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[ACZ, Inc. BHP-Utah International, Inc. CINCO (Coal Industry Consultants, Inc.) Coal Colowyo Coal Company Crane & Hoist Sales, Inc. Cummins Southwest, Inc. Cyprus Coal Company Energy Fuels Corporation Ford, Bacon & Davis Utah, Inc. T.J. Gundlach Machine Company Harnischfeger Corporation Hemscheidt Corporation GH Henley Industries Jennmar Corporation Joy Technologies, Inc. K&P Sales Engineers, Inc. Kennametal, Inc. Kerr McGee Coal Corporation Keystone Resort Neil F. Lampson, Inc. McLanahan Corporation National Mine Service Company NERCO Coal Corporation North American Coal Corporation Peabody Coal Company Pittsburg & Midway Coal Mining Co. Ramsey Technology, Inc. Roberts & Schaefer Company Rocky Mountain Machinery Company Santa Fe Pacific Coal Corporation Scandura, Inc. Southern Pacific Lines Utah Power & Light Company Western Energy Company]

Jan 1, 1990

By R. Canello, J. Jenkins

El Abra has the world's largest leach, solvent extraction and electrowinning facility, The crushing plant capacity is 120,000 metric tonnes per day and the cathode production capacity is 225,000 metric tonnes per year. The El Abra mine and plant are located in the Province of El Loa, in Region I1 of Chile, 55 km. north of the city of Calama. The ore deposit outcrops on the southern slope of Cerro Pajonal at an altitude of 3,900 to 4,100 meters above sea level. The processing plant and camp facilities are located at a lower 3,300 meter elevation on an alluvial slope, 15 km southeast of the deposit. The operating company, Sociedad Contractual Minera El Abra, is 51% owned by Cyprus Arnax Minerals Company through the Cyprus Climax Metals Company subsidiary and 49% owned by Corporaci6n Nacional del Cobre de Chile (Codelco). The present paper describes the ore reserves, mine operations, crushing, leaching, solvent extraction, electrowinning and infrastructure facilities.

Jan 1, 1998

By Stéphane Servant, Jacques Ouellet, Ferri Hassani

This paper presents essentially the logistic and practical aspects involved for in situ testing of mine paste backfill with a self-boring pressuremeter. The investigation discussed in this paper is part of an extensive and ongoing research project to identify and validate an in situ testing technique for cemented mine backfill such as hydraulic or paste backfill as well as Insitu behavior of backfilled stopes. After a literature review on field testing of soils and past experiments on mine backfill in situ testing, the self-boring pressuremeter was selected as the most appropriate instrument for this task. The authors presents in this paper the technical aspect involved in a field trials that was conducted in a Canadian underground mine using paste backfill. The results of this first successful trials show that self-boring pressuremeter test can provide high quality and reliable backfill characteristics results, using analytical techniques developed for soils (Ouellet et al., 1998). The parameters obtained were: estimation of the lateral stress in the ground, the soil stress-strain response and the soil strength. The logistic and equipment required to conduct such testing underground is fully described. Performance achieved in the field and technical difficulties encountered are highlighted. Recommendations for future experiments with such instruments are given. Some potential technical improvements to better adapt this in situ testing technique to mine backfill are proposed.

Jan 1, 2001

By L. C. IlsLey, J. W. Paul, E. J. Gleim

Flame safety lamps have been used in gaseous mines since the Davy lamp was introduced, more than 100 years ago. During the last decade the flame safety lamp has been rapidly replaced by the electric lamp as a device for illuminating the miner's working place; in the United States the electric cap lamp has been widely adopted. For example, in 1911 approximately 45,000 flame lamps and no electric lamps were being used in the Pennsylvania bituminous mines, which were then producing 35 per cent of all the soft coal mined in this country; by 1918 the flame lamps had decreased to 17,000, whereas electric lamps-mostly of one maketotaled nearly 48,000. In Great Britain during the same years the total of 723,934 flame lamps decreased to 590,185 and the electric lamps gained rapidly from 4,298 to 156,521. No later reliable figures are at hand. However, before the flame lamp becomes obsolete, it is fitting that the Bureau of Mines compile a permanent record of a device which has served the mining industry for more than three generations, and not only made possible the development of entire districts that otherwise could not have been worked but undoubtedly saved the lives of thousands of underground workers. Flame safety lamps are capable of doing more than the name indicates. First, under normal conditions, they can be used in a mine atmosphere that contains an explosive mixture of gas and air without great danger of exploding such a mixture, though such use of a flame lamp should not be permitted. Second, to an experienced man they indicate percentages of gas much lower than the explosive limit, and thus can be used to indicate to workers the approach of an unsafe condition in the mine atmosphere. Third, flame lamps will not burn in an atmosphere greatly deficient in oxygen, and they therefore warn the users of such deficiency in time to withdraw to a place of safety. Flame safety lamps are still used rather widely in the United States for general illumination and to a still greater extent for detecting gas. Many coal-producing States require fire bosses to use these lamps in gaseous mines, and the regulations of several States specify that a gIven number of such lamps be kept available for emergency service.

Jan 1, 1924

By Donald W. Gentry

Many firms in the minerals industry are facing enormous capital-equipment requirements for existing operations, planned expansion programs, pollution control systems, etc. Yet, because of existing economic conditions, mining companies find it increasingly difficult to obtain reasonable financing for the acquisition of large, high-cost capital equipment. One way of obtaining the use of mining and other major pieces of high-cost capital equipment is through leasing. The popularity of this approach is evidenced by the growing number of leasing companies, equipment manufacturers, and financial institutions now offering this service to their customers. Indeed, leasing has become a billion-dollar industry, and many commercial banks have developed sizeable portfolios in this area. "Should we buy or lease?" This question eventually comes up whenever a mining company needs additional major capital assets. Unfortunately, many buy-or-lease decisions are made on an emotional basis-rather than on a proper financial evaluation that would yield the…

Jan 9, 1975

By A. W. Fahrenwald

"Cooperation was arranged between the mine operators, the Michigan College of Mines and Technology, and the Bureau of Mines for a study of present milling practice in the copper district of Michigan. Work was actively commenced in January, 1928.In Michigan copper occurs almost wholly as native copper. An insignificant amount of copper sulphide is present. The native copper occurs in two general classes of formations--namely, amygdalaid and conglomerate.In respect to ore dressing, the outstanding peculiarities of the two types of copper are: (1) In the amygdaloid, the relative coarseness of the metallic copper, which is almost completely liberated at approximately 48-mesh comminution; (2) the sprangly and flakey physical character of much of the liberated copper after crushing; (3) in the conglomerate, the extremely fine dissemination of the metallic copper, which is not completely liberated by crushing to -200 mesh.Because the study to date has been confined almost wholly to amygdaloid ores, the conglomerate class is not considered herein. The conglomerate ore is being efficiently treated, and the loss of copper is small.The amygdaloid ore contains a silicious gangue of which 80 per cent has a specific gravity of less than 2.84, 92 per cent of less than 2.94, and 98 per cent of less than 3.17. Epidote of 3.25 specific gravity is noticeably present, and accumulates on the table concentrators, from which it is hard to make clean con¬centrate and middling recovery.The general nature of the amygdaloid ores varies a little from mine to mine, but the general characteristics are the same, as is shown later by flotation tests."

Jun 1, 1928

By E. D. Hummer, J. A. Younkins. J. P. Proctor

Comparatively little has been published relating practical experience with the control of the solid content of washery water systems that must be "closed." A "closed" system is one that for some reason may not be cleaned by the emission Of any effluent Of high ''lid 'content to be rep1aced by 'lean water in Order to hold the solid content of the waste water within reasonable bounds for efficient washing. It is the Purpose of this Paper to describe practical experience with such a water system and to present data that it is hoped may be of some use to those who are faced with a similar problem. The washery clarification system described comprises three thickeners and three filters, and although it is admitted that each of the fields of water settling and thickening and filtration offers a wide scope for investigation, the authors are not attempting to present the answers to these problems but to set down the results of some experience along these lines, making no claims as to the ultimate solution of the problems in hand. The subject of water clarification has vast ramifications; for example, the science of flocculation as applied to water settlillg and filtering opens up fields of wide possibilities of which as yet little is known. A comparatively recent entry into the field of water treatment, which may offer possibilities of practical application, is the use of "wetting" agents such as "Aerosol." General Arrangement of Water System So that the reader may obtain a comprehensive picture of the factors concerned in the control of a closed water system, it is necessary to give a brief description of the washing plant that is serviced by the water system to be described in the following pages. As we are not primarily concerned with the washing plant in detail, only a brief description of the flow of coal as it relates to the water system will be given here. For a more detailed account of this type of washer, the reader is referred to earlier papers,1,2 The washer, which handles o to 4-in, raw coal (750 tons per hour) is an American Rheolaveur plant of two complements; the coarse coal or sealed discharge plant and the fine coal or free discharge plant. The sealed discharge plant (Fig. I) consists of twin 48.in. primary launders, each having two washing boxes, supplemented by one 32-in. rewash launder, which also has two washing boxes. "Push" water for washing and conveying coal in these launders is supplied from a constant-head tank under pressure head of 10½ ft. at the point of introduction at the feed end of the launder. This tank also supplies water for upward or vertical currents used in the Rheolaveur or washing boxes. Each box discharges into a sealed boot elevator (Fig. I).

Jan 1, 1942

By J. A. Younkins. J. P. Proctor, E. D. Hummer

Comparatively little has been published relating practical experience with the control of the solid content of washery water systems that must be "closed." A "closed" system is one that for some reason may not be cleaned by the emission Of any effluent Of high ''lid 'content to be rep1aced by 'lean water in Order to hold the solid content of the waste water within reasonable bounds for efficient washing. It is the Purpose of this Paper to describe practical experience with such a water system and to present data that it is hoped may be of some use to those who are faced with a similar problem. The washery clarification system described comprises three thickeners and three filters, and although it is admitted that each of the fields of water settling and thickening and filtration offers a wide scope for investigation, the authors are not attempting to present the answers to these problems but to set down the results of some experience along these lines, making no claims as to the ultimate solution of the problems in hand. The subject of water clarification has vast ramifications; for example, the science of flocculation as applied to water settlillg and filtering opens up fields of wide possibilities of which as yet little is known. A comparatively recent entry into the field of water treatment, which may offer possibilities of practical application, is the use of "wetting" agents such as "Aerosol." General Arrangement of Water System So that the reader may obtain a comprehensive picture of the factors concerned in the control of a closed water system, it is necessary to give a brief description of the washing plant that is serviced by the water system to be described in the following pages. As we are not primarily concerned with the washing plant in detail, only a brief description of the flow of coal as it relates to the water system will be given here. For a more detailed account of this type of washer, the reader is referred to earlier papers,1,2 The washer, which handles o to 4-in, raw coal (750 tons per hour) is an American Rheolaveur plant of two complements; the coarse coal or sealed discharge plant and the fine coal or free discharge plant. The sealed discharge plant (Fig. I) consists of twin 48.in. primary launders, each having two washing boxes, supplemented by one 32-in. rewash launder, which also has two washing boxes. "Push" water for washing and conveying coal in these launders is supplied from a constant-head tank under pressure head of 10½ ft. at the point of introduction at the feed end of the launder. This tank also supplies water for upward or vertical currents used in the Rheolaveur or washing boxes. Each box discharges into a sealed boot elevator (Fig. I).

Jan 1, 1942

By Reed W. Hyde

SOME information has been published on the sulphur dioxide concentration of gases from Dwight-Lloyd machines sintering lead ores but most of this relates to the customary practice in which the charge is relatively high in lead and is sintered in two passes over the machine. It is thought, therefore, that the following observations on sintering in one pass a low-lead, low-sulphur charge may be of interest. The data were obtained in sintering lead sulphide flotation concentrates mixed with minus 20-mesh oxide ore, the mixture carrying 16.8 per cent Pb and 5.3 per cent S. No returns were used because of the limited amount of sulphur available as fuel, but the mixture pelletized readily to make a satisfactorily permeable bed on the sintering machine. As there was a possibility that the SO2 might be utilized, a series of runs was made to determine the concentration of S02 in the gases at different points along the wind box, and the effect on this concentration of changes in the wind-box vacuum. Several runs each were made with vacuums (as measured in inches of water at the wind box) of (1) 2 to 1 1/3 in., (2) 4 to 3 1/2 in. and (3) 6 to 5 1/8 in. The averages of the determinations from each series are platted on the graph (Fig. I). The vertical scale shows the percentage by volume of SO2 (as determined by the Reich method), and the horizontal scale shows the time expressed as percentage of the total sintering time. Sintering was considered to be complete when no S02 could be detected in the gases. In all cases the depth of bed was 4 ½ in. and the weight of dry charge per square foot of hearth area was 45.2 lb. Other data are given in the table. The volume of gases corresponding to the several points along the wind box at which S02 determinations were made could not be measured, but has been calculated from the S02 content and sulphur elimination on the assumption that the volume is uniform throughout the sintering period. This is not strictly true, as with a given vacuum the volume will usually drop slightly toward the middle of the period and increase toward the end. However, this assumption is a reasonable approximation. Several interesting features are brought out by these data. In general, the published data on S02 concentration in sintering under ordinary conditions show a high S02 concentration in the early stages followed by a rapid decrease in concentration and with relatively little SO2 in the gases from the last half or third of the operation. In other words, the greater part of the sulphur elimination is obtained in the first third or half of the period. In these runs, the 6-in. vacuum, which approximates the usual operating condition, gives a curve that follows this customary pattern. Maximum S02 concentration is obtained 2 ½ min. after

Jan 1, 1942

By Brent A. Slaker, Khaled M. Mohamed

"Understanding coal mine rib behavior is important for inferring pillar loading conditions as well as ensuring the safety of miners who are regularly exposed to ribs. Due to the variability in the geometry of underground openings and ground behavior, point measurements often fail to capture the true movement of mine workings. Photogrammetry is a potentially fast, cheap, and precise supplemental measurement tool in comparison to extensometers, tape measures, or laser range meters, but its application in underground coal has been limited. The practical use of photogrammetry was tested at the Safety Research Coal Mine, National Institute for Occupational Safety and Health (NIOSH). A commercially available, Digital Single-Lens Reflex (DSLR) camera was used to perform the photogrammetric surveys for the experiment. Several experiments were performed using different lighting conditions, distances to subject, camera settings, and photograph overlaps, with results summarized as follows: The lighting method was found to be insignificant if the scene was appropriately illuminated. It was found that the distance to the subject has a minimal impact on result accuracy, and that camera settings have a significant impact on the photogrammetric quality of images. An increasing photograph resolution was preferable when measuring plane orientations; otherwise a high point cloud density would likely be excessive. Focal Ratio (F-stop) changes affect the depth of field and image quality in situations where multiple angles are necessary to survey cleat orientations. Photograph overlap is very important to proper three-dimensional reconstruction, and at least 60% overlap between photograph pairs is ideal to avoid unnecessary post-processing. The suggestions and guidelines proposed are designed to increase the quality of photogrammetry inputs and outputs as well as minimize processing time, and serve as a starting point for an underground coal photogrammetry study.INTRODUCTIONThe stability of underground mine ribs has been a safety concern for underground coal mines for decades. Unfortunately, the average rib fatality rate has been about 1.3 per year between 1996 and 2013 (Jones et al., 2014). In an effort to better understand coal rib behavior, photogrammetry is being investigated in this study as a measurement tool for surveying ribs in an underground coal mine environment."

Jan 1, 2016

By L Terrusi

The Bungaroo Valley hosts a concealed Tertiary channel iron deposit (CID) along a 17 km stretch of its length. Bungaroo Valley is approximately 0.5 km wide upstream at its easternmost extent, and 3.5 km wide downstream where it joins the Jimmawarrada Creek. The valley follows the axial trace of an anticline that plunges gently to the southeast, and the CID infills the valley. Mineralisation extends to a depth of 230 m below the surface, and almost the entire deposit occurs below the water table. Bungaroo Valley cuts through the Buckland Hills and is bounded to the north and south by steep scarps capped with the resistant Dales Gorge Member of the Brockman Iron Formation. Basement rocks are believed to be mostly Wittenoom Formation shales and dolomites, with Mount McRae Shale and Mount Sylvia Formation also present. Deep, localised depressions appear at the base of the CID sequence towards the north edge of the upstream section of the valley, while downstream the basal CID contact is relatively flat and shallow. In both cases the profile of the CID surface closely mirrors that of the basal contact. The localised depressions seen in the upstream basal CID contact produce significant variations in CID thickness of up to 100 m over short strike distances. This uneven palaeotopography is most likely due to eddying and waterfalls forming within the riverbed prior to CID deposition during a time when the water table was much lower than at present. It may also be associated with possible karsting in an underlying dolomite unit and subsequent syn- or post-depositional collapse of the overlying CID. The irregular basal contact of the Bungaroo CID sequence has implications for mining in terms of pit design and resource accessibility.

Jan 1, 2007

By Stuart Brashear, Steven Bell, Donald Smith

This Limestone site required the removal of a bench containing high quality rock located in close proximity to sump and pit pump. The sump and associated electrical box were below the bench that needed to be blasted and located only 70 feet (21.33 meters) away. It was proposed to blast material needed without moving or disturbing the pump or electrical junction box. The area to be blasted was flown with a drone and stitched into a 3D orthographic model. Proprietary blast design software was used to create a blast design solution that would allow for a series of blasts that would provide required fragmentation and muckpile development and not disturb the sump or electrical box. A drill patten was created for each blast using the burden heat map and 3D face profiles created from the 3D orthographic model. Timing contour lines and muckpile displacement predictions were used to create timing sequences for proper face movement away from the sump and electrical box. The shot designs were laid out with a GPS system to insure hole location accuracy. All holes were remeasured for proper face burdens using the 3D model and Boretrak®® data collected after drilling operations were completed to insure hole locations were within face burden tolerances as derived by the burden heat map. After each drill log was reviewed, a charge loading scenario was created for each hole. The timing design created, for each shot and was reviewed and adjusted as needed with regard to desired muckpile displacement away from the sump and electrical box. Blasting results were satisfactory, with fragmentation and muckpile development consistent with the calculated throw from the blast model, with no rock hitting the pump or box and no rocks striking the sump water and disturbing the pump motor.

Jan 21, 2025

By Gennadiy M. Poletayev, Mikhail D. Starostenkov, Alexandra S. Starostenkova

"The process of the combustion synthesis was modeled by computer simulation using the molecular dynamics method. The set of the critical parameters regulating the velocity of the reaction was found from these computer experiments. It was established that the character of structure-energetical transformations at the combustion synthesis in the systems Ni-Al and TiAl depended on the type of boundaries used for the phases delimitation in the bimetal thin films.IntroductionProducing new materials and products, based on the combustion synthesis (CS), is the objective of scientific investigations as one of the most perspective one for industrial applications. But there are several problems connected with theory and experiment. It allows us to forecast the properties of materials. First of all, the main problems are stipulated by structure-energetical transformations taking place at high velocities of the reaction and at high temperatures. It prevents the analyzing of the transformation mechanisms in materials, taking place at microscopic, atomic levels in details.It is evident, that computer simulation allows to decide some problems and to approach to more exact theoretical presentation of structure-energetical reactions taking place at CS. It is known, that the most typical systems, where CS is observed, are bimetals Ni-Al and Ti-Al. The investigation of interphase boundary stability in the systems of Ni-Al and Ni-Fe was made by the method of molecular dynamics in [1]. The bimetal thin film was presented by the packing of atoms in the plane (111) of FCC lattice. It was found that the discrepancy in the sizes of atoms A and B of bimetal was compensated by the formation of 60° top dislocations, set against interphase boundary in the absence of point defects and free volume. The density of top dislocations was proportional to the factor of size discrepancy of atomic components of the bimetal. Diffusional reconstruction of the interphase boundary and areas, situated near it, was observed only at definite concentration of point defects - vacancies, inculcated in the structure of the bimetal at the definite temperature. The atoms of the bimetal component of less size penetrated in the area of the second component with higher velocity. The clusters of intermetallic germs began to form. It led to the growth of the system temperature and acceleration of the process of the diffusional reconstruction of thin film. The following transformations were found: top dislocations splitted into single ones, which climbed from interphase boundary into the zone of more plastic component; the formation of sub grain structures took place."

Jan 1, 2001

By A. Vien

A major thrust in Industrial automation over the past few years has been the exploration and incorporation of higher level (supervisory and optimizing) control strategies aimed at more fully exploiting the existing control system infrastructure. There is little doubt that this is worthwhile pursuit, however, one must not lose sight of the maintenance and development requirements of the basic control system. Statistics on loop performance indicate that this too is an area of considerable potential. In this paper the authors look at some of the less elegant, but arguably equally important issues in mineral processing plant control. The focus is on controller structures, loop tuning, sampling, filtering, and some of the other principal components of the regulatory control foundations. In many cases significant improvements In control performance can be achieved by getting back to the basics.

Jan 1, 1998

By F. L. Sizer

THE mining regulations of British Columbia and Mexico present some features which might well be copied in the United States, if we are to have a complete revision of the laws governing mining titles. 1. First and foremost is the "square" location, which would mean the abolition of extralateral rights. This is a condition in both of the countries above named which has seemed to work no hardship upon any one, and certainly the limitation of underground rights by vertical planes through all lines makes a locator's rights clear. In view of the long and costly litigation which has involved so seriously many of our most important mining districts, it would seem to be the part of wisdom to avoid a repetition of similar trouble on titles of lode mining claims, by the enactment of a law similar to that in force in British Columbia. Objections have been raised by representatives of English companies to the investment of large amounts of money in mining operations in the United States, because of the insecurity of title under the present apex law; and the statement has been made to me personally by one of the largest English operators, that he would never again consent to the purchase of mines in the United States, preferring Mexico with all its revolutionary troubles to the danger of encroachment upon his underground rights by an unscrupulous neighbor. Without going into further argument as to the desirability of the "square location," it should be sufficient to say to those who are inclined to "let well enough alone." and still stick to the "law of the apex" that there have never been any serious objections raised to this feature of the square location in either British Columbia or Mexico. There are well founded and logical reasons for abandoning the doctrine of extralateral rights since it is so difficult of interpretation; the most natural substitute being a law similar to that of British Columbia, giving to each locator an area 1,500 ft. square.

Jan 3, 1914

By J D. McDonald

This paper outlines the function of the Safety and Compensation Division of the Mining Association of British Columbia. After a general discussion of safety and the safety program now being followed in B.C., the author goes on to describe the wide-ranging aspects of compensation payments and company assessment rates. Special attention is also given to the problem of silicosis in mining operations. In appendices to the paper, the experience rating plan of the mining industry is compared to that recently adopted for the construction industry. Introduction The Mining Association of British Columbia consists of fifty-five member companies, including virtually all the producing mines as well as the larger exploration, contracting and development companies. On completion of an extensive study of safety and compensation in the mining industry, the Mining Association of British Columbia instituted a Safety and Compensation Division in 1954. The director of the Safety and Compensation Division reports to the Executive Committee of the Association. There are two main functions of this Division. First is the prevenion of accidents by encouraging

Jan 1, 1965

By Donald B. Evans, Robert D. Pehlke

The solubility of nilrogen in liquid binary alloys of iron with Litanium. zivconium, columbium, vanndiurn, and tantalum was measured for alloy composiLions up to the solalbility limils of lhe alloy nitrides. All five alloying agents were found to decrease markedly the activity coefficient of nitrogen in liquid ivon. The metal/nitvogen mole ralios in the alloy nitrides formed were generally .found to be slighlly greater than 1.0, but in no case greater than 1.5. From the experimental data, the standard free energies of fortmation of titanium and zir-conium nitrides have been calculated for the Lemperaluve range 1550° to 1750 C. The solublily Products for columbium, tantalum, and vanadium nitrides are also reported. A number of research investigations have examined the effect of refractory metals on the solubility of nitrogen in liquid iron. Although data on zirconium are not available, investigators are in agreement that titanium, vanadium, columbium, and tantalum markedly increase the solubility of nitrogen in liquid iron. This fact alone makes desirable the acquisition of thermodynamic data for these elements in liquid iron. Since refractory metals are known to be stable nitride formers, they have been suggested as steel denitrifying agents, and some of their nitrides have recently been considered as containment materials for liquid iron and iron alloys. Most available thermodynamic data for these metals relate to their dilute concentrations, but effective thermodynamic treatment of these applications requires data at concentrations near the solubility limit of the alloy nitride. Although some work has been done at relatively high alloy concentrations in liquid iron (particularly for vanadium 2,3 and titanium 2,4), the results have been somewhat contradictory. Disagreement may be partly attributed to the fact that the compositions of most refractory metal nitrides have been shown to be nonstoichiometric, and to vary 2,5-8 depending on the temperature and nitrogen gas pressure with which the solid nitride phase is in equilibrium. One purpose of this study consequently has been to determine the compositions of the refractory metal nitrides precipitated from a liquid iron solution. EXPERIMENTAL PROCEDURE Rao and Parlee2 and Evans and Pehlke 9 have discussed the technique for measuring the solubility product of an alloy nitride phase in liquid iron by finding the point of departure of the nitrogen solubility from Sieverts' law. The method consists of measuring the solubility of nitrogen in a melt of iron containing a known concentration of a second metal as a function of the nitrogen gas pressure over the melt. In this study the second metal was one of the refractory metals titanium, zirconium, columbium, vanadium, or tantalum. When the nitrogen pressure at which the refractory nitride forms is reached, a deviation of the measured solubility of nitrogen in the melt from Sieverts' law is observed in the form of a "pressure halt." The concentration of nitrogen in the melt associated with this breakpoint in the nitrogen-absorption curve is then used to calculate the nitride solubility. The Sieverts method was used to measure nitrogen solubility as a function of nitrogen pressure and temperature. The experimental equipment for this technique has been previously described in detail. 1,9 Charge materials used were vacuum-melted high-purity iron (Ferrovac-E) and the best commercial grades of the refractory metals obtainable (in all cases at least 99.8+ pct pure). Recrystallized alumina crucibles were used to hold all melts except those containing zirconium, for which zirconia crucibles were necessary. Temperatures were measured by a disappearing-filament type optical pyrometer sighted vertically downward on the melt surface through a 1/4-in.-diameter sight hole in the crucible lid. By means of a technique previously described, 9 in which the refractory-metal nitride was precipitated at one temperature then redis-solved by raising the temperature 50°C and precipitated again at a higher temperature, it was possible to obtain data over a temperature range of up to 200°C on a single melt. It was found that this technique could not be used with melts containing zir-

Jan 1, 1965

By Ava Walker

The first form of a surety bond was an honest handshake between two or more parties agreeing to a decision, and their personal guarantee of following through to completion. This has all changed. In 1895, the United States Treasury Department disclosed that $35 million worth of personal surety guarantees on file had become worthless. A law was then passed requiring all surety bonds, in favor of the United States, must be corporate surety bonds. Today, a surety bond is one of the nation's leading fi¬nancial instruments used to guarantee the completion of an obligation. One hundred-fifty years before cor¬porate surety bonds, outcrops near Richmond, VA, were being mined. These surface mines became under¬ground mines. Today, both are still being used to obtain a leading energy source, coal. Since that time, more than 5956 km2 (1.47 million acres) of coal mined lands have been reclaimed in the US (Coal News, August, 1987). More than 25,000 state and Federal mining permits cover¬ing 14,164 km2 (3.5 million acres) have been issued during the last 10 years. Coal production has exceeded 7.2 Gt (8 billion st). More than 5665 km2 (1.4 million acres) of mined land has been reclaimed by active coal mining opera¬tions and 267 km2 (66,000 acres) of abandoned mined lands have been re¬claimed by others. Reclamation bonds were freely writ¬ten in the 1970s. So why are they almost extinct today? Contract bond losses have been severe in the past several years, sureties reporting losses exceed¬ing 110%. But the same proof is not provided on coal reclamation bonds. A surety bond is generally required when one party has an agreement with another party, and that party wants a guarantee from a third party that a job will be completed according to the terms and conditions of a written contract. In the case of a reclamation bond, the surety company (surety) is the financial party. It extends the credit and a guarantee to the obligee (the State, Commonwealth, or Office of Surface Mining) that the principal (the coal operator/company) will complete the terms and conditions of the contract (the rules and regulations governing mining and reclamation). The Surety Association of America defines a surety bond as an agreement providing for monetary compensation should there be a failure to perform specified acts within a stated period. Webster's Dictionary defines surety in the following ways: "l: the state of being sure; 2a: a pledge or other formal engagement given for the fulfillment of an undertaking and; 3b: one who has become legally liable for the debt, de¬fault, or failure in duty of another." Banks never make accommodation loans. Either the loan is good or no loan is made. Surety companies feel the same way about surety bonds. In fact, the average person does not realize the dangers of becoming surety for another. How does a surety determine if a company is worthy of receiving surety credit? How is a coal account under¬written today for an obligation that may not be released for many years? When a surety company executes a reclama¬tion bond, it financially puts its name behind the coal company and its guaran¬tee that should the coal miner default on the obligation, the surety will fulfill the contract. How is the surety to determine if a coal company may still be in business five, 10, 20, or 40 years from today?

Jan 1, 1989

By M. R. Geer Olds, H. F. Yancey

THE increase in the number of coal-cleaning plants employing dense-medium processes occurring since 1946 is especially interesting when viewed historically. Both sand and magnetite were introduced as material for heavy mediums at about the same time, sand in the Chance process in 1921 and magnetite in the Conklin process in 1922, but from that point on their records diverge. The Chance process enjoyed a steady growth from its inception, whereas no additional magnetite plants were built in the United States for over 20 years. Then, following the close of the World War 11, magnetite was again introduced, this time with marked success. During the following years some 47 plants employing magnetite medium were built. This rapid growth of dense-medium cleaning has been concurrent with widespread adoption of full-seam mining on one hand and a return to a more competitive market on the other. At a time when changing mining practice has provided cleaning plants with dirtier coal and changing market conditions have simultaneously demanded a cleaner product, the industry has through necessity turned to improved preparation. The inherently greater sharpness with which dense-medium processes can separate coal from impurity is thus helping to hold the line against ever-increasing mining costs and at the same time assisting materially in retaining badly needed markets. Although dense-medium cleaning unquestionably offers a distinct advantage when the washing problem is difficult, other methods can provide almost equally high efficiency when the coal is easy to wash. Moreover, fine coal cannot yet be treated by heavy medium in a proved process, although the Driessen cyclone is in the pilot-plant stage. Most of the present types of dense-medium equipment have been in use only a few years, and the dearth of information in the literature concerning their performance characteristics is entirely understandable, Nevertheless this information is necessary if the process is to be intelligently applied to individual cleaning problems. Without data on the efficiency of a process in a particular type of separation, it is difficult to assess the advantage to be expected from it. Similarly, the role of particle size in heavy-medium separation is important in some cases, yet there is little published information on this aspect. To mention only one more of the numerous points on which essential information is lacking, the bearing of medium characteristics on performance has been discussed only in qualitative terms. It was with the hope of providing information on some of these points that the Bureau of Mines built a dense-medium pilot plant for cleaning coal at its Northwest Experiment Station in Seattle in 1950. The plant has been operated continuously since that time, and over 50 runs have been made on 7 coals exhibiting a wide range of washability characteristics. An idea of the magnitude of this work will be gained from the fact that examination of the plant products has involved some 600 float-and-sink separations and about 2500 ash determinations. A laboratory pilot plant is especially well adapted to investigate many aspects of performance because close control over test conditions can be exercised and because a large number of tests can be made rapidly. On the other hand, factors such as consumption of medium and other cost items can be investigated satisfactorily only in a commercial plant. Actually, the two forms of investigation should be complementary, with the laboratory work pointing the way for confirming tests in commercial units. Pilot Plant The dense-medium pilot plant employed for this work comprises a 24x30-in. drum-type separating vessel, a 12-in. densifier, a 12-in. magnetic separator, a 26-in. x 9-ft vibrating screen, and the necessary pumps and conveyors for handling materials. Arrangement of these units corresponds with the flowsheet used in most commercial plants, except that a thickener is not provided for the feed to the magnetic separator. Coal and refuse discharge from the separating drum to the vibrator, which is divided longitudinally down the center. Medium draining through the first 3 ft of the screen is recirculated directly to the drum. Sprays on the middle 3 ft of the screen rinse medium from the products, and the last 3-ft section is for dewatering. Dilute medium from the rinsing and dewatering sections is pumped to the magnetic separator, where magnetic solids are recovered. These are pumped to the densifier, from which they return to the medium-drainage sump by gravity through a demagnetizing coil. The drum-type separating vessel is a scale model of a commercial unit. Feed enters axially at one end of the drum just below the surface of the bath, and float material overflows through a circular opening at the other end. Particles sinking to the bottom of the bath are picked up by lifting flights bolted to the inner wall of the drum, elevated out of the bath, and sluiced to the vibrating screen. Baffles suspended in the bath prevent float material from entering the sink-lifting flights. About 8 gpm of medium is used to sluice the feed into the drum. An additional 15 to 24 gpm, depending upon operating conditions, is added through two pipes dipping into the bath behind the baffle on the side where the sink-lifting flights enter the bath. The bath available for separation is 2 ft long and 13 in. wide, giving an area of 2.08 sq ft. Depth of bath from the surface to the top of the sink-lifting flights, measured vertically below the axis, is 6 in.

Jan 1, 1954

What is your assessment of the current state of the minerals industry? It is no understatement that domestic mining is facing a severe crisis at this time. The sharp decline in commodity prices and demand is putting a great strain on domestic and worldwide mining, causing major declines in profits and market capital of mining companies. This, in turn, has lead to major production cuts, layoffs, shut-downs of operating properties, and the deferral of new and expansion projects. These changes in the minerals industry have played a major role in the health of the economy. Operationally, the industry continues to develop new technologies that are making our work more efficient, more cost effective and more environmentally acceptable and safe. During downturns like this, companies generally pay closer attention to operational efficiencies and process optimization. Historically, new technologies and processes tend to be developed during down markets, and I believe we will see the same thing as companies strive to preserve liquidity and maintain or improve their margins. On the positive side, the drop in commodity prices has resulted in a reduction in operational costs, as the costs for fuel supplies and construction materials have decreased.

Jan 1, 2009