Dynamic optimization of acetylene hydrogenation reactors with considering catalyst deactivation

Ethylene is a very important material in petrochemical industries, whose chief application is producing polymers. The steam cracking of naphtha or ethane is usually applied to produce ethylene. A small amount of acetylene is produced in this process. The amount of acetylene in the product stream should not exceed 1 ppm, because it is harmful to polymerization catalysts in downstream units. The acetylene hydrogenation unit is designed for acetylene removal in industrial plants. In this unit, the removal of acetylene up to 1 ppm in the product stream and ethylene’s selectivity are of great importance. In this paper, the dynamic optimization of acetylene hydrogenation reactors of Marun petrochemical complex with considering catalyst deactivation is presented. In this study, the differential evolution (DE) method is used as a powerful method for determination of a dynamic optimal temperature profile to achieve maximum of ethylene’s selectivity in a period of 720 operating days. Then, the optimal results are compared with the condition wherein the inlet temperatures of the reactors are maintained constant at 55 ˚C and with the condition wherein the inlet temperatures of them increase linearly from 55 to 90 ˚C. The results showed when the inlet temperatures are kept 55 ˚C, the outlet acetylene exceed 1 ppm, but the best selectivity is achieved. With a linear increase in the inlet temperatures, the outlet acetylene is below 1 ppm but the selectivity is decreased. An optimal temperature profile maximizes the selectivity when the outlet acetylene is below 1 ppm.