INDUSTRIAL AND ENGINEERING CHEMISTRY
JULY, 1935
845
Literature Cited
which correspond to complete miscibility between the oil stock and the solvent. Unfortunately, insufficient data are available definitely to fix the effect of solvent-oil ratio upon the over-all efficiency, and these results are further complicated by the variable nature of the air agitation employed. The method of computation is exceedingly useful, particularly for forecasting the most favorable extraction conditions to produce a maximum yield of raffinate of a given V. G. C. The data resulting from such graphical calculations for the countercurrent extraction of stock No. 2, with nitrobenzene a t 10’ C. are shown in Figures 13 and 14. The volume per cent yield of raffinates of varying V. G. C. are plotted against the solvent-oil ratio. Maximum yields of the most desirable raffinate-that is, a raffinate possessing a low V. G. C.-are obtained a t low solvent-oil ratios. At these low solvent-oil ratios, however, a rather large number of ideal extraction stages is required to give a low V. G. C. raffinate. The number of actual stages necessary can be computed from the over-all stage efficiency. The variation of the over-all efficiency for an air-agitated stage as given in Table VI has been plotted in Figure 13. The best extraction conditions to give maximum yield of low V. G. C. raffinate reconcilable with a reasonable number of actual stages and the lowest solvent-oil ratio can easily be determined from these diagrams.
(1) Am. Petroleum Inst. Bull., 14, 39-105 (1933). (2) Clotworthy, Ind. Chemist, 7,111 (1931). (3) Cornish, Archibald, Murphy, and Evans, IND.ENQ.CHEnc., 26, 397 (1934). (4) Evans, Ibid., 26, 439 (1934). (5) Ibid., 26,860 (1934). ( 6 ) Ferris, Birkhimer, and Henderson, IND.EXQ. CHEM.,23, 753 (1931). (7) Ferris and Houghton, Refiner, 11, 560 (1932). (8) Fischer, 2. tech. Physik, 10, 153 (1929). (9) Friedrichs, C h m . Fabrik, 23, 199 (1932). (10) Griffin‘,‘IwD.ENQ.CHEM.,Anal. Ed., 6 , 4 0 (1934). (11) Herz, Der Verteilungsatz,” Stuttgart. 1909. (12),Holleman, Chem. Weekblad,29, 762 (1932). (13) Hunter and Nash, J . SOC.Chem.Ind., 51, 285T (1932). (14) Ibid., 53, 95T (1934). (15) Hunter and Nash, World Petroleum Congr., London, 1933, Proc., 2, 340. (16) Jantzen, “Das fraktionierte Destillieren und das fraktionierte Verteilen,” Dechema Monographie, Band 5, Nr. 48, p. 81, Berlin, Verlag Chemie, 1932. (17) Jantzen and Tiedcke, Ibid., p. 115. (18) Kalichevsky and Stagner, ”Chemical Refining of Petroleum,” A. C. S. Monograph Series No. 63, New York, Chemical Catalog Co., 1933. (19) Kestner, IND. ENQ.CHEW,24, 1121 (1932). (20) Meyer, J . Inst. Petroleum Tech.,17, 621 (1931). (21) Othmer, Trans. Am. Inst. Chem. Engrs., 30, 299 (1934). (22) Saal and Van Dyck, World Petroleum Congr., London, 1933, Proc., 2, 352. (23) Smith, J . SOC. Chem.Ind., 47, 159T (1928). (24) Tuttle and Miller, Am. PetroleumInst.Bull., 14,85 (1933). (25) Underwood, Ind. Chemist,10, 128 (1934). (26) Underwood, J. SOC.Chem.Ind.,47, 805 (1928). (27) Watanabe and Morikawa, J . SOC.Chem. Ind. Japan, 36, 585B (1933). (28) White, J . SOC.Chem.Ind., 47,596 (1928).
Aclrnowledgment The authors wish to record their grateful thanks to the Atlantic Refining Company for permission to use the experimental extraction data with nitrobenzene as a solvent, and to S. W.Ferris of that company for his assistance and interest in this investigation.
RBCEI~BD February 23, 1935.
Graphical Correlation of Solvent Extraction Data SIMPLE method of plotting data obtained in the solvent extraction of petroleum hydrocarbon mixtures (Figure l), which has been used in this laboratory for some t h e , is presented in the hope that it may be of service t o others. This method of plotting has the following advantages: (1) It is not necessary t o d e h e the components of the extracted mixture. (2) Rectangular coordinate aper is used. (3) Experimental data may !e plotted directly. These advantages have made the method more convenient for this work than the three-component phase diagrams (6) which have been applied to data on the separation of petroleum hydrocarbon mixtures by means of selective solvents or precipitants (1, 2, 8-11).
STEWART S. KURTZ, JR. Atlantic Refining Company, Philadelphia, Pa,
The principle of this method of plotting is to graduate the x-axis of a graph in terms of a physical property which is additive on a volume per cent basis (density, refractive index, or viscosity gravity constant, 7) and graduate the y-axis from 0 to 100 volume per cent of solvent. A point called the solvent apex, C, is located on the graph so that its ordinate is 100 and its abscissa is approximately equal to the physical property (for example, viscosity gravity constant) of the stock. I n plotting data for an oil-solvent mix, a line is drawn through the solvent apex and the point representing the physical property of the solvent-free oil and points representing mixtures of the solvent with this oil must fall on ~~
=
TABLE I. BATCHNITROBENZENE EXTRACTION OF STOCK No. 2 AT 0” -------Undissolved Layer---Per -Properties of o-li Cent Per Saybolt VisPer Solrent cent VIBcosity- cent solof A. P. I. cosity, gravity vent in in hfixture stock gravity IOO~I?. constanb layer 33.3 71.0 23.3 487 0.853 20.8 ~
50.0
75.0
58.8 38.0
26.0
28.9
399
327
0.837 0.819
17.0
14.6
-Properties -Dissolved Per cent of A. P:I. stock gravity 29.0 41.4 59.0
14.3 13.2 15.5
c.
of oilLayerPer Saybolt Viscent viscosity- solcosity gravity vent in 100’ F. oonstant layer
1002 1433 1041
0.925 0.935
0.918
52.1 68.0 83.4
this line. _._ . . . . .
Procedure for Constructing Graph The data used for constructing Figure 1 are for the nitrobenzene batch extraction of a naphthenic distillate a t 0’ C . and are from the psper of ~ j + ~ ~ ~ i ~ and , Henderson TheBe data are given in Table 1.
(e),
846
VOL. 27, NO. :
INDUSTRIAL AND ENGINEERING CHE3IISTRY
The additivity o n a v o l u m e p e r cent basis of the specific gravities and refractive indices of oil-nitrobenzene mixes was verified experimentally. It, was also found for both raffinates and extracts obtained from a given stock with a given solvent that the viscositygravity constant varies linearly with the specific gravity. For e x a m p l e , nitrobenzene extraction of stock KO. 3 (d), whether batch or countercurrent, (S,6), yields data reasonably well represented by the equation: Viscosity-gravity constant (V. G. C,) = 1-14 s p gr. - 0 179 In the case of stock No. 2 (4) balch data for several solvents are fairly well represented by the equation :
V.G. C.
Detailed instructions for the construction of Figure 1 are as follows: Graduate the x-axis linearly in terms of viscosity gravity const.ant and plot the viscosity gravity constant of the raw stock on this line (2). Graduate the y-axis linearly in terms of volume per cent of solvent in the oil-solvent mix and choose a point whose ordinate is 100 and which for convenience is approximately above the viscosity-gravit,y constant value of the stock. This point is the solvent apex, C. Draw Cz and on it plot y ~ ~, 2 and , ya which represent the several solvent-stock mixes usedin the batch extractions. Plot the viscosity-gravity constants of the solvent-free , b3 on the x-axis and connect them raffinates bl, b ~ and aith C. Plot the points, bl‘, bz’, and b3’ determined by the composition of the solvent-raffinat,e mixes on the lines blC, bnC, and b,C, respectively. In a similar way locate ai, UZ, and a3 for the extracts on the x-axis and the points al’, az’,and a3’ for the solventextract mixes on the corresponding lines alC, azC, and a3C. Draw the lines al’bl’, al‘bn’, and as%’. Lacking complete data on the extract from mix y1, al’ can be determined by calculating al from bl 2,and the yield, and obtaining the intersection of the line alC and the exten,sion of bl‘yl. The same procedure applies? as‘ and a3 . Draw a smooth curve through the points a3 aa’,al’, bl‘, bz’, b3‘* This curve delineates the regions of complete and partial miscibility. I
= 1.14 sp. gr. -~0.185
I n much of the work done in t h i b laboratory, it h a s b e e n f o u n d convenient t o obtain the data on a weight per cent basis. Theoretically, weight per cent data should be plotted against specific voiume rather than specific gravity, but in view of the narroJT range of possible variation in the specific gravilies of raffinate and extract, for practical purpose$, either specific gravity or specific volume may be used with substantially identical results,
Literature Cited Bray, Swift, and C a n , Oil Gas J * ,32, 14 ( S O Y 2,. 1933), Evans, ISD. ENQ.CHEX., 26, 860 (1934). Ferris, J . Franklin Inst., 217, 591--615 (1934). Ferris, Birkhimer, and Henderson, IXD.ENO. CHEM.,23, 753 (1931). ( 5 ) Ferris and Houghton, N a t l . Petroleum rVews, 24, No. 48, 26 (1932). (6) Findlay, “Phase Rule,” C,hap. XIV, New York, Longman#, Green and Co., 1904. (7) Hill and Coates, IND. ESG.CHEX, 20, 641 (1928). (8) Hunter and Nash, J . Soc. Chem. Ind., 53, 95T (1934). (9) Hunter and Nash, Proc. World Petroleum Congress, 1933, Ii, 340. (10) Hunter, Nash, Saal, and Van Dyck, Proc. World Petroleum Congress, 1933,II,383-4. (11) Saal and Van Dyok, Ibid., 11,352. RECEIVED February 23, 1935.
Courtesy, Bakelzte Corporatzon BOOTH SWOWIKG \-ARIOUS
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