Search Documents

By John C. Galloway, Heinz G. Leistner

ACKNOWLEDGEMENTS The investigations described in this paper were supported by contracts with the Defense Nuclear Agency (DNA) under direction of Lt. Col. John Galloway, and by Boeing Company research funds under supervision of James Wooster. Other engineers of The Boeing Company who contributed to the work of this investigation were Don Armitstead, John McAvoy, and Tom Day. INTRODUCTION In this paper, we are describing a current concept for placing intercontinental ballistic missiles (ICBMs) in sites deep underground to be used as a strategic Future Secure Reserve Force (FSRF). The objective of such concepts is to utilize soil and rock cover to protect high value strategic weapons from destruction by nuclear attack. The burial deep underground achieves two purposes. First, it imposes a miss distance upon the attacking weapon equal to the depth of burial minus any penetration capability the weapon might have. This tends to offset increasing accuracy of weapon delivery. The other purpose is to absorb as much of the weapon's energy as possible, thus reducing the effects of powerful weapons. This use of soil or rock cover over military facilities began with the development of man's capability to loft projectiles. Until recently, underground military installations, by their nature, performed defensive functions. Since they are not mobile and their weapons in the past had very limited range, an enemy would have to approach them before an engagement could take place. Thus, they were often used to control "choke points" on sea lanes as in the case of Gibraltar or

Jan 1, 1979

By Bryn Harris

Chesbar Resources Inc.1 is developing a nickel-cobalt laterite project in Guatemala, Central America, by applying existing atmospheric chloride technology to a known resource. The tropical laterite project has an inferred resource of 133 million tonnes grading 1.51% nickel, which represents ~20% of Chesbar?s land holdings in Guatemala. Within its boundaries, the Sechol area has a measured resource of 14 million tonnes grading 1.46 % nickel and 0.08% cobalt, and an indicated resource of 23 million tonnes grading 1.34% nickel and 0.08% cobalt. Notwithstanding the impressive overall resource, the company has taken an innovative approach to a laterite project and is concentrating on El Inicio, a high-grade starter pit with five million tonnes grading 2.1% nickel and 0.08 % cobalt. The process flowsheet is based on atmospheric chloride leaching in a slightly acidic magnesium chloride brine, solution purification by recycled magnesia, precipitation of a mixed nickel/cobalt hydroxide intermediate product, and lixiviant regeneration by modified pyrohydrolysis technology. Initial results suggest that >90% of the contained nickel and cobalt in the non-magnetic fraction of the feed can be recovered, with <5% of the iron leaching. A metallurgical scoping study has established preliminary capital and operating costs for a production facility at a proposed rate of 20,000 tonnes per year of nickel as the intermediate mixed hydroxide. A preliminary assessment of producing a magnesium oxide by-product has also been carried out. This paper reports on the current development of the project and highlights the advantages of working in a chloride medium at atmospheric pressure and slightly elevated temperatures.

Jan 1, 2003

By McLeod RL

The Tolukuma gold-silver prospect is located approximately 100km N of Port Moresby in the Central Province of Papua New Guinea (PNG). Epithermal "adularia-sericite" style mineralisation crops out over 1200m within an en echelon quartz veined zone 1 to lOm wide. At a 4g/t cut-off grade, a geological resource of approximately 1.47Mt @ 13.77g/t Au is indicated from 38 diamond drill holes completed since discovery by Newmont Pty Ltd in September 1986. At a regional scale, Tolukuma miner- alisation appears localised in a dilatant zone at the intersection of a 1150 magnetic structure, and the western margin of a N-S trending graben which is filled by a Pliocene volcanic complex contemporaneous with the Mt Davidson Volcanics 30km to the W. A l0km diameter circular Landsat feature, which may reflect magma emplacement at depth, occurs immediately N of Tolukuma and nearby mineralisation. Mineralisation at Tolukuma occurs in sub-vertical quartz veins at, or adjacent to the faulted contact between Pliocene basic and intermediate volcanics/intrusives, and quartz mica schists and phyllites of the Cretaceous Kagi Metamorphics. Most veins display evidence of multiple episodes of brecciation and textures indicative of cyclic boiling, including crustiform rhythmic banding and quartz pseudomorphs after platy calcite.

Jan 1, 1991

By N. P. Titkov

This paper presents the results of laboratory and pilot plant investigations for the development of efficient methods of beneficiating hematite ores from the Krivoi Rog, Kursk Magnetic Anomoly, Olenogorsk, and other localities. The tests included gravity, magnetic (in a high intensity field), flota¬tion, and magnetizing roasting methods. It was possible to develop efficient beneficiation methods depending on the mineral composition of the ore and degree of dissemination of ore and gangue minerals. The paper shows the relationship between the iron silicate and quartz content of the ore and the technologic indices of the various beneficiation methods. Some of the conclusions based on these investigations and the technical and economic computations related to the cost of one ton of pig iron produced from concentrates obtained by the various beneficiation methods are: 1. If the hematite ore is not disseminated uniformly, it is expedient to use a combined gravity and flotation process. Ore particles up to 50 am. in size are beneficiated by gravity (heavy suspension, jigging, and others) and yield a lump concentrate. The middlings from this process are recrushed and floated; 2. Finely disseminated hematite ores, containing small quantities (less than 5 percent) of iron silicates, are most effectively beneficiated by flotation. Anionic (sulphate soap, tall oil emulsion with various foam depressors) as well as cationic collectors may be used. Depending on the mineral and chemical composition of the ore, it is possible to obtain concentrates containing up to 65 percent iron with an extraction up to 94 percent; 3. Finely disseminated, mixed hematite-magnetite ores may be beneficiated by flotation or a magnetic separation-flotation process; 4. Finely disseminated hematite ores, containing large quantities of iron silicates and earthy hematite ores are most efficiently beneficiated by the magnetizing roasting method. This method will yield concentrates containing up to 68 percent iron with extractions up to 90 percent. Although beneficiation by the magnetizing roasting process is costly, it will nonetheless, when employed on this type of ore, yield the least expensive pig iron.

Jan 1, 1960

By Valery V. Kostjuk, Victor. N. Bredikhin, Alexander I. Shevelev, Evgeny A. Kazban

"The investigations to improve the process data have been done in order to stabilize the functioning of drying units. The scheme of turnings preparation with centrifuging and subsequent thermal degreasing (tandem) is proposed. To improve the efficiency of the process the scheme of reclamation of the centrifuge fugate is developed with production of oil and service circulating water. Empirical dependences of the turnings temperature influence on the lubricant-coolants content in centrifuging are gained. When the turnings temperature is increased to 80 C the residual content of LC is decreased by 1.5%. The investigations aimed to improve the preparation of non-ferrous turnings have allowed to decrease the melting loss by 15-20%; to stabilize the process of thermal drying of turnings; to decrease sharply (by 60- 70%) the volume of LC combustion products; to reclaim the centrifuge fugate and produce oil and servicecirculating water.Non-ferrous turning and primarily aluminum and copper alloys turning is a stable source of secondary raw materials for metallurgical works.Direct by lubricant-coolants (LC) of various types: synthetic, semi synthetic, oily and emulsions.On the base of investigations concerning various methods of the non-ferrous turning processing the favorable one has been selected taking in to consideration the economy, ecology and quality of the finished product (alloy). Two-stage process is developed. The main idea of the process is the elimination of the lubricant-coolants (LC) to the limit specified in advance. The applied method is centrifuging with subsequent final elimination of LC by thermal method.Constant value of LC content at the inlet of the thermal unit excludes practically the oxidation of metal and as a consequence increases the output by 10 –15 % in metallurgical processing."

Jan 1, 2003

By W. Spencer Hutchinson

It is the purpose of this paper to describe a method used to determine the corundum contents of samples of hard crystalline gneiss containing both corundum and red garnet. A chemical analysis of the rock for alumina would not fix the amount of corundum became at least three other constituent minerals of the rock, mica, feldspar, and garnet, contain alumina combined with silica. Following are the principal minerals found in the samples, together with their specific gravity and hardness as given by Dana: The corundum occurred in crystals of a gray or bluish gray color, in minute grains and coarser up to 0.5 in., and no massive or block corundum was observed. The larger crystals were commonly quite slender, well defined, and the normal hexagonal form clearly developed. They lay with the structural planes of the gneiss, and sometimes appeared prominently in relief on weathered surfaces. In some cases these crystals had suffered partial or total alteration to mica, margarite, or other soft minerals, a condition illustrated by sample D, which appeared to be studded abundantly with corundum on the flat faces. Garnet, a striking feature of nearly all the samples, was present in small rounded crystals of a pink to red color. The samples were first broken to pass a No. 4 mesh screen. This was done with a hammer on an iron plate, particular care being taken to avoid the breaking of the crystals finer than need be to pass the screen. A portion of the sample weighing 500 g. was then taken and, with a little water added, was scoured round and round in an iron bucket with a wooden block, until the coarse crystals of corundum were cleaned of adhering pieces of mica. The bucket was then re-

Jan 1, 1914

By Zia Pirzada

"Time is of the essence" and "Time is money" These are powerful and true statements during a project life cycle and have far-reaching implications on the success and failure of the project Time and progress management is crucial to the project success. Project delays may increase the cost to an unacceptable level and may render the project as economically unfeasible. On the other hand, if the project is completed on time or earlier than as planned, it may generate economic benefits greater than what had been envisioned To take advantage of the financial opportunities and to improve the cash flow as well as Return On Investment (POI), project schedule can be accelerated to complete the project earlier than planned Project schedule acceleration can be achieved by using analytical tools, such as "Schedule Optimization", "Schedule Reduction", "Schedule Compression" or a combination of any of these concepts along with the "Planning for start up". Schedule optimization does not entail any extra cost, however, other acceleration methods, such as Schedule Reduction and Schedule Compression, may require extra expenditures from the owner. Based on the forecasted early start of the revenue stream, the extra expenditure could become a worthwhile venture with a very high rate of return To accelerate the schedule, all aspects of the project should be reviewed with acceleration costs calculated. All risks and opportunities should be evaluated and taken into consideration to determine if the acceleration is feasible and advisable and will provide definite financial advantages Sometimes schedule acceleration may be desired to prevent the company from paying liquidated damages. This is especially true when the project is not expected to complete on the contractual completion date and when the cost of acceleration is less than the liquidated damages that may accrue against the company.

Oct 1, 2010

By G. L. Oldright

THE development of the reverberatory furnace for smelting copper ores up to 1912 was described by E. P. Mathewson1 with details concerning the great changes in dimensions of the furnace. Hayward2 tabulated similar data, giving developments up to about 1924, in his revision of Hofman&apos;s Metallurgy of Copper. DEVELOPMENT OF PRESENT SMELTING PRACTICE Dimensions of Furnace Very great changes were made in the dimensions of the smelting hearths of the furnaces in the period from about 1800 to 1906, the length increasing from about 11 to 116 ft., and the width from 8 to 19 ft. During this time the tonnage smelted increased from about 9 to 250 tons per 24 hr., and the tons of charge smelted per ton of coal increased from 0.77 to 4.3. Dr. Mathewson3 noted no great difference in the "fuel ratio" (i. e., the amount of charge smelted per ton of coal) as the furnace at Anaconda was increased in length by stages from 85 to 116 ft. (The percentage of copper in the slag, however, was lowered from 0.42 to 0.36 per cent. The other components of the slag were not given.) Lump coal fired on grates was the fuel used during this period. The practice in operating the furnaces over such a length of time naturally varied considerably, and there were differences in composition and nature of the charge, yet it may be considered that the improvements made were due largely to increases in the size of the furnace used. Doubt-less some credit should be given to improvements in operating technique, like changes in the methods of firing the lump coal. However, the greater part of the advance was probably due to factors influencing the

Jan 1, 1928

By J. Wiese

Recently the operating philosophy at concentrators processing platinum bearing ores has started to move from a recovery dominated system to one in which the production of high grade concentrates at the expense of some recovery would provide greater benefits in the further upgrading of the platinum group minerals (PGM). The low grades usually obtained are associated with the presence of naturally floatable talcaceous gangue minerals in all PGM ores. Polysaccharide depressants such as guar gum and carboxymethyl cellulose (CMC) are used to improve the grades of the concentrates. Recent testwork has shown that the use of high depressant concentrations can prevent any naturally floatable gangue from reporting to the concentrate. The only gangue present in the concentrates would be due to its entrainment in the froth. Under these conditions much higher grades can be achieved. The sulphide minerals themselves, however, become susceptible to depression at high depressant concentrations. This work examines how the recovery of sulphide minerals in two Merensky ores was affected by the type and concentration of the collector in the presence of high depressant concentration (500 g/t) and that the response of the sulphide minerals was also dependent on the type of depressant used (guar or CMC).

Jan 1, 2009

By M. Kwasniewski, M. Takahashi

Prismatic samples of a medium-grained sandstone from Slask Colliery (Upper Silesian Coal Basin, Poland) were tested under uniaxial compression, conventional triaxial compression and true triaxial compression conditions. The conventional triaxial compression tests were carried out at confining pressure (p) equal to 12.5, 25.0 and 37.5 MPa. In the true triaxial compression tests the minimum principal stress (s3) was equal to 25.0 MPa and the intermediate principal stress (s2) was 1.5, 2 and 2.5 times higher than s3. Results of the studies show that confining pressure strongly inhibited dilatant behavior of rock samples tested under conventional triaxial compression conditions; the increasing confinement resulted in the growing compaction of the rock material. The effect of dilatancy was also highly suppressed by the intermediate principal stress. While important dilatant, negative volumetric strain corresponded to the peak differential stress at low intermediate principal stress conditions, at high intermediate stresses the rock material was damaged to much lesser extent. As a result, faulting of rock samples in the post-peak region was much more violent and was accompanied by a strong acoustic effect. Les échantillons parallélépipédiques du grès à grains moyens de la mine ‘Slask’ (Bassin Houiller de Haute Silésie, Pologne) ont subi les essais de compression monoaxiale (compression simple), de compression triaxiale conventionnelle (compression triaxale de révolution) et de compression triaxiale vraie. Les essais de la compression triaxiale conventionnelle ont été effectués à la pression de confinement de 12,5, 25,0 et 37,5 MPa. Dans les essais de compression triaxiale vraie la contrainte principale minimale (s3) était de 25,0 MPa et la contrainte principale intermédiaire (s2) était 1,5, 2 et 2,5 fois supérieure de s3. Il résulte des essais que la pression de confinement inhibe fortement le processus de dilatance dans les échantillons testés dans les conditions de compression triaxiale conventionnelle; l’augmentation de la pression provoquait l’augmentation du compactage du matériau rocheux. Le phénomène de dilatance était également limité de façon significative par la contrainte principale intermédiaire. Alors que l’importante déformation volumique négative correspondait à la contrainte différentielle ultime avec les faibles contraintes principales intermédiaires, dans les conditions de fortes contraintes intermédiaires, le matériau rocheux subissait l&apos;endommagement de façon beaucoup moins importante. En résultat, la rupture des échantillons rocheux au stade post-maximum était beaucoup plus violente et accompagnée d’un fort effet acoustique. Prismatische Probekörper des mittelkörnigen Sandsteines aus dem Bergwerk ‘Slask’ (das Oberschlesische Kohlengebiet, Polen) wurden unter der einaxialen Druckbeanspruchung, konventionellen dreiaxialen Druckbeanspruchung und der echten dreiaxialen Druckbeanspruchung geprüft. Konventionelle dreiaxiale Druckversuche wurden bei dem Manteldruck von 12,5 25,0 und 37,5 MPa durchgeführt. Bei den echten dreiaxialen Druckversuchen betrug die kleinste Hauptspannung (s3) 25,0 MPa und mittlere Hauptspannung (s2) war 1,5-, 2- und 2,5-mal höher als s3. Aus den durchgeführten Versuchen ergibt sich, dass der Manteldruck die Dilatanzentwicklung bei den Probekörpern unter der konventionellen dreiaxialen Druckbeanspruchung stark bremst; die Erhöhung des Druckes rief die ansteigende Kompaktion des Gesteinsmaterials hervor. Die Dilatanz wurde auch durch die mittlere Hauptspannung beschränkt. Während die wesentlichen volumetrischen, dilatanten Verformungen der Grenzdifferenzspannung bei den niedrigen mittleren Hauptspannungen entsprachen, bei den hohen mittleren Hauptspannungen wurde das Gesteinsmaterial viel weniger beschädigt. Im Ergebnis war der Scherbruch der Gesteinsproben im Post-Peak-Bereich viel heftiger und mit kräftigen akustischen Effekten verbunden.

Jan 1, 2003

By G C. Bolton

Experiments were conducted to access the feasibility of removing zinc from lead slag by sulfation or chlorination or both. Gaseous sulfation with sulfur dioxide and oxygen released only 50 per cent of zinc even under the most severe conditions. Sulfation with concentrated sulfuric acid by a fast-leach process released 95 per cent of zinc while pug-roasting released a maximum of 78 per cent of zinc. Chloridization with NaCl in the presence of sulfating gas released 50 per cent of zinc, while direct chlorination with chlorine gas and oxygen released 85 per cent of zinc and 100 per cent of lead in a chloride condensate containing little impurities.

Jan 1, 1980

Development of a Froth Dropback Measurement Device

Sep 13, 2010

It is now five years since the advent of gold-dredging in Australia, the State of New South &apos;Wales, or colony as it was, being the first to adopt this system of gold-getting, and the credit of its introduction rests with a member of this Institute, Mr. Chas. L. Garland, who commenced operations with his dredge on the Macquarie River, at the junction of the Muckerawa Creek, in the month of March, 1899. In this paper it is intended to give a brief history of the career of the gold dredge in New South Wales from that relate up to the present time, during which period the writer, as a designer of many dredges, has been constantly in touch with the subject in all its phases in this State; the points noted are the outcome of his observation in a general way, and to a great extent are apart from the design proper.Gold-dredging in New South Wales up to the present moment can hardly be designated an unqualified success...

Jan 1, 1904

By Cheryl Lee Vatter

The Lupin mine consists of a gold mining, milling, and refining complex located 400 km (250 miles) northeast of Yellowknife and 100 km (60 miles) south of the Arctic Circle on the southwest shore of Contwoyto Lake in Canada&apos;s Northwest Territories. (Fig.1). The mine was commissioned in 1982 and is presently producing 6 t/a (193,000 oz per year) of gold from 612 kt (675,000 st) of ore. The success of this operation is due to such factors as the continuity and grade of the ore body, the competency of the host rock, low mining costs, efficient milling, the transportation of people and materials to and from the mine site, and the unique work schedule resulting in a stable workforce. Echo Bay Mines operated a silver mine at Port Radium on Great Bear Lake, Northwest Territories, from 1965 to 1982. The company first obtained an option on the Lupin property from Inco in February 1979 and completed an underground exploration program in 1979-1980. Topographic relief is low and vegetation is sparse in the continental subarctic climatic zone, consisting mainly of moss and lichens. Temperature extremes are from 24°C to - 45°C (+75°F to -49°F) with an annual mean of -12°C (+54°F). Permafrost extends from near surface to 500 m (1640 ft) in the ore zone. Its remote location and harsh climate presented some challenging design and logistical problems. Construction began at the Lupin mine site in 1980. Before construction, a 1.5-km (5000-ft) gravel landing strip was prepared, suitable for landing a C 130 Hercules. The entire Lupin project took 20 months to build. All of the men and materials were transported to the site with some 1100 Hercules flights and several hundred Convair 640 flights. The Convairs transported construction crews, which numbered 400 at their peak, and also carried 3.2 kt (3535 st) of supplies during construction. The facilities were constructed and commissioned for a total cost of C$135 million. The operation was originally designed to throughput 860 t/d (950 stpd). Expansion in 1983, circuit refinements, and some capital projects brought the daily throughput to 1.7 kt/d (1850 stpd). The underground mine delivers 612 kt/a (675,000 stpy) of ore to the mill at an average head grade of 8.46 g/t (0.3 oz per st). The ore is nonrefractory and is processed in a conventional cyanide leach using the Merrill Crowe process. Gold recovery is about 95.0%. The average production cost is $US5.85/g ($US 182 per oz) based on 1987 figures. Mining at Lupin – Geology The Lupin deposit occurs in amphibolite grade iron formation overlain by mudstones (phyllites) and underlain by graywacke (quartzites). Contacts between the wallrock units and the iron formation are well defined. It has been folded and tilted into a megascopic antiform-synform-antiform structure (Fig. 2). Gold occurs primarily within the sulfide rich iron formation, with some minor occurrences in sulfide poor iron formation. The distinction between sulfide rich and sulfide poor iron formation is based on a visual cutoff of 5% total sulfide content. Mining widths are determined by an assay cutoff of 4.2 g/t (0.15 oz per st) gold. There are few tons between 1.7 and 4.2 g/t (0.06 and 0.15 oz per st). The amphibolitic iron formation at the mine ranges from 1.5 to 20 m (5 to 65 ft) wide and has been followed over a strike length exceeding 1.7 km (5600 ft). The wider portions of the ore body tend to occur at its north extent and south nose. The gold-bearing iron formation appears on plan as a Z-shaped structure made up of three zones: the West, Center, and East. The West and Center zones dip steeply to the East (75° to 90°). Each of the ore zones plunge at an angle of about 65°. Total strike length of the three zones is more than 610 m (2000 ft). The zones are confirmed at a depth of 650 m (2130 ft) below surface. The Center zone is the widest and varies from 4.5 to 20 m (15 to 65 ft) while the West is the narrowest, averaging 1.5 m ( 5 ft). The footwall is comprised of quartzites that are strongly jointed and locally grades into phyllite, which comprises the hanging wall. The hanging wall and footwall are reversed in the West zone. Mineralogy of the ore at Lupin consists of amphibole minerals (hornblende, cummingtonite, and grunerite), feldspars, quartz, occasionally garnet, pyrrhotite, arsenopyrite, minor pyrite, and trace chalcopyrite. Also found in minor amounts are scheelite, apatite, epidote, calcite, tourmaline, and some arsenides (notable loellingite). Quartz

Jan 1, 1989

By Juan Lizana

El presente trabajo describe el proceso del sistema de gestión estratégica en la mina San Rafael, Puno. En este sentido, la empresa como parte introductoria de sus operaciones, ha propuesto la solución integral, donde la herramienta principal son los índices de gestión por unidades estratégicas de negocio y los índices de gestión por unidad operativa, los mismos que permitirán evaluar el desempeño de su organización frente a sus metas, objetivos y responsabilidades. En este sentido, el establecimiento de este sistema busca crear una cultura en la organización, a través del seguimiento de cada uno de los índices, permitiendo a la alta gerencia y a los demás niveles ejecutivos de la empresa hacer control de gestión, así como una reducción de los costos operativos en el Área de Mina y mejoras en los resultados de voladura.

Sep 12, 2005

By E. Lovera

Social attention to environmental aspects, steadily increasing in European Countries, has been leading to a stricter regulation of many productive activities. Among them, mining and quarrying sectors have been often censured for their potential and real impacts on land and environment. Referring to dimension stone exploitation (also the terms ornamental stone or natural stone are here used as synonymous), quarries are often concentrated in extractive basins, where the resource is localized with suitable quality and quantity: this fact has sometimes raised critical environmental situations. Nevertheless, dimension stone quarrying represents in Europe a traditional and important economical activity, source of wealth and employment. Moreover, many natural stones take on a ?cultural? value and may be considered as ?classic?, as they have been exploited since antiquity and are element of the architectural heritage of many Countries. The sector relevance demands the research of a sustainable balance between social-economical needs and environmental protection. Actually, very restrictive environmental protection policies have led to severe limitations to quarrying activity, but the results do not seem to be completely positive in terms of sustainability: on the one hand, closing-down stone quarrying activities imposes a shrinkage in local, social and economical development; on the other, quarrying activity is pushed towards developing Countries, environmentally un-protected, simply moving and putting off to next future the problem. The challenge of the sustainable development of quarrying sector ? recently explored in the European Commission?s communication ?Promoting sustainable development in the EU non energy extractive industry? (COM-2000-265) ? should be achieved through a positive link between theoretical statements and practical effects: sustainability indicators may be an effective instrument to assess and monitor the environmental performance of the industry. The paper refers to the development of specific ecological criteria and indicators, which can be useful to measure and predict the eco-efficiency of a dimension stone quarry, finally pointing out where improvement efforts have to be focused.

Jan 1, 2003

By Chen Shuwen, Yao Zhihua

In the process of thickening dewatering_the motion state of two- phase flow in a thickener has a very great influence on thickening efficiency. The investigation was made using copper mill tailings. In this investigation the authors explored the formation conditions and motion range of density current in the thickening process by model experiments, and analyzed the influence of density current on thickening efficiency. The results have shown that the formation of density current has relations with the structure parameters of a thickener and thickening process. The density current and its forming location affect thickener’s working efficiency. The author measured the motion state of two- phase flow in a 53-m dial. thickener for copper mill tailings under its operation conditions and analyzed the density distribution and motion state of two-phase flow in the thickener. The results obtained by the industry tests have shown that the motion state of two- phase flow in the thickener can be greatly improved by modification of its structure, achieving a great improvement in its thickening efficiency. It is concluded that, a thickener’s working efficiency depends on the formation and motion range of density current in it, which is of great importance to designing and establishment of thickener’s working parameters.

Jan 1, 2003

By G. Bierie

The conveying of bulk materials is prone to problems. These problems can reduce the capacity and efficiency of the plant, and even threaten the health and safety of the workforce. This presentation will look at new conveyor technologies systems, and how, used separately or in combination, they can improve material handling.

Jan 1, 2007

By Stephen Mansfield, Nathan West, El Khalil Seyed

In October 2017, a multi-bench failure occurred in the east wall of the Guelb Moghrein copper and gold mine in Mauritania. The failure extended 100 m (328 ft) vertically and horizontally and resulted in the sterilisation of ore, but no equipment or personnel were put in danger. The remediation plan successfully removed the failed material and the cutback resumed to a modified pit design, leaving ore reserves behind. In 2021 after completion of mining in another part of the pit, a plan was formulated to develop a narrow cutback behind the failed wall and recover the sterilised ore. Infill drilling defined a resource of approximately 2.9 Mtonne (3.2 Mton) of ore at 0.78% Cu and 0.67 g/t Au at a strip ratio of 5.5:1. The high strip ratio meant that it was necessary to mine thirteen benches of waste, or 156 m (512 ft) vertically, over a two-year period before reaching the first ore, with the cutback only being economically viable if all ore could be depleted at the end of the third year. The high economic risk of the project required a holistic approach to mitigate the risk of another wall failure, by addressing the following areas: 1. Pit Design: with help from an external Geotechnical Consultant, the pit design was optimised to include increased factors of safety, reduced stress points, lower overall slope angles and straight lined walls were replaced with curved walls. 2. Geotechnical Management: the site Geotechnical Superintendent worked closely with an external Geotechnical Consultant to better understand the structural geology. Slope monitoring was improved through an expanded network of prisms, regular in field inspections and the use of a slope monitoring radar. 3. Drill and Blast: new drill and blast designs were developed from first principles, consisting of production, wall control and presplit designs. Blast master polygons and bench development sequences were developed with consideration of the structural geology and the influence of the initiation designs. 4. Mine Operations: improving operational discipline was a critical factor that ensured the accurate execution of drill and blast designs and excavation to bench levels and pit limits. This holistic approach has enabled the safe development of the cutback down to the 936 RL (relative level), two benches below the point at which the previous wall failure occurred. Extraction of ore has occurred from the 960 RL, and due to faster than planned excavation rates, the cutback is expected to be completed ahead of schedule.

Jan 21, 2025

By R. M. Brick

AN increased demand for information in regard to the effect of gaseous elements in steel has accompanied the recognition of the importance of grain size. Attempts to correlate grain-size characteristics with gas con-tent, particularly oxygen in solution or in the form of included metallic oxides, have not been universally successful. Certain definite effects of dissolved gases are recognized; specifically, the role of hydrogen in causing internal cracks or "flakes" and that of nitrogen in preventing excessive grain growth of ferritic chromium steels. When irregular behavior or properties are found in a well-known steel and no definite cause for the abnormality may be assigned on the basis of chemical and metallographic tests, dissolved gases are frequently blamed as the culprits. The solubilities of hydrogen1 and nitrogen2 in pure liquid iron are known but of the ternary systems, iron-alloying element-gas, only the Fe-Si-N3 and Fe-Cr-N systems have received attention and here the study was confined to liquid alloys. Krivobok4 published a curve show-ing the solubility of nitrogen in liquid Fe-Cr alloys but gave no informa-tion on the experimental procedure employed. The considerable experimental work reported on the Cr-N binary alloys has been reviewed by Hansen.5 It is generally agreed that the nitride CrN is a stable phase although the existence of nitrides within limited temperature ranges of stability, viz., Cr3N2 and Cr2N, has been disputed, Adcock6 and others7 have reported a eutectic between Cr and CrN at 1580°C., although the supporting evidence is not complete.

Jan 1, 1940