The Industry rquires specific quality bauxite for both non metallurgical and metallurgical applications.R&D programme has been taken up to upgrade bauxite for its possible utilisation for non metallurgical application.Growth in the markets for raw bauxite in direct non-metallurgical applications is expected to be 3-4% a year, in such products as slag conditioners, cement and alumina-based chemicals.
Demand for non-metallurgical Bauxite has continued to increase and a set of applications have been developed. These include refractories, abrasives (including the recently development proppants), high aluminium cements, aluminium chemicals, activated bauxite and alumina.Other uses include filters and pigments for plastics and elastomers; special calcined aluminas for ceramics, refractories, abrasives, soft burned calcined aluminas, hard burned calcined aluminas to produce alumina cements and calcium-aluminate cements.Calcined bauxite (following iron reduction) is produced by calcining (heating) high alumina containing bauxite (55% to 60% Al2O3) at at temperatures ranging from 900°C to 1200°C for 50 to 60 minutes.
Calcination removes the inert moisture and increases the alumina content by converting tri-hydrate and mono-hydrate (gibbsite and boehmite) into anhydrous aluminium oxide by expulsion of water of crystallisation – similar to a laboratory “Loss of Ignition” (LOI) test.http://www.australianbauxite.com.au/Non-Metallurgical-Bauxite.htm
Iron removal of bauxite deposit is the objective of researchers for two main reasons: low iron bauxite can successfully applied in refractory industries
and reducing bauxite iron content before Bayer process can relieved the environmental concerns related to red mud disposal .Magnetic separation is one of the most common physical beneficiation methods that
studied for iron removal of bauxite deposits.
Demand for non-metallurgical Bauxite has continued to increase and a set of applications have been developed. These include refractories, abrasives (including the recently development proppants), high aluminium cements, aluminium chemicals, activated bauxite and alumina.Other uses include filters and pigments for plastics and elastomers; special calcined aluminas for ceramics, refractories, abrasives, soft burned calcined aluminas, hard burned calcined aluminas to produce alumina cements and calcium-aluminate cements.Calcined bauxite (following iron reduction) is produced by calcining (heating) high alumina containing bauxite (55% to 60% Al2O3) at at temperatures ranging from 900°C to 1200°C for 50 to 60 minutes.
Calcination removes the inert moisture and increases the alumina content by converting tri-hydrate and mono-hydrate (gibbsite and boehmite) into anhydrous aluminium oxide by expulsion of water of crystallisation – similar to a laboratory “Loss of Ignition” (LOI) test.http://www.australianbauxite.com.au/Non-Metallurgical-Bauxite.htm
A process to remove iron from bauxite ore is described in which the ore is first finely crushed, calcined, and contacted with a reducing gas to convert iron present as very weakly magnetic goethite or hematite to magnetite or elemental iron. The ore is then passed through a magnetic separator to remove the iron. A 1.5% Fe2O3 product was produced from an Alabama bauxite ore analyzing 2.7% Fe2O3. Calcination and H2 reduction at 800°C and single-pass magnetic separation at 4000 Gs were used. There was 95% recovery of the iron-free bauxite starting material, and the magnetic fraction contained 21% Fe2O3.http://www.sciencedirect.com/science/article/pii/030175169190028H
Various techniques for removal of iron oxide are wet high intensity magnetic separation (WHIMS), leaching with HCl, dry and wet screening and sieving, roasting etc. JNARDDC has carried out extensive work on Indian bauxite and laterite.
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