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By R. S. Lang, C. C. Merrill

The recovery of zinc from oxidized zinc minerals by the caustic soda leach and electrolytic or chemical precipitation was investigated . With the exception of willemite ( 2 ZnO • Si0₂ ) oxidized zinc minerals were readily soluble in 180 to 240 g / 1 NaOH solutions . A high- grade zinc flake was recovered electrolytically from solutions which had been treated with zinc powder to precipitate copper and lead . Solutions were recycled to the leach stage with a recovery of about 85 percent of the zinc from an ore containing 21.2 percent zinc . Electrolysis was conducted at a current density of 120 amp / ft2 with a power consumption of about 1.5 kwhr /lb zinc . Zinc was also recovered from leach solutions by dilution of the solutions , carbonation of the solution , or the addition of sulfur to boiling solutions . A dilution ratio of 5 : 1 precipitated 59 percent of the zinc in 9 days . Carbonation of the solutions precipitated the zinc as zinc oxide ( ZnO ) and solutions could be recausticized for recycling . Zinc precipitated as the sulfide with sulfur was easily filtered and washed . Approximately half of the sulfur added to solutions was lost in the form of sodium thiosulfate ( Na S₂03 ) .

Jan 1, 1965

By Paul W. Johnson, Ralph C. Kirby, Frank A. Peters

Alumina can be recovered from clay , using 30 percent nitric acid for digestion . Calcined clay is crushed and then digested at 325 ° F and 85 psig pressure with less than stoichiometric nitric acid required to form normal aluminum nitrate . In this way , a solution containing both normal aluminum nitrate , Al ( NO3 ) 3 , and basic aluminum nitrate , assumed to be Al ( OH ) ( NO3 ) 2 , is formed , and in which iron is virtually insoluble . The solution is filtered and then concentrated in vacuum evaporators to crystallize normal aluminum nonahydrate . The crystals are washed with 50 percent nitric acid and then decomposed to alumina and nitrogen oxides . The design that has been developed for this process is based on published work . For a plant producing 1,000 tons of alumina a day , the estimated operating cost is $60.69 per ton of alumina , and the estimated fixed capital cost is $ 76 million using a Marshall and Stevens chemical equipment index basis of 240.0 . This process is not competitive under current economic conditions with the production of alumina from bauxite via the Bayer process . For lowering costs , future research should include study of leaching at lower temperatures under atmospheric pressure and alternate aluminum nitrate decomposition methods .

Jan 1, 1964

By F. R. Cattoir

This Bureau of Mines study investigated molten salt electrorefining for beneficiating low-grade, high-carbon ferrochromium products which can be readily produced from domestic chromite concentrates. A second objective was to refine commercial ferrochromium into low-iron chromium products. Electrorefining of both types of ferrochromium in molten CaC12-NaCl-CrC12, CaCl2-MgC12-CrCl2, or KC1-LiCl-CrCl2 electrolytes produced chromium-iron products with virtual elimination of other impurity elements and some lowering of the iron content, Over 90 percent of the chromium present in the feed materials was recovered. The electrodeposited products were upgraded further by magnetic separation techniques into chromium containing less than 5 percent iron. The technical feasibility of preparing a premium chromium product from a low-grade, high-carbon ferrochromium made from domestic chromite was demonstrated. Chromium virtually free of carbon, oxygen, and silicon from high-carbon ferrochromiums was produced. In addition, the amenability of three commercial grades of ferrochromium to electrorefining and magnetic separation for preparing chromium metal containing less than 5 percent iron was determined.

Jan 1, 1969

By Donald I. Kurth

The Bureau of Mines conducted experimental work on comminuting coal. The size distributions of coarse fragments and fine particles were obtained under different modes of energy application--drop, impact crushing, wedge impact, compression, and shear tests. Four levels of energy application were used in the impact crushing and wedge impact tests. Airborne dust and respirable air-borne dust distributions were obtained for the impact crushing and wedge impact tests. Analyses of nonairborne dust and coarse fragment-fine particle distributions were carried out on impact, wedge, compression, and shear tests. The experimental size data on nonairborne dust were fitted to normal, log-normal, power law, Weibull, log-Weibull, and exponential distribution functions. Both the nonairborne dust and the coarse fragment-fine particle size distributions are best described by Weibull distributions. For the impact crushing tests, mean product size was found to be inversely related to specific crushing energy. The particle counts in a given size range of airborne and nonairborne dust were found to increase with increased input energy and specific crushing energy. However, in another sense the particle distributions were independent of energy level; that is, the percent-ages in a given size range were approximately constant regardless of energy level. Respirable airborne dust was related to respirable-size nonairborne dust by a power law.

Jan 1, 1975

By Y. Miron

Previous studies at the Bureau of Mines outlined the hazards of ammonium nitrate-fuel oil (AN-FO) mixtures in the presence of pyrite-bearing ores. The recent trend in the mining industry to strengthen AN-FO by the addition of aluminum metal raised the question regarding the effect of aluminum in AN-FO in the presence of pyrite-bearing ore. Laboratory work, similar to that done previously, demonstrated that the temperature of a self-sustaining reaction in the presence of AN-FO ore-aluminum is not lower than that for a comparable AN-FO-ore mixture. However, as might be expected from known thermochemical data, once initiated, the resulting reactions between AN-FO, aluminum, and pyrite are much more vigorous than those observed for AN-FO and pyrites alone. The temperature required to produce a self-sustained reaction for the combinations tested in this study is 250°±20° F while in the previous Bureau study, reactions were noted, in some instances, at 150° F. The different pyritic ores may be the cause of this variation.

Jan 1, 1976

By John C. Feeley

The methods used and the funds available for the development and oper- ation of shall mines and the reopening of small abandoned mines frequently present problems that tax the ingenuity and resourcefulness of the mining engineer far beyond that required in the mass production from large deposits. The objective of this paper is to describe in considerable detail the means whereby engineers have solved local problems in reopening an abandoned mine at which equipment, facilities, and funds were limited... The Etowah Coal & Iron Co. Gadsden red-iron-ore mine at Gadsden, Ala., 18 of interest in this category since it is the only independent red-ore mine under active development in the State. All other red-ore mines in Alabama are owned or controlled by the large iron or steel companies. The The mine, located on the southwest end of Shinbone Ridge in the outskirts of Gadsden lies in an ares once productive. but now idle, for many years. ore is relatively highgrade compared with that in the Birmingham area, but the bed is thin and somewhat lenticular. The presence of a large blast furnace at Alabama City, 3 miles from Gadsden, and the growing scarcity of red-iron ore supplies for it offered inducements for reopening the mine in 1946. Up to the time this circular was prepared (1947) only a small quantity of ore (about 1,500 tons) has been produced and shipped to the furnace. A force of 14 men was employed in sinking the main slope and developing a third "lift" (a local term for level) 100 feet below the old mine workings.

May 1, 1949

By G. L. Hundley

The Bureau of Mines has devised a procedure to recover chromium chemicals from concentrates derived from low-grade domestic chromites. These domestic chromites contain silicon and aluminum impurities at levels that are too high to permit processing by present industrial processes. The Bureau procedure consists of reacting chromite with molten NaOH under oxidizing conditions to form sodium chromate (Na2Cr04)' The reaction product is leached with methanol to recover the majority of the unreacted NaOH, then with water to extract the Na2Cr04 and the remainder of the NaOH. The Na2Cr04 product is recovered by evaporative crystallization from the aqueous solution. This report presents laboratory results of studies to determine the optimum leaching conditions for the reaction products of several domestic chromite concentrates. Results of solution purification and crystallization studies are also presented. The concentrates are from a variety of sources including the Stillwater Complex in Montana, Red Bluff Bay and the Kenai Peninsula in Alaska, and a Ni-Co laterite from southern Oregon. Sodium chromate crystals were produced that contained less than 0.01 pct NaOH.

Jan 1, 1988

By A. J. Barry

Recent developments in mechanizing longwall it mining in Europe have aroused considerable interest among American coal-mine operators because this method provides an opportunity to improve safety, production, efficiency, and recovery. The success of longwall mining in Europe has depended to a large degree on development of effective roof-control systems. One of the major contributing factors in designing these systems is development off improved supports, which combine high load-bearing capacities with controlled yield characteristics, to use in the face areas. Other factors that relate to successful longwall mining involve knowledge of the structural properties of the strata above end below the coal bed being mined, movements of these strata induced by mining, and effects of the strata movements on the strata itself, as well as on the support system used. Extensive studies of the above factors relating to long-wall mining have been made in coal-mining countries abroad, and corresponding studies (1, 2, 3, 4, 5)3/ of room-and-pillar operations have been made in this country. Although descriptions and results of experiments of mechanized longwall operations in the United States have been published (6, 7, 8), this is the first instrumented study of roof behavior on a longwall operation. In view of the possible widespread application of this method of mining to American coal mines, where underground mining conditions are different from those found in European mines, an investigation was conducted at a mechanized longwall operation inn the Lancashire No. 15 mine, Barnes & Tucker Co., Cambric County, Bakerton, Pa., to study the factors that affect roof control. This report describes this investigation and discusses the results. ACKNOWLEDGMENTS This investigation was made under a cooperative agreement between the Bureau of Mines and the Barnes & Tucker Co., Barnesboro, Pa., end was conducted in the Lancashire No. 15 mine located at Bakerton, Cambria County, Pa. The authors acknowledge the cooperation given by Richard Z. Todhunter, Sr., president, Richard T. Todhunter, Jr., general manager, and other mine officials and employees of the Barnes & Tucker Co. Mr. Edward Thomas, chief, Roof Control Section, Bureau of Mines, Washington, D. C., and Dr. Leonard Obert, chief, Applied Physics Branch. College Park, Md., collaborated in the planning and promulgation of the program investigation.

Jan 1, 1954

By Michael Sokaski

A dense-medium cyclone pilot plant was built to clean 112-inch to 0 size coal. This pilot plant does not require the removal of the extremely fine material (usually minus 1/2-mm) from the feed, which is necessary in conventional dense-medium cyclone plants. The essential difference between conventional cyclone plants and the pilot plant is in the medium-recovery system. The latter uses a combination of sieve bend screens, classifying cones, and magnetic separators for medium recovery. Eight tests were run in the pilot plant at a feed rate of 5 tons per hour with four different raw coals and one crushed jig middling product. Sharp separations were obtained as indicated by an average error area of 27 and probable error of 0.047 for the 112-inch to 200-mesh size range. Magnetite loss averaged about 2.5 pounds per ton of feed. The influence of several factors on cleaning performance of the cyclone was investigated. The diameters of both the overflow and underflow orifices were found to be important for optimum cleaning performance, but these diameters could vary over a wide range without serious effect; however, if this range was exceeded, cleaning performance deteriorated. Better cleaning performance was obtained when the cyclone inlet pressure was increased from 9 psig to 13 psig. The size of the magnetite particles in the medium was found to have a substantial effect, and the best cleaning results were obtained with grade B magnetite. Demagnetizing the magnetite in an effort to decrease the effective particle size did not improve cyclone performance.

Jan 1, 1963

By W. H. Tomlinson

One of the more important functions of the Federal Bureau of Mines is conservation of the life and health of employees of the mineral and allied industries. Since its very beginning the Bureau has encouraged competition between mine rescue and first-aid teams as a means of stimulating interest in safety and accident-prevention work. In addition to sponsoring competition on a national and international scale during the past 45 years, the Bureau has also assisted State mining departments, mining companies, and mining organizations in holding State, district, company, and other local meets. This assistance includes providing instructors to train teams, judges, and other contest officials. The Bureau has also furnished problems and outlines for working them, judges I discount sheets (scorecards), contest rules, and problem judges. In fact, Bureau representatives participate in nearly all State, district, and company contests and have bad complete charge of some contests.

Jan 1, 1956

By L. C. Brichta

During a study of the Badger-Peacock area from October 1950 to June 1953, the Federal Geological Survey and the Federal Bureau of Mines completed nearly 98 miles of resistivity profiling and drilled 96 test holes aggregating 17,628 feet of bore, In addition, seismic profile measurements were made along 8 traverse lines for an aggregate length of about 16,600 feet. The geophysical surveys were conducted by the Geophysics Branch of the Geological Survey; the drilling was done by the Bureau of Mines. Electrical-resistivity measurements disclosed 21 low-resistivity anomalies and 1 high-resistivity anomaly. Correlation of the resistivity data with the geological information revealed by the drilling disclosed that the low-resistivity anomalies indicated either slumped shale deposits in limestone sinks or undisturbed deposits of shale lying in erosional depressions in the limestone. The high-resistivity anomaly indicated hard, undisturbed limestone at or near the surface.

Jan 1, 1958

By M. E. Hawkins

Mineral analyses and electrical resistivity measurements of 324 representative samples of oilfield brines from 24 oil-productive counties in Mississippi and Alabama are presented in tabular form. Results of the mineral analyses, which include calcium, magnesium, carbonates, bicarbonates, sulfates, chlorides, sodium, and barium (with strontium if present), are reported in milligrams per liter. Electrical resistivity measurements in ohm-meter2 per meter at 75° F are reported in ohm-meters in the tables. Chemical analyses of formation waters are helpful to operators having water problems associated with petroleum recovery; electrical resistivity values are helpful in making interpretations from electric logs.

Jan 1, 1963

By H. E. Powell

A laboratory mineral-dressing investigation was conducted by the Federal Bureau of Mines on four limonitic and four sideritic iron ores from the North Basin of the east Texas iron-ore district. The samples, composited from drill cores, were considered representative of the iron-ore reserves of the area. The objectives of this research were twofold: (1) To devise a mineral-dressing method whereby the yield from currently mined east Texas iron ores might be increased and the grade improved, and (2) to extend such treatment to include the lower grade ferruginous materials that are not amenable to beneficiation by simple washing and, therefore, are not being exploited. Of the mineral-dressing methods used in this investigation, magnetic separation of roasted are was shown to be the most effective. Results show that, by this method, a laboratory recovery of 82 percent of the iron is attainable at a grade surpassing that obtained by current plant practice and that both limonite and siderite are amenable to concentration by the process. The existence of large deposits of iron are in eastern Texas has been recognized for over 100 years. These ores were first exploited during the Civil War and were mined intermittently until about 1911. From that time until 1944 when the Defense Plant Corporation financed the erection of three blast furnaces to use these east Texas ores, production was almost at a standstill.4/

Jan 1, 1960

Objective To develop and evaluate the effectiveness of safety training tools specific to underground metal/nonmetal mining. Background In a series of stakeholder meetings held in the western United States beginning in 1998, participants identified a critical lack of appropriate training materials applicable to metal/nonmetal mining. Participants in the meetings provided many insights into what types of training materials are most effective in dealing with both experienced and inexperienced miners. Most important was that the materials should be realistic and interesting and that some way should be found to capture the wisdom and expertise of older miners before they retired. In response, training videos that focus on safe practices during the mining cycle are being produced. Two videos one on handling explosives underground and one on identifying roof hazards and proper scaling techniques were completed during1999, and a third video is now available. This video, entitled “Ground Support...It’s Important, or Miner Mike Saves the Day,” presents information on why ground supports work and how to install them properly. Approach The new video, “Ground Support…It’s Important,” presents a scenario in which two young miners make a bad decision to leave some supports out in order to catch up in their mining cycle. An expert miner, “Miner Mike,” sees this potentially disastrous situation and educates the young miners about what could happen if they continued to leave supports out. He introduces the young miners to several expert miners, who explain how to install different types of supports correctly, as well as share what experience has taught them over the years. How It Works All footage was taken in operating, underground mines, using14 experts to provide the teaching. Because of the wide variety of supports used underground, it was necessary to focus on those types more common to hard-rock mining. While more complex support systems, such as shotcrete and cable bolts, are mentioned, detailed material is not included. In the course of educating young miners Jeff and Jason, Miner Mike provides information on— •Why supports are necessary in underground mines. •The main types of supports commonly used in underground hard-rock mines. •How supports work. •How holes for bolts are drilled correctly using jacklegs, drill jumbos, and bolting jumbos.• How wire mesh, wire panels, metal mats, and different types of bolts, including mechanical bolts, friction bolts, grouted bolts, and cable bolts, are installed properly. •How to recognize that supports have failed and what to do about it.

Jun 1, 2000

By Manuel Gomez

This report presents low-temperature tar data from studies by the Bureau of Mines of tars produced in an externally heated (entrained state) pilot-plant-scale retort. Analytical data covering 20 low-temperature tars, derived from the. carbonization of various ranks of foreign and domestic coals, are tabulated. The character of the tar is discussed in relationship to carbonizing conditions and the rank of coal. It is seen that in carbonization techniques that employ entrainment or fluidization of the coal particle, carbonization conditions are secondary to coal rank with respect to tar-oil yields and composition. The influence of distillation conditions on recoverable yields of tar products is presented. The probable yield of commercially important chemical products, based on a ton of pure (moisture- and ash-free) coal, are predicted. INTRODUCTION Low-temperature tars produced by entrainment or fluidized carbonization techniques that employ internally heated reactors represent the most nearly primary tart produced by industrial processes. In brief, such a process involves the application of a heat gradient to the coal particle "boiling" or suspended in a turbulent state in the reactor chamber. Conditions are observed so that the coal particle remains suspended within the reaction zone by a gas stream for a time interval commensurate with maximum tar-oil yield. The heat necessary for the carbonization reaction may be obtained entirely from the hot (preheated) gas stream, or it may be derived partly from the combustion of the volatile products and char by the transport gases, usually air. The volatile material moves out of the carbonizing zone at a rate that approaches the velocity of the transport gas. Carbonizing conditions are ideal when a minimum particle residence time is obtained within the reactor at a given temperature and a maximum yield of condensable volatile matter is released. In industrial practice this objective is a compromise.

Jan 1, 1957

By B. W. Moore

The U.S. Bureau of Mines investigated the separation of heavy rare-earth elements (REE) in an ion-exchange process. An ion-exchange column consisting of two sections, a loading section and a separation section, provides high levels of REE loading and good REE separation with an expected processing cycle of less than a month, while current ion-exchange technology requires more than 5 months. A different resin is used in each section: sulfonic resin in the loading section and iminodiacetic resin in the separation section. The separation section is further divided into two segments: the first conditioned with NH4 and the second with acid. Erbium is loaded onto both segments of the separation column as a retaining ion. Bands of mixed REB eluting between separated bands of pure REB were recycled directly to the column. Without mixed-band recycle, over 80% of the REE eluted from the column was separated into fractions with 99% purity of each element; with such recycle, the percentage of separated elements can be increased to around 90%.

Jan 1, 2010

By Edward D. Thimons

This Bureau of Mines report presents expected levels of air pollutants in the face areas of oil shale mines, based upon data collected by the authors and previous investigators. Ventilation requirements to maintain these pollutant levels below their threshold limit values and Federal and local mine air quality standards are discussed. Two practical face ventilation systems are discussed in terms of actual in-mine test experience.

Jan 1, 1986

By Timothy Y. Yen

This Bureau of Mines report evaluates audio dosimeters, 3 sample units from each of 10 currently marketed brands. Each dosimeter was treated as a "black box" with the acoustic stimulus as the input and the accumulated dosage as the output. The dosimeter microphones were exposed to a sound field gener¬ated in an anechoic chamber. Characteristics evaluated include frequency response (100 to 8,000 Hz), level-time trade-off rate (88 to 117 db), status of calibration, crest-handling capability, and power consumption rate. Experi¬mental errors revealed by replication of the tests were found to be generally much smaller than variations in performance among the samples of any brand, and possibilities of further reducing the magnitude of these errors are discussed.

Jan 1, 1977

By N. Kyriazi

A performance study of oxygen self-rescuers from the United States and other countries was undertaken as an assessment of present worldwide technology. The apparatus were tested a an breathing and metabolic simulator in the Life Support laboratories of the Bureau of Mines. Parameters monitored during the testing were inhaled levels of C02 and 02, inhaled gas temperature, and breathing resistance. The metabolic demand placed on the apparatus represented the average demand of the 50th percentile miner performing a 60- min man-test 4, as described in 30 CFR 11H. Results presented include ;apparatus service life and subjective comments as well as averages and peaks of monitored parameters.

Jan 1, 1984

By Dhanesh Chandra

[The U.S. Ucparunent of tlIe III LeriOr, Bureau of 1?Ilnes, lnta dcvcltil- (I a m.?tl,nd to extract nickel, i:ob.tll and IlIIicr Valuc:l,1, mrl?tl., lrom I.ow grad:, dumusI it Inlet itc.: :isin;; a rarb-i mnnnxid:: reducl.iun and ,innnonln/mumonlum sull,h.Ito Icitcll Col lowed by solved. evil let foil and clot tr:,winnfu,;. 'I 'o rain bcLtur undcI'sLandin;; uI the producLs reduced rind leached with the s;:Item, the liureau of t?Ilite; was enf,ngod In a 1 uinL sl.utly IIt1I the Uuttvcr ltc~:c:n-ch LnstiI-IL-. 'I'hr'ut;;h C(Im:drlod ahplit I¬L ion:; of a rotnbIW)L11nl ill eleu Lyon :utJ uplical inicrnscopy, cle trun beau micru,inal?;st?s and X-r.iv tcchnitlaes, Lhc factors jilt] ucncing low nickul e::lracl.on yLrids Iron, ccrlnin l;tteritos wul the hcuefhe al yCferL front addil.I:un u1. r:u)plowt' ruug,ounus and halides have bucn rrvealod. IL leas ht'en shown their nt nliJcrate Lion terlperuLuri's (5S0°C - 6501C) Lhe 111LACl extraction ylolds were low hccausc of the futmetlt-m of rufrill t,urv sillc:Ite compicxcs during ciii lit Hi [hut COOL.tlu sig nlficnnt anutunls of nickel .Lrui LhaL arc resistant Lu discolullull it, a su6r.C?quent ammnnlIca1 Jcaeh. 'This formation ill rulracLorv rnngtieves is altrlbuU?d Lo the prc.srnCV of aluauinum combined with c.ilicun jn addlt.lon In tnnl;neni~im in I.lic Lalerites, Iligb exII.Ictlon yields were oblalneJ when none or only a few I ,fraCLot' e, were InrmeJ. Hit s;intc rcfrarlnry cowl, Icxc5 also lend Lo surround Ow IaaIIiable meI.allle iron-IIIcI:el :iILoy CIUSisling ill the mau'ix, tIll: rrhv nreveu)Ling cuntacr ,Itlt LI5U Jeacl: solution; this, huwrvcr, ran ho ovu:rcoml by At ti itlon .111.11 retieCtiun. 'I'hc eIIcc l of prr.reJIctlun .,Ill itivi's vucli i's lye iii', ',udlum "Ill orIde, hv,Irogrn CIIInrILIC, etc., and Lht? 1111,Lre:InrLlI'll he'e:tleg un Lbe cxLt,icLitin are also iilsr.ussod 111 Lhe rcl,olt.]

Jan 1, 1979