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By M. Shabbir

A study was made to determine the optimum conditions for precipitation of uranium from mill solutions using hydrogen peroxide. Precipitation tests were made on both synthetic and actual mill solutions. Parameters studied included amount of hydrogen peroxide, initial pH, reaction pH, time, and temperature. Also investigated was the effect of varied amounts of vanadium, molybdenum, and sulfate in the test solution on uranium precipitation and product quality. The optimum conditions for complete precipitation and high product quality were (1) the use of 150 percent of the stoichiometric requirement of hydrogen peroxide, (2) initial pH of 1.0, (3) reaction pH between 3.4 and 5.0, (4) 4 hours reaction time, and (5) ambient reaction temperature. The excess hydrogen peroxide requirement is partially dependent on the amount of impurities present in the feed solution. The hydrogen peroxide process appeared applicable to treatment of the several mill eluate and strip solutions tested. The experimental studies also indicated that the hydrogen peroxide technique gives substantially better product quality than that produced by ammonia precipitation.

Jan 1, 1974

By Nabil A. Bibawy

An improved method for preparing gravimetric standard gas mixtures of helium-4 in nitrogen has been developed by the U.S. Bureau of Mines. A single-pan 12-kg analytical balance that has a sensitivity of 3 mg is used to prepare the mixture. The balance will accommodate a cylinder having a volume of approximately 4 L that weighs approximately 5 kg. The method has been improved to a precision of ±O.04 pct by performing four successive dilutions, by improved handling of gases in the manifold, and by using an improved analytical method to select high-purity gases.

Jan 1, 1990

By P. F. Kerr

This is not a conventional professional paper. It deals mostly with personal experiences. These concern a background in applied mineralogy. Your committee asked me to do this. I accepted with a California enthusiasm which has since diminished with the approach of a Chicago winter. Nevertheless, I wish to thank your committee and also to apologize in advance for omissions and inadequate statements, as such a paper must possess. My introduction to applied mineralogy took place in 1922 at Stanford University. Physicists had recently demonstrated that crystalline powders would reflect x-rays in a systematic manner. Professor A.F. Rogers sug¬gested that significant x-ray reflections might be obtained from powdered opaque minerals. With the aid of Professor D.L. Webster in the Physics Department, I constructed an x-ray diffraction outfit. It was a crude affair, but it worked. Starting with 1924, we secured recognizable patterns of a goodly number of ore minerals (1,2,3). Today x-ray diffraction outfits are common, and a card system of mineral identification is constantly used.

Jan 1, 1981

By J. A. Bos, Z. Dai, P. Quinn, A. Lee

A flowsheet is being developed for processing Thompson ultramafic low-grade nickel ores. This type of ore is characterized by high content of serpentinized magnesium silicates which generate slimes during comminution. Flotation of this type of ore proves difficult due to problems associated with the slimes. The flowsheet, based on extensive laboratory and miniplant flotation tests, consists of two key components: desliming by hydrocyclones prior to flotation and using soda ash for pH control in flotation. Satisfactory metallurgical results have consistently been achieved in laboratory full circuit simulation and miniplant tests.

Jan 1, 2009

By Thomas E. Green

A gas volumetric method was developed for determining metallic aluminum at the 0.01-to 0.3-percent level in 100-gram samples of recycled glass. The method is based on the measurement of the change in gas volume produced by the reaction 2 Al + 2 NaOH + 2 H2O ? 2 NaAl02 + 3 H2 using a simple apparatus assembled from readily available glassware. Apart from sampling errors, the precision of the method is within ±5 percent. A minor modification of the apparatus would extend the method to larger samples or samples of higher metallic aluminum content. Metallic iron and metallic zinc do not interfere at the concentrations found in recycled glass recovered from incinerator residues.

Jan 1, 1971

By R. R. Schehl

The Bureau of Mines analyzed the structure of a high-grade metallurgical coke, carbonized at different temperatures in the range 500° to 1,000° C, through X-ray diffraction studies. Growth in the crystallite size with increasing coking temperature was calculated from profile analysis and compared with values obtained from the radial distribution function. The carbonization temperature appeared to have little influence upon the stack height, whereas the layer diameters more than doubled in size between 500° and 1,000° C. These results are comparable to those obtained from other studies of poorer quality cokes.

Jan 1, 1974

By Hongli Wen, Guangkun Shen, Qiong Deng, Xuling Chen, Min Gan, Xiaohui Fan

"In this research, pyrite cinder which contains 53.51% Fe and 0.54% Pb was processed by magnetic roasting separation to obtain a concentrate with 64.62% Fe and 0.56% Pb. The concentrate was then leached with hydrochloric acid to remove lead. Several technological parameters which may influence the removal efficiency were investigated: the mass fraction of hydrochloric acid, pulp density, the leaching time and temperature. On the conditions that the mass fraction of hydrochloric acid of 5%, pulp density of 30%, the leaching time of 30 minutes and leaching temperature of20°C, the lead content in the concentrate was reduced to 0.19%. The product was suitable for agglomeration and pelletization. Through the analysis of the lead distribution and phase change during the whole process, the mechanism of lead separation from pyrite cinder was analyzed.IntroductionPyrite cinder is rich in iron, which defines its most extensive and effective use as raw materials for iron making. However, some pyrite cinders contain much non-ferrous metals, which is detrimental for the iron making process. Lead, one of the harmful elements, will destroy the blast furnace lining. Besides, it causes pollution of the environment[1]. Therefore it is necessary to remove excessive lead before entering the blast furnace. To separate the lead from pyrite cinder, much research was done, including flotation, high temperature evaporation and leaching. High temperature evaporation consumed too much energy. The flotation was difficult to obtain high- grade iron ore concentrate[2]. Majority of the leaching was direct leaching of pyrite cinder, which was also difficult to get high-grade iron ore concentrate[3]. This article explored the magnetic roasting method to get high-grade iron ore concentrate, acid leaching method of the concentrate to remove excessive lead, providing guidance for the efficient utilization of pyrite cinder."

Jan 1, 2013

By George W. Heunisch

The properties of Neutra-Fix® and Neutra-Ment® , two new lime substitutes for the treatment of acid mine drainage (Arm), have been compared with lime and Alkament®, two products presently in use for AMD treatment. The two new products are basically dolomitic byproducts and produce sludges that are more compact than those from lime. Sludge settling rates are faster than lime with iron concentrations after 24 hours that comply with EPA regulations. Material utilization and optimum pit are reported.

Jan 1, 1984

By D. J. Blickwede

PRESENT knowledge of the effects of time and temperature upon stabilization of the austenite-martensite reaction in steel is fairly complete,1-3 but at the time the work described herein was initiated there was no information about the effects of alloy elements on the phenomenon. However, it has been assumed on theoretical grounds that alloy elements, particularly carbide formers, may have a significant effect on stabilization.' The present work was undertaken to provide information about the effect of two common elements, nickel and molybdenum, on stabilization in hypereutectoid and hypoeutectoid steels. Seven induction-furnace melted, 1.2 pct C steels ' with a variation of nickel from 0 to 6 pct and of molybdenum from 0 to 1.0 pct were used for most of the experiments. Along with these a series of 0.4 pct C steels containing 0 to 6 pct Ni were also studied. The chemical compositions of the steels are listed in Table I. Stabilization in these forged, hot-rolled, annealed, and centerless ground steels was measured by aging brine-quenched specimens (aus-tenite temperature, 1800°F) at 95" and 150°F and then determining the change in specific volume produced by subsequent cooling from room temperature to —320°F.³ In presenting the results the decrease in the change in specific volume, ?V, after various stabilization times is used. This is given by ?V -= ?VO - ?V1 where AVO is the change in specific volume on quenching directly to —320°F and aV, is the change in specific volume on quenching to —320°F after stabilizing for time t. In other words, ?V is a direct measure of the amount of martensite that is lost to the subzero quench as a result of stabilization and hence is greater, the longer the aging time or the higher the aging temperature. The results are shown in Fig. 1. The scatter of the data, which are not shown for clarity and brevity, was sufficient to make the relative location of the curves on the ?V axis inaccurate within ±2x10-5 cc per g. However, some generalities appear which are of interest. Effect of Nickel In the 0.4 pct C steels, up to 3 pct Ni has little, if any, effect on the rate or amount of austenite stabilized at 95°F, Fig. la. Increasing nickel from 3 to 6 pct almost doubles the amount of austenite stabilized in a given time. In the 1.2 pct C steels aged at 95°F, increasing the nickel from 1 to 3 pct appears to decrease the amount of stabilization, and a further increase to 6 pct Ni completely eliminates stabilization as shown in Fig. lb (M, of 6 pct Ni steel was below room temperature). The same behavior was exhibited by these steels stabilized at 1500°F, especially after aging for periods longer than 5 hr, Fig. lc. Thus it appears that up to 1 pct Ni has little effect on stabilization at low or high carbon levels. More than 1 pct Ni increases stabilization at low carbon contents and decreases it at high carbon contents. Ward, Jepson, and Rait5 have found that at inter-

Jan 1, 1954

By Leonard Waldo

The recent and rapid development of the physics of engineering materials at temperatures as low as that of liquid air and as high as that of the electric are, has drawn renewed attention to the absence of tables, properly printed and spaced, for the convenient and accurate translation of temperature from centigrade to Fahrenheit scales and vice versa. It is to be noted that the Fahrenheit scale is the almost universal usage in foundries and shops in the United States, though the laboratories of the same works employ the centigrade notation. The growing use of the electric furnace in Germany and France calls for much American citation all in centigrade high temperatures, and while the arithmetical calculation is simple, it becomes burdensome when often repeated. I have been surprised at the numerous reprints of Table I. from centigrade to Fahrenheit degrees, first privately printed for personal use, which have been made by works, blue-prints, text-books, and technical journals, and I hope that Table II., from Fahrenheit to centigrade degrees, will be equally useful. For mental calculation the easiest rule to convert centigrade into Fahrenheit is to add 32° to twice the centigrade reading less one-tenth of this product: Thus 1000' C. = 2000" — 200" + 32" = 1832" F., and to convert Fahrenheit to centigrade, subtract 32" from the Fahrenheit reading, multiply by 10 and divide by 2 and 9 successively : Thus 1000° F. = 1000° — 32° = 968° X 10 = 9680° - 2 = 4840° - 9 = 537.77° C. Another and often very convenient method is by 'use of a graphic construction as follows :

Jan 1, 1913

By F. P. Haver

The purpose of this investigation was to determine the effect of common impurities, that is, oxygen, nitrogen, carbon, and iron, on the Brinell hardness of electrolytic titanium. On a weight basis, nitrogen had the greatest hardening effect, followed by oxygen, carbon, and iron in order. The hardening effects of oxygen and carbon were almost identical up to a concentration of approximately 0.1 percent by weight. Above this concentration, the relative hardening effect of carbon decreased rapidly, possibly because of its limited solid solubility in a-titanium. Hardness vs. composition curves for both oxygen and nitrogen were essentially straight lines over the range of Brinell hardness numbers (B.h.n.) covered in the investigation. The hardness of titanium was also determined as a function of the percentage of impurity atoms. On this basis, iron in concentrations up to 0.17 atomic percent had a greater hardening effect than either oxygen or carbon. INTRODUCTION Determination of the as-cast hardness of arc-melted titanium is a method of quality control widely used in industry. Numerous studies4/ have been made of the effect of impurities on the hardness obtained by this method. However, most of them have been based on the use of either iodide titanium or commercially pure Kroll sponge (B.h.n. >90), as a starting material.

Jan 1, 1959

By Douglas C. Corner

This is the first of a series of papers dealing with modern tunnel-driving methods, compiled in accordance with an outline prepared by engineers of the United States Bureau of Mines and to be published in a series of information circulars by the bureau. This series will supplement a similar and earlier series of papers dealing with mining methods and costs. ACKNOWLEDGMENTS The author desires to express hiss appreciation, of the assistance of A. C. Dennis, manager for the West Construction Co. Contractors, and Franc: E. Winsor, chief engineer for the Boston Metropolitan District mater Supply Commission who furnished much of the data and detailed description of operation appearing in the following pages. C. F, Jackson, mining engineer, United States Bureau of Mines, collaborated in the preparation and arrangement of the text.

Jan 1, 1931

While there have always been mining activities on the outcrops of the copper deposits around Tsumeb, large scale mining activities in Namibia only started in colonial times. Originally focusing on the known deposits, the then German Geological Survey and independent geologists soon discovered significant deposits all over the country. This eventually lead to intensive mining operations all over the country on copper, gold, diamonds, fluorspar and finally uranium. Ever since those days, mining has been one of the major economical factors of Namibia?s development, as shown in picture 1. In the Central Namib Desert mining on base metals started in 1901, and first uranium deposits were discovered as soon as 1910, later followed by others, this did, however, not lead to any mining activities on those uranium deposits in the following decades. [ ] The upswing in the use of nuclear energy in the 1960s and early 1970s triggered some extensive uranium exploration worldwide and also in Namibia. Several airborne radiometric overviews were conducted by the Geological Survey at this stage and eventually the first uranium mine was commissioned in 1976. In the following three decades, the focus of prospecting activities in Namibia shifted away from uranium again. However, since 2000 the forecast for a developing and growing global economy and its even stronger growing energy demand have triggered a large number of nuclear energy projects worldwide, thus increasing the installed nuclear energy generation capacity from 387 GW today to more than 490 GW in 2025.

Jan 1, 2011

By L. A. Haas

In this Bureau of Mines investigation, conditions were determined to form an iron sulfide adherent coating with a metallic golden luster on steel upon anaerobic heat treatment with sulfur. The sulfide formation rate was determined in the temperature range of 105° to 500° C with reaction times up to 68 hours. The optimum temperature and time to form an adhering decorative coating on mild steel was in the range of 105° C for about 70 hours to 285° C for 1 hour. The golden coating consisted of an inner layer of pyrrhotite and an outer layer of pyrite. At temperatures higher than about 300° C, the outer layer thickness decreased owing to the decomposition of pyrite to pyrrhotite.. Small quantities (<0.5 wt-pct) of petroleum oil accelerated the sulfide growth rate. The sulfide coating decreased the corrosion rate of steel in a neutral aqueous medium by a factor of two. The dissolution of pyrite in water was dependent on particle size and surface area with the flat pyrite coatings exhibiting the lowest dissolution rate.

Jan 1, 1974

By Sean Gallagher, William S. Marras, Alan S. Litsky, Velimir Matkovic, Deborah Burr, John Landoll

Study Design. Survival analysis techniques were used to compare the fatigue failure responses of elderly motion segments to a middle-aged sample. Objectives. To compare fatigue life of a middle-aged sample of lumbosacral motion segments to a previously tested elderly cohort. An additional objective was to evaluate the influence of bone mineral content on cycles to failure. Summary of Background Data. A previous investiga¬tion evaluated fatigue failure responses of 36 elderly lumbosacral motion segments (average age, 81 ± 8 years) subjected to spinal loads estimated when lifting a 9-kg load in 3 torso flexion angles (0°, 22.5°, and 45°). Results demonstrated rapid fatigue failure with increased torso flexion; however, a key limitation of this study was the old age of the specimens. Methods. Each lumbosacral spine was dissected into 3 motion segments (L1-L2, L3-L4, and L5-S1). Motion segments within each spine were randomly assigned to a spinal loading condition corresponding to lifting 9 kg in 3 torso flexion angles (0°, 22.5°, or 45°). Motion segments were statically loaded and allowed to creep for 15 minutes, then cyclically loaded at 0.33 Hz. Fatigue life was taken as the number of cycles to failure (10 mm displacement after creep loading). Results. Compared with the older sample of spines, the middle-aged sample exhibited increased fatigue life (cycles to failure) in all the torso flexion conditions. Increased fatigue life of the middle-aged specimens was associated with the increased bone mineral content (BMC) in younger motion segments (mean ± SD, 30.7 11.1 g per motion segment vs. 27.8 ± 9.4 g). Increasing bone mineral content had a protective influence with each additional gram increasing survival times by approximately 12%. Conclusion. Younger motion segments survive considerably longer when exposed to similar spine loading conditions that simulate repetitive lifting in neutral and flexed torso postures, primarily associated with the increased bone mineral content possessed by younger motion segments. Cycles to failure of young specimens at 22.5° flexion were similar to that of older specimens at 0° flexion, and survivorship of young specimens at 45° flexion was similar to the older cohort at 22.5°. Key words: biomechanics, low back disorders, fatigue failure, age, motion segments, vertebral endplate fractures, torso flexion, lifting, bone mass. Low back disorders (LBDs) are a major cause of both short- and long-term occupational disability in the United States, and it is clear that workers in certain occupations are more susceptible to LBD.2-5 Specifically, epidemiologic studies have shown that jobs involving heavy physical demands such as construction,2,3 mining,2,4 and farming,5 engender increased risk of back pain. These occupations are thought to experience high LBD rates as a result of their extreme postural and manual lifting demands. Studies have shown that jobs involving significant lifting 6-9 and jobs that involve frequent bending10-12 are associated with increased LBD risk. Workers in the mining industry, in particular, often have to lift heavy materials in restricted workspaces that compel torso flexion. An understanding of the impact of repeated loading of the spine in flexion on fatigue failure of spinal tissues is thus a critical issue for our research agency, which is concerned with reducing the pain and disability associated with LBD in the mining industry. It is well accepted that loads experienced by the spine during manual lifting tasks are sufficient to cause fractures in the endplates of lumbar vertebrae, particularly on repeated loading. 13-15 Endplate fractures may not be painful in and of themselves 16; however, evidence suggests that the process of internal disc disruption and disc degeneration may be initiated via endplate fractures. 16,17 It has been shown that endplate damage will alter the distribution of stress in the disc, resulting in buckling of the lamellas of the internal anulus.17 Once this process has been initiated, repeated spine loading will cause additional disruption of the anular fibers, resulting in formation of significant fissures or tears. 11-21 If these tears occur near or extend close to the outer portions of the anulus, a wound healing process is initiated, which involves infiltration of mast cells, macrophages, and re¬lease of cytokines and growth factors. 21 The presence of these infiltrates has been strongly linked to discogenic low back pain. 21,22 Indeed, for patients experiencing chronic low back pain, the prevalence of internal disc disruption is at least 39%,19 which represents the most

By Luis Martín Tejeda

La simulación numérica es considerada como uno de los mejores métodos de modelamiento y planeamiento en la evaluación de la estabilidad de los taludes en minería superficial. En ese sentido, el presente texto señala que a través del método de tensión-deformación, implementado en programas computacionales basados en el método numérico de elementos finitos, se puede llegar a localizar la probable superficie de ruptura. Asimismo, con los diferentes modelos constitutivos como el elástico perfectamente plástico, estos taludes pueden ser evaluados. Por último, se describe brevemente los mecanismos de ruptura en taludes altos, el cálculo del FS y algunas características del programa de elementos finitos PLAXIS v. 7.2.

Sep 19, 2006

By Mohammed Sakr

The use of helical piles for permanent foundation applications has become a practical and feasible alternative to the traditional cast-in-place concrete or driven steel piles. Research and development, installation equipment and manufacturing improvements in the helical piling industry have led to this trend. Moreover helical piles are typically smaller in size and weigh less than traditional piles, and require relatively smaller equipment and therefore it is a cost effective option. The latter is a very attractive feature for foundations installed in remote sites across Alaska. This paper presents full-scale pile load test results of helical piles and driven steel pipe piles installed in a site located in Anchorage, Alaska. Four full-scale pile load tests were carried out including two axial compression and two uplift load tests. Both helical piles and driven steel pipe piles were installed and tested at the same site under similar conditions to provide a direct comparison. The results of the full-scale load tests indicate the superior performance of helical piles compared to driven steel pipe piles. This paper describes the pile installation and test setup, presents the test data, and discusses the results.

Jan 1, 2009

By M. L. Wu

A moderately thermophilic acidophiles strain had been isolated from the bio-heap leaching plant in Zijinshan Copper Mine, and the identification based on the PCR-16S rRNA gene sequence homology analysis with morphologic and physiologic methods was conducted by polyphasic taxono-my and phylogeny research. The results show that the strain by depurated belongs to Acidthiobacillus genus and is considered as Acidthiobacillus albertensis.

Jan 1, 2014

By M. Doggett

All 231 Canadian primary gold mines that produced from 1946 to 2004 were analyzed with respect to their production and economic characteristics. Trend analysis revealed that the average annual capacity of Canadian gold mines, as measured by ore processed or gold produced, has increased over time. Conversely, the average grade of gold mines has decreased over time. The distribution of gold output is highly uneven: for example, the 22 giant mines producing more than 100 t (metric tonnes) of gold account for 62% of total output. Small mines producing less than 10 t Au account for 54% of total mines, but less than 4% of total gold. Each historical mine in the database was evaluated on the basis of a set of economic and technical assumptions to determine if it would be economic to develop today. Based on the net present value using an 8% discount rate, only 103 of the 231 mines were determined to be economic. About 80% of the uneconomic mines had less than 10 t of contained gold, and 63% had less than 5 t. It is concluded that these small mines would not be viable today due to a combination of real capital cost increases, and more stringent permitting and environmental regulations. The implication is that future gold supply in Canada will hinge on the discovery and development of a new generation of larger mines. Given that only one giant mine has been discovered in the past 20 years, it seems likely that gold output will decrease in the future.

Jan 1, 2007

By A Giblett, T J. Napier-Munn

This paper presents the results of a test program evaluating the impact of sample mass on the precision of Stage 1 gravity recoverable gold (GRG) test results. Four ore types ranging from low to high GRG contents were the focus of testing. A method to predict the influence of sample mass on the confidence limits of the Stage 1 GRG test result is demonstrated. The results suggest that although small samples tend to overestimate Stage 1 GRG in samples with low gravity gold values due to higher mass pull to concentrate, such samples can give acceptable estimates of the Stage 1 GRG content with focussed sample treatment protocols.CITATION:Giblett, A and Napier-Munn, T J, 2015. Measuring the influence of sample size on the precision and accuracy of gravity gold estimation, in Proceedings MetPlant 2015, pp 367–372 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015