N.W. Johnson

Investigating fine galena recovery problems in the lead circuit of mount isa mines lead/zinc concentrator. Part 1 : Grinding media effects

A plant survey was carried out on the lead secondary rougher and scavenger banks of the Lead/Zinc Concentrator of Mount Isa Mines Limited. Sizing analysis of the survey samples demonstrated that a major limiting factor to overall lead recovery in this section of the plant was the diminished recovery of the fine galena in the minus 5 microns particle size fraction. Batch flotation experiments were carried out on a plant sample of lead secondary rougher feed and a sample of rod mill feed ore. Mineral recovery-size data for these tests showed similar fine galena flotation behaviour to that observed in the plant. Increased collector addition did not improve either the maximum recovery or the flotation rate constant of the fine galena but did reduce the selectivity of galena against sphalerite. Changing of the grinding media used for the ore sample from a high carbon steel to a high chromium alloy steel resulted in a significant increase in the maximum recovery and flotation rate constant of the fine galena. EDTA (ethylene diaminetetraacetic) extractable iron measured for the high carbon steel media were similar in magnitude to those measured within the plant and were higher than those measured for the high chromium alloy steel media. The increased surface concentration of hydrophilic layers of oxidised iron species on the fine galena was a likely reason for their diminished flotation behaviour both in the laboratory and in the plant.

Characterization and treatment of heavy medium slimes in the Mt. Isa mines lead-zinc concentrator

Abstract The fundamental properties of the slime fraction of the run-of-mine ore of a lead-zinc concentrator have been studied. These have been compared to the fundamental properties of the primary grinding circuit product and used to explain differences in flotation response during standard bench scale flotation tests. Inherent difficulties in treating the slime fraction are highlighted. The slimes fraction contained sphalerite which was highly activated as a result of extensive oxidation of the galena. The rate of flotation of galena in the slimes fraction was retarded, again due to oxidation of the galena. Sphalerite activation was best countered by additions of zinc sulphate. It was also found that during combined treatment of the slimes fraction and the primary grinding circuit product, interaction effects resulted in deleterious flotation response. As a consequence separate treatment of the slimes fraction was tested in the concentrator. This showed that improvements in lead concentrate grades were possible by this technique.

Methods to increase fine mineral recovery in the Mount Isa Mines lead/zinc concentrator☆

Abstract Methods to increase the flotation rate of fine (-10 μm) galena relative to sphalerite contained in a lead process stream have been examined. These included separate conditioning and flotation of the fine and coarse particles, both in the presence and absence of High Intensity Conditioning (HIC). Size separation before conditioning and flotation was by conventional hydrocyclone, producing overflow (p8o =10 μm) and underflow, (p80 =80 μm) streams. Flotation of the separately treated fine particles was compared to that of the fine particles in the unclassified stream. The parameter examined was collector concentration. The rate o f galena flotation in the overflow stream was found to be inferior relative to that in the undertow stream, even at high collector concentrations to the overflow stream. However, galena flotation in the overflow stream was more selective against sphalerite than in the undertow stream. This was ascribed to greater levels of galena liberation in the finer stream. The rate of galena flotation in the undertow stream was reduced at high collector concentrations. This phenomenon was ascribed to removal of the fines causing the remaining coarse hydrophobic panicles to destabilise the froth. Separate conditioning was found to result in the selectivity of galena against sphalerite to be slightly inferior to the unclassified feed. This was due to poor galena/sphalerite selectivity in the undertow stream. The galena flotation rate increased in all streams with High Intensity Conditioning.

Control of the solution interaction of metabisulphite and ethyl xanthate in the flotation of the Hilton ore of Mount Isa Mines Limited, Australia

Abstract An investigation of important variables which influence ethyl xanthate decomposition by sodium metabisulphite (MBS) during the laboratory flotation of Hilton ore and in plant pulps of the Hilton Concentrator has been undertaken. The decomposition of ethyl xanthate was monitored by Ultraviolet-Visible (UV-Vis) spectroscopic examination of the pulp liquid phase. Sulphur speciation in plant pulps was monitored by ion chromatographic (IC) examination of the pulp liquid phase. Simultaneous addition of xanthate and MBS decreased galena recovery due to ethyl xanthate decomposition by sulphite ion derived from MBS. The depression increased with increasing MBS addition and pulp temperature. Under these conditions there was an increase in the concentration of metastable ethyl perxanthate in solution, an intermediate product of xanthate decomposition by sulphite ion. Pulp chemical measurements in the Hilton Concentrator also showed increased ethyl perxanthate concentration when MBS was added at the same point in the flotation circuit as ethyl xanthate. In contrast, the application of an aeration stage after MBS addition, but prior to ethyl xanthate addition, decreased the concentration of unreacted sulphite ion. This was demonstrated by a decreased ethyl perxanthate concentration in solution and restored galena flotation recovery. Under these conditions the dependency of galena flotation on MBS and temperature was less marked. Prevention of the solution decomposition of ethyl xanthate by sulphite allows the depressant action of MBS on sphalerite and iron sulphide flotation to be optimised.

An investigation of Galena recovery problems in the Hilton concentrator of Mount Isa Mines Limited, Australia

Abstract Surface analysis results by X-Ray Photoelectron Spectroscopy (XPS) of samples taken from the Hilton Concentrator of Mount Isa Mines Ltd. are presented. Flotation rate data taken during the same sampling period are also presented and discussed. Pulp chemical measurements during the sampling period included Eh, pH, dissolved oxygen, temperature, dissolved metal ion analysis and metal ions extractable by ethylenediaminetetra acetic acid (EDTA). The focus of this paper is on the galena flotation section of the Hilton Concentrator. Historically, the galena exhibits a low flotation rate in the lead roughers when using ethyl xanthate collector alone. Di-isobutyl dithiophosphinate collector exhibits increased galena flotation rate under the same conditions. It is suggested that the flotation rate of galena is restricted due to the presence of an overlayer of precipitated calcium sulphate detected by XPS. The presence of the calcium sulphate restricts the surface exposure of all the sulphide minerals in the feed to relatively low values. The flotation process is selective against minerals which have calcium sulphate predominating at the surface.