Study Of Steam Temperature Characteristic Of An Efficient Flexible Ultra-Supercritical Boiler With Double-Reheat Cycle

With the rapid development of China’s national economy,the pressure of energy conservation and environment protection has been increasingly prominent.In the current technological background,developing ultra-supercritical double-reheat technique has become an essential way to develop efficient and clean coal-fired power generation technology.And the new energy resources have increased their power generation capacity,which has a negative impact on the stability of the grid,demanding higher flexibility of coal-fired units.In this study,taking an efficient flexible tower-type double-reheat boiler as research object,the steam temperature regulation characteristics were studied.Results are as follows:The traditional thermodynamic calculation method was modified to be applicable to the tower-type boiler.According to the arrangement characteristic of this boiler,a cell model for calculation was proposed to simplify the calculation of the combined heating surface in this boiler and finally applied to the thermodynamic calculation of this boiler.The results showed that the maximum deviation of gas and steam temperature were only-59.5℃ and-5.4℃,respectively.Steam temperature characteristics and influence of gas dampers,flue gas recirculation and swinging burners were studied by the cell model: under the load of BMCR,based on the horizontal position,the main steam temperature decreased by1.9℃ for every 10℃ increase in burner angle,and the temperature of primary and secondary reheat steam both increased by 2.0℃;the main steam temperature rose by2.0℃ for every 10℃ decrease in burner angle,and the temperature of primary and secondary reheat steam decreased by 2.0℃ and 1.6℃,respectively.For every 1%increase in the opening of dampers in front pass,the temperature of the primary reheat steam increased by about 1.1℃,and the temperature of the secondary reheat steam decreased by about 1.8℃.For every 5% increase in flue gas recirculation rate,the main steam temperature decreased by 3.6℃,and the primary and secondary reheat steam temperature increased by 3.6℃ and 3.4℃ respectively.The response surface analysis method was adopted and reasonable experimental design was carried to fit the relationship between the temperatures of reheat steam and steam temperature regulations under different loads.Based on the ANOVA and related parameters of the regression models,significance order of influence factors for reheat steam temperatures were also obtained.Under the load of BMCR,the significance order of influence factors for reheat steam temperatures were as follows: gas dampers>flue gas recirculation>swinging burners> interaction of gas dampers and flue gas recirculation > interaction of gas dampers and swinging burners > interaction of flue gas recirculation and swinging burners.