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By R. M. Schuster

This study attempts to compare the costs of transporting coarse coal by pipeline, versus the more conventional use of belt conveyors. Hydraulic conveying of crushed (not pulverized) coal has not had widespread commercial acceptance. However, there is little doubt that the technology is available, so that, should this method be proven economical for a given application, implementation of this technology will become more acceptable. Hydraulic transport by pipeline between the mine stockpile and the coal preparation plant, for distances normally considered practical for an overland belt conveyor, should be an ideal application. In this application there is no need for dewatering facilities at the receiving end of the pipeline, because, the receiving screens at the plant serve this purpose. Further, clarified water from the preparation plant can be recirculated back to the mine, a plus for water resource and environmental considerations.

Jan 1, 1982

By S. R. B. Cooke, J. Bruce Clemmer, F. P. Diener

"The limestone deposit utilized by one of the plants of the Universal Atlas Cement Co. is covered in part by a stratum of cherty limestone. If this overlying deposit could be utilized by removing the excess of chert economically, quarry costs could be reduced and the amount of rock economically available would be increased greatly. On account of the distribution of flint and limestone, a product fairly free of flint can be obtained until the quarry face is about 50 or 55 feet high. As the face is worked farther back into the hill, the comparatively clean stone is overlain with a constantly increasing amount of high-flint limestone. If this flint remained with the limestone, there would be a prohititively high silica ratio in the finished cement; if the flinty layer were removed as overburden a very large tonnage would be handled and much good stone lost. Consequently it was felt that means should be devised for separating the flint from the limestone after it reaches the plant.The investigation was undertaken by the Mississippi Valley Experiment Station of the United States Bureau of Mines in cooperation with the Universal Atlas Cement Co. and the Missouri School of Mines and Metallurgy, Rolla, Mo.CONSIDERATION OF PROCESSESMany schemes for the separation of Minerals are based on differences in the specific gravities of the minerals to be separated. In this case the flint has a specific gravity of approximately 2.62 while the limestone averages about 2.70. This differential is not large enough to permit separation by any method based on specific gravity. Furthermore, all the limestone particles in any given sample are not alike; usually about 10 percent of them have a specific gravity the same as, or lower than, the flint."

Mar 1, 1935

By Kirsi M. Riihilahti

The oxidation characteristics of solid copper matte particles under simulated Kennecott-Outokumpu Flash Converting conditions are presented. The effects of feed matte grade, matte particle size, oxygen-to-matte mass ratio, oxygen content of the process gas and temperature on the particle oxidation rate, quality of conversion, particle size change and particle morphology were determined. The converting quality was highest (~68) with the 58% copper matte at 1100°C. At similar conditions, the 72% copper matte was more likely to produce copper oxides and leave unoxidized particles rather than directly produce sulfur dioxide at 1100°C, resulting in an average converting quality of 55. The quality of conversion was poorest for the 72% matte at 920°C (~45); the sulfur removal was extremely low even with a relatively high degree of oxidation. Fragmentation of the particles was significant in all cases with the 72% matte. A higher O2/matte .ratio and higher temperature, in general, resulted in increased fragmentation while oxygen enrichment had no significant effect. With the 58% matte, particle size was found to increase for the finest fractions rather than to decrease due to particle expansion.

Jan 1, 1998

By Danqing Gao, Brijes Mishra

Heterogeneity in rock formation affects both rock behavior and strength. Spatial variance of rock properties is an important characteristic of rock that addresses the heterogeneity of mechanical and physical properties and their effects on underground mining. Assessing spatial variance can be useful for locating potential difficult grounds and for performing reliability analysis in the mining support system. This study presents a spatially correlated, random model to investigate the influence of rock heterogeneity on rock strength and failure propagation. A random field database with specific spatial correlation was created for each physical-mechanical property using laboratory data and the extreme value stochastic model in MATLAB. Based on the improved microscale random model, we considered one three-dimensional numerical model to study a mine operating in the Pittsburgh seam. The influence of random field data on entry roof was investigated. The realistic random field database added two scale-measured parameters from horizontal and vertical directions to control the spatial correlation length. A number of cutting sequences were also considered in order to identify the effect of spatial variance on roof behavior. The results show that spatial variance provides an accurate prediction of erratic roof falls in coal mines.

By W. H. Ode, W. A. Selvig

Briefly, this swelling test consists in heating 1 gram of pulverized coal in a silica crucible over a gas flame under prescribed conditions to form a coke button which is compared in size and shape with a series of standard profiles numbered 1 to 9. These profiles are intended to cover the size and shape of buttons obtained from coals covering a wide range in plastic properties. The number of the standard profile with which the maximum cross-sectional area of the button most nearly corresponds is recorded as the swelling index. Although the swelling test showed poor relationships with the various tests that were used for measuring expansion or contraction of coal during carbonization, it gave indications of having value in measuring free-swelling and coking properties of coals when burned on fuel tests. An opportunity to investigate this occurred when an engineering company reported pronounced differences in burning characteristics on grates of various shipments of Pocahontas coal. Some of these coals gave trouble by swelling excessively and clogging the grate. Samples were obtained, and it was found that the troublesome coals gave radically higher free-swelling numbers than did the coals that performed satisfactorily. Also, it was found that the free-swelling index test gave better differentiation between coals than could be obtained from the coke buttons from the standard volatile-matter test or iron agglutination-value results. The results of the free-swelling test were confirmed by the Subcommittee on Plasticity and Swelling, Coal, a special group of the Subcommittee, under the chairmanship of R.A. Shuman, worked along with the test method. Estberg, Limacher, and Shuman of the Battelle Memorial Institute investigated the various factors affecting the test and found that the swelling index was a good indication of the suitability of coal for performance on residential-type stokers from the swelling characteristics of the coal. Data were presented that also showed that the index was helpful in the selection of coal for industrial underfeed stokers.

Feb 1, 1948

By M. R. Haibach, M. L. Shema, J. M. Silvis

"Since 2005, longwall coal mine operators in Pennsylvania (US) have been required to collect extensive hydrologic and biological data to document pre- and post-mining conditions of aquatic resources (streams and wetlands) overlying the subsidence control plan areas. Continued operation of the longwall mine is dependent upon empirical data demonstrating that the undermined aquatic resources have either been maintained or restored to an accepted range of pre-mining conditions. This study used quantitative hydrologic methods and comparative biological metrics to examine response of aquatic resources to longwall subsidence at the Bailey Mine located in Greene County, Pennsylvania. This study analyzed data from over 25 miles of streams and over 8 acres of wetlands that traverse the 4,779-acre study area. Hydrologic analysis of flow intermittency suggested that there are variable degrees of change to headwater streams immediately following mining; however, the majority of the effects are reversible through streamflow mitigation measures. Furthermore, the post-mining discharge from streams can be restored to within the range of pre-mining conditions the majority of the time. Biological assessments showed that greater than 95% of assessed stream length has maintained its ability to support benthic macroinvertebrate communities following mining and intervention (i.e., mitigation). Comparative metrics of the benthic macroinvertebrate communities showed that the biological community in 48 of the 50 sample sites is being maintained or restored across both high- and low-gradient streams. The effectiveness of intervention was further substantiated by the similarity in recovery times between streams having no intervention (median = 2.1 years, 95th percentile = 4.9 years) and streams with intervention, when recovery times were measured from the date of the intervention (median = 1.7 years, 95th percentile = 4.7 years). Changes to individual wetlands were observed between the pre- and post-mining assessments, but cumulatively a net gain of 7% in wetland acreage was realized. Hydrologic assessments were used to infer whether there was a potential that streams had been affected by mining; however, the ultimate test of stream recovery is based on biological metrics that establish the relative quality of the biological communities following mining. Overall, the hydrologic balance is being protected and the aquatic life use of streams is being maintained within the Bailey Mine’s subsidence control plan areas."

Jan 1, 2017

By BUREAU OF MINES

PLATINUM

Feb 1, 1922

As a bubble travels through the pulp region of a flotation cell, it will collect the most hydrophobic particles of an intermediate particle size range, this being the primary source of true flotation selectivity. Despite its role on bubble-particle attachment, however, particle hydrophobicity is still missing a mathematical definition that can be used for plant simulation. In this paper, particle hydrophobicity is defined in terms of the induction time necessary for attachment and then linked to the mass of collector adsorbed per particle. This allows particle hydrophobicity to be written as a function of density of collector adsorption as well as particle size and mineralogy. The model is calibrated from the experimental measurement of the flotation rate constant. Liberation data from an industrial flotation rougher is used for model validation. It is demonstrated that the model can describe a broad experimental dataset by means of a minimal number of parameters. Main industrial application is in simulating the effect of the chemical environment upon plant metallurgical performance.

Jan 1, 2006

By Elaine Cristina de Azevedor

Em serviços de radioterapia são utilizados acessórios confeccionados com diversos tipos de polímeros para auxiliar no posicionamento dos pacientes durante o tratamento e na execução das rotinas de trabalho. A radiação gama pode causar nos polímeros degradação de sua estrutura molecular, dificultar a sua na assepsia e seu reduzir o tempo de vida útil. Neste trabalho é apresentado o estudo da degradação causada pela exposição à radiação gama em polímeros utilizados em serviços de radioterapia. Amostras de policarbonato (PC) e polipropileno (PP), foram expostas a doses de radiação gama de 5 kGy e 25 kGy, sendo analisadas por espectrometria de absorção na região do infravermelho e indentação instrumentada. O PC apresentou indícios de fragilização a partir de 5 kGy, reduzindo o tempo de vida útil e o PP apresentou se adequado para o uso em serviços onde haja exposição à radiação gama.

Aug 8, 2018

By Martin J. Gavin

"Before discussing oil shales it may be well to consider briefly the conditions surrounding the petroleum industry in the United States, because these largely explain why so much interest is being manifested in oil shales. The United States is not only the greatest producer of petroleum in the world, its output amounting to about 65 per cent of the world's total production; but is also the world's greatest consumer, using more petroleum than it produces within its own borders. For the past four or five years it has been necessary to import oil at a continually increasing rate to make up the deficit between domestic production and domestic consumption. Experts who have made a close study of the future supply and demand for, crude petroleum are satisfied that under present production practice and with the development of possible undeveloped productive areas, the gap between domestic consumption and production will steadily .increase.As possible solutions for the impending domestic shortage of oil, various expedients are receiving attention. These may be grouped under three heads, as follows:(1) Temporary measures, such as curtailment of consumption, development of more efficient methods of production, and more efficient utilization of supplies of petroleum still available. It is unlikely that there will be any great curtailment in consumption of petroleum in the United States; rather, consumption will continue to increase unless a real shortage of oil actually forces curtailment of consumption. The other two possibilities mentioned deserve, and are resolving, serious thought. Much experimental work along these lines, some of which has already yielded excellent results, is being done. Obviously, however, any of these remedies are temporary ones only, so far as regards domestic production of petroleum."

Oct 1, 1920

By Mariana Sizenando Lyrio, Weslley Luiz da Silva Assis, Harison da Silva Ventura, Gabriella Maria Silveira de Sá, Paulo Rangel Rios, Ana Gabriella Conceição dos Santos

A nucleação em contornos de grão é uma das mais importantes na maioria dos metais utilizados em engenharia. Um exemplo clássico é a nucleação de ferrita no contorno de grão austenítico, mas este tipo de nucleação também é predominante na recristalização. Nesse trabalho, simulações computacionais são realizadas de modo a estudar a transformação de fase nos contornos de grãos equiaxiais e nos contornos deformados. Os grãos equiaxiais são representados por poliedros de Poisson-Voronoi e os grãos deformados por elipsoides de diferentes razões de aspecto. Os resultados são comparados como os modelos analíticos de JMAK e CAHN. A microestrutura final não é visivelmente afetada pela razão de aspecto dos poliedros predecessores. Todavia a cinética de transformação dos grãos recristalizados é significativamente alterada.

Nov 9, 2019

By Silvia França, Hudson Couto

"In this paper, an alternative beneficiation process was developed to recover nickel minerals from low-grade weathered ores. The studied sample, 0.3% Ni grade, is essentially composed of nickel sulfides (pyrrhotite and pentlandite); magnetite and silicates (mostly talc and amphibolites) are the primary gangue minerals. The particle size distribution was controlled using a grinding operation to avoid producing an excess of fine particles by overgrinding. The sample underwent a grinding step for the fine degree of liberation. The slimes (-20 ?m) were removed via two desliming stages in hydrocyclones (diameters of 1.5" and 2"); the ground material, which was classified in a range of (-150+20) ?m, was processed by column flotation in three different stages: rougher flotation for magnesium silicates, rougher flotation for sulfides, and cleaner flotation for sulfides, using pilot flotation columns (2" and 6" in diameter and 20 ft high). The goal of using the preliminary magnesium silicate flotation step was to remove hydrophobic minerals (mostly talc) that would float naturally with the sulfides, which would decrease the Ni grade in the concentrate, as well as to reduce the MgO content because this compound is considered harmful in metallurgical processes when a grade greater than 9% is used. The final concentrate obtained in the cleaner flotation step reached up to 2% Ni and 7.0% MgO. The global and flotation recoveries in the process were approximately 30% and 60%, respectively, due to the losses of Ni during the desliming process. Despite this low global recovery, the adopted beneficiation process can be considered an interesting alternative to produce nickel concentrate from tailings or waste materials."

Jan 1, 2014

By F. M. Doyle, S. Duyvesteyn, K. Sreenivasarao

Toxic metals entering surface or ground water from sources such as metal finishing shop spills and abandoned mines can pose a significant threat to public health and the environment. Ion flotation and similar foam separation techniques show great promise for treating dilute, metal-contaminated solutions, and could also be used to treat effluents from many minerals and metallurgical processing operations prior to discharge. In ion flotation, an appropriate collector is added to the solution to form hydrophobic complexes with the metal ions. These metal-bearing species are then removed by flotation, usually with trace addition of a frother to stabilize the foam. In an effort to better understand the underlying scientific and engineering principles that determine the performance of ion flotation, the removal of Cu(II), Pb(II), Cd(II), Cr(II) and Cr(VI) has been studied using laboratory scale flotation columns in batch mode. The effects of the superficial air velocity, solution and froth height, nature of the collector, collector: metal-ion ratio, ionic strength and several frothers at low concentrations on the flotation kinetics are reported. Finally, results are presented on methods that might allow regeneration of collector and recovery of by-product metal from the foam product.

Jan 1, 1995

By C. Xiao, R. Chi

In recent years, the biosolubilization of rock phosphates by phosphate-solubilizing microorganisms has become a major topic of research studies. However, the microorganisms used in previous studies were mostly single and known species, and studies seldom focused on mixed communities of microorganisms or microbial consortia from natural environments. In this study, a microbial consortium from rhizospheric soil was used to solubilize two different compositions of medium- to low-grade rock phosphates — designated as ore samples 1 and 2 — in a laboratory-scale bioreactor. The microbial consortium showed good growth in the bioreactor, reduced the suspension pH and released soluble phosphates from the ores. Scanning electron microscopy with energy-dispersive X-ray spectroscopy showed the action of the microbial consortium on the ore surface. There was considerable corrosion on the ore surface, and 3.42 and 4.93 percent of the element phosphorus was removed from ore samples 1 and 2, respectively. Microorganisms were sampled from the bioreactor for the analysis of their community structures by Illumina MiSeq high-throughput sequencing. The analysis show that the suspensions added with different ore samples had different microbial diversities and richness. This study provides new insight into the biosolubilization of rock phosphates by a microbial consortium directly taken from rhizospheric soils.

Page Bronze Bearing Metals. By G. H. Clamer............... 162 Pennsylvania Railroad Anti-friction and Bell Metals. By F. M. Waring .. 166 The Tin-plate Industry. By D. M. BUck. Discussed by G. H. ClameR, J. W. RICHARDS............................ 168 The Aluminum Bronze Industry. By W. M. Corse............ 171 Bronzes, Bearing Metals, and Solders. By G. K. BURgess and R. W. Woodward. Discussed by G. H. Clamer, R. T. Roberts......... 175 Babbitts and Solder. By G. W. Thompson................ 184 The Cadmium Supply of the United States. By C. E. Siebenthal. Discussed by M. L. Lissberger, C. W. Hill, F. F. ColcoRd.......... 185 Solder, Its Use and Abuse. By M. L. LissbergeR............ 192 Bronze Bearing Metals G. H. ClameR,* Philadelphia, Pa.—Unfortunately, prior to the war no serious attention was given to the conservation of tin, notwithstanding that this country is practically dependent upon outside sources for its entire tin supply. Tin is of vital importance in many industries, but it is surprising how many and how excellent are its substitutes when we become acquainted with them. Tin has always been a relatively high-priced metal, and it is part of the human attitude to associate high prices with high standards; it is not until the price of a commodity becomes well-nigh prohibitive that we hunt for substitutes, because the idea of substitution seems always to involve an assumption that the substitute must necessarily be inferior. The history of the development of bearing bronzes is a striking example of this policy. In the early days, copper-tin alloys were almost universally used, the idea then being prevalent, which is still held by many, that a bearing to resist wear must be hard, and the harder the better. The favorite bronze bearing contained 90 per cent. copper and 10 per cent. tin; frequently, in service which was considered severe, even higher proportions of tin were used. Such hard alloys have great resistance to compression, but as a rule they had a very wide factor of safety in this

Jan 1, 1919

By A. Lubinski, C. R. Stewart, K. A. Blenkarn

Storage porosity has been considered one of the important pore geometry characteristics of heterogeneous-porosity limestones. Storage pores are only containers for fluids, in contrast to flow channel pores which both contain fluids and provide continuity for fluid flow. The concept of another geometry characteristic, "poro-striction", is presented as a second pertinent variable in describing limestone pore space. In simple terms, poro-striction is a measure of the flow resistance between storage and flow channel pores. Alternating-flow core-testing theory provides flow relationships which can be used to divide the pore space of heterogeneous-porosity media into flow channel and storage pores and to measure the "porostriction" of the latter. Experimental application of this theory to naturally occurring heterogeneous limestones shows that "porostriction" and the ratio of storage to flow channel pores can be estimated. Porostriction and porosity ratio are microscopic characteristics which should influence oil-recovery efficiencies during certain types of displacement processes. A knowledge of pore geometry should be valuable in designing or selecting the most effective oil-recovery process for heterogeneous limestones containing storage porosity. INTRODUCTION The primary and secondary recovery of oil from limestone (carbonate) reservoirs has been and will continue to be a major source of the world's supply of petroleum. Oil recovery from this type of formation is strongly influenced by the size, shape and arrangement of the pore spaces which hold the formation fluids. Therefore, it is expected that better knowledge of pore geometry would lead to design of more effective recovery processes. The concept of storage and flow channel pores has been presented as an important characteristic of limestone porosity.1 In this concept, storage pores are only containers for fluids, whereas flow channel pores are those pores which both contain and transmit the fluids. The work reported herein involves the concept of an additional pore characteristic called "porostriction". This characteristic can be visualized as the flow resistance between the storage and flow channel pores. This resistance is an important pore geometry characteristic because it determines how easily gas and oil can replenish fluids removed from the flow channel pores. Fatt and co-workers at the U. of California have studied the effect of storage porosity and a factor similar to porostriction on transient-flow response of models of porous media during a pressure build-up or drawdown test.55 These models consisted of porous sandstone cores with artificially simulated storage pores. It is the purpose of this paper to describe tests which permit the storage porosity and porostriction of actual reservoir core samples to be estimated. The tests used for this purpose involved not transient tests but, rather, an alternating-flow technique in which pressure and flow are varied according to a sine-wave relationship. This technique may offer advantages over transient methods. THE POROSTRICTION CONCEPT Before discussing alternating-flow (A.F.) tests in core samples, it is necessary to define the porostriction parameter. For this purpose attention is focused upon an elemental volume v representative of a porous medium having both flow channel pores and restricted-access storage pores. For such an elemental volume, it is considered that the storage porosity is combined to form a single pore and that the access into the storage porosity may be represented by a single capillary tube connecting the single pore to the flow channels of the elemental volume. Let the radius of the capillary tube be designated as Rc and its length as L,. When fluid flows into or out of the pore, the following equation (Poiseuille's law) relates flow rate q to pressure drop p, and the physical characteristics of the tube and the fluid of viscosity jx.

At Asarco's Mission mill. located near Sahuarita, Ariz., the 20 500-t/d (22,500-stpd) throughput of highly abrasive and corrosive copper ore can play havoc on equipment wear parts. To minimize frequent replacement work and extend life on key components, Asarco engineers have over the past five years utilized liners made of "Towniprene" in the secondary grinding and flotation area of the plant. Results to date have indicated that these liners last between three and five times longer than those made of metal or ordinary rubber.

Jan 8, 1978

By F. J. Arriagada

Where gold is present in a finely disseminated form within sulfide particles, the porosity and surface area of the calcined material strongly influence leaching since they control the penetration of solution inside the gold-bearing grains. On the basis of a stability diagram for the Fe-O-S in the temperature range of 400 to 750aC, the expected sequence chemical transformations associated with the oxidation of pyrite is discus-sed. By using analytical techniques which include scanning electron microscopy, X-ray diffraction and BET gas adsorption, the chemical and structural changes experienced by auriferous pyrite-arsenopyrite concentrates and pure pyrite samples are studied under an oxidizing roasting atmosphere of com-position 80% N + 20% O2 in the temperature range of 450 to 750°C. The results indicate that as the roasting temperature increases, the surface area of the calcines decreases sharply after a maximum value attained at about 450-500°C. SEM micrographs show that the needle-shaped tips which characterize the surface of the oxide product become wider and the size of the pores between them is decreased when the roasting temperature is in-creased from 550 to 750°C. This effect suggests that the formation of a more "closed" hematite product at higher temperatures is due to sintering associated with a faster growth and crystallization of the oxide. A strong correlation is shown between increasing roasting temperature and increase in gold lost in cyanidation tailings, an effect which may be partly attributed to the loss in surface area of the calcines.

Jan 1, 1982

By Fahimeh Dehghani, Louis Ackah, Tathagata Ghosh, Justin Godbold, Jia Liu, Meisam Peiravi, Manoj Mohanty, Azam Baharlouei

Primary economical deposits of rare-earth elements (REEs) are exhausting all over the world, and it has become necessary to find new sources and methods for their extraction. In addition, increasing the application of REEs in modern technological society has increased its demand globally. One of the important movements to compensate for the future shortages of critical metals is the recovery of REEs from recyclable materials. This paper presents a review of the classification and extraction methods, as well as general applications of REEs with emphasis on secondary sources such as coal and coal byproducts, iron ore tailings, apatite, and phosphate byproducts. An overview of the current state of knowledge on the various methods of REE beneficiation and extraction is covered. These methods include physical separation, as well as hydrometallurgical and bio-hydrometallurgical techniques. The application of these REE extraction techniques for enhanced recovery has been driven primarily by the unique industrial application of these important elements. This paper further explores the existing and potential environmental challenges associated with REE extraction. The authors have presented a wide array of literature, in-depth discussion of the subject, and a succinct summary of processes and relevant case studies.

Sep 23, 2020

By Leonardo Roberto da Silva

Os fluidos de corte são empregados no processo de retificação com o intuito de lubrificar e refrigerar a peça/rebolo, além de amenizar problemas que afetam a integridade superficial da peça e também melhoram a eficiência do processo. Os fluidos de corte são muito utilizados na retificação, porém são tóxicos, dificilmente degradáveis e nocivos ao meio ambiente. Dessa maneira, é pertinente a formulação de fluidos menos agressivos. Neste trabalho, avaliou-se o desempenho de óleos vegetais como fluidos de corte em comparação com o fluido de corte integral no processo de retificação do aço ABNT 4340 temperado e revenido com dureza média de 52 HRc. O desempenho dos fluidos consistiu na análise de rugosidade, formação de espuma e odor. A caracterização dos óleos foi realizada pela viscosidade, densidade, ponto de fulgor, corrosão, índice de acidez total, índice de iodo e de refração. Os resultados mostraram que as peças retificadas com óleos vegetais apresentaram rugosidades próximas às peças usinadas com fluido integral. Na caracterização, os óleos vegetais apresentaram maior viscosidade que o integral e suas densidades foram próximas. No resfriamento, os óleos vegetais foram capazes de resfriar mais as peças que o integral, além de corroer menos. Nos outros aspectos analisados, o óleo de soja foi o que apresentou melhor desempenho. Esses resultados comprovam a eficiência dos óleos vegetais e viabilidade do uso no processo.

Aug 7, 2018