Search Documents

By L. C. IlsLey

So many subjects are covered in State mine-safety regulations that any attempt to compare different State laws in their entirety would be futile. On the other hand, if one selects a single phase or branch of safety work, such a comparison may prove profitable. The subject selected for study in this paper is limited to legislation or regulations dealing specifically with safeguarding (electric) motored equipment used in gassy mines. T When one reads glowing accounts of the safety activities being carried on here and there it is easy to believe that everything which is right and proper is being done to safeguard the mine.workers; but, when one takes time to look into the weakness of many State regulations, it is evident that there is still room for improvement. Undoubtedly it would have been much better for the safety of mines if electrical equipment had been introduced into mines 50 years earlier. If electricity had been in general use when the first mine regulations were pre- pared, those formulating the rules would have covered this hazard along with other hazards, but as electricity came in at a later period, safe mine legisla- tion regarding it has been woefully neglected. Today the United States in general is far behind most other coal-producing nations in the provision of adequate safety rules or laws for the installation and maintenance of electrical equipment and wiring. Returning to the subject of our study, approximately 30 of the 48 States mine coal. More than 20 of these States' produce coal in large quantities. How- ever, of the 30 States only four, 3 Pennsylvania, Utah, Washington, and West Virginia, have laws which specially call for the use of explosion-proof types

Jan 1, 1929

By Gerson Evaristo de Paula Júnior, Bruno Santos Malaquias, Henriquison Magela Bottrel Reis

O desafio no processo de coqueificação está relacionado à elaboração de misturas de carvões que produzam coque com a qualidade para utilização nos altos-fornos. Foi avaliada, em escala piloto, a influência de materiais inertes (coque verde de petróleo [CVP], antracito e carvão com alto teor de inerte [CATI]) às misturas de coqueificação sobre a formação de microtexturas e a qualidade do coque. Os resultados indicaram que, para a mistura avaliada, a adição do CVP até 30% produziu coque com qualidade (DI15-150) adequada para os altos-fornos da Usiminas. As principais microtexturas foram do tipo mosaico, fragmentária, fusita, inerte anisotrópico e o próprio CVP. O antracito provocou redução significativa de DI15-150 e CSR. A análise de microscopia óptica revelou partículas livres na matriz de coque, contribuindo para a queda de qualidade. A adição de CATI às misturas de coqueificação resultou em forte queda na qualidade do coque e a microtextura do tipo mosaico foi predominante. De forma geral, o carvão com alto teor de inertes foi o que apresentou menos benefícios, diferentemente do CVP, que apresentou melhor resultado para ser utilizado nas misturas de coqueificação da Usiminas.

Oct 1, 2019

Using the philosophy that 'change cannot be introduced through memos-you have to get people emotionallyinvolved', SRK's Environmental Group in South Africa is helping clients communicate their environmental management objectives more effectively through the powerful medium of interactive industrial theatre. Existing and pending environmental legislation, international pressures, and growing awareness of the environment have led South African industry to the point where responsible care, for both the environment and the health and safety of those affected by the activities of an industry, is now a focus of management policies.

Jan 1, 1995

By D. Geiselman, A. G. Guy

Single cvystals were grown from high-purity magnesium containing known amounts of nitvogen in the range 0.0008 to 0.0048 wt pet. Crystals of known ovientation were tested in tension in an Instron ma chine to determine the yield strength and to obsevue wheather a yield point occurred. Slowly cooled crystals or those given a solution heat treatment did not show a yield point. However, crystals that were aged following a solution treatment showed a yield point for all of the nitrogen contents studied. It was concluded that nitrogen caused the yield point by the Cottrell mechanism. NITROGEN has been shown to produce sharp yield points in single crystals of cadmium, zinc,2'3 ß-brass,4 and iron,5,6 as well as in polycrystalline iron7 and molybdenum.8,9 Since magnesium has a structure similar to zinc and cadmium, it seemed reasonable that magnesium should also exhibit a sharp yield point provided it contained sufficient nitrogen. Bobalek and Shrader10 reported a total nitrogen content of 0.002 to 0.0065 wt pct in com- mercial magnesium alloys, an amount well in excess of that required by theory. However. magnesium differs from cadmium and zinc in that it forms a stable nitride, Mg3N2, which has a standard free energy of formation of -95,480 cal per mole at 25" c." If rather than being in solid solution, the nitrogen were predominantly combined as the nitride, it could not act to produce a yield point. This type of behavior is the basis for the elimination of strain aging and a yield point in steel by the addition of strong nitride formers such as titanium,12 columbium,13 aluminum,14 vanadium,15 and boron.16,17 Thus, there appeared to be factors both favorable and unfavorable to the production by nitrogen of a sharp yield point in magnesium, and the purpose of this investigation was to determine the actual behavior of magnesium crystals containing known amounts of nitrogen.

Jan 1, 1960

By Frederick W. DeVries

The author was invited by "60 Minutes Australia" to provide on-site technical background on cyanide, mining, and the environment, in their investigation of the January 30, 2000, spill at the Aurul gold-recovery site in Baia Mare, Romania. Some remarks on the incident ?and its implications surround a showing of the fourteen-minute telecast. The thrust of the TV reporter was that aspects of the dam implied the owners' use of standards Jess than would have been met for installations in technologically more advanced locations (like Australia). As a result, the public-relations impact is one of embarrassment for the world mining industry.

Jan 1, 1998

By John A. C. Fortescue

There is a need for better communication between scientists who plan and carry out mineral exploration research in glacial terrain and the exploration geologists who look for mines. In this paper, four ways in which workshops could be used to close this communication gap are described and discussed in relation to the solution of this problem in Canada.

Jan 1, 1973

By J. A. Herbst

Fine coal cleaning by froth flotation has become common practice in the U.S. with more than 80,000 tons treated in this way per day. In spite of this large tonnage, developments in the automatic control of coal flotation circuits have lagged significantly behind those for mineral systems. One reason such developments have been limited is that instruments have not been available for the on-line measurement of carbon or ash and another critical variables in coal slurries. A second reason is that the influence of the operating variables on coal flotation has not been completely understood. During the last few years some of the required instrumentation has been developed and an improved knowledge of the flotation process itself has occurred through mathematical modeling; as a result certain control strategies for coal flotation are beginning to emerge. This paper attempts to evaluate several control strategies using a detailed flotation dynamic simulator, DYNAFLOAT. After constructing a process matrix for the system of interest, promising alternatives for linking manipulated and controlled variables have been analyzed. In order to develop combined grade and recovery control strategies, the authors found it necessary to construct a grade/recovery map with the aid of the simulator to drive the system to known final, feasible grade/recovery operating conditions. Finally, an advanced strategy which uses an on-line model to identify disturbances and take control actions is proposed.

Jan 1, 1983

By B. J. Klee

What is the economic basis for direct, continuous particle size measurement and control? First, precise grinding control is necessary to achieve and maintain a specified recovery and throughput. Second, throughput and recovery are direct functions of particle size-and these two factors control the economic performance of the ore concentration process. Third, only size-based control using a particle size and percent solids monitor (PSM) has achieved the necessary precise control. Recovery, throughput and cost can be accurately measured for various concentrator operating conditions if particle size is closely controlled. From such data the economic results of different particle size grind points can be analyzed. This will reveal the best combination of recovery and throughput to meet objectives established by financial management. Predictable, repeatable response to set-point selection is essential if the projected profitability of the mill is to be reached.

Jan 11, 1976

By Y. Takasaki

For zinc hydrometallurgical extraction, reducing the electric power consumption of the electrowinning process is an important issue for energy savings. At the Zinc & Lead 2000 symposium, the authors suggested that by using the Pb-0.5%Ag-0.6%Ca alloy, the electrolysis energy can be decreased compared to the conventional Pb-0.9%Ag alloy. In this study, the corrosion behaviors of the Pb-Ag-Ca electrode in a sulfuric-acid electrolyte were investigated. Based on the results Or me Pb-0.5%Ag-0.6%Ca anode after 20 days of electrolysis, the bath voltage and the quantity of anode slime decreased compared to the Pb-I%Ag anode. Subsequently, beta-PbO2 on the electrode surface was detected by XRD and its peaks were sharper than the Pb-1 %Ag anode. Moreover, a dense beta-PbO2 layer on the 0.6%Ca a anode surface was observed. Therefore, it was suggested that the dense beta-PbO2 layer on the anode surface is one of the factors that leads to a lower bath voltage and decreasing quantity of anode slime.

Jan 1, 2003

By Surendra Kumar Biswal, Sachida Nanda Sahu, B. C. Meikap

The unutilized iron ore fines (IOF, − 10 mm, 45% to < 60% Fe(T)) left at various mine sites during blasting and processing are rich in goethetic-hematite associated with high clay and considered a potential iron ore resource. The variation of loss on ignition (LOI) from mines to mines is based on the goethite and clay mineral content. The clay containing below 45 μm is mostly brittle, causing beneficiation problems. The IOF has an LOI of 7.83%, with high silica (5.52%) and alumina (4.57%), and 57.17% of Fe(T) subjected to both conventional deep beneficiation (CDB) and magnetization roasting using high-ash non-coking coal to adopt the suitable upgradation process. The CDB and magnetization roasting concentrate has 62.61% and 67.58% Fe(T) with 64.69% and 85.19% yield, respectively. However, the presence of 6.40% LOI in CDB makes the ore challenging for pelletization. Characterization like X-ray diffraction(XRD), scanning electron microscope(SEM), and chemical analysis was used to assess the concentrate quality and potential industrial application.

Jun 4, 2022

By G. G. Marino, J. W. Mahar

This paper provides an utierstanding of the betivior and potenttil damage of homes resulting from sag-type mine subsidence. This is done with extemive research of numerom case histories in Illinois collected by the authors. The howe response to substience-itiuced ground displacements are summarized and evaluuted. A damage level criteriu, specifically developed for residenttil structures, is presented based primarily on repair costs. Damage levels and the associated subsidence profile characteristics for each case history are compared.

Jan 9, 1985

By D. J. Burkhardt

Newer copper SX/EW facilities often incorporate hot water heating for the cell feed electrolyte to obtain the necessary plating temperatures of 40 to 50°C. Heating is most necessary in oxide heap leaching, however it may also be required in bioleaching of secondary sulphides in colder climates or higher altitudes where most of the heat gain in the heap is lost to the environment. Given that the solution flows in the leach, organic circuit and electrolyte circuit are circular in nature, and the fact that the hot lean electrolyte is often exchanged with cooler rich electrolyte, it can be difficult to access the heating requirement for the cell feed. There are energy losses in piping, tankage, raffinate, and energy gains through the PLS and electrowinning process itself; some of these are significant and others are not. This paper discusses the overall heat balance, the relative significance of the various energy gains and losses, and describes a methodology to develop a heat balance to assist the engineer in sizing the heating equipment.

Jan 1, 2003

By Robert A. Rapp, Ronald L. Pastorek

Solid-state electrochemical measurements by three alternative experimental procedures were made with the cell FeO, Fe3O4 |Zro.85Cao.15O1.85 |Cu| Zr0.85CaO.15O1.85 | FeO, Fe304 to establish the solubility and diffusivity of oxygen in solid copper in the temperature range 800" to 1030°C. The solubility of oxygen in solid copper and the diflusivity of oxygen in solid copper Dgu = 1.7 X 10-2 exp(-16,000/RT) Cm2/sec were determined and confirmed in alternative experiments. The enthalpy of solution of oxygen in solid copper equals —10,000 cal per mole; the partial excess entropy of the oxygen atoms in the Cu-O dilute solution is approximately the same as that found for interstitial atoms in other metals. The diffusivity of oxygen in solid copper is consistent with that expected for an interstitial atom. RELIABLE values for the saturation solubility N(s) and diffusivity DO of oxygen in solid copper have not been unambiguously established in the literature. Following three early determinations by others,1"3 Rhines and Mathewson4 reported that the solubility of oxygen in solid copper increased from 0.007 at. pct 0 at 600°C to about 0.015 pct at 1050°C. Phillips and skinner,, using essentiially the same analytical procedure, reported that the solid solubility increases from 0.0018 at. pct 0 at 550°C to about 0.0075 pct at 1050OC. The only previous value for the diffusivity of oxygen in solid copper was reported by Ransley.6 Ransley deoxidized Cu-Cu2O alloys in an atmosphere of carbon monoxide gas to yield a solubility-diffusivity product. He used the solubility data of Rhines and Mathewson to calculate the diffusivity values. Another method for obtaining the solubility-diffusivity product (N(s) DO) is by measuring the widths of internal-oxidation zones in copper alloys as reported by Verfurth and Rapp.7 However, the calculated N(S)Do products depend upon the alloy content of the specimen, so that the internal oxidation of copper alloys does not follow ideal internal oxidation kinetics. As a result, unequivocal values for the N(s) DO product were not obtained by this procedure. A solid-state coulometric titration technique similar to that employed in this work was introduced by C. Wagner8 to study the dependence on silver activity of the Ag/S ratio in silver sulfide in the temperature range of 160" to 300°C. Similar experiments have been carried out by C. Wagner and co-workers9-11 to study the stoichiometry range of silver and copper tellurides, cuprous sulfide, and cuprous selenide. Numerous authors have carried out electrochemical measurements with a solid oxygen-ion-conducting electrolyte to determine the solubility and/or diffusivity of dissolved oxygen in several liquid metals.12-l6 Rickert and Steiner17,18 have used solid-state electrochemical measurements to determine the diffusivity of oxygen in solid silver from 760" to 900°C. Two different cell geometries were used. In the cell of linear geometry Fe, FeO | ZrO2 + (CaO) | Ag + [0 (dissolved)] [1] oxygen diffused from the interior of the silver electrode to the silver/electrolyte interface where the oxygen activity had been lowered from a fixed initial value to practically zero by the application of voltage to the cell. The diffusivity of oxygen in solid silver was determined from the solution of the diffusion equation and the time dependence of the cell current. However, this determination of the diffusion coefficient depended upon a knowledge of the solubility of oxygen in solid silver. A cylindrical geometry was used for the cell Pt, O2(Po2 = 0.21 atm) | ZrO2 + (CaO) | Ag + [0 (dissolved)] [II] which also allowed the diffusivity of oxygen in solid silver to be determined. These values were in agreement with other available data.l9 Recently, Raleigh20,21 used a method involving the measurement of diffusion-limited currents in a cell involving the AgBr solid electrolyte to determine the diffusion coefficient of silver in Ag-Au alloys at 400°C. Diffusivity values on the order of l0-14 sq cm per sec were measured in the alloy composition range 10 to 60 at. pct Ag in a single experiment. From numerous electrical conductivity and galvanic cell measurements,9&apos;22"26 the solid solution Zr0.85 Ca0.15 O1.85 has been established as an electrolyte with predominant oxygen ion conduction over a wide range of intermediate and high oxygen activities. For interrelating the thermodynamics and the kinetics of the dissolution of oxygen in solid copper in this investigation, a galvanic cell was constructed with FeO-Fe3O4 as the reversible reference electrode, the Zr0.85Ca0.15 O1.85 electrolyte, and a pure copper specimen under-saturated in oxygen as the other electrode. THEORETICAL ANALYSIS Three variations of a high-temperature electrochemical technique were used in this study to provide two determinations each of the solubility and diffusivity

Jan 1, 1970

By A. Yazadni-Chamzini

Maintenance strategy selection plays a significant role in mining design. The nature of maintenance strategy selection is a complex multi-criteria decision making (MCDM) problem including both tangible and intangible parameters which are often in conflicting with each other. Moreover, when decision makers are uncertain in determining and defining the ratings and the weights of alternatives and criteria respectively, fuzzy theory provides an appropriate tool to handle the existing uncertainties. In this paper, a new fuzzy MCDM method based on the concepts of TOPSIS and AHP was proposed to evaluate the feasible maintenance strategy. The linguistic terms are employed to assess the ratings and weights. Fuzzy AHP is utilized to calculate the weights of the evaluation criteria; then, the rankings of alternatives are computed based on fuzzy sets theory and TOPSIS. A real world case study is presented to illustrate a potential application of the proposed model.

Jan 1, 2012

By Douglas Martinazzi

O processo de soldagem por fricção com pino consumível (Friction Hydro-Pillar Processing- FHPP) um método de reparo no estado sólido que consiste no processamento termomecânico de um pino metálico em alta rotação e inserido em um orifício criado no material a reparar. O pino é pressionado com uma força axial e o aquecimento resultante do atrito dos materiais é suficiente para garantir a plastificação dos mesmos promovendo o preenchimento do orifício e a união dos componentes. Este trabalho é centrado na análise da distribuição de inclusões não metálicas do tipo Sulfetos de Manganês (MnS) presentes em juntas soldadas produzidas por esta técnica com a aplicação de diferentes forças axiais. Micrografias da zona termomecanicamente afetada (ZTMA) foram realizadas por microscopia ótica em amostras polidas e sem ataque para registrar as inclusões. Essas micrografias foram avaliadas via análise de imagens visando a determinação de quantidade, tamanho e área ocupada pelas inclusões nas juntas em juntas soldadas. O mapeamento identificou a distribuição e o tamanho médio das inclusões em função das forças axiais. Concluiu-se que a região analisada é potencialmente crítica no que diz respeito a tenacidade à fratura, uma vez que foi observada uma quantidade considerável de inclusões fragmentadas de dimensões reduzidas.

Aug 7, 2018

By Paul M. Linebarger

This paper is one of a series of digests of foreign mining legislation and court decisions prepared in advance of a general report relative to the rights of American citizens to explore for minerals and to own and operate mines in various foreign countries. This interpretation of the laws of Mexico has been pro oared from the best information available in Washington but is released subject to correction and amplification, if necessary, by the proper American diplomatic and consular officers, to whom it has been referred through the courtesy of the Department of State. INTRODUCTION Present-day Mexican mining legislation involves, not only the latest minim enactment (August 1, 1026), but many other enactments and regulations, principal among which are the Constitution, the Civil Code, the Code of Commerce, the Foreign Law, the Mining Tax Law, and. the Civil Jurisprudence of Mexico--the last-mentioned being based in Dart on Supreme Court decisions. Ere Mexican Federal Government is supreme in mining legislation because, among other reasons, a large part of the revenue of the Government must come from the fiscal control of the mines. All circulars, decrees, and rulings that affect the mines not only have their origin in the Central Government but are administered thereby. The Department of Industry, Commerce, and Labor is in control of all mines. Attention may here be called, however,

Jan 1, 1929

About 74% of global seismic energy release occurs in the Circum-Pacific zone. Worldwide, about 71% of seismic energy release is in the form of shallow earthquakes, 27% as intermediate, and 2% as deep earthquakes. Seismic energy release is variable in time and has been shown to correlate with the amplitude of the Chandler wobble. It was high during the period 1949 to 1967, and is now at a rather low level, with the latest earthquake over M = 8.0 having taken place in Indonesia in 1971. The average worldwide recurrence rate for the expected largest magnitude earthquake (M "9.5) has been estimated as several tens of years, in marked contrast to the several tens of thousands to hundreds of thousands of years separating the largest volcanic eruptions. Geological studies are needed to establish reliable mean intervals between large earthquakes, and to detect the e;:istence of long-term fluctuations in the ste of occurrence. Seismic gaps have proved seful in static forecasting of large earthquakes, by identifying places where closer study of the variation with time of seismicity, deformation, and other parameters, may lead to the dynamic p_ediction of time, place and magnitude of earthquakes. The model of stress concentration at asperities explains the main features of seismicity in the Circum-Pacific. Slow earthquakes have been detected instrumentally, notably an event immediately preceding the 22 May 1960 Chile earthquake, the largest this century. It seems likely that this type of deformation may explain both instrumentally detected and macroscopically observed pre-seismic deformation, as well as unusual animal behaviour reported before some earthquakes. Seismic and volcanic events are interdependent, with large earthquakes commonly triggering eruptions. Melting of rock and intrusion of magma is likely to accompany many earthquakes.

Jan 1, 1987

By L. B. Pankratz

High-temperature heat-content values of pure lutetium sesquioxide and dysprosium sesquioxide were measured over the temperature range from 298° to 1,800° K. Similar data for cerium sesquioxide were calculated from measurements of a mixture of cerium sesquioxide and dioxide and known values for cerium dioxide. The results for lutetium sesquioxide are regular. Dysprosium sesquioxide has a minor thermal anomaly near 1,590° K, the extra heat absorption being 220 cal/mole, Hexagonal cerium sesquioxide undergoes a transformation around 1,050° K, which is only slowly reversible; consequently results were obtained for both the low- and high-temperature varieties. The original heat-content data are reported, and smooth values of heat content and the corresponding entropy increments are tabulated. Equations were derived to represent the heat-content values.

Jan 1, 1963

By Lancucki C. J, Nickson N. M

X-ray diffraction and differential thermal methods were used to determine the mineralogy of some clays used by the heavy clay industry in the Adelaide area. A detailed analysis was made of the mineralogy and particle size distribution of eighteen samples from beds in two pits in the Recent sediments in the Adelaide plains, of six white clays developed from the weathering of the Adelaide series of sediments, and of four Recent alluvial clays from a pit in the Mount Lofty ranges south of Adelaide. Structural clay products in the Adelaide area are manufactured from mixtures of these clays, so the mineralogy and particle size distribution was determined of eighteen clay mixtures used to make red bricks, cream bricks, facing bricks, pipes and tiles.Knowledge of this mineralogy is important in understanding the ceramic behaviour of the clays.INTRODUCTIONIn this investigation an account is given of the clay mineralogy and particle size distribution of some ceramic clays from the Adelaide area. The clays are used in the manufacture of structura,l clay products and the results to &apos;be described are part of an overall &apos;plan of study covering the heavy industrial clays and shales of Australia. Previous work has been published (Cole and Carthew, 1953; Ferguson, 1954; Ferguson and Hosking, 1955; Cole and Nielsen, 1958/59).In this work no attempt has been made to examine clays from all pits engaged in supplying materials for the structural clay industry. However, in 1954 the senior author collected detailed samples from two pits working in Recent alluvial clays in the Allenby&#183;Gardens and Beverley areas near...

Jan 1, 1963

By Fuzail Siddiqui

"The SIDMIN program aims at filling the mineral processor’s need to know the deportment of ‘minerals of interest’ not just ‘elements of interest’ that pass through the processing plants. Generally, chemistry is used as a tool of routine monitoring on site. Mineralogy, which is relatively much slower, is used more as a tool of research and post mortem investigations and these services are usually provided by a distant facility. The SIDMIN program enables site management to receive chemical and quantitative mineralogical reports on their critical samples daily, simultaneously and affordably.The author developed the SIDMIN program at ZCCM Nchanga Division where it continues to be a powerful tool for monitoring the efficiency of operations. Outlines are given of procedures for quick sample preparation and quantification of significant minerals in process samples. A specimen report is presented, which shows the format of reporting the contributions of individual minerals to metal losses at critical stages of the circuit. It is shown that SIDMIN provides timely information to management, about trends and abrupt changes in the quality of ore, and its processing, in a way never achievable by chemical analyses alone. This greatly helps in resolving the age-old problem of ‘bad ore’ or ‘bad operations’ on a day-by-day basis. For example increase in copper mica in the feed indicates excessive ore dilution during mining. Increased loss of free sulphides was traced to insufficient reagent conditioning time at the Concentrator. Persistent losses of leachable oxides at the Tailings Leach Plant were traced to inadequate leach residence time.SIDMIN is affordable because it can be implemented using basic optical microscopes, minimal quantities of micro-chemical reagents and custom trained site staff who demonstrate good colour perception and an ability to follow laid down procedures consistently."

Jan 1, 2000