Mass Transfer in a Rotating Packed Bed with Various Radii of the Bed

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Mass Transfer in a Rotating Packed Bed with Various Radii of the Bed

Yu-Shao Chen, Chia-Chang Lin, and Hwai-Shen Liu

Ind. Eng. Chem. Res., 2005, 44 (20), 7868-7875 • DOI: 10.1021/ie048962s

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Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan, Republic of China, and Department of Chemical and Materials Engineering, Chang-Gung University, Tao-Yuan,

Taiwan, Republic of China

This work examined the mass transfer efficiency of a rotating packed bed with various radii of the packed bed. Experimental results showed that kLa increased with decreasing volume of the

packed bed. This may contribute to the significant end effects as the volume of the packed bed is reduced. A correlation which takes end effects into consideration for kLa in a rotating packed

bed was proposed and is valid for different sizes of the rotating packed bed and for viscous Newtonian and non-Newtonian liquid systems. In addition, it was also found that the correlation could reasonably estimate most of the kLa data in the Higee literature.

Introduction

A rotating packed bed (i.e., RPB or Higee system), which replaced gravity with centrifugal force up to several hundred gravitational force, was first introduced as a novel gas/liquid contactor to enhance mass transfer in 1981.1_{This system can be operated at a higher gas/}

liquid ratio because of its lesser tendency of flooding. Under a significant centrifugal field, thin liquid films and tiny liquid droplets can be generated, thus decreas-ing mass transfer resistance and, meanwhile, increasdecreas-ing gas/liquid interfacial area. A 1-2 orders of magnitude enhancement in mass transfer could be obtained in an RPB. Consequently, the size and the capital of the processing system would be extremely reduced. The enhancement of mass transfer on gas/liquid and liquid/ solid systems has been experimentally demonstrated in the literature.1-5

The characteristics of mass transfer in a traditional packed column have been well-studied. For example, Onda et al.6_{proposed a correlation, shown as eq 1, to}

predict the mass transfer coefficient (kL) in a packed

column.

According to the correlation, it is expected that the mass transfer coefficient should be independent of the packed height. In 1985, Munz7_{performed experiments of}

strip-ping oxygen and VOCs from water in a packed column. He also found that the packed height has little effect on the mass transfer coefficients.

However, in an RPB, the effects of the radial position and the thickness of the packing on mass transfer could

be quite complicated. In 1985, Tung and Mah8

theoreti-cally analyzed an RPB and proposed a correlation for the mass transfer coefficient.

In 1989, Munjal et al.9_{also proposed a correlation for}

predicting kL in the RPB theoretically.

In 2005, Chen et al.10_{reported an empirical correlation}

for kLa which is valid for mass transfer in Newtonian

and non-Newtonian fluids in an RPB.

The liquid mass flux (L) decreases because of the change of cross-sectional area, while the centrifugal acceleration (ac) increases with increasing radial distance. It is noted

in eqs 2-4 that these two parameters compete with each other as the radial distance increases. In 2000, Burns et al.11 _{experimentally measured the liquid holdup in}

an RPB with a method of electrical resistance. They found that the radial dependence of liquid holdup is mainly due to its influence on centrifugal acceleration and liquid velocity. In 1992, Singh et al.12 _performed

experiments of stripping VOCs from groundwater in an RPB. The dependence of the mass transfer coefficient on the outer radius of the packed bed was investigated. A liquid sampling tube was installed near the outer radius of the bed to minimize end effects (mass transfer outside the packing) in their study. The results showed that the relationship between the mass transfer coef-ficient and the outer radius of the bed was dependent

* Corresponding author. Tel.: 2-3366-3050. Fax: +886-2-2362-3040. E-mail: [email protected].

†_{National Taiwan University.} ‡_{Chang-Gung University.} kL

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10.1021/ie048962s CCC: $30.25 © 2005 American Chemical Society Published on Web 09/02/2005

on the rotor speed. At low rotational speed, the mass transfer coefficient decreased with increasing outer radius of the bed, and the decrease was relatively minor at high rotational speed.

On the other hand, there may be obvious end effects in an RPB. In fact, the regions for mass transfer in an RPB include the region inside the packed bed, the region between the liquid distributor and the inner edge of the packed bed, and the region between the outside edge of the bed and the static housing. In 1989, Munjal et al.2

reported the experimental measurements of gas-liquid interfacial area based on chemical absorption of CO2in

NaOH solutions. The results showed that obvious end effects did exist in an RPB, especially for a smaller bed. Because the experimental measurements include the end effects, the mass transfer coefficient calculated based on the volume of the packed bed will be over-estimated. Therefore, the contribution of the end effects has to be determined to develop a realistic correlation for the mass transfer coefficient in an RPB.

In this study, the influence of the radius of the packed bed on mass transfer was experimentally investigated. In addition, to develop a consistent correlation for the liquid-side mass transfer coefficient in an RPB, experi-mental data of various liquid-phase control systems available in the literature were also included and evaluated.

Experiments

The main structure of RPB-1 is shown in Figure 1. The liquid enters the packed bed from a liquid distribu-tor and sprays onto the inner edge of the packed bed. The liquid distributor has two vertical sets of holes in the opposite direction, and each set has three 0.5-mm-diameter holes. Inside the bed, the liquid moves outward through the packing as a result of the centrifugal force. The liquid is then splashed on the stationary housing and is collected at the bottom. The gas is introduced from the stationary housing, flows inward through the packing, and leaves the rotor through the center pipe.

Thus, the gas and the liquid contact countercurrently in the RPB. The bed can be operated in the range of 600-1500 rpm. The packing used in this study is 0.22-mm-diameter stainless steel wire mesh, with porosity and interfacial area of 0.954 and 829 1/m, respectively. The sphericity of wire mesh was found to be 0.11.13_The

axial height of the bed is 2 cm. The packing support used in this study was a stainless steel ring with 5-mm-diameter holes on it, and the open ratio of the ring was ∼61%. The packing support can be set in the radial direction at 1, 2, 3, 4, 5, and 6 cm, respectively. As the result, the influence of the inner radius, the outer radius, and the thickness of the packed bed on mass transfer can be investigated. The radius of the station-ary housing is 7.5 cm.

Figure 2 shows a diagram of the experimental setup. Fresh water at a temperature of 30 °C was pumped into the RPB. A nitrogen stream with a flow rate of 1 L/min was introduced into the bed and contacted counter-currently with water. The concentration of dissolved oxygen (DO) in the inlet liquid stream was controlled at 2.48× 10-4mol/L, and the concentration in the outlet liquid stream was measured by a DO probe (Ingold type 170). The physical properties of water and oxygen in water were listed in Table 1.

To derive the design equation for an RPB, first consider a differential volume with cross-sectional area 2πrz and thickness dr. Assuming that the gas-side mass transfer resistance can be neglected for the process of deoxygenation, then the mass balance of solute in this volume for a dilute system is

where CLis the concentration of solute (oxygen) in the

liquid phase and kLa is the mass transfer coefficient. CL* is the equilibrium concentration associated with the

gas concentration. The overall mass balance is

i.e.,

where QGis the gas flow rate, H is Henry’s constant, Figure 1. Main structure of an RPB.

Figure 2. Diagram of the experimental setup.

Table 1. Physical Properties of Water and Oxygen in Water density of liquid (F) viscosity of liquid (µ) diffusion coefficient (D) Henry’s constant (H) 996 kg/m3 _{0.001 Pa‚s 2.1× 10}-9_m2_{/s 34.0 (mol/L)/(mol/L)} Q_LdC_L) k_La(C_L* - C_L)2πrzdr (5) Q_L(C_L- C_L,o) ) Q_G(C_G- C_G,i) ) Q_G(HC_L* - 0) (6) C_L* ) 1 S(CL- CL,o) (7)

CL,ois the outlet dissolved oxygen concentration in the

liquid, CG,iis the inlet oxygen concentration in the gas,

and S is the stripping factor defined as follows:

Then the mass transfer coefficient can be obtained by substituting eq 7 into eq 5 and integrating the equation from r ) rito r ) rowith the boundary conditions CL) CL,iand CL) CL,o, respectively.

Results and Discussion

Figure 3 shows the dependence of kLa on rotational

speed at different outer radii of the packed bed for four liquid flow rates. As shown in eq 9, the mass transfer coefficient, kLa, was calculated based on the volume of

the packed bed. Four outer radii of 3, 4, 5, and 6 cm were investigated, while the inner radius was set at 2 cm. First, as expected, it is found in the figure that kLa

increased with increasing rotational speed, indicating that centrifugal force could enhance mass transfer. Besides, it is also noted that kLa increased with an

increase in liquid flow rate. These characteristics have been observed and discussed in previous research. In addition, from Figure 3, it is clearly seen that kLa

increased as the outer radius of the bed decreased. It is suggested that the dependence of mass transfer coef-ficients in the radial direction is due to the variation of centrifugal acceleration and liquid flux. In eqs 2 and 3, it is found that mass transfer coefficients increase with centrifugal acceleration and liquid flux to the power of

1_/

6 and 1/3, respectively. Therefore, it is expected that

the mass transfer coefficients would decrease with increasing radial distance. In addition, it should be noted that, with decreasing the outer radius of the bed, the volume of the bed decreases and, at the same time, the volume between the outer radius of the bed and the stationary housing increases. As a result, the end effects in an RPB would become more significant, and an Figure 3. Dependence of kLa on rotational speed at different outer radii of the packed bed; liquid flow rate ) (a) 258 mL/min, (b) 435

mL/min, (c) 612 mL/min, and (d) 822 mL/min.

S )HQG QL (8) kLa ) Q_L π(ro 2_{- r} i 2 )z ln

[

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overestimated value of kLa, which is calculated based

on the volume of the packed bed, was obtained. The effect of rotational speed on kLa at various inner

radii of the packed bed was shown in Figure 4. Inner radii of 1, 2, 3, 4, and 5 cm were investigated while the outer radius was kept at 6 cm. As shown in the figure,

kLa increased as the inner radius of the bed increased.

Though, by the effect of centrifugal acceleration and liquid flux, the mass transfer coefficient may decrease as the inner radius of the bed increases, the end effects would become more significant because of the smaller volume of the bed. Thus, kLa increased with increasing

inner radius of the bed. Figure 5 shows the dependence of kLa on rotational speed for different radial positions

of the packed bed whose thickness was set to 1 cm. It is found that kLa increased as the radial distance of the

bed decreased. As discussed previously, increasing the radial distance of the bed provides higher centrifugal acceleration, but the liquid flux would decrease because of the larger cross-sectional area. This would lead to a decrease of the mass transfer coefficient. Besides, the volume of the bed would decrease when reducing the radial distance of the bed, and kLa may be overestimated

by the end effects. It can be concluded that the mass

transfer coefficients may be affected by centrifugal acceleration, liquid flux, and end effects for different radii of the bed. However, from the results shown in Figures 3-5, the intrinsic influence of centrifugal ac-celeration and liquid flux may probably be hindered by the end effects.

A correlation was developed to predict the liquid-side mass transfer coefficient in an RPB. Since the end effects obviously influence kLa, they should be included

in the correlation. The end effects in an RPB depend on the volume inside the inner radius of the bed (Vi),

the volume between the outer radius of the bed and the stationary housing (Vo), and the total volume of the RPB

(Vt). Vi, Vo, and Vtcan be expressed as

From a regression of the experimental data shown in Figure 4. Dependence of kLa on rotational speed at different inner radii of the packed bed; liquid flow rate ) (a) 258 mL/min, (b) 435

mL/min, (c) 612 mL/min, and (d) 822 mL/min.

V_i) πr_i2z (10) Vo) π(rs 2_{- r} o 2 )z (11) V_t) πr_s2z (12)

Figures 3-5, a correlation, which takes end effects into consideration, can be expressed as

To verify the correlation obtained above, more experi-ments of deoxygenation in RPB-1 with viscous glycerol solutions (Newtonian fluids) and CMC (carboxymethyl cellulose) solutions (non-Newtonian fluids) were em-ployed.10_{The inner and outer radii of the bed were set}

at 1 and 6 cm, respectively. The packing used was also 0.22-mm-diameter stainless steel wire mesh, whose porosity and interfacial area were 0.954 and 829 1/m, respectively. Furthermore, experiments of deoxygen-ation in RPB-2 packed with 2-mm-diameter plastic beads were also included. For RPB-2, the radii of the inner and outer edge of the bed and the stationary housing were 2, 4, and 6 cm, respectively, while the axial height of the bed was 2 cm. The porosity and the interfacial area of the packing were 0.6 and 1200 1/m,

respectively. These experimental results are listed in Table 2. In Figure 6a, it is found that the experimental values of kLa can be predicted well by the empirical

correlation of eq 13. This indicates that the correlation is valid for different sizes of RPBs (RPB-1 and RPB-2) and for viscous Newtonian (glycerol solutions) and non-Newtonian (CMC solutions) media. The ranges of the dimensionless groups in eq 13 are 9.12 e kLadp/Date 2.54 × 103_{, 0.116 e (1 - 0.93(V} o/Vt) - 1.13(Vi/Vt)) e 0.645, 5.0× 102 e µ/FD e 1.2 × 105, 2.3× 10-3e L/atµ e 8.7, 1.2 × 102 e (dp3F2ac)/µ2 e 7.0 × 107, and 3.7× 10-6 _{e L}2_/Fa

tσ e 9.4 × 10-4. Also, it is noted in the

correlation that the value of kLa depends on centrifugal

acceleration to the power of 0.3, which is close to the exponent (0.3-0.38) proposed by Munjal et al.2_{and the}

exponent (0.3-0.35) reported by Keyvani and Gardner.14

Furthermore, the kLa data available in the open

literature are compared with the values calculated by eq 13. In 1981, Ramshaw and Mallinson1_{reported the}

results of a water-oxygen system in an RPB packed with 1-mm glass beads and copper gauze, respectively. The inner and outer radii of the bed were 4 and 9 cm, respectively, but the axial height of the bed was not reported. In 1989, Munjal et al.2 _{studied the mass}

Figure 5. Dependence of kLa on rotational speed at different radial positions of the packed bed; liquid flow rate ) (a) 258 mL/min, (b)

435 mL/min, (c) 612 mL/min, and (d) 822 mL/min.

kLadp Dat

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transfer characteristics by absorption of CO2from air

into NaOH. Two outer radii of the bed of 7 and 8.7 cm were investigated, while the inner radius was set at 3.8 cm. Keyvani and Gardner14 _{obtained mass transfer}

coefficients with various surface areas of aluminum foam metal as packing in a CO2-water system. In 1990,

Kumar and Rao15_{performed experiments of absorption}

of CO2from air into NaOH solutions in an RPB packed

with wire meshes. In 1992, Singh et al.12_{evaluated the}

performance of an RPB with various outer radii of the bed for air stripping of VOCs from groundwater. A liquid sampling tube was installed near the outer radius of the bed to minimize end effects. In 2004, Chen et al.16

investigated the mass transfer coefficient by absorption of oxygen into water. The specifications of the RPBs and the packings used in the above studies are shown in

Table 3. However, the radius of the stationary housing was not reported in these works. In the studies of Ramshaw and Mallinson1_{and Munjal et al.,}2_{liquid left}

the packed bed through a liquid seal lip, instead of splashing onto the stationary housing. As a result, the end effect in the outer region could be insignificant, and the radius of the stationary housing was assumed to be the same as the outer radius of the bed. Singh et al.12

installed a liquid sampling tube near the outer radius of the bed, and therefore, the end effect in the outer region could be ignored. In other works, estimated ranges of the stationary housing are given, and these are listed in Table 3.

In Figure 6b, the errors bars of the calculated values are the estimated ranges of the unknown parameters listed in Table 3. It is seen in Figure 6b that, with the

Table 2. Experimental Results of Glycerol and CMC Solutions in RPB-1 and Water in RPB-2a

RPB

used systemsexp.

liquid flow rate (mL/min) liquid viscosity (mPa‚s) rotat. speed

(rpm) (mol/L)CL,o (1/s)kLa RPBused systemsexp.

liquid flow rate (mL/min) liquid viscosity (mPa‚s) rotat. speed (rpm) (mol/L)CL,o (1/s)kLa RPB-1 O2-glycerol 143 1.95 600 2.44× 10-5 0.0251 RPB-1 O2-CMC 200 1.72 600 1.76× 10-5 0.0402 solutions 900 1.43× 10-5 _{0.0309 solutions 1.55 900 9.00× 10}-6 _0.0504 1200 1.09× 10-5 0.0339 1.43 1200 5.40× 10-6 0.0582 1500 8.14× 10-6 0.0371 1.35 1500 4.97× 10-6 0.0595 258 1.95 600 2.64× 10-5 _{0.0439 200 5.76 600 2.82× 10}-5 _0.0330 900 1.58× 10-5 _{0.0540 5.07 900 1.99× 10}-5 _0.0383 1200 9.87× 10-6 _{0.0632 4.64 1200 1.27× 10}-5 _0.0452 1500 6.91× 10-6 _{0.0702 4.32 1500 8.30× 10}-6 _0.0517 143 3.98 600 6.09× 10-5 0.0150 RPB-1 O2-CMC 200 19.08 600 6.69× 10-5 0.0199 900 3.47× 10-5 _{0.0211 solutions 16.92 900 4.58× 10}-5 _0.0257 1200 2.40× 10-5 _{0.0251 15.53 1200 3.25× 10}-5 _0.0309 1500 1.48× 10-5 _{0.0304 14.54 1500 2.18× 10}-5 _0.0370 258 3.98 600 6.11× 10-5 _{0.0270 200 34.07 600 7.19× 10}-5 _0.0188 900 3.78× 10-5 _{0.0365 29.34 900 4.71× 10}-5 _0.0253 1200 2.28× 10-5 0.0464 26.39 1200 3.46× 10-5 0.0299 1500 1.33× 10-5 _{0.0570 24.31 1500 2.91× 10}-5 _0.0326 143 9.32 600 9.05× 10-5 _{0.0103 200 204.36 600 1.15× 10}-4 _0.0117 900 4.60× 10-5 _{0.0177 166.92 900 8.35× 10}-5 _0.0166 1200 3.17× 10-5 _{0.0217 144.59 1200 5.76× 10}-5 _0.0222 1500 1.76× 10-5 _{0.0281 129.35 1500 3.80× 10}-5 _0.0285 258 9.32 600 8.58× 10-5 0.0197 RPB-2 O2-water 149 1 300 5.27× 10-5 0.0510 900 4.93× 10-5 _{0.0306 1 600 2.56× 10}-5 _0.0748 1200 3.17× 10-5 _{0.0393 1 900 1.34× 10}-5 _0.0960 1500 1.78× 10-5 _{0.0506 1 1200 1.07× 10}-5 _0.1035 143 14.4 600 9.87× 10-5 _{0.0090 1 1500 8.94× 10}-6 _0.1094 900 5.50× 10-5 _{0.0153 1 2100 7.45× 10}-6 _0.1154 1200 3.52× 10-5 0.0202 258 1 300 6.96× 10-5 0.0786 1500 2.55× 10-5 _{0.0237 1 600 3.23× 10}-5 _0.1263 258 14.4 600 1.14× 10-4 _{0.0133 1 900 1.84× 10}-5 _0.1498 900 6.69× 10-5 _{0.0238 1 1200 1.07× 10}-5 _0.1693 1200 4.06× 10-5 _{0.0336 1 1500 7.45× 10}-6 _0.1873 1500 2.46× 10-5 _{0.0435 1 2100 4.72× 10}-6 _0.2069 RPB-1 O2-glycerol 143 25.1 600 1.08× 10-4 0.0082 435 1 300 7.65× 10-5 0.1137 solutions 900 8.85× 10-5 _{0.0104 1 600 4.17× 10}-5 _0.1724 1200 5.88× 10-5 _{0.0148 1 900 2.73× 10}-5 _0.2135 1500 4.80× 10-5 _{0.0170 1 1200 1.84× 10}-5 _0.2520 258 25.1 600 1.07× 10-4 _{0.0150 1 1500 1.37× 10}-5 _0.2808 900 8.76× 10-5 0.0189 1 2100 9.69× 10-6 0.3142 1200 6.09× 10-5 0.0260 RPB-2 O2-water 612 1 300 9.84× 10-5 0.1259 1500 4.80× 10-5 _{0.0307 1 600 5.22× 10}-5 _0.1866 143 40.5 600 1.13× 10-4 _{0.0063 1 900 3.63× 10}-5 _0.2623 900 1.08× 10-4 _{0.0068 1 1200 2.53× 10}-5 _0.3115 1200 8.20× 10-5 _{0.0099 1 1500 1.76× 10}-5 _0.3611 1500 7.24× 10-5 0.0112 1 2100 1.17× 10-5 0.4177 258 40.5 600 1.09× 10-4 _{0.0122 822 1 300 1.07× 10}-4 _0.1539 900 1.01× 10-4 _{0.0138 1 600 6.46× 10}-5 _0.2300 1200 7.49× 10-5 _{0.0196 1 900 4.10× 10}-5 _0.3307 1500 6.72× 10-5 _{0.0217 1 1200 2.93× 10}-5 _0.3927 O2-CMC 200 1.22 600 1.21× 10-5 0.0459 1 1500 2.38× 10-5 0.4308 solutions 1.20 900 6.13× 10-6 0.0563 1 2100 1.44× 10-5 0.5240 1.19 1200 4.47× 10-6 _0.0611 1.19 1500 3.97× 10-6 _0.0629 200 1.38 600 1.38× 10-5 _0.0439 1.32 900 6.29× 10-6 _0.0559 1.27 1200 4.39× 10-6 _0.0614 1.23 1500 4.31× 10-6 0.0617

a_{Some of the kLa data were presented in our previous study.}10

exception of the data of Kumar and Rao,15 _{eq 13 can}

reasonably estimate most of the liquid-side mass trans-fer coefficients in previous Higee studies.

Conclusion

In this study, the mass transfer efficiency of an RPB with various inner and outer radii has been examined. The mass transfer coefficients were investigated as a function of rotational speed, liquid flow rate, inner radius of the packed bed, outer radius of the packed bed,

and radial position of the bed. Experimental results showed that kLa increased with increasing rotational

speed and liquid flow rate. Besides, a smaller bed showed a higher value of kLa. This is mainly due to the

fact that the contribution of the end effects may be more significant as the volume of the packed bed is reduced. A correlation, which takes end effects into consideration, was developed to predict kLa in an RPB. Results showed

that this correlation was valid for various sizes of the RPBs and for viscous Newtonian and non-Newtonian liquid systems. The mass transfer coefficient increased with centrifugal acceleration to the power of 0.3, which was close to the exponent proposed by Munjal et al.2

and Keyvani and Gardner.14_{Besides, it was found that}

the correlation could reasonably estimate most of the

kLa data in the Higee literature. Acknowledgment

The support from Ministry of Economic Affairs, Taiwan, Republic of China, is greatly appreciated.

Nomenclature

a ) gas-liquid interfacial area (1/m) at) surface area of the packing (1/m)

ac) centrifugal acceleration (m2/s)

CG) concentration of solute in the gas stream (mol/L)

CG,i) concentration of solute in the inlet gas stream (mol/

L)

CL) concentration of solute in liquid stream (mol/L)

CL*) equilibrium concentration associated with the gas

concentration (mol/L)

CL,i ) concentration of solute in the inlet liquid stream

(mol/L)

CL,o) concentration of solute in the outlet liquid stream

(mol/L)

D ) diffusion coefficient (m2_/s)

dp) spherical equivalent diameter of the packing ) [6(1

- )/atψ] (m)

g ) gravitational force (m/s2₎

H ) Henry’s law constant [(mol/L)/(mol/L)] kL) liquid-side mass transfer coefficient (m/s)

kLa ) volumetric liquid-side mass transfer coefficient (1/s)

L ) liquid mass flux [kg/(m2_s)]

QG) gas flow rate (m3/s)

QL) liquid flow rate (m3/s)

ri) inner radius of the packed bed (m)

ro) outer radius of the packed bed (m)

rs) radius of the stationary housing (m)

S ) stripping factor defined as eq 8

Vi) volume inside the inner radius of the bed (m3)

Vo) volume between the outer radius of the bed and the

stationary housing (m3₎

Vt) total volume of the RPB (m3)

a_{Values or range estimated.}

Figure 6. Comparison of experimental values of kLa with results

calculated using eq 13. Experimental data from (a) our work and (b) literature.

X ) surface renewal parameter (m) z ) axial height of the packing (m) Greek Letters

 )porosity of the packing

µ ) viscosity of liquid (Pa‚s)

F ) density of liquid (kg/m3₎

ψ ) sphericity of packing

Literature Cited

(1) Ramshaw, C.; Mallinson, R. H. Mass Transfer Process. U.S. Patent 4,283,255, 1981.

(2) Munjal, S.; Dudukovic, M. P.; Ramachandran, P. Mass-Transfer in Rotating Packed Beds. II. Experimental Results and Comparison with Theory and Gravity Flow. Chem. Eng. Sci. 1989, 44, 2257.

(3) Lin, C. C.; Liu, H. S. Adsorption in a Centrifugal Field: Basic Dye Adsorption by Activated Carbon. Ind. Eng. Chem. Res.

2000, 39, 161.

(4) Chen, Y. S.; Liu, H. S. Absorption of VOCs in a Rotating Packed Bed. Ind. Eng. Chem. Res. 2002, 41, 1583.

(5) Lin, C. C.; Ho, T. J.; Liu, W. T. Distillation in a Rotating Packed Bed. J. Chem. Eng. Jpn. 2002, 35, 1298.

(6) Onda, K.; Takeuchi, H.; Okumoto, Y. Mass Transfer Coef-ficients between Gas and Liquid Phases in Packed Columns. J. Chem. Eng. Jpn. 1968, 1, 56.

(7) Munz, C. Air-Water Phase Equilibria and Mass Transfer of Volatile Organic Solutes. Ph.D. Dissertation, Stanford Univer-sity, Stanford, CA, 1985.

(8) Tung, H. H.; Mah, R. S. H. Modeling Liquid Mass Transfer in Higee Separation Process. Chem. Eng. Commun. 1985, 39, 147.

(9) Munjal, S.; Dudukovic, M. P.; Ramachandran, P. Mass-Transfer in Rotating Packed Beds. I. Development of Gas-Liquid and Liquid-Solid Mass-Transfer Correlations. Chem. Eng. Sci.

1989, 44, 2245.

(10) Chen, Y. S.; Lin, C. C.; Liu, H. S. Mass Transfer in a Rotating Packed Bed with Viscous Newtonian and Non-Newtonian Fluids. Ind. Eng. Chem. Res. 2005, 44, 1043.

(11) Burns, J. R.; Jamil, J. N.; Ramshaw, C. Process Intensi-fication: Operating Characteristics of Rotating Packed Bedss Determination of Liquid Hold-up for a High-Voidage Structured Packing. Chem. Eng. Sci. 2000, 55, 2401.

(12) Singh, S. P.; Wilson, J. H.; Counce, R. M.; Villiersfisher, J. F.; Jennings, H. L.; Lucero, A. J.; Reed, G. D.; Ashworth, R. A.; Elliott, M. G. Removal of Volatile Organic-Compounds from Groundwater Using a Rotary Air Stripper. Ind. Eng. Chem. Res.

1992, 31, 574.

(13) Brown, G. G. Unit Operations; Wiley: New York, 1950. (14) Keyvani, M.; Gardner, N. C. Operating Characteristics of Rotating Beds. Chem. Eng. Prog. 1989, 85, 48.

(15) Kumer, M. P.; Rao, D. P. Studies on a High-Gravity Gas-Liquid Contactor. Ind. Eng. Chem. Res. 1990, 29, 917.

(16) Chen, Y. H.; Chang, C. Y.; Su, W. L.; Chen, C. C.; Chiu, C. Y.; Yu, Y. H.; Chiang, P. C.; Chiang, S. I. M. Modeling Ozone Contacting Process in a Rotating Packed Bed. Ind. Eng. Chem. Res. 2004, 43, 228.

Received for review October 26, 2004 Revised manuscript received July 19, 2005 Accepted August 1, 2005

IE048962S Ind. Eng. Chem. Res., Vol. 44, No. 20, 2005 7875