Effects of flow pattern on CO₂ capture using potassium carbonate in circulating fluidzed bed

Abstract

To investigate the effect of flow pattern/regime in fluidized bed/circulating fluidized bed on CO₂ capture from flue gas, released from a fossil fuel combustion process, at low temperature 60℃ using potassium carbonate supported on alumina (K₂CO₃/Al₂O₃) solid sorbent prepared by impregnation method. The semi-circulating fluidized riser made from glass has 0.025 m of inner diameter and 0.80 m of height. The flow pattern/regime was characterized by measuring pressure fluctuation in the riser. It can be divided into five different flow patterns/regimes including fixed bed, multiple bubbling, slugging, turbulent and fast fluidization as gas velocity increased. The fixed bed and multiple-bubbling bed could adsorb all CO₂ in flue gas (CO₂ removal fraction = 1). The slugging, turbulent and fast fluidization could not remove all CO₂ in flue gas. Maximum CO₂ removal fractions for slugging, turbulent and fast fluidization are 0.98, 0.94 and 0.72, respectively. However, the turbulent regime provides the best CO₂ capture capacity at about 90% of stoichiometic theoretical value. The CO₂ capture capacity for the multiple-bubbling and fast fluidization regimes are secondary with about 66-72% of stoichiometic theoretical value. The fixed bed and slugging regimes provide the poorest CO₂ capture capacity at about 53-60% of stoichiometic theoretical value. For K₂CO₃/Al₂O₃ solid sorbent, this solid sorbent was completely regenerated for temperature higher than 300℃ resulting in higher stability to maintain capacity.