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By W. E. Brigham, P. W. Reed, J. N. Dew

By W. P. Blacutt

A financial-economic model incorporating physical, market, and policy variables is developed for mining investment in Bolivia. Additional risk criteria emanating from political instability. new mining legislation, recent environmental regulations, and a new minerals taxation system are accounted for and are integrated into the investment decision model. Results of the model indicate that geologic and market variables have the dominant effect on the investment-worth function. Among policy variables, exchange rate and taxation policies have the most significant influence. Depreciation allowance for infrastructure development has negligible weight in the investment-worth function. The business structure of the firm considering investing in the Bolivian Polymetallic Project is found to be an instrumental factor in the investment-worth outcome. Specifically, undiversified mining companies whose operations exclude zinc production as the primary source of revenue would benefit most from adoption of this project.

Jan 1, 1993

By R. J. Matetic, J. Noll, C. Zhou, J. DuCarme, M. Reyes, J. Srednicki

"In April 2016, the U.S. Mine Safety and Health Administration (MSHA) began requiring the use of continuous personal dust monitors to monitor and measure respirable mine dust exposures to underground coal miners. Mines are currently using the PDM3700 personal dust monitor to comply with this regulation. After the PDM3700’s implementation, mine operators discovered that it interfered with proximity detection systems, thus exposing miners to potential striking and pinning hazards from continuous mining machines. Besides the PDM3700, other electronic devices were also previously reported to interfere with proximity detection systems. MSHA sought the aid of the U.S. National Institute for Occupational Safety and Health (NIOSH) and mining industry stakeholders to determine how the PDM3700 and some other electronic devices and proximity detection systems interact with each other. Accordingly, NIOSH investigated existing standards, developed test protocols, designed experiments and conducted laboratory evaluations. Some interferences were observed to be caused by electromagnetic interference from some electronic devices, including the PDM3700. Results showed that there was no significant interference when the PDM3700, as well as other electronic devices, and the miner-wearable component of the proximity detection system were separated by distances of 15 cm (6 in.) or greater. In the present study, it was found that the PDM3700 and the personal alarm device needed to be at least 15 cm (6 in.) apart in order for them to be used simultaneously and reduce potential interference. IntroductionUnderground coal miners are exposed on a daily basis to a variety of hazards, such as coal dust exposures, high noise levels, roof and rib falls, potential for fires and explosions, and operating and working with heavy machinery. One of the hazardous jobs is that of operating or working near a continuous mining machine. According to U.S. Mine Safety and Health Administration (MSHA) statistics, 44 miners had been fatally struck or pinned by a continuous mining machine since 1984. In an effort to prevent future striking and pinning fatalities from occurring, proximity detection systems have been developed and are required on all operating continuous mining machines in underground coal mines, with the exception of full-face continuous mining machines, by 2018 (MSHA, 2015a)."

Jan 5, 2018

By VIVEK KASHYAP, Evody Tshijik Karumb, PATRICK TAYLOR

The partial reduction of zinc ferrite to zinc oxide and iron (II, III) oxide can enhance the leaching rate of zinc. Zinc ferrite has often been found as a major component of zinc residues and electric arc furnace dust. The Waelz process is an existing process for zinc ferrite processing, which requires a temperature of more than about 1200 °C to produce Waelz oxide containing ZnO. Since zinc residues have been deemed as a potential way for the extraction of zinc and other critical metals, it is important to analyze the reaction kinetics in the temperature range of interest. This manuscript discusses the chemical kinetics of zinc ferrite reduction by hydrogen gas. Several researchers studied the reduction of zinc ferrite with CO; however, unlike CO, the use of H2 gas as a reductant allows partial reduction of zinc ferrite even at low-temperature range (400–600 °C). Thermogravimetric analyses (TGA) experiments were performed in the temperature range of 300–700 °C with 10% and 30% H2, and the data obtained was analyzed using the isoconversional method of kinetic analyses. The standard models used for isoconversional kinetic analysis were chosen from literature and experimental data were fitted to determine the controlling mechanism and calculation of kinetic parameters of reduction of zinc ferrite. The rate of reaction was found to be increasing with an increase in temperature and partial pressure of H2 gas. The reaction could be divided into three stages, where reaction interface contraction was found to be the controlling mechanism at the initial stage of reaction. As the reaction proceeds, product layer thickness increases, and thus, diffusion was found to be the controlling mechanism. Roasting products obtained from TGA experiments were also characterized using a scanning electron microscope (SEM) to verify critical morphological details.

Jul 26, 2022

By W. C. Taylor

The present fuel situation indicates that, at least for the next 20 to 30 years, the burning of coal will be a main source of energy. All coal contains sulfur, which is converted to sulfur dioxide during combustion. The concentration of sulfur dioxide (SO2) in the resulting flue gas, for most coals, would exceed the limits established by the Environmental Protection Agency (EPA). Therefore, the sulfur must either be removed from the coal prior to its burning, or be collected from the stack gas before it reaches the atmosphere. There is currently a large amount of research devoted to methods of removing the sulfur from the coal before burning, or during combustion in fluidized beds with materials which trap the sulfur in the solid residue. The commercialization of these processes, however, is not expected in the near future. Flue gas desulfurization appears to be the best near term prospect of fulfilling current air quality control regulations. The lime/limestone wet-scrubbing methods are the most advanced flue gas desulfurization processes and will account for the majority of sulfur removal systems in electric power generation. There are currently at least 23 full-scale systems existing or under construction and 17 of these will use the lime or limestone wet-scrubbing process. (1)

Jan 1, 1974

This Bureau of Mines report reviews the development of the world potash industry. The trends leading to the present market situation of oversupply arid low prices, which threaten; the domestic potash industry, are presented and analyzed. Because the major threat to the domestic industry comes from Canadian imports, the report focuses on the comparative economics of United States and Canadian production. The study resulted in these major conclusions: 1. Balance of world supply and demand is foreseeable in 1975, but it could be delayed by planned expansion. 2. Balance of U.S. supply and demand could occur as early as 1974-75 or as late as 1981. 3. Nearly all U. S. production capacity vis-a-vis Canadian competition is now uneconomic. Prices cover out-of -pocket costs for only 30 percent of U.S. production. 4. U.S. producers will be undersold by Canadians in 60 to 90 percent of the U.S. market. Canadians also will have the edge over United States and European producers in export markets. 5. U.S. firms have invested in 60 percent of the planned 1971 Canadian production, and they have large holdings in Saskatchewan. 6. The decline in the U.S. potash industry probably reduced personal income in Carlsbad, Eddy County, N. Mex, the chief potash-producing area in the United States, about $21.5 million between 1966 and 1969.

Jan 1, 1970

By Terry W. Engelhart

"A computer-based approach to online supervisory control and operations management of bulk materials handling terminals". This paper describes an integrated computer facility supporting the functions and responsibilities of shift operations, scheduling, maintenance and management using real-time interactive techniques. The functions and responsibilities as related to coal export terminals are specifically addressed, although these functions would be equally applicable to other terminal configurations and other commodities. A discussion of the resulting benefits are presented: - throughput efficiency - long-term planning and scheduling, using simulation - operations monitoring and protection - demurrage/despatch optimization - preventative maintenance - operational productivity

Jan 1, 1982

By R. W. Borio, T. S. Spicer

Inflammability and crossing point apparatus were used to study the influence of increasing amounts oi such inerts as ash, fly-ash, pyrite, limestone and Portland cement with several pulverized bituminous coals. The results indicate that it requires large proportions of inerts to substantially suppress the ease of ignition. The ignition phase of the combustion of solid fuels has been under study periodically since 1900. With the advent of pulverized coal firing some 60 years ago, a technique now dominating the coal utilization field, the ignitibility characteristics have become increasingly important. Much of the early work was directed toward the prevention of coal dust explosions and improved mine safety rather than combustion. Many factors affecting ignitibility have been studied and numerous methods devised in an effort to measure the ignition temperature and these have been reviewed by other authors. A recent survey was made by Finney and Spicerl in 1959, so a discussion of previous work will be omitted. Despite these efforts, the initial stage of combustion, termed ignitibility, is still a little understood phenomenon. In fact, no ASTM method has been adopted for the calibration of this illusive property. However, a D-5 Subcommittee XVI on Ignitibility of Coal and Coke of ASTM (now inactive) defined ignitibility:' "The ignitibility of a fuel is that char-

Jan 1, 1963

By Thomas S. Falk, Nils G. Lindberg

The first industrial COBO (Cold Bound) pelletizing plant began operation in May 1975 at Trollhiittan, Swede n. A technical description of the process, together with operational experience with the plant, forms the basis of this paper.

Jan 1, 1976

By Arthur Taggart

THIS paper describes the result of a series of experiments run in the laboratory of the School of Mines, Columbia University, during the winter of 1927-28. It shows that the several operating adjustments of a pneumatic table produce effects in the action of a, given coal that may be grouped into two classes, viz.: stroke length, speed and rocker-arm angle, which affect longitudinal travel; air supply and table slope (transverse and longitudinal), which determine transverse travel. The magnitude of the effect of the different adjustments varies. Some of the adjustments affect stratification of the bed, both as respects size and specific gravity of the bed components, as well as direction of travel. Operation of a pneumatic table is fundamentally different from that of a wet table in that the former exerts, through the air supplied, a force on the particles upward away from the deck which is lacking on the wet table while, on the other hand, it lacks the positive control over cross travel that is supplied by the wash and feed water.

Jan 1, 1929

By C. E. Augustine, P. Nicholls

"INTRODUCTION A layer of soot on the heating surface of a boiler decreases efficiency because it increases resistance to the flow of heat, with the result that the heat transfer to the water is lower and the temperature of the flue higher than they would be if the surface remained clean. The percentage of reduction in heat transfer depends on the position and area of the sooted. The percentage of reduction in heat transfer depends on the position and area of the sooted surfaces, the thickness of the most, until the percentage of the total heat absorbed by those surfaces when clean; thus it will vary with the type of boiler and in particular with the ratio of the area of the convection heating surface to the total area. Medium-size and large boilers usually are equipped with soot blowers, and tests have been published giving the increase in efficiency resulting from removal of the soot. Fuel savings up to,8 percent have been reported, but 4 to 5 percent is probably more conservatives. However, these savings may not be due wholly to a reduction the thermal resistance of the surfaces but may be due partly to improvement in the combustion because of better draft or more uniform flow of the gases. In addition, the deposits on the surface of boilers include as a clinker, and as the size of the boiler and the rate of burning increase very little or none will be soot.There are no corresponding test data on small boilers operated at low rates of burning. In stall boilers, deposits are much thicker, and it might be expected that the reduction in efficiency would be greater; in fact, statements have appeared suggesting that the decrease may be as high as 50 percent. This investigation was undertaken because the Bureau frequently receives requests for authoritative information on the effect of soot in small and other heating boilers."

Feb 1, 1935

Agenda ? Where?s Victor ? What work was done to get approval to spend $982m ? a brief history ? Some project facts ? The triple bottom-line accomplishments to date ? Construction A Brief History of Victor ? 1960?s ? first sampling in area ? 1980?s ? stream samples and Victor kimberlite discovered ? 1990?s ? test / bulk samples ? 1999 / 2000 ? large bulk samples ? 2000 / 2003 ? technical evaluation through to Feasibility Study, permitting process

May 1, 2006

By Henry Ferguson

THIS paper is a preliminary statement, intended to present the more important results of the recent studies of the ore deposits of the Alleghany district in advance of the publication of the complete report, now in preparation. The Alleghany district (Fig. 1) has been a producer of gold since the early days of California gold mining. As in other California gold camps, placers yielded the bulk of the earlier production, but during the last 30 years lode deposits have been the only important source of output. The district differs from other California gold-quartz districts in that nearly all the production is from small shoots of high-grade ore. The mining camps of Alleghany and Forest are on the western flank of the Sierra Nevada range about 20 miles west of the crest. The gently sloping lava-covered plateau which controls the upland topography has been trenched by deep canyons of the westward flowing streams, which are cut to depths of as much as 2000 ft. below the crests of the ridges. The district is about 18 miles from Nevada City but the automobile road which connects the two places is 31 miles long. The senior writer first visited the district in 1913 and published a short description of the lode deposits.1 The increasing importance of the district made further study desirable. A detailed topographic map was therefore made by W. B. Upton, Jr., of the U. S. Geological Survey, in the spring of 1924, and the senior writer spent parts of the field seasons of 1924 and 1925 in the district. For the second field season the Geological Survey was fortunate in securing the services of R. W. Gannett, who had already done geologic work in the district for several of the mining companies. Owing to the death of Mr. Gannett in October, 1925, just before the close of his field work, the work of preparation of the entire report fell to Mr. Ferguson. He takes this opportunity of acknowledging how deeply he is indebted to Mr. Gannett for his excellent work in the field, and his realization of how greatly the completion of the report on the district has suffered from lack of Mr. Gannett's assistance in the office. In October, 1.928, after the completion of the first draft of the manuscript, Mr. Ferguson made a short visit to the district.

Jan 1, 1929

By H. E. Elliott, R. S. Busk, A. T. Peters

ONE of the problems of the fabricator of metals and alloys is the propensity of some composition ranges toward abnormal grain growth during certain stages of fabrication. In this respect magnesium alloys are no exception among alloys. Fortunately, convenient foundry control methods have been developed by which the abnormal grain growth possible in certain magnesium-alloy castings can be suppressed. An unusual characteristic of magnesium alloys, however, is that castings of some composition ranges are subject to local grain growth during heat-treatment without the necessity of intentional mechanical stressing of the part prior to heat-treatment. This effect occurs only under certain critical casting conditions, and only in certain alloys of greater than about 8.5 per cent aluminum content, such as C alloy (Mg, o per cent Al, 2 per cent Zn, 0.2 per cent Mn) and G alloy (Mg, i0 per cent Al, 0.2 per cent Mn). The first observation of this phenomenon in cast magnesium alloys occasioned much surprise, since it is not observed in other metals. Jeffries and Archer' have stated that "the grain size of cast metals, provided they have not been plastically deformed, cannot be changed by heating below the melting point." The study of the conditions leading to abnormal grain growth in cast magnesium alloys, and of the mechanism of this phenomenon, has led to some very interesting observations. Perhaps the most significant of these was the observation that stresses originating from cooling contraction in magnesium-alloy castings are the only stresses necessary, under certain conditions, to cause local recrystallization and subsequent grain growth in the casting during heat-treatment. of abnormal local grain growth was a definite problem in the production foundry on C alloy sand castings. Illustrated (Fig. r) is a picture of a casting scrapped because of this defect. A mottled effect is produced in coarse-grained areas by suitable etching solutions. The properties of metal in the affected area are much impaired by such grain coarsening. Ultimate tensile strengths of half the normal value have been measured in metal of this nature. In this paper are described the techniques that have been developed by The Dow Chemical Co. for studying, and in large measure solving, this production problem. Also discussed are studies of the mechanism by which excessive grain coarsening occurs, and the fundamental conditions that produce this effect. The abnormal grain growth discussed in this paper will be referred to as "germination," since this term has been defined' as any process leading to an abnormally coarse grain size. This paper deals only with abnormal local grain growth that may occur during the solution heat-treatment of certain magnesium-alloy castings, as dis-

Jan 1, 1945

By J. D. Patsey

A computer program has been developed for use by the mining engineer for analyzing drum-type hoists prior to the modification of an existing system or the designing of a new one. Its use permits the preliminary evaluation of a system before seeking the technical assistance of mine hoist designers and manufacturers. Compatible with an IBM-PC, the user-friendly program accepts a variety of data and can analyze hoisting systems for any balance state. The extensive program can be used to: (1) calculate skip capacity to yield a desired production rate; (2) solve for required drum face width; (3) select a permissible wire rope from a menu of 50 available rope types: (4) estimate total horsepower of the hoist plant; and (5) estimate power cost. An example of the model's use in evaluating a hoisting system will conclude the paper.

Jan 1, 1986

By John J. Dran

[This paper summarizes the more popular mineral valuation techniques being used by the dining industry, and attempts to demonstrate how they are Interrelated and where some are in error when compared to modern methods of financial analysis. The academic community and the larger and more sophisticated raining companies, have largely rejected the older valuation methods such as the, Hoskold and Morkill concepts and replaced them with "discounted cash flow" (DCF) techniques. The relevancy and usefulness of the older methods have been questioned primarily on the basis of their underlying assumptions that mining companies do not have numerous alternative investments and must use sinking funds deposited at market or ?safe" rates of return to recover the purchase price of mineral reserves. The ability to reinvest In numerous (often non-mining} alternative business ventures, the changing purchasing power of the dollar, corporate income and other taxes, depreciation and depletion allowances, and modern financial management practice, all mitigate against the continued use of the older valuation methods, especially for the larger mining companies. Snail mining companies and Individuals still use these methods largely out of habit and familiarity. This paper attempts to point out the weaknesses and strengths of the valuation methods In current use in the hope that these techniques may be better understood and [rcrn] appropriately applied.]

Jan 1, 1973

By Kenneth L. Cashdollar

This report describes three types of optical dust probes that have been designed, built, and tested by the Bureau of Mines. Each of the probes measures dust cloud concentrations by the attentuation of light. The first is a single-path-length probe, the second is a double-path-length probe, and the third is a single-path-length probe that employs jets of air to keep the windows of the light source and detector free from dust coating. The theory of operation and the calibration procedures for each of the probes are described. The results of the Bureaus laboratory, mine, and field tests of the probes are also reported.

Jan 1, 1981

By J. L. Kearns

The importance of optimizing equipment replacement decisions becomes more critical each year due to the rising costs of buying new equipment versus maintaining old equipment. Replacing equipment when it is physically worn out, or replacing it too soon or too late relative to its Economic Life (when it is economically worn out), is very costly. After extensive literature review and research, Kennecott has developed its Equipment Replacement Guide (ERG) system which identifies, evaluates, and justifies the replacement of uneconomical equipment. The system considers such critical factors as inflation, decreasing work capability, increasing maintenance/repair and operating costs, taxes, time value of money, return on investment, salvage value, and investment tax credit. These factors are used in a system of equations which balance the costs of new equipment against the total operating costs of old equipment. The solution of the equations determines the Economic Life of equipment. Replacement of equipment at the determined Economic Life will earn the specified, required return on investment that is used in the calculation of the Economic Life.

Jan 1, 1979

By David M. Parkes

The hydraulic movement of coal is here defined as the movement of all sizes of coal in pipes and open flumes, by gravity and against gravity. It is not restricted to coal which is in slurry form. In other words, it is not crushed to a size in the 8 to 20 mesh size range. The top size could be as high as 12 inches. The dewatering of coal which is transported hydraulically is carried out to restore the coal to a suitable form for further cleaning, or for transportation by other methods. The process involves complete separation of all the coal, wood and rock from the water so that the water can be recycled without undue damage to pumps, pipes and monitors.

Jan 1, 1976

By S. S. Peng

This paper presents a computer program package for predicting surface movement and deformation caused by under-ground coal extractions. It is capable of: predicting final surface movement and deformation over underground openings; predicting dynamic surface movement and deformation process associated with underground lingual mining operations; processing and bookkeeping subsidence survey data; recommending subsidence parameters for those new coal mines where no subsidence data are available; and deducting subsidence parameters from collected subsidence data.

Jan 1, 1986