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By Takagi T, Seetharam R, Sie SH, Naito K

Tin-polymetallic vein type deposits are one of the major source of metal producers in the Circum Pacific Belt. This type of deposit is of great importance for the modem electronics and medical industries because of their high content of rare metals (especially indium and bismuth). We have studied two representatives, Tosham of India (Cu-In-Bi-Sn-W-Ag-Au), and Mount Pleasant of Canada (Zn-Cu-In-Bi-Sn-W), using proton and electron microprobes in order to delineate the distribution of medical/high-tech rare metals. The electron microprobe study showed that major indium carrier in such type of deposit are roquesite (CulnSZ), sphalerite, stannite and a Cu-Zn-Fe-In-Sn-S mineral; and that indium is incorporated in sulfides by coupled substitution like Cu + In = 2(Zn + Fe). The proton microprobe showed that indium at trace levels is also present in chalcopyrite and pyrite. In addition, zinc, copper, arsenic, antimony, selenium, tin, and bismuth are common in chalcopyrite and pyrite. Arsenopyrite contains nickel, copper, zinc, silver, tin, antimony and bismuth. In chalcopyrite and pyrite, zinc, arsenic, indium, bismuth and lead are higher in Mount Pleasant ore, but silver is higher at Tosham. Also thallium and gold were found only in Tosham pyrite. The Tosham deposit is genetically related to S-type magma, while the Mount Pleasant deposit is related to A-type granite. Tosham ore contains zinc-bearing biotites that coexist with chalcopyrite in ore bodies but Mount Pleasant ore lacks such biotite. We propose that the difference in elemental abundance between the two deposits are caused by the different character of source magma and different mineral associations of the ore body.

Jan 1, 1995

By X. P. Zheng, H. K. Lin

Barium fluorophlogopites were synthesized in the laboratory to investigate the effects of composition and crystal parameters on surface properties and floatability. The negative surface charge of mica is determined by the barium content, the crystal cell volume, the distance between the layer structure and the Ba-O bond length. The higher the barium content, the larger the cell volume and distance between the layer structure, and the longer the Ba-0 bond, the more negatively charged the surface is, and, hence, the more easily adsorbed are cationic collectors. When an anionic collector (sodium oleate) is used, barium oleate forms on the mica surface and hence chemical adsorption occurs.

Jan 1, 1995

In this paper, three types of value-adding in the minerals industry are discussed: downstream processing, improving the efficiency of existing processing and increasing the knowledge base and expertise of the staff. It is shown that, while downstream processing seems to offer a good way of improving Australia's trade position, there are a number of impediments to such development, notably, limited access to the appropriate technology and overseas markets. Transport costs can also be a problem. To reverse the situation will require more positive policies by government. In the meantime, something can be done towards adding value by increasing the efficiency of existing processes. Examples are given, showing how it might be possible to make economies in reagent costs in the gold industry, how innovative technology has led to more complete processing of a tailings dump, how research might lead to an increase in the throughput in the production of synthetic rutile and how it is possible to leach selectively from gold/copper ores.

Jan 1, 1995

By W. A. Van Dyk

Hydrophobic particles with diameters between 1 and 3 mm are poorly recovered by conventional flotation techniques. A novel reverse flotation technique is described whereby coarse particles with surfaces rendered highly hydrophobic, repel the bubble films in a froth and thus drop through the froth under gravity, to be recovered as a sink product. Conversely, gangue or hydrophilic particles are supported by the bubble films in the froth and are therefore recovered as a floating product. Tracer tests were conducted in the cell in order to study the dynamic behaviour of solid particles in the froth. The effects of hydrophobicity, density, particle size and particle shape were investigated experimentally. The higher the hydrophobicity of the particles, the lower the recovery of particles as a floating product, while the recovery of particles as a sink product increases with an increase in particle density. Furthermore, a decrease in particle size results in an increase recovery of hydrophobic particles as a floating product. When treating particles of the same mass-to-surface-area ratio in the froth, flat particles would be recovered as a floating product in preference to cubic, disc-shaped, cylindrical and spherical particles, in that order.

Jan 1, 1995

By B. J. S. Sceresini

The Filblast Cyanidation Process incorporates the advantages of intense high shear mixing, high dissolved oxygen concentra­tion and high pressure to achieve extremely rapid gold dissolu­tion rates. This is made possible without suffering from high energy or wear rates by the unique design of the Filblast gas shear reactor. The reactor is a rugged and compact in-line device which can be constructed from a variety of wear and chemical resistant materials. High temperature tolerance is also possible so that the device can be incorporated into a pressure leach circuit with significant capital cost savings because of the high capacity to volume ratio that is an inherent feature of the device. For cyanidation applications the outer casing is protected by a polyurethane coating and the internal parts are of wear resistant polymer. The largest unit built to date has overall dimensions of 1200 mm length by 300 mm diameter and has a capacity of about 150 dry tonnes per hour at 40-45 % solids. Service life at this throughput is at least three months. Six mines are currently employing the Filblast Process and another six are conducting plant trials. The ore types range from highly reactive, almost impossible to treat, pyrrhotite/ arsenopy­rite to deeply weathered clay ore which forms a highly viscous pulp. It has been found that the effect of shear thinning has resulted in improved leaching and adsorption kinetics resulting in higher carbon loading and reduced soluble gold loss. Total tonnage treated is approximately eight million tonnes per annum. This paper presents the operating benefits and cost savings which have been achieved in four plants, two treating oxide/ sulphide ore blends and two treating highly reactive sulphide ore and concentrate. Filblast leasing and maintenance charges and pump operating costs are about ten percent of the benefits. A conceptual cyanidation circuit based on the Filblast Cyanidation Process is also discussed. The Filblast System is an in-line pressure leach aerator/ reactor which generates very high shear and greatly enhances mass transfer rate by generating extremely small gas particles where oxygen gas is required for oxidation reactions and/or utilising the high shear characteristics to minimise the diffusion boundary layer. Both of these rate limiting factors effect the rate mechanism for gold cyanidation. Initially two multi-stage Filblast aerator cartridges formed a leach train but now the trend is to install a single submersible cartridge of equivalent perfor­mance. This design simplifies installation and minimises change-out times. However the in-line concept can be employed where high pressure leaching or pressure oxidation is required. The reactor is submerged in the leach tank so that the mass of gas micro-bubbles contained in the discharging slurry is entrained in the agitator vortex and is thoroughly dispersed throughout the tank. A diagrammatic representation of a leaching circuit incorpo­rating the Filblast Reactor is shown in Figure 1. The recirculation pump takes new feed directly from the cyclone overflow trash screen either under gravity or pump fed and recirculates the balance to maintain 250 - 270 m3/h total slurry flow. All of the leach feed slurry gets at least one pass through the Filblast thereby eliminating short-circuiting. Typically a 6/4 EAH Warman pump drawing 60-70 kW is required to circulate 250 m3/h through the system. The back pressure generated by the Filblast is in the range of 400-500 kPa depending upon pumping rate, pulp density and slurry rheology. The high shearing rate effectively negates the viscous effect of slurries and the addition of a gas further reduces the pulp density by virtue of the intensely aerated, homogeneous medium. The gold leaching Filblast cartridge elements are made of polyurethane but stainless steel, ni-hard, rubber or ceramics can be used depending on the operating temperature and design duty. The efficiency of the Filblast Leach Reactor in gold cyani­dation is due to the extremely efficient mixing, oxygen dissolu­tion and surface polishing action of the Filblast design. Either air or oxygen may be used but Atomaer recommend the use of oxygen because of the rate benefits gained from cyaniding at [02] significantly > 20 ppm D O in the reactor. Very high DO concentrations have been measured; in excess of 50 ppm. There is some debate as to whether the value is a true measure of the DO or the oxygen meter sensor is measuring the effect of a mass of very fine bubbles of free oxygen. Regardless of the fact the reactor has registered some amazing gold dissolution rates commonly in excess of 80 % during transit of the pulp through the reactor. The elapsed time is less than half a second!

Jan 1, 1995

By Lawson E, Purkiss S. A R, Van Ashwegen p C

It is only in the past decade or so that industrial exploitation of biological resources and techniques has become regarded as a distinct discipline. Commonly referred to as Biotechnology, it embraces biochemistry, microbiology and the engineering sciences and is mainly aimed at the biological conversion of suitable raw materials into desired end products. The catalytic agents are more often than not bacteria although other micro-organisms such as fungi are used. The range of micro-organisms used is wide and the choice depends upon the desired end product, which in turn depends upon the metabolic attributes, genetically engineered or otherwise, of the cells. The metabolic diversity of micro-organisms has been applied to processes such as antibiotic production, food processing, brewing and chemical production, and of course extraction of metals from ores. Metabolic diversity is, to a certain extent, based on nutrition, which, in its simplest form, can be divided into energy source, carbon requirements and nature of the electron donor producing reducing power to the cells. The source of energy may be light, in which case the organisms are phototrophic (eg green plants, algae). The carbon requirements and reducing power may come from organic sources. These organisms are then called heterotrophic (eg man and most bacteria, including the well known Escherichia colt). However, there is a group of bacteria whose energy metabolism depends upon chemical redox reactions, use inorganic carbon (CO2) and obtain their reducing power from reduced chemicals such as metal sulphides. These are known as chemolithotrophs. They play an important role in mineral recycling in nature and are also ideal for extraction of metals from ores. This is because they are extremeophiles being acidophilic (grow at very low pH) and sometimes also thermophilic (grow at very high temperatures). These bacteria operate in such hostile environments that competition, or contamination, by other organisms does not occur. Extraction of metals from ores by chemolithotrophic bacteria is commonly referred to as biohydrometallurgy. Other related areas are bioadsorption of metals from dilute solution,- microbial treatment of metal contaminated wastes and removal of toxic chemicals produced or used during mineral processing. This paper basically reviews the work that Gencor has undertaken in the field of biohydrometallurgy and the advancements it has made in commercialising the technology, but also touches on certain long-term areas of research that are currently under investigation.

Jan 1, 1995

By F D Durao, Muge F. H, Rogado J. Q

In the scope of the project named CAPUME II (EEC BRITE/EURAM contract - project MA2M-CT90,-0042(SMA)) for the development of an integrated mine planning system for underground mines, two of the main tasks were the development of a short-term mining planning procedure (module) and a numerical simulator of the mineral processing plant of Pirites Alentejanas - PA. The short-term mining planning module defines the mining sequences by solving a constrained minimisation problem. The ore grade variability is the objective function subject to the geometrical constraints of the mining method and to the maximum of `internal blending'. The optimisation problem is solved by applying a dynamic programming algorithm. The plant simulator is an essential tool of the planning system allowing the preview of metal grades/recoveries of copper, lead and zinc of concentrates streams, given the corresponding metal assays of the run-of-mine ore, defined by the short-term mine planning module. This way, the management can plan the short-term mining operations (the weekly sequence of exploration blocks and the internal planning) in order to fulfill given required conditions, based on a shipment schedule and on a purchaser's formula. In this paper, after a short description of the short-term mining planning module and of the simulation package named SIMUL, a synthesis of the main model development steps and the results of some simulation runs are presented and discussed.

Jan 1, 1995

By P. Whincup, T. Showell, B. Marchant, R. Dunne

An oversupply of copper on world markets in the early 90' s, coupled with a decrease in demand, resulted in a "tight" market for the sale of copper concentrate. In these conditions small producers of low grade copper concentrates found it difficult to sell their products. The situation was exacerbated for those producers also having reasonable quantities of penalty elements (e.g. As, Bi). The Telfer Gold Mine bulk copper gold concentrate, produced from treating underground sulphide ore, fell into this category (i.e. 16% to 20% copper, 30% to 35% sulphur and 3500ppm to 4500ppm arsenic). The concentrate sulphide minerals are predominately chalcocite and pyrite. Although a higher grade copper concentrate was attainable a substantial decrease in gold recovery ensued. Under the prevailing market conditions a decision was made to stockpile concentrates pending either an easing of market conditions or alternatively finding an on site method for treating the concentrate to recover both the contained gold and copper.

Jan 1, 1995

By Fickera M. A, Marshall S, Burgeese F. L, Burgees J, Estrina H

A new high intensity flotation process FASTFLOT was deployed to recover residual zinc from the zinc circuit tailings at Pasminco Mining's Concentrator, Broken Hill. Performance of the FASTFLOT process is discussed with respect to various size fractions. Results suggest that the process has an affinity not only for fine particles but also for +200 ¦m particles which the conventional flotation cells failed to recover. Various strategies for FASTFLOT deployment are also discussed.

Jan 1, 1995

By R.P. Edwards, B.C. Flintoff

Froth flotation is one of the most widely used and effective processes for mineral benefication. First introduced in 1911, flotation technology has seen many developments over the past 80-plus years. Innovations in reagent chemistry, equipment design, process analysis and process control have given design and plant engineers a powerful set of "tools" for process optimization. However, it does not follow that all flotation systems are optimized. As Klimpel observes: "The problem with the industrial flotation process is that it is relatively easy to get reasonable results, and relatively difficult to get excellent results." Klimpel [1988] While reasonable was sufficient in the past. competitive forces will make excellent necessary in the future. Judging by the activities in many Canadian plants this transition is already underway.

Jan 1, 1995

By Peter Erlynne

Rising costs have affected the cost of operating and install­ing crushing circuits, just as they have affected every other area and there is little possibility that the cost cycle is about to be reversed - power costs, wear materials costs and labour costs continue to increase but a basically stable gold price makes little allowance for these cost increases. Additionally, lower grades of ores being worked, and harder feed materials have a significant effect on the potential for higher processing costs. There are, of course, options for size reduction - some of them newer than others - some are suitable for certain types of ores and less suitable for others and it can sometimes be difficult to ascertain the accuracy of anticipated results before plant design and con­struction are completed - by which time the capital outlayed will preclude a change to another method ofreduction. Nordberg's patented WaterFlush Technology has the potential to change the way that Ball Mill Feed production is viewed: Some of the elements that must be considered are: • Capital Cost • Operating Cost • Efficiency • Flexibility • Availability • Control • Support Efficiency • Expertise • Spares availability • Environmental considerations

Jan 1, 1995

By Peter Bourke

It was in 1982 that the first SK-80 flash flotation machine was introduced at Hammaslahti concentrator in Finland to produce a final grade copper/gold concentrate. Since then the size and number of flash flotation units has steadily developed with the SK-240 being introduced in 1984 and the SK-500 unit in 1990. To date over 130 units have been installed worldwide many of which have been used to maximise the recovery of precious metals such as gold and platinum by preventing overgrinding in the grinding circuit prior to flotation. This paper briefly describes results achieved at several major gold mines in Australia and overseas that operate large flash flotation cells.

Jan 1, 1995

By Jeffrey R. Kelly, Paul M. Kubera, Richard A. Howk

Mixing of solid-liquid slurries is a unit operation that is widely encountered in the minerals processing industry. Applications may range from simple slurry storage in open tanks to complex chemical reaction systems under extreme conditions of temperature and pressure. The specific process requirements dictate both the degree of mixing required and the type of agitation employed to achieve the desired results.' Many continuous-flow process applications feature tanks operating in series to provide a discrete number of stages and a known residence time for the slurry. Because these tanks operate at a constant level in an overflow mode, the mixer must maintain uniform solids concentration and size distribution throughout the tank; failure to achieve uniformity results in accumulation of coarse solids in the tank, ultimately leading to a process or mechanical failure. Downward-pumping, axial-flow mixing impellers are widely employed to produce uniform solids suspension. The specific impeller type, number, size, and power draw is a function of each given situation. The use of high-efficiency, fluid-foil impellers (Figure I) has evolved as a recognized standard for these flow­controlled applications. Recent small-scale experimentation and full-scale experience has demonstrated that, when uniformity is required, capital and operating expense can be minimized by employing an additional upper impeller pumping in the upward direction.

Jan 1, 1995

By David Lunt, Evan Kirby, Peter Mason, Ian Ritchie

The treatment of refractory gold ores, in particular the "competing" technologies and their relative advantages and economics, has become a major segment of most mineral technology oriented conferences in recent years. A common theme is the increasing refractory nature of gold ores being treated. This is despite ores such as those at Kalgoorlie having required roasting for liberation since the last century. Papers on refractory gold treatment have examined the characteristics of refractory ores and the causes of reduced recovery (eg La Brooy 1994), the available technologies and their relative economics eg Litz 1990), and the selection of a suitable process route (eg Nicholson 1993, Weston 1994). The most comprehensive collation of data on such processes is provided in the different editions of Randol. A variety of classifications and definitions of "refractory ore" have been published. Due to the many factors which can impact on the recovery of gold it is perhaps not feasible to develop a universal characterisation that can be applied to all gold bearing rocks. La Brooy et al have provided the framework for characterisation shown in figure 1.

Jan 1, 1995

By S. R. LaBrooy, M. C. Costello, A. C. Bax

Nickel is present in a number of gold ores in Australia, Africa and the United States. The effects and behaviour of the nickel during the cyanidation and adsorption processes, and also during the elution and electrowinning processes have been examined by a number of researchers, usually as a part of a larger investigation. This paper examines the available data on the behaviour and effect of nickel during cyanidation and its associated unit processes. The presence of nickel is often not considered to be particu­larly important as it does not cause the same degree of problems across the circuit as those experienced in the presence of copper. It can however lead to increased cyanide consumption during leaching, and reduced adsorption of gold onto carbon. A proportion of nickel cyanide may be removed from carbon prior to elution by carrying out a hot (90° C) acid wash. The nickel which remains on the carbon will be partially eluted during the main elution step, and, dependent on its concentration in the pregnant solution, part of it may be deposited during electrowinning. There is always a risk that any nickel remaining on the carbon after the elution step will be reduced to metallic nickel during the regeneration step. This may ultimately result in an increasing base level of nickel on the carbon, as metallic nickel is insoluble in both cyanide and hydrochloric acid.

Jan 1, 1995

By Kunibert Hanusch

Copper in recycling material is accompanied by various groups of metals: 1) Metals which are much more negative than copper, such as Fe, Al, Si, P, Be They are mainly removed by fire refining during the recovery of copper and leave the process in form of slag. 2) Metals which are more positive than copper or difficult to separate by fire refining and which are partly reduced together with the copper. These metals are for example As,. Sb, Ni, Ag, Pb, Zn, Sn. They are enriched in intermediate products and recovered from these or remain for their major part in the fire-refined copper and can be separated by electrolytic refining and recovered from the electrolyte or anode slime. This report describes the process of Hüttenwerke Kayser AG in Germany and illustrates how considerable returns of material are partly required to separate or recover associated metals. They are finally removed in saleable products.

Jan 1, 1995

By H. M. Castrantas

Caro's (peroxymonosulfuric) acid has been reported to destroy WAD (weakly acid dissociable) CN-but, until recently, the technology has not been demonstrated in other than a laboratory setting. During the last two years, Caro's acid has been shown to successfully detoxify WAD CN-in tailings at two large North American gold mines. Using on-site FMC generators, Caro's acid reduced the WAD CN-from 40-55 ppm to below 20-35 ppm WAD CN-, the target range for the two mines. The detoxification costs using Caro's acid were less than 50% of the treatment cost of using hydrogen peroxide, the previous oxidant of choice. In addition to the considerable savings in CN-detoxification costs, lower WAD CN-values were achieved and the detoxification time with Caro's acid was greatly reduced compared to hydrogen peroxide.

Jan 1, 1995

By James F. Holzbach

Although Disputes Review Boards have been used for some time, they had not received wide publicity at the time Monroe County first used one. Public owners frequently resist adopting new contracting practices. This paper discusses an owner's experience with Dispute Review Boards, from learning about them to their use on two (2) projects. The experiences of potential and actual contractor claims are compared to a claim on an earlier contract and the ensuing litigation. Suggestions for possible use for Owner-Engineer disputes and recommendations for use are provided.

Jan 1, 1995

By Brian V. Roulston

Potash is Canada's leading industrial mineral in terms of value of production, with 11.1 M tonnes of muriate of potash produced in 1992 for a value in excess of $1 billion U.S. Each tonne of potash produced generates about 2 tonnes of waste salt, together with slimes and brine. The disposal of these waste products, particularly the salt and slimes which are discharged on the surface, has recently become an environmental concern. This concern is forcing companies and regulatory authorities to review disposal practices. In New Brunswick, on Canada's east coast, Potash Company of America operates a mine at which 2 M tonnes of potash ore and 0.5 M tonnes of rock salt are mined each year. The mine is situated in an environmentally sensitive area, noted for its dairy farming and salmon angling. In such an area it was recognized that the storage of waste on surface would be unacceptable, and the mine was designed around this principle. Three main waste streams - salt, slimes, and brine - must be managed as an integral part of the mining system. Around 1.5 M tonnes of fine salt tailings from the milling process and the rock salt screening operation, are sent directly to the active cut-and-fill potash stopes to be used as backfill. Slimes and excess brine from the mill are piped underground as a slurry to be discharged into one of the basin shaped stopes created by mining of the rock salt. While the slimes settle out, the clarified brine is withdrawn from part of the stope to be pumped to surface as a feedstock for the evaporator - a process which recovers the contained potash values in the brine. By designing a system which integrates the mining, processing and disposal of all product streams, and by careful production planning, it has been shown that zero effluent potash mining is possible and points the way for the industry in the future.

Jan 1, 1995

By Hans von Michaelis

Very little has been published about Cia de Minas Buena­ventura. Don Alberto Benavides Quintana, now in his seventies, founded the company in 1953. This venerable gentleman is a Doyon of the Peruvian mining industry and more has been known about him than about his company. Buenaventura is a highly profitable gold producer with excellent potential to expand gold production in joint ventures with Newmont, Southern Peru Copper (ASARCO), and BRGM as well by developing their own new gold mines. On September 15, The Wall Street Journal published an article titled "Peru's Big Rebound Sets Off Foreign Investors' Enthusiasm."

Jan 1, 1995