Top Product Yield Optimization of Depropanizer Column 1-2 in Alkylation Unit At PT. PI

Abstract

Alkylation Unit is a component of PT PI Unit, tasked with processing feedstocks similar to Spent Propane-Propylene from Polypropylene Unit and Residual Butane-Butylene from Polymerization Unit. The Alkylation Unit is used to produce products such as Light Alkilate, Refrigerant, LPG C-4, and by-products in the form of High Alkilate. Depropanizer Column 1-2 found in this component plays an important role in separating the propane-propylene mix from n-Butane and heavier components through pressurized distillation. Depropanizer Column feed comes from the overhead product of Desiobuthanizer Column 1-1, while 1-2 column is equipped with 40 valve trays. Therefore, this research aims to evaluate the performance and efficiency of Depropanizer Column 1-2. The evaluation process was carried out with feed flow rate, temperature, column pressure, and hydrocarbon composition of 40.152 tons/day, 55.48^oC, 17.38 kg/cm², and from the laboratory, respectively. The theoretical number of trays and reflux ratio were 28 pieces and 10 at 69% efficiency. Optimization experiments were conducted to determine the optimal operating conditions to obtain the highest revenue for the top product. Based on trial and error experiments with Aspen Hysys Study Case, the result showed that the optimal conditions are achieved when the column conditions operated at reboiler temperature of 95^oC and reflux flow of 90 tons/day to obtain a top product yield of 5.4592 tons/day with purity of 99.5% w/w.