Experimental study on economic improvement of updraft boiler under low load
Taking a 660 MW secondary reheat tower boiler as the research object,the performance diagnosis test was carried out under the boiler depth peak load to 40%,264 MW load and found that there were problems of large operating oxygen amount7.1%,large dry flue gas heat loss4.68%,high NOx concentration at economizer outlet 426 mg/m3 and large ammonia injection in SCR denitration system(574 kg/h).When the boiler is running at low load,the proper opening of high and low exhaust air is conducive to improving the NOx concentration of boiler SCR denitrifica-tion inlet and the ammonia injection amount of denitrification system.The reduction of boiler operating oxygen is condu-cive to improving the boiler efficiency,reducing the NOx concentration of SCR denitration inlet,the amount of ammonia injection of SCR denitration system and the power consumption of primary fan,air supply fan and induced draft fan.The operating oxygen amount adjustment of the unit operation economy is generally greater than the adjustment of the exhaust air opening.The results show that after the optimal adjustment of exhaust air opening,operating oxygen amount and flue gas recirculation fan output,the boiler efficiency was increased from 94.21%to 94.51%,the NOx concentration at the outlet of the boiler economizer was reduced from 426 mg/m3 to 368 mg/m3,and the ammonia injection amount of SCR denitration system was reduced from 575 kg/h to 487 kg/h.The total power of primary fan,air supply fan and induced draft fan is reduced from 6 023 kW⋅h to 5 748 kW⋅h,the primary reheat steam temperature is increased from 601℃to 607℃,and the secondary reheat steam temperature is increased from 602℃to 608℃,and the operation economy of the unit is significantly improved.
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