Design of bi-objective control system for benzene chlorination distillation

In order to meet the control requirements of high purity and high conversion for the distillation process of benzene chloride, the relationship between the variables related to the purity of chlorobenzene and the conversion of benzene is analyzed. Two kinds of bi-objective control structures are proposed. The CS-1 is a temperature control structure which sets the temperature difference of reaction zone and the temperature of sensitive stage as controlled variables. It improves the system's dynamic performance by introduction of a feed forward compensation loop for feed rate disturbance. The CS-2 is a composition control structure which sets the chlorinated benzene content in the bottom and the output of the feed ratio soft sensing model as controlled variables. Dynamic models of the control schemes are established in Aspen Dynamic to verify the effectiveness. The simulation results show that the two structures can effectively inhibit the changes of purity and conversion which result from feed rate and concentration disturbances.