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By Mahesh C. Jha

Cyanidation has established itself as the main process for extracting gold from ores in this century. However, many ores exhibit refractoriness to the conventional cyanidation process. The main cause of the refractoriness is generally the presence of carbon, tellurium, and sulfides, particularly those of antimony, arsenic, and iron. The problem is usually solved by either modifying the cyanidation conditions or providing an oxidation pretreatment. This paper presents results from studies that help in understanding the causes of refractoriness of various gold ores. This is followed by a discussion of many processes that have been developed to solve the problem such as intensive cyanidation, pressure cyanidation, carbon-in-leach cyanidation, and pretreatment processes such as roasting, chemical oxidation, autoclave oxidation, and bacterial oxidation.

Jan 1, 1986

By W. S. Dyer

Introduction In northern Ontario, refractory clay is found on four rivers of the James Bay watershed: the Abitibi, the Mattagami, the Missinaibi, and the Moose. The clay all belongs to the same geological formation ( the Mattagami of Lower Cretaceous age) , and occurs within a structural depression or 'basin', the boundaries of which have never been defined but which appears to cover at least 1,500 square miles of territory. The recently constructed James Bay extension of the Temiskaming and Northern Ontario railway crosses the northeast end of the basin at the Onakawana lignite field, which by rail is 126 miles north of Cochrane, 605 miles north of Toronto, and 60 miles southwest of Moose Factory. Smoky Falls, the northern terminus of the railway owned by the Spruce Falls Power & Paper Company, Limited, is 7 miles south of one other point in the basin, i.e., the outcrops of refractory clay, sand, and kaolin at the foot of Long rapids on the Mattagami river. Smoky Falls is 50 miles north of Kapuskasing. In a very early report(l) , Dr. Robert Bell, of the Geological Survey of Canada, described '"light coloured marl in horizontal beds" from the Missinaibi river, and noted that the lignite also occurring in the river was probably :associated with the marls. This was undoubtedly the Cretaceous refractory day. Other early writers noted the occurrence of fire-clays, but it was not until Joseph Keele(2), of the Geological Survey, visited thee region in 1919 and studied the clays that their real significance was known.

Jan 1, 1933

By C. G. Anderson

The treatment of materials for the recovery of the precious metals imposes many processing and environmental challenges. Sunshine Mining and Refining Company has developed hydrometallurgical technology for recovery of values from refractory precious metal materials. At Sunshine, the industrial focus of these processes has been for the direct recovery of silver without cyanidation. However, recent work has indicated that these technologies can provide a means for treating complex, refractory gold concentrates. This will be the focus of this paper. The practice of pretreating ores and concentrates to make them more amenable to cyanidation is becoming more common. Several pretreatment options for sulfide concentrates containing gold include roasting, bio-leaching, direct pressure oxidation and nitrogen species catalyzed pressure oxidation. The industrial use of nitrogen species catalyzed pressure oxidation has been limited to the Sunshine refinery where its focus has been for the treatment of silver concentrates. Much of the reluctance, outside of Sunshine, to use this type of technology may be based on the perception that high costs are associated with using nitrogen species (e.g. nitric acid, sodium nitrite) to leach. Also, the use of nitrogen species catalyzed pressure oxidation on an industrial scale is unfamiliar to most metallurgical professionals. A summary of pressure leaching processes which utilize nitrogen species as a catalyst is presented in Tables 1 and 2.

Jan 1, 1996

By C. J. Hunter

Prior to the commissioning of the Sansu Sulphide Treatment Plant (STP), Ashanti Goldfields' treatment facilities were capable of producing some 700 000 ounces of gold per annum. Ore sources were underground refractory sulphides, surface oxides and old tailings dams. In order to increase the mines production to 1 million ounces per annum and to accommodate the change in ore sources as surface mining moved into fresh sulphides, a part of the strategy adopted was -the construction of a new sulphide treatment plant with a capacity to mill 2.2 million tonnes per annum and produce 400 000 ounces of gold. The STP has been designed, built and commissioned. and has been in operation since February 1994. The Plant boasts the world's largest Bio-oxidation facility which is capable of treating 790 tonnes of sulphide concentrate per day at a grade of 11.4% sulphur and is currently undergoing an expansion to increase its capacity to 1050 tonnes per day. The following sections describe the reasons for selecting the BioX® Process, the plant design, the commissioning experience and the plant performance to date.

Jan 1, 1996

By R. C. Dunne

A review of the current ?state of the art? of refractory gold treatment will be provided. This will include a global perspective of refractory processes past and present and the location of currently operating plants. Some discussion on the challenges that face the refractory gold industry will also be provided. Keywords: refractory gold treatment, flotation, roasting, pressure oxidation, bacterial oxidation, preg-robbing gold ores, fine grinding.

Sep 1, 2012

By I. Donohue, M. Pearson, E. Barrette

"This paper presents the technique and benefits of the finite element approach for designing the refractory lining in pressure oxidation autoclaves. One-dimensional equations are used to develop an initial refractory design. ANSYS Parametric Design Language (APDL) scripts are then used to build and analyse a more accurate three-dimensional finite element model to verify the refractory thickness, determine weld overlay requirements, and assess mechanical stability. The APDL scripts provide a cost effective means to quickly evaluate various boundary conditions and multiple designs to determine the optimal lining configuration and nozzle layout.INTRODUCTIONNew ore processing facilities demand increased capacity, requiring hydrometallurgy processes that have larger reactor vessels operating at higher pressure and temperature. Many pressure hydrometallurgy operations require vessels with an impermeable membrane and one or more courses of refractory or ceramic brick. The membrane provides corrosion protection for the vessel shell and the brick provides thermal protection for the membrane. Designing a refractory lining with an economic service life as a thermal barrier requires the refractory to be erosion resistant, chemically compatible with the process fluid, and mechanically stable. A fundamental understanding of the factors affecting the lining system is essential as designs move further away from the industry’s experience base.During basic engineering the refractory lining design is developed using one dimensional cylindrical conduction equations for heat transfer and classical hoop stress-strain relationships for determining mechanical stability. The results of the thermal calculations specify the refractory thickness that should prevent the membrane temperature from exceeding the design limit. Mechanical stability of the lining is determined by examining the sensitivity of lining stability with respect to various parameters. There are three criteria that must be satisfied to conclude mechanical lining stability:"

Jan 1, 2012

By Roselaine Gonçalves Magalhães

São apresentados e discutidos os aspectos teóricos e práticos relativos às principais propriedades físicas, térmicas e mecânicas de três refratários comerciais de MgO Al2O3 C e Al2O3 MgO C para a zona de metal de panelas de aço. Normalmente, o desgaste do revestimento dessa região é governado pela propagação de trincas, penetração de aço e sucessivo destacamento das camadas superficiais deterioradas. A deformação irreversível na direção circunferencial do revestimento também tem despertado interesse. Os resultados da caracterização laboratorial mostraram que o projeto microestrutural exerceu influência significativa nas propriedades desses refratários. Os principais fatores que concorreram para modificar o desempenho dos tijolos foram a pureza das matérias-primas, a quantidade de antioxidantes metálicos e o comportamento dimensional dos refratários. Os tijolos denominados MAC2 (MgO Al2O3 C) e AMC (Al2O3-MgO-C) apresentaram melhor compromisso entre a variação linear dimensional, resistência ao creep e resistência à propagação de trincas, exibindo, assim, maior potencial para suportar as variáveis de processos e práticas metalúrgicas vigentes na Usiminas.

Oct 30, 2017

By Henry H. Tayler, Eric Sturel

1 Triton Square was originally a six-storey building with a one-level basement located within a commercial development near Euston, London. It was designed and constructed in the 1990s and the foundation scheme comprised straight shafted London Clay piles arranged singly beneath columns. The scheme added three storeys and a five-storey infill in the central atrium area to increase the building floorplate by 70% and maintained the usability of the basement space. As the loads to support the additional floorplate area were greater than the capacity of the existing foundations, an optimised strengthening scheme of small diameter piles installed within the existing basement and a slender retro-fitted raft was installed to augment the existing piles. The re-use and strengthening of almost all of the existing foundations enabled re-use of a very high proportion of the superstructure and in approximately 35,000 tonnes of concrete and 1,900 tonnes of reinforcement and structural steelwork being re-used. The structural embodied carbon for the refurbished building scheme is estimated at an average of 136 kgCO2e/m2, achieving a Structural Carbon Rating Scheme (SCORS) “A” rating with components detailed in the paper.

May 1, 2022

By Leo J. Vogel, E. D. Hummer, David J. Akers

INTRODUCTION An efficient refuse-disposal system is a necessary part of the modem cleaning plant. The large-scale refuse system and disposal area, engineered for the lifetime of the plant, has become more important due to the greater tonnages of refuse produced from increased quantities of mechanically mined and prepared coal. Laws and increased government regulations have affected the design and operation of disposal systems. THE EFFECT OF MINE AND PLANT OPERATION Refuse disposal starts at the mining face. The mining system, the type of roof support, the machinery used, and the degree of discipline at the face contribute to the amount and type of refuse that must be removed through the disposal system. Economies gained through modification of the mining system or mining machinery may be partially offset by increased dilution of the mined coal with impurities from associated rock formations. In some cases the change in the mining system and equipment has reduced the dilution. In all cases the ratio of impurities that must be removed from the raw-coal feed to the plant not only affects the maintenance and

Jan 1, 1979

By R L. Brathwaite, R Carver

The REGCHEM (Regional Exploration Geochemistry) database of open file mining company data, managed by GNS Science, has recently been upgraded with the compilation of additional data, especially for the Otago region (see http://maps.gns.cri.nz/website/minmap). In June 2007, data compiled for the Otago region included more than 2000 stream sediment samples from 19 surveys, more than 800 BLEG (bulk leach extractible gold) samples from 12 surveys and a few pan concentrate samples. The stream sediment samples were typically analysed for Au and As, and in many cases for other elements including Cu, Pb, Zn, Sb, W and Mo. The BLEG samples were analysed for Au and in some cases also for As. The main exploration target was mesothermal gold deposits in the Otago Schist, although one survey of the Otago Peninsula targeted potential gold deposits associated with the Dunedin volcanic complex. Geochemically, the mesothermal gold deposits are characterised by anomalous As and Au, with some also characterised by anomalous W and Sb, and these four elements are the best pathfinders in stream sediment geochemical surveys. The introduction of lower detection limits in Au analyses in the more recent stream sediment surveys and in the BLEG surveys enables the use of this element as the primary pathfinder for mesothermal gold deposits.

Jan 1, 2007

By Eric Schaub

Hot Blast Stove Systems are an important equipment of a Blast Furnace plant. During the last years, performance requirements and operation practice for the Hot Blast Systems have changed and have a big influence on the Blast Furnace operation. Therefore it is necessary to keep the Hot Blast System in proper condition in order to maintain the production capacity of the Blast Furnace. It is important for operators to know the condition and relevant constrains of a Hot Blast Stove Plant. Assessing its condition on a regular basis, especially in advance of a Blast Furnace relining is therefore advisable. Considering the individual condition of the Hot Blast Stove Plant, improvements in operation, but also specific and dedicated repairs might be implemented. Design improvements can be implemented as well during such repairs. This paper will describe some of these design improvements, will illustrate their implementation in new hot blast stoves but will also describe repair methods for existing stoves. In addition new developments became popular during the last decade, like the so called Dome Combustion Stoves, which was invented already 30 years ago in Western Europe. Paul Wurth’s development in this regard will be discussed in this paper as well.

Oct 30, 2017

By C. J. Brown

Regeneration of hydrochloric acid steel pickle liquors has traditionally been accomplished by pyrohydrolysis. However, a number of factors have recently conspired to reduce the attractiveness of this approach. Moreover, the process is not amenable to small-scale operations. On the other hand, the standard technique for regeneration of sulfuric acid pickle liquors, which is the low-temperature crystallization of ferrous sulfate is applicable to any size operation. A similar technique has recently been developed to regenerate hydrochloric acid. Sulfuric acid is added to the ferrous chloride-bearing spent HCl pickle liquor. The temperature is then reduced to below 0°C, resulting in the crystallization of ferrous sulfate heptahydrate and liberation of free hydrochloric acid. Depending upon the crystallization temperature, variable concentrations of sulfate are left in the regenerated acid. Although this residual sulfate has an impact on the pickling characteristics of the regenerated acid, tests have shown that by adjusting the conditions, pickling rates will be at least equal to those using pure HCI, and an acceptable surface finish will be produced.

Jan 1, 2006

By David Cronan

"Most of the recent renewed interest in manganese nodule mining has been focused in the Clarion-Clipperton Zone (CCZ) in the NE tropical Pacific where nodules are rich in Mn, Ni and Cu. However, equally interesting, but compositionally different, nodules occur in the tropical central South Pacific (CSP). The CC Zone deposits lie in the International Seabed Area whereas those in the South Pacific lie mainly in the Exclusive Economic Zones of Island States, principally the Cook Islands and Kiribati. The CSP nodules should not be regarded as an alternative resource to CCZ nodules, as they are enriched in different elements. Rather, the CCZ nodules should be thought of as a source of one group of metals (Mn, Ni and Cu) and the CSP nodules the source of another group (see below), mutually complementing each other and to be mined in parallel for their different metals.Manganese nodule mining in the South Pacific has been mooted since the 1970s. However, new data on manganese nodule composition and abundance there have recently appeared. Also, a recently developed interest in 'rare', 'green' and 'technology' elements has necessitated a re-examination of old South Pacific nodule data for information on these elements (previously thought to be economically unimportant), and the re-analysis of the deposits to obtain new data on them. Additionally, current and possibly future applications to the UN to extend island 'continental shelf' areas necessitates an appraisal of the manganese nodules in these areas. These developments have prompted recent work that has helped to refine our understanding of the distribution and abundance of metals of traditional interest in South Pacific nodules, namely Mn, Co, Ni and Cu, but has also drawn attention to other elements of possible economic interest including titanium (Ti), vanadium (V) and the rare earth elements (REE)."

Sep 1, 2014

By D. Duff, R. A. Cameron, R. E. S. Whitehead

"Although CO2 content indicates the quantity of carbonate in altered basaltic rocks, it does not measure the intensity of carbonate alteration. CO/CaO molar ratios, which correlate with the relative proportions of individual carbonate species, measure the intensity of carbonatization. The Timmins gold area is characterized by pervasive carbonatization, with large parts of the area having CO2/Ca0 ratios greater than 1, representing C02 supersaturation relative to CaO. The mean CO/CaO in the Timmins area is0.67, compared to 0.13 in two unmineralized control areas. Regional arsenic abundance in the gold-bearing area averages 4 ppm, compared to about 0.35 ppm for the non-mineralized areas. The average K20 and Rb abundances are similar in both mineralized and non-mineralized areas (about 0.30% K20 and 7 ppm Rb). Although there appears to have been no wholesale addition of K20 or Rb to the mineralized area from external sources, these alkalies have been redistributed internally, resulting in patterns of local enrichments and depletions which are characteristic of the mineralized region.Local target anomalies associated with known mineralization consist of CO2/Ca0 > 1.5, As > 10 ppm and K2O > 0. 75%. Not all three values are required to be above these thresholds in order to identify local targets. Combinations such as C02/ Ca0 > 1.5 and As < 10 ppm, CO/CaO 1-1.5 and K20 > 0. 75 or K20 > 0. 75 and As > 10 ppm are equally indicative of proximity to gold occurrences. Gold-bearing veins and associated anomalies occur throughout the entire volcanic succession and are not restricted to any particular stratigraphic horizons. The levels and patterns of alteration and occurrences of gold appear to be structurally controlled."

Jan 1, 1982

By J. Whyatt

A variety of dynamic failure cases with regional impact were described at a bump symposium held in 1958. These types of events, while rare, are of particular interest because their ability to impact a large area has disaster potential. These cases can be grouped into two broad classes of events by mechanism. These are (1) slip along steeply dipping faults and (2) fracturing of strong strata above, or below, the coal seam. Both failure modes produce dynamic or ?shock? loads on the perimeter (roof, rib, floor) of mine openings. Special consideration should be given to these failure modes in planning of deep coal mines since their occurrence is not within the professional experience of many contemporary workers, and their potential is not evaluated by many of the analysis tools commonly used to evaluate hazards in coal mine plans.

Jan 1, 2009

By F. Varley, J. Whyatt

A variety of dynamic failure cases with regional impact were described at a bump symposium held in 1958. These types of events, while rare, are of particular interest because their ability to impact a large area has disaster potential. These cases can be grouped into two broad classes of events by mechanism. These are (1) a slip along steeply dipping faults and (2) the fracturing of strong strata above or below the coal seam. Both failure modes produce dynamic or “shock” loads on the perimeter (roof, rib and floor) of mine openings. Special consideration should be given to these failure modes in the planning of deep coal mines, since their occurrence is not within the professional experience of many contemporary workers. In addition, their potential is not evaluated by many of the analysis tools commonly used to evaluate hazards in coal mine plans.

Jan 1, 2009

By V. F. Hollister

Although it is apparent that porphyry copper deposits may have formed in the Andean orogen from Permian time onward, commercial deposits thus far developed appear to have Cenozoic ages only. Following Chilean useage, the porphyry deposits are divided into either: (a) a stockwork, or (b) a tourmaline breccia model. Stockwork type deposits tend to occur on major strike-slip structures which may be either transcurrent or transverse faults related to plate movements, while the tourmaline breccia type may more frequently form independently of regional faults. Stockwork types may be conjugate fractures that intersect and ramify as a network of veins and veinlets, cutting altered rock, and genetically related to a major regional fault, or in other cases they may reflect the intersection of two large fault structures. Circular fracture patterns may more rarely occur in stockwork deposits in response to a specific intrusive. Tourmaline breccia types are characterized by circular and radial fractures genetically connected in some way with tourmaline breccia pipe development or an intrusive piercement that preceded it. Each structural model contains mineralized intrusive8 which have a close time-space relationship to ore and in each model, mineral paragenesis is similar, regardless of age or location in the plate. Also, each model contains the same type of alterntion halos (phyllic, argillic, prophllitic) as are developed in intru- sive centers in porphyry copper deposits found in North America. The potassic zone is exposed best in the older deposits. Examples of each type of deposit are illustrated, demonstrating the feature evolved.

Jan 1, 1973

By V. F. Hollister

Although it is apparent that porphyry copper deposits may have formed in the Andean orogen from Permian time onward, commercial deposits thus far developed appear to have Cenozoic ages only. Following Chilean usage, the porphyry deposits are divided into either (1) a stockwork or (2) a tourmaline breccia model. As indicated by evidence cited in the paper, stockwork-type deposits tend to be related to major strike-slip structures which may be either transcurrent or transverse faults related to plate movements, while the tourmaline breccia type may more frequently form independently of regional faults. Stockwork types may be conjugate fractures that intersect and ramify as a network of veins and veinlets, cutting altered rock, and genetically related to a major regional fault, or in other cases they may reflect the intersection of two large fault structures. Circular fracture patterns may more rarely occur in stockwork deposits in response to a specific intrusion. Tourmaline breccia types are characterized by circular and radial fractures genetically connected in some way with touramline breccia pipe development or an intrusive piercement that preceded it. Each structural model contains mineralized intrusions which have a close time-space relationship to ore, and in each model mineral paragenesis is similar, regardless of age or location in the plate. Also, each model contains the same type of alteration halos (phyllic, argillic, propylitic) as are developed in intrusive centers in porphyry copper deposits found in North America. The potassic zone is exposed best in the older deposits. Examples of each type of deposit are illustrated, demonstrating the feature evolved.

Jan 1, 1975

By Henry N. McCarl

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Jan 1, 1966

By H. Forster, F. H. Koenemann, U. Knittel

The greenstone belt developed along the Sandawana line, an anastomosing, transcrustal shear zone. The lode gold is concentrated in veins and along brittle-ductile shear zones and other faults. Gold contents of 200 rock samples were found to be well below economically significant levels, excluding purely syngenetic deposit formation. Average gold content of unmineralised banded iron formation decreases from 7.3 ppb in the east (Manica) to 1.6 ppb in the west (Odzi), where depletion reflects hydrothermal leaching. The mineralising fluids may have been generated during deep crustal deformation, metamorphism and magmatism. Gold was hydrothermally deposited during carbonatisation and sericitisation of ultramafic and mafic rocks and during hydrothermal overprinting of banded iron formation and felsic rocks. It is present in native form and as microscopic to submicroscopic inclusions in pyrite, arsenopyrite and pyrrhotite. Argentiferous galena and other sulphides are commonly observed. Rezende, which produced over 38 t Au, is hosted by a granodiorite stock. By-product gold was produced from Cu-Ni sulphides at Mundonguara. The deposits are related to the older, but not the younger, of the granitoids intruding the belt's supracrustal sequences; the estimated age of mineralisation is 2700-2600 Ma. Odzi district, with 61 mines, has produced only 3.5 t Au as its higher-level host rocks have apparently been eroded. Mutare (formerly Umtali) district, with 133 mines and 9 placers, has produced 68 t Au (65 t from Rezende and adjacent deposits), and Manica district, with 23 mines and 8 placers, 12 t Au. Estimated reserves for the Rezende area are 20 t Au and for Manica district 4 t lode Au and 19 t placer Au

Apr 1, 1996