Research On Temperature Regulation Strategy Of 660MW Ultra-supercritical Double Reheat Boiler

The double reheat is an effective way to improve the thermal efficiency of thermal power units,representing the world's leading power generation technology.Compared with the single reheat unit,the structure,regulation and operation of the double reheat unit are more complex,and the technical difficulty of energy distribution and thermostat is increased.The usual way to solve the above problems is to obtain relevant parameters through combustion adjustment test,and to provide the basis for engineering design and operation control.Although the test method is accurate and targeted,the test cycle is long,the uncontrollability is large,and it is restricted by many objective factors,so it is difficult to obtain systematic and comprehensive results.In this paper,the numerical simulation which was carried out by using power station engineering system simulation software EBSILON and computational fluid dynamics software FLUENT,and field test method were introduced to establish the internal relations between the working side and the flue gas side.Using this method,it was possible to avoid some unavoidable factors in the test and to provide data that can not be obtained in the test method,and then solved the double reheat unit thermostat mode and heating surface heat absorption characteristics of large coupling difficult technical problems.Based on the experimental data of 660 MW actual double reheat boiler,the rationality of the numerical simulation method was verified,and the interface parameters of FLUENT and EBSILON software were determined.The three-dimensional calculation model of furnace and boiler simulation model were established respectively,and then to simulate the heat transfer of each part of the furnace.Combined with the numerical simulation data,it was found that the flue gas recirculation can effectively control the temperature level of the furnace,restrain the furnace slagging and reduce the NOx emission;The influence of flue gas recirculation rate on the bottom flue gas temperature was the key,which determined the heat transfer of the water wall,the screen sup erheater and the platen superheater.The effect of radiant heat transfer on the heat transfer of the superheater was greater than the effect of flue gas recirculation on the heat transfer of the reheater depended on the change trend and the variation range of the bottom flue gas temperature.Based on the field test results,the optimal flue gas recirculation rate of 660 MW,550MW and 330 MW was determined as 15%?18%?30% respectively.The operation of the flue gas recirculation system increased the recirculation fan power and led to the increase of the unit heat consumption.In order to ensure the steam outlet temperature,while the pursuit of higher economy,lower environmental indicators,increased the unit wide load flexible thermostat,further optimized the furnace fan,the reduced the percentage of flue gas recirculation appropriately.In this paper,by comparing the influence of different temperature regulating measures on steam temperature,the coal mill was put into operation from the lower layer to the upper layer,and the burner was placed on the maximum and the tail baffle was in a bias state.Through numerical simulation,Three typical conditions : 660 MW,550MW,330 MW temperature regulation scheme were determined and the optimum flue gas recirculation rate was determined as: 12%,13.5%,20%,which realized the precise temperature regulation of 660 MW ultra-supercritical double reheat boiler and provided theoretical guidance for the efficient and stable operation of the double reheat unit.