Simultaneous Absorption of Carbon Dioxide and Sulfur Dioxide into Aqueous 1,8-Diamino-p-menthane

This article was downloaded by: [University of Chicago Library]On: 10 October 2014, At: 23:43Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK

Separation Science andTechnologyPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/lsst20

Simultaneous Absorption ofCarbon Dioxide and SulfurDioxide into Aqueous 1,8-Diamino-p-menthaneKyu-Suk Hwang a , Dong-Woo Kim a , Sang-Wook Parka , Dae-Won Park a , Kwang-Joong Oh a & Seong-SooKim ba Division of Chemical Engineering, Pusan NationalUniversity , Busan, Koreab Department of Environmental Administration ,Catholic University of Pusan , Busan, KoreaPublished online: 09 Dec 2009.

To cite this article: Kyu-Suk Hwang , Dong-Woo Kim , Sang-Wook Park , Dae-WonPark , Kwang-Joong Oh & Seong-Soo Kim (2009) Simultaneous Absorption of CarbonDioxide and Sulfur Dioxide into Aqueous 1,8-Diamino-p-menthane, Separation Scienceand Technology, 44:16, 3888-3910, DOI: 10.1080/01496390903338444

To link to this article: http://dx.doi.org/10.1080/01496390903338444

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all theinformation (the “Content”) contained in the publications on our platform.However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness,or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of the

http://www.tandfonline.com/loi/lsst20

http://www.tandfonline.com/action/showCitFormats?doi=10.1080/01496390903338444

http://dx.doi.org/10.1080/01496390903338444

Content should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for anylosses, actions, claims, proceedings, demands, costs, expenses, damages,and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of theContent.

This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden. Terms & Conditions of access and use can be found athttp://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

http://www.tandfonline.com/page/terms-and-conditions

Simultaneous Absorption of Carbon Dioxideand Sulfur Dioxide into Aqueous

1,8-Diamino-p-menthane

Kyu-Suk Hwang,1 Dong-Woo Kim,1 Sang-Wook Park,1

Dae-Won Park,1 Kwang-Joong Oh,1 and Seong-Soo Kim2

1Division of Chemical Engineering, Pusan National University,Busan, Korea

2Department of Environmental Administration,Catholic University of Pusan, Busan, Korea

Abstract: Carbon dioxide and sulfur dioxide were simultaneously absorbed intoaqueous 1,8-diamino-p-menthane (DAM) in a stirred semi-batch tank with a pla-nar gas-liquid interface within a range of 0–2.0 kmol=m3 of DAM, 0.01–0.12molefraction of CO2, 0.001–0.012mole fraction of SO2, and 298-318K. Absorptiondata of each gas in the CO2-DAM and SO2-DAM systems are obtained to verifytheir reaction regimes, based on film theory, respectively, which are used to ana-lyze the simultaneous absorption mechanisms of CO2 and SO2 in the CO2-SO2-DAM systems. In the simultaneous absorption rate of CO2 and SO2 into DAMsolution, the absorption of CO2 belongs to the second-order reaction of finite rateand the absorption of SO2 belongs to the instantaneous reaction regime.

Keywords: Carbon dioxide, 1,8-diamino-p-menthane, simultaneous absorption,sulfur dioxide

INTRODUCTION

Carbon dioxide (CO2) and sulfur dioxide (SO2) in the flue gas generatedfrom combustion of fossil fuel are the main cause of global, environmentalproblems such as air pollution and acid rain. The contents of CO2 and SO2

Received 17 December 2008; accepted 7 August 2009.Address correspondence to Sang-Wook Park, Division of Chemical Engineer-

ing, PusanNational University, Busan 609-735, Korea. E-mail: [email protected]

Separation Science and Technology, 44: 3888–3910, 2009

Copyright # Taylor & Francis Group, LLC

ISSN: 0149-6395 print=1520-5754 online

DOI: 10.1080/01496390903338444

3888

Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

are 10–15% and 0.1–0.4% in the flue gas from the combustion of fossil fuelsuch as power plants, respectively. However, the produced volume of fluegas is so large globally that great amounts of CO2 and SO2 are introducedinto the atmosphere.

Many studies have been done on the mechanisms and kinetics of thereaction of CO2 with various alkanolamines, employing simple massbalance analysis and resulting in the zwitterion mechanism proposed byCaplow (1) and Danckwerts (2). Some discrepancies remained accordingto the reaction mechanism (3), particularly the types of amines, gas=liquidcontactor, and analysis method used for the rate data, for example, theorder of the overall reactions, and the rate constants. Recently, a groupof sterically hindered amines were developed (4–6), providing a high capa-city of 1.0mol of CO2=mol of amine and a relatively high absorption rate,even at high CO2 loading. A new alkanolamine containing more aminesthan 1 may be used to provide a high capacity of CO2=mol of amine.

The absorption of SO2 into aqueous slurries of sodium, calcium, andmagnesium compounds, serving as the absorbent (7–14), and alkalinesolutions, has been studied for decades. The medium used in the alkalinesolutions was typically alkaline salts (15–19), inorganic acids (20),organic acids (21–24), and amines for reversible reaction (25–29).Danckwerts (30) showed that SO2 absorption in an alkaline solution isproceeded by an instantaneous reaction while Hikita et al. (31) proposeda penetration theory model based on the two-reaction model usingapproximate analytical solutions to investigate the kinetics of SO2 withreactants in the liquid phase.

Gas mixtures containing more than two gases such as NO=SO2(32)or NO2=SO2 (33) emitted from stationary combustion facilities, andH2S and SO2 (34,35) from natural, coal, and refinery gases, have beenseparated by the simultaneous absorption into aqueous slurries oralkaline solutions. Most of these works have been done towards determ-ing the mechanisms and kinetics of the reaction in the simultaneousabsorption, proposed by Goetter and Pigford (36) and Hikita et al. (37).

In this present work, CO2 and SO2 were absorbed into aqueous1,8-diamino-p-menthane (DAM) containing functional groups of 2amines to obtain the reaction kinetics between CO2 or SO2 and DAM.To predict the simultaneous absorption rates of CO2 and SO2, the filmtheory equation with the absorption of both the gases was formulatedand compared to an approximate solution previously described (6) andthe numerical solution. This study, with the absorber of DAM, will makethe first attempt for the removal of both the gases emitted from powerplant flues and from the viewpoint of energy-efficient separation, andhopefully it will become the preferred treatment over that of conven-tional, individual separation.

Simultaneous Absorption of Co2 and Sulfur Dioxide 3889

Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

THEORY

The zwitterions mechanism originally proposed by Caplow (1) and laterreintroduced by Danckwerts (2) and da Silva and Svendsen (3) isgenerally accepted as the reaction mechanism in the absorption of CO2

into aqueous DAM as follows:

CO2 þH2NRNH2 ¼ H2NRNþH2COO� ðiÞ

CO2 þH2NRNþH2COO� ¼ O�OCH2NþRNþH2COO� ðii-1Þ

O�OCH2NRNþH2COO� þH2NRNH2 ¼ O�OCHNRNH2COO�

þH3NþRNþH3

ðii-2Þ

where R presents

The overall reaction being:

CO2ðAÞ þ 2H2NRNH2ðCÞ ¼ O�OCHNRNH2COO�

þH3NþRNþH3

ðiiiÞ

The reactions of SO2 in aqueous DMA, combined with the SO2

reaction in an aqueous, alkaline solution (15), are as follows:

SO2 þH2O ¼ 2Hþ þ SO2�3 ðivÞ

H2NRNH2 þ 2Hþ ! Hþ3 NRNHþ

3 ðvÞ

The overall reaction being:

SO2ðBÞ þH2NRNH2ðCÞ þH2O ! 2Hþ3 NRNHþ

3 þ SO2�3 ðviÞ

The irreversible reactions between the dissolved species j and the reac-tant (C), as shown in reactions (iii) and (vi), may be formulated as follows:

j þ njC ! products ðviiÞ

where j is A or B, and nj is a stoichiometric coefficients of species j.

3890 K.-S. Hwang et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

The following assumptions are made to set up the mass balance ofspecies j:

1. Henry’s law holds,2. isothermal condition prevails, and3. species C is a nonvolatile solute,4. nA¼ 1 and nB¼ 1, and5. reaction (viii) is mth order with respect to j and nth order with respect

to C, of which the reaction rate (rj) of species j is expressed by:

rj ¼ kjCmj C

nC ðviiiÞ

Respective Absorption of CO2 and SO2 Accompanied by Reaction in

CO2-DAM and SO2-DAM System

The mass balances of species A or B and C in CO2-DAM and SO2-DAMsystem using the film theory accompanied by reaction (viii) and theboundary conditions are given as follows:

Djd2Cj

dz2¼ kjC

mj C

nC ð1Þ

DCd2CC

dz2¼ njkjCm

j CnC ð2Þ

z ¼ 0; Cj ¼ Cji;dCC

dz¼ 0 ð3Þ

z ¼ d; Cj ¼ 0;CC ¼ CCoð4Þ

Depending on the relative rates of diffusion and reaction by using thedimensionless groups listed below, for convenience, the systems may beclassified into four regimes: very slow reaction, slow reaction, fast reac-tion, and instantaneous reaction. The condition for validity of a fastpseudo-mth-order reaction with respect to species j, where the interfacialconcentration of species C is the same as that in the bulk liquid phase, isgiven by the following expression (38):

3 < Ha << Ei ð5Þwhere

Ha ¼

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2

mþ1DjkjCm�1ji Cn

Co

qkLj

and Ei ¼ 1þ CCo

njCji

DC

Djð6Þ


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

Under the condition of Eq. (5), Eq. (1) can be written as:

Djd2Cj

dz2¼ kjC

mj C

nCo ¼ kmC

mj ð7Þ

where

km ¼ kjCnCo ð8Þ

Using the analytical solution of Eq. (7) with the boundary conditionsof Eq. (3) and (4), NA at the interface is:

Nj ¼ Cji

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2

mþ 1DjkjC

m�1ji Cn

Co

rð9Þ

Where the resistance in the gas phase was not negligible, the expressionfor Nj for the pseudo-mth order reaction regime was derived as follows:

Pj

Nj¼ 1

kGþ Hjffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

2mþ1DjkjC

m�1ji Cn

Co

q ð10Þ

According to Eq. (10), Plots of Pj=Nj vs. Hj=(DjkjCCo)0.5 at m¼n¼1 should

be a straight line with slope of 1.

Simultaneous Absorption of Both Gases CO2 and SO2 into

Reactive DAM Solution

For simultaneous absorption of both CO2(A) and SO2(B) into aqueousDAM (C) solution, the following assumptions (6) are made to set upthe mass balance of species j and C:

1. The presence of one gas does not affect the rate of absorption of theother gas because the gases do not compete for the commonliquid-phase reactant C,

2. the reaction orders with respect to A and B are 1 and 1, respectively.

The mass balances of species j and C using the film theory accompa-nied by chemical reaction and the boundary conditions are given asfollows:

Djd2Cj

dz2¼ kjCjCC ð11Þ


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

DCd2CC

dz2¼

XBj¼A

njkjCjCC ð12Þ

z ¼ 0; Cj ¼ Cji;dCC

dz¼ 0 ð13Þ

z ¼ d; Cj ¼ 0; CC ¼ CCo ð14Þ

The flux of species j at the interface of the gas-liquid phase is definedby

Nj ¼ �DjdCj

dz

� �z¼0

ð15Þ

The enhancement factor (b) here is defined as the ratio of molar fluxof Eq. (5) with the chemical reaction to that obtained without chemicalreaction:

bj ¼ � Nj

kLjCji

��Z¼0

ð16Þ

The solution of Eqs. (11) and (12) is used to obtain the value of bjthrough Eq. (16).

The total absorption rate (NT) for the simultaneous absorption ofCO2 and SO2 is obtained using bj and physical absorption rate of speciesj (Njo) as follows:

NT ¼XBj¼A

bjNjo ð17Þ

Simultaneous Absorption of Both Gases CO2 of Second Reaction and

SO2 of Instantaneous Reaction into Reactive DAM Solution

If the reaction between CO2 and DAM of Eq. (iii) is assumed to be asecond-order reaction of finite rate and the reaction between SO2 andDAM of Eq. (vi) to be an instantaneous reaction, the reaction of SO2

and DAM occurs at a reaction plane (k), where the concentration ofboth SO2 and DAM are zero. CO2 diffuses beyond the reaction planeand reacts with C in the region between the reaction plane and thebulk liquid.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

The mass balance describing the diffusion of A, B, and C in the liquidfilm, based on film theory, is as follows:

0< z< k,

DAd2CA

dz2¼ 0 ð18Þ

DBd2CB

dz2¼ 0 ð19Þ

k< z < d,

DAd2CA

dz2¼ kACACC ð20Þ

DCd2CC

dz2¼ nAkACACC ð21Þ

The boundary conditions are:

z ¼ 0 : CA ¼ CAi;CB ¼ CBi ð22Þ

z ¼ k : CA ¼ C�A;CB ¼ 0;CC ¼ 0 ð23Þ

�nBDBðdCB=dzÞ ¼ DCðdCC=dzÞ ð24Þ

z ¼ d : CA ¼ 0;CC ¼ CCo ð25Þ

Eqs. (20) and (21) are nonlinear and cannot be solved analytically.However, Hikita et al. (37) have presented an approximate analytical

solution with the enhancement factors (bA and bB) of species A and Babsorbing two gases, one of which reacts instantaneously in the liquidphase, as follows:

bA ¼ ½1þ rBqB þ rCqCÞ � ð1þ rBqBÞbA�cgð1þ rCqC � bAÞ tanhðcgÞ

ð26Þ

where,

g ¼ 1þ rCqC � bA1þ rBqB þ rCqC � bA

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi1þ rBqB þ rCqC � ð1þ rBqBÞbA

3rCqCbA

s

bB ¼ 1þ rBqB þ rCqC � bArBqB

ð27Þ


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

where,

rB ¼ DB

DA; rC ¼ DC

DA; qB ¼ nBCBi

nACAi; qC ¼ CCo

nACAi; c ¼

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffikACCoDA

p

kL

bA and bB are obtained from Eqs. (26) and (27) by a trial and error pro-cedure with given, dimensionless parameters such as rB, rC, qB, qC, and c.

EXPERIMENTAL

Chemicals

All chemicals were of reagent grade, and used without further purifica-tion. Purity of CO2, N2, SO2 were more than 99.9%. CO2, N2, and SO2

were supplied by Hanna Gas Company, Korea, and 1,8-diamino-p-menthane by Aldrich Chemical Company, U.S.A.

Absorption Rate of CO2 and SO2

Absorption experiments were carried out in an agitated vessel (6,39). Theabsorption vessel was constructed of glass with an inside diameter of0.073m and a height of 0.151m. Four, equally spaced vertical baffles,each one-tenth of the vessel diameter in width, were attached to theinternal wall of the vessel. The gas and liquid phase were agitated withan agitator driven by a 1=4 Hp variable speed motor. A straight impeller0.034m in length and 0.05m in width was used as the liquid phaseagitator and located at the middle position of the liquid phase. Thesurface area was calculated as a ratio of the volume of added water tothe measured height of water in the absorber, and its value was40.947 cm2. The gas and liquid in the vessel were agitated at a speed of50 rpm. The value of the cumulative volume of the soup bubble was mea-sured by a soup bubbler for the change of absorption time to obtain theabsorption rate of CO2 and SO2. Each experiment was duplicated at leastonce under identical conditions. It was assumed that the volumetric risingrate of the soup bubble in the soup bubbler attached to the absorptionvessel was equal to the value of the absorption rate of gases. The gaseouscompositions of CO2 and SO2 at inlet of the absorber were using gaschromatography (column: PTFE, 6 feet� 1=8 inch OD, Chromosorb107, 80=100; Detector: TCD). The absorption experiments were carriedout in a range of 0–2.0 kmol=m3 of DAM, 0.01–0.12mole fraction ofCO2, 0.001–0.012 of SO2, and 298–318K at atmospheric pressure.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

A sketch of the experimental set up is presented in Fig. 1. A typi-cal experimental run was carried out as follows (6): The vent valve Ais initially closed and the purge value B is open. Gas is flowed con-tinuously through the absorber D, so as to make sure that the latteris filled with gas at the start of the experiment. During this initial per-iod, the water bath temperature is brought up to the desired value,and the liquid batch is kept in bottle F inside the water bath. Atthe start of the experiment, the liquid batch is poured into funnel Gand the agitator E in D is started. The liquid feed valve C is closed,the purge value B is closed, and the vent valve A is opened, as simul-taneously as possible. Measurements are started at the soap film meterH taking care that there are always two soap films in the meter sothat a continuous reading of the cumulative volume of gas whichhas flowed through the soap film meter (V) can be recorded as a func-tion of time. The gas absorption rate was obtained as a slope of theplots of V vs. time at an initial time. The molar flux of species j(Nj) was calculated by the following equation with the initial volu-metric absorption rates of CO2, V(t1)=t1, obtained from the cumulativevolume of gas which has flowed through the soap film meter.

Nj ¼PT � Po

W

SRT

Vðt1Þt1

ð28Þ

Figure 1. Schematic diagram of the agitated vessel.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

where PT is the atmospheric pressure, PoW , the vapor pressure of

water, S, the surface area of liquid phase, V(t1), the cumulative volumeof gas during the absorption time, t1.

Physicochemical Properties

Both the solubility and diffusivity of solute gases in the liquid medium tosolve the differential equations of Eqs. (1), (2), (11), and (12) are obtainedas follows:

The Henry constant of CO2 in water is obtained from the empiricalequations (40):

HoA ¼ 2:8249� 106 exp � 2044

T

� �ð29Þ

The Henry constant of SO2 in water was estimated by the empiricalformula (41):

HoB ¼ 101:3= exp

510

To� 26970T1 þ 155T2 � 0:0175ToT3=R

� �ð30Þ

where, To ¼ 298:15;Tl ¼ l=To � l=T :T3 ¼ T3 ¼ To=T � l þ lnðT=ToÞ;T3 ¼ T=To � To=T � 2 lnðT=ToÞ

The solubility (Cji) of species j at a given partial pressure (Pj) in aqu-eous solution of a given concentration of DAM was estimated as follows:

Pj ¼ Hoj Cji ð31Þ

The diffusivity of CO2 in water is obtained from the empiricalequations (40):

DoA ¼ 2:35� 10�6 exp � 2119

T

� �ð32Þ

The diffusivity of SO2 in water was estimated by the empiricalformula (42):

DoB ¼ 5:08982� 10�12T exp 5:15581� 1243:06

T � 53:19

� �ð33Þ

The diffusivity of species j in aqueous DAM solution (43) wasestimated as follows:

Dj ¼ Doj

lwl

� �2=3

ð34Þ

DC was estimated by the method of Wilke (30).


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

Viscosity of aqueous DAM solution was measured using aBrookfield viscometer (Brookfield Eng. Lab. Inc, USA).

RESULTS AND DISCUSSION

Absorption of CO2 in CO2-DAM System

To determine the reaction order with respect to CO2 and DAM in a fastreaction regime of CO2-DAM system, the absorption rates (NA,exp) ofCO2 were measured in a range of 0–2.0 kmol=m3 of DAM,0.01–0.12mole fraction of CO2, and 298–318K.

Figure 2 shows logarithmic plots of NA,exp vs. CAi at a typical CCo of0.1 kmol=m3 and different temperatures.

The plots present straight lines (correlation coefficient (r2)> 0.999)with a slope of unity in each temperature. This, according to Eq. (9), indi-cates that the reaction order with respect to CO2 is 1.

To determine the reaction order with respect to the concentration ofDAM, logarithmic plots of NA;exp=CAiD

0:5A vs. CCo at a typical yA of 0.02

and different temperatures are shown in Fig. 3.

Figure 2. Effect of CAi on NA into aqueous DAM at CCo¼ 0.1 kmol=m3 anddifferent temperatures.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

Figure 3. Determination of reaction rate constant (kA) and order with respect toDAM at yA¼ 0.02 and different temperatures.

Figure 4. Arrhenius plot of the CO2-DAM system.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

Each of these plots as shown in Fig. 3 is a straight line (r2> 0.999)with a slope of 1. This, according to Eq. (9), indicates that the reactionorder with respect to DAM is 1.

The values of the reaction rate constant (kA) of CO2-DAM were cal-culated from the intercept of the plots of data in Fig. 3 and they havebeen found to be 7516, 11998, 19766m3=kmol�s at 298, 308, 318K,respectively. Figure 4 shows the Arrhenius plots of the values of kA at dif-ferent temperatures using data mentioned above.

Linear regression analysis of the Arrhenius plots gives the followingexpression for kA (r2¼ 0.998).

kA ¼ 1:72� 1012 expð�5747=TÞ ð41Þ

Table 1. The values of Ha and Ei in CO2=DAM and SO2=DAM system

T(K) CCo(kmol=m3) yA Ha Ei T(K) CCo(kmol=m3) yB Ha Ei

298 0.1 0.01 159 189 298 0.1 0.001 29 320.02 76 95 0.002 14 160.04 39 48 0.004 7 90.08 21 25 0.008 4 50.12 11 17 0.012 3 4

308 0.1 0.01 184 239 308 0.1 0.001 43 440.02 103 120 0.002 19 230.04 45 60 0.004 10 120.08 21 31 0.008 5 60.12 13 21 0.012 4 5

318 0.1 0.01 219 295 318 0.1 0.001 59 610.02 122 148 0.002 28 310.04 72 75 0.004 14 160.08 26 38 0.008 7 80.12 19 26 0.012 4 6

298 0.1 0.02 76 95 298 0.1 0.002 14 160.5 179 471 0.5 33 771.0 264 942 1.0 48 1532.0 399 1882 2.0 73 306

308 0.1 0.02 102 120 308 0.1 0.02 19 230.5 239 595 0.5 45 1101.0 350 1189 1.0 66 2182.0 521 2378 2.0 98 435

318 0.1 0.02 122 148 318 0.1 0.02 29 310.5 282 736 0.5 66 1481.0 412 1470 1.0 97 2962.0 611 2939 2.0 143 590


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

The corresponding value of the activation energy has been calculated tobe 48.0 kJ=mol.

To validate the condition of a fast pseudo-first-order reaction withrespect to CO2, the values of Ha and Ei were calculated and listed inTable 1. Because the values of Ha and Ei in Table 1 satisfy Eq. (5), theabsorption of CO2 into DAM solution in this study belongs to a fastreaction regime.

To ensure that the gas phase resistance is really negligible in all run,plots of PA=NA,exp vs. Ho

A=ðkADACCoÞ0:5 at different temperatures havebeen made following Eq. (10) for m¼ 1, n¼ 1. These plots are presentedin Fig. 5.

It can be seen from Fig. 5 that all plots of PA=NA,exp vs.Ho

A=ðkADACCoÞ0:5 are straight lines with slope of 1, passing through theorigin with r2¼ 0.991. This, according to Eq. (10), signifies negligiblegas phase resistance.

The specific rate (NA,fem) of CO2 absorption was estimated from thesolution of Eqs. (1) and (2) with the boundary conditions of Eqs. (3) and(4), using the numerical method of FEMLAB program. The comparisonof the observed and estimated molar flux of CO2 in DAM concentrationrange of 0.1–2.0 kmol=m3, 0.02mole fraction of CO2, and 298–313K isshown in Fig. 6.

Figure 5. Verification of no gas phase resistance for absorption of CO2 intoaqueous DAM at yA¼ 0.02 and different CCO and temperatures.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

As shown in Fig. 6, the observed values of the molar flux agreewith the estimated values (r2¼ 0.981) and standard deviation¼ 0.038),suggesting that the governing equation of Eqs. (1) and (2), as well asthe estimated physical properties such as CAi, DA, and DC, may beplausible.

Absorption of SO2 in SO2-DAM System

To determine the reaction order with respect to the concentration of SO2

and DAM in SO2-DAM system, the absorption rates (NB,exp) of SO2

were measured with a range of 0–2.0 kmol=m3 of DAM,0.001–0.012mole fraction of SO2, and 298–318K.

To determine the reaction order with respect to SO2, logarithmicplots of NB,exp vs. CBi at a typical CCo of 0.1 kmol=m3 and different tem-peratures are shown in Fig. 7.

The plots present straight lines (r2> 0.987) with a slope of unity ineach temperature. This, according to Eq. (9), indicates that the reactionorder with respect to SO2 is 1.

Figure 6. Comparison of estimated and measured values of absorption rate ofCO2.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

To determine the reaction order with respect to the concentration ofDAM, logarithmic plots of NB;exp=CBiD

0:5B vs. CCo at a typical yB of 0.002

are shown in Fig. 8.Each of these plots as shown in Fig. 8 is a straight line (r2> 0.985)

with a slope of 1. This, according to Eq. (9), indicates that the reactionorder with respect to DAM is 1.

The values of the reaction rate constant (kB) of SO2-DAM were cal-culated from the intercept of the plots of data in Fig. 8 and they havebeen found to be 12076, 19265, 29224m3=kmol�s at 298, 308, 318K,respectively. Figure 9 shows the Arrhenius plots of the values of kB at dif-ferent temperatures using data mentioned above.

Linear regression analysis of the Arrhenius plots gives the followingexpression for kB (r2¼ 0.991).

kB ¼ 6:43� 1011 expð�5309=TÞ ð42Þ

The corresponding value of the activation energy has been calculated tobe 44.2 kJ=mol.

To validate the condition of a fast pseudo-first-order reaction withrespect to SO2, the values of Ha and Ei were calculated and listed inTable 1. Because the values of Ha and Ei in Table 1 satisfy Eq. (5), the

Figure 7. Effect of CBi on NB into aqueous DAM at CCo¼ 0.1 kmol=m3 and dif-ferent temperatures.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

Figure 8. Determination of reaction rate constant (kB) and order with respect toDAM at yA¼ 0.002 and different temperatures.

Figure 9. Arrhenius plot of the SO2-DAM system.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

absorption of SO2 into DAM solution in this study belongs to a fastreaction regime.

To ensure that the gas phase resistance is really negligible in all run,plots of PB=NB,exp vs. Ho

B=ðkBDBCCoÞ0:5 at different temperatures havebeen made following Eq. (10) for m¼ 1, n¼ 1. These plots are presentedin Fig. 10.

It can be seen from Fig. 10 that all plots of PB=NB,exp vs.Ho

B=ðkBDBCCoÞ0:5 are straight lines with slope of 1, passing through theorigin with r2¼ 0.993. This, according to Eq. (10), signifies negligiblegas phase resistance.

The specific rate (NB,fem) of SO2 absorption was estimated from thesolution of Eq. (1) and (2) with the boundary conditions of Eq. (3) and(4), using the numerical method of FEMLAB program. The comparisonof the observed and estimated molar flux of SO2 in DAM concentrationrange of 0.1–2.0 kmol=m3, 0.002mole fraction of CO2, and 298–313K isshown in Fig. 11.

As shown in Fig. 11, the observed values of the molar flux agree withthe estimated values (r2¼ 0.988 and standard deviation¼ 0.011), suggest-ing that the governing equation of Eqs. (1) and (2), as well as theestimated physical properties such as CBi, DB, and DC, may be plausible.

Figure 10. Verification of no gas phase resistance for absorption of SO2 intoaqueous DAM at yA¼ 0.002 and different CCO and temperatures.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

The diffusivity (DA and DB) and solubility (CAi and CBi), required tosolve the differential equations of Eqs. (1) and (2), are affected by thephysical properties of the solution and the calculated fluxes (NA,fem

and NB,fem) increase with decreasing them. DA and DB were correctedwith the viscosity of the solution using Eq. (34), but CAi and CBi in waterwere used. Because CAi and CBi might be larger than them in the DAMsolution, NA,fem and NB,fem were smaller than NA,exp and NB,exp, asshown in Figs. 6 and 11.

Simultaneous Absorption of CO2 and SO2 in CO2-SO2-DAM System

Mixtures of gases of CO2 and SO2 are simultaneously absorbed into aqu-eous DAM solution within a range of 0.1–2.0 kmol=m3 of DAM at0.2mole fraction of CO2, 0.02mole fraction of SO2, and 298K to obtainthe simultaneous absorption rate (NT).

The experimental absorption rate (NT,exp) was plotted against CCo inFig. 12.

As shown in Fig. 12, NT,exp increases with increasing CCo, due toincrease in concentrations of the reactant of DAM.

The simultaneous absorption rate (NT,fem) of CO2 and SO2 wasobtained from the solution of Eqs. (11) and (12) with the boundary

Figure 11. Comparison of estimated andmeasured values of absorption rate of SO2.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

conditions of Eqs. (13) and (14), using the numerical method of FEM-LAB program and plotted as dotted line in Fig. 12. On the other hand,it (NT,ins) was obtained by Eq. (17) through bA and bB of Eqs. (26)and (27) under the conditions of the fast reaction regime in CO2-DAMsystem and the instantaneous reaction regime in SO2-DAM system andas the solid line in Fig. 12. As shown in Fig. 12, NT,exp approaches toNT,fem more closely with correlation coefficient (r2) of 0.995 than NT,ins

with r2 of 0.983 and NT,ins approaches to NT,fem very well with r2 of0.996. This means that the approximate analytical solution, presentedby Hikita et al. (37), under the conditions that the absorption of CO2

belongs to the second-order reaction of finite rate and the absorptionof SO2 belongs to the instantaneous reaction regime may be used topredict the simultaneous absorption rate of CO2 and SO2 into DAMsolution.

CONCLUSIONS

Mixture of CO2 and SO2 are simultaneously absorbed into DAM in astirred, semi-batch tank with a planar, gas-liquid interface within arange of 0–2.0 kmol=m3 of DAM, 0.01–0.12mole fraction of CO2,

Figure 12. Simultaneous absorption rate of CO2 and SO2 at yA¼ 0.2 andyB¼ 0.02, and 25�C.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

0.001–0.012mole fraction of SO2, and 298–318K. Diffusivity and Henryconstants of CO2 and SO2 were obtained from the reference data.

Absorption data of CO2 and SO2 in DAM solution are used to verifythat the reactions in CO2-DAM system and SO2-DAM are first orderwith respect to both gases and DAM. The measured rates of simulta-neous absorption of CO2 and SO2 were compared with those calculatedby the numerical and approximate solutions of mass balances withreaction regimes of both gases through verification of the reaction regimein the CO2-SO2-DAM system.

ACKNOWLEDGMENTS

This work was supported by Brain Korea 21 Project and a grant(2006-C-CD-11-P-03-0-000-2007) from the Energy Technology R&D ofKorea Energy Management Corporation. Dae-Won Park is also thankfulfor KOSEF (R01-2007-000-10183-0).

REFERENCES

1. Caplow, M. (1968) Kinetics of carbamate formation and breakdown. J. Am.Chem. Soc., 90: 6795.

2. Danckwerts, P.V. (1979) The reaction of CO2 in ethanolamines. Chem. Eng.Sci., 34: 443.

3. da Silva, E.F.; Sendsen, H.F. (2004) Ab initio study of the reaction of cara-mate formation from CO2 and alkanolamine. Ind. Eng. Chem. Res., 43: 3413.

4. Mimura, T.; Suda, T.; Honda, A.; Kumazawa, H. (1998) Kinetics of reactionbetween carbon dioxide and sterically hindered amines for carbon dioxiderecovery from power plant flue gases. Chem. Eng. Commun., 170: 245.

5. Park, S.W.; Park, D.W.; Oh, K.J. (2008) Absorption of carbon dioxide intoaqueous solution of sodium glycinate. Sep. Sci. Technol., 43: 3003.

6. Park, S.W.; Park, D.W.; Oh, K.J.; Kim, S.S. (2009) Simultaneous absorptionof carbon dioxide and sulfur dioxide into aqueous 2-amino-2-methyl-1-pro-panol. Sep. Sci. Technol., 44: 543.

7. Sada, E.; Kumazawa, H.; Nishimura, H. (1983) Absorption of sulfur dioxideinto aqueous double slurries dontaining limestone and magnesium hydroxide.AIChE J., 29: 60.

8. Uchida, S.; Ariga, O. (1985) Absorption of sulfur dioxide into limestoneslurry in a stirred tank. Can. J. Chem. Eng., 63: 778.

9. Egan, B.Z.; Felker, L.K. (1986) Removal of SO2 from simulated flue gas bymagnesia spray absorption. Ind. Eng. Chem. Process Des. Dev., 25: 558.

10. Ruhland, F.; Kind, R.; Weiss, S. (1991) The kinetics of the absorption ofsulfur dioxide in calcium hydroxide suspensions. Chem. Eng. Sci., 46: 939.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

11. Brogren, C.; Karlsson, H.T. (1997) Modeling the absorption of SO2 in aspray scrubbing using the penetration theory. Chem. Eng. Sci., 52: 3085.

12. Berman, Y.; Tanklevsky, A.; Oren, Y.; Tamir, A. (2000) Modeling andexperimental studies of SO2 absorption in coaxial cylinders with impingingstreams: Part I. Chem. Eng. Sci., 55: 1009.

13. Stein, J.; Kind, M.; Schlunder, E. (2002) The influence of HCl on SO2 absorp-tion in the spray dry scrubbing process. Chem. Eng. J., 86: 17.

14. Hikita, H.; Asai, S.; Nose, H. (1978) Absorption of sulfur dioxide into water.AIChE J., 24: 147–149.

15. Hikita, H.; Asai, S.; Tsufi, T. (1977) Absorption of sulfur dioxide intoaqueous solution sodium hydroxide and sodium sulfite solution. AIChE J.,23: 538.

16. Roberts, D.L.; Friedlander, S.K. (1980) Sulfur dioxide transport throughaqueous solutions: Part I. Theory. AIChE J., 26: 593.

17. Chang, C.S.; Rochelle, G.T. (1981) SO2 absorption into aqueous solution.AIChE J., 27: 292.

18. Hikita, H.; Konish, K. (1983) The absorption of SO2 into aqueous Na2CO3

solutions accompanied by the desorption of CO2. Chem. Eng. J., 27: 167.19. Ebrahimi, S.; Picioreanu, C.; Kleerebezem, R.; Heijnen, J.J.; van Loosdrecht,

M.C.M. (2003) Rate-based modeling of SO2 absorption into aqueousNaHCO3=Na2CO3 solutions accompanied by the desorption of CO2. Chem.Eng. Sci., 58: 3589.

20. Colle, S.; Vanerschuren, J.; Thomas, D. (2004) Pilot-scale validation of thekinetics of SO2 absorption into sulfuric acid solutions containing hydrogenperoxide. Chem. Eng. Process, 43: 1397.

21. Erga, O. (1986) SO2 recovery by means of adipic acid buffers. Ind. Eng.Chem. Fundam., 25: 692.

22. Regalbuto, M.C.; Strieder, W.; Varma, A. (1991) An extension ofsemi-empirical gas-liquid equilibrium model for sulfur dioxide absorptionin aqueous sodium citrate solution. Chem. Eng. Sci., 46: 3314.

23. Xia, J.; Rumpf, B.; Maurer, G. (1999) Solubility of sulfur dioxide in aqueous-solutions of acetic acid, sodium acetate, and ammonium acetate in thetemperature range from 313 to 393K at pressures up to 3.3MPa. Ind. Eng.Chem. Res., 38: 1149.

24. Dutta, B.K.; Basu, R.K.; Pandit, A.; Ray, P. (1987) Absorption of SO2

in citric acid-solution citrate buffer solutions. Ind. Eng. Chem. Res., 26:1291–1296.

25. Ho, M.P.; Klinzing, G.E. (1986) Absorption of sulfur dioxide and nitric oxideby amines and N-cyclohexyl-2-pyrrolidone. Can J. Chem. Eng., 64: 243.

26. Riesenfeld, F.C.; Kohl, A.L. (1974) Gas Purification; Gulf Publ. Co.:Houston.

27. Basu, R.K.; Dutta, B.K. (1987) Kinetics of absorption of sulfur dioxide indimethylaniline solution. Can. J. Chem. Eng., 65: 27.

28. van Dam, M.H.H.; Lamine, A.S.; Roizard, D.; Lochon, P.; Roizard, P.(1997) Selective sulfur dioxide absorption using organic solvents. Ind. Eng.Chem. Res., 36: 4628–4637.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

29. Nagel, D.; de Kermadec, R.; Lintz, H.G.; Roizard, C.; Lapicque, F. (2002)Absorption of sulfur dioxide in N-formylmorpholine: Investigations of thekinetics of the liquid phase reaction. Chem. Eng. Sci., 57: 4883.

30. Danckwerts, P.V. (1970) Gas-Liquid Reactions; McGraw-Hill: New York.31. Hikita, H.; Asai, S.; Takatsuka, T. (1972) Gas absorption with a two step

instantaneous chemical reaction. Chem. Eng. J., 4: 31.32. Ho, M.P.; Klinzing, G.E. (1986) Absorption of sulfur dioxide and nitric oxide

by amines and N-cyclohexyl-2-pyrrolidone. Can J. Chem. Eng., 64: 243.33. Sada, E.; Kumazawa, H.; Yoshikawa, Y. (1988) Simultaneous removal of

NO and SO2 by absorption into aqueous mixed solutions. AIChE J., 34:1215.

34. Hix, R.M.; Lynn, S. (1991) Reactive absorption of H2S by a solution of SO2

in poly (glycol ether): Effect of a volatile dissolved reactant on mass transferenhancement. Ind. Eng. Chem. Res., 30: 930.

35. Kenig, E.Y.; Schneider, R.; Gorak, A. (1999) Rigorous dynamic modeling ofcomplex reactive absorption processes. Chem. Eng. Sci., 54: 5195.

36. Goetter, L.A.; Pigford, R.L. (1971) Computational studies of the simulta-neous chemical absorption of two gases. AIChE J., 17: 793.

37. Hikita, H.; Asai, S.; Ishikawa, H. (1979) Simultaneous absorption of twogases in a reactive liquid, one gas reacting instantaneously. Chem. Eng., J.,18: 169.

38. Daraiswany, L.K.; Sharma, M.M. (1984) Heterogeneous Reaction: Analysis,Example and Reactor Design; John Wiley Sons: New York.

39. Yu, W.; Astarita, G.; Savage, D.W. (1985) Chem. Eng. Sci., 40: 1585.40. Versteeg, G.F.; van Swaaij, W.P.M. (1988) Solubility and diffusivity of acids

gases (CO2, N2O) in aqueous alkanolamine solutions. J. Chem. Eng. Data,33: 29.

41. Saha, A.K.; Bandyopadhyay, S.S.; Biswas, A.K. (1993) Solubility and diffu-sivity of N2O and CO2 in aqueous solutions of 2-amino-methyl-1-propanol.J. Chem. Eng. Data, 38: 78.

42. Pasiuk-Bronikowska, W.; Rudzinski, K.J. (1991) Absorption of SO2 intoaqueous systems. Chem. Eng. Sci., 46: 2281.

43. Cussler, E.L. (1984) Diffusion; Cambridge University Press: New York.


Dow

nloa

ded

by [

Uni

vers

ity o

f C

hica

go L

ibra

ry]

at 2

3:43

10

Oct

ober

201

4

Documents

Simultaneous Absorption of Carbon Dioxide and Sulfur Dioxide into Aqueous 1,8-Diamino-p-menthane