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By K. H. Bech, S. T. Johansen

"The mass transfer at fluid-fluid interfaces due to turbulent agitation is investigated theoretically. In particular a theory is derived for interface stresses due to interface energy and surface renewal. This theory indicates that surface renewal may take place if the geometry is sufficiently large and if surface tension is sufficiently low.By using a model for a typical turbulent structure we compute the interface mass transfer for a stressless interface and a fully interface. Results for the general situation is not presently available. The computed results are used to derive analytical expressions for the mass transfer based on turbulent kinetic energy and free stream turbulent length scales.One important application of the theory is the mass transfer at the electrolyte side of the bath-metal interface in the Hall-Heroult process. For this process we show that mass transfer should be expected to be of the rigid surface type."

Jan 1, 1999

By Mikiya Tanaka, Mikio Kobayashi, Kazuya Koyama, Yoshihiro Nishisu

Preparation of multicomponent powders are very useful and important for producing the materials with complicated and homogeneous structure. Therefore multicomponent powders have a lot of attention in the field of advanced value-added materials. The aqueous processing in hydrometallurgy has a broad potential for producing multicomponent homogeneous precipitates. Furthermore the aqueous processing has a future potential for integrating the separation, precipitation and synthesis processes. In this presentation the precipitation from homogeneous solution including rare-earths and/or common metals is presented. These precipitates probably consist of almost monodispersed, multicomponent and spherical particles by precisely controlling several reaction factors, reaction temperature, concentrations of starting materials, pH and so on. The separation of the nucleation stage and the growth stage of the particles is very important and how to control the reaction factors to realize enough separation is discussed. In this presentation the systems of Y-Eu-0, Y-Fe-0 and Y-Al-0 are mainly presented. In addition the precipitation-stripping method from organic phase is presented focusing the synthesis of multicomponent powders of Ni-La-0 system. These precipitates have multicomponents homogeneously and so they are converted to multicomponent ceramic powders by calcination. They are important compounds as phosphor, opto-magnetic materials, optical materials, hydrogen storage alloy or as the related precursors. In this presentation some characterization of these particulate materials is included.

Jan 1, 1998

By Sharon L. Eyer

"FTIR spectroscopy is employed to define mineable ore deposits based on exploration samples. The RAMBO (Robotic Assessment of Mineable Bauxite Ore) technology is operating successfully at an alumina refinery in K winana, Australia, for assessment of a number of critical ore attributes including available alumina, extractable organic carbon and total iron. Classical methods of analyses for these properties require laboratory-scale digestion of alumina ore (bauxite) or XRF analyses.Multivariate calibration is used in the RAMBO system to generate robust mathematical models that are able to estimate classical data from FTIR spectral data. Furthermore the models can highlight regions of ore that are relatively unusual. Unusual ore may be investigated for potential impacts on refinery processes well in advance of mining.The components of the technology are described and some results for an example application (bauxite) are presented. Challenges and difficulties are discussed. The potential to apply the technique to process control is introduced."

Jan 1, 1999

By Patrick R. Taylor

Iron phosphate glasses are promising host matrices for vitrifying actinide rich nuclear wastes materials because of their high solubility of actinide oxides, high chemical durability, and relatively low melting temperatures. An iron phosphate waste form was developed at the University of Missouri-Rolla. The structure and property of the waste form were well characterized by materials techniques. However, to scale the process and advance it to commercial viability, it is necessary to understand the processing parameters, such as the partitioning of waste elements and the viscosity as a function of temperature. Viscosity of 40 Fe203 - 60 P205 mole % iron phosphate melts (prepared with phosphorous pentoxide and ferric oxide) at 1000-1200 C was measured by the rotating-spindle method. It was discovered that this fluid has non-Newtonian behavior. Experiments were performed to study flow properties following the Standard Test methods for Rheological Properties of Non-Newtonian Materials by Rotational (Brookfield) Viscometer (ASTM D 2196-86). Samples prepared using ammonium phosphate and ferric oxide showed Newtonian behavior and the temperature dependence of the viscosity was studied over the range of 1000 to 1200 degrees C. The difference in flow behavior between the two fluids was analyzed in terms of preparation conditions and variation in the final composition and phases. The partitioning behavior of waste elements in the iron phosphate glass was studied by melting in a high temperature furnace and JCP analysis. The experimental results show that the solubility of Ce and Sr in phosphate glasses is significantly higher than the solubility associated with borosilicate glasses. This strengthens the conclusion that iron phosphate may be a viable alternative to borosilicate glass for immobilization of high heavy-metal-content wastes and actinide rich wastes.

Jan 1, 2002

Many studies have been conducted over the past 3 decades on the leaching of gold in solutions containing thiosulfate, ammonia and copper. However, most of these studies have been carried out using ore samples, with very few fundamental studies of this system being attempted. The majority of the published studies have failed to acknowledge the undesirable side reaction between copper(H) and thiosulfate, let alone account for its effect. The fact that the solution chemistry is constantly changing makes it very difficult to perform a fundamental study of gold leaching. With the advent of the rotating electrochemical quartz crystal microbalance (REQCM), such fundamental studies are possible as this instrument measures mass in real time. This has allowed leach kinetics to be measured in a matter of minutes and hence at essentially constant solution conditions; The present paper highlights that a sufficient concentration of copper(II) and ammonia are required in order to achieve appreciable gold leach rates. However, the use of air (oxygen) to maintain the copper(Il) concentration catalyses the undesirable copper(II) reaction with thiosulfate. The presence of ammonium ions is shown to have an effect on this undesirable reaction as well as on the gold leaching ?reaction. Preliminary electrochemical studies into .gold electrowinning using the REQCM show that gold(I) thiosulfate cannot be readily reduced to metallic gold in the potential region at which cementation usually occurs. However, it is well known that gold cementation onto copper occurs rapidly. The current study addresses this discrepancy by studying the effect that copper and silver have on the reduction of gold thiosulfate. It has been found that the presence of both silver and copper enhance gold deposition, particularly at low over potentials. While this is beneficial in cementation, the presence of copper and silver in solution has been found to cause passivation of the cathode surface during electrowinning at 'higher overpotentials.

Jan 1, 1998

By F. J. Tavera

Recently Jameson cell technology has gained acceptance in both mineral and non-mineral applications, mainly because of the high degree of contact between the involved phases in the downcomer, fact that leads to an efficient collection performance. The key for an acceptable performance of the downcomer operation depends on the stability of the jet zone, the mixing zone, and the plug flow zone. in this work the behaviour of the downcomer of a laboratory Jameson cell is reported, as a function of gas hold-up, superficial gas velocity, superficial liquid (or slurry) velocity, and length of the operating zones. The presence of carbon is evaluated in terms of its effect on the gas hold-up and bubble surface area flux. The influence of the downcomer operating conditions on the gas-liquid disengaging cell is presented. Keywords: Jameson cell, downcomer, gas hold-up, mixing, plug flow, conductivity.

Jan 1, 2003

By F. Michael Hosking

Modeling of a furnace brazing process is described. The computational tools predict the thermal response of loaded hardware in a hydrogen brazing furnace to programmed furnace profiles. Experiments were conducted to validate the model and resolve computational uncertainties. The results from selected furnace simulations and measured thermal events were compared. Critical boundary conditions that affect materials and processing response to the furnace environment were determined. "Global" and local issues (i.e., at the furnace/hardware and joint levels, respectively) are discussed. The ability to accurately simulate and control furnace conditions is examined.

Jan 1, 1998

By P. D. Nolan

Smelters operating under pollution control orders have become increasingly dependent upon the reliable operation of sulphuric acid plants and no factor affects the long term reliability of those plants more than efficient gas cleaning. The sources and characteristics of contaminants in smelter of fgases and the conventional approaches to removing these contaminants to accepted levels are discussed. New technology is described which offers advantages of lower capital cost, lower operating cost and reduced space requirements over the conventional approaches. This new technology has been developed by LAB s.a. and is licensed for metallurgical gas applications by Chemetics International Company.

Jan 1, 1983

By Liwen Hu, Jianxun Song, Hongmin Zhu, Qiuyu Wang, Shuqiang Jiao

The subchloride titanium was prepared by sponge titanium and titanium tetrachloride in the CaCl2 at 1173 K. The species were detected are mainly titanium dichloride, and the average valent in the melt are 2.05. The accurate equilibrium constants were obtained for the reaction 3Ti2+ = 2Ti3++Ti after the accurate activities of titanium chloride were evaluated with emf method, and the observed deviations from ideal behavior are discussed.

Jan 1, 2015

By Dengfu Chen, Yunwei Huang, Mujun Long, Kui Lv, Pei Xu, Lin Bai

The surface temperature of continuous casting slab in the secondary cooling zone is a key parameter of production control. However, the accuracy of radiation temperature measurement of high temperature casting slab is greatly affected by the environmental factors, such as water vapor, spray, water film and other participational medias during continuous casting process. In this paper, the radiation characteristics of water vapor and its influences to radiation temperature measurement of continuous casting slab were investigated. Based on the database HITRAN 2004 and the measuring principle of monochrome thermometer & colorimetric thermometer, the measuring errors under different operating infrared spectral wavelength were compared. Results showed that spectral region with wavelength nearby 1.0μm or 1.6μm would be the optimum for high temperature infrared thermometer used under the conditions with moist steam, water spray and water film at the secondary cooling zone in steel continuous casting.

Jan 1, 2016

By Nan Wang

Based on the commercial computational fluid dynamics software, Fluent, a three dimensional finite-volume model has been established, and the fluid flow and heat transfer in the super-wide slab mold (cross section 3250mm×150mm) of Nanjing Iron and Steel Company has been simulated. The basic feature of flow and temperature field in a super-wide mold has been analyzed, and the effects of mold width, the submergence depth of SEN, outlet angle of SEN, casting speed, superheat and cooling rate on the flow and temperature field have been investigated. The results by comparing several simulated calculations for 3250mm×150mm slab show that a more proper fluid flow and temperature field in the super-wide mold can be obtained with 15°outlet angle, 120~150mm submergence depth of SEN and 1.2~1.4m/min casting speed. The results through numerical simulation provide a theoretical basis for optimizing the configuration design of SEN and choosing reasonable processing parameters for the continuous casting mold of super-wide slab.

Jan 1, 2009

By R. N. O'Brien, E. Peters

"It has been discovered that copper concentrates can be leached in strong (40-60%) sulfuric acid with nitric acid, or with oxygen if nitric acid is present as a catalyst. Chalcopyrite is rapidly decomposed at temperatures well below the boiling temperature of the lixiviant (-150 C.) and the resulting copper and ferric salts are precipitated as CuS04.H20 and FeH(S04)z.4H20. Other metal sulfides such as zinc, lead, nickel, etc. are also converted to sulfates that are nearly insoluble. Sulfur is partially converted to elemental and partially to sulfuric acid. Reduction products of nitric acid can be recovered from the distillate with good recovery. Conversion of as-received copper concentrates is largely complete in about 1 hour. Introduction9 molar sulfuric acid is an unusual hydrometallurgical lixiviant: it has a boiling point of about 150 C. and a low solubility for base metal sulfates. Below about 6 molar acid, the boiling point falls below 120 C. and yields much higher sulfate salt solubility, while above 12 or 13 molar acid and at higher temperature sulfuric acid becomes an oxidizing agent, yielding gaseous S02' Thus, sulfuric acid within this range of concentration is capable of acting well above the temperature of boiling water without requiring autoclave conditions, and if typical oxidative leaching conditions are applied to suspended mineral sulfide concentrates, it is possible to obtain a conversion of these sulfides into 'crystalline sulfates. Thereafter, the sulfates can be separated by filtration or by solid - bowl centrifuge and the solution can be recirculated to the reactor vessel. Meanwhile, the solid sulfates can be treated in a typical hydrometallurgical circuit, i.e., dissolved in a return stream that is essentially water, separated from each other by, for example, solvent extraction, and recovered as metals by electrowinning."

Jan 1, 1997

By Manuel Alvarado, David Nemir, Jan Beck

"Thermoelectric generation using special N-doped and P-doped semiconductors is well known as a means for direct heat energy to electrical energy conversion without the need for moving parts. The technology is used today in niche markets for low level electricity production and has been proposed as a scalable means for capturing large scale energy from waste heat streams. The choice of geometry of the thermoelements and conductors is critical to the successful implementation of a waste heat recovery system in order to manage losses due to Joule heating and diffusive heat flows. This paper describes a simulation study to define the performance impact of different aspect ratios for the active thermoelements and the electrical interconnect. The use of a finite element model that incorporates the intercoupled heat and electrical energy flows highlights some of the issues impacting scalability.IntroductionThermoelectric phenomena arise out of the intercoupled electrical and thermal currents in a material. A two-element thermoelectric generator is depicted in Figure 1. It is constructed by connecting an N-type thermoelement and a P-type thermoelement in electrical series, with both elements in thermal parallel between a heat source and a heat sink. The electrical series connection is made by attaching conductors as shown. Ideally, these series connection elements will be both good thermal conductors and good electrical conductors.The two element generator in Figure 1 is disposed between two thermal reservoirs: the heat source, which furnishes heat energy; and the heat sink, which absorbs heat energy. Heat energy flux Q, flows from the heat source to the heat sink, driven by the temperature difference between the source and the sink. As depicted in Figure 1, when a resistive load, R, is attached, electrical current, I, may be extracted from the thermoelectric generator and furnished to the load. The N-type and P-type thermoelements, are the active portions that do the actual conversion of heat energy to electrical energy. Although thermoelements may be built using conductors such as bismuth and antimony, higher efficiency thermoelectrics are built using heavily doped semiconductors. Thermoelectric devices are generally formed by connecting many pairs (couples) of N and P type thermoelements in electrical series and in thermal parallel. A commercially available module having 127 couples (254 elements) is shown in Figure 2."

Jan 1, 2011

By C. Schwandt

Recent research work has led to the development of a new electrochemical hydrogen sensor, which is based on a proton conducting solid electrolyte in conjunction with a self-contained solid hydrogen reference standard and is operated at elevated temperatures. The incorporation of the internal hydrogen reference renders the sensor versatile and user-friendly and makes it attractive for practical exploitation. The present article focuses on the utilisation of the sensor as the integral part of a probe for the quantitative determination of hydrogen in molten aluminium and aluminium alloys. The main features of the sensor and the probe as well as the measuring technique are discussed. Experimental results obtained with the novel analyser in trials under industrial conditions are presented and highlight the good performance of the device.

Jan 1, 2003

By Sacha Neven

Submerged lance technologies combine high intensity processing characterized by rapid mixing and reaction rates using a simple reactor design. The Isasmelt technology uses a central submerged lance to inject oxygen-enriched air and fuel into a bath thus creating large gas bubbles and intensive turbulence and splash. The lance is equipped with swirlers to increase gas velocity and heat transfer. This enables the formation of a frozen slag layer on the lance which protects it from the aggressive environment. Water models as well as high temperature reactors were used to validate the Davidson-Schiiler model on bubbling. Frequencies and pressure amplitudes were measured in a wide range of gas flow rates: from m3/sec using a water model to more than 30 m3/sec in an industrial process. Agreement with the model was satisfactory. The experiments however also clearly showed that cross-flow and bubble wake induce slightly higher frequencies. No influence of the use of swirlers on the bubbling frequency was observed in the water models.

Jan 1, 2002

By Sergey Komarov, Manuela Diaz, Sano. Masamichi

"Mixing time, bubble behavior and absorption rate of gas injected into a liquid bath through rotary L-shaped lances have been studied by cold models with an effort to improve refining characteristics of metallurgical processes. Two kinds of the rotary lances were tested, namely the single-hole lance and the multi-hole lance. The effects of gas flow rate, bath depth and rotation speed were examined.It is found that when gas is injected through the rotary lances, the mixing intensity and the gas absorption rate are larger than that for the gas injection through stationary lances. The effect of rotation speed decreases as the bath depth and the gas flow rate increase.The multi-hole lance produces much smaller bubbles, which lead to an increase in the volumetric mass transfer coefficient by 3-4 times as compared with the single-hole lance. However, the effect of rotation speed is smaller for the multi-hole lance. The obtained results are explained in terms of the bubble coalescence and fragmentation, the rate of which depends on the departure bubble size and the power supplied to the liquid bath.IntroductionIn recent years, there has been a growing interest in the development of gas injector for metallurgical processes. The majority of the previous work was focused on modification to the injector design to improve mixing and to increase the of chemical reaction rate. These two goals can not be necessarily achieved by the same way. Bottom nozzles and stationary immersed top lances, which have been widely applied to steelmaking processes, are effective for the bath mixing, but have a limit to decrease in the bubble size. This results from a vigorous coalescence occurring between the bubbles when they rise in the molten bath as a bubble swarm.One of the ways to ensure the small bubble size and the effective bath stirring is the gas purging through rotary injectors. A number of studies have been undertaken to improve the refining characteristics by using rotary injectors. All of them are related to aluminum refining. The SNIF equipment (The Spinning Nozzle Inert Flotation) has significantly improved the quality of aluminum products at National Luxemburg Aluminum [1]. Rotary injectors made in the form of a disc have been applied to the Alcoa 622 [2] and the GBF processes [3]. A study of the gas injection by a rotary impeller has been carried out by C. Leroy and G. Pignacelt [4]. All researchers note the significant improvement in removal of sodium, calcium, hydrogen and non-metallic inclusion."

Jan 1, 1996

By Yutaka Shiraishi

Two methods were developed to measure the viscosity of the slag from the glassy to the liquid states in an ascending temperature process. The first method employs rotating parallel plates within which is placed a solid cylindrical sample in line with a sphere. The second method uses a tube which is pushed into a sample held in a rotating crucible. Both methods were tested using standard glasses, including boron trioxide and NBS standard glass #711. The main difference between these two methods is in sample preparation. Comparative measurements between two methods were performed using a sodium boro-disilicate glass containing 5%mol of alumina. The results showed good agreement in the mid-range of glassy viscosities, 105 to to7 Pa.s. In the liquid state, there were no significant differences between the two methods.

Jan 1, 2003

By Toshiro Kuji, Masakazu Fujita, Tetsuji Saito

"The magnetic properties of the magnetic materials were deeply dependent on the microstructures. In this study, the novel technique to produce the desired microstructures in a controlled manner was proposed. The technique consisted of the production of the amorphous alloys and the control of the crystallization process. The technique was applied to improve the magnetic properties of Nd-Fe-B permanent magnets. The microstructural control of the magnets exhibited the excellently high energy-products of higher than 430 kJm-1. The relationship between the magnetic properties and the microstructures of the Nd-Fe-B permanent magnets was discussed.IntroductionThe intrinsic properties of the materials are basically determined by the properties of the constituent elements or the compounds. However, it is often noticed the difference between the observed properties and the theoretical values expected from the intrinsic properties of the materials. This indicates that the observed properties of the materials are determined not only by the properties of the constituent elements. In other words, the observed properties of the materials are also strongly dependent on the morphology of materials. This means that the microstructural control may creates a great improvement of the properties of materials.In Nd-Fe-B permanent magnets, the superiority arises from the uniaxial intermetallic Nd2Fe14B compound which has a large saturation magnetization and a high anisotropy field [1,2]. The magnetic properties of the Nd-Fe-B permanent magnets are dependent on the microstructure, that is, the size, shape and degree of the crystallographic alignment of the Nd2Fe14B phase. Currently, the Nd-Fe-B permanent magnets have been produced by either sintering or melt-spinning [3,4]. In the sintered magnets, alignment of the Nd2Fe14B phase is achieved by the prior green compaction of the crushed ingot powders in an applied magnetic field [3]. In the melt-spinning approach, alignment of the Nd2Fe14B phase is achieved by hot deformation [5]. Amorphous melt-spun ribbons are comminuted and then are consolidated into bulk form by hot pressing before hot deformation. As-hot-pressed magnets have randomly oriented Nd2Fe1~ grains [6]. Subsequent die upsetting of as-hot-pressed magnets gives rise to the crystallographic alignment of the Nd2Fe14B phase."

Jan 1, 1998

By Jerome Feinman, Sven O. Santen

"The principles involved in the generation and application of plasma energy are reviewed briefly and the major developments in commercial and semi-commercial primary metal and alloy production are described and discussed in broad outline, with emphasis on present performance and future potential. New concepts in the application of plasma energy in primary operations are described with emphasis on the expected advantages over conventional technology and the problems that have to be solved to enable effective implementation.IntroductionThe use of plasma energy in industrial processes is generally considered to have started in 1905 with the operation of the Birkeland process for nitrogen fixation for fertilizer production. Although it seems logical to apply plasma energy to metallurgical processes, which also usually require considerable energy at high temperature levels, serious development work along these lines did not begin until the early 1970's. The reasons for this hiatus are associated in part with recognized difficulties in applying plasma energy in processes involving tonnage quantities of solids in severe industrial environments and the delicate nature of the earlier plasma generators. Another, and perhaps overriding factor, is the fairly steady improvement in efficiency and economy of most primary metal producing processes by conventional developments and modifications through the 1950's and 60's. Examples of these evolutionary changes include burden preparation and fuel injection in blast furnace applications and prereduction treatments in ferroalloy operations. By the end of the 1970's most primary metal producing processes had been optimized close to the limit, at least in terms of those operations that were able and willing to implement the developed improvements. In this context, plasma energy offered the possibility to achieve further significant improvements in primary operations where conventional means were exhausted."

Jan 1, 1988

By Yutaka Shiraishi

Two methods were developed to measure the viscosity of the slag from the glassy to the liquid states in an ascending temperature process. The first method employs rotating parallel plates within which is placed a solid cylindrical sample in line with a sphere. The second method uses a tube which is pushed into a sample held in a rotating crucible. Both methods were tested using standard glasses, including boron trioxide and NBS standard glass #711. The main difference between these two methods is in sample preparation. Comparative measurements between two methods were performed using a sodium boro-disilicate glass containing 5%mol of alumina. The results showed good agreement in the mid-range of glassy viscosities, 105 to 107 Pa.s. In the liquid state, there were no significant differences between the two methods.

Jan 1, 2003