US1812308A - Process of treating hydrocarbon oil - Google Patents

Description

June 30, 1931. J. D. SEGUY I PROCESS OF TREATING HYDROCARBON OIL Filed Dec. 19, 1928 Patented June tidy-193i a. a rs m r a carter;

JEAN ID. SEG'FUY, OF cmcneo, ILLINOIS, ASSIGNOR T UNIVERSAL OIL PRODUCTS (701V!- EAINY, 9F CHICAGO, ILLINOIS, A CORPORATION 0F SOUTH DAKOTA PROCESS 0E TREATING HYDBGGARBON OIL Application filed December 19, 1928. Serial No. 327,004.

This invention relates to improvements in process of treating hydrocarbon oil, and is more particularly directed to the cracking of such hydrocarbon oils as petroleum for the production therefrom of gasoline or other light hydrocarbons. I

This invention is more particularly directed to that type of cracking process in which the oil may be passed through a heatis ing tube, then to an expansion chamber, the

vapors removed and subjected to dephlegmation, and the reflux condensate recracked. The residuum in such type of process is drawn out of the expansion chamber.

In processes of this t e, particularly in handling heavy oils or 0t er oils tending to produce substantial quantities of coke and sludge difiiculty may beexperienced in getting a high yield of gasoline and at the same so time producing a marketable residuum.

The object of this invention is to obtain from the process a. desired yield of gasoline, While at the same time limiting and possibly preventing the formation of an objectionable amount of coke and sludge in said residuum.

To this end, the liquid products or residue separated from the vapors are continuously withdrawn from the system in such a manner that they remain in the reacting zone only for a minimum length of time, depending upon the characteristics of the oil undergoing treatment, thus avoiding as far as possible, obj ectionable formation of coke, sludge, and the like due to extended retention of this liquid residuum at high temperature. The time limit during which the liquid residuum should remain in the expansion chamber at high temperature is dependent upon the type of oil treated and the extent to which it iii is desired to limit the formation of sludgeand coke and the like, and it iscontrolled by the height to which the residue is permitted to accumulate in the expansion chamber and by the 'rate of withdrawal of said residue therefrom. For a given time limit, this height is dependent upon the size of the sep arating or expansion zone, the rate of feed of the material through the apparatus, and the pressures,.and temperatures used.

59 As a further object of the invention, the

liquid residue is continuously withdrawn from the expansion or separating zone at such a rate that it remains in said zone for the desired length of time, and thereafter is immediately partially cooled as it is withdrawn from the zone and flashed under reduced pressure, and the flashed vapors may be subable cooling agent, preferably the mixture of hydrocarbon products from cracking which goes by the name of pressure distillate bottoms and which, in a process of the character described, is a cut intermediate the reflux condensate and the end point gasoline produced and which in the trade would correspond to heavy naphtha kerosene fractions. This cut may cover a boiling point range between about 400 and 600 F.', more or less.

The primary cooling by direct heat interchange and the subsequent cooling due to flashing, arrestany reaction that may tend to proceed in the residual products after they are withdrawn from the high temperature zone, thereby preventing the formation of objectionable amounts of sludge and coke.

The temperature to which the residual products withdrawn from the high temperature zone may be cooled by, controlled heat interchange before being subjected to flashing, must be properly balanced with the degree of reduction of pressure which they undergo during flashing, so as to produce the desirable total cooling effect, as Well as the desired degree of vaporization of the lighter portion of the residual products withdrawn from the high temperature zone.

-Other features of the invention will be apparent from the following description of the process according to the invention:

In the accompanying drawing, I show an apparatus suitable for carrying out the present invention, it being understood that this is merely a diagrammatic showing and in no sense drawn to scale.

Referring to the drawing, 1 designates a conventional typefurnace in which is mounted the heating tube 2, provided with a. trans:

tion zone fer line 3, having a throttle valve 4: and leadmg to the reaction or vapor separating or expansion chamber 5. The vapors separated therein pass out of the reaction chamber through line 6, having throttle valve 7 to the side of'the dephlegmator 8. From the top of the dephlegmator, the uncondensedvapors pass through line 9 to condenser coil 10 and.

thence to receiver 11. This receiverhas gas control valve 12 and distillate control valve 13 for the discharge of these respective through-the draw-0H pipe 18 connected to the bottom of the chamber 5., The rate of withdrawal is controlled in a suitable manner, depending upon the conditions of the operation to maintain in chamber 5 such liquid level as will provide for the desired time element during which the residual liquid products may remain in the high temperature zone 5 without becoming laden with objectionable quantities of slud" e and coke.

, Additional side draw-o s 18 are shown but should only be used after bottom drawoif 18 has become clogged, although the latter draw-off should be used, if possible, alone during the operation, particularly when the level which must be obtained in chamber 5 is relatively low. The residual liquid products withdrawn from chamber 5 through pipe l8 in which is interposed valve 19 are passed to 1ine'20, in which is interposed valve 21 and into flash chamber 22.

As a feature of the invention, the residual liquid products from chamber 5 "are mixed during their .passagefrom chamber 5 to flash chamber 22 with a suitable quantity of socalled pressure distillate botto'ms, introduced into. line 20 through branch 23, controlled,by valve 24. I r

Before being introduced into the system, the supply of pressure distillate bottoms may be brought to the desired temperature by either heating or, cooling by suitablemeans (not shown) so.that, by a proper control of the temperature and quantity of said pressure distillate bottoms introduced, the mixture of pressure distillate bottoms and residual products from chamber 5 may be partially cooled to a suitable temperature below the temperature at which objectionable extended reaction proceeds' The temperature and amount of the pressure distillate bottoms introduced in line 20 depends not only upon the temperature to which it isdesired to cool the un vaporized products from chamber 5,;but it also depends upon the characteristics of the products desired from the process, particularly upon the viscosity, flash and fire points,

and other characteristics which may be specified for the residuum to be produced by the process.

At the same time as a supply of cooling agent, to wit :pressure distillate bottoms, is introduced from line 23 into the residual products from chamber 5 and in direct physical contact therewith, an additional reduction in temperature of these residual products is obtained by reduction of pressure, such as to cause flash distillation in chamber 22. This reduction of pressure may be effected by the regulation of either or both of the valves 19 or 21, depending upon whether it is desired to introduce the pressure distillate bottoms be fore or after the pressure has been reduced on the unvaporized liquid products with which said pressure distillate bottoms are to be admix (1.

Partial vaporization of the mixture is effected in the flash chamber 22 and the degree of vaporization is dependent upon the degreeof total cooling due to the partial cooling resulting from the admixture of pressure distillate bottoms and the partial cooling resulting'from the reduction in pressure.

The degree of vaporization in chamber 22 may also be controlled or helped by introduction of steam orother heated gas into ghamber 22 or by mildly heating said cham- The unvaporized residue from phamber 22 is withdrawn therefrom through line 25, controlled b valve 26, and thence" cooled, stored, or sent or further treatment. The vapors released in the flash chamber 22 may be passed through line 27, controlled by valve 28, condensed in condenser 29 and collected in receiver 30, or these vapors may b assed through branch 31, controlled by valve 32, and directed to a dephlegmator 233 from which uncondensed-gvapors pass to line 27 through branch 34, controlled by valve 35, and from which condensate may be withdrawn through line 36 and directed to storage. or taken by hot oil pump 37 and returned through line 38 into the dephlegmator 8 from which it is returned to the system for further treatment.

Raw oil or other cooling medium, may be introduced to dephlegmators 8 and 33 in a suitable manner.

The pressure distillate bottoms used in the process to partially cool the unvaporized products from the cracking reaction before they are subjected to'flashiug ma be a product of the same operation or o a (previous operation of the process, depen ing upon the degree of fractionation to which the vapors produced in the process are subjected before collection.

In-the method of carrying out the invensea tion illustrated in the drawing, the pressure distillate bottoms introduced from line 23 will generally result from the re-distillation of the pressure distillate collected in the receiver 13 after dephlegmation of the vapors in dephlegmator 8. In general practice and in carrying out a process of the character described, the vapors leaving the dephleg mator 8 have an end point higher than the end point of gasoline, and it is necessary to subject these vapors after condensation and collection as pressure distillate to distillation for separation of the gasoline. The res idue from such distillation, generally called pressure distillate bottoms, is the product used as described in the process of this invention.

As another method to carry out the invention, the vapors leaving the dephlegmator, instead of being condensed and collected as such and as pressure distillate, may be subjected to additional de hlegmation in a secondary dephlegmator lhot shown) whereby said vapors are separated without additional distillation into end point gasoline vapors and condensed pressure distillate bot toms. The end point gasoline vapors are then condensed and collected as shown, and the pressure distillate bottoms produced from said secondary dephlegmator may then be used alone, or .in admixture with pressure distillate bottoms from other sources, to cool the unvaporized liquid products removed from chamber 5 in the manner heretofore described.

When the process is carried out along the alternative method just described, the pressure distillate bottom return line connecting the bottom of the secondary dephlegmator to the draw-oh? line 18 from chamber 5 may comprise branches and bypass permitting the regulation of the amount of pressure distillate bottoms returned to the system through line 23 and by-passes on which may be interposed coolers, heaters, and hot oil pumps to permit the control of the temperature at which the pressure distillate bottoms are to be admixed with the unvaporized liop uid products from chamber 5 and the pressure under which they are to be charged into the line 18.

In the event such a method is carried out where pressure distillate bottoms are produced in the process by means of a secondary dephlegmator (not shown) the condensate formed in dephlegmator 33, instead'of I'Elllllll. ing to the dephlegmat/or 8, as shown in the drawing, may be returned to the secondary deplil-egmator (not shown) in toto or in part to both the primary dephlegmator 8 and the secondary dephlegmator (not shown).

Among the advantages of the process herein described is the fact that the admixture of'the pressure distillate bottoms with the unvaporized products from the high temperature cracking zone arrests rapidly any extended cracking of said products, and that a relatively small quantity of pressure distillate bottoms is generally sufficient to produce a relatively large cooling on account of products from reaction chamber 5. This reduces the viscosity of these products, and it helps avoiding clogging oi the residuum draw-0d lines which may occur on account of the high viscosity of unvaporized products resulting from the treatment of certain oils, even though said products contain less than 2% sludge or thereabouts. In other words, depending upon the characteristics oi": the oil treated, the unvaporizcd products withdrawn from the chamber 5 and containing about 2% sludge or coke may have viscositics ranging from, say to 1000 seconds Saybolt .turol, even though the cracking reaction has been limited to the extent that will produce about 2% sludge or less in every case. r'ldminture of said unvaporized products with pressure distillate bottoms produces the desired cooling efiect at the same time as it reduces the viscosity.

As another advantage pressure distillate bottoms resulting from processes of the character heretofore described, may contain some light fractions which, if separated, might well come within the rant "e of boiling points of gasoline fractions. Elie admixture of these pressure distillate bottoms with the unvaporized products and the flashing of the mixture thereafter permits vaporization. of such. portions of the p ssure distillate'bot toms as are herein referred to and they are further recovered after cooling and condensation.

inother advantage consists in that the ad mixture or" these pressure distillate bottoms with the heavier unvaporizcd liquid products from the reaction tends to lower the vapor pressure of the products undergoing flashing, which results in a larger amount of distillate carried over-at a definite temperature, therefore resulting in an easier control of the degree of vaporization in chamber 22, and overcoming, to some extent, the reduction in degree of vaporization resulting from reduction of temperature due to the adminture of said pressure distillate bottoms with the residues from the chamber 5.

As an illustration of a method to carry out the invention, California oil having a gravity of about 19 13-. may be heated in coil 2 to a temperature of about 900 F. under a pressure of about 150 pounds. The unvaporized products are withdrawn from the chamber 5 at such a rate that no more than about 65 to 85 cubic feet of liquid is permitted to accumulate therein. These products withdrawn from chamber a 8 at a temperature of about 800 F. are cooled by admixture with about 10 to 3( of pressure distillate bottoms resulting in a partial cooling of the mixture to a temperature of from 400 to 500 F after which the pressure may be reduced from 150 pounds down to about 20 to 25 pounds, or less. a,

Distillation in the flash chamber 23 is so controlled by injection of steam that the viscosity of the residuum withdrawn from the bottomof said chamber 23 is maintained below 500 secqnds Saybolt furol, at 122 F., j

and the flash point at about'150 F., with a coke and sludge content of less than 2% measured by benzol centrifuge:

In this operation about 40 to 45% of 437 F. end point gasoline is produced based on the charge, and about of the residuum, having characteristics heretofore described, is 'withdrawnfrom the flash chamber 23.

I claim as my invention:

1. A process of cracking hydrocarbon oil, comprising subjectingthe oil to cracking temperature under pressure, thereafter separating the vapors from non-vaporous residue, removing, condensing and collecting the vapors, removing the liquid residue from the cracking zone before it contains objectionable amounts of sludge and ,coke, and admixing with said residue a quantity of pressure'distillate bottoms so controlled as to amount and temperature as to cool said residue to-below cracking temperature, thereafter reducing the pressure on the mixture of residue and pressure distillate bottoms so as to cause partial vaporization thereof and additional partial cooling.

2. A process of cracking hydrocarbon oil,

comprising subjecting the oil to cracking temperature under superatmospheric pressure, thereafter separating the vapors from liquid residue, removing, condensing and collecting the vapors, removing) the liquid residue from the cracking zone fore it contains objectionable amounts of sludge and coke, admixing with said residue a controlled quantity of hydrocarbon oil distillate having a boiling point range between approximatel 400 to 600 F., said distillate being in suc amount and of such temperature as to' cool said liquid residue to below cracking temperature, thereafter reducing the pressure on the mixture of residue and said oil distillate so as to cause partial vaporization and addi tional partial cooling.

In testimony whereof I afiix my signature. EAN D.

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