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

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CARBON CARRYOVER (g s-'1 0 I 0 0 0 N W c. CARBON CARRYOVER (g s-') 0 0 - 0 0 0 N w - CARRYOVER (g 5-'1 0 0 N 0 w 0 c. I I I I CARRYOVER (g s-') 0 0 0 0 N W E ul 294 W D 0 - -a 00 DO --00 UlDpIUl- WWWW xxxx
The influence of particle size distribution on the combustion rates in a batch fed fluidised bed E.S. Garbett and A.B. Hedley Sheffield Coal Research Unit, Department of Chemical Engineering and Fuel Technology, University of Sheffield, Sheffield, s1 3JD United Kingdom. Introduction The advantages of burning coal in fluidised bed combustors (FBC) have been repeatedly demonstrated over the past few years and commercial units are now being built and supplied to industry (1). The design of such FBC's is based on the practical experience gained from pilot plant studies and also on the predictions of mathematical models. Central to any model of coal combustion in FBC's is the rate at which particles burn in the bed which determines the carbon loading and hence pollutant emission% heat release rates, coal feed rates and elutriation rates (2). Particle size and temperature usually indicate the controlling mechanism of combustion; large particles and high temperature suggest that diffusion is dominant whereas chemical kinetics became important for small particles and low temperatures (3). In a typical FBC the particle sizes range from that of the maximum of the input feed down to that of particles which are about to be elutriated and particle temperatures can have a value anywhere between the bed temperature Tb and T + 200K (4,5,6). It is not unreasonable to b assume therefore, that the combustion of particles can be controlled by a combination of diffusional and chemical processes acting simultaneously. Indeed, the data of Avedesian and Davidson (7), where the combustion of char particles in a batch fed fluidised bed was assumed to be diffusion controlled, has recently (6) been shown to be consistent with the alternative situation described above where both processes are acting together. The effect on the carbon loading in an FBC where the combustion is either controlled by diffusion or by a combination process has been investigated by Garbett and Hedley (8) who also showed the importance of particle surface temperatures. The particle size distribution of the coal feed is a parameter which is important in the design of FBC's but whose influence on the combustion rates in the bed has not been studied. It is the purpose of this paper therefore, to develop a theory to predict the burnaway, burnout time and particulate phase oxygen concentration in a batch fed FBC and show their dependence on the input particle size distribution which is accurately known. The Model The model of the batch fed FBC employed here is essentially the two-phase bubbling bed model of Avedesian and Davidson (7) where a bed of inert particles at a temperature Tb is fluidised by air at a superficial velocity U and a minimum fluidised velocity U . The oxygen required for combustionOwhich is controlled by a combination diffusion and chemical kinetics, is transferred to the char particles in the particulate phase from the bubbles and the reaction is given by C + O2 -+ CO . The batch is assumed to comprise solely of char particles so that devola&lisation is negl,?cted. It is also assumed that the particles do not swell or break up when introduced to the bed and so retain their original size distribution. The Theory The reaction rate of a single particle of char of mass m in a fluidised bed where both diffusional and chemical kinetics are considered Eimultaneously, can be expressed in terms of diffusional and chemical resistances as follows (3). 295
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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
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P SUMMARY OF TESTS Testing complete
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I Table 1 Comparison of Sulfur Capt
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, NITROGEN OXIDE REDUCTION Single-S
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0 The addition of air at the 96-inc
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m- Y i? 4: BO n 8 c Y l0- Bo- I I I
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E! w 2 z e Y 100 - 3 t 5 80- 0, 40
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0 f 0.so o'm: 0.300 0.zo - - A 5m 4
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&e- -A \ \ \ : ERCENT OVERBED AIR I
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Page 247 and 248: The maximum height that a large par
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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 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: i 7 -_ 0 m\o --n 0 W i 293 a\o 0
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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