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By John J. Baz-Dresch

Catalyzed diesel particulate filters (CDPF's) reduce the concentration of diesel particulate matter (DPM) and may reduce the emissions of carbon monoxide (CO) and hydrocarbons (HC) in diesel exhaust. Asamera Minerals' Cannon Mine first installed CDPF's in 1987, and currently has 12 diesel-powered vehicles equipped with CDPF's. The Cannon Mine and the U.S. Bureau of Mines collaborated to evaluate the durability and performance of a CDPF. One of the CDPF's used at the mine was periodically evaluated in the USBM's diesel emissions laboratory after 839, 1,584, and 2,881 h of in-mine service. The objectives of this report are to present results from the USBM's evaluation of this CDPF, to describe the Cannon Mine's experience and cost analysis of using CDPF's, and to make recommendations for the future use of CDPF's. CDPF's improve air quality at the Cannon Mine, but they frequently become plugged and are subject to excessive mechanical shocks and stress, shortening their useful life. Mine records indicate that CDPF's account for 0.8 to 4.9 pct of the vehicles' operating cost at the lVine. CDPF life to date has ranged from 1,671 h to more than 5,992 h. Laboratory tests of the CDPF determined that DPM removal efficiency decreased and regeneration temperature increased over time.

Jan 1, 2010

By John Organiscak

A majority of continuous mining machines employ a water spray system and a machine mounted flooded-bed scrubber to suppress and capture dust during coal mining. These machine mounted dust control systems must be designed to function within the localized face ventilation system at the mining section to control both dust and methane. Spray systems can impede or improve the scrubber effectiveness in controlling dust or methane at the mining face. Laboratory experiments were conducted to examine the effect of spray type, spray pressure, machine body blocking sprays, and scrubber airflow on dust and gas levels while using a 12.2 m (40 ft) exhaust ventilation curtain setback from the face. These experiments were conducted with the mining machine positioned at the end of a simulated 6.1 m (20 ft) sump and slab cut. Results indicate that the hollow cone nozzles with blocking sprays best complemented the flooded-bed scrubber performance in an exhaust ventilation system. This external spray system notably reduced dust and gas levels on the off-curtain side of the mining machine for both the sump and slab cut as compared to the flat spray nozzles. Higher scrubber airflows reduced dust and gas levels on the curtain side and in the return of the continuous mining machine. The remote operator position, located on the off curtain side and parallel to the inlet end of the exhaust curtain, sustained the most stable and lowest dust levels around the mining machine.

Jan 1, 2010

By Maria I. De Rosa

The U.S. Bureau of Mines conducted a study to determine if correlations exist between the chlorine or nitrogen contents of materials and the hydrogen chloride (HCI) or hydrogen cyanide (HCN) concentrations evolved during the thermal decomposition of these materials. Hydrogen chloride, hydrogen cyanide, and carbon monoxide (CO) were found to be the primary toxic gases evolved during the combustion process. The experiments were carried out in a 20-L furnace with 1-g samples. The furnace temperature, rising from ambient, was set at 1,000 °C with an airflow of 10 L/min. The variables measured were the gas loads (milligrams per gram) of HCI, HCN, CO, and CO2 (carbon dioxide); CO and CO2 concentrations as a function of time were also measured. Other variables included the average concentrations of submicrometer smoke particles and particles' average diameter, mass of particulates, sample and furnace temperatures, and sample weight loss. The data indicate that there are significant correlations between the percentage of chlorine or nitrogen contained in the original samples and the HC1 or HCN concentrations evolved during the combustion of the materials. These correlations may be used to predict and evaluate a material's toxic hazard during combustion.

Jan 1, 2010

By Phillip W. Holland

The U.S. Bureau of Mines has developed a mass spectrometer method for determining helium in the parts-per-million to 10% range to an accuracy of ± 1%. The method employs a mass spectrometer, an inlet system utilizing a chromatographic gas-sampling valve, and an activated coconut charcoal trap cooled with liquid nitrogen. Gravimetrically prepared standards of helium in nitrogen were used to demonstrate the linearity of the method over the concentration range of 10 ppm to 10.66% helium.

Jan 1, 2010

This specification, along with the drawings, encompasses all designs, materials, products, accessories, tools, equipment, services, transportation, labor and supervision, installation techniques, and testing procedures required for the installation of soil nail excavation support or earth retention systems. This is a Guide Specification designed to assist in the development of project specifications for soil nail excavation support and earth retention systems. This Model Specification is based on generally accepted industry standards but may require modification by the specification writer to accommodate unusual and/or unforeseen site and subsurface conditions and the particular circumstances of the project. Care must be taken to avoid internal inconsistencies. It contains language allowing for a Contractor-Designed Soil Nail Wall, which would be removed if the design is provided by the Owner (e.g. See Sections 1.2 and 4.1).

Jan 1, 2010

By A. H. Kaksonen

Numerous reactor designs for biological sulfate reduction have been reported. Fluidized-bed bioreactors (FBR) can efficiently retain biomass and allow high mass transfer and reaction rates. This work reviews the development of various sulfate-reducing FBR processes for treating acidic metal- and sulfate-containing waters and recovering metals from bioleaching liquors. The FBR process performance was evaluated with continuous flow experiments under various operational conditions: fluidization rates, influent pH values, metal, sulfate and salt concentrations, hydraulic retention times, electron and carbon sources, and temperatures. Substrate utilization and sulfide inhibition kinetics were determined with batch FBR-kinetic experiments. An artificial neural network (ANN) model was used to predict the performance of the FBR. Sulfate-reducing bacteria (SRB) were characterized in FBRs with molecular and culture-based approaches with the aim to gain a better understating of the bioprocesses. Based on the studies, FBRs are well suited for the combined removal of metals, acidity and sulfate from water.

Jan 1, 2010

By L. J. Froisland

The U.S. Bureau of Reclamation requested U.S. Bureau of Mines (USBM) assistance in developing design data for moving lead-zinc-gold tailings from their current location without disrupting the existing chemically stable conditions. This report presents results of USBM work in determining (1) the minimum required time to air dry the tailings to approximately 20 pet moisture under various drying conditions both in the laboratory and in the field, (2) the degree of oxidation or reduction that occurs during drying, (3) the effect of lime or cement addition before drying, and (4) the likely equilibrium conditions of the dried tailings after deposition at the new location. The limited number of tests performed by the USBM in the available time frame established trends in oxidation levels but did not provide absolute statistical validity of data values. All data from drying and oxidation testing are included in appendices to this report.

Jan 1, 2010

By Guillermo Turner-Saad

"Best practice in the economic evaluation of mining projects and operations is based on the integration of geological, mining, metallurgical, environmental, marketing, economic and corporate information and strategies. Fundamentally, the economic evaluation takes into account mining, blending, stockpiling, processing, smelting, refining and marketing ore resources with grades estimated by geostatistical methodologies.Nevertheless, a realistic economic evaluation consists of a concurrent and integrated optimization process that maximizes the concentrates or products of liberated and selected ore minerals from mineral deposits. The optimum solution is obtained through a trade-off among mining, blending, stockpiling and processing ore reserves with distinct mineralogy and texture characteristics. The concurrent optimization determines both the practical mining sequence of ore reserves and the dynamic and robust mineral processing flowsheet design over the expected life of mining projects and operations.A combined risk-adverse and concurrent optimization process takes into account the spatial uncertainty of the mineralogy and texture characteristics of ore reserves. Additionally, a variety of mineral processing linear, non-linear, additive and non-additive parameters modeled spatially. The spatial uncertainty of these ore reserves characteristics and parameters has a direct impact in the expected mining sequence, mineral processing flowsheet design, concentrates or products quantity and quality, and economic value of mining projects and operations.Geometallurgical domain constrained stochastic geostatistical methodologies and multivariate mathematical models are applied for spatial uncertainty modeling of ore reserves characteristics and parameters. These mathematical models correlate the mineral processing liberation and selectivity responses of the mineralogy and textures within each geometallurgical domain. These models, in turn, are defined based on results of mineral processing and environmental testwork of unbiased and representative samples chosen for their variability. These samples are selected within mutually exclusive spatial geometallurgical uncertainty domains with similar mineralogical and textural characteristics in mineral deposits.Geometallurgical domains are defined by applying and combining multivariate statistical analysis and implicit modeling methodologies. These involve determining and constraining mineral processing liberation and selectivity properties explicitly contained in the extensive and integrated exploration drillhole database."

Jan 1, 2010

By Susan E. Brink

The first step in determining whether Mn can be recovered by in situ leaching is to develop and test a selective lixiviant. Two column leach tests and one core leach test Were conducted by the U.S. Bureau of Mines on Mn oxide ore using aqueous sulfur dioxide (SO2) as the lixiviant. The column tests showed that aqueous S02 could selectively dissolve available Mn oxides from calcite-rich ore in a heap leach system. However, the core test showed that calcite gangue side reactions can have pronounced negative effects on the likelihood of successful in situ leaching of a calcite-rich ore with aqueous S02. Petrographic and geochemical analyses showed that both Mn (IV, III) oxides and calcite were dissolved. The abundance of dissolved Ca caused precipitation of gypsum. Acid consumption by calcite dissolution caused a rise in pH that caused the SO/S species to shift to S032-(sulfIte), which hindered reductive dissolution of Mn oxide. Gypsum precipitation did not affect complete leaching of the rock fragments in the column tests; however, it plugged the natural permeability in the core. Manganese recoveries were high for the column tests and low for the core test.

Jan 1, 2010

By P. L. Sibrell

The U.S. Bureau of Mines has tested cyanide leaching for recovery of palladium (Pd) from spent petroleum processing catalysts. Three different catalyst samples were supplied by a spent-catalyst processor. These catalysts consisted of a zeolite base and contained 0.4 to 0.7 pct Pd. During alkaline cyanide leaching, the catalysts exhibited ion-exchange properties due to their zeolite matrices. Hydrogen ions were released from the zeolite in exchange for sodium ions in solution, resulting in a significant decrease in solution pH. This could present a safety hazard because of the potential for release of toxic hydrogen cyanide gas. A pretreatment step where the catalysts were contacted with a 1.0M sodium hydroxide solution was found to prevent the pH shift from occurring. Following the sodium hydroxide pretreatment, two stages of leaching at 160 °C with solution containing 1 pct sodium cyanide and 0.1[M] sodium hydroxide gave at least 75 and up to 95 pct Pd recovery. The Pd was quantitatively recovered from the leach solution by thermal decomposition in an autoclave at 250°C for 1 h. The Pd content of the precipitate was over 50 pct. Thermal decomposition also decreased the total cyanide content of the barren solution to less than 0.2 mg/L. The catalyst leach residues passed the Federal Toxicity Characteristic Leaching Procedure and the California Waste Extraction Test, indicating that landfill disposal of the leach residues would be acceptable.

Jan 1, 2010

By J. K. Whyatt

Researchers at the U.S. Bureau of Mines have been exploring recent advances in the use of strain-softening constitutive laws that approximate shear fracturing. The purpose of these tests is to investigate shear-fracture-related rock bursts in hard-rock mines. The capabilities and remaining problems in the use of strain-softening laws in finite-element, distinct-element, and finite-difference methods are reviewed. Performance of the finite-difference implementation of strain softening is compared to classic experimental results and observations of rock mass behavior in the Coeur d'Alene Mining District of northern Idaho. The results show promise for developing methods to identify the general location and orientation of shear fractures and their sequence of occurrence, but such methods cannot be relied upon to quantify post-fracture loads or displacements accurately. Uncertainty over the amount of energy consumed by failing rock and the dependency of energy consumption on model mesh definition prevent direct application of the results to analyses of rock bursts.

Jan 1, 2010

By M. Javier

Management is a major part of sustainability research. Many different aspects of sustainability have already received significant research attention, but the management processes in mining from the perspective of their impact on society are less understood and integrated as a holistic frame. It is evident that mining technology has received major blame in past ecological disasters and major mining-induced environmental hazards, but the management-mining process has escaped unscathed. This should not have happened. Instead, the management processes should share equal blame with obsolete technology for the failure to identify and monitor potential environmental hazards before their inception of mining. We will present an emergent style of management for the future of mining. It challenges the actual ?mind-set? of mining management. It describes balance and equilibrium: physical, chemical, and biological in nature as an understanding of nature?s language, which is Geomimic along side ?the bottom line?. The goal is to minimize loss instead of maximize profits (waste design) at the design stage of mining and to develop clean technologies (nature's values) to achieve non-social environmental impacts that provide a prosperous legacy to future generations.

Jan 1, 2010

By R. A. Cortese

The U.S. Bureau of Mines has developed a flame-radiation-powered trigger device to explosively activate suppression barriers to quench gas and coal dust explosions. The major component of the device is a silicon solar panel, which converts radiation from the developing explosion into electrical energy to initiate an electric detonator, which releases an extinguishing agent into the advancing flame front. Solar panels that are rated to produce 20 W of electrical power when exposed to the sunlight are producing about 200 W when exposed to a full-scale dust explosion. The solar panel is electrically isolated from the detonator by a pressure-sensitive switch until the arrival of the precursor pressure pulse, which always precedes a deflagration. This combination of pressure arming and flame-powered photogenerator prevents false barrier activation and requires no external power supply.

Jan 1, 2010

By G. L. Anderson

The U.S. Bureau of Mines (USBM) has conducted research to improve the nondestructive testing (NDT) of wire hoist ropes. Losses in the diameter of a wire hoist rope are used as one criterion for judging when a rope should be replaced. Losses are determined by periodically measuring the rope diameter and comparing this measurement with the original measured diameter; when the diameter reaches a specified minimum at any point along its length, the rope must be retired. Generally, these measurements are made at randomly selected locations along the length of the rope, using a hand caliper. To provide more accurate measurements and to allow measurements to be taken continuously along the length of a hoist rope, an optical diameter-monitoring system was built for the USBM under contract. Continuous measurements are preferable because, when combined with continuous electro-magnetic NDT results, they can indicate whether losses in metallic cross-sectional area originate from external wear or internal wear and corrosion. Tests of the system showed that the instrument met specifications when measuring wire rope at low rope speeds but was inaccurate at speeds over about 30 m/min (100 ft/min). This report describes the prototype system, presents the results of the test program, and describes the capabilities of the system.

Jan 1, 2010

By Paul C. Turner

The U.S. Bureau of Mines, through an Interagency Agreement with the U.S. Army Tank-Automotive Command (TACOM), has successfully developed a steel expendable pattern casting process (EPC) for the manufacture of armorplate. The new armor is lighter and more ballistically effective than conventional rolled homogeneous armor (RHA), and costs less. An applique armor spinoff from the program was field-tested during the Gulf War. The applique armor withstood direct impacts from enemy munitions without failure.

Jan 1, 2010

By R. P. Bush

The U.S. Bureau of Mines performed Cu exchange capacity (CuEe) tests on Ca and Na mont-morillonites and attapulgite clays. Mathematical models were developed from the data that the CuEe's are derived from for each clay as a function of pH, Cu concentration, and the concentrations of metal ions, which compete with Cu for exchange sites. An analysis was made of the impact of competing ions on Cu losses due to ion exchange. The results show that the CuEC's of clays, and hence Cu losses, are decreased by the presence of competing ions, and that AI and Mg have the largest impact of those cat-ions normally present in Cu leaching solutions.

Jan 1, 2010

By John C. Gagliardi

The size and complexity of modern surface haulage trucks has resulted in an increased reliance upon sensors and electronic-based instrumentation for safe and efficient operation. Design engineers need accurate information about the equipment vibration environment to efficiently and effectively build components for installation on mobile mining equipment capable of withstanding the mine environment. Examples of such components include backup alarms, communication equipment, microprocessor-based controllers, and a wide variety of sensors. Unfortunately, this information is not available to the majority of both original equipment and aftermarket equipment manufacturers. To address this problem, the U.S. Bureau of Mines performed field vibration measurements on a variety of surface mining haulage trucks. The vibration measurements were then analyzed and test specifications were developed in the form of envelopes. In conjunction with test specifications, recommendations to aid manufacturers in implementing a vibration environment test program have been included with an illustrative example.

Jan 1, 2010

By L. Rodd, C. Walker, T. Koehler

"The energy content of slag represents approximately 80% of the total energy inputs to a laterite nickel electric smelting furnace. Conventional slag handling methods produce only low grade heat and the entire thermal content of the slag is wasted. A heat recovery system proven on BOF slag in the mid 1980's can be adapted to a laterite nickel rotary kiln electric furnace (RKEF) plant. Slag is granulated using a high velocity air jet inside a waste heat boiler to produce slag granules. Granules are cooled during flight via radiation to water-cooled boiler walls and by convection to the granulation air. This system has the potential to recover 80% of the total slag energy in the form of hot air and steam.Integration of the recovered slag energy into the RKEF smelter can be achieved by a number of methods, including the use of preheated air at the ore dryers, kiln or existing power plant. Energy from the slag boiler may be used to reheat boiler feed water from the power plant or to produce superheated steam and generate electricity. The heat recovery system can provide up to 25 - 30% of the total electrical requirement of each RKEF line and a reduction in CO2 emissions of 234,000 tonnes per year.The total cost of slag heat recovery, including CAPEX and OPEX, is $2.5/GJ, which is competitive with using coal when CO2 credits are $18 per tonne. With Clean Development Mechanism (CDM) carbon credits currently selling at €13 ($20 USD) per tonne CO2, there is considerable opportunity for slag producers in regions including South America, Korea, Indonesia and Africa. Increasing fuel costs and more wide-spread legislation for GHG emissions will likely create conditions in which slag heat recovery could generate a favourable return on investment."

Jan 1, 2010

By J. B. Salsman

As part of the research effort on investigating the effects of microwave energy on the chemical and physical properties of minerals and ores, the U.S. Bureau of Mines (USBM) Tuscaloosa Research Center has conducted research to measure the dielectric properties of these materials. The objective was to establish a reliable database for use in predicting the effects of microwave heating on a wide range of minerals. The dielectric constants and loss factors of minerals, commonly referred to as the dielectric properties, were determined utilizing the theory of microwave propagation through an open-ended, air-filled coaxial line that was terminated at its open end with the particular mineral under investigation. In this phase of microwave research, the USBM measured the dielectric properties of powdered minerals with medium to high electrical conductivities in the frequency range of 300 MHz to 3 GHz and as a function of temperature from 25 to 325 °C. Since the minerals were prepared as powders, techniques were used to relate the measured dielectric properties of the powdered minerals to the dielectric properties of the mineral at its theoretical or natural density.

Jan 1, 2010

By R. J. Sandberg

The Copper Creek area, part of the Bunker Hill District, Pinal County, Arizona, lies within the southwest porphyry copper province of North America at the intersection of a northwest trend and an east-northeast trend of Laramide porphyry copper deposits. The Copper Creek area has been mined and explored for copper and molybdenum since the early 1900?s. The majority of this work focused on the more than 400 surface exposed breccia bodies. In the 1960 to 1970?s deeper drilling discovered a deep porphyry copper-like setting. Redhawk Copper currently has NI 43-101 compliant resources of about 0.652 billion pounds of measured and indicated and 2.745 billion pounds of inferred copper equivalent in breccia hosted and porphyry style deposits. See Figure 1.

Jan 1, 2010