the coking properties of coal at elevated pressures. - Argonne ...

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Nitric oxide reduction by methane, with reduction of up to 700 mole ppm NO in 0.5 s, was observed in NO-CH4-02-CO2-Ar mixtures at 1323 K by Yamazaki et a1 (13). The temperature dependence of the rate is not reported so the possible contribution of this process at 1040-1100 K cannot be determined. Although the reduction of NO was only significant for O2/CH4 mole ratios of about 0.5 to 2.0, such conditions might exist locally during mixing of gases in the splash zone of the fluidized bed. Reactions of NO with NH3 such as: NO -I NH3 = H20 -I N2 -I 1/2H2 (Duxbury and Pratt (30)) are another possible contribution to the rapid NO disappearance at the top of the bed. Neither ammonia nor NOx was measured in the present experiments, so the contribution of this reaction cannot be precisely estimated. However, the increase in NO observed in run C27 on addition of secondary air is evidence that N-containing species other than NO may be present in the freeboard at least under sub-stoichiometric conditions. De Soete (31) determined an overall rate expression for the homogeneous reaction between NO and NH3 giving N2 from measurements in ethene/oxygen flames over the temperature range 1800 to 2400 K. The reaction is first order with respect to both NO and NH3. The applicable temperature range is far from fluidized combustor conditions, however, the rate expression predicts an initial NO destruction rate of 140 mole ppm/s at 1040 K in a mixture containing 600 mole ppm each of NO and NH3. It is possible that this reaction contrib- utes to NO reduction in the splash zone. If it does contribute, the optimum (from the point of view of NO emissions) primary stoichiometric ratio in a configuration with staged air addition, may be one at which some NO is left unreduced at the top of the bed, providing a reactant for direct conversion of NH3 to N2 in the splash zone. 4.0 Conclusions A mechanistic model for particle entrainment into the freeboard has been developed and used in conjunction with a chemical kinetic description of the NO-char reaction for prediction of the reduction of NO along the height of the freeboard in fluidized coal combustion. Bed conditions, including the mass fraction of char in the bed, are input to the model. Predicted NO profiles showed good agreement with experimental data obtained while burning bituminous and subbituminous coals under a variety of operating conditions. The steep reduction in NO observed in the splash zone immediately above the bed in some cases could not be adequately explained by the present model. This result points to the importance of the reactions in the splash zone, where it is thought that NO reducing reactions other than the NO-char reaction will have to be taken into account for satisfactory prediction of the NO profile under all conditions. The model is now in a form in which it can be integrated into system models for predicting NO emissions as a function of operating conditions. Acknowledgements The development of the models for particle entrainment and nitric oxide reduction was supported by DOE under Contract No.EX-76-A-01-2295. The experimental work was supported by DOE under Grant No. DE-FG22-8OPC30215, Dr. H. A. Webb, Project Manager. 252
Nomenclature A *t cD ‘NO $3 _ _ _ % y dc’ df Ea Ed’ E~ Eo, E 0,c Hf k Lf m P ‘b RO % T TB T g ‘b ug Umf Ut Vd’ vu vs* vsi - V P 2 Specific BET surface area of char (m /kg) 2 Cross sectional area of the bed. (m ) Drag coefficient 3 NO concentration (kmole/m ) Bubble diameter (m) Geometric mean diameters of bed particles, char particles, and fresh coal particles, respectively (m) Activation energy (J/kmol) Mass flow rates of downward and upward moving particles, respectively (kg/s) Initial entrainment rates of stone and char particles from the bed surface, respectively (kg/s) Total freeboard height (m) Rate coefficient (units variable) Expanded bed height (m) Mass of a single particle (kg) 3 Visible bubble volume flow rate (m /s) Gas constant = 8314 J/kmol * K Bubble radius (m) Temperature (K) Bed temperature (K) Gas temperature (K) Absolute bubble velocity (m/s) Superficial gas velocity (m/s) Minimum fluidization velocity (m/s) Particle terminal velocity (m/s) Downward and upward particle velocities, respectively (m/s) Particle local velocity and particle initial velocity, respectively (m/s) Root-mean-square particle initial velocity (m/s) 253
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I / The Coking Properties of Coal a
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Procedure : Hand picked lunips of c
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Apparatus: The equipment for this t
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the total pressure on the swelling
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A comparison of the results obtaine
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was used, however, general trends a
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1 D 13 3 G
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Table 8 L_ Effect os FaeO Compo.lrl
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i-l SPARE SAblPLE Plortlc 209 Figur
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- z c 100,000 50,000 10,000 0 n 5,0
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Flnure 9 SWELLltlG PROPERTIES OF PI
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Fi ure 13 EFFECT OF TOTAL PRESSQRE,
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TABLE 1. OPERATING CONDITIONS Opera
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1. . 2. 3. 4. 5. 6. 7. 8. 9. REFERE
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Figure 4. SCANNING ELECTRON MICROGR
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Turkgodan et al. (18) studied the p
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Materidl balance on packed bed Boun
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These phenomena iiiay be described
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Walker, P. L., Rusinko, F., and Aus
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-""I- *I,".. I Dlrf".,on Co.1flcl.n
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After a variable residence time, th
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Changes in Char Chemistry The infra
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20. 21. 22. 23. 24. 25. 26. 27. 28.
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0s-a 00-a OS'S 00-E os-2 00-2 02.1
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COAL PYROLYSIS AT HIGH TEMPERATURES
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actions, decreasing the secondary c
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01 40 60 TI MEISeC) 80 100 120 140
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Reaction Temperature OC In-situ Ini
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and the gas velocity is often repre
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The mathematical model developed he
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si sio Fraction of solid species i
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Table 2. Differential Equations Mod
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1 60 I I RUN KE-5 50 T.1121K(1557'F
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to condense excess steam, the press
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conversion-time data.* The integrat
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catalyzed and uncatalyzed runs were
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CATALYTIC EFFECTS OF ALKALI METAL S
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%me thermogravimetric measurements
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than in steam. Figure 9 shows data
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C - C02 REACTION C - H20 REACTION L
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1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
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n 'm L u. t m - L 84
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i 5360-096bw \ KINETICS OF POTASSIU
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t 5360-096pj There is an interactio
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1 I > \ i I 5360-096bw bed data. Be
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I 1. I 5360-096bw ranging from atmo
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uY.ku ICHlMAlIC OF MINI-FLUID BE0 R
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800-12-1133 -9 FIGURE IO CALCULATED
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Mexico coal. Table 1 shows an analy
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', Complete results from all runs c
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I the methanol down to atmospheric
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TABLE 3 -----______________________
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\ "I N z 107 c. . 0 0
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I. INTRODUCTION DIRECT METHANATION
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The catalyst development program fo
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Preparing process flow diagrams and
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\ \ i 1. 2,000 4,000 6,000 8,000 10
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(JMS-OlBM-2). The mass spectra were
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I I Fairbridge, R.W. (ed.) 1972, En
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v- W V z d 3 z m 4 ? P m W c3 W m N
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e. \ I , W 2 m 4 t- CI 99-79 noooo
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L Table I: Compositions of High Tem
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\ " \ I For all three coals, the pr
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4 , 1024 1024 3a 3b J Mineral Parti
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The Determination of Mineral Distri
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pyrite crystals in framboids locate
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FIG. 1. TEM MICROGRAPH OF A HIGH VO
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\ \ FIG. 5. SEM MICROGRAPH SHOWING
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\ , species. In fact, combustion ex
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1, It is possible to make a reasona
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\ i SURFACE AND BULK ENRICHMENT OF
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I Coal Ash Sintering Model and the
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5 carried out such sintering measur
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I this ash and other bituminous coa
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forming propensity. However, none o
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t I 153
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CENTRAL ELECTRICIN RESEARCH LABORAT
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157 18 I I a I
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temperature, sulfur species concent
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The facility is fired with coal usi
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Tests have been carried out to dete
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under which conditions sulfur speci
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I TITANIUM L Corn AS A TRACER FOR D
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E 6 i i h \ 1 1 \ on the XRF is cau
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\ ? CONCLUSIONS Titanium can accura
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NY) m * oa
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GFETC constructed a 0.2 square mete
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\: Stage 3. Sulfated ash-cemented a
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I FIG. 1. Initial ash coating on qu
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FIG 9. Limestone bed material alter
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(4) Since the operating temperature
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I I maximum particle diameter leavi
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! suspension chambers and cyclone f
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Pilot Plant of a Coal Fired Fluidiz
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After the fiscal year 1982, the fol
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MBC CBC Fig. 1 Boiler Structure 193
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\ i Table 2. Coal Properties Planne
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-2- more than 3 years, since 1977.
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, I B. 2 which temporarily raised t
Page 201 and 202: -6- abrasion rate at the bottom of
Page 203 and 204: \if F3.3 - Particulate Circulation
Page 205 and 206: \' I/O. analog 1/13. industrial I/O
Page 207 and 208: ACQUISITION DATA UNIT < I L- J (T)
Page 209 and 210: SAMPLING SYSTEM FOR FLUIDIZED BED A
Page 211 and 212: GAS SAMPLING WITH ORIGINAL PROBE-FI
Page 213 and 214: Remove the quartz tube (gas sample
Page 215 and 216: ' ' The modifications have been com
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Page 219 and 220: With regard to the similarity parti
Page 221 and 222: i \ ' 2.2. soz Emission and NOx Emi
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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: assumed to be identical to that of
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 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
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kl k2 k' KC KD m m. m P N P R R g t
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UNBURNT FRACTION UNBURNT FRACTION m
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