US1946939A - Cracking hydrocarbon oils - Google Patents

Description

Feb. 13, 1934. A, w JURRlssEN ET AL. 1,946,939

CRACKING HYDROVCARBON OILS Original FiledrSept. 14, 1928 Patented Feb. V13, 1934 UNVITED STATES PATENT OFFICE CRACKING HYDRO CARBON OILS Alphonsus W. Jurrissen, Wilmington, Albert B.

Cox, Walnut Park, Calif., and Andrew Mc- Gregor Wood, Miri, Sarawak, Borneo, ass'gnors to Universal Oil Products Company,` Chicago, Ill., a corporation of Delaware Original application September 14, 1928, Serial No; 306,024. Divided* March 15, 1933. Serial No. 660,932.

(Cl. ISG-428) 2 Claims.

' economy of operation.

While we have shown the invention as applied to a process wherein the oil is heated, then passed to a reaction and/or separating chamber, residuum removed from the process, fractionated and socalled reilux condensate returned to the process, it is to be understood that the invention is equally applicable to allv cracking processes operating under pressure wherein thev oil is heated in a heating coil to a cracking temperature, and then passed to a chamber where a substantial part of the cracking is effected, lrrespective of the arrangement of connected parts.

Great diiliculties have been experienced in the operation of cracking processes due to the formation of tar-like; coke-containing residues, and the formation and deposit of a large amount of solid coke or carbon for each barrel o1' oil treated, which were permitted to accumulate in vertical chambers; the accumulation of such a large amount of coke caused a loss to the process and decreased the continuity and eillciency of the operation; further, the coke-containing or B. S. laden residues were unsatisfactory products for sale and use as fuel.

We have found that this formation or tar-like fractions or solid coke depositing in the chambers or removed with the liquid residue from the process, is caused by the prolonged exposition to a cracking temperature of the non-vaporized oil in the chamberv where a liquid level is maintained by allowinga substantial body of nonvaporized oil to remain in the chamber.

As one of the features of the invention, to overcome this diiilculty,I we4 propose to withdraw the non-vaporized oil from the chamber of the process at such a rate that the liquid level in the chamber is as low as is possible without drawing oif vapors through the residuum drawoff lines.

As another feature of the invention, we provide inthe upper part of the chamber a means yto discharge the oil from the heating ,coil into and this application the chamber in such a manner that thenonvaporized oil is caused to run in a thin lm along the inner walls of the chamber. Although we are not able to explain with certainty the cause of the benecial result obtained by the use of this feature, we have found that a lower amount of coke forms both in the chamber and in the residuum-from the process, for an equal quantity of raw oil treated, than with the use of the common method of discharging the oil into the upper part of the chamber without providing any means for the direction and distribution of the stream of hot oil, the advantage obtained by the use of this feature being probably due to the fact that the constant washing of the walls of the chamber, coupled with the low level of liquid oil maintained therein, does not permit any fraction of non-vaporized oil to remain in the chamber any longer than another fraction, with the benecial result heretofore explained.

As another feature of the invention, we provide for the withdrawal ofthe vapors from the cham-I ber from the lower part thereof and preferably from a point at or near the center of a horizontal cross section thereofin this manner, beneficial results are obtained in that, as the oil enters the chamber at' one end and the vapors are withdrawn at the other end, every fraction of the oil and vapors is forced to travel throughout the large vapor space of the chamber; the time element is more equally distributed on every part of the vapors and this method avoids the short-circuiting of large portions of insufficiently cracked-vapors which sometimes takes place when the oil enters and the vapors leave the chamber at the same end. The cracking takes place more evenly on every fraction ofthe oil and vapors, which results in increasing the production of lighter condensable products.

Further, we have found that by forcing the vapors downward through the large vapor space maintained in the chamber and by keeping the levelY of the non-vaporized oil near the bottom` thereof, we obtain better results than with a process where the vapors vare caused to travel upwardly throughout the height of the cham.- ber-that is to say, where the oil enters the chamber near the bottom and vapors discharge from the top.

Other features of the invention will appear from the following description and lfrom the attached drawing, wherein Fig. 1 is a diagrammatic view, partly in section and partly in eleva no tion, of an apparatus suitable tocarry out our invention.k

Fig. 2 is a fragmentary detail illustrating the spaced spreader plates.

Fig. 3 is a slightly modified form of an apparatus which can be used to carry out the process of our invention.

Referring to Fig. 1, the oil is withdrawn from any suitable source of supply, not shown, through line 1 and fed by means of pump 2 into direct feed line 3, through which'it is charged into heating oil 4 positioned in suitable furnace 5.

The oil, heated to cracking temperature in heating coil 4 is discharged therefrom in a manner which will be described in detail hereafter, through line 6, having valve '7, into the upper part of chamber 8. In the chamber, vapors separate from unvaporized oil and the latter may be withdrawn intermittently or continuously from the bottom of the chamber 8 through lines 9 `controlled by valves 10. The withdrawal of the non-vaporized oil from chamber 8 may be effected at such a ratethat any desiredlevel of liquid oil may be maintained in chamber 8, but

we preferably regulate such withdrawal so that a Very low level is maintained therein-for instance, about a foot of oil maintained in the bottom of chamber 8 above the lowermost point.

The vapors separated in chamber 8 are kwithdrawn therefromthrough line 11, having Valve 12. As a feature of the invention, vapor drawoif line 11 preferably extends into the inside of chamber 8 by means of extension 11a, which terminates in the lower part of chamber 8 and near the vertical axis thereof. The point of Withdrawal of vapors from the chamber can be changed, according to the results desiredv and the conditions of operation, by changing the length of extension 11a. Suitable nozzles, bushings and packing provide for a tight joint between vapor line 11, extension 11a and the walls of chamber 8. The lower end of extension v11a ,shouldremain preferably above the level of nonvaporized oil in the bottom of chamber 8.

If desired, a part or all of the raw oil charged into the system by means of pump 2 may be diverted from line 3 by suitably controlling valve 3a on said line 3 and valve 16 on line 17; said' raw oil may then be charged into vthe dephlegmator 13 through said line 17'to serve as a cooling medium for the vapors evolved in the process.

The reflux condensate separated in the/dephlegmator 13 is discharged, alone or mixed with preheated raw oil, from the bottom of the .dephlegmator 13 through line 18, having valve 19, and' may be charged by means of pump 20 into the feedA line 3 Where, after mixing with the raw oil which may have been fed directly through line 3, it re-enters the heating tubes 4.

Returning now to the featured method of introducing the heated oil from the heating coil 4 through line 6 into the upper part of chamber 8, line 6 preferably connects with -the upper end of the chamber, which in the designs normally in use form aV manhole closed by a flanged head 27 which may be provided with center nozzle 28 into which transfer line 6 is connected. Nozzle 28 may also serve as support for an extension 29 of transfer line 6 into the inside of the upper part of the chamber. At the lower end of extension 29, inside the chamber, may be fitted Va blind flange device such as shown by collar 30, screwed or welded on the end of extension 29 and supporting by means of studs or bolts 31 a blind flange 32. The blind flange 32 is slightly spaced from collar 30, so as to form a circular thin horizontal channel 33. In this manner, the heated oil ilowing through line 6, and extension 29, spreads through circular channel 33 between flanges 30 and 32 and, on account of its velocity, forms an umbrella shaped film, shown in dotted lines Vat 34.

The length of transfer line extension 29, the diameter of flanges 30 and v32, and the distance between flanges 30 and 32, must be so regulated that the umbrella-like film of oil comes in contact with the walls of the chamber 8 at a point as near as possible to the top of saidchamber,

as shown on Fig. 1, thus forming a continuous circular lm constantly flowing over the inner wall of the chamber towardthe bottom thereof and the shallow pool of non-vaporized oil to be re moved `as residuum thrugh lines 9. e

Referring now to Fig. 3, we have shown a slightly modied method for discharging the heated Aoil from the heating coil into chamber 8 and distributing the stream of inflowing oil into a circular ilm flowing along the inner wall of the chamber.

In this modified form, a horizontal circular plate 40 is positioned in the upper part of chamber 8. Plate `40 is provided at or near the center with an opening 41, provided with upwardly extending ilange 42. The diameter of plate 40 is somewhat smaller than the inside diameter of chamber 8 so as to provide for a narrow circular opening between plate 40 and the walls of chamber 8. The plate 40 is positioned preferably at the upper level of the cylindrical part of the chamber, at or slightly below the bumped heads now in use With such chambers. The transfer line 6 extends through the walls of the upper part of chamber 8, above plate 40, terminating in extension 44 slightly above plate 40. Suitable nozzles, bushings and packings form tight joints between chamber 8 and line 6.

The chamber 8 is also provided with residuum drawoff lines 9, having valves 10, and with vapor line 11 and. its extension 11a, as heretofore de- 120 scribed in connection with Fig. 1, and the opera.- tion of the process in an apparatus provided with the chamber shown as Fig. 2 is the same as that of the process shown as Fig. 1 except for the method of injecting the oil into the chamber 8.

In the arrangement just described in connection with Fig. 2 the hot oil is discharged from line 44 onto plate 40, over which it spreads as a thin film; flange 42 prevents oil from iiowing through central opening 41, and the oil ilows as a cylindrical lm through the opening provided between the outer periphery of plate 40 and the Walls of the chamber 8. The jet-like shape of the oil film leaving plate 40 causes it to come in contact with the walls of chamber 8 and ow down 135 toward the bottom of the chamber, providing for a continuous washing of the walls.

Vapors which may evolve above plate 40 ow through opening 41 into the lower part of the chamber, from which all vapors evolved may be withdrawn through line 11a. as heretofore explained.

A small by-pass line 35 having valve 36 may connecty the top of the chamber 8 with vaporv line 11, as shown on Fig. 1 and Fig. 3, and valve 36, 145 Y which remains normally closed, may be opened intermittently for short periods to prevent accumulation of air or non-condensable gas in the upper part of the chamber.

As an illustration of the operation of the procl line, and a residuum containing less than 1% of;`

sludge or B. S., producing less than 1 coke per barrel of raw oil treated.

These conditions are not to be taken as a limipound of tation of the scope of the invention, but as an i1- lustration of the beneficial results of our process. The conditions will vary with the various charging stocks used and with the various products which may be desired.

While we have illustrated two forms of apparatus suitable to carry out the process of the present invention, other designs may be used and found suitable to carry out the method and obtain the results of this invention; and we do not intend to limit ourselves to the particular forms of apparatus shown.

It may be well to point out here that other beneficial results may be obtained by using this invention, which-although not directly connected with the products of the process, concern the life of the apparatus used. In the cracking processes now in use, much trouble is experiencedy with the rapid corrosion of the apparatus, particularly of the chambers, which are expensive parts lto replace. Various methods have been proposed and tested for extending the life of these parts,

such as lining with a corrosion-resisting metal, or chromium plating, etc. It has been noted that corrosion on chambers is apparently greater when the Walls are in contact with vapors than when they contact with liquid oil, so that when the oil in the iamber is maintained at a low level a large s ace of the walls is exposed to the vapors,

with perceptible increase in the corrosion oi.' the walls and added expense in the operation of the process. On the other hand, by means oi the process o! this invention, we protect the walls of the chamber from contact with the vaporsover the greatest part oi' their total area by owing over them a thin 111m of liquid oil. In this manner, a noted decrease in the degree of corrosion of the chamber is obtained.

We claim as our invention:

1. In combination with an enlarged reaction chamber of an oil cracking system, a hot oil inlet pipe extending downwardly into and terminating adjacent the upper portion of said chamber, a non-rotatable ange iixed to the end of said pipe, an imperforate baille beneath, spaced from and xed to said ange, said ange and baille being disposed substantially at right angles to the direction of discharge of oil from said pipe, and means for removing vapors and residual oil from the chamber.

2. In combination with an enlarged reaction chamber of an oil cracking system, a. hot oil inlet pipe extending downwardly into and termihating adjacent the upper portion of said chamber, a non-rotatable flange xed to the end of said pipe, an imperforate baule, bolts extending through said flange and baille and securing the flange and baille together in spaced parallel relation, said flange and baille being disposed substantially at right angles to the direction of discharge of oil from said pipe, and means for removing vapors and residual oil from the chamber.

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