Research On The Combined Heat And Power Cycle Of Coupling Absorption Heat Pump

Recycling and utilizing the low grade waste heat efficiently is an effective measure to promote the ratio of overall energy utilization for coal fired power plants and achieve energy conservation and emissions reduction. In this thesis, the energy-saving potential of the typical heat pump heating system for one coal-fired thermal power plant in north China was analyzed with energy level method and an optimization solution was put forward. To solve the off-design problem encountered during the actual operation of heat pump, the influence of the variation for turbine load, circulating water inlet temperature and heating network load on cogeneration system from the aspect of the joint system of turbine, heat pump and heating network.In order to analyze the energy-saving potential of the typical heat pump heating system, the model of type I lithium bromide absorption heat pump under rated conditions was developed and the thermodynamic energy analysis, exergy analysis and grade analysis of the typical heat pump heating system for one 300MW coal-fired thermal power plant in north China was carried out. It turns out that the main energy saving potential lies in three points:Firstly, the temperature difference of heat pump components could still be reduced reasonably; Secondly, the exergy loss in the secondary heat exchanger accounts for 48.6% of the total exergy loss and heat supply in heat pump only accounts for 63.9% of the total heat supply, the energy saving property of whole system has been weakened; Thirdly, about 16.7MW recyclable exhaust heat is wasted.In order to give full play to energy saving of absorption heat pump in the heating system, a new system serial-parallel coupled with two type I lithium bromide absorption heat pumps was proposed, which replaced the secondary heat exchanger for the typical heat pump heating system with high pressure lithium bromide absorption heat pump and added the waste heat recovery exchanger at the end of the boiler to raise the grade of the circulating water. The thermodynamic and economic performance contrast between new system and reference system was performed and the results show that the new system increases exergy efficient by 10.5 percent points, increases the heat supply by 16.5% and increases annual coal saving by 59.2% compared to reference system. What’s more, the payback period of the new system is 5.2 years.In order to carry out the off-design performance research of the typical heat pump heating system, the off-design mathematic model of type I lithium bromide absorption heat pump, the condenser and the turbine was developed to make clear the situation without energy saving during the actual operation of heat pump. The results show that when the turbine load is low(under 50% THA) or the inlet temperature of circulating water in the condenser is low(under 10℃), outlet temperature of circulating water in the condenser will below the evaporating temperature of heat pump(34.5℃), causing an adverse impact on the energy saving.This thesis has preliminarily clarified the energy-saving potential of the typical heat pump heating system and made clear the situation without energy saving during the actual operation of heat pump and the influencing characteristic of the variation for heating network load on cogeneration system.