Optimization Research On Thermodynamic System Of Power Generation Unit With 700? Steam Conditions

700? ultra supercritical thermal power generating units is the world's highest and most advanced parameters of high efficiency and low emission power generation technology at present.Study 700? ultra supercritical power generation technology has very important significance to our country electric power industry,environmental protection.The main purpose of this article is about 700? grade single reheat,double reheat and no-reheat units thermal system analysis.Based on the thermodynamics of the equivalent carnot cycle thinking,the establishment of a thermodynamic cycle thermal efficiency calculation method,avoid the effect of the thermal efficiency of the regenerative system of circulation.Thermodynamic conditions of 700? ultra supercritical once and two two units were analyzed by newly proposed thermodynamic method.The cycle thermal efficiency of the two reheating unit is increased by 0.25%,and the heat loss rate of steam turbine is reduced by 31kJ/(kW·h).Although the two reheat unit heat economy improved,but the improvement is not obvious,however,the pressure drop loss of the pipeline pressure drop of the two reheating unit is increased,difficult temperature regulation,start stop operation complex,increase the investment cost of a unit construction,and increase the investment cost.This paper presents a 700? subcritical no-reheat generator unit,verify the feasibility of on-reheat unit.The thermodynamic calculation method is used to calculate the thermodynamic performance of the18MPa/720? natural circulation subcritical no-reheat unit,the average heat transfer temperature is 422?,the cycle thermal efficiency is about 49.79%.Although the steam ability were decreased,but the main steam temperature is high enough,the unit is still high thermal efficiency.The main steam pressure is reduced and the reheat cycle is eliminated,no-reheat unit has obvious advantages.In depth analysis of the technical and economic characteristics of the 18MPa/720? subcritical no reheating unit with 35MPa/700?/720?1000MW ultra supercritical once reheating unit.The calculation results show that the heat loss rate of steam turbine is increased by 466kJ/(kW·h),unit net efficiency decreased 2.17 percentage points,coal consumption increased by 12.61g/(kW·h),the power supply coal consumption increased by 13.15g/(kW·h).Total consideration of 700? nickel base high temperature steel prices,standard coal price,loan interest rates and the number of units operating hours and other economic factors.Comprehensive technical and economic analysis results show that,In the previous forecast of 700? nickel base high temperature steel prices,the economy of the whole life cycle of the sub critical unit is significantly better than that of the super critical one.And taking into account the impact of 700? nickel base high temperature steel prices on the two unit.Calculated only when the nickel base high temperature steel prices reduced to 240 thousand yuan/t,or the price of coal as high as 800 yuan/t,nickel base steel prices dropped to 380 thousand yuan/t,the economy of the two units is the same.