Study On Optimization Of Thermodynamic System For 1000MW Double Reheat Unit

The double reheat unit have unique advantages such as high efficiency and low emission.Double reheat unit have become the main trend of power plant development,but the superheat problem prevent it from further increase of its efficiency.Study on the method of reducing the extraction steam superheat,optimize the thermal system of double reheat unit,make a great significance to the improvement of double reheat technology.Based on fuel specific consumption analysis,the thermal economy of installing different thermal system in a 1000 MW double reheat ultra-supercritical unit was analyzed.Firstly,three arrangement modes including single series connection,double series connection,and double parallel connection were compared and the reasons for the change of system energy consumption were revealed.The results show the feedwater temperature can be increased after adopting the outer steam coolers,and that the major cause of reducing energy consumption for the plant is the decrease of irreversible loss in boiler.The fuel specific consumption reduces by 1.122g/(kW·h)when installing double parallel stages at NO.2 and NO.4 high-pressure heaters.Secondly,the Master Cycle was introduced into the double reheat unit,the optimal allocation scheme of system is calculated.And the difference between it and the former system was compared.The result show that Master Cycle system can reduce the fuel specific consumption reduces by 1.651g/(kW·h).It can reduce the boiler specific consumption and the value in reheaters.Finally,the characteristics of two kinds of schemes under different load conditions were analyzed,and the technical economic of both schemes were compared.The result show that Master Cycle only have better thermal economy in 100% load.Using outer steam coolers not only have better thermal economy in variable condition,but also show better technical economic.