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By G. Kugler, M. Tercelj

"The 1.2690 high alloyed tool steel is usually applied for cold working and is alloyed with carbide-forming elements Cr, V, W and Mo. It exhibits very poor hot deformability. Since there is no enough available data in literature for elucidation of this problem, hot workability and development of microstructure during hot deformation was studied. Hot compression tests were carried out in temperature range 850-1150 °C and strain rates range 0.001-6 s-1. SEM and OM were used for observation of microstructure. Results revealed very complex precipitation of carbides that depends on deformation temperature as well as on strain rate. It was found that especially at lower temperatures of hot working range the precipitation of carbides strongly depends on strain rate. Three different hot deformation behaviors’ were observed depending on temperature and strain rate range.IntroductionThe hot workability of highly alloyed high speed steels is usually described as relatively poor in comparison to other steels due to their tendency of cracking during hot working especially when inappropriate hot working conditions are applied. Alloying elements such as Cr, W, Mo and V in ledeburitic tool steels form carbides that improve hardenability, strength, hardness, wear resistance, etc., but they decrease hot workability and narrow hot working temperature range in comparison to conventional steels. The size, distribution, type and fraction of carbides, as well as the thermomechanical history of material and hot working parameters have major influence on the hot workability. The microstructure of ledeburitic tool steels during hot deformation can be characterized as a two-phase system consisting of an austenite matrix and a combination of ledeburitic carbides [1-4]. In the soft-annealed condition the total volume fraction of carbides is in the range 19-30% and in the quenched condition in the range 9-25%, depending on the chemical composition. During heating before deformation a large quantity of carbides dissolve, but non-dissolved carbides can have an extremely diverse influence on the hot workability due to variations in their composition, size, distribution, hardness and shape, and their different behavior during the deformation phase [5-7]."

Jan 1, 2011

By Yuri Gelfgat

"The report presents the results of theoretical and experimental investigations of the MHD method used for production of composite materials from immiscible melts, e.g., Al-Pb, Zn-Pb, Bi-Ga and others, which, when solidified, can be presumed as ""frozen emulsions""IntroductionThe searching of the methods for controlling the phase distribution in various liquid heterogeneous media is one of urgent tasks in modem material science. The studies [1-3] have revealed that in case of electrically conducting media the influence of electromagnetic body forces on the liquid can be a rather effective mean of such a control. The current paper investigates some physical conformities governing the behaviour of binary liquid metal systems with a immiscibility region under electromagnetic processing designated to produce ingots with homogeneous structure.The main idea of the proposed method rests upon a concept that the electromagnetic forces in the melt are similar to gravity forces due to buoyancy effects in space and have a selective ability to influence the melt components dependent on their conductivity. In crossed electric E and magnetic B fields (fig.I) each component of the medium is influence by the force density f = jXB, where the current density j is determined by the conductivity a of the component j = -oE. When this force is directed parallel or non-parallel to the gravity vector, the buoyancy of suspended particles can be controlled accordingly.This phenomenon allows one to create a situation in binary system, when the sums of all mass forces (gravity and electromagnetic) affecting every component are equal, and two components are under conditions of equilibrium with respect to each other. These conditions are called quasiweightlessness, which is generated in the melt by the electromagnetic forces."

Jan 1, 1998

By R. G. Reddy

To better understand the behavior of bacterial-mineral interfacial reactions, a thermodynamic model based on the- studies of bacteria adhesion on mineral surfaces has been evaluated. The bacteria adhesion to the mineral surface would be increased by l ' d1;1creasing the change in Gibbs free energy of adhesion and it would be reduced if the change in Gibbs free energy of adhesion of the system is increased. From the combination -of Young's equation and equation of state, the change in Gibbs free energy of adhesion -for bacterium-mineral system- was calculated. Influence of liquid surface tension, mineral surface tension on the change in Gibbs free energy of adhesion and consequently bacteria behavior on mineral systems- has been discussed.

Jan 1, 1991

By Robert G. Telewiak

During the past few years, the international nickel industry has taken some important steps to respond to conditions of global production overcapacity, relatively flat demand and low prices. These include the implementation of major cost reduction programs by most producers, closure of some high cost operations and the establishment of the Nickel Development Institute. Consumption in the western world increased by about 7 per cent in 1987 compared to 1986, supplies were less than demand, inventories were low, and late in the year prices increased dramatically. By year-end 1987, most producers were operating at, or close to, their effective capacities. Nickel demand is expected to increase to the year 2000 at an annual rate of about 1.7 per cent, led by increasing usage in the stainless steel sector. If this rate of growth is realized, then there will be need for the effective capacity of the nickel industry to be increased. Producers in Canada have put considerable effort in the past few years into reducing costs - with impressive results. Mining costs, in particular, have been reduced dramatically. While production is still less than the peak years of the yearly 1970's, it has increased substantially from levels of the early 1980's. Over the next few years, production is expected to increase slowly. A key determinant of the level of production in the 1990's could be the effect that regulations on sulphur dioxide emissions have on limiting production.

Jan 1, 1988

By T. Mutoh

Tellurium in raw slime has recently been recovered as copper telluride in Onahama Smelter & Refinery. The slime is decopperized with sulfuric acid solution in conventional leaching tanks. The pregnant leach solution containing 45 g/l of copper and 1 g/l of tellurium is introduced to a copper telluride recovering reactor. The tail solution from the reactor containing less than 20 mg/l of tellurium is recycled directly to circulation tanks of copper electrolysis. The impurities of the product copper telluride is kept below 1% without any purification.

Jan 1, 1990

By Makoto Suzuki

After hot rolling, stainless steel strip is processed by the Hot Rolled Annealing and Pickling line (HAP) , where H2SO4 or mixed acid of HNO3 and HF is normally used. In the pickling bath, metal oxide accumulates in the form of sludge, which should be removed from the bath regularly. A new automatic continuous sludge disposal system has been introduced at Chiba Works of Kawasaki Steel Corporation to increase sludge removal efficiency and improve the working environment. The elements of the equipment are as follows. a. Ejectors in pickling bath: to carry the mixed acid into the circulation tank through the piping system. b. Sedimentation bath : to sediment sludge out of the bath. c. Skip conveyer : to convey a specified volume of sludge into a kneading for device for neutralizing. The sludge removal efficiency of this system is very high. and the volume of sludge accumulation in the pickling bath has substantially decreased.

Jan 1, 1996

By Wayne Bell, Matthew Andriese, Shuqian Xie, Jiann-Yang Hwang, Zhiwei Peng

"Pyrolyzed carbons are generally known as good microwave absorbers and their dielectric properties still remain to be fully explored. In the present study the dielectric properties and dielectric polarization-relaxation phenomenon of a typical activated carbon was investigated. The experimental results indicate the complex permittivity is highly dependent on temperature and frequency. The decrease of permittivity with increasing temperature from room temperature to ~100 °C is probably ascribed to the release of the water vapor adsorbed on the surface of activated carbon, and the variations of permittivity with temperatures between 100 °C and 450 °C in the frequency range of 300 MHz to 3000 MHz are mainly attributed to the decreased relaxation time of dielectric polarization.IntroductionPyrolyzed carbons have been identified as excellent microwave absorbers owing to their high dielectric and electrical loss under microwave irradiations. Among them, activated carbon continues to attract more and more attention from researchers. Due to its special physical properties, the production, modification and regeneration of activated carbon with the assistance of microwave have been widely studied over the last few decades [1-6]. However, only few attempts have been applied to explore the dielectric properties of such materials due to the complexity and variability of their organic precursors and activation processes [7,8]. In order to shed a light on this problem, a typical sample, Norit® A Supra USP powdered activated carbon, was adopted to perform dielectric characterization, which may provide useful information for its wide application in the fields of purification, energy (hydrogen) storage and so on."

Jan 1, 2011

By Laurence Whitty-Léveillé

Proper handling of the radioactive fraction associated with the production of rare earth elements (REEs) in the mining industry is essential for a sustainable environment and human health. Actinides, such as uranium and thorium, have similar chemical properties to REEs, and are often co-dissolved in current hydrometallurgical processes. This causes radioactive contamination of the infrastructure through the extraction cycle. The present study optimizes, through experimental design, a sequential leaching procedure with Na2CO3/NaHCO3 and HCl for the rapid and selective dissolution of REEs and actinides. Optimization focuses on the main operating parameters (time, temperature, and concentration); different types of minerals, REE composites, and ores; on achieving maximal leaching yield; and on minimizing dissolution of the gangue metals (Fe, Si, and Ca). The final sequential procedure was rapid (1 h), effective, and led to the segregation of Th, U, and REEs with limited dissolution of the gangue metals.

By Mohamed Ahmed, A. Kawy

"Smelting of scrap copper and residual anodes and cathodes carried out in a reverberatory type furnace. In this, deoxidation process is carried out by wood, which acts as a resource of reduction gases such carbon monoxide, hydrogen and methane. Use of wood causes the formation of soot pollutants and efficiency of oxygen removal from copper is low leading to added costs in removing contaminants. This expensive problem was solved by using of reformed natural gas as a source of reduction gases (CO+ H2).IntroductionThree reverberatory furnaces were used for smelting of scrap copper and residual anodes and cathodes. Each furnace had a 7tpd capacity and was operated at 1183 °C.In this furnace, Step1-compressed air supplied by tubes from the side of the furnace to remove sulfur from copper matte by oxidation .The copper is also oxidized to copper oxide .[1]Step 2- copper from matte is deoxidized by a reductant. Typically deoxidation process is carried out using wood as a resource of carbon monoxide, hydrogen and methane which are the reduction gases. Use of wood causes the following:1- Forms soot pollutants2- Oxygen removal efficiency from copper is low; more contamination in copper matte increased energy in deoxidation3-the process is highly expensive.In the recent trends, this problem has been solved by using reformed natural gas as a source of reduction gases (CO+ H) .This results in 1-Reduced pollution during smelting.2- High efficiency in the removal of oxygen from copper to produce oxygen free copper. The surface of copper produced from this method is smooth which helps in forming and machining.3- Low cost and natural gas is more readily available in Egypt than wood."

Jan 1, 2010

By G. L. Fredrickson, T. A. Johnson, B. R. Westphal, J. C. Wass, S. X. Li, D. Vaden

"Recovery of uranium from the Mk-IV and Mk-V electrorefiner vessels containing a LiCl/KCl eutectic salt has been on-going during the pyrometallurgical processing of used nuclear fuel for 14 and 12 years, respectively. Although austenitic stainless steels are typically utilized for LiCl/KCl salt systems, the presence of cadmium in the Mk-IV electrorefiner dictates an alternate material. A 2.25Cr-1Mo alloy (ASME SA-387) was chosen due to the absence of nickel in the alloy which has a considerable solubility in cadmium. Using the transition metal impurities (iron, chromium, nickel, molybdenum, and manganese) in the electrorefined uranium products, an algorithm was developed to derive values for the contribution of the transition metals from the various input sources. Weight loss and corrosion rate data for the Mk-V electrorefiner vessel were then generated based on the transition metal impurities in the uranium products. To date, the corrosion rate of the 2.25Cr-1Mo alloy in LiCl/KCl eutectic is ""outstanding"" assuming uniform (i.e. non-localized) conditions.IntroductionLow-enriched uranium products are being recovered from the Experimental Breeder Reactor-II (EBR-II) and Fast Flux Test Facility (FFTF) used nuclear fuels by a pyrometallurgical treatment process at the Idaho National Laboratory (INL). The treatment process comprises a set of operations designed to neutralize bond sodium, recover uranium from radioactive fission products, and place the fission products into acceptable waste forms [1-2]. Reactive sodium metal, essential for heat transfer purposes during reactor operations, is readily converted to chloride during the process. Electrorefined uranium products are currently being stored pending a final disposition decision. Treatment of the EBR-II used driver fuel was initiated in June 1996 while blanket fuel processing started in September 1998. These treatment processes continue on the balance of the used fuels."

Jan 1, 2011

By Vaughan R. Voller

"Numerical methods for dealing with a temperature dependent conductivity are discussed. An approach based on a local application of a Kirchhoff transformation at the discrete level is presented. The application of this transformation - that does not require any inversion- is demonstrated on solving a two-dimensional test problem.IntroductionMuch is said in the recent literature on the modeling necessity of obtaining appropriate thermo-physical properties; in particular the requirement to account for properties that are ""strong"" functions of the depended variables, e.g., Temperature. Of course obtaining appropriate thermo-physical properties serves no purpose unless they can be accurately integrated into a discrete numerical calculation. The purpose of this paper is to examine how temperature dependent conductivities that exhibit discontinuities or rapid changes can be handled in a numerical code.The discussion will be made in the context of a control volume finite element method [1]. After a brief outline of control volume finite element fundamentals basic methods of dealing with discontinuous or rapidly changing thermal conductivity are discussed. This is followed by the presentation of the recently proposed local Kirchhoff method [2,3], The paper concludes with an investigation of the performance of the various conductivity schemes in solving two dimensional problems. This testing clearly shows the advantages (accuracy and implementation) in using the local Kirchhoff method."

Jan 1, 2001

By lonkion M. Font

Due to the known disadvantages of the use of iron silicate slag in the nickel converting stage, i.e., high metal losses, high magnetite content, and low fixation of impurities in the slag, the development of the new proposed "ferrous calcium silicate slag" for smelting and converting processes of nickel is very promising. Hence, considering the successful experimental results of using CaO base slag for the nickel smelting process, a study based on a detailed comparison for the phase equilibrium, and the minor elements distribution between the NilS2-FeS matte with either FeOx-CaO or FeOx-Si02 base slag was investigated. The main results are summarized as: no difference in the nickel losses between both slags was found at high nickel content in the matte, and the fractional distribution analysis for arsenic and antimony pointed out their preferential fixation in the calcium ferrite slag rather than in the iron silicate slag. Considering the energy and pollution issues, the technical feasibility of using calcium ferrite slag in a converting process of the Bessemer matte will have a prominent future for the nickel industry.

Jan 1, 2003

By Lichao Ding, Jingbiao Fan, Yunnen Chen

"With the development of industrial production, more and more wastewater containing high concentration ammonia nitrogen was discharge into the environmemt, which caused serious harm to the environmemt. Treating the wastewater has great significance to protect water resources. Using air-stripping combined with oxidation to uptake high concentration of ammonia nitrogen wastewater. The influence of operating parameters was investigated. Experimental results revealed that pH of solution, aeration time and aeration strength showed heavy influence on ammonia nitrogen removal. Air-stripping combined with oxidation can be considered as an alternative approach for the removal of high concentration of ammonia nitrogen from practical metallurgical wastewater. When pH was 11, aeration time 20 min, aeration strength 1040 Lh-1, and oxidation with 10 % NaClO solution 10 min, the initial ammonia nitrogen 2130 mgr1 could reduce to 12 mgr1. Other items could also be removed to meet the ""Integrated wastewater discharge standard (GB8978-88)"".1. IntroductionThe rapid development of human activities has caused a worldwide increase of nitrogen in rivers, lakes and coastal waters. It leads to considerable eutrophication and an increase in the frequency of toxic algae blooms [1,2]. The concentrations of nitrogen in the water of China are pervading high [3]. The discharge of wastewater containing high concentration of ammonia nitrogen is one of the most important factors. Great efforts have been devoted to the removal of ammonia nitrogen from wastewater. Traditional methods include biological denitrication [ 4 ], chemical precipitation with magnesium ammonium phosphate [5], electrochemical conversion [6], air-stripping [7] and so on. Biological denitrication is the most common process in the treatment of ammonia nitrogen wastewater. But the process is only suitable for the removal of relatively low ammonia concentration due to the requirement of appropriate C/N ratio [8]. Chemical precipitation needs additional reagents, which may introduce new pollutants to water body. Electrochemical method often uses expensive metal or metal oxide as electrodes, and also consumes large quantity of energy [6].Although air-stripping makes use of stripping tower and consumes energy, it is very suitable for the removal of relatively high ammonia concentration. Different air-stripping conditions would appear different removal efficiency. And only air-stripping the effluent can not be attained the ""Integrated wastewater discharge standard (GB8978-88)"". In this study, we use air-stripping and oxidation to removal high concentration of ammonia nitrogen from simulated and real ammonia nitrogen wastewater."

Jan 1, 2011

By Hai-Xing Fang, Bing Xie, Hong-Yi Li

"In the duplex melting process, chromium forms chromium spinels, the study of which will help to exploit the Hongge ores (rich in chromium) in the Panzhihua-Xichang area in China. Mimicked chromium slag was synthesized. The oxidation and decomposition mechanism of the Fe-Cr spinels contained was studied in a sodium roasting process. The effects of temperature, roasting time, amount of soda added and filling reagents were investigated. The leaching-reduction-precipitation-calcination procedure to extract Cr2CO3 was optimized. The results showed that the optimized roasting temperature was 1000~1020°C with a stoichiometric Na2CO3 addition and without any filling reagents. Roasted materials were leached with distilled water and were filtered to obtain a chromium-containing solution, which was adjusted to pH 1.60-1.80. A reducing reagent, NaHSO3, was added in a stoichiometric ratio and the solution was then adjusted to pH 7.25~8.25. Maximum Cr2O3 precipitation was obtained and the precipitate was calcined at 1050°C for 2h to obtain Cr2Ü3 with recovery rate over 96%.IntroductionChromium is widely applied in the metallurgical industry, in refractory materials and in the chemical industry with its particular properties of hardness, wear-resistance, high temperature resistance and corrosion resistance [1]. There is no free state of chromium in nature and chromite is the main chromium containing mineral [2], China is poor in chromium resources, despite its large demand, and there are few deposits of high grade of chromite ores except in some regions in Tibet and Xinjiang province [1, 4]. Hongge, one of largest titanomagnetite mines in Panzhihua-Xichang area, is a polymetallic deposit mainly containing iron and titanium; it is also associated with various beneficial elements such as chromium, copper, nickel, etc. [3]. As investigated in Reference 3, the chromium reserves of Hongge ores are so large that it is of great importance to study how to extract the chromium from them."

Jan 1, 2012

By Niloy K. Nath

Two layer sintering by charging green sinter mix with normal coke rate in the upper layer and reduced coke rate in the lower layer, can substantially reduce the coke rate and also improve the sinter quality by producing more uniform thermal profile through out the bed height. The two-layer sintering process have been analyzed by numerical simulation of the process by a detailed CFD based model, considering all the important phenomena like gas-solid reaction, melting and solidification, flow through porous bed, heat and mass transfer etc. Optimization techniques like genetic algorithm, differential evolution is then applied to evaluate the optimum coke rate in the two layers of the bed to produce the ideal thermal profile and melting fraction in the sinter bed for optimum sinter quality. Through this optimization method both high quality sinter with minimum return fines can be achieved along with reduced coke rate. Application of a genetic algorithm for this type of process optimization has several advantages over the traditional optimization techniques since it can identify global optimum condition and perform multi-objective optimization much easily for complex industrial process like iron ore sintering. Keywords: Two-layer Sintering, Iron Ore Sinter Quality, Ergun's Equation, Gas-solid reaction, Melting Fraction, Multi Objective Optimization, Pareto Set, Genetic Algorithm

Jan 1, 2003

By M. Cavallini, G. Cannavale, P. P. Milella, A. Pescetelli, C. Lupi

Ni-Cd sealed and vented cells have been widely used in the last few years. The environmental hazard related to the heavy metals contained in Ni-Cd batteries is well known. Therefore, a number of scientific studies and commercial processes have been implemented in order to recycle them. Since spent batteries are a heterogeneous and complex material, any kind of recovery process needs some preliminary treatments. The proposed process described in this paper has been tested in laboratory and further developed in a pilot plant. It consists of a combination of mechanical and hydrometallurgical treatment steps, and is able to treat all type of Ni-Cd batteries. In particular, the mechanical treatments have to be done separately on vented and sealed cells, while the hydrometallurgical step is performed on a mixture of the two products obtained from mechanical steps. A fully automated dismantling line would allow the separate recovery of the plastic or metallic casing, terminals, KOH electrolyte, and electrodes to be further processed· for Ni and Cd recovery. The electrodes coming from dismantling line and sealed batteries are submitted separately to an original crushing and elutriation treatment to separate metallic and active paste in the first case and metallic, plastic and active paste in the second case. The hydrometallurgical treatment is carried out on active paste bearing product to produce Ni, Cd, and Fe comn1ercial salts through acidic leaching followed by a multi-step solvent extraction operation to obtain pure solutions.

Jan 1, 2000

By E. Salinas R.

This work is related with a whole characterization of cantera stone, to establish its characteristics that can give it an additional value for the reuse and reutilization of dust, slurries and small pieces of stone which can be treated as wastes. The obtained results reflects that the residues studied can be used as substitutes of feldspars in the production of pieces of ceramic, and also in the elaboration of paints for the same pieces according to the mixes that can be made with the variation of Na2O, CaO and K2O. According to the humidity proofs and specific gravity done, this material can be proposed as a soil improver into hydroponics systems, leading so an important alternative for food production in zones leaking of water. In the same way, it was found the possibility of use this material as a seal 3A in processes of asphalting of roads, highways and streets.

Jan 1, 2009

By M. Kobashi, T. Choh, N. Kanetake

"A new processing route, which enables the cost-effective and energy- saving fabrication of metal matrix composites, have been proposed. The pressureless infiltration of the reactive powder blend with molten aluminum was investigated in this work. The molten aluminum infiltrated into the [Ti + C] powder blend spontaneously, whereas the spontaneous infiltration into the TIC powder phase did not occur under the same experimental condition. The processing time was shortened and· the processing temperature was .lowered by adding the aluminum powder in the [Ti + C] powder. The differential thermal analysis revealed that the aluminum powder in the powder blend melted at 933K and then ignited the reaction between titanium and ·carbon. However there was an .optimum additional amount of aluminum in the powder blend. The TiC formed in situ had three-dimensionally continuous morphologyIntroductionThe squeeze casting process has been used as one of the processing routes for aluminum matrix composites. [1, 2]. Non-reactive metal-ceramic systems have been, generally, used in this technique in order to prevent the degradation of the ceramic phase. Materials obtained by this process basically consist of a continuous metal matrix and discontinuously dispersed ceramic particles. Reactive systems have begun to be introduced into the infiltration process· recently [3A]. Since the ceramics are synthesized in-situ, this process can provide a continuous ceramic matrix [5]. This is one of the outstanding features of this technique in that a bulk ceramic-can be synthesized at relatively lower temperatures in a short time. Another advantage is that the highly reactive combination of a ceramic with a molten metal is in many cases wettable [6], which enables a spontaneous infiltration."

Jan 1, 2000

By D. E. Larson

The U. S. Bureau of Mines has developed a image analysis methodology to correlate the energy consumed during the grinding of an ore to the mineral liberation achieved. Energy consumption values are obtained using a laboratory-scale ball mill equipped with a torque sensor, and an automated image analyzer is used to determine the liberation present in ground products. By combining liberation information with energy consumption data an appraisal can be made of the energy required to liberate the mineral(s) of interest. Results of tests performed on a complex sulfide material determined the effects of grind duration on the liberation achieved and the energy efficiency.

Jan 1, 1995

By Evan O. Jones

Processes involving distillation under reduced pressure were developed at the Pacific Northwest Laboratory several years ago to recover spent acid solutions generated during the manufacture of nuclear fuel for the N-Reactor at the Hanford site. Following construction and testing of a pilot-plant, the technology was licensed to Viatec Recovery Systems, Inc. for commercialization. The technology developed included specialized distillation and rectification of volatile acids, removal of water and/or volatile acid from sulfuric acid, and precipitation of salts. A key feature of the Waste Acid Detoxification and Reclamation (WADR) technology is the development and use of advanced thermoplastic and fluoropolymer materials of construction in all critical process equipment. The technology was then expanded to include crystallization to recover metal salts for possible reuse. Economic and environmental advantages of the procedures include recovery of acids for reuse, simplification or elimination of the disposal of waste solutions, and possible recovery of metals. Industries expected to benefit from such applications include galvanizing, electroplating, sand leaching and any where metals are cleaned in acid solutions. Currently a modular system has been assembled for recovery of several different spent acid solutions.

Jan 1, 1995