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By D. Dimitriadis, T. Polglase, M. M. Botz, W. Phillips, R. Jenny

Cyanidation processes for the extraction of gold or silver frequently involve the processing of sulfurcontaining solids that react with cyanide to form thiocyanate. The formation of thiocyanate is an undesired side reaction, and in many cases thiocyanate formation results in a prohibitively high cyanide consumption. With the increasing number of gold and silver mining projects that involve the processing of sulfide ores or concentrates or that utilize a biological sulfur oxidation process, more attention is being focused on minimizing thiocyanate formation and in treating solutions to eliminate toxicity associated with thiocyanate. Though not yet commercially applied, there are several processes available to recover cyanide from thiocyanate to reduce tailings toxicity and to allow the reuse of cyanide otherwise lost to thiocyanate formation. This paper presents an overview of processes available for recovering cyanide from thiocyanate along with estimated operating costs for the processes. Pilot testing data suggests that in some cases cyanide can be recovered from thiocyanate for approximately the same cost as newly purchased cyanide.

Jan 1, 2002

By Pooyan Asadollahi, Praveen Krishna, Michael Joye

"Durability design for underground structures is an increasing focus of designers and owners in the underground construction industry. Many owners have expanded their requirements for durability design, with specific requirements for structure lifecycle and designer certification of structural durability. This paper describes current trends and best practices including: defining the underground structure lifecycle, historically durable underground structures, design methods for underground structure durability built of reinforced concrete, and durability of materials. Criteria to be used for defining end of structure life and owner’s maintenance responsibilities are crucial to lifecycle contract requirements. Current practices of several major owners are presented. Design methods are presented including United States code requirements. Current best practices for enhancing the durability of materials used in underground construction are discussed including: low permeability concrete, steel reinforcement concrete cover, the use of steel fiber, and testing for verification. INTRODUCTION Durability design is increasingly being recognized as an essential component of good design practice. Infrastructure owners recognize that to serve the public interest, constructed facilities must be lasting and durable. The public understands that structures with limited service life result in increased costs and add to their daily inconvenience with frequent repair and reconstruction. Engineers are increasingly asking not only is the structure strong enough but will it last for generations. Durability design requirements are no longer just adherence to some accepted practices, but are based on analytical approaches, with results that can challenge our beliefs in what construction materials and details result in a durable structure. This paper describes current industry requirements and practices for durability design of underground structures, and offers some suggestions regarding future trends and developments. SERVICE LIFE DEFINITION The service life of a structure is the sum of the time to onset of deterioration, called initiation period (ti), and the subsequent time period of deterioration ending when the structure is no longer functional, called propagation period (tp). Figure 1 shows a conceptual service life diagram. These time periods can be substantially affected by the level of maintenance performed during the life of the structure."

Jan 1, 2016

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 S. D. Thompson, G. T. Lineberry, A. J. Basu

Conveyor belt haulage has become the preferred mainline transport method in underground coal mining, especially for multi-unit mines. Proper designs for belts (width and speed) and surge bins (placement, capacity, and discharge rate) are necessary to achieve efficient mine haul- age. Two computer simulation models, CMBCS and BELTSIM, available for designing these parameters were compared. These comparisons included modeling, input data requirements, statistical flexibility, accuracy of simulated loading, and execution time.

Jan 1, 1991

By E. F. Divers

Adequate ventilation of coal mine working faces is the most important technique for controlling respirable dust and methane. Choosing the right technique presents some tough questions. US Bureau of Mines research has shown that to control respirable dust, you must contain the dust near the face, keeping rollback (turbulence) to a minimum. For methane, the most effective approach has been to use a blowing brattice, or tubing, and to create turbulence and disperse the face methane, allowing it to pass over the machine and into the return. It is immediately apparent that the two approaches may counteract one another, thus complicating the decision as to which system may be best for a given situation. At present. Bureau research has developed two successful machine-mounted face ventilation systems to meet these different needs and allow deeper cutting. The fan- powered dust scrubber is designed to control dust primarily associated with blowing face ventilation systems. The spray- fan controls methane on exhaust-ventilated sections.

Jan 1, 1987

By K. N. Han

A kinetic model for the batch leaching of various metals using different lixiviants was developed. The overall material balances for the reactants and products at the solid/ liquid interface were formulated for various types of heterogeneous reactions at the interface. The solutions to these mass balances are identified analytically, as well as numerically. Applications of these numerical solutions to various leaching systems using rotating discs or powders are discussed. The metal-dissolution systems addressed include cobalt, nickel and copper in acid, cyanide and ammoniacal solutions.

Jan 1, 1996

By James Watson Baxter

Fluxes are used to promote pyrometallurgical processes that rely on adhesion (soldering or brazing) or fusion (gas and arc welding) to join metallic surfaces. In the adhesive processes, the metal surfaces to be joined are not melted; the join is formed using a filler metal with lower melting point than the base metal. Fusion welding involves use of heat in excess of the melting point of the base metal. The fused joint may be achieved either by simply fusing together metal surfaces brought in contact with each other or by introducing additional molten metal of similar composition to form a fused joint. ADHESIVE PROCESSES--SOLDERING AND BRAZING In order for molten filler metal, solder or braze, to spread in a manner that creates a successful join; the work surfaces on the base metal must be thoroughly cleansed. Fluxes remove stubborn oxide films and other surface contaminants, promote wetting of the work surfaces, add fluidity to the solder or braze, and enhance workability and ease of spreading. Brazing processes involve higher temperatures than those reached in soldering. Brazing fluxes, which must remain active and effective at the higher temperatures, differ from those employed in soldering. Some common fluxes used in adhesive processes are rosin for soldering tin and electrical connections, hydrochloric acid for use in soldering galvanized iron and other zinc surfaces, and borax for brazing. Soldering and brazing are similar processes, the primary difference being the temperature at which the joining operation is carried out. Soldered joints, produced with low-melting-point fillers (solders) that melt and flow at temperature less that 450°C (Althouse et al., 1988) can sustain loads of 1 to 1.7 MPa for extended periods of time (Anon., 1966). Brazing involves the use of filler materials with melting points commonly above 500°C and generally provides stronger joints than those obtained with solder. Both processes require local application of heat to melt and spread the filler so that the molten filler can wet (adhere to) the base metals by alloying and diffusion. Soldering Soldering is a means of joining metals by adhesion using a metallic bonding alloy as the filler, commonly a mixture of lead and tin. However, the adhesion of solder depends more on its ability to be keyed into minute surface irregularities than on alloying. The most familiar application is to provide and secure electrical connections. Soft solders can range from 1 to 70% tin with the remainder mostly lead. However, for general-purpose, soft-solder work, the alloy is commonly 50% lead-50% tin. Higher lead contents provide a wider range in the melting temperature and, for this reason, a 60% lead-40% tin alloy, which yields a mushy mixture, is used for wiped joints in lead sheet and pipe work. Conversely, 40% lead-60% tin alloys are used in soldering tin and other low- melting-point materials for which a narrower range of melting temperature is required. There are numerous other solder compositions such as tin-silver, 95% tin-5% silver and antimony-tin, 95% tin and 5% antimony (Carlin, Jr., 1992). Heat needed to melt and spread the solders is commonly provided by electrically heated, copper-tipped soldering irons or by means of torches; the solder is applied by hand, usually face-fed by means of wire. For wiped joints in plumbing and lead-cable splicing, the solder is manipulated with cloth pads. The molten solder wets the joint surfaces and is drawn, by surface tension, into minute fissures and capillary openings. Other applications involve use of induction heaters and furnaces with pre-shaped solder appropriately placed prior to fluxing and heating. In some processes, the joints are immersed in molten solder. Constituents and Role of Soldering Fluxes: Soldering fluxes generally fall into one of three categories: highly corrosive fluxes, intermediate fluxes, and noncorrosive fluxes. These same categories are sometimes designated inorganic, organic and rosin-based respectively (Althouse et al., 1988). Common constituents of each group are discussed briefly below. Corrosive Fluxes (Inorganic). Work with aluminum, magnesium, stainless steel, high alloy steel, aluminum bronzes, and silicon bronzes is carried out at temperatures in the upper portion of the range for solder operations. Soldering these materials requires use of highly active, corrosive fluxes to remove and prevent the formation of the especially stubborn, hard, oxide films that form on these materials upon exposure to the atmosphere. The corrosive fluxes consist of inorganic acids and salts that are applied either as pastes or dry. They are active at elevated temperatures and, since they remain active after the soldering is completed, must be completely removed. The main constituent of most corrosive fluxes is zinc chloride with a melting temperature well above the solidus temperature of most commercial tin-lead solders. It is made by the action of hydrochloric acid on zinc. When zinc chloride is used alone, un- melted particles of this corrosive salt get caught up in the joint and weaken it. For this reason, other inorganic salts such as ammonium chloride (NH4Cl) or sodium chloride (NaCl) may be added to lower the melting temperature. A mixture of zinc chloride and ammonium chloride is very effective because the excellent oxide reducing properties of ammonium chloride and the protective action of the molten zinc chloride combine to produce a fluxing action superior to that achieved when either is used alone. In addition to zinc chloride, ammonium chloride, and sodium chloride; common con-

Jan 1, 1994

By Randal J. Barnes

In, any open pit mine the ability to make accurate production estimations for the shovel-truck system is an important asset. This is true in an operating mine wishing to estimate production under a set of system modifications (i.e. more trucks, fewer loaders, change in roads, etc.), as well as in the pre- mining planning stages of a property. Many different methods have been proposed for solving this problem; some of the methods rely heavily on "rules of thumb" while others are highly mathematical and require access to a high speed digital computer. Analysis of shovel-truck systems with the use of simulation models is a widely accepted technique within the industry. Through the use of such models it is possible to account for much of the inherent variability of the system and thus produce meaningful results. However, simulation studies are expensive. Formulation and setup of the actual simulation model requires a significant commitment of time and energy. In addition, the cost of the necessary computer runs is often of considerable magnitude.

Jan 1, 1979

By L. M. English

A basic model was developed to help assess methane control needs for the longwall mining of coal in gassy areas. Rather than depending on reservoir and rock mechanical theories, it uses an empirically determined gas emission rate as an input, and it operates on the assumption that, within a specific region and zone, gas emissions will be relatively equivalent for uniform incremental volumes of gob created by mining. The computer program divides longwall panels into segments, keeps track of the face advance and generates emission rates and volumes for both the entire panel and for individual zones within the panel by summing values for all undermined segments. This model can aid in the determina¬tion of the number, size and location of vertical wells or other methane-control applications that are needed for gob gas control.

Jan 1, 2000

By B. J. Sauer

Misapplication of ac induction motors for mine crusher and mill applications has long been a frustration for the driven equipment supplier and the mine operator. Proper selection of ac induction motors is critical to providing efficient production. This paper focuses on the selection of ac induction motors for gyratory crusher, conecrusher and grinding mill applications. The criteria for motor selection includes: proper enclosure, driven equipment torque requirements, bearing life, temperature rise, starting requirements, ambient temperature, altitude and accessory requirements.

Jan 1, 2002

By N. D. Cristescu

An analysis of the interaction between a creeping rock and a yieldable lining is presented. The following cases are considered: an elastic lining, a lining made of circular shaft rings that may slide at their joints, a lining made of circular reinforced concrete panels with wooden compressible strips inserted between the longitudinal joints and a yieldable support that has a compressible broken-rock stratum between the support and plane rock. By formulating a mathematical model for the rock-lining interaction, one can optimize the sequence of excavation-lining application. To keep costs to a minimum, one can also choose the most appropriate lining for the corresponding rheological properties of the rock.

Jan 1, 1997

By R. Schmidt

The computational fluid dynamics (CFD) technique was used to analyze and optimize the design of the dynamic air classifier integral to Raymond® Bowl Mills. Flow patterns and particle behaviors were modeled in the RB Bowl Mill equipped with various classifier designs. These CFD simulations resulted in the development of a hybrid turbine classifier that has now been field-tested, yielding significant improvements to both mill throughput and product size distribution. This paper demonstrates the viability of CFD as a tool for air classifier design and as a technique that can be extrapolated for use with other pulverizer and classifier arrangements.

Jan 1, 2004

By P. Mousset-Jones, F. Calizaya

This paper explains and discusses a computer program that has been developed to determine the ventilation design parameters for complex auxiliary ventilation systems such as those found in the construction of long excavations with multiple headings. The program is based on the principle of partitioning the system into segments of finite length, and formulating and solving the resulting networks recursively. The resulting network problems are solved analytically. With this program, the size of fans can be determined in order to reduce the total leakage and minimize the flow recirculation. The application of the program is illustrated by the detailed solution of an auxiliary ventilation system proposed for the Exploratory Studies Facility (ESF) at the Yucca Mountain Project, Nevada.

Jan 1, 1995

By S. Chander

The advantages and disadvantages of various techniques available for controlling reagents in the mineral flotation systems are discussed. Special interest is placed on potentiometric and voltammetric sensors for monitoring flotation pulps. Different approaches to increase the sensitivity of detection and to facilitate in-stream monitoring of solution species are also discussed. The potentiometric sensors are simple to use but are limited by the availability of an electrode reversible to the species to be monitored. In some cases the response signal could be unreliable due to the presence of interfering species. In comparison, voltammetric sensors require a higher degree of instrumentation which, however, provides an opportunity to decrease interferences and increase levels of detection.

Jan 1, 1993

By A. I. A. Salama

A computationally efficient technique for generating a balanced set of density or size separation data is developed. The technique proposed utilized minimization of a modified form of error squares to generate the optimum estimates of outputs mass yields (splits) and balanced direct mass distributions of feed and outputs. The estimated separation data set satisfies mass balance conditions of the streams mass distributions around the separator. The technique proposed avoids the generation of small negative values for the estimated feed and outputs direct mass distributions. Actual data are used to demonstrate the technique proposed.

Jan 1, 1996

By Todd R. Taubert, Kenneth L. Bickel

The U.S. Bureau of Mines (USBM) pioneered the development of disposable filters for reducing diesel particulate emissions from permissible mining machines. The USBM is now evaluating filter media that can withstand the high exhaust temperatures on nonpermissible machines. The goal of the evaluation is to find an inexpensive medium that can be cleaned or disposed of after use, and will reduce particulate emissions by 50 % or more. This report summarizes the results from screening tests of a lava rock and woven fiberglass filter media. The lava rock media exhibited low collection efficiencies, but with very low increases in exhaust back pressure. Preliminary results indicate a collection efficiency exceeding 80 % for the woven fiber media. Testing of both media is continuing.

Jan 1, 1995

By A. J. Monhemius, S. Raghavan, G. W. Warren, E. Peters, D. W. Furerstenau

A lyometallurgical process for extracting copper from an ore containing chrysocolla by leaching it with a kerosene solution containing LM 63 in the presence of small amounts of aqueous ammonia is described. The experimental results indicate that 70 to 75 percent of the copper can be extracted from the ore using an ammonia content that is about one-fourth the stoichiomeaic quantity required to leach copper in an aqueous leaching system. The rate of copper extraction was found to be a function of particle size, ammonia concentration and temperature. The large quantity of physically adsorbed water together with ammonia in the pores of chrysocolla provides a mechanism for the transport of copper to the external surface of the particles where it is complexed by the LM molecules and transferred into the organic phase. When size reduction accompanies leaching, the extraction process was found to proceed when only "trace" quantities of ammonia are present in the system. The kinetics of the extraction process appear to be controlled by a mixed (reaction and diffusion) mechanism.

Jan 1, 1993

By M. L. Nave, R. E. Melley

DC motor drives are available technology for belt conveyors. The success of the application in mining depends on adequate and timely consideration of DC drive features. The purpose of this paper is to familiarize and inform possible mining users of DC drive attributes.

Jan 1, 1996

By James J. Broderick

In the production of Pig Iron - Limestone, Coke and Iron Ore pellets are changed to the blast furnace and reacted at approximately 2,800 degrees F. The resultant products are molten iron and a molten slag - not unlike lava. The molten slag stream is channeled into open pits, cooled with water, crushed and sized for various industrial applications. The production of steel from pig iron in open hearth, B0P, BOF and electric furnaces results in somewhat similar slags: but since free lime is normally the flux, the resultant slags are not satisfactory for use in cement pastes. When exposed to water, the lime slakes, expands by 250% and ruptures the concrete. Thus, the slag discussed first is Blast Furnace Slag composed of 30 to 40% Silica (SiO2) Alumina (AL202) 7 to 16% Lime (CaO) 32 to 45% and Magnesia (MgO) 5 to 15%. The oxides do not exist as free oxides but rather as silicates and alumino silicates which are chemicall inert. Since transportation costs limit the area of use, blast furnace slag can only be found in concrete products produced within 60 to 100 miles of a blast furnace operation. Even within these areas where slag is in heavy supply, quite often the use of slag is minimal for concrete aggregate and the major outlet is road base.

Jan 1, 1985

By I. K. Kapageridis

Environmental management and planning requires the integration of large volumes of disparate information from many sources and the analysis of this information with efficient tools for assessment and evaluation. Effective methods of communication that allow interactive participation in the planning, assessment and decision-making processes are also very important. The VULCAN software package from Maptek (Pty) Ltd comprises a large number of 3D graphical tools within an interactive 3D interface called ENVISAGE. These tools are designed and developed to help engineers and scientists to identify and solve environmental problems. The combination of VULCAN 3D Software and the I-SiTE 3D Laser Imaging system leads to powerful solutions for environmental management. This paper presents the capabilities of this integrated system and its applications for environmental management.

Jan 1, 2002