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By A. Cecala, J. Noll, J. Hummer

"NIOSH has observed that many control rooms and operator compartments in the US mining industry do not have filtration systems capable of maintaining low dust concentrations in these areas. In this study at a mineral processing plant, to reduce respirable dust concentrations in a control room which had no cleaning system for intake air, a filtration/pressurization system originally designed for enclosed cabs was modified and installed. Eighty-seven percent of submicron particles were reduced by the system at static conditions, meaning that greater than eighty-seven percent of respirable dust particles should be reduced. The particle size distribution for respirable dust particles are greater than for submicron particles, and filtration systems usually are more efficient in capturing the larger particles. A positive pressure near 0.02 inches of water gauge was produced which is an important component for an effective system and minimizes particles (e.g. dust) from entering into the room. The intake airflow was around 118 cfm, which is greater than the airflow suggested by ASHRAE for acceptable indoor air quality. INTRODUCTION Chronic overexposure to respirable silica dust (particle diameter < 10 microns) leads to a progressive lung disease known as silicosis. Workers who develop silicosis have an increased incidence of lung cancer and pulmonary disorders. In June 1997, the International Agency for Research on Cancer (1) found sufficient evidence to declare that inhaled crystalline silica in the form of quartz and cristobalite is carcinogenic. Mining is one of the leading industries for occupational exposure to silica dust (2-7). Control rooms located in dusty areas in some mines are of particular concern (8). Many mineral processing operations utilize operator’s compartments and/or control rooms to house workers who are performing particular job functions. Most industrial processing mills have rooms where a worker looks out over the facility and has direct control over the product flow throughout the entire building. In addition, primary crusher operators are often located in a compartment from which they are able to view the primary crushing function. Their job is to control when trucks dump into the primary jaw crusher and the rate of feed of the ore from the hopper into the crusher. Many of these control rooms and operator booths do not have filtration systems capable of cleaning air entering the control room or booth, which can result in elevated concentrations of dust in the room or booth. To reduce the dust concentrations in these rooms, it would make sense to clean the entering air with filtration/pressurization units similar to those proven to provide a clean environment in enclosed cabs."

Jan 1, 2016

By A. Brian Hawkins

"When pyrite oxidizes in dark grey/black, calcareous, mudrocks or in argillaceous limestones, ferrous sulfate is formed and sulfuric acid is released. The sulfuric acid combines with the calcite present in the rock and calcium sulfate (gypsum) develops. When this occurs on the outer edges of aggregate particles, the gypsum forms in the matrix hence there may be little expansion of the general material. However, when the chemical reactions occur within the rock fragments, particularly on microscopic, clayrich, laminae, the developing crystals exert a significant pressure on the host material. If the rock is medium strong to strong, the force of crystallization splits the rock along the weaker planes, facilitating the ingress of the oxidizing agents and the continuation of the chemical reactions. In addition to causing dilation/heave, some of the engineering properties of the material are changed, including the strength, Los Angeles value, water absorption etc. As a consequence material, which at the time of quarrying would be acceptable for use beneath floors or hardstandings, would no longer be considered suitable.INTRODUCTIONMudrocks accreting in aerobic environments are frequently disturbed by organisms and as a consequence there is often little sign of bedding. In contrast, sediments which have formed in anoxic environments commonly have distinct bedding planes which, because of the grain size of the accreting material, are often smooth and planar. These rocks are frequently referred to as shales, which O’Brien and Slatt (1990) define as “characterised by a finely laminated structure, which imparts a fissility approximately parallel to the bedding.” This should not be confused with rhythmic bedding where the variation in grain size results in lithological laminations or colour changes.Early geologists, in the stratigraphic naming of rocks, often used the term shale for material which is now more likely to be described as mudstone or mudrock (Hawkins and Pinches, 1992). In many contexts, the width of the bedding is an important factor, not only in determining the rock name but also in indicating the potential engineering characteristics. Until recently a shale was considered to have bedding separations of less than 20mm, i.e. the bedding was described as laminated. However, in an engineering context, EN 14689: 2003, Annex A, defines shale by specifying a bedding thickness of < 6mm; such a material would be described as thinly laminated in BS 5930:1999. Ideally the term shale should be abandoned and be replaced by fissile mudstone or fissile mudrock."

Jan 1, 2015

By Shilpa S. Haramkar, Bhaskar N. Thorat, Sachin V. Jadhav

The filtration of phosphogypsum is a ubiquitous step in the manufacturing of phosphoric acid. It is highly desired to achieve the minimum concentration of P2O5 in the phosphogypsum cake. This work is aimed at addressing P2O5 losses in phosphogypsum (PG) along with the recovery of P2O5 from slurry by using constant pressure filtration at 1 bar pressure. Laboratory tests were carried out in the phosphoric acid production plant situated in Paradeep, India. Recycled water source near acid plant (i.e., pond water) was used for cake washing to reduce the burden on fresh water stock. The findings indicated that pressure filtration offered the most effective P2O5 recovery (nearly 93.48%). The moisture was reduced to 14–16%, and watersoluble P2O5 in the gypsum cake was found to be negligible. A narrow particle size distribution was observed, which offered effective filterability with average cake resistance of 2.38 × 1010 m/kg, indicating a moderately separable cake.

Aug 23, 2023

By N. P. Gallagher

The U.S. Bureau of Mines investigated a hydrothermal sulfidation (HTS) and chloride leaching procedure to recover lead and silver from plumbojarosite. The plumbojarosite, generated during pressure-oxidative leaching of zinc concentrate in a commercial operation, contained, in percent, 25.4 Pb, 18.8 Fe, 1.4 Zn, 29.5 sulfate (S042.), 3.2 elemental sulfur (SO), 13.4 total S, and 7.4 tr oz/st Ag. The HTS was conducted in an autoclave and converted the plumbojarosite into amorphous iron oxide and liberated the Pb and Ag as sulfides (S2) The best operating conditions were 50 g of plumbojarosite and 7 pct So (2.04 g So added) in 500 mL of 2.0-mol/L NH3 at 150° C for 1 h. The sulfidation product contained, in percent, 37 Pb, 28 Fe, 2 S042., 7 total S, and 11.2 tr oz/st Ag. Flotation of the sulfidation product was conducted at pH 3 with 15-pct pulp density and 2.4lb/st of isopropyl xanthate as collector. The flotation concentrate contained 43 pct Pb, 25 pct Fe, and 13 tr oz/st Ag. FeCl3 leaching of the sulfidation product in a resin kettle extracted 98 pct Pb and 97 pct Ag from the sulfidation product, and HCI-Oz leaching in a shaker glass bottle extracted 99 pct Pb and 98 pct Ag. Both leach residues met the Environmental Protection Agency&apos;s Toxicity Characteristic Leaching Procedure (EPA-TCLP) standards for nonhazardous wastes. The HTS and chloride leaching procedure is a potentially effective method for detoxification of plumbojarosite-bearing residue from the zinc pressure-leaching circuit.

Jan 1, 1989

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 T. Tempel

In 1994 Newmont Gold Company commissioned a 2.5 Mt/a refractory gold ore roasting plant near Carlin Nevada. Many unique characteristics of this facility required use of specialized materials of construction in the areas of dry grinding, roasting, gas cleaning, and sulfuric acid production. Process conditions and design criteria that necessitated the use of special materials include; siliceous and abrasive ore, low roasting temperatures, gas streams with high concentrations of oxygen and sulfur, and stringent environmental regulations. Materials selected for use were ceramics, corrosion resistant steels, high temperature steels, and high temperature polymers, lead, polypropylene and low flammability PVC.

Jan 1, 1997

By A. Yadav, B. Behera, G. S. P. Singh

The size of chain pillars in the Indian geo-mining conditions is primarily decided in accordance with the regulatory provisions. These provisions are of little help for deep longwall workings, exceeding the cover depth of 360 m. Furthermore, these provisions are primarily meant to support pillars in bord and pillar workings. They may not be suitable for the chain pillars owing to a significant difference in layouts and functional requirements. Hence, it is imperative to develop a method to evaluate the stability of the chain pillar considering the complex loading and geo-mining conditions. To this end, a machine learning-based model was developed in this study to assess the stability of the chain pillars under high depth of cover considering the field-representative conditions. The data for this work was generated by conducting a parametric study using a field-validated numerical model. The strength and deformability parameters of the caved, fractured, and continuous deformation zones were established by calibrating the numerical model outcomes against the site-specific field observations. The developed ML model was used to evaluate the influence of pillar width, pillar height, cover depth, abutment angle, face length, coal strength, moduli ratio of the roof and floor strata to the coal seam, and the elastic modulus and unit weight of the overburden on the chain pillar stability. An interesting finding of this study showed that the factor of safety of the chain pillar increased with the increasing abutment angle, which may be indicative of the confining effect of the abutment angle on the pillar. Eventually, the ML model was verified by comparing its outcomes with the calibrated numerical model for a typical longwall working from Indian geo-mining conditions.

Oct 18, 2023

By S. K. Kawatra

A high calcium fluid-bed combustor ash has been shown to be an effective binder at dosages of 1 to 2% of the magnetite concentrate weight. Magnetite pellets 1.3 cm (1/2 inch) in diameter were produced with dry crushing strengths greater than 22.3 Newtons/pellet (5.0 pounds force/pellet), which is comparable to the results produced using conventional bentonite binder. The effectiveness of fly-ash-based binders was considerably improved when calcium chloride was added as an accelerator. Addition of calcium chloride at a rate of 0.1 to 0.2% of the total powder weight increased the strength of dried pellets by as much as 22% compared to the strength of pellets made using fly-ash without accelerators.

Jan 1, 1997

By J. Stachulak

In recent years more emphasis has been placed on the control of nitrogen dioxide (NO2) emissions from mining diesel equipment. Worldwide, diesel engine regulations to control emission and protect the environment are also driving the development of the diesel engine technology to reduce oxides of nitrogen NOx (Nitric oxide, NO + NO2). NOx are toxic gases produced in mines during the operation of diesel equipment. Most of the diesel equipment used in underground operations are equipped with Diesel Oxidization Catalysts (DOCs) designed to reduce carbon monoxide (CO) and hydrocarbons (HC). The effects of DOCs on NO2 production from diesel powered equipment is not well understood. DOCs do not alter NOx concentration, but may promote the oxidization of engine exhaust NO to the more toxic NO2, thus increasing the undesirable NO2 exposure of workers in the mine environment. In 2012, the ACGIH reduced the NO2 TLV concentration value from 3 ppm to 0.2 ppm. Vale and CanmetMINING have been involved in several research projects to reduce diesel emissions exposure to workers. One aspect of the current program is to determine the effects of in-use DOCs on NO2 production. Several in-use DOCs taken from mining equipment were selected for testing in the laboratory using ISO 8178-C1 and mine LHD transient test cycles. The paper presents the laboratory test results and effects of DOCs on NO2 production. The results indicate significant reductions in CO concentration, by over 77%, while increases in NO2 varied from 46% to 315% based on the ISO 8178-C1 8-mode steady state test cycle. The mine LHD transient test cycle showed the same pattern, although the magnitude of CO reduction was less. Consequently, it is recommended the use of only those DOCs that have been properly evaluated and shown not to significantly increase NO2 emission in the environment be used on mine equipment.

Aug 1, 2013

By Claus G. Goetzel

POWDER metallurgy is known as the art of producing metal powders and fabricating them in a nonfusion process by a simultaneous or consecutive application of pressure and heat under controlled operating conditions. Before the advent of powder metallurgy, the high melting points of the refractory metals and nonmetals made their manufacture and use practically impossible. Today, however, the uses of refractory materials in high-speed cutting tools, surgical instruments, brake linings, electrical contact switches, and filaments in incandescent lamps are commonplace in industry. Lately designers have even been turning to powder metallurgists to develop new techniques of fabricating refractory materials for extreme-service use in high-temperature zones of such modern products as gas turbines and jet engines. The new techniques being born will undoubtedly provide industry with a great number of new alloys and materials for future designing.

Jan 1, 1948

By I. Soosaiprakasam

This work investigated inhibition performance of copper carbonate (CuCO3), which is less toxic than conventional heavy-metal corrosion inhibitors in amine treating plants, The investigation was experimentally carried out in a bench-scale electrochemical corrosion cell under an atmospheric pressure, The inhibition performance of CuCO3 in an aqueous solution of monoethanolamine (MEA) was examined under a wide range of operating conditions and reported as a function of process parameters including inhibitor concentration, temperature and solution velocity, The results show that CuCO3 functions as an anodic inhibitor. The addition of CuCO3 decreases corrosion rate of carbon steel but might induce pitting corrosion/

Jan 1, 2005

By D. Lambert

Process modeling for large deformation metal forming processes has been developed into a very successful tool in commercial applications during the last two decades. DEFOR.MTM is a well-known metal forming process simulation program used by many industrial and research institutions. Recent developments include the ability to model multiple deforming body behavior during multi-pass pack rolling and microstructure prediction during multi-pass shape rolling. This paper summarizes how DEFOR.MTM can be applied to a number of rolling processes and briefly describes preliminary work carried out using the ALE technique. Keywords: Simulation, Rolling, Pack, Shape, Microstructure, FEM, ALE, Tantalum

Jan 1, 2003

By Sylwia Zymankowska-Kumon, Rafal Danko, Józef Danko, Mariusz Holtzer

"Burning of ceramic materials is carried out at temperatures 900+ 1300°C, in dependence of the required functional properties. The Faculty of Foundry Engineering together with the Faculty of Material Engineering and Ceramics developed the technology of production of burned ceramic materials with using spent moulding and core sands. The mentioned above waste materials of the foundry industry fulfilled -in plastic masses intended for obtaining ceramic materials -the role of the addition weakening clay raw materials. The laboratory investigations were fully verified by the results of industrial tests. It should be pointed out that none negative effects were observed at the stage of mixing raw materials and preparation of plastic masses. The measurements of exhaust gases emissions performed during burning the products containing spent moulding sands as well as during the normal production did not exhibit any significant differences, which could have indicated the harmful impact on the natural environment.IntroductionSands are used by the foundry industry to make metal casting molds and are a mixture of silica sand, bentonite clay and carbonaceous additives or resins. During the casting process, the molten metal cause thermal decomposition of carbonaceous additives or resins, which results in the formation of potentially hazardous organics, that are emitted to the atmosphere and condense in the molding sand. Each year the U.S. foundry industry landfills about 10 million tones of sand because it is no longer suitable to make metal casting molds. A large high-silica sand content in spent foundry sands (SFSs) generates rational premises for their reuse in other than foundry practice fields. Efforts to divert the SFSs from landfills and encourage their beneficial use in manufactured soils, geotechnical applications, the construction industry (road construction, highway construction), the building materials industry (cement, bricks, limestone manufacture), in the filling of mining cavities or in landfill construction (roads on landfills, permanent covers) are make [1-7]."

Jan 1, 2013

By Allana Cristina Pires Ferreira

O endurecimento secundário de aço rápido AISI M3:2 nome comercial Sinter 23 obtido por uma técnica de metalurgia do pó de sinterização por compactação isostática a quente é objeto desse trabalho de pesquisa. O aço rápido em questão foi austenitizado em banho de sal a 1.140°C, 1.160°C, 1.180°C e 1.200°C, temperado ao ar e revenimento a 540°C, 560°C e 580°C. Amostras do aço rápido foram fabricadas e submetidas ao tratamento térmico acima descrito e submetida a ensaios de dureza Vickers e Rockwell C para a determinação das suas respostas ao tratamento térmico de endurecimento e avaliação do pico de endurecimento secundário através dos resultados de dureza.

Aug 16, 2017

By Xie Hao

According to its raw materials orthogonal test scheme is designed and a large number of systemic experiments were carried out in order to study the sintering characteristics of three types of fine ores in Kunming Iron&Steel Co.Ltd(KISC). The effects of carbon mixture ratio and basicity on sintering time, agglomeration ratio, physical properties and utilize coefficient were researched via single factor analysis and range analysis. The experimental results show the best mixture ratio of each fine ore. Analysis found that the influence of the carbon mixture ratio is more significant than which of the basicity on the sintering process except agglomeration ratio of foreign ore.

Jan 1, 2009

By D. D. Gertenbach

"The successful commercialization of a pressure oxidation (POX) process for recovering metal values, including gold, copper, zinc, nickel and molybdenum, is the result of a carefully planned development program. The initial task involves developing one or more conceptual flowsheets, including the POX autoclave and downstream purification and recovery steps. A laboratory program is completed to determine the technical viability of the flowsheets, define the operating parameters for each step and provide information for an initial economic assessment of the process. The process is then confirmed during a continuous pilot plant program, providing engineering design data and other information for the commercial design. A well-thought-out development program has been shown to be critical for reducing the risk of commercializing POX processes. Experiences developing POX processes for refractory gold ores and copper concentrates are briefly discussed. IntroductionPressure oxidation (POX) has become a common commercial operation for processing sulfide-bearing feedstocks. These feedstocks include gold ores and concentrates; copper concentrates; nickel concentrates and mattes; zinc concentrates; and molybdenum concentrates. Drivers for the development and commercialization of POX processes include:• The high cost for pyrometallurgical processing of sulfide ores, much of which is attributed to environmental controls.• The motivation to implement safe and more environmentally attractive alternatives for sulfide ores.• The need to process increasingly difficult ores with complex mineralogy.• Improvements made over the last 25 years in POX equipment design and experience operating commercial POX plants.Although the capital and operating costs for commercial POX processing can be high, this technology is capable of rapid oxidation of most sulfides and arsenic minerals in the feed, with little noxious gases and environmentally stable iron arsenate and other iron compounds in the POX residue (Marsden and House, 2006).In POX operations, sulfides are oxidized to either sulfates or elemental sulfur in an autoclave at elevated temperature and pressure with oxygen gas. An example is the overall oxidation reactions of chalcopyrite when sufficient oxygen is present, shown in the following reactions:"

Jan 1, 2016

By Jamel Sgaoula

During 1998 COGEMA Resources Inc. announced that operations at the Cluff Lake mine will be suspended indefinitely by the end of year 2000 as a result of deteriorating uranium market conditions. To remain profitable, Cluff Lake mine started an aggressive cost reduction program. A cost reduction team was formed to look for ways to lower production costs. The focus of this team was to screen all areas and to come up with ideas to improve the economy of the mine and ensure the viability of the operations over the remaining three years of operations. Among the areas where significant savings were achieved are: (1) replacement of portion of cement with fly ash in backfill; (2) backfill optimization; and (3) new shotcrete plant installation on site for bulk in-house shotcrete production. This paper details the research work carried out by Cluff Lake mine on these projects and results of its application.

May 1, 2001

By Edmund S. Leaver, Charles E. Van Barneveld

In response to numerous requests from metallurgists and operators for information regarding the status of the sulphur dioxide leaching process , developed at the Southwest experiment station of the U. S. Bureau of Mines , Tucson , Ariz . , the following statement has been prepared . A more complete report is now in course of publication and will appear as Technical Paper 312. This process was devised to provide a cheap and efficient method for treating the so- called "porphyry " copper ores of the Southwest which generally contain both " sulphide " and "nonsulphide " copper minerals , mixed in such proportions that they can only be satisfactorily treated by a method which will concurrently recover both the sulphide copper and the nonsulphide copper . The latter term has been adopted to include all the minerals commonly referred to in operating phraseology in the mills of the Southwest as " oxidized" , " oxide " , or " soluble " copper . confident that the sulphide dioxide leaching process , as developed by us with the cooperation of the Miami Copper Co. and the Arizona Copper Co. , is suitable and commercially available for a wide range of ores .

May 1, 1922

By V. E. Edlund

As part of its efforts to devise new and improved methods for recovering lithium from unconventional resources , the Bureau of Mines investigated a lime -gypsum- roast , water- leach technique for processing lithiumenriched ( 0.01-0.68 pct Li ) clays . This report presents the results of a study of the technical feasibility of extracting lithium from raw material representative of clay beds associated with the McDermitt Caldera complex in Nevada and Oregon . prepared from water used Pellets suitable for bench-scale roasting studies were mixtures of minus 200 -mesh clay , limestone , and gypsum , with as the pelletizing agent . Roasting pelletized charges at 900 ° to 1,000° C temperatures for 1- to 4-h periods produced calcines that leached readily , yielding water - soluble lithium sulfate ( Li₂SO4 ) . A 5-3-3 ( weight ratio ) mix of clay , limestone , and gypsum produced calcines with the best leaching characteristics . More than 91 pct of the contained lithium was extracted from pelletized mix batches roasted in covered refractory boats . Lithium recovery decreased to about 87 pct when the mix was roasted under dynamic conditions in a gas - fired rotary furnace . A reaction mechanism was postulated which indicated that dilution and loss of SO2 and oxygen in the combustion exhaust adversely affected the leachability of the dynamically roasted calcine .

Jan 1, 1983

By James P. Sloss

A PERMANENT assay office is commonly established as part of the general plant equipment of operating gold and silver properties, but during the development stage of a mine, the cost of such an office is usually so assay work must be done elsewhere. In most instances only a few samples will be taken each day, but if the mine is to be developed scientifically, the analyses of those samples will guide further development. Under such circumstances, the time element in assay returns is important, since the lapse between the taking of the samples and the receipt of results may determine the success or failure of a small-mine operator. The following description of fur-

Jan 1, 1935