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By J. Kang

To obtain microbial cultures with the ability to efficiently leach copper ion from chalcopyrite, microbial samples from acid mine drainage sites were mixed and then subjected to mutation using sodium nitrite (NaNO2), diethyl sulfate (DES), ultraviolet light (UV) and their combinations. Mixed cultures with a much stronger ability to leach copper ion (identified as mixed cultures A, B, C, D and E) were obtained by screening on leaching media. Leaching tests showed that mixed culture E had the best leaching performance and increased the Cu2+ content by 120.5% in 20 days, compared to a control without mutation treatment. Mixed culture E grows well on Leathen leaching medium supplemented with Cu2+ (at a final concentration of 32 g/L), reaching 3.2 × 107 cells/L after 15 days, while the unmutated control culture cannot survive beyond 15 days, indicating that mixed culture E is more tolerant of high concentrations of Cu2+. In addition, continuous leaching by mixed culture E is very effective at a pulp density of 1%. These results suggest that it has the potential for industrial applications.

Jan 1, 2008

By Douglas B. Silver

Traditional cycle theory would postulate that if you have a supply shortage relative to demand, the price will increase because buyers will incrementally increase the price they are willing to pay to ensure that their needs are fulfilled. As prices rise, more supply will be brought on and will eventually exceed demand. This supply excess will cause the price to decline as producers have to lower their prices to sell their goods. What is interesting is that cycles are simply volatility over time. Without the time factor, volatility simply goes up and down. When we add the time element, a cycle is created. This cycle can be big or small. In mining?s case, we are talking about a Super Cycle ? a big cycle. But a Su-per Cycle can be formed in two ways. It can form by either increasing the wavelength or the volatility. If these two elements are combined, a Super Cycle is formed. It is bigger than the normal cycle in terms of time duration and extent of volatility. A recent study (Fig. 1) conducted by Cuddington and Jarrett showed an interesting proof of Super Cycles and suggests that these cycles last between 15 and 30 years. So, what causes a Su-per Cycle? Is it a convergence of unrelated events or a consequence of related events? In a global community everything is related. Equilibrium theory would also take the position that a Super Cycle is a consequence of events.

Jan 1, 2008

By M. Nehdi

Deficient surface disposal systems of sulfidic mine waste often cause severe contamination of surface streams and groundwater reservoirs due to the oxidation of sulfide phases. The subsequent generation of leachates characterized by high acidity and elevated concentrations of toxic elements (commonly known as acid mine drainage) jeopardize the health of contiguous ecosystem. Stabilization/solidification (S/S) is recognized as a promising solution for treating such wastes. S/S processes generally mobilize alkaline and/or cementing materials/additives that act as neutralizing and/or binding agents. In the present research, industrial byproducts, namely, cement kiln dust (CKD) and Class C fly ash (FAC) have been used as candidate materials along with the partial addition of sulfate-resistant cement (SRC) in the S/S of polymetallic sulfidic mine tailings (MT). The effectiveness of S/S was assessed by comparing laboratory experimental values obtained from unconfined compressive strength, hydraulic conductivity and leaching propensity tests of S/S samples with regulatory standards for safe surface disposal of such wastes. Despite general regulatory compliance of compressive strength and hydraulic conductivity, some solidified/stabilized-cured matrices were found unable to provide the required immobilization of pollutants. Solidified/stabilized and 90-day cured mine tailings specimens made with composite binders containing (10% CKD + 10% FAC), (5% SRC + 15% FAC) and (5% SRC + 5% CKD + 10% FAC) significantly impaired the solubility of all contaminants investigated and proved successful in fixing metals within the matrix, in addition to achieving adequate unconfined compressive strength and hydraulic conductivity values, thus satisfying U.S. EPA regulations. Laboratory investigations revealed that, for polymetallic mining waste, leachate concentrations are the most critical factor in assessing the effectiveness of S/S technology.

Jan 1, 2008

By G. Bee, Z. Gavelan, R. Espinel, Y. Roditis, X. Ochoa

In August 1996 Barrick Gold Corporation acquired the Pierina property, an advanced stage exploration project, high in the Andean Cordillera of Peru and in November 1998, in a record time of just over two years, poured the first gold. After more than three years of a very successful operation at some of the lowest operating costs in the world, this presentation serves to briefly describe the project through design, construction and start-up and in particular to spotlight some of the challenges that have been overcome in valley heap leaching in a high rainfall, alpine setting.

Jan 1, 2002

By J. C. Yingling

[New stochastic process models are developed to calculate the probability of various fill levels in section feeders as a function of vehicle interarrival times, payloads and feeder-discharge rates. These models may be utilized to establish the minimum feeder-discharge rate necessary to prevent a feeder, with a particular surge storage capacity, from constraining the section's production rate. In addition, it is shown how the output from these models may also be utilized to calculate the probability of various flow rates at junctions in the conveyor haulage network, enabling one to size gathering belts. The model provides a basis for optimizing, (in economic terms) capacity specifications for feeders and conveyor belts in the materials-handling system by considering tradeoffs in the size of the two types of units.]

Jan 1, 1997

By M. F. Bradley, G. M. Schoen

The Magmont Mine, a 50/50 venture between Cominco American Incorporated (the Operator) and Dresser Industries, Inc., (Halliburton), is a metallic mining and milling facility in the new lead belt of Missouri. The mine is located approximately 100 miles southwest of St. Louis. Legislation passed in 1992 by the Missouri legislature requires all metallic mining and processing facilities to apply for a Metallic Minerals Waste Management permit (MMWM) for their waste facilities. Regulations were subsequently promulgated by the Missouri Department of Natural Resources (DNR). Cominco obtained a MMWM permit (MM-006) from the Missouri DNR in 1992.

Jan 1, 2001

By N. A. Abdel-Khalek

The amenability of carbonate separation from a sedimentary phosphate ore using a bioflotation process was studied. Two types of bacteria were chosen for this study. The experiments were performed using oleic acid as collector. The flotation experiments were carried out using statistical designs for optimizing the main operating parameters. A concentrate containing 0.78% MgO and 30.15% P2O5 with a recovery of 92.31% was obtained from a feed containing about 2.45% MgO and 27% P2O5. These specifications could not be obtained using conventional flotation experiments under similar conditions in the absence of bacteria. Measurements of zeta potential, adsorption of bacteria and collector, as well as froth power, were performed to explain the role of microorganisms in the surface modification of both dolomite and phosphate and in their interaction with the collector.

Jan 1, 2009

By Wilfred P. Schmoe

Introduction An integrated oil company has two options in approaching strategic planning. It has to decide whether it is in business for the long-term. I state this in all seriousness. Those who help manage public companies have the responsibility of good stewardship of other people's money. We must decide whether continued investment in our basic business will generate a reasonable rate of return. With a world surplus of petroleum production capacity, and continuing downward pressure on prices, this question should be addressed by all oil companies. And a positive answer is not necessarily a foregone conclusion in all cases. The decision should be made based on proven competence in finding and developing petroleum reserves on a cost-competitive basis with other producers, and on a frank analysis of future prospects. This should include a realistic assessment of the projected rate of return on specific investment projects. If a company did not pass these tests, its strategy could take one of four paths. Diversification First, it could diversify. But recent history suggests that oil companies are not good at managing other businesses. Second, it could seek a buyer for its business at the optimum return for its owners. Third, it could sell its assets on a piecemeal basis. And, fourth, it could adopt a longer-range plan of self-liquidation by living off current recoverable reserves. In other words, by not investing in exploration and development, it could maximize short-term profit and pass the money back to shareholders in the form of dividends. The Conoco component of DuPont has a below-average cost of finding petroleum, a good track record of efficient production, and a full plate of projects that pass the test of return-on-investment. In short, Conoco is in business for the long-term. That fact, in itself, determines at least one key element in strategy. This is to extend the life of the petroleum reserve base while at the same time maintaining maximum efficient rates of production to provide a strong cash flow. A company that is able to maintain a strong reserve base will ultimately see the value of those reserves escalate as world oil supplies tighten. Our planners expect this tightening to occur within the next decade as demand grows and production in non-OPEC areas of the world begins to decline. An exploration program tailored to meet the requirements of reserve replacement and current production should have two basic parts. The first is relatively low-risk exploration in proven oil provinces. This is augmented by

Jan 6, 1985

This paper presents the results of a unique study conducted by the National Institute for Occupational Safety and Health (NIOSH) from 2016 to 2019 to evaluate the effects of longwall-induced subsurface deformations on shale gas well casing integrity and underground miner safety and health. At both deep and shallow cover instrumentation sites, surface subsidence measurements, subsurface in-place inclinometer measurements, and underground pillar pressure measurements were conducted as longwall panels were mined. Comparisons of the deep and shallow cover test site results with those from a similar study under medium cover reveal an interesting longwall-induced response scenario. Under shallow and medium covers, measured horizontal displacements within the abutment pillar are one order of magnitude higher than those measured under deep cover. Conversely, measured vertical compressions under deep cover are one order of magnitude higher than those under shallow and medium covers. However, FLAC3D simulations of the casings indicate that, in all three cases, the P-110 production casings remain intact under longwall-induced deformations and compressions, which has serious implications for future mine design in areas where shale gas wells have been drilled ahead of mining.

Jan 7, 2020

By Yuting Xue, Danqing Gao, Brijes Mishra

Heterogeneity and discontinuity significantly affect rock strength. For accurate stability prediction, intact rock behavior is imperatively included in rock mass behavior. However, past research largely used arbitrary scaling approaches to produce rock strength. This paper considers a stochastic approach in order to determine the strength of a rock. Based on the laboratory data, a MATLAB® with extreme value stochastic model generates a database for each physico-mechanical property. Then FLAC® simulates laboratory-sized rock specimens. The grids developed in the numerical model can in turn develop random material properties in MATLAB®, which researchers then applied to the final FLAC® model. Model runs simulate the approach performed in the laboratory. The results from the model indicate that a stochastic approach produces strengths that are lower than a deterministic approach. Failure modes for each specimen are different, similar to observations in the laboratory. In addition, random density also influences the failure mode, highlighting the importance of stochastic analysis in rocks.

By Yuting Xue, Danqing Gao, Brijes Mishra

Heterogeneity and discontinuity significantly affect rock strength. For accurate stability prediction, intact rock behavior is imperatively included in rock mass behavior. However, past research largely used arbitrary scaling approaches to produce rock strength. This paper considers a stochastic approach in order to determine the strength of a rock. Based on the laboratory data, a MATLAB® with extreme value stochastic model generates a database for each physico-mechanical property. Then FLAC® simulates laboratory-sized rock specimens. The grids developed in the numerical model can in turn develop random material properties in MATLAB®, which researchers then applied to the final FLAC® model. Model runs simulate the approach performed in the laboratory. The results from the model indicate that a stochastic approach produces strengths that are lower than a deterministic approach. Failure modes for each specimen are different, similar to observations in the laboratory. In addition, random density also influences the failure mode, highlighting the importance of stochastic analysis in rocks.

This paper presents a virtual prototype for the stress analysis of cable shovel components based on combination of flexible and rigid body approach. The general mechanical system of the cable shovel is modeled as a multi-body system with rigid and flexible bodies. The relevant theories applied for the dynamic model are described in terms of Lagrangian multi-body dynamics and finite element method. A virtual prototype of the cable shovel is built in the Automatic Dynamic Analysis Mechanical System (ADAMS) environment, which allows visualizing the motion of general mechanical system and analyzing the dynamic stress of structural components of the cable shovel. An example is given to perform dynamic stress of durability analysis for the boom and handle. Attention of this study is devoted to the mechanisms of damage of the cable shovel and also the critical high stress areas. Keywords: Cable shovel, Von Mises stress, Virtual prototype simulation, Stress virtualization.

Jan 1, 2009

By D. Dimitriadis, T. Polglase, W. Phillips, R. Jenny, M. Botz

Cyanidation processes for the extraction of gold or silver frequently involve the processing of sulfur-containing solids which react with cyanide to form thiocyanate. The formation of thiocyanate is an undesired side-reaction, and in many cases thiocyanate formation results in a prohibitively high cyanide consumption. With the increasing number of gold and silver mining projects which involve the processing of sulfide ores or concentrates or which utilize a biological sulfur oxidation process, more attention has been focused on minimizing thiocyanate formation and in treating solutions to eliminate toxicity associated with thiocyanate. Though not yet commercially applied, there are several technologies available to recover cyanide from thiocyanate to both reduce tailings toxicity and allow the reuse of cyanide otherwise lost to thiocyanate formation. This paper presents an overview of technologies available for recovering cyanide from thiocyanate along with estimated operating costs for the technologies. Pilot testing data suggests that in some cases, cyanide can be recovered from thiocyanate for approximately the same cost as newly purchased cyanide.

Jan 1, 2000

By C. R. Copeland

Water sprays are a common method used to reduce particulate matter (PM) emissions. Various factors such as wettability, surface area coverage, fine particle engulfment rates, interparticle adhesion forces, suppressant penetration and suppressant longevity have all been suggested as critical factors in achieving effective PM control. However, it has not been established which of these factors are the most important. Experimental work indicated that suppressant penetration is the most critical of these factors. The length of time after application that suppressants were effective was also improved by using hygroscopic reagents that retained moisture to prevent evaporation. Maximizing suppressant penetration and improving suppressant longevity led to an average 86% reduction in PM10 concentrations in laboratory dust tower tests.

Jan 1, 2008

By Kira Mizell, James R. Hein, Tracy Conrad

"The Ninetyeast Ridge (NER) extends roughly N-S as a topographic feature for 5000 km, from 31° south to 10° north (Fig. 1) where it becomes buried beneath the Bengal Fan at its northern end. These two geographic characteristics make the NER an ideal natural laboratory for determining the influence of latitude and terrestrial input to ferromanganese (Fe-Mn) crust formation and composition. In addition to study of geographic controls on crust composition, the NER is the largest feature in the Indian Ocean that may host crusts of economic interest.Crusts were collected from 9 of 33 dredge sites from 1.4° north to 26° south latitudes during the 2007 R.V. Roger Revelle Knox06 cruise. Nineteen samples were analyzed for 69 elements each. Nine bulk crusts and 10 layers from four crusts were analyzed. Three of the crusts sub-sampled for layers did not have the bulk crust analyzed and the weighted means for those layers were calculated to obtain bulk compositions. One sample was left out of the statistical analyses because it is phosphatized and chemically quite different from the other samples (Table 1).In order to determine changes in composition with latitude, Pearson product-moment correlation coefficients were calculated for the chemical dataset and latitude of dredge sites, as well as water depth. At the 95-99% confidence level, the following elements increase in crusts moving north along the NER: Mg, Ti, S, Cd, Ni, Tl, Mn, Ba, Co, Cu, In, Li, and Zn; and the following elements decrease northward: Fe, Fe/Mn, P, As, Sc, the rare earth elements plus yttrium (REY), Bi, Ge, and Pb. These correlations indicate that the iron oxyhydroxide component and its associated elements are more prevalent to the south, and the manganese-oxide phase and associated elements increase toward the north end of the NER. This change occurs between dredges D20 and D14 (Fig. 1), with crusts from D20 and south having Fe/Mn !1.0 and those north of D20 ""1.2, with the exception of the phosphatized crust. Crust composition also changes with water depth: Th, Ge, Pb, and the middle rare earth elements (REEs) increase with increasing water depth. Thorium commonly increases in deeper water crusts, which explains the higher Th concentrations in Atlantic and Indian ocean crusts in general compared with Pacific crusts (Fig. 2 and Hein et al., 2012), including the samples analyzed here with a mean water depth of 3584 m. However, water depth does not explain the latitudinal changes because the mean water depths of samples along the northern and southern segments of the NER are roughly comparable. Surprisingly, Si and Al, representing the aluminosilicate/detrital phase, do not correlate with latitude; that is as the ridge approaches and is buried by the Bengal Fan the Si and Al contents do not increase. However, overall, Si and Al have higher concentrations in NER crusts than in central Pacific crusts. Ba can be used as a proxy for primary productivity and statistically does increase to the north along the ridge in the direction of the equatorial zone of high biological productivity. Correlations of Mg, Li, and Zn with latitude may also reflect increased primary productivity at lower latitudes."

Sep 1, 2014

By David Belknap, Clay Haynes, David Egger

Rehabilitation challenges were met nearly two months ahead of contract schedule for the Design-Build, Fast Track Scituate Aqueduct & Tunnel project in Cranston, Rhode Island. The aqueduct and tunnel were built in the 1920s and consisted of three sections—a 2.3 m diameter reinforced concrete section that extends approximately305 m before it transitions to a horseshoe-shaped 2.3 m wide by 2.1 m high cast-in-place concrete tunnel that continues for approximately 5.3 km until it transitions back to a 2.3 m circular section that extends approximately 1.9 km to the end of this project. Major repairs were required to assure sustained operation of this water supply tunnel.

Jan 1, 2005

By T. McCallum

Crud is a common concern in SX processes and is formed as a complex solid stabilized emulsion of aqueous and organic.1,3 Crud formation is highly dependent on the amount of solids entering the circuit and is influenced by a number of other operational factors. A common practice for crud processing is interfacial pumping, wherein crud, organic, and aqueous are pumped from the settlers for treatment and utilizes a variety of equipment. These mechanical means of crud processing are effective, however, require significant processing time and require oversight to prevent the return of contaminated organic. Cytec has developed a unique crud treatment process utilizing both chemical and mechanical means to enhance the solid/liquid separation. The use of ACORGA CB? 1000 crud busting reagent allows a rapid separation of solids from the organic phase and provides similar volume recovery to current practices. The process allows operations to return clean organic back to the plant more efficiently and may enable operations to process more crud. In addition, the organic quality of the recovered organic is higher than that recovered by typical means, which can lead to operational cost savings.

Feb 27, 2013

By · J. B. Boisvert, O. Leuangthong, T. Acorn

Optimizing final pit limits for stochastic models provides access to geologic and economic uncertainty in the pit optimization stages of a mining project. This paper presents an approach for optimizing final pit limits for a highly variable and geologically complex gold deposit. A heuristic pit optimizer is used to manage the effect of geological uncertainty in the resources within a pit shell with multiple uncertainty rated solutions. The uncertainty rated pit shells follow the meanvariance criterion to approximate the efficient frontier for final pit limits. Stochastic dominance rules are then used in a risk management framework to further eliminate sub-optimal solutions along the efficient frontier. This results in a smaller set of final pit shells that could be further analyzed for production scheduling. Additionally, the original solutions are analyzed for changes in the mining limits and two regions are targeted as potential regions for further exploration.

By · J. B. Boisvert, O. Leuangthong, T. Acorn

Optimizing final pit limits for stochastic models provides access to geologic and economic uncertainty in the pit optimization stages of a mining project. This paper presents an approach for optimizing final pit limits for a highly variable and geologically complex gold deposit. A heuristic pit optimizer is used to manage the effect of geological uncertainty in the resources within a pit shell with multiple uncertainty rated solutions. The uncertainty rated pit shells follow the meanvariance criterion to approximate the efficient frontier for final pit limits. Stochastic dominance rules are then used in a risk management framework to further eliminate sub-optimal solutions along the efficient frontier. This results in a smaller set of final pit shells that could be further analyzed for production scheduling. Additionally, the original solutions are analyzed for changes in the mining limits and two regions are targeted as potential regions for further exploration.

By M. Karmis, S. K. Weisiger

The traditional method for training personnel in the mining and other heavy industries has been face-to-face, either via a lecturer in a classroom or through an apprenticeship. With the advent of applications tools such as video, computers, and the Internet, however, a much broader range of training delivery methods is available. Especially exciting are the broad capabilities of multimedia packages that combine the best features of numerous delivery methods. Applying multimedia environments in training holds great potential, especially when there is considerable difficulty in reconstructing real training environments. The authors discuss various delivery methods currently used in training employees, including perceived advantages and disadvantages of those methods. The authors then discuss and evaluate current computer-based training efforts of the mining industry and present an example of a multimedia training tool.

Jan 1, 2001