Improving heat transfer and water recovery performance in high‐moisture flue gas condensation using silicon carbide membranes

Abstract

Summary Desulfurated flue gas in coal‐fired power plants contains profuse water vapor and latent heat, the recovery of which is crucial. Herein, a novel use of silicon carbide (SiC) membranes to construct a transport membrane condenser (TMC) for simultaneous water and waste heat recovery from high‐moisture flue gas is reported. The performances of water and heat recovery were systematically compared between typical dense heat exchange materials (304 stainless steel and perfluoroalkoxy [PFA]) and porous ceramic membranes (Al2O3 membrane and SiC membrane). Porous ceramic membranes showed higher heat transfer performance than dense materials, suggesting a non‐negligible mass transfer effect on heat transfer. Compared with the Al2O3 membrane, the SiC membrane exhibited better water and heat recovery performance because of its superior thermal conductivity. Using the SiC membrane as the heat exchange material, a water flux of 11.3‐44.4 kg·m−2·h−1 and a water recovery efficiency of 46.5%‐76.9% were achieved. The thermal resistance from the gas boundary layer dominated the heat transfer process in SiC membrane condensers as the thermal resistances from the membrane and condensate film were markedly reduced. This study forms a basis for future investigations on heat transfer enhancement of membrane condensers used for industrial moisture recovery.

A Thermal Calculation Model for Tubular Condensing Heat Exchanger

“…During the convective-condensation process of the high-moisture flue gas, the heat and mass transfer occur at the same time [11]. The flue gas parameters, such as the composition, the specific heat capacity, the convective heat transfer coefficient, etc., along the flow direction would vary considerably, resulting in a heat transfer process of great complexity.…”