KR法脱硫搅拌桨叶几何结构优化

Geometric structure optimization of impeller for KR desulfurization

KR(kanbara reactor)法是铁水预处理阶段稳定深度脱硫的首选工艺,广泛应用于现代炼钢工业,其通过浸入铁水中的桨叶搅拌带动铁水与脱硫剂混合,因而具有良好的动力学特性。然而,搅拌过程中桨叶附近存在强制涡流区,脱硫剂在参与反应前大量凝并导致利用率较低。因此,设计了2种简便易行的新型搅拌桨(错位式搅拌桨、高低式搅拌桨),旨在通过相邻桨叶的高度差强化桨叶附近的轴向流动,破坏强制涡流区流动特征,增强铁水微元间的相对流动,进而减少强制涡流区对KR法脱硫混匀效果的不利影响,提高铁水与脱硫剂的混合效果。采用VOF(volume of fluid)和DPM(discrete phase model)建立了KR法搅拌过程的三维瞬态数学模型,对比分析了传统四叶桨及2种新型结构搅拌桨的铁水流动、颗粒分散程度、死区范围及液面以下颗粒比例等的影响。数值模拟结果表明,新型桨叶相比传统桨叶供给铁水更多的轴向速度。错位式桨叶和高低式桨叶强化了脱硫剂分散程度,其量化颗粒分散程度Sigma值分别低于传统四叶桨约9.49%、14.18%,脱硫后脱硫剂平均粒径相比传统桨叶工况分别降低约14.91%、13.38%。使用高低式搅拌桨在300 t铁水包进行工业试验,结果表明,高低式桨叶相比同期传统四叶桨平均单硫单耗降低0.27 kg。

The KR(kanbara reactor)method is the preferred process for stable and deep desulfurization in the pre-treatment stage of molten iron and is widely used in the modern steelmaking industry.The mixing of the molten iron and the desulfurizer is driven by stirring the blades immersed in the molten iron,which will benefit good dynamic conditions.However,the desulfurizer will coagulate in large quantities before participating in the reaction by the forced vortex zone at the stirring stage,making its utilization rate low.Two easy-to-use impellers(staggered impel-ler and high-low impeller)were designed,of which purpose is to strengthen the axial flow near the blade by the height difference of adjacent blades,which destroy the flow characteristics in the forced vortex zone and enhance the relative motion between molten iron elements.Thereby,the adverse impact of the forced vortex zone on the KR des-ulfurization mixing effect was reduced,and the mixing effect of molten iron and desulfurizer was increased.In the meantime,the VOF(volume of fluid)and DPM(discrete phase model)models are used to establish the three-dimen-sional transient mathematical model of the KR mixing process.The numerical results depict that the influences of the traditional four-blade impeller and two new types of impellers on the hot metal flow,particle dispersion,dead zone range,and the proportion of particles below the hot metal surface were analyzed and compared.The numerical simulation results show that the new impeller can provide more axial speed than the traditional impeller.The stag-gered impeller and the high-low impeller enhance the dispersion degree of the desulfurizer,and their Sigma values wereproposed to quantify the particle dispersion are lower than those of the conventional impeller by about 9.49%and 14.18%,respectively.The average particle size of the desulfurizer after desulfurization is reduced by approxi-mately 14.91%and 13.38%,respectively,compared with the traditional impeller conditions.A 300tindustrial ex-periment was carried out on the high-low impeller in the Baoshan base steelmaking plant of Baosteel Co.,Ltd.Fur-thermore,the average unit sulfur consumption of the high-low type impeller was reduced by 0.27kg compared with the traditional impeller in the same period.