The Design And Research Of Exhaust Gas Comprehensive Treatment Device For Gas Fired Boiler

With the number of gas boilers used more and more, exhaust from the gas boiler affect atmospheric environment, which drew people's attention. This paper aimed to design a kind of device to purify the gas boiler exhaust and to reduce the harm to environment. The design of the device was divided into four steps:Firstly, we analyze the composition of the gas boiler exhaust. According to the composition of natural gas and the combustion process, complete combustion of 1Nm3 natural gas will produce fumes of 10.2~12.5Nm3, when the excess air ratio ranging between 1~1.25. Exhaust from natural gas combustion are mainly composed of carbon dioxide, water vapor and nitrogen, its volume ratio in flue gas respectively: 14%, 17% and 72%. In addition to these three kinds of components, the gas boiler exhaust contain other pollutants such as CO2,SO2,NO,NO2,solid particles and so on.Secondly, based on haze phenomena analyze the environmental impact of gas boiler exhaust. On the one hand, pollutants,such as SO2,NO2, solid particles and so on, from gas boiler exhaust float in the air and are not its degradation, which increase the concentration of PM2.5 in the air. On the other hand, combustion products contain a lot of water vapor that increase the air relative humidity and provide humidity environment for the formation of aerosol in haze. Therefore, the gas boiler exhaust contribute to the formation of haze.Thirdly, determine the treatment method of pollutants in gas boiler exhaust. The device is mainly deal with the solid particles, water vapor, and gaseous pollutants(CO2,SO2,NO,NO2 and others) from exhaust. According to the characteristics of each material, the device use the treatment methods as follow:The treatment of flue gas drying dehumidifying. Through the high temperature flue gas and cool air mixture, and supplemented by convective heat transfer to reduce the temperature of gas boiler exhaust, the gas condensing when the temperature down to the dew point temperature after mixing, so as to achieve the effect of dehumidification dying.The treatment of flue gas dust removal. On the one hand, the high temperature resistant filter cotton on the smoke deflector inside the device absorb and collide the solid particles in exhaust. On the other hand, the condensate water produced cooling process can absorb some fine particles. The dust from exhaust were removed under the combination function of these two aspects.The treatment of gas pollutants in flue gas. Because of these gas pollutants are water-soluble, the condensate water produced the flue gas drying can absorb these gas, so as to achieve the effect of purification.Finally, the device structure was designed and the device was applied to the actual project. According to the analysis and calculation of data measured the actual project found that the effect of gas boiler exhaust purification was very well, the dust removal rate over 40% and drying rate over 50%. The results show that the device have a good purifying effect for gas boiler exhaust, which can reduce or even eliminate pollution of gas boiler exhaust.