Scholarly article on topic 'Solubility, Kinetics, Absorption Heat and Mass Transfer Studies of CO2 Absorption into Aqueous Solution of 1-Dimethylamino-2-propanol'

Solubility, Kinetics, Absorption Heat and Mass Transfer Studies of CO2 Absorption into Aqueous Solution of 1-Dimethylamino-2-propanol Academic research paper on "Materials engineering"

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{"Carbon dioxide" / Absorption / Solubility / "Reaction Heat" / "Mass transfer" / 1-Dimethylamine-2-propanol.}

Abstract of research paper on Materials engineering, author of scientific article — Helei Liu, Yujiao Liang, Zhiwu Liang, Sen Liu, Kaiyun Fu, et al.

Abstract In this work, the performance of CO2 absorption into aqueous 1-dimethylamino-2-propanol (1DMA2P) solution was investigated for possible CO2 absorption application and compared with those of MEA and MDEA. The CO2 absorption performance was presented in terms of equilibrium solubility, absorption rate, absorption heat, and overall mass transfer coefficient (KGav). The results show that 1DMA2P has a higher solubility and a lower absorption heat than those of MEA and MDEA, a faster absorption rate and a higher KGav than that of MDEA, but a lower KGav than that of MEA. Due to the high performance of the 1DMA2P, it can be considered to be a promising alternative solvent for CO2 capture.

Academic research paper on topic "Solubility, Kinetics, Absorption Heat and Mass Transfer Studies of CO2 Absorption into Aqueous Solution of 1-Dimethylamino-2-propanol"

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Energy Procedia 63 (2014) 659 - 664

GHGT-12

Solubility, kinetics, absorption heat and mass transfer studies of CO2 absorption into aqueous solution of 1-Dimethylamino-2-propanol

Helei Liu,Yujiao Liang, Zhiwu Liang*, Sen Liu, Kaiyun Fu, Teerawat Sema, Wichitpan

Rongwong

Joint International Center for CO2 Capture and Storage (iCCS),College of Chemistry and Chemical Engineering, Hunan University,

Changsha,410082, P.R. China

Abstract

In this work, the performance of CO2 absorption into aqueous 1-dimethylamino-2-propanol (1DMA2P) solution was investigated for possible CO2 absorption application and compared with those of MEA and MDEA. The CO2 absorption performance was presented in terms of equilibrium solubility, absorption rate, absorption heat, and overall mass transfer coefficient (KGav). The results show that 1DMA2P has a higher solubility and a lower absorption heat than those of MEA and MDEA, a faster absorption rate and a higher KGav than that of MDEA, but a lower KGav than that of MEA. Due to the high performance of the 1DMA2P, it can be considered to be a promising alternative solvent for CO2 capture.

© 2014TheAuthors.Publishedby Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.Org/licenses/by-nc-nd/3.0/).

Peer-review under responsibility of the Organizing Committee of GHGT-12

Keywords:Carbon dioxide, Absorption, Solubility, Reaction Heat, Mass transfer, 1-Dimethylamine-2-propanol.

1. Introduction

In recent years, considerable attention has been focused on worldwide global warming and climate change issues, resulting in extensive research being performed on carbon dioxide (CO2) capture. The absorption of CO2 into aqueous amine solutions is regarded to be one of the most promising technologies for CO2 capture due to its maturity, cost effectiveness, and capacity to handle large amounts of exhaust gas streams [1]. This technology relies

* Corresponding author. Tel.: +86-73188573033; fax: +86-73188573033. E-mail address: zwliang@hnu.edu.cn

1876-6102 © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.org/licenses/by-nc-nd/3.0/).

Peer-review under responsibility of the Organizing Committee of GHGT-12

doi:10.1016/j.egypro.2014.11.073

greatly on the performances of solvents, which is dictated by its CO2 loading capacity, reaction kinetics, energy for regeneration, and mass transfer characteristics. Recently, a new tertiary amine, 1-dimethylamino-2-propanol (1DMA2P), has drawn growing attention for its high kinetic performance for capturing of CO2 [2]. However, it is well-known that the overall performances of any solvents are dependent not only on its kinetics, but also, on the absorption capacity, absorption heat, and mass transfer characteristics. Therefore, it is the objective of this study to comprehensively evaluate the performance of 1DMA2P and study these performance criteria parameters (CO2 equilibrium solubility, CO2 absorption heat, and mass transfer characteristics) compared with those of commercially available amines.

In this work, the CO2 capture performances in aqueous solutions of 1DMA2P-CO2-H2O were investigated and compared with the conventional amines (e.g. MEA, MDEA) in the terms of CO2 absorption capacity, absorption heat, absorption rate, and mass transfer.

2. Materials and Method

2.1. Materials

Reagent grade 1-dimethylamino-2-propanol (1DMA2P) with a purity of > 97 wt% was obtained from TCI, Japan. MEA (with a purity of > 98 wt%) and MDEA (with a purity of > 99 wt%) were purchased from Tianjin Hengxing Chemical Preparation Co., Ltd, China. The solutions were prepared by mixing concentrated amines with deionized water to the desired concentrations. Commercial-grade CO2 and N2 (with a purity of > 99%) were supplied by Changsha Jingxiang Gas Co., Ltd., China.

2.2. CO2 Solubility

The apparatus used for the CO2 solubility measurement in this work was similar to that used in the work of Tontiwachwuthikul et al. [3]. Initially, the amine solution at the desired temperature was fed into an absorption reactor which was immersed in a water bath with a temperature controller. After the solution in the reactor had reached the desired temperature, a mixture of N2 and CO2, which were individually controlled by separate mass flow meters and adjusted to the desired CO2 concentration, was fed into the absorption reactor. The experiment was operated for at least 8 hours until equilibrium condition was obtained. Samples of CO2-loaded solutions at equilibrium were taken for measurement of equilibrium solubility of CO2 by titration using a known volume of 1.0 N HCl with methyl orange as the indicator.

2.3. Heat of CO2 absorption in aqueous 1DMA2P solution.

The heat of absorption of CO2-1DEA2P was estimated by applying the Gibbs-Helmholtz equation[4], as shown in Eq (1):

d (ln pco2 ) ah„

1 ï R

where PCO is the CO2 partial pressure, T represents the temperature, AHa represents the heat of CO2 absorption (J/mol), and R is the universal gas constant (J/mol K).

2.4. Mass transfer

The mass transfer performances in terms of the overall mass transfer coefficient (KGav) were experimentally observed and compared using a laboratory-sized column, which was made of acrylic plastic with measurements of 28.0 mm internal diameter and 1.70 m total height. The packing height of the column was 1.20 m. Sulzer DX-type packing (made of 316L stainless steel and with 900 m2/m3 surface area per volume of elements). The schematic

diagram of the experimental setup is shown in Figure. 1 The overall mass transfer coefficient (KGav) of the CO2 absorption in the packed column can be defined as shown in Eq. (2). Details on the determination of KGav can be found in our previous work [5].

KGav =

P(yA,G - y.4 ) dz

where G and YA are the molar flow rate of inert gas and the mole ratio of CO2, respectively. P represents the total pressure (kPa) of the packed column. yA G is the mol fraction of CO2 in the gas phase and yA is the mol fraction of C02 at interface in equilibrium with the bulk concentration.

Figure 1. Schematic diagram of the absorption process.

3. Results and discussion

3.1. CO2 absorption capacity of aqueous 1DMA2P solution.

In this work, the equilibrium solubility of CO2 in 2 M 1DMA2P solutions was measured at 313 K and over a CO2 partial pressure range of 8-101 kPa. It can be found from Figure 2 that the equilibrium solubility of CO2 in 1DMA2P solutions increased as the CO2 partial pressure increased. In addition, it can be easily found that the equilibrium solubility of CO2 in 2M 1DMA2P was higher than those of MEA and MDEA [6,7].

Figure 2. Equilibrium solubility of CO2 absorption into aqueous solutions of 2 M MEA, 2M MDEA and 2M 1DMA2P.

3.2. Heat of CO2 absorption in aqueous 1DMA2P solution

In this work, the heat of CO2 absorption into 1DMA2P was estimated based on the Gibbs-Helmholtz equation (Eq. (1) ). The calculation results presented in Table 1 show that the heat of CO2 absorption in aqueous 1DMA2P solution ( AHa ) was -28.3 kJ/mol, which was much lower than those in MEA and MDEA.

Table 1. Heat of CO2 absorption in aqueous solutions of MEA, MDEA, and 1DMA2P.

Amine Estimated AHa References

(kJ/mol)

MEA -84.3 [7]

MDEA -54.6 [8]

1DMA2P -28.3 This work

3.3. CO2 absorption rates

In this study, the CO2 absorption rate of 1DMA2P was obtained by plotting the CO2 amount in liquid phase as a function of time. The absorption rates for CO2 into 1DMA2P and MDEA at 298K are shown in Figure 3. It can be seen that 1DMA2P had a higher CO2 absorption rate than that of MDEA. This is due to the higher reactivity of 1DMA2P toward CO2, which has been demonstrated by Kadiwala et al. [2] who studied the CO2 absorption kinetics into aqueous 1DMA2P solution using a stopped-flow technology. They found that the second order rate constant (k2) of 1DMA2P was higher than that of MDEA.

3.4. Mass transfer.

The mass transfer performances of CO2 absorption into MEA, MDEA, and 1DEMA2P were conducted at amine concentration of 2M, inlet temperature of 313K and atmospheric pressure. All the experimental results are shown in Figure 4. It can be seen clearly that KGav of 1DMA2P was higher than that of MDEA, but lower than that of MEA. This is because the reaction kinetics of CO2 absorption into the three amines can be ranked as MEA>1DMA2P>MDEA. Although the mass transfer performance of 1DMA2P was lower than that of MEA, the

higher CO2 capacity and reactivity compared with that of MDEA as shown in the previous sections make 1DMA2P more attractive to be used in the C02 capture, especially for the process with high volume of C02. O.S

Si1 o.3 •3

i MDEA258K ♦ 1DMA2P

0 50 100 150 200 250

t(miii)

Figure 3. C02 loading as a function of time for 1DMA2P and MDEA at the temperature of 298K.

ME A 1DMA2P MDEA

Figure 4. Mass transfer coefficient (KGav) of CO2 absorption into aqueous of 2M MEA, 2M MDEA, and 2M 1DMA2P, at atmospheric, temperature of 313K, gas flow rate of 28.02 kmol/(m2.h), liquid flow rates of 4.87m3/(m2.h), initial CO2 loading of 0.19 CO2/mol amine.

4. Conclusion

The performance of CO2 absorption into aqueous 1-dimethylamino-2-propanol (1DMA2P) solution was investigated for possible CO2 absorption application. It was observed that 1DMA2P can be considered to be a promising solvent for CO2 capture due to its good performance on the CO2 absorption capacity, CO2 absorption heat, CO2 absorption rate, reaction kinetics and mass transfer.

Acknowledgements

The financial support from National Natural Science Foundation of China (NSFC No. 21276068, 21376067

and 21250110514), Ministry of Science and Technology of the People's of Republic of China (MOST No. 2012BAC26B01), Innovative Research Team Development Plan-Ministry of Education of China (No. IRT1238), Shaanxi Yanchang Petroleum (Group) Co., LTD, and China's State "Project 985" in Hunan University-Novel Technology Research and Development for CO2 Capture as well as Hunan University to the Joint International Center for CO2 Capture and Storage (iCCS) is gratefully acknowledged.

References

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