No abstract

The basic process of dewatering is the removal of residual liquid left in a filter, centrifuge, or other cake from a soid‐iquid separation step. Forces used for dewatering are compression, expression, and displacement. The mechanical and electrical methods of dewatering as well as the chemical and mechanical pretreatments of slurries to improve the final dewatering step are discussed. Many of the methods are useful for deliquoring in general and are not limited to water removal. Pretreatments enhance the separation of liquid from solid by lowering the viscosity of the liquid (raising temperature, adding another liquid), lowering surface tension (adding surfactants), increasing porosity or changing compressibility (coagulation, flocculation, pelletizing flocculation, oil agglomeration, pH change, hot or cold thermal treatment, biological conditioning, adding filter aids, magnetic agglomeration), or displacement of the residual moisture (with a gas or a different liquid or by extraction of the solid into a different liquid). Electrical processes can be used to increase the migration of water through a filter cake, to retard the movement of particles into a filter cake, or to be combined with an acoustical field to improve the removal of water from a filter cake.