Analysis of Thermal Performance of Water Vapor Pump for Recovering Latent Heat of Flue Gas from Gas-fired Boilers
The high exhaust flue gas temperature of gas boiler is one of the important factors restricting its thermal efficiency enhancement.In this paper,water vapor pump(WVP)technology was used to recover the latent heat of flue gas from gas-fired boilers.A theoretical model was established for 1 000 MW gas-fired boilers.The influence of factors such as return water temperature,air temperature and humidity of heating network and excess air coefficient on the thermal efficiency of gas-fired boilers was analyzed,and the thermal performance of boilers was optimized.The results show that when the return water tempera-ture of the heating network is 45 ℃,the air temperature is 0 ℃ and the air relative humidity is 60％,the exhaust gas temperature of the gas boiler can be reduced to 26.2 ℃,the heat recovery efficiency can reach 83.6％,and the boiler thermal efficiency can reach 106.6％.With the increase of the return water temperature of the heating network,the system capability to recover the latent heat of the flue gas gradu-ally decreases.When the return water temperature of the heating network exceeds 68 ℃,the system can-not recover the latent heat of the flue gas.The influence of air temperature and excess air coefficient on boiler thermal effiiciency is relatively small.Taking a 7 MW heat load boiler as an example,the prelimi-nary technical and economic analysis for latent heat recovered by water vaper pump is carried out,which shows that the investment recovery period is about 7 years.
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