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By Manfred K. Walther

"Tests were conducted on instrumented plates cast in the Abex Experimental Foundry to compare recorded solidification histories with results computed for corresponding models simulated with the C.A.S.T. program. The first plate was cast of low alloy steel and the second of carbon steel with a graphite chill at one end. Both were cast in molds of bonded silica sand. Temperature histories were recorded in the castings, molds and chill. Exceptionally good agreement was achieved between computed and experimental data. Other investigators will find the results useful as a benchmark against which they can compare the results of their own calculations.IntroductionSince the early 1970's our foundry engineers have used both two- and three-dimensional versions of the G.A.S.T. program to gain knowledge of the solidification process [1,2,3]. Study of the computed data gave insight as to how the rigging and risering of specific castings might be changed or adjusted to improve quality and yield. New schemes based on such analyses were then recommended for implementation on the foundry floor. The degree of success of the new practice was subsequently evaluated after the part had been poured, shaken out and examined. Similar conditions were noted in the sectioned castings whenever porosity and voids had been predicted by the computations. Appropriate modifications, when found successful in the model, were applied to the process. This led to a reduction, if not complete elimination, of the defects. Such results gave credence to the use of these programs as an aid in the production of better castings.Earlier investigations on simple shapes revealed excellent correlation between output derived with the G.A.S.T. program and exact solutions. Results also compared favorably with data calculated using other codes as reported in the literature [4] and summarized in the Appendix. However, since the computer program had not been verified by direct experiment, it was decided to run instrumented tests to check the theoretical predictions with actual measurements."

Jan 1, 1986

By Zhou Jiemin

A mathematical model is developed to determine the economic thicknesses of refractories and insulations in rectangular furnaces, Both the heat loss cost and the lining investment are taken into account to achieve a minimum operation cost. For the sake of calculating the heat flux, the paper is particularly concerned with the simulation of the three-dimensional transient heat conduction processes in the lining and a Douglas-Rachford method is used to solve the finite difference equations, The model has been used to design an industrial electric resistance furnace operated periodically. the values of temperatures and power consumption measured from the furnace correspond with the model results.

Jan 1, 1991

By Nozomu Uchida, Uematsu Keizo, Daisuke Shouji

"Grain orientated microstructure was developed for the improvement of ceramic characteristics. Novel polarized light microscopy was developed to examine the grain orientation quantitatively. The degree of grain orientation was estimated from the retardation determined with a Berek compensator. The method was essential to determine a minor grain orientation, which could not be analyzed by means of conventional X-ray measurements. The data were favorably related to ceramics characteristics. The comparis of the ceramics with various degree of orientation was very important to explain the change of ceramic characteristics with processing.IntroductionMicrostructure with grain orientation has a high potential for greatly improving characteristics of ceramic. However, there has been strong restriction on processing and material for developing this structure. It has been crucial to apply forming methods involving high shear such as injection molding1). Grains must have an elongated shape.In recent years, much attention has been paid on the effect of high magnetic field on diamagnetic materials2)3)4), Many ceramic materials are known to be diamagnetic. High magnetic field has a high potential to orient grains. The principal driving force for grain orientation is the magnetic anisotropy of material, which is generated by non-cubic crystal symmetr5). This method of grain orientation is not restricted by grain shape, and can be applied to all materials having non-cubic crystal structure.This study uses alumina as raw materials, and produces alumina ceramics with orientated grain in high magnetic field (10T). Alumina has a magnetic anisotropy due to hexagonal crystal structure. The degree of grain orientation in the green and sintered bodies will be examined and their relevance to magnetic field will be discussed."

Jan 1, 2000

By M. Patel, G. Djambazov, J. Shrimpton

"Removing zinc by distillation can leave the lead bullion virtually free of zinc and also produces pure zinc crystals. Batch distillation is considered in a hemispherical kettle with water-cooled lid, under high vacuum (50 Pa or less). Sufficient zinc concentration at the evaporating surface is achieved by means of a mechanical stirrer.The numerical model is based on the multi-physics simulation package PHYSICA. The fluid flow module of the code is used to simulate the action of the stirring impeller and to determine the temperature and concentration fields throughout the liquid volume including the evaporating surface. The rate of zinc evaporation and condensation is then modelled using Langmuir's equations. Diffusion of the zinc vapour through the residual air in the vacuum gap is also taken into account.Computed results show that the mixing is sufficient and the rate-limiting step of the process is the surface evaporation driven by the difference of the equilibrium vapour pressure and the actual partial pressure of zinc vapour. However, at higher zinc concentrations, the heat transfer through the growing zinc crystal crust towards the cold steel lid may become the limiting factor because the crystallization front may reach the melting point.The computational model can be very useful in optimising the process within its safe limits.IntroductionLead bullion is commonly refined by removing various impurities (e.g. copper, silver, bismuth, antimony, etc) sequentially. This in normally achieved by the addition of reagents which selectively react with the impurities and the resulting compounds removed by various means. To aid efficient mixing (ensure uniform reactions), batch mixing of materials via the aid of impellers is common practice in a number of industrial sectors. Excess zinc, added during the desilvering process can be removed by one of three methods: (1) Vacuum dezincing - During vacuum dezincing, a vacuum is drawn on the agitated molten lead within a hemispherical vessel (Figure 1). Vaporized zinc condenses on the inner top surface of the vessel. The temperature at which zinc commences to vaporize lowers owing to heating under a vacuum. This enables vaporized zinc to be recovered in the form of high purity crystals without oxidation. The zinc crystals are recovered once the vessel lid is removed and the vacuum is broken. (2) Chlorine dezincing - In chlorine dezincing, molten desilvered lead is reacted with chlorine gas, forming a surface layer of zinc chloride contaminated with small amounts of lead chloride."

Jan 1, 2004

By Baicheng Liu, Houfa Shen, Wensheng Li

"In order to understand the formation of macrosegregation in steel ingots, a mixture model has been developed which accounts for coupled mass, momentum, species, and energy transport to describe the sedimentation of free equiaxed grains during solidification. In this model, the mushy zone is divided into the slurry and porous regimes according to a solid packing fraction. Settling velocity of equiaxed grains in the slurry regime is given by an explicit expression. The solidification of a binary steel ingot (Fe-0.36wt.%C) with a two-dimensional geometry is numerically simulated. It is demonstrated that the predicted macrosegregation patterns agree to some extent with classical experimental results. Further refinement of this model is still necessary for realistically simulating steel ingot solidification.IntroductionModeling macrosegregation in steel ingots is still a challenging study, mainly due to the length scale of the products and the complexity of global multiphase transport phenomena coupled with microscopic solidification kinetics [l]. The thermal-solutal convection and the motion of equiaxed grains are the two main mechanisms responsible for macrosegregation. But there are few models that deal with the motion of equiaxed grains, which is confirmed as the main phenomenon that explains the negative macrosegregation along the centerline of large steel ingots [2]. A model which takes into account melt convection and grain sedimentation was first proposed by Beckermann and co-workers ([3], and references therein). More recently, similar multiphase solidification models with advanced nature have been presented by Wu and Ludwig [1,4] and Combeau and co-workers [5,6]. It is known that the application of these sophisticated models to steel ingot casting is at its beginning.In this paper, a solidification model based on continuum mixture approach, using much less sophisticated relations to obtain the settling velocity of free equiaxed grains, has been proposed in order to predict the macrosegregation in steel ingots. The model is applied to simulate the solidification of a binary steel ingot with a two-dimensional geometry, and preliminary modeling results are presented."

Jan 1, 2011

By Patrick R. Taylor

Titanium nitride has been synthesized in a thermal plasma reactor from ilmenite ore concentrate using methane and ammonia as the reactive gases. The product has been characterized by x-ray diffraction and SEM. Results show that a high concentration of methane favors the formation of iron, titanium nitride and titanium carbonitride. The formation of titanium carbonitride can be minimized by controlling the concentration of methane. The formation of TiN proceeds by the progressive reduction of the oxides of titanium to titanium, which is converted to titanium nitride.

Jan 1, 1998

By P. C. Chaubal

The overall kinetics of oxidation of single partic1es of chalcopyrite have been studied for temperatures up to 1273 K. The experiments were conducted in a stationary bed reactor using a non-isothermal technique. Any mass and heat transfer effects on the kinetics of oxidation were eliminated by using a high-enough gas flowrate. Up to temperatures of 873 K, pore-bl1ocking kinetics were applicable, whereas above 873 K, power-law kinetics gave a satisfactory fit of the data. The activation energy was 215 kJ/mol below 754 Kand 23.7 kJ/mol above 1,060 K. Predominance area diagrams were constructed at various temperatures and used in conjunction with X-ray analyses of partially oxidized samples to determine the intermediate phases formed during the reaction. The analysi1s also provides a justification for the kinetic models used. The results indicate that the reaction rate is first order with respect to oxygen concentration and inversely proportional to the square of the particle size throughout the ranges of temperature studied.

Jan 1, 1985

By M. Nilmani, J. Sofra

The transverse distributions of the solids discharge velocity and mass flux at the discharge end of vertical and inclined lances were measured in order to detennine the transverse distributions of the axial momentum flux, which is a dominant factor influencing the penetration behaviour of particles into melts during submerged injection. The effects of gas velocity (10 - 30 m/s), solids loading (5 - 10), lance length (0.15 - 1.0 m), lance inclination (vertical downward - horizontal) and particle density (2500 - 8900 kg/m3 ) were investigated, while the lance diameter and particle size were fixed at 10 mm and 220 µm respectively. The particle velocities and mass fluxes were measured by image analysis of particles illuminated in a laser-generated light sheet aligned vertically through the axis of the lance at the discharge point. The particle discharge velocity profiles for vertical downward flows were synunetrical about the centre-line of the lance, with the maximum velocities occurring at the centre-line. The velocities increased with increasing gas velocity, increasing lance length and decreasing particle density in accordance with previous observations. The transverse mass flux profiles were also synunetrical for vertical downward flows, however at the lower gas velocities the peaks in the profiles were displaced from the centre-line of the lance by a fractional diameter of about 0.15. The particle discharge velocity profiles become increasingly asynunetric as the lance orientation was changed from vertical to horizontal, with higher particle velocities present near the top wall of the lance. The mass flux profile also became asyrrunetric as the horizontal orientation was approached, however in this case, the profile became biased towards the bottom of the lance. The effect was much more pronounced for a gas velocity of 10 m/s than for 30 m/s, showing the relatively stronger gravitational influence as the velocity was reduced.

Jan 1, 1996

By Qian Li, Haiyan Leng, Kuo-Chih Chou, Haoyuan Xiao, Zhigang Yu

Magnesium borohydride and Magnesium alanate were synthesized by mechanochemical metathesis reaction. The thermal decomposition behaviors of Mg(BH4)2-nMg(AlH4)2(n=0.5,1) systems were investigated as potential hydrogen storage materials. The results showed that the systems started to desorb H2 at 120 ℃ and desorbed 3.9 wt. and 4.9 wt.% H2 below 300 ℃ when n equals 0.5 and 1, respectively, while individual Mg(BH4)2 started to desorb H2 at 250 ℃ and desorbed only 0.82 wt.% H2. Because of the exist of the Mg(AlH4)2, the isothermal desorption kinetics of Mg(BH4)2 in the Mg(BH4)2-0.5Mg(AlH4)2 systems was 50% faster than that of pristine Mg(BH4)2. In addition, the re-hydrogenation rates also increased 49.4% and 37.9%.

Jan 1, 2015

In the new flowsheet for Inco Limited's S02, Abatement Project at the Copper Cliff, Ontario operations, a copper/nickel sulphide flotation concentrate will be flash smelted, then converted to Bessemer matte. As in current practice, this will be slow-cooled and separated into components by magnetic separation and flotation. The copper content will emerge as a chalcocite concentrate (impure Cu2S), containing some nickel. This copper sulphide will be converted to copper metal.

Jan 1, 1993

By T. Shibasaki

There is a strong demand in the photo industry to the higher quality of refined silver. Osaka Refinery produces about 27 mtpm of refined silver mainly from copper refinery slimes. Product quality is attained by controlling the impurity level in electrolyte. Copper is cemented with silver oxide and palladium is precipitated by a chelating agent. Both processes were operated previously in batchwise for treatment of bled out electrolyte, Recently these processes have been improved and made continuous to cope with the increased impurity.load. As a result the grade of fine silver has been maintained steadily at Pd < 3 ppm and Cu < 5 ppm.

Jan 1, 1989

By Shuichiro Okada

Various efforts to reduce energy consumption and smelting cost are made at Tamano Smelter. Production of anode copper has been increased by about 30 % and energy requirement has been decreased about 50 % respectively. Challenges toward more higher goal are being continued. Details about the following are described in this paper. 1 Waste heat recovery Steam recovery at up-take of FSFE Heat recovery from waste gas of anode furnaces 2 Application of tonnage oxygen 3 Application of pulverized carbonaceous fuels to the flash smelting furnace with furnace electrodes ( FSFE ) 4 Application of computer control system to copper smelting 5 Improvement of the fugitive gas collecting system 6 Improvement of the mechanical tuyere puncher for the converter furnace

Jan 1, 1983

By K. Dzieciol

The paper presents a study about three image correlation methods ?common cross-correlation, mutual information and phase-correlation ? applied to characterize microstructures reconstructed with X-ray tomography. It is shown that phase correlation is not only the fastest, but also the most sensitive method for detection of similar microstructure features, cavities in the present case. A new image correlation indicator is proposed, which takes into account both the phase shift and the amplitude of similar features in compared images. Some preprocessing aspects related to the tomographic reconstruction and filtering out of characteristic noise are also discussed.

Jan 1, 2009

By Elders. Wilfred A.

Petrological and geochemical methods, the utility of which has long been established in the mining industry, are proving useful and cost-effective in elucidating the thermal evolution of active geothermal fields. In return, they yield insights into sulfide-silicate equilibria, mass and energy transfer in convecting hydrothermal systems, and the genesis of hydrothermal ore bodies. Within the Plio-Pleistocene sediments of the delta of the Colorado River, in the Salton Trough, several active geothermal systems are known. Temperatures vary from 100-365°C, at less than 2 km depth, and salinities vary from 3,000 to 280,000 ppm, total dissolved solids. The hydrothermal alteration causes marked induration of the sediments, producing greenschist facies metamorphic minerals, including hydrothermal ore minerals. Subsurface authigenic minerals show strong correlation with increasing temperature. A typical sequence in sandstones is (below 150°=C) montmoril-lonite-kaolinite, (above 180°C) chlorite + illite, (above 225°C) calc-alumino-silicates, (above 325°C) biotite. There is a transition from porosity-dominated\to fracture-dominated permeability in the hottest and deepest geothermal reservoirs. This regular series of minerals provides a practical tool during exploration drilling. From drill cuttings, we can make predictions on reservoir temperatures, useful in making decisions on well completion. Other types of geothermometry we have employed include light stable isotopes, fluid inclusions and vitrinite reflectance measurements. A combination of these techniques not only improves our temperature predictions, but together with fission tack annealing studies, permits us to model the dynamics of temperature change and fluid flow in these geothermal reservoirs.

Jan 1, 1981

By Marcelo B. Mourão

An experimental investigation was carried out to -study the rates of reduction of pellets containing iron oxides by carbon dissolved in liquid iron, at temperatures ranging from 1720 K to 1973 K. Several different pellet types were employed; the materials used in the pellet&apos;s manufacture were pure hematite, two kinds of commercial iron ores, and mixtures hematite/silica and hematite/lime: Reaction times were determined employing the constant volume pressure increase technique (CVPI). It has been observed that the reaction rate increases as the temperature and the pellet&apos;s specific surface area increases. The reaction rate is also affected by the oxide type: pellets made from commercial ores or from mixtures hematite/silica or hematite/lime show reaction rates lower than those made from pure hematite.

Jan 1, 1996

By Debbie Marshall

Process water is an important consideration in the development of a nickel laterite project. Depending on the location of the ore body, sufficient fresh water may not be available and it may be necessary to use seawater (or saline groundwater) for ore preparation. This introduces various species, which have major effects on materials of construction and leaching chemistry. This paper summarizes batch testwork completed at the Falconbridge Technology Center. The leaching behaviour of eleven different laterite ore samples were compared using seawater and fresh water. For brevity, six of the eleven samples are reported here-the other five samples showed similar results. Each ore type was leached under identical conditions in both freshwater and seawater and the leaching chemistry compared. The batch test results were confirmed in a continuous pilot plant, and leach kinetics for the two systems were compared. Keywords: high pressure acid leaching, laterites

Jan 1, 2004

By João M. S. Rodrigues

The use of sandblasting as a treatment method for conditioning anodes for zinc electro-winning was investigated and compared with conventional fluoride preconditioning. The anodes were made from two different lead-based alloys (Pb-Ag-Ca and Pb-Ag). Laboratory results showed that sandblasting and preconditioning both minimize lead contamination in the zinc and sludge generation. Sandblasting was found to have no aggravating effect on the anode corrosion. The sandblasting treatment was tested on Pb- Ag-Ca anodes on an industrial scale in the celJhouse of a local zinc producer. An unexpected finding of the large-scale tests was that the sandblasting appeared to strengthen the anodes, resulting in reduced warping during handling and operation.

Jan 1, 1996

By Alan DonaldsoN

Plasma Quench production of titanium is the thermal dissociation of titanium tetrachloride into gaseous titanium and chlorine followed by rapid quenching to prevent back reactions. Titanium tetrachloride dissociates into titanium and chlorine atoms at 5000 K. Expansion through a Delaval nozzle accelerates the gas to supersonic speed cooling it very rapidly. Cooling rates are as high as 7exp 1 0 Kelvins per second. Injected hydrogen reacts with condensed titanium particles to form titanium hydride and with the chlorine to form hydrogen chloride. We have produced titanium powder at 20 kglh in a continuous reactor. Costs are projected to be lower than the Kroll Process at large enough scale. Most of the cost reduction would result from elimination of magnesium as a reducing agent and much lower capital costs.

Jan 1, 2001

By Henrlk Gripenberg

To solve the environmental and financial problems of the traditional Rotary Salt Furnace process, a new salt-free method for aluminum dross and scrap melting, ALUREC, has been developed by AGA and its partners, Hoogovens Aluminium and MAN GHH. AGA and Hoogovens Aluminium developed the main process concept and jointly carried out trials on pilot plant scale. Owing to excellent results" the partners decided to jointly erect a commercial scale test plant. The order for the design and erection of the furnace went to MAN GHH. The three companies designed the test plant and began operation in the spring of 1994. The results have been excellent and the process is expected to be a technical and commercial success.

Jan 1, 1995

By Ko-ichiro Ohno

It is recently recognized that the iron reduction and melting as well as the slag separation of a composite of granular iron ore and coal are completed in a very short period of about IO minutes when the composite is rapidly heated up to approximately 1673K. These phenomena are expected to be applied to a new iron-making process. The mechanism of iron ore reduction and iron-slag separation during rapid heating has not yet been revealed and the fundamental research has just started. Carburization of the reduced iron is regarded as one of the most important steps in this process. In the present work, the composite was prepared from four kinds of coal or graphite as a carbon source and electrolytic iron powder as a completely reduced iron ore. The temperature at which the liquid formation and iron carburization occurred was monitored. Direct observation of smelting reduction behavior was made by a confocal laser-scanning microscope combined with the infrared image-heating furnace to clarify the effect of molten ash on iron carburization. It was found that the meltdown temperature of composite became lower as the melting temperature of coal ash decreased. From the observed result, it was presumed that the liquid slag would act as an important media for the carbon transfer from coal to iron. The carburization mechanism during the smelting reduction was estimated as follows. When slag containing iron oxide melted down and contacted carbon, iron oxide in the slag was reduced and the formation of the metallic iron particle as well as the its carburization occurred simultaneously at the slag-carbon interface. Carburized iron particle was carried from slag- carbon to slag-iron interfaces due to the slag convection flow caused by the difference of the interfacial tension between the carbon-slag and iron-slag interfaces. Carburization of reduced iron could proceed with a repeat of the above-mentioned process.

Jan 1, 2003