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By Marcelo Jimenez Bustos

The Chagres Smelter was the first in Chile to follow environmental regulations to control sulfur dioxide emissions. Because of this, the operation and development plans have had to incorporate environmental planning as part of its policies for almost three decades. The present article shows the development of the environmental standards applied to its operations, investments and operational improvements carried out to meet the regulations and improve competitiveness. Results to-date and future plans are outlined, as well as their impact on operations and the environment.

Jan 1, 1993

By Asmo Vartiainen

Background of Direct-to-Blister Flash Smelting is discussed; especially slag chemistry relating to copper solubility, slag fluidity and impurity behavior. In December, 2000, Mini-pilot Flash Smelting test runs were carried out at Outokumpu Research Oy to produce blister copper from Chilean concentrate and white metal and from a mixture of them. Tested slag types were iron silicate slag, ferrous calcium silicate slag and calcium ferrite slag with different slag compositions and different concentrate/white metal ratios. The test runs were successful. The fluxing effect of copper oxide was clearly demonstrated and ferrous calcium silicate slags remained fluid on a very wide liquidus range. The distribution of arsenic between ferrous calcium silicate slag and blister copper is much higher than between iron silicate slag and blister copper. This successful test run with the new slag type offer new possibilities in Direct-to-Blister process design.

Jan 1, 2003

By B. M. Satish

The aim of the present work is to study the effect of annealing on the vibration damping capacity of high-chromium (16%) ferromagnetic steel. The alloys were prepared from raw materials of 99.9% purity melted in a high frequency induction furnace under high vacuum. The samples were heat-treated in vacuum at various temperatures (800 to 1200°C) for 1 hour followed by slow cooling (120°C/h). The inverted torsional pendulum method was used to evaluate the vibration damping capacity. The results indicated that the vibration damping capacity of the alloys is influenced by annealing and there exists a critical annealing temperature after 1000°C. The damping capacity increases quickly below the critical temperature since the magnetic domains move more easily.

Jan 1, 2009

By A. J. Davidson

A novel sensor is described for the measurement of the copper content of copper matte. Due to the high copper concentrations found in matte, potentiometric sensors are not sufficiently sensitive. A highly sensitive sensor has been developed based on a modification of the amperometric technique using a copper ion conductor, Cusicon. The results correlate closely with the theoretical predictions.

Jan 1, 1998

By K. Koike, N. Masuko, Y. Takasaki

At the Zinc & Lead'95 symposium, one of the authors presented several modifications of Pb-Ag-Ca alloy anodes for the zinc electrowinning process, and also, the behavior of some organic additives in the electrolyte. In this study, the mechanical properties of the electrode materials composed by Pb-0.5 wt% Ag-(0~0.8) wt% Ca were studied by the tensile and Vickers hardness methods. Furthermore, experimental research on the influence of rolling and annealing treatments on the electrolytic behavior and mechanical properties of these alloys was carried out. The tensile strengths of the annealed Pb-0.5 wt% Ag-(0.1-0.8) wt% Ca alloys were the same or higher than those of the as-cast Pb-0.9 wt% Ag alloy. The anode potential using the as-cast Pb-0.5 wt% Ag-0.6 wt% Ca alloy decreased compared to the as-cast Pb-0.9 wt% Ag alloy. Moreover, the annealed Pb-0.5 wt% Ag - 0.6 wt% Ca anode after rolling showed a lower anode potential than the as-cast Pb-0.5 wt% Ag - 0.6 wt% Ca anode.

Jan 1, 2000

By Gus Van Weert

Solvent extraction of iron from zinc refinery liquors has been investigated before, mainly on the MEHPA / HC1 stripping combination. Leakage of chloride into the zinc electrolyte and the costs of handling the ferric chloride eluate have prevented this option from being adopted. This work explores the stripping of the ferric loaded organic phase with nitric acid to take advantage of the possibility of regenerating up to 6N nitric acid, and clean spheroidal hematite production by autoclave treatment of ferric nitrate solution. The work was carried out with DEHPA (di 2-ethyl-hexyl phosphoric acid) in kerosine. Degradation testing proved the DEHPA to be very stable, when exposed to nitric acid solutions up to 6N and temperatures up to 70" C over a period of five days. Ferric iron was removed completely froma synthetic hot acid leach liquor, irrespective of the DEHPA concentration. Stripping the ferric turned out to be the problematic step. Although the stripping efficiency was considerable better at 50 than at 20° C, it decreased with increasing DEHPA/Fe ration in the organic phase. Eluates of no more than 5-10 g/l ferric nitrate were produced. surprisingly, nitric acid was found to be a less efficient stripping agent than sulphuric at equivalent normality and its efficacy levelled off above 4N. It was concluded that DEHPA does not appear to be the S.X. reagent to take advantage of the low cost autoclave decomposition of ferric nitrate opportunity in zinc hydrometallurgy and that another S.X. reagent, also resistant to nitric acid, but based on weaker compound formation is needed.

Jan 1, 1998

By Jan Vrestal, Josef Tomiska, Pavel Broz

"Thermodynamic investigations on fcc solid ternary Fe-Ni-Cr alloys have been performed by means of the computer-aided Knudsen cell mass spectrometry. Ternary T.AP.-series (Thermodynamically adapted power series) are used for the algebraic representation of the thermodynamic excess properties. At 1650 K the molar excess Gibbs energy GE is negative over the whole field of stable fcc phase. The molar heat of mixing HE is exothermic in the predominant part of the fcc phase field. Only between the section with a constant ratio of mole fraction Xcr/XNi = 0.64 and the fcc phase field boundary the HE values are slightly endothermic. The results of this work can be used successfully for phase diagram calculations.IntroductionThermodynamic investigations on multicomponent alloy systems such as the Fe-Ni-Cr ternary system including the three binary boundary systems are very time-wasting and usually beset with considerable experimental difficulties. Additionally, the required experimental equipment is very expansive and the obtained results are not always satistying. Therefore it is understandable that many phase diagram calculations are based only on few experimental values of the molar excess free Gibbs energy GE. Consequently, Kundrat and Elliott [1] as well as Hillert and Qiu [2] used in their reassessments of the phase diagram of the Fe-Ni-Cr system thermodynamic data mainly assumed and/or optimized by means of various reasoning.Lee [3] reported recently, a revision of the used thermodynamic description of the Fe-Ni liquid phase is necessary to obtain a better agreement with the experimental data on the bcc/liquid or fcc/liquid tie lines and liquidus temperatures in the Fe-rich region of the Fe-Ni-Cr ternary system than in the previous assessments. This is 'in full agreement with mass spectrometric investigations of Fe-Ni alloys in the liquid and in the fcc solid phase, published earlier [4,5]. Indeed, phase diagram calculations based upon the molar excess free Gibbs energies GE obtained in these studies yield liquidus and solidus lines in excellent agreement with experimental phase diagram data [5]. Nevertheless, these experimental data have not been considered later on any more, not even in the revision by Lee [3]."

Jan 1, 1996

By Shu Yamaguchi

The behavior of halide impurities in pyrometallurgical processes such as Wealtz kiln and MF process has been discussed based on the thermochemical data and the reported data of PbO activity in PbCl2-PbO melts. The role of PbCl(g) has been estimated to be significant in the chloridization evaporation reaction. From reported data on the PbO activity in PbC12-PbO melts, activity of PbCl2 has been calculated by the numerical integration of Gibbs-Duhem equation, and the stability domains and the composition of the liquid phase as well as the vapor pressure of PbCl2 have been estimated as functions of log P2HCI/PH2O and temperature. From the discussion of the path during cooling process on the log P2 HCI . PH2O vs. temperature diagram, the authors proposed a possible dechioridization process that utilize water vapor as a dechloridizer for the direct precipitation of PbO from gas phase.

Jan 1, 2003

By K. Osseo-Asare

Aqueous stability diagrams (25°C) are presented for the systems M-H2O and M-Oxalate-H2O where M=Sm, Nd, Co, and Fe. With the aid of these diagrams (i.e., Eh-pH and log[Metal]- log[Oxalate]), the solution-chemical constraints on metal dissolution and precipitation are identified. By comparing the corresponding stability diagrams, conceptual flowsheets are developed for metal recovery from Sm-Co and Nd-Fe-B magnet scrap.

Jan 1, 1997

By J. A. Brierley

A biooxidation-heap pretreatment process was field tested to evaluate enhancing gold recovery from a preg-robbing sulfidic carbonaceous ore. Newmont Gold Company&apos;s Gold Quarry sulfidic carbonaceous ore was inoculated with an iron-grown culture of Thiobacillus ferrooxidans to form a 495 ton test heap. Biooxidation was conducted for a period of 100 days. The most active period of biooxidation occurred during the first 40 days of pretreatment? About 35 to 40% of the sulfide was oxidized. The extent of biooxidation was considered good as the ore particle size was relatively large 58% >1?9 cm (&apos;/< inch). The larger particle size ore limited the extent of bacterial activity. The field test demonstrated the ability to conduct biooxidation in a small pilot test heap. Thiourea was evaluated for extraction of gold from the biooxidized preg-robbing ore.

Jan 1, 1995

By Tim J. A. Smith

Fundicion Refimet S.A. has operated a custom copper smelter at La Negra, near Antofagasta in northern Chile since 1993. From an initial operation based on Reverb smelting and Peirce-Smith, converting, the plant was expanded from 90 000 t/y to 160 000 t/y copper production in early 1997, by conversion to oxy-fuel smelting and use of concentrate injection on Converters. As part of this expansion a novel reverb gas cooling and cleaning system was developed and designed by Kilborn SNC-Lavalin Europe, the London, UK-based mining and metals; Office of Canada&apos;s SNC-Lavalin group. The reverb gas cooler needed to satisfy several very specific requirements including low cost, flexibility, robustness and simplicity of operation. Of particular importance was the requirement to cool and clean the ,oxy-fuel reverb gases and render them suitable for subsequent treatment in a conventional sulphuric acid plant. It was also important to avoid accretion or dust handling problems. This paper describes the key design features and subsequent successful installation, commissioning and operation of the unit.

Jan 1, 1998

By Qian Li, Li-chen Hou, Yong-bin Yang, Tao Jiang, Jian-jun Hu, Bing Xu

Extraction of gold from refractory gold concentrates usually requires an oxidation step to remove arsenides、sulphides and carbonaceous matter. In this investigation, the gold concentrates were two-stage roasted under different atmospheres and temperatures. Results indicated that at the first stage, under neutral atmosphere, the removal rate of arsenic increases as the temperature rises. Under the oxidizing atmosphere, with the increase of temperature, arsenic content in the residued calcine increases, in addition, the volatilization of arsenic is also affected by the oxidation of carbon that generated CO, which is advantageous to the decomposition of arsenate decomposition. At the second stage of roasting, it is the higher temperature and stronger oxidizing atmosphere, the faster sulfur and carbon oxidated rate is, but at the same time, the calcine appears the phenomenon of consolidation because of the phase of silicate compounds generate.

Jan 1, 2015

By Thomas J. O'Keefe, Pu Yu, George Houlachi, Xuewen Tang

"Impedance measurements were used to investigate the electrochemical characteristics of acidic zinc sulphate electrolytes containing Sb3+, gelatin and their mixtures. The data were correlated with cyclic voltammetry curves made using synthetic as well as industrial electrolytes. The cyclic voltammetry results were similar to those obtained in previous studies in that antimony caused a depolarizing effect while gelatin gave an increase in the potential for zinc nucleation on an aluminum substrate.The electrochemical impedance spectroscopy (ElS) evaluations were conducted on electrodeposited zinc at three overpotential values. The potentials were chosen to represent various current density regions in the zinc polarization curves. The antimony and gelatin gave characteristic impedance plots which correlated with expected behavior, particularly current efficiency. Both antimony and glue appear to modify the intermediate zinc reaction sequence, but in different ways. The data strongly suggest that film formation and stability are major factors in the zinc ion reduction mechanism.IntroductionThe zinc electrodeposition process is sensitive to the presence of a variety of organic and inorganic chemical species in the electrolyte [I]. Such components can produce either beneficial or harmful effects, depending on their relative concentrations and electrochemical behavior. Extensive investigations have been made to gain a better understanding of the changes occurring during zinc deposition in the presence of such additives. Techniques employed include microscopy, x-ray diffraction, dynamic voitammetry, current imd energy efficiency studies [2-5]. Ultimately, the objectives are to identify the factors which most affect the efficiency of the process and to provide a means to effectively control them.One of the most harmful impurities is antimony, which can be detrimental when present at concentrations as low as 10 to 20 parts per billion. Dramatic changes in zinc polarization behavior, deposition structure and current efficiency have been observed with antimony in the electrolyte. Antimony appears to lower the hydrogen overpotential by hydride formation or a similar catalytic mechanism, which allows an increase in localized corrosion and zinc dissolution [6-8]."

Jan 1, 1997

By J. Y. Hwang

The relationship between coal characterization and physical cleaning has not been well understood due to the complex nature of coal. Therefore, it is difficult to apply the results of coal characterization to predict and evaluate the performance of a physical separation (e.g. flotation). Eight U.S. bituminous coals were analyzed and studied petrographically in conjunction with washability and flotation tests. The results show that grindability correlates to ash and fixed carbon contents; liberation determined directly by petrographic techniques is close to liberation determined indirectly by washability; and an ideal separation efficiency can be determined by measuring the inertinite content and the washability separation efficiency using a heavy liquid with a density of 1.4. The ideal separation efficiency was attained for most coals by packed column flotation. The ideal separation efficiency can be used for comparing process technologies and process parameters.

Jan 1, 1988

By A. McLean, S. Dawson, N. D. G. Mountford

"IntroductionIn order to predict the accepted industrial practice for the year 2000, it may be helpful to first consider the rate of development of scientific knowledge. If the speed with which man can travel on commercial vehicles is taken as a criterion for determining the rate of progression, then it can be seen from Figure 1 that advancement in our present century is very rapid. Likewise, if computer technology is used as a criterion for the measurement of scientific advancement, it becomes evident that technological evolution can be highly exponential. These two examples are sufficient to demonstrate that engineers and managers cannot afford to regard scientific development as being linear with respect to time if they are to avoid underestimating the needs of society.Within this framework of overall development, the time required for individual ideas to progress from inception to regular application has decreased considerably. For example, X-rays first discovered by Roentgen in the 1890's and now used widely in medicine and engineering, required a developmental period of some eighty years. The motorcar evolved from early beginnings at the turn of the century to a position of great social impact in sixty years. Rectifier materials used in high frequency radar to the present explosion in communications, required forty years. As illustrated in Figure 2, the period is shortening rapidly.The use of sound waves appears to be following a similar path. There is now a considerable body of knowledge concerning their behaviour and exceptional advances have been made. In medicine and engineering the sonic approach to examination is well established, and acoustic testing forms the basis of several diagnostic and quality control applications. With respect to metals engineering, ultrasonic testing has contributed to the understanding of the relationship between the size and number of internal defects and the probability of premature failure. This has allowed the designer to incorporate appropriate safety factors in his designs; but more importantly, the realization of the deleterious effect of inclusions on the performance of the final product has resulted in a continuous pressure on the material suppliers to reduce the number of defects in their products.It is not only the designer who is demanding defect free material but also the fabricator, as material breakdown during manufacture can be prohibitively expensive. Examples of this can be found in both the aluminum and steel industries where ultra clean sheet is required to ensure that rejections are minimized during beverage can manufacture and other deep drawing operations."

Jan 1, 1988

By Robert R. Beebe

On the night of August 1&apos;9-20, 1995, seepage was seen at the toe of the Omai tailings dam in Guyana. The mill was immediately shut down, and within two hours the flow, then mostly water, was diverted into an inactive mining pit nearby. At about the same time a second more serious break occurred at a point where water and solids could flow directly into the Omai River. By the time Ii coffer dam could be completed in the early morning of August 24, some 4.2 million cubic meters of tailings water and solids had escaped from the dam, of which nearly2.9 million cubic meters had reached the Omai River. This paper outlines some initial Process considerations and operational decisions which might have contributed to the dam&apos;s failure, describes how the Government of Guyana and the operator, Omai Gold Mines Limited, cooperated in dealing with immediate problems and shows how the Government set about investigating the accident. In particular, the paper details the work of a Process Review Committee comprising Guyanese and foreign experts convened to assess the gold processing and effluent management systems at Omai, and to recommend actions where appropriate.

Jan 1, 1998

Hazardous waste has often very complicated chemical compositions in a variety of physical forms and is normally processed in rotary kiln incinerators. Due to large variations in waste types and difficulties in feed characterization, the complex transport processes within the incinerator are not well understood, and the incineration process meets challenges in a smooth operation, and expects various uncertainties in the process chemistry and emission control. For better understanding of the incineration process, simulation was carried out by using Computational Fluid-dynamics (CFD) to characterize temperature and species distribution in the incinerator. In order to catch certain aspects of thermal and chemical behavior, a novel approach is proposed to represent approximately the waste streams and the subsequent combustion process. Hazardous waste in various forms from an industrial-rotary-kiln waste incinerator is firstly converted to a hydrocarbon-based virtual fuel mixture with approximately the same HIC molar ratio and calorific value. The simulation of the combustion process of the simplified hazardous waste was proceeded with a combustion model. The distribution of temperature and chemical species especially the remaining CO in the system is preliminarily investigated. Distribution of CO concentration, as a good indicator of emission level for the incineration process, could be used to evaluate the emission control. The predicted temperature distribution has been compared with available measurement data from an operating rotary kiln waste incinerator at AVR-Chieme, in the Netherlands. Reasonable agreement has been reached between the measured and predicted temperature data. In the next step, measurement of species distribution in the system is planned to further validate the combustion model.

Jan 1, 2003

By Pengfu Tan

In order to understand and control the formation of dioxins and furans in iron ore sinter plants and to possibly avoid expensive end-of-pipe removal stages, thermodynamic calculations on the stability of PCDD/Fs have been combined with sinter process modeling by means of kinetic simulations and computational fluid dynamics. Three thermodynamic databases of PCDD/Fs, derived using the Group Additivity approach and two computational molecular modeling methods, MNDO and PM3, respectively, combined with the SGTE database have been used to model the PCDDIF formation and the PCDD/F isomer distributions in iron ore sintering. The results show very similar conditions for the PCDD/F formation using the different databases. Concerning the isomer distributions of toxic PCDD/Fs, the calculated data derived from the MNDO method showed optimum agreement with measured values from industrial furnaces. The thermodynamic calculations also proved that the isomer distributions found in combustion processes are equilibrium values, while the concentration ratio of PCDDs and PCDFs in the wind boxes does not represent an equilibrium state. A CFD model of iron ore sintering was developed including the kinetics of 15 relevant chemical reactions with the aim of describing the temperature fields and the gas flow patterns in the sintering bed. On the basis of these information and experimental observations reported in the literature possible pathways for the PCDD/F formation in sinter plants have been identified: PCDD/Fs are formed in the critical temperature region of 250 to 450 °C below the combustion zone, are then carried downwards with the gas and condensed close to the bottom of the sinter bed. Transported to the discharge end with the solid mixture, they are again released into the gas phase when the flame front approaches the bottom. PCDD/Fs are also formed in the last wind boxes when the hot off-gases cool down and reach the critical temperature range. Consequently, methods to reduce the dioxin formation reactions are proposed including inhibitor addition to the sinter feed and off-gas quenching.

Jan 1, 2003

By Toshiaki Nakai, Kunihiko Takeda, Kimio Imaizumi, Hiroaki Shirasaka

"The new type of nano-porous silica particle was considered to be constructed by the spinodal decomposition-type process which was found to have narrower pores than those of conventional porous silica prepared from boron silicate or ""Shirasu"" balloon. Nano-porous silica particles were fabricated by the calcination of silica gel mixed with well-dispersed complex salts composed of phosphorous and molybdenum compounds. Both silica and inorganic salts were not perfectly dissolved in the suspension solution. After removing of the water, the silica-inorganic salts complex was volatized and successively calcinated at a temperature ranging from 650 °C to 800 °C. Then, the inorganic salts were removed by dissolving in hot water. Other inorganic salts such as potassium halides were also found to be effective as a pore-size controller.IntroductionControl of structure has an important role in the field of industry as well as in the separation and purification technology for metals and organic syntheses. Many studies on the control of material structures have been reported regarding porous materials with pores ranging from nanometer to micrometer scale. 1 ) One example is zeolite as a naturally yielded porous inorganic material. Various types of synthetic zeolites have been studied as ""molecular sieve"" materials with ordinary pore-size of less than one nanometer. In 1992, crystalline meso-porous material with a large surface area named MCM-41 was synthesized through the use of template synthesis. 2) In direct relation to our study, amorphous borate glass having 4 to 100 nm of fine pores known as Corning glass 3l or SiO2-Al2OrB2O 3-CaO porous glass having large pore dispersity ranging from 4 to 10,000 nm have been reported. 4 ) S) 6 ) Some examples of several reported studies are as follows: phase-separated porous glass consisting of B2OrAl2O3-ZrO2-RO-R2O complex oxide 7 ) glass with finer pore induced from hydrolysis of silane alkoxide, porous material attained by condensation polymerization through the use of sol-gel process 8), alumina meso-porous material 9 ) 10), silica-zirconia material 11), carbon porous material 12), etc.."

Jan 1, 2000

By James M. Fragomeni

"The mechanical behavior of an Al-Li alloy was studied and related to the extrusion processing parameters, the plastic metal flow during defonnation, the anisotropy, and the microstructure. The extrusion temperatures, strain rates, extrusion ratios, billet temperatures, and extrusion geometries were varied during processing and correlated with the microstructure and properties. The extrusion processing variables were related to the mechariicar behavior, anisotropy, and microstructure through the ZenerHollomon parameter i.e., the temperature compensated strain rate. Based on optical and electron microscopy studies it was found that regardless of the extrusion conditions, the various microstructures for the most part were unrecrystallized for both the as-extruded and the solution heat-treated conditions. Smaller grain sizes were correlated to larger Zener-Hollomon parameters. The extrusion temperature and ratio did not significantly affect the strength or ductility as did the section geometry, which had a large affect on these mechanical properties. The anisotropy of the properties varied substantially when comparing the extruded longitudinal versus transverse grain orientations.IntroductionThe extrusion process also has a substantial influence on: the microsfructure and mechanical properties of a material that is Athens, Ohio, 45701 fonned The plastic defonnation that occurs during the extrusion process alters the grain size, crystallographic texture, anisotropy, subgrain size, dislocation density and various other microstructural features. Often the material being extruded is not homogeneous, therefore variations in the microstructure and properties occur across the cross-section of the final extruded product. The mechanical properties and microstructure can also vary with length since it is hard to maintain a constant temperature throughout the extrusion process. The extrusion temperature often varies from the heat generated during the extrusion process. The demonstration material that was extruded for this .study was an aluminum alloy containing 2.6wt, % lithium and 0.09wt.% zirconium. This alloy was strengthened by heat treatment causing nucleation, growth, and coarsening of coherent metastable o' (Al3Li) precipitates in the microstructure. The ? precipitates which are a consequence 9f artificially aging the AlLi alloy, are spherical, ordered, and coherent with the aluminum matrix and impede the dislocation glide inotion during plastic defonnation. Theo particles grow homogeneously in the matrix, and have the Cu3Au (L 12)"" superlattice crystal structure. Aluminum-lithium alloys are used primarily for aerospace structural applications since they have attractive properties such as a lower density and higher elastic modulus than conventional 2XXX and 7XXX alloys."

Jan 1, 2000