Thermodynamic Analysis,Optimization And Integration Of Boiler-turbine Coupling For Large-scale Coal-fired Power Plants

The share of electricity in thermal power plant s has long exceeded 80%of its total amount.Under the energy-saving-and-emission-reduction policy,the high fuel consumption feature of coal-fired power plants has been frequently discussed in the face of storm.Additionally,the restructuring of the power generation industry over the past decade has confirmed the dominant role of large(ultra)supercritical power plants with higher steam parameters in the near future.Thus,research on the thermodynamic analysis,optimization and integration of these plants can play a very significant role in the fuel consumption reduction of the whole coal power industry.Focusing on large-scale coal-fired power plants in this research,the process energy-saving theory was further developed to comprehensively reveal the spatial distribution of fuel consumption in the system and to accurately calculate the thermodynamic interaction among components and the real energy-saving potential of each component.The system structure and parameter optimization was obtained simultaneously and the change of decision variable frontiers was clarified under multi-objective considerations.A general software platform on system analysis and optimization was well developed.Therefore,this research eventually provides one reliable methodology and implementation approach for the design,evaluation,retrofit,integration and optimization of coal-fired power plants.Additionally,"“Tempospacial Energy-Saving Effect”was proposed to provide reference for further energy-saving diagnosis to quantify the detailed energy consumption status of large-scale thermal power plants with different boundaries,which is time-dependent.Firstly,the specific fuel consumption analysis,a variant of exergy analysis,was improved by spliting the additional fuel consumption in each component into avoidable/unavoidable parts on the bases of their sources and avoidabilities,which is advanced ESFC methods.The quantitative computation approach of these four kinds was expressed in detail.The nonlinear thermodynamic interation among components was deduced properly with the discussion of the linear term and coupling term.Then,a new concepted named "temporal-spacial energy-saving effect" is proposed.Additionally,the calculating methods are introduced,in the terms of advanced ESFC methods.The impact of component on the system fuel consumption was also discussed.Secondly,the newly proposed method can find its theory foundation based on the concept of "emporal-spacial energy saving" proposed above,in depth boiler-turbine coupled structures.The basic power plant and the three proposed concepts related the noval energy systems are described.Then,the methods employed for working-fluid selection and system evaluation are introduced.Subsequently,the working-fluid selection is first discussed with the influence on system performance and,afterwards,throughout discussion and comparison of all four cases are given.Finally,the conclusions are drawn.Finally,based on the concept of tempospacial energy-saving effect,the characteristic of energy-consumption within thermal power plants under varying boundaries are calculated.(1)The calculation mode of the off-design conditions are introduced in the forms of algorithm,including those of turbine flow passage,condenser and regenerative heaters;(2)The energy-consumption distribution of main components and thermal processes under varying load conditions are illustrated through terms of figures and tables,as well as the temporal-spacial energy-saving effect;(3)The distributions of energy-consumption and temporal-spacial energy-saving effect are listed,with varying boundaries of ambinent temperature,that is,circulating water temperature.After depth study of the above results,further guide can be provided for operation under low load condition and flexible modification.The proposed method is expected to be applied to the operation diagnosis,system design or modification of large-scale coal-fired power plants in order to achieve the available operating strategies and improved solutions,combined with more practical constraints.