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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 Yang Jian-guang, Deng Zi-xiang, Zhang Xu-liang, Li Jun-yuan

"Hyperaccumulator biomass harvested after heavy-metal phytoremediation must be considered as hazardous waste that should be contained or treated appropriately before disposal or reuse. As a potential method to detoxify the biomass and to convert this material to a suitable bio-energy resource, the hydrothermal upgrading process was applied to remove heavy metals and upgrading crude bio-oil from Pteris vittata stems and leaves harvest. Parameters such as material granularity, temperature, Liquid/Solid (L/S, ml/g), pressure, duration and catalysts were examined for their effect on the removal efficiency of heavy metals and upgrading efficiency of crude bio-oil. Maximum heavy metal removal efficiency of>99% and crude bio-oil upgrading efficiency of 83% were attained with an 200 mesh (75 µm) granularity, LIS 40:1and23 MPa at 380°C in the presence ofO.l mol L-1 K2C03 for 30 min. GC-MS analysis results show that the resulting bio-oil mainly consists of benzene 11 %, ketone 42%, alcohols 14%, alkene 15% and ester 11 %, etc., and the relative molecular weight distribution lies in 94-282, carbon number distribution lies in 6-18, calorific value is 32MJkg-1.IntroductionPhytoremediation of soil or water with hyperaccumulator has been extensively explored in recent years [1-4]. Living plants can clean up soils or waterways. This approach exploits the ability of various plant species to thrive in high metal environments where large amounts of toxic elements are accumulated, such as heavy metals, and is particularly appropriate when slow remediation of relatively low metal concentrations is acceptable. Advantages compared with existing remediation methods include the minimal site destruction and destabilization, low environmental impact, and favourable aesthetics; advantages compared with biosorption include continuous in situ regeneration of the biomass, and the ability of living plant cells to supplement passive sorption of metals with metabolic mechanisms of metal uptake and detoxification [5-8]."

Jan 1, 2014

By J. A. Sekhar

Solidification processing/casting is increasingly being adopted as the preferred manufacturing technique for the fabrication of net shaped complex geometry components. Modeling of solidification processes is important both for design purposes as well as for understanding the physics of morphological evolution of the solidification microstructure. A fundamental aspect of such modeling involves the precise understanding? of heat transfer through the two phase solid/liquid region. A scheme to do this will be presented where the nonlinearity of the fraction liquid with change in temperature can be incorporated into the numerical calculations. The importance of properly accounting for the non-linear mushy zone will be discussed. Typical processes like squeeze casting and electromagnetic stirring will be discussed to illustrate how precise modeling of the solid/liquid region can aid in the calculation of accurate heat transfer coefficients for these processes.

Jan 1, 1990

By J. E. Dutrizac

The mineral forms of silver, lead and cadmium in the zinc concentrates and the various roaster products made by the Kidd Creek Division of Falconbridge Inc. have been elucidated. In the concentrates, all three elements occur mainly in sulphide form, either in solid solution in the principal ore minerals or as discrete mineral grains. During roasting, Ag, Pb and Cd are preferentially concentrated in the hot cyclone and ESP dusts of the roaster train. Silver is converted to <0.5 µm grains of silver metal and to Ag2S04 which dissolves in or impregnates silicates. Lead is converted to Pb-bearing silicates or to PbS04 and PbO which are present either as tiny free grains in ZnO or as an intergrowth with lead silicate. Lead is also a minor constituent of the ferrite phase. Cadmium occurs mostly as cadmium-bearing zno and ZnFe2o4 , but a significant amount also reports as Cd-bearing silicates or zinc sulphate.

Jan 1, 1990

By R. J. St. Eloi

The Kidd Creek Copper Smelter has been expanded from its original design of 59,000 tonnes of copper per year to over 120,000 tonnes per year .. Modifications to the process gas handling system and acid plant have been made to accommodate this higher production rate and to .generally optimize the operation. The gas handling system associated with the continuous smelting process is discussed in terms of boiler accretions and modifications to minimize their impact on operations; design changes to effect reductions in high pressure drop duct configurations; material changes to overcome corrosion and plant additions to &apos;improve gas cleaning capability. The acid plant is reviewed with references to changes made to accommodate the increased S02 gas strength resulting from the higher smelting rates;

Jan 1, 1992

By Kota Nakashima

Residues from titanium smelting tend to contain scandium. The scandiumis discarded because no suitable process exists for its recovery from the residue. Valuable-metal recovery from discharged residue is critical for environmental conservation and to achieve a sustainable society. Since 2015, JXNippon Mining&Metals has been developing a process for scandium recovery from the residue of a titaniumsmelting process. The process consists of the following steps: scandium concentrating by classification or neutralization, selective scandium leaching, impurity removal by neutralization, solvent extraction of scandium by using D2EHPA, purification, and roasting. We optimized the above steps to achieve an effective process to obtain scandium oxide (Sc2O3). In this paper, we introduce results from the bench-scale test of the scandium recovery flowsheet developed by JX Nippon Mining & Metals.

By F. Garcia-Carcedo

This research aimed to develop a clean technology for the production of ZnO from residues generated by the steel making industry. Scientific and technologic parameters were both investigated in order to define an industrial methodology allowing the integral recycling of EAF dusts. A reengineering of the Waelz process was perform,~d, aiming to produce a clean fraction of ZnO, fluorine free, as well as a slag enriched in metallic iron, which can be recycled in electric arc furnaces. The technical conditions used to produce the ultra pure fraction of ZnO are described. The magnetic separation of the EAF dust allowing the production of a phase high in iron and recyclable to the electric arc furnace is also discussed. Thermodynamic of the volatilization of all the elements contained in the EAF dust was performed in order to better control the thermal process in the rotary kiln. Tests were run using different reducing agents, weakly or highly reactive, aiming to determine their specific efficiency.

Jan 1, 2000

By James B. Pfeiffer

TETRA Technologies, Inc., has applied its HDS? metals precipitation system to control a mine drainage problem. The effluent from the mine contains primarily zinc, manganese and iron, plus varying small amounts of cadmium, copper and lead. The flow from the mine averages 350 gpm, and varies considerably depending on season and weather conditions. The plant was designed to treat 1000 gpm of the water and generate a dense sludge suitable for recycling. The HDS? system contains a number of reactors, followed by post filtration and meets stringent metals discharge criteria as specified by New Source Performance Standards.

Jan 1, 1994

By R. E. Burleigh

&apos;Gold-telluride mineralization was deposited in quartz veins which cut a Late Cretaceous tonalite pluton emplaced near the southern margin of the Peninsular tectono-stratigraphic terrane in south-central Alaska. The gold-bearing veins formed shortly after the development of a widespread Cu-Mo sheeted quartz vein system. Early mineral assemblages consist of quartz, white mica, pyrite, and arsenopyrite (wall rock only). Subsequently, pyrite. sphalerite, chalcopyrite, zoned tetrahedrite and gold precipitated within multiply fractured veins. Late stage galena, tellurides (altaite, nagyagite, coloradoite), and Pb-Sb or Pb-Cu-Bi sulfosalta with gold constitute bonanza ore assemblages that are variably associated with quartz, white mica, ankerite, and calcite. Fluid inclusion evidence coupled with mineral assemblage paragenesis suggests the depletion of volatiles (C02, H2S) and cooling resulted in the precipitation of high grade gold mineral assemblages.

Jan 1, 1988

By Shaik Jeelani, Mahesh Hosur, Esperidiana A. B. Moura, Rejane D. Campos, Emilia S. M. Seo, Kerry Kirwan, Francisco R. V. Díaz, Maria Sotenko

The use of natural fibers with polymeric resins has spread rapidly. In order to improve the mechanical properties of material, in this work, two variables were used: mercerization and electron beam irradiation. This paper describes the preparation and characterization of biocomposites that were prepared in two different routes using green high density polyethylene (HDPE) and Brazil nut pod fiber (BNPF): the first was to irradiate the composite with 150 kGy and the second was to irradiate the matrix with 15 kGy followed by composite preparation. In both cases mercerized and non-mercerized fibers were used. The irradiation process was carried out using a 1.5 MeV electron beam accelerator, at room temperature and in the presence of air. The material was characterized to evaluate the effect of treatment on mechanical properties of material.

Jan 1, 2015

By William Petruk

Mineralogical and image analysis studies have been performed on four volcanogenic base metal ores that contain 0.01 to 4.5 wt% Pb to determine the behaviour of galena during mineral processing. The galena in these ores is fine grained and is poorly liberated in both the primacy and regrind mill discharges. Consequently, low grade Pb concentrates are produced to obtain relatively high Pb recoveries. The Pb concentrates contain many impurities including high amounts of pyrite and sphalerite, and small amount of CU-, As-, Ag-, Bi-, and Se-sulfides. These impurities need to be rejected from the Pb bullion during smelting. The galena commonly contains up to 1 wt% Ag in solid solution with an average of 600 to 1460 ppu for the deposits studied to date. The Ag in galena accounts for up to 65% of the Ag in some ores.

Jan 1, 1990

By Goran Vukovic

The use of gas purging plugs in the copper industry is a widely used practice. They provide substantial improvements especially in anode refining furnaces, where savings in process time and energy are obtained as well as refractory wear and buildups inside the furnace are minimized. The newly developed system, enables purging plugs to be implemented in both stationary and tilting furnaces, is in operation in vessels on three continents. An additional advantage in these furnaces above all other benefits is the significantly improved melting rate. This innovative and patented gas purging system consists of a purging plug cooling device and a slidable, cooled piping system. It provides compensation for any thermal expansion in the furnace lining and minimizes the risk of undesirable copper infiltration. User experiences and results of this widely used system are reported in this paper.

Jan 1, 2014

By Alan M. Russell

In recent years, several rare earth intermetallic compounds with the B2-type structure have been reported to exhibit high tensile ductility and high KIC fracture toughness at room temperature. These materials retain considerable ductility even at 77K. These are noteworthy findings because most intermetallics possess poor room temperature ductility and low fracture toughness unless one or more special contrivances are applied (e.g., doping with small additions of interstitial elements, offstoichiometric compositions, testing in ultra-dry atmospheres, etc.). This paper summarizes recent findings on rare earth B2 intermetallics. These include the determination of the active slip systems; the strain rate sensitivities; yield strength maxima at elevated temperatures; the search for possible twinning and stress-induced phase transformations; ab initio calculations of their defect energies and the anisotropy of dislocation line tension. Potential applications of these materials and the possibilities that this study may suggest strategies for increasing ductility in other intermetallic compounds are discussed.

Jan 1, 2008

By J. D. Scott

The counter-current jarosite acid wash circuit presently in operation in the zinc plant produces a combined jarosite plus Pb/Ag residue which is discarded. Extensive pilot-scale testwork, and some past in-plant operational experience, has shown that the zinc plant can be easily reconfigured to produce two residues during periods of high silver feeds and/or prices. Plant.optimized circuit configurations are available for silver recovery to a Pb/Ag residue and are in use for the prevention of Pb/Ag-jarosite formation in both the neutral and high-acid leaching circuits. Silver in the zinc plant undergoes several changes in state as it proceeds through these circuits. The roaster calcine is ~3:1 silver sulfate: silver metal, with metallic silver mainly as micro-Inclusions In an aluminosilicate phase. In neutral leach residue, the majority is as silver sulfide or Pb/Ag/Zn-sulfide coatings on unroasted sphalerite grains, with minor Pb/Ag-jarosite and some residual metallic silver in unreacted alumina-silicate grains. In high-acid leach residue, silver occurs as Se-rich silver sulfide particles in sulfur/jarosite ball aggregates, as silver sulfate impregnations in silica-gel masses and in solid solution in Pb/K/Zn~jarosite. Silver concentrations in solution range from 20 to 60 ppb.

Jan 1, 1990

By Ryosuke O. Suzuki

A new cell concept for calciothermic reduction is proposed in which the titanium dioxide instead of TiCl4 is used as the raw material for reduction, Metallic calcium is needed as the reductant of a thermochemicaily stable oxide, such as TiO2. CaCl2, is selected as the solvent of Ca and simultaneously as the solvent of CaO. The reduction system consists of a single cell where both the reduction reaction and the electrolytic reaction for recovery of reducing agent coexist in the same molten CaCl2 bath. A few mol%Ca dissolves in the melt and gives the media a strong reducing power. Sufficiently deoxidized metallic titanium deposits and forms a slightly sintered granular sponge. Both mechanisms of the halide flux deoxidation and the electrochemical deoxidation work efficiently for these fine precipitates, The reducing agent is in situ recovered by electrolysis of CaO because the molten CaCl2 he a relatively large solubility for CaO Some cell designs and modifications are proposed for industrial applications.

Jan 1, 2003

By Zhang Yongzhu

Developments on bioleaching of low grade ores and refractory gold ores by T. Ferrooxidans in China are summarized. Effect of the ions on bacterial growth, bioelectrochemical reaction mechanism of sulfide minerals and bacterial reaction mechanism are also discussed.

Jan 1, 1992

By Yufeng Guo, Tao Jiang, Jianjun Fan, Haizheng Hao

"Function of High Pressure Roll Grinding (HPRG) in production of oxidized pellets from magnetite concentrate as raw material was systematically studied. It was found that bentonite dosage decreased from 1.3% to 0.8% if specific surface area of magnetite concentrate pretreated by HPRG was up to 2553.41cm2.g-1. The green ball quality improved obviously due to the increase of specific surface area and fine particles content, and the improvements of size distribution and the ballability of pretreated materials. However, the decrease of pellet porosity accelerated the primary solid phase reaction and oxidation reaction, which made the pellets surface form compacted layer that handicapped the diffusion and migration of oxygen, promoting the formation of double layer structure of finished pellet. Consequently, the compression strength of preheated and roasted pellets was not markedly improved by HPRG.IntroductionWith the increase of proportion of pellets in the BF recently, the technical-economic index of BF has obviously been improved. Consequently, the production and the quality of BF pellet are given more attention [1]. However, with the decrease of the quality of iron ore concentrate, the problems such as poor ballability, high bentonite dosage, high preheating and roasting temperature are becoming the great challenges to not only the quality of finished pellets, but also the energy consumption [2, 3]. In order to overcome these problems, mechanical pretreating technologies such as the High Pressure Roll Grinding (HPRG) and Damp-grinding are widely applied. HPRG has a number of advantages such as low energy consumption, high productivity and easy-maintaining. It is more economic and environmentally friendly than the Damp-grinding technology [4, 5]. A great number of experiments have revealed that HPRG can improve the quality of hematite pellets. Although there are some studies of function of HPRG in the magnetite oxidized pellet production, they are not comprehensive and systematic, especially to the preheating and roasting system [1, 2, 6, 7]. Accordingly, the influence of HPRG on the pelletizing system and the preheating and roasting system are systematically studied in production of magnetite oxidized pellets in this article."

Jan 1, 2011

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 Min Chen, Lei Xu, Weijun Huang, Shuai Zhang

For the purpose of extending the service life of MgO-C bricks used as linings of vanadium-extraction converters, the effect of Fe addition on properties of MgO-C bricks was investigated. The results showed the addition of Fe could effectively improve the sinterability of the oxidized layer of the MgO-C refractory at 1400°C due to the effect of FeO (formed by oxidation of Fe) on formation of MgO-FeOss and modification of the microstructure, and excellent corrosion resistance against vanadium containing slag was also obtained due to the increase of compactness of the oxidized layer and concentration of FeO in the oxidized layer. Consequently, it is considered that MgO-C brick by introducing the new phase of Fe is a favorable substitute of MgO-C refractory to be used as linings of vanadium-extraction converters.

Jan 1, 2015

By Y. Y. Liu, H. M. Domanus, W. T. Sha

"Casting is fundamental to manufacturing of many types of equipment and products. Although casting is a very old technology that has been in existence for hundreds of years, it remains a highly empirical technology, and production of new castings requires an expensive and time-consuming trial-and-error approach.In recent years, mathematical modeling of casting has received increasing attention; however, a majority of the modeling work has been in the area of heat transfer and solidification. Very little work has been done in modeling fluid flow of the liquid melt. This paper presents a model of fluid flow coupled with heat transfer of a liquid melt for casting processes. The model to be described in this paper is an extension of the COMMIX code and is capable of handling castings with any shape, size, and material. A feature of this model is the ability to track the liquid/gas interface and liquid/solid interface. The flow of liquid melt through the sprue and runners and into the mold cavity is calculated as well as three-dimensional temperature and velocity distributions of the liquid melt throughout the casting process.IntroductionBower et al. (1), in their 1969 review of the evolution of some of the casting techniques, stated that:""The evolution of technology requires alternatives to be available so that choices can be made that lead to changes. The role of solidification science and other disciplines related to casting technology is to develop a better understanding of process and product, so that a wider range of alternatives is possible.Alternatives, whether from science or from invention, must lead to improvements in casting ""utility."" Utility, or economic advantage, must include consideration of total system costs, and final product value. The cost of materials, melt processing and finishing should be optimized with casting costs, since all are part of the production system. It is the favorable relationship between total processing costs and product value that makes a change in casting technology viable, but the best change is not possible unless technology has provided an understanding."""

Jan 1, 1986