Scholarly article on topic 'Packing Characterization for Post Combustion CO2 Capture: Mass Transfer Model Development'

Packing Characterization for Post Combustion CO2 Capture: Mass Transfer Model Development Academic research paper on "Chemical engineering"

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Abstract of research paper on Chemical engineering, author of scientific article — Chao Wang, Micah Perry, Frank Seibert, Gary Rochelle

Abstract Three mass transfer properties: the effective area (ae), liquid film and gas film mass transfer coefficients (kL and kG) are measured consistently for eleven packings with different surface area and corrugation angle. The effective area and liquid film mass transfer coefficient increases with liquid velocity while gas film mass transfer coefficient increases with gas velocity. The fractional effective area decreases with surface area and barely changes with corrugation angle. kL and kG increase as surface area increases or corrugation angle decreases. A new concept-mixing point density is proposed to represent the packing geometry influence on kL and kG. Correlations for ae, kL, and kG are developed including effects of gas and liquid rates and packing geometry.

Academic research paper on topic "Packing Characterization for Post Combustion CO2 Capture: Mass Transfer Model Development"

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Energy Procedía 63 (2014) 1727 - 1744

GHGT-12

Packing characterization for post combustion CO2 capture: mass

transfer model development

Chao Wangab, Micah Perryb, Frank Seibertb, Gary Rochellea*

a Texas Carbon Management Program, McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 E. Dean Keeton

St., C0400, Austin, TX 78712-1589 Separations Research Program, Pickle Research Campus, The University of Texas at Austin, 10100 Burnet Road, Austin, TX 78758

Abstract

Three mass transfer properties: the effective area (ae), liquid film and gas film mass transfer coefficients (kL and kG) are measured consistently for eleven packings with different surface area and corrugation angle. The effective area and liquid film mass transfer coefficient increases with liquid velocity while gas film mass transfer coefficient increases with gas velocity. The fractional effective area decreases with surface area and barely changes with corrugation angle. kL and kG increase as surface area increases or corrugation angle decreases. A new concept-mixing point density is proposed to represent the packing geometry influence on kL and kG. Correlations for ae, kL, and kG are developed including effects of gas and liquid rates and packing geometry.

© 2014Published byElsevier Ltd.Thisisanopen 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: CO2 capture, structured packing, effective area, mass transfer coefficient, mass transfer model.

1. Main text

* Corresponding author. Tel.: +1-512-471-7230; fax: +1-512-471-6920. E-mail address: gtr@che.utexas.edu

1876-6102 © 2014 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.2014.11.180

Nomenclature

A column cross section area, m2

ae effective mass transfer area, m2/m3

ap packing physical area, m2/m3

C experimental constant used in effective area correlation

HTU height of transfer unit, m

KOG overall mass transfer coefficient, m/s

kG gas film mass transfer coefficient, m/s

kL liquid film mass transfer coefficient, m/s

M mixing point density, pts/m3

NTU number of transfer units

Q volumetric flow rate, m3/s

Ug gas superficial velocity, m/s

Ul liquid superficial velocity, m/s

CT surface tension, N/m

0 packing corrugation angle, deg

1.1. Introduction

Among the major systems for CO2 capture, post-combustion capture with amines is the most mature and readily employable technology. Packing is widely used in post-combustion CO2 capture because of its low pressure drop, good mass transfer efficiency, and ease of installation. In the CO2 capture process, absorber and stripper performance are highly dependent on the effective mass transfer area of the packing (ae). The stripper performance depends on the liquid film mass transfer coefficient (kL), while gas cooler and water wash performance depend on the gas film mass transfer coefficient (kG).

A number of mass transfer models for packing are described in the literature.1-1,2,3-1 In these models, the combination of mass transfer coefficient and area (Ka) was measured. However, a common defect in the previous models is that either a theoretical assumption of area or proposed K models from other work were used to separate K and a. In other words, none of the mass transfer values (kG, kL, ae) were independently validated. In distillation systems, most cases only required the combination (Ka) values, where these models were acceptable, but the design and optimization of the amine scrubbing CO2 capture system requires validated separate values for kG, kL, and ae.

This research is focused on the consistent measurement and mechanistic model development of ae, kG, kL for packing. The specific objective is to explore effects of operating conditions and packing geometry on mass transfer properties. Finally, mechanistic mass transfer models are developed.

2. Experimental

2.1. Apparatus

All experiments were conducted in a pilot-scale PVC column with an inner diameter of 0.428 m (16.8 in) and a total height of 7.62 m (25 ft) located in the Separation Research Program in the University of Texas at Austin (UT SRP). The same column has been used by previous researchers to measure ae.[4,5] A Delta V® control system provided by Emerson was utilized to operate the system and collect data. The experiment setup is shown in Figure 1.

A packed bed of 3.3 m (10 ft) was used to measure the pressure drop, liquid hold-up, and effective area. A packed bed of 1.83 m (6 ft) was used for the kL measurement to avoid the peak tailing in GC analysis of outlet

toluene. The packed bed height was further shortened to approximately 0.51 m (20 in) for the kG measurement to obtain a reliable outlet SO2 concentration.

Air Outlet

Solvent Pump

Fig. 1. Flow Process Diagram for the Packed Column

2.2. Experimental methods

The effective mass transfer area (ae) was measured by the absorption of atmospheric CO2 with 0.1 gmol/L NaOH solution. This method was first proposed by Danckwerts.[6] The reaction between CO2 and NaOH is a pseudo firstorder reaction, and the CO2 flux is controlled by CO2 diffusion and reaction in the liquid boundary layer. The liquid film mass transfer coefficient with chemical reactions can be calculated by Equation (1). The effective area and mass transfer coefficient can be separated, and the area calculated by Equation (2).

k ' =■

4Kh- \°H id

uG ln(

y CO2out

-) UG ln(

yCO2out

ZkG RT

Where:

kOH. is the second-order reaction constant, m3/(kmol*s);

[OH-] is the concentration of free hydroxyl ion in the liquid phase, gmol/L;

Dc02,l is the diffusivity of CO2 in the liquid phase, m2/s;

HCO2 is the Henry's constant of CO2, m3*bar/kmol;

yCO2in and yCO2out are the concentration of CO2 in the gas phase at inlet and outlet, ppmv;

Z is the packed bed height, m.

Physical absorption or desorption of low solubility gas with water has been used by others [7, 8] to measure kL. In this work, the liquid film mass transfer coefficient (kL) was measured by stripping toluene from water into air. This is a liquid phase controlled system because of its very high Henry's constant. The overall mass transfer can be assumed to be equal to the liquid phase mass transfer coefficient. Once the inlet and outlet toluene concentration in water have been measured, the following equation can be used to calculate kLa:

kLa = Zln( CLA1/ cLA2) (3)

Where:

uL is the liquid superficial velocity, m/s;

cLA1/cLA2 are the inlet and outlet toluene concentrations in water, ppm.

kL can then be determined directly from the measured kLa and the measured effective area (ae) under the same liquid and gas rates:

Ul (4)

Absorption of reactive gas with aqueous sodium hydroxide has been used by previous researchers to measure kG [9, 10]. In this study, the gas film mass transfer coefficient was measured by absorption of SO2 mixed with air with 0.1 gmol/L NaOH. The reaction between SO2 and NaOH is an instantaneous reaction making the liquid phase mass transfer resistance negligible. Thus, the overall mass transfer coefficient (KOG) can be assumed to be equivalent to the gas film mass transfer coefficient (kG). The gas film mass transfer coefficient can be calculated by:

uG ln( ^^)

k =-ySo2out (5)

G ZRTae

Where:

uG is the gas superficial velocity, m/s;

ySO2in/ySO2out are the inlet and outlet SO2 concentrations, ppmv; ae is the effective mass transfer area, m2/m3.

Because of the high efficiency of SO2 removal with NaOH, the packed height was reduced from 10 feet to 30-40 inches to obtain a reliable and measurable outlet SO2 concentration. In this case, the mass transfer from the top section above the packing and the bottom section below the packing became comparable with the mass transfer from the packing section. In the kG measurement, the mass transfer from these two ends (NTUend) was measured and deducted from the overall mass transfer (NTUtotal).

2.3. Packing list and operating conditions

Eleven structured packings with different surface area (aP) and corrugation angle (0) were measured to explore how packing geometry influences the mass transfer properties. The packing information is listed in Table 1. Seven liquid flow rates (L) and five gas velocities (uG) were measured to explore the impact of operating conditions on mass transfer performance. The operating conditions are listed in Table 2. The gas and liquid mass transfer coefficients (kG and kL) were separated from the Ka value with the measured effective area (ae) at the same operating condition. The physical properties are listed in Table 3.

Table 1. Packing information

Packing 125Y 2X 200X 250Y 250Y 250X 350Y 350Z 350Y 350X 500Y

Type Mellapak Mellapak Raschig Hybrid Raschig, Hybrid Mellapak Mellapak GT-Pak GT-Pak A B GT-Pak

Area, m2/m3 125 205 200 250 250 250 350 350 350 350 500

Corrugation angle 45 60 60 45 45 60 45 70 45 60 45

Channel base B, m 0.0635 0.0302 0.0318 0.0318 0.0302 0.0254 0.0167 0.0175 0.0254 0.0175 0.0143

Crimp height h, m 0.0254 0.0143 0.0048 0.0048 0.0111 0.0111 0.0075 0.0079 0.008 0.009 0.00635

Mixing point density 58583 266509 721574 1249766 593478 483197 2863768 902394 1171656 1256854 4628764

M, pts/m3

Table 2. Operating conditions

Liquid load (L), m3/m2*h Gas velocity (uG), m/s

6.1 12.2 24.4 36.7 48.9 61 73.3 0.6 1 1.5 2 2.3

ae V V V V V V V V V V V V

kG V V V V V V V V

kL V V V V V V V V V V

Table 3. Average physical properties at 298K

Liquid density, рь Gas density, pG Liquid Gas Liquid Gas Surface

diffusivity, Dl diffusivity, Dg viscosity, Ць viscosity, |iG tension, Gl

Units kg/m3 kg/m3 m2/s m2/s kg/(m *s) kg/(m * s) N/m

Values 998 1.204 8.6E-10 1.31E-5 1.002E-3 1.98E-5 0.072

3. Results and discussion

3.1. Effective area

To explore the influence of surface area, the fractional effective area of four structured packings with the same corrugation angle (45 degrees) and surface area ranging from 125 to 500 m2/m3 is compared in Figure 2. The gas velocity is 0.99 m/s (300 ACFM) for all packings. Every packing shows an increase in effective area with increasing liquid load. At the same liquid load, the fractional effective area decreases with surface area. Rivulets, ripples, and droplets, those mass-transfer-enhancing film instabilities according to Henriques[11] form easily between the sheets in coarser packing with high void fraction. End effects and wall effects could also have a greater impact on coarser packing. Finer packing such as 350Y and 500Y could be more subject to maldistribution and insufficient wetting, causing a lower fractional effective area.

"re c o

MP125Y ♦ ^____—* " ■ —' ■

--- m MP250Y ▲ -— ▲

--""" G 5TC350Y ——GTC5 00Y

Overall: 125Y> 250Y>350Y>500Y

10 20 40

Liquid flow rate, m3/m2*h

Figure 2. Fractional effective area as a function of specific dry area.

The effective area of MP250Y and 250X is compared in Figure 3 to show the effect of corrugation angle. MP250X has equivalent surface area and geometric structure except for a higher corrugation angle (60 degrees), compared with MP250Y (45 degrees). The measured effective area of MP250Y is only 6% higher than MP250X within the range of the experimental error. A comparison of GT-PAKTM 350Y and 350Z also shows that the corrugation angle has an insignificant effect on the effective area. 350Y has a 45-degree corrugation angle while 350Z has a 70-degree angle. The difference in effective area between these two packings is 7%, which is within the 10% experimental error.

The effective area should be determined by the wettability of the packing surface, which is influenced by: (1) the surface tension, which determines the contact angle of liquid and packing surface; and (2) the liquid phase velocity, which determines the liquid flow pattern. Other factors such as gas velocity, liquid viscosity, and packing corrugation angle do not have a significant impact on effective area.

£ 0.8

0 20 40 60 80

Liquid Flow Rate, m3/m2*h

Fig. 3. Fractional effective area comparison between MP250Y and MP250X 3.2. Liquid and gas film mass transfer coefficient (kL and kG)

Figures 4 and 5 compare liquid film and gas film mass transfer coefficients for packings with different surface area. For all packings, kL increases with liquid velocity. At the same gas and liquid flow rate, kL increases as surface area increases. On average, the kL of 500Y is 33% higher than 350Y, and the kL of 350Y is 21% higher than 250Y. These differences are significantly more than the 10% experimental noise. A similar conclusion is reached when gas film mass transfer coefficient of packings with different surface areas is compared (Figure 5). At the same gas and liquid flow rate, the kG of 500Y is 23% higher than 350Y, and the kG of 350Y is 22% higher than 250Y. The difference between 250Y and 125Y is negligible (only 3%) since there could be extra bubbles or ripples creating mass transfer in coarse packing like 125Y.

The liquid film and gas film mass transfer coefficients for packings with different corrugation angles are compared in Figure 6 and Figure 7. At the same liquid and gas flow rate, both kL and kG increase as the corrugation angle decreases from 70 to 45 degrees (350Z to 350Y). The mass transfer coefficient difference between these two packings is between 25% and 35%.

- ------ MP250Y | J—----HZH^ -—---- ■ MP250X ■_____ ♦ ■ I * ♦ ♦

MP250Y > MP250X Overall deviation: 6%

2E-5 1.0E-3

2.0E-3

kL: 500Y>350Y>250Y

4.0E-3 8.0E-3

uL, m/s

1.6E-2

Fig 4. kL comparison of 250Y, 350Y, and 500Y

in "-/

L= 36.6 m3/(m2*h)

GTC ■ 500Y ^^ MP250Y

^-"-'"GTC350Y ^-irs^^ MP125Y

kG:500Y>350Y>250Y>125Y

uG, m/s

Fig 5. ko comparison of 125Y, 250Y, 350Y, and 500Y

ul, m/s

Fig 6. kL comparison of GT-PAK™ 350Y and 350Z

Fig 7. kG comparison of GT-PAK™ 350Y and 350Z

In general, both kL and k^ increase with packing surface area (aP) and decrease with packing corrugation angle (9). Structured packing geometries are studied to understand this phenomenon.

3.3. Mixing point density

Figure 8 shows the flow mechanism in the corrugated metal sheets that compose structured packing. Liquid flow inside the packing can be seen flowing along these corrugated sheets. At the joint points of metal sheets (marked by circles in Figure 8), flows mix with each other, change directions, and create turbulence. Thus, these mixing points are believed to be the key points for mass transfer in structured packing. In packing with a lower corrugation angle or larger surface area, there will be more mixing points, which means liquid and gas flows mix with each other more often, change direction more frequently, and create more turbulence. Both kL and kG increase as corrugation angle decreases or surface area increases.

Low angle High angle Large area

Fig 8. Liquid flow along corrugated metal sheets

Fig 9. Lateral view of a structured packing with a corrugation angle (6)

The number of mixing points vary with the packing geometry. Figure 9 shows the lateral view of a structured packing with a corrugation angle 6. From the lateral view, the corrugated metal sheets can be seen as a series of

parallel lines with a tilt angle to the horizontal line. In the structured packing, each corrugated metal sheet contacts the one next to it. In the lateral view, this is expressed by the parallel lines crossing with another set of parallel lines in a different direction. The crossed corrugated metal sheets form hundreds of square pyramids, which are the triangles in the lateral view. The mixing points are the vertices of the triangles, which are marked in black circles in the lateral view.

Fig 10. Top view of a structured packing with a corrugation angle (6)

The square pyramids formed by the crossed metal sheets can be better seen from the top view of the packing (Figure 10). The height of the square pyramid is B/2*tan6, the bottom area of the pyramid is B*h. Both B and h are structured packing geometric characteristics. B is the channel base length (m) while h is the crimp height length (m).

The volume of the square pyramid is (BhB*tan9)/6. Thus, the number of square pyramids per m3 volume is 6/(BhB*tan9). Each pyramid has five mixing points; however, each pyramid also shares mixing points with four adjacent pyramids, making the number of mixing points per pyramid 5/5. The number of mixing point per m3 (mixing point density M) can be calculated by Equation (6).

M =--(6)

BhB tan#

Where:

B is the channel base, m; h is the crimp height, m; 6 is the corrugation angle, deg.

4. Model development

The effective area model in this study is based on the model by Tsai[12]. The updated model uses liquid superficial velocity per total area (uL/aP) as the liquid flow rate per perimeter term (Q/LP), and changes the experimental coefficient from 1.34 to 1.42, which provides a better fit for our larger data base. The effective area model is:

^ = 1.42[(—) g 1/3( ^L )4/3]°.ii6 (7)

a„ c a„

Figure 11 shows the comparison of experimental data and the effective area model. It includes the data for all packings measured in this work. The effective area model fits most of the experimental data well except for GT-PAKTM 500Y. Some of the packing surface area cannot be wetted efficiently for high surface area packings, causing the measured fractional area for GT-PAKTM 500Y to be lower than expected. The average deviation between the model and experimental results is 10%.

MP2X RSP250

• RSR#0.5 ♦ RSR#0.7

■ GTC350Z 88MP250Y

MP250X — RSR#0.3 A GTC350Y RSP200X GTC500Y A350Y

B350X_

^ = 1.42[( ) g 1/3( Q )4/3]0.ii6

Average Deviation: 10%

0.8 1 ae/ap experiment

Fig 11. Comparison of experimental data a nd the effective area model

The gas and liquid film mass transfer coefficients (kG and kL) are a function ofthe gas and liquid superficial velocity (uG, uL), the packing surface area (ap), and the mixing point density (M). M is the number of mixing points per m3, which represents the effect of the corrugation angle and packing size. M is given by by Equation (6). The mass transfer coefficients models are given by Equation (8) and (9).

kL = 3.08E - 3 * u°L12M 0-42aP115 (8)

kG = 1.08E - 2 * u0G55M 0-2V36 (9)

The comparison of experimental data and values predicted by the kL and kG models is shown in Figures 12 and 13. The deviation between kL, experiment and kL, model is 22% while the deviation between kG, experiment and kG, model is 13%. The standard errors of each parameter in the kL and kG models are listed in Table 4 and Table 5. The p-value for each term tests the null hypothesis that the coefficient is equal to zero (no effect). A predictor that has a low p-value (<0.05) is likely to be a meaningful addition to the model because changes in the predictor's value are related to changes in the response variable. Conversely, a larger (insignificant) p-value suggests that changes in the predictor are not associated with changes in the response. P-values are all less than 0.05 except the p-value for aP in the kG model, indicating that more work is still needed to find out the dependence of gas film mass transfer coefficient (kG) on packing surface area (aP).

Previous kG models (Rocha[2], Hanley and Chen[17]) are compared with data in this work (Figure 13). Both of them are developed based on data measured in distillation systems. Rocha's model under-predicts kG value by 32%, and Hanley's model under-predicts kG by 69%.

Table 4. kL correlation standard error

Average Power Standard error P-Value

Ul 0.72 0.045 2.59E-23

M 0.42 0.086 6.93E-6

ap -1.15 0.252 2.47E-5

Table 5. kG correlation standard error

Average Power Standard error P-Value

Ug 0.55 0.055 3.09E-13

M 0.22 0.056 1.05E-3

ap -0.36 0.179 0.0308

kL,exp

Fig 12. Liquid film mass transfer coefficient model

GTC350Z MP250Y MP250X BS GTC350Y

A350Y O B350X ♦ RSP200X

■ GTC500Y AMP2X

■ RSP250Y MP125Y

kG = 1.08 E - 2* uf M022 a'p36

Average deviation: 13%

kG,exp, m/s

Fig 13. Gas film mass transfer coefficient model

5. Data comparison with previous work

The mass transfer data (ae, kL, and kG) measured in this work is compared with previous work in this section. Figure 14 compares the effective area measured in this work for data from Tsai[ ] Linek[13]. The system used is CO2/air-NaOH for all three researchers. The differences between data in this work and data by previous researchers are 2-3%, showing good agreement.

Liquid Flow Rate L/(m3/m2-h)

Fig 14. Effective area comparison between data in this work and data by previous researchers

Figure 15 compares the kLa predicted by the model in this work to models by previous researchers for MP250Y. The models by Laso and Linek are semi-empirical based on measured data. The system was O2 desorption from water by air (Laso[14]), or by N2 (Linek[13]). The packed height was 0.42 m (Laso) and 0.84 m (Linek) compared to 1.83 m in this work. Because of the diffusivity differences between different systems, the kLa measured in O2-water system is converted to toluene-water system by Equation (10) (assume kLa changes with uL to the 0.5 power).

(ML/ = ( BJoLL )05 = 0.661 (10)

(kLa)c2 DO2,L

Where:

Dtol,L = 8.6E-10 m2/s;

DO2,L = 1.97E-9 m2/s

kLa measured by Laso is 54% higher than kLa measured in this work, and kLa measured by Linek is 31% higher than kLa measured in this work. Since the packed heights in Laso's work and Linek's work were shorter than the packed height used in this work, end effect could play a more significant role in their results, making the kLa value higher than expected. Another reason could be the dependence of kL on uL, which is still quite uncertain. According to previous researchers, the dependence is believed to be in the range of 0.5-1.[15, 16] If higher value of dependence is used, the corrected kLa value from Laso and Linek would be lower, making it closer to kLa value in this work.

Two previous mass transfer models developed from data in distillation systems (Hanley and Chen[17], Rocha[2]) were also compared with the data in this work. Because of the systematic differences, it is suggested to use kLa value, which is the combination of kL model and area model from the same author. The kLa value predicted by Hanley and Chen is 29% lower than kLa predicted in this work, while kLa value predicted by Rocha is 38% lower.

« 0.03 >

eu c eu

Difference: Wang and Linek: 31% Wang and Laso: 54% Wang and Hanley: 29% Wang and Rocha: 37%

0.008 0.012 uL, m/s

Fig 15. kLa comparison between data in this work and data by previous researchers

6. Conclusions

In this work, the effective mass transfer area (ae), liquid film mass transfer coefficient (kL), and gas film mass transfer coefficient (kG) were measured consistently in a pilot-scale packed column. Eleven structured packings with varying surface area (aP) and corrugation angle (0) were tested to explore the influence of packing geometry on mass transfer performance. For each packing, seven different liquid velocities (uL) and five different gas velocities (uG) were tested to explore the influence of operating condition on mass transfer performance. The effective area (ae) and liquid film mass transfer coefficient (kL) increases with liquid velocity (uL) and barely changes with gas velocity (uG); gas film mass transfer coefficient (k^) increases with gas velocity and barely changes with liquid velocity (uL).

The fractional effective area (ae/aP) decreases with surface area (aP) since coarse packing gets good wetting and additional mass transfer area from mass-transfer-enhancing film instabilities at the same liquid flow rate. The effective area barely changes when the corrugation angle increases from 45 degrees to 70 degrees. The liquid film and gas film mass transfer coefficients increase as packing surface area (aP) increases or packing corrugation angle (0) decreases. Packing geometry was studied and a new concept-mixing point density (M) proposed to explain this phenomenon. Mixing point density represents the packing geometry influence and can be quantified.

Mass transfer models are developed in this work. The effective area model is based work by Tsai, slightly changing the experimental constant and exponent. The mass transfer coefficients models are developed based on three factors influencing mass transfer: the liquid/gas superficial velocity (uL/G), the packing size (aP), and the mixing points density (M). The mass transfer models are:

e = 1.42[( ) g )4/3]o.ii6

kL = 3.08E - 3* uf2M 0A2a-;A5 kG = 1.08E - 2* u0G55M022ap036

Appendix A. Calculation of HTUG and HTUL using models developed in this work

An example of calculation for the gas phase and liquid phase Individual Height of Transfer Unit (HTUG and HTUL) is shown in this section. Mellapak 250Y is chosen in this example calculation. The base case operating conditions are listed in Table 6. The gas flow rate (G) is 8.5 m3/min or 300 ACFM in English units, and the liquid flow rate (L) is 36.7 m 3/(m2*h) or 15 gpm/ft2 in English units. The superficial gas and liquid velocities can be calculated.

36.7m3 m2 * 3600s 8.5m3

0.144m2 *60s

= 0.0102 m / s

= 0.98 m / s

(11) (12)

Table 6. Operating conditions in HTUG and HTUL calculation

Parameters

Liquid flow rate, L Gas flow rate, G

Cross-section Superficial liquid Superficial gas area, A velocity, ul velocity, ug

Packed height, Z

i3/(m2*h)

m /min

Values

0.0102

The effective area (ae), liquid film mass transfer coefficient (kL), and gas film mass transfer coefficient (kG) can be calculated using the mass transfer models developed in this work.

ae = ap *1.42[(^)g1/3(^)4/3]0116 a ap

= 250m2 /m3 *1.42[("8*g'm3 *9.8m/s2 *)4/3]0.ii6 = 245 m2 /m 0.072N / m 250m2/ m3

kL = 3.08E - 3* u^M 042ap115

= 3.08E - 3* (0.0102m /s)072 * (593478pts /m3)042 * (250m2 /m3)"115 = 5.27E - 5 m /s

kG = 1.08E - 2* u0G55Ma22ap0 36

= 1.08E - 2* (0.98m /s)055 * (593478pts /m3)a22(2 5 0m2 /m3)~a36 = 2.73E - 2 m /s

Then the HTUL and HTUG can be calculated.

HTUl = =-:——-^^ = 0.79 m

uL 0.0102m / ^

kLae 5.27 E- -5m / ^ * 245m2 / m3

uG 0.98m / ^

kGae 2.73E - 2m / ^ * 245m2 / m

HTUg = =-——-= 0.15 m

The measured HTUL is 1.07 m and measured HTUg is 0.14 m for MP250Y at the corresponding operating conditions, showing that the mass transfer models developed in this work have good prediction.

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