Numerical Simulation And Experimental Research Of The Spray Type Flue Gas Condensing Heat Recovery Process

The gas boiler has been widely used in the district heating system in Beijing. The flue gas emission temperature of water boiler is about 150-180℃. The flue gas emission temperature of steam boiler is about 200-250℃. The high emission temperature of flue gas cause much heat loss. There is only part of sensible heat could be recovered by conventional economizer or air pre-heater. The latent heat accounts for 10 percents of natural gas caloricity gaging. But the latent heat failed to be recycled.Therefore, the running efficiency of gas boiler is just about 80 percents to 90 percents of design efficiency. With the decrease of flue gas emission temperature, the theoretic heat could be recoverd of flue gas and the theoretic heat efficiency of boiler would be gradually increased. When the emission temperature of flue gas reduced to flue gas dew point temperature, the theoretic efficiency of boiler would be significantly increased. If the flue gas emission temperature reduce from ℃ to 35-40℃, the heat efficiency of boiler would be improved 15.1% to 13.9%. In addition, there are benifits for the improvement of boiler heat efficiency and the decrease of air pollutant emissions if flue gas waste heat and moisture in the flue gas could be recovered.The typical technologies in the field of flue gas waste heat recovery could be divided into three categories. It includes the technology utilize heat-exchanger for flue gas waste heat recovery. According to the heat exchange manner, technology utilize heat-exchanger for flue gas waste heat recovery could be fall into indirect contact and direct contact flue gas waste heat recovery.The technology utilize heat pump for flue gas waste heat recovery. According to the application type of heat pump, technology utilize heat-exchanger for flue gas waste heat recovery could be fall into utilize compression heat pump and utilize absorption heat pump for flue gas waste heat recovery. The district heating technology which utilize flue gas waste heat. According to the heating type, the district heating technology which utilize flue gas waste heat could be fall into single stage and double stages flue gas waste heat recovery.The paper is a research which focus on spray type flue gas condensing heat recovery technology belongs to technology utilize heat-exchanger for flue gas waste heat recovery. The formula of heat transfer performance between flue gas and water is derived in the paper. The numerical stimulation method and experiment measures have been used for the research of influence factors which have affect on heat transfer performance of the spray type flue gas condensing heat recovery. A experimental prototype has been designed and built for the spray type flue gas condensing heat recovery. A gas water heater with mechanical exhaust is been used as the source of flue gas.The rated heat load of gas water heater is 20 kW. The operation heat load of gas water heater is set at 12 kW.When the spray water temperature is 20℃, spray flow rate is 0.050 kg/s,the thermal efficiency could be increased to 103% to 104%. Expect the research provides reference significance for the widespread and application of spray type flue gas condensing heat recovery heat-exchanger in the field of flue gas waste heat recovery technology.