The effect of paddle configurations on particle mixing in a soil-fertilizer continuous mixing device

Abstract

The mixing of soil and fertilizer is critically important for the deep application of organic fertilizer. The mixing of soil and fertilizer generally needs to be conducted during the transportation process. Here, a screw auger with paddles was used to improve the mixing performance of particles during the transport of materials. The discrete element method (DEM) and experimental measurements were used to characterize the effect of paddle configurations on particle mixing. Four parameters with five levels were used in the simulations. The paddle configurations had a major effect on the mixing performance and granular behavior. The relative standard deviation (RSD) results obtained from the validated DEM models revealed that devices with larger paddle rotational speeds n, sideward angles α, pitch angles β and 3 paddles conferred higher mixing performance. The effect of paddle configurations on the paddle-particle and particle-particle average contact forces was also analyzed. Higher paddle rotational speeds n, sideward angles α and pitch angles β led to larger average normal contact forces, and the effect of the number of paddles N was small. Analysis of the particle velocity distribution of different configurations revealed that an appropriate paddle configuration with better mixing performance improved the particle velocity. The contributions of both convective and diffusive mechanisms on particle motion were studied, and convection was found to be the dominant mechanism. Generally, the results of this study provide a reference for the selection of an appropriate paddle configuration that confers higher mixing performance and lower power consumption.