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By A. R. Laplante

In this paper, the performance of the Knelson Concentrator and of the batch and continuous Falcon Concentrators are compared. The units are based on different operating principles, and perform quite differently. The Knelson yields very high free gold recoveries over a wide size range of both the recovered and rejected species. It is less effective in recovering very fine (<15 μm) or very flaky gold, as encountered in flotation feeds, concentrates or tails. It is the preferred unit for gold recovery from grinding circuits. The batch Falcon is effective in the fine range, typically less than 37 μm for gold. Its recovery zone is quickly saturated when there is significant heavies in the feed. It works best as a pre-concentration unit, or when sulphide content is low. The continuous Falcon is a versatile unit which is capable of recovering fine heavies (density down to 5 g/cm 3), especially from coarser gangue.

Jan 1, 1993

By S. N. Groudev

Intensive uranium mining activities at the Curilo deposit in Bulgaria has caused widespread contamination over a wide area. A number of receptors including soils and watercourses as well as the ecosystems in the area have been severely affected. Even today, 10 years after the cease of activities, acidic waters generated from the abandoned mining works, the low-grade ore and waste dumps contaminate soil, surface- and groundwater. The present paper describes in general the environmental status of the wider Curilo area and examines the potential of preventive and remedial measures that can be applied in situ to rehabilitate the site and restore the ecosystem. The main rehabilitation technologies examined include modification of the acid generation potential of the pollution sources, treatment of the acidic drainage by means of a natural wetland and in situ bioremediation the of contaminated soils. Finally, a number of efficient indicators are proposed so that the rehabilitation potential at Curilo and similar heavily contaminated sites is assessed.

Jan 1, 2003

By Harry Holle, Gary Johnson

A plant trial was conducted at the Paddy's Flat plant of Dominion Mining Limited with the aim of comparing the ef evenness of oxygen and hydrogen peroxide as leaching oxidants. The Paddy's Flat plant is designed such that the leach train can be divided into two parallel streams, allowing the same or lurry to be eated in two identical trains. By effectively ehminatmg the influence of the ore variations on the results subtle differences in the performance of the two reagents hav been identified. . . The results of the plant trial indicate that the two reagents act m different ways, and that each may be more suitable than the other _for _the treatment of certain types of ore. In some cases a co bmation of the two reagents may be the most cost effective option. . or t e same chemical conditions in the leach pulp, including dissolved oxygen levels , the reagents achieve different gold leaching rates, and in some cases different ultimate leach extraction.

Jan 1, 1992

By P. Whincup, T. Showell, B. Marchant, R. Dunne

An oversupply of copper on world markets in the early 90' s, coupled with a decrease in demand, resulted in a "tight" market for the sale of copper concentrate. In these conditions small producers of low grade copper concentrates found it difficult to sell their products. The situation was exacerbated for those producers also having reasonable quantities of penalty elements (e.g. As, Bi). The Telfer Gold Mine bulk copper gold concentrate, produced from treating underground sulphide ore, fell into this category (i.e. 16% to 20% copper, 30% to 35% sulphur and 3500ppm to 4500ppm arsenic). The concentrate sulphide minerals are predominately chalcocite and pyrite. Although a higher grade copper concentrate was attainable a substantial decrease in gold recovery ensued. Under the prevailing market conditions a decision was made to stockpile concentrates pending either an easing of market conditions or alternatively finding an on site method for treating the concentrate to recover both the contained gold and copper.

Jan 1, 1995

By Ivan Caetano Machado

Good morning ladies and gentleman. During 1995 Prof. R. P. King (University of Utah Comminution Center) presented 2 papers on new horizons in comminution: "Comminution Research in the United States " was presented at the 1995 Meeting of the National Mining Association, while "Comminution: Meeting the Needs of Fundamental Research in the Mineral Industry" was presented at the 2nd SME Research Forum - 1995. In both papers a very interesting graph named "Energy usage for various comminution schemes" illustrated some poignant issues proposed by Prof. King. We do think that some of Prof. King's ideas might very well serve as "warm-ups" for this Comminution Panel Discussion, which are ultimately the goals to be reached by the 3-minute presentations. Thus, we shall be addressing in the sequence Prof. King's most relevant ideas (as well as introducing his graph), intending therefore show how important creative and state-of-the-art Mill Modeling is, if it is to become a Tool to Effective Cost-Saving Optimization Strategies.

Jan 1, 1996

By A. Dan Rovig, C. Kevin McArthur

Technical and managerial innovations in the minerals industry have allowed continuing mining activities in the United States, and elsewhere, as gold orebody quality has diminished or has become more refractory. Of course, world markets, permitting requirements, and political processes also have created a need for innovative practices that contribute to the survival of the mineral industry. The gold industry has been transformed, during the past approximately 40 years, from a predominantly underground mining and milling type of exploitation and extraction to the large-scale, relatively low-grade type of extraction that is common in the United States today. Indeed, with the introduction of gold heap-leaching technology and the development of mines that produce from large, relatively low-grade gold orebodies in the western United States, a "new" industry was born and continues to prosper today. It is worthwhile noting, however, that Dobra (1997) has reported that one of the major trends in the North American gold industry is a movement back toward underground developments.

Jan 1, 1998

By Robert C. Freas

The summer joint meeting of the East Tennessee and Carolinas Sections of SME was held in Morristown, TN, on July 29 and 30, 1994. The Friday portion of the meeting began with a field trip to Asarco Inc.&apos;s Young Mine and Mill, one of four mines operated by the company in the Mascot-Jefferson City district. The Young Mill processes ore from two other mines as well as its own, first by heavy media separation and then by standard flotation processes. Zinc concentrates are shipped by truck and barge to an electrolytic refinery in Clarksville, TN. The heavy media rejects and the dolomitic limestone tailings are sold through Asarco subsidiary American Limestone Co. Saturday&apos;s technical session, organized by Program Chairman Bob Fulweiler of the Tennessee Division of Geology, provided a review and status report of the zinc industry in Tennessee. This article summarizes papers presented, including one on recent developments in underground blasting.

Jan 1, 1994

By James A. Holtkamp

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

Jan 1, 1994

By V. Saltas

In the present work, dielectric spectroscopy experiments were conducted on bentonite samples collected from Milos Island, in order to study their electrokinetic behavior in correlation with water content and mild heat treatment. Low-frequency dielectric spectroscopy has proved to be a power tool in the study of the electrical behavior of clay-water systems, because polarization and relaxation processes typically affect response at frequencies below 100 kHz. Therefore, dielectric and conductivity measurements in the frequency range of 10mHz to 1MHz were carried out by means of a high-resolution broadband spectrometer on bentonite samples, at various levels of hydration. The evolution of dielectric response was also examined after annealing of the samples. Experimental data were computer fitted with the empirical Havrilliak?Negami dielectric relaxation function on which a conductivity term was superimposed. The evaluated parameters of the fitting function are shown to be strongly affected by the water content of the measured samples.

Jan 1, 2006

By Christopher E. Johansson, William J. Kohr, John W. Shield

Heap biooxidation is an economical means to treat refractory sulfidic ores. However, air flow limitations are a major obstacle in commercialization of this technology. Geobiotics, Inc. has developed a new process for heap biooxidation of sulfide ores that renders the ore more susceptible to bacterial oxidation. In this process, air and liquid flows in the heap are greatly improved by first removing clays and other fine particles from the ore. Gold bearing sulfides are recovered from the removed fines and separately biooxidized. Column biooxidations were conducted on two refractory sulfidic ores from which the fines had been removed in order to improve air flow through the column. Gold recoveries increased from 46% to 90% for a mill grade ore and from 52% to 80% for a low grade ore after biooxidation. Fines and clays in these ores had precluded whole ore heap biooxidation from occurring. This new process addresses the most significant problem of large scale heap biooxidation.

Jan 1, 1996

By K. N. Han, M. C. Fuerstenau, T. B. Onlin

A mathematical model describing the concentration profile of fine particles in the axial direction in liquid fluidized beds has been developed for the removal of fine particles. A forward finite differentiation technique has been used to solve a continuity equation with a source term to predict the concentration profile and, hence the recovery as a function of time. With the aid of experimental results obtained using a fluidized bed of 3-cm diam, dimensionless parameters were identified. These parameters were used to predict the concentration profile of fine particles in fluidized beds of larger sizes. Four different sizes of fluidized beds, namely, 1.3, 3.0, 4.0, and 7.5 cm in diam, were used in this investigation. The amounts of bed particles used included 4, 8, 16, 24, 59, and 120 g, and the size of bed particles were 48x100, 100x150 and 150x200 mesh.

Jan 1, 1987

By R. Hogg, R. H. Weiland, P. Bunnaul

The dewatering of flocculated clay suspensions by compression in a centrifugal field was investigated. The results were analyzed with respect to the direct applicability of centrifugal dewatering (as in solid-bowl centrifuges) and indirect applications to gravity sedimentation systems. An important objective of the study was to evaluate the self-weight effect using centrifugal forces to simulate consolidation of deep sediments. Experiments were conducted in which the sediment mass and initial structure were maintained constant while the effective sediment weight was varied by centrifuging at different speeds. The relationship between the limiting sediment density and the applied consolidation stress was found to be the same for both gravity and centrifugal consolidation, indicating that small-scale laboratory tests can be used to predict consolidation in deep beds. The effects of the initial structure were also studied using controlled variations in flocculation conditions. The results imply that, for the flocculated suspensions studied, the longterm consolidation behavior is relatively insensitive to the actual extent of flocculation.

Jan 1, 1995

By Ralph B. Peck

Exploration The technology of underground construction and particularly of tunneling, both now and in the future, starts with knowledge of the properties of the medium surrounding the tunnel. Although we are trying to develop machines that can excavate tunnels independently of the properties of the medium, and although we may achieve some success in this direction, we seem always to be brought up short by a paradox: With increasing sophistication of machines and with increasing complexity of construction jobs, our methods are likely to become more sensitive rather than less sensitive to changes in the medium. I suspect that the need for more precise knowledge of subsurface conditions in advance of construction will increase rather than decrease as time goes by. In the recent anniversary issue of Engineering News Record, Probing the Future, Senior Editor Bill Jacobus prophesies highly sophisticated devices to probe the unknowns of the earth&apos;s soil and rock materials. He envisions that "drill holes to obtain borings will give way to rock-melting coring devices". He may be right; it is hard to argue the accuracy of predictions of the future. It seems to me more likely, however, that the rock-melting probe will be simply one more in

Jan 1, 1974

By Chas. E. Shumate

There is assembled here this morning in Chicago the heartland of America, what is undoubtedly the greatest concentration of Technical, Scientific and "CAN DO" knowledge ever assembled in America. The participation in this Conference by the representatives of so many nations is particularly impressive and is a further indication of the importance of the subject matter of this conference which you will be discussing in much detail during the next few days. Another impressive feature of this Conference is the participation of a large segment of the construction industry in whose hands fall the job of building what others design. Also strongly represented is the manufacturing industry whose capability is well known throughout the world. They have the resources to design, develop and manufacture the machines and specialized equipment needed to do any job which the world requires. You should not expect to gain any knowledge from my few remarks this morning as I am undoubtedly the least qualified individual in this room on the highly technical and scientific subjects you will be discussing during these next few days. However, I shall offer a few broad suggestions on subject matter which I trust may generate serious thought during your discussions.

Jan 1, 1997

By Tony Weeks, J. Loah, Ian Mcgaffin

PT Newmont Minahasa Raya (PT NMR) operates a 700,000 tonne per annum open cut gold mine in the Minahasa region of North Sulawesi. The operation commenced production in the second quaiter of 1996 and is expected to produce an average of 150 000 to 180 000 ounces of gold per year for the mine life. The deposit is predominately refractory in nature and requires a complex treatment route incorporating dry milling and whole ore roasting followed by conventional cyanidation and adsorp­tion of the gold onto activated carbon. Gold is eluted from the carbon to produce <lore bars assaying approximately 94 percent gold. A scrubbing system for the removal of mercury from the roaster off gases was commissioned in late 1997. Due to the location of the operation, close to the coast and in seismic region with high rainfall submarine tailings placement (STP) was the preferred method of tailings disposal. Prior to dis­posal into the ocean the tailings from the CIP plant are detoxified in a three stage detoxification circuit to treat cyanide, arsenic and mercury. This paper reviews some of the design and operational fea­tures of the whole ore treatment process employed at the Minahasa Gold Mine.

Jan 1, 1998

By D. Legg

This is the first in a series of studies commissioned by the European Environment Agency that aim to raise awareness of the use of economic instruments and assess their effectiveness. The emphasis is on sharing good practice and increasing knowledge and understanding across European countries in this emerging policy area. A methodology for evaluating the effectiveness of economic instruments has been developed and this will examine whether the inclusion of economic instruments in complex policy packages can improve the overall performance, particularly as a prevention tool in terms of resource use and waste generation The focus for this initial study is the use of aggregate taxes in four EU countries which include the Czech Republic, Italy, Sweden and the UK so that a range of experiences (e.g. geographical, political etc.) can be included. The findings will be used to inform and influence future policy development in other EEA countries. The methodological approach is divided into two main sections: - Technical analysis, which covers quantitative and qualitative analysis. - Process design, i.e. who should be involved when, where and how. Process design is essential if the full learning benefits are to be gained from the technical analysis, which is the ultimate objective of these evaluations.

Jan 1, 2007

By Al Sylvester

The drill-and-shoot excavation of the two underground Pumphouses for the Metropolitan Sanitary District of Greater Chicago&apos;s Mainstream Pumping Station is described. The construction sequence involved the concurrent excavation and support of the two 19.2 m (63 feet) wide by 83.6 m (274 feet) long by 29.3 m (96 feet) high caverns. Excavation was interrupted after taking the 6.1 m (20 feet) high top heading in order to cast-in-place a 0.2 m (8 inch) thick by 19.2 m (63 feet) wide concrete arch. The remaining 23.3 m (76 feet) of rock was then excavated in benches below the concrete arch. PROJECT DESCRIPTION Twenty-four kilometers (15 miles) southwest of the city of Chicago, Peter Kiewit Sons&apos; Co., in a joint venture with John F. Shea Co., and Kenny Construction Co., has successfully completed the construction of the Mainstream Pumping Station for the Metropolitan Sanitary District of Greater Chicago. The five year, 169 millon dollar project is a vital component in Chicago&apos;s Deep Tunnel and Reservoir Plan in that its function is to lift the sanitary/ storm sewage back up to grade from 107 m (350 feet) below ground, and pump it to the treatment facilities 8 km (5 miles) away.

Jan 1, 1985

By L. Prosser, A. Iannacchione, G. Esterhuizen

The potential for roof falls in underground mines remains a clear and present danger for mine workers. An investigation of ground conditions in nearly 50% of the nation’s underground stone mines found that the state of roof stability is primarily determined in a limited and subjective manner. These large opening mines, with roof heights typically of 7 m or more, make physical observation difficult. Although some mines use monitoring techniques to gain additional information on roof stability, this practice is usually short-term and localized to address ground conditions in a particular section or part of the mine. A methodology to assess the risk for a roof fall is proposed in a preliminary fashion based on engineering judgment acquired from extensive underground stone mine experience and examination of related literature. The proposed method utilizes an observational technique to identify the risk of roof falls in three categories. Case study scenarios provide a realistic picture of model implementation. Providing the mine level decision maker with an accurate assessment tool to ascertain the level of risk related to ground conditions is expected to reduce mine worker injuries and fatalities. Moreover, the presences of danger can be overcome with a clear picture of quantified ground conditions.

Jan 1, 2006

By Jean-Claude Bianchini, Paul Bauernfeind, Erwin Gartung

Introduction The city of Nuremberg, located in Bavaria in the Federal Republic of Germany, started building a subway in 1967. The construction operations began in a southern suburb, where no complications were encountered in the design and execution of the job. As the first subway line approached the downtown area of the city, the civil engineering challenges increased rapidly. Tunnels had to be excavated next to, or below precious historical buildings, and the work of the responsible engineers was closely watched by the public, who were very anxious about any damage to the existing beautiful old houses and churches. The job has been handled successfully to date in cooperation with the owner-designer, the geotechnical consultant and the contractors, who jointly went through a process of systematic learning and gathering of experience, and who developed a modern tunneling technique specifically tailored to the natural properties of the encountered ground conditions and the requirements of the city of Nuremberg. The application of scientific methods has been an important part of this development. Research into the geotechnical properties of the predominantly encountered soft Keuper sandstone, studies of the geomechanical performance of grout reinforced sand sections and finite element analyses of various tunnel problems for the prediction of displacements, for the assessment of stability, or

Jan 1, 1979

By Gastón Díiaz, Enzo Carranza Meza

El Teniente Mine of Codelco-Chile, located at Los Andes Range of Mountains, 90 kilometers South far from Santiago, the capital city, has been exploited for more than 90 years, with over 1000 million tonnes of copper ore extraction. No doubt, this particular record, has been possible to achieve due to an efficient combination of human and technological efforts in the exploitation of one of the biggest ore deposits of the world. Throughout times, the exploitation has evolved from a mainly manual one to a highly mechanized exploitation. Notwithstanding, different and several geomechanical problems that occurred in one of its areas, increased the risks to personnel that should normally operate large equipments in its working face. This last condition, forced El Teniente mine to design and develop systems and technologies that would allow the use of tele-operated LHD, picking hammers and drilling equipment (jumbos) from a safe zone. Currently, El Teniente Mine is using in its extractive works equipment such as LHD, picking hammers, and drilling Jumbos, that can be manually or teleoperated commanded from a Central Control Room located one kilometer away from the production area. In general, a new technological era has been opened in the mining exploitation at El Teniente: the exploitation era with telecommanded robots.

Jan 1, 1998