US2093588A - Process of cracking heavy hydrocarbon oils - Google Patents

Description

Sept. 21, 1937. v L80. FORWARD 2,093,588

' PROCESS QF cnAcKIge HEAVY HYDROCARBQN 01155 Original Filed July 21, 192s 3 Sheets-Sheet 1 nor-on. 1-0 CONDENSER vAPo. HEAT Excmweaa on. aurPLY GASbLINK VAPOR FROM CRACKING cons g SUPERHEATED STEAM PUMP TWATER SUPPLY 5 Oil. FROM PUMb TO F RAC-TIONATING COLUMN HEATER "Po REF-LOX TANK WATER PUMP INVENTOR LOUIS. D-FORW D ATTORNEY Sept. 21, 1937. L D. FORWARD 2, PROCESS OF CRACKING HEAVY HYDROCARBON OILS I Original Filed July 21, 1926 s Sheets-Sheet 2 1 1 i: Z5 6 70 1s H GH P E55 R WATERQUPPBY E TO VPOR HEAT lf\ ExcHANGER Z9 76 3o V 37. I, I I}? I V, f

TOVAPOR HEAT WATER SUPPL* WATER SUPPLY INVENTOR LOUIS D- FORWARD ATTORNEY Sept. 21, 1937. I. D. FORWARD 2,093,588

PROCESS OF CRACKING HEAVY HYDROCARBON OILS Original Filed Jul 21. was s Sheets-Shet .3

CONDENSER WATER SUPPLY FLPSH BOILER INVENTOR LO IS D. FORWARD ATTORNEY 1i; atented Sept. 21, 1937 UNITED STATES OFFICE PROCESS OF @RACKING HIEA 1!:1 m

@ARBON OMS Louis D. Forward, New York, N. T 'assignor to Forward Process Company, New York, N. 1., a corporation or Delaware Original application July 21, 1926, Serial No.

Divided and this application November 3, 1934, Serial No. 751,376

14 Claim.

quired with consequent reduction in the overall capacity of the apparatus, together with loss in fuel due to the cooling and reheating of the system. v

, This application is a division of my pending application Serial No. 123,829 filed July 21, 1926, for Process of cracking heavy hydrocarbon oils. The present invention is particularly applicable to vapor phase cracking processes of the type described in the application of Chauncey B. Forward, Serial No. 682,477 filed December 24, 1923 but may be applied advantageously to other cracking processes in which heavy oils are cracked at high temperature and pressure to produce lighter and lower boiling point oils therefrom. In such processes for cracking petroleum controllable heating means, it has been found possible to raise the oil to and considerably above the cracking temperature, and to continue the operation for a prolonged period without the deposition of carbon in the heating zone. If the vapors liberated are then subjected to a digest-' ing operation in an enlarged heat-insulated chamber or zone, either with or without the presence of a catalytic agent, an additional percentage of the vapors are decomppsed and any small amount of free carbon released may be allowed to settle and be withdrawn from the system. When the vapors are withdrawn from the heating zone or digesting operation and cooled a considerable deposit of carbon is formed during cooling while the vapors are passing through the lower range of temperature at which cracking takes place which deposit is frequently of a hard coke-like nature which adheres to and bakes on the walls of the passage and eventually fouls the apparatus. This condition necessitates stoppage of operation, cooling of the system, and removal of such deposits.

I have discovered that by suddenly cooling the vapors from at or above the cracking temperature to a point below the cracking temperature by the injection of a cooling fluid, such as water, this o'bjectional deposition of carbon during the preliminary cooling operation, may be entirely prevented, thereby avoiding fouling of the apparatus and cessation of operation'and the delays and losses incidentthereto.

Accordingly in practicing or applying the present invention the oil may be heated according to any of the known methods in use, to or above the cracking temperature, and maintained, at such temperature for a sufficient length of time to assure conversion of a substantial amount of the heavy constituents to lighter constituents. The oil may be subjected to this additional treatment while passing through a continuous coil to which heat is supplied in suflicient quantities to pro-----"' vide the heat required for the decomposition of the heavier constituents and compensate for heat lost by radiation, or the oil may be further subjected to a digesting treatment in an enlarged chamber from which loss of heat by radiation is prevented by insulation or by supplying an additional amount of heat thereto, either with or without the presence of a catalytic agent, during which time an additional amount of the heavier constituents are cracked. In some cases it may be advantageous to employ more than one digesting operation, for example, the oil may be maintained at or above the cracking temperature for a considerable time in the heating coils and subsequently heated or digested in an enlarged heat insulated chamber.

At the point of withdrawal of the vapors from the digesting operation and before the vapors have been permitted to cool materially I subject the vapors to a sudden chilling operation by injecting into the vapor line a cooling fluid, for example water, saturated steam or a portion of the condensed distillate. The quantity of cooling fluid injected may be sufiicient to produce a complete condensation or may be merely suflicient to chill the vapors to a temperature below that at which further decomposition will take place. The remaining heat in the partially cooled vapors may be utilized in a heat exchanger to preheat fresh fluid into the hot vapors.

charging stock. The heat exchanger may be advantageously arranged to function as a dephlegmator or fractionating tower the heavier vapors being fractionally condensed, the condensate withdrawn therefrom and the uncondensed vapors passed to a final condenser.

The pressure may be reduced at the'point of withdrawal of the vapors from the digesting chamber to substantially atmospheric pressure or to a pressure intermediate that of the chamber and atmospheric, or pressure may be maintained to or beyond the dephlegmator, heat exchanger, or the final condenser.

According to another modification of the present invention the vapors may be subjected to the above chilling treatment by injecting the cooling fluid into the vapor line direct from the heating zone.

As an exemplification of the scope of the invention and its applicability to various methods of cracking hydrocarbon oils, I present the following description and the annexed drawings showing various forms of devices and apparatuses for practicing my invention including diagrams which illustrate in part the improved method or treating heavy hydrocarbon oils devised by C. B. Forward, and one other known method in which a catalytic chamber is employed. However, it is to be understood that the reference to and showing of the diagram is merely illustrative and that the present invention is not limited thereto, as it is evident that various modifications of the invention may be employed without departing from the spirit of the invention as set forth in the appended claims.

In the accompanying drawings, Fig. 1 is a more or less diagrammatic representation of an apparatus similar to that described in the U. S. application of C. B. Forward. Serial No. 682,477, concerning which I am very familiar, and in connection with which I was led to devise the present invention. Fig. 2 is a diagram showing an adaptation of the present invention in connection with a known oil treating apparatus in which a catalytic chamber is employed. Figs. 3, 4, and 5, are sectional views of several diflerent forms of devices which may be used to introduce the cooling Fig. 6 is a diagram-- matic representation partly in section of the apparatus described in the application of C. B. Forward, Serial No. 682,477, with the exception of the carbon settling chamber 35, which apparatus is modified to include the chilling means described in detail hereinafter.

Referring to Fig, 1, the apparatus shown therein is in part the same as devised and used by C. B. Forward, of Urbana, Ohio, for treating hydrocarbon oils by steam superheated to a high degree of superheat, wherein-the highly cracked product is discharged into a vertical drum A which I have termed a carbon settling column. This drum, in practice, is heavily insulated to prevent heat loss, and it is provided with a manhead 2 which may be removed to permit inspection of the interior. A subcarbon chamber 3 is connected to the bottom of drum A into which any finely divided free carbon which may settle in the column A may be blown through a pipe connection 4. The subcarbon chamber 3 may be cut oil from the main column by means of a valve 5 and a bottom plate 6 may be removed without interrupting operation of the main system.

The oil to be cracked may be pumped through a pipe 1 to a coil 8 in a vapor heat exchanger 9, where the feed oil is heated by the hot vapors discharged from drum A through a connecting pipe I0. Reflux condensation of the heavy insufiiciently cracked vapors is produced by the cooling effect of the feed oil and the condensate which collects in the bottom of heat exchanger 9 may be withdrawn through a pipe connection ll fitted with a suitable control valve I2.

The hot oil passes from coil 8 in heat exchanger 9 to a series of heating and cracking coils in a series of steam heat exchangers (Fig. 6) where it is heated to the cracking temperature and conveyed by a pipe l4 into the drum or carbon settling column A in vapor form. The hot vapors which collect in drum A are maintained under a pressure of approximately 225 lbs. per square inch and temperature of 950 degrees, Fahrenheit.

The hot oil vapors are discharged from the drum or carbon settling column A through pipe line III, which contains a regulator R by means of which the pressure in the carbon settling column may be controlled, and the vapors thence pass to the shell of vapor heat exchanger 9. I have discovered that carbon deposits could be eliminated by pumping water or other cooling fluids under pressure into the line at the point at which the extremely hot vapors are withdrawn from drum A. The cooling fluid is introduced into the line in the form of a jet I5, and the quantity of cooling fluid to be introduced may be regulated by a valve l6 to reduce the temperature of the vapors to any desired temperature.

It is not essential that the cooling fluid shall be water, as other substances such as a portion of the distillate formed, may be used to produce the desired chilling effect, although I prefer water because of its high latent heat and because of the beneficial effect the steam formed therefrom has upon the quality of the distillate obtained. The pressures maintained on the various parts of the system are not an essential part of the present invention, as these may vary considerably with different charging stocks, or when the system is operated to produce different grades or types of distillates therefrom. Any' vapors not condensed in the vapor heat exchanger 9 pass to the final condenser [1.

Referring to Fig. 6 of the drawings, the apparatus of the Forward application Serial No. 682,477 is shown in detail with the chamber 35 omitted and a means inserted in the vapor line to illustrate the form of the invention involving the sudden chilling of the cracked vapors directly as they leave the heated digestion coils of the apparatus. The cracking apparatus shown diagrammatically in Fig. 6 comprises a series of heaters l to ill supplied with a heating medium such as superheated steam. The superheated steam is produced by a flash boiler I 8 which comprises a water heating and superheating coil l9 supplied with water from a source 20 and a condu it 2| in which is mounted a pump 22. Superheated steam of a temperature which may approximate 1200 F. or higher is conducted from the lower part of the boiler through a conduit 23, and supplied to a header 24 which is connected by means of valved supply pipes 25 with the cylindrical heaters 5 to I0. A second header 26 is also connected into cylindrical heaters 6 to ID by means of separate valved steam discharge pipes 21. The superheated steam conducted through the separate pipes 25 to heaters 6 to I is passed aoeatec at reduced temperatures through the connecting pipes 21! into the heater 26 from which the steam is then conducted through a pipe 26 into cylindrical heater 4. Heaters 4 and are providedwith steamdischarge pipes 29 which conduct steam at reduced temperature through a pipe 3t into the cylindrical heater 3. The exhaust steam from the heater 3 is then passed through a pipe ti into the heater 2 and from the latter through a pipe 32 into the heater i. heater l is conducted through a pipe ti into a steam drum 34 from which steam may be conducted through a valved pipe lit to the. pumps or other power and heating apparatus used in the plant. The superheated steam supplied through the line it may be at a pressure of 250 pounds per square inch or higher, and the steam in drum 3t may be at approximately 200 pounds per square inch.

The oil to be treated in the apparatus shown in Fig. 6 may be withdrawn from storage through a line it and passed by means of a pump through a line at, a coil it mounted in a vapor heat exchanger 3t, and then through a line M to a relatively long coil ti mounted in the heat exchange cylinder l. The remaining heaters t to it inclusive containing similar long coils of pipe ti connected in series with each other and with the first coil mounted in cylinder Ii, so that the oil and vapors flow through the coils successively. The oil passing through the coils all is converted into vapor-and heated to a high cracking temperature which is maintained throughout the latter coils in chambers i to it so that the oil constituents receive a digestion treatment.

The oil vapors at a temperature above 900 F. (975 to 980 F.) are discharged from the coil of the last heater it through a line it and directly brought into contact with a cooling fluid such as water discharged into a jet mechanism it so that the vapors are suddenly chilled to a temperature below 700 F. 'Water for effecting this chilling operation may be withdrawn from the water supply ttrthrough a valved line it and forced by means of pump tt and a pipe tit into the Jet mechanism iii. The amount of water supplied through the line it may be controlled by valve it to efiect the specified temperature reduction in the vapors. The fluids other than water referred to above may be used as cooling media and in such case they may be admitted to the pump tit through the valved line t5 instead of water.

The mixture of oil vapors and chilling media is conducted through a line it into the lower part of heat exchanger 3% so that the vapors come in contact with the heat exchange coil W. The vapors passing through the heat exchanger it may be cooled sumciently to condense substantially all constituents of higher boiling point than the desired gasoline or pressure distillate, and such condensate may be withdrawn through a line liprovided with a valve it. The desired gasoline constituents as vapors are conducted from the heat exchanger 39 through a vapor line t1! to a final condenser l'i where the gasoline vapors are condensed. The vapor transfer lines it and ti are provided with pressure-reducing valves R so that the pressure on the oil constituents may be reduced either in the line it or in the line M as stated above.

In cracking a gas oil the following temperature conditions were found to give good results such as would enable the process to be carried on continuously, but it is to be understood that thesev examples are merely illustrative of one particu- The exhaust steam from larly advantageous method of operation, and that the present process should not be limited thereto. as improved results have been obtained in operating over a wide range of temperatures and pressures with a number of different grades of charging stocks. Thus, in one instance the feed oil, a 38 degree Baum gas oil with an initial boiling point of 450 degrees F. was heated to about 550 degrees F. in the vapor heat exchanger. In passing through the first steam preheaters the temperature of the oil was raised to about 900 degrees F. and maintained above this temperature throughout its passage through the remainingheaters and the carbon settling column A. A sumcient quantity oi water was introduced at jet it to reduce the temperature of the vapors very quickly to below 700 degrees F. No carbon was deposited in the vapor line or other part or the system through which said vapors subsequently passed.

A subsequent fractional distillation of the condensate indicated a conversion of 60 per cent of the initial charging stools into a 450 degree F.

end point gasoline. The carbon released during the operation amounted to about .05 per cent of the charging stock and was in the form of a dry finely divided powder which was readily removed from the carbon settling column through blow 0d connection t.

Referring to Fig. 2, this diagram represents another embodiment of the present invention in. a modified iorm oi a vapor phase cracking apparatus. In the arrangement of apparatus shown therein, the oil to be treated is supplied by a pump (not shown) to heat exchanger it where it is preheated by heat exchange with the hot vapors. The preheated oil is then passed to the heater it and from an intermediate point there in the heavy unvaporized oil may be withdrawn. From the heater it the hot vapors pass through apipe it to a catalytic chamber 2t and thence through a pipe it to a heat exchanger 22. A cooling fluid, for example; water, is introduced through a jet it into pipe line it between catalytic chamber 2t and heat exchanger 22, thereby suddenly reducing the temperature of the vapor inthe required degree and preventing the deposit oi carbon in that line and anysubsequent part of the system.

Referring to Fig. 3, the device shown therein is the same as delineated in Fig. 1, except that it is made on a larger scale. The device comprises a flanged coupling member it ailixed to the top or drum it having a vertical passage in which a rotatable and reciprocable clean out plunger it is confined. The plunger is provided with a hand wheel it and an operating screw it which is supported by a yoke it secured to the upper edge of coupling member 2d. The Jet or spray member it through which the cooling fluid is introduced into the horizontal passage it and pipe it may be connected, ior example, with the water supply pipe it which extends through the closure plate it for one end of passage 2t.

pling member and a jet W at the lower end of this extension. Jet 36 has vertical discharge openings in its upper face to jet the cooling fluid upwardly into the mouth of the discharge passage. The drum and vapor pipes are covered with asbestos or other suitable heat-insulating material, not shown in Figs. 4 and 5, but substantially as delineated by the outer layer or covering 31 in Fig. 3.

What I claim is: I

1. The process of cracking hydrocarbon oils for the production of gasoline-like products, which comprises subjecting the oil to be cracked to a high cracking temperature in a heating zone, passing the resulting highly heated products into an enlarged zone and discharging vapors therefrom through a vapor outlet, and introducing a cooling fluid directly intothe Vapors as they enter said vapor outlet in such a manner that the vapors and cooling fluid flow concurrently into said outlet.

2. The process of cracking hydrocarbon oils for the production of gasoline-like products, which includes the steps of discharging'high temperature oil vapors from an enlarged zone through a vapor outlet, and introducing a stream of water directly into the vapors immediately prior to and as they enter said outlet in such a manner that the vapors and water flow concurrently into said. outlet.

3. The process of cracking hydrocarbon oils for the production of gasoline-like products, which comprises subjecting the oil to be cracked to a high cracking temperature, passing the resulting products into an enlarged zone from which vapors are withdrawn through a vapor outlet, and introducing steam having a temperature substantially below that of said vapors directly into the vapors being discharged through said outlet in such a manner as to cause a concurrent flow of vapors and steam into the vapor outlet.

4. In the art of cracking hydrocarbon oils wherein a body of oil vapors is maintained at cracking temperature within an enlarged reaction chamber and vapors of said body are withdrawn from said chamber, the improvement which comprises injecting a relatively cool vaporizable liquid medium only into that portion of the said body of vapors within said chamber which is in substantially immediate proximity of the point of withdrawal of said vapors, remov-,

ing substantially all of the said cooling medium with the said vapors being withdrawn from said chamber, and avoiding cooling of a substantial portion of said body 0! vapors within said chamher.

5. In the art of cracking hydrocarbon oils wherein a body of oil vapors is maintained at cracking temperature within an enlarged reaction chamber and vapors of said body are withdrawn from said chamber, the improvement which comprises discharging as a cooling medium a v aporizable hydrocarbon oil into that portion of the vapor body which is in immediate proximity to the point from which vapors are withdrawn from said chamber, removing substantially all'oi the said cooling oil with the said vapors being withdrawn from said chamber, and avoiding cooling of a substantial portion of said body of vapors within said chamber.

range therefrom which comprises heating hydrocarbon oils to vaporize the oil and bring the oil vapors to an elevated cracking temperature, introducing the heated vapors into an enlarged chamber wherein they are maintained in a body and at a cracking temperature whereby substantial further cracking of the cracked vapors is eifected, removing vapors from said chamber, discharging a liquid cooling medium within the chamber substantially only into the vapors being removed from the chamber, and causing substantially all of said cooling medium to be carried by the outgoing vapors, thereby avoiding cooling of a substantial portion of the body of vapors undergoing cracking in said chamber.

7. Themethod of effecting decomposition of hydrocarbon oils in the vapor phase to produce lighter products in the gasoline boiling point range therefrom which comprises heating hy- 'drocarbon oils to completely vaporize the oil and bring the oil vapors to an elevated cracking temperature, introducing the heated vapors into an enlarged chamber wherein they are maintained in a body and at a cracking temperature whereby substantial further cracking of the cracked vapors is effected, removing vapors from said chamber,

and discharging as a cooling medium a vaporiz-' able hydrocarbon oil within the chamber substantially only into the outgoing vapors, thereby cooling the outgoing vapors and vaporizing said 011, and removing substantially all of said cooling oil with the outgoing cracked vapors, thereby avoiding cooling of a substantial portion of the body of vapors undergoing cracking in said chamber.

8. The process of cracking hydrocarbon oils for the production of gasoline-like products, which comprises heating the oil to a high cracking temperature in a heating zone passing the resulting highly heated products into an enlarged zone from which vapors are discharged through a vapor outlet line and suddenly cooling the vapors as they leave said enlarged zone throughsaid vapor outlet line to a temperature below that at which carbon deposition would take place in said vapor line by introducing a cooling fluid directly into the vapors in the outlet line as they leave said enlarged zone, the cooling fluid passing with the discharged materials in said line.

9. The process of cracking hydrocarbon oils as defined by claim 8 in which a substantial superatmospheric pressure of at least approximately 200 lbs. per square inch is maintained in said enlarged zone and in which the cooling oi! the vapors in the vapor outlet line is eflected at approximately the pressure maintained in said enlarged zone.

10. The process of cracking hydrocarbon oils as defined by claim 8 in which the vapors in said enlarged zone are at a temperature above,900 F.

11. The process of cracking hydrocarbon oils as defined by claim 8 in which the vapors in the vapor outlet line are very quickly cooled to a temperature below about 700 F.

12. In the art of cracking hydrocarbon oils wherein a body of oil vapors is maintained at a relatively high cracking temperature within an enlarged reaction zone adapted to receive a substantial accumulation of carbon and vapors of said body are converted to products in the gasoline boiling point range, the improvement which comprises discharging the highly heated cracked vapor products from said enlarged zone at a relatively high cracking temperature in a stream of substantially smaller cross-section than that of said enlarged zone for subsequent fractionation to recover the products boiling within the gasoline range, and before the vapors have been perzone are supplied to said zone from a cracking mitted to cool to a temperature at which coke formation would occur reducing their temperature very quickly to a temperature below that at which coke formation and deposition would take place by bringing a relatively cool cooling fluid directly into intimate contact with the vapors of said stream but only after they are discharged from said enlarged reaction zone in sufiicient quantity to effect said quick reduction in temperature and thereby prevent formation and deposition of coke from the vapors while the vapors are being cooledthrough the range of cracking temperatures at which such coke formation and deposition would occur, the cooling fluid passing with said vapor products discharged for subsequent fractionation.

13. The process of cracking hydrocarbon oils as defined by claim 12 in which the oil' vapors I subjected to conversion in said enlarged reaction zone in which the oil to be cracked is heated in a confined stream of restricted cross-section and a substantial proportion thereog. converted to products in the gasoline boiling range.

14. The process of cracking hydrocarbon oils for the production of gasoline-like products, which includes the steps of discharging high temperature oil vapors from an enlarged digestion zone through a vapor outlet line, and reducing the temperature of the vapors very quickly to a temperature below that at which carbon deposition in the line would take place by introducing a sufficient quantity of a cooling fluid directly into the vapors in the vapor line substantially at the point of withdrawal of the hot vapors from the enlarged digestion zone, the cooling fluid passing with the vapors in the vapor liner LOUIS D. FORWARD.

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