Interaction mechanism between two stages of separation explains residual rice husk formation in a multi-baffle separation duct

Abstract

Grain cleaning is one of the most important processes in rice processing. Mixtures of rice husks and brown rice with high jet velocity and high feed rates can be separated by multi-baffle separation ducts for grain cleaning. However, the rice husks cannot be completely separated from the brown rice, resulting in the presence of residual rice husks in the cleaned brown rice. Therefore, it is necessary to explore the formation mechanism of residual rice husk. In this work, we simulate the separation process of rice husk from brown rice by coupling Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) and explore the two stages separation based on the interaction between multiple baffles. The results show that the interaction between primary separation and secondary separation affects the quality of separation. Specifically, the collision between rice husk and brown rice in the primary separation region affects the landing position of the husk in the secondary separation region. And the secondary separation quality is related to the landing position of the husk in the secondary separation region and the number of collisions between the husk and the falling brown rice from the primary separation region. It was demonstrated that the residual husk could be effectively reduced by increasing the distance between the landing position of the husk in the secondary separation region and the brown rice outlet. The research results can provide analytical ideas and theoretical direction for the design and parameter selection of multistage separator and similar equipment.