Simulation, Optimization And Retrofit Of Dilute Ethylene To Ethylbenzene Process

Because concentration of propylene in catalytic dry gas is far more than designvalue in Hainan refining ethylbenzene unit, it directly affects the removal rate ofpropylene, which has great influence on the subsequent separation process. Based onfull analysis of the current process, Aspen Plus were selected to simulate and optimizethe propylene separation system and propyl benzene tower, the correspondingoptimization and further retrofit suggestions are proposed.Using the established model of the propylene separation system, it was foundthat the simulation results consisted with the actual process.Using sensitivity analysistool of Aspen Plus, the effects of the feed pressure of catalytic dry gas, temperature,composition and cyclic absorber temperature on propylene removal rate wasdiscussed. The results showed that increasing the feed pressure and reducingcirculation absorber temperature had great effects on propylene removal rate. Afterincreasing pressure of catalytic dry gas from1.0MPaG to1.1MPaG and loweringabsorber temperature from22℃to15℃, propyleneconcentration in dry gasdecreased from0.49%to0.32%. Furthermore, instead of mixed diethyl benzene,several different absorbers were simulated under the working condition. The resultsshowed that propylene has the highest removal rate when using benzene as absorbent,but the loss of benzene is bigger.To overcome the problem of limited capacity of propyl benzene tower based onthe simulation results, fixed valve tray was selected to replace the original combinedguide floating valve tray. The results indicated that the concentration of diethylbenzene reduced from36.41wt%to <10wt%. Futhermore, the reason of abnormalliquid level fluctuations of tower kettle was analyzed, vaporization rate of the reboilerexport was only0.04%for the current installation position, and high installationlocation of reboiler was found to be the inducement and need to be rearranged.