Search Documents

By E. M. Spokes

Starting in 1980, a committee of the National Research Council studied the question of why some underground coal mines are safer than others and what could be done to improve the ones with poorer performance. The results indicated that safety is improved by management commitment to safety, by cooperation between labor and management on safety matters, and by quality training of employees and managers. Younger miners have higher accident frequencies, but are less likely to be killed or permanently disabled by a lost-time accident. Methods for improving safety performance are proposed.

Jan 1, 1987

By F. V. Antonio, R. S. Pizarro

Masbate Gold Mines, dormant since WWI I, are now back in operation. The ore treatment plant incorporates carbon-in-pulp processing, utilized because of the ready availability of coconut shell charcoal in the Philippines and the high clay content of the ore. A detailed description of the plant, including the surprisingly fast and efficient alcohol stripping facility is presented. Operating data for the plant is provided together with an interesting performance evaluation of mechanical versus air- lift agitated leach tanks.

Jan 1, 1981

By Maurice A. Ponti

The D.C. Water and Sewer Authority is implementing the Anacostia River Projects component of its Long-Term CSO Control Plan, including 21 kilometers of 3.7- to 7-meter-diameter CSO near-surface diversion storage/conveyance structures and flood relief, pressurized-face, soft ground tunnels at a maximum depth of 65 meters. This paper describes a project-specific soil grouping system that is primarily based on soil characteristics for tunneling derived from tests including Atterberg limits, grain size, swelling, mineralogy, triaxial, pressure meter, and consolidation, which differentiates the project from past area tunnel projects using descriptive systems based primarily on area geology.

The inquiry into the explosion at the Moura No. 2 Mine in August 1994 recommended -?Emergency procedures should be exercised at each mine on a systematic basis, the minimum requirement being on an annual basis for each mine.? (Windridge et al. 1996). In December 1996 the ?Approved Standard for the Conduct of Emergency Procedures Exercises? was published and has been subsequently revised (Queensland Department of Mines and Energy Safety and Health Division 1999). This document provided guidelines for conducting mine site emergency exercises as well as the requirement for a test of state-wide emergency response by holding a Level 1 Mine Emergency Exercise at one mine on an annual basis. From 1998 to date (January 2008) ten Level 1 Mine Emergency Exercises have been held in Queensland, Australia. This paper discusses each of the exercises conducted to date as well as the logistics, scenario preparation, planning and organising required to conduct emergency exercises at this level.

Jan 1, 2009

By G. M. Bernard

The Andacollo gold mine is located near the small town of Andacollo, Chile (population 14,000) in the fourth region. It is approximately 35 miles by paved road from the coastal city of La Serena, and Santiago lies about 300 miles to the south (see map.) Site elevation varies between 3300 feet and 4200 feet. The climate at the site is moderate but arid, with an average annual rainfall of only five inches. Because there is little rain, and the temperature varies only a few degrees (57"F to 75°F); there are no freezing, solution dilution, or pad saturation problems. The climatic conditions are ideal for heap leaching.

Jan 1, 1996

Nautilus Minerals and Neptune Minerals are betting that the next great metals rush will take place more than 1,500 m (5,000 ft) below the sea. Nautilus is the first company to commercially explore the ocean floor for gold and copper seafloor massive sulfide (SMS) deposits. Its main focus is the Solwara 1 Project, a polymetallic copper, gold, zinc, silver deposit that is under 1,600 m (5,200 ft) of water off the coast of Papua New Guinea in the western Pacific Oceans? Rim of Fire. Nautilus Minerals, in a joint venture with Placer Dome (now Barrick Gold), began its exploration of what would become the Solwara 1 area in 2005 with side scan sonar and dredge sampling. The dredge and grab sampling confirmed the grade tenor of earlier sampling by scientific research programs. The 45 dredge samples aver-aged 10.8 percent copper, 3.7 percent zinc, 224 g/t (6.5 oz/st) silver and 13.7 g/t (0.4 oz/st) gold. Nautilus has since staked out more than 300,000 km2 (115,800 sq miles) of tenement licenses and exploration applications in the waters off Papua New Guinea, Fiji, New Zealand, Tonga and the Solomon Islands. That is an area about the same size of the United Kingdom. Interest in Nautilus and its projects has grown tremendously since its inception. The company is now listed on the Toronto Stock Exchange. It has raised more than $300 million and spent more than $23 million on exploration. The company has gained the backing of mining majors such as Teck Cominco, Epion, Anglo American and Barrick Gold. It is positioned to become an emerging producer in 2010. Teck Cominco recently agreed to exercise share purchase warrants to acquire three million additional common shares of Nautilus at a price of US$15 million. This will take Teck Cominco?s shareholding to approximately 7.2 percent of the issued shares. Teck Cominco will conduct and manage a ship-based exploration program that will run in addition to the exploration that was already planned for 2008.

Jan 1, 2008

By S. K. Kawatra, A. K. Bakshi, T. C. Eisele

An on-line rheometer, suitable for use with slurries, has been developed at Michigan Technological University. This rheometer can be used with both Newtonian and non-Newtonian slurries, and produces complete shear-rate/shear stress curves which characterize the time-independent rheology of the slurry. The sensor utilizes the Hagen-Poiseuille equation and Boyle's Law to calculate the shear rate, slurry flowrate, and shear stress from a series of pressure measurements. The design of the unit allows the measurement sample to be continuously collected from operating process streams in the often-hostile on-line environment. The shear rate/shear stress curves can be used to conveniently calculate the apparent viscosity at any given shear rate, and also to measure any yield stress or other deviations from Newtonian behavior.

Jan 1, 1999

By Russell Miller, Fun-Den Wang

High Pressure Water Jet Assisted Tunneling The high pressure water jet assisted tunneling project was conducted in a granite quarry near Skykomish, Washington, approximately 90 miles east of Seattle. A 7-ft diam tunnel boring machine was modified and equipped with high pressure water jets. The concept that tunneling rates can be improved by using high pressure water jets was validated, with an average increased advance rate of 50% to 60%. For some tests, the advance rate was more than doubled. A comprehensive economic analysis has shown that very significant savings are possible. At a 50% increase in advance rate, cost savings of 14% and 24% were projected for 10-ft and 20-ft diam tunnels respectively. These benefits were seen to be relatively insensitive to water jet equipment costs.

Jan 1, 1976

By H. Maleki, G. Tetreault

This study was initiated by the Bureau of Land Management (BLM) to develop guidelines for determining the maximum economic recovery of resources in coal mines. The work was in response to a requirement in the Mineral Leasing Act of 1920 and Federal regulations. The intent was to address the economic rainability of small, irregular reserves in existing longwall mines. In particular, there was a need to determine if room-and-pillar mining using a continuous miner (CM method) was economically sound, or whether unconventional (short or odd-shaped) longwalls could be used to recover small coal reserves economically. Small reserves, called "widgets" are left in longwall mines on one side of the mains, near outcrops and adverse geological conditions, or near any other location where reserve geometry does not lend itself to mining with a rectangular longwall panel. The work included (1) analysis of the geologic, geo-technical, and economic factors that influence the recovery of small coal reserves, (2) analysis of historic changes in supply, demand, and coal prices, (3) development of typical cost models for room-and-pillar and longwall mines, and (4) development of a practical methodology for determining maximum economic recovery. The methodology included an evaluation of the ratio of coal mined during longwall mining to that mined for development (LDR) as well as costs of maintaining coal quality depending on market conditions. The LDR is a good indicator of mine efficiency and overall coal recovery in modem longwall mines and thus is used to evaluate the

Jan 1, 2001

By Daniel H. Isreal

Because the federal government owns and controls nearly 80% of the most valuable oil shale reserves in the West, it is inevitable that federal leasing and siting will play a prominent role in development of an oil shale industry during the 1980s. Also, because of recent enactment of the Synthetic Fuels Corp. authorizing up to $88 billion in loan and price guarantees-federal financing will provide the critical incentive to permit private investment in a still infant industry.

Jan 1, 1981

By A. El-Midany

Dolomite impurities are increasing in the currently mined phosphate deposits in Florida. Several research efforts have been conducted in various laboratories around the globe to find methods to economically removing the dolomite. However, a universal and cost-effective process is not now in commercial use. In this paper, a new process for dolomite/apatite separation is presented. The differential solubility of dolomite in slightly acidic solution is utilized to generate micro CO2 bubbles at the dolomite/water interface. Particle (dolomite)/bubble aggregates float to the surface leaving phosphate concentrate with low MgO content. Interestingly, up to 6.0 mm particles can be floated by such micro-bubble/particle aggregates. Different surface-active agents were tested to stabilize the bubbles. Results of these tests are presented, and the mechanisms involved are discussed.

Jan 1, 2009

By V. I. Kefeli

Public-private partnership efforts are working to create green landscapes from abandoned industrial sites. Fabricated soils, potentially an essential element of such landscapes, are designed to substitute for topsoil on the areas free from ground cover and plant community. The aluminosilicate matrix and humus form the soil micelle - the primary unit of any soil complex. Humus formation is a process based on carbon-nitrogen interaction. Sources of carbon can be materials rich in easily composted products like cellulose and polyphenols (plant leaves) or aged lignin polymers (saw dust from different woody plants). The pathways of carbon-nitrogen complexes are discussed. Properties of the fabricated soil components were examined by bio-tests and plant models.

Jan 1, 2002

By S. Noll

Ventilation is an essential part of any underground mining operation. It provides fresh air for workers and machinery, keeps up an adequate mine climate and dilutes and dissipates noxious gases. Possible changes in the economic environment for mining in the future, e.g. increasing energy costs, will necessitate optimization of distribution of airflow within most mines. This paper discusses the scientific set-up for measurements as well as the behavior and influence of parameters of ventilation according to airflow distribution under consideration of technically possible set-ups of mine fans. This study was done in an underground mine with a flat seam room and pillar mining method.

Feb 27, 2013

By R. Tamblyn

Vertically stirred media mills are a highly effective low-footprint solution for the ultrafine grinding of industrial minerals. This work investigates the effect of media density on flow patterns within the mill. Direct irradiation of a media particle leads to decay through positron emission, consequently forming two anti-parallel gamma rays, which allow for the real time tracking of particle position. Grinding media of the same size, but with a range of specific gravities are followed using this method, and the effect on the flow within the mill is revealed. The technique is seen to be an effective method to highlight the velocity profiles within the mill, as well as the zones where grinding is less efficient ? areas of relatively low velocity and high residence time. The changing media is seen to effect the overall flow patterns within the mill, having consequential effects on the efficiency of the grind.

Jan 1, 2009

By V. Svalbonas

The process of grinding mill quality assurance brings with it associated truths and myths. When the mill quality assurance process took its first great steps forward in the late 1970s and early 1980s, they were in response to the conditions existing, in our industry, at those times. In the late 1990s, we are faced with different conditions, and problems, and need fresh solutions. Yet the system developed for the early 1980s has produced no new approaches for the late 1990s, becoming instead more hardened and entrenched. This lack of development and actual resistance to research is now costing the industry significant amounts of money in late start-ups and useless scrap loss.

Jan 1, 1999

By Thomas Schwind, Pamela S. Moran

For short tunnels, a reinforced cast-in-place lining is not economical and shotcreteis a logical substitution. In the past, reinforced shotcrete linings have been constructed with lattice girders and welded wire fabric. For the Russia Wharf Tunnel in Boston, MA, the Contractor, with the help of the Dr. G. Sauer Corporation offered the MBTA a VECP to substitute the reinforced cast-in-place concrete lining with a steel fiber reinforced shotcrete lining. The challenge was to adequately model the ductility of the steel fiber reinforced shotcrete and to test the shotcrete prior to and during construction to assure quality control. To our knowledge, this type of numerical simulation has not been used on any other tunnels in the US.

Jan 1, 2005

By Andre Balt, Pierre Hofmeyr

It is only recently that automation has been applied to mining analytical laboratories. This paper describes the use of automation in the laboratory analytical process of hard-rock mining and geological samples and slurries in mining concentrator plant process control laboratories. Types of analysis include fire assay, XRF, ICP and wet chemistry. The benefits of automation are reduced unit cost of analyses, greatly reduced staff requirements, higher quality of data and very fast turn-around times.

Jan 1, 2005

The Río Agrio of northern Patagonia, Argentina, is highly acidic due to inputs of volcanic gases (SO2, HCl, HF) in its headwaters. The watershed includes a hyper-acidic (pH <0.5) volcanic crater lake, a larger glacially carved lake that is also strongly acidic (pH 2.6 to 2.7) and an acidic river that flows for more than 40 km (25 miles) before its pH is completely neutralized. This unique watershed has many geochemical and biological similarities to acid waters caused by mining. This paper describes the Río Agrio watershed and draws a comparison with some famous acid mine waters. Learning more about naturally acidic lakes and river systems could have important applications to the bioleaching of ores or biological treatment of mine waters. Therefore, it should be of interest to the general community of mining and metallurgical engineers.

Jan 1, 2008

By Steve Kral

Worker safety is an issue that transcends industries, whether it be mining, construction, manufacturing or even general office work. In the mining industry, safety and training are particularly important because mining is a dangerous occupation. Throughout the years, federal and state safety regulations have been written and revised to keep up with the changing technologies. And mine operators have installed their own safety and training programs. They have come to realize that a safe and healthy workforce has positive effects on productivity and profitability —not to mention avoiding the high costs of injury-related absenteeism.

Jan 1, 2003

By D. Jacobson

There are many different machine setup parameters and variables that affect the production of cone crushers in a mineral processing plant. One of these variables is the eccentric speed at which the cone gyrates. In June 2012, pilot tests were conducted on a 200 hp high speed cone crusher to determine the production and operating conditions over a wide spectrum of eccentric speed. Every plant will have variations in the ore characteristics and feed rates throughout the life of the mine, and at times throughout a single shift of operation, which result in non-optimal use of the crushing energy and inconsistent process control. For high speed cone crushers, the crusher will exhibit a different capacity, power required, and discharge size distribution as the speed ranges over the design limits of the machine. This study documents the measured variation in production and energy efficiency both when the crusher was ran at full capacity as well as when the feed to the crusher was not sufficient to run at full capacity. Overall, the results match theory and the capacity and power fluctuated by 25% and 17%, respectively, over the speed range when operated full while there was an overall trend of slightly coarser discharge size distribution as the speed decreased. The results with the fixed feed rate were more telling, as the crushers had 4-14% higher production when making a theoretical minus 12.5 mm product when operating at the optimal speed as compared to the worst speed in the ?typical? speed range for this application. Secondary analysis of the fixed tonnage testing also showed that the power draw was more consistent with lower magnitude spikes at the higher speeds (higher cavity level), as on average the standard deviation of the power draw increased from 7% to 18% and the peak power spikes from 20% to 48% over the speed range tested. The findings lay groundwork for more efficient plant design. Varying the speed of the crusher can be used to tune the crusher speed during commissioning, adapt to changing ore conditions over long periods of time, or be used as a dynamic input into an advanced control system. Each action above would serve to make the crusher(s) more productive and more energy efficient, and would also have mechanical benefits for the machine. Key Words: cone crusher, ore reduction, process control, crushing efficiency

Feb 27, 2013