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By J. Grogan

Leaching of galvanized steel coatings allows the steel substrate to be used as a zinc-free scrap source to steel and iron furnaces. In this study the behaviors of sulfuric acid leaching solutions are investigated. The ranked significance of the variables are shown to be acid concentration > temperature > zinc concentration. Examination of the leaching mechanism finds the rate-limiting step to be the cathodic hydrogen reduction reaction. This rate is not only influenced by acid concentration, but also by the hydrogen reduction exchange current density. Dezincing leaching rates are improved by taking advantage of the higher exchange current density of the iron substrate versus the zinc coating. This is accomplished in practice by increasing the exposed interfacial zinc:iron surface area through shredding. Also, a leach control mechanism is proposed through online monitoring of the zinc-iron couple mixed potential.

By E. F. Vegman, Ndabezinhle Dube

"In the practice of conventional sintering, production is always afflicted with the problem of being unable to get a uniform quality of produced sinter in the bed. Invariably the top layer of the sinter cake is composed of weak but highly sinter, while the bottom layer is over-fused, forming a sinter that is very strong but less reducible. These symptoms point to a variable distribution of the heat balance in the process of sintering which results in a deficit of heat in the top layers of the sinter bed and an excess of heat in the bottom layers, due to an increasing input of regenerated heat in the heat balance down the bed. This causes losses in the productivities of the sinter machine and the blast furnace.The current work was designed to improve on the solution to the above problem through the establishment of a more accurate combustion zone heat balance of the sintering process. This development is mostly on the method of determining the regenerated heat input in the overall heat balance. Previous methods were based on the assumption that the width and the velocity of the combustion zone remain constant through out its whole life, which is not the case since tests have shown that both its width and velocity increase as the combustion zone moves down the bed. In this work, these factors have been taken into account. Tests and calculations using the model were carried out for haematite and limonitic ores. The high sensitivity of the model to changes in the sinter mix composition and sintering conditions was demonstrated.The results present the following prospects:• The minimum theoretically possible coke breeze consumption during the sintering of any type of iron ore fines, under any sintering conditions, can be established.• The model can be used to control the metallurgical quality of the sinter in any point in the sinter bed since calculation data includes desired basicity, combustion zone temperature and FeO content in the sinter produced."

Jan 1, 2001

By Petr Sulovsky, Jaroslava Ledererova, Miroslav Svoboda, Michaela Suchardova

"The thinning resources of natural raw materials necessitate an increased degree of waste material recycling. The building industry offers a range of technologies enabling incorporation of industrial wastes into building materials for construction purposes in an economically acceptable way. Our research is focused on finding the appropriate technologies for specific groups of industrial waste materials (IWM). The studied IWM involve coal combustion residues (CCR), desulphurization products, sludges, metallurgical slags, and various other wastes. Many of them contain increased amounts of toxic elements that can under certain conditions get released. In order to prevent this, each specific IWM requires finding the technology that best ensures the binding of toxic elements in the building matter are fixed for the long term.Introduction The sustainable development of mankind is more than ever viewed as a matter of resources. Many aspects of the switch from a throw-away to a recycling society concern one of the largest consumers of natural resources and producer of greenhouse gases, the building industry. One of the biggest tasks lying before the researchers in the field of building materials is to find substitute or alternative raw materials that would save the thinning reserves of natural resources. The most promising and natural way is to replace the traditional raw materials with rejected and unwanted products of industrial processes, classified as wastes. These of course are not produced with the primary intention of achieving some desired properties. The usage of industrial wastes therefore involves finding the optimal way of usage their existing positive (from the point of view of utilizations) properties and minimizing the impact of their undesired properties, i.e. from the perspective of the considered application."

Jan 1, 2008

By Denise Cristina de O. Nascimento

Natural lignocellulosic fibers are increasingly being used as polymeric matrix composite reinforcement owing to economical and environmental advantages as renewable and biodegradable materials. Among these, the piassava fiber extracted from a palm tree native of South America stands as one of the most rigid with a potential to be used as composite reinforcement. Therefore, the present work investigates the notch toughness behavior, by Izod impact tests, of epoxy composites reinforced with up to 40 % in volume of continuous and aligned piassava fibers. It was found that the incorporation of piassava fibers results in significant increase in the impact energy of the composite. Scanning electron microscopy analysis showed that the nature of the piassava fiber interface with the epoxy matrix is the major responsible for the superior toughness of the composite.

Jan 1, 2009

By Zhucheng Huang, Zhikai Liang, Lingyun Yi, Tao Jiang

"In this study, reduction of iron ore pellets was carried out at 800-950°C by simulating the atmosphere of typical coal gasification gas. The effects of temperature, gas composition and reduction degree on swelling were investigated respectively. Reduction degree was obtained according to the weight loss records. And volume changes of pellets during reduction were evaluated by infrared photography. Results showed that the pellet swelling increased with temperature and decreased slightly with hydrogen content in the reducing gas. The swelling peaked when reduction degree reached about 40% and then decreased to be stable finally. The microstructures of pellets during reduction were examined by reflected light microscope and relatively rational explanations were proposed for their swelling behaviors.PrefaceDirect reduction iron is an important and indispensable raw material for high-purified and high-quality steel in the electric furnace smelting. Gas-based shaft furnace direct reduction process has very strong competitative ability; however, this technique requires natural gas as reducing agent, so its development has been restricted by gas source and area. Compared with gas-based reduction method, coal based reduction method has the disadvantages of higher production cost and lower productivity. In China, coal resources are abundant and coal gasification technology is mature, and the development of coal gasification shaft furnace direct reduction process is promising. [1] The gasification methods of fixed bed method (Lurgi method), fluidized bed method (Undok method), airflow bed method (Texaco coal water slurry method and Shell dry powder coal method) have been put into use successfully. These syngas generated by different methods can meet the actual production requirement of shaft furnace. However, the compositions of the effective reduction gas in the syngas are quite different. The ratios of hydrogen and carbon monoxide (H2/CO) of Undok or Shell coal gas, Texaco coal gas and Lurgi coal gas are 0.4, 0.6~ 1.0 and 1.6~2.3, respectively. [2] In the coal gas direct reduction process, the swelling behavior of iron ore pellets is various due to the differences of the gas composition, reduction temperature and reduction degree, and it seriously affects the normal operation ofDRI production. [3-9] Therefore, the research on the swelling behavior and its mechanism of iron ore pellets in direct reduction were carried out in this paper."

Jan 1, 2013

By M. Misra

The removal of lead and other heavy metals present in an active US Army small arms firing range soil was evaluated in a pilot scale test program at Ft. Polk, Louisiana. Two different acid based extraction processes in conjunction with conventional physical separation methods were used. Physical separation processes consisting of screening and gravity operations removed most of the coarse lead particulates and slugs. Hydrochloric acid leaching followed by precipitation of lead as hydroxide recycled clean soil containing less than 500 mg/L. total lead and less than 5 mg/L TCLP lead. Lead extraction efficiency with hydrochloric acid was 96 percent. The results of lead removal by physical separation in conjunction with acetic acid leaching were not consistent over the whole test period and the total soil processed.

Jan 1, 1998

By J. A. Bakken

Thermal plasmas are interesting for a wide range of metallurgical and chemical processing applications. The 300 kW experimental reactor PRESS, which has been in use since 1987, is operated in the transferred arc mode with three or one plasma torches . Tests include remelting of silicon fines and production of ultrafine silica. Work on a novel three stage process for production of silicon metal is under way. A 1:1 model of the plasma reactor is used to measure the wall heat flux distribution calorimetrically. The cold walls of this model are divided into several water-cooled sections. The same plasma torches as in the real hot-wall reactor are used. In parallel to the experiments and calorimetric measurements theoretical work is done on numerical modelling of one and three transferred arcs. A modified version of the flow simulation program FLUENT from Creare Ltd. is used.

Jan 1, 1991

By Alexander I. Raitchenko

"Although one takes into account only thermal expansion usually at analysis of convection onset, the essential factors include magnetic and electric fields. If Lorentz-force originating from intercrossed electric and magnetic fields' action is directed downwards its effect strengthens gravitational action, and value of critical Rayleigh number (limit value for convection onset) must decrease; increasing of critical Rayleigh number should be observed in case of Lorentz-force directed upwards. Extent of such an influence is determined by relation of Lorentz-force to hydrostatic head in gravitational field. Competition between electromagnetic force due to nonuniformity of electroconductivity (on account of its temperature dependence) and electromagnetic buoyancy force may have ambiguous effect: both increase or decrease of critical Rayleigh numbers. Proposed conception is applicable to analysis of situations in liquid conductors and conductive gases.IntroductionStatic or dynamic situations in fluid media are determined besides properties of these media by a variety of external influences. However one correlate~ the onset of the convection and its development with influences of the minimum quantity of external causes frequently. Most known and usual factors are the gravitational and temperature fields. The number of processes includes heat generation in media volume, and theoretical analysis in these cases takes into account this interior heating together with boundary temperature conditions. But explanation of many natural and technical events is not complete and cogent within limits of thermo-gravitational terms. The whole complex of acting factors which influence convective processes in techniques and nature is greater in many cases. In particular the action of · electromagnetic nature often has not less importance than gravitation one. Stability or instability of a current layer in the plasma must be determined by non-uniformity of electroconductivity owing to non-uniformity of temperature [1]. The presence of Joule dissipation in the plasma through which the electric current flows stipulates initiation of origin of overheated instability [2]. It is known that electroconductivity of arc in the boundary zone changes sharply with radial distance [3], and this must influence its stability essentially. If the intercrossed electric current and magnetic field begin to act on an electroconductive fluid besides the non-uniform temperature field and the gravity, the conditions for the onset of the convection change radi- . cally: both the temperature field and their solutions have to be changed also. The analysis of equilibrium single-time correlation functions of fluctuations must be employed for situations with enlarged number of factors as this was in case for the Rayleigh-Benard problem where the object is a horizontal layer of liquid. This can be carried out by taking into account the detached forces' correlations [ 4, 5]"

Jan 1, 1999

By Xiaoyan Xiang, Wenqiang Yang, Wentang Xia

Magnesium aluminate spinel is widely used in the metallurgical industry as refractory material, however, natural magnesium aluminate spinel is rare and most of the magnesium aluminate spinel is synthetic. The traditional synthesis of magnesium aluminate spinel often needs high temperature, which leads to more energyconsumption. In this article, solid phase sintering process was employed to synthesize magnesium aluminate spinel, in which, magnesium and aluminum oxide were used as raw materials and magnesium and aluminum powder were used as composite additives. The mass ratio of magnesium and aluminum on the effect of synthesis of magnesium aluminate spinel and the characteristic of the synthesis at different temperature and time was discussed. Experiment found that the synthesis temperature was observably lowered when the addition of magnesium and aluminum was 2.0% and 1.0% respectively.

Jan 1, 2016

By Pekka Taskinen

The converter-less nickel matte smelting technology (DON) adopted more than 20 years ago in Boliden Harjavalta smelter has been since that applied successfully to the processing of large number of nickel sulphide concentrates of various Ni-to-Cu ratios and MgO contents. The operational point of the technology is far from the conventional primary nickel smelting in the smelting-converting route. Therefore, a careful scouting of distribution equilibria of the base and trace elements in the smelting conditions of DON process has been conducted, in order to obtain quantitative information about the equilibria and thermodynamic properties of the nickel mattes at low iron concentrations, less than 10 wt% [Fe] in matte. The series of investigations has included novel experimental and analytical techniques for increasing the reliability and sensitivity of the phase equilibria as well as the element distribution observations carried out in typical high-grade nickel matte smelting conditions.

By A. S. Block-Bolten

Two innovations in nickel-arsenic separation have been studied on a laboratory scale. The first requires only a nitric acid atmospheric leach without preliminary roasting and leads to favorable final conditions for precipitation of arsenic as highly stable FeAsO4, The second is an NaOH-H2O2 pressure leach which is an alternative to the known NaOH-O2 pressure leach. Either method offers the possibility of rapid and efficient separation of nickel from arsenic and is applicable, for example to the high grade niccolite deposits in the Great Slave Lake area of northern Canada.

Jan 1, 1982

By E. Daniel Baker

"The term ""oxide disseminated gold deposits"" refers to near surface, gold-bearing veins, faults, and shear zones that typically contain appreciable amounts of oxidized ore or gossanous material, resulting from oxidation of sulphides.The concept of oxide gold deposits underwent a dramatic change after the discovery of the Carlin gold mine in north-central Nevada in the early 1960's. Now the term implies large tonnage, low-grade bulk minable deposits that are processed by milling and/or heap leach methods.Oxide gold deposits may now be classified into two types: (1) primacy ores derived directly from the effects of hydrothermal alteration on host rocks, and (2) secondary oxide ores derived from the supergene oxidizing effects of circulating post-mineral meteoric waters on gold-bearing sulphides. Each type of deposit has unique diagnostic mineralogic and metallurgical characteristics that must be addressed to achieve successful exploration strategies and viable metallurgical exploitation.The author would like to thank the management of Newmont Metallurgical Services and Newmont Mining Company for allowing presentation of this paper. Thanks are due Sevkett Acar, Donald M. Hausen, Jerry R. Odekirk, and D. Erik Spiller for their critical review of the manuscript. Also, thanks are extended to all those cited and uncited whose hard work and dedication have led to the discovery and exploitation of near-surface oxide gold deposits. Our knowledge would be greatly limited without the dedication and research of many others."

Jan 1, 1997

By Zhuo Sheng

We have designed a high-temperature Raman micro-furnace and cell that is suited for the electrochemical process study of the NO3 − in molten NaNO3– KNO3 (fraction of NaNO3 50 wt%) salt. During the cycle voltammetry and constant potential electrolysis process, the Raman laser beam was focused near the electrode; subsequently, the Raman spectra are obtained and the reduction process of NO3 − is analyzed. In the CV cathodic scan process, the new peak attributed to the ν1 mode of NO2 − emerges, and the peaks assigned to superoxide ions (O2 −) and peroxide ions (O2 2−) are not found. In the constant electrolysis process, the peaks at 1130 and 800 cm−1 appear when the potentials are between −2.0 V and −3.2 V (vs. Pt). The results show that when the NO3 − is reduced in molten the NaNO3–KNO3 mixtures, the reduction product O2− cannot stably exist, and O2− will react with NO3 − to form of superoxide ions (O2 −) and peroxide ions (O2 2−).

By J. M. Boxall

The electrolytic zinc plant at the Bartlesville division of Z.C.A. originally used lead anodes containing only 0.25% silver because only H.G. zinc and alloy was to be produced. In 1984, a small addition of strontium carbonate was made to control the surf ace morphology of the cathodes which reduced short circuits and increased current efficiency. Later a drastic reduction in colloid addition further reduced short circuits. Increased strontium additions allowed the production of some S.H.G. zinc. Increasing the silver content of the anodes reduced the lead in cathodes only slightly. More important, the anode scale that was not removed during anode cleaning, entered the electrolyte and contaminated the cathodes with lead. A piping system has been installed to purge the contaminated electrolyte directly back to the leaching section. This has allowed the plant to produce S.H.G. zinc consistently.

Jan 1, 1990

By Jiang Feng, Zhang Libo, Peng Jinhui, Guo Zhanyong, Ju Shaohua, Lei Ting

The clean utilization of the residue containing chloride, CuCl residue, produced from zinc hydrometallurgy is very important for the recycle of valuable metals. And drying is the main process in recycling. In this study, response surface methodology was used to optimize operating conditions of the drying of CuCl residue in a convection oven and desirability function used as the methodology for the optimization. Optimization factors were air temperature (80–100°C), material thickness (10–25mm) and process time (80–120min) while investigated responses was final moisture content. The optimum conditions were found to be the temperature of 95.48°C with the material thickness of 13.47mm for the process time of 89.48 min. Under optimum conditions, the predicted moisture content of CuCl residue was 4.11% while the experimental date was 4.13%. The experimental value after process optimization was found to agree satisfactory with the predicted value. After drying, XRD was used to analyze the main phases of CuCl residue. The CuCl residue is made up of CuCl,Cu2O, ZnS and other compounds.

Jan 1, 2015

By F. -Z. Ji

Carbon injection into metallurgical slag is important in electric arc furnace (EAF) steelmaking for foamy slag practices and in nonferrous slag cleaning operations. The current publication presents kinetic data for coal injection into EAF slag to understand the interaction between injected carbon and metallurgical slag. Coal particles were injected into EAF slag and the kinetics were followed by gas and slag analysis. The results were analyzed, in terms of fundamental rate equations for each possible reaction step, as a function of temperature and slag composition.

Jan 1, 2003

By Ivo André

Sorption of copper ions from aqueous solutions by dried biomass of the aquatic plant Potamogeton luscens was studied at laboratory scale. The aquatic plant was collected in water resources in Brazil, washed, dried at 60°C and ground in a bladed mixer. Sorption experiments were conducted in agitated flasks and in a packed bed column. Maximum copper removal was obtained between pH 5.0 and 6.6 when copper was present in the ionic form Cu'. Sorption followed the Langmuir isotherm with saturation attained at 35 mg/g. Free energy of sorption was found, to be of the order of -25 kJ/mol. Sorption kinetics data were better described by a second order reaction and rate constants were calculated in 0.030 1/(min.mg) for - 4.0 mm particles and 0.081 1/(min.mg) for - 0.59 mm particles. Removal of metal ions in a packed bed column showed that Potamogeton luscens biomass can be used in several sorption/dessorption cycles. After sorbent saturation, copper ions can be recovered from the loaded biomass by elution-with H2SO4, solution. Main mechanism responsible for heavy metal uptake was found to be ion exchange. Results are discussed in terms of the surface properties of the biomaterial, solution chemistry of copper ions and thermodynamics parameters.

Jan 1, 1995

By Isabella Lancellotti, Fabrizio Passarini, Luisa Barbieri, Fernanda Andreola, Ivano Vassura, Luciano Morselli

"The techniques able to incorporate wastes by means of a heat treatment present the advantage to fix the residue with chemical bonds. Among these techniques there are vitrification and sintering which are characterised by different operating temperatures in the range of 950-1500°C and the involved raw materials develop silicatic crystalline phases and glassy matrices capable to immobilize heavy metal contents in the waste matrix. In this work incinerator bottom ash, polishing and glazing ceramic sludges have undergone to thermal treatments in order to valorise the waste as secondary raw material for the obtainment of re-products. The chemical efficiency of the process adopted has been evaluated by comparing the results of release tests applied to the as-received wastes and to the thermally treated materials in order to verify the effectiveness of the different matrices to fix the waste components.IntroductionVitrification is one of the most promising technological options for the treatment of some kinds of waste. The high temperature involved in the process (1200-1500°C) leads to the complete destruction of organic pollutants, such as dioxins, and glassy network formed can incorporate heavy metals. Some vitrification processes naturally occur: glasses produced by volcanic eruptions, such as obsidians (Na2O-K2O-Al2O3-SiO2) and basaltic (CaO-MgO-Al2O3-SiO2) rocks, are basically inert materials even when they contain toxic elements, because these are embedded in an extremely stable glassy matrix. The disadvantage of vitrification is that it is an energy-intensive process involving relatively high costs, therefore its use is better justified if a high-quality product with optimised properties can be fabricated. The most effective way to improve the properties of the vitrified material is the transformation into glass ceramic. This is a fine-grained polycrystalline material (typically from 50% to 98% of the volume may be crystalline) formed when a glass of suitable composition is heat treated and hence undergone to controlled crystallisation (phenomenon named devitrification). The three key variables in the design of a glass-ceramic are: glass composition which controls glass viscosity related to the effectiveness of nucleation and rapidity of crystallisation; glass-ceramic phase assemblage (that is, the types of crystals and the proportion of crystals to glass) which is responsible for many of the physical and chemical properties; nature of the crystalline microstructure (crystal size and morphology and the textural relationship among the crystals and glass) which is the key to many mechanical and optical properties. In particular, a partly crystalline material can be obtained by powder sintering."

Jan 1, 2008

By S. Kang, D. G. C. Robertson

Slag cleaning furnaces require extensive wall cooling because they involve the use of a superheated slag bath. This is in direct contrast to smelting furnaces, where the wall is usually (but not always) protected by "banks" of solid charge. In order to understand the heat transfer and flow in slag cleaning furnaces a number of model studies have been carried out using molten wax to simulate the slag. Wax is a good model fluid because, like slag, it has a high Prandtl number. Wax models cannot simulate the behavior close to the electrodes (DC arc or AC submerged), but they can and do give a good simulation of the flow and heat transfer at the wall. An understanding of these phenomena is of great importance for the design of cooling panels in the walls of the furnace. Since superheated molten slag will eventually wear away any refractory bricks over time, the wall cooling must be designed to form a frozen layer of slag, referred to as a "freeze lining". The heat flux density (Q/A) required to do this is given by Q/A = h* ?T, where h is the heat transfer coefficient in the slag phase at the wall, and Li T is the superheat (bulk slag temperature - liquidus temperature). Both Q/A and h vary greatly with position and both are usually a maximum at the slag line. In the experimental work, molten wax baths were heated by block heaters to provide similar energy densities to those encountered in commercial slag cleaning furnaces. This procedure was considered to be valid since most of the electrical energy into a furnace bath is dissipated as heat. Gas stirring was used to simulate the gas evolved at the electrode in real furnaces - the quantity of this gas could be estimated from a knowledge of electrode consumption. The similarity criterion was equal gas flow per unit area of surface, in model and prototype. Heat transfer coefficients were measured in the models as a function of power density, gas stirring, superheat, etc., and could be related to the full-scale operations by the use of dimensional analysis.

Jan 1, 1999

By Malti Goel

"Ferrous and non-ferrous metals industries are source of both direct and indirect greenhouse gas (GHG) emissions. Metal industry accounted for 29.7% of the total GHG emitted from the Indian industry sector in 2007. Aluminum is second largest contributor after steel. Indian Aluminum industry has been growing and is adopting several effective measures for better efficiencies through process change and waste utilization. Improvement in the energy efficiency can form the basis of monitoring reduction in emissions. Under the National Action Plan on Climate Change 2008, National Mission for Enhanced Energy Efficiency (NMEEE) aims to upscale the efforts to unlock the market for energy efficiency improvement on a public private partnership (PPP) basis. For a transition to low carbon economy industry is undertaking voluntary measures through scientific and technological innovations both in upstream and downstream sectors. In this paper an attempt is made to overview recent developments in Indian Aluminum industry as well as summarize scientific & technological challenges and prospects.IntroductionAluminum plays a vital role in industrial development. It is a substitute for different type of materials ranging from wood to copper and steel. The aluminum industry has high energy consumption and high contribution to greenhouse gases from carbon dioxide and perfluorocarbons (PFCs) emissions. It is estimated that CO2 equivalent burden of aluminum industry is about 1% of total anthropogenic emissions. The anticipated world growth rate is 3.5% for aluminum demand. Through measures to reduce both direct and indirect CO2 emissions, electricity consumption was reduced from 25 kWh / kg of Aluminum in 1998 to 15 kWh / kg of Aluminum produced in 2008. It is targeted to further reduce it to 10.8 kWh. Aluminum industry is also responsible to about 60% of all PFC emissions. The PFC emissions are harmful to environment, accumulate in surrounding vegetation and contaminate. Efforts to reduce PFC emissions from aluminum industry started early and reduced to 0.5-1 kg / tonne in 1990 [1] from 12-15 kg / tonne in 1940. Since 1990s to 2000 it further reduced to 0.2 -0.4 kg / tonne as seen in Fig. 1. The Global Aluminum Sustainable Development Initiative (GADSI), targets perfluorocarbon (PFC) specific emissions reduction of 80% for 2010 relative to 1990."

Jan 1, 2011