INDUSTRIAL AND ENGINEERING CHEMISTRY
812 where
180
ai
= lehtive volatility of component 1 with respect to the
7’
= absolute tempeiature =1 absolute boiling point of 1
1
~
170,
boiling point of
-
160
As the average temperatiire in the distillation column will be approximately equal to the c u t point temperatuie, this equation may be siiiiplified to
2
15C-
=
absolute cut point temperature-Le., equally distiibuted component
log
01
$
1
= 4.60 (1 - Toi/l’c)
Details of Calculation. a5 has been calculated for each com20” F. fraction-and the moles remaining in the ponent-i.e., bottoms have been calculated by multiplying the number of moles in the feed by 1/(1 0 1 ~ )in each case. The flash point has been calculated from these values by the same method used in Table 11. A value of 133” F. was obtained. This may be compared with the value of 138” F. 4 hich was obtained for the perfect separation.
I30
,
705
650d7
LINES ARE PREDICTED CURVES FOR 5 PLATES AT TOTAL REF-UX
P O I N T S ARE FROM 1515
equally distributed component
Y’c
I
Vol. 48, No. 4
//
DISTILLATIONS
I-
/
..’
- /// 1
e633
,.
~
.C--
I
I
530
+
120‘70
I
290 INITIAL
I
I
I
310
330
350
VAPOR
370
TEMPERATURE
Figure 9. Effect of initial and final vapor temperature on flash point
ACKNOWLEDGMENT PLANT RESULTS CORRECTED TO 55C’F. FVT,
200
T h e authors would like t o express their appreciation to Imperial Oil, Ltd., for permission to publish the results of this investigation.
,
LITERATURE CITED
(1) Am. Petroieum Inst., A.P.I. Research Project 44, “Selected
(2) 100
‘
250
I
I
300
350 INITIAL
Figure 8.
VAPOR
TEMPERATURE
I
I
400
450
‘F
Theoretical c s . refinery flash points
Theoretioal 550° F. final vapor temperature Redwater cuts at various fraction efficiencies, and typical refinery operations
(3)
(4) (5) (6)
(7)
(8)
Comparison with Experimental Data. I n Figure 7 , the results of a number of calculations of the type described above are compared with the flash points of fractions obtained by 15/5 distillation. The experimental points agree well with the Iine for five theoretical plates. This indicates that a 15/5 distillation produces about the same degree of separation as five plates a t total reflux. This is in good agreement with previous estimates which have been made in the distillation laboratory. I n Figure 8 the same set of curves is compared with practiral results found in typical refinery units. The separation achieved in most cases is approximately equivalent to that which could be obtained in a tower a t total reflux containing about 2*/2theoretical plates. There is a definite limit to the flash point improvement that can be obtained by the use of more efficient fractionating equipment. After a separation efficiency equivalent t o 5 to 10 theoretical plates a t total reflux has been attained, very little further improvement can be made. Effect of Final Vapor Temperature on Flash Point. I n Figure 9 theoretical lines have been drawn relating the flash point t o the initial vapor temperature for fractions having various final vapor temperatures. T h e distillation conditions for each line are fire theoretical plates a t total reflux. The experimental data for f 5 l 5 distillations are plotted as points on this diagram. T h e agreement is good. Any differences betn-een the predicted and measured vnlnes are probably within the experimental error.
(9)
T’alues of Physical and Thermodynamic Properties of Hydrocarbons and Related Compounds,” Carneyie Press, Pittsburgh. 1950. Associated Factory LIutual Fire Insurance Cos., IND.ENG. CHEW32, 880 (1940). Doss, M . P., “Physical Constants of the Principal Hydrocarbons,” Texas Co., Kew York, 1942. Imperial Oil Research Department, data on Redwater aharp cuts. Leslie, E. H., Geniesse, J. C., International Critical Tables, voi. 2,p. 161, hIcGraw-Hill, New York, 1927. Rlaxwell, J. B., “Data Book on Hydrocarbons,” Van Nostrand, New York, 1950. Selson, W. L., “Petroleum Refinery Engineering,” 3rd ed., p. 210, LIcGraw-Hill, New York, 1949. Sax, N. I., “Handbook of Dangeroua Xaterials,” Reinhoid, New York, 1951. Thiele, E. W,, IND. ENG.CHEJI.19, 259 (1927).
RECEIVED for review blarch 3, lQ55.
ACCEPTEDDecember 27, 1955 Division of Petroleum Chemistry, 127th Neeting, ACS, Cincinnati, Obi(,, Xarcli-April 1955.
Correction In the ai t i d e entitled, “Collection of Aerosol Particles i n Presence of Electrostatic Fields” [H. F. Kraemer, H. F. JohiyE ~ GC .H E v . 47, 2426 (1955)], the following coriecstone, IAD. nons should be made. 1. In Equation 1 i on page 2428, the minus Bign befoii V1QL should be deleted. 2 . ~ l r tshould be injetted in the denominator of the last tern of Cqriation 21, page 2129, and c in the denominator of the teiiii utidel the square root sign, page 2432 after Equation 30, wheit. the subscripts 0 appear. 3. Equations 28 and 29 each consist of two equations; the\ should be separated before the terms
G)
preceding the equal
signs in the second equations. 4. I n the Xomenclature, the subscript 1 should be deleted in the symbol for dielectric constant of the aeiosol particle, e.
