Search Documents

By Shadia J. Ikhmayies

SnO2:F/CdS:In bilayers were produced by the spray pyrolysis technique on glass substrates. The structures were characterized by recording and investigating their transmittance curves, I-V plots, X-ray difractograms (XRD) and by observing their scanning electron microscope (SEM) images. From the I-V plots it was found that the SnO2:F forms an ohmic or quasi-ohmic contact with CdS:In. XRD patterns show the polycrystalline nature of the films and show that there is a small shift in the position of the (200) line of SnO2:F without the appearance of new peaks. The morphology of the structures are compared with those of SnO2:F alone and CdS:In alone on glass substrates.

Jan 1, 2009

By Tadafumi Adschiri

"Supercritical water can provide an unique reaction atmosphere for synthesizing metal oxide nanoparticles. Due to the drastic change of properties of water around the critical point, including density, dielectric constant and ionic product, the reaction phase with O 2 or H2 gas and the reaction rate and equilibrium can be varied to synthesize new materials or define particle morphologies. In this work, hydrothermal crystallization experiments are performed with several types of flow apparatus that allow convenient manipulation of variables such as temperature, pressure, and residence time. Key features in the flow modes and material preparation are discussed. The proposed supercritical hydrothermal synthesis method has the following desirable features: i) nanoparticles can be produced, ii) morphology of the produced particles can be controlled with small changes in pressure or temperature, and iii) a reducing or oxidizing atmosphere can be applied by introducing oxygen or hydrogen or other gases. An overview of this method is given for functional material synthesis of significant industrial interest including barium hexaferrite magnetic particles, YAO/Tb phosphor fine particles and lithium cobalt fine crystals.IntroductionHydrothermal crystallization, a method of metal oxide formation from metal salt solutions, is typically used at temperatures ranging from 373 K to 473 K. We are developing a new process for hydrothermal crystallizations that uses temperatures in the range of 673 K to 723 K, which is just above the critical temperature of water1 • 8 • In this work, we refer to this process as supercritical hydrothermal synthesis. The supercritical state of water allows one to vary reaction rate and reaction equilibrium by shifting the dielectric constant and solvent density with pressure and temperature. From of our research on material production in supercritical water, we have identified the following specific features of the supercritical hydrothermal synthesis method: (i) ultrafine particles can be produced, (ii) morphology of the produced particles can be controlled to some extent with pressure and/or temperature, and (iii) a homogeneous reducing or oxidizing atmospheres can be provided by introducing gases, such as O 2, H2, H2O 2• and so on.1"

Jan 1, 2000

By Carla Lupi, Alessandro Pescetelli

"Spent lead battery recycling still shows few weak points in the achievement of a 100% recycling of different waste matters and by- products arising from the recycling process. Some of said problems are dealing with aqueous streams outgoing the recycling plant, and more particularly, a) the waste waters discarded from the breaking and separation unit, b) purification of the spent electrolyte drained from waste batteries and upgrade to a quality compatible with full re-use by the batteries’ manufacturers, c) purification of the mother liquors discarded in the sodium sulfate crystallization process so to produce a salt of commercial grade. All of the above listed problems have been satisfactorily overcome applying an electrochemical process that, through different process conditions and parameters, is able to remove the harmful impurities that hinder the successful commercialization of such by products, or, at least, that can avoid heavy and expensive treatment plant and operation.IntroductionAlmost 100% of commercial lead and lead alloys produced by secondary lead plants is recycled to the new lead accumulators manufacture. The other by-products and residues produced through the lead recycling process may be classified into two groups:a) matters reusable in the new accumulators production processb) matters produced as a result of various reagents and additives used in the recycling process, to be sold to different market sectorsQuality and saleability of by-products are significant points for the economics of the secondary lead plant operation, because, if said by-products are not saleable, they are just wastes, so offsetting potential revenues, and, at the same time, adding a heavy burden to operating cost, like disposal cost [1]. When looking at a typical, modern lead scrap batteries recovery cycle, it is quite evident that we are still rather far from dealing with a waste-less technology (fig.1).The group a) includes 3 by-products produced through the breaking process: among those matters the polypropylene only usually reaches a standard quality suitable for sale to lead manufacturing sector or to other sectors as well. The other two by-products, electrolyte and separators, do not still reach, through a viable and effective regeneration process, a quality standard sufficient for their re-use in the lead batteries sector ."

Jan 1, 2008

By A. MacRae

Campaign life of the converting furnace has been limited by break-outs through the hearth and walls. Throughput of concentrate has increased by 60% since start-up of the copper operations in 1981. The Furnace Integrity program was initiated at Kidd in 1993 to improve the reliability and safety of the smelting-cleaning-converting furnace line. The converting furnace is undergoing a series of upgrades to overcome severe refractory wear to the roof, walls and hearth. A recent shut-down was held in March 1997 to implement improvements to the roof, walls and slag outlet. Wall modifications included a new upper shell, wall coolers which can be supported during a shut-down from outside of the vessel, and an increase in the number of cooling blocks. Improvements to the roof included increased cooling, a novel brick/cooler suspension system, and roof compression for gas tightness. Design is currently underway to deepen the refractory hearth, to decrease hearth erosion and increase resistance to flotation.

Jan 1, 1998

By Igor Zh. Bunim, Valentine A. Chanturiya, Alexey T. Kovalev, Irina A. Khabarova, Elizaveta V. Koporulina

This paper presents new theoretical and experimental data on possible mechanisms for the formation of micro- and nanophases on the surface of sulfide minerals un der the effect of high-power nanosecond electromagnetic pulses (HPEMP). The gas outflow from nanosecond breakdown channels of sulfide minerals under the effect of HPEMP is considered, with allowance for the condensation of iron vapors. The condensation of matter in an outflowing jet is shown to be an effective mechanism for structureal and chemical transformations of sulfide surfaces. It is established that electrode potential of pyrrhotite is moved together in the negative party owing to formation of iron oxides (hydroxides) and iron sulfates by HPEMP, that provides decrease of xanthate sorption and reduction flotation extraction of this sulfide, whereas electrode potential of pentlandite gets more positive values at the expense of additional formation of element sulfur, that causes increase of xanthate sorption and, as a consequence, increase of nickel sulfide extraction.

Jan 1, 2012

By B. J. Scheiner

The presence of organic materials in gold ores interferes with gold extraction by cyanidation. The carbon contained in the ore has been shown to adsorb gold cyanide complex from solution. Removal of the carbon content by roasting or chemical oxidation prior to cyanidation results in gold extractions of 85 to 95%. This paper discusses how the mineralogy of the carbonaceous gold ores affects gold recovery by cyanidation. It also discusses the advantages and disadvantages of roasting and chemical treatment to render the ore amenable to cyanidation.

Jan 1, 1987

By Issa S. AI-Kharusy

Oxidation/reduction (REDOX) alloy media, as used in wastewater treatment, is founded on the exchange of electrons. Because of this electron exchange, many contaminants are converted to harmless components which require no further treatment. Other types of contaminants are removed from the waste stream by electrochemically bonding to the alloy medium. This paper discusses the REDOX reactions, the role of the alloy medium in various treatment processes, and describes specific applications of REDOX alloy media for the removal and minimization of waste. The characteristics and handling of spent treatment media is also reviewed as a further consideration in waste minimization.

Jan 1, 1996

By Jesse White, Arlin Olson

"An Engineering Scale Technology Demonstration (ESTD) unit utilizing the THOR fluidized bed steam reforming technology was built and operated by Hazen Research, Inc. for the purpose of denitrating and solidifying various Department of Energy (DOE) radioactive tank waste surrogates into granular products. The ESTD offered the opportunity to investigate the operational characteristics of two fluidized beds in series to test process system designs such as those for fluidization, feeding, and product collection. Operational characteristics that were evaluated included bed attrition rate, particle growth, and elutriation; and the effects that variations in process parameters (e.g., fluidizing gas flow rate, feed composition, feed injection method, and gas distributor design) had upon these characteristics were observed. Testing of the process systems on this scale allowed for design changes to be made where the cost in time and money were significantly less by comparison to those same modifications being made on the commercial scale.IntroductionFluidized bed steam reforming (FBSR) offers a moderate temperature (620-750°C) continuous method by which various liquid wastes can be processed irrespective of whether they contain organics, nitrates, sulfates/sulfides, chlorides, fluorides, volatile radionuclides or other aqueous components. The FBSR technology has exhibited the potential to process these wastes into either a carbonate or crystalline ceramic (mineral) granular product.Pilot scale testing was performed using the THOR Treatment Technologies, LLC (ITT) FBSR process, as it offered the opportunity to evaluate multiple aspects in an environment more conducive to experimentation. Process changes and system modifications could be made faster and with less cost impact as compared with changes to an assembled commercial plant. These aspects include verification of process chemistry and kinetics, evaluation of materials of construction, equipment sizing and design, and the interactions of the systems. Evaluation of process chemistry allowed for the verification of thermodynamic and kinetic models, and was used in conjunction with these models to improve the database and modeling assumptions. It also allowed for the reevaluation of data from earlier bench scale testing with the opportunity for long-term operations. These long-term effects may include the buildup of one or more elements that results in the formation of eutectics leading to the destabilization of a fluidized bed, or the shift in particle size as a result of attrition or agglomeration. The pilot plant also provided an environment to evaluate materials of construction."

Jan 1, 2014

By H. Kandemir

An experimental study of the bacterial oxidation of naturally occurring high-purity sulphide minerals (FeS2, Fe1-xS, Cu5FeS4, ZnS) is presented using a mesophilic strain of T. ferrooxidans. As well as metal analyses and solution pH, partitioning of sulphide sulphur into elemental sulphur and sulphate has been monitored as a function of leach time. Partially oxidized sulphide substrates have been characterized, at regular time intervals, by X-ray diffraction methods and extracellular organic compounds reporting into leach solution .have been identified by thin layer -chromatography.

Jan 1, 1985

By Takahiko Okura

Japanese non-ferrous industry introduced large-scale smelting plants along seashores for overseas concentrates with increasing demand of metals around 1970s. Although serious environmental pollution became obvious, with economic growth, the industry got rid of pollution by installing new processes and improving operation technologies. At present, over 99.8% of sulfur input to smelters is fixed as stable compounds. Through those decades Japan had steep rises of oil prices, sudden change of exchange rate, and inadequate treating charges, we were faced to consider the closure of smelters. The industry has survived by increasing productivity, saving energy and reducing manpower. Furthermore the industry made great effort to recycle valued metals from scraps and wastes for the resources-recycling society. Academic research also contributes to support these individual technologies. Thus the industry has fostered world-acclaimed technologies in terms of efficiency and energy conservation. This paper presents technology development and environmentally-benign sulfide smelting processes.

By Chen Ya

Layered LiMn0.5Ni0.3Co0.2O2 was prepared from Mn(NO3)2, Ni(NO3)2, Co(NO3)2 and LiOH by co-precipitation and solid state reaction. XRD, C-V and galvanostatic charge-discharge methods were used to examine the structural and electrochemical characteristics. The LiMn0.5Ni0.3Co0.2O2 delivered a high discharge capacity of 167 mAh/g between 2.5 and 4.3 V with excellent cycling stability.

Jan 1, 2006

By Ian G. H. du Preez

It is illustrated how differences in the basic chemistry of individual metal ions can be exploited to develop new or improved separating agents. Factors like coordination number preferred by the specific metal ion, the degree of coordinate saturation reached by the metal ion and its relation to the phase transferability of the complex species, kinetic factors as opposed to thermodynamic factors controlling the success of the separation, the nature and type of the donor atom employed in a separating agent in relation to the preferences of the metal ion, the significance of stereochemical factors and the hydrophobicity of the media are some of the important factors which are discussed and applied for the development of pa1ladiwn(TI) and nickel(TI) specific separating agents, respectively.

Jan 1, 1999

By Irina V. Sokol

Alloyed steel chips and swarf formed during metal processing are looked upon as additional raw material In metallurgycal production. The manuscript presents some new methods for steel waste chips and swarf cleaning. One of them Is swarf and steel chips cleaning In ethylene tetrachloride with ultrasonic assistance and following, solvent regeneration. Thermal cleaning of waste chips and swarf provides exit gas products utilization. Catalyst Influence of metal surface on the process of thermal decomposition of liquid hydrocarbons during cleaning process has been studied. It has been our experience that the efficiency of metal waste cleaning technique depends on the storage time of the swarf. Waste chips and swarf cleaning procedures presented in the manuscript have been proved economically advantageous and environmentally appropriate.

Jan 1, 1995

By Lionel Ryan

In 1996, the Dominican Republic operation of Falconbridge (Falcondo) developed a 5-year Process Control Plan in conjunction with the corporate Process Control group located in Sudbury, Ontario, Canada. This plan was further refined into an analysis of the areas of the highest potential economic return for the company with the reduction shaft furnace operation being the most promising. Historically, the reduction plant, which comprises 12 shaft furnaces, has been the bottleneck of ferronickel production. Since 1996 there has been a history of control development, and the current status is that all 12 furnaces are using advanced model-based multi- variable predictive control. The combination of advanced process control (APC), improved control system performance and improved process information management has resulted in an increased throughput of 6% per shaft furnace and a reduction in operating costs of 4.5 US cent/lb of Ni. This paper reviews some of the major milestones that have been achieved in this development Keywords: Advanced Process Control; Model Based Predictive Control; Connoisseur, Reduction Shatt Furnace; Nickel Laterite Ore; Ferronickel; MonitorMV

Jan 1, 2004

By Manuel Zamalloa

The outstanding metallurgical performance of the Noranda continuous converter (NCv) in operation since November 1997 has allowed the company to meet production and environmental targets. This achievement positions this new technology as a strong alternative continuous converting technology for copper production. Knowledge of slag chemistry has been important in this respect. The purpose of this paper is to discuss the effect of key parameters including temperature, oxygen potential, slag composition and levels of copper oxide in slag on the conditions leading to magnetite precipitation, as well as on the conditions affecting the liquidus ranges of NCv slag. The above variables are evaluated using industrial data and thermodynamic predictions. Practical implications of customizing operational fluxing procedures to determine optimum operating windows are also discussed.

Jan 1, 1999

By S. M. McDeavitt

Waste form alloys are being developed at Argonne National Laboratory for the disposal of remnant metallic wastes from an electrometallurgical process developed to treat spent nuclear fuel. This metal waste form consists of the fuel cladding (stainless steel or Zircaloy), noble metal fission products (e.g., Ru, Pd, Mo and Tc), and other metallic wastes. The main constituents of the metal waste stream are the cladding hulls (85 to 90 wt%); using the hulls as the dominant alloying component minimizes the overall waste volume as compared to vitrification or metal encapsulation. Two nominal compositions for the waste form are being developed: (1) stainless steel-IS wt% zirconium for stainless steel-clad fuels and (2) zirconium-8 wt% stainless steel for Zircaloy-clad fuels. The noble metal fission products are the primary source of radiation in the metal waste form. However, inclusion of actinides in the metal waste form is being investigated as an option for interim or ultimate storage. Simulated waste form alloys were prepared and analyzed to determine the baseline alloy microstructures and the microstructural distribution of noble metals and actinides. Corrosion tests of the metal waste form alloys indicate that they are highly resistant to corrosion.

Jan 1, 1996

By Dewei Zhu

A general purpose computer model for describing the transport phenomena and resulting rate of deposition in Chemical Vapor Deposition (CVD) processes has been described. Partial differential equations describing the conservation of mass, momentum, energy and chemical species are solved by a computer program employing a finite volume method. The program allows for multiple chemical species and natural convection effects. In this paper, the deposition of silicon by the reaction of silicon tetrachloride and hydrogen in a vertical stagnation flow reactor with rotating substrate has been considered. The effects of reactor pressure and substrate rotation speed on the rate and uniformity of deposition have been studied. The predicted rates of silicon deposition along the substrate are in reasonable agreement with experimental results found in literature. The model can be used as a tool for design optimization of such reactors.

Jan 1, 1990

By Maria G. Alves, Alexandre M. Stumbo, Francisca M. A. Pinheiro, Jonas Alexandre, Sergio N. Monteiro, Valdo da S. Marques, Paulo R. N. da Silva

"Brazil is among the few countries with potential for developing all sources of renewable forms of energy. In particular, the country is leading the world efforts of substituting petroleum based fuels for biofuels, such as ethanol and biodiesel. Most of the Brazilian petroleum, which has now achieved self sufficiency, is extracted from offshore wells located at the north region of the state of Rio de Janeiro. In view of the future depletion of petroleum, the State University of the Northern Rio de Janeiro (UENF) has created a Center for Alternative Energies (NEAL) to carry out R&D programs on renewable forms of energy. Today, the main project of the NEAL/UENF is a model park for generation of renewable forms of energy. The objective of this work is to present the structural concept of the park and discuss its contribution in terms of scientific, technological, economical and environmental benefitsIntroductionEnergy is presently a key issue in the world agenda for sustained development and environmental protection. It is of common agreement that the existing status of increasing use of fossil fuels, mainly petroleum, natural gas and coal will not only cause depletion of these resources with a consequent elevation in price but also climate changes, especially global warming. In fact, the humankind may be already facing an irreversible situation of climate alterations as well as reduction of conventional sources of energy. The worse predictions foreseen by specialists, still for this coming century, are dramatic disasters due to catastrophic weather in association with a profound energetic crisis. This scenario may, however, be avoided by actions that could effectively tackle the core of the problem. These actions have been suggested and discussed by scientists and leading authorities, especially in international symposia [1-3]. In particular, the Kyoto Protocol proposed goals for reduction of greenhouse gas emissions as well as a mechanism of carbon credits to allow for decreasing CO2 content in the atmosphere without affecting industrial production [3]."

Jan 1, 2008

By Hideyuki Itou

Municipal wastes are mainly incinerated in Japan. Both bottom ash and fly ash from the incineration treatment are smelted recently to decrease the volume. Direct smelting of municipal wastes is also becoming popular. The smelting treatment generates fly ash which contains concentrated heavy metals such as Zn, Pb and Cu, and the harmfulness is causing concern. The smelter fly ash is mainly landfilled after stabilization. An effective treatment process of the smelter fly ash is required to recover the metals. For the treatment process, an application of chloridizing volatilization technique is considered. Chloridizing volatilization experiments were carried out to determine the effects of various factors on the volatilization behaviors in this study. A pretreated ash was mixed with a main raw material which mainly consists of hematite. Calcium chloride water solution was added into the mixture. The mixture was pelletized, dried and used as samples for the volatilization experiments. The sample was placed in the reaction tube heated in an electric resistance furnace. 5%02-95%N2 gas with controlled humidity was introduced into the reaction tube. Effects of humidity in the carrier gas, addition of calcium chloride and mixed ratio of the ash to the main raw material were investigated on the volatilization of Zn, Cu and Pb. To determine the volatilization behavior, samples were taken from the furnace at specified temperatures on the heating stage. In addition, experiments at specified holding temperatures for 15 minutes with shortened heating time were conducted. The two series of experiments revealed the effect of heating temperature on the volatilization behavior of Zn, Cu, Pb and Cl.

Jan 1, 2006

By Andrey Dmitriev

The solution of set of equations for the bottom zone presented by a condition of a thermodynamic equilibrium, namely, an equilibrium constant of wustite reduction by carbon oxide, material and thermal the balances, supplemented by the equation of the heat balance for the top zone, allows to calculate the base indices of blast furnace smelting. The calculated indices are extreme accessible at the given parameters of charge and blast. Application of actual degrees of the use of gas instead of equilibrium allows the calculations of actual indices of the blast furnace smelting process.

Jan 1, 2006