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By Mansoor Barati, Shaghayegh Esfahani

"The slag from extraction of ferrous and non-ferrous metals is a potential heat source which if treated properly can contribute to recovery of a significant amount of energy. The waste heat of slag may be used to generate steam, synthetic fuel gas, or electricity. Although several technologies have been investigated for this purpose, very little has been achieved in terms implementing the technology in industry. In this article, the development and application of various granulation techniques are reviewed and the methods to recover energy from granulated slag are discussed.IntroductionEvery year, more than 422 million tons of slag is being produced around the world as a by-product of the metal manufacturing at temperatures of up to 1300-1600°C [1, 2]. Currently slags are either disposed of or treated by processes such as granulation. Through the granulation process, most slags can be converted into a material which may be fully used as a cement feedstock. Conventional cement production is an energy intensive process with large emissions of CO2; therefore, the replacement can both be energy saving and environmentally friendly. However, for this purpose, the slag should have what is known as a “glassy” content (i.e. it should be amorphous) which requires rapid cooling rates that are not easily achieved due to the very low thermal conductivity. The main challenge in all these processes is to granulate the slag at a high cooling rate while the heat is also being recovered."

Jan 1, 2012

By Joaquim Luiz Monteiro de Barros

Com base na atual situação de restrição de disponibilidade e do custo da energia no Brasil, sistemas tipo Heat Pipe (tubos de calor) tendem a ser cada vez mais utilizados na recuperação do calor dos gases de exaustão nos processos de produção de gusa, para o pré-aquecimento de ar/gás, aumentando a eficiência energética global do sistema e reduzindo o consumo de combustível. Esta tecnologia agrega uma série de vantagens, quando comparada com os trocadores de calor tradicionais, pois possui um design compacto, transferência de calor uniforme em toda a área de troca térmica, alto grau de vedação, de forma a evitar o risco de vazamento e mistura/contaminação entre os fluidos quente e frio.

Sep 25, 2017

By Francis Foley

IN examining steel under the microscope, one is constantly confronted with structures that are difficult to interpret. Recently, in a collection of samples for exhibition purposes, the writer found apiece of open-hearth runner metal, 2 in. (50 mm.) in diameter, that had been fractured for use as a sample of cast-steel structure. On polishing and etching a section for the purpose of photographing a field to typify the microstructure of steel in the "as cast" condition, a variety of structures was found (Fig. 1) so arranged as to arouse interest at once. For a distance of about 0.065 in. (1.6 mm.) from the skin of the runner, normal ingot structure was found (Fig. 2); this was followed by a zone, about 0.215 in. (5.5 mm.) wide, of considerably lower carbon content in which occurred a most pronounced Widmannstättian structure (Fig. 3); from this point on to the center of the runner, the metal was again of normal ingot structure (Fig. 4). Representative samples taken from the metal in the three zones showed the following analysis: C Ni Cr Metal from skin 0.34 1.26 0.63 Widmannstättian zone 0.21 1.18 0.63 Metal from center 0.34 1.32 0.67

Jan 7, 1919

pAbad, Leopoldo F., Min, Engr,, Div. of Mines, Bureau of Science Manila, P. 1. '23 Abadilla, Quirico A,, Geol., Lago Pet. Corp Box 172, Maracaibo, Venezuela, '20 Abbey, Robert Graham, The W. W. Sly Mfg, Co Train Ave., Cleveland, Ohio. '21 Abbott, A. N., Mines Supt., Mazapil Copper Co., Ltd Concepcion del Oro, Mexico, '28 Abbott, Clarence E., Mgr., Mines & Quarries, Tenn, Coal, Iron & R. R, Co,, 1242 Brown Marx Bldg,, Birmingham, Ala. '04]

Jan 1, 1928

By James P. Ulery, Jon C. Volkwein

The U.S. Bureau of Mines investigated a method of using inert gas to prevent the formation of explosive gas mixtures in auger highwall mining of coal. A combination of gasoline and diesel engine exhaust gases was introduced into the auger drill hole using a short section of pipe located at the collar. Gas samples were taken and analyzed on-site with infrared detectors for oxygen, carbon dioxide, methane, and carbon monoxide. Evacuated bottle samples were also taken and analyzed by gas chromatography in the laboratory. These gas results were analyzed for explosibility. Coal samples from various depths were used to obtain the gas content of the coal using the modified direct method. Personal expo- sure to carbon monoxide was also monitored. The highest methane level observed was 9.55%. The levels of inert gas (carbon dioxide and nitrogen) were sufficiently high to prevent any ignition of the methane. Results showed that for all conditions during mining, gas concentrations were nonexplosive. The gas content of the coal was about 0.30 cm3/g. The maximum personal time-weighted average sample for carbon monoxide was 20 ppm. This system provides a safe, inexpensive, simple method for pre- venting explosions during auger mining.

Jan 1, 1993

By C. Musingwini

The South African mining industry continues to be a major source of employment at a time when at least 25 per cent of the working age population is unemployed. At the same time the industry faces a skills shortage in many of the disciplines necessary for its future health. The University of the Witwatersrand, University of Pretoria, University of Johannesburg, and University of South Africa have historically produced mining graduates for the South African industry, with any shortfall being met by the recruitment of overseas graduates. More recently the global shortage of engineers and other mining industry professionals has seen a reversal of this trend and a very significant emigration of well-educated and highly skilled personnel. The traditional career path for mining graduates is in production and mine management. However, there is the parallel and possibly more pressing need for specialized skills in such fields as ventilation, rock engineering, mine planning, mineral resource evaluation, and mineral asset valuation. It is in these essential areas that chronic shortages continue to hamper the development of the industry and may well frustrate its ambitions to be safe, healthy, and profitable into the future. The permeability of skills across sectorial boundaries within the mining industry requires that skills shortages in the platinum sector are not looked at in isolation, but within the context of the entire industry. This paper reviews the efforts being made by the universities at both undergraduate and postgraduate levels to meet the needs of the South African mining industry, in terms of the required numbers and the range of specialized skills.

Jan 1, 2012

By Maryam Motamed, Jeremy Stone, Leigh Anne Zhang

Controlling and predicting ground movements are essential to the design of shoring systems. The Courthouse Commons tunnel in San Diego, California, included a 56-foot-deep temporary shaft as a launching point for tunneling using the Sequential Excavation Method (SEM). The rectangular shaft was unique in that it was surcharged on one wall by an 11-story building and employed a hybrid support of excavation design. An array of geotechnical instrumentation was used to monitor lateral and vertical movements at the ground surface. This paper compares the measured ground movement with the predicted ground movement from various excavation stages

Dec 1, 2022

By W. J. Fene

A comprehensive study of all bituminous coal-mine fatalities occurring in Pennsyl¬ vania during the 5-year period, 1926-1930, was made to try to determine the factors that in¬ fluence accidents which cause these fatalities. During this study some two thousand reports of fatalities were reviewed, and pertinent information as to causes and influencing factors were tabulated therefrom. These tabulations are discussed in detail, and in some instances recommendations are made with a view to reducing the hazards in certain classes of these accidents.

Sep 1, 1931

Factors which cause thiourea consumption in gold-leaching systems include adsorption by gangue mineral particles, complexation with base metal ions, thermal degradation, and oxidation by air/ferric iron. Of these factors oxidation by ferric iron is the most significant factor. Of course, ferric sulfate is desired as an oxidant for the gold leaching reaction, but an excess of ferric sulfate leads to high thiourea consumption. In this regard, the rate of gold leaching by thiourea must be balanced against the rate of thiourea decomposition. It is important to note that the thiourea decomposition reaction in ferric sulfate solution is relatively slow in pure solutions and has been found to be first order with respect to both thiourea concentration and total ferric iron concentration. However, when mineral particles from gold-bearing ores or concentrates are present, the decomposition rate can become quite significant. As might be expected, the catalytic activity of mineral surfaces varies with particle composition and size. Experimental results are discussed with respect to the consumption of thiourea.

Jan 1, 1997

By I. Dymov, W. Phillips

A process has been evaluated, on a continuous pilot plant scale, to treat refractory gold arsenopyrite/pyrite concentrates. The process consisted of biological leaching to partially oxidise sulphides, followed by pressure leaching for complete sulphide oxidation and arsenic precipitation, followed by liquor neutralisation and cyanidation of the autoclave residue for gold recovery. This paper provides a brief description of the treatment flowsheet and discusses some of the main parameters and results of the process. During integrated pilot plant campaigns, it was confirmed that acceptable sulphide oxidation and gold extraction of 96-98% could be achieved by a two-stage oxidation with BIOX® (4 days total retention time) followed by PDX (40 minutes retention time at 220°C). Only partial arsenic precipitation was achieved in the autoclave, followed by complete precipitation by neutralization under atmospheric conditions. The overall process could be significantly simplified, and capital and operating costs reduced, with a flowsheet modification allowing all of the BIOX® liquor to bypass the autoclave directly to the neutralization circuit.

Jan 1, 2004

By Robert E. Kirby

The potash mine and refinery of AMAX Chemical Corporation is located 26 miles east of Carlsbad on the north end of the potash producing areas. This property was developed between 1949-1952 and production of muriate began in August 1952. Two shafts, located 400 feet apart, were sunk to the ore zone 900 feet below the surface. A 15-foot diameter ore hoisting shaft equipped with a 1000-ton ore pocket, crusher and automatic skip loading equipment plus a 20-foot diameter service shaft with a curtain wall for exhausting air were provided. Sylvinite production to date has been from the first ore zone, stratigraphically, the lowest of ten identified mineralized zones in the salt section. This first ore zone has been the top producer of Muriate of Potash over the years. In our area we do have some very marginal mineralization in the third ore zone some 35 feet above the first. We have not mined from this seam as yet but we are investigating the economics very closely with access slopes and an experimental mining panel. Our ore seam is generally flat lying but does have local gentle rolling with grades from 2% to 5%. The mine was designed and developed from the beginning with conventional mining practices and rail haulage from the mining section to the ore pocket. As mining progressed in the early years, production increased from less than one million tons annually to a maximum of 3,935,000 tons in 1964. Efficiency also kept pace with the increasing production and continually improved until the efficiency of the production crews reached an average of 100.3 tons per manshift in 1964.

Jan 1, 1974

By Serdar Aktaş, Özgün Küçükoğlu, Burcu Nilgün Çetiner, Mehmet Hakan Morcalı

This study compares the cementation performance of metallic iron, metallic aluminum, and metallic tin in terms of the reaction conditions and parameters in synthetic antimony chloride solutions. The effects on the antimony recovery (%) caused by the cementators’ types, stirring speed, reaction time, and temperatures were explored thoroughly. The cementation kinetics of antimony were also explored for each cementator. The activation energies were determined to be 10.99, 9.09, and 13.58 kJ mol– 1 for Al, Fe, and Sn, respectively. The results reveal that the reaction is diffusion controlled, and comparable results were obtained for each cementator. At 25 °C, 40 mg of iron powder was found to reduce all antimony ions (i.e., approx. 99% recovery), but even when 100 mg of Al and Sn cementators were used, the antimony recovery did not reach 100%. This result shows that iron is the best candidate to cement antimony out of the solution.

Jan 28, 2022

By K. E. Waters, J. E. Nesset, F. Rosenblum, J. A. Finch

An advanced laboratory-scale weathering apparatus has been developed at McGill University to study the effects of weathering (ambient temperature oxidation) on the self-heating of sulphides. Previous work by the authors has shown that the problematic self-heating of sulphides is inherently linked to the degree of oxidation (weathering) of the minerals: un-oxidized active sulphides exhibit little or no self-heating while the same material when weathered can generate extensive self-heating bringing temperatures well above 100 0C. In this study the effects of environmental conditions (weathering time, ambient temperature, sample moisture, relative humidity, and oxygen content) were evaluated with respect to the self-heating response of a pentlandite-pyrrhotite nickel sulphide concentrate.

Jan 1, 2015

By W. F. Marshall

This report describes exhaust-emission data from 10 diesel engines: six 4-cycle, direct-injection, naturally aspirated engines; two 4-cycle, direct-injection, turbocharged engines; one 4-cycle, precombustion-chamber, turbo-charged engine; and one 2-cycle, direct-injection engine. These engines were tested over a 3-year period (1968-70). Lowest emissions were obtained with a precombustion-chamber engine. Emissions from the 2-cycle, direct-injection engine fell within the range of emission rates for the 4-cycle, naturally aspirated, direct-injection engines. Excluding the precombustion-chamber engine and excepting one of the 4-cycle, naturally aspirated engines, carbon monoxide emission rates were about the same for all engines tested. Test data on smoke, odor, and emissions of hydrocarbons, oxides of nitro-gen, carbon monoxide, and aldehydes are given.

Jan 1, 1971

By Isabella Lancellotti, Fabrizio Passarini, Luisa Barbieri, Fernanda Andreola, Ivano Vassura, Luciano Morselli

"The techniques able to incorporate wastes by means of a heat treatment present the advantage to fix the residue with chemical bonds. Among these techniques there are vitrification and sintering which are characterised by different operating temperatures in the range of 950-1500°C and the involved raw materials develop silicatic crystalline phases and glassy matrices capable to immobilize heavy metal contents in the waste matrix. In this work incinerator bottom ash, polishing and glazing ceramic sludges have undergone to thermal treatments in order to valorise the waste as secondary raw material for the obtainment of re-products. The chemical efficiency of the process adopted has been evaluated by comparing the results of release tests applied to the as-received wastes and to the thermally treated materials in order to verify the effectiveness of the different matrices to fix the waste components.IntroductionVitrification is one of the most promising technological options for the treatment of some kinds of waste. The high temperature involved in the process (1200-1500°C) leads to the complete destruction of organic pollutants, such as dioxins, and glassy network formed can incorporate heavy metals. Some vitrification processes naturally occur: glasses produced by volcanic eruptions, such as obsidians (Na2O-K2O-Al2O3-SiO2) and basaltic (CaO-MgO-Al2O3-SiO2) rocks, are basically inert materials even when they contain toxic elements, because these are embedded in an extremely stable glassy matrix. The disadvantage of vitrification is that it is an energy-intensive process involving relatively high costs, therefore its use is better justified if a high-quality product with optimised properties can be fabricated. The most effective way to improve the properties of the vitrified material is the transformation into glass ceramic. This is a fine-grained polycrystalline material (typically from 50% to 98% of the volume may be crystalline) formed when a glass of suitable composition is heat treated and hence undergone to controlled crystallisation (phenomenon named devitrification). The three key variables in the design of a glass-ceramic are: glass composition which controls glass viscosity related to the effectiveness of nucleation and rapidity of crystallisation; glass-ceramic phase assemblage (that is, the types of crystals and the proportion of crystals to glass) which is responsible for many of the physical and chemical properties; nature of the crystalline microstructure (crystal size and morphology and the textural relationship among the crystals and glass) which is the key to many mechanical and optical properties. In particular, a partly crystalline material can be obtained by powder sintering."

Jan 1, 2008

By A. Mainza, A. Mabentsela

A finite element model of a 5 m radius DC arc ilmenite furnace in idling mode was used to test the notion that the slag solidifies when it comes in to contact with colder pig iron, thus constituting the initial step in the formation of solid slag at the slag-pig iron interface. It was found that a slag that is 150°C hotter than the pig iron does not solidify at the interface. The 150°C temperature difference between the slag and pig iron is a result of solid slag at the slag-pig iron interface, not the other way around as suggested in the literature. Calculations show that the thickness of the frozen slag at the slag-pig iron interface is 1.7 cm for the furnace used. It is proposed that slag solidification begins with the slow co-current flow of molten slag and pig iron in the outer parts of the furnace. This provides enough time for molten slag to interact with molten pig iron without solidifying. As the reduction products form due to reduction of the slag by carbon in the pig iron, the slag solidifies. This approach negates the need for the slag to solidify by merely coming into contact with an inherently colder pig iron. Making use of a low thermal contact conductance between the slag and pig iron was found to be sufficient to numerically capture the presence of solid slag at the slag-pig iron interface and to preserve the 150C difference between the slag and pig iron phase.

Mar 30, 2023

By A. J. Plumpton

Centrifugal air classification and li-quid-phase sedimentation are the principal methods of industrially sizing materials of dimensions smaller than those handled by screens. Increasing application of materials such as composites and high performance ceramics has furthered the need for closely-sized, fine, industrial mineral and synthetic products of controlled properties. Sedimentation can be used to separate very small sized particles but introduces problems of liquid-solid separation, de-agglomeration and drying. Some of the advantages and limitations of centrifugal air classification will be discussed and laboratory and plant measurements using centrifugal machines will be presented to support the discussion.

Jan 1, 1990

By Cesar Ccorahua, Pabel Alvarado

Los diseños de Open Pit con la Linea Media Del Banco, son la forma más eficaz de construir diseños de Open Pit. El diseño de un Pit puede cambiar en función de los precios de los metales, los costos y otras restricciones económicas, geológicas y ambientales; Estas restricciones deben establecerse en el modelo de bloque y debe establecerse una variable numérica y categórica específica. Los profesionales deben informar lo que está en el diseño basado en el Modelo de Bloques. Aunque el diseño se considera lento en software 3D, el diseño de la línea media del banco ejemplifica la flexibilidad y la eficiencia.

Sep 1, 2017

By K. V. Raj

As open pit mines continues to grow deeper, managing air pollution can become challenging. During arctic air inversion, the temperature of the air over the mine increases with altitude, and the cold, heavy, surface air is trapped in the pit. This problem is complex, and any solution will require an extensive understanding of the interactions between the aerodynamic movement of air, air inversion, meteorology, pollutant sources, and transport phenomena in the open pit mines. The availability of computational fluid dynamics (CFD) has elucidated the pollutant flow mechanism in open pit mines. Very few CFD studies have been published, especially the Large Eddy Simulation (LES), on the contaminant transport in deep open pit mines under arctic air inversion. The contaminant transport in an open pit mine under arctic inversion is due to a stable or nocturnal boundary layer in micro-meteorological terms. Understanding the physics of the stable boundary layer (SBL) is relevant to air flow and pollutant transport in deep open pit mines. This paper focuses on a Large Eddy Simulation (WMLES as Sub-Grid Scale Model) modeling of the SBL and pollutant transport in a large open pit mine.

Feb 23, 2014

By Gustavo Nucci Franco

A indústria do aço passa por seu pior período no Brasil e as empresas vêm buscando soluções para minimizar custos e garantir as operações com menos recursos. Ponto importante nessa busca de ganhos potenciais, a Logística vem, assim, merecendo uma atenção especial. Este trabalho apresenta esforços da AM Juiz de Fora, em parceria com a Franco Arbeit Engenharia, para reduzir o tempo de permanência de veículos em sua unidade e, com isso, evitar custos com o pagamento dos novos valores de permanência. Para isso, foram utilizadas modernas ferramentas de Simulação em Computador para que as soluções mais adequadas pudessem ser implementadas com sucesso.

Aug 17, 2017