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By Arthur P. Chaves, John A. Meech, Vanessa M. Torres

Process choice for a refractory gold ore can become a controversial issue, especially at the early stages of a project. This happens since at preliminary stages, a simple economic comparison among the main process options is not possible as the differences are usually smaller than the precision of estimates. This paper presents a methodology to assess the suitability of each available technologies using a heuristic approach, were technical, economic, operational and environmental aspects are taken into account using a neural network methodology. This methodology is embedded in an expert system for gold ore process design, Intelligold, which is in the final stages of development.

Jan 1, 2000

By S. R. S. Sastri, G. V. Rao

Because the nickel contained in lateritic nickel ores does not occur in an identifiable mineral, it is generally accepted that these ores are not amenable to beneficiation. For this reason, such ores are either directly smelted or leached to extract the nickel. In this paper, a process for enriching the nickel content of the lateritic nickel-bearing chromite overburden, normally a waste material generated during chromite mining, is described. In this flotation process, a nickel preconcentrate containing >1.1% Ni was obtained from material containing as little as 0.36% nickel. An empirical relationship was developed to predict the grade of nickel that can be obtained.

Jan 1, 1997

By Kerstin Malmqvist

Simulation technique has been used for a feasibility study of a deep exploration project for massive, sulphides in an old mining district, the Skellefte field. An interactive computerized mathematical model of an ore field and a drilling procedure has been constructed. It is possible to represent varying geological structures. The model also takes in consideration economical factors such as drilling costs and ore values. On this model Monte Carlo simulations and probability calculations are done in order to estimate the outcome of different drilling strategies under varying geological assumptions. Under the specific conditions of the well known Skellefte field, it is found to be possible to even calibrate the mathematical model.

Jan 1, 1979

By Thomas Fliess, Klaus-Christof Ritter, John R. Sturgul

The optimum flow of materials through a smelter is an extremely important phase of the mining cycle. A typical copper smelter will have up to $US 1,000,000 per day of copper being processed. The motion of the overhead cranes in moving the ladles filled with copper matte and slag from furnace to furnace is prescribed but there can be numerous variables to consider. Some of these variables to the system can be: the speed of the overhead cranes, the number of cranes, the size of the ladles, the size of the furnaces, the number of furnaces and the sequence in loading the furnaces. A simulation model was constructed of a working smelter in the SW of the United States. The model has been used to study the effect of varying parameters of the system. The program runs as follows: an input menu appears on the PC screen and the user can navigate through it and change any of the data; the simulation takes place and the results of the simulation sent to a data file. Animation of the system then is shown on the screen in "cartoon" fashion. The software chosen for the simulation was GPSSI H (') and PROOF Professional (') for the animation. The model presented here is believed to be the first reported simulation and animation model for a complete, working smelter.

Jan 1, 1996

By Dao De Xu, Heechan Cho, Mark S. Klima

A study was conducted to determine the feasibility of using dense-medium centrifugation for separating fine (-150 µm) coal. A centrifuge provides the capability of varying the rotational speed and retention time independently, which offers the potential for a higher degree of control as compared to a dense-medium cyclone. Tests were conducted with a 140-mm diameter by 76-mm long Plexiglas separator, which was fitted with appropriate feed and discharge pipes to allow continuous separations to be made. A suspension of ultrafine (-10 µm) magnetite and water was used as the dense medium. The effects of operating conditions, including the magnitude of the 'g"-force and retention time, on centrifuge performance were investigated.

Jan 1, 1995

By Dwayne C. Kicker, Duk-Won Park

As the use of longwall mining increases in the U.S.. there is a need to better understand the stress redistribu- tions indicative of this method. To control high stress concentrations, the yield pillar concept has been developed. A physical longwall mine model has been designed to study the effect of yield pillars in deep mining. The model in- cludes sensitive stress measuring devices, a new excavating technique, and a new model material. This study includes the use of both regular and yield pillar systems and has successfully simulated the mode of stress change in chain pillars.

Jan 1, 1986

By N. L. Piret, R. J. Wesely, A. E. Melin, A. D. Zunkel

At the end of the sixties new iron precipitation techniques as jarosite, goethite or hematite brought about the new generation of electrolytic zinc plants, thereby terminating the multitude of existing neutral leach residue treatment schemes. Since the eighties, increasing environmental impact considerations urge the conversion of these contaminated waste generating precipitation processes to techniques which either produce environmentally acceptable residues or minimize their formation thereby generating iron-bearing byproducts. Technologies identified and economically assessed include the hematite process either suitably improved or with subsequent upgrading, the iron extraction process and the direct smelting of neutral leach residue to slag and fumed zinc oxide.

Jan 1, 1993

The process design of a metallurgical plant follows logical steps, one built on another, to define the circuit requirements. The methodology used and documentation produced is the same for a pre-feasibility study, feasibility study or a complete design, regardless of the process complexity or the commodity. The only difference is the amount of detail developed at each stage. SRK Consulting, an independent, international consulting practice that provides focused advice and solutions to clients, mainly from earth and water resource industries, has consulted on many mining projects around the world. The company was formed in 1974 and now employs more than 1,600 professionals in more than 50 offices on six continents. According to SRK experts, the first element in plant design is collecting metallurgical testwork or operating data from an existing plant. The testwork identifies the process, the metallurgical recoveries and product qualities and establishes the process parameters for economic recovery of the commodity. Test samples must represent both the whole orebody and the feed over the life of the mine, showing the mineral?s variability. With this data available, the process design can be developed.

May 1, 2013

By P. D. Chamberlain

Agglomeration for the heap leaching of gold and silver ores is the process of attaching fine ore particles-less than 150 µm (100 mesh)-to coarser particles. The fines are thus immobilized and uniformly distributed throughout the heap. This is needed to make heaps more porous and uniformly permeable to the flow of a leaching solution. This article describes liquids and binders used to form agglomerates. Agglomeration techniques and equipment are also described. These include drum and disk agglomerators, stockpile and belt agglomeration, and the use of vibrating deck and reverse-running conveyors. The need for agglomeration The main reason for agglomerating heap leachable ores is to prevent percolation problems in a heap. This is different than pelletizing iron ore. In the latter case, the purpose is to bond very finely ground material into coarser, strong particles. These particles can then withstand the rigors of transportation and the loading forces in a blast furnace. Most percolation problems in heaps are caused by the segregation of coarse and fine particles during heap construction. This segregation creates areas with significantly lower permeability because fines plug the channels between coarse particles. Consequently, the leach solutions are subject to channeling, following the path of least resistance. They percolate downward through the coarse ore areas and bypass or barely wet areas that contain large amounts of fines. This results in lower extraction, longer leach time, and higher reagent consumption. Permeability problems in heap leaching are compounded because of the vertical migration of fine particles after the heap has been built. These fines eventually accumulate in pockets or layers and impede uniform solution flow. The fines move because they are not attached to a coarser particle. Moreover, the sluicing action of leach solution flowing over the surface of particles may break the bond between fine and coarse particles. Some fines are also created by the decomposition of ores after being wetted. Percolation problems are minimized if the fines can be attached to the coarser particles. Fines are thus uniformly distributed and rendered immobile within the heap. Heinen (1979) conducted comparative tests of nonagglomerated and agglomerated gold and silver ores. He showed that percolation rates through agglomerated material usually are improved by 10 to 100 times. This reduces leach time for economic recovery to less than one-third of that for nonagglomerated material, and total recovery may be increased. Cyanide consumption is also reduced in most cases because of the shortened leach time. Even run of mine (ROM) ore should be agglomerated. This can be achieved with moderate success by passing each truckload of ore under a water spray to bring total moisture of the ore up to about 8% to 10%. The ROM ore will mix when the ore is dumped, when it cascades down the slope of a heap, or when it is pushed up with a dozer. Overall, agglomeration allows low-cost heap leaching technology be applied to gold and silver ores and tailings that could not be economically processed by conventional methods, according to Phariss (1982). How agglomeration works Agglomeration means that the clays and fine particles contained in the ore adhere to the coarser particles. This creates a coating of fines around the coarse particles. When the ore has few fines and the percolation problems are not severe, the addition of a liquid may be all that is necessary to make the few fines adhere to coarser particles. However, when the quantity of fines is substantial, e.g., +10% -75 µm (-200 mesh), a binding agent may be needed. Use of solution only for agglomeration There are many forces that cause agglomeration and one of them is the surface tension of water. Water-saturated particles collide with each other or with

Jan 12, 1986

By Duane Jorgensen

Two types of factors direct the search for gypsum deposits-geologic factors and economic factors. The prime control and major economic factor is the market for the possible products. The major geologic factor is the control of the depositional environment, which determines whether or not a deposit exists within a given market area. After discovery of a deposit, the distinction between economic and geologic factors is not as clear as before, and the geologic characteristics of the deposit become the economic factors in evaluating the deposit for production and processing. The geologic characteristics are concerned with 1) the gypsum rock, 2) the host or country rock, and 3) geologic fluids, such as gas and water. Prospecting includes both original discovery and the continuing information-gathering period. During this time the above three characteristics of the deposit are determined, usually from core drilling, from phenomena observed during drilling, and from the core and hole. Important information and means of gathering it include sample analyses, sample volume, impurities and their distribution, water levels, aquifer tests, permeability measurements, rock strength tests, rock and overburden thicknesses, rock types, and direct observations of water and gas. Data gathered or inferred from all of these determine the mining or quarrying geometry and environment: which in turn determine the equipment, development, production, and processing costs. Impurities in gypsum deposits are very important in manufacturing processes. The impurities and their effects vary widely from inert minerals with little effect to reactive minerals with strong and mostly detrimental effects.

Jan 1, 1978

By John C. Ferm

Although roof falls account for approximately half of the fatalities in underground coal mining, the factors that produce them are not clear. Mining methods can account for some, but in others the controlling factors are the geological setting in which the mining takes place. The present investigation was undertaken to determine the kinds of rocks that were most likely to produce roof problems. Such knowledge would be helpful to mine planning since rock samples can be obtained in advance of mining by core hole drilling. The investigation was undertaken in underground mines in the Pocahontas #3 seam in southern West Virginia and southwestern Virginia. The Pocahontas #3 is one of the most widespread in this region and is a major source of high quality metallurgical coal. There are at least ten very large mines in the area and many smaller ones. The region has a very long mining history and considerable experience has been gained in roof control problems. The study was conducted with the support of the U. S. Bureau of Mines.

Jan 1, 1978

By K. L. Whitehead, R. A. Jankowski, N. I. Jayaraman

Most continuous miner sections utilizing flooded-bed scrubbers also use blowing face ventilation. Blowing ventilation, however, interferes with dust capture and minimizes scrubber effectiveness. To enhance the efficiency of the scrubber system and reduce dust concentrations, the Bureau of Mines tested various combinations of operating parameters. Experiments for system efficiency took place in a full- scale model mine at 3.05 m roof height. In general, higher values for scrubber and face airflows resulted in lower dust concentrations. In addition, optimum dust controls would include a face ventilation to scrubber airflow ratio of one. When the airflow ratio was either less than or greater than one, the dust levels in the return and at the operator locations increased. No single dust control technique was the most effective one at all locations due to mutual interaction among techniques.

Jan 1, 1992

By H. D. Freeman

The Pacific Northwest Laboratory (PNL) is developing cover technology for uranium mill tailings that will inhibit the diffusion of radon to the atmosphere. As part of this cover program, an improved radon flux measurement system has been developed. The radon measurement system is a recirculating, pressure-balanced, flow-through system that uses activated carbon at ambient temperatures to collect the radon. With the system, an area of 0.93 m2 is sampled for periods ranging from 1 to 12 h. The activated carbon is removed from the radon trap and the collected radon is determined by counting the 214Bi daughter product. Development of the system included studies to determine the efficiency of activated carbon, relative calibration measurements and field measurements made during 1980 at the inactive tailings pile in Grand Junction, Colorado. Results of these studies are presented.

Jan 1, 1981

By H. P. Schlanger, L. Paterson, B. H. G. Brady, B. E. Hobbs

A novel principle for a waste repository, based on a backfilled thermosyphon as the functional unit, is proposed. Such a unit reduces temperatures and temperature gradients in the vicinity of a waste package and in the repository near field, reducing leach rates from packages and thermomechanical disturbance of the rock mass. Preliminary analyses confirm the mode of performance of the system, and reveal some interesting features of material transport and sealing in backfill and rock fissures. The thermosyphon combines attractively with the prospect of developing a near-field geochemical trap with chemical specificity for radionuclides. It is proposed that a thermosyphon repository may provide superior performance of engineered and natural barriers compared with conventional designs. The achievement of the ability to predict accurately the performance of the thermosyphon, relative to other isolation schemes, will represent a benchmark in the understanding of the absolute performance of any repository.

Jan 1, 1986

By M. Girardeau, J. Blondin, M. Nomine

It is well known that surface moisture and fine content have a strong influence on coal handle- ability. It is known as well that these two criteria are not sufficient to classify coals. It seems that certain types of coals are intrinsically difficult to handle, the reason being still not well understood. For these coals, moisture and fine content are aggravating factors and have to be strictly controlled in order to avoid handling problems (sticking, arching in hoppers.. .). CERCHAR has undertaken research aimed at identifying the role of intrinsic characteristics of coal with regard to handling properties. Two of them have been identified as particularly relevant : the clay content and the "colloidal particle" content. Two simple tests commonly used for soils characterisation, but never used so far for coal, have been applied to characterise a wide range of coals. The derived classification has been compared with an empirical classification based on dry screening tests. DRY SCREENING EXPERIMENTS Dry screening at a relatively low screen aperture (e.g. 6 mm) may be considered as a good tool for assessing the handleability of wet fine coals. Difficult to handle coals always lead to rapid plugging of the screen whilst easy to handle coals can be screened without difficulties. A wide range of coals has been selected with various ash, moisture and fine content. Their characteristics are given in table 1. The experimental set-up consists of a 2 t.p.h vibrating screen equipped with two automatic re- cording balances collecting respectively oversize and undersize material. Provided that the feeding rate is accurately controlled, good reproducibility in the percentage passing as a function of time is obtained. Figure 1 gives examples of different types of relations that were obtained. - LMC coal exhibits a behaviour that is characteristic of easy to handle coals : % passing remains constant in the course of the screening operation. - B coal behaves slightly differently. One observe first a rapid decrease in the flow passing through the screen and then a stabilization. Hand- ling properties can be considered as intermediately - The curve relative to LHB coal is characteristic of a very difficult to handle coal that blinds the screen almost immediately. It is necessary to point out the fact that the classification derived from screening experiments is a global one, including not only intrinsic factors but also external factors such as fines and moisture content. The role of surface moisture is in particular very important and variations in this parameter may upset the empirical classification

Jan 1, 1988

By J. J. Schwoebel

Resource Enterprises, Inc. (REI) is exploiting the coalbed gas resource by working in unison with active underground mining operations. At REI?s pilot project at the Soldier Canyon Mine, Carbon County, Utah, REI has drilled nearly 15,250 m of horizontal in- seam and slant boreholes during the initial two years of drilling activity. Produced gas has been sold to a natural gas transmission company on a continuous basis since mid 1983.

Jan 1, 1986

By Michael Chender

Introduction Clearly, many problems confront the minerals industry today. Yet, at the same time, there is too much energy spent bemoaning the negative effects of difficult economic circumstances, low metals prices, and adverse government policies. These are factors that cannot be altered by individual mineral company reactions. In fact, as we look to the future, the only thing we can be certain of is that we will continue to be faced with uncertainty. Thus, an area that demands close scrutiny and that can significantly affect a company's performance in the future is the posture it adopts to deal with uncertainty. This paper looks at how strategies are developing to deal with this issue. It also examines some of the implications that implementing such strategies have for the role of the individual explorationist. Elements of strategy Whether mineral company strategies are based on diversifying or retrenching, on emphasizing primary production or downstream integration, there seems to be increasing agreement that in the current environment strategies must have several features. They need to be information-based - developed out of access to timely and complete data and analysis about proposed directions and competitor activity, rather than simply following a current fashion. They need to be flexible - adaptable in light of changes in the marketplace and an unpredictable industry. And they need to be cost-efficient - making the most of limited resources. Whether a company is looking for gold financing opportunities, acquiring polymetallic prospects, or doing grassroots exploration for diamonds, these three elements are increasingly essential. They not only allow the company to pursue its current goals most expeditiously, but also open it to hearing and using feedback in the most constructive way. The company can then improve or change strategy as it proceeds. And it can be best positioned to take advantage of opportunities as they arise. These elements of strategy place great emphasis on the skills of the individual. The need for critical intelligence and the reduced amount of capital available to manage are making it more obvious that exploration is a "people" business. This is in accordance with a general trend in many sectors of industrialized economies, reflecting the widely discussed shift from smokestack to information-based industries. Increasing the odds There is a direct connection between successfully implementing the approaches to strategy discussed above and encouraging and improving the quality of work of the individual explorationist. To illustrate the importance of this, some commonly quoted figures on the odds of discovery success can be used. These figures are arbitrary but illustrative. Assume that one out of 100 exploration prospects actually turns out to be a promising ore body, and that one out of 1000 becomes a mine. Based on our research, chances are the most of those

Jan 1, 1986

By David A. Summers, Clark R. Barker

INTRODUCTION The use of high pressure water as a means of excavating valuable mineral from the earth dates back many hundreds of years, but is most familiar through its use in sluicing the gold bearing deposits of California and Alaska. Interestingly, that practice, which dates back from at least 1852, is now nearly defunct with only one known surviving hydraulicking operation.(l) In that particular development water under a relatively low, natural pressure head is carried to a nozzle and from the nozzle it is thrown a distance of perhaps 20 ft to wash the gold bearing material down into a channel from whence it's carried over some mineral collector, and the water is then recirculated. Development of this practice in coal mining began in Russia in 1915, and Dr. Muchnik established the criteria for hydraulic mining during the 1930's. The first water jet mine was established underground in 1939 and has been followed by several larger mines to the present day where there are at least 11 large mines producing about 10 million tons of coal per year in the Soviet Union.(2) Water jet mining has expanded from Russia through Japan, Germany, Poland, Czekoslovakia, and mainland China. The nearest location to the United States is currently at the Kaiser Mine in Sparwood, British Columbia, where a three-man crew has mined up to 3,400 tons of coal in a 6-hr shift. There are many advantages to this particular operation. It is one of the safest mining operations for coal in Canada and has won safety awards because of this. The process is relatively cheap since the cost of the equipment is much lower than that which would be required conventionally using either longwall or shortwall mining, and transportation is achieved by fluming the coal to a central station using a gravity feed and then pumping to the surface, (3) For this

Jan 1, 1976

By G. M. Bernard

This paper provides an overview of the various methods and techniques for transporting and stacking ore on heap leach pads. Towards this end, brief discussions of the various methods and techniques important to this process are presented.

Jan 1, 1993

By Stanley M. Miller

Analysis of discontinuous rock masses for engineering design purposes requires information about fracture characteristics. For such studies, fractures or other elements of the rock fabric (bedding, foliation, etc.) should be considered in a statistical manner because they generally have high frequencies of occurrence and are discontinuous over the design area. A practical design procedure includes defining structural domains as those areas which contain fractures with similar orientation patterns. Within a structural domain, the statistical distributions of fracture set characteristics (spacing, fracture density, dip, dip direction, etc.) may be computed from mapped data and then used to quantitatively describe the rock fabric. These distributions can then be randomly sampled (using Monte Carlo techniques) to simulate the rock fabric and to help define potential failure surfaces along fractures. 1 The prediction of failure geometries is an essential part of stability analyses used in designing rock slopes or underground openings. In current probabilistic design procedures, Monte Carlo techniques that rely upon the iterative generation and analysis of deterministic instability models do not incorporate spatial aspects of the random variation in fracture set characteristics, 1,2 but consider the characteristics to be spatially independent.

Jan 1, 1979