Characterisation of graphite by automated mineral liberation analysis

Abstract

The beneficiation of graphite is very costly and energy intensive and can necessitate multiple processing steps, often including flotation. Products have to satisfy very stringent quality criteria. To decrease beneficiation costs, a careful characterisation of feed and concentrate materials is needed. This study elucidates the additional benefit of methods of automated SEM-based image analysis, such as mineral liberation analysis (MLA), in addition to ‘traditional’ methods [optical microscopy and X-ray powder diffraction (XRD)] for the analyses of graphite raw materials and processing products. Owing to the physical and chemical properties of the mineral graphite, samples require delicate sample preparation as well as particular backscattered electron (BSE) imaging calibration for automated image analysis. These are illustrated in this study. The results illustrate that SEM-based image analysis of graphite feeds and concentrates can provide accurate and reliable information for the graphite beneficiation process. This applies to both mineralogical characteristics and process relevant parameters.

Keywords:

• Graphite
• Beneficiation
• SEM-based image analysis
• Modal mineralogy
• Mineral association
• Liberation
• MLA

Acknowledgement

The authors would like to acknowledge the provision of sample material for this study as well as additional analyses by the AMG Mining AG (formerly Graphit Kropfmühl AG). Fiona Reiser from AMG Mining AG is thanked for providing further information on the samples and related literature as well as data of comparing analytical techniques and kindly reviewing of this study. Authors thank Bernhard Schulz from the Department of Mineralogy (TU Bergakademie Freiberg) for support during the MLA investigation and Martin Rudolph (Helmholtz Institute Freiberg for Resource Technology) as well as Annet Kästner (Department of Mechanical Process Engineering and Mineral Processing, TU Bergakademie Freiberg) for the realisation of the laser diffraction analysis. Robert Möckel (Helmholtz Institute Freiberg for Resource Technology) is thanked for conducting the quantitative XRD analysis. The authors thank an anonymous reviewer for thorough review. Special thanks are due to William John Rankin (Co-editor editor) for his editorial handling and helpful comments to improve the submitted version of the manuscript. Discussions and support by the researchers of the Nordic Researcher Network on Process Mineralogy and Geometallurgy (ProMinNET) is gratefully acknowledged.