A survey on troubleshooting of closed-circuit grinding system

ABSTRACT

An industrial ball mill operating in closed-circuit with hydrocyclones was studied by five sampling surveys. The aim of the present study was to optimise operating parameters (i.e. charge volume, make-up ball size regime, slurry mean residence time, number of hydrocyclones in operation and hydrocyclone’s feed solids content (S_f)) with respect to increasing throughout from 225 to 300 tons per hour (tph). The obtained results showed that increasing charge volume from 32 to 39% led to producing approximately 9% finer product size (P₈₀). Binary ball size regime rather than using mono-sized balls resulted in reduction of the P₈₀ relatively 5%. The S_f was identified as the most effective parameter on grinding efficiency. The cut-size plunged dramatically from 130 to 90 μm by reduction of S_f from 54 to 48%. Finally, it was concluded that the capacity of grinding circuit could be practically increased to 300 tph if all relevant parameters fell into the optimised ranges.

GRAPHICAL ABSTRACT

RÉSUMÉ

On a étudié un broyeur à boulets industriel fonctionnant en circuit fermé avec des hydrocyclones, au moyen de cinq relevés d’échantillonnage. Le but de la présente étude consistait à optimiser les paramètres de service (c’est-à-dire le volume de la charge, l’appoint du régime de taille de boulets, le temps de séjour moyen du coulis, le nombre d’hydrocylones en service et la teneur en solides (S_f) de l’alimentation des hydrocyclones) en vue de l’augmentation du débit de 225 à 300 t/h. Les résultats obtenus ont montré que l’augmentation du volume de la charge de 32% à 39% menait à la production d’une taille plus fine du produit (P₈₀) par approximativement 9%. Un régime binaire de taille de boulets plutôt que l’utilisation de boulets à taille unique avait pour résultat une réduction du P₈₀ d’environ 5%. On a identifié le S_f comme le paramètre le plus efficace sur le rendement de broyage. La taille de coupe a plongé dramatiquement de 130 μm à 90 μm en réduisant le S_f de 54% à 48%. Finalement, on a conclu qu’on pouvait augmenter pratiquement la capacité du circuit de broyage à 300 t/h, si tous les paramètres pertinents se situaient dans la gamme optimale.

KEYWORDS:

• Make-up ball size regime
• closed-circuit grinding
• hydrocyclone
• throughput
• cut-size (d₅₀)

Acknowledgements

The author would like to express his appreciation to National Iranian Copper Industries Company (NICICo.) for supporting this research. Special thanks are also extended to the metallurgy and R&D personnel for their continued assistances.

Disclosure statement

No potential conflict of interest was reported by the author.

Notes on contributor

Ahmad Hassanzadeh is a well-trained process engineer. He studied Mining Engineering at Sahand University of Technology and proceeded to Mineral Processing Engineering at Shahid Bahonar University of Kerman. He gained numerous experiences on grinding, classification, leaching and flotation working at National Iranian Copper Industries Company (NICICO.). Devoting himself to the science, he started his Ph.D. at Istanbul Technical University and continued as an exchangeresearcher in Montan University of Leoben, Austria. Currently, he works actively in Department of Processing at Helmholtz-Zentrum Dresden-Rossendorf, Germany.