Ind. Eng. Chem. Res. 1993,32, 2213-2219
2213
Mass-Transfer Efficiency of a Large-Scale Sieve Tray Extractor A. Frank Seibert' and James R. Fair Separations Research Program, The University of Texas at Austin, Austin, Texas 78758
The mass transfer efficiency and phase flow capacity of a 42.5-cm-diameter (i.d.1 sieve tray extractor has been investigated. The extraction of acetone from water with toluene was chosen because of the large amount of data for comparison with the performance of other devices, and particularly because of available data for a smaller sieve tray extractor tested in the same laboratory. For capacity studies, the Isopar-m/water system was also used. The performance of the sieve trays was compared with that of sprays and packings in the same column. Important parameters were found to be phase flow rates, flow ratios, and column diameter. Mechanistic hydraulic and mass transfer models, found to correlate well the experimental data, are presented in the paper. Sieve trays are often used for continuous extraction in the chemical and petrochemical industries. The sieve tray extractor is simple in design, requires no moving parts, and can handle some slurries. It is similar to the spray column but is more efficient because the trays prevent backmixing of both phases over the entire column. Instead, backmixing is limited to within each tray. The trays also allow for the reformation of the dispersed phase drops, thereby enhancing mass transfer. The sieve tray extractor consists of a series of perforated plates, as shown in Figure 1. In the Operation, the sieve holes function to re-form and redistribute drops. In the case of dispersing the light phase, drops rise through the crossflowing continuous phase and up to a light-phaselayer underneath the tray above, where they coalesce. Drops are then re-formed by the holes and the operation is repeated on up the column. In this case, the continuous phase enters and exits the trays by passing through downcomers. When the heavy phase is dispersed, upcomers are used, a coalesced layer is on top of each tray, and re-formed drops fall through the crossflowing continuous phase. Sieve tray columns can provide good efficiency and high throughputs, especially for systems with low-to-moderate interfacial tensions. The typical range of sieve tray geometries is given in Table I. The objectives of the present research were to obtain mass transfer and capacity data for a 42.5-cm-diameter sieve tray extractor, and to compare the data with those taken in the same column using a commercial structured packing and with efficiency data taken in a small-diameter sieve tray column, with both comparisons based on the same test system. The column size for the present work is considered "large" by university standards but might be called "intermediate" by industrial standards. Another objective of the present work was to determine the fit of the mass transfer data collected to a physical model previously verified for small-diameter sieve tray columns.
Light liquid out
intefface O p
e
m
t
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Previous Work The efficiency of sieve trays under liquid extraction operation was first reported by Row et al. in 1941, who studied the extraction of benzoic acid from toluene with water. In a following work Treybal and Dumoulin (1942) used the same system but with different tray spacings. Allerton et al. (1943) determined the effect of kerosene instead of toluene as the organic phase, to determine physical property effects. While the earlier studies utilized dilute systems where there were insignificant changes in the phase rates due to mass transfer, Moulton and Walkey (1944) investigated the effect of a significant amount of
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i
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2214 Ind. Eng. Chem. Res., Vol. 32, No. 10, 1993 Table 11. Geometry of Sieve Trays Studied in This Work 0.47 hole diameter, cm 30.4 tray spacing, cm 15.2 downcomer length, cm 0.0393 fractional free area 0.081 fractional downcomer area 3 pitch/hole diameter
Table I. TyBical Range of Sieve Tray Geometries parameter range hole diameter, cm 0.32-0.64 fractional free area 0.03-0.08 fractional downcomer area 0.03-0.1 pitch/hole diameter ratio 3-4 tray spacing, cm 15-45
acetic acid/water systems. The interesting discover in this work was that relatively high efficiencies coul be obtained, of the order of 30-50 % , as found also by Pyle and co-workers;this was attributed to the lower interfacial tension of the test systems. An additional contribution by Mayfield and Church was the recommendation that the sieve tray holes be punched such that an extended lip would promote jet formation and prevent wetting of the tray by the dispersed phase. In 1953,Garner et al. studied the effect of enhancing coalescence with a gauze screen using the toluene/diethyl amine/water system. In a second study by Garner and co-workers (1956), the effect of tray wettability by the dispersed phase was studied using Teflon and metallic plates. These researchers also noted that low interfacial tension systems produced higher tray efficiencies; they attributed this to a higher degree of circulation within the drop and the ease a t which solute could be transferred to the interface. After the 1956paper of Garner and co-workers, research shifted to the development of mass transfer correlations for the prediction of tray efficiency and column design. The mass-transfer efficiency of laboratory-scale sieve tray columns has been modeled by Treybal(1963,1980), Skelland and co-workers (Skelland and Conger, 1973; Skelland and Huang,1977,1979),Pilhofer and co-workers (Pilhofer and Goedl, 1977; Pilhofer,l981; Schultz and Pilhofer, 19821, and Rocha et al. (1986). Descriptions of the models are given by Fair et al. (1984) and by Rocha and co-workers (1986,1989a,b). The effect of continuous-
J
phase mixing on a crossflow sieve tray was studied by Eldridge (1986) and Eldridge et al. (1987). The masstransfer efficiency of sieve trays under supercritical extraction conditions has also been investigated by Lahiere and Fair (19871,Seibert and Moosberg (1988),and Seibert et al. (1988).
Experimental Equipment and Procedure The extraction/distillation system used in this study is represented by the flow diagram in Figure 2. In part it has been described previously by Seibert et al. (1990). The extraction and distillation columns with associated piping are fabricated from carbon steel. The 20 sieve trays are of 316 stainless steel and arranged in two 10-tray cartridge bundles. The geometry of the sieve trays is given Table 11. Solvent toluene is fed to the contacting zone through a light-phase distributor located near the bottom of the extractor. The aqueous feed is mixed with acetone, and the mixture enters the contacting zone through a distributor at the top of the column. The extract stream, toluene with acetone, leaving the top of the extractor flows to the distillation feed tank. This mixture is preheated to 125 "C and then separated in a 42.5-cm distillation column containing 610 cm of Flexipac 2 structured packing and operated at 4.1-atm pressure. Toluene is removed as bottoms from the distillation column and is cooled before entering the extractor feed tank. The acetone is taken
I
I
-
d Aqueous Feed Tank
Figure 2. Flow diagram of extraction/distillation test system.
Ind. Eng. Chem. Res., Vol. 32, No. 10,1993 2215 Table 111. Physical Properties of the Test Systems Studied in This Work toluene/ Isopar-m/ acetonelwater water aqueous phase viscosity, CP 1.2 0.89 density, g/mL 0.994 0.994 1.29 X IW solute diffusion coeff, cm2/s organic phase viscosity, CP 0.54 2.24 density, g/mL 0.86 0.78 solute diffusion coeff, cm2/s 2.88 X 106 distribution coeff interfacial tension
0.77 22
I
t
25
overhead and collected in an accumulator. The raffinate stream (aqueous-rich stream exiting the bottom of the extractor) is recycled to the aqueous feed tank. The toluene/acetone/water system was chosen for the mass transfer and capacity study because of the availability of data obtained from smaller columns. It is also one of the three extraction test systems recommended by the European Federation of Chemical Engineering (Misek et al., 1985). In the present work, acetone was extracted from water with toluene as the dispersed phase. The Isopar-m/water system was also studied to obtain additional capacity data, with the organic phase dispersed. Physical properties of the two systems are given in Table 111. Technical grade solvents and solutes of at least 99 w t % purity were used to minimize contamination. The acetone content of the aqueous and organic streams was determined by gas chromatography using a Porapak Q column and a thermal conductivity detector. Runs with material balance closures of less than 90% were discarded. With acceptable closure, the extract composition was checked to ascertain that no pinch occurred between equilibrium and operating lines. To avoid this condition, solvent-to-feed ratios equivalent to that of the distribution coefficient were used.
Experimental Results The flow conditions and measured stage efficiencies for toluene/acetone/water are given in Table IV and illustrated in Figure 3 as a function of throughput and solvent-tofeed ratio. As shown in the figure, the tray efficiency increases with dispersed phase rate until the latter reaches avalue of about 1.0 cm3/(crn2*s),beyond which it declines. An explanation for this is that as dispersed-phase rate increases, dispersed-phase holdup also increases, providing additional interfacial area for mass transfer. A competing effect, however, is the diminishing region for drop rise transfer as the coalesced layer thickens. Also, increased backmixing of the dispersed-phase drops at higher rates was observed through windows in the column; this effect
50
0 Column Dia = 10.2crn, SIF = 1.8 0 Column Dia = 42.5 cm, S/F = 1.6
30 40
Overall Stage Elficiency, %
20 10
0
-
000 O n
0
0
0 0
I
0
I
.
I
.
would tend to lower the mass-transfer rate. The efficiency appears to be essentially independent of solvent-to-feed ratio. In the experiments acetone was transferred from the water (continuous) phase to the toluene (dispersed) phase. It had been found earlier that for sieve trays the reverse direction gave somewhat lower efficiencies (Rocha et al., 1986);Seibert and Fair (1988) obtained similar results for packed columns. The scope of the present work did not include acetone transfer from the toluene phase, and also did not include studies with the water phase dispersed. As shown in Figure 4, the effect of column diameter on the sieve transfer was determined to be small except at high rates where there was a significant reduction in efficiencywith the large-scale device. The 10.2-cm column diameter data are those of Rocha et al. (1986). It appears that the competitive effects noted above are shifted to a higher rate for the smaller column. Another comparison of the data with other devices is shown in Figure 5. The performance of the sieve tray extractor compares favorably
Table IV. Sieve Tray Mass-Transfer Data for the Toluene/Aoetone/Water System toluene toluene aqueous aqueous run rate, kglh velocity, cmls rate, kg/h velocity, cm/s 0.257 1080 0.210 1 1080 0.412 1728 0.332 1800 2 2556 0.490 0.618 2736 3 3420 0.824 0.656 3600 4 0.822 1.030 4284 4536 5 1.133 4716 0.910 5004 6 0.210 0.412 1080 1800 7 0.618 1620 0.315 2736 8 2196 0.420 0.824 3600 9 4536 1.030 2736 0.525 10 1.236 3276 0.630 5436 11 0.680 2196 0.420 2988 12
no. of stages 3.18 3.58 4.72 3.96 4.96 3.74 3.66 4.6 5.5 3.36 1.88
4.68
overall stage efficiency, % 15.9 17.9 23.6 19.8 24.8 18.7 18.3 23.0 27.5 16.8 9.4 23.4
HETS, cm 191 170
129 154 123 163 166 133 111 181
324 130
2216 Ind. Eng. Chem. Res., Vol. 32, No. 10,1993 1
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.
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Table V. Sieve Tray Capacity Data systema udi (cm/s) u d (cm/s) systema Udt (cm/s)
.
0
0
HETS (m)
1
*
’
*
. ’ .
1 1
1 1 1 2 2
0.26 0.41 0.62 0.82 1.03 1.13 1.24 1.55 0.36 0.52
1.58 1.49 1.23 1.18 0.96 0.91 0.63 0.26 2.22 1.78
u d (cm/s)
0.62 0.72 0.83 0.96 0.98 0.89 1.04 1.42 1.36
2 2 2 2 2 2 2 2 2
1.73 1.60 1.33 1.24 1.15 1.24 1.10 0.44 0.63
1 = toluene (d)/acetone/water (c); 2 = Isopar-m (d)/water (c).
for the Isopar-dwater and toluene/acetone/water systems are equivalent at low continuous phase flow rates. However, at high continuous phase rates, the capacity for the toluene/acetone/water system is lower. This could likely be attributed to agreater drag force on the smaller toluene droplets. The experimental data are given in Table V.
Model Development Stage Efficiency. The earliest model for predicting the overall stage efficiency was an essentially empirical one reported by Treybal(1963). Krishnamurty and Rao (1968) modified the Treybal model to account for hole diameter:
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3 0 Toluene/AoetoneANater 2 -
Supenidel Vebdty of Me
0
DlspersedPhaseatFlood
cws
’
bo
where Z = tray spacing, cm; u = interfacial tension, dyn/ cm; and do = hole diameter, cm. u d and Ucare superficial velocities of the dispersed and continuous phases, respectively. The local Murphree stage efficiency based on the dispersed phase may be calculated from eq 2. A more mechanistic model, developed by Treybal(1980), is based on the assumption that the continuousphase is completely mixed on each tray. This local efficiency may be converted
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E,, =
( 0.4Kd T d, ) + 3K,,,j4d(Z d,Ud (-? h) (2))+ f
2
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d,Ud to the overall stage efficiency using eq 3 (Lewis et al., 1951). The equation is applicable when there is complete mixing of the continuous phaee and plug flow in the dispersed phase. +
with that of a structured packing when the same column and auxiliaries are used. It should be noted, however, that the sieve trays were spaced at 30.5 cm; variations in this spacing would influence the value of the height of a theoretical stage (HETS). In general, the value of the HETS will increase with increasing tray spacing. The particular structured packing (Intalox 2T, from Norton Company) was selected as having about the same throughput capacity as the sieve trays tested. Before running the tray column, testa were made with no contacting internals (spray column basis), and Figure 5 also shows the relative advantage of using contacting devices. It is apparent that the trays compare favorably with the packing. The maximum flow (‘flood”) capacities of the sieve trays and structured packing are compared in Figure 6 and it is apparent that there is very little difference between the devices. The effect of system properties on capacity is shown in Figure 7, which also incorporates the effect of mass transfer on efficiency. The capacities of the column
6K,,&& - h)
f
(3) = ( Ud/ uc)mde
(4)
The conversion from local to overall efficiency entails an intermediate step in which the degree of mixing of the phases on the tray is evaluated. The model is based on the assumption of plug flow of the rising or falling drops and complete mixing of the continuous phase on the tray. It was found by Eldridge et al. (1987) that for a range of interfacial tensions there was little if any enhancement of local efficiency due to crossflow effects such as axial dispersion. Thus, the conversion indicatad in eq 3 is direct from local to overall efficiency. The mass-transfer parameters in eq 2 may be calculated from the equations given in Table VI. The applicability
Ind. Eng. Chem. Res., Vol. 32, No. 10,1993 2217 Table VI. Mass-Transfer and Hydraulic Correlations ref
Kd=-
eq
ref
eq
1
-+- mdckc 1
11
where
12
1)
kd
13
= 1.0 c = 1.4 d
-
d, no maas transfer c
14
24
15
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H I59.3
25
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H I59.3
26
pO.149
16
Kdf=-
NRe I
17
27
18
28
1
-+1
kf,d
mdc 'f,c
pn = 0.9
19
CP
29
20
30
21
1
22
32
R e = -doU&d
23
d, = 1 . 5 ~ ( ~ ) " ~ 4%
31
6
33
pd
(1)Seibert and Fair (1988); (2) Laddha and Degaleesan (1978); (3) Handlos and Baron (1957); (4) Higbie (1935); (5) Grace et al. (1976); (6) Pilhofer and Goedl(1977).
column was published by Seibert and Fair (1988) and is given in eq 5. The capacity of a spray extractor would
35 30
25
U, =
20 Predicted Stage Efficiency "% 15
10
5 n "
0
5
10
15
20
25
30
35
Experimental Stage Efficiency, % Figure 8. Parity plot for sieve tray efficiency.
of the equation to larger scale systems has not been previously verified. Comparisons between experimental and predicted efficiencies are shown in the parity plot of Figure 8. Agreement between the two efficiencies is reasonable. Capacity. A correlation for the prediction of sieve tray extractor capacity has not been previously reported. A fundamental model for predicting the capacity of a spray
0.178U, 1+ 0.925( U,l Ud)
represent the maximum capacity that could be obtained from a sieve tray column. As part of the present work,a new sieve tray capacity correlation has been developed which utilizes the coalesced layer height model of Treybal(1980). This correlation is based on the assumption that, at a flooding condition, the coalesced layer height is equal to the downcomer (or upcomer) length
where: (7)
2218 Ind. Eng. Chem. Res., Vol. 32, No. 10, 1993 3
transfer and capacity correlations of Treybal, with some modifications, were found to represent adequately the efficiency and maximum throughput capacity of the columns tested here and are expected to represent those of larger columns that are properly dimensioned.
Acknowledgment
n
0 1 2 3 Actual Continuous Phase Flooding Velocity, c d s
Figure 9. Parity plot for maximum (flood) capacity of sieve trays.
This work was funded by the Separations Research Program at The University of Texas a t Austin. Assistance in operating the extraction-distillation system was provided by Bobby Reeves. The authors are grateful for these contributions.
Nomenclature
and &,!I = downcomer (or upcomer) length,ffA= fractional free area, and ~ D A= fractional downcomer area. If the flooding velocity calculated from eq 6 is greater than the flooding velocity estimated for the spray column, then eq 5 is used to predict the sieve tray capacity. As shown in the parity plot, Figure 9, there is good agreement between the predicted capacity and the experimentally measured value. Design Comments. Good initial distribution is not as essential in the sieve tray extractor as it is in the packed extractor, since the trays provide redistribution. While the same distributors used in packed columns would be applicable, simpler devices can also be used. Capped pipes with holes drilled uniformly have been found to be adequate. Sieve hole velocities of 15-30 cmfs have been tested and found to give negligible secondary or "daughter" drops which tend to be entrained with the continuous phase. The secondary drops cannot be totally avoided, and coalescing pads located a t the ends of the column can recoalesce the smaller drops into larger drops which are not entrained. These coalescing devices have been found to impose little restriction on process flows. However, they should be avoided if solids are present in the feeds. It is noted that pitchfhole diameter ratios should be greater than 3 to prevent coalescence between adjacent sieve holes (Treybal, 1980). The fractional free area and downcomer area should be designed to give a coalesced layer height of 5 cm. In addition, the Weber number given in eq 10 should be designed with a value greater than 2 to ensure that all of the sieve holes produce drops, i.e., to avoid inactive holes.
Summary and Conclusions The efficiency and capacity of a 42.5-cm-diameter sieve tray extractor have been measured, using a standard test mixture. The performance of the sieve trays has been found equivalent to that of a structured packing and, as expected, superior to a spray-type contactor. The experimental data have been compared with those taken earlier witha 10.2-cmsieve tray extractor, and a predictive model has been found to represent the efficiencies a t both scales of operation under normal design conditions. At high throughputs, the efficiency of the larger column was as low as 50% of that of the smaller column. The mass-
A , B, C = parameters in eq 6 C, = concentration of solute in continuous phase, g/cm3 C d = concentration of solute in dispersed phase, g/cm3 c d * = equilibriumconcentration of solute in dispersed phase, g/cm3 do = hole diameter, cm d, = Sauter mean drop diameter, cm D, = diffusion coefficientof solute into the continuousphase, cm2/s D d = diffusion coefficient of solute into the dispersed phase, cm21s E m = Murphree dispersed phase efficiency, fractional E, = overall stage efficiency fDA =fraction of tray area occupied by the downcomer ffA = fraction of tray area occupied by the free area g = gravitational constant, cm/s2 h = coalesced layer height, cm H = parameter defined in eq 28 N , =number of holes on the tray HETS = height equivalent to a theoretical stage, cm k , , = continuous-phasefilm mass-transfer coefficient, cm/s kd,, = dispersed-phase film mass-transfer coefficient, cm/s kf,, = drop formation continuous-phase mass-transfer coefficient, cm/s kf,d = drop formation dispersed-phase mass-transfer coefficient, cm/s K, = overall mass-transfer coefficientbased on the continuous phase, cm/s K d = continuous-phasevolumetricmass-transfercoefficient, cm/s Kd = overall mass-transfercoefficientbased on the dispersed phase, cm/s Kd f = overall dispersed-phasemass-transfer coefficient for drop formation, cm/s L d c = downcomer length, cm m d , = equilibrium distribution coefficient, dCd*/dC, P = parameter defined in eq 27 Q d = volumetric flow rate of the dispersed phase, cm3/s Re, = continuous-phaseReynolds number R e d = dispersed-phase Reynolds number Sc, = continuous-phase Schmidt number, wJpc D, S C d = dispersed-phase Schmidt number, P d P d Dd U,= superficial continuous velocity, cmls Ud.=continuous-phasesuperficial flooding velocity for the sieve tray extractor, cm/s Ud = superficial dispersed-phase velocity, cm/s Ua = dispersed-phase flooding velocity, cm/s &ow = downcomer velocity, cm/s U, = hole velocity, cm/s U, = slip velocity, cm/s V, = characteristic slip velocity, cm/s We = Weber number z = tray spacing, cm 2 = contacting height, cm
Ind. Eng. Chem. Res., Vol. 32, No. 10,1993 2219 Greek Symbols = dispersed-phase holdup, fractional CP = criteria for determining which dispersed-phase masstransfer model to use pc = continuowphase density, glcms Pd = dispersed-phase density, g/cmS Ap = density difference, g/cms Of = time of drop formation, s I . C ~= continuous-phase viscosity, CP I.Cd =dispersed phase Viscosity, CP I . C ~= aqueous Viscosity, CP u = interfacial tension, dynlcm X = extraction factor, mdc(Ud/Uc) dd
Literature Cited Allerton, J.; Strom, B. 0.; Treybal, R. E. Liquid Extractiion in Perforated-Plate and Packed Towers. Trans. AZChE 1943, 39, 361. Eldridge, €2. B. Mixing Characteristics of a Crossflow Sieve Tray Extractor. Ph.D. Dissertation, The University of Texas at Austin, 1986. Eldridge, R.B.; Humphrey, J. L.; Fair, J. R.Continuous Phase Mixing on Crossflow Extraction Sieve Trap. Sep. Sci. Technol. 1987,2, 1121-1134. Fair, J. R.;Rocha,J. A.; Humphrey, J. L. Efficiency of Crossflow Sieve Tray Extractors. Solvent Extr. Zon Exch. 1984,2,985. Garner, F. H.; Ellis, S. R. M.; Fosbury, D. W. Perforated Plates in Liquid-Liquid Extraction. Trans.Znst. Chem. Eng. 1953,31,348. Garner, F. H.; Ellis, S. R. M.; Hill, J. W. Efficiency and Wetting Characteristics of Perforated Plate Columns. Tram. Znst. Chem. Eng. 1956,34, 223. Grace, J. R.;Wairegi, T.; Nguyen, T. H. Shapes and Velocities of Single Drops and Bubbles Moving Freely Through Immiscible Liquids. Trans. Znst. Chem. Eng. 1976,54,167. Handlos, A. E.; Baron, T. Mass and Heat Transfer from Drops in Liquid-Liquid Extraction. AIChE J. 1957,3,127. Higbie, R.The Rate of Absorption of a Pure Gas into a Still Liquid During Short Periods of Exposure. Trans. Am. Znst. Chem. Eng. 1935,31,366. Krishnamurtv. R. K.: Rao. C. V. Perforated-Plate Liauid-Liauid Extraction"Towers: Znd.'Eng. Chem. Process Des. Diu. 1968, 7, 166. Laddha, G. S.;Degaleesan, T. E. Transport Phenomena in Liquid Extraction; McGraw-Hill: New York, 1978. Lahiere, R. J.; Fair, J. R. Mass Transfer Efficiencies of Column Contactors in Supercritical Extraction Service. Znd. Eng. Chem. Res. 1987, 26, 2086. Lewis, J. B.; Jones, I.; Pratt, H. R. C. Part 111. A Study of Droplet Behaviour in Packed Columns. Trans. Znst. Chem. Eng. 1951,29, 126. MayField, F. D.; Church, W. L. Liquid-Liquid Extractor Design. Znd. Eng. Chem. 1952,44,2263. Misek,T.;Berger,R.; Schroter, J. Standard Test SystemsforLiquidLiquid Extraction; Institution of Chemical Engineers: Rugby, England, 1985.
Moulton, R. W.; Walkey, J. E. Liquid-Liquid Extraction in a Perforated Plate Column. Trans. AZChE 1944,40,695. Pilhofer, T. Optimum Design of Unpulsed Sieve Plate Extraction Columns. Chem. Eng. Commun. 1981,11,241. Pilhofer, T.; Goedl, R. Grenzbelastungen von Siebbodenextraktionskolonnen. Chem.-Zng.-Tech. 1977,49 (S),431. Pyle, C.; Colburn, A. P.; Duffy, H. R. Factors Controlling Efficiency and Capacity of Sieve Tray Extraction Towers. Znd. Eng. Chem. 1950,42,1042. Rocha,J. A., Humphrey, J. L., Fair,J. R.Mass Transfer Efficiency of Sieve Tray Extractors. Znd.Eng. Chem. Process Des. Dev. 1986, 25,862. Rocha, J. A.; Cardenas, J. C.; Sosa, C.; Rodes, J. Preliminary Design of SieveTray Extraction Columns. 1. Determination of the Column Diameter. Flooding Velocities in SieveTray. Znd. Eng. Chem. Res. 1989a,28,1873. Rocha, J. A.; Cardenas, J. C.; Garcia, J. A. Preliminary Design of Sieve Tray Extraction Columns. 2. Determination of the Column Height. Overall Efficiency of Sieve Tray Extractors. Znd. Eng. Chem. Res. 1989b,28,1879. Row, S. B., Koffolt, J. H., Withrow, J. R. Characteristics and Performance of a Nine-Inch Liquid-Liquid Extraction Column. Trans. AZChE 1941,37,559. Schultz, L., Pilhofer, T. Tray Efficiency in Unpulsed Sieve Tray Extraction Columns. Znt. Chem. Eng. 1982,22,61. Seibert, A. F., Fair, J. R.Hydrodynamics and Mass Transfer in Spray and Packed Extraction Columns. Znd. Eng. Chem. Res. 1988,27, 470-481. Seibert, A. F.; Moosberg, D. G. Performance of Spray, Sieve Tray, and Packed Contactors for High Pressure Extraction. Sep. Sci. Technol. 1988,23,2049. Seibert, A. F.; Moosberg, D. G.; Bravo, J. L.; Johnston, K. P. Spray, SieveTray, and Packed High Pressure Extraction Columns-Design a n d h a l p i s . h o c . Znt. Symp. Supercrit. Fluids 1988,2,561-570. Seibert, A. F., Reeves, B. E., Fair, J. R.Performance of a Large-Scale Liquid-Liquid Extractor. Znd. Eng. Chem. Res. 1990,29, 1901. Skelland, A. H. P.; Conger, W. L. A Rate Approach to the Design of Perforated Plate Extraction Columns. Znd. Eng. Chem. Process Des. Dev. 1973, 12,448. Skelland, A. H. P., Huang, Y. F. Dispersed Phase Mass Transfer During Drop Formation Under Jetting Conditions.AZChE J. 1977, 23, 701. Skelland, A. H. P.; Huang, Y. F. Continuous Phase Mass Transfer During Formation of Drops from Jets. AZChE J. 1979,25,80. Treybal, R.E. Liquid Extraction, 2nd ed.; McGraw-Hill: New York, 1963. Treybal, R. E. Mass Transfer Operatiom, 3rd ed.; McGraw-Hilk New York, 1980. Treybal, R. E.; Dumoulin, F. E. Liquid-Liquid Extraction in a Perforated Plate Tower. Znd. Eng. Chem. 1942,34,709.
Received for review December 22, 1992 Accepted May 10,1993.
* Abstract published in Advance ACS Abstracts, September 1, 1993.
