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By Fathi Habashi

LEACHING IS the process of extracting a soluble constituent from a solid by means of a solvent. In extractive metallurgy it is the process of dissolving a certain mineral (or minerals) from an ore or a concentrate, or dissolving certain constituents from metallurgical products such as calcines, mattes, scrap alloys, anodic slimes, etc. In this respect, either one of two purposes can be achieved: 1) Opening of ores, concentrates, or metallurgical products to recover the metal values. 2) Leaching easily soluble constituents (usually gangue minerals) in an ore or a concentrate in order to have it in a more concentrated form, e.g., the

Jan 1, 1970

By V. J. Matta, A. A. Pincheira, I. A. Reghezza, Ch. J. Vergara

The growth of solvent extraction in Chile has been astonishing during the last years and has been established as a very successful technology. However, there are still limitations that must be improved, mainly, the problem of carry over from one phase to the other and the losses of organic reagent associated with the crud formation. These are problems that our company has been taking care, solving them with high efficiency and low costs, allowing important increases in the copper output of our plants and capital savings by means of the optimization of the use of nonproductive units in the SX plants.

Jan 1, 1998

By G. V. Krishna Roa, G. Vijaya Kumar

One of the main objectives while planning ventilation systems for mines with multiple fans is minimization of the total airpower consumption of the mine. Solution of this problem by conventional ventilation network analysis programs is tedious and time consuming, and may not yield optimum results in all the cases. The paper presents an algorithm for solving multiple fan networks by finding optimum combination of fan operating points for required airflow distribution in the ventilation system.

Jan 1, 1995

By Roy Norcross

For the past few years Caro's acid has been used for the treatment of cyanide containing slurry effluents, providing a feasible alter­ naive to other slurry treatment processes including !NCO SO2 / Arr and ferrous sulfate. Presently, mines using Caro's acid gen­erate their own Caro's acid onsite making a relatively low quali­ty product. It was at this point where we, at Degussa Corporation, decided to focus our efforts on engineering a Caro's acid genera­tor capable of cost effectively producing a high quality Caro's acid solution, thus reducing operating costs significantly. Caro's acid or peroxymonosulfuric acid is not a new chem­ical nor is it new to Degussa. The product was named after Heinrich Caro (1834-1910), a German chemist who first described its synthesis and its oxidizing properties in 1898. Degussa has been producing the potassium salt of Caro's acid as the triple salt, 2KHSO5 - 2KHSO4 - K2SO4, called Caroat®, for over 30 years. Caroat® is used for household and denture cleansers, as a bleaching agent in dish washing detergents, in printed circuit board etching and for cyanide destruction in the plating industry. From our experience in producing Caroat® Degussa developed its new Caro's acid based DegOX™ technology for the treat­ment of cyanide containing effluents from gold and silver mines.

Jan 1, 1996

By Krzysztof Filek, Anindya Sinha, Bernard Nowak

Taking into account the possibilities of condensation of water vapour contained in air during its flow through a series of spot coolers as well as formation of eventual fog, a mathematical model of dynamic temperature, specific humidity and degree of fogging of cooled air in underground mining galleries with direct ventilation is developed. In the gallery, there situated various heat and moisture sources both of distributive and of concentrated types. The model is represented by three partial differential equations of first order. The cases of cooling with full as well as with partial air stream flowing through the gallery are distinguished. Owing to the fact that in practical designing, more important is the knowledge of the variation process of temperature, specific humidity and fogging of cooled mine air at steady state conditions, the model is modified to a set of three nonlinear ordinary differential equations. Based on the presented algorithm, the obtained set of ordinary differential equations is numerically solved which enables to: • specify the distribution of temperature, specific humidity, relative humidity and degree of fogging of cooled air in mining galleries; • determine the cooling powers of air coolers for their known locations; • indicate the locations of the coolers of known cooling powers. Exemplary calculations of temperature and relative humidity of cooled air are presented graphically in a number of diagrams.

Jan 1, 1997

By Alan G. Mayton, Jon C. Volkwein

The U.S. Department of the Interior, Bureau of Mines, in cooperation with an American firm, has been contributing toward the creation of a new highwall mining system for extracting coal in active, unreclaimed contour strip mines in the United States. The prototype system features the computer-based, remote control, video operation of a thin-seam continuous miner. Haulage is accomplished remotely also with a 76-m (250-ft) long multiple-unit continuous haulage (MUCH) conveyor system on rubber-tire vehicles. One aspect of this multi-faceted effort has been to design a ventilation system for removing dust generated at the face during the extraction process. The remote mining system eliminates the need for personnel in the mined workings. Ventilation is required to remove visible dust from the area inby two video cameras. These cameras are located approximately 6 m (20 ft) from the face, one on either side of a modified Jeffrey 102HP continuous miner. Removing the dust from this area provides the remote operator with constant visual monitoring of coal extraction at the face and thus, insures the effective operation of the mining system. A ventilation system was designed for use in a mine opening with a maximum cross-sectional area of roughly 4 sq m (44 sq ft) excluding the mining machinery. This paper describes the ventilation system and discusses how it was developed in view of the constraints imposed by the mining equipment, mining conditions, and the extraction process.

Jan 1, 1989

By P. S. Parobeck, T. F. Tomb, R. S. Ondry

From October 1980 through August 1982, surveys were conducted on 19 longwall mining operations to obtain data relative to respirable dust levels associated with particular longwall operations and occupations, to make recommendations for enhancing dust control, and, where applicable, to evaluate the effectiveness of new technology implemented to control dust. The paper summarizes the data collected during these surveys and, where possible, draws conclusions and discusses actions that can be utilized to reduce exposures to respirable coal mine dust on longwall mining operations.

Jan 1, 1987

By Dean J. Soderstrom

Soil and sands were contaminated with depleted uranium from weapons testing. This resulted in the formation of a complex mixture of uranium compounds. Characterization studies of the soil indicated the uranium was present as uranium metal, uranium oxides, silicon-bearing metallic uranium, and uranium silicates. A process was developed to selectively remove dense uranium compounds using gravity separation and a chemical extraction system to remove uranium which was not available for separation by gravity methods. Results from characterization studies and pilot scale testing are presented for background information. The primary purpose of this presentation is the report of the results achieved in the field application of the processes.

Jan 1, 1995

By N. N. Manu

In the Central African Copper Belt, sulfidization flotation is the standard practice for dolomitic copper oxide ores. It is a delicate process, and its plant application requires close control of the reagent addition. This paper presents the results of a thorough laboratory investigation. It features the monitoring, during sulfidization, of the pulp pH, the residual sulfide ion concentration and redox potential. Variables examined during the process were: retention times, sulfidizer additions, pH, collector type, dispersant dosage and reducing agent addition. Implications of the findings for plant application and process control are also briefly examined.

Jan 1, 1994

By P. Somasundaran, D. R. Nagaraj, Jing Wang

Polysaccharides have been widely used as depressants in mineral processing for decades. They constituent one of the most abundant family of biopolymers. However, only a small number of them have been used by industry so far because of a general lack of understanding of interactions between these polymers and minerals. In this work, adsorption tests, electrophoretic mobility measurements, microflotation and fluorescence spectroscopic tests were performed along with computer simulation to explore the mechanistic aspects of guar gum adsorption and conformation on talc as a function of relevant variables such as ionic strength, pH, solvent composition and polymer molecular weight. From microflotation tests, it was found that talc hydrophobicity decreased markedly due to the adsorption of guar gum even at very low concentrations and reached a plateau below moximum adsorption. Guar gum adsorption on talc was found to be not affected significantly by changes in solution conditions such as pH and ionic strength, ruling out electrostatic force as controlling factor for adsorption. Fluorescence spectroscopic studies showed no evidence of the formation of hydrophobic domains at talc-aqueous interface. Also urea, a hydrogen bond breaker, reduced the adsorption of guar on talc. All of the above results suggest that one of the main driving forces for guar adsorption on talc is hydrogen bonding in preference to electrostatic or hydrophobic force. This information should help toward designing reagents of optimum molecular architecture for efficient depression, dispersion or other such surface modification of particles.

Jan 1, 2005

By David Williamson

In the post-World War II years, metals analysts and statisticians have tracked the demand for metals in line with changes in Organization of Economic Cooperation and Development (OECD) industrial production (IP) growth rates, Williamson said. This was because the correlation between IP growth and metal demand was reasonable. "However, the correlation was exaggerated," he said. During times of expanding IP growth, metal demand increased at a faster proportional rate than IP growth. This was probably due to industry restocking in anticipation of growing demand at the start of each economic cycle. Conversely, metal demand would slacken at a greater rate than would be suggested by negative IP growth as industry destocked to reduce costs. Nonetheless, he said, a reasonable correlation could be painted between IP growth over the longer term and metal demand. "Yet, although this correlation has stood well since the last world war, it has been based on the fact that the bulk of the world's IP growth stemmed from the industrialized countries of the western world, lately including Japan," Williamson said. The so-called "developing world" had been of little consequence. The Soviet Union and other communist bloc countries were deemed to be closed, self-contained entities that, for each metal, would either be net exporters or importers, he said. These quantities would be used by analysts to calculate the overall supply/demand equation for the western world only and to deduce whether a commodity was in shortage or surplus. It is now believed that this method of projecting total world supply and demand for raw materials is outdated, Williamson said. It does not take into account the worldwide political changes that have occurred since the collapse of communism and the revitalization of China. "It is no longer appropriate to assess global balances for raw materials on the basis of three economic blocs," he said, including the western world, developing world and communist bloc. Rather, global balances need to be projected on a global basis. In this regard, since the collapse of communism and the removal of many other totalitarian regimes, capitalist forces are attempting to satisfy the expectations of the great mass of the world's poorer people, Williamson said. Such people, usually located in Asia, Africa and Latin America, have aspired to the same standard of living as people living in western Europe, North America and Japan. "Now, with free market forces at work, their aspirations will start to be met." Consequently, the demand for metals and other raw materials will now rise at a much faster rate. The production of raw materials has to keep pace with rising IP in the developed world. It will also have to keep pace with the demands associated with the rising expectations of increasing populations in the developing world, as well as from within the old communist bloc countries.

Jan 1, 1997

By M. C. Roberts

To assess the future markets for a mineral from a producing district, the following three aspects must be considered: the future growth of the markets, the competitiveness of the district in terms of production costs and reserve adequacy, and the competition from alternative sources of supply. This paper focuses on the first issue by developing a method for predicting the demand for phosphate from trends in the major market for phosphate products, the fertilizer and agricultural market. The paper shows how broad changes in this end-use market for phosphate has evolved over time. These trends are then projected into the future to make an assessment of future phosphate requirements.

Jan 1, 2000

By James P. Cooney

The global mining industry is in the process of redefining its activity and purpose in terms of sustainable development. This process is impelling a growing number of companies to engage their stakeholders on environmental and social issues. Nongovernmental organizations (NGOs) have customarily acted as critics of the mining industry's performance. A new relationship between mining companies and NGOs is emerging in the context of sustainable development, ranging from dialogue to joint action. If positive interaction among mining companies and NGOs is to succeed, clear terms of engagement must be articulated, and measurable progress toward achieving both corporate and NW objectives must be demonstrated. The experience of Placer Dome is illustrative of the rewards and challenges of engaging with NGOs.

Jan 1, 2001

By Kevin L. Purdy

Chemical dewatering aids for mineral slurries generally fall into two classes: surfactants and flocculants, which can be used separately or together. Current industrial use of both types of reagents is summarized for sulfide and non-metallic minerals, as well as uranium and gold leach residues and coal refuse. Laboratory testing for reagent selection is briefly discussed along with reagent preparation. Chemical properties of the reagents which affect the suitability for particular applications are analyzed. [BLANK PAGES - Are in the original]

Jan 1, 1986

By M. Ploc

The grinding process in the mining industry has seen an increased throughput to accomplish greater production and lower overall production costs. Up to 8-9 MW, a single motor can be connected to drive the mill through a pinion and ring gear. Above the single-pinion drive limit, the dual pinion approach was developed to allow two drive motors to be used. This allowed the mill input power to be increased to 16-18 MW. Recent developments in clutch and ring gear materials and design are allowing greater input powers of up to 20 MW to be considered. To avoid damage to the ring gear by uneven load sharing between the two motors, it is critical that the two machines accurately share load. This is typically achieved by either drives capable of controlling load torque between motors or using a GE proprietary control system that accurately controls the load torque from each motor.

Jan 1, 2010

By E. De Souza, H. Heidrich

In underground operations the evaluation of blasting fume dilution times and the application of recirculation techniques require accurate determination of the concentration of toxic fumes produced by the explosive used. This paper describes a methodology for obtaining concentrations of detonation products from commercial explosives tested under typical rock confinement and looks into the development of techniques for reducing toxic gases produced by explosives. This paper also analyses the application of techniques for the removal of toxic gas which would enable reduced re-entry times, a reduction in the quantity of fresh air and the use of air recirculation techniques, thereby providing substantial economic benefits to the industry. INTRODUCTION Toxic fumes from blasting operations are among the most common and serious hazards encountered underground. The implication of high concentrations of toxic gases emitted from blasting on the mine ventilation system are very significant and, in many cases, catastrophic results have occurred. Because blasting is a routine practice underground, the mining engineer is always confronted with the problem of controlling the fumes within acceptable levels. Typical control procedures employed underground include preventing or reducing the amount of fumes liberated from blasting through the proper selection of explosives and proper blasting techniques; removing the fumes through local exhaust systems or auxiliary ventilation (dilution ventilation); blasting off-shift, or at restricted times; localizing or isolating the effects of blasting where workings are isolated or sectionalized in the ventilation system; and absorbing some of the components of the fumes using air-water sprays. Dilution is one of the most effective control measures against blasting fumes and is universally applied. However, for precise determination of the dilution times for the fumes to reach safe concentrations, accurate determination of the concentration of toxic fumes produced by the explosives used is required. Research work has been carried out in determining the types and volumes of gases produced from blasting. In the case of ideal detonations, the nature and quantity of the fumes produced can be predicted by thermo-hydrodynamic calculations. However, commercial explosives exhibit non-ideal behaviour which is enhanced by the relatively small diameters of application in underground mines. The confinement offered by the surrounding rock further complicates the situation. It is well recognized that confinement affects performance and consequently fume generation. A detailed data base of fumes generated by commercial explosives at various conditions is introduced and the effect of blasting parameters such as, confinement, shock desensitization and incomplete detonations on toxic fume production is described for a variety of commercial explosives in use today. Thermodynamic predictions on fume production by the explosive compositions tested are also presented and compared with experimental results and their significance in assessing the quantity of fumes produced is discussed. A mathematical model capable of determining dilution ventilation requirements and dilution times to reduce the fume concentrations in the blasting zone to acceptable levels has been developed and it is being incorporated into a network system so that the effects of blasting can be simulated in typical mine ventilation systems. Solutions to the problem of controlling blast fumes within acceptable levels are described. These solutions include the use of control procedures which prevent and reduce the amount of fumes liberated from blasting. The use of low fume explosives, proper blasting techniques, dilution ventilation and filtration can be combined to effectively control fume production and save on costs. The application of these techniques to enable recirculation of underground air with reduced quantities of fresh air requirements is evaluated in a case study.

Jan 1, 1993

By A. B. Szwilski

The mineability and coal processing costs are influenced largely by the structural and physical properties of the coal seam. The mining process involves coal cutting, pillar support, crushing, and floating. A correlation between the rank, ash content, and coal strength/stiffness is discussed. The coefficient of variability of rebound tests on the face of various coal seams are compared with those of laboratory compressive strength tests by other investigators.

Jan 1, 1988

By F. Seymour

A modified three-dimensional Lerches-Grossmann (LG) graph tree algorithm that generates the complete set of nested maximum valued pits in a single run is presented. This modified LG algorithm looks at the relative strength (average value) of the branches (groups of blocks). Pointers are allocated and pruned until there are no members of weaker (lower average value) branches overlying members of stronger (higher average value) branches. The final set of strong branches arc listed in order of decreasing strength. The pits they represent form the maximum valued convex hull for a single-variable pit-limit parameterization. A description of the algorithm is given along with examples of lion it has been applied at Newmont.

Jan 1, 1996

By R. F. Hüttl

World-wide Germany is the leading lignite mining nation. Most of the lignite is produced in opencast operations. However, opencast mining causes enormous impacts on natural ecosystems and even on entire landscapes. The extensive production of lignite particularly in eastern Germany results in large devastated areas, which so far have been reclaimed only to some part. For the restoration of the post-mining area of more than 80,000 ha the major land use option is the reestablishment of forest ecosystems. However, adverse site conditions of the post-mining landscape such as extreme soil acidification and salt concentrations call for specific recultivation practices. Therefore, after the German reunification new reclamation and reforestation concepts have been developed for these brown coal areas of eastern Germany by the Collaborative Research Center (SFB 565) at the Brandenburg University of Technology at Cottbus (Germany). As a case study our comprehensive investigations into forest ecosystem development on terra nova in the Lusatian lignite mining district, south-east of Berlin, will be presented.

Jan 1, 2003

The 71st Annual Meeting of the Minnesota Section of SME and the 59th Annual University of Minnesota Mining Symposium were held jointly April 14-16, 1998, in Duluth, MN. Registration was estimated at 450 people, about the same as last year's attendance. A short course on mine productivity and a trade show that included about 75 exhibitors were also held in conjunction with the SME meeting. This year's theme was "Iron ore and integrated steel - where are we going?" Although generally optimistic in the near term, the general feeling among the attendees is that the industry faces serious competitive challenges. The iron mining industry in Minnesota experienced a tremendous rebound from the devastating downturn of the 1980s. Today, however, all seven of Minnesota's taconite plants are operating at full capacity. And these high production levels are expected to continue during the next several years. Longer-term, however, Minnesota's producers face an increasingly competitive worldwide market, including stiff competition from Canadian operations. Because of the increasing competition, industry representatives in Minnesota believe that it is critical to strengthen their operations. To accomplish this, companies are looking to: ? Further reduce production costs. ? Bring new technologies into their operations. ? Develop value-added facilities such as direct-reduced iron. ? Expand their markets. The industry is also seeking more collaboration between industry and government. The National Steel Pellet Co. and Minntac are looking at using ported kilns, which would reduce energy consumption significantly. Cleveland Cliffs, EVTAC, Northshore Mining and Minnesota Iron and Steel are all looking at building value-added plants. One such project that received attention among the attendees was Minnesota Iron and Steel's proposed $1.2 billion combined mine, taconite plant, direct reduced iron facility and steel production facility. If the operation is built, it would produce about 3.4 Mt/a (3.39 million ltpy) of direct-reduced iron pellets. Financing is pending. An announcement is expected in the fall of 1998. The pellets, containing 70% iron, would be processed into steel in electric arc furnaces. The steel produced would then be processed into hot-rolled coil, which is used by the appliance and automobile industries. The keynote addresses and technical sessions focused on these issues as well as on environmental issues.

Jan 1, 1998