聚乙烯装置排放气的工艺选择方法研究

he conventional methods for recovering vent gas in polyethylene processes include compression condensing, membrane separation, pressure swing adsorption and cryogenic separation units. Since the vent gas content varies with the process, the combined recovery approach for different processes should be different. Therefore, it is blind for selecting processes since a lack of selection methods in process. This paper characterizes the vent gas content by three groups: N2, H2, and heavy hydrocarbon. A combination selection guide has been proposed to maximize both recovery efficiency and profit. For the separation of N2 and C2 in vent gas, compression condensing, compression condensing combined with membrane separation, compression condensing combined with cryogenic separation and compression condensing combined with pressure swing adsorption four processes are proposed. After simulating by Aspen Plus and optimizing by Equation Oriented modeling, the economic benefits and exergy efficiency of four processes are be compared each other by , then a zoning map of process scope is generated. On this basis, the paper amends the influence of mole fraction of H2 and heavy hydrocarbon in vent gas by sensitivity analysis in Aspen Plus so as to make the process selection guide more completely. An industrial case from high density polyethylene unit of a plastic company is studied by this method, the combination of compression condensing, cooling and cryogenic separation has been proposed for this case, and it has achieved economic benefits.