Search Documents

By Dan Nilsson

INTRODUCTION There are many mine planning factors in sublevel caving, as in the other mining systems, which when varied can substantially alter mining costs and profit¬ability. In this chapter, the following four topics are addressed with regard to economic optimization of sub¬level caving: production planning, haulage level spacing, orepass spacing, and extraction cutoff. The costs used here are the right order of magnitude but since each mine is unique, they should be considered only as examples. The objective is to demonstrate the tech¬niques which can be used. In a real mine, the evalua¬tions must be done using actual costs and conditions. It is difficult to predict exactly the costs involved, and therefore it is valuable to perform a sensitivity analysis to evaluate the effect of making incorrect as¬sumptions. Since the mining industry is very capital intensive, the effect of the interest rate must also be studied. PRODUCTION PLAN FOR AN IRON ORE DEPOSIT Introduction The first and most important thing to do before de¬signing an underground mine is to establish a long-range production plan. Such a plan is necessary for all eco¬nomic evaluations and should provide information about the lifetime of the mine, how much ore and waste must be handled per year, how much development per year is required, etc. An example is given in the following section. Problem In an iron ore mine sublevel caving is used. The iron content is 42%, and the mine supplies a pelletizing plant with an annual capacity of 3 million t/a. The ore body is shown in Fig. 1. The length of the ore body is 1000 m and the width is 100 m. Each slice is 10 m high, and there are 10 m be¬tween crosscuts, each of which has an area of 20 m2. The density of the ore is 3.5 t/m3. The spacing between rings is 2 m, and the extraction is 100%. The iron con¬tent is 66% in the pellets and 6% in the tailings. The problem is to develop a detailed production plan. A typical sublevel caving sequence is shown in Fig. 2. Solution Amount of ore per meter of crosscut: 20 X 3.5 = 70 t. Number of crosscuts per slice= 100. Length of crosscuts per slice: 100 X 100 = 10 000. Ore from crosscuts per slice = 10 000 m X 20 m2 X 3.5 = 700 000 t. Number of sublevel caving rounds per slice: 10 000/2 = 5000. Area for each blast in sublevel caving: 10 X 10 - 20 = 80 m2. Amount of ore per blast: 80 m2 X 6 m X 3.5 = 560 t. Extraction: 100% (see extraction curve Fig. 12). Loaded ore per blast: 75% or 420 t. Loaded waste per blast: 25% or 140 t. Total: 560 t. Total amount of rock from each blast in the sublevel caving: Ore: 560 t of which 2 X 70 = 140 t from develop¬ment work and 420 t from sublevel caving. Waste: 140 t. Total: 700 t. The ore needed per year is 3 X (66-6)/42-6 5 mil¬lion t. Necessary number of blasts per year= 5,000,000/ 560 = 8929. Distance to develop per year = 8929 blasts per year X 2 m per blast 17 858 m. Total amount/year: Ore from development work 17 858 m x 70 t/m = 1.25 million t/a Ore from sublevel caving: 8929 blasts per year X 420 tons per blast = 3.75 million t/a 5.00 million t/a Waste rock dilution: 8929 blasts per year X 140 tons per blast 1.25 million t/a Total amount to hoist 6.25 million t/ a The amount of ore from development work will in¬crease a little if the horizontal drift is placed in the ore body and not in the footwall. In this example the ore loss in 20%, and the waste rock dilution is also 20%. After taking the ore loss into account, the lifetime for 100 m of the ore body will be:

Jan 1, 1982

By B. A. Carbon

Western Australia is the largest state in Australia with an area one and three quarter times the size of Texas. Most of the State is desert or semi-desert, and only the southwest corner is heavily populated. The State has a population of one and a half million people, and one million of these live in and around the city of Perth. Perth is located on the narrow Swan Coastal Plain and is flanked by the Indian Ocean and the Darling Plateau. The Darling Plateau is an ancient peneplain rising some 300 metres above sea level, and forms an important resource base for the population. The Darling Plateau is old, having been formed some 200 million years ago, and its soils are deeply weathered. The parent materials were granite and gneis which have broken down to form lateritic gravels, overlying dense kaolinitic clays. Some 30 million years ago, in the Tertiary period, a sub - tropical climate prevailed. Appropriate conditions of moisture, temperature and drainage led to extensive laterisation. Some of the laterite contains bauxite of mineable quality. Some 1.9 million hectares of the south-west of Western Australia is covered by eucalypt forests. Threequarters of this forest is referred to as "Jarrah

Jan 1, 1984

By K. Holmberg, D. Herriot

This paper by Mr. McIvor is yet another contribution to the eternal controversy surrounding the benefits, or otherwise, of high circulating loads in closed circuit grinding. Throughout the paper it is difficult to establish whether the author is referring to effects relating to the mill, classifier, or to the overall circuit. Table 1 is put forward as indicating the advantage of operating at high circulating loads. From the two (it would be interesting to see more) product sizing points provided in each case, the conclusions to be drawn are that cases one and two have very similar size analyses. The third case, however, indicates a much flatter curve, that is to say, higher fines production and a very wide spread of size ranges. If the objective of this circuit is to provide a closely sized product with minimum overground slimes to the downstream process, then it would appear to be the less "efficient" by far. No data is given for product pulp densities either. The term "efficiency" should never be used without a careful and clear definition. In this case, "efficiency" is used to express an apparent percentage reduction in operating work index (Bond) from the measured "standard" at 250% circulating load operation. The Bond calculation is itself based upon

Jan 1, 1990

By Thomas E. Browne

The Electric Power Research Institute Energy Supply Program is developing coal supply forecasts. By coal supply forecasts I mean the future relationships between coal price and production levels. A representative supply curve is shown in Figure l. It will make the rest of my presentation clearer if at this point I give you some background about EPRI and the Energy Supply Program. EPRI is funded by the nation's electric utility industry to develop new technologies for the production and conservation of electricity. Most of the research is conducted by outside contractors. We participate in joint projects with the Department of Energy and other organizations. The Energy Supply Program is one of three "economic" programs. The other two are Energy Demand and Conservation, and Systems. The Systems Program's main function is to provide the means to integrate the output of the other two Programs. The primary function of the "economic" programs is to provide information pertaining to future energy prices, availability, requirements, etc. to the EPRI personnel planning R&D programs. A secondary role that is becoming more and more important is providing information of direct use to the electric utility industry. I should note that the results of all EPRI's contract work are available to the general public. A "Coal Supply Analysis System" is being developed for EPRI by Charles River Associates. To the extent possible it will draw upon existing work, but much additional work needs to be done in the area of coal supply economics.

Jan 1, 1977

By R. S. Mateer

Linear programming on desktop computers is commonly used to optimize coal blending proportions. The objective function is usually the cost of the blend. The constraints consist of materials and heat balances as expressed as linear functions of the blend. This is illustrated in Example 1. Inclusion of a sulfur compliance constraint is more complex because the maximum permitted sulfur percentage is not a pre-specified constant. Rather, it is a function of the calorific power of the blend itself. The current limit of 1.2 pounds of sulfur dioxide per million Btu may be expressed as: Sulfur Max % = 0.6 • H/10,000 with H in Btu/lb.

Jan 1, 1994

By Darrell E. Young

This presentation will define what talc is, how it is mined and processed, and how talc is used in the paper industry. It will also give you some idea about who Luzenac America is and from where it came. Luzenac America was formed in July, 1992 as a result of the acquisition of the talc assets of Cyprus Minerals by RTZ of the United Kingdom. Cyprus Industrial Minerals was then merged with the other RTZ talc interests under the Luzenac name. Luzenac is a town in the Pyrenees of Southern France -and the home of Talc de Luzenac, RTZ's first talc acquisition. The Luzenac Group is the largest talc producer in the world.

Jan 1, 1993

By H. Soto, G. Barbery

The effect of particle size on the flotation of coarse particles is analyzed. It is concluded that turbulence and the presence of the froth layer are detrimental to the recovery of coarse particles during conventional flotation. A counter-current column cell is proposed to avoid these two factors. In this column, a net upwards flow of water is prevalent, such that no froth is allowed to form on the top. Also, the levitation of heavy bubble-particle aggregates is helped by the ascending water current. Preliminary work at laboratory level with kilogram-size samples indicated that under similar conditions recoveries in the column were much higher than in conventional cells. Flotation results obtained with coarsely sized phosphate and quartz samples are presented. One interesting feature of this type of column is very fast flotation kinetics. Thus, a short column (only 55-cm collection zone) yielded, full recovery of floatable values.

Jan 1, 1992

By Farlow C. Davis

Magma Copper Company, San Manuel Division, is a wholly owned subsidiary of the Newmont Mining Corporation and located at San Manuel, Arizona. The ore body is a dessiminated porphry copper deposit in quartz monzonite. The primary copper mineral is chalcopyrite with minor amounts of chalcocite, bornite, and covellite. The molybdenite occurs mainly on fracture faces or else associated with quartz veinlets. Pyrite is the major sulphide mineral in gangue. The feed to the concentrator from the underground mine is approximately 0.720 percent copper and 0.029 percent molybdenite. The concentrator has a design capacity of 62,000 tons of ore daily. After a standard ore treatment circuit consisting of grinding, rougher flotation, regrinding, and cleaning, a bulk concentrate is produced which contains 27 to 29 percent copper and 1.0 to 1.2 percent molybdenite. This concentrate is pumped to the molybdenite plant feed thickener.

Jan 1, 1977

By J. A. Pagliero, R. T. Quiroz, S. H. Castro

Selected voltammograms in tetraborate buffer solutions in the presence of ethyl xanthate or isopropyl xanthate at pH 9.3, for chalcocite, covellite, chalcopyrite, and enargite mineral electrodes, are presented. The concept of critical Eh of dixanthogen condensation (Ehc) is introduced, and the line of Ehc is thermodynamically defined in plots of log [X i] vs Eh, for methyl, ethyl, propyl, and butyl xanthates. A reaction scheme of xanthate oxidation in four steps, involving the dixanthogen condensation step, is proposed. A first attempt to interpret mineral flotation from a more general point of view is made. The electrochemical mechanism of dixanthogen formation and condensation is considered as a particular case of a more general and relevant phenomenon, which is the decomposition of the collector giving hydrophobic colloidal forms, whose associative behavior in bulk solution and at the mineral/solution interface is governed by colloid chemistry.

Jan 1, 1989

By David G. Laughton, Richard Poulin, Michael R. Samis

Real options (RO) valuation is an alternative net present value (NPV) framework that is able to incorporate both management flexibility and dynamic project risks. In this paper, management is considering the development of a satellite low-grade zone while operations in a developed high-grade zone continue. If the low-grade zone is developed prior to high-grade zone exhaustion, mine capacity must be expanded before additional production from the low-grade zone can be processed. This expansion can be avoided only if low-grade zone development is delayed until the high-grade zone is exhausted. The RO model presented here allows the development and capacity expansion decisions to be reconsidered on a discrete half-year basis. It delineates price regions, for given levels of high-grade zone reserves, in which it is optimal to develop the low-grade zone, defer low-grade zone development and abandon the mine irrevocably.

Jan 1, 2002

By John M. Hird

Texasgu1f's Lee Creek Mine in Eastern North Carolina is usin8 a combination Dredge-Dragline method for mining deep phosphate ore at a rate of 8.5 million tons per year. The matrix is thick, uniform in grade, and is processed into agricultural products. As in many other good mineral deposits, there are tough obstacles to overcome in recovering the ore. The deposit is in an area with a land surface of about ten feet above sea level, is close to tidewater, is overlain with 90 to 130 feet of unconsolidated overburden, and is underlain by an artesian aquifer with over 140 feet of natural hydrostatic head at the bottom of the bed, The upper 40 feet of overburden will not support stripping equipment and is unstable when cast as spoil. Barriers are emplaced to prevent flooding from hurricane tides. The ground water problems have been successfully controlled by pumping 60 million gallons per day from the aquifer. Only recently have the severe ground problems been overcome by this unusual Dredge-Dragline combination of mining equipment.

Jan 1, 1978

By Don Rose

I. INTRODUCTION The Atlanta Research Chamber is an UMTA-sponsored applied research facility studying tunnel design, excavation and support systems. It is located directly below Peachtree Street in downtown Atlanta, Georgia. It is included in the CN-120 contract to build the Peachtree Center subway station, a part of the Metropolitan Atlanta Rapid Transit Authority (MARTA) multi-billion dollar "Phase A" 53-mile transit project, which is 80 percent funded by UMTA with 20 percent provided by local authorities in Atlanta and Fulton and DeKalb counties (Figure 1). The Research Chamber is located immediately south of the main Peachtree Center Station cavern, and is in part an enlargement of the pre-existing Pilot Tunnel excavated to provide bidders on the CN-120 contract a view of the rock conditions (Figure 2). The Research Chamber lies some 3 meters above, and is approximately parallel to, the twin Running Tunnels. The Research Chamber is 18 meters long and has the same 5.5 meter diameter horseshoe shape design dimensions as the twin Running Tunnels.

Jan 1, 1979

By K. T. Cunningham

The Oakfield, New York Hine of the United States Gypsum Company is a shallow, room and pillar mine developed in the Camillus Formation of Silurian Age on the up-dip edge of the northern Appalachian Basin. The gypsum comes to subcrop beneath a variety of glacial materials and is subject to solution activity by groundwater. A geologic environment unfavorable to mining activity is thus created. Since 1978 seismic studies have been used to supplement core drilling to determine a conservative boundary between normal and questionable mining environments. A single channel seismograph, originally in use, is now replaced by a twelve-channel unit and is used to determine bulk material velocity which is the basis for defining the mining limit.

Jan 1, 1987

Reclamation of surface mines is a crucial environmental issue and a key challenge to the worldwide mining industry. One of the goals of reclamation is to ensure that the area is left in a condition permitting safe future use. Hence, the reconstruction of open pits, waste piles and tailings dams must satisfy appropriate geotechnical stability and safety conditions for the planned use. Landscaping in the final stages is highly relevant as the topography around the mining areas is sometimes dramatically modified by ore extraction. The reclamation strategies must be applied not only after ore exhaustion, but also during its extraction. This is a sound business strategy that leads to considerable environmental benefits and increased security of the mining operations.

Jan 1, 2003

By Fathi Habashi

At the Duisburger Kupferhütte plant in Germany, pyrite cinder is collected from the sulfuric acid manufacturers in that country and processed to recover the nonferrous metals contained in the cinder, before charging it to the blast furnace for iron recovery. A typical analysis of the cinder is given in Table 9-1. The pyrite cinder is mixed with NaCl and treated continuously in a multiple hearth furnace. The evolved gases are scrubbed with water to form a weak acid which is used for the leaching process. Each batch requires about 2 days for leaching. The concentrated leaching solution obtained in the first 15 to 20 hr is sent for copper recovery, while that subsequently obtained, being poor ill metal content, is recycled. The residue, called purple ore, now a high-grade iron ore (61-63 % Fe); is sintered and delivered to the blast furnace.

Jan 1, 1970

By Robert W. Bartlett

Pretreatment of sulfidic refractory gold ore by biooxidation in coarse-crushed ore heaps is a promising new technology, especially for low-grade ores that cannot afford pressure leaching or roasting. An algebraic equation for determining the economically optimum biooxidation of the sulfide minerals in the ore is provided that is based on the empirical biooxidation rate constant for the ore, the project's financial discount rate, the ore grades of both refractory and non-refractory gold, and the gold price. Then, the economically optimum duration of bioheap pretreatment, t$, is determined from its logarithmic relation to the optimum fractional extent of ore biooxidation, F$, through the ore's biooxidation rate constant. In doing so, it is assumed that the ore is adequately crushed and amenable to bioheap pretreatment and that the cumulative oxidation of the ore with time is known from ore testing so that the rate constant can be determined.

Jan 1, 1995

By Boris M. Vorobjev

The paper in question discusses a wide range of topics on the coal mining environment in general and on computerized coal mine environment systems in particular. The emphasis is being made on methodological aspects of coal mine environment with reference to computerized monitoring systems Classification of computerized coal mine environment monitoring system is suggested by the author with specific reference to coal mining operations. Coal quality control system at all levels (coal face to regional levels) is also discussed briefly hereunder, since coal quality is one of the major factor for environmental management. An integrated coal mining economic and environmental management super-system is presented in this paper Review Of the UN/DTCD, UNDP European Regional project "Computerized Coal Mining Systems" is presented here. Conceptualization of a new European Regional project on Coal Mining Environment and Economic Management is also a topic discussed in the paper.

Jan 1, 1992

By DeVerle P. Harris

The structure of an exploration model reflects a number of design considerations, one of which is the question or issue-to be investigated by the model. Thus, a model designed to evaluate the magnitude of risk and its economic implication to optimal decision making at each decision juncture of a multistage exploration architecture differs considerably from one designed to evaluate, say, the long run average cost of discovery, in which the architecture of exploration is suppressed and risk is simply an element of average cost. The perspective of the model examined in this paper is that exploration is investment in (purchase of) information and that the next stage of an exploration program is undertaken only when the expected value of information to be acquired in that stage exceeds its cost. The degree to which this perspective is honored influences considerably model design. Consider two design objectives:

Jan 1, 1989

By Patrick M. James

Many in mining believe that the industry is slipping behind in public image, in public mineral education and, particularly, in mining's basic right to do business. It is critical to turn things around - to change the rules of the game soon - before mining loses any chance of recovery. In the industry's experience, there is a technique of project development and operation that can help gain ground on public opinion. Only recently has this technique had a name, and that is sustainable development. What is sustainable development? Sustainable development is broadly accepted and supported by the international business community. And significant thought and work has been devoted to the subject. Research into the topic was initially confusing because the definitions of sustainable development are written in terms the writer, and his or her constituency understands. To some, it refers to environmental protection. To others, it is about social responsibility. And to the developer, it is about economic benefit. Slowly a theme emerged from the research that seemed to be part of all the definitions. That theme has three parts. First, the development, whatever or wherever it is, must contribute economic value to the developer and the stakeholders of the development. Stakeholders in this context include employees, neighbors, residents of the surrounding area, citizens of the country, suppliers and all others affected by the development. Next, sustainable development must contribute environmental value. This means that at a very minimum it must be neutral and not cause irreparable damage. And last, and what is new for miners and most other businessmen, it must contribute real social value to the stakeholders. How to use the concept? With that three-part theme as a working definition, the mining industry must find ways to use that “the challenge is for an individual company to translate what sustainable development means for them. There is no one model..." Donald W. Gentry is president and chief executive officer of Polymet Mining and former professor emeritus of mining engineering at Colorado School of Mines. He added: "While simple to state, the concept is anything but simple to implement. Present trends indicate ... one wins the sustainable development argument by staking out the high ground early..." In other words, start using sustainable development principles at the beginning of the project. New ways of doing business The mining industry's challenge is to implement sus¬tainable development universally around the world. Paternalism as a way of doing business is dead and a new model of doing business is emerging. All types of businesses are learning to deal with the stakeholders of new developments. Mining cannot be an exception to these trends. To understand how the international mining business came to sustainable development, it is useful to look back a few years. For many North American mining engineers, there were few opportunities for foreign assignments from the 1960s to the 1980s. American companies had been asked to leave many of the Latin American countries. Africa was going through a continent-wide upheaval. The Soviet Union and China had Eastern Eu-

Jan 1, 2000

Introduction Surface mining is a business, and the objective of most businesses is to make as much money as possible within certain responsible constraints. Businesses normally measure their potential to make money by estimating the discounted cash flow rate of return on new projects or the net present value for ongoing projects. These estimators of profitability are calculated using the following well-known equation: [ ] where i is the year, n is the total number of years, A, is the after tax net cash generation in year I, r is the discount rate and NPV is the net present value. In its simplest form, when the value of r makes the NPV equal to zero, the discounted cash flow-rate of return (DCF-ROR) is defined. The maximum economically recoverable reserve is identified at the point where the NPV or DCF-ROR is at a maximum. Depending on the measure used (DCF-ROR or discount rate) for calculating the NPV, the definition of recoverable reserve will be different for exactly the same deposit. Maximization of the measure of profitability and the economically recoverable reserves should not be separated from the mining method and sequence of exploiting the reserve. The surface mining methods may involve multiple-pass development of the resource, mining to the ultimate limit in one pass or a combination of the two methods with backfill. Multiple-pass development When planning a multiple-pass mining operation, it is important to determine the width of pit expansions that are appropriate for a specific situation. Production personnel typically want wide, open work areas where operations can be set up to run at peak efficiency. While this is understandable, the trade-off between highly efficient production operations and an overinvestment in stripping should be carefully weighed. As long as safety is not compromised, a few cents per bank cubic yard increase in operating cost due to lower productivity by working in more confined spaces may well be offset by a decrease in the overall short-term stripping requirements. A mini study on productivity and cost should help quantify this cost before deciding on minimum phasing requirements. The bigger challenge associated with establishing smaller work areas is securing operations and management buy-in to marginally lower productivity when reporting results. When cost reduction is the important management goal and everyone is focusing on unit costs, one sometimes loses sight of the goal of total cost management and, even more importantly, maximum profitability. The first pit should be defined by the first grouping of recoverable mineral that has the highest after-tax unit value and forms a feasible mining unit. The assumed mining of the first pit should be followed by the assumed mining of the second most profitable practical pit or pit expansion. If this process of grouping and sequencing is followed until the profitability approaches zero, the general sequence required to extract the maximum economically recoverable reserve is identified. The curve in Fig. 1 is constructed for a rate of production, R, and a quality management strategy, Q, by calculating the NPV for a series of sequences, with each sequence assuming that the operations are terminated on successively lower profit pits. These values are plotted to form the curve in Fig. 1. If the operation ceases on a pit that has too high of a profit, opportunity is lost, and the NPV is lower than the maximum. The NPV curve peaks and starts to decline before the zero-profit pit is assumed mined. This occurs because the money invested in advanced stripping would have made more money invested at the discount rate than by mining the next pit expansion. Therefore, the maximum economically recoverable reserve is defined by the pit limit corresponding to the maximum NPV. There may be an opportunity to refine the definition of the "ultimate pit" around the maximum-value point. The precise definition of the ultimate pit early in the mine life may or may not be important today, depending on how far off in the future these limits will be reached. By the time an operation must decide on its last increment of economically recoverable reserve. much of the

Jan 1, 2000