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By John McNeil

Mr. President, and Members of the Rocky Mountain Coal-Mining Institute-Gentlemen : I appreciate the distinction of addressing this representative body of men upon a subject that lies so close to the heart of each one of us, and which is one of the principal objects of our gathering here today, in this beautiful city-so beautiful, with its grand and glorious mountains looking down upon us, that its charm makes us almost forget the men we left toiling "underneath the ground." But that object-the safeguarding of our coal-miners, who spend the greater part of their lives delving in the bowels of the earth-is the cause of our gathering from the "rock-ribbed" States of Utah, Wyoming, New Mexico, and Colorado. And, as I look about me, my eye lights on the face of many an old-time friend- on some with whom I have walked for more than thirty years; so, whatever the merit of this little talk of mine, it cannot be said that it was made by a "tenderfoot." You must not for a moment think that I shall attempt the impossible task of completely covering so comprehensive a subject as '(Accidents in Coal Mines,' and take much more time than has been allotted me, or would be advisable for me to consume. So I shall confine myself, as briefly as possible, to some of the most common causes of accidents, and the possible means by which these disasters may be diminished. For a great many years the cause of mine accidents and their prevention have been the subject of grave thought and investigation by both national and state governments. As early as 1835 Great Britain appointed a royal commission of talented men, possessing special knowledge in the conduct of coal- mining, also eminent authorities in science and its application, to search into these matters. Since 1835 there has been a succession of such commissions of research, at frequent intervals, in all countries wherever coal has

Jan 1, 1913

By C. G. Anderson

Today, with a stringent economic and environmental climate prevailing in the copper business, there is increased interest in evaluating new processing alternatives for production. Hydrometallurgical pressure oxidation of copper concentrates is one of the more viable approaches and several technological candidates have emerged. Of these, an overlooked but, ironically the first industrially proven methodology, utilized nitrogen species catalyzation in the oxidizing pressure leach system to produce copper via SX/EW. Given its many inherent process advantages, this may prove to be a feasible process alternative for the future. In this paper, the history of the system and its application to copper concentrates and ores will be outlined. In particular, a novel methodology for effective recovery of precious metals from chalcopyrite concentrates will be discussed. Finally, the perceived economics of chalcopyrite concentrate treatment with this unique industrially proven process will be delineated.

Jan 1, 2001

By I. D. Nock, R. M. Parkin

Paper presented at a meeting on: Artificial intelligence in the minerals sector, held in Nottingham, UK, 20 April 1993 (original title: Knowledge-based condition monitoring of cone crushers). A large proportion of the electricity used by the quarrying industry is consumed in the comminution and sizing process. In most cases aggregate processing plants operate with minimum control features resulting in limited operational efficiency. Improved control is required to increase operational efficiency with concomitant savings associated with reduction in re-circulating load and improved resource utilisation. Development work has suggested that a combination of adaptive control and process condition monitoring could improve control of comminution plants. Many commercial process control and condition monitoring systems are available, but none were deemed suitable due to the domain specific characteristics of the application. An assessment of the particular characteristics of cone crushing concluded that the application was best suited to the use of small domain specific process control combined with bespoke condition monitoring. The processing power of the control system for the project is a function not of the academic requirement, but rather the economic and practical constraints imposed by the application. As a result of the constraints a high-end PC system has been designed in preference to a workstation. Within the research project work packages are sub-divided into novel wear sensor development, knowledge based control/condition monitoring and the investigation and mathematical modelling of the wear mechanisms inherent in cone crushing. Numerous strategies were considered to implement the control system outlined. The system currently under development is a modular design which utilises intelligent novel sensors to provide a variety of data inputs

Apr 1, 1994

By M. B. Bever, A. K. Jena

THE heats of formation ?H at 273°K of the compound AgMg as a function of composition have been measured by solution calorimetry.1 The value at the stoichiometric composition is -4.41 kcal per g-atom. From electromotive force measurements2'3 the heat of formation at 773°K of stoichiometric AgMg has been determined as -5.19 kcal per g-atom.4 The combination of these two values results in an unusually high negative temperature coefficient of the heat of formation d?H/dT = ?Cp = -1.6 cal per g-atom-OK. By contrast, published heat contents of the compound AgMg and the component elements above room temperature5 indicate that the temperature coefficient of the heat of formation of AgMg is nearly zero. In this communication calorimetrically measured heats of formation of A.K.JENA,Junior- MemberAIME,andM.B. BEVER,Member AIME, are Staff Member, Division of Sponsored Research, and Professor of Metallurgy, respectively, Massachusetts Institute of Technology, Cambridge, Mass. Manuscript submitted July 1, 1968. IMD AgMg below room temperature are reported and the temperature dependence of the heat of formation is discussed. The heat effects of additions of samples of the compound AgMg containing 50.1 at. pct Mg to liquid tin-rich solutions at 623°K were measured in a solution Calorimeter.6 The heat effects of additions plotted against the average of the atom fractions of solutes in the solution before and after each addition were a linear function of composition from which the heat effect at infinite dilution was obtained, Table I. The calorimeter was calibrated by additions of tin; the heat content (H623°K - H273°K) of tin was taken as 4.08 kcal per g-atom.4 The heat effect at infinite dilution of an addition of where heat of formation of AgMg at T°K, T = temperature from which samples are added (78°, 195°. and 273°K), Xi = atom fraction of i in AgMg, ?Hi = relative partial gram-atomic enthalpy of i in tin-rich solution.

Jan 1, 1969

By Michael J. Brown

Load testing is important for controlling the quality of piled foundations. The Statnamic test is an alternative to existing testing methods with a load duration that lies between that for static and dynamic tests. Current methods of analysis offer excellent correlation between static and Statnamic tests for coarse-grained soils but often over-predict the capacity for fine-grained soils. Thus a calibration chamber is being used to produce instrumented beds of clay with reproducible properties. A model pile placed in the beds can be loaded at varying rates using a computer controlled servo-hydraulic system. Results from the modelling will be used to improve methods of analysis and govern the design of a full-scale study. Initial results suggest the rate effect can be represented by a power law relating pile velocity and resistance. Statnamic loading of the model pile produced large negative pore pressures in the clay bed.

Jan 1, 2002

By David Schlain

The Bureau of Mines investigated methods for electrodepositing platinum-group metals from molten cyanide baths. The preparation of thick, protective coatings on molybdenum, Inconel, graphite, stainless steel, copper, and other structural metals were studied, as well as the electroforming of platinum and iridium crucibles. Iridium, rhodium, and ruthenium can be electrodeposited under an inert atmosphere, while platinum and palladium require the presence of air. Electrolytes may be prepared by direct-current electrolysis in NaCN or mixtures of NaCN and KCN using anodes of the particular platinum-group metal. When the concentration of metal increases to about 0.3 or 0.4 percent, the deposits become bright, adherent, and coherent. Current densities may be 10 to 25 ma/cm2, and plating rates are often 0.5 mil/hr. Platinum and palladium baths deteriorate because of the oxidation of cyanide to cyanate and carbonate, and the precipitation of metal. Changes in the platinum cyanide bath are relatively slow. The protection against oxidation afforded by the platinum-group metal coatings is evaluated by testing encapsulated specimens in a thermogravimetric balance. Surface pretreatment and the use of undercoats are discussed.

Jan 1, 1977

By S. K. Basu, H. H. Kellogg

THE physical-chemical behavior of the system Pb-S-0 is of prime importance to the understanding of lead smelting processes, yet little accurate information is available on either equilibrium or kinetic behavior in this system. This paper is the first report of a program designed to fill gaps in our knowledge of this system. In the total ternary Pb-S-0, the region of greatest metallurgical interest is that bounded by the compositions Pb-PbS-PbS0,-PbO-Pb. Systems richer in sulfur, or richer in oxygen,* than those essentially pure SO2. This conclusion follows from the fact that all systems are in a highly reduced state, since either PbS or Pb is a constituent of all the equilibria. The content of 02, SO3, S2, S6, S8, and so forth, can be shown to be negligible compared to SO, in all such systems.* corresponding to this region can only be obtained at gas pressures exceeding 1 atm, a condition seldom met in lead smelting practice. Not only is the present study limited to condensed phases within this portion of the total system, but it is limited to temperatures at which all phases are pure solids, except for lead, which is liquid. In this limited system the following seven condensed phases are known to exist: Pb(l), PbS(c), PbO(c), PbSO,(c), PbSO,•PbO(c), PbSO4 • 2PbO(c), and PbSO, -4PbO(c). PbO exists in two crystal modifications,' but only the high-temperature yellow form is considered here. Schenck and co-workers2-4 reported the compound PbSO4 3Pb0 to be stable at high temperature, but the more recent work of Lander,5 and the present work, prove that the tetra-basic sulfate, rather than the tri-basic sulfate is stable. Fig. 1 shows the composition diagram for the binary PbO-PbSO2, based primarily on the work of Lander. In this study the univariant boundaries and invariant points existing among these seven condensed phases and the gas phase have been determined. In a ternary system, the phase rule indicates that an invariant point involves the simultaneous equilibrium of five phases—four condensed phases and the gas phase. A univariant relation involves four phases—three condensed phases and the gas phase. The gas phase in the systems studied is The following stable univariant equilibria between SOz and the condensed phases were identified: (a) PbS + 7PbS04 = 4(PbSO, - PbO) + 4SO2 (b) PbS + l0(PbS04 • PbO) = 7(PbSO4- 2PbO) + 4SO2 (c) PbS + 8(PbSO4 • 2PbO) = 5(PbSO4 . 4PbO) + 4SO2 (d) Pb + PbSO, • 4PbO = 6PbO + SO2 (e) 3PbS + PbSO4 . 4PbO = 8Pb + 4SO2 (f) 3PbS + 16(PbS04 PbO) = 7(PbSO4 . 4PbO)+ 12SO2 (g) 2PbS + PbSO,2PbO = 5Pb + 3SO2 (h) Pb + 3(PbSO4 . 2PbO) = 2(PbSO,. 4PbO) + SO, Of these eight univariant equilibria, five were measured in this work (a, b, c, d, and g) and the behavior of the other three (e, f, and h) was calculated by thermodynamic analysis of the measured data. Two invariant points were found corresponding to simultaneous equilibria as follows: Point 1: PbS, PbSO4PbO, PbSO4.2PbO, PbSO, - 4PbO, and SO2 Point 2: Pb, PbS, PbSO, . 2PbO, PbSO, - 4PbO, and SO2, From the measurements it was also possible to calculate the thermodynamic properties of the three basic sulfates of lead at 298.16°K. EXPERIMENTAL Apparatus—The experimental method consisted of the measurement of the gas pressure exerted by a given reaction mixture at a given temperature. An iridium crucible was used to contain the reaction mixture. There was no evidence of attack of the iridium,* but after use at high temperature for a week

Jan 1, 1961

Despite the wealth of information available on phase equilibria of oxide systems there remainmany gaps and inconsistencies in our knowledge base. From an industry perspective there is anongoing need to adequately describe the phase chemistry of slag systems in order to optimizeprocess performance and improve productivity. Since this chemical behaviour cannot be predictedfrom first principles it follows there is also an ongoing need for accurate experimental data. The advances made in recent years in the capabilities of sophisticated analytical and measurement equipment have made it possible to develop new experimental techniques for the direct determination of phase equilibria in low order and complex multi-component slag systems. In addition the development of powerful computer modelling tools makes it possible to provide more comprehensive descriptions of the phase chemistry, to present the information in a range of perspectives, and to critically analyse the various types of related thermodynamic and structural information available. This review provides an overview of the types of information that can be used to determine phase equilibria in slags systems, analyses the influence of uncertainty and the relative importance of these types of data, and describes the advantages and limitations of the various experimental techniques that can be employed to obtain this information. Examples of recent studies are provided that demonstrate how an integrated approach to the determination of phase equilibria in complex systems, involving the use of targeted experimental studies and systematic thermodynamic model development, can lead to a better utilization of our current research capabilities and resources and more accurate descriptions of these systems. Keywords: slags, phase equilibria, experimental techniques

Jan 1, 2004

By Hasan Ozturk

Laboratory testing examined the effect of a variety of intrinsic rock properties and environment conditions that influence the adhesive bond between rock and thin spray-on liners. The liner materials used for these tests were Tekflex, provided by Fosroc, Castonite, provided by Rohms and Haas Co., Rockweb provided by Spray-on Plastics, and CS 1251 2K, provided by Master Builders. Some of the variables examined include: rock strength (tensile/compressive strength) rock mineralogy, rock surface roughness (grain size, fracture/joint roughness), and surface contamination (oil, water or dust). Under optimal conditions, adhesive strengths reaching at least 3 MPa can be achieved. Where the rock surface is contaminated with dust or the rock is weak in tension, it may be difficult to reach adhesion strengths of 1 to 1.5 MPa.

May 1, 2004

By T. C. Souza Pinto

Because shape is an assessment of the three-dimensional form of a particle, it may be described in terms of sphericity (?), which is a measure of how closely a particle approaches a spherical configuration. In this study, Darcy?s law and the Kozeny-Carman model for fluid flow through porous media were applied to packed beds to determine the sphericity (?) of apatite particles. The beds were composed of glass spheres or particles of apatite (igneous from Brazil and sedimentary from the United States) of three classes of size (Class 1: -297 +210 µm; Class 2: -210 +149 µm; Class 3: -149 +105 µm). Glass spheres were used to validate the model because of its known sphericity (? = 1.00). Apatite particles, either igneous or sedimentary, showed very close values for particle sphericity (? ? 0.6). Observations on particle images conducted by scanning electron microscopy illustrated that igneous (? = 0.623) and sedimentary (? = 0.644) particles of apatite of Class 2 predominantly exhibit elongated shape. The close value of particle sphericity (? ? 0.6) showed by either igneous or sedimentary apatite may be justified by the similarity in particle shape.

Jan 1, 2009

By S. J. Swart

This paper discusses the principles and application of risk assessment and management as the basis for environmental management within the mining industry. Unlike in other industries, mines are required to obtain closure certificates in terms of section12 of the Minerals Act, which should ultimately release them from further environmental responsibilities. It is emphasized that the concept of environmental risk assessment and management, when applied correctly will mean that the mine will be identifying and managing environmental issues beyond those set by current legal requirements and management strategies. The focus shifts from conventional minimum legal compliance management to management of real environmental risks. The advantage of this approach is that the perceived ?shifting of legal and management goal posts? due to changing environmental laws or management principles, will not influence or dictate the mine?s short or long-term management objectives or actions, mine closure funds can be more accurately determined and mine closure should become a relatively simple procedure. The risk assessment approach has been applied to the planning of mine closure at Iscor?s Durban Navigation Collieries (Durnacol) in Kwa-Zulu Natal and certain key risk issues such as the long-term risk of water pollution from coal discard dumps have already progressed to fully quantitative risk assessment. This paper will discuss the process, which has been followed to date, with particular emphasis on the most recent phase, namely quantitative risk assessment and management of pollution from coal discard dumps. It is believed that the approach that is being pioneered at Durnacol and which overcomes some of the more obvious deficiencies of both the EMPR and the traditional IEM process will ultimately serve as the model for all responsible mines in South Africa. It is also believed that this approach will enable the authorities to issue closure certificates with the confidence that there will be no unforeseen surprises in the years after closure.

Jan 1, 1998

By H. A. D. Kirsten

Shotcrete has become a strategic component of support in underground mines. The ductility of reinforced shotcrete makes it a safe and economic means of surface support under adverse static and dynamic loads. The ability of ductile shotcrete to sustain load at large deflections enables excavations in squeezing conditions to be stabilized and the safety in excavations subject to rock bursting, to be assured. A Shotcrete Working Group was formed to find the configurations of fibre reinforcement that would give shotcrete the same ductility as when reinforced with mesh. Beams and panels reinforced with various types and lengths of fibre were accordingly tested. A single mix design consisting of river sand, ordinary Portland cement, fly ash, condensed silica fume and gunite dust and segregation suppressant was used. Steel and polypropylene fibre varying in length from 25 to 50 mm were used in nominal contents of 5 % and 0.5% by mass respectively. Beams, panels and control specimens were shot into specially made formers. Suitable mixing procedures were developed for the different types of fibre. The test specimens were shot in a semi-dry mix process. The shotcrete was cured until tested 28 days after shooting. The fibre contents and uniaxial compressive and Brazilian tensile strengths of the shotcrete were determined from the control specimens. The beams and panels were tested in bending in specially manufactured test rigs. The beams were examined for simple supports and fixed ends. The panels were fixed in a manner that simulated underground conditions and were loaded statically under uniform pressure. The beams were loaded and the corresponding deflections measured up to failure. The panels were loaded up to mid-span deflections of 150 mm. The results are presented in the form of load-deflection graphs. The peak loads and ultimate deflections for the fixed end beams were considerably larger than for the simply supported beams for the various types of fibre considered. None of the beams tested, however, were able to sustain load at relatively constant value beyond the peak load. The panel tests showed that 40 mm and 50 mm long steel fibre and 30 mm, 40 mm and 50 mm long monofilament polypropylene fibre reinforcement gave shotcrete the same ductility as mesh.

Jan 1, 1998

By Fulton Flick

THE micrography and macrography of aluminum and its alloys present certain difficulties. Many of the difficulties attendant on the micrography have been removed by methods developed during the past few years, notably those of E. H. Dix, Jr.1 The development of grain size in aluminum and its alloys may be equally troublesome, yet comparatively little detailed attention appears to have been given to it. Satisfactory reagents. are available for the development of such structures in ferrous and most non-ferrous metals, but those applied to aluminum and its alloys, i. e., alcoholic or aqueous solutions of sodium hydroxide or hydrofluoric acid are not entirely satisfactory. Hanson and Archbutt,2 in speaking of these two reagents, state that "These two reagents give fairly satisfactory results, but they sometimes produce badly tarnished surfaces from which the surface deposit is difficult to remove." It has been our experience that neither of these reagents is to be entirely relied on for developing structures suitable for study or photography. This means that when the etch fails to produce satisfactory results the, specimen must be repolished, through the 000-paper at least, and then etched with another reagent. This procedure entails a con¬siderable loss of time, and the final results may not be all that might be desired. However, the reagent to be described, although not a panacea for all etching troubles, has improved results so markedly that it is felt that it is worth offering as a grain-size etch generally applicable to aluminum and aluminum alloys. Czochralski3 in 1915 mentioned the application of a solution of 10 to 20 c. c. concentrated hydrofluoric acid in 100 c.c. absolute alcohol, etching in this reagent being followed by dipping in concentrated hydrochloric-acid solution.

Jan 2, 1925

By Linda C. White

The use of red mud, a waste product of the ?Bayer? process for bauxite refining, was investigated for its arsenic removal effectiveness from aqueous solutions under various conditions. Red mud efficiently removed As(III) between a pH range of 7.6 and 9; and As(V) in the pH range between 5.5 and 6. Pre-washing of the red mud with salt water considerably improved its arsenic adsorption capabilities. With appropriate red mud dosage, the residual arsenic in solution was decreased below the regulated acceptable arsenic limit (0.1 mg/L) from aqueous industrial wastes. The arsenic adsorption followed first-order rate kinetics and fitted the Langmuir isotherm model. Results suggest that red mud is potentially a useful adsorbent for removal of arsenic from contaminated water or industrial waste solutions.

Jan 1, 2003

By Ned Baker

Details are given of a fuel-induction system for a hydrogen, fueled engine. The induction system was designed to preclude backfire otherwise common in hydrogen fueled engines. System features and test data are presented and discussed in the context of the requirements peculiar to use in an underground mine environment. The fuel induction-system when tested in conjunction with a modified Caterpillar 3304 engine provided backfire free engine operation and satisfactory engine performance.

Jan 1, 1982

By G. J. Hearn

between particles in the classifying region is then

Apr 1, 1995

This paper describes the oil engihe plant owned and operated by Gold Mines .of Kalgoorlie Limited, and gives some details of installation, operational, and maintenance experiences which have arisen during the years of service, the last 5 years of which have been under the writer's control. Nos. 1, 2, 3 and 4 alternator units have run 50,276, 48,006, 49,677 and 25,930 hours respectively, and much knowledge has been obtained of their performances and faults. During the war years, it has not been easy to obtain spare parts; this, coupled with the loss of No. 4: alternator unit to the Commonwealth Government, made operation and maintenance a very difficult problem.All engines are of the enclosed vertical, single acting, 4-stroke cycle, airless injection type.The electrical power plant originally consisted of four 6-cylinder Belliss & Morcom heavy oil engines, direct coupled to Bruce Peebles alternators, running at 375 r.p.m., and generating 3-phase electric power at 3,300 volts, 50 cycles.No. 1 unit, installed in 1936, is a 6-cylinder 450 b.h.p. standard 12A Belliss & Morcom heavy oil engine, direct coupled to 280 kw. 0.8 p.f. alternator. The remaining three units are 6-cylinder, 660 b.h.p., lSA oil cooled piston type Belliss & Morcom heavy oil engines, direct coupled to 410 kw. 0.8 p.f. alternators, making a total capacity of 1,510 kw.No. 4"alternator. unit, an 18A Bellis.& Morcom set, was taken over by the Commonwealth Government in June 1943.

Jan 1, 1945

By B. J. Barfield

Standard erosion plots (4.6 m by 22.1 m on 9 percent slope) were constructed on the Alston Surface Mine of Peabody Coal Company in Western Kentucky to evaluate the effects of placement technique and density on the erodibility and eroded size distribution from mine spoil and reconstructed topsoil. PLots were constructed with a dozer and scraper pan from shale spoil material, topsoil (A horizon) and subsoil (B and C horizon mixture) using soils stockpiled at the Alston Surface Mine. Plots were evaluated under fallow conditions with a tilled plot surface and two compacted conditions. One compacted condition was generated by tracking the surface with a dozer and rolling with a loaded scraper pan. The second was generated by rolling the surface with a solid wheel compactor. Rainfall was supplied with the Kentucky Rainfall Simulator at a rate of 63.5 mm h-l with the plots in three different soil moisture conditions; dry, field capacity, and very wet. Runoff was evaluated for flow rates, sediment concentrations, and aggregate and primary particle size distributions. Sediment yields and the Universal Soil Loss Equation E130 indexes were calculated from the data for each plot. The erodibility was calculated from the tilled plot data using a weighted soil loss and E130 value from the dry, field capacity and wet runs, and a cover management factor calculated for every other condition. For the topsoil and subsoil plots, sediment yield was greatest for the dozer scraper pan plots and lowest for the tilled plots. For the shale plots, erosion rates from the wheeled compacter plots were the highest and tilled plots the lowest. Average erodibilities were 0.14, 0.38, and 0.41 tons ac h ft-1 tonf-1 in-1 hundred ac-1 for the shale, subsoil, and top-soil plots. Cover management factors for each plot were 1.29, 1.42, and 1.17 for shale, topsoil and subsoil plots compacted with the solid wheeled compacter and 1.29, 3.79, and 2.51 for shale, subsoil, and topsoil plots compacted with the dozer scraper pan conbination. The accuracy of the Wischmeier erodibility nomograph was evaluated on the data collected. Erodibilities were accurately predicted for the topsoil plot and poorly predicted for the sub-soil plot. The accuracy of the CREAMS procedures for predicting the composition (size distribution) of eroded particles was also evaluated. The composition was well predicted for the topsoil plots, moderately well predicted for the shale plots and poorly predicted for the subsoil plots.

Jan 1, 1983

By David Baughman, Steven Axen, Ray V. Huff, Donald H. Davidson

Introduction In situ leaching (ISL) is an alternative method of mining uranium from deposits that are low-grade, deeplying, and water-saturated. ISL recovers uranium by transporting fluids through rock rather than by moving rock, a concept the Chinese developed over 2000 years ago for water production. This technique eventually evolved into production systems for oil, gas, sulfur, and salt. More recently, in situ methods have been developed to produce shale oil, gasified coal, geothermal energy, uranium, and copper. ISL uranium operations began in the early 1960s with Sabine Production Co. in south Texas. About the same time, Utah Construction and Mining Co. (Anderson and Richie, 1968) started similar operations in Wyoming's Shirley Basin. During the 1970s, six commercial operations were started in south Texas, (USBM, 1978) and a number of pilot operations were in various stages of development in Colorado, Wyoming, and New Mexico. This paper reviews some of the technical and economic aspects of the ISL process and briefly discusses key subsurface engineering functions as¬sociated with well pattern design and operation. While flow characteristics of a deposit are of prime importance, the following information is also needed: Depth, ore grade, total contained metal, ore thickness, flow conductivity (permeability), void space in rock (porosity), mineral type and distribution, natural groundwater flow, and structural features. Solvent selection, which is important to the economic success of the operation, takes these factors into account: Composition, rate of metal solubilization, interaction with gangue minerals, impact on rock permeability, impact on materials of construction, trace metal solubilization, cost, availability, and handling problems. Overview of ISL An ISL operation consists of these functions (Fig. 1): 1. Chemicals to dissolve and maintain uranium in solution are prepared at the surface extraction facility. 2. A set of injection wells forces the solvent into rock pores of fractures using pressure in excess of the deposit's hydrostatic pressure. 3. Solvent travels through the rock and reacts with uranium minerals to dissolve them. The solvent usually consists of an oxidant and a complexing agent in an acidic or alkaline medium. 4. A set of production wells creates a low-pressure sump where metal-enriched solution is collected for transport to the surface. 5. The enriched solution is processed to recover uranium and to separate the leaching solution for recycling through the system. The economic performance of an in situ operation may be estimated by integrating these related factors: (1) the flow rate of solution processed through the system, (2) rates of fluid injection and production from wells, (3) the rate of mineral solubilization in the liquid phase, and (4) the volume of rock swept by the fluid. As these factors reveal, ISL involves the technical disciplines of petroleum engineering, ore deposit geology, and hydrometallurgical processing. Wellfield Design Just as mineral engineers use drillhole information to plan a conventional mine, in situ engineers use similar information to design a well field. A thorough knowledge of deposit geology and reservoir properties is required. Early application of pressure transient testing, such as

Jan 2, 1980

By Andy Lemay

Vale (previously known as CVRD) is: ? The second-largest mining company by market capitalization (NYSE:RIO) ? Headquartered in Brazil ? Global workforce of over 100,000 employees including outsourced workers. Vale Inco Limited is a wholly?owned subsidiary of Vale Vale Inco Limited ? is based in Toronto, Ontario Canada: ? Operations and Projects in 20 countries ? Marketing Network extending to 40 countries ? Over 12,000 employees worldwide ? Last years sales of US $8 Billion

May 1, 2008