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By I. H. Gundiler

Sandia National Laboratories (SNL) is tasked to support The Department of Energy in the dismantlement and disposal of SNL designed weapon components. These components are sealed in a potting compound, and contain heavy metals, explosive, radioactive, and toxic materials. SNL developed a process to identify and remove the hazardous sub-components utilizing real-time radiography and abrasive water-jet cutting. The components were then crushed, granulated, screened, and separated into an aluminum and a precious-and-base-metals fraction using air-tables. Plastics were further cleaned for disposal as non-hazardous waste. New Mexico Bureau of Mines & Mineral Resources assisted SNL in investigation of size- reduction and separation technologies.

Jan 1, 1995

By Linfeng Zhou, Rong Sun, Guanghui Li, Zhiwei Peng, Tao Jiang

The effects of microwave roasting on separation of rhenium (Re) and molybdenum (Mo) from a molybdenite concentrate have been investigated based on evaluation of the heating characteristics of the concentrate in the microwave field. The results show that a variety of operating variables, namely microwave power, sample weight, sample geometry, roasting temperature, roasting time and atmosphere significantly impact on the volatilization rates of Re and Mo. The optimum conditions for Re-Mo separation are microwave power 1300 W, sample weight 20 g, sample geometry pellets, temperature 600 oC, time 1.5 h, and atmosphere 20%O2. Under these experimental conditions, the volatilization rate of Re reaches 88.12%, while that of Mo is just 5.15%. Microwave-assisted roasting provides an alternative route to separating Re and Mo from molybdenite concentrate.

Jan 1, 2016

By Pengcheng Li, Wei-Tong Du, Yu Wang, Gang Wen

Carbon dioxide could be utilized as a weak oxidant and a kind of coolant to oxidize elements, meanwhile, helping control the temperature during the converter vanadium extraction process. However, the optimum content of CO2 and the cooling effect of CO2 at low content have not been reported. In this study, experimental research based on the influence of different CO2 contents from 0% to 25% injected to the vanadium-containing hot metal was carried out, as well as contrast experiments of O2-N2 mixed blowing. The results indicated that the optimum content of CO2 was 15%. Under the optimum condition, the oxidation of [C] was the lowest and the oxidation rate of [V] was 96.9%, while the temperature was also lower than the O2-N2 mixed blowing. This paper provide a potential property for utilizing CO2 during the converter vanadium extraction process.

Jan 1, 2016

By Fang Wu

The paper designs an extraction flow for the total recovery of nickel and cobalt and removing magnesium simultaneously from the cadthodic materials of the spent hydrogen-nickel and cadmium-nickel batteries. The separation of Co, Ni and Mg though P507 extraction .The extraction equilibrium pH is 4.5~5.0, ßNi/Co is 140~180, and ß Ni/Mg is 20~25; nickel and magnesium are scrubbed in two steps, in which the equilibrium pH of nickel and magnesium scrubbing is controlled at 5.0±0.1 and 4.4±0.1 respectively. The stepwise scrubbing technique is adopted to remove 94.5% of magnesium and to recover 99.45% of nickel and 95.35% of cobalt. During the integrated extraction and precipitation process the total recovery fraction of nickel and cobalt are 99.99% and 99.95%, and the recovery fraction of magnesium is 94.02%.The recovered NiSO4 and CoSO4 solution are enriched and crystallized.

Jan 1, 2009

By M. D. Strachan

Technical & Procurement Services Limited (TECHPRO) in Ashford, Kent, UK, have been appointed as Project Managers for the major rehabilitation of the Copper Smelting complex of Nkana Division, Zambia Consolidated Copper Mines Limited, (ZCCM) Zambia. In outline, the overall scope covers three main areas: a) Transfer and implementation of new technology into Zambia for the production of primary copper. b) Replacement of gas collection and gas treatment circuits to guarantee high quality feed to the acid plants. c) Completion of a number of minor projects in the copper smelter and associated utility plants to complement changes in the primary smelting technique. This paper describes the Project Management methodology and style used by TECHPRO to tackle typical problems that arise in retrofit projects of this type. Reference is made specific aspects of the smelter projects to illustrate solutions to the problems. The subjects. addressed highlight the complexities not only of having a -Client 5,000 miles from the Project Office, but also the difficulty of co-ordinating and controlling the performance of min sub-contractors who are also geographically distant.

Jan 1, 1991

By Vaughan R. Voller

"The wide range of length and time scales found in solidification processes are outlined and discussed. Methods for Direct Microstructure Simulation (DMS) are introduced. Key features in sharp interface and phase field models are presented. Concepts in micro-macro solidification modeling are covered. Basic details of microstructure and segregation models are provided. A description of a recent segregation micro-macro model is presented in detail.IntroductionA solidification process involves the containment of a liquid region, which, due to cooling, transforms over time to form a fully solid product. The development of the solid microstructure and the segregation of solute components during this transformation are controlled by phenomena that occur across a wide range of length and time scales. A ""successful"" model of a given solidification process needs to account for these phenomena. Standard models of solidification employ a discrete grid of node points and associated volume elements in the special domain, with a discrete time step to track the transient changes of nodal values, describing the composition and microstructure. Through the use of such models significant progress has been made towards a complete understanding of solidification process and phenomena (see the conference proceedings in Refs [1-9]). As solidification models become more sophisticated, however, they all run into the problem of resolving the full range of disparate space and time scales.Two approaches can deal with this problem1. Direct Microstructure Simulation (DMS) where the grid size and time step are chosen to scale with the smallest length and time scales of the given problem.2. Micro-macro modeling where the grid size and time step scale with the macroscopic process scale and phenomena at smaller scales are accounted for via sub-grid modeling and volume averaging.Currently full DMS of solidification is beyond the reach of available computer power and the application and development of micro-macro models is an important and critical research area."

Jan 1, 2001

By N. B. Gray, I. F. Taylor

"Gas injection to promote chemical reactions or mixing is a feature of many metallurgical processes. Often the aim of gas injection is to bring about a chemical reaction between the gas and liquid but most of the past physical and mathematical modelling work has ignored the influence of such reactions. In the work reported here, cold model studies have been conducted in which gas reacts with the liquid into which it was injected. The rate of liquid mixing has been measured as an indication of the mechanical energy transfer. It has been found that gas generated chemically within the liquid is significantly less effective at promoting mixing than the equivalent volume of inert gas. The relative ineffectiveness of chemically produced gas is thought to be due to smaller bubble sizes in comparison to the inert gas case. Small bubbles characteristic of chemically generated gas move with low slip velocities relative to the liquid and lead to different turbulence generation mechanisms.IntroductionIn processes such as steelmaking, copper conversion, bath smelting and ladle steel finishing gas is injected into liquid metal where it reacts chemically or simply serves as a source of agitation. An understanding of fluid flow phenomena in such situations is an essential pre-requisite to the calculation of process intensity and the optimisation of vessel productivity. Traditional physical cold modelling approaches to prediction of liquid flow in such situations are now often augmented by the techniques of computational fluid dynamics. Even with the availability of numerical modelling techniques cold physical models continue to have an important role for validation because it is generally difficult to obtain quantitative data from high temperature processes.Almost all previous cold modelling work has been based on the injection of an inert gas into water or some other non-reactive liquid. Such models do not include the significant increase in gas volume inherent in some processes. For example the oxidation of carbon in steelmaking leads to a twofold increase in molar gas flux through the reaction:"

Jan 1, 1996

By Soumendra Basu, Uday Pal, Yang Yu, Srikanth Gopalan, Karl Ludwig, Deniz Cetin, Jacob Davis

"A limiting factor for Solid Oxide Fuel Cell (SOFC) performance is the oxygen reduction reaction (ORR) at the cathode surface. Changes in the surface composition and structure on annealing at 800°C has been studied, since these can influence the ORR. Idealized single crystals of cathode materials La0.8Sr0.2MnO3 (LSM) and La1-xSrxCoyFe1-yO3 (LSCF) were grown as heteroepitaxial thin films on lattice matched single crystal substrates. Changes upon heating the films to operating temperature and pressures were characterized using various synchrotron x-ray techniques. Total Reflection X-ray Fluorescence (TXRF) measurements, which probe compositional changes, were made at high temperature in real time. The LSM surfaces were found to develop manganese enrichment when heated. Highly strontium doped LSCF were found to develop strontium-rich surfaces. HArd X-ray PhotoElectron Spectroscopy (HAXPES) was used to investigate the electronic structure of the materials. Highly strontium doped LSCF precipitates a surface strontium phase that contains both oxide and carbonate contributions.IntroductionSolid oxide fuel cells (SOFCs) are chemical to electrical energy conversion devices that could potentially reshape how energy demands are fulfilled. SOFCs have a potential efficiency over 70%, fuel flexibility, low emissions, and low degradation over long time scales. Commonly, SOFCs are operated at high temperatures (above 800°C). At these temperatures expensive housing is needed to contain an operating stack as well as coatings to contain the oxidation of the metallic interconnects. Lowering the temperature of an operating device would allow for more conventional materials to be used, thus lowering overall cost. Understanding the reaction kinetics of the oxygen reduction reaction at the surface of the cathode is vital to designing a system that will perform well at lower temperatures. A commercialization goal is to reduce operating temperatures without sacrificing performance.In order to exploit the advantages of SOFCs, an understanding is needed of the surface chemical states of cations on the surface of the cathode and how this relates to the oxygen reduction reaction (ORR):"

Jan 1, 2014

By Xirneng Zhu

The electrochemical behavior of Pittsburgh and Illinois coal pyrite in basic and neutral borate/sulfate solutions was investigated. In the transpassive region, aggressive oxidation of pyrite occurred. The reaction products in this region were Fe(III) oxide, sulfate ion and partially oxidized sulfur intermediates. The formation of sulfur and polysulfides was identified by in-situ Raman spectroscopy. The growth kinetics of the reaction product film, resulting from transpassive oxidation of coal pyrites, were studied using chronoamperometry measurement with both stationary and rotating disk electrodes. The reaction rate was well correlated by a paralinear rate equation. The effects of electrode rotation speed, solution pH and temperature were examined. The kinetics were compared to those for mineral pyrite.

Jan 1, 1994

By Yoshinao Kobayashi

he removal of oxygen from titanium and zirconium is important for use in application because it significantly affects the mechanical and physical properties such as ductility and toughness. However, thermodynamic properties of oxygen in molten titanium and zirconium have not been clarified and the effective deoxidation process of molten titanium and zirconium has not been established. In this study, the standard Gibbs energy of reaction of oxygen and yttrium in molten titanium and zirconium have been measured by a chemical equilibrium technique. Molten titanium, zirconium, and their alloys with aluminum were equilibrated with a Y2O3, A12O3, or Zr02 pellet in a cold crucible. The results are summarized as follows:

Jan 1, 2000

By Y. Pokhvisnev, S. Vandariev, A. Yatshenko-Juk, V. Valavin, V. Romenets

The technology of the liquid-phase reduction process known as Romelt was developed in the Moscow Institute of Steel and Alloys in 1979. The pilot plant was constructed at the Novolipetsky Steel Works (Russia) in 1984. Investigations into processing zinc-containing blast oxygen furnace dust and slag from the Lead and Zinc Works at the pilot Romelt plant proved the perspective of using this technology for processing zinc and lead-containing materials. In this article, the description of Romelt technology, basic technological information of trials at the Romelt plant using zinc-containing materials, compositions of charging materials, metal, slag, gas and dust are presented. The influence of flue gas composition on the composition of zinccontaining dust is shown.

Jan 1, 2000

By He De-wen

The municipal solid waste is a by-product of the daily life of urban residents. The quantity and ingredients of municipal solid waste has exceeded the current management and disposal ability, which has done a great harm to municipal environment and sanitation quality and threatened people?s health. On the basic of analysis on the amounts and main elements of municipal solid waste of Changsha City, the sanitation landfill, incineration, composting, reclamation and utilization technology of household waste were compared specifically in this paper. Based on the concrete conditions of Changsha City, the paper has proposed a disposal proposal combined with reclamation and landfill of municipal solid waste of Changsha City, and the environmental benefit, social benefit and economical benefit of the prepared processing routes were also analyzed in the paper.

Jan 1, 2009

By A. G. Merma

In this work, the electrocoagulation technique was studied in order to treat chemically stabilized concentrated oil-water emulsions. This study was mainly focused on the effects of operating parameters such as initial pH, current density, reaction time, electrode distance and inlet concentration on the separation of oil as measured by the chemical oxygen demand -1(COD) method. The synthetic emulsion was prepared from Shell - Talpa 30 oil (3g.L-1) and sodium dodecyl sulfate (1.0 g.L), having a Zeta potential around -70 mv at pH 8.7. The process was carried out in an electrocoagulation cell with a set of four parallel monopolar electrodes. This set consisted of two aluminum plate anodes and two 316L stainless steel plate cathodes. Kinetic curves showed that the electrocoagulation process exhibits three phases: (1) an initial phase, where the COD did not decrease because the solution had not reached the minimum amount of dissolved aluminum required to cause the break-up of the emulsion, (2) a reactive phase during which COD decreased due to possible agglomeration of the precipitates and (3) a steady-state phase where the COD did not change. The results showed that the period to reach the reactive phase decreased as the current density increased and the pH values decreased.

Jan 1, 2009

By Cem Colakoglu

In this study, nickel containing iron alloys were produced by carbothermal reduction of lateritic nickel ores obtained from Manisa - Caldag region of Turkiye in order to investigate the reaction mechanism of nickel and cobalt. In the experiments, the lateritic ore containing 1.58 wt.% Ni and 0.12 wt.% Co was calcined in a semi-pilot scale rotary furnace at 1100°C for 1 hour. Then, a mixture of calcined ore and metallurgical coke was reacted in sintered alumina crucibles using a graphite resistance tube furnace at different time (0- 60 min) and temperature (1500-1600°C).

Jan 1, 2009

By Youn-Bae Kang, Jong-Jin Pak, Min-Kyu Paek

The critical evaluation and thermodynamic optimization of Mn-Si-C and its sub-binary systems have been carried out over the whole composition range from room temperature to above the liquidus temperature. The solution properties of the liquid systems have not been clearly described because the liquid solution exhibits a high degree of short-range-ordering. In order to predict the thermodynamics of the liquid solution, the liquid phases were optimized by the modified quasichemical model. The model parameters of the solid phases were also optimized by the compound energy formalism to best reproduce the phase diagram and important thermodynamic properties in Mn-Si-C system. Using the model parameters, various thermodynamic calculations were carried out. The present database will be a part of larger thermodynamic database for the ferromanganese alloy database.

Jan 1, 2014

By A. E. Torma

In recent years the copper industry has gained considerable economic stability. An essential part of this industrial wealth is attributable to the successful application of bio-mediated heap and dump leaching techniques in the recovery of copper from low-grade resources. This study evaluated the leachability of a chalcopyrite conlentrate using naturally occurring mixed culture of predominantly Thiobacillusferrooxidans and Thiobacillus thiooxidans. For the effects-of pulp density, the overall reaction rate constant (k) and the order of reaction (n) have been determined to be 1.93 h-1 and 1.36, respectively. Cyclic voltammetric measurements revealed that intermediate reactions are involved in the chalcopyrite oxidation. Using the Price approach, it was shown that the dissolution of chalcopyrite is solid state diffusion controlled.

Jan 1, 1992

By Patrick R. Taylor

A novel method for Chemical Vapor Infiltration (CVI) using plasma technology is proposed, Plasma Enhanced CVI (PE-CVI). Due to the low rates at which CVI is currently performed, the use of plasma as a source of heat may be considered to be a faster and less expensive production method. Precursors fed in the hot region of the plasma gas are completely vaporized and forced by the same flow through a porous preform where it condenses as a new material. In this research, silica and methane where used as precursors to form SiC/on a / graphite felt (preform). To enhance the infiltration process, vacuum was used to increase the flow through the preform. Characterization of infiltrated graphite was perfontied using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). A uniform distribution of Sic was observed along the felt with only twenty minutes of infiltration process, yielding a 178% increment in weight.

Jan 1, 1997

By Toshihide Takenaka

The management of radioactivated stainless steel from a terminated nuclear reactor will become an important subject in the near future. The separation of the elements in stainless steel should be effective to reduce the management labor. In this study, the separation of the elements in stainless steel by an electrorefining tcchnique was investigated in an aqueous solution. The electrochemical reactions of the elements in stainless steel werc studied by voltammetry and potentio-static electrolysis was carried out. A stainless steel anode was dissolved electro-chcmically with good anodic current etliciency in a chloride solution. The residue, where Ni was concentrated, was found on the anode after electrolysis. The electrodeposit in a stainless steel cathode consisted mainly of Fe and Cr and the Ni content in it was less than 0.5wt% under suitable condition. It is concluded that an electrorefining technique is effective for the separation of the elements in stainless steel.

Jan 1, 2003

By Ting Liu, Qian Li, Peng Deng

The wastewater containing Hg2+ and Pb2+ does great harm to the environment and human bodies. Traditional wastewater treatment cannot fundamentally put a stop to heavy metals pollution for producing secondary pollution. In this paper, Hg2+ and Pb2+ in wastewater were removed and recovered by sulfide precipitation- flotation. Sodium sulfide was used as precipitant and butyl ammonium aerofloat was used as collector. Results indicated that Hg2+ and Pb2+ could be reduce to less than 0.03mg/L and 0.16mg/L respectively by both coprecipitation- floatation and fractional precipitation- floatation. In these two methods, fractional precipitation flotation could not only remove Hg2+ and Pb2+ from wastewater, but also could recover mercury and lead effectively. The infrared spectrograms showed that the adsorption between butyl ammonium aerofloat and mercury precipitate or lead precipitate is chemisorption.

Jan 1, 2015

By Eric J. Grimsey

Steady state Excel models for a copper flash smelter and an iron blast furnace are used to enhance the teaching of pyrometallurgical smelting principles within a fourth year level process engineering unit delivered at the Western Australian School of Mines. A lecture/workshop approach has been adopted in which student teams undertake process simulation assignments that illustrate the multifaceted responses of process outputs to variation of inputs, the objectives being to reinforce their understanding of smelting principles. The approach has proven to be popular with students, as evidenced by the consistently high ratings the unit has received through student feedback. This paper provides an overview of the teaching approach and process models used.

Jan 1, 2014