Equilibrium Flash Vaporization of Petroleum Fractions AT REDUCED PRESSURES K. KEITH OKAMOTOl AND MATTHEW VAN WINKLE University of Texas, Austin, Tex.
T
HE data presented in this report are the result of one of a series of experimental investigations whose purpose is the systematic study of vapor-liquid equilibrium characteristics of complex systems as represented by petroleum oil mixtures. This long-term program includes the study of the variables of pressure, boiling range, boiling level, and chemical characteristics of petroleum stocks. In addition, it is proposed to relate the data from the common analytical distillation methods with flash vaporization characteristics of feed stocks and products obtained from the equilibrium operations. Equilibrium flash vaporization is a n operation that is encountered extensively in the petroleum processing industry. Because of its frequent occurrence the phase data obtained from equilibrium flash vaporization are extremely important in making design calculations for petroleum process equipme-nt as well as in the economical operation of existing equipment. For systems whose compositions are known, equilibrium relations between the vapor and liquid phases can be treated mathematically by thermodynamic relations. This method is commonly referred to as the theoretical component method for treating equilibrium systems. Calculations based on the component method are generally not suitable for petroleum oil systems because the component compositions are unknown. For petroleum oils the phase relations are usually estimated by empirical methods which relate characteristics of equilibrium flash vaporization t o analytical distillations such as the true boiling point and ASTM distillations. Despite the importance of equilibrium flash vaporization data, relatively little experimental work has been reported on complex systems, particularly at reduced pressures. This situation undoubtedly has been caused by the complexity and cost of the required equipment and the tedious operational procedures necessary to obtain these data. I n recent years petroleum distillation processes have been changing toward higher temperature and lower pressure operations in order to increase the ultimate recovery of useful products from the crude oils. At reduced pressure adequate data and correlations are lacking for designing of petroleum process equipment. Most of the available experimental data (4-7, IS, 19, 26) are a t atmospheric pressure. At higher pressures three sets of data (1,6, 6) are reported. Only recently have there been any significant equilibrium flash vaporization data reported in the reduced pressure range. Okamoto and Van Winkle have presented calculated equilibrium flash vaporization data (99,93) for nine hypothetical hydrocarbon mixtures over a pressure range from 3000 to 10 mm. of mercury absolute. Othmer et a2. (94) reported equilibrium vaporization data for eight petroleum samples at pressures from atmospheric to 5 mm. of mercury. Smith et al. (66) reported equilibrium data for a mid-continent reduced crude from 400 to 2.5 mm. of mercury. The present investigation was undertaken to provide additional equilibrium flash vaporization data on petroleum fractions a t reduced pressures. 1
EQUILIBRIUM FLASH VAPORIZATION UNIT
,
Three different vacuum flash vaporization stills have been described (16,94,26), by which vapor-liquid equilibrium data were obtained on petroleum oils. The unit used in this work was an all-metal continuous vacuum flash vaporizer utilizing a n electrical preheat furnace as its heat source. Designed for laboratory use, the unit occupies relatively small floor area. It is mounted on a metal frame 6 feet long, 6 feet high, and 2.5 feet wide. A novel device for obtaining equilibrium between the vapor and liquid under flow conditions consisted of an atomizing nozzle for introducing the feed into the flash chamber. The attainment of equilibrium is mainly influenced b y the extent of the vapor-liquid interfacial area, intimacy of contact between the vapor and liquid, and duration of contact time. B y using the atomizing nozzle which caused the liquid to break up into spherical particles the vaporliquid interfacial area was greatly increased. The intimacy of contact between the vapor and liquid was ale0 improved with the turbulence created by the liquid issuing from the nozzle into the flash chamber.
STOCK FLOW SYSTEM. Figure 1 shows the schematic stock flow diagram. The unit was designed for a throughput range of 30 to 65 ml. per minute. The petroleum stock was pumped from the feed reservoir tank by a Tuthill gear pump. Before entering the pump, the stock passed through two filters consisting of 75-mesh stainless steel screens, A pressure relief valve was used in conjunction with a by-pass circuit which recycled the excess stock pumped by the gear pump back to the stock reservoir. By adjusting this 'relief valve the throughput rate was maintained constant. The stock passed through an electrical preheat furnace, where it was brought to proper temperature before being introduced to the flash chamber. The preheat furnace consisted of 80 inches of stainless steel pressure tubing, 1/8 inch in outside diameter,, which was electrically insulated with several layers of thin asbestos sheets and wrapped with four 800-watt, 22-gage Nichrome heaters, controlled by Powerstats. The tubing and the heating elements were completely surrounded and well insulated with insulating firebricks and Foamglas insulation. Because of the high heat flux attained in the preheat furnace, it was necessary to keep the feed stock flowing a t all times. Should this flow stop for any reason, the furnace tubes would coke up immediately. T o prevent this, appropriate valves and lines were installed just before and after the furnace to allow the removal of all residual oil in the furnace tubes by means of steam. The feed stock from the preheat furnace was introduced to the flash chamber from the top. Details of the flash chamber are shown in Figure 2. Approximately 4.5 inches of l/r-inch steel pipe extended down into the flash chamber. By means of the nozzle attached a t the end of this ipe, the feed was discharged into the flash chamber some 6 incKes from the top. This extension was completely immersed in the vapor space. Four 800-watt, 22-gage Nichrome heaters were wrapped around the flash chamber to maintain constant temperature. Each was controlled by a separate Powerstat. The flash chamber and all auxiliary lines and equipment were well insulated. The vapor traveled through two revolutions of spiral heuces to remove liquid entrainment by centrifugal force and left at the top of the flash chamber through a 1-inch standard steel pipe outlet. This means of removing liquid entrainment proved t o be very satisfactory. The vapor temperature was measured.
Present address. California Reaearch Gorp., Richmond, Calif.
429
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 45, No. 2
fl
-
TO DRAIN
Figure 1. 1.
2. 3. 4.
5.
6.
7.
Schematic Flow Diagram
Stock reservoir Tuthill gear pump, 25 gal. per hour Pressure relief by-pass valve Orifice flowmeter Preheat furnace Flash chamber Liquid stock cooler
with a calibrated Chromel-hlumel thermocouple placed in this line. The vapors were condensed and cooled in a countercurrent vertical shell-and-tube type of exchanger equipped with removable tube bundles and containing two half-moon baffles in the shell side. The vapors passed through the two-pass shell side, and the water coolant passed through the one-pass tube side. The two half-moon baffles had a 14’ slope in the direction of flow of the condensed vapors to keep the liquid holdup in the condenser t o a minimum. The condensed vapors flowed by gravity t o the calibrated accumulator in which the vapor rate was determined. The equilibrium liquid was removed a t the bottom of the flash chamber by a constant-level overflow method. I n order to prevent vapors from escaping from this overflow line, a small rise was provided in this line just outside the flash chamber to serve as a reservoir for a liquid seal. The equilibrium liquid temperature was measured with a calibrated Chromel-Alumel thermocouple placed in the cone section below the liquid level. The liquid flowed by gravity to a cooler and thence to the liquid accumulator. The cooler was a vertical coil-and-shell type. The coil inside the shell was made of soft drawn copper tubing inch in outside diameter and 85 inches long. The water coolant passed through the shell side and the hot liquid stock entered a t the top of the tube, was cooled, and flowed by gravity to the calibrated liquid accumulator in which the liquid rate was determined. Both equilibrium liquid and vapor samples were removed from their respective accumulators by Tuthill gear pumps. TEMPERATURE h‘IEASUREMENT. Equilibrium temperatures were measured with calibrated Chromel-Alumel thermocouples. Temperatures were read to the nearest 0.5’ F. The equilibrium vapor temperature was measured in the vapor outlet line from the flash chamber The equilibrium liquid temperature was measured at the bottom of the flash chamber. By adjustment of the flash chamber heatersothese two temperatures could be easily maintained to within 1 F. of each other. Both thermocouples were installed using a Conax thermocouple gland, which has a positive seal for vacuum or pressure. This type of installation made it possible to place the bare thermocouple directly in the fluid stream and completely insulate it from the surrounding metal equipment. By this means measurement of the actual fluid temperature and quick response t o fluid temperature changes were assured. PRESSURE MEASUREMENT. The unit was evacuated for low pressure work by two Welch, two-stage, oil-sealed, rotary vacuum pumps, which were connected to a metal surge tank having a volume of 146 cubic inches. This reservoir acted not only to dampen pressure fluctuations in the system but also as a possible trap t o prevent hydrocarbon vapors from reaching the vacuum pumps. For pressure regulation two l/a-inch needle vaf%es were used in series and vented into the surge tank. Because the equilibrium pressure is one of the important observed variables, accurate measurements are highly desirable.
Vapor stock condenser Liquid stock accumulator Vapor stock accumulator Vapor knock-back condenser 12. Differential manometer 13. McLeon gage T.C. Thermocouple 8. 9. 10. 11.
A copper tube pressure-measuring line inch in outside diameter was connected to the top of the flash chamber through a knock-back condenser and to a differential manometer and a McLeod gage. The knock-back condenser was a double pipe heat exchanger made of 12 inches of 1-inch standard steel pipe capped a t each end. The pressure-measuring line was passed through the 1-inch pipe and sealed to the two end caps. Cold water was used as the cooling fluid. This condenser prevented the condensation of vapors in the pressure-measuring gages.
I 6 - g C A P SCREWS
VAPOR OUTLET I”STD. P I P E
I
? , : E D INLET STD. PIPE
Figure 2. Flash Chamber
For pressures below 100 mm. of mercury absolute a special R‘IcLeod-type gage was designed and calibrated. It could be read to the nearest 0.1 mm. of mercury. For pressures above 100 mm. a differential manometer in conjunction with the barometer was used. A special vernier was made for the manometer, which enabled the reading of each leg of the manometer to the nearest 0.1 mm. The barometer could be read to the nearest 0.1 mm. Therefore, the accuracy of all pressure measurements above 100 mm. was b0.3 mm. of mercury. MEASUREMENT FLOW RATE. The feed rate was determined by
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1953
the orifice meter laced directly in the line just before the preheat fUrnace. TEe orifice Plate made of 2'-kWge Copper sheet and the orifice diameter was approximately 0.060 inch. With this orificediameter the pressure drop across the plate ranged from 2 to 10 inches of water for all the petroleum stocks investigated.
TABLE I. EVALUATION OF FLASH UNITWITH TOLUENE%-OCTANE BINARYSYSTHM x = weight y = weight
Pressure 60
50 50 50 100 100 100 100
200 200
200 200 200
200 400 400 400 400 760 760 760 760
43 1
I
% toluene in liquid % toluene in vapor
X
2i
35.2 32.4 58.2 57.2 32 8 33 7 57.1 56 6 37 4 37.5 32.6 32.6 57.2 56.7 33.6 33.2 59 2 57.7 36.9 36.5 62.0 61 7
53.2 50.8 71.7 70.9 52.3 53.2 69.9 69.7 55.3 54.9 51.0 50.7 70.7 69.7 51.2 51.0 70.5 70.1 53.0 53.0 72.0 71.2
Equilibrium Temperature, F. 107.5 108.7 103.0 103.0 136.0 135 0 131.5 132.0 165 0 165 0 167.0 166.5 162.0 162.0 202.0 202.0 197.0 197 5 239.5 239.5 235.0 235 0
The vapor-liquid composition data (s-y) show a mean deviation of less than 1% from those of Berg and Popovac (I)for all presused. The temperature-composition data (t-z) and (t-!/) Show a mean deviation of less than 1' F. from the data of Berg and Popovac (I)a$ all pressures studied. Agreement of the data is excellent. This indicates little possibility of entrainment or vapor superheating in the operation of the equipment and tends t o justify the conclusion that the flash unit was operating under equilibrium conditions for the test mixtures. ATOMIZATION. The qualitative effects of the physical properties of the liquid, nozzle diameter, and liquid velocity on the atomization characteristics of a pressure nozzle can be shown. By use of dimensional analysis the following dimensionless coefficient relationship was derived:
where
Z = degree of atomization d
V
p p
6
9/
Calibrated accumulators were used for the measurement of the equilibrium vapor and liquid rates. These were calibrated for volume at room temperature. Calibration marks were milled onto an aluminum strip l/g inch thick and 1 inch wide and attached to the accumu]ators adjacent to a glass pressure sight gage 6/8 inch in outside diameter. By means of these accumulators the rate of vapor and liquid was determined in millimeters per minute, over timed intervals. EVALUATION OF EQUILIBRIUM FLASH VAPORIZATION UNIT
In all equilibrium flash vaporization work it is necessary to determine if actual equilibrium conditions are being established. I n continuous flash vaporization units with relatively large throughput this information is difficult to obtain. Generally, several different feed rates are run at steady-state conditions of temperature and pressure and if the results agree within attainable experimental accuracy, the units are considered to be operating under equilibrium conditions. However, this test is not conclusive. For smaller units equilibrium conditions can be readily tested by the use of binary mixtures for which vaporliquid equilibrium data are available. TESTMATERIALS AND METHOD USED. The flash vaporization unit used in this work was tested using the toluene-n-octane binary system. Berg and Popovac (9)presented vapor-liquid equilibrium data for this system a t pressures from 760 to 20 mm. of mercury absolute. A minimum of four test runs each a t 760, 400, 200, 100, and 50 mm. of mercury absolute pressure was made. Reagentrgrade toluene from Merck & Co., Inc., and pure research-grade n-octane from Phillips Petroleum Co. were used. The n-octane was reported as 99+% pure, and the properties of the toluene indicated that its purity was acf$z:i therefore, no further purification of these samples was attempted. The flash vaporization unit was thoroughly cleaned, first with benzene, then with acetone, and flushed with air for about 6 hours. Refractive indices were used for the analysis of all toluenelz-octane compositions. Three different feed compositions were used. Feed 1 had a composition of 42.2 weight % toluene and 57.8 weight yon-octane. Feed 2 had a composition of 36.6 weight % toluene and 63.4 weight yo n-octane. Feed 3 had a composition of 56.5 weight % toluene and 43.5 weight % n-octane. With feed 1 only two points at 200 mm. of mercury were run. With feeds 2 and 3 four points were determined at each of the following pressures: 50, 100, 200, 400, and 760 mm. Results are presented in Table I.
= nozzle diameter, om.
linear velocity of liquid through nozzle, em. per second = density of liquid, grams per ml. = absolute viscosity of liquid, grams/cm. second = surface tension of liquid, gf/cm. 980.7 g m cm./gj sec.l unit system
=
=
From this equation i t is evident that the degree of atomization of liquids when forced through a pressure nozzle is a function and a function of a dimennumber), @1 (d+), Of Re sionless number incorporating properties of the materials, Ohnesorge ($0,21) investigated the formation of drops and the atomization of liquids using a pressure jet nozzle. His experiments were performed using two fairly viscous mineral oils, castor oil, two gas oils, glycerol, aniline, and water. The nozzle diameter varied from 0.4 to 4.0 mm. His results show that above a well-defined Reynolds number (Rel) the jet will completely atomize a t the nozzle. Below this Reynolds number the jet will disintegrate by means of helicoidal lateral vibrations, changing to a simple surface vibration a t a second well-defined Reynolds number (Rez). When the dl (d+)
and @z(
-&%J)
data of Ohnesorge ( W O , 2 1 )
are plotted on log-log graph paper, both Rel and Rez lie on straight parallel lines which define three distinct regions (Figure 3). I n region I the fluid jet exhibits only a surface vibration with axial symmetry. I n region I1 helicoidal lateral vibrations are present and the zone of complete atomization of the jet moves closer to the nozzle. I n region I11 the jet completely atomizes a t the nozzle. I n this present work a hollow-cone atomizing nozzle was used rather than d jet nozzle. However, both nozzles are of the same type, the driving force being the difference between the upstream pressure and the pressure surrounding the nozzle. Furthermore, the hollow-cone atomizing nozzle is inherently designed for atomization, whereas the jet nozzle is not. I n order to make a quantitative comparison of the degree of atomization obtained for the test mixture of toluene-n-octane
(")
and the six petroleum stocks used, two values of 61 - and
@*(F%~)
were calculated for each.
These two calculations
for each of the six stocks and t h e test mixture were made a t the highest temperature and pressure of operation and at the lowest temperature and pressure of operation. Therefore, all
432
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
Vol. 45, No. 2
the ASTM viscosity-temperature charts (D 341),theviscositytemperature curve for petroleum fractions can be closely approximated from known viscosities a t two temperatures, as they will plot as straight lines on these charts. The viscosities of the petroleum stocks at 210" and 100" F. were determined using the correlations of Watson, Nelson, and Murphy ( 2 7 ) . These correlations make possible the determination of kinematic viscosities (relative viscosities in centistokes) a t 210" and 100" F. from the API gravity and cubic average boiling point or characterization factor for the petroleum fraction. Surface tension values for toluene and n-octane are given in the International Critical ,000 Tables (10). Katz and Saltman ( I d ) have shown that for all practical purposes the surface tensions of hydrocarbon mixtures Figure 3. Atomization Characteristic of Pressure Nozzles are additive on a weight fraction A s function of physical properties and flow rate of liquid basis. Thus, the surface tensions for the test mixtures a t other points will lie between these two conditions of operation the desired temperatures were calculated on this basis. for all runs. Surface tensions for the petroleum stocks were determined by using the correlations of Katz and Saltman ( I d ) . When the Lipkin and Kurtz ( 1 4 ) have reported temperature coefficients of density for pure hydrocarbons, hydrocarbon mixtures, and molecular weight of the petroleum fraction is known, surface petroleum fractions in the liquid state. If the molecular weight tensions can be determined up to 150" F. Above this temperaand the density a t 20" C. for a particular hydrocarbon are known, ture extrapolated values of surface tensions must be used. its density can be calculated for any desired temperature. This The conditions of temperature and flow rate, the values of method was used to calculate the densities of the toluenen-octane physical properties including density, p , viscosity, /*, and surface test mixture a t the desired temperatures. Compositions of the and $2 tension, 6, and the calculated values of $1 test mixtures were known. Therefore, the molecular weights, which are additive on the mole fraction basis, and the densities for the six petroleum stocks and the test mixtures are presented a t 20" C., which are additive on the volume fraction basis, were and +z( are in Table 11. These values of +I calculated. The densities of toluene and n-octane a t 20" C . are reported by the National Bureau of Standards (16). plotted on a log-log basis in Figure 3. The above method for determining densities can be used for The significant conclusion that can be drawn from Figure 3 petroleum fractions. Nelson ( 1 7 ) also gives a method for obis t,hat, upon considering the factors which influence atomization taining the densities of petroleum fractions a t elevated temperatures. Both methods give approximat.ely t h e same TABLE 11. DATAFOR CALCUL.4TIOS AXD RESULT.4NT VALUES $1 AND $2 density values. (43 Viscosities for toluene and 111 Ti,& Ri, Vi> PI, Gra6/ 61, n-octane a t various temperaF. Ml./hIin. Cm./Sec. Gram/hll. Cm. Seo. Dynes/Cm. @I(?) 42 tures are given in the InterStock I 150 60 770.9 0.775 0,0095 19.6 2,556 0.01.21 national Critical Tables (11). I1 220 57 732.4 0.790 0.0096 20.4 2,449 0.0119 52 6 6 8 . 1 0 . 8 2 5 0 . 0 0 9 5 1 9 . 7 2 , 3 5 8 0 .0117 I11 180 Direct and reliable mathe0.0119 IV 220 56 719.5 0.820 0.0097 20.2 2,472 matical calculations of viscosiV 160 55 706,7 0.770 0.0085 19.0 2,602 0.0110 VI 190 53 681.0 0.786 0.0119 21.2 1,826 0.0145 ties for liquid hydrocarbon mixTest tures are not available, as vismixture 103 45 578,2 0,770 0.0046 23.1 3,933 0.0054 cosity is not a n additive propP2, T2,b Rz VZ Grnm/ 62 erty. Therefore, a graphical F. Ml./hIin. Cm./Sec. GI.~%/MI, Cm. Sea. DynebCrn. means of determining the visSrock I 190 35 449.7 0.605 0.0021 5.5 5,265 0.0057 I1 530 40 514.0 0.655 0.0025 10.0 5,473 0,0048 cosities a t any desired temperaI11 475 49 629.6 0.705 0,0028 8.2 6,442 0,0057 9.5 6,049 0.0046 0,0024 0.695 540 40 514.0 ture for oil blends as presented 11' 7.8 5,532 0.0059 0.0027 0,650 410 44 565.4 V by Nelson (18)was used for the VI 540 42 9.2 5,712 0.0050 0.0024 539.7 0.625 Test test mixtures. mixture 245 40 514.0 0.667 0.0023 14.0 6,058 0,0037 Viscosities for the petroleum a Lowest temperature of operation. stocks were also obtained by a b Highest temperature of operation. graphical means. By use of
(d3 ( d i d ~
('G)
~5~)
( / *1
)J*(
3
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1953
433
- EXPERIMENTAL
C URVE
--- PREDICTED CURVE ( F R O M P H A S E DIAGRAM
)
100 . V O L U M E PER CENT VAPORIZED
Figure 4. Equilibrium Flash Vaporization Curves 0
Stork I
Stock I1
600
500
400 I
LT W
---
O *O Il
PREDICTED C U R V E ( FROM P H A S E DIAGRAM)
3 t( 4 r
2
300
5b0
0
10
30 4 0 50 60 70 80 V O L U M E PER CENT VAPORIZED
20
SO. 100
200
Figure 6. Equilibrium Flash Vaporization Curves
I
j
1
j
---
!
Stock I11 100
produced by a hollow-cone atomizing nozzle, the conditions under which the test mixtures were operated are similar to the operating conditions for the petroleum stocks. Therefore, it is reasonable to conclude that if proper atomization were obtained for the test mixtures to establish equilibrium conditions, similar conditions were obtained for the petroleum stocks used in this work.
I
0
0
IO
PREDICTED CURVE ( FROM P H A S E DIAGRAM 1
30 40 50 60 70 80 V O L U M E PER CENT VAPORIZED
20
90
I
100
Figure 7. Equilibrium Flash Vaporization Curves Stock IV
OPERATIONAL PROCEDURES
For operation with petroleum fractions the preheat furnace and flash chamber heaters, as well a8 the vacuum pumps, were turned on. The vacuum in the system was adjusted t o the desired value by manual operation of a dual-needle bleed valve. This pressure, once set, usually required no further adjustment; however, periodic checks were made.
The charge feed pump and the cooling system water pump were switched on. The stock feed rate was adjusted to constant desired throughput of 30 to 65 ml. per minute by means of a relief by-pass valve. Cooling water rates were adjusted to condense and cool the equilibrium vapors and to cool the equilibrium liquid to room temperature.
INDUSTRIAL AND ENGINEERING CHEMISTRY
434
Vol. 45, No. 2
TABLE 111. EXPERIMENTAL EQUILIBRIUM FLASH VAPORIZATIOW DATA -
Stock I Pressure, mm. H g Vapor, % Liquid, % Temp O F . O A P i' vapor OA:P:I:: liquid Pressure, mm. Hg Vapor, % Liquid, % Temp., F. O A P I vapor OA:P:I:: liquid Pressure, mm. Hg \'apor, % Liquid % Temp.,' F. OA P I. vapor OA:P:I.: liquid Pressure, mm. Hg Vapor, % Liquid, % Temp., O F. OA.P.I., vappr 'A.P.I., liquid Pressure, mm. Hg Vapor, % Liquid, % Temp., F. OA.P.I., yappr OA.P.1.. liquid Pressure, mm. Hg Vapor, % Liquid, r0 Temp., F. 'A.P.I., vapor OA.P.I., liquid Pressure, mm. H g Vapor, % Liquid, % Temp., F. OA.P.I., vapor "A.P.I., liquid Pressure, mm. H g Vapor, % Liquid, To Temp. O F , OA.P.1:. vapor 'A.P.1.. liquid Pressure, mm. Hg Vapor, % Liquid, % Temp O F . : A . P . ~ , vapor A.P.I., liquid
lo
B.P. 130.0
. .. ...
100 B.P. 227.0
... ...
400 B.P. 304.0
...
10 B.P. 184.0
...
... 100 B.P.
302.0
... ...
400 B.P. 390.0
...
...
10
163 .O
...
... 100 B.P. 278.0
...
... 400
B:P: 369.0
... ...
10 11.6
10 28.9
10 46.6
10 69.7
88.4 156.0 50.1 41.9 100 11.8
71.1 181.5 48.2 40.7 100 30.5
53.4 195.6 46.9 39.8 100 47.1
30.3 215.1 45.3 38.1 100 68.1
13.4 235.9 43.9 36.2
88.2 260.1 49.8 41.8 400 13.1
69.6 283.3 48.0 40.7 400 33.4
52.9 299.0 46.1 39.8 400 46.5
31.9 318.3 45.2 38.3 400 74.3
11.5 345.1 43.7 36.7 400 89.5
86.9 343.8 49.3 41.9
66.6 368.3 47.4 40.7
53.5 379.4 46.5 39.8
25.7 402.5 44.7 37.9
10.5 421.5 43.7 36.4
10 8.5
10 27.1
10 47.9
10 66.1
10 87.2
91.5 217.8 45.2 33.5 100 15.0
72.9 249.5 41.2 32.3 100 37.7
52.1 273.4 38.4 31.1 100 50.7
33.9 293.6 37.2 29.9 100 69.1
12.8 325.0 35.9 26.8 100 85.0
85.0 356.3 42.3 33.2 400 10.7
62.3 380.7 39.6 31.7 400 31.1
49.3 395.8 38.3 31.0 400 49.6
30.9 415.3 37.1 29.4 400 75.2
15.0 439.7 36.1 27.8 400 84.3
89.3 444.5 41.2 33.7
68.9 471.4 38.7 32.7
50.4 486.8 37.4 31.9
24.8 511.3 36.4 29.3
15.7 527.9 35.9 28.2
10 19.1
10 32.1
10 48.3
66.1
80.9 182.0 36.8 30.9
67.9 190.6 35.7 30.3
100
100
10
10
86.6
100
88.5
10 83.8
33.9 223.7 33.9 28.5
16.2 252.2 32.7 28.3
ion
100
70.5
86.0
13.9
29.3
51.7 205.1 34.9 29.5 io0 49.3
86.1 296.7 37 0 31.2 400 17.0
70.7 311 5 35.9 30.3 400 34.5
50.7 331.2 34.6 29.4 400 50.7
29.6 352.7 33.3 28.6 400 69.3
14.0 381.2 32.5 29.4 400 82.0
83.0 392.7 35.5 31.2
65.5 409.6 34.5 30.6
49.3 426.0 33.6 30.3
30.7 449.4 32.8 30.2
18.0 470.0 32.1 30.9
From 1 to 3 hours were required to bring the unit to steadystate operations with constant temperature, pressure, and flow rate. While the unit was approaching equilibrium temperature, the contents of the accumulators were recycled to the feed reservoir. When steady-state equilibrium conditions were attained, the excess vapor or liquid samples were pumped out to the drain. Approximately 480 ml. of the vapor and liquid samples were collected a t each equilibrium determination. The following data were taken for each equilibrium point: 1. Equilibrium temperature 2. Equilibrium pressure 3. Vapor rate and sample (480 ml.) 4. Liquid rate and sample (480 ml.) Equilibrium vaporization equipment can be operated under isothermal or isobaric conditions. The flash unit used in this work was operated under constant pressure conditions. Raising the temperature by adjusting the heaters made constant pressure operating conditions relatively easy to maintain. A minimum of six points per pressure was obtained. Points near the middle of the equilibrium flash vaporization curve (30, 50, and 70% vaporized) required from 0.75 to 2 hours to obtain, while points a t the ends (10 and 90% vaporized) required from 2 to 4 hours.
10
50
D.P.
B.P.
260.0
197.0
.. .. ..
... ...
100
200
D.P.
B.P.
364.0
265.0
...
...
... ...
400
760
D.P.
D.P.
439.0
359.4
... ...
-Stock 10
.. . .. .
II50
D.P.
B.P.
355.0
263.0
... ...
100 D.P. 476.0
... ...
...
... 200 B.P.
342.0
... ...
50 11.6
50 29.1
5n 48.3
50 72.7
50 89.3
88.4 226.4 49.9 42.0 200 13.3
70.9 251.7 48.1 40.9 200 28.4
51.7 267.5 46.6 39.7 200 54.1
27.3 290.0 45.1 37.9
10.7 310.2 43.9 36.0
200 64.8
200 88.8
86.7 299.9 49.8 41.8 760 9.1
71.6 321.0 47.8 40.8 760 29.0
45.9 343.8 46.2 39.2 760 45.8
35.2 354.8 45.4 38.7 760 66.3
11.2 379.4 43.8 36.5 760 75.0
90.9 401.2 47.8 42.4
71.0 426.0 46.0 41.6
54.2 438.3 45.2 41.2
33.7 467.7 44.1 40.7
25.0 468.0 43.1 42.2
50 10.2
50 29.1
89.8 306.2 43.5 33.4 200 10.7
70.9 334.8 40.5 32.2 200 33.1
89.3 386.5 43.0 33.4
50 16.1
50 D.P. 329.0 , ,
.. ,.
200
-U.Y399.0
. ,. , ,
.
760 h _
U.I.
en
74.3
50 90.2
50.1 356.8 38.5 31.1 200 50.2
25.7 382.5 36.7 28.9 200 69.9
9.8 411.8 36.7 27.6 200 86.2
66.9 414.0 39.7 32.0
49.8 430.4 38.2 30.9
30.1 452.9 36.9 29.2
13.8 480.2 35.8 26.8
50 27.7
48.7
50
49.9
513.0 ,
,
.
... 50
n p - .438.0 35.7
...
200
-1j.Y.
I
516.0 , ,
. .. .
400 D.P.
B.P.
568.0
-Stock I11 -
in
50
D.P.
B.P.
301.0
240.0
100
200
D.P.
B.P.
424.0
320.0
... ...
...
...
50
50
70.7
83.9 259.0 37.1 31.1 200 17.4
72.3 270.2 36.1 30.4 200 30.7
51.3 286.9 34.8 29.4
29.3 315.1 33.6 28.6
200
zoo
82.6 342.0 36.3 31.1
69.3 354.5 35.4 30.4
46.9 374.5 34.0 29.6
53.1
5n 87.8
69.2
12.2 348.7 32.4 29.1 200 85.2
30.8 395.4 33.1 29.5
14.8 428.2 32.1 30.7
50 n _
u.r
383.0
. .. . .. zoo
D.P. 471.0
. ., ,
..
400
D.P. 522.0
EXPERIMENTAL DATA
EQUILIBRIUM FLASH VAPORIZATIOS. Equilibrium flash vaporization data a t 10, 50, 100, 200, and 400 mm. of mercury were obtained for six petroleum fractions. One set of data was obtained a t 760 mm. of mercury. Because erratic flow rates were obtained a t atmospheric pressure, only one set of data was taken. Petroleum samples were obtained from various process unit streams of the Pan American Refining Co. and the Humble Oil and Refining Co., ranging from light naphthas to residual tars. These samples were blended to give as broad a range as pos~ible with respect to gravity and boiling points. All stocks run in the flash unit were blended material, with the exception of stock V, -which was a commercial white kerosene marketed by the &lagnolia Petroleum Co. The experimental equilibrium flash vaporization data are presented in Table 111. Flash vaporization data include three variables: temperature, pressure, and per cent vaporized. These variables are generally plotted graphically in two ways: temperatures versus per cent vaporized for lines of constant pressure, and pressure versus temperature for lines of constant per cent vaporized. The first method is the one most coin-
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1953
435
TABLE 111. EXPERIMENTAL EQUILIBRIUM FLASH VAPORIZATION DATA (continued) Pressure, mm. H g Vapor, % Liquid, % Temp., F. OA P I vapor OA:P:I:: liquid Pressure mm. H g Vapor: % Liquid, % Temp F. O A P ~ vapor ' 'A:P:I:: liquid Pressure, mm. Hg Vapor, %
10 B.P.
170.0
...
... 100
281.0
.. .. ..
400 B.P.
377.0
Pressure, mm. Hg Vapor, %
lo
Liquid, % Temp., O F. OA.P.I., vapor OA.P.I.,liquid Pressure, mm. Hg Vapor, % Liquid % Temp., O F. O A P I vapor 'A:P:I:: liquid
... ...
B.P.
147.0
.... ..
100 B.P.
254.0
...
... 400
B.P.
337.0
... ...
10
10 16.5
10 26.0
52.4
10 66.3
10 84.7
83.5 223.7 37.1 28.2
74.0 242.3 35.2 27.8 100 28.5
47.6 272.9 32.4 27.0 100 50.5
33.7 288.2 31.5 28.4 100 71.8
15.3 318.3 30.8 25.3 100 84.8
100
14.3 B.P.
Liquid, % Temp. O F OA.P.I:,vapor OA.P.I., liquid
Liquid, % Temp O F . O A P i' vapor OA:P:I:: liquid Pressure, mm. H g Vapor, %
Liquid, % Temp., a F. "A.P.1 vapor OA.P.1:: liquid Pressure, mm. Hg Vapor, % Liquid, % Temp O F OA P i: vapor "A:P:I.:liquid Pressure, mm. Hg Vapor, % Liquid, % Temp., a F. OA.P.1 vappr OA.P.1:: liquld
lo B.P. 152.0
... ...
100
B.P.
279.0
...
... 400 B.P.
370.0
... ...
50 D.P.
349.0
... ...
B.P.
247.0
... ...
100
200 B.P.
475.0
324.0
71.5 360.7 35.1 27.8 400 30.9
49.5 388.3 32.8 27.1 400 46.9
28.2 415.3 31.5 26.0 400 66.1
15.2 437.5 30.8 25.4 400 87.5
85.2 438.8 35.7 28.7
69.4 465.2 33.5 28.2
53.1 486.2 32.1 27.7
33.9 511.3 31.2 27.4
12.5 538.0
568.0
...
...
10 16.4
10 31.0
10 44.5
10 67.1
10 86.0
...
50
D.P.
85.7 335.2 37.8 28.3 400 14.8
...
...
... ...
Stock V 10 50 D.P.
B.P.
32.9 211.0 44.3 40.2 100 71.8
14.11 229.5
248.0
216.0
39.8 100 85.2
100
200
84.3 272.5 47.2 42.1 400 16.9
69.2 287.0 46.1 41.6 400 30.4
50.4 303.0 45.1 40.8 400 48.5
28.2 323.0 44.2 40.0 400 71.8
14.8 335.0 43.5 39.3 400 81.3
83.1 365.0 45.9 42.3
69.6 375.0 45.2 42.0
51.5 386.0 44.4 41.5
28.2 402.0 44.0 40.4
18.7 408.7 43.5 40.4
10 14.2
10 28.8
10 52.4
65.2
10 89.0
85.8 193.8 46.0 36.1 100 16.1
71.2 221.9 44.4 34.8
47.6 260.3 41.6 32.9 100 52.8
34.8 278.3 40.6 32.1 100 74.1
11.0 322.7 38.5 30.2 100 86.1
100
31.0
83.9 321.4 45.2 35.8 400 13.7
69.0 347.8 43.4 34.7 400 26.0
47.2 379.4 41.4 32.9 400 56.2
25.9 410.5 39.6 31.3 400 68.4
13.9 433.0 38.6 30.7 400 84.8
86.3 418.4 43.5 36.4
74.0 445.3 42.0 35.7
43.8 490.0 40.1 34.9
31.6 505.3 38.9 34.4
15.7 534.9 38.0 34.4
monly used and is more convenient for direct plotting of experimental flash vaporization data, as shown in Figures 4 to 9. The second method was first proposed by Bahlke and Kay (1) and later extended by Edmister et al. (6, 6). Logarithms of the absolute pressure are plotted against the reciprocal of the absolute temperature for lines of constant per cent vaporized. The constant per cent vaporized lines are straight and, when extrapolated, intersect a t a common point designated as the "focal point." These plots are essentially phase diagrams and have an advantage over the first method in that additional flash vaporization data can be predicted for other specific operating pressures. The data for these plots were obtained from Figures 4 to 9 as temperaturw at the bubble point, 10, 30, 50, 70, and 90%, and dew point. These results are plotted graphically in Figures 10 to 15. Edmister and Pollock (6) present empirical correlations for determining the critical temperature and pressure and the focal temperature and pressure of petroleum fractions. These are based on OA.P.1. gravity and ASTM distillation characteristics. These correlations were used to determine the critical temperature and pressure and focal temperature and pressure for the six stocks used in this work. Derived values are plotted on Figures
57.9
50 78.0
50' 86.9
86.8 294.5 38.2 28.3 200 13.1
65.6 331.0 34.2 27.5 200 37.0
42.1 359.8 32.5 26.7 200 54.4
22.0 386.5 31.2 25.5 200 69.7
13.1 401.6 30.7 24.5 200 86.2
86.9 381.2 37.6 28.5
63.0 418.4 33.6 27.9
45.6 439.2 32.2 27.3
30.3 459.1 31.5 26.5
13.8 481.9 30.7 24.8
50 16.3
50 29.6
50 50.8
50 75.4
50 85.4
50
50
D.P.
433.0
...
... 200
D.P
520.0
... ...
...
55.5 187.4 45.0 40.8 100 49.6
10
50 34.4
D.P.
69.0 176.1 46.0 41.4 100 30 8
...
50 13.2
400
83.6 163.3 46.9 41.9 100 15.7
c
Pressure, mm. H g Vapor, %
-
Stock IV
r
... ...
... ..
D.P.
B.P.
359.0
292.0
... ...
... ...
83.7 235.5 47.3 42.0 200 15.7
70.4 248.6 46.3 41.5 200 31.8
49.2 266.2 45.3 40.9 200 51.4
24.6 290.5 44.1 39.8 200 69.8
14.6 300.0 43.7 39.3 200 84.7
84.3 316.5 46.9 42.5
68.2 330.8 45.7 41.9
48.6 342.0 45.0 40.9
30.2 356.3 44.2 40.2
15.3 370.1 43.5 39.8
50 10.8
50 30.3
49.0
50 70.2
50 86.9
89.2 266.2 45.7 36.0 200 16.6
69.7 300.8 44.0 34.7 200 31.6
51.0 332.6 41.9 33.2 200 51.2
29.8 364.7 40.0 31.4 200 73.3
13.1 390.6 38.8 29.7 200 87.4
83.4 368.3 44.7 36.0
68.5 392.3 43.1 34.9
48.8 423.4 41.1 33.7
26.7 455.1 39.4 32.1
12.6 481.1 38.2 31.2
50 D.P.
322.0
...
... 200 D.P.
398.0
... ...
400 D.P
440.0
... ...
Stock VI 10 50 D.P.
B.P.
345.0
234.0
...
...
... ...
1002
200
D.P.
B.P.
468.0
319.0
..... .
...
...
50
-
50
D.P.
425.0
... ...
200 D.P.
518.0
400 D.P
572.0
...
...
10 to 15. The focal points derived from extrapolation of the data for all six stocks disagree with the values derived from the empirical correlations. At present the authors have no satisfactory explanation for this discrepancy. Development of more experimental data a t other pressures and on other stocks of different characteristics may do much to clear up this point. Othmer et al. (24) report flash vaporization data at reduced pressures for four petroleum stocks, together with their corresponding ASTM distillation data. Phase diagrams were constructed and focal points determined from empirical correlations ( 5 )for these four stocks. Here again, no agreement was found. SLOPE. Slopes are good criteria for characterizing distillation curves and have been used extensively for correlation purposes. The two most common slopes are: (7oY0temperature 'F.) - (10% temperature O F.) (10-70) Slope = 60%
=OF./%
(10-90) Slope =
(90% temperature 'F.) - (10% temperature
80%
=' F./%
The calculated slope data are presented in Table IV.
F.)
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
436
Vol. 45, No. 2
600
500
k 400 I
w ( I
3
G
E
0
300
I w
)r
20 0
100
..
-
-EXPERIMENTALC u
RVE
--- PREDICTEDC U R V E
( F R O M PHASE DIAGRAM )
:171
0
V O L U M E PER C E N T V A P O R I Z E D
Figure 8. Equilibrium Flash Vaporization Curves Stock
50
v
60
70
80
90
IO0
V O L U M E PER CENT V A P O R I Z E D
Fipnre 9.
Ihpiilibrium Flash Vaporization Curves Stock VI
500,000 1,000,000
500,000
100,000
10,000
E E I
W (I
3 v)
w (I a
100
0
P
0 0 L u
0
%
0 0
o
0 0
m
0
g
0 0 0 0 0 0 0 0 0 0 0 0 0 0 IC
m m g =
15
T E M P E R A T U R E --E
Figure 10. Phase Diagram for Stock I
Griswold and Klecka (9) observed that a t higher temperatures and pressures the slope of the equilibrium flash vaporization curves of petroleum mixtures decreases and must equal zero at the critical temperature and pressure. As indicated in Table IV, the slopes of the experimental equilibrium flash vaporization curves from this investigation increase with decrease in pressure.
0
0
0 Lu 0
0
0
0
0
0 0 0 0 0 0 0
T E M P E R ATU R E - 'E Figure 11. Phase Diagram for Stock I1
Because the range of slopes for the test stocks in this work was small, correlations involving the slope characteristics were not considered indicative.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
February 1953
437
CORRELATION
EQUILIBRIUM FLASH VAPORIZATION CURVE SLOPES
TABLE IV.
(10-70) Slopea, Pressure
Stock
I
10 50 100 200 400 760 10 50 100 200 400 10 50 100 200 400 10 50
I1
I11
IV
100
200 400 10 50 100 200 400 IO 50 100 200 400
V
VI
TABLE V. ASTM IBP 10 20 30 40 50 60 70
Stock I 33 1
371 391 408 423 437 453 472 492 53 1 581 96.0 2.0 2.0 43.0 138
OF./%
1.050 1.000 0.983 0.967 0.950 0.933 1.317 1.217 1.200 1,167 1.067 1,000 0.983 0.967 0.967 1.017 1.683 1.517 1.500 1.483 1.433 1.733 1.650 1.617 1.583 1.617 0.900 0.883 0.867 0.783 0 ; 750
(10-90) Slopeb, O
F./%
1.100 1.088 1.075 1.063 1.038 1.025 1.375 1,325 1.300 1.288 1,250 1.213 1,200 1.188 1.175 1.238 1.738 1,550 1,463 1.450 1.317 1.775 1.688 1.675 1.663 1.675 0.975 0.963 0.938 0.863 0.825
EQUILIBRIUM FLASH VAPORIZATION A N D ASTM DISTILLATION. Kumerous correlations were tried to utilize fully the equilibrium flash vaporization data presented in Table 111. The final result is as shown in Figure 16. Four variables are used: equilibrium flash vaporization temperature, ASTM distillation temperature, per cent vaporized, and equilibrium pressure. Except for the 0% vaporized (bubble point) and the 100% vaporized (dew point) lines, the correlation shows extremely good agreement with experimental data. The average deviation of the correlation from all experimental points is 4.6' F. Since the 0 and 100% vaporized points show considerably more scattering, these correlation lines are indicated with dashed lines. From this correlation the equilibrium flash vaporization data for petroleum fractions a t reduced pressures can be determined directly from the atmospheric ASTM distillation data. The following example will illustrate the use of the correlation : The 30% vaporized atmospheric ASTM temperature is 400' F.
500,000
INSPECTION DATAON BLENDED STOCKS Stock I1 356 437 467 492 515 532 550 572 606 674 727 95.0 4.9 0.1 34.7 209
Stock I11 Stock I V 358 238 393 426 407 460 423 486 435 509 453 530 472 551 900. 578 536 613 670 592 662 725 96.0 96.5 2.5 2.0 1.0 2.0 32.0 30.1 159 205
Stock V
Stock VI
340 371 391 400 414 430 441 457 472 495 522 97.0 1.8 1.2 43.0 135
345 402 423 452 481 512 545 575 611 661 708 97.0 2.1 0.9 37.5 195
ASTM DIGTILLATION. ASTM distillations were run on the six stocks according to specifications. Three check runs were made on each stock, with a maximum deviation among any three check temperatures of 3' F. The high-temperature range ASTM thermometer used was cali' rated against National Bureau of Standards thermometers. Tldse ASTM distillation data for the six stocks are presented in Table V. MOLECULAR WEIGHT. The molecular weight of the six stocks 0 0 0 0 0 0 0 0 0 0 0 0 0' 0 was determined cryoscopically. Several determinations were 0 0 5? 8 % , o g : a g g g q TEMPERATURE-'E made for each stock, with a maximum deviation of less than 3%. The apparatus used was a modification of that employed by Figure 12. Phase Diagram for Stock I11 FitzSimons and Thiele (8). C.P. benzene was used as a solvent. Ita molar cryosopic conTABLE VI. COMPARISON OF EQUILIBRIUM FLASH VAPORIZATION-ASTMDISTILLATION stant was taken as 65.6 and its CORRELATION WITH LITERATURE DATA molecular weight as 78.11. The Mean Dev. of Mean Dev. of procedure used was identical to 10 30 50 30, 50, 70% Mean Dev. of No. of Operating 70, 96% Poi&, Polnts, 50% Points, Petroleum Pressures, that described by FitzSimons Source of D a t a F. F. F. Stocks Mm. Hg and Thiele (8),except that 4 Experimental (this work) 4.7 4.1 3.3 6 10,50, 100 200 g r a m s of m a g n e s i u m p e r 400: 760: 1000 chlorate were used as a dehyOthmer, Ten Eyck, and Tolin (24) 9.6 9.2 9.9 2 50,100, 200, 760 drating agent for the solvent Edmisterand Pollock (s) 20.3 13.6 11.9 23 760 instead of 2 grams of barium Edmister Reidel, a n d Merwin (6) 20.2 14.0 4.3 3 760 Brown a i d Skinner (3) 18.3 14.0 10.6 5 760 perchlorate. The results are Piromoov a n d Beiswenger (86) *. .. 14.4 5 760 given in Table V.
z
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
438
Vol. 45, No. 2
It is desired to find the corresponding 30% vaporized equilibrium
1,600,000
flash va orization temperature a t 50 mm. of mercury. On igure 16 find 400' F. on the left atmospheric ASTM distillation temperature scale. Move horizontally to the right to the 50-mm. isobar. Move vertically t o the 30% vaporized line, then move horizontally to the right, and read 251" F. on the right ordinate equilibrium flash vaporization temperature scale. This 261" F. is the desired 30y0 vaporized equilibrium flash vaporization temperature a t 50 mm. of mercury.
9
500.000
It was desirable t o check the agreement of the correlation shown in Figure 16 with other experimental data reported in the literature. The equilibrium flash vaporization data of Othmer et al. ( d 4 ) are the only ones available a t reduced pressures that were applicable to the correlation. At atmospheric pressure the data of Edmister and Pollock ( 5 ) ,Edmister, Reidel, and Nerwin (6), Brown and Skinner (S), and Piromoov and Beiswenger (66) were used. The mean deviations of the correlation from these reported experimental data were calculated for 10, 30, 50, 70, and 90% points. For comparison, these three mean deviations are presented in Table VI. These mean deviations show that the 50% vaporized points correlate best and that the 10 and 90% vaporized points result in poorer agreement. Furthermore, it is evident that the correlation shows better agreement a t lower pressures. CONCLUSIONS
The following conclusions can be made from this work:
0
0
(v
m
0
0
0
0 P
0
8
The equilibrium flash vaporization unit operated under equilibrium conditions with little or no liquid entrainment or vapor superheating. The lines of constant per cent vaporized in the phase diagrams are straight in the pressure range of 760 to 10 mm. of mercury and they converge t o a common point a t some high pressure for the petroleum stocks run. The critical and focal point correlations of Edmister and Pol-
0 0 0 0 0 0 0 0 0000 0 0
+ w a g = TEMPERATURE-'F. (D
'22
Figure 13. Phase Diagram for Stock IV 1,000,000~ ! 500,000
0 0
0
z
0
4
0 0
d
0
0
0
0
In
w
TEMPERATURE
0 0 0 0 0 0 0 0 0 0 0 0 0 0
r - m m , o = n y -OF
Figure 14. Phase Diagram for Stock V
I
1,000,000
I
500,000
0
0
0 0 N
0
m 0
0 0 P
0 0 u7
0 0
w
0 0 0 0 0 0 0 0 0 0 0 0 0 0
r-a,a,o=
TEMPERATURE -'F.
Figure 15. Phase Diagram for Stock VI
February 1953
INDUSTRIAL AND ENGINEERING CHEMISTRY
439
(3) Brown, G . G., and Skinner, E. M., IND. ENG.CHEM., 22,278-88 (1930). (4)Dunetan, A. E.,Nash, A. W., Brooks, B. T., and Tizard, H. T,,“Science of Petroleum,” Vol. 11, p. 1657,London, Oxford University Press, 1938. ( 5 ) Edmister, mi. C., and Pollock, D. H., Chem. Eng. Progr.,44,905-26(1949). (6) Edmister, W. C., Reidel, J. C., and Merwin, W. J , , Trans. A m . Inst. Chem. Engrs., 39,457-89 (1943). (7) Fancher, G . H.. Petroleum Engr., 2, No. 6, 176-80 (1931). (8) FitzSimons, O., and Thiele, E. W., IND.ENG.CHEW, A N A L .E D . , 7 , 11-14 (1935). (9) Griswold, J., and Klecka, M. E., Petroleum Refinor, 24,NO.10,388-93(1945). (IO) I n t e r n a t i o n a l C r i t i c a l Tables, Vol. IV, pp. 456, 458,NewYork, McGrawHill Book Co., 1928. (11) Ibid.,Vol. VII, pp. 218,220, 1930. (12) Katz, D. L., and Saltman, W., IND. ENG.CHEM., 31, 91-4 (1939). (13) Leslie, E. H., and Good, A. J . , I b i d . , 19,453-60 (1927). (14)Lipkin, M.R.,and Kurtz, S. S., Jr., IND.ENQ. CHEM., ANAL. ED., 13, 291-5 (1941). 115) Lockwood, J. A , , LeTourneau, R. L., Matteson, R., and Sipos, F., Anal. Chem., 23, 1398-1404 (1951). (16) Natl. Bur. Standards, Circ. C410, 7-31 (1936). (17) Nelson, W. L., Oil Gas J . , 36, No. 37,184-5 (Jan. 27,1938). (18) Nelson, W.L., “Petroleum R e f i n e r y Engineering,” 3rd ed., pp. 161-2, New Figure 16. Correlation of Atmospheric ASTM Distillation Temperature with York, MoGraw-Hill Book Equilibrium Flash Volatilization Temperature Co., 1949, X% vaporized, various pressures (19) Obryodchokoff, S. N., IND. ENG.CHEM.,24,1155-60 (1932). lock (6) do not appear to be applicable to the stocks investiOhnesorge, W., 2. angew. Math. Mech., 16,No. 6,355-8 (1936). gated here at pressures below atmospheric. Ohnesorge, W., Z . Ver. deut. Ino., 81, NO. 16, 405-6 (1937). The slo es of the equilibrium flash vaporization curves inOkamoto, K. K., and Van Winkle, M., Petroleum Refiner, 28, crease witR decrease in pressure over the pressure range of 760 NO.8,113-20(1949). t o 10 mm. of mercury. Ibid., 29,N O . 1,91-6 (1950). Othmer, D. F., Ten Eyck, E. H., and Tolin, S., IND.ENG. ACKNOWLEDGMENT CHEM.,43,1607-13(1951). Piromoov, R. S., and Beiswenger, G. A., Proc. Am. Pedroleum The petroleum samples used in this work were supplied b y Inst., 10,No. 2,52-68 (1929). the Pan American Refining Co. and the Humble Oil and Refining Smith, R . B., Dresser, T., Hopp, H. F., and Paulsen, T. H. IND. ENG.CHEM.,43,766-70(1951). Co. The complete insulation of the equipment was donated by Watson, K. M., Nelson, E. F., and Murphy, G . B., Ibid., 27, the Johns-Manville Co. 1460-4 (1935). LITERATURE CITED
(1) Bahlke, W.H., and Kay, W. B., IND. ENQ.CHEM.,24,291-301 (1932). (2) Berg. L.,and Popovac, D. O., Chem. Eng. Progr., 45,683-91 (1949).
review J u l y 11. 1952. ACCEPTEDOctober 25, 195 2 Abstracted from a thesis presented by K. Keith Okamoto in partial fulfillment of the requirements for the degree of doctor of philosoph y, University of Texas. RECEIVED for
