Study On Discrete Element Simulation Of The Particle Movement/Mixing Process

The movement and the mixing of particles have been attracted by many researchers.However,it is mainly focused on the experimental study of the phenomenon observation on the particle movement.Due to the limitations of the experimental method,the complex particle movement process is still difficult to reveal accurately.The mechanism of particle movement/mixing is lacking a systematic understanding.The particle packing process is a basis for studying the particle movement.The particle packing angle is also a crucial physical parameter that reflects one of the general macroscopic characteristics of the particle group.It is influenced by various factors such as the physical properties of the particles.Therefore,it is necessary to study the particle packing angle in detail to enhance the understanding of the particle movement process and mechanism.The movement of particles in the reactor is a typical particle process,judging whether the reactor structure is desirable by studying the movement behavior of the particles inside the reactor;and then can sequentially optimize and improve the container structure design.Particle mixing is a typical particle processing process.Quickly and efficiently mixing particles has considerable significance for improving the industrial production processes.The discrete element method is(self-programming DEMMS software)widely used in particle research.In this paper,the particle movement as well as the mixing process is simulated.Due to the large number of particles in the system,GPU is applied for large-scale parallel computing.First,the accumulation process of particles under different physical properties is computed to investigat the variation of the particle packing angle under different conditions.It is found that the rolling friction coefficient and the sliding friction coefficient of the particles present greater effects on the particle packing angle.As the two parameters increase,the particle packing angle also increases.The particle size and particle density have little effect on the particle packing angle.Moreover,the movement of the particles in a square cone moving bed when feeding and discharging is analyzed.The position variation,the velocity distribution and the residence time distribution of the particles are obtained,respectively.It is found that a dead zones at the bottom exit wall of the square cone moving bed tends to occur.Therefore the whole bed can be divided into three different regions based on the motion state of the particle,i.e.the plug flow zone in the top area of the bed,the convergent zone in the bottom area of the bed and the transition zone in the middle area.A new jet method is introduced in the particle mixing process.Compared with the traditional mixers such as the square cone and conical TOTE mixers,the proposed jet mixing has the advantages of continuous operating.The mixing rate and the mixing efficiency are both comparatively high.The mixing effects in both macro and micro scales are quite excellent.In addition,the dimension analysis method to study and analyze the various influencing factors that affect the jet mixing performance is carried out.The effects of the gas conditions on the particle jet mixing are studied.It was found that under the same conditions,the mixing effect of single-phase jet mixing in various scales is clearly better than that of the two-phase jet mixing with gas.