Experimental Study Of Flue Gas Condensation Heat Recovery And Purification By Air Humidification Using Filler

China is the largest energy consumer in the world.Due to the rapid economic development,the energy self-sufficiency rate is decreasing as the energy production is increasing by years.In order to solve the air pollution problem by coal-fired heating,Beijing has fully implemented gas heating system which led to"gas shortage".Gas-fired boilers used in small central heating systems have high exhaust temperature and high emission of nitrogen oxides.A large amount of latent heat contained in flue gas can be utilized to improve boiler efficiency and reduce gas consumption.Therefore,it is of great value to research the recovery and reduction of waste heat from flue gas in such gas-fired boilers.In addition to FGR technology,air humidification can also be used to reduce the emission of nitrogen oxides.However,two sets of pumps are needed to recover waste heat from flue gas and humidify air by direct spraying.The pipeline is complex and the flow adjustment is difficult.In view of the above problems,this paper puts forward the technology of humidifying air by gravity self-flowing water distribution to fillers and recovering waste heat from flue gas by direct spraying.The larger equipment space required by the filling system can be installed by using the ceiling of the upper space of the boiler or overhaul path.Therefore,a packed air humidifying flue gas condensation waste heat recovery and purification system is designed.The design key points are summarized.An experiment system of“flue gas condensation heat recovery and purification by air humidification using filler"is designed and tested.The experiments include different return water temperature and different liquid-gas ratio.Experiment shows that the quantity of heat recovery increase as the liquid-gas ratio increase under low return water temperature.When the return water temperature of the heating network is 45°C and the spray liquid-gas ratio is 7,the flue gas temperature can be reduced to below flue gas dew point.The heat recovery is4.23 kW,and the boiler efficiency can be increased by 8.3%.The quantity of heat recovery increase and then decrease as the liquid-gas ratio increase under high return water temperature.The concentration of nitrogen oxides in flue gas has nothing to do with inlet water temperature,but with air humidity ratio.The concentration of nitrogen oxides decrease as the air humidity ratio increase under a certain excess air coefficient.The emission of nitrogen oxides can reach 26mg/Nm~3 under humidity ratio is 54g/Nm~3 and the excess air coefficient is1.25,which meets the local standard of Beijing.