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By Kato T, Eguchi M, Seino T, Itagaki K, Kimura T, Muto T, Shimizu T, Kobayashi T

Behaviour of minor elements in the dust collecting system connected with fluidized bed roaster for zinc concentrate was investigated by use of the bench scale experimental appara- tus. The dust collecting system was consisting of two dust chambers, hot electrostatic precip- itator, washing tower, mist electrostatic pre- cipitator, drying tower, absorption towers and potassium permanganate solution towers. Some volatile elements such as lead, cadmium and arsenic tend to concentrate in the fine calcine obtained in hot electrostatic precipitator especially in the case of the roasting with insufficient air supply. Special attention was paid to behaviour of mercury. In the roasting tests for plain zinc concentrate, it was considered that most mercury volatilizes at first as elemental vapour in the roaster, but with decrease in temperature of gas around a half of mercury forms compound, and both elemen- tal and compound forms of mercury were found in the gas stream. Elemental mercury is of course difficult to be trapped in the dust collecting system. To promote the compound formations, some additives for concentrate, such as selenium and halogens were effective, especially selenium of a few times equivalent to form HgSe repre- sented complete conversion of mercury from elemental to compound. To clarify the behaviour and removal mech- anism of mercury, various small scale laboratory tests were also carried out. It was confirmed that mercury sulfate formation is possible if temperature and flow rate are adjusted adequate- ly for gas stream consisting of 02-SO2-N2. To trap elemental mercury, various substances were tested, and excellent results were obtained with selenium. Satisfactory results were obtained with a selenium disc heated at 100 to 200¦C in a mercury containing gas stream. Also, applica- bility of scrubbing method with SeO2 solution was investigated, and the solution containing a few hundred ppm SeO2, 0.01 per cent additive and 6 per cent H2SO4 proved to be satisfactory.

Jan 1, 1980

By Henry J. Miller, Marcella Lindeman

DURING some experiments made by Henry J. Miller, partly in Germany and partly in the United States, in which it was found necessary to melt metals in quantities up to 60 kg. in a vacuum or under low pressures of hydrogen, molybdenum was tried as the resistor in the electric melting furnaces. Molybdenum ribbons 16 by 0.55 mm. and 18 by 0.45 mm. were used as resistors. The furnaces were of the type shown in Fig. 1. [ ] About the heating tube, Y, are wound parallel resistors of molybdenum ribbon from the water-cooled electrodes, E1, E2. The whole is within a copper container having outlets for the removal or introduction of gases and a window, W, for observation, the space about the heating tube and electrodes being filled with insulating material. The life of the molybdenum used as the resistor was found to depend very much on the manner of using it, its failure being due in some cases to thinning by evaporation or chemical reaction and in others to hardening, which prevented it from following the expansions and shrink¬ing of the heating tubing without cracking. As such failures are often rather expensive in commercial work, it was thought worth while to determine the causes. The factors influencing the behavior of molybdenum resistors used in this manner may be briefly stated as follows:

Jan 1, 1928

By Lassi Klemettinen

For better understanding and maximal value utilization of the WEEE smelting process, the behavior and distribution of different trace elements must be known. In this study, the behavior of nickel as a trace element was studied in an equilibrium system with metallic copper—spinel saturated iron silicate slag (with 3 wt-% K2O)—iron aluminous spinel—gas. The experiments were conducted in alumina crucibles at 1300 °C, in oxygen pressure range of 10−10–10−5 atm. A time series of 15–60 min experiments was also conducted for investigating the formation rate of the primary spinel phase in the system. The results show that the distribution coefficient of nickel between metallic copper and liquid slag changes from approximately 70 to 0.4 along the increasing oxygen pressure range. In addition, a significant part of the nickel deports into the spinel phase. The spinel formation was investigated based on composition analysis results and visual observations from SEM-images.

By James Rowland, Marcia Harris, Richard Mainiero, Michael Sapko

All explosive materials produce a cloud of reaction products, the most toxic of which is nitrogen dioxide (NO2). In the study reported here, 4.5-kg (10-lb) charges of blasting agent confined in either thin-wall 10-cm (4-in) diameter galvanized pipe or 10-cm (4-in) schedule 80 seamless steel pipe were detonated in a closed chamber. The detonation gases were analyzed for NO2, nitric oxide (NO), ammonia (NH3), hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), nitrogen (N2), oxygen (O2), and methane (CH4). Data were evaluated to determine the kinetics of the oxidation of NO to NO2. Analysis revealed that the only mechanism for NO loss for the conditions existing in the chamber was the reaction 2NO + O2 6 2 NO2. The rate constant was 2.08 ?? 10-38 cm6 molecules-2 sec-1 for the rate equation -??d [NO]/dt = K ?? [NO]2 ?? [O2] for NO concentrations up to 100 ppm. The rate constant is in agreement with that recommended by Baulch, Drysdale, and Horne (1973).

Jan 1, 2006

By Richard J. Mainiero, Michael J. Sapko, James H. Rowland III, Marcia L. Harris

All explosive materials produce a cloud of reaction products, the most toxic of which is nitrogen dioxide (NO2). In the study reported here, 4.5-kg (10-lb) charges of blasting agent confined in either thin-wall 10-cm (4-in) diameter galvanized pipe or 10-cm (4-in) schedule 80 seamless steel pipe were detonated in a closed chamber. The detonation gases were analyzed for NO2, nitric oxide (NO), ammonia (NH3), hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), nitrogen (N2), oxygen (O2), and methane (CH4). Data were evaluated to determine the kinetics of the oxidation of NO to NO2. Analysis revealed that the only mechanism for NO loss for the conditions existing in the chamber was the reaction 2NO + O2 6 2 NO2. The rate constant was 2.08 @ 10-38 cm6 molecules-2 sec-1 for the rate equation -½d [NO]/dt = K @ [NO]2 @ [O2] for NO concentrations up to 100 ppm. The rate constant is in agreement with that recommended by Baulch, Drysdale, and Horne (1973).

By D. E. Larson

In cooperation with the National Institute of Environmental Health Science and the National Institute for Occupational Safety and Health the U.S. Bureau of Mines conducted grinding research on non-asbestiform tremolite. The goal of this effort was to prepare ground tremolite samples containing a considerable percentage of acicular grains with aspect ratios (approximately = 8um long with widths = 1 um) similar to those of asbestos particles suspected of causing cancer, Optical-and electron-microscopic examinations were used to monitor the size and shape of the grains in the ground products. Although customized milling techniques do have noticeable effects in producing acicular grains, the prismatic nature of fracturing in the non-asbestiform tremolites limited the number of acicular grains that could be purposely produced, and indicates that the likelihood of high concentrations of acicular particles occurring under normal mining and milling conditions is small.

Jan 1, 1991

By Zhitao Ma

The Cast-in-place Concrete thin-wall Pipe pile, referred to as PCC pile, is a new kind of pile for soft ground improvement. In this paper, firstly, the general introductions of the new pile technique, mainly including the technique principle, the structure of pile-driving machine, and the technological process were given, then based on the results of in-situ static lateral loading test, the pile lateral capacity, the relationship of load-deflection of pile at the ground surface, the lateral deflections versus depth and the soil reaction along the pile shaft were analyzed.

Jan 1, 2006

By Renato P. Cunha

The paper explores a parametric analysis of a four-pile group in contact (hence piled raft) and without contact (hence standard pile group) with the superficial soil layer, under a combined set of loadings (moment M, vertical V and horizontal H forces). The major design parameters of interest, as total and differential settlements, and raft bending moments and shear stresses are assessed under aforementioned distinct conditions. The slenderness ratio of the piles is also varied along the analyses, allowing the establishment of its influence on the derived parameters.

Jan 1, 2006

By Merete Tangstad, Fei Li

This paper studies the quartz and carbon black pellets at elevated temperature with varying temperature and gas atmosphere. High-purity quartz and commercial ultra-pure carbon black was mixed (carbon content wt.15%), and then pelletized into particles of 1-3mm in diameter. The stoichiometric analysis of the pellet during heating is studied in thermogravimetric analysis (TGA) furnace at different temperature in CO and Ar atmosphere. The microstructure, phase changes and element content of sample before/after heating is characterized by X-ray diffraction, scanning electron microscope, X-ray fluorescence and LECO analyzer. The reaction process can be divided into two stages. Higher temperature and argon atmosphere are the positive parameters for SiC formation.

Jan 1, 2016

By G. Labonte

The behavior of four different redox sensing electrodes (gold spiral, black platinum, chalcopyrite, and galena) during roughing and cleaning flotation is examined and related to the flotation response. Although it is difficult to provide unequivocal interpretations of the different potentials measured, the results indicate that the solution potential (as sensed by the black platinum electrode) is different from that of the pulp potential (gold spiral) and is only weakly related to the flotation response. On the other hand, the potentials exhibited by the gold spiral and the two mineral electrodes are related to the floatation response. The gold and mineral electrodes exhibit different transcient responses during the addition of flotation modifiers (e.g. NaCN, SO2). These responses appear to be related to the reactivity of the minerals and could indicate the conditioning time required to achieve flotation or depression of selected minerals.

Jan 1, 1989

By Giacobbe Braccio, Alessandro Blasi, Assunta Romanelli, Massimo Morgana, Corradino Sposato

The solvent extraction technique is the only industrial way used to separate and purificate yttrium from other rare earths. In order to improve this process several extractants have been tested during last years. In this work, the behavior of sec-octylphenoxy acetic acid (CA-12) in Yttrium recovery from high concentrated heavy rare earth mixture was investigated. Sodium hydroxide solution was used in order to presaponify organic phase composed by CA-12 and Tributyl phosphate (TBP) diluted in kerosene. In the investigated condition, TBP confirmed its role of phase modifier not significantly altering the extraction behavior of CA-12. The CA-12-TBP system showed a high affinity in extraction for lighter rare earths such as Sm, Eu, and Gd, leaving yttrium in aqueous phase. Using a feed concentration (P [RE]) of 1 M, organic mixture is capable to extract around the 70% of metals in a single extraction test showing this extraction sequence Y < Lu < Yb < Tm < Er < Ho < Dy < Tb < Gd < Eu < Sm. Moreover for [CA-12] = 1.79 M and [RE] = 2 M the instability of extraction system occurs.

Mar 1, 2017

By Nabil F. Ismael

The axial capacity of step tapered bored piles in sand was examined by field tests at one site in Kuwait. Two straight piles, and two step tapered piles were load tested in compression to failure. All four piles were 3 m deep. The straight piles were 0.2 m in diameter. The step tapered piles had a diameter of 0.3 m for the upper segment which extended up to 40% of the pile length changing to 0.2 m diameter for the lower section. The soil profile consists of medium to dense sand with minor cementation and no groundwater was encountered. Both the ultimate bearing capacity and the settlement at working loads were examined. The axial capacity of the step tapered piles was greater, and the settlement at working loads was less, compared with the straight shaft piles. The increase in capacity is mainly attributed to the added side friction along the larger diameter top segment of the shaft.

Jan 1, 2008

By Murali M. Gadde

Welded wire mesh is the most commonly used skin control technique in the United States underground coal mines. Currently, selection of the mesh is based on trial and error rather than any rigorous design methodology. Several factors affect a wire mesh?s performance including the amount of rock material to be supported and how the load is distributed, wire gauge, aperture size, grade of steel, weld strength, bolting pattern and sheet size. Although the best way to choose the mesh is to conduct full-scale physical load tests, because of the limitations on the number of variables that can be considered in such tests and the requirement of an elaborate test set-up, it may not always be possible to use this option. An alternative would be to use numerical modeling to study the load-deformation behavior of a wire mesh. In addition to providing a very detailed stress, strain distribution in the entire mesh, the advantage of this approach is the ease with which parametric studies can be conducted. In this paper it is shown that the load-deformation curves generated by nonlinear numerical models match closely with laboratory derived ones. Then, based on parametric studies, design guidelines are developed to choose the mesh appropriate for different loading conditions. The modeling studies also bring forth the limitations of the current lab studies. For example, under some conditions it was noticed that the small sheet size considered in lab tests would produce higher mesh deformations than a full-size one used in actual practice.

Jan 1, 2006

By T. Damyanov

Spherical grinding media (balls) are the most widely used media for comminution of ores by grinding. A modelling simulation study of the behavior of two grinding media in the grinding process was conducted to determine the possible advantages of the new shape milling bodies called tetraballpebs. Tetraballpebs are in the shape of tetrahedrons with spherical convex walls. A three dimensional CAD model of the mill drum with a diameter of 1200 mm was used. A continuous operating mode was simulated in terms of the 3D contact elements of the model (milling bodies and mill drum). Simulation tests were carried out in a typical grinding mode and at a typical rotational speed of the drum mill (75 per cent of the critical speed in cataracting mode). Studies carried out with both grinding media include equal number of milling bodies with the same weight and volume. Having thus ensured a uniform mass of the grinding media and same number of milling bodies, and constant other conditions and process parameters, conclusions can be drawn about the influence of the shape of the milling bodies on the grinding process. A kinematic analysis of the system using CAE (computer-aided engineering) model parameterization was conducted. The controlled parameters are: ? Power draw; ? Kinetic energy of each milling body; ? Motion of milling bodies inside the drum Keywords: grinding, grinding simulation, balls, tetraballpebs, DEM, CAD-CAE

Sep 1, 2012

By Launa G. Mallett, Charles Vaught, Kathleen M. Kowalski, Charles D. Litton, Michael J. Brnich, Ronald S. Conti, Henry P. Cole, William J. Wiehagen

How do people behave when they are trying to get out of a fire? Are escape activities different in each incident, or will most actions be predictable across events? Do persons make the same sorts of decisions whether they are responding as individuals or as group members? Because the social costs of fire-related deaths and injuries are likely to continue to rise, societal pressure for greater safety will also undoubtedly increase. There are, therefore, compelling reasons to further our understanding of action in fires. If human behavior in fire is studied scientifically and predicted according to some well-defined principles, the benefits will be significant. Design engineers could incorporate real-world findings into their plans. Equipment manufacturers could gain from insights into how their technology is actually used in fire emergencies. Safety personnel would have a better appreciation of what constitutes adequate evacuation procedures. Trainers could upgrade the content of their courses that teach escape skills. The result would be an overall improvement in the quality of fire preparedness and safety.

Jan 1, 2000

By Edward A. Barrett

A significant number of injuries resulting from fa118 of roof and rib may be avoided by modifying the reactive behavior of miners as they encounter potentially hazardous ground conditions. In 1984-85, the Bureau investigated barriers which prevent miners from recognizing and correcting groundfall hazards. One basic problem from which these barriers originate is the inability of miners to recognize dangerous roof and rib conditions. This study is a report of experimental research on the use of stereo scopic (3-D slides for presenting visual cues associated with hazardous roof and rib conditions. Findings reveal that, in comparison to conventional slides, 3-D provides for significantly greater hazard recognition among both experienced and inexperienced miners. Details such as the presence of t cracks and gaps in the surrounding rock are more accurately and realistically perceived. Acceptance by the mine training community has been affirmative and is additionally encouraged by the fact that 3-D slides stimulate trainees&apos; overall interest.

Jan 1, 1986

By Y. Hwang, C Kang

To understand the effect of thermal loading from HLW on the groundwater flow nearby, the coupling of TH in an equivalent porous medium is studied. Results indicate that under given conditions the alteration of groundwater flow by decay heat is localized phenomena. More comprehensive studies are underway for THM coupling. Zum Verstandnis fur die Wirkung der thermischen Belastung von HLW in der Nahe von Grundwasserstrom, ist die Verbindung von TH in den entsprechenden porigen Medium erarbeitet. Die Ergebnisse zeigen, dass unter vorgegebenen Bedingungen die Anderung von Grundwasserstrom durch Zerfallwarme lokalisiert wird. Zusatzliche umfassende Arbeiten sind fur die THM Kupplung auf dem Wege. Pour comprendre l&apos;effet du chargement thermique de HLW sur l&apos;écoulement d&apos;eaux souterraines tout près, l&apos;accouplement du TH dans un milieu poreux équivalent est étudié. Les résultats indiquent que dans des conditions données le changement d&apos;écoulement d&apos;eaux souterraines par la chaleur d&apos;affaiblissement est des phénomènes localisés. Des études plus complètes sont en cours pour l&apos;accouplement de THM.

Jan 1, 2003

By Vassiliki G. Stavropoulou

Although plane-strain is the preferred method of analysing many rock mecahnics problems, little is known about the behaviour of rock under this loading condition. A simple and inexpensive apparatus has been built for laboratory testing of rocks in plane-strain conditions. A thorough .investigation of the specimen geometry and the friction end effects showed that the results can be considered as reliable. The behaviour of a brittle sandstone in the simplest plane-strain condition [(03 = 0)] is significantly different than that of the uniaxial compression [(02 = U3 = 0)]. The plane-strain values of the Young&apos;s Modulus and the Poisson&apos;s Ratio are decreased in comparison to the corresponding uniaxial values. Dilatancy is also reduced in plane-strain, whereas the pre-failure brittleness of the rock increases. The most dramatic effect of the plane-strain condition is that on the strength of the sandstone, which increases by 49 per cent in comparison to its uniaxial compression value.

Jan 1, 1982

Behaviour of Bubble Clusters in a Turbulent Flow

Sep 13, 2010

By G. M. Evans, S. Mitra, G. J. Jameson, M. M. Hoque, E. Doroodchi, R. Moreno-Atanasio

In this study, the detachment behaviour of 314 μm diameter silica particles from a single 3 mm diameter bubble rotating in a confined cavity connected to a cross-flowing water channel was investigated. The liquid cross-flow generated a rotating flow inside the confined cavity, which was quantified using 2D particle image velocimetry (PIV) measurements. The fluctuating (x-y) velocity components inside the cavity for each cross-flow velocity, U, were then used to estimate the corresponding time/volume average turbulence intensity values, Ti. Turbulence intensity ranged from 9.3-16.2%. In the absence of a bubble, the rotating vortex within the cavity created a pressure field which decreased towards the centre of the vortex; wherein the lowest pressure zone was located at the centre of the cavity. The vorticity into the cavity was found to increase with increasing the turbulence intensity. A bubble, both without and with particles attached, was introduced into the cavity under different flow conditions and its motion was tracked using the shadowgraphy technique. Experimentally, it was found that the bubble-particle aggregate was trapped at the centre of the cavity (low-pressure region) following a spiral trajectory. An interface resolved 3D computational fluid dynamics (CFD) model was developed to predict the particle detachment conditions within the confined cavity. CFDpredicted vorticity in the absence of a bubble agreed well with experimental observation. The CFD analysis indicated that the vorticity inside the cavity was not significantly changed when a single bubble was introduced. On this basis, the computed vorticity was utilised in describing the force balance applied to the attached particle. Computationally, it was found that the critical turbulence intensity, beyond which the particle was detached from the bubble, was 14%. This value was consistent with the experimental observation of detachment at Ti at 15.7%, and above, but not at lower values. Keywords: Bubble, particle, turbulence intensity, vorticity, particle detachment, CFD, PIV

Jan 1, 2020