DEM-DDM study on the humidification uniformity of brown rice in a pan coater

Abstract

In the milling process, proper humidification of brown rice can significantly improve milling performance. However, uneven humidification may lead to cracks in the rice, negatively affecting milling performance. In this paper, the DEM-DDM (discrete element-discrete droplet) simulation method is used to numerically simulate the humidification process of brown rice in a pan coater. The influence of coater rotational speed and inclination angle on humidification uniformity is studied. Through the analysis of the mixing behaviour and kinetic characteristics of brown rice particles within the pan coater, the causes of changes in uniformity are explained, and optimal parameters are proposed. The results show that the rotational speed of the coater mainly affects the radial mixing of particles, while the inclination angle primarily affects the axial mixing of particles. The optimum humidification parameters are the rotational speeds of 40 rpm and inclination angle of 80°. It has been found that the primary cause of uneven humidification of brown rice is the ineffective exchange of positions between the centre of the particle group and the spray zone. Compared to the inclination angle, rotational speed has a more significant effect on improving this phenomenon. This study is helpful to the digital design and optimisation of brown rice humidification process.