Experimental Investigation into Flue Gas Water and Waste Heat Recovery Using a Purge Gas Ceramic Membrane Condenser

The direct discharge of wet saturated flue gas from a coal-fired power plant boiler causes a lot of water and waste heat loss. An inorganic ceramic membrane condenser recovers water and waste heat from the flue gas, which has great significance to improve energy utilization efficiency and reduce water consumption. However, the flue gas temperature is relatively low; thus, it is difficult to effectively utilize waste heat. In this paper, it is attempted to use the boiler secondary air as the cooling medium of the ceramic membrane condenser to realize the flue gas waste heat reuse. Based on the above ideas, a purge gas ceramic membrane condenser experimental platform was built for the water and waste heat recovery from the flue gas, and the water and waste heat recovery characteristics and the purge gas outlet parameters were discussed. Simultaneously, the heat transfer resistance and water recovery power consumption are also analyzed. The experimental results show that the water and waste heat recovery characteristics are enhanced with the purge gas flow increases. Increasing the flue gas temperature will increase the water recovery rate and heat recovery power. The ceramic membrane transmission efficiency is a key factor in restricting the actual water recovery efficiency. The purge gas absorbs the water and waste heat from the flue gas, the purge gas temperature and moisture content are significantly increased, and the purge gas relative humidity is also close to saturation. The Biot number of the ceramic membrane condenser is about 3.2 × 10^-3 to 1.9 × 10^-2; thus, the ceramic membrane tube wall thermal resistance can be neglected. There is a temperature difference between the flue gas and the purge gas, and the entropy production value of the ceramic membrane condenser increases with the flue gas temperature increases by the irreversible process.