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By Ronald Klepper

In hydrometallurgy, pure gases like oxygen and hydrogen are used for oxidation and reduction. The gases are expensive and therefore should be used efficiently. Non reacted gas can be recycled into the liquid. Historically vortex gassing has been used; Le. a mixing impeller close to the liquid surface entrains gas from the headspace into the liquid through a gas vortex. Novel and more efficient methods are surface gassing with up pumping impellers and self- inducing gassing impellers. These alternative impeller systems are well established and common in the chemical industry, but have not been used until recently in hydrometallurgy. Gassing impellers act as internal compressors and increase the interfacial surface for a much higher mass transfer compared to alternate methods mentioned. In the paper results from lab and pilot tests and data from operated plants will be presented. The reactions with gases normally take place under moderate to high pressure, therefore a safe enclosure with mechanical seals and the safety "philosophy" is important. Experienced life and replacement cycles will be reported.

Jan 1, 2000

By Mingmei Zhu, Lang Hu, Yu Wang, Hongpo Wang, Congjing Zhang

Magnetic field has a great effect on the crystallization behavior of mold flux and properties of the flux film between mold and strand, on which the surface quality of strand was deeply depended in continuous casting process. Therefore, studying the change law of the crystallization properties of mold flux in magnetic field is of great significant. In the present work, based on intensity of the applied magnetic field with the range from 0mT to 60mT, the crystallization ratio, crystal size and mineralogical phases of the flux film were discussed. The results show that crystallization ratio increases with the increasing magnetic field intensity, and the crystal size becomes bigger at the same time. The magnetic field promotes the crystallization ratio and growth speed of the crystallized grains of mold flux. However, magnetic field doesn’t change types of the mineralogical phases.

Jan 1, 2015

By Zhang Duomo

A novel homogenous precipitation method, including microwave heating, solution conductivity controlling and freeze drying, was developed for the preparation of US nanoparticles. The effects of the precipitation conditions on the structure and morphology of CdS particles were discussed individually. It was found that under the experimental conditions the particle sizes were controllable in the range of 14nm to 100nm. Blend-type CdS was obtained from nitrate or sulphate solution and the more stable wurtzite-type US was obtained from chloride solution, which was ascribed to the coordination of C1 and Cd2+ altering the supersaturation of the solution as well as the different growth units and their connecting patterns, In the precipitation process the surface of US nanoparticles were surface modified with CH3CHSCOOH. The results demonstrate that the bifunctional thiols of thioglycolic acid modified the surface through Cd-S coordination bonding and the induced counter ion AOT-SO3 as the balance charge further increased the stability and dispersity of US nanoparticles. This surface-modified US nanoparticles had been used to prepare nonlinear optics and self-assemble catalysts.

Jan 1, 2003

By M. S. Moats

Galvanic stripping, in conjunction with solvent extraction, has been proposed as a technical option to the challenging problem of iron removal in certain hydrometallurgical processes. The galvanic stripping process is based on the ability of a solid metal to directly reduce ferric ion to the ferrous state in an organic media. Stripping the iron into the aqueous phase is then easily accomplished. Previous work has shown the reaction kinetics and efficiency are affected by such operating parameters as water and oxygen contents, temperature, time and metal reductant. In this study, the optimum operating range for some of these variables was determined. Both zinc and iron metal were used in the separate stripping of iron from D2EHP A. Reasons for the differences in the extent of the reaction obtained using the various conditions are discussed.

Jan 1, 1996

By Zhang Chuanfu, Tan Pengfu

"A thermodynamic model is developed to simulate nickel flash smelting process. In the nickel flash furnace, oxidation of concentrate occurs at one end, and reduction of slag occurs at the other. The model makes use two zones, namely the reaction shaft/settler zone and the appendage zone and accounts for 6 phases (matte, slag, silica, magnetite, Cu-Ni alloy and gaseous phase), 13 elements (Ni, Co, Cu, Fe, S, 0, N, C, H, Si, Al, Mg and Ca) and 33 chemical components in nickel flash smelting system. The compositions of matte, slag and gaseous phases in equilibrium are calculated by using the data of free energies of formation and activity coefficients of components. Two nickel sulfide species are used to allow for the modeling of sulfur-deficient mattes. The model predictions are compared with the known industrail data from Kalgoorlie Nickel Smelter, and excellent agreement is obtained. The model can be a very useful tool for monitoring and optimizing the actual industrial operations of nickel smelting process. The distribution behaviors of Ni, Co, Cu, Fe, S and 0 in the nickel smelting furnace depend on the process parameters such as smelting temperature, volumes of air, the content of the elements~ charge and oil.1. IntroductionThe nickel flash smelting furnace essentially consists of a reaction shaft where nickel sulfide concentrate is partially oxidized with air, a settle zone where matte and slag are allowed to separate, and a slag cleaning end where coke is added to provide for the reduction of the oxidized nickel from slag, and electrodes are used to provide heat.The theoretical model to consider a mass balance for copper flash furnace is developed by S. Goto and R. Shimpo[1][2J. However, this can not be true for nickel flash furnace as a whole since oxidation of concentrate occurs at one end (in the reaction shaft/settler), and reduction of slag occurs at the other (in the appendage). Despite these limitations, an acceptable pseudo-thermodynamic description of the furnace can be achieved using essentially two zones, namely the reaction shaft/settler zone and the appendage zone. Compositions of gas, slag and matte in two zones are calculated."

Jan 1, 1998

By Sne?ana Devi

Mineralogy is a significant scientific discipline, essential in establishing the nature and the character of raw materials, regardless of whether they are monomineral or polymineral. Mineralogical characterization is very important, because its results give valuable information on features and nature of examined materials. Information's on mineralogical nature of mineral raw materials influence directly the quality assessment of a raw material, and thus the possibility of its use. The possibility of use of mineralogy in different industrial branches confirms constant activity of this scientific discipline. By use of methods within mineralogical analysis (optical microscopy, x-ray diffraction and others) data on mineral raw materials can be obtained as support in mineral raw materials quality assessment. Short description of results of mineralogical analysis of some mineral materials (granodiorite, dolomites, clay, refractory materials, slags and casting powders) in this paper shows the importance of its support to quality assessment and determine the possibilities of their use.

Jan 1, 2009

By Lori Bassman, Cassandra George, Cullen McMahon, Md. Zakaria Quadir, Michael Ferry

"Complete and accurate analysis of subgrain microstructural features must include three-dimensional information. Three-dimensional electron backscatter diffraction (EBSD) data can be used to characterize these features; however their boundaries first must be determined. This cannot be accomplished simply with pixel-to-pixel misorientation thresholding because many of the boundaries are gradual transitions in crystallographic orientation. Fast Multiscale Clustering (FMC) is an established image processing technique that we have combined with quaternion representation of orientation to segment this kind of data. Segmentation algorithms often have issues handling images with both distinct and subtle boundaries. Our implementation of FMC addresses this by using a novel distance function and statistical analysis to take into account the variance in orientation of each feature. Although FMC was originally a twodimensional image processing algorithm it can be generalized to analyze threedimensional data sets. As an example, a segmentation of microbands in cold-rolled aluminum is presented.IntroductionThree-dimensional electron backscatter diffraction (3D-EBSD) is a method for mapping the local crystallographic orientations of points in a volume. The technique uses a dual beam platform consisting of a focused ion beam (FIB) and SEM with EBSD, where FIB is used for serial sectioning and EBSD for orientation mapping of 2D slices. These 2D slices may then be stacked to create a 3D volumetric data set.Typical uses of such a data set include characterizing the geometries and crystallographic orientations of surfaces between structures in 3D [1-5]. This involves identifying boundaries accurately, either in 2D slices with subsequent 3D reconstruction (as illustrated in Figure 1) or in the 3D data set. All such data sets present the challenges of i) aligning data slices to correct for instrument drift, ii) identifying relevant boundaries, and iii) implementing appropriate smoothing or interpolation algorithms. The focus of this paper is boundary identification."

Jan 1, 2011

By Thomas Niehoff

"Oxyfuel combustion systems are state of the art for many melting operations. Airfuel systems have been stepwise modified to oxygen enrichment, oxygen lancing and oxyfuel. Every change of the melting process will have consequences with regards to emissions and energy usage. The uniqueness of many operations requires unique skills to resolve potential issues. This paper will give some examples of how airfuel systems can successfully be converted to oxyfuel.IntroductionOxyfuel technology – meaning the combustion of fossil fuels such as natural gas, oil or coal with technical oxygen instead of air for industrial melting or heating processes is widely used in many industries these days. Even though oxygen production, storage and handling has been state of the art for decades other opinions exist. Often oxyfuel is regarded with fear and potential hazards like: “Oxygen makes the process too hot.”, “Oxygen will melt away the refractory.”, Liquid oxygen is dangerous.”, “Oxygen will cause explosions.”, ……etc.Typically a more detailed discussion about a specific industrial process and how oxygen can be applied in a safe and economic way the seeming issues go away."

Jan 1, 2010

By J. R. Sarazin

Density driven convection during solidification has been recognized for some time to result in macrosegregation particularly when lower density alloying elements are rejected into the interdendritic liquid. The resulting segregates are commonly referred to as channels, freckles or A-segregates. Buoyancy driven convection leading to channel formation has been examined in three model systems possessing somewhat different materials parameters. They are the Pb-Sn eutectic system, the transparent aqueous-salt NH C1-H 0 4 2 eutectic system and the transparent organic succinonitrile-ethanol monotectic system. Convection in these systems is controlled by a balance of buoyant and viscous forces, which are strong functions of composition and temperature. Composition, temperature and flow velocity were measured and elimination of channels through heavier ternary additions is discussed.

Jan 1, 1991

By J. P. Evans

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

Jan 1, 1992

By Yuhsuke Mizukami

Crude high Cr containing steel such as tool steel, heat-resistant steel or stainless steel is produced by dissolution of high carbon ferro-chromium into molten crude steel. In the refining process, decarburization is performed at the first stage, and deoxidation is followed in the next stage. Therefore, the equilibrium relation between dissolved Cr and 0 in molten Fe-Cr alloy after decarburization is very important when yield of deoxidizer is considered for the ovemll control and optimization of the process. It is well known that the yield of deoxidizer does strongly depend on the kinds of refractories of furnace in the secondary refining process. In the present work, the equilibrium relation between dissolved Cr and O in molten Fe-Cr alloy has been measured in a Cr2O3, MgO or Al2O3 crucible at steelmaking temperature. O contents at given Fe-Cr components have been lower in order of Cr2O3, Al2O3 and MgO crucible. The present results have been discussed based on the activities of the constituents in pure solid Cr2O3, and FeO-Cr2O3, MgO Cr2O3 and (AI,Cr)2O3 solid solutions.

Jan 1, 2003

By Moenster J. A., M. J. Sankovitch

Doe Run's Buick Smelter was converted from a primary lead smelter to a secondary lead smelter in 1991. The recycling facility was designed to produce 60,000 tons of refined lead per year from 110,000 tons of spent starting-lighting-ignition (SLI) batteries and 10,000 tons of lead contained in drosses and scrap. Since commissioning, Buick's refined lead output has steadily increased to exceed 120,000 tons for 1999. The production gains have been the result of continuous process improvements, empowerment of the workforee, and development of additional scrap lead streams. The production gains were accomplished while setting industry standards for employee safety, reducing plant environmental emissions and employee blood leads, achieving ISO 9002 certification, and expanding product lines to meet customer requirements. This paper highlights Buick's major accomplishments through the 1990's.

Jan 1, 2000

By Zhenjun Tan, Lei Zhang, Jigang Li, Yifang Zheng, Jilai Xue

"Water electrolysis in 0.4 mol/L NaOH solution for hydrogen generation was carried out with ultrasound introduced through the anode. It was found that the cell voltage reduced by 150-300 mV in the current range of 20 mA to 40 mA with ultrasound frequency at 25.3 kHz. The cell operation became unstable when the cell current was larger than 75 mA with ultrasound. This reduction in cell voltage was due to removal of the gas bubbles on the electrode surface, which can be directly observed in the see-through cell of water electrolysis. Ultrasound with frequency of 33.3 Hz was also tried, but no better effect was obtained. The results suggest that ultrasound assisted water electrolysis can have potential in energy savings for hydrogen production.IntroductionIn electrolytic process, the electrode that the bubbles generated on its surface usually covered a thin gas film, which can be caused an additional voltage about 0.15-0.25V[l,2], especially in aluminum electrolysis. To solve the problem, loading the ultrasound removes the gas bubbles from the electrodes, this subject had been researched in recent years. From 1995 Jilai Xue et al[3,4,5]. applied the ultrasound in aluminum electrolysis in lab. The results from Sheng-De Li et al.[6] reveals that can decrease the cell voltage and have influences about the hydrogen and oxygen's output ratio. Although there are many paper about the applying of ultrasound such as in electrolysis[5,6], deposition[7,8], plating[9,10], oxidation of salts substance on the surface of electrodes[l 1] and so on, the effect of different frequencies ultrasound hadn't been investigated deeply.We focus on the anode voltage by different frequencies ultrasound and the bubble behaviors in this paper. The environment of this experiment is in alkaline solution. Through this exploration it can offer a basis for the applying of ultrasound in electrolysis."

Jan 1, 2011

By Lætitia H. Delmau

SXFIT is the latest in a series of programs developed in our group to model solvent extraction systems of increasing complexity. SXFIT permits the user complete freedom to define the constituents from which the composition of each phase is to be specified in the data and from which all species of a model for a system are assumed to be formed. Activity coefficients in the nonaqueous and aqueous phases, water activity, apparent molar volumes of aqueous species, and solution density needed for the conversion of concentration from the molarity to the molarity scale are all taken into account by the program. Several extraction systems relevant to nuclear-waste treatment were modeled successfully using this program. As an example, the cesium extraction efficiency of the CSSX process chosen by the USDOE for cesium removal from high-level waste stored at the Savannah River Site can be predicted correctly for varying feed composition.

Jan 1, 2003

Reduction of titania and ilmenite ores by Cf4-H2-Ar gas mixture was investigated in a laboratory fixed bed reactor. Titania was reduced to titanium oxycarbide in the temperature range of 12OO-1500°C. At 1400-15000C, the extent of reduction of titania to titanium oxycarbide achieved more than 85% in 90 min. Optimum conditions for titanium oxycarbide synthesis by reduction of titania include temperature in the range of 1300-1450°C, methane content 8 vol% and hydrogen content above 35 vol%. Ilmenite ore was reduced by Cf4-HrAr gas mixture to metallic iron and titanium oxycarbide. Metallic iron catalyzed methane cracking and solid carbon deposition. Titanium oxycarbide formed at temperatures as low as 950°C. The optimum temperature for reduction of ilmenite is 1200°C and the optimum methane content is 8 vol%. Increase in hydrogen content increased both rate and extent of reduction. With 5 vol% CH4-75 vol% Hr20 vol% Ar gas mixture, the reduction of ilmenite completed in 60 min. Reduction of titanium oxides to oxycarbide with following chlorination may be an efficient alternative technology for processing of titanium minerals.

Jan 1, 2001

By Hartmut Rossel

VAW aluminium AG has built a "Recycling-Technikum" (Recycling Research Centre) to add a new arm to the company's Corporate Research and Development Department. The Recycling Research Centre, a pilot plant for scientific research, has been in operation since September 1993. These state-of-the-art facilities allow the investigation and optimisation of recycling techniques in 'a global way and in detail. Research is concentrated on the unit operations - processing, melting and waste-gas purification - with the available installations making it possible to compare different alternative process combinations on a 100-kg scale. One of the main targets of VAW research is the development of recycling techniques for packaging. The paper presents an approach to recover the aluminium contained in flexible packaging materials using an integrated melting and waste-gas purification system.

Jan 1, 1995

By A. C. Wadhawan

In the present context of rapid industrialization, production of Lead-Zinc metals from low grade materials, residues and wastes can make substantial contribution to the supply of these metals in India. Recovery from secondary sources also plays an important role in conservation of mineral resources and lower power consumption. Conscious effort is therefore, required to increase the secondary metals which, besides saving in energy cost will also help in waste material management and keeping environment clean. The major thrust is, therefore, needed in this direction. During all these years, the Indian Lead- Zinc industry has made sustained efforts for recovery of metals from low grade ores and from metallurgical wastes and residues. The paper identifies the treatment of low grade ores by various technologies and techniques and the treatment of metallurgical residues and wastes generated during primary Lead and Zinc smelting in India. Some of the major achievements in past decade have also been elaborated in the paper. The strategies to be followed for continuing treatment of low grade ores and waste materials by adopting newer, environmental friendly technologies, in consonance with the rigid standards being adopted by most of the countries including India. have also been dealt with in the paper.

Jan 1, 1994

By J. P. Evans

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

Jan 1, 1992

By Vaughan R. Voller

"Over the last ten years an increasing number of heat and mass transfer models of solidification processes have been presented in the literature. A key component in these models is the coupling between thermal and solute fields. This is achieved by developing relationships based on the behavior at the microscopic scale in the casting (typically a secondary dendrite arm space). An important class of models in this respect are models that describe the local scale redistribution of solute alloy components-collectively referred to as microsegregation models. This paper explores this class of models.IntroductionModeling takes a key role in processing materials for properties. This is particularly time in solidification processes where current computer techniques allow for a detailed treatment of the critical macroscopic phenomena. Typically these macro scale models consist ·of three main coupled components.1. A model of flow in the melt and solid + liquid mushy region.2. A model of heat transfer.3. A model of solute transport.The focus of this paper is the solute transport component, in particular the manner in which process scale transport is coupled to transport ·at the local scale of the solid-liquid interface. This step requires a modeling of the redistribution of solutes at the scale of the secondary arm spaces in the dendritic mushy region-a process referred to as microsegregation. Basic microsegregation models use the limit assumptions of no mass diffusion in the solid (Gulliver-Scheil [l]) or complete diffusion in the solid (equilibrium lever rule) in a fixed and space. Recently, however, more sophisticated microsegregation models that account for finite mass diffusion and coarsening of the arm space have been developed [2-19]. In this paper governing equations for a general microsegregation model for a multi-component alloy in a coarsening and spacing _are introduced. From these general equations various models for a binary system are developed and tested"

Jan 1, 2000

By L. A. Bertram, F. J. Zanner

"The goal of this paper is to present a tool to simulate transient melting of the electrode tip. This capability is needed to develop and test furnace control algorithms since experimental determination is difficult and expensive. Simulation incorporates parameters (including arc voltage, arc current, electrode gap and furnace pressure) from previous quasi steady experiments with 460 mm diameter Inconel 718 electrodes.Cathode heating rates (determined by classical as well as experimental arc models) are linked to these independent variables. After radiative loss adjustments to the heating, transient one dimensional melting is computed. IntroductionThe vacuum arc remelting (VAR) process attempts to improve the physical and chemical homogeneity of a static-cast electrode by remelting and solidification in a quasisteady manner. To achieve steadiness of furnace operation requires automatic controls based on inputs measuring physically relevant state variables of the process. Previous industrial scale VAR studies (1,2,3) involving stainless steels, superalloys, and other alloys have provided a basis on which control strategies of some generality can be proposed (4). Of these measurements, the data for Inconel 718 is the most complete, so discussion in this paper is restricted to this alloy.Studies of the In 718 alloy subjected to the VAR process have established that melt rate M (kg/hr) depends not only on the melt current 1m (kA) supplied to the furnace, but also on ambient gas pressure of CO, PCO (micron), and electrode gap ge (mm) as well (1):"

Jan 1, 1986