Beneficiation Process of Kaolinite Clay: Kaolin Processing

Kaolin is an important industrial mineral having numerous uses and requiring various market specifications. High brightness kaolin clays represent a continuing challenge to the producer. An advancement in this field of Kaolinite Clay Beneficiation has been a patented process developed by Minerals and Chemicals Philipp Corporation and termed Ultra Flotation. Contaminants that are 1 micron and finer are separated from a feed which is virtually 100% finer than 3 microns and 48% finer than 0.5 microns. Removal of the contaminations by conventional froth flotation has never been commercially successful previously.

Ultra Flotation is a new concept of mineral separation that extends the flotation principle to the submicron range well beyond its present limits. The key to Ultraflotation is the increased surface available for floating fine particles by the addition of a suitable carrier mineral usually in the —325 mesh range. In conventional flotation air bubbles alone do the job. In Ultra Flotation the reagent loaded slime particles to be floated attach themselves to the carrier mineral and are readily floated as a froth product.

Beneficiation of Kaolin Clay

Beneficiation Process of Kaolinite Clay and Kaolin Processing

Production advantages are that the process uses conventional equipment and ordinary flotation reagents. Minerals such as calcite, fluorspar, silica, barite, sulphur, etc., are possible carriers.

The Flowsheet

The first step in processing kaolin clay is to slurry it in a blunger with water and a dispersing agent. Degritting using screens, cyclones and hydro-classifiers is the next step. The minus 325 mesh degritted clay is fractionated using centrifugal sizers to produce the fine fractions demanded by the various markets. Bleaching, filtering, and drying complete the general processing steps.Kaolin Clay Ore Processing Method

The flowsheet in this study follows the general steps outlined above but Ultraflotation is included to produce a high brightness product from the fine fraction. Bleaching alone will not produce the desired brightness.

The Ultraflotation feed (90-94% finer than 2 microns) is stored in a holding agitator and then pumped through a density and flow control apparatus to three Conditioners arranged in series. The mineral carrier (ground limestone, 200-400 lbs. per ton) and ammonium sulphate (4-8 lbs. per ton) are added to the first conditioner. The discharge from the final conditioner containing 20% solids is fed directly to a six cell High Energy Conditioner. An emulsion of tall oil (3-5 lbs. per ton), neutral calcium petronate (3-5 lbs. per ton), aqua ammonia (2-4 lbs. per ton), and water are added to the first cell of the high energy conditioner. The conditioned pulp has a pH of 9.0. Fuel oil (6-10 lbs. per ton) is added to the fourth conditioning cell.

A total of 24 “Sub-A” Flotation Machines (cell-to-cell design) are used for the flotation separation. The conditioned pulp is first floated in a six-cell machine and then this froth, which contains the mineral carrier and color contaminants, is successively refloated in stages using a six-cell machine for the first stage and four-cell machines for the second and third cleaning stages. Dilution water is added to each stage of flotation to maintain dilute pulp conditions. The rougher tailings and reflotation tailings are combined and scavenged of any additional contaminant in a 4-cell “Sub-A” Flotation Machine. The tailings from this final flotation step represents the beneficiated kaolin and is pumped to a thickener. Sulphurous acid is added to the pump to produce a pH of 2.8 to 3.0 for flocculation.Kaolinite clay

The froth products from the reflotation and scavenging steps are combined and impounded. The principal contaminant removed in the Ultraflotation process is a titaniferous mineral which does not bleach and imparts a yellowish-brown cast to the finished kaolin if present. Typical results of the Ultra-flotation separation are shown in the table.

In brief, the thickened kaolin from the thickener is bleached, filtered, dispersed and dried. The Ultra White 90 product is then shipped in bulk or bags or as a 70% slurry in tank cars.

The Fe2O3 content, which affects the brightness of the clays is controlled by careful mining and by the reducing bleach using zinc hydrosulphite. The ferric iron is reduced to the ferrous state and the slip washed to remove soluble salts.

In general, Ultraflotation enhances the brightness of the kaolin by more than 5%. By incorporating bleaching for additional color improvement, the beneficiated product (Ultra White 90) has a brightness of 90-92. Brightness is a measurement of light reflectance by a standard method of the Technical Association of the Pulp and Paper Industry.

PROPERTIES AND USES OF ULTRA WHITE 90 CLAY

Brightness (G.E. brightness range)…………………………………………………..90-92%
Particle size percent finer than 2 microns…………………………………………90-94%
Maximum screen residue wet, 325 mesh…………………………………………..0.005%
Refractive index…………………………………………………………………………….1.56%
Specific gravity………………………………………………………………………………2.58
pH range………………………………………………………………………………………6.3-7.0

Ultra White 90 is a pre-dispersed premium clay that has applications in the filling of high quality papers to reduce TiO2 requirement for brightness and in coatings for high brightness, easier finishing, gloss improvements and ink holdout. It is available in bulk, slurry, or bags and is produced by the Ultra-flotation process developed by Minerals & Chemicals Philipp Corporation.

how is kaolin processed

how is kaolin processed


Source: This article is a reproduction of an excerpt of “In the Public Domain” documents held in 911Metallurgy Corp’s private library.

By |2017-03-29T16:34:08+00:00May 24th, 2016|Categories: Flowsheets & Flowcharts|Tags: , , |Comments Off on Beneficiation Process of Kaolinite Clay: Kaolin Processing

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