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

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.本研究以浸渍法制备的氧化铝负载碳酸钾（K₂CO₃/Al₂O₃）固体吸附剂为实验介质，在60℃低温条件下，探究流化床/循环流化床内流型对化石燃料燃烧烟气中CO₂捕集效果的影响。本实验所用的玻璃制半循环流化床提升管内径为0.025 m，高度为0.80 m。通过测定提升管内的压力波动对流型进行表征，随着气体流速升高，流型可分为固定床、多泡床、节涌床、湍流流化床和快速流化床五种类型。固定床与多泡床可完全吸附烟气中的CO₂（CO₂脱除率=1）；节涌床、湍流流化床与快速流化床则无法实现CO₂的完全脱除，三者的最大CO₂脱除率分别为0.98、0.94和0.72。然而，湍流流化床的CO₂捕集性能最优，可达理论化学计量值的约90%；多泡床与快速流化床的捕集性能次之，为理论化学计量值的66%~72%；固定床与节涌床的捕集性能最差，仅为理论化学计量值的53%~60%。对于本研究使用的氧化铝负载碳酸钾固体吸附剂而言，当再生温度高于300℃时可实现完全再生，因此具备良好的吸附容量稳定性。