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By B. J. Scheiner

Oxidation procedures based on the chlorine-hypochlorite system were investigated for improving gold recovery from carbonaceous gold ores. The oxidation pretreatment prior to cyanidation was accomplished by (1) addition of sodium hypochlorite to ore pulp, (2) by addition of chlorine to ore pulp, and (3) by generation of hypochlorite in situ by electrolysis of a brine solution used to pulp the ore. Gold extraction of 90 pct was achieved by cyanidation of carbonaceous ore that had been pretreated with 20 Ib per ton sodium hypochlorite at 50° C for 4 hours. Similarly, pretreatment of the ore pulp with 35 1b chlorine per ton at 24° to 30° C and 15 hours reaction time resulted in 89-pct gold extraction by subsequent cyanidation. Concomitant studies showed that electrolyzing the pulp prepared with a brine solution was equally as effective as electrolyzing hypochlorite and chlorine for oxidizing carbonaceous ore constituents that are deleterious to cyanidation. Gold extraction of 90 pct was obtained by electrolysis when 275 lb of are was treated at 200 amp for 7 hours in an 8-to 10-pct salt solution. Power consumption was in the range of 60 kwhr per ton.

Jan 1, 1972

By John P. Gooch

The solubility of 1,1,2,2-tetrabromoethane (TBE) in water was determined from 1.0° to 97.0° C. The solubility (S) of TBE in grams of solute per 100 grams water was correlated with [S = 1,920.55 [exp (40292L7 11, T2 10 T 737.577 + 9.923962 ] where T is in degrees Kelvin. A thermodynamic analysis conducted on a system consisting of a TBE phase and a water phase in equilibrium with a vapor phase led to the calculation of the activity coefficient, vapor-liquid equilibrium distribution coefficient, relative volatility, and heat of mixing for saturated solutions of TBE in water. Data required for these calculations were the solubility of TBE in water and the vapor pressures of TBE and water as a function of temperature.

Jan 1, 1972

By Valois R. Shea-Albin

An accurate assessment of the vertical stress on a coal seam at depth is important for mine design. Vertical stress calculation techniques presently available either are not sufficiently accurate or cannot handle complex surface topography. Therefore, the U.S. Bureau of Mines developed a computerized method to calculate vertical stress exerted on surfaces at depth that includes the effect of topography. Two input data sets are required: a digital elevation model containing topographic elevations and a coal seam file defining coal seam elevations at depth. Boussinesq's equation then quantifies the vertical stress resulting from topography. The computerized method was tested on a coal seam overlain by a complex topography where a vertical stress map encompassing several square miles was produced. Results show that depth mitigates the affects of surface topography, while the coal seam topography has a direct effect on the vertical stress. In comparison to the computerized method, the direct stress method overestimates stress under hills and underestimates stress under valleys. The largest difference between the two methods occurs under the steepest topographic relief. A limitation of the computerized method is that stresses cannot be accurately determined near an outcrop.

Jan 1, 2010

By A. C. Rice

This report describes a chemical process for preparing solutions of trivalent rare-earth chlorides from sulfate solutions obtained by treating bastnasite concentrate. The chief impurity in the final solution is cerium, and this element is less than 1 percent of the rare-earth oxides. The solution is used directly in the separation of rare-earth elements by ion-exchange methods. The attractive features of the process are that the chemicals are inexpensive and the steps few. The process starts with precipitating the rare-earth hydroxides from sulfate solutions with caustic soda. After the hydroxides are dried to oxidize the cerium, they are treated with dilute hydrochloric acid to dissolve away the trivalent rare-earth elements, leaving the tetravalent cerium. Details for controlling the leaching step are described. The process shortens older procedures by omitting the usual oxalate or double-sulfate-precipitation step.

Jan 1, 1959

By J. M. Mutmansky, C. Lee

"IntroductionRecognition of Coal Workers' Pneumoconiosis (CWP) as a major occupational disease has affected various aspects of the coal mining industry in the United States as well as in almost all major coal producing countries, Regulations related to the control of coal mine dust forced mine operators to modify their mining and ventilation practices. As the coal production record of the last 15 years shows, this had both direct and indirect impacts on the productivity and production costs.To identify the causes of CWP, many research efforts have been made throughout the world. Most of these studies were epidemiological in nature, attempting to pinpoint exposure and seam variables that affected the incidence of the disease. Other studies have been oriented toward the elemental and mineralogical composition of the coal dust in the mine atmosphere and in the miners' lungs. These studies indicate that there may exist some relationships between the characteristics of the coal mine dust and the prevalence of the disease. Some of the variables that are thought to affect the occurrence of CWP are the mass of the dust in the working place, the rank of the coal, the existence of certain trace elements, the free silica content of the coal, and the existence of other minerals in the respirable dust. A more complete description of these previous research studies has appeared elsewhere (Mutmansky and Lee, 1984).The behavior of particles in the human lung is known to be governed by their aerodynamic diameter, which is defined as the diameter of a hypothetical spherical particle with unit density that exhibits the same settling velocity as the given particle. Because of this fact, the aerodynamic size distribution of coal mine dust is one of the parameters to be determined along with the other physical, elemental, and mineralogical characteristics. The objective of this paper is to establish a strategy for providing coal mine respirable dust samples for characterization purposes using instruments that classify according to the aerodynamic diameter. In addition, several findings concerning characterization methods will be presented"

Mar 1, 1989

By F. E. Block, Robert R. Brown, A. W. Henderson

The chlorination of Cr₂ 03 (chromic oxide ) in the presence of carbon with CC14 (carbon tetrachloride ) and COCl2 (phosgene ) chlorinating agents was investigated by employing the radioactive tracer carbon By tagging carbon mixed with Cr₂ 0з , the chlorination reaction was evaluated in terms of the competitive reaction of the elemental carbon and the carbon contained by the chlorinating agent . A unique gas - analysis train was used to separate the chlorination product gases ; CO , CO₂ , and COC12 . The C¹ activity of the gases was determined and used to calculate the reactivity of each source of carbon . Reactivities were determined for the temperature range from 600 ° to 900 ° C. The results of the investigation show that each source of carbon reacts significantly with the Cr2 03 and that the reactivity of each form of carbon depends on the reaction temperature , and each form is independent of the other . Radioisotope and gas - analysis techniques are discussed and a description of the experimental apparatus is given .

Jan 1, 1964

By M. M. Kirk

Forced-air cooling of cold-mold arc furnaces for melting zirconium and similar metals has been investigated and found to be practical from the stand-point of heat transfer. It is believed that this technique offers a significant reduction in explosion hazard from that inherent in water cooling, the current industrial practice. A copper crucible, with longitudinal, integral-type fins and with an outer jacket to confine the airstream, appears to be the best general design for air-cooled operation. Cutting the fins into short segments and bending the segments to produce a herringbone effect increased the airstream's turbulence and was found, on test, to increase the heat transfer up to 35 percent.

Jan 1, 1959

By Robert W. Gordon

This report describes the results and conclusions of the further development of a lightweight probe drill for use in anthracite mines. Improvements to the drill previously developed under Contract H0282044 were made and tested at an Eastern Pennsylvania mine. These improvements were: 1. Better hole cleaning due to the development of an air-water mist flushing system. 2. The application of roof drill bits to allow drilling through rock seams and lenses. 3. The development of a quick coupling drill system which reduced total steel change time. 4. Adaptation of a swivel to the drill anchoring system which greatly reduced set-up time between holes. With these improvements the probe drill demonstrated its ability to drill the required 11 holes in one shift. It also gained miner acceptance as a viable underground working tool. The probe drill proved to meet all of the design requirements of portability, low weight drilling controllability, structural integrity and reliability. In addition to its ability to drill the required probe pattern, the probe drill has the capability of drilling long holes. By drilling several holes over 80 feet deep the probe drill has demonstrated a potential for use in robbing pillars and for methane drainage.

Jan 1, 1981

By George A. Bell

This paper reviewing the leaching practice of the New Cornelia mines of the Calumet & Arizona Mining Co. at Ajo, Ariz., is the first of a series being prepared by the Bureau of Mines on leaching methods and costs in the various mining districts. ACKNOWLEDGMENTS The author acknowledges the assistance of T. G. Chapman, consulting engineer, and E. D. Gardner, supervising engineer of the Southwest Experiment Station, Bureau of Mines, Tucson, Ariz.

Jan 1, 1930

By Martin Hertzberg

The early and reliable detection of the self-heating of combustible substances in mines is of considerable importance to the mining community. This Bureau of Mines report describes the results of a variety of studies of incipient combustion and its detection. Heated samples of coal, wood, and various polymers were used to evaluate the relative sensitivities of several types of detectors. The laboratory results indicate that submicrometer particulate detection is the most universal and sensitive method. Carbon monoxide detection was as sensitive as submicrometer particulate detection for pyrolyzing coal but was relatively insensitive to pyrolyzing wood or plastics. The conventional type of ionization smoke detector was the least sensitive for coal and of intermediate sensitivity for wood and plastics. Self-heating experiments with Pittsburgh seam coal piles of varying particle sizes gave ignition temperatures of 170° C for 4-to 7-µm dust, which increased monotonically with particle size. The measured heating rates were compared with data from an adiabatic calorimeter to obtain preexponential rate constants. The preexponential rate constants varied linearly with the surface area per unit mass of sample as would be expected for heterogeneous surface oxidation. The propagation behavior of ignition waves and the overall self-heating appears to depend critically on the magnitude of the convective flows induced, which counteract the depletion of oxygen in the void spaces of the pile. Classical theories of thermal ignition require substantial modification to be applied reliably to such cases.

Jan 1, 1977

By McHenry Mosier

The diamond-drill method was tried at the site selected for driving a 5- by 6 -foot air shaft at the east end of the Bellefonte mine . This method of sinking consisted , first , of drilling a 5-3/4 -inch-diameter cut hole from the surface , then drilling parallel 1.5 - inch ( EX ) holes around it at appropriate distances for a balanced blasting round . The cut hole was not charged with explosive but served as a relief chamber for the incipient expansion of the ground broken by. blasting the surrounding 1.5 - inch holes . The length of each hole was 236 feet , which was the finished depth of the shaft . The nature of the work in the air shaft was largely experimental , and many difficulties arising from the lack of special equipment and proper technique for precise alinement of the drill holes caused expensive delays before they could be overcome . Drilling the 5-3 /4 - inch hole , which was impeded by frequent core blocks in the core barrel , required 10 shifts . average advance per shift for an EX hole was about 150 feet . The The holes were charged and fired from the surface . The length of the section blasted in one cycle was 10 feet . Blasting progressed from the bottom of the shaft upward . The broken stone dropped into a chute , from which it was drawn into cars on the haulage level . The Bellefonte mine is an underground limestone mine.3/ The primary objective in undertaking the research on shaft sinking by diamond drilling was to perfect a method for driving connections between levels of the mine .

Oct 1, 1948

By H. S. Caldwell

A magnesium-base incendiary alloy, containing about 20 percent cadmium, 4 percent aluminum, and 0.5 percent zinc, was investigated in a series of vacuum-distillation experiments to determine the feasibility of recovering magnesium and cadmium as refined metals. Alloys prepared in the laboratory and actual bomb-casing alloy were studied at temperatures of 550° to 750° C. and pressures of 100 to 150 microns. Simple distillation and fractional distillation methods were only partly effective in separating the cadmium and magnesium. They were separated satisfactorily, however, with a special vapor baffle designed to condense the metals selectively. Magnesium and cadmium products were 99 percent pure and together comprised 82 percent of the total condensate. About 17 percent of the condensate was intermediate-grade alloy that could be recycled with new charge and contained about 70 percent magnesium and 30 percent cadmium.

Jan 1, 1959

By J. V. Batty

The Bureau of Mines devised techniques involving the use of beta-and gamma-ray-emitting radioisotopes and successfully adapted these techniques to the density of mineralized flotation froths) the rate of flow of finely ground ore pulps) and the residence time of pulps in processing circuits. Specifically, the water and mineral loads of flotation froths were continuously measured by determining the proportion of a constant-strength beam of beta rays that was absorbed by the froth column. Continuous measurement of the rate of flow of an ore pulp was accomplished by measuring the changing width of a free-falling stream of the pulp with a collimated beam of beta rays. The residence time of solids in conditioning and resin-in-pulp circuits was accurately measured by following the progress through these circuits of a portion of the pulp that had been tagged with the gamma-emitting Ag110 radioisotope.

Jan 1, 1966

By Linda C. Carrico

Those who manage the Nation's mineral resources rely upon a variety of organizations both public and private--to give them accurate mineral data, technical guidance, and expert advice. This directory provides a list of such organizations--a list that should prove a useful tool for those seeking mineral-related information and technical assistance. The directory lists Federal and State governmental agencies and national, regional, and State associations with activities in the mineral, metal, and material sectors of the economy. These organizations regulate mining, monitor mineral production, establish and enforce health and safety standards, identify and evaluate mineral resources, conduct scientific research, predict market trends, resolve environmental issues, and promote the interests of the mineral industry, its individual sectors, and its workers--to name a few of their functions. The listings in this directory--arranged by State--should help users who manage mineral resources identify agencies and organizations that can provide mineral-related information or technical assistance.

Jan 1, 1993

By R. G. Sandberg

The Bureau of Mines investigated a hydrometallurgical procedure to recover gold, silver, and byproduct lead from a complex lead-zinc sulfide ore. A ferric chloride (FeCI3) preleach, at 40° C in 6 h, extracted about 50 pct of the zinc and formed insoluble silver and lead chlorides. Subsequent acid thiourea leaching, for 1 to 3 h at 40° C, extracted about 85 pct of the gold and silver. Lead chloride was solubilized from the remaining residue with NaCI brine solution at 55° C in 1 h. Lead metal was recovered from the brine solution in an electrolytic cell with an anion perms elective membrane at a current efficiency of 95 pct and current density of 100 A/m2. Spent FeCl3 leach solution was reoxidized in the anode compartment at a current efficiency between 75 and 95 pct.

Jan 1, 1986

By J. E. Pahlman

Spontaneous oxidation and combustion of sulfides and resultant fires are serious problems in underground mines. The Bureau of Mines has con-ducted fundamental thermal gravimetric analysis (TGA) research to deter-mine the mechanisms and factors governing the rate of low-temperature pyrite oxidation, and to identify possible inhibitors to spontaneous oxidation and combustion. The mechanism of low-temperature pyrite oxidation was found to be topochemical, meaning that the oxidation process is controlled by the chemical reaction at the interface between pyrite (FeS2) and iron sulfate (FeS04)' An activation energy of 8.9 kcal/mol FeS2 was obtained for oxidation of minus 500-mesh pyrite in an atmosphere of 60 vol pct water vapor and 40 vol pct . Water-vapor content of the atmosphere was found to be the critical factor in the rate of spontaneous oxidation of pyrite, with a water-vapor content greater than 20 vol pct needed for accelerated oxidation. An atmosphere of pure oxygen resulted in negligible oxidation. The rate of pyrite oxidation is also greatly affected by the particle size of pyrite. Pyrite-oxidation rate increased drastically for particles less than 40 ~m. Room-temperature pyrophoric behavior was observed for freshly ground unoxidized pyrite (55 pct minus 5 ~m) upon exposure to air. Addition of water-adsorbing materials such as activated alumina (Alz03) decreased the rate of pyrite oxidation.

Jan 1, 1986

By H. E. Powell, T. E. Hill, W. A. Calhoun

The object of this investigation was to determine the effectiveness of certain cationic flotation collectors , Ethomeens , in recovering fine particles of lead minerals from mill tailings at a grade equal , at least , to that of the mill feed ( 1.7 percent lead ) . The Ethomeens , derived from tertiary amines having one fatty alkyl group and two polyoxyethylene groups attached to the nitrogen , were evaluated by bench- scale flotation tests . The 14 Ethomeens tested consisted of four groups : Coco amine , soybean amine , tallow amine , and stearyl amine . The best results were obtained with coco amine C / 12 , soybean amine S/ 15 , tallow amine T / 12 , and stearyl amine 18/20 . From a feed containing 0.23 percent lead , rougher concentrate grades of 2.12 to 3.89 percent lead were obtained , with recoveries of 17.3 to 27.5 percent of the total lead . Some of the lead mineral particles recovered had diameters of less than 1 micron . In comparative tests , the Ethomeens , or polyethoxylated amine types of cationic surface active agents , were more selective than conventional xanthate collectors for flotation of slimed lead minerals .

Jan 1, 1964

By M. B. Royer

Sulfur is present in many ores and other raw materials that are used in the production of metals and alloys of industrial importance. Its presence, especially in ferrous-metal products, generally is undesirable because of its detrimental effect during processing and upon various physical properties of the finished metal. Therefore, various methods are resorted to for elimination of the element to some specified maximum final content. Such removal or elimination of sulfur is designated as desulfurization.

Jan 1, 1948

By Charles Will Wright

This paper has been written to aid the owner of a small gold mine or prospect in preparing a report on his property for the purpose of interesting capital. If an owner can afford to do so, he should employ a mining engineer of recognized standing and experience to examine and report on his property, but many owners of small -mines and particularly of prospects cannot make the expenditure required for this. Further, many of them do not know how to prepare a description which will cover those features of a deposit on which a potential investor promises his opinion as to its worth. If such an owner is convinced that he possesses an orebody of sufficient grade and size to warrant the required expenditure for a thorough investigation and wishes to present his property to prospective investors, then the following suggestions concerning the proper way to sample his deposit, estimate the tonnage of developed and probable ore, and prepare a report may be of assistance.

Jan 1, 1933

By C. C. Stevenson, Thomas Varley

"The art of treating ores by the chloride volatilization process is still in the experimental stage. The process has not been sufficiently developed along chemical and metallurgical lines to state definitely just what place it will occupy in the metallurgical industry. The theory upon which the process operates has received the attention of prominent metallurgists for the past twenty years, and research and experimental work has been conducted by many investigators.Much of the experimental work done has never been published, and it seems that the accumulation of such results if made known would be an important aid to the further development of the process. The object of this paper is, therefore, to bring salient features of the process to the attention of the metallurgical industry, both for the purpose of furnishing information, and receiving from interested parties any comments which the reading of this article may suggest. A bulletin covering the work done at the Intermountain experiment station of the U. S. Bureau of Mines, situated at Salt Lake City, Utah, is in course of preparation.The chloridizing roast is usually accompanied by appreciable losses due, to the volatilization of the metals as chlorides during the roast, these losses often running as high as 30 per cent, depending upon the temperature, the character of the ores and the associated gangue material. It was not until 1891 that Croasdale, (Croasdale, Stuart, Engineering and Mining Journal, Aug. 29 1903) by observing this and stack deposits from the chloridizing roast, recognized the possibility of making volatilization a major instead of a minor feature of the roast. He then made tests on a large number of tires from different, localities, the result of which showed the, general application of the process. The main difficulty, as stated, by Croasdale, was the lack of a suitable means for recovering the fume from the furnace gasesIn 1913, Cottrell (See Mining and Scientific Press, March 29, 1913; alsoTrans. American Institute of Mining Engineering, September 1918. (Additional informa-tion is available from the owners, The Research Corporation of New lark, and Western Precipitation Co., .Los Angeles, Calif.), announced his invention of the electrostatic precipitator, which solved the problem of separating the solids from the furnace gases."

May 1, 1921