MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ...
MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ... MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ...
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8. Summary and Conclusions The objective of this project was to develop a model that can be used to explain and unify char oxidation rates over wide ranges of experimental conditions, including temperature, total pressure, oxygen mole fraction and particle size. A secondary objective of this work was to explore how the apparent reaction order of char oxidation changes with experimental conditions. The theoretical challenge in carbonaceous solid combustion, known as the rough sphere combustion phenomenon, was also explored. The accomplishments are summarized and conclusions are drawn below. Analytical Solutions of the Effectiveness Factors Bischoff (1965) proposed a so-called “general asymptotic solution” for predicting the effectiveness factor for an arbitrary rate form. Based on the work of Bischoff, a general modulus (Eq. 2.30) was obtained in this study for the Langmuir rate equation. This is the first time that the general modulus for the Langmuir rate equation has been applied to char oxidation. The asymptotic solutions of the effectiveness factors for both the Langmuir rate equation and the m-th order rate equation were examined by comparison with numerical solutions. It was found that the general asymptotic solutions lead to errors as high as 17% in the intermediate range of the Thiele modulus. A correction function was developed to improve the accuracy of the general asymptotic solutions. The corrected 121
- Page 90 and 91: Single-Film Char Oxidation Submodel
- Page 92 and 93: where and An energy balance is used
- Page 94 and 95: where is the empirical burning mode
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- Page 100 and 101: Effective Diffusivity The major obs
- Page 102 and 103: where r p1 and r p2 are the average
- Page 104 and 105: where r p1 is the macro-pore radius
- Page 107 and 108: 7. Model Evaluation and Discussion
- Page 109 and 110: experiments are non-porous, the rat
- Page 111 and 112: and 2850 K). For consistency with t
- Page 113 and 114: The value of the roughness factor w
- Page 115 and 116: = S int S ext D e r p a 2 2M C M O2
- Page 117 and 118: Reactor Head Flow Straightener Reac
- Page 119 and 120: the large size of the particle, and
- Page 121 and 122: taking into account convection, rad
- Page 123 and 124: 2.5x10 -4 2 /sec) 2.0 1.5 Rate (g/c
- Page 125 and 126: Table 7.5. The Experimental Conditi
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- Page 129 and 130: The HP-CBK was used to predict the
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- Page 133 and 134: This equation can be derived as fol
- Page 135 and 136: q = A 1p e − E 1 p / RT P os 1 +
- Page 137 and 138: m obs = 0 at high temperatures) and
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- Page 151 and 152: References Ahmed, S., M. H. Back an
- Page 153 and 154: Essenhigh, R. H., D. Fortsch and H.
- Page 155 and 156: Mehta, B. N. and R. Aris , “Commu
- Page 157 and 158: Szekely, J. and M. Propster, "A Str
- Page 159 and 160: Appendices 139
- Page 161 and 162: Introduction Appendix A: Experiment
- Page 163 and 164: detaching the flame from the burner
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- Page 171 and 172: Table A.5. Moisture, Ash and ICP Ma
- Page 173 and 174: Table A.9. Elemental Analyses of Fo
- Page 175 and 176: temperature profile of the post-fla
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- Page 179 and 180: This observation is somewhat surpri
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- Page 183 and 184: The N 2 BET surfacea areas and H/C
- Page 185 and 186: collected in the #4 reactor conditi
- Page 187 and 188: Rate (gC /g C remaining /sec) 1.6x1
- Page 189 and 190: close to zero, the accumulated erro
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