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By Jin Liu

The mechanism and rate of carbon reduction of each of the phases that are formed in the flash flame, i.e. sulfide (matte) and oxysulfide, was investigated. Graphite-slag reduction was conducted for comparison purposes. The objective of these tests was to measure the rate of solid graphite reduction of respectively matte, oxysulfide, slag, and matte+slag mixture at different temperatures. More in particular, these tests were expected to permit understanding and explaining the reduction mechanism of each material by comparing the respective reaction rates, product reaction gas compositions and CO/CO2 ratios, reduced material assays, activation energies, and other relevant parameters. Direct visual inspection of the test crucibles would provide additional information.

Jan 1, 2006

By Byung-Su Kim

Most electric arc furnace dust (EAFD) treatment processes employ carbon as a reducing agent for the zinc oxide in the EAFD. In the present work, the reduction reaction of zinc oxide with carbon in the present of various additives was studied. The effects of temperature and the additives of calcium carbonate, magnetite, and mill scale on the kinetics of the reduction reaction were measured in the temperature range of 1173 K - 1373 K under nitrogen atmosphere using a weight-loss technique. The mill scale is one of byproducts generated from the steel rolling process. From the experimental results, it was concluded that all three additives accelerates the reaction rate of zinc oxide with carbon, but the effect of addition of calcium carbonate is the highest. It was also found that magnetite, mill scale, and calcium carbonate in the reduction reaction of zinc oxide with carbon promotes the carbon gasification reaction.

Jan 1, 2006

By Bernhard J. Ralph

In refractory gold ores much of the gold occurs in sub-microscopic form in sulfide minerals, most commonly pyrite and arsenopyrite Bacterial leaching is being developed as a pretreatment for these minerals to aid the liberation of gold and a variety of extracting reagents. This paper reviews the nature of the principal micro-organisms involved, the effects of various physico-chemical factors on the rate and extent of extraction, and likely mechanisms involved.

Jan 1, 1989

By David E. Jones

In any manufacturing process, the generation of secondary, associated or waste products along with the primary product is inevitable. Today there is great emphasis on the concept of waste minimisation. As part of that overall strategy, the search .for markets for these materials formally regarded as wastes, can mean the development of whole new industries. This paper examines some of the work necessary to develop recycling and markets for associated products with particular reference to iron and steelmaking slags.

Jan 1, 1994

By N. L. Piret, E. N. Mounsey

Ausmelt technology is successfully used to process primary and secondary materials to produce lead in large-scale commercial operations and to meet stringent environmental standards. The development and commercial data covering these applications and the results with respect to metallurgical, cost and environmental performance are reviewed in commercial operations. A new smelter is scheduled for commissioning in 2000 at Korea Zinc's Onsan site to process lead fume and other secondary materials to produce 50,000 tonnes per annum of lead bullion. The unique features of Ausmelt technology also allow for the efficient processing of polymetallic concentrates and secondary materials, particularly copper and lead, through the effective separation of these elements into metal, slag and fume species. This capability has been successfully demonstrated at a commercial scale and the results and implications for the industry are discussed.

Jan 1, 2000

By W. John Rankin

Professionals, technical and non-technical, working in the mineral and metal commodity industries need to understand the concept of sustainability and its implications for the industry. Undergraduate courses have not done this well in the past. Much has been written in this field, and there have been great advances in understanding. However, much of what has been published is superficial and sometimes misleading, and there is as yet no coherent, single account that can serve as an introduction or overview for mineral industry graduates. This paper presents an outline which can guide readers in developing an understanding of the topic and its relevance to their work. Key references are provided, particularly those accessible on the internet, which will serve to introduce the reader to the important principles and understandings. The guide should also be useful to academics preparing students to work in the minerals and metal production sectors.

Jan 1, 2010

By G. Cifuentes

When the applied current is interrupted in a copper electrowinning plant, and then is back in operation, the lead anodes tend to corrode. In order to decrease the corrosion, the damage protective ("back up") anodic currents are applied during the period of interruption. The current work aims to establish the effect of the concentrations of sulphuric acid, copper and cobalt on the anode corrosion, to quantify the effect of various anodic protection levels on the anode corrosion and to propose a method to select the appropriate protective current density value.

Jan 1, 1999

By Z. S. Wronski

In rapidly solidified Fe-Nd-B permanent magnet alloys, the content and distribution of Nd-rich intermetallic and Fe-phases determine coercivity Hc and remanence Br. Consequently, microstructure plays a crucial role in deter- mining the (BH) max-product of permanent magnets fabricated from these alloys. A study has been initiated to investigate changes in microstructure and the effects on magnetic properties as the material is processed from arc-melted ingot to melt-spun flakes and finally to a product consolidated by hot-forming. Anisotropic magnetization behaviour has been observed in rapidly solidified flakes after low-temperature annealing.

Jan 1, 1989

By M. A. Gerdel

In carboxylate collector flotation of bastnasite from other semisoluble salt type minerals such as barite various modifiers must be added in order to achieve selective flotation. One such modifier is a lignin sulfonate. It may function in part by acting as a sequestrant for metal ions present, preventing autoactivation in the system by metal ions derived from the minerals themselves. It also functions as a depressant for both bastnasite and barite, chemisorbing on both. However, it is shown that the lignin sulfonate functions as a much stronger depressant for barite than for bastnasite. It is suggested that the; strong depressing action on barite is related to a good fit of the sulfonate into the barite structure.

Jan 1, 1989

By M. Pineau, G. A. Monteith, M. Laliberte, G. Houlachi

Conventional physico-chemical treatment methods, either hydroxide or sulfide precipitation, can hardly achieve a high removal of selenium from the liquid effluents which can be generated in some metallurgical operations. In weak acid solutions, selenium exists mainly as anionic species (selenite Se03-2 and selenate SeCV2) which, therefore, cannot precipitate as metal hydroxide or metal sulfide compounds. At the same time, neither selenite nor selenate form stable precipitates with the common cations (Ca, Mg, Fe, etc.) that are typically used in water treatment. At Noranda Inc., CEZinc Division in Valleyfield, Canada, the introduction of new discharge requirements for effluent toxicity initiated a R&D program which resulted in the full-scale implementation of a new treatment method for selenium removal. The goal of this paper is to present this new method which is now being patented by CEZinc. The process chemistry will be presented along with pilot-scale developments and full-scale operational results.

Jan 1, 2000

By S. C. Grand, T. J. Auping, K. Born

Process control, environmental monitoring, budgeting and accounting are based on process data. Without appropriate tools for data analysis, the process data could remain unused and wasted. This paper demonstrates how data reconciliation can be used as a tool to develop closed mass balances. Mass balances are the initial step in plant optimisation (technical, economical or environmental). From mass balances, fundamental process models can be developed. These balances link process parameters (e.g., feed materials) to process performance (e.g., recovery of valuable elements). Some of these models could find their way into simulators useful to plant operators. Classical regression methods regularly fail when they are applied to complex non-linear problems involving a large number of variables. Alternatively, multiparametrical regression analysis can be successfully applied with the aid of neural networks based on reconciled data. Both methods have been applied to plant data originating from the hydrometallurgical zinc plant at Ruhr-Zink, which in this paper serves as a case study. Very promising and useful results were obtained from this study.

Jan 1, 2000

By Xu Weihong

After being pre-treated, composite electro-deposits of semi-bright nickel/nano-SiO2 with bright nickel or with amorphous Ni-P alloy, and Composite electro-deposits of Zinc were prepared on Nd-Fe-B magnetic material. The effect of cathodic current density, nano-SiO2 concentration, stirring strength and surfactants on the corrosion resistance of electro-deposits were studied. In addition surface appearance and structure of the composite coatings were analyzed by SEM. The present investigation shows that the corrosion resistance of composite electro-deposits of semi-bright nickel/nano-SiO2 with amorphous Ni-P alloy was the best, the solution system of semi-bright nickel/nano-SiO2 with bright nickel was stable and its electro-deposits also had an excellent corrosion resistance, composite electro-deposits of Zinc not only had good corrosion resistance, but also low cost, thus making it an excellent electro-deposit for medium or low-class Nd-Fe-B magnetic material.

Jan 1, 2006

By Irsan Chandra

It is generally recognized that the gold thiosulfate leaching system requires the presence of copper and ammonia in order for acceptable leaching kinetics to be observed. However, the presence of copper and ammonia complicate the chemistry of the system as thiosulfate is rapidly oxidized by oxygen under these conditions. In addition, the environmental impact of ammonia would need to be considered before the adoption of this system. This paper describes fundamental studies into the thiosulfate oxygen system. The two reagents for this system are thiosulfate and oxygen, and leaching is carried out at pH < 7. It will be shown using electrochemical techniques that both the reduction of oxygen and the oxidation of gold-to-gold thiosulfate are hindered. Thus, if leaching is to work under these conditions, then both half reactions need to be improved. The use of additives, such as thiourea and lead have been shown to dramatically improve the oxidation of gold and the reduction of oxygen respectively. The leaching of gold in the presence of such additives is discussed.

Jan 1, 2003

By K. A. Natarajan

Microbe-mineral interactions in the leaching of complex sulfides are discussed with respect to (a) role of galvanic interactions in selective dissolution, (b) bacterial attachment to sulfide mineral substrates and (c) the utility of specially adapted metal tolerant bacterial strains. Experimental results obtained in the leaching of two types of complex sulfides, namely, a lead-zinc-copper sulfide and a copper-nickel sulfide are illustrated.

Jan 1, 1985

By Y. Mori, K. Kawanaka

The permeability changes during the sintering of the feed for the Imperial Smelting Process (ISP) were investigated using an experimental sintering pot, as well as with a mathematical model. The results obtained were as follows. The blowing resistance in the sintering bed changes as the sintering reaction proceeds. It increases at the beginning of the reaction when the temperature of the bed is still low. Then it decreases as the reaction continues, accompanied by an increase of the bed temperature. The increase of the blowing resistance in the bed during the sintering process mainly occurred in the drying zone, and was comparatively small in the reaction and cooling zones. Based on Erugen's equation, the change of the permeability during sintering is explained by the decrease of the apparent fractional void volume in the drying zone of the bed.

Jan 1, 2000

By Thomas A. Post

The methodology of determining the optimum SX pumper-mixer system based on bench top, pilot, or small-scale solvent extraction systems, is demonstrated. The design of small-scale SX-plants is different than a full-scale plant. The difference is explained here. The use of dimensionless parameters Nh, Nq, and Np that describe the head, flow and power of the pumper is shown and how to use them for the scale-up. Additional data is required to determine the optimum operating range. Applications of this methodology were used to design well known currently operating SX plants. The emphasis on the optimization of hydraulic efficiency will be shown on examples, including how the hydraulic efficiency is affected when the throughput of the system goes beyond the design. Designs of all sizes of equipment will be shown which optimize the hydraulic efficiency.

Jan 1, 2003

By K. A. Elbarawy

Processing of Egyptian barite ore with a composition of 85.5% BaSO4; 2.75%SiO2;1.56%Fe2O3 and 5.1% Al2O3 was performed with the aim to prepare pure barium salts. The process took place through pelletization-solid state reduction and leaching steps. Each of these steps was optimized. Pure barium sulphate (99% < 0.82µm) and carbonate (99%<0.75µm )were the final products. This article deals with the reduction process that occur whn coal was added to the ore during pelletization in the ratio of 5:1 stoichiometry. Optimum reduction of pellets of 8-12mm in diameter was achieved after 60 minutes at 1050oC and under a rate of 5 lmin-1 of nitrogen atmosphere, where 87.79% of the ore was reduced. The kinetic studies showed that the reduction process could be modeled according to the core mechanism of diffusion control in which the effective diffusivity is based on the surface area of unreacted ore. The activation energy calculated was 92.7 kJmol-1.

Jan 1, 2006

By Michael J. Nicol

One of the preferred methods for the recovery of gold from refractory gold ores and concentrates involves pressure oxidation in acidic solutions. The main refractory gold-containing minerals are pyrite and arsenopyrite and there is evidence that the presence of even small amounts of chloride can inhibit the oxidation of these minerals and also substantially reduce the recovery of gold. In this paper, the results of a study of the anodic (oxidation) and cathodic (reduction) behaviour of pyrite electrodes in acidic sulfate solutions containing ferric ions at different chloride concentrations and temperatures up to 200oC and pressures of 2000KPa are presented. The electrochemical studies have been complemented by pressure oxidation experiments on a refractory gold concentrate. Results have shown that, as the chloride concentration increases, the anodic reactivity of pyrite is largely unaffected but the rate of the cathodic reduction of iron(III) decreases. The rate of oxidation of a sulfide concentrate and the recovery of gold by cyanidation of the residues decreases at high concentrations of chloride.

Jan 1, 2003

By Kamal Adham

Hydrochloric acid is used as lixiviant in such hydrometallurgy processes as synthetic rutile production and nickel extraction. The intermediary metal chloride is normally roasted to release gaseous HCl and a solid metal oxide. A large amount of fuel is required for this thermal regeneration, mainly to vaporize the water content of the feed solution. To conserve fuel, some energy recovery from the off-gas is currently achieved, but the fuel costs can further be reduced by process optimization and energy recovery from the gaseous, aqueous and solid products of the regenerator. Here, first the existing limitations to fuel efficiency in the industrial scale HCl regeneration roasters are described. Then, for the case of a dilute feed solution, options for pre-evaporation and fuel minimization are modeled and compared. Finally, energy recovery technologies including heat pumps, acid heat exchangers and solid waste heat boilers are described, and their potentials as the heat source for pre-evaporation of the feed are evaluated.

Jan 1, 2003

By P. Ruz

A melt transfer ladle was 3D modeled by means of a mathematical fluid dynamics and heat transfer program. Internal temperature profiles were calculated as a time function for a normal ladle and for a pre-heated refractory lined ladle. It was shown that in a normal ladle the molten metal cools down quickly forming accretions. By using an inner lining there are practically no accretions build up within a typical time of operation. Therefore, by applying a refractory lining to a melt transfer ladle and keeping it at a moderate to high temperature it is possible to reduce cold dope circulation in the smelter.

Jan 1, 1999