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By S. K. Murphy

A partial shaft pillar extraction project was embarked on at a mine in the West Wits mining region in South Africa. Prior to the extraction, a rock engineering assessment was conducted with the main objective being to establish which areas of the shaft pillar could be extracted without unduly affecting the stability of major infrastructure within the shaft pillar. Standard numerical modelling methods were used to conduct this assessment and several areas were identified for extraction. However, during the extraction process, it was found that the infrastructure was affected more than was originally predicted by linear elastic modelling. In addition to this, several large events resulted in far more large aftershocks than would normally be predicted. In order to gain an understanding of this phenomenon, seismic data was integrated with numerical modelling as follows: > The seismic data in the form of displacements was integrated in 3D space within the model to assess the effect of static stress changes associated with seismic activity > Data from large events was integrated onto specific structures, where displacements associated with large events were integrated onto the plane of structure in question. This paper describes the methodology and results obtained from each of the above processes and include insights into the mining process that were previously unfathomable using standard linear elastic numerical modelling. The way forward for this rock engineering assessment of partial shaft pillar extraction is also discussed.

Jan 1, 2012

By Charles A. Sorrell

Two red muds, two fly ashes, and several aluminosilicate minerals were subjected to direct treatment with concentrated H2SO4 at temperatures of 175°C and below. X-ray analysis showed that virtually all the sulfate reaction products remained in the solid residue because of their low solubilities in x SO Substantial portions of the Al2O3 Fe2O3TiO2, Na2O, and K2O components of the materials reacted to form water soluble sulfates, which were then removed by H2O leaching at 55°C. The solid residue after water leaching consisted largely of amorphous silica and, in lime bearing compounds, CaSO4, The reaction and leaching processes were effective in removing all or nearly all the Al2O3. Fe2O3, TiO2, Na2O, and in lime components in the fly ashes, red muds, china clay, bentonites, the nephelioe fraction of nepheline syenite, and a plaster insulating brick composed of anorthite and mullite. Reaction with potassium feldspar and petalite took place, with formation of alkali aluminum sulfates, but the reaction rates and yields were extremely low. Potassium feldspar can be heated with Na2O and x O in air at 700°C for 24 hours, or with CaO at 1000°C for 24 hours, after which the reaction product kaliophilite, nepheline, and leucite-like phases, prove to be very susceptible to H2SO4, reaction and H2O leaching, providing yields near 100% of the Al2O2 content. An alternative method of H SO treatment consists of heating the sample in a silica tube and passing H2SO4 vapor over it. Preliminary results indicate that this method can be effective in enhancing the kinetics of reaction with the Al O component of potassium feldspar and offer the possibility that formation of Al2 (SO ) Fe2(SO4)3 and TiOSO4 can be accomplished selectively by taking advantage of the fact that the upper stability limits of the respective sulfates in the presence of H2SO4 vapor will be different.

Jan 1, 1982

By J. T. I. Poijärvi

The smelter off-gas cleaning and the weak acid treatment at Outokumpu Harjavalta Metals Oy are presented and described in this paper. The smelter consists of the copper and nickel smelters and the acid plant of three separate acid plants two of which are double contact and one single plant and of one liquid sulphur dioxide plant. The preliminary cooling and flue dust separation of the smelter off-gases from the copper and nickel flash smelting furnaces and converters in the waste heat boilers and in the hot electrostatic precipitators are described. The final cooling and cleaning of the gases in the scrubbers at the sulphuric acid plant and the treatment of the weak acid in the vacuum and in the submerged combustion evaporators for the removal of impurities are pre¬sented as well as the treatment of the condensates from the evaporators. The attention is paid to the generation of sulphur trioxide in the smelter off-gas and to the treatment of that in the weak acid bleed-off and to the utilization of the treated acid.

Jan 1, 1992

By S. K. Kawatra

It is common in coal-cleaning operations to produce a fine waste stream which contains a considerable amount of coal, but which is not economical to recover both because it is mixed with large amounts of difficult-to-remove clay slimes, and because the fines are often heavily oxidized. Conventional froth flotation machines cannot produce an acceptable product from such material in a single stage of flotation, and even flotation columns often have difficulty cleaning this type of feed. A new type of flotation column was designed specifically to deal with these problems, and was installed and tested in a coal-cleaning plant in Ohio. The feed coal contained 39.8% ash as fine clay, and 2.83% total sulfur, and was 80% passing 176 micrometers. The coal was a thickener product which had oxidized for some time, and was very difficult to float. However, using the new column it was possible to recover up to 85% of the calorific value in a product containing less than 11% ash, and up to 60% of the calorific value in a product of less that 8% ash. The bulk of the pyritic sulfur was rejected from the coal as well. Multistage flotation tests showed that the flotation column was able, in a single stage, to produce the best froth flotation product that it was possible to recover from this coal.

Jan 1, 1994

By W. E. Selnes

Introduction In 1938, a survey conducted by the Ontario Mining Association revealed a rather startling fact. Injuries incurred in chute pulling were more numerous than those from any other single cause. This report prompted Mr. W. B. Paton, then Inspector of Mines for Manitoba, to make a similar survey of the mines of his Province. It indicated that, in Manitoba mines, chute accidents ranked second only to those from falls off roofs and sides. Why has the mining industry been so slow to recognize the dangers of chute pulling? A partial answer may be the lack of any systematic classification of accidents according to their real cause. The result has been to attribute to other causes injuries which were a direct outcome of chute pulling, and, indeed, has made it difficult to analyze accidents in the industry as a whole. Perhaps, too, because chutes are generally located in the comparative safety? of the drifts, there has been a tendency to consider the occupation as not very hazardous. Not until enough statistics were obtained on this particular task could it be appraised correctly. The Mining Association's survey has been most helpful, and latterly the industry has done a great deal toward analyzing the causes of chute accidents and toward determining an effective means of overcoming them. Much, however, remains to be done. An effort will be made in this paper to outline methods which have been found successful in materially reducing the number of injuries. Qualifications of the Chute Puller First of all it must be realized that chute-pulling is a specialized occupation. The men require proper training for the job, just as in other mining operations. Care must, therefore, be taken to choose persons whose qualifications fit them for the job. Chute-pulling is an integral part of the general mining operation and cannot be considered as isolated from the tasks of other workers. One of the essential qualifications of a chute-puller is a sufficient knowledge of mining operations to appreciate the effect his work will have on the safety of others in the vicinity. He must take the necessary precautions, by verbal warnings, by placing barricades and signs, or by personally guarding the chutes, to prevent accidents to fellow workers.

Jan 1, 1947

By N. D. Wineinger, J. Jodouin

"An Independent Electricity System Operator Industrial Accelerator Program (IESO IAP) case study was completed for a mine in Ontario, Canada by SRK Consulting, Inc. The purpose of the study was to analyze the ventilation system to determine whether and which system improvements could reduce the overall electrical power demand of the mine. Financial incentives are offered by the IESO IAP grant program to help cover the capital costs of these improvements. This study included the completion of a full mine ventilation survey as well as measurement of a full suite of electrical parameters of the surface and underground ventilation fans. After these measurements, a base ventilation model was created and established as the system baseline. Changes to the ventilation system were modeled, and their effects on the power demand were projected. The results of the study showed that several improvements were possible which may significantly improve the efficiency of the ventilation system and reduce mine electricity demand.INTRODUCTIONIn 2017, a ventilation study was conducted in accordance with the Independent Electricity System Operator Industrial Accelerator Program (IESO IAP) at a mine in Ontario, Canada. The IESO IAP is designed to assist eligible transmission-connected Canadian companies operating in Ontario to fast track capital investment in major energy conservation projects. The program will provide financial incentives to encourage investment in innovative process changes and equipment retrofits to reduce electricity consumption on the provincial system and to help companies become more competitive by positively impacting their bottom line. There are now four initiatives under the Industrial Accelerator Program:1. Retrofit2. Process & Systems, including Small Capital Projects3. High Performance New Construction4. Energy Managers – a new initiative under the Industrial Accelerator ProgramWithin the program, companies may propose energy saving changes to their current systems where applicable and appropriate. Companies may then be awarded funding to implement the proposed changes. The program allows partial financial compensation to implement certain energy saving changes that would otherwise not be considered due to high capital costs. For larger projects, such as underground mine ventilation systems, a detailed engineering study must be submitted. This study must detail each energy saving change or measure, its savings, and calculate the financial incentives using the IESO IAP Payment Structure. The payment structure for a project is an amount equal to the lowest of the following (Independent Electricity System Operator, 2015):"

Jan 1, 2019

By Ronald. Machaca, Angel Pinto, Christopher Robben, Pedro Condori

San Rafael es la primera productora subterránea de Sn en el mundo, la gravimetría y flotación son los principales procesos de concentración. Se implementó una planta de Pre-Concentración con la tecnología Ore Sorting para tratar un depósito de desmonte con ley debajo del cut-off. Se usa sensores de Transmisión de Rayos X, que identifica inclusiones de Sn y los separa con eyectores neumáticos, lográndose incrementos de ley promedio de 0.6 % a 2.76 % Sn con recuperación de 90.4% y reduciendo el producto a 20 % en peso.

Sep 1, 2017

H. McD. Lorain says in regard to his son, Captain S. H. Lorain; "It might be of interest to you to know that, although but 23 years of age, my son is captain of Co. C 107th U. S. Engineers, Thirty-second Division. He landed in France about the middle of February, 1918, and was commissioned a captain on Sept. 5, 1918. He started for the front the latter part of June and was there continuously until the armi-stice was signed, on Nov. 11, being on the front lines in the Argonne at that time. He is, at present, in Coblenz, Germany, with the Army of Occupation. Although much of his work was clone under artillery and machine-blur fire, as well as airplane bombs and fire, he escaped without a scratch. Once, he was the only one of a group who escaped without a scratch from an exploding shell." Lieut. Bernard H. Lasky, on a post card received a short time ago, gave the following brief record of his military career. "I have been serving with the 316th Engineers in France and in Flanders and had the satisfaction of being in the last big drive in Belgium which sent the enemy beyond Avaenarde and did much to increase their gait on their way to Brussels. On Oct. 1, I received a commission as second lieutenant and was assigned to Co. C of the 316th Engineers."

Jan 3, 1919

Engineering programs usually do not provide sufficient opportunities for students to develop written communication skills. The responsibility for developing those skills is frequently delegated to the humanities faculty, who in a single technical writing course are supposed to transform engineering students into proficient communicators. A general template which was developed for report writing in our senior level capstone design courses is discussed. Students have improved their writing skills by using the template. The writing assignments have provided the students the opportunity to write and revise more technical reports that communicate their design.

Jan 1, 1995

By K Whelan

The Land Access Branch of the Mines Division of the Northern Territory Department of Mines and Energy is responsible for Aboriginal Liaison and cross-cultural matters that affect the Department. In essence, it exists to provide a basis for communication between the Department, industry. Aboriginal organisations and Traditional Owners. The paper outlines the various ways in which this is accomplished including the preparation of detriment submissions for pending land claim hearings, the use of promotional material to support access to Aboriginal Land for NTGS Mapping Programs and field work, and advice/assistance on exploration and mining issues.

Jan 1, 1994

By C. H. Lee, K. Adham, D. Lemieux, J. P. Mai, A. M. S. Hussein, S. Francey

Copper concentrates contain an increasing amount of arsenic, as the older sources of cleaner ores are depleted. At the same time, the market-determined price penalties on arsenic rich concentrates are rising due to limited arsenic treatment capacity at smelters and increasingly stringent environmental emissions limits, necessitating arsenic removal from the copper concentrates. Heating the concentrate to about 700°C can remove significant amounts of arsenic (as elemental and/or sulfide); however, it is important to achieve that removal economically and with due consideration to post-roasting arsenic (toxic waste) treatment. A comparison is made among different roasting options (kilns, multi-hearths and fluid beds) to qualify their potential application to arsenic roasting of copper concentrates. Both direct and indirect methods of heating as well as inert, air and oxygen atmosphere options are considered. Technology comparisons are made with respect to the roaster’s operation, its off-gas treatment and arsenic stabilization. INTRODUCTION In the last twenty years, the arsenic content in globally produced copper concentrates have risen steadily due to the depletion of cleaner ores and the increase in complex concentrate production. Smelter contracts typically limit arsenic to less than 0.5wt%, with a penalty paid per unit of additional arsenic and other contaminants such as antimony. While penalties can vary, they can be on the order of $70/dry metric tonne of concentrate per 1% of arsenic. Strategies used by miners to avoid the price penalties have been to blend clean and complex concentrates, and to remove arsenic from complex concentrates to achieve smelter limits. Arsenic can be removed from copper concentrates by the heat-induced decomposition of the predominant enargite mineral (Cu3AsS4) at ~700°C. Roasting at such elevated temperature is a commercially proven option, but still suffers from process, cost and environmental challenges. After roasting, the released arsenic sulfide fumes can be separated from most of the entrained concentrate dust in cyclones. Then, the As2S3 laden off-gas can be oxidized to generate a still volatile oxide (As2O3), which can be further separated from the residual concentrate dust in a hot electrostatic separator. Next, the off-gas can be cooled with air or water, to either deposit the arsenic oxide in a dry or dissolved state. Dissolved arsenic acid can be oxidized to As(V) and reacted with iron to yield a stabilized ferrihydrite precipitate or scorodite that can be safely disposed. In the case of dry arsenic trioxide, it can be mixed with reactants (e.g. iron) and fluxes before thermal stabilization in a glass matrix, thus eliminating the need for costly oxidation.

Jan 1, 2019

By R Burke, G Ramage, C Donnelly

Over the decades, Redpath has undertaken a multitude of tunnelling and underground excavation projects for civil and mining clients both domestically and internationally. These projects have been undertaken through varying strata conditions with differing excavation methods in remote locations and in central business districts.With the recent turbulent nature of the global financial environment, project drivers have been challenged with the emphasis being placed on methods to gain early access to orebodies, rapid development techniques, lower capital costs and reduced labour requirements to name a few.A number of mining companies seeking to achieve these objectives have commenced the journey to better understand the operational constraints, challenges and opportunities that may be available with the use of alternative excavation methods.The development of safe and effective alternative excavation methods that comply with both domestic and international mining legislation and regulatory requirements is a challenge the industry needs to embrace. Given the current cost pressures being faced by the Australian mining industry, some alternative excavation methods offer the potential for longer term sustainability and rapid development of resources.More recently work has been undertaken on a project that challenged the norm and implemented an alternative excavation method with the use of an excavator with a rotating drum cutter head.This paper will review this recent project and provide technical and operational insight into some of the challenges faced in implementing an alternative excavation method in the metalliferous industry.CITATION:Donnelly, C, Ramage, G and Burke, R, 2014. Challenging the norm – alternative excavation method in mining, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 187–190 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014

By Jefferson Lisboa Lelis, Marcos Roberto Soares da Silva, Maiara Rodrigues Gouveia

Nowadays, due the development of new hot rolled strips at USIMINAS, established the necessity of realizing studies to define new parameters for the welding machine of new pickling line, in order to improve mechanical and metallurgical properties of these materials. The aim of this study was to evaluate the weldability of high strength low-alloy steel with low boron content with tensile strength above 600MPa.The influence of energy input and preheating temperature on the mechanical properties of hot rolled strips were analyzed at three distinct thickness (2, 4 and 6 mm). To perform these evaluations were used tensile test, micro-hardness, metallography (micro and macro examination) and scanning electron microscopy analysis. In resume, a good welding performance was achieved, increasing preheating temperature and the welding energy higher than 60%.

Oct 13, 2019

By Albert Ladd Colby

PAGE I. Introduction,...........577 11. PRocess of Manufacture. 1. American Specifications. 2. Foreign Specifications, . ......... 580 III. Chemical Properties. I. Chemical Composition: (a) American Specifications ; (b) Foreign Specifications. 2. Chemical Analysis: (a) American Specifications ; (b) Foreign Specifications ; (c) Number of Analyses Required ; (d) Sample for Analysis ; (e) Check-Analyses Impracticable ; (f) Rejection Solely on Variation in Com-' position,............581 IV. Physical Properties. 1. Drop-Test and Drop-Testing Hachine: (a) American Specifications ; (b) Foreign Specifications ; (c) Limits in Deflection. 2. Tensile Test: (a) American Specifications; (b) Foreign Specifications ; (c) Test-Pieces are not Representative ; (d) Specified Tensile Strength is Affected by the Section ; (e) BpeciBed Tensile Strength is Often Inconsistent with Specified Chemistry ; (f) Specified Tensile Strength is Often Inconsistent with Specified Elongation ; (g) Amount of Tensile Testing Required is Excessive ; (11) Conclusions. 3. Dead-Weight Test: (a) American Specifications; (b) Foreign Specifications; (c) Number of Tests Specified. 4. Bending-Test: ((1) American Specifications ; (b) Foreign Specifications,..........589 V. Section. 1. American Specifications. 2. Foreign Specifications: (a) Templets ; (b) Sample Piece of Rail; (c) Allowable Variation from Templet,...........601 VI. Weight. 1. American Specifications. 2. Foreign Specifications,. . 603 VII. Length. 1. American Specifications. 2. Foreign Specifications, . . 604 VIII. Drilling. 1. American Specifications. 2. Foreign Specifications, . 604 IX. Finish. 1. American Specifications. 2. Foreign Specifications, . . 50.5 X. Branding. 1. American Specifications. 2. Foreign Specifications : (a) Data to be Rolled in Raised Letters on Web of Rail ; (b) Marking of the Blow-Number on Each Rail; (c) Additional Marking and Painting of Rails,........605 XI. Inspection. 1. American Specifications. 2. Foreign Specifications: (a) Prior Notice of Rolling; (b) Free Access to the Works ; (c) Cost of Inspection, Analyses and Tests to be Borne by the Manufacturer ; (d) Rails after Inspection by Manufacturer to be Sorted into Lots Prior to Inspection by the Engineer ; (e) Disposition of Rejected

Jan 1, 1907

By V. K. Chandaliya

N-Methyl-2-pyrollidone (NMP) has already been proven a good solvent for extraction of coal. It is believed that organic components of coal are likely to be dissolved with the solvolytic power of NMP. During dissolution process, original coal also gets disintegrated and thus helps in further extraction. Coal extraction highly depends on temperature, coal to solvent ratio, N-Methyl-2-pyrollidone (NMP) to Ethylenediamine (EDA) ratio and the size of coal particles. The process has been established in the laboratory. There is no reference available beyond lab scale. In present study, we are running a bench scale plant with 40 kg/batch capacity. Design of experiment was done in such a way that the optimum zone of the process gets evaluated for clean coal having low ash with high yield. Bench scale plant trial was conducted based on optimum zone developed during design of experiments (DOE). From the DOE analysis it was observed that feed size and coal to solvent ratio are important parameters for this process. Total 27 experiments (four factors with 3 level of variation) were designed through Box-Behnken model. It was observed that -0.5 mm feed size of coal, 150 °C extraction temperature, 17:1 NMP to EDA ratio, 1:9 coal to solvent ratio was optimum conditions. The results obtained at optimum conditions are 50% clean coal yield with 5% ash.

Sep 1, 2012

By R. S. McDonald

Auburn began operations 40 years ago with an office in Sudbury, Ontario, Canada, to provide services to Inco Limited. Over the next 40 years, operations expanded considerably, with projects being undertaken around the world, servicing the smelting and refining industry. Operating bases have been established in Canada, United States, Mexico, Chile, and Spain, with further growth expected to continue with an operating presence in South Africa. The Auburn Group of companies has serviced the smelting and refining industry for over 35 years. Auburn services a variety of metallurgical plants, and our worldwide experience has gathered considerable knowledge on industry processes and maintenance solutions. Today, the ?Business of Smelting? tackles demanding challenges, and operators search for opportunities and solutions to improve smelter maintenance, reduce operating costs, and decrease downtime. The Auburn Group has developed project teams, technologies, and equipment that provide specialised and innovative solutions to the non-ferrous metal industry to help address these challenges. Our Furnace Services team offers a variety of repair and maintenance services for metallurgical furnaces. Our specialised team has proven methods for completing projects quickly and safely. Our worldwide experience includes turnkey project management, construction, and various scopes of work for demolition and refractory repairs on all types of smelting and refining furnaces. Auburn developed the Results FirstTM programme to provide optimized solutions and results for smelter projects. The programme utilises a proven three-step model for improved results for schedule, budget, safety, and ramp-up to production. Our experienced Project Management teams can handle the planning and construction management of capital projects and plant shutdowns. Our projects have involved smelter/refinery modifications, oxygen plant installations, and sulphuric acid plant audits and maintenance. Our Equipment & Products division supplies specialised equipment and products, which are used in the metals industry for plant maintenance tasks. Our capability to design unique equipment, combined with our ability to source products worldwide, makes us a useful resource to find the best-suited equipment to meet the work-site demands. We specialise in custom remote-control units to handle specific maintenance solutions for smelters and refineries, and custom equipment designs for catalyst handling for Acid Plant maintenance. Our extensive knowledge of and experience with industrial technologies allows us to provide a wide range of Industrial Services. These services include vacuuming, high-pressure water blasting, chemical cleaning, pelletizing, dredging, ore bin clearing, roaster repairs, baghouse/ESP services, and manpower supply for both industrial plants and mines. Auburn?s combined strength of personnel experience, knowledge of industry processes, innovative project methods, and equipment technology make Auburn a unique resource for problem solving on every facet of smelter operations.

Jan 1, 2006

By David A. Benjamin

The USBM (U.S. Bureau of Mines) studied mines, prospects, and mineralized sites in the Roberts WSA (Wilderness Study Area) in 1984. The 15,090-acre WSA, located 35 miles northwest of Eureka, NV, is underlain by alluvial deposits of Quaternary age, extrusive and intrusive volcanic rocks of Oligocene through Miocene age, and metasedimentary rocks of Cambrian through Permian age. The Roberts Mountain Thrust fault cuts through the WSA, dividing the metasedimentary rocks into upper and lower plate rock units. One mine, the Kelley, which produced 397 tons of lead-zinc ore prior to 1940, and two prospects are within the WSA; no resources were identified. Exploration for precious metal deposits is presently being conducted in and adjacent to the WSA on large claim blocks. The study area contains six sites in and near these claim blocks that have anomalous gold and silver. Detailed exploration is needed to delineate resources. High purity silica rocks are present in the WSA. Barite, phosphate, oil shale, and vanadium occurrences just outside the WSA may extend into it, but no such occurrences were observed during the USBM study.

Jan 1, 1986

By A. E. Powers

YEARS of experience and research have shown that molybdenum, tungsten, and vanadium are among the most useful and effective elements in augmenting the high-temperature strength of heat-treatable, ferritic steels. Grün, for example, in conducting an early survey of the strengthening effects of various elements in annealed, low-carbon steel at 750° and 930°F (400° and 500°C), found molybdenum and vanadium to be the most effective.' Holtmann comprehensively studied the strengthening effects of molybdenum and vanadium in quenched and tempered steels at 930°F as a function of microstructure and carbon content.' He found creep strength to be related to the saturation of the austenite at the austenitizing temperature, such that strength is increased by alloying until the y loop is reached—the terminus of complete austenitization. Beyond this degree of alloying, the inability to heat treat will result in lower strength, at least for low and moderate creep temperatures. Tungsten, owing to higher cost than molybdenum, has been little used in ferritic high-temperature steels. As a result, very few investigations have been made of its high-temperature strengthening ability, and reliable data on its effectiveness are not available. Grün rated tungsten far less effective than molybdenum at 930°F (500°C) on a weight-percentage basis.' However, Tammann has found that tungsten is as effective as molybdenum in raising the recrystallization temperature of iron. For this reason Smith, in a review of the subject, has advocated a re-examination of the influence of tungsten on the high-temperature strength of steel.' In any study of the effects of alloying additions on high-temperature properties, recognition must be made of the many variables involved, some of which can be controlled but have been ignored in innumerable investigations of the past, and some of which are difficult or even impossible to control. One cannot, for example, assign a definite strengthening index to any one alloying element, for this will be dependent upon the microstructure (heat treatment and mechanical treatment), testing con- ditions (temperature, time, and stress), and the complete composition of the steel (accompanying alloying elements, impurities, etc.). One ever-appear ing variable, hardness or tensile strength at room temperature, may be eliminated by heat treating all of the alloys to a single hardness level. An attempt may be made to control the variable of primary quenched structure by oil or water quenching the test specimen. The control of such variables may not be possible in cases of widely varying compositions, but at least such deviations should be recognized. Material and Procedure The alloys, made as 30-lb ingots in an induction furnace, all had the same base composition of about 0.18 pct C, 0.85 pct Mn, and 0.48 pct Si. They were grouped as follows: Mo Group—Containing up to 5.2 pct Mo. W Group-Containing up to 6.0 pct W. V Group—Containing up to 3.3 pct V. Mo-V Group—Containing up to 2.7 pct Mo and up to 1.4 pct V. Mo-W Group—Containing up to 2.5 pct Mo and up to 2.5 pct W. The steels, listed in Table I, were forged to ¾ in. sq bars and the material for the high-temperature, rupture-test specimens was further swaged to %-in. round bars.

Jan 1, 1957

By Fred D. DeVaney

DURING the past few years a radically new process for the magnetic roasting of iron ores has been investigated and developed by Pickands Mather & Co. and the Erie Mining Co. in the Erie laboratory at Hibbing, Minn. This process, originally devised by Dr. P. H. Royster of Washington, D. C., involves the use of a roasting technique quite different from older methods. It has now been demonstrated that iron-bearing materials can be roasted as effectively as by any previously known method, and at a much lower cost. The increasing shortage of highgrade iron ores in this country has accelerated the search for new methods that would permit low grade materials to be utilized. The concept of magnetically roasting low grade nonmagnetic ores such as the oxidized taconites and then separating such material magnetically has always had considerable appeal. The magnetic concentration idea is attractive because of the sharpness of the separations and cheapness of the method. Heretofore, however, the equipment and the processes available for the magnetizing-roasting -step have left much to be desired. The customary equipment available for reduction roasting has been: 1-multiple hearth furnaces, 2-rotary kilns, and 3-shaft type kilns. In addition, it is understood that some work has been done in magnetically roasting fine ores by a process using the FluoSolids principle, but little information on this process is available. The multiple hearth kiln has been used the most but first costs and operating costs have been high because of low capacity, high maintenance, and poor gas utilization. Magnetic roasting can be done in a rotary kiln, but the radiation losses are high and the conversion to magnetite is usually unsatisfactory because of poor contact between the gases and the solids. Of the shaft-type furnaces, probably the most efficient yet developed is that designed by E. W. Davis of the Minnesota Mines Experiment Station. This furnace was operated at Cooley, Minn., during 1934-1937 but was abandoned in 1937 because the operation was uneconomic. Heretofore the basic concept behind most magnetic roasting processes has been the idea of heating iron ore to a temperature of 800° to 1100 °F in a strong reducing atmosphere, preferably either carbon monoxide or hydrogen. Temperatures under 800°F were undesirable since excessive roasting time was required. Temperatures over 1100°F were avoided because of the danger of converting part of the iron to ferrous oxide which is nonmagnetic. In the new roasting process, the operation is carried on in a shaft furnace using a controlled atmosphere containing a low percentage of reducing gas. The temperature in the roasting zone is considerably higher than with the usual reducing gas and this speeds up the reduction time. Portions of the spent furnace gases are cooled and recirculated and this together with the good contact between ore and gas makes for high reducing gas utilization. High heat economy is secured by recuperating heat from the roasted ore by passing the cold reducing gases countercurrent to flow of ore. The heat transfer principle is similar to that employed in a pebble stove and to that used in the Erie Mining Co. furnace at Aurora, Minn., for pelletizing fine magnetite concentrates derived from taconite. The theory of controlled atmosphere during the roasting operation can best be appreciated by inspecting the equilibrium diagram of the Fe-C-O system shown in Fig. 1. An inspection of this diagram shows that in certain areas magnetite, Fe3O4, is the only stable form of iron. A further inspection of this table shows that if the proper ratio is maintained between carbon dioxide to carbon monoxide, such a gas will be reducing with respect to hematite, Fe2O3, and will be oxidizing with respect to both ferrous oxide, FeO, and iron, Fe. It should be kept in mind that the formation of ferrous oxide in a roasting operation is harmful, since this oxide is nonmagnetic; if it forms in any quantity, it will cause substantial loss of iron in the ensuing magnetic separation step. If a ratio of approximately three parts carbon dioxide to one of carbon monoxide is maintained, the resulting operation can be carried on at a relatively high temperature without fear of over-reduction. Specifically, most of the tests in the Erie furnace have been made at a temperature of 1500° to 1600°F, with an entrant gas containing approximately 5 pct carbon monoxide and 15 pct carbon dioxide, with the remainder largely nitrogen. It should be remembered that the ratios of carbon monoxide to carbon dioxide shown in Fig. 1 hold even though the bulk of the gas is an inert gas such as nitrogen. It may surprise many to learn that a gas containing as low as 3 pct carbon monoxide, and 12 pct carbon dioxide with the remainder nitrogen is an extremely effective reducing gas in the 1000° to 1600°F temperature range. The reducing gas is not limited to carbon monoxide, and mixtures of hydrogen and carbon monoxide may be used effectively, provided that a similar ratio is maintained between the reducing gases and carbon dioxide and water vapor. For a more detailed explanation of the theory involved, the reader is referred to U. S. patents 2,528,552 and 2,528,553. From a safety standpoint, the weak reducing gas used in the furnace offers an advantage. Its composition is such that it is well below the limits of explosion should air enter a hot furnace. This condition is not true with the usual reducing furnace, in which a gas rich in carbon monoxide or hydrogen is used. The general furnace design and method of operation may best be understood by an inspection of

Jan 1, 1952

When I was first asked to give a paper on work-life balance in the mining industry I was both excited and aware of the incongruity of my position. I have never worked in mining operations nor have I had any experience that approximates the on-site lifestyle. IÆm not really an adventurer or a traveller, I prefer writing and research to hands-on activities and IÆve never worked further than twenty minutes away from home. The perspective I offer is thus largely an objective one. I say largely since I grew up in a family where my parents work arrangements involved long-distance commuting; my dad continues to work FIFO at a coalmine in Blackwater until this day. Perhaps my tortoise-like existence is a rebellion against his flighty movements. The analysis I will be presenting today draws together a variety of sources, from member anecdotes and research on FIFO and work-life balance to the popular philosophy writings of a bald Englishman with a French name. I am speaking of the famous writer, Alain de Botton, whose television show æThe Consolations of PhilosophyÆ you may have seen on the ABC. Work-life balance is a term that gets a lot of mileage in corporate brochures and at breakfast seminars. But like many terms that get bandied around in the human resources circuit, from æteam synergyÆ to æperformance optimisationÆ, I am frequently perplexed as to what it actually means. Corporate websites are at pains to emphasise the high priority that they place on the needs of the whole person. Yet in terms of substantive content, a commitment to work-life balance often seems to translate into little more than the option to take a few morning yoga classes in exchange for working a seventy-hour week. As extended work hours have taken their toll, leading to high attrition of professionals across all industries, employers are increasingly expending resources to discover just what lies behind this buzz word. The challenge for companies is to find meaningful strategies to help employees better integrate different aspects of their lives in a new era of work, as employees are sending the message that they are not willing to play work, social life and leisure off against each other in a zero sum game.

Jan 1, 2005