Study on Performance of Gas Boiler Tail Gas Hydrothermal Recovery System based on Heat Pump and Low Temperature Air Preheater
The flue gas emitted by the gas boiler contains a large amount of water vapor,and the conden-sation latent heat of water vapor cannot be effectively recovered due to the failure of the exhaust gas tem-perature to fall below the dew point.In this paper,the compressed heat pump combined with low temper-ature air preheater is used to recover the flue gas waste heat of gas boiler in depth.The effects of heating return water flow rate and heating return water temperature on flue gas temperature,waste heat recovery efficiency,heating performance coefficient of heat pump unit and condensation rate of water vapor under different excess air coefficients are mainly studied.The results show that when the excess air coefficient is 1 and the return water flow rate is 80 t/h,the heat pump can increase the return water temperature from 50 ℃ to 65.1 ℃,and the heating performance coefficient is 4.25;when the air inlet and outlet tempera-tures of the low-temperature air preheater are-3.8 ℃ and 33.0 ℃ respectively,and the flow rate is 15 360 m3/h,the exhaust temperature drops from 90 ℃ to 20 ℃,and the flue gas waste heat recovery efficiency reaches 14.8％;for a 29 MW gas boiler with a heating area of 5.2 x 105 m2 and 151 days of heating,the amount of condensate recovered from flue gas is 8 000 tons,accounting for 54.1％of the boiler water replenishment rate;the payback period for this waste heat recovery system is 2.1 years.The flue gas waste heat recovery system of compressed heat pump has a significant energy saving effect.
flue gas waste heat recoverycompressed heat pumplow temperature air preheatercon-densation water recovery
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