Heat Transfer From a Molten Phase to an Immersed Coal Particle During Devolatilization

1993 ◽  
Vol 115 (3) ◽  
pp. 717-723 ◽  
Author(s):  
R. H. Hurt ◽  
T. H. Fletcher ◽  
R. S. Sampaio
Keyword(s):  
Heat Transfer ◽  
Coal Gasification ◽  
Volatile Matter ◽  
Molten Carbonate ◽  
Transfer Coefficients ◽  
X Ray ◽  
Heat Transfer Coefficients ◽  
Coal Particles ◽  
Bath Smelting ◽  
Molten Phase

In several developmental and commercial processes, coal particles come into direct contact with a high-temperature molten phase. These processes include molten carbonate coal gasification and bath smelting for the production of iron. Recently, real-time X-ray fluoroscopic images have been published that show volatile matter evolving rapidly from coal particles immersed in molten phases, displacing the surrounding melt and producing a periodic cycle of formation, rise, and detachment of gas cavities. The present work makes use of these observations to develop a model of heat transfer from the melt to particles undergoing gas evolution. The model is developed for the general case and applied to predict melt-particle heat transfer coefficients under conditions relevant to bath smelting processes. The model shows that the presence of the gas film can actually increase the overall heat transfer rate under certain conditions.

Heat Transfer in a Simulated Downer Entrance

2003 ◽  
Author(s):  
Jieguang Wang ◽  
Jianzhong Yao ◽  
Weigang Lin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Dimensionless Analysis ◽  
Bed Temperature ◽  
Coal Particles ◽  
Experimental Apparatus ◽  
Coefficient Corrélation

Heat transfer experiments were performed in a reactor, which was built to simulate the mixing between particles and particles in the entrance zone of a downer reactor being applied in the ‘coal topping process’ developed at Institute of Process Engineering, Chinese Academy of Sciences. Superficial heat transfer coefficients were measured with a ball probe. The experimental results show that the heat transfer coefficient increases with the bed temperature and the solid holdup, and decreases with the diameter of bed materials. A semi-empirical heat transfer coefficient correlation was obtained based on dimensionless analysis, taking into account the effect of the important operating parameters under simulated downer entrance conditions. The results calculated from the correlation show a fair agreement with the experimental data. The correlation was applied to estimate the heating rate of the coal particles used in a bench scale experimental apparatus for studying the coal topping process.

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