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By José Brant, Douglas Torres, Rogério Navarro, Rodrigo Souza, Eduardo Brocchi

The steelmaking process requires the input of ferro-alloys to implement the adjustment of some elements composition in the final product. In the particular case of stainless steel production, the high carbon FeCr alloy stands out as one important precursor. However in the production of this material a certain quantity of fine powder with remarkable chromium and carbon content is also generated, which, in turn, could be processed through alkaline roasting in order to selectively recovery this element in a subsequent aqueous route. In the present work, this process is investigated, using excess of NaOH as oxidizing agent, and H2O2 for precipitating chromium as Cr(OH)3, which is next calcinated to Cr2O3. According to the results, the global achieved recovery has shown to be around 98%, suggesting that the proposed route can be seen as a potential process for chromium oxide production from the mentioned fine powder.

Jan 1, 2015

By Jianhua Xin, Min Chen, Lei Xu, Haohua Deng, Nan Wang

A mathematical model of converter slagging and steelmaking process by replacing part of lime with limestone is established. The rate equations of oxidation reactions and lime dissolution in converter under the limestone substitution proportion increasing from 25 to 50% can be obtained and the effects of limestone substitution proportion on the variations of the composition of hot metal, slag and converter gas during the steelmaking process are investigated. In the process of converter slagging and steelmaking by replacing part of lime with limestone, increasing the hot metal temperature and the lance height could be favor to increase the content of FeO in the slag and accelerate the limestone decomposition and dissolution. With the limestone substitution proportion increasing from 25 to 50%, the maximum of oxygen supply ratio increases from 10.7 to 19.7% and the temperature drop of converter bath is 8–60 °C.

Mar 1, 2018

By R. M. Taylor

Lime addition to acid mine drainage (AMD) leads to precipitation, predominantly of metal hydroxides and calcium sulfate, and is the benchmark for remediation by precipitation. Geo2 Limited of Melbourne, Australia has developed and patented a novel alternative precipitation scheme based on the formation of mixed valency, M(I1)-M(III), hydroxide sulfate salts. When the composition of AMD is appropriate, the Green Precipitate Process provides a useful and more effective alternative to conventional liming. The characteristics and utility of the Green Precipitate Process are described in terms of the underlying chemistry, and a case study where the Green Precipitate process outperforms conventional liming. A mobile pilot pipe reactor rig which was built by Geo2 to demonstrate the process, and used successfully in both Australia and the United States, is described.

Jan 1, 1998

By Maija-Leena Metsärinta

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. SEMIEDS 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 G. Belardi

A study has been conducted to assess a new wet beneficiation treatment for the recovery of the sulphuric-acid-soluble titanium oxide contained in the waste from an Italian TiO2-pigment facility. The waste is produced during treatment of a Ti-enriched slag and contains as main components TiO2 (54%, of which 42% acid-soluble and 12% insoluble), SiO2 (27%) and A1203 (6%). Eighty percent of the material is finer than 50pm. The first step was to ascertain the possibilities offered by size classification, wet gravity separation, froth flotation and wet high-intensity magnetic separation to improve the grade and recovery of Ti02 and reduce the SiO2 content. The next step was to optimize the operating conditions of the various separations and assemble them into a complete flow- sheet. Beneficiation ensures potentially 70% recovery of the TiO2 with a concentrate grade of 80%.

Jan 1, 1998

By Saskia Duyvesteyn

Small ion-exchange resin particles provide faster mass transport than conventional-sized beads. Unfortunately, high pressures are needed to pump solutions through columns containing small resin particles. It is preferable to disperse fine resins in the solution being treated. Screens have been used to separate the resin from the solution, but screens do not retain fines created by attrition of the resin particles. We have developed a separation process based on flotation, which relies on the surface characteristics of the resin, instead of size. The resin is conditioned with a surfactant before dispersing it in the solution to be treated; this increases the hydrophobicity of the resin sufficiently for froth flotation, without introducing surfactant directly into the solution. The surfactant adsorbed on the resin surface does not appear to impair the kinetics of metal ion removal. A flowsheet for an effluent treatment process is proposed; other applications are clearly possible.

Jan 1, 1998

By B. J. Scheiner

The presence of organic materials in gold ores interferes with gold extraction by cyanidation. The carbon contained in the ore has been shown to adsorb gold cyanide complex from solution. Removal of the carbon content by roasting or chemical oxidation prior to cyanidation results in gold extractions of 85 to 95%. This paper discusses how the mineralogy of the carbonaceous gold ores affects gold recovery by cyanidation. It also discusses the advantages and disadvantages of roasting and chemical treatment to render the ore amenable to cyanidation.

Jan 1, 1987

By E. Açma

In this study, the production of Cu, Co, and magnetic iron oxide from the ancient copper, slags, located in Küre-Turkey, is investigated. In the process under development, fayalitic slags containing 1% Cu, 0.43% Co are reduced in a D.C. arc furnace with coke or graphite additions. A metallic alloy, consisting of 3.8% Cu, 3.3% Co, 2.1% S, and the rest being Ice, is produced by granulation of the liquid metal. About 85% recoveries of Cu and C:o are achieved by hot sulfuric acid leaching of these granules followed by H2S precipitation. The, production of magnetic iron oxide is possible from the discarded leach solution, loaded v:ith FeS04, by using a method with geothite precipitation, dehydration, controlled reduction, and re-oxidation steps. The magnetic oxides produced have 20 m2Jg surface area, 1:8.3 aspect ratio, and the coercivity of 330-380 Oersted.

Jan 1, 1993

By Jun Sugiyama, Hiroyuki Sano, Toshiharu Fujisawa, Hideki Takeuchi, Chikabiuni Yamauchi

"The solid .state electrotransport (SSE) is one of the most promising methods for the elimination of gaseous impurities from chemically active metals, such as rare earth metals. . In the present work, the SSE process was applied for the oxygen removal from praseodymium. The SSE factors, such as effective valence, were measured under the various temperatures, electric field intensities and initial oxygen contents, and the effects of those conditions on the SSE process were discussed. Furthermore, the solubility of oxygen in .solid praseodyillium was also measured·, by using the SSE method and metal-oxide equilibrium method.IntroductionWhen a direct current is passed through a solid alloy, not only electrons but also solute atoms are transported as charge carriers toward the anode or cathode. This phenomenon is referred to as an electrotransport or electromigration. The solid state electrotransport (SSE) is the application technique, based on this principle, to the pUrification of the solid metallic materials.Rare earth metals are used for various functional materials, such as magnetic, optical or electronic materials, therefore their high purity metals are required [l ,2]. However, rare earth metals are chemically active and have a strong affinity with gaseous elements (e.g. oxygen, nitrogen, hydrogen and carbon). In many cases, eliminating operations of gaseous elements have not been always made commercially, because these impurity elements could not be eliminated by usual treatments applied to the purification of ·common metals. As an alternative method, authors have proposed the· application of the SSE process to the elimination of gaseous impurities from rare earth metals. Investigations have been carried out on the yttrium-oxygen and neodymium-oxygen systems and the results were already reported[3,4]."

Jan 1, 2000

By Jian Li, Pei Liu

In recent years, focused ion beam (FIB) has become a powerful microscopy tool. Creating large FIB cross sections are often required to characterize important microstructure features e.g. the depth and morphology of pitting corrosion and stress corrosion cracking in natural gas pipeline steels. Large FIB sectioning often takes long time that not only occupy valuable FIB microscope time, but also consume often expensive consumables that include gallium ion source, aperture and deposition gas etc. The new plasma FIB developed by FEI can speed up milling process by using much larger beam current. However, for most of the laboratories that is limited by conventional Gaion FIB, the milling speed is limited by the relatively small beam current. In this paper, FIB milling rate are studied against milling parameters that include beam dwell time and pixel overlap. By optimizing the milling parameters, milling rate can increase significantly.

Mar 1, 2018

By Rodney Hundermark

At Anglo American Platinum’s Polokwane Smelter, radar instruments are being used to provide continuous measurement of the concentrate feed level in the six-in-line electric furnace used for smelting of nickel-copper concentrates containing platinum group metals (PGMs). The radar instruments are installed directly on the furnace roof, and a mechanical system has been designed to protect them from radiation and elevated freeboard temperatures and pressures. Signal validation criteria have been implemented to ensure that proper level measurements are being used by the PLC system. The feedback from the radars has provided an improved understanding of the furnace behaviour with respect to concentrate feed level control, individual feeding events, global feed rates, feed distribution and bath disturbances. In combination with a dynamic mass balance for continuous calculation of liquid level in the furnace, the radar measurements have enabled more precise feedback control of the concentrate blacktop depth. In turn this has yielded improvements in furnace stability.

By Yasuhiro Konishi

Hydrolytic stripping is the process in which metal ions are simultaneously stripped from a loaded cation-exchange solvent extractant and precipitated as oxides or hydroxides. Hydrolytic stripping is usually effected by contacting the loaded organic phase with water at elevated temperatures. The possibility of using hydrolytic stripping to prepare ceramic powders with controlled size and morphology is now being evaluated for different systems, using carboxylic acid extractants. As part of this work, mathematical models were developed to describe the kinetics of nucleation and growth of nickel ferrite particles. This paper describes the development of the models, along with estimation of key parameters appearing in the rate equations from experimental data.

Jan 1, 1990

By T. Langthaler, H. W. Engl, H. Holl, K. L. Schwaha

"The trend towards near net shape casting requires the development of more complex design and control algorithms for continuous casting ""machines in particular with respect to the solidification process.Compared to conventional continuous casting the reduction in casting thickness allows to influence more directly the solidification rate by control variables like surface cooling and/or casting speed.In order to enable the determination of these control variables for a given solidification profile, an algorithm (inverse solidification analysis) has been developed based on nonlinear constrained optimization. The application of the model is illustrated by practical examples ranging from conventional continuous casting to advanced thin slab casting.IntroductionProcess development in the Iron and Steel Industry is directed towards the realization of continuous process sequences. Since the direct linkage of processes imposes some restrictions onto the individual process steps, more complex algorithms are needed for design of equipment and control of operation. In particular the recent trend to reduce casting thickness, i.e. to cast thin slabs, has made the direct coupling of continuous casting and rolling absolutely necessary. The prospective development in strip production is schematically shown in fig. 1."

Jan 1, 1988

By Baozhong Zhao

The direct smelting of copper concentrates to copper metal in a single furnace offers environmental and energy advantages over conventional two-stage copper smelting processes. However, the direct copper making results in unacceptably high level impurities (As, Sb and Bi) in the anode copper. Experimental studies have shown that it is possible to remove these impurities from molten copper by injection of sulfur-hexafluoride. This paper discusses the experimental findings on the influence of various factors on the rate of removal of impurities, such as the impurity inter-effects, initial oxygen content in the metal and injection rate of SF6.

Jan 1, 1995

By Douglas J. Harvey, Chi-Mou Ni

"This paper presents an analysis technique for the solidification of metal castings. This method, based on a modified finite difference scheme with an irregular mesh, is capable of dealing with the complex geometries of castings. The nonlinearities in material properties of specific heat and thermal conductivity, arising from the phase change during solidification, are accounted for in the step-by-step calculations. Two solidification problems are solved with this analysis technique and the calculated results compare satisfactorily with experimental data. IntroductionCasting process design engineers are often faced with the difficult problem of designing castings to be produced porosity-free. Since the solidification of metal is affected by many interacting variables such as the thermal conductivity, density, and specific heat of both the molten metal and the mold, it is easily seen why this is a difficult task.Typically, casting tooling design is an intuitive process which builds on past successful methods. After processing equipment is constructed, trial castings are made and examined for dimensions and integrity. Changes in the tooling are generally required to improve casting soundness or to reduce cycle time. In the permanent mold process, tooling is complex and difficult to alter after initial construction. The water-cooled steel molds are part of the complete automated system. Associated holding furnaces, pouring ladles, casting conveyers, and utility connections all make other than minor adjustments a costly and time consuming task. An analytical method for using the principles of heat transfer for predicting solidification patterns would be of great value in the permanent mold process by minimizing costly changes."

Jan 1, 1986

By Takao Yasugi

The majority of copper in the raw material migrates to the de-copperized dross that forms when the crude lead produced in the blast furnace is treated in the de-copperizing process. The de-copperized dross is treated in the electric furnace producing matte, speiss, and crude lead. The de-copperized dross also contains the silver. Therefore, it is important to improve the rate of silver migration to the crude lead. For this reason, the behavior of silver between the matte, speiss and crude lead phases was examined. At the same time, several tests to improve the percentage of silver migrating to crude lead were conducted.

Jan 1, 2003

By Cui Wang, Qian Li, Kexin Jiao, Haibin Zuo, Jianliang Zhang

Abstract：A rational cooling water system is the assurance for long campaign life of blast furnace．In the paper, the heat transfer of different furnace period and different furnace condition based on the water quality characteristics were analysed, and the reason of the heat flux over the normal from the hydrodynamics was analysed. The results showed that, the vapour-film and scale existence significantly influenced the hearth heat transfer, which accelerated the brick lining erosion. The water dynamic characteristics of the parallel inner pipe or among the pipes were the main reason for the abnormal heat flux and film boiling. As to the reasonable cooling water flow, the gas film and the scale should be controlled and the energy saving should be considered.

Jan 1, 2015

By Suzanne Young

The effect of LiF additions on liqt.1id1.:1s temperature and electrical conductivity over a wide range of cryolite bath ratios (1.0 to 1.5 weight ratio) was investigated. Results did not agree with multi-regression equations reported by Dewing and Choudhary over the entire region. New regression equations were developed. Reasons? are given for the differences. The models are used to discuss the economic implications of LiF additions to Hali cell electrolytes.

Jan 1, 1985

By A. Rawat

The removal of oxyanions of arsenic present in mine process water and drinking water to a regulatory level is a challenging problem. Recently a patented adsorbent lanthanum oxide has been developed which has shown strong specificity for the anions of arsenic. In this paper the kinetic and thermodynamic aspects of arsenic adsorption on to lanthanum oxide are discussed. Adsorption tests were performed at different temperatures using synthetic solutions of arsenic of varying concentrations. From the kinetic data and adsorption isotherms thermodynamic properties such as Gibb's free energy, standard enthalpy of adsorption, standard entropy, isosteric heat of adsorption and activation energy were determined. The results showed that temperature had a positive effect on the rate and degree of adsorption:The activation energy decreased with increase in the initial concentration thus indicating solute-solute interactions in the system. Also, the isosteric heat was found to decrease with increase in the adsorption density implying a heterogeneous adsorbent surface.

Jan 1, 1998

By M. Furuta, M. Hasimoto, Y. Komoda, K. Haiki

"Tamano Smelter & Refinery started its operation in 1972 with high current density electrolysis (350Nm2 of maximum) applying PRC technology. After the start up, four times of expansion have been done, the cathode production capacity has increased from- 84,000 t/y to 191,000 t/y. However, recent refining technology with permanent stainless steel cathode enabled to increase current density up to 300 Nm2 or more without PRC method. In order to increase current density more than 350 A/m2 , experimental work using commercial size cell has been carried out at several conditions, such as current density, PRC conditions, electrolyte composition and electrode condition. As a result, it was found that high quality (LME A grade) cathode can be produced at such a high current density as 405 A/m2•IntroductionWhen considering the production increase of electrolytic copper, what becomes important is the improvement of productivity per unit of production facility. Conventionally, production had been expanded by increasing the number of cells but a huge investment required for this had a influence to the business profitability. Because of this, increase of current density, which is one of the methods to improve unit productivity, 'was expected and this method at the same time has another advantage of shortening the retention time of copper and other precious metals in the cells. At present, the average current density at Tamano during full capacity production is around 350 A/m2 and this used to be the limit throughout the world (1)."

Jan 1, 2000