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 ...
and, therefore, will not be repeated in this paper. Sulfur capture and nitrogen oxide reduction are the two items that will be discussed in the following sections. SULFUR CAPTURE No Fly Ash Recycle Numerous non-recycle tests have been run on the 6' x 6' AFBC at a fluidizing velocity near 8 ft/sec. This large data bank provides information enabling a better understanding of sulfur capture with various operating parameters. A plot of percent sulfur removal versus calcium-to-sulfur ratio showed that sulfur removal is a strong function of the amount of fresh limestone feed (Figure 1). However, the data is quite scattered, indicating that other factors such as particle size, entrainment loss, bed temperature, coal combustion, and sulfur release level may also have a significant influence on sulfur capture efficiency. To more thoroughly investigate these factors, data from a narrow range of Ca/S ratio were subjected to analysis. Sulfur removal was shown to be related to the size of limestone being fed into the unit (Figure 2). The plot indicates that larger limestone feed sizes result in a decreased ability to remove sulfur, a trend which is most pronounced at higher Ca/S values. This suggests that the effect of the fresh limestone feed is predominant since the spent bed lime utilization in these tests range between 23% and 40%. Consequently, the rate of sulfur capture for the bed material is many times smaller than for freshly calcined limestone at all size ranges that exist within the FBC unit. For average limestone feed sizes below 1200 microns (weight-mass average), a significant drop in sulfur retention occurred as a result of high elutriation loss of limestone feed. Further analyses were performed by restricting both the Ca/S ratio and limestone feed size. The data scatter, evident in Figure 2, was found to be related to the effects of bed particle size, extent of bed lime utilization, and bed voidage (Figures 3 and 4). Sulfur removal decreases with: 1. An increase in bed particle size for a narrow range of bed lime .utilization (0.30 - 0.33). 2. High bed lime utilization. 3. Higher bed voidage. Also, spent bed lime utilization is related to both residence time and Ca/S feed ratio, reaching 35% with a residence time of 13 hours at a Ca/S of 2.5 (Figure 5). Increasing the fluidizing velocity to 12 ft/sec resulted in lower sulfur capture, as shown in Table 1. We believe the causes of this reduction to be: 1) higher elutriation of limestone from the bed, and 2) increased freeboard combustion of coal and its volatile matter. The table shows that carbon and limestone carryover losses were 12% and 55%, respectively. These are about 50% and 34% more than the loss at 8 ft/sec, respectively. Reducing fluidizing velocity to about 5 ft/sec generally resulted in an improvement in sulfur capture. This was due to smaller limestone feed size and lower elutriation loss (Table 2). 40%. In addition, spent bed lime utilization reached 228
I Table 1 Comparison of Sulfur Capture Efficiency and NOK Emissions for 8 ftlsec and 12 ftlsec Fluidizing Velocities Under Similar Conditions of: 1) Non-Recycle and 2) Ca/S : 2.4 - 2.8 - Item %SO2 Capture Combustion Efficiency - Z NOx - ppm co - ppm Bed Voidage Limestone Feed Sire (weight mean average) Spent Bed Sire (weight mean average) Spent Bed Lime Utilization - X Elutriation of Available Lime Per Limestone Feed Elutriation of Carbon Per Carbon Feed From Coal Table 2 Fluidizing Velocity 8 ftlsec 12 ftlsec 78.5 46.2 92 88 285 158 106 1696 0.62 0.72 2908p 984P 233711 127911 31 29 41 55 8 I2 Comparison of Sulfur Capture Efficiency and NO Emissions for 5 ftlsec and 8 ft/sec Fluidizing Velocihs Under Similar Conditions of: 1) Non-Recycle and 2) Ca/S : 1.6 - 1.8 - Item XS02 Capture Combustion Efficiency - % Spent Bed Lime Utilization - X Z Carbon in Carryover Per Carbon Feed NOx - 1bIHKb Bed Voidage Limestone Feed Size (weight mean average) Spent Bed Size (weight mean average) CO in Stack Gas - ppm 229 Fluidizing Velocity 5 ftlsec 8 ftlsec 58 54 94 92 40 33 7.7 9.6 0.22 0.39 0.55 0.66 815p 12oop 923p 82411 173 126
- Page 177 and 178: \: Stage 3. Sulfated ash-cemented a
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- 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
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- Page 193 and 194: MBC CBC Fig. 1 Boiler Structure 193
- Page 195 and 196: \ i Table 2. Coal Properties Planne
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- 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
- 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: P SUMMARY OF TESTS Testing complete
- 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 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
I<br />
Table 1<br />
Comparison <strong>of</strong> Sulfur Capture Efficiency and NOK Emissions<br />
for 8 ftlsec and 12 ftlsec Fluidizing Velocities<br />
Under Similar Conditions <strong>of</strong>: 1) Non-Recycle and 2) Ca/S : 2.4 - 2.8<br />
- Item<br />
%SO2 Capture<br />
Combustion Efficiency - Z<br />
NOx - ppm<br />
co - ppm<br />
Bed Voidage<br />
Limestone Feed Sire<br />
(weight mean average)<br />
Spent Bed Sire<br />
(weight mean average)<br />
Spent Bed Lime Utiliz<strong>at</strong>ion - X<br />
Elutri<strong>at</strong>ion <strong>of</strong> Available<br />
Lime Per Limestone Feed<br />
Elutri<strong>at</strong>ion <strong>of</strong> Carbon<br />
Per Carbon Feed From Coal<br />
Table 2<br />
Fluidizing Velocity<br />
8 ftlsec 12 ftlsec<br />
78.5 46.2<br />
92 88<br />
285 158<br />
106 1696<br />
0.62 0.72<br />
2908p 984P<br />
233711 127911<br />
31<br />
29<br />
41 55<br />
8 I2<br />
Comparison <strong>of</strong> Sulfur Capture Efficiency and NO Emissions<br />
for 5 ftlsec and 8 ft/sec Fluidizing Velocihs<br />
Under Similar Conditions <strong>of</strong>: 1) Non-Recycle and 2) Ca/S : 1.6 - 1.8<br />
- Item<br />
XS02 Capture<br />
Combustion Efficiency - %<br />
Spent Bed Lime Utiliz<strong>at</strong>ion - X<br />
Z Carbon in Carryover<br />
Per Carbon Feed<br />
NOx - 1bIHKb<br />
Bed Voidage<br />
Limestone Feed Size<br />
(weight mean average)<br />
Spent Bed Size<br />
(weight mean average)<br />
CO in Stack Gas - ppm<br />
229<br />
Fluidizing Velocity<br />
5 ftlsec 8 ftlsec<br />
58 54<br />
94 92<br />
40 33<br />
7.7 9.6<br />
0.22 0.39<br />
0.55 0.66<br />
815p 12oop<br />
923p 82411<br />
173 126
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