US1832928A - Process for cracking hydrocarbon oils - Google Patents

Description

G. EGLOFF ET AL PROCESS FOR CRACKING HYDROCARBON OILS Nov. 24, 1931.

Original Filed July 6 Patented Nov. 24, 1931 UNITED STATES PATENT OFFICE GUSTAV EG-LOFF AND HARRY P. BENWER, OF CHICAGO, ILLINOIS, ASSIGN'ORS 'I O UNI- V'ERSAI OIL PRODUCTS COMPANY, OF CHICAGO, ILLINOIS, CORPORATION OF SOUTH DAKOTA PROCESS FOR CRACKING HYDROCAIRZ BON OILS Original application filed July 6, 1920, Serial No. 394,083. Divided and this application filed August 26,

- 1921. Serial No. 495,573.

are to provide a process of thermal and pressure distillation of heavy hydrocarbon oils to produce light oil therefrom by means of a double pressure still, a carbon settling tank and spraying oil over-the surface of the oil is in the up er still of the double pressure stills to provi e a process ofproducing light oils from heavy oils by means of pressure distillation in a double pressure still while pumping raw oil into the lower still of the double pressure still; to provide a process of thermal and pressure distillation of hydrocarbon oils to produce gasoline or other light oils therefrom by means of mixing the relatively cool dephlegmated oil with raw oil and pumping same to the bottom of the lower still of the double pressure stills; to provide a process of pressure distillation in which the carbon and heavy oil from the lower pressure still are drawn into a settling tank having baffle plates therein to settle out the carbon and draw the carbon free oil by means of a pump and spraying said oil upon the liquid of the upper still of the double pressure stills; and, in general, to provide an improved process of the character referred to.

In the drawingnthe single figure illustrates a view partly in side elevation and partly in vertical section of our novel form of apparatus used in carrying out our process.

Referring to the drawing-1 designates a gas burner, 2 the furnace provided with a bridge wall 2a and stack 27). In the furnace is mounted the still which. as shown, may consist of a pair of cylindrical shells 3 and 4. the former mounted below and the latter above bridge well 2a. These shells 3 and 4 are connected by means of the pipes or conduits 5, the upper ends of which preferably project above the bottom of the shell 4. To the upper end of the shell 4 is connected a goose-neck or vapor line 6 which is connected by pipe 7 to a dephlegmator 7a. This dephlegmator 7a consists of the cross headers 77 and 70 connected by right angle pipes 7d. The vapors pass from the dephlegmator 7a Charging stock or fresh oil is fed to the shell 3 from charging line 18 connected to pump 20 leading to any suitable source of supply. A valve 21 may be interposed in the charging line, if desired. The reflux condensate which falls back from dephlegmator 7 a passes through pipe 7 into branch 22 which is connected as shown at 23 to charging line 18. It is to be noted that line 22 is of larger diameter than charging line 18 for the reason that there is more reflux condensate than fresh oil normally fed into the still. In other words, this difi'erential capacity of the line 22 and the charging line 18 causes the process to be carried out so as to maintain the rate of condensation in said reflux condenser such that the amount of condensate formed per unit of time will be greater than the amount of raw charging oil supplied to the heating zone for the same period, and consequently maintain a greater proportion of reflux condensate than raw charging oil in the mixture supplied to the heating zone. The feed line 24 is preferably somewhat larger than the line 22. The vapors which are generated in shell 3 pass up through pipes 5 into the upper portion of the still or in other words the shell 4. Preferably the shell 3 is normally kept three quarters full of liquid. The vapors which pass to the upper shell 4 will be subjected to a s'uperheating action. Oil is continuously drawn off through line 20a controlled by valve 20?) into the bottom of the carbon settling tank 21a. i This tank 21a is providedwit-h baffles 22a and 230 which tend to cause the carbon to precipitate out into the bottom of this tank. This carbon settling tank is provided with manhole plate (not shown) so that it can be readily cleaned out. The heavier oil containing a maximum amount of carbon is drawn off through line 25 controlled by valve 26. The cleaner oil passes through line 24a controlled by valve 27 to pump 28 whence it is returned by line 29 into the upper end of the shell 4. This line 29 terminates in a perforated pipe 30 extending horizontally through the shell 4. A valve 31 is preferably interposed in line 29. The hot oil which passes through the perforated pipe 30 is in part vaporized and the unvaporized portioncan pass out through pipesbinto the shell 3 flowing counter-current to the ascending vapors. The lines 22, 24, 20a, settling tank 21a, pipe 24a and pipe 29 are preferably lagged or insulated so as to prevent as far as possible any reduction in temperature of the oil passing therethrough.

The following description of the operation of the process may be given. The shell 3 is charged and kept charged to approximately 75% of its capacity with, say, a. mid-continent gas oil of 32 Baum gravity. The oil temperature in the shell 3 may be 750 F.

while the vapors that pass to shell 4 may be subjected to a vapor temperature of 820 F. A pressure of 105 pounds may be maintained on the entire system by suitably regulating the valves in the receiver 10 and the residuum draw-off valve 26. If desired, a differential pressure may be maintained by regulating the valve 32 interposed between line 9a. and dephlegmat-or 7 a. By regulating this valve 32 a pressure of 100 pounds may be maintained on the still and dephlegmator and a pressure of 50 pounds on the water condenser and receiver or atmospheric pressure on the latter. These shells 3 and 4 may each be of 6 diameter and 30' long with the rest of the apparatus approximately the proportionate size shown in the drawing. By means of this process, 65% of the gas oil may be converted into pressure distillate having a gravity of 51 Baum and upon the basis of raw oil treated 36% of oil may be thus converted into 58 Baum gravity gasoline.

The following modification of the process may be described. Instead of filling the shell still 3 three quarters full of oil, the oil may be fed in sufllcieut quantity into the still so as to maintain a liquid level of approximate ly of the total capacity of the entire still. In other words, the liquid level of the oil will be maintained in shell l slightly below the perforated pipe 30.

In certain cases it may be desirable to carry out the modified process as, for example, in refractory oils difficult to crack, such as Pine Island gas oil, kerosene, steam still bottoms or Mexican gas oil, it is advisable to have a maximum heating area per gallon of oil treated compared to dephlegmation surface. There are some easily cracked oils such as heavy asphaltie of the type of Iol'a crude, fuel oil from wayside fields of Kansas, residuums or the like which require much less radiating surface in relationship to heating surface for equivalent production of results from said hydrocarbon oils.

With reference to the novel form of appa ratus it is to be noted that the double pressure still shown permits of the use of smaller units which have a much greater factor of safety than a single shell of the same capacity. In addition, a maximum heating area is obtained for a given capacity and also by means of this apparatus the vapors can be readily superheated.

We claim as our invention 1. A process for cracking hydrocarbon oils consisting in maintaining a body of oil at a cracking temperature taking off vapors therefrom, superheating said vapors, drawing off liquid residue from said body, passing said liquid residue through a carbon settling chamber, removing the cleaner portion of said oil from said carbon settling chamber and returning it directly to that portion of the apparatus in which the vapors are superheated.

2. A process for cracking hydrocarbon oils consisting in heating the oil to a cracking temperature, superheating the vapors in a secondary zone connected therewith, refluxing and condensing the vapors released from the secondary stage, removing the unvaporized oil from the initial heating stage, settling out the heavier end and returning the lighter ends in an individual stream to the superheating stage.

3. A process for cracking hydrocarbon oils consisting in passing the oil to an initial cracking zone and heating the same therein to a.vaporizing and cracking temperature, superheating resultant vapors in a secondary zone connected with said initial cracking zone, refluxing and condensing the vapors released from the secondary zone, removing the unvaporized oil from the initial cracking zone, settling out the heavier end of the unvaporized oil and passing the lighter ends thereof to the secondary zone and there introducing them in dispersed form while maintaining a regulated vapor pressure upon the system during operation.

4. A process for cracking hydrocarbon oils, consisting in introducing a bulk supply of oil to a cracking still disposed within a furnace where said oil is subjected to a cracking temperature, in superheating the vapors from said oil by passing said vapors to a superheating drum located adjacent said cracking zone,

in discharging vapors from the drum to a reflux condenser, in passing the uncondensed vapors to a final condenser, in returning reflux condensate to said cracking still, and in continuously withdrawing residuum from said cracking still, in removing carbon therefrom, and in introducing the clean residual 011 to said superheating drum.

5. A process for cracking hydrocarbon oil, consisting in subjecting the oil to a cracking temperature'in a heating zone to cause substantial vaporization thereof, in superheating the vapors evolved from the oil by passing the vapors through a su erheating drum, in discharging the vapors mm the drum to a reflux condenser, in continuously supplying charging oil mixed with reflux condensate to said heating zone, in maintaining the rate of condensation in saidreflux condenser such that the amount of condensate formed per unit of time will be greater than the amount of raw charging oil supplied to the heating zone for the same period, to thereby maintain a greater proportion of reflux condensate than raw charging oil in the mixture supplied to the heating zone.

.6. A process for cracking hydrocarbon oil comprising maintaining a quantity of the hydrocarbon oil in a cracking zone under cracking conditions, removing residual hydrocarbons from said zone, separating the lighter from the heavier constituents of said residual hydrocarbons, passing said lighter constituents to a second zone wherein they are again subjected to cracking conditions,

and admitting vapors from said first zone to said second zone.

' GUSTAV EGLOFF.

HARRY P. BENNER.

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