Search Documents

By J. S. Gardner

Fortunately, few mining professionals have dealt with what all mining professionals fear---a mine disaster. Unfortunately, many have dealt with ?accidents? which may or may not claim lives but nevertheless rise to the level of a ?disaster? given the fallout of liability and litigation in today?s society.1 The undersigned authors published an article some ten years ago regarding crisis management2 based upon their collective first-hand experiences in actual disasters to that point in history. Unfortunately, disasters have occurred since that time, prompting legislation, and a fresh analysis and expansion of those basic principles is certainly in order. Without question, no two disasters are ever alike, yet general guidelines for forming an effective plan of action can be formulated?and if a mining operation is to have any chance of survival after a disaster, such a plan is vital. The primary concern as any disaster evolves remains as stated a 2003 SME article3--the protection of human life. From that point, the focus moves to any assistance that may be needed given the magnitude of the situation. Permeating throughout this process is "damage control." The first step in dealing with a disaster, however, begins long before any threat of danger arises?formulation and implementation of an Emergency Response Plan.

Feb 23, 2014

By Rodolfo Espinosa Gómez

"Industrias Peñoles, S.A. de C.V. – Mining Division, has initiated in the last ten years, six Mining Operations (Bismark, Tizapa, Ciénega, La Herradura, Rey de Plata, and Francisco I. Madero) and it has expanded several of their existing Operations (Sabinas, Fresnillo, Tizapa, Ciénega) one or more times.This work aims to share the experiences learned on this growing process. Some of these lessons are: 1) Project leaders must have a leadership that fosters good communication and team work; and this leadership style must come from top management. 2) A good communication must exist between the personnel from Engineering, Construction, and Operation. Also, this good communication must come from top management. 3) Starting the project with a solid Engineering Study. 4) Do not misunderstand cost with cost/benefit; always look at the cost/benefit. 5) Selecting good Contractors and good Suppliers. 6) Good training before the project commissioning is essential to reduce the learning curve period, this is even more important in areas where local people do not have any background in mining activities. 7) Recognizing that any project has a learning curve and it must be reflected on the production budget. 8) Avoid an over optimistic Mine preparation time schedule.BACKGROUNDIndustrias Peñoles S.A. de C.V.The mission of Industrias Peñoles, S.A. de C.V. (Peñoles) is to add value to non-renewable natural resources in a sustainable manner. Peñoles seeks to build long-term shareholder value; provide their customers with the highest quality products and services; maintain productive longterm relationship with their suppliers; develop and promote the capabilities of their personnel; foster mutually beneficial relationship with the communities in which it operates, and preserve the environment.Peñoles was established on 1887. It is a Mining Group with integrated Mining, Smelting and Refining operations of non-ferrous metals, and also produces inorganic chemistry materials. Peñoles is the main World producer of refined silver, metal bismuth, and sodium sulphate; Latin American leader in the production of refined gold, lead, and zinc.The Mining Group is made-up of nine mining operations producing concentrates with high gold, silver, lead, zinc, and copper contents. It produced in 2002, 365,900 ounces of gold; 52.7 million ounces of silver; 86,820 tonnes of lead; 266,000 tonnes of zinc, 11,840 tonnes of copper; with a total values of 3,780.6 million of Mexican pesos (~ $ 378.0 million U.S. Dollars)."

Jan 1, 2004

By R. A. Wagstaff

Since the time of the early Egyptians, the use of copper: has been a boon to the life of most of the civilized world. Its use has been varied; in many connections, the art by which it attained its greatest usefulness has been lost. In this paper an endeavor will be made to take into consideration some of the many changes that have occurred during the last 40 years of copper-smelting operations. During that period the copper blast furnace has been almost forced out of existence by new methods of ore concen-tration—first, gravity concentration, and then flotation. These new methods of concentration introduced many new factors into the metallurgy of copper. The product was wet, it was fine and it was high grade. To overcome all these factors many changes have been necessary throughout the smelting agenda. New equipment has been necessary for transportation, unloading, sampling, bedding and moisturing in all smelting plants, especially the custom smelter' During the early days of "flotation," little was known about filtering or the use of an alkaline circuit; often the concentrate going to the smelter contained 2' to '5 Per cent moisture. It is easy to imagine the difficulty arising with a product of this nature when it had to be shoveled by hand labor. To meet these conditions, mechanical unload- ing and sampling devices were soon developed. In many instances such good progress was made that actual costs for handling this unfavorable product were lower than those formerly incurred on the old product. Today most sampling of copper ores and concentrates is being done by mechanical sampling, pipe or augur sampling, or shovel sampling. Where concentrates are uniform in metal content, a great many of the plants now use pipe or augur sampling. For spotty ores, the old shovel sample with cone and quartering during the final stages is still in' use. Where big tonnages are handled, mechanical sampling of concentrates is being done, with satisfactory results. To curtail slow and tedious cutting and mixing procedure, mechanical mixing boxes, splitters and cutters are used to cut down labor costs. Milling As crude ores become scarcer, the use of milling operations increases. The few crude ores that are still smelted are used as fluxing types. To use these ores finer grinding has been found advantageous. This has made for better bedding and fluxillg conditions, which in turn makes for faster smelting, lower fuel consumption and better metal recovery. The degree of fineness is more or less determined by the nature of the product. Most plants have set a standard of through 3/8-in. mesh screen for roaster -reverberatory smelting and through 3/4-in. mesh screen for converter fluxes. For some refractory Ores, even finer grinding has been found to be advantageous for good reverberatory smelting-

Jan 1, 1944

By Y. Y. Zhou

This paper introduces the application of CRIMM high-gradient magnetic separator in refinement of feldspar powders as well as the supporting technical outfits needed by the refining process with the high-gradient magnetic separator as main equipment. It could reduce the content of Fe2O3 to 0.03% with a deferrization rate of 85.88% from the feldspar raw ore containing 0.17% Fe2O3by using the above refining technology, producing an ultrapure feldspar product.

Jan 1, 2014

By Warren E. Fife

This paper will discuss the application of a continuous miner using a fixed drum milling type cutting head for the underground mining of hard rock and salt ores. Continuous mining machines of the ripper chain cutting head, oscillating milling cutting head and boring arm designs have been used in rock and salt applications with various degrees of success. The large boring arm miners have been successful in potash, trona and salt, but they have not been successful in mining rock materials like iron ore. The main method used in underground mining rock materials is the conventional drilling and blasting the ore from the solid. This is particularly true for the harder, more abrasive copper and iron bearing ores. The softer salt based ores of potash, trona and rock salt can use several underground mining methods depending on seam conditions. Several of these methods use underground coal mining equipment that has been extensively redesigned to adapt it for use in mining noncoal materials. Conventional mining methods employ the use of a universal cutting machine to undercut or topcut the ore body before face drilling and blasting takes place to produce a smooth parting of the ore. The boring arm continuous miner is widely used in underground mining of potash and trona ores. It produces a tunnel with a smooth semicircular contour which results in good rib and roof stability. The ripper chain continuous miner is also widely used in mining the salt based ores of potash, trona and rock salt. They are used more frequently in Europe than in the United States and Canada. Some reasons for using the mechanical mining machines as opposed to the conventional drilling and blasting techniques for mining hard rock ore bodies are the resulting improved rib and roof control, facilitates selective mining of the ore body, and requires less man-

Jan 1, 1974

By Theodore B. Comstock

Prior to 1885, the College of Engineering in the State University was under the care of such professors and instructors as were required for efficient work in the Schools of Mechanical Engineering, Civil Engineering and Architecture. The development of the coal and other important mineral resources of the commonwealth led gradually to a considerable demand for instruction in the branches more closely related to mining engineering, and a very creditable effort was made to meet this want by arranging special work in the field and in the laboratory for students of mining and metallurgy. This plan, while it gave much added labor to several already heavily taxed professors, caused such students to become something like undesirable excrescences upon the regular courses. But its partial success gave abundant proof of the real necessity for a complete course in Mining Engineering. The famous Braidwood disaster emphasized anew the importance of thorough training on the part of those to whom the responsible duties of mining must be confided. As is well known, a very excellent beginning was made some years ago by the Legislature in the matters of inspection and regulation by the enactment of a reasonably effective law, which was afterward much improved.* About the date of the last Acts, it was deemed wise to enlarge the facilities at the University arid to furnish adequate training for the increasing number of applicants. Accordingly, in August, 1885, the writer was requested to assume the duties of the professorship, it being the expressed desire of the Board of Trustees and the Regent of the University that a School of Mining Engineering should be founded which might eventually come to rank with the other engineering schools already flourishing here. It is the main object of this paper to state plainly the steps thus

Jan 1, 1887

By Louis C. McCabe

The control of dusts and fumes of submicron size is involved in many process industries. This paper presents in tabular form the quantitative data from a number of metallurgical operations and discusses allowable discharge in terms of effluent-weight ratio. Typical installations for recovery of stack effluents are cited. THERE are many sources of smoke, fumes, gases, and dusts that may cause undesirable contamination in an industrial area. Fumes and gases are the result of chemical action or volatilization, while dusts are produced in processes of disintegration and dispersion. Commonly, smokes are suspended particles formed by combustion or destructive distillation. Methods for controlling smoke are generally known, and great improvements have been made in equipment for removing fine dusts and fumes from gases. In most of the industrial centers of the country, the chief duty of the air-pollution abatement agency is the elimination or reduction of emissions resulting from improper combustion. Correct methods of firing, proper fuel selection, and installation of properly designed equipment may accomplish this. It is becoming more widely recognized that much of the contamination of an industrial atmosphere is caused by dusts, fumes, and gases that are not related to the process of combustion. As such emissions are usually a functional part of plant operation, they rarely can be prevented even by better design and careful operation. When dusts, fumes, and gases are an integral part of the operation, mechanical equipment must be designed to remove these emissions. Most of the dusts and fumes that should be controlled are less than 1 micron in size. Control of such small particles is largely a new and untried field in many industrial areas. However, where conditions have been critical, effective control equipment for dusts, fumes, and gases has been in operation for many years. The problem is not one of smoke abatement and requires an entirely different set of standards for effective solution. Identical standards need not be applied to all industrial areas because of differences in meteorology, physiography, plant location, plant density, and nature of stack effluents. In this paper, discussion of control of atmospheric contamination by industrial plants refers specifically to the Los Angeles area, but the method of approach is applicable to any area where similar problems are encountered. Quantities of particulate matter reported in analysis of stack effluents indicate the need for standards of emission. Many types of dusts and fumes that contribute materially to the air-pollution problem are discharged into the atmosphere at a lower rate than 0.40 grain per cu ft at standard conditions. On the other hand, some stacks discharge at a higher

Jan 1, 1951

By Louis C. McCabe

The control of dusts and fumes of submicron size is involved in many process industries. This paper presents in tabular form the quantitative data from a number of metallurgical operations and discusses allowable discharge in terms of effluent-weight ratio. Typical installations for recovery of stack effluents are cited. THERE are many sources of smoke, fumes, gases, and dusts that may cause undesirable contamination in an industrial area. Fumes and gases are the result of chemical action or volatilization, while dusts are produced in processes of disintegration and dispersion. Commonly, smokes are suspended particles formed by combustion or destructive distillation. Methods for controlling smoke are generally known, and great improvements have been made in equipment for removing fine dusts and fumes from gases. In most of the industrial centers of the country, the chief duty of the air-pollution abatement agency is the elimination or reduction of emissions resulting from improper combustion. Correct methods of firing, proper fuel selection, and installation of properly designed equipment may accomplish this. It is becoming more widely recognized that much of the contamination of an industrial atmosphere is caused by dusts, fumes, and gases that are not related to the process of combustion. As such emissions are usually a functional part of plant operation, they rarely can be prevented even by better design and careful operation. When dusts, fumes, and gases are an integral part of the operation, mechanical equipment must be designed to remove these emissions. Most of the dusts and fumes that should be controlled are less than 1 micron in size. Control of such small particles is largely a new and untried field in many industrial areas. However, where conditions have been critical, effective control equipment for dusts, fumes, and gases has been in operation for many years. The problem is not one of smoke abatement and requires an entirely different set of standards for effective solution. Identical standards need not be applied to all industrial areas because of differences in meteorology, physiography, plant location, plant density, and nature of stack effluents. In this paper, discussion of control of atmospheric contamination by industrial plants refers specifically to the Los Angeles area, but the method of approach is applicable to any area where similar problems are encountered. Quantities of particulate matter reported in analysis of stack effluents indicate the need for standards of emission. Many types of dusts and fumes that contribute materially to the air-pollution problem are discharged into the atmosphere at a lower rate than 0.40 grain per cu ft at standard conditions. On the other hand, some stacks discharge at a higher

Jan 1, 1951

By B. Thompson

"1. AbstractMagnesium alloys have been successfully recycled for decades and have won acceptance for use by die casters and most of the automotive industry. As the supply chain for magnesium and magnesium alloys continues to change, due to the consolidation of producers, it is essential that quality control methods be closely examined with each new supplier added. An examination of the various process steps that are needed to assure quality in the final product will be discussed thus giving a basis for the auditing of new magnesium suppliers.2. IntroductionMagnesium recycling in the past has been somewhat limited due to its use more as an alloying agent for aluminum based alloys and as a desulfurization agent in iron and steel than in more readily recycled structural products. Recycling efforts continue to improve as more production is finding its way into automotive structural components, hand tools, and a variety of computer and cellular telephone applications.With the closure of several large North American primary magnesium production facilities over the past decade we have only recently witnessed a tightness in supply that is driving magnesium prices significantly higher, nearly doubling the price in the last year alone. The rapid escalation in pricing will provide additional economic incentives to fully utilize recycling for the recovery of an even greater percentage of both old and new sources of magnesium scrap. Political pressure continues to intensify towards the secondary recovery of any and all recoverable resources of which magnesium recycling readily applies.Economics will also likely drive the development of new sources of magnesium production, both from primary and secondary production. As new sources of magnesium are offered to the marketplace the potential for product quality issues may increase. When considering any new raw material supplier a decision must be made as to the impact of defective material on the intermediate or finished product. Quality defects in magnesium ingot can result in a variety of appearance, corrosion, and even adverse structural effects in the finished product. The potential severity of the impact of defective raw materials on the finished product will determine and often justify a close look at any new supplier. An on-site audit of a new supplier of a critical raw material is often justified to ensure that an adequate quality assurance system is in place. We will now look at a number of key production points that should be examined during an on-site audit that have can have an impact on the overall quality of the finished product."

Jan 1, 2008

By Chengguo Zhang, Bruce Hebblewhite, Faham Tahmasebinia, lsmet Canbulat

"Coal burst is a dynamic release of energy within the rock (or coal) mass leading to high velocity expulsion of the broken/ failed material into mine openings. This phenomenon has been recognised as one of the most catastrophic failures associated with the coal mining industry, which can often lead to injuries and fatalities of miners as well as significant production losses. This paper aims to examine the mechanisms contributing to coal burst occurrence, with an emphasis on the energy release concept. In this study, a numerical modelling study has been conducted to evaluate the roles and contributions of difference energy components. The energy analysis presented in this paper can help to improve the understanding of energy release mechanisms especially under Australian conditions.INTRODUCTIONCoal burst is one of the most hazardous problems encountered in underground coal mines, which occurs at different locations in a variety of mining systems and operations. This phenomenon always involves a violent and dynamic energy release with large rock mass/coal deformation and ejection that can cause severe damage to openings, equipments and may result in fatalities and injuries.The first coal burst occurrence was reported in Britain in 1738 (Dou 2001). Since then, international experiences are available in Canada, South Africa, USA, former Soviet Union, China, India, France, Germany, Poland and Czechoslovakia. Rice (1935) classified coal bursts as two general types, namely excessive pressure bumps and shock bumps and he further mentioned that pressure bumps are caused when pillar stress exceeds bearing strength. Shock bumps are induced by the breaking of thick, massive strata at a considerable distance above the coal-bed, causing the immediate roof to transmit a shock wave to the coal."

Jan 1, 2016

By K. A. Slagle

Hydraulic analysis of the wellbore has become increasingly inzportant for designing cementing operations and selecting equipment, materials and techniques to complenzent modern well-c-ompletion practices. Non-Newtonian fluid technology has advanced beyond the point where former empirical methods of analysis adequately define the hydraulic system and fluid properties. In view of these factors, this paper describes a series of rheological calculations which have been found practical, through field usage, for assistance in selecting a cementing program. A relatively simple laboratory method using standard viscometric equipment is suggested for determination of the rheological properties of slurries, and clrrta are presented on some of the more common cementitrg conzposition.A. A criterion for divergence from laminar-flow characteristics has been proposed. Usefulness of the calculations is indicated by examples of cementing operations where they have been used. INTRODUCTION With the changing aspects of well-completion practices during the past few years, it has been increasingly important to have a relatively simple method of analyzing the flow conditions existing in the well during cementing operations. This is particularly true in view of the improved economics toward which most of the changes have been directed. Rheological characteristics of slurries used for cementing should be a major consideration in the trend toward smaller casing sizes, either single or multiple strings. Receiving increased attention is the practice advocated in 1948 by Howard and Clark' of attaining turbulent flow with the fluids circulated during a primary cementing operation. While there may still be a difference of opinion concerning this technique, most available information indicates that superior primary-cementing results are generally obtained when high displacement rates are employed. Fluid properties of the slurry to be used must be available, as well as calculation methods, to determine what flow rates should be attained and the probable consequences in terms of frictional pressure and horsepower utilization. It would certainly be inappropriate to attempt high displacement velocities if sufficient pressure might be developed to create lost circulation. Since cementing slurries are non-Newtonian fluids, it is not possible to define their rheological or fluid properties by the single factor of viscosity and then make calculations for the quantities just described. Because the shear stress-shear rate ratio is not constant: it becomes necessary to establish at least two parameters for adequate fluid-flow calculations. It is not the purpose of this paper to delve into the mathematical development of non-Newtonian technology, nor to discuss the arbitrary classification system under which a single fluid may resemble two or three different classes depending upon experimental conditions. Rather, the intention is to present a useful series of calculations based on a concept applicable to both Newtonian fluids and to the preponderance of non-Newtonian fluids encountered in the oil-producing industry. Development of this approach was begun some 32 years ago,' and has most recently been brought to fruition by Metzner and his co-workers at the U. of Deleware. Some non-Newtonian fluids encountered in the petroleum industry, other than cementing slurries, have also had the benefit of this method of analysis."' The two parameters required to define the fluid are usually denoted by the symbols n' and K' and, for the purposes of this discussion, are called "flow behavior index" and "consistency index", respectively. These two slurry properties permit calculation of the Reynolds' number and the "critical" velocity, or the velocity at which departure from laminar flow begins. EXPERIMENTAL DETERMINATIONS The two principal instruments used for rheological studies are the pipeline (capillary-tube) viscometer and the rotational viscometer. When conveniently possible, a capillary-tube viscometer (where the pressure drop and flow rate of the material can be measured) is the better method for rigorous determination of the flow behavior index and consistency index for non-Newtonian fluids. With pressure-drop data at various flow rates, it is then possible to prepare a logarithmic plot of shear rate as the abscissa-shear stress as the ordinate. For fluids which do not exhibit time-dependency, these data will usually produce a straight line. The flow behavior index n' represents the slope of this line, while the consistency index K' becomes the intercept of this line at unity shear rate in accordance with the mathematical derivations associated with this concept of rheology. Due to the difficulties anticipated in maintaining a uniform, pumpable cement slurry for the time interval required to obtain measurements from the pipe viscometer, the n' and K' data reported herein were obtained using a direct-indicating rotational viscometer (Fig. 2). The

By D. K. Sarkar, Jiawei Xiong

"Self-assembled monolayers (SAM) on the aluminum substrates are used as the adhesion promoter between two aluminum substrates when bonded with the adhesive in adhesive bonding technology. Traditional surface analysis tools are not capable of identifying the presence of SAM on a surface; therefore, EIS has been used to determine their presence on the aluminum substrates. In this study SAMs have been deposited on aluminum using the monomer of (3-Glycidyloxypropyl)trimethoxysilane (GPTS) organosilane. AA6061 aluminum alloys substrates were chemically cleaned with NaOH and HNO3 to remove the native oxides, followed by immersion in silane solutions. In a second method, SAMs were prepared by applying a spin coating of silane solution to the samples. The prepared SAM coated aluminum samples were analysed by EIS in the three electrode corrosion cell using a diluted alkaline solution. The impedance of the SAM coated aluminum is found be higher than the as-received aluminum. It has been also observed that the open circuit potential (OCP) of the SAM coated aluminum is higher than the as-received aluminum. Both elevated values of the impedance and OCP confirm the presence of SAM on aluminum.INTRODUCTIONSelf-assembly (Schreiber, 2000) is defined as the spontaneous formation of complex hierarchical structures from pre-designed building blocks, typically involving multiple energy scales and multiple degrees of freedom. Generally speaking, SAMs are created by the chemisorption of ""head groups"" onto a substrate from either the vapor or liquid phase followed by a slow organization of ""tail groups"" of a molecule. Typically, head groups are connected to a molecular chain in which the terminal end can be functionalized with groups such as –OH, –NH2, –COOH, or –SH to vary the wetting and interfacial properties (Chauhan et al., 2007; Ulman, 1996; Vashist, Lam, Hrapovic, Male, & Luong, 2014). Though there exist several methods to prepare SAM (Chauhan et al., 2007; Chen, Yang, & Zhang, 2014; Cho, Park, Jon, & Choi, 2007; Igor Luzinov, 2000; Reis, de Melo, & Costa, 2006; Song, Zhai, Wang, & Jiang, 2006; Sugimura, Hozumi, Kameyama, & Takai, 2002; Vashist et al., 2014), the two methods vapor phase (Song et al., 2006; Sugimura et al., 2002) and solution(Chen et al., 2014; Igor Luzinov, 2000) are commonly used. Recently, many articles have been published on the fabrication of superhydrophobic surfaces with SAM technology (Cho et al., 2007; Pan, Shen, Shang, & Xing, 2012; Siddaramanna, Saleema, & Sarkar, 2014; Song et al., 2006). Brassard, Sarkar, and Perron (2011) successfully obtained a superhydrophobic film by applying fluoroalkylsilane via self-assembly on monodispersive silica. SAMs are also reported as good candidates for anti-corrosion and adhesion promotion (Chen et al., 2014; Saleema, Sarkar, Paynter, Gallant, & Eskandarian, 2012). However, papers on the characterization of SAM properties are rarely seen. The most commonly used substrate for SAM is silicon and the method implemented is scanning probe microscopy (SPM) such as atomic force microscope (AFM) (Igor Luzinov, 2000; Moores, 2011; Zhang, 2003, 2005). Igor Luzinov (2000) analyzed the epoxysilane SAMs’ surface morphology and microstructure properties using scanning probe microscopy (SPM) and ellipsometry on single-crystal silicon wafers. SAMs have been used to improve the adhesion bonding of aluminum or plastics but no characteristic data have been presented yet (Saleema et al., 2012; Telegdi, 2007; Wang, Xu, Luo, Wang, & Wang, 2009). Recently, Reis et al.(Reis et al., 2006) have studied SAM of alkane diphosphonate (Gardobond X4661) on Al 5052 alloy samples by EIS in a naturally aerated sodium sulfate solution."

Jan 1, 2016

By Arthur F. Wendt

In the manufacture of charcoal-blooms, washing or cleansing of the ore from adhering gangue has been practiced for many years. A sluice-box is even to-day used for that purpose in the Southern Appalachian Mountains. For the Lake Champlain bloomaries hard magnetic ores are crushed with stamps and then sluiced or jigged in hand-jigs. The stamps used in the Lake Champlain region are of the most primitive kind. They consist of a trip-hammer, dropping on a perforated cast-iron plate, through which the crushed ore escapes. Only friable rock can thus be successfully treated. To render the raw ore friable, a calcining or burning in piles on a bed of cordwood is resorted to. An expense of 35 cents per ton of crude rock treated is thus incurred. The crushed ore is shovelled or otherwise fed into jigs without previous sizing, except such as is incidental to crushing through the perforated bottom of the stamping-machine. In jigging this ore, it is allowed to pass through the bedding into the "hutch." The tailings are scraped off and wasted. They contain a large percentage of fine ore. In many instances, this is regained by subsequent sluicing. Such was the condition of the industry, when the writer's attention was first called to it in 1882. No attempt had been made to introduce into thiS branch of ore-dressing the notable improvements adopted in concentrating the ores of other metals. The result of the writer's investigations was the building in 1882 of the "Crown Point Separator." At the Crown Point Mines, N. Y., lean ore unfit for the blastfurnace (containing less than 331/3 per cent. of iron), was concentrated and used in the bloomary connected with the mines. The ore was burned here as elsewhere, and treated as described. The plant designed by the writer for Crown Point, is nearly a counterpart of that since erected by Messrs. Copeland and Bacon, contractors, for the Theal mine, Putnam County, New York, which is illustrated by the accompanying plate. The only difference is in

Jan 1, 1885

By D. G. C. Robertson

The thermodynamics and kinetics of the reactions involved in fuming zinc from oxide slags using coal or coke were first studied in 1955 and have been the subject of many investigations since that time. The key reaction is ZnO(in slag) + CO Zn(g) + COl. This paper will review the some of the recent work, and will add new insights obtained in experiments carried out by the authors. In the first series of experiments it was shown that the reaction 2Fe2+ + ZnO = 2Fe3+ + Zn(g) or 2FeO + ZnO = Fe2O3 + Zn(g) does not occur at an appreciable rate, as is expected from thermodynamic considerations. In the second series of experiments it was shown that zinc does not fume from the slag at a significant rate unless a reductant has been added. This again is in accord with thermodynamic considerations, but is in contradiction to some of the experimental results reported in the literature. A third series of experiments was carried out with excess coke being present, so that the rate of supply of reductant was not in any way controlling the rate. The kinetics of zinc oxide reaction were then found to be independent of the zinc oxide concentration, but increased with increasing basicity, and temperature. The presence of high concentrations of FeO in the slag also improves the kinetics. At low zinc oxide concentrations iron oxide reduction occurred in parallel with zinc oxide reduction. We propose that (under the conditions of this work) the kinetics were controlled by a chemical step, namely the rate of desorption of an adsorbed CO2 species. This is the same mechanism as reported by Belton and co-workers for the kinetics of the reduction of FeO. This explains why the reduction of metal oxides in slags by hydrogen is often faster than by CO.

Jan 1, 2003

By B. P. Watson, T. J. Maphosa, D. P. Roberts, L. J. Gardner

The results of FLAC3D modelling on chromitite Upper Group 2 Reef pillars from the Bushveld Complex of South Africa are described. The model input parameters were determined from laboratory triaxial tests with post-failure measurements. These geomechanical tests were performed on rock materials within the pillars and the immediate pillar foundations. In the models, postfailure behaviour was simulated using the concept of cohesion softening. Models were built to determine the strength and behaviour of pillars with a width-to-height ratio of approximately two. The original research aimed to find a suitable depth below the surface where Impala Platinum Ltd could safely introduce crush pillars; however, the paper only describes the model results: the ideal depth of the crush pillar introduction is not discussed. The results of the modelling are compared with the PlatMine formula for peak pillar strength and with an underground instrumented pillar located elsewhere on the same reef. Some insight into the effects of grid size on strength is also provided. Further underground measurements are recommended to verify the model results

Sep 9, 2024

By H. J. Liang

In this study, zeta potential and contact angle measurements of pyrite before and after interacting with Thiobacillus ferrooxidans are carried out to investigate the changes in its surface properties. The results show that, after pyrite interacting with Thiobacillus ferrooxidans and its metabolite, the surface electricity of pyrite changes obviously, resulting in a notable shifting of isoelectric point to lower pH value, but the contact angle varies little. Bacterial protein plays the most important role in the interaction. This work is helpful to disclose the mechanisms of Thiobacillus ferrooxidans de-pressing pyrite flotability.

Jan 1, 2014

By Eduardo Côrtes de Castro

O presente trabalho aplica o modelo de análise de capacitação tecnológica desenvolvido por Figueiredo (2001) para definir um método de aumento de competências e melhoria de performance numa unidade de prestação de serviços da Companhia Siderúrgica Nacional, a gerência de oficina de cilindros de laminação. A utilização deste método permitiu o aumento da capacitação técnica da unidade, através dos processos de aprendizagem subjacentes, e a melhoria de performance, medida por indicadores chave de desempenho relevantes para o resultado da empresa (qualidade, custo, atendimento e produtividade da mão de obra). São apresentados, além dos resultados, a estrutura analítica do modelo proposto e as evidências associadas às capacidades tecnológicas acumuladas e aos processos de aprendizagem.

Oct 30, 2017

By D. J. Robertson

"THE copper smelting operation of the Hudson Bay Mining and Smelting Company, Limited, at Flin Flon, Manitoba, generates a gas flow of 350,000 c.f.m. at n.t.p. This gas stream passes to atmosphere through a 20-foot diameter by 250-foot brick stack, carrying with it an appreciable dust burden in the form of metallic oxide fumes. The flow constituents during the period 1952 and 1953 and •before gas filtration was included in the treatment scheme are shown in Table I. This paper describes the gas filtration treatment which was installed in 1957, using glass cloth media to recover this dust burden, and discusses the associated problem as its treatment for recovery of zinc and cadmium.The metallurgical details associated with the problem are illustrated by a description of the material flow sequence of the Company's hydrometallurgical zinc plant and copper smelter. In this ore processing complex, the zinc plant and copper smelter form an integrated unit within which intermediate zincrich products of each operation enter the treatment circuit of the other."

Jan 1, 1960

By Agbo Chima

Low-lying sections of open-pit mines accumulate water, especially during the rainy seasons, preventing access to resource-bearing areas. To sustain mining operations, the water must be lifted out of the flooded pits at a high flow rate using pumps. These pumps need to be mobile so that they can be removed during drill-and-blast operations. Most mobile pumps rely on diesel engines with high maintenance requirements. A special pump design was developed to address the unique needs of open-pit mining while making the dewatering process more sustainable. Using the target flow rate and head data, an efficient pump was designed, encased, and deployed in the open pit. A variable speed drive (VSD) was installed in a protective skid so that the pump could be tuned to match the preferred flow rate at any point during its operation. This system was tied to the national electrical grid instead of being powered by diesel pumps, which reduced the carbon intensity per kilowatt-hour. The high availability, low maintenance requirement, and greater reliability reduced the use of spare parts, the fuel consumption, and the logistics associated with operating the pump. This further reduced the carbon footprint of the dewatering process. This paper provides some of the two-year performance metrics for a deployment in West Africa. With a focus on availability, maintenance costs, average cost per volume lifted, and carbon footprint, this encased pump system is compared to the diesel-driven pumps that it aims to replace.

Jan 1, 2023

By Z. F. Oszter

This paper discusses the materials handling problems encountered in cement plants in the areas of raw and finished product grinding and cement storage. It illustrates by examples taken from actual installations, how optimum feed rate is maintained in grinding circuits with properly applied bin dischargers (vibrating hoppers, Mexican feed boxes and aerated bin bottoms) for materials with high moisture content and/or difficult handling characteristics. Initial operating problems with the equipment will be discussed and maintenance requirements will be indicated for comparison purposes. In a modern cement plant, properly functioning bins and feeders are as essential as process control, for no process control system, however sophisticated, can perform efficiently if raw materials do not flow into the plant processing facilities at the required time and rate. Most materials used in the manufacture of portland cement - such as silica sand, iron ore fines, crushed limestone, gypsum, clinker or cement itself-have difficult handling characteristics under specific conditions. High moisture content or even dampness due to condensation may create bin hang-ups, arching and ratholing, all of which result in improper functioning of the feeders or proportioning equipment. The occurrence of these problems in existing cement plants spurred a search for the corrective devices discussed in this article. The equipment investigated included bin dischargers in the form of vibrating hoppers for moist raw materials, Mexican feed boxes for clinker and aerated bin bottoms for cement. Operating experience with different types of bin dischargers showed that the actual performance of some did not come up to the expected level under prevailing operating conditions. The aim of this paper is to record the results of this experience and there- by aid designers and/or operators in selecting the most suitable equipment for their requirements. BIN DISCHARGERS (GENERAL) A discharger is a device that causes stored solids to flow out of a hopper without metering the rate of flow as a feeder does. The investigation discussed here encompasses the following types of bin dischargers used in a cement plant: (1) vibrating hoppers (horizontal motion), (2) whirlpool hoppers (horizontal and vertical motion), (3) aerated bin bottoms (air fluidization), and (4) Mexican feed boxes. Most of the bins used in the cement industry are of the plug flow type. Raw materials with difficult handling characteristics such as high moisture content may cause flow problems when fed through small openings (12 x 18 in.), even if two walls of the bin are vertical.' The most appropriate solution to these flow problems would be the installation of separate mass flow bins for the different materials such as silica sand, iron ore fines, crushed limestone and gypsum, with each bin correctly designed from test data obtained by measuring the flow properties of representative samples. However, limited storage capacity and plant space usually preclude this approach. Quantitative design of bins for flow based on measured flow properties of representative samples of the bulk solid to be handled is no longer an "engineering art," thanks to the basic research done on the flow of bulk solids in bins during the last decade.2, Where space limitations exist, however, or where improvements are being sought for equipment already installed, bin dischargers offer a satisfactory solution to flow problems. They can be applied effectively under flat-bottom bins or mounted to existing plug-flow bins with very little modification to these facilities. In both the foregoing cases, plug flow will be maintained, but the flow channel will be considerably increased so that it is larger than the discharger's bin-side diameter, and material flow can be sustained if the discharger is correctly selected. The main purpose of a bin discharger is to draw the bulk solids across the whole area of the bin outlet, to make the opening fully effective. As long as the bin-side opening of the discharger is large enough

Jan 1, 1969