The importance of coal particle characterization in setting up a dem model for the flow of fine coal through a hopper

Abstract

Processed coal has to adhere to an additional requirement of being able to pass through chutes, transfer points, hoppers and other handling or discharge systems with little or no difficulty to ensure efficient transportation thereof from a mine, through subsequent processing until delivery. Various handling difficulties such as irregular flow and decreased flow capacities occur as a result of the formation of dead zones, ratholing and arching. With the new worldwide focus on processing finer coal fractions it has also increased the need for understanding fines handling. The true behaviour of a material during handling can only be understood by means of experience or by evaluating the handling performance, which requires extensive financial resources as well as time. However, if a Discrete Element Model (DEM) is readily available with which assesses the handling performance easily and quickly, it would result in improved plant operations as well as aid in hopper and chute design. One of the most crucial aspects to consider when creating a validated DEM model of the coal flow is the coal particle characterization. With this particle characterization it is important to look at differences in shape, size and density as this will influence the coefficients of restitution, static and rolling friction. The DEM software, used in this study, makes use of spherical particles with default values assigned for the coefficients of restitution, static and rolling friction. It was found that the difference between the DEM default parameters and those measured is significantly different, by as much as 97%, which illustrates the importance of experimentally determining these parameters. This study will aim to show what the influence of shape, size and density have on the various coefficients. The study will also show that with proper coal characterization it is possible to create a validated DEM model of the coal flow through a hopper with 95% accuracy.