Search Documents

By Luben Xie, Lin Hu, Qiang Wang, Min Gan, Tao Jiang, Wenqi Li, Xiaohui Fan, Zhiyuan Yu

"Crystal precipitation behavior of calcium ferrite (CF) during iron ore sintering process along with the effect of cooling rate, SiO2 and Al2O3 on crystalline condensation were studied. The results show that CF, has strong ability of precipitation. The precipitation is barely affected by extenal factors. It begins to precipitate when the liquid phase cools down to about 1200oC. CF could crystallize rapidly at the cooling speed of 150 °C /min. Furthermore, decreasing of the cooling rate favors the development of crystal. Binder phase transformed from CF system to silicate system when SiO2 content was increased to 5~6%, with a constant basicity (R) 2.0. Increasing Al2O3 content could promote the precipitation of CF and the development of crystal.IntroductionCrystalline condensation is the last stage of sinter mineralization. It includes the processes that crystalline substance and amorphous substance precipitate from high temperature solution phase and the consolidation of material when melt cools down. During the crystallization process, minerals precipitate following the order from high to low melting point coupled with the decreases of free energy. Most of binder phase minerals and part of iron oxides crystallize in this process, which have an important influence on mineral composition and microstructure of sinter. They finally determine the sinter strength and metallurgical properties."

Jan 1, 2011

By Renato G. Bautista

The chemistry of the separation of metals from each other and from the other undesirable components involve multiple simultaneous chemical reactions. In the case of leaching, the heterogeneous chemical reactions between the solid and the liquid phase may be limited to a few reactions. In the homogeneous liquid phase, the number of simultaneous chemical reactions could be double or triple that of the number of heterogeneous reactions:. The rate of dissolution becomes very dependent on the changing concentrations of the significant chemical species taking part in the multiple reactions in both the heterogenous and homogeneous phase. The rate expression developed for the process must take into account the mechanism of chemical reactions in order to best represent the actual process. This paper also examine the role of mass transfer with chemical reaction in the develpoment of the rate equations for dissolution, liquid-liquid extraction, membrane separation, precipitation, and electrodeposition.

Jan 1, 1996

By Suzanne Young

The effect of LiF additions on liqt.1id1.:1s temperature and electrical conductivity over a wide range of cryolite bath ratios (1.0 to 1.5 weight ratio) was investigated. Results did not agree with multi-regression equations reported by Dewing and Choudhary over the entire region. New regression equations were developed. Reasons? are given for the differences. The models are used to discuss the economic implications of LiF additions to Hali cell electrolytes.

Jan 1, 1985

By D. J. Webb, D. G. Reynolds, D. W. Ashman, D. W. Goosen

Cominco Limited operates an integrated zinc-lead complex at Trail, British Columbia, Canada. Central to the successful operation of this complex is the treatment of zinc leach residues through the lead smelter. In 1997, Cominco started up a new lead smelter using KTVCET flash smelting, a state-of-the-art conventional slag fuming furnace, and a new drossing plant. The smelter has fully met the requirements for environmental performance, reduced energy consumption, and lowered labour costs. This paper provides a description of the new smelter and discusses the problems encountered during the start-up, as well as the solutions to those problems. Recent operating results are presented. Lead-Zinc

Jan 1, 2000

By J. D. Miller

Gold adsorption from cyanide solutions by activated carbon has been studied at great length during the past decade. Findings from past research are reviewed and discussed with respect to structural features of various carbons, including carbon black, activated carbon, graphite and diamond.

Jan 1, 1991

By M. Furuta, M. Hasimoto, Y. Komoda, K. Haiki

"Tamano Smelter & Refinery started its operation in 1972 with high current density electrolysis (350Nm2 of maximum) applying PRC technology. After the start up, four times of expansion have been done, the cathode production capacity has increased from- 84,000 t/y to 191,000 t/y. However, recent refining technology with permanent stainless steel cathode enabled to increase current density up to 300 Nm2 or more without PRC method. In order to increase current density more than 350 A/m2 , experimental work using commercial size cell has been carried out at several conditions, such as current density, PRC conditions, electrolyte composition and electrode condition. As a result, it was found that high quality (LME A grade) cathode can be produced at such a high current density as 405 A/m2•IntroductionWhen considering the production increase of electrolytic copper, what becomes important is the improvement of productivity per unit of production facility. Conventionally, production had been expanded by increasing the number of cells but a huge investment required for this had a influence to the business profitability. Because of this, increase of current density, which is one of the methods to improve unit productivity, 'was expected and this method at the same time has another advantage of shortening the retention time of copper and other precious metals in the cells. At present, the average current density at Tamano during full capacity production is around 350 A/m2 and this used to be the limit throughout the world (1)."

Jan 1, 2000

By C. M. F. Vieira

The main characteristics and physical and mechanical properties of clays from the county of Campos dos Goytacazes, located at the northern part of the State of Rio de Janeiro, Brazil, are presented. The characterization included mineralogical composition, chemical composition and particle size distribution. The properties related to water absorption, linear shrinkage and flexural rupture strength were obtained in samples that were prepared by 20 MPa uniaxial pressing and fired at 950 and 1100oC. The results showed that the clays are predominantly kaolinitic with high percentage of clay minerals. The kaolinitic structure associated with a small amount of fluxes confers a refractory behavior which makes difficult the sinterization and impairs the ceramic consolidation.

Jan 1, 2009

By Dianyuan Dang, Guihong Han, Wenjuan Wang, Tao Jiang, Yanfang Huang

In this study reduction kinetics and swelling behaviors in "two-step process” were investigated by weight-loss technique and visualizing physical changes of pellet. Results showed that reduction degree (r) increased with increasing temperature and time. According to the dynamic calculation, when reduction temperature was lower than 1000°C the reduction process was controlled by chemical reaction with apparent activation energy of 72.27 kJ/mol. When reduction temperature was higher than 1000 , the equation of t/[1-(1-r)1/3] against [1+2(1-r)-3(1-r)2/3]/[1-(1-r)1/3] followed straight lines, demonstrating that reduction was mixed-controlled. Swelling experiments indicated that the maximum swelling index increased with the increase of reduction temperature and CO content.

Jan 1, 2016

By Irshad A. Rana

In a modern copper smelter, the capital cost of a sulfuric acid plant constitutes the largest single cost item of the total investment. It is thus essential to properly size the acid plant in order to reduce its capital cost and enhance the economic viability of a new smelter project. Whereas the off-gas from a smelting furnace is continuous and generally uniform, the gas flow from the Peirce-Smith converters is intermittent with significant fluctuations. The converters off-gas volume is dependent upon a number of interrelating factors. The most significant factors are the matte feed grade, the system air infiltration, the converter's size and blowing rate, the maximum number of converters simultaneously blowing and the gas cooling system employed. The acid plant size, therefore, is heavily influenced by the converter off-gases. Several of these factors are discussed, and their impact in determining the acid plant size is explored.

Jan 1, 1993

By Masatoshi Ogasawara

Saganoseki smelter & refinery operated two flash smelting furnaces, producing a combined 330,000 metric tons per year (hereinafter mtpy) of copper. [n 1996, however, it successfully shifted to a single fumace operation while maintaining production at the same level. Since then, the production capacity has been further increased to the present 470,000 mtpy by technological improvements. Also, in order to reduce the converter load which represents a bottleneck in efforts to increase production, the matte grade was gradually increased and currently runs at 65 to 66% attaining the low copper content in the slag (hereinafter slag loss) of 0.7 to 0.8%. This ' paper introduces some improvements, recent operation results and thermodynamic analyses.

Jan 1, 2003

By D. L. Jones

The leaching of natural chalcopyrite was studied in both ferric sulfate and ferric chloride solutions. The chemistry of the two reactions is quite different, with substantial sulfur oxidation occurring only in sulfate solutions. Ferric chloride is a more effective reagent, for the leaching rate is greatly increased with finer particles and higher (Fe+++), and unaffected by high (Fe++); none of these advantages are found with ferric sulfate. In addition, the morphology of leaching appears to be different, with ferric sulfate leaching preferentially along fissures or grain boundaries. The kinetics were found to be linear over an extended period, rather than parabolic as reported elsewhere. An explanation of the observed phenanena is proposed using the electrochemical theory of leaching, and experimental measurement of the mixed potential of the mineral during leaching.

Jan 1, 1976

By Nicholas E. Vanderborgh

Projections show that domestic coal will serve for the majority of energy supplies during the next decades. Thorough chemical cleaning of this coal can be accomplished in long-residence time, slurry-transport systems to produce high-quality fuel product. Concurrently, mineral recovery from coals will supplement existing ores. This paper describes this concept and gives preliminary engineering considerations for mineral recovery during transport operations.

Jan 1, 1982

By A. Patti, S. Reutzel, D. M. Herlach, L. Ratke, I. Egry

Cu-Co shows a metastable miscibility gap in the region of the undercooled melt. Undercooling of the melt below the binodal leads to separation of the melt into a Co-rich LI-phase and a Curich L2-phase. Experimentally, undercooling into the metastable miscibility gap is realised by means of electromagnetic levitation (EML), processing in drop tube (DT) and by melt flux embedding. As undercooling is large in these experiments, the velocity of the solidification front is high and the microstructure is frozen in instantaneously. Samples have been undercooled and solidified in the TEMPUS-facility (container less electromagnetic processing under weightlessness) during parabolic flight under reduced gravity conditions. Microstructures of solidified samples have been analysed and compared to those processed under gravitational conditions. The influence of convection on phase growth is much lower in reduced gravity. The microstructure shows spherical droplets of the minority phase, statistically dispersed in the majority phase.

Jan 1, 2004

By Omid Marzoughi

In this research, both the kinetics and the mechanisms of the roasting of a sphalerite concentrate from the Bafgh mining complex in Iran were investigated. The oxidation process was performed in a muffle furnace in air and the effects of time and temperature on the degree of oxidation of the zinc sulfide sample were quantitatively studied. The experimental data were fitted to the shrinking core model. In the temperature range of 650–800 °C, the rate-controlling step was the chemical reaction between the zinc sulfide and oxygen with an activation energy of 103 kJ mol−1. On the other hand, in the temperature range of 850–950 °C, the rate-controlling step was oxygen diffusion with an activation energy of 50 kJ mol−1. Also, the roasting process was studied using thermogravimetric (TGA) and derivative thermogravimetric (DTGA) techniques.

By Tracy Lucas, Ian Hamill

"Issues of importance in the area of continuous casting centre around product quality. This can be affected by particle inclusions transported into the mould from upstream processes and by draw-down of particles from the meniscus. Turbulence of the meniscus can increase the latter and is also detrimental to product surface quality.Suitably validated Computational Fluid Dynamics (CFD) modelling can provide the operator with an efficient tool with which to investigate the effects of changes to the design and operation of the caster and associated plant.In this paper, examples are presented of the use of the CFD software, CFX, to simulate:•,free-surface shape and turbulence in the mould using deforming meshes•,solidification in the mould using a fixed-grid, source-based method•,argon gas injection through a submerged entry nozzle using a full multiphase model•,inclusion motion and removal in tundishes using an algebraic slip model.The CFD simulations of the free surface shape are complemented by detailed Particle Image Velocimetry measurements performed on a full-size water model of a thin-slab mould and upper strand. Close agreement is demonstrated between the predictions and experiments."

Jan 1, 1999

By Shengli Wu, Wei Huang, Xinliang Liu, Kaifa Zhang

The slagging behavior, the phase of primary blast furnace slag and its transformation law of structure for the single furnace burden were studied in this paper. The results showed that the formation of primary slag was controlled by CaO/SiO2, Al2O3 content, MgO content, reducibility, iron content and porosity of the furnace burden. Fayalite (2FeO•SiO2) was easily formed from acid ferrous furnace burden while kirschsteinite (2(Fe,Ca)O•SiO2) was produced from alkaline ferrous furnace burden

Jan 1, 2015

By Jiang Fan, Liu Shi, Wang Haigang

Winter-time natural convection in gravel embankments has been suggested as a technique to provide passive cooling and thereby avoid thaw-settlement of roadways located in permafrost areas. Numerical simulation by finite volume method on the proposed model is perf9rmed using the software FLUENT. A gravels model, in which the embankment is composed of stones and air, has been adopted to investigate the temperature and velocity fields in embankment. Simulation results show that in summer, a weak clockwise circulation of the pore air extending throughout most of the embankment. The pore-air motion is very weak which results in relatively straight horizontal isotherm lines. And heat transfer is mainly maintained through conduction. But in winter, pore-air velocities are higher and multiple vortexes are formed in the embankment. Natural convection then becomes the dominant influence on the isotherm shapes within the embankment. As a result of low ambient temperatures exerted on the embankment surface during winter months, an unstable air density gradient develops within the embankment. This convection increases the heat flux out of the embankment. Therefore, the winter-time convection can further reduce the temperature of the foundation soil beneath the open-graded embankment. In addition, the effects of the size of the stones within the embankment have been analyzed and compared in the gravel model. It shows that in winter, 200mm stones lead to stronger vortexes in the embankment compared with those of 60mm stones. Consequently, the zone oflow-temperature beneath the embankment is extended.

Jan 1, 2004

By Harald Laux, Stein Tore Johansen

The plunging jet in tapping of steel from converters or electric arc furnaces entrains gas into the steel bath contained in a ladle. Gas entrainment rate and the effect of the gas on the flow pattern in the ladle are studied by means of Computational Fluid Dynamics CFD. The work focuses on the mathematical modeling. Two numerical methods, one for free-surface flows and one for dispersed multiphase flow are combined. A transport equation for the average bubble diameter that incorporates the effect of coalescence and breakup is presented. Results from computations for one ladle and tapping configuration are shown. Our findings indicate that the gas entrainment rate is affected by the material properties of the liquid in the sense that the material properties determine the shape of the jet. Moreover, bubble sizes in the range of two-orders of magnitude are predicted in the ladle. The dispersed diameter model seems to work well. It showed the expected response to material parameters and the turbulent field. However, the presented analysis is just a first step that was limited due to certain simplifications. In order to obtain better insight in the tapping process improvements of the analysis seem necessary.

Jan 1, 1999

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 W. Hoffelner

Plasma technology has become increasingly important for the treatment of several types of waste (toxic, nuclear, metal-bearing scrap). Plasma furnaces combine the advantages of a closed hearth process with a very versatile (several plasma gases can be employed) and effective heat source. It can be successfully used for recovery of metals with subsequent purification and/or vitrification of residuals from drosses or filter dusts.

Jan 1, 1994