Search Documents

By A. Uribe-Salas, J. A. Finch, B. J. Huls

Gas holdup profiles in the collection zones of a pilot flotation column (0.91 m x 13.5 m) and a laboratory flotation column (0.057 m x 9.5 m) operated with air and water only were determined from pressure measurements. The profiles were determined discretely and continuously. For the pilot column, a minimum distance between pressure measurements was necessary to give reliable results. For the laboratory column, a third-degree polynomial fit to the pressure vs. height data was required. Water manometers proved to be less sensitive to sensor and process noise than pressure transducers. The profiles showed that gas holdup approximately doubled over a height of 8 to 10 m. The profiles were not linear, and the gradient increased towards the top of the column, especially for gas rates greater than 1 cm/s. The profiles cannot be predicted by a simple bubble expansion model. The implications of this new finding of a significant gas holdup increase with height in the collection zone on various aspects of flotation column design and operation are discussed.

Jan 1, 1996

By A. M. Esteves

This paper addresses the question ?What constitutes the right level of investment in community goodwill?? Mining companies are still grappling with this subject even though the business case for community investment has been accepted at a general level, as a strategy for competitive differentiation, risk mitigation and a desire to deliver - and to be seen to deliver - a ?net benefit? to affected communities. Gaining senior management commitment to long term social projects, by definition characterized by uncertainty and complexity, is made easier if projects are shown to benefit the site?s strategic goals. Case study research amongst mining companies, including interviews with social investment decision-makers, has assisted in developing a SI-DAT (Social Investment Decision Analysis Tool), a decision model for evaluating social projects in order to create value for both the company and community. Multi-criteria decision analysis techniques integrating business planning processes with social impact assessment have proved useful in assisting mining companies think beyond seeking access to required lands and peaceful relations, to how they can meet their business goals and contribute to regional development.

Jan 1, 2007

By R. Ciccu

Permeable reactive barriers (PRB) are one of the most promising systems for groundwater remediation. PRB are constructed with the purpose to intercept the contaminated flow and to degrade it as a big reactive filter. The most common type of reactive barriers is realized by excavating a trench and by filling it with a substance able to treat the contaminants dissolved in the water. Another type of PRB is obtained by realizing a line of wells in which chemically active compounds are injected. A new method for barrier construction has been studied at DIGITA?s laboratories. It makes use of the waterjet technology to increase soil permeability and to inject active compounds. This technology is especially suitable in the case of deep contaminated aquifers where traditional construction methods are difficult to apply. The paper describes the experimental apparatus especially designed and constructed and the activities carried out to investigate the relationship between waterjet operative parameters and the penetration of the jet in the soil. In conclusion, on the basis of the experimental results, the economical feasibility of the technique is evaluated.

Jan 1, 2008

By Ruoming Gong, Arindam Samanta, Ragula Bhaskar

Three studies conducted at the University of Utah relating to the effect of scrubbers on face airflow patterns, the resulting dust exposure of operators and the development of a throat scrubber for continuous miners are summarized in this paper. The first study involved full-scale laboratory tests to determine the potential dispersion patterns and transport of dust at a continuous miner face, using different ventilation configurations and a scrubber. Concentration maps were developed and potential exposures at operator positions were examined. The second study involved the development of a 3-D numerical model to predict airflow patterns generated by a scrubber at a continuous miner face. The model was designed to evaluate the role of various face parameters on airflow patterns at a miner face and to complement the full-scale testing. The third study involved the design and fabrication of a low profile hydraulically powered continuous miner throat scrubber. The scrubber uses three hydraulic motors and small diameter fans to draw about 3000 cfm (1.42 m3/s) of air and uses a flooded bed scrubber to filter dust particles.

Jan 1, 1993

By Y. Topkaya, R. E. Johnson, B. R. Palmer, R. B. Bhappu, A. E. Clark, R. P. Bush, L. E. Schultze

The U.S. Bureau of Mines conducted copper exchange capacity (CuEC) tests for six common clays under simulated in situ leaching conditions. Regression equations were obtained from the data expressing the CuEC as a function of Cu concentration, pH, and temperature. Further testing resulted in regression equations expressing CuEC's of Na and Ca montmorillonites and attapulgite as a function of Cu concentration, pH, and the concentration of metal ions which compete with Cu for exchange sites. Using these equations, an analysis was made of the impact each clay could have on overall copper recovery. The results suggest that Ca and Na montmorillonite clays could have a major impact on Cu recovery and that attapulgite and illite clays could have a smaller, but still significant, impact. Kaolinite and ripidolite clays pose little threat to loss of copper from in situ leaching solutions. Copper losses are decreased by the presence of competing ions, and A1 and Mg have the largest impact of those ions normally present in Cu leaching solutions.

Jan 1, 1993

By Don Macfarlane, Brian Heer, Tom Martin

The Manapouri Power Station, commisioned in 1969, is located in Fiordland National Park in the South Island of New Zealand. It is the country’s largest hydro power scheme and can generate 700MW of electricity. The power station utilizes the hydraulic head of Lake Manapouri, using an underground power station and a 10 km-long tailrace tunnel was constructed by drill-and-blast to allow discharge to Doubtful Sound. Power generation fell short of expectations due to higher than expected friction in the tailrace system. To remedy this a second tailrace tunnel was constructed between June 1998and May 2002. It consisted of a 10 m diameter, 10 km long tunnel in predominately gneissic rock and was excavated using an Atlas Copco Robbins TBM. High water inflows, Owner/Contractor production incentives and a major claim settlement were handled during the 5 1/4 year project. This paper discusses TBM advance rates, utilization factors that increased in the second half of the project plus an innovative method for sealing Tunnel 1 to construct the bifurcation.

Jan 1, 2003

By F. Calizaya, I. Duckworth

An ore-pass is an underground conduit used to transfer ore from one level of a mine to another. This method of transportation depends on the elevation energy only; therefore, it has very low operating cost. However, two inherent problems may hamper this process: (1) hang-ups of interlocked pieces and (2) a sudden release of trapped air from the ore-pass (belching). These events can create unsafe conditions with the potential for catastrophic consequences. This paper presents a summary of CFD modeling studies that were formulated to investigate the pressure build-up and belching of dust and rock particles from long ore-passes. The models were calibrated against field data collected from an actual ore-pass system and used to predict the airflow-pressure distributions in the mine for various ore feed rates and ore-pass geometries. P.T. Freeport Indonesia’s Grasberg ore-pass system (240,000 tpd capacity) was used for this purpose. This system comprises of four active ore-passes, with each being more than 600 m in vertical length.

Jan 1, 2004

By H. G. Fleshman

?Wyoming bentonite? has become almost a world-wide trade mark for high quality sodium bentonite. Although bentonite is produced in more than a dozen U.S. states the largest producing area covers Wyoming and adjacent parts of Montana and South Dakota. Bentonite was originally known as Taylorite and later renamed Bentonite by Dr. Sam Knight, the State Geologist of Wyoming. The new name came from the Fort Benton shale member of the Mowry Formation. Bentonite is a clay consisting essentially of the montmorillonite group of minerals. Since bentonite has good ion exchange capabilities, various cat-ions are easily replaced. These cations are usually calcium and sodium; however, magnesium, lithium, potassium, and others can be exchanged. One way of classifying the clay is based on its swelling capacities when wet or added to water. Bentonite having sodium as the dominant exchangeable ion typically has very high swelling capacities and forms gel-like masses when added to water. Bentonite in which exchangeable calcium is more abundant than other ions has much lower swelling properties than sodium varieties.

Jan 1, 1987

By Michael J. Howes

The nature of business in a free enterprise system is to maximise the return on an investment i.e. to maximise the wealth of the shareholders. This is normally achieved within constraints dictated by many agencies, one of which is the health and welfare of the employees. In the mining industry considerable effort has been expended in improvements in this field, however, the major problem still confronting the practicing ventilation or environmental engineer is the determination of what standards he should design for, which satisfy both the economic and health requirement s. Normally the basic health requirements are satisfied by the minimum standards defined in regulations and codes of practice. These are, however, based on an acceptance of a certain risk or lower production potential. A prime function of the ventilation engineer is therefore to financially justify and implement improvements to both standards and systems. The main purpose of this paper is to examine the basis and techniques of providing this financial justification. Changes in existing methods to achieve the same standards but at lower costs are also covered.

Jan 1, 1980

By C. Patrick

Annually, the U.S. coal industry generates and must dispose of over 200 million tons of coal refuse, expanding a major environmental problem. The purpose of this research was to investigate the feasibility of utilizing coal refuse as an aggregate in concrete. This paper reports on findings of the initial phases of a project to determine the viability of replacing traditional concrete blocks, used for under-ground ventilation stoppings, with refuse blocks. Refuse was collected from three active preparation plants in Eastern Kentucky and used as the primary aggregate for concrete cylinders. The refuse fell within ranges normally observed for size consist, moisture, and ash. Stress-strain analyses yielded compressive strengths of the refuse cylinders from 59% to 77% of the control group strengths. Low variability within groups while significant differences between groups were found. On-going determination of effects of weathering on the refuse cylinders is being conducted and will be completed in early 1995. The research results are favorable for the future direction of the overall project objectives.

Jan 1, 1995

By R. K. Paramguru, K. Srinivasa Rao

This paper describes a new approach for examining the kinetics and mechanism of zinc dissolution from sphalerite concentrate in acidic ferric sulfate solution in the presence of manganese dioxide. A literature search was performed to access the possible action of the two oxidizing agents, i.e., ferric ion and manganese dioxide. The possibility of galvanic coupling between ZnS and MnO2 and the cyclic action of the redox couple, Fe2+/Fe3+, on these two minerals were theoretically examined based on corrosion principles. Expressions for the mixed potential (Em) and the mixed current (im) were derived for the relevant corrosion and galvanic couples. Leaching experiments were conducted to establish which of the above phenomena is operative during leaching. The results indicated that the dissolution mostly occurs by the action of ferric ion on ins producing ferrous ions. The presence of MnO2 enables a quick conversion of ferrous to ferric, which maintains the rate of in dissolution. The process has promising features for commercial exploitation.

Jan 1, 1999

By Robert F. Randolph

New technologies confront mining organizations with unprecedented human factors challenges. Likely problem areas range from the design of the human- machine interface to the design of work groups and mine organizational structures. However, these human design considerations are commonly ignored in most industries, resulting in a failure rate of 75% for advanced technology programs. The U.S. Bureau of Mines is addressing these concerns through a program of research on the human side of high technology mining systems. Interviews with mining industry participants and researchers have identified concern in several areas, including training and equipment design. Although new mining technologies promise to improve overall safety by relocating miners away from hazardous areas, data from MHSA accident reports and other sources suggest that certain types of new hazards may be created. Many of these new hazards can be reduced though a systems approach to ergonomic design of equipment, tasks, and work processes. This evidence, combined with reviews of high technology human-machine systems in other industries. can help in the design of safe and efficient future mining technologies.

Jan 1, 1992

By Raymond E. Connell

From a macro business process perspective, if what we do in the Mining Industry is find material, dig it out of the ground, convert it to a product and sell it, we are in what might be considered a "simple business". If it is so simple, where does information technology fit? How does it affect our industry? Is it a strategic tool for our industry? What approach should we be employing to ensure we are utilizing information technology effectively? How is information technology integrated or tied together with other areas in the organization such as process control? What kind of people and skill sets are required to support the whole area of information technology? What effect does information technology and automation have on streamlining and rethinking the way we do business in the 90's. This paper covers how these areas have been addressed within the Noranda Group of Companies. It reviews how information technology has evolved, the approach, and what effect it has had on a diversified natural resources company in the mining and metals, forest products, and oil and gas industries.

Jan 1, 1993

By B. J. Arnold

A coal's size distribution clay content and moisture content can affect its handling behavior. But the combined effects of these properties and the effects of other properties are not known. Research underway at CQ Inc.'s (formerly EPRI's) Coal Quality Development Center (CQDC) and at Iowa State University (ISU) will answer these questions as part of a four year project to develop a coal handleability index for utilities to use when specifying coals. This paper will present preliminary data from the first year of the project, which focused on obtaining data on the chemical and physical properties of carious coals and their measured handling properties. Additionally, size, ash and moisture analyses and shear test data for several coals used at one power plant will be presented along with correlations between these physical and chemical properties and the measured handling properties. These data lead to the conclusion that while moisture content is the most important variable, the amount of -44 µm (-325 mesh) coal fines is a significant factor in determining coal handling behavior.

Jan 1, 1992

By J. B. Zachwieja

Cationic reagents have been utilized in mineral processing since the mid 1930's and are based upon fatty nitrogen derivatives. The initial commercial development was centered around a flotation collector capable of separating potassium chloride from sodium chloride - potash flotation. The first commercial sale for Akzo, known then as Amour and Company, was realized in the summer of 1940 to a potash producer in Carlsbad, New Mexico for the flotation of potash. The success of the potash flotation collector led to the development of other cationic mineral processing reagents. Flotation collectors for iron ore, phosphate, calcium carbonate, silica sand, feldspar, and other silicates materialized into a large commercial business. Another area that realized commercial success was the development and use of anticaking/antidusting reagents for hygroscopic salts, fertilizer mixes, and granular fertilizers. A more recent development has found use in the trona industry as a defoamer and crystal growth modifier during the crystallization of sodium carbonate liquors. A review of cationic reagent chemistry and applications will be given and the potential for new application areas will be explored.

Jan 1, 1994

By O. J. C. Runnalls

Canada has played a significant role in the international uranium industry for some three decades. Although there have been many challenges in the past, the future offers a more extensive range of problems and prospects as Canada moves to expand its activities in all aspects of the nuclear fuel cycle. World uranium demand could grow to an annual requirement of 500,000 tons U308 by the year 2000. A substantial fraction of this material is likely to come from Canada because the country's reserves and resources are large, and because of a favourable geological potential for future discoveries. There has been a long history of association between the producing industry and the federal government, and it has provided the foundation for existing national uranium policies. Close industry-government association will be maintained and developed in future because of the anticipated rapid growth of the industry and the consequent need for continual refinement of government policies relating to exploration, mining, processing and export of uranium.

Jan 1, 1975

By C. Menidiatis

The first cement plant of TITAN Cement Co was founded in Elefsis in 1902. It was the first cement industrial facility to operate in the Balkans and in the Eastern Mediterranean region. Currently have four cement plants in Greece producing 5.4 million tons per annum, and 25 ready-mixed concrete sites producing 1.4 million m3 annually. It has a total of 20 quarries, 14 of which are producing materials used in the making of cement while the remaining six produce aggregates used in the production of ready-mixed concrete. All plants in Greece are accredited for ISO 14001. The restoration of quarries began in 1976 at the company?s limestone quarry of the Patras plant, and was soon extended to all quarries. At that time, a department responsible for all environmental issues was established. To date, over 700.000 shrubs and trees have been planted and maintained at quarries, plants and ready-mixed concrete facilities, while over 100,000 trees have been donated to municipalities, communities, customers and to the Greek state.

Jan 1, 2002

By Silvano Perla

Peabody Western Coal Co. operates two mines in northern Arizona. The Black Mesa and Kayenta coal mines are unique for several reasons. They both have only two customers: Southern California Edison’s Mohave generating station near Laughlin, NV and the Navajo generating station near Page, AZ. Both mines are close together. Between the two, they ship nearly 11 Mt/a (12 million stpy) of coal. Material is shipped to the power stations in two ways. This first is a 440- km-long (273-mile-long) underground slurry pipeline, the longest in the world. The second is an 11 -km-long (17-mile- long) long conveyor to four storage silos. Product is then shipped by train from the storage silos to the plant sites. Another factor makes these mines unusual. They are both situated in the middle of the 68,795km2 (17 million- acre) Navajo Reservation, home to the Navajo Nation and Hopi Tribe members. Nearly 90% of the Black Mesa and Kayentamines’ 850 employees are tribe members. Peabody Western Coal is the United States’ largest private employer of Native Americans.

Jan 1, 1995

By Joseph B. Alberts, David D. DiPonio, Francis B. Manning

From 1996 to 2001, Wayne County and 13 suburban Detroit communities constructed the Downriver Regional Storage and Transport System (DRSTS) to improve area water quality, protect public health and alleviate basement flooding. The project consisted of a 10-mile long storage and transport tunnel, a pump station at the existing wastewater treatment plant, 9 miles of relief sewers (6 in tunnel and 3 in open cut). The work was separated into 10 contracts. Due to hydraulic design requirements and other constraints, the tunnel profile was located generally 65 feet below ground surface within a soft to medium clay strata which skimmed along the top of a very dense glacial till “hardpan” overlaying bedrock. Boulders within the tunnel bore were recognized as a significant, but indeterminate risk. This paper presents a case history of the owner’s contracting strategy for risk assumption and management of the boulder impacts on the project. Actual conditions encountered during construction and contractual adjustments made to address problems are reviewed, and recommendations for future contracts are included.

Jan 1, 2003

By T. D. Arnold

The Barrick Bullfrog underground mine was established as an afterthought to the main open pit. As open pit ore dwindles, the underground mining becomes increasingly more important as an ore source, and to the overall economics of the project. This situation is similar to many other mines, and there is a strong move towards underground mining in the United States today. There are inherent problems in starting and operating underground mines in the shadow of any open pit operation, and at the Bullfrog there were several attempts at productive increases that were both successful and unsuccessful.

Jan 1, 1996