| Biomass power generation is one of the main ways to deal with biomass.In recent years,the energy supply mode of biomass power generation has gradually changed from pure power generation to cogeneration.In the biomass cogeneration system,the heat loss of exhaust gas is the largest heat loss of biomass boiler,and the recovery and utilization of exhaust heat is an important means to improve the energy utilization rate.The absorption heat pump driven by low-pressure steam has been widely used in the thermal power plants to expand the heating capacity.There are few examples of direct use of flue gas waste heat to drive absorption heat pump auxil iary heating,and the use of medium and high temperature flue gas above 200 ?.For the low-temperature flue gas which still has great potential of waste heat recovery,the existing technology is difficult to achieve efficient recovery and utilization.This paper presents an absorption heat pump system driven by flue gas waste heat,which will recycle residual heat of below 145? low temperature discharged gas and produce heating water of 70?.Aspen Plus was used to simulate the biomass direct-fired boiler and the absorption heat pump system driven by flue gas waste heat.Based on the simulation data,the exergy analysis of the system were carried out.This paper studies the effect of absorption heat pump assisted heating with flue gas waste heat drive on the performance of biomass direct combustion cogeneration system,and analyzes the energy saving and environmental protection benefits and economics of flue gas waste heat driven absorption heat pump system.Based on the demand of heating in winter and cooling in summer,an optimization scheme is proposed to recover the residual heat of flue gas more comprehensively and deeply.The main research contents and conclusions are as follows:(1)The exergy efficiency of biomass direct fired boiler is 41.69%,and the exergy loss of biomass direct fired boiler is mainly caused by the irreversibility of combustion process and heat transfer process.The absorption heat pump system driven by flue gas waste heat has an exergy efficiency of 32.56%,and the exhaust smoke exergy loss accounts for the largest proportion of the system exergy losses.The flue gas finally emitted by the system still has the potential for further recycling.The absorption heat pump heating coefficient reaches 1.775,and the biggest exergy loss component of absorption heat pump is the absorber,followed by the generator.(2)Compared with the traditional biomass direct fired cogeneration system without flue gas waste heat recovery,the energy-saving rate,comprehensive energy utilization rate and flue gas waste heat recovery rate of the biomass direct fired cogeneration system increased by 4.76%,6.66% and 10.99% respectively after the absorption heat pump system driven by flue gas waste heat was added.The heat supply in each heating season can be equivalent to 2075.80 t of standard coal,and can reduce carbon dioxide emissions by 5348.58 t,Sulfur dioxide 17.64 t,nitrogen oxide 15.36 t,dust 31.14 t,ash 539.71 t.The dynamic investment recovery period of the absorption heat pump system driven by flue gas waste heat is 5.93 years.The auxiliary heating of the absorption heat pump system driven by flue gas waste heat has considerable energy saving and environmental protection benefits and economics.After adding this system,various performance indicators o f the biomass direct combustion cogeneration system have been significantly improved.(3)The optimization scheme takes into consideration the two conditions of heating in winter and cooling in summer.The optimized flue gas waste heat deep recovery system adds low-temperature heating in winter,and the system exergy efficiency is improved by 16.83% compared with before optimization.After adding the system,the energy saving rate,comprehensive energy utilization rate and flue gas waste heat recovery utilization rate of the biomass cogeneration system have increased by 8.64%,12.73% and 21.01%,respectively.Each heating season can save 3969.61 t of standard coal,reduce carbon dioxide emissions by 10400.39 t,sulfur dioxide 33.74 t,nitrogen oxides 29.38 t,dust 59.54 t,and ash slag 1032.10 t.In summer cooling conditions,the refrigeration coefficient of absorption heat pump refrigeration cycle driven by residual heat of flue gas is 0.767,which can be used as a cold source for regional cooling.The optimized flue gas waste heat recovery system can recover the exhaust gas waste heat more efficiently in winter,meets the different heat demand of more users,and significantly improves the performance indicators of biomass cogeneration system.In summer,the heat pump is converted to the cooling mode,which not only improves the annual utilization rate of the heat pump,but also alleviates the power shortage in summer. |
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