竖式移动床层中散料颗粒破碎的离散元分析

Analysis of particle breaking in the shaft moving beds with discrete element method

建立了竖式移动床层中颗粒破碎的炉料下降运动模型,采用离散单元法对干法熄焦炉和烧结余热回收竖罐两种竖冷装置内不同形状、尺寸及强度颗粒料的下落运动和破碎过程进行了数值计算。结果表明,颗粒在下落过程中所受压力先逐渐增大,进入出料区后又逐渐减小,颗粒破碎情况与所受压力密切相关;焦炭在干熄炉内下落到斜道区时,由于炉体直径扩张,料层所受平均压力减小,破碎速率有所减慢。由于烧结矿强度相对较小,刚进入烧结竖罐就发生破碎现象,而炉体直径扩张对破碎影响不大;受固定炉墙的影响,颗粒在靠近炉墙位置处更容易破碎。分析不同形状颗粒的破碎过程发现,正方形颗粒从某一顶点沿对角线逐渐破碎,长条形颗粒从一侧向另一侧逐渐破碎,而缺角的不规则颗粒从形状缺失一侧开始向内破碎。

The breaking behavior of the burden in the vertically arranged cooler will cause the change in the voidage of the material layer,which will seriously affect the gas permeability of the material layer,and reduce the heat recovery efficiency of vertically arranged cooler.In order to investigate the break of particles in the coke dry quenching(CDQ)chamber,and sintering waste heat recovery vertical tank,the discrete element method was used to explore the falling movement of the burden material via considering the particle breakage in the shaft moving bed.The falling movement process of the particles with different shapes,sizes and bond strength in two vertically arranged cooler was simulated.The velocity and pressure distribution of burden were analyzed.The breaking of coke and sinter particles were compared.The results indicated that the device structure,burden height and particle strength were the main factors affecting particle breakage during the falling movement of the burden.During the falling process,the pressure of particle increased first,then decreased after entering the discharge zone,and the particle breakage was closely related to the pressure.When the coke fell into the corbel zone in the CDQ chamber,the average pressure of the material layer reduced and the breaking rate was slowed down due to the expansion of the device body diameter.Because the strength of the sintered ore was relatively small,the breaking phenomenon occurred when it entered the sintering vertical tank,and the expansion of the device body had little effect on the breaking.Owing to the influence of fixed furnace wall,particles were more likely to be broken near the device wall.Additionally,the square particles were broken along a diagonal from a certain apex.The rectangular particles were broken from one side to the other,and the irregular particles were broken inward from the missing side.