US2136715A

US2136715A - Conversion of hydrocarbon oils

Info

Publication number: US2136715A
Application number: US145021A
Authority: US
Inventors: Swartwood Kenneth
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1937-05-27
Filing date: 1937-05-27
Publication date: 1938-11-15
Anticipated expiration: 1955-11-15

Description

NOV. 15, 1938.. K. SWARTWOQD 2,136,715

CONVERSION OF HYDR OCARBON OILS Filed May 27, 1957 CONDEN FURNACE 2| FURNACE FURNACE FURNACE INVENTOR KENNETH SWARTWOOD A NEY Patented Nov. 15, 1938 PATENT OFFICE CONVERSION OF HYDROCARBON OILS Kenneth Swartwood, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 11]., a corporation of Delaware Application May 27, 1937, Serial No. 145,021

6 Claims.

This invention relates to an improved process for the pyrolytic conversion of hydrocarbon oils to produce high yields of good quality gasoline accompanied by the production of gas and the production of liquid residue as an intermediate product, the latter being reduced to coke in a zone separate from that wherein it is formed and vaporous products evolved from the residual liquid in the coking operation being subjected to appreciable cracking following their removal from the coking zone, to produce additional yields of good quality gasoline therefrom, by commingling said vapors with highly heated gaseous products of the process.

In modern cracking processes designed for the production of maximum yields of gasoline, it is common practice to coke the residual liquid resulting from cracking of the charging stock and intermediate liquid products of the process in order to obtain high yields of gasoline to the exclusion of a residual liquid product. In operations of this character, the volatiles evolved from the residual liquid in the coking step consist prin- -cipally\of liquid products, boiling above the range of gasoline, and gas. Only minor yields of ma terials boiling within the range of gasoline are normally produced in the coking step, particularly when the latter is accomplished at substantiallyatmospheric or relatively low superatmospheric pressure, as is usually th case. n a major portion of the additional yields of gasoline which are produced as the result of coking the residual oil are obtained by further cracking of intermediate liquid products of the coking step. To accomplish this, the usual practice is to subject the vaporous products of the coking step to fractionation, either alone or together with vaporous products of the cracking step wherein the residual l quid is produced, and returning the reflux condensate resulting from fractionation of the coking-still vapors to further cracking in a heating coil of the system; the fractionated,

gaseous products of the process and are sub-,

jected therewith to appreciable conversion time at a relatively high temperature. This improved method obviates fractionation of the vaporous products of the coking step to produce a reflux condensate and further obviates the use of a heating coil for cracking said reflux condensate. It has a further advantage in that any materials of gasoline boiling range produced in the coking step, and which are normally of inferior antiknock value, are subjected to additional cracking together with the normally liquid products of the coking step boiling above the range of gasoline under the high temperature conditions prevailing in said vapor reaction chamber to which the total vaporous products from the coking zone are supplied. This results in a substantial improvement in the antiknock" value of these gasoline fractions. I have further found that the gasoline produced by further cracking of the coking still vapors in the manner herein provided is of improved antiknock value as compared with that i normally produced by cracking reflux condensate resulting from fractionation of the coking-still vapors in the conventional manner. This is very likely due in part to reforming of the gasoline fractions contained in the vaporous products of the coking step, but, due to the relatively small quantity of such fractions normally produced, I am led to believe that this does not fully account for the good quality of the total gasoline produced by said further cracking of the total vapor stream. Another factor which may enter into the production of good antiknock gasoline in this step of the system is the fact that these products are cracked at high temperature under substantially vapor-phase conditions, since high temperature vapor-phase conditions are known to produce both olefinic and aromatic compounds of good antiknock value. However, I believe that a third factor of material importance is the presence of the highly heated normally gaseous products in the reaction zone to which the vaporous products of the coking step are supplied and that there is some interaction between the commingled materials in this zone which results in a material improvement in the antiknock value of the gasoline produced not fully accounted for by the other two factors mentioned.

Another important feature of the invention which, however, is not to be construed as a limitation, resides in the segregation of vaporous and heavy liquid products in the reaction chamber to which the volatiles evolved by coking of the residual liquid are supplied and the provision for subjecting the vaporous components in this reaction chamber to more prolonged conversion time than that afforded said heavy liquid components. This is accomplished by directing the materials removed in vaporous state from the flow rapidly downwardly thereover to the outlet of this zone while the vaporous components are intimately commingled with the highly heated gases supplied to this zone and are subjected therein to more prolonged conversion time as they pass through the chamber.

One specific embodiment of the invention comprises subjecting reflux condensate formed within the system, as will be later described, to cracking temperature at superatmospheric pressure in a heating coil and communicating enlarged reaction chamber, supplying both vaporous and liquid conversion products from the reaction chamber to a reduced pressure vaporizing and separating chamber wherein vapors and non-vaporous liquid residue are separated, subjecting said vapors to fractionation for the formation of said reflux condensate which is supplied to the aforementioned heating coil, subjecting fractionated vapors of the desired end-boiling point to condensation, collecting and separating the result ing distillate and uncondensed gases, supplying said non-vaporous liquid residue from thevaporizing and separating chamber to a separate zone wherein it is reduced to substantially dry coke, supplying vaporous products of the coking operation directly from the coking zonerto-another reaction chamber, heating regulated quantitles of said uncondensed gases to a high oilcracking temperature in a separate heating coil, introducing the heated gases into said separate reaction chamber wherein they commingle with the vaporous products supplied to this zone from the coking step, subjecting the commingled vapors and gases to substantial conversion at high cracking temperature in said separate reaction zone and supplying the total vaporous, liquid and gaseous products from said separate reaction chamber to said vaporizing and separating chamber. v

The accompanying diagrammatic drawing illustrates one specific form of apparatus in which the process of the present invention may be successfully conducted.

. 'Referring to the drawing, charging stock for the process, which may comprise any desired type of hydrocarbon oil, is supplied through line I to valve 2 to pump 3 wherefrom it is fed through line 4 and, depending upon its gharacteristics and the method of treatment to which the charging stock is best suited, it may be fed to any one of a plurality of points within the system or may,

when desired, be supplied in part to several of said points. The charging stock may pass from line 4' through line 5 into fractionator in, entering this zone at any desired point or plurality of points by means of a plurality of lines such as indicated at 6 and 1 in the drawing and controlled by the respective valves 8 and 9. Other manners in which the charging stock may be supplied to the system will be later described and are not to be considered equivalent since they are employed principally to give the process greater flexibility with respect to the type of charging stock employed and may be selected to suit requirements.

Reflux condensate formed in fractionator It and comprising either the total reflux condensate or selected high-boiling fractions thereof,

as will be later explained, is directed from the lower portion of this zone through line H and valve I! to pump l3 by means of which it is supplied through line H and valve l5 to heating coil l6.

In case the charging stock is an oil corresponding in cracking characteristics to the reflux condensate supplied to heating coil IE, it may, when desired, be supplied directly to this zone by means of lines l1, l8, l9, valve '20 and'line H or it may be supplied to the fractionator, as previously described, to commingle in this zone with the reflux condensate formed therein.

The oil supplied, as described, to heating coil ,IB is heated during its passage through this zone to the desired cracking temperature, preferably at a substantial superatmospheric pressure, by means of heat supplied from furnace 21 and the heated products are directed through line 22 and valve 23 to reaction chamber 24,

Chamber 24 is also preferably maintained at 1 a substantial superatmospheric pressure and, al-

though not illustrated in the drawing, this zone is preferably insulated to conserve heat so that the heated products supplied thereto are subjected to appreciable continued conversion time in the reaction chamber. Both vaporous and liquid conversion products are, in the particular case here illustrated, withdrawn in comrningled state from the lower portion of chamber 24 and directed through line 25 and valve 26 to vaporizing and separating chamber 21.

Chamber 2! is'preferably operated at a substantially reduced pressure relative to that employed in chamber 24 and functions as a zone wherein appreciable further vaporization of the liquid products supplied thereto are subjected to appreciable further vaporization and wherein the vapors are separated from non-vaporous liquid L point, which, in case chargingstock is supplied to valve 3| to condensation and cooling in condenser 32, the resulting distillate and uncondensed gases are directed through line 33 and valve 34 to collection and separation in receiver 35. The gaseous products produced within the system and collected in receiver 35 are removed from this zone through line 36 and may pass, in part, through valve 31 in this line to storage or elsewhere as desired. Regulated quantities of the gaseous products are, however, diverted from line 36 through line 38 and valve 39 to pump or compressor 40 by means of which they are supplied through line ll *and valve 42 to heating coil 43 for further treatment therein, as will be later described.

The distillate recovered in receiver 35 may be directed therefrom through line 44 and valve 45 to storage or to any desired further treatment.

When desired, regulated quantities of the distillate collected in receiver 35 may be recirculated by well known means, not illustrated, to the upper portion of fractionator ill to serve as a cooling and refluxing medium in this zone.

The residual liquid which is separated from the vaporous products of the process in chamber 211 is withdrawn from the lower portion of this zone and directed .through line 46 and valve ll to pump 48 by means of which it is supplied through line M and valve 50 to line 5! and thence supplied either through line 52 and valve. directly to coking chamber 54 or through valve 55 in line 5i to heating. coil 56 wherefrom it is supplied through line 51, valve lit and line 52 to coking chamber 54.

In case the charging stock is a residual oil of relatively high-boiling characteristics'unsuitable as cracking stock for heating coil it, it may be commingled with the liquid residue withdrawn from chamber 211 and supplied therewith to coking chamber 5 3 by passing the charging stock through valve Ed in line it into line hi or by directing the same from line it through line it and valve ti into chamber 21!. On the other hand, other types of charging stock may, when desired, be supplied all or in part to chamber it, as described, and, by directing the same into the upper portion of this zone, it may serve as a refluxing and cooling medium for assisting separation of vaporous and heavy liquid products in this zone.

Coking of the residual liquid from. chamber it or a mixture of residual liquid and charging stock may be accomplished, within the scope of the invention, in any desired manner and, as an illustration, two alternative but non-equivalent methods of coking are provided in the case here illustrated. One of the methods illustrated comprises passing the heavy oil to be coked through heating coil 56 in the manner previously described, and therein heating the same, by means of heat supplied from furnace M, to a temperature adequate to eflect its subsequent reduction to coke in chamber 5t. Preferably, when this method of operation is employed, the heavy oil is heated to a relatively high temperature in coil 56, but highyelocity and high rates of heating are employed in this zone such that the oil is heated to the desired high temperature without permitting it to remain in the heating coil and communicating lines for a sumcient length of time to form appreciable deposits of coke therein.

The other mode of operation herein illustrated, with reference to the coking step, involves the use of a heat carrying medium which is introduced at high temperature into direct contact with the materials undergoing coking in the coking chamber, the heavy oil to be coked preferably being supplied directly to this zone without passing through heating coil 5%, although the latter may be employed in conjunction with the use, of a heat carrying medium, when desired. Heating coil M, which is disposed within furnace it, is employed in the case here illustrated for heating the heat carrying medium to the desired relatively high temperature and serves at the same time as a cracking zone for low-boiling fractions of the reflux condensate formed in fractionator it! and/or charging stock for the process. In accordance with this mode of operation, the reflux condensate formed in fractionator it may be separated into selected relatively lowboiling and high-boiling fractions, the highthe fractionator and directed through line 65 and valve 86 to pump 81 by means of which they are supplied through line 68 and valve '89 to heating coil 63, either alone or together with any corresponding fractions of the charging stock, in case the latter is supplied to the fractionator. All or regulated quantities of the charging stock may, on

the other hand, be supplied directly to heating coil 63 by diverting the same from line H through line l and valve M into line 88, through whichit is supplied to heating coil 53. In case the charging stock is a relatively low-boiling oil having cracking characteristics similar to those of the low-boiling fractions of the reflux condensate, it is preferablyv commingled therewith either in fractionator id or in line 68 and supplied therewith to heating coil 63. On the other hand, relatively heavy'charging stock or charging stock of relatively wide boiling range may, when desired, be supplied alone to heating coil 63 and the total reflux condensate from fractionator it supplied,'as previously described, to heating coil it.

Heated products are discharged at the desired cracking temperature from heating coil t3 and directed through line if and valve it preferably into the lower portion of chamber t wherein they comrningle' with the materials undergoing coking in this zone and supply heat thereto for efiecting or assisting their reduction to coke.

The coke produced in chamber ht may be allowed to accumulate therein until the chamber is substantially filled or until its operation is suitable cooling material such as steam, water, H

or the like intothe chamber after its operation has been completed and preferably after it has been isolated from the rest of the system, in order to hasten cooling and facilitate removal of the coke. Although only one coking chamber is shown in the drawing, it will, of course, be understood that a plurality of such zones may be employed, when desired, in which case they may be operated either alternately or simultaneously.

Vaporous products are removed from the upper portion of the coking chamber through line it and may be directed through valve 'lll'in this line into the upper portion of'reaction' chamber it, wherein they are preferably. directed by means of a suitable spreader flange or spray arrangement indicated at it against the interior surface of the walls of the chamber whereby any ento the lower portion of the chamber, while the lower boiling uncondensed components of the vapors are subjected, as will be later described, to substantial continued conversion time at high temperature as they pass downward through chamber it.

he an alternative method of operating chamber iii, the vaporous products from chamber 54 may be directed from line it through line 90 and valve i into the lower portion of the reaction chamber and are preferably directed against the walls of the chamber by means of a suitable spreader flange or spray device 19', whereby their heavy liquid components may pass rapidly downward to the bottom of the chamber to be quickly withdrawnv therefrom without being subjected to appreciable cracking time in this zone, while their scribed, to substantial cracln'ng time at high temperature during their passage through this zone.

Gaseous products of the process directed, as previously described, from receiver 35 to heating coil 48 are heated therein to a relatively high temperature by means of heat supplied from a suitable furnace 88 and the highly heated gases are discharged through line 8| into reaction chamber 18, means being provided for supplying the same either to the upper portion of this zone through line 82 and valve 83, in case the vaporous products from chamber 54 are supplied to the upper portion .of chamber 18, or the lower portion of the chamber through line 84 and valve 85, in case the vaporous products from chamber 54 are supplied to the lower portion of chamber 18. The highly heated gases thus introduced into chamber 18 commingle therein with the non-residual vaporous components of the materials supplied thereto from the coking chamber, heating the latter to a high cracking temperature, whereby they are subjected to substantial cracking as they pass through chamber 18. Although not illustrated in the drawing, chamber 18 is preferably insulated to conserve heat but this zone is preferably not heated externally so that the walls are relatively cool and will serve to condense entrained heavy liquid particles from the vapors which come in'contact therewith.

In case the vaporous products from chamber 84 are supplied, as described, to the upper portion of chamber 18, the total products resulting from the cracking operation in this zone may be removed in commingled state from the lower portion thereof and directed through line 88 and valve 81 into chamber 21, wherein their vaporous and heavy liquid'components separate; the latter being returned to the coking zone and the former passing from chamber 21 to fractionation in fractionator I8. I

In case vaporous products from chamber 84 are supplied, as described, to the lower portion of chamber 18, liquid products are. directed fromthe lower portion of this zone through line 88 and valve 8'! to.chamber 21, while all or a major portion of the vaporous and gaseous conversion products are separately removed from the upper portion of the chamber and directed through line 88 and valve 88 into chamber 21.

The preferred range of operating conditions which may be employed, within the scope of the invention, in an apparatus such as illustrated and above described, may be approximately as follows: The temperature employed at the" outlet of heating coil I8 may range, for example, from 850 to 975 F. or thereabout, preferably with a superatmospheric pressure at this point in the system of from 100 to 500 pounds or more per square inch. Substantially the same or somewhat lower superatmospheric pressure may be employed v measured at the outlet therefrom, ranging, for example, from 750 to 1050 F. or more, with any desired pressure of from 30 to 300 pounds or thereabout per square inch at this point in the system, the preferred range being a temperature from 950 to 1000 F. and a superatmospheric pressure of from 50 to 150 pounds per square inch. Heating coil 88, when utilized and when the material supplied thereto for conversion is a relatively low-boiling oil such as light reflux condensate from fractionator l0, preferably employs a high conversion temperature, as measured at the outlet therefrom, which may range for example, from 900 to 1000 F, or thereabouts and preferably a superatmospheric pressure of the order of 200 to 800 pounds or more per square inch is employed at this point in the system. The coking chamber may employ any desired pressure no higher than that utilized in the communicating heating coil or coils, the preferred range being from 50 to 150 pounds per square inch, superatmospheric. Heating coil 43 preferably employs a high cracking temperature of the order of 950 to 1200 F. or thereabouts and any desired pressure ranging from substantially atmospheric to several hundred pounds superatmospheric pressure may be employed in this zone. Chamber i8 is preferably operated at substantially the same pressure as that employed in the coking chamber, although lower pressure down to substantially atmospheric may be utilized in this zone, when desired.

As a specific example of one of the many possible operations of the process which may be conducted in an apparatus of the character illustrated and above described, the charging stock is a heavy Mid-Continent gas oil of approximately 22 A. P. I. gravity and is supplied to vaporizing and separating chamber 21, wherein it serves as a cooling medium and, being substantially vaporized in this zone, is thence supplied to fractionator 21 together with the vaporous conversion products of the process. The total reflux condensate formed in the fractionator and the charging stock, which is condensed in this zone, are supplied to heating coil l8. The

stantially the same pressure is utilized in the succeeding fractionating, condensing and collecting equipment. The residual liquid from chamber 21 is quickly heated in heating coil 88 to an outlet temperature of approximately 980 F. at a superatmospheric pressure of about 150 pounds per square inch and is thence introduced into alternately operated coking chambers wherein the high-boiling components of the residual liquid are reduced to coke. The vaporous products from the coking chambers are supplied to reaction chamber I8 wherein high-boiling entrained liquids are quickly separated therefrom and the remaining vapors commingled with highly heated gases from heating coil 48, the latter being introduced into chamber 18 at a temperature of approximately 1050 F. The pressure employed at the outlet from heating coil 48 is approximately 200 pounds per square inch and is reduced in chamber 18 toapproximately 150 pounds per square inch. The total materials from chamber I8 are supplied to vaporizing and separating chamber 21. This operation will produce per barrel of charging stock approximately 63% of 400 F. end-point gasoline having an octane number of approximately '72 by the motor method and approximately 65 pounds, per barrel of charging stock, of low volatile petroleum coke, the remainder being chargeable principally to uncondensable gas.

I claimas. my invention:

1. In a process wherein hydrocarbon oils are cracked at cracking temperature and superatmospheric pressure to produce primarily gasoline, liquid residue, and normally gaseous materials, which are separated, and wherein said liquid residue is reduced to coke in a zone separate from that wherein it is separated from the vaporous and gaseous products of the cracking operation,

the improvement which comprises introducing vaporous products of the coking operation into a reaction zone separate from that of the atommentioned cracking operation, heating regulated quantities of said normally gaseous materials, following their separation from said gasoline, to a high oil-cracking temperature, introducing the highly heated gases into said reaction zone wherein they commingle with said vaporous prod ucts of the coking operation, raising said vaporous products to cracking temperature by the heat of. said gases, maintaining said commingled vaporous and gaseous materials at an active cracking temperature in said reaction zone'ofor a sumcient length of time to effect the production therefrom of additional yields of good anti knock gasoline, and recovering the latter.

2. In a process wherein hydrocarbon oils are cracked at cracking temperature and superatmospheric pressure to produce primarily gasoline, liquid residue and normally gaseous materials, which are separated, and wherein said liquid residue is reduced to coke in a zone separate from that wherein it is separated from the vaporous andgaseous products of the cracking operation,

the improvement which comprises introducing vaporous products of the coking operation into a reaction zone separate from that of the aforementioned cracking operation, heating regulated quantities of said normally gaseous materials,

following their separation from said gasoline, to r a high oil-cracking temperature, introducing the highly heated gases into said reaction zone wherein they commingle with said vaporous products of additional yields of good antiknock gasoline, separating gasoline and residual liquid from the products of the last mentioned cracking step, recovering said gasoline, and returning said residual liquid to the coking step.

3. In a process wherein hydrocarbon oils are cracked at cracking temperature and superatmospheric pressure to produce primarily gasoline, liquid residue and normally gaseous materials, which are separated, and wherein said liquid residue is reduced to coke in a zone separate from that wherein it is separated from the vaporous and gaseous products of the cracking operation, the improvement which comprises introducing vaporous products of the coking operation into a reaction zone separate from that of the aforementioned cracking operation, heating regulated quantities of said normally gaseous materials, following their separation from said gasoline, to a high oil-cracking temperature, introducing the highly heated gases into the reaction zone wherein they commingle with said vaporous products of the coking operation, raising said vaporous products to cracking temperature by the heat of said gases, maintaining said commingled vaporous and gaseous materials at an active cracking temperature in said reaction zone for a sufiicient length of time to effect the production therefrom of additional yields of good antiknock gasoline, separating the products of the last mentioned cracking step into residual liquid, intermediate liquid products boiling above the range of gasoline and gasoline, recovering said gasoline, and

returning said intermediate liquid products to the first mentioned cracking operation.

4. In a process wherein hydrocarbon oils are cracked at cracking temperature and superatmospheric pressure to produce primarily gasoline, liquid residue and normally gaseous materials, which are separated, and wherein said liquid residue is reduced to coke in a zone separate from that wherein it is separated from the vaporous and gaseous products of the cracking operation, the improvement which comprises introducing vaporous products of the coking operation into a reaction zone separate from that of the aforementioned cracking operation, heating regulated quantities of said normally gaseous materials, following their separation from said gasoline, to a high oil-cracking temperature, introducing the highly heatedgases into said reaction zone wherein they commingle with said vaporous products of the coking operation, raising said vaporous products tfi cracking temperature by the heat of said gases, maintaining said commingled vaporous and gaseous materials at an active cracking temperature in said reaction zone for a suficient length of time to effect the production therefrom of. additional yields of good antiknock gasoline and commingling the products of the last mentioned cracking operation with the products of the first mentioned cracking operation in the zone wherein said separation of vaporous and residual liquid conversion products is accomplished.

5. A process for the pyrolytic conversion of hydrocarbon oils which comprises subjecting an oil to conversion conditions of cracking temperature and substantial superatmospheric pressure, separating the resulting vaporous and residual liquid conversion products, subjecting said vapors to fractionation for the formation of reflux condensate which is returned to the aforementioned cracking step, subjecting fractionated vapors of the desired end-boiling point to condensation, collecting and separating the resulting distillate and uncondensed gases, removing said residual liquid conversion products from the zone wherein they are separated from said vaporous products and reducing, the same to coke in a separate zone, heating regulated quantities of said uncondensed gases to a high oil-cracking temperature, comminglin'g the highly heated gases with vaporous products removed from the coking zone, subjecting the last-named vaporous products to appreciable cracking in substantially vapor-phase by the heat of said gases, and sup plying resulting products of the last mentioned cracking operation to the zone wherein said separation of vaporous and residual liquid conver sion products is accomplished.

til

6.. In a process wherein hydrocarbon oil is heated to cracking temperature at superatmospheric pressure 'in a heating coil, the heated products passed through an enlarged reaction chamber, also maintained at substantial superatmospheric pressure, and then introduced into a reduced pressure vaporizing and separating chamber, vaporous and residual liquid conversion products separately removed from said vaporizing and separating chamber, the residual liquid reduced to coke in a separate coking zone, said vaporous products subjected to fractionation for the formation of reflux condensate, the latter returned to further cracking within the system, fractionated vapors oi the desired end-boiling point subjected to condensation and the resulting distillate and uncondensed gases separated,

the improvement which comprises heating regulated quantities or said uncondensed gases to a high oil-cracking temperature in a separate heating coil, supplying highly heated gases directly from the last mentioned heating coil and vaporous products from the coking zone to a separate enlarged reaction chamber and therein raising said vapors to an active cracking temperature by the heat of said gases, maintaining the vapors and gases at the attained temperature of the mixture in commingled state for a suflicient length of time to effect the production therefrom of. substantial quantities of good antiknock gasoline, and supplying the total products from the last mentioned reaction chamber to said vaporizing and separating chamber.

KENNETH SWAR'I'WOOD.