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By K. A. McDonald

This paper will describe the experiences of Hibernia Holdings, Inc. in constructing a mineral processing facility in Mexico. It will attempt to set forth a guideline on what companies attempting to operate in Mexico can expect and what actions they can take. Ownership laws, import/export laws, labor laws, security, transportation and operating experiences will be discussed.

Jan 1, 1994

By Steven Wright

The reduction of a slag produced 6om the recycling of lead batteries was studied in a kilogram scale laboratory investigation by reacting with graphite at temperatures of 1180 and 1200°C. Simultaneous reduction of PbO, Fe203, Sb203 and As203 occurred with the Sb and As reporting to the metal while the lead content in the slag was above 2 wt%. The Sb and As distributions between metal and slag were strongly affected by temperature and slag oxidation state. The rates of reduction of PbO and Sb203 increased with increasing slag basicity and temperature and decreased as the PbO content in the slag decreased. The reduction rate of PbO from these slags was similar to other industrial lead slags at the same CaO/SiO2 ratio and temperature. The implications of the behavioural similarities of the antimonous slags during reduction with carbonaceous reductants and other lead slags are briefly discussed.

Jan 1, 1994

By T. J. Fenner

Research conducted in South African mines has demonstrated the benefit of ground penetrating radar for the detection of geologic features and hazards. This is crucial for safety and production considerations in underground mines that are as much as 4 kilometers deep. This paper describes a new ground penetrating radar system designed specifically for high quality data acquisition, in the harsh conditions of deep underground environments, for use by operators with minimal geophysical experience. Design criteria included automated functions, intrinsic safety, light weight and minimal power requirements. Data is processed on the ground surface by geoscientists using a PC.

Jan 1, 1994

By William E. Hill

The blasting program at the Valdez Creek Placer Mine must deal with challenging situations throughout the year. During the short summer, extreme water conditions must be confronted, while the winter months present problems of a different nature, where the overburden freezes to a depth of up to 18 feet. These obstacles require techniques borrowed from hardrock blasting combined with creative experimentation to overcome.

Jan 1, 1994

By Harold R. Kokal, Madhu G. Ranade

A metallurgical/flux is a substance that is added to combine with gangue (unwanted minerals) during ore smelting, with impurities in a molten metal, or with other additives in metal refining processes to form a slag that can be separated from the metal. Because slags are immiscible with the metallic melt and are of lower density, a separation of the slag and metal occurs if the viscosity and surface tension are of the proper values. The chemistries of slags are adjusted to provide the proper melting point, viscosity, surface tension, conductivity, specific heat, density, or chemical properties to effect the desired task. In addition to absorbing impurities from the metal, the purposes of the slag are to thermally insulate the metal bath, protect the molten metal from the atmosphere, and control the chemical potential of the system. Several excellent references on slags and metallurgical fluxes are available (Boynton, 1980, Lankford, Jr., et al., 1985, Turkdogan, 1983, Rosenqvist, 1974, Fine and Gaskell, 1984). The function of the slag might vary at different stages within a process prior to final melting. For example, the slag composition and behavior will change as materials descend in the iron blast furnace, or as they melt in the early stages of formation of steel- making slags. Selection of the chemistry for a slag might be influenced by factors outside the primary function as when blast furnace slags are used to make cement, rock wool insulation, or fertilizer supplements. Sometimes slags contain a sufficient amount of valuable recoverable elements to be sold as raw materials for other processes. Fluxes are often referred to as acid, basic, or neutral. Acid fluxes are those that generally form acids in water and bases are those that would generally form bases in water. Typical acid fluxes are silica, alumina, and phosphorus, although alumina can function as either an acid or base. Typical basic fluxes are lime and magnesia. Fluorspar, or calcium fluoride, is a neutral substance because it can be viewed as the reaction product of a base and an acid. The degree of acidity (ratio of acids to bases) or basicity (ratio of bases to acids) is often specified to characterize the slag chemistry for a particular system. The system might also be referred to as acid or basic depending on the choice of slag, for example, basic steelmaking uses slags with more bases (lime and magnesia) than acids (silica and alumina). Many forms of minerals and compounds have been used as fluxes depending on the process requirements, availability, costs, requirements for recycling of intermediate products, and environmental concerns. Because slags are most often mixtures of oxides and silicates, fluxes are usually oxides, carbonates (which decompose to oxides) and silicates. Slags comprising phosphates, borates, sulfides, carbides, or halides have also been used (Rosenqvist, 1974, Moore, 1981, Szekely et al., 1989). In ironmaking and steelmaking, some acidic components are sometimes added. In nonferrous processes slags and fluxes are acidic with silica as the primary component, and although the use of basic flux such as limestone or lime is not extensive, some amount is used to modify slag properties and some refining slags are lime based. The production of iron is accomplished by smelting of ores, pellets, and sinter in blast furnaces with subsequent refining of molten iron and scrap in oxygen-blown processes. The electric furnace is used to make steel, stainless steels, ferroalloys, and special alloys, whereas ferromanganese is often made in blast furnaces. Fluxes are used in all of these processes, and either limestone or lime is the major flux component with some dolomite, dolomitic lime, silica, alumina, and fluorspar being used. In ironmaking, the flux is added either by direct charging or through sinter and fluxed pellets. In steel refining by the basic oxygen process, flux is added as lime and dolomitic lime that are either charged as lumps or injected as fines. Some small amount of limestone is sometimes used. Fluorspar is often added as lumps or mixed with other fine materials in briquettes. Alumina is sometimes added to blast furnaces either by direct charging of sized lumps or through sinter. Typical acid fluxes are sand, gravel, quartz rock, used silica brick, or raw siliceous ore (Lankford, Jr., et al., 1985). Olivine, which is a magnesium-silicate mineral, has been added to iron blast furnaces to enhance removal of alkalis (Lankford, Jr., et al., 1985). Alumina in the form of bauxite, aluminiferous clay, and recycled alumina brick has been used as flux. Alumina can function amphoterically as either an acid or base, for example it can form aluminum silicate in high silica slags or calcium aluminate in lime-bearing slags (Lankford, Jr., et al., 1985). Limestone (calcium carbonate) and dolomite (magnesium-calcium carbonate), or fluxstones as they are sometimes called (Boynton, 1980), and their calcined forms, lime and dolomitic lime are the major basic fluxes. In the latter cases, the carbonates are de- composed in a kiln-type process to drive off carbon dioxide that might otherwise interfere with the subsequent smelting or refining process or require expensive forms of energy to effect the decomposition (e.g., by combustion of coke in the iron blast furnace). Limestone is considerably less expensive than lime because it is not calcined; however, lime is far more difficult to handle and reacts readily with water. Dolomite and dolomitic lime are used for their magnesia content. Fluorspar is a neutral flux often used as an additive in steel- making slags to improve fluidity, but it has also been used in combination with lime as a primary slag in electroslag refining (Duckworth and Hoyle, 1969). Fluorspar is available in several grades, with the lowest grade often used for steelmaking. When the price of fluorspar has risen, substitutes including aluminum smelting dross, borax, manganese ore, titania, iron oxides, silica sand, and

Jan 1, 1994

By T. N. Moore, E. M. De Souza

Because jackleg rock drills are a potential source of hand vibration exposure, they can effectively produce Hand Arm Vibration (HAV) Syndrome in their operators. This will affect operator efficiency and mine productivity. As a result, a significant amount of work has focused on redesigning rock drill handles using new materials to minimize hand-transmitted vibration. In previous work developed by the authors (1991), a detailed study was undertaken to determine the effectiveness of using elastomer covered handles in place of the standard steel design. The results indicated that, for an elastomer-based handle design, the overall acceleration level experienced by the hand can be reduced by as much as a factor of three, relative to the steel handle. It was also shown that this reduction takes place predominantly in the frequency range above 500 Hz. This paper presents an investigation of the long-term effectiveness of an elastomer-cushioned handle under different conditions underground. In this study, sponsored by the Mining Industry Research Organization of Canada (MIROC), a number of cushioned handles were quantitatively and qualitatively tested in five operating mines. The vibration testing program has indicated that the cushioned handle can reduce overall vibration levels by as much as a factor of three. The qualitative assessment program of the cushioned handles by the drill operators has indicated some degree of preference for the cushioned handles over the steel handles, if certain design modifications are performed. This research program indicated that cushioned handles have the potential to become the dominant method with regard to vibration reduction and operator performance.

Jan 1, 1994

By J. R. Koehler

The U.S. Bureau of Mines (USBM) ground control research program includes several projects focused on developing design criteria for yielding-pillar-based longwall gate road systems. As part of this program, mining practices at the Sunnyside Mines, Sunnyside Reclamation and Salvage Co., Sunnyside, UT, are being documented to preserve the long history of yield pillar system evolution on the property. Published information describing the specific in-mine performance of the numerous gate road configurations utilized at the Sunnyside Mines is very limited. To overcome this deficit, USBM personnel interviewed 30 longtime mine employees representing nearly 700 years of mining experience at the Sunnyside operations. Mining conditions in 12 specific areas in the Nos. 1, 2, and 3 Mines were discussed in the interviews. Also, broad topics such as general mining practices, safety, and geology were often addressed during the discussions. Comprising the body of this report is an extensive record of the events and conditions experienced while mining the identified areas. In addition, eight significant conclusions were developed that accurately summarize the general opinions of the interviewed personnel regarding mining conditions and practices at Sunnyside.

Jan 1, 1994

By K. J. Stanaway

Environmental pressures on waste disposal are forcing pigment producers to use higher content TiO2 feedstocks with lower levels of trace elements. Despite this, 50% of the worlds TiO2 comes from ilmenite concentrates with only 37 -54 % TiO2 An industry growth rate of 25 % in the next ten years combined with trends to diminishing resources and lower grades for rutile (95 % TiO2) and leucoxenized ilmenite (55 to 90% TiO2) mean that unless new discoveries are made soon, the industry will become even more reliant on ilmenite. A hypothetical ideal feedstock is presented and strategies to obtain it are suggested. Reasons for some of the mineral specifications are given.

Jan 1, 1994

Provide the technology to remotely reset circuit breakers on continuous mining machines used in extended cuts.

Jan 1, 1994

By James C. Duchon

The use of extended workdays (regular shift lengths of 10 or 12 h (hour), while still maintaining a 4O-h workweek) in mining operations is attracting growing interest in the United States. There is very little doubt that extended workdays is a very popular alternative among the work force because of the significant increase in days off, including weekends, especially when compared with traditional rotation schedules of working seven straight shifts or having only one weekend off every 4 to 6 weeks. However, there are some serious concerns by management, workers, unions, and various governmental policymakers that working 10-or 12-h days may create an added risk of accidents and health problems. The U.S. Bureau of Mines reviewed the literature studies related to the safety and performance issues of extended workdays. This report presents a summary of those findings. The studies examined in this review are divided into three sections: (1) laboratory, (2) field, and (3) accident and injury analysis. In general, results are inconclusive. Studies have shown both positive and negative effects. It is concluded, therefore, that in industries such as mining where accidents are a serious concern, special measures and evaluation in the use of extended workdays be considered.

Jan 1, 1994

By D. Malhotra

Metallurgists are continuously striving to improve recovery. But optimization of profits and/or revenue dictates that recovery can be sacrificed at the expense of throughput. However, recently there has been significant interest in the concept of retreatment of tailings to enhance recovery and hence revenue while maintaining high throughput. The authors discuss the technical and economic factors that need to be considered in evaluation of the feasibility of retreatment of tailings including the potential feed streams (i.e., rougher tailings, cleaner tailings, etc.) and processing options (i.e., physical beneficiation, chemical processing, etc.). A case study for base metals is discussed.

Jan 1, 1994

By L. N. Hill

The classifiers on the primary grinding circuit at Cyprus Sierrita have been upgraded from 0.66 m (26 in) diameter hydrocyclones to 0.84 m (33 in) diameter hydrocyclones. This has resulted in a 4.3 % (11 t/h) (12 standard tons/hour) increase in mill throughput while producing a flotation feed which contains 4.8% less +300 micron (48 mesh Tyler screen size) material. This reduction in flotation feed particle size has increased copper (CU) recovery by 0.8 %. Various grinding circuit relationships were evaluated. These relationships include circulating load versus throughput, horizontal versus vertical cyclone configuration, and the effect of cyclone components on performance. We conclude that the improvements achieved are due to a shift in the overflow size distribution created by a cyclone diameter more suited to our operation, and by eliminating the cyclone capacity constraint in the grinding circuit.

Jan 1, 1994

By A. Kar, J. Mazumder

"Laser ablation is a process that can be used to synthesize novel nanoscale particles as well as to deposit thin films of various materials. Usually, nanoscale particles and thin films are formed at relatively high and low pressures, respectively, inside the ablation chamber. This paper presents a mathematical model to predict the particle size distribution in the plasma generated during laser ablation. The model is developed by considering the effects of the laser-matter and laser-plasma interactions, the Stefan condition, and the discontinuity across the Knudsen layer. The nanoscale particles are found to be located at the central region of the plasma near the target. The particles have very high velocity and temperature. A good qualitative agreement is observed between the results of this model and experimental data. IntroductionRapid solidification produces novel microstructures whose atomic arrangements and/or chemical compositions are different from those of conventional materials. The conventional materials are either crystalline or amorphous. The crystalline materials have both short- and long-range orders, whereas the amorphous materials have only the shortrange order. The nanocrystalline materials have neither short- nor long-range orders, and for this reason, they exhibit novel properties which are important for synthesizing new materials. The atoms of a nanocrystal can be classified as ""crystal atoms"" and ""boundary atoms"", where the ""crystal atoms"" have the nearest-neighbor configurations similar to the lattice configuration, whereas the nearest-neighbor configurations of the ""boundary atoms"" differ from the lattice configurations 1. Various aspects of the nanoscale materials have been discussed in Refs. [1-7]."

Jan 1, 1994

By John B. Cocanour

The U.S. Bureau of Mines (USBM) has developed a laboratory-scale on-line analysis and process control system for a decopperization electrolytic circuit. This system is software driven, running on a 486DX-33 personal computer (PC) utilizing a portable energy- dispersive x-ray fluorescence (XRF) spectrometer as the sample analyzer. The XRF copper reading obtained was used as the control variable through an RS-232 serial interface to the PC for software-based control of feed flowrates. When the copper concentration in the electrolytic cell (as measured by the XRF) deviated from the set point, the feed flowrate to the cell was automatically altered using software-based proportional-integral-differential (PID) computer control to yield the desired copper concentration at the electrolytic cell outlet.

Jan 1, 1994

By J. P. Ducarme

The eastern U.S. contains vast reserves of thin seam coal deposits, particularly in the Appalachian mountain region. These typical 355 to 710 mm thick reserves are difficult or uneconomical to recover with present technology. The U.S. Bureau of Mines is developing technology that would allow nearly 100% recovery of thin seams in these mountaintop regions. This paper details the research that has been conducted on these new techniques and presents results of testing on a cross-ridge full-scale physical model.

Jan 1, 1994

An explosive's velocity of detonation (VOD), can be used to indicate a number of important characteristics regarding the product's performance under specific field and test conditions. A number of new characteristic and transient VOD curves have been identified in the field, which can be used to evaluate explosive performance, control ground vibration amplitudes and frequencies, select the correct amount and type of stemming for use at the collar and in stem decks, eliminate explosive desensitization, evaluate primer performance, design air deck based blasts, evaluate contaminated explosives and to overcome post blast noxious fumes.

Jan 1, 1994

China's coal energy development, characteristics and relationships with atmospheric pollution are reported. Atmospheric pollution sources from coal combustion are analyzed. Some of the projects for clean coal combustion in the Shanghai area include use of industrial briquettes, investigation of coal combustion additives, and blending combustion of coal with industrial wastes. Coal is China's main energy source, and 80 percent of China's annual coal production is used in combustion devices. Coal-flue gases from the domestic stoves and industrial furnaces are the main atmospheric pollution source. China's atmospheric pollution is, in fact, the pollution of coal-flue gases. To 2000, in view of China's energy needs as a developing nation, the atmospheric pollution from coal combustion must receive our utmost attention.

Jan 1, 1994

By Daniel L. Hanson

This paper presents a case history of the design, installation and performance of a tied-back tangent caisson retaining wall which was constructed as part of the Third Harbor Tunnel project currently underway in Boston, Massachusetts. The Third Harbor Tunnel project consists of a large multi-lane transportation tunnel which is being constructed by the sunken tube method. In this type of construction, the tunnel alignment, slopes and bedding are excavated and installed underwater and the tunnel sections floated over the proper alignment and sunk in place. The tangent caisson retaining wall discussed in this paper was constructed to provide support of the upper portions of the tunnel excavation at the East Boston Portal where the tunnel exited from below the harbor and continued underground on shore. A portion of the tangent caisson retaining wall was also utilized to provide earth support for the barge unloading facility where spoil from the tunnel excavation was transferred to surface vehicles for removal from the site. PROJECT BACKGROUND The tangent caisson retaining wall was constructed by The Millgard Corporation (TMC) as a subcontractor to the Boston Third Harbor Tunnel Contractors, a Joint Venture which consisted of the firms of Morrison-Knudsen Corporation, Interbeton Inc., and J.F. White Contracting Company. The entire project team is listed below on Table 1. The design of the tangent caisson wall system was performed by Hanson Engineering, P.C. (HE) acting as design consultant to TMC. The retaining wall system incorporated a single row of pressure injected earth anchors (tie-backs) as part of the design. The earth anchors were designed and installed by Drill Tech as a subcontractor to TMC.

Jan 1, 1994

By Frank M. Kimmerle

Spent Potlining (SPL) contains recoverable chemical elements (C, F, Na and Al) which are lost in stabilization or immobilization processes primarily aimed at eliminating cyanides and reducing leach rates of soluble fluorides prior to landfiling. They can be recovered in a variety of mineral forms for recycling in the aluminum industry and elsewhere. Alcan has developed a cost-effective hydrometallurgical route, combining a number of proven unit processes to destroy cyanides, recycle the chemical values and provide a zero-discharge process. Pilot plant studies of this Low Caustic Leach and Liming (LCL&L) Process prove that the fluoride scan be converted to acid grade fluorspar, while the sodium and aluminum are recovered as a sodium aluminate and caustic feed to the Bayer Plant operations. The remaining brick and carbon fraction constitutes a high ash solid fuel which meets TCLP leach criteria and whose reduced sodium content enhances its value as a chemical reducing agent.

Jan 1, 1994

By Baozhong Zhao

In-situ vitrification (ISV) is a new technology used for treating radioactive, organic and inorganic contaminated soils. In this process, electricity is applied through electrodes buried in the contaminated soil to melt it and form an environmentally stable glass-like solid. The organic contaminants and volatile metals are vaporized during heating up, the non-volatile inorganic elements are dissolved and incorporated into the melt. In present full-scale operation, the ISV process can treat 4 to 6 tons of soil per hour at consumption of about 1000 kwh per ton of soil. In this study, various configurations of electrodes were examined in a mathematical model. The results may be used to optimize the ISV process.

Jan 1, 1994