干扰流化床中粗煤泥颗粒运动轨迹数值分析

Numerical analysis of motion trajectory of coarse coal particle in interfering fluidized bed

干扰床分选机(Teetered Bed Separator,TBS)对粗煤泥的分选,本质上是不同密度和粒度的颗粒在流化床流场中运动轨迹差异化的过程,因此分析研究不同性质的颗粒的运动轨迹可以直观地识别颗粒的最终分选状态,从而评判分选效果的好坏。本文使用Fluent软件提供的基于拉格朗日-欧拉方法研究颗粒运动的DPM模型,模拟计算密度为1550 kg/m^3、不同粒度的粗煤泥颗粒在流化床流场中分选过程的运动轨迹,并且使用小波计算的方法对颗粒的轨迹信息进行分析。模拟计算的结果:在0.25~1.25 mm内平均分布的同一密度的粗煤泥颗粒,其中处于该范围两端的颗粒,亦即:较细颗粒与较粗颗粒,均容易受到流化床的分选作用而各自分别进入溢流与底流;处于分离粒度附近的难分选的粗煤泥颗粒,需要较长时间才能进入溢流或者底流达到分选的效果,颗粒的运动轨迹杂乱。小波计算杂乱运动轨迹的分析结果:进入溢流的与进入底流的难分选颗粒的轨迹,二者均存在周期性变化规律;在低时间尺度下(35,70 s),进入溢流和进入底流颗粒的运动轨迹具有周期相似性;在高时间尺度下(110,140 s),进入溢流和进入底流颗粒的运动轨迹则表现出明显的周期差异性。本文研究表明:具有杂乱运动轨迹的难分选颗粒的处理问题,是流化床设备分选粗煤泥的难点;难分选粗煤泥颗粒进入溢流和底流的运动轨迹,具有在高时间尺度下周期差异性的规律,以此可为粗煤泥在分选之前进行精确分级提供思路与借鉴,提高粗煤泥分选的整体效果。

The separation posed by TBS(Teetered Bed Separator)to the coarse coal slime is essentially a process that trajectories differentiation of particles of different density and particle size in the fluidized bed.Analyzing these trajectories of particles of different properties can visually identify the ultimate separation state,then to evaluate the process.The DPM model based on the Lagrangian-Eulerian method provided by Fluent was adopted to simulate the separation process of coarse coal slime particles with different sizes in the fluidized bed with the density of 1550 kg/m 3.These trajectories of particles have been analyzed,and trajectories information of particles analyzed using a wavelet method.The simulation calculation results that among the coarse slime particles of the same density,distributing from 0.25 to 1.25 evenly,those near to the upper or lower limits of the size range,as much finer or much coarser particles,are easily to be separated.Those particles being hard to be separated in the vicinity of the cutting size need a long period to reach the sufficient separated state,and the particles trajectories were messy,furthermore the instantaneous optimal separation time occurred.The analysis results of the cluttered motion trajectory by wavelet:the trajectories of the hard-to-separate particles that were reported to the overflow and entering the underflow,both of which had periodic variation laws;at low time scales(35,70 s),the trajectories of those particles reported to the overflow and the underflow have periodic similarity;at high time scales(110,140 s),the trajectories of particles reported to the overflow and the underflow showed significant periodic differences.The problem of the treatment of hard-to-separate particles with disordered motion trajectory is the difficulty of separating coarse coal slime particles in fluidized bed equipment.The trajectories of hard-to-separate particles reported to the overflow and underflow announced the law of periodic difference at high time scale.Therefore,it can provide ideas and reference for the accurate classification of coarse coal slime before separation,and improve the overall performance of separating coarse coal slime.