US1839020A - Process for cracking oil - Google Patents

Description

Dec. 29, 1931. c. P. DUBBs PROCESS FOR CRACKING OIL Original Filed March 9, 1923 mm1 ww wm 751 e' z 'fr (07507? u 0715.

4llatenated Dec. 29, 1931 NWB STATE-.s oFI-'ICE CARBON' P; DUBBS, 0F WILMETTE, ILIJNOIS, ASSIGNOR TO THE 'UNIVERSAL OIL PROD 'UCTS COMPANY, CHIGAGO, ILLINOIS, A GORPORATION OF SOUTH DAKOTA Y PROCESS non onoxrna oII.

, Application led March 9, 1923, Serial No. 623,987. Renewed March 15, 1928.

The present invention is directed more particularly to'that type of process and apparatus in which the oil to be treated is fed in a relatively small stream through a heat- 5 ing coil, and thence to an expansion chamber, preferably located outside of the fire zone. The -insuiiciently cracked products which are not vaporized in the expansion chamber or which. are condensed /in the l dephlegmator are preferably returned to the heating zone for further treatment.

Une object of the invention-is to crack a maximum quantity of the raw charging stock, leaving as little residue as possible which is l not finally converted into distillate. To do this, it is necessary or desirable to recrack a substantial quantity of the residue in the expansion chamber. At the same time, if the residue be returned directly to the `heating 2@ tubes, as for example in well knownmethods p `of circulating the oil from the tubes to the tanks and back to thel tubes, the tubes will become quickly clogged with carbon, and the operation of the process interfered with, necessitating all too soon the shutting down of the plant. At the same time, it is desirable as above stated, to recrack this residue as far as possible.

To this end, I preferably continuously draw off the residue and convey it to a settling tank, whicliris in eifect a storage tank. The heaviest part of the carbon settles out of the residuum` in this tank and the remainder of the residuum passes to a second storage tank, where itis mixed with the raw oil'in regulated quantities. Care should be taken to properly proportion the supplies of residuum and raw charging stock so that the residuum, which of course contains a substantial amount of carbon, will not predominate in the mixture and cause the final charging stock to be too heavily charged with carbon. At the same time, by this method, I have been able to reuse as much of the residue as possible. If desired, the residue may be' introduced to a tank where pressure is reduced so that the sensible heat -will vaporize substantial portions thereof, which vaporized fractions 5o are collected for recracking. vAdditional heat may be used to effect this distillation if found to be desirable.

To more clearly understand the invention, reference is made to the accompanying drawing in which the single figure represents= a side elevational view of my improved apparatus. It may be 'here stated that the parts here' shownrare not intended to proportionately represent the various elements, but the relative proportions ofheating coils, expansion tanks, dephlegmators, water condensers storage tanks are so well known to those skilled in the art, as to need no detailed description.

. Referring to the drawing, 1 designates the furnace 'in which is mounted a cracking coil 2 which may take the form of a plurality of tubes of two to six inches in diameter, preferably connected in series. Also the invention may be carried out by making them in multiple.

From the cracking coil the heated oil passes to an expansion tank 4 which may belocated outside of the fire zone, and may or'may not be insulated, and may or may not be externally heated. A throttling valve 5 may be interposed in the transfer line 6 so as to permit of a diii'erential of pressure between the oil in the heating coil, and that in the eX- f pansion tank, if desired. 30

The oil entering the expansion tank vaporizes, and the generated vapors may pass out of the upper end of the tank through vapor line 7 having a throttle valve 8 into the lower portion of the dephlegmator 9. This dephlegmator 9 may be provided with suitable baiiies l0 or any other means for interrupting the travel of the vapors and restricting their flow, so as to cause a more effective separation of the heavier insufficiently cracked vapors from those of a lower boiling point.

The uncondensed vapors may pass out in the vapor pipe 11 controlled by the throttle valve 12 into a water condenser 13, and thence into the receiver 14. A valve 15 may be nterposed in the line leading from the water condenser to the receiving tank. The receiving tank may be provided with gas outlet pipe 16 controlled by a throttle valve 17 and 10o in a well known manner, or even may be eX- ternally heated by mounting it in a suitable furnace setting 21. The residue may be drawn fiom the expansion tank 4 in the following manner: it may all be drawn out through line 22 controlled by the throttle valve 23 to a main line 24 controlled by a throttle valve 25 and leading to tank 20.

If desired, however, it may be drawn off from different levels, thus permitting of some separation of the very heaviest part of the residue from the lighter parts.

This might be accomplished by means of the various pipes 26, 27 and 28 having throttle valves 29, 30 and 31 respectively. The very heaviest residue might be drawn ofi' from the bottom of the tank by pipe 32 controlled by the valve 33. OnlyY one of these drawoif pipes may be used as for example, 22, 26, 27 or 28, or any two or more be used.

When the residue enters the chamber 20, it may overfiow through pipe 34 controlled by valve 35 into the raw storage tank 36, the very heaviest part of the residue being drawn off by pipe 37 controlled by throttle valve 38. In such case it may not be necessary or desirable to heat the tank 20,` but inasmuch as preferably the pressure is reduced by means of the valve 25, there maybe more or less distillation by residual heat taking place in the tank 20, and if desired, the vapors may pass off through the pipe 39 controlled by throttle valve 40 to the tank 36, or if desired, heat may be supplied through the furnace 21 and y the greater part of the residue passed over into the tank 36. v

Instead of reducing the pressure at the valve 25, it may be held to the val- ves 35 and 38, the valve 40 being shut and the contents of the tank allowed to cool and then permitted to pass into the tank 36. If desired, a cooler,i

might be 5.000-gallons of residuum allowed to choke up the heating coils 2.

Care

Lesaoeo This combined charging stock may be drawn off from the tank 36 through the line 41 controlled by the throttle valve 42 and thence forced by a pump 43 through the line 44 controlled by the throttle valve 45 to the top of the dephlegmator. The charging stock is thus fed overhead, s0 to speak, into the dephlegmator, and there tends to positively control the temperature of the dephlegmator.

A pump not shown, may be interposed in the feed line to the coil if the gravity head is not sutiicient to effectively feed the charging stock to the coils 2. This preheated oil may enter the coils 2 at the lower end of the latter, or into the upper ends of the tubes, but the present invention is not directed to the particular construction of the heating coils.

In carrying out the process, the oil may be heated to uniform pressure on the entire system of say from 100 to several hundred pounds, although in its broader aspects the invention is not limited to any specific pressure. If desired, the invention may be carried out in such a manner that differential pressures are used, as for example, a pressure of 400 pounds on the heating coil, 200 pounds in the expansion chamber, 100 pounds in the dephlegmator and pounds in the receiver. These figures are somewhat illustrative, and may be varied in wide limitations and still be within the present invention.

By means of the present invention from 40% to 50% of the charging stock may be converted into gasoline, for example 32 gravity Mid-Continent gas oil may have 50% thereof converted into 400 end point gasoline. It is possible to convert a larger percentage into gasoline because of the fact that the residue in due proportion is recracked.

I claim as my invention: f

1. A process for cracking hydrocarbon oil, consisting in passing oilthrough a heating coil, wherein it is raised to a conversion temperature, in delivering the heated oil to an enlarged reaction zone,V wherein conversion occurs and substantial vaporization takes place, in passing the vapors evolved from the oil to a dephlegmating column, in taking oft' unvaporized oil from said enlarged reaction zone, in collecting the same in a second enlarged zone, wherein it assumes a quiescent state and wherein substantial quantities of the free carbon held in suspension in such unvaporized oil is precipitated, in uniting regul'ated quantities of such unvaporized oil, from which the free carbon has been precipitated, with incoming charging oil, in passing the resulting commingled oils to said dephleginating column, to flow therethrough in physical Contact with the vapors undergoing dephlegmation, in passing such commingled oils, diluted with hotreflux' condensate separated from the vapors in said column, to said heating zone, and. in maintaining a, superatmospheric pressure in said heating zone, en-

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larged reaction zone and dephlegmating co1- umn.

2. A continuous process for cracking hydrocarbon oil, consisting in passing oil through a heating coil, wherein it is raised to a cracking temperature, in delivering the heated, oil to anf enlarged reactionr zone wherein conversion occurs and substantial vaporization takes place, in passing the vapors evolved from the oil to a dephlegmating column, in maintaining a superatmospheric pressure in said heating zone, enlarged `reaction zone and dephlegmating column, in passing unvaporized oil from said enlarged reaction zone to a",second enlarged zone, in permitting the oil to assume a quiescent state in said second enlarged zone, to permit substantial quantities of the free carbon held in suspension in such oil to precipitate therein, in

uniting unvaporized oil, from which the car- I bon has been precipitated, with incomin charging oil, to produce a mixture compose of a minor portion of unvaporized oil and a major portion of incoming charging oil, in

introducing the resulting commingled oils to said deplegmating column, to How therethrough counter-current to the flow of the vapors undergoing reflux condensation, to act as a cooling medium for the vapors and to heat such comingled oils, and in passing such commingled oils, diluted with hot reflux condensate separated from the vapors in saidl dephlegmating column, to said heating zone,

CARBON P. DUBBS.

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