Abstract:

The tubular ceramic outer membrane with average pore diameters of 5, 20 and 50 nm was made into a membrane condenser, and a membrane condensation pilot test device with a membrane area of 0.3 m² was set up to carry out the recovery of water and waste heat resource from flue gas using ceramic membrane condensers. The recovery performance of two-stage membrane condensers with different installation types was investigated. The effects of relative humidity of inlet gas, inlet gas temperature, inlet gas velocity and average pore size of membranes on mass and heat transfer performances were systematically studied. The results showed that the higher flux and recovery ratio can be achieved when the gas and water flowed within the membrane condenser in a tandem way. The water flux increased with the increasing of relative humidity, temperature and velocity of the inlet gas. The water recovery ratio can be enhanced by increasing relative humidity, temperature of the inlet gas and decreasing gas velocity. In addition, a three-stage condenser installed with 50 nm pore-sized ceramic membranes displayed a better water and heat recovery performances. The average pore size of ceramic membranes had remarkable impact on the mass transfer process rather than the heat transfer process. In this work, the highest water flux and recovery ratio of three-stage membrane condensers were 38.5 kg·m^–2·h^–1 and 50.6%, respectively. Compared with conventional heat exchangers, ceramic membrane condensers can recover water and heat simultaneously, during which the overall heat transfer coefficient could reach as high as 415 W·m^–2·℃^–1. The ceramic membrane condensers can not only effectively relieve the visible pollution known as “smoke plume”, but also have great potential applications in the resources recycling and environmental protection.

Key words: ceramic membranes, flue gas dehumidification, waste heat recovery, smoke plume, pilot-scale

摘要：

将平均孔径5、20和50 nm的管式陶瓷外膜制成膜冷凝器，并搭建膜面积0.3 m²的膜冷凝中试实验装置，开展陶瓷膜冷凝器在烟气水、余热资源回收及脱白烟领域的中试研究。对比采用不同排布方式的两级陶瓷膜冷凝器的水、热回收效果，考察进气相对湿度、进气温度、进气线速度等操作条件和不同孔径陶瓷膜的排布方式对膜冷凝器水通量及水回收率的影响。研究表明，在两级膜冷凝器中，烟气、冷却水均为串联流动时，可得到更高的水、热通量及回收率。过程水通量随进气相对湿度、进气温度、进气线速度的增加而增加；水回收率随进气相对湿度、进气温度的增加而增加，随着进气线速度的增加而降低。在三级膜冷凝器中，采用每级均填充平均孔径50 nm的管式陶瓷外膜的排布方式时，可获得最佳的水、热回收效果；不同孔径陶瓷膜的排布方式对膜冷凝器水回收效果影响明显，对热回收效果影响不大。在各实验工况下，三级膜冷凝器水通量及水回收率最高分别可达38.5 kg·m^–2·h^–1和50.6%。与传统换热器相比，陶瓷膜冷凝器不仅可实现水、余热的同时回收，且其总传热系数为415 W·m^–2·℃^–1，换热效果更佳，并能明显缓解“白色烟羽”等视觉污染。基于陶瓷膜的膜冷凝技术在中试实验阶段展现出良好的回收效果，在资源回收及脱白烟过程有广阔的应用前景。

关键词: 陶瓷膜, 烟气脱湿, 余热回收, 烟羽, 中试