采用水-蒸汽泵回收燃气锅炉烟气潜热的热力性能分析

Analysis of Thermal Performance of Water Vapor Pump for Recovering Latent Heat of Flue Gas from Gas-fired Boilers

燃气锅炉较高的排烟温度是制约其热效率提高的重要因素之一。本文采用水-蒸汽泵技术回收燃气锅炉烟气潜热,针对兆瓦级燃气锅炉建立理论模型,分析提高热网回水温度、空气温度和湿度及过量空气系数等因素对燃气锅炉热效率的影响规律,并对锅炉的热力性能进行了优化分析。结果表明:当热网回水温度为45℃、空气温度为0℃、空气相对湿度为60%时,燃气锅炉的排烟温度可降低至26.2℃,热回收效率可达到83.6%,锅炉热效率可达到106.6%;随着热网回水温度的升高,系统回收烟气潜热的能力逐渐降低,当热网回水温度超过68℃时,系统不能回收烟气潜热;空气温度和过量空气系数对锅炉热效率的影响相对较小;以7 MW热负荷锅炉为例,对水-蒸汽泵回收潜热进行了初步技术经济分析,表明投资回收期约为7年。

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 gasfired boilers.A theoretical model was established for 1000 MW gasfired 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 gasfired boilers was analyzed,and the thermal performance of boilers was optimized.The results show that when the return water temperature 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 gradually decreases.When the return water temperature of the heating network exceeds 68℃,the system cannot recover the latent heat of the flue gas.The influence of air temperature and excess air coefficient on boiler thermal efficiency is relatively small.Taking a 7 MW heat load boiler as an example,the preliminary 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.