Thickening

thickening [′thik·ə·niŋ]

(chemical engineering)

The concentration of the solids in a suspension in order to recover a fraction with a higher concentration of solids than in the original suspension.

(mining engineering)

Concentrating dilute slime pulp into a pulp containing a smaller percentage of moisture by rejecting the free liquid.

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Thickening 

the removal of the liquid phase, for example, water, from disperse systems, for example, pulps, suspensions, and colloids. Thickening forms the basis for the production of condensed milk, fruit and vegetable juices, syrups, and purees. The process consists in the removal of moisture from the starting products in evaporators. After thickening, moisture content in milk and juices is reduced by a factor of 10–15.

As a production operation or, more frequently, an auxiliary operation in production, thickening is used in processes where one stage requires water but subsequent stages require a drastic reduction in the amount of water. Processes of this type include the production of paper, the concentration of ores, and processes in hydromechanization and hydrometallurgy. In the production of paper, the ground fibrous mass is mixed with water, thereby forming a suspension. After stirring and the removal of mechanical impurities, the suspension is subjected to thickening prior to shipment to the factory. In wet concentration of ores, a pulp is formed, which consists of a concentrate and 40–60 percent water. Since the water content in the concentrate shipped to the factory should not exceed 5–15 percent, the pulp is first thickened, which reduces the water content by a factor of 1.5–2, and then dehydrated, which results in an almost total removal of water. When dredges are used to work gravel deposits containing sand, the content of the material in the pulp is 3–6 percent by volume. Prior to screening and hydraulic separation, the sand in the pulp is thickened to a concentration of 10–15 percent.

V. V. BERDUS