The effect of particle breakage mechanisms during regrinding on the subsequent cleaner flotation

Stirred mills have been widely used for regrinding, and are acknowledged to be more energy efficient than tumbling mills. These two types of mills present different particle breakage mechanisms during grinding. In this study, the effect of regrinding by both mills on surface properties and subsequent mineral flotation was studied, using chalcocite as the mineral example. A rod mill and a stirred mill with the same stainless steel media were used to regrind rougher flotation concentrates. Different chalcocite flotation recovery was achieved in the cleaner stage after regrinding in tumbling and stirred mills. The factors contributing to the different recovery included particle size, the amount of created fresh surfaces, surface oxidation and the redistribution of collector carried from rougher flotation. All the factors were examined. It was determined that the predominating factor was the different distribution of collector resulting from different particle breakage mechanisms in the stirred and tumbling mills, in line with ToF-SIMS analysis. In the tumbling mill, the impact particle breakage mechanism predominates, causing the collector to remain on the surface of newly produced particles. In the stirred mill, the attrition breakage removes collector from the surface, and decreases particle floatability. Furthermore, the type of grinding media in the stirred mill also influences the subsequent flotation, again due to the change of particle breakage mechanisms. The results of this study demonstrate that the selection of regrinding mills and grinding media should not only depend on the required energy efficiency, but also on the properties of the surfaces produced for subsequent flotation.     

无机抑制剂在低碱度铅锌硫分离中的作用研究

四川某铜铅锌矿属于易选难分离多金属硫化矿,矿物中的伴生银在选矿过程中主要随铅一起富集于铅精矿而得以回收利用。由于矿石中存在大量黄铁矿,在磨矿过程中受到次生硫化铜矿产生的铜离子的活化作用而变得易浮,使得铅锌硫难分离。针对生产中存在的上述问题,从无机抑制剂的选择入手,通过试验室对比试验、小型闭路试验及工业试验,最终找到一种对黄铁矿抑制能力较好的无机组合抑制剂———ZnSO4＋YD,并对该无机组合抑制剂的浮选机理进行了分析。     

Hot Ductility of Tool Steels

Abstract

Four tool steels (A2, D2, M2 and W1) representing a wide variety of compositions (and carbide content) were hot deformed in torsion between 900 and 1200 °C at strain rates of 0.1, 1 and 4 s^?1. Carbides contribute to an increase in strength but to a lower ductility. The plain carbon tool steel (W1) with no carbides was very ductile at all test conditions, but the alloy steels displayed poor ductility due predominantly to void formation around the carbides at lower and medium temperatures and incipient melting at higher temperatures. The effects of carbides on ductility depend on their morphology and distribution. Alloy tool steels experience eutectic solidification of the networks of primary carbides that are broken up by hot working thereby improving ductility. Hot rolled stocks experience directional ductility; such anisotropy is reduced by further working. The alloy steels display parabolic ductility curves for each strain rate; the ductility increases with decreasing strain rate and a rise in temperature up to a maximum of about 1000 °C for A2 and D2 and about 1050 °C for M2. The M2 steel, despite having the highest volume fraction of carbides and strength, displays the greatest ductility followed relatively closely by A2. D2, though close to M2 in carbide volume and strength, has much lower ductility.

On a déformé par torsion à chaud, entre 900 °C et 1200 °C, à des taux de déformation de 0.1, 1 et 4 s-1, quatre aciers à outils (A2, D2, M2 et W1), couvrant une bonne variété de compositions (et de teneurs en carbure). Les carbures augmentent la résistance à la traction mais diminuent la ductilité. L'acier à outils au carbone (W1), sans carbures, était très ductile sous toutes les conditions d'essais. Les aciers alliés ont affiché une faible ductilité à cause, principalement, de la formation de lacune autour des carbures, aux températures basses et intermédiaires, et à cause de la fonte initiale, aux plus hautes températures. L'effet des carbures sur la ductilité dépend de leur morphologie et de leur distribution. Les aciers alliés à outils subissent une solidification eutectique des réseaux de carbures primaires qui sont brisés par le formage à chaud, ce qui améliore la ductilité. Les matériaux laminés à chaud montrent une ductilité directionnelle; une telle anisotropie est réduite par le formage additionnel. Les aciers alliés affichent des courbes de ductilité paraboliques pour chaque taux de déformation, la ductilité augmentant avec une diminution du taux de déformation et une augmentation de la température, jusqu'à un maximum d'environ 1000 °C pour le A2 et le D2 et d' environ 1050 °C pour le M2. L'acier M2, en dépit de sa plus grande fraction volumique de carbures et d'une plus grande résistance, affiche la plus grande ductilité, suivi de relativement près par le A2 puis par le D2 qui, bien que se rapprochant du M2 pour ce qui est du volume en carbure et de la résistance, a une ductilité beaucoup plus faible.     

Chemical and Mineral Analysis of Flotation Tailings from Stratiform Copper Ore from Lubin Concentrator Plant (SW Poland)

ABSTRACT

The study involved the chemical and mineralogical analysis of actual tailings production from Lubin Concentrator Plant (KGHM Polska Miedz SA Group). KGHM Polska Miedz SA Group is the world’s leading company that mines and processes sediment-hosted stratiform copper deposits in SW Poland. From the beginning of copper ore mining, the problem of utilization and managing the deposited tailings has been discussed. Annually, all three concentrators produce above 30 million tons of flotation tailings. Lubin Concentrator Plant processes the most complex in upgradeability ore from the other two concentrators. The total loss of copper-bearing minerals in 0.020–0.071 mm size fraction was found to be 52%. The analysis of liberation showed that in fines (–0.020 mm) over 50% of sulfides is released while the amount of totally locked sulfides in the sample constitutes for 65%. The main cause of significant decline in the finest fractions should be attributed to inappropriate flotation time or too low collector dose. Insufficient liberation of sulfides in the coarser fractions can be a reason for the loss of copper in these fractions. The presented results of final tailings confirm the main cause of metal losses in tailings to be very complex mineral properties.     

新疆某伴生银硫化铅矿石选矿试验研究

新疆某硫化铅矿石中铅品位为13.35%、伴生银品位473g/t,铅主要赋存在方铅矿中,部分呈白铅矿、铅矾、磷氯铅矿形式存在。针对该矿石特点采用一次粗选、两次扫选、两次精选的闭路浮选试验,得到的铅精矿品位为铅66.12%、银1913g/t;铅精矿中铅、银回收率分别为:铅93.47%、银76.63%。试验结果可以为合理开发该矿石资源提供依据。     

On the mechanism of the flotation of oxides and silicates

The mechanism of flotation of oxide and silicate minerals was established long ago as being due to the electrostatic attraction between the charged surface and the charge of the collector. What is less well established is the mechanism of the charging of the mineral surface. Most researchers have postulated that the adsorption of H⁺ is the cause. However, the adsorption model and its derivatives (such as the amphoteric and multisite-adsorption models), do not successfully describe the data for the zeta potential as a function of pH. In particular, these adsorption models have the following features that are not observed: (i) they are symmetrical about the point of zero charge, whereas the data is asymmetrical, (ii) they have an inflection at the pK_a values, leading to an asymptotic approach to the point of zero charge, whereas such an inflection is not observed, and (iii) they only fit the data in its extremes, that is, when the pK_a values differ by orders of magnitude, or are very close to one another. An alternative mechanism of charging is proposed here that is based on the dissolution of ions from and deposition of ions onto the mineral surface. It is shown that this model (a) fits the data, (b) is consistent with the thermodynamic model for reversible interfaces, (c) is consistent with the thermodynamics of the overall reaction and its solubility, (d) indicates reasons for the ageing of surfaces and (e) displays the observed features of zeta potential measurements as a function of pH, that is, it is pseudo-Nernstian and asymmetrical in nature. Application of the proposed theory is discussed for the flotation of quartz and corundum.     

The effect of zinc cyanide on the flotation of gold from pyritic ore

In gold processing plants, the process water contains a considerable amount of weak acid dissociable (WAD) cyanide species. The cyanide-containing water recycled to flotation circuits has a deleterious effect on mineral flotation. Zinc cyanide can be a major constituent of the process water due to the cyanide leaching of zinc minerals and the zinc cementation applied to precipitate gold and silver. In the present study, the effect of zinc cyanide on the flotation of gold from a pyritic ore was evaluated and the competitive adsorption between zinc cyanide species and the collector, potassium amyl xanthate (PAX) or Aerophine promoter (3418A), on gold was studied by surface enhanced Raman spectroscopy (SERS). It was found that free cyanide did not depress the flotation of liberated gold, but zinc cyanide with a CN/Zn ratio of 2 did. The depression of gold flotation by zinc cyanide was due to the preferential adsorption of Zn(CN)₂ on gold surface over either 3418A or amyl xanthate in the solution, rendering gold surface hydrophilic.     

Effect of pulp rheology on flotation of nickel sulphide ore with fibrous gangue particles

Abstract

Tests are carried out with suspensions of fibrous chrysotile particles and nickel sulphide ore containing chrysotile as a gangue. They corroborate published results, and indicate a very strong effect of particle shape on slurry rheology. Such suspensions exhibit time dependent properties. The flotation tests revealed that the viscosity of this system strongly affects flotation performance. At a solids concentration of 15–20% (w/w), the concentrate yield increases and the concentrate grade dramatically declines. This deterioration is observed when the Casson yield stress exceeds 1·5–2 Pa. The tests imply that the rheological properties of the investigated system are mainly determined by fibrous components. However, because of the presence of anisotropic mineral particles, the effect of particle–particle interactions cannot be separated from the effect of particle shape in this system.

On effectue des essais avec des suspensions de particules fibreuses de serpentine et de minerai de sulfure de nickel contenant de la serpentine comme gangue. Ces essais confirment les résultats publiés et indiquent un effet très prononcé de la forme des particules sur la rhéologie de la boue. De telles suspensions exhibent des propriétés dépendantes du temps. Les essais de flottation ont révélé que la viscosité de ce système affecte grandement le rendement de la flottation. À une concentration en solides de 15 à 20% (poids/poids), la production de concentré augmente et la qualité du concentré décline dramatiquement. Cette détérioration est observée lorsque la contrainte de Casson excède 1·5 à 2 Pa. Les essais impliquent que les propriétés rhéologiques du système étudié sont déterminées principalement par les composantes fibreuses. Cependant, à cause de la présence de particules minérales anisotropes, on ne peut pas séparer l’effet des interactions particule-particule de l’effet de la forme des particules dans ce système.     

Optimisation of air rate and froth depth in flotation using a CCRD factorial design – PGM case study

Air rate and froth depth are the most commonly adjusted levers in PGM flotation plants. The optimisation of these levers on each flotation cell has traditionally been done by varying either air rate at a fixed froth depth or vice versa. This approach does not consider the interaction relationship between air rate and froth depth and this effect on flotation performance.Factorial type experimental designs are best suited for investigating interaction effects between variables. This paper presents the use of a factorial type of experimental design being the (CCRD) Central Composite Rotatable Design for plant scale flotation optimisation of air and froth depth. The results obtained include three dimensional response surfaces and models of flotation response variables such as 4E PGM recovery and grade as a function of air rate and cell level. This paper illustrates the experimental methodology and discusses the results for normalised 4E PGM grade and recovery for a rougher cell treating a Platreef ore.These results indicate that interaction effects of air and froth depth are significant and are more pronounced at conditions of higher air and shallower froth depth. In addition, indices which are based on an optimisation objective such as grade multiplied by recovery and/or grade multiplied by recovery squared allows application of this technique as an optimisation tool. These indices can be used to determine an optimum operating range for air and level with the consideration of interaction effects.     

The influence of pyrite content on the flotation of chalcopyrite/pyrite mixtures

In the flotation of copper ores, several processing plants report that copper recovery is affected by the proportion and reactivity of pyrite in the ore, with the effect becoming more intense when the feed particles are finer as a result of regrinding. In this work, a mixed model mineral system consisting of chalcopyrite (CuFeS₂) and pyrite (FeS₂) with varying pyrite content (20–80 wt.%) was used to investigate the effect of pyrite on the pulp chemistry and chalcopyrite recovery. Flotation tests showed that chalcopyrite flotation rate, recovery and grade, as well as the pulp oxidation potential, decreased with increasing pyrite content whilst pyrite recovery increased. Surface analysis (XPS, ToF-SIMS and EDTA) indicated that copper activation of pyrite increased with increasing pyrite content, facilitating pyrite recovery. The decrease in chalcopyrite recovery can be attributed to increased surface oxidation.