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Dec 31, 2020Keywords:
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Main Article Content
Assessment of the Performance of Grinding Circuit for Buzwagi Gold Mine
Abstract
It had been reported by the managementof Buzwagi Gold Mine (BGM)thatgrinding circuit was designed to produce final product size of 125 μm, which hadnot been achieved for a long period of time under both, low to normal (i.e. 450-600t/h) and high (i.e. > 650 t/h) throughputs.Also, the performancebehaviourof thecircuit had not been reviewed after long time of operation. Hence, an evaluationstudy was conductedin order to recommendimprovementin mine operations. Thestudy was realized through threecircuit survey campaigns and laboratoryexperimentations. From the surveys, size distributions and solids contents of thesamples were determined for all selected circuit streams. Furthermore,grindabilityand work indices of the ores were determined through standard Bond tests. Thestandard Bond tests data revealed increased Bond work indices for currently treatedores vs. those during design, indicating change in ore hardness over the years.Consequently, a periodic review of the ore blends was recommended as hardermaterial requires more energy,which increases operationcosts. Such reviews couldhelp in establishing better ore blending and optimum throughput for existing plantdesign. Furthermore, the SAG mill circuit indicated varying feed sizes (i.e.xF,80=102 to 185 mm) which could be rectified by closer monitoring and control of ratiosfor theSemi-Autogenous Grinding (SAG)mill feeders drawing the ore from thestockpile. The ball mill performance was poorasindicated by only 5-9 % of<125μ m (target product) in the discharge. This had a direct impact onhydrocyclones, where significantly poor performance indicators were observed;coarser overflow xP,80: >200 μ m as well as cutsize, xT: >200 μ m. Also, the Bondefficiency factors in the range of 48-61 % were obtained, indicating an inefficientoperation that could only achieve targets by lowering the current throughput.Hence, an optimization study of the existing design through computer modelling andsimulation isrecommended.Through simulation ofmulti-effects, a deeperunderstanding of the efficiency problems for the BGM grinding will be facilitatedand also may provide possible solutions.
