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By J. S. Kirkaldy

A theoretical procedure is demonstrated for calculating two-dimensional binary cellular single-valued interfaces and extended to triple-valued (remelt) shapes. The numerical calculations for the single-valued local equilibrium problem which yield unique shapes as functions of the supersaturation parameter a and the partition coefficient k are reviewed. The cell amplitude L and wavelength A scale identically as the inverse velocity to the 112 power and the aspect ratio r is a constant equal to 312, independently of a and k for a < 0.5.. For 0.5 < a < m, L, A and r decrease asymptotically to zero indicating the finite amplitude nature of the instability at a = 1 and the existence of sub-marginal states which converge to a flat interface at a- m (Glv- m). Scaling comparisons between equilibrium single-valued and triple-valued and deep-rooted non- equilibrium cells are made.

Jan 1, 1992

By D. I. Davidov, D. A. Shishkin, M. B. Rigmant, E. P. Romanov, N. N. Stepanova, N. V. Kazantseva

The Co-19 at.%Al-6 at.%W alloy was prepared by two methods of casting. We used arc melting under an argon atmosphere with casting into a copper water-cooled casting mold and induction melting furnace with casting into a ceramic Al2O3 mold. According to the X-ray and SEM analyses, phase compositions depend on the cooling rate of the ingot after melting. After arc melting, the cast alloy has a three-phase structure, consisting of  cobalt (FCC), intermetallic phases CoAl (B2) type, and Co3W (DO19) type. After the induction melting, the alloy has a three-phase structure, consisting of  cobalt (FCC), intermetallic phases CoAl (B2) type, and Co7W6 () type. All phases in the investigated ternary alloy at the room temperature are ferromagnetic. Curie temperatures of all obtained phases were defined. It is shown that the magnetic properties of the studied alloy are typical for soft magnetic materials.

Jan 1, 2015

By Oscar Perales Perez, Atsuo Kasuya, Kazuyuki Tohji, Yoshiaki Umetsu

"The removal of iron and various heavy-metal ions by their incorporation into stable ferrite-type precipitates at 25°C is a promising alternative to clean up large volumes of polluted aqueous effluents. Our research work investigated the conditions to produce magnetite and various M-bearing ferrites (where M: Zn, Cu, Co, Ni, Cd, etc.) directly from aqueous solutions at 25°C by simultaneous control of the oxidizing conditions and pH. The formation of the solids was followed by monit9ring the oxidation-reduction potential (ORP) and rate of proton release during the aerial oxidation of the suspensions at constant pH (contact stage). Only mildly oxidizing conditions, represented by ORP values between -110 mV and -150 mV and a moderate oxidation rate of Fe(II) species were conducive to well-crystallized ferrites at ambient temperature.' It was also found that increasing the Fe/M mole ratio in starting· solutions enhanced the stability ·of the M-bearing ferrites at ambient temperature. When the formation of the ferrite was incomplete, aging of the sludges in their mother liquors at 25°C promoted the crystallinity of the precipitates. The mentioned conditions ·favored the suitable progress of the ferrite-forming reaction involving the oxidation of Fe(II) entities, subsequent hydrolysis of produced Fe(III) species and dehydration of the intermediate:· Furthermore,· the ferrite formation at· low temperature permits the elimination of iron and co-existing heavy metal ions to sufficiently low concentration.In tum, the characterization of the precipitates evidenced their magnetic nature (room-temperature saturation magnetization above 60 emu/g) as well as the effective incorporation of target metal ions into the ferrite structure."

Jan 1, 2000

By Katsunori Yamaguchi

Secondary materials, that contain relatively high concentrations of platinum group metals, (PGMs) are treated in copper smelting process. The PGMs lost in the slag is increasing with increasing quantities of scrap treated amount. To determine the portion of the PGMs chemically dissolved and that associated with the mechanically trapped matte in the slag will be a key factor to improve the recovery of those metals. An experimental study was carried out to determine the distribution of palladium between the FeOx–SiO2 slag and the liquid Cu2S–FeS matte at 1573 K and a fixed partial pressure of SO2 of 0.1 atm. It was found that the distribution ratios are around 10−3 for platinum and palladium. The distribution ratios show a tendency to increase when the grade of matte is increased above 60 mass% Cu. In addition, the solubility of platinum in FeOx–SiO2 slag equilibrated with a pure palladium and the Pd-Cu alloy was determined at 1573 K and the range of oxygen partial pressure from 10−9 to 10−7 atm. The solubility of palladium in the slag tends to increase with increasing oxygen partial pressure and activity of CuO0.5 in the slag.

By Jesse White, Tyler Salisbury

Research projects contain many stages of development from the conception of an idea to a fullscale commercial operation. The transition from laboratory-scale research to bench-scale roasting can represent a significant increase in complexity and cost, depending on how many variables are being evaluated. Thermogravimetric analysis (TGA) can simulate roasting conditions and produce a small sample for chemical analysis or materials characterization. A simultaneous thermogravimetric and differential scanning calorimetry (TG–DSC) can identify endothermic and exothermic reaction temperatures. Using thermal analysis, some of the process variables can be tested and eliminated such as ore and reagent blends, retention times, operating temperatures, and some atmospheres.

Jan 1, 2015

By Guo Xueyi

The environmental impact assessment of the Imperial Smelting Process for metallic zinc and lead production in Shaoguan Smelter, China, was carried out by the life cycle assessment method. The detailed inventory analysis of the Input/Output in the process during 1998-2000 was conducted and the allocation was done among the main products of zinc, lead and sulfuric acid, according to the system expansion and substitution principle, The environmental impacts were assessed by using the following five Eco-indicators: Gross Energy Requirement (GER), Global Warming Potential (GWP), Acidification Potential (AP), Heavy Metal Toxicity (HMT) and Solid Waste Burden (SWB). The results from this study are useful to address the environmental situation of the technology practice in this smelter, and provide a scientific basis for the further improvement.

Jan 1, 2003

By C. Acuna

The standard procedure of fire refining consists of sulphur removal via air injected through tuyeres, arsenic slagging via soda-lime flux and oxygen reduction by air or oxygen deficient air or a steam fuel mixtures. The use of porous plugs to stir with an inert gas has been mainly considered as a surface renewing agent that increases the product quality and shorten the refining cycle. In the present study the effect of the bottom stirring by nitrogen gas injection through porous plugs for the treatment of the crude copper in the range of 400-150 ppm sulphur, 3,000?2,000 ppm arsenic and 14,000-7,000 ppm oxygen content was investigated. The combined effect stirring-reducing, by the use of air or a steam fuel mixtures through tuyeres for oxygen removal, follows a kinetics of first order where the constant, K, can be represented by the following polynomial expression: K = A .* R2 + B * R + C Where A, Band C are constants that depend on the nitrogen flow rate and R is the air-fuel ratio or the steam-fuel used in the reducing step. Depending on the optimization of the flow of nitrogen and the air-fuel or steam-fuel mixture and only if just the oxidation, complexing and reducing steps are considered, the process cycle might be shortened by 45%.

Jan 1, 2003

By Samantha Moodley, Rauf Hurman Eric, Cevat Kucukkaragoz, Aditya Kale

"Two titania slags, rutile and synthetic rutile were chlorinated with petroleum coke and CO in a small bubbling fluidized bed reactor. The study aims to identify differences in chlorination mechanism, compare conversion rates, blowover and the chlorination of impurities for the various titania feedstocks at different temperatures.Chlorination rates were highest at 1000ºC; rutile chlorination significantly increases as temperature increases from 800ºC to 1000ºC. At 1000ºC, synthetic rutile had the highest chlorination conversion rate; this was followed by Slag B which in turn was more reactive than Slag A and rutile. The mechanism for slag, synthetic rutile (SR) and rutile chlorination differs. Synthetic rutile feed is porous, providing a larger surface area for the chlorination reaction, hence the highest conversion rates was attained. Titania slag becomes porous with the initial chlorination of FeO and MnO whilst rutile remains solid. As the porosity of slag particles increases so does its tendency to be elutriated. Ti2O3 is oxidized within the early stages of chlorination during the chlorination of FeO and MnO. Ti2O3 not oxidized is then rapidly chlorinated.IntroductionTitanium dioxide (TiO2) is the most common compound of titanium, about 95 - 98% of extracted titanium minerals is processed into TiO2 white pigment [1]. Two processing routes exist for the production of TiO2 pigments, i.e., sulphate and chloride based processes. In the chloride process, titania feedstock is fed to a fluidized bed reactor together with reductant and chlorine gas. A temperature of 1000 - 1300ºC is maintained in the reaction zone and apart from silica, zirconia, uranium and thorium, virtually all the metal oxides in the feed are converted to their respective chlorides [2]. Chlorine is recovered and recycled back to the reactor."

Jan 1, 2012

The standard procedure of fire refining consists of sulphur removal via air injected through tuyeres, arsenic slagging via soda-lime flux and oxygen reduction by air or oxygen deficient air or a steam fuel mixtures. The use of porous plugs to stir with an inert gas has been mainly considered as a surface renewing agent that increases the product quality and shorten the refining cycle. In the present study the effect of the bottom stirring by nitrogen gas injection through porous plugs for the treatment of the crude copper in the range of 400-150 ppm sulphur, 3,000-2,000 ppm arsenic and 14,000-7,000 ppm oxygen content was investigated. The combined effect stirring-reducing, by the use of air or a steam fuel mixtures through tuyeres for oxygen removal, follows a kinetics of first order where the constant, K, can be represented by the following polynomial expression: K = A * R2 + B * R + C Where A, Band C are constants that depend on the nitrogen flow rate and R is the air-fuel ratio or the steam-fuel used in the reducing step. Depending on the optimization of the flow of nitrogen and the air-fuel or steam-fuel mixture and only if just the oxidation, complexing and reducing steps are considered, the process cycle might be shortened by 45%.

Jan 1, 2003

By Shaohua Ju, Feng Jiang, Chuanhua Li, Jinhui Peng, Libo Zhang

A T-junction microchannel is proposed to overcome the existing problems in conventional solvent extraction of indium from zinc hydrometallurgical process. Experiments were performed to separate In3+, Fe3+ and Zn2+ from sulfate solutions using Di-(2-ethylhexyl)phosphoric acid (D2EHPA) as the extractant. The effect of parameters such as pH, microchannel size and contact time on the extraction behavior of In3+, Fe3+ and Zn2+ was investigated. At contact time of 2.52 s and initial solution pH of 0.48, the extraction efficiency of In3+, Fe3+ and Zn2+ was 99.13%, 8.31% and 2.45%, respectively and separation factor of In3+/Fe3+ and In3+/Zn2+ were almost 1229.54 and 4864.98, respectively. Then, the loaded organic phase was stripped in T-junction microchannel. At contact time of 33.6 s, 99.64% of stripping efficiency of In3+ and stripping equilibrium were reached, while concentration of Fe3+ and Zn2+ was lower than 0.01 g/L with good separation of In3+ from Fe3+ and Zn2+.

Jan 1, 2016

By B. A. Paponetti

The following report discusses the bioleaching of chalcopyrite of italian origin catalyzed by Thiobacillus ferrooxidans. The developments vcr.ius time of the main .biochemical and chemical reactions involved in the production of soiuble and insoluble species were investigated focusing on the times at which they begin and bow long they last. The precipitates were characterized both in quantity and in quality relating the rate of the process to the precipitates fonnatiom. A material. balance has been made to verify the proposed mechanism.

Jan 1, 1991

By Guy Xueyi

The environmental impact assessment of the Imperial Smelting Process for metallic zinc and lead production in Shaoguan Smelter, China, was carried out by the life cycle assessment method. The detailed inventory analysis of the Input/Output in the process during 1998-2000 was conducted and the allocation was done among the main products of zinc, lead and sulfuric acid, according to the system expansion and substitution principle, The environmental impacts were assessed by using the following five Eco-indicators: Gross Energy Requirement (GER), Global Warming Potential (GWP), Acidification Potential (AP), Heavy Metal Toxicity&apos; (HMT) and Solid Waste Burden (SWB). The results from this study are useful to address the environmental situation of the technology practice in this smelter, and provide a scientific basis for the further improvement.

Jan 1, 2003

By Neale R. Neelameggham

"Ferrous and non-ferrous metal industries are used to handling several billion tons a year of ore bodies, fuel and fluxing agents by mineral processing techniques and varieties of extractive metallurgy ""Reduction"" processes. Metal industry know-how can be applied to meet the challenge of Reducing CO2 in the atmosphere. Processes for generating alloys of carbon and hydrogen by Reducing the CO2 and water mixture, [carbonated water or water vapor] called Soda, to easily stored fuels are normally endothermic. The processes are similar to generation of hydrogen alone from water which is also endothermic. But hydrogen is more difficult to store than compounds [or alloys] of carbon and hydrogen. This recycling of CO2 and water are possible by using other forms of energy by innovative carbon capture methods.Thermodynamic Diagrams developed for Soda [CO2 and H2O] - metal reactions provide hints for using low cost unused stored energy in un-recycled metallic waste for thermal conversion. Choices for conditions for the electrochemical approaches [using solar - wind - hydropower] are also discussed.INTRODUCTIONIn 2006, I was reading some of the arguments put forth by learned scientists on the benefits and lack of benefits of bio-fuels. I found that the arguments rose partly from the differing system boundaries that were chosen by one versus the other. Some part of the argument may have been based on political climate or atmosphere rather than the analytical science. This situation is seen when scientists discuss which came first - the chicken or the egg, the fuel or biological matter, the oxide or the element, and so on.Then I thought –[just like many of the learned persons participating in this symposium] that common fuels - regardless of them being simple hydrocarbons or oxygenated hydrocarbons or carbohydrates - can all be made from the respective oxides of carbon and hydrogen by simple chemical reductions efficiently carried out in an economical fashion. This is the systematic approach we take when designing a chemical or metallurgical process facility."

Jan 1, 2008

By Larry G. Twidwell

The removal of dissolved arsenic from mine waste waters utilizing a lime/phosphate precipitation technique has been studied on a laboratory scale at Montana Tech of The University of Montana and on a pilot scale at MSE Technology Applications as a wastewater treatment process potentially capable of removing dissolved arsenic to <50 µg/L. Arsenic bearing lime and lime/phosphate slurries were subjected to laboratory extended-time air-sparged aging for over four years. The lime slurries released their arsenic back into solution in a relatively short period of time, whereas the lime/phosphate slurries showed limited release of arsenic. The developed process has been pilot scale tested by MSE-TA for the EPA Mine Waste Technology Program on three waters, ASARCO smelter blowdown water, ASARCO thickener overflow water, and Mineral Hill Mine groundwater. The laboratory study results will be presented and discussed in this presentation. The pilot scale results will be presented and discussed in a companion presentation. Stability, Aging, Apatite, Johnbaumite

Jan 1, 2005

By Akira Kaneda, Nozomu Hasegawa

"In the Mitsubishi Continuous Copper Smelting and Converting Process, slag/matte mixture overflowed from the smelting furnace is separated continuously in an electric furnace (slag cleaning furnace, CL-furnace). In order to improve the separation efficiency of slag and matte and to minimize power consumption, the design and the operating conditions of the CL-fumace should be optimized. In the previous study, the authors developed a mathematical model for simulating phenomena in the CL-furnace. The model consisted of 3 modules, electric field analysis, heat and fluid flow analysis and the particle tracking method. In this study, the model was partially modified: k -E. model was adopted, and the effects of various conditions, such as furnace shape (including accretion) and scale, electrodes configuration, immersion depth of electrodes, and thickness of slag layer, were evaluated. And the optimum design and operating conditions were discussed.IntroductionUnder the recent environmental restriction, advantageous features of the Mitsubishi process have attracted much attention. The process uses 3 furnaces connected by launders. Mixture of matte and slag formed in a smelting furnace flows continuously to a slag cleaning furnace (CL-furnace), where the matte is separated from the slag. The matte is continuously siphoned out to a converting furnace and converted to blister copper. The slag overflowed from the CL-furnace is discarded. Because the slag contains about 0.6 % copper, improving slag/matte separation efficiency and decreasing copper loss make a great profit. Moreover the process requires a large amount of electric energy, so reduction of electric power consumption brings in enormous benefit.The objective of this study is to optimize the design and the operating conditions of the process, especially the CL-furnace. This will be achieved by developing the mathematical model and clarifying relations between the design or the operating conditions and various phenomena in the furnace. Fig. 1 shows an outline of the CL-furnace. The mixture entering through an inlet is separated to slag layer and matte layer . In order to maintain the temperature of the melt at a predetermined level, 6 electrodes are immersed into the lag and Joule's heat is generated by 3-phase alternating current flowing."

Jan 1, 2000

By L. Filip

The roast-leach-electrowinning (RLE) process for zinc was modified to treat two typical complex concentrates containing zinc, lead, copper, gold and silver. Laboratory testwork results indicated that the optimum roasting temperature ranged from 700 to 800°C, in order to produce acceptable residual sulfur levels. The calcined concentrate was subjected to a three-stage leach sequence. The resulting leach solution was purified by hematitic precipitation and directed to the recovery of copper and zinc by solvent extraction and electrolysis. Alkaline smelting and subsequent electrolytic purification recovered the lead and precious metals from the leach residue. A flowsheet was developed based on the laboratory testwork results, and demonstrated in a large-scale pilot plant. The recoveries produced during the pilot plant operation ranged from 90 to 92% for zinc and copper, 85% for lead and 90% for gold and silver, respectively.

Jan 1, 1999

By Jyri Talja, Shaolong Chen, Hannu Mansikkaviita

"Drying (water removal) prior to smelting is always economically feasible. Unnecessary heating of vapour can thus be eliminated resulting in savings of5-15 MUSD every year.Thermodynamically removal of one ton of water out of copper concentrate at 100 °C (with 10 % moisture) requires approximately 3150 MJ/tH2o, consisting of heating of the water (377 MJ), heating of the concentrate (509 MJ) and water evaporation (2260 MJ). This is quite independent of the selected drying technology. In reality some more heat is needed as higher temperature is practiced to enhance the drying performance and to reduce the equipment size.Major nominator in drying energy efficiency is amount of gases, which depends greatly on the drying technology. Dryers based on direct heating with fossil fuels have high gas flow rates, and thus they require additional energy of about 1400-1600 MJ/tH2o, compared to indirect modemsteam drying at 250-400 MJ/tH2o.Significant benefits in energy consumption (900-1300 MJ/tH2o) with additional potential for a bonus profit of 2-4 MUSD/y year, together with full elimination of some 40 000 tpy CO2 per mid-size dryer is available by selecting sustainable, energy efficient steam drying.IntroductionRemoval of water from the concentrate is very energy intensive thus having a significant environmental impact. However, drying prior to smelting is always economically feasible and very often viable also from the perspective of process operations. This environmental impact of drying can, however, be decreased or even fully eliminated with proper selection of the drying technology.Energy incorporated in drying consists always of a number of phases like liquid (water), solids (concentrate) and gases (water vapour, purging I dilution air, combustion gases). Each phase is heated to a specific temperature during the drying process.Heating of water, heating of the concentrate and water evaporation consumes more or less the same amount of energy despite of the drying technology (3150 MJ per ton of water). In conventional drying this amount of energy is achieved by combustion of fossil fuels wirg subsequent CO2 emission. Alternatively, chemical energy derived from sulphide smelting can be utilized in a form of steam thus generating zero emission ofCO2, in modem steam drying."

Jan 1, 2012

By John A. Mavrogenes

Reflected light microscopy and electron microprobe techniques were used to determine the mineralogy, phase percentages, grain sizes, and textures of Co-Ni-rich mattes. The mattes were produced by submerged bath smelting at the University of Missouri-Rolla Pyrometallurgical Center of a flotation concentrate with 4.S% Co and 5.1% Ni that was prepared at the United States Bureau of Mines Rolla Research Center by flotation up-grading of the cobalt and nickel content of a copper concentrate from the Magmont mine, Viburnum Trend, Southeast Missouri. Nine distinct phases were distinguished in the matte samples, and three of these contain cobalt and nickel. The phases that were free from cobalt and nickel are bornite, chalcocite, pyrrhotite, magnetite, metallic copper, and galena. Submerged bath smelting serves to segregate the cobalt and nickel into phases that can subsequently be recovered by flotation. These phases are: shandite (Ni3PbZSZ)&apos; cobaltpentlandite ((Co,Ni,Fe)9SS)&apos; and Co-bearing Fe-rich sphalerite ((Zn,Fe,Co)S). Most of the cobalt occurs in cobaltpentlandite, but some is present in sphalerite. High total air conditions during smelting favor the development and segregation of cobalt into cobaltpentlandite. Nickel occurs in cobaltpentlandite and shandite. Shandite contains lead, a deleterious constituent in the smelting of cobalt and nickel.

Jan 1, 1989

By John E. Litz

The Denver Process is a chemical/metallurgical process for treating radioactive or mixed wastes by extraction and concentration of the radioactive and/or hazardous component(s). The process was developed at bench scale, evaluated at pilot scale, and will be implemented at full scale to remediate a low-level radioactive sludge. Six unit operations comprise the process: feed handling, leaching, solvent extraction, electrodeposition, precipitation, and tailing preparation. Unit operation design may be modified to tailor the process for varying feed stock composition. Radioactive or mixed waste is reacted with aggressive reagents in an aqueous phase, solubilizing targeted components. These components are then selectively extracted and concentrated in subsequent steps. Waste solids and solution exit the process as non-hazardous non¬radioactive waste. Dehydration of aqueous waste by submerged combustion eliminates aqueous discharge.

Jan 1, 1994

By D. Mukerjee, Ramen Datta, Sanak Mishra, R. Veeraraghavan, K. L. Rohira

"Recent efforts at Steel Authority of India Limited (SAIL) has led to the successful development of atmospheric and marine corrosion resistant high tensile Thermo Mechanically Treated (TMT) bars with minimum specified yield strength of 50 kg.mm-2. These rebars are increasingly being used for a wide range of end-applications, namely, concrete reinforcement structures, bridges, flyovers, dams etc. Welding is an important processing tool for each of the above applications. In view of the importance of welding, a comprehensive evaluation of the weldability properties has been carried for the two grades of steels using Submerged Metal Arc Welding (SMAW) process; the most popularly used technique of welding of reinforcement bars (re bars).Implant tests were conducted to assess the cold cracking susceptibility of the steels. The static fatigue limit (SFL) value, determined for the atmospheric corrosion resistant (Cu-TMT) rebars under no preheat and no rebalcing conditions was found to be 63.8 kg mm-2, which was significantly higher than the Minimum Specified Yield Strength (MSYS) (50 kg.mm-2). This indicates adequate resistance to hydrogen induced cracking (HIC). On the other hand, the SFL value obtained for the marine corrosion resistant rebars (Cu-Cr TMT) under no preheat, no rebaking conditions was found to be inconsistent. Repeat of the test with fully rebaked electrodes (350°C-2h) resulted in a high SFL value (60.3 kg mm-2)_The rigidity of the structure or restraint influences the susceptibility of the weld joint to cracking. The cracking tendency increases with restraint intensity (K) of an assembly. The critical restraint intensities determined for the two steels were found to be· in excess of 1680 kg/mm.mm, indicating good welding behaviour with the following welding conditions : for Cu-TMT rebars with no preheat and no rebaking and for Cu-Cr TMT rebars with no preheat and fully baked electrodes; that is under low hydrogen levels."

Jan 1, 1998