Simulation And Optimization For Unit Of Reactors In Etherification Of Light Gasoline

Etherification technology of FCC light gasoline could efficiently increase thequality because of reducing the olefin content, increasing octane number andimproving the stability, which had attracted the attention of companies and institutionsat home and abroad. The etherification units of light gasoline with two reactors andone distillation column developed by CNPC were simulated and optimized with theaim of guiding the design of reactor in the industrial test plant of100kt/a.The etherification units were composed of the first reactor with circulation as thefirst stage, and followed by a distillation column coupled with the second reactor asthe second stage. The axial dispersion model with the assumption of neglecting themass transfer resistances was employed to calculate the fixed-bed reactor operatedadiabatically at steady state. The rigorous algorithm of BP method was used tosimulate the distillation column in which the gas phase was considered as ideal gas,the liquid phase was nonideal and the pressure drop was negligible. The nonideality ofliquid phase was evaluated by UNIQUAC method. At condition of given ratio ofmethanol to olefin, reactor diameter and operated variables of distillation column, thesimulated results of reactor lengths and conversions of the first and second stageunder different circulation ratios were obtained with the constraint of upper tolerancelimit of temperature of catalyst bed. The model validation of reactor and distillationcolumn were examined by the experimental results andASPEN plus, respectively.A multi-objective optimization problem for maximizing the final conversion andminimizing the equipment cost and energy consumption was establish to obtain theoptimal circulation ratios by using NSGA-II. A sensitivity analysis was used to obtainthe optimal reactor diameter and operated variables of distillation column. Theoptimization results were obtained that the circulation ratios were1.8and1.4,respectively; the lengths of reactors were5.849m and9.539m, respectively, with thediameters being both2m，when the final conversion of reactive C5alkenes was90.28%.