PZ Mixture Using

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Kinetics of CO2 Absorption in Concentrated K2CO3/PZ Mixture by using a Wetted-Wall Column Qiangwei Li, Yi Wang, Shanlong An, and Lidong Wang Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b00793 • Publication Date (Web): 31 Jul 2016 Downloaded from http://pubs.acs.org on August 10, 2016

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Gas Phase

Gas-liquid interface

Liquid Phase

HCO3-

HCO3PZCOO-

CO2 PZ(COO-)2

PZ

CO2 CO2 PZCOO-

ACS Paragon Plus Environment

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Kinetics of CO2 Absorption in Concentrated K2CO3/PZ Mixture by using a Wetted-Wall Column Qiangwei Li1, Yi Wang2, Shanlong An1, Lidong Wang1,∗∗ 1. School of Environmental Science and Engineering, North China Electric Power University, Baoding 071003, China 2. Mianyang Environmental Monitoring Central Station, Mianyang, 621000, China

Abstract Using a K2CO3/piperazine (PZ) mixture as a typical phase change absorbent has promising applicability for carbon dioxide (CO2) capture in coal-fired power plants, which would contribute to a low energy consumption for solvent regeneration. In this study, the reaction rate of CO2 with a concentrated K2CO3/ PZ mixture was measured in a wetted-wall column. At a CO2 loading close to the saturable absorption correlative physical parameters were calculated. The effects of operating conditions, including gas flow rate, slurry flow rate, PZ concentration, CO2 loading, K2CO3 mass fraction, and temperature, on the absorption rate of CO2 were investigated. The results showed that absorption rates were sensitive to the effects of the gas flow rate and CO2 loading. PZ concentration and K2CO3 mass fraction also substantially influenced the CO2 absorption rate. However, minor changes in the CO2 absorption rate were observed when the slurry flow rate and temperature increased. On the basis of the pseudo-first-order model, the absorption rate determined in this study was controlled ∗

Corresponding author. Tel.: +86 312 7525511. E-email address: [email protected]


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by the mass transfer in both gas film and liquid film. The results can serve as a useful reference for designing CO2 removal mechanisms by using the K2CO3/PZ mixture. Keywords: Carbon dioxide; Wetted-wall column; Phase change solvent; Absorption rate; Enhancement factor

1. Introduction Carbon dioxide (CO2) emissions, which are mainly produced from coal-fired power plants, have attracted growing concern in recent decades. Different technologies, including membranes, cryogenics, adsorption, and absorption, for capturing CO2 from flue gas streams have been studied1. CO2 post-combustion capture through chemical absorption has been commonly used in power plants. Most chemical absorbents are amine-based

organics,

such

as

monoethanolamine,

diethanolamine,

and

2-amino-2-methylpropanol2-6. However, using such absorbents for CO2 capture is marred by a high operating cost. CO2 capture was estimated to incur an 80% increase in the cost of electricity in coal-fired power plants7, and this is mainly because of the high energy consumption associated with regenerating absorbents. Recently, a novel absorption process that entails using a phase change solvent, which can form two phases under specific condition8, has attracted considerable attention. Because the absorbed CO2 is concentrated in one of the two phases, only a portion of the absorbent must be sent to a stripper. Therefore, the phase change solvent demonstrates a potential in reducing energy consumption for solvent regeneration. Several studies on phase change solvents have been published. The DMX™ process was tested by IFPEN in the EUOCTAVIUS project, in which solvents could


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form two immiscible liquid phases9. Combining primary/secondary and tertiary amines resulted in the formation of two liquid phases that could be separated on the basis of different densities after CO2 absorption10. Precipitating systems with amino acid salts11 and carbonated solutions12 demonstrate a potential for large energy savings in CO2 capture processes; in such systems, the solid phase is formed by precipitation during the absorption of CO2 with aqueous solutions. Aqueous potassium carbonate (K2CO3) is a typical phase change solvent. In the traditional hot-CAP (carbonate absorption process), potassium bicarbonate (KHCO3) is produced during CO2 absorption, and precipitated in aqueous solutions because of its low solubility. The heats regenerated in various processes, including the benchmark MEA, amine-based solid adsorption and the baseline hot-CAP, are compared in Tab. 1. The results indicated that the hot-CAP decreased the energy penalty of CO2 capture by 33.3%. Although the heat duty of the amine-based solid adsorption system is slightly lower than that of the hot-CAP process, the recycling of solid is a critical issue for its practical application. Furthermore, the low loading capacity of the solid sorbent resulting in the enormous amount of the solid sorbent also retards its application. Table 1 Comparison of the regeneration heat by the different CO2 absorption process Types of heat,

benchmark 30wt%

amine-based solid

baseline hot-CAP

kJ/kg CO2

MEA system13

adsorption system13

system14

Sensible heat

1505

457

580

Reaction heat

1932

1619

650

Vaporization heat

462

380

420

Dissolution heat

-

-

950


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Total heat duty

3900

2460

2600

Regarding research on the use of aqueous K2CO3 as a CO2 absorbent, most literatures15-17 provided useful correlated kinetic data of a low concentration of aqueous K2CO3 and low CO2 loading, which could barely form sufficient potassium bicarbonate to achieve the goal of separating liquids and solids. Studies on concentrated K2CO3 slurry at a loading close to saturation absorption are scarce, in which the precipitation of KHCO3 could be gradually observed owning to the CO2 absorption. It should also be noted that the CO2 absorption rate of pure aqueous K2CO3 is relatively slow. Hence, adding a promoter to aqueous K2CO3 is necessary to expedite the CO2 absorption rate, enabling to downsize the absorber and hence lowering the cost of CO2 capture by the hot-CAP process. Therefore, the use of concentrated and promoted K2CO3 slurry as a CO2 absorbent warrants further investigation. In the present study, the concentrated K2CO3 slurry was used for CO2 absorption, and piperazine (PZ) was used as a promoter. The reaction rate of CO2 was measured in a wetted-wall column (WWC), and correlative physical parameters, which provide a useful reference for CO2 removal by using concentrated and promoted K2CO3 slurry, were calculated. 2 Experiment 2.1 Apparatus and procedure Fig.1 illustrates a schematic of the apparatus used for CO2 absorption in this study.


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A WWC was fabricated according to a design reported in the literature17-19, which used the gas-liquid contactor to measure the absorption rate of CO2. The column was constructed from a stainless steel tube with an interfacial area for mass transfer of 38.52 cm2. The outside diameter of the stainless steel tube was 1.26 cm and the length was 9.1cm. Hot K2CO3 slurry was pumped from inside and formed a liquid film over the outer surface of the stainless steel tube, and CO2 entered the WWC from the bottom and contacted with the liquid film.

Fig.1 Overall experimental flow diagram for CO2 absorption with WWC

The slurry was prepared first by bubbling CO2 into the K2CO3/PZ. The CO2 loading was measured by hydrochloric titration as detailed in the supplementary materials. The absorption slurry was then reserved in a 2000-mL of flask in a heating bath at the


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temperature ranging from 60 to 80 °C and pumped through the WWC in a closed loop. The flow rate of absorption slurry, which varied from 1.37 to 2.65 cm3.s−1, was controlled using a peristaltic pump. Thermostatic water in the water bath was also circulated around the WWC, maintaining the temperature of the entire apparatus. The inlet temperatures of the slurry were measured using a thermocouple and kept constant by a temperature controller with a heating tape. N2 and CO2 mixtures were pre-saturated with vapour by passing them through a water bath and continually fed into the WWC. The gas flow rate and CO2 concentration were regulated by the mass flow controllers. The gas exiting from the top of WWC was directed to a condenser tube with ice water and a dry tube with silica gel. The GXH-3011N infrared CO2 analyzer was used to measure the outlet CO2 concentration continuously. 2.2. Materials K2CO3 (≥ 99% purity) and PZ (≥ 99.99% purity) were purchased from Aladdin reagent (Shanghai, China). N2 (≥ 99.9% purity) and CO2 (≥ 99.9% purity) were supplied by Baoding North Special Gases CO., LTD. (China). All reagents were used as received without any further purification. 2.3 Methods 2.3.1 Reaction process The absorption of CO2 into aqueous K2CO3 is generally described by two parallel and reversible reactions20.

CO 2 (aq ) + OH − ⇔ HCO 3−

（1）

HCO 3− + OH − ⇔ CO 32 − + H 2 O

（2）


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As a promoter, PZ was added into the absorption slurry, in which the reactions occurred as follows21:

PZH+ + H 2O ⇔ PZ(l ) + H 3O +

（3）

PZ(l) + CO2 (aq) + H 2O ⇔ PZCOO− + H3O+

（4）

H + PZCOO − + H 2 O ⇔ PZCOO − + H 3 O +

（5）

PZCOO− + H 2O + CO 2 ⇔ PZ(COO− ) 2 + H 3O

（6）

PZ(COO − ) 2 + 2H 2 O ⇔ PZ + 2HCO 3−

（7）

Studies have shown that the aforementioned CO2 absorption in K2CO3/PZ mixture follows a pseudo-first order reaction. 2.3.2 Physical and chemical property estimation Viscosity was estimated using a correlative data given by Bocard and Mayland22. In the following equation, T denotes the temperature in Kelvin and WE denotes the equivalent weight percent of K2CO3. µ ( cp ) = A1 × T 2 + B1 × T + C1

（8）

A1 = 2.79 ×10−7 ⋅WE 2 − 2.04 ×10−6 ⋅WE + 9.65 ×10−5

（9）

B1 = −2.00 ×10−4 ⋅WE2 + 1.37 × 10−3 ⋅ WE − 7.23 ×10−2

（10）

C1 = 3.63 × 10 −2 ⋅ WE2 − 0.225 ⋅ WE + 13.86

（11）

The density of solutions was also estimated using correlation data provided by Bocard and Mayland22. In the following equations, W is a function of the weight percent of K2CO3.

（ ρ g/cm）= A2 ×T + B2

(12)

A2 = −1.93 ×10−6 ⋅W − 4.74 ×10−4

(13)


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B2 = 9.787 ×10−3 ⋅W + 1.147

(14)

The diffusivity of CO2 in the solution was determined by a correlation proposed by Ratcliff and Holdcroft23. DCO2 ,K 2CO3

µ  = DCO2 ,H 2O  H 2O  µ K 2 CO3  

0.82

(15)

Henry’s law constant, HCO2, was calculated as a function of ionic strength according to the equations developed by Schumpe and Markham24, 25 as follows: H  Lg CO 2 , K 2 CO3  = ∑ (hi + hG )C i H CO , H O 2 2  

(16)

2.3.3 Data analysis The concentration profile of CO2 reacting with an amine in a second order reaction20 was given by: DCO2

∂ 2 [ CO 2 ] − k1 [ PZ ][ CO 2 ] = 0 ∂x 2

（17）

If the reactant concentration across the reactive boundary layer is constant and equal to the bulk liquid concentration, k2 is a pseudo-first-order rate constant that can be used26 to represent k1[PZ]. DCO 2

∂ 2 [ CO 2 ] − k 2 [ CO 2 ] = 0 ∂x 2

（18）

The solution to this equation (for reversible reactions) is as follows in which the subscript b denotes the bulk solution composition26: N CO 2 = − DCO 2

∂[CO 2 ] ∂x

x=0

=

DCO2 k1 [ PZ ] H CO 2

b

( Pi − P *)

(19)

Meanwhile, the mass transfer process was enhanced by chemical reactions between the gaseous and liquid phases. The total resistance to mass transfer (1/KG) was


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modeled as the sum of gas film (1/kg) and liquid film resistance (1/ kL) as follows: 1 1 1 1 H CO2 = + = + K G k g k L k g Ek L0

N CO2 = K G ( P − P* ) =

(20)

Ek L0 ( Pi − P* ) H CO2

(21)

Hence the enhancement factor, i.e., the Hatta number, is the ratio of flux with chemical reactions to that without chemical reactions which is defined as follows: E = Ha =

DCO2 k1 [ PZ]

b

(22)

kL0

The physical liquid phase mass transfer coefficient kL0 was calculated as1:

Q (1 − θ )  31/321/2   Q1/3h1/ 2W 2/3   g ρ  k = =  1/ 2     F F  π   µ 

1/6

0 L

D CO2 1/ 2

(23)

The gas phase transfer coefficient of the WWC, kg, was derived as follows27: d Sh = 1.075(Re ⋅ Sc ⋅ )0.85 h

(24)

The specific absorption rate of CO2, N CO 2 , was characterised according to the overall gas phase mass transfer coefficient.

N CO2 = K G ( P − P* ) = K G P − K G P*

(25)

The overall mass transfer coefficient KG was derived from the slope of the N CO 2 versus the log mean pressure Plm. Several data points of inlet and outlet CO2 partial pressures were obtained on the basis of the CO2 concentration. The specific absorption rate, N CO 2 , was calculated from these data and the interfacial area (F) of the WWC, as shown in equation (21). Plm is the log mean average of bulk gas partial pressures of CO2 across the WWC and is assumed to represent P. Plm is the partial pressure of CO2 in the contactor and was calculated according to the log mean average as shown in


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equation (22): N CO 2 =

Plm =

(cin % − cout % )Vg

（26）

22.4F

Pin − Pout P  ln  in  P out  

（27）

The equilibrium partial pressure, P*, was calculated when the specific absorption rate was equal to zero. Fig.2 shows an example of the equilibrium partial pressure derived for 40 wt% K2CO3 with 0.5 M PZ at a loading of 1.23 mol.L-1.

12.0

-2

9.0

-7

-1

Flux (×10 mol·cm ·s )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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6.0

Slope=KG

3.0 P *=3440Pa

0.0 5000

10000

15000

20000

25000

Plm (Pa)

Fig.2 Graphical representation of P* for 40 % wt K2CO3 with 0.5 M PZ at a loading of 1.23 mol.L-1 at 70 °C

3 Results and discussion 3.1 Comparison of promoting performance of PZ with MEA The promoting effect of PZ on the absorption rate of 40% K2CO3 was compared with MEA. The comparison in terms of the absorption capacity was performed at CO2 loading of 0.37 M with 0.5 M pure PZ. The results shown in red bars in Fig.3


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indicated that the absorption rate of mixture (40 % K2CO3 / 0.5 M PZ) is slightly higher than the combined one when the K2CO3 (40%) and PZ (0.5 M) were used alone. The absorption rate follows the order: (40 % K2CO3/0.5 M PZ)> (40 % K2CO3+ 0.5 M PZ) > (40 % K2CO3) > (0.5 M PZ). It is also proved that PZ acted as a promising promoter instead of an absorbent.

12.0

5M MEA 9.0

loading=1.23M loading=0.37M

-7

-2

-1


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6.0

3.0

0.0

40%K2CO3

0.5 M PZ

40%K2CO3/

40%K2CO3/

40%K2CO3/

0.5 M MEA

0.5 M PZ

1.26 M PZ

Fig.3 Comparison of promoting performance of PZ with MEA: gas flow rate of 30 mL.s−1, slurry flow rate of 2.23 mL·s-1, and inlet CO2 concentration of 10 % at 70°C.

When the CO2 loading increased to 1.23 M, the absorption rate of K2CO3/PZ mixture was 2.44 times greater than that of pure K2CO3, although the pure PZ (0.5M) had approached the saturation in which the absorption rate was almost zero. However, only 1.39 times of increment was observed for the MEA at the same concentration (, see the blue bars in Fig.3). The results suggested that PZ provided better performance than MEA as a promoter; and this finding is consistent with those published elsewhere18, 28.


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Moreover, the experiment using 5 M MEA solvent as benchmark was conducted for the purpose of comparison. Although the absorption performance of pure PZ was better than MEA, the concentration of PZ was 3.74 M less than MEA in order to keep the total alkaline at 5 M. The results indicated that the absorption rate of 5 M MEA is 1.8 times greater than that of the mixture of (40% K2CO3/0.5 M PZ) with the same CO2 loading at 1.23mol/L. However, the absorption will be considerably promoted with the increase of PZ.

3.2 Effect of temperature on CO2 absorption rate The effect of temperature on the absorption rate is shown in Fig.4. The dependency of CO2 absorption rate on temperature is associated with the chemical reaction rate and diffusion rate. The chemical reaction rate will be enhanced with the increasing of temperature. Meanwhile the Henry coefficient will increase, resulting in a considerable decline of diffusion rate. As a result, the temperature, varying from 60 0

C to 80 0C, has little effect on the overall absorption rate with the high CO2 loading

of 1.23 mol.L−1. Thus, the following experiments were all carried out at 70 0C.

4.0

3.0

-7

-2

-1


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2.0

1.0

0.0 60

70

80

Temperature (°C)

Fig.4 Effect of temperature on the CO2 absorption rate: 40 % K2CO3/0.5 M PZ, CO2


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loading of 1.23 M, gas flow rate of 30 mL.s−1, slurry flow rate of 2.23 mL·s-1, and inlet CO2 concentration of 10 %.

3.3 Effect of the PZ concentration on the CO2 absorption rate The effect of PZ concentration on the CO2 absorption rate is shown in Fig.5. It indicated that the absorption rate increased considerably with the PZ concentration, which was in good agreement with the Dang’s results18. Regarding the PZ concentration, changes in the total mass transfer resistance were influenced by the enhancement factor (Table.1). It can be figured out that the absorption rate with respect to the pseudo-first order kinetics was associated with the diffusion coefficient, equilibrium pressure and the concentration of PZ. Thus the reaction order of PZ concentration with respect to the overall absorption rate should be 0.5, which agreed well with the results in Fig.5. The overall mass transfer coefficient, KG, at 0.5M PZ (5.63×10-11 mol·cm-2·s-1·Pa) is approximately 15% higher than Cullinane's result (KG=4.88×10-11 mol·cm-2·s-1·Pa), which was carried out with 0.6 M PZ at 60°C. It might because our experiments were conducted about 10 °C higher than Cullinane's work.


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10.0

8.0 1.8 7

ln(NCO2 ×10 )

-11

-2

-1

KG (×10 mol·cm ·s ·Pa)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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6.0

4.0

1.5

y=0.44x+1.57

1.2 0.9 0.6

-1.8 -1.2 -0.6

0.0

ln(cPZ) 2.0

0.0

0.3

0.6

0.9

1.2

1.5

-1

Concentration of PZ (mol·L )

Fig.5 Effect of the PZ concentration on the CO2 absorption rate: 40 % K2CO3, CO2 loading of 1.23 M, gas flow rate of 30 mL.s−1, slurry flow rate of 2.23 mL·s-1, and inlet CO2 concentration of 10 % at 70°C.

When PZ concentration increased from 0.15 mol·L−1 to 0.7 mol·L−1, the intrinsic reaction rate was enhanced substantially, resulting in a considerable decline of liquid film resistance. Hence the percentage of gas film resistance, KG/kg, increased from 13.4% to 33.6%. Thus the overall reaction rate is controlled by both the gas film resistance and the liquid film resistance, in which the liquid film resistance dominants the total mass transfer resistance.

3.4 Effect of the gas flow rate on the CO2 absorption rate The effect of gas flow rate on the CO2 absorption rate was shown in Fig.6， indicating that the gas flow rate substantially influenced the CO2 absorption rate. Specifically, the absorption rate increased considerably with the gas flow rate, particularly at flow rates exceeding 25 mL.s−1. The equilibrium partial pressure was


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3440 Pa (Fig.2). Other relevant data, including the enhancement factor, are listed in Table1.

12.0

9.0

-11

-2

-1

-1

KG (×10 mol·cm ·s ·Pa )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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6.0

3.0

18

24

30

36

-1

Gas flow rate (mL·s )

Fig.6 Effect of gas flow rate on the CO2 absorption rate: 40 % K2CO3/0.5 M PZ, CO2 loading of 1.23 M, slurry flow rate of 2.23 mL·s-1, and inlet CO2 concentration of 10 % at 70°C.

Table.1 Data for CO2 absorption in the K2CO3/PZ slurry at 70°C in the wetted wall

KG µ

ρ

Conditions (cp)

(g/cm)

H

kg k0L

D (mol/cm2.s

(mol/cm2.

.Pa)

s.Pa)

2

(cm /s)

(Pa.cm3/

E

(cm/s) mol)

16.67

1.56

1.35

1.73E-05

2.14E-11

1.47E-10

5.54E-03

9.68E+09

43.67

Vg

25

1.56

1.35

1.73E-05

2.72E-11

2.08E-10

5.54E-03

9.68E+09

54.80

(ml/s)

30

1.56

1.35

1.73E-05

5.63E-11

2.43E-10

5.54E-03

9.68E+09

98.33

33.33

1.56

1.35

1.73E-05

9.81E-11

2.65E-10

5.54E-03

9.68E+09

271.95

1.37

1.56

1.35

1.73E-05

4.43E-11

2.43E-10

4.71E-03

9.68E+09

111.45


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Vl

1.78

1.56

1.35

1.73E-05

5.03E-11

2.43E-10

5.14E-03

9.68E+09

119.45

(ml/s)

2.23

1.56

1.35

1.73E-05

5.63E-11

2.43E-10

5.54E-03

9.68E+09

128.20

2.65

1.56

1.35

1.73E-05

6.25E-11

2.43E-10

5.87E-03

9.68E+09

138.88

0

1.56

1.35

1.73E-05

2.64E-11

2.43E-10

5.54E-03

9.68E+09

48.51

0.15

1.56

1.35

1.73E-05

3.27E-11

2.43E-10

5.54E-03

9.68E+09

66.03

cPZ

0.3

1.56

1.35

1.73E-05

4.43E-11

2.43E-10

5.54E-03

9.68E+09

94.74

(mol/L)

0.5

1.56

1.35

1.73E-05

5.63E-11

2.43E-10

5.54E-03

9.68E+09

128.20

0.7

1.56

1.35

1.73E-05

8.16E-11

2.43E-10

5.54E-03

9.68E+09

215.09

1.26

1.56

1.35

1.73E-05

9.68E-11

2.43E-10

5.54E-03

9.68E+09

281.13

0

1.57

1.34

2.63E-05

1.89E-10

2.58E-10

6.81E-03

9.18E+09

944.37

Loading

0.37

1.57

1.34

1.72E-05

1.10E-10

2.42E-10

5.51E-03

9.33E+09

339.94

(mol/L)

0.75

1.56

1.35

1.73E-05

8.46E-11

2.43E-10

5.53E-03

9.68E+09

227.43

1.23

1.56

1.35

1.73E-05

5.63E-11

2.43E-10

5.54E-03

9.68E+09

128.22

25

0.93

1.21

2.63E-05

7.94E-11

2.58E-10

7.31E-03

3.82E+09

59.95

Wt

30

1.27

1.26

2.04E-05

6.97E-11

2.49E-10

6.15E-03

5.15E+09

81.01

（%）

35

1.32

1.30

1.98E-05

6.47E-11

2.48E-10

6.06E-03

6.95E+09

100.43

40

1.56

1.35

1.73E-05

5.63E-11

2.43E-10

5.54E-03

9.68E+09

128.22

As shown in Tab.1, when the gas flow rate increased, the gas mass resistance would decrease and the enhancement factor substantially increased, resulting in a considerable decline in the total mass transfer resistance. The enhancement factor increased approximately 7 times from 43 to 271 when the gas flow rate varied from


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16.67 to 33.33 mL.s−1, in which the gas phase resistance played a crucial role. The percentage of gas film resistance, KG/kg, increased from 13% to 37%, indicating that the gas film resistance was crucial for the CO2 absorption rate in K+/PZ mixtures. Nevertheless, the overall reaction rate is controlled by both the gas film mass transfer and the liquid film mass transfer, in which the liquid film resistance dominant the total mass transfer resistance.

3.5 Effect of the slurry flow rate on the CO2 absorption rate Fig.7 illustrates the effect of the slurry flow rate on the CO2 absorption rate, indicating that the absorption rate increased slowly with the slurry flow rate. The ratio of the CO2 partial pressure to the equilibrium partial pressure (P/P*) was less than 3.0. The calculation of equilibrium partial pressure under these conditions was the same as that presented in Section 2.3.3. The equilibrium partial pressure was also 3440 Pa (Fig.2). A previous study revealed that the total mass transfer coefficient that corresponded to a physical liquid mass transfer coefficient varying from 0.002 to10 cm.s−1 with a low driving force, which is in the pseudo-first-order region, was not significantly different. The absorption rate determined in this study was mainly controlled by the kinetics instead of liquid phase transfer26. The present study was performed at a physical liquid mass transfer coefficient of 0.005 cm.s−1 (Table.1) and a low driving force (Plm

PZ Mixture Using

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