Multi-objective Evaluation Of The Novel Cogeneration Heating System Based On Condensed Waste Heat Recovery

Effective utilization of the condensed waste heat resources with low energy level in cogeneration plant has become a key direction to achieve both energy-saving and clean urban heating.For the technical problems of utilization of the condensed waste heat of multi turbine units in cogeneration plant efficiently and simultaneously,the authors’ research group proposed a novel cogeneration heating system,which can significantly improve the heating capacity and the energy efficiency of the cogeneration system.Therefore,in order to provide theoretical basis for the system integration and full operating conditions optimization of the novel system,this paper establishes the multi-objective evaluation index and method,which concerns the thermodynamic perfection,the heating energy consumption and the technical economy.Based on reducing the return water temperature,the novel system is established by using the absorption heat pump and increasing the backpressure of the turbine unit.For the multi-heat sources cascaded heating process,the heat balance equations of the heating links are established,and the off-design condition characteristics of the absorption heat pump component are analyzed.Taking the heating system which contains two sets of 300 MW water-cooling turbine units as the research objects,the influence of key parameters on the system performance is explored.In order to decrease the irreversibility of the system,improve the comprehensive energy efficiency of the system and reduce the heating cost,the multi-objective evaluation index and method of the novel system is established.Combined with the second law of thermodynamics,point out the direction of improving the thermodynamic perfection of the multi-heat sources cascaded heating process.Based on the method of equivalent electricity of heating,explore ways to improve the comprehensive energy efficiency of the novel system by adjusting key system parameters.According to the composition of the economic cost of heating in the novel system,the calculation method of the unit heating cost is established.Compared with the conventional cogeneration system and other waste heat recovery systems,the novel system has evident advantages in the aspects of the thermodynamic perfection,the actual heating energy consumption and the economy.Aimed at investment and operation characteristics of the novel system,the division principle of the economic benefit of waste heat heating is formulated,and then the price of the heat sold by power plants to heating companies can be determined.Through the overall project analysis,the novel system has significant benefits in energy saving and economy.Furthermore,the influence of uncertain factors such as return water temperature and electricity price on the economic benefit of the system is analyzed to verify that the novel system has the risk resistance capacity.