NONISOTHERMAL ANALYSIS OF THE KINETICS OF THE COMBUSTION OF COKED SAND

被引:14
作者
LIN, LC [1 ]
DEO, MD [1 ]
HANSON, FV [1 ]
OBLAD, AG [1 ]
机构
[1] UNIV UTAH,DEPT FUELS ENGN,SALT LAKE CITY,UT 84112
关键词
D O I
10.1021/ie00056a016
中图分类号
TQ [化学工业];
学科分类号
0817 ;
摘要
The kinetic parameters for the combustion of carbonaceous residue or coke deposited on the sand during the fluidized bed pyrolysis of tar sands have been determined. Nonisothermal thermo-gravimetric experiments at a fixed heating rate were performed at various oxygen partial pressures on coked sands produced at three different retorting temperatures. Direct Arrhenius plot analysis which invoked a first-order assumption with respect to the unreacted fraction of coke yielded an oxygen partial pressure dependence of 0.5 and activation energies in the range of 127-148 kJ/mol. A second-order assumption with respect to the residual carbon gave an oxygen partial pressure dependence of 0.75 and activation energies of 175-217 kJ/mol. The first-order model was found to be applicable for lower oxygen partial pressures (< 5 kPa), and the second-order model was appropriate for high oxygen partial pressures (> 5 kPa). In the overall range of oxygen partial pressures, the second-order model seems to provide a better fit to the data. These observations were consistent with the chemisorption/surface reaction mechanism proposed for the combustion of small carbonaceous particles. The Freeman and Carrol analysis indicated a reaction order between 1 and 2 with respect to the uncovered coke fraction, with high oxygen partial pressures resulting in reaction orders close to 2 and lower oxygen partial pressures yielding orders nearer to 1.
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页码:1795 / 1801
页数:7
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