球磨机中颗粒混合运动的数值模拟

Numerical Simulation of Particle Mixing Movement in a Ball Mill

针对球磨机在火电厂应用广泛而对其内部颗粒混合运动的信息了解甚少的现状,采用离散元法直接跟踪球磨机内的每一个颗粒,考虑其所受重力、摩擦力和碰撞阻力的联合作用,建立了颗粒的三维动力学模型,对球磨机中颗粒复杂混合运动的全过程进行了数值模拟,并着重探讨了颗粒大小、颗粒密度及颗粒粒度不均等关键参数对球磨机中颗粒混合运动特性的影响。结果表明,随着球磨机的转动,球磨机内各区域的颗粒均逐渐混合均匀,但球磨机内不同区域颗粒混合的均匀程度不同。相同填充率条件下,小颗粒混合达到均匀的时间较长;相同粒径条件下,密度较大的颗粒其混合达到均匀的时间也较长。颗粒粒度不均时,随着球磨机的转动,颗粒出现分层现象。

In view of the current situation that ball mills are widely used in thermal power plants and very little information about their inner particle mixing movements is known to us,a discrete elementary method is used to directly track every particle in a ball mill.By considering the joint action of gravity force,friction and collision resistance received by these particles,established was a threedimensional dynamic model for the particles and numerically simulated was the whole process of their mixing movement in the ball mill.The influence of the key parameters,such as particle diameter,density and granularity unevenness etc.on the characteristics controlling the complex movement of particles in the ball mill was emphatically studied.The research results show that with the turning of the ball mill,all the particles in every area of the ball mill are gradually well mixed.The uniformity of such mixing in the ball mill at various places,however,is different.In the case of an identical filling rate,the time required by the small particles to mix uniformly is relatively long.In the event of an identical particle diameter,the time required by the particles with a higher density to mix uniformly is also relatively long.When the particle diameters are not uniform,with the turning of the ball mill,a layer-separation phenomenon will occur to the particles.