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By O. A. Orumwense

The liberation of intimately disseminated impurities from the coal matrix often demands that the material be ground to a high degree of fineness. Similarly, some technologies for coal utilization require superfine particles (i.e., sizes less than ten microns). This implies additional costs for coal preparation plants due to the high energy and media costs associated with fine grinding operations. Besides, there are problems such as sever product contaminations due to media wear and impairment of the quality of coal. Hence, proper choice of grinding media type is important from the viewpoints of cost reduction and product quality.

Jan 1, 1993

This paper on the relation of Granite and Sedimentary Contacts to Victorian Mining will, it is hoped, be of interest to members of the Institute.The broad fact that gold often occurs' at or near the junction of granite with sedimentary silurian or metamorphic rocks has been noted by some Victorian geologists, miners, and prospectors; but the fuq practical value -of the fact does not seem to have been fully realised by prospectors. Glancing at the Geological" Map of Victoria, one can see that many of our goldfields 'are situated at or near the junction of granite with Palceozoic sedimentary formations, and that some of our alluvial fields are on granite. Many prospectors are possessed of this knowledge but when prospecting a contact locality, they would be just as likely to confine their search for auriferous matrices to spots a quarter of a mile on the sedimentary side, as on the actual contact line of two formations.

By AIME AIME

ON May 5, the Washington, D. C., Section, A.I.M.E., devoted its meeting to the many-sided and perplexing question of mineral stock-piling for peace. Opening the symposium, Harry J. Wolf, of the War Production Board, outlined the problem under six heads: (1) Technical. Mechanical, chemical, or metallurgical importance of specified materials, emergencies that might arise, relative scarcity, and critical value of stock piles during emergencies. (2) Economic. Cost to Government, influence of Government stocks on commercial relationships and markets, effect of availability of items as a con¬structive influence on industry, Administration policies now and during postwar period. (3) Legislative. Need for immediate legislative action, need for legislation on postwar conditions as well as on current requirements, a constructive basic policy to prevent political manipulation. (4) Military. Consideration of re¬quirements and supplies bearing on national safety and needed for manufacture of equipment, and adequate reserves of scarce materials for research or experimentation by military agencies. (5) International. Interests of the United Nations in contradistinction to those of the United States; effects of nonisolation policy on nature, location, and administration of stock piles. (6) Negative stock-piling. Question of United Nations' legislation to prevent stock-piling by Axis nations after the war and who shall purchase stock-pile materials and during what periods.

Jan 1, 1943

By Rodrigo Vitorino da Silva

Ligas a base de zircônio utilizadas na indústria nuclear estão sujeitas à formação de hidretos que são causadores de efeito deletério no material. Para aumentar o tempo de operação desses componentes, é necessário o desenvolvimento de novas ligas que retardem ou diminuam esse efeito. Este trabalho tem como objetivo avaliar a influência da adição de elementos de liga em uma liga inédita a base de Zr-Nb na absorção de hidrogênio, através de testes que avaliam a absorção de hidrogênio e a formação de hidretos no material após processamento termomecânico e comparar seu desempenho com duas ligas comerciais. Para tal, foram realizados ensaios de microdureza, cinética de absorção de hidrogênio e micrografias. Os resultados de microdureza Vickers das três ligas estudadas, após o processamento termomecânico, são muito próximos. As curvas de cinética de absorção de hidrogênio mostram que a liga Zr-Nb-Sn-Fe apresenta melhor comportamento que as demais uma vez que o tempo para o início de absorção foi maior. As micrografias indicam que a liga proposta apresenta um desempenho superior em relação à morfologia dos hidretos visto que os mesmos são mais curtos e alinhados.

Aug 17, 2017

By João Paulo Sousa Coelho

A sedimentação consiste em uma operação unitária de separação entre sólidos e líquido, realizada em tanques denominados sedimentadores, que se baseia na ação do campo gravitacional sobre as partículas para decantá-las e removê-las da água. Sua eficácia é extremamente dependente do tamanho das partículas, tendo em vista que a velocidade de sedimentação é diretamente proporcional ao tamanho delas. Dessa forma, no espessamento das lamas, é imprescindível a utilização de reagentes químicos (coagulante e floculante) que possibilitem a formação de agregados de maior tamanho. Neste contexto, realizou-se esse trabalho para investigar o efeito da dosagem desses reagentes sobre a sedimentação de lamas de minério de ferro. Para isso, empregou-se o Planejamento Fatorial, por meio do qual se planejou uma série de ensaios de sedimentação, variando-se as dosagens desses reagentes. As variáveis resposta monitoradas foram: a área unitária de sedimentação, o índice de turbidez do líquido sobrenadante e o percentual de sólido do material sedimentado. Baseado nos resultados experimentais, concluiu-se que os menores valores de área unitária de espessamento foram obtidos em dosagens maiores de coagulante e floculante, ao passo que dosagens excessivas desses reagentes, especialmente de floculante, provocaram um aumento do índice de turbidez do líquido sobrenadante e uma redução do grau de adensamento da polpa espessada.

Oct 30, 2017

By Paula Aliprandini

Os minérios limoníticos de níquel apresentam na sua composição metais como ferro, níquel e cobalto, sendo o primeiro o elemento majoritário. A presença majoritária de ferro prejudica a separação dos demais metais que possuem interesse comercial. Para remoção do ferro, técnicas hidrometalúrgicas são usadas. A extração por solventes é uma técnica com foco na separação seletiva de metais. Neste trabalho, foi preparada uma solução sintética baseada nas concentrações dos metais presentes na lixiviação de um minério limonítico de níquel. A solução foi colocada em contato com o extratante Cyanex 272. Este extratante é conhecido pela sua seletividade ao ferro em valores de pH próximos a 2,0. As amostras foram analisadas utilizando a técnica de Espectroscopia de Fluorescência de Raios X por Energia Dispersiva (EDX). Após concluídos os ensaios foi encontrado que durante a extração do ferro, o cobalto foi coextraído junto, mesmo em pHs entre 0,5 e 2,0, indicando que a presença do ferro altera o comportamento do cobalto.

Aug 17, 2017

By S. J. Schatzel, J. D. Addis, V. Gangrade, L. L. Chasko, C. A. Hollerich

A ventilation study using tracer gas was conducted at a western US coal mine. The objective of the study was to evaluate the movement of longwall face air exchanges between the face and worked-out area and to document the presence or absence of face airflow pathways between these locations. The mine operator uses a bleederless longwall ventilation system with a back return and a blowing mine ventilation system. The study was conducted on an active panel and included both underground and surface monitoring sites. The study used sulfur hexafluoride (SF6) released as a slug on the longwall face and in the front of the gob inby the face. The velocity of the tracer gas movement in the gob was 0.019 m/s (3.7 fpm). The rate of movement for the overall tracer gas slug averaged about 0.0091 m/s (1.8 fpm). A separate tracer gas test initiated with the release of SF6 into the legs of the first shield showed the existence of more than one pathway of face air in the general direction from the headgate towards the tailgate corner. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of methane emitted from the face and caved gob. A more detailed characterization of longwall system air and gas movement allows a mine to better assess its ventilation design for controlling gas on the face and in the gob.

By Patrícia Ortega Cubillos

O objetivo do presente trabalho foi avaliar e comparar a composição química e microestrutura de dois fabricantes (nacional e importado) de haste femoral fabricados em aço inoxidável austenítico ABNT NBR ISO 5832-9. As análises químicas dos principais elementos foram realizadas utilizando espectrometria de emissão ótica por descarga luminescente. A microestrutura das hastes foi caracterizada por microscopia óptica, microscopia eletrônica de varredura e difração de raios X. Medidas de dureza Vickers também foram realizadas neste estudo comparativo. As hastes nacionais e importadas exibiram pequena quantidade de partículas de nitreto (fase Z) dispersas na matriz austenítica e tamanhos de grão similares da austenita. Por outro lado, o aumento de 32% observado nos resultados de dureza da haste importada em relação à haste nacional foi atribuído às diferenças de composição química entre estas hastes. Foram identificadas microinclusões ricas em Al nas hastes importadas e microinclusões ricas em Mg nas hastes nacionais. Embora tenham sido observadas algumas diferenças entre as hastes nacionais e importadas, ambas atenderam os critérios de composição e microestrutura da norma ABNT NBR ISO 5832-9.

Aug 17, 2017

By D. Moradkhani

The heap leaching of oxide copper ores with copper cathode recovery by solvent extraction and electrowinning is now well established as a low-cost method of copper recovery. The main purpose of this study was to extract copper from the copper low-grade oxide ore of Chodarchaei mine using column leaching. The copper oxide ore contained 1.1% Cu and 1.75% Fe. The mineralogical analysis indicated the malachite (Cu2(OH)2CO3) was mainly composed of oxidized phases. The sulfuric acid leaching experiments were performed under the laboratory conditions. The influence of several parameters on the course of the reaction such as particle size, acid concentration, flow rate, and time was examined. The optimum collective extraction of copper and iron was obtained at a particle size of +10-15 mm for a leaching duration of 3 days with sulfuric acid concentration of 100 gpl and using a flow rate of 2.5 cc/min. Under these conditions, the recovery of copper and iron were 98.54% and 41.99%, respectively. Keywords: column leaching, copper, iron, working diagram.

Sep 1, 2012

By Jouko L. Lehtonen

Sheet pile walls can be sealed watertightly using various methods. The objective of this paper is to introduce a new innovation comprising the use of continuous cement grouting during embedding. The method has been tested on a field test site and installation and permeability features have been observed and analyzed. Installation can be carried out using traditional sheet piling machinery, merely some additional grouting equipment is needed. Installation speed of grouted sheet piles corresponds to that of conventional embedding. The permeability of the tested method is satisfactory in applications where e.g. polluted soil or water has to be isolated from the surrounding environment. In addition, this method can be used for conventional retaining walls where very low permeability is required or for reduction of soil vibration, e.g. close to a railway embankment. The new method to grout simultaneously and continuously during embedding has been developed based on respective innovations on impact driven steel piles.

Jan 1, 2006

By Anderson Azevedo Agra

O Pó de Aciaria Elétrica (PAE) é um resíduo sólido gerado durante a fabricação de aços em usinas com Forno Elétrico a Arco (FEA). Esse resíduo contem quantidades apreciáveis de metais, tais como ferro e zinco, tornando sua reciclagem interessante não só do ponto de vista ambiental como econômico. Assim, esse trabalho teve como objetivo avaliar a autorredução de misturas de pó de aciaria elétrica e coque verde de petróleo (CVP). Para isso, misturas e pelotas de PAE:CVP, com variados teores de redutor, foram submetidas a ensaios de autorredução em termobalança e, na forma de pelotas autorredutoras, numa retorta aquecida em forno elétrico vertical. A redução das amostras foi analisada a partir da perda de massa das misturas. Além disso, a redução das pelotas autorredutoras foi observada através de análises de difração de raios X. Nestas análises foi possível verificar decomposição da Franklinita e a redução dos óxidos de Ferro e Zinco.

Aug 17, 2017

By Khamis Y. Haramy

This U.S. Bureau of Mines report describes the use of Bureau-developed flat and cylindrical hydraulic borehole pressure cells. A brief description of the fabrication, installation, and pressurizing equipment is given and pressurizing procedures are discussed. Theories available on evaluation of data from the flat and cylindrical pressure cells and examples of data analysis and stress evaluation are also presented.

Jan 1, 1991

By W. J. Huff, G. W. Jones, I. Spolan, R. E. Kennedy

"INTRODUCTION Information on the exploeibility and ease of ignition of acetylene is important in connection with investigations by the Bureau of Mines and others seeking the causes of explosions in medium-pressure acetylene generators.A previous report 6/ gave preliminary results of an investigation made by this Bureau to determine the causes of these explosions. This report indicated the need of amending Federal specifications for ""1/4 by 1/12"" carbide to reduce the amount of fine sizes permitted under the specifications then in force. Tests described in the above report showed that certain sizes of carbide may, under certain conditions, attain excessively high temperatures when acetylene-water vapor mixtures are passed through carbides for extended periods.Federal specifications P-0-101, Amendment 5, June 28, 1944, are now in effect. These latest specifications permit a maximum of 7 percent of ""1/4 by 1/12"" carbide by weight to pass through a 0.0661-inch sieve and a maximum of 2 percent to pass through a 0.0555-inch sieve. Experience has shown that these specifications have insured a safer size range of carbide for medium-pressure acetylene generators.Although the improvement in the size range of the carbides has aided in the prevention of explosions, there have been explosions in which the carbide used at the time of the explosion met the latest Federal specifications."

Sep 1, 1945

By J. Masinja

The mining industry is known to be a potential major contributor to the industrial development of any economy. Large-scale mining has been going on in Zambia for the last 100 years. The impact of mining in Zambia has been to create a development corridor along the line of rail to the Copperbelt Province, where hitherto, mining was concentrated, and then to develop a large consolidated high-density economic zone covering an area of about 72 km by 60km. This area is home to a number of very large integrated copper/cobalt mining complexes. The mining zone has expanded to the Northwestern Province in the last 10 years, where the largest copper mine in Africa now exists, having produced about 300 000 tonnes of copper in 2011. The total output of the Zambian mining industry is now about 820 000 tonnes per annum with projections of reaching 1.5 million by 2015, due to new Greenfield investments expected to come online by then. These new mining industry developments have come on the back of strong and sustained high base metal prices, in the last 10 years or so, due to demand mainly from China and India. This new lease of life has increased the contribution of the sector to the national treasury. The mining industry in Zambia has undergone a very important ownership restructuring with the sale of the previously Government owned parastatal, Zambia Consolidated Copper Mines (ZCCM) which dominated the sector, to allow for private sector participation. The privatization process lasted from about 1995 to about 2002. The recent growth of the mining sector has unfortunately not been matched by an adequate supply of skilled manpower for various reasons. These include: (i) A lack of strong in-house training strategies by the new mine owners (ii) Decrease in industry support to the training institutions (iii) The demise of and restructuring of ZCCM which has consequently limited the Government human resources planning tools for the mining sector (iv) The cyclic nature for the fortunes of the sector has lead to fluctuating interest of student recruitment into training institutions (v) Limitations, both staff and equipment, in the training institutions (vi) A re-structuring of the training institutions This paper examines the current status, and student output from tertiary training institutions for the mining sector in Zambia. This is then compared to the skilled labour demands of the sector. The various cause and effect issues are considered and a proposal on how this skills gap could be addressed sustainably is proposed. Keywords: skills gap, graduate training, quality of graduates

Sep 1, 2012

By G R. Hancock, S Grant, T Whiteside, J B. C Lowry, J Boyden, T J. Coulthard

Physically-based landform evolution models (LEM) provide a spatial framework to forecast the long-term geomorphic stability of post-mining landscapes. When used to test the relative stability of different landform designs, LEMs may assist with the development of optimal closure designs for rehabilitated mines. However, in order to reduce prediction error, factors controlling landscape evolution must also be accurately represented by models. This requires that the correct sets of processes are represented and that driving parameters used in LEMs are, if necessary, calibrated to the landscape of interest.Vegetation exerts strong controls on the hydrologic and geomorphic processes that drive landscape evolution. Hence, the spatial and temporal scales over which typical patterns in vegetation are represented in different landscapes are important considerations in LEM calibration. However, vegetation is rarely accounted for in LEMs and even when integrated is often represented simply, without representing spatial dynamics of vegetation cover that may impact landform development.This study focuses on characterising vegetation patterns to calibrate a new vegetation module of the The Cellular Automaton Evolutionary Slope and River (CAESAR)-Lisflood LEM to be applied to a conceptual rehabilitated landform of the Ranger uranium mine located in the Alligator Rivers Region (ARR) of northern Australia. In the ARR the spatial dynamics of vegetation over time are largely driven by monsoonal rains and topography. Extensive dry season fires are also common in the region, temporarily reducing vegetation cover where they occur. Hence, hydrology, topography and fire disturbance interact to shape a distinct, yet dynamic, mosaic of different vegetation types of varying cover density. As a basis for calibrating the new vegetation function, the distribution and dynamics of vegetation are characterised for this savannah landscape by remote sensing, in conjunction with ground data.CITATION:Boyden, J, Lowry, J, Coulthard, T, Whiteside, T, Hancock, G and Grant, S, 2016. Accounting for vegetation dynamics in landform evolution modelling, in Proceedings Life-of-Mine 2016 Conference , pp 63–66 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 28, 2016

By John H. Lichtblau

There are three parties to the oil imports controversy: the domestic oil producers, whose side has just been ably summarized by Mr. Jameson; the oil importers; and the public. Domestic producers and importers are both motivated by economic self-interests, that is by their natural and legitimate desire for profit maximization, in their respective positions. Thus, domestic producers, rightly, regard every barrel of imported crude oil (with the exception of some specialty crudes) as a displacement of a barrel of their own crude. Hence, the lower the import Level the better they like it. Conversely, U .S. refiners whose plants are located at the seaboard or at certain inland waterways generally welcome a higher level of imports because refiner profits are based primarily on the spread between the crude oil price and the refined products price, since crude oil represents by far the refiner?s largest cost factor. The relatively low cost of foreign oil means therefore higher profits to those refiners able to process such oil, This applies particularly to integrated companies whose own domestic oil production is insufficient, to meet their refinery requirements but who have developed ample low-cost foreign oil supplies.

Jan 1, 1962

By W. E. Miller, G. S. Scott, G. W. Jones

"An important activity of the Bureau of Mines is the promotion of safety in mining and industry. In connection with these activities, the Bureau determines the explosion hazards of combustible gases, liquids, and solids and investigates means by which explosions may be eliminated or reduced in violence.The limits of inflammability and ignition temperature of combustible gases, vapors, and solids are of practical importance because such materials can be manufactured, transported, and used with greater safety, provided the range of concentrations and temperatures that cause explosions are known.Many organic compounds, which until a few year ago were merely laboratory curiosities, are now being manufactured in large quantities owing to the national emergency, particularly those chemicals entering into the manufacture of synthetic rubber, a product that is playing a major role in the Government program of national defense. This re Jolt gives results relative to the limits of inflammability of styrene and its ignition temperature in air and oxygen. This combustible liquid is now used extensively in the manufacture of synthetic rubber."

Mar 1, 1942

By Jerry C. Tien, Yingjiazi Cao

"Coal spontaneous combustion (SponCom) is a natural phenomenon in underground operations, which can either happen naturally or be triggered by human activities. For underground operations, espe-cially in coal, SponCom can happen frequently as a result of air leakage, although its incubation period may vary depends on types of coal and surrounding environment, resulting in uncertainty in control. In China, most of the underground coal operations now use longwall mining method because of its superior safety, high productivity and efficiency. With an increased popularity, there is also an increasing necessity to study spontaneous combustion, its occurrence and management. There have been many theoretical analysis and experimental studies over the past half century hoping to understand the occurrence of coal combustion and its control measures to better understand the occurrence and to design controlling measures to limit the dam-age it causes. In this paper, research on coal spontaneous combustion fundamentals from these three aspects will be reviewed, gaps highlighted and possible directions for future studies. INTRODUCTION The history of anthropic development is the history of human's energy utilization progress. From the first usage of fire, people have been continuingly seeking energy resources on earth. Coal, as an abundant, economic and convenient source of fuel quickly became indispensable and made significant contribution to economic growth worldwide. With technology and societal development, people are becoming more and more coal-dependent, but at the same time, problems of fossil fuel combustion came into sight. In global coal mining industry, spontaneous combustion has now presented one of the most challenging safety issues, it is also believed that it has contributed significantly toward the climate change. It is essential that more effort be invested to examine the cause of SponCom and its control measures. Coal SponCom is a complex process, with both physical and chemical inter-actions among various interrelated factors such as local airflow distribution, ventilation pressure, methane emissions (if any), and physical surroundings underground. With the advent of powerful computers, simulation techniques and af-fordable modelling packages in recent years, significant advances have been made in understanding sponta-neous combustion. But because of the complex nature of combustion and varying underground conditions, there are still areas that need further examining. This paper will focus on illustrating the current research of coal spontaneous combustion and addressing research gaps and future study areas."

Jan 1, 2019

By J. L. Jambor, R. W. Boyle

"The Magnet Cove barite-sulphide deposit is a raking pipe-like body that replaced and partly filled a large brecciated zone at the junction of two faults at the contact between sedimentary rocks of the Horton and Windsor Groups of Mississippian age. The principal minerals in the deposit are siderite, barite, hematite, pyrite, marcasite, galena, sphalerite, chalcopyrite, tennantite, proustite, pearceite, acanthite and stromeyerite. The mineral assemblage and textural relationships indicate that the minerals were deposited from low-temperature solutions. The source of the elements in the deposit is believed to be the enclosing sedimentary rocks, with connate or ground waters as the transporting medium, and solubility products as the governing factor controlling the abundance and order of deposition of the minerals."

Jan 1, 1966

By Mohammed Faizal, Abdelmalek Bouazza

"The operation of ground source heat pumps combined with foundation piles can have an effect on the thermal behaviour of the pile and the surrounding soil. This paper presents the effects of continuous heating, continuous cooling, and alternate heating and cooling operations on ground and pile temperatures as well as the thermo-mechanical behaviour of a field scale energy pile. The effect of pile operation on the ground temperatures is highest near the pile and reduces with increasing radial distance. The results of the present studies generally showed that the thermal elasticity of the pile is not affected.INTRODUCTIONGeothermal energy piles are foundation piles used as underground heat exchangers to maintain thermal comfort in buildings, via the use of ground source heat pumps (GSHPs). Ground source heat pumps are more economical and environmental friendly compared to conventional heat pumps. Energy piles can be combined with supplemental surface heaters or coolers, known as hybrid systems, for forcefully recharging the ground during non-operational times of the GSHP. Alternative heating and cooling of the GSHP improves geothermal energy usage and alleviates heat build-up in the ground and provides a balance of ground temperatures around the heat exchanger (Jalaluddin and Miyara, 2012).The temperatures induced in the piles during GSHP operation can lead to a complex response of thermal strains and stresses in the pile concrete. An assessment of the thermo-mechanical response of energy piles for various thermal loads may assist engineers in the design process. Furthermore, an assessment of ground temperatures will also highlight any potential thermal interactions with other energy piles in actual building operations.At present, the thermal strain and stress distribution in field scale energy piles has mostly been studied for continuous operation (Laloui et al., 2006; Bourne-Webb et al., 2009; McCartney and Murphy, 2012; Akrouch et al., 2014; Mimouni, 2014; Murphy and McCartney, 2014; Murphy et al., 2014; Wang et al., 2015). These studies have contributed considerably to the understanding of the axial thermal strain and stress distributions in the piles and have shown that pile thermal behaviour is mostly thermo-elastic without inducing major structural concerns.The present paper adds to the current knowledge by assessing the pile thermo-mechanical and ground thermal response for continuous and alternating thermal loads of a field scale energy pile. The operation modes studied are 24 hours continuous cooling (Faizal et al., 2015), 24 hours continuous heating, (Wang et al., 2015) and alternate heating and cooling operation (Faizal and Bouazza, 2016). The forced ground thermal recharging is done during the non-operating times of the cooling unit, simulating a solar hybrid GSHP system for a scheduled intermittent mode of operation."

Jan 1, 1900