膜吸收CO_2工艺中不同吸收液对膜润湿的影响

Effects of different absorb liquids on membrane wetting during membrane absorption process

以单乙醇胺(MEA)、二乙醇胺(DEA)和N-甲基二乙醇胺(MDEA)作为吸收液,利用聚丙烯(PP)中空纤维膜组件进行分离模拟烟气中CO_2的实验研究,考察不同吸收液的脱除效率以及长时间连续运行下的膜润湿现象。建立膜相传质阻力随时间变化模型,与实验数据拟合较好。同时将膜丝在不同吸收剂中浸泡,结合接触角、场发射扫描电镜(FE-SEM)、衰减全反射红外光谱(ATR-IR)以及热重(TG)表征分析膜性能的改变。结果表明,相同浓度下,单一吸收剂的CO_2脱除效率大小为MEA>DEA>MDEA;当吸收液为1mol/L MEA时,16天后CO_2脱除效率从93.3%下降到72.1%;而吸收液为1mol/L DEA时,脱除效率从88.3%到第16天的78%,下降约12%;理论计算得吸收液为1mol/LMEA和1mol/LDEA时,膜相传质阻力分别为10564.06s/m和4881.08s/m;浸渍时间增加,膜接触角减小,疏水性减弱,同时膜孔径变大,出现润湿现象;红外光谱和热重分析表明在MEA溶液作用下膜丝出现溶胀。

This research presented separation of CO2 from flue gas by polypropylene(PP)hollow fiber membrane contactors,using aqueous solution of monoethanolamine(MEA)、diethanolamine(DEA)and methyldiethanolamine(MDEA)as absorption solvents.The CO2 removal efficiency and dynamic flux were monitored under different absorption solvents conditions.A theoretical model was put forward between the membrane resistances and operation time,and successfully fitted the change of membrane resistance results in gas absorptions.PP hollow fibers were immersed in different absorbents to observe the change of membrane properties dynamically.The contact angle,Field emission scanning electron microscope(FE-SEM),Attenuated total reflection-infrared spectroscopy(ATR-IR)and Thermogravimetry(TG)were used to study the changes of membrane properties.The results revealed that the CO2 removal efficiency was in the following order:MEA>DEA>MDEA.The MEA and DEA solutions of 1 mol/L were used for comparison during 16 days of operation.The CO2 removal efficiency of MEA and DEA used as absorbents continuously declined roughly 22.7%and 12%of initial removal efficiency.The membrane resistances were 10564.06 s/m and 4881.08s/m for MEA and DEA.The contact angel and hydrophobicity decreased,however,pore size increased during the long-term immersion.The results of ATR-IR and TG indicated that in the MEA solution the surface properties of the membrane were changed.