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By J. M. Skeaff

As much as 100% of the gold and 67% of the silver in a sulphur-bearing hydrometallurgical leach residue have been transferred to copper metal at copper smelting temperatures by dissolving the partially calcined residue in an iron-bearing slag maintained in equilibrium with the liquid copper metal and matte phases. The precious metals can then be recovered by conventional refining techniques. Copper can be recycled at least four times without any detrimental effects on gold and silver transfers and recoveries. Apparent copper recovery in the .process can be over 100% because of the copper content of the residue. Based on slag analys.es, the overal1 recovery of gold in the copper metal and matte phases varies from 94% to 100% under all conditions investigated. On the? same basis, silver recovery varies .from 9S% ?to 99% under optimum conditions, but is only 4S% to 73% under other, less attractive conditions. Unaccounted for silver losses of' about 30% make it difficult to determine the major factors affecting ?silver transfer and recovery. A method for implementing the technology on a commercial scale at a Canadian copper/zinc smelter has been proposed. A preliminary economic assessment and comparison of the proposed pyrometallurgical process with conventional cyanidation indicates that either process is economically attractive for recovering gold and silver from leach residues. Although the capital costs are higher, the pyrometallurgical process is simpler, has higher recoveries, lower operating costs and no .potential environmental problems related to cyanide disposal.

Jan 1, 1989

By John R. Goode

The fist part of this paper comprises a general discussion on refractory gold ores and their mineralogy. Processing methods now in use are reviewed and test procedures for the important methods are discussed. Factors determining the selection of a process are outlined. The paper includes a survey of production plants using pressure oxidation, roasting and biological oxidation to process refractory ore. The status of processes under development is briefly reviewed.

Jan 1, 1993

By Anja Pfennig, Thomas Böllinghaus, Marcus Wolf

During CCS components are exposed to a corrosive environment and mechanical stress which results in corrosion fatigue and is inevitably followed by the lifetime reduction of these components. The lifetime reduction of the cyclically loaded high alloyed stainless injectionpipe steel AISI 420C (X46Cr13, 1.4034) constantly exposed to highly corrosive CO2- saturated hot thermal water is demonstrated in in-situ-laboratory experiments (T = 60 °C, brine: Stuttgart Aquifer, flow rate: 30 l/h, CO2) in an environment similar to the on-shore CCS-site in the Northern German Bassin. In-situ tension-compression experiments were established simultaneously along with electrochemical measurements using a newly designed corrosion chamber in a resonant testing machine at a frequency as low as 30 – 40 Hz. In addition technical CO2 was introduced into the closed system at a rate close to 9 L/h. S-N plots, micrographic analysis and surface analysis of the fracture surface are demonstrated. X46Cr13 (surface roughness Rz = 4) reached the maximum number of cycles (12.5 x 106) at stress amplitude of 173 MPa producing a low scatter range of 1:3.5. Hydroxide and siderite layers were found on pits and crack surfaces. No typical fatigue limit exists. Pit corrosion prior to crack initiation may be identified as failure cause.

Jan 1, 2016

By Ramana G. Reddy

Thermodynamic modeling and experimental study on impurity capacities and their distribution between mattes or metal and slags in smelting, converting and refining of non-ferrous metals was discussed. A brief review on the recent developments in copper smelting and converting is presented. The analysis showed that, copper smelting capacity increased by a factor of 10 since 60's, smelting rate increased by a factor of more than 5 and process fuel equivalent decreased by a factor of 2. A thermodynamic model for prediction of impurities capacities in slags and their distribution in mattes and slags was developed. The impurities capacities (i.e. sulfur and arsenic) of slags were calculated a priori with no adjustable parameters using the Reddy-Blander model. The capacities predictions were made in a wide range of matte and slag compositions, Pso, and temperatures in conditions pertaining to copper and lead industrial slags. The calculated results for sulfide and arsenate capacities are in good agreement with the available experimental and industrial copper and lead industrial slags data. The sulfide and arsenate capacities in copper slags (fayalite, ferrite and olivine) and lead slags are reviewed. The application of RB model predicted ratios of 02 and S2 partial pressures in industrial copper smelting processes are discussed. Application of this model for the prediction of Sb, Bi and other impurity capacities and their distribution ratios in mattes or metal and slags, in industrial smelting and refining processes is discussed.

Jan 1, 2003

By S. Agatzini-Leonardou

The objective of this work was to prove repeated loading capacities and investigate the selectivity of physically stabilized algal biomass from Spirulina platensis and Chlorella sp. for the removal and recovery of cobalt, nickel and chromium from laterite heap leach liquors. The testwork was carried out on a bench scale in small glass columns and proved that it was possible to immobilize the biomass on the highly porous surface of pumice stone (kissiris). Nickel and cobalt could be removed from pure aqueous solutions of each metal by the immobilized cyanobacterial biomass. Nickel and also cobalt biosorption was sensitive to the initial solution pH. Cobalt recoveries up to 80% were achieved after 5 loading cycles, from low concentration solutions, at pH 6.0. Nickel removal was complete under the same conditions, whereas chromium sorption was ineffective. Desorption of the metal loaded columns was effected by dilute sulfuric acid. The algal species giving the best adsorption capacities for the metals under consideration was selected for further experimental work with real laterite heap leach solution produced by column leaching. A statistical analysis of all obtained results was conducted using the fraction of metal removed as response. The ratio "mass of metal removed to mass of protein contained in the immobilized cells" was determined as well. The described method might be applicable for recovery of cobalt and nickel from diluted laterite heap leach solutions, such as heap wash waters, or for their removal from waste streams of a hydrometallurgical extraction process.

Jan 1, 1997

By Miroslav Raudensky, Kallol Bera, Jaroslav Horsky, Jee G. Chang, Ampere A. Tseng

"A combined experimental and finite element approach to study the local heat transfer coefficient is presented in this paper. The heat transfer coefficients at different cooling regimes in a roll are quantified by an inverse heat conduction technique; the heat transfer phenomena involved are then discussed. A discussion of the application of the heat transfer information found in the present study for better design of a roll cooling system is also included. Finally, an identification of areas where further work is needed is presented.IntroductionIn metal rolling processes, the roll is used as a tool to deform the workpiece at very high speeds. As shown in Fig. 1, the heat transfer phenomena involved in the process are complicated by the interaction between the roll and the strip, mainly including 1) the heat transferred from the workpiece to rolls in the contact regions, 2) the heat created in the interface due to the deformation of the workpiece and the friction between the workpiece and roll, and 3) the heat removed by watercooling as well as the ambient air. All of these transport phenomena occur at extremely high pressure, high speed, and high heat flux; these make the control of the roll temperatures an extremely challenging problem.In hot rolling, proper cooling of rolls can lead not only to improve the roll shape quality by controlling the thermal crown of the roll, but also to extend the roll life by minimizing the thermally induced stresses [1,2]. Also, knowledge of roll temperatures can contribute to insights about the roll/workpiece interfacellubricant behavior, and lead to the desired surface condition of the workpiece. Therefore, adequate roll cooling or control of roll temperatures is of critical concern to mill designers and process engineers. In order to have proper operation of the process, a good understanding of the influence of cooling practices on the roll is essential [3]."

Jan 1, 1994

By Alan M. Russell

In recent years, several rare earth intermetallic compounds with the B2-type structure have been reported to exhibit high tensile ductility and high KIC fracture toughness at room temperature. These materials retain considerable ductility even at 77K. These are noteworthy findings because most intermetallics possess poor room temperature ductility and low fracture toughness unless one or more special contrivances are applied (e.g., doping with small additions of interstitial elements, offstoichiometric compositions, testing in ultra-dry atmospheres, etc.). This paper summarizes recent findings on rare earth B2 intermetallics. These include the determination of the active slip systems; the strain rate sensitivities; yield strength maxima at elevated temperatures; the search for possible twinning and stress-induced phase transformations; ab initio calculations of their defect energies and the anisotropy of dislocation line tension. Potential applications of these materials and the possibilities that this study may suggest strategies for increasing ductility in other intermetallic compounds are discussed.

Jan 1, 2008

By K. Osseo-Asare

The molecular structural and solution chemical characteristics that underlie the surface activity of solvent extraction reagents are highlighted, with particular emphasis on the tendency towards reverse micelle and microemulsion formation. The physicochemical factors that lead to microemulsion-enhanced solvent extraction with chelating extractants are elucidated Membrane-based contactor systems are described which are uniquely suited for enhanced solvent extraction with microemulsions. The possibility of combining solvent extraction with microemulsion-mediated materials synthesis is discussed.

Jan 1, 1996

By Florian Kongoli

New operating conditions and process parameters are often necessary in today's industrial practice of non-ferrous smelting and converting in order to accommodate various new chemical compositions of mineral charges and environmental requirements or to conceive new and more efficient industrial technologies. An important parameter in non-ferrous smelting and converting is the liquidus surface of multicomponent slags. This surface is affected by multiple factors such as temperature, gaseous potentials, the content of each component in the slag, etc., and cannot be quantified by the existing ternary liquidus diagrams. In this work a new type of representation of the liquidus surface of multi component systems has been presented by means of a thermodynamic model. This representation waives the need of the multidimensional representation of multi component systems and yields practical two-dimensional diagrams, which can be easily used in the industrial practice.

Jan 1, 2000

By M. Kawakami

In relation to the designing of a new-type blast furnace, the reaction of carbonaceous materials with CO2 is expected to occur at as low temperature as possible. In order to get a highly reaetive carbonaceous material at low temperature, the reaction kinetics was investigated by measuring such quantities as the reaction rate from weight loss, the amount of CO adsorption and specific surface area by BET method. The reaction rates were large in the order of the Bintyo char, metallurgical coke, graphite and glassy carbon. If the rate was converted to the rate per unit area, however, those of the Bintyo char was smaller than that of graphite. Thus, it is suggested that the rate of the Bintyo char is influenced by the pore diffusion of CO2. The rate had a positive relation with the amount of CO adsorption, showing that the rate determining step would be the desorption of CO from the active side on the surface. The rate independent of surface area was derived, combining all the obtained data.

Jan 1, 2003

By Chang Wei, Zhigan Deng, Minting Li, Cunxiong Li, Xingbin Li

A direct hydrometallurgical process of extraction molybdenum and nickel from molybdenum-nickel ore by pressure water leaching without reagent was studied. The extraction of Mo and Ni from molybdenum-nickel ore by oxygen pressure leaching, which exploit the characteristic of molybdenum-nickel minerals contain high concentration amorphous sulfide which has highly active, and make the most of easily oxide to sulfuric acid and sulfate at low temperature and excess oxygen presence of the amorphous sulfide. Under oxygen pressure conditions, considerable molybdenum and almost all the nickel were extracted into solution in the leaching process. The results show that with the leaching time for 3~4h, temperature at 150o C, liquid-to-solid ratio of 2mL/g, mineral granularity of 0.074mm, oxygen partial pressure of 0.4~0.5MPa without other reagent, molybdenum leaching percentage can be over 80% and nickel leaching percentage can be more than 97%. Furthermore, about 80% sulfur in the Mo-Ni ore has been transformed into sulfuric acid.

Jan 1, 2014

By E. vanHuyssteen

A method of establishing the relationship between the mineralogy of a sinter and its subsequent processing behaviour in a lead blast furnace is demonstrated. It involves: 1) analyzing the Zn-spinels, hardystonite, larsenite, Pb-silicates, Pb-arsenates, Pb-(Ca)-sulphates and other femtes with an electron microprobe; 2) determining the extent of elemental substitutions in various mineral structures; 3) establishing a sequence in which the various phases formed during sintering. In this manner the relationship between the bulk chemistry of a sinter formulation and the speciation of elements into various phases in the sinter can be established. Specifically, the-substitution of Mg for Zn in hardystonite significantly influences sinter production. Mg substitution releases Zn into the surrounding matrix. This Zn reacts with the Pb-silicate to form larsenite thereby reducing the amount of Pb-silicate available for anhydrite digestion. Excessive amounts of residual anhydrite thus result if the sinter formulation is based solely on the CaO/Si& ratio.

Jan 1, 1993

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 Shunhong Huang

Thirty-five soils were sampled from three sites at different distances from chromium slag heap of a Iron-alloy factory, namely, nine from site A located under the chromium slag and eighteen from Site B in the vicinity of the factory and eight from site C far from the factory. The contents of total Cr in these soils from site A, B and C were 1666.0±1310.9 mg? kg - 1,1136.2±1844.6 mg? kg - 1 ,300.4 ±165.1 mg? kg ? 1, respectively. The contents of water soluble Cr were 59.3±77.57 mg? kg ? 1,0.6 ±0.3 mg? kg - 1 ,0.5±0.3 mg? kg - 1 , respectively. In order to evaluate soil health, the activities of four soil enzymes (catalase, polyphenol oxidase, dehydrogenase, alkaline phosphatases) were analyzed. The results have shown that dehydrogenase activity was greatly depressed by conditions in the heavy chromium-contaminated sites. Negative correlation was observed between dehydrogenase activity and the distance from the chromium slag heap, however, the activities of catalase, polyphenol oxidase, alkaline phosphatases in soils from the three sampling sites mentioned above did not differ significantly. The result imply that of dehydrogenase activity could be used as an indicator for the chromium pollution level in the area of Iron-Alloy factory and for the stability level of the soil ecosystem.

Jan 1, 2008

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

The basics of microwave drying process of CuCl residue were studied by comparing the dielectric property of the residue with different moisture contents. The dielectric properties were measured by microwave cavity perturbation method. The dielectric constant and dielectric loss factor of the CuCl residue have a linear correlation with the moisture content. With this relationship, we can realize on-line measurement of moisture content of the CuCl residue by dielectric properties. The microwave drying experiments with different thicknesses (1-5cm) of CuCl residue were carried out, and the heating curve of the materials under different microwave powers (250-450W) was made. From these parameters, an optimized operation parameter of microwave roasting technology, the thickness of CuCl residue filter cake to be microwave roasted should be 2cm , was deduced.

Jan 1, 2015

By Kafui Nyavor

The indirect, and the direct contact mechanisms of bacteria oxidation of sulfides were studied using Thiobacillus ferrooxidans and pyrite. The aim was to determine which of the two generally aeeepted mechanisms played a dominant role, if any, during acid mine drainage (AMD) formation from the oxidation of sulfide minerals. The results show that at a pH of 4.5 where T. ferrooxidans are quite active, but where initial chemical oxidation of pyrite to Fe2+ is limited, the bacteria were unable to directly oxidize pyrite to any significant extent. Whereas, in the presence of Fe2+, T. ferrooxidallS assisted oxidation of pyrite by the indirect mechanism was observed and sustained over the pH and Eb range where the bacteria is active. The results lead to the conclusion that the direct contactmechanism of pyrite oxidition by T. ferrooxidans is insignificant. The predominant, and possibly the only, pathway involves the indirect bacteria oxidation of available Fe2+ to Fe3+, which in turn oxidizes FeS2 to generate additional Fe2+ and acidity in a cyclic process.

Jan 1, 1996

By Zemin Ma

A novel chromate [Cr(VI)] reducing bacterium was isolated from chromite ore processing residue disposal site of China and identified as a Leucobacter sp. by 16S rRNA gene sequence homology. The minimum inhibitory concentration of strain CRB1 was 820 mg l-1 of Cr(VI). The reduction of Cr(VI) occurred only under aerobic conditions. With an initial concentration of 2.5×108 cells ml-1, 1800 mg l-1 of Cr(VI) was reduced entirely within 38 h under the optimum conditions, at 30 °C and pH 9.0. Increasing Cr(VI) concentrations prolonged reduction process and higher cell densities meant quicker reduction. A blue precipitate was produced during chromate reduction of strain CRB1, which was binding to the surface of bacterial cells and determined as trivalent chromium with electron paramagnetic resonance (EPR) spectrometry. The conspicuous chromate reduction ability of Leucobacter sp. CRB1 suggested a potential for bioremediation of Cr(VI) containing wastes.

Jan 1, 2008

By Christina Viklund-White

Life Cycle Assessment has been used to compare the environmental performance of landfilling versus recycling of the zinc used for galvanizing steel. Hypothetical process routes were com-posed involving four different EAF dust treatment processes; Waelz kiln, DC-furnace, EZINEX and slag fuming, as well as scrap dezincing. The study shows that recycling of zinc used for galvanizing steel has environmental benefits in that it saves zinc resources. However, zinc recovery does not necessarily decrease the potential impact on global warming and acidification. The magnitude of these two impact categories is tightly correlated with the amount and type of primary energy consumed in a process. Due to the high electricity consumption in the dezincing process, this route has the highest impact on Global Warming Potential as well as Acidification Potential. The major part of the energy requirement for the production of zinc from primary and secondary sources is consumed in the reduction of ZnO to Zn. The consequence is that the theoretically possible savings in primary energy by recycling zinc-containing materials are relatively minor. The impact categories "land use" and "waste generation" are not considered in this study, but most likely the evaluation of such impacts would further increase the potential environmental impact of the landfill alternative. The results also show that the location of an electricity-intensive process highly affects the potential environmental impact. Comparing process and material alternatives in LCA studies where branch average data is used, is considerably more complex than when LCA is used within a company.

Jan 1, 2000

By Peter Sylvén, Darwin Morales

Despite being crucial for the smelting process, furnace tapping using oxygen lances has not been considered an operation that brings value. Therefore, these important tools have not seen a significant change in over 100 years. Problems related to the use of oxygen lances include: • Inaccurate tool: causing damages shortening the life of the taphole refractories. • Safety: extended exposure to the operator in an unsafe area of the furnace. • Cost: high oxygen consumption & high lance consumption. • Time consuming and frustrating to connect one lance to another. This paper will suggest a very good solution; new concept thermal lances. We will show how these provide an outstanding performance for a more efficient, faster and cost-effective furnace tapping operation. These new lances are very accurate tools that enable the operator to perform a more controlled operation; resulting in longer taphole life, fewer repairs and less down-time.

Jan 1, 2016

By L. Klinger, T. Werber, LA Levin, A Katsman

"The process of catastrophic carburization known as ""metal dusting"", whereby a solid metallic material is converted into fine particles in a carburizing atmosphere, was analyzed. It was shown that this conversion is the result of plastic deformation and subsequent fracture accompanying diffusional phase formation in the near-surface layer. The process is controlled by internal stresses arising during phase transformation. Competition between stress generation and relaxation may result in the attaining the ultimate strength in the near-surface layer and its fracture. Such a mechanism of metal disintegration may occur in a certain temperature interval depending on the kinetic and geometrical parameters of the system - the diffusivities of the alloy's components, the ratio between specific volumes of the new and the old phases, and the ultimate plastic strain. The temperature interval for disintegration of carbon steel, the rate of disintegration, and the period of the disintegration cycle, were evaluated and compared with experimental data. IntroductionCatastrophic carburization, known as ""metal dusting"", consists in conversion of a solid metallic material into fine particles. The process occurs in a carburizing atmosphere at elevated temperatures. The corrosion product, usually named ""coke"", consists of metallic particles dispersed in a loose carbon matrix. Under industrial conditions metal dusting takes place, for example, in a gas mixture of CO and H2 or in hydrocarbon environments. Steels, nickel- and cobalt alloys are susceptible to this kind of wastage in the temperature range 400-800°.A mechanism of metal dusting in steels was proposed by Hochman [1] and later developed by Grabke and coworkers [2-5]. According to the proposed model, the process consists of the following reaction steps:"

Jan 1, 1996