污染土壤直接热脱附二燃室低氮燃烧器优化设计

Optimization design of secondary combustion chamber low nitrogen burner for direct thermal desorption of contaminated soil

为解决直接热脱附设备二燃室燃烧器氮氧化物排放高的问题,利用热平衡方法建立其输入输出能量平衡关系式,得到二燃室温度维持1100℃时所需燃气量和助燃风量;结合空气分级技术和燃料分级技术对燃烧器进行优化设计,利用数值模拟研究燃料分级比例对其燃烧情况影响,并选取NO_(x)排放最低的燃烧器结构进行现场试验。研究结果表明,维持二燃室燃烧温度1100℃所需燃气量和助燃风量分别为702 m^(3)/h和14508 mg/m^(3);增大外层燃料比例利于燃气径向扩散,有助于避免火焰集中,有效降低NO_(x)生成量;当外层燃气与内层燃气的比例到达12:4时,NO_(x)浓度稳定在51 mg/m^(3)左右,相比于现有燃烧器减少了85%,满足设计需求。该研究结果可为直接热脱附设备二燃室燃烧器的低氮设计提供参考。

In order to solve the problem of high NO_(x) emission from the secondary combustion chamber burner of the direct thermal desorption equipment,the heat balance method wasused to establish its input and output energy balance relationship,and the gas volume and combustion air volume required to maintain the temperature of the secondary com⁃bustion chamber at 1100℃were obtained.Combining air classification technology and fuel classification technology to optimize the burner design,numerical simulation was used to study the effect of fuel classification ratio on its combus⁃tion condition,and the burner structure with the lowest NO_(x) emission was selected for field test.The results showed that the gas volume and combustion air volume required to maintain the combustion temperature of 1100℃in the second combustion chamber were 702 Nm^(3)·h-1和14508 Nm^(3)·h^(-1),respectively;increasing the ratio of outer fuel facilitated the radial diffusion of gas,which helped avoid flame concentration and effectively reduced the NO_(x) generation.When the ratio of the outer gas to the inner gas reaches 12∶4,the NO_(x) concentration is stable at about 51 mg·m^(-3),which is 85%less than the existing burner and meets the design requirements.The research results can provide a refer⁃ence for the low nitrogen design of the secondary combustion chamber burner of the direct thermal desorption equipment.