MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ...
MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ... MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ...
Mass release (%) 70 60 50 40 30 20 10 0 Koonfontain chars Middleburg chars #1 #2 #3 #4 Reactor conditions Figure A.2. Mass releases of the Koonfontain and Middleburg chars prepared at four different reactor conditions. Tap Densities and True Densities The bulk densities in Table A.10 were converted to apparent densities using Eq. A.1 (White et al., 1991) and shown in Figure A.3. It can be seen that the presence of oxygen in the char preparation environment slightly decreases the bulk densities of both Koonfontain and Middleburg chars (#2 vs. #1, #4 vs. #3), and that steam also has only a slight effect on the bulk density of either Koonfontain or Middleburg chars (#1 vs. #3, #2 vs. #4). 156
Apparent densities 1.00 0.75 0.50 0.25 0.00 Koonfontain Middleburg char #1 char #2 char #3 char #4 Figure A.3. The apparent densities of Koonfontain and Middleburg chars prepared at four different conditions and collected at 1”. The true densities of both Koonfontain and Middleburg chars in condition #3 are lower than in the other conditions (see Table A.10). The reason for this decrease is not clear. Part of this disagreement may be due to the unstable readings of the pycnometer used in this project, but the fact that both coals showed the same relative behavior seems more than coincidental. N 2 BET Surface Area and CO 2 Surface Area The N 2 BET surface areas and CO 2 surface areas of the Koonfontain and Middleburg chars (see Table A.10) are plotted in Figures A.4 and A.5. These figures show that the presence of oxygen in the char preparation environment (#2 vs. #1, #4 vs. #3) reduces both N 2 BET surface area and CO 2 surface area of each char for both coals, and that the reduction of the N 2 BET surface area is much more marked than that of CO 2 surface area. This implies that the presence of O 2 affects the pores of intermediate size (mesopores) rather than those of small size (micropores). The effect of the reduced steam 157
- Page 125 and 126: Table 7.5. The Experimental Conditi
- Page 127 and 128: The burnout and particle velocity d
- Page 129 and 130: The HP-CBK was used to predict the
- Page 131 and 132: TGA and FFB Data-This Study The rea
- 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
- Page 139 and 140: Currently the correlations between
- Page 141 and 142: 8. Summary and Conclusions The obje
- Page 143 and 144: 0.5 due to the contribution from th
- Page 145 and 146: Langmuir rate equation, the reactio
- Page 147 and 148: II, in agreement with many observat
- Page 149 and 150: 9. Recommendations The predictive c
- 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
- Page 165 and 166: To study the effects of steam, CO w
- Page 167 and 168: times at heights of 1, 2, 4, and 6
- Page 169 and 170: analysis. The char reactivities (in
- 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: temperature profile of the post-fla
- Page 179 and 180: This observation is somewhat surpri
- Page 181 and 182: It is interesting to compare Figure
- 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
- Page 191: Appendix B: Errors and Standard Dev
Apparent densities<br />
1.00<br />
0.75<br />
0.50<br />
0.25<br />
0.00<br />
Koonfontain<br />
Middleburg<br />
char #1 char #2 char #3 char #4<br />
Figure A.3. The apparent densities of Koonfontain and Middleburg chars prepared at<br />
four different conditions and collected at 1”.<br />
The true densities of both Koonfontain and Middleburg chars in condition #3 are<br />
lower than in the other conditions (see Table A.10). The reason for this decrease is not<br />
clear. Part of this disagreement may be due to the unstable readings of the pycnometer<br />
used in this project, but the fact that both coals showed the same relative behavior seems<br />
more than coincidental.<br />
N<br />
2 BET Surface Area and CO<br />
2 Surface Area<br />
The N 2 BET surface areas and CO 2 surface areas of the Koonfontain and<br />
Middleburg chars (see Table A.10) are plotted in Figures A.4 and A.5. These figures<br />
show that the presence of oxygen in the char preparation environment (#2 vs. #1, #4 vs.<br />
#3) reduces both N 2 BET surface area and CO 2 surface area of each char for both coals,<br />
and that the reduction of the N 2 BET surface area is much more marked than that of CO 2<br />
surface area. This implies that the presence of O 2 affects the pores of intermediate size<br />
(mesopores) rather than those of small size (micropores). The effect of the reduced steam<br />
157
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