Application Of Double-Effect LiBr Absorption Heat Pump Heat Recovery System In Cogeneration Plant

At present, thermal power generation dominated the electric power industry in our country. As the world energy crisis intensifies, traditional energy price rises and environmental concern enhanced, people had paid more attention to energy conservation and emission reduction technologies. Although we could greatly increase the energy efficiency of the power plant by using CHP (Combined Heat and Power), there was still much low grade heat in the CHP plant. Recovery of the waste heat would improve the efficiency of the primary energy.In this paper, a heat recovery system was designed to applied in steam boiler of the CHP plant. The heat recovery system used 0.8MPa steam generated from the boiler as power, and steam operated double-effect LiBr absorption heat pump as the centre equipment. By rebuilding the original HVAC system, it could achieve the aim that recover heat from the desulfurizing tower circulating water at the temperature of 45℃in winter and recover condensation heat of heat pump in summer by means of using the boiler demineralized water whose temperature was 20℃as cooling water. The HVAC system design heating load was 403kW and cooling load was 574kW. In design condition this system could recover 467kW heat in winter and 991kW in summer.Through the theoretical calculation and experimental methods, this paper presented design of another important equipment of the system—water to water heat exchanger. And after referring to domestic and foreign literatures, this paper gave the heat transfer coefficient and flow resistance calculation formula of shell and tube heat exchanger. This paper presented the friction factor of the desulfurizing tower circulating water which was the most important factor that influenced the flow resistance of the heat exchanger. The article provided how to calculate the life cycle cost of the heat exchanger, then Genetic Algorithm (GA) was applied to select the minimal total cost of the heat exchanger and determined heat transfer area as 82.9 m2.In the end of the paper, EnergyPlus was used to simulate energy consumption of the original HVAC system. It is proved that EnergyPlus was accurate enough to predict energy consumption by comparing the simulation result and the actual operation cost. Then, this software was used to simulate energy consumption of the original and the heat recovery system, results showed that heat recovery system could reduce annual primary energy consumption 30.4 tce and CO2 emission 74.14t, and recover waste heat up to 90.6 tce. The heat recovery system could decrease annual operation cost up to 226,000 RMB, and could recouping investment in 3.35 years. It meant that heat recovery system could obtain certain economic and environment benefits.