膜法氨水吸收脱除烟气中CO2的研究

以氨水为吸收剂,对聚丙烯中空纤维膜分离烟气中CO2进行了实验研究.结果表明:随着气体流量和入口CO2浓度的增加,CO2去除率下降而传质速率增加;随着氨水浓度和氨水流量的增加,CO2去除率和传质速率均显著增加,但当氨水浓度大于2.5 mol·L-1,吸收液流量大于80m L·min-1后,膜接触器对CO2去除率和传质速率基本保持不变;膜接触器连续运行15 d后其吸收性能显著下降,CO2去除率、传质速率、总传质系数均下降约40%~50%.接触角测量、SEM及XPS表征结果表明:随着操作的进行,聚丙烯膜在吸收液环境中接触角逐渐降低,疏水性减弱,造成膜孔润湿;同时碳酸盐在膜孔形成结晶,堵塞膜孔,使得传质阻力进一步增加,从而造成膜接触器吸收性能的下降.

Ammonia absorption of CO2 from flue gas using hollow fiber membrane

The removal of CO₂ from flue gas through membrane absorption was studied. Polypropylene hollow fiber membrane contactor was selected as absorber, and ammonia was chosen as absorbent. Results show that with the increase of gas flow rate and CO₂ concentration, the removal efficiency of CO₂ decreases and mass transfer rate increases. And with the increase of ammonia concentration and liquid flow rate, the decarburization efficiency and mass transfer rate both increase significantly. However, the removal efficiency of CO₂ and mass transfer rate almost keep unchanged when ammonia concentration is higher than 2.5 mol·L^-1 and liquid flow rate is above 80 mL·min^-1. The performance of membrane contactor degrades significantly after 15 days continuous operation, with 40% to 50% decrease of CO₂ removal efficiency, mass transfer rate and total mass transfer coefficient. Contact angle measurement, SEM and XPS results show that contact angles of polypropylene membrane in absorption solution reduce as the experiment continues, resulting in membrane wetting and decreased hydrophobicity of membrane. At the same time, the crystallization of carbonate in the membrane hole could cause the mass transfer resistance increase, resulting in membrane performance degradation.