| At present,the flue gas recovery and treatment equipment in the biomass energy utilization system is simple,and the exhaust temperature is high.There is still the phenomenon of "white smoke",which causes energy waste and environmental pollution.Aiming at the above problems,based on the principle of "grade matching and step utilization",this paper proposes a total heat recovery heat pump system of biomass flue gas: a)applying double-section absorption heat pump to recover the obvious part of waste heat of biomass flue gas;B)Using a compression heat pump,including two screw compressor units and one scroll compressor unit,to recover the latent heat in the waste heat of biomass flue gas.The main conclusions are as follows:First of all,based on the actual biomass boiler flue gas composition,to establish the mathematical model,the biomass gas analysis of flue gas energy levels,the results showed that the biomass gas sensible heat and latent heat quantity than close to 1:1,latent heat of flue gas quantity is bigger,latent heat recovery of flue gas measuring tool has important significance,based on the analysis of flue gas energy,biomass gas hot poor heat pump system is put forward.Second,the simulation models of double-section absorption heat pump and multistage parallel compression heat pump were established to simulate and analyze the effects of high and low temperature heat source temperature,heating return water temperature and evaporative heat source on the performance of double-section absorption heat pump and compression heat pump.The simulation results show that COP and concentration of concentrated solution increase with the increase of heat source temperature.The temperature of heat source should not exceed 120℃.Too high temperature will lead to too high concentration of concentrated solution and solution crystallization.The COP of double-section absorption heat pump heating increases with the temperature of low temperature heat source,and the concentration of dilute solution decreases with the temperature of low temperature heat source.The temperature of low temperature heat source should not exceed 58℃,which is easy to cause the concentration difference is too large to exceed the reasonable operation range.The COP of double section absorption heat pump heating decreases with the increase of heating return water temperature,and the concentration of concentrated solution increases with the increase of heating return water temperature.The heating return water temperature should not be less than 36℃,too low temperature leads to too high concentration of concentrated solution,easy to occur solution crystallization phenomenon;The COP of compression heat pump increases with the increase of evaporation heat source temperature,and the compressor power decreases with the increase of evaporation heat source temperature.Thirdly,an experimental platform was set up to study the performance variation of biomass flue gas total heat recovery heat pump system with different high and low temperature heat source temperature,heating return water temperature and evaporation heat source temperature.The results showed that: When the inlet and outlet temperature of the double-section absorption heat pump is 120℃/86.5℃,the inlet and outlet temperature of the low-temperature heat source is58℃/37℃,and the inlet and outlet temperature of the heating water is 45℃/72.6℃,the COP of heating is 1.76.Compression heat pump in the evaporation heat source inlet and outlet temperature of 38℃/32℃,heating water inlet and outlet temperature of 42℃/67.4℃,heating COP is 4.1;The minimum biomass exhaust temperature can be reduced to 34℃;The heat of the recovered flue gas is up to 485 k W,accounting for 75.6% of the heat of the flue gas at 165.8℃,and 82.2% of the latent heat is recovered.The waste heat recovery rate of the system can reach 23.35%,the relative energy saving rate increases by 12.5%,and the comprehensive energy utilization rate increases by16.4%.Fourthly,based on simulation and experimental research,the reliability of the model was verified.The results show that the COP deviation of the double-section absorption heat pump is0.12%～5.7%,and the COP deviation of the compression heat pump is 3.63%～18.08%.It can be seen that the double-section absorption heat pump and the compression heat pump models are more reliable. |
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