NUMERICAL SIMULATION AND EXPERIMENTAL STUDY OF INNER FLOW FIELD OF SEED PELLETING PREMIXER IN SPOUTED FLUIDIZED BED

In order to explore the temporal and spatial distribution and motion state of the grains of wheatgrass (Agropyron) seeds and powder in pelleting process, and to find the optimal inlet air speed of pelleting premixer, the pelleting forming mechanism was revealed. Based on Herz-Mindlin contact theory, the contact mechanics model of seed and powder was established. Besides, CPFD software was used to model and simulate the pelleting premixer, and the contact, collision and friction rules among particles were analysed. The simulation and experimental results show that with the increase of inlet wind speed, the bed expansion increases and the unit volume particle concentration decreases, while the air pressure difference only slightly increases. When the inlet wind speed is set at 3.5 m/s, the atomizing nozzle velocity is set at 4.1 m/s, and the seed coating agent flow rate is 0.36 L/min, the particles are suspended due to air isolation, forming a spouted fluidized bed. It is good for seed and powder contact and rapid prototyping. In this time, the pelleting qualified rate was 95.8%. The results provide theoretical basis and technical support for the research of small irregular seeds pelletizing technology.