Abstract:

The combustion process within the vertical fire passage of a coke oven encompasses flow, heat and mass transfer, as well as chemical reactions. However, existing research predominantly emphasizes combustion characteristics while neglecting the influence of flow and transfer on reaction dynamics. This study employs computational fluid dynamics (CFD) to investigate the effects of blast furnace gas and second-stage air inlet velocity on the flow, transfer, and combustion processes in a large coke oven’s vertical fire passage. The findings indicate that increasing gas inlet velocity enhances mass transfer, facilitates better mixing of air and gas, lowers local maximum temperatures, reduces NO _x emissions, and improves temperature uniformity across high-temperature regions. The optimal gas inlet speed is approximately 4.22m/s; under these conditions, the average temperature at each section in the upward direction peaks when the second-stage air inlet speed is around 1.25m/s. Furthermore, a judicious increase in second-stage air inlet speed can diminish NO _x emissions without significantly deteriorating combustion performance or adversely affecting temperature distribution uniformity. The primary mechanism for optimizing combustion through adjustments in inlet speed lies in its ability to alter turbulent states, effectively controll velocities and refine turbulent structures, which ultimately enhances mixing between gas and air thereby improving overall combustion efficiency.

Key words: coking, nitrogen oxides, gas velocity, transport processes, computational fluid dynamics, combustion simulation

摘要：

焦炉立火道内的燃烧过程包含流动、热质传递及反应，但现有研究多关注燃烧特性，较少涉及流动及传递对反应特性的调控。本文采用计算流体力学（CFD）方法研究高炉煤气和二段空气入口速度对某大型焦炉立火道内流动、传递和燃烧过程的影响。结果表明，适当提高煤气入口速度可以强化传质，促进空气与煤气的混合，降低局部最高温度，减少NO _x 产出的同时增强高向温度分布的均匀性。最佳的煤气入口速度约4.22m/s。在此条件下，二段空气入口速度约1.25m/s时高向各截面的平均温度最高。在此基础上适当提高二段空气入口速度能够降低NO _x 产出，且不会显著恶化燃烧情况，对高向温度分布均匀性影响较小。调节入口速度优化燃烧的主要机制在于：调节入口速度可以改变湍流状态，合理控制速度优化湍流结构，从而增强改善煤气和空气混合，最终优化燃烧效果。

关键词: 焦化, 氮氧化物, 气速, 传递过程, 计算流体力学, 燃烧模拟