Search Documents

By Jon Y. Kaneshiro, Gregory E. Korbin, Stephen J. Navin, Larry J. Stout

Sewage presently being discharged into the Tijuana River Valley pollutes the valley as well as the beaches in the South Bay of San Diego, making the beaches unusable nearly year round. The SBTO will convey flows down a 8.5 m (28 ft.) by 58 m (190 ft.) deep drop shaft, through a 3.35 m (11 ft.) by 5.8 km (3.6 mile) long tunnel, and up a 46 m by 2.7 m (150 ft. by 9 ft.) riser shaft connecting to a 1.5 km (0.95 mile) of seafloor pipeline and 1.2 km (0.76 mile) of diffusers on the ocean floor. The drop shaft will be sunk through 38 m (125 ft.) of saturated sands and gravels and 20 m (65 ft.) into the dense fine sands of the San Diego Formation. The tunnel liner has been designed as a five piece, single pass, gasketed, bolted, reinforced concrete liner designed to withstand an external head of 76 m (250 ft.) of water and internal operating head of up to 27 m (89 ft.) and to accommodate movement at the numerous fault crossings. The tunnel is contemplated to be driven with a state-of-the-art Earth Pressure Balance Machine (EPBM) or slurry shield machine through a wide range of conditions from clay to gravel with boulders.

Jan 1, 1995

By Franklin J. Stermole

The current financial state of the mineral industry, in general, is bad. Economic prospects for improvements in the near future are uncertain. What will improve mineral investment economics so the mining industry can return to a more normal (in terms of past experience) production level? Basically, mineral commodity prices must rise. They must rise to economically justify reopening closed mines and for management to seriously consider expansion or development of existing and new mines. With the worldwide economy depressed for more than a year now (longer for most segments of the mineral industry), supply/demand relationships for mineral commodities are such that prices are depressed-except for precious metals. In investment analysis of the economic potential of existing or new investments in any industry, product price generally is one of the key parameters having great impact on the economic viability of projects. Petroleum and synfuels industry development contracted last year for the same product price reasons that have brought mineral industry development to a standstill. Much of the new mine development activity now underway or in the serious planning stages around the world involves precious metals ore body development simply because precious metal prices are high enough now or are projected to be high enough in future production years to give overall satisfactory project economics. It will take significant improvement in nonprecious metal mineral commodity prices in 1983 to develop significant new mine investment interest except in very high grade ore body special situations. Mineral Investment Decision Making Before progressing further with the discussion of mineral investment considerations for the coming year, it should be emphasized that mineral investment decision making-like all industry or individual investment decision making does not relate just to economic considerations. Investment decision making should and generally does involve three analyses: • Economic analysis • Financial analysis • Intangible analysis Economic analysis evaluates the relative economic merits of investment situations from a profitability viewpoint based on discounted cash flow analysis of projected investment revenues and costs. Financial analysis, on the other hand, refers to where and how the funds for proposed investments will be obtained. Regardless of the project's economic potential, if you can't finance it, the project will not be done. Intangible analysis considers factors affecting investments but which cannot be quantified easily in economic terms. Typical intangible factors are legal considerations, public opinion, goodwill, environmental and ecological impacts, and regulatory or political considerations, to name a few. New mine development investment decision making in the US has been impacted heavily by intangible considerations in the past decade and will probably continue to be impacted by them in 1983. There is a common tendency in literature and management practice to interchange the terms economic analysis and financial analysis. This often leads to confusion about the rationale for investment decisions. For example, in the past year a majority of companies in all types of industries cut back budgets for new projects. Often this was done not because new project economics were unsatisfactory, but because cash flow from existing operations was reduced compared to previous years due to the recession, and debt service requirements were high from existing loans so new borrowing was undesirable. For financial reasons, in other words, many projects were shelved last year. That included some precious metal mining projects and many petroleum projects. Many other projects were shelved for economic reasons (sometimes combined with financial reasons in the case of marginal economic projects). New mine development for copper, lead, zinc, molybdenum, iron ore, and synthetic fuels are a few examples. Economic Uncertainty and Financial Considerations Mineral project analysis has always involved a lot of uncertainty with respect to determining ore grades, tonnage of producible reserves, operating and capital cost projects, and mineral commodity prices estimates. The wide swings in mineral commodity prices in recent years and the almost impossible task of projecting future prices with any degree of confidence or accuracy concerns mineral project investment decision makers. In developing a new copper or silver mine, it is not today's price of copper or silver that is relevant to economic analysis of the mine, but what the price will be during the producing years. There is no way to avoid projecting the escalation (or de-escalation) effects on revenues and costs. To analyze a project in terms of today's dollar revenues and costs implicitly assumes that escalation will not change today's project costs and revenues; or that, if they do change, the project economics will be unaffected by the changes. This often is not the best or even a realistic assumption. The inherent uncertainty associated with historical mineral price swings is exacerbated in 1983 by the uncertainty of when

Jan 2, 1983

By Thomas Van Riper

Newmont Mining Corporation started as one man's investment vehicle. William Boyce Thompson, Newmont's founder, was already a millionaire many times when he incorporated his existing Newmont company in Delaware in 1921. The initial stake in the company was $8 million in capital contributed by Thompson and several close associates. In its infancy the company was truly a holding company. It did not operate or manage any properties. This situation changed drastically over time. By 1939 Newmont was actively mining 12 gold mines in North America. The following year, the first copper mine that Newmont ever managed directly, came into full production in South Africa. The period after World War I1 was a glorious one for Newmont. Plato Malozemoff took the helm of the company, and expanded its operations over the next 30 years into copper in Arizona, oil and gas in the U.S. and the North Sea, into domestic coal and thankfully, into significant gold operations.

Jan 1, 1989

By R. Fields

Nevada is primarily known today for its nation-leading production of gold and silver. However, industrial mineral production continues to play an important role in providing construction materials to help make the state the fastest growing in the United States. Aggregate production in Nevada was about 20 million tons in 1991. Most of that was used in construction in the fast-growing Las Vegas area. The state leads the nation in the production of barite and mined magnesite and has significant production of lithium carbonate, diatomite and gypsum. Other industrial minerals produced in the state include specialty clays, silica, lime and dolomite and relatively small production in salt, perlite and dimension stone. Industrial minerals operations are subject to state and federal permitting requirements, especially in the areas of air and water quality and mined land reclamation. As in all segments of the mineral producing industries throughout the nation, the amount and complexity of regulations affecting industrial minerals has increased significantly in recent years. Nevada is no exception.

Jan 1, 1993

By James A. Holtkamp

Environmental regulation in Mexico has matured dramatically and effectively in the last decade. The gap between environmental regulation in the United States and Mexico is rapidly narrowing. From a regulatory perspective, it is no longer necessarily less burdensome to operate in Mexico. Principal laws and regulations Mexico has two principal environmental regulatory systems. The first consists of the laws and regulations governing domestic activities. The second consists of the treaties, agreements and understandings between the United States and Mexico dealing with transboundary pollution and maquiladoras (see Maquiladora Decree, next column). The following are the principal major laws and regulations governing environmental protection in Mexico: General Law: The General Law on Ecological Balance and Protection of the Environment, effective March 1, 1988. Water Regulations: Regulations for the Prevention and Control of Water Pollution, effective May 29, 1973. Environmental Impact Regulations: Regulations of the General Law on Ecological Balance and Protection of the Environment, regarding Environmental Impact, effective June 8, 1988.

Jan 1, 1994

By Martin Valeri

The operation described in-this paper will be confined to the Nemacolin Mine of The Buckeye Coal company, Nemacolin, Pennsylvania.' This mine is-located on the Monongahela River approximately sixty miles south of Pittsburgh. The mining is in the Pittsburgh seam that has an average thickness of 88 to 90 inches. The current practice is to mine approximately 80 inches, leaving 8 to 10 inches of roof coal. All of the coal produced is used solely for by-product coking by the parent Youngstown Sheet & Tube Company, Youngstown, Ohio. Eight to ten inches of top coal are left by the miners to prevent air slacking of the draw slate. In addition, this top coal which will float at the washing gravity has a very high ash and sulphur content, and when mined, seriously affects the quality of the clean coal product.

Jan 1, 1961

By Yuji Tsuneno, Yoshikazu Mikami, Yasuo Takeuchi

A new device was successfully developed in order to overcome the difficulty of drilling longer holes for anchors in soft soil bedrocks or swelling bedrocks, which is one of the major impediments to rapid excavation by NATM (New Austrian Tunnelling Method). With higher rotation (1200 - 1800 r.p.m.) and lower percussion energy (4 - 6 kg.m), the new drill has following advantages: (1) Applicability covers soils and medium hard rocks with the same drifter. (2) Longer hole (more than 9m) is achievable only with air flushing even in cohesive soils or rocks. (3) Better borehole stability is obtainable even in earth or in fissured rocks.

Jan 1, 1981

By M. S. Bickers

Prior to 1970, the environmental liabilities associated with mine construction and management were few. Mostly, they were aimed at health and safety matters. At that time less than two dozen codes were incorporated into the engineering design and they were somewhat static and well known by the engineering designers and managers. These codes issued by governmental agencies and professional associations are listed in Table 1

Jan 1, 1988

By R. H. Goodman

The development of techniques for separating minerals based on differences in their specific gravities is reviewed and their present applications in process technology outlined. Special emphasis is placed on the development, in Australia, of new models of the spiral concentrator. The mechanics of separation of spiral separators are stated, including the effects of operating parameters, Some of the traditional areas of spiral application are described, together with examples of new applications such as treatment of fine alluvials and tailings, separation of liberated minerals at coarse sizes and fine coal recovery.

Jan 1, 1984

By D. John Curtis, Gordon S. Crighton, John C. Hester

The six main drives needed to build 55 miles of 4.8 and 7.7 metre i.d. tunnels in 33 months called for careful co-ordination of the design of tunnel boring machines and linings. The implications of these requirements are discussed, with particular reference to the selection of tunnel liners. The solutions adopted are detailed and details are given of the specifications and procedures adopted. The design methods employed for liners are outlined. The construction methods are described and current performance figures given.

Jan 1, 1991

By Elvin R. Beach, Jaroslaw Drelich

Pull-off forces were measured for 8-9 pm diameter polystyrene (PSI particles on smooth spin- coated polystyrene films and hexadecanethiol (HDT) self-assemble monolayer surfaces using atomic force microscopy (AFM). Three parameters were controlled during experimentation: (i) the maximum applied load pressing the particle onto the substrate was varied from 50 to 4,000 nN, (ii) loading/unloading rate for the particle to attach and separate from the substrate varied from 0.01 to 9.3 Hz, and (iii) contact time for particle to reside on the substrate surface before retracting the particle to separate it from the surface changed from I µsecond to 200 seconds. the pull-off forces increased with increasing applied loading, increasing loading/unloading rate, and increasing contact time for the PS particle on PS film and on HDT monolayer. The PS particles experience elastic and plastic deformations duringpull-08 force measurements. Plastic deformation is primarily associated with flattening of surface irregularities. The results obtained in this research suggest that the particle-substrate contact areas of the magnitude comparable to those predicted by the JKR contact mechanical model can be reached in the AFM experiments by using high applied loads and long particle-substrate contact times. This result re-opens the prospect of' using AFM for studying surface energies of deformable micro-particles, even if the micro-particles have small irregularities on the surface.

Jan 1, 2003

By R. P. King, S. Middlemiss

A method is developed to convert a measured distribution of fracture energies to the equivalent work index. The method assumes that the energy required to grind the material from the feed size distribution to the product size distribution is equivalent to the sum of the impact energies that are required to reduce the feed material by successive single impacts to the required product size. The method was tested by measuring the fracture energy distributions for quartz and comparing the resulting calculated value of the work index with the work index for this material measured using the conventional Bond laboratory procedure.

Jan 1, 1998

By N. Ohmura, H. Saiki, T. Nagaoka

A microbiological flotation system that facilitates the removal of pyritic sulfurfrom coal is reported. The chemoautotrophic bacterium Thiobacillus ferrooxidans is utilized as a pyrite-selective biological surfactant that augments the flotation-mediated rejection of pyritic sulfur. The bacteria were produced by continuous cultivation in 50-L tanks, where it was possible to produce 3.8 x 1012 cells/day when the dilution rate was optimal and the pH was 1.6, a condition that prevented ferric precipitation. Prior to flotation, the bacteria were mixed with coal, which allowed cells to selectively adhere to the pyrite. The adherence of bacteria made the pyrite surfaces more hydrophilic, which facilitated separation by increasing the tendency of pyrite to sink, while the hydrophobic coal floated. When a synthetic coal/pyrite mixture (10.1 % sulfur) was subjected to microbial flotation, the level of sulfur rejection was stable during the entire period of operation (i.e., one hour). In the absence of bacteria, flotation reduced the sulfur content of a coal/pyrite mixture to within the range of 6.7% to 7.4%, with the combustible recoveries ranging from 93.9% to 99.0%. In the presence of bacteria, the sulfur content of cleaned coal was in the range of 1.3% to 1.4%, with the combustible recoveries ranging from 80.8% to 86.3%. Bacterial activity accounted for 57% of the total sulfur rejected through flotation. The desulfurization capacity of the system was further confirmed by testing it with run-of-mine coal. The pyritic sulfur content was reduced from 2.9% in the feed coal to around 1.2% in the froth product, while 80% of the combustible recovery was retained. Microbial flotation removed 60% of the pyritic sulfur from the feed. These findings demonstrated that micro¬bial flotation could be utilized for the removal of pyritic sulfur from coal in a semicontinuous system.

Jan 1, 2000

By Andrew B. Allen, Charles W. Robinson, Robert L. Schneider

In April, the US Synthetic Fuels Corp. broke a three-year silence and made its first financial award by approving a $820,750 loan for the First Colony peat-to-methanol project in North Carolina (ME, May, page 403). Peat Methanol Associates (PMA), a partnership between Koppers Co., ETCO Methanol Inc., Transco, Peat Methanol Co., and l. B. Sunderland, broke ground at First Colony last year and plans to begin production in Dec. 1985. Although the award is only a small part of Synthetic Fuels Corp.'s $15-billion budget, it does signal the corporation's intention to move aggressively ahead. It also is a positive indication that First Colony will be completed and operated successfully. This article describes the methods and equipment that will be used to harvest peat at First Colony, as well as how the peat will be converted to methanol. Introduction Peat deposits found along North Carolina's coastal plain contain high-quality fuel-grade peat with an average heating value of more than 23.3 MJ/kg (10,000 Btu/lb) (dry), with a low sulfur and ash content. The deposits differ from other US peats in that they contain large, sound Atlantic White Cedar and Cypress logs, stumps, and roots that may extend throughout the full depth of the deposit. A second difference is that these deposits are much more highly decomposed and, in the raw state, have the appearance and feel of a heavy, reddish-brown grease. These factors make it impractical to use standard production equipment so a new line was developed. Also, because of these conditions, techniques were modified to facilitate production. First Colony Farms, located near Creswell, NC, developed and evaluated a milled peat program. Equipment for this production method was designed and built, production rates were established from field operations, drying rates were established, weather data were analyzed, and total operating and capital costs were estimated. The method depends on the sun and wind for drying peat to the desired moisture content, in this case around 40%. Therefore, field preparation is actually the construction of a large solar collector to dry the peat so it can be harvested and stockpiled. It is essential that this collector be properly profiled initially and maintained during production to prevent precipitation from ponding. Initial Field Preparation Initial field preparation includes cleaning existing canals and constructing ditches and water control structures for proper drainage of rainwater run-off, building adequate roads for site access, removing surface vegetation, and profiling and sloping the fields. At First Colony, the 60.7-km2 (15,000-acre) harvesting area was divided into 129.5-hm2 (320-acre) blocks about 1.6 km (1 mile) long and 805 m (0.5 mile) wide. This was accomplished by cleaning main outfall canals with adjacent roads built from canal spoil at 1.6-km (1-mile) intervals. Existing intermediate canals that feed into main outfall canals at 805-m (0.5-mile) intervals also are cleaned. Headland roads are constructed from canal spoil along each side of each intermediate canal. This 129.5-hm2 (320-acre) block is then divided into 32 harvest strips by small V-ditches constructed at 50-m (165-ft) intervals. At the end of the field with the lowest elevation, corrugated steel pipe culverts are installed under the headland road in each V-ditch to control rainwater runoff into intermediate canals. Runoff water from the fields is diverted to a holding pond to prevent any increase in peak water runoff rates and to allow for more uniform drainage rate than experienced to date. After the drainage system is installed, harvest strips are ready for grinding and sloping operations. Surface vegetation, made up of small, waxy-leafed shrubs such as Gallberry, Bayberry, Magnolia, and scattered pond pine, can be effectively ground and incorporated into the upper surface of the peat layer. Here, it will rapidly decompose and have little effect on overall peat quality, thus eliminating the standard practice of pushing the vegetation and upper wood layer into long windrows with bulldozers and hauling this debris from the fields. Incorporating vegetation into the upper surface is known as the initial 102-mm (4-in.) surface vegetation grind and is accomplished by using a modified Bros Rota Mixer. Following this operation, and by using the same unit, a sec¬ond grind with a depth of 200-255 mm (8-10 in.) is made. This reduces the debris to a finer consistency, mixes it with the upper peat layer, and grinds any wood found in the upper 200-255 mm (8-10 in.). After initial grinding operations are completed, the augering or sloping operations can be accomplished with little or no hin-

Jan 7, 1983

By Robert Stefanko

The results of a recent study on the influence of continuous and conventional mining techniques on the size consist and wash- ability characteristics of coal are presented. Eight samples, four each from continuous and conventional mining sections were collected. Each sample was screened in seven size fractions, and each size fraction was totally fractionated at five gravities. The data thus collected was statistically examined for the influence significance of mining techniques, size, and gravity on the quality of the mined product. The paper presents the sample collection method, data gathering and analysis procedures, and major conclusions. The study revealed that there are pronounced differences in the products from the two mining systems and that conventional mining yielded a better product in terms of size-consist, and yield, ash, and sulfur in both the raw and washed products. The results of the study are significant in regard to consideration of resource utilization and conservation, and environmental impacts.

Jan 1, 1974

By K. N. Han

The dissolution kinetics of cobalt in iodine/ iodide solutions were investigated using a rotating-disc technique. Variables studied included temperature, rotating speed, concentration of lixiviants and the pH of the solution. The overall dissolution reaction appeared to be limited by the mass transfer of tri-iodide through the diffusion boundary layer with an Arrhenius activation energy of <16.2 kJ/mol (4 kcal/mol) over the temperature range of 2 to 42ºC. The pH of the solution had little effect, as long as the pH of the solution was <8. However, when the pH of the solution became >8, the dissolution rate decreased dramatically, due to passivation. The rate of dissolution was in good agreement with the dissolution model developed by the authors earlier.

Jan 1, 1995

By T. M. Campoy, J. R. Jones

When extending the life of an existing mine in Appalachia, it is common to acquire the adjacent reserves and extend the existing mine into it. The existing mine is often renovated to accommodate the new conditions. The existing mining system and the track and belt haulage systems may he modified while the new property is integrated into the old one. All of these changes create new constraints for the mine ventilation system (MVS) that require proper planning and control procedures. This paper presents a study that was carried out for the ventilation system of a newly expanded underground coal mine in the Appalachian region. The process of correcting the ventilation system of the existing mine is discussed. That is followed by a discussion of some of the stages of controlling the expanded system. Numerical data for these steps are also presented.

Jan 1, 1994

By E. S. Bianchin

The more complex control needs of today&apos;s mineral processing plants combined with ever-changing digital technology have brought numerous improvements to process control systems. This paper discusses recent advancements in distributed control systems (DCS) which facilitate the implementation of process plant automation. Some of the topics of discussion include integrated function controllers, weigh scale and analyzer interfacing, operator interfacing, personal computers, process information management and process plant management.

Jan 1, 1988

By Malcolm J. McPherson

Observations of environmental parameters in mines have traditionally been made by means of hand-held instruments, these being employed as a basis to ensure that atmospheric conditions in the mine remain within limits commensurate with safety, to safeguard the health of personnel, and to ensure that statutory requirements are met. Thus, starting from the first flame safety lamps of the early nineteenth century, numerous portable instruments have been devised over the years to indicate levels of dust, temperature, humidity, and concentrations of gases including oxygen, methane, and carbon monoxide. Similarly, portable instruments have been used to measure air velocity and pressure. For routine monitoring purposes, hand-held equipment suffers from many disadvantages. Readings are intermittent, often with long delays between successive observations, making short-term trend analysis impossible. Portable instruments are more liable to damage; they are labor intensive and provide a very limited amount of information either for control or planning purposes. The 1960&apos;s and 1970&apos;s have seen an accelerated development of mine environmental monitoring equipment. Alarm methanometers to give localized audiovisual signals became more common. These were followed by a variety of instruments which gave local, then local/remote continuous records, particularly of methane concentration and airflow. More sophisticated transducers and transmission systems were developed allowing further parameters to be monitored. This led to a proliferation of paper strip and chart recorders which had to be maintained and inspected regularly for trends and abnormalities.

Jan 1, 1979

By Steven W. Hunt, Ronald E. Heuer, Safdar A. Gill

A 3.3 m (11 feet) diameter, 51 m (168 feet) deep temporary steel casing which had been sunk within glacial soils buckled and collapsed on July 29, 1985. The collapse occurred at the CT-8 Dropshaft site in Milwaukee while two workmen were contact grouting outside the casing in an attempt to stop groundwater inflows through a bottom plug. This paper describes the soil and groundwater conditions at the site, the casing design, the method of shaft construction, and probable causes of the buckling failure. Specific aspects of the paper include: slurry method of shaft excavation and casing installation, soil creep, earth pressure due to three dimensional arching, and buckling strength of a casing surrounded by slurry rather than grout and firm soil. The paper should be of interest to designers and constructors of temporary ground support systems for deep shafts.

Jan 1, 1995