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By A. Lakschevitz

The Amazon region offers a large potential for gold extraction but its peculiar characteristics such as heavy rains, lacking of roads and general infra-structure, nature of the ore deposits, etc.. do require special care in plant design. REMETÁLICA has developed a know-how is designing leaching plants which have been demonstrated to be profitable under those tropical weather conditions. The solutions adopted are related to general process route, leach liquor distribution and flow pattern, conditioning of solids and effluent treatment. These plants, now operating in South America countries, demonstrate the success for the technology developed. A tipical plant with 800 t/day ore processing capacity, may require an investment of US$ 1.200.000,00, arid have? a pay back period of a few months, depending on ore grade.

Jan 1, 1989

By Anestis Vlyssides, Elli Maria Barampouti, Sofia Mai, ?postolos Vlyssides

"A new anaerobic reactor variation, the UASB/CO2-stripper reactor was conceived. It consisted of a conventional UASB reactor that recirculated the biogas produced. The sludge characteristics of this system were examined when treating high strength wastewater. From the data collected, it was obvious that the UASB/CO2-stripper system can satisfactorily operate at higher loading rates (25 g COD·L-1·d-1). A pronounced effect on the quality of the granular sludge was observed. The VSS/TSS ratio decreased sharply. A considerable decrease in the mean granule diameter was observed, while the specific gravity of the granules increased. The sludge bed porosity increased significantly leading to a considerable expansion of the sludge bed. These changes in the sludge properties led to a gradual shift of the system towards a fluidized bed process as far as its hydraulic characteristics were concerned.IntroductionIn recent years energy considerations and environmental concerns have increased the interest in direct anaerobic treatment of industrial wastes. The anaerobic method of waste treatment offers, under the present circumstances, a number of significant advantages with trivial or more serious drawbacks over other treatment methods. The major obstacle to the application of the process for this specific purpose is perhaps the difficulty of extending it to a stable and simple operational form. A number of reactor configurations has been developed leading to high biomass concentrations, e.g. the contact process, the filter reactor, the UASB reactor, and the fluidized bed systems, but the process stability problem still remains [1].A prime objective in the operation of anaerobic waste treatment process is the maintenance of a proper pH range. Thus, a possible solution to the process stability problem could be obtained by increasing alkalinity in the anaerobic systems. Therefore, the main objective of this paper is to present and evaluate the results of a system (UASB/ CO2-stripper) with increased alkalinity concentrations."

Jan 1, 2008

By Jian Li, S. Penttilä, P. Liu, W. Zheng, C. Bibby

"The materials selection for Gen IV supercritical water reactor in-core components faces major challenges due to severe operating condition. The current Canadian pressure-tube supercritical water (SCW) concept design requires core outlet temperature of 650 °C at 25 MPa with peak cladding temperature reaching as high as 850 °C. Aside from oilier challenges, there is currently very limited data on candidate stainless steels' corrosion resistance under this operating condition. Austenite stainless steels that include 316L, 304H, AL6XN and 3 l0S that cover a wide range of Cr contents are promising candidates for either direct in core applications or as base coating materials. However, their corrosion resistance has not been tested systematically under this stringent condition. In this study, these types of stainless steels are tested, and their corrosion resistances are compared.IntroductionThe Canadian pressure-tube supercritical water (SCW) concept will operate at a core outlet temperature of 650 °C at a pressure of 25 MPa, with potential peak cladding temperature reaching as high as 850 °C. High-temperature corrosion resistance is one of the key design requirements for fuel cladding components. As summarized by Allen [1 ], most testing to date has been carried out at temperatures below 730 °C. To date, SCW corrosion data above 600 °C is very limited. Even at relatively low temperature exposure to SCW (e.g. 500 °C), F/M steels develop a thick oxide layer rapidly, while some austenitic stainless steels develop thinner surface oxide. Ni based alloys appear to form very thin surface oxide, however pitting was observed in the vicinity of intermetallic precipitates [2-5]. Dissolution of major alloying components from all of these alloys could also pose significant problems for downstream piping [6]. Kaneda et al. [7] suggested some modified stainless steels provide better SCW general corrosion resistance, with no sign of SCC under the slow-strain rate test.Cho [8] suggested that as the Cr content increase, general corrosion resistance improved at 510 °C and 25 MPa. However, similar to Cho's work, most of the SCW corrosion resistance assessments were based on weight change measurement. This can be unreliable due to potential exfoliation of thick oxide film. Besides, there have been no systematic SCW corrosion resistance tests for candidate stainless steels under higher temperatures. SCW corrosion rate increase dramatically for alloys tested at 600 °C [1]. It is also important to understand the role of major alloying elements under this stringent operating condition, not only for fuel cladding components' materials selection, but also for coating materials development."

Jan 1, 2013

Electrocrystallization studies were conducted in a concentrated acid-copper electrolyte to determine the influence of chloride ions and glue on copper nucleation and on the structure of thin copper layers. Electrochemical experiments allied to SEM and XRD examination were performed to characterize the mechanism of nucleation in the presence of additives at 65°C. Results indicated that most of the copper nucleation from a 83 g dm-3 Cu2+ solution, with 140 g dm-3 of H2SO4 is achieved in a matter of milliseconds, Although the presence of chloride and glue, at the concentration levels tested, does not seem to substantially modify the nucleation mechanism, the morphology, nuclei density and the copper film structure and orientation are changed by the presence of additives and by electrolyte stirring.

Jan 1, 1999

By S. de Vries, B. Wasmund, J. Metric, N. Voerrnann, S. Kasinger

Gulf Chemical & Metallurgical Corporation (GCMC) operates a circular DC electric smelting furnace to treat nickel and cobalt bearing residues at its plant in Freeport, Texas. The furnace, originally built by others, has experienced problems including runouts through the hearth and the lower sidewall. Hatch has designed several improvements to the furnace to alleviate these problems. The single anode at the centre of the hearth was replaced with a patented system of twelve air-cooled copper anodes evenly spaced around the furnace lower sidewall. The DC power supply comprises two transformers and two rectifiers operating in parallel. The water-cooling system on the bottom and lower sidewall shell plates was replaced with an air-cooling system using copper cooling fins. The existing row of water-cooled copper coolers in the metal bath zone was re-designed for greater heat removal capacity and better element joint sealing, and a new row of water-cooled copper coolers was added to cool both the alumina bath and freeboard zones. The existing water-cooled metal and alumina tapblocks were also re-designed for more robust cooling. A binding system was added to provide refractory compression that reduces the risk of liquid leaks. Finally, the furnace tilting frame was relocated to the top of the furnace where it is less likely to be damaged.

Jan 1, 2000

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 Linfeng Zhou, Rong Sun, Guanghui Li, Zhiwei Peng, Tao Jiang

Dust, or airborne particulate matter, from metal smelting can be either mechanically or thermally generated and it negatively affects the indoor air quality as well as the fugitive emissions from the plant. The thermally generated dust is often referred to as fume and it is typically generated whenever liquid metal comes into contact with air. For practical reasons, such as vehicle access, etc. it is often difficult to collect 100% of the fume. It is therefore highly desirable to develop processes and optimize operational procedures so that fuming can be kept to a minimum. In this series of experiments, the mechanism of active oxidation and fume formation from liquid silicomanganese under an impinging air jet in the temperature range 1400-1600°C has been explored. Characteristic properties of the fume have been established; particle diameter, shape, size distribution, and elemental composition are reported. The oxidation process is described in terms of vaporization, oxidation and agglomeration. In the boundary layer, two competing mechanisms seem to be operative in parallel: a direct oxidation of Mn vapor, and a two-step oxidation of silicon. The thermodynamic and kinetic conditions governing the two mechanisms are discussed.

Jan 1, 2016

By Yuzo Hiroshige, Kiyotaka Tahara, Hiroki Hatayama, Masaharu Motoshita, Tomohiko Akahori

Large amount of rare earth metals is stored in the used electric products. Hitachi has started to develop the environment-friendly process for rare earth metals recovery from used magnets. We report here the environmental impact of our process, in comparison with the conventional recycle process utilizing solvent extraction. As an evaluation method, Life-cycle Impact assessment Method based on Endpoint modeling ver.2 (LIME2) developed by the National Institute of Advanced Industrial Science and Technology (AIST) in Japan is applied. It was found that the environmental impact of the new process was more than that of the conventional process. For further reduction of its environmental impact, minimization of energy consumption to operate the equipment was most effective. Decreasing the amount of magnesium, used as an extractant, and the improvement of the extraction rate of rare earth metals were also considered as specific options for reducing energy consumption in the plant development.

Jan 1, 2014

By Robert Matusewicz

Ausmelt Technology has been applied to the recycling of spent pot liner (SPL) generated from primary alnminum production. The process is centered on the Ausmelt furnace, in which the SPL is converted under high temperature, oxidizing conditions to an HF containing gas stream and inert slag. fluorine is recovered from the SPL as HF gas and is concentrated and used to manufacture AIF) for recycle to the aluminum smelters. Approximately 87% of the fluorine can be recovered and converted to AIF), with the remainder being effectively tied up in the by product slag. Cost projections show that the recycling process will be competitive with other processes for SPL. The production and recycling of AIF) provides available credit that significantly offsets the operating cost of the facility. Ausmelt Technology for recycling of SPL is currently being marketed in North America by Ausmelt Technology Corporation in Denver, Colorado, and in the rest of the world by Ausmelt Limited of Dandenong, Australia.

Jan 1, 1996

By D. J. Cassidy

This document discusses commercial strategies and applications of specialty processing plants for the recycling of nickel, copper, zinc and cobalt bearing by-products. For this discussion, I will focus on materials originating from the metal plating, electronic circuit board· and chemical industries. The review of select processes and the required service, sourcing, material handling, processing and marketing strategies necessary for a successful recycling program are highlighted. Materials discussed in this summary include filtercakes, filters, dusts, spent catalysts, spent solutions and solids. Both pyrometallurgical and hyrometallurgical applications to these materials are addressed. A comparison of targeted finished markets, including smelter feeds and value added products are also reviewed.

Jan 1, 2000

By Jesse White, Arlin Olson

"An Engineering Scale Technology Demonstration (ESTD) unit utilizing the THOR fluidized bed steam reforming technology was built and operated by Hazen Research, Inc. for the purpose of denitrating and solidifying various Department of Energy (DOE) radioactive tank waste surrogates into granular products. The ESTD offered the opportunity to investigate the operational characteristics of two fluidized beds in series to test process system designs such as those for fluidization, feeding, and product collection. Operational characteristics that were evaluated included bed attrition rate, particle growth, and elutriation; and the effects that variations in process parameters (e.g., fluidizing gas flow rate, feed composition, feed injection method, and gas distributor design) had upon these characteristics were observed. Testing of the process systems on this scale allowed for design changes to be made where the cost in time and money were significantly less by comparison to those same modifications being made on the commercial scale.IntroductionFluidized bed steam reforming (FBSR) offers a moderate temperature (620-750°C) continuous method by which various liquid wastes can be processed irrespective of whether they contain organics, nitrates, sulfates/sulfides, chlorides, fluorides, volatile radionuclides or other aqueous components. The FBSR technology has exhibited the potential to process these wastes into either a carbonate or crystalline ceramic (mineral) granular product.Pilot scale testing was performed using the THOR Treatment Technologies, LLC (ITT) FBSR process, as it offered the opportunity to evaluate multiple aspects in an environment more conducive to experimentation. Process changes and system modifications could be made faster and with less cost impact as compared with changes to an assembled commercial plant. These aspects include verification of process chemistry and kinetics, evaluation of materials of construction, equipment sizing and design, and the interactions of the systems. Evaluation of process chemistry allowed for the verification of thermodynamic and kinetic models, and was used in conjunction with these models to improve the database and modeling assumptions. It also allowed for the reevaluation of data from earlier bench scale testing with the opportunity for long-term operations. These long-term effects may include the buildup of one or more elements that results in the formation of eutectics leading to the destabilization of a fluidized bed, or the shift in particle size as a result of attrition or agglomeration. The pilot plant also provided an environment to evaluate materials of construction."

Jan 1, 2014

By Carla Lupi, Alessandro Pescetelli

"Spent lead battery recycling still shows few weak points in the achievement of a 100% recycling of different waste matters and by- products arising from the recycling process. Some of said problems are dealing with aqueous streams outgoing the recycling plant, and more particularly, a) the waste waters discarded from the breaking and separation unit, b) purification of the spent electrolyte drained from waste batteries and upgrade to a quality compatible with full re-use by the batteries’ manufacturers, c) purification of the mother liquors discarded in the sodium sulfate crystallization process so to produce a salt of commercial grade. All of the above listed problems have been satisfactorily overcome applying an electrochemical process that, through different process conditions and parameters, is able to remove the harmful impurities that hinder the successful commercialization of such by products, or, at least, that can avoid heavy and expensive treatment plant and operation.IntroductionAlmost 100% of commercial lead and lead alloys produced by secondary lead plants is recycled to the new lead accumulators manufacture. The other by-products and residues produced through the lead recycling process may be classified into two groups:a) matters reusable in the new accumulators production processb) matters produced as a result of various reagents and additives used in the recycling process, to be sold to different market sectorsQuality and saleability of by-products are significant points for the economics of the secondary lead plant operation, because, if said by-products are not saleable, they are just wastes, so offsetting potential revenues, and, at the same time, adding a heavy burden to operating cost, like disposal cost [1]. When looking at a typical, modern lead scrap batteries recovery cycle, it is quite evident that we are still rather far from dealing with a waste-less technology (fig.1).The group a) includes 3 by-products produced through the breaking process: among those matters the polypropylene only usually reaches a standard quality suitable for sale to lead manufacturing sector or to other sectors as well. The other two by-products, electrolyte and separators, do not still reach, through a viable and effective regeneration process, a quality standard sufficient for their re-use in the lead batteries sector ."

Jan 1, 2008

By Igor Zh. Bunim, Valentine A. Chanturiya, Alexey T. Kovalev, Irina A. Khabarova, Elizaveta V. Koporulina

This paper presents new theoretical and experimental data on possible mechanisms for the formation of micro- and nanophases on the surface of sulfide minerals un der the effect of high-power nanosecond electromagnetic pulses (HPEMP). The gas outflow from nanosecond breakdown channels of sulfide minerals under the effect of HPEMP is considered, with allowance for the condensation of iron vapors. The condensation of matter in an outflowing jet is shown to be an effective mechanism for structureal and chemical transformations of sulfide surfaces. It is established that electrode potential of pyrrhotite is moved together in the negative party owing to formation of iron oxides (hydroxides) and iron sulfates by HPEMP, that provides decrease of xanthate sorption and reduction flotation extraction of this sulfide, whereas electrode potential of pentlandite gets more positive values at the expense of additional formation of element sulfur, that causes increase of xanthate sorption and, as a consequence, increase of nickel sulfide extraction.

Jan 1, 2012

By Dewei Zhu

A general purpose computer model for describing the transport phenomena and resulting rate of deposition in Chemical Vapor Deposition (CVD) processes has been described. Partial differential equations describing the conservation of mass, momentum, energy and chemical species are solved by a computer program employing a finite volume method. The program allows for multiple chemical species and natural convection effects. In this paper, the deposition of silicon by the reaction of silicon tetrachloride and hydrogen in a vertical stagnation flow reactor with rotating substrate has been considered. The effects of reactor pressure and substrate rotation speed on the rate and uniformity of deposition have been studied. The predicted rates of silicon deposition along the substrate are in reasonable agreement with experimental results found in literature. The model can be used as a tool for design optimization of such reactors.

Jan 1, 1990

By B. J. Scheiner

The presence of organic materials in gold ores interferes with gold extraction by cyanidation. The carbon contained in the ore has been shown to adsorb gold cyanide complex from solution. Removal of the carbon content by roasting or chemical oxidation prior to cyanidation results in gold extractions of 85 to 95%. This paper discusses how the mineralogy of the carbonaceous gold ores affects gold recovery by cyanidation. It also discusses the advantages and disadvantages of roasting and chemical treatment to render the ore amenable to cyanidation.

Jan 1, 1987

By Rumen Markov, Lubomir Kuzev

"The treatment technologies for municipal solid waste (MSW) are effective mainly for components sized over 40 – 50 mm. This fraction is separated by screening in the beginning of the process. Usually the undersized product is deposited without additional treatment. Its quantity is variable from several up to 30 – 40 % of the total MSW. Both oversized and undersized fractions are formed by all types of primary matter. Adapted technologies from mineral processing will provide a suitable technology for treatment of MSW under 40 – 50 mm. The MSW content depends on the geographical location, the degree of urbanization and other factors. The methods can be applied for separations of different components suitable for recycling or other utilization are: • Separation by density; • Separation in thin liquid layer; • Selective grinding and screening; • Flotation, etc. Introduction Municipal solid waste (MSW) represents an integral part of public urbanization. However, there are some drawbacks stemming from MSW, in regard to its collection, transport and elimination. Different approaches exits worldwide for tackling the problems arising from MSW. For a short period of time, the attitude towards MSW has evolved in several levels, each further level being characterized by higher percentage of utilization of MSW components. Thus, the bottom line has been shifted from safety storage towards processing that includes recycling and maximal utilization of MSW components. Technologic processes applied for treatment of MSW have a common feature – that the fine components, having sizes under 20 mm, 30 mm, 40 mm, or 50 mm are excluded from treatment process trough screening, and in most cases diverted without any additional treatment to preliminary prepared storage sites. MSW in Sofia – current situation The amount of MSW collected daily in Sofia as around 1000 t/24 h. It is stored or baled. Baling is a spare alternative of storage, since baling insures only temporal keeping of MSW, till the building of suitable storage site where the bales will be transported and buried. The morphologic composition of MSW in Sofia has been determined several times at different time intervals, from some Bulgarian organizations as well as from the Japanese organization JICA. So far, however, there is still a lack of enough systematical and comprehensive study. Generalized results from the studies on the MSW components, as well as some important parameters are given in Table 1."

Jan 1, 2008

By R. A. Sharma

Neodymium metal was successfully produced by the reduction of Nd203 with Na in the presence of CaC12-NaCl melts by the overall reduction reaction Nd203 + 3 CaC12 + 6 Na ? 2 Nd + 3 CaO + 6 NaCl at -750°C. The metal produced was extracted from the salt media by dissolving it in a Nd-Fe alloy pool. The yield (percentage of theoretical neodymium produced) was found to depend on the salt composition and the mass ratio of salt to neodymium in the reactor. A yield of 95% was obtained with salt ratios as low as 3.5. Further decrease in the salt ratio below 3.25 decreased the yield. Stirrer position had little effect on yield; while increasing the temperature and placing fins in the reactor increased the yield. The Nd-Fe alloy produced was of as good quality as that produced using Ca reductant, and was suitable for direct use in producing General Motors MAGNEQUENCH? alloy for permanent magnets.

Jan 1, 1989

By Chen Ya

Layered LiMn0.5Ni0.3Co0.2O2 was prepared from Mn(NO3)2, Ni(NO3)2, Co(NO3)2 and LiOH by co-precipitation and solid state reaction. XRD, C-V and galvanostatic charge-discharge methods were used to examine the structural and electrochemical characteristics. The LiMn0.5Ni0.3Co0.2O2 delivered a high discharge capacity of 167 mAh/g between 2.5 and 4.3 V with excellent cycling stability.

Jan 1, 2006

This symposium is dedicated to the lifetime achievements of Professor H.Y. Sohn. It covers the scientific fields, processing routes and investigation techniques in which Prof. Sohn has worked during his career and is based in the equally important three topical areas: Principles, Technologies, and Industrial practice. Professor Sohn was General Chair of the very first TMS Fall Extraction and Processing Symposium in 1983 in San Francisco which led to the Annual such symposia as this International symposium. Furthermore, the theme of that symposium was sulfide smelting, which is also included in this symposium. [ ] Professor Sohn was born in a beautiful dynastic capital Kaesung, Korea on August 21, 1941. He received his B.S. degree in 1962 from Seoul National University, M.Sc. in 1966 from the University of New Brunswick, Fredericton, N.B., Canada, and his Ph.D. degree in 1970 from theUniversity of California at Berkeley all in Chemical Engineering. After working as a Research Associate at the State University of New York at Buffalo and as a Research Engineer at Du Pont?s Engineering Technology Laboratory, Dr. Sohn joined the Department of Metallurgical Engineering at the University of Utah in 1974 and currently holds the ranks of Professor of Metallurgical Engineering and Adjunct Professor of Chemical Engineering.

Jan 1, 2006

By Jie Ma, Shun-Li Zhao, Jian Zhao, Jie-Yu Zhang

"Microstructural morphology evolution of Ni-45wt.%Mo droplets during rapid solidification process was investigated using an advanced modified 3D cellular automaton-finite element(CAFE) model by CALCOSOFT software. The model was modified by User-defined functions (UDFs) and validated with experimental solidification microstructural morphology of Ni-45wt.%Mo droplets available in the literature. Then, the influences of convection heat transfer coefficient, superheat of the alloy droplets and droplets size were investigated during the rapid solidification process. The predictions show that microstructural morphology is obviously sensitive to convection heat transfer coefficient and droplet size. With the decrease of convection heat transfer coefficient, the grain density decreases. In addition, the decrease of the droplet size could obtain refined microstructure. However, decrease the superheat ofNi-45wt.%Mo droplets has little effect on microstructural morphology.IntroductionFor several decades, much attention has been paid to undercooled alloy droplets of rapid solidification process for which can obtain refined microstructure, decreased microsegregation and extended solubility of alloying elements [1-3]. Extensive prior work shows that solidification of droplets plays an essential role in advanced material properties [ 4]. Consequently, it is very important to investigate the microstructural morphology evolution, especially for dendrite growth during non-equilibrium solidification process, for dendrite growth reflected the kinetics of the crystal growth process."

Jan 1, 2013