Ecc International Limited

William E Thompson

Bomi M Bilimoria

Kirt L Matthews

A process for producing a high solids aqueous slurry of a beneficiated kaolin. An impure crude kaolin clay is initially subjected to wet processing including a size classification step, to recover a beneficiated fine particle size kaolin fraction which is formed into a dilute aqueous slurry of deflocculated kaolin particles. The dilute slurry is filtered by flowing it generally parallel to and in contact with the surface of a microporous barrier while maintaining a pressure drop across the barrier in a direction transverse to the slurry flow. A gel permeation layer is thereby formed of kaolin overlying the surface of the microporous barrier. The gel permeation layer and underlaying surface are substantially impervious to the passage of clay solids while being pervious to the passage of water molecules, ions and dissolved salts; whereby water molecules, ions and dissolved salts are caused to pass through the barrier, thereby increasing the concentration of the solids in the kaolin slurry. The water having passed through the barrier as a substantially solids-free permeate is collected and, the retentate is collected as a more concentrated aqueous slurry of beneficiated kaolin particles. Additional water may be thermally evaporated from the more concentrated aqueous slurry to provide a higher solids product slurry.

Process for producing a kaolin clay product

A process for producing a high brightness, high solids kaolin clay aqueous slurry. An aqueous low solids suspension of crude kaolin clay is degritted, and subjected to a particle size classification. The aqueous suspension of the fine particle fraction is acidified to a pH of 5.0 or lower to produce an acid flocculated suspension which is treated with a bleaching agent to reduce ferric ion impurities to ferrous ion impurities. A ferrous ion chelating agent is added to the bleached acid flocculated suspension after which an alkaline agent is added to raise the pH to a level greater than 5.0 to form a dispersed aqueous suspension of the beneficiated kaolin. The dispersed suspension is then subjected to membrane filtration to partially dewater same, and additional water is thermally evaporated from the partially dewatered dispersed kaolin suspension to produce the high solids product suspension.

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Sandersville, GA, United States of America

William E Thompson