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A Knelson concentrator is a type of gravity concentration apparatus; it is predominantly used in the gold mining industry. The apparatus is used for the recovery of fine particles of free gold, which is, the gold that does not require gold cyanidation for recovery.
The Knelson concentrator utilizes the principles of [centrifuge] to enhance the gravitational force experienced by feed particles, which aids in the separation process based on particle density. The key components of the unit include: a cone shaped "concentrate" bowl, which is rotated at high speed by an electric motor and a pressurized water jacket encompasses the bowl. Feed material, typically from a ball mill discharge or cyclone underflow bleed, is fed as a slurry toward the center of the bowl from above. The feed slurry contacts the base plate of the vessel and, due to its rotation, is thrust outward. The outer extremities of the concentrated bowl house a series of ribs, and between each pair of ribs is a groove. During operation the lighter material flows upward over the grooves and the heavy mineral particles (usually of economic value) becomes trapped within them. Pressurized water is injected through a series of tangential water inlets along the perimeter of each groove to maintain a fluidized bed of particles in which heavy mineral particles can be efficiently concentrated. The Knelson concentrator typically operates as a batch process, with lighter [gangue] material being continuously discharged via overflow and a heavy mineral concentrate periodically removed by flushing the bowl with water.
The first Knelson concentrator was developed by Byron Knelson in 1978.
Knelson concentrators are used in a number of gold mines operated by AngloGold Ashanti, like Geita, Sunrise Dam and the Serra Grande Gold Mine as well as Barrick's Bulyanhulu Gold Mine, in 2014 AIM listed Anglo Asian Mining fitted a Knelson concentrator at their flagship Gedabek mine in Western Azerbaijan.