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PROCESS

The principal operation in wet dressing of kaolin is the classification process which has two objectives:

(1) to separate other minerals,
and
(2) to obtain required particle size

Screening, settling, hydro cyclones and centrifuges are mainly used for classification.
  
Additional processing stages generally to increase brightness and to adjust other physical characteristics are also included in the refining circuits. In TKCL to improve brightness, bleaching process is used in which iron bearing minerals are removed by addition of a reducing agent (usually sodium hydro sulphite) at low pH. The coloured iron compounds are rendered colourless and soluble by bleaching and removed during water washing and filtration stages.

Dewatering is done through high pressure filter presses and product is finally dried in a spray drier. Spray drier is modern equipment in which clay slurry is atomised into an exceedingly fine spray on entering top of a large conical chamber. The fine droplets slowly descend passing through a stream of hot air. A fine powder is formed that is both free flowing and virtually dust free.