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By Takahiko Okura

Most non-ferrous raw materials are associated with sulphur. To extract the metals, the sulphur is recovered typically as sulphuric acid or liquid SOz, On the other hand, natural gas may contain over 20% of hydrogen sulphide (HzS) and a huge quantity of elemental sulphur is produced through oil and gas refining processes in the world. A large fraction of the sulphur mined from natural sources is eventually returned to the earth as fertilizers, by-products of desulphurisation and neutralisation processes, or as fugitives to the atmosphere. However, the supply and demand for sulphur are in imbalance. Such situation urges to develop a new smelting process without sulphuric acid production. This paper briefly reviews the global sulphur balance and the technologies for recovering elemental sulphur. The core of this paper is a proposal to convert SO2 gas to elemental sulphur by using organic materials. Some results of thermodynamic calculations and experiments are presented.

Jan 1, 2003

By Lev Levin, Sergei Lesokhin

"The formation of titanium carbide during hot filament assisted carburizing of NiTi alloy was investigated. Phase content and morphology of the diffusion zone were examined by X-ray diffraction, X-ray microanalysis, SEM, and Auger electron spectroscopy. The growth of stable and adherent TiC film was observed. A non-planarity of interphase boundary was noticed. The applicability of the chemical diffusion approach to the analysis of the experimentally observed interface instability is discussed. A criterion, taking into account the influence of growth stresses on the stability of the flat interface, is developed by means of linear perturbation analysis.Introduction.Equiatomic intermetallic NiTi belongs to a class of materials exhibiting the shape-memory effect. The unusual property of this compound promotes its application in many fields, from aerospace technologies to medicine. The relatively high ductility ofNiTi also permits its use as a matrix material in metal-ceramic composites. The objective of this work was to investigate the possible incorporation of a ceramic material (titanium carbide) into NiTi by gas carburizing.Free energy calculations indicate the potential to obtain TiC by carburizing Ni-Ti binary phases. The main obstacle to such a process is the high affinity of titanium to oxygen. At moderate temperatures the formation of TiC is preferable to titanium oxidation only if the partial pressure of oxygen is extremely low [1]. This problem was overcome in this work by the use of hot filament assisted gas carburizing. Due to chemical reactions occurring near the hot filament, the gas mixture, initially consisting of methane and molecular hydrogen, was enriched by atomic hydrogen [2], drastically decreasing the content of free oxygen in the carburizing atmosphere.The second part of this article concerns the theoretical analysis of reasons that lead to the development of the experimentally observed morphology of the diffusion zone. In particular, the influence of the growth stresses on the morphology of an interphase boundary is investigated."

Jan 1, 1996

By R. Luo, R. V. Kumar

"The co-deposition of cobalt and nickel as a binary alloy has been studied by both cyclic voltammetry and long-period controlled-potential electrolysis. Cyclic voltammetry experiments showed that the cathodic current density for the mixed Co-Ni (Co-Ni=1:3) electrolyte is noticeably higher than that obtained on electrolyte containing single CO2+ or Ni2+ (II) salt of the same ionic strength. The onset potential observed for the mixed salts electrolyte was also less cathodic (negative) than that for the single metal salts, respectively. The effects of a number of operational and compositional parameters on the co-deposition of cobalt and nickel were studied. The parameters under investigation include cathode (deposition) potential, temperature, CI-/Sol ratio in the electrolyte, the amount of additives such as H3B03, and acidity of the electrolyte.Optimum operational conditions were established for the deposition of cobalt and nickel binary alloy. These results are discussed with respect to feasibility of reclaiming cobalt, nickel and chromium from mixed superalloy scraps by melt-refining (under nitrogen and/or ammonia), followed by electrorerining of cast anode for co-depositing Co/Ni and thermal decomposition of chromium nitride for recovering chromium metal."

Jan 1, 1997

In the new flowsheet for Inco Limited's S02, Abatement Project at the Copper Cliff, Ontario operations, a copper/nickel sulphide flotation concentrate will be flash smelted, then converted to Bessemer matte. As in current practice, this will be slow-cooled and separated into components by magnetic separation and flotation. The copper content will emerge as a chalcocite concentrate (impure Cu2S), containing some nickel. This copper sulphide will be converted to copper metal.

Jan 1, 1993

By D. M. Hausen

The term "auriferous pyrite" relates to an association of gold with pyrite in a variety of textural forms that affect metallurgical treatment. Extraction of the gold depends not only on the grain size and distribution of the gold in the pyrite, but also on the crystal size and surface area of the pyrite. Occlusions of medium to coarse gold may be liberated by moderately fine grinding. The amenability of finely dispersed (submicroscopic) gold depends in part on the activity of the pyrite surface for oxidation. Two types of auriferous pyrite at Carlin, Nevada, have been examined by optical microscopy and SEM methods before and after aqueous oxidation test work to show how differences in morphological features can affect rates of oxidation and amenability to gold extractions by methods of chlorination and low temperature oxidation.

Jan 1, 1981

By R. Nilsson

In the present work, an assessment of the sulphide capacities of a number of binary and ternary slag systems have been carried out in the light of a sulphide capacity model. The model is based on the expression: {CS- exp (-A G °/R T) ? ao2 / fs2-} where AGO is the standard Gibbs energy change for the above reaction, ao2 is the activity of oxygen ions and f, is the activity coefficient of the sulphide ion in the slag. In the present model, the ratio (ao2/fs2) is optimized for the experimental data available in literature. The systems assessed are the binaries MnO-SiO2, CaO-SiO2, Al2O3-CaO, as well as the ternaries CaO-Al2O3-SiO2 and CaO-MnO-SiO2. In the case of all these systems, the experimental data available in literature were complemented by measurements carried out at the Division of Theoretical Metallurgy. The sulphide capacities of some FeO- containing binary, ternary and quaternary slags are also examined. The potentiality of the model to estimate the sulphide capacities of complex slag systems from binary and ternary data is demonstrated.

Jan 1, 1996

By Jianhua Xin, Min Chen, Cuihuan Huang, Shan Yu, Xiaoao Li, Nan Wang, Guanghao Chen

Copper enrichment behavior in continuously cast slab induced by scale formation after continuous cooling in H2O vapor atmosphere and consecutively in air has been experimentally investigated by combining with SEM-EDS analysis, for the purpose to examine the effects of initial slab surface temperature and contents of copper and nickel. For Slab 1 with copper content of 0.1 percent, no visible copper enrichment is found at scale-substrate interface irrespective of the various scale microstructures formed at different initial slab surface temperatures. For Slab 2 with higher contents of copper and nickel, copper-rich phase accumulates and stays at scalesubstrate interface under the condition of lower initial slab surface temperature; while Cu-rich phase in the porous scale formed at higher initial slab surface temperature is noted with simultaneous Ni-enrichment appearing in front of the steel-scale interface. Both a porous scale and high nickel content work together to provide pores for copper-rich phase migration away from interface and occlude within the scale layer.

Jan 1, 2016

By Thais Cristina da Costa Caldas, Carlos Mauricio Fontes Vieira, Alline Sardinha Cordeiro Morais, Sergio Neves Monteiro

"This work has as its objective to evaluate the effect of the incorporation of a glass powder waste obtained from discarded and Hg-cleaned fluorescent lamp into clayey ceramics used to fabricate bricks and roofing tiles. Formulations were prepared with incorporation of the waste in amounts up to 10 wt.% into the clayey body. Rectangular specimens were prepared by uniaxial mold-press at 20 MPa to fire at 850 and 1050°C. The physical and mechanical properties evaluated were: linear shrinkage, water absorption and flexural rupture strength. The microstructure of the fired ceramics was evaluated by optical microscopy. The results showed that the waste incorporation significantly improved the evaluated properties mainly at 1050°C.IntroductionFluorescent lamps use mercury as a main component for its operation. This metal is potentially toxic and can contaminate soils, animals and water bodies. The problem is aggravated if considerations are made with respect to the amount of lamps that are commercialized and discharged in emergent countries like Brazil [ 1].By using appropriate recycling processes applied to discharging fluorescent lamps it is possible to reuse most constituents of these lamps into new productive processes. A study has shown that one million common fluorescent lamps can generate 900,000 tubes of clean glass [2]. Moreover, this Hg-cleaned gloss may be recycled in different products.In fact, to recovery and recycle all materials that constitute the lamp instead of discharging them. This action protects the soil avoiding the formation of environmental passives [3]. It is also relevant to mention that the glass from fluorescent lamps is 100% recyclable while its permanence in the environment would correspond to very long time pollution, since its decomposition time is undetermined [4]."

Jan 1, 2011

By R. Burkhard

Recovery of metals from complex mixed wastes is a challenging task of modem material and waste management strategies. Thermal methods are an important tool in this respect. Plasma turned out to be particularly useful for treatment of complex or toxic wastes and residuals. In order to study plasma processes at reasonable costs, a pilot plasma plant has been used and wastes like ~pent Raney-Nickel catalysts, copper and ah.:lminum drosses, and. other metal containing wastes were investigated. The paper summarizes the most significant findings

Jan 1, 1995

By Edward Rosenberg

The synthesis and characterization of silica polyamine composites modified with a variety of sulfur containing ligands is described. The two most successful ligands in terms of sulfur in-corporation and mercury capture are ethylene sulfide and carbon disulfide. The ethylene sulfide forms either an amino mercaptane or a polysulfide upon reaction with amino groups on the composite. The carbon disulfide undoubtedly forms a dithiocarbamate functional group upon reaction of the amino group under basic conditions. Both materials posses excellent capture kinetics and capacities for mercury, Once captured, the mercury is extremely difficult to remove from the composite materials, even with concentrated acids, and they easily pass the TCLP test. The materials are compared with related thioether modified silica polyamine composites and appropriate potential applications are discussed.

Jan 1, 2003

By P. Maraboutis

Iron removal by precipitation as jarosite from Fe-Ni-Co sulfate solutions, (synthetic or real, resulting from laterites leaching) has been investigated. Precipitation was carried out at 95 C, and at an initial pH 1.6, which was either kept constant with CaCO3 or Li2CO3 additions, or left to drift with the evolution of the reaction to lower values. The precipitation of K-, NH4- and Na- jarosite was initially examined using synthetic solutions. In all cases, hydronium ions were incorporated into the precipitate as well. Residual iron in solution was lower (0.2-1 g/1) and equilibrium was achieved faster (within 4-8 h) when precipitating K¬jarosite at constant pH, using CaCO3 for neutralization. Nickel and cobalt losses were small. Na- jarosite precipitation was also studied from real solutions with high initial iron content, under constant pH=1.5, controlled with CaCO3 additions, and it was shown that low residual iron concentration in solution (0.3-0.5 g/1) can be achieved again, with relatively small nickel and cobalt losses. The thickening and filtration characteristics of the precipitates were excellent in all cases examined.

Jan 1, 1988

By Xu Weimin

The existing copper electrorefining tankhouse of Jinchuan Nonferrous Metals Complex (JNC) was commissioned in 1986 for refining blister copper anodes. Blister copper is produced by reverberating chalcocite separated from converter high grade nickel-copper matter by means of flotation. Special chemical analysis of the anodes shows, a composition of 93.02 - 95.72 % copper, 3.0 - 4.96 % nickel and 0.5 - 1.23 % sulfur. The wide range of composition makes the electrorefining process fairly different from others throughout the world. The initial nickel content of 20 ppm and sulfur 40 ppm or more in copper cathodes are reduced to 8.5 ppm and 11 ppm respectively. Since 1986 the tankhouse has undergone significant evolutionary modifications and implementations to ameliorate cathodes quality desirably. The important fact is that the N-additive was utilized through many studies and pilot and field trials successfully. While our primary purpose is to improve chemical quality of the cathodes, tankhouse capacity is increased considerably and the process is perfected satisfactorily. The tankhouse is described with special emphasis on JINCHUAN PROCESS. The upgrading of our product by the utilization of the N-additive is highlighted. The other aspects of the tankhouse including spent electrolyte treatment and by product nickel sulfate manufacturing are briefed as well. Key words: JINCHUAN PROCESS, anode, cathode, electrolyte, electrorefining, N-additive.

Jan 1, 1993

By Xiangru Chen, Honggang Zhong, Qijie Zhai, Qingqing Sun

"A horizontal directional solidification equipment, with an in-situ pouring system, was employed to physically simulate the solidification behavior of continuous casting. In this paper, the 2304 duplex stainless steel (DSS 2304) was investigated using this equipment due to its microstructure produced by continuous casting process was usually not satisfied. The grain size combined with the position of columnar to equiaxed transition (CET) of DSS 2304 were observed and the results showed these microstructure characteristics were very close to those of the continuous casting slabs. In addition, the influences of pouring temperatures and cooling conditions on the CET behavior were investigated. The results revealed that the length of the columnar grains decreased with decreasing the pouring temperatures and flow rates of the cooling water. Besides, the content of austenite decreases with increasing the distance from the chilled sidewall.IntroductionDuplex Stainless Steels (DSSs) have been widely used in industry for their excellent mechanical strength and superior corrosion resistance in Cl- environments when compared with other stainless steels [1,2]. Their good performances are mostly on account of the duplex phase structure-ferrite (d) and austenite (?) and the high proportion of alloying elements. Although, DSSs have good ductility, but worse formability compared to the austenitics, and this is the key to restrict DSSs application [3]. This is due to the differences properties between the two phases. The hot workability of ferrite (d) is better than austenite (?) and exhibits a lower flow stress during hot rolling processing [4]. The early workers had revealed that coalescent force of phase interface, microstructure, difference of mechanical property between two phases and the precipitations are the main factors affecting the formability of DSSs [5,6]. Another important reason that affects the alloy’s mechanical properties is columnar to equiaxed transition (CET) [7]. It often occurs during continuous casting solidification process and induces inhomogeneous mechanical properties and the microstructure varies with different processing parameters, such as pouring temperatures, cooling conditions (water flow rates in the cooling zones) and casting speed [8]."

Jan 1, 2012

By Dmitri Nassyrov, In-ho Jung

"All relevant thermodynamic and phase diagram data in the CaO-Fe10-CaF2 system were critically reviewed. One set of model parameters describing the Gibbs energy of all phases has been obtained as a result of critical evaluation of the available data and optimization of the model parameters. The Modified Quasichemical Model was used to describe the interactions in the liquid phase. All calculations were performed using the FactSage thermochemical software.IntroductionSlags contaimng CaF2 are of significant interest to the steelmaking community. Notable examples of slags containing significant amounts of CaF2 include Electro-slag Remelting (ESR) slags [1] and mould flux for continuous casting [2]. The role of these slags is, among other things, to refine steel by absorbing inclusions and dissolved impurities. During slag-steel interaction, some iron from the steel will inevitably get oxidized and form iron oxides which will dissolve into the slag. With this in mind, it is important to understand the interaction between CaF2 and Fe,0 for accurate prediction of slag composition and process optimization. A thermodynamic optimization of the CaO-FetO-CaF2 was thus undertaken."

Jan 1, 2013

By De-qing Zhu, Feng Zhang, Jian Pan

Sintering performance of a series of sinter blends with high ratio of limonite was investigated. The metallurgical performance and mineralogy of product sinter were also examined. The results show that good sintering performance could be obtained when the ratio of limonite was below 43% in the blends of iron ore fines, while good microstructure and metallurgical properties were achieved under optimum sintering conditions. In contrast, sintering performance will rapidly deteriorate when the ratio of limonite is elevated up to 63% in the blends.

Mar 1, 2017

By A. Christlo

Short circuit detection in 1984 involved nine inspectors for production rates of 43,000 tpa. Trials indicated the feasibility of applying cell voltage monitoring to short circuit detection and improving operational efficiency. A computerised cell voltage monitoring system was commissioned in February 1986, to read voltages from 648 cells. The system incorporates 16 evenly distributed work face units which communicate with a central computer system. Provision has been made in the computer program for the automatic adjustment of cell reference voltages. This allows for the effect of polarization and other process variables which might other wise interfere with short circuit detection. The work face units can continue to work independently for several days should this become necssary. Current efficiencies have been maintained and the number of inspectors reduced from nine to five.

Jan 1, 1987

By H. Y. Sohn

"The nonferrous production industry has gone through a remarkable transformation in recent years in terms of developing and adopting new technologies. Technology innovations have largely been driven by the need for greatly improved environmental protection in addition to increased productivity. One of the most notable aspects of the new technologies is their ability to reduce the emission of sulfur and other pollutants to extremely low levels.The current industry trends towards more environmentally friendly technologies are bringing about additional benefits of developing more efficient, technically advanced, and continuous processes in closed reactor vessels. Key aspects of these modem trends include the use of increased oxygen enrichment in the process gas, better process control, reduced manpower requirements, and plant operations with more skilled personnel.Computer simulation and modeling of complex processes have become more reliable, realistic, and thus increasingly useful in metal production. Some of the notable examples are reviewed.Finally, the need and advantages for value-added production in the nonferrous industry are discussed.I. IntroductionMost recently commissioned technologies for nonferrous metals production have been developed largely in response to environmental concerns. One of the most remarkable improvements made by the nonferrous industry in the last decade has been the rapid increase in sulfur capture. Before the start of the last decade, 90% capture of sulfur was considered good. Since then, strict emission regulations have become the norm in advanced societies, although smelters in many parts of the world still operate with limited pollution control. Other emissions and discharges have also been substantially reduced, resulting in much improved working conditions and worker hygiene in addition to the overall environmental protection. The development of the more environmentally friendly technologies has accompanied other advantageous advances made in the nonferrous industry, i.e., the trend towards more gas-tight, continuous processes and larger plants. This has increased the competitive edge enjoyed by the industry in the industrial countries, offsetting the higher costs of labor and pollution abatement that they have to overcome in those countries. Experience has shown that clean technology often leads to a profitable business, because its adoption forces the concomitant advancement of related technologies in addition to the avoidance of penalties imposed by the public on pollution-prone industries. Needless to say, there are other driving forces for new technologies such as reduction of operating and capital costs, improved product quality, and energy considerations in terms of reduced consumption and utilization of readily available sources."

Jan 1, 2000

By Shengli Wu, Fengjie Zhang, Feng Chang, Hua Lu, Kaiping Du

In order to make a complete understanding of steel plant metallurgical dusts and to realize the goal of zero-waste, a study of their properties was undertaken. For these purposes, samples of two sintering dusts (SD), two blast furnace dusts (BFD), and one electric arc furnace dust (EAFD) taken from the regular production process were subjected to a series of tests. The tests were carried out by using granulometry analysis, chemical analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy via SEM (EDS), and Fourier transform infrared spectroscopy (FTIR). The dominant elements having an advantage of reuse are Fe, K, Cl, Zn, C. The dominant mineralogical phases identified in sintering dust are KCl, Fe2O3, CaCO3, CaMg(CO3)2, NaCl, SiO2. Mineralogical phases exist in blast furnace dust are Fe2O3, Fe3O4, with small amount of KCl and kaolinite coexist. While in electric arc furnace dust, Fe3O4, ZnFe2O4, CaCO3, CaO, Ca(OH)2 are detected.

Jan 1, 2015

By David S. Holmes

An overview of existing biological technologies for the recovery of copper and uranium is presented. Engineering and biological challenges and opportunities in these areas. are discussed. New opportunities for the biooxidation of refractory gold ore are described. Techniques for the development of new strains of microorganisms. for commercial metal recovery applications are discussed with special reference to the genetic manipulation for bacterial strain improvement.

Jan 1, 1991

By B. Mishra, W. A. Averill

"The application of various hydrometallurgical, pyrometallurgical and electrochemical processes in the extraction, purification and production of radioactive metals as well as the use of various materials, ego metals and alloys, ceramics, polymers, etc. in the process, construction and handling equipment in the nuclear industry has generated a large stockpile of radioactively contaminated waste material and scrap metal which can not be directly discarded, recycled or considered for long-term storage due to its volume and potential hazards, without the separation of radionuclides. This paper reviews the emerging methods that have been investigated and suggested for dealing with some of these wastes and scrap material.The separation technologies studied for the recovery of radioactive components from the pyrometallurgical and electrochemical processing wastes have been discussed in details with results from some of the recent theoretical and physical modeling work as well as the data obtained from the actual waste treatment. Specific processes shall be described in terms of its advantages and limitations. These emerging separation technologies are being considered by the US Department of Energy as alternatives for dealing with the issues of environmental management [EM] and decontamination and decommissioning [D&D].IntroductionThe high temperature carbothermic or metallothermic smelting reduction methods for metal production are associated with the generation of significant quantity of waste as slags, flue dusts, sludges, residues, effluent salts etc. Certain hydrometallurgical processes also generate lots of aqueous waste due to the inherent nature of the technique. Also, the gas-based reduction processes are not applicable to many stable metal compounds, such as alumina, titania, beryllia, lanthanide and actinide oxides, etc. due to thermodynamic considerations. All these methods cause substantial environmental hazard. There is a need to develop alternative processes which have low waste or ideally a ""zero-waste"" generation.Pyrochemical processes using molten salts provide a unique opportunity for the extraction and refining of many reactive and valuable metals either directly from the beneficiated ore (aluminum, beryllium, neodymium, plutonium, uranium, etc.) or from other process effluent that contain reactive metal compounds. The processes reduce metal compounds electrolytically (A12O 3 and BeCI2) on a carbon anode or by calciothermic reduction (Po, Nd). The by-product, in the latter case, is a calcium oxide saturated halide salt. The waste-treatment to recycle the halide has to be done as a separate step or stored as a contaminated waste. A successful separation technology can provide a new insight to the waste minimization strategy for the nuclear industry."

Jan 1, 1996