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By R. E. Molnar

A number of flowsheets have been designed and operated, or are currently being considered, to extract copper from leach solutions having much more copper than the 4 g/L levels typically found in heap leach liquors. Dealing with these solutions has required that the envelope for ?normal? copper solvent extraction be pushed beyond the usually considered limits. Others have published information on flowsheets to recover copper from leach liquors containing over 25 g/L copper. Secondary solvent extraction circuits are often required to attain satisfactory overall recoveries. This paper reviews some of the issues faced in three pilot plant circuits that were operated by SGS Lakefield Research to produce cathode copper from solutions containing 8 to 20 g/L Cu. The primary objective was to maximize copper extraction using one solvent extraction circuit. The role of feed acidity and the disposition of impurities such as iron and chloride are considered. The challenges of running short SX piloting campaigns are discussed.

Jan 1, 2003

By Eliezer Martinez-Jimenez, Gretchen T. Lapidus

"Electro-assisted reduction is an effective pretreatment to render chalcopyrite less refractory towards oxidative leaching. In this process, chalcopyrite is selectively converted to chalcocite or copper metal in an electrolytic cell under ambient conditions, while ferrous ion is leached into solution. However, the reaction velocity is hampered by the formation of a ferrous sulfide passivating layer on the solid surface, especially at elevated solid to liquid ratios. In the present work, several strategies for overcoming this problem were evaluated. On one hand, specific ligands for ferrous ion were added in order to increase its solubility and, on the other, an anode material which promotes the oxidation of the sulfide ion was chosen. Leaching tests showed citric acid to be an effective ligand for both ferrous and ferric ions and, in combination with a lead-silver anode, significantly increased the kinetics of chalcopyrite reduction and subsequent copper leaching.IntroductionAttempts to oxidize chalcopyrite at a rapid rate in aqueous solutions, below their normal boiling point, have met with difficulties because of passivation by some of its own components. An alternative line of research explores reductive pretreatment, transforming the chalcopyrite into less refractory copper phases, which can later be oxidized. A recompilation of these efforts up until 2000 was published by Dreisinger and Abed [1]. However, this practice usually requires large excesses of reducing agents, such as copper, lead, aluminum or iron, and in this last case at near-boiling temperatures, in highly"

Jan 1, 2012

By Shigehito Isobe

The Li-N-H system composed of LiH and LiNH2 catalyzed by titanium compound desorbs ~6 mass% hydrogen and a quite small amount of ammonia in temperature range from 150 to 250 °C under He flow atmosphere. In this work, hydrogen desorption (H-desorption) mechanism in the reaction from LiH+LiNH2 to Li2NH+H2 in a non-equilibrium condition was clarified by TDMS, TG and FT-IR analyses for the products replaced by LiD or LiND2 for LiH or LiNH2,respectively. The results suggested that H-desorption reaction progresses through two-step elementary reactions mediated by ammonia. As a next step, we carefully determined the amount of the ammonia containing in desorbed hydrogen for the Li-N-H system in a closed system from the practical point of view. The results indicated that a quite small of ammonia thermodynamically coexisted in the desorbed hydrogen in closed system, although ammonia could not be almost detected in emitted hydrogen gas by TDMS under some non-equilibrium conditions. Moreover, for understanding the role of titanium, the chemical bonding state of the titanium compounds doped as catalyst in the mixture was examined by XAFS measurement. The results indicate that the Ti atoms, which can induce catalytic effect, are in a particular chemical bonding state.

Jan 1, 2006

By Garry W. Warren

The brass foundry industry produces a significant amount of waste sand containing Cu, Zn and Pb which is often classified as a hazardous waste due to Pb content. The potential application of a hydrometallurgical process to treat the sand by extracting metal values and thus detoxifying the material has been investigated. The process involves leaching of metal values followed by cementation. The emphasis of this investigation was on the leaching step, although some preliminary cementation experiments have been performed. In order for any alternative treatment scheme to be successful, the smaller size fractions of the sand must be addressed. Experiments have been performed on five individual size fractions using various lixiviants HCI, acetic acid and HCI/NaCI. Cu extraction was found to be slower than either Zn or Pb. Results obtained in this investigation indicate that copper is present in two forms, an oxide form which dissolves rapidly and is insensitive to the level of oxygen, and a less soluble form, probably metallic which dissolves more slowly and requires an oxidizing agent. The presence or absence of oxygen had no influence on the rate of Zn dissolution indicating that zinc is present mostly in oxide form. Toxicity Characteristic Leaching Procedure (TCLP) tests showed that residues could be produced which meet the toxicity limit for lead. Preliminary cementation experiments have also demonstrated the feasibility of Cu and Pb recovery.

Jan 1, 1991

By John C. Carpenter

Solvent extraction is used to selectively recover copper from iron containing sulphate solutions. As chloride ions, which form series of complexes with transition metals, are now being used for leaching. Little is known of the effects of these ions, on solvent extraction behavior. It has been shown that commercial extractants of the L1X and Kelex series extract copper from chloride media: (1) at a lower pH than from sulphate solutions, (2) to similar loadings, and (3) except for L1X 63, without transferring chloride to the organic phase. A process for selective extraction of copper from chloride solutions should thus be compatible with standard stripping and electrowinning practice. Of several diluents, differing in aromaticity, kerosene gave enhanced extraction only with L1X reagents. A change in operating temperature had little effect on equilibrium metal distribution. All the extractants examined gave adequate separation of copper from iron. L1X 63 was found to extract chloro-complexes of copper and of iron and thus transfer chloride to the organic solution. Consequently this extractant and its mixtures are not preferred for use with chloride leaching systems.

Jan 1, 1976

By Anurag Tripathi, J. K. Saha, S. K. Ajmani, J. B. Singh

"The quality of steel is a major concern in the metallurgical industry. The control of liquid steel temperature can enhance the level of cleanliness in steel. Ladle is one of the major vessels used to transfer liquid steel between different stations. The heat transfer phenomenon taking place in this vessel needs to be monitored for controlling the liquid steel temperature. A CFD model was developed for prediction of liquid steel temperature during complete process cycle of ladles in direct heats. The model was validated with liquid steel temperature measured at on-line purging station and tundish during teeming from one of the actual steel plant. The accuracy of model was 96 %. The results obtained show insignificant effect of slag thickness, tapping temperature and ladle life on liquid steel temperature in the ladle. However, the importance of initial refractory temperature was noticed. The CFD model developed in present work can generate the thermal history of liquid steel and refractory walls of any ladle at any stage.1. IntroductionThe control of liquid steel temperature is desired to achieve required steel quality. The low casting temperature is detrimental and may result in nozzle blockages due to premature solidification in the tundish. The phenomenon of heat losses taking place in ladles needs to be understood for prediction of liquid steel temperature. The assessment of thermal profile of liquid steel from BOF converter to caster can be done through consideration of heat losses at all points. Hlinka and Miller [1] showed that the ladle pouring temperature varies due to heat losses from molten steel into surrounding refractory layers. The phenomenon of thermal stratification was numerically simulated by Ilegbusi and Szekeley [2]. The effects of slag cover on heat loss and liquid steel flow in ladle before and during teeming to a continuous casting tundish was numerically simulated by Chakraborty and Sahai [3]. Investigators also developed some simple models to predict the steel temperature for some of the processes taking place in ladles [4-9].The present work is an effort to generate the full information about the temperature drop taking place in any ladle throughout its process cycle. This information can be used to predict liquid steel temperature and to take decisions to minimize heat losses."

Jan 1, 2012

By R. H. Hanewald

INMETCO, a subsidiary of Inco Limited, is the only facility in North America that provides High Temperature Metals Recovery for nickel-, chromium-, and iron-bearing wastes. Since 1978, this process has prevented more than 775,000 tons of materials from becoming part of the nation's waste stream. The paper describes Inco's experience in metals recovery, traces the development and explains the operation of the High Temperature Metals Recovery Process, and examines the procedures and criteria used to determine whether spent catalysts meet process feed specifications. An overview of the current requirements for transporting spent catalysts is provided. The paper concludes with brief case histories of catalysts users employing High Temperature Recovery to manage spent catalyst.

Jan 1, 1995

By Ximena Diaz

Mercury is one of the most undesirable contaminants in gold bearing ores. During cyanidation mercury cyanide compounds accompany gold in all the extraction and recovery processes. Of course mercury in the carbon eluates creates environmental problems in subsequent refining steps. One possible process alternative for the separation of gold from mercury in such concentrated alkaline cyanide solutions is the selective solvent extraction of gold by undiluted Dibutyl Butyl Phosphonate (DBBP). In order to describe the behavior of mercury during extraction by DBBP, the results from a preliminary research program are presented. In this study, temperature and cyanide concentration have been found to be the most significant variables which influence the separation of gold from mercury by solvent extraction using DBBP. It was found, using plant eluate from a carbon strip, that excellent separation of gold from mercury can be obtained at 60' C with 98% gold recovery and complete mercury rejection in a single stage of extraction. The influence of pH is also discussed in terms of the extraction chemistry. These results complement previous research which described the DBBP solvation extraction of an aurocyanide ion pair. In addition, these results extend our understanding of the alkyl phosphorous ester extraction systems by illustrating that neutral ionic species such as Hg(cN)02sq, can be extracted at low cyanide concentrations, a phenomenon which had not been observed previously for other cyanoanions.

Jan 1, 1993

By Asmo Vartiainen

The viscosity of liquid Fe-O-SiO2 -slag at copper smelting conditions was investigated using a rotational viscometer. The studied parameters were oxygen partial pressure (10" °-10"6 bar ); composition of slag (Fe/SiO2 ratio), and temperature (1250-1400°C). The viscosity values are presented as a function of Fe/SiO2 ratio and as isoviscosity curves in ternary FeO-Fe2O3-SiO2 diagrams. The increase in viscosity at high silica contents can be accounted for the polymerisation effect of SiO4/4- -anions. At high ferric iron contents, higher oxygen partial pressure, the viscosity values increase especially near the magnetite saturation. The viscosity values are highest at the double saturation of silica and magnetite. At lower silica and ferric iron contents the viscosity values are more uniform in the homogenous liquid slag area. The viscosity values were lowest at high temperatures and highest at low temperatures.

Jan 1, 1998

By Karl A. Gschneidner

Magnetic refrigeration was first used in the mid-1920's and new developments seem to have taken place about every 20 years, and this is especially true for the mid-1990's. The active magnetic regenerator magnetic refrigerator has the promise to become the first practical machine utilizing the magnetocaloric effect for cooling (and also heating). The basic principles are briefly discussed. Since the temperature lift for the magnetocaloric effect spans about 50 K, one will need to utilize several ferromagnets with different magnetic ordering temperatures in order to reach temperatures below ~250 K. The basic properties, behaviors, limitations, and new phenomena and knowledge are discussed.

Jan 1, 1997

By I. U. Onyenanu, C. E. Ilochonwu, E. I. Nwonye, C. O. Nwajagu

This work shows how pure silica was derived directly from rice husks ash (RHA) in different temperatures for reduction to Silicon (Si). The processes to form Si materials are usually complex, costly and energy-intensive. The silica in the ash undergoes structural transformations depending on the conditions of combustion. A high purity silica was produced at 650oC after burning the rice husk (RH) for up to 7 hours. The purity of the silica was determined by dissolving the RHA with alkali solution to form sodium silicate solution of pH 11.0. This was added to hydrochloric acid of pH 1.5 which lowered the pH of the solution to 4.0 to form silica gels. The silica gels produced were washed and dried to powder and then characterized using XRD and EDX techniques. This study was done to reduce energy waste and environmental pollution in Nigeria as silica is used to develop many materials.

Jan 1, 2015

By Donald L. Stewart, Ken Overfield, Edward M. Williams

"Recent increases in energy cost have lead to a renewed focus on energy efficiency during aluminum melting operations to reduce fuel usage. The goals of a batch melting operation are to melt the charge using the minimum required energy, to melt the metal to the required temperature within the required timeframe, and to avoid generating unwanted contaminants by overheating the charge.The heat transfer efficiency of a conventional hydrocarbon fired aluminum melting furnace varies over the course of the melt cycle, depending on the conditions in the furnace. The purpose of this work was to develop a method of determining the transient heat transfer efficiency throughout the furnace cycle and to take advantage of this knowledge to optimize the melting process through furnace controls and proper production operations. This furnace survey methodology has been developed and used to evaluate a number of furnaces.Description of a Typical Batch Melting Furnace CycleA typical batch melting furnace cycle will consist of three stages:1. Charging – Solid metal charged through an open roof, solid or molten charged through an open door, and/or molten poured through a furnace blister2. Melting – From the time the door or roof is closed and the burners are turned to high fire until the charge is all liquid and has reached a temperature suitable for alloying (typically ~1350 °F / 730 °C)3. Holding – From the end of the melting stage until transfer or casting is completeIn some cases, further charging can take place after the melting cycle has started. This can happen when the entire solid charge will not fit in the furnace in one load, or if additional molten metal is added while the charge is melting. The bulk of the energy used in the melter is consumed during the melting cycle. The thermodynamic minimum energy requirements for melting pure aluminum are:• Energy required to heat pure aluminum from room temperature to the melting point at 1220°F (660°C) is 288 BTU/lb (670 kJ/kg)• Energy required to change state of pure aluminum from solid to liquid (heat of fusion) is 171 BTU/lb (397 kJ/kg)• Energy required to heat molten from melting point at 1220°F (660°C) to 1350°F (730°C) is 36 BTU/lb (83 kJ/kg)• Total energy required to melt a solid charge from room temperature to 1350°F (730°C ) is 495 BTU/lb (1151 kJ/kg)"

Jan 1, 2009

By C. Geenen

At its Olen site, Union Minière Copper operates a new full-size deposit tank house. A first 200,000 t/y module was commissioned in October 1996, and an additional 130,000 t/y unit started in April 1998. The main objectives of the new tank house project were to produce grade A cathodes starting from anodes with a wide range of compositions and at a minimal operating cost. The tank house uses Isa Process technology. Based on the process parameters agreed upon with MIM, UM Copper developed the basic design and UM Engineering was the in-house contractor for the engineering. The new tank house is equipped with advanced technology polymer concrete cells, automated two-bale cranes and high-capacity machines. The first 200,000 t/y module treats anodes with a more conventional composition at 330 A/m2; the second 130,000 t/y module treats anodes with a high slimes fall (12- 13 kg/t) at current densities up to 285 A/m2. After some teething problems, the new tank house is meeting all set targets. This paper illustrates and comments on the design characteristics and operational results.

Jan 1, 1999

By Mike Adams

A comprehensive pre-feasibility study has been conducted by Companhia Vale do Rio Doce CVRD) for Niquel do Vermelho nickel laterite deposit. Within this study, five integrated flowsheet options were evaluated via batch and pilot campaigns at Lakefield Oretest, over an intensive six-month period from receipt of ore to final reporting. Key technical objectives set by the client included demonstrating the technical viability of the beneficiation of several ore types, processing through integrated pressure acid leach/mixed hydroxide precipitation (PALIMI-IP) and mixed sulfide precipitation (PALIMSP) circuits, and the treatment of barren liquors to meet stringent environmental requirements. Refining of the MHP was by ammonia re-leach and solvent extraction (SX) to produce LME-grade nickel cathodes, NiCO3, NiO and CoS. LME grade nickel and cobalt was also produced by oxidation of the MSP and hydrogen reduction on the leachate. The database and data acquisition system, along with web-based reporting, enabled rapid turnaround on both daily and more comprehensive run reports, making it possible for speedy and confident decisions on operating conditions of the complex flowsheets. The high value of developing such data is emphasized and discussed as pivotal in the successful progression of laterite projects through to sustainable commercial viability. Keywords: Flowsheet, CVRD, Nickel, Piloting, Pressure, Leach, Refining.

Jan 1, 2004

By Sergio Demetrio

Based on the current reality of the copper smelters industry, besides the advances that have been and are expected for the next few years, the authors present a futurist vision of the processing of copper concentrates and copper smelters in the years 2000. Outlined new development strategies and ways of improvement in this business, including research, development and management of the works that today posses characteristics of a profitable operation, as well as the changes expected with respect to the entry of new actors and the creation of new products The authors finally bet for small or tailor-made smelters with ad hoc technology for their raw materials and few units to coordinate -devoted to specific concentrates using high technology and low manpower. Considering the in-situ hydrometallurgical route, as well as the pyrometallurgical route in works or conversion facilities that buy or process white metal and produce copper and other metals associated with this such as gold and silver, besides sulfuric acid, plants which should be strategically located in zones with high sulfuric acid price to make this a product which contributes to the profitability of the business.

Jan 1, 1999

By J. W. Dini

Introduction The mission of the Materials Fabrication Division (MFD) is to provide fabrication services and technology in support of all programs at Lawrence Livermore National Laboratory (LLNL). MFD involvement is called for when fabrication activity requires levels of expertise, technology, equipment, process development, hazardous processes, security, or scheduling that is typically not commercially available. Customers are encouraged to utilize private industry for fabrication activity requiring routine processing or for production applications. MFD is .a large diversified service organization including approximately 400 full time employees. The group provides a wide variety of processes including all common machining and fabrications operations, laser and water jet cutting, electrical discharge machining, lapping, electron beam and laser welding, vacuum brazing, heat treating, forming, electroplating and metal finishing, optical polishing and grinding, vacuum coating, vacuum engineering and a variety of plastics operations. These operations occupy more than 1,250,000 square feet of floor space. For more detail on the many fabrication related services available from MFD, see Reference 1.

Jan 1, 1992

By U. M. Mutnti

In order to meet the stringent market requirements for high purity cobalt, ZCCM commissioned the VIR plant in December 1982. The plant comprises a 4.1 tonne/heat vacuum induction furnace with a rated annual capacity of 2,500 MT of barstock. In the VIR furnace, molten cobalt is held under vacuum at 1600°C resulting in the removal of more volatile impurity elements by distillation. Operations todate have demonstrated that Pb, Zn and Cd have good distillation rates in excess of 95%, leading to cobalt containing 1 ppm or less of the above elements. Removal of other impurities such as Se, Bi is about 65% with the finished product still assaying around 1 ppm of each of these elements. Vacuum refining of cobalt offers an economic route for producing higher grades of cobalt from the type of concentrates and treatment processes available within ZCCM. The consistency of VIR cobalt quality has been confirmed by ZCCM and some of its alloy customers.

Jan 1, 1988

By M. Misra

The bacterium?Mvcobacterium Phlei has a demonstrated potential to be used for the flocculation of a variety of finely divided minerals. The microorganism possesses both hydrophobic surface and high negatively electrostatic charge. It can adhere to many mineral surfaces ?if the charge and hydrophobic interaction? between the microorganism and the minerals are favorable to adhesion. Experimental results showed that the dolomitic phosphate slime from Florida and fine hematite can be :readily flocculated from dilute suspension.. In the case of dolomitic phosphate slime, a consolidated sediment containing 24'-25 weight% :solids can be obtained from .a dilute slurry .in a short time. Sediments obtained from hematite flocculation are rather massive and more .consolidated than phosphate slime. Mycobacterium Phlei has a specificity for selective flocculation of hydrophobic fine coal particles from pyrite and ash containing minerals. Because of mutual hydrophobic interaction of coal and Mycobacterium Phlei, it was noticed that coal particles appear to be strongly held in the aggregate by adhesion or bridging of bacteria. However, Mycobacterium Phlei is not a good flocculant for either associated pyrite or ash present in coal.

Jan 1, 1991

By Ozgul Dere Ozdemir, Muge Sari Yilmaz, Sabriye Piskin, Deren Sibel Kasap

"Galvanic sludge is generated at the end of the waste water treatment process of metal plating system. The waste sludge is one of the main hazardous solid wastes produced by metallurgical industries. It is caused the harm of human health and damage of the environment due to containing reasonable amounts of toxic metals (e.g., nickel, zinc, copper, chromium, iron, lead, cadmium, etc). The concentration of those toxic metals in the wastewater might reach 30% (w/w, dry weight) making their removal and recovery an interesting issue.In this study, synthesized titanium dioxide is used as adsorbent to remove nickel in leachate of galvanic sludge. The adsorption experiments were carried out isothermally at four different temperatures. The effects of pH, temperature, and contact time on nickel adsorption efficiency were investigated, and the optimum parameters were determined from the experimental studies. The experimental results indicated that pH, temperature, and contact time played a significant role on the adsorption capacity of nickel.IntroductionRapid industrialization has caused increasing the heavy metal concentration in biosphere with the industrial wastes. These wastes are generated in various industrial processes such as electroplating. Galvanic sludge is a hazardous waste that generates from metal plating industry by chemical precipitation of heavy metals from acidic or alkaline solutions during the waste water treatment process. Heavy metals are tend to bioaccumulate thus they are treated the living organism [1-2].Galvanic sludge is mainly disposed on landfills for these reason it is a big problem for environment. Galvanic sludge containing nickel (II) is common because nickel (II) is used in electroplating process [3]. In drinking water, nickel may cause health problems if found in amounts greater than the health standard set (MCLG: 0.1 mg/L) by the United States Environmental Protection Agency (EPA). The higher concentration of nickel (II) in ingested water may cause severe damage to lungs, kidneys, gastrointestinal distress, e.g., nausea, vomiting, diarrhea, pulmonary fibrosis, renal edema, and skin dermatitis [ 4]. For these reasons, it must be treated before disposed to landfill."

Jan 1, 2011

By Ju Shao-hua

Although nowadays gold extraction methods are very abundant, none of them is satisfying, especially, in the field of heap leaching of low grade gold ore. The traditional heap leaching method of cyanide method plays an inglorious role of badly environmental pollution. In this paper, a bran-new and innoxious method of gold extraction system, metal-ammonium-chloride-ammonia (MACA), was proposed, and also analyzed both thermodynamically and practically. Thermodynamically, according to the principles of simultaneous chemical equilibrium and electronic charge neutrality, the thermodynamics of Au-NH4Cl-NH3-H2O system was studied by using the exponential computation method and through MATLAB programming, and the solid figure of its potential - c(NH4Cl) - c(NH4OH) was drawn. The results showed when the concentrate of ammonia is higher than 0.6 mol?L-1, fAu+/Au is only about -0.2 v. Practically, the leaching results of a cuprous gold ore showed that the extraction of gold can reach to 80% in this system. The preliminary results of reduction of the rich solution with copper and zinc powders showed that with deoxygenizing, the reduction effects were relatively good. These new findings and results have established a theoretical and practical base for developing a new process for heap leaching of low grade gold ores in this system. And the new process owns a series of merits such as, non-cyanogens, nontoxic, broader applicability.

Jan 1, 2006