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By J. L. Parks

Designs, installation procedures, and performance characteristics of martensitic cast steel concaves are reviewed. Longer wear life, fewer pieces to install, and eliminating the need to scarf joints are the principal benefits of using martensitic steel to replace austenitic 12% Mn (Hadfield's) steel, the traditional concave material for large gyratory crushers. Installation procedures that reduce the risk of breakage are described. Operating practices that affect concave performance are also discussed.

Jan 1, 1992

By Adrian C. Dorenfeld, John T. Oleksy

John D. Maefadyen Subject paper unfortunately has some serious flaws negating the usefulness of the paper. The authors claim that sulfur is the major source of production problems in cement kilns. This is not the case. Sulfur is not a problem as long as the mole ratio of sulfur to alkali oxides is less than, or equal to, 1. This is attributed to the sulfur preferentially combining with the alkali oxides and not acting as a clogging agent due to the nature of the pre-heater vessels. Where the mole ratio exceeds 1, many methods are available to eliminate or reduce the clogging problems such as using the preheater bypass or a precalciner with up to 100% kiln gas bypass. In non-preheater kilns, the presence of sulfates is hardly ever a problem anyhow. Thus, the level of sulfur in the fuel and raw material that might cause problems is not a fixed amount, but is predictable. The purpose of the paper is to discuss the economics of conversion of kilns in the Indonesian and Phillippine cement industries from oil firing to coal firing. This economic analysis has very little to do with the sulfur levels. Thus, the section of the paper on sulfates is actually rather meaningless. The economic analysis is also rather meaningless because the authors have failed to follow accepted economic analysis procedures by including interest charges. They have fallen into the trap of confusing financing with economic evaluation. When the accepted methods of economic evaluation are used, the return on investment increases to about 35%. In conclusion, the paper is not a meaningful contribution, and sadly, quite erroneous.

Jan 11, 1982

By B. A. Slaker, T. Miller, M. M. Murphy

An underground limestone mine in eastern Ohio was experiencing significant floor heave and roof falls, attributed to high horizontal stresses. Areas of the mine showing floor heave were monitored with roof-to-floor extensometers and photogrammetry surveys to determine the rate and magnitude of heave. Extensometer data were recorded hourly at four locations across adjacent entries while photogrammetry surveys of the floor were performed at the same locations every two to five weeks. A final survey was performed using an I-Site 8200 laser scanner. Following instrumentation, floor heave up to 10.1 cm (4 in.) was measured by the extensometers, photogrammetric reconstructions and laser scanner over a six-month period. The extensometers were biased by the location where they were placed, failing to consistently capture the location and extent of floor heave and cracking. The photogrammetry surveys were not precise enough to capture small magnitude movements. Mining in the area was halted and within several months the floor movement and incidence of roof falls were significantly lessened.

Jan 1, 2018

By Kevin D. Lofftus

This paper presents a dynamic model for column flotation. The model equations are normalized and the dimensionless groups that are directly responsible in determining the column flotation behavior are identified. The resulting model equations are incorporated for computer simulation. Numerical results from computer simulations are analyzed to gather information about design and operation of column flotation devices.

Jan 1, 1988

By V. Scovazzo

Cost-effective underground mine configurations have been designed in highly fractured rock masses where the stone possesses a high material strength. A limestone mine in the eastern United States is used to demonstrate procedures for the geotechnical design of one such operation. The mine discussed is located in both limbs and the axis of a recumbent fold that fractured the rock mass. In a highly fractured rock mass, where the host rock has high strength, a design can be developed to alleviate intact rock failure. This is possible because in most cases as the stress levels needed for intact failures are approached, the stresses are quickly dissipated due to movement along discontinuities, which represent planes of weakness. As a result most underground failures in highly fractured rock are due to sliding or toppling. Even when intact rock fails in a highly fractured rock mass, it is the movement along an existing joint or other weakness plane that often initiates or causes this failure. It is therefore important to obtain the characteristics of weakness planes that are the discontinuities within the mass. The required information on weakness planes, geology, and strength of materials is discussed and recommendations for obtaining this information are presented. A discussion is provided on failure modes and the use of developed information for their evaluation. The impact on geotechnical design is demonstrated through pillar sizing procedures; however, this approach can also be applied to mine roof and pillar foundations.

Jan 1, 2004

By Subash Chander, B. Arnold

Many developments have occurred in coal flotation with regard to increasing recovery from the flotation circuit and its impact on overall coal preparation plant recovery. This includes innovative design of flotation circuits, equipment modification and development, methods of enhancing the use of reagents, effect of slimes, and recognizing the effect of water chemistry. This paper will review recent advances and present some guidelines to improve process efficiency.

Jan 1, 2005

By J. J. Moore, I. Iwasaki, L. A. Lindeke

Correlation of scale-up from small-scale batch laboratory mills to large-diameter industrial mills was established by performing two series of laboratory and pilot plant grinding tests using a magnetic taconite ore and a siliceous sulfide ore. In one series, controlled batch grinding tests in 203-, 508-, and 914-mm (8-, 20-, and 36-in.) diameter mills were carried out followed by a second series involving continuous grinding tests using 305-mm (12-in.) and then 1067-mm (42-in.) diameter pilot plant ball mills in open circuits. The effects of ball diameter on wear and of mill diameter on grinding power and ball wear are illustrated.

Jan 1, 1988

By S. Simske, K. Boakye, D. Winters

The application of digitization to operations and logistics is commonplace. From advanced data analytics to intelligent networks, digitization offers tremendous opportunities to create value, raise the efficiency of production processes, and reduce emissions. Several manufacturing industries have already implemented solutions to good effect by using digitization. Mining companies, for example, are using historical data about equipment health to predict potential failures, while aeronautics and automotive companies are using robotics and end-to-end digital twins to improve their design and production processes. Not surprisingly, first adopters of digitization in many industries have gained an edge over their competition. The cement and aggregate industry can better manage the enormous energy consumption, rising cost challenges, inefficient uses of raw material, logistic problems, emissions, and overall process complexity that are inherent in their operations by doing the same. This paper presents the results of a literature review and analysis and conveys the challenges for adaptation and implementation of digitization and artificial intelligence (AI) in the cement and aggregate production industry.

Mar 2, 2022

By L. Bernoth, I. Firth, S. Rhodes, P. McAllister

As biotechnologies emerge from laboratories into main-stream application, the benefits they offer are judged against competing technologies and business criteria. Bioremediation technologies have passed this test and are now widely used for the remediation of contaminated soils and groundwaters. Bioremediation includes several distinct techniques that are used for the treatment of excavated soil and includes other techniques that are used for in situ applications. They play an important and growing role in the mining industry, for cost-effective waste management and site remediation. Most applications have been for petroleum contaminants, but advances continue to be made in the treatment of more difficult organic and inorganic species. This paper discusses the role of biotechnologies in remediation and pollution control from a mining-industry perspective. Several case studies are presented, including the land application of oily wastewater from maintenance workshops, the composting of hydrocarbon-contaminated soils and sludges, the bioventing of hydrocarbon solvents, the intrinsic bioremediation of diesel hydrocarbons, the biotreatment of cyanide in water from a gold mine, and the removal of manganese from acidic mine drainage.

Jan 1, 2000

By R. R. Dorfler

The existing regrind circuit at the Climax Operations uses sodium cyanide and Nokes reagent to reject pyrite, copper, and lead minerals. Laboratory flotation studies were performed using feed to flotation following first-stage regrinding. The effects of conditioning time, pH, and the concentration of depressants such as Nokes reagent and sodium cyanide on the rejection of pyrite, lead, and copper minerals were investigated. The metallurgical results indicate that, in the presence of depressants, the rejection of copper is strongly dependent on the pH. Preliminary mill testing confirmed the finding. The rejection of impurities is also dependent on conditioning time. The recovery of molybdenite is independent of the variables investigated.

Jan 1, 1981

By John L. Habberstad, Robert R. Thompson, George B. Wallace, Robert C. Bates

INTRODUCTION Rock bolts are one of the most common mine support systems in use today with approximately 90 to 95 million used annually in the nation's coal, metal and non-metal mines. By far the largest majority of these are steel bolts with mechanical expansion shell anchors. Many theories have been advanced to explain the ground control achieved through the use of rock bolts. Most of the theories are applicable to a specific set of circumstances, geology, geometry, rock properties and in-situ stresses. Examples are those which relate the beam building or strata-hanging theories of ground support used in the rectangular openings of a coal mine(l). In tunneling and most metal mining, either circular or horseshoe shaped openings are normally used. Here, bolts may be used to develop a radial stress around the opening, which adds stability to that opening, or merely pin blocks of rock back into more stable ground so that they cannot slip. In most cases, the bolts are torqued to a specified value to seat the anchor and to achieve the pre-load or tension that is desired. To be effective, however, this tension cannot be lost through bolt slippage or creep frequently caused by blasting, moisture attack or raveling of the rock surrounding the drill hole, etc. Furthermore, in soft rock or in oversized holes, sufficient anchorage cannot be achieved with the mechanical anchor, and in very brittle rock the concentration of forces produced by the expanding anchor might cause a crack to propagate from one drill hole to the next. Mechanically anchored bolts are also short lived in mines or tunnels having a corrosive seepage. The steel in these installations can fail

Jan 1, 1974

By Gabriel K. Nzulu, Lars Hultman, Per Eklund, Martin Magnuson, Abu Yaya, Prosper M. Nude, Hans Högberg

This study aims to identify individual elements and to gain an understanding of the surface reaction mechanisms, as well as the properties of precipitated pyrite particles observed during the hydrothermal formation of an ore deposit. A combination of X-ray diffraction (XRD), air annealing in a furnace, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), and X-ray photoelectron spectroscopy (XPS) was applied to investigate the crystal structure and identify the individual elements, permanence, transformation and chemical/electronic properties of such pyrite.

Jun 1, 2024

By Richard H. Sailors

Data from full scale marked ball tests are used to demonstrate the effects of abrasion, corrosion, and impact on overall wear rate. The predominate wear mechanism need be identified before the optimum alloy can be chosen for the grinding media. Use of high chromium grinding media often results in increased mill efficiency due to shape retention. Thus, a benefit from energy savings can result as well as a reduction in wear rate. Converting from steel to east high chromium grinding media requires close association and cooperation between producer and consumer in order to properly conduct these studies.

Jan 1, 1990

By Michael G. Nelson

A computer simulation of the automatic control of continuous mining machines has been prepared, similar to previous simulations of longwall mining systems and coal thickness sensors. The simulation allows for programmed variation of the horizon detection method, the azimuthal guidance system, the type and configuration of the miner, varying hardness in the unmined face material (leading to varying error in the machine heading), and the miner's cutting cycle. It simulates control of the miner in three axes. Use of the simulator makes it possible to anticipate problems arising from the complex character of underground mining, which include unpredictable multi-pass coupling and unpredictable variation in geological conditions.

Jan 1, 1993

By C. Widham

Introduction It is generally accepted as dogma that sampling contributes most of the error in gold fire assays. Differences in assay results on pulps from the same sample interval are frequently regarded as evidence of the presence of the so called "nugget effect" of relatively coarse gold particles. It is true that coarse gold particles can contribute to substantial sampling fluctuations. But, while the process of sampling is probably the major source of error, the analytical process cannot be completely ignored as a possible contributor to erratic assay results. To maintain a stable assay process, the analytic part of the system must also be kept in control. One method of monitoring the performance of the analytic system is to systematically assay standard materials, whose sampling characteristics are carefully controlled. Gold assay standards are not prepared, nor can they be prepared, to account for both sampling and analytical errors. It is not possible to send coarse material to a lab for both preparation (i.e., comminution and splitting) and fire assaying and then come to conclusions only about the fire-assay process. Because most gold ores are very heterogeneous, sampling errors would, in most cases, completely mask the contribution of the analytical errors. Assay-standard material is prepared only to assess the accuracy and variability in the fire assay process. Because the objective of the assay standard is to provide information about the fire assaying, it is necessary to control the sampling error of the standard material, so that it is only a minor constituent of the discrepancies observed in any assay results. To do this requires that the particle size of the standard material be reduced to a point where the relative standard deviation of the sampling error (i.e... the standard deviation of the errors divided by the average gold content of the material) is 2% or less. For all but very homogeneous mineralization, this means that the material must be reduced to 100% -150 mesh before the sampling errors are adequately controlled. However, even reducing the particle size can contribute to sampling problems. The liberation of gold may cause segregation that can cause large sampling fluctuations that are not easily controlled while maintaining the desired grade. Because, in most cases, the standard material would already be in the "pulp" state when it is submitted to a lab for assay, it is not possible to entirely conceal the nature of the sample from the lab. This is a problem inherent in using assay standard material. Because of the contribution of sampling to error generation in the assay process, the use of "coarse" material does not solve the problem of submitting a totally "blind" standard to the lab. In the sections that follow, the selection, preparation, testing and use of gold fire assay standard material is discussed. While some may dismiss the production of standard material as folly, it is possible to produce and utilize standard material to stabilize and improve the fire-assay process to produce more reliable assay results. Material selection It is desirable to use material that has as nearly the same metallurgical characteristics as the samples with which the standards will be included. However, this is usually difficult. For many reasons, including the particle size at which a significant amount of the gold mineral is liberated, the sampling characteristics of even -150-mesh material may preclude the use of geologically and metallurgically similar ore as a standard. It is usually easier to get material having desirable grade characteristics with the necessary sampling properties than it is to find geologically and metallurgically similar material with the required sampling characteristics. High-grade standards are especially difficult to find and prepare. This is because, as grade increases, the size of the gold particles usually increases. Larger gold particles are liberated and tend to segregate during comminution, and the homogeneity of the material cannot be maintained. For grades much above 3 g/t (0.088 oz/ton), it is very difficult to find material that has the proper sampling properties. Old mill tailings are likely candidates for assay standards. Some of these have sufficiently homogeneous mineral contents, so that the sampling errors can be effectively controlled. Where mill tailings are either not available or are not acceptable, mineralization that has exhibited homogeneous results in reassays of the pulp material is also a good candidate for the standard. Finally, the mineralized rock being sampled may (and should) be used if adequate homogeneity in the -150mesh material exists. "Adequate" ("acceptable") homogeneity is defined below.) It is important to use standards having a wide range of grades. This alone may preclude the material being

Jan 1, 1997

By Michael Francis, Chris Darton

More than 55 km of tunnels have been constructed by TBM in the last 12 years to refurbish and upgrade the high voltage cable network in London. These include a tunnel of 20km length using EPBM machines in both clay and granular soils. Route selection was made with reference to subsurface structures, existing ground conditions, using suitable shaft locations addressing environmental concerns. The complex interfaces to manage included obtaining of consents to the coordination of multiple suppliers. The paper describes how all these challenges have been met successfully and how technology has been employed to provide for safe construction and operation in the congested urban environment.

Jan 1, 2003

By A. J. Basu

Rock mass properties testing for determining strength parameters is an integral part of geomechanics. These tests are performed either in a laboratory environment or in a field (in-situ). The authors share their experience in using numerical modelling in simulating the laboratory test procedures. This approach helps studying the rock breakage and failure mechanism more efficiently and provides a high degree of visualization. Moreover, imperfections and discontinuities can be easily incorporated in these models. This capability of providing arbitrary fractures and discontinuities facilitates in building a large knowledgebase of rock strength and failure mechanisms. This knowledgebase may then be used to generate heuristics for determining rock strengths for rock mass with fractures and discontinuities.

Jan 1, 1997

By W. Hopkin

INTRODUCTION Necessary science and technology are not well established for the design of responsible treatment and disposal of arsenical residues from refractory gold ores. Specifically, there is uncertainty about the precise composition and behaviour of oxidised arsenic species in these wastes, and an analysis of possible chemical behaviour suggests that potentially difficult control and disposal problems remain to be so 1 ved. In tackling these the undoubted toxicity of arsenic in excess and its bad press should not blind one to the realities of actual behaviour in the environment, and that some adverse behaviour inevitably has to be to 1 erated as a cost in return for the recovery of an operation's gold for society. The problem is to minimise any such cost. Each refractory ore will be different. Many will contain so little arsenic that it will cause only trivial problems in disposal, but there remain others with significant arsenic content, say in the order of 1% or more, to cause concern. As already implied, concern can be over emphasised but equally underestimated. The balance which must be struck in the design of responsible disposal in the widest sense requires objective and practical assessment of a complex range of chemical, biochemical, engineering and economic design factors, all of which should involve the process design team in constructive dialogue with the 1 oca l regulatory authorities. In British terms, the general objective should be the Best Practicable Environmental Option. Arsenic is ubiquitous in waters, rocks and soils and all living things. Its compounds undergo natural geochemical and bi ochemi cal cycles including powerful adsorption and precipitation processes which return to nature all leakage from the inevitable disturbance of mining and extraction operations. Within limits, all life is tolerant to its presence, and adaptation and detoxication processes occur to deal with local excesses.

Jan 1, 1991

By Efstratios Karampinos, John Hadjigeorgiou, Philippe Morissette

"Ground support is a critical element in maintaining the stability of mining drives in deep and high stress mines. In challenging ground conditions, it is necessary to continuously explore ground support strategies that can control the resulting large deformations. It is an objective of mining operations to optimize the ground support by selecting appropriate systems at the time of installation of each reinforcement element. A successful ground support strategy will result in the use of a system that ensures both the structural and operational integrity of the excavations and mitigates the need for rehabilitation.Preliminary ground support design is often based on empirical observations and methods. Once a design is implemented, field trials, observations and in situ pull tests are used to fine tune or improve the design. Although not often employed during this process, numerical modelling can provide helpful insights into the impact of different ground support strategies. In this respect, it is possible to explore the use of multiple options before selecting the most promising ground support system for implementation in field trials. The challenges associated with the numerical modelling of rock support for mines have been described by Lorig and Varona (2013) and Potvin (2017). The employed numerical models should capture all potential failure modes of reinforcement throughout the mining sequence of the excavation. In particular, it is important to emulate the observed in situ ground support performance, as well as the influence of the installation sequence of the support. However, the time and expertise required for this type of modelling of ground support is often not available at mine sites. Even when the expertise is available, it requires a major time commitment and commitment of resources to set up, run and calibrate the sophisticated models capable of explicitly capturing the behavior of ground support.Rock reinforcement is an integral part of all ground support systems used in underground mines. Long, flexible tendons can reinforce the rock mass deeper into the walls and create a thicker reinforced shell around the underground excavation. This article focuses on the optimization of the cable-bolting strategy in squeezing conditions at the LaRonde Mine in Quebec, Canada by integrating the 3D distinct element method (DEM) in the design process. A calibrated numerical model is used to investigate a series of cable bolt configurations and provide recommendations for the ground support design."

Jan 4, 2018

By Dan G. Wasyluk, Meryl J. Klassen, Tony J. Morris, Clive H. MacKay

The Rogers Pass Project in British Columbia has involved the construction of two railway tunnels totalling 16.6 km and a 345 m deep shaft. Systematic geological mapping was carried out at four headings during construction. The paper discusses the procedures used to record the geology, structure, rock mass characteristics and excavation performance. Coded data from the geological mapping and shift inspector reports was entered into a computer data base. The rock mass quality was evaluated for both the Geomechanics and Q classification systems. Continuous computer generated graphic logs were produced showing the excavated perimeter map, geological parameters, installed support and construction activities. The tunnel logs were updated on daily basis and used during construction by project staff for evaluating support requirements and monitoring excavation progress. The specific requirements, difficulties and advantages in mapping tunnels using a computer based system are compared to those of a conventionally mapped tunnel excavation with hand drafted tunnel logs.

Jan 1, 1987