Search Documents

By Carlos Alexandre Cavalcante de Sousa

A energia elétrica é uma das formas de energia mais utilizadas pela sociedade. Com a modernização dos meios de produção e o aumento populacional, a sua demanda cresce cada vez mais. Por este motivo, existe uma grande necessidade de fazer o transporte dessa energia de forma eficiente. O desenvolvimento de novos materiais para serem utilizados como cabos de transmissão e distribuição é de suma importância. O presente trabalho visa estudar a liga de alumínio Al-0,05%Cu-0,40%Fe-0,30%Si-0,22%Zr para transmissão de energia elétrica. A liga foi obtida por fundição direta em lingoteira metálica em formato de "U". As pernas correspondentes ao perfil foram seccionadas, usinadas e separadas em dois grupos, o primeiro sem tratamento térmico e o segundo com tratamento térmico. Após esta etapa os corpos de prova foram submetidas ao processo de laminação a frio para os diâmetros de [2,7; 3,0; 3,8 e 4,0] mm e encaminhados para a caracterização elétrica e mecânica. Verifica-se que o tratamento térmico de 150ºC/2h melhorou a condutividade elétrica para o diâmetro de 3,0 mm. Após a aplicação dos testes de termorresistividade para o diâmetro de 3,0 mm, constata-se que para ambas as orientações, tanto a liga sem quanto com tratamento térmico se enquadram como termorresistentes..

Oct 30, 2017

By William Gleason

"The mining industry tends to focus on very large numbers, whether it’s talking in terms of size of deposits, tons of material mined, the equipment used or the dollars spent. The numbers associated with mining projects are often in the hundreds of millions, but sometimes it’s the little things that can have the biggest impact.Take, for example, the Rosemont Copper Project in Arizona. Owned by HudBay Minerals, the Rosemont Copper project, when in production, is expected to be one of the largest copper mines in the United States, accounting for about 10 percent of total copper production with annual production expected to be 110 Mt/a (243 million lbs/year). However, the project is currently mired in a years-long permitting process. At the 2017 SME Arizona Conference in Tucson, AZ, Kathy Arnold, director of environmental and regulatory affairs for Hudbay Minerals, spoke about the project and the efforts to get it into production.She opened her presentation with the unfortunate news that her 2017 presentation would not be that much different than the 2016, 2015 or 2014 presentations she gave to the same conference. That’s because, as of Dec. 4, 2017, the project had been in the permitting process for 3,797 days, more than 10 years. The process began when Rosemont submitted its initial mine plan in 2006 and a revised one in 2017. The official start to Rosemont Copper’s National Environmental Policy Act (NEPA) started in 2008.In June 2017, the project received its Final Record of Decision from the U.S. Forest Service, moving it a step closer to production. Yet it still faces stiff opposition from opponents while it works to secure the Clean Water Act Permit from the U.S. Army Corps of Engineers and to complete its final mine plan of operations.In her presentation, Arnold said the long process taught her many lessons, including approaching things with a different mindset. More than 130 pages worth of public comments have been collected over the years. The concerns expressed range from lighting issues to pavement to preserving land for a jaguar that was spotted on the property and named El Jefe.“A lot of things that people worry about seem to be small things, but we had to have a different mindset and be open-minded to the concerns,” Arnold said. “That is the commitment we made.”"

Jan 1, 2018

By Jorgen Elbrond

Shovels, trucks and repair bays for the trucks each play their role in the capacity of an open pit operation. It is therefore convenient to have a procedure for the capacity calculation which takes all 3 factors into consideration in a comprehensive manner. This can be done by means of a cycle model, earlier developed for the shovel-dumper circuits, when the repair facility with its number of repair bays is added as a superimposed service system, which the trucks visit at certain specified intervals. The calculation model transforms the mechanical availability of the trucks into their operational availability. The system's capacity in truckloads per shift and the trucks' operational availability of certain combinations of shovels, trucks and repair bays are shown.

Jan 1, 1981

By Patrick E. Durnal

The Richmond-San Rafael Bridge was built in the early 50s' and was first opened to traffic on August 31, 1956. Among California's longest steel bridges, it spans more than 21,000 feet across the northern portion of San Francisco Bay. It is one of six toll bridges currently undergoing seismic retrofit in the Bay area. Current retrofit criteria require the structure not to collapse in a Magnitude 8.3 earthquake lasting 45 seconds on the San Andreas Fault. The earthquake epicenter is 10 miles to the west of the Bridge, near the mouth of San Francisco Bay. Another major fault is the Hayward Fault, with a potential of a 7.5 magnitude earthquake. It is only 4 miles east of the eastern end of the bridge. The retrofit criterion is that the structure survives these earthquakes without collapse or loss of life, and that they are capable of repair within a period of one year. Therefore an energy absorbing, ductility and nominal resistance based approach to the retrofit design have been adopted for the retrofit of this bridge. Foundation Retrofit The foundation retrofits were designed to satisfy of drift criteria of 6 inches at the base of the footings, and to keep the existing H-piles from experiencing unacceptable levels of permanent soil displacement and /or structural rupture. Full-scale structural lateral load testing of BP14x89 piling, to rupture, has helped to determine the drift criteria. However recent non-linear analytical results, have led to a redesign, which may allow for 12 inches of drift. The as-built analysis of the Micropile piers determined that those piers would not exceed the 6-inch drift criteria so lateral resisting shear piles were not needed at those piers.

Jan 1, 1998

By Gabriel Böde Jimenez Leon, Michael Karmis, Christopher Newman, Zach Agioutantis

"When utilizing high recovery underground mining methods, such as longwall or high-extraction room-and-pillar mining, the movement and deformation of the overburden propagate toward the surface and may affect the integrity of overlying surface streams (Peng et al, 1996). Published studies cite three major mechanisms of subsidence as most likely to impact streams: displacement, slope and strain. While subsidence-induced vertical displacement cause little structural damage to the stream bed, it may create adverse drainage and stream flow issues as the subsidence trough allows for ponding (Dawkins, 2003). Subsidenceinduced changes to the slope, or tilt, of a stream may have adverse effects on water flow. As the stream enters the subsidence trough, the gradient increases providing potential erosion control problems. When exiting the subsidence trough, a reduction of the gradient may inhibit stream flow, causing localized ponding (Peng, 2008). While vertical displacement and tilt both may have detrimental effects to surface streams, the resulting strains have been documented as being the most damaging to surface streams and structures causing distortion, fractures, or failure (Singh, 1992). When stream beds are subjected to high tensile strain, tensile cracks may form at the surface level allowing for the direct loss of stream flow through fissures. When stream beds are located in areas of high compressive strain, rock layers forming the stream bed can fail as the stream bed ruptures, upward, blocking stream flow or having the stream diverted into the fracture zone at the base (Iannacchione, et. al., 2010).Recent investigations on the effects of underground mining on surface bodies of water suggest that to determine the degree of stream impact one must also consider the geologic structure and thicknesses, surface topography, watershed drainage areas, width of river bed and rate of mining. Due to the complex nature and number of parameters affecting surface streams, subsidence modeling tools and software packages should be implemented throughout all stages of subsidence planning, prediction and control. The Surface Deformation Prediction System (SDPS) utilizes the influence function for the calculation of final subsidence deformations with respect to the angle of influence, supercritical subsidence factor as a function of the percent hard rock, edge effect offset distance, and surface topography. Developed more than 25 years ago, SDPS has been continually updated with new analysis and prediction features, providing a reliable and versatile program for subsidence management methodologies. Most recently, the program has been updated to evaluate the effect of varying surface topography in the prediction of horizontal displacements, referred to as ground strain, allowing for the accurate three-dimensional representation of surface deformations in mountainous terrain (Agioutantis and Karmis, 2014). Ground strain has become one of the predominant deformation indices used in the evaluation of potential damage to surface structures (Karmis et al., 1995). Ongoing work with SDPS software seeks to investigate the calculation of ground strain in SDPS and its ability to accurately and realistically predict damage to surface streams due to underground mining operations."

Jan 1, 2015

By Catharine T. Fogg

The Bureau of Mines investigated the availability of flake and high-crystalline natural graphite from 4 domestic and 25 foreign mines and deposits in 11 market economy countries (MEC's). Demonstrated resources were estimated to be 95 million metric tons (Mmt) containing 5.61 Mmt of recoverable flake and high-crystalline graphite products. Fifty-five percent (3.17 Mmt) of the total recovered product is estimated to comprise plus 100-mesh (150-µm) flake pro-ducts and "lump" and "chip" high-crystalline products, designated as "graphite A" in this study; 45 pct (2.44 Mmt) of the total is minus 100-mesh (150-µm) flake products and "dust" high-crystalline products, designated as "graphite B." Total production costs, including all costs needed over the life of each operation, were determined at a 0-and 15-pct discounted-cash-flow rate of return (DCFROR) for both graphite A and graphite B products. For a 15-pct DCFROR, 1.74 Mmt (54.9 pct) of the graphite A products is available at $600/mt or less and 2.13 Mmt (67.2 pct) is available for $800/mt or less. For the same DCFROR, 1.08 Mmt (44.3 pct) of the graphite B is available at $200/mt or less, and 1.71 Mmt (70 pct) is available at $325/mt or less. No domestic resources were determined to be economic at present prices. A sensitivity analysis of the relative economics of the Alabama graphite deposits under various operational parameters is presented in an appendix. All evaluations are in January 1984 dollars.

Jan 1, 1987

By K. Morsi

The interest in spark plasma sintering has been growing considerable over the past few years. This has been brought about by the unique advantages of the process, which include reduced sintering temperatures and times and the production of materials with unique microstructures and properties. Despite its current reputation as an outstanding process that has solved major problems such as nano-powder consolidation, it has so far been largely limited to the manufacture of simple shapes, due to its inherent geometric configuration. In this paper we present preliminary results on spark plasma "extrusion" that can allow the production of extended geometries via electric-current processing. Preliminary results on the processing and microstructure of spark plasma extruded aluminum are discussed.

Jan 1, 2009

By Robert A. Field

Static-Load Piledriving utilizes a hydraulic push to facilitate the installation of a pile. The pile is not rotated, impacted or vibrated. A smooth pushing force advances the pile incrementally into the ground. Static-Load devices must have a reaction mass to push against. The most simple form of a Static-Load device is a jack; more advanced equipment, such as the Still Worker, also utilizes this approach. This paper focuses on the use of the Still Worker on three challenging projects. In each case, the existing site conditions made it risky, or unattractive, to utilize conventional impact, vibratory, or drilled-shaft equipment.

Jan 1, 1997

By Mark Rybak

On Aug. 31, 2006, Tropical Storm Ernesto hit the city of Richmond, VA. The Battery Park area was hit particularly hard, as flooding forced an evacuation of the area. A large sinkhole collapsed a sewer line in the Battery Park area, blocking the pipe and causing more serious flooding. This article describes the fast track design, bidding and construction of an emergency tunnel to bypass the collapsed sewer. Innovative value engineering, tunneling and shaft-sinking methods and final lining design all contributed to the success of this project. The storm inundated Richmond, VA with up to 305 mm (12 in.) of rain that, in some areas, caused widespread flooding and damage. One of the hardest hit areas of Richmond was Battery Park. A major trunk sewer in the Battery Park area collapsed and caused local combined sewer and stormwater flooding. The collapsed sewer was a 2.4-m x 76-mm (8-ft- x 3-in.-) wide by 2.7-m- x 152-mm- (9-ft- x 6 in.-) high arch sewer that was constructed in the 1920s and later filled over with municipal solid waste and a soil fill cap to cur-rent elevations. A sinkhole was created in the area of collapse approximately 18 m (60 ft ) deep and 31 m (100 ft) in diameter. This caused the existing arch sewer to become blocked. As a result of this blockage, contaminated floodwaters reached depths in low-lying areas in excess of 8 m (25 ft).

Jan 1, 2008

By Jeff Dean

As the Society celebrates its 35th year as an explosives industry association, it is clear that we are part of an industry that covers many sectors of economic activity. We are the voice of those who use, transport, store, manufacture, and dispose of commercial explosives products and others that serve the end user of explosives products. Along with other associations in this industry, we have a combined membership of hundreds of companies and tens of thousands of individuals in the U.S. and around the globe.

Jan 1, 2010

By Frank E. Cash, Max S. Peterson

"INTRODUCTION Falls of ground cause the greatest number of accidents at underground metal mines. Statistics compiled by the Federal Bureau of Mines show that during a 13 - year period ended in 1943, falls of ground caused 35 percent of the fatalities and 16.8 percent of the nonfatal injuries at underground metal mines in the United States. 4/ Expressed on a basis of a million man-hours worked, the frequency rate was 0.355 for fatalities and 11.76 for nonfatal injuries. Although some progress has boon made in preventing rock-fall accidents over a 30- or 40-year period, the problem is still a major one requiring the diligent efforts of management and employees.In the Lake Superior district: where organized safety programs have been in effect for more than 30 years, the record is more favorable. Statistics compiled by the Lake Superior Mining Section of the National Safety Council reveal that over a 6-year period ended in 1945 the frequency rate of fatalities per million man-hours was 0.277, and the rate for nonfatal injuries was 2.38 from falls of ground.Although the above-given statistics do not cover equal or concurrent periods, the improvement in accident experience in the Lake Superior district over the national average, is obvious. This improvement is due to more effective methods of ground support or more rigid enforcement of the use of known methods.It is hoped that the following information about ground-support practices in the Lake Superior district will assist operators of other mines in their efforts to reduce accidents from falls of ground."

May 1, 1948

By M. P. Davies

"Risk, the product of probability and consequence, is an integral part of mining. Whether evaluating exploration priorities, determining property acquisition potential, reviewing the components of an operating mine or assessing environmental/closure issues, the concept of minimizing risk is central to economic and technically appropriate decision making.Until recently, risk evaluations have tended toward a strongly mathematical basis. With this previous trend, it was essential to establish precise probability density functions to all assessed components or issues where often little information was available. The combined effect of the seemingly complex analyses with corresponding insufficient data often resulted in either a poorly executed risk evaluation or no evaluation whatsoever; either result not acceptable for optimal decision making. This paper presents a simple and practical procedure to carry out risk assessments for the mining industry. Although simplistic in nature, the power and usefulness of the technique is immense. The basis for the procedure involves combining deterministic assessments (often “gut feel”) with appropriate probabilistic descriptors. The resulting procedure, termed Potential Problem Analyses, or PPA, can be used anywhere an evaluation of risk will assist in optimizing technical and/or economic decisions. As will be shown, a key element of the PPA procedure is the multi-disciplinary input the framework allows which makes the method ideal for a teamwork approach to decision making."

Jan 1, 1997

By Glenn Lyle

CEMI Introduction ? Introduction of the CAF VOD Project ? Who are our partners ? What were the Outcomes What is next

May 1, 2011

By Ian M. F. Arnold

"Occupational health programs and their role in improving the quality of working life in the mining industry are discussed. Attention is directed to some problems peculiar to the Canadian mining industry. Factors affecting program development are reviewed, as well as parameters affecting cost-benefit analyses.IntroductionThe quality of working life in the mining industry is a more important consideration than in many other industrial environments because of the very nature of the undertaking. It was a strange paradox of the 1960s that preventive maintenance programs for machinery and equipment were well accepted, whereas the concept of ""preventive people medicine"" was basically ignored. Fortunately, there seems to be a swing toward the development of occupational health programs in many sectors of the business community; however, there is a noticeable lack of consistency and uniformity for thought among the members of the mining industry. The blame for this lack o f progress in the occupational field cannot be entirely attributed to the industry, but must also rest with (for the most part) apathetic and inadequately trained physicians. This latter problem is slowly improving with the growing recognition that a well-planned and executed occupational health program may improve the quality of working life for mining employees and their families.There are a number of factors which relate to occupational health in mining, and its effect on working life quality. Included among these are:1. Community isolation.2. High accident risks.3. Occupational disease risks.4. Production demands and the state of the economy.5. Government regulatory requirements.6. Travel demands.These, and others, reflect on all levels of the mining industry. To examine how these factors can be moderated by an occupational health program, it is necessary to first review the rationale for such a program and some of the costs related to it."

Jan 1, 1983

By Peter B. Lilly

Thank you, Syd, for the kind introduction and for inviting me to give the Keynote Address at this very prestigious gathering of some of the finest intellect and talent in the domestic and international coal industry. CONSOL Energy has been a part of this conference for its entire 24-year existence. We have presented 27 papers over that time. CONSOL employees have also been members of the planning committee for the conference, and we have been pleased to support the event both financially and with many participants. So I am honored to be here with all of you this morning, especially during such a positive period for coal. You can just feel the enthusiasm in this room for our industry, and for this conference. I can tell you, there?s also a lot of enthusiasm and excitement in CONSOL Energy?s boardroom. And our enthusiasm is mirrored on Wall Street. But there remains an ironic twist to all of this attention. Even when times are good, the coal industry seems to go largely unnoticed by the mainstream. Outside of West Virginia and other coal-producing regions, the industry still seems to lack influence and support, at least here in America. As an example, last month, an ABC News crew visited our Blacksville 2 Mine, near here, to do a feature story on increased employment in the coal industry.

Jan 1, 2006

By M. Foguenne, A. van Lierde, P. Henry

Leaching experiments were carried out on a spent catalyst sample with a honeycomb structure, containing 47.5% Ti, 5.8% Mo, 2.7% Si, 2 035 ppm As, 52 ppm Pb and 8.8 ppm Hg. More than 93% of the Mo and As was removed by direct alkaline leaching after grinding to 80% -36 micrometres. The residue contained 0.3% Mo and 60 ppm As. To obtain a TiO2 matrix with 30 ppm As, acid leaching at controlled pH with 90 kg/t Al scrap was followed by oxidising alkaline leaching. Treatment of the direct alkaline leach solution or of the mixed solutions from the two-stage process involved two successive operations: purification by neutralisation with Al(OH)3 addition to raise the Al concentration to 4 g/l, and ion exchange on Amberlite IRA 94 S resin. Whatever the type of solution treated, elution with 200 g/l NH4OH solution gave an eluate of very high purity containing 164 g/l Mo, less than 70 mg/l V and less than 2 mg/l As

Jun 19, 1905

By Forrest T. Moyer

Need for lightweight building materials was created in the latter part of the nineteenth century by a radical change in building design in which dead load or structural weight was transferred from thick, heavy, load- bearing walls of former construction practice to a load-carrying framework of beams and columns with thin walls. This new design was brought about by the introduction of structural steel followed by reinforced concrete and structural concrete as materials for the erection of the load-supporting frame. The new materials and method of construction made possible the erection of skyscrapers and the building of bridges with long spans, and made feasible additions of one or more floors to existing buildings. As size and design of the load-bearing framework are controlled chiefly by dead load, the natural result was a. search for and use of light- weight materials in partitions, floors, and exterior walls. However, these thin walls created problems of heat and sound. insulation, so that building materials which possessed good heat- and sound-insulating properties in addition to light weight were objects of extensive research. One group of materials developed to fill this need comprised lightweight concretes, of which some were obtained by the use of lightweight aggregates. Although the advantages of lightweight.materials were evident from the first skyscrapers, there was a transition.stage.between the old bearing- wall and modern skeleton-frame types of building, with the heavy and massive construction of the former superimposed upon the latter. Hence, it was not until the period between 1910 and 1930 that the new lightweight concretes were recognized and used more extensively in the erection of large, nonresidential buildings. From this type of construction, light- weight-aggregate concretes entered-fields of residential and small non- residential building; in which they were found desirable for production of prefabricated, large-size; masonry units. Although the weight of each unit was reduced sufficiently to enable one man to handle it easily, properties of the new concretes other than light weight were the principal factors in the ready acceptance of these new materials in residential building. Manufacture of precast units includes complete lines of masonry and back-up blocks, bricks; floor beams, columns and partition, roof, and floor tiles and slabs. Recent improvements in casting machinery, development of the vibration-pressure machine, and a more thorough study and knowledge of the requirements and properties of the concrete mix have all contributed materially to the rapid expansion in use of lightweight aggregates in this industry.

Jan 1, 1942

By R. J. Stevens

THE Roan Antelope Smelter commenced operations in October, 1931. As originally designed, its equipment consisted of one reverberatory furnace, 120 X 25 ft, two Peirce-Smith converters 12 X 20 ft, and one straight line casting machine. Since that time the following additions have been made: One reverberatory furnace 120 ft X 28 ft (1934) One reverberatory furnace 95 ft X 28 ft (1943) Two 12 X 20 ft Peirce-Smith converters (1934 and 1938) One 13 X 30 ft holding furnace 6 (1938) One straight line casting machine and 2 ladle tilting quadrants (1934) The metallurgy of the smelting process is comparatively simple. However, there are several features of operation which are uncommon to most copper smelters: (1) The high grade of concentrate treated; this has always been about 50 pct copper. (2) The high flux burden on the charge. This is necessary because of the deficiency of bases'in the concentrate and the high alumina content of the concentrate. (3) The frequent necessity of adding coal to the furnace charge to control the matte grade. (4) The high grade of matte produced. This has led' to unusual converter problems. From the commencement of operations, the ore mined has come from the Roan Basin orebody. The concentrate produced from this ore consists mainly of chalcocite and shale with small proportions of other copper minerals. As mining operations extend to the Roan Extension orebody, the proportions of bornite and chalcopyrite in the concentrate will increase with a corresponding decrease in the copper content of the concentrate. Because of the concentrate grade the capacity of the reverberatory . furnaces in terms of tons of copper produced per ton of coal burned is high.. This ratio is usually over 2.2, and on especially favourable runs has reached 2.6. Reference to Table , shows that the iron content of the concentrate is unusually low. Only part of this iron is available for slag formation, the balance going to the matte. To make up this deficiency in bases, limerock is added to the furnace charge. This flux ensures a slag that is of the correct silicate degree, is sufficiently fluid, of low specific gravity, and it counteracts the thickening effect of the alumina present. An ample supply of flux is obtainable from Ndola, 2 2 miles distant by rail. Although the reverberatory slag has a high copper content, the slag fall is low and the copper loss in the slag now rarely exceeds 1.0 pct of the total copper charged. The blister copper shipped is of such purity that only one fire refining operation has been necessary to produce a wirebar with properties comparable to electrolytic copper. Bismuth has always been the most troublesome impurity and consequently the problem of its control in the finished product has been of prime importance. Practically none is removed in the reverberatory furnace. The bulk of the elimina-

Jan 1, 1947

By L. Sandbak

The Turquoise Ridge Joint Venture (TRJV) is located in northern central Nevada, and is situated within the Basin and Range province, near the northeast end of the Osgood Mountains (see Figure 1). The TRJV mine consists of typical Carlin type- gold mineralization characterized by low strength rock of altered limestones, siltstones, and mudstones. The weak nature of the ground facilitates the underhand cut and fill mining methods. TRJV has been working to optimize ground support and mechanize top cut drift sizes and eliminate operating hazards associated with jackleg drilling. Safety Factor analysis based on bolt strengths has allowed us to pursue larger sized top cut drifts and to evaluate bolt length sizes and spacing. Switching from jackleg sized drifts of 10?W x 10?H to a mechanized 12?H x12?W top cut drift design has the potential to decrease overbreak, provide more uniform drift design sizes and bolt patterns, and increase ore production by at least 38%.

Feb 23, 2014

By R. J. Stevens

The Roan Antelope Smelter commenced operations in October, 1931. As originally designed, its equipment consisted of one reverberatory furnace, 120 X 25 ft, two Peirce-Smith converters 12 X 20 ft, and one straight line casting machine. Since that time the following additions have been made: One reverberatory furnace 120 ft X 28 ft ('934) One reverberatory furnace 95 ft X 28 ft (1943) Two 12 X 20 ft Peirce-Smith converters (1934 and 1938) One 13 X 30 ft holding furnace (1938) One straight line casting machine and 2 ladle tilting quadrants (1934) The metallurgy of the smelting process is comparatively simple. However, there are several features of operation which are uncommon to most copper smelters: (I) The high grade of concentrate treated; this has always been about 50 pct copper. (2) The high flux burden on the charge. This is necessary because of the deficiency of bases in the concentrate and the high alumina content of the concentrate. (3) The frequent necessity of adding coal to the furnace charge to control the matte grade. (4) The high grade of matte produced. This has led to unusual converter problems. From the commencement of operations, the ore mined has come from the Roan Basin orebody. The concentrate produced from this ore consists mainly of chalcocite and shale with small proportions of other copper minerals. As mining operations extend to the Roan Extension orebody, the proportions of bornite and chalcopyrite in the concentrate will increase with a corresponding decrease in the copper content of the concentrate. Because of the concentrate grade the capacity of the reverberatory furnaces in terms of tons of copper produced per ton of coal burned is high. This ratio is usually over 2.2, and on especially favourable runs has reached 2.6. Reference to Table I shows that the iron content of the concentrate is unusually low. Only part of this iron is available for slag formation, the balance going to the matte. To make up this deficiency in bases, limerock is added to the furnace charge. This flux ensures a slag that is of the correct silicate degree, is suficiently fluid, of low specific gravity, and it counteracts the thickening effect of the alumina present. An ample supply of flux is obtainable from Ndola, 22 miles distant by rail. Although the reverberatory slag has a high copper content, the slag fall is low and the copper loss in the slag now rarely exceeds 1.0 pct of the total copper charged. The blister copper shipped is of such purity that only one fire refining operation has been necessary to produce a wirebar with properties comparable to electrolytic copper. Bismuth has always been the most troublesome impurity and consequently the problem of its control in the finished product has been of prime importance. Practically none is removed in the reverberatory furnace. The bulk of the elimina-

Jan 1, 1949