不同粒级煤泥在TBS分选过程中运动特性分析

Dynamics characteristics analysis of coarse coal slime separation with different particle sizes in TBS

煤泥因粒度组成较宽常常造成干扰床分选机(Teetered Bed Separator,TBS)的分选过程出现底流中夹杂细粒煤的现象,造成部分精煤损失于尾矿中,同时细颗粒又使得煤泥压滤效率降低,所以解析不同粒度颗粒的运动特性情况对于优化TBS的机体结构、提高TBS分选效率具有积极的意义;数值模拟作为一种高效率、低成本的研究方法,基于计算流体力学数值模拟软件Fluent对均一密度、不同粒级煤泥在TBS分选过程中运动特性分析,分别得出了粗粒级(1.60~1.25 mm)、中等粒级(1.0~0.6 mm)以及细粒级(0.45~0.25 mm)颗粒群在TBS分选过程中的速度场、湍动能情况以及颗粒群运动的迹线,计算不同粒级颗粒群的溢流理论产率,并且开展了与模拟仿真实验相同参数的TBS分选论证实验。结果表明:随着颗粒粒度的减小,颗粒群运动轨迹受TBS内部流场影响逐渐增大、运动轨迹越来越紊乱;粗粒级颗粒群在TBS机体上部至底部引起的速度场、湍动能的规律变化使该颗粒群有序全部进入底流;中等粒级颗粒群在TBS机体中下部开始出现紊乱运动趋势,该颗粒群经反复运动后,大部分颗粒仍进入底流,仅有少量颗粒进入溢流;细粒级颗粒群同样出现紊乱运动趋势,且紊乱区域增加至机体上部,大部分颗粒进入溢流,有部分出现至机体上部的颗粒出现回流,回流的煤粒进入底流,细粒煤被底流夹带而损失的现象出现;TBS分选实验得出的不同粒级颗粒溢流产率与对应的理论溢流产率误差较小,证实模拟选取的颗粒曳力模型的合理性,即:较粗颗粒选取non-spherical模型,较细颗粒选取spherical模型。研究结果侧面反映出选前对煤泥进行粒度的精确分级以减少细粒物的影响,可提高TBS分选效率。

Due to the wide size fraction of coarse slime particles,the phenomenon of entrainment of fine coal in the underflow occurs in the separation process when the Teetered Bed Separator(TBS)is involved.The phenomenon will result in that the clean coal products will be contaminated in the tailings and the lower efficiency of treatment of fine coal particles with chamber press.It is of significance to analyze the motion characteristics of particles with different particle sizes for optimizing the structure of TBS and improving the efficiency of separation.The kinematic characteristics of coarse coal particles with identical density but different sizes during the TBS separation process was analyzed by CFD software FLUENT.For the coarse,middle and fine size fractions,the velocity field,the solution of turbulence kinetic energy and trace lines of particles had been obtained,and the theoretical yields of overflow were calculated,and the verification experiment that had the same parameters with the numerical simulation was conducted.The results show that the extent of trace lines of particles affected by the internal flow field was gradually intensive,and these traces became more chaos with the decrease of particle size.The coarse particle group reported into the underflow in an orderly manner because of the regularity of the velocity field and the turbulent kinetic energy caused by the particle group from the upper part to the bottom of the TBS.The middle particle group shown chaos from in the middle and lower part of the TBS,most of particles of the group reported to the underflow with a minority reporting to the overflow after some repeated movements.The chaos phenomenon occurred in the fine particle group as well,the chaos domain reached to the top part of TBS.The majority of fine particles reported to the overflow,some of them would report to the underflow in the motion of flowing back,the entrainment phenomenon of fine particle happened leading to the losses of some clean coal products.Rationality of choosing the drag law for particles was justified by the consistency between theoretical yield and experimental yield of overflow,i.e.the drag law of non-spherical is suitable for coarse particles and the drag law of spherical is suitable for fine particles.The study shows the weakening effect of particle size by an early accurate size classification,so that the efficiency of TBS could be improved.