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By V. Rajaram

A mine fire or roof collapse may necessitate the reversal of main fans to isolate the fire or provide an escapeway. Hence, to assist the mine operator in estimating the flow and pressure during reversal, Engineers International Inc. conducted a laboratory and field study of the reverse performance characteristics of main mine fans. Laboratory tests were performed using a 2.4-m (96-in.) diam vane axial fan to establish the forward and reverse performance characteristics under controlled conditions. Subse¬quently, a field test was conducted in a Colorado oil shale mine during which two 2-m (79-in.) diam fans were reversed. The data obtained indicate that reverse performance characteristics depend on the blade angle and the hub-to-tip ratio. The quantity in the reverse mode ranged from 30% to 65% less than in the forward mode, and the static pressure was directly proportional to the square of the quantity.

Jan 1, 1987

By B. R. Reddy, Y. V. Swamy, B. V. R. Murthy

Chromitiferous overburden containing nickel in oxide form is reduced with CO-CO2-N2 gas mixtures. This converts the nickel oxide to metallic nickel and restricts the iron oxide to the magnetite state to extract the nickel. Reduction experiments were carried out on 500-g samples in a bench-scale vertical reactor. The tests were run to establish the process parameters, including the optimum partial pressure of CO, the reducing gas flow rate, granule size and roasting time. The reduced calcine is then subjected to an ammonia-ammoniacal carbonate leach to extract nickel selectively as its amine complex. More than 90% of the nickel could be extracted with a volumetric CO/(CO+CO2) ratio of 0.57 at 750°C and a roasting time of 90 min. The addition of 2.5% (by weight) charcoal to the granules improved nickel extraction by 11 % to 19%. Nickel leaching efficiency with ammoniacal solution is compared to the bromine-methanol method.

Jan 1, 2000

By M. W. Ryan

The US Bureau of Mines investigated cold-cutting alternatives to oxyacetylene torch cutting of metal. The alternatives examined were a pneumatic circular saw with an abrasive cutting wheel, a handheld abrasive water-jet cutting tool, an ultrathermic-cutting system, hydraulic punches and cutters, and a pneumatic reciprocating hacksaw. Sparks generated with the pneumatic circular saw or ultrathermic-cutting system were not completely eliminated with the use of water sprays. The water sprays also reduced the cutting rate of the pneumatic circular saw by 70%. The safety and performance of a handheld abrasive water jet cutting system requires additional research. The hydraulic cutters and punches are readily available and do not introduce any hazards. However, they are not comparable in price to the oxyacetylene gas torch and many different attachments would be needed to replace the torch. The pneumatic reciprocating hacksaw, which did not produce any sparks, is an acceptable alternative in terms of cutting rates. However, the price of the saw and blades is not comparable to that of the oxyacetylene gas torch. The results of this study will further the advancement of safe, efficient alternatives to oxyacetylene gas torches, which will improve miner safety.

Jan 1, 1996

By N. Choi, W. D. Cho

Distribution coefficients of gold and silver between matte and slag during the pyrometallurgical treatment of nickel-copper sulfide concentrates were evaluated as a function of matte and slag compositions in the temperature range of 1,250oC to 1,300oC. It was observed that the composition of the matte phase, including matte grade and copper content in the matte, significantly affected the distribution behavior of gold and silver in the matte-slag system. Both gold and silver preferentially concentrated in the matte phase as the matte grade increased With increasing temperature and copper content in the matte, the distribution coefficients of silver increased, while the gold distribution coefficients decreased. It was also, found that slag additives such as CaO, MgO, and A12O3 caused a significant decrease in the solubility of both gold and silver in silica-saturated iron silicate slag. An activity coefficient of gold in matte was derived from the experimenta1 results.

Jan 1, 1999

By R. Hogg, R. C. Klimpel, D. T. Ray

The sedimentation and dewatering characteristics of flocculated slurries are determined by the size and density of the flocs. Studies of the formation and growth of flocs reveal that floc size is limited by breakage of the agglomerates due to shear in the suspension. Floc density measurements indicate that there is an inverse relationship between size and density. This relationship appears to be determined primarily by the nature of the solid particles, especially the size distribution, but it appears that agitation of the suspension can lead to some densification of the flocs, in addition to breakage. It follows that both size and density can be controlled to a significant extent by regulating the physical conditions (agitation, method of flocculant addition, etc.) during flocculation. The use of physical floc conditioning to control the sedimentation and dewatering (filtration) behavior of flocculated, fine-particle suspensions is evaluated in terms of its effects on floc size and density.

Jan 1, 1988

By T. E. Walsh

Introduction I will address two important alternative energy resources, solar and geothermal, with emphasis on their potential application in electric power generation. As a result of this presentation, I hope to leave you with a realistic view of the principal technology options that are being developed or that are available. Solar Types of Collection In terrestrial solar applications, the biggest challenge is to find ways of collecting the sun’s relatively low intensity energy so it can be converted economically to useful thermal or electric energy. Fig. 1 shows that there are both natural and technological ways of collecting solar energy. In nature we find that solar energy aids in the production of biological growth, rainfall, and wind, all of which can, in one form or another, be put to use in the production of heat or electric power. The sun’s rays also are collected and stored naturally in the form of heat in the upper layers of the ocean which can be put to use in the production of electric energy by means of ocean thermal energy conversion (OTEC) approaches. On the technological side, the sun’s rays can be intercepted by materials that directly absorb and convert its energy to low-grade heat, or by mirrors or lenses that focus the rays onto a material to produce high-temperature heat. The higher temperature systems can be used to drive efficient heat engines in the production of electricityy. The sun’s rays also can be collected on photosensitive materials, in either a direct or concentrated form to generate DC electricity directly. The systems I will discuss employ all of these means of collection and conversion, excluding biological and hydroelectric. The former is too ex

Jan 1, 1980

By J. Y. Perez, H. M. Ewoldsen, L. L. Oriard

Near the village of Villarino de los Aires, in the province of Salamanca, Spain, is an existing underground hydroelectric power plant. A major enlargement was undertaken to increase the electrical generating capacity, under a contract awarded to a joint venture of Dragados & Construcciones, S.A., Entrecanales y Tavora, S.A., and S.A. Conrad Zschokke. The enlargement required the excavation of an underground system of tunnels, shafts and chambers adjacent to existing facilities and interconnected with these facilities. The existing machine hall and transformer chamber were both extended, requiring excavation of the rock that constituted the existing end walls of these chambers. The drilling, blasting and excavating of the underground system had to be done without damaging existing underground openings or any of the existing structures, equipment or instrumentation facilities. This required careful control of vibrations, air waves and dust. The joint-venture contractors preferred to use electric blasting methods, if these methods could be implemented in a safe manner. The safety question had to be evaluated carefully. High electrical potentials existed at the site because of the electrical generating and transmitting facilities that could not be shut down. Electrical fields were carefully studied prior to the beginning of the work. This was done both in the underground environment and above the ground surface. Special procedures were followed to ensure safety with

Jan 1, 1974

By F. K. Letowski

Leaching of zinc sulphide concentrate by nitric acid which is simultaneously regenerated by oxygen in the reactive froth has been investigated. The reactive froth was formed by a recycled zinc sulphate electrolyte containing nitric acid, a mixture of gaseous 02 and NOx, entrapped in the foam and particles of the zinc concentrate suspended in the foam. In the reactive froth the multiple regeneration of nitric acid proceeded owing to the encapsulated oxygen and amount of nitric acid used can be considerably lower than in the continuous liquid phase. 93 to 97% of zinc was extracted to a solution containing 30 to 409/1 HNO, during 40 to 60 min of leaching in a batch reactor without regeneration of nitric acid. 50 to 100% of the consumed nitric acid was regenerated during continuous leaching in froth carried out in the ‘flotation column’-type reactor at 80 to 90°C and under pressure of 100 to 200kPa. The rate of HNO, regeneration in the froth was proportional to oxygen pressure and inversely proportional to nitric acid concentration in the froth. A two-stage process flowsheet is proposed. In the first, the reduction stage, removal of nitric acid from the leach solution directed to standard purification and electrolysis is carried out by its reduction to nitric oxide using fresh concentrate in the froth. In the second, the oxidation stage, nitric acid is continuously regenerated by oxygen in the froth.

Jan 1, 1995

By Timothy P. Smirnoff, Arthur P. Chase, Herman J. Smith

INTRODUCTION The Newtown Creek Pollution Control Project (P.W. 53) is a major system of facilities designed to collect wastewater from large areas of the Boroughs of Manhattan, Brooklyn and Queens, then channel it to a treatment plant where the wastewater is processed and discharged. The North Branch interceptor collects wastewater along the east side of Manhattan and transports it downstream to a Junction Chamber at Avenue "D" near East 13th Street. The South Branch interceptor similarly collects wastewater from the southern part of Manhattan Island on both east and west sides of Manhattan and transports it to the same Junction Chamber from where both flows are delivered to the adjacent Manhattan Pumping Station which pumps the wastewater under the East River to a treatment plant in Brooklyn. This system is shown in Figure 1. Construction of the Manhattan Pumping Station began in the Summer of 1966 and was delayed by a number of mishaps. In the vicinity of the North and South Interceptors, approximately 3,060 cubic meters (4,000 cubic yards) of soil flowed into the excavation: 765 cubic meters (1,000 cubic yards) at the North Branch Interceptor, and approximately 2,300 cubic meters (3,000 cubic yards) at the South Interceptor. These movements were accompanied by surface subsidence, collapse, or both. On June 4, 1973, while pumping station construction was underway, approximately five to seven cubic yards of sand entered the junction chamber through a temporary bulkhead valve in the North Branch Interceptor.

Jan 1, 1979

By Charles R. Garrett

The American Borate Company, a wholly owned subsidiary of the Owens Corning Fiberglas Company under a management contract to the Hanna Mining Company, owns and operates an underground borate mine in Death Valley, California. The mine, named the Billie Mine, is located 24 km (15 miles) southeast of Furnace Creek along Highway 190. The ore body is under Death Valley National Monument with the major portion of the surface facilities located just outside the monument boundary. (See Figure 1.) The Billie Mine produces approximately 227 000 metric tons of crude ore per year. About 65% of finished product is supplied to Owens-Corning, the remainder is sold to other fiberglass producers. Geology The borate minerals in the Billie ore body were deposited in the lower main member of the Furnace Creek Formation, which is Pliocene in age. The ore body is thought to have formed from volcanic springs in or near a small lake basin. The deposit is essentially a limestone breccia that is permeated with borate minerals and surrounded with limey lake bed mudstones and shales. The ore body is mineralized with two main borate ores, colemanite and probertite. A third borate ore, ulexite, mainly occurs in the upper part of the ore body. The original mineral of deposition is thought to have been ulexite. Ulexite is a sodium-calcium borate hydrated with eight molecular waters. Due to heat and pressure from burial by later sediments, the ulexite had water forced out of its structure and recrystallized as probertite. Probertite is another sodium-calcium borate, with five molecular waters. Colemanite formed when surface water seeped into the prober-

Jan 1, 1985

By T. E. Walsh

I will address two important alternative energy resources, solar and geothermal, with emphasis on their potential application in electric power generation. As a result of this presentation, I hope to leave you with a realistic view of the principal technology options that are being developed or that are available. Solar Types of Collection In terrestrial solar applications, the biggest challenge is to find ways of collecting the sun’s relatively low intensity energy so it can be converted economically to useful thermal or electric energy. Fig. 1 shows that there are both natural and technological ways of collecting solar energy. In nature we find that solar energy aids in the production of biological growth, rainfall, and wind, all of which can, in one form or another, be put to use in the production of heat or electric power. The sun’s rays also are collected and stored naturally in the form of heat in the upper layers of the ocean which can be put to use in the production of electric energy by means of ocean thermal energy conversion (OTEC) approaches. On the technological side, the sun’s rays can be intercepted by materials that directly absorb and convert its energy to low-grade heat, or by mirrors or lenses that focus the rays onto a material to produce high-temperature heat. The higher temperature systems can be used to drive efficient heat engines in the production of electricityy. The sun’s rays also can be collected on photosensitive materials, in either a direct or concentrated form to generate DC electricity directly. The systems I will discuss employ all of these means of collection and conversion, excluding biological and hydroelectric. The former is too exi

Jan 9, 1980

By R. K. Singhal, R. D. Lama

Underground coal mining systems have kept pace with developments that have occurred in other types of mining. A diversified group of machines are now available with high horsepower motors, built-in microprocessor technology, and numerous options to satisfy miners' needs in various geological environments. The results will be a greater degree of mechanization and recovery of coal from inclined seams, thins seams, and seams mined in lifts from shallow as well as deeper deposits. This article is based on a general suvey carried out by the authors to detemine the current status of mechaniztion and systems development in underground coal mining. It indicates that the next two decades will see increasing use of longwall mining, which has already reached a high degree of sophistication. Automation, remote control, and robotics are the key words of the future. Data transmission from underground to surface and over long distances will be almost routine. Many components of the high technology industry that are just being considered by the mining industry regarding equipment health and perform¬ance monitoring, quality control, application of expert systems, and computer networking will become a routine part of underground mining technology. Within the next 21 years, "manless" mining, first attempted about 25 years ago, will become a reality. References to any trade name are meant to aid understanding of the text and do not imply endorsement by the authors or their users. Current coal face developments Developments in underground mining equipment, its application, and associated technology have made phenomenal progress compared to those in other types of mining. Room-and-pillar systems, on one hand, and longwall mining, on the other, have sophisticated equipment at their disposal. Both of these systems have become highly productive, with output per manshift about 50% higher than that achieved a decade ago. Continuous miners continue to be the mainstay of room-and-pillar coal mining. Numerous developments, how-

Jan 1, 1989

By Frank Hagar, George M. L. Robinson

NTRODUCTION The Resource Conservation and Recovery Act and CERCLA (SUPERFUND), in many instances, has had an adverse economic impact on the hardrock mining industry. Over the last few years, many abandoned and active mining operations have been added to the Environmental Protection Agency (EPA) National Priority List (NPL) . When the property is placed on the NPL the operator or EPA is required to conduct extensive environmental assessments to determine if historical mining practices have degraded the existing environmental. If degradation has or will continue, the responsible party is required to implement appropriate remedial action plans. If a responsible party is not identified, the EPA implements a cleanup program. Experience has demonstrated abandoned and active mining operations are subject to RCRA, and possibly Super- fund, if the mine has not adopted appropriate hazardous waste disposal management procedures. If off-site contamination has occurred, the operator will be required to mitigate the impacts and will be required to adopt additional procedures to minimize future impacts. Since the passage of RCRA and Super- fund, many mining operators are adopting management procedures to monitor and inventory hazardous sub- stances and wastes generated, stored and disposed on site. Many operators are in a difficult position because ore, waste rock, process chemicals or other solid waste, in many instances, can be classified as hazardous waste. If the process or other solid waste is deemed to have the characteristics of a hazardous waste, the operator can inventory and adopt appropriate, in- expensive management procedures. However, if the ore or waste rock has hazardous waste characteristics, in- expensive control technologies are impossible to implement. Since existing statutes and regulations require hazardous waste control, the operator will be required to inventory, characterize and monitor all aspects of the mining operations including but not limited to exploration, mining, ore processing and waste disposal. During this process, geological, geotechnical, geochemical, waste and ore volumes, and process materials must be tracked throughout the mining process. To accomplish this task, the most cost effective method to maintain documented and accurate records, is through the implementation of an integrated database management system. The database management system can be used to model and simulate the entire mining operation and if necessary, used to predict whether the operation is in compliance with existing regulations. The developed database can also be used to operating optimize mining and disposal costs.

Jan 1, 1987

By Michael Brittan

The Delkor Linear Screen represents an important screening innovation in the minerals industry. Applications geared to the enhancement of gold processing efficiency through coarse screening are presented. Recent developments in the use of the Linear Screen as a fine screening classification device in mill circuits are also discussed.

Jan 1, 1998

By L. P. Hendriks

Consolidated Murchison, the only antimony producer in South Africa, is situated in the northeastern part of Transvaal. Phalaborwa, an important copper/phosphate mining town is situated about 60 km to the east of Consolidated Murchison, on the border of the Kruger National Park. The mine is jointly controlled by Johannesburg Consolidated Investment Co. Ltd. (JCI) and Anglovaal Limited.

Jan 1, 1998

By J. E. Spencer

Mesozoic and Tertiary mineral deposits in west-central Arizona are commonly associated with Mesozoic thrust faults and Tertiary detachment faults, respectively. Quartz-kyanite rocks and pyritic quartz-sericite schists with local anomalous gold are the product of probable Jurassic argillic alteration of Jurassic volcanic, sedimentary, and plutonic rocks followed by Cretaceous thrust burial and associated metamorphism. Slivers and sheets of Paleozoic carbonates along Mesozoic thrust faults were locally sites of syn-and post-thrust mineralization. Widespread brecciation along Tertiary detachment faults resulted in increased permeability along fault zones. Elevated thermal gradients also resulted from detachment faulting and apparently caused convective aqueous-fluid circulation along detachment faults and associated Fe+Cu±Au mineralization.

Jan 1, 1988

By J. Kircher

Nevada Goldfields' Aurora Mine consists of a 270 mtpd (300 tpd) precious metals mining and milling facility located 28 miles southwest of Hawthorne, Mineral County, Nevada and lies within five kilometers of the Nevada-California border. (Figure 1) Ore production presently is derived 85% from an open pit source with the balance from underground. The Aurora Mill is a compact conventional cyanide plant utilizing a carbon-in-leach extraction process followed by stripping of loaded carbon and electrowinning at Nevada Goldfields Kingston Mine, located near Austin, Nevada. Production commenced in December 1987 and annual gold production is currently 20,000 troy ounces of gold and 22,000 troy ounces of silver per annum, produced at an average cash cost of $178 per ounce of gold. Tailings handling at, Aurora was originally accomplished using a belt filter press producing a solid cake that was then transported to a final storage area. Although overall operating costs at the mine were' in the lower percentile of producing gold mines, the tailings handling portion of the operating costs were inordinately high.

Jan 1, 1989

By D. A. Dahlstrom

Crushing and grinding consumes about 1.3% of the nations produced electrical energy.( Furthermore, only one in the first ten highest consumers comes from an industry other than mineral processing. This is the grinding of wheat to make flour. The other nine are all in the metallurgical industry and are easily the largest consumers.

Jan 1, 1988

By J. D. Miller

X-ray computed tomography (CT) techniques have been developed for the medical services field in order to provide accurate internal images of the human body.(l-7) Now, a decade later, CT techniques are starting to be used in non-medical applications such as, non-destructive testing(8), flow pattern analysis(9), drill core examination (10,11), and coal characterization(12,13). In these fields of application, CT techniques offer the potential to extend our knowledge and understanding beyond that provided by more traditional methods of analysis. Although, CT systems involve very specialized and expensive equipment, the advantage of x-ray CT in revealing the detailed internal structure of an opaque material non-destructively should make it an important tool to provide a more complete analysis of mineral processing phenomena. X-ray CT systems generally consist of an x-ray source/collimation unit and a detector/data acquisition unit. The object to be examined is placed between the two functional units as shown in Figure 1. With this system the density array of selected cross sections of a chosen opaque object can be obtained in two dimensions. There are numerous areas in mineral processing to which x-ray CT technology can be applied and it is the aim of this article to identify these potential areas noting the advantages and limitations of the technology. Particular emphasis is placed on particle composition distribution and multiphase fluid flow measurements. In the case of particle composition distribution, liberation analysis and coal washability are considered. While in the case of multiphase fluid flow, swirl flow in the air-sparged hydrocyclone is given by way of example.

Jan 1, 1989

By M. M. Rajkovich, J. J. Zaluski, S. J. Gardner

The telephone rings at 3:20 a.m. and an exasperated voice on the other end says, “There’s been a mine explosion at Mine No. 5 and we have not heard from three units of men!” Twenty-three minutes later, the phone rings again and another panicked voice says, “There’s something wrong at the slurry impoundment, the pool level has just dropped five feet and we’re trying to figure out what’s wrong!” Thirty minutes later, the mobile phone rings and an excited security guard says, “We have reports of thick black water running down both the right fork and left fork of Straight Creek and both seem to be rising in the banks!” As if this isn’t enough excitement, the mobile phone rings again and a stressed company official says, “I just heard a report that black slurry is running out of the portals of XYZ Company No. 2 Mine, which is adjacent to our No. 5 Mine!” Is this all some kind of dream or nightmare? More importantly, however, if this could happen, what on earth do you do? Although we all like to think that “It can’t happen to me,” we all must admit that mine explosions do happen, slurry impoundments can rupture and creeks can flood with black water causing damage to others, including competitors. Your response must be quick, cool-headed, calculated and effective. This paper will examine the issues, concerns and ramifications of this hypothetical “disaster” and then present a systematic crisis management response. While each situation is different, there are general guidelines for forming an effective plan of action.

Jan 1, 2003