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By A. J. Forney

The hot-gas-recycle process, for the hydrogenation of carbon monoxide, was investigated in a 12-inch-diameter reactor. Initially because the distribution of gas was poor, hotspots developed in the catalyst bed. After the velocity profile of the gas flowing through the bed was studied, the method of packing the catalyst was altered. Because this change improved the distribution of gas, temperature control was excellent. The l2-inch-diameter reactor was operated successfully in the synthesis of gaseous and liquid fuels. When high-Btu gas was synthesized in two stages, parallel-plate assemblies of Raney nickel were almost as active as granular Raney nickel in the second reactor. The pressure drop through the second reactor, however, was reduced 90 percent by the use of these assemblies.

Jan 1, 1962

By Tony Iannacchione

A close look at the Loyalhanna Limestone of southwestern Pennsylvania reveals a complex structural environment. Most exposures of the Loyalhanna occur along Chestnut Ridge and Laurel Hill within the Allegheny Mountain Section of the Appalachian Plateaus Province. Because the Loyalhanna is rated as a super pavement aggregate by the Pennsylvania Department of Transportation and because of its proximity to the population centers of southwestern Pennsylvania, the Loyalhanna has been extensively mined along these prominent anticlinal structures. Geologic and engineering analyses were performed using gas well and core logs, outcrop examinations, underground observations, and mine maps. Strata exposures from both outcrops and quarries were used to construct geologic maps, stereonet, and rose diagram projections so that the Loyalhanna's structural environment could be understood better. Many of these structural conditions cause ground control problems at local quarries. These problems ranged from small-to-moderate sized rock falls associated with roof jointing to pillar failures associated with dipping discontinuities. Stresses ranged from tensional on structural domes where weathering dominates, to high levels of compression within structural saddles. A greater understanding of these characteristics is a prerequisite to develop engineering controls, such as improved mine layouts. pillar sizes, etc., that lessen miner exposure to these hazards.

Jan 1, 2002

By C. Gu

Flow field design is critical for PEM fuel cells. The flow field design can affect reactant distribution to the catalyst surface, water management, thermal management and current collection. Therefore, it has tremendous impacts on the fuel cell performance and durability as well as reliability and operational flexibility. In this paper, an optical method is used to study the reactant distribution in the flow field channels of two commonly used flow field designs, straight channel design and serpentine channel design. Images of the flow patterns are shown followed by discussions of the flow patterns.

Jan 1, 2005

Suppression of the explosion of the world population and the surprising increase of waste and emissions are major targets confronting mankind in this century. Recycling and waste minimisation are key words for sustainable development in a highly industrial society. The argument is really whether or not recycling done well is the solution to the environment problem for the following generation. If energy is not necessary in the recycling, all materials have to be recycled. The greatest interest among the environmental issues is the regulation of CO2 gas emission. It must be recognised that it is not possible to completely renew expended energy. Some of the recycling systems currently used are thought to increase the load on the environment rather than to be beneficial. Although metal industries have consumed tremendous amount of energy and discharged a large quantity of CO2 and solid waste, the metals have supported a high quality of life. The metal production industries such as the iron and steel industry and the non-ferrous metals industry can work well recycling of not only metals but also other materials without consuming more energy. Waste plastics, for example, are use as a reductant in a blast furnace. The role of metallurgical industry in the recycling-based society is introduced in the present paper to recognise how the metal industries can contribute recycling and waste minimisation.

Jan 1, 2002

The Olympic Dam copper/uranium deposit was discovered in 1975 and subsequently commenced production in 1988 at a rate of 1.5 Mtpa using the sublevel open stoping mining method. In the following five years the operation underwent two optimisation programs that have increased mine output to the current rate of 3.4 Mtpa of ore. The pre-expansion requirements were annual development of approximately 10 000 m and the placement of around 500 000 m 3 /yr of cemented backfill. Previous to 1995 all hoisting was carried out by the Whenan shaft. The Robinson shaft was commissioned during that year to hoist increasing development mullock tonnages and to allow for increased ore hoist via the Whenan system. In 1996 WMC committed to expanding the output of the operation from 85 000 tpa (1996/97 budget) copper metal to 200 000tpa. The corresponding increase in mine ore production requires expansion to a nominal rate of 9.0 Mtpa. To achieve these increased tonnages, major hardware installations will include sinking of a third shaft capable of hoisting in excess of 9.5 Mtpa, a rail haulage horizon utilising automatic trains, expansion of the existing backfill plant to a production capacity of over 1.8 million m 3 /yr, increasing long term development rates to 15 000 m/yr and increasing the production drilling and blasting rates in line with the higher stope production output. This paper provides detail into the intended hardware (shafts, equipment, etc) of the mining system, and outlines the intended long-term operation and management of the operation. Of particular note is the background requirement of ensuring existing production targets are met to provide critical cashflows into the project during the period of expansion.

Jan 1, 1998

By E. Stemn

Incident investigation is of utmost importance in most high-risk industries. This study was undertaken to study the content of past investigation reports to determine the effectiveness of the incident investigations. The study uses a semi-quantitative method to assess the effectiveness of incident investigations in the Ghanaian mining industry by evaluating the quality of past investigation reports. The assessment tool consists of 5 elements with several indicators and rating scales for assessing the quality of an investigation report as a measure of the effectiveness of the investigation. The method was applied to 304 investigation reports of 3 Ghanaian large-scale gold mines, and the results correlated with incidence rates of the mines to determine if any relationship existed. The results showed that the mines differ significantly in the quality of their investigation reports, suggesting differences in the effectiveness of their investigations. In addition, the incidence rates of the mines negatively correlated with some elements of the assessment tool. In general, the method was found useful and revealed areas where improvement is needed. INTRODUCTION The importance of learning from incidents is well documented in the literature. For instance, some scholars regard learning from incidents as important for improving safety [1,2]. Thus, many organisations spend considerable resources in identifying lessons from incidents and subsequently on the process of improvement that follows the identification of lessons. It is therefore important for such organisations to determine the effectiveness of their learning from incidents processes, in order to identify specific areas where improvements are needed, so that interventions can be as specific as possible. The learning from incidents process models the plan-act-check-do approach of management systems, often consisting of four major stages, namely; data collection and incident analysis, planning interventions, implementing interventions and follow-ups and evaluation [3,2]. The investigating and analysis of incidents have been regarded as one of the vital stages of the learning process since it is the stage where lessons are identified [3,2,4]. It has also been noted elsewhere in the literature that results of the previous stage of the learning process are important for the next stage [3]. For example, ineffective incident analyses could result in the planning of ineffective remedial measures. One of the primary aims of incident investigations is to identify lessons from previous incidents which when implemented can prevent future recurrences or minimise the effects of future incidents. There is thus the need for organisations to assess the quality of their investigations periodically since it is one of the means they adopt to improve safety and the quality of remedial measures to some extent depends on the effectiveness of the investigations. Although previous studies [5,2] have assessed the effectiveness of the learning process, and some aspects of the learning process, such as incidents reporting, there is less focus on the effectiveness of incident investigations. The research described in this paper was therefore conducted to contribute to this gap, focusing more closely on incident investigation reports.

Jan 1, 2019

By George Aristorenas, Carlos Englert, Jesús Gómez

"Laboratory test data of strain softening soils exhibit the development of a maximum (peak) shear strength followed by a decrease in the strength with continued straining. The rate of strength loss decreases such that an asymptotic minimum value, known as the residual strength, is approached. This paper presents an investigation of the evolution of strength degradation in excavation supported soils that exhibit strain softening behavior. The paper presents a numerical investigation of excavation support of slicken-sided clay, and results of shear testing on materials with similar strain softening behavior. A strain softening constitutive law is presented that can be used with the finite element computer software Plaxis for analysis of excavation support. A typical design section of a deep excavation support in stiff, fissured clay is presented that illustrates the limitations and conservatism of the residual strength approach for excavation support design. Finally, a discussion is presented on the impact of stiffer walls such as diaphragm walls, compared to less stiff systems such as sheet piles, on the design parameters.INTRODUCTIONIn the Washington, D.C. metropolitan area, the Potomac Formation is generally composed of stiff, fissured clays. Geotechnical engineers often associate the presence of slicken-sided planes within the formation as evidence that the soil cannot develop its peak strength. Although it is unclear how old and continuous these slicken-sided planes are, their occurrence, persistence and orientation appear to be somewhat random. Due to this uncertainty, the design of open cut slopes in these materials is often conservatively performed assuming residual shear strength values. This design approach may be justified for long-term open cuts when there is limited amount of geotechnical information and in view of back stability analyses of past slope failures. Furthermore, the lack of confinement in open cuts allows relatively high shear strains near the surface and toe throughout their existence, which promote mobilization of post-peak strength values and the ensuing progressive failure. Indeed, such behavior has been discussed in the past (Skempton, 1970; Schnabel et. al., 1982; Derrenbacher, 1998). A thorough study by Mesri et. al. (2003) of numerous slope failures concludes that the lower bound strength for stability analysis of non-failed slopes is the fully softened strength, which is intermediate between the peak and residual strengths, but that part of the slip surface may be in a residual condition prior to failure."

Jan 1, 2015

By R. R. Knill

With the advent of mechanical loading the need of definite information has become more apparent. The co-ordination of all the individual units of operation has become very necessary From these two essential features in running a mechanized coal mine has come the demand for the "time study." The time study is nothing more or less than the recording of each operation together with the time of clay or the total time expended during a period of work. Using the latter, it is impossible to have information showing just when each piece of work was clone and to what extent they overlap. The studies used here are of the former type, being based on the recording of the operation together with the time of day so that the details of performance of the machine or crew may be followed from starting to quitting time by' referring to the graph upon which the study is taken.

Jan 1, 1928

By C. N. Bailey

Let's review the economic factors in mill design. Talking about engineering economics in mill design reminds me of an old' saying "There are several ways to handle women but nobody knows what they are." I'm sure that the same economic factors do not apply to each of our mill designs, but for the sake of emphasis, it is well to review a few of them. They are so simple that we are apt to feel they are not important. Other speakers today are talking about the engineering factors of mill design, but I'm asking the question "Have we checked the economic factors involved in these designs? Have we checked the obvious? Many great discoveries have resulted from analysis of the things that appeared to be obvious all the time. What are some of these economic factors? Perhaps the most basic one is simply the value of minerals in place if minerals have value in the ground, they have value only because many important and different considerations add up to the probability that the minerals can be mined, beneficiated and disposed of profitably. The size formation and quality of the ore body, the distance from market, and the transportation available to the market area, depreciation rates, taxes, and the ownership interests involved are but some of the factors that must dovetail into the answer of profit, an answer prerequisite to hoped-for financing.

Jan 1, 1961

By Hans Adden, Anne Lehan, Markus Thewes

"1. INTRODUCTION AND MOTIVATION Traditionally design processes are focussed at creating new tunnels for lowest building cost. But the trend towards sustainable constructions in tunnelling has greatly increased in recent years. A critical subtask of this approach is to realize the potential for optimizing and reducing the life-cycle costs (LCC) of tunnels and their components. To evaluate underground infrastructure projects from an economic point of view is therefore a highly topical subject of public authorities as well as private companies participating in Public Private Partnerships (PPP) projects. Nowadays, in the case of public works contracts, the contracting authorities shall draw up rules not only for the design but also for life-cycle costing. Within the scope of the decision-making process of building a new tunnel, planning the maintenance activities or the refurbishment of a tunnel in operation, the decision-makers need detailed knowledge about the current and future financial conditions of the planned projects and selected sub-measures. But in practice, the initial costs still represent the primary decision criterion in the planning phase, whereas the subsequent or follow-up costs, respectively, are only estimated roughly. Although tunnels are the key components and the most costly parts of the transport infrastructure, only a small number of scientific papers deal explicitly with the calculation of life-cycle costs for underground infrastructure. And in these cases, most authors use as the starting point only the basic form of the Net Present Value method which is known as the frequently applied life-cycle costing technique in building construction. The present study explains the strategic concept of life-cycle costing and its fundamental instruments for operational implementation. It shows the necessity to take into consideration that there are fundamental methodical problems when the life-cycle concept is transposed without modifications from building construction to civil engineering. The paper will discuss in detail some selected associated problems with the net present value method. On the basis of operational and safety related tunnel equipment it is shown, what impact this may have on principle determining the LCC of tunnels. Selected best-practices of maintenance planning for tunnels undertaken by the German Ministry of Transport fill the theoretical approach of the concept with life and give a practical orientation. In particular government authorities but also construction companies are interested parties in modern cost management considerations. The reason for this development is the replacement of aged excisting structures and the advancement of technical standards. The increase in the total numbers of tunnels (Fig. 1) as well as the need for future re-investments in existing tunnels show the overall economic impact and justify the change towards the life-cycle perspective."

Jan 1, 2016

By M. Rudolph, T. Leißner, TU Bergakademie Freiberg, C. Mämpel, R. Möckel, M. Embrechts, T. Leistner

Tin-mining activities have taken place in the region of the German Erzgebirge (Ore Mountains) for over hundreds of years up until 1991. For long times, gravity separation processes used to be the dominating beneficiation approach in those mining districts to recover cassiterite, the main tin-bearing mineral. For fine (< 100 µm) and very fine (< 20 µm) particles these approaches might not represent effective techniques, significant valuable materials could not be recovered and reported to tailings, where it was subsequently disposed. Thus, there are substantial amounts of cassiterite still present in these tailings disposals, most of it as very fine particles with already high degrees of liberation. That fact brings these tailings disposals into focus for potential reprocessing using beneficiation approaches, which are more sensitive to fine and very fine particles. In this paper we present results concerning the laboratory-scale treatment of material from exemplary heaps of the former Altenberg and Ehrenfriedersdorf mining sites using various flotation methods (including conventional froth flotation and oil-assisted flotation). Different size ranges of the material were previously prepared in order to investigate their response to the different techniques. For the study, special emphasis is put on agglomeration flotation, an oil-assisted flotation method. Therefore, an aliphatic oil phase of alkane basis is used to either selectively aggregate or collect the cassiterite particles. Recovery and flotation performance results are presented with respect to different process parameters: various collectors (including sulphosuccinamates and phosphonic acids) and depressants (including sodium fluorosilicate and oxalic acid) regime, oil dosage, agitation time and pulp density during oil/pulp agitation. Furthermore, the oil/particle aggregation behavior is analyzed via particle image analysis and, additionally, collector adsorption characteristics are investigated by contact angle measurements and zeta potential analysis. The data obtained is correlated with the testwork results achieved in order to interpret the flotation response of very fine cassiterite particles.

Jan 1, 2016

By William K. Tolley

The U.S. Bureau of Mines (USBM) is investigating hydrometallurgical processing techniques to recycle metals from semiconductors and other advanced materials. Cadmium and tellurium were recovered from mixed CdTe/CdS scrap produced in the manufacture of thin-film photovoltaic devices. Cadmium and tellurium dissolution was achieved using hydrogen peroxide in dilute sulfuric acid. Leaching the scrap in 2.2 N H2SO4 yielded 99% Cd extraction and 98% Te extraction. Sulfur remained in the leach residue primarily in the elemental form. Elemental tellurium was precipitated from the leach liquor by adding Na2S2O5. Cadmium sulfate was recovered by evaporation. A preliminary process evaluation suggests that the process may have economic potential. Alternative recovery schemes are discussed.

Jan 1, 1995

By Eugene W. Pearson

In a marked departure from conventional practice, the Power Plate process combines the two unit operations of leaching and electrowinning into a single continuous step for direct recovery of copper from sulfide concentrates, cement copper, copper scrap, and copper oxide slurries. Considering how environmental controls are pre- venting development of smelters for additional capacity or new construction, the Power Plate process provides a welcome pollution-free alternative to the smelting-electrorefining routes. And its low capital investment and low operating costs also recommend it to copper producers who are now using or investigating various hydrometallurgical methods.

Jan 12, 1974

By D. J. Bauer

A primary amine extraction system was investigated for fractionating a cerium-group, lanthanide sulfate mixture. Addition of diethylenetriaminepenta-acetic acid (DTPA) to the amine extraction system resulted in separation factors as high as 5.4 for lanthanum-cerium, 8.0 for cerium-praseodymium, 3.7 for praseodymium-neodymium, and 7.0 for neodymium-samarium. In multistage studies on a cerium-free lanthanide mixture, 96 percent of the lanthanum was recovered with a purity of 95 percent.

Jan 1, 1968

By Russell S. Sage

THE electric motor has steadily replaced the steam and air engine for use in mine hoists, until today a new installation with other than electric drive is a rarity. Much existing steam-driven equipment has been changed over to electric drive. Driving power has grown in capacity since the initial electric unit rated 10 hp installed at Aspen, Colorado, in 1888, to 3000 hp and 4000 hp in the United States, and to 5500 hp in Canada-the largest in the Western Hemisphere. Electric installations now total in the thousands of units, a growth largely made possible by the development of large central electric-power stations and the extension of electric-power service to more mining areas.

Jan 1, 1949

By A. W. Fahrenwald

The gyratory mill shown in Figures I and II is a ball mill in every sense of the term, in that the grinding media are balls. The media container, called the shell, is of the form of a shallow cylindrical tank whose position is with axis vertical The mechanism of the mill is designed to swing the shell in a circular path of small radius and, at the same time, to hold the shell in a position of constant orientation, i.e., the motion of the shell is such that every point on the shell surface -- bottom, wall and cover--travels in a perfect (horizontal) circle. The gyratory mill is definitely not a centrifugal ball mill. The balls do not, individually Qr in mass, travel in a circular path. Each ball, under heavy pressure from all directions, develops a sphere, or zone, of activity. Particles entering this sphere are crushed by impact. The gyratory ball mill, unlike the conventional tumbling mill, does not have, and is cursed by, a "critical speed". The speed of gyration, and in turn the power drawn by the mill--and ball potency--is limited only by the mechanical en- durance of the machine parts.

Jan 1, 1959

By E. H. Dix

The success of the Charpy impact test in the steel industry has led those interested in aluminum alloys to investigate the possible application of this test to aluminum and its alloys. In this paper are set forth the results of a few preliminary tests made at the Lynite Laboratories of the Aluminum Manufactures, Inc. In order to study more thoroughly the significance of the Charpy test, slow-bending tests have been made duplicating the arrangement of the impact machine. Tests have been made on both notched and unnotched specimens of a series of copper-aluminum alloys. Apparatus The standard American-made Charpy impact machine delivering a blow of over 200 ft.-lb. was much too large to test aluminum-alloy specimens of the same type used for steel, so that it was necessary either to adopt a larger specimen or to have a special light-weight hammer made. Since there is no known relation between specimens of different sixes, even though geometrically similar, it was decided to adhere to the 10 by 10 mm. specimen. Accordingly, Sauveur and Boylston, the American makers of the machine, were asked to construct a special light-weight pendulum adapted to their standard machine, this pendulum to have one-tenth the capacity of the standard. The writer wishes here to acknowledge his indebtedness to Mr. H. M. Boylston for the personal interest and care exercised in constructing this pendulum. The machine with the light-weight hammer in place is shown in Fig. I. It is mounted on a concrete foundation with the concrete covering the flange on the base of the machine. Vibration is further prevented by four 5/8-in. (15.8 mm.) foundation bolts. The large standard hammer shown against the wall was also used for some of the unnotched bars that required more than 20 ft.-lb. to rupture. When the light-weight hammer was received, it was carefully cali-

Jan 1, 1921

By Wen Xuan

Concentrados ?midos de minério de ferro podem se congelar durante o inverno e ficarem presos nos vagões de transporte, dificultando o descarregamento e a operação. Este problema vem sendo observado nas minas de Kryvyi Rih, Ucrânia e Mont-Wright, Canadá, onde o minério de ferro possui respectivamente 10,5% e 3,5% de umidade e, durante os invernos rigorosos, as temperaturas podem chegar a valores abaixo de -20°C. Nestes locais, uma grande quantidade de energia e tempo tem sido gasta para aquecer e descongelar os vagões. Este artigo mostra que polímeros superabsorventes, como o poliacrilato de sódio, podem evitar o congelamento e facilitar as operações de descarregamento e manuseio, além de possuír fácil aplicação, sendo eficientes quando aplicados apenas no fundo dos vagões, sem a necessidade de se misturar o polímero com o concentrado de minério de ferro.

Aug 17, 2017

By Donald R. Williamson

Statistical studies at Cyprus Pima Mine indicate that samples from 22 blastholes are necessary for determining average copper grades, within a desired range of precision, for mine-model blocks by arithmetic averaging. The average number of holes in such blocks is 14. Many considerations show that more holes will not be drilled for sampling. A way to determine block grades more reliably than by" arithmetic averaging was sought. Thus far arithmetic averaging has proven to be the best procedure for the particular operation characteristics despite the small number of samples. It naturally follows that expenditure of great effort in sampling blasthole cuttings is unwise.

Jan 1, 1977

By C. W. Schultz

Earlier publications from The University of Alabama have indicated that column flotation performance is improved when operating at low pulp levels and when the feed is directed into the froth phase. To validate these early observations a series of tests were performed in which the position of the feed entry to the column and the pulp-froth interface were systematically varied. The optimum grade-recovery relationship was achieved with high feed entry (WA) of column height) and very low pulp levels (<10% of column height). The position of the pulp-froth interface appears to be the more critical variable. When operating in this mode (1. e. at low pulp levels) column flotation becomes. in reality. a froth separation process.

Jan 1, 1991