US1936289A - Hydrocarbon oil conversion - Google Patents

Description

Nov. 21, 1933. R. c. COOK HYDROCARBON OIL CONVERSION- Original Filed May 21, 1928 .27 1 7/6711, to r." a [JD/Z 6. (00727,

Patented Nov. 21, Q 1933 HYDROCARBON OIL CONVERSION Ralph C. Cook, Houston,

Tex., assignor to Universal Oil Products Company, Chicago, 111., a corporation of South Dakota Continuation of application Serial No. 279,227,

May 21, 1928. Serial No. 540,399

This a pplication May 27, 1931.

1 Claim. (01. 196-61) This application is a continuation of my former application Serial No. 279,227 filed May 21st, 1928.

This invention relates to the conversion of low 5 Baum gravity hydrocarbons into lighter hydrocarbons of higher Baum gravity by the agency of heat.

In one specific embodiment, the invention comprises subjecting charging stock which may comprise a reduced crude, residuum, or other so called heavy or high Baum gravity hydrocarbon to the action of heat to cause vaporization of a substantial portion thereof, said vapors being then heated to a proper vapor phase cracking temperature.

One of the principal features of the invention resides in taking the successive close out vaporized fractions of the charging stcok and separately subjecting said close cut fractions to a tem- 26 perature or temperature range determined to be most efiicient, depending upon the characteristics of each close out fraction, for maximum conversion into desirable high Baum gravity hydrocarbons with a minimum gas and coke loss.

In vapor phase cracking it is essential to have suitable temperatures in order to prevent, or at least reduce, over-cracking of the heavier fractions and under-cracking of the lighter fractions. In the ordinary vapor phase cracking process it is practically impossible to avoid this over-cracking and under-cracking when a hydrocarbon fluid of widely varying composition is passed through a vapor phase cracking zone as one mass.

According to the present invention, by taking advantage of the increase in temperature of the charging stock as it passes through a heating zone, successive fractions of close out composition are obtainable and may be passed through separate vapor phase cracking zones wherein the most desirable conditions of temperature and pressure for maximum conversion with minimum coke and gas loss may be maintained.

In this manner the conditions most suitable for maximum conversion into low boiling point hydrocarbons for each difierent cut can be readily determined and utilized.

An apparatus to carry out the invention is illustrated in the attached sheet of drawings wherein Fig. 1 is an elevational view, partlyin vertical section, of apparatus for carrying out the invention, and

Fig. 2 is an enlarged fragmentary elevational view, partly in vertical section, illustrating a sectional detail of the vapor separator.

The utility of the invention as well as objects and advantages thereof will be more apparent from the following description:

Referring more in detail to the drawing, 1 designates a charging stock inlet line in which may be interposed a pump 2, the line 1 diverging 63 into two branches 3 and 4, controlled, respectively, by valves 5 and 6, the arrangement being such that all or any regulated portion of the charging stock may be passed directly through the line 3 or the line 4. The line 3 communicates with the 65 upper part of a conventional dephlegmator '7; The'line 4 communicates with a liquid heating coil8 mounted in a furnace designated as a whole at 9. The oil passing through the heating coil 8 is gradually raised in temperature. The lighter or low boiling point fractions will be first vaporized through the agency of such heat. It is to be understood that as the oil traverses from the inlet to the outlet of the heating coil 8 it is gradually raised in temperature, that is, the oil passing 3'5 through the lower portions of the heating coil is at a much lower temperature than the oil passing through the upper sections of the heating coil,

and that only the fractions which are of lighter gravity will vaporize in the lower portions of the coil and as the oil passes up through the heating coil, the temperature being'increased, fractions of progressively heavier gravity will be vaporized.

Interposed at predetermined points throughout the length of the heating coil 8, for instance, 5 at the return bends of certain tubes, I may provide a vapor separator 10,- lllustrated in Fig. 2. The separator v10 may comprise a chamber 57 containing a riser 52 connected with pipe 52', the end of which riser is preferably disposed above the liquid level in the separator in orderthat the vapors discharged will not disturb the liquid level.- This liquid level should always be maintained higher than the top tube 53 so that the vapors will not re-enter tube 53, but will pass out under the bafiie plate 54 into the tube 55. The flow of vapors through pipe 55 is preferably controlled by automatic valve 49, which may be actuated by float 48 in level column 56. This column 56 may be dispensed with, but it is employed in order to have minimum fluctuation of liquid level due to disturbances in chamber 57.

At the start of the operation automatic valve 49 will be preferably adjusted in such a manner that it is partially or completely opened, the control of the liquid level being maintained by hand valve 50 as determined from the level shown in sight glass 51, after the operation has steadied itself automatic valve 49 may be then cut in and the valve50 opened. It will be understood, of 0 course, that the level of liquid in chambers 56 and 57 will be adjusted to sucha point that automatic valve 49 will never be completely closed inasmuch as this might result in the coking up of tubes 16. Furthermore, the levels must be high enough so that the liquid will not get below the top of outlet pipe 53 whereby vapors would be carried through without being subjected to the cracking reaction in tubes 16, at the proper point.

It is to be understood that pipe 52 is the pipe which introduces the heated hydrocarbon fluid into the chamber 57 while the pipe 53 is the pipe which removes the liquid from the chamber 57. The arrangement is such that the vapors passing out through the line 55 pass into a vapor phase treating coil 16. Each vapor treating coil 16 may be mounted in its own individual furnace or it may be disposed in the same furnace as the other vapor phase heating coils if provision is made for regulating the temperature within the range found suitable for the most efficient conversion of any particular fraction.

For the purposes 'of illustration only, and not for any purposes of limitation, the vapor phase heating coils 16 may be disposed in a combustion chamber associated with the furnace designated as a whole at 9. A burner 17 is adapted to generate heat. The gases f combustion pass up through the chamber in which the vapor phase heating coils 16 are located then through the communicating passageway 18 and down through the chamber in which the heating coil 8 is disposed, the spent gases of combustion passing out through flue 19 being exhausted through stack 20.

The unvaporized liquid passing through that portion of the heating coil beyond the last vapor separator 10 may be passed into vapor separator 24 wherein further conversion may be permitted to take place which may result in the release of more vapors. A line 25 controlled by valve 26 may communicate with the vapor space of the separator 24, the line 25 communicating with the vapor phase heating coil 16 in the same manner as the lines 15. The outlet from each of the vapor phase heating coils 16 may communicate through the medium of transfer lines 2'7 with a header transfer line 28 in which may be interposed a valve 29 communicating with the lower portion of the dephlegmator '7.

It is to be noted that after each of the close out vapor fractions has been subjected to the most desirable temperature conditions to bring about maximum conversion with a minimum of coke and gas loss, they may be united in the header .28. The vapors ascend through the dephlegmator 7 in the usual way, being subjected to dephlegmation, for instance, by being brought into direct or indirect contact with the portion of the charging stock fed to the dephlegmator through line 3. In this manner a separation of sufficiently converted fractions from insufliciently converted fractions takes place, the insufficiently converted fractions condensing as reflux condensate and passing together with the unvaporized portions of the charging stock through the reflux leg 30, in which may be interposed a pump 31 and valve 32, which line 30 merges with the direct charging stock line 4. A drawoif 33 controlled by valve 34 may be provided in the reflux leg 30 for diverting all or any regulated portion of the recycle stock passing down the reflux leg 30.

The vapors remaining uncondensed after passirig through the dephlegmator, which comprise the sufficiently converted fractions, pass out through the vapor outlet line 35, controlled by valve 36, being condensed in the condensing coil 37 and passing from the latter through line 38, controlled by valve 39, into the receiver 40 where the condensed vapors collect as liquid distillate. The receiver 40 is of conventional type provided with the usual pressure gauge and liquid guage (not shown). This receiver may be also provided with the conventional liquid drawoff line 41, controlled by valve 42, and with the noncondensable gas relief line 43, controlled by valve 44.

The operation of the device should be apparent from the following description:

The oil passing through the heating tubes 8 is gradually raised in temperature, the fractions vaporizing as the temperature gradually increases, being released from time to time and passed through the lines 55 into the vapor phase heating coils 16, wherein each fraction is subjected to the particular conditions of temperature and pressure determined to be the most efficient to produce maximum conversion with no substantial coke and gas loss. The vapor from the different vapor phase cracking coils may be passed into the dephlegmator 7 wherein it is subjected to controlled conditions of dephlegmation in the conventional manner. The residual oil from vapor separator 24 may be withdrawn through the line 45, controlled by valve 46, cooled in the cooling coil 47 and collected in any desirable receptacle.

The operation may be carried out by maintaining a uniform pressure, either vacuum, atmospheric, or superatmospheric, throughout the entire system, or, through manipulation of the valves illustrated in an obvious manner, diiferential pressures may be maintained on different parts of the system, it being understood that the invention is not to be limited to any particular pressure condition, but residing broadly in the idea of separating close out fractions of vapors released during the raising of a hydrocarbon oil to a high temperature and the separate subjection of each fraction to a predetermined temperature for the purpose desired.

Referring more in detail to the operation of the apparatus illustrated it will be noted that burner 1'7 is provided at that end of the furnace adjacent the chamber containing the vapor phase heating coils 16 and that the flue gases pass up through the communicating flue 18 and then down through the chamber containing the liquid heating tubes 8, then out through flue 19 into the stack 20. In this manner it will be seen that the lower coils 16 containing the lighter vapors are subjected to a higher temperature than the upper coils 16 containing the heavier vapors. Since the temperatures in coils 16 will vary from, say 1000 to 1500 F., more or less, the flue gases will still contain suflicient heat to raise the temperature of the oil passing through the coil 8 to the required vaporization points. The outlet temperature of coil 8 adjacent the separator 24 will be, say 800 to 900 F., more or less, while the outlet temperatures on the vapors emerging from the vapor phase heating coils 16 will be from 1000 to [1200 F. more or less.

It will be understood, of course, that in certain cases where insufficient heat is obtainable in the chamber housing the coil 8 from the flue gases control the proper temperature for each of the vapor phase heating coils 16 inthe manner shown, it is within the contemplation of the invention to utilize a separate furnace for each of said coils 16, the flue gases from this separate furnace preferably communicating with the chamber housing the coil 8 in order to obtain maximum efiiciency from the fuel consumed.

By carrying out the process abovedescribed,

, those skilled in this field will readily appreciate the advantages of being able to treat successive close out fractions of the charging stock under the conditions most suitable to give maximum yields of low boiling point hydrocarbons with to be limited to this specific device, as it has been illustrated merely to show one form which will operate.

I claim as my invention:

A hydrocarbon oil cracking process which comprises passing the charging oil in a restricted stream through a heating zone and gradually heating the same during its passage therethrough at progressively higher distillation temperatures, removing vapors from said heating zone at spaced points in the path of travel of theoil therethrough, and thereby segregating the vaporized fractions of difierent boiling points from each other, passing each of said vaporized. fractions to a separate vapor phase cracking zone, independently cracking the fractions in the vapor phase in the separate cracking zones under conditions best suited for the cracking of the individual fractions, heating the fractions in said cracking zones and the oil in said heating zone by passing hot combustion gases in indirect heat exchange relation first with the lighter fractions, then with the heavier fractions, and finally coun-. ter-current with the charging oil passing through the heating zone, discharging the cracked fractions from said cracking zones and subjecting the same to dephlegmation, and condensing th dephlegmated vapors.

- RALPH C. COOK.

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