Thermal design of heat-exchangeable reactors using a dry-sorbent CO₂ capture multi-step process

The present study proposes a multi-stage CO₂ capture process that incorporates heat-exchangeable fluidized-bed reactors. For continuous multi-stage heat exchange, three dry regenerable sorbents: K₂CO₃, MgO, and CaO, were used to create a three-stage temperature-dependent reaction chain for CO₂ capture, corresponding to low (50-150°C), middle (350-650°C), and high (750-900°C) temperature stages, respectively. Heat from carbonation in the high and middle temperature stages was used for regeneration for the middle and low temperature stages. The feasibility of this process is depending on the heat-transfer performance of the heat-exchangeable fluidized bed reactors as the focus of this study. The three-stage CO₂ capture process for a 60Nm³/h CO₂ flow rate required a reactor area of 0.129 and 0.130m² for heat exchange between the mid-temperature carbonation and low-temperature regeneration stages and between the high-temperature carbonation and mid-temperature regeneration stages, respectively. The reactor diameter was selected to provide dense fluidization conditions for each bed with respect to the desired flow rate. The flow characteristics and energy balance of the reactors were confirmed using computational fluid dynamics and thermodynamic analysis, respectively.