高炉喷吹煤粉配加兰炭的回旋区燃烧数值模拟

Numerical simulation on combustion characteristics of pulverized coal and semi-coke co-injection in blast furnace raceway

为了探究喷吹煤粉配加兰炭后回旋区燃烧特性的变化,构建了同时考虑粒径分布和燃料成分差异的数值模型,对温度场、组分浓度场、颗粒轨迹及燃尽率进行分析。研究表明,配加兰炭后,由于挥发分含量降低、平均粒径增大,导致着火位置延后、燃尽率略有降低。配加不同兰炭后对比发现,燃料平均粒度较大但其粒径分散性好,50μm以下颗粒占比大时,整体燃尽率反而较高。随着燃料粒径的增大,预热阶段升温变慢,燃烧阶段比表面积变小,轨迹分散性变差,颗粒聚集处氧气相对匮乏等因素共同导致燃尽率降低,且在50~75μm处急剧下降。通过燃料优选与配加,提高整体挥发分含量,增加50μm以下小粒径颗粒占比,是未来喷吹燃料优化的一个方向。

To investigate the effect of semi-coke injected together with pulverized coal on the raceway combustion characteristics,a numerical model was developed considering the specific fuel composition and particle size distribution.Temperature field,species distribution,particle trajectories and burnout rate were analyzed.The results show that after adding semi-coke,due to a decrease in fuel volatile content and an increase in average particle size,the ignition position is delayed and the burnout rate slightly decreases.After adding different semi-coke contents,it was found that the overall burnout rate is higher even for the condition with higher average particle size,of which the better particle size dispersity,especially the larger fraction of particles smaller than 50μm plays an important role.As the fuel particle size increases,the heating rate slows down during the preheating stage,the specific surface area decreases during the combustion stage,the trajectory dispersion deteriorates,and a relative lack of oxygen at the particle aggregation site collectively lead to a decrease in the burnout rate,dramatically at diameters of 50-75μm.By optimizing and adding fuel,increasing the overall volatile content,increasing proportion of small particle sizes below 50μm is a direction for optimizing injection fuel in the future.