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By Theo Lehner

The Rönnskär smelter has wide experience in the field of recycling of non-ferrous metals. Today, smelting and refining from primary and secondary raw materials are integrated in a complex flow sheet. Boliden operates a lead flash smelter, a lead refinery, a copper smelter and refinery, a sulphuric acid and sulphur dioxide plant, a slag fuming plant and precious metal plant at its Rönnskär smelter in the North of Sweden. The Business Area Smelter Operations also incorporates Boliden Bergsöe, Sweden's lead-acid battery recycler, and Norzink, Norway, where recycled zinc accounts for more than 20% of it's production. Raw materials for the Rönnskär smelter include concentrates, ashes, slags, metallic scrap, electronic scrap and electric arc furnace (EAF) steel-making dust. This paper briefly describes current operations and illustrates current measures to improve productivity. Limits to recycling as experienced by a non-ferrous smelter are, illustrated. The deportment of critical elements contained in raw materials is also discussed.

Jan 1, 1998

By J. L. Holman

The Bureau of Mines is investigating recovery of Ni, Co, Cr, and other metals from mixed contaminated supera110y scrap. The scrap is melt-refined and cast into anodes for electrodeposition of recyclable Ni-Co alloy. Melt oxidation using roasted superalloy grinding sludge as oxygen source can divert the Cr to the slag but with excessive Ni-Co loss. Melt oxidation-carburization or direct melt carburization retains -95 pct of the Ni-Co in the anode alloy. With direct carburization, -90 pct or more of the Cr and other refractory metals report to the anode alloy, largely as carbide phases insoluble in electrolysis. Electrorefining data relate parameters such as controlled cathode potential, Fe and Cr impurities, pH, and compartmented cell use, to current efficiency and Ni-Co deposit quality. Recovery of -90 pct of the Ni-Co in the scrap can be achieved. Preliminary experiments to recover Cr, W, and other metals from the anode sludge and other byproducts are discussed. 347

Jan 1, 1987

By P. Thapliyal

The petroleum refining industry generates over a million tons of spent catalyst per year, containing valuable metals. Currently, these materials are recycled to smelting furnaces, but the fundamental mechanisms controlling the recovery processes are poorly understood. Furthermore, submerged injection of finely divided materials is potentially a means to obtain high recoveries of pay metals. In this study, a catalyst containing 10% Ni and 1% Co was injected into 45 kg heats of matte. A copper matte was chosen so that the nickel and cobalt recoveries were measurable. It was found that the recovery ranged from 40 to 700Al, increasing with catalyst feed rate, decreasing with catalyst particle size and decreasing with the oxygen content of the carrier gas. A mathematical model was developed to account for the results, and to permit extrapolation to nickel mattes. The industrial implications are discussed.

Jan 1, 1996

The effect of change in slag composition upon metal losses to the slag and the relationship between slag composition and slag matte separation was investigated at 1400°C. The synthetic slags containing CaO, MgO, SiO2,, A1,0, and FeO were similar to those employed in the electric furnace smelting of sulphide Cu-Ni concentrates containing PGM (Precious Group Metals) from the Merensky Reef of South Africa. The matte with a grade of 9.3% Cu and 16.0% Ni was a typical electric furnace product. The results indicated that the Cu and Ni solubility in the slag increases with the increase of the basicity ratio and CaO and MgO contents of the slag. At constant CaO/MgO ratios the rise in basicity decreases the metal losses. When FeO and SiO2 contents of the slag are kept constant, the substitution of MgO with CaO decreases the metal losses. The relationship between slag composition and matte-slag separation was found to depend primarily on the basicity ratio and the FeO content of the slag. The net effect comes from a strong interaction of the two in such a way that increasing basicity and decreasing FeO contents deteriorate the clean separation of the two phases.

Jan 1, 1994

By Deventer Johanna van

Ore bodies around the world are declining in grade, whilst increasing in complexity. The level of impurities relative to the valuable metal is steadily increasing, posing new challenges to existing operations. Ion exchange is widely used in the hydrometallurgical industry for both primary recovery of metals and the removal of impurities. The superior selectivity of ion exchange resins makes them exceptionally suitable for the removal of target impurities to very low levels, thereby saving operating costs, increasing the value of the final product and significantly improving revenue. The ion exchange process in these applications is very simple, using standard ion exchange equipment and acid regeneration. The process can be fully automated, requiring minimal operator interference and supervision Examples of impurities that are successfully removed via ion exchange include iron, antimony and bismuth from copper electrolyte. In the copper electrolysis process, antimony, bismuth and arsenic tend to form slimes which are dispersed in the electrolyte. These slimes contaminate the cathode and/or decrease the quality of the copper deposition. A special chelating resin was developed to remove antimony and bismuth, while at the same time ensuring minimal chloride leakage to the sulphate matrix. The work is described in more detail in this paper. Ion exchange is also used to remove copper, zinc and nickel from cobalt electrolyte. This paper addresses a few of these examples in more detail.

By Mark Tsirlin

Kinetics of the initial oxidation stages of diffusive silicide coatings on 8 molybdenum and niobium at 1100 - 1700 and under the pressure of 400 and 1330 Pa has been studied using methods of gravimetry and gas phase analysis of oxygen, as well as by SEK, XRD and EDMA methods. The first oxidation stage described by asymptotic equation in case of NbSi coating changed over to the stage described by parabolic equation. The asymptotic law was shown to depend on non - stationary conditions on the oxide layer boundaries. Interconnection between silicides and quartz structures, on the one hand, and peculiarities of oxidation kinetics, on the other, is [discussed. The possibility of estimation oxygen atom jump frequency in quartz and fractions of oxygen reacting with metal and with silicon proceeding from the analysis of the kinetic data was ascertained. Conditions of oxidation kine- tics transfer from asymptotic (or parabolic) stage to a non - protective "linear" stage, associated with volatile ~roduct formation, are also discussed.

Jan 1, 1995

By Eoghan T. M Doyle

Oxide mixtures of nickel (NiO), cobalt (COO) and chromium (Cr203) were prepared with graphite in stoichiometric amounts and the powder mixtures were compacted to produce cylindrical pellets. The composition of chromium oxide in these mixtures were varied. Pressed pellets were reduced in a flowing stream of argon-4% hydrogen gas (500 ml/min). Both slow and rapid heating methods were adopted to raise the temperature of a pellet during reduction of oxides to form superalloy powder. The reduction temperature was varied between. 1523 and 1623K. The effect of heating rate and niobium oxide addition on the microstructure of the superalloy produced was studied by using ordinary light and scanning electron microscopes. New phases formed as a result of reduction were identified by X-ray powder diffraction technique. The mechanism of reduction of oxides together with the microstructure of NiCrCo alloy are discussed. The thermodynamics of formation of ternary alloy phase is elucidated on the basis of binary phase equilibria and Gibbs free energy of mixing data for the constituent alloy compositions.

Jan 1, 1992

By R. M. Cunningham

Asarco operates one of the largest individual copper electrolytic refineries in the world at Amarillo, Texas. The feed for this refinery is a mixture of anodes produced at Asarco smelters and copper purchased t?om a number of primary and secondary sources. The variation in feed makes it imperative that the refinery practices state-of-the-art quality control to minimize the effects'of unwanted impurities in the electrolytic refining process. In late 1993, a plant designed to sigru6cantly reduce the antimony and bismuth levels in the electrolyte was commissioned. The purification plant uses ion exchange technology in conjunction with a novel strippiing system developed by Zeneca Specialties (U.K.). The strippiing system permits the recycling of the eluant and thus avoids the extremely high costs of stripping with conventional reagents. In addition, the environmental impact of treating the eluant for recovery of antimony and bismuth is minimized. This paper outlines the development of the technology and, in particular, describes the operational practices and improvements at Amarillo since the commissioning of the plant.

Jan 1, 1997

By J. E. Clemson

The Black Pine sediment-hosted, disseminated gold deposit is located in Cassia County, Idaho. Gold mineralization occurs in flat-lying zones 50 to 100 feet thick. Total geological ore reserves are 5.6 million tons grading 0.049 oz/t. Ore types include: non-carbonaceous, oxidized ore; carbonaceous, sulfide ore; and carbonaceous, partly oxidized ore. In the oxidized ores, native gold grains commonly occur in porous hematite pseudomorphs that have replaced disseminated framboidal and euhedral pyrite, and this gold should be readily leached by cyanide solutions. Approximately 4 % of the native gold observed in the oxidized ores is locked within gangue and may be refractory to cyanide solutions. Native gold has not been observed in the unoxidized samples, all of which are characterized by primary sulfides. It is suspected that the bulk of the gold mineralization in the sulfide ore occurs as submicroscopic particles within pyrite and will be refractory to cyanidation. It is believed that much or all of the gold observed in the oxidized samples was originally in pyrite but was released and re-precipitated during oxidation. The degree of oxidation of the pyrite and the presence/absence of preg-robbing carbonaceous material is used as a guide in delimiting zones of mineralization amenable to heap leaching.

Jan 1, 1988

By C. E. Abbey

Cobalt, iron and manganese play various roles in copper electrowinning using lead–calcium–tin alloyed anodes. Cobalt catalyzes electrochemical water decomposition resulting in lower anode potential and reduced corrosion rates. Iron reduces cathodic current efficiency, but is used to reduce higher oxidation states of manganese that oxidize organics in solvent extraction. Manganese also produces anode scale and is generally considered a problematic impurity. The effect of the combined interaction of these three metal ions on the anode potential has not been quantified yet. The current work used a three factor, two level, three replicate central composite design of experiments to analyze the effects and potential interactions among cobalt, iron and manganese. The experiments consisted of chronopotentiometric analysis to assess anode potential after 24 h of operation. Higher [Co], lower [Mn] and either high or low [Fe] yielded lower anode potentials. Two regression models were developed to predict anode potential as a function of [Co], [Fe] and [Mn]. A method to estimate electrical energy consumption for copper electrowinning is also presented.

By R J. Singh, E. Z. Chacko, Devilal, S. K. Jha, Rina Sahu, Sheshank Shekhar

"Breakouts are one of the biggest problems encountered during continuous casting of steel billets. Billets get cracked locally or break completely in two parts during solidification causing the liquid part of the partially solidified billet to empty inside the cooling chamber. Proper control of important parameters is necessary to avoid break outs during continuous casting. In the present work, the nature of the break outs at a billet caster at Tata Steel was studied. Data analysis was also done for certain casting parameters and the Sulphur tracer test was conducted to understand solidification in the mould. It was found that to reduce the occurrence of break outs, it was necessary to tune the operations based on the grade being cast and the design of the mould tube being used.IntroductionA break out during the continuous casting process is a rupture of the partially solidified shell inside the secondary cooling chamber, causing the contained liquid steel to spill out. In the mid 1970s while continuous casting technology was still in early stage of development, causes of breakouts was not well understood. Today, with technological development much has been understood about breakouts but, most of the understanding has been in the slab casting process wherein due to the higher level of instrumentation, a lot of information has been gained. In billet casting however, due to the geometry of the mould housing with the tube mould, multiplied by the complexity of the multiple strands, instrumentation has not been used and obtaining data for analysis has been difficult.Breakouts at billet casters are still the main hindrances to production. A break out results in a loss in production since the strand which has had a break out is now not available to produce and thus a six strand caster would be reduced to a five strand caster, increasing the time for casting the same tonnage. Additionally extra set up time is required as more often than not a mould change is required in order to have the strand casting again."

Jan 1, 2014

By Karin Soldenhoff

Recovery of uranium in conventional ion exchange circuits, using strong base or weak base resins containing quaternary or tertiary amine functional groups, is based on an anion exchange mechanism. In saline liquors, chloride competes with uranium for the active resin sites and reduces resin loading. This results in significant negative impacts on the IX process in terms of plant throughput and operating costs. In this paper we present the results of a study on the recovery of uranium from an acidic in situ leach liquor containing approximately 9 g/L chloride. A range of resins was tested, and a high capacity strong base resin was identified with significantly enhanced loading compared to conventional resins. Other process-relevant criteria such as loading kinetics and elution efficacy are also discussed. The process developed was successfully tested during a recent ion exchange pilot plant operated in conjunction with a field-leach trial.

By Shivendra Sinha

Total pressure oxidation (TPOX) is widely outreached leaching practice for base metals from sulfide minerals, wherein high temperature (T ∼ 200 °C) and oxygen pressure (pO2 ∼ 25 bar) are required. These aggressive conditions intensify the oxygen mass transfer, and therefore facilitate metal dissolution. However, challenging-cum-negative aspects of such practice are energy and material intensive requirements and high oxygen demand. Thus, the present study explores the novel emulsified medium for enhancement of oxygen mass transfer, which assists faster metal dissolution at significantly lower temperature and pressure condition. It is possible to achieve quantitative dissolution (>95%) of Cu, Ni and Co from mixed sulfide minerals at T ∼ 95 °C and pO2 ∼ 2 bar using an emulsion of 2.5% (v/v) n-Hexadecane in dilute sulfuric acid. In addition, n-Hexadecane was found to be inert, stable and immiscible in a pressurized leaching system, thus can be easily separated and recycled in subsequent leaching stages. Thus, this study offers an energy efficient route for low temperature-pressure leaching of sulfides.

By Dorothée Proffit

Characterization of solids containing cyanides is carried out according to recommendations and standard guidelines. Most of these procedures are based on the analysis of leachates collected either on site or after leaching in the laboratory of samples. Unfortunately, these sole results are often insufficient to identify the source of the pollution. To provide 'a more complete characterization of polluted solids, optical and electron microscopy, XRD, Mossbauer spectroscopy, and transmission infrared spectroscopy were combined to analyze leachates and raw or ground samples. This combination of techniques allows the determination of the kind of cyanoferrate complexes are present in the solid state, different from insoluble Prussian Blue, since they do not have the same extraction' behavior. The use of all these techniques to characterize solid samples combined ,to the usual analysis of solutions gives a better understanding of ' the cyanide behavior.

Jan 1, 1998

By Xianwen Dai

One of the biggest challenges for the gold industry in the 21st century is the presence of copper in gold containing ore bodies. This is because copper consumes large quantities of cyanide. In addition, copper cyanide species are more stable than free cyanide, and hence are problematic in events of tailings spillage. The present paper compares cyanide and thiosulfate leaching for the recovery of gold from a copper containing ore. For cyanide leaching, the extraction of gold using copper cyanide complexes instead of free cyanide was tested in the presence and absence of added ammonia. For the thiosulfate leaching, the effect of the minerals present in the ore on the solution potential and thiosulfate consumption are illustrated.

Jan 1, 2003

By R. S. Krarner

Fly ash, a by-product of coal burning power plants, poses a major problem for the utility industry since most fly ash must be landfilled. These quantities may represent as much as 20% of the total material going into landfills. A major problem with fly ash utilization is that although the ash consists of useable components, ash composition can vary depending on the types of coal burned and plant operating conditions. Ash is first characterized using SEM, image analysis, and chemical methods. Processing techniques were developed to separate ash into various components including cenospheres, magnetic spheres, carbon, and clean ash. These products are again evaluated for various utilizations before being used to produce valuable products such as mullite, activated carbon, fillers in plastics, and concrete.

Jan 1, 1994

By Suzzann Nordwick

The metallurgical treatment of mercury-containing materials for precious or base metals recovery imposes many processing and environmental challenges. Mercury is usually present as elemental or cinnabar. Historically, mercury has been removed from mined ores pyrometallurgically by roasting, but hydrometallurgical methods have also been employed. For example, alkaline sodium sulfide solution acts as an universal solvent for most mercury compounds. While, most other metals are highly insoluble in this solution. This allows for a high degree of selective separation of mercury from other metals with the exception of tin, antimony and arsenic. Mercury leached with a solution of sodium hydroxide and sodium sulfide or sulfur can be re-covered by cementation or stabilized through sulfide precipitation. Hydrometallurgical technology for the pretreatment of mercury removal from gold, silver, and base metal ores using alkaline sulfide leaching will be discussed with a focus on alkaline sulfide leaching of mercury sulfide-containing materials.

Jan 1, 2003

By Alexandra Anderson

A computational fluid dynamic (CFD) model has been developed using ANSYS Fluent 17.0 to help identify areas of high wear within the refractory lining of a secondary lead reverberatory furnace. Once a base case simulation was validated using data from an operational furnace, areas of potentially high refractory wear were determined through the calculation of the temperature and velocity distributions within the furnace and on the hot face of the refractory lining. The CFD model was used to assess whether the predicted areas of high refractory wear could be minimized through changes burden geometry. The results showed that shape of the burden geometry greatly affected the overall flow patterns and heat transfer within the furnace.

By Paul Pajunen, Michael Sheedy

"Acid separation using short bed ion exchange is a now well established technology in copper refinery tankhouses. Refinery bleed streams from liberator cells are treated by short bed systems to produce an acid-free byproduct stream that contains the bleed metals and valuable nickel salts. Removing the acid eliminates the need for a black acid evaporator and reduces the amount of sodium carbonate required in nickel selective precipitation processes. The recovered sulfuric acid can be recycled to the tankhouse. This same technology is routinely used to treat other acids such as hydrochloric, nitric, and hydrofluoric. In the case of hydrochloric acid, the process can selectively separate chloro-anionic complexes such as Zn, Pb, and Cu, which are then eluted with water. The acid recovery technology can also be closely coupled with ion exchange processes in order to minimize regenerant acid consumption. In many hydrometallurgical applications resin regeneration often requires an acid dosage multiple times the stoichiometric minimum. Coupling an acid recovery bed with the IX column allows recovery and recycle of the free acid in the spent regenerant, thus reducing the overall acid consumption to just slightly more than stoichiometric.Short Bed Ion ExchangeThe short bed ion exchange process has been extensively used in the metal finishing industries since the early 1970s [1,2]. Short bed systems have also been sold to primary metals producers for the separation of sulfuric acid from copper refinery bleed streams [3] and for the recovery of nickel and cobalt from plant effluent streams. This unique technology optimizes the ion exchange process and offers a number of significant advantages over conventional ion exchange. The principal features and benefits of this technology are presented below."

Jan 1, 2012

By J. Avraamides

Some operational difficulties have been encountered in the transfer of carbon-in-pulp technology to Australian conditions. Many gold mines? are located in remote and arid areas where the available ground water is highly saline. There is a gradual depletion of free milling oxidised gold ore reserves resulting in the necessity to treat deeper primary sulphide .deposits which can be refractory. Some near-surface ore-bodies and tailing dumps are contaminated by natural vegetative matter which can interfere with the adsorption of gold from the cyanided pulp,. Advances which have been? made include potable water conservation in elution, a new type of regeneration kiln, inter-stage screens, alternative leaching systems transportable carbon-in-pulp plants and efficient open-cut mining methods. Academic and applied research is well supported by government and industry and the results are normally rapidly disseminated and put into practice by the gold mining industry.

Jan 1, 1989