Search Documents

By M. Bwalya, L. Mabokela, L. C. Woollacott

This paper presents a study on the ability of the King stratification modelto describe density stratification patterns that are achieved under idealizedconditions. Tests were conducted in a batch jig using artificial particles inseven density classes. All particles in a density class had essentially thesame density, size, and shape. Tests were conducted for particle systemsinvolving from two to seven components. Good agreement was obtainedbetween measured and modelled data to an extent that gave strongendorsement of the mathematical appropriateness of the core equation inthe King model. Somewhat ambiguous results were found with regard toclaims about the independencies of the single experimentally-determinedparameter required by the model.

Jan 1, 2015

By A. -M. Lafront

The corrosion resistance of die-cast and freely-solidified and electromagnetically-stirred thixocast AZ91D alloy has been studied using electrochemical noise technique in a 0.05M NaCI solution at pH 6.1 and 25°C. Specimens polished at different depths were immersed for a period of 75 min in order to assess the influence of the microstructure on corrosion kinetics and morphology. At depths between 10 and 50 µm (skin), all specimens showed general non-uniform corrosion with the lowest corrosion resistance. Between 100 and 200 µmn (interior skin), the observed corrosion was accompanied by superficial undefined pits due to metastable pitting. The corrosion form for 100-200 µm gave the best corrosion resistance. Stable pitting corrosion was observed beyond 400 µm deep on the bulk specimens. The skin of all thixocast specimens prepared billets showed a more corroded surface than that of die-cast. The interior skin as well as the bulk specimens showed better performance than that of the die-cast specimens.

Jan 1, 2007

By S H. Son, M K. Wang, H K. Jeong, B K. Cho, J I. Park

The utilisation of low-grade raw materials such as fine iron ore and semi-soft coking coal, and reduction of CO2 emissions are important issues in the ironmaking process. To solve these issues, a new process called PosPRA (POSCO prereduced agglomeration process) has been developing at POSCO. It focuses on the reduction of carbon composite iron ore briquette in travelling grate. In this study, the possibility of manufacturing the prereduced agglomerate (PRA) under oxidising atmosphere with travelling grate and the optimum manufacturing conditions of carbon composite iron ore briquette are investigated. The results have shown that controlling the temperature and oxygen potential in the range from 1100 to 1200°C and below 10 vol per cent respectively is very important to increase the reduction efficiency of briquette in travelling grate. High quality properties of the green briquette and PRA could be manufactured by using the briquette mixed with 20 wt per cent of coal under 0.1 mm in size under compacting pressure in the range from 3 to 7 t/cm. Adding 1 wt per cent water as a binder is proper under the condition of high compacting pressure. In a pot grate test, the compressive strength and metallisation degree of PRA are achieved over 150 kgf/p and about 55 per cent respectively, at bed temperature 1150°C and oxygen potential of 10 vol per cent when 20 wt per cent of coal is mixed in the briquette.CITATION:Wang, M K, Son, S H, Park, J I, Jeong, H K and Cho, B K, 2017. Development of prereduced agglomeration process using carbon composite iron ore briquette in travelling grate, in Proceedings Iron Ore 2017, pp 111–116 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By Steve Kral

Improved metals and other commodity prices have caused the mining industry to open new mines, re-evaluate development opportunities at potential mines and increase production at existing ones. This sense of renewed optimism is being seen at operations and development projects around the world. Except in the United States. The regulatory structure there has not allowed the domestic industry to share much in mining’s resurgence. It can still take up to 10 years to permit a new mine. And, while Clinton-era regulations regarding mill sites have been put on hold, existing mines that wish to expand operations still face significant regulatory and environmental hurdles. But things may begin to improve in the United States.

Jan 1, 2005

To meet the energy requirements, hydroelectric projects are planned and executed in many countries. Though these projects requires a high capital investment, the returns are regular with minimum maintenance after commissioning of the project and are ecofriendly. Bhutan is situated in the eastern Himalayas and covers an area of 38,394km2 (14824.01sq. miles. It is bordered by India in East, South and West and by Tibet in the North. The hydropower potential of the country is estimated at 30,000MW, out of which around 5% has been harnessed.

Jan 1, 2016

By María Cristina Ruiz

Enargite rich copper concentrates can not be treated by conventional smelting/converting technology and thus nonconventional methods such as leaching must be used. Since enargite (Cu3AsS4) is a hard to dissolve mineral in acidic solutions, pyrite, a common impurity in copper concentrates, could be used to increase the enargite dissolution rate. On this matter, we present in this work experimental data on the pressure leaching of a mixed enargite-pyrite concentrate in H2SO4-O2. The results show that the dissolution of enargite from the mixed concentrate is considerably faster than the dissolution of pure enargite mineral. The leaching rate increases significantly with temperature. Over 98% of enargite was dissolved in leaching 64 micron size particles at 200 ºC and 100 psi of partial pressure of oxygen in just 30 minutes. A change in the partial pressure of oxygen from 50 to 150 psi showed also a large influence in the leaching rate.

Jan 1, 2010

This paper gives an overview of the difficulties associated with determining the strength of hard rock pillars. Although a number of pillar design tools are available, pillar collapses still occur. Recent examples of large scale pillar collapses in South Africa were caused by weak partings which traversed the pillars. Currently two different methods to determine the strength of pillars are used namely, empirical equations derived from the back analyses of failed and stable cases and numerical modelling tools with an appropriate failure criteria. Both techniques have their limitations and additional work is required to obtain a better understanding of pillar strength. Empirical methods are popular and easy to use, but care should be exercise that the results are not extrapolated beyond the range of the data which were used to derive them. An example is the Hedley and Grant formula (derived for the Canadian uranium mines) that has been used for many years in the South African platinum and chrome mines (albeit with some adaptation of the K-value) to design the pillar layouts. Very few collapses have nevertheless been reported and it might even be too conservative an assumption of pillar strength in these mines. As an alternative, some engineers strongly advocate the use of numerical techniques to determine pillar strength. A close examination unfortunately reveals that these techniques also rely on many flawed assumptions. An area where numerical modelling is invaluable, however, is to study specific pillar failure mechanisms, such as the influence of weak partings on pillar strength. In conclusion, it appears that neither empirical techniques nor numerical modelling currently provide a solid basis to conduct pillar design. It is therefore recommended that both these techniques be utilised when confronted with a pillar design to obtain the best possible insight into the problem.

Nov 25, 2010

By Yao Zhou

Under the United Nations Convention on the Law of the Sea (UNCLOS), the international seabed area (Area) and its resources are the common heritage of humanity (CHH). Patent rights can be incompatible with the CHH doctrine and its underlying principles because patent holders might charge unjustifiably high prices to license patented technology for exploring and exploiting the Area’s resources (creating a "patent holdup" situation), might choose not to license, or might license exclusively when doing so would contravene CHH principles. However, a reasonable patent licensing regime can contribute to sharing the benefits derived from the Area and promote environmental sustainability. Provisions of the UNCLOS that stipulated compulsory technology and financial transfers were removed in the 1994 Agreement relating to the Implementation of Part XI of the UNCLOS but to promote equity and sustainability I propose a voluntary licensing regime modeled on the concept of reasonable and non-discriminatory patent licensing that has been used in other contexts. The International Seabed Authority or another entity will need to coordinate and promote this licensing regime through governance of intellectual property derived from the Area. This proposed approach can better effectuate the CHH doctrine and its underlying principles.

Sep 1, 2014

By I. H. Warren, Forward F. A

The reduction of aqueous slurries of uranyl carbonate at elevated temperature with compressed hydrogen m the presence of metal catalysts and certain organic promoters has been shown. to yield uranium dioxide. The reduction takes place in a sequence of steps. The purity and sintering properties of the dioxide make it of interest as a starting material for fuel element production. Simple control can be exercised over the surface area and oxygen/uranium ratio of the product during reduction. URANIUM dioxide for fueling atomic power reactors 1s conventionally produced as a powder by simultaneously decomposing and reducing ammonium diuranate with hydrogen in a furnace at high temperature. Fuel elements are then generally made from this powder by compacting and sintering ( 1). In order that elements approaching theoretical density may be obtained,

Jan 1, 1961

By J. T. McLendon

As part of its research project in developing improved refractory materials for metallurgical applications, the Federal Bureau of Mines obtained hot modulus of rupture data at 1,500°,1,550°, and 1,600° C on samples of 13 refractory periclase materials produced from seawater, lake brines, and natural magnesite. The periclase samples also were characterized to establish chemical and mineralogical composition and microstructure. The results indicated that a high MgO content does not necessarily assure good hot strength and that an optimum and varying CaO-Si02 ratio exists for each individual periclase sample.

Jan 1, 1979

By Charles R. Fettke

In connection with the gathering of data for a report on the geology of the Humacao district of southeastern Porto Rico during the summer of 1916, under the auspices of the Scientific Survey of Porto Rico and the Virgin Islands, conducted by the New York Academy of Sciences, the writer had an opportunity to make a brief examination of the magnetite deposits of the eastern portion of the island. Inasmuch as these deposits have attracted some attention as possible future sources of iron ore, and as there is only scanty reference made to them in literature,' a short description based on this reconnaissance survey was deemed to be worthy of record. The magnetite deposits of eastern Porto Rico occur in association with a belt of limestone, trending approximately S 53° E, which begins 11/2 miles east of Juncos and can be traced for about 6 miles toward the coast. Four outcrops of magnetite were observed, which are designated as Nos. 1, 2, 3, and 4, respectively, on the map shown in Fig. 1. Others are probably present, but escaped notice on account of the thick mantle

Jan 1, 1924

By G. M. Scamans

In the past ten years there has been considerable penetration of aluminum automotive body sheet (ABS) into automotive structures. The exponential increase in demand is resulting in major investments in heat treatment and finishing capacity across the globe. Line speed and tonnage throughput is limited by the continuous heat treatment (CHT) floater furnace rather than the cleaning and pretreatment section where electrolytic treatments that offer higher line speeds should come into favour and roll coating of pretreatment should predominate. The capacity limiting surface texturing pass will either be eliminated or moved to the finishing line or a dedicated mill. The key to making aluminum both embedded carbon and cost competitive with steel for more and more affordable classes of vehicles lies in recycling of both prompt scrap and, in the longer term, end of life vehicle scrap. For the first time scrap separation technology is available that can compete effectively with hand sorting and can sort aluminum shredded vehicle scrap into wrought and cast alloys and then into individual alloy groups. The challenge is to use more end of life scrap in alloy formulation whilst at the same time extending the property range in terms of both strength and formability.

Jan 1, 2015

By G. M. Scamans

In the past ten years there has been considerable penetration of aluminum automotive body sheet (ABS) into automotive structures. The exponential increase in demand is resulting in major investments in heat treatment and finishing capacity across the globe. Line speed and tonnage throughput is limited by the continuous heat treatment (CHT) floater furnace rather than the cleaning and pretreatment section where electrolytic treatments that offer higher line speeds should come into favour and roll coating of pretreatment should predominate. The capacity limiting surface texturing pass will either be eliminated or moved to the finishing line or a dedicated mill. The key to making aluminum both embedded carbon and cost competitive with steel for more and more affordable classes of vehicles lies in recycling of both prompt scrap and, in the longer term, end of life vehicle scrap. For the first time scrap separation technology is available that can compete effectively with hand sorting and can sort aluminum shredded vehicle scrap into wrought and cast alloys and then into individual alloy groups. The challenge is to use more end of life scrap in alloy formulation whilst at the same time extending the property range in terms of both strength and formability.

Jan 1, 2015

By Archie Richardson

The trona mines in the Green River Basin, commonly known as the "trona patch," present an interesting set of rock mechanics issues stemming from mining in a unique underground environment. Like other minerals occurring in tabular deposits, trona is mined using high-productivity room-and-pillar and longwall methods. However, trona does not behave quite like other evaporites and behaves far differently than coal. In this paper, the following key issues in trona patch rock mechanics are discussed: material properties, in situ stress field, water and gas pressure effects, creep characteristics, pillar behavior, roof span stability, floor stability, underground tailings storage, longwall mining, two-seam mining. and solution mining. Many of the existing trona producers are entering potentially more difficult mining conditions, and much consideration is being given to "new" technologies such as longwall mining and solution mining. In analyzing 20 years of experience with trona patch rock mechanics issues the authors have identified key comparisons and contrasts with conventional tabular deposit rock mechanics that will help illuminate what has been learned as the trona patch enters the 21" century.

Jan 1, 1999

By Dale S. Preece, J Paul Tidman, Stephen H. Chung

A discrete element computer program named DMC-BLAST (Distinct Motion code) has been under development since. 1987 for modeling rock blasting (Preece & Taylor, 1989). This program employs explicit time integration and uses spherical or cylindrical elements that are represented as circles in two dimensions (2-D). DMC-BLAST calculations compare favorably with data from actual bench blasts (Preece et al, 1993).

Jan 1, 1998

By R. J. Watson, A. H. Juch

About half a million sucker-rod pumps are installed in oil wells in the U. S. alone. In Venezuela, too, the system is widely used; some 5,000, or 90 percent, of Cia. Shell de Venezuela's wells produce a total of 400,000 BOPD by this method. Most of the crude pumped is viscous, gassy and contains relatively small amounts of free water. API gravities vary from 90 to 16O; dead oil viscosities vary from 10 to 10,000 cp at the pump; and GOR's range from 100 to 2,000 cu ft/bbl. Pumps are set at depths ranging from a few hundred to 6,000 ft; the average setting depth is about 2,500 ft. From the literature, it appears that although recent years have seen significant progress toward understanding the rod pumping system as a whole, relatively little attention has been paid to those key items, the sucker-rod pump and the subsurface gas separator or gas anchor. Perhaps because of proration in the U. S., pump manufacturers have seemingly concerned themselves more with the durability of their product, achieved mainly through robust design and metallurgical know-how, than with its working efficiency. In 1963, CSV commenced a major rehabilitation and expansion of its heavy oil fields along the Bolivar Coast. The advent of the more efficient gravel-packed completion and of large-scale thermal recovery (mainly steam soak) operations resulted in well potentials *Now with B. I. P. M., The Hague, The Netherlands. greater than pump capacities. Hence, an urgent need arose to improve over-all pump efficiencies and to attack those special problems related to the production of both the extremely viscous and the hot, steam-laden crudes that formed an increasing proportion of the total stream. There followed a detailed investigation and testing program, carried out in close cooperation with a major pump manufacturer. This culminated in the introduction to the oil industry of a new line of sucker-rod pumps. Early Investigations and Experiments Field Tests Extensive field tests were carried out in three primary Bolivar Coast wells with an in-situ dead oil viscosity ranging from 400 to 6,000 cp. In these installations provision was made to (1) monitor bottom-hole pressures below, in and above the pump by means of pressure transducers, and record casing- and tubing-head pressures continuously; (2) measure accurately the annulus gas, as well as measure the tubing gas and liquid production from the well; (3) take special PVT samples of the well fluid; (4) measure power consumption of the prime mover; and (5) measure the rod loads at the polished rod. A typical test installation is illustrated in Fig. 1. It was established from the pressure transducers that with viscous oils, there is considerable flow resistance across the pump and gas anchor assembly. Pressure surges were observed over each pump cycle,

Jan 1, 1970

By Brian R. Zuckerman

The Capitol Area East End Complex is currently being constructed under contract with the State of California Department of General Services on two sites adjacent to the grounds of the California State Capitol Building in downtown Sacramento. The complex will consolidate the headquarters of the Departments of Health Services and Education, which currently occupy several facilities located throughout Sacramento. When completed in 2003, the complex will be the largest civic office project in California history, with approximately 1.5 million square feet of office space and housing nearly 6,300 state workers. The total project is being constructed on five separate blocks in downtown Sacramento, Blocks 171 through 174 and 225. Separate design/build contracts were executed for the construction on Blocks 171 through 174 and the construction on Block 225. The scope of this paper is limited to construction on Blocks 171 through 174, which comprise a square, two blocks on a side, bounded by 15th, 17th, L, and N streets, located immediately to the east of Capitol Park and the State Capitol Building, as pictured in the image shown below.

Jan 1, 2002

The method of investigation was to study the distribution of ore in great detail, to make a thorough structural study of the lode and the mine area, and then to compare the results of the two studies. Such a comparison usually reveals a very close relationship between geological structure and ore distribution, and can often lead to important conclusions which would not be reached in the ordinary working of a mine.The Triton mine lies 30 miles E.N.E. of Cue, or 380 miles N.W. of Kalgoorlie, in typical pre-Cambrian rocks, consisting of gTeenstone lavas and tuft's, interbedded with slates and some sediments, and intruded by granite and porphyry. Fig. 1 (at end of paper) is a longitudinal section of the mine and shows that the workings consist of the main North Emu and the smaller South Emu, separated by a distance of about 1 of a mile. Both orebodies occur on the same lode, which strikes north and south and dips practically vertically. On the same line, and of 1/2 a mile and a mile respectively to the north of the North Emu, are the small Rand and North Rand workings, where a big width of lode material has proved to be very low grade. In the North Emu the lode width averages 12 to 15 feet; it is seldom less than 5 feet and in places reaches 30 feet. In the South Emu the lode is wide, but only portion of it is payable.The lode is a mineralised bed occurring between massive lava flows on the east and a mixed series of tuft's and thin lava flows on the west. The lode material is hard, fine grained, and dark coloured, and generally has a faint banding which is believed to indicate a tuft'aceous origin of the original lode rock. Microscopic examination shows that the original lode rock has undergone considerable albitisation;' there has also been considerable formation of biotite which gives the lode material a characteristic sheen. The mineralisation consists of abundant fine pyrite, which is auriferous, and a lesser development of pyrrhotite which is, however, barren of gold.THE OREBODIES AND THEIR CHARACTERISTICSThe distribution of ore is best studied from gold contours, as these reveal features that cannot be detected in an ordinary assay section. Gold contours (see Fig. 3) are developed' by plotting the width and grade of all development and stoping assays throughout the mine on a longitudinal projection, representing each sample by a coloured dot according to a suitably chosen range of assay values, and then outlining areas of similarly coloured dots (see H. J. C. Conolly, Econ. Geol., April, 1936). Both width and grade must be taken into account and the simplest method of gold contouring is to use dwt.lft. values, but difficulties arise here with big widths of low grade and small widths of high grade ore. To choose an extreme case, 30 ft. of 2 dwts. and 2 ft. of 30 dwts. both equal 60 dwts.lft., and would therefore be given the same value in dwt.lft. contouring...

Jan 1, 1943

By AIME AIME

FIVE days, extending from Monday, Feb. 18 to Friday, Feb. 22, inclusive, will be required for the annual meeting this year. The first fours days will be devoted to reading and discussion of papers, general and committee business meetings, two lectures, luncheons, dinners and all the pleasures of a big, general reunion. The fifth day will be given over to an all-day excursion for both men and women by special train to West Point, in celebration of the birthday of the first President of the United States. Washington having been an engineer and now after one hundred and thirty-one years the country having selected as President another engineer in the person of Herbert Hoover, our own past president and honorary member, it is proposed to celebrate with a good old-fashioned picnic and inspect the school. The authorities at the Military Academy have undertaken to welcome the engineers and do whatever they may to make our pilgrimage notable. Other social features planned for the week are numerous. Luncheon will be served as usual at the building each day of the meeting to all members and guests. This year a very nominal charge will be made, primarily to overcome deficits due to irregular attendance. Monday noon, the Non-metallic Minerals Committee will lunch at the Engineers' Club and in the evening the Milling Methods Committee will dine there. The Annual Smoker will be held at Hotel Astor after dinner. Professional entertainment of high order is promised, but not too much to interfere with the numerous group reunions that characterize this func- tion.

Jan 1, 1929

By Dirk van Zyl

As part of the North American regional activities during the Mining, Minerals and Sustainable Development Project (MMSD) one project focused on the development of sustainability evaluations at the operations level. Engagement was identified as one of the seven important questions to be addressed. Engineers and scientists employed in the mining, minerals and materials production arenas must understand the importance of stakeholder engagement, both within and outside the operations as it is essential in the ongoing activities required to contribute to sustainable development. After developing the awareness that a social license can only be contemplated if engagement is in place, they also have to develop skills in engagement processes. This presentation will present the business case for engagement as well as an approach to motivate undergraduate mining engineers to embrace it. The presentation will also review some recent and ongoing research to improve the engagement process.

Jan 1, 2010