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By Varadarajan Seshadri

A physical model based on similarity principles was constructed for simulating the RH degasser of CST (Companhia Siderurgica Tubarao, Vitoria, ES, Brazil) to evaluate the circulation rate of the metal which essentially defines the degree of exposure of the metal to vacuum in the chamber and thus of the refining rate. The circulation rate on the other hand will influence the decarburization rate and removal of dissolved gases like nitrogen and hence it is essential to optimise this parameter to get maximum refining efficiency with minimum refming times, thus improving the productivity of the secondary refining process. Mixing characteristics in the ladle is evaluated by pulse tracer addition using conductivity-meters located at the down leg as well as at several locations in the ladle. The influence of gas injection through nozzles in the upleg with simultaneous bottom injection of gas as well as nozzle blockage on the circulation rates were investigated. Also simulation experiments of kinetics of decarburization were carried out using C02 adsorption-desorption process in sodium hydroxide solution as circulating fluid and the effect of, bottom gas flow rate in this case was also evaluated. The results were carried over to prototype and to optimize the process.

Jan 1, 2003

By Lev Levin, Sergei Lesokhin

"The formation of titanium carbide during hot filament assisted carburizing of NiTi alloy was investigated. Phase content and morphology of the diffusion zone were examined by X-ray diffraction, X-ray microanalysis, SEM, and Auger electron spectroscopy. The growth of stable and adherent TiC film was observed. A non-planarity of interphase boundary was noticed. The applicability of the chemical diffusion approach to the analysis of the experimentally observed interface instability is discussed. A criterion, taking into account the influence of growth stresses on the stability of the flat interface, is developed by means of linear perturbation analysis.Introduction.Equiatomic intermetallic NiTi belongs to a class of materials exhibiting the shape-memory effect. The unusual property of this compound promotes its application in many fields, from aerospace technologies to medicine. The relatively high ductility ofNiTi also permits its use as a matrix material in metal-ceramic composites. The objective of this work was to investigate the possible incorporation of a ceramic material (titanium carbide) into NiTi by gas carburizing.Free energy calculations indicate the potential to obtain TiC by carburizing Ni-Ti binary phases. The main obstacle to such a process is the high affinity of titanium to oxygen. At moderate temperatures the formation of TiC is preferable to titanium oxidation only if the partial pressure of oxygen is extremely low [1]. This problem was overcome in this work by the use of hot filament assisted gas carburizing. Due to chemical reactions occurring near the hot filament, the gas mixture, initially consisting of methane and molecular hydrogen, was enriched by atomic hydrogen [2], drastically decreasing the content of free oxygen in the carburizing atmosphere.The second part of this article concerns the theoretical analysis of reasons that lead to the development of the experimentally observed morphology of the diffusion zone. In particular, the influence of the growth stresses on the morphology of an interphase boundary is investigated."

Jan 1, 1996

By Elias Rigopoulos

In the present study the reductive behavior of dust from the rotary kilns (RK), in ferronickel production from nickeliferous Greek laterites, is investigated. The study concerns dust of various origins (washing towers, electrostatic filters, polycyclones) and pellets made from the dust. Reducibility was studied in the temperature range of 700 °C to 850 °C in a laboratory tube furnace. Experimental results showed that reduction degree increases with temperature up to about 800 °C. The rate of reduction is great during the first minutes, giving a reduction degree R% equal to about 25%, in only a few minutes. After this, the rate is decreasing until it diminishes to zero after about 10-20 minutes of reaction. Maximum reduction degree achieved is 26 to 28%. Rates and reduction degrees at various temperatures are higher for the dust samples than those of the respective pellet samples. Keywords: Ferronickel, metallurgy, laterites, pellets, reduction

Jan 1, 2004

By J. L. Holman

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

Jan 1, 1987

By P. G. Comba

Many gold producing states are requiring rinsing of spent heaps to render the leached ore compatible with the environment and are placing restrictions on effluent pa, cyanide, and metals concentrations. Parameters which may affect efficient rinsing of heaps have been investigated by the U.S. Bureau of Mines in laboratory column studies. Rinse profiles for cyanide, metals, and pH as a function of the volume of water passed through the spent ore are presented. Fresh water rinsing of spent ore in columns showed that rinsing of cyanide was not affected by the rinse solution application rate. Interrupted rinsing with a rest period between applications reduced the volume of water required to meet effluent cyanide concentrations. chemical oxidation of the effluent with recycle of the rinse solutions reduced effluent cyanide concentrations and the volume of waste solution generated. Water rinsing was not successful in reducing the alkalinity of the cement agglomerated ore. A dilute acid solution had to be applied after cyanide removal to reduce effluent pa levels to specified limits.

Jan 1, 1992

By James E. Simpson, Suresh V. Garimella, III de Groh

"An experimental and numerical study of the horizontal Bridgman growth of pure succinonitrile (SCN) and of a succinonitrile-1.0 mol. % acetone alloy (SCN-1.0 mol. % ACE) has been performed. Experiments at growth rates of 0, 2 and 40 µmis were investigated. The solid/liquid interface was stable (non-dendritic and non-cellular); however, it was not flat. Rather, it was significantly distorted by the influence of convection in the melt and, for the growth cases, by the moving temperature boundary conditions along the ampoule. For the alloy, the interface was determined to be unstable at growth rates greater than 2.8 µmis, but stable for the no-growth and 2 µmis growth cases. When compared to the pure SCN interface, the alloy interface forms closer to the cold zone,· indicating that the melting temperature has been suppressed by the addition of the alloying element. Two-dimensional computer simulations were performed for the no-growth case for both the pure and alloy materials. These simulations indicate that a primary longitudinal convective cell is formed in the melt. The maximum magnitude of velocity was calculated to be 1.515 mmls for pure SCN and 1. 724 mm/s for the alloy. The interface shape predicted by the computer simulation agrees well with the experimentally determined shape for the pure SCN case. In ongoing work, numerical simulations of the process during growth conditions are being performed.IntroductionIncreasingly, advanced materials used in the aerospace, automotive, optics and electronics fields require low levels of defects and high levels of solute uniformity. Directional solidification by the Bridgman process is widely used for synthesis of these high-quality materials. During Bridgman crystal growth, heat and mass transfer by both thermal and solutal gradient-driven convection and diffusion influence the shape of the solid/liquid interface and dopant segregation levels, and hence, directly determine the final crystal quality. Key process parameters include the applied furnace temperature distribution and rate of translation, ampoule properties and furnace orientation."

Jan 1, 1999

By V. A. Luganov

The behavior of arsenopyrite under heating has been studied by many scientists. It has been already established that under heating at more than 650°C and without air access the arsenopyrite dissociates with the formation of one atom arsenic. Under vacuum the dissociation process begins at 550 DC with the formation of elemental arsenic. The residue of dissociation process contains pyrrhotite and throilitc. In the presence of pyrite, arsenopyrite dissociates under lower temperature and with a higher velocity than without it. The industrial realization of fool scale processing of arsenic bearing raw materials is possible only by the use of standard equipment and oxygen containing blast In this view the paper presents the results of the study on the effect of oxygen in the gaseous phase and its addition into the charge of pyrite in the process of arsenopyrite decomposition. Thermodynamic analyses showed that under thermal processing of arsenopyrite in the presence of pyrite and limited quantities of oxygen in the gaseous phase the formation of arsenic sulfides is possible according to the following reactions:

Jan 1, 2003

By Nagy El-Kaddah

One of the emerging technologies for the production of ultra-clean metals is electromagnetic filtration. The theory and the mechanism of electromagnetic separation of inclusions from molten metal are briefly reviewed along with basic electromagnetic separation systems. This paper focuses on inclusion removal in the induced current separators, with specific reference to a new separator developed at the University of Alabama. A simple analytical model is presented for the analysis of particle separation in such a system. The role of the applied magnetic field on inclusion removal will be discussed. It is shown that particle velocity increases exponentially with increasing magnetic field strength. At moderate field strengths, the velocity of 50 to 100µ inclusions are an order of magnitude larger than those achieved by buoyancy. The separator developed at the University of Alabama is described together with experimental results of laboratory and large scale experiments on purification of molten aluminum. These results demonstrate ?the capability of the system for producing super-clean metals.

Jan 1, 1996

By S. Agatzini-Leonardou

The objective of this work was to prove repeated loading capacities and investigate the selectivity of physically stabilized algal biomass from Spirulina platensis and Chlorella sp. for the removal and recovery of cobalt, nickel and chromium from laterite heap leach liquors. The testwork was carried out on a bench scale in small glass columns and proved that it was possible to immobilize the biomass on the highly porous surface of pumice stone (kissiris). Nickel and cobalt could be removed from pure aqueous solutions of each metal by the immobilized cyanobacterial biomass. Nickel and also cobalt biosorption was sensitive to the initial solution pH. Cobalt recoveries up to 80% were achieved after 5 loading cycles, from low concentration solutions, at pH 6.0. Nickel removal was complete under the same conditions, whereas chromium sorption was ineffective. Desorption of the metal loaded columns was effected by dilute sulfuric acid. The algal species giving the best adsorption capacities for the metals under consideration was selected for further experimental work with real laterite heap leach solution produced by column leaching. A statistical analysis of all obtained results was conducted using the fraction of metal removed as response. The ratio "mass of metal removed to mass of protein contained in the immobilized cells" was determined as well. The described method might be applicable for recovery of cobalt and nickel from diluted laterite heap leach solutions, such as heap wash waters, or for their removal from waste streams of a hydrometallurgical extraction process.

Jan 1, 1997

By S. P. Mathew

The ISASMELT Lead Process is a continuous two stage process for the production of crude lead from concentrate. It is based on the use of a top entry submerged Sirosmelt lance to produce turbulent baths in which high intensity smelting or reduction reactions can occur. The process involves oxidizing the concentrates in the first stage to produce a high lead slag. This slag is tapped continuously and transferred down a launder to a second furnace where it is reduced with coal. Crude lead and discard slag are tapped continuously from this furnace through a single taphole and separated in a conventional forehearth. Process and engineering design work for a commercial scale Lead ISASKELT plant designed to produce 60000 tpa crude lead has been completed. This plant is planned to be operational in 1991.

Jan 1, 1990

By Takeshi Nagano

Copper pyrometallurgy in Japan has experienced quite fundamental changes in last fifteen years. The severe environmental restriction coupled with increase of energy costs accelerated the development work of the new continuous process in Mitsubishi Metal Corporation. After several years of pilot plant test work the commercial plant was put into operation at Naoshima Smelter in 1974, the design capacity of which was 4,000 tonnes of copper per month. Many modifications and improvements have been incorporated into the process and 7,200 tonnes per month of copper production was achieved in 1983, proving that continuous process was much more economical than conventional process. It is now possible to design and operate the continuous process in wide range of capacity. This paper will review the process and describe the progress of the process in these 10 years. 311

Jan 1, 1985

By Tetsuro Ohashi, Tooru Matsumiya, Yoshio Abe

"The three-dimensional deformation of a continuously cast slab was modeled into two-dimensional deformation by developing the solidified shell of the slab. The developed solidified shell was divided into rectangular elements. The thermal strain produced as the slab is wi thdrawn over one roll spacing in the casting direction was calculated from the temperature change during that time and the increment of the geometrical unbending strain during the time was calculated from the change in the radius of curvature of the slab by assuming that the neutral axis of bending is located at the mid-thickness of the slab and that the transverse section of the slab is kept in a plane during unbending. These strains were imparted to each element as initial strains. The interaction between the elements and the overall deformation of the solidified shell were analyzed by the finite element method.The analysis was performed on a slab being cast on a machine of the circular arc type with progressive unbending. The following findings were obtained as a result. The effect of unbending is spread in the upstream and downstream directions of the slab by the shear deformation of the narrow and wide faces. As the shear deformation increases, the strain in the unbending zone decreases and the strain outside of the unbending zone increases. The effects of secondary cooling conditions, slab size, radius of caster circular arc section, compression casting, etc., were also analyzed. IntroductionTo develop a method for preventing the internal cracking of continuously cast slabs, it is important to acurately analyze the deformation of the slab and this subject has been extensively investigated. Many researchers, including the present authors, have analyzed slab bulging. (1)- (11) Analysis has also been made of thermal deformation that assumes importance in continuous casting of small-section blooms.(12)-(18) However, unbending deformation, an extremely important subject for continuous casters of the circular arc type, has not been fully analyzed."

Jan 1, 1986

By Zhang Yongzhu

The metallogeneticy and mineralogy of three types of Chinese refractory gold deposits (Au-As; Au-As-MeS; Au-As-C) which are somewhat different from those abroad are discussed. The modes of occurrence, the distribution of grain size, and the morphological features of gold in minerals and their influences on gold recovery by direct cyanidation are also discussed. According to the mineralogy of gold and minerals, bacterial leaching, pressure leaching and roasting technology are suitable for the pretreatment of arsenopyrite-Au, pyrite-Au and carbonaceous-clay-Au refractory gold ores prior to cyanidation, respectively. The most important sulfide pyrite bearing much gold is difficult to be oxidized, its crystalline structure, conduct-types , and minor elements in different mineralizing stages are also discussed. The pyrite aggregates in different deposits are very complicated and much different. Gold grade of arsenopyrite is much higher than that of pyrite for some deposits which have a high correlation coefficient of Au vs As.

Jan 1, 1992

By Tianming Sun, Gabriella Tranell, Ragnhild E. Aune, Mark William Kennedy

Rare Earth Elements (REEs) are critical for the production of many advanced materials and products. Mining and primary production of REEs are generally associated with significant environmental impacts. By recovery of REEs from secondary sources, through recycling or as a byproduct, the adverse environmental impacts may be partly avoided. In the present study apatite concentrate originating from iron ore beneficiation done by LKAB in Kiruna, Sweden, is explored as a possible source for REEs. The composition and distribution of the REEs within the concentrates are studied using ICP-MS, XRD and SEM-EDS/EPMA, as well as the melting point and heat of fusion using DTA-TGA-MS. The behavior of the material during melting has also been studied through wetting and slag saturation experiments. The overall aim of the study is to evaluate the implications for future smelting experiments aimed at concentration and recovery of the REEs.

Jan 1, 2015

By Bing Gao, Zhe Wang, Xiangdong Xing, Xueqi Zhang, Shan Ren, Jianliang Zhang

"In sintering, the flame front speed (bed permeability) and sinter qualities are greatly depended on the feed size, especially coke breeze and limestone particle size. It is well known that coke breeze provides sinter bed with heat to meet the demand of partial fusion and diffusion bonding while limestone reacts with iron ore to generate bonding phase in the sintering process. Accordingly, it is necessary to find the optimum combination of different particle size of coke breeze and limestone to yield sinter associated with better qualities. In this study, sinter was produced in the sinter pot with varying coke breeze and limestone particle size together in sintering of a coarse hematite iron ore. The sintering productivity was measured and all of the result sinters were examined by microstructure analysis and reduction degradation test (RDI test). For the sintering of a coarse hematite iron ore, it was found that the optimum mean particle size combination of coke breeze and limestone was 1. 71mm and 1.55mm in the sinter mix. On such a circumstance, sintering productivity was higher and the properties of sinter were better.IntroductionNowadays, as the main iron bearing burden material of modem blast furnaces, sinter has a great influence on the blast furnace operation. Sintering is a greatly complex process involving various chemical reactions to form kinds of mineral phases [1, 2]. In the sintering process, coke breeze is used for fuel and it generates heat to raise the green bed temperature. Limestone serves as flux and it reacts with iron ore to produce various mineral phases. On one hand, during the sintering process, the particle size of coke breeze can have an effect on temperature, atmosphere, the flame front speed and all of them act on the microstructure and mineral constitutions of sinter [3, 4]."

Jan 1, 2013

By B. Mishra

The application of various bydrometallurgical, pyrometallurgical and electrochemical processes in the extraction, purification and production of radioactive metals as well as the use of various materials, eg. metals and alloys, ceramics, polymers, etc. in the process, construction and handling equipment in the nuclear industry has generated a large stockpile of radioactively contaminated waste material and scrap metal which can not be directly discarded, recycled or considered for long-term storage due to its volume and potential hazards, without the separation of radionuclides. This paper reviews the emerging methods that have been 'investigated and suggested for dealing with some of these wastes' and scrap material. The separation technologies studied for the recovery of radioactive components from the pyrometallurgical and electrochemical processing wastes have been discussed in details with results from some of the recent theoretical and physical modeling work as well as the data obtained? from the actual waste treatment. Specific processes shall be described in terms of its advantages and limitations. These emerging separation technologies are being considered by the US Department of Energy as alternatives for dealing with the issues of environmental management [EMI' and decontamination and decommissioning [D&D].

Jan 1, 1996

By Tapio Ahokainen, Asmo Vartiainen

"Outotec's portfolio contains a wide variety of smelting solutions for non-ferrous metals. Some of these include flash smelting for primary copper and nickel, flash converting for copper, Ausmelt technology for primary and secondary copper, nickel, tin, lead, and zinc residues and waste, Kaldo technology for secondary copper, lead, and precious metals recovery. Outotec also offers slag cleaning technologies and much more.Company provides complete process solutions tailored to each customer's individual needs. Decades of experience have resulted in extensive metallurgical know-how that ensures the most profitable process choice and optimal performance. Outotec's life cycle technology partnership with their customers spans from the early stages of process solution design through the supply and commissioning of the entire process chain. They include integrated process control and holistic service and support concepts. Continuous research and development ensures that the customer is provided with the latest advancements in process and equipment solutions.IntroductionOutotec develops and provides technology solutions for the sustainable use of the Earth's natural resources. Solutions are ranging from various processes and special equipment needed for metallurgical extraction and mineral processing of ores to the production of refined metals and minerals. The processes include not only the grinding and physical separation of ores but also the smelting and leaching of base metals and precious metals. The company provides engineering services for whole projects as well as life cycle services on the equipment and products that they supply."

Jan 1, 2012

By J. T. I. Poijärvi

Outokumpu Harjavalta Metals Oy operates copper and nickel smelters, three sulphuric acid plants and nickel refinery at Harjavalta and copper refinery and precious metal plant at Pori. The by-products of these plants are presented in this paper. The by-products of the smelters include products from slag cleaning of flash smelting furnaces and converters, flue dusts and smelter off-gases. Weak acid and sludges from cleaning of smelter off-gases and acids are the by-products of the acid plants. The by-products out of the copper refinery are crystallized metal sulphates and sludges from electrolyte purification, on which a co-production process of the copper tankhouse is based. The main by-products of the precious metals plant are products from anode slime treatment and platinum metal group concentrates in the recovery of precious metals. Sludges from nickel matte leaching and precipitates from solution purification are the by-products of the nickel refinery. The formation, treatment and processing as well as the research work done for the utilization instead of dumping of the by-products in the production of copper and nickel will also be discussed in this paper.

Jan 1, 1995

By Chonghun Han, Tae-Hwa Choi, Young-Hwan Chu

"A statistical optimization method is proposed to maintain stable operation in a blast furnace with stave coolers. The objective of this study is to find the operating condition which maximizes productivity as well as minimizes the heat load on the stave coolers. In this method, we first analyzed historical data and calculated the heat flux of stave coolers and the burden distribution by mathematical models. In this approach, we determined the variables to optimize and manipulated variables to adjust these response variables. Next, we collected the necessary data for the data variables after preprocessing such as removal of noise and outlier. Finally, we constructed empirical models describing the patterns of response variables in terms of manipulated variables by partial least squares regression method, and then these models were used as objective functions for entire optimization problem. By using appropriate optimization algorithm, we determined the compromised optimum operating condition considering all response variables from the past operating conditions.IntroductionBlast furnace operation which is accompanied by complex physical and chemical phenomena is an essential process for steel industry. In this process, iron ore which is charged into the blast furnace from the top goes downward. It is reduced to iron by CO gas and is melted by the heat of combustion of coke and pulverized coal. The pig iron is tapped at the bottom in liquid phase after removing the slag, which floats on the pig iron.The cooling equipment of the blast furnace wall is changed from the plate type to the stave cooler recently. In order to cool the shell uniformly and eliminate shell spray cooling, Pohang No.2 blast furnace of POSCO (Pohang Iron & Steel Company) was equipped with 11 rows of stave coolers. These staves are only 350mm-thick including the 170 mm-deep refractory on the hot face."

Jan 1, 2001

By Dai Yongnian

The methods of treating zinc crust and its development in the last hundred years are compared and reviewed. There are better effects from normal pressure metallurgy turned into vacuum metallurgy. The traditional methods dezinc only. But we must consider that delead on further step. From lab tests to industrial scale experiment are researched. The first step-dezinc, second-delead, crude ,metal of, zinc, lead and silver are produced, The flowsheet of treating zinc crust are simplified, material consumption reduced, work condition improved, environment protect mended. This method is pointed out that its application can be expanded.

Jan 1, 1992