Experimental Research On Air Humidification Flue Gas Condensation Waste Heat Recovery System

With the rapid development of China's economic level,energy consumption has increased year by year.In order to adjust and optimize China's energy structure and change the situation of relying solely on coal resources,in recent years,coal consumption has been declining year by year.Correspondingly,natural gas consumption has been increasing by year.In 2017,China's natural gas energy consumption was 237.3 billion cubic meters,increased of15.3%.For Beijing,the total natural gas consumption during 2017 is 16 billion cubic meters.Among them,under the guidance of the“Coal reform clean energy”and“Coal to gas”policies,the proportion of gas heating in Beijing during the heating season reached 97%.At the same time,in order to solve the people's livelihood problems caused by hazy weather,Beijing has implemented a new boiler emission standard on 1^st April,2017.Through the investigation and test of the boiler,it was found that even after installing the waste heat recovery device and low-nitrogen burner,the boiler still has problems with high exhaust gas temperature,high concentration of nitrogen oxides,and low boiler operation energy efficiency.In order to improve the amount of waste heat recovery,recover more latent heat in the flue gas,and at the same time,reduce the nitrogen oxide concentration in the boiler flue gas.This paper proposes a method to increase the dew point temperature of flue gas by increasing the temperature and humidity of combustion gas in gas-fired boilers,and increase the amount of waste heat recovery.At the same time,because the temperature and humidity of the combustion air increase,the water content in the air rises,which leads to a decrease in the combustion temperature of boiler burners.Therefore,the method for reducing the amount of nitrogen oxides generated can solve the problems of low operating efficiency,high concentration of nitrogen oxides,and high exhaust gas temperature in existing boilers.In order to verify this theory,an"Air warming and humidifying flue gas condensation heat recovery test bench"was designed and built.Through the experiment,the performance of the experimental bench was tested.The heat source was a hot water boiler with a heat supply of 58 kW.The results show that the greater of the combustion air temperature and moisture content,more amount of residual heat recovery and the greater the amount of latent heat recovery;the better the nitrogen oxide emission reduction effect.Among them,the residual heat recovery effect and the waste heat recovery efficiency are the best when the spray water temperature is 15°C and the spray mass flow rate is 0.075 kg/s.The thermal efficiency of the boiler system is up to 105.04%.The nitrogen oxide emission reduction rate can reduce to 50%.