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By Dai Yongnian

The methods of treating zinc crust and its development in the last hundred years are compared and reviewed. There are better effects from normal pressure metallurgy turned into vacuum metallurgy. The traditional methods dezinc only. But we must consider that delead on further step. From lab tests to industrial scale experiment are researched. The first step-dezinc, second-delead, crude ,metal of, zinc, lead and silver are produced, The flowsheet of treating zinc crust are simplified, material consumption reduced, work condition improved, environment protect mended. This method is pointed out that its application can be expanded.

Jan 1, 1992

Hazardous waste has often very complicated chemical compositions in a variety of physical forms and is normally processed in rotary kiln incinerators. Due to large variations in waste types and difficulties in feed characterization, the complex transport processes within the incinerator are not well understood, and the incineration process meets challenges in a smooth operation, and expects various uncertainties in the process chemistry and emission control. For better understanding of the incineration process, simulation was carried out by using Computational Fluid-dynamics (CFD) to characterize temperature and species distribution in the incinerator. In order to catch certain aspects of thermal and chemical behavior, a novel approach is proposed to represent approximately the waste streams and the subsequent combustion process. Hazardous waste in various forms from an industrial-rotary-kiln waste incinerator is firstly converted to a hydrocarbon-based virtual fuel mixture with approximately the same HIC molar ratio and calorific value. The simulation of the combustion process of the simplified hazardous waste was proceeded with a combustion model. The distribution of temperature and chemical species especially the remaining CO in the system is preliminarily investigated. Distribution of CO concentration, as a good indicator of emission level for the incineration process, could be used to evaluate the emission control. The predicted temperature distribution has been compared with available measurement data from an operating rotary kiln waste incinerator at A VR-Chieme, in the Netherlands. Reasonable agreement has been reached between the measured and predicted temperature data. [n the next step, measurement of species distribution in the system is planned to further validate the combustion model.

Jan 1, 2003

By J. D. Miller

Low-level radioactive contaminated soils (10-500 pci/gm) created by defense-related activities at certain superfund sites, such as Nevada Test Site (NTS), is a current environmental concern. Many of these contaminated sites may require appropriate cleanup and restoration, which could cost billions of dollars and put tremendous pressure on our limited financial resources. Therefore, the development of a selective flotation process to separate such radionuclides from contaminated soils should be considered. In this study, both a pure depleted UO2 sample and three synthetic UO2/soil mixtures were used to evaluate surface chemistry features and to examine the possibility for the flotation of fine UO2 particles from selected soils. It was intended that this model system would be a reasonable representation of contaminated soils such as those found at the Nevada Test Site which are reported to be contaminated by PuO2 fallout. The effect of reagent schedule, particle size distribution, and surface charge are discussed with respect to the flotation separation of the UO2/soil mixtures. It was found that both commercial fatty acids and reagent grade sodium oleate are effective collectors for UO2 flotation provided the pH is adjusted to the range of pH 8-9. The bench-scale flotation results successfully demonstrated that froth flotation technology can be used to remove UO2 from such model contaminated soils with appropriate flotation chemistry conditions which depend on the soil characteristics and other pretreatment procedures. In the best case, 90.2% of the UO2 was removed from a UO2/NTS soil mixture (119 ppm UO2) and the soil reduced in UO2 contamination from 119 ppm to 17 ppm in a single stage bench flotation. The impact of clay slimes present in the soil is revealed by the results which show that, for example, for a deslimed soil (28x400 mesh and 100 mg UO2/kg soil) 85¬90% UO2 recovery can be obtained with a reduction in contamination to 4.6 mg U02/kg soil.

Jan 1, 1995

By Y. Ono

In lightweight metal processing such as aluminum (AI) and magnesium (Mg), metal cleanliness is a crucial process parameter for refining, part manufacturing and recycling in order to obtain high quality parts and products. In this paper, techniques for cleanliness evaluation of molten AI and Mg using ultrasonic probes with clad steel buffer rods having high signal-to-noise ratio (SNR) are presented. Due to the high SNR of the ultrasonic probes used, backscattered ultrasonic signals from inclusions, which may be oxide films and/or particles, in molten Mg and those from silicon carbide particles, having an average size of 50f.Ull, added in molten AI are successfully detected with reflection configurations of pulse-echo and/or pitch-catch modes at an ultrasonic frequency of 10 MHz. In addition, relative cleanliness evaluation of molten Al and Mg is demonstrated. In order to establish the procedure and to investigate the optimum system configurations for cleanliness evaluation of molten metals, particle flow simulation system using water and polyvinyl chloride (PVC) particles has been constructed. Counting the number and measuring the size distribution of the PVC particles, having an average diameter of 128um, suspended in water with the PVC volume concentrations of 5ppm and 10ppm are performed with ultrasonic pitch-catch mode. The counted numbers of particles by the presented method and system have good agreement with the calculated results with a count error of less than 10% or two counts. Based on the results obtained with water simulation experiments, the prototype system for cleanliness evaluation of molten Mg by counting and sizing inclusions has been developed. Keywords: Ultrasound, Clad buffer rod, Molten metal, Aluminum, Magnesium, Inclusion detection, Cleanliness measurement, Counting, Sizing

Jan 1, 2003

By Ludwig Hermann

"Phosphorus is required by every cell of living organisms and essential for plant growth. It is a non-renewable resource that must be mined from natural deposits, going gradually into depletion. Abundant secondary resources are available in sewage sludge and meat and bone meal, with the highest exploitable P concentrations in ashes that remain from their widely used combustion with energy recovery. ASH DEC has successfully removed heavy metals and transformed sewage sludge ash into a marketable P fertilizer by application of a thermo-chemical treatment process. Pilot scale investigations in which ash was treated proved that generally heavy metal limits required by fertilizer legislation can be attained. To achieve a high P availability for crops – an essential fertilizer quality feature – was a more challenging R&D task. Our presentation demonstrates the scientific approach and R&D results that lead from assessment of market requirements to licensed products.IntroductionPhosphorus (P) is required by every cell of living organisms. It is one of the major elements for plant nutrition and therefore essential for crop production. P supply in plant nutrition depends entirely on external inputs into soils [1]. This is achieved by P-fertilizers deriving from rock phosphate deposits that are gradually going into depletion. Serious prognoses anticipate that rock phosphate will be the first low running resource in the world [2]. In the EU, last year 2.530 kt of phosphorus (P2O5 in fertilizers) was consumed and only 313 kt (P2O5 in rock phosphate) was mined. Since 2007, rock phosphate prices have increased by 500% because of a tight supply situation [3].For these reasons, P recycling is becoming an increasingly important issue. Suitable secondary raw materials with regard to their high P-content and abundance are sewage sludge and meat and bone meal. In the EU 989 kt P2O5 are accumulated annually in theses materials, of which 632 kt P2O5 are permanently lost to landfills and other forms of disposal. The main reasons for their limited recycling are concerns on heavy metal contents and organic pollutants that may incite health hazards. As an additional shortcoming, the availability of P from these materials to plants is poor and storage and transportation are problematic issues [4, 5]."

Jan 1, 2008

By Cynthia Belt

"Energy management is critical to aluminum processing given the high energy requirements of melting and processing aluminum. Energy costs have always been a high percentage of the total production costs within this industry. Energy management at many plants relied on better technology that many times required high capital. As carbon management has grown in importance and project payback becomes more critical, a larger view of a plant's process is required. This paper looks at the energy requirement due to current typical practices in overall product recovery, metal loss, utilization, and technology to understand potential methods of reducing overall energy within a plant and within the aluminum processing industry.IntroductionFor many companies that process aluminum, energy is a major portion of their costs that can surpass the cost oflabor. Aluminum processing can include secondary processing of scrap and prime aluminum into sows and/or molten aluminum or casting aluminum by various methods such as direct chill, continuous casting, low or high pressure casting, mold casting, and extrusions. In the case of this paper, we are considering only plants that include the melting process as a portion of their process. The process of melting aluminum takes energy. In most cases, the aluminum must then be heat treated one or more times. Post processing of the aluminum includes rolling mills used for making sheet, extrusion lines, and machining such as saw cuts, drilling, or surface finishes that all take additional energy.While these high energy costs directly affect the profits of the company, energy management within the metals industry is still not widespread. A co=on misconception is that the solution to high energy costs is high cost capital equipment. While state-of-the-art equipment can certainly improve energy efficiency, it is not the only solution. To obtain a truly energy efficient plant, several directions needs to be addressed through an energy management thought process with a wider scope. Impact on potential savings is possible through: product recovery, metal loss, utilization, and new technologies. An understanding of the potential costs and savings from these means is important. Several of these methods provide low cost approaches to saving energy.The background data used in this paper is not a random sample within aluminum processing but yearly averages from various plants in different aluminum processing industries. As is normal in this industry, the plants have been under different corporate management over the years with different strategies for energy management. This data is not meant to be accurate for the entire industry but to suggest areas for energy efficiency work."

Jan 1, 2012

By S. B. Bortnikova

This paper presents the results of an investigation of the gold-silver oxidized ores at the Salair mine. West Siberia. High losses of precious metals during primary ore processing are the result of outdated technology that is not suited to treat the present ore compositions. The main mineralogical forms of gold and silver and their confinement to different grain size fractions have been determined. About 50% of gold in the slime fraction and 60% of the silver in the form of acanthite that are scattered from the secondary minerals are lost to the waste. The results of these investigations have provided the basis for the recommendation of a new technological process to upgrade the current practice of the gold extraction plant and for methods to reprocess the concentrates.

Jan 1, 1995

By David G. C. Robertson

A new approach is described for the calculation of the kinetics of metal/slag, metal/slag/gas, and metal/matte/slag/gas reactions. The algorithm assumes that equilibrium is achieved at the interface between phases, and uses an equilibrium solver (such as SOLGASMIX) to compute the equilibrium state at the interface at each time step during the reaction. For multiple phase systems a number of unit operations, representing the different phases and interfaces, must be connected together in a reasonalbly complex manner, and the METSIM software package has been utilized for this purpose. The new approach is superior to the SMAK software developed by the author and his co-workers over the past decade, for the reasons discussed in this paper.

Jan 1, 1995

By Luben Xie, Lin Hu, Qiang Wang, Min Gan, Tao Jiang, Wenqi Li, Xiaohui Fan, Zhiyuan Yu

"Crystal precipitation behavior of calcium ferrite (CF) during iron ore sintering process along with the effect of cooling rate, SiO2 and Al2O3 on crystalline condensation were studied. The results show that CF, has strong ability of precipitation. The precipitation is barely affected by extenal factors. It begins to precipitate when the liquid phase cools down to about 1200oC. CF could crystallize rapidly at the cooling speed of 150 °C /min. Furthermore, decreasing of the cooling rate favors the development of crystal. Binder phase transformed from CF system to silicate system when SiO2 content was increased to 5~6%, with a constant basicity (R) 2.0. Increasing Al2O3 content could promote the precipitation of CF and the development of crystal.IntroductionCrystalline condensation is the last stage of sinter mineralization. It includes the processes that crystalline substance and amorphous substance precipitate from high temperature solution phase and the consolidation of material when melt cools down. During the crystallization process, minerals precipitate following the order from high to low melting point coupled with the decreases of free energy. Most of binder phase minerals and part of iron oxides crystallize in this process, which have an important influence on mineral composition and microstructure of sinter. They finally determine the sinter strength and metallurgical properties."

Jan 1, 2011

By E. A. van Dijk

Dusts from steel-making processes contain substantial amounts of zinc. Such dusts are also a hazardous waste and dumping them becomes unacceptable from environmental point of view. Therefore processes that can recover zinc and possibly other metals from steel-making dusts are being investigated. The aim of this paper is a contribution to the more fundamental kinetic aspects of zinc reduction from silica free calcium ferrite slags. The effects of alumina, lime and magnesium oxide contents of the slag, the COICO, ratio and the effect of initial Fe2O3/CaO ratio were studied experimentally at 1400°C The results indicated that the reduction of zinc from molten slag was possibly a first order reaction. As expected higher COICO, ratios increased both the extent and the rate of reduction. It was also observed that a higher iron content of slag improved the reduction of zinc from calcium ferrite slags. This fact seems to support the proposed mechanism that zinc is partly reduced by ferrous iron to zinc vapour and that ferric iron is reduced by carbon monoxide. The reduction rate of zinc in these slags was decreased by increasing alumina content of the slag. Alumina decreased the calculated optical basicity of the slag showing the fact that reduction of zinc oxide was more favorable in more basic slags. Probably the formation of complex ions by alumina and zinc oxide such as ZnAl2O32+ lowers the activity of Zn2+ ions in the slag and hence render them more difficult to reduce.

Jan 1, 1999

Hazardous waste has often very complicated chemical compositions in a variety of physical forms and is normally processed in rotary kiln incinerators. Due to large variations in waste types and difficulties in feed characterization, the complex transport processes within the incinerator are not well understood, and the incineration process meets challenges in a smooth operation, and expects various uncertainties in the process chemistry and emission control. For better understanding of the incineration process, simulation was carried out by using Computational Fluid-dynamics (CFD) to characterize temperature and species distribution in the incinerator. In order to catch certain aspects of thermal and chemical behavior, a novel approach is proposed to represent approximately the waste streams and the subsequent combustion process. Hazardous waste in various forms from an industrial-rotary-kiln waste incinerator is firstly converted to a hydrocarbon-based virtual fuel mixture with approximately the same HIC molar ratio and calorific value. The simulation of the combustion process of the simplified hazardous waste was proceeded with a combustion model. The distribution of temperature and chemical species especially the remaining CO in the system is preliminarily investigated. Distribution of CO concentration, as a good indicator of emission level for the incineration process, could be used to evaluate the emission control. The predicted temperature distribution has been compared with available measurement data from an operating rotary kiln waste incinerator at AVR-Chieme, in the Netherlands. Reasonable agreement has been reached between the measured and predicted temperature data. In the next step, measurement of species distribution in the system is planned to further validate the combustion model.

Jan 1, 2003

By W. D. Cho

The slag chemistry in steel processing plays an important role in terms of the removal of impurities including alumina particles. In the present study, the dissolution of solid alumina particles in CaO-based fluxes at the temperatures between 1450 and 1550 °C has been investigated to determine dissolution kinetics and mechanism. Alumina particles were added directly in the slags and the size of alumina particles was measured as a function of time using optical and scaru;ling electron microscopes. The dissolution rate has also been obtained as a function of Si02, CaF2, MgO and MnO contents in the slags. The diffusion boundary layer between alumina and bulk slag phase has been observed and analyzed using SEM and EDX. In addition, some experiments have been performed for the dissolution of alumina in BaO-based fluxes.

Jan 1, 2003

By B. Q. Li

A numerical study of the developing fluid flow and thermal aspects during the staning phase of aluminum continuous casting processes is presented. The deforming finite element method, coupled with a quasi-Lagrangian formulation, is used to represent the growth of an ingot and the dynamic fluid flow and thermal behavior that evolves in the growing ingot. The mathematical formulation of the problem and the numerical treatment are discussed. The algorithm solves the free moving nodes as part of total unknowns with an automatic time step control for time integration. This permits an optimal computing efficiency while still keeping the computational errors under control. A selection of the results obtained using the algorithm is presented. The results are concerned with the evolution of fluid flow, temperature and solidification phenomena during a DC round ingot casting process, as it evolves from the beginning of casting operation to a steady state. These results show that the time-varying, complex fluid flow and thermal phenomena during continuous casting processes can be very well represented by the computational algorithm. The results also illustrate that, during the casting process, ~e fluid flow and temperature fields change drastically at the initial stage but evolve slowly afterwards

Jan 1, 1993

By V. I. Lakshmanan

Wastes when produced can be reused or recycled prior to disposal. Industries that cause environmental concerns during manufacturing include primary materials and primary metals. Pollution prevention mechanisms to achieve waste reduction require new separation, reclamation, control and process simulation technologies. Substituting recyclables for virgin resources will reduce energy use, water pollution, air pollution, water use and mining wastes. Shrinking landfill space will spur new technologies for waste treatment and recycling. These situations hence offer opportunities for innovative flowsheets with appropriate separation technologies. Development of innovative flowsheets to treat recyclables offer unique opportunities for process/product development, obtain green products and hence market advantage. The paper will illustrate with selected innovative flowsheets to treat recyclables.

Jan 1, 1996

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade. The most visible technological innovation was the commissioning of the Pb-Cu smelter. Its flexibility towards very different types of feed makes it perfectly suited as main entry to the Hoboken flow sheet. A new Cu-leaching & electro winning plant and precious metals refinery make up the Precious Metals Operations (PMO) whose targets are fast throughput and maximized yields for gold, silver and the platinum group metals. The Base Metals Operations (BMO), flexibly process the by-products from the PMO, valorizing ?impurities? like indium, tellurium, selenium and others. Off gas and waste water treatments ensure compliance with strict environmental standards. Precious metals recycling is an art that goes beyond mastering a unique flow sheet. Umicore Precious Metals Refining offers a complete recycling service, taking care of sampling and assaying, metals management and logistics. The quality of this integral service is recognized through the attribution of ISO certifications for our operational activities, sampling and the environmental care. And it?s an art that follows Michelangelo?s experience: ?Art is 5% of inspiration and 95% of transpiration.?

Jan 1, 2006

By S. Neven

The smelting of copper anode slimes, a material which contains mostly lead, silver, copper and selenium, has been practiced for many years with a view to recovering the silver and associated small amounts of gold. However, a theoretical understanding of the process has been lacking and this handicaps efforts to improve and intensify smelting operations. In the past few years work has been done in this area and this work will be reviewed in the paper. The underlying thermodynamics of the oxidation of silver-copper selenide mattes has been developed and used as a basis for the construction of a computational thermodynamics model which attempts to predict the composition of all condensed phases during the course of smelting. The model will be outlined and its successes in matching experimental data, as well as its current deficiencies, will be considered. Supporting work on the thermodynamics of silver solubility in slags, on activity-composition relationships in the Ag-Se system and work in progress on the oxidation state of copper in the slags will be reviewed. These projects are designed to provide further detailed data which will improve the robustness of the thermodynamic model.

Jan 1, 1999

By Kenneth L. Nash

The control of solubility of waste actinide ions, by conversion to highly insoluble mineral phases has been demonstrated in the laboratory. Actinide metal ions are removed from neutral pH solutions by a combined ion exchange-decomposition-mineralization process based on the application of the naturally-occurring hydrolytically unstable.polyphosphate organic compound phytic acid.

Jan 1, 1999

By Florian Kongoli

"Lime ferrite" slag with limited silica content has proven to be a valuable choice in the modem processes of copper smelting and converting due to several advantages that this slag offers compared to classical silicate slags. Nevertheless the liquidus surface of this slag has been experimentally measured only at low oxygen potentials such as in equilibrium with iron or hear it and in air. Although most of the smelting and converting processes that use this slag occur at intermediate oxygen potentials, the liquidus surface of this slag is not known at these conditions and the effect of oxygen potential and silica has not been correctly understood. This has brought some confusion in literature as well as in the industrial practice. In this work the liquidus surface of the calcium ferrite slags has been quantified by the means of a new thermophysicochemical model and a new type of liquidus surface diagrams which are very convenient for any industrial process that uses calcium ferrite slags. These diagrams can be easily used to select the lowest liquidus temperature of calcium ferrite slags at a minimum cost and can help design several fluxing strategies in copper smelting and converting processes. The effect of the oxygen potential and silica is also quantified and important industrially related conclusions are drawn.

Jan 1, 2003

By Osamu Takai, Yoshiki Sato, Nobuhiro Tajima, Hiroyuki Sugimura

"Amorphous carbon thin films doped with nitrogen ( a-C:N) have been synthesized by means of shielded arc ion plating (SAIP). Their electron field emission properties, that is, threshold field strengths for electron emission and maximum emission current densities, were evaluated and compared with those of pure amorphous carbon (a-C) films prepared by the same SAIP apparatus. Among all of the fabricated a-C:N films, the a-C:N films with a N concentration of 23 %, which prepared using Nz arc plasm at a pressure of 1 Pa with applying a sample bias voltage of -100 V, showed the lowest threshold filed of 13.4 V/µm and the highest emission current density of 1.87 µAfcm2 at a field of20 V/µm. These field emission properties of the a-C:N film were much better than those of the a-C films. The best results obtained on the a-C film in this study were the lowest threshold filed of 15.5 V/µm and the highest emission current density of 0.052 µA/cm2 at a field of 20 V /µm. Nitrogen doping to aC was found to be effective for lowering threshold voltage for field emission and for increasing emission current density. The electron field emission characteristics of the a-C:N films depended not only on N concentration but also on chemical bonding state of nitrogen in the a-C:N films. The presence of the ~-C3N4-like phase, which contributes to improve wear resistance of a-C:N as well, distinguished by the NlsXPS peak at 400.5 eV is proved to be crucial in order to enhance field emission properties of a-C:N.IntroductionThere has been much interest in electron field emission from a cold cathode due to its potential applications in vacuum microelectronic devices including field emission displays which are expected as flat panel displays in next generation [l]. It is well known that efficient emission can be rather readily realized using tip-like shape cathodes, e.g., microfabricated three-dimensional electrodes [2], carbon nanotubes [3-5], etc. However, electron emission from planar surfaces is of particular importance since such a type of cathode is· simply fabricated and assembled into microelectronic circuits. Currently, amorphous carbon thin films doped with nitrogen (a-C:N) prepared by plasma processes have attracted attention because their threshold voltages of field emission are relatively low [6]. Among various methods for preparing a-C:N films, the process using arc plasma is of special interest since, in arc plasma, nitrogen is highly activated and new types of carbon nitride phase are expected to be synthesized. However, field emission properties of a-C:N prepared by arc plasma have been studied in less detail compared with that prepared by the other methods such as sputtering."

Jan 1, 2000

By I. D. Reznik

Results of thermodynamic computations have been presented for reactions occurring in the process of segregation roasting of oxide nickel ores to describe more accurately the mechanism of the process. Under conditions of laboratory-scale roasting in combination with close-circuit flotation flow-sheets and magnetic separation, a recovery of 80-82% of nickel into 8 to 10% Ni concentrate and a recovery of up to 66% of cobalt was achieved. Process conditions have been selected for processing of both high-iron and high-magnesium ores. The feasibility of conversion of 94-98% of nickel and cobalt into solution by oxidizing pressure leaching with sulfuric acid has been demonstrated. It has been substantiated that it is reasonable to introduce double-stage segregation roasting.

Jan 1, 2003