwithinthesystem.Carbondioxidewillconvertdirectlyfromaliquidtoasolidiftheliquidisdepressurizedbelow76psia(61psig).Theuseofmaterialswhichbecomebrittleatlowtemperaturesshouldbeavoidedinapplicationswheretemperatureslessthan-20F(-29C)areexpected.VesselsandpipingusedincarbondioxideserviceshouldbedesignedtotheAmericanSocietyofMechanicalEngineers(ASME)orDepartmentofTransportation(DOT)codesforthepressuresandtemperaturesinvolved.在液态和气态时二氧化碳是不可燃、无色、无嗅的。气体比空气重大约1.5倍。二氧化碳是空气的含量较小但很重要的组成成分，体积比平均约为0.03%或300ppm。由于干燥的二氧化碳是相对不活泼的气体，不要求特殊的建材。在水蒸汽浓度很高的情况下，可以生成碳酸，这时应使用对该酸有抵抗力的材料。系统的高流速或迅速降压可以在系统内获得接近升华点(-109.3F[-78.5C])的温度。如果液体压力降到76psia(61psig)以下，直接从液态转化到固态。在预期温度低于-20F(-29C)的应用中应该避免使用在低温下变脆的材料。用于二氧化碳设施的容器和管道要根据相关的压力和温度按照美国机械工程师协会(ASME)或交通部(DOT)的规范来设计。。Carbondioxidecanbestoredasabulkliquidinlargestoragevesselswithcapacitiesupto50tonsandlarger.Theliquidinthetankismaintainedbetween245psigand305psig.Whenthetankpressurereaches305psig,amechanicalair-cooledrefrigerationunitisactivatedwhichcoolsthetankcontentsandtherebyreducesthepressuretoabout295psig.Whenpressuredropsto245psig,aportionoftheliquidispassedthroughapressurebuildupcoilwhichvaporizestheliquidinthecoil,andtheresultantvaporissenttothetank’svaporspaceuntilatankpressureof255psigisattained.Inisolatedinstanceswherecarbondioxideusageisextremelylow,heatleakintothetankissufficienttomaintainthecontentsabove245psigandapressurebuildupcoilisnotneeded.Thebulkstoragetankcaneithersupplygasfromthevaporspaceorliquidfromthebottomofthetank.Ifwarmercarbondioxidegasisdesired,vaporiswithdrawnfromthevaporspaceinthestoragetankandsuperheated.Bulkstoragetanksarefilledbyliquidtransporttrailers.二氧化碳可以作为液体大量储存在容量大到50吨和更大的大型储存容器内。容器内的液体压力维持在245psig和305psig。当容器压力达到305psig时，启动机械空气冷却制冷设备，使容器内容物降温，从而压力降到约295psig。当压力降到245psig时，部分液体流过一个压力积累蛇管，蛇管使其内部的液体蒸发，产生的蒸气送到容器的蒸气空间，直到容器压力达到255psig。在二氧化碳用量极低的隔热场合，泄漏进容器的热量足以使内容物的压力维持在245psig以上，因此不需要压力积累蛇管。大容量储存容器能够或者从蒸气空间供应气体，或者从容器底部供应液体。如果需要温度更高的二氧化碳气体，可以从蒸气空间提取出蒸气，并使其过热。由液体运输拖车来灌装大容量容器。Carbondioxideisalsopumpedasaliquidintohigh-pressurecylinderswhicharefilledbyweight.Theamountofcarbondioxidegascontainedinacylinderisdeterminedbymultiplyingtheweightoftheliquidbythespecificvolumeat68F(20C)and1atmosphe...