start-up and control of an autothermal reforming (atr)...
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Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Start-up and Control of an
Autothermal Reforming (ATR) Reactor
Donald J. Chmielewski and Yongyou Hu
Department of Chemical & Environmental Engineering
Illinois Institute of Technology, Chicago, IL
Dennis Papadias Chemical Engineering Division
Argonne National Laboratory, Argonne, IL
Presented at the Annual Meeting of the AIChE: November 2005
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Outline
Introduction / Motivation
Reactor Modeling and Analysis
• 1-D Transport and Kinetic Model
• Model Validation
Controller Design
• 0-D Model and Temperature Regulation
• Start-up Transition Control
Route to Predictive Control
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Fuel Cell System
Fuel
Processor Fuel Cell
Stack
Spent-Fuel
Burner
Thermal & Water Management
Air
Air
Fuel
H2
Exhaust
H2O CO2
Electric Power
Conditioner
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Hydrogen Storage vs. On-Board Reforming
Transportation
Applications
PEMFCReformerLiquid Fuel
Storage Tank
Cm
Hn
H2
CO
H2O
CO2
PEMFCHydrogen
Storage Tank
H2
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Hydrogen Storage vs. On-Board Reforming
Transportation
Applications
PEMFCReformerLiquid Fuel
Storage Tank
Cm
Hn
H2
CO
H2O
CO2
PEMFCHydrogen
Storage Tank
H2
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
PEMFC and CO Poisoning
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Fuel Processing Reactors
PEMFCPreferential
Oxidation
(PrOx)
Water-
Gas
Shift
(WGS)
Reformer
Hydrocarbon Feed
Large Hydrocarbons Cracked:
Low H2 to CO ratio Most CO converted to CO2: ~ 1% CO remaining
CO levels down to ~ 10 ppm
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Fuel Processing Reactors
PEMFCPreferential
Oxidation
(PrOx)
Water-
Gas
Shift
(WGS)
Reformer
Hydrocarbon Feed
Large Hydrocarbons Cracked:
Low H2 to CO ratio Most CO converted to CO2: ~ 1% CO remaining
CO levels down to ~ 10 ppm
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Partial Oxidation
Hydrocarbon Fuel
Air (at a sub-
stoichiometric rate)
PO
Reactor
Total Oxidation: OHnmCOOnmHC nm 222 2/)2/(
Steam Reforming: 22 )2/( HnmmCOOmHHC nm
Water Gas Shift: 222 HCOOHCO
22
2
COOH
COH
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Partial Oxidation
Hydrocarbon Fuel
Air (at a sub-
stoichiometric rate)
PO
Reactor
Oxidation: OHnmCOOnmHC nm 222 2/)2/(
Steam Reforming: 22 )2/( HnmmCOOmHHC nm
Water Gas Shift: 222 HCOOHCO
22
2
COOH
COH
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Partial Oxidation
Hydrocarbon Fuel
Air (at a sub-
stoichiometric rate)
PO
Reactor
Oxidation: OHnmCOOnmHC nm 222 2/)2/(
Steam Reforming: 22 )2/( HnmmCOOmHHC nm
Water Gas Shift: 222 HCOOHCO
22
2
COOH
COH
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Water Gas Shift Reaction
At High temperatures equilibrium favors:
222 HCOOHCO
At Low temperatures equilibrium favors:
222 HCOOHCO
More H2O in the feed will also favor the forward direction
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Autothermal Reforming
Hydrocarbon Fuel Air (at a sub-
stoichiometric rate)
ATR
Reactor
Oxidation: OHnmCOOnmHC nm 222 2/)2/(
Steam Reforming: 22 )2/( HnmmCOOmHHC nm
Water Gas Shift: 222 HCOOHCO
22
2
COOH
COH
Steam
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Autothermal Reforming
Hydrocarbon Fuel Air (at a sub-
stoichiometric rate)
ATR
Reactor
Oxidation: OHnmCOOnmHC nm 222 2/)2/(
Steam Reforming: 22 )2/( HnmmCOOmHHC nm
Water Gas Shift: 222 HCOOHCO
CO
H
Less
More 2
Steam 222 ,,, COOHCOH
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Outline
Introduction / Motivation
Reactor Modeling and Analysis
• 1-D Transport and Kinetic Model
• Model Validation
Controller Design
• 0-D Model and Temperature Regulation
• Start-up Transition Control
Route to Predictive Control
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Fuel Processor System at Argonne
Water
WG
1
AirWater
Fuel
AirW
G2
WG
3
WG
4
PrO
x1
PrO
x2
PrO
x3
ATR
Water
WG
1
AirWater
Fuel
AirW
G2
WG
3
WG
4
PrO
x1
PrO
x2
PrO
x3
ATR
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
ATR Reactor at Argonne
Vaporized gasoline,
Steam
Liquid water
Heat exchangerAir (25 °C)
Hot air
Nozzle
7 m
m1
2 m
m1
2 m
m
96 mm
Catalyst bed
Heater rod
Thermocouple1 2 3 4
5 6 7
8 9 10
Metal wall
thickness=1.7 mm
High Space Velocity
(GHSV ~ 50,000/h)
Noble Metal Catalyst
(Rh on a Gd-CeO2 substrate).
Operating Temperature
~ 700 – 1000o C
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Reactor Model (Axially Dependent, Nonlinear Dynamic Version)
)()()(,
)()(
0s
jg
jg
jccc
gj
g
kAx
m
N
i
iijj
g
j
s
j
g
jc rMk1
)()()(
,0
)()()()(
)()( ˆ0 sggccc
gg
pg TThA
x
Tcm
)()()(
)()( )(ˆ wsw
w
ww
pw TTxh
t
TSc
Mass Balances:
Catalyst Phase:
Gas Phase:
Energy Balances:
Gas Phase:
n
1i
c
)()(
llreactor wa fer toHeat trans
)()()(
,
)()()(
...)(1ˆ
ii
sg
cc
sw
ww
s
axe
ss
p
s
rHTTh
TTxhx
T
xt
Tc
Solid Phase:
Reactor Wall:
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Model of Reaction Kinetics (1)
)()(
11 2
s
O
s
fuel yyAr
Total Oxidation Reaction :
OHnmCOOnmHC nm 222 2/)2/(
1A
Rate Expression:
where
Oxidation rate is Fuel Diffusion Limited.
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Model of Reaction Kinetics (2)
222 HCOOHCO
Water-Gas Shift Reaction:
Rate Expression:
029.22073)()(
)()(
33 10;22
2
3
T
e
e
s
CO
s
Hs
OH
s
CO
RT
E
KK
yyyyeAr
Wheeler, Jhalani, Klein, Tummala, Schmidt, J. Catal. (2004).
Parameters Adapted from:
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Model of Reaction Kinetics (3)
22 )2/( HnmmCOOmHHC nm
Steam Reforming Reaction:
Rate Expression:
2
)(
2
2)()(
22
2
2
2
1
s
fuel
RT
H
s
OH
s
fuel
RT
E
yeKyyeAr
Activation Energies from:
Dubien, Schweich, Mabilon, Martin, Prigent, Chem. Eng. Sci. (1998).
A2 and K2: Fit to Experimental Data:
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Micro-Reactor Tests (Steady-State Analysis)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.75 1.25 1.75 2.25 2.75 3.25
H2O/C ratio (-)
H2,
CO
2 m
ola
r fr
ac
tio
n (
dry
)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
CO
mo
lar
fra
cti
on
(d
ry)
O2/C=0.45
CO2
CO
H2
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.30 0.35 0.40 0.45 0.50 0.55 0.60
O2/C ratio (-)
H2,
CO
2 m
ola
r fr
ac
tio
n (
dry
)
0.05
0.08
0.10
0.13
0.15
0.18
0.20
CO
mo
lar
fra
cti
on
(d
ry)
CO2
H2
CO
H2O/C=1.5
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Reactor Start-up: A 2 Step Procedure
Partial Oxidation Mode (to quickly increase temperature)
ATR Mode (for greater CO conversion)
Hydrocarbon Fuel Air
ATR
Reactor
Steam
Hydrocarbon Fuel
Air
PO
Reactor
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Reactor Start-Up: CPOX Mode
0
100
200
300
400
500
600
700
800
900
1000
20 40 60 80 100 120 140 160 180 200
Time (s)
Te
mp
era
ture
(°C
)
Experimental Data
Simulation
@ 7 mm
@ 19 mm
Inlet temperature
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Reactor Start-Up: ATR Mode
0
100
200
300
400
500
600
700
800
20 40 60 80 100 120 140 160 180 200
Time (s)
Te
mp
era
ture
(°C
)
Experimental Data
Simulation
@ 7 mm
@ 19 mm
Inlet temperature
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Exit Concentrations
0.00
0.05
0.10
0.15
0.20
0.25
50 70 90 110 130 150 170 190
Time (s)
Mo
lar
fra
cti
on
dry
(-)
Experiment H2
Experiment CO
Simulation H2
Simuation CO
CPOX Mode: ATR Mode:
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
30 50 70 90 110 130 150 170 190
Time (s)
Mo
lar
fra
cti
on
dry
(-)
CO Simulation
H2 Simulation
CO Experimental
H2 Experimental
@ reactor exit @ GC
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Steady-State Axial Profiles
0.00
0.05
0.10
0.15
0.20
0.25
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Dimensionless x-axis (x/L)
Mo
lar f
ra
cti
on
s w
et
(-)
H2
CO
H2O
CO2
Fuel
CPOX Mode: ATR Mode:
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Dimensionless x-axis (x/L)
Mo
lar f
ra
cti
on
s w
et
(-)
H2
CO
H2O
CO2
FuelO2
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Outline
Introduction / Motivation
Reactor Modeling and Analysis
• 1-D Transport and Kinetic Model
• Model Validation
Controller Design
• 0-D Model and Temperature Regulation
• Start-up Transition Control
Route to Predictive Control
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Need for Temperature Regulation
Vaporized gasoline,
Steam
Liquid water
Heat exchangerAir (25 °C)
Hot air
Nozzle
7 m
m1
2 m
m1
2 m
m
96 mm
Catalyst bed
Heater rod
Thermocouple1 2 3 4
5 6 7
8 9 10
Metal wall
thickness=1.7 mm
0 200 400 600 800 10000
100
200
300
400
500
time (sec)
Inle
t A
ir T
em
pera
ture
(deg C
)
Inlet Air Temperature Trajectory
Primary Disturbance:
Inlet Temperature
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Open-Loop System
ATR
System T3
Inlet Air Flow
T4
T5
T2
T1
Inlet Air
Temperature
Inlet Steam Flow
} } Unmeasured
(but simulated)
Measured
(and simulated)
• Step Tests Performed Using the 1-D Nonlinear Model
• CPOX and ATR Modes Simulated
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
First Order Plus Dead Time Modeling (CPOX Mode)
Air Flow Rate Inlet Temperature Steam Flow Rate
1,
s
eK
F
T
i
s
i
inAir
ii
1,
s
eK
T
T
i
s
i
inAir
ii
1,
s
eK
F
T
i
s
i
inSteam
ii
0 20 40 60 80 100800
850
900
950
1000
1050
time (sec)
AT
R T
em
pera
ture
(oC
)
T1
T2
T3
T5
T4
0 20 40 60 80 100800
850
900
950
1000
1050
T1
T2
T3
T4
T5
AT
R T
em
pera
ture
(oC
)
time (sec)0 20 40 60 80 100
650
700
750
800
850
900
950
1000
1050
time (sec)
AT
R T
em
pera
ture
(oC
)
T1
T2
T3
T4
T5
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
First Order Plus Dead Time Modeling (ATR Mode)
0 20 40 60 80 100800
850
900
950
1000
1050
T3
T1
T2
T3
T4
T5
AT
R T
em
pera
ture
(oC
)
time (sec)0 20 40 60 80 100
800
850
900
950
1000
1050
time (sec)
AT
R T
em
pera
ture
(oC
) T1
T2
T3
T4
T5
0 20 40 60 80 100650
700
750
800
850
900
950
1000
1050
AT
R T
em
pera
ture
(oC
)
time (sec)
T2 T
1
T4
T5
T3
Air Flow Rate Inlet Temperature Steam Flow Rate
1,
s
eK
F
T
i
s
i
inAir
ii
1,
s
eK
T
T
i
s
i
inAir
ii
1,
s
eK
F
T
i
s
i
inSteam
ii
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Feedback Control
ATR
Reactor
T3 Inlet Air Flow
+ +
+ +
T4
T5
T2
T1
+
- PI
Control
T3, set point
Inlet Air Temperature
T3, measured
Sensor Noise
Temperature Fluctuations in Reactor
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Feedback Control
ATR
Reactor
T3 Inlet Air Flow
+ +
+ +
T4
T5
T2
T1
+
- PI
Control
T3, set point
Inlet Air Temperature
T3, measured
Sensor Noise
Temperature Fluctuations in Reactor
Manipulated
Variable
Control Variable
Disturbances
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Simulated Disturbances
0 200 400 600 800 10000
100
200
300
400
500
time (sec)
Inle
t A
ir T
em
pera
ture
(oC
)
Inlet Air Temperature Trajectory
0 200 400 600 800-80
-60
-40
-20
0
20
40
60Temperature Fluctuations and Sensor Noise
time (sec)
Dis
turb
ance I
nput
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Analysis of the Feedback Controller
Regulation During Partial Oxidation Mode:
0 200 400 600 800800
900
1000
1100
1200CV (T
3) Response: Open vs. Closed-loop
time (sec)
Tem
per
atu
re (
oC
)
Open-loop
Closed-loop
0 200 400 600 800-50
0
50
100
150MV (Air Flow) Response: Open-loop vs. Closed-loop
time (sec)
Inle
t A
ir F
low
Rate
(sl
pm
)
Closed-loop
Open-loop
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Analysis of the Feedback Controller
Regulation During ATR Mode:
0 200 400 600 800800
900
1000
1100
1200CV (T
3) Response: Open- vs. Closed-loop
time (sec)
Tem
per
atu
re (
oC
)
Open-loop
Closed-loop
0 200 400 600 8000
50
100
150
200MV (Air Flow) Response: Open vs. Closed-loop
time (sec)
Inle
t A
ir F
low
Rate
(sl
pm
) Open-loop
Closed-loop
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Outline
Introduction / Motivation
Reactor Modeling and Analysis
• 1-D Transport and Kinetic Model
• Model Validation
Controller Design
• 0-D Model and Temperature Regulation
• Start-up Transition Control
Route to Predictive Control
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Transition from CPOX to ATR Mode
TF w.r.t.
Air Flow
T3 Air Flow
+ + +
- PI
T3, set point
Steam Flow Rate
+ +
TF w.r.t.
Steam
-
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Transition from CPOX to ATR Mode
0 50 100 150 2000
400
600
800
0 50 100 150 2000
50
100
Reacto
r T
em
pera
ture
(deg C
)Impact of Steam Injection
Ste
am
Flo
w R
ate
(g/m
in)
time (sec)
With Feedback Controller
Without Feedback Controller
Steam Flow Rate
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Transition from CPOX to ATR Mode
0 50 100 150 200
400
600
800
0 50 100 150 2000
50
100
0 50 100 150 200
Impact of Steam Injection Rate
With Feedback Controller
Without Feedback Controller
Steam Flow Rate
time (sec)
Reacto
r T
em
pera
ture
(deg C
)
Ste
am
Flo
w R
ate
(g/m
in)
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Feed-forward Control
Gp(s) T3
Air
Flow +
+ +
- PI
T3, set point
Steam Flow Rate
(Measured)
+ +
Gd(s)
Gff(s)
-
)()(
)()( sH
sG
sGsG
p
d
ff
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Impact of Feed-forward Control
0 20 40 60 80 100500
600
700
800
900
Reacto
r T
em
pera
ture
(deg C
)
time (sec)
Steam Injection: With and Without Feed-forward
Feedback Controller Only
Feed-forward / Feedback Controller
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Model Mismatch in Feed-forward Control
Gp(s) T3
Air
Flow +
+ +
- PI
T3, set point
Steam Flow Rate
(Measured)
+ +
Gd(s)
Gff(s)
-
)()(
)()( sH
sG
sGsG
p
d
ff
• If the Gd(s) or Gp(s) used to define Gff(s) are
different than the actual plant then mismatch occurs.
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Impact of Model Mismatch
0 20 40 60 80 100400
600
800
1000
1200
time (sec)
T3 T
em
pera
ture
(oC
)
Feedback Controller Only
Feed-forward Without
Model Mismatch
Feed-forward With Model Mismatch
Impact of Model Mismatch on Feed-forward
0 20 40 60 80 100200
400
600
800
1000
T3 T
em
pera
ture
(oC
)
Impact of Model Mismatch on Feed-forward
time (sec)
Feed-forward Without Model Mismatch
Feedback Controller Only
Feed-forward With
Model Mismatch
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Conclusions
• Modeling
– 0-D model sufficient for feedback design.
– Nonlinear model likely needed for feed-forward design.
• Feedback Control (CPOX and ATR Modes)
– Good performance w.r.t. inlet conditions and sensor noise.
– Good performance during CPOX to ATR Transition, if transition is
slow enough.
• Feed-forward Control
– Model mis-match is a major concern
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Use of Predictive Control (for CPOX to ATR Transition)
• MPC can incorporate a nonlinear model during transition.
• Can enforce explicit bounds on process variables
(i.e., maximum flow rates and minimum temperatures).
• However, fast running model is needed to meet the
computational requirements of on-line optimization.
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Reduced Order Modeling
20 40 60 80 100 120 140 160 180 2000
200
400
600
800
1000
Time, s
Tem
per
ature
,oC
@ z = 7 mm
Measured Inlet Temperature
@ z = 19 mm
Experimental Measurements - "*"
High Order CFD Simulation - Solid
Reduced Order Simulation - Dashed
Computational
Effort:
NLM: ~10 min
ROM: ~30 sec
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Reduced Order Modeling
0 0.2 0.4 0.6 0.8 1-0.05
0
0.05
0.1
0.15
0.2
Dimensionless Axial Position, 1 unit =7mm
Mo
le F
ract
ion
, w
et b
asis
H2 CO
CO2 Fuel H
2O
High Order CFD Simulation - SolidReduced Order Simulation - Dashed
Computational
Effort:
NLM: ~10 min
ROM: ~30 sec
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
Acknowledgements
Collaborators
Shabbir Ahmed (ANL) Sheldon Lee (ANL)
Herek Clack (IIT) Jai Prakash (IIT)
Students
Kevin Lauzze (IIT)
Funding
Argonne National Laboratory
Graduate College, IIT
Armour College of Engineering, IIT
Chemical & Environmental Engineering Dept, IIT
Department of Chemical and Environmental Engineering
Illinois Institute of Technology
ATR Reactor Model
0
100
200
300
400
500
600
700
800
900
20 40 60 80 100 120 140 160 180
Time (s)
Tem
pera
ture
(°C
)
7 mm
19 mm
Inlet temperature
Partial Oxidation Start-up: (Liquid Water Spray at 75 s)
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