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, ablaszczuk@is.pcz.czest.pl

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