1000MW Double Steam Reheat Unit Bleed Parameters Determination And Thermodynamic System Research

Efficient and clean coal-fired power generation is still the main power supply way for a long time in the future in the world.The question of how to improve the unit generation efficiency is the central problem in power generation industry. As the installed capacity increasing and the main steam parameters improved,the research about the700 ℃ high parameter and large capacity second reheat unit has been attracted great attention all around the world.The bleed parameters of thermal system have a determined impact on the unit efficiency and important influence on the bleed location and design of the steam turbine.On the basis analysis of the feed water equivalent heat rise method,and with secondary reheat unit,hybrid heater for regenerative system analysis model,the article develops the relationship equation between regenerative system efficiency and the bleed enthalpy,and derives the recursive relations between the adjacent bleed enthalpy for the maximal regenerative efficiency,then determines the optimal bleed enthalpy of the 700℃high parameter and large capacity second reheat unit regenerative system and lays foundation for further research of the thermal system.For the analysis of the common 1000 MW second reheat unit with the main steam parameters of 35MPa/700℃/720℃/720℃,it is determined the regenerative system is ten stage and the first reheat pressure and second reheat pressure is respectively 9.125 MPa and 3.118 MPa.The lower reheat pressure brings higher unit efficiency.With the higher inlet steam parameters of the Auxiliary Turbine,it gains higher unit efficiency and achieves the highest unit efficiency of 55.52% and the the lowest regenerative system exergy loss of 82.757 kJ.kg-1/MW when the bleed steam after first reheat is the steam resource.For the 1000 MW MC thermal cycle second reheat unit, it analyzes the bleed parameters and the bleed coefficient of the regenerative system.The unit efficiency is higher as the steam resource parameters is higher.With the determined steam resource,the unit efficiency increases firstly and then reduces an the auxiliary turbine bleeds increases, and the efficiency is the highest of 57.27% when the steam resource is the bleed before first reheat and the number of bleeds is three.The reheater whose bleed from the Auxiliary Turbine has lower exergy loss and higher exergy efficiency.Compared with the common thermal system, it has lower bleed temperature which improves the proble of the bleed steam superheating and the unit efficiency.