| With the rapid development of China’s economy,energy conservation and emission reduction has become a key issue in development.At present,main energy source of heat supply in China is coal.However,a large number of coal-fired boiler houses and thermal power plants rarely recover waste heat from flue gas,which causes serious environmental pollution and energy waste.Although these problems have attracted attention,current solutions are not perfect,and more efficient,advanced and reliable waste heat recovery technologys are urgently needed.The flue gas waste heat recovery system combining waste heat recovery tower and absorption heat pump can significantly reduce exhaust temperature,effectively recover latent heat of steam vaporization and condensate in the flue gas,and make full use of waste heat of coal-fired flue gas for heating,thus significantly improving efficiency and economy of system.Firstly,mathematical model of countercurrent heat and mass exchange in the waste heat recovery tower between flue gas and water is established,and the model is solved and verified.At the same time,the expression of heat exchange efficiency between flue gas and water is derived.The results show that the established mathematical model is of high accuracy,and ratio of liquid to gas,particle size of spray droplets and size of waste heat recovery tower are main factors affecting heat exchange efficiency of direct contact between flue gas and water,while velocity of flue gas has little effect on it.Secondly,content of each component in flue gas,volume of flue gas,physical parameters,heat recovery of flue gas waste,etc.were obtained through theoretical calculation.On this basis,energy recovery calculation software of thermal power plant(Flue Gas Heat Recovery)FGHR1.0 was developed,and the software was validated using actual engineering-related design and operational data.The results show that the dew point temperature of flue gas is mainly affected by partial pressure of water vapor in flue gas,and change of air temperature has a greater influence on the dew point temperature of flue gas than the change of humidity.Through comparison and verification,the FGHR 1.0 software developed has high reliability.On this basis,this paper establishes corresponding mathematical model for the flue gas waste heat recovery system based on technology of direct contact heat exchange and absorption heat pump,explores main parameters affecting initial investment of the system,and analyzes the influence of return water temperature on the energy efficiency of the system and the influence of the exhaust temperature on the heating capacity of the system.The results show that appropriate decrease of plate heat exchanger of the cold end temperature difference can improve the economic benefit of the system,reduce a net return water temperature can improve the efficiency of the system,appropriate to reduce exhaust smoke temperature can improve recovery heat recovery capacity of the system.Finally,a thermal power plant in Jilin is taken as research object.Using the theoretical research results of this paper to design and calculate,and carry out feasibility analysis on economic,energy-saving and environmental protection of the new system.The results show that the dynamic investment recovery period is 5.3 years,and it has good energy saving,economy and environmental protection. |
