Abstract:
Coal fines produced during processing are difficult to dewater and result in a
lower quality product and consequent lower value. A South African coal
mine experiences severe difficulties with belt filter dewatering operations
due to the presence of fines reporting from the thickener underflows. Plant 2
currently handles super-fine particles of size −34 μm and has low belt filter
efficiency: excessive moisture retention lowers the product quality and
strains downstream processing. It was necessary to determine an alternative
method for dewatering these fines. Blending of fine material with coarser
material was proposed as a solution. The effect of coal particle size and
layering during ultrafines belt filter dewatering was evaluated using various
blends of the fine Plant 2 material with coarser Plant 1 material. The best
layering arrangement of the two materials and its optimum blend required
to achieve reduced filter cake moisture content was determined in practise
using a vacuum filter to simulate belt filtration. A blend of the two materials
gave improved dewatering efficiency for the belt filters compared with that
of the Plant 2 material alone. The best layering configuration was with Plant
2 material at the bottom and Plant 1 material on top. The optimum blend for
industrial applications comprised 48% fines from Plant 2.
