Beneficiation Studies on Low Grade Chromite Ores using Multi Gravity Separator

Chromite is the most important mineral of chromium and is essential raw material for the production of
special steel and ferrochrome alloys. From the mineral conservation point of view it is necessary to
maximize the utilization of low grade ores and minimize the high grade ore consumption. Generally low
grade and finely disseminated ores need fine grinding, posing problem in recovering of chromium values.
In many cases the finely ground feed does respond well to process involving simple gravitational force
for recovering the valuable minerals, hence processing under higher G-force may be worth investigating.
Multi gravity separator (MGS) is such an equipment which uses enhanced gravitational force for
processing ultrafine particles. In the present study, a laboratory Mozley MGS was used for upgrading a
low grade chromite ore assaying 26.8% Cr2O3. The chromite ore under study contained gangue minerals
such as olivine, serpentine, chrysotile and magnetite. Liberation study on different size fractions reveals
that 80% liberation occurs at a size 150μm. Considering the mineralogical information, as received ore
was ground separately to three top sizes, namely -250μm, -150μm and -75μm respectively and were
subjected to concentration using MGS separately. The other parameters such as drum speed and wash
water flow rate were also varied to get the optimum condition with respect to grade and recovery. Under
the optimum operating conditions, low grade chromite sample was upgraded to 41.1% Cr2O3 with 62%
recovery using MGS.