US2066808A - Art of converting hydrocarbon oil - Google Patents

Description

Jan. 5, 1937.

P. SULLIVAN ART OF CONVERTING HYDROCARBON OIL.

Filed July 11, 1953 VINVENTIOR PIKE H. SULLIVAN I I ATTORNEY Patented Jan. 5, 1931 UNITED STATES ART OF CONVERTING HYDROCARBON OIL Pike H. Sullivan, New Rochelle, N. Y., assignor to Gasoline Products Company, Inc., Newark, N. J., a corporation of Delaware Application July 11, 1933, Serial No. 679,832

4 Claims.

My invention relates to improvements in the art of converting higher boiling hydrocarbons into lower boiling products.

My invention is particularly adapted to a process in which separate streams of hydrocarbon oils are separately cracked in vapor and liquid phases and are thereafter blended at a point where objectionable constituents are being formed in the vapor phase stream in order to substantially prevent the deleterious effectsof the objectionable constituents. The combined streams are then passed into a soaking zone wherein the desired further reaction thereof is accomplished.

In cracking a stream of hydrocarbon oil under vapor phase cracking conditions, the cracking reaction reaches a, stage where asphaltenes or tarlike particles are formed. These objectionable constituents upon formation contact the walls of the heating zone and due to the heat being imparted thereto immediately decompose into coke which is deposited on the walls of the heating zone. This deposition of 'coke not only shortens the length of run but" also limits the final vapor phase cracking which may be accomplished in the cracking zone. operation the deposition and consequent coking of the small, asphaltenes or tar-like particles does not occur to the extent it does in the vapor a second heating coil. The cracking of the light oil' under vapor phase conditions may be carried to a point where the asphaltenes or tar-like particles are beginning to be formed in. the vapors to a substantial or undesired degree. At this point the partially converted vapor phase stream may be blended with the streamof the liquid phase operation and the blended mixture passed through a soaking or reaction zone maintained at or above or below the temperature of the mixture wherein further cracking of the blended oil takes place. In this manner the asphaltenes or tar-like particles are incorporated in the liquid phase particles in the heavier oil and carried in suspension through the soaking zone In' a liquid phase cracking wherein any desired additional cracking and the desired soaking of the blended streams may be accomplished without an undesired deposition of coke or carbon upon the walls of the soaking passageway.

The accompanying drawing illustrates apparatus suitable for carrying my invention into practical effect, although it is to be understood that. my invention is not limited to the particular constructions shown, which, for the purpose of explanation, have been made the subject of illustration. Y

Figure 1 is an elevational view of an apparatus capable of carrying out my invention.

Figure 2 illustrates diagrammatically an-injector that may be used in connection'with my invention.

Referring to Figure 1, there is shown a furnace structure I having a radiant section 2 and a radiant section 3. A convection section formed by bridge walls 5 and 6 may be in open communi- 20 cation with the radiant sections 2 and 3 to receive the hot products of combustion therefrom. A vapor phase cracking coil 1 adapted to be heated substantially entirely by radiant heat produced by suitable burners 8 may be positioned in the radiant heating section 2. A liquid phase heating or cracking coil 9 may be positioned in the radiant section 3 and is. adapted to be heated substantially entirely by radiant heat by means of suitable burners II. A coil I2 may be positioned in the convection section 4 and in accordance with my invention is operated as a soaking or reaction section for the combined liquid and vapor phase streams of hydrocarbons.

While I have shown a unitary furnace structure for heating the plural streams of oil in accordance with my invention, it is to be clearly understood that such a structure is merely for illustrative purposes and is not indicative as to the only.way in which the oil may be heated. For instance, separate furnaces may be employed for the heating coils 'l, 9, and I2, or if desired the coils may be arranged so as to require only two furnace structures.

The additional apparatus that may be employed in carrying out my invention may consist of a vaporizer I 3, a dephlegmating column M, such as a bubble tower, a condenser l5 and a gasoline distillate receiver l6 having a gas outlet line I! and a liquid drawoif line l8.

In carrying out my. invention a relatively heavy hydrocarbon oil, in the nature of a heavy gas oil, may be forced through a line l9 by means of a pump 21. The oil may then be passed through a 55 heat exchanger 22 positioned within the dephlegmator 14 wherein the fresh charge is preheated by indirect heat exchange with upwardly rising vapors. From the heat exchanger coil 22, the fresh charge may be passed through a line 23 and thence through a second heat exchanger coil 24 positioned in the upper portion of the vaporizer l3 wherein it is additionally heated by indirect heat exchange with the upwardly rising vapors in the vaporizer I3. From the heat exchanger 24 the oil may then be passed through a line 25 into the radiant heating coil 3 wherein it is subjected to suitable liquid phase cracking conditions of temperature and pressure.

The oil passing through the radiant heating coil 9 is maintained substantially entirely in liquid phase by the pressure produced thereon by means of the pump 2| and may then be passed to the convection heating coil I2.

The charge for the vapor phase cracking coil I may be a substantially clean gas oil, such for example as the reflux condensate collected in the lower portion of the dephlegmator I 4, as will hereinafter be explained. The reflux condensate in the dephlegmator [4 may be withdrawn therefrom through a line 25 by means of a pump 21 and forced through the vapor phase cracking coil 1. The clean reflux condensate being passed through the vapor phase cracking coil 1 may be subjected to suitable vapor phase cracking conditions therein and the firing of the burners 8 regulated so as to control the cracking reaction in such a manner that the production of objectionable asphaltenes or tar-like particles has not begun to any objectionable extent when the vapors reach the exit of the vapor phase cracking coil I and enter the soaking or reaction coil l2. As shown' in the drawing, the stream of oil being subjected to vapor phase cracking conditions is blended with the heavier stream of 011 being subjected to liquid phase cracking conditions. The partially converted vapor phase stream may be introduced into the partially converted liquid phase stream, as at 28, and any asphaltenes or tar-like particles being formed therein would be taken in solution and surrounded by the liquid particles in the heavier oil and the combined streams then subjected to any desired additional cracking and soaking in the soaking coil l2. In this manner the deposition of the asphaltenes and tar-like particles onto the walls of the heating coil may be prevented and the blended streams further heated to maintain or increase the temperature thereof in order to complete any further desired cracking and digestion thereof.

When maintaining a higher pressure on the oil being cracked in liquid phase than on the oil being cracked in the vapor phase and in order to maintain a higher pressure on the blended streams passing through the soaking coil l2 than is being maintained on the vapor phase stream, an injector may be employed for drawing the vapor phase stream into the liquid phase stream, as will be later explained.

The blended streams of oil after being maintained in the soaking coil l2 for a period sumciently long to accomplish the desired additional cracking and soaking thereof, may be passed through a line 29 into the vaporizer IS. A pressure reduction valve 30 may be provided in the transfer line 29 for maintaining a differential pressure between the soaking coll l2 and the vaporizer I3. The blended streams of oil entering the vaporizer I 3 are therein vaporized and a separation of the vaporous and liquid constituents effected. Any undesired heavier constituents present in the upwardly rising vapors may be condensed by indirect heat exchange with the fresh feed passing through the heat exchanger 24 and returned to the lower portion of the vaporizer IS. The vapors resulting from the vaporizer l3 may be conducted through a line 3| into the lower portion of the dephlegmator l4. Any suitable refluxing medium to accomplish the desired cooling of the vapors in the dephlegmator l4, in addition to the cooling provided by the indirect heat exchange with the fresh charge passing through the heat exchanger 22, may be employed. In accordance with my invention, the vapors entering the dephlegmator l4 are fractionated to produce an overhead vaporous product of the desired boiling range and a clean reflux condensate. The reflux condensate is returned to the vapor phase cracking coil as hereinbefore described. The overhead vapors of the desired boilingrange may be conducted through a line 32 into the condenser l5 wherein the vaporous products may be condensed into the desired low boiling distillate product such as gasoline. The distillate and any gases present may be passed through the line 33 into the gasoline distillate receiver l8 from which the gases may be removed and used as desired.

The unvaporized liquid constituents collected in the vaporizer I 3 which may be in the nature of a heavy fuel oil may be removed through a line 34 and sent to storage. In addition to refluxing the vapors in the dephlegmator 14 with a. suitable refluxing medlum, the upwardly rising vapors in the vaporizer l3 may also be refluxed by means not shown with'any suitable refluxing medium. In this manner heavier ends from the upwardly rising vapors are knocked back before entering the dephlegmator l4 resulting in the production of a clean reflux condensate therein free from objectionable heavy constituents.

In Figure 2, there is shown an injector 35 for blending the vapor phase and liquid phase streams when different pressures are being maintained thereon. As shown, the coil 9 may be connected to a nozzle 36 within the injector 35 thereby increasing the velocity of the liquid phase stream entering the injector. The vapor phase stream passing through the coil 1 is drawn into the injector 35 through a suitable connection 31 by means of the partial vacuum set up by the liquid phase stream entering the injector. The combined streams passing through the remainder of the injector 25 are then conducted to the soaking coil l2 as hereinbefore described. While I have shown and described a particular type of injector that may be used in carrying out my invention, it is to be clearly understood that the injector shown is merely for illustrative purposes and any suitable type may be employed.

In operating in accordance with my invention, a heavy gas oil or reduced crude of about 24 A. P. I. gravity may be forced through the heat exchangers 22 and 24 at a rate of about barrels per hour. The charge in passing through the heat exchangers may be preheated to a tem-, perature of about 500 F. and thereafter passed through the heating coil 9 wherein it is raised to a cracking temperature of about 850 F. while being maintained under a superatmospheric pressure of about 600 pounds per square inch. The reflux condensate in the nature of a light gas oil collected in the bottom of the dephlegmator l4, at a temperature of about 575 F., and having a gravity of 18 A. P. I. may be forced by means of the hot oil pump 21 at a rate of about 100 barrels per hour through the vapor phase crack ing coil 1 wherein it is ralsedto a cracking temperature of about 1000 F. while being maintained under a superatmospheric pressure of about 200 pounds per square inch. The 'light gas oil in passing through the vapor phase coil is subjected to a high crack per pass, of about 30 to 40%, or higher. in order to impart anti-knock qualities theret0,.and the desired temperature is obtained at a point in the coil where objectionable asphaltenes and tar-like particles are being formed. At this point, such as the exit of the vapor phase cracking coil 1, the vapor phase stream is combined with the liquid phase stream by means of the injector 35. The asphaltenes or tar-like particles that are formed by the reaction and those being formed are immediately taken in solution by the liquid phase stream and/or surrounded by liquid oil thereby preventing deposition and consequent coking thereof on the walls of the heating zone.

The blended streams are then passed through soaking or reaction coil 52 at a temperature of about 925 F. and the desired digestion thereof accomplished without objectionable coke troubles The pressure maintained on the oil after passin through the injector 351s about 300 pounds per square inch.

The combined streams at a temperaturepf about 925 F. are then passed through the transfor line 29 to the vaporizer it which may be maintained at a pressure of about 25 pounds per square inch by means of the pressure reduction valve 30. The oil entering the vaporizer is distilled therein and the resulting vapors fractionated in the dephlegmator M to obtain the desired low boiling distillate overhead fraction, such as gasoline, of about 400 to 420 F. end point.

In lieu of maintaining different pressures on the separate streams, a pressure of about 400 pounds per square inch may be maintained on each. Whenoperating in this manner the injector 35 may be dispensed with and the two streams combined, as at 28. With equal pressures being maintained'on the two streams of oil, the vapor phase stream may be subjectedto a high crack per pass in order to improve its antiknock qualities and raised to a temperature of about 1000 F. and the liquid phase stream may be raised to a temperature of about 800 F. The

streams after being combined, as at 28, are then passed through the soaking coil I! at the same pressure and at a temperature of about 900- F.

While specific examples have been set forth for practicing my invention, it is to be clearly understood that the various operating conditions may be modified without departing from the spirit and scope thereof. My invention contemplates any suitable temperature and pressure conditions.

For instance, the vapor phase stock may be of a gravity of from about 16 to 20 A. P. I. and may be raised to a temperature of from about 950 to 1100 F. while being maintained under a to 1000 pounds per square inch. The combined streams may be passed through the soaking coil H at a temperature of from about 875 to 925 F. while being maintained under a pressure of from 300 to 750 pounds per square inch. The pressure being maintained in the vaporizer l3 may be the same as that being maintained on the oil passing through the soaking coil II or, ii desired, any suitable pressure may be maintained on the vaporizer "and the remainder of the system by properly regulating the pressure reduction valve 30.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

'What I claim is:

1. A process of converting higher-boiling hydrocarbon oils into lower-boiling ones which comprises passing a relatively heavy oil, containing constituents unvaporizable under maximum temperature and minimum pressure conditions subsequently obtaining, in a restricted stream through a heating zone, heating said oil during its passage through said heating zone to a conversion temperature, maintaining said oil during its passage through said heating zone under a pressure above 400 pounds per square inch, simultaneously passing a. relatively lighter oil, which is substantially completely vaporizable under maximum temperature and maximum pressure conditions subse- "quently obtaining, in a confined stream through "a separate heating zone. heating said oil during its passage through said heating zone to a temperature sumcient to effect substantially complete vaporization thereof, subjecting the resulting first-named heating zone and under a pressure suflicient to prevent vaporization of a substantial quantity of heavier constituents of said merged stream during passage through said last-named heating zone, the unvaporized heavier constituents serving as a solvent and vehicle for asphaltines or tar-like particles which are formed, thereafter separating the converted products from said last-named conversion treatment into vapors and residue, and fractionating'said vapors to separate a final distillate product therefrom.

2. The process of converting higher-boiling hydrocarbons into lower-boiling hydrocarbons which comprises passing. a confined stream of relatively heavy 'oil, containing constituents unvaporizable under maximum temperature and minimum pressure conditions subsequently obtaining, through a heating zone, heating said oil during its passage through said zone to a conversion temperature, maintaining the products within said heating zone under a pressure sufficient to prevent complete vaporization thereof, subjecting said oil during its passage through said heating zone to conversion conditions, simultaneously passing a confined stream of relatively lighter oil, which is substantially completely vaporizabl'e under maximum temperature and pressure conditions subsequently obtaining in vapor form, through a separate heating zone, heating the vapors during their passage through said zone to a cracking temperature relatively higher than that maintained within said first-named heating zone, maintaining the vapors formed within said last-named heating zone at said relatively higher cracking temperature until the cracking has reached a stage where objectionable asphaltenes or tar-like particles are beginning to be formed, but before the asphaltenes or tar-like particles are converted to coke merging the converted products from said heating zones, passing the merged products through a final heating zone in a confined stream without materially reducing the velocity thereof so that the vapor and liquid constituents of said merged products are held in intimate contact with each other, maintaining said merged products at a conversion temperature substantially higher than the temperature attained by the heavy oil in said first-named heating zone and under a pressure sufficient to prevent vaporization of a substantial quantity of heavier constituents of said merged stream during their passage through said lastnamed heating zone, the unvaporized heavier constituents serving as a solvent and vehicle for asphaltenes or tar-like particles which are formed, thereafter separating the merged products into vapors and residue, and fractionating said vapors to form a final distillate product.

3. The process of converting higher-boiling hydrocarbons into lower-boiling hydrocarbons which comprises heating a confined stream of relatively heavy oil, containing constituents unvaporizable under temperature and pressure conditions subsequently obtaining, to a conversion temperature within a heating zone, maintaining said heavy oil under a pressure above about 400 pounds per square inch, simultaneously heating a confined stream of relatively lighter oil, which is substantially completely vaporizable under maximum temperature and pressure conditions subsequently obtaining in vapor form in a separate heating zone to a relatively high cracking temperature in excess of about 950 F., maintaining the vapors at said temperature within said second heating zone until the cracking has reached a stage where objectionable asphaltenes or tar-like particles are beginning to be formed, but before the asphaltenes or tar-like particles are converted to coke merging the converted products from said second-named heating zone 59 with the products from said first-named heating zone, passing the merged products while in a confined stream through a final heating zone without materially reducing the velocity thereof so that the vapors and liquid constituents of said 55 merged products are in intimate contact with each other, maintaining said combined products within said last-named heating zone at a conversion temperature substantially higher than the temperature attained by the heavy oil during its 50 passage through said heating zone and under 9.

pressure sufficient to prevent vaporization of a substantial quantity of heavy constituents of said merged products, the unvaporized heavier constituents serving as a solvent and vehicle for asphaltenes or tar-like particles which are formed, separating the converted products from said last-named heating zone into vapors and residue, and fractionating said vapors to form a final distillate product.

4. The process of converting higher-boiling hydrocarbons into lower-boiling hydrocarbons which comprises passing a confined stream of relatively heavy 011, containing constituents unvaporizable under maximum temperature and minimum pressure conditions subsequently 0btaining, through a heating zone, heating said oil during its passage through said zone to a conversion temperature, maintaining the products within said heating zone under a pressure suflicient to prevent complete vaporization thereof, subjecting said oil during its passage through said heating zone to conversion conditions, simultaneously passing a confined stream of relatively lighter oil, which is substantially completely vaporizable under maximum temperature and pressure conditions subsequently obtaining in vapor form, through a separate heating zone, heating the vapors during their passage through said zone to 'a cracking temperature relatively higher than that maintained within said first-named heating zone,

maintaining the vapors formed within said lastnamed heating zone at said relatively higher cracking temperature until from 30 to 40% of the charge to said separate heating zone has been converted into constituents boiling within the boiling range of gasoline and until the cracking has reached a stage where objectionable asphaltenes or tar-like particles are beginning to be formed, but before the asphaltenes or tar-like particles are converted to coke merging the converted products from said heating zones, passing the merged products through a final heating zone in a confined stream without materially reducing the velocity thereof so that the vapor and liquid constituents of said merged products are held in intimate contact with each other, maintaining said merged products at a conversion temperature substantially higher than the temperature attained by the heavy oil in said first-named heating zone and under a pressure suflicient to prevent vaporization of a substantial quantity of heavier constituents of said merged stream during their passage through said last-named heating zone, the unvaporized heavier constituents serving as a solvent and vehicle for asphaltenes or tarlike particles which are formed, thereafter separating the merged products into vapors and residue, and fractionating said vapors to form a final distillate product. 5

PIKE H. SULLIVAN.

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