湿煤聚团碰撞破碎模式及分离机制

Impact failure patterns and separation mechanics of the wet coal agglomerates

利用图像处理技术分析了湿煤聚团与壁面的碰撞过程,研究了湿煤聚团碰撞破碎模式.借助于接触力学理论和液桥理论研究了湿颗粒聚团的碰撞分离机制,从动力学角度得出了分离湿颗粒所需条件.研究表明:湿煤聚团碰撞呈现3种破碎模式:碰撞式、重力-碰撞式和剪切-碰撞式.聚团与壁面的碰撞打破了颗粒速度的一致性,使得颗粒间发生接触碰撞而产生分离运动,从而引起粒间液桥发生拉伸断裂;当粒间最大分离距离超过液桥断裂距离时,湿颗粒实现分离;对湿颗粒分离起主要作用的是法向速度,切向速度的贡献不及法向速度的十分之一.湿颗粒的分离需要一最小法向分离初速或切向初速.水分的增加使湿颗粒难分的主要原因是液桥难以断裂造成的.湿颗粒聚团的破碎随着碰撞速度的降低、颗粒粒径的减小以及水分的增加而变难.

Applying image processing technology,collision course of the wet coal group with a wall is investigated and the failure patterns of wet coal agglomerate are analyzed.Using contact mechanics theory and liquid bridge theory,dynamics mechanics of breakage in wet agglomerates has been studied and the dynamics conditions needed for the breakage of wet agglomerates is obtained.Three failure patterns are observed termed as impact failure,gravity-impact failure and shear-impact failure.It is found that impact against a plate results in a heterogeneous distribution of primary particle velocities and a tendency of separation.Separations of granules bring about stretch and rupture of liquid bridge.If the maximum separation distance exceeds the rupture distance of liquid bridge,breakage happens and the breakage needs a critical normal initial velocity or shear initial velocity.Shear velocity can help rupturing of liquid bridge,but the effect is limited.Breakage of wet agglomerates gets difficult with the decrease of impact velocity and particle size,as well as the increase of the water content.