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By Craig Naudé

"An enhanced gravity concentrator was installed in conjunction with an Intensive Leach Reactor at the Sadiola plant in Mali last year and commissioned in Dec 2007.There has been much debate over the years as to the effect of gravity concentration on overall plant performance. The late Dr Laplante suggested that for every 10% of gold recovered by gravity, there was a corresponding 0.1% to 1% additional overall plant recovery. The results at Sadiola are consistent with this hypothesis with an overall 4% gain in plant recovery.With total gold recovery of 12% in the gravity section, grades are increased from 3.54g/t in the gravity feed to an average of 2 600g/t in the concentrator feed to the in-line reactor. The recovery of gold in the in-line reactor is in excess of 98.5%.This paper discusses the background to the project, the laboratory testwork prior to the equipment selection, the operational results of the system, as well as the benefits of the future application of high mass yield centrifugal concentrators in base metals, sulphides and industrial minerals. Bench scale, pilot scale and plant practice examples are also presented.INTRODUCTIONBesides picking nuggets off the ground or out of riverbeds, gravity concentration is arguably one of the oldest methods of recovering gold. In circa 6000BC people discovered that gold can be found behind the rocks and in depressions of creek beds. By placing rocks in a stretch of channel with the proper slope the first sluice is built, probably around 4,000 BC, and this method is still practiced today."

Jan 1, 2009

By William H. Schiffbauer, Timothy Lutz, Michael R. Yenchek

The National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Research Laboratory (PRL) participated in an experiment to facilitate the remote control of dozers used on coal stockpiles. The experiment consisted of supplementing the normal sensory cues an operator requires to manipulate the dozer from a remote location. NIOSH provided and tested a vision systems intended to give the operator the ability to operate the dozer safely and efficiently from a remote position. This paper highlights the genesis of the experiment, identifies the contributions of Consol Energy and Caterpillar, and details the NIOSH efforts and successful test results. Keywords-remote-control; vision system; stockpiles; safety

By John Owens, Hamid Maleki

Efficient and safe use of mobile roof supports (MRS) depends on the interaction between the MRS and coal strata. Of particular interest to this study are the mechanics of strata deformation as influenced by geologic conditions, pillar extraction methods, and MRS load-bearing capabilities. To provide a better understanding of the mechanics of strata deformation, the authors have collected and reviewed measurements of convergence and stress in one western U.S. mine and have completed pseudo-three-dimensional, boundary-element modeling for two typical pillar-pulling plans. Stress distribution in the mine roof above pairs of MRS’s was calculated to demonstrate how MRS’s contributed to the control of roof block movements. It was shown that overall stress and roof-floor convergence patterns were most influenced by the stiffness of coal-measure rocks and by pillar-pulling sequences and layouts. MRS’s and other support systems play a critical role in controlling the stability of both the immediate roof and the middle roof for a distance of up to 18 m (60ft) above the seam. MRS’s provide unique ground control advantages over other types of secondary support by significantly reducing the time between mining and installation of secondary support. Although MRS’s are similar to posts in stiffness and capacity, they are more effective than posts under static loads because they can yield and still maintain loads at near-peak capacity, whereas posts fail and loose their ability to limit mine roof deformation.

By E. J. Fuller, J. C. Monette

"Gold and silver cyanide complexes are presently desorbed from activated carbon by means of hot caustic elutions. These solutions may or may not contain additional sodium cyanide. There are several parameters which affect the rate of stripping. Some of these include pH, ionic strength, and temperature. (1) Stripping is conducted in recirculating (ZADRA) or once through (AARL) circuits.This paper describes the development of a new chemical eluant which significantly increases the rate of stripping of both gold and silver cyanide complexes from activated carbon. Two case history applications are also described.INTRODUCTIONAdditional cyanide is used in strip circuits in order to prevent its depletion which could lead to precipitation of base metals or lead to a change in the nature of the gold cyanide complex to one which does not strip as easily. (2)The strip circuits that are able to function efficiently without the use of cyanide are mostly those where the carbon is acid-cleaned after stripping.Once the minimum cyanide requirement to maintain the complexes in their proper state are fullfilled, any futher incremental increase in the level of cyanide will have no bearing on the rate of stripping. (3)DEVELOPMENT OF THE NEW ELUANTGeneral DiscussionVarious carboxylated materials were investigated including octanoic acid, polycarboxylic acid (various molecular weights), salicylic acid, polymaleic acid, acetic acid. benzoic acid, terephthalic acid, 4, bi-phenyl carboxylic acid, phosphoric acid and stearic acid.The initial work was done on medium activiiy, non acid-cleaned carbon. The silver to gold ratio on the carbon varied greatly.Two different blanks were used. The first was an elution using a 2% caustic and 0.4% cyanide solution while the second was a 2% caustic elution."

Jan 1, 1992

By W. J. Long

As a part of the strategic mineral exploration program, examining engineers of the Bureau of Mines collected samples of ore from four manganese properties in Yavapai, Yuma, Maricopa, and Mohave Counties, Ariz. As all of the ores were too low in grade to be acceptable by manufacturers of ferromanganese beneficiation studies were made to determine the amenability of the ores to concentration.

Jan 1, 1948

By K. R. Griffin

Atmospheric conditions underground are constantly changing and from a safety perspective, it is critical to identify when conditions are trending abnormally. Atmospheric monitoring in underground coal mines allows mine operators to analyze atmospheric conditions underground in real-time. Real-time monitoring can then be used to identify whether atmospheric conditions underground have become problematic. The implementation of a risk assessment and management process allows operators to then use a risk-informed decision making to identify comprehensive site specific ventilation parameters. Establishing risk-informed ventilation parameters and tracking conditions relative to these parameters, management can modify ventilation plans as mine conditions develop to manage evolving risks. Ventilation risk assessment and management allows developing atmospheric monitoring technologies to be fully utilized in order to increase safety standards in the United States. This paper reviews general risk assessment approaches, state of the art ventilation based risk assessment, and the risk assessment and management application within the United States regulatory framework.

Feb 27, 2013

By Daniel Tao, Jike Qiao, Hao Ren, Feifei Ji, Gonglun Chen

The floatation of niobite was studied using a number of collectors at various dosages and solution pH’s. Octyl diphosphonic acid was found to be an effective collector for niobite flotation with good selectivity. A flotation recovery of 91.2% was obtained with 140 mg/l octyl diphosphonic acid at pH’s less than 5.0. Infrared absorption spectroscopy (IAS) and X-ray photoelectron spectroscopy (XPS) were used to characterize the interactions of niobite with octyl diphosphonic acid. Species distribution diagram of octyl diphosphonic acid and niobium species was used to elucidate the flotation behavior of the mineral with octyl diphosphonic acid. A chemical adsorption mechanism of niobite with octyl diphosphonic acid was proposed. Keywords: octyl diphosphonic acid, electrokinetic measurements, niobite flotation, XPS.

Jan 1, 2005

By Alain Blouin, Mohamad Sabsabi, Aissa Harhira, Paul Bouchard, Greg Lithgow

"The objective of this study was to demonstrate the application of Laser-Induced Breakdown Spectroscopy (LIBS) to the continuous analysis of online monitoring of Al, Mg, Ni, Mn, Si and Fe in nickel ore limonite and saprolite slurry samples. Analysis was performed on slurry samples in air at atmospheric pressure. Two pure samples of limonite and saprolite were used. Mixtures of the two samples in varying proportions were used to build calibration curves, study the influence of solid/liquid ratio, and evaluate short and long term reproducibility. The LIBS measurement of these elements is independent of the water content (from 70-85%, the range allowed by our setup). Repeatability of the measurement and long term reproducibility (from day-to-day) were below 1.2 % and 2% respectively for all the elements studied in our conditions. The results obtained showed that an industrial LIBS analyzer could provide the chemical composition of the six elements Al, Mg, Ni, Mn, Si and Fe within 1-2 minutes.IntroductionThe metal-producing industry faces the major challenge of increasing productivity, reducing costs, and maximizing benefits from existing equipment. By pyrometallurgy, metal making involves the basic steps of charging the furnace, melting the charge and refining. By hydrometallurgy, the metal refining is carried out through the dissolution of the metal by chemical reaction and electrolysis. During refining either by pyrometallurgy or hydrometallurgy, it is critical that operating parameters be adjusted and controlled so that the chemistry of the melt or the solution is within predetermined limits. Presently, the complete turnaround time for sampling, sample transfer, analysis and communication of the results to the operators is often 30 minutes or more."

Jan 1, 2016

Kinetic Dependence of Refractory Gold Sulfide Biooxidation Using Different Microorganism Association In this investigation, refractory sulfide concentrate from a deposit located in northern Russia was treated using biohydrometallurgical technology. The objective of this work was to compare the accelerated refractory sulfide concentrate biooxidation abilities of the pure and mixed mesophilic and moderately termophilic acidophiles cultures. Pure culture of Acidithiobacillus ferrooxidans and two associations of the: Acidithiobacillus ferrooxidans + Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans + Acidithiobacillus thiooxidans + Leptospirillum + Sulfobacillus were used in this investigation. Results of sulfide concentrate bioleaching were analysed using the enzyme catalysis theory. Different effective kinetics parameters were calculated for Michaelis-Menten equation, such as Michaelis' constant and maximum rate of the enzymatic reaction. It was shown that the increase of microorganisms' species decreased Michaelis' constant. Lower Michaelis' constant characterises increasing bacteria ferment affinity to substrate (treated concentrate). As a result, the rates of sulfide minerals biooxidation have increased. This investigation has demonstrated that cultures of the different microorganism species, including moderately termophilic, allow to enhance different parameters of the biohydrometallurgical technology for the refractory gold sulfide concentrate treatment. We can see that bacterial leaching stage duration decreased and sulfide minerals oxidation increased. When the bioresidues were subjected to the hydrometallurgical stage, which includes aeration and sorption cyanidation, the operation factors were also enhanced. The decrease of aeration duration and the growth of the precious metal extraction by sorption cyanidation was achieved. Cyanide consumption was also reduced. The results of this investigation were used in design of an industrial plant.

Sep 13, 2010

By J. Noll

Many underground metal/nonmetal mines are using enclosed cabs on mining equipment to reduce the exposure of miners to diesel particulate matter (DPM). However, some enclosed cab systems may not be meeting their expected efficiency in capturing DPM, which could be a result of inappropriate filter use, cab leaks, or insufficient pressurization. NIOSH investigated several types of filters for reducing DPM to determine which type had the best capture efficiency. The laboratory results indicated that a MERV 8 (Minimum Efficiency Reporting Value, as defined by the American Society of Heating, Refrigerating and Air- Conditioning Engineers) filter captured about 50 percent of the DPM, a MERV 16 filter collected 96-98 percent of the DPM, and two HEPA (high efficiency particulate air) grade filters captured over 99 percent of the DPM. NIOSH also performed a field study to measure the efficiency of two cabs at a limestone mine. The cab filtration systems of a loader and haul truck were found to be over 90 percent effective in removing DPM except under certain operating conditions when the efficiency was as low as 41 percent. Evidence seems to suggest that these conditions were when a window was open in the cab.

Jan 1, 2011

By Ramón Alanís, Filiberto Orrante, Andrea Festa, Baldomero Gutiérrez, Fernando Cornejo

"SGS implemented two rules-based fuzzy logic expert applications on two grinding circuits operated by Peñoles Group in Mexico. Both expert systems are based on control strategies that push against process constraints to improve throughput. Based on proven methodologies, the projects also required some new approaches that led to permanent changes to the mill control strategy.This paper provides descriptions of the implementation, operation and performance of both expert systems. It also reviews how improved production rates were achieved through the use of a common set of expert technology tools. An overview of the resulting control strategies implemented on the two circuits is presented. The paper also discusses the identification of the process constraints within each circuit and how these constraints are used within the expert systems.INTRODUCTIONMexico-based mining company Peñoles Group and the Advanced Systems group at SGS, formally known as MinnovEX Technologies Inc., collaborated on the implementation of two expert systems in two grinding plants, both located in Northern Mexico.The primary objective of the expert systems was to increase throughput whilst still maintaining the cyclone overflow product size within an acceptable range. The secondary objective was to achieve a high level of utilisation of the expert technology.In order to achieve these objectives, SGS proposed a proven methodology which leveraged the existing operating and technical expertise at site through the client’s involvement in the design and implementation stages. The in-house operating and technical expertise of SGS was also brought to the project and implemented with the client’s approval at all stages. At both sites the final acceptance was defined upon meeting both process and utilization parameters.The development and deployment of rules-based fuzzy logic applications has matured as a technology and consequently, clear definition of process states and their place in the logic structure to control a given circuit are now transferable. The key to the robustness of the control logic depends on selection and tuning rules for maintaining stability and optimizing a given circuit. Application integrators need to have a standardized approach for timely integration and deployment; a critical component to avoid the common critiques that expert applications are idiosyncratic and difficult to maintain."

Jan 1, 2009

By W. Z. Rogers

U.S. feldspar output sold or used in 2005 was an estimated 760 kt (838,000 st), valued at $44 million free-on-board plant. This was below the 2004 volume and was the second year of decline in a row. Output included flotation concentrates, feldspar content in feldspar-silica mixtures, potash feldspar and aplite. The strong housing market in the United States maintained demand for ceramic tiles, plumbing fixtures and fiberglass insulation requiring feldspar. Shipments of glass containers were about the same as in 2004. Imports of ceramic tiles and plumbing fixtures continued to increase, taking the place of U.S.-produced goods and the feldspar required to make them. For 2005, 80 percent of the ceramic tiles sold and 50 percent of the plumbing fixtures sold in the United States were imported. Since 2000, manufacturing plant closures in the plumbing fixtures industry have reduced the demand for feldspar and feldspar-silica mixtures by 100 kt (110,000 st). Increased demand from the ceramic tile industry has partially offset the lost volume.

Jan 1, 2006

By Welby G. Courtney

The Bureau of Mines conducted an exploratory field survey to determine the amount of airborne coal dust, the size distribution of the dust, and the rate of dust deposition in coal mine airways. The survey was taken at eight underground locations in operating coal mines. The rate of dust deposition in the airways depended upon the concentration of air-borne dust and decreased exponentially with distance from the dust source. The rate was seemingly independent of the size of the airborne dust particles. The rate of deposition, along a return, for the coal dust from a fade being mined with a continuous mining machine closely matched the rate for the rock dust from a trickle duster. A sample rock-dusting schedule for that return is presented; that is, the trickle duster should be operated for 3-112 hours after every five shifts to protect the average deposit of new float coal dust in the return, but operation after every three shifts is preferred, to protect an occasional heavier deposit.

Jan 1, 1982

By Phil Pennington, D. Jack Adams

Mining and processing of minerals, metals, and fossil fuels can release selenium and arsenic into wastewaters. Both selenium and arsenic are difficult to remove to levels that meet current drinking water and discharge criteria. These metalloids can be used as electron acceptors by microorganisms transforming them back to reduced states, thus removing or stabilizing them. Bioremediation cost effectiveness will be discussed in terms of site information required, microbial populations, co-contaminants, pH, redox, and nutrients. Full-scale, economical ex situ and in situ biotreatments are possible and can produce 1,000’s of times less sludge than conventional precipitation technologies.

Jan 1, 2005

By Charles H. Wells

This paper describes a commercial installation of a sophisticated instrumentation and control system designed to maximize the performance of heavy medium cyclones. Samples of plant feed and its products were collected and analyzed for ash content so that measures of efficiency could be determined for plant operation under (1) manual control and (2) automatic (computer) control. The heavy medium cyclone control strategy and its digital computer implementation are discussed in detail. The sample results are analyzed and the economic benefits of automatic control are discussed. Results from the initial data sets quantify the economic benefits of automatic closed-loop control; viz, increased recovery and reduced clean coal variability have been clearly demonstrated.

Jan 1, 1981

By J. Sandford, S. Hennings

EXECUTIVE SUMMARY An approach borrowed from the petroleum industry was applied to the gas development evaluation for the Bulga underground coal mine in New South Wales, Australia. The results enabled the coal mine operator, Xstrata Coal, to systematically plan the extraction of gas in harmony with mine production planning of multiple coal seams. This has allowed for a more proactive approach in preparing the resources and infrastructure needed to capture the gas and accelerate coal mining while maintaining their high level of commitment to safety. Norwest has for decades used gas recovery simulation models to assist the petroleum industry and the coal bed methane (CBM) industry in understanding and forecasting fluid saturations and flow behavior. Norwest developed a similar process with Xstrata to migrate existing mine data at Bulga into reservoir simulation models to study various drainage alternatives. An interesting feature to the evaluation was also developing an understanding of test procedures and nomenclature from the mining industry to properly translate the data for input in simulators developed for the petroleum and CBM industries. The model was then calibrated to actual field data collected from drainage pilot tests that Norwest helped design and monitor at Bulga. The resulting calibrated predictions were then used to develop budgets, schedules, resource requirements, and alternatives for capturing the gas and delivering it to market ahead of mining. Increasing revenue, reducing emissions, improving schedules and cutting costs for the mining operations have all contributed to justifying this advanced approach at Bulga. It has also allowed Xstrata to expand their focus to the sizable gas reserves in seams not currently planned for mining. Several of these seams would be economic gas development targets once the gas recovery infrastructure is installed for the mine. The evaluation process was refined throughout this project and the resulting approach will benefit Xstrata with their broader strategic development of resources in the Hunter Valley and beyond to their worldwide operations.

Jan 1, 2007

By Jacolien P. Wyethe

Zincor uses a Roast-Leach-Electrowinning circuit to process zinc sulphide concentrates. It also processes zinc oxide fume, originating from a slag smelting operation in the Democratic Republic of the Congo (DRC). Zincor achieved an average zinc recovery of 90.3% during the period January 2006 to May 2007. The bulk of the losses occurred in the iron and lead silver residues, both as soluble and un-dissolved losses. The un-dissolved losses in the iron residue constituted around 33% of the total zinc lost from the circuit, and were largely attributed to the presence of zinc-ferrite in the calcine used for neutralization during iron removal. As part of Zincor?s continuous improvement programme, the un-dissolved zinc losses in the iron residue were targeted by: the partial replacement of calcine with zinc oxide fume (from the DRC); and the preferential use of ?low-ferrite content calcine? as neutralizing agents in the iron removal circuit. These initiatives, coupled with other operational factors, resulted in a marked improvement in recovery to 92.6% during June to December 2007. The zinc oxide fume, directly fed to the circuit, required investigation of the halide rejection capacity of the Zincor circuit. Rejection of chloride via the magnesium bleed operation was considered adequate. Fluoride was mainly rejected via the iron (~70%) and lead silver (~27%) residues. Fluoride rejection via the lead silver residue varied significantly, probably as a result of variations in the sparingly soluble CaF2 content in the feed. The mechanism for fluoride rejection in the iron residues is uncertain. The fluoride rejection capacity of the Zincor iron residue (comprising of mainly jarosites, schwertmannite and ferrihydrite) at 2 ? 4 mg/L F in solution, was estimated at 0.14 ? 0.19 kgF/tFe residue.

Jan 1, 2008

By D Rubery, C Croker

The Boddington Gold Mine (BGM) is located 120 km south east of Perth, Western Australia. The operation is managed by Worsley Alumina Pty Ltd and mined by contractor Henry Walker Eltin (HWE). The mine has been operating since 1987 with ore extracted from a series of pits along strike. Ore is contained within the basement rock, which is overlain by a cap rock layer and transition zone. Cap rock and basement zones require blasting.As the mine neared completion, a high-grade deposit was discovered within 50 m of an existing Western Power substation and 100 m from the processing mill. The substation provides power to the Boddington area and is a back-up power supply to the city of Perth. Due to the delicate nature of the transformers located at the power station, overhead power lines and the mill, blasting in the area was considered very high risk. As such blasting needed to be controlled for flyrock, airblast and most importantly peak vibration and frequency limits which had the potential to damage the transformers.The mine was due for closure in March 2001. The decision to mine the pit was based on its high grade, ability to be blended with lowering grades from other pits and changing of the processing technique with the expansion. This decision extended the life for a further six months.Due to the high potential risks a detailed risk assessment was conducted by Orica, Worsley and Henry Walker Eltin. The completed assessment and the major design parameters were presented to Western Power for approval. The ability to reduce the blasting risk was focused on limiting of vibration through controlling maximum charge initiated per delay, blast timing and firing direction, and other innovative control measures. OricaÆs SHOTPlan« and Sabrex« computer modelling packages were used to predict the outcome of blasts.The success of this project has opened the doors for other high risk blasting projects, which otherwise may be left unmined.

Jan 1, 2002

By Wenbing Guo

Strip pillar mining method is one of the most important techniques for mining subsidence control in China. Mining depth is one of the most important factors that affect subsidence in strip pillar mining method. Six numerical simulation models were set up in this paper to simulate surface subsidence of strip pillar mining at different mining depths. The mining depth in these models ranged from 300 to 800 m. The simulated results were compared and analyzed. The results showed that the subsidence factor of strip pillar mining is related to mining depth. While other things being equal, the subsidence factor of strip pillar mining increases logarithmically with increase in mining depth. Their quantitative relationship was established based on the simulated results.

Jan 1, 2007

By G. J. Slavens

The Bureau of Mines has devised technology to recover cobalt, nickel, and byproduct copper from domestic lateritic material using an oxidative, ammoniacal ammonium sulfate leach. Nickel, cobalt, and copper were recovered by solvent extraction and electrowinning. To reduce the cost and complexity of cobalt recovery, an alternate method using lig-nite to extract Co3+ was investigated as reported herein. In the first 25 BV (bed volumes) of solution contacted with lignite, 97 wt pct of the Co3+ was extracted in & downflow column at pH 9.3. After 85 BV, the lignite was loaded to 1.5 wt pct Co3+ and further ex-traction was minimal. The lignite extracted cobaltic ammine complexes rather than cobalt ions and was nonselective as to other -metal cations and ammonium ions. Deleterious cations and 80 wt pct of the nonammine ammonium ions were removed prior to acid elution of the lignite. The removal of the ammines prior to elution to produce an ammonium-ion-freeCo3+ eluate was only partially successful. Thus Co3+ removal from ammoniacal solutions by lignite is technically difficult and economically unfeasible. It was also determined that reduction of Co3+ to Co2+ occurred during the extraction-elution process.

Jan 1, 1984