MODULAR METHODS FOR THE DESIGN AND SIMULATION OF …fft.szie.hu/Efce/efce/RecentMtgs/Tsotsas_Magdebg_02.pdfMODULAR METHODS FOR THE DESIGN AND SIMULATION OF FLUIDIZED BED DRYERS WITH

1

MODULAR METHODS FOR THE DESIGNAND SIMULATION OF FLUIDIZED

BED DRYERS WITH INDIRECT HEATING

Evangelos Tsotsasand

Hans Groenewold

Thermal Process EngineeringOtto-von-Guericke-University

Magdeburg, Germany

New apparatus or debottlenecking

* compact

* with high capacity

* lower thermal exposition of the solids

Thus interesting for

* vendors

* users

While in open literature

* no experimental results

* no validated simulation tools

2

MOTIVATION

3

MODULAR MODELLING

1. Fluidized bed module

* Fluidization → Werther et al.

* Particle – Fluid heat and mass transfer

→ Tsotsas et al.

2. Product module (Single particle)

- Normalization after van Meel

- Normalization / Hygroscopicity

3. Drying module

- Mass transfer + Adiabatic saturation temperature

- Mass transfer + Heat transfer in detail

4. Heat transfer from immersed element

???

Impact of solids moisture on indirect heating?

Impact of indirect heating on drying?

What can we learn from experiment?

How accurately can we calculate?

4

PARTICLE-TO-FLUID MASS TRANSFER

1 10 100 1000Re0 [-]

0.001

0.01

0.1

1

10

100

Sh p

lug [

-]

experimental resultscalculated with new model

ψ=1.0

ψ=0.4

Average error: prediction: 33.6%, original correlations: 35.4%

5

MATERIALSCharge Description Producer, Market name

G1800 γ-Al2O3 with dp ≈ 1800 µm Condea Chemie, Hamburg, Ak-tivtonerde

G1150 γ-Al2O3 with dp ≈ 1500 µm Condea Chemie, Hamburg, Ak-tivtonerde

G0800 γ-Al2O3 with dp ≈ 800 µm Condea Chemie, Hamburg, Ak-tivtonerde

G0260 γ-Al2O3 with dp ≈ 260 µm, produced by narrow sieving from Charge NWA

NWA γ-Al2O3 with dp ≈ 255 µm Condea Chemie, Hamburg, NWA-155

AOS γ-Al2O3 with dp ≈ 100 µm Aluminium Oxid Stade, Stade, Aluminiumoxid

NG100 γ-Al2O3 with dp ≈ 50 µm Nabaltec GmbH, Schwandorf, NG100

NO203 α-Al2O3 with dp ≈ 50 µm Nabaltec GmbH, Schwandorf, NO203

Charge Material dp

µmρp

kg/m³εmf-

Geldart-Group-

G1800 γ-Al2O3 1820 1070 0.40 D

G1150 γ-Al2O3 1140 915 0.40 D

G0800 γ-Al2O3 770 1350 0.39 B, D

G0260 γ-Al2O3 255 1325 0.365 B

NWA γ-Al2O3 255 1325 0.365 B

AOS γ-Al2O3 100 1870 0.47 A

NG100 γ-Al2O3 49 1850 0.40 A

NO203 α-Al2O3 52 2040 0.44 A

6

EXPE

RIM

ENTA

L SE

T-U

P

Air

in

Air

out

7

FLUIDIZED BED

250

mm

50 m

m

Glass

Steel

Pt100Thermo-couple

Distributor

Usu

al b

ed h

eigh

t

Steel

50 m

m30

0 m

m25

0 m

m

150 mm

300 mm

8

HEATING ELEMENT

MEASUREMENTS

( )Xm&• Drying curve,

from (infrared spectroscopy)( )tYout

• Heat transfer coefficient cylinder-bed

during drying,

from

bedw ,α

dtdTQTT HelbedH /,,, &

Teflon Copper TeflonHeating cartridge

Temperature sensor

electric contact

dd

12

dd

21

dd

25

155 562

dd

17

52

10 10

9

PHENOMENOLOGY, DRYING CURVES

0 0,1 0,2 0,3 0,4 0,5 0,6

X [-]

0

0,1

0,2

0,3

0,4

m. [kg/

m2 h]

ohnemit

0 0,1 0,2 0,3 0,4 0,5

X [-]

0,00

0,05

0,10

0,15

0,20

0,25

m. [kg/

m2 h]

ohnemit

0 0,1 0,2 0,3 0,4 0,5

X [-]

0,000

0,005

0,010

0,015

0,020

0,025

0,030

0,035

m. [kg/

m2 h]

ohnemit

0 0,1 0,2 0,3 0,4 0,5

X [-]

0,000

0,005

0,010

0,015

0,020

0,025

m. [kg/

m2 h]

ohnemit

0,00 0,05 0,10 0,15 0,20 0,25

X [-]

0,000

0,005

0,010

0,015

m. [kg/

m2 h]

ohnemit

0 0,1 0,2 0,3 0,4 0,5 0,6

X [-]

0

0,1

0,2

m. [kg/

m2 h]

ohnemit

G0800

AOS

G0260

NWA

withoutwith

withoutwith

G1800withoutwith

G1150

withoutwith

withoutwith

withoutwith

10

Charge indirect heating

Tin °C

TW

°C airM&

kg/h

Re0

- ε

- H

mm

G1800 without with

50 50

- 100

65.2 83.9

102 131

0.495 0.553

90 105

G1150 without with

50 50

- 100

67.3 75.6

65.4 73.3

0.616 0.646

85 98

G0800 without with

50 50

- 100

64.9 79.9

42.2 51.8

0.640 0.688

82 82

G0260 without with

50 50

- 100

16.81 16.37

3.77 3.65

0.617 0.615

104 106

NWA without with

50 50

- 100

17.3 16.6

3.9 3.7

0.619 0.617

87 84

AOS without with

50 50

- 100

10.25 10.19

0.90 0.88

0.691 0.693

89 100

NG100 without with

50 50

- 70

3.38 2.64

0.15 0.12

0.639 0.623

72 78

NO203 without with

50 50

- 70

3.12 3.09

0.14 0.14

0.640 0.645

78 80

0,00 0,05 0,10 0,15 0,20 0,25

X [-]

0,0000

0,0005

0,0010

0,0015

0,0020

0,0025

m. [kg/

m2 h]

ohnemit

0,00 0,05 0,10 0,15 0,20 0,25

X [-]

0,0000

0,0005

0,0010

0,0015

0,0020

0,0025

m. [kg/

m2 h]

ohnemit

NO203withoutwith NG100

withoutwith

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PHENOMENOLOGY, HEAT TRANSFER COEFFIENTS

Impact of particle moisture partly present, but

- indirect? (material properties, fluidization) or

- direct? (local heat and mass transfer)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

X [-]

0

100

200

300

400

500α

W,b

ed[W

/m2 K

]

G1800G1150G0800G0260NWA

0 0.05 0.1 0.15 0.2 0.25

X [-]

0

200

400

600

800

αW

,bed

[W/m

2 K]

AOSNG100NO203

1. Fluidized bed module* Fluidization → Werther et al.* Particle - Fluid heat and mass transfer → Tsotsas et al.

2. Product module (Single particle)- Normalization after van Meel- Normalization / Hygroscopicity

3. Drying module- Mass transfer + Adiabatic saturation temperature- Mass transfer + Heat transfer in detail

4. Heat transfer from immersed element- Single particle → Martin modified, cp →∞,

transformed into a fictitious overtemperature ofinlet air

- Single particle → Martin original,directly considered

- Packet models- more complex models

WSMOD:- accurate concerning hygroscopicity and energy balances- complicated in normalization - relatively complicated to implement / use

12

MODEL „WSMOD“

13

0exp

exp*expexp ==→=→ X

calc

calcrel

calcrel x

αα

αα

ααα

αα

ISOLATE THE DIRECT INFLUENCE

0 0,1 0,2 0,3 0,4 0,5 0,6

X [-]

0,8

1,0

1,2

1,4

αre

l* [-

]

G1800

AOS NG100

0.00 0.05 0.10 0.15 0.20 0.250.00 0.05 0.10 0.15 0.20 0.25

0 0,1 0,2 0,3 0,4 0,5

X [-]

0,8

1,0

1,2

1,4α

rel*

[-]

0 0.1 0.2 0.3 0.4 0.50 0.1 0.2 0.3 0.4 0.5 0.6

G0260

1.4

1.2

1.0

0.80.00 0.05 0.10 0.15 0.20 0.25

1.4

1.2

1.0

0.8

1.4

1.2

1.0

0.8

1.4

1.2

1.0

0.8

αre

l*[-]

αre

l*[-]

αre

l*[-]

αre

l*[-]

14

CONSEQUENTLY

Large particles → no direct impact ofparticle moisture

Small particles → large directimpact

Very large particles → direct impact+ agglomeration

OVERVIEW EXPERIMENTAL PROGRAMME

Charge Number / Heating element Tin TW Re0 εtotal without verti. horiz. °C °C - -

G1800 23 12 9 2 50.100.120 100.140 96.3-228 0.43-0.74G1150 30 16 11 3 50.100.140 100.140 35.3-158 0.43-0.86G0800 18 7 8 3 50.100.140 100.140 19.4-98.5 0.44-0.85G0260 24 14 8 2 50.100 100.140 2.48-9.75 0.54-0.67NWA 18 8 7 3 50.100 100.140 2.17-8.07 0.54-0.75AOS 18 11 5 2 50 100 0.50-2.18 0.62-0.80NG100 17 8 6 3 50 70 0.04-0.24 0.53-0.69NO203 12 5 5 2 50 70 0.11-0.40 0.61-0.74Sum 160 81 59 20 50-140 70-140 0.04-228 0.43-0.86

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MODEL „FLUBED“1. Fluidized bed module

* Fluidization → Werther et al.* Particle - Fluid heat and mass transfer → Tsotsas et al.

2. Product module (Single particle)- Normalization after van Meel- Normalization / Hygroscopicity

3. Drying module- Mass transfer + Adiabatic saturation temperature- Mass transfer + Heat transfer in detail

4. Heat transfer from immersed element- Single particle → Martin modified, cp →∞,

transformed into a fictitious overtemperature of inlet air

- Single particle → Martin original,directly considered

- Packet models- more complex models

FLUBED:- approximate conc. hygroscopicity and energy balances- simple in normalization- relatively simple to implement / use

16

COMPARISON HEAT TRANSFER

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

X [-]

0

20

40

60

80

100

120

140

160

180

200

αW

,bed

[W/m

2 K]

ExperimentWSMODFLUBED

G1800

0 0.1 0.2 0.3 0.4 0.5 0.6

X [-]

0

20

40

60

80

100

120

140

160

180

200

αW

,bed

[W/m

2 K]

ExperimentWSMODFLUBED

G1150

0 0.1 0.2 0.3 0.4 0.5

X [-]

0

20

40

60

80

100

120

140

160

180

200

αW

,bed

[W/m

2 K]

ExperimentWSMODFLUBED

G0800

0 0.1 0.2 0.3 0.4 0.5

X [-]

0

50

100

150

200

250

300

350

400

450

500

αW

,bed

[W/m

2 K]

ExperimentWSMODFLUBED

G0260

17

X [-]0 0.1 0.2 0.3 0.4 0.5

X [-]

0

50

100

150

200

250

300

350

400

450

500

αW

,bed

[W/m

2K

]

ExperimentWSMODFLUBED

NWA

0.00 0.05 0.10 0.15 0.20 0.250

100

200

300

400

500

600

700

αW

,bed

[W/m

2 K]

ExperimentWSMODFLUBED

AOS

0.00 0.05 0.10 0.15 0.20 0.25

X [-]

0

250

500

750

1000

1250

αW

,bed

[W/m

2 K]

ExperimentWSMODFLUBED

NG100

0.00 0.05 0.10 0.15 0.20 0.25

X [-]

0

250

500

750

1000

1250

αW

,bed

[W/m

2 K]

ExperimentWSMODFLUBED

NO203

14

COMPARISON DRYING

0 0.1 0.2

X [-]

0.000

0.005

0.010

0.015

m.[k

g/m2 h]

withoutwithWSMODFLUBED

0 0.1 0.2 0.3 0.4 0.5 0.6

X [-]

0

0.1

0.2

0.3

m.[k

g/m2 h]

withoutwithWSMODFLUBED

G1150

0 0.1 0.2 0.3 0.4 0.5 0.6

X [-]

0

0.1

0.2

0.3

0.4

0.5

m.[k

g/m

2h]

withoutwithWSMODFLUBED

G1800

0 0.1 0.2 0.3 0.4 0.5

X [-]

0

0.1

0.2

0.3

m.[k

g/m2 h]

withoutwithWSMODFLUBED

G0800

AOS

0 0.1 0.2 0.3 0.4 0.5

X [-]

0.000

0.005

0.010

0.015

0.020

0.025

m. [kg/

m2 h]

withoutwithWSMODFLUBED

0 0.1 0.2 0.3 0.4 0.5

X [-]

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

m. [kg/

m2 h]

withoutwithWSMODFLUBED

NWA

G0260

19

0,00 0,05 0,10 0,15 0,20 0,25

X [-]

0

250

500

750

1000

1250

αW

,bed

[W

/m2 K]

MessungWSMODFLUBED

0,00 0,05 0,10 0,15 0,20 0,25

X [-]

0

250

500

750

1000

1250

αW

,bed

[W

/m2 K]

MessungWSMODFLUBED

NG100 NO203

SUMMARY OF COMPARISON

Drying rate Heat transfer coeff. vertical

Heat transfer coeff. horizontal

CHARGE FLUBED WSMOD FLUBED WSMOD FLUBED WSMOD G1800 1.01 0.99 1.31 1.18 0.74 0.66 G1150 1.11 1.02 1.01 0.90 0.98 0.90 G0800 1.39 1.33 0.97 0.87 1.11 1.02 G0260 0.78 0.78 0.81 0.72 1.15 1.04 NWA 0.86 0.84 0.88 0.78 1.20 1.08 AOS 0.81 0,72 0.99 0.84 1.51 1.26 NG100 1.48 1.12 2.26 1.55 3.64 2.43 NO203 1.57 1.23 2.71 1.94 2.89 2.05

20

CONCLUSION

* Indirect and direct impact of latent heat sink

* Direct impact:

dp > 800 µm → negligible

dp > 100 µm, → enhancement of heat transfer

255 µm by 25 % - 30 %

dp < 50 µm → enhancement is blurred by

agglomeration

* Large increase of dryer capacity is possible

by indirect heating

* In-situ delivery of heat can be beneficial forproduct quality

* Satisfactory simulation by modular modelling, relation between difficulty and accuracyadjustable,

further sophistication is possible