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By J. T. Sitarski, R. C. Emmett, L. W. Luinstra, R. P. Klepper

A mining operation in Zimbabwe produces a pyritic gold concentrate that requires oxidative pretreatment prior to cyanidation in order to liberate 80 percent of the gold values. Bio- oxidation offered the potential of increased gold recovery and was considered to be an economically advantageous alternative to the existing practice of roasting the concentrate. Based on bench- scale test work, a small bio-oxidation plant, capable of processing approximately 50 percent of the concentrator production, was installed at the mine to evaluate this approach. The plant included two 57 m3 bioreactors in series and the ancillary equipment needed to prepare the feed concentrate, to wash the leached residue prior to cyanidation, and to neutralize the waste liquor. The plant was operated for a year-and-a-half, and the conditions needed to achieve a 90 percent liberation of gold values were determined. A number of critical technical problems were encountered, and many were resolved on-site. Others have been addressed since the pilot plant was moth-balled in June 1988. Valuable insight was gained from the operation of the pilot plant, which has provided useful guidance for continued process and equipment improvement.

Jan 1, 1990

By K. Hiroto, H. Tamamoto, G. J. Kusuma

"Acid mine drainage (AMD) has become a serious environmental problem in the mining industry in the last decade. Many efforts have been made in an attempt to find a better method to manage this problem in a proper manner, both through prevention and mitigation. One of the methods to prevent AMD generation is a dry dump cover system that has been proposed to minimize oxidation of sulphide waste rock in dumping sites. The performance of this system depends on the physical and geochemical stability of a barrier layer to minimize water and oxygen influx. In the mining industry, this barrier layer is formed by using Inert/Non Acid Forming (NAF) waste rocks to cover Potentially Acid Forming (PAF) underneath. However, the availability of NAF waste rocks, due to the geological condition, mining sequence and capability of equipment, is limited in some mines. This paper will discuss the acid generation mechanism, application of a cover system and its problem being faced in an Indonesian coal mine, and describe a preliminary laboratory result of a multi layer cover system in an attempt to overcome this problem."

Jan 1, 2011

By Matthew Horsnell

Greenbank Terotech is a member of the Halley & Mellowes Group of Companies and is accredited t AS3902. Greenbank has been involved within the wear resistant lining industry for over 20 years. Initially supplying cast Basalt piping systems through to the present day breakthroughs with SiTech cyclone linings. The challenge of finding the most cost effective cyclone lining has been a difficult process. Over the years many varieties of ceramics have come and gone. In particular within cyclone applications, many people have become disillusioned with the term "Ceramic." In practice, it was discovered that if a ceramic worked in one part of the plant, it did not necessarily work in the cyclone area. A good example of this is Alumina chute and pipe linings. An Alumina lined cyclone underflow bend would provide exceptional wear resistance, whereas an Alumina Spigot would have failed miserably. After Alumina's were tried, Silicon Carbides were experi­mented with. The results in many trials were mixed. What worked at one mine did not work at another. The results did not conclude decisively that ceramics were here to stay within the hard rock cyclone area. It was then that Greenbank Terotech started to look at the reason "Why do some linings work and others don't." We came to the conclusion that the matrix holding the particles together had to be the key to a successful cyclone material. At the time we looked at materials such as Alumina Bonded Silicon Carbides, Metallic (Aluminium) Bonded Silicon Carbide, 99% Alumina Ceramics and Nitride Bonded Silicon Carbides, but all these materials either suffered from chemical attack on the Aluminium matrix (via cyanide) or the matrix simply was not hard enough causing wear rates to be excessive. It was then we looked at SiTech. SiTech is a unique material in that the primary particles are Silicon Carbide, but the matrix is made up of a Secondary Silicon Carbide formed within the reaction bonding process.

Jan 1, 1995

By David Wright, Colin Burns

Successful leaching of gold depends on appropriate chemical conditions; contact between leach solution and the gold particles; separation of the leach solution from the solids and extraction of the valuable ion from the solution. Irrespective of the leaching method employed the chemical conditions required are similar as is the dependence of solu­tion/gold contact on liberation. The various leaching methods available vary in the means by which gold/solution contact and solid/liquid separation are achieved. The essential difference between heap or vat leaching techniques and those involving agitation of a slurry is dependence on percolation for effective gold/solution contact. The most significant factor preventing uniform percolation is the presence of fines or clays. The quantity and character of the fines fraction is ore type dependent and may result from crushing, degradation during stacking or leaching, or the natural size distribution of the ore. The problems associated with fines can be aggravated during stacking and preparation of the heap. Segregation during stacking can result in concentration of fine particles at the centre of heaps. Further concentration of fines may also occur during irrigation by the movement of the fine particles with the solution. The end result is that the areas in which fines are concentrated become areas of low permeability. The contact between leach solution and the ore in such areas is, at best, slowed down dramatically and, in some cases, prevented altogether. The consequences of this phenomena are slow leaching and a reduction in recovery. The conventional solution to this problem is well known. Agglomeration of ore prior to heap leaching is practised widely. The effect of agglomeration is to immobilise the fines by causing them to adhere either to each other or to larger ore particles. The net effect is that the ore behaves as if no fines were present. The use of agglomeration is limited only by its cost, the most significant components of which are the cost of binding agent, commonly cement, and the capital cost of the agglomerating equipment.

Jan 1, 1995

By S. Chander

A mineral or metallurgical process uses various inputs, such as ores, energy and other raw materials, to make different products that fulfill societal needs. The processing of raw materials has changed in recent years due to the increased complexity of processing low-grade ores, intensifying competitiveness and greater constraints. For process improvement, various plant optimization and process modifications must be conducted under environmental, social, political and economic constraints. Processing research and education's success in meeting the process industry's future needs depends on an adequate balance between micro- and macro-engineering approaches. In its simplest form, macro-engineering is concerned with the "big picture," while micro-engineering requires looking at a subset of the process. So macro-engineering may be defined as an investigation of the larger or "whole" system to achieve the desired goals. And micro-engineering may be viewed as a quantitative investigation of a subset of the process, to determine cause-and-effect relationships within the subset. Two different approaches might be used in macro-engineering analysis. In one, the big picture may be viewed without a detailed knowledge of the subunits. With this approach, statistical tools are used to relate input and output parameters. Also, actual plant data or analog models might be used to obtain the desired information. The usefulness of such an approach increases with problem complexity. To attain the desired goals using the second, "model-based," approach, a detailed knowledge of the subunits is often useful and their interactions may be considered. In complex process analysis, the first of these approaches is more useful since less information is needed. However, it is also less exact and more likely to fail if there are significant changes in conditions and interactions. The second approach, on the other hand, is more exact, with greater predictive ability within the narrow subset being considered. Consequently, it is difficult and costly to conduct.

Jan 1, 1992

By Joseph F. Shirley

Introduction Inorganic depressants are chemicals added to the froth flotation process to maintain or produce hydrophylic surfaces on one or more minerals so they will remain in the pulp rather than attach to the air bubbles. Whether a depressant will be effective in depressing a given mineral depends on how it is used and the environment in which it is used. Some depressants must be added and conditioned into the pulp before the collector is added. Other depressants can be added in the presence of previously added collectors and effectively depress the desired minerals. Often the concentration of depressant relative to the collector concentration is critical to making an economic separation. It should be noted that some depressants will only work when specific collectors have been used. Some reagents such as sulfuric acid and hydrogen peroxide essentially act as depressants by altering the previously added collectors so that they are no longer effective. Some depressants such as sodium ferrocyanide are only effective in a very limited pH range and an essentially collector free environment. Major Depressants CaO Milk of Lime is by far the most used depressant both in tonnage and dollar value. Although it is most commonly listed as a pH modifier, it is also an important depressant for pyrite in copper and copper molybdenite flotation plants. Although a simple pH adjustment will often depress pyrite, there are times when grinding with fresh milk of lime is required to obtain optimum depression. Lime is also a molybdenite and gold depressant. NaSH Sodium hydrosulfide is by far the most commonly used reagent to depress copper and iron sulfide minerals in by-product molybdenite flotation plants. NaSH also depresses gold, silver sulfides and silver chloride. ZnSO4 Zinc sulfate is commonly used to depress sphalerite in lead-zinc and copper-lead- zinc flotation plants. It has also been used to effectively depress talc in by-product molybdenite circuits at a pH of 6.5.

Jan 1, 1986

By C. Tsamantaki

Water-bentonite suspensions exhibit a yield stress which is defined as the minimum applied stress for flow. Considerable debate exists about the yield stress being a material property, hence different measuring methods should give similar answers, but several investigators have demonstrated that it is an engineering reality. Yield stress is normally estimated indirectly from the rheogram obtained with a viscometer following an extrapolation to zero shear rate (the dynamic yield stress), but the technique may be prone to errors because of slip flow. Direct measurements, not prone to such errors, rely on an independent assessment of the yield stress, normally carried out with the vane method (the static yield stress). In this paper results are presented and compared regarding the yield stress of 14 different water-bentonite suspensions measured using both the direct and the indirect methods. In order to obtain a wide range of yield stress values, two different types and two concentrations of bentonite at various pH were tested. Rheological data were obtained using a rotational speed viscometer and a yield stress vane measuring device. Measured vane yield stress values ranged from 5 Pa to 83 Pa. Rheological data collected with the rotating viscometer were fitted using various conventional techniques (interpolation, linear and non-linear regression analysis) as well as using a golden section yield stress search methodology based on Herschel-Bulkley model, developed in house. The vane instrument measures directly the yield stress of the suspensions and requires no further data handling. A comparison of the measured values of the yield stress with the direct and the indirect method is then made for the water-bentonite samples. Not very large differences are observed among different techniques and the variations are discussed. Similar data from literature are also analyzed and the comparison shows that differences on the various estimation methods are much larger than the differences observed in this study.

Jan 1, 2006

By Julius Rubinstein, Victor Badenicov

The development of column flotation is the most significant achievement in the area of mineral processing in the last few decades. The high efficiency of column flotation allows a reduction in process time, a decrease in the number of cleaner stages and in the volume of the circulating load in the flotation circuit, and, as a result of this, an increase in consistency and reliability of operations. Unique multisectional column flotation apparatuses were developed. Such designs have a number of essential advantages as compared to monocells. A change from monocells to multisectional column allows to provide favourable conditions for separation of particles of various floatability. To attain that aim particular hydrodynamics and aeration regime is established in each section of the column, operational variables being adjusted according to the floatability of the material. Therefore in multisectional column machines the material-apparatus feedback can be established, process variables optimized depending on the characteristics of the floated materials. This concept forms the basis of column designs we have developed. For the first time column cell with alternating slurry Rows (combination of co- and counter-current flows) were developed and commercialized . Successful operation was reported of the new generation of columns with cell volumes of 10 to 80 m3 and the height of 4-6 m in copper, molybdenum, antimony, tungsten and nickel ores and coal slurry processing at different plants. Operation experience of these cells showed their considerable design and operational advantages and verified the proposed options and relationships. The new apparatus is provided with a pneumohydraulic aerator allowing to control bubble size distribution, the service life of the aerator is not less than two years. A multilevel flotation model was developed and used to work out a technique of column design and process parameters calculation. A method of the apparatus design parameters calculation based on laboratory test results (scaling up) was worked out. The method is based on flotation macro and micro-hydrodynamics simulation.

Jan 1, 1995

By K. E. Robinson, G. Re, L. Skoski

Introduction A new technology is evolving as a result of growing industry and government concerns over the potential impacts of possible airborne emissions from uranium tailings piles. A major component of the technology is the use of earth covers to stabilize the tailings after mill operations have ceased. While various analytical models have been used to predict the thickness of required covers, experimental validation of the models has been necessary. This paper presents the results of a field program to select and test cover material to determine its suitability for eventual reclamation of a currently active tailings pile. The two main criteria guiding the study were the U.S. Nuclear Regulatory Commission radon flux requirements (reduction to less than twice background pre-1979, and to 2 pCi/m2 -sec above background post-1979) and the desire to employ locally available material. The methodology chosen for this study consisted of three main elements: o Determination of the background radon flux. o Determination of the radon flux from the tailings pile. o Experimental determination of the cover material diffusion coefficient and and calculation of cover thickness. The first two elements of the study are relatively straightforward, the last phase is discussed in detail. Background Radon Flux Measurements of radon-222 emanation rates from the surface of the ground were taken at three sampling locations. Samples were collected by means of the accumulator can method described by Wilkening, 1977. Both morning and afternoon samples were collected at each site to obtain an average. The measured fluxes were fairly uniform and did not differ greatly among sites. The overall average flux for all sites was 0.63[+]0.28(o) pCi/m2 -sec. This value is equal to the average radium-226 concentration determined in the soil, thus yielding a one to one ratio of radon-222 emitted (in pCi/m2 -sec) to soil radium content (in pCi/g). Tailings Pile Radon Flux Two sites on the tailing pile

Jan 1, 1980

By Laura J. Carroll, Gordon A. Goldsmith

Experts, like many of the speakers at the SME Annual Conference, are frequently called upon by lawyers to assist them in litigation. Due to the technical nature of many cases, the testimony of an expert with knowledge and experience in a particular field is necessary to help a judge or jury understand and decide certain issues. Environmental litigation is no exception. Experts routinely are called upon to offer testimony to establish the existence of contamination and its source, as well as the potential health and environmental risks associated with the contaminants. This article will briefly discuss the factors courts apply to determine whether to admit expert testimony after the recent Supreme Court decision in Daubert v. Memell Dow Pharm., Inc., 509 U.S. 579 (1993). The Court's decision in Daubert overruled a long-standing test that had based the admissibility of scientific evidence on its "general acceptance" in the field in issue. Next, the article will discuss in general terms what a party must do to "link a particular defendant's conduct to the contamination involved in order to recover from that defendant. This link, known as causation, varies depending upon the type of claim being asserted. Expert witnesses are used extensively to help establish causation. JUNK SCIENCE OR GOOD SCIENCE- HOW DOES A COURT DETERMINE WHAT TO LET IN A frequent complaint in litigation involving technical or scientific issues is that one party or another is trying to use so-called "junk science" to prove its case. While some expert testimony might be so clearly lacking in support or so "off the wall" that a court can easily determine to exclude it, other testimony, especially testimony on the "cutting edge," is much more problematic. In 1923, the District of Columbia Circuit Court of Appeals decided the case of Frye v. United States, 293 E 1013 (1923). In deciding whether to admit certain expert testimony, the court in Frye stated that while a court will "go a long way in admitting expert testimony deduced from a well-recognized scientific

Jan 1, 1998

What is your assessment of the current state of the minerals industry? It is no understatement that domestic mining is facing a severe crisis at this time. The sharp decline in commodity prices and demand is putting a great strain on domestic and worldwide mining, causing major declines in profits and market capital of mining companies. This, in turn, has lead to major production cuts, layoffs, shut-downs of operating properties, and the deferral of new and expansion projects. These changes in the minerals industry have played a major role in the health of the economy. Operationally, the industry continues to develop new technologies that are making our work more efficient, more cost effective and more environmentally acceptable and safe. During downturns like this, companies generally pay closer attention to operational efficiencies and process optimization. Historically, new technologies and processes tend to be developed during down markets, and I believe we will see the same thing as companies strive to preserve liquidity and maintain or improve their margins. On the positive side, the drop in commodity prices has resulted in a reduction in operational costs, as the costs for fuel supplies and construction materials have decreased.

Jan 1, 2009

By Harry R. Asche, Manfred K. Lechner

The Cross City Tunnel comprises 2km of a new underground traffic route in Sydney, Australia. The route is very complex, involving some six separate tunnels and three underground Y-junctions. For almost 200m the six tunnels run parallel at different level sunder William Street, Sydney. Almost all of the route runs adjacent to the City Business District of Sydney and adjacent to or below many major buildings and services. The planning and design of this project is described. The geometric arrangement is achieved with a strong dependence on 3D road design packages. Road alignment constraints include land acquisition and proximity to existing tunnels and basements as well as maintaining separation from the other tunnels in the scheme. Geotechnical and hydrogeological studies are described. Findings discussed include the high horizontal stress field in the Sydney area and investigation of incised palaeochannels on the route. Methods of design for the tunnels and Y-junctions are described, as well as methods of settlement prediction for the buildings and services. The latter includes the settlement assessment for more than 200 buildings, many in excess of 20 storeys, as well as services including all of the city railway lines in Sydney.

Jan 1, 2003

By I. K. Kapageridis

Digital photography combined with three dimensional models of topography, mining operations and restoration plans can lead to extremely realistic images and animations of the current and future states of a mine or quarry. The amount of work and the time required for the successful modeling of a mine and its restoration plan are surprisingly low nowadays. All this means that the visual impact of mining and quarrying operations can be easily assessed using common computer hardware and some dedicated software packages. LAVA Mining and Quarrying SA is a company committed to strive continuously for the highest possible environment protection at the company?s quarries. The pozzolanic rock quarry located at Xylokeratia is one of the company?s quarries on the island of Milos and the subject of the study presented in this paper. A thorough restoration plan of the Xylokeratia quarry is being completed by the company. For its purposes, a complete visual impact assessment study was performed at the Department of Geotechnology and Environmental Engineering of the Technological Education Institute of Western Macedonia. The procedures used in this study and the produced visual results are presented in this paper.

Jan 1, 2006

By Faruk Oksuz, Clay Haynes, David Egger

The United States Army Corps of Engineers (USACE) has committed to solve a major drainage problem in the suburban Chicago community of Griffith, Indiana. The Cady Marsh Ditch is currently undersized and on occasion spills its banks causing flooding and economic setbacks to the community. Preliminary studies have identified both tunnel and surface solutions as being attractive and viable. The USACE has decided that this project is an opportunity to use the design-build contracting approach to maximize ingenuity in project approach and to allow the market to dictate whether a surface or subsurface solution is most attractive. The tunnel would be over one-mile in length through sands, gravels and clay. Water control will be an issue during tunneling. The paper will explore the contracting approach to the project and the adaptation of Underground Technology Research Council (UTRC) guidelines for underground contracting to a design build project. The roles of Owner, Owner’s consultant, and design-build contractor will be defined as interpreted by the USACE and key contract provisions will be described and contrasted with a traditional design-bid-build approach to tunnel construction.

Jan 1, 2003

By T. Shungu, N. Vermaut

The various copper-cobalt ores mined by Gecamines, together with typical plant applications and results, are briefly described. Intensive laboratory investigations have been undertaken in recent years to improve the metallurgical performances of the various concentrators. As a result of these tests, it was shown that the flotation of the siliceous oxide ores could be improved by increasing the efficiency of the palm oil collector (energetic conditioning, chemical emulsifier, petroleum sulfonate addition) and by varying the froth depth in the cells. A new flowsheet incorporating these modifications and a regrinding stage has been approved for the rehabilitation of the Kolwezi concentrator. For what affects dolomitic oxide ores, hydroxamates were tested as secondary collectors and, based on successful laboratory results, plant trials were run but failed due to excessive frothing. In other plant tests, xanthates were replaced by a xanthate- fatty acid mixture; plant trials over more than one year proved successful for copper, but not for cobalt. Mercaptans were tested as secondary collectors for the sulfides flotation from sulfide or mixed oxide-sulfide ores; laboratory results proved successful but, to date, no plant test has been run.

Jan 1, 1987

By J. Herbst, H. W. Kropholler, L. A. Cramer, E. T. Woodburn, J. C. A. Greene, G. Poling

A generalized mathematical structure is proposed whereby internal species mass flows within a flotation network are defined uniquely by a matrix of enhancement factors. An element of the enhancement factor matrix is defined as the ratio of the mass flow of that species leaving a given cell in the concentrate to the species mass flow leaving the same cell in the tailings. To predict the enhancement factors, knowledge of flotation kinetics effects is required. Recently experimental data has become available relating to the performance of industrial flotation circuits which indicate that the discrete or discrete-distributed kinetic schemes are capable of reasonably effective simulations. These simulations show the importance of including froth effects. The prediction of performance of networks from small-scale batch tests on flotation streams shows that the model for the froth phase used in the simulations does not scale-up well and that aeration effects are also difficult to predict. The network analysis should be useful in differential flotation of complex ores and it is disappointing in this context that little information on the kinetics of activation and depression is available.

Jan 1, 1976

By P. Kolettas

The development of novel methods for the investigation of the subsoil contributes to the improvement of geotechnical research, enhances the obtained geotechnical characterization and may reduce the investigation cost by reducing the number of required tests. Non-destructive testing methods, performed either in situ (i.e. electrical tomography, seismic refraction, etc) or in the laboratory can provide initial data and perhaps estimates of rock/soil properties. This study focuses on the development of rock material properties and/or characteristics based on non-destructive laboratory testing of a number of stones, ranging from porous (bioclastic) limestones to impervious marbles. Seismic velocity measurements as well as attenuation signals were digitally recorded using a digital oscilloscope. Data were processed using a novel technique of spectral analysis available through special Matlab packages employing Fourier transform methods. More specifically, the NFFT (Non Equispaced Fourier Transform) transformation was applied to seismic waves traveling through the subsoil using the Autosignal program (by Seasolve) and the Specgramdemo program included in the Signal Analysis toolbox of Matlab 6.5 (Mathworks). Results indicate a definite relationship between the frequency content of the signal and the rock type as well as the degree of saturation of the specimen.

Jan 1, 2008

By G. Newman, C. D. Sellars, E. A. Portfors

Power for mine operation in remote locations is usually provided by diesel generators. For gold mines where processing is normally desirable on-site, power requirements can be significant and the operating cost for diesel generation then becomes an important factor in mine feasibility. If a suitable site is available, a small hydroelectric power facility near the minesite can provide a significant portion of the mine power requirements. The hydrological, engineering and economic factors involved in small hydroelectric power development are described in this paper. Capital costs are minimized by run-of-river hydro development which does not require a dam and reservoir and has less environmental impact. During periods of low flow, diesel generators are used to make up the power demand. The hydrologic analysis required to determine unit energy costs is described and technical requirements for linking the hydroelectric power facility with diesel generation are outlined. Case studies are presented demonstrating the economic advantages of a small hydro installation. One case study is for a proposed gold mine in British Columbia and the second is a large operating gold mine overseas, for which the hydroelectric power scheme is presently under construction .

Jan 1, 1987

By M. A. Ackerson, R. E. Griffin, W. H. Pomroy

Two automated fire detection system configurations have been used successfully in underground mines: the pneumatic "tube bundle" approach and the electronic telemetry approach. The electronic telemetry approach is more widely used, owing to its greater speed, flexibility, and capacity to both monitor other underground conditions, and remotely control underground equipment. However, depending on specific mine conditions and layouts, pneumatic detection, or a combined pneumatic/telemetered system may offer significant advantages over the telemetered approach alone. This paper describes research by the U.S. Bureau of Mines to design and in- mine test a rapid response pneumatic fire detection system tailored to the unique requirements of multilevel metal mines. The relative merits of pneumatic detection are discussed in the context of typical multilevel mine layouts and environments. A Bureau developed proto- type system is described with emphasis on design features which counter commonly perceived and/or experienced pneumatic detection system operating problems. Finally, the results of a 3-yr in-mine performance evaluation of the prototype hardware are discussed. Included are descriptions of system layout and coverage, response time, tube leakage, sample dilution, elimination of accumulated water from sample lines, and system maintenance and reliability.

Jan 1, 1989

By Masahiro Lnoue, Kenichi Uchino

Airflow velocity vectors by a forcing auxiliary fan at a heading face were measured in an actual size model gallery and an actual mine. The location of an outlet of ventilation duct gives significant effects on the airflow at the heading in the gallery. It was also found that there were several stagnated regions which may have danger of methane accumulation. The flow were also examined using the visualization technique by laser light in a reduced scale model. The flow in reduced scale model showed similar behavior to those observed in actual size galleries. The air velocity at the outlet has no significant effect on the airflow. It was found that a region to be ventilated by the direct flow of the exhaust fan is limited to a relatively short distance but a secondary flow region is generated near the heading face. CFD ( Computational Fluid Dynamics ) method was also developed to examine the airflow. The calculated results coincides with those measured by actual and reduced scale models. It is concluded that the CFD is useful tool for the analysis of ventilation at the headings.

Jan 1, 1997