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By J. D. Miller

Reaction kinetics for gold dissolution in acid thiourea solutions were investigated using formamidine disulfide as an oxidant. For the conditions studied it appears that a surface reaction limits the rate of gold dissolution. The rate was found to be first order with respect to thiourea concentration and half order with respect to the concentration of formamidine disulfide; the apparent activation energy for the reaction was 10.40 kcal/mol (43.40 kJ/mol); and the reaction rate was independent of pH for the pH range 1.0 to 3.0.

Jan 1, 1999

By J. L. Moreno, A. L. Williamson, R. D. Bartlett

Large open pit mines in desert climates, such as the Phelps Dodge Morenci copper mine in Arizona, can create groundwater cones-of-depression of considerable size and stability. The hydraulic containment provided by the groundwater depression prevents migration of process solutions into the surrounding regional aquifer. Copper leach operations that fall within the groundwater depression may not require costly lining if passive containment can be demonstrated. An approach is presented in this paper that was successfully used to demonstrate passive containment. The approach includes a combination of groundwater modeling and a water balance analysis of leaching operations failing within or immediately near the open pit.

Jan 1, 1999

By T. F. Torries

The primary criteria used by the mining industry to judge the merit of a project is internal rate of return (IRR) rather than net present value (NPV), although NPV is favored by academicians. This paper discusses the problems of IRR and NPV and compares the multigoal nature of the decision¬makers and their need for informa¬tion having the characteristics of NPV and IRR. The conclusions reached are that both NPV and IRR can be used for investment ranking, that NPV suffers the same multiple root problem as does IRR, and the use of conventional incremental IRR to reach NPV¬consistent project ranking is mis¬leading.

Jan 1, 1999

By Pfeifer H. C, Nicacio P. A D

Sinter has been used as part of the metallic charge in large-scale blast furnaces for many years with the well-known benefits in terms of productivity and fuel consumption. However, because of the high investment in a conventional sinter plant, small blast furnaces and the associated integrated mini steel plants have not taken the advantages of using sinter. Recently KTS Korf Tecnologia Siderurgica, a division of Mannesmann Demag Ltda in Brazil, has developed a mini sinter plant for which the investment is compatible with small blast furnaces. Consequently, it is of great interest to evaluate the economical impact of using sinter in such small-scale integrated steel plants. In order to compare two alternatives, ie 100 per cent ore and 70 per cent sinter in the blast furnace burden, mass and heat balances for the entire operation from sinter plant through the blast furnace and EOF-based melting shop, were performed to evaluate the final production cost of the liquid steel. It was found that, depending on the sinter feed price, substantial savings can be obtained with the use of sinter.

Jan 1, 1999

By M. Bélanger, H. -L. Jacob

"The province of Quebec has a strong tradition in industrial minerals. Ten commodities are produced and the annual total shipments have exceeded $600 million in recent years. Quebec is a world renowned producer of chrysotile, titanium slag, graphite, and ilmenite. Quebec is an important North American producer of mica, talc, and peat moss. This paper reviews the main minerals and commodities that have been the object of exploration or development in recent years, namely graphite, wollastonite, dolomite, and silica. Some of the leading projects concerning magnesium minerals and apatite-ilmenite are described. IntroductionQuebec has a strong tradition in industrial minerals. It goes back to the second half of the 19th century when the first graphite and apatite mines in the Gatineau area and asbestos mines in the Eastern Townships were opened. Since then, more than 25 commodities have been produced in Quebec, making industrial minerals an integral part of the Quebec mineral industry. Today, industrial minerals and building materials count for one third of the total mineral production in Quebec.Present industrial mineral production includes 10 commodities (Table 1). In the last five years, the value of industrial mineral shipments has varied between 500 and 700 millions dollars annually, which represents 20% to 25% of Quebec’s total mineral production. For many years, Quebec has been a major producer of chrysotile and titanium slag, the only producer in eastern North America of mica, graphite and ilmenite, and a leading Canadian producer of talc and peat moss. Quebec also produces, mainly for domestic markets, dolomite, limestone, salt and silica.Quebec’s industrial mineral sector has been quite active in the recent years. Exploration by government geologists and companies has led to the outlining of new deposits, some of which are now in production; others are currently being evaluated. Technical and economic studies are also underway to determine the feasibility of various development projects."

Jan 1, 1999

By Y. Fautrelle, F. Felten, O. Metais, Y. Du Terrail

"We deal with the prediction of electromagnetically-driven turbulent flows by means of a Large-Eddy- Simulation method (LES). The model is applied in the case of a liquid metal pool submitted to a polyphase linear electromagnetic stirrer. We investigate two cases: (i) the frequency of the magnetic field is equal to 50 Hz; in that case the effects of the pulsating part of the Lorentz forces may be neglected; (ii) the frequency of the magnetic field is low (f= 1 Hz), then the oscillating part of the electromagnetic forces is taken into account. The LES predictions agree well with the mean velocity measurements, as does the standard k-a model. However, as for the turbulent kinetic energy predictions, there is a large discrepancy between the two models. When the oscillating part of the Lorentz forces is taken into account, the computations show that the fluid flow is sensitive to the unsteady part of the forces. We find that the mean velocity is not affected by the fluctuating component of the force. As for the turbulence parameters, the presence of the pulsating part leads to a significant reduction of the turbulent kinetic energy, whilst the turbulence length scale decreases.IntroductionElectromagnetic stirring is commonly used in various metallurgical processes. In continuous casting for example, it may improve the structure of the solidified metal products. Fluid flows generated by electromagnetic stirrers have been extensively investigated (1 ). As for numerical predictions, many works have been published on the subject. In most of the previous works, onepoint closure models have been used. The most used model is the well-known k-i:: model. Those models yield fairly good results as for the mean velocity prediction. However, it has two main drawbacks:(i) the turbulence is not predicted accurately,(ii) it is not well fitted for unstationary flows as well as transitional turbulent motions, where theReynolds number is moderate."

Jan 1, 1999

By Nico Steenekamp

At Lonrho Platinum in South Africa, ores from both the Merensky and UG2 reefs of the Bushveld Igneous complex are treated by flotation and smelting to produce a nickel-copper matte which serves as a collector for the platinum group metals (PGM' s). The nickel-copper matte was originally shipped to Norway for treatment and recovery of the contained base metals, with the return of the PGM rich concentrate to South Africa. The Lonrho Platinum Base Metal Refinery was commissioned in 1985. The original process employed a Shenitt Gordon design. The converter matte is treated in a refinery which utilises both atmospheric and pressure leaches for the dissolution of base metals to produce nickel sulphate crystals, copper cathode and a PGM concentrate. This paper refers to flowsheet and operating changes as well as improvements within the Base Metal Refinery.

Jan 1, 1999

By Jorge Alberto Soares Tenório

Household zinc based batteries contain some heavy metals such as zinc, manganese and mercury. There is a large effort from manufacturers in order to eliminate the last one. As a municipal waste, the disposal of batteries has become an increasing worry. The aim of the present work was to characterize dry batteries scraps, and establish a flowsheet for their processing. This was done using unit operations of mineral processing and parameters and yields of each stage have been defined. Such procedures have been chosen due to their low cost. The operations were hammer mill grinding, size separation, magnetic separation and specific weight separation in water. The characterization step was done through chemical analysis and x-ray difiactometry. After size classification, it was verified that 76.6% of the total amount of zinc was over 1.70mm. This fiaction was constituted basically of zinc and some coarse pieces from the steel body, paper and plastics. This fraction was submitted to magnetic separation followed by specific weight separation in water. A visual examination showed that during the grinding process, graphite was concentrated in the finer fractions. Manganese concentration in the fractions over 6,35mm was less than 2%. This means that there was low contamination by the paste in this fraction. It was due to the entrapment of the paste by steel scraps (from the body) and zinc (from the cup) during grinding.

Jan 1, 1999

Laboratory testwork was carried out on an overall orebody composite, of 2.9 per cent Cu and 4.2 per cent Zn, prepared from drill core taken from the Currawong fine-grained, copper-zinc massive sulphide deposit near Benambra in Victoria. While 90 per cent of the copper was readily recovered in a concentrate of 20 per cent Cu, after grinding to 95 per cent passing 38 microns, zinc responded poorly to conventional flowsheet/reagent regimes. Experience elsewhere with the use of reverse cleaning, to separate pyrite from sphalerite, led to a series of tests in which better (but still modest)metallurgical results were obtained. The best result was a zinc recovery of 55 per cent in a concentrate of 50.5 per cent Zn. The major loss of zinc occurred in the reverse cleaning stage where the unit recovery of zinc was similar to pilot plant results achieved at Mount Isa Mines on similar feedstock. Diagnostic mineralogy suggested that an overall zinc recovery of 70 per cent was probably the practical upper limit, at a 50 per cent Zn grade.

Jan 1, 1999

By F. G. Rinker

The world demand for metallized iron continues to increase, keeping pace with steelmaking requirements for lower cost hot metal. Virgin iron ore and in-plant oxide fines can be reduced to direct reduced iron (DRI) and hot briquetted iron (RBI). MR&E has developed an improved coal-based process for cost-effective production of either DRI or HBI. Starting with dry compaction, the process combines the latest technology for material preparation, rotary hearth furnace construction and environmental control. Coarse iron ore fines are blended with pulverized non-metallurgical coal to produce a highly metallized (>90%) product. This paper presents production and installation cost data based on operating and under-construction iron oxide reduction facilities.

Jan 1, 1999

By Detlef Sulzer, Winfried Rosenstock

"At the end of this century a great breakthrough in the field of blasting technology is finally going tobecome reality. That, in the true sense of the word, is the long expected and desired “HighTechnology Blasting”. So far trials have been carried out in Australia, Africa and Europe with remarkable results, that have been predicted by the authors. As a result, significant reductions of explosives and drilling expenditure are emerging for the future."

Jan 1, 1999

By D. H. Carlson, J. H. Johnson, C. F. Renders

Introduction Diesel-powered vehicles are used extensively in underground mines throughout North America. The bulk of the diesel vehicles found in underground mining operations are used for loading and ore haulage, as well as for transportation of personnel and supplies. Along with the advantages of using diesels underground is the disadvantage associated with diesel-tailpipe particulate-matter emissions (DPM). The concentration of DPM in the ambient air of US underground metal mines is not now regulated by the Federal Mine Safety and Health Administration (MSHA). However, recent studies have shown DPM to be mutagenic (National Institute of Occupational Safety and Health, 1988), and the American Conference of Governmental Industrial Hygienists (ACGIH) has recommended that the exposures of per¬sonnel to DPM be limited to an 8-hr time-weighted average concentration (threshold limit value or TLV) of 0.15 mg/m3 (Anon., 1995). The authors, while making measurements in a number of US underground mines that use diesel haulage equipment, found mine air DPM concentrations ranging from 0.2 to 2.36 Mg/M3 (McCawley and Cocalis, 1986; Watts et al., 1989; Cantrell et al., 1991; Haney, 1992; US Bureau of Mines, 1992; Watts, 1992; Watts et al., 1995). If the proposed DPM TLV were to be adopted as a permissible exposure limit (PEL) for US underground mines, the proposed limit of 0.15 mg/m3 PEL would be lower than any of the concentrations measured in the earlier studies and would represent more than a 15-fold reduction from the maximum 2.36 mg/m3 concentration. A 0.15 mg/m3 PEL would also represent a 4.5-fold reduction from the average 0.68 mg/m3 measured mine ambient air DPM concentration reported in this paper. Other diesel tailpipe emissions that are now regulated underground include carbon monoxide (CO), with a PEL of 50 ppm; nitrogen dioxide (NO,), with a PEL of 5 ppm; nitric oxide (NO), with a PEL of 25 ppm; and sulfur dioxide (SO,) with a PEL of 5 ppm. Because the concentrations of these gaseous pollutants and DPM are affected by the state-of-maintenance (Waytulonis,1992), it is important that a means be developed to measure emissions from engines that are now in service to determine when maintenance is needed. The current study was the result of an inquiry by mine¬maintenance personnel who had been receiving complaints about high concentrations of diesel soot (DPM) in mine headings from load-haul-dump (LHD) vehicle operators. Mine-maintenance personnel were searching for an objective test to determine if the diesel tailpipe particulate emitted was excessive. The mine was also evaluating electronically controlled, two-cycle, naturally aspirated, direct-injection diesel engines on some of their JCI (John-Clark Inc.) load-haul-dump (LHD) vehicles. These LHD vehicles were used to haul freshly blasted ore from mine headings to a feeder breaker. The feeder breaker breaks down the larger chunks and feeds the broken ore onto a conveyor. Michigan Technological University, in past studies, developed an emissions-measurement apparatus (EMA) ca¬pable of measuring diesel vehicle tailpipe pollutant concentrations (Chan et al., 1992; Chan et al., 1993; Carlson et al., 1994). At the time of the study reported here, most of the mine's LHD vehicles used a 12-cylinder, four-cycle, naturally aspirated prechamber diesel engine. The study was undertaken in cooperation with mine maintenance supervisors from late 1992 through July 1993. The objectives were to compare diesel exhaust emissions between the 6-cylinder, two-cycle, electronically controlled, direct-injected diesel engine and the 12-cylinder, four-cycle, prechamber diesel engine and to, then, use the data collected, in conjunction with mine ambient air measurements, to demonstrate the application of the "deterioration factor" (Chan et al., 1992), which is a measure of the state-of-maintenance of mine-vehicle engines that are now in service. The information would be used to identify vehicles that need maintenance to reduce emissions. The data reported here are unique in the sense that they combine underground diesel vehicle ambient and tailpipe

Jan 1, 1999

By H. H. Murray

Recently developed clay deposits that will impact regional and world markets are described. These deposits, their location, geology, and physical properties are delineated. Kaolins from the State of Para in Brazil and from Ukraine; bentonites from Argentina and India; and palygorskite and sepiolite from China are world class deposits that when processed using modem technology will produce excellent products. Other deposits that may affect regional markets are kaolins from China, Australia and Indonesia; bentonites from Georgia (formerly USSR) and China; and palygorskite from India and Ukraine. New ball clay deposits that will affect regional markets are in China and Indonesia.

Jan 1, 1999

By D. Potter

In 1990, Freeport Exploration began regional reconnaissance exploration programs in Irian Jaya, the easternmost province of the republic of Indonesia (Fig. 1). Irian Jaya occupies the western half of the island of New Guinea. Freeport was awarded an initial contract of work that totaled 2.6 million hm2 (6.4 million acres). The company was subsequently awarded additional concessions that added 1 million hm2 (2.5 million acres). The concessions require work commitments and periodic relinquishments. Due to these relinquishments, Freeport’s current land position totals 1.9 million hm2 (4.7 million acres). Freeport began the exploration program to locate additional Grasberg deposits, the largest deposit in the Ertsberg district. But the company recognized that other types of deposits could be present in the largely unexplored area of Irian Jaya.

Jan 1, 1999

By S. H. Castro

In 1997 Chile was the world's largest copper mine producer with around 3.4 million metric tomes of copper. Conventional technology (conminution-flotation- smelting-converting-electrorefining) for copper sulfide ores was used. For copper oxidized ores hydrometallurgical processes (heap leaching-solvent extraction- electrowinning) were employed. Consequently, the most important waste effluents include flotation tailings, gaseous emissions, smelter slags, acidic and alkaline wastewater, electrolytic sludges, solid residues from leaching, etc. The introduction of stricter environmental regulations are forcing the Chilean industry to minimise the generation of waste and promote cleaner production. Gas emissions such as SO2 and arsenic from smelters and process wastewater are the major problems at this stage. The environmental impact assessment of gas emissions in all six largest smelters namely Chuquicamata, Caletones, Potrenllos, Ventanas, Paipote and Chagres led to design a "decontamination plan." The implementation of this plan resulted in (i) the installation of sulfuric acid plants for SO2 abatement and (ii) the installation of electrostatic precipitators to remove arsenic oxides condensed from cooling gases. The aim of this paper is (i) to describe the type of waste associated to the various stages of the metallurgical processes and (ii) review the main abatement technologies used in medium and large size companies.

Jan 1, 1999

By Adam J. Gesing

The eddy current separator (ECS) is designed to separate nonmagnetic (nonferrous) electrically conducting (metallic) particles from nonconductive residue. Nonferrous metallic particles are repelled out of the material stream passing over the eddy current rotor (ECR). The rotor is housed in a fiberglass composite outer shell that serves as a conveyor head pulley. This results in the desired metaVnonmeta1 separation. The behavior of ferromagnetic particles, mainly iron and iron oxide (i.e. rust), is quite different. These particles are strongly attracted to the magnets and the smaller particles tend to align their long axis in the direction of the magnetic flux. Since the direction of the flux changes with the passage of each magnet pole, the small particles spin at very high rates causing wear of the belt and of the composite outer shell housing the ECR. Large particles, when trapped under the ECS belt, cannot spin, but can be heated by the eddy current effects and subsequently can burn through the composite outer shell. We discuss the practical implication of this behavior of iron and rust on the design, performance and maintenance of eddy current separators.

Jan 1, 1999

By S. R. Reddy

Thennodynamic properties of several quaternary systems are calculated using our recently modified Margules equations. The modified Margules equations are expressed up to infinite order in the vicinity of solvent. Quaternary system of one solvent and three,solute partials are derived. First order interaction coefficients of binary, ternary and cross -interaction parameters of quaternary system are used to'evaluate the partial functions. In the original fonn of Margules equations,derived partial functions are convergent and same 'as Unified ,Interaction Parameter Fonnalism. But considering up to infinite order of the Margules coefficients, the functions are divergent, in order to overcome this restriction, Margules equations are modified to get consistent equations. Derived partial functions are thennodynamica Hy consistent with Maxwell and Gibbs Duhem relations. The derived logarithmic activity coefficient of the solvent and solutes are consistent with the ternary systems. The calculated data, ie., activity coefficient values of nitrogen and interaction coefficients are in good agreement with the data of Fe-Cr-V -N. Fe-Ni-V -N, Fe-Cr-Ta-N and Fe-Ni-Ta-N systems.

Jan 1, 1999

By John Stankus

Seam interaction in multiple seam mining has significant effect on entry stability. The remaining pillar in an old working usually creates a high stress concentration zone while the gob creates a stress release zone. A good panel layout should take advantage of the stress release effect created by old workings. This paper presents two case studies of multiple seam mining. The Jennmar Finite Element Analysis System (JFEA) is utilized to analyze the seam interaction effect and identify the mess concentration and relief zones Panel layouts are designed bad on the results of the finite element analysis Appropriate roof support system are also designed for different seam interaction areas.

Jan 1, 1999

By P. A. Davidson, D. J. Short

"In this paper we describe a 'non-contact' electromagnetic nozzle suitable for sprayforming and gas atomization processes. In such processes there is a need to control the flow rate and diameter of the liquid metal jet whilst minimising contamination of the stream. This can be achieved using an electromagnetic valve, which partially levitates the jet in freespace, using a segmented cylinder surrounded by an induction coil. This valve will significantly enhance the quality of the titanium alloys and nickel-based superalloys used in sprayforming and gas atomization. This paper describes the design and test of a laboratory prototype valve based on experiments performed with liquid tin.1. Introduction In many industries there is an increasing need for clean, high quality metals and alloys based on titanium and nickel. Two important processes are: 1) Spray deposition which allows the liquid metal to be converted to a near-net shape, thus alleviating the need for subsequent forging and extensive machining and; 2) Powder production of titanium by gas atomisation.In centrifugal spray deposition of titanium (see figure 1) the metal is induction melted in a cold crucible. The crucible consists of a number of water-cooled segments, which allows the high frequency magnetic field of the coil to pass through the crucible, and into the melt. The charge is melted by the induced eddy currents. Locally at the crucible walls the liquid metal solidifies, and is contained within a. 'skull' of its own solid, thus reducing contamination from the crucible wall. Once melted the metal is poured through an electrically heated graphite nozzle and into the spray forming chamber. The principal limitation of the process to-date, however, is that it currently uses a graphite and /or ceramic nozzle to direct the flow of liquid metal to the atomizing disk and as such there is considerable risk of nozzle erosion with inevitable effects in terms of contamination of the melt stream and variability in flow conditions. In this research programme we develop a. non-contact electromagnetic nozzle, which will totally eliminate refractories and/or ceramic materials from the melting and casting process. This will greatly enhance the technological capabilities of sprayforming and gas atomization processes."

Jan 1, 1999

By J V. Lawless

Two types of low sulphidation epithermal deposits that have different gangue mineralogies and ore shoot geometries are recognised. One has laterally near-continuous ore shoots over a significant vertical interval that consist of quartz, chalcedony, pyrite, minor base metal sulphides and adularia, with electrum. The other type of deposit has discrete near-vertical ore shoots of a lesser vertical extent, that consist of quartz, pyrite, base metal sulphides, sulphosalts, electrum and in their upper parts barite, which are enclosed in veins of earlier quartz. The gold mineralisation in both deposit types is considered to be a co-precipitate of pyrite, with that in the first type of deposit produced by prolonged boiling in an upflow of a hydrothermal system (Upflow Deposits); an example is Waihi in New Zealand. The other type is produced by mixing, a deep water primed for gold deposition by prior limited boiling, with an iron-bearing oxidised condensate of the steam released by the boiling, in an outflow of a hydrothermal system (Outflow Deposits); an example is Thames in New Zealand. Early recognition of these different types of deposits can be used to develop mineralisation models of predictive value on which to focus exploration drilling. Early recognition of an Upflow Deposit promotes an extensive program to delineate the extension of the main ore shoot. In contrast recognition of an Outflow Deposit requires a more intensive approach to find individual ore shoots which, although smaller than those found in Upflow Deposits, may be high-grade, particularly if there is earlier mineralisation present to act as a protore.

Jan 1, 1999