The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Kejiang Li - One of the best experts on this subject based on the ideXlab platform.
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influence of sio2 reduction on the local structural order and fluidity of molten coke ash in the high Temperature Zone of a blast furnace a molecular dynamics simulation investigation
Fuel, 2016Co-Authors: Jianliang Zhang, Kejiang Li, Mohammed Bouhadja, Rita Khanna, Yapeng Zhang, Tianjun Yang, Veena Sahajwalla, Yindong Yang, Mansoor BaratiAbstract:Abstract An in-depth understanding about the transformation of molten coke ash is significant to uncover the mechanism of coke reaction at high Temperature inside a blast furnace. The evolution of local structural order and fluidity of molten coke ash (SiO2-Al2O3-CaO) with the reduction of SiO2 at a fixed Al2O3/CaO ratio was investigated by means of molecular dynamics (MD) simulation. While [SiO4] tetrahedral was the main structural units forming Si-O network, due to the high levels of Al2O3 in coke minerals [AlO4] and a small amount of [AlO5] were the two key structural units forming the Al-O network. The effect of chemical composition on the bond length of Si-O, Al-O and Ca-O is very weak, while the coordination number of Al-O can be slightly influenced by the reduction of SiO2 due to the unstable structure of Al-centered polyhedron compared with [SiO4]. The concentration of bridging oxygen decreases, while that of tricluster oxygen increases with the reduction of SiO2 from the system. Al-centered polyhedrons prefer to be connected by O triclusters, while Si-centered polyhedron favor a link by bridging oxygen. With the decrease of SiO2, more [AlO4] will change from edge-sharing to corner-sharing with similar units. The angular distribution of Si-O-Si exhibits an asymmetric shape with the average value around 151°, while two peaks were observed in the Al-O-Al angular distribution because of the edge-sharing (∼90°) and corner-sharing (∼122°) features in Al-centered polyhedrons. With the reduction of SiO2 from the system, the diffusivity of all atoms increase considerably since the amount of strong Si-O bond decreases. Viscosity estimated from MD simulation decrease with the reduction of SiO2. The good agreement between MD simulated data and experimental data indicates that MD simulation can be adopted to estimate the property change of molten coke ash at high Temperature.
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gasification of graphite and coke in carbon carbon dioxide sodium or potassium carbonate systems
Industrial & Engineering Chemistry Research, 2014Co-Authors: Kejiang Li, Xiaojun Ning, Jianliang Zhang, Tianqiu WangAbstract:The thermodynamics of possible reactions, including gasification and reduction reactions, in carbon–carbon dioxide–sodium or potassium carbonate systems was analyzed first. And then, the gasification reactions of graphite and coke with CO2 in this system were studied kinetically by Temperature programmed thermogravimetry. The results showed that the carbon conversion curve shifted to a lower Temperature Zone after Na2CO3 or K2CO3 was added, and graphite was more susceptible than coke to be catalyzed by Na2CO3 or K2CO3. Ten kinetic equations were adopted to simulate the reaction process using the method of Coats–Redfern. The Avrami–Erofeev equation was found to be the most probable kinetic equation, with which the values of activation energy and frequency factor were calculated. The kinetic simulation indicated that the activation energy of coke carbon had been activated to the lowest level by its inner factors, thus it was difficult to be reduced by adding Na2CO3 or K2CO3. The kinetic compensation effect ...
Muhamad Rasat Muhamad - One of the best experts on this subject based on the ideXlab platform.
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the effect of source Temperature on morphological and optical properties of zno nanowires grown using a modified thermal evaporation set up
Current Applied Physics, 2011Co-Authors: Ramin Yousefi, Muhamad Rasat MuhamadAbstract:Abstract In this paper the effect of source Temperature on the morphological and optical properties of ZnO nanowires using a thermal evaporation set-up was investigated. A simple horizontal double-tube system was used to grow the ZnO nanowires. The nanowires with different morphology were obtained by the same substrate Temperature and different source Temperatures. Vertical and aligned nanowires with hexagonal shape were grown at the source Temperature of 950 °C, while the nanowires with spear shape were grown at the source Temperature of 1050 °C. The diameters of nanowires were the same for the both set of nanowires, approximately. In addition, characterizations showed that the growth direction of the both set of nanowires was [0001]. Room Temperature photoluminescence and Raman spectroscopy studies demonstrated that the ZnO nanowires were grown in lower source Temperature Zone had better crystalline quality and optical properties than those were grown by higher source Temperature.
Georges Guiochon - One of the best experts on this subject based on the ideXlab platform.
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use of isopycnic plots in designing operations of supercritical fluid chromatography ii the isopycnic plots and the selection of the operating pressure Temperature Zone in supercritical fluid chromatography
Journal of Chromatography A, 2011Co-Authors: Abhijit Tarafder, Georges GuiochonAbstract:Abstract In SFC, the key chromatographic parameters, the retention factors and the column efficiency, strongly depend on the density of the mobile phase. This indicates that the isodensity or isopycnic plots, drawn on the pressure–Temperature plane, can provide an effective tool to help analyzing how the chromatograms obtained in SFC evolve, when the experimental conditions, the inlet and outlet pressures and the column Temperature, are changed. In a companion paper, we analyzed the role of density in controlling the physical properties of the mobile phase, which in turn controls solute retentions and column efficiencies. In this report, we analyze the operating conditions in SFC with reference to the isopycnic plots of carbon dioxide. This analysis clarifies the differences and similarities between the operating conditions selected in the subcritical Zone and those located in the supercritical Zone. It also sets out an operational map illustrating how retention factors vary with respect to the operating Temperatures and pressures. This study is focused on the use of pure carbon dioxide as the mobile phase, but the same method of investigation is also applicable when the mobile phase contains a modifier.
William Yang - One of the best experts on this subject based on the ideXlab platform.
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numerical modeling of victorian brown coal combustion in a tangentially fired furnace
Energy & Fuels, 2010Co-Authors: Zhao Feng Tian, Peter J Witt, Phillip M Schwarz, William YangAbstract:A computational fluid dynamics (CFD) model of a 375 MW brown-coal-fired furnace in the Latrobe Valley, Australia, has been developed using ANSYS CFX 12.0. To improve the model predictions, a coal combustion model that takes into consideration carbon monoxide reactions has been utilized in ANSYS CFX 12.0. A level of confidence in the current CFD model has been established by carrying out a mesh independence test and validation against the furnace gas exit Temperature (FGET), concentration of flue gas components, total boiler heat supply, and the wall incident heat fluxes measured in the power plant. The validated CFD model is then applied to investigate the effects of several operating conditions at full load, such as different out-of-service firing groups and different combustion air distributions on the coal flame. It is found that the selection of out-of-service firing groups has a considerable effect on coal combustion in terms of high-Temperature Zone shape and location and distribution of incident ra...
Arash Tahmasebi - One of the best experts on this subject based on the ideXlab platform.
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thermogravimetric study of the combustion of tetraselmis suecica microalgae and its blend with a victorian brown coal in o2 n2 and o2 co2 atmospheres
Bioresource Technology, 2013Co-Authors: Arash Tahmasebi, Mohd Asyraf Kassim, Sankar BhattacharyaAbstract:Abstract The combustion characteristics of microalgae, brown coal and their blends under O 2 /N 2 and O 2 /CO 2 atmospheres were studied using thermogravimetry. In microalgae combustion, two peaks at 265 and 485 °C were attributable to combustion of protein and carbohydrate with lipid, respectively. The DTG profile of coal showed one peak with maximum mass loss rate at 360 °C. Replacement of N 2 by CO 2 delayed the combustion of coal and microalgae. The increase in O 2 concentration did not show any effect on combustion of protein at the first stage of microalgae combustion. However, between 400 and 600 °C, with the increase of O 2 partial pressure the mass loss rate of microalgae increased and TG and DTG curves of brown coal combustion shifted to lower Temperature Zone. The lowest and highest activation energy values were obtained for coal and microalgae, respectively. With increased microalgae/coal ratio in the blends, the activation energy increased due to synergy effect.
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pyrolysis and combustion behavior of coal gangue in o2 co2 and o2 n2 mixtures using thermogravimetric analysis and a drop tube furnace
Energy & Fuels, 2013Co-Authors: Fanrui Meng, Arash Tahmasebi, Yanna HanAbstract:Combustion of coal gangue is extensively used for power generation in China. In this paper, pyrolysis and combustion characteristics of a low-rank coal gangue have been investigated under oxy-fuel (O2/CO2) and air (N2/O2) conditions using a drop tube furnace and thermogravimetric analysis. Pyrolysis experiments were carried out in N2 and CO2 environments, which are the main diluting gases of air and oxy-fuel environments, respectively. The burnout and yields of volatile matter were analyzed during DTF experiments. At lower Temperatures, the weight loss rate of coal gangue during pyrolysis in N2 was higher than that in CO2. However, further weight loss took place in CO2 atmosphere at Temperatures above 800 °C due to CO2 gasification of chars. The thermogravimetric analysis (TGA) results confirmed that the pyrolysis in CO2 environment can be divided into three stages: moisture release, devolatilization, and char gasification by CO2 in a higher Temperature Zone. Combustion experiments were carried out in fou...
