US1948492A - Process and apparatus for the conversion of petroleum hydrocarbon - Google Patents

Description

Feb. 27,1934. w. M. CROSS PROCESS AND APPARATUS FOR THE CONVERSION OF PETROLEUM Filed May 21, 1927 308615 Tau/EA [rape/m HYDROCARBON Patented Feb. 27, 1934 UNITED STATES PATENT OFFICE PROCESS AND APPARATUS FOR THE CON- VERSION OF P E T R O L E U M HYDRO- CARBON Delaware Application May 21, 1927. Serial No. 193,145

14 Claims.

This invention relates to improvements in a process and apparatus for converting hydrocarbon oil and refers more particularly to the conversion of relatively heavy oils, such as fuel oil, or the like.

The particular novelty of the process lies in the treatment of heavy oil, such as fuel oil, in a pipe still and simultaneously therewith cracking. intermediate products separated from the vapors of both the cracking stock and the fuel oil stock, ,and blending the cracked hydrocarbon and hi hly heated heavy stock in common distillation stage or zone, while maintaining separate pools of the cracked hydrocarbon and the heated heavy stock in the distillation stage, the separate pools having communication below and above the liquid levels of said pools. Among the objects of the invention are to provide a process in which a relatively heavy stock, such as fuel oil, and an intermediate or cracking stock, are simultaneously treated in separate stages, the intermediate stock or oil having a greater portion of its constituents below the boiling point range of kerosene, and above the boiling point range of fuel oil, being subjected to relatively high temperatures and pressures, and the heavier oil heated for distillation under substantially atmospheric conditions; to provide a process in which the blending of the oils in a common distillation stage improves the fluidity of the residual material drawn off therefrom and produces a blended vapor from which is separated a distillate of improved quality.

The single figure is a diagrammatic side elevational View of the apparatus, in which the process may be operated, parts shown in section and 'parts broken away.

Referring to the drawing, at 1 is shown a furnace consisting of a combustion chamber 2 and a tube chamber 3 divided by a partition wall 4. At 5 is shown an insulated reaction chamber, preferably formed of a single ingot of steel by forging. Removable end plates being attached to the flanges of the chamber facilitate the cleaning of the chamber at intervals when carbon and hydrocarbon polymers accumulate to an objectionable amount. To the reaction chamber is connected by a transfer line 6 an evaporator 7, centrally divided by means of a partition 8. A withdrawal line 9 serves to divert the heavy residual oil from the system to storage. The overhead line 10 communicates with the lower portion of the bubble tower, 11, which has the usual interior bubble tower arrangement, in which the vapors rise through a plurality of liquid pools while the condensate separated from the vapors gravitates in the opposite direction. A withdrawal line 12, from the bottom of the tower, communicates with the tank 13 where the condensates are directed to be recharged by means of the pump 14 to the heating coils 15. From the top of the bubble tower is a vapor line 16, which terminates in a spiral condenser coil 17 in the condenser box 18. The discharge end of the coil 1'7, terminates in a line 19, which is connected into the gas separator 20. The gas separator is equipped with a gas draw-of]? line 21, controlled by a valve 22, and a liquid draw-off line 23, regulated by a valve 24. In a furnace is positioned a pipe still, or coil 26. The furnace is heated by means of gas burners, or by other fueling means, not shown, the combustion gases passing over the tubes and out through the flue 27.

Referring now to the operation of the process, the charging stock, which consists of a relatively heavy oil such as fuel oil, is introduced through the line 28, and is circulated through the pipe still 26, where it is heated to a temperature sufficient to vaporize a substantial portion of the oil. Such temperatures will normally range from 600 to 1000 F., 700 to 900 F. being normal temperatures at the discharge from the pipe still. After passing through the pipe still the highly heated oil is directed through the line 29 to the evaporating tower '7. It will be understood that all of the pipes, including the reaction chamber, evaporator and bubble tower, besides all of the intermediate lines are heavily insulated to prevent loss of heat by radiation. A valve 30 is interposed in the line 29. In the evaporator the heavy oil accumulates to a level controlled by the automatic liquid level device 31, which regulates the valve 32 in the draw-off line 9. The vapors separated from the oil in the evaporator pass off through the line 10, in which is a valve 33 to the bubble tower 11.

In the bubble tower the vapors are subjected to a reflux condensing action, both by the condensate which accumulates in the tower, or by the additional cooling means such as closed coils of pipes through which the cooling medium, such as water or cool oil are circulated. The latter means are not shown in the drawing, being well known in refinery practice. The vapors remaining uncondensed in the bubble tower pass over through the line 16 regulated by a valve 34, and are subjected to a final condensing action in the coil 17.

The liquid distillate accumulates in the gas separator and is drawn-off through the line 23,

the gas being taken out and used for heating the furnaces or is further stripped of any light liquid fraction in a separate apparatus. The reflux condensate from the bottom of the bubble tower accumulates and is drawn off in a regulated flow by means of the automatic liquid level regulator 35, manipulating the valve 36 in the line 12. This condensate is returned and co lected in the tank 13 from which it is withdrawn through the line 37 and returned to the heating coils 15 by means of the pump 14 and pipe 38.

There may also be added to the tank 13 additional cracking stock through the pipe 39, regulated by a valve 40. The oil charged to the heating coils 15 by means of the pump 14 is raised to a high temperature and pressure, sufiicient to crack the oil but not sufficiently high to produce objectionable accumulation of carbon in the tubes. The velocity at which the oil is circulated through the coils 15 is an important factor in the accumulation of carbon or polymerized hydrocarbon material which collects in the coils.

Sufficient heat must be added to the oil in the coils 15 to produce the proper cracking conditions in the insulated reaction chamber 5, to which the oil is directed through the line 41, after being heated in the continuous coil or tubes 15. In the reaction chamber the oil is accumulated in a considerable body and held under high temperature and pressure sufiiciently long for the reaction to progress to the extent that there is formed in the oil body a considerably greater percent of low boiling point fractions. In other words, there is produced from an oil containing a relatively small amount of lighter fractions a considerably greater amount of lighter fractions or a synthetic crude, or crude equivalent from which the lighter fractions are subsequently distilled. There is created in the oil body in the reaction chamber what may be termed as a progressing equilibrium, or a condition in the oil body in which the vapor and liquid phases of the constituent hydrocarbons tend to arrive at a balance, or equilibrium.

After the conversion has taken place in the reaction chamber, the oil is withdrawn through the transfer line, 6, and the pressure reduced at the valve 42. The synthetic crude or cracked hydrocarbons is discharged into the evaporating tower '7 on the opposite side of the partition 8 to that into which the heavier oil is emptied. The oils blend in their liquid phasesbeneath the partition and the vapors passing off into the top of the tower blend with the vapors from the pipe still stock above the top of the partition 8. Thus, while the oils are not permitted to promiscuously intermingle when they are emptied into the evaporating tower, there is a blending of both the liquid and the vapor phases which improves the type of residual material withdrawn from the evaporator and the final distillate recovered in the gas separator.

Where in certain types of processes the oils are combined in the transfer l'me 6 and intimately intermixed at the point of evaporation, or substantially at the point of their introduction into the evaporator, there is under certain circumstances an objectionable amount of heat extracted from the heavier oil so that an insuilicient proportion passes overhead in the form of vapor, and consequently an excess of fuel oil is made at the expense of the recharging stock. By means of the present invention this separation of the two stocks in the evaporator and at the same time procuring the advantages of the blending by the separate union of the liquid and vapor phases an improved result is obtained.

In a specific operation a reduced crude oil having a gravity of 20 A. P. I., an initial boiling point of 500 F., 60% off at 700 F., may be charged through the coil 26, and the stock charged through the coil 15 may be a light oil, comprising mainly virgin and cracked stock, having a gravity of 25 A. P. I., an initial boiling point of 400 F., 90% off at 700 F. With the foregoing stocks the following conditions of operation may be employed: The cracking temperature to which the oil is heated in coil 15 and at which it is maintained in the chamber 5 will ordinarily be between about 700 F. and about 1100 F., a preferred range of temperature being between about 800 F. and about 1000? F. A substantial superatmospheric pressure is ordinarily maintained on the oil in the coil 15 and chamber 5, a pressure upwards of 500 pounds per square inch being preferred, for example, a pressure of from 700 to 1000 pounds. The heavy oil charged to the coil 26 preferably should not be heated to as high a temperature as that attained by the light oil going through the coil 15, for example, the heavy oil may be heated to a temperature between about 600 F. and about 850 F., while maintaining thereon a superatmospheric pressure somewhat lower than that maintained on the oil in the coil 15 and chamber for example, a pressure between about 50 and 400 pounds.

The heavy oil heated in the pipe still is raised to a temperature at which a considerable portion of the oil will vaporize off. This temperature is also sufficient to produce cracking to an extent of from 5% to 10% but such cracking is not considerably more than the degree of cracking which would take place under the same temperature, using the same oil under atmospheric conditions. In practically all commercial distillation in a pipe still, or in shell stills, where a considerable percentage of the oil is vaporized off, there is cracking, but not cracking to a degree that it is commercially feasible to operate as a cracking process. Normally this cracking of the less refractory oils amounts to from 5% to 10%.

I claim as my invention:

1. A continuous process of onverting hydrocarbon oil, comprising, treating a stream of relatively light hydrocarbon oil under cracking conditions of temperature and under relatively high superatrnospheric pressure; separately heating another stream of a relatively heavier hydrocarbon oil to temperatures above the boiling point of the lighter constituents; passing the two heated streams of oil to a common evaporating stage maintained under a relatively low pressure, above the liquid level therein, and therein separating the vapors from the two oils before mixing the unvaporized portions of the two oils, preventing the vapors evolved from one stream from contacting unvaporized oil resulting from the other stream while blending the vaporized and unvaporized portions of the two oils and separately removing the blended vaporized and unvaporized portions from said zone.

2. A continuous process of converting hydrocarbon oils comprising, cracking and digesting a relatively light oil in a cracking stage under a 1 A uid level therein; simultaneously and separately heating another hydrocarbon oil of adifierent character to temperatures above the boiling point of. the lighter constituents thereof, passing the second heated oil to the said vaporizing zone above the liquid level therein, permitting separation of the vapors from the two oils, in the vaporizing zone, before admixture of the unvapor ized'portions of the two oils, preventing the vapors evolved from one stream from contacting unvaporized oil resulting from the other stream while blending the liquid residues from the two oils and the vaporized fractions of the two oils in the said vaporizing zone, and continuously withdrawing liquid residues and overhead vapors from said vaporizing zone.

3. A process of converting hydrocarbon oils comprising cracking one hydrocarbon oil in liquid phase under a relatively high superatmospheric pressure while simultaneously heating another hydrocarbon oil of a different character in a separate heating zone, passing the two heated oils to acommon vaporizing zone maintained under a relatively low pressure, above the liquid level therein, and permitting evolution of vapors therein from the two oils before admixture of liquid residues, preventing the vapors evolved from one stream from contacting unvaporized oil resulting from the other stream while blending the liquid residues in a low point in said vaporizing zone and blending the evolved vapors from the respective oils at a high point in said vaporizing zone and separately withdrawing the blended liquids and vapors from said vaporizing zone.

4. A process of cracking hydrocarbon oil comprising, heating a relatively light oil having the characteristics of gas oil in a tube and tank under temperature and relatively high superatmospheric pressure conditions regulated to effect conversion substantially in the liquid phase, passing the products of conversion to a vaporizing zone maintained at a substantially lower pressure, above the liquid level therein; separately and simultaneously heating a heavier hydrocarbon oil to temperatures above the boiling point of the lighter constituents thereof, passing the last-mentioned heated oil in a stream to the said vaporizing zone, above the liquid level therein; regulating the introduction of the two oils into the vaporizing zone so as to permit the evolution of vapors from the two oils before admixture of the unvaporized portions while preventing the vapors evolved from one stream from contacting unvaporized oil resulting from the other stream, withdrawing blended unvaporized. residues, passing blended vapors to a dephlegmating stage, withdrawing and condensing the vapors recovered from the dephlegmating stage, and recycling reflux condensate formed in thedephlegmating stage to the tube and tank for retreatment.

5. A process of convertinghydrocarbon oils comprising, subjecting a relatively light hydrocarbon oil to cracking temperature while maintaining it under a relatively high superatmospheric pressure, thereby causing conversion substantially in the liquid phase, passing the heated oil to a vaporizing zone maintained at a substantially lower pressure, above the liquid level therein so as to effect vaporization of certain of the lighter fractions thereof; simultaneously and separately heating a heavier hydrocarbon oil to temperatures above the boiling point of certain of the lighter constituents thereof, and to effect a light cracking of said heavier oil, passing the said heated heavier oil to the said vaporizing zone, above the liquid level therein, permitting the evolution of vapors from the two heated oils, in. the said vaporizing zone, before blending the liquid portions of the two oils, pre-- venting the vapors evolvedfrom one stream from contacting unvaporized oil resulting from the other stream while blending the liquid residual portions of the respective oils, withdrawing the blended residues, and passing the evolved vapors overhead to a fractionating stage.

6. A process of converting hydrocarbon oils comprising, subjecting a relatively light hydrocarbon oil to cracking temperature while maintaining it under a relatively high superatmospheric pressure, thereby causing conversion substantially in the liquid phase, passing the heated oil to a vaporizing zone maintained at a substantially lower pressure, above the liquid level therein, so as to effect vaporization of certain of the lighter fractions thereof; simultaneously and separately heating a heavier hydrocarbon oil to temperatures above the boiling point of certain of the lighter constituents thereof, and to effect alight cracking of said heavier oil, passing the said heated heavier oil to the said vaporizing zone, above the liquid level therein, permitting the evolution of vapors from the two heated oils, in the said vaporizing zone, before blending the liquid portions of the two oils, preventing the vapors evolved from one stream from contacting unvaporized oil resulting from the other stream while blending the liquid residual portions of the respective oils, withdrawing the blended residues. and passing the evolved vapors overhead to a fractionating stage, and recycling to said firstmentioned cracking and conversion zone an in termediate fraction formed in the fractionating stage to be recracked substantially in liquid phase.

7. A process of converting oil comprising heating a stream of relatively light oil of the charactor of gas oil under a relatively high pressure in a cracking zone so as to effect substantially liquid phase conversion; separately heating a stream of relatively heavy oil to a temperature above the boiling point of the lighter constituents thereof; passing both heated oil streams to a common vaporizing zone maintained under substantially low pressure conditions, above the liquid level therein, and therein permitting the vapors from each of the heated oils to separate before the respective unvaporized residual portions thereof are mixed while preventing the vapors evolved from one stream from contacting unvaporized oil resulting from the other stream, thereafter effecting a mixture of the unvaporized portions of the oils in the vaporizing zone; withdrawing the mixed residue from the vaporizing zone; dephlegmating the mixed vapors from the two oils, and recycling the reflux condensate formed during dephlegmation to the cracking zone. 7 3. An apparatus for converting hydrocarbon oil comprising, a cracking unit including a heating and digestion means, a distillation unit including a pipe still, an evaporator, means to maintain a liquid level in the evaporator, separate discharge means connecting the cracking unit and the pipe still to the evaporator at separate points above the liquid level in the evaporator pressure reducing means associated with the discharge means for said cracking unit, a vertical partition in the evaporator interposed between the discharge points from the cracking III unit and still and arranged to permit vapor and liquid products from the said cracking unit to admix in said evaporator with the corresponding products discharged from the said pipe still, and means to withdraw vapors from the evaporator.

9. A continuous process of converting hydrocarbon oils comprising subjecting a flowing stream of oil to a substantial cracking temperature under a relatively high superatmosphere pressure, separately heating another stream of a relatively heavier hydrocarbon oil to temperatures above the boiling point of the lighter constituents thereof, discharging the heated streams of oil into a common evaporating zone maintained under a relatively low pressure, above the liquid level therein, and therein discharging one of the streams of oil introduced thereinto against an extensive surface, separating evolved vapors from the two oils in the said vaporizing zone before admixture of the unvaporized portions of the two oils, preventing the vapors evolved from one stream from contacting unvaporized oil resulting from the other stream while admixing the un vaporized portions of the'two oils, and separately withdrawing the blended vapors and admixed unvaporized portions from the said evaporating zone.

10. A continuous process of converting hydrocarbon oils comprising subjecting a flowing stream of oil to a substantial cracking temperature under a relatively high superatmosphere pressure, separately heating another stream of a relatively heavier hydrocarbon oil to temperatures above the boiling point of the lighter constituents thereof, discharging the heated streams of oil into a common evaporating zone maintained under a relatively low pressure, above the liquid level therein, 'and therein discharging each of the streams of oil introduced thereinto against sepa-' i rate extensive evaporating surfaces} separating evolved vapors from the two oils in the said vaporizing zone before admixture" of the unvaporized portions of the two oils, preventing the vapors evolved from one stream from contacting unvaporized oil resulting from the other stream while admixing the unvaporized portions of the two oils, and separately withdrawing the blended vapors and admixed unvaporized portions from the said evaporating zone. V

11. A continuous process ofccnve'rting hydrocarbon oils comprising subjecting a flowing stream of oil to a high cracking temperature under a relatively high supera'tmosph'eric pressure, sepa-' rately heating another stream of a relatively heavier hydrocarbon oil to a relatively light cracking temperature, discharging the heated streams of oil into a common evaporating zone maintained under a relatively low pressure, above the liquid level therein, and therein discharging one of the streams of oil introduced thereinto against an extensive surface, separating evolved vapors from the two oils in the said vaporizing zone before admixture of the unvaporized portions of the two oils, preventing the vapors evolved from one stream from contacting unvaporized oil resulting from the other stream while admixing the unvaporized portions of the two oils, and separately withdrawing the blended vapors and admixed unvaporized portions from the said evaporating zone.

12. A continuous process of converting hydrocarbon oils comprising subjecting a flowing stream of oil to a high cracking temperature under a relatively high superatmospheric pressure, separately heating another stream of a relatively heavier hydrocarbon oil to a relatively light cracking temperature, discharging the heated streams of oil into a common'evaporating zone maintained under a relatively low pressure, above the liquid level therein, and therein discharging each of the streams of oil introduced therein against separate extensive evaporating surfaces, separating evolved vapors from the two oils in the said vaporizing zone before admixture of the unvaporized portions of the two oils, preventing the vapors evolved from one stream from con-'- tacting unvaporized oil resulting from the other stream while admixing the unvaporized portions of the two oils, and separately withdrawing the blended vapors and admixed unvaporized portions from the 'said'evaporating zone.

13. The method of converting hydrocarbon oil which comprises, subjecting a confined flowing stream of oil to cracking, heating another and independent stream of oil to a temperature above the boiling point of the lighter constituents thereof, discharging'the two heated streams into a common zone, above the liquid level therein, wherein vapor and liquid products separate and therein admixing the resulting vapor and liquid products of one of said streams with corresponding products of the other of said streams while preventing the vapors evolved from one stream from contacting with separated liquid products resulting from the other stream, and separately withdrawing from'said zone resulting blended vapors and blended liquids.

14. The method of converting hydrocarbon oil whichcomprises, subjecting a confined flowing stream'of oil to cracking, heating another and independent stream of oil to a temperature above the boiling point of the lighter constituents thereof, discharging the two heated streams into a common zone, above the liquid level therein, wherein vapor and liquid products separate and therein admixing the resulting vapor and liquid products of one of said streams with corresponding products of the other or said streams while preventing the vapors evolved from one stream from contacting with separated liquid products resulting from the other stream, separately withdrawing from said zone resulting blended vapors and blended liquids, fractionating the withdrawn vapors, and passing reflux condensate from said fractionating operation to said cracking operation.

' WALTER M. CROSS.

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