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By Chuanfu Zhang, Jinliang Wang

"Brickless reaction shaft is the latest progress for flash smelting furnace. However, there are many factors influence the melting point of the freeze slag inside brickless reaction shaft, and their variational regularities are not obvious, thus, it is difficult for conventional methods to analyze accurately the complex data. In this research, the experiment data of slag melting point were processed based on optimal discrimination plane. For this method, two orthogonal vectors were firstly built up based on the Fisher's criterion, and then the experiment data were projected onto the two vectors, thus, two-dimensional feature vectors were extracted as criteria to determine the factors effect degree on the slag melting point. Results show that the CaO content is the greatest factor to the melting point of the freeze slag inside brickless reaction shaft, the content of Fe3O4, SiO2, Cu2 O and MgO is the second, and the FeO content is the last.IntroductionBrickless reaction shaft is the latest progress of flash smelting furnace reaction shaft. To research the influence factors on the slag melting point inside the brickless reaction shaft is significant to form freeze slag with compact structure, good heat insulation, certain intensity, appropriate thickness and reasonable distribution, to extend furnace life, to reduce energy consumption, and to promote safe production.However, due to the complex components, there are many factors influence the melting points of the freeze slag inside brickless reaction shaft, and their variational regularities are not obvious. Therefore, it is difficult for conventional methods, such as variance analysis, data fitting, etc., to analyze accurately the complex experiment data.Pattern recognition can easily classify information, even if there are many influencing factors. For pattern recognition, there are some sub-disciplines such as discriminant analysis, feature extraction, error estimation, cluster analysis (together sometimes called statistical pattern recognition), grammatical inference, parsing and matching (sometimes called syntactical and structural pattern recognition) [1, 2]."

Jan 1, 2012

By Zhitong Sui

Based on several case studies on the precipitating behavior of valuable nonferrous metal compounds (VNMC) in molten slags a green technology for the recovery of VNMC from molten slags was proposed. This technology involves three steps: (I) The selective enrichment of the dispersed VNMC into the designed mineral phase in the molten slag; (2) The selective coarsening of the designed mineral phase to a critical grain size in the molten slag; (3) The selective separation from tailing of the grown mineral phase in the solidified slag by dressing or hydrometallurgy processes. This is a clean and low cost technique and has a great capacity to deal with a large quantity of slags. The utilization of the recovered VNMC such as Titanium, Boron, Vanadium compounds was summarized as examples of application. It was confirmed by experiments that the precipitating behavior of the designed mineral phases like Perovskite(CaTiO3), Suanite(2MgO*B2O3) and Sincosite(CaOoV2O5*P2O5) in molten slags is obviously affected by operation factors such as temperature, chemical composition, heat-treatment, additives and so on. The precipitating kinetics and mechanism of the VNMC from molten slags during solidification processes were also investigated.

Jan 1, 2003

By Bin Xu, Qian Li, Yong-bin Yang, Tao Jiang, Jian-jun Hu

It could significantly increase the leaching rate of refractory gold concentrate containing sulfur and arsenic by roasting pretreatment with adding certain amount of sodium sulfate, and the mechanism of that was systematically researched with DSC, XRD and SEM in this paper. Results indicated that the mechanism of Na2SO4 on double refractory gold concentrate at roasting pretreatment can be summed up in the following three aspects：Firstly, Na2SO4 can react with SO2 and SO3 which is produced by the oxidation of sulfides and generate Na2S2O7(l), which plays buffer effect on sulfides exothermic oxidation, avoiding the secondary-encapsulated of gold. Secondly, the liquid phase of Na2S2O7 can cover mineral particles' surface that possesses a sintering effect, it leads to internal cracks of the particles. Finally, mineral particles will gather with sodium sulfate particles as the center that can improve the permeability of the layer.

Jan 1, 2015

By Boxun Lu, Juan Wei, Kun Chen, Wanlin Wang, Lejun Zhou

"Slag system is an indispensable part during the continuous casting process, and playing various important roles like absorbing inclusions, modifying heat transfer rate, preventing oxidation of molten steel, etc. to ensure the smooth process and excellent slab quality. However most slags contains more than 8% fluorides which tend to introduce a series of environmental and health problems. This study involves the research of the removal of fluorine through the chemical composition optimization. Through the studies of CCT, DHTT, XRD and SEM, it has been successfully founded that the crystalline phase of Ca11Si4B2O22 discovered in this study shows very similar crystallization property as Cuspidine (Ca4Si2O7F2), which is the most important crystalline phase in the current fluorine bearing slags. Moreover, the optimized free/low fluorine slag shows the opportunity to replace conventional high-fluorine mold slag for casting medium carbon steels that is regarded as the bottleneck of green slag development for continuous casting.IntroductionMold flux has been widely used in continuous casting to control heat transfer, lubricate the strand, absorb inclusions, provide insulation and prevent oxidation of the molten steel[1-3]. It usually contains fluorides, like CaF2, NaF etc., which are used to control the viscosity and solidification temperature of mold fluxes [4-5]. However, the presence of fluoride leads to corrosion of equipment, serious environmental pollution (toxic volatiles and water pollution), and high processing cost of cooling water[6-7]. Therefore, the study of low or free fluorine mold flux is of interest and attracts worldwide attention.S. Y. Choi et al. [4] used B2O3 as a substitute for cuspidine in steel B2PB2) however, B2O3 content was extremely high (up to 30 w%). Other studies have investigated F-free mold flux by adding or optimizing components as MgO, Li2O, B2O3 et al[8-11]. However, most of these focused on the melting and viscosity issues or for low or ultra-low carbon steels, where crystallization tendency is not significantly strong. Very few studies regarding to the development of low/free Fluorine mold flux for casting medium carbon (MC) steels have been conducted, due to the difficulty of the crystallization and heat transfer control without the formation of cuspidine."

Jan 1, 2014

By Kimiaki Utsunomiya, Yasumasa Hattori, Yoshiaki Mori, Toyokazu Okubo

"The effect of various operating conditions on splashing behavior in a Peirce-Smith converter has been investigated with a 1/5.7 scale cold model. Dynamic similarity between the model and a commercial converter was attained by setting the modified Froude number in the model experiments in· the range for normal converter operation. It is known that for a given modified Froude number the dimensionless penetration length of gas into the liquid phase increases as the liquid density decreases. Moreover, penetration· length has a large effect on splashing behavior. Therefore, a heavy liquid, a mixture of water and lead concentrate was used as the liquid phase. It was concluded that the amount of splash dramatically decreases with a reduction in the buoyancy energy per, unit liquid mass and an increase in the horizontal distance between the tuyere tip and the edge of the mouth.IntroductionSubmerged gas injection is widely used in practice in ferrous and nonferrous pyrometallurgical operations to achieve large gas-liquid contact areas and good agitation of liquid for rapid chemical reaction. The common application in ·nonferrous industry is the Peirce-Smith converter with multi-tuyere for copper and nickel matte converting. This process has been used for over 100 years because of its effectiveness in mixing of the molten bath, as well as its merits of the engineering simplicity. However, the mechanisms which · determine the blowing performance is poorly understood, and the design and operating conditions of the Peirce-Smith converter varies widely from plant to plant, such as by diameter, length, mouth angle, tuyere position and level of molten matte. Smelters have continuously made an effort to increase converter productivity, implying maximum tuyere blowing rate. Above a certain critical blowing rate, splash of molten matte from the converter mouth becomes unacceptable because of dangerous ejection and accretion buildup around the converter mouth, which results in interference with effective hood sealing. In fact, a 1993 converter survey[!] reported that splash was a major limiting factor for blowing rate and 54% of responding plants from around the world regard it as a limiting condition[2]. In order to increase tuyere blowing rate a study of the effect of various operating conditions on splashing behavior is expected."

Jan 1, 2000

By Ali Nadir Khan

Depleting copper resources and advancing technologies have challenged industries to develop more viable, adaptable and cost efficient processes using also secondary raw materials in copper production. This study is targeting to that goal by dynamic modelling of flow and heat transfer coupled with chemical kinetics in an industrial scale flash smelting furnace settler using commercial CFD software ANSYS Fluent. First, different physical phenomena occurring inside the settler, for example, settling and separation of the matte/slag phases, and heat transfer between slag/matte phases and settler walls are studied. Secondly, reaction kinetics between matte and slag, and between slag/matte and settler walls, and impurity element distribution will be studied. This would also include phase changes phenomena due to these reactions and the flow of the reaction gases inside the settler. Settling of polydispersed droplets, their coagulation, breakage, and WEEE particle behavior are further targets of the modelling work.

By A. McLean, Y. Uchida, M. Iwase, M. Myochin, K. Wiikimoto

"Phase diagrams of FeO-containing ternary systems could be derived from experimental data for the activities of FeO. The systems investigated are CaO-CaF2-FeO, SrO-SrF2-FeO; BaO-BaF2-FeO, CaO-CaCl2-FeO, SrO-SrC12-FeO, BaO-BaC12-FeO, CaO-A12O3-FeO and BaO-SiO2-FeO.IntroductionThe importance of phase diagram cannot be overemphasized. In a book, ""Alloy Phase Equilibria""[l], the author, Professor A Prince, states, ""A metallurgist has been defined as a person who thinks in terms of phase diagram"". Whether one accepts this statement or not, it is self-evident that an ability to interpret phase equilibria is essential to the professional metallurgists.The physical chemistry studies of iron and steelmaking process often require phase diagrams of FeO-containing slags. Iso-thermal section of the phase· diagrams of such systems can be derived from experimental data for chemical potentials of FeO. Due to the recent developments in the area of solid state electrochemistry, rapid determinations of the FeO activities have become possible. The present paper is aimed at documenting the derivation of the phase diagrams of FeO containing slags.Experimental AspectsAn electrochemical method incorporating stabilized zirconia can be used for the measurements of the activities of FeO in various slags and fluxes[2]. For the details of the experimental technique, reference should be made to reference 2"

Jan 1, 2000

By Shizhe Liu, Bing Li, Heng Wang, Zuxin Zhao

In this paper, cyclic voltammetry and chronoamperometry have been applied to investigate the effects of Nd2O3 concentration on the anode effects, critical potential for the anode effects and Nd2O3 reduction in LiF-NdF3-Nd2O3 melts at 950℃. The results show that the oxidation peaks in the potential of about 2.7V are attributed to the oxygen ions oxidation and the peak current density increases with Nd2O3 concentration increase from 0 to 0.5wt%. The critical potential caused the anode effects shifts to 0.3V more positive value as Nd2O3 content in the melts decreases from 0.01wt% to 0.5wt%. The cyclic votammograms on W electrodes in the LiF-NdF3-Nd2O3 melts present two pairs of reduction and oxidation peaks, indicating that the reduction of Nd ions in the LiF-NdF3-Nd2O3 melts in two steps rather than one step.

Jan 1, 2014

By G. J. Abbaschian, A. B. Gokhale, M. M. Kunjapur

"A laboratory scale model furnace was constructed for obtaining radially inward oriented columnar grains in disc shaped castings. The furnace consisted of eleven circular, concentric, equispaced resistance heaters on each half of a split graphite mold. Water or air flowing through a copper pipe along the periphery of the disc constituted the heat sink. After filling the mold, the heaters were turned off consecutively in top and bottom pairs from the rim towards the center, causing the temperature gradients to move inward. Equiaxed structure was obtained at the center by turning off the inner coils together when desired. Sn:15%Pb alloy was used to cast integral blade disc castings using the above technique to obtain dual-property discs with a central equiaxed structure and an outer columnar grain structure projecting inwards from the blades to the rim. A numerical technique was used to predict the temperature profile in the disc during solidification, and good correlation was obtained with the experimentally measured temperature profiles. The corresponding heat transfer coefficient values obtained were h = 544 Wm- 2k-1 (0.013 cal/cm2- ° C-sec) for cooling between metal and chill and h' = 71 Wm- 2k-1 (0.0017 cal/cm2- ° C-sec) for the heat input from the hot mold to the liquid metal. BackgroundHigh temperature alloys used in the current generation of gas turbine engines have evolved through two main stages of development: in 1950's, the increase in the efficiency of gas turbines was paced by improvements in alloy design, which led to the development of Ni and Co-based superalloys (1). By mid-1960's, it was realized that improved alloy chemistry alone was inadequate in meeting the increasingly stringent service requirements. The focus of research then shifted from alloy development to process development, and resulted in the introduction of directional solidification (DS) techniques for the production of turbine blades and vanes (1,2).Under typical operating conditions, the blades and vanes are subjected to aerodynamic loading, while the blades are additionally subjected to high centrifugal loading and vibratory stresses. The primary material requirements for blades may be summarized as follows (1,3):•,High creep resistance•,Good high temperature tensile strength (typically in the range of•,275 to 550 MPa at temperatures in excess of 750°C)•,Resistance to both low cycle and high cycle fatigue (LCF and HCF)•,Resistance to erosion, corrosion, and oxidation•,Resistance to thermal fatigue"

Jan 1, 1986

By T. Fujita

The removal of phosphorus is essential 1n order to increase the recycling of steelmaking slags for their manganese, iron and lime contents. This study aims at establishing the phosphorus mineralogy and its distribution in steelmaking slags, the effect of slow cooling, and the methods of phosphorus removal. A series of steelmaking slag samples was prepared at different cooling rates, and the mineralogy, chemistry and grain size of the samples were investigated with SEM/EDS and x-ray diffraction. The test results using high gradient magnetic separation are discussed.

Jan 1, 1988

By Rak-lun Choi

Plasma-induced damage of InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) has been studied in terms of forward turn-on and reverse breakdown voltages, together with etch rate and surface morphology. The physical degradation of sidewall along with rough surface morphology of n-GaN caused by increased ion scattering induced the deterioration of the forward and reverse voltages. It was found that the turn-on voltage is sensitive to the surface roughness of the etched n-GaN and the breakdown voltage is strongly affected by the sidewall contamination. Annealing under nitrogen after the mesa etching improved the electrical properties of the InGaN/GaN MQW LEDs. Efficient blue light-emitting diodes (LEDs) were fabricated using InGaN/GaN triangular MQWs. The LEDs with triangular QWs showed a lower operation voltage and 2.4 times higher light output power than those with the rectangular MQW LEDs at 20 mA and 20 °C. The intensity of electroluminescence (EL) at 20 mA was almost independent of ambient temperature in the triangular QW LED, but decreased substantially in the rectangular one.

Jan 1, 2003

By Petr Dvorak, Jana Selucka, Hong Vu, Petra Starkova, Tomas Frydl

Waste, generated during high pressure leaching of lateritic nickel ores, contains about 50% of iron in form of magnetite but high chromium content ( *3%) does not allow its extensive utilization as the raw material for pig iron production in blast furnace. The chromium removal from the waste was carried out by two methods: (1) oxidative alkali roasting with NaOH and/or Na2CO3, followed by water leaching and (2) oxidative leaching in KOH sub-molten salts solutions. The results show that about 90.1% of Cr was removed when the waste was roasted at 900 °C for 3 h with 33.1 wt% of NaOH. The removal of 88.2% of Cr was achieved if the waste was roasted at 900 °C for 3 h with 40 wt% of Na2CO3. The sodium content in the water-leached residues was reduced from 5% to about 0.5% by reaction with CaO in aqueous solutions at 80 °C for 2 h. About 70% of Cr was removed if the waste was leached at 190 °C in 73 wt% KOH for 8 h.

Mar 1, 2017

By R. G. Reddy

Viscosities of alkaline metal oxide-silicate melts were estimated using our previously developed mathematical model. The structural based model considers depolymerization effects and related breakdown of the silicate network structure, on the addition of metal oxides to the melt. The developed expression: n =4.9x10 9 NO 0 T ½ exp(E/RT) poise was used to calculate the viscosities of various binary silicate systems such as, CaO-SiO,, MgO-SiO, and MnO-SiO,, as a function of temperature and composition. Excellent agreement was obtained between the calculated and experimentally determined viscosities.

Jan 1, 1991

By E. F. Vegman, Ndabezinhle Dube

"In the practice of conventional sintering, production is always afflicted with the problem of being unable to get a uniform quality of produced sinter in the bed. Invariably the top layer of the sinter cake is composed of weak but highly sinter, while the bottom layer is over-fused, forming a sinter that is very strong but less reducible. These symptoms point to a variable distribution of the heat balance in the process of sintering which results in a deficit of heat in the top layers of the sinter bed and an excess of heat in the bottom layers, due to an increasing input of regenerated heat in the heat balance down the bed. This causes losses in the productivities of the sinter machine and the blast furnace.The current work was designed to improve on the solution to the above problem through the establishment of a more accurate combustion zone heat balance of the sintering process. This development is mostly on the method of determining the regenerated heat input in the overall heat balance. Previous methods were based on the assumption that the width and the velocity of the combustion zone remain constant through out its whole life, which is not the case since tests have shown that both its width and velocity increase as the combustion zone moves down the bed. In this work, these factors have been taken into account. Tests and calculations using the model were carried out for haematite and limonitic ores. The high sensitivity of the model to changes in the sinter mix composition and sintering conditions was demonstrated.The results present the following prospects:• The minimum theoretically possible coke breeze consumption during the sintering of any type of iron ore fines, under any sintering conditions, can be established.• The model can be used to control the metallurgical quality of the sinter in any point in the sinter bed since calculation data includes desired basicity, combustion zone temperature and FeO content in the sinter produced."

Jan 1, 2001

By Tuula Mäkinen

One of the latest applications of the Outokumpu Flash Smelting Technology is the direct smelting ,of nickel concentrates to metallised low-iron nickel mattes. Compared to the conventional nickel smelting, the new DON process needs a lower number of smelting vessels resulting in considerable economic and environmental benefits. Fundamentals of smelting nickel concentrates in one stage to low-iron mattes are presented. Properties of nickel. smelting slags with an emphasis of the slag fluidity at high MgO-levels are also discussed. Conditions prevailing in DON mattes at high oxidation degrees are presented as well as their influence on the behaviour of such mattes in the settler and on tapping the furnace. Distributions of elements in the direct smelting are presented and compared with the conventional process. A further comparison is made with pilot-plant data and the industrial scale.

Jan 1, 1998

By George E. Cook, Peter C. Levick, Francis M. Wells

"Relationships are established between the peak current of a pulsed, rectangular current waveform and the pulse current duty cycle under conditions of constant arc power. By appropriate choice of these interrelated parameters, it is shown that the arc pressure may be varied over a wide range even though the arc power is held constant. The methodology is suggested as a means of countering the effect of gravity in 5-G welding, while maintaining constant heat input to the weld. Combined with appropriate penetration sensors, the methodology is additionally suggested as a means of controlling penetration. IntroductionBoth low frequency pulsation (typically 0.1 - 20 Hz) and high frequency pulsation (> 100 Hz) are often used with GTA welding. Benefits derived from pulsing include improved weld quality and better process control.Advantages cited for low frequency pulsation include claims that the total heat input to the weld is reduced, the weld bead size is reduced, weld penetration is increased, grain size is reduced, porosity is reduced, weld distortion is reduced, thinner materials can be welded successfully, and the tolerance of the welding process to material and production variations is improved (1-16). With respect to the latter, pulsing aids control of weld bead penetration by increasing the tolerance to component dimensions and joint fit-up. It also reduces the sensitivity to disparities in heat sink, and it helps to reduce distortion in thin section material or distortion attributable to poor clamping. In certain materials it can reduce the sensitivity to surface oxides and to cast to cast compositional variations (16). Low frequency pulsation is also useful in welding thick materials mated by a prepared groove. In these applications the low frequency pulsation is used to obtain proper sidewall fusion as the tungsten electrode is weaved from one side of the groove to the other. In this case the weld current pulsation is synchronized with the cross seam weave pattern, such that the high current pulses occur at each sidewall. This type of low frequency pulsation has proven particularly useful in welding with narrow width groove designs (17-21). Finally, Ecer (22) has shown that the pulsed current arc is more stable against magnetic disturbances than an equivalent constant current arc."

Jan 1, 1986

By Wang Jingsong, Ma Tengfei, Feng Fu, She Xuefeng

In this paper the direct reduction melting separation-leaching process is investigated on recovering rare earth from rare earth Bayan Obo complex iron ore (REBOCIO). The REBOCIO was reduced and melting separated to produce iron nugget and rare-earth-rich slag at 1400°C for 12 or 15 min. The RE2O3 is enriched into Ce 4.667(SiO4)O or Ca 3Ce2[(Si,P)3O4]3F, which closely depend on chemical components, especially basic. The optimal acid-leaching parameters of rare earth elements from the rare earth slag are suggested as the hydrochloric acid concentration, the ratio of solid to liquid, leaching temperature, and the leaching time are 1 mol/L, 1:14, 50 °C and 120 min, respectively. The rare earth elements leaching efficiency are more than 95%. Adding of calcium CaCO3 and sodium Na2CO3 in direct reduction process have great in fluence on leaching ef ficiency of thorium.

Mar 1, 2018

By William Petruk

The concentrator of the Iron Ore Company of Canada consists of spiral circuits, a cone plant and a magnetics plant with regrind. The proportions of liberated and unliberated grains of iron oxides at each point throughout the concentrator were measured by image analysis, and recoveries were calculated for each particle type by the MATBAL materials balancing program. The results show that spirals and cones recover more than 92% of the liberated iron oxide grains in the size range of 848 to 150 um,, but the recovery drops off rapidly for finer grained particles. The tailings from the spirals and cones are reground and low intensity magnetic separators are used to recover liberated magnetite in the -37.5 um size range. The concentrator does not have a unit that efficiently recovers iron oxide grains in the size range of 150 to 37.5 um Consequently about 25% of the iron oxides in the ore are lost to tailings as liberated. grains in the size range of 150 to 37.5 um

Jan 1, 1989

By Jianxin Zhang

A process, in which arsenic in the residue is transformed directly into scorodite and copper dissolves into the solution simultaneously, was studied. The process was carried out in acidic ferrous sulfate solution under oxygen pressure. The optimum conditions of the process were determined as follows: the initial H2SO4 concentration of 10 g/L; liquid/solid ratio of 10; Fe/As molar ratio in the feedstock of 1; the addition of calcium lignosulphonate was 1% of sludge; oxygen pressure, temperature and reaction time were 1.5 MPa, 150 °C and 6 h, respectively. Under these conditions, arsenic transformed to crystalline scorodite in size of 5–10 μm, and the transformation efficiency reached 97.60%; meanwhile, the copper was leached with a high efficiency of 93.34%. The stability of the leaching residue was evaluated by TCLP testing, and the results indicated the concentration of arsenic in the leaching solution was extremely low as 0.04 mg/L and met the standard of safe stockpile.

By K. Murayama, M. Kawakami, T. Takenaka, S. Yokoyama

"Cokes play an important role of spacer in blast furnace. However, they degenerate during Boudouard reaction. Blast furnace cokes are reacted with pure C02 at I 072 to 1673 K. Reaction rate was obtained by the weight change of spherical specimen. The specimen after reaction was examined by microscopic observation. The reaction rate increased with temperature and was expressed by two Arrhenius type lines. The activation energy was 126 KJ/mol at higher temperature than 13 73 K and 202 KJ/mol at lower temperature range. At the higher temperature range, the reaction proceeded from the surface leaving unreacted core, whereas homogeneously whole inside at lower temperature. The porosity increased from the center to surface at higher temperature, whereas it was almost constant at lower temperature.IntroductionThe cokes have the function of fuel, reductant and spacer to keep gas and liquid flow in the blast furnace. Thus, the reaction mechanism of coke with several gas and the strength after the reaction should be important factor to control the blast furnace operation. The reaction mechanism of coke with C02 has been studied extensively. The rate equations were derived by Gadsby[ I], Ergun[2] and Turkdogan and Vinters[3]. They were compared and discussed by Kobayashi and Omori [ 4]. Effect of crystallization degree on the reaction rate was examined by Kashiwaya and Ishii[5]. Catalytic enhancement effect of ash componets have been clarified by Kashiwaya et. al. [6]. Although degradation of coke in blast furnace has been examined recently[7], however, the degradation of coke after the reaction with C02 has not been well clarified yet. In the present work, the metallurgical coke specimen was heated in N2 and C02 and the reaction mechanism and degradation behavior after the reaction was investigated."

Jan 1, 2000