In order to improve the rate of coating and pelleting of forage grass seeds, our team is researching the pellet coating of small-particle irregular forage grass seeds under the action of vibration force field. Besides, we establish the three-dimensional model and simulation model of coating pan by using Solid-Works and EDEM (enhanced discrete element method). At the same time, the movement law of seed pelleting coating process is studied for forage grass seed. Simulation results show that when the coating pan speed is 40 r/min, the vibrating frequency of coating pan is 20 Hz, and the amplitude is 0.02 mm, the particle swarm can be dispersed at different time points and in the same spatial region. In addition, the movement of particle swarm accelerates the dispersion degree of the particles. The forage grass seed and powder can reach a boiling state immediately. Meanwhile, by observing the simulation graph, we can see that the forage grass seed and powder can enter each other's gap easily to increase the collision times between seeds and powder, and achieve the ideal effect of pellet coating eventually. According to relation curve of average velocity and average displacement of all forage seeds and powder with time, we can notice that the seed and powder fall into the coating pan before 0.36 s, while the seed and powder is pelleted and coated after 0.36 s. The reason is that this time point is the extreme point of the curve. After this point, the displacement of seed and powder is gradually becoming larger, while the velocity is gradually becoming lower. We can easily draw a conclusion that forage grass seeds will come into contact with the powder more frequently during the long distance of the movement; the longer the bonding time, the better effect the bonding. However, when the coating time is 0.81 s, the trend of the increase amplitude of the powder displacement has little change, but the velocity is becoming smaller. At this time, the speed of powder and forage grass seed begins to slow down and be coated under the influence of particle collision and friction. This is the best time for the pellet coating of forage grass seed and powder. Otherwise, through the force analysis diagram of the powder and forage grass seed, we can notice that the collision force reaches the maximum at 0.61 and 0.81 s. It shows that the bonding effect of the powder and forage grass seed is the best, and it is easy to seed pelleting. The conclusions are consistent with the velocity and displacement curves. Furthermore, the results of experiment show that when the coating pan speed is 40 r/min, the vibrating frequency of the coating pot is 20 Hz, the dip angle of the coating pot is 35°, the coating time is 20 min, the single seed rate of pelleting coating can be reached 82.08%, the coating qualified rate can be reached 98.22%. The results can provide references for the coating of small irregular seeds.%为提高牧草种子丸粒化包衣合格率,对振动力场作用下的小粒不规则牧草种子进行丸粒化包衣研究.运用Solid-Works和离散元仿真软件EDEM建立了包衣锅三维模型及仿真模型,研究了牧草种子丸粒化包衣过程的运动规律.引入振动后的仿真结果表明:在包衣锅转速为40 r/min,包衣锅振动频率为20 Hz,振幅为2 mm,包衣锅倾角为35°的条件下,种群能在不同的时间点、相同的空间区域分布较为离散,种群的运动剧烈加速种粉间的离散程度,促使种粉达到"沸腾"状态,使其进入彼此间隙,增大种粉间碰撞摩擦次数,达到丸粒包衣的理想效果.试验结果表明:随包衣锅振动频率的增加,单籽率及有籽率均略有提高,而当振动频率为20 Hz时,单籽率及有籽率可达到较理想的丸粒化效果;正交试验结果表明:当包衣锅转速为40 r/min,包衣锅振动频率为20 Hz,包衣锅倾角为35°,包衣时间为20 min时,单籽率达到82.08%,包衣合格率达到98.22%,研究结果可为小粒不规则种子包衣提供参考依据.
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