Search Documents

By J K. Claflin, S R. La Brooy, A M. Claflin

Rotary kilns have been in service in the gold industry to regenerate carbon for 65 years. At the time oxide ores with gold head grades of 8 to 10 g/t were being treated. Carbon could be regenerated adequately at 650°C and solution losses were less than 1%. Forty years ago, research indicated that heavily fouled carbon from flotation circuits had to be held at 750 to 850°C for ten to twenty minutes for full reactivation (Avraamides and La Brooy, 1987), gold head grades were typically 5 g/t and solution losses typically 0.02 ppm – still less than 1%. In 2017 it was determined (Claflin et al., 2017) that a residence time of less than 1 minute at 750°C can be adequate to reactivate carbon fouled with organics sufficiently to achieve 0.005 ppm solution losses in a flotation tailings leach plant.With the potential for discovery head grades to drop below 0.6 g/t, solution losses of 0.02 ppm represent over 3% loss. Tight operation of the whole carbon circuit is required to keep gold solution losses below 1% going forward.There are alternatives to a rotary carbon kiln, e.g. vertical kilns of which the Minfurn, Rintoul and Combustion Air kilns are examples. The alternative kilns can be heated using electrical heating elements, induction, and microwave. These kilns can operate successfully under the right conditions, however, they are almost exclusively for small carbon throughputs and are not suitable for the large carbon advance rates that are required to process low head grade ore deposits. Large throughput carbon kilns are are almost exclusively fossil fuel fired rotary kilns and the subject of this paper. In the view of the principal author, a fossil fuel fired vertical carbon kiln is preferred to a rotary kiln, however, it is not currently used in the industry.Thermal regeneration of activated carbon has a major impact on gold recovery in the carbon circuit. The carbon kiln and associated equipment constitute 3 to 5% of the capital cost for an oxide processing plant and up to 10% of the capital cost if flotation tails are leached. Despite the capital cost and impact on recovery, the carbon kiln is often poorly selected, operated and maintained.Six years ago Ausenco embarked on the Carbon Kiln Initiative to reduce solution gold losses. This body of knowledge has been published in a series of papers culminating in this paper on how to:1. Select a kiln appropriate for the flowsheet;2. Maintain the kiln to achieve design operation; and3. Operate the kiln to minimise costs and maximise reactivation.CITATION:Claflin, J K, La Brooy, S R and Claflin, A M, 2018. Carbon kiln selection, operation and maintenance, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 251–274 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By W. Valderrama, D. G. Almond

Operation of large SAG mills requires a change in the conceptual approach to grinding processes. The traditional energy consumption criteria are now enhanced with new criteria derived from the mechanical dynamics of the mill load. This new approach demands instrumentation capable of providing accurate information about the load movement and the ratio of balls and ore inside the mill. This paper discusses two new performance enhancing tools available to meet these needs.

Jan 1, 2004

By T. P. Dolley

Domestic production of industrial sand and gravel in 2004 was about 29 Mt (32 million st), a 6-percent increase from 2003. This increase was buoyed by a robust construction sector of the U.S. economy. U.S. apparent consumption was 30.3 Mt (33.3 million st) in 2004, an in-crease from 2003. Imports were about 490 kt (540,000 st) in 2004, an 11-percent increase from 2003. Imports of silica are generally of two types. They include small-quantity shipments of very-high-purity silica or a few large shipments of lower grade silica that were shipped only under special circumstances (such as very low freight rates).

Jan 1, 2005

By C. Ozgen Karacan, William P. Diamond

In This Chapter [Measuring the gas content of coal Predicting gas emissions based on geologic and coal reservoir property data Determining the gas storage capacity of coalbeds and other gas-bearing strata Methane drainage borehole monitoring to forecast the remaining gas-in-place and the influence on mine emissions Forecasting gas emissions during mining as a function of mining parameters and Gas emission prediction based on numerical simulation] This chapter provides guidelines for determining the gas content of coalbeds, estimating the gas-in-place, and predicting gas flow and emissions before and during coal mining operations. The techniques are discussed briefly in the following sections. However, detailed information on the techniques is provided in the cited references. INTRODUCTION Coalbed methane, if not properly controlled in the underground mine environment, is a safety concern due to the potential risk for an explosion. This is a particular problem during longwall mining, where the high rate and volume of coal extraction can result in the release of large amounts of methane from the mined coalbed and other adjacent gas-bearing strata. The variability and potential hazards of these sometimes unexpectedly high gas flows provide the impetus to develop methods to predict methane emissions into the underground workplace. A forecast of the volume of gas that might be released during coal mining is helpful for designing ventilation systems and for implementing optimum methane drainage strategies to help mitigate expected gas emission problems. A complete assessment of the need for methane drainage prior to mine development generally requires both an empirical and a theoretical approach. If there are active mines in the general area with similar geologic conditions and coal characteristics, a review of gas problems in those mines provides an initial insight into the level of gas emissions to be expected at a new location. In addition, relatively simple methods exist to determine the in situ gas content (volume of gas per unit weight of coal) of the coalbeds in a particular mining area, as well as the gas-in-place (volume of gas in the coalbed(s) within a defined geographic area).

Jan 6, 2006

By R. G. Aspden, D. A. Colling

THE {120}(001) texture has been reported in near 50 pct Ni-Fe alloys <0.004 in. thick1,2 and in copper 0.014 in. thick.3 This texture is one of two types of secondary recrystallization textures observed to replace a cube texture matrix and is desirable in Fe-Ni alloys because of its unique magnetic characteristics.1,2 However, the conditions for and mechanism of the {120}(001) formation are not well understood.3 During an investigation of the influence of alloying elements on the magnetic characteristics of 49 pct Ni-Fe alloys with a sheet thickness of 0.014 in., we have observed the growth of {120}(001) secondaries when strong deoxidizers such as aluminum and calcium were present. It is believed that this observation in unique and provides additional insight with regard to the mechanism for {120}(001) texture formation. Three alloys were prepared with electrolytic iron and nickel and contained a nominal 49 wt pct Ni. Alloy A was a straight binary Fe-Ni alloy, whereas intentional additions of 0.013 wt pct Ca to alloy B and of 0.59 wt pct A1 to alloy C were made. Ingots were forged at 1100 C, hot-rolled to 0.150 in. gage, pickled, and cold-rolled to 0.014 in. Standard U-shaped magnetic test specimens were punched, deburred, sprayed with MgO, and annealed in ~50°C dew point hydrogen. Textures were identified with the aid of etch pits, the

Jan 1, 1970

By R. L. Zick, D. C. Finn

Introduction The high-density sludge process was originally developed by Bethlehem Steel Corp. for use on acid mine drainage (AMD) and diluted waste pickle liquor discharges requiring continuous chemical-treatment. This work began in the early 1970s and was first put into practical use around 1973. To date, there are approximately 15 operating systems that have been installed to treat mine drainage in the United States. In addition, there are another 10 systems installed outside of the United States. The dense-sludge process is an innovative and improved method for treating acidic metal-bearing streams in a manner that minimizes the volumetric generation of sludge for disposal. The technology utilizes a sludge-recycle process that forms particles with a low affinity for water. These particles are unlike conventional metal hydroxide solids that contain tightly bound interstitial waters. Typical acid mine drainage streams contain high sulfate concentrations that combine with calcium ions in lime-based treatment systems to form gypsum crystals. Compared to the form generated in conventional lime treatment systems, the physical form of the gypsum is radically altered when the dense-sludge process is utilized. The characteristics of the metals particles are also changed in this process, as the metal hydroxides are converted to metal oxides. The dense-sludge particles settle faster, dewater more readily, are more easily pumped and hold much less water than conventional precipitates. In some cases, because the metal content of the sludge is more concentrated, it can be economically recovered. In general, the conventional and dense-sludge treatment processes are very similar. The changes required to implement the dense-sludge process are minor, and, typically, much of the existing equipment can be utilized. The net results of the process are: reduced operational costs associated with sludge generation, improved process control (particularly pH control), reduced gypsum deposition (i.e., less scaling) on system components and reduced sludge generation resulting in less return water for treatment. Despite the relative simplicity of the process, the application of the technology requires careful discrimination, and the "experience factor" for implementation is an important consideration that should not be over looked.

Jan 1, 2000

By Fernando Vital Silva

O processo de lingotamento contínuo consiste de uma série de etapas que promoverão a extração de calor de maneira controlada do aço líquido, com o objetivo de promover sua solidificação. Uma vez que a solidificação é considerada uma transformação de fase, regida essencialmente pela troca térmica, o enfoque do processo de lingotamento contínuo se encontra direcionado para o perfil térmico de resfriamento do aço desenvolvido ao longo dos veios da máquina. É extremamente importante para a qualidade final do tarugo que este processo de extração de calor ocorra a taxas controladas, de maneira contínua e uniforme em todas suas faces. Segregação, trincas e romboidade são alguns dos problemas de qualidade que podem ser originados devido a um controle não assertivo ou deficiência do sistema de refrigeração. Os tarugos lingotados do aço 1545-D, produzidos na máquina de lingotamento contínuo da Votorantim Siderurgia Barra Mansa, apresentavam com frequência trincas sub-superficiais nas quatro direções de resfriamento e a uma distância constante da superfície do tarugo. Através de equações de solidificação foi constatado que a profundidade em que as trincas se encontravam nos tarugos correspondia a um trecho da máquina no qual existia gap de refrigeração, provocando reaquecimento do material e o surgimento de trincas devido ao regime de contração/dilatação ao qual o mesmo estava submetido. Tais conclusões permitiram comprovar falha no projeto de refrigeração secundária da máquina.

Jul 30, 2018

By Liming Yuan

Barometric pressure changes affect air density, leading to change in the mass of the gas in the gob. When the barometric pressure decreases, the volume of gas in the gob expands, while the volume of gas contracts when the barometric pressure increases, causing the gob to breathe out and in. Although the concept of gob ?breathing? is simple, its effect on spontaneous heating of coal in the gob area is not clear. In this study, computational fluid dynamics (CFD) simulations were conducted to model the spontaneous heating of coal in longwall gob area under measured barometric pressure changes. A single longwall panel using a bleederless ventilation system was simulated. If there is no barometric pressure change, the intake airflow rate is equal to the return airflow rate. When the barometric pressure changes, these two airflow rates are no longer equal, and the difference between the two airflow rates represents the airflow rate the gob breathes in and out. The effect of inflow and outflow of gas on the potential spontaneous heating in the gob was investigated using the CFD model developed in our previous study. The effect of barometric pressure changes on the spontaneous heating was found to be dependent on the gob permeability and the coal oxidation rate. The effect of barometric pressure changes on oxygen concentrations in the gob was also examined.

Jan 1, 2010

By G. R. Dasari

New Austrian Tunnelling Method (NATM) has been analysed by Finite Element method in two and three dimensions by Strain Dependant Modified Cam Clay (SDMCC) Model. The effects of construction sequence, stiffness of shotcrete and time dependency of shotcrete on surface settlement magnitude due to the NATM have been studied. Settlements obtained in 2D analysis, as expected, found to be more than the observations. The surface settlements obtained in 3D analysis found to be about 3 times less than equivalent plane strain analysis. This is due to mobilisation of soil strength around the tunnel face and soil-tunnel lining interaction. About 40% settlements occurred due to excavation of face at the monitor section and 60% after the excavation crossed monitor the section.

Jan 1, 1996

By Robert Hopler

In accordance with the 57th section of the Explosives Act, 1875, the following report on the working of the Act during the year ending December 31, 1903, is submitted. There have been no modifications of the law during the year. No complaint is made of any falling off in the general condition of factories and magazines, and in one instance only during the year have legal proceedings been taken for any irregularity. The occupiers of factories and magazines have invariably shown perfect readiness to remedy any defects, and the managers have themselves in many instances introduced improvements tending towards greater safety. The number of deaths (5) from accidents by fire or explosion in the manufacture of explosives is below the average for the decade (6•4). Looking to the large number of persons employed in this trade, the number of deaths is not excessive and will compare favorably with the death-rate in other dangerous trades. Notwithstanding the large increase in the manufacture of explosives, the average number of deaths has greatly decreased since the passing of the Explosives Act, whereas the number of fatal accidents with explosives under conditions to which the Act does not apply appears to increase with the extension of trade.

Jan 1, 2006

By Danny Riley, Brian Curry, Sandya Govindaraju, James Bain

Acute vibration causes vasoconstriction in naïve human subjects1. Vibration-induced decrease in skin perfusion has also been reported in the rat-tail vibration model 2. After vibration exposure, rat-tail arteries demonstrate vacuoles in smooth muscle cells, similar to that caused by pharmacological vasoconstrictors3. This study addressed the effects of different frequencies, durations and patterns of vibration on lumen size and vacuole formation using the rat-tail vibration model in male Sprague-Dawley rats (~300 g). Methods The different groups were: 4-hr continuous vibration at 30, 60, 120 and 800 Hz; continuous exposure durations of 5 min, 1 hr and 4 hr at 60 Hz; and 4-hr cumulative exposure of 60 Hz delivered intermittently in cycles of 10 min on and 5 min off. Acceleration was set at 49 m/s2 r.m.s. for all frequencies. Unanesthetized rats were restrained in cages on a nonvibrating platform with their tails placed on a vibrating stage driven by a B&K motor (4809). The sham control animals were also placed in the vibration apparatus but not vibrated. Room temperature was controlled at 25 ± 1°C. Ventral arteries from proximal tail segments 7 were immersion fixed in aldehydes, embedded in epon-araldite and sectioned (0.5 µm) for morphological analysis. Vascular lumen sizes were measured as the percent ratio of the lumen perimeter to internal elastic membrane length using Image J software (NIH). The number of vacuoles in the smooth muscle layer of each artery section was counted. Results Fig 1: Semithin sections of arteries. A. Sham control. B. 4-hr vibration 60 Hz. In vibrated arteries, the lumen decreases in size, and smooth muscle cells (SMC) exhibit vacuoles (arrow). Bar equals 40 µm for each panel. [ ]

Jan 6, 2006

By Fredrick L. Johnson

No mineral resources were identified during the investigation of the White Cloud-Boulder RARE II area. Only a few claims have been located in the area and only two workings were found. However, there has been considerable exploration and mining activity near the RARE II area. Sand and gravel resources are abundant but similar deposits occur closer to market areas. There are no known coal, oil, or gas deposits. Most of the RARE II area is underlain by volcanic rocks. The likeliest host rocks for metallic minerals are the metasedimentary rocks exposed in the south part of the area; there is potential for zinc and silver resources at a prospect in that part. Traces of scheelite and powellite were observed in the Kent Peak-Ryan Peak area along hair-line fractures in calcareous country rock. While no significant concentrations of the minerals were found, their presence, a northwest alignment of prospects with similar deposits, and an abundance of dikes near the deposits, suggest that the intrusive system (Summit Creek stock) exposed near the head of Little Fall Creek may extend to the northwest under the RARE II area.

Jan 1, 1983

By S. Fawell, H. R. Manouchehri

The main electrophysical properties, i.e., dielectric constant and electrical conductivity, of pure calcite, quartz and wollastonite mineral samples were measured and their triboelectric charge attributes were investigated by contacting minerals particles with different tribochargers made from different materials. In addition the energetic work function values for mineral samples were estimated due to their acquisition charge. Besides, the behaviour of triboelectrically charged of different particle size fractions of mineral samples were inferred. Finally an attempt were made to translate the findings from single mineral systems to a real carbonate ore. The results exposed good prospects to beneficate the examined minerals by triboelectric separation.

Jan 1, 2002

By A. Martikainen

Field tests concerning a fog mesh method for fog removal are discussed. The first tests were performed at the Pyhäsalmi Mine, Finland. As this study gave promising results, further studies were completed at the Orivesi Mine. The results of these most recent field tests are presented and the two studies are compared. The Orivesi test set consisted of four materials. These included air filter fabric, fibrous filter fabric, a plastic greenhouse mesh, and an aluminium mosquito net. The variation of the Orivesi results was more noticeable than what was found previously. The best fog removal effect of all tests was achieved with the aluminium mosquito net, while the plastic green-house mesh performed worst. The humidity reduction by aluminium net was more profound than any of its precedents. More mesh materials will be tested in the near future.

Jan 1, 2007

By M. Lu, E. Broch

Abstract: The formation and mechanism of rock cavern roof arches are studied and effects of rockbolts reinforcement are evaluated. It is concluded that a self-supported roof arch may be formed by the excavation. To stabilize such a roof arch, fully grouted rockbolts are effective. Tensioned cable anchors may have a negative influence on the arch stability. Zusammenfassung: Die Formation und der Mechanismus von Deckenbögen in Bergkavernen wird studiert und der Effekt von Verstärkung mit Bergbolzen wird bewertet. Es wird festgestellt, dass die Exkavation einen selbst-stützenden / freitragenden Deckenbogen formen kann. Eingegossene Bergbolzen sind effektiv um einen solchen Deckenbogen zu stabilisieren. Spannkabel können unter Umständen eine negative Einwirkung auf die Stabilität des Bogens haben. Résumé: Le mécanisme et la formation de voûtes dans les cavernes rocheures sont étudiés et l&apos;effet du renforcement par boulonnage est évalué. Nous arrivons à la conclusion qu&apos;une voûte autosupportêe peut être formée par excavation. Des boulons entièrement scellés par coulis de bêton s&apos;avèrent efficaces pour stabiliser de telles voûtes. Les tirants d&apos;ancrage peuvent quant à eux nuire à la stabilité de la voûte.

Jan 1, 2003

By Avery H. Reed

RECORD production of portland cement, crushed limestone, marble, lime, and clays highlighted the mineral industry of Alabama in 1959. Among the States, Alabama ranked second in production of bauxite, and third in output of iron ore, scrap mica, and native asphalt. Alabama&apos;s mineral industry was dominated by the mining and processing of coal and iron ore, which accounted for 51 percent of the total value of production in 1958 and 1959. Other important industries were cement manufacturing, petroleum, and stone quarrying. Leading companies were Tennessee Coal & Iron Division of United States Steel Corp. (coal;. iron ore, limestone, lime, and magnesium compounds), Southern Cement Co. Division of American-Marietta Co. (cement, lime, limestone, and miscellaneous clay) , Woodward Iron Co. (coal and iron ore), Alabama Power Co. (coal), and Ideal Cement Co. (cement lime, and miscellaneous clay) .

Jan 1, 1960

For the third successive year it appears that demand for platinum will exceed supplies of newly-mined metal, forecasts Johnson Matthey in its "Platinum 1987 Interim Review." Based on data available at the end of August 1987, Johnson Matthey estimates that western world demand for platinum could exceed 93t (3 million oz) for the first time ever in 1987. Given a likely increase in demand of 4.3t to around 94t (140,000 oz to around 3.02 million oz), up by about 5% over 1986, there would be a 1.8- to 2.2-t (60,000- to 70,000-oz) shortfall in 1987 supply. South African mines enjoying undisrupted production last year after strikes affected Impala&apos;s output in 1986. The rate of increases in western world supplies, though, has probably not kept pace with the growth in demand. A downturn in US demand for platinum was counterbalanced by substantially increased purchases from Japanese and Western European consumers of the metal. Total imports of platinum into Japan in 1987 may have reached a record level of 45t (1.45 million oz). The largest source of demand for platinum remains its use in autocatalysts US and Japanese auto manufacturers reduced their platinum purchases in the wake of falling car production. Therefore, a small decline in overall 1987 sales of perhaps 780 kt (25,000 oz) was expected in 1987. Western European demand, however, rose strongly as a result of increased output. The spread of exhaust emission control regulations has sharply boosted the number of cars equipped with three-way catalysts containing platinum and rhodium. Western European auto makers probably needed 5.6t (180,000 oz) of platinum last year, a 50% increase over 1986. The jewelry industry, the second largest user of platinum, increased its offtake of platinum in 1987. Japan, the key to the jewelry industry&apos;s consumption of platinum, could absorb 24.8 to 26.4 (800,000 to 850,000 oz) in 1987, compared with 23t (740,000 oz) in 1986. Platinum has wide and diverse applications in industry. Other major users are the chemical, glass, electronics and petroleum industries. They were expected to increase their aggregate demand by about 1.8t (60,000 oz), or 11% in 1987. Investment demand for small platinum bars and coins of up to 311g (10 oz) dropped back in relatively inhospitable conditions. This, after rapid increases in recent years and a surge in US demand in 1986. However, Japanese investors purchasing bars weighing 500g or 1 kg (16 to 32 oz), and considered more speculative, recovered last year. Over the first eight months of 1987, platinum performed strongly on the open market with average prices well up from 1986 in dollar terms. But the increase was less marked where measured in sterling or yen. Platinum ad¬vanced by $3.70/g ($115 per oz) between Jan. 1 and mid-September with the average price having been surpassed only in the heady days of 1980. Johnson Matthey believes that supply and demand appear likely to keep more or less in step on a gently rising path. The recent open market volatility will continue with prices fluctuating widely over short periods. Writing in mid-September, and basing its view on the tangible evidence of platinum&apos;s price fall since the review was written, the company&apos;s assessment of price prospects is unchanged. Demand for platinum remains strong all-round. In October, imports of platinum into Japan were exceptionally high. And in the US and Japan there was a marked resurgence of demand from private investors. Although market sentiment may have been influenced in part by the news of several potential new platinum mines in South Africa, the full effects of these prospects on supply, even if they were all to materialize, would not be felt before the early-mid 1990s, Johnson Matthey said. According to the review, no radical change in platinum supplies is discernible in the near-term. Incremental growth from South Africa can be expected as the major producers continue to make the most of their existing resources. The Soviet Union may be keener to sell than it appeared earlier in 1987, especially if prices hold up, but a substantial increase is improbable. Canadian supplies are not capable of much variation from present levels. The palladium-rich Stillwater mine will make a modest contribution. Referring to the investment market, Johnson Matthey concluded that despite this year&apos;s reduction in sales of small-denomination investment products, platinum does appear to have established itself with private investors. Bearing in mind how business multiplied in comparatively unfavorable conditions before 1986, it is reasonable to look for a resumption of growth once the climate improves.

Jan 2, 1988

Study on Mineral Processing for a Cassiterite Ore in Southwest China

Sep 13, 2010

By Arthur Aracely de Araujo Alves, Joelson Inacio Dantas Teixeira, Flanelson Maciel Monteiro, Carlos Vinicios Galdino de Melo, Pedro Henrique Medeiros Câmara, André Luiz Moura dos Santos, Kleison Barbosa Cândido da Silva

A argila é uma matéria prima com diversas finalidades na indústria. Entre as principais características desse material, destaca-se por ser terrosa, de granulometria fina, e suscetível à moldagem em função da consistência plástica que adquire em presença de certa quantidade de água. No caso do revestimento cerâmico, estes podem ser classificados de acordo com características do processo, propriedades tecnológicas e aplicações. A cor de queima do suporte é um fator de grande importância tecnológica e classifica os revestimentos em produtos de cor vermelha e produtos de cor branca. Contudo, este trabalho tem como objetivo o estudo das propriedades tecnológicas de uma argila de coloração branca, oriunda da cidade de Vera Cruz/RN que é localizada na microrregião do agreste potiguar, a fim de analisar suas propriedades tecnológicas e indicar sua viabilidade econômica. Para tanto, os corpos de prova foram confeccionados por pressão uniaxial, usando uma prensa hidráulica com uma pressão de 21 MPa. As amostras foram sinterizadas em um forno tipo mufla nas temperaturas de 900°C, 1000°C e 1100°C, com taxa de aquecimento de 10 °C/min e isoterma de 60 minutos. As propriedades tecnológicas das amostras foram analisas usando os ensaios de retração linear (RL%), massa específica aparente (MEA), absorção de água (AA%), perda ao fogo (PF%) e porosidade aparente (PA%). A composição química da argila foi analisada através da fluorescência de raios-X (FRX). Ao final do processo observou-se que a argila pode ser usada para compor massas cerâmicas, especialmente pela sua coloração clara, todavia os valores dos ensaios de AA% e PA% foram elevados o que demostra que o material necessita de outros componentes mineralógicos para ser usado industrial, especialmente na indústria de revestimentos.

Mar 1, 2019

By E. G. King

Heat of formation values for mercuric sulfide appear in all the comprehensive listings of thermodynamic data, but experimentally determined entropy values have been lacking. Consequently, all free energy calculations involving mercuric sulfide have been based upon estimated entropy values. This paper reports Bureau of Mines measurements of the low-temperature heat capacity of red mercuric sulfide (cinnabar) and the entropy value at 298.15° K. derived therefrom. The entropy value was combined with heat data to obtain free energy values for the formation of red mercuric sulfide from liquid or gaseous mercury and from rhombic or gaseous diatomic sulfur.

Jan 1, 1962