cfd model of a fluidized bed chemical · interconnected multi-phase cfd chemical looping model glt...
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Lehrstuhl für Energieanlagen und EnergieprozesstechnikP f D I V S hProf. Dr.‐Ing. V. Scherer
CFD model of a fluidized bed chemicalCFD‐model of a fluidized bed chemical looping system:
Design of a heat and mass flow control
H. Kruggel‐Emden; S. Wirtz; V. Scherer
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Chemical looping combustion- A solid oxygen carrier (metal oxide) is circulated in the
O2, N2 CO2, H2Ooxidized
i
A solid oxygen carrier (metal oxide) is circulated in the system and is alternately oxidized/reduced
- Air reactor: Oxidation of the oxygen carrier
carrierAirReactor
FuelReactor- Fuel reactor: Bonded oxygen of the carrier reacts with
the gaseous, liquid or solid fuel
Airreducedcarrier Fuel
Gaseous products are CO2 + H2O
=> No additional separation of N2 necessary: good efficiencies
=> Low formation of thermal NOx due to low temperatures
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Scale up of chemical looping processes
Existing CFB power plants:e.g. Lagisza III – 460MW
?
Hereby necessary:Simulation methods
0 1kW 1kW 10kW 100kW 1MW ?? ??
Simulation methods
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
0.1kW 1kW 10kW 100kW 1MW ?? ??
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Applicable simulation methods for fluidized systems
- Macroscopic models
- Multi-phase CFD
- Fuel reactor - gaseous fuel [Jung/Gamwo 2008, Deng et al. 2008, Jin et al. 2009,…]Solid fuel conversion [Mahalatkar et al 2009]- Solid fuel conversion [Mahalatkar et al. 2009]
- Fuel reactor model validation [Mahalatkar et al. 2011]- Interconnected modeling [Shuai et al. 2011, Mahalatkar et al. 2010, Kruggel-g gg
Emden et al. 2010]
- Particle based models & CFD
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Interconnected multi-phase CFD chemical looping modelG l t
oxsm ,
exhaustairm
General parametersTime step Δt [s] 0.0002Mean particle diameter dp [mm] 0.1525Angle of internal friction ξ [°] 30Maximal packing limit ε [-] 0 6
Air-reactor Fuel-
reactor
Maximal packing limit εs,max [ ] 0.6Restitution coefficient e [-] 0.9Kinetic model Spherical shrinking coreThermal power P [MW] 0.5 (0.4, 0.3)
bubsm ,
XBuffer
fuelmredsm ,
bubsX ,
airm bufsm ,feedsm ,
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Interconnected multi-phase CFD chemical looping modelG l t
oxsm ,
exhaustairm
General parametersTime step Δt [s] 0.0002Mean particle diameter dp [mm] 0.1525Angle of internal friction ξ [°] 30Maximal packing limit ε [-] 0 6
Air-reactor Fuel-
reactor
Maximal packing limit εs,max [ ] 0.6Restitution coefficient e [-] 0.9Kinetic model Spherical shrinking coreThermal power P [MW] 0.5 (0.4, 0.3)
bubsm ,
X
Buffer specificationsInitial mass [kg] 0Initial state of reduction X [-] 0.65Initial temperature [K] 1200
Buffer
fuelmredsm ,
bubsX , Initial temperature [K] 1200Initial mass flow dm/dts,feed [kg/s] 3.5Initial mass flow dm/dts,red [kg/s] 0Feed temperature [K] 1200Feed state of reduction X[-] 0.65
feedsm ,airm bufsm ,
Feed state of reduction X[ ] 0.65
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Interconnected multi-phase CFD chemical looping modelG l t
oxsm ,
exhaustairm
General parametersTime step Δt [s] 0.0002Mean particle diameter dp [mm] 0.1525Angle of internal friction ξ [°] 30Maximal packing limit ε [-] 0 6
Air-reactor Fuel-
reactor
Maximal packing limit εs,max [ ] 0.6Restitution coefficient e [-] 0.9Kinetic model Spherical shrinking coreThermal power P [MW] 0.5 (0.4, 0.3)
bubsm ,
X
Air reactor specificationsWidth of vessel [m] 0.225Height of vessel [m] 8.0G id b [ ] 1500
Buffer
fuelmredsm ,
bubsX , Grid number [-] 1500Inlet gas temperature [K] 300Inlet gas velocity [m/s] 1.45Inlet gas composition [kg/kg] N2: 0.77; O2: 0.23Initial bed height [m] 0
feedsm ,airm bufsm ,
Initial bed height [m] 0Inlet solid velocity [m/s] 0
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Interconnected multi-phase CFD chemical looping modelG l t
oxsm ,
exhaustairm
General parametersTime step Δt [s] 0.0002Mean particle diameter dp [mm] 0.1525Angle of internal friction ξ [°] 30Maximal packing limit ε [-] 0 6
Air-reactor Fuel-
reactor
Maximal packing limit εs,max [ ] 0.6Restitution coefficient e [-] 0.9Kinetic model Spherical shrinking coreThermal power P [MW] 0.5 (0.4, 0.3)
bubsm ,
X
Fuel reactor specificationsWidth of vessel [m] 0.25Height of vessel [m] 0.8W i h i ht [ ] 0 4
Buffer
fuelmredsm ,
bubsX , Weir height [m] 0.4Initial bed height [m] 0.21Initial solids packing [-] 0.42Initial temperature [K] 1223Initial state of reduction X [-] 0 5
feedsm ,airm bufsm ,
Initial state of reduction X [ ] 0.5Grid number [-] 2500Inlet gas temperature [K] 300Inlet gas velocity [m/s] 0.061Inlet gas composition [kg/kg] CH4: 1 (0.594, 0.354);
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
4CO2: 0 (0.406, 0.646)
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Governing gas/solid reactionsOxygen Carrier Materials: Mn O -Mg-ZrO NiO/MgAl O Fe O /MgAl O
Unreacted zone
O2HCO12MnOCHOMn 22443 432 OMn4O212MnO
Oxygen Carrier Materials: Mn3O4-Mg-ZrO2, NiO/MgAl2O4, Fe2O3/MgAl2O4
Reacted
4NiO2HCOCH4NiO 224 4NiO2O4Ni 2
O2HCOO8FeCHO12Fe 2243432 zone
O2HCOO8FeCHO12Fe 2243432 32243 O2Fe1O2O8Fe
Reaction model and kinetic data
32~1exp3 /ngas )X-(C
TREkbdX/dt
Q Zafar, A Abad, T Mattisson, B Gevert, M Strand, Chem. Eng. Sci. 2007, 62, 6556.Q Zafar, A Abad, T Mattisson, B Gevert, En. & Fu. 2007, 21(2), 610.
n, k, E, b - Derived according to experimental data from:
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
A Abad, et al., Chem. Eng. Sci. 2007, 62(1-2), 533.
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Operation of the interconnected modeloxsm ,
Air-t
Fuel-
exhaustairmoxsT ,
reactor reactor
bubsm ,
X
q
redsX ,
Buffer
fuelmredsm ,
bubsX ,
feedsm ,airm bufsm ,
dm/dts,buf=fixed=3.5kg/sCarrier: Mn3O4-Mg-ZrO2
=> Heat and mass flow control essential
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Temperature control design
oxsm ,
exhaustfuelmexhaustairm
oxsT , act
oxgset
oxgoxgoxgpactoxs
setoxsoxsoxsp TTmcTTmcQ ,,,,,,,,
Excess heat flux and excess heat flux density
Air-reactor Fuel-
reactor
t
surf dQTnQAKpq
0/1/
setoxs
setoxg TT ,, where
B ff
qbubsm ,
bubsX ,
Kp and Tn from an open loop step response
Kp=0 35·Tg/Ks/TuBuffer
fuelmredsm ,
Kp=0.35 Tg/Ks/Tu
Tn=1.2·Tg
feedsm ,airm bufsm , KL Chien, JA Hrones, JB Reswick, in: Transact. of the Am. Soc. of Mech. Eng.74 Cambridge 1952
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
74, Cambridge 1952
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Temperature control designOpen loop step response for Mn3O4-Mg-ZrO2
exhaustairm
oxsT ,
oxsm ,
1 2
1.6
2
Open loop step response for Mn3O4 Mg ZrO2
dm/dts,buf Kp Tn
2 k / 1 85 3 24Air-reactor
0.4
0.8
1.2
x(t)
dm/dt s,buf=2kg/sdm/dt s,buf=4kg/s
)(tx 2 kg/s 1.85 3.24s
4 kg/s 0.61 2.76s
6 kg/s 1.91 2.40s
setqq 00 1 2 3 4 5 6 7
t [s]
dm/dt s,buf=6kg/s
(A)Closed loop progression of Ts,ox (left), solid mass flow rate dm/dts,ox (right)
1300
1400
1500
[K] 6
8
10
(t) [k
g/s]
dm/dt s,buf=2kg/sdm/dt s,buf=4kg/sdm/dt s,buf=6kg/s
1100
1200
T(t)
[
T s,ox (dm/dt=2kg/s)T s,ox (dm/dt=4kg/s)T s,ox (dm/dt=6kg/s)T s,ox,set
airm
setbufsbufs mm ,,, 2
4
dm/d
t s,o
x
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
10000 4 8 12 16
t [s]
, ,
(C)
00 2 4 6 8 10
t [s](D)
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Temperature control designOpen loop step response for NiO/MgAl2O4
exhaustairm
oxsT ,
oxsm ,Open loop step response for NiO/MgAl2O4
dm/dts,buf Kp Tn
0 5 k / 0 61 2 765
6
7dm/dt=0.5kg/sdm/dt=1kg/sdm/dt=1.5kg/s
Air-reactor
)(tx 0.5 kg/s 0.61 2.76s
1.0 kg/s 0.88 3.00s
1.5 kg/s 1.17 3.00s1
2
3
4
x(t)
Open loop step response for Fe2O3/MgAl2O4
setqq 00 1 2 3 4 5 6 7
t [s](A)
1.6
2
2.4
dm/dts,buf Kp Tn
2 kg/s 1 91 2 40s
0.4
0.8
1.2x(t)
dm/dt=2kg/sdm/dt=4kg/sdm/dt=6kg/s
airm
setbufsbufs mm ,,,
2 kg/s 1.91 2.40s
4 kg/s 2.06 2.40s
6 kg/s 7.61 2.40s
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
00 1 2 3 4 5 6 7
t [s]
dm/dt 6kg/s
(B)
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Mass flow control design
M fl di PI lloxsm ,
exhaustfuelmexhaustairm
Mass flow rate according to a PI-controller
tact
redsset
redsact
redsset
redsbufs dXXTnXXKpm
0,,,,, )(/1)(
Air-reactor Fuel-
reactorKp and Tn derived from a simplified model
0
exhaustfuelm
B ff
bubsm ,
bubsX ,
redsX ,
exhaustfuelmbubsV ,bubsX ,
tBuffer
fuelmredsm ,
bufsm ,act
redsX ,oxsm ,oxsX ,
setredsX ,
feedsm ,airm bufsm ,
fuelm
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Mass flow control design
t
t
actreds
setreds dtXXTnKpf
0,, )(,Optimization of:
P t f PI t ll ith t [3 4 5 ]
exhaustfuelmbubsV ,bubsX ,
through a genetic algorithm
Parameters of a PI-controller with tdel =[3s , 4s, 5s]bufsm ,
actredsX ,
oxsm ,oxsX ,
setredsX ,
Xox[-]
ms,buf[kg]
Kp[-]
Tn[s]
Kp[-]
Tn[s]
Kp[-]
Tn[s]
fuelmMn3O4/MnO 0.25 60 52.1 9.7 39.5 11.5 31.9 13.5
NiO/Ni 0.18 85 60.0 12.1 46.3 16.3 38.2 20.5
Fe2O3/Fe3O4 0.01 50 19.1 8.8 14.1 10.3 11.6 11.82 3 3 4
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Chemical looping system: Load change P=(0.5;0.4;0.3)MW Solid mass flow (left) and temperatures (right) for Mn3O4-Mg-ZrO2 as carrierSolid mass flow (left) and temperatures (right) for Mn3O4 Mg ZrO2 as carrier
25
30
35
40
/s]
dm/dt s,reddm/dt s,feeddm/dt s,bufdm/dt s,ox
1200
1300
1400
1500
5
10
15
20
dm/d
t [kg
/
800
900
1000
1100
T [K
]
T s,bufT s ox
Heat flux density (left) and degrees of reduction (right) for Mn3O4-Mg-ZrO2 as carrier
00 50 100 150 200
t [s](A)
700
800
0 50 100 150 200t [s]
T s,oxT s,ox,set
(B)
0
-20000
-10000
0
m2 ] 0.4
0.5
0.6
0.7
-40000
-30000q [W
/m
0.1
0.2
0.3X
X s,redX s,oxX s,red,set
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
-500000 50 100 150 200
t [s](C)
00 50 100 150 200
t [s](D)
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Chemical looping system: Temperature setpoint changeSolid mass flow (left) and temperatures (right) for Mn3O4-Mg-ZrO2 as carrier
1200
1300
1400
1500
20
25
30
35
/s]
dm/dt s,reddm/dt s,feeddm/dt s,bufdm/dt s,ox
Solid mass flow (left) and temperatures (right) for Mn3O4 Mg ZrO2 as carrier
00
800
900
1000
1100
T [K
]
T s,bufT s ox
5
10
15
20
dm/d
t [kg
/
0 7
600
700
0 20 40 60 80 100 120 140 160 180t [s]
T s,oxT s,ox,set
(B)
00 50 100 150 200
t [s](A)
Heat flux density (left) and degrees of reduction (right) for Mn3O4-Mg-ZrO2 as carrier
0.4
0.5
0.6
0.7
-30000
-20000
-10000
0
m2 ]
0.1
0.2
0.3X
X s,redX s,oxX s,red,set-60000
-50000
-40000q [W
/m
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
00 20 40 60 80 100 120 140 160 180
t [s](D)-70000
0 50 100 150 200t [s](C)
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Chemical looping system: Reduction rate setpoint changeSolid mass flow (left) and temperatures (right) for Mn3O4-Mg-ZrO2 as carrier
30
35
40
45
/s]
dm/dt s,reddm/dt s,feeddm/dt s,bufdm/dt s,ox
1100
1300
1500
Solid mass flow (left) and temperatures (right) for Mn3O4 Mg ZrO2 as carrier
5
10
15
20
25
dm/d
t [kg
/
500
700
900
T [K
]
T s,bufT s ox
00 50 100 150 200 250 300
t [s](A)
3000 50 100 150 200 250 300
t [s]
T s,oxT s,ox,set
(B)
0 0 7Heat flux density (left) and degrees of reduction (right) for Mn3O4-Mg-ZrO2 as carrier
-30000
-20000
-10000
00 50 100 150 200 250 300
2 ] 0.4
0.5
0.6
0.7
70000
-60000
-50000
-40000
q [W
/m2
0.1
0.2
0.3X
X s,redX s,oxX s,red,set
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
-80000
-70000
t [s](C)
00 50 100 150 200 250 300
t [s](D)
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Chemical looping system: Other carrier materialsSolid mass flow NiO/MgAl2O4 (left) and Fe2O3/MgAl2O4 (right)
30dm/dt s,reddm/dt s,feed
25dm/dt s,reddm/dt s,feed
Solid mass flow NiO/MgAl2O4 (left) and Fe2O3/MgAl2O4 (right)
15
20
25
dm/d
t [kg
/s]
dm/dt s,feeddm/dt s,bufdm/dt s,ox
10
15
20
dm/d
t [kg
/s]
dm/dt s,feeddm/dt s,bufdm/dt s,ox
0
5
10
0 10 20 30 40 50 60 70 800
5
0 10 20 30 40 50 60 70 80 90
t [s](A)t [s](A)
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011
Lehrstuhl für Energieanlagen und EnergieprozesstechnikProf. Dr.‐Ing. V. Scherer
Conclusions
An interconnected multiphase CFD-model was derived
T t d fl t l i l t d dTemperature and mass flow controls were implemented and necessary
parameters derived
Various setpoint changes for a selection of carrier materials were considered
The applied controllers allow steady operation of the chemical looping model
Detailed investigations of the dynamics in further refined model frameworks g y
become possible
2nd International Conference on Energy Process Engineering | Frankfurt | June 20, 2011