多孔陶瓷膜内含湿烟气选择性跨膜输运的电渗驱动传热传质机理研究

The capillary condensation and transmembrane transport of water steam in the multiscale complicated pored configuration of porous ceramic membrane with high mechanical strength and anti-corrosion characteristic is significant for realizing the simultaneous water and waste heat recovery for flue gas, and it has a valuable perspective for industrial applications. However, there still exist several issues for current applications which include high resistance of draining condensation water, high energy consumption of pressure-based pumping approach, complexity of system and lack of quantitative instruction for designing pore and operating parameters. In order to overcome the above barriers, and based on the fact that the condensation water includes a certain amount of ions and the high efficiency, easy control of electroosmosis pumping, a novel approach for pumping condensation water using electroosmosis phenomenon instead of pressure-based pumping is offered. The pore-scale capillary condensation and transmembrane transport mechanism of water steam under multicomponent flue gas effect in the multiscale-complex pores should be clarified. Hence, the current project develops a multicomponent-phase change-electroosmosis lattice Boltzmann method. The coupled effects of physicochemical properties of multicomponent flue gas, pore size and morphology of porous ceramic membrane, roughness and wettability of pore surfaces on the capillary condensation are investigated, and the mechanism of water condensation electroosmotic pumping is studied with respect to voltage magnitudes, pore configurations, Zeta potential, and PH value of condensation. Based on this, the choice of pore geometric parameters, high efficient condensation water pumping as well as water and waste heat recovery for flue gas using porous ceramic membrane could be theoretically guided. The current project consolidates the theory of capillary condensation and transmembrane transport and contributes to developing new waste and heat recovery technologies.

多孔陶瓷膜通过多尺度复杂孔隙内水蒸气的毛细冷凝跨膜输运实现含湿烟气的水热同时回收，且机械强度高、耐腐蚀，具有广阔的发展前景。但目前采用的压力驱动孔隙内冷凝水排除的方式能耗高、系统复杂，且孔隙和操作参数设计缺乏定量指导。针对以上瓶颈，基于冷凝液具有一定离子浓度和电渗驱动高效、易操控的特点，本项目创新性地提出利用电渗驱动代替压力驱动来促进陶瓷膜孔隙内冷凝液的排除；并综合考虑孔隙内多组分烟气聚集抽吸扩散和水蒸气毛细冷凝电渗输运作用，发展多组分-相变-电渗流格子玻尔兹曼数值模型。通过数值模拟和实验研究孔隙尺度下多组分烟气物化性质和陶瓷膜孔径、孔隙形状、孔壁粗糙度、润湿性等影响下的毛细冷凝机理，以及电极电压、孔隙结构、Zeta电位、冷凝液PH值对冷凝液输运的电渗调控机制，为陶瓷膜孔径和操作参数设计及冷凝液高效输运提供指导。本项目对丰富毛细冷凝跨膜输运理论和发展新的烟气水热回收原理及技术具有重要价值。

多孔陶瓷膜通过孔隙内水蒸气的毛细冷凝及冷凝液跨膜输运实现含湿烟气的水热同时回收，且机械强度高、耐腐蚀，具有广阔的发展前景。但冷凝水排除能耗较高、系统复杂，且孔隙和操作参数设计缺乏定量指导。针对以上瓶颈，本项目对多孔陶瓷膜内多组分烟气中水蒸气冷凝、冷凝水跨膜输运以及陶瓷膜水热回收特性三方面开展研究工作。围绕多组分烟气中水蒸气在多孔陶瓷膜上的冷凝机理，开展了粗糙陶瓷膜表面纯蒸汽以及多组分烟气冷凝时液滴成核过程及动力学行为的LBM数值仿真，研究不同润湿性粗糙表面以及烟气中不凝气体含量、过冷度、粗糙元几何结构对液滴行为、三相接触线以及热流密度等的作用规律，并提出强化烟气中蒸汽凝结的亲疏水二元润湿粗糙结构，其成核时间相对于疏水表面可缩短44%，平均热流密度提高17%。围绕冷凝水跨膜输运及电渗调控，建立了陶瓷膜多孔介质数值重构模型并研究了孔隙率、孔隙形貌和外加电场作用力对陶瓷膜上蒸汽冷凝及冷凝水跨膜输运的作用机制。搭建了陶瓷膜电渗驱动冷凝液输运实验台和烟气冷凝跨膜输运综合性能测试平台，对不同电渗电压条件下冷凝水输运以及不同烟气流量、温度、冷却水流量条件下的水热通量、水热回收效率进行了实验研究。采用陶瓷膜进行水热回收时水回收效率约为70-85%，热回收效率约为30-45%。采用电渗方式可以实现冷凝水跨膜输运，但使用寿命需进一步提高。本项目为陶瓷膜孔径和操作参数设计及冷凝液高效输运提供理论指导，对发展新的烟气水热回收技术具有重要价值。