污染土壤直接热脱附燃烧器低氮优化设计及数值模拟

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，利用热平衡计算方法建立其输入和输出能量平衡关系式，得到二燃室温度维持1 100 ℃时所需燃气量和助燃风量；同时，结合空气分级技术、燃料分级技术和部分预混燃烧技术对燃烧器进行优化设计，并对其燃烧情况进行了数值模拟计算。热平衡计算结果表明，维持二燃室燃烧温度1 100 ℃所需的燃气量和助燃风量分别为1 003和22 066 m³·h⁻¹。数值模拟结果表明，增加燃气预混喷口可显著强化燃气/空气混合，使燃烧更为迅速，可防止滞后的火焰冲刷壁面，也有助于分散火焰，避免局部高温。增加二级空气通道可降低空气的出口流速，防止出现脱火现象，且利于燃气径向扩散，避免火焰集中。以上2种方法均能有效降低氮氧化物排放量，且采用燃气部分预混后二燃室出口处一氧化碳浓度大幅降低。在同时采用燃气预混喷口和二级空气通道后，NO_x浓度稳定在45 mg·m⁻³左右，相比于现有燃烧器减少了85%。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。

Low nitrogen optimization design and numerical simulation of burner for direct thermal desorption of contaminated soil

In order to solve the problem of high NOx emission from the burner of the second combustion chamber of the direct thermal desorption equipment. The input and output energy balance equations were established by using the heat balance calculation method, and the required fuel and combustion supporting air volume when the temperature of the secondary combustion chamber was maintained at 1 100 ℃ were obtained. Combined with air classification technology, fuel classification technology and partial premixed combustion technology, the burner was optimized, and its combustion was numerically simulated. The heat balance calculation results showed that the fuel gas and combustion supporting air volume required to maintain the combustion temperature of the second combustion chamber at 1 100 ℃ were 1 003 and 22 066 m3·h−1, respectively. The results showed that increasing the gas premixing nozzle can significantly strengthen the gas/air mixing, make the combustion more rapid, prevented the lagging flame from scouring the wall, dispersed the flame and avoided local high temperature. The addition of secondary air channel can reduce the outlet flow rate of air, prevent misfire, facilitate the radial diffusion of gas and avoid flame concentration. The above two methods can effectively reduce NOx emissions, and partial premixing of gas can also effectively reduce the concentration of carbon monoxide at the outlet. After the gas premixing nozzle and secondary air channel were adopted at the same time, the NOx concentration was stable at about 45 mg·m−3, and the NOx emission was reduced by 85% compared with the existing burner. The research results can provide a reference for the low nitrogen design of the secondary combustion chamber burner of the direct thermal desorption equipment.