Coupling Characteristics And New System Research Of Double Reheat Ultra-supercritical Unit

In recent years,material technology has become increasingly mature,and large-capacity,high-parameter ultra-supercritical double-reheat units have become the preferred choice for coal-fired generating units.The power generation efficiency of the ultra-supercritical unit is determined by the combination of the steam parameters and the structure of the regenerative system.As a consequence,the choice of the steam parameters and the structure of the regenerative system is of great significance for improving the thermal performance of the unit.In order to improve the power generation efficiency of the traditional double-reheat power station,this paper mainly proposes a new type of boiler-turbine coupling system,which is based on the "energy level mismatch" phenomenon in both sides of the power plant boiler and turbine.Base on the variation rules of energy grades between the air endothermic process and the steam turbine exothermic process,this paper proposes a new way to fully integrate the heat absorption process and heat release process between the boiler side and the turbine side,and the energy cascade utilization of between the air preheating process and the regenerative heating process can be realized by heat transfer integration of flue gas,steam,water and air between the boiler side and turbine side.Based on the EBSILON simulation platform and the actual operation data of the typical 1000MW double reheat super-supercritical coal-fired unit of Taizhou Power Plant,the heat transfer characteristics and energy-saving benefits of the new boiler-turbine coupling system are analyzed.At the same time,according to the principle of "fixed power,variable coal volume",the coupling model of the furnace and the furnace under the conditions of 100%THA,75%THA,50%THA,40%THA and 30%THA was established,and compare of the parameters between the coupling model of the furnace and the original system within the range of each load,and probe the variation law of the coal consumption change of the boiler-turbine coupling system under the full working condition,and the energy consumption characteristics of the whole process are investigate.The variation rules law of energy consumption of the unit are obtained,which can provide valuable data for system reconstruction and parameter optimization.The results show that the coal consumption rate of standard coal of the overall system is reduced by 3.6g/kW h under THA condition,which greatly improves the power generation efficiency and economic benefits.The goals of energy saving and emission reduction have been achieved,and the standard coal consumption rates of the overall system are lower than those of the original system under all conditions.Based on the first law of thermodynamics and the second law of thermodynamics,the heat balance and enthalpy balance calculation model of the thermal system of coal-fired generating units is established,which provides a theoretical basis for the structural optimization of the secondary reheat unit system and the reheat steam parameter analysis.Based on the secondary reheater coupling system proposed on the basis of the traditional secondary reheat unit,the thermal performance analysis results show that the heat consumption rate is reduced by 32.139kJ/kW·h compared with the original system;the power generation efficiency is increased by 0.21 percentage.In this paper,an economic analysis model is established and the economic performance of the new system is analyzed.