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By Thais Cristina da Costa Caldas, Alline Sardinha Cordeiro Morais, Carlos Maurício Fontes Vieira, Sergio Neves Monteiro

"This work has as its objective to evaluate the firing behavior of a kaolinitic clayey body from Campos dos Goytacazes-RJ incorporated with flat glass waste (FGW) from civil construction. Incorporations of the waste, with a particle size less than 74 µm (200 mesh), were performed in the red ceramic in the following amounts: 0, 2.5, 5 and 10 wt%. Specimens were prepared by uniaxial press-molding and then fired at 850 and 1050°C. The characterization of FGW was done by X-ray Fluorescence. The physical and mechanical properties evaluated were: linear shrinkage, water absorption and flexural rupture strength. The microstructure of the fired ceramics was evaluated by optical microscopy (OM). The obtained results showed that the flat glass waste can be used as a component of ceramic bodies once it was noticed tolerable modifications of technological behavior.IntroductionBrazil is one of the world’s largest producers and consumers of clayey ceramic. Campos dos Goytacazes is located in the north of the State of Rio de Janeiro, southeast of Brazil, it’s known as a large producer of red ceramics. It is estimated that the production of bricks can reach 1 billion pieces per year [1].Nowadays, recycling processes became more and more important, due the generation of wastes in large scale and the preoccupation with environmental. The amount of glass waste has been exponentially growing with the growth of the population. It is estimated that the amount of discarded glass as bottles, construction windows, packing and other glass waste represented in 2006 an amount of 7.5% of the total weight of the world´s domestic garbage [2]."

Jan 1, 2012

By Vinod K. Sikka, René Cooper

"Cohoes, New York 12047 Intermetallics are an attractive class of advanced materials. The aluminide intermetallics offer advantages including: (1) lower density, (2) oxidation resistance, (3) carburization resistance, and (4) interesting mechanical properties because of their ordered crystal structure. Even though the attractive properties of the aluminides and other intermetallics have been known for nearly four decades, their practical applications have not been developed for two reasons: (1) the poor ductility (in some cases, both ambient and high temperatures) and (2) the lack of processability into meaningful components. Recent advances such as ductilization of Ni3Al by small additions of boron and the knowledge that environmental effects are the major cause of poor ductility in Fe3Al and FeAl systems have brought the intelmetallics into the forefront of research and their commercial applications. This paper has described a method for melting Ni3AI-based alloys that successfully utilize the exotherrn for the formation of NiAl from the elemental materials. The reaction-synthesis method has also been utilized for the production of NiAI and NiAI-based alloy powders from the elemental powders. The reaction-synthesized powders of NiAI and NiAI-based alloys were consolidated by hot extrusion and evaluated for tensile properties over a temperature range from room temperature to 1050ºC. The powder-processing conditions have been found to have more influence on the ductile-to-brittle transition temperature of NiAI than the powder-production method.IntroductionIntermetallics are an attractive class of advanced materials [1-11]. The alum in ide interrnetallics offer advantages including: (1) lower density, (2) oxidation resistance, (3) carburization resistance, and (4) interesting mechanical properties because of their ordered crystal structure. Even though the attractive properties of the aluminides and other interrnetallics have been known for nearly four decades, their practical applications have not been developed for two reasons: (I) the poor ductility (in some cases, both ambient and high temperatures) and (2) the lack of processability into meaningful components. Recent advances such as ductilization of Ni3Al by small additions of boron and the knowledge that environmental effects are the major cause of poor ductility in Fe3Al and FeAl systems have brought the intermetallics into the forefront of research and their commercial applications. The paper will briefly review the processing techniques being pursued for the commercial applications of Ni3Al-based intermetallics. The major emphasis of the paper will deal with synthesis of Ni3Al and NiAI intelmetallics."

Jan 1, 1994

By Pengfu Tan

NiModel, a thermodynamic model, database and computer program, has been developed to predict the distribution behavior of Ni, Cu, Co, Fe, S, O, As, Sb and Bi, and heat balance in the nickel pyrometallurgical processes such as Outokumpu flash smelting, Outokumpu direct high-grade matte smelting, INCO flash smelting, and Peirce-Smith converting processes. In this model, as much as 16 elements (Ni, Cu, Co, Fe, As, Sb, Bi, S, O, Al, Ca, Mg, Si, N, C and H) are considered. The compositions of matte, slag and gaseous phases, and heat balance are calculated using the thermodynamic data and the activity coefficients of the components derived from the experimental data. The model predictions were compared with the known industrial data from Kalgoorlie Nickel Smelter in Australia, Outokumpu Harjavalta Nickel Smelter in Finland and INCO Metals Company in Canada, and an excellent agreement was obtained. In this paper, the applications of NiModel in the nickel pyrometallurgical industries have been presented. NiModel has been used by Jinchuan Group Limited in China.

Jan 1, 2004

By Thomas E. P. Wechsler

The limiting factor for most pyro-metallurgical processes in secondary cop- per melting is the time required to heat and melt the product. American Combustion's proprietary PYRETRON variable £uel/air/oxygen combustion system improves the throughput of existing scrap melting and heating furnaces for copper and copper alloy production by increasing the rate of heat transfer from the flame to the product. The increased productivity and energy savings obtained from this technology can result in sizable reductions in operating costs for smelting operations.

Jan 1, 1991

By Jing-she Li, Hai-yan Tang, Cheng-song Liu, Wei Liu

"In order to effectively utilize cheap and low quality iron ores, a hematite ore in a certain steel plant in Xinjiang was researched on to obtain ""iron increase and silicon reduction"" by ore dressing operation experiment and the performance indexes of the hematite ore were optimized. Based on the fundamental characteristics and high-temperature properties of the concentrate after ore dressing and other five kinds of iron ores which were co=only used in this steel plant, ore matching principles were proposed and a sintering ore blending optimization model was established. Finally, sinter pot test was carried out to verify the validity and practicability of the sintering ore blending optimization model which was aimed at giving consideration to the sintering indexes and the cost.IntroductionIn recent years, the price of imported iron ore with high quality is always at a high level, while iron ore self-sufficient rate in China is less than 50%. Enormous market demand and high dependence of domestic enterprises on imported iron ore makes the price of it hardly return to rational. In order to get rid of the situation of long-term meager profit and even deficit, more and more iron and steel enterprises in China transit their focus of reducing production cost to the utilization and development of relatively cheap but low-grade iron ore resources at home[l-4l_ However, besides the disadvantages of low iron grade, high content of impurities and complex embedded properties, the high-temperature properties of iron ore often go beyond the suitable ranges for producing sinter with high quality. Thus directly utilization of this kind of iron ore without ore dressing process would probably affect the metallurgical performance and indexes of sinter ore.Previous research and production practice have shown that traditional iron ore matching in sintering mainly focus on the reasonable collocation of properties of iron ores with low quality and high quality, but pay less attention to ore dressing process of low quality iron ores and matching them with high quality iron ores. Actually, compare with directly utilization, iron ores with low quality after ore dressing have higher suitability for matching with high quality ones which is beneficial to reduce the consumption of iron ores with high quality and control the production cost of sintering [5-s1."

Jan 1, 2014

By Xie Zhang, Chongyang Zhao, Qingyun Huang, Bing Xie, Xiaopeng Zhen

"Extracting vanadium from vanadium containing hot metal into vanadium slag by BOF is the main vanadium production process in China. In this paper, the influence of Si content in hot metal on the quality of vanadium slag is analyzed. Synthetic vanadium slag with different SiO2 content were melted at 1673 K and then cooled to 303K at the cooling rate of 3?/min. Optical microscopy, SEM, EDS and XRD were used to analyze the mineralogical phases and crystallization behavior of vanadium slag. The results show that vanadium slag mainly contains spinel phase and silicate phase; V is enriched in the spinel phases while Si is concentrated in Fe2SiO4 CaFeSi2O6 and (Fe,Mn)2SiO4 as silicate phase. The melting point of slag increases gradually with the addition of SiO2; whereas viscosity decreases with an addition of 15~19% SiO2 and increases with an addition of 19~27% SiO2.IntroductionVanadium is an important element which is used almost exclusively in ferrous and non-ferrous alloys. The major vanadium products include FeV, V2O5, V2O3, VN and Al-V-Ti alloy. Furthermore, vanadium slags are mostly produced by oxidizing the elements in V-containing hot metal during a duplex refining process. Therefore, the process of removing vanadium from hot metal has its significance on the subsequent process[1].The extraction of vanadium is greatly affected by the mineralogical composition of vanadium slag[2], the distribution of the elements between the spinel and silicate phases and its physic-chemical properties. These characteristics of vanadium slag have been studied in some details. It has been reported that Si mainly exists mainly in the form of silicate which wraps the spinel crystals while small amount of Si stands as phosphorus quartz or diopside[2]. Chen et al.[3, 4] points out, when SiO2 content in vanadium slag increased every 1%, V2O5 decreased 1.48%. Moreover, silicate phases would embarrass the oxidation of V-containing spinels through decreasing the exposing probability[5]. Meanwhile, melting point and viscosity of vanadium slag has been greatly influenced by the SiO2 content. Therefore, this work attempts to analyze the above-mentioned questions systematically."

Jan 1, 2012

By Shengqin Zhang, Jagannath Pal, Yousef Mohassab, Hong Yong Sohn, Mohamed Elzohiery

The kinetics of magnetite reduction with mixtures of hydrogen and CO of various compositions has been investigated as part of the development of a flash ironmaking process at the University of Utah. This new process bypasses the cokemaking and pelletization or sintering steps required for the blast furnace. The particle kinetics were studied using magnetite concentrate particles of different sizes. Reduction degree of 60% was achieved in a few seconds in at 1350 oC using CO reductant alone and over 90% when H2 + CO gas mixture was used. The effects of reductant partial pressures, temperature, and particle size on the reduction kinetics were studied.

Jan 1, 2016

By Andrea Bernardes

Printed circuit boards (PCBs) of varying compositions have been converted by incineration and following melting into an environmental agreeable slag and a copper-nickel-tin alloy, containing the precious metals. The environmental compatibility of the slag was determined according to the German standard DIN 38414 - Part 4; pollutants' concentration in the lixiviates is smaller than the thresholds of drinking water (CE-Standards). Each experiment the charge were 500g scrap from PCBs and ca. 100g slag forming material. The products were a kind of mullite slag, poor on iron, which was recirculated, and an alloy containing up to 0.3% Gold. With a burner to the retort coal gas, the waste gas was burned without soot, and the produced mixed zinc-lead oxide containing silver was collected in the flue dust.

Jan 1, 1997

By Shengqin Zhang, Yousef Mohassab, Feng Chen, Hong Yong Sohn, Mohamed Elzohiery, Amr Abdelghany

A novel ironmaking process is under development at the University of Utah aimed at producing iron directly from iron oxide concentrate in a flash reactor. This process will reduce hazardous emissions and save energy. The kinetics of magnetite reduction with hydrogen was previously investigated in our laboratory in the temperature range 1150 to 1400 oC at large temperature increments (~100 oC increments). Due to the significant melting that occurs above 1350 oC, the reduction kinetics was measured and analyzed in two distinct temperature ranges of 1150 to 1350 oC and 1350 to 1600 oC (~50 oC increments). Experiments were performed using magnetite concentrate particles of different sizes under various hydrogen partial pressures and residence times. Reduction degrees of more than 90 % were achieved in a few seconds at temperatures as low as 1250 ºC. Different rate expressions were needed to obtain reliable agreement with experimental data.

Jan 1, 2016

By B. R. Davis, Neale R. Neelameggham, R. E. Brown

The element Calcium element has a unique place in the production of etals, intermetallics and other compounds. The unusualness arises from the fact that we have several possible reductants – metallic calcium, calcium carbide, calcium cyanamide and calcium hydride. A review of how metallic calcium is manufactured and utilized is presented. The difficulties involved in producing the metal in large quantities and price implications are noted. . Fundamental thermodynamics of how these act as reductants are shown, along with the historic application of these in metal production during the past century and a half. Alternate applications as to how to control the cost of the reductant is indicated, such as the numerous attempts in making low cost titanium utilizing direct or indirect calcium reductant.

Jan 1, 2014

By Renato G. Bautista

The solvent extraction separation of nickel, cobalt and their associated metals have been considered for industrial application since the early 1960's. This review of the solvent extraction processes is limited to the industrial applications, pilot plant and the more extensive bench scale studies reported in the literature. The processes with their significant chemical and technological contributions are discussed in detail whenever the information are available. The application of solvent extraction to the nickel-cobalt processing has so far been limited to the secondary separation of nickel-cobalt containing feedstocks derived from other primary nickel-cobalt separation methods.

Jan 1, 1993

By Yousef Mohassab, Hong Yong Sohn, Mohamed Elzohiery

As part of the development of a novel flash ironmaking process at the University of Utah, a labscale flash reactor was used to produce iron directly from iron oxide concentrate. This work tested the feasibility of the novel flash ironmaking process using the partial combustion of hydrogen as fuel and reductant. In this flash reactor, the energy required to reduce concentrate particles was obtained from the internal combustion of hydrogen and oxygen with complementary energy from electrical resistance heating to compensate for the heat loss. After the reaction shaft was electrically pre-heated, hydrogen and oxygen streams produced a non-premixed flame inside the reaction shaft. Various conditions such as flame configuration, flame power, positions of concentrate feeding ports, excess hydrogen amount and residence time were tested. More than 90% reduction of magnetite or hematite was achieved at temperatures as low as 1175 oC with < 100% excess hydrogen in <10 s of residence time.

Jan 1, 2016

By T. K. Bundtzen

Placer gold in the Iditarod and Innoko mining camps of western Alaska is derived from a suite of comagmatic, Late Cretaceous to Early Tertiary, alkali-calcic, meta-aluminous. volcanic-plutonic complexes and peralumi-nous rhyolite sills that intrude Mesozoic flysch. Heavy-mineral concentrates from 42 mining operations and streams draining known mineralized areas in the igneous complexes contain placer gold and a variety of ore minerals derived from epithermal to hypothermal conditions of formation. The minerals include cassiterite, ilmenorutile, samarskite, cinnabar, scheelite, chromite, stibnite, silver sulfosalts, monazite, and zircon. Results of the study show that 1) cinnabar. stibnite, and quartz formed with the bulk of the placer gold in an epithermal lode environment, 2) chromite appears to have originated in mafic phases of monzonite plutons and alkalic basalts, and 3) niobium-tin-tungsten-uranium-silver values may have been derived from stockwork accumulations in cupolas of monzonite plutons.

Jan 1, 1987

By I. M. Ritchie

Cyanide owes its great success as a lixivant for gold to the great strength of the Au-CN bond. A replacement for cyanide must similarly be a strong complexant for gold (I) or gold (III). The various alternatives are briefly considered and it is concluded that only thiosulfate has a reasonable chance of replacing cyanide as a relatively non-toxic lixivant at the present time. However, there are considerable technical problems to be overcome before thiosulfate can be considered to be a realistic alternative to cyanide. Firstly, the leaching of gold using aerated ammoniacal thiosulfate with copper as a catalyst is a complex process which needs to be understood and controlled carefully in order to achieve maximum recoveries with minimum reagent losses. Secondly, there needs to be an option similar to the CIP process for recovering and concentrating the dissolved gold thiosulfate complex from pulps produced in the processing of low grade gold ores. The prospects for overcoming these technical&apos; challenges are evaluated and discussed.

Jan 1, 1998

By C. Coetzee

Additives are commonly used in copper electrowinning to improve cathode morphology. Polysaccharides such as guar are generally favoured as additives due to their compatibility with solvent extraction. Polyacrylamides are, however, being considered as possible alternatives. Understanding the influence of the structural chemistry of additives on electrowinning performance is critical to utilise them efficiently. This paper investigated polyacrylamide additives which are structurally different; their effects on copper electrodeposition were characterized and compared to that of guar. Electrochemical impedance spectroscopy (EIS) were used to characterize the effects of molecular weight and ionic charge of the polyacrylamides on electrodeposition. The findings were compared against results obtained with an industrially used guar product. Equivalent circuit modelling of EIS data indicated that an increase in polyacrylamide concentration and a decrease in additive molecular weight increased the overall system resistance.

By Wilhelm Brandstätter, Johannes Steiner, Alois Triessnig, Christian Redl

"The results of numerical simulations of bubble detachment from an orifice in a horizontal plate submerged in liquid are presented. The bubbles are created by forcing gas through this orifice into stagnant liquid. The simulations are performed with a two-dimensional incompressible Lattice Boltzmann (LB) scheme. In previous works the same problem was investigated by two-phase simulations in which surface tension effects were considered by an interaction potential formulation between the phases. In contrast, in the present work a volume of fluid (VOF) model consisting of a carrier fluid and a passively advected scalar function for the calculation of gravitational and surface tension forces, respectively, is used. The aims of this study are to examine the applicability of the one-phase LB method to the numerical analysis of bubble formation and to verify the theoretical and experimental predictions of the dependencies of the departure diameter on gravitational forces, surface forces and wettability effects. To this purpose the simulations were performed at different values of gravitational acceleration g, surface tension coefficient s and contact angle ß. Nonlinear fits to the data yield functional dependencies which are in good agreement with the predictions. IntroductionBubble formation behavior is an extensively studied subject, especially in chemical engineering, power industries and metallurgical processing. Knowledge of the underlying physics of bubble motion is, for example, required for the design of chemical reaction towers and agitation tanks. Another important application is the argon gas injection through the wall of the tundish nozzle into liquid steel stream to deter clogging with solid inclusions. Argon bubble motion and its effect on flow depends greatly on different parameters, e.g. gas flow rate and size of the bubbles. Thus, if these bubbles are not managed properly, they can become encapsulated upon solidification and result in undesirable impurities in the material [1, 2]."

Jan 1, 2004

By Vladimiros G. Papangelakis

During the past five years, chemical modelling work at the University of Toronto has elucidated the role of soluble magnesium on the autoclave acidity and has demonstrated why feeds rich in magnesium, and other divalent metals, require more than the stoichiometric requirements in acid to produce a leaching performance comparable to that of low magnesium feeds. This understanding has allowed the calculation of acid additions to the pressure acid leach (PAL) on a less empirical basis. Optimizing acid additions to the PAL confers savings in neutralization costs, ensures high productivity and minimises corrosion problems. Hence, our picture of the solution chemistry inside the autoclave during the PAL process has been substantially improved and is reviewed here. Experimental techniques based on solubility and direct acidity measurements that support the theoretical predictions are presented. Concepts of chemical modelling of electrolyte systems at high temperature and software issues are also discussed. Finally, a better understanding of the solution chemistry at temperature has led to better kinetics models because all metal dissolution and precipitation reactions are acid driven and controlled. . Therefore, reactor modelling efforts by our group are also presented and a reactor model with very good performance, as compared to pilot-plant data, is also made here. Finally, in spite of the above success in PAL solution chemistry and reactor modelling, significant challenges lie ahead in theoretical data gaps and instrumentation; these are also discussed in this paper. Keywords: Laterites, process modelling, pressure acid leach, solution chemistry, chemical modelling, reactor simulation

Jan 1, 2004

By Zemin Ma

A novel chromate [Cr(VI)] reducing bacterium was isolated from chromite ore processing residue disposal site of China and identified as a Leucobacter sp. by 16S rRNA gene sequence homology. The minimum inhibitory concentration of strain CRB1 was 820 mg l-1 of Cr(VI). The reduction of Cr(VI) occurred only under aerobic conditions. With an initial concentration of 2.5×108 cells ml-1, 1800 mg l-1 of Cr(VI) was reduced entirely within 38 h under the optimum conditions, at 30 °C and pH 9.0. Increasing Cr(VI) concentrations prolonged reduction process and higher cell densities meant quicker reduction. A blue precipitate was produced during chromate reduction of strain CRB1, which was binding to the surface of bacterial cells and determined as trivalent chromium with electron paramagnetic resonance (EPR) spectrometry. The conspicuous chromate reduction ability of Leucobacter sp. CRB1 suggested a potential for bioremediation of Cr(VI) containing wastes.

Jan 1, 2008

By Rina Kim

The addition of lead to a gold leaching reactor can effectively accelerate or retard the gold cyanidation reaction. This study explored the effect of lead on the gold dissolution kinetics using cyclic voltammetry (CV) experiments. It was illustrated that the gold leaching kinetics in the cyanide solution enhanced with the addition of lead salt in the low overpotential region (–0.35 V vs. Ag/AgCl). The similar behavior was observed in the presence of ore containing 0.25% galena. In contrast, the gold oxidation kinetics retarded at –0.35 V (vs. Ag/AgCl) in the presence of silicate and lead-bearing mineral under certain conditions. Likewise, the lead addition was not functional for the high sulfur ore. This was attributed to the oxidation of the sulfides to the elemental sulfur, which subsequently formed a passivating layer on the gold surface. The results were evidently affirmed by the electrochemical tests and X-ray photoelectron spectroscopy (XPS) analysis.

By Magnus Ek

After the installation of three new converters as part of the recent expansion of the Rönnskär smelter completed in 2000 work continues to further improve the converter operation. The converter upgrade led to an increase in blister copper taps from 150 tons per batch to more than 300 tons. The total cathode copper production increased from 130,000 tons in 1999 to 230,000 tons in 2001, the first year in full production. In recent years focus has been to improve operating practise, maximize the blowing time, extend the converter campaigns hence to reduce the specific brick consumption and improve the converter slag composition.

Jan 1, 2005