MULTI-CRITERIA OPTIMIZATION OF SERIES-CONNECTED DISTINATION COLUMNS
The paper solves a static optimization problem by the example of two series-connected columns in the system of isopropyl benzene extraction from benzene alkylation products with propylene. A peculiarity of optimization purpose is finding of compromise solution for minimization of energy consumption, on the one hand, and increasing of product stream extraction of required quality, on the other hand. The object of investigation is two-column rectification unit, consisting of columns K-50 and K-70. In column K-50 propane, hexane and benzene are distilled with distillate and in column K-70 polyalkylbenzene and tar are distilled with cube product. The static optimization in a form of finding compromise solution by two optimality criteria for each of the columns was carried out. Optimization criteria reflects cost component in the form of heat fluxes to each of the columns and performance of these columns in the form of product withdrawals carrying the target component. The method for determining the compromise solution is based on achieving equal values of the relative units of the degree of achieving the minimum steam flow and the degree of achieving the maximum product withdrawal carrying the target component. for each of the columns. In the process of searching the output stream of the first column in the form of cube product is the raw material of the second column, where the compromise solution of this column is found. The results of compromise solution are presented and the structure of control system supporting compromise modes of these columns is proposed.