Search Documents

By J J. J Chen, J C. Zhao

A water/air model was developed to simulate the refining of molten aluminium by the sparging of gas through an impeller. The optimal gas dispersion depends upon selecting the correct gas rate for a given impeller rotational velocity to prevent flooding or channelling. Correlations illustrating this flooding behaviour exist for standard impellers within standard tank geometries. However the validity of these correlations has not been substantiated for gas dispersion in high temperature molten metals with non-standard tank and impeller dimensions. Metal refining is most efficient when fine bubbles are generated and uniformly distributed within the treatment tank. The application of some measuring technique able to detect this distribution within a non transparent operating treatment tank would be invaluable, enabling the optimisation of gas flow and impeller speed.   A technique has been developed to measure the pressure fluctuation levels at specific points in the water model. Comparison of these pressure fluctuation data with photographic evidence obtained in the water model suggests that the flow regime in the metal treatment unit may be determined using this technique.

Jan 1, 1995

"This generic study has been developed in response to the frequently asked question, ""That is the best treatment route for refractory gold ore?"". The study has developed operating and capital costs for many potential treatment routes and they are presented here in a generic form. All costs are in relation to the value of 1.00 given to the base case, a 1000 mtpd bio-oxidation plant, operating at 25% solids and 72 hours residence time.There is unfortunately no simple answer to the above quest ions. The treatment of refractory ores is a complex subject, with many variables, such as mineralogy, chemistry, environment and tonnage. However this study does offer information and relative numbers that we believe will be of assistance to gold metallurgists in obtaining a ""first shot"" at estimating costs.Equally, this technology is a rapidly evolving one. As more plants are commissioned, and test programs completed, better data is constantly being generated. For a generic study of this type to remain useful it will need regular updating and adjustment."

Jan 1, 1989

By Maurice Hunter

The paper outlines recent design developments in the computerization of surface crawler drills for the quarry industry. It references the technology firstly developed for the underground mining and construction industry, where automation and computerization has been in demand for a number of years.

Jan 1, 2003

By C. C. Miller, A. R. Belyea, C. H. Herty, E. B. Burkart

The removal of sulfur from steel has been studied by many investigators, but the quantitative relationships between the factors involved have not been determined. This is undoubtedly due to the number of variables encountered in practice, an attempt to study any one reaction or relation being affected by other reactions the relative importance of which cannot be estimated. The factors that affect the extent of removal of sulfur in the basic open-hearth process are generally considered to be: 1. Basicity of the slag: (a) Iron oxides in the slag; (b) carbon in the metal or carbide in the slag; (c) temperature. These factors affect the reactions: FeS + CaO = CaS + FeO FeS + CaO + C = CaS + CO + Fe. 2. Amount of sulfur in the gas. 3. Amount of manganese in the metal. The factors which affect the rate of removal of sulfur include, in addition to these: 4. Fluidity of the slag: (a) Normal changes in fluidity with temperature; (b) changes in fluidity because of the addition of special reagents such as fluorspar. 5. Agitation of the bath. Within the past two years, two papers have been presented dealing with the influence of sulfur in the gas on slag and metal. Nead' has shown that if a gas high in sulfur be used for heating, the metal and slag will absorb sulfur. Whitely2 concluded from his experiments that if a

Jan 1, 1925

By D J. Holden

Prospectivity, the relative value of gold, investor confidence, general economic stability and legislation driven by public attitudes are seen as the major influences on the gold mining industry in New Zealand. Since the 1860s the gold mining industry in New Zealand has been subject to the complex interaction of these influences resulting in three successive boom and bust periods. The booms are related to periods of greatest potential economic growth. The busts are more strongly related to downturns in the economy and falling gold price. The influences may be expressed as trends over time. The role of gold has changed from being a currency base to that of a traded commodity. This change has caused price instability and rapid fluctuations in its value. Increased competing land uses, shifting public attitudes and legislative changes have added to the instability of the industry. Reaction against change is to be expected from the companies until new legislation is seen to be functioning efficiently. Other trends show that there has been a tendency towards reduced exploration and consolidation of active gold mining projects. The future consequences of this are likely to be felt both regionally and nationally as there will be no new discoveries to fill production voids which will develop as currently producing mines close. The review of New Zealand's resource use statutes is nearly complete. A period of legislative stability can now be expected. There are some positive signs that consents will be obtained much more quickly than under previous legislation, particularly by those companies which develop the skills to work with the system. The new regime is about consideration of impacts rather than specific activities. This, together with excellent prospectivity, bodes well for the identification of mineral resources in New Zealand.

Jan 1, 1992

By R. Luhrman, E. Christ, B. Gores, S. Fischer, E. Johanning

North American railroad locomotive operators (engineers and conductors) are exposed to multi-axis vibration and shocks (1, 2). A recent epidemiological survey showed a prevalence of serious type of neck and lower back disorders nearly double that of a control group (3). Ergonomic working conditions are important co-factors in a vibration and shock exposure risk assessment (4, 5). The goal of this study is to illustrate typical work stations (cabs and seats) in US/Canadian type locomotives and assess shock related exposure risk by calculations of the new proposed shock risk indicators according to the new ISO 2631-5 (2004) (6). Methods Locomotive cab and seat inspections were conducted and operators’ activities were assessed by a trained observer. Field measurements (n=50) were obtained during normal revue service following generally accepted guidelines (ISO 2631 (1)). A sub-sample of n=20 locomotives were selected for the calculation of proposed shock indicators (ISO 2631 (5)). Results There has been little change in basic locomotive cab and seat design in the U.S.. Two locomotive cab design concepts are used: the Association of American Railroad (AAR) Control Stand and in newer series wide-body locomotives the “Control Consol” (Figures 1-2), with varying seating conditions, but frequently subjecting the operator to an awkward body posture in addition to the vibration and shock exposure. [ ]

Jan 6, 2006

By Donald A. Bruce

The paper reviews aspects of the construction and performance of prestressed ground anchors installed in soils and weak rocks. Attention is focused on good practice for drilling, tendon fabrication and handling, grouting, stressing and testing. Regional variations - not always logically justified - are described. The performance of anchors in a variety of geological conditions is illustrated with reference to recent full scale test programs. 1. Introduction In the United States there has been steady growth in the use of prestressed anchors in materials other than competent or hard rock, in the years since their introduction in the late 1960's. This expansion has to a large extent been driven by specialty geotechnical contractors who both imported foreign developments and conducted their own basic researches, in locally prevailing conditions. With such data and experience, these engineers have had the confidence to promote "alternative solutions" for difficult earth support problems to receptive designers and owners. In turn, being engaged in the details of design and performance monitoring has given these parties the close exposure necessary for the real transfer and understanding of the technological concepts, and this knowledge has generated positive feedback for the contractors.

Jan 1, 1991

A simple and cost effective technique to increase fragmentation and burden velocities without making major modification to the overall blast design is with ALTERNATE VELOCITY LOADING OR BOOSTERING OF ANFO. The technique requires the placement of a cartridge or slug of explosive, having higher density and detonation velocity than ANFO, every few feet in an ANFO column. The greater the difference in density and detonation velocity of the Alternate Velocity Load to ANFO, the more pronounced are the results. Emulsions were selected as the Alternate Velocity test explosives because they detonate closer to ideal conditions than most other commercial explosives.

Jan 1, 1989

By M. Reuter, C. Schuffeneger, T. Seppälä, L. Holappa

Reaction kinetics of solid-state reduction of chromite pellets (laboratory made and industrial) and lumpy ore was investigated by the thermogravimetric analysis (TGA) technique. Carbon monoxide was used as the reducing agent, with the presence of graphite in proximity to chromite. The experiments were carried out at both rising temperature and constant temperature in the range of 1450 - 1550°C. Scanning electron microscopy was employed to observe and analyse the structure and composition changes of the chromite samples. For the lab-made chromite pellets, the effects of particle size and bentonite addition on the reduction behaviour were studied. The pellet with smaller particle size gave a higher reduction rate. Bentonite addition had slightly negative effect on the reduction rate. When reducing industrial pellets, temperature and CO flow rate had positive influence on the reduction rate. Reduction of lumpy ore took place slower than reduction of a pellet. In all samples, chromite reduction proceeded longer in the outer part of the sample than in the centre part. The porosity of the chromite samples was determined before and after the experiments. The porosity of lumpy chromite increased significantly during the reduction. However, the porosity of lab-made chromite pellet decreases due to sintering effect. The reaction mechanism is discussed on the basis of experimental results and earlier investigations.

Jan 1, 2004

By Gábor Csicsovszki

We have developed a novel method - at the laboratory scale - comprising an ion-exchange separation and a membrane-electrolysis step for the purpose of zero-waste regeneration of spent HCl pickling liquors originating from hot-dip galvanizing of common steels. It is aimed at the parallel regeneration of HCl and iron. Experiments revealed that iron can be electrodeposited at high current efficiencies by maintaining the following conditions: 0.04-0.08 M HCl, 500-1000 A/m2, 20°C and stationary electrolyte in a conventional cell. Zinc in the solution did not disturb the deposition of iron, however it contaminated the product and it poisons the anion-exchange membrane required to tackle acidity during electrolysis. For a preliminary separation, anion-exchange tests were carried out to produce pure iron solutions. Beyond the equilibrium studies, column experiments were carried out showing that low flow rates of the loading solution and the ~1.5 M HCl eluent are essential for separation.

Jan 1, 2006

By S. C. Sun

Pennsylvania has ample reserves of high-alumina clays which are potential sources of alumina, but many of these clays contain large amounts of iron, which makes them unsuitable for treatment by acid processes(1). The purpose of this investigation was to determine the optimum conditions for the selective hydrochloric acid leaching of iron (2-4) prior to the sulfuric acid extraction of alumina from Pennsylvania ferruginous high-alumina clays. This was accomplished by first testing the iron-bearing minerals and the clay minerals most often encountered in Pennsylvania clays to determine their rate of dissolution in hydrochloric acid solutions. The results of individual minerals were then based for leaching Pennsylvania clays with a 19% hydrochloric acid solution at the boiling point of the acid for approximately 30 minutes to achieve as high as 90% iron removal and only 2-5% alumina losses.

Jan 1, 1968

By Thomas G. Murdock

The possible contribution of an improved mineral economy to the further advancement of the lesser developed regions of the world is a vital consideration today. Many of the newly independent countries recognize the problems and the challenge involved in orderly development of mineral resources. Some countries are inventorying resources, planning development, and encouraging local and foreign participation. The Malagasy Republic, composed of the island of Madagascar and the immediately adjacent islands, formerly the French Overseas Territory of Madagascar, is one of the members of the French Community which achieved independence in 1960. It is making real progress towards improving its mineral economy, an effort particularly remarkable considering the generally unfavorable geographic location of the area with respect to world markets and what is, after all, a comparatively sparse-economic mineralization in the light of discoveries to date. Most of the development of the Malagasy economy before independence was fostered by French private enterprise, although the State participated in some ventures. Since independence, the Government has encouraged private investment from a variety of sources through favorable legislation and has indicated that legitimate investment projects that will further advance social and economic programs will be welcome.

Jan 1, 1963

By Thomas G. Murdock

The possible contribution of an improved mineral economy to the further advancement of the lesser developed regions of the world is a vital consideration today. Many of the newly independent countries recognize the problems and the challenge involved in orderly development of mineral resources. Some countries are inventorying resources, planning development, and encouraging local and foreign participation. The Malagasy Republic, composed of the island of Madagascar and the immediately adjacent islands, formerly the French Overseas Territory of Madagascar, is one of the members of the French Community which achieved independence in 1960. It is making real progress towards improving its mineral economy, an effort particularly remarkable considering the generally unfavorable geographic location of the area with respect to world markets and what is, after all, a comparatively sparse economic mineralization in the light of discoveries to date. Most of the development of the Malagasy econorny before independence was fostered by French private enterprise, although the State participated in some ventures. Since independence, the Government has encouraged private investment from a variety of sources through favorable legislation and has indicated that legitimate investment projects that will further advance social and economic programs will be welcome.

Jan 1, 1963

The roasting of sulphide ores and concentrates is often the first step in the production of metals or chemicals. In many processes, the production of sulphuric acid is viewed as a by-product, while in some plants production is an important economic factor. Regardless of the purpose, a pyrite roasting plant consists of mainly three plant sections: roasting, gas cleaning and sulphuric acid. With the addition of air, the pyrite concentrates are transformed into solid oxides and gaseous sulphur dioxide at temperatures of 600 - 1000° C. After cleaning and cooling, the sulphur dioxide in the roasting gas is further processed to sulphuric acid. Two types of reactors are used depending on the application: stationary or circulating fluid bed . For over 60 years, Outotec has progressively been developing the principle of fluidised bed technology in several different reactor types for a multitude of process applications. The versatility of the fluidised bed reactor system has manifested itself in the treatment of minerals, including solid fuels, and for metallurgical processes both in the ferrous and non-ferrous fields. Process applications have included roasting, calcining, combustion and charring of coals, as well as off-gas treatment. This paper provides a summary of the pyrite roasting technology currently used along with a simple cost comparison of pyrite roasting and sulphur burning processes.

Jan 1, 2009

The roasting of sulphide ores and concentrates is often the first step in the production of metals or chemicals. In many processes, the production of sulphuric acid is viewed as a by-product, while in some plants production is an important economic factor. Regardless of the purpose, a pyrite roasting plant consists of mainly three plant sections: roasting, gas cleaning and sulphuric acid. With the addition of air, the pyrite concentrates are transformed into solid oxides and gaseous sulphur dioxide at temperatures of 600 - 1000° C. After cleaning and cooling, the sulphur dioxide in the roasting gas is further processed to sulphuric acid. Two types of reactors are used depending on the application: stationary or circulating fluid bed . For over 60 years, Outotec has progressively been developing the principle of fluidised bed technology in several different reactor types for a multitude of process applications. The versatility of the fluidised bed reactor system has manifested itself in the treatment of minerals, including solid fuels, and for metallurgical processes both in the ferrous and non-ferrous fields. Process applications have included roasting, calcining, combustion and charring of coals, as well as off-gas treatment. This paper provides a summary of the pyrite roasting technology currently used along with a simple cost comparison of pyrite roasting and sulphur burning processes.

Jan 1, 2009

By Marc Arpin

La Bolivie possède tout pour réussir. Son vaste territoire de plus d'un million de km2 et qui occupe une position stratégique au coeur du continent sud-américain recèle des ressources naturelles (forêts, minéraux, gaz naturel, etc) variées et abondantes. Elle a une frontière avec pas moins de 5 pays dont le géant que constitue le Brésil ainsi qu'avec l'Argentine, l'autre puissance régionale. Pourtant, malgré tous ces atouts, la Bolivie demeure l'un des pays les plus pauvres du continent. Ce paradoxe n'est nulle part mieux reflété que dans le secteur minier. Celui-ci fait face à une situation de crise en dépit d'une tradition minière de plus de quatre siècles et d'un potentiel géologique indiscutable ayant conduit à la découverte et à l'exploitation de fabuleux gisements d'argent et d'étain. Les habitants des districts miniers vivent dans des conditions de pauvreté extrême et les indicateurs de développement humain de ces régions sont parmi les plus bas en Amérique du Sud. La Bolivie réussit difficilement à attirer les compagnies minières alors que, chez les voisins, et particulièrement en Argentine, qui n'a pas de tradition minière, les investissements miniers majeurs affluent. Dans cette conférence, nous chercherons à expliquer les causes de cette situation et proposerons des solutions possibles.

May 1, 2001

In the USA, the National Institute for Occupational Safety and Health (NIOSH) does a lot of work and has provided news of interesting new developments. Marcia L. Harris describes an ?Explosibility Meter: ?In underground mines, coal dust explosions are prevented by the addition of rock dust sufficient to render the coal dust inert. Federal [US] regulations require 65% and 80% incombustible content in samples taken in intake airways and return airways, respectively, assuming a nominal coal dust size of 20% minus 200 mesh. The Coal Dust Explosibility Meter (CDEM), a hand-held instrument developed by NIOSH uses optical reflectance to measure the explosibility of a rock dust and coal dust mixture.? The CDEM is now commercially available. It provides real-time results during rock dust surveys instead of waiting weeks for laboratory results1. ?With real-time results, the potential for a disaster can be mitigated immediately. The CDEM displays the percent incombustible content as well as a colour indicating the relative explosibility of the coal and rock dust mixture. A red read-out indicates that more incombustible material is required to inert the coal and rock dust sample, while a green read-out indicates that the dust sample is sufficiently inert. When the mixture is marginally explosible, a yellow read-out is indicated. The red-yellow-green output depends upon the particle size distribution of the rock and coal dust mixture with the finer size fraction being more explosible.?

Jan 1, 2008

By R J. deMelo, A, V Suckal, R A. Vilela

Massive hematite ore (MHO) is a special high-grade iron ore used as lump ore in the process of obtaining direct reduced iron (DRI). The influence of porosity on the reducibility was investigated using optical and scanning electron microscopes. Hematite is the main component of the samples and occurs as granular crystals (10 ¦m), microplates (1 ¦m) and euhedral martite (10 to 30 ¦m). Quartz, maghemite, kenomagnetite and goethite are minor components. Primary micropores (+ to 1 ¦m) are associated with microplaty crystals that fill cavities between granular hematite. Secondary micropores (+ to 5 ¦m) related to euhedral martite crystals are the most important. The total porosity of weathered samples, measured using nitrogen adsorption and mercury injection, attains values up to 18 per cent, whereas unweathered samples have a porosity less than 2.5 per cent. Varajpo et al, 2002 showed that reducibility is strongly enhanced by porosity and this work shows that reducibility can be indirectly evaluated by bulk density.

Jan 1, 2002

By G B. Ebsworth, J Krokowski de Vickerod

Several drilling programs at Maldon have produced 7790 core samples, which were assayed for gold, with 2825 of the samples assayed for nine other metallic elements. There is a lack of correlation between gold and all other elements. The situation, however, changes dramatically when sorted according to the abundance of arsenic. In the populations where As >200 ppm, there are strong, positive correlations between gold and several elements. There is also a strong positive correlation of Au with the weighted sums and products of all elements with the elemental averages as a weighting factor, and Bi*Sb and Bi*As elemental products. In these populations, there is also a strong positive correlation between the logarithms of Au and logarithms of each element, as well as the elemental sums and products described above. The correlation coefficients increase with higher As cut-off values.All elemental distributions but especially gold show a high-nugget effect and display high skewness and dispersion, low kurtosis, and common outliers. The distributions of their logarithms are several magnitudes less scattered and without outliers. Thus, the logarithmical distribution correlations are best for practical use.Correlation coefficients were T-tested and are statistically significant. The elemental correlations, particularly those of logarithmic values of weighted sums and Bi, could be used as a gold path finding tool at Maldon. After a preliminary assay for gold and arsenic, only samples with As > 200 ppm should be assayed for other elements. Higher values of gold-correlated elements or elemental ratios, in samples with low gold grades, may increase confidence that gold is under reporting due to its highly nuggetty nature.CITATION:Krokowski de Vickerod, J and Ebsworth, G B, 2012. Correlation as a gold path finding tool at Maldon, Victoria, in Proceedings Narrow Vein Mining 2012 , pp 131-144 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 26, 2012

By Pengfu Tan

Electric arc furnace (EAF) dust from the steel industries is listed by the United Sates EPA as a hazardous waste under the regulations of the Resource Conservation and Recovery Act due to the presence of lead, cadmium and chromium. The disposal of the approximately 650,000 tons of EAF dust per year in the U.S. and Canada is an expensive and unresolved problem for the majority of steel companies. The Waelz process has been considered as the best process for treating EAF dust. A process model, combined thermodynamic modeling with heat transfer calculations, has been developed to simulate the chemical reactions, mass and heat transfer and heat balance in the kiln. The injection of air into the slag and the temperature profile along the kiln has been modeled. The effect of (CaO+MgO)/SiO2 on the solidus temperature of slag has been modeled also and discussed. Some optimizing results have been presented in this paper.

Jan 1, 2005