Revamping of Crude Distillation Unit for enhancement of Processing Capacity & LPG extraction through Steady State Simulation Modeling

The scope of this work covers the debottlenecking of operational constraints for increasing the processing capacity of crude distillation units and LPG extraction from crude oil. Simulation modeling on Aspen HYSY V7.1 is used for thoroughly investigating and evaluation of retrofit alternatives. Design and operations data of a crude distillation unit at Attock Refinery Limited is used as a case study. Capacity expansion through the addition or rearranging of circulating reflux/Pump-around is selected among the various available revamp alternates like addition of Pre-flash columns, tray geometry and hydraulics, etc. Then crude distillation unit is revamped for maximum possible expansion in processing capacity by re-arranging Pump-around circuits. Pump-around balances re-arrangement based on specific crude oil operating blend. Distillation column circulating reflux re-arrangement with different overhead configurations carefully modeled on Aspen HYSYS for evaluation. Some modifications are also incorporated in stabilizer column of the simulation model of crude unit to start On Spec. LPG extraction from stabilizer section. The results of Simulation Modeling validate propose modifications for revamping of processing capacity and LPG extraction.