Zeolite-Based Process for CO2 Capture from High-Pressure, Moderate-Temperature Gas Streams

A novel CO2 capture process was developed using a zeolite suitable for CO2 removal at warm-gas temperatures in high-pressure coal gasification gas streams. The process involves sorption of CO2 at 150 degrees C and regeneration at 350 degrees C. Regeneration at 350 degrees C removes the moisture absorbed during CO2 sorption. This sorption temperature is ideal for CO2 removal downstream of the water gas shift reactor in an integrated gasification combined cycle (IGCC) power plant but is also applicable to other warm gas cleanup processes. Most solvent-based processes require energy-intensive drying to remove moisture prior to CO2 removal. Using zeolites for CO2 capture at 150 degrees C and regeneration at 350 degrees C eliminates the problem with moisture in the gas stream traditionally causing deactivation of the zeolite. The results of using this capture scheme in an IGCC power plant is advantageous because of the high-pressure CO2 product stream and because removal of CO2 and H2O from the syngas generates high-quality H-2 for the combustion turbines. In the example used in this work, the resulting CO2 stream separated from the fuel gas is delivered at 280 psi significantly reducing the energy required for compression from 27.6 MW in the EPRI report utilizing Selexol to 9.9 MW in this work. The overall thermal efficiency of the plant utilizing this CO2 removal scheme was estimated at 36.5, which is 0.5% less than the comparable Selxol plant. However, this process, combined with other warm gas cleanup technologies, offers the ability to significantly reduce the auxiliary load associated with syngas clean up, thereby increasing overall power plant efficiency.