Abstract
M.Tech. (Chemical Engineering)
The exploration of fluorspar ore in mining results in large amount of unrecovered valuable products found associated with fluorspar in the ore, representing 60% of the run of mine. Several million tons of valuable minerals are discarded every year into tailings ponds, incurring disposal costs, loss of potential company revenue and environmental pollution. This study was undertaken to identify the valuable mineral in the fluorspar tails with an aim of recovering such minerals, thus contributing to an ongoing treatment of waste minerals.
A representative sample was received from Vergenoeg Mine, South Africa, in 2014. Characterisation of the sample was conducted to determine physical, chemical and mineralogical properties. Particle size distribution analysis using Micratrac Particle Size Analyser showed that the sample was of fine texture, with 80% passing 120μm. Chemical analysis using X-ray fluorescent spectrometer (XRF) showed that the major element was Fe assaying 48.9þ. Major gangue minerals were SiO2 (16.8%) and minor presence of CaO (3.8%) and F (2.25%) while all other components were reported at <1%. The metal distribution showed that iron was concentrating in the finer size range with 33.59þ reported in the +150μm and 52.09þ in the <38μm size fraction. The mineral phase test using X-ray powder diffraction (XRD) showed that iron was abundantly (>50%) found in the form of hematite while minor presence (3-10%) of iron in a form of goethite and magnetite was observed. The Quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) results showed that the largest portion of iron oxides (12.04wt%) occurred between the 40-50μm particle size range and the majority of Fe-oxide in the sample occurred between 10-70μm size range. Mineral liberation analysis showed that 81% of the iron oxide is liberated, while 16% and 3% were middling and locked Fe-oxide respectively. The locked particles were found to be in the <20μm size range. From the characterization results the sample was classed as low grade iron oxide and reverse cationic flotation was selected as the best concentration method.
This study used reverse cationic flotation to concentrate the iron, whereby two types of depressants and amine collectors were studied. The objective was to concentrate the low grade iron into quality standards required for blast furnace feed; ≥63þ, alumina to silica ratio of ≤1% with alumina <2%. The collectors investigated were the primary mono-amine (Dodecylamine) and tertiary amine (Betacol 373). The investigated depressants were soluble starch and a dextrin (Betachem 30D). The flotation parameters investigated were collector dosage, depressant dosage, pH, solids content, conditioning time, agitation speed, air rate and...