Processing and Manufacturing
    The processing of kaolin varies greatly from company to company.  Each kaolin producer uses different equipment and methods.  Companies that use identical methods may use them at different points during processing.

    A good example of the extensive processing of kaolin is found in those products intended for the paper industry. The greatest demand for kaolin-based pigments comes from the paper industry, which uses them to coat and fill papers and boards. There are many ways to produce these pigments. One of the methods used is called the "water washed process." Generally, in the processing of water washed clays, water is used as a transport and process medium involving the following:

    • Blunging

      The kaolin is mixed with water and chemical dispersants to create milk-shake-like slurry. Slurry is simply the water and dispersed clay mixture, which puts the clay particles in suspension.

    Blunging

     

    • De-gritting

      The slurried kaolin is usually transported through pipelines to degritting facilities, where sand, mica and other impurities are extracted with the help of gravity.

     

    • Centrifuging

      The centrifuge separates the fine kaolin particles from coarse particles.

    Fine particles, still in the form of slurry, move on for further processing to enhance brightness.

     

  • Brightness enhancement

    With both the fine and coarse kaolin particle fractions, brightness is enhanced through one or move processes including bleaching, magnetic separation, flocculation, ozonation, flotation, and oxidation, which will remove iron, titanium, organic, and other undesirable materials.

  • Delamination

    For customers who want a delaminated clay product suited for lightweight coating applications, coarse particles are used. Delamination occurs as the coarse particles of kaolin which when magnified appear as "booklets" are broken into thin platelets.

After delamination, the brightness of the coarse particles may be enhanced through one or more of the same processes used in the fine particle fraction.

 

  • Filtering and drying

    Large rotary vacuum filters remove water from the slurried kaolin. Large gas-fired spray dryers remove and evaporate the remaining moisture.

 

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