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By Romeo U. Pagador

After privatization in 1999, PASAR Corporation initiated a plant modernization program to optimize the performance of the smelter by increasing plant availability. This initiative required operational adjustments to the converting and anode furnace procedures, to support the higher throughput in the flash furnace, while continuing to meet government environmental regulations. The major shift in production direction was to eliminate the 30-35 day maintenance shutdown every two years, and replace it with a 15-day shutdown. This paper discusses the changes implemented in the converter and anode operation that have resulted in an increase of 10% in flash furnace throughput, an 18% increase in blister output, to 170 tonnes per cycle, and a converter campaign tonnage increase of 10%. Since privatization, PASAR has instituted a series of ?management of change? programs that have facilitated an industrial cultural change needed to achieve the company?s vision, mission and strategic goals.

Jan 1, 2005

By A. D. Besser

The world production of lead has been growing continuously and reached over 7 million tonnes in 2005. At the same time, the structure of lead consumption has changed: the use of lead compounds to liquid fuel has been virtually terminated; the proportion of lead for manufacture of lead-acid batteries has been growing and reached 76.7% of the overall world production of this metal. This has taken place against the background of increasingly stringent environmental norms and environmental legislation. This is due to the lack of an alternative for lead in manufacture of local power sources. A solution to the problem of meeting the industrial demand for lead with simultaneous reduction in the primary lead production is in recycling. A large amount of batteries manufactured worldwide and their short life cycle, as well as the positive economics and a possibility to comply with the environmental requirements encourage the development of secondary lead production. Currently, over 60% of the world demand for lead is met due to recycling. The current situation with collection, transportation, storage and processing of spent lead-acid batteries has been analyzed in this paper. Examples are given to illustrate technological and equipment solutions and trends for improvement of secondary lead production discussed.

Jan 1, 2006

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 José García-Antón, Valentín Pérez-Herranz, José Luís Guiñón, Henry Reyes

"The majority of chromium electroplating operations employ Cr(VI)-based baths. During these processes, Cr(VI) is reduced to Cr(III). Besides Cr(III) other undesirable impurities are present such as iron, copper and nickel. The build-up of the impurities limits the lifetime of the plating solutions. Since the disposal of spent chromic acid baths is expensive and can cause significant environmental degradation, there is increasing interest in finding ways to regenerate waste chromium liquors.In this work, an electrolytic cell separated by microporous ceramic diaphragms was used to regenerate chromium plating solutions. The effect of the ceramic diaphragm structure parameters, such as porosity and pore size, on the performance indicators of the electrochemical reactor (fractional conversion, current efficiency, product yield, specific energy consumption) was investigated.The fractional conversion, the product yield and the current efficiency increased and the specific energy consumption decreased with the decrease in porosity.IntroductionChromic acid is widely used in industrial applications such as steel manufacture, metal finishing industries, aluminium anodising, pasivation of cadmium, magnesium, and zinc, etching of plastics and another industrial operations related with processing ferrous and no ferrous metals [1]. These processes employ baths with high concentrations in chromic acid, about 180 and 350 g/L, where hexavalent chromium is reduced to Cr(III):"

Jan 1, 2008

By Marco A. S. Aguiar, Luis G. S. Sobral, Vânia Mori, Paulo A. Medeiros da Silva

"Copper occurs in the crust of the earth, predominantly, as sulphides. Among the copper sulphide minerals, the chalcopyrite is the most abundant and the most refractory to the conventional oxidative processes. This work aims at developing an electrolytic process for treating a copper sulphides flotation concentrate, more precisely chalcopyrite (CuFeS2) and bornite (Cu5FeS4) in the percentages of 70 and 30%, respectively.This paper presents a low-cost operational electroleaching process for treating copper sulphides flotation concentrates, with a high chalcopyrite content. This research practical work aims at improving the copper extraction from that sulphide mineral, in a relatively short time with low-operating cost taking into consideration the influence of a cationic surfactant. The electrolyte of the electrolytic reaction system was a 2,0 mol.L-1 NaCl solution containing CTAB, a cationic surfactant. The electroleaching system contains one DSATM (dimensionally stable anode) anode and two nickel or copper foams (threedimension electrodes. During the electroleaching process the chloride ions are oxidized to chlorine at the anode surface, which in contact with the aqueous phase generate enough hypochlorite ions to oxidize chalcopyrite.The copper ions released from the chemical oxidation process are reduced at the cathode surface as metallic copper."

Jan 1, 2008

By N. Lohja

Metallurgical industries are generally big producers of solid residues of various kinds. In contrast with the past where environmental sensibilities were not so elevated and the accumulated mass of these residues were not considerable, these days the solid residues are everywhere scrutinized among others in term of their harmful environmental impact and as possible materials for valuable elements extraction or secondary utilisation. As a case study, the present paper gives an overview of the solid residues discharged by the metallurgical industry in Albania for the last tens of years. The results of two monitoring study on the solid residues of copper, iron and ferrochromium producing industries are also summarized. The first deals with the origin, quantities and chemical composition of these residues and the second one with the impact of harmful ingredients of these residues in the environment. Some methods for the processing of these solid residues are also proposed in order to ensure a clean environment and to make not just possible but also economically viable their secondary utilisation. This work is part of a bigger cooperation project among local institutions and foreign expert companies such as Flogen Technologies Inc and other in various countries that will not only monitor the situation but will also develop appropriate technologies for treatment of these specific residues.

Jan 1, 2006

By Tae-Hyun Kim, Shun Myung Shin, Jin-gu Kang, Jeong-Soo Sohn

We investigated about synthesis of Mn-Zn ferrite with spinel structure using sulfuric acid leaching solution of mixed spent zinc-carbon batteries and spent alkaline batteries. The waste batteries were prepared by physical treatment such as crushing, magnetic separation, and screening. After screening, the crushed batteries were separated to +8 mesh and -8 mesh powder. Among these, under 8 mesh powder was selected for leaching test. The leaching test was investigated at 2 M H2SO4, 4 vol.% H2O2, reaction temperature 60 ?, agitation speed 250 rpm, solid/liquid ratio 50 g/ 500 ml, reaction time 1 h. The leaching efficiency of zinc, manganese and iron were 99.0%, 98.9%, 58.5%, respectively. For co-precipitation of zinc, manganese and iron, 5M NaOH solution was used for pH control. Then in order to synthesize Mn-Zn ferrite powder, it was investigated according to reaction temperature, agitation speed and O2 partial pressure. We could synthesize about 20 nm of Mn-Zn ferrite with spinel structure.

Jan 1, 2008

By C. A. Morais

The present work describes the development of an efficient and relatively simple process to obtain high grade CeO2 from a mixed rare earth chloride solution. The process involves cerium oxidation and precipitation by addition of a KMnO4-NaCO3 solution. The experiments were carried out at room temperature (25 1° C). The results indicated that the major parameters affecting cerium recovery are the molar ratio of KMnO4/Ce, the initial acidity of the chloride feed solution and final pH of Ce(OH)4 precipitation. In strong acid solutions (pH < 1), the oxidation of Cl to Clo took place in addition to the oxidation of Ce(III) to Ce(IV), so increasing the permanganate consumption. Conversely, low acidity (pH >3) led to coprecipitation of the other rare earth elements. Under the selected conditions, cerium was selectively precipitated as ceric hydroxide, together with some manganese dioxide. Further purification was carried out by the dissolution of Ce(OH)4 in HCl, followed by precipitation as cerium carbonate. The filtrate was neutralised with a Na2CO3 solution in order to recover the associated rare earth elements for further separation. The final product, assaying 99.7 % CeO2, was obtained with a recovery of nearly 100%.

Jan 1, 2003

By S. N. Ashrafizadeh

Nowadays, hard carbides have found various industrial application in the manufacture of cutting and drilling tools as well as metal forming devices. About 60% of the world tungsten production is consumed in the manufacture of hard carbide pieces. Regarding the high economic value of hard carbide components, i.e., Ni, Co, TaC, TiC, and WC, their recovery from scrap species is attracting much interest. In the current research, the cobalt and tungsten content were recovered from scrap cemented carbide pieces through the application of high voltage electrolysis in nitric acid media. By this method, cobalt and tungsten were initially recovered as cobalt nitrate and tungstic acid, respectively. The precipitate of tungstic acid was calcined at 800ºC after being washed twice with distilled water. A pure tungstic oxide was obtained. The effects of current density, electrolyte concentration, speed of agitation, and the surface area of the anode on the efficiency of the electrolysis process were investigated. The optimum conditions of current density of 1500 A/m2, an acid concentration of 1.5 M, and a cell temperature in the vicinity of 60 to 80ºC were obtained. At the optimum conditions, an acceptable rate of collapse for the anodic carbide pieces of about 3.1 g/h was achieved, which remained constant up to the completion of the recovery process without any passivation .

Jan 1, 2003

By Hector M. Lizama

A new technology, known as the HydroZinc? process, is described for the recovery of zinc from sulphide ores that includes heap leaching, neutralization, solvent extraction and electrowinning. Unit operations were scaled up from bench-scale to a 1-t/d zinc cathode demonstration plant. Bench-scale studies defined the process chemistry and a process flowsheet. Column tests were used to design full-scale heaps for zinc bioleaching, and mini-pilot equipment was used to design a solvent extraction circuit. The characteristics of the process required development of a bleed circuit for water and impurities. The complete integrated process was tested on a demonstration plant scale for two years, with about 10 000 t of zinc sulphide ore being bioleached in two 6-m-tall test heaps. In addition to 1 t/d of zinc cathode, iron hydroxide and gypsum residues were produced. The process also generated a small effluent bleed. Over the course of the two-year demonstration test, a number of technical hurdles were overcome and several improvements were made. Some of the more significant ones are presented along with process descriptions and experimental and demonstration plant data. Some engineering aspects and economic evaluations of the new process are also discussed.

Jan 1, 2003

By D. J. Sellmyer

This paper is Intended to review recent developments in the application of rare earth-transition metal alloys as high density, rewritable data-storage media. First generation magneto-optic media are based on amorphous Tb-FeCo or GdTb-Fe alloys which are adequate but could use improvements In certain respects. A very difficult materials-design problem is encountered because of the following requirements: a sufficiently large Intrinsic uniaxial anisotropy, a Curie temperature in the range 100-300°C, a sufficiently high coercivity, a sufficiently high optical absorption, a high Kerr rotation, reflectivity and high carrier-to-noise ratio, a high storage density, a very fine and homogeneous nanostructure, long-term stability, and inexpensive production. , Fundamental issues such as the relationships between the nanostructure and perpendicular magnetic anisotropy, and electronic structure and Kerr rotation are discussed. Attempts to tailor the properties by rare-earth alloying and by preparing compositionally-modulated, nanostructured multilayers are outlined. Challenges and opportunities in competitive materials such as garnets, ferrites and Co/Pt multilayers are briefly discussed.

Jan 1, 1992

Testing is in progress to address compatibility issues with regard to long term storage of plutonium in contact with two different intermetallic systems. The two intermetallic systems are: 1. dental amalgam, i.e., mercury plus silver alloy powder, and 2. liquid gallium alloy plus copper powder. Both of these are plasto-metallic materials that undergo a solidification reaction at room temperature. Each system is allowed to react in contact with both high-purity alpha plutonium and a delta stabilized plutonium alloy at varying temperatures in an argon atmosphere. Wetting characteristics and possible interaction will be studied metallographically in the post-mortem condition. Complete results including metallographic examinations will be presented.

Jan 1, 1995

By Li Cheng

The SKS copper smelting process was jointly developed by Shuikoushan Mining Corp. and ENFI (Beijing Central Engineering and Research Institute for Non-ferrous Metallurgical Industries) in China. It is a new bath copper concentrate smelting process with oxygen enriched air. The pilot plant testwork was completed successfully in 1993. SKS has demonstrated to be an advanced bottom blown smelting process. This technology got the First Class Prize of Scientific and Technological Progress awarded by CNNC (China National Non-ferrous Metal Industry Corp.) in 1994. The SKS process has significant capital and operating cost advantages. Its environmental and industrial safety and hygiene performance represents a substantial improvement when compared to conventional technologies. The technology has generated great interest in the Chinese metallurgical industry. Feasibility studies and basic designs have been carried out to incorporate in retrofit and green field smelter projects in China and abroad. This paper describes the history of the pilot plant operating data (50 tonnes dry feed/day), and discusses the features of the SKS technology, its application and possible future trends.

Jan 1, 1999

By T. Taniguchi

The existing Mitsubishi Process line at Naoshima Smelter and Refinery has been operating successfully since 1991, and its present production capacity is 270,000tpy of copper. Furnace relining works have been carried out every two years to coincide with the compulsory bi-yearly boiler inspection, but the next target is to extend the furnace refractory life to four years, while still undergoing the mandatory boiler inspection every two years. Although the damage of hearth bricks beneath lances in the Smelting furnace was a matter of concern, it was reduced by controlling gas velocity and evening solid distribution to each lance. The life of bath level bricks in the Converting furnace was also a concern, but four-years continuous use of the bricks was achieved in the course of the last two campaigns. Several other improvements were also carried out to the cooling systems during the shutdown in 2005 to ensure longer campaign life. This paper summarizes recent improvements implemented to enhance the advantages of the Mitsubishi Process.

Jan 1, 2006

By S. H. Amini

The effects of CaF2 and ilmenite on dissolution rate and diffusivity of CaO in calcium alumino-silicate based slag in a temperature range of 1500 ? 1600 ºC were studied by using the rotating disk/cylinder technique. The effect of rotation speed on the rate of dissolution in the base slag indicated that mass transfer in liquid slag played a significant role in controlling the dissolution. At a constant rotation speed, the effect of 5 wt% addition of fluxes tothe slag on the dissolution rate was investigated at various temperatures. While CaF2 had the highest effect, addition of ilmenite increased the rate of dissolution significantly. The diffusivity of lime in these slags was quantified using the dimensionless mass transfer correlations for rotating disk/cylinder in the melt. The diffusivity values were deduced using the data on dissolution rate and solubility of lime in the slags. The measured diffusivity in base slag at 1500 C was found to be about 1.32 10-5 cm2/s and increased to 3.07 10-5 cm2/s at 1600 °C. Addition of 5wt% CaF2 increased the diffusivity by a factor of 3 to 5, while 5wt% ilmenite increased the diffusivity by a factor of 2 to 3 in the temperature range of 1500 to 1600 ºC. The two examined fluxes reduced the activation energy of diffusion.

Jan 1, 2006

By I. A. Ibrahim

Ilmenite, in its natural form, is an inactive mineral from which the selective removal of iron is rather difficult. The reactivity of ilmenite. so that it can be leached with dilute hydrochloric acid, can be enhanced by chemical reduction in solution using a suitable metal as a reducing agent. The present paper aims at the evaluation of an Egyptian ilmenite ore for the production of synthetic rutile by direct leaching with hydrochloric acid in presence of iron powder. In this process, the titanium and iron contents are dissolved; meanwhile, the dissolved titanium is hydrolyzed and re-precipitated leaving mainly iron in solution. Leaching conditions were optimized to obtain less iron in the final solid product. Addition of sufficient amount of iron powder during leaching reduces the dissolved Fe3+ to Fe2+ and reduces the dissolved Ti4+ to Ti3+. The creation of Ti3+ in solution is assumed to have a role in dissolving the ferric iron and hence increasing the reactivity of the ilmenite ore. Synthetic rutile of about 90% TiO2 and 0.77% Fe2O3 was obtained from ore with a grain size 100% passing 200 mesh and a 5-hour leach time with 20% HCl at boiling temperature (110°C) and 0.11 g iron powder / g ore.

Jan 1, 2003

By C. G. Anderson, L. G. Twidwell

"Throughout the world, there are many orebodies or materials which have significant value but also contain arsenic, antimony, and mercury. As regulations on the transport, exposure, disposition and emission of these elements have become more stringent; it has become increasingly more difficult to derive the values from the resources. This paper outlines the fundamentals of alkaline sulfide hydrometallurgy and its successful application to arsenic, antimony and mercury bearing ores, concentrates, by-products, and other materials.Fundamental Alkaline Sulfide HydrometallurgyHydrometallurgical methods can be employed for treatment of gold, arsenic, antimony, tin and mercury containing materials, concentrates and ores as well as complex ones containing any number of metals. The alkaline sulfide system is one of these and is essentially a mixture of sodium sulfide and sodium hydroxide. This is a unique hydrometallurgical system as it is a very selective lixiviant for the distinct leaching of tin, gold, antimony, arsenic and mercury [1-7]. Worldwide, it is employed industrially in the CIS, China and the United States for the production of antimony [8-15].As an example, when the system is applied to an arsenic containing material like orpiment, As2S3, a solution of sodium thioarsenite is formed. This is illustrated as:"

Jan 1, 2008

By Ken Baxter

The Sepon Copper Project is located in Laos and has a mineable reserve of approximately 16Mt of ore grading 5% copper with minor gold and silver values. The deposit is a clay-hosted secondary copper mineral suite, predominantly chalcocitic in nature with associated pyrite. The current project design is based on the production of 60,000t/a of LME Grade A cathode by an acid leaching process followed by solvent extraction and electrowinning. Significant metallurgical testwork was conducted as part of the Definitive Feasibility Study (DFS) with process challenges identified and overcome at each phase of testing. Flowsheet configuration is geared to autogenously generating sufficient acid and ferric iron to meet gangue acid consumption and to leach the copper. The ability to maintain acid and ferric levels in the process liquors is strongly influenced by the proportion of pyrite in the ore presented to the autoclave. This paper will outline flowsheet development from preliminary variability testing to pilot plant and DFS design. The Sepon process solution seeks a balance between operability and capital/operating costs, and provides insights into the basic mechanisms influencing flowsheet selection for these ore types.

Jan 1, 2003

By Funsho K. Ojebuoboh

With several "green" applications in the horizon, bismuth has become an even more important minor metal in the smelting and refining of lead. Smelters with a complex sulfide feed invariably deal with bismuth. Its behavior during the smelting of lead in conventional sinter - blast furnace operation is discussed. Because it readily deports to the lead phase during the refining of lead, its separation from refined lead remained unsatisfactory in early lead production. When commercial requirements of bismuth in lead became more stringent early this century, the procedure whereby calcium and magnesium is used to debismuthise lead was developed. The present conduct of this 1936 process, the Kroll Betterton process, is discussed with emphasis on operational improvements.

Jan 1, 1995

By L. Cifuentes

Electrodialysis (ED), i.e. a technique based on the effects of electrically charged membranes on ions in solution in an electric field, has been applied to Cu-Fe-As-Sb- H2SO4 electrolytes similar to those used in copper electrorefining and electrowinning operations. The effects of current density, time and species concentration have been studied in a batch ED cell. The technique has shown to be effective in concentrating and separating a range of ions and points to possible new methods of treating copper electrometallurgy effluents.

Jan 1, 1999