Search Documents

By J. A. Herbst, R. Zaragoza

Conventional control schemes in use today are not able to produce satisfactory control when high-frequency disturbances are present in the flotation feed. An advanced model-based control scheme is presented here as a promising solution to this control problem. The main feature of this control scheme is the real time identification of the unknown disturbances in the first few cells of the flotation circuit. This information is used to control the rest of the flotation plant in a feedforward fashion. This control scheme also provides flexibility to meet any metallurgical, economical, or management objective.

Jan 1, 1987

By Andrew Middleton, Mick Stadter, Chris Crowe, David Chong

"The Level Crossing Removal Project – Package 1 is part of the Victorian Governments commitment to remove 50 of the most dangerous and congested level crossings across Melbourne. This involved removing three crossings on the Frankston Line in the south east suburbs of Melbourne. The works involved replacing approximately 2.5km of at grade track with three rail cuttings up to 8 m deep at each of the bridges that replace the level crossings. The cuttings are retained by piled retaining walls and during the main construction occupation approximately 250,000 cubic metres of soil was removed. The project has presented significant geotechnical challenges due to the location in residential suburbs and tight rail corridor and rail occupation timeframe. These challenges included temporary and permanent wall stability, foundations, earthworks and dewatering. As a result, careful design and innovative construction techniques have been necessary to limit impacts on the community and meet the project timeline.INTRODUCTIONThe Level Crossing Removal Project – Package 1 is part of the Victorian Governments commitment to remove 50 of the most dangerous and congested level crossings across Melbourne. This involved removing three crossings on the Frankston Line where it crosses North Road in Ormond, McKinnon Road in McKinnon and Centre Road in Bentleigh.The project involved replacing approximately 2.5km of at grade track with three rail cuttings up to 8 m deep at each of the bridges that replace the level crossings. The cuttings will accommodate three lines of rail tracks with the cuttings up to 25 m wide. The cuttings are retained by piled retaining walls and during the main construction occupation approximately 250,000 cubic metres of soil has been removed.The project presented significant challenges due to the location in residential suburbs and tight rail corridor and rail occupation timeframe. As a result, careful design and innovative construction techniques have been necessary to limit impacts on the community. The geotechnical challenges generally fell into one of three areas, earthworks, structures and groundwater. The primary earthworks challenge for the project was moving the 250,000 cubic metres of soil in a 10 day window, however, from a geotechnical viewpoint, obtaining a stable subgrade on which to operate the necessary construction plant in a short time frame with constrained site access and time to import materials was the key. Whilst closely watching the performance of the dewatering system, a range of contingency plans were developed to cope with any difficulties."

Jan 1, 1900

By A. J. Kraemer

The Bureau of Mines for a number of years has been carrying on an investigation of properties of crude petroleum from producing, fields in the United States and the Western Hemisphere, and has published a series of reports on these fields, including oil fields of Oklahoma2. Acknowledgements Thanks are due to R. R. Brandenthaler and Peter Grandone, of the Petroleum Experiment Station of the Bureau of Mines, at Bartlesville, Oklahoma, who reviewed the manuscript and contributed valuable suggestions. The samples were analyzed under the direction of E. C. Lane at the Bartlesville station of the Bureau of Mines.

Jan 1, 1927

By S. Gopalakrisbn, J. D. Miller, M. Misra

Pilot-scale tests indicate that effective concentration of fine gold from Colorado River sands can be achieved by flotation with the air-sparged hydrocyclone. The fine sands (55% -400 mesh and 0.01 opt*) from gravity concentration were processed with a 5-cm air-sparged hydrocyclone (capacity ~1.0 t/h dry solids). Concentrate grades as high as 5.0 opt were produced in a single stage at a recovery of 75%. The separation efficiency was significantly better than that achieved in conventional batch flotation experiments.

Jan 1, 1987

By I. Barin

The thermodynamics of cyclone smelting of sulphidic copper ores is described using as example the production of copper matte with 75 wt % Cu. Equilibrium calcualtions and material and energy balances show that an increase in process temperature from 1600 K to 1900 K results in the extensive transfer of minor elements such as As, Sb, Bi, Pb, Zn,.... to the gas phase. A pilot plant for carrying out the cyclone smelting process is described. Calculations of material and heat transfer for the reaction of ZnS show that the smelting reactions of sulphides in the cyclone take place very rapidly at high temperatures. The dissociation of the sulphides with subsequent oxidation reactions in the gas phase plays an important part in. the process and is mainly controlled by heat transfer.

Jan 1, 1983

By Qing Wang

Open pit mines require substantial capital investment at the beginning of the operation and replacement investment at later years. The objective of obtaining the highest possible return on investment in a mining project can only be achieved with an efficient long term production plan. This plan consists of optimally determining four principal elements: 1) the amount of ore and waste to be mined each year, 2) the specific blocks to be mined each year, 3) the optimum mine life, and 4) the ultimate pit limits, which delineate the total reserve to be mined. The existing methodologies only provide solutions to one or two elements, by assuming the others known. Furthermore, the cost of mining each block in the deposit is assumed to be known and independent of the production schedule. The four elements of production planning are interrelated and the cost of mining any block is a function of the production schedule. The ultimate goal of this study, ,whose first steps are' discussed in this paper, is to develop a solution methodology that can simultaneously optimize all four elements of the production planning problem in open pit mines without making a priori assumption on any of the four elements.

Jan 1, 1992

By Bartho J. Admiraal

"As part of the Schiphol-Amsterdam-Almere project, the largest aqueduct in Europe is being built in order for the A1 motorway to cross the Vecht River. The A1 consists of 12 lanes and the total width of the aqueduct will be 65 m (213 ft). The total length of the structure will be 620 m (2035 ft). Speed of construction is essential for the DBFM-contract, which forms the primary reason for choosing a building method with a horizontal water retaining barrier created by low pressure grouting. After final checks on the water tightness of the silica based layer (softgel), excavation to a depth of approximately 12 m (40 ft) below the water table could be started in order to build the aqueduct.This paper presents a new approach for the calculation of the required grout volumes needed to ensure a “softgel” layer without gaps or holes. The approach applies measurement of deviations due to execution aspects in a probabilistic model. With this model, one is able to study the effects in a field application, i.e. multiple rows of grouted spheres. The results are visualized in order to analyze the risk of holes more easily. It is evident that the existence of a hole means a major leakage. By completing multiple runs, the strategy for grout volumes can be adjusted to minimize this risk.INTRODUCTIONThe Dutch Department of Waterways and Public Works invests over € 4 billion between 2012-2020 to increase the capacity of 63 km (41 mi) motorways of one of Holland’s major corridors. The A1/A6 will be transformed over a distance of 20 kilometers (13 mi). Near Muiden, the current drawbridge on the A1 for crossing the Vecht river will be replaced by a new aqueduct to be located slightly south of the existing bridge."

Jan 1, 2016

By T. H. Alden

A correlation has been found in rock-salt structure single crystals between the latent hardening, measured by the direct stress activation of oblique slip systems, and the stress-strain behavior in simple compression. Materials with high latent hardening, like LiF, strain-harden at a low rate (Stage I) even when severely constrained. KCl, in contrast, shows low latent hardening and a tendency to strain-harden at a high rate (Stage 11). This correlation suggests that oblique slip is essential for Stage II hardening of these materials. THE role of secondary slip in the strain hardening of metal single crystals is a topic of lively controversy. On the one hand are theories in which secondary dislocations participate directly in Stage II hardening in the fcc metals, for example through the production of sessile dislocations,1 forest intersections, or jog formation. Much of the experimental evidence on which these theories are based has been reviewed by Clarebrough and Hargreaves.~ On the other hand, a recent theory5 denies that secondary slip has an essential role in Stage II hardening or in the transition from Stage I to Stage 11. In the latter view, Stage I is not terminated by an increase in the activity of secondary systems but by the exhaustion of undeformed material.6 The experiments reported in this paper will not resolve this controversy since the materials being studied are cubic ionic crystals rather than metals. However, the results do show in an unusual way a direct connection between "secondary" (nonortho-gonal or oblique) slip and strain hardening in these materials. Specifically, a correlation has been found between two independently measured properties, first the latent hardening of oblique (110)(1i0) slip systems as measured by direct stress activation of these systems, and second the stress-strain behavior at small strains. From prior work, it was known that in most cubi-cally oriented rock-salt structure crystals, two orthogonal slip systems operate and exclude the other equally stressed pair, oblique to the first pair.7'8 This observation apparently indicates that a significant interference exists between slip on oblique (110) planes and a relatively small interference between orthogonal (110) planes. The present experiments were begun with the intent of obtaining a quantitative measure of this difference by means of a study of latent hardening in these crystals. I) EXPERIMENTAL METHODS The experiments were basically of two types, first the determination of stress-strain curves by compression along a single (100) axis, and second the measurement of latent hardening by compressive prestrain along one cube axis followed by the determination of the yield stress in a second (latent) cube direction. All tests were done at room temperature in an Instron machine by compression between lapped, parallel steel faces. Three specimen shapes were used. For long crystals (nominal dimensions, 1/8 in. square by 1/2 in. long) the ends were lubricated with an oil-graphite mixture. Superior results with short crystals (about 1/8 in. cube) were obtained using 0.003-in. teflon film.' Thin crystals (1/4 in. square by 3/32 in.) were used for latent-hardening measurements and similar results were obtained with either lubricant. Test specimens were cleaved from Harshaw single crystals which had been irradiated to a dose of lo8 roentgen using a cobalt-60 source. The irradiation raises the yield stress and tends to prevent plastic deformation during sample preparation.10 Prior to testing, the irradiation hardening was removed by an anneal at 400°C. Ideal compression specimens have flat, parallel faces. In short specimens particularly, satisfactory results demand a close approximation to this ideal. In the present work, cleaved surfaces were often used directly as compression faces. The degree of success using this method depends on two factors: 1) the smoothness of cleavage faces, and 2) the extent to which the crystal is deformed or crushed by the chisel during the cutting of a long crystal into short pieces. Unfortunately, only one material of those studied, LiF, was completely satisfactory. NaF, NaC1, KC1, and KBr behaved less well so that

Jan 1, 1964

By James A. Clem

Approximately 2000 years ago, the Lord admonished the scribes (lawyers) and pharisees (religious leaders of that time) that they had paid the tithe but had omitted the weightier matters of law, judgment, mercy, and faith. (Matt. 23:23) I want to talk about "The Weightier Matters of Law." In a situation where big government is trying to have an effect on even small details of a work activity, otherwise simple situations become complex. Regulations are written to such detail that constant compliance with strict interpretations can be a nightmare-not to mention off the target of the intended purpose for the regulation. One soon recognizes the onerous characteristics of federal statutes. Another admonition the Lord gave those lawyers and pharisees back then was that they tended to strain at a gnat and swallow a camel! He meant that the pharisees were given to devoting themselves to the strict interpretation of law by writing hundreds of subrules or interpretation to law. In doing so they eventually lost sight of the original purpose of the law. I think they were being told, keep the law-but don't neglect to humanize it Keep it simple Recognize the purpose of why the law. "Mix in" a common sense approach. Someone once said, "Common sense is instinct -enough of it is genius." Today, as 2000 years ago, we need more "genius" displayed by legislators in considering the weightier matters of law. First of all true legislature genius calls for a declarative statement about the purpose of the statute and a fair, objective analysis of the ground rules by which it will be implemented. In the Health & Safety Act of 1969, the "findings and purpose" as set forth in Section 2 do define its purpose. I believe most of us affected can be in accord with the reasons advanced for the legislation. However, beyond those well-intentioned few paragraphs, we very quickly run into trouble. Congress complicated the simplicity of the statement of purpose by mandating government intervention into areas that cannot be effectively legislated, nor even should be legislated. The Act provided for broad gaged regulation which is unnecessary, inappropriate, and tremendously costly. Frankly, it detracts from a constructive, cooperative effort by the parties involved. These are strong negatives which characterize inappropriate legislation. Appropriate legislation and subsequent regulation, which is realistically conceived and practically enforced must be born of an honest desire for improvement, based on a working knowledge of common problems which are thoughtfully analyzed. Then the legislation must be written in clear concise language so that there can be little or no doubt as to its literal meaning and intent. To be practically enforced, it must be understood by all who will enforce it and by all who are subject to it. That is to say, an effective law or standard cannot be fixed or inflexible so that it cannot be tempered in human judgment. There must be an elasticity in the statute to provide for consideration of all of the relevant facts of a given situation. Such elasticity makes the compliance effort as meaningful as it can be for the time and dollars invested. Meaningful compliance requires room for common sense. Today, we in business along with our associates in government and labor, urgently need to pause, and assess our current situation. The problems arising from the 1969 Act have been intensified through the Mine Safety & Health Act of 1977. After reading the "findings and purpose" of this legislation, and by process of elimination, we should all clearly see what is and is not the purpose of the Act. 1) It is not to turn the management of private industry over to government. 2) It is not to impair the efficient operation of business. 3) It is not to reduce productivity and profits. 4) It is not to reduce national unemployment. 5) It is not to perpetuate the bureaucracy. 6) It is not to increase the tax burden on an already overburdened people. 7) It is not to increase our balance of payments deficit. 9) It is not to replace management/labor relations in working together to solve problems.

Jan 1, 1981

This Information Circular from the National Institute for Occupational Safety and Health (NIOSH) documents and supplements the information presented in a series of workshops held during 2002 and 2003. The primary intended audience consists of all who are involved in developing and conducting miners' training. According to the Mine Safety and Health Administration (MSHA), mine operators reported 240,000 full-time equivalent workers and independent contractors reported 42,000 full-time equivalent workers working on mine property during the year 2000. Unfortunately, these workers have a relatively high risk of suffering serious work-related injuries and illnesses. The mining industry has the highest rate of occupational fatalities among all U.S. industries. The fatality rate is 30 deaths per 100,000 workers compared to 4.6 for all private industry (Morbidity and Mortality Week Report, 2001; NIOSH, 2002). Compared to workers in other industries, miners also have a relatively high rate of nonfatal lost-time injuries, and their injuries tend to be more severe (Bureau of Labor Statistics, 1999). Many miners are also exposed to significant health hazards, including coal and silica dust, diesel exhaust, and noise. More than 1000 U.S. miners die of lung disease each year (NIOSH, 1999). Mine safety and health professionals have long recognized training as a critical element of an effective safety and health program. Federal regulations (30 CFR, Parts 46 and 48) require mine operators to provide initial safety and health training to all new miners, as well as a minimum of 8 hours of refresher training each year. The time and money being spent to train U.S. miners is substantial, and so there is a strong and steady demand for new and better mine training materials and methods. A growing concern among mine safety professionals regards the training of new workers. A major change in the mining workforce is anticipated within the next decade. In major segments of mining, especially coal, relatively few workers have been hired since the 1970's. Thus, as an entire cohort of miners in the current workforce nears retirement, the replacement of these employees will require an influx of new workers. New miners may be young people who lack the ability to recognize and respond to mining hazards in an appropriate manner. They may also have had different educational experiences than their older counterparts. Many safety professionals believe that these two cohorts require different approaches to training. The papers in this report should help prepare mine trainers for the changes about to occur in the workforce and acquaint them with strategies they can use to enhance the effectiveness of their training. The first three papers present basic principles for teaching adults. The five remaining papers are intended to illustrate how these principles can be applied to the development and imple¬mentation of effective training for miners. Below is an overview of these papers. 1. Kowalski and Vaught review the process and principles of adult learning. The learning model they present includes a discussion of goals, content, delivery, assessment, and remediation. Adults are viewed as active learners, experienced-based, expert in their own right in specific areas, independent, real-life centered, task-centered, problem-centered, solution-driven, skill-seeking, self-directing, and internally and externally motivated. Basic aspects of curriculum development are briefly reviewed. For further information about adult learning, see Camm and Cullen's paper. 2. Mallett and Reinke's first paper discusses issues related to training new miners who have recently or will soon be entering the mining workforce. These new generations of miners have different learning style preferences and training needs than Baby Boomers and other older miners. Even trainers who have been highly effective in the past should reassess their training styles and their classroom materials to determine if they are prepared to meet the needs of these young new workers. This paper provides information that will help mine trainers communicate across the generation gap. 3. Mallett and Reinke's second paper provide an overview of training evaluation. Trainers and decision-makers are given a framework for planning and assessing training evaluation strategies. The authors present Kirkpatrick's (2001) model of evaluation categories and discuss how to start an evaluation plan and various ways to collect data. They do not provide detailed instruction in evaluation methodologies, but give trainers a review of the things they need to consider when developing an evaluation plan. A good evaluation plan can inform revisions to a training course, assess trainee learning, and/or answer managers' questions about program effectiveness. 4. Brnich, Derick, Mallett, and Vaught discuss a technique for incorporating worker participation into fire prevention and safe equipment operation training. This technique involves development of short (5 to 7 minutes) videotapes coupled with toolbox talks that ground the content of the videos within the context of a miner's workplace. An example of one of these training modules is presented, along with the results of an evaluation performed on its effectiveness at improving miners' understanding of what types of information they should be sure to communicate during a mine emergency. 5. Wiehagen, Conrad, Friend, and Rethi discuss on-the-job training (OJT) as a method for teaching miners safety and production skills. Much of the training is done by experienced workers. This paper describes how small investments can help improve the effectiveness of on-the-job training. Effective on-the-job training involves some structure and planning in the transfer of responsibility for task performance from the trainer to the novice. Assisting the trainer could involve helping develop up-to-date job analyses and offering strategies for teaching and evaluating job skills. This paper addresses organizational considerations supporting structured on-the-job

Jan 1, 2002

By M. H. Pelkki, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

Research has shown that excessive soil compaction is detrimental to the establishment of trees in reclaimed soils. Dry bulk density and penetration resistance are two soil parameters that can be used to indicate the level of compaction in reclaimed soils. It is believed that reclamation practices that minimize soil compaction will produce better results when forestland is the intended postmining use. The University of Kentucky has developed reforestation test cells on reclaimed soils at a surface mine in eastern Kentucky to test this hypothesis. Each test cell has been planted with various species of trees. Since 1997, data have been collected at these test cells for soil average dry bulk density, average penetration resistance, average depth to refusal and average survival rate of trees. These data have been correlated to determine the relationship between soil compaction and tree-survival rate. It is believed that these two soil-compaction parameters may ultimately be used to predict tree-survival rates on reclaimed surface mined lands.

Jan 1, 2003

By Hui Zhang, Fei Yang, Tong Guan, Guangqin Fu, Lihong Deng, Yuanlin Chen, Xiaotong Zhou

"For a copper-sulfur polymetallic mine in south China, the main valuable minerals were chalcopyrite, pyrite and pyrrhotite. The flotability of pyrrhotite was similar with chalcopyrite and pyrite and it was easy to be oxidized. As a result, the indexes of copper concentrate and sulfur concentrate were unsatisfactory. Furthermore, the recycling of tailings water ulteriorly deteriorated the technical indexes of copper-sulfur ore beneficiation. After a large amount of experimental studies, under the condition that the tailings water recycling rate was 100%, the copper concentrate with a grade of 22.25%Cu and a recovery of 82.46% on average was obtained for the raw ore containing 0.517%Cu, 15.94%S, 25.46%Fe on average, through using new technology “magnetic separation-flotation” and effective adjustment of parameters in the industrial test which was continuously conducted for 14 shifts in 5 days with a scale of about 75t/d. Comparing with the production indexes (the copper concentrate with a grade of 17.49%Cu, the recovery was 62.27%) during the corresponding period, the grade of copper concentrate increased 4.76%Cu, and the recovery increased 20 percentage points. Besides, the indexes of sulfur concentrate gained a considerable improvement. Currently, the new technology was adopted in the design of the new-built plant with a scale of 7000t/d of this mine. The new technology provided powerful support for the tailings water recycling and indexes improvement of copper-sulfur ore beneficiation.INTRODUCTION Chalcopyrite was usually associated with pyrite and pyrrhotite in copper-sulfur ore. Due to the similar flotability, it was difficult to obtain copper concentrate and sulfur concentrate with high grade. Furthermore, sulfide ore was easy to be oxidized and a large amount of ions formed in the pulp by the dissolution of minerals, which made the pulp become acidic. As a result, pyrite and pyrrhotite were easy to be activated in acidic solution and their flotabilities became stronger. Meanwhile, hydrophilic film formed on the surface of chalcopyrite in raw ore. The flotability of chalcopyrite became weaker and it made the separation of chalcopyrite from pyrite and pyrrhotite more difficult. So it was more difficult for copper and sulfur recovering with the recycling of tailings water containing high content of heavy metal ions and reagents."

Jan 1, 2018

By P. M. Kelly, E. P. Butler

Four Mn-CLL alloys, containing 60, 70, 80, and 90 pct Mn, respectively, have been examined in the quenched and the quenched and aged conditions using electron microscopy and electron, neutron, and X-ray diffraction. After certain heat treatments the alloys transform from fee to fct and in the tetraom1 condition show a domain structure parallel to {101} planes. Neutron diffraction indicates that the domains are antiferrornagnetically ordered. The domain boundary contrast has been examined using bright- and dark-field microscopy, and the contrast effects observed under favorable conditions have been used to deduce the c axis orientation in each domain. The domains are extremely mobile and can be nucleated at precipitate particles and screw dislocations. The domain mobility is responsible for the high damping capacity. In the aged material a Mn precipitates in the Kurdjumov-Sachs orientation and results of both electron microscopy and neutron diffraction indicate that the matrix separates into two components—one rich in manganese and the other rich in copper. ALLOYS of manganese and copper have the unusual combination of a high damping capacity and good mechanical properties and have been the subject of a number of investigations as part of a general interest in high damping capacity alloys for engineering purposes.&apos;,&apos; SO far, however, there has been no reported electron metallographic study of these alloys. The Mn-Cu system has an extensive range of solid solubility at high temperatures, and the equilibrium phases are expected to be y (fee) and a Mn. The high damping capacity is associated with a metastable tetragonal structure of variable c/a ratio, which forms from the high-temperature y phase. This latter phase becomes more difficult to retain as the manganese content increases, and alloys containing more than 82 wt pct Mn undergo a reversible martensitic fcc — fct transformation on quenching. The X-ray work of Basinski and christian3 showed that the Ms temperature for the transformation was below room temperature for alloys in the range 70 to 82 pct Mn and increased linearly with manganese content. When quenched from the y region, alloys in the range 50 to 82 pct Mn are cubic at room temperature, but become tetragonal if aged at temperatures between 400" and 600°C. The martensite transformation occurs on cooling from the aging temperature. Tetragonal alloys have a banded microstructure and the bands analyze to be traces of (110) planes. Similar microstructures have been observed in In-Tl4 and in other manganese-base systems, such as Mn-Au5 and Mn-Ni.6 The mobility of the bands in Mn-Cu alloys can be demonstrated by optical examination of a polished specimen surface subjected to a cyclic stress.7 The bands appear and disappear as the stress is varied, and X-ray measurements of the (200,020) and (002) peak intensities confirm that a reversible reorientation of the tetragonal structure occurs. Meneghetti and sidhu8 investigated the magnetic structure of Mn-Cu alloys and found antiferromagnetic ordering in furnace-cooled alloys of composition >69 at. pct Mn. Magnetic super lattice reflections occurred at the (110) and (201) positions and the proposed structure was fct with the spins along the c axis. A more complete investigation by Bacon et al.9 confirmed this structure. The magnetic ordering temperature Tn was found to increase linearly with manganese content in the same way as the Ms temperature, and at any composition, Tn > Ms. This relationship suggested that the magnetic ordering was responsible for the cubic — tetragonal transformation in the manganese-rich alloys. The purpose of this investigation was to study the mechanism of high damping and the structural changes that occur on aging. The main technique used was transmission electron microscopy, but X-ray and neutron diffraction experiments were also carried out. EXPERIMENTAL Materials and Heat Treatment. The four alloys, provided by the Admiralty Materials Laboratory. were of nominai composition 60, 70, 80, and 90 Mn and all had low impurity levels, <0.05 pct C, <0.2 pct Fe. This material was cold-rolled to 200-µ strip with intermediate annealing and then given a final heat treatment of 24 hr in the range 800° to 900°C followed by water quenching. An identical heat treatment was given a length of 3/4-in.-diam bar of the 70/30 alloy from which the neutron diffraction specimens were machined. It was suspected that the tetragonal structures would be metastable at room temperature, and so the alloys were not aged until required for experiments. After aging in a salt bath the alloys were water-quenched. Thin Foil Preparation. Initial thinning to 50 to 75 µ was possible in a solution consisting of: 50 ml nitric acid 25 ml acetic acid 25 ml water The surface deposit and grain boundary etching was removed by a final electropolish at around 20 V in an electrolyte consisting of:

Jan 1, 1969

By J. A. Venter, M. K. G. Vermaak, J. G. Bruwer

Electrostatic separation is employed in the concentration of zircon and rutile. The zircon concentrate undergoes an acid treatment to remove impurities from the surface of both the zircon and rutile. The purpose of the acid treatment is to increase the difference in the resistivities of the two minerals, thus ensuring the best possible electrostatic separation efficiencies. Previous test work suggested that these impurities are not removed, but only modified; the surface modification seemed more prevalent in the case of the rutile. The resistivity of the rutile changes with pH and thus the electrostatic separation of the rutile is influenced. X-ray photoelectron spectroscopy (XPS) indicates that there is an increase in the OH and adsorbed H2O concentrations on the rutile surface. XPS also showed significant differential charging on the rutile surface, which indicates that the species on the rutile surface have different resistivities. The zircon particles from the conducting and non-conducting streams have similar resistivities and no major differences in their surface species. Zircon losses during the final electrostatic separation appear not to be due to surface effects, but due to shielding of particles during the separation.

Jan 1, 2007

By Hugh M. Roberts

DEVELOPMENT at Steep Rock lake has given rise to renewed interest in the geology of the iron ore deposits in the Lake Superior Region and has implications of no small moment bearing upon methods of exploration in the Precambrian Shield generally. Following upon the Regional Lake Superior meeting of the American Institute of Mining and Metallurgical Engineers in August, 1941, the authors prepared a paper on the Steep Rock deposits, which appeared in the A.I.M.E. publication, Mining Technology, for January, 1943. Between Januar7 and April, 1943, exploration at Steep Rock was continued by means o vertical, Mesabi-type churn-drill holes put down from the ice. This drilling has enlarged the tonnage of ore previously known and has disclosed further facts relating to the origin of the ore. The added evidence, we believe, goes to support the hypothesis that the deposits were formed by a process of replacement due to upward-moving, iron-bearing solutions which came in as igneous after-effects. Accordingly, in presenting the subject to the Canadian Institute of Mining and Metallurgy, it seems best not to change our first explanation, but to prefix the original paper with an interpretation of the results of the more recent explorations completed after its publication.

Jan 1, 1943

By J. H. Rowland, A. C. Smith, K. A. Teacoach

Current regulations for fire suppression systems in underground coal mines to protect conveyor belt installations have been in place since the Coal Mine Health and Safety Act of 1969 was enacted. Over time, the coal conveyer equipment being used and ventilation conditions underground have changed significantly, particularly the width of the conveyor belts and the use of belt air at the face. The effect of these new conditions on the effectiveness of suppression systems during a fire is not known. The National Institute of Occupational Safety and Health (NIOSH) conducted a study to evaluate the effect of air velocity, water sprinkler activation temperature and a limited water application time on the effectiveness of water sprinkler fire suppression systems to extinguish large-scale conveyor belt fires. The fire tests were conducted using both new and used 1.8-m-wide, fire-resistant rubber belt that met the Mine Safety and Health Administration (MSHA) flame-resistant requirement specified in Title 30, Code of Federal Regulations, part 18, section 18.65 (also known as the 2G test). Tests were conducted using standard response sprinklers with activation temperatures of 68° C and 141° C at air velocities of 0.5 and 5.1 m/s. Two tests were conducted at both air velocities for each sprinkler activation temperature, one using a new belt and one with a used belt. The results showed that the suppression system was able to suppress the fires in ten minutes to the point that a miner could extinguish it with a fire hose. However, in several of the tests, the fire reestablished itself a few minutes after the sprinkler water supply was cut off and quickly grew out of control. This report discusses the large-scale experimental configuration, the installation specifications of the fire suppression system and the results and conclusions regarding the effect of air velocity, sprinkler activation temperature and limited water application on the suppression system performance.

Jan 1, 2010

By A. F. Baker, E. R. Palowitch, A. W. Deurbrouck

As air-pollution regulations become increasingly more stringent, increased significance is being placed on the amount of sulfur present in coals used for steam generation. These regulations are aimed at minimizing the pollution of the atmosphere with noxious gases such as the sulfur oxides that are formed and emitted when coal is burned. Two meet these future requirements, a definite need exists to reduce the sulfur content of some of the coals used for steam generation. Reducing pyritic sulfur involves liberating the pyrite from the coal and then removing it. The specific gravity of pyrite is high (5.0) compared to that of coal (about 1.2, mineral-free), and standard coal-washing devices, such as wet concentrating tables, will efficiently remove pyrite particles larger than about 100 mesh. Particles below this size will be entrained in the table water and will be carried into the clean coal product. Techniques such as froth flotation are of little benefit for pyrite reduction because the flotation characteristics of pyrite are similar to those of coal.

Jan 6, 1966

By Yanan Zhang, Hongwei Deng, Feng Gao, Bo Ke

Recently, liquid carbon dioxide (L-CO2) blasting technology has attracted attention due to its good fracturing effect and safety performance, especially in coal seam permeability improvement. This paper analyzes the blasting effect of L-CO2 based on experiments and studies the fracturing mechanism from the perspective of stress wave action via theoretical analysis and peridynamic simulations. The results indicate that L-CO2 blasting achieves a good fracturing effect without forming a crush zone, and the loading rate and strength of the stress wave are key factors.

Jan 19, 2022

By O&apos, Malley G. B

The properties of bearing metals are of considerable interest to mine engineers, since continuous running of mine and mill machinery is of vital importance. Of the several available types of bearing metal, the low melting point lead or tin base alloys are most generally used in mining plant because of the ease of replacement and the possibility of remelting scrap metal from old bearings. The most valuable property of these &quot;white metals,&quot; however, is the plasticity which gives a self-aligning character to the bearings, enablingthem to adjust themselves to inequalities which may exist at the time of fitting, or which may develop during running. The object of the present paper is to explain in general terms the physical structures of white bearing metals, and to point out that constitution rather than composition determines the physical properties of these alloys. The same, indeed, is true of most engineering alloys. In steels, for example, a change in the structure may affect the properties to a far greater extent than a change of chemical composition.Structural changes in steels are produced chiefly by heat treatment. In the case of bearing metals no good purpose is served by heat treatment; the microstructure is determined by the conditions of casting, and striking differences in constitution (and therefore in properties) are encountered in an...

Jan 1, 1932

By C. RAMADINI, F. NURJAMAN, A. SHOFI, B. SUHARNO

In this work, the selective reduction of lateritic nickel ore was carried out using sodium sulfate, sodium carbonate, and sodium chloride as additives. The 5 wt% of anthracite coal, which contains 60.35% of fixed carbon and 1.9% of sulfur, was used as a reductant. All raw materials were mixed homogenously prior to the pelletization process into 10–15 mm of diameter. The reduction process was carried out to 50 g of pellets at 950 °C, 1050 °C, and 1150 °C for 60 min in a muffle furnace at atmospheric pressure. It continued with a wet magnetic separation process to separate ferronickel (concentrates) and impurities (tailings). Iron and nickel grade analysis was performed using XRF, while phase transformation and microstructure were analyzed with XRD and SEM–EDS. The results showed that the sodium sulfate was superior, resulting in the highest nickel grade in concentrate, i.e., 15.06%. The sulfidation mechanism, which could inhibit the metallization of iron, effectively increased the nickel grade in concentrate than decomposition of carbonate and chloridization process. The sulfur content in the reductant also influenced the selective reduction process. It promotes more sulfidation of iron, thus increasing the nickel grade in concentrate.

Jul 7, 2021