采用给水加热实现660MW超临界机组宽负荷脱硝的理论研究

Theoretical Study on Wide Load Denitration of a 660MW Supercritical Unit by Retrofitting the Feedwater Heating System

为了解决燃煤机组低负荷运行时脱硝效率低、热经济性差的问题,以某660MW超临界机组为例,对采用蒸汽喷射器的低负荷给水加热系统进行改进,添加了喷射器旁路和高低压蒸汽入口调节阀,以实现宽负荷脱硝.计算得到No.0高压加热器的温升范围,以及高负荷时喷射器的运行优化方法.结果表明:在满足脱硝及省煤器稳定运行的条件下,当机组负荷高于30%负荷时,No.0高压加热器可选温升范围较大,可根据脱硝要求选择合适的给水温升;当机组高负荷运行时,可降低喷射器入口高压蒸汽压力,提高机组热经济性.

To improve the denitration efficiency and thermodynamic performance of a 660 MW supercritical unit operating at low load, a bypass line and high/low-pressure steam regulating valves were added to its original low-load feedwater heating system including a steam ejector, so as to achieve wide load denitration of the unit. The temperature rise of No. 0 high pressure heater was calculated, while the operation mode of the steam ejector operating at high load was optimized. Results show that for the unit load greater than 30%, the No. 0 high pressure heater has a large range of temperature rise to satisfy the denitration require ment. When the unit operates at high load, the thermal efficiency of the unit could be improved by reduc ing the pressure of high-pressure steam at inlet of the steam ejector.