| At present,the proportion of natural gas consumption in China is increasing,the total consumption of natural gas is increasing year by year,especially the daily consumption of heating period,and there is a huge gap in domestic natural gas supply.As far as Beijing is concerned,natural gas consumption of gas fired heating boilers accounts for 14%of the total gas consumption in the whole city.As the main consumption equipment of natural gas,it is an important way to solve the imbalance between supply and demand of natural gas by deep recovery and utilization of flue gas waste heat and improving its thermal efficiency.Therefore,the characteristics of various flue gas waste heat recovery technologies and related heat recovery equipment of gas fired boilers are first studied.And the operation performance and energy saving test of the existing small and medium-sized gas fired heating boiler in Beijing less than 20 tons are carried out.Through field tests,the energy saving potential of low-temperature flue gas waste heat during actual operation and operation performance are studied.The test results show that the temperature of flue gas emitted by the boiler is higher.Even if the flue gas waste heat device is added to the boiler,the exhaust temperature of the flue gas is still higher than the dew point temperature of flue gas,and there are still a lot of low grade residual heat in the flue gas.If the temperature of flue gas is reduced to the dew point temperature,the thermal efficiency of the boiler can be increased by6%~11%,and it has great energy saving potential.Therefore,according to the characteristics of various waste heat recovery devices and the characteristics of small and medium gas fired boilers,a spray heat exchanger with high heat exchange efficiency and a certain purification effect is selected for the study of many waste heat recovery methods.Currently,the return water of heat-supply network is used as spray water.Because of its high temperature,it is impossible to recover the condensing heat from the flue gas.Therefore,finding the suitable low temperature and cold water source as spray water is the key to the application of spray heat exchanger.Therefore,the heat pump type gas boiler flue gas condensing waste heat recovery system with a spray heat exchanger and a compression heat pump is used to recover the residual heat of the flue gas condensing,and the problem of the cold source is solved by the characteristics of the heat pump.And A 58 kW vertical gas fired boiler is used as a flue gas source.the experimental platform of the heat pump type gas boiler flue gas condensing waste heat recovery system is designed and built.The influence of inlet temperature andf flow tate if the heat pump condenser on the performance of the waste heat recovery system is explored through experimental means.The influence of two heating adjustment modes on the performance of the heat pump type gas boiler flue gas condensing waste heat recovery system is explored by simulation.The two adjustment modes are constant flow control and constant-variable flow control.In the operating conditions of the gas boiler with a gas consumption of5.13 Nm~3/h and an excess air coefficient of 1.2,the average recovery efficiency of the heat pump type condensing waste heat recovery system can reach 13.5%.The water vapor content in the exhaust flue gas will be reduced by more than 75%,and the exhaust temperature of the flue gas will be reduced to about 30. |
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