MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ...
MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ... MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ...
Table A.2. Measured Centerline Reactor Temperatures Condition number #1 #2 #3 #4 Condition name CH 4 fuel-rich CH 4 fuel-lean CO fuel-rich CO fuel-lean Height Above Burner Gas Temperature Profile (K)* 0.25 1542 1677 1650 1718 0.50 1637 1628 1687 1670 0.75 1640 1608 1703 1647 1.00 1644 1592 1696 1630 * Measured along reactor centerline, corrected for radiation loss. Procedures and Apparatus Char Preparation Coal particles were injected through the flame, reacted, captured by a suction probe at a certain distance away from the injection point, quenched by nitrogen in the probe tip, and separated from the soot and the gas in a virtual impactor and cyclone system. The distance between the injection point and the suction probe (called the reaction length or sampling height) was set to one inch for most of the experiments, corresponding to a residence time of 14 ms. Studies of Koonfontain char were also made at the methane fuel-lean condition at increased residence times by sampling at heights of 2, 4, and 6 inches (corresponding to about 25, 44, and 63 ms, respectively). The particle residence time as a function of sampling height was measured for several different coals with a high-speed video camera by Ma (1996). The residence time was found to be dependent on the gas temperature profile and the total flow rate through the reactor, but almost independent on the coal type. The total flow rate and gas temperature profile were therefore kept very similar from one reactor condition to another in order to achieve similar particle residence times. In this project the particle residence 146
times at heights of 1, 2, 4, and 6” are taken as 14, 25, 44, and 63 ms respectively, which are the values measured by Ma (1996). Proximate and Ultimate Analysis ASTM standard procedures were followed for the moisture, ash and volatile measurements in the proximate analysis. Volatile content measurements were only performed for the parent coals, since complete devolatilization was achieved in the chars. Moisture and ash contents were measured for chars and the their parent coals before the ICP tracer analysis was performed in order to obtain the mass release of the chars. CHNS data were measured on a dry basis, then converted to dry ash free (daf) basis using the ash contents measured in the proximate analysis. Oxygen concentrations (daf) were calculated by difference: O% = 100% - (C% + H% + N% + S%). A Leco CHNS analyzer (model 932) was used to perform the CHNS analysis. Internal Surface Area Nitrogen BET multi-point surface area and carbon dioxide surface area (0°C) were measured for all chars using a Micromeritics Gemini 2360 instrument. TGA Reactivity The reactivities of chars were measured in a Perkin Elmer thermogravimetric analyzer (model 7) at 550 °C in a gas flow of 10% oxygen and 90% nitrogen. 147
- Page 115 and 116: = S int S ext D e r p a 2 2M C M O2
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- 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: To study the effects of steam, CO w
- 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
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- Page 183 and 184: The N 2 BET surfacea areas and H/C
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times at heights of 1, 2, 4, and 6” are taken as 14, 25, 44, and 63 ms respectively, which<br />
are the values measured by Ma (1996).<br />
Proximate and Ultimate Analysis<br />
<strong>AS</strong>TM standard procedures were followed for the moisture, ash and volatile<br />
measurements in the proximate analysis. Volatile content measurements were only<br />
performed for the parent coals, since complete devolatilization was achieved in the chars.<br />
Moisture and ash contents were measured for chars and the their parent coals before the<br />
ICP tracer analysis was performed in order to obtain the mass release of the chars.<br />
CHNS data were measured on a dry basis, then converted to dry ash free (daf)<br />
basis using the ash contents measured in the proximate analysis. Oxygen concentrations<br />
(daf) were calculated by difference: O% = 100% - (C% + H% + N% + S%). A Leco<br />
CHNS analyzer (model 932) was used to perform the CHNS analysis.<br />
Internal Surface Area<br />
Nitrogen BET multi-point surface area and carbon dioxide surface area (0°C) were<br />
measured for all chars using a Micromeritics Gemini 2360 instrument.<br />
TGA Reactivity<br />
The reactivities of chars were measured in a Perkin Elmer thermogravimetric<br />
analyzer (model 7) at 550 °C in a gas flow of 10% oxygen and 90% nitrogen.<br />
147
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