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By W. J. Dolinar

The U.S. Bureau of Mines implemented the Fe2+ /Fe3+-SO2 anode reaction in a Cu electrowinning cell with full-size electrodes. Electrowinning was conducted using industrial electrolyte at 258 A/m2 (24 A/ft2) and 40 'C. Manifold injection of electrolyte provided circulation between the electrodes. Five-day operation using an optimized manifold gave an average cell voltage of 0.94 V at 89% current efficiency, which amounted to an energy savings of 2.82 MJ/kg (0.355 kW-hr/lb) compared to conventional electrowinning. Acid misting was completely eliminated, and SO2 concentration 23 cm (9 in.) above the cell averaged 0.06 ppm.

Jan 1, 1995

By J. W. Leonard

By using physical and chemical method to increase the bulk density of newly mined coal, the productivity of a mine can be significantly increased. Greater amounts of coal can be placed in fixed volume shuttle car by increasing bulk density. This can increase mine productivity by about 15%. Small, easy to achieve changes in mining operations are required to obtain the increased productivity. This article deals with chemical methods used to increase coal bulk density, the results and discussion are based on experiments performed in the laboratory.

Jan 1, 1992

By V. R. Burkhart

Pennsylvania Power & Light Company is an investor-owned public utility which was incorporated under the laws of the Commonwealth of Pennsylvania on June 4, 1920, with general offices at 901 Hamilton Street, Allentown, Pennsylvania. At the present time PP&L is operating five coal-fired steam electric stations, two hydroelectric stations and one steam heat plant which is being converted from anthracite to oil fired. In addition, PP&L is a partner in both the Keystone and Conemaugh mine mouth bituminous coal-fired steam electric stations in Central Pennsylvania and also part owner of a company which operates another hydroelectric station. PP&L plants, other than the two mine mouth stations, are located in Central Eastern Pennsylvania. (Figure 1) The company derives about 99% of its operating revenues from supplying electric service, while the balance is from the one steam heat plant serving the city of Harrisburg. The entire service area covering 10,000 square miles in 29 counties, has a population of approximately 2,300,000 people. The area served is mostly suburban. It includes 109 communities each having a population in excess of 5,000 people. The largest cities served are Allentown, Bethlehem, Harrisburg, Hazleton, Lancaster, Scranton, Wilkes-Barre, and Williamsport which range from 50,000 - 120,000 in population. So you see our service area does not include any major cities. The area has industrial, commercial, residential, agricultural and recreational activities that are linked with the Eastern Megalopolis by an extensive interstate limited-access highway system and railroad networks. We consider this Central Eastern Pennsylvania area we serve as the "heart of the market" -- an area with great growth potential.

Jan 1, 1973

By K. Biswas

In general, it cannot be assumed that the strength of coal pillars remains constant over long time periods. Field observations indicate that a coal seam, especially when it contains a parting layer, deteriorates over time, reducing load-bearing capacity of the pillars. This paper discusses a unique approach to determine the time dependent strength of coal pillars in the field. Three coal pillars that were developed 5, 15 and 50 years ago were chosen for the study. Holes were drilled in coal and parting layers in each pillar and the strength profiles were determined for each hole using the Borehole Penetrometer. The strength data were treated statistically to establish time dependent strength equations for different layers. The results can be used to help estimate the loss of pillar capacity over time.

Jan 1, 1999

By R. P. Fischer

Traditionally, molybdenum and vanadium have been used chiefly as alloy metals in steel. They impart similar characteristics to most steels, and to some extent one can be substituted for the other. In the United States during the 1950's the production of steel increased about 5 percent, and the reported consumption of both of these alloy metals in steel increased some 40 percent. In Europe during the 1950's the production of steel in¬creased nearly 100 percent. Data on the actual consumption of these alloy metals in European steels are not available, but production and trade records show that the European supplies of molybdenum increased about 150 percent and those of vanadium about 350 percent during the 1950's. If most of the molybdenum supplies in Europe are being added to steel, as seems likely, then the European steel industry has nearly caught up with the United State in the rate of consumption of molybdenum in steel. The vanadium supplies, on the other hand, are puzzling--unless Europe is adding mach more vanadium to steel than is done in the United States, it seems reasonable to assume that other uses are consuming moderately large quantities of this metal or that appreciable amounts of it are being transshipped from Europe. To the extent that a changing volume of supply signifies a changing pattern of use, the increased demand for molybdenum and vanadium in Europe should be of interest to domestic producers and consumers of these metals.

Jan 1, 1964

By Armando Correa de Araujo

Cationic flotation of quartz is currently utilized for the concentration of iron ores and for the cleaning of phosphate concentrates. The present work deals with depression of quartz in the presence of aluminum ions during cationic flotation. It was established-that aluminum ions depress the flotation of quartz with an amine, especially under neutral and very slightly alkaline conditions. Studies of adsorption of Al ions on the quartz surface as a function of pH correlated with depression of this mineral with an amine as collector. The presence of Al ions also enhanced the depressant action of corn starch on quartz The sodium salt of ethylenediaminotetra-acetic(EDTA) was found to be an effective complexing agent to supress the depression caused by aluminum ions.

Jan 1, 1984

By Robert M. Stevens, Arnoldo Acuña

INTRODUCTION In the early 1950s, underground miners and tunnel¬ing contractors were experimenting with ways to supple¬ment or eliminate track-bound loading and hauling equipment. Diesel-powered crawler and rubber-tire mounted front-end loaders and trucks designed for use on the surface were being modified and tried with limited but encouraging success. Miners began working with interested manufacturers to explore the develop¬ment of vehicles specifically designed to meet the de¬mands and constraints of underground material han¬dling. By the mid 1960s, load-haul-dump (LHD) vehicles were firmly established as a fundamental part of what has become known as the "trackless" mining concept, used in many mines and many countries around the world. The flexibility, mobility, and versatility of these units have given the industry a useful tool and have added new dimensions to mine development and produc¬tion. Many old mines have been redesigned to accom¬modate these trackless vehicles, and few new mining plans have failed to find some use for the concept during some phase of development and production. By 1977, several manufacturers in several different countries were producing a variety of LHD vehicles to meet the growing worldwide demand. GENERAL DESCRIPTION LHD vehicles combine certain characteristics of conventional front-end loaders and dump trucks, spe¬cifically designed for materials handling in underground mining and tunneling. The design intent is to provide one vehicle with one man, with the vehicle loading itself, hauling the load over level or inclined haulageways, and dumping the load. A typical production cycle of the most popular units has the operator driving the vehicle forward, forcing the bucket into the muck at or near floor level, and using the tractive effort of the vehicle and the prying action of the bucket to roll out and tilt back the load as shown in Fig. 1. With the bucket rolled back into the carrying position on the boom and the boom resting on the main frame of the vehicle, the load is hauled (trammed) to the dump point as shown in Fig. 2. At the dump point, the boom is raised, the bucket is rolled forward, and the load slides out as shown in Fig. 3. After dumping, the bucket is rolled back to the carrying position, the boom is returned to rest on the main frame, and the unit is driven back to the loading point for another load. There are two other types of LHD units that are slightly different in the cycles that they perform. One uses a hopper arrangement carried on the front of the machine, with a small bucket mounted ahead of the hopper. Several passes with the small bucket load the hopper, which is dumped by opening its floor. Al¬though this concept is several years old, it has gained less than 0.5% of the total market. The most recent LHD concept differs in that it has one bucket nesting inside another. The smaller inner bucket is loaded first, and it is then tilted back and above the larger bucket. When the larger bucket has been loaded, it is rolled back, and the total load is trammed to the dumping point. The dumping operation tilts the buckets in the reverse order from that of the loading operation. The impact of this new concept on the mining industry has not been measured yet. This chapter concentrates on the LHD vehicles employing the cycle described by Figs. 1 through 3, since these LHD units constitute an estimated 99% of the units in current use. MAIN VEHICLE FEATURES In general, the LHD vehicles available from most manufacturers share the same basic features.

Jan 1, 1982

By R. L. Loofbourow

The Sunro Copper Mine is near the south coast of Vancouver Island about 35 miles west of Victoria. Failure of the roof of a large open stope let a good sized mountain stream into the mine. Broken are, boulders and sand were washed into the underground mill and out through a 7 800-foot adit. The adit became plugged; water burst out an a ridge above the adit, washing out the portal and o trestle by which it was reached, Rock and ore are strong but several systems of steep, pronounced but generally tight fractures are found on and parallel to the walls of the orebody. The stope was started from a slusher drift 390 feet below the bed of the River and brought up to an elevation 155 feet below the River by blasting vertical and horizontal rings of longholes in the nearly vertical orebody. Mining was stopped there and five months were given to grouting and bolting the pillar under the bed of the River, During this time and for several months thereafter sloughing increased the width, length and height of the stope. At the last known observation the stope was 77 to 96 feet wide, 185 feet long and the highest point of the domed back was only 55 feet below the River. The flooding took no lives. In other respects, however, it might be difficult to find in mining lore o more savage example of the application of "Murphy's Laws".

Jan 1, 1968

By P. K. Sims

One-day field trip via U.S. Highway 6 and Colorado Highways 119 and 279 from Golden, Colorado to Idaho Springs. This field trip provides an opportunity to observe aspects of the Laramide ore deposits in the Central City and Idaho Springs mining districts and the Proterozoic basement rocks, which host the ore deposits.

Jan 1, 1986

By C. J. Webb

Abandoned uranium mines in the southern Black Hills of South Dakota were sampled for uranium, radium, and rare earth elements during 1992 and 1993. Analyses of water samples from several shallow ponds in the mine pits showed pH values between 3 and 4 with uranium concentrations between 1600 and 2600 ppb. Rare earth elements and their respective isotopes were analyzed with an inductively coupled plasma mass spectrometer and were referenced to a shale normalization pattern. All samples showed an enrichment in the middle rare earth elements. Rare earth levels often were greater than 0.2 ppm. At one site, the concentrations of lanthanides were 150,000 times above background levels. While the southern Black Hills have long been known for rich uranium ore deposits, these analyses show that significant levels of rare earth elements also are present, indicating that the potential exist for future development.

Jan 1, 1995

By William J. McCutheon

This paper presents some personal observations obtained during the course of visits to Europe, Africa, Latin America and the United States to talk with senior decision-makers in the copper industry about their views of markets, prices and the future of copper. The industry's future has never been particularly easy to define; with the changes of recent years, prediction has become even more difficult. The author's personal assessments of the present and future are offered for comment.

Jan 1, 1986

By Yoginder P. Chugh

The mining methods used at many opencast brown coal mines in Poland and the German Democratic Republic are not used in the US to any extent. Using bucketwheel excavators, bucket chain excavators, and mobile conveyor bridges, the mining techniques may offer efficient, economic alternatives for operators in the US. These mining methods were observed during visits to several open-cast brown coal mines in Eastern Europe over the past two years. Some of them may be particularly attractive for the large lignite mines being planned in North Dakota and Texas.

Jan 11, 1980

By Irving Hoch

INTRODUCTION The demand for tunnelling can be related to urban population size and density; often, tunnelling occurs when a certain city size and density threshold is reached, and increases thereafter as a function of those population characteristics. Subways for rail mass transit are the most notable example, of course, but tunnels for water supply and perhaps for sewerage can also be related to size and density. As cities grow large they sometimes outgrow their local water supply and have to import water from distant places via tunnels; witness New York City, Los Angeles and San Francisco. And it has been suggested that Chicago use deep tunnels for storm water storage because tertiary treatment to meet water quality standards will require treating storm water runoff.(1) Other uses of underground space also increase with urban density, e.g., underground parking, concourses and shopping centers such as Rockefeller Center in New York City and the Place Ville-Marie in Montreal. These examples can be viewed as illustrative of the central point of urban land economics. As the number of people locating in a place increase, they bid up land values and make the more intensive use of land economic, with land defined to embrace the space both above and below the surface. Hence, we are led to think about the city, and of urban land use, in three dimensions. Now, if we accept the relation of underground space use to urban size and density, recent demographic trends seem anything but hopeful for future tunnelling demand: urban density is declining, population growth is slowing down generally, and there

Jan 1, 1974

By C. Garcia, C. L. Lin

Characterization and analysis of multiphase particles and/or particulate systems (such as the packed particle bed) are of great technological importance for mineral processing applications. In general the performance of these applications depends on the statistical characteristics of particle microstructures, such as composition distribution, surface exposure of mineral grains, pore network structure, etc. For continued technological progress in the field of multiphase particulate processes, the need for quantitative spatial analysis of multiphase particles in three dimensions has increased sign6cantly. Such quantitative information must be accurate enough that the measured values can be used as parameters for simulation models, process design procedures, and control strategies. Modern 3D image-acquisition techniques, such as X-ray microtomography (XMT), offer a unique imaging capability that can produce high-resolution (a few micrometers) three-dimensional images of the internal structure of multiphase particulate samples. These three-dimensional image data present new challenges for image analysis, image processing, and visualization. Furthermore, important issues should focus on how to use the 3D information and derive new insights into the improvement, design, and operation of mineral processing processes. In this paper, utilization of XMT for characterization and analysis of leaching process involving multiphase particulate system is discussed.

Jan 1, 2005

By K. T. Valsaraj

The separation process called solvent sublation for the removal of two hydrophobic compounds (penta-and tri-chlorophenols) from the aqueous phase is discussed. A steady state mathematical model for the process is discussed. The process was conducted in a continuous countercurrent mode. The underlying mechanisms, theory and experimental details on the effects of process variables on removal efficiency are reported.

Jan 1, 1992

By Kwangmin Kim, Taehee Lee, Minkyu Kim, JUNHYEOK PARK

Mine tailings storage facilities (TSFs) can be a significant source of fine, respirable dust. About 25 percent of the mass fraction of tailings from a hard-rock mine consists of particles of a respirable size (smaller than 10 μm) [1]. This dust poses concerns, especially for nearby communities, because of its detrimental impact on respiratory health. Respirable tailings dust, primarily composed of quartz or free silica (SiO2), may cause silicosis, chronic pulmonary disease, bronchitis, collagen vascular diseases, and chronic granulomatous infections [2]. 

By Gunnar Nord, Per-Anders Persson, Duri Prader

The paper gives a short resumé of the findings of the joint US - Swedish "Mechanical Boring (MB) or Drill and Blast Tunneling (DB) ? Workshop" in Stockholm December 1976. New developments and trends in both MB and DB techniques in Europe since 1976 are described, and information is given on some interesting new projects. Differences in contracting principles between the US and Europe lead to different practices for preinvestigations, design, excavation and arbitration and legal affairs. It is shown that this often leads to a higher cost in the US than in Europe for similar excavation jobs. A typical US tunnel job also has more men on the site than a similar job in Europe. This adds to the cost difference and is only partly balanced by a slightly higher rate of excavation in the US. A comparison is made between two quantitative methods of predicting MB penetration rates. These are in reasonable agreement. A probable future development in machine design is an increase in cutter load towards perhaps 25 tons per disc where the tunnel diameter is large enough to house the machine size dictated by the size of the very large electric motors required. Recent European developments in drill and blast technique include improved methods for cautious blasting, precision hydraulic drilling of small diameter holes, and non-electric interval blasting techniques. These developments still keep the drill and blast method ahead of mechanical boring costwise for tunnels in igneous rock whereas for most sedimentary materials mechanical boring has a lead, particularly for long tunnels.

Jan 1, 1979

By M. L. Smith

SAG mill throughput is often a bottleneck in increasing metal productivity. Improved size distribution control in the mill feed can be used to increase mill production. This can be accomplished by controlling blast fragmentation as a function of energy input and rock characteristics. Such an approach requires the integration of rock fragmentation and comminution modeling. The optimal mill feed size distribution is determined by adapting a population balance comminution model to a measure of rock hardness or fragility which is also relevant to the rock fragmentation that is achieved by blasting. The relation between the size distribution and fragility of the feed and of the mill's product and the critical size in a SAG mill is examined.

Jan 1, 1993

By W. D. Bullock

The King-Beaver mine of Asbestos Corporation Limited operates an open pit in the city of Thetford Mines, Quebec. The approximate loca-tion of the open pit is at Latitude 46° 02' North and Longitude 71° 20' West. The general topography is 1020 feet above sea level. Thirty-six percent of the company's scheduled asbestos ore production, for the Thetford Mines area, comes from the King-Beaver pit. The pit operates 24 hours a day, six days a week. Normal production is 10,500 tons of ore per day at a waste to ore ratio of 2 to 1. The remaining ore requirements are mined from the King-Beaver underground mine and the British-Canadian mine.

Jan 1, 1980

By Richard S. Kunter

The Bulldog CIP plant treats the slime portion of current tailings and reclaimed flotation tailings from the adjoining 350 tpd (3.67 kg/s) silver-lead flotation mill. Changes to the dredge reclaimer, pulp storage tank and trash removal system have allowed an increase in tonnage treated to a sustained 460tpd (4.83kg/s). CIP feed is 3-4 oz/T Ag (102.9-137.1 ppm). Following conventional cyanidation, carbon is added to the slurry. Silver loaded carbon is stripped in atmospheric-pressure vessels using hot caustic cyanide. Silver recovery from this solution is by Zadra- type cells. Some of the modifications to the plant and operating techniques are discussed.

Jan 1, 1981