回转窑内二元颗粒物料的径向混合

研究了颗粒尺寸差异和密度差异对二元物料在回转窑内混合的影响. 采用离散单元法建立颗粒物料的运动模型,模拟滚落运动模式下二元物料在回转窑内的径向混合过程;通过颗粒接触数定义混合程度评价指数,结合Hong的渗流与凝聚竞争理论分析颗粒体积比σ和密度比η对二元物料混合程度的影响. 结果表明:增大体积比σ会增强渗流作用,增大密度比η会增强凝聚作用,无论渗流或凝聚占据主导作用,均会导致物料在混合过程中产生径向分离,使混合程度降低;对σ与η进行配置后,可以使渗流与凝聚两种机理彼此平衡,达到物料混合均匀的目的;物料的渗流-凝聚平衡曲线中,σ与η呈幂函数关系.

Transverse mixing of binary solid materials in a rotating kiln

In order to investigate the effect of particle size difference and density difference on the mixing mechanism of binary granular materials within a rotating kiln, a kinematic model of particles was established using the discrete element method, and the transverse mixing process of granular materials in the rolling regime within the rotating kiln was simulated. The mixing index was defined by contact-number between particles, and the effects of particle volume ratio and density ratio on the mixing index were analyzed using Hong's theory: competition between percolation and condensation. The results show that the percolation mechanism improves with increasing volume ratio σ between particles, but the condensation mechanism improves with increasing density ratioη. Segregation will occur in the radial direction of the rotating kiln no matter percolation or condensation plays the leading role resulting in the decrease of mixing degree. Percolation and condensation can balance each other for some reasonable particle volume and density combinations, where the binary granular materials could get uniformly mixed. There is a power function relationship between particle volume ratio and density ratio when percolation and condensation balance each other.