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By Z. Trojanová

Mg micropowders generated by gas atomisation of a magnesium melt with argon were mixed and ball milled with ceramic nanoparticles prepared by laser-induced gas phase reaction. The materials were then hot extruded. Specimens were deformed in tensile as well as compression tests at temperatures between 20 and 300 °C at a constant initial strain rate. The flow stress is significantly influenced by the test temperature. The yield stress decreases with temperature. This decrease and the flat character of the stressstrain curves at elevated temperatures indicate possible contributions of softening processes. The materials studied exhibit high-damping characteristics. The results are analysed and possible mechanisms are discussed.

Jan 1, 2006

By Janos de Warga

"After a short introduction to the history of the semi-conductor theory, the paper describes the principles of electron and hole flow in the semiconducting materials, the operation of the PN junction, and the rectification process in multi-layer devices (diodes and SCR's). The various methods of purification and zone-refining of the silicon are illustrated prior to the discussion on the most commonly used junction-forming processes (alloying, diffusing, etc.). Modern device fabrication and packaging operations are illustrated. Factory testing, evaluation, electrical parameters and guaranteed rating characteristics are listed. It is explained in this paper how the various device parameters affect the electrical performance of the finished unit and how the finished unit characteristics (turn-on, turn-off time, etc.) will influence the equipment rating. In concluding, some typical items of equipment are highlighted, and the applications of these semiconductor rectifiers in the chemical, mining, pulp and paper, and steel industries, etc., are dealt with."

Jan 1, 1967

By J. Pepin

When using alternating current submerged arc welding (SAW) to produce pipes from microalloyed linepipe steels, it is critical to balance penetration depth and deposition rates, in order to minimize the number of weld passes while still maintaining good heat affected zone (HAZ) microstructures and properties. A series of bead-on-plate (BOP) submerged arc welds were performed on X70 steel, using different waveform variable settings (i.e., balance, offset and frequency). Weld bead cross-section profile deposition and penetration areas were measured, and both Vickers hardness and Charpy V-notch impact testing were performed. Both single electrode and tandem electrode welds were evaluated.

Jan 1, 2011

By J. A. C. Ross

Introduction To enlighten those who may be wondering where anyone could find sufficient data to write a paper on underground concrete work, the author would like to explain that, at Copper Mountain, we have found it necessary to line numerous headings with a layer of concrete in order to keep them in a safe and serviceable condition. The majority of these headings are scram drifts and ore-pass raises. This paper will therefore deal, in the main, with the methods of and reasons for placing concrete in these headings. During recent years, radical changes have been made in the methods of mining ore at the Copper Mountain mine. After considerable experimenting, a mining system has been developed making use of diamond drills for primary breaking and transfering such broken ore through scram drifts with slusher hoists. With the advent of scram drifts, it soon became apparent that some substantial means of reinforcement and protection for the scram drifts themselves would be necessary. Since the orebodies in this mine are cut by numerous dykes or faults, and often both, it was anticipated that some means of support would be required where headings necessarily passed through these incompetent zones. Further, as experience was gained, scram drifts were driven into pillars and in close proximity to old workings so as to recover the maximum amount of ore. In such places, the ground is often severely fractured, either as a result of previous mining or from the effect of excessive rock pressures.

Jan 1, 1950

By T. H. Patching, D. F. Coates

The Sub-Committee on Rock Classification, Canadian Advisory Committee on Rock Mechanics, has evolved a classification of rocks which should prove useful in studies of rock mechanics. Considered in two stages -actual rock substance and rock mass -the five-point classification involves the geological name of the rock, the rock strength and rock deformation, and, in the second stage, the gross homogeneity of the rock mass and the formation continuity.

Jan 1, 1968

By M. H. Cullender

THE determination of the flow characteristics of gas wells depends upon the analysis of pressure data obtained under shut-in conditions and under one or more known flow conditions. These data are commonly referred to as back-pres-sure test data, and I know you are all familiar with the back-pressure equation where, Q rate of flow, Mcfd @ standard conditions C coefficient of the back-pres-sure curve P 1 formation pressure, psia P • sand face flowing pressure, psia P2 (psia)2/1000 n exponent of the back-pres-sure curve Figure 1 is a graphical presentation of the back-pressure equation; the coefficient is the rate of flow at a difference in squared pressures of 1, in this case 2250 Mcfd, and the exponent defines the manner in which the rate of flow changes with a change in the difference in squared pressures. In Figure 1, the exponent of the back-pressure curve is 0.554 which means that for a 10-fold change in the difference in squared pressures, there will be a 3.58-fold (10 raised to the 0.554 power) change in the rate of flow.

Jan 1, 1961

By W. Dong

This paper presents the fundamental study of the temperature distribution in a reforming planar solid oxide fuel cell (SOFC) using mathematical modeling and experimental testing approaches at Versa Power Systems (VPS). In order to investigate the on-cell temperature distribution under high rates of Natural Gas direct internal reforming (DIR), both the computer simulation approach and the experimental testing approach have been developed. In this work, comprehensive in-house DIR and SOFC models were developed and employed for the computational fluid dynamics (CFD) based 3D computer simulation. The current SOFC module has been corrected to take into account both the on-cell electrical leaking effect and the stack stage structural resistance. Meanwhile, an instrumented single-cell test jig with multiple thermocouples was built, and a series of experimental tests were performed at various conditions. The numerical results based on the single-cell jigs are in very good agreement with the physical test results.

Jan 1, 2005

By Alan E. Gallie

FOR many years the Witwatersrand has been the leading gold mining r camp in the world and, to a Canadian mining student, could not fail to be of overwhelming interest. The vast scale upon which the operations are conducted, the enormous production accomplished, and the perfection of the operative technique, have all so forcibly impressed themselves on his memory that it is difficult to select any one feature as more outstanding than another. For the purposes of this paper, however, the author has selected the very first feature of mine operation with which he came in contact, namely, shaft sinking, as it reflects, quite as well as any other, the spirit of mining in South Africa. Early mining in Johannesburg was by open cuts or trenches, dug along the outcrops of the reefs. The ore was thrown from bench to bench to the surface. As the depth increased, rock was hoisted by bullocks. In 1887, the first shafts were sunk and true underground work began. At the same time, boreholes were put down to test the continuity of the reefs at depth. The first was at the Village Main reef. It cut the South reef at 517 feet and the Main reef leader at 581 feet. The Main reef leader assayed eleven penny-weights. Subsequent boreholes proved the reefs down to thousands of feet. Many companies secured deep-level claims as a direct result of the information obtained from the early holes. These companies then held land on which there was no readily available ore. In order to get to their pay rock, vertical shafts through the upper strata were necessary. Shareholders were impatient, and shafts had to be sunk as speedily as possible. The old methods of shaft sinking were investigated, new methods developed, and soon all records were being broken. In the last thirty-five years, the record has been slowly advanced, and last summer it was again broken to stand at 430 feet in a 31-day month. During the period from 1915 to 1935 inclusive, in the Witwatersrand district, 96 miles of shafts were sunk. Today, with the advance in the price of gold and the increase in the mining area, there are over twenty-five major shaft-sinking operations being carried on.

Jan 1, 1937

By K D. Conroy

For the past year, Lowphos Ore Ltd. has been operating two desliming hydroseparators on a fully automatic basis. Automatic operation is achieved by sensing the position of the silica-magnetite interface and automatically controlling the jet water addition to maintain a desired interface position. The system further provides automatic control of the underflow pump speed in order to assist in maintaining interface position when an <Ore change occurs. Interface position is maintained at 12 inches below the surface and is -controlled within plus or minus one inch. Metallurgical unit recovery is held above 98.5 per cent, and a 10 to 12 per cent increase in concentrate grade is normally achieved.

Jan 1, 1963

By T. Marolt, J. Likar, E. Grøv, J. Žarn

"Underground structures are an integral part of the infrastructure of modern society and are used for a wide range of applications, including subways and railways, highways, not at least nuclear facilities. When the wider area is subject to earthquake activity, underground constructions should be analyzed on seismic and static loading. Observations showed that the underground structures have significantly less seismic risk than surface structures. Available methods allowed analyzing the magnitude of risk for different input parameters of seismic loads in different ground environment. Simulation of earthquake loading on underground structures, in the present paper is given the various aspects of analyzing the potential damage and instability of underground facilities. INTRODUCTIONThe development of methods and computing resources used for para-seismic engineering has finetuned the evaluation of the seismic strength of buildings and equipment. Reinforcements may therefore be decided, not simply on the basis of a reassessment of the hazard, which constitutes input data for the calculation of structures and equipment, but also on the basis of developments in para-seismic engineering. Underground facilities are an integral part of the infrastructure of modern society and are used for a wide range of applications, including subways and railways, highways, material storage, and sewage and water transport and not at least nuclear facilities. Although in the past showed that the underground structures are significantly less seismic risk than on the surface, the professional researches and their results are accessible. Seismic resistance of underground structures is analyzed from several aspects. The currently available methods allowed analyzing the magnitude of risk for different input parameters of seismic loads in different ground environment. For better interpretation of earthquake loading on underground structures, are given below the various aspects of analyzing the potential damage and instability of underground facilities in rock. One of the early studies which covered this are of investigation were prepared by Dowding and Rozen (1978). They grouped damages due to earthquakes in underground structures into three main categories:- damage from ground shaking- damage from fault dislocation- damage by earthquake-induced ground failures (e.g. liquefaction and landslides)."

Jan 1, 2015

By D. F. Machuca-Mory

The new algorithm for high-order simulation of ore deposit grades termed HOSIM is based on the concept of spatial cumulants. The algorithm is tested using data from Apensu, a structurally controlled gold deposit in Ghana. The required high-order spatial structures are obtained from a training image or analogue of the deposit. Using the available drillhole data and training image, HOSIM realizations are able to model well the grades and geometry of the large and well sampled mineralized structures. However, under-sampled small structures remain difficult to model. HOSIM offers a promising alternative for the spatial simulation of complex non-Gaussian orebody attributes of interest.

Jan 1, 2011

By F. Rashchi, N. Naseri Joda

Recycling of electronic wastes is an important subject both from an environmental point of view and also the recovery of valuable materials. In this research, PC board scraps were leached to recover Cu, Ag, Au and Pd. Due to the high cost of the shredding process and to avoid secondary pollution from odors and dusts, board scraps were cut into 5X5 cm2 pieces. To determine the most effective leachant, aqua regia, nitric acid, hydrochloric acid, ammonium persulfate and potassium persulfate were tested. The effect of the leaching parameters, the leachant concentration, temperature, leaching time and liquid to solid ratio were studied and optimized using response surface methodology.

Jan 1, 2011

By W. N. Hamilton

Industrial minerals are plentiful in Alberta. Although exi ting in variety and in quantity, they constitute a minor segment of the province's mineral industry, which is based on oil and gas. In 1983 Alberta led all the other provinces in value of mineral production with a total of $22,2 18 million, 62 per cent of the total for Canada. Of Alberta's total, $22 million or about 3 per cent came from the indu trial minerals. Nearly two-third of this production is accounted for by sulphur, which is actually a by-product of the oil and ga industry. Alberta ranked third among the province in industrial minerals production for 1983, with about 20 per cent of the national total.

Jan 1, 1984

By W. F. Scott, K. L. Somerville

"This paper outlines the development and inplementation of functional training at the Thompson Mine of Inco Metals Company, Manitoba Division. This training is an extension of similar methods implemented throughout the company to meet safety and health and productivity objectives. It consists of the orientation to the mine, induction in the basic mining skills, and specific training in drilling and other skills in the mine. Initial results indicated a positive effect on the safety performance and proficiency of the mine workforce.IntroductionThe primary mining method at the Thompson Mine is mechanized cut and fill, with secondary recovery of pillars by undercut and fill . These methods require a workforce of about 900 hourly operating employees to obtain capacity production of 6500 tons of ore per day.Historically, turnover of mine employees has been high and large numbers of new recruits are introduced to the mine every year. These men are recruited primarily in Manitoba, but also from distant areas of Canada; most of the se people have no previous mining experience.Training has always been an important component of mine operations. Mine supervisors and experienced miners have committed an appreciable amount of time and effort to training these new recruits. As well, training efforts have been directed toward upgrading the skills of experienced workers.Recently, a growing awareness of the significance of this training effort and its impact on accident frequency, productivity, turnover and other important parameters of the mine operation has led to a review of training methods. The training program described in this paper has resulted from this review."

Jan 1, 1981

By B. Arlyuk

On the basis of research of relations among the market participants the analytical model has been created which connects the price of industrial good at stock exchange with volume of sales and the stock of the sellers and buyers, Also a model was developed for assessment of these parameters of the market status by the actually fixed stock exchange and general market indicators. The composition of these models made it possible to create reliable system of short-term price forecasting for commodities or base metals up to one quarter ahead. Imperfectability of creation a model for reliable price forecasting by purely statistic methods (by the "black box" principle) was shown. A model of price behavior qualitative forecasting till one quarter ahead has been developed, which determines the probability of reaching in future of the given level as well as of the price maximums and minimums, Optimal values of threshold probability were determined for forecasting the future price maximums and minimums securing the maximum profit from the forecasting system application for commercial activity. The developed system of forecasting was identified for primary aluminium at the period of 1990-2003. The system was tested daily during 20 months period for speculations on 3M primary aluminium forwards at London Metal Exchange with high commercial result.

Jan 1, 2004

"Liberation is a key requirement for efficient separation in mineral processing. As a consequence of this an understanding of the inherent textural features of an ore is no longer possible since during the process of liberation, texture is destroyed. Knowledge of key textural features, such as mineral grain size and distribution, prior to breakage processes provides the opportunity to understand the textural drivers for ore hardness. Modern characterisation methods, including automated SEM-based techniques, provide the possibility of measuring mineral characteristics at a range of scales. This paper discusses how textural features of two different ore types in a porphyry copper deposit can be measured and interpreted at a number of scales. Standard breakage tests conducted on the ores indicate that one of the ores can be characterised as hard and the other as soft. The impact of mineral grain size and the presence and scale of vein type structures in the two ores have been used to determine the extent to which these features influence ore hardness.INTRODUCTIONIn order to effectively convert ore into metal, knowledge of both the processing stages and the characteristics of the ore are essential. Prior to the advent of technologies that enabled the fundamental understanding of the sub-process at each stage of processing and the measurement of appropriate ore properties the most effective way to understand how an ore would respond to a process was to put it through that process, for example the way to determine how an ore would break was to first break it. Existing comminution models seek to predict the size distribution of rock fragments as the result of applied energy based on knowledge of the rock strength. It is common for these models to consider the rock as homogeneous and despite providing important data for the design and optimisation of industrial comminution circuits these models are only applicable within a narrow range of operation. In order for reliable predictive models to be developed that account for the inherent ore characteristics, a step change is required in the type of measurements that are carried out to characterise an ore and the type of data that is extracted and used as model inputs."

Jan 1, 2016

By Pura Alfonso, Sarbast Hamid, Hernan Anticoi, Eduard Guasch, Josep Oliva

"Av. Bases de Manresa 61-63, Manresa (08242) Barcelona, SpainTantalum is a strategic metal and an improvement of the mineral processing is an important issue. The main objective of this work is to optimize the grinding technologies for tantalum ores with high pressure grinding rolls. The selected ore for this study was an altered leucogranite from the Penouta Open Pit Mine (NW Spain). In the present work mono-size experiments have been carried out using grinding rolls with controlled pressure. The particle size distribution has been monitored in the input and output of the high pressure grinding rolls for each experiment. The cylinder pressure that is transmitted to the particles has been determined. New population balance models are presented for high pressure grinding rolls with parameter adjust for tantalum ore. The obtained model uses the physical description of particles under the comminution action of the grinding rolls. The obtained results are in agreement with other models and the errors in the adjustment are low. The selection function proposed for this model describes adequately the breakage probability of the particles inside the high pressure grinding rolls. The presented model can be a good alternative for simulating a high pressure grinding roll process. INTRODUCTIONTechnology for grinding have been improved for many years, introducing new variables and parameters involving energy consumption, mechanical stress analysis of the compression particles or pressure application for optimizing the comminution (Morrell et al, 1997). High pressure grinding rolls is a modern technology that is proven to reduce the operating costs in full scale plants when compared with other milling technologies. Its benefits on energy saving and simplicity in the process have been studied and applied, first in the cement clinker industry (Abouzeid & Fuerstenau, 2009) and after in mining activities, especially in metallic ore deposits (Austin et al, 1991; Guevara & Menacho, 1992; Morrel et al, 1997; Torres & Casali 2009; Numbi & Xia, 2015). Many author structures of the High Pressure Grinding Rolls modelling in three main branches; (a) throughput modelling, (b) Power and energy model and (c) particle size distribution modelling (Austin et al, 1991; Guevara & Menacho, 1992; Austin & Trubelja, 1994; Morrel et al, 1997; Torres & Casali, 2009)."

Jan 1, 2016

By D. B. Apel

As depths to the ore bodies keep increasing around the globe, the problem how to deal with the increasing temperature of undisturbed rock mass becomes very important. In extreme cases the rock temperature at the bottom of the mine could raise up to 80 °C. In deep mines, geothermal heat is considered as the primary heat load contributor, which accounts for 50?90% of the total heat load depending on different geological conditions. Thus the geothermal heat control in underground mines is the most important and demanding issue to ensure a suitable working environment. In this study, expanded perlite aggregate (EPA) was incorporated as a lightweight substitute for sand. Five mixtures were prepared using 0, 25, 50, 75 and 100% replacement ratios of sand by EPA. These, mixtures were tested in the laboratory for both the insulating and strength properties of the developed shotcrete. The goal of this research was not only to develop shotcrete which would exhibit good insulating properties but also which would exhibit strength properties similar to the regular shotcrete. This paper not only reports the results of the laboratory tests but also discusses the output of numerical model which was performed to evaluate the benefits of using the insulating shotcrete in reducing the cooling costs at hot underground mines.

Aug 1, 2013

By F. Chiesa

Forty aluminium A356 castings were poured on a Low Pressure Permanent Mould industrial machine, 500x700mm in platen size. The 152mm wide casting comprised three steps, 25mm, 13mm, 6mm in thickness and a 2.5mm overflow which allowed to assess the thin wall capability of the process. The casting campaign, which produced 40 parts, allowed to test the influence of various production parameters including the time of application of the pressure in the crucible, artificial cooling of the mould and casting rate. The thermal history in the mould was recorded over the 40 cycles, which allowed to construct a reliable thermal model of the mould/casting assembly. The metallurgical quality of castings representative of the various conditions was assessed in the 25mm, 13mm and 6mm plates. This included measuring the level of microporosity, the dendrite fineness (DAS), along with the tensile properties in the T6 condition. The radiographic quality per ASTM E155 was also determined. Modelling filling and solidification allowed to verify the validity of the predictions based on available relationships relating microporosity, secondary dendrite arm spacing (DAS) and local tensile properties (Quality Index, Q) to the local thermal solidification parameters.

Jan 1, 2007

By M. Fafard, M. Dupuis, P. Goulet, J. Bédard

Start-up of a Hall-Heroult cell is a delicate task that can affect pot performance and pot life. Modem practices for high amperage cells involve preheating the lining before the molten electrolyte is poured in. Different preheating methods and heat-up schedules are used throughout the industry, and the optimum between a short start-up and damage minimization to the cell is elusive. Direct electrical coke-bed preheating is one of the most common techniques. This practice typically results in a non-uniform surface temperature distribution and can generate detrimental thermal gradients in the cathode blocks. Numerical modeling is an invaluable tool to study this complex problem and can help improve the preheating procedures. The modeling of the mechanical response of the lining is critical to detect risks of cathode block cracking or the development of gaps where liquids could leak into. Taking into account the baking of ramming paste, the quasi-brittle nature of carbon and the contact interfaces between different materials are examples of key elements to consider. A finite element slice model of a cell was built and simulations of different electrical preheating scenarios were performed using the inhouse code FESh++ to demonstrate what can be learned through thermo-chemomechanical modeling. The potential industrial application of the model is discussed.

Jan 1, 2006