Study Of Solid Mixing And Mixing Enhancement In Double Cone Blenders

Powder operation is a traditional practice with a long history for more than thousands of years. And solid/powder mixing is a very important unit operation in many industrial processes. However, granular materials are typical complex systems. Previous studies are largely at a macroscopic or global scale by experimental research on solid mixing, while the microscopic fundamental understanding of the motion characteristics of particles and mixing mechanisms is relatively insufficient. In recent years, with the rapid development of computer technology, Discrete Element Method (DEM) has been an effective numerical method to solve such non-continuum mechanics problem.In this paper, a commonly used rotary mixer - double cone blender is investigated. By means of numerical simulation, particle flow characteristics and mixing properties in this blender are studied. Then the characteristics and mechanisms of the mixing enhancement in the drum mixer set with a baffle are researched. And based on this, the effect of baffles fixed at the axis of rotation of the double cone blender on solid mixing is analyzed. The main research work is as follows:(1) Numerical study of the solid mixing properties and mechanisms of mixing enhancement by setting an internal structure in a drum mixer. Micro-dynamics studies of mixing and segregation between two kinds of particles of different sizes in the drum mixer by use of DEM are performed. And the effect of baffles of "-", "+" and "*" type and the size ratio of these baffles to the blender on solid mixing are evaluated. Simulation results reveal that segregation will be largely restrained by an axial baffle. Baffles can enhance the solid mixing no matter what shape. And the "+" type baffle is an optimal selection.(2) 3D numerical studies on solid mixing characteristics in the double cone blender. The flow and mixing characteristics of mono-sized particles in the double cone blender are analyzed. And the effect of rotational speed of blender and loading mode on mixing is investigated. Then the studies of the effect of fill level in the blender on mixing of binary-sized particles are carried out.(3) Studies on mixing enhancement of binary-size particles by setting baffle in the double cone blender. The effect of restraining the radial separation by setting a "+" shaped baffle in the double cone blender is investigated. Further, setting "+" inclined baffles in this blender is proposed. And then the effect of the baffle width-diameter ratio on the enhancement of the axial mixing and the mixing mechanism are analyzed.