CO2 Capture in Natural Gas Production by Adsorption Processes

Natural gas (NG) is the fossil fuel with the lowest emissions of CO2 per kilowatt of energy produced. In the case of transporting the natural gas through pipelines, the CO2 specifications depend on each country but are around 2-4%, so in case that the natural gas contains more than this percentage, CO2 has to be removed to meet specifications. In this study, we have evaluated the feasibility of using a Pressure Swing Adsorption (PSA) process for the removal of carbon dioxide from natural gas. This process is not commercially available yet and thus faces several challenges regarding the utilization of proper materials and efficient regeneration schemes. Our study has considered the effect of different PSA process operation modes. The PSA unit was designed to upgrade natural gas with a composition of 83% CH4, 10% CO2 and 7% C2H6 available at 70 bars at a temperature of 313 K and with an inlet flowrate of 500,000 Sm3/h. The analysis also considered several process variables. An economic comparison of the price of capture has also been done. Our analysis indicated that the cost of CO2 capture using PSA is around 40% higher than using amines dominated by poor performance in process recovery (NG lost with CO2). Since this is the first study of its kind, there is a lot of room to improve process performance and that adsorption processes for this application should not only be limited to very low concentrations.