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A Real-Time Embedded Control System for Electro-Fused Magnesia Furnace  [PDF]
Fang Zheng,Yang Jie,Tao Shifei,Wu Zhiwei,Chai Tianyou
Journal of Control Science and Engineering , 2013, DOI: 10.1155/2013/719683
Abstract: Since smelting process of electro-fused magnesia furnace is a complicated process which has characteristics like complex operation conditions, strong nonlinearities, and strong couplings, traditional linear controller cannot control it very well. Advanced intelligent control strategy is a good solution to this kind of industrial process. However, advanced intelligent control strategy always involves huge programming task and hard debugging and maintaining problems. In this paper, a real-time embedded control system is proposed for the process control of electro-fused magnesia furnace based on intelligent control strategy and model-based design technology. As for hardware, an embedded controller based on an industrial Single Board Computer (SBC) is developed to meet industrial field environment demands. As for software, a Linux based on Real-Time Application Interface (RTAI) is used as the real-time kernel of the controller to improve its real-time performance. The embedded software platform is also modified to support generating embedded code automatically from Simulink/Stateflow models. Based on the proposed embedded control system, the intelligent embedded control software of electro-fused magnesium furnace can be directly generated from Simulink/Stateflow models. To validate the effectiveness of the proposed embedded control system, hardware-in-the-loop (HIL) and industrial field experiments are both implemented. Experiments results show that the embedded control system works very well in both laboratory and industry environments. 1. Introduction Fused magnesia is an important and widely used refractory and raw material for many industries, which has lots of merits such as high melting point, antioxidation, structural integrity, and strong insulating features [1]. Nowadays, high-purity fused magnesia is produced mainly by three-phase electro-fused furnace [2]. Magnesia is melted by absorbing heat released by the electric arc of three graphite electrodes. Stability of the current of three electrodes is the key factor that influences product quality. Therefore, the most important object of electro-fused magnesia control system is to keep three-phase current stabilizing within a desired range through adjusting position of electrodes, thereby stabilizing the operation of smelting process and achieving corresponding control indices. However, smelting process of electro-fused magnesia furnace is a complicated process that has characteristics like complex operation conditions, strong nonlinearities, and strong couplings, which make it difficult to achieve
Effect of zircon on sintering, composition and microstructure of magnesia powders  [PDF]
Peng C.,Li N.,Han B.
Science of Sintering , 2009, DOI: 10.2298/sos0901011p
Abstract: The effects of zircon on sintering, composition and microstructure of fused magnesia powders were studied by XRD, SEM and EDAX. With the increase of zircon content up to 6 wt%, the strength of sintered samples increased but the apparent porosity decreased. 6 wt% is an appropriate content of zircon to possess better properties of samples, and in this case the samples have a dense microstructure and lower content of glass phase. The presence of a liquid phase resulting from zircon addition is the main reason to improve sintering of magnesia powders.
RESEARCH ON PLASMA SMELTING OF ILMENITE
LAN Yaozhong,Panzhihua Institute of Iron,Steel Research,Sichuan,ChinaZHU Zuze,LIU Chunpeng,Kunming Institute of Technology,Kunming,China LAN Yaozhong,Panzhihua Institute of Iron,Steel Research,Dukou,Sichuan,China,
LAN Yaozhong
,Panzhihua Institute of Iron and Steel Research,Sichuan,ChinaZHU Zuze,LIU Chunpeng,Kunming Institute of Technology,Kunming,China LAN Yaozhong,Panzhihua Institute of Iron and Steel Research,Dukou,Sichuan,China

金属学报(英文版) , 1992,
Abstract: The process of Luda ilmenite smelting by plasma furnace has been studied by means of self-designed plasma torch. The prereduced Luda ilmenite was melted satisfactorily in plasma furnace to produce Ti enriched slag containing 90-98% TiO_2.
THERMODYNAMIC STUDY OF CHROMITE CAUSTICFUSION PROCESS
THERMODYNAMIC STUDY OF CHROMITE CAUSTIC FUSION PROCESS

SL Zheng,Y Zhang,
S.L.
,Zheng,and,Y.,Zhang

金属学报(英文版) , 2001,
Abstract: A new method for chromate cleaning production named chromite caustic fusion process, is advanced by Institute of Chemical Metallurgy, the Chinese Academy of Sciences. With sodium hydroxide as reaction medium, the new process is composed of three procedures: liquid phase oxidation of chromite - metastable phase separation - carbonation ammonium transition. Generally illustrating the new process and its features, this paper mainly studies the thermodynamics of chromite oxidation. The new process has much better practical results than the conventional chromate production process in which sodium carbonate is used as reaction medium. The superiority is also shown through thermodynamic studies.
Thermodynamics Study on the Decomposition of Chromite with KOH
THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Z Sun,SL Zheng,Y Zhang,JY Zhang,
Z.
,Sun,S.L.,Zheng,Y.,Zhang

金属学报(英文版) , 2007,
Abstract: Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature,which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.
Modelling burned area in Africa  [PDF]
V. Lehsten,P. Harmand,I. Palumbo,A. Arneth
Biogeosciences Discussions , 2010, DOI: 10.5194/bgd-7-4385-2010
Abstract: The simulation of current and projected wildfires is crucial for predicting vegetation as well as pyrogenic emissions in the African continent. This study uses a data-driven approach to parameterize burned area models applicable to dynamic vegetation models (DVMs) and global circulation models (GCMs). Therefore we restricted our analysis to variables for which either projections based on climate scenarios are available, or which are calculated by DVMs and the spatial scale to one degree spatial resolution, a common scale for DVMs as well as GCMs. We used 9 years of data (2000–2008) for the variables tree and herb cover, precipitation over the last dry season, wet season and averaged over the last 2 years, a fire-danger index (the Nesterov index), population density and an annual proportion of area burned derived from the MODIS MCD45A1 product. Since the effect of fires on vegetation depends strongly on burning conditions, the timing of wildfires is of high interest too. We related the seasonal occurrence of wildfires to the Nesterov index and found a lognormal relationship with a maximum at a value of 104. We parameterized two generalized linear models, one with the full variable set (model I) and one (model II) considering only climate variables. All introduced variables resulted in an increase in model performance. Model I correctly predicts the spatial distribution and extent of fire prone areas though the total variability is underrepresented. Model II has a much lower performance in both aspects (correlation coefficient of predicted and observed ratio of burned area: 0.71 model I and 0.58 model II). An application of the models with simulated climate data ranging from 1980 to 2060 resulted in a strong decrease of burned area of ca. 20–25%. Since wildfires are an integral part of land use practices in Africa, this indicates a high loss in areas favourable for food production.
Modelling burned area in Africa
V. Lehsten, P. Harmand, I. Palumbo,A. Arneth
Biogeosciences (BG) & Discussions (BGD) , 2010,
Abstract: The simulation of current and projected wildfires is essential for predicting crucial aspects of vegetation patterns, biogeochemical cycling as well as pyrogenic emissions across the African continent. This study uses a data-driven approach to parameterize two burned area models applicable to dynamic vegetation models (DVMs) and Earth system models (ESMs). We restricted our analysis to variables for which either projections based on climate scenarios are available, or that are calculated by DVMs, and we consider a spatial scale of one degree as the scale typical for DVMs and ESMs. By using the African continent here as an example, an analogue approach could in principle be adopted for other regions, for global scale dynamic burned area modelling. We used 9 years of data (2000–2008) for the variables: precipitation over the last dry season, the last wet season and averaged over the last 2 years, a fire-danger index (the Nesterov index), population density, and annual proportion of area burned derived from the MODIS MCD45A1 product. Two further variables, tree and herb cover were only available for 2001 as a remote sensing product. Since the effect of fires on vegetation depends strongly on burning conditions, the timing of wildfires is of high interest too, and we were able to relate the seasonal occurrence of wildfires to the daily Nesterov index. We parameterized two generalized linear models (GLMs), one with the full variable set (model VC) and one considering only climate variables (model C). All introduced variables resulted in an increase in model performance. Model VC correctly predicts the spatial distribution and extent of fire prone areas though the total variability is underrepresented. Model VC has a much lower performance in both aspects (correlation coefficient of predicted and observed ratio of burned area: 0.71 for model VC and 0.58 for model C). We expect the remaining variability to be attributed to additional variables which are not available at a global scale and thus not incorporated in this study as well as its coarse resolution. An application of the models using climate hindcasts and projections ranging from 1980 to 2060 resulted in a strong decrease of burned area of ca. 20–25%. Since wildfires are an integral part of land use practices in Africa, their occurrence is an indicator of areas favourable for food production. In absence of other compensating land use changes, their projected decrease can hence be interpreted as a indicator for future loss of such areas.
Tunnel magnetoresistance in alumina, magnesia and composite tunnel barrier magnetic tunnel junctions  [PDF]
Oliver Schebaum,Volker Drewello,Alexander Auge,Günter Reiss,Markus Münzenberg,Henning Schuhmann,Michael Seibt,Andy Thomas
Physics , 2010, DOI: 10.1016/j.jmmm.2011.01.011
Abstract: Using magnetron sputtering, we have prepared Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions with tunnel barriers consisting of alumina, magnesia, and magnesia-alumina bilayer systems. The highest tunnel magnetoresistance ratios we found were 73% for alumina and 323% for magnesia-based tunnel junctions. Additionally, tunnel junctions with a unified layer stack were prepared for the three different barriers. In these systems, the tunnel magnetoresistance ratios at optimum annealing temperatures were found to be 65% for alumina, 173% for magnesia, and 78% for the composite tunnel barriers. The similar tunnel magnetoresistance ratios of the tunnel junctions containing alumina provide evidence that coherent tunneling is suppressed by the alumina layer in the composite tunnel barrier.
Recovery of Chromite Values from Plant Tailings by Gravity Concentration  [PDF]
Sunil Kumar Tripathy, Y. Ramamurthy, Veerendra Singh
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2011, DOI: 10.4236/jmmce.2011.101002
Abstract: Large tonnages of chromite tailing were discarded during processing of chromite ore in the conventional circuit. A typical chromite plant tailing was treated in wilfley table for the recovery of chromite values. Optimisation study was carried out for the process parameters of wilfley table using empirical models, developed from the experimental data. It was found that grade and recovery (% Cr2O3) in the concentrate fraction majorly depended on the variation of deck tilt angle. To achieve high grade (>45%) with acceptable recovery (>40%), set of optimisation condition of parameters have derived which resulted large quantity of wash water (>5lpm of flow rate) is necessary. Validation of the empirical models were done with set of tests which resulted good agreement with the predict values (R2 is 0.96 and 0.99 for the grade and recovery respectively).
Changes in the surface morphology of magnesia particles due to the leaching using hydrochloric acid
Alena Fedoro?ková,Pavel Raschman,Gabriel Su?ik,Jaroslav Brian?in
Acta Montanistica Slovaca , 2007,
Abstract: Thorough kinetic analysis of the magnesia leaching based on measuring the changes in lixiviant composition revealed that there are differences between the actual leaching behaviour and predictions obtained using the non-porous shrinking particle model (NSPM). A detailed study of the morphology of the solid during the leaching process using SEM showed that observed deviations from the NSPM model depend on the particle size; chemical (mineralogical) composition and the polycrystalline nature of magnesia.
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