Journal of Environmental Science and Health, Part A
Toxic/Hazardous Substances and Environmental Engineering
ISSN: 1093-4529 (Print) 1532-4117 (Online) Journal homepage: https://www.tandfonline.com/loi/lesa20
Removal of CO2 in a multistage fluidized bed
reactor by diethanol amine impregnated activated
carbon
Dipa Das, Debi Prasad Samal & Bhim C. Meikap
To cite this article: Dipa Das, Debi Prasad Samal & Bhim C. Meikap (2016) Removal of
CO2 in a multistage fluidized bed reactor by diethanol amine impregnated activated
carbon, Journal of Environmental Science and Health, Part A, 51:9, 769-775, DOI:
10.1080/10934529.2016.1170462
To link to this article: https://doi.org/10.1080/10934529.2016.1170462
Published online: 10 May 2016.
Submit your article to this journal
Article views: 410
View related articles
View Crossmark data
Citing articles: 6 View citing articles
Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=lesa20
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH, PART A
2016, VOL. 51, NO. 9, 769–775
http://dx.doi.org/10.1080/10934529.2016.1170462
Removal of CO2 in a multistage fluidized bed reactor by diethanol amine impregnated
activated carbon
Dipa Dasa, Debi Prasad Samala, and Bhim C. Meikapa,b
a
Department of Chemical Engineering, Indian Institute of Technology (IIT) Kharagpur, West Bengal, India; bDepartment of Chemical Engineering,
School of Engineering, Howard College, University of Kwazulu-Natal, Durban, South Africa
ABSTRACT
To mitigate the emission of carbon dioxide (CO2), we have developed and designed a four-stage fluidized
bed reactor. There is a counter current exchange between solid adsorbent and gas flow. In this present
investigation diethanol amine (DEA) impregnated activated carbon made from green coconut shell was
used as adsorbent. This type of adsorbent not only adsorbs CO2 due to the presence of pore but also
chemically reacts with CO2 and form secondary zwitterions. Sampling and analysis of CO2 was performed
using Orsat apparatus. The effect of initial CO2 concentration, gas velocity, solid rate, weir height etc. on
removal efficiency of CO2 have been investigated and presented. The percentage removal of CO2 has
been found close to 80% under low gas flow rate (0.188 m/s), high solid flow rate (4.12 kg/h) and weir
height of 50 mm. From this result it has been found out that multistage fluidized bed reactor may be a
suitable equipment for removal of CO2 from flue gas.
Introduction
The onset of the industrial revolution, burning of fossil fuels
and deforestation has led to increase in atmospheric CO2, thus
resulting in climate change and global warming. As the concentration of the carbon dioxide in air increases, it traps more heat
and raises the temperature of the earth’s surface due to which
various natural calamities like change in rainfall patterns,
increases of sea level, and lots of bad impacts on vegetation,
human beings and wildlife occur. Fossil fuels based plants
account for 52% of the world current CO2 emission. Petroleum
oil, natural gas, and coals are the main fossil fuels burned by
humans. The atmospheric concentration has increased to
384 ppm in 2007 from its pre-industrial level of 280 ppm and is
expected to reach 550 ppm by 2050 even if CO2 emission is stable for the next four decades.[1] The present concentration has
reached down to 401.52 ppm in March, 2015 based on Scraps
CO2 Program at the Mauna Loa Observatory in Hawaii. Unfortunately there will be no big change in the next few years as far
as energy consumption is concerned. Biomass-based fuels, solar
energy and nuclear energy are the other forms of energy sources but they still cannot replace fossil fuels on a larger scale. By
2030 the energy demand will rise by 53%.[2] For reduction of
the atmospheric CO2 concentration attention has been given to
develop process equipment for carbon dioxide removal from
the flue gas in a very cost effective manner to meet the demands
of technology and with stringent environmental laws and regulations. The important thing is the selection of a suitable adsorbent which can adsorb CO2 from the flue gas in a cost effective
manner. Different adsorbents used for CO2 capture are
ARTICLE HISTORY
Received 17 December 2015
KEYWORDS
Activated carbon; adsorbent;
adsorption; carbon dioxide
capture; fluidized bed;
multistage
activated carbon,[3–5] coal,[6–8] calcium based adsorbents,[9–12]
sodium or potassium based adsorbent [7,13] etc. Among which
activated carbons (ACs) are highly microporous materials having large specific surface area and considered to be the most
efficient adsorbents.[14] As CO2 comes from acidic pollutants,
various efforts have been made to increase the alkalinity of
ACs. Different methods are used to increase the alkalinity of
the surface. The impregnation of ACs with a basic solution [15–
18]
is the most effective one. The main advantage is that it is
easy to handle the solids with no corrosion problems.[19] Amine
containing solvents are generally environmental friendly which
are generally non-toxic, cheaper and easily available. Hence solvent containing ammonia group like diethanol amine was taken
here as impregnating solvent for activated carbon for amine
group. Till now this activated carbon adsorbent has been tested
in common reactors and single-stage fluidized reactor. To
improve the efficiency of CO2 adsorption these amine impregnated adsorbents have been used in our newly designed fourstage fluidized bed reactor. The major advantage of multistage
fluidized bed reactor is that the residence time distribution of
solid becomes narrow so flow pattern is plug flow. Also gas
bypassing is reduced. Multistage fluidized bed reactor with a
down comer using a suitable adsorbent is a very recent concept
for removal of carbon dioxide from flue gas.[20–23] But till now
no work has been done to capture CO2 from flue gas by amine
impregnated activated carbon. The aim of this work was to
evaluate the influence of the operation of four-stage fluidized
bed reactor for sorption of CO2 gas on diethanol amine impregnated activated carbon particle for a wide range of operating
CONTACT Bhim C. Meikap
bcmeikap@che.iitkgp.ernet.in
Department of Chemical Engineering, School of Engineering, Howard College, University of
Kwazulu-Natal, Durban, South Africa.
Color versions of one or more of the figures in this article can be found online at www.tandfonline.com/lesa.
© 2016 Taylor & Francis Group, LLC
770
D. DAS ET AL.
conditions. DEA impregnated activated carbon is an efficient
adsorbent for carbon dioxide (CO2) due to the formation of
more stable carbamate ion.[24,25] So DEA based adsorbed has
the ability to adsorb more CO2 compared to non-impregnated
activated carbon.
Materials and methods
Preparation of sorbent
Chemicals were supplied by MERCK Specialities Private Limited,
Mumbai, India. Green coconut shells were collected from nearby
local market of IIT Kharagpur, then cut into small pieces, and
washed with tap water to remove dirt followed by drying in the
sunlight for 15–20 days till it becomes completely dry. Dried materials were kept inside the furnace at 150 C for 24 h to get rid of
moisture and other volatile impurities. Dried samples were crushed
with a locally made crusher and sieved to a size of 512 mm. Then
chemical activation was done with ZnCl2. According to the literature chemical activation is better than physical activation in order
to avoid high temperature and prolonged time activation inside
furnace.
500 gm of dried precursor was mixed well with 2000 mL of
concentrated solution of ZnCl2 that contains 500 gm of ZnCl2.
The impregnation ratio (activating agent/precursor) was 100%.
The powdered material in slurry form was properly mixed and
kept for 24 h for proper soaking of ZnCl2 on the surface of
powdered precursor. The slurry was kept inside the oven at
100 C for 24 h. The resulting chemical impregnated samples
were placed inside a galvanized iron pipe of dimensions of
length 8 cm and inner diameter of 1.5 cm and kept inside the
furnace. The material inside the furnace was heated (10 C
min¡1) to the final carbonization temperature of 600 C under
the nitrogen flow rate of 100 cm3 min¡1STP. The material was
kept inside the furnace for 1 h at 600 C. Then it was cooled
under the constant flowing of nitrogen gas till the temperature
reaches the room temperature. The dried material was washed
with 0.5 N HCl for 2–3 times and then washed with warm distilled water to remove any kind of residual organic and mineral
matter. Then it was finally mixed with cold water till the solution becomes neutral. Finally, the sample was dried for 24 h at
100 C inside an oven till it becomes completely dry.
Preparation of diethanol amine impregnated activated
carbon
The dried activated carbon was impregnated with diethanol
amine solution (HO-CH2-CH2-NH-CH2-CH2-OH) (in the
weight ratio 0.4). Then this amine-impregnated activated carbon was dried in the oven at temperature of 100 C for 48 h till
it becomes dry and kept inside an air tight container for our
experiment.
Characterization of adsorbents
The adsorbent used for removal of CO2 in our experimental
setup was diethanol amine impregnated activated carbon
(DEA) of impregnation ratio (IR) 0.4. Physical characteristics
and pore structure parameters of DEA impregnated AC are
given in Table 1.
Experimental setup and procedure
Four-stage fluidized bed reactor was developed and used in this
study, and the schematic diagram is shown in Figure 1. The fluidized bed column consisted of four stages (0.21 m height per stage
and 0.095 m internal diameter). The stages were assembled
together with a flanged joint. Four stainless steel plates (S1, S2, S3,
S4) of 0.002 m thickness were used as internal baffles between two
stages. Hole of diameter 0.002 m on a triangular pitch arrangement
was present in each plate. To avoid solids from falling down
through the plate, grid plates were covered with fine weir mesh
(100 mesh size) with openings smaller than particle size. Down
comers (D1, D2, D3, D4) were made up of Perspex cylinder of
0.024 m internal diameter and height of 0.265 m. Each section was
provided with down-comers and further fitted with a cone of diameter 0.007 m and 0.024 m height at the exit end so that up-flow of
the gas through the down-comer is reduced as a result of which stable operation is maintained. On the gas distributor, the downcomers were further fitted in special threading arrangement and
there was a provision for adjustment of weir height as required.
The weir height was considered to be bed height. The material
flows from stage to stage through the down-comer. There were
provisions for measuring pressure drop. For uniform distribution
of the gas to the fluidization column, gas distributor was present at
the bottom of the column. Calibrated rotameter was fitted to measure the air flow rate. A conical hopper was attached at the bottom
of the column for storage of the solid. A feeding funnel was present
at the top of the column to hold the activated carbon particle and it
was attached to the screw feeder. Screw feeder was fitted to a motor
of 0.25 HP, and the speed of the motor was controlled by a variable
rheostat. 5 HP compressor was used to supply the air as fluidizing
gas. The solid is fed to the first stage of the down-comer from the
top of the funnel connected to screw feeder and then through Perspex tube (0.011 m internal diameter). The gas leaving the top stage
is passed through 0.14 m diameter cyclone. To collect the fines
coming out from the fluidized bed, a bag is attached at the bottom
of the cyclone. The solids were fed from the top through the screw
feeder to the first stage of the down comer of the reactor. Compressed air at 2 kg/cm2 pressure and 80–150 L/min flow rate was
passed through the pipeline and regulated by valve. At that time
CO2 from the cylinder was passed through a gas regulator at a certain flow rate. CO2 and air mixture was passed through the throat
of the ejector and the mixture was fed into the gas chamber at the
bottom stage of the fluidized bed reactor. Counter-current flow of
the solids and the gas flow occurred at each stage. The experiments
were conducted by setting the gas velocity to 0.188–0.353 m/s corresponding to solid flow rate of 2.15–4.12 kg/h. The weir height of
the down comer was kept at 0.03 m and 0.05 m. From the literature
we have studied that the flue gas containing CO2 coming out from
stack of industries generally has very high concentration. Hence we
have taken an approximate range (low concentration to high concentration) in ppm scale of 3000–20000 ppm. For each gas flow
rate, the inlet CO2 loadings were varied from 3000 to 20000 ppm in
four stages.
Sampling and analysis
When all stages of the reactor were identical in their operation and the pressure drops across each stage were almost
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH, PART A
771
Table 1. Physical characteristics and pore structure parameter of DEA impregnated AC.
Sample
Average particle
diameter (mm)
Density
(kg/m3)
Sphericity
(Fs)
Porosity
(emf)
BET SSA
(m2/g)
VTot
(cm3/g)
VMicro
(cm3/g)
Amicro
(m2/g)
Avg. pore
radius (A0)
DEA-AC
512
2870
0.62
0.77
572.776
0.2621
0.198
9.79635
491.324
equal, then it indicated steady and stable operation reactor.
At that time samples at the inlet and outlet of the column
were drawn with the help of aspirator bottles and the
obtained CO2 gas samples were analyzed by Orsat analysis.
The gas samples i.e. concentration of CO2 in CO2 C air
mixture were analyzed for carbon dioxide by the “Orsat
Analysis” method. Simply we took an aspirator bottle filled
with kerosene; one end of the bottle was fitted below the
inlet section of the first stage fluidized bed reactor through
a pipe and the other end is connected to the collecting jar.
By downward displacement of kerosene we collected CO2 C
air mixture into the aspirating bottles. Then this air and
Figure 1. Schematic of experimental setup for a four-stage fluidized bed reactor.
CO2 mixture from the cylinder was taken inside Orsat
apparatus. By noting the level difference of initial and final
marking of measuring burette the volumetric percentage of
concentration of CO2 has been found out and then the volumetric concentration of CO2 was converted to ppm.
Orsat analysis method
Figure 2 shows the Orsat apparatus. It consists of measuring
burette and absorption pipette. Measuring burette is connected to leveling bottle which contains a mixture of potassium dichromate, water, and sodium chloride. Absorption
pipette contains potassium hydroxide which absorbs CO2. The
772
D. DAS ET AL.
Figure 2. Orsat apparatus for CO2 analysis.
aspirating bottle is used to collect and analyze CO2 sample.
First the mixture of solution (potassium dichromate, sodium
chloride, water) in measuring burette is adjusted as 100 mL
using a leveling bottle by opening and closing the inlet valve.
The potassium hydroxide level in adsorption pipette is noted,
and then one end of aspirator bottle is connected to the capillary tube and the other end is connected to the leveling bottle
that contains water. Then the valves of aspirator bottle and
inlet valve are opened. After lifting the water bottle, the reading in burette decreases as CO2 enters into the burette simultaneously. When the reading reaches zero, the inlet valve is
closed. The absorption pipette valve is opened, and then the
leveling bottle is adjusted for 30–50 times till all the CO2 gas
samples are absorbed in the KOH. After that the valve was
closed and the final reading is noted. The change in reading
gives the volume % of CO2 absorbed by the KOH solution.
Then it was converted to ppm. The percentage removal of
CO2 has been calculated for each experimental run by Equation 1:
% Removal of CO2 D
CO2
¡ CO2
CO2 inlet
inlet
outlet
£ 100
(1)
The % Removal of CO2 in stage i can be calculated as
hCO2 D
Ci C 1 ¡ Ci
£100
Ci C 1
(2)
where Ci and C iC1 are outlet and inlet carbon dioxide concentrations in gas.
Results and discussion
Effect of gas flow rate on the percentage removal
efficiency of CO2
Figure 3 represents the percentage removal efficiency of CO2 at
different inlet CO2 loadings and at different gas flow rates. It
may be seen from the figure that increasing the inlet CO2 loading decreases the removal efficiency of CO2 at a particular solid
velocity and weir height. The maximum removal efficiency of
carbon dioxide for inlet concentration 3000 ppm was 75.8% at
50 mm weir height with solid flow rate 2.15 kg/h. The minimum removal efficiency of carbon dioxide for inlet concentration 20000 ppm was 70.9% at 50 mm weir height under the
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH, PART A
773
found to be 74.4% at 20000 ppm. While increasing the velocity
of gas, the percentage removal of carbon dioxide also decreases
since solids held up in the bed decreased thereby decreasing the
probability of diffusion of gas to DEA impregnated activated
carbon particles. Similar observation has been reported by
Mohanty et al.[21] and Roy et al.[23] The reason for such
decreasing trend may be due to an increase in concentration on
the surface of activated carbon particle and formation of monolayer which results in decrease of the sorbent activity.
Effect of solid flow rate on the percentage removal
efficiency of CO2
Figure 3. Effect of gas velocity on CO2 removal efficiency at hw D 50 mm and Sa
D 2.15 kg/h at Ug D 0.188 and 0.353 m/s.
same other operating conditions. From Figure 4 it can be
observed that at 4.12 kg/h and for inlet concentration
3000 ppm the maximum removal efficiency of carbon dioxide
was 80.3% and the minimum removal efficiency of CO2 was
Figure 4. Effect of gas velocity on CO2 removal efficiency at hw D 50 mm and
Sa D 4.12 kg/h at Ug D 0.188 and 0.353 m/s.
Figure 5 describes the effect of the percentage removal efficiency of CO2 at different inlet CO2 loadings and at different
solid flow rates on the percentage removal efficiency of CO2 at
50 mm weir height and particular gas flow rate (0.188 m/s). It
can be seen that increase in flow rate of solids increases carbon
dioxide removal efficiency. A similar tendency of increasing
removal efficiency CO2 is also reported by Mohanty et al.[20]
and Roy et al.[23]
At 50 mm weir height and gas velocity of 0.188 m/s the maximum removal efficiency was 80% for inlet concentration of
3000 ppm. The minimum removal efficiencies were 72.5% for
inlet concentration of 20000 ppm. From Figure 6 it can be seen
that, at gas velocity 0.353 m/s and at 50 mm weir height, the
maximum removal efficiency was 78.1% for inlet concentration
of 3000 ppm. The minimum removal efficiency was 70.9% for
inlet concentration of 20000 ppm. It can be seen that increasing
the flow rate of solids increases carbon dioxide removal efficiency. The results indicate that as the solid flow rate increases,
Figure 5. Effect of solid flow rate on CO2 removal efficiency at hw D 50 mm and
Ug D 0.188 m/s at Sa D 2.15 and 4.12 m/s.
774
D. DAS ET AL.
Figure 6. Effect of solid flow rate on CO2 removal efficiency at hw D 50 mm and
Ug D 0.353 m/s at Sa D 2.15 and 4.12 m/s.
the solid hold in each stage increases. These increases in holdup of solids augment to adsorb more quantity of CO2 on DEA
impregnated activated carbon particle.
Figure 8. Effect of weir height on CO2 removal efficiency at Sa D 4.12 kg/h and
Ug D 0.188 m/s at hw D 30 and 50 mm.
Effect of weir height on the percentage removal efficiency
of CO2
Figures 7 and 8 represent the effect of inlet CO2 concentration on
the percentage removal efficiency of CO2 at different weir heights.
It can be seen from these figures that the percentage removal of
CO2 at the higher weir height was maximum as the solid reactants
available was maximum. At 50 mm weir height, solid flow rate of
2.15 kg/h, and the gas velocity 0.353 m/s the highest removal efficiency was 74.2% for 3000 ppm inlet CO2 concentration and
66.5% for 20000 ppm inlet concentration. At solid flow rate of
4.12 kg/h and the gas velocity 0.188 m/s the range of removal efficiencies was 79.6% for 3000 ppm inlet CO2 concentration and
72.3% for 20000 ppm inlet concentration. As observed, increasing
the weir height increased the removal efficiency due to increase in
bed volume resulting in more gas-solid interaction. However, the
effect of weir height at lower concentration was not as much as
observed at higher concentration indicating the presence of less
quantity of reactive solids at lower height.
Reaction mechanism for secondary amine
Zwitterion mechanism
Zwitterion mechanism was originally proposed by Caplow [26]
and reintroduced by Danckwerts.[27] It consists of a two-step
mechanism, that is the reaction between CO2 and the amine
proceeds through the formation of an intermediate called zwitterion and the deprotonation of the zwitterion by a base B.
CO2 C R1 R2 NH $ R1 R2 NH C COO ¡
Figure 7. Effect of weir height on CO2 removal efficiency at Sa D 2.15 kg/h and Ug
D 0.353 m/s at hw D 30 and 50 mm.
R1 R2 NH C COO ¡ C B $ R1 R2 NCOO ¡ C BH C
where R1, R2 are alkyl groups.
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH, PART A
The actual reaction is shown for DEA in presence of solvent
water:
OH ¡ CH2 ¡ CH2 ¡ NH ¡ CH2 ¡ CH2 ¡ OH C CO2
$ OH ¡ CH2 ¡ CH2 ¡ NH C ¡ COO ¡ ¡ CH2 ¡ CH2 ¡ OH
(2 carbamate i.e. zwitterion)
OH ¡ CH2 ¡ CH2 ¡ NH C ¡ COO ¡ ¡ CH2 ¡ CH2 ¡ OH
C OH ¡ $ OH ¡ CH2 ¡ CH2 ¡ N ¡ COO ¡
¡ CH2 ¡ CH2 ¡ OH C H2 O
The rate determining step is the 1st which results in the formation of a secondary carbamate ion for diethanol amine solution. The second step occurs rapidly in the presence of base. So
the tendency to adsorb more CO2 depends critically on the first
step. Thus more is the stability of carbamate ion formed more
is the forward side reaction and hence adsorption. Due to this
chemistry, DEA based adsorption has the ability to adsorb
more CO2 compared to non-impregnated activated carbon.
Conclusion
In this study, a four-stage fluidized bed reactor has been used
for removal of CO2 using a DEA impregnated activated carbon
prepared from green coconut shell. The maximum removal
efficiency of CO2 was 80% under low gas flow rate (0.188 m/s)
and high solid flow rate (4.12 kg/h) and large weir height of
50 mm. The DEA impregnated adsorbents trap CO2 in two
ways i.e. chemical reaction and surface porosity. The chemical
reaction occurs due to base-acid interaction of amine group
with carbon dioxide gas resulting in formation of secondary
zwitterion and thus the removal efficiency capacity of DEA
impregnated adsorbent carbon increases manifold compared to
plain activated carbon.
Funding
This work was supported by the Chemical Engineering Department,
Indian Institute of Technology, Kharagpur.
References
[1] Canadell, J.G.; Le Quere C.; Raupach M.R.; Field C.B.; Buitenhuis E.
T.; Ciais P.; Marland G. Contributions to accelerating atmospheric
CO2 growth from economic activity, carbon intensity, and efficiency
of natural sinks. Proc. Natl. Acad. Sci. 2007, 104, 18866–18870.
[2] Yu K.M.K.; Curcic I.; Gabriel J.; Tsang SCE. Recent advances in CO2
capture and utilization. Chem. Sus. Chem. 2008, 1, 893–899.
[3] Pevida C.; Plaza M.G.; Arias B.; Fermoso J.; Rubiera F.; Pis JJ. Surface
modification of activated carbons for CO2 capture. Appl. Surf. Sci.
2008, 254, 7165–7172.
[4] Plaza M.G.; Pevida C.; Arias B.; Fermoso J.; Rubiera F.; Pis JJ. A comparison of two methods for producing CO2 capturesadsorbents.
Energy Procedia. 2009, 1, 1107–1113.
[5] Plaza M.G.; Garcia S.; Rubiera F.; Pis J.J.; Pevida C. Post-combustion
CO2 capture with a commercial activated carbon: comparison of different regeneration strategies. Chem. Eng. J. 2010, 163, 41–47.
[6] Krooss B.M.; Van Bergen F.; Gensterblum Y.; Siemons N.; Pagnier
HJM.; David P. High-pressure methane and carbon dioxide adsorption on dry and moisture-equilibrated Pennsylvanian coals. Int. J.
Coal Geology. 2002, 51, 69–92.
775
[7] Mazumder S.; Van Hemert P.; Busch A.; Wolf K.A.; Tejera-Cuesta P.
Flue gas and pure CO2 sorption properties of coal: a comparative
study. Int. J. Coal Geology. 2006, 67, 267–279.
[8] Saghafi A.; Faiz M.; Roberts D. CO2 storage and gas diffusivity properties of coals from Sydney Basin, Australia. Int. J. Coal Geology.
2007, 70, 240–254.
[9] Manovic V.; Anthony E. Sequential SO2/CO2 capture enhanced by
steam reactivation of a CaO-based sorbent. Fuel. 2008, 87, 1564–
1573.
[10] Nikulshina V.; Gebald C.; Steinfeld A. CO2 capture from atmospheric air via consecutive CaO-carbonation and CaCO3-calcination cycles in a fluidized-bed solar reactor. Chem. Eng. J. 2009,
146, 244–248.
[11] Salvador C.; Lu D.; Anthony E.J.; Abandes JC. Enhancement of CaO
for CO2 capture in an FBC environment. Chem. Eng. J. 2003, 96,
187–195.
[12] Seo Y.; Jo S.H.; Ryu C.K.; Yi CK. Effects of water vapor pretreatment
time and reaction temperature on CO2 capture characteristics of a
sodium-based solid sorbent in a bubbling fluidized-bed reactor. Chemosphere. 2007, 69, 712–718.
[13] Yi C.K.; Jo S.H.; Seo Y.; Lee J.B.; Ryu CK. Continuous operation of
the potassium-based dry sorbent CO2 capture process with two fluidized-bed reactors. Int. J. Greenhouse Gas Control. 2007, 1, 31–36.
[14] Schlapbach L.; Z€
uttel A. Hydrogen-storage materials for mobile
applications. Nature. 2001, 414, 353–358.
[15] Park S.J.; Kim KD. Adsorption behaviors of CO2 and NH3 on chemically surface-treated activated carbons. J. Colloid Interface Sci. 1999,
212, 186–189.
[16] Park S.J.; Kim YM. Influence of anodic treatment on heavy metal ion
removal by activated carbon fibers. J. Colloid Interface Sci. 2004,
278, 276–281.
[17] Meng L.; Cho K.S.; Park SJ. CO2 adsorption of amine functionalized
activated carbons. Carbon letters. 2009, 10, 221–224.
[18] Raymundo-Pinero E.; Cazorla-Amoros D.; Linares-Solano A.;
Find J.; Wild U.; Schl€
ogl R. Structural characterization of N-containing activated carbon fibers prepared from a low softening
point petroleum pitch and a melamine resin. Carbon. 2002, 40,
597–608.
[19] Veawab A.; Tontiwachwuthikul P.; Chakma A. Corrosion behavior
of carbon steel in the CO2 absorption process using aqueous amine
solutions. Ind. Eng. Chem. Res. 1999, 38, 3917–3924.
[20] Mohanty C.R.; Mallavia G.; Meikap BC. Development of a countercurrent multi-stage fluidized bed reactor and mathematical modeling
for prediction of removal efficiency of sulfur dioxide from flue gases.
Ind. Eng. Chem. Res. 2009, 48, 1629–1637.
[21] Mohanty C.R.; Sivaji S.; Meikap BC. Hydrodynamics of a multistage countercurrent fluidized bed reactor with downcomer for
lime-dolomitemixed particle system. Ind. Eng. Chem. Res. 2008,
47, 6917.
[22] Mohanty C.R.; Rajmohan B.; Meikap BC. Identification of stable
operating ranges of a counter-current multistage fluidized bed reactor with downcomer. Chem. Eng. Process: Process Intensification.
2010, 49, 104–112.
[23] Roy S.; Mohanty C.R.; Meikap BC. Multistage fluidized bed reactor
performance characterization for adsorption of carbon dioxide. Ind.
Eng. Chem. Res. 2009, 48, 10718–10727.
[24] Auta M.; Umaru M.; Yahya M.D.; Adeniyi O.D.; Aris I.M.; Suleiman
B. Diethanolamine Functionalized Waste Tea Activated Carbon for
CO2 Adsorption. International Conference on Chemical, Environmental and Biological Sciences (CEBS-2015), Dubai (UAE), March
18–19, 2015; 18–19.
[25] Auta M.; Hameed BH. Adsorption of carbon dioxide by diethanolamine activated alumina beads in a fixed bed. Chem. Eng. J. 2014,
253, 350–355.
[26] Caplow M. Kinetics of carbamate formation and breakdown. J. Am.
Chem. Soc. 1968, 90, 6795–6803.
[27] Danckwerts PV. The reaction of CO2 with ethanolamines. Chem.
Eng. Sci. 1979, 34, 443–446.