The key challenge in post combustion capture from gas fired power plants is related to the low CO2 concentration in the flue gas (3 to 7% by volume). This means that conventional amine processes will result in a relatively high energy penalty while novel adsorbents and adsorption processes have the potential to improve the efficiency of separation. High-selectivity adsorbents are required to achieve relatively high CO2 uptake at low partial pressures, which means that the separation process should be based on either very strong physisorption or chemisorption with thermal regeneration. From the process point of view, the main challenge is to develop efficient separation processes with rapid thermal cycles.
With this regard, adsorption processes based on rotary wheel technology represent a promising alternative to traditional Thermal Swing Adsorption (TSA) processes. They can treat large volume of gas with relatively low pressure drop and efficient heat integration allowing to perform rapid thermal swings with cycle times of few minutes, which is over one order of magnitude faster than tradition TSA fixed bed processes.
As part of the “Adsorption Materials and Processes for Gas fired power plants” (AMPGas) project an innovative bench scale Rotary Wheel Adsorber has been designed and it is being built at the University of Edinburgh. The apparatus is a 12-columns system able to capture CO2 from dilute streams using rapid thermal swing adsorption cycles. Novel materials specifically designed for CO2 capture from dilute streams have been developed and characterised as part of the project (Zeolites, amine-containing MOFs, amine-based Silicas, amine-based activated carbons and carbon nanotubes). By operating at conditions which are representative of the typical conditions of the flue gas from gas fired power plants, the system aims to produce experimental data needed to demonstrate the proposed capture process and validate the detailed model developed using CySim®, the adsorption simulator at the University of Edinburgh. The performance of the capture process are here evaluated by exploring the use of different types of adsorbents and cycle configurations, allowing to identify the optimal operating conditions for the different capture strategies.