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Although milk replacers are widely used to feed orphaned and injured marsupial joeys in Australia, little is known about the nutrient composition of these foods. We analysed two milk substitutes, Di‐Vetelact (DiV) and Wombaroo Kangaroo (Wom) [milk stage >0·7 (joeys having completed 70% of their pouch life)], for their content of fatty acids, amino acids, and minerals and trace elements. The protein contents of DiVand Wom were 25·0% and 17·3% of fresh weight, respectively, and, except for tryptophan, the amino‐acid profile compared favourably with three high‐quality proteins. The fatty‐acid content of DiVand Wom was 9·65% and 17·6%, respectively. Relative to marsupial milk, linoleic acid (DiV, 18·3%; Wom, 9·32%) and α‐linolenic acid (DiV, 2·97%; Wom, 3·94%) were well represented in both milk replacers, but docosahexaenoic acid was not detected. Comparable amounts of zinc, iron, potassium, calcium, magnesium and phosphorus were present in DiVand Wom, but the copper content of DiVwas only 5% that of Wom and manganese was not detected in DiV. These data indicate that two popular marsupial milk replacers contain healthful amounts of many essential nutrients relative to marsupial milk but lack the docosahexaenoic acid that is critical for brain growth and development in mammals.

Abstract: The height and width of spouts in a water model of a gas-stirred ladle were measured photographically. The shapes were found to be Gaussian, and correlations were developed for the height and width. To mathematically model the free surface effects, a novel combined staggered-grid and volume-of-fluid computational code was developed. It was tested successfully against an established code in the “broken dam” validation test. The new free surface code was added to an existing code for a gasstirred plume to model the entire vessel. It was found that the code under-predicted the actual spout height. The model handled the momentum of the plume accurately, but did not account for the phenomena associated with the bubbles breaking the surface. The importance of these inter-related phenomena had not been appreciated previously.

Abstract: A physical model of a ladle degassing operation was developed to simulate the reactions at rising bubbles and at the free surface. Carbon dioxide desorption from a sodium hydroxide solution was used to simulate the liquid-phase diffusion-controlled decarburization of liquid steel. It was found that under reduced pressure, the reactions were faster than attributable to solely the increase in volumetric flow rate. It was possible to separate the reactions with the bubbles from the free surface reactions; 20 to 40 pct of the reactions occurred at the free surface, depending on injection conditions. The free surface desorption rate depended on the gas flow rate and the number of injectors. The mass transfer coefficients to the bubbles were in reasonable agreement with previous work. Plume bending was observed when small bubbles were influenced by the bulk liquid flow patterns.

Abstract: A combined three-dimensional, Lagrangian-Eulerian model for gas-liquid flow in a ladle was developed. The model compared very well with available experimental results in Wood’s metal in terms of void fraction, liquid velocity, and plume bending. From the model, it was clear that the lateral lift force is responsible for plume spreading, whereas lateral drag forces bend the plume. The model was extended to include mass transfer to rising bubbles and at the free surface. The rate of reaction compared very well with the results of part I on the desorption of carbon dioxide from sodium hydroxide solutions.

Abstract: The clustering of alumina particles during their incorporation into pure liquid aluminum by stirring was studied experimentally. It was found that these particles together with entrained oxide films formed clusters of various sizes and shapes. When the stirring stopped, these clusters settled to form a loose sediment (containing about 0.18 volume fraction of alumina) on the bottom of the crucible. A mathematical model was developed to describe the settling of multisized clusters. Information regarding the size distribution of the clusters was obtained by matching the model results with the experimental data. The size distributions of the alumina clusters were comparable to those estimated from metallographic measurement.

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Abstract: An experimental study was undertaken to determine how several variables affect the size of gas bubbles formed at nozzles in liquid pig iron. The frequency of bubble formation was measured by an acoustic device, which could detect the vibrations produced by the bubble release. Accurate knowledge of the gas flow rate then enabled the calculation of bubble volumes. The use of large baths (60 Kg), melted by induction heating, permitted a wide range of experimental parameters: gas flow rate (0.5 to 1000 cc/s), outside nozzle diameter (0.64 to 5.1 cm), inside diameter (0.16 to 0.64 cm), chamber volume (23 to 2200 cc), nozzle depth (7.6 to 20 cm), surface tension (700 to 1500 dynes/cm) and nozzle orientation (up, down and sideways). The resulting bubble volumes were between 0.5 and 100 cc. The bubbles were found to form at the outer diameter of the nozzles due to the nonwettability of the nozzles. Furthermore, the bubbles were of a uniform size at low flow rates, but increased in volume with the flow rate, so that a constant frequency was established. In addition, the bubble volume was strongly dependent on the chamber vol-ume upstream from the nozzle. This is known as a “capacitance” effect and is due to compressibility of the gas. “Doublet” or “double bubbles” at small chamber volumes and bubble “pairs” at large chamber volumes were also observed. These phenomena re-sult in smaller bubbles, which make precise predictions of bubble size difficult. The re-sults are compared with those obtained by other investigators in aqueous and metallic systems.

Abstract: A mathematical model has been developed to describe gas flow, combustion reactions, and heat transfer in converter-type steelmaking processes. Thek- ε two-equation turbulent model, a finite reaction model, and the DeMarco-Lockwood flux model have been incorporated in this model to deal with the turbulent flow, postcombustion reactions, and radiation heat transfer. Local gaseous flow patterns, temperature, and heat flux distributions were calculated for a 300 tonne Klckner Oxygen Blowing Maximillanshuette (KOBM) converter. Comparison between the heattransfer fluxes calculated based on the model and those measured industrially indicates the validity of the model in this application. The postcombustion has been found to be determined by the decarburization rate (DCR) which is directly related to the hardness of blowing not by the entrainment of surrounding gas to the oxygen jet as previously reported. The model revealed that about 20 pct of what is normally considered to be recovered heat has actually been lost through the vessel wall and to the lance. It is shown that this model is useful in studying the detailed mechanisms of postcombustion to optimize operations in converter-type steelmaking processes.

Abstract: A novel electrical resistance probe technique to measure thein situ volume fraction of ceramic particles in molten metals was applied to the measurement of sedimentation rates of 90-�m-diameter silicon carbide particles in molten aluminum. The results indicate that the rate strongly depends on volume fraction; the time to clarify a 0.15-m depth increased from approximately 60 to 500 seconds as the particle volume fraction increased from 0.05 to 0.30. Maps showing the changes in volume fraction throughout the melt were generated. A multiphase hydrodynamic model was developed to describe the sedimentation. Using volume fraction-dependent drag coefficients from work in aqueous systems, the model was able to simulate the experimental results remarkably well. The experimental and modeling results indicate that there was little agglomeration or network formation during sedimentation. The implications of the results for solidification and particle pushing are discussed.

Abstract: Gas injection into liquid metals has been studied extensively with gas injection into water models. While the general features of such flows are appreciated, the structure of the two-phase region has not been well characterized. To improve our understanding of the fundamental transport phenomena in the two-phase region, a combined laser Doppler anemometry (LDA) and electrical probe (EP) technique has been developed to measure the time-averaged and fluctuating liquid velocities, bubble velocities, and void fraction. The primary findings are: (1) The slip velocity of the bubbles is close to the terminal rising velocity of bubbles in stagnant fluids. (2) The intensity of turbulence in the two-phase region is generally higher than 0.5, which is higher than in the single-phase region. (3) The turbulence is not isotropic; it is greater in the vertical direction. The implications for mathematical modeling and process analysis are discussed.

Abstract: A one-dimensional steady-state model for momentum transfer in ascending gas-liquid-powder plumes has been developed for conditions relevant to powder injection refining processes. Inter-phase transport of momentum permits the calculation of the volume fraction and velocity of the gas, liquid, and solid phases as they rise in the melt. The effects of plume geometry, initial conditions, density of the phases, head of liquid, bubble size, and powder loading and properties are assessed. Liquid velocities in gas-only injection into water compare favorably with available experimental data. Significantly lower liquid velocities are predicted in liquid metals. At solids loadings used in commercial powder injection stations, the powder is expected to have only a small effect on liquid velocity. For wire injection conditions with little gas release, liquid velocities are considerably smaller.

It is necessary that the treatment of arteriovenous malformations in general be undertaken by a team that consists of a radiologist who is experienced in angiography and embolization and a plastic surgeon. The latter should be well versed in angiographic techniques and should be able to comprehend the dynamics of these malformations. In this report, three patients with high-flow, high-shunt arteriovenous intraosseous malformations of the head are presented. Two of these presented as emergencies with almost uncontrollable bleeding and were initially treated with embolization and then mandibular resection and reconstruction within the first 48 hours. In one patient, a further reconstructive procedure using free vascularized tissue was carried out. A third patient with involvement of the maxilla, again presenting with bleeding, was treated with embolization and because of the deformity that would be created by resection, was simply observed. However, this patient is to be reassessed in the future and may well come to maxillectomy. It is emphasized that the treatment of these patients requires careful assessment, embolization, and resection as indicated after discussion between radiologist and surgeon.

Chemical thermodynamic calculations show that selenium removal from copper melts using sodium carbonate (soda ash) is only effective under reducing conditions. Reducing conditions can be generated by carbon, but even more effectively by calcium carbide which has not been used previously for such a purpose. To clarify the kinetics of these multiphase, multicomponent reactions, various mixtures were either placed on top of or injected into 70 kg heats of molten copper. The following reagents were found to be effective in removing selenium: soda ash-graphite mixtures, calcium carbide, and calcium carbide-soda ash mixtures, in increasing order of effectiveness. Experiments were also performed with synthetic blister copper containing oxygen, selenium, tellurium, bismuth, nickel, silver, and lead. As expected from the thermodynamic analysis, only the first three of these elements were removed. A mathematical model was developed to describe the diffusion-controlled reaction kinetics of selenium and oxygen removal at calcium carbide particle interfaces. Very good agreement between the model and experiments was achieved for the reaction paths of selenium and oxygen when 35 pct of the particles were in contact with the melt. The utilization of powder varied over a wide range (0 to 10 pct), depending on the selenium and oxygen contents. The industrial implications of this work are discussed in terms of multielement removal, refractory erosion, temperature loss, and reagent utilization.

The production of ceramic particle-reinforced metal-matrix composites by the melt-stirring technique involves two different steps: firstly, the establishment of particle-melt contact, and secondly, the wetting of the particles by the melt. The wetting behaviour of metal-ceramic systems has been studied extensively, whereas the contacting problem has been largely neglected. In this paper, a novelin situ thermal method has been used to investigate the kinetics of particle-melt contacting, based on melt cooling during and immediately after the particle addition. An enthalpy balance relates the amount of cooling and the fraction of the particles contacting the melt. For the aluminium alloy (A356) with 15 vol% silicon carbide (17 µm diameter), it was found that only 16% of the particles contacted the melt after mixing times of 15 min, but contact could be improved to 36% by adding magnesium to the melt. The fraction contacting the melt agreed well with the particle volume fraction calculated independently. Sampling of the froth layer on top of the melt revealed that a large portion of the particles resides there prior to incorporation into the melt.

Abstract: An experimental study was conducted on the twin- wire electric arc spraying of aluminum coatings. This aluminum wire system is being used to fabricate heater tubes that emulate nuclear fuel tubes for use in thermal-hydraulic experiments. Experiments were conducted using a Taguchi fractional factorial design parametric study. Operating parameters were varied around the typical process parameters in a systematic design of experiments to display the range of processing conditions and their effect on the resultant coating. The coatings were characterized by hardness tests, optical metallography, and image analysis. This article discusses coating hardness, roughness, deposition efficiency, and microstructure. The study attempts to correlate the features of the coatings with the changes in operating parameters. A numerical model of the process is presented, including gas, droplet, and coating dynamics.

Abstract: The injection of powder into liquids has been investigated by physical modeling and by multi-phase fluid dynamic modeling. The transition from gas-particle jets which penetrate deeply into the liquid and a gas bubbling regime was found to depend on the coupling between gas and particle phases in the conveying line; fine particles at high loading couple well and form jets, whereas coarse particles separate from the gas during bubble formation. The measured penetration depths of submerged jets in water and lead and top jets in water were very well described by equations balancing the momentum of the jet and its buoyancy. A regime of particle-liquid jets that forms in conjunction with bubbling also appears to depend on coupling, between the particle and liquid phases. The effect of surface tension on the particle penetration through a bubble interface was modeled for the single particle and multi-phase cases and compared with the work of others. On the basis of this modeling, the expected regime of flow for many powder injection conditions can be predicted. The flow regimes of existing processes are discussed, and guidelines for the design of processes employing various types of reactions are presented.

Abstract: There has never been any fundamental explanation presented for the transition from the bubbling regime to the jetting regime when gas is injected into liquid at high velocity through submerged tuyeres. This is an important issue in metallurgical processes, since the flow regime is known to influence refining rates, refractory erosion, and the penetration of the liquid into the tuyere. Based on the observation that many small droplets of liquid and gas bubbles are formed to create the jets, a combined Kelvin-Helmholtz and Rayleigh-Taylor instability analysis has been applied to bubbles forming at submerged tuyeres. For particular wavelengths of disturbances, the interface will be unstable and create bubbles and droplets. The critical injection velocity for instability depends on surface tension, tuyere diameter, and the gas-to-liquid density ratio, which can be summarized by We = 10.5(ρ*)−1/2, where We is the Weber number based on the gas velocity and density and tuyere diameter, and ρ* is the gas-to-liquid density ratio. The importance of surface tension had not been appreciated previously for this regime of gas injection. There is considerable controversy in the literature concerning the measurement of the transition from bubbling to jetting. The 70 pct “linking” point, proposed by Ozawa and Mori, describes the situation where 70 pct of the bubbles link with the preceding bubbles and produce a reasonably steady jet. The theoretical correlation developed above predicts the velocity to reach this point �20 pct (95 pct confidence level) in a variety of systems from six different groups of workers. The theoretical analysis demonstrates that the instabilities are primarily capillary in nature, not gravity waves, which explains the observation that orientation has little effect on the jetting transition.

Continuous exposure of cells to neurotransmitter or hormone agonists often results in a rapid desensitization of the cellular response. For example, pretreatment of Chinese hamster fibroblasts (CHW cells) expressing β2-adrenergic receptors (β2AR) with low (nanomolar) concentrations of isoproterenol, a β-adrenergic agonist, causes decreases in the sensitivity of the cellular adenylyl cyclase response to the agonist, without changing the maximal responsiveness. In contrast, exposure of CHW cells to high (micromolar) concentrations of isoproterenol results in decreases in both sensitivity and the maximal responsiveness to agonist. To explore the role(s) of receptor phosphorylation in these processes, we expressed in CHW cells three mutant β2AR genes encoding receptors lacking putative phosphorylation sites for the cAMP-dependent protein kinase A and/or the cAMP-independent β2AR kinase. Using these mutants we found that exposure of cells to low concentrations of agonist appears to preferentially induce phosphorylation at protein kinase A sites. This phosphorylation correlates with the decreased sensitivity to agonist stimulation of the adenylyl cyclase response. At higher agonist concentrations phosphorylation on both the β2AR kinase and protein kinase A sites occurs, and only then is the maximal cyclase responsiveness elicited by agonist reduced. We conclude that low or high concentrations of agonist elicit phosphorylation of β2AR on distinct domains, with different implications for the functional coupling of the receptors with effector molecules.

We have studied cyclic AMP-mediated regulation of the β2-adrenergic receptor (β2AR). The effects of cAMP were assessed in Chinese hamster fibroblast (CHW) cells expressing either the wild type human β2AR receptor (CH-β2) or mutated forms of the receptor lacking the consensus sequences for phosphorylation by the cAMP-dependent protein kinase. Treatment of the CH-β2cells with the cAMP analogue dibutyryl cAMP (Bt2cAMP) induces a time-dependent “down-regulation” of the number of β2AR. This down-regulation of the receptors is accompanied by a decline in the steady state level of β2AR mRNA. Moreover, the treatment with Bt2cAMP induces an increase in the phosphorylation level of the membrane-associated β2AR. Both the reduction in β2AR mRNA and the enhanced phosphorylation of the receptor are rapid and precede the loss of receptor. The down-regulation of β2AR induced by Bt2cAMP is concentration-dependent and mimicked by the other biologically active cyclic nucleotide analogue, 8-Br-cAMP, by forskolin, and by the phosphodiesterase inhibitor, isobutylmethylxanthine.

Abstract: Nitrogen and silica particles of 30, 130, and 450 μm average diameters were injected at solid-to-gas loadings up to 280 kg/m3 into liquid lead at 400C through a steel lance equipped with four thermo-couples. The lance was positioned adjacent to a transparent wall in the lead retort so that the flow patterns could be photographed. It was found that 130 and 450 μm particle injection produced bubling in the lead and clogging at high loadings, while the 30 μm particles produced jetting with no clogging. Analysis of the thermocouple responses permitted the determination of the heat transfer coefficients at the inner and outer lance surfaces. The inner surface heat transfer coefficient increased with loading, whereas the one at the outer surface was independent of loading. A two-phase, unsteady-state, one-dimensional model was developed for momentum and heat transfer in the lance permitting the calculation of gas and particle velocities, volume fractions, and temperatures as well as the lance temperatures. Using the experimentally determined heat transfer coefficients, it is shown that the gas and particles are heated only 20 to 40 K in the lance. Nevertheless, this is a large heat demand which chills the lance so that clogging will occur in the bubbling regime.

Abstract: A Monte Carlo method was developed to simulate the formation of clusters of alumina particles suspended in a turbulent pure liquid aluminum melt. With this approach, the chaotic movements of small alumina particles suspended within eddies smaller than the Kolmogoroff microscale were treated in a similar way to Brownian motion, and clusters were assumed to form once these particles collided with each other. The results obtained from the simulation indicate that clusters form very quickly during vigorous stirring and that the formation kinetics at the very beginning of mixing follow a second-order behavior. Clustering has been observed previously in the SiC-Al system and was also observed in the Al2O3-Al system in the present work.

Magnesium vapor was injected into 60 kg heats of carbon-saturated iron at 1523 K. The magnesium dissolution and desulfurization rates as well as magnesium bubble size were monitored over sulfur contents ranging from 0.0002 to 0.2 pct S. The magnesium dissolution mass transfer coefficient was found to be 0.046 ± 0.034 mm · s−1(for 30 mm diam bubbles). Further analysis indicated that most of the desulfurization took place at magnesium sulfide inclusions present in the bath; there was good agreement between the experimental precipitation rate constant and that predicted for diffusion to the number of inclusions observed by chemical analysis and inclusion counts. The seed magnesium sulfide inclusions were probably stripped from the ascending magnesium bubbles. These particles were quickly eliminated from the melt by bubble and induction stirring, resulting in a steady-state number of inclusions. This allowed a pseudosteady-state model to be developed.

Averaged and turbulent fluctuating liquid velocities in the gas/liquid plume zone of a gas-stirred water model ladle were measured with a combined laser Doppler anemometer (LDA) and elec-trical probe technique. The measured turbulence fields, void fraction distribution, and gas and liquid velocities in the plume zone were used for evaluation of various turbulence models. It was found that, among all of the turbulence models tested, only a modified k-ε model, with extra source terms to take into account the generation and dissipation resulting from the inter-action of the bubbles with the liquid, yielded good agreement with both the mean liquid flow field and the turbulent kinetic energy distribution. However, the values of the coefficients orig-inally proposed by their authors were found inapplicable to the bubbly plume situation; more appropriate values of the coefficients were determined based on comparison with experimental measurement.

Bubbly plumes are widely encountered in metallurgical processes when gas is injected into liquid metals for refining purposes. Based on the experimental findings from a water model ladle, this phenomenon was simulated with a mathematical model, paying special attention to the dynamics of the bubbles in the plume. In the model, the liquid flow field is first calculated in an Eulerian frame with an estimated distribution of the void fraction. The trajectories of bubbles are then computed in a Lagrangian manner using the estimated flow field, experimentally measured information on bubble drag coefficients, lateral migration due to lateral lift forces, and variation in bubble size due to breakup. Turbulence in the two-phase zone is modeled with a modifiedk-εmodel with extra source terms to account for the second phase. The computed void fraction and turbulent liquid flow field distributions are in good agreement with experimental measurements.

In slag-based, smelting-reduction processes, the overflow of slag from the vessel is considered a major limitation to productivity; this phenomenon is commonly called slag foaming. While much has been learned from laboratory-scale studies of foaming, the superficial gas velocities are well below those encountered in production (centimeters per second compared to meters per second). A multiphase fluid dynamic model was developed to determine the relationship between gas velocity and void fraction (holdup) at industrial production rates. In the model, the drag between the gas and slag is balanced against the weight of the slag. Within the framework of the model, the only unknown quantity is a drag factor which can be extracted from experimental data. Values of this factor from water models, smelting-reduction converters, and other slag systems fall in a narrow range. The model can be used to estimate slag height in smelting-reduction vessels. The behavior of slags at high rates of gas injection is markedly different from foaming observed at low flow rates.

The production of ferromolybdenum by the plasma decomposition of molybdenite concentrate to molybdenum and sulfur is used to illustrate the industrial application of plasmas to metallurgical processes. This process has stringent requirements for very high sulfur elimination (<0.15% S in the product) and low specific energy consumption in order to be competitive with the conventional process (roasting to the oxide, followed by thermite reduction). Direct-current transferred arcs appear to offer the most promising approach to the design of commercial reactors for this application. Following a brief review of the development work on the thermal decomposition of molybdenite, a process flowsheet and the results of an economic assessment for a commercial plant are presented. The latter show the relative cost breakdown between key process units. The sensitivity of costs to factors such as scale of operation, specific energy consumption and electricity prices, raw materials, gas system (recycle versus once-through), and product recovery is illustrated. It is concluded that, while the plasma generator/reactor may be the technical heart of the overall process, industrial development programs must consider the capital and operating costs of a complete plant, including peripheral equipment and product marketing, as well as the duration, cost, and risk associated with the development project.

The solidification behavior of ceramic particle-reinforced metal-matrix composites (MMCs) is different from that of the bare matrix, not only because of the presence of the ceramic particles, but also due to their redistribution in the melt that results in nonhomogeneous thermophysical properties. The MMCs comprised of 10-to 15-μm SiC particles of varying volume fractions, dispersed uniformly in a modified aluminum A356 alloy by the melt stirring technique, were solidified unidirectionally in a thermocouple-instrumented cylindrical steel mold. The cooling rates were continually monitored by measuring temperatures at different depths in the melt, and the solidified MMCs were sectioned into disks and chemically analyzed for SiC volume fraction. The results point out that the cooling rate increased with increasing volume fraction of SiC particles. A small increase in the bulk SiC volume fraction of the cast MMC was observed due to particle settling during solidification. A one-dimensional enthalpy model of MMC solidification was formulated, wherein particle settling occurring in the solidifying matrix was coupled to the enthalpy equation by means of the Richardson-Zaki hindered settling correlation. A comparative study of simulations with experiments suggested that the thermal response of SiC particles used in this study was similar to that of single crystals, and their presence increased the effective thermal conductivity of the composite.

An experimental study was undertaken to determine how several variables affect the size of gas bubbles formed at nozzles in liquid pig iron. The frequency of bubble formation was measured by an acoustic device, which could detect the vibrations produced by the bubble release. Accurate knowledge of the gas flow rate then enabled the calculation of bubble volumes. The use of large baths (60 Kg), melted by induction heating, permitted a wide range of experimental parameters: gas flow rate (0.5 to 1000 cc/s), outside nozzle diameter (0.64 to 5.1 cm), inside diameter (0.16 to 0.64 cm), chamber volume (23 to 2200 cc), nozzle depth (7.6 to 20 cm), surface tension (700 to 1500 dynes/cm) and nozzle orientation (up, down and sideways). The resulting bubble volumes were between 0.5 and 100 cc. The bubbles were found to form at the outer diameter of the nozzles due to the nonwettability of the nozzles. Furthermore, the bubbles were of a uniform size at low flow rates, but increased in volume with the flow rate, so that a constant frequency was established. In addition, the bubble volume was strongly dependent on the chamber volume upstream from the nozzle. This is known as a “capacitance” effect and is due to compressibility of the gas. “Doublets” or “double bubbles” at small chamber volumes and bubble “pairs” at large chamber volumes were also observed. These phenomena result in smaller bubbles, which make precise predictions of bubble size difficult. The results are compared with those obtained by other investigators in aqueous and metallic systems.

Abstract: A three-dimensional mathematical model was developed to simulate the distributions of electrical potential, heat release, temperature, and velocity in the slag and matte in a six-in-line 36 MVA capacity furnace for smelting nickel calcine. From Part I of this series, it was found that there was a substantial electrical potential drop at the electrode surface, likely due to arcing through evolved carbon monoxide. The incorporation of this phenomenon into the model permitted accurate calculation of the current, power, and temperature distributions in the slag and matte. The slag was found to be thermally homogenized due to the evolved gas, and to a lesser extent by natural convection. In contrast, the matte was thermally stratified; this finding was attributed to poor momentum transfer across the slag/matte interface. Ninety percent of the electrical energy was used in smelting reactions in the calcine; to simulate the heat transfer from the slag to the calcine, a heat transfer coefficient was deduced from plant data. The implications of these findings for stable furnace operation are discussed.

Abstract: An electric potential probe was constructed so that simultaneous, multiple measurements of electric potential could be made in a six-in-line electric furnace for smelting nickel calcine having a maximum transformer capacity of 36 MVA. When the electric potential distributions were compared with those calculated from the solution of the Laplace equation, it was evident that there was significant electric potential drop at the electrode surface, 100 to 120 V for an applied potential of 180 to 230 V and currents of 20 to 30 kA. The Soderberg electrodes were continuously oxidized in the slag, likely creating carbon monoxide. The electric potential drop at the surface was attributed to arcing through the carbon monoxide. Thus, heat was released in the immediate vicinity of the electrode due to arcing, as well as in the bulk of the slag by Joule heating. The proper distribution of heat dissipation is required for the transport model, developed in Part II of this series.

The settling of 14-μm silicon carbide particles in an aluminum-silicon alloy was monitored with an electrical resistance probe to measure thein situparticle voluem fraction. The rate of settling was much greater than expected from hindered settling of single 14-μm particles. From the observed settling rate, an equivalent hydrodynamic diameter and density of clusters of particles were deduced, 38 μm and 2740 kg/m3, respectively. Other work was analyzed with the same procedure; it was concluded that if the stirring prior to settling were intense, then the clusters would be smaller than with weaker stirring. The implications for foundry practice and mechanical properties are discussed.