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By J. P. Evans

The modem copper smelter today utilizes tonnage oxygen for smelting concentrates, generating a high strength S02 off-gas leaving the smelter vessel. This gas stream, which also contains any unreacted oxygen, plus C02, N2 and H20, also carries with it the volatilized portion of heavy metals in the feed, plus partly oxidized sulfide concentrates. The time/temperature history and subsequent treatment of this off-gas stream emerging from the smelting furnace exit up to the acid plant can influence the partitioning and segregation of heavy metals in the off-gas circuit. Depending on this history, the type and characteristics of the chemical and physical reactions which. occur in the gas handling system can be influenced. This fact can also be used as a tool to adjust the separation of copper from heavy metals. In this paper, the impact of different time/temperature histories of the gas, due to different furnace geometries .and design, on the subsequent formation and characteristics of the smelter dust is examined. Based on the available data, several case histories drawn from examples using both bath and flash smelting technologies are analyzed from this perspective.

Jan 1, 1992

By J. P. Evans

The modem 'copper smelter today utilizes tonnage oxygen for smelting concentrates. ,generating a high strength S02 off-gas leaving the smelter vessel. This gas stream. which also contains any unreacted oxygen, plus CO2; N2 and H20. also carries with it the volatilized portion of heavy metals in the feed, plus partly oxidized sulfide concentrates, The time/temperature history and subsequent treatment of this off-gas stream emerging from the smelting furnace exit up to the acid plant can influence the partitioning and segregation of heavy metals, in the off-gas circuit. Depending on this history. the type and characteristics of the chemical and physical reactions which occur in the gas handling system 'can be influenced. This fact can also be used as a tool to adjust the separation of copper from heavy metals. In this paper, the impact of different time/temperature histories of the gas, due to different furnace geometries and design. on the subsequent formation and characteristics of the smelter dust is examined. Based on the available data. several case histories drawn from examples using both bath and flash smelting technologies are analyzed from this perspective.

Jan 1, 1992

By Lu Lin, Yanping Bao, Xiang Li, Linzhu Wang, Xiaobai Yan

The results showed the microinclusions were mainly Al2O3 and sulfide inclusions from tapping to the beginning of LF refining. Al2O3 inclusions were modificated into calcium aluminates after calcium treatment. Lots of spherical calcium aluminates composite inclusions containing MgO, TiO2 and MnS were found after soft blowing and during tundish metallurgy and left in the slab which caused the defects of beam plates. Pure Al2O3 inclusions were observed again after soft blowing 8min. Average sulfur content in inclusions decreased because of the high desulfurization ability of refining slag. Average Ca/Al ratio value in inclusions increased during LF refinging because of the reduction of CaO in slag by carbon and it increased obviously during the process of soft blowing 8min because of the dissolusion of calcium wire.

Jan 1, 2015

By G. A. Irons, D. Colbert

Several electric arc furnace (EAF) shops have increased the zinc and lead grades of EAF dust by reinjecting it into their furnaces; however, the kinetics of this operation are poorly understood. To understand the kinetics, EAF dust was injected into 70 kg heats of iron or steel in an induction furnace. Supplemental additions of carbon and oxygen to overcome the heat load on the system were also investigated. In all cases, the dust was chemically transformed, and the zinc content increased from 16% Zn to 60 - 80% Zn. About 50% of the zinc in the EAF dust dissolved in the iron or steel. The zinc oxide in the dust is thought to be reduced by carbon and the zinc vapour subsequently dissolved in the iron. A kinetic model for the dissolution process is proposed, and the implications for EAF dust recycling are discussed.

Jan 1, 2000

By Zhucheng Huang, Ronghai ZHONG, Liangming Wen, Tao Jiang

The reduction roasting-magnetic separation and its strengthening of high silicon coal-containing mini-pellets by sodium additives were researched. The results show that the carbon gasification reaction and reduction of fine hematite in high silicon coal-containing mini-pellets with 3% sodium additives were enhanced. Comparing with no sodium additives, the gasification rate of carbon with 3% sodium additives reacting with CO2 for 40 minutes at 950 and the metallization rate of reduced pellets with 3% sodium additives after roasting for 35 minutes at 960 increased from 35.15% and 58.72% to 86.98% and 86.15%, respectively. The analysis of SEM equipped with EDS demonstrates that the inner pore of reduced pellets with 3% sodium additives was more developed and the iron grains size significantly enlarged, meanwhile, the iron grade of concentrate increased from 60.45% to 80.23% and the iron recovery rate decreased from 84.67% to 80.78% after grinding-magnetic separation.

Jan 1, 2016

By K. Narayana Swamy

Experimental results of 3-phase mixing in a physical model of a CCRL for metals refining, at high levels of bottom gas injection (up to a superfIcial gas velocity (Us) of 12.5 cm/min), are presented. A thermal tracer technique was used to elucidate both longitudinal mixing and interphase heat transfer. The results indicate that even under conditions of significant bottom gas injection, it should be possible to maintain acceptably low longitudinal mixing (D. < 20 cm2/s and D/uL < 0.1) in the CCRL. Interphase mass-transfer coefficients of the order of 0.02 cm/s and higher, are predicted from the measured interphase heat transfer coefficients using the mass and heat transfer analogy. Adequate performance is likely to be possible for an industrial CCRL, based on extrapolation of these results to full-scale conditions.

Jan 1, 1996

By K. D. Peaslee, V. L. Richards, C. H. Rawlins, S. N. Lekakh

"Steel-making processes generate carbon dioxide air emissions and a slag co-product. The aim of this project was to develop a functional sequestration system using steelmaking slag to permanently capture carbon dioxide emitted in steelmaking offgas. A possible parallel benefit of this process would be rapid chemical stabilization of the slag minerals with reducing swelling or leaching.This paper summarizes the original results of the project, including mineralogical and structural features of carbon sequestration with steel making slag, mathematical modeling of reaction phenomena using a modified shrinking core model, METSIM modeling of several possible industrial applications, a thermo-gravimetrical study of the reaction between slags and different gases, and design and testing for a lab scale apparatus consisted of two reactors.1. IntroductionThe U.S. produces 9-14 Mt of steelmaking slag annually, which represents approximately 10-15 wt. % of crude steel output.1,2 Primary uses for steelmaking slag include high quality mineral aggregate, Portland cement, unconfined fill, soil conditioning, and pH neutralization of abandoned mine drainage.3,4 The key factor prescribing slag use is the alkaline-earth metal (e.g. Ca and Mg) oxides content, which contribute to overall basicity and cementitious strength. However, as-produced steelmaking slag is chemically unstable. Calcium and magnesium oxides readily form hydroxides and carbonates through reaction with atmospheric gases. Both hydroxide and carbonate formation produce substantial mechanical swelling leading to heave failure in confined construction applications, thus many states dictate stockpile aging for 3-6 months prior to commercial use.5,6 Sequestration of carbon dioxide is a natural corollary to forced carbonation. The conversion of CaO/MgO to carbonates serves both to stabilize the slag, and permanently capture and store the CO2."

Jan 1, 2008

By D. Mishra

Electric arc furnace dust (EAFD) generated during the recycling of steel- scrap is classified as a hazardous waste for landfilling. This is because it contains leachable heavy metals such as zinc, lead,... Recovery of these metals could result in both resources conservation and resolving waste disposal problems. A study of the thermal reduction of a sample of EAFD was carried out in an inert gas atmosphere using coke as a reducing agent. Preferential volatilization of zinc and lead was achieved during the reduction process at about 800 "C. More than 96 % of both zinc and lead were removed from the dust and were recovered in the condensates. The treatment residue was essentially composed of iron oxides and almost free from heavy metals.

Jan 1, 2002

By I. D. Reznik

On blowing nickel matte in a converter without quartz, first the oxidation of metallic iron and a part of FeS occurs without evolving sulfur dioxide, the formed FeO dissolves in a sulphide smelt and form a homogeneous oxysulphide smelt. On further increasing the FeO content, the oxysulphide separates into 2 layers. Based on the laboratory investigation of FeO-(FeS+Fe°) - (Ni3S2+Ni°) ternary phase diagram we have identified the separation region at 1250°C. The boundaries of the separation region have the form of an arc and the composition of the separated oxysulphide layers is defined by the canodes. In the nickel or copper-nickel matte - silicacalcium oxide slag system at 1250°C three layers, namely sulphide, oxysulphide, and slag may be formed. A high slag basicity due to the presence of CaO can serve to enhance the activity of FeO; a low nickel content in the matte corresponds to a high concentration of FeS therein; FeO from slag and FeS from the matte form a homogeneous FeO-FeS solution, i.e. an oxysulphide layer. The investigation on the "Camebaks" apparatus and by the nuclear gamma-ray resonance spectroscopy method of the phase composition in a slowly cooled oxysulphide layer has shown the presence of four phases: wustite, troilite, ferronickel grains, and calcium oxide-silica inclusions. Knowledge of regularities in the oxysulphides formation makes it possible to use them in pyrometallurgy of nickel and cobalt or preventing their formation.

Jan 1, 1997

By Nicola Baldo, Marco Pasetto

"Recycling of tyre rubber in the road pavement, may be one of the best way to reduce waste tires in large quantities and, at the same time, improve some engineering properties of asphalt mixtures. The paper discusses the results of an experimental study, developed in order to analyse the potentialities of crumb rubber from road tyres in bituminous mixtures, using the dry process. Two types of porous asphalt mixtures and reference mixes without rubber were formulated by the traditional Marshall methodology, and mechanically evaluated by means of the Indirect Tensile Stiffness Modulus test, the Creep test (with confinement), and the Indirect Tensile Fatigue Test. Results of this study indicate that the tyre rubber has a positive influence on the performance characteristics, depending also on the grading and volumetric properties of the mix being studied: an interesting increase of the fatigue life, a better stiffness behaviour at lower temperatures and a bigger permanent deformation resistance at high temperatures are guaranteed. Introduction Recycling the rubber from used tyres, in the construction of road pavement layers, is potentially one of the more interesting and advantageous solutions from both the technical and environmental points of view, in order to reduce the total amount of car and lorry tyres to dispose. In road-building techniques, a technology, termed “wet”, for modifying bituminous binders with crumb rubber has by now become well consolidated. There have been numerous scientific studies conducted on this technology and its applications, particularly in the United States, where it has been adopted and codified in specific technical regulations (ASTM D-6114). If the wet process can be considered amply tested, the same cannot be said for a second technology, termed “dry”, which deserves careful study to evaluate its suitability and advantages. In “dry” processes, the rubber is usually used as a partial substitute of aggregate of equivalent grading and mixed with bitumen after integrating the crumb rubber in the lithic skeleton."

Jan 1, 2008

By Tatsuo Itou

Both sales volume of Aluminum Can and its recycling rate are remarkably increasing here in Japan. In 1993, recycled can volume was 11.78 billion cans ( 116,258 metric tons ) and its recycling rate 57.8 percent. We, MITSUBISHI MATERIALS CORPORATION. the leading manufacturer of aluminum can in Japan and our affiliated companies are very deeply involved in recycling used beverage cans ( U.B.C ) and recycling them back to can stock. In this paper. I would like to present the following; 1. Recent trend of beverage can consumption in Japan. 2. Trend of aluminum can and its recycling rate in Japan. 3. Future of aluminum can business in Japan.

Jan 1, 1995

By Guohui Zheng

The ever increasing quantities of solid wastes generated by various industries are at the source of the growing need for proper waste disposal methods. Thermal treatment of combustible wastes is a proven technology which permits the reduction of hazardous material having to be landfilled. However, this method is not universally applicable to waste disposal. For example, the transferal of heavy toxic metals into the thermal remediation products is a major issue of public concern. This paper focuses on the analysis of morphology changes from solid sludge to ash which is a product of the sludge combustion. The morphological parameters analyzed were particle size and external surface. They were determined using Jeol 840 Super Probe. The experiments were conducted in a computer-controlled high-temperature combustion system consisting of the thermogravimetric furnace coupled with Fourier transform infrared spectrometer (TGA-FTIR). Sludge particles were made of complex fibers trapped in the aluminosilicate matrix. At low temperatures, up to 680 K, the solid residue looked similar to the initial sludge. Between 680 K and 1180 K the sludge underwent intensive burning and steadily changed into powdered ash. At the temperature of 1050 K the ash was composed of separate, flat flakes with sizes ranging from 5 to 20 um. At 1470 K the flakes aggregated into large particles. The surface observed at 1670 K was a mixture of mullite crystals. Such structure could result from the solidification of the ash material after its melting. Morphological changes influenced the distribution of metals in the solid residue. For example, Cr was concentrated in small aggregates. Such distribution should allow for recovery of valuable metals from the solid waste residue.

Jan 1, 1996

By Gervais Soucy, François Quesnel, Pierre Hovington, Wen Zhu, Karim Zaghib, Jocelyn Veilleux

The properties of lithium titanates anodes in Li-ion batteries are highly dependent on their secondary constituents. While their main phase is usually constituted of Li4Ti5O12, significant quantity of lithium titanates compounds of various stoichiometry are often present, due to either the processing, usage or aging of the material. These may go underreported, as many of these spectrums overlap or display low signal in X-ray diffraction (XRD). Samples of nanosized lithium titanates synthetized by inductive plasma were characterized by XRD and scanning electron microscopy (SEM), as they provide a regular yet typical crystallite size and shape including multiple phases. A Rietveld refinement was developed to extract the composition of these samples. Mass balance through further annealing and differential scanning calorimetry (DSC) enthalpy measurements from phase transformations were also used as identification and validation techniques.

Jan 1, 2015

By Y. W. Chung, W. I. Chia

"The interaction of water vapor with single crystal Ni3(Al,Ti) and polycrystalline Ni3Fe, with and without the presence of oxygen, has been studied with Auger electron spectroscopy, photoemission spectroscopy, thermal desorption and isotope exchange. Water dissociates to produce atomic hydrogen above 200 K on both Ni3(Al,Ti) and Ni3Fe surfaces. For Ni3(Al, Ti), the reaction is structure-sensitive. Pre-adsorbed or co-adsorbed oxygen on Ni3(Al,Ti) and Ni3Fe significantly suppresses hydrogen production due to water dissociation. This suppression process occurs more efficiently on Ni3Fe than Ni3(Al, Ti).IntroductionOrdered intermetallic compounds such as aluminides, silicides and titanides are very attractive for structural applications at high temperatures. This is because these intermetallics tend to form adherent oxides in oxidizing environments which protect the base materials from excessive oxidation and corrosion. In addition, they have low density, relatively high melting points and good high-temperature strength. However, the moisture in air severely embrittles many ordered intermetallics such as FeAl [1-3], Fe3A1 [4,5], C03Ti [6,7], (Co,Fe)) V [8], Ni3Si [9], Ni3(Si,Ti) [10], Ni3(AI,Mn) [Ill, and Ni3A1 [12-14], resulting in low 'ductility and brittle fracture at room temperature. Recent studies by Liu and coworkers (see review by George and Liu [15]) provide a qualitative description of the mechanism for this moisture-induced embrittlement. During elongation testing, cracks are formed, thus exposing fresh alloy surfaces. One or more active components of the alloy react with water vapor in the environment to produce atomic hydrogen which penetrates into crack tips and causes hydrogen embrittlement. This is similar to that proposed for moisture-induced embrittlement of aluminum alloys [16]."

Jan 1, 1996

By Jorge Alberto Soares Tenório, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Franco Alves Lavacchini Ramunno

"The traditional process for recovery of metals from waste electric and electronic equipment (WEEE) usually involves pyrometallurgical processing. However, the application of this technology to processing waste printed circuit boards (WPCBs) might lead to the formation of dioxins and furans, due to thermal degradation of flame-retardants and polymeric resins present in the board substrate. Therefore, this paper proposes a hydrometallurgical route for the recovery of copper. The acid leaching behavior of copper has been investigated at three different temperatures (25°C, 50°C and 75°C) with and without the addition of an oxidizing agent (hydrogen peroxide - H202). The dissolution kinetics for acid copper leaching was calculated based on chemical analysis by ICP-OES (Inductively Coupled Plasma - Optical Emission Spectroscopy). At 50°C with 1 mol/L H2S04 added 10 mL H202 (30%) each half hour under pulp density of 1 g I 10 mL, 100% of copper was extracted after 3 hours. The dissolution kinetics of copper with H2SO4-H2O 2 followed 1 - (1 - X)113 =Ket, i.e. chemically controlled reaction model.IntroductionThe information regarding the generation of waste electric and electronic equipment (WEEE) are still difficult to obtain because the estimates should take into consideration the historical production and sale of various products and the rate at which they reach the end of their life cycle, whose duration depends on the behavior of consumers [1]. Thus, the estimated overall WEEE generation varies between 25 and 50 million tons each year, which corresponds to more than 5% of all municipal waste generated [2], and this amount will increase at a rate of 3 to 5% per year, approximately three times faster than other individual types of waste [3].Printed circuit boards (PCBs) are essential parts of electric and electronic equipment (EEE), being found in virtually all electronic products, as well as in weapons systems [4]. A PCB is a basic component, which consists of a board where copper tracks are deposited. While the board behaves as an electrical insulator, the tracks connect electrically the various components attached to the board [ 5]. In addition to glass fibers, paper and resins, the PCBs contain significant amounts of metals, such as copper, iron, nickel, lead, stain, silver, gold and palladium [6]. In general, the weight fraction of metal is around 28% and the remainder of the boards is composed of plastic (19%), bromine (as flame retardant - 4%) and ceramic material (49%) [7]."

Jan 1, 2014

By S. Ozbilen, B. Erdogan, M. Erdogan

To study by thermal analyses the response of precipitation hardenable alloys of Al-Cu-Mg and Al-Li-Cu-Mg system to natural and artificial ageing, a series of ternary and quaternary Al-alloys with nominal compositions of Al-l.13wt%Cu-0:65wt%Mg (alloy-I), Al-1.15wt%Cu-0.57wt%Mg-0.07wt%Li (alloy-2), Al-l.19wt%Cu-0.56wt%Mg-0.75wt%Li (alloy-3), Al-2.0lwt%Cu-0.89wt%Mg (alloy-4), Al-2.14wt%Cu"0.56wt%Mg-0.07wt%Li (alloy-5) were used in the present investigation. Samples in the form of rolled sheets are subjected to water quenching at 25EC after solution treatment at 530EC for 20 min. Alloys were aged naturally at room temperature (25EC) up to 2 months and artificially at 190EC up to 2 days. By using differential scanning calorimetry (DSC) in the temperature range of25-300EC, differential thermal analysis (DTA) in the temperature range of25-600EC together with Vicker's hardness measurements, the response to natural and artificial ageing of the alloys used in the present study were investigated. It was observed that in these alloys, GPB(Cu, Mg) zones [Guinier-Preston zones with Cu and Mg] do form during water quenching at 20EC following solutionizing heat treatment. Natural ageing of the same alloys causes formation of more GPB(Cu, Mg) zones, which results in hardening in the alloys. Artificial ageing at 190EC up to l day results in GPB zone dissolution causing preliminary decrease in hardness values while two days of artificial ageing in the alloys cause S' (Al2CuMg) precipitation confirmed by DSC/DTA analyses resulting in an increase in hardness values. Li addition up to 0.75wt% helps T1 (Al2CuLi) and T 2 (Al6CuLi3) phase formation together with S' precipitation as DSC/DTA analyses show after the same heat treatment.

Jan 1, 1998

By Takuya Shinagawa

After vitrification of the residues from a municipal solid waste incinerator, the vitrified products can be used as a construction material, and the dust can be used as raw materials for the non- ferrous industry. The NKK electric-resistance furnace is operated under a reducing atmosphere, and heavy metals such as zinc and lead in the ash vaporize to form dust. Also, dust from the NKK electric-resistance ash melting furnace is composed of water insoluble zinc and lead components and water soluble NaCl and KCI. This is why, The concentration of zinc and lead in the dust after washing is sufficiently high for the dust to be used as a raw material for the zinc and lead industry. NKK developed a heavy metal recovery process in which zinc and lead in the dust are reclaimed as a raw material for smelting by making the best use of the characteristics of the dust.

Jan 1, 2002

By Ramana. G. Reddy, Haoxing Yang

The electrodeposition of zinc from zinc oxide using urea and choline chloride mixture in a molar ratio 2:1 is investigated in different experimental variables, namely, the concentration of added [BMIM]HSO4, temperature, and applied cell voltage. The additive, [BMIM]HSO4, was determined to have beneficial effect on the current efficiency, energy consumed in the process and surface morphology of the deposits. The highest current efficiency (92.6%) and lowest energy consumption (2.92kWh/kg) was obtained for solution with 20mg/mL [BMIM]HSO4. The morphology showed the formation of absorbed additive layer on the cathode at higher concentration of additives. Experiments were conducted at different temperatures between 343K and 388K and at various applied cell voltages between 2.7V to 3.6V to determine the best experimental conditions. By varying temperature, highest current efficiency (91.3%) and lowest energy consumption (2.69 kWh/kg) was obtained at 373K. The electrodeposition process is enhanced between the applied voltage 3.0-3.3V by achieving lower energy consumption (2.75~3.06kWh/kg) and higher current efficiency (88.4~89.7%). SEM images showed grain size is significantly increased in higher applied voltages. While at higher temperatures, it seemed to generate particle growth as clusters at the outer deposit layer.

Jan 1, 2014

By Boyd Davis, Vladimiros Papangelakis, Joshua LaMarre, Jan de Bakker

"HCl leaching using molten salt hydrates has the potential to improve the extraction of nickel from laterite ores. However, as in other HCl leaching applications, recovery of HCl is key to process economics. Spray pyrohydrolysis, which is used in current chloride-based flowsheets, is associated with a high energy cost. The authors have developed a proposed laterite leach circuit using an alternative HCl recovery route. The leach circuit envisions a leach by concentrated (33%) HCl in an MgCl2 molten salt hydrate (MSH) or brine medium, followed by Ni/Co recovery and iron precipitation. Magnesium and chloride are precipitated from solution as magnesium hydroxychloride; this hydroxychloride is thermally decomposed to produce HCl gas. The proposed flowsheet employs a chloride leach circuit with simpler equipment and lower energy cost than in the conventional practice of pyrohydrolysis. Laboratory work investigated key aspects of the flowsheet, including precipitation of magnesium hydroxychlorides and their composition; magnesium hydroxychloride thermal decomposition; and iron control.Introduction As sulphide nickel ores become harder to mine and more complex to process, laterite ores will increase in importance. Laterite ore deposits can be divided into two main mineralogies. Limonite ores consist mostly of hydrated iron oxide, FeOOH, with 1-3% nickel substituting for the iron. Saprolite ores consist of iron-magnesium silicates, (Fe, Mg)2Si04, again with some nickel substituting for the metal ions. Limonite ores can be treated using the HP AL (High Pressure Acid Leach) process, in which the ore is reacted with sulphuric acid at high temperature in an autoclave. HP AL, however, cannot in general be used to treat saprolite ores because the magnesium enters solution and consumes sulphuric acid, which results in excessive spending on lixiviant. It is therefore desirable to find a hydrometallurgical process specifically for saprolite ores that can provide better results than the treatment options currently available."

Jan 1, 2011

By F. Tailoka

Microporous membranes have been used to create a very fine dispersion of bubbles which greatly enhances the mass transfer of electroactive species to the electrode. Using this system, it has been shown that it is possible to electrowin copper as a coherent planar deposit, at high current densities, from copper chloride solutions.

Jan 1, 1990