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By Susan B. Robertson, Gregory E. Hinshaw

Many injuries are caused each year by rock falls in coal mines. Most of these injuries are not caused by major roof collapses, but from falls of smaller rocks from the immediate top or roof skin. Various surface controls are used in mines to control this surface rock. One that has been found to be very effective is roof screening. Depending on the size of the screen, roof coverage approaching 100%can be achieved. Many mines are reluctant to use screen for primary skin control because of additional costs of time and materials, but others are having great success at both controlling costs and surface rock. Data is presented from two mines that show a dramatic reduction in roof skin injuries when screening is used. Much of this success is due to innovations in roof bolting machines. Four case studies of roof screen experience are presented along with associated costs of materials, impact on bolting advance rates, and potential ergonomic risks. The effects of roof screening on skin control and safety are also included. Finally, this paper will provide information about features of different roof bolting machines that affect production and safety.

By Carlton E. Brown

Brown and Yant6/ recently described a microprojection method for determining the particle-size distribution and number concentration of samples of dust collected from the air by such samplers as the Owens jet dust counter7/ and the thermal precipitator8/. This method was developed to obviate or reduce the eyestrain consequent to the regular filar-micrometer method9/ and to save time and work. The article stated that work was in progress on a microprojection method for courting impinger dust samples; this article describes the method developed. ACKNOWLEDGMENTS The assistance of the personnel of the Ventilation Department of the Anaconda Copper Mining Co., Butte, Mont., in developing this method and particularly in suggesting a suitable material to use for the microprojector screen is sincerely appreciated. Much of the work was done in the laboratory of the Anaconda Copper Mining Co. on samples collected in Butte mines during a cooperative study with this Bureau.

Jan 1, 1938

By Carlton E. Brown

Broom and Yant6/ recently described a. microprojection method for determining the particle-size distribution and number concentration of samples of dust collected from the air by such samplers as the Owens jet dust counter) and the thermal precipitator8/ . This method was developed to obviate or reduce the eyestrain consequent to the regular filar-micrometer method9/ and to save time and work. The article stated that work was in progress on a micrcprojection method for counting impinger dust samples; this article describes the method developed. ACKNOWLEDGMENTS The assistance of the personnel of the ventilation Department of the Anaconda Copper Miring Co., Butte, Mont., in developing this method and particularly in suggesting a suitable material to use for the microprojector screen is sincerely appreciated. Much of the work was done in the laboratory of the Anaconda Copper Mining Co. on samples collected in Butte mines during a cooperative study with this Bureau.

Jan 1, 1938

By Jack S. Greber

The mining industry generates an estimated 2.3 billion tons of solid waste each year and the total accumulated mineral resource solid waste at both active and inactive mine sites, approaches 30 billion tons. Five industries generate 85 percent of mine solid waste: copper, phosphate, iron, uranium, and coal. Over the past several years, the Federal government has shown increasing interest in the proper disposal of solid wastes generated by the mining industry. Three new pieces of federal legislation have been passed recently beginning with the most comprehensive regulatory authorization passed in 1976, the Resource Conservation and Recovery Act (RCRA) which has been amended to the Solid Waste Disposal Act Amendments of 1980. RCRA is implemented and enforced by the Environmental Protection Agency (EPA) and intended to control municipal and industrial solid wastes. Next came the passage of the Surface Mining Control and Reclamation Act (SMCRA) of 1977 which is implemented and enforced by the Department of Interior to control coal surface mining and the surface effects of underground coal mining, and finally, the recent Uranium Mill Tailings Radiation Control Act (UMTRCA) of 1978 implemented by EPA and enforced by the Nuclear Regulatory Commission (NRC) to control uranium mill tailings disposal.

Jan 1, 1981

By A. J. Kwitowski

Remote control is usually associated with deep mine, continuous mining machines. This is because thin-seam operation precludes an onboard operator's compartment or the mine has approval to conduct extended cut mining. Using a tethered or radio-linked control box, the remote operator is typically situated 3 to 15 m (10 to 50 ft) from the working face. The operator receives direct operational cues through senses like vision, hearing and feel. Remote control is sometimes touted as a safety feature. However, this is not always true, as operators are not provided protection from roof and rib falls or being crushed between the machine and a rib. Remote control operators are also left exposed to dust and noise. Teleoperation described here is the computer-based, distant control of mining machinery from a protected operator compartment located out of the line-of-sight from the operational site. Video, sound and other sensory information are gathered through sensors and electronically transmitted to and displayed at the operator's location. The teleoperator responds to the information and makes decisions that are initiated by control devices (usually switches). These control commands are then electronically transmitted to the re¬mote machinery and the appropriate machine function(s) are carried out. Teleoperation increases the safety of mining machine operators as it removes them from the immediate vicinity of hazards. The US Bureau of Mines' involvement with teleoperation dates back to 1979. Following feasibility studies, a highwall milling system (HMS) was developed and tested. A deep, thin-seam, room-and-pillar system (TSRPS) has been designed and is currently being surface tested.

Jan 1, 1992

By A. Pomianowski

A spectrophotometric study of xanthate solutions alone and their mixtures with equimolar amounts of alkyl trimethyl ammonium bromide (CnTAB) has established the additivity of ultraviolet spectra (190 - 400 my) for potassium ethyl xanthate (KEtX) and C12TAB. No obvious effect of C12TAB addition on the decomposition rate of KEtX was observed. The kinetics of collector abstraction by copper, nickel and sphalerite powders were studied in 10-5 - 10-3M solutions of KEtX alone and in equimolar mixtures of KEtX and C12TAB. Presence of C12TAB caused a 2 - 3 fold increase in the amounts of xanthate (equivalent to many monolayers) abstracted by copper and, nickel powders but had no effect on the abstraction of xanthate by unactivated sphalerite. The adsorption of C12TAB itself from the mixed solutions was very low, at most ore monolayer only, and was not influenced by the nature of the solid powder used. The results are interpreted in terms of molecular associations and synergistic action of xanthates and quaternary amines.

Jan 1, 1963

By Sylvie Poirier

This paper focuses on new developments regarding thermal rock fragmentation applications. The technology consists in a strong burner powered by diesel fuel and air. The thermal reaction, which is created, allows for the enlargement of 125-mm to 450-mm holes by breaking the rock in a spalling effect. It has been used for over 30 years in Russian open pit mining. Following an agreement between Dynamitage T.C.G. Inc. and the owner of the technology, major improvements have been brought to this technology, allowing for the fabrication of a prototype suitable for the Canadian industry. In Russia and Ukraine, thermal rock fragmentation is actually used to drill large diameter holes in surface mining. Upon having acquired a better knowledge of this technology, it seems that it presents a great potential for selective mining in narrow-vein operations, for either surface or underground mining. Rocmec International Inc., a subsidiary of Dynamitage T.C.G. Inc., and Natural Resources Canada are technical partners in the evaluation of the operational parameters and environmental aspects, such as gas, heat, dust and fog emissions. Furthermore, Canada Economic Development is a financial partner in this project. This paper presents the technology and its history. It also reports on the changes brought to the equipment to adapt it to North American environments. A summary of the tests realized since 1995 is provided, along with the main conclusions obtained. The anticipated applications for the use of this technology in both surface and underground environments are described, such as open pit mining, bulk sampling and narrow-vein ore extraction. An estimate showing a comparison between the thermal fragmentation mining concept and the long-hole mining method is presented and, finally, the future developments planned are listed.

May 1, 2002

By Joner O. Alves

The disposal of scrap tires has been a serious environmental problem. The treatment of this waste by pyrolysis and combustion has advantages since the landfill space is dwindling and the production of fuel becomes of technological interest. However, that processes needs a rigid control of emissions. This work presents a study of the light hydrocarbon gases (HC) generated during the burn of waste tire chips in a two-stage laminar-flow horizontal furnace. Different temperatures in the primary and secondary stage of the furnace were tested, and the oxygen/nitrogen percentage was also varied during the combustion process. A gas chromatograph was used to identify and quantify the components of the gaseous products of combustion and pyrolysis. The results showed the behavior of the gases during the burn of tires, providing valuable information to the control of hydrocarbon emissions.

Jan 1, 2010

By C. A. Rowland

Autogenous grinding, defined as grinding with like material, while quite an old art has recently been revitalized. Two phases of autogenous grinding, primary and secondary, have been the subject of recent papers, technical articles and discussions. The purpose of this paper is to discuss a third phase of autogenous grinding - Intermediate Autogenous Grinding - comparing it to and indicating advantages over the other two phases. Autogenous grinding can also be called ?Rock grinding?1; that is, grinding using ore or rock from the same deposit as the mill feed as grinding media contrasted with using as grinding media steel rods, steel or ironballs, natural or manufactured iron, free pebbles, or other shapes and materials foreign to the mill feed.

Jan 1, 1964

By David G. Adam

Syncrude Canada Ltd. is currently mining over 120 million tons per year of overburden and oil sands to produce 40 million barrels per year of synthetic crude oil. Production increases are planned. This paper reviews the technical and economic assessments of feeder breaker applications in both ore and waste mining which led to an extensive testing and development program and finally to the procurement of full scale production equipment.

Jan 1, 1985

By Jimmy Guarnizo

El yacimiento de La Zanja ubicada en el caserío La Zanja, Santa Cruz de Succhabamba, Cajamarca, inició sus actividades de exploración en 1991 y las de producción en el 2010. MLZ construyó el embalse o reservorio llamado Bramadero, que acumula las aguas de escorrentía de la quebrada del mismo nombre durante el periodo de lluvias, las cuales son empleadas para el consumo humano en la unidad minera, y en menor escala durante la época de estiaje para los procesos de operación. En este sentido, el presente texto señala la construcción de la presa Bramadero, la cual genera agua para beneficio de las poblaciones ubicadas aguas abajo de las instalaciones. Asi también cuenta con un programa de monitoreo ambiental para vigilar la calidad y la cantidad de aguas superficiales y subterráneas. Por tal motivo, cuenta con estaciones hidrométricas para evaluar en tiempo real la calidad del agua en los cuerpos receptores del área de influencia de la unidad minera.

Sep 1, 2015

Australia is not capitalizing on the raw gems and precious minerals that it produces in abundance. In particular, there is an unrealised value for diamonds due to lack of processing after mining. Australia could enhance the value of its raw jewellery products by developing and integrated jewellery industry. For instance, initiation of a diamond industry would require training programmes to educate people in the requisite skills, such as diamond sorting, cleaving, sawing, bruting and polishing. Equally important would be the training of people in design jewellery, manufacturing, and appropriate diamond grading and sales techniques. Future technological advances in diamond processing will decide where the major diamond processing centres of the world will be. Australia, for a relatively small investment, could develop a highly productive diamond processing capacity using the new technology available. Australia's geographical position, and advanced banking and communication facilities provide the potential for this country to become a major trading centre for diamonds. KEYWORDS: Argyle Diamond Mine, Diamonds, Diamond Production, Diamond Sorting, Jewellery Industry

Jan 1, 1989

By Richard J. Wilson

The importance of coal as a major source of energy used by the steel industry has been increasing due to the gradual changeover from steel- making by the open hearth process to steelmaking by the basic oxygen process. Since the production of steel by the BOF process increases the demand for hot metal, there is a growing need to ensure the supply of coke required for the production of hot metal. Coal used for cokemaking has become, therefore, an increasingly important raw material for the steel industry in recent years. Our current projections indicate that coal will be the source of 71% of the total energy requirements of Inland Steel Company in 1985. As a result of the energy shortages of the last few years, various conservation programs have been initiated by the steel industry to reduce the consumption rate of fuel. The efforts to conserve energy have been successful to a great extent due to the rapid advances made in the technology of ironmaking that facilitated gradual reductions in the quantity of coke used per ton of hot metal produced in the blast furnaces. The decrease in the consumption rate of coke was made possible by the use of improved raw materials, such as iron ore pellets and fluxed agglomerates, the operation with high blast temperatures, the injection of auxiliary fuels, and the enrichment of the blast with oxygen. It is expected that additional reductions in the fuel consumption rate will be possible in the ironmaking operations of the large blast furnaces that are being equipped with facilities for proper burden distribution and for operation with higher blast temperatures at high top pressure. The purpose of this paper is to show the effects of coke quality on the production of BOF steel. The importance of coke quality will be pointed out by discussing the effects of the physical strength of coke on both the blast furnace productivity and the steelmaking operations of an integrated steel plant, such as Inland Stee1 Company.

Jan 1, 1980

By Y. S. Sun, P. Gao, Y. F. Li, J. W. Yu

"Oolitic hematite ore is one of the most refractory iron ores in the world. It is not feasible to separate iron minerals from raw ore by conventional mineral processing methods. In recent years, a new technology called coal-based reduction followed by magnetic separation has been employed to produce metallic iron powder from oolitic hematite ore effectively. In order to find the nucleation mechanism, a thermodynamic analysis of the carbothermic reduction of oolitic hematite ore was conducted by the HSC 6.0 thermochemical software. The phase transition and microstructure changes during the coal-based reduction were also investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the iron oxides in the oolitic ore were reduced to metallic iron following the route of Fe2O3–Fe3O4–FeO–Fe in reduction process. The reduction reactions preferentially occur in the high activity regions to form a higher concentration of Fe elements, and then more supersaturated Fe separated out to form new phase nuclei. Under the action of homo-aggregation and principle of minimum free energy, the iron cores continuously absorbed migratory Fe around and grew into quasi-spherical iron particles embedded in slag phase. INTRODUCTION With the rapid increase of steel industry, premium grade iron ore in China has been gradually exhausted, and its supply has become bottleneck for the development of iron and steel industry (Guo et al., 2015). Therefore, it is urgent to exploit the refractory iron ores, such as oolitic hematite ore. Oolitic hematite ore is widely distributes in France, Germany, America, Canada, Pakistan, China, and among other countries (Maynard and Van Houten, 2004; Li et al., 2011). In China, the explored reserve of oolitic hematite ore is 3.72 billion tons, which accounts for approximately 1/9 of total iron ore resources of China (Gao et al, 2016). Oolitic hematite ore possesses complex composition,"

Jan 1, 2018

By N. Moony

The benefit of gravity separation in improving total gold recovery in grinding circuits has been outlined in a significant number of papers to date. However, the use of batch centrifugal concentrators (BCC) as an industry standard to extract gold has limited the potential for maximizing gravity recoveries -particularly in coarse gold deposits. This is a reflection of the high upgrade ratios obtained by BCC's which has an inverse relationship with recoveries. Survey work in Australia has indicated that installation of the InLine Pressure Jig as an alternative to the Bee will significantly increase recoveries of gold by gravity and, accordingly, increase total gold recoveries and lower operating costs.

Jan 1, 1998

By I. Donohue, M. Pearson, E. Barrette

"This paper presents the technique and benefits of the finite element approach for designing the refractory lining in pressure oxidation autoclaves. One-dimensional equations are used to develop an initial refractory design. ANSYS Parametric Design Language (APDL) scripts are then used to build and analyse a more accurate three-dimensional finite element model to verify the refractory thickness, determine weld overlay requirements, and assess mechanical stability. The APDL scripts provide a cost effective means to quickly evaluate various boundary conditions and multiple designs to determine the optimal lining configuration and nozzle layout.INTRODUCTIONNew ore processing facilities demand increased capacity, requiring hydrometallurgy processes that have larger reactor vessels operating at higher pressure and temperature. Many pressure hydrometallurgy operations require vessels with an impermeable membrane and one or more courses of refractory or ceramic brick. The membrane provides corrosion protection for the vessel shell and the brick provides thermal protection for the membrane. Designing a refractory lining with an economic service life as a thermal barrier requires the refractory to be erosion resistant, chemically compatible with the process fluid, and mechanically stable. A fundamental understanding of the factors affecting the lining system is essential as designs move further away from the industry’s experience base.During basic engineering the refractory lining design is developed using one dimensional cylindrical conduction equations for heat transfer and classical hoop stress-strain relationships for determining mechanical stability. The results of the thermal calculations specify the refractory thickness that should prevent the membrane temperature from exceeding the design limit. Mechanical stability of the lining is determined by examining the sensitivity of lining stability with respect to various parameters. There are three criteria that must be satisfied to conclude mechanical lining stability:"

Jan 1, 2012

By Mihaita Matei

An adaptive approach to control the deformation in tube hydroforming process is presented. This requires: the use of an existing non-linear FE software (ABAQUS) that incorporates a user material model (VUMAT), the development and implementation of an adaptive control strategy to coordinate the internal pressure and the axial load so as to prevent fracture and wrinkling failures (knowledge-base controller) and the application of the developed adaptive simulation approach for finding the optimal loading path required to hydroform a defect-free part with as uniform thickness distribution as possible (user's load subroutine (VDLOAD). In order to validate the approach, the case of conical hydroforming and the case of bending followed by hydroforming component is discussed.

Jan 1, 2011

By R. J. Marcotte, C. T. Eddy, R. J. Smith

The objectives of the investigation herein reported were to determine: (I) the S-curves for certain selected cast steels, (2) whether or not the published S-curves for wrought steels are satisfactory for use on cast steels of similar composition, and (3) to prepare hardenability curves of the selected cast steels. In order to make the final comparisons between cast and wrought steel more completely tangible, it was deemed advisable not only to determine S-curves for the steels submitted in the cast condition but also to roll some of the cast-steel test bars and determine comparison S-curves on such wrought material. This procedure eliminates the composition variable and makes it possible to reveal the differences resulting from plastic deformation of the cast structure in addition to providing the comparison with published data on wrought steels. Cast Steels The cast steels selected for the preparation of S-curves, or time-temperature transformation curves, were similar to S.A.E. series 1030, 2330, 4130 and 4330. Of these the 1030 was supplied by The Crucible Steel Casting Co., Cleveland, Ohio, and the other three by The Sawbrook Steel Castings Co., Lockland, Ohio. The steels were furnished in the as-cast condition. The manufacturers supplied the chemical analyses and the properties that could be obtained in the heat-treated condition—all of which is summarized in Table I. The metallographic and dilatometric procedures and equipment were in general standard. The specific technique employed was described in a report of the Steel

Jan 1, 1945

By E. T. Tuzcu

Microscale information about single particle fracture can be incorporated into the macroscale model of the whole size reduction process in the mill. The ultrafast load cell (UFLC) device provides a substantial amount of information about fracture characteristics of a particle under impact loading. UFLC captures high-resolution compressive force signals during particle breakage. The measurement of the compressive force at the instant of fracture of the particle allows computation of a number of comminution-related particle properties, as well as the energy absorbed during fracture. In the current study, limestone particles 50 mm in size were fractured to obtain specific fracture energies. Then, based on the experimental data, two models were proposed to quantify the fracture process. The specific fracture energy distribution of the particles in the range of 6 to 50 mm was defined by the well-known Weibull distribution. The other model is a probabilistic fracture model. This model is a link between energy events occurring in a grinding mill and the breakage rates of particles. The impact energy spectra or energy events occurring in a grinding mill can be obtained with a discrete element method (DEM) simulation. One can model the breakage rates of the mill material by combining the energy spectra with the probabilistic fracture model. This novel approach for the modeling of breakage rates via DEM and UFLC is shown here.

Jan 1, 2011

By E. T. Tuzcu

Microscale information about single particle fracture can be incorporated into the macroscale model of the whole size reduction process in the mill. The ultrafast load cell (UFLC) device provides a substantial amount of information about fracture characteristics of a particle under impact loading. UFLC captures high-resolution compressive force signals during particle breakage. The measurement of the compressive force at the instant of fracture of the particle allows computation of a number of comminution-related particle properties, as well as the energy absorbed during fracture. In the current study, limestone particles 50 mm in size were fractured to obtain specific fracture energies. Then, based on the experimental data, two models were proposed to quantify the fracture process. The specific fracture energy distribution of the particles in the range of 6 to 50 mm was defined by the well-known Weibull distribution. The other model is a probabilistic fracture model. This model is a link between energy events occurring in a grinding mill and the breakage rates of particles. The impact energy spectra or energy events occurring in a grinding mill can be obtained with a discrete element method (DEM) simulation. One can model the breakage rates of the mill material by combining the energy spectra with the probabilistic fracture model. This novel approach for the modeling of breakage rates via DEM and UFLC is shown here.

Nov 1, 2011