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The Big Bend and Cobra molybdenum prospects which occur near the margin of the Karamea Batholith in the Northwest Nelson molybdenum province are compared. The Big Bend Prospect is a 3000 m by 800 m area of disseminated pyrite and anomalous molybdenum associated with Cretaceous porphyry intrusives and later argillic and potassic alteration within Ordovician schists and phyllites adjacent to the batholith margin. The Cobra Prospect is a 1200 m by 1200 m area of weakly disseminated pyrite mineralisation and anomalous molybdenum-in-rock associated with moderate to strong quartz-molybdenite and quartz-orthoclase-molybdenite veining in quartzite.

Jan 1, 1979

Basicity(aO2−) has been known to affect the physicochemical properties of molten slags in the metallurgical processes. However, because of the impossibility of direct measurement of single-ion activity, various indirect measures such as capacity, redox equilibrium of transition metal ions, activity of basic oxides, and (theoretical) optical basicity have been proposed; but these basicity measures have been restricted within slag systems and the interaction between measuring elements and slag components has affected the quantitative estimation of slag basicity. Recently, since it was reported that solubility of noble metals in molten slags could be an indirect measure of basicity, the influence of slag basicity on the solubility of platinum and silver has been reported. The reaction mechanism of platinum dissolution into basic slags has been reported, whilst that in acidic slags has not (Nakamura and Sano, 1997; Sano and Nakamura, 1997; Nakamura et al, 1998). Richardson reported that the solubility of metals such as cupper, gold, silver, and lead in the CaO-SiO2-Al2O3 slag was presumably dependent on the atomic radius and the accommodation ability of the silicate network (Richardson, 1974). Swinbourne and You measured silver solubility in the Na2O-SiO2 slag over a wide range of oxygen partial pressure and suggested that silver would be present as both Ago and Ag0.5 in the slags (Swinbourne and You, 1999). For brevity, these previous works discussed the dissolution mechanism of silver into the slags based on the existence of silver as a neutral or molecular species. However, because the almost chemical reactions occurring in the slag are affected by the basicity, the reaction formula with O2- ion is required based on the ionic characteristics of the slag such as desulphurisation and dephosphorisation reactions as given in Equations 1 and 2, respectively.

Jan 1, 2000

By J Webb

Anoxic limestone drains (ALDs) have been widely used in the passive treatment of acid mine drainage (AMD), but their effectiveness has often been less than anticipated. Iron hydroxide often precipitates around limestone particles and inhibits neutralisation. To determine the conditions under which iron hydroxide precipitates, a small-scale laboratory ALD system was built to enable a detailed examination of the chemistry of iron within the drain. For one experiment, a mixture of limestone and quartz was introduced to the drain to assist in the determination of the key mechanism governing iron precipitation. Synthetic anaerobic acid mine drainage containing Fe2+ (~130 ppm), SO4 2- and H+ was pumped at a rate of 30 mL/min up a 90 cm tall, 15 cm diameter vertical column filled with limestone gravel of 98 per cent purity. Three sampling ports were fitted at equal intervals along the column; water was periodically extracted for analysis at the sampling ports over an 11-hour period. Experiments were run at influent pH levels of 2 and 4. Results show that acid neutralisation to pH greater than 6 occurred at the inflow end of the drain. The greatest amount of iron precipitation (19.5 per cent) also occurred in this area. The lack of iron precipitation on the quartz surfaces in the quartz/limestone mixture indicates that neutralisation is the key mechanism for the precipitation of iron hydroxide on limestone particles. A pe-pH stability diagram derived for the laboratory ALD system indicates that ALDs will not be effective for AMD with pH 2. Influent waters with pH 2 require a pe of -2 (Eh: -118.4 mV) to avoid Fe precipitation upon neutralisation. Influent waters of pH 4 require a pe between -2 and -4.

Jan 1, 2003

By K Nakashima, K Aya, T Sumita, N Saito

Electro slag remelting (ESR) is one of the methods used to produce high-cleanliness steel. In the ESR method, the product steel electrode is immersed in flux, and the electrode is melted by the Joule heat of the flux generated by high current. CaF2-based melts are mainly used as fluxes, but the electrical conductivity of CaF2-based melts varies widely among researchers and measurement methods. Therefore, this experiment aims to measure the electrical conductivity of CaF2-based melts based on the van der Pauw-Ohta method, which does not require the cell constant that is a fundamental error factor in electrical conductivity measurement at high temperatures. The measurement temperature was set at 1450–1600°C, and dehydrated Ar flowed through the furnace at 200 mL/min. Electrodes were fabricated by Pt-30mass per cent Rh alloy, and the electrodes were connected to an impedance analyser using a four-terminal probe. The electrodes were immersed in the melt, and the impedance and phase angle were measured by AC frequency sweep (50 Hz to 200 kHz). The electrical conductivity was then calculated by utilising the impedance’s real part values when the impedance’s imaginary component was zero. The electrical conductivity showed a positive temperature dependence. The electrical conductivity of 60(CaO⋅Al2O3)-40CaF2 melt increased with increasing temperature but was found to be roughly one-third of those of the previous studies. In the conductivity measurement of 60(CaO⋅Al2O3)-40CaF2 melt, the AC frequency with a phase angle of 0° was found to be different depending on the temperature and immersion depth. By sweeping the frequency, the impedance at the phase angle of 0° can be obtained, which enables us to measure the electrical conductivity more accurately.

Jun 19, 2024

By H Plewes, A Bur, L Murray, J Pottie

Water recovery from tailings for reuse in mineral processing is essential to operation of mines in the Atacama Desert of Chile. With annual rainfall of 5 mm, the prudent and efficient use of available water resources is a major issue for the Escondida Mine and other mines in the area. The Escondida Mine is located at an altitude of 3100 m, in a very arid, seismically active part of the Atacama Desert of northern Chile. The site is located about 170 km from the coastal city of Antofagasta. From 1994 to 2002, tailings were discharged into the Hamburgo Tailings Facility, which comprises a series of æpaddiesÆ located near the open pit and mill. Because water in the region is only obtainable from groundwater sources, the paddy system incorporated a number of design features with the aim to maximise water recovery from the tailings. As part of the recent mill expansion to 237 500 metric tonnes per day, a new tailings facility, the Laguna Seca Tailings Facility, projected to be one of the largest tailings facilities in the world, was commissioned in 2002. Extensive studies were conducted for the design of the new facility to predict water recovery from the conventional wet disposal of tailings. The predictions were calibrated against the performance of the Hamburgo Tailings Facility and subsequently re-calibrated against actual performance during the first year of operation at the Laguna Seca Tailings Facility. Initial operation of the Laguna Seca Facility was marked by a coincidental change in tailings characteristics from design, which highlighted the need for thoroughly understanding tailings behaviour during deposition, and the parameters and deposition techniques that could enhance water recovery. Systems have been put in place to manage the tailings deposition and respond to changes in key parameters such that water recovery targets can be reliably achieved. This paper describes the background studies that were conducted to evaluate evaporation and tailings behaviour, summarises the water balance and then presents some observations from the commissioning and start-up of the facility.

Jan 1, 2003

The Ramu chromite deposit occurs in the Marum Ophiolite complex and is the most economically attractive chrom-ite deposit in Papua New Guinea. Its lateritic nickel, chromite and cobalt potential has attracted several compan-ies to prospect the deposit.In the present work, the compositions of chromite in the Ramu lateritic deposit and coexisting olivine-chromite pairs in Marum Ophiolite dunite were analysed with the electron microprobe for Fe, Mg, Cr and Al. The results were used to determine the relationship between the cations in the tetrahedral and octahedral structures of the chromite. In addition, the Fe, Mg, Cr and Al cations of the coexisting olivine-chromite pairs were used to calculate the equilibrated temperatures of crystallisation of the chromite. The variation of Fe", Mg and Cr cation values of the chromite in relation to the calculated temperatures was studied by regression analysis.

Jan 1, 1994

By I Gipps

The mining industry has come through a period of major change in community expectations regarding safety and environmental impact and these changes can be expected to continue in the future. These changes are ultimately reflected in Government regulations and industry safety standards and form the basis of the ælicense to operateÆ. Equally, advances in technology have made possible new equipment and processes either available now, or close to completion, that will allow mines to meet these more stringent expectations if properly introduced. Changes in technology provide opportunities for mine management to introduce new systems that will remove people from hazardous areas and lead to improvements in the ætriple bottom lineÆ. In a longer time frame of five to ten years, novel and advanced technologies that are currently being developed will deliver new mining methods and conversion of presently uneconomic resources to ore. This is consistent with the time frame required to develop a new mine from discovery. Strategic decisions can be taken now by mine designers to enable the introduction of these major technology changes. Examples of both practical and strategic opportunities are drawn from the integration of rock cutting/blasting, automation, electronic communications and new mining methods. This paper discusses emerging industry trends, changes to legislative framework and some practical choices for existing and imminent technology.

Jan 1, 2003

By Sano S, Ishikawa T, Nagaoka H, Hayashi Y, Hasegawa M

The stirred mill is regarded as one of the most efficient devices for micronising materials and has come to be actively used for preparation of fine particles. Recently, the demand for ultrafine particles was increased in many kinds of industries. In this paper, autogenous grinding to get submicron particles based on mutual friction feed material has been carried out using a stirred mill. The mill used was made of stainless steel and its volume was about 5.5 litres, and has 12 impeller blades. Sample used was limestone. In the present work, two operating parameters such as stirring speed and feed size of limestone were considered. The ground products were sieved in the size range from feed size to 325 mesh (45 lun), and from 45 to 0.17 pm the size distributions were measured by a laser diffraction and scattering method. The progress of grinding was evaluated by the increasing amount of submicron particles in products. As a result, the rotational speed of impeller with the minimum energy consumption to produce submicron particles was observed. It was found that the autogenous grinding with a stirred mill is an effective method for producing submicronized limestone.

Jan 1, 1993

Magnesium-rich olivine is used as an additive in LKABÆs iron ore pellets in order to improve the high-temperature properties of the finished products. Olivine is only added to the pellets that are manufactured for ironmaking in the blast furnace process. The olivine comes from Minelco/LKABÆs mine at Seqi in Greenland. This dunite complex of Archean age contains about 95 - 98 per cent olivine. The grain size is typically 1 - 3 mm but much larger euhedral olivine crystals are common in the porphyritic type. The serpentinisation is absent or weak. The most common minor minerals are chromite, chlorite, talc, phlogopite, amphibole and pyroxene. The crushed olivine is transported to LKABÆs pelletising plants in Northern Sweden. After grinding, small amounts of olivine are mixed with the magnetite concentrate. The concentrate is rolled into green balls, about 10 - 14 mm in diameter. The moist green balls are transferred into the pelletising machine where the maximum temperature is about 1250¦C. The residence time in the pelletising machine is about one hour. Olivine is used in order to get pellets with better high-temperature properties. This paper deals with the olivine alteration during the pelletising process and the behaviour of magnesium following the decomposition of magnetite. The reactions are quite complex in the pellets because the physico-chemical conditions vary considerably in the process from one process step to another, and in the pellet bed from the top to the bottom. Some olivine particles in the finished product show very slight alteration, some particles are completely decomposed. The formation of the iron-rich coronas around the olivine particles is the most typical alteration. In the finished pellets the magnesium is mainly distributed between the following phases: unaltered olivine, coronas, Mg/Fe-ferrite and silicate slag.

Jan 1, 2008

Studying the ore textures in a discrete orebody is a novel approach to estimating liberation potential of the ore minerals present. As part of a PhD thesis, this project aims at classifying and quantifying the textures of the Hilton North orebodies, and at estimating their liberation characteristics.

Jan 1, 1993

By He BQ

Static attachment of bubbles to solids is contrasted with dynamic attachment in flotation cells. The times of contact during particle-bubble collisions in dynamic attachment are compared with the induction time determinations and the kinetics of thinning of the liquid films separating solids and bubbles. The thinning is examined mainly in terms of electrostatic and dispersion (van der Waals) contributions to the disjoining pressure existing in the films. The local heterogeneity (on a molecular scale) of charge distribution invariably present at all interfaces (even at conditions of zero zeta potential) calls for some means to minimize possible electrostatic repulsions which arise when the electrical double layer at the air-bubble interface begins to overlap that present at the solid surface, on encounter between particles and bubbles. It is postulated that dipoles of frother molecules, owing to their ability to "flip over" (polarise), replace localized electrostatic repulsion by attraction within fractions of a milli- second, as long as the structure of the frother molecules is sufficiently "bulky" to maintain diffuse films (of mixed collector-frother) at the air/liquid interface of bubbles. The relaxation times of dipoles (signifying their "flipping over" ability) have to be shorter than the collision times between particles and bubbles for particle-bubble attachment to be facilitated under dynamic Conditions.

Jan 1, 1984

By Xueqiu H

Since the hypothesis of coal and methane outburst mechanisms based on elastic mechanics gives no consideration to time, it cannot give satisfactory explanation of the outburst occurrence and its development. A creep mathematical model of coal containing gas has been set up through creep tests and analysis under a condition of triaxial compression. Such a model can explain the phenomenon of coal and methane outbursts successfully. The tests proved that there is no essential difference between the rheological properties of prone outburst coal and non-prone outburst coal. Outburst can take place in any kind of coal if the rheological conditions of coal containing gas are met. The creep mathematical model provides a basis for establishing a comprehensive index of coal and methane outburst potential.

Jan 1, 1992

By M Zhu, J Safarian

Understanding the slag composition-structure-property relationship remains challenging due to the amorphous nature of slag melts and the difficulty of high-temperature experimental investigations. Since the CaO-Al2O3-SiO2 slag system is maybe the most important slag system for various hightemperature metallurgical process, the present research employed high-throughput molecular dynamics (MD) simulations on the entire composition region of the CaO-Al2O3-SiO2 slag system to determine physical properties like molar volume, density and diffusivity, structural properties such as distribution of different oxygen types for each simulated slag melt. The obtained slag properties result from the simulations displayed good consistency with experimental data, underscoring the reliability of the MD simulation as a novel tool to predict reasonable slag properties and to study slag behaviour from atomistic insight. The simulated results demonstrate a near-linear relationship between molar volume changes and composition, highlighting the predominant role of oxygen atoms, which is attributed to the significantly larger size of oxygen compared to other cations in the slag melts. This disparity in size leads to oxygen ions occupying most of the space in slags, thereby playing a major role in determining the overall molar volume. The simulation results of slag density revealed a decreasing trend with increased SiO2 content and identified a local minimum at constant SiO2 when Al2O3 content increases, also consistent with established slag density models. Furthermore, the simulated oxygen self-diffusion coefficients reveal a strong composition-structureproperty relationship, where an increase in CaO content enhances slag diffusivity, while a minimum in diffusivity is observed near a CaO/Al2O3 ratio of unity. The diffusivity minimum also corresponding to the local viscosity maxima, indicating effective simulation of charge compensation effects and dynamic characteristics of slag melts. The simulated distribution of oxygen types in slag — bridging oxygen (BOs), non-bridging oxygen (NBOs), free oxygen (FOs) and tricluster oxygen (TOs) — reveals a composition-dependent pattern: BOs peak near CaO/Al2O3 = 1, NBOs and FOs are abundant in CaO-rich areas with NBOs peaking near the Ca3SiO5 composition, FOs in the CaO corner, and TOs predominantly in the Al2O3 corner, highlighting the complex interplay of network formers and modifiers for the charge compensation effects on the slag’s structural properties. The successful application of MD simulations in this study paves the way for a powerful approach to explore the complex relationships in multicomponent slag systems and bridges the gap between mathematics modelling and experimental observations in high-temperature metallurgical processes.

Aug 21, 2024

This paper outlines the thermodynamic and mass balance principles which affect the distribution of cobalt between matte and slag during the pyrometallurgical treatment of nickel - copper sulphides and considers the implications with regard to maximising the recovery of cobalt from the smelting and converting circuit.

Jan 1, 1992

Tumbling mills have been used in the minerals indusu) for occr WO years, with the design changing little, but the size of the individual pieces of equipment increasing significantly with the lowering of head grades, and the push for greater

Jan 1, 1997

The considerations which led to the decision to_ install discs at the Dampier Pellet Plant of Hamer ley Iron Pty. Ltd. are described. Initial testwork showed that the ore could be ground dry in open circuit to a Blaine index of 2500 cm2/g and that it pelletized readily. The various design criteria including diameter, slope, speed, motor size, depth of sidewall, feed point and water spray location were then determined. Plant performance after commissioning is described including the various problems encountered and the modifications since carried out to overcome them. The main problem was quickly identified as disc feed rate control. Various bin and bin feeder modifications were tried to overcome the effects of the fluidising characteristics of the dry ground ore. Other factors found to affect disc operation are ore size distribution, additives and operator competence.

Jan 1, 1974

By Dobos SK

The Black Ridge Gold Deposit is located in the northern part of the Clermont Goldfield, which is situated at the boundary of the Bowen Basin and Anakie Inlier, Queensland. The goldfield comprises a series of NNW-trending semi-isolated basins, which are tectonically aligned with the Denison Trough, the west-most division of the Bowen Basin (Fig. 1-1).The main stratigraphic units in the deposits in younging sequence are the Anakie Metamorphics, the early Permian Blair Athol Coal Measures, the late Permian(?) White Section, and the Tertiary basalts which are regionally widespread, and intruded by abundant mafic and felsic plugs.

Jan 1, 1990

Cobar Mines Pty. Limited (CMPL) uses sodium sulphite as the principal depressant to attain selectivity in copper flotation prior to sequential recovery of lead and zinc. The usage of sodium sulphite is examined both from a theorectical viewpoint ana from the manner in which the copper circuit at (MPL has developed. The results of relatively recent investigations, both in the laboratory ana the plant, are discussed aria shown to support the present operating Techniques.

Jan 1, 1983

By Lukaszewski GM

The indiscriminate surface disposal of coal waste in the past has created a serious fire hazard in the bush of the northern New South Wales coalfields. Spontaneous or bushfire-induced combustion in large neglected dumps of this material has increased in recent years causing a rise in air pollution. Surface methods of coal waste disposal are still being practised, and in many cases new material is being added to old dumps, many of which are burning. CSI RO has conducted research on methods of preventing and controlling fires in coal waste and recommends practical methods of overcoming these problems. Some laboratory and on-site investigations are described and the hazards of improperly constructed dumps are considered. The available techniques of fire prevention and control are discussed in relation to Australian conditions. Proposals for the safe and economical disposal of coal waste are outlined.

Jan 1, 1970

By Y-B Kang, W-Y Cha, Y-M Cho

Molten slag used in the secondary refining process (RH process) for the production of Ultra-Low C (ULC) steel is typically composed of CaO-Al2O3-MgOsat.-FetO with minor constituents. FetO in the RH slag is the main source of reoxidation of the molten ULC steel in the ladle by 2Al + 3(FetO) = (Al2O3) + 3Fe, thereby serving as the source of the alumina inclusions. On the other hand, FetO also enhances the fluidity of the slag, thereby increasing inclusion absorption capacity. Optimum slag chemistry design is therefore required to produce clear ULC steel. The reoxidation kinetics was investigated in the present study by employing high-temperature experiments and developing the reaction rate model. Initial compositions of slag ((% CaO)0/(% Al2O3)0 and (% FetO)0)) and reaction temperature were varied and change of [% Al] in the molten steel was measured. The rate-controlling step was analysed. It was found that the rate-controlling step in some cases changed during the reoxidation: from a mass transport of Al in the molten steel to a mixed transport including Al2O3 in the molten slag. The experimental data validated the reaction rate model based on the elucidated reaction mechanism and FactSage thermodynamic database. The model suggested that high (% CaO)0/(% Al2O3)0 suppresses the reoxidation only when (% FetO)0 is low (5 or lower in the present study).

Jun 19, 2024