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By E. M. Alcântara

This paper describes some aspects about the relationship between copper electrorefining addition reagents and the hydrogen in the cathode. The conditions of electrorefining were studied by factorial design methods. The advantages of this technique are reduction in the number of tests, well organized experiments; improvement in productivity and reliability of results. The dosage of the two main addition agents, glue and thiourea, were varied simultaneously and compared with the hydrogen content in the cathode. The influence of these factors, as well their interactions were analyzed by statistical methods denominated ANOVA (Analysis of Variance). The increase of thiourea quantities, within of levels studied, influenced significantly at 95% confidence in the hydrogen content in copper cathode.

Jan 1, 1999

By P. Aguirre

Recovery of zinc, copper and nickel from electroplating waste solutions was achieved 'by using a Pulsated Percolated Porous Electrode "3PE" reactor on a pilot plant scale. Intensity - potential curves were used to study the possibility of metal removal and to define the working potential range. The present study describes the use of the 3PE reactors in several electroplating industrial units for the decontamination of their effluents. These effluents were issued from different industrial solutions such as cyanide, sulfate, chloride and Watts baths. Using the stripping curves, deposition rates and electrical efficiencies were determined as function of the metal concentrations in these effluents. Their decontamination could be achieved to the level of few ppm of metals with reasonable current efficiencies. The recovery rates of zinc and copper were about 93 and 99 %, respectively. The. treated effluents contained less than 7 and 1 % of the initial contents of Zn and Cu, respec¬tively. This process allows the recycling of the recovered metals and leads to water saving.

Feb 13, 2014

By Kaspar Tall, Dmitri Goljandin, Kristiina Vilsaar, Jaan Kers, Valdek Mikli, Lifeng Zhang, Riho Tarbe, Viktor Laurmaa, Mart Saarna, Priidu Peetsalu

In this paper, the mechanical milling of the Printed Circuit Boards (PCB) was carried out. First goal of the work was to examine the management of the WEEE, in particular the re-use of PCB. Firstly, recycling methods of PCBs were summarized. During the study mechanical separation methods (magnetic-, density- and air separaten), electrical, and chemical methods were examined. Secondly the optimal particle size for air-classification was determined. Several tests were carried out to find the most effective separation method for separation of different material groups from PCB scrap. The new air classification stand was developed for testing the separation of lightweight particles like tinfoil stripes and plastics. The test results showed sufficiently good separation of heavier Al and Cu. For milled materials characterization the SA, IA, laser diffraction analysis and SEM were used. The chemical composition of the PCB powders was studied by means of energy dispersive X-ray microanalysis (EDS).

Jan 1, 2011

By Levent Özmen

Colemanite is a mineral containing varying amount of boron that is found in abundance in Turkey. It has a good possibility to be used as a flux in iron and steel industry. In this study a review of the use of colemanite, as a flux agent in steel production has been carried out and various related aspects such as its influence in metal-slag reactions, solubility of lime and magnesia in the slag are discussed along its performance in several points of views including its technical and environmental usage characteristics. Positive and negative factors of using this material as a flux are also underlined.

Jan 1, 2006

By V. L. Richards, S. N. Lekakh, S. A. Dutler

"This study presents determination on the thermal properties of investment casting shell molds used in casting process modeling. Superheat and latent heat from solidification and cooling of a casting can either be accumulated by ceramic shell for thin-walled casting or transfer to environment for massive casting. Heat capacity and thermal conductivity both play important roles in casting solidification. Thermal properties of ceramic shell depend on shell composition and fabrication techniques as well as thermal history during shell preparation process due to multiple phase transformations. Inverse modeling was combined with corrected Laser Flash method to determine the applicable thermal properties of the shell during casting solidification. Pure nickel was poured into ceramic shells containing two thermocouples and experimental cooling curves were obtained. These curves were then fitted to the model by adjusting temperature dependent heat capacity and thermal conductivity.IntroductionCasting solidification in investment casting shell affected by shell thermal properties including specific heat capacity and thermal conductivity. For relatively thin walled casting, most of the melt superheat and part of latent heat are accumulated by the shell. This process is mainly controlled by shell heat capacity. In the case of massive casting, significant part of latent heat transfers to environment through the shell so that this process is mainly controlled by shell thermal conductivity."

Jan 1, 2012

By Tong Deng

Clean processing of copper converter slags for reclaiming cobalt and copper could be a challenge. An innovative and environmentally benign approach for recovering metal values from such a slag was developed in the present work. Curing the slag with sulfuric acid, without re-smelting or roasting as currently practiced in the industry, made it amenable to leaching, and more than 95% of the cobalt and up to 90% of the copper was extracted, together with iron, by water leaching, leaving silica behind in a residue. Copper in the leach liquor was recovered by cementation with iron, and the dissolved iron crystallized as ferrous sulfate monohydrate. Cobalt in the pregnant solution rich in iron was recovered by either cementation or sulfide precipitation. Chemical and mineralogical characterization of the slag and its products were examined and compared to determine the nature of the changes occurring during curing and leaching. Operating variables were also investigated and optimized.

Jan 1, 2003

By Lauri E. K. Holappa

Ferrochrome, as the central constituent in stainless steels is one of the most rapidly growing primary metallic products. In this contribution results of a comprehensive study on the reduction process of chromite ore to FeCr are presented including thermodynamic examination, experimental work on kinetics and mechanisms in solid state, and smelting reduction conditions as well as kinetic modelling of solid state reduction.

Jan 1, 1999

By Liwen Hu, Jianxun Song, Hongmin Zhu, Qiuyu Wang, Shuqiang Jiao

The subchloride titanium was prepared by sponge titanium and titanium tetrachloride in the CaCl2 at 1173 K. The species were detected are mainly titanium dichloride, and the average valent in the melt are 2.05. The accurate equilibrium constants were obtained for the reaction 3Ti2+ = 2Ti3++Ti after the accurate activities of titanium chloride were evaluated with emf method, and the observed deviations from ideal behavior are discussed.

Jan 1, 2015

By J. C. DeSantis

Thin, highly reflective rhodium films with metal compositions greater than 98% (elemental -weight percentage) have been deposited by chemical vapor deposition using Rh(allyl)3 (ally1 = q3-C3H5) in the presence of a hydrogen plasma. Uniform, crystalline films that adhere well to several types of substrates result from depositions at temperatures as low as 150°C. Depositions using H2 (no plasma), or an argon plasma yields material that is amorphous, contains a significant amount (>14%) of residual carbon, and has a dramatically slower growth rate. The composition of these materials does not vary significantly from that of the materials obtained from the in vacuo thermal deposition with Rh(allyl)3.

Jan 1, 1992

By Roderick 1. L. Guthrie, Mei Li

"A mathematical model was developed to study the role of orifice shape in the detection of inclusions in LiMCA (Liquid Metal .cleanliness Analyzer) system. The fluid flow field within the ESZ was obtained by solving the Navier-Stokes equations. The trajectories of entrained particles were calculated using the equations for motion of particles. A numerical study of the effect of orifice shape on signal shape generated by inclusions passing through orifice showed that the signals in a parabolic orifice are gaussian in shape, while those in a cylindrical orifice are trapezoidal in shape. This signal shape difference needs to be taken into account when performing particle discrimination. Orifice shape influences also pass-through fraction of inclusions. Finally, a study of the orifice shape on critical conditioning currents suggested that as the polynominal coefficient of the parabolic orifice increases, the critical conditioning current, which is also the maximum operating current, decreases dramatically. These critical conditioning currents also increase as the fluid flow velocity within the ESZ increases. IntroductionThe presence of non-metallic inclusions in metals often leads to impaired mechanical properties such as a reduction in fatigue strength, and to processing problems such as tear-offs in deep drawing and increased breakage rates in wire drawing operations. Similarly, inclusions cause a variety of surface defects in rolled or extruded products.Prior to the development of the LiMCA system (1) at McGill University in the early 1980's, it was not possible to measure inclusions, in situ, in liquid metals. Compared with other techniques, such as sedimentation, filtration and metallography, which require considerable amounts of labor and time, the LiMCA method has the advantage of providing not only information on the volume concentration of inclusions, but also on the size distribution of inclusions immediately and quantitatively."

Jan 1, 2001

By Charles H. Rawlins

Reported is work done on processing of steel mill effluents in the areas of dewatering and separation. Much of the waste from these operations is in the form of sludges from scrubbers, in which the primary constituent is iron oxide. Recycling of the sludge&apos;s magnetic fraction has become economically attractive in order to reduce the overall volume placed in landfills. The objective of this research is to determine the effectiveness of combining magnetic and cyclonic forces, to recover iron oxide particles from waste water stream, while decreasing the volume to be disposed. Three different size hydrocyclones, operating within the field of a quadripole magnet, were tested using varying feed pulp densities of magnetite, magnetite/dolomite, blast furnace (BF), and basic oxygen furnace (BOF) slurries. In the first three cases, the percentage of magnetics recovered increased to greater than 95%. The limiting operational factors are; high pulp density for small cyclones, which can cause flow blockage within the magnet field, and extremely fine particle sizes (<2 microns), which cannot be recovered. The results indicate this technique can remove virtually all the magnetic particles from some steel effluents to a 40-50% weight percent solids pulp, on an in line continuous basis.

Jan 1, 1994

By Vladyslav M. Sokolov

The cost effective and environmentally friendly recycling technology was developed and tested. It enables utilization of the fine nickel-base superalloy scrap in a form of heavily oxidized scarfing granulates. The process of granulates generation was discussed in details. Their properties were investigated. The results of literature search showed anticipated sufficient improvement of the properties of cast iron by its alloying with the elements from the scarfing granulates. The novel alloying approach is based on the two stage reduction operation. Firstly thegranulates were partially reduced in a solid state by their exposure with powdery carbon at the range of 1550 ? 1700°C. Then the gotten product was efficiently introduced into liquid iron since it has a form of fine natural agglomerates for arranging the optimal conditions for reduction of the granulates. The thermodynamic evaluation demonstrates higher reduction efficiency of carbon and silicon dissolved in iron than of the same elements in a form of the separate phases. The considered process partially provides itself by energy since the reaction of reduction of the chromium oxide by silicon dissolved in liquid iron has exothermal character. The mostly complete extraction of Ni was received. The sufficient reclamation of Cr was gotten at the same time.

Jan 1, 2006

By Ko-ichiro Ohno

It is recently recognized that the iron reduction and melting as well as the slag separation of a composite of granular iron ore and coal are completed in a very short period of about 10 minutes when the composite is rapidly heated up to approximately 1673K. These phenomena are expected to be applied to a new iron-making process. The mechanism of iron ore reduction and iron-slag separation during rapid heating has not yet been revealed and the fundamental research has just started. Carburization of the reduced iron is regarded as one of the most important steps in this process. In the present work, the composite was prepared from four kinds of coal or graphite as a carbon source and electrolytic iron powder as a completely reduced iron ore. The temperature at which the liquid formation and iron carburization occurred was monitored. Direct observation of smelting reduction behavior was made by a confocal laser-scanning microscope combined with the infrared image-heating furnace to clarify the effect of molten ash on iron carburization. It was found that the meltdown temperature of composite became lower as the melting temperature of coal ash decreased. From the observed result, it was presumed that the liquid slag would act as an important media for the carbon transfer from coal to iron. The carburization mechanism during the smelting reduction was estimated as follows. When slag containing iron oxide melted down and contacted carbon, iron oxide in the slag was reduced and the formation of the metallic iron particle as well as the its carburization occurred simultaneously at the slag-carbon interface. Carburized iron particle was carried from slag-carbon to slag-iron interfaces due to the slag convection flow caused by the difference of the interfacial tension between the carbon-slag and iron-slag interfaces. Carburization of reduced iron could proceed with a repeat of the above-mentioned process.

Jan 1, 2003

By Daniel Chen, Jewel Andrew Gomes, Venkata Palla, Sadia Afrin Jame, David Cocke, Paul Bemazzani

"Textile industries use various kinds of chemicals including dyestuffs and pigments during dyeing and finishing processes. The effluent from these processes includes suspended particles, strong color, high pH and high chemical oxygen demand (COD) that are extremely toxic and make environmental hazard. Although physical, chemical, photochemical, and biological methods are available for treating such wastewater, the electrochemical technique, electrocoagulation (EC), has emerged as an efficient, simple, and cost-effective technology in the last few decades. In this study we present the applicability of EC technique for removing dye, such as direct red dye using iron electrodes, and the optimized conditions such as dye concentration, current density and pH. The degradation of dye molecules was investigated using UV-visible spectroscopy. The EC-floe was also characterized using SEM/EDS, XRD and FTIR.IntroductionWastewaters generated by textile industries contain large amounts of toxic aromatic compounds, especially azo dyes. Azo dyes and their degradation products, such as aromatic amines, are highly carcinogenic. These effluents are also responsible for causing high levels of color. The colored wastewater released into the environment is also a source for disruption of aquatic life and aesthetic pollution as well [1].In most textile industries, dyeing and finishing are the two important processes which are generally applied. These two common processes generate significant amount of wastewater, which may contain, suspended particles, high pH, strong color and high chemical oxygen demand (COD) concentration [2]. Low pH and high temperature are other polluting factors from the waste water. Textile industries make use of about 10,000 dyes and pigments [3]. Disposal of these colored wastewaters poses a major problem for the industries as well as a threat to the environment. In textile industries, because of the low efficiency (60-90%) of dye fixing on textile fibers, substantial amounts of unfixed dyes are released in waste waters. The conventional method for treatment of textile wastewater was a combination of biological, physical and chemical methods [2]."

Jan 1, 2011

By Daniel Kim, Michael Free, Justin McAllister, Urian Marshall, Shijie Wang

"Cathode impurity levels of electrorefined copper were evaluated based on 1/10* scale laboratory electrorefining tests. Cathodes were evaluated near the top, mid-section, and bottom sections of cathodes on both the set and mold sides and strip and scrap cycles. Slime weights were measured, and slime and electrolyte samples were also evaluated for impurities. Results from these tests have been compiled and compared to evaluate the effects of changes in operating conditions and electrode location on cathode impurities.IntroductionMany types of impurities are commonly found in commercial copper electrorefining anodes. The smelter operations that produce the anodes process concentrates that contain a wide variety of impurities that vary based on the mineralogy of the ore. Most anode impurities are removed during electrorefining. However, a portion of the anode impurities is incorporated into the copper cathode product. The mechanisms by which impurities are transported from the anode to the cathode are not well understood. Some impurities can be transported as anode slime particles to the cathode where they are incorporated into the cathode. Other impurities can be transported as dissolved species that are electrochemically reduced with the copper to become part of the cathode. Although research has been performed on anode slimes and impurities [1-4], there is a need for additional information regarding the relationships associated with electrorefining cycles, electrode faces, local electrode positions, anode impurities and specific cathode impurities. The objective of this study was to evaluate lead, arsenic, and antimony cathode impurity trends associated with electrorefining cycles, electrode faces, local electrode positions, and anode impurities. A variety of techniques including electrolyte filtering, anode heat treatment, high electrolyte arsenic concentration, high arsenic and/or lead in anodes, flocculation of slime particles, and appropriate current density control were used to vary cathode impurity levels. Each test was performed only once for a strip cycle and once for a scrap cycle. Consequently, the results for the individual conditions are preliminary and are not the focus of this study. However, the collective set of data with varying impurity modifying techniques provides a broad range of impurity levels, and the associated trends with respect to lead, arsenic, and antimony are discussed in this paper. Approximately 180 analyses of copper cathode were used to track the antimony, arsenic, and lead impurities. Eighteen anode slime samples were also analyzed for antimony, arsenic, and lead."

Jan 1, 2012

By J. Boltano

This paper discusses the study, design and implementation of the new gas handling system for the Caletones Smelter of Codelco-Chile. A discussion on design conditions for a future Sulphuric Acid Plant using Teniente Converter gases is also included. The old system which started to be modified in 1985 and relied on natural draft and used balloon flues, resulted in a limited gas handling capacity for operation under future process conditions. This system also caused excessive fugitive gases in the smelter working areas. The new system permits handling of process gases from the higher capacity Teniente Converters Installed in 1987-1989 improving the gas handling of the reverberatory furnaces and Peirce-Smith converters as well as the environmental conditions of the smelter. This system utilises improved converter gas hoods, evaporative cooling and electrostatic precipitators gas cleaning, and is based on natural draft.

Jan 1, 1992

By Lan Li, Izaak Williamson

"The efficient separation and storage of CO2 from power plant flue gases can reduce the amount of CO2 released into the atmosphere and mitigate global warming. Potential candidates for industrial applications are solid sorbent materials. Crucial factors to control the efficiency of porous sorbent materials include the framework and pore structure, and the chemical and physical reactivity of CO2 within the pores. Computational modeling approaches, based on density functional theory (DFT) and van der Waals-DFT, have been applied to nanoporous solid – manganese dioxide a-MnO2. We found that the types and charges of cations as dopants in the a-MnO2 and the concentration of CO2 influence the structural features of a-MnO2, which control its CO2 selectivity performance within the flue gases.IntroductionCarbon capture and storage is a technique to separate large quantities of CO2 from power plant flue gases before being released into the atmosphere. Porous solids are a potential candidate as sorbents to “trap” CO2 through chemical or physical adsorption on their porous surfaces[1]. Such separation efficiency is determined by the size and shape of its pores and by the interaction between the porous surface and the gas adsorbates. The incorporation of cations into the pore can act as a means of structural support and alter the pore diameter to be comparable to the kinetic diameter of the gas adsorbate, such as CO2.A porous solid of particular interest for CCS is manganese dioxide a-MnO2, an octahedral molecular sieve (OMS) composed of edge-sharing MnO6 octahedra that are linked into a nanoporous framework[2]. The framework consists of (1×1) and (2×2) tunnels, referred to as OMS-2. Due to the larger tunnel size, cations and gas adsorbates prefer to reside along the (2×2) tunnel axis of the OMS-2. As seen in Figure 1, a potassium cation K+ is located in the (2×2) tunnel, known as cryptomelane-type MnO2. Its pore diameter of ~ 4.6 Å gives it a good CO2 selectivity performance, because the diameter is comparable to the kinetic diameter of 3.3 Å for CO2[3]. Alternatively, replacing potassium K+ with other cations, e.g. barium Ba2+, sodium Na+ or lithium Li+, in the OMS-2 tunnel is of great research interest, due to the effects of their concentrations, types and charges on the CO2 selectivity efficiency and sorption hysteresis phenomenon[2,4]."

Jan 1, 2014

By Robert W. Hyers

Electromagnetic levitation has proven important in a wide range of experiments, all affected by fluid flow. For some experiments such as viscosity measurements, only whether the flow is laminar or turbulent must be established. For other experiments, however, quantitative assessments of velocity, shear stress, or shear strain rate are required. In most cases it is difficult or impossible to measure the internal flow in levitated droplets directly. The samples are usually small, opaque, reactive, high-temperature, metastable, or all of these. Furthermore, recirculating flow limits the utility of tracking surface particles, since they collect in stagnation points ratherthan following the flow. Most research groups have chosen mathematical modeling to assess the internal flow in levitated droplets. A variety of analytical and numerical methods have been applied, including both laminar flow and various turbulence models. A number of these models are reviewed and their impact on different containerless experiments is assessed. Much of the research reviewed here was performed by alumni of Professor Julian Szekely, and by others using similar methods.

Jan 1, 2006

By Leon E. Laforest

An early commitment by Kidd Creek Mines Ltd. (formerly Texasgulf Canada) to follow a stringent environmental control programme from the initial stages of design and development of its metallurgical facilities in Timmins, Ontario, has resulted in the on-going attainment of extremely low levels of industrial waste emissions. This paper outlines the monitoring programme initiated and maintained by the company&apos;s environmental control section. Comparative results of environmental sampling for the periods before and after the copper smelter start-up are highlighted.

Jan 1, 1983

By S. Goto, S. Yamashita, K. Hata

"The average consumption of zinc dust for purification of zinc leaching solution is more than 25 kg per tonne of electrolytic zinc. Authors proposed to remove impurities in zinc leaching solution by electrolysis instead of cementation by zinc dust. The effects of copper and arsenic on electrodeposition of cobalt in zinc sulfate solution were examined fundamentally using a potentiostat. It is observed that cobalt is easily deposited on a cathode at potentials under -480mV with arsenic. Mesh cathodes of stainless steel and lead anodes were used in a small electrolytic cell and the electrolyte was circulated through 'the electrodes during the electrolysis. The effect of electrolyte circulating rate , pH, cell temperature, current density, and concentration of copper and arsenious ions on removal of cobalt were studied. Removal of Cd and Ni are also examined.IntroductionCobalt is difficult to remove from a zinc leaching solution by a simple cementation reaction using zinc dust. However, it is easily precipitated by zinc dust with co-addition of arsenious or stibinous oxide and copper ion in practical operations(I), (2), (3). The consumption of zinc dust for purification is 16-152 kg per tonne of electrolytic zinc and 65% of this zinc dust consumption is used for cobalt purification. The average retention time for purification of cobalt is 4.5 hours (1). A more economical process for purification is desired instead of zinc dust. The mechanism of this acceleration effect of copper and arsenious oxide on removal of cobalt are explained by the authorsas follows; a galvanic cell is formed between zinc dust and copper which is precipitated firstly, and cobalt is reduced on copper as Co-As alloy by this galvanic current(2). This assumption was confirmed in experiments using a galvanic cell with a membrane( 4). The following galvanic reactions occur between zinc dust and copper precipitate; on copper cathode,2H+ + 2e -= Hz(g)2Coz+ + 2HAs02 + 6H ++ 10e -= 2CoAs + 4HzOand on zinc anode,Zn = Zn = 2+ 2e –This galvanic current becomes almost zero in a zinc sulfate solution which includes only cobalt and no arsenious oxide, and cobalt is weakly deposited on a copper cathode. Cobalt deposition requiers a high degree of cathodic polarization. However, the galvanic current flows almost constantly in an electrolyte, which includes arsenious oxide, and the cathode potential is kept at about -500mV. Cobalt is precipitated as Co-As on the cathode.The authors assumed that cobalt may be removed by electrolysis at a very low current density instead of zinc dust and the following experiments were carried out. In the first part of this paper, the fundamental experiments using a potentiostat on the behaviour of cobalt in zinc sulfate solution are described. In the second part, the results of the electrolysis are reported. Cobalt is removed by a new type of an electrolytic cell, which was desigoed to <Iccelerate the rate of deposition of cobalt. The removal of cadmium and nickel in a solution which includes cobalt and arsenic are also examined."

Jan 1, 1997