Extraction and Treatment of Raw Kaolin

Raw kaolin is mainly extracted by open cast mining. Secondary deposits can be exploited using excavators, whereas primary deposits of kaolin are often washed out of the rock with a high pressure water jet. 

To obtain a uniform mineralogical composition with a high alumina content (AI2O3 content 37%), the raw kaolin is elutriated and simultaneously classified in hydrocyclones, whereupon kaolinite and the other layer silicates are separated from the accompanying quartz and feldspar on the basis of their different particle size distributions. 

After leaving the hydrocyclone, the water content of the fine product, so-called kaolin milk, is reduced to 25 to 30% in settling tanks and filter presses. The filter cake is often only dried to a water-content of 10 to 15%. 

Different feldspar qualities and particle size-classified quartz sands are obtained as byproducts of the kaolin elutriation. 

Separation of kaolin and other clay minerals from the accompanying quartz and feldspar by elutriation and particle size classification in hydrocyclones 

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