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Recovery of Tantalum Capacitors from Waste Printed Circuit Boards Using a Pneumatic Separator

Sep 13, 2010

The efficiency of water sprays in suppressing airborne colliery dust depends on many variable factors. A survey of previous work in this field shows that swirl spray nozzles are the best dust suppressors.Investigations carried out in an experimental dust chamber show that, in spite of limitations to the application of water sprays in underground use, promising dust suppression efficiencies in mechanised mining can be obtained with swirl spray nozzles.INTRODUCTIONA dust hazard has always been associated with coal mining, and the recent growth of mechanisation has resulted in a greater production of fine coal and dust, thus increasing the hazard. A better knowledge and appreciation of the medical aspects and dust explosion factors has led to practices reducing the seriousness of the problem. However, the dust hazard still exists and its control is basically an engineering problem.Dust, as with any atmospheric pollution, may be removed from the, mine by ventilation, which is an indirect method of control. Direct methods, in which the dust is prevented from being produced and from becoming airborne, should be employed where possible. Of these direct methods the most significant is the use of water sprays.THE DUST HAZARDAn appreciation of the physical nature of the more important dust hazards is necessary before considering the removal of the hazard. The main hazards associated with colliery dusts are the health hazard and the explosion hazard. "Dust" comprises solid particles of size minus 20 mesh Tyler (833 microns).

Jan 1, 1964

"The effective thermal conductivity (ETC) is one of the most important thermo-physical properties of porous media. Due to the lack of higher precision influence of temperature on thermal conductivity, we took 6 groups of experiments on rock samples (including igneous rock, sedimentary rock and metamorphic rock) under different operating temperatures from 20? to 50? by 7 acquisition points. The general equation of thermal conductivity drives the value of it increasing along with the decreases of the temperature. While in our experiments, it is easy to find a singularity among them for each sample. The experimental investigations we attempted to observe and interpret the alteration mechanism. According to the Heat Capacity Theory in solid state physics, this research gives the explanation about the “singularity” from 3 understanding of specific heat, average free path, and thermal conductivity. Our research divided the condition of the rock thermal conductivity into 3 different types. INTRODUCTION The effective thermal conductivity (ETC) is one of the most important thermo-physical properties of porous media(Huang & Han ,1988; Peierles ,1955). This parameter is necessary for analysis of heat transfer(Vaferi et al, 2014;Hans-Dieter & Rudiger,2003). It’s well known that a general equation for ?(T) was set by Sass et al. (1992) which based on the coupled effect of composition and temperature on the thermal conductivity(Jesse et al, 2013; Mongelli et al,1982).The equation was further successfully verified for other rock (Zumrud et al,2010;Abdulagatova et al,2009;Seipold& Huenges,1998).Thermal conductivity is also related to other physical proper ties of porous rock, such as thermal diffusivity, heat capacity(Brettmann et al,2011;Abuel-Naga et al,2008). It is well known that ETC and other thermo physical properties of rock materials are affected by various factors, such as temperature, pressure, mineralogical composition, porosity, stratification, size and shape of the components, and nature of pore fluid, etc. (Tiedje & Guo, 2014; Touloukian et al,1970).The understanding of heat transport processes still requires the knowledge of thermal properties of rocks."

Jan 1, 2015

By Raj P. Singh Gaur

Due to high concentration of NaOH in the digested slurry after scheelite digestion, it is diluted to about 4N before filtration to separate sodium tungstate solution from the sludge (residue). However, in practice there may be deviations in the normality of NaOH present in the slurry. There may also be variations in the temperature of the slurry and filtration time. Slight variations in these parameters could cause tungsten losses in the sludge via the back reaction: Ca(OH)2 + Na2WO4? CaWO4 + 2NaOH This paper pertains to the effect of normality, temperature and time on the tungsten losses in the sludge that is separated from ?diluted-scheelite-slurry-in-NaOH? via filtration. Results indicated that tungsten losses in the filtered residue (sludge) were quite significant when the slurry temperature was kept at 70°C or higher. The effect of high temperature was less significant at the slurry normality of 3.6 or higher. Combination of low slurry normality (<3.6) and high temperature (>60°C) resulted into large W-losses in the sludge.

Jan 1, 2006

By Moskovits E. E

Spodumene was recovered from pegmatite by flotation in laboratory and pilot-plant tests using an anionic collector emulsion. A similar process applied to beryl pegmatite gave encouraging results.INTRODUCTIONOver the past two decades lithium and beryllium have aroused increasing interest in the metallurgical world. Both these light metals have potential uses in nuclear shielding and cooling and in lightweight alloys, and there is a growing demand for lithium chemicals for ceramics, air conditioning and lubricants. The use, technology and history of lithium has been surveyed by Schreck (1961).For many years, the only commercial production of lithium and beryllium was from pegmatite deposits amenable to hand cobbing. The most important minerals of these ores are spodumene and beryl, which are respectively lithium aluminium silicate and beryllium aluminium silicate. Norman and Gieseke (1940) investigated the treatment of lithium ores by froth flotation. The process of flotation of the pegmatite constituents away from the spodumene was applied commercially in 1951, and the operation has been described by Goter, Rainey and Hudspeth (1953). Subsequently, the flotation of the spodumene from the pegmatite was studied by Munson and Clark (1955) and Browning and McVay (1961), and this method has superceded the reverse flotation process commercially. Muskett, Tasker and Hobson (1962), in applying the method of Browning and McVay in pilot-scale tests, reported difficulty because of activation of quartz and felspar by iron salts introduced during milling of the ore.The flotation of beryl, reported by Ashton and Weir...

Jan 1, 1963

By G. L. Humphrey

Although silicon carbide has been an important manufacture refractory for many years, knowledge of its thermodynamic values has been seriously lacking. In fact, some of the very properties that make it a useful substance, particularly chemical inertness, obstruct determination of its heats of formation and reaction. This paper reports the results of new measurements of the heats of combustion and formation, low-temperature heat capacity, entropy at 298.16°K., and heat-content and entropy increments between 298° and l,800°K. Two varieties of silicon carbide were studied -the common, hexagonal (type II) and cubic. The data are combined to obtain heat and free-energy-of-formation functions, which are given in tabular form. It is shown that the cubic variety is the more stable at temperatures to at least 1,800°K but, because of the inherent difficulties and errors in the heat-of-formation determinations at 298°K, it was not found possible to specify the free-energy difference accurately. The mechanism of silicon carbide formation from silica and carbon is not known and is not ascertainable from thermodynamic data. It appears improbable, however, that it can be a single-step reaction. Some reactions involving silicon monoxide gas and metallic Silicon, as possible intermediates in silicon carbide formation, are considered and shown to be thermodynamically feasible.

Jan 1, 1952

By G. H. Gronhovd

This report describes the design and initial operation of a slagging gasification pilot plant installed by the Bureau of Mines at the Lignite Research Laboratory, Grand Forks, N. Dak., in 1958-59. The tests covered in this report were conducted over a period of about 2 years, beginning in April 1959. The pilot plant was designed for eventual operation at pressures ranging from 400 to 600 p.s.i.g. (pounds per square inch gage); however, for the preliminary test reported here, the gasifier was fitted with a low-pressure slagging section and operated at atmospheric pressure and at 80 p.s.i.g. The reason for using a low-pressure slagging section for initial operation was to facilitate modifications in design during the development of a reliable slagging procedure.

Jan 1, 1962

Seam correlation in the central Rapahoe Sector (Greymouth Coalfield) can be enhanced by detailed lithostratigraphy and chronostratigraphy. Rewanui Coal Measures are overlain comformably by lacustrine, deltaic and fluvial strata, and this upper contact can be located using lithological and geophysical log character. The Cretaceous-Tertiary Boundary (KTB) occurs near the top of Rewanui Coal Measures and has been identified palynologically in 16 drillholes. The Rapahoe Sector can be subdivided into two palynostratigraphic domains which adjoin along a basement normal fault which was downthrown to the north during coal measure deposition. The KTB provides an isochronous surface which is independent of the lithostratigraphic datum. Using the KTB as a datum, the æUpperÆ, æMainÆ and æSubmainÆ seams can be reliably correlated throughout the southern and central Rapahoe Sector. Similarly, the æSubmainÆ seam can be correlated with æcÆ seam of the Strongman Mine area, though other Strongman seams are absent from the central and southern Rapahoe Sector.

Jan 1, 1996

By O. Nyandoro, K. Khoza-Shangase, M. Madahana, N. Moroe

"Occupational noise-induced hearing loss (ONIHL) is classified as the leading work-related disability in the mining industry. ONIHL has a negative impact, on not only the health and occupational productivity of affected individuals, but arguably also on the country’s mining industry and economy. Hearing conservation programmes (HCPs) are an effective strategy in the management of ONIHL. However, current literature indicates that HCPs are not achieving the anticipated and desired outcomes in the South African mining sector despite the efforts focused on the management of ONIHL. Therefore, the purpose of this study is to propose the use of a feedback-based noise monitoring model as a tool for monitoring and managing ONIHL in the South Africa’s mining sector. This model is a basic static feedback model with practical applications such as estimating, monitoring. and providing quantitative information to aid miners, mining administrators, and policy-makers in decision-making around HCPs. Additionally, the model could form part of an early intervention and management strategy for ONIHL in the workplace. The strength of this model, although currently static, is that it encompasses all the pillars of HCPs and takes into account the policies concerned with the management of ONIHL in the mining sector. IntroductionHazardous noise levels (above 85 dBA) in the workplace place exposed employees at risk of developing a disabling occupational noise-induced hearing loss (ONIHL). ONIHL is the ‘partial or complete hearing loss in one or both ears as a result of one’s employment’ (Nandi and Dhatrak, 2008, p. 1). This type of hearing loss develops gradually as a result of being exposed to continuous or intermittent high levels of noise over a long period of time (McBride, 2004; Patel et al., 2010; Rappaport and Provencal, 2001). A hearing threshold below 40 dBs is classified as a disabling hearing loss (Yadav et al., 2015), resulting in a hidden condition that does not readily manifest itself (Tye-Murray, 2009, p. 3). Dugan (2003) describes disabling hearing loss as the ‘most prevalent, least recognized and least understood physical disability’, while Copley and Frederichs (2010) and Hermanus (2007) argue that permanent disabling hearing loss is a major contributor to the global burden of disease on individuals, families, communities, and countries."

Jul 1, 2019

By Jr. Norman

The Bureau of Mines investigated the thermoelectric properties of yttrium selenides and tellurides from room temperature to 900° C. X-ray crystallographic data were determined for the yttrium-selenium and yttrium-tellurium compounds that were orthorhombic with a cubic substructure. The yttrium selenides and tellurides exhibited semimetallic to insulator conduction properties with figures of merit of 10-9 to 10-4 °C-1. The mono-selenide and monotelluride behavior was partially degenerate; unsatisfied bonds were the source of the large number of charge carriers. The higher stoichiometry selenide compounds were intrinsic semiconductors) but with high electrical resistivities. A critical defect or impurity ionization energy for carrier activation appeared to exist in the majority of telluride compounds. Mobility and energy band determinations are required to interpret completely the observed effects in most of the compounds studied.

Jan 1, 1966

By K. Rainer Massarsch

In some parts of the world, vibrators are used extensively for different types of foundation engineering projects. If used correctly and in suitable soils then vibratory pile driving for example is very efficient. However, soil conditions and the installation procedure have great significance for the driving resistance and affect the bearing capacity of vibrated piles. Also the intensity of ground vibrations which are transmitted to the surrounding soil is affected by the vibration process. In spite of the increasing use of vibrators and the rapid development of vibrator technology, many aspects of pile-soil interaction are not yet understood. In order to asses the importance of factors, which govern pile installation (and extraction), it is necessary to consider the entire chain of vibration energy transmission from the vibration source to the pile, the interaction between the vibrating pile and the soil and the wave propagation in the subsoil, Fig. 1. [ ] Fig. 1. Transfer of vibration energy from the vibrator through the pile into the ground In the present paper, some important aspects of vibratory driving and their significance for pile installation and soil compaction will be discussed.

Jan 1, 1995

The revised estimate of coal production in January 1977, is 39 million tons -- down 12 mi 11 ion tons compared with production in January of last year, largely as a consequence of the snow storms and cold. The major coal-hauling railroads operating in Eastern and Midwestern States reported to the Bureau of Mines that they loaded approximately the same number of cars for the week ended February 5, as in the preceding week. The Bureau of Mines estimates that U.S. coal production for the week ending February 5, 1977, was approximately 8.5 million tons, or nearly 3.5 million tons less than production for the corresponding week in 1976. Coal production from January 1 - February 5, 1977, was approximately 47.8 mi 11 ion tons compared with production of 63.5 million tons for the corresponding period in 1976. As of the first week in February, river and truck shipments of coal in the Eastern U.S. were about one-half of the normal traffic. Despite the freezing weather and ice and snow conditions of rivers and highways and reduced rail shipments, there was reportedly little or no shortage in coal supply to consumers. Inventories at electric utility plants and steel company coke plants at the beginning of the severe weather were sufficient in most cases for at least 30 days" operations. There have been no reports of coal shortages at other industrial plants.

Jan 1, 1977

By Adrián Del Carpio

Desde 1995 la planta de Lixiviación de Toquepala desarrolló un sistema de control automático para los procesos de extracción por solventes y electrodepositación. Sin embargo, con el desarrollo de la tecnología y las nuevas versiones de control, dicha plataforma se tornó arcaica. En ese sentido, el presente texto señala la modernización de los sistemas relacionados con el control y supervisión de las áreas de extracción por solventes, depositación electrolítica y áreas auxiliares. Como consecuencia de ello, se incrementó la operatividad, disponibilidad y fiabilidad con cero paradas por perturbaciones eléctricas, así como redujo el tiempo utilizado para el diagnóstico y solución de problemas.

Sep 12, 2011

By Joseph Blake Smith

Coal resource data from published sources and company files were used by the Bureau of Mines to determine the location and extent of strippable coal reserves in Wyoming. Total strippable reserves of 23 billion tons were estimated in seven major coal areas. Seven large strip mining operations were active in 1969, and their production totaled 45 million tons of coal. Cutoffs used to define strippable reserves were (1) minimum coalbed thicknesses of 5 feet; (2) overburden-to-coal ratios of less than 10 cubic yards of over- burden per ton of coal; and (3) total overburden thicknesses of less than 120 feet, except where reserves occur in multiple beds or a single thick bed. Tertiary rocks along margins of the Powder River basin contain most of the strippable coal reserves in Wyoming. The Wyodak beds, ranging in combined thickness from 30 to 1.30 feet, crop out on the east flank of the basin and contain an estimated 19 billion tons of strippable subbituminous C-rank coals under less than 200 feet of overburden. Partings between these beds total less than 60 feet. The 100- to 200-foot-thick. Healy bed on the western flank of the basin and the 35-foot-thick School and 20-foot-thick Badger beds on the south also contain large strippable reserves. Elsewhere in Wyoming, strippable reserves. Elsewhere in Wyoming, strippable deposits are subbituminous coal of Late Cretaceous and Tertiary ages, mostly in the Hanna and Great Divide basins in the south-central portion of the State and in the Kemmerer-Hamms Fork region in the southwestern corner.

Jan 1, 1972

By Armstrong M

The Coal Mining Engineering Branch of the New South Wales (NSW) Department of Mineral Resources, in its continuing effort to improve coal recovery from underground coal mining operations, has undertaken a study of the mechanics of sub-surface deformation caused by caving of the extracted area behind retreating longwall faces. The strata movement was monitored by a multi-wire borehole instrumentation system consisting of mechanical anchors installed at different horizons in a borehole extending from the surface to the coal seam. The mechanical anchors were connected to the suspended weights on the surface by stainless steel multi-strand wires. The movement of these weights was monitored as the longwall face approached and retreated past the borehole. The anchors started subsiding as soon as the face retreated past the borehole and continued to subside until the subsidence levelled off when the face retreated 900 m past the borehole. The zone of major caving and bed separation extended to roughly 10 to 13 times the extracted seam thickness and high tensile strains developed inthis zone. The bulking factor of broken strata was less than 1.14 which indicated that the roof layers collapsed in big blocks. The goaf compaction was almost complete when the face retreat was 200 m. Low tensile strains prevailed in the strata overlying the zone of caving and bed separation.

Jan 1, 1986

By B. J. Moore

This publication contains 14,242 analyses of gas samples from oil and gas wells and natural gas pipelines in 40 States and 24 foreign countries. These gas samples were collected in the period 1917-85 as part of the Bureau of Mines survey for helium occurrences. The gas analyses contained herein were made by several methods over the period covered. Analytical work on samples collected early in the period was done on the Orsat apparatus. The one-cut apparatus and four-cut fractional distillation equipment were added later. A mass spectrometer was acquired in 1949 and used for all gas analyses made after that time. From 1917 to 1978, helium analyses were made on special helium analytical equipment designed and built by the Bureau of Mines Helium Operations Laboratory. In 1978, this apparatus was replaced in the quantitative helium analysis work by a gas chromatograph.

Jan 1, 1987

By Brian Fulcher

The Arrowhead Tunnels Project represents the final portion of a 70 km (44-mile) long water conveyance facility that will bring up to 28 m3/sec (1,000 ft 3/sec) of water into Southern California. The 13 km (8-mile) tunnelling project is well underway and consists of two, 5.8 m (19-ft) diameter TBM bores through extremely variable geological conditions. An extensive and essential pre-excavation drilling and grouting program was performed in all reaches of the Arrowhead Tunnels Project, located north of San Bernardino, CA. This program supported the advance of two hybrid hard rock TBMs though extremely challenging ground conditions under substantial ground cover and up to 27 bar (900 ft) of ground water pressure. The well known San Andreas Fault lies nearby and has greatly influenced the local geological conditions. This paper will describe the means, methods and materials used throughout the numerous phases of the pre-excavation grouting program. It will also describe many versatile, flexible and innovative drilling and grouting methods and equipment systems utilized to improve performance, save time and costs in constantly changing geological conditions. Considerable lessons learned have been learned while overcoming some extremely formidable ground conditions and safely advancing the tunnels.

Jan 1, 2008

Thirty mixed cultures of microorganisms from soil, water and mineral samples from the Groote Eylandt Mining Company mine site were approximately three times more effective in biodegrading manganese dioxide (34&#177; 18 mg Mn++/1/day) than sixteen purified strains (11 &#177; 10 mg Mn++/1/day) isolated from the primary enrichment cultures. Two pure bacterial genera identified as a Pseudomonad and a Bacillus, with an excess MnOz and nutrient, were able to dissolve 106 mg Mn++/litre/day in mixed culture compared with 29 mg Mn++/litre/day when grown separately.

Jan 1, 1983

By E. P. Dowding, J. Schlocker, C. H. Fuchsman, R. R. Lloyd, Mahan. W. M., O. C. Garst, W. T. Rawles

"INTRODUCTION The United States, although the leading consumer of chromite, depends almost entirely on imports for its supply. For instance, the consumption during. 1941 amounted to 714,645 long tons, whereas the domestic chromite production, although the highest since 1918, was 12,731 long tons or only 1.78 percent of the domestic consumption. 9/ Domestic production was tremendously, accelerated,after 1941 by war demands; however, only a small proportion of this domestic product was of sufficient quality to be substituted for the high-grade imported chromite demanded for metallurgical purpose. Chromite is used largely for making ferrochromium, an alloy containing 60 to 70 percent chromium which is used in making alloy steels. Peacetime specification for ferrochromium required that it should contain 68 to 69 percent chromium. These specification were lowered to between 60 and 63 percent, chromium in 1941 to permit the use of lower-grade ores. The specifications for metallurgical chromite, used for making ferrochromium, were established first by the Metals Reserve Company at 48 percent Cr203 and a Cr. Fe. ratio of 3 : 1 but later were lowered to 45 percent Cr203 and a Cr : Fe ratio of 2.5 : 1. The ratio of chromium to iron in chromite is important, because the contained iron enters the alloy in making ferrochromium and, although an ore may contain the required 45 percent Cr203, it may contain too much to be suitable for ferrochromium production. The principal sources of domestic chromite are California, Oregon, Montana, and Alaska minor, small, and widely scattered deposits in another dozen States. Without exception, these deposits are low-grade, require beneficiation to produce a commercial product, and are not competitive with imported high-grade ore in normal times. Nevertheless, these deposits form strategic reserve, which must be utilized in periods of national emergency. Recognizing this fact; the Bureau of Mines for many years has undertaken investigations to develop methods of utilizing domestic chromite ores. The problem has been approached from three angles: (1) Mechanical methods of concentration; (2) beneficiation by chemical or metal¬lurgical methods; and (3) production of metallic chromium by electrolysis of solutions prepared from ore or concentrate."

Feb 1, 1946

By Luis Haro

Puesto que el deslizamiento de relaves constituye uno de los principales riesgos para la vida y seguridad de los embalses, se desarrolló un programa que rehabilite los depósitos de los relaves a través de los gaviones y geomallas como elementos que estabilizan los relaves descargados. En este sentido, el uso de geosintéticos revolucionó el diseño de los relaves y sistema productivos y permitió un mejor manejo ambiental de los relaves. Asimismo, la utilización de gaviones como paramento externo en el sistema suelo armado, otorga mayor rigidez al mismo en el caso de paredes, taludes más verticales, drenaje y protección contra la erosión. En consecuencia, el uso de gaviones y geomallas es aplicable para la construcción de depósitos de relave y estabilización de depósitos inactivos.

Sep 13, 2001