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By Luciano Ramos, Daniel Santos

Igarape Bahia Mine, which is currently the largest gold producer in Brazil, belongs to Companhia Vale do Rio Doce - CVRD and is situated 250 miles south of Belem, state of Para, Brazil. It came into operation in 1992 with the startup of the CIP plant, fed with high grade ore, presently at 3.4gAu/t. The ore is totally oxidized, containing extremely fine particles of free gold. The ore is soft and low cyanide consumer, with a maximum work index of 12kwh/sht. In 1993 a Heap Leaching Plant was set into operation, handling low grade ore of · 1.s g Ault. The Heap Leaching Plant has undergone two major expansions. In 1994 its capacity was raised from lMtpy to 2,2Mtpy and in 1998, with a thorough remodeling of crushing operations, it was raised again to 3.5Mtpy. The CIP plant, which was originally designed with a capacity for l. lMtpy of ore, was expanded to a 2.2Mtpy capacity in 1994. Presently, the CIP plant accounts for most of Igarape Bahia's total gold output, with approximately 220,000oz per year. Igarape Bahia's annual output is around 360.000 oz. Over the last three years, work has been intensified to improve performance of both processes, aiming at maximizing productivity of the two industrial plants. Reduced costs and increased revenues have been given a special emphasis in the unified improvement program. Cost · reduction has involved developing methodologies to rationalize consumption of materials and inputs, while increased productivity has been given top priority as a means of generating increasing revenues. Thus, all of the improvement and development efforts have had a common goal: to increase operating income.

Jan 1, 2000

On-stream determination of xanthate concentrations can be made by photometric measurements at 313 nm.A simple double-beam instrument was developed for this purpose. A mercury lamp is used as the light source and a composite filter of UGll glass and chromate solution is used to isolate the required spectral region. The light beam is split into two components of approximately equal intensity. One component is passed through a reference cell containing water to a photo detector; the other component is passed through the xanthate solution to a second photo detector. The reference signal controls amplifier gain to eliminate effects of lamp intensity changes and the amplified sample signal can then be used to measure xanthate concentration.Plant trials showed that provided a clear solution free of air bubbles was obtained from an on-stream filter, the instrument indicated the xanthate concentration and operated satisfactorily for long periods.

Jan 1, 1973

By Peter J. Clarke

The Soviet-controlled Government in Afghanistan continued to emphasize development of the country's mineral resources, primarily to supply raw materials and fuel to industrial areas in the Soviet Central Asian republics. In addition to expanding production of natural gas for export to the U.S.S.R., a $600 million2 Soviet-Afghan cooperation project, 1 of 167 such projects established since 1981, was devoted to exploiting the Ainak copper deposit, south of Kabul in Logar Province. Also being developed was the large Hajigak iron ore deposit in the Hindu Kush Mountains, 100 kilometers northwest of Kabul. In addition to these minerals, Afghanistan already produced small quantities of barite, cement, coal, gypsum, salt, and possibly some lapis lazuli. Afghanistan was the world's leading producer of lapis lazuli, a semiprecious gem stone, prior to the Soviet invasion in 1978, but production, although no longer reported, has probably been significantly reduced. It was also reported that Soviet mining engineers and technicians have commenced producing uranium from Lashkangah in the mountainous Khawaja Rawash area near Kabul.3 The Government was also considering mining chromite from Herserak and Mohammed Agha Kulanger, near the border with Pakistan.4 Afghanistan's overall economy remained stagnant in 1983, a result of continuing armed resistance to the Soviet-installed government. The gross domestic product (GDP) was estimated at about $2.8 billion, only marginally higher than the 1982 level. The value of exports was estimated at $720 million, up less than 2% over that of 1982, while imports rose approximately 8% over the same period. Natural gas was by far the leading export, earning about $295 million, up 4% over that of 1982. Approximately 90% of Afghanistan's natural gas production was exported to the U.S.S.R. Gas exports were used to pay the country's debt to the U.S.S.R., and also to pay for its supplies of petroleum products and other goods, which were imported almost exclusively from the Soviet Union. Some of Afghanistan's petroleum products were supplied by the U.S.S.R. as grants in aid, as Afghanistan did not have any domestic petroleum refining capacity.

Jan 1, 1985

By Matheus Porto Trindade, Marcos Menino de Macedo Filho, Isau de Souza Alves Junior, Sandro Griza, Brenno Lima Nascimento, Gustavo Dória Lima

O tratamento de oxidação térmica da liga Ti-6Al-4V foi realizado ao ar a 600 °C durante 2h, 5h e 10 h. O comportamento à fadiga foi analisado e comparado com aquele da liga não tratada. Foi feita caracterização através de análise por microscopia ótica e eletrônica, difração de raios-x e medição da rugosidade. Os resultados do DRX demonstraram crescimento dos picos de rutilo. Verificou-se um aumento na espessura média da camada formada de 0,12 μm para 1,09 μm ao elevar a duração do tratamento de 2 para 10 h. Os resultados apontaram redução de resistência a fadiga de 35 % para amostras oxidadas durante 2 h, 27 % para amostras oxidadas por 5 h e 29 % para as amostras tratadas durante 10 h, em relação ao ensaio com corpos de prova não submetidos ao tratamento. O efeito prejudicial causado pela camada formada após oxidação de 2 h foi tão danoso quanto o causado pela camada formada após 10 h, apesar da diferença entre as espessuras das camadas. A morfologia encontrada nas amostras fraturadas indicou fragilização na superfície das amostras oxidadas, contribuindo para a nucleação de trincas iniciais nos primeiros ciclos de fadiga na camada que favoreceram a propagação de fadiga, independendo da espessura de camada.

Oct 19, 2019

By R. Snoby

Since its introduction in 2002, the modern air jig has processed a wide array of coals throughout the world. This paper explores the reasons and justifications for the installations and provides case history performance data. Specifically highlighted are air jig plants processing metallurgical coal in Colombia, bituminous coal in the United States and India and lignite in the United States and Spain. Each installation has unique reasons to justify an air jig facility. It is important to note that not all of the justifications were based on the ?most cost effective yield?, normally a mantra for coal preparation plant designers and owners. Dry jigging of coal has long been a proven technique for upgrading coal, the modern air jig, with its improved efficiency and operating systems simply extended the range of applications. In some cases, it even allows market quality coal to be produced when no other option is possible.

Jan 1, 2009

By R. F. Dickerson, D. A. Vaughan, A. F. Gerds

ALTHOUGH the metallurgy of uranium has been under intensive study since the early 1940's, no systematic effort has been made to identify the non-metallic inclusions in uranium. Uranium carbide (UC), which is probably the most common inclusion found in graphite-melted metal, has been tentatively identified by previous investigators, but the other nonmetallic inclusions have received little attention. Since metallography is a valuable tool in metallurgical studies, the metallographic identification of the nonmetallic inclusions in uranium is important. Such an investigation has been completed and the identification of slag-type inclusions and of uranium monocarbide, uranium hydride, uranium dioxide, uranium monoxide, and uranium mononitride is described. Metallographic Preporation It is often possible to prepare specimens for metal-lographic examination equally well by several methods. The specimens which were examined in this work were prepared by one of two acceptable methods. For the convenience of the reader, both methods will be discussed in detail and will be referred to simply as Method I or Method II in the subsequent sections. For both Methods I and 11, specimens for microscopic examination usually were mounted either in bakelite or in Paraplex room temperature mounting plastic. Method I—Specimens were ground in a spray of water on a revolving disk covered successively with 120-, 240-, and 600-grit silicon carbide papers. It was necessary to perform the final grinding operation carefully on worn 600-grit paper to keep the scratches as fine as possible. After washing and drying, the specimens were polished for 3 to 4 min on a slow speed wheel (250 rpm) covered with a medium nap cloth. Diamet Hyprez Blue diamond polishing paste, Grade 00, 0 to 2 µ, was used as abrasive with kerosene as lubricant on the wheel. Specimens were washed thoroughly in alcohol and final polished electrolytically in an electrolyte composed of 1 part stock solution (118 g CrO, dissolved in 100 cm3 H2O) with 4 parts of glacial acetic acid. A stainless steel cathode was used. At an open circuit potential of 40 v dc, a polishing time of 2 sec retained inclusions well with the bath at room temperature. If additional etching was required to sharpen the interface between the metal and the inclusions, an electrolyte composed of 1 part stock solution (100 g CrO3 and 100 cm8 H20) and 18 parts glacial acetic acid was used at room temperature. Best results were obtained by etching for from 10 to 15 sec at 20 v dc in the open circuit. Surfaces obtained by this method are suitable for microscopic examination. However, if desired, they may be etched further with other chemicals. Method 11—Rough grinding was done on a wet 180- or 240-grit continuous grinding belt. The specimen was then ground by hand successively on 240-, 400-, and 600-grit silicon carbide papers in a stream of water. Final polishing was accomplished on a 4 in. high speed wheel (3400 rpm) covered with Forstmann's cloth. Linde B levigated alumina, suspended in a 1 volume pet chromic acid solution, was the abrasive. Specimens usually were polished in 5 min or less by this technique. Often the inclusions present in the metal were identified in the mechanically polished condition. When etching was required to outline inclusions more sharply, one of the two following methods was used. In the first method, the specimen is etched lightly while electropolishing in the chromic-acetic acid solution described above (1 part of stock solution to 4 parts of acetic acid). The electrolyte was refrigerated in a dry ice-ethyl alcohol bath and specimens were etched at 60 v dc on the open circuit for 2 or 3 cycles of 3 to 4 sec each. The second technique utilizes electrolytical etching at about 10 v dc (open circuit) in a 10 pet citric acid solution at room temperature. X-Ray Diffraction Technique The major problem in the identification of inclusions in metals by X-ray diffraction techniques is the extraction of a sufficient amount of each type of inclusion to obtain an X-ray diffraction pattern. In the present study, X-ray diffraction patterns were obtained from individual inclusions of the order of 10 µ diam. The polished and etched samples shown in the micrographs were examined at a magnification of X54 or XI00 with a binocular microscope. This allowed sufficient working distance to extract the inclusions with a needle probe for powder X-ray diffraction analysis. Friable inclusions such as MgF2, CaF2, UO2, and UH3 could be freed from the metal by probing the as-polished and etched surface. The fine particles then were picked up on the end of a Vistanex-coated glass rod (0.002 in. diam) which was held in a brass adapter made to fit the powder X-ray diffraction camera. The end of the glass rod was centered in the path of the X-ray beam. In the case of the UC, UO, and UN inclusions which are smaller in size, more metallic in appearance, and less friable than the other inclusions, it was necessary to etch the inclusion in relief before extraction. UN inclusions etched sufficiently in relief in the electrolytic polishing solution described in Methods I and II by increasing the polishing time. UN inclusions were relief etched by extending the

Jan 1, 1957

By Peter Ay, Vincenz Mehlstaubl, Satyanarayana Narra

"This study gives an insight into non-destructive testing methods suitable for porosity analysis at a small scale, firstly summarizing relevant state-of-the-art technology and pending patents, secondly realizing and documenting the start-up of the VHX-2000 digital microscope by the manufacturer Keyence and thirdly demonstrating practical application with the extended analysis of three fundamentally different agglomerates for which important application-related parameters are determined. Various analysis procedures on the different agglomerates the efficient and timesaving operational features of the digital microscope are outlined. Firstly an analysis of flax fibre agglomerates determines the process conditions best suited to produce agglomerates with specific properties by determining sphericity, cubicity, density and porosity as well as fibre damage and alteration. Secondly the production of iron-hydroxide - hemp-fibre agglomerates serves to obtain information on porosity values as a result of a cauterization of the fibres. The third analysis provides estimations of porosity values for acid-treated lignin agglomerates. Measurements were carried out with compact dry agglomerates and with soaked, expanded agglomerates, determining factors for total water carrying capacity. Practicability of non-destructive testing by digital microscopy is demonstrated and explained concerning the applications in this study by obtaining definite structural findings about the analysed agglomerates. Information on its operation is made available by a practice-oriented manual for the VHX-2000 digital microscope. Further suggestions for more in-detail analysis results with different instruments are given."

Jan 1, 2014

By M. U. Savich

In Canadian mines, ear muffs are now an essential part of safety equipment. Because of this, a research study was conducted to investigate their efficiency. The main characteristics of eleven commercially available ear muffs were investigated in the laboratory and analyzed by: (I) a psychophysical method; and (2) a physical method. These investigations showed the following effects: head size has a significant influence on the attenuation because of a different clamping force; the amount of hair trapped between the ear muff cushion and the head decreased ear muff attenuation; attenuation and comfort are not in a causal relationship; with the use of glasses and their adapters, attenuation decreases-the adapters are not effective sound barriers; there are no great differences in attenuation with neck movement; the efficiencies of various brands of ear muffs are not equal; ear muffs with a small cushion area start serving their purpose more quickly because the force per unit area is larger; a clamping force larger than 900 g wt, in most ear muffs, does not cause an increase in attenuation; attenuation characteristics (ANSI 224.22 - 1957) of ear muffs show some correlation with physical tests. Nine ear muffs out of the eleven were tested under uniform conditions in mines. Three ear muffs were found to be the best. All three ear muff s have bands passing behind the head. The ear muff with a support strap, which improves comfort and maintains a good fit during wear, showed the best attenuation. Causes of poor attenuation are numerous: bad mounting of ear muffs on helmets, improper fitting, interferency by hair and glasses, improper wearing by miners, unsatisfactory enforcement by supervisory personnel, incomplete training of miners, etc. Results of this research have indicated that none of the ear muff s tested in this study contain all of the characteristics desirable in an ideal unit. Because of unsatisfactory ear muff attenuation in working conditions (/5 dBA), it should be a mandatory requirement that workers wear both ear muff s and ear plugs if the noise level is higher than 105 dBA (various literature recommends t io dBA). The key to the solution lies in the following: the foreman must be capable of helping and controlling miners in their task of wearing ear muffs properly; the program must be introduced to miners; and constant contact must be maintained with manufacturers.

Jan 1, 1979

By William Reisz

Over the years as surface mining operations have become more sophisticated, angle drilling has become a more popular blast design technique, especially in areas where overburden and stripping ratios have increased. Another method of blast design is the staggered pattern, which greatly improves explosives distribution within the blast. While both methods present some engineering challenges, this paper will discuss how the two methods can be combined to enhance fragmentation, improve cast percentage, drill production ratios and highwall control. A practical engineering approach will be presented as well as a discussion on the discipline required to maintain a quality blasting plan.

Jan 1, 2002

By Kouichi Tomisawa

Two bridges were constructed for extension work of Central Hokkaido Connection Road in 2005 at two different sites. Pile group foundations were employed for the foundations of abutments of the two bridges. In order to assess the performance of the constructed piles in the sites and to obtain design parameters for design in future, static alternating cyclic horizontal load test was carried out on one of the open-ended steel pipe piles constructed at each site. The ground at one site was characterised as a thick deposit of volcanic soils, and the ground at the other site was characterised as a very soft peat layer near the surface. In this paper the results of static alternating cyclic horizontal load tests on the piles at the two sites are presented and discussed in detail.

Jan 1, 2006

By Lennart Mukka

The Kiruna Mine in Sweden currently has three ventilation systems. The first two (a new and old system) serve the production areas. The third system is used for the facilities on the former main haulage level 775. That area includes offices and workshops for load haul dumpers (LHD) and drill rigs. The third ventilation system also covers the crushing and haulage on level 1045. At the present time, the total airflow for the mine is 1,600 m3/sec(3.4 million cfm). The current system serves the levels above the 775 level. The new one is for the levels between 775 and 1,085 m (2,540 and 3,560 ft), which are needed for the new ore body. When all of the production is below level 775, the old ventilation system will be closed down.

Jan 1, 2002

By A. D. Fowler, M. T. Anderson

A phenomenological model is presented that relates Pb-Zn mineralisation to proximal geopressure zones. Typically, geopressure zones (GPZ) consist of masses of undercompacted sediment encapsulated within impermeable shales and are characterised by high formation fluid pressures. Heat flow is perturbed in some GPZ on account of their insulating properties. Geothermal gradients as high as 150 degrees C/km have been observed over short distances in the sediments of the US coast of the Gulf of Mexico. Some modern geopressure zones are known to reach temperatures of 120-150 degrees C at depths of 2.5-3.5 km. It is demonstrated that the zones may act as proximal sources of hydrothermal fluids, thus explaining the high temperatures of mineralisation observed in the deposits, which are hosted in basins characterised by thick, rapidly deposited, shale-rich clastic sequences

Jan 1, 1991

By G. Abowitz, R. B. Gordon

The velocity of sound, mass density, and thermal expansion coefficient were measured in dilute lead, tin, zinc, bismuth, cadmium, indium, and potassium amalgams as a function of composition. Measurements in the Hg-TI system extended ovev the wider range of composition, 0 to 40 at. pct TI. The sonic velocity was measured as a function of temperature. The calculuted adiabatic compressibility in all cases was found to decrease much more rapidly than would be expected on the basis of a linear variation with composition. An interpretation of the results is given in terms of changes in the Debye characteris -tic temperature of mercury on alloying and a possible change in the bonding of mercury itself. If a liquid is considered as an isotropic elastic medium, the phase velocity of a longitudinal elastic wave traveling in the liquid is given by where K is the bulk modulus, G the shear modulus, and d the mass density. G can be neglected for liquids of ordinary viscosity, i.e., approximately 1CT2 poise, because the shear stress component is relaxed essentially at once. That is, for liquids of ordinary viscosity and at frequencies of the applied stress up to several hundred megacycles, the relaxation time of the shearing process is much shorter than the period of the applied stress. Eq. [I] then reduces to The adiabatic rather than the isothermal compressibility is measured at the megacycle frequencies used in ordinary ultrasonic velocity measurements. The sonic velocity and compressibility have been determined for many organic liquids and aqueous eletroltes,' and the results have been interpreted in terms of existing theories for these fluids. The velocity of sound and compressibility are important parameters in theories of the liquid state. For example, equations of state have been proposed relating the free volume of liquids to the acoustic velocity.3 Comparatively very little work has been done on the acoustic properties of liquid metals and alloys. leppa,' orddon, and several other investigators

Jan 1, 1963

By L. C. IlsLey

Minin,g Qr col-cu.ttint till:I chines are 1?;\i9ng the _m9t wideiy .used de1sses ()f mining equipment.· These 1T:.i:1Chines ,.--re practicaily t-tl\·operc1_ted eiyher_by compressed .iir or by electric. ·motors. According to &.ta• compiled _ from the 122. issue COAL CATALOG\JE. OJMEINED WITH; OOAL "FIELD 'pf!:fC'TOTl1, bf 7,088. mnes from which reports were obttiined there -are 3895 mines that u.se coal-cutting eql;lipmen:ts,, 'f'hi report lists 20,031: r.ct:lchines, 17,&75 being operated by·elct:i.c.m<;>_tors··:r;id :the remtiinder by compressed i.r motors,· ,-. · ', .. . · .. ··, .. _ ,· .,, .. .. . . . . . : ; "'l t:: On tl.Ccou-nt .. of the wide· use of coc:11-cutting -.:i"cliine_- any Stat!;ls have issued regulationa as "to their operation dnd be to safety precautions that.should be observed J especially in gaseous mines.

Oct 1, 1922

By Nava-Vasquez E, Torres-Torres J, Mendez-Nonell J

The ZA-27 zinc base alloy was poured into cylindrical moulds and solidified under different conditions ie normal freezing and unidirectional freezing. In addition a cylindrical ingot with rheocast material was obtained by stopping the stirring action and, at a specific solid fraction, gravity casting it into a graphite mould. It was observed that the material obtained under normal freezing conditions is likely to present both segregation and inverted pipe. In contrast, the unidirectional solidified and the rheocast cylinders showed the absence of inverted pipe. The segregation pattern was quite irregular in the rheocast ingot while such segregation was more uniform in the unidirectional solidified cylinder. By virtue of these observations, the inverted pipe formation may be ascribed to the interdendritic flow, while the irregular segregation pattern in the rheocast ingot may be attributed to an irregular distribution of the liquid and solid fraction along such a cylinder.

Jan 1, 1993

By C. C. Pretorius

3D seismic surveys have become a well-accepted method of imaging sub-surface geology in the Bushveld Basin. Because both the seismic sources and receivers are placed at surface, most surveys are limited to imaging faults with >=7 m throw. However, some areas such as shaft infrastructure can benefit from the ability to detect smaller structures prior to shaft sinking. Borehole radar and logs such as the acoustic televiewer can identify these structures in the shaft barrel, but not within -200 m from the shaft. Therefore, Anglo Platinum has developed the method of high-resolution 3D vertical seismic profiles (VSPs) for structural sterilization of shaft sites prior to shaft sinking. VSPs utilize a surface source and sub-surface receivers deployed down a borehole. This means that seismic energy goes through the near surface only once, and therefore suffers less frequency loss than when both source and receivers are on surface. Furthermore, VSPs can record 3 component (3C) data which comprises P wave, Sh (horizontal) and Sv (vertical) wavemodes. Because S waves travel at about 0.6 of the velocity of a P wave, shorter wavelengths and therefore higher resolutions are possible using S wave data. VSPs were first used in their one dimensional, zero offset, mode to correlate borehole geology with seismic stratigraphy within seismic surveys. This showed that VSPs record -30% higher frequencies than surface seismic surveys. The program then applied two dimensional VSPs to the problem of imaging geological structure close to a borehole. 2D VSPs confirmed that high frequency results could be achieved, and that this enabled a more accurate image of the Merensky Reef than could be achieved by surface seismic data. Finally, the program has achieved the successful recording and processing of 3D VSP data, with both compressional and shear wavemodes giving a high resolution structural result. Although P wave data gives -30% frequency improvement over surface seismic surveys, S wave data can give as much as 80% improvement, further improving the structural image achieved. The high fixed costs of VSP surveys mean that they should ideally be run in multi-client batches, which can reduce the per borehole cost by up to 50%. Their application is anticipated to be on high value capital infrastructure with a geological risk from faults which are not imaged by surface seismics-generally in the sub-7 m range. Keywords VSP, 3D seismic, bushveld, platinum, resolution, imaging, shear waves, shaft sinking.

Jan 1, 2011

Geopolymerization is a process by which Al-Si minerals undergo dissolution and polymerization in an alkaline solution to form a monolithic material with a high mechanical strength (Davidovits, 1991; 1994). In this study, Na-feldspar (albite) and K-feldspar (microcline) have been selected to investigate their abilities to undergo geopolymerization. The interaction between alkali metals present in the alkali-feldspars and alkali metal cations contained in alkaline solution during geopolymerization has also been studied. It has been found that both albite and microcline can be applied in geopolymerization to produce geopolymers with a high compressive strength. Although the dissolution of M-feldspar (where M = Na and/or K) in concentrated MOH solution is inhibited when the alkali metal cations of the alkaline solution differ from the alkali metals structured in M-feldspar, the resulting geopolymers are found to demonstrate a higher compressive strength. Moreover, a proper molar ratio of Si/Al in the geopolymeric gel phase and a higher average hardness of the undissolved particles remaining in the geopolymers are found to greatly increase the ultimate compressive strength of the geopolymers.

Jan 1, 2002

By Lukas Erkurt, Wolfgang Holzer, Stefan Auderer, Richard Gradnik

SEM/ NATM Tunnelling contracts in Austria and Germany are usually tendered applying unit price contracts. The purpose of this paper is to show how contractual problems are resolved in these countries. The focus will be put on describing the theoretical approach, several case studies will show how contractual problems were dealt with on site.

Jun 23, 2024

Techniques have been developed for the dissolution of a wide range of rocks and minerals by a sodium peroxide sinter process. A olarge number of elements are determined by atomic absorption spectroscopy, and other elements such as arsenic and sulphur are determined by chemical analytical methods. The methods adopted to overcome inter-element and ionization effects on the atomic absorption results are discussed.

Jan 1, 1974

By Barry C. Slocombe

The development of new ports, extensions of existing facilities and reclamation of former docks will involve consideration of a variety of geotechnical problems. This paper presents data including instrumentation of structures from three UK projects involving vibro techniques to provide economic engineering solution.

Jan 1, 2008