Search Documents

By Lilong Zhu, Shaoda Zhang, Qian Wang, Shengping He

The effects of ZrO2, Y2O3 and Sc2O3, which are transition metal oxides, on the melting temperature, viscosity at 1300 °C, and break temperature of three mold fluxes (two weak-reactive type and one non-reactive type) designed for the high manganese and high aluminum steels, and one another conventional CaO-SiO2 based mold flux is studied. The results indicate that the melting temperature and viscosity increases slightly, and the break temperature increases dramatically with the addition of ZrO2, Y2O3 and Sc2O3 content in the conventional CaO-SiO2 based mold flux system. While, the addition of ZrO2, Y2O3 and Sc2O3 in the weak-reactive or non-reactive mold flux systems has a negligible in fluence on the melting temperature, viscosity and break temperature, suggesting that these transition metal oxides are possible to regulate radiation heat transfer without changing the basic properties of mold fluxes.

Mar 1, 2018

By Richard F. Zaffarano

The Bureau of Mines compiled information for the nonspecialist about natural gas liquids recovery from hydrocarbon streams in natural gas processing plants. Attention is directed to the impact of the technology of processing and the quality of gas processed in view of the increased availability of natural gas for processing. Significant changes in product and market trends within the natural gas processing industry are highlighted. Fixed capital-plant costs for grassroots, refrigerated-oil absorption and conventional adsorption schemes, adapted from published studies, are presented giving ranges of cost estimates for medium-sized plants. Marketed products of the natural gas processing industry are briefly discussed in relation to automotive air pollution problems and approaches to their control.

Jan 1, 1970

By P. Somasundaran, D. W. Fuerstenau

This article presents the results of an analysis of grinding of 1:1 mixtures of 4x8-mesh quartz and limestone in laboratory ball and rod mills. From these experiments, the amount of energy consumed in grinding each component of the mixture was determined. In the ball mill, limestone consumes slightly more energy than quartz in the initial stages of grinding, but as the grinding proceeds quartz begins to consume a slightly greater fraction of the energy. The postulate that the fraction of energy consumed by any material in a ball mill is proportional to its volume fraction has been shown to be approximately true. On the other hand, in a rod mill energy consumption by quartz and limestone is equal only in the initial stages of grinding, with energy consumption by quartz greatly exceeding that by limestone as rod milling proceeds. Preferential energy consumption in tumbling mills has been discussed in a number of papers. For example, from an analysis of the kinetics of comminu- tion in ball mills, Arbiter and Bhrany' obtained rate equations based on the postulate that only coarse particles are ground, indicating that fine particles are protected from the action of the balls by coarser particles. In rod mills this protective action is much more pronounced than in ball mills. Recent studies on the rod milling of limestone-quartz mixtures have shown that this protective action causes the mineral with the lowest grindability (quartz in this instance) to consume the greater fraction of energy. 2 However, in the ball milling of mixtures it has been postulated that the consumption of energy by one of the constituents is determined by its volume fraction within the mill. 3 Possibly this hypothesis may be a simplification of the ball milling of mixtures since the protective action suggested by Arbiter and Bhrany may result in some preferential energy consumption by one of the constituents of a mixture. The objective of this study has been to determine preferential energy consumption in laboratory ball and rod mills by analyzing size distributions of each material in the products obtained from grinding 1:l mixtures of quartz and limestone. MATERIALS AND METHOD The procedure for carrying out the tests on wet grinding quartz-limestone mixtures has already been described.'r3 In the present investigation, 1:l mix-

Jan 1, 1963

By C. Damiani

The Chuquicamata smelter, operating since 1952, has gone through several developing stages which have been characterized by the addition of peak technology for copper concentrate smelting (Teniente converter and Outokumpu flash furnace) with an intensive use of technical oxygen, which has permit-ted to partially discontinue the reverberatory furnace utilization. This paper shows the main indicators and operational practices at present, as well as those concerning maintenance aspects. Finally, the most relevant topics related to the future development of the smelter are mentioned with special remarks on the Decontamination Plan, which allows US to keep the high level of production, reducing the emission of contaminants according to the legal requirements in force.

Jan 1, 1993

By James L. Weeks

Introduction This paper attempts to summarize some of the major criticisms of drug testing. Eight problems with drug testing are discussed. These are: • It does not measure something employers have a reasonable need to know, • It is a distortion of priorities, • Drug use is not known to be associated with increased risk of occupational injuries, • Drug testing is proposed as a dangerously simplistic solution to poorly conceived problems, • In the absence of safeguards, it is unacceptably inaccurate, • In the absence of treatment commitments and confidentiality protection for persons dependent on drugs, it is an unethical practice of medicine, • Drug testing is an invasion of privacy, and • It will have a negative effect on treatment of persons with drug or alcohol dependencies. Employers' need to know It does not measure something employers have a reasonable need to know. It is reasonable for employers and fellow workers to want to know if workers are functionally impaired (intoxicated) while on the job. Drug testing does not measure impairment. It measures the concentration of drug metabolities in urine or blood. Unlike measurements of blood alcohol concentration (BAC), drug metabolites are not correlated with impairment or intoxication. They indicate only drug use in the one to two weeks before a urine sample. And, in some instances, they indicate chronic use. Impairment caused by drug use, on the other hand, occurs immediately and declines rapidly within hours. Drug metabolites may linger for days afterwards. Drug metabolite concentrations in urine are a function of (Morgan, 1984; Schartz and Hawks, 1985; MMWR, 1983): • the amount and purity of drug consumed before taking the test, • when the drug was consumed, • whether the person was a chronic user, in which case a certain amount of drug metabolites would be stored in body fat and slowly released, • the person's metabolic rate, and • for metabolites in urine, any dilution effects of urine. Only the first two factors has

Jan 11, 1987

By Paulo Henrique da Silva Gomes

A melhoria contínua dos processos é fator fundamental para o sucesso do negócio. Avaliar as melhores práticas e propor soluções que equilibrem os custos e o uso consciente dos recursos naturais transformará o negócio sustentável e sólido. Com esse ideal, foi realizado um estudo de viabilidade econômico-financeira e operacional para a implantação de um novo modelo de peação (fixação) de cargas conteinerizadas com produtos siderúrgicos (bobinas de aço) da CSN movimentados pelo Sepetiba Tecon - Porto de Itaguaí - RJ. O processo de peação de bobinas era basicamente realizado utilizando-se de madeiras fumigadas para a fixação das bobinas dentro do contêiner. O estudo objetivou a implantação de um processo de peação utilizando cintas de poliéster, reduzindo o uso de madeira, proporcionando maior segurança pessoal e agilidade nas operações. Além disto, propôs também a utilização de um implemento para acomodações das bobinas dentro do contêiner que pode ser operado por uma empilhadeira de menor capacidade, reduzindo assim a emissão de gases poluentes e o consumo de combustíveis fósseis.

Jul 29, 2018

By Susana Marraccini Giampietri Lebrão, Jorge Alberto Soares Tenório, Renato Souza e Silva, Guilherme Wolf Lebrão, Viviane Tavares de Moraes

Os resíduos eletroeletrônicos podem ser compostos por equipamentos ou parte deles, que se tornaram obsoletos, pararam de funcionar ou ainda por apresentar defeitos durante a sua produção. As placas de circuito impresso (PCIs) são peças presentes em equipamentos eletroeletrônicos compostos por materiais metálicos, cerâmicos e poliméricos. Para alguns destes metais já existem processos para recuperação, contudo estes processos baseiam-se em técnicas pirometalúrgicas que podem liberar substâncias tóxicas. A fim de minimizar os impactos ambientais propõe-se o beneficiamento das PCIs através de rota hidrometalúrgica para a obtenção de cobre em solução e, posteriormente fazer a redução do cobre. Para tanto se fez a moagem das PCIs, seguida de caracterização química. Partiu-se para rota hidrometalúrgica em meio ácido e em meio oxidante. A solução resultante de cobre foi reduzida para cobre metálico por reação de redução com ácido ascórbico. Os resultados apresentam recuperação de 97 % de cobre das PCIs com obtenção de cobre metálico.

Oct 11, 2019

By A. C. Butterworth

M OST operators of open-pit mines in the Lake Superior iron ore district are quite familiar with the use of fuel oil in the heavy-duty Diesel engines commonly used in truck-haulage service but some operators, including my own company, Pickands Mather, have had butane-engine trucks in service for several years, and less is known of their operation. One of the first installations of trucks for iron-ore haulage was in 1939 at a deep open-pit mine on the Cuyuna Range. These superseded standard-gauge steam haulage. Trucks then obtainable were equipped with 150-hp Diesel engines, and the speed of these units on an 8 % grade would have been so slow, considering the depth of the pit, that plans for an all-truck haul out of the pit were rejected. About this time one of the engine manufacturers brought out an auto-

Jan 1, 1948

By T M. Campos, H A. Petit, L M. Tavares, R Olympio

Much practical experience has been gathered in the last 30 years of application of high-pressure grinding rolls (HPGR) integrated with ball milling in size reduction of fine iron ore concentrates. The company Vale S.A, in Complexo de Tubarão (Brazil), was one of the pioneers applying the technology prior to pelletisation with an outstanding size reduction energy efficiency in the circuit and a significant increment in the specific surface area of the product. Recent studies by the authors demonstrated benefits of modelling and simulation to improve the performance of HPGRs in this particular application, with the model being able to describe HPGR performance under different operating conditions and under variations of feed size distribution. Despite these important advances, this modelling approach has only been used offline and under steady-state conditions. The present work applies the modified Torres and Casali model proposed by the authors in pseudodynamic simulations. The ability of the model to predict the characteristics of the product in real-time is evaluated using data available online for the pellet feed preparation circuit. Results demonstrated the model capabilities to map the physical operation and give a realistic representation of the process. Additionally, the model is demonstrated to be able to support the pellet feed production by providing extended real-time information of the process, making it a useful tool for improvement of the operational strategies and process stability.

Aug 24, 2022

By André Luiz Vasconcellos da Costa e Silva

O sistema ferro-oxigênio alumino tem sido investigado há muitos anos em função de sua importância para a indústria do aço. Uma grande fração de todo o aço plano produzido é de aço de baixo carbono acalmado ao alumínio, não apenas pelo baixo conteúdo de oxigênio residual em solução que pode ser obtido mas, também, pela importância do alumínio residual na formação de AlN, ferramenta importante no controle de estrutura e textura obtidas. O sistema Fe-O é relativamente bem compreendido e quantificado, da mesma forma que o sistema Fe-Al. Entretanto, há discrepâncias significativas na quantificação do comportamento do sistema Fe-Al-O havendo, ainda, bastante controvérsia com respeito a equilíbrios importantes. Assim, o objetivo deste trabalho é (a) realizar uma revisão crítica dos experimentos e avaliações termodinâmicas principalmente do equilíbrio Al-Fe-O–Al2O3 (b) avaliar os métodos atualmente usados para descrever este equilíbrio e (c) apresentar recomendações sobre os dados, com base em sua confiabilidade e consistência.

Aug 16, 2017

By José Beltrán

El monitoreo de condiciones es una herramienta importante en las operaciones mineras -en tanto asegura una buena salud de los equipos de producción. En ese sentido, el presente texto muestra los resultados de un equipo evaluador que opera el sistema de condiciones MineCare y valida distintos casos de análisis reales y cotidianos, verificando las ventajas de utilizar esta herramienta en ejemplos reales para las mejores prácticas operacionales dentro de la operación extractiva minera.

Mar 1, 2016

By Mehih Demirkan, Kevin Tehansky

Located about an hour drive south from Washington, D.C., the Maryland Transportation Authority (MDTA) contracted with Skanska-Corman-McLean (SCM) to deliver a new Governor Harry W. Nice Memorial/Senator Thomas "Mac" Middleton Bridge, which takes U.S. 301 over the Potomac River, spanning 1.9 mi (3 km) from Maryland to Virginia. The new bridge aimed to improve capacity, safety and access of the roadway and was planned as a four-lane span with deep foundations that would be constructed fewer than 150 ft (45 m) north of the existing alignment of the more than 80-year-old bridge. The new Harry Nice Bridge opened in the fall of 2022 with a design life of more than 100 years, servicing 12 ft (4 m) wide lanes with 2 ft (0.6m) shoulders, doubling capacity, enhancing emergency response, upgrading maintenance and inspection activity access, and featuring lane sharing for cyclists.

Apr 1, 2023

By Anderson Esteves Bragança

Foi identificado na área da unidade técnica da laminação de tiras a quente uma necessidade de cruzamento de dados de diversos sistemas de nível 1 (Instrumentação), nível 2 (Automação) e nível 3 (TI), para análise do processo. Todo esse processo de extração e formatação dos dados levava dias, com necessidade de suporte da equipe de TI, ou às vezes nem era possível devido à complexidade de cruzamento de informações. A ideia era prover uma ferramenta capaz de acessar diferentes bases de dados permitindo a integração dessas informações de forma simplificada e ágil. Após avaliação de ferramentas disponíveis no mercado (Ferramentas de Analytics e BI) a opção foi por uma que trouxe: a integração dessas bases, redução do tempo gasto na preparação de indicadores e um maior tempo disponível para investigação e solução de problemas por parte dos especialistas. A conclusão do projeto foi uma unidade técnica mais produtiva e autônoma, com uma menor dependência da equipe de informática e automação.

Oct 30, 2017

By James L. Oleson, Hunter R. Propsom, Kevan J. R. Ford, Robert D. Henderson, Bob Musgrove

"Kinross’ Fort Knox Gold mine, near Fairbanks, Alaska has successfully implemented two major metallurgical continuous improvement projects resulting in growth of gold production and an extension of mine life. In 2009, Fort Knox produced 263,153 oz of gold at a cash operating cost of $543/oz. In 2010, approximately 63% of the gold will be produced from the CIP circuit, 15% of the gold from the gravity circuit and 22% of the gold from the heap leach.In 2009, a 44,000 ton per day run-of-mine valley fill heap leach facility was constructed and commissioned as a cost effective treatment option for low grade ores to supplement the higher grade mill. The heap leach facility will produce approximately 100,000 ounces of gold per year under severe winter conditions. Heap leach gold recovery, based on test work shows 30% after a 55-day leach cycle, with long term ultimate gold recovery targeted at 65%. The paper presents the heap leach design concepts and production data.Additionally in 2009, installation of a Knelson gravity concentrator unit (XD70) was completed. This together with an Acacia intense leach reactor (AILR) has increased overall mill gold recovery from 79.3% to 80.7%. A manual shaking table gold recovery operation has been replaced by batch intensive cyanidation of the high grade Knelson concentrates. Increased removal of coarse gold and difficult-to-leach gold species from the grinding circuit, via the gravity circuit, has improved gold leach recovery in the conventional whole-ore tank leach CIP circuit. The paper presents plant operating data, showing the improvements over the old flowsheet.Focus on the metallurgical properties of the high grade and low grade end components of the Fort Knox ore has resulted in significant improvement to gold recovery."

Jan 1, 2011

By G. Deschênes

In an earlier study (Deschênes et al., 2009), gold and silver were shown to be efficiently extracted from samples taken from the Kupol Mine in Russia using lead nitrate in a cyanide leach system. In the current study, a com-parison of the technical and economic merits of a new technology called CANMET enhanced leaching process (CELP) was made with the cyanidation/acidification-volatilization-recycling (AVR) process using eight metal-lurgical variability samples, as well as a large composite sample, which was to represent the initial two years of Kupol mill feed. The composite sample leach feed assayed 33.4 g/t Au and 289 g/t Ag. The metallurgical results from the large composite sample demonstrated that CELP produced very similar gold and slightly higher silver leach extractions compared to the conventional cyanidation/AVR leach conditions at 1/2 the cyanide concentra-tion (1,000 ppm NaCN in CELP vs. 2,000 ppm for cyanidation/AVR leach conditions). It was estimated that the total cost per ton was approximately the same for the two technologies (total cost of CELP with the use of Merrill-Crowe at $46.48/t, with cyanidation/AVR at $46.13/t). However, the implementation of CELP would eliminate a capital expenditure of approximately $5 million for an AVR system based on a 2005 feasibility level cost estimate. Eight variability samples used to confirm the composite sample results showed that, on average, the gold leach extractions with CELP and the conventional leach conditions were very similar, but the average silver leach extraction was 2.1% higher for CELP. Furthermore, CELP silver leach extraction was 4.6% higher on average compared to conventional cyanidation for the four mid-grade variability samples evaluated. The decision was made to remove AVR cyanide recovery from the flowsheet and implement CELP at Kupol. The ability to use the conventional leach equipment with CELP and simplify the flowsheet was also a factor, given the remote location of the Kupol Mine.

Jan 1, 2010

By James P. Kimball

Jan 1, 1885

By R. F. Hehemann, Darrell W. Smith

The kinetics of alloying- in W-5 rot pct Re powder compacts were investigated at temperature about the upper limit for the formation of the x phase, such that a single intermediate phase was involved in the process. The rates and directions of motion of the a-o and o-b interface were assessed as functions of tinze at the sintering teri7peraticve by quantitative izetallog-ralhic techtziques. The iiotion 01 these interjuces could be specified approxitnate1.y by u Parabolic )-ate law and deviations from this ,rate law were attribuled to a complex interaction between surface dif'fusion and volume diffusion during the initial stages of sintering. WHEN binary or more complex alloys are produced by sintering compacted blends of elemental powders, a complication is encountered which does not arise in the sintering of pure metals. In addition to concern for grain size and densification, the rate of inter diffusion of the component elements must be considered. The general problem of alloying during sintering has been treated by numerous investigators.'-7 These investigations have been concerned only with systems that form continuous series of solid solutions and a concentric-sphere diffusion model4 provides a useful description of homogenization in these stems.' Some controversy remains, however, over the contribution of surface and grain boundary diffusion to the homogenization process. Heckel% ePorts that homogenization can be described by volume diffusion at all temperatures, whereas other invetiators'' recognize the importance of surface and grain boundary diffusion, particularly at lower temperatures. Analysis of the homogenization process in partially miscible systems is complicated by the motion of the interfaces separating the individual phases. A simple analytical solution does not exist for such finite systems with spherical symmetry. It was the purpose of this work to examine the kinetics of the formation and dissolution of an intermediate phase in a binary system through an assessment of the motion of the interfaces separating this phase from the terminal solid solutions. PROCEDURE The W-Re system is an example of a partially miscible binary system and was selected for study because of its current importance in refractory-metal technology. The equilibrium phase diagram, Fig. 1, shows that the o phase will be formed by interdiffu-sion between tungsten and rhenium. At temperatures between approximately 2125" and 282O°C, the o phase will appear as the only intermediate phase in the diffusion system. In this work, a mixture of elemental powders containing 5 pct Re was employed. In such a mixture, the rhenium particles will be distributed randomly in a tungsten matrix. During sintering, a o-phase layer will form at the W-Re interface. The development and subsequent disappearance of the o phase are controlled by the relative rates and directions of motion of the 0-0 and a-p interfaces. The motion of these interfaces can be inferred from quantitative metallographic measurements of the average radii of the o shells surrounding rhenium particles. Elemental tungsten and rhenium powders of commercial purity were employed in these investigations. The rhenium powder was spheroidized from +200 mesh agglomerates by plasma-arc spraying and was then classified to yield a powder composed of essentially

Jan 1, 1967

By Smortchevskyk N. J.

THIS paper describes the electrical features of the locomotive now (August, 1962) under construction for Craigmont Mines. Intended for non-specialists, it avoids details of design and calculations interesting to electricians only. The paper is divided into three sections. The first deals very briefly with the mine layout and with operating conditions -existing and expected. Reference is made to economic considerations leading to the selection of the type and size of locomotive, as well as to traction diagrams and the calculations. This material is not included in the paper because of its length and because it does not represent anything new. The second section deals with engineering and economic considerations and shows, in some detail, why the A.C. system was chosen. The third section describes the basic components of the locomotive, including the voltage regulator, the rectifiers, the control arrangement and the filter, and deals with considerations affecting the selection of their rating and design. A concluding sub-section describes, very briefly, the track and trolley details and the power distribution switchgear.

Jan 1, 1963

By F. W. Newhall

DURING the latter part of the year 1931, the Republic mine of the Republic Steel Corporation, at Republic, about 4 miles south of Browns-ville, Pa., was mining coal along four rib or fracture lines. One of these lines, the west butt rib line, was retreating towards a concrete-lined air shaft, 320 ft. deep, which had been sunk in 1911 for ventilation purposes. With the normal rate of mining at that time, it was expected that this rib line would pass the shaft in three or four months and the shaft would then be abandoned and allowed to cave. Realizing the opportunity presented for the study of an unusual case of ground movement, the question of conducting the study was presented by the junior author to the chairman of the Institute's committee on Ground Movement and Subsidence, Mr. George S. Rice, who presented the matter to Mr. G. H. Morse, General Manager of the Northern Mines, Republic Steel Corpora-tion, and he agreed to cooperate with the Bureau of Mines in making the study, the results of which are presented in this paper. Acknowledg-ments are due to Mr. Morse for his full cooperation in this work and to Mr. G. S. Rice and Mr. J. W. Paul, both of the U. S. Bureau of Mines, for their advice and guidance during the course of the work. The authors are indebted to Mr. B. F. Herbert, mining engineer, Northern Coal Mines, Republic Steel Corporation, who assisted in all the surveys, and Mr. W. H. Smith, draftsman, U. S. Bureau of Mines, who prepared all illustrations for publication.

Jan 1, 1934

By G. Roger Miller, Kristine M. Krajnak, Stephen S. Leonard, Stacey Waugh

Repeated exposure to hand-arm vibration through the use of vibrating hand tools can result in the development of the disorder known as hand-arm vibration syndrome (HAVS; (1,3)). One of the hallmark symptoms of HAVS is cold-induced peripheral vasospasms that result in finger blanching (4). Although the vascular and neural pathology associated with vasospasms has been described, little is known about cellular mechanisms leading to this damage (4). To understand how vibration may alter vascular and neural physiology and anatomy, rats were exposed to a single bout of tail vibration and the molecular responses of neural and vascular tissues were measured to determine if there are immediate or sustained affects of vibration that may underlie longer term changes in physiology. Methods Experiment 1. Male Sprague Dawley rats (n = 32, 6 weeks of age) were housed in AAALAC accredited facilities. All procedures were approved by the NIOSH Animal Care and Use Committee and were in compliance with the CDC guidelines for care and use of laboratory animals. Vibration exposures were performed by restraining rats in Broome-style restrainers, and securing their tails to a vibration platform using 6 mm wide straps that were placed over the tail every 3 cm. Restraint control rats were treated in the same manner, except that the tail platform was mounted on isolation blocks and not on a shaker. The vibration exposure was 125 Hz, 49 m/s2, for 4 h. Rats were euthanized with an overdose of pentobarbital (100 mg/kg) 1 h or 24 hours after the exposure. RTqPCR was used to measure transcript levels for endothelin 1 (ET-1), the 3 forms of nitric oxide synthetase (NOS) NOS-1, NOS-2, NOS-3 and norepinephrine receptor subtypes 1D, 2A, 2C, in artery tissue, and to measure calcitonin gene-related peptide (CGRP) and nitric oxide synthase-1 (NOS-1) in ventral nerves. Data were analyzed using 2-way ANOVAs. Experiment 2. Male Sprague Dawley rats (n =24, 6 weeks of age) were maintained as described above. Animals were exposed to a single bout of restraint or vibration. Another group of animals served as cage controls. All animals were euthanized 24 h after the exposure, and tail arteries were isolated and frozen. Reactive oxygen species ROS) were measured using electron spin resonance spectroscopy (ESR). Arteries were homogenized over ice in 1 ml of PBS with protease inhibitor cocktail, using a tissue tearer (Biospecs Products Inc. Racine, WI USA). The sample was split into two 0.5 ml samples. One set had PBS and the spin label hydroxyl-TEMPO [0.1 mM] added while the other set had hydroxyl-TEMPO [1.0 mM] plus the specific hydroxyl radical scavenger, dimethylthiourea (DMTU), added to confirm the presence of the hydroxyl radical. Samples were vortexed and then placed in a flat cell for ESR analysis. The ESR spectrometer settings were: receiver gain, 6.32 x 102; time constant, 0.02 s; modulation amplitude, 1.0 G; scan time, 20 sec; magnetic field, 3490 ± 100 G (2). Data were analyzed using 1-way ANOVAs.

Jan 6, 2006