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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 Richard Hogg, Heechan Cho

Investigations of long-time grinding of fine quartz (to about 80% passing 0.35 pm) in a 0.6 liter stirred-media mill are described. Breakage rates and primary breakage distributions have been determined based on extensive characterization of the ground products by laser scattering/diffraction and gas adsorption. The results indicate that, while there is qualitative similarity between the breakage parameters for ultrafine and conventional (coarse) grinding, there are important, quantitative differences. In particular, it is found that primary breakage distributions become significantly narrower in the submicron sizes. The trend can be described using double-truncated log-normal distributions in which both a maximum (breaking) size and a grind limit are specified. The breakage distributions become progressively narrower as the size being broken becomes finer. Breakage rates follow a typical, consistent pattern in which the rate decreases with size according to a simple power law. Further decrease in the rates seems to occur after very long grinding times when the entire mill contents become finer than about 1µm. The effect is explained as a result of changes in the rate/size relationship in the submicron range.

Jan 1, 1995

By Walter C. Labys

There has been considerable growth in public enterprise institutions involved in mineral commodity markets. These institutions typically consist of trading organizations (STO1s), regulatory agencies, and mixed agencies. The particular character of these institutions varies according to whether they reside in developing countries, in Eastern Europe (COMECON Countries), in industrialized countries, or in the form of international agencies. The purpose of this paper is to explain recent attempts to assess the growth of public enterprises as well as their impacts on mineral markets and trade. Some earlier analyses of market impact made by the author have been up- dated for four major mineral markets: copper, tin, bauxite and iron ore. Conclusions are drawn regarding the dynamics of market structure changes and their impacts.

Jan 1, 1986

By R. N. Chakravorty, R. J. Kolada

Explosions of methane in coal silos and coal ships is an ever present hazard. Recent investigations have shown beyond question that considerable accumulations of methane do occur in coal storage silos and numerous recent explosions in coal transport shipping strongly indicates that the same conditions also exist in ship storage holds. Investigations have shown that the main concentrations of methane occur within the actual coal pile. Within this region normal silo and ship ventilation systems are ineffective. The main 1ine of defence is therefore to exclude potential sources of ignition or to place the coal in an inert atmosphere, or both. This paper presents the results of a methane survey of all operating silos in Western Canada. These results demonstrate that a serious and widespread hazard of explosion exists. This paper also discusses various methods by which this hazard may be reduced including methods of venti1ation, inertization, microbiological control and early warning systems.

Jan 1, 1987

By Neil Hepworth

Neves Corvo Mine employs four mining and four backfill methods, including paste fill. The paper shows how the strength requirement for backfill in primary stopes was calculated and the relationship between laboratory strength and in situ strength requirement. The liquefaction of paste in secondary stopes is discussed with methods to determine the liquefaction potential. It was found from laboratory tests and the preliminary results of the underground trial, that the liquefaction potential of the paste is low at 2% and is high at 0.5% cement. The results to date are inconclusive regarding 1% cement.

Jan 1, 2001

By Jane Morrison

Permanent magnets are used in most electromechanical and electronic devices to convert electrical to mechanical energy and vice versa. More than fifty are commonly found in the average American home and car. A new species of permanent magnet composed of iron, neodymium, and boron has recently been developed which combines superior magnetic properties with compact size. The reduced size of the magnets has enabled significant new developments in such areas as robotics and consumer electronic, among others. The objective of the present work is to efficiently and economically separate valuable rare earth materials from the relatively worthless iron constituent in NdFeB magnet scrap. Several magnet producers have expressed interest in the development of such a process and have provided information and scrap samples to aid in research. Scrap is generated in a variety of forms from different stages in the processing stream. Pieces of magnetic and non-magnetic metal as well as sludge and ribbon from jet casting must all be treated. Beneficiation techniques have been studied and size distributions developed for the different scrap types. Slag from the casting process is resistant to crushing and may need to be embrittled first, but all other types are amenable to crushing and ball mill grinding using stainless steel balls and water. Tabling was found to be useful in classification of magnet sludge. Two major techniques for separation of rare earths have been studied:

Jan 1, 1990

By P. Mousset-Jones, F. Calizaya

This paper explains and discusses a computer program that has been developed to determine the ventilation design parameters for complex auxiliary ventilation systems such as those found in the construction of long excavations with multiple headings. The program is based on the principle of partitioning the system into segments of finite length, and formulating and solving the resulting networks recursively. The resulting network problems are solved analytically. With this program, the size of fans can be determined in order to reduce the total leakage and minimize the flow recirculation. The application of the program is illustrated by the detailed solution of an auxiliary ventilation system proposed for the Exploratory Studies Facility (ESF) at the Yucca Mountain Project, Nevada.

Jan 1, 1995

By Jim Jonas

The Berkeley pit-lake was sampled during two seasons, fall 1997 and spring 1998, from the surface to the bottom. Various parameters were measured to determine what effect the seasons had on the water column. It was determined that a seasonal turnover did occur between the fall and the spring sampling; however, the depth of mixing due to turnover could not be established. Trends were observed which suggested that microbial activity was altering the iron speciation at depth, and subsequently masking the extent of mixing. Various trace metals were removed from the surface water by either co-precipitation with schwertmannite or adsorption.

Jan 1, 2000

By D. J. Cook, R. H. Fan, D. R. Maneval, Y-H. Shen

In this study, two placer mine processing plant effluent waters of significantly different characteristics were tested to determine the applicability of polymers along with other techniques to achieve reduced levels of turbidity. The waters from a Gilmore Creek mine and a Crooked Creek mine were characterized both as to their chemical and physical properties. The inorganic minerals were in large measure identified, and the principal cations were identified. The fine solids were studied as m their mineral identification and the extent of their electrical charges. Test work was done using polyrthylene oxide (PEO) and a liquid cationic polymer along with adjunct additives to determine optimum amounts of these coagulants for minimum consumption and optimum settling efficiency.

Jan 1, 1990

By Alberto Sarmentero

Venezuela, once a world's top gold producer until 1886 Witwatersrand discovery, did let fall its role then because of a serious lack of infrastructure and population, and lately (since World war II times), because of discouraging mining and taxation laws, laying upon an oil prizes bonanza. Recent research leading to estimates of about 5.000 mt. of gold, mainly related to the greenstone belts of the Guiana Precambrian shield outcropping in Venezuela, are opening the scope for both Government and international investing and mining companies, for gold exploration and development projects in the country. This paper overviews Venezuelan Gold mining industry, as seen from the point of view of a participating mining company.

Jan 1, 1989

By Jorma Miettunen

The Plant. The annual production of the Pyhasalmi mine is 900 000 tons of copper- zinc-pyrite ore containing approximately 0.7 % Cu, 2.5 % Zn and 30 % S. During 1976...1981 altered surface ore, 850 000 tons in all, was also treated at the concentrator. The surface ore was crushed and ground in a separate plant and was then fed into the copper or zinc flotation or was flotated in its own circuit, depending on the degree of alteration and the content of copper and zinc in the ore. The surface ore was exhausted in October 1981. Flotation comprises three consecutive flotation circuits; copper, zinc and pyrite circuit. The zinc circuit includes an open circuit roughing and scavenging. The scavenger concentrate and cleaner tailing are pumped to the middlings flotation. Rougher concentrates of the open circuit and the middlings flotation are pumped to cleaning which includes four stages. Figure 1 describes the flowsheet of the zinc circuit.

Jan 1, 1982

By G. T. Adel

During the past decade, researchers at Virginia Polytechnic Institute and State University have worked to develop a novel flotation process for treating very fine particles. This process, which is now commonly known as [microbubble column flotation] (MCF), has been shown to be very effective in a number of applications related to fine coal processing. These applications include the retrofit of existing preparation plant circuits and the recovery of additional coal fines from refuse streams. In addition, work conducted under the sponsorship of the United States Department of Energy indicates that the MCF process is capable of producing superclean and ultraclean coals from many eastern U.S. coals. This paper describes some of the basic problems associated with fine particle flotation and the design and operational features of the MCF process used to minimize these problems. Also presented are the results of ongoing pilot- and field-testing programs.

Jan 1, 1989

By Jr. Wilkinson

In today's work environment a tremendous amount of data is required to provide the regulatory agencies justification to issue a mining permit. The demands for data, specifically environmental characterization data, grow and the mine plans must address the issues raised by the interpretation of that data. Computers and computer software can provide operators and consultants with the tools necessary to assimilate, digest and interpret these seemingly unmanageable data sets. This paper presents some examples of how Mincom's MineScape software can be applied to the task of developing coal mine permits in an electronic format.

Jan 1, 1996

By Takayuki Sakai, Takefumi Takuma, Lee Roesner

"70-foot deep rectangular-shaped bulkheads were built with sheet piles as launching and receiving shafts for a pipe jacking operation for new underground waterlines in a densely populated section of Los Angeles, California. The Press-in Piling Method was specified to drive 95-foot long sheets (a record for the method) to form the bulkheads for the Los Angeles Department of Water and Power’s LA-29 (DWP) Connection Modification and Pipe Jacking. The piling was chosen because of its very low noise and practically vibration-free nature since the site is surrounded by houses, an apartment complex, and existing water lines. The out front areas of the bulkheads were grouted to let the TBM go through without major ground water leaks. Hydrophilic foam grout was also injected in addition to welding steel scab plates on the inside to seal them to achieve sufficient watertightness behind a few split interlocks. BACKGROUND This project was located in the Crescent Heights area of Los Angeles which is a few miles south of Beverly Hills. The project represents the completion of the last phase of the Stone Hollywood Trunk Line. This was an 8-mile long water trunk line that averaged 60 inches in diameter and was built to improve the reliability of the DWP’s major water system. This section of the project involved driving 2 deep shafts to allow for the installation of a 350-foot-long 72-inch steel casing using microtunneling construction. See Figure 1 for the shaft locations and the tunnel alignment. The challenge for the project was that this water line would have to pass beneath the Hollyhills buried box drain (15 feet high by 20 feet wide). Further complicating the construction was the soils beneath the drain. The DWP chose to drive the tunnel at a depth of approximately 65 feet to ensure that the ground conditions were uniform and suitable for the microtunneling equipment. There were two previous attempts to construct this work which failed because of poor ground conditions and very high water levels. This third attempt was critical because the DWP could not afford to have another failure due to the fallout with the residents being impacted by the project."

Jan 1, 2016

By Frederick T. Graybeal

Silver Bell is located about 56 km (35 miles) northwest of Tucson, AZ. It is a classic porphyry copper deposit containing enriched disseminated chalcocite ore in altered porphyritic rocks with chalcopyrite in adjacent skarn zones. The discovery of Silver Bell was an evolutionary process that occurred over a 75-year period. Recorded mining activity began about 1865 on Boot Hill east of El Tiro pit (see Fig. 1) where outcrops of altered limestones were found to contain 425 to 482 g (15 to 17 oz) Ag mixed with copper oxides. By 1874, the Young America Copper Co. was mining shallow occurrences of 30% Cu along the north side of the present Oxide pit. The ore was shipped by wagon to Yuma, AZ, and then by boat to San Francisco for smelting. By 1881, the district supported several mining companies, two small smelters, and was being favorably compared to Bisbee in local newspapers. Most of the ore mined in the period 1865-1903 came from pods of massive sulfide or their oxidized products which were distributed in an unpredictable fashion through a large skarn zone in Paleozoic limestone east of El Tiro pit. Ore grades varied from 5 to 10% Cu.

Jan 1, 1991

By G. R. Rao, K. A. Natarajan, P. Devasia

The role of growth conditions and adhesion of Thiobacillus ferrooxidans on the leaching of chalcopyrite was investigated. Thiobacillus ferrooxidans grown on sulfur, thiosulfate and ferrous ion substrates was used in this comparative study. Growth on sulfur, a solid substrate, requires bacterial adhesion unlike that required in the presence of soluble thiosulfate and ferrous ion in a mineral-salts medium. Solid substrate-grown cells showed higher rates of leaching than those grown in liquid media. An initial lag period noticed during leaching by solution-grown cells was absent when solid substrate-grown cells were used. Such a behavior is attributed to the presence of an inducible proteinaceous cell-surface appendage on the sulfur-grown cells. This appendage aids in bacterial adhesion onto the mineral surfaces. Such an appendage is absent in solution-grown cells, as substantiated by electrophoretic measurements. The importance of bacterial adhesion and the direct mechanism in leaching by Thiobacillus ferrooxidans are demonstrated.

Jan 1, 1997

By R. K. Mehta, K. N. Han, P. B. Queneau, V. Dieudonne

A study based on a statistically designed sets of experiments (central composite design) was conducted to determine the optimum conditions for leaching a subbituminous coal (7.0 % ash) from the middle Wyodak seam in mild sulfuric acid solutions. The statistical analysis was conducted with the ash content and ash removal as the dependent variables and with the coal loading, acid concentration, ferric ion concentration, and temperature as the independent variables. Treatment of the experimental data via a simple genetic algorithm (GA) revealed that acid concentration and temperature are the two most critical variables. Unlike the case with bituminous coal, the ferric ions addition shows no beneficial effect. The optimum "macro response" predicted by GA was verified experimentally; the ash content was reduced to 2.7%, which is close to the value predicted by GA. The ash content was further reduced to 1.7% in a two-stage leaching process devised by incorporating the optimization results with that of leaching kinetic studies.

Jan 1, 1993

By J. E. Murphy, R. Y. Wan, K. R. Sandgren, M. C. Fuerstenau

As part of a U.S. Bureau of Mines program to evaluate alternatives to sodium cyanide in gold leaching, three organic nitrile compounds were tested for their effectiveness as gold lixiviante. The organic compounds examined were malononitrile, acetonitrile, and cyanoacetamide. The reagents were tested on an oxide ore, two carbonaceous ores, and a eulfidic ore. Acetonitrile and cyanoacetamide were shown to be ineffective gold leachante. Malononitrile was the most successful of the organic lixiviants. On an oxide ore, malononitrile performed shilarlyto sodium cyanide with extractions of around 80 pct. For carbonaceous "preg-robbing" oree, sodium cyanide was completely ineffective while malononitrile extracted 24 pct of the gold. When using a resin-in-leach technique, extraction with sodium cyanide increased to 60 pct and the extraction with malononitrile increased to 80 pct. On the sulfide ore, sodium cyanide and malononitrile performed similarly with 80+ pct extraction as long as the pH of the malononitrile solution wae maintained above 10.5. Malononitrile is six times less toxic than sodium cyanide as measured by LD, levels. Therefore, malononitrile has a significant advantage over eodium cyanide, but its high cost and undemonstrated usefulnees make it unlikely to gain acceptance.

Jan 1, 1993

By Steven Johnson

The regulatory landscape has changed considerably since the first passage of Oklahoma's land-reclamation requirements in 1968 (Open Cut Reclamation Act of 1968). The Oklahoma Legislature revised the reclamation requirements in 1971 with passage of the Mining Lands Reclamation Act. With the passage of this Act, the Legislature empowered the Oklahoma Department of Mines with jurisdiction for permitting and regulatory authority over non-coal (industrial-minerals) mining operations. This act required all operators to file with the State, through the Department of Mines, a written application for a permit to engage in non-coal mining. Each application consisted of a mining plan, which included location maps of the proposed mining area along with a reclamation plan for the area to be covered. Additionally, a reclamation bond is required prior to issuance of a permit to ensure that the site would be reclaimed. Since 1971, the Act has been amended to include public notification and public participation in the review process of any application. Also, the operator can request that the Department review the mining plan based on the Life Expectancy of the mine, instead of the original one-year plan (HB 1409 in 1993). Even though the operator is granted a mining plan tied to the "Life Expectancy" of the site, the permit is reviewed annually for compliance as required by law.

Jan 1, 1999

By Gilles A. Tremblay

Acidic drainage has been long recognized to be the largest environmental liability facing the Canadian mining industry and to a lesser extent the public through abandoned mines. The Mine Environment Neutral Drainage (MEND) Program was the first initiative formed in 1989 to develop scientifically-based technologies to combat acidic drainage. This 9-year volunteer program reduced the liability by several hundreds of million dollars and established Canada as the recognized leader in research and development on acidic drainage for metal mines. MEND 2000 is a three-year program that started in 1998. The key to MEND 2000 is technology transfer- providing state-of-the-art information and technology developments to users. MEND-developed technologies are being verified by long-term monitoring of large-scale field tests. Maintaining linkages with a number of foreign government and industry-driven programs is also important to the successful completion of the program. Through these efforts a further reduction of the environmental liability associated with acidic drainage will be realized.

Jan 1, 2000