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By G. Van Weert

The pellet reactor was developed approximately 20 years ago in the Netherlands for softening drinking water. Since then, some 35 plants have been built, ranging in capacity up to 8500 m3/h. Applications now also include removal of phosphates and fluorides and the production of metal carbonates and sulphides from waste streams. The pellet reactor consists of a fluidized bed, wherein the process solution is thoroughly mixed with the precipitation reagent at special inlet nozzles to give over-saturation of the compound to be precipitated. In water softening applications, the compound is CaCO,. In the case of nickel or other metal waste streams, Na2CO3 solution is added in sufficient amounts to precipitate metal (hydroxy) carbonate on the fluid bed particles. These grow typically to dense spheroids, which are removed when they reach 0.8 to 1.0 mm diameter. These spheroids are easily dewatered, free flowing and low dusting. The latter property is becoming an attractive advantage in connection with new plant hygiene regulations. The operation of a 60 cm diameter pellet reactor on nickel containing plating waste is described and the properties of the produced nickel carbonate spheroids are discussed.

Jan 1, 1993

By A. Blackmore, D. Baker, L. Human

"Mechanical mixing equipment is common in a wide variety of mining, metals and process applications, such as hydrometallurgical reactors, solvent extraction, digestors, and tanks for storage of slurry or hydrocarbons. Computational Fluid Dynamics (CFD) has been applied successfully to single-phase mechanical mixing problems for several decades and is established as a reliable design tool. As computational power and CFD codes have improved over the years, there have been significant advances in modelling capabilities including improved models of turbulence, interaction of rotating and stationary components, multiphase flows, and modelling of free surface interfaces, for example. This paper will provide an overview of the application of CFD to mechanical mixing problems. First, it will review the traditional single phase Multiple Reference Frame (MRF) approach and introduce a range of advanced modelling techniques. Three examples of the application of CFD to industrial mixing problems will be given. It will be demonstrated that CFD is an effective tool for reducing technical risk in design, for identifying the root-cause of mixing problems, and testing modifications to existing operations."

Jan 1, 2015

By Brian J. Gorva

The key objective of forming a cartel is to increase profits to members of the cartel by taking the following action: a) control output; and b) control price. However, while attempting to obtain monopoly profits the cartel members have to contend with costs associated with cartelization and such costs include the following: political costs; the cost of coordinating output and price; organizational costs (such as cheating); and administrative costs (such as the cost of attending cartel meetings). The objective of commodity exchanges is to provide an open, free market where buyers and sellers may openly complete transactions and pricing information can be immediately disseminated. These transactions include the following: a) to provide facilities for "hedging", or transferring price risk from buyers and sellers of physical commodities to "speculators" through the medium of buying and selling futures contracts, and b) taking physical delivery of metal on due dates.

Jan 1, 1983

By Joo Hyun Park, Soo Sang Park

The distribution behavior of Pb between molten copper and FetO-SiO2 (-CaO, Al2O3) slags was investigated at 1473 K (1200 oC) and p(O2)=10-10 atm in view of the reaction mechanism of Pb dissolution into the slag. The distribution ratio of Pb (LPb) decreases with increasing CaO content (~6 mass pct) irrespective of Fe/SiO2 ratio (1.4~1.7). However, the addition of alumina into a slag with Fe/SiO2=1.5 linearly decreases the LPb, whereas a minimum value is observed at about 4 mass pct Al2O3 at Fe/SiO2=1.3. The log LPb continuously decreases with increasing Fe/SiO2 ratio, and the addition of Al2O3 (5 to 15 mass pct) into the silica-saturated iron silicate slag (Fe/SiO2 < 1.0) yields the highest Pb distribution ratio. The log LPb linearly decreases by increasing the log (Fe3+/Fe2+) value. The Pb distribution ratio increases and the excess free energy of PbO decreases with increasing Cu2O content in the slag. However, from the viewpoint of copper loss into the slag, the silica-saturated system containing small amounts of alumina is strongly recommended to stabilize PbO in the slag phase at a low Cu2O content.

Jan 1, 2014

"A bed, British Columbia, Canada, coal, carbonizingproperties B 510Pa., coal, washing characteristics RI 4941A' bed, Pa., coal, washing characteristics RI 4834"

Jan 1, 1960

By Tomás Vargas

The catalytic role of Thiobacillus ferrooxidans in the dissolution of chalcopyrite was studied by leaching pure massive samples of this sulfide with a pure strain of Thiobacillus ferrooxidans (ATCC 19859). Monitoring of the bacterial activity showed that an important fraction of the total bacteria generated during leaching remained attached to the chalcopyrite surface. Bacteria grown in the system, which were the offspring of bacteria adhered to chalcopyrite, was well explained as the result of the utilization of ferrous ion and sulfur as energy sources. The potential for indirect and direct action was fully utilized by the existing bacteria and the leaching process was controlled by the kinetics of chalcopyrite dissolution.

Jan 1, 1990

By R. J. Sawyer

The Greens Creek underground polymetallic mine restarted production in 1996 from a newly discovered high grade ore zone. Efforts to improve payable gold recovery have focused on gravity separation. The paper compares testwork and plant results for a newly installed gravity circuit.

Jan 1, 1997

By M. Brozek

The particle settling velocity is the argument of separation in such processes as classification and enrichment in jigs. It characterizes material forwarded to the separation process and belongs to the so-called complex arguments because it is the function of particle density and size. i.e. the function of two simple arguments. The affiliation to a given subset is determined by the values of two mag-nitudes and the distribution of such argument in a sample is the function of distributions of particle density and size. The paper will present a method of determining the distribution of settling velocity in the sample of spherical particles for the turbulent particle motion in which the settling velocity is expressed by the Newton formula. Because it depends on density and size of particle which are random variable of certain distributions, the settling velocity is a random variable. Applying theorems of probability, concerning distributions of function of random variables, the authors will present general formula of probability density function of settling velocity for the turbulent motion and particularly calculate probability density function for Weibull?s forms of frequency functions of particle size and density. Distribution of settling velocity will calculate numerically and perform in graphical form.

Jan 1, 2014

By E. G. King

Cerium and thorium sulfides have found use as crucible materials for melting certain radioactive metals. However, thermodynamic treatment of these sulfides has been hampered by lack of experimentally derived entropy values. This Bureau of Mines report describes heat-capacity measurements between 51° and 298° K, and entropy evaluations at 298.15° K, for cerium monosulfide (CeS), cerium sesquisulfide (Ce2S3), and thorium disulfide (THS2). The entropy values, with Literature results for the heats of formation, are used to obtain free energies of formation at 298.15°K. MATERIALS The samples used in this work were supplied by Prof, Leo Brewer of the Department of Chemistry, University of California. The methods of preparation and some of the physical and chemical properties of these sulfides were given by Eastman and coworkers.3 4/ Chemical analyses, conducted in our laboratory, gave the following results:

Jan 1, 1959

By David E. Swanson

The U.S. Bureau of Mines undertook a basic investigation of collimated abrasive water-jet behavior because a more complete understanding of the fundamental process may lead to further technical advances. Laboratory experiments used 2-mm water-jet nozzles and new entrainment apparatus to analyze collimated abrasive water jets operating under varied conditions. Maximum water pressure was 69 MPa to permit use of conventional hoses with a burst-to-operating-pressure ratio of 4. Nozzle and induction line pressures, abrasive induction rates, and jet reactive thrust forces were recorded for each operating condition. Average jet velocity and power were determined from component mass flow rates and reactive thrust force measurements. Relative velocity and cross-sectional distribution of abrasive particles were determined using impact analysis techniques. Other jet characteristics were determined photographically. Properties of free water jets, collimated water jets, and collimated air-water jets were determined for comparison.

Jan 1, 1989

By Thomas J. Peters

The Lime Creek study area lies 100 air km east of Boise, and 70 air km northeast of Mountain Home, Idaho. The eastern boundary of the 28,000-hectare, east-west-elongate study area lies 0.2 km west of the 3,077-m-high Smoky Dome. The area is mainly underlain by Cretaceous granitoid rocks of the Idaho batholith. No mineral resources were identified, but two mines and one prospect were found in the study area. At the President and the Last Chance mines, in the southwest corner of the study area, gold mineralization occurs along steeply dipping east-northeast-trending faults and associated quartz veins, and within adjacent Cretaceous granitic rock. The mineralized material is not rich enough to mine underground, and near surface, open-pit-mineable deposit areas could not be identified. The third prospect, the Ventura, is within altered pink granite of probable Tertiary age, but metal concentrations are very low. Geothermal activity was not observed within the study area, but hot springs do occur in the Vicinity. Bedrock observed is only suitable for the most basic high bulk and low end value applications, such as crushed aggregate. Numerous sources for crushed stone occur closer to markets. Alluvial concentrate (placer) samples did not contain free gold, and no substantial alluvial bars were seen; deposits were too small to contain resources.

Jan 1, 1993

By L A. Martinez Tipe, J McKibben, S Barry

"Metal prices are central to a mineral investment decision and have a profound impact on the financial performance of companies in the mining industry. At its most basic level, metal prices are influenced by the disequilibrium between international metal volume supply and demand. That is, the commodity price is a regulator that equates international metal supply and demand where inventories act as a buffer between the emergence of this disequilibrium and its dissolution through a price change.From this viewpoint, mining companies are required to forecast metal and bulk commodity prices when evaluating minerals projects through discounted cash flow (DCF) analysis. While supply-demand models are instructive, many companies use historical prices, spot prices, futures/forward pricing and consensus opinion (or a combination of all of these) to develop price forecasts.This paper discusses the definition, fundamentals and differences between futures/forward and consensus pricing and the appropriateness of each in a DCF model for mine project economic evaluation.Our results demonstrate that great care is required when using either futures/forward or consensus pricing and that the decision to use one rather than the other requires consideration of other important elements in the DCF model (ie the risk-adjusted discount rate).CITATION:Martinez Tipe, L A, McKibben, J and Barry, S, 2016. Metal prices and the differences between forward and consensus pricing – which one is better for use in a discounted cash flow model?, in Proceedings Project Evaluation 2016, pp 149–158 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

By O. Forsén

A new cell construction was designed for the study of the electrochemical behaviour of additives in conditions that simulate real copper, electrorefining. The behaviour of gelatine and thiourea was studied by applying different electrochemical methods, i.e. polarization resistance and voltametric measurements. In this study, individual galvanostatic electrolysis experiments were carried out for 120 hours. The organic additives were introduced to the electrolyte at certain intervals and their concentration was varied in the range &om zero to four ppm. An optical microscope was applied for the examination of copper cathode deposit microstructures. The results show that gelatine has a polarizing effect on the deposition potential of copper whereas even small amounts of thiourea depolarize the electrodeposition of copper. The maximum inhibitor efficiency of gelatine was obtained at a gelatine concentration of slightly lower than two ppm. When both gelatine and thiourea were present in the electrolyte, the depolarizing effect of thiourea exceeded completely the polarizing effect of gelatine. If chloride ions were added to gelatine and thiourea containing electrolyte, the electrochemical behaviour of the system was altered drastically. Chloride ions resulted in the prevailing of polarization effect caused by gelatine while the depolarizing effect of thiourea disappeared in this system. The polarizing effect of gelatine increased until chloride ion concentration of 30 ppm was reached. Also, the above electrochemical phenomena could be detected in the optical examination of copper deposit microstructure.

Jan 1, 1995

By P Holt, M Allen

On the first of July, 2012, the Australian GovernmentÆs Clean Energy Act commenced. From this point, a price of $23/t of CO2-e will apply to facilities that trip the liability threshold. This first part of this paper concentrates on the mechanics of the Clean Energy Future legislation and how it will be applied to the mining and mineral processing industry.The second part of this paper contains analysis of the data presented for typical mine operations. Methodologies for constructing a carbon strategy are also presented. This will entail determining what the objectives of the carbon strategy are, and defining what the strategic priorities for a business should be. An action plan to address the risks identified from the Clean Energy Act is also developed as part of the strategy.Details such as the advantages and disadvantages of opting into the carbon price scheme for liquid fuels are shown. Other considerations such as the ability to acquire permits through the carbon farming initiative or through overseas clean development mechanism projects are explained.CITATION:Allen, M and Holt, P, 2012. Implications of the carbon price and developing a carbon strategy, in Proceedings International Mine Management 2012, pp 105-114 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

By Henry E. Blake

The Bureau of Mines has been engaged in a continuing research effort to develop processes for increasing the recovery and utilization of fluorine from low-grade resources. This current research has shown that over 98 percent of the fluorine in phosphate rock is extracted when the ore is treated with excess phosphoric acid in the presence of water vapor at 150° to 180° C. More than 80 percent of the fluorine can be recovered as fluosilicic acid, which can then be converted to commercially useful hydrogen fluoride or fluorspar by previously developed Bureau processes. Extraction of P205 from the ore was about 98 percent in batch tests and 90 percent in semicyclic tests.

Jan 1, 1974

By C. L. McKenzie

American Girl Mine is located in the Cargo Muchacho Mountains in the southeastern Imperial Valley of Southern California. Production from the current open pit mine and heap leach recovery system began in early 1989. Previous mining and gold recovery took place commencing in 1987 at the Padre Madre site, situated adjacent to the American Girl site to the southwest. In mid-1990, a 790-tonne-per-day underground gold mine and mill went into production. Approximately 6,500 troy ounces of gold per month are recovered from the combined open pit underground mine operation. Copper in the form of Azurite [Cu3(CO3)2(OH)2] and Malachite [Cu2CO3(OH)2] are abundant in the mined ores (Henshaw, 1942). The high solubility of these minerals in caustic cyanide solutions has a negative impact on carbon adsorption and electrowin processes. This paper presents the results of monitoring programs, process chemistry, and control changes introduced at American Girl Mine to abate production complications in the refinery and measures taken to minimize solution gold losses in the adsorption circuit(s).

Jan 1, 1993

By J. S. Contreras, E. Córdova, I. Gottreux, A. Anani, A. Ferrada

Cave mining is an underground mass mining technique. The largest projects, which are known as ‘super caves’, produce hundreds of thousands of tons of ore per day, which involves large footprints with considerable column height, and have a life of mine of over 20-40 years. These operations are typically located deep, under high stresses and in competent rock masses, making initiation and propagation of the caving process harder to manage. These challenges must be confronted by optimizing the fragmentation of the orebody to achieve smaller size blocks that will result in consistent caving and improved flow of the ore from the drawpoints. To achieve better performance from the drawpoints, preconditioning is applied to fragment and damage the material required to cave. We present a proposed design for preconditioning in underground mines, considering the challenges that these large-scale mines are already facing, based on a comprehensive analysis of current design parameters, case studies, and sensitivity analyses using numerical models.

Feb 2, 2021

By J. A. Abols, P. M. Grady

Recovery via gravity is one of the oldest mineral processing methods available. Unfortunately, the use of gravity techniques for gold recovery has been in decline for the past century as more effective chemical processes such as flotation and leach/CIP have been developed. Recently, with the push towards more sustainable environmental outcomes, the benefits of gravity separation have become more apparent. While gravity as a unit process is not usually capable of achieving as high a recovery as flotation or whole ore cyanidation, a combination of gravity devices alone or in conjunction with these processes can offer significant advantages to the operator. This paper reviews the range of gravity devices available, their application and the results that can be achieved by maximizing gravity through the use of a combination of gravity recovery devices. Three case studies are provided.

Jan 1, 2005

By Hani S. Mitri

Strainbursts in brittle rock are common to deep underground mines. The state of stress at the boundary of mine openings is dictated by a biaxial stress/loading condition. This paper reports the results of a series of biaxial compression tests carried out on 100 mm cubic samples of norite rock, under different horizontal-to-vertical stress ratios. The results indicate that the biaxial compressive strength is considerably higher than the uniaxial one. It is found that the norite sample behaviour under biaxial loading mirrors field behaviour where shearing and progressive spalling of the opening boundary are observed prior to strainbursting. Sample failure is initiated by rock spalling at the sample free faces, i.e. in the plane of biaxial loading. Finally, it?s the out-of-plane shear failure mechanism that causes the sample to collapse. Shear failure takes place violently and abruptly and is accompanied with considerable audible noise.

Apr 1, 2005

By H. Masuda

The lijima Zinc Refinery started operation in 1972, and has today an annual capacity of 200, 000+-Zn. The hematite process was employed for the first time and the ideal of waste-free refinery has been pursued for 30 years. In recent years, however, only half of the hematite produced would be sold to the cement industry and hence a reduction of arsenic level has been necessary in order to sell the entire amount produced, The arsenic cementation process with zinc powder, developed through a long time laboratory research was found among some options as the best for the hematite process. The construction work started in 2000 and the facility was put into operation in 200 I. As a result in the same year all hematite were sold to the cement industry. The outline of this project, present operations and technical issue are reported in this paper.

Jan 1, 2003