sluice(redirected from Kokers)
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in ore dressing, an inclined, rectangular trough, usually with a rough bottom of napped fabric covered with a pattern of wood planks, corrugated rubber, or the like, designed for gravity concentration of minerals. As the pulp passes through the sluice, the particles separate into layers according to their density and grain size; the heavier minerals settle to the bottom and are held by the friction created by the roughness and the bottom pattern. The vortices that form promote selective concentration. After the material has accumulated, the sluice is rinsed out by washing the concentrate into a separate receptacle with a powerful stream of water.
A distinction is made between fixed and band-type sluices. Fixed hydraulic sluices are designed to process large amounts of material. They are made of from six to eight consecutively laid boards several meters long with a slope of 0.03–0.06. They can extract 70–80 percent of the tin from ore concentrates containing 15–30 percent SnO2; the extraction of gold is 40–60 percent. Other sluicing devices, cradles, and trommels are used for processing crude concentrates.
Band-type sluices consist of a continuous rubberized band, the upper part of which moves against the stream of pulp. The lighter fraction is unloaded in the lower section, and the heavier fraction is washed from the upper section of the band by a sprinkler. A band-type sluice 3 m long and 1.5 m wide has a productivity of 5 cu m/hr and can extract 92–95 percent of the gold in an ore.
Automatic multideck movable sluices have been in use since the 1970’s. The type used in the USSR has five decks arranged in parallel above one another in tiers. The feed is stopped automatically every 4 min, the decks are tipped to an angle of 45°, and a petcock is opened for 1 min for rinsing. The use of vibration in sluices increases productivity.
REFERENCESpravochnikpo obogashcheniiu rud, vol. 2, part 1. Moscow, 1974.
L. A. BARSKII