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By P. Scinto, P. Hudson

"Modern day ore bodies are becoming increasingly harder, more abrasive and lower grade. The Mako deposit is located in Senegal and consists predominantly of primary mafic and felsic lithology that are both very competent and very abrasive ores (Axb < 30, BWi >20 and Ai >1.0). The deposit was initially discovery in 2010 and the Toro Gold management team fast tracked the Mako Project through development and into production to achieve its first gold pour in January 2018. The comminution circuit comprises primary crushing single stage SAG milling with recycle crusher (1oCR SS-SAC). The mill reached design throughput and grind size seven weeks after first ore. The Mako project marks another successful international application of single stage milling, which represents a simple and easy to operate comminution circuit for small-to-mid size projects with a low capital cost. This paper describes the ore interpretation, comminution modelling, grinding circuit selection and design, as well as an overview of the commissioning and ramp-up of the mill.INTRODUCTION The Mako Gold Project is operated by Toro Gold Ltd., which holds a 90% interest in the project. The project is located in south-eastern Senegal in the Kedougou region, close to the Gambia river and township of Mako. The Mako deposit lies in the “Kenieba Window” of eastern Senegal and western Mali, which hosts a number of gold mining operations and development projects. The Mako Gold Project has an estimated life of 8 years with overall recoverable gold estimated at 924 koz. The process plant is designed to treat 1.8Mt/a of ore and produce 128 – 143 koz of gold per annum. Lycopodium Minerals Pty Ltd (Lycopodium) was appointed to provide feasibility studies and EPCM services for the greenfield project. Forming part of consultancy services provided by Lycopodium, Orway Mineral Consultants (OMC), a subsidiary of Lycopodium, was involved in the design, commissioning, ramp up and ongoing post commissioning support of the comminution circuit."

Jan 1, 2019

By Wallace W. Roepke

The Bureau of Mines conducted a series of experiments using Illinois No. 6 coal to determine the effect of asymmetric wear on airborne respirable dust (ARD), specific energy, cutting force, and normal force. Plumb-bob-type bits--one new bit and four ground with different sized flats--were used. Constant-depth linear cuts at 0.32, 0.64, 1.27, and 2.54-cm cut depths were made. Both cutting force and normal force increased as the flat area increased. Specific energy demonstrated a statistically significant increase with flat area at the 0.32-and 1.27-cm cut depth only. Specific ARD showed a statistically significant decrease with increasing flat area only at the 0.64-cm cut depth. Increasing cut depth increased cutting force but decreased specific energy and specific ARD. Normal force increased with increasing cut depth for the new bit but exhibited a maximum at 0.64 cm for the bits with flats.

Jan 1, 1983

By Whitmell J. Smithwick

Lime is one of the most extensively used chemicals in industry. Other than sulfuric acid, it is used in greater quantities than any other man-made industrial chemical. In 1974 there were 20,368,000 tons of lime used in the United States, which amounts to approximately 190 pounds for each man, woman and child in our nation. Lime also is perhaps the most diversely used of any industrial chemical. It is used in such areas as pharmaceutical, chemical, steel making, glass making, production of copper and aluminum, sugar refining, agriculture, construction, ecological endeavors, potable water treatment and sanitation. Figure I lists the major uses of lime for 1974, which is the latest year for which this data is available. The impact of the use of lime for ecological reasons did not show up to any appreciable extent in 1974, but we expect this to be a significant factor within the next few years. Fortunately, in the United States and also in most of the world, there are many deposits of high quality limestone available for the production of hood quality lime. For this discussion, we will assure that a limestone of a suitable quality and size consist will be available in a storage bin or stockpile near the kiln. Quality requirements for the lime product will be covered. We also will give a brief description of the three most popular types of lime calcining systems, how they function, and expected lime product quality from each of these. Commercial fuels and major accessory equipment will be discussed briefly.

Jan 1, 1976

By Jeremy Cawley, Horry Parker Jr., Clint Wilson

The 5180 m EPBM drive on the Lower Olentangy Tunnel (LOT) is predominantly within glacial overburden. To connect LOT with the existing OARS deep tunnel in limestone bedrock, the upper 15 m inside diameter Vine Street retrieval shaft telescopes down to 6.7 m in diameter and extends into the karstic Columbus Limestone to a depth of 51 m, where a 104 m SEM tunnel will connect to OARS shaft 6. Pre-excavation grouting was reuired prior to lower shaft excavation to reduce potentially high groundwater inows. This paper discusses the secant pile installation, grouting program, shaft excavation, and hydrogeologic observations.

Jun 23, 2024

By Christopher Mark, Gregory M. Molinda, Timothy M. Barton

The Coal Mine Roof Rating (CMRR) was first presented at this Conference nine years ago. Since its introduction, the CMRR has been incorporated into many aspects of mine planning, including longwall pillar design, roof support selection, feasibility studies, and extended cut evaluation. It has also become truly international, with involvement in mine designs and funded research projects in South Africa, Canada, and Australia. The purpose of this paper is to bring the mining community up to date with recent improvements and applications of the CMRR. The most important new development is a streamlined process for determining the CMRR from exploratory drill core. Just three types of information are now required: •Fracture spacing (or RQD) •Uniaxial compressive strength (or axial Point Load Testing) •Diametral Point Load Testing The moisture sensitivity adjustment has also been changed, and new research has related the immersion test to slake durability. Most recently, the CMRR has been implemented in a computer program, which can be obtained from NIOSH free of charge. The program facilitates calculation of the CMRR from either underground or drill core data. Values from many locations can be saved in a single file, and an interface with Autocad allows CMRR contour plots to be integrated into mine planning.

By AIME AIME

WHEN "Chief" Buehler in mid-September set out on his official 10,000 mile swing-around-the-circle visiting Local Sections he decided not to tell his audiences how to organize and operate a state geological survey. As the director for 28 years, of the Missouri Bureau of Geology and Mines (which, he concedes, is the best in existence) lie could have done this to good advantage; but he preferred to discuss affairs of the Institute. In 25 speeches made to member and student groups, he dwelt on sonic or all of the following phases of activities. He stressed the vital importance of the Local Sections in providing the opportunity for members to associate under pleasant auspices with others in their profession. The benefits of Institute membership he classified as tangible and intangible. Of the two lie felt that the latter were more important. A man&apos;s progress in his profession depends in large measure upon a broad acquaintance and friendship with others. The Institute is incomparably the best medium for meeting fellow engineers. The primary, function of the new enlarged Membership Committee is to obtain a comprehensive list of engineers eligible to be members, always hearing in mind that the standards of membership must not be lowered in any degree. These men are to be invited by individual letter to apply for membership. Whether they become members or not is of less importance; but it is vital that no qualified man should be outside the fold for the reason that membership had never been suggested to him. Dr. Buehler emphasized repeatedly his feeling that the younger man that had never had Institute membership brought specifically to his attention had been cheated:

Jan 1, 1935

By Emanuele Catelli, Paolo Vicentini, Manuel Petitat, Paolo Lanfranchi

"More than 800 million tons of material will be excavated during large underground projects such as tunnels, undergrounds and power plants by 2030 in Europe only. The raw material excavated is often classified as waste, which involves environmental impact and transport issues: landfill areas, CO2 emissions and noise. But how can such massive amounts of material be transported, processed and deposited? Using the example of the AlpTransit Ceneri Base Tunnel (15.4 km), we show that suitable excavated materials can be used sustainably as a primary resource for tunnel concrete. This requires careful planning of the installations and storage areas by the client, timely building of the processing plants and other handling facilities outside the tunnel and a continuous evaluation of the raw material quality. 1. INTRODUCTION Spoil management is a central element of large construction projects. The systematic reuse of suitable excavated material not only saves natural resources, reduces transport distances and landfill volume, but can also decrease overall construction costs. Ideally, all of the concrete needed for tunnel lining can be produced with this on-site material. Such a natural resource management concept was applied for the construction of the new Gotthard Base Tunnel (L = 57 km). Spoil management concepts are, how-ever, difficult to implement and call for innovative techniques, sophisticated logistics and organization. In the context of large projects, environmentally friendly transport, processing and storage of millions of tons of excavated loose material represent another logistics challenge (Simmen & Lieb, 2010). This paper shows key factors that led to the successful completion of spoil management at the Ceneri Base Tunnel, which constitutes a part of the AlpTransit Gotthard Project (Figure 1)."

Jan 1, 2016

By S Gillies, H W. Wu

A study has been undertaken into mine ventilation systems currently in use within Australian modern coal longwall (LW) extraction mines. It reviews systems and discusses evolving changes being adopted to address the more complex challenges. There is a strong move to longer panels, wider faces, greater extraction heights, increased production rates, more efficient ventilation and decreased personnel. Each of these changes is motivated by improvement in productivity and generally leads to cost reduction. In addition, mine workings are moving deeper, which results in increased ventilation control issues such as higher total and respirable dust levels, greater seam gas contents in parallel with lower in situ permeabilities, spontaneous combustion and heat management issues. A comprehensive database of Australian LW ventilation practice is analysed. Currently there are a variety of LW panel ventilation circuits used in Australian underground coal mines due to various combinations of seam characteristics, gas emission rates, spontaneous combustion, geological features and surface constraints. The main issues usually addressed in the designing and planning of ventilation circuits for LW panels are airway velocity, gas concentrations, LW cutting methods (eg Bi-di, Uni-di or half web), ventilation of control devices, pressure differentials and leakage paths and understanding gas concentrations across the length and width of the goaf. If the ventilation circuit can manage the applied contaminant load (gases, heat and dust) at an acceptable cost and circuit duty, then supplementary controls, such as gas drainage, refrigeration and dust sprays and scrubbers, may not be required. CITATION:Gillies, S and Wu, H W, 2013. Review of Australian longwall panel ventilation practices, in Proceedings The Australian Mine Ventilation Conference , pp 87-94 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By T. Bhambhani

Research at Cytec over the past two decades has shown that the traditional approach for ore metallurgical characterization (typically conducted via laboratory-scale batch flotation tests), which involves changing reagents and conditions one-factor-at-a-time, leads to several pitfalls. The chemical solution thus selected has a narrow un-optimized window of performance and will likely fail in the plant. A holistic approach, called the Flotation Matrix 100? process for ore metallurgical characterization, was developed at Cytec about a decade ago and has been successfully used to develop robust reagent solutions for several operations around the world. The premise for the approach is that flotation outcome from ores is variable and is determined by complex interactions between various physical, chemical and operational factors. A key component of the process is the use of efficient multivariate designs focused on the chemistry aspects (reagents and pulp chemistry), which helps identify the best processing conditions for each ore type, as well as the conditions resulting in poor performance. It also includes advanced statistical methods for dealing with the complexity and variability of experimental data. The holistic approach is illustrated in this paper with a case study on Pb/Zn ores. Using just 18 carefully designed batch tests, it is possible to partially simulate the behavior of each ore type in the plant. The best conditions for each ore type, along with the conditions to avoid, are identified. Along with this, insights are obtained into the reasons for high reagent dosages for certain ore types, and interactions between variables. Keywords: flotation, holistic approach, metallurgical characterization, multivariate experimental designs, base and precious metals recovery, sulfide collectors and modifiers, Pb/Zn sequential flotation

Sep 1, 2012

By Cade Mweemba, Alex Mwanza, Jackson Sikamo

"The Zambian Copper mining industry as we know it today has its genesis from early in the 20th century in the 1920s. Consistent private sector-driven investment in the industry over a period of over 50 years in exploration, mine development and operation, development of minerals processing facilities, building of infrastructure for pyrometallurgical and hydrometallurgical processing, with attendant support facilities, including building of whole new towns, resulted in copper production going from zero to a peak of 769 000 tons of copper in 1969. At the same time, the industry created jobs to the extent that in 1972 the industry had over 62 000 direct jobs. The industry was nationalized in 1973 and remained in government hands for just over 24 years. During this period, the industry experienced a serious decline in production levels, reaching the lowest level at the dawn of the 21st century in the year 2000 when production was 250 000 tons. In terms of jobs, an average of just under 2000 jobs were lost every year in the 24-year period, reaching just over 22 000 direct jobs in 2000. Following the return of Zambian politics to pluralism and liberalized economic policies, the government decided to privatize the mining industry. The process started in 1996 and by the year 2000 all the mining assets had been privatized. The new investors embarked on serious investment to upgrade the assets and to develop greenfield mining projects. Fourteen years later and investments of over USD 12 billion, the industry production levels increased year- on-year to reach a peak of 763 000 tons in 2013 with direct jobs reaching 90 000. This paper discusses the impact of the mining industry in Zambia on the economy in areas such as employment, support to other industries, direct contribution to the national gross domestic product (GDP), foreign exchange earnings and social amenities. The paper also focuses on the performance of the mines during these periods vis-à-vis mineral availability, mineral grades and complexity, new technologies and human capital. This is looked at particularly in the light of current challenges the industry is facing and makes suggestions on how the industry can be nurtured to continue being a major driver for the Zambian economy and a major player in the international copper mining business."

Jan 1, 2015

By R. H. Reist, R. D. Dey, V. Castranova, J. P. Durham, Y. Rojanasakul

"Silicosis is a fibrotic pulmonary disease produced by inhalation of silica-containing dusts (Peters, 1986). Chronic silicosis may develop 20-40 years after initial exposure to crystalline silica, and the disease may progress from a simple to a complicated form. Few symptoms are evident in simple silicosis with pulmonary function being relatively normal. However, chest radiographs reveal small rounded ·opacities in the upper lobes of the lungs. These silicotic nodules consist of collagen arranged in a distinctive circular pattern. As fibrotic changes become more severe, the disease progresses to complicated silicosis (progressive massive fibrosis). Complicated silicosis is associated with shortness of breath and decreases in pulmonary function characteristic ofrestrictive lung disease. Chest x rays reveal numerous large silicotic nodules which may be associated with scar emphysema. Several mechanisms have been proposed to explain the cellular events which result in silica-induced lung damage and fibrosis (Lapp and Castranova, 1993). They include: ( l) direct cytotoxicity of silica, (2) activation of oxidant and enzyme release from alveolar macrophages, (3) recruitment and activation of polymorphonuclear leukocytes, and (4) stimulation of fibroblast proliferation and collagen synthesis.Tetrandrine is a bisbenzylisoquinoline alkaloid derived from the Chinese herb Radix Stephania tetrandra. It has a molecular weight of 622.73 and an empirical formula of C38H420 6N2. The chemical structure of tetrandrine has been published previously by our laboratory (Castranova et al., 1991 a). Its structure is characterized by methoxy groups at C7 and C12 , uncharged nitrogens at N2 and N’2 and two 17-carbon ring members connected by a double oxygen bridge between Ca-C7 and C11-C12. Tetrandrine has been shown to reduce both silica-induced fibrosis and the elevation of lung collagen content in rats (Huang et al .. 1981; Yu et al., 1983; ldel, 1987). Furthermore, tetrandrine has been used as an antifibrotic agent in Chinese clinical trials (Li et al.. 1981 ). Preliminary results suggest that administration of tetrandrine to patients with silicosis results in substantial improvement of symptoms, increases in diffusion capacity, and decreases in the size of shadows on lung x rays."

Nov 1, 1995

By M. Sadegh Safarzadeh, Erich U. Petersen, Jan D. Miller

"An acid bake-leach process has been identified and applied to an enargite concentrate containing ~67% enargite, ~27% pyrite (FeS2), ~3% chalcopyrite (CuFeS2), ~6% sphalerite (ZnS) and <1% galena (PbS). Sulfuric acid baking of this concentrate resulted in the transformation of the concentrate to S8, As2O3, HFe(SO4)2•4H2O, PbSO4 and Cu0.47Fe0.53SO4•H2O, all of which (except elemental sulfur and PbSO4) dissolved during the water leaching step. More than 87% Cu and 64% As were leached when the concentrate was baked at 200°C over 7 hours with a sulfuric acid-toconcentrate weight ratio of 1.6. Less than 1% As was lost to the gas phase. Upon water leaching, copper and arsenic were released to the solution at a concentration ratio of about 3:1. While enargite is very reactive during the sulfuric acid baking reaction, other minerals present in the concentrate such as pyrite, galena and sphalerite may compete to consume sulfuric acid and be converted into their corresponding sulfates at different concentrations. The purpose of this paper is to present our examination of the effects of sulfuric acid dosage on the extractions of Cu, Fe, and As from an enargite concentrate. In this regard, the concentrate, baked concentrate, and the leach residues are characterized and a conceptual process flowsheet is described for the acid bake-leach process for the treatment of enargite concentrates.IntroductionThe occurrence of enargite (Cu3AsS4) in copper ores and concentrates and the associated high arsenic values in such resources have resulted in a considerable decrease in the demand for such concentrates because they cannot be economically processed using conventional technologies such as smelting and atmospheric leaching (Mihajlovic et al., 2011). The exploitation of such problematic deposits through competitive treatment strategies will be required in the near future in order to satisfy increasing pressure from the copper market. It is expected that the average arsenic grade of copper concentrates will increase from 0.17% in 2008 to 0.22% by 2020 (Mayhew et al., 2011).The acid bake-leach process was identified and selected for further investigation at the University of Utah as a possible process alternative for the treatment of enargite concentrates. In this case, adequate amounts of concentrated sulfuric acid are mixed with the concentrate and heated to the temperature range 150-300°C. Subsequently, the baked material is leached with water/weak acid and the acid bake-leach process has some advantages over conventional sulfuric acid leaching (Prater et al., 1970). During water leaching, metal sulfates are released in solution, after which they can be extracted through well-known hydrometallurgical techniques. While the majority of the work has been done on oxide minerals, there is a limited record of sulfuric acid baking of sulfides."

Jan 1, 2015

By John W. Harbaugh, Alfredo Prelate

The goal of the study described here is to develop objective. quantitative methods for estimating the outcome probabilities of exploratory oil wells. The study employs the &apos;re-experience&apos; approach, in which historical data are used in a manner which attempts to recreate the past. Our past experience, of course, is the principal guide to the future. To appraise present-day oil prospects, however, we must analyze prospects that have been drilled in terms of how these former prospects were interpreted before they were drilled. An analysis of how they are interpreted after they were drilled is an inadequate guide to the future because our hindsight knowledge is superior to our foresight knowledge. Objective calculation of future outcome probabilities, then, requires that we attempt to treat past information in a manner analogous to that in which we must treat present information in forecasting future outcomes.

Jan 1, 2014

By Ivor Hawkes

The purpose of the development described in this report and as stated in the contract work statement is to "design, develop, fabricate, test and demonstrate, and deliver to the government permissible low cost cylindrical stress gauges and associated components capable of measuring change of stress as a function of time in underground coal mines. The cylindrical stress gauges shall be suitable for installation in bore holes". The technique adopted for measuring rock stress changes is to preload a steel cylinder diametrically across the sides of a 1-1/2 in diameter bore hole and detect deformation of the cylinder from stress changes in the rock, by means of a vibrating wire transducer. By calibration, changes in the period (time for one wire oscillation at the natural frequency) of a high tensioned wire stretched diametrically across the cylinder in the direction of load application are related to stress changes in the rock. To completely evaluate the stress field change in the plane of the bore hole, three gauges set at an angle to each other are required.

Jan 1, 1973

By M. Kinnunen

Handling of municipal solid waste (MSW) and control of its potential resources is becoming increasingly important in modern society. The OECD (Organization for Economic Co-operation and Development) average on municipal waste produced in 2003 was that of around 570 kg per inhabitant. In European Union countries around half amount is of MSW landfilled. In Finland still 88% of MSW was landfilled in 2004. Since incineration reduces MSW volume significantly while producing heat energy, it has become one of the most common waste handling techniques. The shortcoming of incineration is however, that incinerated MSW is often not pre-sorted and it produces slags and ashes as side streams from which recovery of metals is difficult. This paper looks into possibilities of scrap metal recovery for recycling from municipal solid waste incineration (MSWI) bottom ash. In order to do that, a flow sheet of physical separation methods was developed and tested with Finnish rotary furnace MSWI bottom ash. In addition, an empirical model for estimation of the recoveries of scrap metals with physical separation methods for treatment of MSWI bottom ash was developed. According to the results of this study, for 1 Mt of incinerated MSW with 30% mass reduction, a minimum resource potential of 100 kt for magnetic metal scrap of roughly 24 % grade and about 19 kt of non-magnetic metal scrap of roughly 65 % grade. In other words, 57 kg magnetic scrap and 12 kg non-magnetic scrap per inhabitant at the mentioned grades, respectively. Although wide variations of parameters affect the MSWI bottom ash quality, it can be said that a considerable amount of metals is drained into MSWI bottom ash. Results of this study show that from MSWI bottom ash significant material streams metal scrap can be reintroduced into the resource cycle which would otherwise be lost.

Jan 1, 2014

El presente trabajo explica el panorama historiográfico del proyectoToquepala, -en tanto proyecto industrial de la historia minera del cobre-, así como su influencia en el desarrollo económico y manufacturero del Perú. El depósito mineral de Toquepala está situado en el departamente de Tacna, zona sur del país. El reconocimiento como zona cuprífera es partir de Velarde en La Minería enel Perú (1908) y Basadre en Estado actual y porvenir de la industria minera en los departamentos del sur del Perú (1918). Posteriormente en 1937, Juan Oviedo de Villegas denunció los depósitos en Toquepala y fue el geólogo Schmedeman de la cerro de Pasco Corporation, quien reconoció la mina como un depósito de pórfido de cobre. Es a partir de 1938 que se inicia la explotación y en 1948, la Northern Peru Mining and Smelting Company se hace propietario de la zona minera. La exploración del depósito de Toquepala se realizó por medio de taladros verticales, perforados con máquinas de diamantina y de percusión. Durante el periodo de perforación, se realiza un sondaje de percusión previo que determina la extensión hacia otros hoyos para muestrear los valores y así medir la capa y espesor del mineral, mientras que el sondaje diamantino informa sobre la interpretación geológica del subsuelo de esa sección. Para la comprobación de los resultados de la perforacíón se buscó comparar los resultados de perforaciones de diámetro pequeños y grandes, con aquellos del minado del mineral en volúmenes de muestras relativamente grandes. Los métodos de muestreo empleados fueron acorde a las prácticas más estrictas actualmente recomendadas en este tipo de trabajos y supervisados bajo el control de un personal técnico. Luego del trabajo de comprobación del depósito de Toquepala, a mediados del año 1955, se unieron cuatro compañías para formar la Southern Peru Copper Corporation y en ese mismo año el gobierno peruano aprueba el desarrollo del programa y operación de este proyecto . Los planes de minado fueron terminados en 1955 minero. El avance de los trabajos de preparación de este proyecto se realiza a través de dos partes: la construcción de los servicios necesarios para la operación y los trabajos de preparación preliminares a la explotación minera. El ajuste de constucción y minado del programa se culminó en cuatro años (1952 - 1954), dando inicio a la operación en 1955. Finalmente, hablar la inflluencia del proyecto de Toquepala en el desarrollo económico industrial en el sur del Perú, es señalar su apoyo en el manejo de las vías de comunicación, favoreciendo el intercambio comercial entre las zonas ganaderas de la sierra de Tacna, Moquegua y el resto del país, así como del progreso de pequeñas industrias. El acceso a la educación y la erradicación de bajas condiciones sanitarias son elementos que también ayudan al avance social de la población, otorgándole a este proyecto sureño, un lugar importante en el panorama industrial y minero del país.

Jul 20, 1957

By C. Garcia, J. J. Opazo, A. Potulsha, T. Comi

"Sierra Gorda SCM is a joint venture partnership of KGHM International (owned by KGHM SA, Poland), Sumitomo Metal Mining and Sumitomo Corp. (Japan) operating in northern Chile. The Sierra Gorda openpit mine and coppermolybdenum processing plant will become one of the largest mines in the world. The need for optimum production efficiency and sustainability has driven the creation of the most modern, wellinstrumented mine in Chile. This article contains a general review of the project including geology and history.This was a fast-track project going from greenfield site acquisition to mill startup in 10 years. Highly experienced and motivated engineers and technical staff have overcome many significant challenges resulting in a rapid ramp-up of production capacity. A potential expansion to double the production rate in the fourth year of operation has also been intensely studied.The Sierra Gorda property is located in the Atacama Desert of northern Chile, in the District of Sierra Gorda, Region II of Antofagasta, Chile (Fig. 1). There is almost no precipitation in this area. The mine site is generally flat with some rolling hills. The project is located about 5 km (3 miles) from the village of Sierra Gorda at an elevation of approximately 1,700 m (5,600 ft) above mean sea level. The village is near a highway and railway line. The city of Calama, home of the famous Chuquicamata Mine, is located about 60 km (37 miles) northeast of Sierra Gorda. In addition, the SG mine is in the midst of numerous other mines including Spence, Esperanza, Mantos Blancos, El Tesoro, Lomas Bayas, Gabriela Mistral, El Abra, Radomiro Tomic and Escondida, to name a few.The primary organizational value at Sierra Gorda is "Zero Harm." This includes employees, contractors, the environment, the community, plant facilities and mine equipment. A cornerstone of this program is called 5X5S (five by five S), which combines the lean principles of 5S with the safety model of taking five steps back and thinking about the task at hand for five seconds, five minutes, the time it takes to assess and manage the risk. "People caring about people" promotes proactive engagement in the safety of coworkers and others at work and at home."

Jan 1, 2014

By A. H. Sharbaugh

It is believed that considerable economic benefit would arise if run of mine (ROM) coal from the underground mines in the Winifrede seam could he enriched before shipment to the preparation plant by partial removal of the shale. Shale could comprise up to 50% of the ROM product. Complete mine-mouth separation is not necessary, but any process must be dry and have high Btu recovery. We have conducted a preliminary analysis of coal/shale mixtures from the Winifrede seam and we find that it is quite possible that a 50-50 ROM mixture of coal and shale could be converted to a 60-40 coal-shale mixture by inspection of individual lumps coming from the mine. The device would consist of a feeder/siever section to deliver the ROM coal > 5 cm (2 in) to an inspection station via a conveyor belt. This inspection station decides if a piece is coal or shale, and if it is shale, activates an air jet to blow shale off of the belt. We have evaluated a dielectric loss technique for the inspection device. The potential advantages of the dielectric loss method are high throughput, low capital cost, and no special handling or licenses would be required. Such a single lump inspection technique is made possible because of advances in high speed electronics and servo systems. This paper provides a summary of our analyses on the Winifrede coal sample, a description of a proposed apparatus to separate coal from shale, some of the experiments needed to demonstrate our ideas.

Jan 1, 1984

By Kevin A. Foo, Murray D. Bath, John H. Canterford, Arnaldo Ismay

There is no doubt that the dominant future source of gold will be the so-called refractory ores, especially those with gold in a pyrite/arsenopyrite matrix. Minproc Engineers is taking an active role in establishing detailed design criteria for a number of apparently competing processes. This involves generating a detailed understanding of the metallurgy involved, systematic pilot plant testing, and the application of advanced engineering technologies. This presentation outlines the approach adopted by Minproc as well as the design criteria for several current projects.

Jan 1, 1989

By M. S. Seltzer

High temperature steady-state creep rates have been determined jor lead sulfide single crystals whose defect concentrations were fixed by equilibration under controlled sulfur pressure. The activation energy of creep, Qc , for undoped lead sulfide, is a function 01 composilion, decreasing from 2.9 to 2.2 ev as the carrier concentration increases from 9 x 1016 to 8 1018 electrons cm-3 for lead excess crystals, and increasing from 1.7 to 2.3 ev as the concentration of holes increases from 4 x 1017 to 1 x 1018 cm-3 in sulfur excess material. For five different composilions, Qc for undoped and bismuth-doped crystals has been found to be equal to Qpb + Qs, the self-diffusion activation energies for lead and sulfur in PbS. It is well-established1 that high-temperature steady-state creep of pure metals is a diffusion-controlled process, where the activation energy of creep is equal, within experimental error, to the activation energy of self-diffusion. The relationship between the activation energy for steady-state creep and those for self-diffusion in binary compounds is more complicated, however, because two different diffusing species must be considered, and becayse the activation energies may be influenced by compositional variations and by foreign atom additions.2-4 In some cases experimentally determined creep activation energies are correlated with those for self-diffusion of the slower-moving species, but such agreement is by no means universal. Interpretation of experimental results is difficult because few investigations include measurements of creep rates and self-diffusion coefficients of both diffusing species on single crystals of similar composition and foreign atom concentration. The objective of this investigation, therefore, is to determine the influence of stoichiometric defects and foreign atoms on steady-state creep and self-diffusion for a well-characterized binary compound. Lead sulfide, a compound semiconductor which crystallizes in the NaC1-type structure, and whose homogeneity range includes compositions on either side of the 1:l atom ratio, was chosen for study in this investigation. The pressure-temperature-composition relations for PbS are available,5,3 and deviations from stoichiometry may be monitored by electrical measurements.7 Single-crystal specimens are available to allow observation of effects due to bulk phenomena without interference from grain-boundary effects. These crystals have been employed to determine steady-state creep rates under compressive stress for "pure" and bismuth-doped PbS as a function of sulfur pressure and temperature as well as crystal orientation and applied stress in order to establish the relationships between defect concentrations and creep rates. EXPERIMENTAL PROCEDURES Crystal Growth. Lead sulfide crystals, prepared by the Bridgman method, are grown in evacuated quartz crucibles, filled with almost equal atomic proportions of high-purity (99.999 pct) lead and sulfur, and heated to a temperature above the melting point of PbS (about 1127°C) so that the lead and sulfur react to form molten PbS. The crucible and melt are dropped through the hot zone of the crystal-growing furnace at the rate of 1 cm per hr. The maximum melting point of PbS is slightly on the lead-rich side of the 50:50 composition; hence crystals grown from a near stoichiometric melt are usually n-type semiconductors containing excess lead atoms. Typically the lead excess concentration in solid solution with the PbS is 3 x 1018 atoms cm-3. Crystals containing either 1/20 or 1/2 mole pct Bi2S3 were prepared by addition of the foreign atoms prior to crystal synthesis. Preparation of Specimens of Controlled Stoichiom-etry. Since it is difficult to grow crystals of desired composition, the process of crystal growth and control of stoichiometry are separated into two distinct operations. Equilibration of as-grown PbS to a desired composition is most easily accomplished by first annealing the n-type crystals under high sulfur pressure (about 1 atm) at temperatures above 700°C. This process serves to put excess lead precipitates into solution, yielding 0 -type crystals upon quenching to room temperature. Inter diffusion occurs readily in crystals so treated, and the methods described by Bloem may then be employed to obtain crystals of controlled stoi-chiometry. For the creep measurements made in this study, this involves heating crystals in mixtures of H2 and H2S The equilibrium constant for H2S is given by: Thus the sulfur partial pressure is obtained from knowledge of the H2/H2S ratio and Kh2S for the temperature in question. Fig. 1 shows the p-T-x diagram for PbS. It can be seen that, within the stability limits for single-phase lead sulfide, desired compositions may be obtained by equilibrating under a specified sulfur pressure and temperature. Characterization of Crystals. The principal methods for evaluating PbS crystals include measurement of electrical properties and mass-spectrographic analysis. The measured electrical parameters include Hall coefficient, conductivity type, and electrical resistivity Bloem7 has shown that there is a 1:l relation between the defect concentration and carrier concentration obtained. Hence, if the contribution to the carrier con-

Jan 1, 1968