A cascade-arch-firing low-NO_x and high-burnout configuration (CLHC) is developed to strengthen low-NO_x combustion and maintain high burnout in down-fired furnaces. Numerical simulations of the in-furnace flow field, coal combustion, and NO_x formation are performed in a 600 MW_e down-fired furnace to evaluate the staged-air location's effect on the low-NO_x and high-burnout performance. The furnace, which is in service with a deep-air-staging multi-injection and multi-stage combustion technology (MIMSCT), was modified with the CLHC combustion system for the present simulations. Various staged-air location coefficients of C_H = 0.65, 0.70, 0.75 and 0.80 were analysed. Moving downward staged-air to enlarge C_H initially improves but then deteriorates the in-furnace flow-field symmetry. Similar changes in the gas temperature and species distribution patterns in the furnace are evident. As C_H increases from 0.65 to 0.75, levels of the residual O₂ concentration, carbon content in fly ash, and NO_x emissions at the furnace outlet decline continuously. The highest setting C_H = 0.80 generates severely asymmetric combustion accompanied by poor performance indexes, raising the unburnt rate and NO_x emissions by 20–30%. The staged-air location of C_H = 0.75 achieves a symmetric flow-field pattern, satisfactory low NO_x emissions of ~670 mg/m³ at 6% O₂ and high-burnout performance with carbon in fly ash of 5%. NO_x emissions are reduced by 26% without affecting burnout in comparison to the currently advanced deep-air-staging MIMSCT.

开发了级联拱形燃烧低 NO _x和高燃尽配置 (CLHC)，以加强低 NO _x燃烧并在下燃炉中保持高燃尽。在 600 MW _e下燃炉中对炉内流场、煤燃烧和 NO _x形成进行了数值模拟，以评估分级空气位置对低 NO _x和高燃尽性能的影响。使用深空分级多喷射和多级燃烧技术 (MIMSCT) 的熔炉使用 CLHC 燃烧系统进行了修改，以用于当前的模拟。C _{H 的}各种分级空气位置系数 = 0.65、0.70、0.75 和 0.80 进行了分析。向下移动分级空气以扩大C _H最初会改善但随后会恶化炉内流场的对称性。炉内气体温度和物种分布模式的类似变化是明显的。随着C _H从0.65 增加到0.75，残余O ₂浓度、飞灰中碳含量和炉出口NO _x排放水平不断下降。最高设置C _H  = 0.80 会产生严重的不对称燃烧，伴随着较差的性能指标，将未燃率和 NO _x排放量提高 20-30%。C _H的舞台空气位置 = 0.75 实现了对称流场模式，在 6% O _{2 下}达到约 670 mg/m ^{3 的}令人满意的低 NO _x排放，以及在飞灰中的碳为 5% 时的高燃尽性能。与目前先进的深空分级 MIMSCT 相比，NO _x排放量减少了 26%，而不会影响燃尽。