Effect of bed particle size on heat transfer between ...
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Engineering Conferences InternationalECI Digital Archives
Fluidization XV Proceedings
5-23-2016
Effect of bed particle size on heat transfer betweenfluidized bed of group b particles and vertical rifledtubesArtur BlaszczukCzestochowa University of Technology; Institute of Advanced Energy Technologies, Poland, [email protected]
Wojciech NowakAGH University Science and Technology, Poland
Jaroslaw KrzywanskiJan Dlugosz University in Czestochowa, Poland
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Recommended CitationArtur Blaszczuk, Wojciech Nowak, and Jaroslaw Krzywanski, "Effect of bed particle size on heat transfer between fluidized bed ofgroup b particles and vertical rifled tubes" in "Fluidization XV", Jamal Chaouki, Ecole Polytechnique de Montreal, Canada FrancoBerruti, Wewstern University, Canada Xiaotao Bi, UBC, Canada Ray Cocco, PSRI Inc. USA Eds, ECI Symposium Series, (2016).http://dc.engconfintl.org/fluidization_xv/13
Czestochowa University of Technology, Institute of Advanced Energy Technologies
ul. Dabrowskiego 73, 42-200 Czestochowa, POLAND
Artur Blaszczuk, Wojciech Nowak*, Jaroslaw Krzywanski**
*AGH University of Science and Technology
**Jan Dlugosz University in Czestochowa
FLUIDIZATION XV May 22-27th , 2016, Fairmont Le Chateau Montebello, Ontario, Canada
Introduction Key parameters for heat transfer conditions, Heat transfer mechanistic model.
Description of CFB facility (large scale)
Arrangement of heating surfaces, Data of water membrane walls, Measuring ports of furnace data, Experimental conditions for all tests.
Results
Temperature distribution vs furnace height, Solid suspension density profiles, Heat transfer coefficient distributions, Contribution of heat transfer mechanisms.
Conclusions
SCHEDULE A PRESENTATION 2
KEY PARAMETERS FOR HEAT TRANSFER CONDITIONS
Heat transfer behaviour inside furnace chamber can be depended on upon following parameters: • particle size distribution of granular materials (i.e. fuel, sorbent, make-up sand), • suspension density, • bed voidage, • solid circulation rate, • air staging, • carbon dioxide concentration, • circulation rate of bed material between combustion chamber and return system, • fuel moisture content and heating value.
exit region
dilute region
Furnace
dense region
Bottom region
Sep
arat
or
Sep
arat
or
Bubbling region
Primary air
Flue gas duct
indistinct boundary
cluster phase
lean phase
Splash zone
Fig. 1. Core annulus structure of CFB.
3
Fig. 2. Single cluster forms in the vicinity of the membrane wall inside CFB furnace [1, 2, 3].
HEAT TRANSFER MECHANISTIC MODEL
[1] A. Blaszczuk, W. Nowak, Bed-to-wall heat transfer coefficient in a supercritical CFB boiler at different bed particle sizes, Int. J. Heat Mass Transfer 79 (2014) 736–749. [2] A. Blaszczuk, W. Nowak, Heat transfer behavior inside a furnace chamber of large-scale supercritical CFB reactor, Int. J. Heat Mass Transfer 87 (2015) 464–480. [3] A. Blaszczuk, W Nowak, Sz. Jagodzik, Bed-to-wall heat transfer in a supercritical circulating fluidised bed boiler, Chem. Process Eng. 35(2) (2014) 191-204.
pw
bp
wb
w
d
x
H
z
T
T
TT
TT0054.0exp294.0094.0Re023.01
rdrcgpradconv hffhhffhhhh 11
g
p
ccc
c
p
k
d
ck
th
5.0
4
1
Pr
21.02
3.0
p
t
p
d
gp
pgg
gd
U
cd
ckh
wbwd
wbrd
TTee
TTh
111
44 wcwc
wcrc
TTee
TTh
111
44
22.039.114300exp1 HDf h
59.010282.0
pd 5.0
596.0
75.0
0178.0
gpp
b
c
cc
gdU
Lt
YY gpd 1
Convection components hconv
Radiation components hrad
pc ee 15.0 5.01
25.015.01
5.0
p
p
p
p
p
pd
e
e
e
e
e
ee
4
ARRANGEMET OF HEATING SURFACES
INTREXtm RH II INTREXtm SH IV
Water/Steam
Separator SH
II
Primary air to grid
Flue gas duct
Separator
inlet
Secondary air
L = 27.6 m W = 10.6 m
H = 48 m
Refractory line
9 m
Fig. 3. Arrangement of heating surfaces in circulating fluidized bed boiler with steam capacity 1296t/h [4].
[4] A. Blaszczuk, J. Leszczynski, W. Nowak, Simulation model of the mass balance in a supercritical circulating fluidized bed combustor, Powder Technol. 246 (2013) 313–326.
5
Win
g w
all
evap
ora
tor
Win
g w
all
evap
ora
tor
Win
g w
all
evap
ora
tor
Win
g w
all
evap
ora
tor
Radiant
superheaters
SH II
Wat
er m
embra
ne
wal
l
Water
membrane wall
(vertical riffled
tubes)
Slope
section
Tra
nsp
ort
zone
Adiabatic
region
Water
membrane wall
(vertical riffled
tubes)
DATA OF WATER MEMBRANE WALLS ( vertical riffled tubes)
Fig. 4. Horizontal cross section of the membrane wall of CFB boiler [2].
Parameter Symbol Unit Value
Tube outside diameter dt mm 38
Tube pitch s mm 63
Lateral fin thickness f mm 6
Ratio - 1.24
Table 1. Membrane structure for water walls.
s
d ft
12
1
The ratio of the contracted area to the projection area 1.24
[2] A. Blaszczuk, W. Nowak, Heat transfer behavior inside a furnace chamber of large-scale supercritical CFB reactor, Int. J. Heat Mass Transfer 87 (2015) 464–480.
6
MEASURING PORTS OF FURNACE DATA
z
x
y
z
x
y
Fig. 5. Arrangement of the measuring points inside furnace chamber of 1296t/h CFB reactor: (a) pressure taps, (b) temperature ports.
(a) (b)
7
[2] A. Blaszczuk, W. Nowak, Heat transfer behavior inside a furnace chamber of large-scale supercritical CFB reactor, Int. J. Heat Mass Transfer 87 (2015) 464–480.
# Bed temperature – classical bare
thermocouples with weights made of metal with high density and
resistant to high furnace temperature.
# Gas temperature –
the shielded termocouples with
insulated junction. The outside of the shield was polished. This eliminated
the reflection of the membrane wall radiation.
# Wall temperature – thermocouples at the front wall CFB
furnace were imbedded in the water membrane wall with the front end
flush with the fin.
EXPERIMENTAL CONDITIONS
Parameter Unit Overall range
Superficial gas velocity, Uo m/s 2.99-5.11
Terminal velocity, Ut m/s 1.99-2.91
Minimum fluidization velocity, Umf m/s 0.0164-0.0544
Solids circulation rate, Gs kg/(m2s) 23.3-26.2
Sauter mean particle diameter, dp mm 0.219-0.411
Suspension density, b kg/m3 1.36-6.22
Bed temperature, Tb K 1037-1209
Wall temperature, Tw K 700-902
Pressure drop, p kPa 8.23-8.44
Ultimate analysis (air dried basis) Unit Overall range
Cad, carbon wt.% 52.32-57.09
Had, hydrogen wt.% 4.02-4.41
Oad, oxygen wt.% 6.09-6.98
Nad, nitrogen wt.% 0.73-0.85
Sad, sulphur wt.% 0.87-1.17
Proximate analysis (as-received)
Qar, caloric value MJ/kg 19.91-22.91
Var, volatile matter wt.% 24.48-29.65
Aar, ash wt.% 11.12-20.11
Mar, total moisture wt.% 13.01-19.97
Table 2. Experimental conditions.
Table 4. Fuel characteristic.
Parameters Accuracy
Thermocouple sensor 9C
Temperature transmitter 0.1C
Pressure sensor 2.5Pa
Stopwatch 0.2s
Table 3. Accuracies of measured parameters.
0 15 30 45 60 75 90 105 120 135 1504000
4500
5000
5500
6000
6500
7000
7500
8000
8500
9000
[s]
Z = 0.25m; n = 164 Pa
Z = 0.4m; n = 185 Pa
p [P
a]
0 15 30 45 60 75 90 105 120 135 150-1000
-500
0
500
1000
1500
2000
2500
3000
3500
4000
Z = 2.0m; n = 65 Pa
Z = 5.0m; n = 60 Pa
[s]
Z = 8.3m; n = 56 Pa
Z = 31.0m; n = 42 Pa
p [P
a]
8
0.01 0.1 1 10 100
0.0
0.2
0.4
0.6
0.8
1.0
dp = 0.219 mm @Test#1
dp = 0.246 mm @Test#2
dp = 0.365 mm @Test#3
dp = 0.411 mm @Test#4
Cu
mu
lati
on
mas
s fr
acti
on
[
-]
dp [mm]
Fig. 6. Particle size distribution of bed material during performance tests.
pi
i
p
dx
d1
RESULTS
1
2
1
N
xxSD
N
ii
N
iix
Nx
1
1
Standard deviation SD
Table 5. Error analysis of bed temperature. (average value for each test)
Test No Statistical parameter
SD
Test #1 @ dp=0.219mm 8.2K 867K
Test #2 @ dp=0.246mm 10.4K 911K
Test #3 @ dp=0.365mm 7.5K 804K
Test #4 @ dp=0.411mm 4.4K 872K
x
9
Fig. 7. Lateral temperature profiles inside furnace chamber of CFB boiler.
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.30.80
0.84
0.88
0.92
0.96
1.00
Test #1
Ug = 4.27 m/s
p = 8.44 kPa
dp = 0.219 mm
z/H = 0.25 m
z/H = 0.5 m
z/H = 0.65 m
z/H = 0.87 m
Tb/T
b m
ax [-
]
y/L [-]
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.30.80
0.84
0.88
0.92
0.96
1.00
z/H = 0.25 m
z/H = 0.5 m
z/H = 0.65 m
z/H=0.87 m
Test #2
Ug = 5.11 m/s
p = 8.25 kPa
dp = 0.246 mm
Tb/T
b m
ax [-
]
y/L [-]
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.30.80
0.84
0.88
0.92
0.96
1.00
d)c)
b)
z/H = 0.25 m
z/H = 0.5 m
z/H = 0.65 m
z/H = 0.87 m
Test #3
Ug = 2.99 m/s
p = 8.23 kPa
dp = 0.365 mm
Tb/T
b m
ax [-
]
y/L [-]
a)
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.30.80
0.84
0.88
0.92
0.96
1.00
Test #4
Ug = 3.13 m/s
p = 8.44 kPa
dp = 0.411 mm
z/H = 0.25m
z/H = 0.5 m
z/H = 0.65 m
z/H = 0.87 m
Tb/T
b m
ax [-
]
y/L [-]
Transport zone @ z/H = 0.25-0.87
RESULTS
Fig. 8. Solids suspension density profiles inside furnace chamber of CFB boiler.
111
181.9
iiiib HHpp
Suspension density, b
Table 6. Error analysis of the suspension density. (average value for each test)
Test No Root-Sum-Square approach
b [kg/m3]
Test #1 @ dp=0.219mm 0.41
Test #2 @ dp=0.246mm 0.21
Test #3 @ dp=0.365mm 0.22
Test #4 @ dp=0.411mm 0.30
2122
2
2
2
1
1
...
i
i
xx
fx
x
fx
x
fx
The root-sum-square approach (RSS)
10
0.2 0.4 0.6 0.8 1.010
-4
10-3
10-2
b = 1.36 - 6.22 kg/m
3
Tb = 1037 - 1209 K
Ug = 2.99 - 5.11 m/s
Gs = 23.3 - 26.2 kg/(m
2s)
b/
p [-
]
z/H [-]
Experimental data
dp = 0.219mm @ Test#1
dp = 0.246mm @ Test#2
dp = 0.365mm @ Test#3
dp = 0.411mm @ Test#4
Transport zone @ z/H = 0.25-0.87
RESULTS 11
Table 7. Relative uncertainty of the bed-to-wall heat transfer data. (average value for each test)
Test No Relative uncertainty
h [%]
Test #1 @ dp=0.219mm 18.7
Test #2 @ dp=0.246mm 15.8
Test #3 @ dp=0.365mm 11.5
Test #4 @ dp=0.411mm 8
Fig. 9. Local heat transfer coefficient as a function of mean particle sizes.
Fig. 10. Variation of bed-to-wall heat transfer coefficient versus suspension density.
10-4
10-3
10-2
60
100
1000
h [
W/(
m2 K
)]
b/
p [-]
Approximation h = a(1 - exp(-dp
b))
0.95
dp = 0.219 mm a = 141 426 R
2= 0.98
dp = 0.246 mm a = 126 643 R
2= 0.97
dp = 0.365 mm a = 87 070 R
2= 0.98
dp = 0.411 mm a = 77 790 R
2= 0.96
b = 1.36 - 6.22 kg/m
3
Tb = 1037 - 1209 K
Ug = 2.99 - 5.11 m/s
Gs = 23.3 - 26.2 kg/(m
2s)
Experimental
data region
0.20 0.24 0.28 0.32 0.36 0.40 0.440
50
100
150
200
250
300
350
400 h = a + b exp( jd
p)
a b j R2
167.2 634888 -38.6 0.96
141.4 1.12x109 -73.1 0.99
106.5 510094 -39.5 0.93
77.6 18100 -24.8 0.95
h [
W/(
m2 K
)]
dp [mm]
z/H = 0.25 z/H = 0.65
z/H = 0.50 z/H = 0.87
0.365 - 0.411mm
RESULTS 12
Fig. 11. Contribution of heat transfer mechanisms as a function of bed particle size inside furnace chamber: (a) at z/H=0.25, (b) at z/H=0.5.
(a) (b)
0.24 0.28 0.32 0.36 0.40
0
10
20
30
40
50
60
70
80
90
100
Dominance region of
convective heat transfer
Rel
ativ
e co
ntr
ibuti
on [
%]
dp [mm]
Present data @ z/H = 0.25
hp/h h
g/h
hrc/h h
rd/h
dp = 0.366mm
Dominance
region of
radiative
heat transfer
b = 1.36 - 6.22 kg/m
3
Tb = 1037 - 1209 K
Ug = 2.99 - 5.11 m/s
Gs = 23.3 - 26.2 kg/(m
2s)
0.24 0.28 0.32 0.36 0.40
0
10
20
30
40
50
60
70
80
90
100
b = 1.36 - 6.22 kg/m
3
Tb = 1037 - 1209 K
Ug = 2.99 - 5.11 m/s
Gs = 23.3 - 26.2 kg/(m
2s)
dp = 0.310mm
Present data @ z/H = 0.5
hp/h h
g/h
hrc/h h
rd/h
Dominance region of
convective heat transfer Dominance region of
radiative heat transfer
dp = 0.237mm
Rel
ativ
e co
ntr
ibuti
on [
%]
dp [mm]
hrd / h 0.20 % – 41% hp / h 26% – 82% hrc / h 16% – 17% hg/h 0.1% – 16%
hrd / h 13% – 46% hp / h 19% – 58% hrc / h 11% – 18% hg/h 8% – 22%
RESULTS
Fig. 12. Contribution of heat transfer mechanisms as a function of bed particle size inside furnace chamber: (a) at z/H=0.65, (b) at z/H=0.87.
13
(a) (b)
0.24 0.28 0.32 0.36 0.40
0
10
20
30
40
50
60
70
80
90
100
b = 1.36 - 6.22 kg/m
3
Tb = 1037 - 1209 K
Ug = 2.99 - 5.11 m/s
Gs = 23.3 - 26.2 kg/(m
2s)
Dominance region of
convective heat transfer
Dominance region of
radiative heat transfer
Present data @ z/H = 0.65
hp/h h
g/h
hrc/h h
rd/h
Rel
ativ
e co
ntr
ibuti
on [
%]
dp [mm]
dp= 0.233mm
0.24 0.28 0.32 0.36 0.40
0
10
20
30
40
50
60
70
80
90
100
b = 1.36 - 6.22 kg/m
3
Tb = 1037 - 1209 K
Ug = 2.99 - 5.11 m/s
Gs = 23.3 - 26.2 kg/(m
2s)
Dominance region of
radiative heat transfer
Present data @ z/H = 0.87
hp/h h
g/h
hrc/h h
rd/h
Rel
ativ
e co
ntr
ibuti
on [
%]
dp [mm]
hrd / h 35% – 56% hp / h 8% – 29% hrc / h 6% – 12% hg/h 22% – 31%
hrd / h 42% – 59% hp / h 5% – 20% hrc / h 4% – 10% hg/h 25% – 35%
CONCLUSIONS
The computational results exibit that: For the same non-dimensional distance from the grid, the smaller bed particles result in higher bed-to-wall heat transfer coefficient than larger ones. For dp<0.241mm particles, the heat transfer coefficient increased rapidly; For particles tested, 0.365<dp<0.411mm, the impact of particle diameter on local heat transfer coefficient is not important; The overall heat transfer coefficient is strongly dependent on particle diameter and suspension density at vertical rifled tubes, The bed-to-wall heat transfer coefficient increases with the decrease of bed particle size,
14
The contribution of radiation from dispersed phase in bed-to-wall heat transfer coefficient increased with the increase in bed particle size, especially for coarse bed particles with diameter dp>0.365mm With increase in bed particle diameter, cluster radiation component in the heat transfer mechanism gradually decreases along the furnace height, For all particle tested, 0.240<dp<0.411mm, the bed particle diameter had an essential impact on gas convection heat transfer and cannot be ignored,
CONCLUSIONS 15
The authors would like to gratefully acknowledge the staff of Tauron Generation S.A. Lagisza Power Plant for technical support with supplying operating data and construction data. This work was financially supported by Scientific Research Grant No BS-PB-406/301/11 funded by Polish Ministry of Science and Higher Education.
FLUIDIZATION XV May 22-27th , 2016, Fairmont Le Chateau Montebello, Ontario, Canada
Czestochowa University of Technology, Institute of Advanced Energy Technologies
ul. Dabrowskiego 73, 42-200 Czestochowa, POLAND