Abstract
Votorantim Metais — CBA’s alumina refinery produces 0.9 Mtpa of SGA. Recently the particle size of the rod-ball mill product has suffered an increase of 35% in the +590 μm fraction. This results from higher grinding charge and variation of bauxite blend, with a rise in proportion of higher Work Index bauxite. Additionally, the top entry design digesters favor low residence time, compromising digestion efficiency even further. This increases residue generation with alumina and caustic loss.
The solution studied was a Closed Grinding Circuit, which aims to control particle size by sieving the mill product at 590 μm, returning the oversize to grinding. This improves digestion efficiency, since smaller particles react faster and suffer less shortcircuits.
This work describes the study and estimated gains, along with tests conducted to prove the residence time distribution and analyze the effects of residence time and particle size in digestion efficiency.
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References
J. Woloshyn et al., Digester Design Using CFD, Light Metals (2006), 350–355.
O. Levenspiel, Chemical Reaction Engineering (1999), 3rd Edition, 1998.
B. Pei et al., Reaction Kinetics of Weipa Monohydrate Bauxite, 6th Alumina Quality Workshop (2002), 122–127.
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© 2014 TMS (The Minerals, Metals & Materials Society)
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Meira, J.M., Junior, R.S. (2014). Increasing Extraction Efficiency Using a Closed Grinding Circuit. In: Grandfield, J. (eds) Light Metals 2014. Springer, Cham. https://doi.org/10.1007/978-3-319-48144-9_9
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DOI: https://doi.org/10.1007/978-3-319-48144-9_9
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-48590-4
Online ISBN: 978-3-319-48144-9
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