Design of a bench scale unit for continuous CO2 capture via temperature swing adsorption—Fluid-dynamic feasibility study

Abstract

The design of a bench scale unit (BSU) for continuous CO2 capture via temperature swing adsorption (TSA) is introduced. The BSU comprises two, interconnected multi-stage fluidized bed columns that allow for counter-current contact of adsorbent and gas streams during adsorption and desorption, respectively. From a fluid-dynamic point of view, the system is capable to capture 100kg of CO2 per day from a feed gas stream having 5vol.% CO2 content. In order to study the fluid-dynamic operability of the proposed BSU design, a cold flow model (CFM) representing half of the BSU system was constructed and operated. The CFM consists of five consecutive stages of bubbling fluidized beds and a recirculation line that comprises a mechanical screw conveyor, a pneumatic transport riser and a gas–solids separator. A comprehensive CFM campaign that included variations of the main operating parameters was conducted using air as fluidizing agent and polystyrene particles as bed material. Pressure drops across the individual stages and along the transportation riser were continuously measured to monitor the solids distribution within the system. Results from CFM experiments showed that continuous operation of the multi-stage fluidized bed system is possible within a broad range of operating conditions. After completion of the first experimental campaign, a further test was conducted to study the expansion of the dense phase of the fluidized bed within an individual stage, using long-time exposure photography. The obtained pictures delivered qualitative explanations for the results obtained from the parameter variations conducted in the first campaign. Altogether, the CFM test campaign clearly proved the fluid-dynamic feasibility of the proposed BSU design. In a next step, the results of this study will be used to elaborate the detailed design of the actual BSU for continuous CO2 capture via temperature swing adsorption.