Abstract
Energy consumption and pollution are current strategic issues that need to be addressed in the mining industry. Both have an economic and environmental impact on production, so their optimization, control, and mitigation are, at the very least, mandatory. Although rod milling has fallen into disuse in recent decades, some companies still use it in their processing plants. This is due to the ability of rod milling to reduce particle size while avoiding overgrinding. In this study, a material that is particularly difficult to characterize was used to study how to control rod-milling particle size distribution product: potash ore, which is deliquescent and soluble under certain conditions. A laboratory-scale tumbling rod mill was designed for this study, and six operative parameters were tested and analyzed in order to detect the main influences on the mill product, attending to material requirements for further processes such as recirculation load or froth flotation for beneficiation. Although the rotational speed of the mill is the parameter that shows the greatest reduction in energy consumption, reaching almost 40% improvement in specific energy applied to the particles, it is not possible to control particle size reduction ratio. However, when a low percentage of grinding media is used, it reduces around 25% of the energy used and, in turn, reduces the amount of overgrinding (40% reduction in the F300 control parameter, for example), which is a strategic objective of this study. In addition, by controlling other process parameters, such as slurry density or lifter geometry, energy consumption and its subsequent saving and pollution can be controlled, depending on process plant requirements.
Highlights
Used in conventional processing plant flowsheets, tumbling mills are predominant in mineral processing operations
Each batch of experiments was carried out under the same operating conditions, except slurry density, which was varied from 50% to 65%
Slurry density is the best operating condition for controlling particle size distribution, observed in the finer generation control by means of the 60% reduction for the F300 parameter (Figure 9B), from 47% to 20% (Table 5), but with a relatively low 10% energy reduction ratio (Figure 9A)
Summary
Used in conventional processing plant flowsheets, tumbling mills are predominant in mineral processing operations They are responsible for achieving the key objective in this field, which is to separate ore from gangue. In the milling stage, in order to avoid the generation of finer particles, the most desirable effect should be impact and compression, rather abrasion and shear, as occurs in ball mills [2]. In this respect, rod mills generate relatively fewer of these finer particles compared to ball milling under exactly the same operating conditions, i.e., to obtain the same particle size distribution product, the operating conditions should be varied [3]. Such mills have throughput and scalability problems [1]
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