Episode 10 – Understanding Mineralogy in Regrind and Cleaner CircuitsIn the tenth episode of the Mineralogy Matters series, Dr. Chris Greet, Global Minerals Processing Expert, discusses the role of mineralogy in the design of regrind and cleaner circuits. The regrind feed, composed largely of sulphide minerals, contains only limited amounts of non-sulphide gangue. Much of this gangue is either coarse and value-deficient, or very fine liberated particles carried into the circuit by entrainment. |
To understand how this feed should be treated, the first piece of mineralogical data required is the target grind size. This parameter defines the level of liberation needed to separate valuable sulphides (such as chalcopyrite) from sulphide gangue (such as pyrite). Liberation studies provide this information by showing how minerals are locked together across different size ranges, and from this, we can determine the grind size required to achieve at least 80% liberation of the valuable mineral from the gangue.
Modal analysis also gives indications about wear. In regrind feeds with high sulphide content, the dominant wear mechanism is corrosion, making high-chrome or ceramic grinding media the preferred choice.
The high sulphide content strongly influences pulp and surface chemistry. An understanding of the regrind feed provides clear indications of the chemistry of the pulp leaving the regrind mill and how this will affect flotation behavior in the first and subsequent cleaner flotation stages. For example, a high pyrite feed will invariably lead to a pulp devoid of oxygen – conditions that are ideal for pyrite flotation, resulting in lower concentrate grades and recoveries.
The mineralogy also provides an indication of the ability to produce a saleable concentrate and, from this, the potential profitability of the process.
Finally, mineralogical analysis provides insights into the deportment of penalty elements (such as arsenic, antimony, mercury, or bismuth), indicating whether they are associated with sulphide gangue or occur in solid solution within valuable minerals. This knowledge gives metallurgists essential clues on how best to remove these species from the concentrate.
A clear understanding of the mineralogy of the regrind feed is therefore essential. It not only defines the grind size required for effective liberation, but also provides guidance on wear, pulp chemistry, concentrate quality, and the management of penalty elements – factors that directly affect the overall profitability of the process.
Key Takeaways – Understanding Mineralogy in Regrind and Cleaner Circuits