Search Documents

By Bruno Vidal de Almeida

A campanha dos refratários à base de carbono aplicados como revestimento de trabalho de diversos equipamentos siderúrgicos depende da soma de diversos fatores como resistência à corrosão, resistência à oxidação do carbono, estabilidade termomecânica, entre outros. Durante a etapa de aquecimento inicial de revestimentos refratários novos ocorre a oxidação prematura do carbono presente no revestimento refratário, reduzindo a vida útil do revestimento precocemente. Para reduzir a oxidação precoce do carbono foi desenvolvido um novo coating cerâmico que atua como uma eficiente barreira física, reduzindo o contato do oxigênio da atmosfera de aquecimento com o carbono presente no refratário. O coating desenvolvido possui uma fase ligante com pega química ativada termicamente e possui como carga refratária um composto sílico-aluminoso com elevada estabilidade térmica. Os resultados laboratoriais de avaliação de desempenho revelaram que com a aplicação do novo coating desenvolvido reduz-se a oxidação prematura do carbono em até 77% e elevase a vida útil do revestimento em alguns casos em até 15%. O coating desenvolvido revelou possuir excelente desempenho quanto a proteção do refratário MgO-C contra a oxidação do carbono que ocorre durante a etapa de aquecimento de equipamentos com refratários novos, comprovando sua aplicabilidade em diversos equipamentos siderúrgicos que possuem revestimentos refratários à base de carbono.

Aug 17, 2017

Flue dust from the sintering of base metal sulphides was leached to remove cadmium and arsenic. Leach liquor contained cadmium, zinc and small amounts of other base metals as chlorides. Results are reported of the use of a cation exchange resin Zeocarb 225 to separate the base metals from the arsenic. The resin was eluted with sodium chloride or sulphate to give a solution of relatively concentrated cadmium suitable for recovery by zinc cementation. The limited solubility of sodium sulphate presented some practical problems which were investigated. Another problem was the precipitation of lead sulphate in the resin during elution.INTRODUCTIONWhen lead-zinc sulphides are sintered prior to smelting, the gases passing to the flue are mainly uncondensable but contain a certain proportion of sublimates and dust particles which deposit in the flue or are carried, after condensation in the gas stream, to some form of dust extraction equipment.The recovered dust is a complex mixture of base metal sulphates, sulphites, sulphides, chlorides and oxides, the composition depending on the original concentrates. A large proportion of the cadmium and some of the arsenic originally in the concentrates finds its way to this flue dust, the treatment of which can be a convenient means of removing these elements and controlling their concentrations in the main lead-zinc smelter circuit. However, disposing of this material represents an appreciable waste of base metals as well as a serious toxicity hazard.Sulphide Corporation Pty. Ltd. was faced with this problem in planning the flow sheet of the new lead-zinc smelter at Cockle Creek, N.S.W. From a test run carried out on a pilot plant at Avonmouth, U.K., using a mixture of lead and zinc concentrates, a sample of dust was obtained for...

Jan 1, 1960

By Charles Will Wright

Brief descriptions of the occurrence of the various deposits of strategic minerals then known in South America are published in "The Mineral Deposits of South America," by B. L. Miller and J. T. Singewald, 1919; in "Ores and Industry in South America," by H. F. Bain and T. T. Read, 1934; and in many publications on the individual countries. To give a gen.era1 idea of the situation today and possibilities for future output of strategic minerals in several of the countries, the following notes are offered. All tonnages are in metric units.

Jan 1, 1940

Jan 1, 1991

By B. P. Watson

The first crush pillars on the Bushveld platinum mines were introduced at Union Section in 1978. Before the introduction of crush pillars, serious problems were experienced when stoping advanced to a point 30 m to 40 m on both sides of the centre gully. At least three to four stopes were collapsing per month. The introduction of the pillars stopped the stope collapses in the mining area where they were introduced. The residual stresses of these pillars were never measured; however, the successful elimination of the ?back-break? problem suggests that the original pillars had a residual strength of at least 8 MPa. Apart from back analyses, very little work has been done to determine the residual strength of crush pillars and only very recently have any measurements been made. The lack of knowledge in this field has resulted in pillars being designed based on experience. Concerns about stope collapses, similar to the Coalbrook disaster, have led to larger pillars being cut in more recent times. If such pillars were cut in brittle quartzites they would always fail violently but the ductile nature of the Merensky Reef generally allows large pillars to fail without bursting. Occasionally, however, one would burst in a working area. Increased incidence of bursting has been reported on some mines at deeper levels but most of these bursts occur in the back areas. Nevertheless, the incidence of bursting increases the risk of falls of ground in already dangerous areas, and the larger pillars decrease the extraction ratio. This paper describes the evaluation of stress measurements conducted in two boreholes over a crush pillar with dimensions 2.5 m x4.0 m, and a height of 1.2 m. Boussinesq equations for vertical and shear stress were used to analyse the original measurements and provide a stress profile across the pillar as well as the residual strength of the pillar. The results showed an unexpectedly high peak stress of 280 MPa at the centre of the pillar and a residual strength of 48 MPa. The reason for the high residual strength is suspected to be the result of the stiff environment under which the pillar failed and the small height of the siding on the up-dip edge of the pillar. More measurements should be conducted on several mines to establish a range of residual strengths for narrow crush pillars.

Jan 1, 2008

By Daniel Costa Bezerra

Este trabalho tem como objetivo, fazer uma explanação sobre a aplicação de tecnologias emergentes de informação e automação no cenário de indústria, onde serão descritos casos de uso com potencial de alavancar resultados para a empresa, através do aumento de produtividade e redução de custos operacionais. Para fazer este trabalho, foram selecionados os projetos mais recentes, provas de conceito e laboratórios, onde a solução explorada possui aplicações de característica inovadora. Em seguida foram avaliados os resultados alcançados ou, nos casos de projetos não concluídos, os potenciais ganhos projetados. Desta forma pode-se avaliar e concluir que os custos de grande parte das iniciativas de apelo inovador, com foco no aumento de produtividade, trazem ganhos substanciais ao negócio, não só financeiro, mas também no quesito de segurança ao homem, e qualidade do produto ou serviço prestado.

Aug 17, 2017

M.S. Azun I have many objections to the content of the author's paper. Before discussing it, however, I would like to repeat the property of semivariogram function. Second order stationary properties of regionalized variables (ReV's) such as semivariogram function y(h) are perfectly known in geostatistics. Also, the kriging equations in the language of mathematical statistics using second order stationary properties are well understood. However, the way to use the sample (estimated) semivariogram function in any one of the kriging procedures is vague. The sample semivariogram function is given as follows: [ ] where N is the total number of samples, Xi is the sample value at the i - th location, Xi+h is the sample value at the i + h - th location, and h is the distance among the samples. An estimation variance of sample semivariogram function of first lag is smaller than that of higher order lag. The theoretical semivariogram function reaches the variance of samples asymptotically. But this is not easily observable because of the larger variation involved in the estimate of semivariogram function. In general, an estimation procedure is done for h = 0, 1, 2, up to the greatest integer less than N/2, even though sample semivariogram function can be computable through N-1. After estimating semivariogram function, the critical question of how to model sample semivariogram function arises. As seen in the above equation, sample semivariogram function is discrete and can be smoothed by the model being selected. Therefore, modeling of sample semivariogram function is the most important step in geostatistics. It not only smoothes a discrete function but also affects the results of the kriging procedure. When the only aim is to model the semivariogram function, which is the basic point of the author's paper, one can employ any fitting techniques, such as curve fitting, or any arbitrary functions, which are called submodels in the paper. The term "arbitrary function" is used rather than "submodel" because there is no basic understanding of developing them. The author suggests that the sum of those submodels can also be used for the modeling of sample semivariogram function. The combination of any arbitrary functions brings many problems instead of giving an insight of the domain structure considered. The author used two arbitrary functions and the nugget effect in response to sample semivariogram function (Fig. 10). For the same example, he stated that the parameters involved in the mixed arbitrary function model can be accepted when the discrepancy between sample semivariogram function and the model is small visually. For verifying the fitting behavior of any selected model, one should not be contented with the visual satisfactory. Some statistical measure such as goodness of fit has to be used. The author's practice is no more than an exercise in curve fitting without any fundamental understanding or conceptualization of the underlying physical mechanism. Furthermore, the selection of any model is not an easy task if the purpose is the search for the "best" response to the observed second order properties of ReV's. I suggest that the Markovian model (Azun, 1983), on the basis of a theoretical understanding of underlying mechanism, which gives more information about the occurrence of regionalized variables, is used to respond all properties of ReV's. There are a lot of problems for modeling of one-dimensional sample semivariogram function. Thus, it is not appropriate to go to higher order dimensional sample semivariogram function modeling. In the meantime, I would recommend that one can connect the values of standardized sample semivariogram function rather than simple values of semivariogram function in the two-dimensional estimation. The standardized values can be computed in dividing the semivariogram function value by the number of sample pairs involved in each lag regardless of the directions. In conclusion, geostatistics is an interdisciplinary area in mining that uses the principles of mathematical statistics. Thus, it should not violate any probabilistic and statistical rules. When Matheron was developing the theory of geostatistical study in the early years of geostatistics, many mining people had a reservation accepting the geostatistical tools. However, this does not mean that we, the geostatisticians, might try to convince those people using some "strange" tools or rules as some authors implied (Baafi and Kim, 1984). Instead, we have to develop and explain the geostatistical tools staying only in the framework of statistical concepts and properties. References Azun, M.S., 1983, "Stochastic Process Modeling of Spatially Distributed Geostatistical Data," Columbia University, Ph.D. Thesis. Baafi, E.Y., and Kim, Y.C., 1984, "Discussion - Comparison of Different Ore Reserve Estimation Methods Using Conditional Simulation," Mining Engineering, Vol. 36, No. 3, p. 280. Reply by J.M. Rendu The interactive method proposed by Rendu allows practitioners to develop semivariogram models that take into account not only the numerical information obtained by sampling, but also highly significant additional information that often cannot be quantified. The geology of the deposit - including hypotheses concerning its genesis, sampling methods, assaying methods, and mathematical methods used to calculate the semivariograms - all have an influence on the numerical results obtained and on how these results should be interpreted. If all the information concerning the spatial distribution of values in a mineral deposit was contained in the sample values, it could be argued that statistical techniques alone would produce optimum models. However, this is rarely, if ever, the case. Methods that allow the user to take into account his experience and his geologic understanding of the deposit should not be rejected for the sake of theoretical statistical purity.

Jan 11, 1985

By Juliano Walter Silva

O rápido crescimento da indústria automotiva em meados de 1920 impulsionou de forma significativa o desenvolvimento dos processos de estampagem. Hoje, esse processo de fabricação está consolidado e abrange desde a produção de utensílios domésticos até a de componentes automotivos. O estudo realizado tem como objetivo comparar e mensurar a capacidade de lubrificação de três produtos lubrificantes que atuam durante o processo de estampagem. O material estampado foi uma folha de flandres convencional com quatro variações de acabamentos superficiais. O ensaio utilizado foi o ensaio de estampabilidade, o qual nos fornece como parâmetro final o índice de estampabilidade Erichsen (h). Pela comparação dos índices Erichsen de estampabilidade obtidos pôde-se estimar a eficiência de cada regime de lubrificação.

Aug 17, 2017

By M. K. G. Vermaak

Spiral concentration forms a crucial part of gravity separation circuits. The application of process models in the operation of gravity separation circuits offers significant benefits in recoveries and grade control. Significant strides in the modelling of spiral concentrators have been made during the last couple of decades. Despite these advances in modelling techniques and models, application in industrial processes is not fully optimized. The adjustment of splitter positions to accommodate changes in the feed parameters is impractical and difficult, resulting in losses. In this work an optical method is employed to detect the concentrate band position as a function of operating variables. As expected, the results indicate a strong influence of the solids content and total heavy mineral (THM) feed grade on the predicted gangue-mineral interface. Viscosity modifiers indicated the band position to be sensitive to viscosity and therefore the slimes content. Validation on an industrial sample indicated the possibility of using this model in feed-forward control application.

Jan 1, 2008

By Jarinson Ribeiro Rodrigues

Os aços resistentes à abrasão da classe 450 HB foram desenvolvidos para operações em ambientes onde ocorre desgaste excessivo, sendo estes aços martensiticos de elevada dureza e uma difícil soldabilidade. Este trabalho propôs-se a otimizar os parâmetros de soldagem do processo FCAW (Flux Cored Arc Welding) através da análise do projeto de experimentos (Design of Experiments - DOE) utilizando a Metodologia de Superfície de Resposta (Response Surface Methodology – RSM). Após a determinação dos parâmetros de soldagem ideais, foi realizado a caracterização mecânica e metalúrgica de uma junta soldada com estes parâmetros a fim de certificar-se das propriedades da junta com parâmetros de soldagem otimizados.

Aug 16, 2017

By T. J. Lynch

A new class of polymeric dispersants for industrial minerals has been synthesized and evaluated. Currently available dispersants give initial low viscosities at high mineral loadings, however slurry viscosities can rapidly double or triple on standing over the first several days. The new dispersants give low initial viscosities that are more stable and maintain a lower viscosity for at least one month. The new dispersants are made possible by controlling the polymer molecular weight distributions during their manufacture such that essentially all of the dispersant is adsorbed onto the mineral surface, preventing depletion flocculation.

Jan 1, 2012

By F. Habashi

The changes that took place in China between 1984 and 2004 are remarkable. Visits were made to universities, research institutes, metallurgical industry, and many cultural centers within five trips during this twenty years period. The impressions of these visits are outlined.

Jan 1, 2007

By R. J. Colony

MINING geology does not lend itself - very readily to a review embracing "improvements in methods," as perhaps do shop practices or laboratory procedures. The "methods" used in mining geology are simply the application of geology to mining; winning the ore, the handling of material, mechanical appliances, all belong strictly to mining proper, and have no place in a review of geology as applied to mining. A comprehensive review would necessarily cover a .very broad field, which could be subdivided into many -parts. Only a few of these can be discussed here. .Those that have been suggested to the chairman indude :

Jan 1, 1930

By Rob Domotor

This paper tells the story of using controlled surface and underground blasting methods to excavate hard rock in three areas on Australia’s largest road infrastructure project; the Airportlink Project in Brisbane; worth a total value of AUD $4.8 billion. The project used blasting methods including design, modelling, drilling and loading of the explosives that had never been used before in Australia, some of these were probably unique in the world.

Jan 1, 2012

By Donald W. Baggs

This report describes economic mining feasibility studies conducted by the Bureau of Mines to estimate mining costs in the Porcupine mining area of the Juneau Mining District, southeastern Alaska. Investigations were conducted on the economics of three mineral deposit types: 1) massive sulfide deposits containing zinc, copper, and silver, 2) vein gold, and 3)disseminated gold. Cost estimates were developed using the Bureau of mines Cost Estimating S,-stem. Discounted cash flow rates of return were calculated using the Bureau of Mines MINSIM (mining simulation) computer program. Three sets of metal prices were used in the study based on recent historical price information. Underground longhole stope mining of a massive sulfide deposit containing 25 pct zinc. 1 pct copper, and 63.6 g/mt silver was found to be economic at high metal prices at a quantity of 13,200,000 mt ore. Cut-and-fill mining of a 26,400,000 mt massive sulfide deposit was found to be economic at medium metal prices. Open pit mining of a similar deposit was found to he economic at medium metal prices and 26,400,000 mt ore, or at high metal prices and 6,600,000 mt ore. Underground mining of a vein gold deposit was found to be economic at a grade of 17.1 g/mt medium metal prices and 1,320,000 mt ore. Open pit mining of a disseminated gold deposit was found to be economic at a grade of 1.71 g/mt medium metal prices and a quantity of 39,600,000 mt ore.

Jan 1, 1986

By W Valery, A Jankovic

The ball mill in closed circuit with hydrocyclones is an industry standard, and well known methodologies exist for equipment sizing, selection and design. However, the potential to improve the capacity of ball mill circuits by replacing cyclones with screens has been recognised for many years and recently has been successfully realised, thanks to developments in fine screening technology. Proper methodology for equipment sizing and selection is required to capitalise on this opportunity, but there is currently insufficient information and few guidelines available on how to design such a circuit. This paper discusses the differences between ball mill circuits closed with cyclones and with screens. A methodology is described for equipment sizing and selection for a circuit closed with screens, and the laboratory testing requirements are described for low grade base metal ores and magnetite ores. An economic evaluation is also presented for a case study demonstrating the potential benefits of closing a ball mill circuit with screens.CITATION:Jankovic, A and Valery, W, 2013. Energy efficient ball mill circuit - Equipment sizing considerations, in Proceedings MetPlant 2013 , pp 285-295 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

Jan 1, 1970

By J. D. Clendenin

Systematic practices for protecting crops from frost damage began in the United Metes more then 40 years ago when the Weather Bureau Fruit-Frost Warning Service was organized; however, various practices employed in frost protection are centuries old. Although there are areas where little doubt exists as to whether protection is needed, there are also circumstances where there is some doubt as to the need for frost protection. Many factors influence this, including not only critical temperatures but also the maturity dates of the crops relative to marketing. Critical temperatures for frost damage to trees, plants, blossoms, and fruits very with weather, plant variety and nutrition, and stage of growth. In the case of truck crops, a single night of protection from frost injury might yield big dividends with a variety of sweet corn or tomato that matures early while price is high yet be worth very little with a midseason or late-maturing variety. Consequently, it is the individual grower who must decide whether to use frost-protective measures on the basis of his returns, the quantity and quality of his crop, the marketing situation, the sensitivity of his crops to frost damage, and the frequency of damaging frost in his area.

Jan 1, 1955

By Rossiter W. Raymond

(Canal Zone Meeting, November, 1910.) THE death of Professor Blake removes the oldest of American economic geologists and mining engineers, and deprives this Institute of one of its, earliest and most illustrious members. To many of us it brings a personal loss also, the loss of a friend. William Phipps Blake was born June 21, 1826, in New York City. -His father, Elihu Blake, was a surgeon-dentist of eminence, a direct descendant of William Blake, who settled in the Massachusetts Bay Colony about 1630. He was prepared for college at private schools in New York, and entered the Sheffield School of Yale, where he was graduated as Ph.B. in the chemical course, class of 1852, the first graduating-class of the institution. In the same year he became chemist and mineralogist of the New Jersey Zinc Co., and chemist of chemical works at Baltimore, Md. In 1853, lie started the Department of Mineralogy of the World's Fair at New York City. In 1854, 1855 and 1856, he was mineralogist and geologist of the United States Pacific Railroad Surveys of Williamson, Pope, and Whipple, and for the War Department at Washington. His writings, during this period comprise reports on the geology and mineralogy of California and other parts of the Southwest, and constitute well nigh the earliest scientific accounts of the regions described. One of them. was a translation of the Resume and Field Notes of Jules Marcou, of Whipple's expedition. From 1856 to 1859, he was engaged in explorations of the geology and mineral deposits of North Carolina, :and other parts of the country. In 1859, he became editor and proprietor of The Mining Magazine. This was a monthly periodical, founded in 1853 by W. J. Tenny, who conducted it until 1858, when it passed into the hands of Thomas McElrath, a New York publisher, and appeared in May of that year as The Mining and Statistic Magazine, with the name of

Sep 1, 1910

By William D. Macdonald

The Upper Devonian Kettle Point black shale of southern Ontario is poorly exposed. Structural maps pre-pared from the data of numerous wells show that the upper surface of the formation has low regular relief, and that the lower surface reflects domes in the Middle Devonian and also local subsidence of the Devonian rocks due to solution of salt in the Silurian Salina Formation. The appearance of minor amounts. of marcasite, pyrite, and calcite, m that order, as interpreted from the evidence of concretions from the type locality at Kettle Point is thought to have been influenced by a rise m the pH within anaerobic sediments preceding compaction.

Jan 1, 1960