Entropy generation analysis of heat and water recovery from flue gas by transport membrane condenser

摘要

The transport membrane condenser (TMC) has been used for heat and water recovery from coal-fired power plant flue gas. The capillary condensation of water vapor in membrane pore structure is the main gas separation mode. A lumped parameter model was established to study the heat and mass transfer in TMC. Recovered water and heat flow rates, water recovery ratio, heat recovery efficiency, and pressure drops were calculated. The temperature and humidity ratio distributions were displayed. The influences of structural parameters and operating conditions on the water and heat recovery performances were analyzed. In addition, the entropy generation model was proposed to calculate entropy variations and entropy generation components. The aim is to provide insights into TMC parameter selection and operation optimization. Moreover, the relationship between entropy generation components and TMC performances were confirmed. The results show that increasing packing fraction, or decreasing the membrane inner diameter or membrane pore size can improve the heat and water recovery performances. Besides, high water flow rates and low water temperatures have advantages in the operation. Increasing the mass/heat transfer driving force can enhance heat transfer performance, but the heat transfer entropy generation rate also increases. The maximum mass transfer entropy generation rate often corresponds to the best water recovery performance. (C) 2019 Elsevier Ltd. All rights reserved.