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By V. A. Bryukvin

It has been found that by superimposing symmetric alternating current over the process, the rate of nickel and cobalt leaching from metallized products with copper sulfate solutions increases by a factor of 1.5 to 2.0 and the apparent activation energy of the process investigated is reduced from 12 down to 6.6 kcal/mole. It appears especially attractive to use alternating current for anodic dissolution (oxidation) of metallic scrap of refractory metals and their alloys in ammonia electrolytes permits production of high-grade commercial products in the form of respective ammonium salts using a short and virtually reagent-free process flowsheet. Similar approaches can be applied also for electrochemical processing of nickel and copper scrap in sulfuric acid media with subsequent recovery of pure sulfate salts or electrolytic processing. Electrochemical technology for recycling of tungsten-cobalt (WC 15) and tungsten-rhenium (WR 20) alloys has been also investigated. In the former case, anodic oxidation of carbide alloy was carried out in nitric acid electrolyte with production of pure tungstic acid. The research conducted has indicated that the physicochemical effect of alternating current results in a lower activation energy of electrode reactions due to changes in the mechanisms of the electrode reactions themselves.

Jan 1, 2006

By A. Korbel

The progress in understanding the nature of strain localization in metallic materials and in particular the understanding of the role of external (deformation conditions) and internal (material substructure) factors in the development of the tendency toward concentration of plastic flow within transgranular shear bands was the background of the concept given in the title. Following this idea, the practical possibility of replacing the homogeneous in a micro scale mode of deformation by transgrasnular shear bands gives a chance to change the arrangement of the dislocation substructure in the material from that typical for homogeneous deformation into long wavelength (transgranular), pseudo-periodic dislocation walls. The presence or formation of such a substructure in a thermodynamically unstable matrix may result in the formation of the products of phase transformation along shear bands, giving rise to a composite-like structure. This work is aimed to provide a coherent justification to the concept of Natural-Metal-Matrix Composite and summarizes the results of experimental works in this area.

Jan 1, 1997

By John Gordon

Rare earth elements (REE) required in modern technological products are found in shale rocks above and below coal seams. Often during the process of mining coal, shale rock adjacent to the seam inadvertently is removed then diverted to landfill sites. Ecologically sound and potentially economic methods of extracting the REEs from these landfills are proposed. Methods include utilizing geomemembrane barrier beneath the landfill site, ion exchanging with moderate pH, slightly acidic, sodium chloride solutions. Sodium hydroxide is utilized to precipitate the REE-hydroxides subsequently converted to REE-chlorides with suitable amount of hydrochloric acid. All acid and base streams are co-produced with efficient membrane/electrolysis technology. Concentrated-REE chlorides are transported tocentralized solventextraction facilities for isolation and purification. Solvent extraction processes also employ the methodology of using co-produced acid/base streams. This paper details minimization of environmental impacts and maximizing economics to produce valuable REEs while increasing the economics of coal mining.

Mar 1, 2018

By F. A. Fasoyinu

The mechanical properties of yellow brass (C85800), high strength yellow brass (C86300), and high manganese brasses (C99700 and C99750) cast in permanent molds have been studied. The tensile properties as well as fracture and impact toughness of these alloys are strongly dependent on the chemical composition. Alloys and/or compositions exhibiting relatively high zinc equivalent often exhibited high ultimate tensile strength and yield strength with significant reduction in ductility (% elongation). In order to achieve optimum properties with a good balance between strength and ductility, a calculation of the zinc equivalent before alloy preparation can be useful.

Jan 1, 1999

By Kiyoshi Shibata

A new assessment model has been proposed for metal production and its recycling system. The model consists of three processes, smelting of ore, cascading and upgrading of metal scrap. The present approach is to assess the total energy consumption of the system, by introducing two equations for describing the relationships between critical impurity content and the mass of production or scrap recycling. The total energy consumption in the system can be described as a function of recycling rate and performance of the upgrading process. The present model suggests that the impurity removal efficiency and yield in the upgrading process are essential to reduce the energy consumption in the systems. Especially, such points should be explicitly controlled in recycling of aluminum. The potential capability of this model was also discussed by obtaining several quantitative information required for the process design and the operational control of beneficial recycling of metals.

Jan 1, 1998

By Sayan Sarkar

HAMR (Hydrogen Assisted Magnesiothermic Reduction) process is a promising alternative route of titanium production, which is convenient due to reduction at relatively lower temperatures below 750 °C and usage of cost-efficient TiO2 as the starting material. A crucial step involved in this process requires the Mg reduction of TiO2 subjected to H2 atmosphere which produces porous TiH2 along with residual magnesium impurities. Before the final heat treatment and deoxygenation steps for consolidation of the Ti powder, leaching plays a significant role in the removal of Mg impurities. In this report, we present a systematic study on the role of acid concentration (HCl), temperature and the kinetics of MgO dissolution. In addition, we also report the controlling mechanism during kinetics of MgO dissolution in acid. This parametric study will provide a platform to ensure very low Mg content that meets with ASTM standards during production of Ti in the HAMR process.

By Dirk Verhulst, V. I. Lakshmanan

Why Chloride Hydrometallurgy?The most available, cheapest and best known reagent for treating ores and other raw materials for the metallurgical industry is sulfuric acid. Hydrochloric acid is second in line. What often happens is that a process is developed on the basis of sulfuric acid, and that at some point the question arises: wouldn't hydrochloric acid do this better?Considering hydrochloric acid immediately opens a very interesting field of research. To summarize a few comments from another paper presented at this symposium [1]: chlorides are far more soluble than sulfates (with a few interesting exceptions); the hydrogen ion activity is greater in chloride than in comparable sulfate solutions; higher oxidative conditions are possible; regeneration is more straightforward; more diversity is possible and better conditions for the separation of species can be found for solvent extraction and ion exchange; sulfur in the ore can be separated as elemental S; higher metal concentrations in solution and more flexibility in the chosen oxidation state means significantly lower energy costs.Also, the volatility of many chlorides at higher temperature allows further separation without the need to go to a different system. Chlorides also form molten salts with a low melting point, providing another means of separation and purification in the same chloride medium.

Jan 1, 2011

By Ligang Zhang, Wen Chen, Xinghua Liu, Jialin Li, Xiaoyin Liu, Zhenhong Liao

A research-scale fluidization and magnetization roasting device was developed to evaluate a processing option that might offset the complexity and high cost of the conventional magnetization roasting process on siderite. In this study, the operating parameters of the fluidization and magnetization roasting device for siderite were evaluated through cold-flow tests and magnetization roasting tests. The reaction mechanism functions of the fluidized roasting process are revealed with kinetic studies.

Jan 1, 2015

By James R. Craig

Petroleum coke is becoming an increasingly important source of light hydrocarbon products as product crudes become heavier and of poorer quality. The use of petroleum coke to generate synthesis gas results in the formation of residual slags that are enriched in silica, alumina, sulfides, oxides, and free metals. The characterization of these slags and their con? stituent phases is an essential step in considering the ultimate use or disposal of such slags and in understanding how to alter the properties of the slags to optimize the efficiency of gasifiers. Depending upon temperatures and bulk compositions, quenched slags typically consist of silicate glasses, calcium silicates, iron-nickel oxide-sulfide masses, aluminate spinels and free metals. Whereas the glasses contain relatively uniformly dispersed metals and sulfur, the iron-nickel oxide-sulfide masses highly concentrate nickel and sulfur. The aluminate spinels very effectively concentrate vanadium and chromium, thus depleting glasses or other adjacent phases. The abundance as well as the make up of the slags strongly affects the physical behavior of the slags within the gasifiers

Jan 1, 1989

By Shanlu Yang

In this study, laser-GTAW hybrid welding was used to the lap joint of galvanized dual-phase (DP) 980 steel in a gap-free configuration. The effects of welding parameters such as the laser power, the distance between the laser beam and the electrode torch, the arc current on the quality of hybrid welds were fully studied. The reason for the formation of different weld defects arises from the development of the highly-pressurized zinc vapor at the interface of two metal sheets. Experimental results demonstrated that the elongated molten pool introduced by the GTAW can suppress the formation of spatters to some extent. However, the hybrid laser-arc welding process still suffers from a large amount of spatters that degrade the weld quality. Furthermore, it was found that the weld quality was enhanced with the increase in the laser beam-arc distance and welding current.

Jan 1, 2009

By Corale L. Brierley

Bioheap leaching, commercially applied for secondary copper ores and agglomerates, is rapidly gaining popularity. Bioleaching of chalcopyrite concentrates is imminent. Copper bioheap leaching encompasses the bioleaching of acidified and agglomerated coarse, secondary copper ore, stacked on permanent or on/off pads. The stacked ore is irrigated with raffinate containing bacteria. LME-grade cathode copper is produced by SX/EW. Low capital and operating costs, rapid start-up, environmental benefits, operational simplicity and a good performance record make bioheap leaching an attractive technology. This paper looks at the state-of-the-art of copper bioheap leaching and chalcopyrite concentrate leaching, the risks, the benefits, costs, bioheap performance and the future prospects of copper bioleaching.

Jan 1, 1999

By Atsuhiro Nabei, Ken-ichi Yamaguchi

"Wet chlorination process of de-copperized anode slime is followed by de-chlorination stage in which lead-sulfate and metallic silver form silver residue. The silver residue is subsequently reduced to Ag2Se matte and PbO-SiO2 slag to remove lead to the slag in a short rotary furnace. Although this smelting process is proven well in actual operations, few papers have investigated its metallurgical aspects. This paper will describe the effectiveness of controlling parameters adopted at the Naoshima Smelter & Refinery and discuss the decisive factors influencing silver loss to PbO-SiO2 slag.IntroductionThe precious metals plant at Naoshima smelter & refinery was established in 1989, and has produced electrolytic silver, refined gold and platinum-group metals (PGM) from de-copperized anode slime as by-products of electrolytic copper. The process for gold production has been innovated from conventional smelting process to hydrometallurgical process since 2004 [1], while the process for silver production has still remained the same.The process for silver production at the Naoshima smelter & refinery is illustrated schematically in Figure 1. De-copperized anode slime is, at first, concentrated in the froth flotation process, then leached in the wet-chlorination process, and converted to silver residue in the de-chlorination process. The silver residue, which is a mixture of lead-sulfate and metallic silver, is charged to a short rotary furnace for the oxidation roasting to volatilize selenium dioxide and subsequent reduction smelting. In the smelting stage, silver residue and reverts containing selenium are smelted with flux and carbonaceous materials to form PbO-SiO2 slag and Ag2Se matte. Furthermore, Ag2Se matte is transferred to a rotary cupell and oxidized by air with the addition of sodium carbonate and sodium nitrate to produce silver anodes while removing impurities into litharge. Silver anodes are electrolytically refined by the Moebius process. Electrolytic silver is washed, dried and, finally, cast into 30kg-bars."

Jan 1, 2011

By A. Schönecker, P. Y. Pichon, B. Kraaijveld, Y. Meteleva-Fischer

"Ribbon-growth-on-substrate is a casting method, which offers a possibility to control heat flow, nucleation and subsequent crystal growth at the liquid-substrate interface. This technology allows for low-cost and high throughput shaping of silicon sheets with controlled crystal grain size and orientation for use in solar cells. In this work, sheets of silicon- metal silicide composite materials were produced and their microstructure was studied. It was shown that depending on the relevant phase diagram and casting conditions, a micro/nano-sized eutectic structure of the casted sheet can be formed. Such composite materials possess properties promising for various applications in energy generation, storage and conservation. The advantages, potential and challenges of the ribbon-growth-on-substrate technique for production of composite sheet materials as well as novel areas of application for such materials are discussed.IntroductionThe Ribbon Growth on Substrates (RGS) process is well known in the solar industry as a process to produce multicrystalline silicon wafers. An industrial size pilot production line for continuous casting of silicon wafer was developed by RGS Development B.V. in the Netherlands (Figure 1). A comprehensive review of this technology and properties of the produced silicon wafers were reported by Schönecker et al [1]. The principle of the RGS process is explained in Figure 2. The relatively cold substrate extracts the crystallization heat from the liquid silicon in the casting frame. This results in the growth of a silicon ribbon (Vc) in contact with the substrate. When the substrate (Vp) is transported from the casting zone into the cooling section, the crystal growth stops, the wafer can be removed and the substrate can be re-used. Last few years large work was done on the industrialization and market development of RGS wafers for the solar industry. Part of this work was discussed by Schönecker et al [2]. Although there is still a good perspective on the middle and long term solar market for the RGS wafers, the current market situation was found to be unfavorable for new entrants."

Jan 1, 2014

By Linlin Wu, Marlen Bertram, Chris Bayliss, Bernard de Gelas, Samantha Jones, Kurt Buxmann

"Environmental management is one of the industry cornerstones of sustainable development. In order to understand fully the environmental aspects associated with the raw material acquisition, production, use, and end-of-life operations of aluminium products, the Aluminium Industry has developed an approach based on Life Cycle Analysis (LCA) methodology.Within this framework, the Primary Aluminium Industry has established a global Life Cycle Inventory (LCI) data set. Inventory flows include inputs of raw materials, energy and water, emissions to air and water, and solid waste.This paper presents the latest LCI data update by the International Aluminium Institute for the year 2010, based on a survey of aluminium plants globally, including bauxite mining, alumina refining, anode production, electrolysis and casting. This update also includes some performance tracking based on the last LCI data collection in 2005, reflecting progress in efficiency and technology, as well as changes in the geographical location of the industry [2010 data pending]. IntroductionIn 2010 the Primary Aluminium Industry produced a total of 41 Mt of aluminium. The International Aluminium Institute (IAI) membership represents approximately 70% of total global production. The industry recognises the importance of co=itting to reducing the environmental impacts of producing primary aluminium, and the significance of working towards a more sustainable future. As part of this co=itment the IAI has developed an in depth Life Cycle Inventory programme, in which data is collected every five years, with supplementary key metrics collected annually.In 2003 the IAI released its first Report ""Life Cycle Assessment of Aluminium: Inventory Data for the Worldwide Primary Aluminium Industry"" based on the year 2000 with an update Report released in 2007, based on 2005 data.This paper presents the latest update for the year 2010 [2010 data pending]. It has been prepared with the same view of collecting all significant Life Cycle Inventory data (raw materials and energy use, air and water emissions and solid waste generated) associated with producing primary aluminium ingot from bauxite ore, with worldwide coverage. The intended purpose of the Inventory Report is to accurately characterize resource consumption and significant environmental aspects associated with the worldwide production of primary aluminium. It reflects the fuct that primary aluminium is a globally traded co=odity."

Jan 1, 2012

By P. R. Taylor, B. N. Carlson

Rare earth magnets play an increasingly important role in high end technology, and the manufacture of rare earth magnets, such as the NdFeB type, consume a large amount of the rare earths produced. Recycling of this material could provide an important domestic source for these materials. A selective sulfation roast has been proposed; the central principle of which is to take advantage of the differing stabilities of the rare earth sulfates as compared to those of iron under an air/SO2 atmosphere. Experiments show iron is found to be stable as an oxide, however, neodymium is found to form an oxy-sulfate phase.

Mar 1, 2017

By Steve Lloyd, Ryan J. Foy, Brandon Steinborn, Jerome P. Downey

Research was performed to evaluate copper and silver extraction from samples of bornite flotation concentrate. Sulfation roasting experiments were performed in a rotary tube furnace, a fluidized bed reactor, and a static bed muffle furnace. Roasting was plagued with rapid, lowtemperature calcine sintering, apparently related to the presence of organic matter in the concentrate. Calcine entered a weak acid leaching process to remove copper, and silver was extracted from the weak acid leach residue in a ferric chloride and hydrochloric acid solution. Copper extraction efficiencies in excess of 90% were attained in the weak acid leach while 90% silver extraction was achieved in the ferric chloride leach, along with copper and lead extractions as high as 93% and 99% respectively. The two-stage leaching process resulted in overall extraction efficiencies of 99% copper and 90% silver.

Jan 1, 2015

By Florian Kongoli

New operating conditions and process parameters are often necessary in today's industrial practice of non-ferrous smelting and converting in order to accommodate various new chemical compositions of mineral charges and environmental requirements or to conceive new and more efficient industrial technologies. An important parameter in non-ferrous smelting and converting is the liquidus surface of multicomponent slags. This surface is affected by multiple factors such as temperature, gaseous potentials, the content of each component in the slag, etc., and cannot be quantified by the existing ternary liquidus diagrams. In this work a new type of representation of the liquidus surface of multi component systems has been presented by means of a thermodynamic model. This representation waives the need of the multidimensional representation of multi component systems and yields practical two-dimensional diagrams, which can be easily used in the industrial practice.

Jan 1, 2000

By Michael Sheedy

Sulfuric acid is widely used as an electrolyte for the electrorefming and electrowinning or metals. Impurities in this electrolyte are controlled by continuously bleeding solution from the tank house. In addition to the contaminant these bleed streams contain high levels of sulfuric acid and the metal being recovered. Subsequent treatment of these bleed streams often requires neutralization which generates large volumes of solid waste. Absorption resin technology employing a novel ion exchange technique known as Recoflo® allows the separation of the mineral acid from dissolved metal salts. The recovered acid is suitable for recycle back to the electrolyte circuit. The metal salt and other contaminants leave the process free .of the sulfuric acid. In this process, known commercially as the APU®, ion exchange resin is used to sorb sulfuric acid while excluding the metal salts. The purified acid is then removed by washing the resin with water. The process has been extensively used for the recovery of waste pickling acids in the steel industry and anodizing solutions in the aluminum industry. In the mining and metallurgical industries the process has been successfully evaluated for the separation of excess sulfuric acid from copper electrolytes, the removal of magnesium and manganese contaminants from zinc electrolytes, and nickel and copper from copper electrolytes. A full scale installation on a copper refinery bleed stream at Palconbridge's Kidd Creek plant in Timmins, Ontario has now been operating successfully for more than 1 year while pilot field trials have been successfully completed on other applications.

Jan 1, 1997

By Magdalena Regel-Rosocka

Extraction of zinc(II) from hydrochloric acid solutions is discussed. The literature on the extraction of zinc(II) in the presence of iron(III) and iron(II) with various basic and solvating reagents has been reviewed. It was found that tributyl phosphate (TBP) is the best compromise, and permits both effective extraction of zinc(II) and its stripping with water. The process was confirmed in a continuous laboratory mixer-settler circuit.

Jan 1, 2003

By Xiping Chen, Wangxing Li, Jiemi Zhou

"Desulfurization methods suitable for anode-grade petroleum coke (coke for short) used in primary aluminum industry are coke desulfurization during calcination, desulfurization in soakage and desulfurization in mediums. Coke desulfurization during calcination is discussed in this paper. Influences of calcination temperature, holding time and coke granularity on coke desulfurization were discussed. Experimental results show that calcination temperature has a remarkable influence on coke desulfurization. When the temperature is high enough desulfurization ratio of coke can reach 85% only by calcination. Holding time has a definite influence on coke desulfurization, but desulfurization ratio is low at the temperature of 900~1300°C. The influence of holding time is obvious when calcination temperature surpasses 1400°C. The influence of coke granularity is smaller compared with calcination temperature and holding time.IntroductionPetroleum coke is main raw material for carbon anode in primary aluminum industry, and its weight percentage in carbon anode is about seven percent. Green coke can not be directly used for anode production because of its immanent moisture and volatiles. Green coke must be calcined in order to meet the request of anode production. Calcination is a heat-treatment process during which green coke is heated to a given temperature to remove volatiles, moisture and some sulfur. Real density, strength, electrical conductivity and anti-oxidation ability of petroleum coke can be improved by calcination and calcined coke can be received [1, 3, 4]. Sulfur in calcined coke finally goes into carbon anode. During baking or aluminum smelting, the sulfur in anode ultimately changes into SO2 and emits from anode into the atmosphere. Excess SO2 easily leads to acid rain which brings heavy pollution to the environment [1, 2]. With the development of Chinese aluminum industry, consumption of anode-grade petroleum coke increases year by year, the total consumption in 2007 surpassed 4.5 million tones and the yearly emission of SO2 from aluminum smelters has exceeded 270 kilotones. From 2005 Chinese government began to limit the emission of SO2 from primary aluminum industry, so desulfurization of anode-grade petroleum coke becomes more and more urgent. Some relationship need to be found and used to guide desulfurization of petroleum coke."

Jan 1, 2008