Zu Fragen der Charakterisierung, Aufbereitung und Veredlung von natürlichen Grafiten
Research output: Thesis › Doctoral Thesis
Due to special functional properties graphite belongs to the group of industrial minerals and is used in a wide range of industrial applications. Austria has graphite mining activities and numerous resources of both microcrystalline and macrocrystalline graphite. Within this dissertation (i) Austrian resources were explored, (ii) a methodology for the characterisation of graphite was developed and (iii) innovative graphite processing methods were tested by experimental processing studies. Exploration work in the claims "Maria" and "Rudolf" of Grafitbergbau Kaisersberg Ges.m.b.H. is described in detail. The exploration work in the Kaisersberg mine predicts a continuation of graphite lenses into the depth and the presence of 52,800 t of raw graphite. 130,000 t of raw graphite are estimated for the resource Zettlitz. According to the classification of the International Committee for Coal and Organic Petrology (ICCP) various types of graphite were classified by X-ray diffractometry, and Raman spectroscopy is introduced as a practical routine to distinguish between semi-graphite and graphite. The evaluation of Raman spectra with the area ratio R2 = 0.4 and the half width at half maximum of the graphite band GHWHM = 13.0 cm-1 discriminates those two types of graphite. Kaisersberger graphite is identified as a representative for semi-graphite. The experimental investigations, examining the use of two innovative mineral processing methods, include electrodynamic fragmentation as a wet comminution method and triboelectrostatic belt sepa-ration as a dry sorting method. Comparative comminution studies using conventional comminution and electrodynamic fragmentation were performed on raw graphite from Mozambique. The investigations on electrodynamic fragmentation were carried out on the discontinuously operated Selfrag Lab and those for conventional comminution by crushing and grinding units. The results from comparative investigations according to the energy-optimized comminution sequence revealed significant differences with respect to the liberation behaviour of graphite flakes and the specific energy input. The electrodynamic fragmentation shows earlier liberation of graphite flakes in the particle size range > 100 microns compared to conventional comminution, but is accompanied by a significantly higher specific energy input. Triboelectrostatic belt separation represents a promising, dry sorting method for processing of minerals and waste materials. The suitability for processing microcrystalline graphite from Kaisersberg and macrocrystalline graphite from Tanzania was tested at the triboelectrostatic ST belt separator M6. The results indicate an opposite charging of macrocrystalline graphite particles in comparison to gangue minerals. Enrichment effects are clearly identified, justifying a recommendation to continue research activities. With the current state of knowledge, it is conceivable to use this method in graphite pre concentration, not (yet) for the production of marketable concentrates. Experiments with microcrystalline graphite did not give satisfactory separation results. Comparative flotation experiments in the laboratory and on pilot scale showed a significantly better selectivity.
|Translated title of the contribution||On the characterisation and processing of natural graphite|
|Publication status||Published - 2018|