Effects of process parameters on water and waste heat recovery from flue gas using ceramic ultrafiltration membranes

A membrane condenser was established by using tubular ceramic membranes with a separation layer of 20 nm in pore size, which are coated on the inner/outer-side of the tube (IM/OM), respectively. Experiments of water and heat recovery from simulated flue gas were conducted using deionized water as coolant. Effects of air flow rate, cooling-water flow rate, inlet gas temperature and inlet water temperature on mass and heat transfer across the IM and OM were investigated. Results showed that both water and heat fluxes of IM and OM increased as the increment of the air flow rate and inlet gas temperature. Water and heat fluxes of both IM and OM increased as the cooling-water flow rate elevated, while this tendency of variation was not remarkable when the cooling-water flow rate reached a certain value. Reducing the inlet water temperature effectively enhanced heat fluxes of IM and OM, but had little effect on water fluxes. The influence of coolant water flow rate on water and heat fluxes of OM is more significant, indicating that mass and heat transfer across the OM was more susceptible to the boundary layers effect. Compared with the IM,the OM exhibited much higher water fluxes and lower heat fluxes. In this work, water and heat fluxes of ceramic membranes were up to 23.1 kg·m^-2·h^-1 and 47.5 MJ·m^-2·h^-1, respectively. With the development of the TMC, it has broad application in dehumidification and utilizing industrial waste heat. This technology will also bring new ideas in many fields such as energy and water conservation and environmental protection.