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ScienceDirect
Energy Procedia 00 (2017) 000–000
www.elsevier.com/locate/procedia
1876-6102 © 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the Scientific Committee of
The 15th International Symposium on District Heating and
Cooling.
Cooling
Assessing the feasibility of using the heat demand-outdoor
temperature function for a long-term district heat demand
forecast
I. Andrića,b,c*, A. Pinaa, P. Ferrãoa, J. Fournierb., B.
Lacarrièrec, O. Le Correc
aIN+ Center for Innovation, Technology and Policy Research -
Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001
Lisbon, Portugal
bVeolia Recherche & Innovation, 291 Avenue Dreyfous Daniel,
78520 Limay, France
cDépartement Systèmes Énergétiques et Environnement - IMT

Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France
Abstract
District heating networks are commonly addressed in the
literature as one of the most effective solutions for decreasing
the
greenhouse gas emissions from the building sector. These
systems require high investments which are returned through the
heat
sales. Due to the changed climate conditions and building
renovation policies, heat demand in the future could decrease,
prolonging the investment return period.
The main scope of this paper is to assess the feasibility of using
the heat demand – outdoor temperature function for heat
demand
forecast. The district of Alvalade, located in Lisbon (Portugal),
was used as a case study. The district is consisted of 665
buildings that vary in both construction period and typology.
Three weather scenarios (low, medium, high) and three district
renovation scenarios were developed (shallow, intermediate,
deep). To estimate the error, obtained heat demand values were
compared with results from a dynamic heat demand model,
previously developed and validated by the authors.
The results showed that when only weather change is
considered, the margin of error could be acceptable for some
applications
(the error in annual demand was lower than 20% for all weather
scenarios considered). However, after introducing renovation
scenarios, the error value increased up to 59.5% (depending on
the weather and renovation scenarios combination considered).
The value of slope coefficient increased on average within the
range of 3.8% up to 8% per decade, that corresponds to the
decrease in the number of heating hours of 22-139h during the
heating season (depending on the combination of weather and
renovation scenarios considered). On the other hand, function

intercept increased for 7.8-12.7% per decade (depending on the
coupled scenarios). The values suggested could be used to
modify the function parameters for the scenarios considered,
and
improve the accuracy of heat demand estimations.
© 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the Scientific Committee of
Cooling.
Keywords: Heat demand; Forecast; Climate change
Peer-review under responsibility of the scientific committee of
the 2017 International Conference on Alternative Energy in
Developing Countries and Emerging Economies.
10.1016/j.egypro.2017.10.238
10.1016/j.egypro.2017.10.238 1876-6102
Peer-review under responsibility of the scientific committee of
the 2017 International Conference on Alternative Energy in
Developing Countries and Emerging Economies.
Available online at www.sciencedirect.com
ScienceDirect

Peer-review under responsibility of the Organizing Committee
of 2017 AEDCEE.
2017 International Conference on Alternative Energy in
Developing Countries and Emerging Economies
2017 AEDCEE, 25‐26 May 2017, Bangkok, Thailand
Computational Fluid Dynamics Model of CO2 Capture in
Fluidized Bed Reactors: Operating Parameter Optimization
Chattan Sakaunnapaporna, Pornpote Piumsomboona,b, Benjapon
Chalermsinsuwana,b,*
aFuels Research Center, Department of Chemical Technology,
Faculty of Science, Chulalongkorn University,
254 Phayathai Road, Pathumwan, Bangkok 10330, Thailand
bCenter of Excellence on Petrochemical and Materials
Technology, Chulalongkorn University,
Abstract
Alternative energy is one of the methods for decreasing fossil
fuel consumption. However, conventional fossil fuel process
improvement is also considerably interesting issue due to the
fact that adjusting existing process is easier and cheaper
comparing
to the development of the process compatible with the
alternative energy. At present, the global warming and climate
change
phenomenon cause the increasing of average earth temperature.
The CO2 emission to the atmosphere is mainly produced by
fossil

fuel combustion from power industry. This is because the CO2
has high heat capacity. Therefore, in order to use the
conventional
fossil fuel process efficiently, CO2 should be eliminated from
the flue gas before releasing it to the environment. Currently,
there
are many methods that use to capture CO2 such as using
circulating fluidized bed riser with solid sorbent. The
advantages of
circulating fluidized bed riser are uniform solid particle and
temperature distributions, high contacting area between gas-
solid
particle and suitable for continuous operation. In this study, the
effect of operating parameters on CO2 capture in circulating
fluidized bed riser with solid sorbent is investigated using 2D
computational fluid dynamics model. The basic simulation step
has
to find the suitable computational mesh cells or grid
independency test (5,000, 10,000, 15,000 and 20,000 cells) and
compare the
simulation result with the real experimental result. According to
the simulation results, the suitable mesh cell is 10,000 cells and
the obtained result is matched with the experimental results.
Then, the effect of operating parameters on the CO2 capture
conversion is optimized.
of 2017 AEDCEE.
Keywords: Circulating fluidized bed reactor, CO2 capture;
Computational fluid dynamics,Optimization; 2k factorial
design.

* Corresponding author. Tel.: +662-218-7682; fax: +662-255-
5831.
E-mail address: [email protected]
ScienceDirect
of 2017 AEDCEE.
Abstract

comparing
change
fossil
conventional
there
advantages of
solid
has
compare the

of 2017 AEDCEE.
design.
5831.
2 Author name / Energy Procedia 00 (2017) 000–000
Nomenclature
k number of considered parameter
1. Introduction
Nowadays, the emission of carbon dioxide (CO2) from chemical
industry is a major cause of the global warming
because CO2 can absorb and maintain the heat which then has
an impact on climate change. Currently, alternative
energy is one of the methods for decreasing fossil fuel
consumption such as solar energy and wind energy. It can
decrease air pollution which is primary cause of the global
warming, but the investment of equipment in building
alternative energy plant is very expensive. Thus, conventional
fossil fuel process improvement is also considerably
interesting issue due to the fact that adjusting existing process
is easier and cheaper comparing to the development

of the process compatible with the alternative energy. There are
many methods that use to capture CO2 such as using
circulating fluidized bed riser with alkali-based solid sorbent.
Alkali metal carbonates such as Na2CO3 and K2CO3
react with CO2 and H2O and transform to alkali metal hydrogen
carbonates after CO2 adsorption [1]. In fluidized bed
reactor, the solid flow pattern is important quantitatively due to
difference solid flow pattern will affect the rate heat
and mass transfers.
There are many researches that study the effect of operating
parameter on CO2 adsorption in circulating fluidized
bed riser. Wang et al. [2] researched about CO2 capture using
potassium-based sorbents in circulating fluidized bed
reactor at different inlet gas velocities using simulation method
by considering effect of particle clusters. According
to their results, the simulation with particle cluster effect
predicted the system hydrodynamics similar to the
experimental result more than the simulation without particle
cluster effect. Yi et al. [3] studied the effect of
operating parameters, gas inlet velocity, solid circulation rate
and water content in feed gas, on CO2 removal
percentage in circulating fluidized bed reactor by using K2CO3
solid sorbent. As a result, the increase of the overall
CO2 removal is owing to the increasing solid circulation rate
and water vapor content and the decreasing gas
velocity. Zhao et al. [4] studied the effect of amount of K2CO3
on CO2 sorption capacity. The CO2 sorption capacity
increased when increasing the amount of K2CO3. Yafei et al.
[5] investigated the CO2 capture performance of some
wood materials by using fluidized bed reactor. The component
of employed wood materials was investigated by
XRD which showed high K2CO3 component. According the
results, the CO2 capture capacity increased when the
reaction temperature decreased (60 to 100oC) and mole ratio
between water and CO2 increased. Apart from the

experimental method, the simulation method was used to study
the CO2 capture processes. Emadoddin et al. [6]
simulated CO2 sorption in circulating fluidized bed using
deactivation kinetic model and compared the results with
experimental information and other chemical reaction models.
According the results, differential pressure from
simulation result was similar to experimental result [3]. In
addition, the deactivation kinetic reaction model
predicted the CO2 removal percentage accurately more than the
other chemical reaction model. However, the
systematically study of the effect of operating parameters on the
CO2 removal percentage is still lacking in the
literature. Most of the studies were considered the experiment
using one factor at a time methodology. With this
methodology, the interaction effect between operating
parameters cannot be obtained.
The main objective in this study is therefore to investigate the
effect of the different inlet gas velocities and the
solid circulation rate on the CO2 conversion using two-
dimensional computational fluid dynamics model. The
numerical model is comparing its correctness with the literature
experimental data by Yi et al. [3]. In this study, the
response surface via 2k factorial statistical experimental design
(with literature base case condition) was found for
determining the operating parameter optimization on the CO2
conversion in circulating fluidized bed reactor.
2. Methodology
2.1 Computational model
In this study, the circulating fluidized bed riser was constructed
by using computer–aided design program,
DESIGN MODULER and was simulated by using computational
fluid dynamics simulation program, ANSYS

FLUENT. The model in two-dimensional Cartesian coordinate
system which consisting of 5,000, 10,000, 15,000,
20,000 mesh cells and 80 s flow time was used. The gas and
solid particles entered to the circulating fluidized bed
http://crossmark.crossref.org/dialog/?doi=10.1016/j.egypro.201
7.10.238&domain=pdf
Chattan Sakaunnapaporn et al. / Energy Procedia 138 (2017)
518–523 519
ScienceDirect
of 2017 AEDCEE.

Abstract
comparing
change
fossil
conventional
there
advantages of
solid

has
compare the
of 2017 AEDCEE.
design.
5831.
ScienceDirect
of 2017 AEDCEE.

Abstract
comparing
change
fossil
conventional

there
advantages of
solid
has
compare the
of 2017 AEDCEE.
design.
5831.

Nomenclature
k number of considered parameter
1. Introduction
Nowadays, the emission of carbon dioxide (CO2) from chemical
industry is a major cause of the global warming
because CO2 can absorb and maintain the heat which then has
an impact on climate change. Currently, alternative
energy is one of the methods for decreasing fossil fuel
consumption such as solar energy and wind energy. It can
decrease air pollution which is primary cause of the global
warming, but the investment of equipment in building
alternative energy plant is very expensive. Thus, conventional
fossil fuel process improvement is also considerably
interesting issue due to the fact that adjusting existing process
is easier and cheaper comparing to the development
of the process compatible with the alternative energy. There are
many methods that use to capture CO2 such as using
circulating fluidized bed riser with alkali-based solid sorbent.
Alkali metal carbonates such as Na2CO3 and K2CO3
react with CO2 and H2O and transform to alkali metal hydrogen
carbonates after CO2 adsorption [1]. In fluidized bed
reactor, the solid flow pattern is important quantitatively due to
difference solid flow pattern will affect the rate heat
and mass transfers.
There are many researches that study the effect of operating
parameter on CO2 adsorption in circulating fluidized
bed riser. Wang et al. [2] researched about CO2 capture using
potassium-based sorbents in circulating fluidized bed
reactor at different inlet gas velocities using simulation method
by considering effect of particle clusters. According

to their results, the simulation with particle cluster effect
predicted the system hydrodynamics similar to the
experimental result more than the simulation without particle
cluster effect. Yi et al. [3] studied the effect of
operating parameters, gas inlet velocity, solid circulation rate
and water content in feed gas, on CO2 removal
percentage in circulating fluidized bed reactor by using K2CO3
solid sorbent. As a result, the increase of the overall
CO2 removal is owing to the increasing solid circulation rate
and water vapor content and the decreasing gas
velocity. Zhao et al. [4] studied the effect of amount of K2CO3
on CO2 sorption capacity. The CO2 sorption capacity
increased when increasing the amount of K2CO3. Yafei et al.
[5] investigated the CO2 capture performance of some
wood materials by using fluidized bed reactor. The component
of employed wood materials was investigated by
XRD which showed high K2CO3 component. According the
results, the CO2 capture capacity increased when the
reaction temperature decreased (60 to 100oC) and mole ratio
between water and CO2 increased. Apart from the
experimental method, the simulation method was used to study
the CO2 capture processes. Emadoddin et al. [6]
simulated CO2 sorption in circulating fluidized bed using
deactivation kinetic model and compared the results with
experimental information and other chemical reaction models.
According the results, differential pressure from
simulation result was similar to experimental result [3]. In
addition, the deactivation kinetic reaction model
predicted the CO2 removal percentage accurately more than the
other chemical reaction model. However, the
systematically study of the effect of operating parameters on the
CO2 removal percentage is still lacking in the
literature. Most of the studies were considered the experiment
using one factor at a time methodology. With this
methodology, the interaction effect between operating
parameters cannot be obtained.

The main objective in this study is therefore to investigate the
effect of the different inlet gas velocities and the
solid circulation rate on the CO2 conversion using two-
dimensional computational fluid dynamics model. The
numerical model is comparing its correctness with the literature
experimental data by Yi et al. [3]. In this study, the
response surface via 2k factorial statistical experimental design
(with literature base case condition) was found for
determining the operating parameter optimization on the CO2
conversion in circulating fluidized bed reactor.
2. Methodology
2.1 Computational model
In this study, the circulating fluidized bed riser was constructed
by using computer–aided design program,
DESIGN MODULER and was simulated by using computational
fluid dynamics simulation program, ANSYS
FLUENT. The model in two-dimensional Cartesian coordinate
system which consisting of 5,000, 10,000, 15,000,
20,000 mesh cells and 80 s flow time was used. The gas and
solid particles entered to the circulating fluidized bed
520 Chattan Sakaunnapaporn et al. / Energy Procedia 138
(2017) 518–523
Author name / Energy Procedia 00 (2017) 000–000 3
riser and entrained out the circulating fluidized bed riser at the
bottom and top sections, respectively. The simplified
schematic drawing of the circulating fluidized bed riser is
shown in Fig. 1. The mixing zone was set about 0.6 m
height and the fast fluidization zone was set about 5.6 m height.

Fig. 1. The simplified schematic drawing of the circulating
fluidized bed riser.
2.2 Mathematical model
The mathematical model that used in this study consisted of
four conservation equations, which were mass,
momentum, energy and fluctuating kinetic energy (granular
temperature) conservation equations, and other related
constitutive equations similar to the ones formulated by
Chalermsinsuwan et al. [7]. For the constitutive equations,
the kinetic theory of granular flow concept was used to explain
the solid particle flow behaviour. In this study, three
reaction kinetic models for simulation the CO2 adsorption that
were the Homogenous model [8], the Deactivation
model [9] and the Equilibrium model [10] were simulated and
compared the result with experimental information by
Yi et al. [3].
2.3 Boundary and initial conditions
In this study, the gas phase consisted of CO2, H2O and N2 that
had mass fraction of 0.10, 0.15 and 0.75,
respectively. The solid particles were potassium carbonate
(K2CO3) particles, with average diameter of 98 microns
and bulk density of 1,100 kg/m3. For the boundary condition,
no slip condition was used for gas phase at the wall
and partial slip condition was used for solid particle phase. For
the initial conditions, there were no gas and solid
phases in the circulating fluidized bed riser. The operating
gravitational force was –9.81 m/s2 in y direction and the
operating pressure was set equal to 101,325 Pa. To analyse the

system hydrodynamics and the CO2 conversion, the
2k factorial statistical experimental design (with literature base
case condition) was used to determine the effect of
the inlet gas velocity and the solid circulation rate on the CO2
conversion as summarized in Table 1.
Table1. The statistical experimental design cases.
Case Inlet gas velocity (m/s) Solid circulation rate (kg/m2s)
CO2 removal percentage (-)
0 (base case) 1 21 58.46
1 1 10 32.35
2 1 30 70.38
3 3 10 0.65
4 3 30 4.23
3. Results and discussion
3.1 Grid independency test and experimental validation
The grid independency test and the comparison of the
simulation result with literature experimental results are
important steps for performing computational fluid dynamics
simulation. This study results were averaged after the
system reached quasi steady state condition (simulation time of
60-80 s). Fig.2 (a) shows the differential pressure at
four elevation heights (at elevation heights of 0.52 m, 2.27 m,

4.07 m, 5.87 m, respectively) comparing between
simulation result and the experimental result. It was found that
simulated differential pressure results were consistent
with the experimental result. The selected suitable mesh cell
should be the lowest mesh cells for saving time but still
could predict the obtained result accurately. Fig.2 (b) illustrates
the averaged CO2 mass fraction with different mesh
cells and chemical reaction kinetic models. As a result, the
suitable mesh cells was 10,000 cells because the
predicted average CO2 mass fraction was similar to the ones
with 15,000 and 20,000 cells and similar to
experimental result of Yi et al. [3] with the outlet CO2 mass
fraction of 0.042. All the reaction kinetic model,
homogenous model, deactivation model and equilibrium model,
was well predicted the CO2 capture process in
circulating fluidized bed riser. However, due to the
experimental data comparison and the easier of the
methodology, the homogeneous model was then used in the
subsequence simulation. From the validation of the
results, this confirms the correctness of the employed
computational fluid dynamics model.
(a) (b)
Fig. 2. (a) Differential pressure at differential elevation heights
and (b) averaged CO2 mass fraction at different riser heights.
3.2 Solid volume fraction and CO2 mass fraction
The interaction between solid particle phase and gas phase in
circulating fluidized bed riser has an important effect
on the CO2 removal percentage inside the system. This is
because the K2CO3 captures CO2 with the chemical
reaction:

Therefore, the contacting between solid particle phase and gas
phase is crucial for occurring the adsorption. The contour of
solid volume fraction for base case operating condition,
inlet gas velocity of 1 m/s and solid circulation rate of 21
kg/m2s, is shown in Fig. 3 (a). The color scale bar
represents the quantity of the solid volume fraction which red
color is highest value and blue color is lowest value.
According to the results, the mixing zone had higher solid
volume fraction than the fast fluidization zone because
the mixing zone had larger system diameter. The large area will
have an effect on the reduction of gas and solid
particle velocities. In addition, the solid particle moved down to
the mixing zone by the energy loss from wall effect.
These obtained phenomena are consistent with the results in
Fig. 3(b). Fig. 3(b) depicts the contour of CO2 mass
fraction for base case operating condition. The meaning of color
scale bar is similar to the ones for solid volume
fraction. The CO2 mass fraction was high and low at the bottom
zone and top zone, respectively, because the CO2
reacted with K2CO3.
518–523 521
Author name / Energy Procedia 00 (2017) 000–000 3
riser and entrained out the circulating fluidized bed riser at the
bottom and top sections, respectively. The simplified
schematic drawing of the circulating fluidized bed riser is
shown in Fig. 1. The mixing zone was set about 0.6 m
height and the fast fluidization zone was set about 5.6 m height.
Fig. 1. The simplified schematic drawing of the circulating

2.2 Mathematical model
The mathematical model that used in this study consisted of
four conservation equations, which were mass,
momentum, energy and fluctuating kinetic energy (granular
temperature) conservation equations, and other related
constitutive equations similar to the ones formulated by
Chalermsinsuwan et al. [7]. For the constitutive equations,
the kinetic theory of granular flow concept was used to explain
the solid particle flow behaviour. In this study, three
reaction kinetic models for simulation the CO2 adsorption that
were the Homogenous model [8], the Deactivation
model [9] and the Equilibrium model [10] were simulated and
compared the result with experimental information by
Yi et al. [3].
2.3 Boundary and initial conditions
In this study, the gas phase consisted of CO2, H2O and N2 that
had mass fraction of 0.10, 0.15 and 0.75,
respectively. The solid particles were potassium carbonate
(K2CO3) particles, with average diameter of 98 microns
and bulk density of 1,100 kg/m3. For the boundary condition,
no slip condition was used for gas phase at the wall
and partial slip condition was used for solid particle phase. For
the initial conditions, there were no gas and solid
phases in the circulating fluidized bed riser. The operating
gravitational force was –9.81 m/s2 in y direction and the
operating pressure was set equal to 101,325 Pa. To analyse the
system hydrodynamics and the CO2 conversion, the
2k factorial statistical experimental design (with literature base
case condition) was used to determine the effect of
the inlet gas velocity and the solid circulation rate on the CO2

conversion as summarized in Table 1.
Table1. The statistical experimental design cases.
Case Inlet gas velocity (m/s) Solid circulation rate (kg/m2s)
CO2 removal percentage (-)
0 (base case) 1 21 58.46
1 1 10 32.35
2 1 30 70.38
3 3 10 0.65
4 3 30 4.23
3. Results and discussion
3.1 Grid independency test and experimental validation
The grid independency test and the comparison of the
simulation result with literature experimental results are
important steps for performing computational fluid dynamics
simulation. This study results were averaged after the
system reached quasi steady state condition (simulation time of
60-80 s). Fig.2 (a) shows the differential pressure at
four elevation heights (at elevation heights of 0.52 m, 2.27 m,
4.07 m, 5.87 m, respectively) comparing between
simulation result and the experimental result. It was found that
simulated differential pressure results were consistent
with the experimental result. The selected suitable mesh cell

should be the lowest mesh cells for saving time but still
could predict the obtained result accurately. Fig.2 (b) illustrates
the averaged CO2 mass fraction with different mesh
cells and chemical reaction kinetic models. As a result, the
suitable mesh cells was 10,000 cells because the
predicted average CO2 mass fraction was similar to the ones
with 15,000 and 20,000 cells and similar to
experimental result of Yi et al. [3] with the outlet CO2 mass
fraction of 0.042. All the reaction kinetic model,
homogenous model, deactivation model and equilibrium model,
was well predicted the CO2 capture process in
circulating fluidized bed riser. However, due to the
experimental data comparison and the easier of the
methodology, the homogeneous model was then used in the
subsequence simulation. From the validation of the
results, this confirms the correctness of the employed
computational fluid dynamics model.
(a) (b)
Fig. 2. (a) Differential pressure at differential elevation heights
and (b) averaged CO2 mass fraction at different riser heights.
3.2 Solid volume fraction and CO2 mass fraction
The interaction between solid particle phase and gas phase in
circulating fluidized bed riser has an important effect
on the CO2 removal percentage inside the system. This is
because the K2CO3 captures CO2 with the chemical
Therefore, the contacting between solid particle phase and gas
phase is crucial for occurring the adsorption. The contour of
solid volume fraction for base case operating condition,
inlet gas velocity of 1 m/s and solid circulation rate of 21

kg/m2s, is shown in Fig. 3 (a). The color scale bar
represents the quantity of the solid volume fraction which red
color is highest value and blue color is lowest value.
According to the results, the mixing zone had higher solid
volume fraction than the fast fluidization zone because
the mixing zone had larger system diameter. The large area will
have an effect on the reduction of gas and solid
particle velocities. In addition, the solid particle moved down to
the mixing zone by the energy loss from wall effect.
These obtained phenomena are consistent with the results in
Fig. 3(b). Fig. 3(b) depicts the contour of CO2 mass
fraction for base case operating condition. The meaning of color
scale bar is similar to the ones for solid volume
fraction. The CO2 mass fraction was high and low at the bottom
zone and top zone, respectively, because the CO2
reacted with K2CO3.
522 Chattan Sakaunnapaporn et al. / Energy Procedia 138
(2017) 518–523 Author name / Energy Procedia 00 (2017) 000–
000 5
(a) (b)
Fig. 3. (a) Contour of solid volume fraction and (b) contour of
CO2 mass fraction (at three different quasi-steady state
simulation times).
3.3 Analysis of variance for the statistical experimental design
The 2k factorial statistical experimental design methodology
(with literature base case condition) is useful in
performing the experiment due to its many advantages. It gives

the smallest number of runs for k factors. However,
the full parameter analysis can still be obtained. With this
methodology, the two levels of each factor represent the
low and high values. In this study, the statistical experimental
design had the inlet gas velocity as a first factor and
solid circulation rate as a second factor. The response variable
was CO2 removal percentage at the outlet of
circulating fluidized bed riser. The analysis of variance result
for the statistical experimental design is summarized
in Table 2. The p–value was used for the statistical testing. If
the p–value is lower than 0.05, the factor significantly
affects the interested response. From the results, it can be
summarized that inlet gas velocity had significantly
affected on the CO2 removal percentage. In addition, it was
found that effect of the solid sorbent loading and the
interaction between inlet gas velocity and solid sorbent loading
did not have an effect on the CO2 conversion
significantly. Fig. 4 illustrates the main effect plot of the inlet
gas velocity and the solid circulation rate on the CO2
removal percentage. When increasing the inlet gas velocity and
the solid circulation rate, the CO2 removal
percentage was lower and higher, respectively. The high gas
velocity will decrease the system residence time and
reduce the contacting between gas and solid particles. The high
solid circulation rate will increase the quantity of
reactant material of the adsorption inside the circulating
Fig. 5 shows the response surface of CO2 removal percentage
with the changing of inlet gas velocity and the solid
circulation rate. The response surface can be used to choose the
operating condition with desired outcome or
response. For this circulating fluidized bed riser, the highest
CO2 removal percentage is preferred. Therefore, the
low inlet gas velocity and high solid circulation rate is needed
to operate the system to obtain the high CO2 removal

percentage.
Table 2. The analysis of variance result for the statistical
experimental design.
Source Sum of DF Mean F Prob > F
Squares Square Value
A 3076.67 1 3076.67 171.75 0.05
B 440.82 1 440.82 24.61 0.13
AB 303.33 1 303.33 16.93 0.15
Residual 17.91 1 17.91 Cor Total 3920.26 4
Fig. 4. This study main effect plot. Fig. 5. This
study response surface contour.
4. Conclusion
In this study, the computational fluid dynamics model which
had 10,000 mesh cells and three reaction kinetic
models was accurately used to predict CO2 removal percentage
and system hydrodynamics of circulating fluidized
bed riser comparing with the experimental results of Yi et al.
[3]. From the 2k factorial statistical experimental
design (with literature base case condition), the increasing of
inlet gas velocity and solid sorbent circulation rate
gave lower and higher CO2 removal percentage, respectively. In
addition, the analysis concluded the significant
effect of inlet gas velocity on the CO2 removal. The low inlet

gas velocity and high solid circulation rate is needed to
operate the system to obtain the high CO2 removal percentage.
Acknowledgements
This study was financially supported by the Scholarship from
the Graduate School, Chulalongkorn University to
commemorate the 72nd anniversary of his Majesty King
Bhumibol Aduladej, the 90th Anniversary of
Chulalongkorn University Fund, the Graduate School Thesis
Grant, the National Research Council of Thailand, the
Thailand Research Fund for fiscal year 2016–2019
(RSA5980052), and Ratchadapisek Sompoch Endowment Fund
(2016), Chulalongkorn University (CU-59-003-IC).
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[2] Wang S, Wang Q, Chen J, Liu G, Lu H, Sun L. Assessment
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[4] Zhao C, Chen X, Zhao C, Wu Y, Dong W. K2CO3/Al2O3
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Fuels 2012; 26:3062–3068.
[5] Yafei G, Chuanwen Z, Xiaoping C, Changhai L. CO2
capture and sorbent regeneration performances of some wood

ash materials. Appl Energ
2015; 137:26–36.
[6] Emadoddin A, Hamid A. CFD simulation of CO2 sorption in
a circulating fluidized bed using deactivation kinetic model.
10th International
Conference on Circulating Fluidized Beds and Fluidization
Technology - CFB-10, US, May 1 – May 5, 2011.
[7] Chalermsinsuwan B, Piumsomboon P, Gidaspow D. Kinetic
theory based computation of PSRI riser: Part I–Estimate of mass
transfer
coefficient. Chem Eng Sci 2009; 64:1195–1211.
[8] Garg R, Shahnam M, Huckaby ED. Continuum simulations
of CO2 capture by dry regenerable potassium based sorbents.
7th International
Conference on Multiphase Flow, ICMF 2010, US, May 30 –
June 4, 2010.
[9] Park SW, Sung DH, Choi BS, Lee JW, Kumazawa H.
Carbonation kinetics of potassium carbonate by carbon dioxide.
J Ind Eng Chem 2006;
4:522-530.
[10] Kongkitisupchai S, Gidaspow D. Carbon dioxide capture
using solid sorbents in a fluidized bed with reduced pressure
regeneration in a
downer. AIChE J 2013; 12:4519-4537.
518–523 523 Author name / Energy Procedia 00 (2017) 000–000
5
(a) (b)
Fig. 3. (a) Contour of solid volume fraction and (b) contour of

CO2 mass fraction (at three different quasi-steady state
simulation times).
3.3 Analysis of variance for the statistical experimental design
The 2k factorial statistical experimental design methodology
(with literature base case condition) is useful in
performing the experiment due to its many advantages. It gives
the smallest number of runs for k factors. However,
the full parameter analysis can still be obtained. With this
methodology, the two levels of each factor represent the
low and high values. In this study, the statistical experimental
design had the inlet gas velocity as a first factor and
solid circulation rate as a second factor. The response variable
was CO2 removal percentage at the outlet of
circulating fluidized bed riser. The analysis of variance result
for the statistical experimental design is summarized
in Table 2. The p–value was used for the statistical testing. If
the p–value is lower than 0.05, the factor significantly
affects the interested response. From the results, it can be
summarized that inlet gas velocity had significantly
affected on the CO2 removal percentage. In addition, it was
found that effect of the solid sorbent loading and the
interaction between inlet gas velocity and solid sorbent loading
did not have an effect on the CO2 conversion
significantly. Fig. 4 illustrates the main effect plot of the inlet
gas velocity and the solid circulation rate on the CO2
removal percentage. When increasing the inlet gas velocity and
the solid circulation rate, the CO2 removal
percentage was lower and higher, respectively. The high gas
velocity will decrease the system residence time and
reduce the contacting between gas and solid particles. The high
solid circulation rate will increase the quantity of
reactant material of the adsorption inside the circulating

Fig. 5 shows the response surface of CO2 removal percentage
with the changing of inlet gas velocity and the solid
circulation rate. The response surface can be used to choose the
operating condition with desired outcome or
response. For this circulating fluidized bed riser, the highest
CO2 removal percentage is preferred. Therefore, the
low inlet gas velocity and high solid circulation rate is needed
to operate the system to obtain the high CO2 removal
percentage.
Table 2. The analysis of variance result for the statistical
experimental design.
Source Sum of DF Mean F Prob > F
Squares Square Value
A 3076.67 1 3076.67 171.75 0.05
B 440.82 1 440.82 24.61 0.13
AB 303.33 1 303.33 16.93 0.15
Residual 17.91 1 17.91 Cor Total 3920.26 4
Fig. 4. This study main effect plot. Fig. 5. This
study response surface contour.
4. Conclusion
In this study, the computational fluid dynamics model which
had 10,000 mesh cells and three reaction kinetic
models was accurately used to predict CO2 removal percentage

and system hydrodynamics of circulating fluidized
bed riser comparing with the experimental results of Yi et al.
[3]. From the 2k factorial statistical experimental
design (with literature base case condition), the increasing of
inlet gas velocity and solid sorbent circulation rate
gave lower and higher CO2 removal percentage, respectively. In
addition, the analysis concluded the significant
effect of inlet gas velocity on the CO2 removal. The low inlet
gas velocity and high solid circulation rate is needed to
operate the system to obtain the high CO2 removal percentage.
Acknowledgements
This study was financially supported by the Scholarship from
the Graduate School, Chulalongkorn University to
commemorate the 72nd anniversary of his Majesty King
Bhumibol Aduladej, the 90th Anniversary of
Chulalongkorn University Fund, the Graduate School Thesis
Grant, the National Research Council of Thailand, the
Thailand Research Fund for fiscal year 2016–2019
(RSA5980052), and Ratchadapisek Sompoch Endowment Fund
(2016), Chulalongkorn University (CU-59-003-IC).
References
[1] Abanades JC, Antrony EJ, Wang, J, Oakey JE. Fluidized-bed
combustion system integration CO2 capture with CaO. Environ
Sci Technol
2005; 39:2861–2866.
[2] Wang S, Wang Q, Chen J, Liu G, Lu H, Sun L. Assessment
of CO2 capture using potassium-based sorbents in circulating
fluidized bed
reactor by multiscale modeling. Fuel 2016; 164:66–72.
[3] Yi CK, Jo SJ, Seo Y, Lee JB, 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.
[4] Zhao C, Chen X, Zhao C, Wu Y, Dong W. K2CO3/Al2O3
for capturing CO2 in flue gas from power plants. Part 3: CO2
capture behaviors of
K2CO3/Al2O3 in a bubbling fluidized-bed reactor. Energy
Fuels 2012; 26:3062–3068.
[5] Yafei G, Chuanwen Z, Xiaoping C, Changhai L. CO2
capture and sorbent regeneration performances of some wood
ash materials. Appl Energ
2015; 137:26–36.
[6] Emadoddin A, Hamid A. CFD simulation of CO2 sorption in
a circulating fluidized bed using deactivation kinetic model.
10th International
Conference on Circulating Fluidized Beds and Fluidization
Technology - CFB-10, US, May 1 – May 5, 2011.
[7] Chalermsinsuwan B, Piumsomboon P, Gidaspow D. Kinetic
theory based computation of PSRI riser: Part I–Estimate of mass
transfer
coefficient. Chem Eng Sci 2009; 64:1195–1211.
[8] Garg R, Shahnam M, Huckaby ED. Continuum simulations
of CO2 capture by dry regenerable potassium based sorbents.
7th International
Conference on Multiphase Flow, ICMF 2010, US, May 30 –
June 4, 2010.
[9] Park SW, Sung DH, Choi BS, Lee JW, Kumazawa H.
Carbonation kinetics of potassium carbonate by carbon dioxide.
J Ind Eng Chem 2006;
4:522-530.
[10] Kongkitisupchai S, Gidaspow D. Carbon dioxide capture
using solid sorbents in a fluidized bed with reduced pressure
regeneration in a
downer. AIChE J 2013; 12:4519-4537.
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