Investigating the effect of operating parameters on the performance of acetylene hydrogenation reactors

Ethylene is a very important material in petrochemical industries, whose chief application is producing polymers such as polyethylene. The steam cracking of ethane or naphtha is commonly used 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 modeling and the dynamic simulation of acetylene hydrogenation reactors of Marun petrochemical complex with considering catalyst deactivation are presented. Then, here investigated is the effect of the operating conditions such as temperature, pressure and flow rate of the reactor feed on the amount of outlet acetylene as well as ethylene’s selectivity.

The simulation results show that in order to compensate for catalyst deactivation, it is necessary to gradually increase the reactor inlet temperature. With a linear increase in the inlet temperature of the reactors from 55 to 90 ˚C in a period of 720 operating days, the amount of outlet acetylene and ethylene’s selectivity are decreased. The reactions of acetylene to ethylene and ethylene to ethane are increased by increasing the inlet temperature of acetylene hydrogenation reactors. By increasing the feed flow rate from 50 to 100 kg/s, the amount of outlet acetylene and ethylene’s selectivity are increased. The residence time is decreased by increasing the feed flow rate and thus the conversion of acetylene to ethylene is decreased (increasing the outlet acetylene in the product). The amount of outlet acetylene and ethylene’s selectivity are decreased by decreasing the inlet pressure from 40 to 33 barg.