一种双级耦合膜法烟气余热回收系统的仿真研究

Natural gas is an effective way to the clean heating. However, the lack of natural gas is still serious in China nowadays. By recovering the flue gas waste heat, the caloric utilization efficiency of natural gas can be improved much, which will help to relieve the energy crisis. This study proposes a two-stage coupled membrane-based flue gas waste heat recovery system, in which two membrane total heat exchangers achieve the cascade heat recovery of the gas boiler exhaust. On one hand, the combustion temperature is lowered and therefore the emission of nitrogen oxides is reduced; on the other hand, with the boiler exhaust humidity elevated, the mass transfer potential difference driving the total heat transfer process of the flue-gas-to-water membrane total heat exchanger is enlarged, as well as the overall recovery capacity of the entire system. This study establishes the mathematic model for the heat and mass transfer of the membrane total heat exchangers, takes the numerical simulation, and conducts the system performance analysis. The simulation results show that the total heat recovery efficiency can reach 0.874 at highest and meanwhile the system efficiency based on net caloric value can reach 1.090.