Analysis of pelleting movement characteristics of BYW-400 type vibrating seed coating machine for wheatgrass

Abstract: Seed pelleting coating is an important step in the pretreatment of forage seeds, and understanding the dynamic process of pelleting can better set up coating parameters and improve the qualified rate of pelleting. In order to understand the characteristics of pelleting movement of pelleted seed coating machine, the dynamic movement law of pellets needs to be studied accurately. The theoretical analysis, simulation and experimental verification of the BYW-400 type vibrating pelleting machine for wheatgrass seeds were studied. Based on Hertz contact theory, the vibration model and rotation model of single particle impact workpiece surface were established for vibration coating of pill coating machine. Meanwhile, the flow characteristics of material flow were analyzed. The results of theoretical analysis showed that the pelleting of wheatgrass seeds was related to the collision depth, maximum load, roughness of material flow and the thickness of cohesive bottom. The introduction of vibration can change the speed and increase the inertia force. Thus, the collision depth and maximum load of seed and powder were affected, the roughness height was increased. Besides, the turbulent flow property was enhanced, and the movement complexity between particles was increased. At the same time, the mixing degree between seed powder was improved, and the qualified rate of seed pelleting was finally improved. The same solution can be achieved when the pot body angle should not be smaller than the natural feet of the material, otherwise the material would stick on the pan surface, and lost the role of rolling together with its rotation. So it was necessary for us to choose the right size of the dip angle. The analysis of material flow characteristics showed that the introduction of vibration can increase the inertia force and increase the Reynolds number, which can improve the turbulent flow property, increase the irregular movement degree between particles, and improve the qualified rate of seed pelleting. In addition, EDEM software was used to simulate the simulation which the vibration intensity was 21% and no vibration and different tilt angles were simulated by 10 s, respectively. At the same time, the trajectory curve was plotted. The simulation results were analyzed by mixing degree, and the broken line diagram was obtained. Besides, the specific data was used to reflect the quality of mixed pelleting. The simulation results were consistent with the theoretical analysis, and the effect of vibration and inclination angle on the results of coating pelleting was verified. In addition, the effect of vibration and rotation angle was determined by coating single factor contrast experiment. Single factor experiments with six different factors were carried out, and the average value of each group was calculated many times. The qualified rate(the percentage of the coated area more than 80% particles accounting for the total number of samples and the weight is 7~10 times that of the original), seed rate (the percentage of the pelleted seed to account for the percentage of the total) and single seed rate(the percentage of the pelleted seed only 1 grains account for the total number of the samples) of pelleted seeds were calculated as the evaluation index of coating quality. When the speed of coating machine was 48.6 r/min., the dip angle of coating pot was 40.3? and the vibration intensity was 21%, the qualified rate of pelleting was 89.5%. Therefore, the change of vibration intensity can obviously affect the rate of pelleting. When the tilt angle of the coating pot was about 45?, the qualified rate of pelleting reached 89.7%. Thus, the dip angle of the coating pot was 45?, which was an ideal coating state. The results provide reference for the coating of irregular seeds.