(164a) Methodology For Screening Adsorbents For CO2 Capture

As is increasingly recognised world wide, global warming is mainly caused by emission of greenhouse gases (mostly CO2) from the burning of fossil fuels. Correspondingly, adsorbents for CO2 capture have attracted significant research efforts recently. To understand the impact of improvement in adsorbent characteristics on the CO2 capture process and economics, an assessment tool is needed. Various such tools (experimental and theoretical) have been used previously. Theoretical tools include use of isotherms (isothermal working capacity, adiabatic working capacity and selectivity) and experimental tools include thermal gravimetric analysis (TGA). However, the actual operation of a pressure swing adsorption process is not readily captured reliably with these methods. In this study, different adsorbent screening approaches were applied to CO2 capture, using hypothetical adsorbents, NaX, NaY and Activated Carbon, and the results from different methods were analysed and compared. It was found that isothermal approaches are not suitable for the screening of adsorbents for CO2 capture, because of the great amount of heat of adsorption for CO2. A new index, ?Capture Figure of Merit? (CFM) is a better assessment tool for developing adsorbents and it can also be readily converted to CO2 capture costs. Robust numerical simulation and experimental process data have confirmed the validity of CFM. In addition, it is shown that heat of adsorption plays a very important role in cyclic adsorption process and such thermal effect should be given sufficient consideration in adsorbent design and assessment.