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By Yongqi Sun, Zuotai Zhang

Our study investigated the influence of P2O5 and B2O3 on the viscosity and crystallization behavior of Ti-bearing blast furnace (Ti-BF) slags for the purpose of Ti extraction. The investigation of the crystallization behaviors were carried out using a single hot thermocouple technique (SHTT) and the viscosity was obtained by rotating cylinder method. For the viscosity, the results showed that P2O5 substantially increased the slag viscosity. P2O5 is a network-forming oxide, which increased the degree of polymerization of slags and accordingly increased the slag viscosity. However, both of slag viscosity and apparent activation energy for viscous flow remarkably decreased with B2O3 addition. As a typical network forming oxide, B2O3 was introduced into the network and existed dominantly as 2-D structure, BO3 triangular, which caused a simpler structure and a decreasing slag viscosity. As for the crystallization behaviors of Ti-BF slags, both P2O5 and B2O3 enhanced the crystallization trend of rod-shape rutile and suppressed the crystallization trend of dendrite CaTiO3. Therefore the added P2O5 and B2O3 caused the primary phase change from CaTiO3 to rutile. Additionally, it was found that the rod-shape rutile showed a 1-D growth, whereas the dendrite CaTiO3 showed a 3-D growth style.

Jan 1, 2015

By Peter Forschner

Classical Mixing Theory is based on applying many fundamental correlations to standard baffled dished bottomed vertical cylindrical vessels with high degrees of symmetry. Horizontal autoclaves operating at elevated temperatures and pressures have been used for more than two decades. All compartments and especially the first and last compartments are asymmetrical. To date no comparison of the effects of the asymmetric geometry on mixing system design and scale-up has been published. The results of investigating solids suspension, mixing time, momentum transfer from the impeller to feed slurry and feed inlet location in the first autoclave compartment are presented as influences on residence time distribution. CFD modeling was developed and verified with the test apparatus.

Jan 1, 2003

By Ann M. Hagni

Reflected Light Microscopy (RLM) And Scanning Electron Microscopic-Energy Dispersive Spectroscopic Analysis (SEM-EDS) Study Of Electric Arc Furnace (EAF) Dusts Have Shown That Their Mineralogy Is Complex And Varied. The Particles Are Largely Spherical, And Can Be Seen In RLM Sections To Be Composed Of Franklinite, And Zincite, But They Show Significant Solid Solution With Each Other And May Contain Small Amounts Of Chromium. These Crystalline Phases Occur As Crystals And Skeletal Growths Within Ca-Fe-Si Glass. Because Chlorine Is A Deleterious Constituent In Recovered Zinc Products From EAF Dusts, Special Attention Has Been Given To Chlorine-Bearing Phases, And They Include Hydrophylite (Cacl2), Lime (Cao), And Organic Phases. Pyrohydrolysis-Treated EAF Dusts With Silica (Si02), Tungstite (W03), Alumina (A1203), And Bunsenite (Nio) Additives Contain Franklinite, Scheelite (Cawo4), Willemite (Zn2SiO4), And Hematite (Fe2O3)

Jan 1, 1992

By C. M. Davidson

Contamination of by-product: sulfuric acid, by dissolved oxides of nitrogen ('nitrates') occurs under some operating conditions encountered in sulfide roasting and smelting,, notably when oxygen-enriched air is used. This 'nitrate' lowers the value of the acid and increases the effective cost of smelter gas desulfurization. The present paper describes measures taken at one smelter acid plant to remove this 'nitrate'; it discusses the mechanism by which 'nitrates' in some cases concentrate in one part of the plant and can be purged for more efficient treatment; and it describes a process developed by C-I-L Inc. for removal of 'nitrates' from such a purge stream. Advantages of the process include very low reagent cost, recovery of all sulfuric acid values and safe handling of nitrous fumes.

Jan 1, 1983

By Baicheng Liu, Houfa Shen, Wensheng Li

"In order to understand the formation of macrosegregation in steel ingots, a mixture model has been developed which accounts for coupled mass, momentum, species, and energy transport to describe the sedimentation of free equiaxed grains during solidification. In this model, the mushy zone is divided into the slurry and porous regimes according to a solid packing fraction. Settling velocity of equiaxed grains in the slurry regime is given by an explicit expression. The solidification of a binary steel ingot (Fe-0.36wt.%C) with a two-dimensional geometry is numerically simulated. It is demonstrated that the predicted macrosegregation patterns agree to some extent with classical experimental results. Further refinement of this model is still necessary for realistically simulating steel ingot solidification.IntroductionModeling macrosegregation in steel ingots is still a challenging study, mainly due to the length scale of the products and the complexity of global multiphase transport phenomena coupled with microscopic solidification kinetics [l]. The thermal-solutal convection and the motion of equiaxed grains are the two main mechanisms responsible for macrosegregation. But there are few models that deal with the motion of equiaxed grains, which is confirmed as the main phenomenon that explains the negative macrosegregation along the centerline of large steel ingots [2]. A model which takes into account melt convection and grain sedimentation was first proposed by Beckermann and co-workers ([3], and references therein). More recently, similar multiphase solidification models with advanced nature have been presented by Wu and Ludwig [1,4] and Combeau and co-workers [5,6]. It is known that the application of these sophisticated models to steel ingot casting is at its beginning.In this paper, a solidification model based on continuum mixture approach, using much less sophisticated relations to obtain the settling velocity of free equiaxed grains, has been proposed in order to predict the macrosegregation in steel ingots. The model is applied to simulate the solidification of a binary steel ingot with a two-dimensional geometry, and preliminary modeling results are presented."

Jan 1, 2011

By H. Y. Sohn, Y. Mohassab, D. Q. Fan, M. Elzohiery

A flash ironmaking process is being developed at the University of Utah in which iron is produced directly from magnetite concentrate. The kinetics of magnetite reduction by a mixture of H and CO gases was determined in the 2 temperature range 1150–1600 °C. Over 90% reduction degree was achieved at a temperature as low as 1250 °C within 4–6 s which is the typical residence time available in a flash reactor. The kinetics results were applied to experimental data obtained in a laboratory flash reactor in which H and CO gas mixtures were 2 produced from in situ partial oxidation of natural gas with oxygen. CFD was used to simulate the laboratory reactor,and the results were in good agreement with the experimental data.

Mar 1, 2017

By Brian R. Green

Resin-in-pulp (RIP) technology has been developed for recovery of gold. It is now time to look forward to the potential for application of the technology to other situations. Some cases have been identified and have merited preliminary testwork. Four examples, which illustrate the potential of RIP, are dealt with in this paper. These include removal of metal-cyanides from pulps, recovery of manganese that is difficult to wash from filter cakes, recovery of nickel from low grade pulps, and recovery of zinc from process residues. The discussion includes descriptions of the problems, factors that affect the choice of resin, and factors that will affect the economics of the process.

Jan 1, 1998

By Bo Björkman

Four different arsenic containing dusts from the Boliden plant, Boliden mineral AB, Sweden have been examined. A kinetic study of the As elimination was performed in a laboratory scale roasting furnace for roasting furnace ESP dust and smelting furnace ESP dust. Characterisation and thermodynamic calculations were carried out to determine the mineralogy, and the stability of compounds in the dusts studied. The characterisation methods used were chemical analysis, X-ray diffraction analysis and microprobe analysis. It was found in the experiments that a high degree of As elimination was obtained for roasting fumace ESP dust and a low degree for smelting fumace ESP dust. Derived kinetic models are given. A prediction of the As-elimation for settling furnace dust and converter ventilation dust is presented.

Jan 1, 1994

By Elsa Agante

Recycling of solid wastes, a common practice nowadays, requires the separation of the different materials in order to increase the products added value. The separation of one plastic from mixtures of different types of plastics is not easy due to their similar physical properties, but different techniques are available, from automatic sorting systems based on optical sensors to techniques adapted from mineral processing, namely gravity, froth flotation and electrostatic processes. In the last decade, many researchers have addressed the separation?s problem of different polymers, like Polyethylene Terephthalate (PET) and Polyvinyl Chloride (PVC), two polymers commonly used in packaging which have similar density. One proposed technique is the classical froth flotation performed in agitated cells. Froth flotation is a versatile and relatively cheap process widely used in mineral separation. It is based on the different behaviour of particles in the presence of an inter-phase air-water, which depends on the materials surfaces properties. Froth flotation can be affected by some variables such as impeller speed and air flow rate. Agitated cells, when used with low density materials, like plastics, can produce overstated turbulence that prevents the adhesion and collection of particles in the froths. In this case, separation is favoured by column flotation smoother hydrodynamics. This paper proposes the separation of PET from PVC by column flotation. The experimental work was carried out in a column of 9cm diameter and 1m high. The effects of some operating conditions, such as depressor and frother concentration, air flow rate and feed grain size on products grade and recovery were evaluated and the best flotation conditions for the separation of these plastics were established.

Jan 1, 2006

By A. A. Bustos

Four Air Liquide Shrouded Injectors (ALSI ) were installed and operated for over one year in a Peirce-Smith converter at the Falconbridge nickel smelter in Falconbridge, Ontario, Canada. A shrouded injector consists of an inner pipe and an annulus, through which high oxygen enriched air and nitrogen flow, respectively The nitrogen cools the injector and protects the refractory in the vicinity of the injector tip, allowing for substantial increases in oxygen flow rates to the converting reactions. Several injector designs were tested to study the effect of changes in the cross-sectional area and changes in the entrance geometry of the annulus. An optimum design would minimize the injection pressure required for a given flow rate to achieve choked flow conditions at the tip of the injector. The operation of the ALSI was simple and did not require any special care or maintenance, either between blows or between converter cycles. In particular, the shrouded injectors did not require punching, as is the case with conventional tuyeres. In terms of refractory performance, the ALSI, operating at 30-40 % oxygen enrichment, were superior or equal to the conventional tuyeres, which operated at 21-23% oxygen. The results of the demonstration program led Falconbridge Limited to implement the ALSI technology on a commercial scale The paper presents the demonstration program results in terms of gas flow rates, accretion formation, punchless operation and refractory wear.

Jan 1, 1999

By Toshiyuki Nohira, Eiichi Takeuchi, Tetsuo Oishi, Hideki Ono, Hirokazu Konishi

Liquid metals were investigated as alloy diaphragms in molten salt electrolysis. Liquid metals have higher diffusion rates of elements than those of solid metals during electrolysis. Sn electrodes were used for the first step to study the electrochemical formation of Dy and Nd alloys in LiCl-KCl eutectic melts, demonstrating selective recovery of rare earth metals into liquid tin electrodes.

Mar 1, 2017

By Rachel De Lucas

In recent years, as the price of oil soars upward, scientists have started to focus on other energy sources, such as hydrogen. As magnesium can be used for hydrogen storage by forming MgH2, industry will see a growing demand for the hydride. In hydrogen storage and release cycles using magnesium, hydrogen is released from magnesium hydride through hydrolysis and magnesium hydroxide is produced. Therefore, recycling magnesium hydroxide back to magnesium becomes important. The solid oxide membrane (SOM) process is an emerging technology for this process. In the SOM process, MgF2-CaF2-MgO flux is contained in a stainless steel crucible, which works as the cathode. An ionic-conducting YSZ membrane, connected to a liquid metal anode, is partially immersed in the flux. During electrolysis, when the voltage between anode and cathode is higher than the dissociation potential of magnesium oxide, magnesium ions move toward the cathode and are reduced into magnesium vapor. The oxygen ions move toward the anode, passing through the YSZ membrane. They are then oxidized, forming pure oxygen, CO/CO2 or steam (by reaction with hydrogen). The magnesium vapor, generated at the cathode, is collected in the condenser as high purity magnesium. SOM experiments have been conducted with different liquid metal anodes and without reductants. The SOM technique is a highly energy efficient process and with by-products being oxygen or steam, it is also an environmentally friendly green process. A 2-D electrostatics mathematical model was developed as an initial step towards optimizing the design for a three-tube scale-up SOM electrolysis cell. Several possible geometries were examined to develop the scale-up model and convergence of the model was achieved.

Jan 1, 2006

By Mokka Rao, Arturo Valles, Jose Rodríguez

"This paper shows a mathematical model based on finite elements, applied to bottom poured shell ingots of C.V.G. Sidor Plant. The model was used as a strategy to determine the thermal effects that are produced when solidification conditions are modified without interfering with the production process. The modification consisted of placing a thermal insulator on top of mould.The results obtained by the model indicated that the solidification time increases with insulator on base of the mould. With these results a significant number of casts were run with and without insulator. Latter by means of a metallurgical analysis it was determinated that the ingots cast with insulator reduce the level of non-metallic inclusions and the presence of internal blistering in seamless pipes.IntroductionThe process of fabrication of seamless pipes in SIDOR involves various steps of processing, such as heating the ingots, fabrication of the prelaminated, fabrication of the bored pipe, lamination of the pipe by passing through the pellegrine mill, heating the pipe in a walking bean furnace and final calibration through a calibrator mill. The material utilized for producing these pipes is provided entirely from a electrical arc furnace and casted ingots, especifically, from the superintendence of bottom pouring.The process of bottom pouring consists of positioning twelve moulds of diameters 415, 480 or 505 mm over a plate of grey cast iron in which exists a system of communicating vessels. The ingots are distributed around a central duct from which the steel flows down and filling gradually, each one of the moulds (Fig. 1)."

Jan 1, 1997

By Marcelo B. Mourão

An experimental investigation was carried out to -study the rates of reduction of pellets containing iron oxides by carbon dissolved in liquid iron, at temperatures ranging from 1720 K to 1973 K. Several different pellet types were employed; the materials used in the pellet's manufacture were pure hematite, two kinds of commercial iron ores, and mixtures hematite/silica and hematite/lime: Reaction times were determined employing the constant volume pressure increase technique (CVPI). It has been observed that the reaction rate increases as the temperature and the pellet's specific surface area increases. The reaction rate is also affected by the oxide type: pellets made from commercial ores or from mixtures hematite/silica or hematite/lime show reaction rates lower than those made from pure hematite.

Jan 1, 1996

By Guanghua Wen, Jian Li, Mingmei Zhu, Fei Xiong, Shengjian Cao

"Small inclusions removal from molten steel in a continuous casting tundish by gas bubbles, which were generated in the turbulent flow region by introducing inert gas, was analyzed theoretically and the inclusion-bubble adhesion and flotation process was also observed by high-speed photo-graph in water model. Results showed that small inclusions in the range of 20-50µm removal from molten steel by bubbles flotation involves three stages: contact, adhesion and flotation. The inclusion-bubble adhesion processes include two ways: inclusions adhering to the upper part of the bubble and inclusions adhering to the lower part of the bubble. As the bubble floats up, the number of inclusions adhering to the bubble are increased. The proper size of bubbles, which could enhance small inclusions removal efficiency, should be controlled in the range of 1-2mm.IntroductionReducing inclusions content in molten steel is a very important way to improve quality of steel, and one of the main tasks in steel making process.A variety of methods have been used for inclusions removal in molten steel. At present, the main approaches to remove inclusions are gas stirring, slag cleaning, filtering, centrifugal separating, and by means of ultrasonic or electromagnetic field. Among these techniques, gas stirring is the most widely and effectively method for inclusions removal. Inclusions in molten steel will be aggregated and generated to form larger size inclusions, and subsequently floated to the surface of molten steel by buoyancy; meanwhile, some inclusions will be adhered to bubbles and floated together to metal-slag interface where inclusions are absorbed by the covering slag layer. Some research work showed that flow behaviors of small bubbles are different from that of big ones [1-2], and smaller bubbles are more efficiency for fine inclusions removal in molten steel.There are many methods to generate bubbles. During steelmaking process, highly turbulent flow in the ladle shroud can split introduced inert gas into small bubbles, which enhances the removal of fine inclusions from molten steel. Turbulent flow of molten steel injected into tundish from ladle shroud has a high speed and it is a strong turbulent area in continuous casting. The gas can be introduced into the shroud below the slide gate. The high turbulence flow would break up the gas into small gas bubbles. Fine inclusions will be easily adhered to small bubbles and subsequently floated to the surface of molten steel. Generation of small bubbles in ladle shroud have been studied in some literatures [3-4]. Some research have analyzed the fine inclusions removal with injecting gas from the ladle shroud by mathematical simulation, and the results show that the refining method can obviously improve the removal efficiency of fine inclusions in tundish [5-8]."

Jan 1, 2013

By W. B. Carter, A. T. Hunt, G. W. Book

"Combustion Chemical Vapor Deposition (CCVDSM ), an open air, flame assisted CVD process, is under development. The CCVD process produces non-line-of-sight, epitaxial deposition. Materials deposited include YBa2Cu3Ox' Y2BaCuOx, BaTiO3, Y2FesOI2, ZrO2, yttria stabilized ZrO2 (YSZ), partially (yttria) stabilized ZrO2 (PSZ), and amorphous silica. Two modifications of the CCVD process are being studied. Liquid fuel CCVD deposition, involves the combustion of an organic solvent that contains dissolved reagents carrying the desired coating cations. Gaseous fuel CCVD deposition uses a flammable gas as fuel. A non-flammable solution containing dissolved reagents is either aspirated into the flame or mixed with the fuel gas as an aerosol prior to its combustion. Substrates to be coated are held near the flames' ends.IntroductionThin films and coatings can be deposited using a wide variety of techniques including chemical vapor deposition (CVD). CVD is ""a materials synthesis process whereby constituents of the vapor phase react chemically near or on a substrate surface to form a solid product.""lIn conventional CVD processing, gases carrying coating constituents flow into a reaction vessel where deposition occurs onto a heated substrate. The deposition process is often conducted at reduced pressure. Both cold and hot wall reaction chambers are used. Heat can be provided by a resistance furnace, rf induction, or high-intensity radiation lamps. Plasma, microwave, photo, laser, RF, and electron-enhanced CVD processes have been developed. The necessity of using a reaction vessel limits the substrate size and affects coating economics. Although most CVD depositions are performed as batch processes, continuous deposition can be accomplished with the use of appropriate hardware.The chemical vapor deposition of thin, dense oxide films has been accomplished in the open atmosphere with a flame assisted process. The process is called combustion chemical vapor deposition (CCVDSM).2 Two modifications of the CCVD process have been developed. The liquid fuel CCVD process involves the combustion of an organic solvent in which reagents (containing the coating cations) are dissolved. The gaseous fuel CCVD process uses a flammable gas as fuel. In this modification, a non-flammable solution containing dissolved reagents is either aspirated into the flame or mixed with the fuel gas as an aerosol of small droplets prior to its combustion. Substrates to be coated are held near the flames' ends."

Jan 1, 1994

By Ludy C. Motta, Denise C. O. Nascimento, Sergio N. Monteiro

"Natural cellulose-based fibers are nowadays of growing interest for modern industrial composites. Relatively unknown fibers like piassava, curaua and gourde have shown promising behavior as reinforcement of polymeric composites. However, the hydrophilic characteristics of the natural fibers impair its adhesion to the normally hydrophobic polymeric matrix. Surface treatments can, in principle, improve this adhesion and the fiber/matrix interfacial strength. In this paper, the effect of alkali treatment of the surface of piassava (Atallea funifera) waste fibers was investigated in terms of the change in strength of epoxy composites reinforced with these waste fibers.IntroductionThe consequences of global warming and the increase in the price of petroleum are motivating the use of natural materials as substitute for energy intensive synthetic materials [1]. In particular, natural fibers obtained both, from cultivated plants such as jute, sisal, hemp and flax as well as from industrial waste such as sugar come bagasse and coir, are being considered to replace synthetic glass fibers [2,3]. These natural fibers, also known as lignocellulosic fibers, present the comparative advantages of being renewable, recyclable and biodegradable. Moreover, lignocellulosic fibers require less amount of processing energy and are neutral with respect to CO2 emission, which causes the atmospheric greenhouse effect responsible for the global warming [4]. Low cost is another important economical advantage of the natural fibers over the synthetic ones and the application of lignocellulosic is also associated with a lower wear of processing equipment and better finishing of molded components [5]. Moreover, for some fibers, properties such as the mechanical strength and impact resistance can be superiors to the corresponding properties of synthetic glass fiber [6]. The characteristics and properties of several lignocellulosic fibers are, nowadays being extensively discussed in the literature. It is beyond the scope of this work to comment on the hundreds of papers dealing with this subject. However, there are still less known fibers with great potential as engineering material that deserves investigation."

Jan 1, 2008

By F. Guevara

The paper presents results of physical and turbulent three-dimensional numerical simulation of the gas flow in the wind box and reaction shaft of the concentrate burner of a flash furnace. Physical simulation work was carried out in a 1:5 linear scale model, where the velocity field was measured using a Pitot tube. The mathematical model consists of the three-dimensional averaged Navier-Stokes equations, turbulent kinetic energy and dissipation of turbulent kinetic energy using the Renormalization Group (RNG) theory for the k-e turbulence model. Computations were performed using FLUENT, based in a finite- volume code. The geometry of the concentrate burner was separated in two sections: wind box and reaction tower. Results obtained at the exit of the wind box were used as boundary conditions for the reaction shaft. The effect of boundary conditions on the numerical results was also studied. Results of physical and numerical simulations show an asymmetry of the velocity field at the exit of wind box. This asymmetry is possibly due to existence of a separated flow in the back of the exit ring. The agreement of physical and numerical results assess the capacity of the turbulence RNG k-e model to reproduce correctly the behaviour of the velocity field at the exit of the concentrate burner.

Jan 1, 1999

By Kwang-suk You

This paper describes the characteristics of electric arc furnace slag (EAF slag) as an aggregate of concrete along with the chemical composition, leaching concentration of heavy metals, the soundness of EAF slag and compressive strength of mortar with 20% and 50% replacements of sand. The results showed that leaching of heavy metals and soundness of EAF slag satisfied Korean environmental limit and Korean Industrial Standard for aggregates. The compressive strength of mortar increased as the replacement ratio of EAF slag for sand increased.

Jan 1, 2006

By Srinath Viswanathan, Zhijing Zhang, Ramana G. Reddy

"The viscosity measurements were carried out on melts of 380 aluminum alloy containing 20 volume % SiC particulates under various shear rates at different temperatures using a Brookfield viscometer. Results showed that viscosities of the melts increased with decreasing temperature and decreased with increasing shear rate. These results were compared with those of 356 alloy and it was found that the temperature had a more significant effect on viscosity of 356 alloy than that of 380 alloy containing SiC particulates. Based on the present experimental data an empirical viscosity model, which considers the effects of both solid fractions in the melt and shear rate, is proposed.IntroductionDiscontinuously reinforced metal matrix composites materials (MMCs) such as aluminum alloy containing SiC particulates have considerable potential for applications in the automotive industry because of their superior stiffness, higher specific mechanical properties, better dimensional stability and strength retention at elevated temperatures when compared to their monolithic counterparts. They have a great advantage in the specificity of their properties, meaning that specific materials can be engineered for specific applications. With such freedom of design, materials engineers have to accumulate a very large database of mechanical properties. Among these properties, the viscosity of alloy slurries is very important for producing, casting and forming process of metal matrix composites materials because viscosity has a decisive influence on fluid flow. The understanding of the rheological behavior of alloy slurries is necessary for these materials to become economic reality. Therefore, a study was carried out to measure the viscosities of 380 aluminum alloy containing 20 volume % SiC particulates under various shear rates and temperatures. In addition, a viscosity model representing the primary features of the alloy slurries was developed."

Jan 1, 1999