Search Documents

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

Eastern US oil shale contains approximately 10 to 12 gallons of oil per ton and 7 to 10% pyritic sulfur. Physical beneficiation of these low grade shales using froth flotation provides a high grade material that makes extraction of oil more economically attractive. The Alabama oil shale used in the present study contained 16.46% organic carbon and 14.5 gallons of oil per ton as determined by Fischer assay. Liberation size of the kerogen was estimated at 10 µm. `Ken-Flote' column flotation technology provided a high grade concentrate containing as much as 60% organic carbon. However, carbon recovery was about 60%. Carbon recovery was improved to 75-85% while maintaining concentrate grades in excess of 40% carbon by providing longer retention time in the column, which facilitated effective bubble-particle collision and attachment.

Jan 1, 1994

By N. Parra, M. N. Herrera, T. Vargas, C. González, B. Escobar

The bioleaching of mineral sulfide pulps in a bench-scale rotating-drum reactor was studied. The reactor contained horizontal paddles on the inner wall for lifting the mineral pulp. The performance of the reactor was tested by bioleaching a refractory pyritic gold concentrate in the presence of pure Thiobacillus ferrooxidans (ATCC 19859). The concentrate was efficiently bioleached at a 50% pulp density with the drum operating at from 0.5 to 1.0 rpm. Attempts at bioleaching the concentrate at the same pulp density used in a conventional stirred reactor showed severe inhibition of bacterial activity. The results demonstrated that the drum reactor allows the process to operate at much higher pulp densities than conventional stirred-tank reactors. This results in improved bacterial activity because of better attrition control of the mineral particles.

Jan 1, 1999

By Christof Brewka

Los Pelambres, 200 km north of Santiago, Chile, is the latest in a series of mega-projects developed in this part of the world. While most of its predecessors are spread over open desert, the Los Pelambres mine is nestled inside a narrow alpine valley high in the Andean Mountains. To handle the daunting task of transporting the mined copper ore more than 12 km and 1,400 vertical meters downhill to the concentrator plant, a gigantic belt conveyor system (capacity of 8700 mtph, 1800 mm wide ST 7800 steel cord belt, 2.5m diameter pulleys, an elaborate braking system including a mechanical failsafe and large reducers with a total installed drive power of 25,000 kW) has been employed. Many of these components have pushed the limits of conventional belt conveyor design.

Jan 1, 2000

Since gold was first discovered in Colorado in the late 1850s' mining has been a major part of the state's economic history, according to Stanley Dempsey, chairman and chief executive officer of Denver- based Royal Gold Inc. While the mining industry has seen some lean times throughout the past century, it has always bounced back. Today, dozens of major gold companies are headquartered in the Denver area. The state's coal mines produced record amounts during 1996. And even some of Colorado's uranium mines are resuming production. Dempsey joined other speakers in addressing the state of Colorado's mining industry during the Colorado Mining Association's (CMA) National Western Mining Conference. Some 800 people attended the CMA meeting, held Feb. 2-5 in Denver. The meeting was the association's 100th since it was incorporated in 1897.

Jan 1, 1997

By W. E. Cobb

The financial implications of environmental liabilities are becoming staggering, particularly for mining companies. The Environmental Protection Agency's (EPA) Record of Decision (ROD) list for Superfund mining sites has some pretty hefty financial commitments, such as the $10 million operable unit remedy for the Yak Tunnel at California Gulch (in Colorado) or the $40 to 60 million remediation at Bunker Hill (in Idaho). These costs are driven by the large volume and areal extent associated with historical waste management practices at mining sites. (It's difficult to have a low-cost remedy for a 20-square-mile site.) Unfortunately, there are other ways of generating environmental liabilities besides Superfund, such as non-compliance with Clean Air Act provisions, stormwater permits, or National Pollutant Discharge Elimination System (NPDES) permits. In the last 2 years, EPA has increased enforcement in its regulatory programs, which has resulted in increased fines and criminal actions. Leaders in other industries (primarily the chemical and manufacturing industries) are viewing environmental liabilities as a strong motivator to select engineering approaches carefully based on technical, legal, economic, and philosophical perspectives. Industry interest in waste minimization programs comes from the concept that it is economically advantageous not to create waste in the first place. Waste minimization programs typically balance increased front-end capital investment with the minimization of potential long-term environmental liabilities as a way to achieve the lowest total-or life-cycle-cost. A side benefit of waste minimization programs is that they tend to improve overall regulatory compliance. Waste management practices are also becoming philosophical, as evidenced by a May 11, 1992, Business Week article: Companies that incorporate innovative thinking on sustainable development will do more than clean up or prevent their own pollution. They'll make and distribute a product more efficiently than ever, worry about its lifelong environmental impact, plan for recycling, and get their suppliers on the bandwagon. This type of approach will require a new mind-set, new tools, and adjustments throughout the organization. A key aspect of waste minimization or life-cycle waste management programs is the incorporation of environmental costs into economic analyses that compare various waste management alternatives. However, the incorporation of environmental costs into an economic analysis can be more difficult than initially thought. As noted above, new tools-or even a new toolbag-are needed, such as new accounting methods that track and assign the true lifetime environmental costs of a particular product. One piece of the new toolbag is life-cycle cost analysis, which is discussed in this paper. To simplify the discussion, this paper looks at the total costs associated with a given mining site. The concepts presented in this paper, however, can be applied to any mine waste management decision. The ultimate extension of life-cycle costing, as presented in the Business Week article, is to include the potential environmental costs throughout the life of a metal. At this point, I am perplexed on why, let alone how, to include the potential downstream environmental costs (i.e., the costs associated with smelting, manufacturing, use, and recycle or disposal) throughout the life cycle of mined copper, lead, or zinc.

Jan 1, 1992

By S. Pollak, J. Rickard

The Long Baseline Neutrino Facility Far Site in Lead, South Dakota is currently under construction and involves drill and blast excavation of the largest and deepest caverns in North America. This paper will review how the geotechnical risks are being managed through careful consideration of excavation sequence, completion of exploratory pilot tunnels, implementation of a robust instrumentation and monitoring program, and validation against the design. Aside from having a cross section of 5,900 square feet and being situated at a depth of one mile, the caverns also employ a unique permanent rock bolt solution which underwent a significant pre-production pull testing program involving varying installation methods and being subject to blast vibrations. The behavior of the schistose rock mass and performance of the ground support are being continually monitored throughout the construction phase.

Jun 13, 2023

By W. J. Halvorsen

Means for minimizing the disadvantages of thermal drying are suggested. The other ap¬proach of substituting other techniques in place of thermal drying is also discussed. Recent devel¬opments in fine coal screening dry down to 3.2 mm (0.125 in.) and 2.0 mm (10 mesh) offer an econom¬ical means in certain cases.

Jan 1, 1988

By C. Y. Kao, Roger Y. Cheng, C. S. Hsieh

The mushroom-shaped Minghu power cavern located in central Taiwan is 21.2 m (W) by 40.5 m (H) by 127.2 m (L) and is designed to house 4 units of power generating-pumping equipment with a total capacity of 1,000 MW. This paper presents an introduction to the geological conditions at the cavern site; the rock mechanical tests undertaken; the design approach adopted; the construction method and sequence followed; and the instrumentation provided in the roof arch to monitor the behavior of the surrounding rocks. The measured data collected from the embedded instruments will be compared with those obtained from theoretical analyses and presented in this paper. Several technical problems encountered during the construction stage are covered and the solutions of these problems are also described therein.

Jan 1, 1983

By Russell E. Martin

Excavating and lining twin interstate highway tunnels each 11.3 m (37 ft) high by 14.6 m (48 ft) wide by 183 m (600 ft) long. A discussion of the geology of the site and problems occurring at the portals and the solutions to the problems. The methods used in placing the concrete lining are also discussed.

Jan 1, 1987

By Julio C. Martinez, Jeffrey L. Rice, Hayden Weschler

This paper details the extensive underpinning required to hold up the 39th street Bridge while demolishing its massive support piers and building a 30ft deep Cut/ Cover RR tunnel beneath it. The underpinning/SOE support required the construction of 16 large hand dug pits 36ft deep that were reinforced and concrete filled. In addition, an extensive steel support system was tied into the bridge super structure. All of the underpinning/tunnel construction was done while a 110ton crane sat directly atop the heavily trafficked – 66 ft. wide bridge. The tunnel excavation, concrete lining and final bridge pier support work will also be presented. All work was done within 5ft of active mainline tracks and that required tight grouting behind all lagging to eliminate any track settlement.

Jun 13, 2021

In general, it cannot be assumed that the strength of coal pillars remains constant over long periods of time. Field observations indicate that a coal seam, especially when it contains a parting layer, deteriorates over time, reducing the load-bearing capacity of the pillars. This paper discusses a unique approach to determining 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 a 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, 2012

By Gordon M. Pugh, David G. Rasmussen

INTRODUCTION Shrinkage stope mining can be employed in steeply dipping veins where both the wall and the vein material are sufficiently strong to stand with only minimal ground support. Shrinkage stope mining takes advantage of the swell in volume produced in breaking in-place ore. This expanded volume of ore is allowed to occupy part of the mined-out vein, and in so doing provides ground sup¬port and a working surface for the miners. Only enough of the ore is drawn after each stoping cut to allow work¬ing room. Not until the entire mining block has been broken is the full amount of broken ore drawn from the stope. DEVELOPMENT PRACTICES FOR SHRINKAGE STOPING The vein is developed into stoping blocks, each of which is 76 to 91 m (250 to 300 ft) in length and 61 m (200 ft) between levels. Level development, described later, is either on the vein or parallel to it with crosscuts periodically driven over to the vein. There are usually two exits from each stope. The first entry is a raise at one end driven either conventionally by raise climber, or by a raised borehole. Present practice is that this raise, put in from level to level, is either a 2.1- x 2.1-m (7- x 7-ft) Alimak raise or a 1.2- to 1.8-m (4- to 6-ft) diam borehole. Either raise system will require pro¬visions for an ore chute carried with the stope to the haulage level or the scram drift. At 9- to 12-m (30- to 40-ft) vertical intervals, dogholes are developed from the raise so that when stoping breaks back into these dogholes, timber or steel sets and necessary service facilities can be installed. The second entry to the stope may be either a similar raise at the stope endline, or more economically, a cribbed raise carried with the stope. As previously stated, development of the ore block is achieved by either drifting on the vein or by paralleling the vein with a footwall lateral and then crosscutting over to the vein at specified intervals. In the following discussion, three basic cases are illustrated in Figs. 1, 2, and 3. In Fig. 1, development is in the footwall by a 3- x 3-m (10- x 10-ft) trackless lateral. A heading is also driven on the ore and taken either full width or driven a standard size and slabbed to the vein width. Approxi¬mately 9-m (30-ft) long crosscuts on 7.6-m (25-ft) cen¬ters are driven from the lateral to the vein. For ease in muck handling they are usually put in on a slant rather than at right angles. A single orepass, located off the lateral and in the center of one stope block, can serve not only that stope, but also one on either side, up to a tramming distance of not more than 137 m (450 ft). Raises are put at the stope endlines on 91-m (300-ft) centers. The back of the vein is shot down and just enough broken material is drawn off to permit access for men to work off the broken ore. Development in Fig. 2 progresses by driving a 3- x 3-m (10- x 10-ft) trackless heading on the footwall side of the vein. The ore block is delineated by raises on 91-m (300-ft) centers. Crosscuts are again driven on 7.6-m (25-ft) centers over to the vein. Approximately four rounds are then taken up to the vein and each round is successively belled out so that all the crosscuts (pockets, in this case) connect. In this development, as opposed to that in Fig. 1 where there were no belled

Jan 1, 1982

By David E. Thompson, Edward S. Plotkin

The Massachusetts Bay Transportation Authority (MBTA) Red Line Extension Northwest is nearing the final stages of construction. The 3. 1 mile extension of the Red Line from the existing Harvard Square Station in Cambridge, Massachusetts to Alewife Brook Parkway in Cambridge, includes a large, near surface, hard rock, rapid transit chamber at Porter Square in Cambridge (Figure 1).

Jan 1, 1983

By Diane Moody

I have been asked to give you the National Coal Association's (NCA) view of the future of the coal industry. However, before discussing the outlook for the future I would like to set the stage by taking a brief look at how the industry has changed over the last decade. In 1977 the coal industry was in the midst of a period of steady growth. Although most of the gains in the early and mid 1970's occurred in the west, the industry was still predominately eastern, with eastern production accounting for 76 percent of the 697 million total tons produced in 1977. The labor force was nearing a high - at over 220,000 workers, and the number of active mines was also at a decade high of over 6,000. Productivity on the other hand was at a low. The average miner produced 1.80 tons per hour, and labor relations were also at a low point. Projections for coal's future were very optimistic, mainly because of the unprecedented growth in coal use by the utility industry. In 1977 the 477 million tons of utility coal accounted for 68 percent of U.S. coal production, and the utility industry planned on 129,000 MW of new coal-fired capacity over the next decade. Consumption of metallurgical coal at coke plants was the second largest market at 78 million tons; the industrial and residential market consumed 70 million tons and exports were at 54 million tons. But in retrospect, a lot was happening in 1977 that signalled many changes in the coal industry: - Amendments to the Clean Air Act were passed, which required that utilities take an entirely different approach to meeting New Source Performance Standards at new plants, and required that standards be set for industrial boilers as well; - the Surface Mining and Reclamation Act became law; -electrical generation, despite the optimistic forecasts, was nearing the end of a period of close to five percent annual growth; -1977 ended and 1978 began with the longest coal strike in U.S. history. -crude oil imports in the U.S. reached an all time high as did both total consumption of petroleum products in the U.S. and oil consumption at utilities. The high level of oil imports set the stage for the oil price increases of 1979 and 1980 which resulted in an immediate increase in demand for coal, not only in the United States, but world wide. Labor strikes in Australia and Poland sent foreign buyers to the U.S. literally in droves, and quickly made the U.S. a force in the world steam coal market. The U.S. coal and transportation industries responded to this overwhelming potential demand for coal. In a very short time, the capability had been developed to mine and transport the 1.2 billion tons of coal that forecasters said would be needed by the mid 1980's. What was not anticipated was that the economic effects of sharply higher oil prices would dampen demand for energy, especially for electricity, as quickly as we have seen; that coal industries in other countries would respond as rapidly as the U.S. coal industry, and at a rate

Jan 1, 1988

By P. Riveros, J. Binvignat, V. M. McNamara, D. Koren

The feasibility of recovering cyanide and copper from a gold mill barren solution was evaluated in a small A VR pilot plant. The campaign lasted 64 hours, during which time about 4,000 L of gold mill barren solution were processed. The results showed that A VR is an effective technology for recovering cyanide and copper from barren solutions. Under the best conditions, the copper precipitation and the cyanide volatilization attained 94% and 98%, respectively. Using 5 MNaOH as the absorbent, practically all the HCN gas was recovered in the form of a concentrated NaCN solution containing 70 g/L free CN. Basic engineering design parameters applicable to a large-scale operation were obtained, including the Henry's Law constant and the mass transfer coefficient for HCN gas.

Jan 1, 1997

By Harold Wahlborg, George Owusu

In a study using butyl diglyme as an organic extractant, essen­tially complete extraction of gold from chloride leach solution was achieved. The extraction kinetics are so fast that the process could be completed in 30 seconds. Except for iron, co-extraction of other ionic species was insignificant. Co-extracted iron species were successfully scrubbed from the loaded organic using 10% HCl solution. High grade, >99.9%, gold was recov­ered from the loaded organic using 5% oxalic acid solution as the stripping agent at a temperature of 70°C to 80°C. Over 99% of the organic-loaded gold was stripped from the organic phase. The butyl diglyme extractant is being tested on a variety of gold-bearing feedstocks. Presented here are results obtained from two gravity concentrates.

Jan 1, 1999

By R. J. Rice, K. F. Denning

Effect of iron on the removal of arsenic, mercury and selenium from gold mining effluents. Arsenic, mercury and selenium are common trace elements in gold tailing effluents that require removal before the water is either recycled or returned to a receiving body. One of the better methods of removal of these elements is the use of iron salts whereby, the metal is trapped on the freshly precipitated hydrolyzed iron oxides either by adsorption or enmeshment of the fine particulate and hence, removed from solution. The metal removal is effected by iron to metal ratio, pH, temperature etc. Pilot plant tests have shown that mercury can be reduced to < 5 ppb Hg, while full scale tests on arsenic and selenium have achieved levels of < 50 ppb As and < 10 ppb Se in well controlled systems.

Jan 1, 1993

By Carl E. Williams

During the past two years a computer program called "COPOR," Computerized Open Pit Optimization Routine, has been developed and used for mine planning of several base metal deposits. This routine utilizes a three dimensional computerized block model of an orebody, some economic parameters and operating constraints to locate the mineable or economic limits of the deposit schedule the yearly production from the mine and produce bench by bench ore reserve summaries and maps of the yearly and ultimate pit configurations. The moving cone method is used to perform these functions with a conventional block model. This model is conventional in the sense that each block is assumed to be homogenous; i.e., either ore or waste but not a mixture of the two. Due to the nature of a seam type deposit this approach is not realistic; therefore, revisions have been made to form a new version of the COPOR program. This version has been named "COALOR," Coal Optimization Routine. COALOR contains all of the power of the COPOR program but is equipped to handle the intricacies of coal seam type deposits. The deposit can be composed of a single seam or multiple seams which are horizontal or dipping at any angle. The numerous coal quality values can be incorporated to aid the optimization of the economic pit limits and yearly scheduling.

Jan 1, 1978

By P. M. Soupios

A near geophysical surface investigation of a landfill area close to the Hania city, in Crete Island, Greece, was conducted as inextricable phase of a preliminary geotechnical, geological and hydrogeological study of the area under investigation. Electrical Resistivity Tomography (ERT), one of the most promising prospecting techniques mainly concerning its effective contribution to resolve several environmental problems, was applied for the geophysical modelling. ERT is a robust imaging method the theory and implementation of which are well documented in geophysical research literature. The survey site is located in Akrotirion Peninsula, about 7km east of Hania city in Crete I. The geological setting comprises Trypalion limestones, marly limestones and a clayed weathered layer. Cavities are also identified at various scales which are recent tectono-karstic voids resulted from the combined actions of karstic erosion and tectonic stress on the Trypalion limestones where they are located. Due to the above-mentioned geological singularity and in the light of the requirement for an environmentally safe construction of the landfill, an ERT survey was carried out by deploying the dipole?dipole electrode configuration. Specifically, seven geoelectrical tomographies were conducted reaching the prospecting depth of 36m. The resulted images conduced, a) to overcome geotechnical problems, b) to plan the future sites for waste disposal and c) to reliably estimate the thickness of the already deposited wastes.

Jan 1, 2005

By Gunnar Thaning

The iron ores mined by LKAB in the north of Sweden have excellent beneficiation properties. This gives LKAB a favourable position as regards the production of low silica pellets for direct reduction. LKAB have concentrated on developing and marketing grades of pellets for the Midrex-Purofer-HyL process group, i.e. such D.R. processes which are carried out in a shaft furnace or a static bed using reformed natural gas as a reducing agent. The paper deals with properties and quality demands of iron ore pellets for such processes. Matters such as the effect of the residual magnetite in the fired pellets on the degree of metallization, the amount and composition of the slag phase in the pellets, the mechanism of the disintegration during reduction, the state of swelling of the pellets during the conditions prevailing in these processes, the importance of the porosity, the improvement of the reducibility and lowering of the sticking tendency of the pellets by small additions of suitable additives and the influence of the pellet size are discussed. A special test procedure for D.R. pellets has been elaborated by LKAB. Thus, three metallurgical properties are routinely determined separately, namely reducibility, reduction strength and sticking. The test methods are described. Finally the present and future LKAB pellets for direct reduction are presented with respect to chemical analyses and metallurgical properties.

Jan 1, 1978