基于调峰的汽轮机回热系统优化研究

Optimization study of steam turbine heat regenerative system on peak loading

随着发电设备年平均利用小时逐年下降,1000 MW等级超超临界机组也参与低负荷调峰运行。参与调峰造成机组热经济性下降,50%THA负荷以下工况脱硝装置退出,锅炉NOx排放超标。研究发现,增加汽轮机回热系统级数,提高锅炉给水温度,可以降低锅炉温差传热产生的不可逆传热损失,提高机组的热经济性;提高锅炉给水温度可有效抬升脱硝装置入口烟气温度,扩展脱硝装置运行负荷区间。采用0号高压加热器的汽轮机回热系统优化方案,汽轮机热耗最大下降值达11. 6 k J/k Wh,锅炉脱硝装置入口烟气温度可抬升至310℃以上。采用汽轮机高压缸补汽阀倒抽蒸汽作为0号高压加热器的加热汽源,不影响汽轮机本体结构,优化方案技术风险低。回热系统优化方案投资费用1075万元/台,机组实际运行综合收益200万元/a,优化方案静态投资回收期为5. 3 a,具有较高的经济性。经工程实践验证,汽轮机回热系统优化方案能够满足机组调峰要求。

The 1000MW grade ultra supercritical units were operating in peak loading with the average annual utilization hours of power generation equipment decreasing year by year in China.The unit thermal economy would be decrease in operating of peak loading,while the denitration device would be removal under the50%THA load condition and the NO x excessive discharge of boiler would be happened.The study found that the boiler heat transfer irreversible heat loss would be reduced and the unit thermal economy would be improved through increasing the number of steam turbine regenerative system and the boiler feed-water temperature.The flue gas temperature before the boiler denitration device could be improved with rising the temperature of boiler feed-water,and the operating load range of denitration device would be expanded.The heat rate of steam turbine could be reduced to11.6kJ/kWh and the flue gas temperature before the boiler denitration device could be raised to more than310℃by using the optimization scheme of steam turbine heat regenerative system with No.0high-pressure heater.The technical risk of optimization scheme was low because the steam turbine proper structure was not changed with using the steam between steam turbine high pressure cylinder and overload valve to heating the No.0high-pressure heater.The cost of optimization scheme of steam turbine heat regenerative system was10.75million RMB per unit and the operation income was2million RMB/a per unit.The static investment recovery period of optimization scheme was5.3years,and the economic was high.It has been verified that the optimization scheme of steam turbine heat regenerative system could satisfy the technical requirement of peak loading.