层燃锅炉横向空气分级脱硝技术的试验研究

Experimental Investigation on Air-staging Process along Grate Direction to Control NO_(x) Emission in Grate-firing Boiler

与大多数燃煤层燃锅炉炉膛装有纵向空气分级脱硝工艺不同,尝试在炉排上实现横向的空气分级技术,即使用一次风不均匀配置,减少中心火焰段的供风量,减少量补充到炉床后段,在高温火焰段创造深度还原性气氛,再通过侧壁上的烟气循环射流,让热解气与燃料层有更长的接触停留时间,实现燃料型NO_(x)排放的降低。该技术在某46 MW燃煤层燃锅炉上进行尝试,试验结果展示:燃烧室中炉排上火焰被拉长,火焰峰值温度的位置由距前墙2.62 m延后至3.52 m处,火焰中出现高CO浓度的还原区。炉排上NO_(x)的峰值浓度从改造前的535 mg/m^(3)降低至322 mg/m^(3)。尾部烟气中NO_(x)浓度从350 mg/m^(3)左右降低至260~290 mg/m^(3),实现脱硝效率17.1%~25.7%。改造对大渣燃尽率、锅炉功率、炉内烟气温度等没有影响。该技术对于层燃锅炉实现炉内火焰脱硝有一定的工业指导意义。

Different from the conventional vertical air-staging technology in the coal-fired grate boiler,a horizontal air-staging technology is put forward,in which the primary-air feeding is decreased under the flame zone and the recirculating flue gas is fed from the side wall to create a strong reducing atmosphere near the grate in order to reduce fuel NO_(x) emission.The technology was implemented on a 46 MW coal-fired grate boiler.The experimental results showed that the flame was postponed along the grate in the combustion chamber.The position of the peak temperature was extended from 2.62 m to 3.52 m distanced from the inlet,and a reduction zone with high CO concentration appeared.The peak concentration of NO_(x) on the grate decreased from 535 mg/m^(3)to 322 mg/m^(3).And the NO_(x) concentration in flue gas is reduced from 350 mg/m^(3)to about 260~290 mg/m^(3),achieving de-NO_(x) efficiency of 17.1%~25.7%.Furthermore,the burn-out level of final dis-charged slag is not impacted.The new technology is significant to achieve the realization of deeply NO_(x) emission control in grate-firing furnace.