Resonance and it application to a vibratory mill

The dynamics of a driven oscillator, consisting of a cylindrical container suspended by springs and filled with a large number of freely moving balls, is investigated around the principal resonance frequency. The theoretical findings are applied to a cantilever resonance vibratory mill and allow for the experimental determination of the dynamical properties of the mill, estimation of the power input and its absorbed and dissipated fractions. The results are tested for the mechanical activation of quartz.     

Removal of sulphate from mine water with barium sulphide

The Barium Sulphide Process removes sulphates from mine water by precipitating BaSO₄ with BaS. Barium sulphide is regenerated thermally by reducing the BaSO₄ with coal at 1000–1100°C for about 15 minutes. The process produces elemental sulphur and CaCO₃ as by-products. Laboratory studies achieve typical sulphate reductions of about 95%. Metals such as Fe, Ni, Co and Mn are also removed and pH can be increased from 1,4 to 8,3. The process has a water recovery of about 70%. For a 25 Ml/d plant (2g/l SO₄ ^2?), the capital cost is estimated at US$ 0,48m/Ml/d, while the detailed running costs amount to a net value of 27 c/m³. This compares well with that of other processes for desalination and is less than the fresh water price for new mines in South Africa, viz. 30c/m³.     

A rheological investigation of the behaviour of two Southern African platinum ores

With the installation of ultrafine grinding on many platinum operations in southern Africa, there were concerns as to whether this would cause rheologically complex behaviour during the subsequent flotation of the ore. Rheologically complex behaviour refers to the non-Newtonian behaviour experienced by some suspensions, associated with exponential increases in yield stress and viscosity with increasing solids content. This is attributed to particle size and solids concentration effects, surface chemistry, and mineralogy. In this study, the rheological behaviour of two different platinum ores; a western limb UG2 ore and a Great Dyke platinum ore were investigated and compared with that of single mineral studies of the major gangue minerals of platinum ores (chromite, orthopyroxene, plagioclase and talc). The results show that Great Dyke ore is considerably more rheologically complex than UG2 ore. Great Dyke flotation concentrate shows high yield stress and viscosity at low solids concentrations (>20 vol.% solids). Should the ROM ore in a Great Dyke flotation operation suddenly show significant changes in ore mineralogy, the rheological properties of the slurry should be considered since they may be detrimental to the overall performance of the operation (e.g. loss of recovery through poor gas dispersion). In contrast, the rheological behaviour of UG2 flotation samples shows little cause for concern for the plant operator. Comparison of the pure mineral samples shows that the complex rheological behaviour of the Great Dyke ore may be attributed to the high degree of low temperature alteration and the formation of phyllosilicate minerals such as talc, more than particle size effects.     

The mineral phase quantification of vermiculite and interstratified clay minerals-containing ores by X-ray diffraction and Rietveld method after K cation exchange

Hydrothermal transformations and weathering are important mineralizing processes in carbonatite-related ores. But the transformation products of mafic minerals, such as the clay minerals, vermiculite and interstratified phases, preclude the use of X-ray diffraction, particularly the Rietveld method, for mineral phase quantification. After treatment with KCl, vermiculite and interstratified phases (all peaks roughly at 1.2, 1.4-1.5 and 2.4 nm) are converted to a phlogopite-like structure with d(0 0 1) = 1.0 nm, which can successfully be refined. The method was tested using three carbonatite-derived ores, with a total phlogopite-like phase content ranging from 1.2 to 32.3 wt.%. Comparison of the chemical analyses with the calculated chemical composition, based on the phase quantification and the mineral composition is in good agreement for major elements, such as Si, Fe and Al. For P results were also very good, but Ti and Nb are generally underestimated, and Ba is overestimated. Minerals with lower contents, as pyrochlore, approach the diffraction detection limit. Problems to accurately determine mineral composition for some of the phases also impacts on the reconciliation. The chemical composition of the pyrochlore group minerals changed, but not to an extent to constrain the usefulness of the technique. Cation exchange successfully extended the amenability of the Rietveld method for phase quantification.     

Developments in mineralogical techniques - What about mineralogists?

Conventional mineralogy was mainly based on optical microscopic techniques. Years of experience in studying ore and gangue minerals using an optical microscope allowed for quick identification of minerals, opinions on abundances of certain minerals, liberation, required grind size and reasons for high mass pulls or tailings losses. More detailed investigations involving point counting techniques, XRD and chemical methods provided additional information to quantify certain aspects of the problem studied.Developments in automation of SEM-based techniques, computerised XRD processing and identification, imaging software, etc. has impacted on the tasks of mineralogists. Future equipment developments and the implementation of plant systems will probably minimise the need for experienced mineralogists for the more routine applications.This publication discusses how processing requirements have driven developments on current systems. The changing role of mineralogists is discussed, as well as knowledge and experience requirements to drive applied or process mineralogy forward.     

Assessment of critical dragline boom suspension components: An essential for planned replacement policy

The replacement period for dragline boom suspension links components that are critical to safety and production but cannot easily be inspected, has been based on a fatigue life prediction using design load ranges and reinforced by known failure histories. Improvements to the design and the fact that the links do not experience the maximum design load range in every dig cycle have made the replacement period unnecessarily conservative. Because of the cost of replacement, it was worthwhile to undertake a programme of strain-gauge testing, finite element analysis, and fatigue life and crack growth prediction to derive an accurate estimate of the expected service life for a known probability of failure, appropriate to the safety requirements for the links. It is shown that this exercise has enabled the planned service life of the links to be extended with confidence.     

Characterisation of coarse composite sphalerite particles with respect to flotation

The flotation response of a typical zinc-lead (Zn/Pb) ore, with respect to coarse composite (sulphide/non-sulphide) particles is reported. The flotation tests were carried out on a selected feed particle size range (−600 + 75 μm, at P₈₀ of 390 μm) and the recovery of Zn composite particles analysed on a size by size basis. The best results were achieved with the use of 75 g/t sodium isopropyl xanthate (SIPX), obtaining a Zn recovery of 77%, with a significant improvement at the coarse end of the particle size distribution. Computerised scanning electron microscope (QEMSCAN) was used to characterise value mineral grain size and degree of liberation, as well as gangue and sphalerite association in particles reporting to both concentrate and tailings. A new characterisation function (Locking ratio, LR) was developed based on the data from the automated mineralogical analysis to characterise particles into two-phase composites with different degree of locking texture (simple and complex). The function, which is based on the mode of occurrence of sphalerite, grain size, proportion and composition of the constituent minerals in each particle, was used to study the flotation response of the particles with different degrees of locking. The results highlight the difference in recoverability of the sphalerite bearing particles with different degrees of locking, with simple locking texture giving higher recovery than complex locking texture, for the same overall liberation.     

中国商用车领域的铂族金属需求依然强劲

2020年以来中国商用车市场发生了很多变化,近期卡车销量从疫情萧条中大幅反弹,物流、基建以及排放标准升级共同推动了2020年商用车市场需求,对铂族金属的需求更加有利,对铂金需求的预期增长似乎比对钯金需求更有保障。     

Developing an experimental procedure for charge media wear prediction

Typical mining operating costs can be divided between extraction (30% to 70%), comminution (30 % to 50 %) and separation (5 % to 20 %). Comminution process costs, representing an important contribution to mining operating costs, can themselves be divided roughly between energy (50 %) and liner/charge wear (50 %). Developing the ability of predicting mill wear will allow a more accurate estimation of wear costs. In this paper, an overview of abrasive and corrosive wear mechanisms is made from which an experimental procedure is proposed that allows the prediction of the effect of changes in charge media composition. Experimental results for four cases are presented and used to predict changes in media wear.