立式退火炉低氮控制技术研究与应用

Research and application of low NOx control technology for vertical annealing furnace

利用数据分析法,分析了某连退机组立式退火炉NO_(x)排放浓度与带钢规格和加热段热负荷输出之间的相关性。结果表明:在加热段热负荷输出低于41%时,折算后的NO_(x)排放浓度不大于150 mg/m^(3);随着热负荷输出的进一步增加,NO_(x)排放浓度呈现线性增加。为了降低高热负荷下NO_(x)排放浓度,基于NO_(x)的生成机理开展了低氮控制技术研究。首先,通过试验确定了不同额定功率的烧嘴烟气中的残氧量与NO_(x)生成量的关系,得到烧嘴烟气中的残氧量控制范围为2.5%~4.4%。通过进一步定量分析残氧量对烧嘴功率的影响,发现随着残氧量的降低,一方面可以降低NO_(x)生成量,另一方面又可以提高退火炉加热能力。当残氧量由6.0%降低至3.5%时,额定功率为80.0、120.0、160.0 kW的烧嘴NO_(x)生成量分别降低了41.53、28.51、26.96 mg/m^(3),而烧嘴功率分别增加了14.7、22.0、29.3 kW。其次,研究了残氧量与助燃空气压差以及烟气温度之间的关系,制定了烧嘴烟气中残氧量调整的Z字法,有效解决了烧嘴烟气中残氧量超出控制上限的问题。最后,研究了烧嘴换热器不同喇叭口直径对NO_(x)生成量和退火炉加热能力的影响,结果表明:将喇叭口直径由?29.5 mm缩小至?27.5 mm,可在不影响加热能力的前提下,使NO_(x)的生成量降低44.78%。应用低氮控制技术后,NO_(x)排放浓度的平均值由149.22 mg/m^(3)降至111.57 mg/m^(3)。

The correlation between the NO_(x) emission concentration and the strip gauge and the heat load in the heating section was analyzed by data analysis method.The results show that when the heat load is less than 41%,the NO_(x) emission is less than 150 mg/m^(3).With the further increase of heat load output,the NO_(x) emission showed a linear increase.In order to reduce the NO_(x) emission concentration under high heat load,low NO_(x) control research based on the formation mechanisms of NO_(x) was carried out.First of all,the relationship between the residual oxygen in the flue gas of the burner with different rated power and the amount of NO_(x) production was determined through the test,and the control range of residual oxygen in the flue gas of the burner was determined to be 2.5%—4.4%.Through further quantitative analysis of the impact of residual oxygen on burner power,it was found that not only NO_(x) generation decreased with the residual oxygen,but also the heating capacity of the annealing furnace was improved.When the residual oxygen content decreased from 6.0%to 3.5%,the NO_(x) generation of 80.0,120.0 and 160.0 kW burners decreased by 41.53,28.51 and 26.96 mg/m^(3),respectively,while the burner power increased by 14.7,22.3 and 29.3 kW,respectively.Secondly,the relationship between residual oxygen,combustion air pressure difference,and flue gas temperature was studied,and the“Z”method of adjusting the residual oxygen in the flue gas of the burner was formulated,which effectively solved the problem of the residual oxygen in the flue gas of the burner exceeded the control upper limit.Finally,the influence of different diameter of bell mouth from heat exchanger on NO_(x) generation and annealing furnace heating capacity was studied.The results show thatreducing the diameter of bell mouth fromϕ29.5 mm toϕ27.5 mm can reduce the NO_(x) generation by 44.78%without affecting the heating capacity of annealing furnace.With the application of low nitrogen control technology,the average NO_(x) emission concentration decreased from 149.22 mg/m^(3) to 111.57 mg/m^(3).