Controllability
y and Flexibilityy Analysis
y
of a CO2 Capture Plant using
MEA and
d PZ/K2CO3
Jozsef Gaspar*, John Bagterp Jørgensen**,
Luis Ricardez Sandoval***
Sandoval , Kaj Thomsen*
Thomsen , Philip Loldrup Fosbøl
Fosbøl*
* Center for Energy Resources Engineering, Technical University of Denmark
** Department of Applied Mathematics and Computer Science, Technical University of Denmark
*** Department of Chemical Engineering, University of Waterloo
PCCC3
Regina, Canada
September 9 – 11, 2015
Outline
• Why flexible operation?
• dCAPCO2 rate-based
rate based dynamic model
• CO2 absorber and desorber model validation
• Sensitivity analysis:
• Importance of make-up flow control
• Effect of rich feed’s
feed s temperature
• Conclusions
Wind Power in Denmark - 2013
33% of electrical energy
gy generated
g
from wind
Back Up Generation Need in DK
33% Wind (2013)
50% Wind (2020)
(
)
80% Wind (2025)
Objective
• Develop and implement a mechanistic first-principle
first principle
based rate-based model for CO2 capture simulation
using MEA and PZ promoted K2CO3 solvents
• IInvestigate
ti t
th
the
t
transient
i t behavior
b h i
combustion CO2 capture process
off
a
postt
Dynamic Model Development
Assumptions:
• Radial gradients in temperature and
concentrations
co
ce t at o s a
are
e negligible.
eg g b e
• No accumulation in the gas and liquid films.
• MEA and PZ/K2CO3 are non
non-volatile.
volatile.
• Reaction takes place only in the liquid phase.
• Heat loss to the surroundings is negligible.
negligible
dCACPO2 – dynamic model
Gas phase
CO2
H2O
Energy
CCO2 ,g
t

CH 2O ,g

t
Eg
t

N CO2 ,g
z
N H 2O ,g
z
Qg
z



aeff
 1  hL 
aeff
 1  hL 
aeff
 1  hL 
J CO2 , gl
J H 2O , gl
qcond
Liquid phase
CO2
H2O
Energy
CCO2 ,l
t
CH 2O ,l
t


N CO2 ,l
z
N H 2O ,l
z
aeff


aeff
 hL
aeff
 hL
J CO2 , gl
J H 2O , gl
El Ql
 qconv  qcond  qgen 


t
z  hL
Pressure drop and liquid hold-up given by the Rocha et al. model (1993)
Mass and Heat Transfer
CO2 and H2O mass transfer
•
kl,CO2a, kg,CO2a, KG,CO2a and hL
using theory of Rocha et al.
Heat transfer
CO2 reaction with amine
•
Enhancement factor (E) using the
DTU General model
Colburn analogy to mass transfer
Extended
E
t d d UNIQUAC:
UNIQUAC
VLE and thermal properties (solubility, heat of reaction)8
Absorber validation
Operating conditions
+10%
-10%
Inlet CO2 mol %
PZ concentration ((mol/kgg water))
K2CO3 concentration (mol/kg water)
Lean CO2 loading (mol/mol alk.)
L/G ratio (kg/kg)
Gass temperature
G
e pe u e ((ºC)
C)
Lean temperature (ºC)
8 – 18
1.6 and 2.5
2.5 and 3.2
0.07 – 0.30
4.6 – 8
40
40 – 46
Column characteristics
Height (m)
Diameter (m)
Packing type
P ki area ((m2/m
Packing
/ 3)
6.1
0.43
Flexipac AQ 20
213
* Data from Chen, E., Carbon Dioxide Absorption into Piperazine Promoted Potassium
Carbonate using Structured Packing, PhD thesis, The university of Texas at Austin, 2007
Absorber validation
Lean CO2 loading: 0.20
L/G ratio: 5.2
7.2
CO2 loading: 0.24
L/G ratio: 5.9
4.8
Desorber validation
+10%
+10%
-10%
10%
-10%
Operating conditions
PZ concentration (mol/kg water)
K2CO3 concentration (mol/kg water)
Rich CO2 loading (mol/mol alk.)
Top temperature (ºC)
Bottom temperature (ºC)
Reboiler heat duty (MW)
2.5
2.5
0.30 – 0.44
103 – 115
117 – 118
0.19 – 0.64
Column characteristics
Height (m)
Diameter (m)
Packing type
Packing area (m2/m3)
6.1
0.43
Flexipac AQ 20
213
* Data from Chen, E., Carbon Dioxide Absorption into Piperazine Promoted Potassium
Carbonate using Structured Packing, PhD thesis, The university of Texas at Austin, 2007
Desorber validation
Rich loading: 0.40
Reboiler duty: 0.54 MW
Rich loading: 0.36
0.24 MW
Reboiler duty: 0.36 MW
0.54 MW
Sensitivity study
Importance
p
of make-up
p flow rate:
• Flue gas flow and composition is specified.
• Lean flow rate adjusted to reach approximately 90% CO2 capture.
• The
Th water
t content
t t off the
th lean
l
is
i changed
h
db
by ±1% and
d ±2%.
±2%
Effect of the stripper’s
stripper s feed temperature:
• Composition and flow rate to the stripper is specified.
• The reboiler duty is fixed.
• The temperature of the feed is changed by ±4 C and ±8 C.
Importance of water make-up
make up
Low water
make-up flow
High water
make-up flow
Kinetics
the
reaction
between CO2 andCase
the Camine
solution
Case of
A -1
% water
make-up
1 % water
make-upplay
Case B -2 %role
waterin
make-up
Case D 2to
%awater
make-up
an important
how the system responds
perturbation
Importance
p
of water make-up
p
Case B: -2 % water make-up
Low water
make-up
p flow
Case A -1 % water make-up
Case B -2 % water make-up
High water
make-up flow
Case C 1 % water make-up
Case D 2 % water make-up
1.5 m PZ / 6 m K2CO3
Control of water make-up flow plays a weak influence for
precipitating systems!
Case A -1 % water make-up
Case B -2 % water make-up
Case C 1 % water make-up
Case D 2 % water make-up
Effect of rich feed
feed’s
s temperature
TINIT = 100 C
TINIT = 100 C
Rich temperature exerts a strong influence on
the strippers’ efficiency
Conclusions & Future work
• Flexible operation of power plants is mandatory, thus capture plants
have to be operated with varying loads.
• A comprehensive mechanistic dynamic rate-based model for CO2
absorption and desorption simulation using MEA and PZ/K
/ 2CO3 was
developed.
• The proposed model was validated against experimental data from
Chen (PhD thesis, 2007).
y
• Sensitivityy study:
• PZ promoted K2CO3 system has a slower response but it is a selfregulatory process.
• Control of water and amine make-up flow is essential for MEA but
it exerts a lower effect for precipitating systems.
• Rich
Ri h feed’s
f d’ temperature
t
t
h a strong
has
t
i fl
influence
on the
th regeneration
ti
process’ efficiency.
Thank you!
For more information contact:
Jozsef Gaspar
[email protected]
John Bagterp Jørgensen
Luis Ricardez Sandoval
Kaj Thomsen
Philip Loldrup Fosbøl
[email protected]
[email protected]
[email protected]
[email protected]
Simulation Scenarios
Start Up
Operation
Parameter
Gas flow rate (kmol/s)
CO2 concentration (mol %)
Load Following
Operation
Low
9.64 ± 1.5
14.1 ± 0.15
Meter accuracy
Medium
9.64 ± 0.8
14.1 ± 0.08
High
9.64 ± 0.3
14.1 ± 0.03
21
Start Up Operation - Absorber
Parameter
Gas flow rate (kmol/s)
CO2 concentration (mol %)
Low
9.64 ± 1.5
14.1 ± 0.15
Meter accuracy
Medium
9.64 ± 0.8
14.1 ± 0.08
High
9.64 ± 0.3
14.1 ± 0.03
22
Start Up Operation - Desorber
Parameter
Gas flow rate (kmol/s)
CO2 concentration (mol %)
Low
9.64 ± 1.5
14.1 ± 0.15
Meter accuracy
Medium
9.64 ± 0.8
14.1 ± 0.08
High
9.64 ± 0.3
14.1 ± 0.03
23
Load Following Operation - Absorber
Parameter
Gas flow rate (kmol/s)
CO2 concentration (mol %)
Low
9.64 ± 1.5
14.1 ± 0.15
Meter accuracy
Medium
9.64 ± 0.8
14.1 ± 0.08
High
9.64 ± 0.3
14.1 ± 0.03
24
Load Following Operation - Desorber
Parameter
Gas flow rate (kmol/s)
CO2 concentration (mol %)
Low
9.64 ± 1.5
14.1 ± 0.15
Meter accuracy
Medium
9.64 ± 0.8
14.1 ± 0.08
High
9.64 ± 0.3
14.1 ± 0.03
25
Load Following Operation
FULL
Limited storage tank capacity
70%
40%
20%
Rich tank
capacity
26
Load Following Operation - Absorber
FULL
Limited storage tank capacity
70%
40%
20%
Rich tank
capacity
27
Load Following Operation - Desorber
FULL
Limited storage tank capacity
70%
40%
20%
Rich tank
capacity
28
Power plant with CO2 capture
Power plant interaction with
post-combustion
post
combustion plant
Source: http://www.captureready.com/en/Channels/Research/
29
Why Flexible Operation?
FOCUS:
Start-up operation
L d ffollowing
Load
ll i operation
ti
Blue: base load
Green: switch-off
Bl k lload
Black:
d following
f ll i
Magenta: peaking
Red: switch-on
Typical behavior of a coal-fired power plant
Source: Data from Elexon, N. Mac Dowell , N. Shah, Computers & Chemical Engineering,
Volume 74, 2015, 169 - 183
30
Dynamic Model Development
31
Importance of water make-up
make up
Low water
make-up flow
High water
make-up flow
Case A -1 % water make-up
Case B -2 % water make-up
Case C 1 % water make-up
Case D 2 % water make-up