Search Documents

By Guo Chang Jiang

In order to improve the IIAZ toughness of X-60 pipe steel, the intragranular ferrite plate (IFP) technology was used. The characteristics of IFP is claimed to be much fine ferrite plates appear inside the original austenite grains. By means of suitable Re, Zr, Ti additions in a bath with a higher initial oxygen potential, a good control of the peak temperature and the cooling rate during welding simulation, one can get a %IFP in volume over 50%, and the toughness gets up from 55 J to 160 J. It was found that the inclusions most effective in nucleating IFP are some deformable complex silicates which either entrap Re, Zr, Ti oxides or contain these elements. The greater the number of the evenly distributed and effectively nucleating inclusions, the more the %IFP in volume, and the finer the microstructure of the HAZ, so the better the relevant toughness. Generally, these silicates bahave as fine spheres along a line. The present authors revealed that these fine spheres result from the remelting of the shuttle- like silicates due to heating in the process of welding simulation. These silicates used to get a higher sulphur capacity, so MnS deposits might be observed on the periphery of the silicates. IFP was proved to be directly rooted in the [Mn] depleting zone which locates beside MnS deposits.

Jan 1, 1997

By W. G. Davenport

Smelting oxidizes Cu-Fe-S concentrate to matte. Converting oxidizes this matte to metallic copper. Smelting and converting are, therefore, part of the same oxidation process. It would seem natural, then, that smelting and converting should be combined to produce metallic copper in one step. This would: (a) maximize S02 capture by restricting S02 emission to a single, continuous source (b) minimize industrial oxygen and fuel requirements (c) minimize cost. This chapter discusses one step, direct-to-copper flash smelting as it is practiced in 2000. It then uses. the matrices of this book to determine: (a) the industrial oxygen and oil requirements of direct-to copper flash smelting (b) the distribution of Cu between metal and slag during direct-to-copper flash smelting. It concludes that direct-to-copper flash smelting: (a) captures?S02 efficiently from its single continuous stream of SO2 off gas (b) minimizes oxygen/oil consumption but: (c) sends -114 of its Cu-in-feed to slag.

Jan 1, 2001

By Wiraseranee. Chompunoot, Kazuki Morita, Toru H. Okabe

"Aiming at the development of more effective recycling processes, dissolution behavior of rhodium into molten slag was investigated. Using a pure rhodium crucible and Na2O-SiO2 slag system, equilibration experiments were carried out for 18 h at 1423-1623 K under various oxygen partial pressures of 0.005-1 atm with varied slag basicity. Rhodium solubility increased with increasing oxygen potential, slag basicity, and temperature. Rhodium dissolved into slag as rhodate ion ([RhO2]-) by the endothermic reaction: Rh(s) + 3/4O2(g) + 1/2O2-(in slag) = [RhO2]-(in slag). In the dissolution reaction, the “rhodate capacity” of slag is newly-defined. The correlation between rhodate capacity and optical basicity is reported.IntroductionDue to its high chemical resistance and outstanding catalytic properties, rhodium (Rh), one of the platinum group metals (PGMs), is utilized in various applications such as catalysts, molten glass vessels and containers, and electronic devices. Owing to the rarity of Rh resources in nature, recycled Rh from scraps such as spent automobile catalytic converters is currently considered as an important source of Rh supply [1]. According to the recycling practices, Rh is currently mainly recovered from scraps along with other PGMs such as platinum (Pt) and palladium (Pd) by a dry process (e.g., smelting), a wet process (e.g., leaching and subsequent separation of PGMs from aqueous solution), or a combination of both processes [2]-[4]. Among these processes, smelting is commonly applied because PGMs can be effectively separated from a relatively large amount of various impurities coexisting in scraps. In the smelting process, Rh and other PGMs are collected in the collector metal (e.g., iron and copper), and impurities in scraps are removed into slag [4]-[6]. The process may be carried out at a temperature range of 1573-1973 K, in either an oxidizing or reducing atmosphere. Due to the high oxidation resistance at high temperatures, Rh is expected to be collected efficiently in the metal collector rather than being oxidized and forming RhOx in a molten slag. However, Rh loss into slag does occur in this process [7]."

Jan 1, 2011

By T. A. Chepushtanova, B. Mishra, E. O. Kilibayev, V. A. Luganov

"The paper contains the results of studying about modification of pyrite and arsenopyrite specific surface and porosity at their thermal decomposition. The studying of specific surface was carry out by B.E.T. – adsorption of nitrogen at his boiling-point. In our work were using the electron-microscopical, X-ray structure analysis and chemical analysis. There was established that the decomposition of pyrite and arsenopyrite accompany by increasing of pores volume from 0.303 · 10-3 to 1.23 · 10-3 at increasing of pyrite degree of decomposition about 41 % and then decrease about 0.131 · 10-3 m3/g at degree of decomposition near 100 %. The surface area of pores increase from 0.31 to 1.085 m2/g with following lowering due to enlargement and confluence of minor, small pores. Increasing of porosity accompany with increasing of particles windage that appear the result of heightened dust-furnace partially decomposing pyrite and arsenopyrite particles by air flow from furnace reaction zone. This explains heightened contention of sulfide sulfur in roast dust of sulfide concentrate. 1. INTRODUCTION As a result of ore base exhaustion of ferrous and nonferrous metallurgy at metallurgical treatment are involving more complicated and less qualitative ores. Magnetiting ores content considerable quantity of pyrite complicative the technology of iron extraction. At the same time the pyrite concentrates wining at dressing content different nonferrous metals in industrial quantities. Extracting ores of nonferrous metals are contenting considerable quantity of arsenic at the present time. Extraction of base metals from complicated raw materials demands new technologies. Arsenic contenting in ores is necessary to utilize (waste burial) in more ecological compatible form. Arsenic on acting metallurgical and chemical enterprises from technological cycle is withdrawing in the form of arsenate – arsenite cakes, burial of their may lead to seriously ecological problems as times goes by. In Kazakh National Technical University is carry out the cycle of researching by pyrite, arsenopyrite and arsenate – arsenite cakes treatment with the object of arsenic withdrawal in sulfide form – in more ecological and safe form and with the object of preparation of initial ore raw materials to following pyro- and hydrometallurgical treatment. As a result of sulfidizing of arsenate – arsenite cakes by pyrite are forming the volatile arsenic forms and pyrrhotite of variable structure."

Jan 1, 2008

By Lucas Nana Wiredu Damoah, Lifeng Zhang

"The use of electromagnetic field to remove suspended particles from metals such as aluminum by pushing to the boundary has been well studied. However, the potential of this method is yet to be exploited for the removal of inclusions from silicon. Considering the increasing amount of Top-cut SoG-Si scraps year upon year, there is the need to harness all the potentials of technologies to recycle this materials to ensure sustainability. This study investigates, and discusses new results on the effect of processing parameters such as composition, coil current, and frequency on the removal of inclusions from silicon under high frequency AC electromagnetic field.IntroductionThe solar cell silicon making industry requires pure and clean silicon in order to maximize the conversion potential of the solar cell material. The conversion efficiency of solar cells is limited by minority carrier recombination at dislocations and those intra-granular defects such as impurities, small clusters of atoms, or precipitates [1]. Recent global developments in the energy sector with a drive for the production of clean, reliable, and affordable energy have stirred a rapid growth in the production of photovoltaic (PV) cells.[2] Thus over the years, silicon based PV cells has seen a lot of growth as it has a PV market share of over 90 % [3] either as single-crystalline silicon, or multi-crystalline Si (MC-Si), or amorphous Si [4]. MC-Si produced by directional solidification of solar grade silicon melt dominates the silicon PV market. During the directional solidification process, SiC and Si3N4 particles within the melt are pushed by the solidification front to the top of the ingot which is the last to solidify. Therefore the top of the ingot is cut generating what is known as top-cut solar silicon scraps. The Si3N4 particles are mainly from the coating material at the inside surface of the silica crucible and from the air absorption during solidification process. The SiC particles mainly stem from the carbon reduction process of the primary production of silicon [5]. For sustainability the silicon in the top-cut silicon scraps must be recovered. Therefore methods for removing non-metallic particles, such as SiC and Si3N4, from the silicon are important in order to recycle the top-cut scraps to a useful feedstock for the silicon solar cells manufacturing."

Jan 1, 2012

By Philip L. Sibrell

A new process utilizing pulsed fluidized limestone beds was tested for the remediation of acid mine drainage at the Friendship Hill National Historic Site, in southwestern Pennsylvania. A 230 liter-per-minute treatment system was constructed and operated over a fourteen-month period from June 2000 through September 2001. Over this period of time, 50,000 metric tons of limestone were used to treat 50 million liters of water. The influent water pH was 2.5 and acidity was 1000 mg/L as CaCO3. Despite the high potential for armoring at the site, effluent pH during normal plant operation ranged from 5.7 to 7.8 and averaged 6.8. As a result of the high influent acidity, sufficient CO2 was generated and recycled to provide a net alkaline discharge with about 50 mg/L as CaCO3 alkalinity. Additions of commercial CO2 increased effluent alkalinity to as high as 300 mg/L, and could be a useful process management tool for transient high flows or acidities. Metal removal rates were 95% for aluminum (60 mg/L in influent), 50 to 90% for iron (Fe), depending on the ratio of ferrous to ferric iron, which varied seasonally (200 mg/L in influent), and <10% of manganese (Mn) (10 mg/L in influent). Ferrous iron and Mn removal was incomplete because of the high pH required for precipitation of these species. Iron removal could be improved by increased aeration following neutralization, and Mn removal could be effected by a post treatment passive settling/oxidation pond. Metal hydroxide sludges were settled in settling tanks, and then hauled from the site for aesthetic purposes. Over 450 metric tons of sludge were removed from the water over the life of the project. The dried sludge was tested by the Toxicity Characteristics Leaching Protocol (TCLP) and was found to be non-hazardous. Treatment costs were $43,000 per year and $1.08 per m3, but could be decreased to $22,000 and $0.51 per m3 by decreasing labor use and by on-site sludge handling. These results confirm the utility of the new process in treatment of acid impaired waters that were previously not amenable to low cost limestone treatment.

Jan 1, 2003

By Takaaki Ishikawa

The distribution equilibria of lead, zinc and copper between CaO-Si02-Ah03 melts and liquid copper were measured at 1623K under a controlled H2-C02 atmosphere. The distribution ratios were plotted against the oxygen partial pressure, and reasonable oxide forms dissolved in the melts were estimated from the slopes of the plots. The activity coefficients of zinc oxide (ZnO), lead oxide (PbO) and cuprous oxide (CuOQs) increased with increasing slag basicity, defined by Xcao /XSiO, The temperature dependence of the activity coefficients was also measured.

Jan 1, 2003

By Takaaki Ishikawa

The distribution equilibria of lead, zinc and copper between CaO-Si02-Ah03 melts and liquid copper were measured at 1623K under a controlled H2-C02 atmosphere. The distribution ratios were plotted against the oxygen partial pressure, and reasonable oxide forms dissolved in the melts were estimated from the slopes of the plots. The activity coefficients of zinc oxide (ZnO), lead oxide (PbO) and cuprous oxide (CuO0.5) increased with increasing slag basicity, defined by XCao/Xsio2 The temperature dependence of the activity coefficients was also measured.

Jan 1, 2003

By Keith M. Axler

This report addresses issues specific to the generation of hydrogen fluoride via reaction of calcium fluoride with sulfuric acid. This process has been established on a commercial scale and is under consideration for treatment of calcium fluoride residues from uranium processing. Magnesium fluoride slags are also available as a product of uranium processing. The technique of using sulfuric acid for the production of hydrogen fluoride from magnesium fluoride is also under consideration as a residue processing scheme. In the current study, thermodynamic modeling was used to investigate these chemical processing systems. The results presented herein reveal information relevant to the selection of processing temperatures and conditions. Details include predicted effects in system composition based on operating temperatures for both the calcium fluoride and the magnesium fluoride systems.

Jan 1, 1996

By Sutham Niyomwas

Biomorphic Cellular TiCIC ceramics were produced by vacuum-infiltrating carbon preforms with Ti02 sol and subsequent synthesis by the carbothermal reduction process. The carbon preforms used in the study were obtained by pyrolysis of parawood and neem wood. The effect of infiltration time on the composition and microstructure of the biomorphic TiCIC ceramic was analyzed by X-ray diffractometry and scanning electron microscopy. The biomorphic structure of the TiCIC ceramic is consistent with that of the biotemplate natural parawood and neem wood.

Jan 1, 2008

By Laszlo Kadar, J. D. Lavers

"In the continuous casting of aluminum killed steel, the tundish nozzle often experiences clogging problems. Water model studies have shown that the clogging problem is dependent on the flow pattern in the nozzle entry region. In particular, the flow can separate at the entrance to the nozzle, leading to the development of a recirculation region. Although a nozzle can be designed such that no recirculation develops, even a small misalignment from the vertical positioning of the nozzle may render the design ineffective.To reduce the possibility of nozzle clogging, the recirculation zone must be reduced or eliminated. This may be achieved by moving the fluid downwards or raising the turbulence level in the separation region. In the case of a tundish nozzle, it is proposed that this can be achieved by using electromagnetic forces.To generate the required electromagnetic force, two systems are considered. The first is based on injecting a DC current; the second by using electromagnetic induction. Both methods are described in this paper. Order of magnitude calculations are provided to illustrate that both methods are essentially feasible. The performance of each method in terms of modifying the turbulent flow characteristics in the nozzle entry region is then examined using a numerical model. It is shown that both methods can greatly reduce the recirculation zone. A cylindrical nozzle was chosen for the model studies since it represents a worst case situation.On the basis of the model studies, it can be concluded that whereas both of the proposed methods have the potential to reduce the troublesome recirculation zone, the induction method appears to be simpler in terms of practical implementation."

Jan 1, 1999

By Li Kaihua, Li Liang, Miao Qingdong, Wang Cong

The current process of production of titanium sponge involves the use of TiCl4 as a feed material and a huge amount of heat is generated during the magnesiothermic reduction process. For this reason, it is possible to agglomerate into a titanium lump with the partial high temperature. And, it is difficult to obtain soft titanium sponge with low content of impurities. In order to solve the current problems in the titanium sponge production process, process optimization experiments study of TiCl4 feeding speed, vacuum distillation temperature, system pressure and time control had been conducted for obtain high quality titanium sponge. Experimental results show that lower feeding speed can improve the output capacity of titanium sponge and softer products can be obtained. The product grade rate of titanium sponge improved significantly.

Jan 1, 2015

By Chris Doyle

From 1997-2000. PT INCO undertook the Fourth Line Expansion Project (FLEX) to increase annual production rates from 90-100 to 150 Mlbs Ni/year (68,000 MT Ni/yr). In 2003, PT INCO nickel production underwent a major sustainable step jump that finally exceeded the targeted rate. This paper presents the changes that led to this achievement. The focus of mining changed. Improving Ni grade was important but only if electric furnace feed met target chemistry so that on-specification slag could be produced. The intensity of diamond core drilling for exploration was dramatically upgraded, mine planning strategy was totally re- vamped and an ore chemistry quality assurance team was formed. In the processing plant, measurement systems were upgraded for better control. Teamwork between sections vastly improved. The final step jump in production occurred when the fifth hydro-electric power generator was added to the furnace grid to allow the power-starved furnaces to cruise in operation at 70+ MW. Keywords: Free cash flow, Ore Chemistry, Measure, Control, Improve

Jan 1, 2004

By Osamu Takai, Yoshiki Sato, Nobuhiro Tajima, Hiroyuki Sugimura

"Amorphous carbon thin films doped with nitrogen ( a-C:N) have been synthesized by means of shielded arc ion plating (SAIP). Their electron field emission properties, that is, threshold field strengths for electron emission and maximum emission current densities, were evaluated and compared with those of pure amorphous carbon (a-C) films prepared by the same SAIP apparatus. Among all of the fabricated a-C:N films, the a-C:N films with a N concentration of 23 %, which prepared using Nz arc plasm at a pressure of 1 Pa with applying a sample bias voltage of -100 V, showed the lowest threshold filed of 13.4 V/µm and the highest emission current density of 1.87 µAfcm2 at a field of20 V/µm. These field emission properties of the a-C:N film were much better than those of the a-C films. The best results obtained on the a-C film in this study were the lowest threshold filed of 15.5 V/µm and the highest emission current density of 0.052 µA/cm2 at a field of 20 V /µm. Nitrogen doping to aC was found to be effective for lowering threshold voltage for field emission and for increasing emission current density. The electron field emission characteristics of the a-C:N films depended not only on N concentration but also on chemical bonding state of nitrogen in the a-C:N films. The presence of the ~-C3N4-like phase, which contributes to improve wear resistance of a-C:N as well, distinguished by the NlsXPS peak at 400.5 eV is proved to be crucial in order to enhance field emission properties of a-C:N.IntroductionThere has been much interest in electron field emission from a cold cathode due to its potential applications in vacuum microelectronic devices including field emission displays which are expected as flat panel displays in next generation [l]. It is well known that efficient emission can be rather readily realized using tip-like shape cathodes, e.g., microfabricated three-dimensional electrodes [2], carbon nanotubes [3-5], etc. However, electron emission from planar surfaces is of particular importance since such a type of cathode is· simply fabricated and assembled into microelectronic circuits. Currently, amorphous carbon thin films doped with nitrogen (a-C:N) prepared by plasma processes have attracted attention because their threshold voltages of field emission are relatively low [6]. Among various methods for preparing a-C:N films, the process using arc plasma is of special interest since, in arc plasma, nitrogen is highly activated and new types of carbon nitride phase are expected to be synthesized. However, field emission properties of a-C:N prepared by arc plasma have been studied in less detail compared with that prepared by the other methods such as sputtering."

Jan 1, 2000

By K. Sanjay

Factorial optimisation technique has been used to develop regression equations at different time intervals for extraction of manganese from precipitated manganese oxide/hydroxide in sulphuric acid using charcoal as the reductant. The three parameters chosen for a 23 full factorial design were : acid concentration, amount of carbon and temperature. The regression equations were used to predict >> 90% extractions as well as kinetic data.

Jan 1, 1996

By B. S. Terry

Experiments have been conducted to assess the feasibility of capturing bearing emissions arsenic with CaO during the roasting of enargite (Cu3AsS4). Enargite/CaO mixtures have been heat treated in air, nitrogen or oxygen for various times and the products of reaction analysed by X-ray diffraction and cleaned analysis. The results show that substantial capture of arsenic can be achieved via the formation of calcium arsenates and/or calcium arsenides. In addition significant capture of sulphur is achieved by the formation of calcium sulphate andlor sulphide. Complete conversion to copper sulphide with total removal of arsenic can be achieved within 30 minutes at 700°C. Further heat treatment in air or oxygen leads to the formation of copper oxide and copper oxysulphate. Without optimisation of reaction conditions, it has proved possible to achieve retention of in excess of 85% of the arsenic content of enargite in the form of calcium arsenates.

Jan 1, 1994

By D. Pradhan, R. G. Reddy

"Electrorefining of aluminum scrap was investigated from AlCl3 –1-Ethyl-3-methyl-imidazolium chloride (EMIC) (Molar ratio 1.65) chloroaluminate electrolyte using copper cathodes at temperature of 90±3°C and cell voltage of 1.5 V. The deposits were characterized using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The study was focused to determine the effect of electrode surface modification as well as deposition time on dendritic depositions of aluminum. Their effect on current density was investigated also. It was shown that the surface modification of electrodes reduced the dendritic depositions of aluminum. Pure aluminum (>99%) was deposited for all experiments with the current efficiency of 94-97%. The use of ionic liquids not only reduced the energy consumption but also minimized pollutant emissions (CO, CO2 etc.) compared to the commercial high temperature aluminum production.1. IntroductionAluminum electrorefining/recycling from aluminum scrap using ionic liquid electrolyte is an attractive process today because of the unique chemical and physical properties such as wide temperature range for the liquid phase, high thermal stability, negligible vapor pressure, low melting point and wide electrochemical window. But in conventional practice, melting of aluminum scrap and high temperature molten salt electrolysis makes this process more expensive and less energy intensive (average 13 kWh/ kilogram of aluminum) [1] . Although recycling scrap aluminum requires only 5% of the energy used to make new aluminum [1-2], but the green house emissions like CO2, CO and HF have to be counted for environmental reason. Approximately, 5.31 kilogram of CO2 emitted per kilogram of aluminum production in most of the US industries."

Jan 1, 2009

By Dai Xi

In the present work, the viscosities of molten FenO-MgO-SiO2 and FenO-MgO-CaO-SiO2 semi-synthetic slags for nickel flash smelting were measured in the temperature range from 1473 to 1723K by a rotational viscometer. The ratio of Fe to Si02 was fixed at 1.2, calcium and magnesium oxide contents varied in the range from 2 to 8 mass% and 9 to 12 mass%, respectively. The results showed that silicate anions became smaller by increasing CaO content, which results in a decrease of the viscosity of the slag. In the case of MgO addition the viscosity behavior was complicated. At MgO content below II mass%, the viscosity increased with the increase of MgO at all temperatures tested. However, when the MgO content was above II mass%, the viscosity decreased slightly for FenO-MgO-CaO-SiO2 system. At higher MgO contents, low-viscosity slags can be obtained by adding CaO. At a given composition, .the viscosity decreased with increasing temperature. The higher the temperature, the more MgO can be added before saturation. The effect of Fe3O4 on the viscosity was quite significant. The viscosity of slag increased by 300mPa-s at 1573K when Fe3O4 content varied from 3 to 9 mass%. The viscosity values are presented as the functions of temperature and composition. A comparison between FenO-MgO-SiO2 and FenO-MgO-CaO-SiO2 systems is given in this study.

Jan 1, 2003

By G. G. Richards

"The slag fuming process has operated for close to 70 years to recover zinc from lead blast furnace slag. The process is normally carried out through the batch treatment of slag by submerged injection of coal and air. Within the bath the coal acts as both a reductant, to reduce Zno to zinc vapour, and a fuel, to maintain bath temperature during the endothermic reduction process. The partition of coal between the slag, combustion and bypass is dependent on factors such as bath depth and injection pressure. The option of continuous fuming has been pursued at the D. Blagoev smelter in Bulgaria using heavy fuel oil as reductant/fuel. There has, however, been little attempt at commercial continuous fuming with coal. This paper presents an analysis of a coal-based continuous slag fuming furnace. The data on the Plovdiv fumer is used as a reference point. Critical design criteria for continuous fuming include the slag feed rate, degree of coal combustion and furnace size. Mathematical modelling analysis suggests that continuous fuming with coal can achieve respectable zinc/coal ratios.IntroductionThe slag fuming process was developed in the early part of this century to recover zinc from non-ferrous smelting slags [1-3]. The majority of installed furnaces were put in place to fume zinc from lead blast furnace slag on a batch basis. In most cases coal is used to effect reduction of zinc oxide, but one furnace uses natural gas [4] and, in a curious twist, a continuous fumer was developed based on fuel oil [5].Given the general nature of blast furnace lead smelting, it is not surprising that slag fuming has remained a batch process, in spite of the advantages that could be gained by moving to continuous fuming. Blast furnaces are usually operated as relatively independent units, and tapping has traditionally been done into ladles. The presence of a crane aisle makes direct coupling of the blast furnace to a slag fumer difficult, especially in a retrofit situation. Furthermore, steady-state blast furnace operation is not easy to achieve. The size of these furnaces and the nature of their feed make it difficult to guarantee constant operation."

Jan 1, 1996

By Christian Wögerer

For material or process development as well as for quality checking of materials, thermal diffusivity measurement may be the tool of choice in many applications. Especially if diffusivity is measured locally resolved, a lot of information can be read out of such a ?diffusivity image?. This paper explains the method to measure coplanar specimen like plates and lists some interpretations of diffusivity images, like inhomogeneity of sintered materials, structural voids or inclusions. Diffusivity is a material property, describing transportation of heat in solids in spatial and temporal terms. With thermo cameras it is possible, to measure diffusivity of larger areas simultaneously. The result is an area of diffusivity values that may be plotted or displayed like an image. Locations with lower diffusivity values could be caused by the presents of structural differences in the material, by decomposition of the material components or by inclusions of other material like air.

Jan 1, 2009