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By R. Mensah-Biney, M. T. Hepworth, K. J. Reid

The kinetics of gold-bromide loading onto activated carbon was investigated in a batch stirred reactor. Based on a second-order equation, the amount of gold adsorbed by the carbon was correlated with time. From a 30ºC solution containing 25 ppm Au and 0.8 g/L carbon, the rate constant for gold-bromide species onto activated carbon ranged from 0.27 x 10-3 to 1.2 x 10-3 (kg/t)-1 min-1. The equilibrium saturation capacity (Qe) was 36 ±3.0 kg/t from the same system. The rate of loading increased with increasing temperature and decreasing particle size, pH and solution gold concentration. The calculated activation energy (Ea) was 8.8 kcal/mole, significantly higher than those reported for physical adsorption. The equilibrium saturation capacity (Qe) increased with increasing concentration of gold in solution but was independent of other variables such as temperature, agitation speed, particle size and pH. These rate constants and equilibrium saturation capacity for the gold-bromide species are higher than those reported for the gold-cyanide systems.

Jan 1, 1998

By P. G. Tzeferis

Factory beet molasses media were used as cheap sources of sucrose for microbial leaching of Greek nickeliferrous laterites using strains of Penicillium and Aspergillus sp. Nickel recoveries of up to 62% and cobalt recoveries of up to 50% were obtained by leaching in a two-phase system in which bioacids were produced by fungal metabolism in molasses ferrocyanide pretreated media. The addition of potassium ferrocyanide to the molasses substrates prior to leaching was found to have a beneficial effect by increasing the level of citric acid bioproduction, thus improving the leaching efficiency of the fermentation liquid. The metals known to interfere with citric acid production (i.e., Fe, Cu, Ca and Mn) were those most efficiently precipitated. Considering the much lower commercial price of molasses in the industrial market compared to sucrose and glucose carbohydrate media, molasses could prove to be a promising alternative, despite the cost of the required pretreatment.

Jan 1, 1995

By Reinhard Gnilsen

Ground pillar control in soil and weak rock often represents a critical and sometimes a determining factor for mined underground civil structures. A concept is desirable that minimizes the restrictions possibly imposed by pillar control requirements on geometrical tunnel characteristics and on the mining operation itself. Conventional concepts are discussed and an alternative concept is introduced. This concept reduces pillar control requirements to ground control measures required with "regular" tunnels. The conventional model of pillar mechanics with potential yielding of a ground body in more than one direction, is then avoided. Due to the complexity of pillar mechanics, the level of engineered design furnished to the contractor is crucial to optimizing ground pillar control. Conventional versus alternative contractual arrangements for pillar control are described and their important role is illustrated. The concept introduced relates to principles inherent to the New Austrian Tunneling Method (NATM). However, tunnel projects using other mining concepts can employ alternative ground pillar control principles as well, if certain criteria are observed. Case histories in the United States and abroad are presented and the impacts from different concepts of ground pillar control are illustrated. The paper concludes by analyzing concept characteristics that can infer monetary impacts on both the owner and the contractor.

Jan 1, 1987

By Mustafa Kumral

The study area is located in the Alpine-Himalayan zone in Turkey. Geologically, this is a very complicated region, and the rock units generally are divided into two groups as either allochthonous and autochthonous. Tectono-stratigraphically, the units are Paleozoic quartzite, black limestone, arkosic sandstone, interlaminated radiolarite and Triassic limestone, thick Jurassic limestone, detritic limestone with alternating Eocene Nummulites beds and cream-green marl, Miocene siltstone, and ophiolite. Trachyte, trachyandesite, feldspathoidal trachyandesite porphyry, tuff, and pumice formed by volcanism during the Plio-Quaternary also are present. Recent alluvium and slope detritus locally cover all the other rock units. A number of sulfur outcrops occur in the area. Among them are outcrops at Keciborlu, Yelliyatak Hill, Buyuk, and Kucuk Kukurt Dere. The most important sulfur deposits are found in volcanic tuff and siltstone-marl, and they include highly organic material. Sulfur may accumulate around recent gas diffusions and also as massive formations. The information about local geology and sulfur isotopes shows that the sulfur originated From the crust and probably comes from organic-rich Paleozoic and Triassic units. The sulfur did not move between Triassic and Pliocene time. However. Plio-Quaternary volcanism did cause movement of the sulfur, and this was followed by formation of the secondary sulfur due to post-tectonic thermal activities and the mixing of other surface waters.

Jan 1, 1999

By I. Iwasaki, X. Cheng

A series of batch flotation tests was performed on chalcopyrite-quartzite, on pyrrhotite-quartzite and on chalcopyrite-pyrrhotite-quartzite mixtures. Pulp potential measurements in the flotation tests with single sulfide minerals indicated that each sulfide mineral had its own optimal potential range for flotation. When these results were used to select the potential ranges for the separation of the two minerals from their mixture, their flotation responses changed, and the selectivity of separation was adversely affected. A possible mechanism involving surface alteration through galvanic interaction is discussed, and a method to improve the selectivity of flotation separation is proposed.

Jan 1, 1993

By L. Stas

The authors have been interested in stress measurements in the rock mass for a long time. This paper describes the development of new apparatus for stress measurements in a rock mass. The principle of stress measurement by this device is based on the relief method as applied on the conical shaped surface of the bottom of a borehole. The design started based on the experience of K. Sugawara and Y. Obara who have been using the compact conical borehole over-coring system (CCBO). The conical shape of the strain gauge probe CCBO makes the fixation of the probe in borehole easy and, also, makes the measurement of stress in independent directions possible. The principle of the measuring method, the preparation of the borehole, the design of the probe for continuous measurement of stress during the course of overcoring are described. Also, a simplified version of the probe for long term monitoring of stress variations in the rock mass by means of the inserted body method and the initial laboratory results and in-situ testing of the development sample are described. Additionally, testing was done regarding the possible glues in relationship to the creep effect for this case.

Jan 1, 2006

By C. D. Harrison, G. S. Stallard

The 199O Clean Air Act Amendments specify national objectives for reducing sulfur dioxide emissions from coal fired power plants. System-wide reductions can be achieved by combining various emissions control technologies and allowances, or compliance credits, that can be purchased, sold or traded. As part of the Coal Quality Expert development project funded by the US Department of Energy and the Electric Power Research Institute (EPRI), Black & Veatch has developed an interactive computer tool, the Acid Rain Advisor (ARA). Through this program, integrated, system-wide compliance plans are generated by comparing the costs and emissions reduction benefits of emissions allowances and various SO2-control technologies (coal cleaning, fuel switching, scrubber retrofits, etc.)

Jan 1, 1993

By M. Elzeky, A. Attia

The effects of bacterial adaptation and partial replacement of leaching solution on the rate and extent of bioleaching reactions of a complex sulfidic gold ore were investigated. The ore was first concentrated by bulk sulfide flotation and the sulfide concentrate was treated by bioleaching using T. Ferrooxidans bacteria. The residues from bioleaching were treated by cyanidation to extract the gold and silver. Bacterial adaptation before bioleaching significantly increased the rate and extent of bioleaching reactions. Similarly, the daily partial replacement of leaching liquor enhanced to a great extent the leaching rate and in some cases up to ten fold increase was observed. Both bacterial adaptation and solution replacement increased the gold recovery by about 2-fold and that of silver by about 1.3-fold. In this work more than 95% of the gold and more than 98% of the silver could be recovered from the sulfidic gold ore, when bioleaching was used ahead of cyanidation compared with 18.3% and 52.3% by direct cyanidation.

Jan 1, 1989

By R. H. Lesernann

Copper has held up extremely well as we have moved through the trough of the economic cycle. In the aluminum, lead and zinc industries at least half of the Western World production was unable to cover its operating costs at the prices prevailing throughout most of 1991. In copper, less than 10 percent of production ran in the red last year. Most of that was in Peru where the government has not allowed its currency to devalue at the same pace as inflation. Thus, mining company revenues in local currency terms have risen very modestly while costs have escalated tremendously. Excluding such governmentally imposed distortions, virtually every mine in the Western World ran at a profit last year. While copper producers have to be extremely happy about staying in the black through the trough of the consumption cycle, consumers have to be worried. They must be asking themselves, "If copper held at over $1.00 in a year when consumption declined, how high will prices go when demand picks up?" Consumers are accustomed to paying high prices at the peak of the cycle, but they are also accustomed to paying low prices at the trough of the cycle. What went wrong this time?

Jan 1, 1992

By Peiwei Xiao, Xiang Li, Biao Li, Haoyu Mao, Nuwen Xu

As an advanced method of rock engineering construction safety monitoring, microseismic monitoring technology can monitor the micro-fracture of rock masses within an effective range, and then perform forecast analysis of rockburst, cracking, falling blocks and other disasters. Although the application of microseismic monitoring technology has become more mature, how to improve its application efficiency remains to be further studied. At present, artificial intelligence has been extensively developed, and the use of intelligent algorithms to improve the efficiency of rockburst forecast can provide a valuable reference for the safe construction of underground engineering. To this end, this paper proposes a microseismic multi-parameter rockburst early warning model based on dynamic Bayesian networks. First, the sensitivity of microseismic source parameters to rockburst forecast is analyzed based on microseismic monitoring data and actual rockburst information of a hydropower station. Second, the main seismic source parameters and their data are selected and imported into a dynamic Bayesian network for learning to obtain the rockburst forecast model. The model is confirmed in its self-validation and K times cross-validation, and the receiver operating characteristic curve of the model is also analyzed, it is found that the area under the curve is close to 1, indicating that the model has good accuracy. Finally, the analysis of the influence strength of the parent and child nodes in the model reveals that the moment magnitude and source scale are the most sensitive parameters, which can be used as an important reference for rockburst forecast.

Apr 26, 2022

By Jack W. Murphy, Kent J. McGrew, Rudolph H. Jacobson

Introduction Maximization of profit consistent with environmental protection is the principal goal of new applications development for any conventional or in-situ mining technique. Efficient evaluation of all the parameters that contribute to mining costs and production hinges on proper design and evaluation of testing programs and data. The program discussed herein utilizes several field and laboratory procedures to estimate ore deposit characteristics and optimize lixiviant compositions. The ore characteristics and lixiviant compositions are then used in a long path leaching test (stream tube test). The stream tube test data are analyzed by mathematical models with computer assistance to predict such well-field rate parameters as target metal production, lixiviant consumption, and restoration. When these predicted rates are combined with market values for target metals, capital expenditures, prices of lixiviant chemicals, and other economic variables such as labor costs, power rates, licensing fees, and others, an assessment of the relative feasibility of various proposed mining plans is possible. The flowsheet in Figure 1 illustrates this process.

Jan 1, 1984

By V. Vesselinov, S. Orr

"Enhanced heap leaching - Part 1: Insights" (Orr, 2002), different flow and transport phenomena that could significantly reduce leaching recovery were investigated. The combination of such understanding with advanced flow and transport modeling establishes the link between cause and effect, thereby, directing operators to optimal design and construction of new heaps. Modeling of flow and transport in heaps could also point to a unique change in application method or rate that would maximize leaching enhancement of an existing heap under existing situation and leaching history. The use of such a model is cost effective in that it can simulate multiple scenarios of alternative leaching enhancement methods. By simulating a large number of irrigation scenarios, such a model can point to the optimal and/or the most promising alternatives for a particular heap. The authors' simulations concentrate on the effects of changes in application rates and heap design on changes in flow paths and enhanced leaching recovery. Based on such simulations, an intelligent control agent, such as Multiple Resolution Decision-Support System (MRDS) (Meystel and Albus, 2002), could build a new representation of the complex heap-leaching system. And, by learning from historical data and current information, it could provide optimal management of heap leaching and heap decommissioning.

Jan 1, 2003

By Salama

In the conventional approach, the separator feed incremental masses are assumed to be concentrated at the midpoints of the density or size intervals and subjected to a model partition function. The resulting separation predictions would change if the locations of the incremental masses were changed. As a result. the predicted results depend on the choice of locations where the feed incremental masses are concentrated in the density or size intervals. A technique that utilizes the cumulative-mass-distribution of the circuit feed and the derivative of the partition (separation) function relative to density or size variables is proposed. The proposed technique eliminates the dependency of the predictions on choice of where the feed incremental masses are concentrated within the density or size intervals. Since the proposed technique is based on the cumulative masses at the upper limits of the density or size intervals, the technique produces a single prediction whereas the existing techniques produce predictions that depend on where the incremental masses are concentrated. In fact, it has been demonstrated that the existing conventional technique, in which the incremental masses are concentrated at the midpoints of the density or size intervals, is a first-order approximation of the technique proposed.

Jan 1, 2002

By R. Fraher

The control of mine roof is of vital interest in underground coal mining not only for reasons of safety, but also to avoid the high costs of cleanup, resupport and production losses that can result from roof falls. The difficulty in determining roof stability mine-wide is due in large part to the broad variation of geologic and structural conditions that typically exist throughout a mining area. To ensure a stable roof over the entire mine, support systems must be selected to minimize the possibility of failure. The magnitude and cost of the support selected is a trade off against the cost of the number of falls that can still occur after it is installed. Because of the large number of variables involved in analyzing and optimizing roof stability versus support, a digital computer simulation was selected to find a cost effective solution to roof support design. A total cost approach is used which includes the actual cost of the roof support as well as the cost of the roof fall in terms of resupport and loss of production (Fraher 1990a). A Monte Carlo simulation program called ROCSIM (Roof control Optimization Cost SIMulation) has been developed for determining the optimum roof control system and design layout for underground room-and-pillar mining.

Jan 1, 1992

By Lars Söderberg, Eric Sandström, Per G. Broman

INTRODUCTION Boliden Mineral AB currently mines sulfide ores in 18 mines and processes them in eight concentrators. Most ores are typically complex. Gold consti¬tutes a considerable part of the value of the ore reserves. The value of total production in 1984, distributed by different metals is shown in the pie chart below. Traditionally, gold has been recovered as a byproduct, or coproduct, along with silver in floated copper and lead concen¬trates. Gold-price trends over the past decade have prompted comprehensive efforts by Boliden to increase the recovery of gold in concentration processes. Gravimetric recovery of gold in the grinding circuit is one method that has led to quick results. This method supplements tradi¬tional recovery processes based on flotation. The development of a feasible circuit, and the results obtained by its application in the central concentrator at Boliden, in the northern Swedish province of Västerbotten, are reported below. GOLD MINERALOGY IN BOLIDEN ORES The gold content in Boliden Mineral's ores is primarily in the form of alloys with the elements silver and mercury. A minor quantity appears in an unalloyed form.

Jan 1, 1986

By Peter Fordham

A Norbridge review of 25 top mining companies highlighted financial problems for many firms. To better understand these results, Norbridge benchmarked 17 mining companies to understand the problems that companies face, the methods being used to improve performance, and the results that have been achieved. The study indicates that many mining companies in three sectors-coal metals, and non- metallic minerals-have implemented new strategies to improve performance. Many of these strategies supplement traditional initiatives with two types of process improvement efforts, facility-specific and company-wide, to help generate performance gains. The study compares the results of these strategies in each sector. INTRODUCTION imes are tough in the mining industry. Norbridge reviewed financial results of 25 top mining companies for the past 2 years-seven coal companies, twelve metals companies, and six non-metallic minerals firms.*The study found that 40% lost money in 2002, and * Coal companies include Alliance Resource Partners, Arch Coal, Consol Energy, Massey Energy, North American Coal, Peabody Energy and Westmoreland. Metals producers include Barrick Gold, Cleveland-Cliffs, Coeur d'Alene, Falconbridge, Freeport McMoran, Grupo Mexico, Inco, Newmont Mining, Noranda, Phelps Dodge, Placer Dome, and Teck Corninco. Non-metallic firms include Florida Rock, IMC Global, Martin Marietta Materials, Oglebay Norton, PotashCorp and Vulcan Materials. Information is from public sources, e.g., annual reports, company Web sites.

Jan 1, 2004

By D. V. Professor Keller

The production of premium coal-based fuels (<3% ash) and ultra clean coals (<1% ash) using the process of selective agglomeration requires proper selection of raw coal, rough preparation procedures, milling equipment, product coal size distribution, water purity, agglomerants, agglomeration equipment and operational procedures. Each of the variables can contribute a small fraction to the impurity load in the product coal or limit the ability of the process to separate mineral matter-free coal. Each of the variables and their importance will be examined from data produced at the bench by batch and continuous agglomeratons as well as the results from pilot plant and tonnage production units. The results are discussed which have indicated that some standard commercial coals can be produced with ash contents as low as 0.2 % ash (batch/bench) and several tonnage lots of 0.6% ash in as 200 lb/hr pilot plant. In most cases iron pyrite released from the coal matrix and with proper pH control is rejected from the product coal agglomerates.

Jan 1, 1995

By Byron N. Cooper

The Revenue Act of 1926 provided for five simple categories of natural resources to have the benefit of depletion allowances. In the 1947 Revenue Act, the number was increased to twenty-five, and in the 1951 Revenue Act to fifty-four. Of this number, fourteen were allowed 5 per cent; nine, 10 per cent; twenty-nine, 15 per cent; one, 23 per cent; and one (oil and gas), 27.5 per cent. The 1951 Revenue Act created a host of difficulties, including application of the "end- use criterion" and determination of the commonly accepted meaning of such terms as limestone, dolomite, chemical- and metallurgical-grade limestone, marble, calcium carbonates, and magnesium carbonates. Dolomite, for example, was listed at 10 per cent depletion allowance, but without definition. In the great amount of litigation growing out of the 1951 Revenue Act and its administration, it became essential to understand the derivation and subsequent usage of these common geologic terms. One thing that became clear was that our definitions changed significantly between the time that the 1951 Revenue Act became law and the time that later cases were tried. Some geologists neglected to learn about first usages of such terms as metallurgical limestone, and about meanings that were applicable when the 1951 Revenue Act was written and passed. Legal meanings in this paper are discussed in the light of certain famous cases that have been tried and settled.

Jan 1, 1966

By M. J. Virnig, C. P. J. Van Vuuren, A. J. Botha

The Zadra, AARL and organic elution processes and variations of them are presently widely used to recover gold from activated carbon. Despite this the study of the kinetics of elution have received relatively little attention. It is the aim of this study to investigate the rate processes taking place during elution in both inorganic and organic solutions. Batch adsorption and elution rate and equilibrium experiments were performed. The spatial concentration of gold inside carbon particles at various stages of the adsorption and elution processes were measured with a scanning electron microscope using an image analyzer to control and manage the micro-analysis data. The activated carbon particles exhibited film and intra-particle mass transfer rate- controlled behaviour during adsorption in a caustic aqueous solution at 95°C. Elutions in the aqueous caustic acetone solution at 30°C and the caustic aqueous solution at 95°C were unaffected by change in stirring rate. Elution was modelled by desorption reaction rate-control at the outer surface of the carbon particle. Adsorption and elution isotherms under duplicated solution conditions showed reasonable agreement for the inorganic solution and a large disparity for the organic solution.

Jan 1, 1993

By Charles L. Karr

Grinding is a necessary component in the processing of a number of minerals, and improvements in this area could provide substantial cost savings for the minerals industry. Optimizing the process of grinding, however, is a difficult task because there are multiple objectives; i.e., several aspects of the process are important including the fineness of the ground product, the energy consumed in the process, and the viscosity characteristics of the final slurry. Genetic algorithms (GAs) are search algorithms based on the mechanics of natural genetics and have been proven capable of solving multiple objective optimization problems. These robust search techniques are able to rapidly locate near-optimum solutions across a broad spectrum of very difficult optimization problems. In this paper, two varieties of GA are used to optimize a grinding process as it is described by a computer model: (1) a simple genetic algorithm (SGA) and (2) a micro genetic algorithm (MGA). The performance of these techniques is compared to the performance of a more conventional search technique, a simplex algorithm. Results indicate that the GAs are efficient, versatile, quite capable of improving the grinding process, and easily incorporated into the toolbox of today&apos;s process engineer.

Jan 1, 1993