Search Documents

By David A. Campbell

There has been a long history of ironmaking on the North East coast of England centered around the River Tees. The industry developed here because of the availability of good coking coals to the North in Co. Durham, and the discovery in 1851 of ironstone in the nearby Cleveland Hills, South of the .River. Cleveland ironstone is relatively poor in quality, with an iron content not exceeding h% and high proportion of sulphur and phosphorous. The iron exists in chemical association with alumina and silica, and physical beneficiation processes involve a serious loss in iron unless the upgrading is limited, when the economics of the process become doubtful. Over the years, richer foreign ores have replaced the local ironstone, and the last operating mine was closed in 1964.

Jan 1, 1982

Conflicting claims and views on the priming of ammonium nitrate/fuel oil (ANFO) are reviewed; certain fallacies and misconceptions are rectified. Optimum priming systems for a range of blasthole conditions are indicated. Moves towards optimum priming lead to reductions in the combined cost of drilling, blasting and handling the material. With shallow blastholes, two-point priming is rarely warranted. Best blasting results from single priming are usually obtained when the primer is located near, but not at, the bottom of the blasthole. As blast- hole depth increases, two-point priming becomes more reliable and effective than single priming. For two-point priming, primers should be located such that detonation waves in the ANFO collide at grade level or, if preferred, within a hard band in the burden. Where blastholes are very deep and/or strata variations can be appreciable, three or more spaced primers are often justified. The effectiveness of a primer varies with its detonation pressure, diameter and length. Primer properties influence the velocity of detonation (VOD) near the primer, but do not affect the final (steady-state) VOD in the ANFO. Some primers cause 'run-up' (i.e. lower than steady-state) velocities whereas others cause

Jan 1, 1974

By Ross Glanville

The Optimum Production Rate (OPR) is one of the most important parameters in the evaluation of a mineral deposit. The OPR cam also be expressed as the Optimum Mime Life (OML) in years since the expected mime life is determined by dividing the OPR per year into the estimated ore reserves. Unfortunately, very little time and effort has been directed towards the determination of the OPR. Instead, "rules of thumb" are often applied to select a mime life without due consideration of the economic implications of such a selection. A "justification" for a particular production rate is often based on a pre-conceived arbitrary requirement for a mime life of 5, 10, or 15 years, for example. In this paper it is demonstrated that such arbitrary selections for high-grade/low¬-tonnage mines (such as many underground gold/silver deposits) often lead to sub¬optimal results. In fact, am apparently uneconomic deposit at am arbitrary production rate may be economic at the OPR. Consequently, investment opportunities may be overlooked if one analyzes mime' properties based on arbitrary production rates.

Jan 1, 1984

By Norman D. Fitz, Gerald

BOTH physical and economic factors are concerned in determining the optimum rate of depletion of a mineral deposit. The physical limitations are, in a large measure fixed by nature. Economic influences on the other hand, are man-made and subject to wide changes. Analyses of the interrelations of these two groups of factors are of major importance in selecting the optimum rate of production of petroleum and mining properties and in their valuation. Physical Influences PRIMARY limitations on the rate of mining are the rate of shaft sinking and underground development, the rate of hoisting, and the rate of sloping. These rates are largely determined by the physical features of a property. Technical methods which may be employed, and consequently the length of time required, are governed by the dimensions of the deposit, its attitude, depth, regularity, the unit value and character of the ore, the nature of the wall rocks, and similar factors.

Jan 1, 1938

By Prashanta K. Chatterjee

The planning of an underground coal mine requires a complex blend of technical expertise, experience and subjective design criteria implemented by the mining engineer. Currently the procedure is largely manual and requires considerable resources to generate a single mine plan. Often three or four people are assigned to work in the development of a single draft layout. Evaluation of the layouts is also tedious as it requires many repetitive calculations. The evaluation of layouts developed manually generally attempts to derive a single economically feasible solution. Operational constraints in underground coal mining such as manpower, time, equipment, etc, do not allow the generations of more than one alternative layout. As a result, the first plan is generally the only one considered. Computer-aided mine planning can automate many of the manual procedures and calculations involved in mine planning thus allowing to evaluate many layouts and mining strategies and to select the optimum plan with confidence. An optimized planning procedure will also provide the capability to evaluate mine performance continuously and critically, thereby helping to maximize return on investment.

Jan 1, 1986

By Ben L. Seegmiller

How to obtain optimum slope angles for future open pit mines using the rock mechanics approach is the subject of this paper. In the past ten years significant developments in open pit rock mechanics have come about. This has been due to the mining industry's need for the steepest, yet safe, pit slope angles attainable. Requirements for economically achieving slope stability and the actual payoff that may be achieved through stability studies have been previously discussed', by stability engineers. While the emphasis has generally been placed on the concept of "stable slopes" in the past, it is suggested that emphasis now be placed on "optimum slopes" or "optimum slope angles". A definition of an optimum slope angle is one which (1) is as steep as possible and practical from orebody and mining constraint standpoints and yet, (2) maintains the accepted standard of safety defined by a safety factor against failure and/or a probability of failure. In other words, the emphasis is placed on achieving practical stability results as defined by safety and economic considerations, as opposed to simply achieving stability. The essential purposes of this paper are to (1) outline the need for optimum slope angles, (2) discuss the procedures for using the rock mechanics approach in slope angle design for a future open pit and (3) specify the end results that may be achieved by using such an approach. While the basic concepts and recommendations outlined in this paper may be equally applicable to soil as well as rock slopes, the emphasis and procedures have been directed at rock slope angle design.

Jan 1, 1976

By W. A. Hodgson

"In order to be able to map the variation in the concentration of elements in soils, it is necessary to sample at intervals that will give adequate coverage of the area and will allow determination of the rate of fluctuation of concentration with distance in any environment. This rate of fluctuation with distance can be referred to as the continuity of concentration.The continuity of concentration in soils varies according to the chemical characteristics of the element being considered, the underlying rock type or orebody and in response to the dispersion processes that operated during soil formation. Within any environment there is a maximum distance between sampling points within which adjacent sample values are related. This distance, the critical sampling interval, can be determined by means of a correlograrm.Where the sampling grid has been chosen to provide an adequate coverage over unmineralized rock, adjacent samples being related, anomalies may be missed if the element continuity in the anomaly is less than in the background. Results show that a knowledge of the critical sampling interval of the environment being examined may used to select a more efficient sampling pattern for a geochemical survey."

Jan 1, 2014

By L. M. Dwarkin

Strip mining in Western Canada, though of considerable importance, is a fairly recent development for many of the operators in the district. Adding to the difficulty of unfamiliarity is the fact that a great deal of the stripping is done on pitching seams, for which the engineering and economic principles of setting the most advantageous strip ratio are not readily apparent. The novelty of the operation combined with the complexity of the principles involved can easily lead to misconceptions as to the determination of the economic ratio. Definition of Strip Ration There are two commonly accepted meanings of the term strip ratio: (1) The ratio of feet of overburden to be stripped per foot of coal recoverable. (2) The ratio of cubic yards of overburden per cubic yard or ton of coal. The first definition is inapplicable to pitching seams so, throughout this paper, strip ratio will be taken as the ratio of cubic yards of overburden to be removed per cubic yard of coal recoverable. Economic Ratio In the case of flat seams, the strip ratio is fixed by existing natural conditions, and the magnitude of this ratio determines whether stripping is economically feasible. With pitching seams, however, the strip ratio is a variable. On the outcrop, there is usually some coal which can be obtained with little or no stripping. As the work is carried down the pitch of the coal seam, the proportion of overburden continually increases until a point is reached where it is no longer economical to continue the operation. The question immediately arises as to the location of this point, and this resolves into the problem of determining the most favourable strip ratio, or, to use the accepted term, the economic ratio.

Jan 1, 1949

By Fengyu Ren, Ruslan Puscasu, Kunpeng Yu, Gideon Chitombo, Liangliang Kang

Weak rock mass and poor flow of material can cause excessive ore loss and dilution in sublevel caving. This paper proposes a method to establish design parameters for an inclined deposit within a weak rock mass and evaluates its effectiveness through a case study. In order to solve the problem of low production capacity and poor safety conditions of sublevel caving mining at the Yingfangzi silver mine in China and to ensure a smooth production from the refractory ore body, it is necessary to select appropriate stope structure parameters. Based on random medium theory of gravity flow and the improved equation of ore discharge in random medium, an end wall drawing experiment is carried out to determine the optimum design and flow parameters. It was observed from the experiment that, due to the influence of the randomness of particle movement, there is a mismatch in the flow parameter measurement. The flow characteristics and distribution of the marker particles are different from that of the tested particles resulting in large drawbody shape distortion. The study finds that the flow parameters obtained by the new method are more practical and account for drawpoint width and recommends that the new method for determining the sublevel stope height is used when the drawbody is a non-standard ellipsoid. The outcomes have shown a significant reduction in the dilution and improvement in the recovery rates, and the safety and efficiency of mining have been greatly improved.

By Fengyu Ren, Ruslan Puscasu, Kunpeng Yu, Gideon Chitombo, Liangliang Kang

Weak rock mass and poor flow of material can cause excessive ore loss and dilution in sublevel caving. This paper proposes a method to establish design parameters for an inclined deposit within a weak rock mass and evaluates its effectiveness through a case study. In order to solve the problem of low production capacity and poor safety conditions of sublevel caving mining at the Yingfangzi silver mine in China and to ensure a smooth production from the refractory ore body, it is necessary to select appropriate stope structure parameters. Based on random medium theory of gravity flow and the improved equation of ore discharge in random medium, an end wall drawing experiment is carried out to determine the optimum design and flow parameters. It was observed from the experiment that, due to the influence of the randomness of particle movement, there is a mismatch in the flow parameter measurement. The flow characteristics and distribution of the marker particles are different from that of the tested particles resulting in large drawbody shape distortion. The study finds that the flow parameters obtained by the new method are more practical and account for drawpoint width and recommends that the new method for determining the sublevel stope height is used when the drawbody is a non-standard ellipsoid. The outcomes have shown a significant reduction in the dilution and improvement in the recovery rates, and the safety and efficiency of mining have been greatly improved.

By P. R. Jochens

It is interesting to note that, when the Technical Programme Committee-Mining first decided on this particular topic for a colloquium, the proposed title was different in that it used the words 'rising price of gold'. The very fact that the title was reworded to use the words 'fluctuating gold price' highlights the problem that faces the South African gold-mining industry.

Jan 1, 1981

By Scott K. Palm, Neil D. Pearson, Jr. Read

"Uncertainty is an important feature of many investments, but it is especially important for mineral properties. Mine properties often entail large investments and fixed commitments. Managers in the mining industry often view price uncertainty as undesirable, due to the possibility that the price of the mined commodity will fall to a level that prevents the firm from recovering its investment and fixed costs. This paper identifies pitfalls in conventional valuation methods and outlines a new approach to valuation based on option pricing theory and dynamic programming. In the process, it identifies generic strategies for organizing mine production in ways that allow the owner to benefit from the uncertainty in mineral prices. IntroductionRisk is pervasive in the mining industry. The operation and maintenance of a mine may involve high, and unavoidable, fixed costs. A mine owner can only begin to recover these fixed costs if the price of the mined commodity is greater than the incremental cost of production. But the prices of many minerals are extremely volatile. The price volatility of copper has been significantly higher than the price volatility of a typical stock, for example. A mine owner cannot be sure that the price of the mineral product will remain high long enough for the firm to recover its capital and fixed costs.Mine owners are able to minimize their losses during periods when the output price is below the incremental cost of production by temporarily closing operations. During these periods they incur only fixed costs. While shut-downs help minimize losses, the y do not help the firm recover its initial investment. If output prices remain low long enough, the fixed costs and original investment may never be recovered. High fixed costs, therefore, lead to substantial downside risk."

Jan 1, 1986

"Option pricing is used in finance for valuing options to buy (or sell) shares at some future date because it provides a convenient framework for quantifying values subject to uncertainty. As one of the main sources of uncertainty in mining is the price (sales) of the metal, this approach can also be used for valuing mining projects.The first part of this paper reviews options and option pricing; the second part presents the approach developed by Brennan and Schwartz (1985) for using option pricing to value natural resources. Several applications of this methodology have been published; these are described. From a mining point of view, the assumptions made by Brennan and Schwartz are too simplistic. The weaknesses are discussed with a view to improving an apparently promising new way of assessing the value of projects. IntroductionThe collapse of the British merchant banking group, Barings, has highlighted the risks that can be incurred by speculators and arbitragers in the futures and options markets. But this negative attention on futures and options should not make us forget their positive aspects. They can provide producers and consumers of metals with more predictable sales prices. The introduction of the new traded average price options, TAPOS, by the London Metal Exchange in January 1997 is a response to this need. Equally important, the theory that the finance industry has developed for valuing options provides an interesting framework for valuing mineral projects as well. While this paper was being revised, the South African gold mining house, JCI, announced that it was using a methodology based on option pricing for valuing the mineral rights to deeplevel gold resources (see Box 1)."

Jan 1, 1997

During the construction of storage caverns, and during their lifetime if the use to which they are put so requires, it is necessary to provide adequate ventilation to ensure the safety and comfort of the underground workforce. An analysis of likely contaminants during construction has indicated that where a large facility is situated in a rock mass of even moderate temperature climatic conditions are likely to be the limiting factor during most of the mining operation and atmospheric pollution when blasting is undertaken. Possible options for improvement are increased air flow, cooling of intake air and reduction of the heat source by altering the number and type of haulage units employed in the cavern. Local solutions are an alternative approach where heat problems are confined to a few specific locations

Aug 1, 1994

By M. A. A. de Klaver

Functional Description Figure 1 is a typical flowsheet for a system for solid fuel addition to filter cake. Solid fuel, coal, coal breeze, or charcoal, is fed from a,stockpile to a surge hopper. The solid fuel is metered into a grinding mill. The fuel is dried and ground in a grinding mill. The on-size particles are removed from the mill by air sweeping. The ground solid fuel is separated from the air stream by a cyclone and stored in a surge hopper. The ground solid fuel is then pneumatically conveyed to a small hopper in the balling area. The fuel is proportioned into the filter cake just prior to mixing. An efficient mixer is very important to have a successful operation. The exact flowsheet would depend on a number of factors including what fuel is used, how the fuel is received, and the cnaracteristics of the fuel as received. Availability of floor space in the plant may also affect the flowsheet. For example, drying air may be supplied from the pellet furnace if the grinding mill can be located near the grate, or the pneumatic conveying system and a surge hopper may be eliminated by placing the grinding mill adjacent .to the mixing area. Also, for a multiple line plant, a ball mill rather than a roller mill may be more suitable.

Jan 1, 1980

By Jack Thibodeau

During the past six years, most states have promulgated water quality regulations which contain numerical aquatic life standards for heavy metals. In addition, the Environmental Protection Agency (EPA) promulgated national water quality standards in 1992 which also include numerical aquatic life criteria for heavy metals. Numerous wastewater discharge permits have been issued by the states and EPA to industrial facilities which include low microgram per liter heavy metal limitations. In many instances, the limitations are below detection limits or treatability limits using state-of-the-art analytical methods or treatment technologies. This paper will discuss options for conducting studies, including the use of water-effect ratios, metal partitioning coefficients, and recalculation procedures to develop site-specific metals criteria and higher permit limitations. The installation of expensive metal treatment systems to remove trace metals may be avoided if higher permit limits are indicated by the site-specific studies.

Jan 1, 1996

By H Lehtonen, H Mansikkaviita

In primary copper smelters, the received copper concentrate and other materials contain a certain amount of moisture, ranging from six to 14 per cent. Moisture in wet concentrate has a negative effect on the performance of the smelting furnaces when it is fed directly to the furnaces, namely increasing the energy consumption and the off-gas flow. There are several drying technologies available for drying copper concentrate, varying from direct heated rotary dryers and flash dryers to indirect heated steam dryers. Application of steam dryers has changed the drying process for copper smelters. Produced from a waste heat boiler, steam as heating medium enables plant-wide heat utilisation. Fossil fuel used from outside sources to remove water is no longer required and the combustion chamber is not required. In addition special attention has been paid to overcome the known problems of pollution emissions, excessive wear, clogging and frequent maintenance. The Kumera steam dryer is featured with many advantages based on principal improvements in reducing tube element wear and increasing drying efficiency. Thus, it has been considered as the first choice for those smelters where steam is available.

Jan 1, 2006

By Damian Connelly

The option to leach iron from low grade copper concentrates could reduce transport costs and significantly improve the saleability of the concentrate. In addition, it reduces smelting costs and can remove undesirable impurities. The trend to produce cleaner and higher grade copper concentrates is very appealing to the smelters. A recent copper project came on line and there were three serious deficiencies which were not identified in the feasibility study. This came as a surprise and resulted in a number of projects to investigate ways of rectifying the problems in the shortest timeframe possible and using minimal new capital. The first serious issued not identified when commissioning was the lower than expected copper recovery, which was 70% compared to a predicted recovery of 80% to 87% in the feasibility study. This required investigating new flotation reagents and incorporating controlled potential sulphidisation. The second serious issue overlooked is the presence of significant amounts of talc minerals (insol) in the ore which are naturally floatable. This leads to lower concentrate grade and attempts to remove the talc resulted in lower copper recovery. Smelters have limits on the amount of talc in concentrate because it produces viscous slags and difficulties for the smelter. It also incurs higher transport costs. The third serious issue not identified in the feasibility study was the high arsenic reporting to the concentrate. Arsenic is a penalty element for smelters and at levels exceeding 0.3% the smelters may reject the concentrate. Arsenic is a problem environmentally for copper smelters and penalties apply when it is high. This paper describes the options for penalty element removal and suitability to incorporate into the modified flowsheet. It also highlights where the geometallurgy was not properly addressed and how these surprises could have been avoided. INTRODUCTION From 1970 to 1985, a copper company undertook metallurgical testwork on the Peruvian project copper ore. The ores were mined underground and treated over many years previously. Various other groups undertook studies and work until Aker Kvaerner undertook a feasibility study in 2006. Three ore composites were tested and grind-recovery relationships were developed. The feasibility study testwork identified that talc was a possible concern and will have an impact on copper concentrate grade. This was to be managed by blending. The current operating reality is that there is so much talc in the ore body it is not possible to blend it out. There was far more emphasis on molybdenum recovery. No mention was made of arsenic issues other than blending. There was a Concentrate Leach Study and a Molybdenum Hydrometallurgical Plant Study but these options did not proceed to a final flowsheet. A Scoping Study in 2006 looked at a Heap Leach project. The heap leaching gave very poor copper recovery on the sulphide ore. Heap Leaching was evaluated and tested for the high talc and high arsenic ore but recoveries were poor. The Aker Kvaerner feasibility study opted for a simple primary crush SAG/ball grind followed by flotation and sale of a concentrate. This is the current flowsheet utilised and the scale of the project is very large based on processing 117,200 tonnes of ore per day. A feasibility study does not guarantee success and the deviations from the feasibility study suggest there is a lot of technical work required to improve the current metallurgical performance.

Jan 1, 2019

By John R. Goode

"This paper reviews options for the separation of a mixture of rare earth elements (REE) into its component elements. Earlier separations used selective chemistry such as double salt precipitation and reductive/oxidative processes – methods that still have a place in the industry. Fractional crystallization was developed for more complete separations of adjacent REE. The latter method was replaced by ion exchange (IX), which was in turn replaced by solvent extraction (SX). Two main SX chemistries are in use, solvation and cation exchangers, with several variants (mixed solvents, ionic liquids, etc.) now under investigation. SX plant configurations have evolved including advanced techniques like “hyperlinking”, novel saponification methods, and alternative stripping techniques. The classic mixer-settler is the most commonly employed device although centrifugal contactors have been pilot-tested. Non-dispersive SX options including microfluidic devices and membrane-assisted SX techniques are being developed and could revolutionize the SX option. Other REE separation techniques now being studied include Molecular Recognition Technology (MRT), Free Flow Electrophoresis (FFE), newer IX systems, and electrolytic processes. Additionally, the classical crystallization and selective precipitation methods and newer bacteria-mediated processes, chloride volatilization, high performance liquid chromatography, and magnetic separation systems have been studied. This paper reviews the options and concludes that conventional SX is the technology of choice but viable alternatives could be demonstrated and acceptable within a couple of years.INTRODUCTIONThe chemical properties of the individual REE are very similar which is why REE minerals and ore deposits almost invariably contain a mixture of all fifteen REE, i.e., La to Lu plus Y. That said, the distribution of REE in a given deposit is frequently dominated by the light REE (LREE, i.e., La to Nd). Examples include the Bayan Obo, Mianning, Lynas Mt. Weld, and Molycorp Mountain Pass deposits where heavy REE (HREE – Sm to Lu and Y) typically account for well under 5% of the REE content. The LREE operations produce some HREE but the main sources of these important elements are the ionic clay deposits of Southern China. Importantly, all of the REE recovery operations referenced above, except for cerianite-bearing ionic clay deposits, initially produce a mixed REE precipitate or calcine with a REE distribution similar to that in the ore (Goode, 2016). However, the consumers of the REE, the manufacturers of magnets, phosphors, catalysts, optical glass, etc., require separated products with purities generally ranging from 99% to as high as 99.9999% depending on the element in question and the end use. Hence there is a need to separate the individual REE one from the other. This paper is intended to review the options."

Jan 1, 2016

By Markus Papst, Denise Millier, Daniel Beckers, Axel Preusse

"At an open-pit lignite extraction mine in Germany, groundwater has to be pumped over a large area, which leads to subsidence at the surface. As long as the geology of the area of influence is homogeneous, the subsidence is uniform and has marginal influence on buildings.Since the geology of many regions is characterized by faults, there are different rates of subsidence along those faults, which can lead to considerable consequences. Those different rates of subsidence on both sides of a geological fault are associated with the structure of the geology and soil mechanical properties. Horizons with various thicknesses and types of soil are affected differently by the groundwater pumping because of the offset of the faults, and thus react dissimilarly to dewatering.The smaller the grain of the geological horizon, the stronger the chance of shrinking, which leads to a stronger effect at the surface; therefore, dewatering impacts on clayey soil are different to those on sand and gravel. Regions consisting of meadows with turf inclusions are endangered as well; compared to the surrounding geology, those areas react in an entirely different way to water removal, which leads to immense differences in subsidence.The differences in area and respective subsidence impacts, as well as if it is possible to localize those areas, is an issue which needs to be analyzed. Furthermore, detailed mapping can help in the development of future forecasts about those subsidence differences and can also help with monitoring geological faults. In the context of subsurface spatial planning, this mapping has to be kept under review medium- to long-term.INTRODUCTIONThe utilization of underground mining is of increasing significance and of high interest, both for the common good and for future generations. For decades, humanity has been extracting resources from the subsurface, and salt, coal, lignite and water - just to mention a few resources - have been extracted from underground (Sailer, 2013)."

Jan 1, 2016