This presentation discusses carbon dioxide capture and sequestration using activated carbon adsorption. It begins with an introduction to climate change and carbon capture and storage technologies. It then presents the objective to model CO2 adsorption on activated carbon. A mathematical model is developed based on Dubinin's theory of micropore filling. Governing equations are presented and discretized. Results show the model validates experimentally. A parametric analysis examines the effects of bed thickness, cooling temperature, heat transfer coefficient and initial bed temperature on CO2 adsorption. It concludes lower bed radii and higher temperatures and heat transfer rates increase adsorption while noting temperature effects on materials. Future work could extend the model and realize challenges of practical implementation.

1. A
Presentation
on
Carbon Dioxide Capture and Sequestration by Adsorption on
Activated Carbon
Presented by
Vinod Kumar Singh
Ph.D. Research Scholar
Guided by
Dr. E. Anil Kumar
Assistant Professor
Discipline of Mechanical Engineering
Indian Institute of Technology Indore

2. OUTLINE
 Introduction
CCS
 Objective of the Study
Significance
Limitations
Physical
Model
 Mathematical Modeling
Definition
 Results and Discussions
 Conclusions
Validation
Parametric
Analysis
Kinetic
Models
Governing
Equations
 Scope of Future Work
Discretization
Equations
CO2 Capture
Technology
Importance
of AC

3. Introduction
 With the rapid development of modern civilization, the widespread use of fossil
fuels within the current energy infrastructure is considered as the largest source of
anthropogenic emissions of CO2, which is largely responsible for global warming
and climate change
 The International Panel on Climate Change (IPCC) predicts that, by the year 2100,
the atmosphere may contain up to 570 ppm CO2, causing a rise in the mean global
temperature of around 1.9 C
 CCS is not the „silver bullet‟ that in and of itself will solve the climate change
problem, it is powerful addition to the portfolio of technologies that will be needed
to address climate change
Source: Martinez et al. (2013), IPCC (2007) and Bernstein et al. (2006)
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4. Table : Fossil fuel emission levels (Pounds/Billions BTU of energy input)
Pollutant
Natural Gas
Coal
Oil
117000
208000
164000
Carbon Monoxide
40
208
33
Nitrogen oxide
92
457
448
Sulphur dioxide
1
2591
1122
Particulates
7
2744
84
Mercury
0
0.016
0.007
117140
214000
165687
Carbon dioxide
Total
IPCC Climate Change: Impacts, Adaptation and Vulnerability
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5. Fig. Atmospheric CO2 concentration during 1958-2012
Source: Carbon dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of
Energy
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6. Significance
of
Carbon
Sequestration (ccs)
Capture
and
 Fossil fuels will continue to be used in absence of any fast and easy alternatives
used at large scale
 CCS enables to continue use of fossil fuels with reduced emissions while other
alternatives are being developed
 CO₂ capture technologies are commercial and widely used in industrial processes
mainly in petroleum industries, ammonia processing and natural gas refining
 Applied to several gas fired and coal fired boilers but at smaller scales than current
power plants
Source: Special Report on “Carbon dioxide capture and storage.” Chapter 3, Intergovernmental Panel on
Climate Change (IPCC), (2006)
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7. Limitations of ccs
• Small Scale: Demonstrated in several industrial applications but not yet at a modern
electric power plant of capacity of as high as 500 MW
• Energy Penalty & High costs involved for the implementation of CCS (CO₂
separation, compression, delivery in pipeline and injection of compressed CO₂ in
geologic reservoirs)
Source: IPCC (2006)
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8. Carbon dioxide Capture and Sequestration (CCS)

9. Definition of CCS
Fossil
Fuels;
Biomass
Air or
Oxygen
Power Plant
or Industrial
Process
CO2
CO2
Capture &
Compress
- Post – combustion
- Pre - combustion
- Oxyfuel combustion
CO2
Transport
- Pipeline
- Tanker
USEFUL
PRODUCTS
(e.g., electricity, fuels,
chemicals, hydrogen)
CO2 Storage
(Sequestration)
- Depleted oil/gas fields
- Deep Saline formations
- Unmineable coal seams
- Deep Ocean
- Mineralization
- Reuse
Fig. Schematic of a CCS system, consisting of CO2 capture, transport and storage
Source: Rubin, E.S. (2010)
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10. Fig. Schematic CO2 Capture Options (Source: Figuerea et al. (2008))
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11. CO2 Capture Technologies
CO2 Separation and Capture
Absorption
Chemical
Adsorption
Cryogenics
Adsorber
Beds
Membranes
Gas Separation
MEA
Caustic
Zeolite
Other
Activated Carbon
Polyphenyleneoxide
Alumina
Physical
Microbial/Algal
Systems
Polydimethylsiloxane
Gas Absorption
Regeneration
Method
Selexol
Pressure Swing
Rectisol
Temperature Swing
Other
Polypropelene
Washing
Ceramic Based
Systems
Fig. Technical options for CO2 capture (The choice of method depends strongly on the
particular application)
Source: Rao, A.B. et al (2002)
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12. Importance of Activated Carbons (AC)
• High Thermal Stability
• Favorable Adsorption Capacity
• Wide Range of Starting Materials for Production of Activated Carbons
• Leads to Lower Raw Material Costs
• Large Adsorption Capacity at Elevated Pressures
• Desorption can Easily be Accomplished by the Pressure Swing Approach
Source: Spigarelli, B.P. et al. (2013)
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13. Objective of the Study
 To select as a suitable adsorbents for the CO2 capture and a numerical analysis is
carried out to study the rate of adsorption of the gas
 A one dimensional mathematical model is proposed based on the Dubinin‟s
Theory of volume filling of Micropore, and analyzed along with the unsteady
heat transfer
 A parametric analysis is carried out to study the effect of various crucial
parameters like thickness of bed, cooling fluid temperature, supply temperature
and heat transfer coefficient on the adsorption amount
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14. Mathematical Modeling

15. Problem Formulation And Solution Methodology
Physical Model
D
Fig. Physical model of adsorption system
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Fig. Side view of the reactor bed
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16. Assumptions
1.
2.
3.
4.
5.
6.
7.
8.
9.
Reactor is one dimensional i.e. only radial variations are considered.
Variation of porosity with adsorption is negligible inside the bed. There is no
swelling of the solids.
Thermo-physical properties of both the gas and solid phases are constant.
Local thermal equilibrium exists between the gas and solid. The gas velocities in
the bed are small. Hence, the gas and solid phase have sufficient time to attain
equilibrium.
Carbon dioxide acts like an ideal gas inside the bed.
Natural convection and radiation effects are neglected.
CO2 pressure within the bed is uniform (at any given instant; no radial variations).
Cooling fluid temperature is taken to be constant throughout the process with
convection occurring for cooling of the bed.
Other gases in stream have a very low ppm hence no effect on the adsorption of
CO2 by AC. Sorption capacity of AC towards moisture is very low.
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17. Kinetic Model for ACs
 Dubinin Astakhov (D-A) and Radushkevich (D-R) Equation
Na
W
N ao exp
W0 exp
n
A
E0
A
E0
Dubinin Astakhov Equation
2
Dubinin Radushkevich Equation
Where;
Na = Amount adsorbed at relative pressure P/Ps
Nao = Limiting amount of gas adsorbed in micropores where W0 = NaoVm
A = Thermodynamic potential RT ln (Ps/P)
Eο = Characteristic energy for a given adsorbent system
β = Scaling factor depending on adsorbate
Wο = Micropore volume
Vm = Molar volume at specified pressure and temp.
Source: Stoeckli, F. et al. (1995, 2001)
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18. Properties of Activated Carbons
S.
No
Name of
Activated
Carbon
Micropore
Volume
Wo (cm3/g)
Surface area
of
Micropore
Smi (m2/g)
Average
Micropore
width
Lo (nm)
Characteristic
Energy
Eo (kJ/mol)
1.
PSAC
(coal tar)
0.26
413
1.25
20.04
2.
Commercial AC
MAXSORB 30
(petroleum
coke)
0.34
2250
0.97
22.5
3.
ACP-750-2.0
(coconut shell)
0.40
1018
0.78
25.14
Source: Guillot, A. et al. (2001), Linares (2005)
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19. Empirical Relations Used to calculate the
Characteristic Energy Eo
(Assuming single slit shaped micropore)
Source: Stoeckli, F. et al. (1995)
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20. Governing Equations
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21. Boundary Conditions
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22. Solution through Discretization of Equations
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23. Internal Node Equation
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Surface Node Equation
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24. Table: Thermophysical Properties of AC and CO2
S.N.
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
Parameter
Density (Kgm-3)
Specific heat (JKg-1K-1)
Effective thermal conductivity (Wm-1K-1 )
Diffusivity (m2s-1)
Heat of adsorption (kJmol-1)
Universal gas constant (Jmol-1K-1)
Characteristic Energy (KJmol-1)
Scaling Factor
Limiting amount adsorbed (mol)
Saturation Pressure (atm)
Inlet Pressure of CO2 (atm)
Activated
Carbon (AC)
530
0.92
0.25
Carbon
Dioxide (CO2)
1.98
5e-7
15
8.314
25
0.36
0.000755
1.1
0-1
Source: Guillot, A. et al. (2001), Linares (2005), Martin, C.F. et al. (2010)
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25. Table: Operational parameters (* represents
variable quantities)
S.N.
Parameter
Range of Value
(1)
Initial temperature of bed T0* (K)
(2)
Diameter of the bed D* (m)
(3)
Cooling fluid temperature Tf *(K)
273 - 303
(4)
Heat transfer coefficient h* (Wm-2K-1)
50 - 250
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313 - 373
0.15 – 0.70
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26. Results and Discussions

27. Validation of Kinetic Model
Nao = Wo/Vm (Vm = Molar Volume)
T = 50 C
Ps = 1.1 atm
Eo = 25 kJ/mol
βCO2 = 0.36
Wo = 0.4 cm3/g
Vm = 530 cm3/g
Average Relative Error: 2.8%
Fig. Graphical comparison of Theoretical and Experimental results for stream at 40°C
and 0-1 atm (Experimental values: Chang et al., 2006 )
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28. Parametric study of carbon dioxide capture system

29. Radial
Variations
of
Adsorption Amount of CO2
Fig. Radial variations of Temperature
Process conditions:
Initial Temperature of bed: 80 C
Cooling fluid temperature: 10 C
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Temperature
&
Fig. Radial variation of Adsorption
Quantity (mol kg-1 of adsorbent)
Heat Transfer Coefficient: 150 W/m2K
Dimensions: 0.30 m diameter
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30. Effect of Radius on amount of CO2 adsorbed with
time
• Maximum quantity of CO2
adsorbed does not vary
significantly while changing
the diameter
• Time to reach the max.
adsorbed state increases as
the bed thickness is increased
Fig. Variation of CO2 adsorption with time for
different radii (packing density kept same)
Process conditions:
Initial bed temperature: 80 C
Cold fluid temperature: 10 C
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• Bed with lesser thickness
facilitates heat conduction
faster
• At any given time, the lower
thickness bed would have
cooled down more than the
one with more thickness
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31. Effect of Cold Fluid Temperature on amount
adsorbed
• Higher
cooling
fluid
temperature values, the heat
is dissipated faster with
more adsorbed CO2 at any
given time due to the lower
average bed temperatures
• Time to reach maximum
adsorption state does not
vary significantly
Fig. Variation of CO2 adsorption with cooling fluid temperature
Process conditions:
Initial bed temperature: 80 C
Heat transfer coefficient: 150 W/m2K
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32. Effect of Heat transfer coefficient on amount
of CO2 adsorbed with time
• Maximum adsorption state is
reached faster for higher „h‟
values
• Amount adsorbed does not
increase significantly after h =
100 W/m2K
Fig. Variation of CO2 adsorption with time for different heat transfer coefficient
Process conditions:
Initial bed temperature: 80 C
Cold fluid temperature: 10 C
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33. Effect of Initial Bed Temperature on amount
of CO2 adsorbed with time
• For higher initial temperatures,
the maximum amount of CO2
adsorbed is more, though
insignificant differences exists
• Time to reach that state is also
almost the same in all cases
Fig. Variation of CO2 adsorption with different inlet bed temperatures
Process conditions:
Heat transfer coefficient: 150 W/m2K
Cold fluid temperature: 10 C
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34. Conclusions

35. Conclusions
1.
The adsorption model (rate as a function of temperature & pressure) for AC is
best described by Dubinin‟s Theory of Volume Filling of Micropores (TVFM)
2.
Lower reactor bed radii are preferred to minimize the time required to reach the
maximum adsorption state although the CO2 adsorbed does not have significant
differences. Hence, a bed diameter of D = 30 cm is selected
3.
Higher heat transfer coefficient results in faster adsorption as well as higher
amount of CO2 adsorbed. But after h = 100 Wm-2K-1, the maximum amount
adsorbed tends to be the same. Hence, an „h‟ value of 150 Wm-2K-1 is selected
4.
Lower cooling fluid temperature results in faster adsorption. Hence, a value of
10 C is selected for the operation
5.
Higher initial bed temperature results in greater amount of CO2 adsorbed with
the steady state being reached in same time. It leads to the selection of To=
353K as the preferred value. Although, temperature should not be increased to a
level which tends to degrade the material of the reactor bed
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36. Scope for Future Work
• 1D study can be extended to a 2D and 3D model followed by practical
implementation to realize the real-time difficulties associated with the model
• AC used in the present work have the basic form without the impregnation of basic
functionalities like amines. This study can thus be used to incorporate those
modifications and then analyze the system
• Mathematical approach discussed in the present work can be used to carry out the
comparison of different adsorbents
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37. THANK YOU
for
Your Kind Attention

38. Queries ?