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By F. Elgersma

A high purity electrolysis solution is essential for hydrometallurgical zinc winning processes. For this reason ferric iron containing compounds such as jarosite are precipitated as iron and impurity collector during the calcine leaching. Jarosite thus forms a chemical waste and creates environmental problems. This research contributes to the development of a wet jarosite treatment process, where less contaminated jarosite is produced which can act as an iron source. The present work studies jarosite precipitation kinetics and the uptake of zinc cations in batch and continuous experiments. The distribution coefficient for zinc in continuous experiments is constant for a wide ratio of zinc over ferric ions in the solution. Addition of NH, + ions in batch experiments accelerates the conversion rate equivalent to the driving force increment. Addition of 50,2-ions above the stoichiometric ratio increases the conversion rate less then could be expected from the increase in the estimated driving force. Zinc ions tend to retard the conversion rate. An increasing reaction temperature increases the conversion rate. Below 75 ?C the conversion rate approximates zero.

Jan 1, 1990

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 D. A. Robbins

The Resource Conservation and Recovery Act. of 1976 (RCRA) requires testing of waste materials as part of the determination of whether these materials are classified and managed as hazardous wastes. The adoption of one standard testing procedure and its application to all types of waste materials has stirred much controversy. In the center of this controversy is the appropriateness of this testing procedure in characterizing non-ferrous metal intermediates and slags. The authors have evaluated the relative availability of metals in several types of copper and lead slags as defined by various testing protocols. Also discussed is the relationship between the chemical character of the slag and the availability of metals to leaching and certain metallurgical practices that can influence metals availability.

Jan 1, 1983

By M. Misra

The removal of lead and other heavy metals present in an active US Army small arms firing range soil was evaluated in a pilot scale test program at Ft. Polk, Louisiana. Two different acid based extraction processes in conjunction with conventional physical separation methods were used. Physical separation processes consisting of screening and gravity operations removed most of the coarse lead particulates and slugs. Hydrochloric acid leaching followed by precipitation of lead as hydroxide recycled clean soil containing less than 500 mg/L. total lead and less than 5 mg/L TCLP lead. Lead extraction efficiency with hydrochloric acid was 96 percent. The results of lead removal by physical separation in conjunction with acetic acid leaching were not consistent over the whole test period and the total soil processed.

Jan 1, 1998

By Florian Kongoli

Non-ferrous smelting slags .can contain magnesia, which substantially increases the liquidus temperature. One option to counter this increase is to flux with calcia. In this work, experimental liquidus measurements including new measurements on industrial slags have been compared with a FACT-based thermodynamic model, which predicts the liquidus surface of multi-component iron silicate smelting slags containing both magnesia and calcia. The predictions, which agree well with experimental results, are summarized in both isothermal and non-isothermal diagrams to give a quantitative description of the liquidus surface.

Jan 1, 1998

By Robert Hanson, Mayur K. Patel

"Pneumatic conveying pipelines are used throughout a variety of industries, from food processing/packing to power generation plants, as an efficient means of transporting materials between storage and processing points. In general, different phases of pneumatic conveying exist when material is conveyed from point A to point B in a pipeline. This depends on the operating pressure and the material conveyed. Lean phase conveying exists when pipelines are operated at high airflow rates, relatively low pressures, inducing sufficient turbulence for particles to become entrained in the air stream. Thus, particles are conveyed along the pipelines at velocities in the range of IS-2Sm/s. Generally, the initial capital costs for lean phase system is low, however the running costs are high. The opposite is true for dense phase, high-pressure systems. In considering either conveying system, it is important that the rate of erosion of the pipeline be considered when designing such a system, since it is the rate of erosion that dictates the lifetime of components. In general, the high level of erosion occurs for lean phase flows, where high impact velocity contribute substantially to the rate of erosion as well as other processes such as particle breaking, if the particles are friable. This would lead to poor quality of material, not normally desirable. On a positive note, the process of erosion is used in other applications, which benefits from this process, e.g. abrasive guns.The failure, by puncture, of pneumatic conveyor bends in industry causes several major problems. Two of these are: (a) escape of the conveyed product causing health and dust hazard and (b) repairing and cleaning up after punctures necessitates shutting down conveyors, which will affect the operation ofthe plant, thus reducing profitability.The paper reports on modelling strategy used in the development of a modelling framework and the initial validation phases of the models incorporated within. The modelling framework encompasses Computational Fluid Dynamics (CFD) related engineering tools, based on Eulerian (gas) and Lagrangian (particle) approaches, to represent the two distinct conveyed phases, to represent the erosion process which is used to ascertain the lifetime of conveyor bends."

Jan 1, 2001

By Qingyu Deng, Shiwei Ma, Guibao Qiu, Hua Wang

"The flow behavior of the blast furnace slag bearing titanium, like viscosity, play an importance role during the iron-making process with the vanadium-titanium magnetite, which is a very special minerals in Panzhihua, China. The dependency of the viscosity on the chemical composition like TiO2, Al2O3, MgO, binary basicity (CaO/SiO2), temperature, reaction time were studied. The experiments showed that the viscosity decreased with the increase of TiO2, MgO content and binary basicity, and it increased with the increase of Al2O3 content and temperature. The viscosity showed a slight decrease within 60mins’ reaction with graphite crucible, however, it increased rapidly afterwards with the formation of Ti(C, N).IntroductionThe ordinary iron ore has been an essential part of raw materials for vanadium-titanium magnetite smelting in Panzhihua to avoid a series of problems, such as slag thickening, adhesive bond of slag and hot metal, etc. The ratio of vanadium-titanium magnetite has been decreased gradually since 1970s, and has down to about 65% now. However, with the substantial appreciation of price of imported ordinary iron ore, Panzhihua Iron and Steel Group aims to increase the ratio of vanadium-titanium magnetite and decrease the dependence on ordinary iron ore in order to lower the cost of smelting process."

Jan 1, 2012

By Jenq-Gong Duh, Jyh-Wei Lee

"Hard chromizing process is a method for developing a surface modified coating providing wear, corrosion resistance and high temperature surface protection. Two carbon steels with 0.45 wt% and 0.95 wt% carbon contents, respectively, were chromized with pack cementation process at 950'C for 4 and 9 hours, respectively. The phase transformation and microstructure phenomena of chromized coating layer and matrix of two steels were studied with X-ray diffractometer and electron probe microanalyzer. (Cr,Fe)23C6 and (Cr,Fe)7C3 carbides and (Cr,Fe)2N1-x nitride phases were observed on the chromized surfaces. The thickness of chromized layers obeyed the parabolic rate law. The mechanism and diffusional kinetics of the chromizing process were proposed. The diffusivity of chromium in the (Cr,Fe)7C3 carbide phase was calculated using the moving boundary method.IntroductionChromizing process is one of the surface treatment technologies that can produce a chromium contained surface layer with sufficient corrosion and wear resistance on the steel matrix [1-7]. The relatively low cost and no ""line-of-sight"" restrictions are main advantages of chromizing. Adequate bonding strength of these coatings to the substrate was reported [7]. Chromizing process can be classified into soft chromizing and hard chromizing [2]. Soft chromizing is applied to steels containing less than 0.1wt% carbon through which chromium will be diffused. High temperature oxidation resistance improvement is the main purpose of soft chromizing process. On the contrary, the hard chromizing can be applied to steel containing more than 0.3wt% carbon, and very hard chromium nitride and carbide layers will be formed on the surface, which are very resistant to wear, corrosion and temperature [5-7]. In the previous studies on the Fe-Mn-Al-Cr alloy [5,7] and carbon steels [6], the thickness (X) of chromizing layers was analyzed and found the parabolic rate Jaw prevailed:"

Jan 1, 2004

By Maija-Leena Metsiirinta

The behaviour of copper and lead in zinc roasting has been studied in laboratory scale roasting experiments as well as in large scale trials in an industrial fluidized bed, with the background of Outokumpu Kokkola Zinc smelter. Commercial zinc concentrates with a low and high ( up to 3 wt % ) copper content and with a low and high ( up to 3.5 wt % ) lead content were oxidized to various desulphurisation degrees in the fluidized bed to establish the reaction mechanisms and the paths for copper and lead oxidation in the roasting. Influences of the agglomerate size on the roasting kinetics and micro- scale phenomena were also determined. Optical microscopy was used on the calcine and the findings are presented as numerous photographs of the polished cross sections. SEM/EDS techniques were used for analyzing chemically the phases and particle morphologies present in the samples. Computational thermodynamics was applied to the complex phase equilibria occurring during roasting in the agglomerating calcine. A complete oxidation of zinc concentrate with a high copper and lead content requires a careful control of oxygen coefficient in the roasting in order to maintain a stable operation of the fluidized bed. Oxygen coefficient thus seems to have a significant impact on the hydrodynamic stability of the fluidized bed with fine raw materials.

Jan 1, 2003

By Thomas E. Weyand

Prior to 1975, lead-based paints were commonly used in protecting steel structures. Because of the toxic effects of lead on human health and the environment, their use has been significantly reduced. However, problems with these paints persist when they are removed during normal maintenance by pneumatic blasting with mineral abrasives. Technologies are developed to contain the spent abrasive and paint during blasting operations. This paper reports on A study to identify beneficial reuses for the spent blasting material. Nine samples were gathered from different projects within Pennsylvania. The samples were thoroughly characterized with regard to composition, morphology, and EP and TCLP leach test performance. Potential reuse applications will be reviewed with regard to technical adequacy, economics, and environmental constraints.

Jan 1, 1992

By A. S. Rao

In the original roast-leach-electrowin (RLE) circuit at the Chambishi Cobalt Plant, commissioned in 1978, the separation of nickel and zinc from cobalt in aqueous streams was achieved by successive stages of precipitation using lime. However, this technique was not able to meet the increasingly stringent metal quality requirements of customers whilst maintaining acceptable process recoveries. Intensive process development work was carried out and, in July 1988, an ion exchange circuit for nickel removal was commissioned using DOW XFS 4195 resin and for the first time Z.C.C.M. produced high purity cobalt metal containing less than 0.10% nickel. Following further work, a solvent extraction circuit for zinc removal, using DZEHPA, was commissioned in February 1991 in order to enhance cobalt recovery by reducing co-precipitated cobalt losses. This paper outlines the process development, design, commissioning and subsequent operation of these nickel ion exchange and zinc solvent extraction circuits.

Jan 1, 1993

By S Ivanaj

Oxidation of chalcopyrite from a copper concentrate in an electrochemical cell having separate-anodic and cathodic compartments was studied by potentiodynamic, potentiostatic and galvanostatic experiments. Oxidation of chalcopyrite particles was mainly realized by in-situ electrogenerated FeIII and Cull ions. The use of an ion exchange membrane, in this experimental set, avoids the reduction of the ferric and cupric ions. The effects of particle size, current feeder potential, current intensity and pulp density were studied to optimize the oxidation parameters. Selective complete oxidation of chalcopyrite was achieved. Oxidation of pyrite was negligible. Mom than 85 % of sulfur was obtained in its elemental form. This may allow selective extraction- of copper from the chalcopyrite concentrate without sulfur dioxide emissions.

Jan 1, 1995

By Maija-Leena Metsärinta

The behaviour of copper and lead in zinc roasting has been studied in laboratory scale roasting experiments as well as in large scale trials in an industrial fluidized bed, with the background of Outokumpu Kokkola Zinc smelter. Commercial zinc concentrates with a low and high ( up to 3 wt % ) copper content and with a low and high (up to 3.5 wt % ) lead content were oxidized to various desulphurisation degrees in the fluidized bed to establish the reaction mechanisms and the paths for copper and lead oxidation in the roasting. Influences of the agglomerate size on the roasting kinetics and micro-scale phenomena were also determined. Optical microscopy was used on the calcine and the findings are presented as numerous photographs of the polished cross sections. SEMIEDS techniques were used for analyzing chemically the phases and particle morphologies present in the samples. Computational thermodynamics was applied to the complex phase equilibria occurring during roasting in the agglomerating calcine. A complete oxidation of zinc concentrate with a high copper and lead content requires a careful control of oxygen coefficient in the roasting in order to maintain a stable operation of the fluidized bed. Oxygen coefficient thus seems to have a significant impact on the hydrodynamic stability of the fluidized bed with fine raw materials.

Jan 1, 2003

By Kenneth N. Ham

Hydrometallurgy covers a wide spectrum of areas and its knowledge base is enlarged and enhanced by contributions from many other fields. Dissolution of metals and alloys in aqueous media will be used to illustrate how rich the field of metal extraction can be. Comprehensive understanding of the fundamentals of metal and alloy dissolution in aqueous systems requires creative application of thermodynamic principles, solutions chemistry, ligand complexation theory, electrochemistry, transport phenomena and heterogeneous kinetics. In addition, recent developments in instrumentation in the fields of interfacial phenomena and corrosion have tremendously advanced the field of metal extraction in aqueous system. The close relationship between metal extraction in aqueous systems and various physicochemical phenomena occurring in corrosion and interfacial systems will be discussed and illustrated with examples.

Jan 1, 2002

By Dmitri Nassyrov, In-ho Jung

"All relevant thermodynamic and phase diagram data in the CaO-Fe10-CaF2 system were critically reviewed. One set of model parameters describing the Gibbs energy of all phases has been obtained as a result of critical evaluation of the available data and optimization of the model parameters. The Modified Quasichemical Model was used to describe the interactions in the liquid phase. All calculations were performed using the FactSage thermochemical software.IntroductionSlags contaimng CaF2 are of significant interest to the steelmaking community. Notable examples of slags containing significant amounts of CaF2 include Electro-slag Remelting (ESR) slags [1] and mould flux for continuous casting [2]. The role of these slags is, among other things, to refine steel by absorbing inclusions and dissolved impurities. During slag-steel interaction, some iron from the steel will inevitably get oxidized and form iron oxides which will dissolve into the slag. With this in mind, it is important to understand the interaction between CaF2 and Fe,0 for accurate prediction of slag composition and process optimization. A thermodynamic optimization of the CaO-FetO-CaF2 was thus undertaken."

Jan 1, 2013

By Shijie Wang

In pressure oxidation leaching of copper anode slimes, than 65% of the tellurium is m' cxtraoted during decopperizing. About l0- 15% of the selenium is also dissolved simultane¬ously by severe leach conditions. Current operation for the treatment of the leachate is to constantly recirculate the leach solution through a bed of copper turnings. The tellurium and sele¬nium are precipitated from the leach liquor as copper telluride and copper selenide and sepa¬rated from the solution by filtration. In order to improve the reaction efficiency and reduce the process cost, viz, minimize the copper addition, cut retention time, and reduce the energy consumption; a chemical reducing agent is studied and the cementation process tested in the laboratory. In this paper, the test results are presented and the process chemistry is discussed.

Jan 1, 2003

By Tomás Vargas

The catalytic role of Thiobacillus ferrooxidans in the dissolution of chalcopyrite was studied by leaching pure massive samples of this sulfide with a pure strain of Thiobacillus ferrooxidans (ATCC 19859). Monitoring of the bacterial activity showed that an important fraction of the total bacteria generated during leaching remained attached to the chalcopyrite surface. Bacteria grown in the system, which were the offspring of bacteria adhered to chalcopyrite, was well explained as the result of the utilization of ferrous ion and sulfur as energy sources. The potential for indirect and direct action was fully utilized by the existing bacteria and the leaching process was controlled by the kinetics of chalcopyrite dissolution.

Jan 1, 1990

By Shuqiang Guo, Xionggang Lu, Yuyang Bian, Weizhong Ding, Lan Jiang, Kai Tang, Changyuan Lu

For recovery of rare earth elements from the NdFeB based permanent magnet scraps, a high temperature process was used. Permanent magnets scraps were firstly oxidized in air. The optimal oxidation conditions under air are at temperature of 700oC holding for 30min. After the oxidation process, the oxides were reduced by graphite crucible at 1500oC under Ar atmosphere. By this way, the rare earth elements were recovered in the form of oxides, and Fe was separated to the metal phase. Boron distributed in both the rare earth oxides (REO) containing slag and the metal phase. In order to reduce the boron contents in the rare earth oxides, the carbon saturated iron bath and NdFeB added carbon saturated iron bath were used to refine the slag. By this process, the rare earth oxides with a comparatively high purity of 98.2% were gotten.

Jan 1, 2015

By E. T. White

The population balance is one of the basic relations for a:n:aIysing particulate minera1 processing operations. It is an exact relation. The principles of the population balance are reviewed and applications in the minerals industry discussed.

Jan 1, 1996

By Kimio Itagaki

The distribution behaviours of the VA elements between the gas, slag and matte phases in copper smelting were evaluated on the basis of the thermodynamic data, most of which were determined by the authors. The distribution is basically dependent on the process factors such as temperature, the content of the element in charge, the amount of the waste gas and degree of vapour saturation with the elements. The thermodynamic quantities such as the activity coefficients of the VA elements in matte, the activities of iron and copper, SO2 or 02 potential and the distribution ratio of the elements between the slag and matte phases seriously affect the distribution, and the behaviours in various smelters could be explained systematically and reasonably by considering the changes in these quantities, In oxidation smelting at PSO2= 0.1 to 1 atm, the proportion of arsenic and bismuth in gas is predomi22t for the arsenic and bismuth distributions in both smelting and converting stages. The degree of vapour saturation has serious effect on the distribution, and sufficient contact between gas and matte phases is desirable for transferring arsenic and bismuth into gas phase.The elimination of antimony by means of vaporization is not significant. In reduction smelting at po2 = 10-11 atm, the proportions of arsenic and antimony in the gas phase are quite small, but the proportion of bismuth does not change significantly.

Jan 1, 1983