水力溢流分级机内碳化硅微粉体积分率时空分布的模拟

Simulation for volume fraction spatio-temporal distribution of silicon carbide micro powders in hydraulic overflow classifiers

为了进一步理解水力溢流分级机的分级原理,采用双流体模型中的Mixture模型,应用Fluent软件模拟了直径1.8 m的水力溢流分级机分级碳化硅微粉的过程,研究了不同粒径的颗粒在分级机内的体积分率时空分布规律,探讨了沉降颗粒和溢流颗粒在不同分级时间下的粒径分布情况。模拟结果表明:粒径<3.36μm的细颗粒和粒径在3.36～7.16μm的中等粒度颗粒在分级机内的体积分率自上而下逐渐减小,中等粒度颗粒在分级机上半部分会发生积累现象,而粒径>7.16μm的粗颗粒在分级机的体积分率自上而下逐渐增加;所有颗粒的体积分率都存在径向分布,在中心处体积分率较低,在壁面附近体积分率较大;随着分级时间增加,沉降颗粒和溢流颗粒的粒度分布与原料的相比都变窄。并将分级14 h后沉降颗粒粒径分布的计算值与实验值进行了比较,发现计算值与实验值吻合较好。模拟结果对于优化水力溢流分级机的结构,提高分级机分级效率有一定的指导作用。

In order to further understand the classification principle of hydraulic overflow classifiers,the Mixture model was utilized to simulate the classification process of silicon carbide powders in the 1.8 m（diameter） hydraulic overflow classifier.The simulation was conducted by Fluent software.Volume fraction spatio-temporal distribution of particles with different sizes was studied.At the same time,the size distribution of settled particles and overflowed particles at different classification time was calculated.The simulation results from top to bottom prove that the volume fraction of fine particles（particl diameter less than 3.36 micronmeters） and medium size particles（particle diameter between 3.36～7.16 micronmeters） in classifiers decrease gradually,while the volume fraction of coarse particles（particle diameter larger than 7.16 micronmeters） increase gradually.Medium size particles will accumulate in the upper part of classifiers,the volume fraction distribution of all particles exists radial distribution,which means the volume fraction is low in the center and high in the wall attachment.While the classification time increases,the size distribution of settled particles and overflowed particles turns to be narrower than the size distribution of material.The calculated and experimental values of the size distribution of settled particles after 14 hours＇ classification turn out to be well matched.The simulation result is essential in the structure improvement of hydraulic overflow classifiers and the enhancement of classification efficiency.