High in-bed heat transfer and low corrosive environment imply that the loop seal of a circulating fluidized bed (CFB) boiler is an advantageous location for superheaters. In order to increase the knowledge on the flow pattern and the heat transfer distribution to the tubes within a loop seal, measurements were performed in the loop seal of a 30MW CFB boiler as well as in a 13 scaled-down seal operated according to simplified scaling laws. The scale model measurements show that the solids recirculation flux can be maintained with a substantial decrease of the fluidization flow in the seal compared to that currently used at full load conditions. It was also possible to significantly decrease the fraction of the bottom of the seal that was fluidized without affecting the solids flux through the seal. A gradient in the solids flow were detected in the vertical direction.

1.
Kunii
,
D.
, and
Levenspiel
,
O.
, 1991,
Fluidization Engineering
,
2nd ed.
,
Butterworth-Heinemann
,
Stoneham
, Vol.
172
, pp.
359
363
.
2.
Werderman
,
C. C.
, and
Werther
,
J.
, 1993, “
Solids Flow Pattern and Heat Transfer in an Industrial-Scale Fluidized Bed Heat Exchanger
,”
Proc. 12th Int. Conf. Fluidized Bed Combustion
,
ASME
,
New York
, pp.
985
990
.
3.
Wang
,
Q.
,
Luo
,
Z.
,
Fang
,
M.
,
Ni
,
M.
, and
Cen
,
K.
, 2003, “
Development of a New External Heat Exchanger for a Circulating Fluidized Bed Boiler
,”
Chem. Eng. Process.
0255-2701,
42
, pp.
327
335
.
4.
Basu
,
P.
,
Luo
,
Z.
,
Boyd
,
M.
,
Cheng
,
L.
, and
Cen
,
K.
, 1999, “
An Experimental Investigation Into a Loop Seal in a Circulating Fluidized Bed
,”
The 6th Int. Conf. on Circulating Fluidized Beds
, August, Würzburg, pp.
22
27
.
5.
Cheng
,
L.
, and
Basu
,
B.
, 1999, “
Effect of Pressure on Loop Seal Operation for a Pressurized Circulating Fluidized Bed
,”
Powder Technol.
0032-5910,
103
, pp.
203
211
.
6.
Johnsson
,
F.
,
Zijerveld
,
R. C.
,
Schouten
,
J. C.
,
van den Bleek
,
C. M.
, and
Leckner
,
B.
, 2000, “
Characterization of Fluidization Regimes by Time-Series Analysis of Pressure Fluctuations
,”
Int. J. Multiphase Flow
0301-9322,
26
, pp.
663
715
.
7.
Glicksman
,
L. R.
,
Hyre
,
M.
, and
Woloshun
,
K.
, 1993, “
Simplified Scaling Relationships for Fluidized Beds
,”
Powder Technol.
0032-5910,
77
, pp.
177
199
.
8.
Glicksman
,
L. R.
, 1988, “
Scaling Relationships for Fluidized-Beds
,”
Chem. Eng. Sci.
0009-2509,
43
, pp.
1418
1421
.
9.
Andersson
,
B-Å.
, and
Leckner
,
B.
, 1989, “
Particle Mass Flux in the Freeboard of a Fluidized Bed Boiler
,”
Powder Technol.
0032-5910,
58
, pp.
25
37
.
10.
Incropera
,
F. P.
, and
DeWitt
,
D. P.
, 1990,
Fundamentals of Heat and Mass Transfer
,
3rd ed.
,
Wiley
,
Singapore
, pp.
226
228
.
11.
Kim
,
S. W.
,
Namkung
,
W.
, and
Kim
,
S. D.
, 1999, “
Solids Flow Characteristics in Loop Seal of a Circulating Fluidized Bed
,”
Korean J. Chem. Eng.
0256-1115,
16
, pp.
82
88
.
12.
Kim
,
S. W.
,
Namkung
,
W.
, and
Kim
,
S. D.
, 2001, “
Solid Recycle Characteristics of Loop Seals in a Circulating Fluidized Bed
,”
Chem. Eng. Technol.
0930-7516,
24
, pp.
843
849
.
13.
Basu
,
P.
, and
Cheng
,
L.
, 2000, “
An Analysis of Loop Seal Operating in a Circulating Fluidized Bed
,”
Chem. Eng. Res. Des.
0263-8762,
78
, pp.
991
998
.
14.
Wunder
,
R.
, 1980, “
Wärmeübergang an Vertikalen Wärmetauscherflächen in Gaswirbelschichten
,” Dissertation, TU München.
15.
Andersson
,
B-Å.
, and
Leckner
,
B.
, 1994, “
Bed-to-Wall Heat Transfer in a 10m2 Bubbling Fluidized Bed
,”
Proc. of Congreso Europeo de Fluidizacion
, Las Palmas de Gran Canaria,
1
, pp.
251
260
.
16.
Nafari
,
A.
, and
Nylund
,
A.
, 2003, “
Field Study on Superheater Tubes in the Loop Seal of a Wood Fired CFB Plant
,”
Mater. Corros.
0947-5117,
55
, pp.
909
920
.
17.
Olsson
,
S. E.
, and
Almstedt
,
A. E.
, 1995, “
Local Instantaneous and Time-Averaged Heat Transfer in a Pressurized Fluidized Bed With Horizontal Tubes: Influence of Pressure, Fluidization Velocity and Tube-Bank Geometry
,”
Chem. Eng. Sci.
0009-2509,
50
, pp.
3231
3245
.
18.
Rong
,
D.
,
Mikami
,
T.
, and
Horio
,
M.
, 1999, “
Particle and Bubble Movements Around Tubes Immersed in Fluidized Beds—A Numerical Study
,”
Chem. Eng. Sci.
0009-2509,
54
, pp.
5737
5754
.
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