Abstract
Pelletisation of Indian chromite ores is challenging due to their higher Cr/Fe ratio. Attaining the required strength of fired chromite pellets, even after high temperature firing, is difficult due to their refractory nature. To improve the pellet strength, laboratory studies were carried out with activated bentonite in place of normal bentonite, which is used as a binder in pelletisation. A remarkable improvement in both green and fired pellet properties was observed with the use of activated bentonite. Laboratory results were also validated in a plant scale trial conducted in 0·1 Mtpa capacity chromite pellet plant. Plant scale trials resulted in improving the green pellet strength by ∼70% and dry pellet strength by ∼45%. Mean strength of the fired chromite pellets increased by 65% from 64 to 107 kg/pellet and variation in fired pellet strength reduced from 30–100 to 90–120 kg/pellet. The role of activated bentonite in improving the strength has been examined through optical and electron microscopic studies. The amount and distribution of silicate melt were found to play a vital role in controlling the porosity and pore distribution and thereby the pellet strength.
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