Novel integrated acid gas removal and forward osmosis draw solution regeneration system for saving energy and water treatment

Abstract

Chemical absorption is the most common technology used in the Acid Gas Removal (AGR) systems for treating sour gases, but suffers from high regeneration energy and co-process produced water. Co-process produced water is often considered a waste by-product, but recently the industry is beginning to exploit it as a potential profit. In this study, a novel integrated AGR and Forward Osmosis (FO) regeneration system is proposed to reduce the energy consumption in both systems, as well as treating the wastewater from the AGR units. This process utilizes ethanol as a draw solution (DS) along with n-pentane as a low boiling point agent for facilitating the separation of ethanol-water mixture at low temperature. N-pentane is the cross component between the AGR & FO units, through a new economizer coolant fluid replacing the circulated lean amine conventional cooling equipment “air cooler and trim cooler”. This work has been developed using Aspen HYSYS V8.8 amine package along with CPA package for FO-DS regeneration. The results show that, this proposal could save 15% of new AGR plants capital cost (Capex) due to eliminating the lean amine air cooler, trim cooler, reduce electrical consumption by more than 20% for new and existing plants. The net capex savings for the new AGR unit is $9687/MMSCFD, while added capex for existing units is $6504/MMSCFD. In addition, a 93.6% by wt. diluted draw solution could be recovered as a treated water. This proposal is promising for retrofitting an existing AGR process and desalination (FO) units.