US1885387A - Method and apparatus for producing motor fuel from residual oils - Google Patents

Description

Nov. 1, 1932. SW RTZ 1,885,387

METHOD AND APPARATUS FOR PRODUCINGMOTOR FUEL FROM RESiDUAL OILS Filed May 28, 1928 kgy///% W 6/4] Patented Nov. 1, 1932 STEPHEN SWABTZ, OF CHICAGO, ILLINOIS, ASSIGNOR TO ENKINS PETROLEUM PROCESS COMPANY, OF CHICAGO, ILLINOIS, A OORPORATION OF WISCONSIN METHOD AND APPARATUS FOR PRODUCING MOTOR FUEL FROM RESIDUAL OILS Application filed ma as,

My invention relates to the production of motor fuel from residual oils and is of particular service in the conversion of residual petroleum products which are free of motor fuel constituents, where pipe stills or tubular heaters are employed as converters.

When residual petroleum oils are subjected to predetermined temperatures above their normal boiling points for predetermined lengths of time, a part of the heavier hydrocarbons will change into lighter hydrocarbons. Such conversion is termed controlled cracking.

Cracking is usually accompanied by the formation of'free carbon, and the greater the cracking, the greater is the amount of resultant carbon produced. Such carbon tends to deposit on the walls of the converters. In

the case of tube stills, the carbon deposits and builds up on the inner walls of the tubes with the result that either the tubes become eventually so completely clogged as to stop the flow of fluid therethrough, or the passage of heat through the tube wall may be so retarded as to cause the wall to become overheated and endangered. In either case, the accumulation of, carbon eventually reaches a point at which it is necessaryto stop the operation of the equipment and clean the carbon from the tubes, an expensive undertaking, particularly in view of the attendant loss of use of the equipment.

My invention has for its ob ect the rovision of a process and apparatus w ich permit operation of tube heaters without excessive deposition of carbon, making possible a longer continuous operation of theheaters than hitherto, and giving a greater percentage recovery of motor fuel from a given charging stock.

During the raisingof the temperature of an oil to aboveits normal boiling point, a temperature is reached at ,whichan appreciable amount of crackingcommences, this tem-' perature being termed the-specific cracking temperature. No material degree of crackingoccurs below such specific cracking tem-' perature. At higher temperatures cracking occurs more rapidly. The specific cracking temperature depends upon the nature of the 1928. Serial No. 281,333.

I provide just sufficient initial heating surface to bring the temperature of the oil to the specific cracking temperature. residual oil has reached this correct temperature, it is removed from the direct heating After the I effect of the furnace, but it is maintained at this cracking temperature for a predetermined period of time usually of from one to twenty minutes. To this end, the heated oil is conducted through a stream of flue gases having approximately the specific. cracking temperature. While the oil is prevented from cooling materially below the specific cracking temperature, it is kept in motion in the heater tube and during this time the cracking reaction will progress- The tube may, therefore, be termed a timing tube. Various kinds of residual oil are maintained for differing lengths of time attheir respec-' tive specific cracking temperatures in order to form the same quantity of gasoline, each diflering length of time being correlated to its respective specific cracking temperature and termed the specific time factor. During the operation, carbon will deposit on the walls of the tube, the longer the operation, the greater the amount of carbon precipitated. The cracking progresses from zero or no gasoline content at the inlet end of the timing tube to a maximum gasoline content at the discharge end of the tube, wherefore the inlet part of the tube will be practically free of carbon for a long time and other parts of the tube will contain the residual oil with 1 or alternate the flow of oil in such tube at 9 intervals during the cracking process either by operating a suitable valve arrangement by hand or automatically. lBy thus reversing or alternating the flow of the oil, the ends of the tube are alternately made the inlet and outlet ends, whereby the deposit of carbon will take place uniformly on the tube. Thus with use of this timing tube at least twice as much raw material may be handled as with an equal length of the ordinary cracking tube before it is necessary to stop the operation to clean the tube. y

In addition to the method above described which principally consists in the utilization of the full inner surface of the timing tube as a carbon depositor instead of only part of it as in other methods, ll adjust the concentration of the carbon in the liquid to such a point that the deposition of carbon will be reduced to a minimum, it being well known that the greater the amount of solid material or carbon carried in the stream of oil flowing through the tube, the greater is the tendency of the carbon to settle out on the walls of the tube.

In order to regulate the concentration of the carbon to the desired degree, ll dilute the oil with a carrier oil such as light gas oil injected into the timing tube from any outside source most conveniently available for this purpose. This carrier oil is preheated to a temperature equal to that of the oil in the timing tube. The carrier oil used is of such character that its specific cracking temperature is above that of the oil in the timing tube so that it undergoes no decomposition but acts only as a diluent.

By adding the carrier oil and thus increasing the fluid volume, the rate of flow is increased, producing a turbulence which is unfavorable to the deposition of carbon and the actual concentration of the carbon in the' fluid is decreased to a point where carbon deposition is reduced to a minimum. The amount of the carrier liquid depends on the nature of the charging stock and the amount of cracking desired in the operation.

By means of my invention, I am able to maintain operating cycles two or three times the duration of the operating cycles of prior processes and I am able to recover in one operation, a greater part of the heavier hydro-carbons into the lighter hydro-carbons suitable for motor fuel.

The accompanying drawing is a diagrammatic illustration of one form of apparatus with which the method of my invention may be practiced.

Referring to the drawing, 1 represents a pressure pump, taking suction from a tank or other source of supply not shown, discharging by line 21, as controlled by valves 22, 22 and 22", through the heat exchanger 2' located in the fractional condenser 2; the dlscharge from such exchanger flowing by eases? line 23 to the insulated accumulator 3. By proper manipulation of the valves 24, 24 and 24", a portion or all of the stock flowing through line 23 maybe by-passed through the heat exchanging coil 12, contained in exchanger 12.

The insulated tank of accumulator 3 is connected by line 25 to the suction of the pressure pump 5, from whencethe discharge line 26 extends to the tubular roof coil 7, located in the upper portion of furnace 6; the roof coil then connecting by line 27 to the main heating tube bank 8. The discharge line 28 from the latter joins the timing coil 9, with entrance thereto and discharge therefrom controlled by valves 10 10 and 10, 10", which are so interconnected by suitable levers that one movement of the main lever 10 (preferably automatically operated) will open valves 10 and 10 at the same time closing valves 10 and 10 aflording circulation from the bottom of the timing coil upwards; while the reverse movement of the main lever 10 will close valves 10 and 10 and open valves 10 and 10 thus aflording circulation through the timing coil in the opposite direction. An inlet line 57 containing valve 58, is connected to line 28 for admission of light refractory oil directly through line 28 to the timing coil 9.

Final discharge from the timing coil 9 is effected through line 29, past pressure control valve 30, to the expander or vaporizer 11. A liquid seal is maintained in the latter by float mechanism 32 operating the balanced valve 33, on line 34, which connects to exchanger 12'; final discharge from the latter being effected through line 35 and cooling coil 36. v r

The vapor line 37 connects the top of the vaporizer 11 to the bubble tower 4. Stripping plates 13 are located in the lower section of the tower, from which residuum discharges through line 38 and cooling coil 39, with flow therethrough controlled by float mechanism 40 and balanced valve 41. Reboiler trays 14 are installed in the mid-section of the bubble tower 4, with condensate therefrom discharging through line 44, as

controlled by float mechanism 42 and balanced valve 43 to separator 15. Provision is made for. the lighter vapors separated therein to discharge through line 45 and cooling coil 46 to tank 16, while the condensate from theseparator 15 passes off through line 47 to the suction of pump 14' from whence it is discharged by line 48 to the insulated tank'or accumulator 3.

Above the reboiler trays 14- are bubble trays and caps, 17 and 18. The auxiliary spray 19 regulates the temperature of the tower 4, as fed by the pumps 19, taking suction through line 49 from separator 20, excess of condensate therefrom not utilized by spray pump, being released by float mechanism and balanced valve 51, through line 52 to a point without the system. From the top of the tower 4, vapor lines 53 enter the fractional condenser 2, which is provided with a vapor line 5 passing through cooling coil 55, and discharging into separator 20; the vapor line 56 'afiording discharge of the finished vaporized product from the system.

In the actual operation of the process, the residual oil to be converted is forced by pump 1 through the fractional condenser 2 where the oil is preheated and then flows through the line 23 to the insulated tank or accumulator 3; such accumulator also receiving all or a portion of the hot condensate from the mid-section of the bubble tower 4. Whether a portion or all of such condensate is used depends on the desired diluent action on the residual to be converted.

The mixture of the two oils in accumulator 3 is forced by pump 5 through the heating elements located in the furnace 6, first through the roof coil 7, discharging therefrom at about 350 F, then upwardly through the main bank of heating tubes 8 and issuing therefrom at the specific cracking temperature desired, for instance, 760 to 780 F.

From the main heating bank, the oil undergoing treatment then passes through the timing coil 9, first in one direction and then in the reverse by the automatic operation of the control lever 10 and valves 10 10 and 10 10 After remaining in the timing coil at its specific cracking temperature for a predetermined period, depending upon the nature of the oil and the amount of cracking desired, the treated oil then discharges into the expander or vaporizer 11; the" separated residual fuel oil being removed therefrom after passing through exchanger 12 by a pump not shown.

If desired, a petroleum distillate, which is substantially u'nconvertible at the cracking temperatures employed may be introduced directly into line 28 to coil 9 bymeans of line 57 controlled by valve 58. This petroleum distillate acts as a diluent, and being lighter than the oil undergoing cracking, vaporization is effected which increases the turbulence of the oils in coil 28 without forming ,additional carbon decomposition products.

The increased turbulence of the oils in coil 9 aids in maintaining carbon reaction products in suspension and in carrying said products out of the cracking coil into the expander.

The vaporous products of conversion leave the expander 11 through vaporline 37 and enter the bubble tower 4, where the heavier portions are condensed by stripping plates 13 and are withdrawn through line 38 and cooling coil 39 to any suitable tank, from which they may be returned to the system for further conversion if desired.

The reboiler trays 14: efiect a further dephelgmation, the condensate from such trays flowing through line 44 to separator 15, where the lighter fraction may be separated if desired, passing out of the system by line 45 and cooling coil 46, the heavier fractions being returned to the system through line 47 by pump 14 discharging through line 48 to accumulator 3. If no light gas oil out is desired, the overflow from the reboiler trays 1 1 is mixed with the heavy gas oil in the bubble tower discharging through line 38; suitable liquid seals being maintained by the float mechanisms and balanced valves previously described.

A further dephlegmation is effected in the bubble tower 4 by bubble trays and caps 17 and 18, these trays serving also to separate any permanent gas entrained in the gasoline, pumped from the separator 20 through the spray nozzle 19. The fractional condenser 2 serves to efiect a final dephlegmation of vapors released from the tower 4, such condenser, in conjunction with the return of a portion of the asolin'e from the separator 20 by pump 19 through spray nozzle 19, serving to produce a final grade of gasoline of any desired marketable specification, such product finally being discharged from the system through line 56.

Having thus described my invention I claim:

1. An apparatus for the production of motor fuel from heavy petroleum oils which in cludes a bank of heating tubes through which said petroleum oils are initially passed, a furnace, a cracking coil within said furnace through which the petroleum oils are subsequently passed, connections between the discharge end of said bank of heating tubes and the ends of said cracking coil, an expander,

connections between the ends of said crack-- ing coil and said expander, and means located for) in said connections for reversing the direction of How through said cracking coil of the petroleum oils passing therethrough from the bank of heating tubes into the expander. 2. An apparatus for the production of motor fuel from heavy petroleum oils which includes a bank of heating tubes through which said petroleum oils are initially passed,

a furnace, a cracking coil within said turnace through which the petroleum oils are subsequently passed, connections between the 1-. discharge end of said bank of heating tubes and the ends of said cracking coil, valves in each of said connections, an expander, connections between the ends of said cracking coil and said expander, valves in each of said lastmentioned connections, and means for simultaneously operating said valves to reverse the direction of flow through said cracking coil of the petroleum oils passing therethrough from the bank of heating tubes into the expander.

3. An apparatus for the production of motor fuel from heavy petroleum oils which includes a bank of heating tubes through which said petroleum oils are initially passed, a furnace, a cracking coil within said furnace through which the petroleum oils are subsequently passed, an expander, connections between the discharge end of said bank of heating tubes and the inlet end of said cracking coil and between the outlet end of said cracking coil and said expander, additional connections between the discharge end of said bank of heating tubes and the outlet end of said cracking coil and between the inlet end of said cracking coil andsaid expander, means for alternately interrupting and establishing communication through said first-mentioned connections, and means for alternately interrupting and establishing communication through said additional connections so that the end of the cracking coil which was formerly the outlet for the oils becomes the inlet for the oils passing from the bank of heating tubes through said cracking coil into the expander.

4:, An apparatus for the production of mo- ,tor fuel from heavy petroleum oils which includes a bank of heating tubes through which said petroleum oils are initially passed, a furnace, a cracking coil within said furnace through which the petroleum oils are subsequently passed, connections between the discharge end of said bank of heating tubes and the ends of said cracking coil, an ex pander, connections between the endsof said cracking coil and said expander, means located in said connections for reversing the direction of flow through said cracking coil of the petroleum oils passing therethrough from the bank of heating tubes into the expander, a dephlegmator in communication with the vapor space of said expander, and means for returning a portion of the condensed vapors separatedin said dcphlegmator together with additional petroleum oils to said bank of heating tubes.

5. An apparatus for the production of motor fuel from heavy petroleum oils which includes a bank of heating tubes through which said petroleum oils are initially passed, a furnace, a cracking coil within said furnace through which the petroleum oils are subsequently passed, connections between the, discharge end of said bank of heating tubes and the ends of said cracking coil, an expander, connections between the ends of said cracking coil and said expander, and means located in said connections and automatically controlled for reversing the direction of flow through said cracking coil of the petroleum oils passing therethrough from the bank of heating tubes into the expander.

6. A. process for the production of motor fuel from heavy petroleum oils which includes the steps of continuously flowing a stream of said petroleumoils through a bank of heating tubes, heating said flowing stream of petroleum oils under pressure to establish a cracking temperature therein substantially at the discharge end of said bank of heating tubes, then progressively advancing the stream of petroleum oils under pressure through a cracking coil into an expander, externally heating said cracking coil to main tain the advancing stream of petroleum oils therein at a cracking temperature, at intervals during the process interrupting the advancing stream of petroleum oils through said cracking coil and progressively advancing the stream of petroleum oils in the opposite direction through said cracking coil. into said expander.

7. A process for the production of motor fuel from heavy petroleum oils which 111- cludes the steps of continuously flowing a stream of said petroleumoils through a bank of heating tubes, heating said flowing stream of petroleum oils under pressure to establish a specific cracking temperature therein substantially at the discharge end of said bank of heating tubes, then progressively advancing the stream of petroleum oils under pressure through a cracking coil into an expander, externally heating said cracking coil to maintain the advancing stream of petroleum oils therein at said specific cracking temperature for a )redetermined period of time, at intervals during the process interrupting the advancing stream of petroleum oils through said cracking coil and progressively advancing the stream of petroleum oils in the opposite direction through said cracking co l into said expander.

8. A process for the production of motor fuel from heavy petroleum oils which includes the steps of continuously flowing a stream of said petroleum oils through a bank of heating tubes, heating said flowing stream of petroleum oils under pressure to establish a cracking temperature therein in the neighborhood of 780 F, substantially at the dis charge end of said bank of heating tubes, then progressively advancing the stream of petroleum oils under pressure through a cracking coil into an expander, externally heating said cracking coil to maintain the advancing stream of petroleum oils therein at said cracking temperature for from 1 to 20 minutes, at intervals during the process interrupting the advancing stream of petroleum oils through said cracking coil and progressively advancing the stream of petroleum oils in the opposite direction through said cracking coil into said expander.

9. A process for the production of motor fuel from heavy petroleum oils which includes the steps of continuously flowing a stream of said petroleum oils through a bank HMD testes? of heating tubes in a furnace, heating said flowing stream of petroleum oils under pressure to establish a cracking temperature therein substantially at the discharge end of said bank of heating tubes, then progressively advancing the stream of petroleum oils under pressure through a cracking coil into an expander, externally heating said cracking coil by indirect heat of the flue gases from said furnace to maintain the advancing stream of petroleum oils therein at a cracking temperature, at intervals during the process interrupting the advancing stream of petroleum oils through said cracking coil and progressively advancing the stream of petroleum oils in the opposite direction through said cracking coil into said expander.

10. A process for the production of motor fuel from heavy petroleum oils which includes the steps of continuously flowing a stream of said petroleum oils through a bank of heating tubes, heating said flowing stream of petroleum oils under pressure to establish a cracking temperature therein substantially at the discharge end of said bank of heating tubes, then progressively advancing the stream of petroleum oils under pressure through a cracking coil into an expander,

' externally heating said cracking coil to maintain the advancing stream of petroleum oils therein at a cracking temperature, at intervals during the process interrupting the advancing stream of petroleum oils through said cracking coil and progressively advancing the stream of petroleum oils in the opposite direction through said cracking coil into said expander, separating in said expander generated vapors from unvaporized residual oils, dephlegmating the generated vapors into a light motor "fuel vapor fraction, an intermediate condensate traction and a heavy condensate fraction, and returning a portion of externally heating said cracking coil to maintam the advancing stream of petroleum oilstherein at a cracking temperature, at intervals during the process interrupting the advancing stream of petroleum oils through said cracking coil and progressively advancing the stream of petroleum oils in the opposite direction through said cracking coil into said expander, separating in said expander generated vapors from unvaporized residual oils, dephlegmating the generated vapors into a light motor fuel vapor fraction, an intermediate condensate fraction and a heavy condensatefraction, mixing a portion of said intermediate condensate fraction with additional petroleum oils, and introducing the mixture of petroleum oils thus formed into said bank of heating tubes.

12. A process for the production of motor fuel from heavy petroleum oils which includes the steps of continuously flowing a stream of said petroleum oils through a bank of heating tubes, heating said flowing stream of petroleum oils under pressure to establish a cracking temperature therein substantially at the discharge end of said bank of heating tubes, mixing with said petroleum oils a petroleum distillate substantially unconvertible at said temperature to efi'ect a partial vaporization in said stream of oils, then progressively advancing said stream of oils containing said partially vaporized distillate through a cracking coil into an expander, externally heating said cracking coil to maintain the advancing stream of petroleum oils therein at a cracking temperature, at intervals during the process reversing the direction of flow through said cracking coil of said progressively advancing stream of petroleum oils and the contained partially vaporized distillate ,to increase the turbulence of the oils in said cracking coil and carry carbon reaction products out of said cracking coil into said expander.

13. A process for the production of motor fuel from heavy petroleum oils which includes the steps of continuously flowing a stream of said petroleum oils through a bank of heating tubes, heating said flowing stream of petroleum oils under pressure to establish acracking temperature therein substantially at the discharge end of said bank of heating tubes, then progressively advancing the stream of petroleum oils under pressure through a cracking coil into an expander, externally heating said cracking coil to maintain the advancing stream of petroleum oils therein at a cracking temperature, adding a petroleum distillate to said petroleum oils prior to heating to said cracking temperature to assist maintaining in suspension carbon reaction products formed in the oils flowing through said cracking coil, at intervals during the process interrupting the advancing stream of petroleum oils through said cracking coil and progressively advancing the stream of petroleum oils in the opposite direction through said cracking coil into said expander.

14. A process for the production of motor fuel from heavy petroleum oils which includes the steps of continuously flowing a stream of said petroleum oils through a bank of heating tubes, heating said flowing stream of petroleum oils under pressure to establish till a cracking temperature therein, progressively advancing the stream of petroleum oils under pressure through a cracking coil into an expander, externally heating safl cracking coil to maintain the advancing stream of petroleum oils therein at a cracking temperature, at intervals during the process interrupting the advancing stream of petroleum oils through saidl cracking coil andl progressively advancing the stream of petroleum oils in the opposite olirection through said cracking coil into saidl expander.

lln Witness whereof, I hereunto subscribe my name STEPHEN SWARTZZ;

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