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By M. A. Hammer

In this study by the Federal Bureau of Mines Pennsylvania anthracite from the Eastern Middle field was oxidized by concentrated nitric acid at steam-bath temperature for 24 to 1,000 hours. The quantitative data obtained include yields of nitric-acid soluble and insoluble products and the distribution of carbon and ash in each. The acid-insoluble residues were examined for solubility in aqueous sodium hydroxide. With a sodium hydroxide concentration of at least 1 normal, a portion of the residue could be extracted in the form of a true solution. With lower alkali concentrations, peptization occurred. Alkali solubility of the residue increased with length of oxidation. However, when expressed in percentages of original coal weight, the alkali solubility remained essentially constant after 192 hours of oxidation. This suggests that the alkali-soluble products are converted to acid-soluble products at the same rate as the original coal substance is converted to alkali-soluble material. Microscopic observations of the peptization of the acid-insoluble residues revealed a gross micellar physical structure. The action of nitric acid is apparently not restricted to the surface of a coal particle. The acid penetrates the particle through the pore structure, dissolving some of the ash and altering the bonds between the coal micelles. The bond alteration, as indicated by ultimate analyses, involves the physical and chemical adsorption of the components of nitric acid. Some of the altered bonds are not thermally stable; this instability is shown by the complete loss of peptizing ability when the acid-insoluble products are heated above 200° C. This loss is accompanied by the evolution of water, oxides of nitrogen, and hydrocyanic acid.

Jan 1, 1961

By Gregory R. Gorrell

The legal issues surrounding the regulation of subsidence are among the major concerns facing the underground mining industry today. Whether subsidence occurs almost immediately as a result of longwall mining or without warning as a result of room and pillar mining conducted years ago, the resulting disputes are highly controversial and typical of the disputes involving the competing interests of surface and mineral estate owners. Until recently, the law governing these disputes was firmly established under the common law. The passage of the Surface Mining Control and Reclamation Act 1, the utilization of new mining technologies, and the general heightened environmental awareness of our times, however, have interjected new issues into this area of the law. State and Federal court decisions and administrative agency interpretations have helped clarify some of the issues. However, as evidenced by the many recent lawsuits between operators, surface owners, and regulatory agencies, many uncertainties still exist.

Jan 1, 1986

By P. R. Day, W. K. Webster

"The introduction of large boreholes underground initially involved taking the techniques of open-pit bench blasting to the production stope, but with deeper boreholes and narrower stopes more controlled techniques must be developed in order to maintain good stope walls and prevent dilution of ore or structural damage to pillars due to blasting overbreak. The points discussed are drilling accuracy and drill pattern, the relationship between open-pit wall control and underground mining, the varied explosives products and initiation devices available, and some of the many ways that variations in loading, such as deck charging, etc., can produce desirable results.IntroductionThe use of large-diameter blastholes for underground mining began ten years ago and today they are widely employed in a variety of orebodies and stope configurations. These big blastholes, which range in size from 4.5 to 8 inches in diameter, were originally employed in the same manner ' as open-pit bench blasts; that is, the stope was silled out to full width and all holes were drilled vertical and parallel. This was suitable for competent, massive orebodies, however the popularity of the big drills saw their usage in more narrow stopes, often with poor ground conditions. The dipping orebodies and small drill sublevels resulted in inclined drilling.Today, there is full-ring drilling of 4.5-inch holes. Some 6.5-inch holes are drilled up to 350 feet deep. A 350-foot borehole may contain 6000 to 7000 pounds of explosive. The detonation of this size of charge weight within the confines of an underground stope can have considerable effect on the stability of stope walls and adjacent pillars. Obviously, precautions must be taken to minimize the damage which would result from the large charge weights possible with these big boreholes."

Jan 1, 1982

By Michael Day, Paul Kos, Scott Brinton

A hydrogeologic characterization and impact analysis was performed for a proposed quarry at the Hitch Rack Ranch located in the Little Turkey Creek watershed southwest of Colorado Springs, Colorado. Continuous multiple channel tubing, nested piezometers, stream flow measurements, and mapping of known seeps were used to define the three-dimensional potentiometric distribution and areas of groundwater recharge and discharge. Water balance considerations, mass balance calculations, and potentiometric response to earth tides and barometric fluctuations confirmed that the granite fracture system in the ridge area of the proposed quarry has an extremely low bulk hydraulic conductivity resulting in minimal groundwater discharge to sustain the baseflow of Little Turkey Creek. The Little Turkey Creek valley forms the major conduit for groundwater flow exiting from the upper part of watershed underlain by granite. This conclusion has significant implications with respect to mine planning to minimize projected impacts to the hydrologic system and preserve this recharge component to downgradient Denver Basin sedimentary deposits.

By W. M. Dressel

This Bureau of Mines report describes a shaft closure demonstration project in which 11 inverted pyramid-shaped plugs were used to plug abandoned open mine shafts in Galena, KS, The inverted pyramid-shaped forms, fabricated from steelplate, were designed so that the inverted base would be larger, by 4 ft on a side, than the approximate size of the shaft opening at the surface residuum-solid rock interface. After the surface openings of the shafts were trimmed with a backhoe, the steel forms, complete with reinforcing, were lowered into the openings and filled with concrete; the remaining portions of the openings above the plugs were backfilled to slightly above the surrounding surface level with waste rock and soil. Location and elevation monuments were installed for long-tern evaluation of the success of the project.

Jan 1, 1985

By Robert L. de Beauchamp

The Bureau of Mines designed a chlorination apparatus to prepare CrCl2 free of CrCl3 by the direct reaction of chlorine and chromium. Equipment and procedures were developed for routine preparation of 25-pound batch quantities of anhydrous CrCl2. Calcium, iron, nickel, and silicon impurities were in the 0.01 to 0.05 percent range, and all other impurities were below 0.01 percent.

Jan 1, 1968

By Christophe Bragard, Brett Robinson

This paper reflects the challenges encountered during the construction of the light rail tunnels under Boyle Heights, in Los Angeles, California. Equipped with two state-of-the-art EPB TBMs, the construction team undertook the mining of twin bored tunnels in the Los Angeles alluvium. The gassy underground conditions dictated many aspects of the design of the tunnels, as well as the tools and means used for their construction. This paper will detail the challenges encountered during construction, as well as the means, methods and logistics used on the project. Discussion includes: EPB TBM machines with some very unique/specific features; complex assembly sequence due to limited shaft access; final precast concrete liner with double gaskets; NATM cross passage excavation in soft ground and below the water table; compensation grouting; mucking shaft arrangement.

Jan 1, 2007

By Joseph Grumer

Theory pertaining to the exchangeability of fuel gases on appliances has been extended to exchanges of propane or butane with mixtures of these. In particular, new considerations were developed bearing on the hazard of an occasional emission of carbon monoxide and flashback and blowoff possibilities. The new considerations involve using current requirements for approval of liquefied petroleum gas appliances. These requirements were used to predict allowable tolerances in chemical composition of liquefied petroleum gases for existing appliances. In addition, changes in gasline pressure were computed which may be substituted in place of fuel exchanges during testing of appliances,

Jan 1, 1962

By Adams F. C, Ridley K. L

Economic conditions after WorId War II made the recovery of Australian sources of sulphur one of considerable national importance. From 1947 to 1949 an investigation was made of recirculation techniques to produce acid plant grade gas from the Dwight-Lloyd down-draught sintering plant.During 1949 it appeared feasible to produce a gas of suitable 802 concentration and a decision was made to construct a gas purification train and a 150 tons/day contact acid plant. However, a number of difficulties remained in the production of the gases for sulphuric acid manufacture and as a result of research conducted to overcome these troubles the continuous up-draught sintering process was developed.The principal difficulties were:(a:) The down-draught sintering practice, as developed, produced an unusually high metallic lead precipitation in the windboxes. The disposal of this lead interrupted sintering operations and the delivery of gas to the acid plant.(b) The production capacity of the existing sintering plant was fully extended and the adoption of recirculation of gases, in an endeavour to satisfy acid plant requirements, would probably reduce the plant production capacity.(c) The prevailing high temperature of water available for purification train cooling required a higher than...

Jan 1, 1956

By J. Talja

Keywords: drying, steam drying, concentrates, copper, lead During the past twenty years steam drying has become a prominent technology for drying of non-ferrous metals concentrate. This is mainly because of its low energy consumption and very low emissions. The first applications of significant capacity were stationary steam dryers, which however, faced severe challenges in maintenance costs and availability. That technology was soon replaced by Kumera?s rotary steam drying technology, which has been the dominant technology in new dryer installations world-wide for the past ten years, ever since the first installation in Hamburg in 1999. There are ten Kumera steam dryers in operation today and five more to be commissioned during 2011. Practically every dryer is different owing to continuous development, new innovations and operational experience with continuous feedback from the operators. Most significant improvements relate to capacity increase with the Kumera steam-dryer family, new feeder systems at the wet end, a completely new design of the dry material discharge with increased availability, heating element design and material selection, and control systems. This paper discusses the modifications and improvements introduced which have enabled the Kumera steam dryer to become the global leader in new dryer installations.

Jan 1, 2011

By A Cox

It has been demonstrated that all the cadmium from spent batteries, typically 4 g per battery, can be recovered by burning polyvinyl chloride waste to yield hydrogen chloride; this reacts to produce volatile calcium chloride, which can then be condensed and collected in a separate reactor. Alternatively, chlorine may be used to chlorinate the cadmium with equal efficiency. There is also a prospect of using very low concentrations of these gases, less than 1%, to effect the separation. The Cd was recovered more quickly when exposed to sustained, controlled flow rates of chlorinating gases, whereas when PVC was burnt most of the gas was produced in a very short time, not allowing complete reaction. This problem can be overcome by recirculation of the gas into the reactor. The technology is efficient and clean and the equipment used is simple, enhancing the prospects for a pilot-scale version of the process

Jun 21, 1905

By Steven W. Wilson, Brigitte Lacouture, Nichola A. McKay

"The Aqqaluk deposit is a lead-zinc ore body that lies immediately north of the Main Pit at Teck Cominco’s Red Dog Mine in Alaska. It is scheduled to begin production in 2011 or 2012. A project team was formed in late 2004 to plan and implement an ore characterisation and metallurgical evaluation on the Aqqaluk ore. The main objective of this program was to facilitate the transition from Main Pit to Aqqaluk ore in the Red Dog concentrator. The program will develop a detailed, spatially-oriented characterisation of the Aqqaluk deposit attributes including lithology, ore geochemistry, bulk mineralogy, ore texture, as well as evaluating the metallurgical characteristics of ore hardness, process water geochemistry, bench-scale floatability and mineral liberation in ground feed, concentrate and tails. Developing correlations between the metallurgical response and the ore characterisation data is key to the emerging science of geometallurgy. This on-going program is a technical due diligence study that aims to reduce the risk associated with processing a new ore and to provide predictive information for mining and stockpile preparation.The test work to date has focused on characterising the five ore zones currently identified in the Aqqaluk deposit, namely: Siliceous (sub-divided to High Zn:Fe and Low Zn:Fe), Vein, Median Plate and Baritic ores. It identified a number of challenges associated with surface oxidation, or weathering, of the core samples and outlined a program for future sample collection and storage. Metallurgical testing evaluated ore hardness by a variety of methods. Preliminary floatability studies have been completed and some initial links have been established between the ore characteristics and the flotation response. Soluble mineral weathering products, the relative abundance of pyrite and marcasite and the iron content in the sphalerite grains have all shown a correlation to mineral recovery.As new core is received, both the ore characterisation and the metallurgical testing will be continued with a view to strengthen the existing correlations and develop new links."

Jan 1, 2007

By Woodcock J. T

When an aqueous suspension of pyrite and manganese ore reacts with oxygen, manganese is dissolved by the ferrous sulphate and sulphuric acid produced by the oxidation of pyrite. The kinetics of certain steps in the overall reaction were studied. A rate equation for the oxidation of ferrous sulphate by gaseous oxygen was derived for the temperature range from 1000 to 200° C. An exact rate equation for the production of ferrous ion from pyrite could not be established but it was shown that the temperature, oxygen pressure, pyrite surface area, and the reduction of ferric ion by pyrite are important. A rate equation was derived for the reaction of manganese dioxide with ferrous sulphate. A major facfor controlling the rate was whether or not ferric oxide was formed by hydrolysis at the manganese dioxide surface.It was shown that if hydrolysis was prevented the factor cpntrolling the rate of the overall reaction ,was the rate of production of ferrous ion, and little ferrous ion was oxidised by oxygen. When hydrolysis of iron did occur, the overall rate was not a simplefunction of anyone factor and much ferrous ion was wasted by oxidation with oxygen.INTRODUCTIONIn another paper (Cornelius and Woodcock, 1958) the results of the reaction of an aqueous suspension of a manganese ore and pyrite with oxygen are reported. It is shown that the ferrous ion and sulphuric acid generated in situ by the oxidation of pyrite, dissolves manganese as manganous sulphate. To obtain a better understanding of the process as a whole, the kinetics of certain steps in the overall reaction were studied.When an aqueous suspension of a manganese ore and pyrite reacts with oxygen, the overall reaction may be conventionally represented by equation (1) (Cornelius and Woodcock, 1958).2Mn02 + 2FeSz + 6i02 + 2HzO= 2MnS04 + 2H2S04+ F'ez03 ... , .. (1)

Jan 1, 1958

By J. E. Friant

Until 1956, drill and blast was the only way to excavate rock. In that year, a tunneling machine using disc type cutters economically bored a small Toronto tunnel. Its amazing 105 ft/day set a new world record and set the stage for a new industry. The Disc Cutter Role in Excavation Mechanical excavation of hard rock is by now deeply ensconced in the heavy civil construction industry. All over the world, from the Swiss Alp Melange to Hong Kong Granite, to New York Gneiss, huge Tunneling Boring Machines (TBMs) create transportation, water and sewer tunnels. Powerful machines, boasting as much as 6000 hp, bore through rock, excavating in excess of 1400 tons per hour. The tool that makes this tunneling phenomenon possible is the single blade, rolling disc cutter. These hardened steel discs, from 15 1/2 to 19 inches diameter are arranged on a rotating cutterhead, to cut concentric circles in the rock. As the machine is propelled forward under great pressure, rock below each cutter is crushed. But the efficiency of the cutterhead is derived from the science of cutter spacing (distance between cutter paths). The majority of the rock excavated is not crushed, but flakes off in chips and chunks. No pick, tooth, or drag type cutting tool can duplicate the performance of a disc cutter. The economic use of drag type tools is limited to as low as 5,000 psi UCS rock strength in massive formations. In weakly bonded, foliated rock, drag tools do better, but are still limited to rock generally less than 15,000 psi.

Jan 1, 2002

Stope support systems, typically consisting of props and packs, are used extensively in the gold and platinum mining industry to stabilize the rock mass in the excavation vicinity and to reduce the hazard associated with rockfalls and rockbursts. The design of stope support systems was historically based predominantly on past experience and practices, and cost considerations. The recent development of a new and improved support design methodology, has led to the potential for significant increases in worker safety and support cost savings. This paper reviews some of the fundamental rock mass and support criteria that form the basis of the improved support design methodology. The considered design criteria are the height of potential fall; quasi-static stope closure rates; dynamic stope closure rates; compressive hangingwall stresses; discontinuity spacing, orientation and interface properties; effect of support length (stoping width); effect of compression rate; consistency of support performance; a real coverage; support spacing; and zone of support influence. The proposed support design methodology combines both the zone of influence and key block stability theories, resulting in optimized support systems for rockfall and rockburst conditions. The site-specific methodology consists of two stages: (i) a tributary area analysis, and (ii) a zone of support influence and a stability analysis, considering hangingwall failure due to buckling, shear and block rotation, which gives maximum safe spacing of individual support units. The methodology is suitable for designing support systems for both blocky hangingwalls and hangingwalls fragmented by face-parallel extension and shear fractures.

Jan 1, 2001

By A. J. Davidson

A Cu-conducting solid electrolyte was used to develop the sensor. Instead of measuring the potential across the electrolyte from the reference material to the Cu-containing phase, a potential was applied and the stable current measured. This gave reasonable readings for copper-tin alloys, which agreed with the theoretical calculations, but was less satisfactory in the case of mattes because the surface area of electrolyte presented to the matte phase varied from sensor to sensor. To overcome this problem the potential was applied, the current was measured and then reversed and remeasured and the ratio of the currents was calculated. The current ratio is shown to be independent of the resistance of the electrolyte and the surface area of the electrolyte offered to the melt, but strongly dependent on the activity of the copper

Jun 21, 1905

By John H. Wright

The United States Antarctic Program (USAP), through its principal support contractor Raytheon Polar Services Co. (RPSC), has recently completed a three-year project comprising nearly 936 m (3,071 ft) of undersnow utility tunnels at Amundsen-Scott Station, South Pole, Antarctica. The tunnel serves the new station facilities that are currently under construction. It houses the piping that conveys fresh water from current and future water well sites, as well as waste water to repositories in abandoned wells. The undersnow tunnels permit year-round access for system operations and maintenance. The network of tunnels is entirely unlined and unsupported. And, for the most part, it maintains a rectangular cross section of 1.8-m-wide x 3-m-high (6 x 10 ft).The tunnel runs from 6 to 14 m (18 to 45 ft) below the surface. Eight 1-m- (3.3-ft-) diam raises bored from the surface serve the network as emergency escapeways.

Jan 1, 2002

By P. D. White, J. T. Moss, J. S. McNiel

Results of experimental work on the in situ combustion process were first published in this country in 1953' when Kuhn and Koch described results of a three-well test in Jefferson County, Okla. Shortly there-after Grant and Szasz2 described field studies in Nowata County, Okla., in which several modifications of the basic combustion process were investigated by injection of various oxidizing gas mixtures other than air. In the past five years speculation concerning this method of oil recovery has continued, with a number of interesting papers on various aspects of in situ combustion appearing in the literature3,4,5,6,7. However, only one of these' provided actual engineering information on pattern-type field experiments. The primary objectives of the Oklahoma three-well test were to check operation of specially designed electrical ignition equipment and evaluate problems associated with initiation of combustion in a natural oil sand reservoir. Immediately following successful completion of this test in the Pontotoc sand, plans were activated for a second field experiment to be conducted in the same sand a short distance away. The objective of this second field test1 as to establish a relationship between field observations and information derived from laboratory experimentation and computations. Secondary objectives of the test were to develop operating tech- niques and define operating problems, and to obtain information that would assist in the economic and engineering appraisals of the process. Careful planning was required since this test was designed with the hope of providing basic information on the characteristics and operation of a combustion drive. It was necessary to include test facilities which would not only permit precise control and measurement of the process variables but would also provide sufficient flexibility of control to insure that variables in the combustion process could be studied during the course of the test under a wide range of conditions. In order to accomplish these objectives elaborate instrumentation and several control wells were included in the design of the test installation. This type installation was felt to be well suited for an experimental study, but was in no respect intended as a counterpart of a commercial-scale operation. PRELIMINARY LABORATORY WORK An important objective of the field experiment, as stated previously, has been to obtain reliable data on operating variables which might be compared with similar data obtained in laboratory combustion tests. The value of successful correlations between quantities that can be measured in the laboratory and those obtained in a full-scale commercial venture has been well established for other industrial processes. The difficulty of following a process underground should make such correlations even more essential here. Also. approaching the field test phase of development of in situ combustion, it was considered desirable to precede design of test equipment with laboratory combustion studies under a variety of conditions to establish likely ranges of variables. These included temperature, air injection rate, frontal advance rate and produced gas composition.

By Bijan Taheri, Behrouz Maghsodi, Monireh Heshami, Reza Kohan

A common problem recently encountered with the increase in the rate of input feed at Enrichment Plant 2 of the Sarcheshmeh Copper Complex is the loss of value to the tails, translating to lower recoveries. The feasibility of the direct transfer of part of the high-grade concentrate from rougher stages to an appropriate position along the circuit was studied, and two positions were proposed for direct transfer of the concentrate. One position was the feed flow into cleaner cells, and the other was the feed flow into the recleaner cell. The results indicated that transferring the concentrate from the first unit of the rougher stage to the feed flow into the cleaner cells was feasible, with no limitations, while the second position required the installation of a set of hydrocyclones. It was found that the transfer of concentrate to the proposed positions not only addressed the problem of limited cell capacity, resulting in debottlenecking of the circuit, but also improved metallurgical separation efficiency up to 1.4%.

The epithermal Au-Ag deposits of the Hauraki Goldfield have formed in the convergent plate margin setting of the Coromandel Volcanic Zone (CVZ). The deposits form as siliceous lodes in the upper parts of geothermal systems associated with andesitic and rhyolitic volcanism. Two types of low sulphidation epithermal mineralisation are recognised in these volcanic terranes. Vein deposits within the rhyolitic terrane in the east and south of the CVZ (Whitianga Province) are typified by Chalcedonic Silica-Adularia-Illite type mineralisation. The veins are hosted by both rhyolite-dacite volcanic rocks and the underlying andesitic basement. The mineralisation formed by episodic violent decompressional boiling of deeply circulating meteoric water, with some magmatic fluid contribution; this boiling was associated with hydraulic fracturing and hydrothermal eruptions in geothermal systems where the piezometric surface of the deep geothermal reservoir lay near-surface. Such episodic boiling provides chalcedonic veining, banding and brecciation textures, adularia stability, bladed calcite, and extreme loss of H2S gas from the fluid to cause major gold deposition.   Crystalline Quartz-Illite-(Adularia-Kaolinite) type mineralisation is widespread in the andesitic terrane forming the northern and western portions of the CVZ (Kuaotunu Province). There is a spatial association with weak mineralisation of the high sulphidation (Vuggy Silica-Alunite-Kaolinite-Illite) epithermal type and porphyry eu-Au type. Crystalline Quartz mineralisation is probably formed by the mixing of shallow acidic groundwaters with the ascending deep geothermal fluid in geothermal systems beneath andesitic stratovolcanoes. The piezometric surface to the deep geothermal reservoir in these systems is likely to lie at considerable depth, with acidic gases rising from the geothermal reservoir condensing within the overlying vadose zone. The cooling effect, oxidation and pH decrease accompanying mixing apparently overcomes the dilution effect, and results in quartz deposition, illite (and locally kaolinite) alteration, and precipitation of gold. A high level of base-metal sulphide precipitation also enhances gold deposition. Violent boiling of the mixing fluids may occur at local structural dilation sites, producing high grade "bonanza" gold mineralisation.

Jan 1, 1991