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By P. Cowx

The carbothermic reduction of zinc oxide rich Electric Arc Furnace baghouse dust in the Tetronics transferred arc plasma furnace to produce a non-toxic slag and a metallic zinc product is described. In particular, the operation of the zinc splash condenser coupled to the plasma furnace is examined and the effect of process variables on zinc recovery is discussed.

Jan 1, 1990

By David K. Melgaard

Electroslag Remelting (ESR) is a complex process used to produce high quality specialty alloy materials. The quality can be directly correlated to variances in melt rate and immersion depth. Conventional ESR furnaces control these quantities using two independent control loops using proportional changes in current for melt rate and driving the electrode up and down to match a voltage set point for immersion depth. However it is well known that the control loops are highly coupled, i.e. changing the current to account for melt rate deviations changes the voltage depth relationship and vice verse. In addition the noise in measurements of the ESR process can be considerable, forcing conventional controllers to use highly damped responses. A new model-based controller has been developed to embody the coupling and improve responsiveness by using estimates from a reduced-order linear ESR model and the typical process measurements to control melt rate and immersion depth simultaneously. Kalman filtering is used to optimally combine the model estimates of eight process states and the measurements of voltage, current, position and mass to estimate the instantaneous melt rate and immersion depth. Several ESR melts under steady state and transient conditions were conducted to evaluate the performance of the new controller. This paper will discuss the design of the new ESR model and controller and will present experimental results demonstrating its much improved control and responsiveness. While this controller was developed for the ESR process, the effectiveness of model-based control in managing such a complex process with relatively simple equations suggests the approach could be employed for many other processes as well.

Jan 1, 2006

By M. Tomita

One of the most essential factors for a custom smelter to strengthen its competitive power is to Improve its comparative standing in purchase of concentrates from the world market. It is especially critical for Japanese smelters who depend almost 90% of their raw materials on import. In order to accomplish this breakthrough, the development of the new technology which enables us to treat concentrates containing higher Impurities is inevitable. Nippon Mining Company Ltd. made an intensive research on processing complex ore for three years from 1979, and successfully developed an original hydrometallurgical process to treat converter dust for eliminating impurities from the copper smelting circuit. The commercial plant was constructed at the Saganoseki Smelter & Refinery in 1982, and its nine years operation has been satisfactorily proven the advantages of the technology. The concept of this process and its operational performance are discussed.

Jan 1, 1992

By Jürgen Antrekowitsch

Typical zinc oxides recovered from wastes like steel mill dusts and neutral leaching residues are of a low quality because of impurities like fluorine, chlorine, lead and others. Therefore, they are not comparable to technical grade zinc oxides produced in “French” or “American Process”. Some new developments, most of them still in pilot scale, try to establish processes where higher qualities of the product should be achieved. Zinc oxides are not only supposed to be an input material for electrolytic zinc production. Far more, they should find their way into the zinc oxide market as a substitute for technical grade zinc oxides. Furthermore, a new field of application for these oxides has been investigated at the department of Nonferrous Metallurgy, University of Leoben. Because of a higher acceptance concerning different impurities in relation to zinc winning electrolyses, a use in electrolytic galvanizing shows an interesting option. Therefore, synthetic zinc oxides with different impurities were generated to study the effect of these impurities especially on the quality of the zinc layer. Typical steel sheets, as used for car bodies, were electrolytically galvanized and the resulting layer was analysed, as main impurities compounds of fluorine, chlorine, iron, lead and calcium were used for the investigations. Beside the layer quality, the current efficiency and the possible galvanizing speed were examined. The results give an indication, weather such an alternative application can be feasible from a technical and economical point of view or not. 597

Jan 1, 2008

By D. R. Flynn

The recovery of nickel and cobalt from electromachining sludges in the form of relatively high-purity marketable products has been investigated. The investigation has shown that a series of metallurgical unit operations can be performed to recover nickel and cobalt from electromachining sludges in the form of al kal i nickel ic hydroxide and cobalt sulfate/cobal t metal, respectively. The recovery unit operations for nickel include high pH cyanide complexation, followed by oxidation and precipitation of alkali nickel hydroxide. The resultant filtrate can be treated for cobalt recovery by neutralization and acid baking to produce cobalt sulfate. The cobalt sulfate can then be treated for cobalt recovery by electrowinning. Results from laboratory bench scale test work are discussed in terms of appropriate operating conditions.

Jan 1, 1991

By Eduard Ouerra, Nuo Jin

"The use of polytetrafluoroethylene, PTFE, as a solid sorbent for elemental sulfur during pressure oxidation of chalcopyrite was investigated. The effects of agitation, PTFE particle size and lingin sulfonate addition were evaluated using leaching conditions that were otherwise similar to those employed in the CESL process. The effects of these factors and their interactions on chalcopyrite oxidation are explained in terms of interfacial forces and solid-solid interactions. Using relatively fine PTFE powder with vigorous agitation resulted in about 100% copper extraction in less than 90 minutes without the need for grinding of the flotation concentrate.IntroductionThe extraction of copper from sulfide ores has always been dominated by the conventional pyrometallurgical smelting process. Though much effort has been made to develop various hydrometallurgical processing routes, smelting remains as the dominant process, treating approximately 80% of the chalcopyrite concentrates worldwide [1]. However, some of recently emerged techniques for treating chalcopyrite through hydrometallurgical routes are showing results that are competitive with smelting in terms of economical feasibility. Representative methods include: Activox Process, CESL Process, Anglo/UBC Process, High Temperature Pressure Oxidation, and Bio-Oxidation. Among these, the CESL processes operate at a medium temperature range (typically 140-150GC) and oxygen pressure of 100 psi, with chloride as a catalyst, and reportedly achieve copper extractions of about 95% with a light regrinding of flotation concentrate to a p95 of 45 ìðé [2]. In spite of this satisfactory extraction result, the leach residues contain significant amounts of conglomerates which contain a small amount of unreacted concentrate [2], The conglomerations are formed because the elemental sulfur generated is liquid and sticky (melting point of sulfur being 119°C), and has a tendency to wet the sulfide mineral surface, a fact which inhibits the oxidation of the minerals. The overall process chemistry of the CESL process may be summarized as follows [3]:"

Jan 1, 2012

By Feng Liu, Bingji Yan, Zhiwen Shi, Hongwei Guo, Jianliang Zhang

During production of a large quantity of steel, slag is produced at the same time. This paper chooses blast furnace slag (BFS) as the main material for the research. The purpose of the research is to explore its optimal physicochemical properties and the use of BFS in building stone field. The paper elaborates the experimentation process of producing glass-ceramics and presents the results. The results show that SiO2 content in BFS and amount of Cr2O3 and Fe2O3 added as nucleating agents have certain effect on the properties of glass-ceramics. The results also show that the exothermic peak temperature of base glass is the lowest when adding 20% SiO2 to the BFS, and 2% Cr2O3 and 3% Fe2O3 as nucleating agents, which makes easy crystallization and optimal properties of the glass-ceramics.

Jan 1, 2015

By R. K. Mehta

Microorganisms have been increasingly used in applications such as-metal solubillzation, precipitation and recently being used as flocculants. Optimal control and on-line monitoring of these processes occurring in microbial reactors are of extensive interest but often difficult because of the unavailability of a mechanistic model of the process and on-line direct sensors. In this paper a dynamic populatlon balance model of microbial desulfurization will be presented. The influence of certain physical and biological parameters on the leaching rate will be illustrated via computer simulations and an extended continuous-discrete Kalman filter will be Implemented for estimation of unknown states.

Jan 1, 1991

By Kazuhiro Asai

Nippon Mining and Metals Company has an annual indium production capacity of 30 tons at its Saganoseki smelter and refinery. Lately, indium content in the. zinc smelting dust, one of the main sources, has been on the decrease while the amount of impurity in it on the increase. The present process at Saganoseki does not permit efficient elimination of a large. amount of impurity. Therefore, studies were conducted to improve its recovery process. As a result, a new indium recovery process consisting of leaching, solvent extraction and electrowinning has been developed. The new process was tested at a pilot plant and satisfactory results were obtained. This new process is discussed in this paper.

Jan 1, 1995

By Kohei Yajima

The dusts and fly ash generated from the steelmaking processes and municipal solid waste incineration processes contain metallic elements such as Fe, Zn, Pb and Cd with considerable amount of halogens. In Japan, zinc in dusts is recovered by Waelz kiln or MF process, etc. However, the presence of halogen in the dust affects the evaporation and condensation behavior of zinc and other metals, and disturbs the direct recycling of dust to steelmaking processes, because alkali or heavy metals reacted with halogen vaporize easily as halides and/or oxyhalide compounds in pyrometallurgical process. Recently, the formation mechanism of zinc oxychloride vapor was investigated and the formation of zinc oxychloride such as ZnOCl was proposed. However, considering the practical operation, the effect of water vapor on the evaporation behavior of oxychloride is not fully clarified yet. This study is focused on the investigation of evaporation behavior of ZnO with Ar- O2-HCl-H2O atmosphere.

Jan 1, 2008

By Jack S. McPartland

The recent developments on the concentration and recovery of gold from leached gold thiosulfate solutions by solvent extraction, reduction-precipitation, and electrochemical deposition are reviewed in this paper. Alkyl phosphorus esters have been found to extract gold only in alkaline thiosulfate solutions, The recovery of gold increases with thiosulfate concentration in the aqueous phase and with alkyl phosphorus esters concentration in the organic phase with aliphatic hydrocarbon diluents. The addition of ammonia improves the extraction. The extraction of gold with amines in either aliphatic or aromatic diluent decreased in the following order: primary>secondary>tertiary amines. Increase in the extractant concentration at high pH increased the extraction of gold. At pH < 9, the primary amine, RR&apos;CHNH2 with 1&apos;9-23 carbon atoms is the main extractant with TBP as the synergistic reagent and at pH >9, the primary amine shows a synergistic effect on the extraction of gold&apos; with TBP. TheAu(I) ions in thiosulfate solution are reduced by sodium borohydride (SBH) to metallic gold, with particles in the sub micron range, At an SBH/ Au ratio of 6.25, pH = 6, and at room temperature, the I e ppm Au(I) in a solution of ] 0 gil thiosulfate was completely reduced to metallic gold in about 60 minutes.

Jan 1, 1999

By Toshihiro Kuzuya

A hydro metallurgical process has been developed for the recovery of metal values such as Co, Ni and rare earths from the electrode materials of spent nickel metal-hydride(Ni-MH) secondary battery. MmNis_xCo. (Mm : Misch metal) intermetallic compound could be separated from the electrode materials mixture by sedimentation. A typical chemical composition of MmN5-xCox was approximately, in mass%, 56.0%Ni, 13.4%Ce, 10.6%La and 7.9%Co. The time dependency of leaching intermetallic compound with sulfuric acid solution was examined with processing factors such as sulfuric acid concentration, temperature and agitation intensity, The leaching of rare earth metals proceeded very rapidly, reaching completion in less than 1.8ks. On the other hand, the slow leaching of nickel was observed. The percent of nickel leached at 328K could only reach about 70%.

Jan 1, 2003

By Alexandre Bonan

This paper reports the results of a kinetic study on the oxidation of free cyanide and Cu-cyanide complex ions with HO,. The variables and respective ranges studied were the following: [CN] total =10 - 500 mg/l; pH=10-11; (H2O2/CN) mole ratio = 1- 3; (Cu/CN) mole ratio = 0.10 - 0.25. The results were interpreted by a semi-empirical model that incorporates the useful oxidation reactions and the parallel alkaline decomposition of H2O2

Jan 1, 1994

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 Masahiro Hirasawa

"As a fundamental study on pyrometallurgical process that involves recycling steel-making dusts, of which major components are oxides of Zn and Fe, and waste polyvinyl chloride simultaneously ·at. a temperature below 1273 K, the reactions between the mixture of ZnO + Fe20 3 and PVC or the compound ZnFez04 and PVC are investigated in a series of thermogravimetric and small scale reactor experiments under inert atmosphere at below 1273 K. The reaction mechanisms are discussed· on the .basis of the thermogravimetric data. From the results of reactor experiments, it is shown that the chlorination of Zn in the oxides by Cl in PVC, the vaporization of ZnC12, the reduction of iron oxide to metal Fe by C and H in PVC, and, thereby, the separation of Zn and Fe in the oxides take place simultaneously at the temperature ~= 1200 K.IntroductionSteelmaking dusts are metallurgical wastes consisting mainly of oxides of Zn and Fe with smaller amounts of other heavy metal elements, such as Pb. In the recent investigation, [1] the present authors have investigated the fundamental aspects of a potential pyrometallurgical process· of recycling steel-making dust with polyvinyl chloride (PVC) at temperature T < 1273 K under Ar atmosphere. The performance of a similar process, in which HCl in the combustion gas of PVC is used to chlorinate Zn in the EAF dust under oxidizing atmosphere, has been investigated by Tailoka and Fray [2] with fundamental experiments. Figure 1 shows an example of the potential ·diagram of Zrt-Cl-0 and Fe-Cl-0 systems. In the figure, we can find two regions where ZnCl2(g) can be separated from Fe containing compounds. One is ZnCiz-Fe20 3 coexistence region at higher oxygen and chlorine potentials and the other is ZnCl2-Fe coexistence region at lower oxygen and chlorine potentials. The process adopted by Fray and coworkers is aimed mainly at the performance of Zn/Fe separation in the higher oxygen potential region. In the present study, the lower oxygen potential region is focused on."

Jan 1, 2000

By Liu Wei-feng

In this paper, the practice of separating precious metals from base metals in gold-antimony alloy by selective chlorination leaching under controlling potential in China has been introduced in detail. The precious metals and the base metals can be separated completely when the complex gold-antimony alloy is treated by this process. The impurity metals were removed effectively since the leaching efficiencies of copper, nickel and antimony are over 99%, with direct recovery of gold being 99.83% that is about 20% higher than that of the original process and silver, antimony, copper and nickel are also recovered effectively. The gold grade of the resulting crude gold powder can reach to 94%.The new process has been applied in the treatment of gold-antimony alloy for two years, and many former procedures have been cancelled, such as electrolysis, Anode slime leaching by nitric acid, smelting in crucible and blowing in muffle. The new process is more shorten, lower cost and friendly to the circumstance comparing to the original process.

Jan 1, 2008

By Zhitong Sui

Based on several case studies on the precipitating behavior of valuable nonferrous metal compounds (VNMC) in molten slags a green technology for the recovery of VNMC from molten slags was proposed. This technology involves three steps: (I) The selective enrichment of the dispersed VNMC into the designed mineral phase in the molten slag; (2) The selective coarsening of the designed mineral phase to a critical grain size in the molten slag; (3) The selective separation from tailing of the grown mineral phase in the solidified slag by dressing or hydrometallurgy processes. This is a clean and low cost technique and has a great capacity to deal with a large quantity of slags. The utilization of the recovered VNMC such as Titanium, Boron, Vanadium compounds was summarized as examples of application. It was confirmed by experiments that the precipitating behavior of the designed mineral phases like Perovskite(CaTiO3), Suanite(2MgO*B2O3) and Sincosite(CaOoV2O5*P2O5) in molten slags is obviously affected by operation factors such as temperature, chemical composition, heat-treatment, additives and so on. The precipitating kinetics and mechanism of the VNMC from molten slags during solidification processes were also investigated.

Jan 1, 2003

By Fathi Habashi

Solid gas reactions of metallurgical importance can be classified into three groups: Physical processes, e.g., drying and sublimation Chemical processes which may be an addition or a thermal decomposition reaction Electrochemical processes which may be addition, oxidation-reduction, or displacement reactions. Examples are given and the role of the boundary layer is emphasized.

Jan 1, 1996

By Chang Wei, Fan Zhang, Zhigan Deng, Minting Li, Cunxiong Li, Gang Fan, Xingbin Li

Marmatite is an important resource of zinc, which exist in forms of high iron and high indium. In order to recycle the valuable metal from these ores, the testwork of simultaneous leaching on neutral residue mixed with zinc concentrate of high iron and high indium has been conducted. The primary objectives are to leach the zinc and indium remaining in the neutral leach residue as ferrite using acid, and to reduce the ferric iron in solution to the ferrous by zinc concentrate, thereby extracting the zinc and indium in the zinc concentrate. The results indicated that in the following conditions, mass ratio of neutral residue to zinc concentrate of 1:0.25, particle size of 74-58 μm, initial sulfuric acid concentration of 150 g/L, liquid to solid ratio of 8 L/kg, temperature of 90°C, reaction time of 4h, the leaching efficiency of zinc and indium were over 95%, nearly 90% Fe was Ferrous in the leaching solution. This process effectively extracted zinc and indium and converted Fe3+ into Fe2+ in solution, and simplified the traditional process of reduction after leaching.

Jan 1, 2016

By Kezhuan Gu

Data on the kinetics and thermodynamics of dephosphorization are analyzed in terms of the dynamic partition ratio, determined by a combination of slag thermodynamic properties and the balance of oxygen supply and consumption. A recently developed phosphate capacity correlation is combined with data on kinetics to quantify the most significant parameters in controlling the interfacial oxygen potential. The role of slag composition, entrained gas fraction and temperature are discussed in addition to metal carbon and sulfur content. It is demonstrated that the mass transport of oxygen in the slag is enhanced by factors increasing conductivity and inhibited by entrained gas. The mass transfer of phosphorus in the metal is described considering surface renewal induced by CO bubbles.