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

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INTRODUCTION RESEARCH AND DEVELOPMENT OF COAL-FIRED FLUIDIZED-BED BOILER Bao Dong-wen and Ruan Yi-shao Research and Development Division Dong-fang Boiler Works Zigong, Shichuan, China The power industry in many countries is now facing a problem: how to achieve the inevitable shift from oil and natural gas to coal and low-grade coals while remaining in compliance with the regulatory limits on emissions. Fluidized-bed combustion (FBC) has demonstrated its potential to solve this problem, because it has the advantages of adaptability to low-grade coals and feasibility for sulfur emissions control. Due to FBC's relatively low combustion temperatures, NOx emissions from a fluidized bed are lower than those from conventional furnaces. As a new technology it is natural that there are many technical problems to be investigated and difficulties to be overcome in the development of fluidized-bed boilers (FBB). Since 1971, Dong-fang Boiler Works (DBW) has carried out developmental work in FBB in the following areas: o Combustion efficieacy. o Arrangement of floidized-bed heating surfaces. o Immersed superheater. 0 Erosion of immersed tubes. o Start-up of fluidized bed. A 463 x 324 mm FBC test unit was built to investigate methods of improving the combustion efficiency of the FBB. Later, a 24 t/h stoker-fired boiler was converted into an FBB by DBW. It has now been successfully operated for 196
-2- more than 3 years, since 1977. The performance of the unit has been satisfactory to the user. Figure 1 shows the general arrangement of this modified boiler. Its major parameters are as follows: Steam capacity 24 t/h 2 Steam pressure Superheated steam 32 kg/cm temperature 45OEC Feed water temperature Gas temperature at 150 C boiler exit 20o0c Designed fuel Bituminous coal Natural circulation was adopted for the immersed evaporating surface. To date no problem in water circulation has occurred. An experimental immersed superheater was placed in the bed and its behavior observed. For distribution of combustion air, a refractory covered bubble cap plate was installed. In order to facilitate bed start-up and load changes, the windbox was divided into four separate compartments. Because bituminous coal was to be used, no carbon recycling was considered; thus the uncertainty of a recycle system was avoided. The once-through combustion efficiency (i.e., elutriated fines) was measured as 94.8 to 95.5 percent. without reburning of TEST RESULTS AND DISCUSSION A- Combustion Efficiency When compared with pulverized coal firing, carbon losses from a fluidized bed are high as a result of the relatively coarse coal particulates and low combustion temperature. Combustion efficiency depends on the bed velocity and temperature, excess air, and on the coal character- istics (which have significant influence on carbon losses). Coal with high ash content and less volatile matter would have lower combustion efficiency. The following experimental data from the test rig demon- strate that c.e. values in burning different coals may differ greatly, even when the superficial ve$ocity, bed temperature, and excess air rate are approximately the same. Volatile matters Ash on combustible on analytical Total basis basis carbon losses Bituminous coal 35.48 31.40 3.77 Lean coal 17.50 39.04 10.67 Colliery wastage 48.09 76.50 7.95 If anthracite is burned, carbon losses will be higher than the above values. It is evident that application of FBC in utility boilers will require significantly increased combustion efficiencies. 197
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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
Page 145 and 146: I Coal Ash Sintering Model and the
Page 147 and 148: 5 carried out such sintering measur
Page 149 and 150: I this ash and other bituminous coa
Page 151 and 152: forming propensity. However, none o
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Page 155 and 156: CENTRAL ELECTRICIN RESEARCH LABORAT
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Page 159 and 160: temperature, sulfur species concent
Page 161 and 162: The facility is fired with coal usi
Page 163 and 164: Tests have been carried out to dete
Page 165 and 166: under which conditions sulfur speci
Page 167 and 168: I TITANIUM L Corn AS A TRACER FOR D
Page 169 and 170: E 6 i i h \ 1 1 \ on the XRF is cau
Page 171 and 172: \ ? CONCLUSIONS Titanium can accura
Page 173 and 174: NY) m * oa
Page 175 and 176: GFETC constructed a 0.2 square mete
Page 177 and 178: \: Stage 3. Sulfated ash-cemented a
Page 179 and 180: I FIG. 1. Initial ash coating on qu
Page 181 and 182: FIG 9. Limestone bed material alter
Page 183 and 184: (4) Since the operating temperature
Page 185 and 186: I I maximum particle diameter leavi
Page 187 and 188: ! suspension chambers and cyclone f
Page 189 and 190: Pilot Plant of a Coal Fired Fluidiz
Page 191 and 192: After the fiscal year 1982, the fol
Page 193 and 194: MBC CBC Fig. 1 Boiler Structure 193
Page 195: \ i Table 2. Coal Properties Planne
Page 199 and 200: , 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
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The maximum height that a large par
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3.0 Nitric Oxide Reduction in the F
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assumed to be identical to that of
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Nomenclature A *t cD ‘NO $3 _ _ _
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TABLE 2. OPERATING CONDITIONS AND E
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i 1 \ ', References 1. 2. ( 3. 1 4.
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\ ” Y) I 259
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t I 100 - - I I ] , I , I , I 'ii 9
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Feeding of the carbonaceous materia
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! Table 2 Proximate and ultimate an
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lb, , --pp---p-- 4 p? CHAR 1 Tu-IWO
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I CHAR Y Y /I TIME O i ' ' ' ' 1 '
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could not be assumed constant. Thus
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\ greatly acknowledged. Literature
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constructed and operated to demonst
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The experimental procedure for the
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atmospheric pressure fluidized bed
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1' TABLE 2 Screen Analysis of Sand
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n RECORDER I Ill I ’ NO. NOX THER
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\ 285 Y 0 I- 5 B 5 3 m "9 E5 3 uz 0
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CHAR1 TOC 0.85 M3/k 600 0 700 V 750
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f Durin all the experimental runs t
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Assuming that large coal particles
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i 7 -_ 0 m\o --n 0 W i 293 a\o 0
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The influence of particle size dist
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all the initial values of x for whi
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\ - + 1) x. = 1 bL/n YO Defining di
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$ 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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