CO₂ capture from high concentration CO₂ natural gases by pressure swing adsorption at CO2CRC Otway site, Australia

Natural gas is one of fossil fuels with the lowest CO2 emissions per unit energy produced. However, roughly half of the natural gas reservoirs contain high sour contents[1], which makes the exploitation of those sources uneconomical. Rejecting CO2 from high concentration CO2 natural gases with low cost and easy-to-implement processes could greatly expand the worldwide recoverable natural gas amount. CO2CRC Ltd, the leading CCS R&D organization in Australia, has designed and implemented a carbon capture demonstration skid in Australian Otway National Research Facility. The skid includes a Pressure Swing Adsorption (PSA) rig which is designed to remove CO2 from high CO2 content natural gas in Otway. Two months of operation had been carried out from May 2017 to June 2017, with the feed natural gas containing CO2 in a range from 30 % to 50 % using commercially available adsorption materials to obtain benchmarking data. The results of operation showed that the PSA rig can successfully capture CO2 from high pressure high soured natural gas with a recovery rate of 66 %. However, the purity of the final CH4 product was found to be not up to the mark to meet general natural gas requirement (80 % as opposed to 95 %). This was attributed to the fact that the desorption pressure was higher (~5 bar) than the design value close to atmospheric pressure. Process simulation was also carried out to verify the PSA operating results, which predicted that the separation performance can be further enhanced if the desorption pressure can be dropped to lower values.