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By Peter McKenna

Different reefs being extracted from a mine will, in all likelihood, have significantly different semi-variogram models - and these will probably vary from geozone to geozone. As errors of estimation are dependent on the semi- variogram parameters, it follows, if a mine samples all reefs in all sections using the same sampling grid pattern, that estimation errors (or limits of confidence) will not be the same throughout the mine. This may be an undesirable situation! A geostatistical study of the relative merits of alternative sampling arrangements has been carried out by considering different reefs in different sections of a South African gold mine.

Jan 1, 1989

By N. J. Themelis, W. H. Dresher

Research is probably the least understood and the most underrated or overrated, depending on the circumstances, function of the corporate enterprise. Some companies become engaged in research because they consider it to be vital to their very existence, others in order to develop new business, and some with no clearer objective than to keep up with the competition. Whole new industries have resulted from research activities, such as the Xerox copier, the transistor, the computer, and have affected considerably our way of life. Companies have prospered or perished by pursuing the successes or failures of their research organizations. However. despite the tremendous effect that research has had on our modern civilization and the billions which are spent on it annually, we have not as yet been able to develop many hard and fast rules as to how to conduct it effectively and to a successful end.1 This section discusses the role of research in the United States and in the mineral industry and describes a few of the criteria and guidelines which have been developed to assist in increasing the probability for success in industrial research. Broadly speaking, the purpose of industrial research is to make a significant contribution to the long-term viability and the profitability of the sponsoring company. The sum total of technological developments has been a principal factor in establishing the United States as a world leader and the controlling element in the nation's balance of trade with foreign powers. The international aspect of most mineral commodities is a significant factor in the business decision-making of most domestic mining companies and should be an important factor in the operation of research and development (R & D) programs in these companies. The National Science Board has reported that in recent yean other nations have been gaining on the United States over practically the entire range of science. 2,3 On the positive side, the NSB reported a strong position for the US in the results derived from its investment in R & D. If the United States is to maintain a favorable trade balance, it must create new know-how through technological innovation in order to create new industrial products, processes, and services for which there is a global demand. As expressed by Chauncey Starr, president of the Electric Power Research Institute, "Unlike resources found in nature, technology is a man-made resource whose abundance can be continuously increased, and whose importance in determining the world's future is also increasing."' In recent years, the greatly in- creased pressures for environmental quality and energy conservation have enhanced further the role of technical innovation in insuring the future survival of the domestic industry. Technology is the challenge of American industry, and it is a challenge which the mineral industry must also accept, for processed minerals are the very raw materials and energy on which all of industry is based, it is technology which makes a mineral deposit into an ore reserve. The Natural of Industrial R D Research is usually thought of as being either basic or applied. Basic or fundamental research is the quest for knowledge and need not have any practical objective. Applied research is the search for a solution to a particular problem and therefore has a specific objective beyond the acquisition of new knowledge. Development is the next stage to the applied research experimentation and it generally consists of larger-scale tests to establish the technical and economic feasibility of the new process or product and to provide design information for its industrial implementation. The terms research and development are usually interconnected for the good reason that in many cases it is difficult to define where one ends and the other begins. For instance, in many cases, thermodynamic, kinetic, corrosion, and other research studies, which are needed to provide design data for an industrial plant, may prod in parallel with the pilot plant activities preparatory for this plant in order to conserve time. Often the final stages of a development project may involve the trial production of a new product for markeing tests or the trial operation of a new process on a "semi-industrial" scale pilot plant. Such operations may be termed "demonstrations"; hence, more

Jan 1, 1985

By Lu Yang

In the last two decades, acid iron ore pellets have established their predominant position as the iron-bearing burden material for blast furnace ironmaking in North America. It is a general practice that pelletization plants are asked to produce pellets of certain chemical composition and in a narrow range of sizes. A minimum amount of fines created during handling and transportation is desirable. Such a requirement is often expressed indirectly by the minimum compression load causing a pellet to break. The behavior of pellets inside a blast furnace, of course, is very important for a smooth and efficient operation. Before its melting in the lower part of a blast furnace during this period of several hours the behavior of pellets depends on their properties after induration as well as conditions inside each furnace. Among properties of indurated pellets, the ability to maintain their physical integrity in the burden and to be reducible are most important. To maintain the integrity of pellets (i.e., minimal low temperature breakdown, swelling and softening) so that there will be adequate overall permeability for certain wind rate and local permeability for gas/solid contact for reduction. A higher reducibility will moderate the adverse effects of swelling and softening and contribute to a smooth operation and efficient use of heat and reductants in a blast furnace. An article devoted to the relationships between the quality of iron ore pellets and blast furnace practice has been published elsewhere(1); therefore, no further discussion is needed here. The mechanism of strengthening of iron ore pellets during firing has been the subject of investigation of many authors(2). There is no doubt that the bridging of the growing hematite grains, particularly starting with magnetite concentrates, is very significant in the production of strong pellets. Recently, there are many reports from blast furnace operators that they have noticed the adverse effect of LTB in their plants. It is obvious that the strength derived from bridged hematite grains may disappear when hematite is converted to magnetite with thorough breakdown of grain structures. It is suggested that some other strengthening mechanism may be required in order to improve the LTB index of acid pellets. The influence of porosity on both compression strength and reducibility follows regular patterns. It has been suggested(1) that the amount of liquid slag in pellets during firing determines to a large extent the porosity, hence, indirectly, strength and reducibility.

Jan 1, 1983

By L. Gertsch, R. Gustafson, J. Rostami, C. Swope

Development of a permanent human base on the moon for exploration requires a self-sustaining system. Such a system entails the production and processing of limited amounts of raw material on the moon. Any mining and construction activities on the moon can only be performed by a robust excavation machine that can excavate a variety of material, from loose surface regolith to consolidated (frozen) regolith with embedded rocks in the mixture. Meanwhile, a limited amount of information on lunar regolith is available to develop and optimize a machine for lunar ground conditions. Therefore, any excavator designed for use on the lunar surface should have the ability to adapt to a wide range of operating conditions. A prototype cutterhead for the lunar excavator was built and tested at the Kennametal facility in Latrobe, PA. This paper discusses the results of initial material characterization, as well as full-scale tests of a prototype cutterhead in relevant material. A brief review of anticipated production rates under various assumed ground conditions is also presented.

Jan 1, 2010

By Andrew C. Katen

The mining industry faces increasing geopolitical risk in the coming decades. Constraints such as resource nationalism, corruption and social license could grow to outweigh fundamental limitations like geology or supply and demand (Ernst & Young, 2013; Verrastro et al. 2010). Lurking beneath these more immediate and palpable concerns, however, may be more significant risks entrenched in geography and history. Deep-rooted cultural and strategic forces that emerge slowly ? or erupt suddenly and unexpectedly ? can generate momentous and far-reaching political, social and economic changes. While multinational enterprises routinely assess for political risk, the nature of minerals extraction means long-term and systemic geopolitical conditions are especially important for mining companies to identify and understand. Mine development is a decades-long process that binds companies to the land and makes changing course to avert emerging threats a difficult and costly option. Consequently, geopolitical assessment is a pertinent and valuable tool that mining companies can use to more comprehensively evaluate strategic threats and opportunities. Geopolitics is the study of society, politics and strategy through the lens of geography (Gray, 1996). Its emphasis on relatively permanent physical features of the earth makes geopolitics a uniquely valuable tool for assessing political risk. Topography, climate and natural resources have shaped, constrained and motivated peoples and governments throughout history. These influences transcend regimes, policies and borders ? and even states themselves ? which, by contrast, change often and dramatically. Framing politics against mountains, deserts and rivers supports identification of historical patterns and forecasts of emerging trends. In other words, the physical map provides an objective and consistent model for studying a subjective and dynamic subject such as politics (Sloan and Gray, 1999). Consequently, geopolitical assessment can highlight threats and opportunities that go unaddressed by other risk methodologies that emphasize current conditions (Glancy, 2012). Taken together, the permanence of geography, hindsight afforded by centuries of political history, and interconnectedness of world events makes geopolitical assessment a valuable approach for conceptualizing strategic risk.

Mar 1, 2014

By F. G. Hyde

Passage of the Public Utilities Regulatory Policy Act ("PURPA") in I 978 created an entirely new industry that is referred to today as the Independent Power Producers ("IPP"). Requirements of project owners, environmental compliance, project design, the financial community and most of all, the need to be a low-cost producer presented a unique situation for the sourcing and the utilization of fuels. Depending on the specific type of project being developed, (e.g. coal-fired, wood/biomass, natural gas, petroleum coke or a blend of several fuel types) and the type of boiler design, it is important to acquire fuels that will optimize both the project's operating efficiency and flexibility. This paper will focus on the acquisition of fuel for coal-fired projects, but will describe the necessary steps in the sourcing, contracting for, and the utilization of fuels and transportation resources in the IPP industry today.

Jan 1, 1996

By S. Chatterjee, S. Bandopadhyay

A spatial modeling technique based on the Bayesian neural network (BNN) is proposed. Incorporation of the Bayesian method for posterior probability of the output parameter helps calculate the uncertainty associated with the estimate. Parameters of the BNN model were selected using a grid search algorithm. The expected value and the variance of block support were calculated by Markov chain Monte Carlo sampling of the posterior distribution at discretized points within the block. The BNN model was validated by applying it to the Walker Lake data set and comparing the results with ordinary kriging results. The comparison revealed that the proposed BNN method performs marginally better than ordinary kriging. The variance map is less smooth than with ordinary kriging, and the proportional effect is less in the BNN-based model than in the ordinary kriging model. The developed BNN model was applied to the Coho block of a placer gold deposit in Nome, AK. Results reveal that the BNN model is globally biased for the Coho block and underestimates the sample mean. The grade volume curve was developed by calculating the block mean and block variance after discretizing the block into a number of points and applying the BNN model to each discretized point.

Jan 1, 2011

By Jodie Robertson, Isabel Barton, Cristian Caro

Prior to mining, all rocks contained in a mineral deposit must be placed in one of several categories known as ore types. Each ore type describes a different way that the rock will behave in processing. The ore type determines which process stream a particular mined unit will be sent to, sets expectations for process engineers and metallurgists, and forms the basis for recovery predictions and production estimates. At first, ore types are assigned mainly by geologists based on visible geological criteria (dominant ore mineralogy, estimated grade, rock type, alteration type). As metallurgical tests are carried out and process data accumulate, the resulting criteria may be factored into the ore typing process, typically as assays and recoverable metal using the relevant process(es). Other variables may also be incorporated into ore typing at operations if they are particularly important, such as grindability, preg-robbing, gangue reagent consumption, and the presence of especially deleterious minerals such as talc or smectite. The mine operation department may also redefine ore types and/or process destinations based on economic criteria. A “best” ore type is designated that (in theory) best describes how the rock will behave in processing. Codes representing this ore type are entered into the drill hole database, then interpreted on cross sections and level plans, and finally added to the block model. Ore types are iteratively reexamined and adjusted over the life of a project. Major difficulties in effective ore typing are (1) lack of communication between geologists and metallurgists, (2) the imprecision inherent in imposing clean categories on messy natural systems without discrete divisions, (3) the need for ore types to provide useful information for a wide range of processes, (4) difficulties in scaling up laboratory test results to mine production, and (5) conflict among geological, metallurgical, and economic criteria for ore typing.

Nov 8, 2023

By Raj K. Rajamani, Samira Rashidi

Wear is an extremely important topic when considering high-pressure grinding rolls (HPGR) for any new application. Given the inevitable variations in ore properties throughout a mine’s life, it is difficult to predict the effect of material and operating conditions on the wear parts: specifically, the HPGR rolls. However, the possibility of continuous scanning of rolls provides ample information to review the wear pattern and ways to optimize it. In this regard, as part of a broader investigation, the feasibility of in-line scanning of HPGR rolls in a laboratory-scale HPGR is studied and presented. The choice of scanners and methods adopted to achieve high-level accuracy for determining wear is discussed in this paper, and the inherent variability affecting the measurements is evaluated. 

By A. G. Journel

Accurate prediction of recoverable reserves are key to the development and planning of a mining operation. Recovery functions for tonnage, quantity of metal and ore grade are defined and two approaches for their estimation are proposed. The indicator kriging (IK) approach draws on the data rank orders, whereas the multi-gaussian (MG) approach relies on a grade multi-variate distribution hypothesis. Although based on different premises, both approaches yield remarkably similar--and accurate--estimates for recoverable reserves.

Jan 1, 1984

By Atmesh K. Sinha

The market for thermal coal has recently been growing rapidly and it is projected to continue to do so in the foreseeable future. Both the national and international markets often demand high Btu low sulfur thermal coal in order to minimize the cost of utilization and meet the environmental restrictions. High quality thermal coal can be prepared to compete in the utility market by desulfurizing the high Btu midwestern coal and blending it with low sulfur western coal which is usually low in Btu content. The methods that can be used for optimizing the coal preparation plant operating parameters for physically desulfurizing coal is presented.

Jan 1, 1984

By Ronald J. Roman

As in every business venture, the primary objective of a mining operation is to make money for those who supply the venture capital. Therefore, all decisions concerning the operation of the mining operation should be made in light of the resulting effect on profit. The ultimate control is on profit, but the process is controlled, for example, by aiming for a recovery or concentrate grade knowing its effect on profit. The normal procedure used to determi.ne the profitability of a venture is to "present worth" all costs and incomes back to some arbitrary year zero. Every company has formed a management decision as to what it will require as a minimum return before it will undertake an investment. Once the economic analysis is completed, investment will be made only if the venture shows a positive present worth. If two alternatives are available, the alternative with the larger positive present worth is the one chosen. The same principles can be applied to the selection of a production schedule.

Jan 1, 1971

By B. Andersen, P. Somasundaran

An accurate knowledge of the interactions among mineral particles and between such particles and dissolved and precipitated species is important in developing efficient separation processes. In this investigation, interactions relevant to dispersion and selective reagent adsorption (the two main prerequisites for selective flocculation) within Florida phosphatic clay Waste were studied. Initial studies with artificial slimes, consisting of pure clay and phosphate minerals, showed dispersion of artificial slimes to be relatively easy. The problems that were encountered during selective flocculation of the artificial slimes were due to unselective polyacrylic acid adsorption on clay, which was caused by the presence of multivalent calcium ions on the exchangeable cation positions on the clay surfaces. This problem could be solved by exchanging calcium for sodium, which reduces the interaction between the polymer and the clay surface. This procedure, however, was not successful for mineral mixtures. Natural slimes were found to be much more difficult to disperse. This was attributed to the presence of cementing materials such as humic substances and Al and Fe (hydr)oxide precipitates. Selective removal of these cementing materials resulted in good dispersion and partial separation. A further increase in the separation of natural slimes is most likely determined by the presence of calcium on the clay surfaces, as was found for the artificial mixtures.

Jan 1, 1994

By M. Z. Rashad

The intersection of joint sets and excavation planes leads to removable blocks which can be expected to fall or slide. The amount and cost of supports required to stabilize these blocks of excavation are related to the number and dimensions of key blocks, the mechanical properties of joints and the active forces present. In this work, the application of the block theory in the study of the kinematics and stability of removable blocks is investigated considering any number of sliding faces for some Egyptian limestone quarries.

Jan 1, 1993

By Robert J. Brison

The intent of this paper is to try to answer the complex question: "How much grinding capacity should be designed into a new mining - milling project?" Much work has been devoted to the technical aspects of grinding, the "how" of grinding. But, in the writers' opinion, the economically important subject of optimizing grinding capacity in mill design has not received the attention it deserves, at least not in published literature. For the purpose of this paper it is necessary to distinguish clearly between optimizing operation and optimizing design. Optimizing operation involves making the best use of the available plant and equipment. Much excellent work has been done and is being done in this area. In operation, one can make tradeoffs of production rate and recovery, or recovery and grade, to maximize profits. However, this must be done within the limitations imposed in the design stage. Flexibility is limited by the existing plant. In project design, on the other hand., there are no preexisting physical limitations except as imposed by nature itself; the planners and designers have considerable latitude in their efforts to optimize the overall project. They have complete control over a large number of important design variables from the mine to the finished product. The grinding process design is one of these variables. It not only determines the capital cost charges for grinding and the maximum grinding capacity that operating management will have to work with, but also determines the range of capability of the auxiliary equipment, which fixes the degree of flexibility possible in operation. This paper is concerned with optimizing design rather than operation. The terms "optimum" and "optimize" are sometimes used in a technical sense in connection with grinding, recovery or grade. In this paper, these terms are used only in the economic sense. In this age of working large deposits of ever lower grade ores, it is in¬creasingly essential to design projects and plants for optimum economics, based on the most applicable economic. criteria. Since grinding represents a large part of both capital and operating cost of the project, and largely determines percentage recovery of metal, it should be included as one of the factors in optimizing the project design. This paper is written primarily with reference to medium to large copper concentrators employing conventional wet grinding. However, the principles involved should be applicable to other ores and other methods of grinding.

Jan 1, 1972

By J. Y. Kim

Silver contained in zinc calcines undergoes several phase changes as it proceeds through the leaching circuit of a roast-leach-electrowin zinc plant. In the present study, the flotation response of silver from leach residues prepared under a variety of carefully controlled operating conditions in the pilot plant has been examined. Flotation of neutral leach residue is shown to be technically viable and to merit consideration for those plants without a high acid leach circuit, but having significant silver values in the feed. Residue leach conditions must be kept slightly acidic to promote the formation of Ag2S, (Ag, CU)2S and Ag2S rims on residual unroasted sphalerite, while simultaneously avoiding the hydrolysis of soluble iron which depresses silver recovery and grade. Factors to be considered during integration of a flotation process into an electrolytic zinc plant are discussed.

Jan 1, 1990

By Fred C. Bond

The perennial subject of comminution is deserving of a fresh approach if one can be found. This is attempted here by directing attention primarily to principles rather than to theories. While theories attempt to explain how a certain process acts, principles delineate the laws which the action-must follow. Comminution may be defined as the progressive separation of particulate matter. At the present time this is accomplished commercially by applying energy in the form of compressive and, shearing forces. Such forces strain and distort the particles they contact. When-the applied stress locally exceeds the breaking strength at the weakest flaw in the particle, a crack tip forms. The surrounding strain energy flows to the crack tip, which rapidly extends through the particle as a break. The minute changes in shape and the resulting energy flow cause the failure of other highly stressed flaws, with the consequent formation of a progeny (1) of new smaller particles out of its destroyed progenitor. The applied mechanical energy is transformed into strain energy as the particle is distorted, and then into heat when it fails. Only a tiny fraction of the order of 1/1000 of the applied energy necessary for breakage appears as new surface energy in the product particles. The comminution problem is the relationship between, energy input and product particle size. Its solution is of great-economic importance,

Jan 1, 1961

By James D. Bennett

Relationships among mine and injured miner characteristics and HSAC's degrees of injury are examined for 91,404 injuries in under- ground bituminous coal mines in the United States from 1975 through 1982. Injury severity varies by the mining system, geographical region, circumstances surrounding the injury, the injured miner's age, whether the miner was using powered equipment, the year which the injury occurred, and the location in the mine where the injury happened. Injury severity is not related to the injured miner's total mining experience, job experience, and experience in the mine in which the injury occurred.

Jan 1, 1984

By Madan M. Singh

Although roof bolting has been a major means of strata support for nearly two decades, little attention has been directed towards the design of bolt Installations. The variables involved are interdependent and their study complex. However, some simple tests may be employed to serve as guides to the efficient design of roof bolt systems. Local conditions are continually varying and are important to pattern design. This paper discusses such considerations and suggests techniques which may be employed to effect improved roof control with bolts.

Jan 1, 1967

By D. L. Leach

This report covers laboratory experiments simulating in situ copper recovery from primary sulfide ores in sulfuric acid systems pressurized with oxygen. Copper extraction and acid consumption data are correlated with temperature in the range 50-150°C and quenched pH in the range 0.25-2. Adverse changes in the chemical composition of the leach solution and the formation of gangue-mineral alteration products and secondary sulfides can severely limit the extraction of copper above 90°C. Keeping the pH below the self-buffered value of about 2 and the temperature below about 110°C produces the maximum extraction rates. Forcing the pH too low not only results in excessively high acid consumption but may also limit the extraction of copper at temperatures above 100°C.

Jan 1, 1975