(788b) Preliminary Studies of CO2 Removal From Simulated Pre-Combustion Syngas Via a Pressure Swing Membrane Absorption Process

In a conventional integrated gasification combined cycle (IGCC) for coal as a solid fuel, pre-combustion CO₂ capture from post-shift reactor synthesis gas is of significant interest since CO₂ (~40% of the dry gas) is present at a much higher partial pressure. The low temperature water gas shift reactor product stream is likely to be available at ~20 atm and around 150-200⁰C.  In a conventional IGCC plant the post-shift reactor synthesis gas is cooled, humidified and expanded to recover some electrical energy and then sent to Claus and Selexol units for H₂S and CO₂ separation and a purified H₂ stream. The object of this research is to carry out CO₂ absorption at a high temperature and pressure to purify the hydrogen and obtain simultaneously a purified CO₂ stream. Helium was used here as an inert surrogate for H₂.

Laboratory-based preliminary experiments were carried out via an advanced pressure swing absorption-based device and a cyclic process to produce purified helium at a high pressure and simultaneously obtain a purified CO₂ stream useful for subsequent sequestration steps. The device employed was a hydrophobized porous membrane absorber containing a CO₂-selective high-temperature stable absorbent on one side and a simulated post-shift reactor synthesis gas introduced periodically on the other side. We will illustrate the nature of the cyclic process and the usefulness of various steps in producing the desired level of purification.