the coking properties of coal at elevated pressures. - Argonne ...
the coking properties of coal at elevated pressures. - Argonne ... the coking properties of coal at elevated pressures. - Argonne ...
Rate of "NO'! reduction by char under an excess air condition Kinetic information concerning whether or not "NO" can be reduced by char in the presence of oxygen is required in order to analyze the mechanism of "NO" destruction within the bed and freeboard. The use of a fixed bed of diluted char particles was restricted to a range of lower temperatures and lower oxygen concentrations since the char was consumed by combustion reaction. The rate of char combustion is approximately a hundred times faster than the "NO" reducton. The "NO" destruction accompanied by oxidation of char was also assumed to be first order with respect to "NO" concentrations. This assumption was verified under low oxygen and "NO" concentrations. The results are shown in Fig. 6. The reaction was significantly accelarated by adding oxygen. An increased rate was also observed for "NO" destruc- tion by activated carbon. Over a range of higher temperatures the effects of the added oxygen on the rate could not be investigated since the carbon concentration - - I IO 5 10 5 El0 I Y 5 Id 5 I TEMP. ( 'C ) 800 720 600 500 420 370 I e IChar Oxidation I 1.0 1.2 1.4 VT x lo3 ( OK-~ 1 I 1.6 Fig. 6 Rate of NO reduction by char and the effect of oxygen on "NO" reduction 270 A ,/
could not be assumed constant. Thus a fluidized bed reactor with a continuous feed and discharge of carbon (150mm height) was used to analyze the rate for higher oxygen concentration; namely, a large value of a and a higher temperature. Furthermore, the reduction of “NO“ in a Simulated combustion product containing C02 was studied. A remarkable result from these experiments is that a significant reduction of “NO“ was realized even under an excess air condition in which oxygen remained in the outlet flow. The simplified bubbling bed model by Kunii and Levenspiel was used to evaluate the reaction rate in the presence of oxygen. First, the effective bubble diameter was calculated as an adjustable parameter by curvefitting the experimental data obtained in the absence of oxygen to the curve calculated theoretically by the above model and the kinetic data shown previously. Then the increased rate in the presence of oxygen was evaluated by changing the rate, but by keeping the other parameter, including the effective bubble diameter, constant. In this evaluation of the rate, the effect of fuel “NO” formed by the simultaneously occuring combustion of char was compensated for. The details are shown elsewhere. The estimated rate is shown in Fig. 5. An increased rate of “NO“ reduction was observed in the presence of oxygen at both 60OoC and 750°C. The rate was not significantly reduced by the presence of oxygen at 8OO0C. At 853’C the rate of “NO“ destruction was reduced by coexisting oxygen. The extent of “NO“ reduction by both char and activated carbon in both the absence and presence of oxygen was measured over a temperature ronge of 700Q990O0C where the heiyht of the bed was 150mm. The results together with the extent of oxygen consumption is shown in Fig. 7. The increased rate for char was verified up to approximately 75OoC and that for the activated carbon up to 95OoC. Reduction of “NO” in the presence of carbon monoxide and hydrogen8’12) The preliminary investigation concerning the reduction of nitric oxide by char in the presence of hydrogen or carbon monoxide was carried out over a temperature range of 700-800°C in a fixed bed reactor mentioned previously. The reaction was first order with respect to nitric oxide. Ammonia was formed in the nitric oxide hydrogen-char system. The presence of hydrogen and carbon monoxide decreased the consumption of carbon to nearly zero, as: NO + CO+COz + %N2 NO .+ Hg+H20 + ‘/2 Nz NO tV2H2-+NHB + H2 0 (1) (2) (3) The rates and activation energies obtained for the above catalytic reac- tions for (1) or (2) + (3) agreed with the rate of noncatalytic reduction of nitric oxide by char within the experimental error. This strongly suggested that the activated adsorption of nitric oxide on the char sur- face controlled the overall rates. The ratio of ammonia formed by reaction (3) to the consumed nitric oxide which is found to be constant at each temperature is decreased with an increased temperature. 271
- Page 219 and 220: With regard to the similarity parti
- Page 221 and 222: i \ ' 2.2. soz Emission and NOx Emi
- Page 223 and 224: 223
- Page 225 and 226: Figure 9: Sulphur captLTre as 0 fun
- Page 227 and 228: P SUMMARY OF TESTS Testing complete
- Page 229 and 230: I Table 1 Comparison of Sulfur Capt
- Page 231 and 232: , NITROGEN OXIDE REDUCTION Single-S
- Page 233 and 234: 0 The addition of air at the 96-inc
- Page 235 and 236: m- Y i? 4: BO n 8 c Y l0- Bo- I I I
- Page 237 and 238: E! w 2 z e Y 100 - 3 t 5 80- 0, 40
- Page 239 and 240: 0 f 0.so o'm: 0.300 0.zo - - A 5m 4
- Page 241 and 242: &e- -A \ \ \ : ERCENT OVERBED AIR I
- Page 243 and 244: PARTICLE ENTRAINMENT AND NITRIC OXI
- Page 245 and 246: i 1' 1 ! I. i Chaung (15) showed th
- Page 247 and 248: The maximum height that a large par
- Page 249 and 250: 3.0 Nitric Oxide Reduction in the F
- Page 251 and 252: assumed to be identical to that of
- Page 253 and 254: Nomenclature A *t cD ‘NO $3 _ _ _
- Page 255 and 256: TABLE 2. OPERATING CONDITIONS AND E
- Page 257 and 258: i 1 \ ', References 1. 2. ( 3. 1 4.
- Page 259 and 260: \ ” Y) I 259
- Page 261 and 262: t I 100 - - I I ] , I , I , I 'ii 9
- Page 263 and 264: Feeding of the carbonaceous materia
- Page 265 and 266: ! Table 2 Proximate and ultimate an
- Page 267 and 268: lb, , --pp---p-- 4 p? CHAR 1 Tu-IWO
- Page 269: I CHAR Y Y /I TIME O i ' ' ' ' 1 '
- Page 273 and 274: \ greatly acknowledged. Literature
- Page 275 and 276: constructed and operated to demonst
- Page 277 and 278: The experimental procedure for the
- Page 279 and 280: atmospheric pressure fluidized bed
- Page 281 and 282: 1' TABLE 2 Screen Analysis of Sand
- Page 283 and 284: n RECORDER I Ill I ’ NO. NOX THER
- Page 285 and 286: \ 285 Y 0 I- 5 B 5 3 m "9 E5 3 uz 0
- Page 287 and 288: CHAR1 TOC 0.85 M3/k 600 0 700 V 750
- Page 289 and 290: f Durin all the experimental runs t
- Page 291 and 292: Assuming that large coal particles
- Page 293 and 294: i 7 -_ 0 m\o --n 0 W i 293 a\o 0
- Page 295 and 296: The influence of particle size dist
- Page 297 and 298: all the initial values of x for whi
- Page 299 and 300: \ - + 1) x. = 1 bL/n YO Defining di
- Page 301 and 302: $ m. 1 Results and Discussion Evalu
- Page 303 and 304: kl k2 k' KC KD m m. m P N P R R g t
- Page 305 and 306: UNBURNT FRACTION UNBURNT FRACTION m
R<strong>at</strong>e <strong>of</strong> "NO'! reduction by char under an excess air condition<br />
Kinetic inform<strong>at</strong>ion concerning whe<strong>the</strong>r or not "NO" can be reduced<br />
by char in <strong>the</strong> presence <strong>of</strong> oxygen is required in order to analyze <strong>the</strong><br />
mechanism <strong>of</strong> "NO" destruction within <strong>the</strong> bed and freeboard. The use <strong>of</strong><br />
a fixed bed <strong>of</strong> diluted char particles was restricted to a range <strong>of</strong> lower<br />
temper<strong>at</strong>ures and lower oxygen concentr<strong>at</strong>ions since <strong>the</strong> char was consumed<br />
by combustion reaction. The r<strong>at</strong>e <strong>of</strong> char combustion is approxim<strong>at</strong>ely<br />
a hundred times faster than <strong>the</strong> "NO" reducton.<br />
The "NO" destruction accompanied by oxid<strong>at</strong>ion <strong>of</strong> char was also<br />
assumed to be first order with respect to "NO" concentr<strong>at</strong>ions. This<br />
assumption was verified under low oxygen and "NO" concentr<strong>at</strong>ions. The<br />
results are shown in Fig. 6. The reaction was significantly accelar<strong>at</strong>ed<br />
by adding oxygen. An increased r<strong>at</strong>e was also observed for "NO" destruc-<br />
tion by activ<strong>at</strong>ed carbon.<br />
Over a range <strong>of</strong> higher temper<strong>at</strong>ures <strong>the</strong> effects <strong>of</strong> <strong>the</strong> added oxygen<br />
on <strong>the</strong> r<strong>at</strong>e could not be investig<strong>at</strong>ed since <strong>the</strong> carbon concentr<strong>at</strong>ion<br />
-<br />
-<br />
I<br />
IO<br />
5<br />
10<br />
5<br />
El0<br />
I<br />
Y<br />
5<br />
Id<br />
5<br />
I<br />
TEMP. ( 'C )<br />
800 720 600 500 420 370<br />
I e IChar Oxid<strong>at</strong>ion I<br />
1.0 1.2 1.4<br />
VT x lo3 ( OK-~ 1<br />
I<br />
1.6<br />
Fig. 6 R<strong>at</strong>e <strong>of</strong> NO reduction by char and <strong>the</strong> effect <strong>of</strong><br />
oxygen on "NO" reduction<br />
270<br />
A<br />
,/
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