基于离散单元法,建立引入Areal Gas Distribution(AGD)技术COREX竖炉物料运动行为的DEM模型.模型计算结果与文献物理实验结果一致,证明模型的合理性.模拟结果显示,AGD竖炉内存在三种类型的流动区域:活塞流区、准停滞区及沟流区.物料运动流型呈现Flat→波浪→W的演变过程.AGD梁下方形成的三角形空隙是还原煤气导入竖炉中心的主要煤气通道.竖炉围管区域AGD梁的安装会影响该区域物料的均匀下降,局部区域的较大法向力可能导致物料的挤压黏结,诱发围管slot堵塞.
COREX shaft furnace(SF)is a typical screw feeder with a storage container coupled with eight screw casings and screws.The structure of screw casing plays an important role in the moving behavior of burdens,stress distribution,abrasive wear of screws,and energy consumption during the operation of SF.Therefore,a three-dimensional semi-cylindrical model of actual size of COREX-3000 SF was established based on discrete element method to investigate the influences of screw casing structure.The results show that the increase in the gap between the outside of screw flight and screw casing is beneficial for the smooth operation of SF,resulting in uniform descending velocity along the radius of SF in the lower part,decreasing the size of recirculation region,and alleviating stress concentration in the screw casing.Moreover,raising the gap appropriately is also beneficial to weaken screw abrasive wear,decrease energy consumption,and then prolong the service life of the screws.However,enlarging the gap also leads to more undesired high temperature reduction gas into the SF from melter gasifier,thereby deteriorating the operation of SF.Thus,an ideal distance exists between the outside of the screw flight and the screw casing,which is suggested to be equal to the average of particle diameter.
Zi-long QiuZhi-guo LuoHeng ZhouRen ChenFeng WangZong-shu Zou
COREX熔化气化炉风口回旋区是炉况顺行的基础,在冶炼过程中起着十分重要的作用,为了描述其形状和大小,建立了CFD+DEM(Computational Fluid Dynamics and Discrete Element Method)耦合模型,对回旋区形成过程及大小进行了颗粒尺度的分析.得到床层高度为0.4m,气体速度11.74m/s的条件下回旋区颗粒空隙度分布,当吹气时间为0.13s时,气体入口附近有颗粒被吹开,随着时间的推进,气体动能吹开的颗粒增多,0.19～0.21s时,形成的回旋区开始稳定.对入口处不同气体速度条件下回旋区及其附近颗粒速度进行了计算模拟.模拟结果显示,风口附近颗粒在做回旋运动,并且随着入口气体速度的增大,吹开的颗粒增多,回旋区空腔增大,当入口气体速度为11.74m/s和16.83m/s时形成的回旋区较稳定,当入口气体速度大于21.90m/s时形成的回旋区不太稳定.
为研究COREX预还原竖炉内煤气流动特性,利用数值模拟方法研究了炉内煤气停留时间分布(RTD),考察了AGD(Areal Gas Distribution)梁对COREX预还原竖炉炉内RTD的影响以及不同熔炼率下COREX预还原竖炉的RTD变化规律.模拟结果表明,随着2#COREX预还原竖炉AGD梁的安装,其整体时间密度分布函数变宽,平均停留时间变短,无量纲方差变大.AGD梁的安装增大了炉内的死区体积分数,2#COREX预还原竖炉炉内死区体积分数达到了26.81%.随着竖炉熔炼率的增加,炉内平均停留时间逐渐减小,无量纲方差逐渐增大.当熔炼率从150 t/h增长到180 t/h时,1#COREX竖炉死区体积分数降幅为68.1%,2#COREX竖炉降幅仅为15.52%.
Based on the principles of the discrete element method(DEM),a scaled-down model was established to analyze burden descending behavior,including asymmetric phenomena,throughout an entire COREX shaft furnace(SF).The applicability of the DEM model was validated by determining its accordance with a previous experiment.The effects of discharge rate and abnormal conditions on solid flow were described in terms of solid flow pattern and microscopic analysis.Results confirmed that the solid flow of the COREX SF can be divided into four different flow regions;the largest normal force exists at the top of the man-made dead zone,and the weak force network exists in the funnel flow region.The basic solid flow profile was identified as a clear Flat→U→W type.Increasing the discharge rate decreased the quasi-stagnant zone size,but did not affect the macroscopic motion of particles or the shape of patterns above the bustle.For asymmetric conditions,in which particles were discharged at different rates,the solid flow patterns were asymmetric.Under an abnormal condition where no particles were discharged from the left outlet,a sizeable stagnant zone was formed opposite to the working outlet,and"motionless"particles located in the left stagnant zone showed potential to increase the period of static contacts and sticking effect.
Zhi-guo LUOHeng ZHOUTao ZHANGYang YOUHai-feng LIZong-shu ZOU
