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By Xi Zhang

A technique for fabricating free-standing, high-aspect-ratio porous and pillar-type Ni structures has been developed using wet Si processing. A wafer of (100) Si was initially etched in HF solution to form deep pores with micron-sized diameter. The aspect ratio can exceed 200. By introducing the as-etched Si into a defined aqueous Ni2+ solution, Ni deposits grew rapidly onto the sidewalls and replaced the Si. Long-time immersion allows the Si sidewalls to be completely converted and thus form a metallic Ni structure with high-aspect-ratio pores. It is known that close-packed submicron Si pillars can be formed by oxidizing and subsequent etching of the macropore sidewalls. Treated in the same Ni solution, high-aspect-ratio Ni pillars were correspondingly emerged by replicating the original pillar-type Si structure.

Jan 1, 2006

By V. Baltazar

The behaviour of arsenic and antimony during copper electrorefining was studied in order to identify the conditions under which good quality copper cathodes could be produced from anodes with high levels of these impurities. Examination of the effect of current density over the range 21 to 37 mA/cm2 indicated that the relative amounts of As and Sb entering the electrolyte affected the onset of passivation. When the ratio of As/Sb entering the electrolyte was greater than 2, the anodes showed no sign of passivation even at the highest current density; when the ratio was less than 2, the anodes passivated at 37 mA/cm2. Cathode analyses showed that anodes with an As/Sb dissolution ratio less than 2.0 tend to produce cathodes of inferior quality even at normal current densities (25.7 mA/cm2). The criterion of a minimum As/Sb dissolution ratio of 2.0, and mathematical correlations for the distribution of As and Sb between the electrolyte and slime developed in a previous study, allow the calculation of the maximum allowable Sb level in en anode for a given As concentration. Analyses of plant data at the CCR Division of Noranda Inc. for the last four years of operation have demonstrated that the use of this as a quality control tool has allowed the quality of copper cathodes to be maintained despite a significant increase in the average Sb levels in anode receipts.

Jan 1, 1987

By John L. Sundstrom

Complete systems were designed -and are in operation to recycle the effluent streams and to remove impurities from tankhouse. electrolyte, Heavy em¬phasis was placed on making usable products from as many streams as poss¬ible at minimum capital and operating costs. Almost complete recycling: and reuse of water and sulfuric acid were paramount. Techniques used in-clude solvent extraction - electrowinning, evaporation - crystallization and filtration.

Jan 1, 1992

By Teixeira

An experimental investigation on the kinetics of oxidation of As(III) with H202 in synthetic effluent solutions followed by precipitation of Fe/As (V) compounds was carried out. The variables investigated were: As concentration (200 -3000 mg/l) , oxidation pH (2.0 -11.0), oxidation temperature (25 -800C) , H202 stoichiometric excess (50% -100%), precipitation pH (5.0 -7.0), precipitation agent (Fe2+ -Fe3+). Fixed conditions were, Fe/As molar ratio (6:1) and stirring speed (560 rpm). The results were empirically modelled. The precipitates obtained were amorphous. The precipitates were checked upon their environmental stability according to the United States Environmental Protection Agency (U.S.E.P.A.) Toxicity Test, and were considered to be adequate for deposition in impermeable waste dumps. The combined Fe/H202 detoxification process, in selected conditions, was able to reduce the As contents of effluents containing 1600 mg/l As to 0.1 mg/l, in about 2 1/2 hours of total processing time.

Jan 1, 1990

By Donggen Fang, Liu Xuan, Jilai Xue

SiO2 and Al2O3 in the metallurgical slag of nickel laterite ore have great recycling values. In this work, Si and Al were extracted from the slag in NaOH based molten salts through alkali roasting and water leaching process for preparing zeolite materials. The extraction ratio of SiO2 increases with increased temperature and appropriately prolonged time, and more than 80% SiO2 can be recycled from the slag after roasting at 550°C. Si and Al from the slag are in the filtered liquor for producing zeolite materials, while Mg, Ca, Fe and other impurities remain in the leached residues. Adding Na2CO3 into the alkalin-slag roasting process can reduce the amount of pure NaOH used with minor decrease in extraction ratio of SiO2, while make better separation of Ca to avoid it getting into the filtered liquor. Adding Al2O3 into the alkalin roasting process can replace part of more expensive NaAlO2 addition that is required for preparing zeotite material, which may bring out a minor decrease in extraction ratio of SiO2 due to formation of NaAlSiO 4 in the filtered residues. Quality X zeolite and 4A zeolite materials can be made from the starting liquor containing Si and Al recycled from the laterite nickel slag through alkali roasting and water leaching process.

Mar 1, 2018

By Jian-Xun Fu, Hong-Qiang Liu, Si-Yu Liu

The production of zinc-bearing solid dust is up to 4%~8% of total crude steel in steel plant, which is difficult to be recycled in traditional methods. To fully utilize the resources and reduce environmental pollutions, Chinese steel plants are using rotary hearth furnace (RHF) process to recycle solid dust. A consequential life-cycle inventory was carried out to assess the impact of dust recovery on greenhouse gas emissions based on the local production status. In the study system, the selected steel plant named which have 10.5 million tons of Crude steel productivity and 0.48 million tons solid dust come out meanwhile. To research, a RHF production line of 0.3 million tons directly reduced iron (DRI) a year was established to recycle the solid dust. The DRI will be obtained from RHF and sent to the blast furnace as raw materials to reduce the demand for iron ore and coke in steelmaking processes. By researching on the life-cycle inventory in the system, the steelmaking process with RHF was 2299.3kgCO2/ton steel. It’s a little higher while compared with the process without RHF, which data is 2297.0 kgCO2/ton steel. The small production of DRI make a small difference to reduce the carbon footprint of steelmaking process, the added carbon footprint of RHF process is more than BF and other steelmaking processes reduced. It is concluded that dust recovery has no contribution to the greenhouse gas emission reductions in the technic condition of Chinese steel plants currently.

Jan 1, 2016

By T. R. A. Davey

A simple model for metal solution behaviour may be derived, on the basis of dilute solution solubilities (where? log concentration of solute varies linearly with reciprocal temperature) and not-so-dilute region solubilities (where the log of the alpha-function at saturation frequently varies linearly with reciprocal temperature) and assuming activity to vary according to the quadratic formalism in between. Matte binary systems usually exhibit regular .solution behaviour when the constituent species are chosen appropriately. In many recent papers, metal solubilities in .slags are expressed as the sum of several different and supposedly independant molecular species (e.g. oxides, sulfides, chlorides), Such a view is untenable because of the now proven ionic nature of slags. Some possible reasons for the great effect of sulfur on copper solubilities in slags are discussed.

Jan 1, 1985

By Jianhua Xin, Min Chen, Jin Xu, Hui Li, Nan Wang, Ming Chen

The kinetics study of blast furnace dust (BFD) recycling with flash reduction process at high temperature has been carried out using a high temperature drop tube furnace in laboratory scale. A combination characterization methods of chemical titration and SEM-EDS were used to track the reduction kinetics. The experiments using CO and CO2 mixtures with range of CO/CO2 (1:0, 1:1) at different temperature (1623–1723 K) and at different reduction time (1560– 2340 ms) were conducted. It was found that the reduction degree increases with the increase of temperature and reduction time as well as CO concentration. The carbon contained in the original BFD has weak in fluence on the reduction potential in the form of gasification. The unreacted core model was adopted based on the observation of the cross section and the measurement of iron element content, the effective diffusion coef ficient and reaction rate constant were determined and the rate controlling step was also analyzed.

Mar 1, 2018

By C. M. F. Vieira

This work has as its objective to characterize ceramic bodies for vitrified tiles elaborated with the mixture of nepheline-syenite flux and kaolinitic clay. Formulations were prepared with 0, 30 and 50 wt.% of nepheline-syenite incorporated in a kaolinitic clay. To determine the physical and mechanical properties such as dry bulk density, linear shrinkage, water absorption and flexural rupture strength, specimens were prepared by 30 MPa uniaxial pressure-molding and then fired in a laboratory furnace at 1150oC. The microstructure of the fired ceramics was evaluated by scanning electron microscopy. The results indicated that the nepheline-syenite improved the evaluated properties of the clay and attended the specifications of vitrified ceramic tiles.

Jan 1, 2010

By C. P. Manning

This paper reports recent progress in the development of a unique metal extraction technology utilizing zirconia-based inert anodes for the electrolytic reduction of metals from their oxides. In this process, the target metal oxide is dissolved in an ionically conducting liquid solvent phase. An extended anode consisting of an oxygen-ion-conducting stabilized zirconia membrane in intimate contact with a catalytically active electronic phase and an inert electronically conducting cathode are inserted into the molten flux containing the oxide. When the appropriate electric potential is applied between the electrodes the target metal is reduced at the cathode and oxygen ions are selectively transported across the stabilized zirconia membrane and oxidized at the anode. When the process is conducted at temperatures between 1200-1400°C, the ohmic resistance drop across the stabilized zirconia membrane is low, and high current densities on the order of I A/cm2 or greater can be obtained. In addition, the process efficiency can be increased further by directly reforming hydrocarbon fuel over the anode. Laboratory experiments at Boston University have demonstrated the technical viability of employing zirconia-based inert anodes for environmentally sound production of metals such as magnesium, tantalum, aluminum, etc., directly from their oxides. Significant progress has been made in the application of this concept to the electrolytic reduction of magnesium at 1300°C. The research topics covered include stability of the zirconia membrane in the selected molten solvent (flux), volatility of the flux, electrochemical characterization of the electrolytic cell, and analysis of the metals produced.

Jan 1, 2003

By Aiyuan Ma, Tu Hu, Chenyu Sun, Yonggang Zuo, Hongying Xia, Jinhui Peng, Libo Zhang, Yongguang Luo

"In this study, the adsorption characteristics of tannin acid in aqueous solution were investigated using regenerated activated carbon (AC), with the aim to remove the tannin acid organic matter from the solution after zinc hydrometallurgy and Ge precipitation. Results showed the temperature has little effect on the adsorption ability (q.) of the regenerated activated carbon. The experimental equilibrium data were tested for the Langmuir and Freundlich isotherms. The adsorption equilibrium was better described by the Langmuir isotherm (R2 > 0.99). Pseudo first- and second-order kinetic models were used for describing kinetic data. It was determined that the kinetics of tannin acid removal was well fitted by second-order reaction.IntroductionGermanium recovery is a complex processes [1]. Hydrometallurgical processes are favoured and these are based on the precipitation of germanium as hydroxide or sulphide or alternately with tannic acid [2]. However, in the germanium recovery process, too much tannin is consumed by the germanium-tannins complexation process, and results in a high content of tannic acid remaining in solution, which is harmful to the valuable metal recovery [3]."

Jan 1, 2014

By Wenjun Duan, Zhimei Wang, Tianwei Wu, Qingbo Yu

In order to recover the waste heat of molten blast furnace slag, a reactor with top-submerged lance was established. The numerical simulation and experiment study of the flow characteristic in the reactor were conducted. The mathematical model of reactor was established and the Euler-Euler model was employed to simulate the gas-liquid flow in molten slag bath. Meanwhile, the experiment results were obtained and compared with the simulation to testify the accuracy of the established model. According to the bubble behavior in bath, there were four stages: initial expansion stage, bubble detachment stage, freedom lift up stage and bubble broken stage. When the flow field in bath fully developed, the gas fraction decreased with the increasing of bath depth. During injection process, the area near the nozzle and lower the bath would first generate two symmetric heliciform flow regime, and then the flow regime in whole bath would become irregular because of bubble lifting up and rupturing. The gas fraction in bath, the average velocity and turbulence energy of slag would decrease before it increased to maximum and then it would keep fluctuate in a range.

Mar 1, 2018

By John M. Gaines

Lead concentrates from the Viburnum Trend in the Southeast Missouri Lead district are sintered prior to smelting to bind the particles together homogenize the feed, and reduce the sulfur content. Good sinter forms competent masses about 4 to 6 inches across, that hal!e about 15% porosity and good mechanical strength to withstand transport and the weight of the overlying load in the smelter. Bad sinter has poor mechanical strength and forms fine fragments that retard the circulation of reducing gases in the furnace and lengthen the time required for reduction. The productivity of the lead smelter depends on good sinter feed. Because some lead sinter plants produce bad sinter about 20% of the time, this applied mineralogy study has been undertaken to determine the mineralogical and microtextural differences between good and bad sinter. A reflected light microscopic study of 130 polished sections has shown that good and bad sinters differ distinctly in their mineralogy, tex1ure. and character of, porosity. Good sinter consists of hardystonite, franklinite. lead-zinc-bearing magnesium-calcium silicate, lead silicate matrix, and large crystals of calcium-magnesium-iron silicate, together with minor amounts of lead oxides, lead-zinc silicate, metallic lead, specular hematite, magnetite, lead-iron-bearing zincite and zinc-Iead-magnesium-bearing wustite in a tightly intergrown mesh of crystals and with an evenly distributed porosity of 15% to 20%. Electron microprobe analyses show that the principal phases contain lead (or zinc): hardystonite (4-20% Pb) franklinite (2-14% Pb) and lead silicate matrix (65-74% Pb). Bad sinter differs from good sinter in the greater abundance of lead silicate matrix, galena metallic lead, and lead oxides and the lesser abundance of hardystonite, franklinite and calcium-magnesium-iron silicate. Bad Sinter is characterized by a lack of an intimate intergrowth of the constituent phases. Its porosity is much lower commonly 0 to 5% and those pores are concentrated in local areas rather than distributed evenly throughout the sinter.

Jan 1, 1991

By Stavros A. Argyropoulos, Henry H. Hu

"The assimilation of exothermic additions in liquid metals exhibit an array of unique coupled heat, mass and momentum transport phenomena. These phenomena are further complicated by the presence of a moving boundary.This paper describes a) A mathematical model which simulates the complex phenomena, and b) An extensive verification of the mathematical model. The SIMPLER algorithm was employed to solve numerically the pertinent partial differential equations. The computational results indicated that the exothermic heat of mixing led to a rapid increase in temperature around the moving boundary, which produced an enhanced convective flow in the liquid phase. The intensification of fluid flow around the moving boundary resulted in an acceleration of the melting process.Verification of the model was carried out in two contexts. The first was, in a low temperature physical model consisting of ice immersion in different sulfuric acid solutions. In this physical model, both temperature and velocity measurements were carried out. The model results were compared with experimental measurements and they were found to be in excellent agreement. The second context employed high temperatures, involving the assimilation of silicon in high carbon liquid iron. The model was also applied to predict fluid flow, heat and mass transfer for these high temperature experiments and a good agreement was obtained.In addition new dimensionless heat transfer correlations that quantify these complex phenomena will be presented."

Jan 1, 2001

By Claudio Toro, Alex Moyano, Jonkion Font, Carlos Caballero, Pedro Morales

"Codelco-Chile in the last decade has carried out industrially-oriented research as an alternative to the traditional batch-type converting process. In a first stage carried out preliminary evaluations in a rearranged Peirce Smith (PS) converter, and then an exploratory test in a “Convertidor Teniente” (Teniente converter, TC) for the Codelco-Chile Continuous Converting Process. However, the validation test for this process in the TC was delayed up to the second quarter of 2007 where the validation studies were done satisfactorily.Thus, the objective of this paper is to present the results of the campaign tests validating the Codelco-Chile Continuous Converting Process in the TC1 of the Codelco Norte smelter.The results of charging the solid or liquid matte or high grade matte (“white metal”) by Garrgun, or by mouth of the 22 m x 5 m TC1 are presented. Some features of the industrially validated process are discussed, and the pilot test results of the matte injection are also presented."

Jan 1, 2009

By Nils Eivind Kamfjord, Roar Jensen, Ingeborg Solheim

"SINTEF has carried out several pilot scale silicon process experiments in the past, but always with an open off gas system. In order to test the possibilities in running a semi closed furnace operation, a new off gas hood has been designed and tested. The off gas hood is designed to collect all off gases to gain insight into the phase compositions in the off gas and at the same time have the opportunity to monitor and maintain the charging/stoking of the furnace. The furnace hood has regulation and control of the air inlet into the combustion zone in two different heights. The off gas temperature and composition was continuously monitored and analyzed during the experiment. In order to expand the knowledge on NOx- formation in silicon metal production, such information is vital.IntroductionBecause of the negative environmental impact, the attention towards all kinds of NOX emissions increases in Norway. The authorities’ demand towards better surveillance and control of emissions increases as well.Earlier and new industrial measurements in FeSi- and Si-metal furnaces reveal quite high NOX-emission. The measurements also show that the NOX formation (mainly as thermal NOX) is distinct connected to the formation of dust (SiO?SiO2) in the combustion chamber above the furnace surface, when the temperature is high and the access to N2/O2 is good. This means that stoking, charging and temperature straight above the furnace surface is important factors for the NOX formation."

Jan 1, 2012

By Wenming Wang

Recycling of retired cadmium telluride (CdTe) photovoltaic (PV) modules has attracted attention due to new European environmental regulations. Recycling tellurium from CdTe PV modules is becoming more important because of the low availability of this metal. We investigated several treatment paths for reclaiming tellurium from solutions obtained from leaching fragments of CdTe PV modules. Our experiments showed that conventional soda ash neutralization/hydrolysis methods recovered only 50~60% of tellurium. However, by appropriately combining neutralization and sulfide precipitation, almost all the tellurium present in the leaching solution was precipitated and recovered; the concentration of tellurium in the processed solution was reduced from 900-1000 mg/L to less than 1 mg/L, yielding a tellurium recovery greater than 99%. This method can be incorporated in the scheme of recycling spent CdTe PV modules and manufacturing wastes. It may be also an alternative to the current operations for removing tellurium from copper anode slime leaching solutions.

Jan 1, 2006

By Gerald Onyedika, Tochi Onwumere, Martin Ogwuegbu

"The kinetic study for the leaching of iron from cassiterite ore in KOH solution was studied. The effects of KOH concentration, particle size and reaction temperature on the leaching rate of iron were also examined. The results of leaching studies showed that the leaching of iron from cassiterite ore in KOH solution is significantly influenced by the reaction temperature, KOH concentration, and decrease in particle size. The study showed that 90.62% of iron ore was leached in 8M KOH solution at 80°C within 120 minutes. The experimental data were well evaluated using the shrinking model for surface chemical reaction and diffusion control through the product layer. The activation energies for the iron ore dissolution using the two models were calculated to be 32.06KJmor1 and 97.97 KJmor' respectively.IntroductionIn recent times, there has been increasing attention on the kinetic study of mineral dissolution. In most of these studies, the experimental results were analyzed with a suitable shrinking core model under the assumption that the ore is a homogeneous spherical solid phase [1-4]. A study of the dissolution kinetics of a Nigerian cassiterite ore by hydrochloric acid showed that increase in the hydrochloric acid concentration is accompanied with increase in the amount of cassiterite ore dissolved at various times [4]. The optimal concentration was found to be 4.0M HCl, after which there was a decline in the amount of the ore dissolved, which showed that the concentration of the reagent has a significant effect on the leaching rate of the ore. Also in studying the effect of stirring speed on the rate of cassiterite ore dissolution while keeping other conditions constant for 120 minutes, the result showed that the rate of cassiterite ore dissolution was dependent on the stirring speed over a range of 0 to 630 rpm. Above 360 rpm, the stirring speed no longer had any effect on the solid dissolution. The dissolution rates of cassiterite were analyzed using a suitable shrinking model. The results showed that the reaction was controlled by the diffusion of tin through the porous product layer, a reaction order with respect to hydrogen ion concentration of 0.92 M and activation energy of 50.05KJmor'. In another kinetic study on the leaching of a low grade niobium-tantalum ore with concentrated KOH solution the effect ofreaction temperature, KOH concentration, agitation speed, particle size and alkali-to-ore mass ratio on the dissolution rate of niobium were examined [5]. The result of niobium leaching from low grade niobium-tantalum ore with concentrated KOH, solution at different agitation speeds showed that the dissolution rate increased with increase in agitation rate. In the case of particle size effect, the results show that small particles require much shorter time for complete dissolution than the large ones."

Jan 1, 2013

By Shaik Jeelani, Esperidiana A. B. Moura, Vijaya K. Rangari, Roberta A. Lima, Rene R. Oliveira

This work present the preparation and characterization of biodegradable nanocomposites based on aliphatic-aromatic copolyester (PBAT)/polylatic acid (PLA) blend reinforced by TiO2 nanoparticle. The biodegradable polymeric nanocomposites were prepared by melting extrusion process using a twin-screw extruder machine. The influence of the TiO2 nanoparticle addition on mechanical and thermal properties of PBAT/PLA blend was investigated by tensile and impact tests, SEM, DSC and XRD analysis and the correlation between properties was discussed.

Jan 1, 2015

By B. R. Baldock

The converting of high-grade nickel matte for production of low-sulphur matte or nickel metal is a process which has eluded metallurgists in the past because of the limitations of conventional converting furnaces. The high temperatures required and the refractory nature of nickel oxide has prevented practical success in a process which has been known to be theoretically feasible for a long time. The Ausmelt top submerged lancing system is capable of operating under close control of the smelting conditions. High temperatures and both rapid oxidation and rapid reduction can be achieved. These features have provided the basis for successful pilot plant trials of the desulphurisation of high-grade matte from the Kalgoorlie Nickel Smelter. Sulphur level in product was lowered from 20 to 25% to as low as 0.2%, with iron levels in matte in the range of 1.0 to 3.5%. The theoretical background of matte desulphurisation is surveyed and the pilot plant operations described. The implications of the results in relation to commercial plants and possible refinery operations are summarised.

Jan 1, 1993