scholarly journals Sulfur retention by ash during coal combustion - Part I: A model of char particle combustion

2003 ◽  
Vol 68 (2) ◽  
pp. 137-145 ◽  
Author(s):  
Mladen Ilic ◽  
Borislav Grubor ◽  
Vasilije Manovic
Keyword(s):  
Physical Properties ◽  
Dynamic Behavior ◽  
Calcium Oxide ◽  
Coal Combustion ◽  
Parametric Analysis ◽  
Particle Combustion ◽  
Spatial Changes ◽  
Mineral Components ◽  
Char Particle ◽  
Temporal And Spatial

A model for the combustion of porous char particles as a basis for modeling the process of sulfur retention by ash during coal combustion is developed in this paper. The model belongs to the microscopic intrinsic models and describes the dynamic behavior of a porous char particle during combustion taking into account temporal and spatial changes of all important physical properties of the char particle and various combustion parameters. The parametric analysis of the enhanced model shows that the model represents a good basis for the development of a model for the process of sulfur retention by ash during coal combustion. The model enables the prediction of the values of all parameters necessary for the introduction of reactions between sulfur compounds and mineral components in ash, primarily calcium oxide.

Dynamic behavior of coal char particle combustion

1989 ◽  
Vol 76 (3-4) ◽  
pp. 311-323 ◽  
Author(s):  
K. Reményi ◽  
V. Kertész ◽  
L. Vörös ◽  
F. Horváth
Keyword(s):  
Dynamic Behavior ◽  
Coal Char ◽  
Particle Combustion ◽  
Char Particle

scholarly journals Sulfur retention by ash during coal combustion - Part II: A model of the process

2003 ◽  
Vol 68 (3) ◽  
pp. 171-182 ◽  
Author(s):  
Vasilije Manovic ◽  
Borislav Grubor ◽  
Mladen Ilic ◽  
Branimir Jovancicevic
Keyword(s):  
Coal Combustion ◽  
Parametric Analysis ◽  
Coal Particle ◽  
Product Layer ◽  
Coal Rank ◽  
Influence Of Temperature ◽  
Particle Combustion ◽  
Solid Diffusion ◽  
Kinetics Of ◽  
Porous Grains

An overall model for sulfur self-retention in ash during coal particle combustion is developed in this paper. It is assumed that sulfur retention during char combustion occurs due to the reaction between SO2 and CaO in the form of uniformly distributed non-porous grains. Parametric analysis shows that the process of sulfur self-retention is limited by solid diffusion through the non-porous product layer formed on the CaO grains and that the most important coal characteristics which influence sulfur self-retention are coal rank, content of sulfur forms, molar Ca/S ratio and particle radius. A comparison with the experimentally obtained values in a FB reactor showed that the model can adequately predict the kinetics of the process the levels of the obtained values of the SSR efficiencies, as well as the influence of temperature and coal particle size.

scholarly journals Significance of the particle physical properties and the Geldart group in the use of correlations for the prediction of minimum fluidization velocity of biomass–sand binary mixtures

2021 ◽  
Author(s):  
Louis Edwards Cáceres-Martínez ◽  
Diana Carolina Guío-Pérez ◽  
Sonia Lucía Rincón-Prat
Keyword(s):  
Physical Properties ◽  
Binary Mixtures ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Mass Fractions ◽  
Char Particle ◽  
Geldart Groups ◽  
Biomass Particles

AbstractThe present study explores the relevance of the physical properties of biomass particles on the determination of the minimum fluidization velocity (Umf) of binary mixtures. Fluidization experiments were performed in a cold flow unit with diverse biomasses mixed with sand in different mass fractions. Gas velocity and pressure drop across the bed were used to determine Umf. Different correlations reported in the literature were evaluated on their ability to accurately predict Umf of the mixtures. Results showed satisfactory predictions when appropriately identifying correlations according to the corresponding Geldart groups for the biomass particles. This perspective opens new possibilities toward the generalization of correlation factors and helps in improving the accuracy of the prediction for highly heterogeneous mixtures. The methodology also allows the analysis of mixtures for which the experimental approach is difficult, such as those including char particle, with the only requirement of carefully measuring the physical properties of the particles.

scholarly journals Temporal and spatial changes in wall shear stress during atherosclerotic plaque progression in mice

2018 ◽  
Vol 5 (3) ◽  
pp. 171447 ◽  
Author(s):  
R. Xing ◽  
A. M. Moerman ◽  
Y. Ridwan ◽  
M. J. Daemen ◽  
A. F. W. van der Steen ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Mouse Model ◽  
Atherosclerotic Plaque ◽  
Proximal Part ◽  
Plaque Progression ◽  
Plaque Composition ◽  
Spatial Changes ◽  
Temporal And Spatial ◽  
Wall Shear

Wall shear stress (WSS) is involved in atherosclerotic plaque initiation, yet its role in plaque progression remains unclear. We aimed to study (i) the temporal and spatial changes in WSS over a growing plaque and (ii) the correlation between WSS and plaque composition, using animal-specific data in an atherosclerotic mouse model. Tapered casts were placed around the right common carotid arteries (RCCA) of ApoE −/− mice. At 5, 7 and 9 weeks after cast placement, RCCA geometry was reconstructed using contrast-enhanced micro-CT. Lumen narrowing was observed in all mice, indicating the progression of a lumen intruding plaque. Next, we determined the flow rate in the RCCA of each mouse using Doppler Ultrasound and computed WSS at all time points. Over time, as the plaque developed and further intruded into the lumen, absolute WSS significantly decreased. Finally at week 9, plaque composition was histologically characterized. The proximal part of the plaque was small and eccentric, exposed to relatively lower WSS. Close to the cast a larger and concentric plaque was present, exposed to relatively higher WSS. Lower WSS was significantly correlated to the accumulation of macrophages in the eccentric plaque. When pooling data of all animals, correlation between WSS and plaque composition was weak and no longer statistically significant. In conclusion, our data showed that in our mouse model absolute WSS strikingly decreased during disease progression, which was significantly correlated to plaque area and macrophage content. Besides, our study demonstrates the necessity to analyse individual animals and plaques when studying correlations between WSS and plaque composition.

The Spatial-Temporal Change Pattern of Wetland in the Middle-Lower Yangtze River: A Case Study of Wuhu, Anhui

2014 ◽  
Vol 513-517 ◽  
pp. 3228-3232 ◽  
Author(s):  
Xiao Li Tao ◽  
Yong Ping Bai
Keyword(s):  
Quantitative Methods ◽  
Temporal Change ◽  
Remote Sensing Image ◽  
Land Uses ◽  
Change Pattern ◽  
Spatial Changes ◽  
Temporal And Spatial ◽  
Gis Software ◽  
Urban Sprawling

Wetlands play a number of roles in the environment, which are also considered the most biologically diverse of all ecosystems. Utilizing RS and the GIS software, remote datum were matched and classified. By these transactions, the temporal and spatial changes of wetland landscape are explored in Wuhu, combining qualitative analysis and quantitative methods. This paper analyzed the time-spatial revolution process which indicated that, firstly the area of wetland reduced rapidly from remote sensing image in 1988, 2001 and 2005, secondly the exterior of urban changed acutely and the interior were protected well in view of spatial pattern. Moreover, driving force factors were pointed out. Human activities, especially urbanization were the main causes of wetlands degradation. Simultaneity, the development of farming, the construction of infrastructure and nature were important factors. Owing to rapid economic development and urban sprawling, wetlands are encountering threaten to be converting to other land uses. Thus, the paper provides policy advices for wetland conservation and urban planning toward sustainable development.

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