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By L. W. Laage

Throughout recorded history, underground fires have plagued mining operations. Compared with other hazardous situations in underground mining, a fire can become a global problem by swiftly spreading deadly carbon monoxide and other products of combustion (POC's) throughout the whole mine, often without warning. Experience has shown that when fires are detected and located in their early stages, they are much easier to control and proper escape routes can be more intelligently selected. Recent advances in sensor and data communication technology have made reliable mine fire .detection system installations possible. Unlike building construction. in a mine, it is impractical to install detectors at every desired location. Abandoned workings and unsafe locations preclude sensor installations from both safety and economic standpoints. The net effect is that some fires are detected and located early while the location of others, even if detected early, remains unknown too long for effective evacuation and fire fighting.

Jan 1, 1989

By J. A. Domenico

A safe and precise mineral separation alternative to heavy liquids is being used for mineral sands exploration on large scale orebodies. The separation process, Magstream®, uses ferro-fluids and magnetic and centrifugal forces to produce precise split points over a range of specific gravities from 1.5 to 18.0 g/cc. This paper describes a commercial scale exploration program treating, roughly, 90 samples per day in Senegal (West Africa). Separation results comparing Magstream® and conventional heavy-liquid separation are presented.

Jan 1, 1994

By K. Ueda

Lead concentrates from Kuroko (black ore) mines, which contain Cu 4 ? 7%, Pb 55%, Zn 3 - 7%, As 0.5 - 0.9% are treated by hydrometallurgical process in order to smelt the product by electric furnace smelting together with other lead resouces from Kuroko. The hydrometallurgical pretreatment involves sulfuric acid leaching at first stage, ferric leaching at second stage. This paper describes the short history of lead recovery from Kuroko and the performance of laboratory test, pilot plant and commercial operation.

Jan 1, 1982

By Norman Haber

The Haber Gold Process (HGP) is a proprietary. hydrometallurgical extraction methodology that was developed in 1983-1984 by Norman Haber and Dr. John Lee of Haber, Inc., a small public company in Towaco, New Jersey specializing in hydrochemical process development for precious metals. It was pilot tested repeatedly in 1985 at our pilot plant in Tombstone, Arizona, with different types of gold bearing mineralization. Both Pincock, Allen and Holt (USA), and PA Technology (Australia) were involved with some of these pilot tests. The ores tested included easily cyanide-extractable oxide type gold ore from Australia, marginal heap-leach type ore from Cripple Creek, USA, and a hematite bearing ore from California. In all cases, extraction time was 6 hours or less yielding 90-99% recoveries of assayed gold values. The HGP operates as a lixivient which parts the gold from the rock matrix, yielding gold in solution in a fully recoverable form. Both precipitation methods, such as zinc participation or Carbon in Leach systems ( or Carbon in Pulp) have been shown to be feasible with this technology for the recovery of gold from the pregnant solution. Both batch vat leaching as well as continuous processing are realistic for use with the HGP. It has also been considered that the HGP might also benefit heap leaching due to several advantageous factors over cyanide. One such consideration is that the HGP can operate effectively with acidic ore types. The use of cyanide with such ores often requires attention to pH and neutralization with lime. This tends to reduce and even clog the permeability of the leach bed.

Jan 1, 1998

By E. Fahrenkrog

An intelligent supervisor developed using expert system tools and applied to a crushing plant is presented in this paper. The structure of this supervisor, based on a model of a human operator, consists of a Knowledge base containing a qualitative model of the process, and a Rules base with the heuristic logic used by an operator when supervising a plant. The simulation results obtained show the potential of this type of systems to supervise the automatic operation of a plant.

Jan 1, 1989

By D. F. Symonds

INTRODUCTION Dense medium processes have been used to separate coal and ores for over a hundred years. In fact Sir Henry Bessemer first patented a process in 1858. In recent years, their importance relative to other gravity dependent processes has increased. This is particularly true in the coal industry where over 60% of all preparation plants operating in 1984 in North America (1) contained either dense medium vessel or cyclone circuits. In addition, the stringent product quality demands of the consumer, together with increases in mining costs, dictate that the cleaning circuits be both predictable and efficient. Dense medium systems are the most predictable and efficient of all gravity- dependent processes. The majority of the text of this chapter will be concerned with dense medium applications as they relate to the coal industry. However, the techniques and calculation procedures can be applied, in general, to all non-coal minerals (such as diamonds, marginal iron and lead-zinc ores and gravel) which take advantage of a difference in specific gravity between the saleable product and the reject. The object in dense medium cleaning is to produce a liquid whose effective specific gravity is between that of the concentrate and the reject. In which case the lighter product will float to the surface and the heavier product will sink to the bottom. Unfortunately, this simple process becomes complicated by the following practical necessities: (a) collecting and removing the float and sink products from the medium without disturbing the free settling effects; (b) maintaining and controlling the specific gravity of the medium; (c) separating and reclaiming the medium once the products have left the separating vessel; and (d) separating finer sized particles which take longer to fall through the dense, and often viscous, medium. As a result of the last issue (item d) two main types of dense medium separators have evolved: dense medium vessels and dense medium cyclones. Dense medium vessels are essentially large baths through which the dense medium flows at a relatively slow velocity. The lighter products float to the surface and are carried out of the vessel by the medium flow. The heavier products sink to the bottom of the vessel and are physically transported out either by means of a conveyor (usually a chain conveyor) or a rotating, lifting arrangement (Figure 1). They generally

Jan 1, 1986

By C. I. Huang

The mining industry is an easy target for criticism from an environmentally sensitive society. Recent researches discovered that human activities, including mining. cannot be blamed for all of the pollution observed on earth. Interdisciplinary research is providing diagnostic and remedial solutions to problems such as acid mine drainage and cyanide-polluted streams. Researchers have also found that mercury-bearing hot springs and volcanic eruptions are partly responsible for some pollution. Geochemists, mining geologists, engineers, and environmental scientists can pool their efforts to make the environment cleaner and safer. Remote sensing of the environment and the use of microbes may become much more popular in the near future in the mining-environment arena.

Jan 1, 1988

By Claude A. Chapallaz, Dominique L. Butty

Bauxite is derived by surficial weathering of aluminosilicate rock forming minerals under warm and humid climatic conditions. Variations in climate combined with base level changes promote cyclical, evolutionary weathering/concentration patterns, the residual products of which are closely controlled by biological activity. Rock decomposition results mainly from hydrolysis, chelation and solution, the effects being (a) removal of bases and silica in dilute solution, (b) depletion of iron in areas where low pH-Eh prevail and, (c) concentration through direct precipitation, or more generally via intermediate amorphous phases, of aluminium hydrates in variable associations with iron hydrates and clay minerals. Bauxites can be regarded as aluminous soils, and as such they result from cyclic or polygenetic pedogenesis. The ferralitic pedological evolution is essential for bauxite formation. Under some specific conditions, related to local climate and parent rock composition, the podsolic- or andosolic-type of pedogenesis is an effective precursor to bauxitization.

Jan 1, 1984

By J. D. Raulerson, R. P. Farias, G. A. Gruber

A flotation process has been developed to successfully treat ore from the Santo Domingo phosphate deposit in Baja California Sur. The ore contained less than 4% P2O5 with quartz, silicates, and carbonates as gangue minerals. Flotation of the low- grade feed in seawater required that the conventional Crago process, comprising direct anionic flotation, deoiling, and inverse cationic flotation, be augmented by an anionic cleaner flotation step, phosphate depression, and a calcite flotation step.

Jan 1, 1988

By Charles E. Melbye

INTRODUCTION In a discussion of South American exploration, it is difficult to know how much area to cover, as there has been such intense exploration for many years in all of the South American countries. Therefore, I have decided to discuss only Argentina, Bolivia and Peru in this paper, since I am most familiar with these three countries. This familiarity has been gained during my last 12 years of nearly continual exploration and mine development. Furthermore, these three countries form a contiguous block straddling the Andes Mountain chain for 2,200 miles in length N-S. Although Chile is part of this block, I excluded that country because it has had the longest recent history in South American exploration, and it is now in a mature stage where new important mines are being placed in production every year. Exploration must progress a lot for the other three countries to attain the stature of Chile. However, major exploration successes such as Yavacocha and Pieriva in Peru, Kori Khollu in Bolivia and Bajo Alumbrera, Agua Rica and Cerro Vanguardia in Argentina certainly indicates that these countries are rapidly accelerating in exploration successes and the resulting new mine developments. Also, by concentrating on three countries, I have avoided making this paper too lengthy. This paper will cover activities of both junior and senior mining companies, both of whom are making significant contributions to exploration. The junior companies often make the initial discovery, develop it further and then bring in a major company when large capital is required. Since most exploration is for gold and copper or combinations of these, most descriptions will cover these types. However, there are significant new exploration successes for zinc and for silver-lead-zinc, and they will be covered, as well. After descriptions of the various properties, there is included a discussion of the governmental policies of Argentina, Bolivia and Peru, as to how they are affecting exploration activities and budgets. Some of these problems could have a major negative affect on the future exploration plans of many companies. I have intended to cover what I think are significant exploration developments in each country, and if a company project is omitted, there was no intention to slight anyone. Since exploration results change monthly, there could be

Jan 1, 1998

By V. A. L. Breguncci, A. H. Martins, C. P. Ribeiro Jr.

This work presents experimental results for the recovery of gold present in alkaline cyanide solutions by using the electroelution technique of strong-base anionic polymeric resins IRA 402-CL from Rhom and Haas-Brazil Ltd. loaded with gold. This technique of electroelution of anionic polymeric resins is based on the removal of metal ions adsorbed to the resin, resulting from a potential difference applied between the cathode and anode in an electrolytic cell. The electrolytic cell was composed of an aqueous solution with suitable chemical characteristics and an anionic polymeric resin bed loaded with gold. The resin used in the experiments was loaded using synthetic alkaline gold cyanide solution with 1.0 g/L of gold. The variables studied were electroelution time, cathode current density, distance between cathode and anode and the electrolyte chemical composition. Statistical methods made it possible to establish the optimum conditions that would achieve satisfactory gold recoveries by the electroelution technique. The statistically predicted response for the resin loaded with gold by percolation was 16.5% gold recovery, 2.0 A/m2 cathode current density, 20-mm distance between electrodes and 6.0 hrs electroelution time. For the centrifuging system, the statistically predicted response was 7.41% gold recovery under the following conditions: 0.25 A/m2 cathode current density, 1-mm distance between electrodes, 3.5 hrs electroelution time and 10.9% NaOH in the electrolyte chemical composition.

Jan 1, 2002

By J. S. Hu

FTIR spectroscopy has been used for the characterization of adsorbed oleate at the fluorite surface. It has been found that modest changes in the adsorption density at high temperature and high oxygen potential do not provide a satisfactory explanation for the significant increase in the hydrophobic character of the system under similar conditions. Rather, FTIR spectroscopic measurements suggest that chemical interaction between adsorbed oleyl groups occurs at high temperature and/or oxygen potential and accounts for the increased hydrophobicity. Specifically, the intensity of the =CH bond of the adsorbed oleate diminishes at high temperature and/or high oxygen potential. Such a phenomenon was not observed in control tests with the calcium oleate soap. For extensive reaction at the fluorite surface, the presence of a new surface species has been identified. These results indicate that the fluorite surface catalyzes an oxidation and/or polymerization reaction between adsorbed oleyl groups which results in a more hydrophobic structure at the fluorite surface.

Jan 1, 1986

The strength of anchorage of various types of roof bolts in permafrost depends on the types of rock in which they are installed. Variation in the mine thermal regime results in weakening of the roof and walls, and at times total loss of ice cement bonds takes place in the surrounding rockmass. In mines with positive ventilation air temperature, the wedge or expansion types of bolts may become weakened due to the transfer of heat into the anchorage through the metal rod and subsequent thawing of rocks. Effective operation and evaluation of roof bolt systems for mine workings in permafrost require predictions of the dynamics of wall thawing by warm ventilation air. This paper presents an analysis of the temperature distribution in the frozen host ground surrounding roof bolts, the area of interest being the vicinity of the anchors for point anchored bolt and the entire length for split set bolt

Jan 1, 1994

By A. Pincomb

After determining minable acreage, tons are calculated by multiplying minable acreage by average thickness and by a volume-tonnage conversion factor. Converting from tons in the ground to tons sold across the scale takes fines and internally used and wasted stone into consideration, resulting in minimum losses of about 10% for limestone and 15% for sand and gravel. A high degree of certainty about thickness, lateral continuity and geologic character defines proven reserves. Assuming continuity of these characteristics defines probable reserves. By using tpa estimations and annual tonnage requirements, the life of a deposit can be quantified. The decision can then be made regarding the necessity of securing more acreage. Some landowners choose to multiply aggregate price, operating income, or a royalty rate by tons to arrive at a value for their reserves. In doing so they probably overstate the value of their land.

Jan 1, 2003

By Jin Kim, Jerry C. Tien

Water is still the most economical and popular means of controlling dust underground. It is a process that captures dust by bringing water droplets into intimate contact with coal particles. Wetting agents, also known as surfactants, can be added to greatly facilitate such a process since they tend to reduce the interfacial tension between the coal particles (usually hydrophobic) and the liquid. The surfactants used in the study were first chosen on the basis of their HLB (Hydrophile-Lipophile Balance) value, and later tested in order to select the right type and amount of surfactants to give the best performance. Both static and dynamic tests were later conducted using different types of surfactants to examine their respective wetting effectiveness on coal particles. Experimental results show close correlation with the theoretically calculated collection efficiency that is based on a horizontal tunnel and a solid-cone water spray.

Jan 1, 1993

By David M. Miller, Pramod C. Thakur, Larry D. Taylor

The most common technique used to suppress respirable coal dust in air is that of spraying with fine water particles. The water droplets are typically much larger than respirable dust particles and they collect dust particles mainly by interception. Dust collection efficiencies can be improved by reducing the droplet size and in- creasing the droplet velocity. This is typically done by reducing the surface tension of water and increasing the water pressure. Dust collection efficiency can be further improved by in- creasing the electrical attraction between the water and dust particles through electrostatic charging. A technique developed by Conoco accomplishes both surface tension reduction and electrostatic charging by discharging weak solutions of surfactants in water at high pressures, 13.8 to 27.6 MPa (2000 to 4000 psi) in an intrinsically safe manner. The paper de- scribes the process and presents related dust suppression data.

Jan 1, 1986

By J. W. Langhans, B. D. Blake

The U. S. Bureau of Mines has been investigating the application of thiosulfate to recover gold directly from low grade refractory carbonaceous ores for the past four years. Statistical experimental methods were used to determine the effects of various leaching parameters on both gold extraction and thiosulfate consumption. Seven variables were investigated, including thiosulfate, copper, ammonia, sulfite, and sulfate concentrations, leaching time, and leaching atmosphere. This information was used in face-centered cubic (FCC) surface response experiments to define the optimum leaching conditions for a low grade ore. Two models were generated from the data to predict gold extraction and thiosulfate consumption as a function of the leaching parameters. The models predicted a gold extraction of 67 pct and reagent consumption of 2 kg [S2032/mt ore at 0.25 M S2032-, 0.0014 M Cu2+, 0.27 M NH,OH, 0.00625 M SO;-,] and leaching for 16 h. Actual tests resulted in 62 pct gold extraction with 0.93 kg S2032- consumed/mt ore. Subsequent column leaching tests have further demonstrated the viability of applying this technology to recover gold from carbonaceous ores without first pretreating the material. Gold extractions in the column tests ranged from 69 to 78 pct with thiosulfate consumption ranging from 0.4 to 5.4 kg/mt ore. These results compare to <5 pct gold extraction using standard cyanide leaching conditions.

Jan 1, 1996

The world&apos;s largest hydraulic excavator was recently introduced at Syncrude&apos;s North Mine at Fort McMurray, Alberta, in Canada. O&K&apos;s 826t (910-st) behemoth RH400, with a 42-m3 (55-cu yd) bucket, is capable of loading 72.5 t (80 st) in one pass. Syncrude&apos;s Alberta operation is the nation&apos;s largest single source of crude oil. It is also the world&apos;s largest producer of oil from oil sands. Syncrude produces 205,000 bbl/day, expects to increase production to 225,000 bbl/day by 1999 and to 320,000 bbl/day by 2005. That translates to 73.5 million bbl of Syncrude Sweet Blend (SSB) produced in 1996, 82 million bbl in 1999 and 114 million bbl in 2005. The North Mine is a new development that will replace the current East Mine, to be depleted of oil sand by the end of 1999. The North Mine will feature hydrotransport, a new and unique method of transporting oil sand from the pit to the process plant. Oil sand from the truck-and-shovel operation will be processed through a double-roll crusher and placed in a cyclofeeder where it mixes with hot water. The material is then screened and transported by pipeline to the extraction plant. Hydrotransport will replace conventional conveyor transport for moving raw product from the pit. Mine development will also use two 290-t (320-st) haul trucks to compliment the fleet of existing 218-t (240-st) trucks.

Jan 1, 1998

By R. H. King

The US coal industry has been using continuous room-and-pillar mining (CRPM) machines for more than 30 years for longwall development. This equipment has also been used for production mining in areas that are not appropriate for longwall mining. From 1977 to 1987, the portion of annual US production mined by continuous miner (CM) sections grew slightly from 65% to 70%. Over this time, mine operators and manufacturers have made some advances to attain the full production potential of this method. This is evidenced by the fact that average tons per eight hour shift for continuous miners in the US grew from 180 t (200 st) in 1977 to 431 t (475 st) in 1987. The authors (1990) reported that the increase in productivity was due to several factors: • a drop in prices; • a more mature workforce; • union stability and incentive programs; •procedural improvements; and •technological advances. The authors estimated that about one-third of the increased production came from the first three and other unaccounted for factors and one-third each for the last two. Even though improvements were considerable, continuous miner capacity is much higher than 431 t/shift (475 st per shift). For example, the machinery is capable of mining more than 9 t (10 st) per machine for the 6.5 available hours per shift or 3.5 kt (3900 st). However, this has never been attained on development. The averages of most mines are less than 900 t/shift

Jan 1, 1991

By J. Maiti, A. Bhattacherjee

A literature review on quantitative analysis of mine safely studies revealed that numerous investigators explored a wide- range of techniques, including the investigation of bivariate and multivariate statistical models. Although these researchers addressed various issues of accident causation and prevention, they, in general, did not investigate through the use of quantitative models the multivariate relationships of several factors affecting mine safety in a causal framework. In this paper, systems dynamics and structural equation modeling are presented to simultaneously represent and study the effect of policy variables related to accident prevention along with the factors causing accidents and injuries. The application of these models to a group of mines revealed that current training practices at these mines do not appear to alleviate accident occurrences. It is inferred that the use of these quantitative techniques can provide a new direction of research in mine-safety studies.

Jan 1, 2000