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By M. M. Papic, J. C. Whitehead

"A sample of Hat Creek coal has been extracted using supercritical aromatic solvents in a laboratory-scale extraction unit. Extract yields in the range 21 to 27 per cent of dry-ash-free coal were obtained.These yields are significantly lower than yields available from high-volatile bituminous coal and some lignites. Thus in a combined extraction/hydrocracking scheme for the production of liquid fuels from Hat Creek coal the char product would exceed that required to supply the energy and hydrogen requirements of the process. Excess char could be used for the production of power or gas for sale.IntroductionThe Supercritical Gas Extraction (SGE) process developed by the U.K. National Coal Board operates in two stages: an extraction stage in which a coal extract is separated from mineral matter and undissolved coal and a subsequent hydrogenation stage.The SGE process is based on the ability of a compressed supercritical fluid to dissolve relatively high molecular weight substrates. It is operated under conditions where a hydrogenrich portion of the coal is selectively extracted in a short residence time extraction stage leaving a hydrogen-deficient char. The process schematic shown in Figure I illustrates that the extract produced is separated from the solvent and passed to a conventional hydroprocessing stage while the char product is utilized in the production of heat, power and hydrogen for the process. An extract yield in the order of 50 per cent dry-ash- free coal represents a ""balanced"" case for such a process in which there is just sufficient char for the provision of these commodities."

Jan 1, 1985

By D. Reddish

The combination of free standing steel supports, such as arches, and rock bolts (mixed support) has Frequently been in used in UK coal mine roadways when it is considered that the strata and/or environmental conditions would not be suitable for rock bolts solely. However, how such mixed support systems operate is not fully understood. Due to the differences in the support method provided by rock bolts and free standing steel, the total support generated is not simply a case of adding the contribution to the support of the roadway given by the two systems. This paper describes a numerical investigation into mixed support systems when used in coal mine roadways. A series of 2D and 3D geomechanical models are described and the method of modelling the rock bolts and steel supports in coal mine tunnels is discussed. The numerical models described include rock boltd only roadways, steel supported roadways and mixed supported roadways in a variety of geological and in-situ stress conditions. Conclusions are formed that allow an insight into mechanisms of strata reinforcement provided by the support systems modelled. Further to this, a review of the numerical modelling of pre-tensioned rock bolted systems is described identifying the contribution to support efficiency given by the adoption of tensioning in full column resin anchors. The results obtained highlight that the effectiveness of the pre-tensioned load is dependant on the rock mass quality and in- situ stress level at the site where it is to be used.

Jan 1, 2004

By Ronald R. Bauer

Wollastonite is a little known industrial mineral of the silicate group. The largest and purest known deposit in the free world is being mined and beneficiated in Millsboro, New York by NYCO, A Division of Processed Minerals Incorporated. The associated garnet and diopside are separated from the wollastonite using dry high intensity magnetic separators. Beneficiated wollastonite is used extensively as an additive and filler in the ceramic, paint, refractory, and wallboard industries. Wollastonite acts as a functional filler due to its unique chemistry and physical acicularity.

Jan 1, 1982

By Benjamin H. Clark

"For over 50 years, Derrick Corporation has been renowned for its innovative and durable fine screening equipment and screen surface technology. Derrick’s latest innovation, the patented Stack Sizer, offers mineral processors both high tonnage capacity and high separation efficiency on an extremely small footprint.The Stack Sizer is suitable for separations from 6.3 mm down to 75 microns (200 mesh). The Stack Sizer, coupled with Derrick’s patented urethane screen surface technology, offers an extremely economical alternative to hydraulic classifiers, hydrocyclones, and less efficient low volume wet screening systems. Stack Sizers have been used in feed preparation for flotation, spirals, and a variety of jigs. Mineral processors wishing to reduce grinding circuit circulating loads and generation of slimes due to over grinding, thereby enhancing the efficiency of flotation and gravity circuits, now have another technology at their disposal to perform this critical sizing and grade control function.Over 200 Stack Sizers have been installed in numerous mineral processing applications worldwide attesting to the rapid acceptance of this technology. Stack Sizers are currently screening ferrous and non-ferrous metal ores, mineral sands, silica sand, kaolin clay, feldspar, garnet, phosphate, aluminum dross, potash, coal, tantalum, spodumene, niobium, and other rare earth mineral ores.INTRODUCTIONDerrick engineers have long understood and demonstrated the importance of screen width in coupling both high capacity and high separation efficiency for fine wet sizing applications. As opposed to fine dry sizing, where the length of the screening machine is critical for high separation efficiency, introducing slurry feed to screens in a thin and even layer at minimal velocities across wider screen surfaces allows for high capacities and efficiencies, with maximum screen cloth life. This is due primarily to the combination of free liquid and high frequency vibration of the Derrick motors, which allow fine undersize material to pass through the screen apertures. Lacking either of these factors would be extremely detrimental to the screening process. Without the high frequency vibration of the motor, the screen is essentially a low efficiency sieve bend. Without the free liquid to carry fines through the screen openings, the screen is for all intents and purposes a glorified conveyor or dewatering unit, as little or no sizing takes place once the screen is devoid of free liquid. For optimal screening results, Derrick recommends feeding slurry to a screen at approximately 20% solids by volume. Figure 1 shows the Stack Sizer design concept. Note that a single feed point is used to evenly distribute the flow to the five separate feed points."

Jan 1, 2007

By Jessie L. Bonner, W. Stephen Blomberg, Mark Leidig, Heather Hooper

Understanding the effects of the bench on ground motion can improve the design of cast blasts and achieve improved blast efficiency while remaining below vibration requirements. A new dataset recorded in September 2003 from a coal mine in Arizona has allowed us to examine the excitation of short-period Rayleigh-type surface waves from four simultaneously-detonated explosions in and below a topographic bench of a mine. The explosions were recorded on a network of over 150 seismic sensors, providing an extensive understanding of the ground motion radiation patterns from these explosions. We detonated two separate explosions (~3 tons and ~1.5 tons ANFO) in the deepest pit of the mine, thus the explosions were shot to solid rock. Within 25 meters of these two explosions, we detonated two additional explosions of similar explosive yields in a bench, thus these explosions were shot to the free face. Radiation patterns and spectral ratios from the explosions show increased amplitudes (by a factor of 1.5 to 2) at azimuths behind the bench relative to the amplitudes in front of the bench. We compared these findings to seismic observations from two ~1.5 million pound cast blasts at the same mine and found similar radiation patterns. Modeling of these blasts shows that the variations in ground motion are caused by the topographic bench as a result of 1) horizontal spalling of the rock falling into the pit and 2) non- linear scattering near the free- face. We also note that shooting to a buffer (previously blasted rock) causes the azimuthal variations to be significantly reduced.

Jan 1, 2005

Safety is the No. 1 concern of any drill contractor or mine operator. Everyone in the industry knows a safe site helps stabilize operational costs and enables higher productivity. When it comes to exploration drilling, research has proven a majority of injuries are caused by the mishandling of coring rods. A driller helper will typically handle up to 50 rods per shift or up to 15,000 rods per year. With an annual 340 t (750,000 lb) in rods managed by hand, the risk of serious injury is extremely high. Because of this, the top request from the exploration industry is diamond rod handling. The Boart Longyear 4200 surface exploration drill, slated for release in 2009, will give the industry a hand-free, operationally safe rig.. Developed through the collaboration of its global drilling services and products divisions and targeted at the 1,200-m (3,900-ft) NQ market, the upcoming Boart Longyear 4200 surface exploration drill features the safest and most flexible rod management sys-tem in its class. The rig includes the industry?s first, truly hands-free rod handling system. This increases operator safety on the jobsite. In addition to the rod handler, the rig also features many new innovations that boost productivity and rig efficiency while minimizing the risk of downtime due to component failure or operator error. Boart Longyear has also included an intelligent PC-based operating system designed to allow complete drilling control as well as diagnostics reporting for the rig.

Jan 1, 2009

By W. A. Ahrens, J. H. McNamara, J. G. Franek

"An economical, pollution-free process has been developed for the hydrometallurgical extraction of copper from sulphide ores. The extracted copper, in the form of cuprous chloride (CuC/), is converted by reduction to copper metal. The metal is melted and fire -refined into wire bars which meet the standards of electrolytic tough pitch (ETP) copper wirebars. IntroductionThe successful development of the Cyprus Copper Process has been an evolutionary series of events covering a time span of some nine years. The original process, based on an electrolytic membrane cell principle , was abandoned in 1975 because of technical, economic and pollution problems. During the past four years, the pilot plant has been reconstructed based on a new flowsheet and operated successfully in several campaigns, some for as long as four months. The pilot-plant hydro section operates at a 225-lblhr copper rate. In October 1977, a feasibility study was completed by Jacobs Engineering, Pasadena, California. The study showed favourable economic and technical feasibility. Jacob's studies in 1978-79 revealed favourable comparative economics with other known pyrohydro processes and favourable economies of scale.The Cyprus Copper Process converts copper concentrates of varying composition into copper metal, which has been proven to be equivalent in every way to electrolytic tough pitch copper, suitable for electrical applications. This is accomplished at capital and operating costs which are estimated to be lower than those associated with any other known currently applicable technology. Also, the total energy requirement is equal to or less than any other known process and the process is essentially pollution free."

Jan 1, 1980

By None None

Use this month wisely — go online and take advantage of your new member benefit. As an SME member, you can read and download for free all of the full-text papers of the Mining, Metallurgy & Exploration (MME) journal, including the 22 papers in the launch Special Issue on Mineral and Metallurgical Processing in Honor of Professor Emeritus Douglas W. Fuerstenau as well as the archived articles of Minerals & Metallurgical Processing (MMP), all the way back to Vol. 1, No. 1. Just follow the instructions on this page.

HIGH-GRADE manganese ore, from which manganese is obtained commercially, is not found in large quantities in any major steel-producing nation in the free world. The U. S. is a "have not" nation with respect to deposits of directly mineable high-grade manganese ore. Known resources of 48 pct Mn or better grade ore amount to less than 200,000 tons. In 1950 the U. S. steel industry consumed 1.8 million short tons of metallurgical grade manganese ore that contained about 800,000 tons of manganese. About 16 pct of the manganese content was lost in processing, so that about 650,000 tons, or 13 pounds per ton of steel actually entered into steel production. Under present practices use expands directly with steel output, and by 1975 the demand in both the U. S. and the rest of the free world is expected to be roughly 60 pet greater than in 1950. In peacetime about 80 pet of manganese consumption goes into steel production; high-manganese steel, dry cells, and chemicals account for the remainder. The manganese supply problem centers around high-grade ore for ferromanganese production. Use of ores containing less than 35 pet Mn sharply increase the costs of making ferromanganese. Use of ferro-manganese of grade below 70 pet in turn requires changes in steelmaking that increase steel cost. Under normal conditions the present small domestic production cannot be expected to increase. Major resources in the U. S. consist of 12 low-grade deposits. The cost of mining and treating these ores to extract a product as good as that yielded by imported ores is at least twice and in some cases more than four times the 1951 price of foreign ores delivered to the U. S. However, as long as trade relations and overseas shipping are not interrupted, deposits in India, Africa, and Brazil can meet steadily increasing demand at approximately present costs. Cost considerations indicate that the U. S. should continue to rely upon overseas sources for its peace-time supply, and that this situation is satisfactory. But, this does not take into account the question of how the U. S. will be able to meet its needs in war. Position of the Rest of the Free World In 1950, free world steel producers outside the United States, with a steel output of 70 million ingot tons, consumed about 1.3 million tons of metallurgical-grade ore. Their manganese ore demand, expected to increase directly with steel production, will by 1975 be about 2.3 million tons. Russia possesses over half the known manganese ore reserves of the world and is producing twice the tonnage of any other country. It supplied more than a third of the U. S. manganese requirements up to 1938 and again in 1948, but by 1950 Soviet manganese exports to the free world had virtually ceased. The free world's supply of manganese now comes mainly from India and Africa. Somewhat over 10 pet of U. S. imports came from Brazil and Cuba. Security Considerations In the event of war the U. S. might be substantially cut off from 90 pet of present sources. Reduction in manganese specifications might cut consumption by over 10 pet without seriously affecting steel quality. By elimination of losses in the production of ferromanganese savings as high as 10 pet might be possible. But, wartime manganese requirements cannot be met through conservation alone. To meet possible future emergencies the U. S. should continue its comprehensive security program for manganese, including stockpiling and research on the economic use of low-grade ore, domestic ores, the recovery of manganese from slag and the reduction of manganese requirements in steel production. If this work, including additional pilot plant operation is pursued vigorously, it should be possible in an emergency to get an adequate supply of manganese from domestic sources. The national stockpile then can be looked upon as a source of supply during the period of at least 2 years required to reach full-scale production from low-grade resources. Ferromanganese Smelting In comparison with smelting of pig iron, ferro-manganese smelting is a very wasteful process. Under present ferromanganese blast-furnace smelting practice, about 8 pet of the manganese in the furnace charge is lost to the slag, and roughly the same amount is lost to the stack gases; the total loss approaches 15 pct. Present practice is a compromise between excessive slag loss and excessive stack loss. In fact, it may be seriously questioned whether conventional blast furnace design is suitable for manganese smelting. U. S. Resources The known manganese deposits of the U. S. contain a total of 3500 million long tons of raw material and 75 million long tons of metallic manganese. More than 98 pct of this contained metal is in 12 large low-grade deposits of which the most important are those at Chamberlain, S. Dak; Cuyuna, Minn.; Aroostook County, Maine; and Artillery Peak, Ariz. Reserves of high-grade ore (48 pct Mn) amount to less than 200,000 tons. About 20 million tons of ore average over 15 pct Mn, and when grade is decreased to 10 pct Mn reserves amount to about 100 million long tons. If cut-off grade is decreased to 5 pet Mn, resources amount to 800 million long tons. Many of these low-grade ores may be beneficiated by flotation or other concentration methods. Pyrometallurgical Methods For smelting ferromanganese, it is essential to have an ore containing at least 50 pct manganese, with an Mn:Fe ratio of about 8:1. Direct smelting of 20 pct Mn concentrates is not promising. The only method that offers any promise involves two-step smelting.

Jan 1, 1952

By B. C. Allen

Grain boundary grooving has been studied in chromium, molybdenum, and tungsten under a variety of conditions using high vacuum techniques and tantalum -gettered argon. The average surface free energy of solid chromium, and the chromium-liquid silver interface free energy were respectively found to be 2200 ± 250 and 500 i 130 ergs per sq cm from groove formation kinetics and estimates of pertinent volume difffusion coefficients. The results for chromium were unffected by variations in interstitial content ranging from 0.003 to 0.09 pct C, or 0.003 to 0.03 pct O. Surface diffusion is the primary mechanism of groove formation in chromium under 1 atm argon at 1200" to 140O°C, and is essentially unaffected by 0.003 to 0.09 pct C, 0.003 to 0.03 pct O , metastable nitrogen contents up to -0.01 pct, and up to 2 torr Ag vapor. At higher temperatures, the major mechanism is volume diffusion in argon or evaporation-condensation in stutic vacuum. Surface diffusion occurs in molybdenum at 0.5 to 0.96 and in tungsten at 0.5 to 0.9 of the absolute melting tempera -ture by a single mechanism, possibly by the migration of single adatoms or vacancies. Results were slightly affected by up to 23 tory Sn vapor, and in molybdenum were essentially unaffected by 0.5 Ti or carbon in the range 0.002 to 0.02 pct. Volume difffusion through the liquid is the mechanism of groove formation in chromium-liquid silver at 1200" to 1400°C and in molybdenum-, Mo-0.5Ti-, and tungsten-liquid tin at 1200" to 2000°C. The solid-liquid interface free energies involved were estimated from grooving kanetics. WHEN a grain boundary intersects a solid surface, a groove tends to form along the line of intersection at temperatures above about half the absolute melting point (0.5 TM). The groove progressively grows by preferential atomic migration either by diffusion or evaporation. Establishment of a groove angle occurs in accordance with the grain boundary and surface free energies involved. The motivation for groove formation is a reduction in the total surface free energy of the system. This study is a continuation of previous work on thermal grooving of chromium, molybdenum, and tungsten.&apos; The temperature ranges were extended, and the effect of metallic and interstitial impurities was evaluated. The results were such that certain interface free energies and surface self-diffusion coefficients were deduced from the grooving kinetics. EXPERIMENTAL WORK Materials and Preparation. As indicated in Table I, the 0.05-0.08-cm-thick chromium, molybdenum, and tungsten sheet used was nominally 99.99 pct after recrystallization. Two lots of molybdenum with about the same analysis, Mo-0.5Ti,* and tungsten were ob- *Alloy compsitions are expressed in weight percent . tained commercially. Extruded chromium rod,&apos; prepared from iodide process crystals, was warm rolled to sheet at 700°C. Sheet of three Cr-0 impurity alloys containing up to 0.03 pct 0 was prepared by warm rolling arc melted, extruded, and swaged rod. Two Cr-C impurity alloys containing up to 0.09 pct C were made by equilibrating unalloyed chromium with a known amount of CH4 for 24 hr at 1150°C in previously evacuated quartz capsules. Chromium containing nominally 0.015 and 0.06 pct N was similarly prepared by equilibration with NH3. The sheet was recrystallized to give a stable grain size about equal to the sheet thickness. Molybdenum and Mo-O.5Ti were recrystallized in a tantalum resistance furnace 1 hr at 1 x lo-5 torr at 2300" and 220O°C, respectively. Tungsten was similarly annealed for 1 hr at 2500°C. Chromium and its impurity alloys were outgassed at 1100°C and recrystallized 1 hr at 1700°C under 1 atm Ar. Except for nitrogen, the impurity content stayed roughly constant. Nitrogen in both alloys was reduced to <0.001 pct. In fact, over 80 pct of the added nitrogen was lost after outgassing at llOO°C and annealing sheet 1 hr at 1300°C in argon in the presence of tantalum. Such a rapid loss can be rationalized since -2 torr N are required for equilibrium with 0.04 pct N in solution,3 while the equilibrium pressure is ~10-5 torr over tantalum at 1300°C.4 The recrystallized sheet was cut into small coupons which were metallographically ground and polished on one side with a minimum of grain boundary relief. The surface roughness was on the order of 0.01 µ. The tin and silver used were nominally 99.999 spec-trographically pure. After being outgassed at 1100°C and equilibrated in a molybdenum crucible for 0.5 hr at 1800°C in argon, the tin contained 3 ppm 0, <0.3 ppm N, and 0.1 ppm H. Following outgassing at 900°C and equilibration in a chromium crucible 1 hr at 1400°C in argon, the gas content of the silver was 1 ppm O, <0.5 ppm N, and 0.3 ppm H. Grooving Under Argon or Vacuum. All specimens were placed in unsealed containers made from rod or sheet of the same alloy, thereby enabling the polished surface to achieve gas-solid equilibrium. The annealing fixtures are shown in Fig. 1. The specimen was placed in a resistance furnace with a tantalum or Ta-10W heating element plus tantalum fixtures or radiation shields. Chromium was outgassed at 1100°C, and molybdenum and tungsten were outgassed at 1900°C to 1 x l0-5 torr or at the grooving temperature, whichever was lower. In vacuum anneals, the specimen was then heated directly to the intended grooving temperature. In argon anneals, 99.996 Ar was admitted

Jan 1, 1970

The implementation of NAFTA in January of 1994 was expected to have small but beneficial effects for the Mexican economy, mostly through increased investment flows. Mexico&apos;s mining industry was especially likely to benefit, as mineral investment funds would be diverted to the now safer Mexico and away from similarly endowed but more risky Latin American mineral economies. The results of the past two years have shown that it is governments and macroeconomic factors that influence investment flows, rather than the fine-tuning of trade flows through so called "free-trade" agreements.

Jan 1, 1996

By Nagy El-Kaddah, Thinium T. Natarajan

A modeling strategy is presented for computing the electromagnetic field and the shape of the molten metal in electromagnetic confinement systems. This strategy involves the use of a hybrid finite element/integral technique to calculate the electromagnetic field and force distribution in the melt. The free surface shape is determined from minimization of electromagnetic, gravitational and surface tension energies using the Lagrange method of multipliers. This approach was applied to model the electromagnetic levitation melting process. The model was found to accurately predict the measured shape of levitated droplets.

Jan 1, 2014

By D. E. Fogelson

In a factorial experiment, blasting caps were detonated in three sizes of shotholes in mortar with three types of stemming--dry sand, wet sand, and hydrostone. Free-surface displacement pulses were recorded with a capacitive-displacement gage at a distance of 15 inches. The effects of decoupling and the type of stemming on the amplitude and the duration of the displacement pulse were determined. Both the amplitude and the duration of the displacement pulse were significantly decreased by increasing the decoupling, but they were little affected by the type of stemming.

Jan 1, 1965

By J. Frenzel

The computation of hydrometallurgical equilibria is very difficult because of the many complex species in solution, the precipitates, condensed species, or solids, and the activity coefficient corrections necessary to non-ideal thermodynamics. Our objective was to tryout recently developed genetic algorithms to minimize free energy and solve the equilibrium computation. We selected test problems that were seemingly unsolvable with more traditional algorithms, and we applied genetic algorithms to them. We were pleased to find that genetic algorithms succeeded where other algorithms did not. We concluded that they are an effective tool for hydrometallurgical equilibria.

Jan 1, 1992

By K. K. Kelley, W. W. Weller

The heat capacities of four crystalline silicates of barium ( BaSiO3 , BaSiO4 , Ba Si¸0 , and BaSi₂0 ) and two crystalline silicates of strontium (SrSio and Sr₂Sio ) were measured over the temperature range from 51 ° to 298° K. The results were used to evaluate the entropies at 298.15 ° K. The entropy values were joined with known heats of formation to obtain the free energies of formation of the silicates with respect to their constituent oxides at 298.15 ° K.

Jan 1, 1964

By Pandey H. D.

The paper describes a fluidised bed ion exchange method for simultaneous removal of phenols and cyanide from the effluent. Use of an eluant enables regeneration of the resin in the continuous operation mode. The breakthrough experiments conducted both on the laboratory scale and on a pilot plant scale have shown that while the level of phenol can be brought down from 462 ppm to about 6 ppm, the free cyanide is almost totally removed. An examination of data indicates that the method can serve the twin objectives of pollution control and phenolic compounds recovery.

Jan 1, 1992

By Elio Ferreira

This report describes the design, and development work performed to reduce the volume and weight of the miners caplamp battery, as well as a headpiece with a swivel mechanism containing a halogen bulb with two filaments. Work was also conducted in the development of a maintenance free battery. The design concept is based on non-sintered Ni-Cd technology, with an energy density of 22 Wh/lb. The cap lamp system developed has been approved by the Mine Safety and Health Administration (MSHA) and can be manufactured for mine use.

Jan 1, 1988

By Kaushik Dey

Bord and pillar is the most predominant method of wining of coal in Indian underground coal mines. Development heading in coal mines often encounters roof stability problem and results in roof overbreak. Research on this reveals that the blast-induced ground vibration may have significant contribution in roof overbreak, especially, when solid blasting is carried out in the bord and pillar method. Solid blasting, in general, is associated with higher charge confinement due to lack of free face and generates higher ground vibration, which in turn results in excess overbreak.

Jan 1, 2008

By Forrest T. Moyer

The National Safety Competition was inaugurated in 1925 by the Bureau of Mines, U.S. Department of the Interior, in cooperation with the Explosives Engineer. In the first nationwide contest, 210 mines and quarries were enrolled. In 1962, the thirty-eighth anniversary of the competition, 910 mines and quarries were enrolled. These participating plants were worked a total of 133,292,989 man-hours. Of the enrolled plants, 415 achieved injury-free operations for the year, the largest number of perfect safety records in the history of the contest.

Jan 1, 1964

By A. De, J. S. Zuback, T. Mukherjee, T. DebRoy

For successful commercial applications of additive manufacturing, metallic parts need to be defect free, structurally sound and reliable. However, additively manufactured metallic parts are susceptible to distortion, lack of fusion defects and compositional changes. Methods to measure susceptibilities of various alloys to these defects are needed but not currently available. Here we show that the necessary theories can be developed based on a well-tested numerical heat transfer and fluid flow model and decades of research in the field of welding. The proposed theories are validated with experimental results reported in the literature.

Jan 1, 2016