关键词: W火焰锅炉, SCR, 分区混合, 动态调平, 超低排放, 氨逃逸

Abstract: Burning anthracite in W-flame boiler inevitably results in the emission of high concentrations of NO_x as much as 700~1 200 mg/m³ even with the low nitrogen combustion technology implemented. Therefore, the combination of “SNCR+SCR” is often adopted as the traditional route of ultra-low emission control. However, in addition to the high investment and operating costs, this technical route is extremely likely to cause excessive ammonia slip, which eventually leads to air preheater blockage. In this paper, the SCR transformation project of two 330 MW W-flame boilers are conducted by adopting the “SCR zone-based hybrid dynamic leveling technology”. The test results show that after the completion of the project, the SCR removal efficiencies of both boilers have been raised to more than the super high value of 94% while the ammonia escape rate is controlled under 2 μL/L. In this way, not only the goal of ultra-low emission can be achieved but also 14 million RMB of the SNCR investment and 7.6 million RMB of annual operation costs is saved respectively. Besides, to remove the same amount of NO_x, 19% less ammonia is consumed after the transformation while the differential pressure of air preheater is still maintained stably in the long term.

Key words: W-flame boiler, SCR, partition mixing, dynamic leveling, ultra-low emission, ammonia escape