转炉内废钢预热可行性的数值模拟分析

Numerical simulation analysis of the feasibility of preheating scrap in the converter

废钢预热技术作为高炉-转炉长流程提高废钢使用量的重要手段,已成为当前钢铁企业关注的热点。相比于炉外预热,在转炉内部加热废钢可避免热废钢输运过程的热量散失。针对转炉内燃气加热废钢工艺,建立了转炉内天然气燃烧预热废钢的瞬态非热平衡流固耦合模型。模拟结果表明:转炉内天然气纯氧助燃产生的高温气流可快速预热废钢;可在20 min内将废钢平均温度预热到800℃以上,其燃气利用率在40%左右。随着燃气流量增加,加热废钢速度更快、温度更高,但煤气利用率降低。采用高枪位预热时,预热范围大,利于上层废钢的预热;低枪位时,气流的冲击能力增强,利于下层废钢的预热。枪位为1 m时,废钢温度、均匀性综合效果最佳。废钢空隙度为0.8左右时,炉内气流分布均匀,预热效果较优。

As a significant method to improve scrap ratio in the converter process,scrap preheating technology has been paid great attention from iron and steel enterprises.Compared with preheating process outside the converter,heating scrap inside the converter can avoid heat loss of hot scrap transportation.In this paper,a transient non-thermal equilibrium fluid-solid coupling model for scrap preheating with natural gas combustion inside the converter was developed.The results showed that the high-temperature gas stream generated by the pure oxygen-natural gas combustion in the converter could preheat the scrap rapidly so that the average temperature of the scrap could reach above 800℃within 20 min with a gas utilization efficiency of around 40%.With the increase of gas flow rate,the heating rate and temperature of the scrap became higher,while the gas utilization efficiency was decreased markedly.Under a condition of high lance position,the range of preheated scrap zone became larger,as a result,which facilitated the heating process of upper zone of the scrap.When a low lance position was considered,however,the great enhancement of gas stream penetration could be observed,leading to an improvement of heating effects in the lower zone of the scrap.The comprehensive preheating effect can be achieved when the lance tip is 1 meter above the stack surface.When the porosity of scrap is roughly 0.8,the gas flow in the converter is evenly distributed and a high and uniform temperature of the scrap can be obtained.