Mesbah, M., Jafari, M., Soroush, E., Shahsavari, S. (2017). Mathematical Modeling and Numerical Simulation of CO2 Removal by using hollow ﬁber membrane contactors. Iranian Journal of Oil & Gas Science and Technology, (), -. doi: 10.22050/ijogst.2017.48143

Mohammad Mesbah; Masumeh Jafari; Ebrahim Soroush; Shohreh Shahsavari. "Mathematical Modeling and Numerical Simulation of CO2 Removal by using hollow ﬁber membrane contactors". Iranian Journal of Oil & Gas Science and Technology, , , 2017, -. doi: 10.22050/ijogst.2017.48143

Mesbah, M., Jafari, M., Soroush, E., Shahsavari, S. (2017). 'Mathematical Modeling and Numerical Simulation of CO2 Removal by using hollow ﬁber membrane contactors', Iranian Journal of Oil & Gas Science and Technology, (), pp. -. doi: 10.22050/ijogst.2017.48143

Mesbah, M., Jafari, M., Soroush, E., Shahsavari, S. Mathematical Modeling and Numerical Simulation of CO2 Removal by using hollow ﬁber membrane contactors. Iranian Journal of Oil & Gas Science and Technology, 2017; (): -. doi: 10.22050/ijogst.2017.48143

Mathematical Modeling and Numerical Simulation of CO2 Removal by using hollow ﬁber membrane contactors

Articles in Press, Accepted Manuscript , Available Online from 01 April 2017

^{1}Young Researchers and Elites club, Science and Research Branch, Islamic Azad University, Tehran, Iran

^{2}Russ college of engineering & technology, Ohio university, Athens, OH

^{3}Young Researchers and Elite Club, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran

^{4}Department of Chemical Engineering, Sahand University of Technology, Tabriz, Iran

Receive Date: 09 July 2017,
Accept Date: 09 July 2017

Abstract

In this study, a mathematical model is proposed for CO_{2} separation from N_{2}/ CO_{2 }mixtureusing a hollow fiber membrane contactor, by various absorbents. The contactor assumed as non-wetted membrane; radial and axial diffusions were also considered in model development. The governing equations of the model are solved via the finite element method (FEM). To ensure the accuracy of the developed model, the simulation results were validated using the reported experimental data for potassium glycinate (PG), monoethanol amine (MEA) and methyldiethanol amine (MDEA). The results of the proposed model indicated that PG absorbent has the highest removal efficiency of CO_{2}, followed by potassium threonate (PT), MEA, Amino-2-methyl-1-propanol (AMP), diethanol amine (DEA) and MDEA in sequence. In addition, the results revealed that the CO_{2} removal efﬁciency was favored by absorbent ﬂow rate and liquid temperature, while the gas flow rate has the reverse effect. Simulation results proved that the hollow ﬁber membrane contactors have a good potential in the area of CO_{2 }capture.

It is well known that the emission of the greenhouse gases such as carbon dioxide (CO_{2}), which is accounted for about 80% of greenhouse gas emission, associated with global warming and climate change (Herzog, Eliasson et al. 2000). While there are veracious natural sources of CO_{2} emission, the emissions associated with human related activities are the main reason of carbon dioxide increase in the atmosphere in recent decades. The main human related CO_{2} emission is combustion of fossil fuels (oil, natural gas, and coal). However, 80% of the world’s total energy sources supply of fossil fuels (Wang, Li et al. 2004). In the other hand, concentrated CO_{2} is needed for some industrial applications such as enhanced oil recovery (Herzog 2001). Therefore, development of CO_{2 }capture methods is so attractive (Esmaili and Ehsani 2014, Rahmandoost, Roozbehani et al. 2014).

Recently many researchers have been studied CO_{2} capture from flue gas. Several factors such as different absorbents, gas, and liquid flow rate and membrane type have been investigated (Lee, Noble et al. 2001, Wang, Li et al. 2004, Ren, Wang et al. 2006, Atchariyawut, Jiraratananon et al. 2007, Lu, Zheng et al. 2007, Yan, Fang et al. 2007, Al-Marzouqi, Marzouk et al. 2009, Faiz and Al-Marzouqi 2009, Rezakazemi, Niazi et al. 2011). Wang et al. (Wang, Li et al. 2004) studied the effect of Amino-2-methyl-1-propanol (AMP), MDEA and DEA absorbents on CO_{2} Capture. Their simulations indicated that AMP and DEA have a higher removal efficiency than MDEA. Ren et al. (Ren, Wang et al. 2006) studied CO_{2} capture by poly vinylidene fluoride (PVDF) hollow fiber membranes. Lu et al. (Lu, Zheng et al. 2007) investigate the effect of AMP and piperazine (PZ) activators on CO_{2} removal. The results show that the mass-transfer ﬂuxes of activated solutions are much higher than that of the non-activated solution. Yan et al. (Yan, Fang et al. 2007) used MEA, MDEA and potassium glycinate (PG) as absorbents for CO_{2} capture from flue gas. Experiments were conducted in a polypropylene (PP) hollow fiber membrane contactors. They concluded that the PG absorbent is more suitable than MEA and MDEA because it has a lower potential of membrane wetting (which has a direct effect on removal efficiency) and higher reactivity toward CO_{2} compared to MEA and MDEA. Reza kazemi et al. (Rezakazemi, Niazi et al. 2011) studied experimentally and theoretically on simultaneous removal of CO_{2} and H_{2}S through a HFMC using MDEA as chemical absorbent. Their results indicated that MDEA is very efficient for H_{2}S removal.

In this study CO_{2 }absorption with different absorbents (MEA, MDEA, DEA, AMP, PG and potassium threonate (PT)) in the case of non-wetted HFMC is simulated. The proposed model is validated using experimental data. The effect of different factors, including gas velocity, absorbent temperature, absorbent concentration and hollow fiber membrane module’s specification for preferred absorbent were investigated using the proposed model.

2. The model development

A comprehensive 2D mathematical model has been developed for separation of CO_{2} from CO_{2}/N_{2 }mixture,through a hollow fiber membrane contactor, which included 7000 fibers. . Three different kinds of aqueous solutions were studied as an absorbent to compare capability of the solvent for CO_{2} removal. The model was proposed based on “non-wetted mode”. The schematic of the hollow fiber membrane used in the present work is shown in Fig1.

Figure 1: Schematics of hollow fiber membrane contractor.

One of the fibers in the membrane module, surrounded by a laminar gas flow has been simulated. The hollow fiber membrane consisted of three sections: (1) Tube side, (2) Membrane, (3) Shell side. The flue gas including a mixture of Nitrogen and Carbon dioxide is fed downward into the shell side at Z=L. On the tube side, the fully developed laminar flow solvent is fed upward at Z=0. The only portion of gas flow Carbon dioxide is removed from the gas mixture by diffusing through the membrane and then will be absorbed by solvent. Fig. 2 represents the cross sectional area of the hollow fiber membrane contractor. Based on Happel’s free surface model (Happel 1959), only a portion of fluid enveloping the fiber is considered and could be approximated as a circular cross section.

Figure 2: Cross sectional area of the hollow fiber membrane contractor.

The assumptions for model simulation can be summarized as below.

1- Steady-state and isothermal conditions.

2- Fully developed velocity profiles for the fluid through hollow fiber.

3- The gas mixture is considered ideal gas.

4- Non-wetted mode in which the gas mixture fills the membrane pores.

5- Henry’s law is applied for gas-liquid interface.

6- No homogenous reaction takes place at shell side

2.1. Mass transfer equations

2.1.1. Tube side

The steady state continuity equation for transport of CO_{2} in the tube side, consisting of Fick’s law to predict diffusion flux, can be written as below.

(1)

Where i refer to CO_{2} or absorbent and R_{i}is the reaction rate of component i. It is assumed that the velocity distribution in the tube side follows the Newtonian laminar flow (Bird, Stewart et al. 1960):

(2)

The boundary conditions on the tube side are considered as:

@ z=0 ,

(3)

i: solvent (MEA, DEA, AMP, MDEA, PG, PT)

@

(4)

@ (symmetry)

(5)

Where, m is the partition coefficient of CO_{2} in the solvent.

2.1.2. Membrane

As the membrane is assumed to be non-wetting in which only CO_{2 }could diffuse through the membrane, therefore the steady state continuity equation for transport of CO_{2} in the membrane can be written as follows.

(6)

The effective diffusion coefficient of the porous membrane is calculated by Eq.7 (Faiz and Al-Marzouqi 2009), where and are porosity and tortuosity, respectively, which are defined by membrane manufacturer.

(7)

The boundary conditions on the shell side are considered as follows:

@

(8)

@

(9)

2.1.3. Shell side

The steady state continuity equation for transport of CO_{2} in the Shell side can be expressed as

below.

(10)

The velocity distribution in the shell can be evaluated by considering Happel’s free surface model:

(11)

Also, The Happel’s free surface model can be applied to estimate the radius of the shell:

(12)

Where, is the volume fraction of the void, and can be defined as follows:

(13)

In which, n is the number of fibers, and R is the module inner radius.

The boundary conditions on the shell side may be considered as:

@

(14)

@

(15)

@ (insulation)

(16)

The reaction rates and transport properties for different absorbents are given in Table 1.

Table 1: Reaction rates and transport properties that used in this study (Tg=298 K, Tl=298K, C_{Absorbent}=1M )

The governing equations for CO_{2 }removal related to tube, membrane and shell are solved numerically using COMSOL Multiphysics software, which uses the finite element method (FEM) for the numerical solution of the governing equations of the model. FEM analysis along with an error control and an adaptive meshing technique are applied using the solver of with parallel direct linear solver (PARDISO). This solver is well suited for solving stiff and non-stiff nonlinear boundary value problems. In order to assure mesh independence of the model, the CO_{2} removal efficiency of MEA absorbent (at Vl=0.0503m/s; Vg= 0.317 m/s; Tl=308K; Tg=298K; Volume fraction of CO2 in gas=14 volume %; MEA concentration= 1M) was investigated with different mesh numbers.) The result is shown in Fig.3. As it could be seen from the figure, the efficiency does not change for the number of elements more than 25000 so it was chosen as mesh number for this study. Characteristics of HFMC that used in numerical simulation are summarized in Table 2.

Figure 3: Checking mesh independence

Vl=0.0503m/s; Vg= 0.317 m/s; Tl=308K; Tg=298K; Volume fraction of CO_{2} in gas=14 volume %; MEA concentration= 1M.

The model was validated using experimental results from Yan et al. work (Zhang, Seames et al. 2014) for CO_{2} absorption in MEA, MDEA and PG. In this section the results of the model are compared with experimental data. The removal efficiency of CO_{2} may be defined as below:

(17)

where is removal efficiency of CO_{2} , and are the gas flow rates at the inlet and outlet, respectively and and are the concentration of CO_{2 }at inlet and outlet, respectively. The concentration of CO_{2} at shell side outlet using Eq. 18.

(18)

The CO_{2 }removal efficiency at different gas velocities for MEA and PG is presented in Fig. 4. The effect of CO_{2} volume fraction in gas phase on CO_{2 }removal efficiency for MEA,MDEA and PG are presented in Fig. 5. As it is shown, the simulation results are in a good agreement with experimental data. The characteristics of the hollow fiber membrane module are given in Table 2.

Figure 4: Comparison of experimental results with model results for effect of gas velocity on the CO_{2} removal efﬁciency. Vl=0.0503m/s; Tl=308K; Tg=298K; Volume fraction of CO_{2} in gas=14 volume %; Absorbent concentration= 1M.

Figure 5: Comparison of experimental results with model results for effect of CO_{2 }on gas phase on the CO_{2} removal efﬁciency. Vl=0.0503m/s; Tl=308K; Vg=0.211m/s; Tg=298K; Absorbent concentration= 0.5M.

3.2 CO_{2} concentration distribution

Fig. 6 indicates the dimensionless concentration distribution of CO_{2} when PG used as absorbent. The gas mixture containing N_{2} and CO_{2} enters at the shell side from the top (Z=L), where the concentration of CO_{2} is maximized. The fresh chemical absorbent (PG) enters at the tube side from the bottom (Z=0) where the concentration of CO_{2 }is zero. As the gas flows through the shell side, CO_{2} transfer across the membrane due to concentration difference (or in other words chemical potential difference) between shell side and tube side, gradually decreases. Note that the concentration difference is the driving force for diffusion of CO_{2 }through the membrane from the shell side to the tube side. CO_{2} is transferred to the tube side of contactor by two mechanisms, diffusion in radial direction due to concentration difference and convection in axial direction. The removal of CO_{2 }increases by increasing in the diffusion of CO_{2} through the membrane, therefore, the diffusion mechanism is favorable. Due to non-wetted mode assumption, the concentration of CO_{2 }at the same Z-coordinate in the membrane and shell side is uniform.

3.3 Effect of gas and liquid velocity on removal efficiency

In this section, the performance of different absorbents is compared. The effect of liquid (absorbent) velocity on CO_{2} capture is presented in Fig. 7. As we can see from Fig. 7 initially the removal efficiency of CO_{2 } is a relatively strong and increasing function of absorbent velocity. As the inlet absorbent velocity increases, the removal efficiency of CO_{2} becomes a weak but still increasing function of absorbent velocity for MEA, DEA, AMP, PG and PT absorbents. Therefore, the optimum amount of absorbent could be attained and costs due to expensive absorbents and environmental problems assigned to it, will be decreased. It is obvious that as the absorbent velocity increases, the removal efficiency of CO_{2} increases, because increasing absorbent velocity increases the concentration gradient at the tube-membrane interface; thus, the removal efficiency of CO_{2 }is increasing. Fig. 7 also clearly depicts the fact that the PG absorbent has the highest removal efficiency of CO_{2}, followed by PT, MEA, AMP, DEA and MDEA in sequence, which is similar to the trend for reaction rate. Amino acids (PG and PT) also have higher partition coefficients which improving the physical absorption and CO_{2} capture. It can be seen from Fig. 7 that the removal efficiency for MDEA is much lower than other absorbent, which is again justiﬁed from the reaction rate of MDEA with CO_{2}.

Figure 7: Effect of liquid phase velocity on removal efficiency of CO_{2} for various absorbents. Vg=0.423m/s; Tl=298K; Tg=298K.

Fig. 8 illustrates the variation of CO_{2} removal efficiency with gas velocity. As we expected, the increasing in gas velocity decreases the residence time of gas phase in the membrane contactor, which leads to decreasing removal efficiency of CO_{2}. The removal efficiency of CO_{2} sequences similar to previous part.

Figure 8: Effect of gas phase velocity on removal efficiency of CO_{2} for various absorbents. Vl=0.0503m/s; Tl=298K; Tg=298K.

Therefore, from the above discussion, it can be concluded that, CO_{2} removal efficiency in absorbents follows the sequence PG> PT> MEA> AMP> DEA> MDEA . Therefore, the PG is preferred absorbent.

3.4 Effect of PG concentration on removal efficiency

Fig. 9 illustrates the removal efficiency of CO_{2} at various PG inlet temperatures. It is evident that increasing in absorbent temperature increase removal efficiency of CO_{2}. As the temperature increases the reaction rate (Kumar, Hogendoorn et al. 2002, Dindore, Brilman et al. 2005) and diffusivity (Snijder, te Riele et al. 1993) of CO_{2 }in absorbent increase, which results in an increase in the removal efficiency of CO_{2}. Also, increasing in absorbent temperature increase the absorbent evaporation (Tan and Chen 2006), which leads to reduction in removal efficiency of CO_{2}. In this temperature interval (293 K - 313 K) the effect of temperature on the reaction rate and diffusivity is higher than evaporating in the solvent. At other temperature, different results may be attained.

Figure 9: Effect of absorbent temperature on removal efficiency of CO_{2}. Vl=0.0503m/s; Vg=0.528m/s; Tg=298K; PG concentration= 1M.

3.5 Effect of packing density on removal efficiency

The effect of packing density on the removal efficiency of CO_{2 }presented in Fig. 10. Increasing in the number of fibers resulted in an increase the packing density. In other words, as the packing density increases the effective area for mass transfer increases, which cause to improve the removal efficiency of CO_{2 }even to a hundred percent.

Figure 10: Effect of packing density on removal efficiency of CO_{2}. Vl=0.0503m/s; Tl=298K; Vg=0.8m/s; Tg=298K; PG concentration= 1M.

3.6 Effect of fiber diameter on removal efficiency

The effect of fiber diameter on the removal efficiency of CO_{2} is illustrated in Fig. 11. If the enlargement factor denoted by σ, then the inner (R_{1}) and outer (R_{2}) radius of fiber multiplied by σ, and then the shell diameter (R_{3}) is calculated by Eq. 12. Therefore, increasing in the enlargement factor resulted in an increase in contact area, which in turn reduces the CO_{2} outlet concentration. In agreement with prior expectations, as the enlargement factor increases the removal efficiency of CO_{2} is improved.

Figure 11: Effect of fiber diameter on removal efficiency of CO_{2}. Vl=0.0503m/s; Tl=298K; Vg=0.528m/s; Tg=298K; PG concentration= 1M.

4. Conclusion

A comprehensive two-dimensional mathematical model was developed to describe CO_{2} capture by absorption in HFMC using various absorbent. In this study, the function of six absorbents of PG, PT, MEA, AMP, DEA and MDEA was compared. The model was established for non-wetted mode and parallel countercurrent gas-liquid flow arrangement. The radial and axial diffusions in the transport equations were assumed. The equations solved by FEM and the model was validated using the results reported by Yan et al. (Yan, Fang et al. 2007). The simulation results were in good agreement with the experimental data. PG absorbent has the highest removal efficiency of CO_{2} followed by PT, MEA, AMP, DEA and MDEA in sequence. The results of the proposed model indicate that the removal efficiency of CO_{2} increases with increasing absorbent velocity, absorbent temperature, packing density, and enlargement factor. Increasing gas velocity in the shell side has a reverse effect. It is worth mentioning that the assumptions of ideal gas may introduce some limitations to the model and it may not be applicable for high pressures. It is suggested to investigate the effect of using Equations of state for the future works.

Nomenclature

C

Concentration (M or mol/m^{3})

D

Diffusion coefficient (m^{2}/s)

R

Reaction rate (mol/m^{3}.s)

L

Hollow fiber membrane length (cm)

R

Hollow fiber membrane module radius (cm)

R_{1}

Inner radius of fiber (μm)

R_{2}

Outer radius of fiber (μm)

n

Number of hollow fiber

Tl

Inlet liquid phase temperature (K)

Tg

Inlet gas phase temperature (K)

Vl

Liquid phase velocity (m/s)

Vg

Gas phase velocity (m/s)

Average velocity (m/s)

ε

Membrane porosity

τ

Membrane tortuosity

η

CO_{2} removal efficiency

σ

Enlargement factor

r

Radial coordinate (m)

Z

Axial coordinate (m)

Q

Volumetric flow rate (m^{3}/s)

m

Partition coefficient

References

Al-Marzouqi, M. H., M. H. El-Naas, S. A. Marzouk, M. A. Al-Zarooni, N. Abdullatif and R. Faiz (2008). "Modeling of CO 2 absorption in membrane contactors." Separation and Purification Technology59(3): 286-293.

Al-Marzouqi, M. H., S. A. Marzouk, M. H. El-Naas and N. Abdullatif (2009). "CO2 Removal from CO2− CH4 Gas Mixture Using Different Solvents and Hollow Fiber Membranes." Industrial & Engineering Chemistry Research48(7): 3600-3605.

Atchariyawut, S., R. Jiraratananon and R. Wang (2007). "Separation of CO 2 from CH 4 by using gas–liquid membrane contacting process." Journal of membrane science304(1): 163-172.

Bird, R. B., W. E. Stewart and E. N. Lightfoot (1960). "Transport Phenomena John Wiley & Sons." New York: 413.

Dindore, V., D. Brilman and G. Versteeg (2005). "Modelling of cross-flow membrane contactors: mass transfer with chemical reactions." Journal of membrane science255(1): 275-289.

Esmaili, J. and M. R. Ehsani (2014). "Development of New Potassium Carbonate Sorbent for CO2 Capture under Real Flue Gas Conditions." Iranian Journal of Oil & Gas Science and Technology3(3): 39-46.

Faiz, R. and M. Al-Marzouqi (2009). "Mathematical modeling for the simultaneous absorption of CO 2 and H 2 S using MEA in hollow fiber membrane contactors." Journal of Membrane Science342(1): 269-278.

Gabelman, A. and S.-T. Hwang (1999). "Hollow fiber membrane contactors." Journal of Membrane Science159(1): 61-106.

Hamborg, E. S., W. P. van Swaaij and G. F. Versteeg (2008). "Diffusivities in aqueous solutions of the potassium salt of amino acids." Journal of Chemical & Engineering Data53(5): 1141-1145.

Happel, J. (1959). "Viscous flow relative to arrays of cylinders." AIChE Journal5(2): 174-177.

Herzog, H., B. Eliasson and O. Kaarstad (2000). "Capturing greenhouse gases." Scientific American282(2): 72-79.

Herzog, H. J. (2001). "Peer reviewed: what future for carbon capture and sequestration?" Environmental science & technology35(7): 148A-153A.

Kumar, P., J. Hogendoorn, P. Feron and G. Versteeg (2002). "New absorption liquids for the removal of CO 2 from dilute gas streams using membrane contactors." Chemical Engineering Science57(9): 1639-1651.

Lee, Y., R. D. Noble, B.-Y. Yeom, Y.-I. Park and K.-H. Lee (2001). "Analysis of CO 2 removal by hollow fiber membrane contactors." Journal of Membrane Science194(1): 57-67.

Li, J.-L. and B.-H. Chen (2005). "Review of CO 2 absorption using chemical solvents in hollow fiber membrane contactors." Separation and Purification Technology41(2): 109-122.

Li, K., J. Kong and X. Tan (2000). "Design of hollow fibre membrane modules for soluble gas removal." Chemical engineering science55(23): 5579-5588.

Liao, C.-H. and M.-H. Li (2002). "Kinetics of absorption of carbon dioxide into aqueous solutions of monoethanolamine+N-methyldiethanolamine." Chemical Engineering Science57(21): 4569-4582.

Lin, S.-H., P.-C. Chiang, C.-F. Hsieh, M.-H. Li and K.-L. Tung (2008). "Absorption of carbon dioxide by the absorbent composed of piperazine and 2-amino-2-methyl-1-propanol in PVDF membrane contactor." Journal of the Chinese Institute of Chemical Engineers39(1): 13-21.

Littel, R., G. Versteeg and W. Van Swaaij (1992). "Kinetics of CO2 with primary and secondary amines in aqueous solutions—II. Influence of temperature on zwitterion formation and deprotonation rates." Chemical Engineering Science47(8): 2037-2045.

Lu, J.-G., Y.-F. Zheng, M.-D. Cheng and L.-J. Wang (2007). "Effects of activators on mass-transfer enhancement in a hollow fiber contactor using activated alkanolamine solutions." Journal of membrane science289(1): 138-149.

Lyngfelt, A. and C. Azar (1999). "Proceedings of minisymposium on carbon dioxide capture and storage."

Oexmann, J. and A. Kather (2009). "Post-combustion CO 2 capture in coal-fired power plants: comparison of integrated chemical absorption processes with piperazine promoted potassium carbonate and MEA." Energy Procedia1(1): 799-806.

Park, H. H., B. R. Deshwal, I. W. Kim and H. K. Lee (2008). "Absorption of SO 2 from flue gas using PVDF hollow fiber membranes in a gas–liquid contactor." Journal of Membrane Science319(1): 29-37.

Paul, S., A. K. Ghoshal and B. Mandal (2007). "Removal of CO2 by single and blended aqueous alkanolamine solvents in hollow-fiber membrane contactor: modeling and simulation." Industrial & engineering chemistry research46(8): 2576-2588.

Portugal, A., P. Derks, G. Versteeg, F. Magalhaes and A. Mendes (2007). "Characterization of potassium glycinate for carbon dioxide absorption purposes." Chemical Engineering Science62(23): 6534-6547.

Portugal, A., F. Magalhaes and A. Mendes (2008). "Carbon dioxide absorption kinetics in potassium threonate." Chemical Engineering Science63(13): 3493-3503.

Qi, Z. and E. Cussler (1985). "Microporous hollow fibers for gas absorption: II. Mass transfer across the membrane." Journal of Membrane Science23(3): 333-345.

Rahmandoost, E., B. Roozbehani and M. H. Maddahi (2014). "Experimental Studies of CO2 Capturing from the Flue Gases." Iranian Journal of Oil & Gas Science and Technology3(4): 1-15.

Ren, J., R. Wang, H.-Y. Zhang, Z. Li, D. T. Liang and J. H. Tay (2006). "Effect of PVDF dope rheology on the structure of hollow fiber membranes used for CO 2 capture." Journal of membrane science281(1): 334-344.

Rezakazemi, M., Z. Niazi, M. Mirfendereski, S. Shirazian, T. Mohammadi and A. Pak (2011). "CFD simulation of natural gas sweetening in a gas–liquid hollow-fiber membrane contactor." Chemical engineering journal168(3): 1217-1226.

Saha, A. K., S. S. Bandyopadhyay and A. K. Biswas (1993). "Solubility and diffusivity of nitrous oxide and carbon dioxide in aqueous solutions of 2-amino-2-methyl-1-propanol." Journal of Chemical and Engineering Data38(1): 78-82.

Snijder, E. D., M. J. te Riele, G. F. Versteeg and W. Van Swaaij (1993). "Diffusion coefficients of several aqueous alkanolamine solutions." Journal of Chemical and Engineering data38(3): 475-480.

Tan, C.-S. and J.-E. Chen (2006). "Absorption of carbon dioxide with piperazine and its mixtures in a rotating packed bed." Separation and purification technology49(2): 174-180.

Tuinier, M., M. van Sint Annaland, G. Kramer and J. Kuipers (2010). "Cryogenic CO2 capture using dynamically operated packed beds." Chemical Engineering Science65(1): 114-119.

Versteeg, G. F. and W. Van Swaalj (1988). "Solubility and diffusivity of acid gases (carbon dioxide, nitrous oxide) in aqueous alkanolamine solutions." Journal of Chemical and Engineering Data33(1): 29-34.

Wang, D., W. Teo and K. Li (2004). "Selective removal of trace H 2 S from gas streams containing CO 2 using hollow fibre membrane modules/contractors." Separation and purification Technology35(2): 125-131.

Wang, R., D. Li and D. Liang (2004). "Modeling of CO 2 capture by three typical amine solutions in hollow fiber membrane contactors." Chemical Engineering and Processing: Process Intensification43(7): 849-856.

Xu, S., Y.-W. Wang, F. D. Otto and A. E. Mather (1996). "Kinetics of the reaction of carbon dioxide with 2-amino-2-methyl-1-propanol solutions." Chemical Engineering Science51(6): 841-850.

Yan, S.-p., M.-X. Fang, W.-F. Zhang, S.-Y. Wang, Z.-K. Xu, Z.-Y. Luo and K.-F. Cen (2007). "Experimental study on the separation of CO 2 from flue gas using hollow fiber membrane contactors without wetting." Fuel Processing Technology88(5): 501-511.

Zhang, X., W. S. Seames and B. M. Tande (2014). "Recovery of CO2 from Monoethanolamine using a Membrane Contactor." Separation Science and Technology49(1): 1-11.

Zhao, L., E. Riensche, R. Menzer, L. Blum and D. Stolten (2008). "A parametric study of CO 2/N 2 gas separation membrane processes for post-combustion capture." Journal of Membrane Science325(1): 284-294.