1. CHARACTERIZATION OF FOAMING BEHAVIOR IN AMINE-BASED CO2 CAPTURE PLANTS
Research Review Meeting
January 10 – 11, 2008
University of Texas at Austin, Texas
BHURISA THITAKAMOL AND AMORNVADEE VEAWAB
Faculty of Engineering, University of Regina
CANADA

2. OUTLINE Introduction Objectives Experiment Results and discussions1
Introduction
Objectives
Experiment
Results and discussions
Foam model
Conclusions
Future works
Acknowledgements

3. INTRODUCTION Foaming problem in the CO2 absorption process5
INTRODUCTION
Foaming problem in the CO2 absorption process
One of the most severe operational problems causing extra expenditures
Occurring in both an absorber and a regenerator during plant start-up and
operation
Causing many adverse impacts on the plant operation
Impacts based on plant experiences
Excessive loss of alkanolamine solvents
Premature flooding
Reduction in plant throughput
Off-spec products
High alkanolamine carryover to downstream plants

4. INTRODUCTION Research on foaming problem:6
INTRODUCTION 9
Research on foaming problem:
For the CO2 absorption process in gas treating services
Research group
Alkanolamine type
Contaminant
Operating condition
Pauley et al.,
1989
MEA
DEA
MDEA
Two formulated
MDEA (with non
specified additives)
Formic acid
Acetic acid
Propionic acid
Butyric acid
Pentanoic acid
n-hexanoic acid
Octanoic acid
Decanoic acid
Dodecanoic acid
Liquid hydrocarbon
Atmospheric
pressure
McCarthy and
Trebble, 1996
Methanol
Corrosion inhibitor
Antifoam agent
Lubrication oil
Organic acid
Degradation product
Suspended solid oC
MPa
Harruff, 1998
DGA
93oC
up to 6.9 MPa
Current foaming knowledge in the CO2 absorption process
for a coal-fired power plant is limited:
The application of the CO2 absorption process is relatively new for a coal-fired power plant.
No reports of plant experiences and research work has published.

5. 7
OBJECTIVES
To obtain comprehensive foaming information from bench-scale experiments under well-simulated environments.
To reveal the parametric effects as listed below on foaming
Gas flow rate
Solution volume
CO2 loading
Alkanolamine concentration
Solution temperature
Degradation product
Corrosion inhibitor
Alkanolamine type
To establish the foam model to predict a steady-state pneumatic foam height (H) from the physical properties and operating conditions

6. EXPERIMENTS The pneumatic method modified from8
EXPERIMENTS
The pneumatic method modified from
the standard ASTM D892 (ASTM, 1999)
Recorded foam volume

7. (average steady foam volume)9
EXPERIMENTS
Recorded data: Foam volume (cm3) vs. Time (min) for each minute during the 25-minute blowing time o
(average steady foam volume)
Raw data
; o = Average foam volume (cm3)
G = Gas flow rate (cm3/min)
The foaminess coefficient () (Bikerman, 1973)

8. RESULTS AND DISCUSSIONS10
RESULTS AND DISCUSSIONS
EFFECT OF GAS FLOW RATE
At 20 – 80 cm3/min, N2 flow rate
, 
At 80 – 110 cm3/min, N2 flow rate
,  CONSTANT
MEA
MEA
Working flow rate at 94 cm3/min
(Test condition: 2.0 & 5.0 kmol/m3 MEA, 400 cm3 solution volume, 0.40 mol/mol CO2 loading and 40oC)

9. RESULTS AND DISCUSSIONS11
RESULTS AND DISCUSSIONS
EFFECT OF SOLUTION VOLUME
At 200 – 400 cm3, solution volume
, 
At 400 – 700 cm3, solution volume
,  CONSTANT
Working Volume at 400 cm3
(Test condition: 2.0 kmol/m3 MEA, 94 cm3/min N2, 0.40 mol/mol CO2 loading and 40oC)

10. RESULTS AND DISCUSSIONS12
RESULTS AND DISCUSSIONS
EFFECT OF MONOETHANOLAMINE (MEA) CONCENTRATION
Decreased surface tension
Surface tension of CO2-unloaded aqueous MEA solution replotted from experimental data [Vázquez et al., 1997]
MEA concentration
,  initially
and then
Increased bulk liquid viscosity
Predicted viscosity of CO2-loaded aqueous MEA solutions from correlation [Weiland et al., 1998]
(Test condition: MEA, 94 cm3/min N2, 400 cm3 solution volume, absorber top: 0.20 mol/mol CO2 loading/ 40oC & absorber bottom: 0.40 mol/mol CO2 loading/ 60oC)

11. RESULTS AND DISCUSSIONS13
RESULTS AND DISCUSSIONS
Decreased surface tension
Surface tension of CO2-loaded aqueous MEA solution measured by Spinning Drop Interfacial Tensiometer Model 510
EFFECT OF CO2 LOADING
CO2 loading
,  initially
and then
Increased bulk liquid viscosity
Predicted viscosity of 5.0 kmol/m3 MEA solution from correlation [Weiland et al., 1998]
(Test condition: 5.0 kmol/m3 MEA, 94 cm3/min N2, 400 cm3 solution volume and 40, 60 and 90oC)

12. RESULTS AND DISCUSSIONS Reduced bulk viscosity14
RESULTS AND DISCUSSIONS
EFFECT OF SOLUTION TEMPERATURE
Solution temperature
, 
0.20 mol CO2/mol MEA
0.40 mol CO2/mol MEA
Reduced bulk viscosity
Decreasing 
(Test condition: 5.0 kmol/m3 MEA, 94 cm3/min N2, 400 cm3 solution volume and 0.20 & 0.40 mol/mol CO2 loading)
Predicted viscosity of 5.0 kmol/m3 MEA solution from correlation [Weiland et al., 1998]

13. RESULTS AND DISCUSSIONS15
RESULTS AND DISCUSSIONS
EFFECT OF DEGRADATION PRODUCT
Most degradation products added into aqueous MEA solution induce foam.
Degradation product
Average  (min)
None
0.80 
Ammonium thiosulfate
0.97 
Glycolic acid
0.94 
Sodium sulfite
0.92 
Malonic acid
0.92 
Oxalic acid
0.90 
Sodium thiocyanate
0.90 
Sodium chloride
0.89 
Sodium thiosulfate
0.85 
Bicine
0.85 
Hydrochloric acid
0.83 
Formic acid
0.83 
Acetic acid
0.82 
Sulfuric acid
0.77 
(Test condition: 10,000 ppm of degradation product, 5.0 kmol/m3 MEA, 94 cm3/min N2, 400 cm3 solution volume, 0.40 mol/mol CO2 loading and 60oC)

14. RESULTS AND DISCUSSIONS16
RESULTS AND DISCUSSIONS
EFFECT OF CORROSION INHIBITOR
Corrosion inhibitors added into aqueous MEA solution enhance .
(Test condition: 1,000 ppm of corrosion inhibitor, 5.0 kmol/m3 MEA, 94 cm3/min N2, 400 cm3 solution volume, 0.40 mol/mol CO2 loading and 60oC)
Surface tension of 5.0 kmol/m3 MEA solutions containing no CO2 loading at 25oC with/without 1000 ppm corrosion inhibitor (measured by KrÜss Tensiometer K100 using the Wihelmy plate’s principle)

15. RESULTS AND DISCUSSIONS17
EFFECT OF ALKANOLAMINE TYPE
Foam formation in MEA and MDEA but not in DEA and AMP solutions
Only small amount of foam in AMP+MEA solution with the mixing ratio of 1:2 mol/mol
Viscosity of CO2-unloaded aqueous alkanolamine solution
at 60o replotted from experimental data
Type of alkanolamine
Average 
MEA
0.85  0.004
DEA
No foam
MDEA
0.32  0.019
AMP
MEA + MDEA (1:1)
MEA + MDEA (2:1)
MEA + MDEA (1:2)
DEA + MDEA (1:1)
DEA + MDEA (2:1)
DEA + MDEA (1:2)
MEA + AMP (1:1)
MEA + AMP (1:2)
MEA + AMP (2:1)
0.13  0.001
(Test condition: 4.0 kmol/m3 total alkanolamine conc., 94 cm3/min N2, 400 cm3 solution volume, 0.40 mol/mol CO2 loading, 60oC and mixing ratio of blended solution = 1:1, 2:1 and 1:2 (mole:mole))
Predicted viscosity of the CO2-unloaded aqueous blended alkanolamine solution
(4.0 kmol/m3 total alkanolamine conc. and 60oC)
from Grunberg and Nissan’s equation (Mandal et al., 2003))

16. FOAM MODEL: LITERATURE18
FOAM MODEL: LITERATURE
Researcher
Foaming system
Method
Proposed equation
Solution
Gas
Ito and Fruehan (1989)
28%Cao-42%SiO2-30%FeO slags
Argon
Dimensional analysis
=  (, , )
Jiang and Fruehan (1991)
30%FeO (Cao/SiO2=1.25) and 0%FeO (Cao/SiO2=1.25) slags
=  (, , , g)
Zhang and Fruehan (1995)
40%Cao-40%SiO2-15%Al2O3-5%FeO slags
=  (, , , g, Db)
Ghag et al (1998)
Water + 78 – 95% glycerinate +SDBS N2
1. =  (, , , g, Db);  is surface tension depression
2. =  (g, , Db, EM); EM is surface elasticity
3. =  (g, , Db, Eeff); Eeff is effective elasticity
Pilon et al (2001)
Results from other research works
Dimensional analysis of the governing equation for the pneumatic foam layer proposed by (Bhakta and Ruckenstein, 1997)
Pilon and Viskanta (2004)
Dimensional analysis of the governing equation for the pneumatic foam layer proposed by (Bhakta and Ruckenstein, 1997) + Prediction of minimum superficial gas velocity (jm)

17. FOAM MODEL: DEVELOPMENT19
Pilon et al (2001)

18. FOAM MODEL: RESULTS Foaming height equation20
FOAM MODEL: RESULTS
Foaming height equation
where
INSIGNIFICANT
Pout = Pdispersion + Pfoam + P*
when
when
when

19. 21
FOAM MODEL: RESULTS

20. 22
CONCLUSION
Solution volume affects  when it is small. Increasing the solution volume to a certain quantity
results in a constant foam volume or .
An increase in gas flow rate decreases . The gas flow rate can lead to a constant  when
increases to a certain value.
Ranges of solution volume and gas flow rate that lead to a constant  were found for the CO2-
aqueous alkanolamines. These ranges enable the generation of foam data that do not depend
on solution volume, gas flow rate, pore size of gas disperser, and dimension of test cell.
Variations in MEA concentration, CO2 loading and solution temperature affect .
An increase in temperature decreases .
 increases and then declines with increasing MEA concentration and CO2 loading.
Most degradation products and corrosion inhibitors enhance .
MEA, MDEA and AMP + MEA (1:2 mixing mole ratio) generate apparent foams
FOAM MODEL is established to predict the steady-state pneumatic foam height from the
physical properties and operating conditions and also to identify the important dimensionless
numbers for a scaling-up hydrodynamic experiment. 31

21. FUTURE WORK FOAM MODEL HYDRODYNAMIC23
FUTURE WORK
FOAM MODEL
Sensitivity analysis of input parameters on the predicted foam height.
Model improvement by incorporating the minimum superficial gas velocity predicted
based on the one-dimensional drift-flux model (Pilon and Viskanta, 2004)
HYDRODYNAMIC
Study the foaming behavior occurred in the packed absorber during absorption
process based on dimensionless numbers in terms of the foaming tendency and the
foam stability by measuring  and foam half-life, respectively.
Investigate the effect of foaming on the hydrodynamic parameter s (e.g., pressure
drop, liquid holdup and flooding point) of the packed CO2 absorption column based
on dimensionless numbers.  FOAMING CHART

22. ACKNOWLEDGEMENT 24
Faculty of Graduate Studies and Research (FGSR), University of
Regina
Faculty of Engineering, University of Regina
The Natural Sciences and Engineering Research Council (NSERC)