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By Fred N. Kissell, Andrew B. Cecala

In This Chapter [Where methane is emitted at longwall faces Where methane accumulates at longwall faces Using the modified shearer-clearer to eliminate ventilation eddy zones Using a walkway curtain to reduce methane buildup during the headgate cutout Control of frictional ignitions and The best location for the methane monitor] The methane released along a longwall face represents only 10%–20% of the total methane emitted from the entire longwall panel. Nevertheless, in very gassy coal seams, this methane released at the face can pose a problem because the shearer is a ready ignition source. Preventing methane ignitions at longwall faces requires four actions. The first is to provide better ventilation around the shearer to eliminate the ventilation eddy zones at the drums where methane builds up. These eddy zones are eliminated by mounting additional water sprays on the shearer to direct air into them. The second action to prevent methane ignitions is to install a water spray behind each cutter bit and regularly replace worn bits. Water sprays behind each cutter bit act to quench the hot metal streak that follows a worn bit when it strikes rock. The third is to ensure that no ventilation eddy zones are inadvertently created by poor placement of water sprays. The fourth is to ensure that the methane monitor on the shearer is in the best location to detect methane accumulations. ADDRESSING METHANE ACCUMULATIONS AT LONGWALL FACES3 Cecala et al. [1985a, 1989] and Denk and Wirth [1991] studied methane emission and ventilation patterns at longwall faces to find where methane accumulations are most likely. Although not always the case, the major source of methane at longwall faces is usually the breakage of coal by the shearer. Stress-related fracturing of the coal seam at the face, called bumps or bounces, can cause the release of additional gas (Figure 4–1).

Jan 6, 2006

By Steve Kral

Good times make for happy miners. And the past few years have seen a lot of smiling mining engineers, geologists, metallurgists, corporate executives, analysts, investment bankers and shareholders. And nowhere was that more evident than at the 74th Prospectors and Developers Association of Canada’s (PDAC) annual meeting. The meeting, held in Toronto March 5-8, attracted a record 14,500 people. Of those, the PDAC said attendees came from an estimated 100 countries. And about 40 countries sent national delegations to the meeting. Argentina, for example, sent nearly 100 people. The PDAC meeting has always been a event where companies and individuals can get a look at numerous properties in all parts of the world that could potentially become major mines. And through the many receptions, hospitality suites and just sitting in the local restaurants and taverns, deals are usually made.

Jan 1, 2006

By Q. Zhang, J. A. Finch

"Sphalerite flotation in the absence of copper activation at moderately alkaline pH has been observed in laboratory studies. An in-plant test of this observation was conducted at Kidd Creek Mine LTD. using a portable minicell flotation circuit. The results confirm that raising the pH causes sphalerite flotation.The testwork with the minicell circuit is described. The circuit, built around 2, 51 cells donated by the Noranda Technology Centre, was funded by Air Liquide and NSERC. It includes a data acquisition system to monitor continuously dissolved oxygen, pH and Pulp potential.INTRODUCTIONFlotation of sphalerite is normally practised by adding CuSO4 as an activator under alkaline pH. Recently there have been a number of laboratory and plant examples of sphalerite flotation without deliberate addition of cu++ ions (Girczys, 1972; Mukherjee, 1976; McTavish, 1980; Marouf et al., 1986; Mielczarski, 1986; Leroux et al., 1987; Palsson and Forssberg, 1989; Sandoval-Caballero et al., 1990; Zhang et al., 1991).In batch tests, with a sample of Pb/Zn ore from Polaris, Leroux et al. (1987) found that sphalerite became floatable after adjusting pH to 9. 5-11: they ruled out natural floatability or the formation of elemental sulphur on the surface but suspected iron hydroxy compounds were responsible. Sandoval-Caballero (1990) conducted a continuous minicell test at Brunswick Mining and obtained a 44 % Zn recovery and 40.5 % Zn grade concentrate without deliberately adding CuS04 at pH= 10.5. With single mineral studies, Zhang et al. (1991) revealed good sphalerite floatability (over 80% recovery) in pH range 8 to 11 and found that this floatability was related to pH, dissolved oxygen (DO) level and Fe++ species present in the system.To explore further the conditions under which sphalerite can float without addition of CuSO4 , a continuous pilot test using minicells was performed at Falconbridge Ltd., Kidd Creek division. The set-up is briefly described (a more detailed description is given elsewhere in these proceedings) with emphasis on the data acquisition system - dissolved oxygen, pulp potential and pH were monitored continuously. Results of testwork investigating pH, CuS04 addition and gas composition are presented."

Jan 1, 1992

B. P. Thomson (South Aust. Dept. of Mines): Dr. A. B. Edwards presents in the published discussion on the above paper, his interpretation of the dolerite dyke-lode relationship as a major objection to the syngenetic origin for Broken Hill ore bodies to which Mr. Condon subscribes.Dr. Edwards claims that the dyke-lode relationships indicate clearly that the Broken Hill orebody was formed after the folding and regional metamorphism of the Willyama Series. Field evidence compels m:e to join with H. F. King (1958), in finding this conclusion unacceptable-as follows:(1) Broken Hill type mineralization, as defined by King and Thomson (1953), is clearly confined by the regional sillimanite isograd and does not extend into the lower temperature almandine and biotite zones as does the Thackaringa type mineralization.(2) In the Corruga area the writer has mapped a dolerite dyke apparently cutting a conformable quartz gahnite lode of the Broken Hill type (see Edwards 1958, p. 12).(3) At the Champion mine a similar lode is cut by a fine grained granite dyke.An alternative history of the dolerite dykes to that given by Stillwell & Edwards (1956, p. 26) appears possible. It has been suggested by the writer in an unpublished thesis, (Thomson 1955, p. 30), that the pyroxenite and serpentine plugs and dolerite dykes are rheomorphic end-products of a complex regional metamorphic and metasomatic process involving the formation of amphibolite and pegmatite. The analogy in composition between the dolerite and normal amphibolite is close (see Edwards 1958, Fig. 1, p. 22).

Jan 1, 1959

Conventional waste management practices produce two waste streams for the construction of separate disposal facilities. The design of tailings impoundments is usually controlled by physical stability. Waste rock materials offer high shear strength characteristics for waste dump construction, however the hydraulic properties promote oxidation. The problem of oxidation is significantly reduced for tailings due to a fine texture that augments water saturation. Co-mixing of tailings and waste rock involves the intimate blending of tailings and waste rock to create a new material with superior physical and hydraulic properties. The new material has a low hydraulic conductivity, low compressibility, high water retention capacity and high shear strength. Co-mixed tailings and waste rock restrict oxygen entry and water seepage to minimize acid generation and metal leaching. Co-mixed tailings and waste rock may be used to construct cover systems, internal barriers and seals, confinement structures and full depth waste repository. The results of a laboratory program to characterize the physical and hydraulic properties of Comix tailings and waste rock are presented here. Various ratios of tailings were blended with three distinct waste rock materials. The saturated hydraulic conductivity for the Co-mixed materials was found to vary between 2 x 10-7 m/s and 5 x 10-8 m/s depending on blend ratio, waste rock type and compaction. This paper introduces concepts for the co-disposal of tailings with waste rock and evaluates the hydraulic behaviour of a Co-Mix waste system. The potential benefits of Co-Mix are shown for a typical mine.

Nov 1, 2002

By Deno Pappas, Chrisropher Mark, John Rusnak, Linda McWilliams

Mine planning for a new reserve is based on information obtained from exploratory coreholes. A critical component of an exploration program is the geotechnical evaluation. Poor assumptions about roof conditions greatly add to the risks of mining. Rock mechanics testing is central to a geotechnical exploration program. Typically, 3 to 5 uniaxial compressive strength (UCS) tests are made to characterize a particular roof unit at a given corehole. The average (mean) of these tests is taken as “The UCS” for that location. Isopach contour maps are then used to show spatial trends in roof strength. Two issues are raised by this traditional approach. The first is due to the large variability in UCS values that is typical even within a single unit from a single hole. The average UCS might be higher at Corehole A than it is at Corehole B, but the difference may not be statistically significant. The second issue is whether widely spaced coreholes can identify valid spatial trends in rock strength. The answer depends upon whether rock strength changes over distances that are longer or shorter than the corehole spacing. This is a classical geostatistical problem. While geostatics have been used to investigate many coal quality parameters, they have seldom been used to evaluate rock strength. This paper describes an extensive investigation of these issues conducted by the National Institute for Occupational Safety and Health (NIOSH) in collaboration with Peabody Energy. The study employed the Peabody Rock Mechanics Data Base which contains more than 10,000 individual test results. Data from four important roof units were subjected to statistical analysis: • Brereton Limestone above the Herrin 6 seam (Illinois) • Turner Mine Shale above the No. 9 Seam (Kentucky) • Sandstone above the Eagle Coal (West Virginia) • Shale above the Eagle Coal (West Virginia) The study did not find significant spatial trends in rock strength in any of the cases. Perhaps there are none, or perhaps the exploration coreholes were just too far apart to see them. These results have valuable implications for the design of geotechical exploration programs.

The ability to track miners and communicate with them while they work in underground coal mines is important during normal daily operation, and critical in emergency conditions. This was evident during recent incidents at underground coal mines worldwide. Communication with miners and the knowledge of their location is of great importance for rescue efforts and the preservation of life. Numerous technologies have been developed, adapted and deployed to meet tracking requirements of the Mine Improvement and New Emergency Response (MINER) Act of 2006. Evaluating the performance of these systems has proven to be dif?cult for mine operators, system manufacturers and regulatory agencies. The MINER Act requires operators to improve accident preparedness by developing an emergency response plan speci?c to each mine. With the recent implementation of the provisions of the MINER Act of 2006, all underground coal mines in the United States are subject to the mandates of legislation concerning communication and tracking system installation. As of June 2011, 203 new or revised tracking and/or communication systems had been approved by the U.S. Mine Safety and Health Administration (MSHA), with nearly 50 other systems or revisions in the approval process (MSHA, 2011). At that time, the available approved systems for underground coal mine use included these types: ? Leaky feeder communication systems. ? Fixed node-based communications and/or tracking systems. ? Wireless node-based communications and/or tracking systems. ? Medium frequency (MF) communication systems. ? Communication system peripherals. Other types of tracking systems have since been developed and some manufacturers are seeking approval for use in this application. Some of the new products include through-the-earth (TTE) systems and various radio frequency (RF) adaptations. New technologies that are currently being developed and deployed in other industrial applications should also be considered, including acoustical, optical, inertial and hybrid technologies. To date, no uniform method has been employed in the industry to effectively compare and evaluate the performance of installed systems. Neither industry operators nor regulatory agencies can accurately assess the capabilities of installed systems in the continuously changing mine environment. There is a need for a uniform evaluation method that provides the ability to assess how different systems and technologies perform in various mining applications, and whether they can satisfy the regulatory requirements.

By Raymond W. Hiteshue

Experiments were conducted al temperatures of 480° to 800° C. and hydrogen pressure of 6,000 p.s.i.g. to determine the effect of coal residence time on the conversion of a high-volatile bituminous C coal to liquid and gaseous products when using a semicontinuous apparatus designed fur rapid heating and cooling of reactants. The objective of the studies at high temperatures was to determine if appreciable quantities of coal could be converted to gaseous hydrocarbons and low-boiling liquid hydrocarbons. Experiments at lower temperatures were designed to indicate shifts in product distribution with respect to temperature and to learn more about the general mechanism of the reaction when using close control of coal residence time. One percent molybdenum, based on m.a.f. (moisture-and ash-free) coal, was used throughout this investigation. At 800° C., 6,000 p.s.i.g., and "zero" residence time) the yield of gaseous hydrocarbons was about 38 percent and the yield of oil about 4.5 percent, based on m.a.f. coal. With IS minutes residence time, under the same conditions, the yield of gaseous hydrocarbons was approximately 80 percent with no increase in yield of oil. Apparently at 800° C., and hydrogen pressure of 6,000 p.s.i.g. coal was rapidly carbonized to char with expulsion of volatiles. Char was then slowly hydrogenated to gaseous hydrocarbons without production of oil.

Jan 1, 1962

By G. S. Littlejohn

In anticipation of the flooding of an adjacent dolomitic groundwater compartment, five rough parallel sided boundary plugs at 58 and 50levels have been designed to resist safely hydrostatic heads of 1500and 1250 metres, respectively, over a service life of 100 years. Following a description of the engineering properties of the surrounding rocks, the paper details the design considerations relating to structural length and strength, hydraulic gradient, rock mass watertightness, constituent materials of mortar intruded concrete, pregrouting of permeable discontinuities within the surrounding rock mass, a bentonite barrier to resist aggressive mine water, plug tightening and design performance requirements. Routine quality control tests include permeability of the rock mass, fluidity, bleed and strength development of the intruded mortar, and temperature of the intruded concrete during curing. A special test programme includes determination of strength and stiffness of cored concrete and rock samples, shear strength of the rock/plug interface and associated in situ contact stress in order toe stimate the load safety factor against plug failure by shear.

Jan 1, 2006

By Zhang Chuanfu

Keywords: solid solution, Ni-Co alloy powders, thermal decomposition, fibres. Synthesis of fibrous Ni-Co alloy powders was achieved by thermal decomposition of precursor of complex Ni-Co oxalates solid solutions obtained via modified coprecipitation method among intimate mixing solution of NiCl2?6H2O , CoCl2?6H2O and H2C2O4?2H2O in the presence of surfactant polyvinylpyrrolidone (PVP) and organic solvent ethanol. Scan electron microscopy (SEM), X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), disperse energy X-ray analyses (EDX) were used to characterize the structure features and chemical compositions of the as-prepared fibres. The influences of decomposition conditions, including temperature, time, the flow rate of N2+H2, and the heating rate, on the morphology, average size and specific surface area of the Ni-Co alloy powders were investigated. It is found that a trend of the mutual alloying of nickel and cobalt: the formation of perfect solid solution for any compositions NixCo100-x was indicated and corresponding NixCo100-x alloys with fcc phase can be obtained under the optimal conditions.

Jan 1, 2005

By M Rattenbur, A B. Christie, S C. Cox

A new minerals initiative to increase the level of understanding of New Zealand's mineral resources and to promote the development of minerals began earlier in the year in a partnership pilot-project between Crown Minerals and the Institute for Geological and Nuclear Sciences (GNS). The project aims to gather a set of comprehensive geoscientific data and build a series of digital GIS packages to highlight New Zealand's mineral prospectivity. The pilot study was carried out at a regional scale, and is focussed on mesothermal gold mineralisation in the South Island. A significant amount of geological data and information was sourced from open file technical reports held by Crown Minerals and from various databases held by GNS and has now been compiled into a single GIS dataset, which will soon be made freely available to interested parties. In addition to this comprehensive data compilation, prospectivity modelling using Weights of Evidence techniques was undertaken to highlight those areas likely to contain ore deposits. It is clear from this study that the South Island of New Zealand remains highly prospective for mesothermal gold mineralisation. Many of the highly prospective areas, which also contain historic mine workings, remain open for exploration. The study not only highlights these areas, but also other areas where the potential for similar mineralisation exists, in all likelihood with no surface expression. The study has also highlighted the value of many of the open-file technical reports held by Crown Minerals and the need to carry out additional studies using this and other available data at a more detailed level, possibly as the basis for a web-based minerals information system.

Jan 1, 2002

By Alain Dorval

"''Purification of marine sands from Les Iles-de-la-Madeleine''This paper presents the results of the work that has been done at CRM pilot plant for «Les Silices du Golfe Inc.». Essentially the purpose of this piloting was to demonstrate, on a semi-industrial scale, the process of purification of marine sands from Les Iles-de-la-Madeleine; that had been developed by CRM Process Development Service. This purification is necessary to produce silica suitable for the glass sand and the foundry sand markets.Introduction«Les Silices du Golfe Inc.» is a company who intends to dredge marine sands around the «Les Iles-de-la-Madeleine» coasts. The material will be transported to Gaspesia where electricity, water supply, and a convenient site is available to treat it. A high purity silica intended for glass sand and foundry sand markets will be produced. The objectives of this purification process are to remove organics, calcium, feldspars and iron.Material ReceivedCRM received 50 tons of sand with Si02 varying between 80,6 and 99,3 % (see Figure.1). The highest variations in impurities were the calcium and lost on ignition. We notice direct relation between% SiO2, % CaO and % L.O.I. as you can see on the following Figures 2, 3 and 4."

Jan 1, 1994

A way back in 1851-2 an army of diggers had commenced the conquest, of the now famous goldfields of Australasia. At that time, and in the Colony of Victoria, more that 10,000 were camped on and around the slopes of the silurian ridges over which Ballarat East h'as been built. A wonderfully rich golden harvest was soon gathered from the alluvial found high on these slopes, and from runs (or gutters) which got their rise on them, and were traced down gullies into a broad valley. In due course it was ascertained that the valley carried a main gutter which represented the unity of the higher ones, and further explorations proved this gutter to have a westerly and then a southerly trend toward and under a basaltic plateau, on the top ofwhich Ballarat West and Sebastopol now stand. In the records of alluvial gold mining all the world over the Ballarat field can be classed amongst the richest. Gold in pieces the size of beans, in, stringy filigree bits, in dust and in solid lumps (the largest of which weighed more than 2,200 ozs.), was obtained in the comparatively shallow ground on the slopes; and speaking generally, great and uniform richness was met with along a belt of country on which, in a north and south line, the present quartz mines of Ballarat East are at work. It was noticed by the diggers that when the gutters crossed the upturned edges of the ,strata, the gold deposits in them were patchy, and that when they trended north and south on this beltthey carried rich deposits for longer distances. In time it was also noticf!d that a class of stringy, irregular shaped quartz occurrences, in a bottom of soft slates, in the, immediate vicinity of tpe g)ltter, meant greater richness, and (in the aIluvial) on the higher ground slabs of quartz would now and then be met with, in which strings and spongy masses of gold were found. As the shallow alluvial became worked out the diggers turned their attention to the quartz occurrences, and, now and again the striking of a flat make of a very golden nature would cause quite a stir in the local mining world.

The work described herein is the opening phase of an extensive system of underground excavation undertaken under contract with a Malayan authority.The specifications called for the lining of all tunnels in earth or broken rock with circular segmented cast iron lining, similar to that of the London tubes, and it is the installation of these linings which it is proposed to discuss.Owing to the long deferred delivery quoted and the obvious need for speed of access to the internal installation, it was decided to defer driving the completed circular section and substitute two small timbered headings.These could later be opened out in turn to full section and lined without prejudice to traffic, since both of them had access to the internal workings.NATURE OF ROCKThe rock series through which the circular sections were driven consisted of:(a) A wide zone of intrusive porphyritic granite, consisting generally of orthoclase phenocrysts in a ground mass of micro pegmatite. This area showed advanced weathering, varying from a stage showing slightly tinted kaolin containing approximately 20% of small boulders to one of ultimate decomposition to pure kaolin;(b) A narrow zone of weathered augite diorite, consisting of rock masses of a maximum weight of some 100-150 tons, isolated by clay seams up to 1 ft. 6 in. in width.The whole area was in a state of quasi-hydrostatic equilibrium, which resulted in heavy pressure immediately after excavation. Freshly broken faces would appear to be quite solid but, within a few minutes, would commence to sweat and "slab off" under pressure and, unless support was placed promptly, the whole face would burst out and run from above. Mucking was slow, owing to the plastic nature of the clay and the ease with which it puddled into slurry.In zone (b) a good deal of trouble was experienced because of the fact that the somewhat heavy blasting necessary tended to cause movement of the large rock masses. Subsequent scouring out of the supporting clay bands by the waterflow permitted settlement of the ground on to the timbers and many reinforcing sets were therefore required.The timbering of the pilot headings and its relation to the cross-section of the circular tunnels is shown in Fig. 1. Top and side spiling was driven in the ordinary way, but in bad ground intermediate sets and breast boards had to be placed. These sets were usually withdrawn after the...

Jan 1, 1941

By G. Coetzer

During galena flotation of Rosh Pinah milled material, metal ions and salts contents of various water resources (deionized, simulated circulated, lead concentrate thickener, lead tailing thickener and borehole) influenced mineral recoveries, upgrade ratios, selectivities, froth stability and flotation kinetics. The various water resources employed during galena flotation caused activation, depression or selectivity effects on minerals due to the presence of different ions in solution. Metal ions in these water resources were adsorbed by the ore, whilst ions associated with gangue minerals (dolomite and quartz) were released into the flotation pulp. Lead concentrate thickener water caused depression of sphalerite and pyrite, increased fast floating fractions for silver, copper minerals, sphalerite and quartz (unwanted), and improved slow floating rate selectivity against pyrite and sphalerite. Lead tailing thickener water enhanced sphalerite recovery during galena flotation (unwanted), and increased fast floating fractions of pyrite. Western borehole water did not affect galena recovery, but sphalerite and pyrite recoveries were unacceptably too high. Ions from copper, lead, and zinc salts tended to release high amounts of ions, such as calcium, magnesium, silicon, and manganese from gangue minerals (dolomite and quartz) during milling. During galena flotation, lead ions depressed sphalerite, pyrite and dolomite at a lead concentration of 400 ppm, but sphalerite was activated at a concentration of 800 ppm. Sphalerite was activated with copper ions (89% recovery, 2.09 upgrade ratio) and depressed with zinc ions (maximum recovery of 25%). This corresponds with findings in previous investigations. Dolomite and quartz were slightly activated with zinc ions. No evidence was found that lead and copper ions activated any gangue minerals during galena flotation. Keywords: galena, water resources, metal ions, activation, depression, selectivity.

Jan 1, 2003

By Catalin Florin Petre, Elahe Ghasemian Langeroudi, Abdelaaziz Azizi, Éric Proulx, Caroline Olsen, Paul Blatter, Faïçal Larachi, Claude Gagnon

"The recovery of gold from ores is often accompanied by the release of other species in the leach solution. This state of affairs leads to depleted free cyanide levels in the slurry. Therefore, separation and quantification of these cyanicides and free cyanide at different stages of the cyanidation process as well as in waste solutions is crucial to provide mitigation tools by preventing leaching of deleterious metals for environmental considerations.COREM and the research group of Prof. Larachi have been working together on the control of gold passivation and cyanicides during cyanidation for several years. Previously, a first capillary electrophoresis (CE) protocol for the speciation of sulfur and cyanicides (SCN-, Cu, Fe) during cyanidation of gold complex sulfide ores was developed and validated for assessing industrial process water.The separation of zinc cyanide complexes used to be confronted with a number of difficulties due to the weak and/or undetectable cyanocomplexes in formally available CE protocols. Moreover, according to our knowledge, no direct CE protocol exists to separate free cyanide. Therefore, a new study aimed at developing a second CE protocol for the detection and quantification of cyanide complexes of zinc and nickel as well as of free cyanide in the cyanidation process water.To achieve this goal, six common carrier electrolytes such as pyridine, trimellitic acid, 4-methylbenzylamine, sodium chromate, phthalic acid and tris base were studied, using an indirect UV detection method. The best results were obtained using sodium chromate for which all ions were successfully separated and quantified. In addition, the effect of electric field strength, injection volume, electro-osmotic flow (EOF) modifier and background electrolyte (BGE) concentration were examined, while peak height, peak area and noise were considered for optimization.As a result, the new protocol is expected to complete the initial CE protocol by detecting cyanide complexes of zinc and nickel as well as free cyanide. Moreover, analytical determination of free cyanide in the presence of weak cyanide complexes achieved by the new protocol was also compared to conventional titration using silver nitrate solution. This new CE protocol will contribute to applied research and help plants to better understand and eventually control the behaviour of cyanidation circuits."

Jan 1, 2011

By F. T. Cawood

This research report was produced in response to the release of the Mineral and Petroleum Royalty Bill. It involved are view of the mineral investment environments of selected countries in order to form an opinion on the appropriateness and competitiveness of the proposed royalty structure for South Africa. Many emerging countries have recently attracted a significant share of foreign investment, as a direct result of changes in policy. These are, by implication, the least risky and most favourable destinations for the ?investment dollar?. The five most competitive countries, namely Chile, Argentina, Peru, Mexico and Brazil have been identified as succeeding with their policy visions of creating favourable domestic investment environments. The investment rules of these countries served as a basis for the compilation of a Competitive Investment Framework (CIF). This is a template of best practice against which other investment environments, such as that of South Africa, can be measured. The framework indicates that mineral royalties should ideally be no more than three per cent, demonstrating that the regime proposed in the Royalty Bill is out of step with international best practice. Mineral royalties can never be viewed in isolation and in the assessment of the rates proposed in the Royalty Bill, one must consider the total taxation package. Such assessment appears in Section 5 of this report, demonstrating that there is reason for concern if National Treasury were to impose the rates stipulated in the Royalty Bill. The alternatives, conclusion and recommendations of the review appear in Sections 9 and 10. These are the result of independent analysis and assessment of the fundamental principles. It is done through the application of a Competitive Investment Framework that avoids the highly subjective and emotional views that often accompany a process like this.

Jan 1, 2003

The corrosion behaviour of a low carbon steel was investigated in natural seawater and various synthetic seawaters. It was found that the steel corroded nearly four times faster in a 3.5% NaCl solution than in natural seawater for an exposure time of 21 days. The corrosion rate after immersion in synthetic seawaters (ASTM D1141 and Marine Biological Laboratory seawater) is similar to the corrosion rate after immersion in natural seawater. Calcium carbonate (aragonite) deposits were found on the surface of the steel after immersion in natural seawater and the synthetic seawaters. Some magnesium-containing deposits were also found after immersion in the natural seawater. These deposits act as a barrier against oxygen diffusion and thereby lower the corrosion rate. The morphology of the calcium carbonate deposits that formed during immersion in the natural seawater is different from those formed during immersion in the synthetic seawaters. This may explain the slightly lower corrosion rates obtained in the natural seawater. X-ray diffraction also showed that the oxy-hydroxides formed in the 3.5% NaCl solution differed from those formed in the other solutions. Keywords: Corrosion, seawater, low carbon steel, 3.5% NaCl, aragonite

Jan 1, 2006

By J. Rogans

This paper discusses the comparative performances of the three activated carbon adsorption circuits at the West Wits operations of Anglogold. These circuits consist of two pump-cell circuits (at Two Plant, formerly Elandsrand and at Three plant) and a conventional counter-current adsorption circuit (at Mponeng plant). The implications of the improved performance of the pump-cell plants are discussed.

Jan 1, 2002

By George A. Morgan

Output of mineral products was estimated to be unchanged in 1983 from that of 1982 with the exception of petroleum. The country began production of crude oil from the Seme Oilfield, and all output was exported. Wd and charcoal constituted 72% of Benin's total energy consumption, and imported petroleum products and electric power accounted for the remainder. Cement was produced from imported clinker. The gross domestic product (GDP) was $1,061 million in 1982, the latest year for which information was available.2 COMMODITY REVIEW Gold.-Exploration was underway at Perma by the U.S.S.R. as part of the United Nations development program. Gold had been produced previously at Perma, where a grade of 0.289 troy ounce of gold per ton was reported, An exploitation program for the deposit was to employ about 100 people, and output was targeted to reach 1,600 troy ounces per year. Recoverable reserves were put at 96,000 troy ounces.

Jan 1, 1985