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By Riyad N. Ahmad-Bitar, Shadia J. Ikhmayies

"CdS/CdTe solar cells were built by depositing a 200 nm layer of Sn02:F on glass substrates by the spray pyrolysis (SP) technique, a 500 nm CdS:In layer by the same technique and a 1-1.5 µm CdTe layer by vacuum evaporation. The cells were CdCh heat-treated in nitrogen atmosphere for 30 minutes at 350 -.C. The photoluminescence (PL) spectra were measured at the CdS/CdTe interface for two cells with different values of the CdTe layer's thickness at temperature T = 60 K. A deconvolution peak fit was performed from which it is found that the peaks are characteristic of the solid solution CdSxTei-x· The parabolic relation that relates the bandgap energy with the composition was used to estimate x, where xis [S]/([Te]+[S]) and [Te], [S] are the concentrations of Te and S atoms respectively. The results show that the interface is smooth and the change of the bandgap occurs gradually.IntroductionCdS/CdTe heterojunctions represent a combination of materials promising various applications, and for solar energy conversion in the first place [1]. In photovoltaic cells the CdS material acts as a wide bandgap window. Direct bandgap CdTe with high optical absorption coefficient is used as an absorber [1]. Solar cells with efficiencies of 10 to 16% have been obtained with CdTe grown by close space sublimation, electrodeposition, vacuum evaporation and rf sputtering methods [2]. In this work the CdTe layer was prepared by vacuum evaporation because it results with films of minimum impurities, while the Sn02:F and CdS:In layers were deposited by the spray pyrolysis technique because it is a low cost method which enables intentional doping and large area thin films."

Jan 1, 2011

By L. A. Neumeier

The Bureau of Mines, U.S. Department of the Interior, is investigating the feasibility of partitioning complex sulfide minerals to simpler sulfide .phases by sulfldation reactions. Such partitioning can afford opportunity to improve selective extraction of mineral constituents of value. This report describes initial research involving sulfidation partitioning of chalcopyrite concentrates. Small chalcopyrite samples were sulfidized with elemental sulfur in glass capsules sealed after evacuating and backfilling with helium, by heating for 1 to 24 h at specific temperatures in the range of 250° to 500° C. which extends from below to above the boiling point of sulfur (-445° C). Above the boiling point of sulfur, the overall reaction with adequate sulfur (13.9 wt pct of CuFeS2) is 5CuFeS2 + 4S g ? Cu5FeS6 + 4FeS2.

Jan 1, 1989

By Payal Bakshi, Sangeeta Tiwari, Mohini Saxena, Anusha Sharma

"Recycling and reuse is perhaps the most favorable and beneficial way to solve the problem of industrial waste disposal. However, the use of industrial wastes like fly ash, tailings etc is in practice for brick manufacturing, land filling, embankments filling etc. These existing practices do not add enough value to the wastes. Moreover, some wastes may have very good potential to be incorporated in valuable products like paints. This study reveals about the value addition of industrial wastes like fly ash, copper tailing and blue dust as an extender in paints. Comparative properties and characteristics of these three wastes for application in paints are discussed. Fly ash, copper tailing and blue dust were characterized for physical, chemical and mineralogical properties and used in different paint formulation based on their potential to the particular application. Fly ash has been found very useful in enamel, primers and flat paints while copper tailing was found suitable in oil based paint formulations. The performance of fly ash and copper tailing paints were evaluated by comparing with those of conventional whiting extender. Blue dust was compared with conventional iron oxide for use in priming coats. The extender properties of these new material and paints prepared out of blue dust, fly ash, copper tailing, were found better than the existing related materials.IntroductionIndustrial development and environmental reforms should run parallel to benefit each other. This is the best policy, which must be adopted by industries for the sustainability of the current modern life. The high degree of industrialization and urbanization adds scads of waste resulting problem of pollution and challenges of their safe disposal. The nature of waste depends on the process that produces waste as its by-product. Therefore, policies/plans are prepared by keeping the view of possible potential hazards. Among the different wastes some are generated in the industries, which have great importance in the country’s economy, like fly ash waste from thermal power industry and mining waste. In India the total contribution of thermal power in the total electricity generation is more than 70% and it produces about 123 million ton of the fly ash annually [1]. On the other hand mining plus extraction of ferrous and nonferrous metals also produce waste in million tonnes of categories [2]. Since the generation of this waste is very high they cover large land area for their disposal and dumping [3]. The storage of this waste in the dumping sites for long time duration may cause problem of land, surface water, ground water and fertile soil contamination [4]. As far as Indian fly ash is concerned it does not contain toxic element over the limits of hazardous waste [5]. However, in general most of the metals deposits are found in the form of pyrite based ores. Mining wastes contain toxic elements e.g. heavy metals in varying amount, which get mobilized when pyrite get oxidized to sulphate producing sulphuric acid [6,7]. These ores contain very less amount of targeted metals in themselves thus they require extensive preprocesses for concentration of the metals [8]."

Jan 1, 2008

By O. Nakai

In the copper electrorefining process, the quality of the starting sheet is one of the basic factors for producing high quality copper cathodes. A highly automated and advanced facility for the production of copper starting sheets was constructed at the Toyo Copper Refinery in 1992, bringing various improvements into an automatic stripping system using stainless steel mother blanks. In 1998, the refinery expanded the tankhouse by another 128 commercial cells, and introduced 64 polymer concrete cells in a first stage conversion. As a result, the Toyo Copper Refinery now has the capacity to produce 103,200 t/y of cathode copper. Construction has led to great improvements in the materials handling facilities and computer associated short-circuit detection technology. This report summarizes the improvements made in the quality of the cathodes and in plant productivity.

Jan 1, 1999

By O. Ryosuke Suzuki

A new metallurgical process via sulfide is proposed: a sulfide is produced at a high temperature from its metallic oxide using gaseous CS2, and this sulfide is electrochemically reduced to its metallic state using molten salt. This combined process via sulfide is effective to obtain high purity of metallic powder, even if the metal in its oxide is strongly combined with oxygen. For example, it is not easy to reduce stable oxide TiO2, and only Ca can remove oxygen to form α-Ti. However, a fairly large amount of oxygen remains as Ti–O solid solution. Because the solubility of S in Ti is very small, this proposal was examined experimentally both on the conversion of TiO2 to TiS2 and on the successive reduction of TiS2 to Ti. TiO2 powder was exposed to CS2 gas flow at 1073 K, and the conversion to TiS2 was confirmed. TiS2 could be reduced to Ti powder either by calciothermic reduction or electrolysis in a CaCl2 melt. By Ca reduction at 1133 K in CaCl2 melt, sulfur concentration decreased to 0.03 mass%S when the amount greater than twice the stoichiometric calcium amount is added. By electrochemical reduction at 1173 K in CaCl2–CaS melt, S concentration significantly decreased to 0.01 mass% S when four times larger amount of electric charge was supplied.

By Jing Zhang, Qing Xiao, Xulong Liu, Qiuju Li

"Pickling sludge generated from stainless steel production process contains large quantity of Cr, Ni, and Fe. The disposal of and fill sludge directly not only leads to the heavy metal dissolves in the soil and underwater, but also loss value metals. However, the major mineral phases of value metal are hydroxides and there are lots of calcium fluoride and water in the sludge. So the pickling sludge has to be pretreated before reduction-magnetic separation. The TG analysis, reduction reaction and magnetic separation were all used to study the pickling sludge. The result indicated that up to 900°C the total weight loss of pickling sludge was 22.32%. The mass contents of Fe, Cr and Ni in the tailings (non-magnetic) were 4.27%, 0.067% and 0.041% respectively.IntroductionSince 21st century, the stainless steel production in the world has been continuously increasing because of its excellent performance [1]. However, high stainless steel production means a high pickling sludge production. For example, in a stainless steel plant with waste water quantity of 100m3 /h, the production of pickling sludge will exceed 15 Kt/a. Pickling is essential for generating of a homogeneous and corrosion-resistant surface during stainless steel production subsequent process. Pickling of stainless steels is predominantly carried out with an aggressive solution, sulfuric acid H2S04 or composed of nitric acid HN03 and hydrofluoric acid HF [2]. During the pickling process, the pickling acids are recovered through ion exchange and metal ions such as Fe3+, Cr3+ and Ni2+ get into the acids forming the pickling waste water [3]. Then, the pickling waste water is precipitated with lime, forming pickling hydroxide sludge. It is not feasible to recycle or treat the pickling sludge using conventional methods, because the sludge has high contents of calcium fluoride and water but low contents of iron, chromium and nickel. However, it would also pose a potential environmental problem if deposited outdoors over a long term because it contains heavy metals such as Cr and Ni. At present, solidification/stabilization (S/"

Jan 1, 2014

By C. K. Gupta

The paper reports on the experimental work and results obtained in processing a xenotime concentrate. The rare earth resource concentrate has been treated by three different methods namely, hydrothermal leaching, alkali roasting and alkali pugging or baking. The recovery in hydrothermal leaching with caustic soda at 150-160°C has been 89%. En comparison, processes involving alkali roastings with soda ash at 850°C and with caustic soda at 500°C, and alkali pugging or baking with caustic soda at 200°C have given recovery values close to 100%

Jan 1, 1992

By Pradip

The selective adsorption of chemisorbing fatty acids at high temperatures together with the addition of soda ash and lignin sulfonate as depressants is the key to the industrial processing of bastnaesite ores. This paper presents the results of a fundamental investigation that indicate that alkyl hydroxamates can be an alternative collector for the beneficiation of bastnaesite ores that contain barite and calcite as the principal gangue minerals. The primary mechanism for providing sites for the chemisorption of hydroxamate on bastnaesite appears to be through dissolution of cations, formation of the respective hydroxo complexes and readsorption at the interface.

Jan 1, 1989

By Charles Zimmerman

The Genesis gold mine, owned and operated by Newmont Gold Co., is located in section 31, T36N, R50E within Eureka County, Nevada along the Carlin Trend of sediment-hosted disseminated gold deposits. Mining commenced in 1986 with present mineable and stockpiled reserves listed at 17,711,000 tons of ore averaging 0.073 opt Au, totalling 1.292 million ounces of gold. Ore is primarily hosted within Devonian calcareous siltstones that have been subjected to intensive argillization and silicification episodes. Additional mineralogic and geochemical features of the Genesis ores include enrichment in iron-oxides, kaolinite, arsenic and antimony; the ore zone is relatively depleted in carbonates and sulfides as a result of supergene and hypogene oxidation. Two major structural zones enhanced the permeability of the siltstones and served as the main hydrothermal conduits within the deposit. Prior to the main ore stage, the host rocks were subjected to metasomatic effects caused by emplacement of the Juro-Cretaceous Goldstrike granodiorite pluton and associated dikes and sills. Micron-size gold occurs in clays, micro-crystalline quartz, and in arsenical complexes. Non-oxidized carbonaceous and sulfidic ores and silica-locked ores result in variable preg-robbing and refractory responses during cyanide recovery. Selective mining and milling has resulted in the successful treatment of the Genesis orebody.

Jan 1, 1988

By Eliezer Martinez-Jimenez, Gretchen T. Lapidus

"Electro-assisted reduction is an effective pretreatment to render chalcopyrite less refractory towards oxidative leaching. In this process, chalcopyrite is selectively converted to chalcocite or copper metal in an electrolytic cell under ambient conditions, while ferrous ion is leached into solution. However, the reaction velocity is hampered by the formation of a ferrous sulfide passivating layer on the solid surface, especially at elevated solid to liquid ratios. In the present work, several strategies for overcoming this problem were evaluated. On one hand, specific ligands for ferrous ion were added in order to increase its solubility and, on the other, an anode material which promotes the oxidation of the sulfide ion was chosen. Leaching tests showed citric acid to be an effective ligand for both ferrous and ferric ions and, in combination with a lead-silver anode, significantly increased the kinetics of chalcopyrite reduction and subsequent copper leaching.IntroductionAttempts to oxidize chalcopyrite at a rapid rate in aqueous solutions, below their normal boiling point, have met with difficulties because of passivation by some of its own components. An alternative line of research explores reductive pretreatment, transforming the chalcopyrite into less refractory copper phases, which can later be oxidized. A recompilation of these efforts up until 2000 was published by Dreisinger and Abed [1]. However, this practice usually requires large excesses of reducing agents, such as copper, lead, aluminum or iron, and in this last case at near-boiling temperatures, in highly"

Jan 1, 2012

By Takashi Nagai, Hideaki Sasaki, Masafumi Maeda

"The production of solar cells is increasing dramatically and the shortage of polycrystalline silicon for these cells has become a serious problem, making development of a low-cost production process for solar grade silicon essential. An electron beam melting technique is known to be effective for the removal of phosphorus from molten silicon. Although the phosphorus is removed by preferential evaporation in this process, the rate of removal is not sufficient, and its improvement requires thermodynamic information on phosphorus in the molten silicon. In this research, the vapor pressure of phosphorus in equilibrium with a siliconphosphorus alloy was measured by double Knudsen cell mass spectrometry with a system blowing gas into the Knudsen cell. The activity of phosphorus in silicon, the Gibbs energy change of the dissolution of phosphorus in silicon, and other factors were estimated from the results. Using these data, we provided guidelines on how this process can be improved.IntroductionSolar energy is in great demand since it is inexhaustible and cleaner than that from conventional energy resources. Silicon is the material most widely used to convert solar energy into electricity. Figure 1 shows the recent production of solar cells. High purity silicon for solar cells, namely solar grade silicon (SOG-Si), has been commercially supplied mainly from off-grade high purity silicon in the semiconductor industry. However, production of solar cells has increased rapidly in recent years, and the shortage of SOG-Si has become a serious problem, so that a new processes which can produce SOG-Si economically are required.Directional solidification was applied to remove transition metal elements such as Fe or Ti by segregating them from the remaining melt. However, such solidification is useless for phosphorus because the segregation coefficient of phosphorus is nearly unity. Numerous approaches have been made in an attempt to produce a resource of low cost SOG-Si from metallurgical-grade silicon (MG-Si). [1,2]"

Jan 1, 2012

By Florian Kongoli

While calcium ferrite slags have been successfully used in continuous copper converting for the last 30 years, ferrous calcium silicate slag was proposed about 8 years ago as an additional alternative for copper smelting. Although both slags are normal extensions of each other their phase relations have not been completely clarified. In this paper the liquidus relations of both slags have been quantified at various areas that cover both of them. The existing experimental data have been first reviewed and discussed in relation to the solidification procedure. An original physical model is then used to predict various diagrams of the liquidus surface of both slags. It is shown that the ternary liquidus diagrams normally used for FeOx-SiO2-CaO system are not suitable for industrial slags. The new model diagrams of Fe/CaO versus SiO2 and Fe/SiO2 versus CaO as well as Fe/CaO versus Temperature and Fe/SiO2 versus temperature are proven to be much more convenient for ferrite and ferrous calcium silicate slags. Based on these diagrams the effect of SiO2 and CaO on the melting temperature is quantified. The effect of Cu2O is also quantified through the model. Some Fe/CaO versus Cu2O and Fe/SiO2versus CaO at various copper contents are predicted and the results show good agreement with the experimental data. It is also shown that in the presence of liquid copper, Cu2O is dissolved in the slag depending on the oxidation degree of the system and might lower the liquidus temperature. Some discussions are also presented taking into account plant observations and important conclusions are drawn for copper smelting and converting

Jan 1, 2006

By Michael J. Nicol

This paper summarizes some of the results of a study of the reactions involved in the Caron leaching process and identifies the roles of the major dissolved species in the kinetics of dissolution of iron alloy particles formed during reductive roasting. Using rotating disk electrodes and synthetic leach solutions, the reduction of water with the evolution of hydrogen was found not to occur on a dissolving iron surface under typical leach conditions. It has been established that the oxidative dissolution is governed primarily by a reaction involving reduction of Co(III) to Co(II) ions. The reduction of oxygen was also found to make a significant but largely indirect contribution to the kinetics of the dissolution process. The dissolution rates of various iron-nickel-cobalt-copper alloys which simulate the dissolving alloy particles in a Caron plant were measured in synthetic leach solutions under aerobic and anaerobic conditions. The initial dissolution rates of iron, nickel and the iron alloys were found to increase in the presence of thiosulphate, whereas the thiosulphate had a negative effect on the dissolution rates of cobalt and copper. It is shown that the eventual passivation of the iron occurs sooner in solutions rich in Co(II) ions. Whilst these conditions are present in the quench slurry, on-site measurements have shown that due to the very high concentration of reduced dissolved species, passivation does not occur until the slurry is strongly aerated. In the light of these fundamental findings, options for optimizing the rate of dissolution and minimizing the extent of passivation of the iron and iron alloys are discussed. Keywords: Ammonia, leaching, alloy, kinetics, passivation.

Jan 1, 2004

By Tracy T. Morris, Luis G. Navaro

"Anodic copper slimes produced during the electrolytic refining of copper are routinely batch leached to remove copper. At the Amarillo Copper Refinery, an atmospheric leaching process was converted to an autoclave pressure leaching system to improve the removal of copper, reduce the consumption of oxygen, improve leaching times and enhance tellurium recovery. The benefits of pressurized versus atmospheric leaching of slimes were soon realized by obtaining the desired level of decopperization in a shorter time and with lesser quantities of reagents. The autoclave was designed and constructed with a unique oxygen injection system that enables good control of the leaching process and with no plug-ups. Other features include a mass measuring system that balances the quantity of slimes to be leached to the desired final solution concentration based on initial feed concentrations. The end result was a more efficient and controllable leaching process for removing copper from anode slimes.IntroductionThe electrolytic refining of copper consists of an electrolytic cell filled with a sulfiiric acid based electrolyte and pairs of copper anodes and cathodes. When a current is applied, copper in the anode dissolves and is plated onto the cathode. Impurities within the anode that are more noble than copper do not dissolve and end up at the bottom of the cell and are referred to as slimes. Gold and silver are the main slimes constituents of interest because of their monetary value, but there typically are significant quantities of selenium, tellurium, lead, antimony, arsenic, bismuth, nickel, silica and tin. Copper is also present, usually as a metallic or as a reactant with tellurium, selenium, oxygen or sulfur and can range from 10 to 30% of the slimes fall."

Jan 1, 2012

By Asmo Vartiainen

The viscosity of liquid Fe-O-SiO2 -slag at copper smelting conditions was investigated using a rotational viscometer. The studied parameters were oxygen partial pressure (10" °-10"6 bar ); composition of slag (Fe/SiO2 ratio), and temperature (1250-1400°C). The viscosity values are presented as a function of Fe/SiO2 ratio and as isoviscosity curves in ternary FeO-Fe2O3-SiO2 diagrams. The increase in viscosity at high silica contents can be accounted for the polymerisation effect of SiO4/4- -anions. At high ferric iron contents, higher oxygen partial pressure, the viscosity values increase especially near the magnetite saturation. The viscosity values are highest at the double saturation of silica and magnetite. At lower silica and ferric iron contents the viscosity values are more uniform in the homogenous liquid slag area. The viscosity values were lowest at high temperatures and highest at low temperatures.

Jan 1, 1998

By Naiyang Ma

"High oil concentration is one of the major barriers for recycling of mill scale of steel hot rolling mills. It is of vital importance to find cost-effective technologies of reducing oil concentration in mill scale in order to recycle the mill scale without causing detrimental effects on production and environment. This paper discusses in-process separation of mill scale from oil at steel hot rolling mills. Formation of mill scale and status of oily wastewater at hot rolling mills are reviewed in the first place. A mathematical model is then formulated to relate oil concentration in mill scale to physical properties of mill scale, chemical and physical properties of wastewater and interacting parameters between mill scale particles and wastewater. From this model, three approaches of in-process separation of mill scale from oil are derived: (1) avoiding contacts between mill scale particles and oily wastewater, and (2) maintaining low oil concentration in wastewater, and (3) collecting mill scale in upper streams of wastewater flows. In-process separation of mill scale from oil might have advantages of lower capital cost, lower operating cost and less additional environmental concerns, compared to other strategies of separating mill scale from oil.IntroductionHot rolling is an inevitable step in producing finished steel products. Figure 1 schematically shows a steel hot rolling process. Semi-finished steel products, slabs here, are reheated first, and then the reheated slabs are discharged from the furnaces and transported on hot rolling trains to descaling units for removing scale with pressurized water. After being descaled, the slabs are rolled by roughing mills. After treated with cropping and the second descaling, the slabs are finally rolled into finished products, coils here, by finishing mills."

Jan 1, 2012

By Victor Stancovski, Uday Pal, Stephen C. Britten

"An in situ electrochemical technique for measuring the concentrations of easily dissociable oxides in slags at temperatures between 1200-1600°C is being developed. The technique utilizes a partially-stabilized-zirconia solid electrolyte (PSZ), which conducts oxygen ions, to separate a reference-gas compartment from the slag of interest. Three types of measurements are currently under investigation which yield different information concerning the slag phase and hence will be combined into a single amperometric device for monitoring the properties of easily dissociable slags.Type I utilizes an open-circuit-voltage measurement between the reference gas and the slag phase. Type II utilizes a potentiostat to apply a direct current potential step or sweep between the inner and outer compartments of the electrolyte, driving oxygen ions from the slag into a reference gas. With the use of open-circuit-reference electrodes, the resulting current-potential profile reveals the dissociation potential and concentration profile of dissociable oxides such as those of iron, manganese, and chromium. Information on the transport properties of the cations can also be generated from these measurements. Type III utilizes a potentiostat with reference electrodes to carefully electrolyze a known volume of slag by removing large quantities of oxygen ions from the slag to the reference gas. The coulombs of charge removed at different applied potentials can be used as a direct indication of the concentration of each dissociable oxide species present within the slag."

Jan 1, 1997

By Mary Cunningham

The EPA and DOE have collaborated on a series of studies to evaluate the effectiveness of treatment technologies at stabilizing bulk elemental mercury and wastes containing high concentrations (i.e., with greater than 260 mglkg total mercury) and multiple forms of mercury. The data from these treatment demonstrations are intended to help EPA to determine if regulatory revisions to allow a stabilization alternative for high-mercury subcategory wastes are warranted. In addition to mercury-contaminated wastes, the disposal of bulk elemental mercury is of concern because of the excess quantity of mercury in the Defense Logistics Agency (DLA) stockpile, as well as other potential sources of excess elemental mercury. The studies evaluated the effectiveness of several technologies at: I) stabilization of mercury in a "hard-to-treat" matrix; and 2) conversion of elemental mercury into a stable waste form for disposal. A surrogate waste was designed for the study on high-mercury wastes, which included an organic form of mercury, elemental mercury, and several mercury salts in an inorganic matrix. The surrogate waste and the bulk elemental mercury were treated by the vendors, and the treated waste forms evaluated for mercury Icachability, using both the TCLP and an automated, constant-pH leaching protocol. Constant pH leaching was conducted at pH 2,4,6,8 10 and 12 for 14 days at each pH. The leaching data demonstrate that the stability of the mercury in three treated waste forms varies widely across the pH range tested. Clearly, the stability of mercury in these treated waste forms will be highly dependant on the disposal conditions. The combination of site-specific disposal conditions and appropriate treatment technology must be considered as decisions are made about disposal of high-mercury wastes.

Jan 1, 2003

By Jennifer Mager, G. P. Martins, Dean Mussatti

"The role of lead, at low concentrations in high pH cyanide-electrolytes, on the dissolution behavior of gold, has been a topic of scientific and industrial concern for well over a century. The recent paper by Kondos et al [1] at CANMET (1995) this continuing interest and apparent importance. Nevertheless, the mechanism(s) by which this (and other heavy metal) component influences the electrodics of this electrochemical system has still not been unequivocally demonstrated. Instead, several plausible hypotheses, by pioneering researchers in this field, have been advanced and reiterated OVer the ensuing years. While it is generally accepted, based on equilibrium elctrode-potential calculations, that reduction (or co-reduction when oxygen is present in the electrolyte) of lead on the gold surface may occur due to cementation (contact reduction), the cemented lead has never been characterized. The work presented has reexamined the role of lead in this system, by delineating the species distribution of these system components and by interpreting the results of potentiodynamic studies in conjunction with SEM analyses of a gold electrode.1. INTRODUCTIONThe leaching of gold ores in cyanide electrolytes has been practiced for well over a 100 years. Research conducted on this topic has been primarily focused on the effects of operating parameters such as concentrations of oxygen and cyanide, and the pH of the electrolyte; or the leaching behavior of carbonaceous and sulfitic gold-bearing materials.Mechanisms by which pure gold is leached in alkaline cyanide media, with oxygen serving as the oxidant, have been subjected to continual examination and re-examination in the published technical literature during this century. Recently, it has been speculated that without the presence in the electrolyte of trace heavy metals, such as lead or mercury, that gold would not be leachable. Researchers who have tackled this topic, have either considered heavy metals to be a natural occurrence in these systems and ignored the role they may serve in the leaching process, or they have deliberately focussed on controlling their concentrations in the system to undetectable limits. As a result, conflicting findings have been reported for what would appear - depending on the details provided in these reports - to be identical systems."

Jan 1, 1997

By P. Tapp, T. Evans, N. A. Molloy, J. Lucas

"Consideration of the protoype tuyere geometry for injection of inert gas through the bottom in a basic oxygen steel furnace and a requirement to specify an optimal flow for bottom wear and metal penetration led to experimental investigations[l,2] to apply the results of previous workers to this specific case, Flow velocity profile development within the tuyere was proposed as significant and the experimental scheme was designed to test this. It is proposed that the design criterion for the conditions of optimal flow of the prototype geometry be based on the non-dimensional mass velocity.INTRODUCTIONSharma[3] tested small diameter tuyeres in a laboratory hot model using molten iron to define a flow criterion for prevention of penetration of the bath liquid into the tuyere. Using argon, nitrogen and helium through a range of tuyeres (1 to 3 mm ill ) he proposed the jet Froude number C Fr' ) with the critical value being 2400 - 2500 or higher. Sonic or supersonic velocity was not a sufficient criterion. The tuyere design was a parallel tubular duct of moderate aspect ratio CAR) i.e. the ratio of length to diameter ranging from about 22 to 36 in the experimental furnace.Farmer et al[4] stated their their aim ""to develop a unifying explanation and procedure for the proper design of tuyeres"" but disagreed with Sharma's jet Froude number criterion. Recalculating Sharma's data they proposed instead a fully expanded Mach number of 1.75 with an initial expansion angle of ten degrees as the lower bounds of flow to meet the design requirement. They experimented with tuyeres in a water model using tubular, annular and convergent-divergent nozzles. The aspect ratio of the parallel duct tuyeres was from 533 to 762 using diameters of 1.4, 1.7 and 2.0 mm C the diameters being of tubes to be used full scale). Subsequently these results were applied to a prototype tuyere using a diameter of 1.7 mm with beneficial results in practice. This tuyere had an aspect ratio of 1067."

Jan 1, 1996