Simulation of a Process to Capture CO₂ From IGCC Syngas Using a High Temperature PBI Membrane

Capture of carbon dioxide from an advanced integrated gasification combined-cycle (IGCC) process offers several technical and economic advantages over the conventional coal-combustion systems. The pre-combustion gas stream is at high pressure, has low volumetric flow rates and is capable of producing relatively pure hydrogen for conversion into electricity by gas turbines or fuel cells without generating additional carbon dioxide. Polybenzimidazole (PBI) polymer shows promise as a high temperature membrane material for pre-combustion-based capture of CO₂ from IGCC gas streams. We are developing a process that is based on PBI membrane to achieve a capture of 90% CO₂ as a high pressure stream with about 10% increase in the cost of energy. A significant advantage of the PBI membrane compared to other sorbent-based technologies and conventional polymeric membranes is that PBI membrane is capable of operating at over a broader temperature range (∼100-400 ^{{ring operator}}C). In contrast, solvent-based processes such as Selexol require syngas cooling prior to treatment, followed by reheating the processed fuel gas stream. In this paper, we are presenting the preliminary results of a process simulation using the ASPEN program under several scenerios including the IGCC with no CO₂ capture, IGCC with Selexol, and IGCC with PBI membrane separator. The high temperature membrane-based CO₂ capture method compares favorably against the Selexol-based CO₂ capture method. If H₂S remains with the CO₂ stream and can be sequestered, then the cost of electricity appears to be lower than Selexol-bsed separation systems.