Search Documents

By Jörg Buchmayer, Menno Eisenga, Erik Muijsenberg

"In the past decade, advanced multiple input/multiple output (MIMO) process control systems have found their way into high temperature melting processes. Today a growing number of high temperature melters have been equipped with a supervisory control system. Daily regulation of fossil fuel firing and electric energy supply to stabilize temperatures is no longer in the hands of the operator, but fully taken over automatically by the ES III™ MPC controller, which provides consistent process control, 24 hours per day, focused to operate the entire glass production process in the most efficient way. The presentation will show practical results and benefits achieved in the high temperature glass and cement industry.IntroductionThe Expert System, either version ESII™ or ESIII™, provides supervisory multi-variable model based predictive control in time and space This definition is not very understandable to people who are not familiar with advanced process control, thus let's try to explain it word by word.The word supervisory means that the Expert System implementation preserves the primary control level: all devices (PLCs, internal switches) as well as up to date control mechanisms (PID loops, availability to change inputs manually). ES III™ can even use primary control level elements as part of the advanced process control.The next word, multi-variable, means that multiple inputs can be handled at the same time to affect multiple outputs. This property is very important for supervisory control of the glass melting and conditioning processes. For example, in a float furnace the total amount of gas is only one of the inputs that affect the crown temperatures. The next one is batch feed rate. And batch composition (the next one) is maybe even more important. An ambient temperature also correlates with crown temperatures. So it can be concluded that crown temperatures are affected not only by one variable ""total gas"", but by many more. On the other hand, there are usually several crown temperatures with different importance for process control. And we have not discussed yet the effects of glass level, canal temperatures, oxy-boosting, etc. All of them affect (or are affected by) process control too. Overall, the process control is a complex problem where multiple inputs and outputs play strongly together at various levels of importance."

Jan 1, 2012

By C. A. Natalie

Prediction of average residence times for different particle size intervals during sulfide roasting was investigated. Calculations were done to predict average residence times using a model which employs empirical correlations for elutriation constants. Experimental average residence times were determined using a continuous., six inch diameter,. fluid bed roaster and compared with calculated residence time values. Comparison of calculated and experimental data showed that geometry effects may have .been significant when attempting to apply elutriation data to this roaster.

Jan 1, 1985

By Jun Iwai, Osamu Takai, Yasushi Inoue, Hiroyuki Sugimura

"Infrared reflection absorption measurement was performed during plasma-enhanced chemical vapor deposition of silicon dioxide films at room temperature. Hydrocarbon contaminants adsorbed onto growing film surface are oxidized by oxygen radicals in plasma resulting functional groups which include C=O and C-O bondings. These groups exist only near the surface and are hydrolyzed rapidly after exposure to air.IntroductionRecently low-temperature silicon dioxide (SiO2) deposition has been in a growing industrial demand in pa1ticular, polymelic substrates such as polycarbonate and polyethylene telephthalate, which have poor heat resistance, need low process temperature (near room temperature) in coating of SiO2 which is a suitable material to improve optical and mechanical properties of polymenc products. Plasma enhanced chemical vapor deposition (PECVD) using organosilicon reactants is one of the most promising technique for lowering process temperature, so that it has been extensively studied1-12. In the present; however, hydrocarbon contaminants and a plenty of Si-OH termination in Si-O-Si networks tend to exist in the films, which degrade mechanical, optical and electrical properties of the films. It is necessary to understand the deposition mechanism at, low temperature in order to solve the problems. We have studied the low-temperature PECVD of Si02 by spectroscopic diagnosing techniques such as optical emission and mass analysis6-7, 11- 12Infrared reflection absorption spectroscopy (IR-RAS) has been a well-established technique for characterization of thin films on metals as· well as on semiconductors and insulators13-17. In this paper, we report on' the surface reaction of room-temperature PECVD of Si02by using in situ IR-RAS."

Jan 1, 2000

By P. Hajiani

Rare earth elements (REEs) are critical materials in many leading-edge technology products. However, REE separation outside China has remained a challenge in addressing environmental concerns of current production. The author has worked on a technique employing the emphasised variability in the electrophoretic mobility (μi) of REE for the purpose of REE separation. In continuation of the results presented in IMPC 2016 [1], this contribution summarizes the progress achieved in 2016 and 2017. The major goal was to increase the REEs concentration by a factor of 1000 and to attenuate the consequent drawbacks, specifically joule heating effect. Amphiprotic hydroxylic solvent was selected to replace water, which has a major impact on the complexation mechanism and buffer requirement. Non-aqueous media result in a significant drop in the specific molar conductivity of the electrolyte, whilst μi reduces several times only. Moreover, a quasi-steady state electrophoretic separation in conjunction with temperature gradient focusing is adapted to improve scalability.

By C. Beckermann

"A diffuse interface model is derived for the direct simulation of two-phase flows with surface tension, density differences between the phases, and phase change. The derivation starts from the balance equations for a sharp interface and uses a formal averaging procedure on an atomic scale to obtain diffuse interface versions of the equations. Two approaches are considered: (i) the two phases have different velocities inside the interface and separate conservation equations are solved for each phase, and (ii) the two phases have the same velocity inside the diffuse interfuce and mixture conservation equations are solved. Based on a superposition of microscopic (atomic-scale) and macroscopic interface morphologies, an expression for the interfacial momentum source term is introduced that models surface tension effects and accounts for immiscibility between the phases.IntroductionDiffuse interface methods have been a popular tool in the direct simulation of two-phase flows [I]. In diffuse interface approaches, the interface between the two phases is characterized by a rapid but smooth transition in the properties, such as density and viscosity. Usually, a phase function ? is introduced to represent this transition, and the evolution of ? in the domain is computed from a separate equation or recipe. A unique set of conservation equations (e.g., mass and momentum) is solved on the entire domain, irrespective of the phase present, by accounting for the transition in the properties and introducing terms that account for interfacial sources. The continuum surface force (CSF) model of Brackbill et al. [2], which accounts for surface tension, is an example of the latter. The volume-of-fluid (VOF), level set, and phase-field methods are all examples of diffuse interface approaches. The major advantage of diffuse interface methods is that explicit tracking of the interface and the application of traditional sharp interface conditions are avoided. A disadvantage can arise from the artificial smearing of what is in reality an interface of atomic-scale width; however, techniques have been developed to overcome this problem."

Jan 1, 2004

By Shoji Taniguchi, Lifeng Zhang

"In this paper, firstly the 3D single-phase turbulent steady fluid flow in a vessel with four baffles stirred by a single impeller is mathematically simulated. Turbulence is modeled by using the standard k - e model. Sliding-grid method is used to model the impeller. The flow domain is divided into two cylindrical, the inner one rotates at the same speed as the impeller, and the outer one is fixed with the baffles. Results indicate that the high-speed zone is near the paddles, and larger stirring speed generates larger fluid flow velocity. The calculated stirring intensity data are used to analyze the experimental results. Secondly the effects, such as filter pore size, gas flow rate and NaCl concentration, on bubble size are studied by experiment. For the particle removal rate by bubble flotation in this vessel, first order kinetics is adopted. The effects of initial number of the particles, gas flow rate, particle and bubble size, stirring speed and surface condition, on the removal rate constant are discussed, and an empirical equation is derived by experimental data. At last, a simple model is developed to study the particle attachment probability on bubble surface under turbulent flow conditions. IntroductionIt is well known that inclusions have a bad effect on steel quality. Trying to remove inclusions from liquid steel as many as possible is one of the main objects for the metallurgical workers. Lots of ways are developed to remove inclusions from liquid steel. Gas injection is an effective one. This technique is used to achieve homogeneity in the temperature and metal composition and to assist in the removal of second phase and dissolved impurities from molten steel. Gas injection is commonly applied to the secondary metallurgy processes and continuous casting, for example the ladle argon gas treatment, RH vacuum degassing, and the gas injection in the Submerged Entry Nozzles (SEN) of continuous casting mold, etc. The development of these processes focuses on achieving two conditions: fine bubbles and good mixing. Fine bubbles provide a large gas/liquid interfacial area and a high attachment probability to inclusions, and good mixing enhances the efficiency of impurity transfer."

Jan 1, 2000

By Z. Sadowski

The influence of organic acids simple salts and A. niger saccharose and molasses worts on sodium oleate adsorption on the salt-type mineral surfaces has been studied. It was found that salts of organic acids had an effect on the sodium oleate adsorption on barite calcite and magnesite. The collector adsorption on the barite and calcite surfaces decreased under the influence of investigated worts. Experimental data suggest that the biomodification of salt-type mineral surfaces can be used for the selective separation of these minerals.

Jan 1, 1991

By Zuoren Huang

The flowsheet of the hyd.rametallurgical zinc plant which is in use at Zhuzhou Smelters is described. The principal features of the process are fluid bed roasting, continuous calcine leaching, solution purification, zinc electrolysis, electrolyte cooling, and finally, the melting and casting of zinc forms. The Zhuzhou process for the flotation of silver from the leach residue collected on the Moor filters is described. The technical details of the process are outlined and the operating data are analyzed. The flotation facilities are described in detail and concentrate grades and recoveries are presented. The waelz process is used to concentrate In, Ge and Ga remaining in the leach residue after silver flotation. These elements subsequently are recovered by selective leaching in sulphuric acid, and details of this operation also are presented.

Jan 1, 1990

By A. D. Neuman, C. C. Davis, M. R. Lopez, A. C. Martinez, T. A. Nothwang, S. L. Voit

"One of the thrust areas for the Global Nuclear Energy Partnership (GNEP) program is the development of actinide bearing fuels for transmutation in a fast reactor. Mixed Oxide (MOX) fuel has an extensive fast reactor irradiation history and thus is being considered for use as a baseline composition from which minor actinides (MA) can be incorporated for use as a transmutation fuel. This study involves characterization of precursor powders and pellets to be inserted into the Advanced Test Reactor in Idaho. These pellets will have three compositions: one standard MOX composition, (U80Pu20)O1.98, and two compositions of MA-MOX with oxygen to metal ratios (O/M) of (U75Pu20Am3Np2)O1.98 and (U75Pu20Am3Np2)O1.95. The precursor powders, which consisted of, highly enriched uranium oxide, HEUO2, depleted uranium oxide, DUO2, neptunium oxide, NpO2, americium oxide, AmO2, and plutonium oxide, PuO2, were characterized using a field emission gun scanning electron microscope (FEG-SEM) for particle morphology, size, and size distribution prior to pellet production.IntroductionThe Global Nuclear Energy Partnership (GNEP) was created in order for “fuel-cycle supplier” nations to provide assured supplies of nuclear fuel to “fuel-cycle customer” nations. The customer nations would utilize the fuel for electricity generation and subsequently return it to the supplier nation after it is spent. This spent fuel would then be reprocessed by the supplier nation in order to recycle the actinide constituents, mainly uranium and plutonium, in advanced nuclear power reactors, and thus reducing waste volumes [1, 2]. Nuclear materials would also be strictly controlled through the International Atomic Energy Agency. One of the thrust areas for the GNEP program is the development of these actinide bearing fuels for transmutation in a fast reactor under the U.S. Advanced Fuel Cycle Initiative (AFCI) in order to transmute long-lived transuranic actinide isotopes into shorter-lived fission products [3]."

Jan 1, 2008

By A. V. Tarasov, V. M. Paretsky

"The design is based on the thermal processing of the wastes in· the intensively bubbled melt in the Vanyukov furnace at the relatively high temperatures (1350- 1450 °C), In this case: -the secondary wastes are not formed; - the especially toxic substances at the outlet from the furnace are absent. The technology was tested on a large scale (on semicommersial bases). Technical and economical basis show profitability of recovery complex for processing of hard garbage waste (HGW) using this technology: the period of capital, investments refunding for the, recovery, complex construction with process annual capacity of 240 thousands tons of wastes is 1,5-2,5 years,"

Jan 1, 2000

By Alexandre Monteiro

Alumina precursor powders can be precipitated from aqueous solutions, using hydrothermal decomposition of urea to deliver base homogeneously to the system. Primary particles agglomerate early in the process, generating a wide size distribution. The presence of a polymeric surfactant such as polyacrylate can suppress or delay agglomeration, reducing particle size and narrowing the size distribution. The stabilization of commercially available a-Alp03 powder with polyacrylate was studied, investigating the effects of polyacrylate molecular weight, ionic strength and temperature. The effect of aluminum concentration, polyacrylate molecular weight and urea concentration on the precipitation of alumina precursors in a sulfate- urea system in the presence of polyacrylate/polyacrylic acid was then studied. The hydrolysis kinetics were followed, and particle sizes were determined. Precipitates were further characterized using energy dispersive spectroscopy. The particle characteristics are discussed in terms of the process conditions.

Jan 1, 1994

By P. A. Davidson, D. J. Short

"In this paper we describe a 'non-contact' electromagnetic nozzle suitable for sprayforming and gas atomization processes. In such processes there is a need to control the flow rate and diameter of the liquid metal jet whilst minimising contamination of the stream. This can be achieved using an electromagnetic valve, which partially levitates the jet in freespace, using a segmented cylinder surrounded by an induction coil. This valve will significantly enhance the quality of the titanium alloys and nickel-based superalloys used in sprayforming and gas atomization. This paper describes the design and test of a laboratory prototype valve based on experiments performed with liquid tin.1. Introduction In many industries there is an increasing need for clean, high quality metals and alloys based on titanium and nickel. Two important processes are: 1) Spray deposition which allows the liquid metal to be converted to a near-net shape, thus alleviating the need for subsequent forging and extensive machining and; 2) Powder production of titanium by gas atomisation.In centrifugal spray deposition of titanium (see figure 1) the metal is induction melted in a cold crucible. The crucible consists of a number of water-cooled segments, which allows the high frequency magnetic field of the coil to pass through the crucible, and into the melt. The charge is melted by the induced eddy currents. Locally at the crucible walls the liquid metal solidifies, and is contained within a. 'skull' of its own solid, thus reducing contamination from the crucible wall. Once melted the metal is poured through an electrically heated graphite nozzle and into the spray forming chamber. The principal limitation of the process to-date, however, is that it currently uses a graphite and /or ceramic nozzle to direct the flow of liquid metal to the atomizing disk and as such there is considerable risk of nozzle erosion with inevitable effects in terms of contamination of the melt stream and variability in flow conditions. In this research programme we develop a. non-contact electromagnetic nozzle, which will totally eliminate refractories and/or ceramic materials from the melting and casting process. This will greatly enhance the technological capabilities of sprayforming and gas atomization processes."

Jan 1, 1999

By Hideaki Tokuyarna

Recovery of metal such as V, Ni and Fe from oil fly ash is important for efficient use of natural resources and protection of environment. Leaching of metals from fly ash followed by ion exchange of leached metals has been examined to develop a process which can selectively recover V and Ni from the fly ash. Experiment of leaching with water, HCI, H2S04 and NaOH leads us to propose a two-step leaching process as an effective and mild operation. The first step is leaching with water for removal of Ni, Mg, A1 and Zn and the second step is leaching with acidic solution for the recovery of V. The metals V and Ni are then separated from other metals in each leached liquor by ion exchange. Advantage of this separation process is that acidic leachant can be reused, which contribute to save separation energy.

Jan 1, 2002

By M. K. Yelloji Roa

Effect of conditioning with Thiobacillus ferrooxidans on the floatability of sphaierite and galena has been determined in this work. The flotation behavior of the conditioned minerals clearly shows that such bacterial conditioning does produce marked modification of their surfaces. The variables affecting the surface modification and thereby the flotation response of the minerals were found to be cell concentration used for bacterial conditioning, the period of biotreatment and the pulp density. Importantly, while the enhancement in flotation obtained due to sulphuric acid treatment was retarded by biotreatment in the case of galena at all cell concentrations due to electrochemical effects, such decrease occurred in the case of sphalerite only at cell concentration sufficiently high for their attachment to the mineral surface. The effect of bacterial conditioning has significant implications to the differential flotation of sphalerite and galena. Mechanisms responsible for the modification of the surface properties of these sulphides due, to bacterial conditioning are discussed.

Jan 1, 1991

By Akira Yazawa, Kazuo Koike, Mitsuhisa Hino

"The vapor pressures of MS (PbS, SnS and Sb2S3) in the molten Cu2S-MS, FeS-MS pseudo-binary and Cu2S-FeS-MS ternary systems were measured by means of a transportation method in the temperature range of 1323 and 1423K to calculate MS activities in the sulfide melts. The activities of MS in these systems show negative deviation from ideal behavior except the FeS binary systems which exhibit nearly ideal behavior in the homogeneous melts. The activities of the Cu2S-FeS pseudobinary system, which is fundamentals of the copper matte, were estimated from the activity values in the ternary systems and exhibit negative deviation from ideality.The distribution behavior of tin between the ·matte and silica saturated fayalite slag was investigated under the controlled partial pressures of S02 at l 523K. It was found that, in general, tin is distributed in the both phase, while tin is concentrated to the slag phase with increasing copper content in the matte. The activity coefficient of SnO in the slag was calculated based on the distribution ratio combined with the activity coefficient in the Cu2S-FeS system.IntroductionThe thermodynamic properties related to the Cu2S-FeS system and the Cu2S-FeS-MS systems (where MS can be PbS, SnS, Sb2S3, As2S3, Bi2S3, etc.) is required to be better understanding of the copper smelting process. However, thermodynamic analysis such as the distribution of impurities among the gas, slag and matte phases is difficult due to lack of thermodynamic data. In this study, the vapor pressures of MS (PbS, SnS and Sb2S3) in the Cu2S-MS, FeS-MS. and Cu2S-FeS-MS systems were measured by a transportation method. The distribution behavior of tin between the matte and silica saturated fayalite slag was also investigated. The results in the present experiments are useful to analyze thermodynamically the behavior of component in the copper matte smelting."

Jan 1, 2000

By Peter Fischer

A demonstration plant for QSL technology with a continuous through-put of up to 10 t/h concentrate has been in operation at the Berzelius smelter, Duisburg, Germany since early 1981. In the QSL-process, both oxidation and reduction steps are performed in a single horizontal long cylindrical reactor. In the present demo-reacior, 2.5 M diameter by 22 M long, these steps are separated by a low partition wall with an underflow opening, to prevent backmixing of slag. -Tests on a variety of concentrates, including high-lead Missouri-type material and lower grades, have shown recoveries and consumables indicating very attractive economics. Investment cost estimates further enhance the economic attractiveness. Environmental protection afforded by the QSL system is a major advantage. The process has proven its reliability and versatility and is now ready for commercialization. Continued test work, including smelting secondary lead materials, is planned.

Jan 1, 1983

By Guo Chen, Jin Chen, Jinhui Peng

In this paper, solving common problem of electrostatic precipitator (ESP), which was frequently ruptured of the cathode insulation in the production process were studied. The microwave heating airflow technology was introduced, which takes full advantage of its unique properties, solves the output problem of the high temperature air, achieves purpose of energy conservation, important economic significance and environmental significance. The mathematical models and designing of microwave high-temperature hot air system was calculated. The common forms of heat exchangers and comparative analysis were also introduced. The conditions found to be at the temperature of 240 °C. Under optimum conditions, the microwave heating power was 1482 W. Based on the mention results, this microwave heating method can be applied effectively and efficiently way for the production process of electrostatic precipitator.

Jan 1, 2015

By Cao rong-jiang, Tang Xin-he

"In ordinary manufacture process of tungsten powder, a preferable intermediate product used is ammonium paratungstate (APT). The particle size of tungten powder made from it through W2OO58 is larger than 1. 0 um. In order to obtain ultrafine tungsten powder with narrow size distribution, a new type of tungstate, hydraziniull tungstate, was studied. Its formula is 5(N2H5)2O·12 WO.s , with tetragonal crystal structure of a=5.821 , c=18. 468. Three methods for preparing hydrazinium tungstate (ART) were set up and ART can be produced by current industrial APT process with little modification of operation and without any change of equipment.Under certain PH and operation condition of the solution from which ART was produced, an autoreduction of tungsten occured, which produced a lower valency tungstate with blue color when ART was heated at different temperatures, in N atmosphere, tungsten bronze, tetragonal W0290 and W02.7E could be obtained respectively. They all have the superiorities, in the production of tungsten powder, of superfine size and narrow size distribution [average size of 0.5um or even smaller.The rate of autoreduction of ART is very fast at elevated temperature. The reduction reaction, which gaves tetragonal WO290, could be handled smoothly without explosion. To research their behaviors at autoreduction temperatures and the products of autoreduction will be new advances of tungsten chemistry and may also serve tungsten industry with new processes and materials."

Jan 1, 1988

By B. Q. Li, S. P. Song

"This paper describes an on-going research on developing coupled boundary element and finite element algorithms for the solution of thermal and electrodynamic problems relating to materials processing. The coupled methods are uniquely suitable for field problems involving composite regions, in which detailed information on field distributions within one particular region is of more interest and yet the solution can be obtained only if the effects of other regions are all considered. Problems of this type include heat transfer in multiple regions and also magnetic induction involving an infinite boundary. The hybrid boundary and finite element formulation, algorithm development and the applications are discussed. Two examples are given to demonstrate the capability and accuracy of the coupled algorithm for heat transfer problems. Various treatments of corner discontinuity are discussed. It is found that the double flux treatment is an ideal choice amongst those tested as it is easy to implement and also gives the most accurate solution. 1. INTRODUCTIONElectrodynamic and transport problems occur frequently in materials processing systems. Accurate solution of these problems is of great importance not only for our fundamental understanding of physical principles governing these phenomena in the processing systems but also for optimization of the existing processes as well as development of new processes. For this purpose, many numerical algorithms have been developed. These computational schemes in general can be classified into three categories, that is, the finite element and finite difference schemes and the boundary element scheme. The former two are domain based numerical algorithms while the latter the boundary-based algorithm.The finite element method, which is based on the variational calculus, is a very useful and yet popular engineering numerical method for boundary value problems defined over irregular boundaries. The use of the method requires the discretization of the entire domain. It can be applied to solve both linear and nonlinear problems, but is particularly powerful for nonlinear problems that involve the field variables defined within the computational domain. On the other hand, the boundary element method, with its root in the Green's function method, is very efficient for linear boundary value problems or nonlinear problems that involve field variables only along the boundaries. The primary advantage of the boundary element method lies in the fact that only the boundaries of the computational domain need to be discretized, and hence the dimension of the problem is reduced by one, compared with the finite element method."

Jan 1, 1994

By Liping Gu, Gordon A. Irons

"A 1/3 scale ""thin-slice"" model of an electric arc furnace was developed so that gas could be injected to simulate foaming gas evolution. The influence of arc jets, oxygen lancing and bottom bubbling was also simulated. Liquid velocities were measured by a white light particle image velocimetry system. Numerical simulations of some of these effects were made using commercial CFD packages. Comparisons with measured results show that considerable care is required to select the appropriate model and to interpret the computational results.INTRODUCTIONDuring recent years electric arc furnaces (EAF) have captured a significant share of steel production, partially due to increased productivity through the introduction of advanced technology such as oxygen injection, slag foaming and long-arc operation, process automation and post-combustion. However, systematic analysis of the process and these effects on heat transfer and fluid flow in the furnace is still in its infancy. Most investigationsl1 6l have been restricted to a specific application such as oxygen lancing or bottom stirring. In addition, it is very difficult to make comparisons between these computed results and experimental/industrial results. In this work a 1/3-scale ""thin-slice"" model of Dofasco's 190 ton EAF was built. The fluid flow in the bath due to the arc jets, bottom stirring, oxygen lancing and CO evolution was simulated. The velocity distributions in the bath were measured using Particle Image Velocimetry (PIV) System. In addition, numerical simulations of bottom stirring and CO evolution were carried out using two commercial CFD packages (Fluent and Phoenics). The objective of this work is to validate the mathematical models so that they can be applied to the full-scale furnaces."

Jan 1, 1999