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This paper describes basic parameters, such as surface forces and film elasticity, affecting the stability of foams (two-phase froths). We used the thin film pressure balance (TFPB) technique to measure the surface forces in foam films stabilized with various frothers such as pentanol, octanol, methyl isobutyl carbinol (MIBC), and polypropylene glycol (PPG). The results were compared with the foam stabilities measured experimentally and the film elasticities calculated using a new model developed by Wang and Yoon (2006). It was found that at low electrolyte (NaCI) concentrations foam stability is controlled by both film elasticity and surface forces (or disjoining pressure), the relative contributions from each changing with frother type and concentration. Further, the kinetics of film thinning was studied at a high electrolyte concentration. The results obtained in the present work showed that the major role of a frother is to decrease the hydrophobic force rather than to increase the film elasticity. This conclusion is drawn from the observation that at the typical frother (MIBC) concentrations employed in flotation, frother additions cause sharp decreases in hydrophobic force while causing relatively little changes in film elasticity.

Jan 1, 2006

By P. Zhang, D. W. H. Su, M. Van Dyke, H. Dougherty

This paper describes the scientific data acquisition, data interpretation, and sophisticated 3-dimensional modeling processes of an ongoing gas well stability research program by the National Institute for Occupational Safety and Health (NIOSH). Results from the NIOSH field instrumentation programs and the parallel 3-dimensional numerical modeling programs indicate that overburden depth, overburden geology, surface topographic relief, strata dip of the coal measure rocks, and casing cementing alternatives are the dominant factors affecting longwall-induced subsurface deformations and gas well casing stresses. Topographic relief could produce localized longwall-induced deformations if weak-to-strong rock interfaces are present near the bottom of stream valleys. Strata dip has significant impact on longwall-induced subsurface deformations. Cementing alternatives are found to have significant impacts on longwall-induced deformations and gas well casing stresses.

By Serhat Özdemir, Derya Öz Aksoy, Pınar Aytar Çelik, Ahmet Çabuk, Sabiha Koca, Hüseyin Koca

In carbonate flotation, oleate has been used for many years as a collector in industrial scale. Compared to sulfide minerals, the flotation of carbonate minerals requires more collector consumption and has lower yield and selectivity. It has been previously shown that surfactin provides higher yields in smaller amounts than oleate in the bioflotation of calcite as one of the carbonate minerals. In this study, the usability of surfactin as a flotation collector for magnesite was investigated. For this purpose, the adsorption of surfactin on the magnesite surface was inspected with analyses such as FTIR, SEM–EDS, contact angle, and zeta potential measurements. In addition, the effect of surfactin on the surface tension of water was also revealed. The same analyses were also performed for oleate as a reference point. All flotation experiments were performed without optimizing with both collectors. FTIR results showed that the surfactin, like oleate, was chemically adsorbed on the magnesite surface. Surface tension analyses showed that the surface tension of water decreased to approximately 32 N m− 1 at 10− 4 M oleate concentration, and this value decreased to below 25 N m− 1 at the same surfactin concentration. According to contact angle measurement results, the contact angle of magnesite was 85° after the surfactin adsorption of 2 × 10− 4 M concentration, while this value remained at 46° for oleate. Finally, according to flotation experiments, high temperatures and high collector dosages are necessary for acceptable flotation recovery with oleate, yet surfactin can produce the desired result at ambient temperatures and lower collector amounts.

Dec 13, 2022

By B. Besa, S. Nalukui

Globally, the demand for mineral products is ever increasing. Extraction of these mineral resources results in the continuous production of a huge volume of waste material, including tailing dumps. The mass of tailings usually exceeds the actual resource and often contains hazardous contaminants. This study investigated the effects of tailings disposal on soil, water, and air quality in the Nampundwe area. Water, soil, and dust samples were collected from different locations in the surrounding communities. The constituents analysed in the samples included copper, cobalt, iron, sulfate, and silica. According to the results obtained, some seepages occurred from the tailings impoundment to the shallow aquifer in the area. However, the general water quality meets the Zambia Environmental Management Agency (ZEMA) statutory limits. Recorded concentrations of sulfate (1500 mg/l), copper (1.5 mg/l), cobalt (1.0 mg/l), iron (2.0 mg/l), and silica were between 0.003 mg/l and 705 mg/l, which is far below ZEMA’s statutory limit. Silica concentration was also evident in the air. The highest concentration recorded was 260 ppcc (particle per cubic centimeter) recorded in July 2019 from the northern direction of the tailings dam. The concentration was below the statutory limit of 350 ppcc. The topsoil from the northern part of the tailings recorded a silica dust concentration of 39.9 ppcc. Iron was evident in the underground soil with a concentration of 8.01 ppcc, cobalt 0.005 ppcc, copper 0.051 ppcc, while sulfate was recorded as 0.41 ppcc.

Oct 9, 2024

By G. S. S. Raman, M. S. Klima

Coal refuse slurries stored in tailings impoundments can potentially lead to environmental concerns such as effluent seepage, property devaluation, and in extreme cases, dam failures. Pressure filtration offers an opportunity to reduce the impoundment requirements by providing significantly drier solids. A full-factorial design was used to study the effects of temperature and pH on dewatering a refuse slurry obtained from a coal preparation facility in Pennsylvania, USA. The experimental results indicated a strong effect of temperature on cake moisture as the cake moisture after about 2800 s was 22% at 43 °C and only 36% at 10 °C for tests conducted at pH 3. ANOVA results confirmed the statistical significance of pH, temperature, and their interaction effect. Also, the results showed no significant differences between the tests conducted near neutral and alkaline pH values at low and ambient temperatures. On the other hand, Tukey’s test indicated higher reductions in cake moisture at higher temperatures for lower pH values. This study affirms the need to monitor and control the pressure filtration process as throughput could significantly vary with changes in temperature and slurry conditions.

By Guilherme Corrêa Soares

The effects of temperature and strain rate on the mechanical behavior of a superelastic NiTi wire were investigated by uniaxial tensile testing. A universal testing machine with an attached heating chamber was used for the tensile tests. Temperature influence was studied through straining of samples until rupture at a fixed strain rate and temperatures of 25, 50, 75, 100, 125, 150, 175 and 200 °C. Strain rate effects were investigated by straining samples until rupture at room temperature and strain rates of 10-2, 5 x10-3 , 10-3, 5 x 10-4 and 10-4 s-1. The effects of temperature and strain rate on NiTi mechanical behavior were discussed in terms of critical stress to induce martensite and austenite yield strength, when applicable; upper plateau stress, transformation plateau length and ultimate plateau stress. It was found that increasing test temperature and strain rate shifted the stress-strain curve upwards, albeit temperature displayed a greater influence. Plateau length increased with temperature, but no significant changes were detected as a result of different strain rates.

Aug 17, 2017

By Charles Austin

IN an earlier series of studies on 18-8 stainless steel at 600°, 700°, and 800°C.1 one pretreatment was used throughout; viz., 15 min. in hydrogen at 950°C., followed by an air quench. Several manufacturers of this alloy since have expressed doubt as to the suitability of the temperature employed, recommending instead the more customary Strauss treatment as promising superior results. In this subsequent investigation on the effects of the temperature of pretreatment several interesting points have arisen, which are described in this paper. Previous work on our equipment had shown a marked difference between alloys of "similar chemical composition" that had been manu-factured by different companies. Accordingly, one mill-bar length was selected from which to prepare all specimens. It could then be assumed that any marked differences in creep characteristics would be due to effects resulting from variations in the pretreatment of the alloy. The material was furnished by the Allegheny-Ludlum Steel Co. in the form of 5/16-in, dia. rod, finished by air cooling from a mill anneal at 1950°F. (1066°C.). It was analyzed only for the elements shown: carbon, 0,07 per cent; chromium, 18.73; nickel, 9.46; manganese, 0.40. Three pretreating temperatures were chosen, the specimens being held for 15 min. in hydrogen at either: (1) 1150°C., to conform to the recom-mended Strauss treatment; (2) 950°C., to compare with the results of previous tests; or (3) 750°C., to initiate precipitation of carbides in the material before testing. As the test cross sections were only 1/8 -in. dia., air cooling followed the annealing treatment. These treatments per-mitted two direct comparisons: (1) between the 1150° and 950°C. treat-ments to indicate the effect of grain size when all carbides were probably in solution at the start of the test; and (2) between the 950° and 750°C. treatments to indicate the effect of carbide "nucleation" for similar grain sizes.

Jan 1, 1940

By P. T. Bissert, L. Yan, M. D. Klein

"Federal regulations require the installation of refuge alternatives (RAs) in underground coal mines. Mobile RAs have a limited ability to dissipate heat, and heat buildup can lead to a life-threatening condition as the RA internal air temperature and relative humidity increase. The National Institute for Occupational Safety and Health Office of Mine Safety and Health Research performed heat testing on a 10-person tent-type training RA and contracted ThermoAnalytics, Inc. to develop a validated thermal simulation model (TSM) of the tested RA. The TSM was used to examine the effects of the constant mine strata temperature assumption, initial mine air temperature (MAT), initial mine strata surface temperature (MSST), initial mine strata temperature at depth (MSTD), and mine strata thermal behavior on RA internal air temperature using 117 W of sensible heat input per simulated miner. For the studied RA, when the mine strata temperature was treated as a constant, the final predicted RA internal air temperature was 12.8°F lower than it was when the mine strata thermal behavior was included in the model. A 10°F increase in the initial MSST resulted in a 7.1°F increase in the final RA internal air temperature, whereas a 10°F increase in the initial MSTD yielded a 2.5°F increase in the final RA internal air temperature. INTRODUCTION Since 2008, the Mine Safety and Health Administration (MSHA) has required the installation of refuge alternatives (RAs) in underground coal mines (1). MSHA requires that RAs provide an environment with breathable air for entrapped miners for a 96-hour period. Heat buildup inside an occupied RA is a serious concern. Without a means to dissipate the heat and humidity generated by the occupants and the carbon dioxide scrubbing system, the temperature and humidity inside RAs could lead to severe discomfort or heat stress depending on the mine ambient temperature before and during occupation of the RA. NIOSH recommended an apparent temperature limit of 95°F in its 2007 report to Congress (2). In 30 CFR 7.504, MSHA has specified a maximum apparent temperature of 95°F inside an occupied RA (3). The apparent temperature is calculated using both air temperature and relative humidity (4). Calculations could be used to determine if the air within an occupied RA will reach the apparent temperature limit. In these calculations, in order to simplify the problem, the mine temperature could be assumed to remain constant. With this assumption, the effects of the mine strata thermal mass and thermal conductivity on the heat buildup in an RA are ignored. OMSHR research has shown that the mine air and strata temperatures surrounding an RA increase when subjected to the heat of an occupied RA (5). Thus, calculations performed with the assumption that the mine temperature is constant would under-predict the resulting dry-bulb temperature and apparent temperature for a given RA occupancy. The mine air temperature has been used as the basis for RA temperature calculations. However, research has not been used to confirm that the mine air temperature is the appropriate basis."

Jan 1, 2016

By Richard H. Olson

Talc is currently mined in the U.S. in six major districts. The size and depth of the ore bodies and their mineralogy dictate the types of products manufactured and the mining and processing methods which must be employed. The geology of the major deposits is well known and will be but briefly discussed The major emphasis will be placed upon the past history of the districts, the size and depth and configurations of the ore bodies, the ore mineralogy, and how all of these factors govern the types of mining and processing operations which may be employed in each of the districts.

Jan 1, 1984

By Andressa Alves da Silva

Nowadays, population growth and the interest of food industry, makes the research and applications of biodegradable polymers increase, because under favorable conditions its degradations may occur within weeks or in a few months, reducing the environmental impact. This work presents the processing and characterization of flexible films by the incorporation of 3 % (% wt) of modified bentonite light green clay in the Copolyester/PLA biodegradable blend. The clay incorporation was carried out by melt-mixing processing, using a twin screw extruder machine. The films were obtained by cast extrusion tape. The films obtained were submitted to tensile tests, SEM and XRD analysis, and the correlation between their properties was discussed. The XRD results of clay showed that the quaternary salt and sodium carbonate addition increased the interlayer distance of clay making it easier to intercalation of blend in the nanoclay. The XRD results of PBAT/PLA/Clay nanocomposite show no characteristic organoclay peaks. This result suggests intercalation between nanoclay and matrix (blend). The tensile test results showed an increase of around 30% in tensile strength at break of nanocomposite film when compared with blend film.

Aug 8, 2018

The tensile test results of as-cast A356.2 grain-refined alloy castings show that the tensile strength can be improved by strontium modification (`SrM'), superheating at 900°C OM, and melt thermal treatment of the Sr-modified alloy melt (`SrMTT'). Both SrM and SrMTT processes can greatly improve the ductility (percent elongation) of the as-cast alloy. During solution heat treatment at 540°C, eutectic Si particles undergo fragmentation, spheroidization, and coarsening, thereby affecting their morphology. The effects of solution heat treatment on the tensile properties of the variously treated A356.2 alloy castings can be summed up as follows: the yield strength of the castings is significantly improved after 8 h solution heat treatment due to the precipitation of Mg2Si, after which it remains more or less the same with the further increase in solution treatment time up to 80 h; the ultimate tensile strength is also greatly improved within the first 8 h of solution heat treatment and then remains at the same level thereafter, up to 80h of solution treatment. The improvement in UTS is attributed to Mg2Si precipitation, dissolution of Si within the aluminum matrix, and changes in the Si particle morphology (spheroidization). The ductility of the as-received grain refined non-modified (`NM'), grain refined and superheated at 900°C (`SH'), and melt thermal-treated grain refined (`MTT') A356.2 alloy castings can be improved considerably with solution heat treatment e.g. from ~6% in the as-cast non-modified casting to ~10% after 80 h solution treatment.

Jan 1, 2011

By Lijuan Chen

During the detoxification of chromium-containing slag by Achromobacter sp. CH-1, anionic surfactant Sodium Dodecyl Sulphate(SDS) and its mixed systems with different Tween surfactants(Tween 20, Tween 60 and Tween 80) were used to promote the interaction between the bacteria and the chromiumcontaining slag and the rate of acid-soluble Cr( ? ) leached from the slag. The effects were evaluated by the surface tension, the pH of the leaching solution and the leaching rate of total Cr( ? ) from the slag. The results showed that the surfactants systems improved Cr(VI) leaching and its detoxification of chromium-containing slag. The mixed surfactants of SDS combined with Tween surfactant revealed better effectiveness of detoxification than SDS only. When the mass ratio of SDS to Tween 80 was 1:1, the rate of Cr( ? ) leached from the slag increased by 12%.

Jan 1, 2009

By Jian Pan, Zhen He, Deqing Zhu, Shouyan Yue

"The differences of raw material characteristic among six kind of iron concentrates and the influences on ballability were studied from the aspect of the size distribution, specific surface area and particles morphology. The results show that the specific surface area of iron concentrates has crucial influence on ballability, and the effective method of improving ballability for weak ballability iron concentrate has been found. It is of important guidance for Chinese steel mills to import and use iron concentrate from the whole world.IntroductionChina's steel industry has developed rapidly in recent years, crude steel production in 2011 is an unprecedented 683 million tons, which is almost half of the world crude steel production, and it is equivalent to the total sum production of the nations which rank at 2,3,4,5 and 6 in the world [1]. In order to match the development of steel industry, the blast furnaces are becoming larger and more modernization, therefore charging burden of higher quality is requested, and the reasonable blast furnace burden structure is more and more important, at the same time, for iron ore powder sintering process's continuous improvement and development, another method providing ""concentrate"" for blast fumace-pelletizing is also taken seriously. The grate-kiln method of pelletizing has achieved great development for its unique advantage, and in just a few years, there are over 60 rotary kiln production lines have built or being built in China, the sum of pellets has reached to more than 140 million [2, 3]. The rapidly growth of pelletizing yield demands diverse source of pellet, which include not only domestic magnetite concentrate, but also imported hematite which is high in iron and low in silicon. Usually the ratio of imported hematite concentrate increased gradually. The imported hematite concentrate has high grade and fine particle size (the content of -0.074 mm mostly higher than 90%), but the ballability of part of the concentrates is poor."

Jan 1, 2013

By H. J. Liang

In this study, zeta potential and contact angle measurements of pyrite before and after interacting with Thiobacillus ferrooxidans are carried out to investigate the changes in its surface properties. The results show that, after pyrite interacting with Thiobacillus ferrooxidans and its metabolite, the surface electricity of pyrite changes obviously, resulting in a notable shifting of isoelectric point to lower pH value, but the contact angle varies little. Bacterial protein plays the most important role in the interaction. This work is helpful to disclose the mechanisms of Thiobacillus ferrooxidans de-pressing pyrite flotability.

Jan 1, 2014

By J. Zollinger, J. R. Kennedy, J. H. Park, D. Daloz

"In order to improve the properties of cast Ti-Al alloys to replace Ni-based superalloys past the low pressure stages of aircraft engines investigations into inoculation for grain refinement were carried out. Previous work showed isomorphic self-inoculation using Ti-Al-Nb particles was effective for grain refinement, however the relatively fast diffusion of Nb in Ti-Al make it difficult to observe the mechanism of nucleation. An alternative alloy was developed in the Ti-Ta system for isomorphic self-inoculation, maximizing the Ta content to improve the particles survivability in the melt. The powder processing produced comparatively small inoculant particles which dissolved, however larger particles were seen to survive solidification. The density difference between the inoculant particles and melt resulted in an inhomogeneous mixing of the particles and the melt with larger particles found near the outer edges of the ingots. Variations on particle size and interaction time between the inoculants and the melt resulted in the Ti-Ta inoculant reducing the as-cast equiaxed grain size by a factor of two compared to non-inoculated samples as well as increasing the equiaxed fraction in the ingot.INTRODUCTION Lightweight metals are of particular interest in aerospace applications. The hot sections of turbines are dominated by blades made of nickel based superalloys. Recently the GEnx turbine introduced TiAl blades in the last low pressure stage of the turbine to reduce weight and improve fuel efficiency (Kim & Dimiduk, 1991). In order to carry these benefits deeper into the turbine the high temperature (>800oC) properties of the alloys must be improved. Current grain refinement methods to improve properties rely on boron additions which may not be applicable for all blades as brittle precipitates may be formed during processing (McCullough, Levi, Mehrabian, & Hyman, 1991). A novel grain refinement process was previously introduced called “isomorphic self-inoculation” using Ti-Al-Nb particles to successfully grain refine TiAl (Kennedy, Zollinger, Bouzy, & Daloz, 2016). In order to better understand the mechanism of this process an investigation was carried out using the same process but with a Ti-Ta alloy which is more stable in the TiAl melt than the Ti-Al-Nb."

Jan 1, 2017

By D. G. Lee

Diesel particulate matter (DPM) often contains small amounts of metal as a minor component but this metal may contribute to adverse health effects. Knowledge of the mechanism for particle formation as well as the size preference of the trace metals is critical to understanding the potential for health concerns. To achieve this, the size and the composition of each particle should be optimally measured at the same time. Single particle mass spectrometer (SPMS) would be the best tool for this objective. In this paper, we therefore will introduce new findings about the mechanism and distribution of the trace metals in DPM, derived from a study where an SPMS was used to analyze freshly emitted DPM. KEY WORDS : Single particle mass spectroscopy, Diesel particulate matter, Characterization, Metal contents

Jan 1, 2006

By H. Yen, D. E. Walsh, H. K. Lin

"Comminution circuits are widely used in nonferrous and precious metals milling. Steel crushers, grinding mills and grinding media are typically used in comminution circuits. Comminution circuit wear products, in the form of metallic iron (steel) fines, are unavoidably produced and report to undersize products in the classification circuit, i.e., flotation or leach feed, while tramp grinding steel (TGS) reports to classification oversize products and returns to the grinding mill, building up in the circulating load. In laboratory studies, TGS reduced grinding efficiency significantly, the impact being dependent upon the size of the TGS present in the mill. Because iron fines adsorb flotation reagents effectively, iron fines increase reagent consumption and reduce flotation recovery. Iron fines are also capable of reducing gold recovery in cyanidation circuits via a cementation reaction. When using filtered gold solution from the cyanidation circuit of an Alaskan gold mine, the gold concentration in solution was reduced by 0.2 to 2.6% over various reaction periods when iron fines were present in the solution.IntroductionComminution circuits are widely used in copper, lead, zinc, nickel, cobalt, molybdenum and precious metal mills. Flotation and leaching processes are usually preceded by comminution (crushing and grinding) circuits in order to liberate valuable minerals for effective separation, concentration or dissolution by the subsequent flotation or leaching processes.Steel crushers, grinding mills and grinding media are typically used in comminution circuits. Comminution circuit wear products, in the form of metallic iron (steel) powder, are unavoidably produced and report to undersize products in the classification circuit (flotation or leach feed), while tramp grinding steel (TGS) reports to oversize productions during classification and returns to the grinding mill, building up in the circulating load. Variables affecting the amount of metallic iron powder and TGS produced in a comminution circuit include ore hardness, grinding mill operating conditions, comminution circuit design and the metallurgy of the steel used for manufacturing crusher liners, mill liners and grinding media. As one example, a comminution circuit product of 80% passing 200 mesh at the Pogo Mine, AK is estimated to contain approximately 2 kg/t of metallic iron. A finer grind will generally produce a comminution circuit product with higher metallic iron fines content."

Jan 1, 2015

By Anastasia M. Suchowerska

The design of effective ground support requires a sound understanding of the pre-mining state of stress in the stratum to be mined. Irregularities in the stress field encountered during multiseam mining are governed primarily by the previous mining in the surrounding strata. The aim of this study is to quantify the effects of rock mass transverse isotropy on the vertical stress redistribution in the rock strata beneath supercritical longwall panels. Wilson?s equations for determining the stress distribution induced in and beyond a single longwall panel after it has been mined have been adopted, and a plane strain finite element analysis of an elastic medium, together with the stress changes predicted by Wilson, was used to calculate the final pre-mining stresses in the underlying strata. Values of the independent shear modulus (G¢) of the rock strata, ranging from 0.1 to 1 times the isotropic shear modulus (Giso) in the plane of the strata, and a Poisson?s ratio (?) of 0.25 have been investigated. The key finding of this study is that the predicted magnitude of vertical stress in the transversely isotropic strata beneath a mined supercritical longwall panel is larger and changes more quickly with horizontal distance than is the case for an isotropic rock mass. This finding is of significance for the design of ground support measures in multi-seam mining operations.

Jan 1, 2012

By Mohammad Mainul Hoque, Linhan Ge, Ai Wang, Geoffrey Evans, Subhasish Mitra

"Dispersed phase interactions involving bubbles and particles in the turbulent environment play a significant role in the flotation process. The conventional collision models only account for the deterministic rather than the stochastic behavior of turbulenct flow. What the bubble-particle collisions would be like remains an open problem due to the complex nature of turbulent flow. To address this research question, the present study aims to quantify the bubble-particle collision efficiency incorporating turbulence using the computational method. Multiple solid particles were released to interact with a single stationary rigid bubble (non-deformable interface). Effect of particles Stokes number, turbulent intensity (TI) and integral length scale on the bubble-particle collision efficiency (Pc) was examined. Large Eddy Simulation method (LES) was used to compute the continuous phase. Fluctuating velocity required at the inlet boundary condition was derived from Gaussian energy spectrum to generate the upstream turbulence. Discrete Phase Model (DPM) is used to simulate particle trajectory. The characteristics of turbulent flow were analyzed through Energy spectrum and energy dissipation rate. The critical initial releasing radius of the annulus, where Pc equals zero, reaches up to 1.5(Rb+Rp) under high turbulent intensity (TI) 20.48% compared to 0.23(Rb+Rp) calculated from the traditional Pc model. Pc decreases as the distance of initial releasing annulus between bubble centre increases. Pc increases as particle Stokes number increase up to 0.66. The collision efficiency for particles of St less than 0.38 is higher under TI 11.78% compared to TI 4%.INTRODUCTION To increase mineral recovery, interactions between bubbles and particles are essential. All flotation devices achieve it through introducing some level of turbulence into the system by increasing specific energy dissipation rate. Figure 1 shows three different flotation equipment, traditional floatation cell, Concorde cell and cyclonic-static micro-bubble flotation column (FCSMC), with different turbulence generation mechanisms – impeller, down-flow liquid jet and pump recirculation, respectively."

Jan 1, 2018

By X. B. Zhao, J. G. Cai

When stress wave propagates through fractured rock masses, the wave will be slowed and attenuated due to the presence of these fractures. If the amplitude of stress wave is large enough to mobilize nonlinear deformation of these fractures, they will present different effects on one-dimensional P-wave propagation compared with those of linear deformational fractures. The static BB model is adopted to describe the nonlinear deformational behavior. Method of characteristics combined with displacement discontinuity theory is used to build analytical solutions of wave particle velocities and wave stresses. These equations are numerically solved with sufficient accuracy.

Jan 1, 2003