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By D. Tahija

"Carbonic acid prepared on-site from carbon dioxide gas is widely used in water treatment and increasingly in some industrial applications. It has not seen extensive use in mineral processing but is an attractive alternative to sulphuric acid for pH control, with the need to counteract high pH levels caused by cemented backfill of particular interest. The fundamental chemistry of carbonate solutions as applied to flotation and flocculation circuits is described as well as plant-scale application. A project to introduce use of carbon dioxide for pH control at the Hecla Greens Creek lead-zinc-silver-gold operation is planned to begin operation in the first half of 2015. INTRODUCTION Flotation pH Control and Backfill Most sulphide flotation circuits are run at pH values ranging from slightly acid to strongly basic, with slightly basic pH the most common. Lead sulphide circuits are typically run at values from 7.5 to 9, with zinc circuits running at higher values of 9.5 to 10.5. This has been the case with ores that produce a natural pH in the circumneutral range, so that the pH needs to be raised. Although lime [Ca(OH)2] is the cheapest reagent in use to raise pH, soda ash (Na2CO3) or caustic soda (NaOH) are also employed where sodium ions in solution are preferred to dissolved calcium, or, in the case of soda ash, the presence of carbonate is desired. The use of soda ash for pH control in lead circuits has been widely recommended for many decades (1). The situation is necessarily different at operations where cemented backfill is used in underground mines (2). Backfill, whether emplaced as rammed paste or pumped slurry, is composed of mill tailings mixed with around 10% Portland or similar cement. When later mining occurs near or adjacent to previously backfilled areas, a considerable amount of old backfill is inevitably mixed with new ore and shipped to the mill. Depending on orebody geometry, mining methods etc., the amount of backfill in mill feed can easily approach 20%, with periods of higher content not unheard of. The presence of so much backfill, with its high cement content, produces results largely indistinguishable from adding a large amount of lime to run-of-mine feed: mill pH in the grinding circuits can range above 11 and high concentrations of calcium ions are present. The need to raise pH disappears; the problem becomes to lower it."

Jan 1, 2015

By Nathaniel Arbiter, Robert R. Beebe

The U.S. mining industry - once world dominant and largely independent of foreign sources for most major commodities - has today lost this position, with little likelihood of regaining it. But even though Business foretold The Death of Mining four years ago, the current outlook is less pessimistic because of drastic restructuring of the industry; a major reduction in its labor force, with resulting large increases in productivity; and introduction of improved technology. In the face of this clearly changed climate for domestic mining, it is important to examine the role of the development and research establishment in the industry's future, which raises a complex set of questions: 1. Where and to what extent can new technology assist in the continued survival of the industry ? 2. What is the past record of the research establishment in developing new technology; and what is the industry's record in supporting and adopting it ? 3. In the light of these records, and of the drastic cuts in both research staffs and expenditures, what areas should be the most important targets for new technology? New Technology vs. Old A1 though mineral processing's origins can be traced back through five or six millennia, its modern structure is about 200 years old.

Jan 1, 1989

By A. P. Grippo, L. B. Phelps

Many coal mining companies have potential surface mine reserves that either are known or suspected to have had prior drift mining activity on them. In many cases, there is no documentation on these mines or, at best, very fragmented records. These undocumented abandoned underground mines are creating engineering, financial, and environmental difficulties and concerns for both surface coal mine operators and regulatory personnel. This paper examines the use of resistivity techniques in detecting entries of abandoned drift coal mines. The detection of such a drift mine entry would confirm the presence and orientation of an abandoned underground coal mine.

Jan 1, 1987

By John G. Viets, J. Robert Clark

A multielement extraction system is being used successfully to provide essentially interference-free geochemical analyses to aid in gold exploration. The Methyl isobutyl ketone-Amine synerGistic Iodide Complex (MAGIC) extraction system separates Ag, As, Au, Bi, Cd, Cu, Ga, Hg, In, Mo, Pb, Pd, Pt, Sb, Se, Sn, Te, T1, and Zn from interfering geological matrices. Quantitative extraction of these elements is accomplished over a broad range of acid normality, making it possible to economically determine all 19 elements from a single digestion or leach solution. The resulting organic extracts are amenable to analysis by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and flame atomic absorption spectroscopy (FAAS). For many years the principal shortcoming of ICP-AES was the complex spectral and stray-light interferences that were caused by the extreme variability of components such as Fe. Na, and Ca in common geological matrices. The MAGIC extraction allows determination of the extracted elements with enhanced sensitivity, from a virtually uniform matrix, by ICP-AES and FAAS. Because of its simultaneous multichannel capabilities, ICP-AES is the ideal instrumental technique for determining these 19 extracted elements. Ultratrace (sub-part-per-billion) determinations of Au and many of the other extracted elements can be made by graphite furnace atomic absorption spectroscopy (GFAAS), following back stripping of the extracts. The combination of the extraction followed by stripping of the organic phase eliminates 99.999% of potential interferences for Au. Gold determination by GFAAS from these extracts under the specified conditions yields a fourfold improvement in sensitivity over conventional GFAAS methods. This sensitivity enhancement and the interference-free matrix allow highly reliable determinations well into the parts-per-trillion range.

Jan 1, 1990

By D. H. Carlson, J. H. Johnson, C. F. Renders

Research was conducted at a western coal mine on a wide variety of underground mining vehicles to develop testing procedures for portable instrumentation monitoring of tailpipe concentrations of diesel particulate matter (DPM), carbon dioxide (CO2) carbon monoxide (CO) and nitric oxide (NO). DPM was measured using the Emissions Measurement Appa¬ratus (EMA) developed by Michigan Technological University (MTU), and an ECOM-KL five-gas analyzer was used to measure gaseous tailpipe concentrations. Baseline concentrations of the tailpipe pollutants were measured using vehicle systems to load the engine. Concentrations before and after the water scrubber were measured and water scrubber efficiencies were estimated by calculation. Field measurement procedures were established. Heavy-duty vehicles with automatic transmissions were loaded using the torque converter to stall the engine. Consistent engine loading for light-duty vehicles with manual transmissions involved placing the transmission in neutral and adjusting the throttle to maintain a constant engine speed of 2,500 rpm. Tailpipe CO2 concentrations for Caterpillar 3306 and 3304 engines were compared to laboratory CO2 data from Caterpillar and MSHA to help determine if engine settings were correctly adjusted for operation at high altitudes. (Perfect agreement between the mine vehicle tailpipe and laboratory measurements would not be expected because of the differences in the test conditions.) DPM concentrations for light-duty vehicles ranged from about 20 to 160 mg/m3, and one light-duty vehicle averaged near 1,000 mg/m3. DPM concentrations for heavy-duty vehicles ranged from about 55 to 200 mg/m3. Widely ranging DPM concentrations for a particular vehicle type reflect the state of maintenance, fuel rate settings and different engine loading procedures as well as differences between samples collected upstream and downstream of the waterscrubber. The calculated DPM removal efficiencies due to the water scrubber varied considerably between vehicles, ranging from 13% to 51%. Calculations indicate that, under worst-case conditions, very large reductions in DPM may be required to meet the proposed DPM PEL of 0.15 mg/m3, even on vehicles with water scrubbers. In-mine ambient air studies, which are needed to actually measure the impact of the tailpipe concentrations on the work environment and the effect of mine ventilation on the dilution of DPM were not done in this first set of tests.

Jan 1, 2000

By Joseph Peterson, Alexander May

The Bureau of Mines used geochemical modelling computer programs to characterize a site containing lead slag generated by a lead processing facility. Tests for toxic elements by the U. S. Environmental Protection Agency (EPA) extraction procedure showed that all elements except lead were in compliance. Concentrations for lead ranged from 28 to 30 ppm. However, analysis of water samples from monitoring wells resulted in no lead concentrations that exceeded the National Drinking Water Standard. A discussion of a computational program to calculate concentrations of lead species and several other ions is presented.

Jan 1, 1991

By B. Kolonja

A SIMAN and CINEMA PC-based simulation model was developed to simulate and animate the truck-shovel operations of surface mines. The model is capable of simulating one mathematical dispatching strategy using linear and dynamic programming and six heuristic dispatching strategies. Data were collected from an actual operating mine through time studies and analysis of historical records. The statistical analyses were performed and appropriate theoretical distributions were fitted for various time events in the truck-shovel work cycle. The model was then applied to study overall impact of these dispatching strategies on constrained and unconstrained mine productivity. The simulation/animation model developed in this study seems to be an efficient planning tool for choosing optimal fleets and finding an 'optimal" dispatching strategy to produce an equilibrium between "the quality and quantity of production.

Jan 1, 1993

By G. G. Marino, Z. R. Widup

Marino Engineering Associates, Inc. (MEA) was asked to determine the effects of mining beneath a proposed roadway structure. In order to determine the subsidence potential and the magnitude of the mine stabilization costs it is important to know whether underground mining is present, and if so, to what a real extent. The site investigated had the potential to have mining in three different coal seams. To determine where mining was present MEAÕs borehole radar system was used. In summary, the borehole radar subsurface investigation validated that the available mine map in the most shallow coal seam was fairly accurate despite its age (1888), found no mining in the underlying coal seam and detected an area of unknown mining at a depth of about 300 ft in the lowest coal seam which was verified by subsequent drilling.

Jan 1, 2004

By I. Iwasaki

A low-grade copper-nickel deposit, with an estimated size of 4.6 billion tonnes and with average analyses of 0.6% copper, 0.2% nickel, occurs in northeastern Minnesota. In addition to copper, nickel, cobalt, and precious metals, the Duluth gabbro contains magnetite, ilmenite, olivine, plagioclase and biotite. It is estimated that the flotation tailings that would be produced by a concentrator of optimal size to sustain a smelter would amount to 20 million t per year. The flotation tailings, having already been ground, warrant a closer examination for the recovery and utilization of potential by-products. The residual sulfide minerals and fibrous minerals may also be isolated and treated separately for useful purposes or for disposal in an environmentally acceptable manner. Two flowsheets were developed; one involving preconcentration by low- and high-intensity magnetic separation and another involving preconcentration by gravity concentration. The concentration methods for recovering and purifying individual by-product minerals were investigated. From their chemical, physical and mineralogical characteristics, the potential areas of application and marketabilities of each product fraction were surveyed.

Jan 1, 1983

By R. A. Kirkland

The oxygen consumption method utilises an oxygen sensor to monitor the gas-phase oxygen concentrations in sealed chambers filled with reactive waste rock with subsequent confirmation of the oxygen content by gas chromatography. Results of experiments utilising low sulphide (<0.5w1%) waste rock yielded reproducible oxygen consumption rates on the order of 10-10 mol O2.kg-1. s-1. Petrographic analysis of the waste rock material indicated that the dominant sulphide mineral is pyrite (FeS2). Assuming a stoichiometry of 1.75 moles of O2 per mole of SO4 sulphate release rates were inferred to be between 6 and 18 mg SO4 kg-1 wk-1 Typically these results are 2 to 3 times greater than measured sulphate release rates from humidity cells. Our findings suggest that this techniques offers a rapid. cost efficient method for determining sulphate release rates in waste rock piles, even at low sulphide concentrations.

Jan 1, 2000

By A. G. Royle

Although these exhibit similar structures overall, there are more acute valuation problems in alluvials. Most of this description will therefore be about alluvials with comments on bedded vis-a- vis alluvial deposits where necessary. Although geological comments refer mainly to lateritic deposits the method of valuation described applies to all bedded deposits, e. g. coal, limestone, phosphate. In general, the more a deposit suffers alteration during or after its formation and the more the sampling process disturbs its material, the greater the difficulties of valuation. Emphasis is laid on structure, as in any kind of deposit valuation cannot proceed until its structures are understood. Not all the structures found in alluvials will occur in bedded deposits, of course.

Jan 1, 1982

By Ihsan Berk Tulu, Deniz Tuncay, DYKE MARK ALEXANDER VAN, Ted M. Klemetti

Bleeder entries are critically important to longwall mining for the moving of supplies and miners as well as the dilution of mine air contaminants and must stay open for many years. In this study, standing supports in moderate cover bleeder entries were observed, numerically modeled and instrumented by researchers at the U.S. National Institute for Occupational Safety and Health (NIOSH). The measurements of the installed borehole pressure cells (BPCs), standing support load cells and convergence meters, and roof extensometers are presented in addition to the numerical modeling results and visual observations made by the NIOSH researchers in the bleeder entries. The results include the effects of multiple panels being extracted in close proximity to the instrumented site as well as over one and a half years of aging. As expected, standing supports closer to the longwall gob showed the greatest load and convergence. The roof sag appeared generally independent of the proximity to the longwall gob. The BPC readings were driven by both the proximity to the gob and the depth into the pillar. The results of this study demonstrated that the entry roof can respond independently of the pillar and standing support loading. In addition, the rear abutment stress experienced by this bleeder entry design was minimal. The closer the mine development, pillar or supports are to the gob, the greater the applied load due to rear abutment stress.

By Charles C. Y. Chen, Duane R. Skidmore

Batch leaching of Ohio #1, Ohio #4A and Ohio #5 coals was conducted with the thermophilic. sulfur, oxidizing microorganism: Sulfolobus acidocaldarius. Four different size fractions of each coal, with median sizes of 508, 200, 90, and 49 microns, were subjected for 10 days to leaching in a 5% coal-water slurry at 72°C and a pH of 2. Release rates and extent of sulfate and iron I1 and I11 ions from the coals during the leaching process and distribution of sulfur forms (sulfate, pyritic and organic) in the coal samples before and after treatment were determined. Data indicated that Ohio #1 coal, with an initial sulfur content of 0.6%, showed no significant changes with leaching in total sulfur content or forms of sulfur. The Ohio #4A coal, with initial total sulfur content near 5%, yielded product, for sizes below 200 microns with 90% reduction of pyritic sulfur while the extent of organic sulfur removal varied with coal particle size. Results similar to those for Ohio #4A were observed on the Ohio #5 coal, which had an initial total sulfur content of 3% and a final sulfur content near 1%. The findings were interpreted in terms of basic biological, chemical and physical mechanisms.

Jan 1, 1989

By G. Davis

It is well known that the anticipated mineral price at the start of a prospective mineral project can have an overwhelming effect on a property&apos;s ex ante value. However, possible price movements throughout the life of a project can also have an impact on this value. This paper demonstrates how different potential price paths can affect project value. When considering commodity price projections for mine valuations, it is thus necessary to estimate not only the expected commodity price at the start of the project, but also the manner in which that price is likely to fluctuate throughout the project&apos;s life.

Jan 1, 1995

By J. M. King, C. J. Boggs

Acquisitions of mineral properties and companies can saddle the acquirer with unexpected and substantial liabilities and obligations incurred by the acquired or selling company that are not readily apparent from review of the company&apos;s books or files. This paper will address selected areas of concern, such as environmental and reclamation liabilities, problems of foreign ownership by the buyer or seller, pension obligations, plant closing laws, effective title review, land use and zoning.

Jan 1, 1992

By Thomas J. Ferree

A Reichert cone concentrator was installed in an aggregate plant circuit to recover the extremely fine "flour gold" known to exist in the deposit. The gold content of the bank-run gravels averages about 0.1 grams per ton (about $1.45 per ton), based upon $14.47/g (345O/ounce) gold. Tine Reichert cone, in conjunction with a conventional shaking table, re- covers in excess of 85% of the gold. A screen analysis of the gold particles shows 44.1% is -i4 microns (-200 mesh) in size. The plant operates with a two-man crew.

Jan 1, 1981

By M. J. Meulendyke

Within the mineral processing Industry. a range of grinding conditions exists which include semi-autogenous grinding (SAG), rod milling. and conventional ball milling. Each of these mill environments presents a unique environment for grinding media, requiring the application of specific physical and chemical properties for optimum grinding media performance. The environments are characterized by varying degrees and combinations of abrasive, corrosive, and impact wear. An extensive test program has been conducted to determine the extent wear rates vary between these different applications. Test results are related to production results, ball size, and mill operating conditions.

Jan 1, 1989

By Richard C. Corson

Modern microprocessor systems make it possible to use several variables to anticipate changes in the process and to react with responses before upsets can be magnified by the process or by control action. Through tighter control, "insurance" can be eliminated from process set points without affecting product quality. In actual operation with a traveling grate furnace this control philosophy has produced savings of up to 20% in fuel consumption and 8% in fan power usage while producing a more consistent quality product.

Jan 1, 1982

Table A. Conversion of English to SI Units Table B. Strength Properties of Rocks Table C. Engineering Properties of Rock Table D. Properties of Common Minerals Table E. Material Properties and Characteristics Table F. Heat Value of Various Fuels Table G. Geometrical Relationships and Mensuration Formulas Table H. Standard Sizing and Meshes Table I. Ship Measures Table J. International Atomic Weights Table K. Time Value of Money Factorsfor Discrete Compounding

Jan 1, 2008

By H. Sevim

The utilization of high sulfur Illinois coal by utility plants has been decreasing since the enactment of 1990 Clean Coal Air Act Amendment. Illinois coal producers can make their coal saleable by offering the choice of taking the combustion by-products from the utility plants and placing them in the abandoned sections of their mines. To be competitive, however, coal producers need to select an environmentally acceptable transportation-handling-placement system through which the cost-per-ton of by-product disposed can be minimized. In this paper, a few such systems are presented. The favorable operating range of each system is determined in terms of distance and tonnage. A case study is given whereby cost analysis is conducted for an underground coal mine receiving by-products from two Illinois utility plants.

Jan 1, 1997