CFD-DEM simulation of fluid particle spatial distribution characteristics in the whole process of fine coal spiral separation

Spiral separation is one of the core technologies for the efficient green separation of fine coals, and the investigation of fluid-particle spatial distribution characteristics in the whole process of spiral separation of fine coals is beneficial to the in-depth understanding of spiral separation behavior. Taking the whole process of spiral separation as the research object, the spatial distribution law of flow field and particles in the whole process of spiral separation is studied. By establishing the particle spiral separation kinetic equations and based on the multi-flow characteristics of the spiral separation flow field, a computational model of fluid drag force in the composite flow state is constructed. The results show that: ① According to the flow field distribution and particle motion behavior, the whole process of fine coal spiral separation can be divided into initial stage (0−1/3 turns), transition stage (1/3−2 turns) and sub-stable stage (after 2 turns). In the initial stage, the distribution of different density and particle size in the spiral trough is basically the same: distribution along the spiral trough inclination direction and gradually gathering to the outer edge of the spiral trough. ② In the transition stage, high-density particles gradually gather to the inner edge as the particle size increases, and low-density particles gradually gather at the outer edge of the trough. ③ In the sub-stable stage, more high-density particles gather at the inner edge of the spiral trough as the particle size increases, and low-density particles with different particle sizes are mainly gathered at the outer edge of the spiral trough. In addition, particle size has a significant effect on the spatial distribution of high-density particles but has little effect on the separation behavior of low-density particles. When the particle size is less than 0.1 mm, the tendency of separation between particles according to density difference is decreased. Therefore, it is difficult for high-density fine particles to sink to the bottom of the spiral trough to participate in the radial transport of secondary circulation by density difference, causing them to mainly gather at the outer edge of the spiral trough and mix with low-density particles, which is unfavorable to the separation of fine coals.