Hydrotransport of solids in horizontal pipes: Effects of solids concentration and particle size on the deposit velocity

Correlations previously proposed in the literature for the deposit velocity in the flow of settling slurries in horizontal tubes generally predict increasing values with increasing solids concentration. However, the present comprehensive investigation which has drawn on data from a broad geographical base, confirms that the deposit velocity shows a maximum with respect to concentration and decreases above about 15% by volume solids. It is also shown that the presence of fine particles (<75 μm) is particularly significant in determining the degree of the reduction in the deposit velocity for the higher concentrations. This reduction would appear to be due primarily to a significant increase in the drag coefficient for particles settling in a fine particle suspension, i.e. heavy medium. The data are summarized in graphs for a variety of materials including sand, gravel, iron ore and coal.