Direct absorption heat pump and the direct contact heat exchanger of flue gas waste heat recovery project cases

1 the gas boiler flue gas waste heat recovery technology is a major component of natural gas (methane CH4) , burning in the back of the smoke contains large amounts of water vapor, water vapor latent heat of gasification accounted for the proportion of low calorific value of gas reaching 10% ~ 11%, and the direct emissions to basically have no use. In addition, the natural gas in the flue gas water vapor condensation after discharged into the atmosphere, the white smoke phenomenon, the formation of landscape, pollution and PM2. 5 emissions index increase. Therefore, depth of recycled flue gas, including steam gasification of latent heat, waste heat to save energy and reduce emissions has important significance. To take advantage of gas boiler flue gas waste heat, the domestic and foreign scientific research units was studied. In view of the gas boiler flue gas waste heat recovery technology at present, mainly in the add condensing heat exchanger and air preheater is used to reduce the exhaust temperature. Conventional gas boiler equipped with condensing heat exchanger, phase change process, exist in the process of flue gas temperature of phase change of starting temperature of flue gas. Above, the boiler heat efficiency ( Calculate according to the low calorific value of gas boiler heating load and the ratio of the amount of gas heating) Improvement is to rely on the sensible heat of the flue gas by cooling. After the flue gas temperature is lower than the boiler heat efficiency mainly by water vapor condensation latent heat, at this point reduce the heating efficiency of boiler flue gas temperature, the influence is significant. Only when the heat supply network backwater temperature below 20 ~ 30 ℃, using a condensing heat exchanger will have good effect. For the heating system in general, especially the district heating system, its heat supply network return water temperature is much higher than this value. Therefore, direct use of heat supply network backwater to reduce flue gas temperature is often limited. This reason has seriously restricted the condensing boiler is used widely in the field of heating. If the documents mentioned in the absorption of heat exchange technology, can significantly reduce the heat-supply return water temperature. The return water temperature is 20 ℃, if the network USES the condensing heat exchanger in the flue gas temperature can be dropped to a lower level, so as to increase efficiency of the boiler heating.