On the mass transfer of CO2 in enzyme enhanced solvents ... · PZ/MDEA 21/29 wt% PZ/MDEA 0 0.2 0.4...
Transcript of On the mass transfer of CO2 in enzyme enhanced solvents ... · PZ/MDEA 21/29 wt% PZ/MDEA 0 0.2 0.4...
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On the mass transfer of CO2 in enzyme
enhanced solvents - comparison with
conventional solvent systems
Arne Gladis, Philip L. Fosbøl, John M. Woodley, Nicolas von Solms
Technical University of Denmark
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15
35
55
75
95
115
0 20 40 60 80 100
Te
mpera
ture
°C
Wt % Piperazine
ExtendedUNIQUAC
PIPH2·6H2O
PIPH2·½H2O
PIPH2
Ice
Experimental
• Physical Properties
• Equilibrium
• Kinetics
Modelling
• Energy consumption
• Heat of reaction
• Thermodynamics
• Kinetics
Simulation
• Variance analysis
• Optimization of energy use
• Optimization of packing
• Rate based approach
• Equilibrium approach
• Aspen Plus
• Cape-Open
Pilot tests
• Real life tests
• Solvent study
• Packing testing
• Energy requirements
• Mass transfer
DTU CO2
Research
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Overview
Benchmarking overall mass transfer
Energy consumption
Benchmarking solvent capacity
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Ideal solvent for postcombustion CCS
Low capital costs
High mass transfer rates
Low operational costs
High solvent capacity
Low energy demand for regeneration
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Solvents
K2CO3
Alkanolamines are the most prominent group of solvents for CO2 capture
Carbonate salt
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K2CO3PZ
Solvents in CCS
Primary amine Tertiary amine Carbonate salt
Absorption rate of CO2
Secondary amine
Carbonate salt solutions and tertiary amines are not even
considered as potential solvents because of slow absorption
kinetics
∆𝑯𝑹≈ 𝟖𝟎 − 𝟖𝟓 𝒌𝑱
𝒎𝒐𝒍 ∆𝑯𝑹≈ 𝟓𝟎 − 𝟔𝟓
𝒌𝑱
𝒎𝒐𝒍 ∆𝑯𝑹≈ 𝟏𝟓 − 𝟐𝟕
𝒌𝑱
𝒎𝒐𝒍 ∆𝑯𝑹≈ 𝟕𝟓 − 𝟖𝟓
𝒌𝑱
𝒎𝒐𝒍
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K2CO3PZ
Primary amine Tertiary amine Carbonate salt
Absorption rate of CO2
Secondary amine
∆𝑯𝑹≈ 𝟖𝟎 − 𝟖𝟓 𝒌𝑱
𝒎𝒐𝒍 ∆𝑯𝑹≈ 𝟓𝟎 − 𝟔𝟓
𝒌𝑱
𝒎𝒐𝒍 ∆𝑯𝑹≈ 𝟏𝟓 − 𝟐𝟕
𝒌𝑱
𝒎𝒐𝒍 ∆𝑯𝑹≈ 𝟕𝟓 − 𝟖𝟓
𝒌𝑱
𝒎𝒐𝒍
The enzyme carbonic anhydrase (CA) can catalyze the reaction of
bicarbonate forming solvents and speed up the absorption rates
𝑪𝑶𝟐 + 𝑯𝟐𝑶𝑪𝑨
𝑯+ + 𝑯𝑪𝑶𝟑−
Solvents in CCS
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WWC Experiments
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Determine effect of:
• Temperature (298- 333 K)
• Solvent loading
Solvent Solvent type
30 wt% MDEA + 8.5 g/L CA Enzyme enhanced solvent
30 wt% MDEA + 5 wt% PZ Chemically promoted solvent
30 wt% MEA Primary amine
Comparison of absorption behavior of conventional solvents and
enzyme ehanced solvents on a wetted wall column
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WWC – measurements
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-0.01
-0.005
0
0.005
0.01
0.015
0.02
0 10000 20000 30000Ab
sorb
ed f
lux
(m
ol/
m2/s
)
Driving force mean log pCO2 (Pa)
30 wt% MDEA, 313 K 0.02 ldg 3 g/l CA
0.02 ldg 1.5 g/l CA
0.35 ldg 3 g/l CA
0.35 ldg 1.5 g/l CA
Measurement of absorption kinetics
Comparison of different solvents
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• Opposing trends for
conventional and enzyme
enhanced solvents
• Reaction kinetics increase for
conventional solvents
• Enzyme kinetics are not
increasing with temperature
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0.0E+00
1.0E-06
2.0E-06
3.0E-06
4.0E-06
5.0E-06
290 300 310 320 330 340
kli
q (
mo
l p
a-1
m-2
s-1
)
Temperature (K)
MEA MDEA + PZ MDEA + CA 30 wt% MEA, unloaded
30 wt% MDEA 5 wt% PZ, unloaded
30 wt% MDEA + 8.5 g/L CA, unloaded
Effect of temperature on CO2 mass transfer
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0.0E+00
1.0E-06
2.0E-06
3.0E-06
0 0.1 0.2 0.3 0.4 0.5 0.6
kli
q (
mo
l p
a-1
m-2
s-1
)
Loading (mol CO2/ mol solvent)
MEA MDEA + PZ MDEA + CA
• Rapid decline in mass
transfer upon loading for
conventional solvents
• Just slight deline in mass
transfer for enzyme
enhanced solvents
Effect of solvent loading on CO2 mass transfer
30 wt% MEA,
30 wt% MDEA 5 wt% PZ,
30 wt% MDEA + 8.5 g/L CA
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0.0E+00
1.0E-06
2.0E-06
3.0E-06
0 0.1 0.2 0.3 0.4 0.5 0.6
kli
q (
mo
l p
a-1
m-2
s-1
)
Loading (mol CO2/ mol solvent)
MEA MDEA + PZ MDEA + CAReaction Rates:
Conventional solvents:
Dependent on active amine concentration
Enzyme enhanced solvents:
Independent on active amine concentration
Am
ov Am Amk k C
3
2
2
2
1
CA CACA
ov
HCO
MS CO
MP
HOC kk
CK
C
CK
Effect of solvent loading on CO2 mass transfer
Different reaction mechanism can explain the different mass transfer of conventional and
enzyme enhanced solvents.
Modelling results [1] [2] [3]
[1] G. F. Versteeg, L. A. J. . van Dijck, and W. P. M. van Swaaij, “On the Kinetics between CO2 and Alkanolamines
both in aqueous and non-aqueous solutions. An overview,” Chem. Eng. Commun., vol. 144, pp. 113–158, 1996.
[2] J. Gaspar and P. L. Fosbøl, “Practical Enhancement Factor Model based on GM for Multiple Parallel Reactions:
Piperazine (PZ) CO2 Capture,” Chem. Eng. Sci., 2016.
[3] A. Gladis, M. T. Gundersen, R. Nerup, P. L. Fosbøl, J. M. Woodley, N. von Solms, R. Neerup, P. L. Fosbøl, J. M.
Woodley, and N. Von Solms, “CO2 mass transfer model for carbonic anhydrase enhanced MDEA solutions,” Chem.
Eng. J., vol. 335, no. October 2017, pp. 197–208, 2018.
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Benchmark of experiments
Comparison of the average liquid side mass transfer coefficient as well
as the cyclic capacity of the different solvents
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Definition of average kliq by Li and Rochelle [4].
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Benchmark of experiments
[4] L. Li, H. Li, O. Namjoshi, Y. Du, and G. T. Rochelle, “Absorption rates and CO 2 solubility in new
piperazine blends,” Energy Procedia, vol. 37, pp. 370–385, 2013.
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0.2
0.4
0.6
0.8
1
1.2
0 2 4 6 8 10 12
Cy
clic
ca
pa
city
(mo
l C
O2 /
kg
(so
lven
t +
wa
ter)
)
average kliq (*107 mol Pa-1 s-1 m-2)
30 wt% MEA
5/30 wt% PZ/MDEA
30 wt% MDEA 8.5 g/L CA
Comparison of the average liquid side mass transfer coefficient as well
as the cyclic capacity of the different solvents
𝑷𝑪𝑶𝟐𝒈𝒂𝒔
= 12 kPa
𝑷𝑪𝑶𝟐𝒈𝒂𝒔
= 1.2 kPa 𝑷𝑪𝑶𝟐𝒍𝒊𝒒∗
= 0.5 kPa
𝑷𝑪𝑶𝟐𝒍𝒊𝒒∗
= 5 kPa
Top
Bottom
DF=0.7 kPa
DF=7 kPa
Isothermal
at 40°C
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Benchmark of experiments
40 wt% PZ
30 wt% PZ
30 wt% AMP
9/42 wt%
PZ/MDEA
21/29 wt%
PZ/MDEA
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0.2
0.4
0.6
0.8
1
1.2
0 2 4 6 8 10 12
Cy
clic
ca
pa
city
(mo
l C
O2 /
kg
(so
lven
t +
wa
ter)
)
average kliq (*107 mol Pa-1 s-1 m-2)
conventional amines
30 wt% MEA
5/30 wt% PZ/MDEA
30 wt% MDEA 8.5 g/L CA
Comparison of the average liquid side mass transfer coefficient as well
as the cyclic capacity of the different solvents
• Enzyme enhanced MDEA has
highest average kliq in own
experiments
• Just solvents with high PZ
concentration (>21%) have a higher
mass transfer
• MDEA+CA solvents have a
comparable cyclic capacity at 298 K
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Benchmark of experiments
Comparison with literature values [5]
• Enzyme enhanced MDEA has
highest average kliq in own
experiments
• Just solvents with high PZ
concentration (>21%) have a higher
mass transfer
• MDEA+CA solvents have a
comparable cyclic capacity at 298 K
30 wt% MEA
5/30 wt%
PZ/MDEA
30 wt% MDEA
8.5 g/L CA
0
0.2
0.4
0.6
0.8
1
1.2
0 2 4 6 8 10 12
Cy
clic
ca
pa
city
(mo
l C
O2 /
kg
(so
lven
t +
wa
ter)
)
average kliq (*107 mol Pa-1 s-1 m-2)
PZ PZ blends PZ derivates
Amino acids primary monoamines secondary monoamines
hindered monoamines Diamines
[5]: G. T. Rochelle, “Conventional amine scrubbing for CO 2 capture,”
in Absorption-Based Postcombustion Capture of Carbon Dioxide,
2016.
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Benchmark of experiments
𝑷𝑪𝑶𝟐𝒈𝒂𝒔
= 12 kPa
𝑷𝑪𝑶𝟐𝒈𝒂𝒔
= 1.2 kPa 𝑷𝑪𝑶𝟐𝒍𝒊𝒒∗
= 0.5 kPa
𝑷𝑪𝑶𝟐𝒍𝒊𝒒∗
= 5 kPa
Top
Bottom
DF=0.7 kPa
DF=7 kPa
Isothermal
at 40°C
0.0E+00
1.0E-06
2.0E-06
3.0E-06
0 0.1 0.2 0.3 0.4 0.5 0.6
kli
q (
mo
l p
a-1
m-2
s-1
)
Loading (mol CO2/ mol solvent)
MEA MDEA + PZ MDEA + CA
Enzyme enhance solvents show a good performance compared to conventional solvents,
because of the high mass transfer at higher solvent loadings (higher driving forces in the
bottom of absorber)
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• Reaction mechanism of enzymes different than amines
• Enzyme enhanced solvent have potential to utilize lower
absorption temperature to maximize cyclic capacity
• Enzyme enhanced solvents show comparable mass transfer
as well as cyclic capacity compared to conventional solvents
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Conclusion
Need of precise process modelling for comparison and
benchmark of total systems
(See also our Poster: Process Model Validation of enzyme
enhanced CO2 capture)
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Thank you for your attention
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