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By Jilai Xue, Jun Zhu, Germain Kouma Ndong, Qiaochu Liu, Luxing Feng

"High-temperature oxidation and corrosion behaviors of Ni-Fe-Cr alloy as inert anodes for aluminum electrolysis have been studied in oxygen and molten electrolyte. The oxidation and corrosion scales on the anodes tested were analyzed using XRD and SEM-EDS. The oxidation rate is found to increase with increasing temperature from 700 °C to 950 °C, which can be approximately described by an inverse power rate function. The oxidation scales at 750 °C, 920 °C and 950 °C contain Cr-rich phase along with FeCr204 and (Feo.6Cro4)203. The corrosion extent of Ni-Fe-Cr anodes in electrolyte is dominated by temperature, which can make the scales thickness double from 700 °C to 750 °C or from 920 °C to 950 °C. Cr and Fe in the scales on the anode in electrolysis corrode preferentially into the molten electrolyte, while the nickel oxides could better sustain the corrosive environment in electrolysis. The results can be useful for developing inert anode material for potential application in aluminum electrolysis.IntroductionThe development of an inert anode for aluminum electrolysis has been a long term goal for aluminum industry. The present process for primary aluminum production involves the reduction of alumina with carbon anodes, forming carbon dioxide:"

Jan 1, 2013

By J. D. Law

The presence of long-lived radionuclides presents a challenge to the management of radioactive wastes. Separation of the radionuclides from the waste solutions has the potential of significantly decreasing the costs associated with the immobilization and disposal of the waste by minimizing waste volumes. Several solvent extraction processes have been developed at the Idaho National Engineering and Environmental Laboratory for the separation of transuranic elements (TRUs), 90 Sr, and/or 137 Cs from acidic radioactive waste solutions. The TRUEX and POR processes for the separation of TRUs, the SREX process for the separation of 90Sr, the cobalt dicarbollide process for the separation of 137Cs and and a universal solvent extraction process for the simultaneous separation of TRUs, 90Sr, and 137Cs have all been developed in centrifugal contactors using actual liquid radioactive waste solutions and simulated dissolved calcine waste solution. In addition, the behavior of metals with each of the solvent extraction processes was evaluated. This article summarizes the most recent results of the each of the flowsheet demonstrations and provides Information on the centrifugal contactor equipment used for the testing.

Jan 1, 1999

By Jinqian Zhao, Jiarong Li, Shizhong Liu

"Creep cavitation of in single crystal (SX) superalloy was investigated. The constant load creep tests, in single crystal superalloys DD6, were conducted at the conditions of 800°C/700MPa, 850°C/550MPa and 900°C/450MPa, respectively. It was found that there were square facets on the stress fracture surface, and microscopic cavities in the ruptured specimens in the vicinity of the fracture surface. Both the square facets on the fracture surface and microscopic cavities in the section of the ruptured specimens show the morphology of the same thing at the different views, namely creep cavities, which are take the form of flatten cuboid. In fact, creep cavities are the longitudinally tensiled creep cracks slowly growing during the stress tensiling. The factors of creep cracks nucleation and growth conditions include: (a) enough high temperature to activate diffusion (b) casting pores as nucleation origination (c) high strains and strain rates. Eventually, the instantaneous fracture mechanism of creep specimen is cleavage fracture.IntroductionFor the materials used in elevated temperature service, creep behavior has to be accounted for. It is well recognized that creep rupture in polycrystalline materials at high temperature occurs principally by the nucleation and growth of microscopic cavities at grain boundaries, followed by microscopic cavities linkage to form micro- and eventually macro-intergranular cracks[l,2]. Without the usual grain boundaries, SX superalloys have superior capabilities at high temperatures to polycrystalline superalloys, and have become an established feature of gas turbine technology where they are commonly employed in the manufacture of high performance blades[3]. A considerable amount of work has been done over the past tens of years, and many models for nucleation and growth of creep cavities have been proposed, however, those are mainly for polycrystalline materials.In order to improve creep resistance that single crystal superalloys, in which grain boundaries are removed, have been developed. Because there don't exist grain boundaries in SX superalloy, the mechanism of nucleation and growth of creep cavities must be different from that in polycrystalline materials.Understanding the formation and characteristics of creep cavitation is crucial to model the lives of single crystal superalloys.M. Marchionni and L.G. Zhao et al. found that there were square facets on the stress fracture surface [4,5]. Roger C. Reed pointed out creep cavities lie in the necked region[6]. In this paper, the effects on the formation of creep cavities are discussed, as well as the morphology of creep cavities and fracture mechanism of SX superalloys."

Jan 1, 2013

By W. J. Guay

Scrubbing of simulated copper reverberatory furnace gases containing 1.0 percent sulfur dioxide with the minus 74 ~m fraction of the San Manuel tailings has shown sulfur dioxide removals of almost 100 percent over an effluent pH range of 3.1 to 4.6 and a wide range of liquid to gas ratios with absorptions of 11 to 17 Kg of sulfur dioxide per tonne of minus 74 um slimes. The high reactivity of the tailings slimes with S02 indicates that the reaction rate is not controlled by the slow dissolution of calcium carbonate in sulfurous acid which characterizes scrubbers using ground limestone. The interpretation of these results has been considerably enhanced by wet chemical analysis and emission spectrographic analysis which show that calcium and iron account for about 90 percent of the SO2 absorption with the rest being accounted for by aluminum, magnesium, potassium, and sodium. Mineralogic examination confirms the, chemical and spectrographic analyses showing that the major constituent removed from the slimes is calcium carbonate, with lesser amounts of chlorite and montmorillonite (silicates containing iron, magnesium, aluminum, and calcium) being removed.

Jan 1, 1981

By M. -L. Metsärinta, J. Nyberg, A. Roine

The Kokkola roasting plant uses more than 20 different zinc concentrates every year. During recent years there has been an increase in the variation in concentrate quality; in particular, the amount of fine-grained and low-grade concentrates has increased. Therefore, a great deal of development work has been carried out to improve the operational flexibility, online availability, production capacity and calcine quality of the roasting plant. This work consisted of a heat and material balance model of the roasting based on HSC Chemistry software, a new water admixture system for the concentrate feed, a new oxygen feed system for the process air line, improved cooling of the furnace and boiler and improved operational practices, dust removal and concentrate mixing. These new process control tools and other improvements, as well as some test results, will be described in this paper. The oxygen feed may be used to improve production capacity and to decrease the sulfide content of the calcine. The water feed may be used with fine concentrates to decrease both dust carry-over and the temperature in the top part of the furnace. Improved cooling of the furnace and boiler helps to increase production capacity.

Jan 1, 2000

By Baptiste Laubie

Agromining is a phytotechnology aiming at producing commercial metal compounds from low-grade ores thanks to hyperaccumulating plants. The fern Dichranopteris dichotoma is a rare earth element (REE) hyperaccumulator, which naturally grows on former mine tailings in China. It accumulates up to 0.35% of REEs in its aerial parts. Different hydrometallurgical processes are currently developed to recover these elements directly from the biomass or from ashes after combustion. The process presented here consists of a direct extraction by EDTA solution, followed by precipitation with acid oxalic. Optimal precipitation pH and influence of organic matter are determined by modelling and by experimental studies. The final solid contains 4.3% of REEs, with calcium as the main cationic impurity (0.45% of the precipitate). The recovery yield is similar for major REEs and is around 70%. After optimization, upscaling of the process will allow the agromining development to recover REEs from secondary resources with more environmentally friendly techniques.

By Cong Wang, Siyang Long, Pengcheng Zhang, Haibin Zuo

The present study describes central segregation of the High-carbon steel billets of 150mm square and its heredity to the following hot-rolled wire rods, whose sizes are 10mm and 6.5mm in diameter separately. The relationship between center segregation of the billets and solute element distribution of rods, the mechanical properties and microstructure of rods were studied experimentally. The results show that segregation index of C is higher than that of Mn. With the increase of central segregation, the stability of the mechanical property of the rods becomes worse. The formation of carbide network and central martensite in the rolled products can be attributed to the heredity of the as-cast central segregation. The 6.5mm-diameter-rod has higher tensile strength than that of 10mm diameter which might be due to bigger reduction ratio. Thermo Mechanical Control Process (TMCP) should be used together with Billet Centersegregation- controlling (BCSC) to improve the overall properties of rolled products effectively.

Jan 1, 2016

By Hector Henao

To provide thermodynamic data for converting the nickel matte to liquid nickel, an experimental study was conducted in the phase equilibrium between the Ni-S alloy and the CaO-Al2O3 based slag melted in a MgO crucible at 1873 K under controlled Pso2 of 10.1 kPa and Po2 in a range between 2.5x 10-and 10.1 Pa by using CO-CO2-SO2 gas mixtures. The content of nickel in the slag at Po, of 10.1 Pa, above which solid NiO is expected to precipitate in the equilibrium state, was found to be 4, I mass% and the contents of sulfur and oxygen in the nickel melt were 0.4 and 02 mass%, respectively. ft was clarified that increase in the temperature reduces the solubility of nickel in the slag and the contents of sulfur and oxygen in the alloy, The distribution of minor elements such as gold, silver, copper, cobalt, iron, arsenic and antimony between the Ni-S alloy and the CaO-Al2O3 based slag was also studied. The distribution ratios of iron and cobalt, defined by (%X in slag)/[%X in alloy] where X is the minor element, are larger values than that of nickel, while those of copper, silver and antimony are similar to that of nickel. The distribution ratios of arsenic and gold are lower than that of nickel in the higher range of oxygen partial pressure.

Jan 1, 2003

By Tong Zhilin

The reasons why the pits were formed on the cathode in the process of Ni electrowinning and the methods how to prevent these pits from forming are described. Some examples are presented. It has 'been proven that P507 and P204 present in the electrolyte can effectively prevent pits from forming on the cathode.

Jan 1, 1993

By A. P. Pavia

Investigation on profitable ways to recover significant quantities of silver remaining dissolved in highly concentrated chloride solutions frequently pass through the development of solvent extraction (SX) routes. In this work, the general pathways involving Ag(I) extraction by dibutylthiourea (DBT) or tetraethylthiuram disulfide (disulfiram, DSF), from concentrated acidic chloride solutions, are investigated. With this purpose, the dependence of Ag(I) distribution coefficient on ligand and chloride concentrations has been analysed. Furthermore, in order to check whether there is some protonation at any site of DBT or DSF after contact with adequate chloride phases, lH NMR has also been used. The collected spectroscopic data suggest that anionic Ag(I) extraction reactions are not likely to occur. Based on the overall results achieved, proposals for the most probable Ag(I) extraction reactions are made.

Jan 1, 2001

By Zhang Hengzhong

Based on thermodynamics of surfaces and a proposed two-dimensional state equation for surfaces, the relationship between the surface tension (Y) of a solution and the activity (a1) of its component (i) was derived: (1/Y)r2-.¬E (ai/Yl) The derived equation was verified with reported experimental data of water-alcohol systems and water-acetone system, the calculated results showed astonishing coincidence with experimental. Applications of the equation to the five matte systems Cu2S-FeS, Ni3S2-FeS, FeS-PbS, Cu2S-PbS and FeS-Cu22S-PbS also demonstrated that at given matte compositions the calculated surface tensions agreed with experimental fairy well.

Jan 1, 1993

By V. Jiricny

There is a growing need to process galvanized steel scrap from automobiles, etc., in order to remove the zinc coating that otherwise causes problems in remelting of the scrap in electric arc furnaces. One approach that has moved to the pilot plant stage is that of Metal Recovery Technologies, Inc., of East Chicago (MRI). That company leaches the zinc fiom the scrap with a sodium hydroxide solution. The leached and washed scrap can then be returned to the steel industry. What is left is a sodium hydroxidelzincate solution which must be processed to recover the zinc and the NaOH. Presently, this is done by MRI using electrodeposition on planar electrodes at moderate current density and the resulting zinc is in the form of fine powder which is hard to process into, say, zinc for galvanizing. MRI has supported an investigation of a novel electrode, the spouted bed electrode (SBE), for zinc electrodeposition. In laboratory cells, zinc particles with low porosity have been grown up to 3mm in size. Microanalysis of the deposited zinc showed low level of impurities. DC energy consumption values were usually in the range of 2-2.5 kWg which is well below the energy consumption of the existing cells (and of present-day cells for electrowinning from acid sulfate electrolytes). These results were achieved at current densities (few thousand A/m2) that are much higher than possible with conventional electrodes. Discussion is provided of the scale-up of the cell to a commercial scale.

Jan 1, 1998

By Richard D. Hagni

Quantitative techniques have become increasingly important in recent years in the study of ore minerals. Precise measurement of indentation hardness and reflectance is the most important quantitative ore microscopic technique for mineral identification. Reflectance measurements of various wave lengths under monochromatic light provide the data necessary for the preparation of spectral reflectance curves and for the quantitative determination of an ore mineral's color. The procedures for the measurement of indentation hardness, reflectance, and color coordinates have recently been standardized and 204 items of quantitative data for ore minerals are now available in the first issue of the quantitative data file of the International Mineralogical Association's Commission on Ore Microscopy. A number of systems utilizing these quantitative data for systematic ore mineral identification have been published and others are in preparation. Rotation properties, although not included on the data cards, are useful in the identification of certain groups of minerals. Other aspects of quantitative ore microscopic techniques include the utilization of automatic image analysis for mineral percentage determinations and the use o~ various microbeam instruments for elemental analyses. These techniques provide a greatly improved basis for mineral identification in mineralogical and beneficiation studies.

Jan 1, 1981

By Fu-Shen Zhang, Mengjun Chen, Jianxin Zhu

"A novel approach for foam glass preparation, namely vacuum-aided powder sintering technique, was preliminarily investigated in the present communication. The key point of which was to prepare foam glass at a negative pressure. Compared to normal powder sintering process, the new approach could benefit the foaming process by shorting the holding time, reducing the amount of foaming agent and especially decreasing relative density of the product. Optimum conditions were 750 °C, 1000 Pa, 5 min and 1 wt.% foaming agent, respectively.IntroductionFoam glass represents a highly valuable solution for thermal and acoustic insulation, since it possesses a generally higher mechanical, chemical and thermal stability than other foams'1'. The first industrial processing for foam glass production, the direct introduction of gases (""blowing"") into the special molten glass, can be dated back to the end of 1930s'2'. At present, almost all foam glasses is prepared by powder sintering technique instead of blowing,3 since it reduces the temperature by several hundred degrees. Moreover, as fine glass powders or similar powders can be used to substitute corresponding glasses by this technique, considerable attention has been focused on the production of foam glass by considering fully recycled glasses, coal fly ash, or other solid wastes as raw materials,4 especially CRT glasses'3' 5', on the point of environmental protection.In a previous report'6', when discussing the lead removal and recovery from CRT funnel glass by a pyrovacuum process, we found that foam glass could be prepared at a negative pressure. Therefore, in this communication, the similarities and differences between the powder sintering process for foam glass at normal and negative pressure was preliminarily discussed."

Jan 1, 2011

By Faustino G. Prado

In the, quest for an economical and environmentally friendly reclamation of metallurgical dusts generated during pyrometallurgical operations, our goal has been the separation and recovery of most of the components, as well as the complete recycle of all the reagents. Effluents have been avoided, within acceptable economic parameters. This presentation, which can be applied to a large spectrum of dusts and other residual-materials-, has focused on the dusts generated by the operation of Secondary Copper Smelters. Those dusts show a wide range of components, including zinc, lead-, copper, cadmium, tin, chlorine and-alkalies. Our present work deals with the use of ammonium salts in the separation and recovery of-the above mentioned elements in a marketable form. Most of the chemistry and techniques involved have teen already confirmed in commercial scale operations. Others have gone through pilot scale tests or bench scale tests. The recycle of reagents has also been- confirmed at the same operating levels. A preliminary evaluation indicates that the chosen route, in addition to a viable economy, offers a complete and safe reclamation within the most strict environmental regulations.

Jan 1, 1995

By Hylton McWhinney, Doanh Tran, Jewel Andrew Gomes, George Irwin, Sameer Pallavkar, Md Islam, David Cocke, Mohammad Rafiqul Islam

"High-performance nickel-based nanocrystalline zinc oxide adsorbents have been prepared adjusting Ni/Zn mol ratio of 1 :5 by thermal decomposition, coprecipitation and sol-gel method for selective adsorption of thiophene in liquid hydrocarbon fuels at ambient temperature and pressure. To understand the nature of reactive adsorption of thiophene (C4H4S) on Ni/ZnO, the effect of preparation techniques, morphological and textural structure on the desulfurization activity was investigated. A model fuel (20 mL) consisting of pentane (C5H12) and thiophene was prepared and adsorption experiments were performed by a batch method under ambient conditions. The physicochemical behaviors of the fresh adsorbents were obtained using X-ray diffraction (XRD) with EDAX, scanning electron microscopy (SEM). The sulfur concentration in the mixture was monitored by UV-vis spectrophotometry. The adsorption reaction confirmed that ZnO played a crucial role in taking up S element to convert it into ZnS. The deposition of nickel on ZnO is an innovative approach which takes advantage of the selectivity of Ni towards S-species and the high adsorptive capacity of ZnO support.IntroductionLow temperature deep desulfurization of fuels via selective adsorption of sulfur compounds keeping coexisting aromatic hydrocarbons and olefins intact is receiving increasing attention in the research community worldwide in order to satisfy the upcoming environmental regulations and fuel specifications. The sulfur compounds in the transportation fuels is a matter of concern when global crude oil slate is becoming heavier and sourer and environmental restrictions on both the refining process and the refined products are becoming more stringent. According to the current refinery technologies, the sulfur content in refinery fuel is typically around 300-500 ppm by weight (ppmw) [1-3]. Starting in 2006, sulfur limits in highway diesel and gasoline were set to 15 ppm and 30 ppm, respectively. During combustion sulfur in the fuel are converted to toxic sulfur oxide (SOx) and contributes to air pollution and acid rains [ 4]."

Jan 1, 2011

By John C. Carpenter

Solvent extraction is used to selectively recover copper from iron containing sulphate solutions. As chloride ions, which form series of complexes with transition metals, are now being used for leaching. Little is known of the effects of these ions, on solvent extraction behavior. It has been shown that commercial extractants of the L1X and Kelex series extract copper from chloride media: (1) at a lower pH than from sulphate solutions, (2) to similar loadings, and (3) except for L1X 63, without transferring chloride to the organic phase. A process for selective extraction of copper from chloride solutions should thus be compatible with standard stripping and electrowinning practice. Of several diluents, differing in aromaticity, kerosene gave enhanced extraction only with L1X reagents. A change in operating temperature had little effect on equilibrium metal distribution. All the extractants examined gave adequate separation of copper from iron. L1X 63 was found to extract chloro-complexes of copper and of iron and thus transfer chloride to the organic solution. Consequently this extractant and its mixtures are not preferred for use with chloride leaching systems.

Jan 1, 1976

By G. L. Hundley, D. N. Nilsen

The U.S. Department of Energy investigated the use of liquid-emulsion membranes (LEM) for the selective removal and recovery of metals such as copper and zinc from mine waste waters. This investigation included field tests of a mobile, pilot plant-scale, continuous-flow LEM system. The system was tested at copper mines with solutions containing from 100 to 1,400 ppm Cu, and at a zinc mine with a solution containing 115 ppm Zn. Typical results from the copper tests were >90% copper recovery, and zinc extraction from waste water also was typically>90%. Although all of these waste waters contained high impurity levels, pure products were produced. On several of these field tests, integrated systems were tested that resulted in recovery of metal by-products, selectiv~ precipitation of iron, and polishing to reach discharge targets for essentially all of the contained metals. In addition, some results are included from laboratory-scale tests.

Jan 1, 2000

By Joseph Goodwill

1. PURPOSE The objective of this paper is to summarize a study undertaken by the EPRI Center for Metals Production (CMP). The overall purpose of the study was to identify electrolytic opportunities that might merit consideration for joint development by industry and EPRI. 2. SCOPE The electrolytic technologies of interest to this study include: Electrorefining, Electrowinning, and Fused-salt electrolysis. Recovery from primary, secondary, and waste materials were included in this effort; however, we excluded from consideration: Plating and coating operations, such as electrogalvanizing; Mining and milling operations in which electric energy is predominantly used for comminution; Electrothermal processes in which submerged-arc, open electric-arc, and plasma-based smelting processes use electric energy largely to provide a melting or refining ("heating") capability; and Aluminum electrotechnologies since these were the subject of a separate study (CMP 86-2). We recognize that there may be some "gray areas" between these excluded areas and the electrolytic sectors of interest. For this reason, a secondary criterium was used, namely, if the major use of electric energy was to extract or refine the

Jan 1, 1990

By N. L. Piret

In copper smelting minimization of solid waste generation is receiving increased attention with more stringent environmental legislation and lower disposal space availability. Copper smelting slags generally being valorizable, solid waste generation is attributed to the presence in the feed of unvalorizable impurities which do not report to the slag and to the unavoidable formation of contaminated dilute acid solutions which need neutralization. As to unvalorizable impurities, solid waste minimization is achieved by rejecting them in the highest possible concentration. Dilute acid is mainly due to the formation of SO3 in the smelter gases and to the discard of decopperized bleed-off electrolyte. Its generation is substantially lowered by preventing SO3 formation, by converting the dilute acid to a valorizable product, e.g., by thermal decomposition for H2S04 recovery or by precipitation as chemical gypsum, and by suitable treatment of the bleed-off electrolyte for impurity removal. Industrial processes are evaluated and alternatives are discussed.

Jan 1, 1994