高炉出铁场高温烟尘扩散与捕集特性模拟

高炉出铁场在出铁过程中产生的高温烟尘污染范围广、时间长、阵发性强。高温铁水上方的气流运动为热羽流,受通风气流影响极大,现有除尘罩设计方法无法有效解决高温烟尘的污染问题。针对我国中小型高炉出铁场厂房形式及出铁特点,建立了出铁场厂房内的两相流动模型及高温烟尘扩散与捕集过程的数值模拟方法。模拟发现,高炉前方的气流上升速度先增加后减小,形成了典型的受限空间热羽流。由于出铁口除尘罩与高炉间存在间隙,在抽吸作用下,底部气流在高炉壁面产生向上的高速气流,使除尘罩对高炉间的气流不具有捕集作用。因屋顶通风量较自然通风少2/3,在仅设屋顶通风除尘时,带走的热量减少,使厂房内温度整体偏高。加设出铁口除尘罩后,厂房整体温度明显降低。出铁口除尘罩对颗粒物的整体捕集率可以达到89.66%,但主沟前方颗粒物大量逃逸,捕集率仅为47.71%,铁水沟后方释放的颗粒物距除尘罩较远,捕集率为86.34%,造成的污染范围较大,是目前出铁场作业环境质量不达标的主要原因。

SIMULATION STUDY ON DIFFUSION AND COLLECTION CHARACTERISTICS OF HIGH TEMPERATURE SMOKE AND DUST IN BLAST FURNACE CAST HOUSE

The particulate matters in the unorganized emission of flue gas from the blast furnace cast house has the characteristics of scattered pollution sources, wide pollution range, long time and strong paroxysmal occurrence. Because the hot plume that the airflow above the high-temperature molten iron was greatly affected by the ventilation airflow, the existing dust cover design method couldn’t effectively solve the pollution of high temperature smoke and dust. In this study, a two-phase flow model and a numerical simulation method for the diffusion and trapping process of high temperature smoke and dust, in China’s small and medium-sized blast furnace cast house were established. The simulation results showed that the rising velocity of air flow in front of blast furnace increased first and then decreased, forming a typical confined space thermal plume. Because of the gap between the blast furnace and the dust cover of the tapping hole, the bottom airflow produced upward high-speed airflow on the blast furnace wall under the suction action, which made the dust cover had no trapping effect on the airflow between the dust collector and the blast furnace. When only the roof ventilation was used, the heat that could be carried away by ventilation was reduced, because the roof ventilation volume was two-thirds less than that of natural ventilation, which led to the overall temperature in the cast house on the high side. The temperature of the cast house decreased obviously after adding the dust cover. The overall capture rate of particulate matter by the dust cover could reach 89.66%. However, a large number of particles in front of the main ditch escaped, and the capture rate was only 47.71%. The capture rate of particulate matter released from the rear of the hot metal was 86.34%, because it was far from the dust cover. It caused a wide range of pollution, resulting in the working environment of the cast house was not up to the standard at present.