(329a) PSA Based Warm Gas CO2 Capture from Synthesis Gas

TDA is developing a novel sorbent based PSA process that removes CO₂ via physical adsorption from synthesis gas. The relatively strong affinity of the sorbent to CO₂ enables effective operation at temperatures up to 300^oC (well above the dew point of synthesis gas stream generated by commercial gasifiers). However, because the sorbent and the CO₂ do not form a true covalent bond, the energy needed to regenerate TDA’s sorbent (5.4 kcal per mol of CO₂) is much lower than that observed for either chemical absorbents (e.g., 29.9 kcal/mol CO₂ for sodium carbonate) or amine-based solvents (e.g., 14.2 kcal/mol CO₂ for monoethanolamine). TDA’s sorbent can be regenerated isothermally and CO₂ can be recovered at pressure (as high as 150 psia). Thus, the energy needed to regenerate the sorbent and compress the CO₂ for sequestration is significantly lower than that for any other technology reported to date. The high surface area and favorable porosity of the sorbent also provides a unique platform to introduce additional functionality, such as active groups to catalyze the water-gas-shift (WGS) reaction or to remove trace metals (e.g., Hg, As). Hence, TDA’s CO₂ sorbent could be used to do a warm gas capture of CO₂ above the dew point of the synthesis gas in an Integrated Gasification Combined Cycle (IGCC) power plant. TDA's pre-combustion CO₂ capture system achieves a net plant efficiency of 34% on a coal high heating value basis when operated on bituminous coal, which is significantly higher than that can be achieved with the Selexol^TM scrubber at 31.6% (state-of-the-art pre-combustion carbon capture technology).

In a current DOE sponsored project, TDA is carrying out field tests with the warm gas CO₂ capture unit integrated with WGS catalyst at 10 cfm scale. In this paper we present the results from the 8-bed PSA cycle performance in the field test with real synthesis gas.