Beneficiation and Evaluation of Mutaka kaolin
Kaolin is a soft, white, plastic clay consisting principally of kaolinite, which is a well ordered hydrated aluminium silicate Al2Si2O5(OH)4. It is formed by the alteration of granitoid rocks, mainly feldspar and muscovite. Naturally, kaolin occurs with impurities, which have to be removed for most of its commercial application, particularly in the paper filling and coating applications. The two principal objectives of kaolin beneficiation are the removal of impurities and production of a desired particle size distribution. Mineralogically and chemically, kaolins contain quartz as the major impurity and iron (in form of Fe2O3) and titania (in form of anatase) as minor impurities (Carty, et al 1998; Murray and Keller, 1993; Pinheiro, et al, 2005). The presence of impurities, particularly iron and titania bearing minerals, imparts colour to kaolin (low brightness) and are detrimental in most kaolin applications. Kaolin beneficiation & processing
Basically, two different processes are used in beneficiating of kaolin – a dry process and a wet process. The dry process is the simpler and less expensive of the two but yields a lower quality product. In the dry process, kaolin is crushed, dried, pulverized and air floated. The air floating process removes most of the coarse particles from the fine ones, but in order to really obtain a
high quality product, the wet process must be used. Consequently, the latter process was used in the present work.Kaolin beneficiation & processing
A combination of wet screening and hydro cycloning was used. The 100 kg sample with size fractions less than 2.36 mm was attrition scrubbed to make it ready for the hydro cyclone test rig. The fraction was fed into a receiving cone of a laboratory 2-inch stub hydro cyclone test rig and water was added to make a pulp of 16% solids. The pulp was left to run for ten minutes to allow for scrubbing action on the material before collection of the cyclone products. The pressure was set to 0.21 MPa (30 Psi) and the spigot was 6.3 mm. The vortex finder was set to 11.1 mm. The under size from the screening operation was fed into a hydro classifier (rougher-stage). From its overflow, a product rich in kaolin, was collected and fed to another cleaner hydro classifier. There it was further processed in order to obtain a cleaner product. The underflow fraction normally consists of sand and other heavy mineral impurities but also contains an appreciable amount of kaolin. In order to recover this kaolin it was fed into a scavenger which completes the kaolin extraction from the waste. The extracted kaolin from the scavenger was fed into the rougher hydro classifier stage together with the underflow fraction from the cleaner stage.Kaolin beneficiation & processing