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 ...
ash and moisture free basis. This indicates that the conversion rate of fuel bond nitrogen to nitric oxide was reduced with the increased vola- tile contents. Jonke et a1 . ')reported that "NO" emission under a substoichiometric combustion of coal was increased at decreased temperature. This behavior was observed in Fig.l(a). Thus "NO" emission level from high volatile coal at elevated temperatures, approaches the level of "NO" emission from less volatile fuels at lower temperatures. This fact together with the decreased ammonia formation at elevated temperatures suggests also the efficient combustion modification for the reduction of "NO" emission. Formation of nitrogenous compounds and staged combustion4' 586) A series of experiments were carried out to investigate the influence of air staging. In this operation, the primary stage, which was a fluidized bed, was maintained at substoichiometric conditions while the balance of air, (the secondary air) was introduced through a nozzle into the freeboard. A significant reduction of "NO" emission by staged air firing can only be realized provided the emission of "NO" as well as other nitrogeneous compounds from the primary stage are significantly reduced. Thus the ammonia emission from coal and char are measured by the detector tube method. Typical results are shown in Fig. 3. Ammonia emission was not detected under an excess air condition. Under a substoichiometric condition, this could be reduced by elevating the combustion temperature, or reducing moisture, or volatile contents. In the case of char combustion, the ammonia emission under starving combustion at 85OOC was approximately 1/7 of the "NO" emission under an excess air condition. These results suggest that a significant reduction of "NO" emission can be achieved by a staged combustion of char. A preliminary experi- ment was carried out to evaluate the possibilities of staged air firing. Experimental results indicate that an approximately 90% reduction of "NO" emission was attained in the case of staged combustion of char where this was evaluated on the basis of an "NO" emission indexobtained for conventional operations. However, the maximum level of "NO" reduc- tion in this operation for coal remained at 33.5%. Effect of in situ formed carbon on "NO" Carbonaceous materials within the bed were reported to be effective in "NO" destruction. The steady state carbon concentration within the bed was measured. After terminating the feed of fuel solids, the amount of carbon dioxide and monoxide originating from the remaining carbon particles was measured by means of the gas bag method. results obtained are compared with the level of "NO" emission in Fig. 4. These results indicate that "NO" emission was inversely related to the steady state carbon concentration. Furthermore, the steady state car- bon concentration within the bed was found to be considerably small. 266 The ' I . I
lb, , --pp---p-- 4 p? CHAR 1 Tu-IWO'C 0' 06 OB 10 12 AIR RATIO 9 1-1 (a) (b) Fig. 3 Emission of ammonia from combustion of coal and char Fig. 4 NO emission decreased with the increase of steady state carbon concentration within the bed 267
- Page 215 and 216: ' ' The modifications have been com
- Page 217 and 218: n n D 217
- 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: ! Table 2 Proximate and ultimate an
- Page 269 and 270: I CHAR Y Y /I TIME O i ' ' ' ' 1 '
- Page 271 and 272: could not be assumed constant. Thus
- 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
lb, ,<br />
--pp---p-- 4 p?<br />
CHAR 1<br />
Tu-IWO'C<br />
0' 06 OB 10 12<br />
AIR RATIO 9 1-1<br />
(a) (b)<br />
Fig. 3 Emission <strong>of</strong> ammonia from combustion <strong>of</strong> <strong>coal</strong> and char<br />
Fig. 4 NO emission decreased with <strong>the</strong> increase <strong>of</strong> steady<br />
st<strong>at</strong>e carbon concentr<strong>at</strong>ion within <strong>the</strong> bed<br />
267
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