US Patent 7754087 Dewatering process

A process of dewatering aqueous suspension employing a flocculating system comprising treating the suspension with a flocculating amount of a first flocculant and a dewatering amount of a second flocculant, and subjecting the suspension to mechanical dewatering to form a cake, wherein the first flocculant brings about flocculation and assists thickening of the suspension and the second flocculant is a water-soluble or water swellable polymer that is mixed into the suspension is a water-soluble or water swellable particulate polymer having a particle diameter of at least 20 microns.