Preparation and Properties of Coal Ash Ceramic Membranes for Water and Heat Recovery from Flue Gas

In this paper, the manufacturing process of microceramic membrane is summarized. The main material of this membrane is fly ash which can reduce the sintering temperature and save the costs. The coal ash ceramic membrane (CACM) was characterized by XRD, SEM, and mercury intrusion method. The results show that the mullite phase formed by CACM at the sintering temperature of 1250 degrees C has morphology and structural characteristics similar to the commercial microceramic membrane. The membrane surface is uniform and dense, without cracks; the pore diameter is 1-4m, and the porosity is 26.6%. Furthermore, the CACM and CMCM were compared at the aspects of water and heat recovery performance using flue gas. The experiment indicated that when the flue gas temperature was 50-85 degrees C, the water recovery performance of these two kinds of membrane was similar. Also, the heat transfer capability of the coal ash ceramic membrane was close to that of the commercial microceramic membrane when the temperature range of flue gas was controlled between 50 degrees C and 70 degrees C. When the temperature of flue gas reaches 80 degrees C, the heat transfer performance of the commercial ceramic membrane is better, and the difference of heat recovery between these two kinds of membranes is 19.3%. In general, the CACM and CMCM have similar mass transfer performance, and the heat transfer efficiency of CACM is lower than that of CMCM, but the costs of CACM is much lower than that of CMCM which has a good research prospect in the future.