TABLE OF CONTENTS With few exceptions, most mineral-separation processes involve the use of substantial quantities of water and the final concentrate has to be separated from a pulp in which the water-solids ratio may be high.
Dewatering, or solid-liquid separation, produces a relatively dry concentrate for shipment. Partial dewatering is also performed at various stages in the treatment, so as to prepare the feed for subsequent processes.
Dewatering methods can be broadly classified into three groups:
sedimentation;
filtration;
thermal drying.
Sedimentation is most efficient when there is a large density difference between liquid and solid. This is always the case in mineral processing where the carrier liquid is water. Sedimentation cannot always be applied in hydrometallurgical processes, however, because in some cases the carrier liquid may be a high-grade leach liquor having a density approaching that of the solids. In some cases, filtration may be necessary.
Dewatering in mineral processing is normally a combination of the above methods. The bulk of the water is first removed by sedimentation, or thickening, which produces a thickened pulp of perhaps 55 65% solids by weight. Up to 80% of the water can be separated at this stage. Filtration of the thick pulp then produces a moist filter cake of between 80 and 90% solids, which may require thermal drying to produce a final product of about 95% solids by weight.
Rapid settling of solid particles in a liquid produces a clarified liquid which can be decanted, leaving a thickened slurry, which may require further dewatering...
