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

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Effect of Char Loading on Nitric Oxide Reduction The effect of char loading in the fluidized bed on NO reduction by char is illustrated in Figure 9. As can be seen, the reduction of NO increases with increase in char loading. A t bed temperature of 75OoC, the effect of char loading is most important around 1 percent where it results in a NO reduction of 87 percent. A t higher char loading, the reduction of NO is generally higher; however, the effect of , the char loading becomes less significant. The same trend can also be observed at the temperatore range below 75OoC, even though the reduction of NO falls below 60 percent due to the strong temperature dependence of the reduction reaction. Higher char loading in the bed may increase the chances of clinker formation which is caused by local temperature excursion as a consequence of the poor solid mixing and the inability to dissipate the heat of combustion. In addition, the loss of unburnt carbon in the drained spent-bed material may become unacceptable if the char loading in the bed becomes too high. However, recent developments in fluidized-bed combustion technology have indicated that two-stage combustion systems with the increased char loading in the first stage enhances the overall reduction of nitric oxide emission significantly5. Prediction of NO Reduction by Char 1 Recent experimental studies6 on the reduction reaction of nitric oxide with char have concluded that the reaction is f irst order with respect to the NO concentration. This practice is, hence, adopted in the present study. The reaction rate constants of the reaction of NO with Char 1 at the corresponding temperatures and char load- ings were calculated based on the experimental data presented at Table 3. The activation energy and the frequency factor within the range of operating conditions are 31.7 kcal/mol and 9.66 x 10' sec-' respectively. The rate constants of NO-char plotted as a function of inverse temperatures for several experimental studies' are compared with the present results in Figure 10. As can be seen, the reaction rate constants obtained from the present experiment show good agreement with previous investigations. The NO-char reaction kinetics can be represented by the following correlation and this was employed in the NO emission modeling. In view of the low k = 9.66 x loa exp (- 31,700) sec-l , RT superficial velocity, the shallow bed, and relatively small bed diameter, a two- phase bubble model' with both the bubble and emulsion phases treated as plug flow was employed for the prediction of NO conversion. The NO reduction by Char 1 was calculated using this approach over the range of experimental conditions. The comparison of calculated versus test data values may be observed in Table 3, as well as Figure 7. As can be seen in Figure 7, the calculated values for NO reduction show excellent agreement with experimental data. Conclusions Tests to determine the NO reduction capability of two different chars and a metallurgic coke were conducted in an electrically heated, batch, fluidized-bed reactor in the absence of oxygen. Based on the experimental results, the following conclusions can be drawn. o Reduction of nitric oxide depends strongly on the physical properties of the carbonaceous solids such as specific surface area and pore size distribution; and, to a lesser extent, on the carbon content. 0 Reduction reaction between NO and carbonaceous solids was found to be strongly influenced by bed temperature. Within the range of operating conditions, the degree of NO reduction increases with bed temperature. However, the formation of thermal NO and the unfavorable sulfation reaction for natural sorbents in an 278 I I r
atmospheric pressure fluidized bed at higher temperature posts an upper limit on temperature range for NO and SO emission control. A preferred operating temperature range from thisxstandpo?nt appears to be 80Oo-85O0C. NO reduction by char increases with char loading in the bed. With 1 percent of char loading in the bed, 90 percent or better NO reduction is attainable for both Char 1 and Char 2 provided that bed temperature is maintained at or above 8OOOC. Reaction rate cotstants based on the present experimental data show good agreement with the previous investigations. The rate constant can be represented by the following correlation: k = 9.66 x lo8 exp (- 31 AT 700) see-' Prediction of nitric oxide reduction by Char 1 using a two-phase bubble model gives good agreement with the experimental data within the range of experimental conditions. References 1. Proceedings of the Fifth International Conference on Fluidized-Bed Combustion, Washington, DC, December 1977. 2. Proceedings of DOEIWW Conference on Fluidized-Bed Combustion System Design and Operation, Morgantown, WV, October 1980. 3. The proceedings of the Sixth International Conference on Fluidized-Bed Combus- tion, Atlanta, Georgia, August 1980. 4. Pereira, F. J. M. A., "Nitric Oxide Emission from Fluidized Coal Combustion," Ph.D. Thesis, University of Sheffield, 1975. 5. Gibbs, B. M., F. J. Pereira, and J. M. B;er, "The Influence of Air Staging on the NO Emission from a Fluidized-Bed Coal Combustor," Paper Presented at 16th Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, PA, 461, 1977. 6. Bier, 3. M., A. F. Sarofim, S. S. Sandhu, M. Andrei, D. Bachovchin, L. K. Chan, T. Z. Chang, and A. M. Sprouse, "NO Emissions from Fluidized Coal Combustion," EPA Grand NO. R804978020 Report, 1979. 7. Furusawa, T., D. Kunii, A. Oguma, and N. Yamada, "Kinetic Study of Nitric Oxide Reduction by CarbOnaCeOuS Materials," Kagaku Kogaku Rombunshu, 5 (6), 562 (1978). 8. Davidson, 3 . F. and D. Harrison, "Fluidized Particles," Cambridge University Press., 1963. 3: sw:515f 279
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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
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-6- abrasion rate at the bottom of
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\if F3.3 - Particulate Circulation
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\' I/O. analog 1/13. industrial I/O
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ACQUISITION DATA UNIT < I L- J (T)
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SAMPLING SYSTEM FOR FLUIDIZED BED A
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GAS SAMPLING WITH ORIGINAL PROBE-FI
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Remove the quartz tube (gas sample
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' ' The modifications have been com
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n n D 217
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With regard to the similarity parti
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i \ ' 2.2. soz Emission and NOx Emi
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223
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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
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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.
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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
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Page 275 and 276: constructed and operated to demonst
Page 277: The experimental procedure for the
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
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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
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the coking properties of coal at elevated pressures. - Argonne ...

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