US3399116A - Laboratory-scale flash still for petroleum oil fractions - Google Patents

Description

Aug. 27, 1-968 J. J. DU BOIS ETAL LABORATORY-SCALE FLASH STILL FOR PETROLEUM OIL FRACTIONS 2 Sheets-Sheet 1 Filed Jan. 17, 1966 Jab A, GIN/8K Rabeel 7: Radian M11340, 777041 00, gaszea ATTORNEY J. DU B L 2 Sheets-S e R m m R W w H fin A kc n a ATTORNEY b mm, 27

Aug 27, 1968 LABORATORY-SCALE FLASH STILL FOR PETROLEUM OIL FRACTIONS Filed Jan. 17, 1966 E v 3:55 A I u "I" r n llllll 4 United States Patent 3,399,116 LABORATGRY-SCALE FLASH STILL FOR PETROLEUM OIL FRACTIONS Jule J. Du Bois, Schenectady, N.Y., and John A. Glover,

Munster, and Robert J. Buchler, Whiting, Ind., assignors to Sinclair Research, Inc., New York, N.Y., a corporation of Delaware Filed Jan. 17, 1966, Ser. No. 521,165 Claims. (Cl. 196-98) ABSTRACT OF THE DISCLOSURE A laboratory scale flash still, employing a preheating coil surrounding a flash chamber with dual removing means, the preheating coil and flash chamber being substantially immersed in a molten salt heating medium, and means for maintaining the dual removing means at equal subatmospheric pressures.

This invention relates to a laboratory scale flash distillation still. of improved utility in flashing such materials as reduced crudes, heavy residues, and penetration asphalts. More particularly, this invention concerns a laboratory scale flash distillation still which can be used to produce petroleum products of the quality generally expected from commercial operations.

For a long time there has been a need for a continuous laboratory scale equilibrium flash distillation still which can be used for processing various heavy hydrocarbon crudes in performing general assay work. Such a still is particularly necessary because bench scale reactor studies do not produce products in large enough volume to be utilized in the pilot plant scale flash distillation still. Some of the problems which have acted as a deterrent to the construction of such a still have been the overall poor operability of previously constructed small stills and a general reluctance to operate in a distillation laboratory a still which utilizes a mercury vapor heating jacket.

An improved laboratory scale equilibrium flash distillation still has now been developed which has eliminated the operability problems and those associated with the use of a mercury vapor heating means. Thus, the improved flash distillation still of the present invention can be used to process various crude hydrocarbons in producing petroleum asphalts and corresponding vacuum gas oils of the quality normally expected from only commercial operations. Further, by substituting a molten salt bath for the more hazardous mercury vapor heating means used by existing laboratory stills, the flash still of the present invention can be operated in distillation laboratories without the problems and dangers associated with mercury vapor heating.

The equilibrium flash still of the present invention broadly comprises a flash zone, a preheating zone and a heating zone, with the preheating zone surrounding the flash zone and the preheating zone and flash zone being disposed within the heating zone; means for introducing a heat transfer medium into the heating zone, means for removing the heat transfer medium from the heating zone, means for heating the heat transfer medium in the heating zone, means for introducing feed sequentially into the preheating zone and then into the flash zone, a first removing means for recovering the light end product from the flash zone, a second removing means for recovering the heavy end product from the flash zone and means for maintaining the first and second removing means at an equalized su'batrnospheric pressure.

The present invention will be more fully understood from the detailed description hereinbelow and the accompanying drawings wherein FIGURE 1 shows a distillation apparatus incorporating the still of this invention;

Cir

FIGURE 2 is a sectional elevational view of the still;

FIGURE 3 illustrates details of the bottoms adapter for the distillation apparatus; and

FIGURE 4 illustrates details of the overhead adapters.

More specifically, the equilibrium flash still of the present invention comprises a flash chamber 10, a preheating coil 12, and a heating vessel 14 with flash chamber 10 and preheating coil 12 being arranged within the heating vessel. Preheating coil 12 consists of tubing which is wound around, and in contact with, flash chamber 10 from the upper to the lower portion thereof. Feed material passes from the outside connection 16 of coil 12 through the coil 12 which serves to preheat the feed. The preheated feed is then introduced into the flash chamber 10 tangentially at a point slightly above the bottom portion thereof through opening 18 (see FIGURE 2). Heating vessel 14 surrounds flash chamber 10 for substantially its entire length and is provided with closures at its bottom and its top. The closure at the bottom includes a packed gland exit opening 20 which has a bottoms recovery line 22 extending therethrough. The closure at the top is removable and includes a fill port 24 through which the heat transfer medium 32 can be introduced into the heating vessel 14, a stirrer port 26 and a thermowell 28. Stirrer port 26 is provided so that the heat transfer medium 32 can be gently agitated by a stirrer (not shown) to maintain uniform temperatures through the entire bath. Therm-owell 28 is provided to permit measurement of the temperature gradient in flash chamber 10. Electric immersion heaters 30 are arranged in vessel 14 to supply the heat to maintain the heat transfer medium in a molten state. Heaters 30 are powered by an electric source which can supply suflicient electric power to heat the heat transfer medium, e.g., up to about 400 watts per heater, which source is not shown. The heat transfer medium 32 used in the present invention is, for example, a molten salt bath, such as sodium or potassium salts. Skin thermocouples 34 are spaced on the outside surface and along the entire length of the heating vessel 14 to furnish temperature data 'for temperature control. Several inches of insulation 36 on vessel 14 serve to limit heat loss from the vessel. A drain 38 is provided in vessel 14 for drawing oil the heat transfer medium when desired, such as when the apparatus is not being used.

Flash chamber 10 has in addition to a bottoms recovery line 22, an overhead vapor line 40. A shut-off valve 42 is located in the bottoms recovery line 22 which line then enters a liquid seal device 50 within bottoms adapter, generally designated by numeral 44, which is provided with a. plugged access port 46 and drip rod 48. The bottoms pass through line 22 into the seal device 50, i.e., an overflow cup, and then to receiver assembly 52. The bottoms line 22 and shut-off valve 42 are enclosed by an electric heater 54 which insures optimum heat control and sample protection.

Overhead vapor from flash chamber 10 passes through vapor line 40, condenser 56, e.g., air or water cooled, and a quick-opening diaphragm valve 58 into an overhead receiver assembly, i.e., overhead adapter 60. Overhead adapter 60 is attached to overhead receiver 62 and includes a drip rod 64 which extends into the overhead receiver. The overhead product passes from overhead adapter 60 to the overhead product receiver assembly 62 which is identical with the bottoms product receiver assembly 52. A vacuum controller 66 maintains the overhead vapor line 40 and bottoms recovery line 22 at equal ized subatmospheric pressures and provides satisfactory pressure stability down to about 1 mm. Hg. Still pressure is measured through a tap '68 in the overhead line 40 below the condenser 56 by a pressure measuring device (not shown) such as a Dubrovin gauge a closed end mercury manometer or, at higher pressures, by an open end mercury manometer. Suitable manometers indicate the pressure at each receiver for control of pump-out pressures or differential settings. An adjustable liquid level bubbler may be used to provide a pressure differential between the overhead and bottoms receivers, thus providing control on the liquid level within the flash chamber. Howunder vacuum, taking cuts to a 650 F. atmospheric boiling point. The vacuum bottoms (35.6 volume percent on crude) are next flashed in the flash still of the present invention at 680 F. Several runs are made at various pressures. The flash chamber conditions, along with the feed, gas oil and bottoms yield and quality measurements are listed in Table I.

TABLE I.-MIDGET STILL VACUUM FLASH DIS'IILLATION OF 35.6 VOL. PERCENT MID- CONTINENT REDUCED CRUDE Pressure, mm. Hg

Temperature, F Liquid, pereelni; on crude.

Pour, E Flash, COC. Aniline Point,

Reduced Gas Oil Overhead Crude ever, this unit can be operated without this device, and although the liquid level may be below the heating vessel, there is no evidence of deterioration in product quality. Operation of the equilibrium flash still is as follows: Heat transfer medium, e.g., salt, is introduced through fill port 24 until flash chamber 10 is substantially surrounded. Electric immersion heaters are then turned on and the medium heated to the desired operating temperature. Flash chamber 10 is then evacuated to the desired operating pressure and the feed, which is measured by scale 70, is pumped 72 from tank 74 through line 16 into preheat coil 12 to be introduced into the lower portion of the flash chamber at inlet 18. The feed is cracked into the resulting products in chamber 10.

Feed rates of about 50 to 200 grams per hour are generally used in the flash still and upon introduction of the feed into the bottom of the flash chamber 10, the vapor liquid equilibrium is essentially complete. The flash still is generally run at a temperature of about 680 F. to 740 F. Temperature control is not a problem in the distillation apparatus of the present invention and thus when using the heat transfer medium, e.g., molten salt bath, temperatures of up to 800 F. and even higher are not considered excessive in this type of unit.

The flash still has proved to be very valuable in that it can be used for a variety of feedstocks such as reduced crudes, heavy residues, penetration asphalt, and even feedstocks yielding zero penetration bottoms, which can be handled by the use of auxiliary heat sources such as infrared lamps. These lamps can be assembled promptly when needed and removed when the condition Warrants. The still has also proven to be very useful in crude assay work, producing petroleum asphalt and corresponding vacuum gas oils of the qualities to be expected from commercial operations. Example I demonstrates such use.

EXAMPLE I A mid-continent crude is fractionated on a glass trueboiling-point still yielding cuts to a nominal 400 F. end point. The crude is further reduced on the same still EXAMPLE II To further illustrate the versatility of the still, a severely cracked residual is flash distilled at two different sets of conditions. Yields and product quality measures on the gas oils and asphalt bottoms are listed in Table II. The high viscosity and low penetration of bottoms produced are of particular interest from the standpoint of the operability of the still.

TABLE II.MID GET STILL VACUUM FLASH DISTILLATION OF A SEVERELY CRACKED RESIDUAL OIL Flash temperature, F 740 678 Flash pressure, mm. Hg 30 10 Gas oil overhead:

Yield, Wt. percent of feed 47. 0 40. 0 Gravity, API 19. 6 19. 6 Carbon res., rams 1. 248 0. 951 Wt. percent:

Carbon 86. 83 86. 59 11.71 11. 72 0.771 0.727 0. 34 0.35 399 392 s: Yield, wt. percent of feed 53. 0 60.0 Gravity, .API 1. 0 2.8 Carbon res., con 35. 74 32.14 N05 insolubles, Wt percent 28. 66 22. 54 Furol vis. at 27 213.0 Penetration, 77 F 5 12 It 1s claimed:

1. A laboratory scale flash still for separation of a petroleum fraction which comprises a preheating coil and a vertically disposed flash chamber, said preheating coil being wound externally about said chamber from the upper to the lower end thereof and interconnecting at its lower end with the interior lower section of said flash chamber for delivering the preheated petroleum fraction thereto for flash distillation separation of said fraction, an enclosed heating vessel substantially surrounding said preheating coil and flash chamber, said heating vessel containing a molten salt heat transfer medium and a heating means in said heat transfer medium for maintaining said medium at a predetermined temperature, a charge pipe for introducing the petroleum fraction feed into said preheating coil at its upper end an overhead recovery means near the top of said flash chamber for removing the light end product from said flash chamber, a bottoms recovery means near the bottom of said flash chamber for removing the heavy end product from said flash chamber, and a vacuum controller means for maintaining both of said recovery means at equalized subatmospheric pressures.

2. The still of claim 1 wherein said flash chamber comprises an elongated flash chamber.

3. The still of claim 1 including insulating means surrounding said heating vessel.

4. The still of claim 3 wherein said bottoms recovery means includes a seal means comprising an overflow cup, and a bottoms recovery line interconnecting the bottom of said flash chamber and the interior of said overflow cup.

5. The still of claim 4 wherein said bottoms recovery means includes a receiver and said overflow cup has a drip rod thereon adapted to pass liquid from said cup to said receiver.

References Cited UNITED STATES PATENTS 754,687 3/1904 ONeall 196-98 1,266,281 5/1918 Lapp 1961 14 1,990,831 2/1935 Lea 202-177 2,224,014 12/1940 Dunham et al 23288.4 2,226,828 12/1940 Moran 202-177 2,310,399 2/1943 Cox et al. 202-205 2,642,386 6/1953 Piros 202177 2,702,268 2/1955 Egger et al. 203-100 2,751,281 6/1956 Cohn 23255 NORMAN YUDKOFF, Primary Examiner. F. E. DRUMMOND, Assistant Examiner.

Images