双微观结构中空纤维膜捕集燃煤烟气CO2过程中膜润湿行为作用机理研究

Membrane absorption process is a promising alternative technology to conventional chemical absorption process for CO2 capture from flue gas. Since a detailed mechanism for membrane wetting in the membrane absorption process is still unclear, it is very difficult to take effective measures to control the wetting evolution, which has become the bottleneck for the application of the membrane absorption process. Based on the MN-PVDF hollow fiber membrane with the micro/nano-textured surface, a novel membrane absorption process for CO2 capture from flue gas is proposed in this study. By means of ESEM, AFM and XPS analysis and CFD simulation, studies on membrane wetting are conducted with respect to the membrane surface structure, absorbent solution and absorption process. The relationships between the micro/nano texture of MN-PVDF and the membrane surface free energy as well as the membrane anti-wetting capability are explored. The effects of absorbent molecular characteristics and its interface reaction with the membrane MN-PVDF on the membrane wetting are discussed. The responses of the submerged membrane adsorption process conditions to the membrane wetting are also.investigated. The interactions among the above three respects are expecially highlighted. The present study is supposed to theoretically contribute to the membrane wetting control and benefit the improvement of the membrane absorption process.

膜吸收法是一种有潜力的可替代化学溶剂吸收法的燃煤烟气CO2捕集方法。由于目前膜吸收过程中膜润湿机理尚不明确，无法对膜润湿行为进行有效调控，从而制约了膜吸收法在燃煤烟气CO2捕集中的应用。本项目基于前期研究得到的“微米-纳米”双微观结构PVDF中空纤维膜，从膜表面结构、吸收液和膜过程出发，借助ESEM、AFM、XPS等分析手段和CFD模拟方法，系统研究膜表面双微观结构对膜表面自由能及抗润湿性的影响规律、吸收液溶质分子特性和界面反应特性与膜润湿行为之间的构效关系、浸没式膜吸收过程关键参数与膜润湿率的响应机制，阐明上述三者在浸没式膜吸收法捕集燃煤烟气CO2过程中对双微观结构中空纤维膜润湿行为的作用机理。本项目研究成果将为有效调控膜润湿行为，提高膜吸收效率提供理论指导。

本课题在国家自然科学基金“双微观结构中空纤维膜捕集燃煤烟气CO2过程中膜润湿行为作用机理研究”（项目号：21506159）的支持下，课题研究工作的完成情况良好。本课题组围绕任务书中的主要研究内容，将含有良好分散效果的疏水改性SiO2纳米粒子（HMSNs）的乙醇溶液用作凝固浴，通过NIPS法构建了具有双微观结构的超疏水PVDF/SiO2膜，该改性方法不但可以改善膜表面的疏水性，同时也增强了孔隙和通道内表面的疏水性，在与吸收液长时间接触后（20天）仍表现出很强的抗润湿性，CO2吸收通量下降明显减少，有效地抑制了润湿问题；利用CFD技术动态模拟分析浸没式膜吸收系统内流场分布特征，考察了气液相界面压差、气液流速、吸收液浓度等影响因素与膜润湿之间的响应关系和作用机理，并将该模型的计算结果和实际运行系统结果作对比，对比结果表明该模型具有较高的精度。. 除此之外，在本项目的资助和启发下，我们还开发并合成了具有超疏水性和抗润湿性的ZIF-7/PVDF杂化膜。结果表明，由于ZIF-7纳米晶体具有疏水性，在相转化过程中有效地调节了溶剂非溶剂交换速率。与原始的PVDF膜相比，杂化膜的上下表面形态及内部结构发生了明显的变化，显示出更多的扭曲指状大孔隙层和更厚的海绵状层，尤其当ZIF-7的添加浓度大于1 wt%时，杂化膜的疏水性和抗湿性明显提高。