Master of Engineering - Research
Faculty of Engineering
Bishop, Damon, Minerals processing reactions induced by electrical discharge assisted mechanical milling, Master of Engineering - Research thesis, Faculty of Engineering, University of Wollongong, 2009. http://ro.uow.edu.au/theses/3552
Spark Milling (Electrical Discharge Assisted Mechanical Milling) utilises a novel chemical reactor which combines the features of mechanical milling and transferred-arc plasma processing. This combination of techniques has shown great promise in inducement of chemical reactions whilst simultaneously controlling powder morphology. During synthesis reactions, orders of magnitude increases in reaction rates are experienced compared to mechanical milling in the absence of a plasma arc.
Recent work has extended the application of Spark Milling to the inducement of reduction reactions in a commercial grade mineral concentrate. This has identified the need to undertake further experimentation. Firstly, to assess the possibility of inducing other minerals processing reactions that might have commercial value and secondly to characterise the effect that variation of physical and electrical set points on the Spark Mill has on the processing conditions within the reactor. The two groups of materials selected for this study are basic Steelmaking fluxes (carbonate minerals) and metallurgical coke.
This research demonstrates the ability of Spark Milling to induce calcination of the raw Steelmaking fluxes limestone and dolomite as well as the ability of Spark Milling to induce graphitisation of metallurgical coke. Phase changes which occur during these reactions are identified using XRD (X-ray Diffraction) and selected microstructures are also characterised by using SEM (Scanning Electron Microscopy). In addition, the average crystal plane height of coke processed by this method is calculated for coke samples Spark Milled over a range of set points and subsequently used to quantify the impact of these set points and to show that the temperatures experienced during Spark Milling can be greater than 1873K (1600ºC).
This thesis report provides an overview of previous Spark Milling work as well as modern methods of calcination of raw Steelmaking fluxes. An explanation of the mechanism of coke graphitisation is also provided. Following this, the experimental method and results from laboratory work are presented. These results are analysed and discussed with a view to understanding their mechanisms, relevance and limitations with regard to the use of Spark Milling in industry as a bulk minerals processing reactor.