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1.6% of the chroniium was reduced when the cake was extracted with 1 to 1 sulfuric acid, No attempt was made to purify the precipitated vanadium. The analysis of the dry crude material indicates that the substance is disodium dihydrogen hexametavanadate, Na2H2VeOl7,as reported in the literature (3). The analysis of the crude product is given in Table VII.
The application of this process for purification of chromate liquors depends upon the end use of the liquors and the quantity of vanadium contained in the liquor. It is possible in the processing of chromite ores to alter the conditions of operation and t o allocate liquors containing more or less vanadium so as to meet the needs of the customers.
COAGULATION OF VANADIUM FROM ACID EXTRACT
(1) Argall, George O., Jr., Quart. Colo. School Mines, 38, No. 4, 36,37
LITERATURE CITED
(October 1943).
By adding leach liquor to the acid extract until the p H reaches 2 and heating to 90” C. while gently agitating for 3 hours, colloidal Na2H2V& forms and coagulates into an easily filtered product. The coagulation is best when the vanadium pentoxide content of the acid solution is 15 grams per liter or more. It is important to control the pH and time of reaction as shown by Tables VI11 and IX.
(2) Mellor,
J. W., “A Comprehensive Treatise on Inorganic and Theoretical Chemistry,” Vol. IX, p. 754, New York, Longmans, Green and Go., December 1939. (3) Ravitz, F.,et al., Metals Technol., 14, 12 (June 1947); Am. Inst. Mining Met. Engrs., Tech. Pub. 2178. (4) Van Wirt, A. E., et al., U . S. Patent 2,357,988 (1944). RECEIVED February 24, 1951.
Performance o development UNDER CONTROLLED AGITATION GEORGE FEICK
AND
HARRY M.ANDERSON
ARTHUR D. LITTLE, INC., CAMBRIDGE 49, MASS.
E
QUIPMENT for carrying out liquid-liquid extractions
may conveniently be divided into two basic classes (9) according as the separation of the two immiscible phases is effected by gravity or by centrifugal force. The most common forms of apparatus employing gravity separations are the countercurrent columns and the various mixer-settler combinations. In general, the countercurrent columns suffer from the disadvantage that the only energy available for agitation and maintenance of the dispersion is that which is derived from the density difference of the two liquids. Since this energy is usually insufficient to produce any subdivision of the dispersed-phase droplets, there is no mechanism for counteracting the effects of drop coalescence and the resulting decrease in the surface of contact between the two phases The result of this energy deficiency is that a column is a much less efficient device when used for extraction than it is when used for contacting a liquid with a vapor or a gas supplied by forced flow. On the other hand, the mixer-settler combinations provide abundant power for agitation and dispersion but have the drawback that they inherently involve batch operation. It is, therefore, awkward and expensive to carry out extractions in such equipment where the process requires a large number of equilibrium stages I n recent years, several types of apparatus have been devised which combine in some measure the desirable countercurrent feature of the column with the excellent interphase contact of the power-driven mixer ( 2 , 6, 8 IO, IS). Most of these devices consist essentially of a number of mixers arranged vertically to form a column with packed or baffled settling zones between each mixing zone. An experimental study of such a device has recently been published by Scheibel ( 1 2 ) . Although some of these devices are relatively complicated mechanically, their efficiency appears to be high. A different arrangement for combining countercurrent action with mechanical agitation is that of van Dijck ( 8 )who provides
an unpacked column 15 ith a number of close-fitting perforated plates which are so constructed that they may be moved up and down with respect to the column and its liquid contents. Alternatively, the plates niay be made stationary and the liquids reciprocated by means of an external piston and cylinder, Unfortunately, no experimental results with such a column appear to have been published. However, the operation of this device is still stepwise t o some degree rather than being perfectly continuous. From the foregoing considerations, it would seem that a more desirable way of conducting an extraction would be to use a packed column and to supply the desired agitation by moving the liquids up and down. I n this way the packing becomes, in a sense, a stirrer, with the advantage that its energy of agitation is uniformly supplied over the entire volume of the liquids under treatment without interfering in any way with the continuity of the countercurrent action. The desired agitation may be supplied by means of a flexiblediaphragm, a piston and cylinder, or other suitable apparatus located outside the column, or perhaps more simply by periodically interrupting the flow of liquids into the column. Such an apparatus has the practical advantage that its moving parts are readily accessible and out of contact with the liquids under treatment. The vigor of the agitation can be kept under close control by regulating the frequency and amplitude of the reciprocating motion. In order to test these ideas, a small experimental column was built with which the extraction of benzoic acid from toluene with water could be studied under various conditions of agitation. It was found that the drop size of the dispersed toluene phase could easily be controlled over the entire range from about inch in diameter to a very fine emulsion. The performance of this column with and without agitation was compared by calculation of extraction co.efficients, HTU values, and number of equilibrium contacts. By any of these criteria, agitation
February 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY OUT
A-
TOLUENE IN
405
lies in the toluene rather than in the water. A convenient solute which fulfills this requirement is acetic acid. If then with this solute a similar increase of Ka under agitation is not observed, i t may be concluded that the effect of the agitation is chiefly on K. If tbe increase in Ka is of the same order of magnitude with acetic acid as with benzoic acid, however, i t may be concluded, within the limits of the working hypothesis, that the chief effect of the agitation is on the area of contact between phases. The experiments indicate that a substantial increase in extraction efficiency under agitation is indeed observed with acetic acid as solute. The weight of the evidence must therefore be regarded as favoring the conclusion that the chief effect of the agitation is on the area of contact between the phases. Because the runs with acetic acid were made a t different flow rates than those with benzoic acid, however, i t is not possible to make a direct comparison between the two. Therefore, the possibility of a minor effect of agitation on K cannot be completely excluded by the present data. APPARATUS AND PROCEDURE
v-
WATER
OUT
Figure 1. Diagram of Agitated Extraction Column
improved the performance of the column severalfold. [During the course of these experiments, the authors’ attention was called to the recent work of Goundry and Romero (6),under the direction of Wiegandt at Cornell University, who have used the system methyl isobutyl ketone-acetic acid-water to test the performance of a similar agitated, packed column. Their results are not known to have been published, but appear to be in general agreement with those presented here.] Although it was found that the agitation lowered the flooding point of the column t o some extent, large throughputs could still be obtained by proper choice of packing. For this purpose a packing with a very high void fraction is desirable. One packing which answers this requirement has been described by McMahon (7). By proper agitation, it was found that the extraction coefficients could be made almost independent of the rate of flow of the liquids. I n considering the causes for the increased extraction coefficient under agitation, it is convenient t o regard this quantity as the product of K , the over-all coefficient per unit area, and of a, the area of interphase contact. It is evident that an increase in either of these quantities will result in an increase in the value of the extraction coefficients Ka. An increase in K might be attributed to a decrease in thickness of the stagnant film on either the water or the toluene side of the interface, or both. An increase in the quantity a could be due not only to the finer subdivision of the dispersed phase but also to the fact that the total holdup of the dispersed phase is increased because of the slower rate of the rise of the finer droplets. It seems probable that as far as K is concerned, the principal effect of the agitation will be to reduce the thickness of the continuous-phase film, since the turbulence should be much less in the droplets of dispersed phase than in the continuous phase. If this supposition is accepted as a working hypothesis, it should be possible to ascertain experimentally whether the major effect of the agitation on the extraction coefficient is through increase in K or increase in a. This may be done by substituting for benzoic acid another solute whose major diffusional resistance
The experimental apparatus was constructed as shown diagrammatically in Figure l. The packed section of the column was a borosilicate glass pipe, 17/1s inches inside diameter (ll/z inches nominal) by 36 inches long. The packings used were llrinch, stainless steel McMahon saddles and a/&nch ceramic Raschig rings of which the detailed characteristics are given in Table I. The packing was confined top and bottom by 4mesh copper screens and was kept tight by a short conical spring between the packing and the upper screen. Since the packing when first placed always settled somewhat under the agitation, i t was shaken down with addition of more packing until no further settling occurred. For this reason, the actual packing densities are estimated to be 5 to 10% higher t h n the values shown in Table I, which refer to the packings in the “asdumped” condition. The water forming the continuous phase was brought into the column through a single ‘/Finch pipe connection above the packing while the toluene containing the acid was introduced through a 4-point distributor below the lower screen to form the dispersed phase. The two fluids were fed through rotameters and regulatin valves from overhead tanks. The level of the interface in t f e column was controlled by two outlet valves and a rotameter in the outgoing water stream.
TABLE I. PACKING CHAR~CTERISTICS l/r-Inch McMahon” Saddles 52,000 19 333
a/s-In ch Raschig Rings (Ceramic) 24,000 51 134 68 1/16 inch
Number of pieces per cubic foot Weight, pounds per cubic foot Surface area, square feet per cubic foot Per cent void volume g! Wall thickness a See reference ( ). b Stamped from &IX 60 mesh stainless steel screen. Wire diameter 0.0075 inch.
The column was agitated by means of a reinforced neoprene diaphragm attached to the bottom section of the column. This was actuated by a rod going to an eccentric which could be adjusted to provide an amplitude of l / ~ e , 1/8, or ’/+inch. The diameter of the diaphragm was such that the motion of the fluids in the column was about one and one-half times that of the diahra m. The eccentric was driven through variable-pitch pulpeys,%y means of which its speed could be varied between 200 and 1000 r.p.m. The upper a r t of the column was provided with a blind lateral branch whicx formed an air chamber to cushion the pulsations of the liquid. In making a run the feed tanks were filled and brought to the desired temperature by means of a steam coil. The column was filled with water and the two inlet rotameters were set to give the desired flow rates. The position of the interface was held con-
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check with the present authors' measured values. Agreement of the authors' values with Appel and Elgin, however, was good., Equilibrium data for acetic acid were taken from Seidell (14). Material balances were made on all runs and the data were rejected if the error exceeded &6%. EXPERIMENTAL RESULTS
The operation of the column is shown in a qualitative way in Figures 2 through 5 . These pictures were made with the aid of an Edgerton lamp, which is fast enough to stop the motion. The column was packed with s/rinch Raschig rings and was operated with toluene and water. Figure 2 shows the appearance of the column without agitation. The toluene has a strong tendency to channel and flow in the form of Figure 2. Column without Agitation Figure 3. Column with Mild streams. Figure 3 shows the effect of Agitation mild agitation a t l/lo-inch stroke and stant by means of the outlet valves. l/is-inah stroke 500 r.p.m. The streams have disap500 r.p.m. The agitator was then started and set peared and the toluene is dispersed into to the desired meed by meansof a tachometer. drovs. The increasinalv fine disoerThe operation was continued until a t least 3 liters of each liqsion the speed is increased t o 750 and 1000 r.p.m. is shown uid had passed through the column. Flow rates were then by ~i~~~~ 4 and 5, respectively. ~h~ uniform distribumeasured by noting the amount of each liquid collected in a suittion of the toluene over the cross section of the column is able interval, At the same t h e samples of the effiuentstreams especially noteworthy. It was found that when a longer were taken for analysis. The measurements were repeated after a t least an additional liter of each liquid had run through the column. stroke is used, a lower frequency will produce the same degree The samples were analyzed by titration with standard sodium of dispersion of the droplets. The results obtained with the hydroxide using thymol blue as an indicator, The toluene sam'/*inch McMahon saddles were similar but with this packing before titration in order to ples were mixed with ethyl a more vigorous agitation was required to produce a given render them miscible with the titrating liquid. degree of dispersion. The extraction coefficients were found from the equation The results of the first series of runs in which data were taken are shown in Table 11. In this series the column N Ka = was packed with 1/2-inch McMahon saddles, The dispersed BVACl, -
I
For the special case where the incoming water phase contains no solute ACL,,, is given by
The height of a transfer unit (HTU) was found from the equation HTU =, L/Ka
(3)
For a more detailed discussion of them calculations, see (11). The number of equilibrium stages was found by the usual graphical procedures used in calculating theoretical plates in distillation or absorption work Details of this procedure are given by Sherwood (15). The equilibrium data used for benzoic acid were those of Appel and Elgin (1)supplemented by a few measurements from this laboratory for the higher temperatures. The data of Row, Koffolt, and Withrow (11) covered a wide temperature range but did not
Figure 4. Column with Agitation of 750 R.P.M.
Figure 5. Column with Agitation of 1000 R.P.M.
'/winch stroke
'/la-inch stroke
February 1952
INDUSTRIAL A N D ENGINEERING CHEMISTRY
phase was toluene and the extraction of benzoic acid was from the toluene to the water. The first four runs in this tabre were made without agitation. The extraction coefficient under this condition averages about 10 pound moles per (hour)(cubic foot) (unit AC), and the HTU is about 7.5 feet. The remaining runs show that under various conditions of agitation, the extraction coefficients are increased from three- to fivefold and the HTU values are decreased to values ranging from about 0.8 to 1.6 feet. The increase in the effectiveness of the column under agitation is even more strikingly shown by Figure 6 in which run 1 is compared with run 15 (1jl&nch stroke, 1000 r.p,m.). In the agitated run the water leaving the column is very nearly in equilibrium with the entering toluene. The number of equilibrium stages as measured by “stepping off” the curve is slightly more than one. Run 1, on the other hand, departs widely from equilibrium a t all points in the column. The number of equilibrium stages is somewhat difficult t o estimate but is certainly less than 0.10. Table I1 shows that the runs made with the column stationary show a lower efficiency based on HTU than might be expected from some of the published work with more conventional packings. For example, Row, Koffolt, and Withrow (11) report HTU values averaging about 3 feet with 1/2-inch Raschig rings. It was, therefore, thought desirable to determine the influence of agitation on the column when packed with a more conventional packing The results of these tests are shown in Table 111. which shows the results obtained when the column was packed with a/,inch Raschig rings. Runs 19 and 20, made without agitation, correspond closely to the results of Row, Koffolt, and Withrow. Runs 21 and 22 were made with reduced feed rates and show the expected decrease in extraction efficiency. Runs 23 t o 28, inclusive, were made under varying degrees of agitation and show that a very considerable increase in efficiency has again been obtained. In all the preceding runs the volume ratio of the two liquids fed to the column was kept about equal. Because benzoic acid is much more soluble in toluene than in water, this method of operation produces a close approach to equilibrium or “pinch” at the bottom of the column, while the top of the column departs widely from equilibrium. This effect is well shown in Figure 6 by run 15. I n order to approach equilibrium at both ends of the column, a series of runs was made in which the toluene feed rate was held at about l/lo the water rate. These runs are shown as numbers 29 through 32 in Table 111, from which it
TABLE 11.
Run No. 1 2 3 4 9 10 11 12 13 14 15 16 17 18
407
Figure 6 . Comparison of Run 1 with R u n 15
will be seen t h a t a large increase in efficiency is produced by agitation. A more illuminating analysis of the situation, however, is shown in Figure 7 in which run 30 (unagitated) is compared with run 32 (’/Finch stroke, 400 r.p.m.). The number of equilibrium stages has been increased by the agitation about nineteenfold. Run 35 was made with an intermediate ratio of feed rates and likewise shows good efficiency A convenient way of correlating data of Tables I1 and I11 ie ahown in Figure 8, where the extraotion coefficients are plotted against the flow rate of the dispersed phase. This graph shows data collected from the literature as represented by the linea A-A, B-B,and C-C(18). The various points plotted on Figure 8 are from the present work, the numbers corresponding to the run numbers shown in Tables I1 and 111. Since these points represent various conditions of agitation, no attempt has been made to connect them with lines. Runs 9,11,12,and 14 were made with McMahon saddles under various degrees of agitation. Not only do the coefficients for these runs exceed those for packed columns a t corresponding O of spray columns, as ~ h o min toluene rates but ~ R those Figure 8. The remaining points of Figure 8 show data obtained with Raschig rings. These data, especially runs 32 and 35, indicate that a high toluene rate is not necessary to the maintenance of a high value of the extraction coefficient. The somewhat low value of K,,,a for run 28 probably indicates acondition of over-agitation, sinoe the conditions (l/Binch stroke, 400 r.p.m.)
PERFORMANCE OF COLUMN WHEN EXTRACT~NQ
BENZOIC ACID W O M TOLUENE WlTH
WATER
Dispersed phase, toluene; packed height, 361/r inches: l’/la-inch column packed with l/z-inoh MoMahon saddles Acid Concentrations, Pound Moles per Cubio Foot Flow Ratea, Cubio Feet water per H~~~ per square F~~~ Eccentric Diaphragm Extraction Toluene W.ater Toluene Speed Travel, Coefflcient, in In out out Toluene Water R.P.M. Inch Kcoa 0.0 0.000281 0 10.2 0.0 0,000255 9.1 0 0.000301 0.0 10.5 0 0.0 11.8 0.000301 0 0.000815 0.0 38.5 750 I/ 11 36.9 0.000812 0.0 750 1/11 0.0 66.1 0.000834 500 1/11 0.000787 0.0 51.2 500 ‘/a 0.0 28.6 0.000748 260 1/11 0.000753 0.0 27.2 250 1/11 0.01131 0.0 0.000910 47.2 1000 1/18 0.01131 0.0 0.000890 37.6 1000 1/16 0.01131 0.0 0.000877 56.1 lo00 1/10 0.01131 0.0 0.000770 33.9 1000 i/lb
Height of Transfer Unit, Feet 7.5 8.6 7.0
6.9 0.93 0.97
0.78
1.14 1.44 1.35 0.76 0.92 1 .oo 1.63
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Vol. 44, No. 2
~~
TABLE 111.
PERFORMANCE O F
COLUMN WHEN EXTRACTING BENZOIC ACIDFROM TOLUENE WlTH WATER
Dispersed phase, toluene: packed height, 361/4 inches: Run
No. 19 20 21 22 23 24 25 26 28 29 30 32 35
a
l’/is-inch column packed with a/a-inch Raschig rings
Acid Concentrations, Pound Moles per Cubic Foot Flow Rates, Cubic Feet Toluene Water Toluene Water p ? in In out out Water Toluene 0.01085 0.01085 0.01085 0.01085 0,01088 0.01.088 0.01088 0.01088 0.01088 0.01095 0.01095 0.01095 0.01095
0 0
0 0
0 0 0 0 0 0 0 0 0
0.01042 0.01032 0.01023 0.01027 0.01007 0.00998 0.00904 0.00993 0.00990 0.00875 0.00849 0.000951 0.00763
23.1 23.6 13.9 14.3 19.5 19.8 13.1 13.0 7.87 23.1 23.5 22.9 19.5
0.000541 0.000530 0.000592 0.000587 0~000801 0.000801 0.000801 0.000801 0.000806 0.000155 0.000155 0.000752 0.000784
19.6 19.1 14.2 14.1 18.3 17.4 15.2 13.8 8.58 ‘2.01 1.72 1.78 4.23
Eccentrio Speed, R.P.M.
Diaphragm Travel, Inch
Extraction Coefficient, KWl
Height of Transfer Unit, Feet
7.53 7.47 1.45 1.40 29.2 29.9 19.7 19.7 14.1 1.70 1.76 38. 7a 23.3
3.07 3.16 9.58 10.2 0.668 0.673 0.665 0.659 0.558 13.6 13.4 0 . 5924 0.837
0 0
0 0
200 200 300 300 4 00 0 0 400 300
Because in this run the operating line lies close to the equilibrium curve, a large favorable error would be introduced if these values were calculated by
the method used for other runs-namely, the method based on the logarithmic mean driving force, The values shown have therefore been computed by graphical integration. See reference ( 1 7 ) for a discussion of this method.
are more severe than the other runs with Rasrhig rings. Taken together, the data of this figure seem to indicate that under proper conditions of agitation the extraction coefficient can be maintained at a high value without regard to the flow rate of the dispersed phase. This figure shows that for the McMahon saddles, throughp u t rates can be made almost as high with agitation as without. For the Raschig rings, however, agitation reduces the maximum throughput by a considerable factor. The reason for this difference in behavior is probably due to the much smaller fraction of void volume (see Table I) in the case of the rings. The results obtained with acetic acid as the solute are shown in Table IV. The column was packed with l/zinch McMahon saddles in these runs and the extraction was from the dispersed toluene phase to the water. Runs 36 and 37 show the performance of the column without agitation, while runs 40 through 47 show the effect of varying degrees of agitation. -4s with benzoic acid, an increase of extraction coefficient and a decrease in the value of HTU are evident in the agitated runs. A similar improvement in performance under agitation is shown by runs 50 through 59 in which the solvent ratio has been changed. The tabulated values of Kta are somewhat high for these latter runs because of the error introduced in the calculations by the use of a logarithmic-mean driving force with a curved equilibrium line, while the HTU values are correspondingly low. This error, however, is not sufficient to invalidate the conclusion that a considerable improvement has taken place Because of the “pinch” a t the top of the column, it is difficult to estimate the number of equilibrium stages for some of these runs by the stepping-off procedure. A practical idea of the improvement effected by the agitation, however, may be gained by comparing the concentration of acid in the effluent toluene streams. For run 47 (1/4-inch stroke, 400 r.p.m.) this value is about 1 / 2 6 ~ the effluent concentration obtained in the unagitated run 36; for run 59 (l/s-inch stroke, 600 r.p.m.) it was about l/qao of that for the unagitnted run 50.
doubtful that any apparatus which depends on gravity for the separation of the phases can successfully compete with apparatus in which this separation is accomplished by centrifugal force. It is believed, however, that this condition becomes serious for only a relatively small number of commercial processes. Within this limitation, the agitated column appears to possess a number of advantages over its stationary counterpart. Some of these advantages are: (1) The large extraction coefficients obtained under agitation indicate that the volume of the agit,ated column may be much less than that of a stationary column designed to achieve the same result. (2) The low value of HTU (and of the height of an equilibrium stage) indicates that an agitated column may be made much shorter than the equivalent stationary one. This feature is particularly valuable in cases where the process demands a large number of equilibrium stages, since under these conditions a conventional column may be inordinately high. (3) Since by proper control of agitation, the extraction coefficient can be made nearly independent of dispersed-phase flow rate, the agitated column is a more flexible piece of equipment than its stationary counterpart. For this remon i t will be better able to handle fluctuations and changes in flow with minimum change in product quality or recovery. (4) The use of agitation should allow greater freedom t o the
CONCLUSIONS
In considering the applicability of agitated columns of this type to commercial extraction processes, the properties of the liquids to be treated are a matter of primary concern. For liquid systems which show a marked tendency to form stable emulsions, it seems
e
4
0
eo:,.,
OF
Figure 7.
Awoic
IN WATER J L 0
MoLEBsieu FT;
10-4
Comp’arison of R u n 30 with R u n 32
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1952
TABLE IV.
Run
No. 36 37 40 45 46 47 50°
51 57 59b
PERFORMANCE OH’COLUMN WHENEXTRACT~NQ ACETICACIDFROM TOLUENE WITH WATER Dispersed phase, toluene: packed height, 361/4 inches; ll/ta-inch column packed with I/z-inch iUcMahon saddles Acid Concentrations, Pound Moles per Cubic Foot per Flow Hour Rates, per Square Cubic Feet Foot E;=Tc Diaphragm Extraction To!uene WFter Toluene Water Travel, Coefficient, in in out out Water Toluene R.P.M. Inoh Kta 0.00 0.00628 0.0547 18.6 0.07540 28.2 21.2 0 27.0 21.2 0.00603 0.0575 19.0 0.00 0 0.07540 28.2 0.000168 0.0623 0.07540 23.2 48.2 0.00 250 30.0 0.000056 0.0735 71.6 0.00 0.07540 28.0 258 63.1 0.00 29.7 23.4 0.000037 0.0625 250 0.07540 69.5 0.07540 28.5 24.6 0.000025 0.0677 0.00 400 0.00966 0.320 47.7 0.00 8.5 51.8 0.0660 0 0.00194 0.374 93.2 0.00 53.2 8.9 0.0660 200 0.00 123.8 52.1 0.374 8.7 0.0660 0.00068 400 0.407 0.00 0.00002 8.4 280.0 0.0660 52.1 600
409
.
Height of Transfer Unit, Feet 1.14 1.11 0.484 0.391 0.371 0.354 1.09 0.572 0.422 0.185
a The values of K t a shown here for runs 50 through 59 are somewhat high due to the curvature of the equilibrium line, while the HTU values are correspondin ly low. % In this run a coalescence of the toluene phase took place in the lower half of the column with the result that both phases became continuous in this region. The water, however, clung to the packing and remained more or leas stationary while the toluene moved with the agitation.
L N
V
0
= = = =
liquid flow rate, cubic feet per hour amount of solute transferred between phases, moles volume of column, cubic feet time, hours
Subscripts w = water phase
= toluene phase 1 = top of column 2 = bottom of column
t
LITERATURE CITED
Appel, F. J., and Elgin, J. C., IND.ENG.CHEM.,29, 451 (1937). Borrmann, C. H., Ger. Patent 403,252 (1922). Dijck, W.J. D. van, U.S. Patent 2,011,186(1935). Fisher, A. W., and Bowen, R. J., Chem. Em-. Progress, 45, 359 (1949).
Goundry, P. C., and Romero, V. M., Senior Project Report, School of Chemical Engineering, Cornel1 University, Ithaca, N. Y. McConnell, E. B., U. S. Patent 2,091,645(1937). McMshon, H.O.,IND,ENG.CHEM.,39, 712 (1947). Maschinen and Apparatebau Ges. Martini and Hunecke m.b.H., Ger. Patents 521,541 (1931),566,945 (1932). Morello, V. S., and Poffenberger, N., IND. ENO.CHEM..42, 1021 (1950).
Othmer, D.F., U. S. Patent 2,000,606(1935). Row, 5. B., Koffolt, J. H., and Withrod, J. R., Trans. Am. Inst. Figure 8.
Extraction Coefficient vs. Flow Rate of Dispersed Phase
process designer, since he is not limited to high dispersed-phase flow rates in order to obtain high extraction coefficients. (5) By applying agitation equipment to existing columns, substantially greater recovery of product should be realizable in many cases. ACKNOWLEDGMENT
The authors take pleasure in expressing their thanks to
T. K. Sherwood for much helpful advice and criticism, and to M. H. Rood, F. R. Gage, and W. S. Colburn for their aid with
Chem. Engrs., 37, 559 (1941).
Scheibel, E. G., Chem. Eng. Progress, 44, 681,771 (1948). Scheibel, E. G., U. S. Patent 2,493,265(1950). Seidell, A., “Solubilities of Organic and Inorganic Compounds,’’ supplement to 2nd ed., Vol. 11, p. 1008, New York, D. Van Nostrand Co., Inc., 1928. Sherwood, T. K.,“Absorption and Extraction,” 1st ed., P. 82, New York, McGraw-Hill Book Co., 1937. Sherwood, T. K., personal communication. The original data from which the lines of Figure 7 were plotted are: A-A ( I ) , B-B, and C-C (ll).. Walker, W. H., Lems, W.-K., WeAdams, W. H., and Gilliland, E. R.. “Principles of Chemical Engineering,” 3rd ed., p. 481. New York, McGraw-Hill Book Co., 1937. RECEIVED May 22, 1851,
the experimental work. NOMENCLATURE
area of interphase contact, square feet per cubic foot C solute concentration, pound moles per cubic foot C* equilibrium solute concentration, pound moles per cubic foot ACZ, = logarithmic-mean interphase concentration difference, pound moles per cubic foot HTU = height of transfer unit, feet K = over-all coefficient per unit area, pound moles per (hour) (square foot) (unit AC) Ku = over-all coefficient per unit volume, pound moles per (hour) (square foot) (unit AC) In = natural logarithm u
= = =
Correction
I n the article on “Explosive Characteristics of Hydrogen Peroxide Vapor” [Satterfield, C. N., Kavanagh, G. M., and Resnick, Hyman, IND.ENG.CHEM.,43, 2507 (1951)] on page 2507 the eleventh line of the abstract should read: “or by changes in the water vapor-oxygen ratio.” On page 2510,the seventh line from the bottom of the second column should read: “by the points shown in the upper portion of Figure 7.” C . N. SATPERFIELD
