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By Robert W. Bartlett

Heap biooxidation of sulfidic refractory gold ore requires large amounts of oxygen, as shown in Figure 1. Bacteria, Thiobaci/lus ferrooxidans, are donnant at oxygen concentrations below about 3% in air (1 ppm in aqueous solution) because ofmonod kinet­ics. Hence, the maximum possible utilization is only about 75%, and it may be much less than that due to poor air sweep effi­ciency. At the maximum oxygen utilization, an ore containing two percent pyrite requires nearly 100 cubic meters of air per tonne (4,000 cubic feet per ton). The stoichiometric air require­ment to oxidize arsenopyrite is similar to that of pyrite. While the leaching solution percolating through the heap introduces some dissolved oxygen, the amount is insignificant because of the low solubility of oxygen in water, 7 to 8 ppm at atmospheric saturation. There are only three ways to provide oxygen to the heap: either air flow by natural convection, diffusion of oxygen from the surface (through stagnant air in the air-filled void space in the heap), or forced air ventilation of the heap. Each of these processes will be reviewed.

Jan 1, 1996

By Richard H. Johnson

The Castle Mountain Mine (CMM) is located in the eastern por­tion of San Bernardino County, Southern California, 70 miles south of Las Vegas. The CMM is a joint venture between Viceroy Gold Corp. (75% and operator) and MK Gold (25%). The CMM initially started gold production with an 8,000 tpd cyanide heap leach operation in February, 1992 when the first ore was crushed and delivered to the leach pads. Even during construction and commissioning, design work was under way to engineer and construct a 1,200 tpd Mill circuit to process the higher grade fraction of the ore through use of pulp agglomera­tion. The need for a grinding circuit became evident with the quantity of high grade material delineated during drilling and the amount of visible gold that the geologists were finding in the drill core and R.C. cuttings. Viceroy did not want to stack the higher grade ore on the heap, and it was clear that permitting a tailings pond would, at best, be a long drawn-out affair. An alternative to a tailings facility had to be found.

Jan 1, 1996

By R. Pakalnis

A comprehensive project has been completed at the University of British Columbia that focused on the development of a commercially competitive composite cable bolt. Laboratory evaluation consisted of pull tests, preliminary shear tests, grout column testing and scanning electron microscope evaluation of the composite cable bolt. Field implementation at five underground mines throughout Canada were completed for technical and overall performance evaluation of the new product. The project began in 1989 under the sponsorship of HDRK Ltd., a consortium of mining companies including Inco, Noranda and Falconbridge Ltd. The objective was to develop a cuttable cable bolt that would serve as support for a continuous miner within a hardrock environment (Mah, 1994). The bolt was required to be cuttable by a continuous roadheader without adverse effects to equipment, personnel and the milling process. From the beginning, the focus was to employ existing cable bolt installation technology (Goris et al., 1994) whereby the cable bolts are grouted within a 4.8-cm-diam (1.08-in.diam) or larger employing a portland cement grout having a water:cement ratio between 0.35:1 to 0.4:1.

Jan 1, 1994

By R. M. Ocampo-Franco

The line seven, as part of the development of the Subway Master Plan in Mexico City, will tunnel under different subsoil conditions of clay with high water content and low shear resistance located between 8 and 12m beneath the surface. Boulders in silty sand and gravel to a 40m depth underlay this stratum. Economics, scheduled time of construction, and the obligated interconnection with existing lines one and two determined the construction of the tunnels to have an overburden of 1.0 to 2.2 times the diameter. In the north part of line seven there is a track of 251m length that was decided to attack with an open shield of 9.14m of diameter due to the characteristics of the sub-soil, minimum section needed as well as a minimal overburden, of 10.41m. The paper explains the construction procedure from the excavation stage to the reinforcement of the final lining obligated for the ground subsidence as a result of volumetric changes of a stratum of 4m thick of clay overlying the crown of the shield. Manuscript not received in time for publication.

Jan 1, 1983

By Jugal Kar

Yilgam Star treats a gold bearing ore which has an association with pyrohotite and pentlandite (Fe,Ni)9S8 Nickel behaves similar to gold in cyanide solution, it leaches in cyanide to form a number of species. It adsorbs like the noble metals on carbon. During smelting Nickel causes significant problems in the crucible as the melting point of nickel is much higher (1452 °C) than gold (1040 CC). The crucible became overheated, holed and increases furnace downtime. To overcome such dif­ficulties an investigation was carried out to reduce the amount of nickel on steel wool during stripping. Yilgam Star has got I.P.S. high pressure zadra stripping system which works on 400 kpa, at 140 °C. The trend of gold and nickel profiles has been observed with varying caustic concentrations. The gold and nickel profile has been monitored with the addition of cyanide in the stripping liquor. It has been ascertained that at lower caustic levels the nickel ion remains in solution and is subsequently not electro­won. The cyanide concentration of0.4% (Wt/Vol) keeps nickel ion in solution and induces metallic nickel to produce nickel ion as NiCN.

Jan 1, 1995

By Kevin Stuffle, James E. Sharp, Sean Premeau

Two process enhancements for the biological oxidative pretreatment of sulfidic gold ore for subsequent treatment with cyanide are discussed. These are the use of a high areal density ring and pin packing (BioBalls™) as substrate, and the use of a novel biological ferric generator. The BioBall™ packing when coated with concentrates for heap leach processing offers higher areal densities, while leaving more open volume for fluid flow than more commonly used substrates such as aggregate. An oxidation rate study was performed on crushed auriferous arsenopyrite whole ore to demonstrate the benefits of using the packing. The auriferous arsenopyrite grading 2.9% Fe and .212 OPT gold was 50 percent oxidized in 24 days. The biological ferric generator is a passive air-side trickle bed reactor that efficiently converts ferrous to ferric in a process stream. Conversion rates of .8g/L h ferrous to ferric are routinely obtained. Although the biologically generated ferric solutions have not yet been tested on gold ores or concentrates, prior work has demonstrated that the high ferric solutions which will result in rapid oxidation of sulfidic gold ores or concentrates.

Jan 1, 1997

By Henry E. Bakkila

Introduction United States Steel Corporation's, Texas Uranium Operations operates in-situ mines located approximately 70 miles north of Corpus Christi near the town of George West in Live Oak County, Texas. In 1977, Texas Uranium Operations became the operating entity for the Burns Ranch mines 100% United States Steel ownership and also operates the Clay West mines a 50150 joint venture of United States Steel Corporation and N M Uranium, Inc. Until mid-1982, Texas Uranium operated eight (8) satellites where uranium was captured on resin and two central plants where the loaded resin was eluted, acidized, precipitated and dried to yellowcake. At present, the Clay West Central Plant is operating, as are four (4) satellite plants in a mode designed to optimize results while depleting remaining reserves. United States Steel's Texas Uranium Operations, as have some other uranium producers, managed to continue successful production during the plunge to the recent floor price of $17. Despite the fact that United States Steel does not intend to continue as--a uranium producer beyond the life of its present reserves, we naturally hope the recent trend to the pre- sent price of $24 will continue to increase.

Jan 1, 1984

By Ian McFeat-Smith, Odd G. Askilsrud

Introduction Given the mountainous nature of the local igneous terrain, hard rock tunnelling plays an important role in the development of Hong Kong's infrastructure. In 1990, tenderers for two tunnel projects were encouraged to consider using hard rock TBMs, the territories' first. As a result the 7.5km long, 3.56m diameter Tolo Effluent Tunnel and the 5.3km long, 4.8m diameter Hong Kong Electric Cable Tunnel were excavated by hard rock TBMs. The successful completion of both projects in 1992 should make the TBM method an attractive construction alternative for planned, upcoming projects in Hong Kong. Tunnelling Conditions Tunnelling solutions are frequently adopted in Hong Kong due to the intensity of development, lack of flat landscape and proximity of mountainous terrain to the main centers of population. This is carried out primarily in granites or granitic-type rocks which surround Victoria harbour, and to a lesser extent in the outlying volcanic rocks which include extremely hard tuffs and lavas. Tunnelling will generally take place in granitic rocks, normally about 100-250 MPa in strength, and with an average joint spacing of 0.3m and a quartz content of 30-

Jan 1, 1993

By G. Van Weert, J. F. Breedveld

Both regular and Silver Impregnated Activated Carbon (SIAC) were studied for their effectiveness in removing WAD (Weak Acid Dissociated) cyanides from solutions at pH = 10. SIAC has already been shown to be effective in the removal of free cyanide down to 30 ppb or less. The present work deals with complexed cyanides. Zinc cyanide was used to represent the WAD component. At pH=10, in either batch or column tests it was not possible to lower the total cyanide in solution from either 30 or 8 ppm to less than 1 ppm, using SIAC, regular activated carbon as received, or after grinding. Silver (metal) impregnation of the carbon was not beneficial in the removal of WAD cyanide. However, when silver is added as silver ions (nitrate), the cyanide is adsorbed as silver cyanide in preference to zinc cyanide. The latter compound converts to zinc (hydr) oxide. This way, the cyanide concentration in solution can be lowered below 1 ppm, even when zinc cyanide is already adsorbed on the carbon used. A single exploratory test with added copper ions indicated a similar effect for that system.

Jan 1, 2004

By G. M. Bernard

Cerro Colorado lies on the eastern edge of the Atacama Desert in the foothills of the Andean Cordillera of northern Chile. Compañía Minera Cerro Colorado SA (CMCC) operates Cerro Colorado. CMCC, headquartered in Santiago, Chile, is wholly owned by Rio Algom Ltd., of Toronto, Ontario. Cerro Colorado is located 120 km (75 miles)east of the port city of Iquique. Access is by 30 km (19 miles) of paved highway and 70 km (43 miles) of upgraded road. The mine site is located at an altitude of 2600 m (8531 ft) on a gentle west-sloping plateau adjacent to a deep canyon (Quebrada de Parca) to the north. Temperatures are moderate, ranging from 5° to 30° C (41° to 86° F) with an average annual rainfall of 20 mm (0.8 in.). The plateau is generally covered with 20 to 30 m (65 to 100 ft) of Quatemary sand and gravel overlaying bedrock. In the immediate vicinity of the Cerro Colorado deposit, a semicircular embayment has been eroded into a steep canyon wall that cuts through the surface gravels to expose a considerable section of the underlying bedrock.

Jan 1, 1995

By Steve Kral

The power industry throughout the world is in the midst of a significant transition that will result in a major restructuring. Deregulation of utilities in the United States is continuing, resulting in increased competition among power providers. The traditional ways that electric power is globally bought, sold and delivered will also change. However, according to the Department of Energy's (DOE) Pat Godley, one thing is clear: "Those who provide the power during the 21 st century will be those who are willing to change - those who are willing to accept new ways of doing business and willing to employ new technologies." Godley is assistant secretary of fossil energy with DOE. Her comments came during the opening remarks at the Fourth Annual Clean Coal Technology Conference, held in Denver, CO, Sept. 5-8, 1995. The conference was sponsored by DOE and the Center of Energy and Economic Development. Under the theme "Global Opportunity," more than 300 coal and utility executives spent three days discussing the new face of the electric-power industry throughout the world and the new, mostly clean coal technologies (CCT) that will be available to power providers.

Jan 1, 1995

By J. G. Groppo, B. K. Parekh

A series of performance studies were conducted using countercurrent column flotation to recover a marketable clean coal product from existing preparation plant fine waste streams. The test work was conducted at several preparation plant sites in Kentucky and Virginia using a 150-mm (6-in.) inside diameter column that was 5.8 m (19 ft) high. Both thickener feed and classifying cyclone overflow with a typical size distribution of 150 µm (100 mesh) X 0 were tested. The percent solids of the column flotation feed varied from 1.5% to 15% while the ash content ranged from about 30% to 60%. The concentrates produced contained 2% to 10% ash with Btu recoveries of nearly 90% using 0.12 to 1.25 kg/t (0.25 to 2.5 lbs per st) fuel oil and 0.12 kg/t (0.25 lbs per st) MIBC. These results were consistent with or better than results obtained in preliminary laboratory scale column flotation evaluation. Test results from seven different seams are discussed as well as scale-up relationships used to design a full-scale installation presently in operation.

Jan 1, 1991

By Brian Fulcher

The Fort Lawton Parallel Tunnel was built in 1990 - 1991 by Morrison Knudsen Corporation (MK) as an integral part of Seattle METRO's planned expansion of the Westpoint Treatment Plant. The project included a concrete lined 2542 m (8,340 ft) long tunnel bored in sands and clays under the presence of methane gas and over 27.4 m (90 ft) of ground water table. The tunnel roughly paral¬lels an existing and still operating 3.65 m (12 ft) diameter tunnel originally completed in 1909. The parallel tunnel was constructed using a Lovat 4.72 m (15 ft-6 in) earth pressure balanced TBM with ribs and timber lagging as primary support. The tunnel alignment crossed under as much as 91.4 m (300 ft) of overburden as well as twin mainline railway tracks; terminating in a shaft adja¬cent to the Seattle ship canal. The project was completed in June, 1991 after a final "wet-tap" tie-in to the existing brick-lined sewer; over five months ahead of the contract schedule. This paper will describe the construction methods, job site conditions and difficulties encoun¬tered on this very challenging and successful project.

Jan 1, 1993

By M. R. Peterson, C. R. Ferguson, T. H. Jeffers

The ability of microorganisms such as yeast, bacteria, and various aquatic flora to sorb metals from dilute aqueous solutions is well documented. Although microorganisms have significant potential in decontaminating waste waters, techniques and equipment suitable for bioassisted decontamination are limited. The Bureau of Mines has investigated the use of microorganisms immobilized in porous polysulfone beads for extracting toxic and heavy metals from dilute waste streams. The minus 8- plus 12-mesh beads were fabricated from high-density poly- sulfone dissolved in dimethylformamide (DMF). Dried, thermally killed yeast, algae, duckweed, xanthan gum, and alginates were blended into the polysulfone-DMF, and spherical beads were formed by injecting the mixture into water. Microscopic analysis revealed microorganisms immobilized within the bead pores. The beads had excellent handling characteristics and were tested in stirred reactors, fixed bed columns, and fluidized bed columns for their ability to remove metal contaminants from several waste waters. The effluents resulting from these waste waters met or exceeded the National Drinking Water Standards for cadmium, copper, manganese, and zinc. Other heavy metal contaminants readily sorbed by the beads included arsenic and mercury. Elution of metal values from the beads was accomplished using dilute nitric acid or sodium carbonate.

Jan 1, 1989

By Ching-Yi Tsai

The effect of various constituents on the pyrolysis and combustion of a pulverized coal in an entrained-flow reactor has been inves¬tigated. Predicted time-temperature histories of the coal' particles and experimental weight loss data indicate a strong coupling of heat and mass transfer to the pyrolysis and combustion rates. A higher combustion rate following ignition was observed as particle size was increased to 112 µm. This is related to a higher particle temperature after ignition for the larger particles. Although the heating rate prior to ignition decreases with increasing particle size, higher slip velocities and surrounding gas temperatures for the larger particles promote early ignition. The presence of liptinite in the coal increases the weight loss rate before and immediately after ignition. Similar behavior was observed for pyrolysis. Fractions of a HVA bituminous coal which were rich in mineral matter or semi-fusinite were found to have a higher heterogeneous char combustion rate than vitrinite rich samples.

Jan 1, 1984

By Charles B. Dugger

Sacrificial linings for grinding mills have been a necessary state of the art of mineral dressing since the inception of comminution. Long recognized as the final link in energy transmission from power line to ore, mill liners as a scientific endeavor have not expanded as rapidly as other branches of mineral dressing engineering. Several reasons for this technological lag are apparent. Typically in the past, labor intensive foundries were freely located geographically, at a time when transportation charges made up a significant portion of the casting cost. Alloying agents had not gained their current level of sophistication and were relatively inexpensive in the quantities required. Precise foundry controls were not economically justified, or totally understood. Coincidental to these elements, liner consumption per unit processed did not categorically contribute as a major cost item to the mill operator. Grinding equipment was small, and many times lining life exceeded that of the promoter. These unique conditions no longer exist. Ore dressing equipment has grown to meet modern mining demands. Larger processing facilities, utilizing fewer pieces of equipment, have replaced operations of the past. Emphasis today and tomorrow is on larger and larger equipment, with an eye on lower and lower unit processing costs.

Jan 1, 1979

By M. T. Atwood

For more than sixty years the rich oil shale formations of Colorado, Utah and Wyoming have been evaluated as a future source of petroleum. After many false starts the commercial production of shale oil is near. Union Oil and Colony (Exxon and Tosco) have begun construction of commercial plants. Occidental and Rio Blanco (Gulf and Standard of Indiana) are well along in the development of modified in situ (underground) processes. A number of other companies and groups are in advanced stages of development. This paper will review some of the major elements involved in the production of shale oil with emphasis on means available to express the efficiency of production of pyrolysis liquids and gases from oil shale rock.

Jan 1, 1982

By J. Sohn

The most promising near-term alternative to fuel cell driven vehicles is probably Hybrid Electric Vehicle (HEV or EV) technology. HEV technology combines the best characteristics of fuel-driven engines, electric motor drives, and energy storage components. It is designed with a combustion engine that functions as the primary power source, and an electric power storage system that functions as the secondary power source. The presence of the secondary power source allows designers to size the combustion engine for cruising power requirements. A new energy source for HEV or EV market will become lithium ion batteries (LIBs) in the near future. LIBs for HEV or EV has large scale about more 10,000 times than small size one for IT devices in order to achieve high electric density/capacity and high efficiency, etc. In those reasons, physical treatment of the batteries is more difficult for stable dismantling in comparison with the smaller one. Hybrid vehicle sales will grow by nearly 400 percent during the next seven years, according to a new report from analyst firm ABI Research. By 2013 hybrids will make up 6 percent of annual U.S. auto sales. The traction battery pack will become air-cooled LIBs which consists of several modules of Li ion battery and connected in series/parallel configuration to provide about >450 VDC, >150 kW peak power, and >80 Ah capacity. As the use of these batteries tends to increase significantly for the next years, it is relevant issues that development of new recycling methods as well as optimization of existing processes to treat spent LIBs for HEV have being addressed in order to obtain sustainability. In this study, physical treatment containing stable electrical discharge of spent LIBs for HEV was carried out for recovery of valuable metals from the batteries. Also In order to increase the yield of valuable metals through physical treatments such as electric discharge of spent batteries, crushing, and classification, we also focused on the recovery of cobalt from +8 mesh fraction due to its large portion in crushed intermediates.

Jan 1, 2010

By R. D. Hammett

This paper describes an investigation that MS carried out using the three-dimensional, stress analysis computer program "NFOLD" to assess pillar stability in relation to existing mining conditions and the proposed layout of future stopes. The stress analyses were designed to assess the present stability of the mine (particularly the pillars adjacent to the shaft), the change in pillar stresses as mining proceeds, and the optimum stope geometry to minimize ground control problems. The existing conditions were modelled first, and rock mass strengths were adjusted until a good agreement between the predicted and observed conditions was obtained. Analyses of alternative mining layouts, based on the calibrated rock mass strengths, were then compared. The paper describes the results and the conclusions of the study.

Jan 1, 1983

By Robert E. Charles

Much has been said about digital computer control of metal and mineral ore dressing processes, but little has been done. This pa- per discusses what practical use can be made today of a digital computer in an ore concentrator and how such application can be made successfully. A hypothetical, but commercially common, grinding and flotation circuit is presented in terms of analog measurements which can and are being made in existing plants and a centralized computer control system which is reasonable in terms of today's technology. Dangers and possible disadvantages of such an approach are discussed as well as estimated benefits. Possible future benefits are presented in terms of improved control technology. Development of new measuring devices is not considered as a criterion for computer benefits. The control systems described have been utilized successfully in existing ore dressing operations. However, the degree of success or failure of analog systems is generally left to the interpretation of management rather than absolute analysis. Many factors affect the economic operation of a mineral recovery circuit such as size of facility, flow sheet design, number of operating personnel, percent of recoverable mineral in the ore body, loss to tails, and haulage rates. In existing mills where little or no instrumentation has been used, it is extremely difficult to prove or disprove the advantage of analog control systems on one mill line versus its sisters due to the lack of standards and the lack of ability to separate final products by ton.

Jan 1, 1969