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Using inclined vibrating plate (IVP) to gather spherical coated fuel particles is an important process in nuclear fuel particulate technology, especially in the manufacture of nuclear fuel elements for high-temperature gas-cooled reactor (HTGR). In order to get a satisfactory separation result, fuel particles are required to discharge uniformly and slowly into the IVP at a stable flow rate. To this end, the vibrating feeding system composed of a hopper and a new designed multi-layer multi-channel (MLMC) feeder is proposed in this paper to increase the discharge rate, optimize the uniformity of particle distribution and reduce the particle velocity near the outlet, which can produce a better separation of odd fuel particles. Subsequently, discrete element method (DEM) is used to investigate the motion of coated fuel particles in the feeding hopper. The accuracy of DEM is verified by comparing the experimental results with the simulation results. At the same time, the mass discharge rate (MDR) of particles in the hopper and the influence of geometry structure of hopper are studied. Finally, the motion of fuel particles in the new designed MLMC feeder is investigated, and the distribution characteristics of particles discharging out from the new feeder are analyzed. The simulation results demonstrate that the new designed feeding system can meet the optimal feeding requirements that the particles are discharged uniformly with the rather stable flow rate and the relatively lower particle velocity.

Odd-shaped coated nuclear fuel particles are the main reason for the failure in the manufacture of fuel element, and the sphericity separation of fuel particles is one of the most significant process to improve the safety of high-temperature gas-cooled reactor (HTGR). The separation of particles by inclined vibrating plate (IVP) is based on the different friction force acted by the distinct shapes of particles. In this paper, Discrete element method (DEM), which is a numerical simulation method for analyzing and solving the dynamic properties of discrete systems, is used to investigate the separation process on the IVP. In view of the realistic fuel particles are all non-spherical particles with irregular shape, the super-ellipsoid model is utilized to describe the particles in the DEM simulation. A method to evaluate the separation efficiency is proposed in this paper to quantify the numerical simulation results of particle sphericity separation. The relationship among the operating parameters such as amplitude, frequency and inclination angle is combed, and the selection of the optimal value of these parameters are obtained. The effects of feeding-rate and height of feeder are investigated, and the particle collision is analyzed to explain the effect of feeding-rate. A set of optimized parameters are proposed, and it is identified that the DEM simulation results received by using these parameters meet the requirement of the fabrication process of coated fuel particles.

Particle mixing is a very important process in many industrial reactors. It is important to consider how to quantify the particle mixing behavior accurately under different conditions. In this paper, the drawbacks of traditional mixing indexes, such as Lacey index are discussed, and then a novel particle mixing index, without grid dependency and particle color dependency was proposed based on the neighbor distance method and coordination number concept. Its characteristics such as parameters selection, calculation method and multi-direction were discussed in details. The proposed mixing index was used for investigating particle mixing behavior in the multiple-spouted bed under conditions of different gas velocity ratios and different particle density ratios. The experimental results have been used to validate the simulation results at first. It is found that the improved mixing index is more superior and effective compared with the traditional mixing index methods, and suitable for the investigation of particle mixing behavior. It was indicated that the density ratio is a key factor to influence particle mixing process. The novel particle mixing index without grid dependency and particle color dependency is recommended to study particle mixing behavior in other particulate processes in the future.

Vibration sorting is a common means in separating non-spherical particles from spherical particles. In this paper, the discrete element method (DEM) is applied to simulate the behavior of spherical particles and non-spherical particles motion on an inclined vibrating plate (IVP), and the influence of different operating parameters on the separation performance of the mixed particles is investigated. In the DEM simulations, both the spherical and non-spherical particles are modeled by super-ellipsoids. The simulation results show that the optimal vibration amplitude and frequency exist for the high separation efficiency of the mixed particles. The separation efficiency can also be enhanced by properly increasing the friction coefficient or decreasing the restitution coefficient between particles and plate. It is easier to separate the non-spherical particles from the spherical particles by diminishing the sphericity of particles. Besides, as long as the inclination angle of the plate is set at appropriate range and the feed rate of the mixed particles is moderate, the non-spherical particles can be separated effectively from the spherical particles. This research could be helpful for the understanding and optimal design of vibration sorting device.

CFD–DEM coupling simulation method is used to study the fluidization behavior of particle with different densities in the spouted bed. The simulation results show that the particle spouting behavior is incoherent and periodic in the stable spouting state. The cycle periods of the whole bed and single particle are obtained from particle trajectory and compared with experimental results. The relationships between the minimum spouting gas velocity, the steady pressure drop and the particle density are obtained. It can be found that the gas velocity range of stable spouting state expands when the particle density increases. The dual, single and multiple dominant frequencies are found in the stable spouting process of high density particle. Through detailed analysis on the mechanism of spouting dominant frequency, the flow pattern map with different superficial gas velocities and particle densities is given and can be divided into five regions: fixed bed with internal spouting, transitional stable spouting state with dual dominant frequency, main stable spouting state with single dominant frequency, transitional stable spouting state with multiple dominant frequency, and unstable spouting state. The stable spouting gas velocity is influenced by the particle density, while the dominant frequency of the particle spouting process will keep invariant even if the particle density increases, as long as Ug/Ums is not changed. The influence of particle density on the particle residence time distribution in the spout region, which can be used to characterize the gas solid contact efficiency, is also discussed based on simulation results.