US2160814A - Processing hydrocarbon oils - Google Patents

Description

Patented June 6, 1939 UNITED STATES PATENT OFFICE PROCESSING HYDROOABBON OILS ration of Indiana Application June 25, 1937. Serial No. 150,808

'IClaims.

This invention relates to the process oi converting heavy hydrocarbon oils, including reduced crude oil and gas oil, to lower boiling oils, particularly gasoline. In the cracking oi hydrocarbon oils it has generally been the practice to remove from the crude oil a distillate charging stock or gas oil which was then subjected to pyrolysis at elevated temperatures to convert a portion of it into gasoline, gas and tar. The high boiling point oi the tar made it possible to eflect a separation between undesirable coke-forming tarry by-products and the unchanged gas oil which was separated as a distillate in an evaporator tower and iractionator and recycled to the 16 zone of pyrolysis. When charging residual stocks to the cracking unit, however, such a sharp separation cannot be made by distillation between the undesirable tar and the unchanged charging stock, and accordingly considerable unchanged 20 cracking stock was lost by being discarded with the undesirable tar.

An object of this invention is to make a clean separation between the unchanged heavy charging stock and the tar produced in the cracking system and to recycle the charging stock until its gasoline-producing potentialities are exhausted. Another object of the invention is to combine a gas oil cracking operation with a residual oil cracking operation, discharging both stocks into the same evaporator tower and extracting the combined tar with a liquefied normally gaseous hydrocarbon to produce an ultimate asphalt and a recovered oil which may be recycled to the cracking zone. Still another object of the invention is to separate from the recovered oil fraction containedin the tar two fractions of diil'erent average molecular weight, recycling the heavier fraction to the residual oil cracking zone and the lighter fraction to the gas oil cracking zone.

0 The accompanying drawing, which forms a part of this specification, shows an arrangement 0! three cracking zones, one for reduced crude, and

one-each for light gas oil and heavy gas oil, and extraction apparatus for separating asphalt from 45 the recycle oil in the tar and for separating and recycling to different cracking zones, two grades of recycle oil.

Referring to the drawing, reduced crude, which, in this example, may be a Mid-Continent reduced 50 crude, is introduced by line ID to heater II and for this purpose a 40% residual fraction from Mid-Continent crude oil may be employed. In heater II the oil may suitably be maintained under a pressure 0! about 100 to 750 pounds per 55 square inch with an outlet temperature of about 850-930' F. The hot products are conducted by line I! to evaporator tower II where volatile products are removed and unvaporlzable constituents are withdrawn as a tar through line ll.

Simultaneously, a heavy gas oil fraction having I an A P. I. gravity of about 25-30 is introduced by line It into heater l6 where it is suitably heated to a temperature of about 900-950 F. at any suitable pressure, for example between 200 and 800 pounds per square inch. The hot gas oil l0 vapors are conducted by line II to evaporator tower I! where they mingle with the vapors discharged irom heater Ii.

Similarly, a light gas oil which may have an A. P. I. gravity or about 30 to 40 is introduced 18 by line Ill into heater is where it is subjected to a high cracking temperature in the range of 925 to 1050 F., the pressure being suitably maintained between 200 and 800 pounds per square inch. The light gas oil introduced through line l8 go may contain a considerable proportion of heavy naphtha boiling within the gasoline boiling range which it is desired to reform in order to increase its knock rating. The oil discharged from heater i9 is conducted by line 2|] and soaking drum 2| to evaporator tower H where it is commingled with the oil and vapors from furnaces ii and I6. Sufllcient soaking volume may be supplied in the furnace with the elimination of the drum 2|. The hot vapors from the gas oil furnaces assist an in distilling the product from heater I i to produce a clean distillate vapor which is withdrawn from evaporator tower It by line 22. Buflicient heat is introduced into evaporator tower l3 by the three hot oil-vapor streams I have just described to 35 eil'ect a clean separation between the volatile fractions and the non-volatile tarry fractions in tower [3. This separation is assisted by reflux cooling coil 28 or other equivalent means or cooling, such as returning a cooled portion or the m distillate fraction to the top of the evaporator tower. At an intermediate point of the evaporator tower a heavy gas oil fraction is removed as a side stream by line 24 and conducted to the inlet of heater it for recirculation. This stock will have about the same distillation characteristics as the fresh 01] charged by line ll, although the A. P. I. gravity will usually be lower. Vapors from evaporator tower II are led by line 22 to bubble tower 2i. Gasoline vapors are conducted from the top of said bubble tower to condenser and receiving drum 28 and 21. The condensed liquid fraction separating in bubble tower 25 is withdrawn at the bottom through line 2! by which it is recycled to the inlet of the light gas oil cracking furnace. I! desired. reduced crude oil may be introduced by line 2! into the lower portion of evaporator tower l3, the amount so introduced being regulated to control the temperature and performance 0! the evaporatortower.

The unvaporized oil or tar withdrawn from evaporator tower II by line H is conducted through cooler 30 and thence to extractor 31 where it is brought into contact at ordinary temperature, for example 70 to 100" R, with a solvent which is introduced by line 32, the tar suitably passing over bailles for this purpose. The extract solution is withdrawn at the top of the separator through line 33 leading to heater 34 where the temperature is increased to a point in the vicinity oi the critical temperature 0! the solvent. For example, when employing liquid propane as the solvent the temperature of the extract in heater 34 may suitably be about 140 to 220 F. In the case where butane is employed as the solvent the temperature may suitably be raised to about 250 to 315 F. The heated oil is introduced into separator 35 where the increased temperature causes a separation of the extracted oil into two fractions, a light oil and a heavy oil, the light oil together with the major portion of -the solvent being withdrawn from the top of separator 35 by line 36 leading to propane evaporator 31 and the heavier oil fraction being withdrawn by line 38 to propane evaporator 39.

The insoluble portion of the tar collecting in the base oi extractor 3| is withdrawn by line Ml leading to evaporator H where propane is removed and the normally solid asphalt which is substantially free from oil fractions is discharged in the heated condition by line 42. Propane withdrawn from separators 31, 39 and ll is conducted by lines 43 and II to condenser 45, where the propane vapor is reliquefied under pressure and conducted to propane storage drum 46 whence it is withdrawn by line 32 and pump 41 as desired.

The light extract from the base of separator 31, which may have an A. P. I. gravity of about -30, is conducted by line 48 to the inlet of the heavy gas oil heater i6 where it is commingled with the heavy gas oil previously described. Thus gas oil which is insufiiciently volatile to dlstil into the upper section 01 evaporator tower l3 and to recycle to the heavy gas oil heater lli as a side stream in line 24 will be conducted to the propane extraction system where it may readily be recovered and returned to the gas oil heater l6 as desired. Likewise, heavy constituents oi: the reduced cmde oil which are charged'into the system and escape cracking in the initial pass through the heater II are recovered in the solvent extraction operation in drum 38, and returned by line 49 to the cracking system for further conversion into gaso1ine.- As a result of this combination of steps I am enabled to obtain a higher yield of gasoline from a given charging stock and at the same time obtain a higher knock rating by virtue of the separation o! the stock into a relatively clean light gas oil fraction which may be cracked at a much higher temperature to produce a maximum 01' anti-detonating constituents. It is preierred'to employ a large amount of reflux in evaporator tower II for the purpose oi knocking back tarry constituents which would otherwise be carried through vapor line 22 into bubble tower where contamination of the feed to furnace is would result. The heavy gas oil fraction withdrawn by line 24, being of higher molecular weight and more readily cracked, is required to be subjected to less severe cracking conditions and therefore trouble with coking oi furnace it is avoided. A still lower temperature is used in furnace II, the main purpose of which is to viscosity break the reduced crude into products which are subsequently cracked in heaters l3 and I8. By my process I am enabled to employ a high reflux ratio in the upper, bellied section of evaporator l3 without loss oi valuable cracking stock in the tar withdrawn through line ll, since this stock is subsequently treated with propane and recovered.

Although I have described my process by speciflc examples thereof, I intend that my invention be limited only by the following claims.

I claim:

1. The process of converting heavy hydrocarbon oils into motor fuel which comprises viscosity breaking a residual oil in a viscosity breaking zone, cracking a gas oil in a gas oil cracking zone, evaporating the hot products oi. said viscosity breaking and gas oil cracking operations, separating gasoline from the vaporized fraction of said products, combining and cooling the unevaporated portions 0! said products, extracting said cooled unevaporated products with a liquefied normally gaseous hydrocarbon solvent at a temperature substantially below the critical temperature of said solvent, separating the undissolved traction oi. said products from the extract, heating said extract to a temperature in the vicinity of .the critical temperature of the said solvent whereby it is separated into a light recycle oil fraction and a heavy recycle oil fraction, recycling said light recycle oil traction to the said gas oil cracking zone and recycling the said heavy recycle oil fraction to the viscosity breaking zone.

2. The process of converting heavy hydrocarbon oils into gasoline which comprises subjecting a heavy residual oil to viscosity breaking in a viscosity breaking zone, subjecting a heavy gas oil to cracking in a heavy gas oil cracking zone, subjecting a light gas oil to cracking at a higher temperature in a light gas oil cracking zone, separating the products of said cracking operations into a vaporized and an unvaporized fraction, removing gasoline from said vaporized fraction, cooling said unvaporized fraction and subjecting it to extraction with a liquefied normally gaseous hydrocarbon at a temperature substantially below the critical temperature thereof, separating an insoluble asphaltic fraction from the extract, heating the extract to a temperature in the vicinity of the critical temperature oi the said solvent whereby two liquid phases are produced, recovering a relatively light recycle oil from one of said phases and recycling it to said heavy gas oil cracking zone and recovering a relatively heavy recycle fraction from the other of said phases and recycling it to said viscosity breaking zone.

3. The process of claim 2 wherein a distillate fraction boiling above the boiling range of gasoline is separated from said vaporized traction in a fractionating zone and recycled to one oi said gas oil cracking zones.

4. In the process of converting heavy hydrocarbon oils into gasoline of high knock rating wherein a heavy residual incompletely vaporizable oil, a high boiling gas oil and a low boiling gas oil are separately heated to cracking conditions under pressure, whereby the oils are partially converted into gasoline which is separated from the hot products and the unconverted portions oi the oils are recycled to the cracking operations, the improvements comprising viscosity breaking the residual oil at a temperature of about 850 to 925 F. and discharging the hot products into an evaporating zone, heating said heavy gas oil to a temperature of about 900 to 950 1''. and conducting the hot products to said evaporating zone, heating the said light gas oil to a temperature oi about 925 to 1050' F. and conducting the hot products to said evaporating zone, separating an unvaporized traction from the vaporized products in said evaporating zo'ne, condensing a portion oi said vaporized products as heavy reflux condensate therein and in troducing said heavy reflux condensate into said heavy gas oil cracking zone, Iractionating said remaining vapors in a tractionating zone to pro duce a gasoline distillate and a reflux condensate, introducing said reflux condensate into said light gas oil cracking zone, withdrawing and cooling said unvaporized fraction from said evaporating zone and extracting it with a liquefied normally gaseous hydrocarbon solvent selected from the class consisting of propane and butane, removing solvent from the insoluble portion and discarding the high boiling insoluble portion as a high melting asphalt, conducting the extract to a separating zone maintained at a higher temperature in the vicinity of the critical temperature of the said solvent whereby separation into two phases occurs and separating said extract into a light recycle oil phase and a heavy recycle oil phase, removing solvent from said light recycle oil phase and introducing the oil into the said heavy gas oil cracking zone, removing propane from said heavy recycle oil phase and introducing the oil into said viscosity breaking zone.

5. The process of claim 4 wherein solvent removed from said insoluble fraction and said light and heavy recycle all phases is condensed and returned to said extraction zone.

6. The process of claim 4- where in a portion of said heavy residual incompletely vaporizable oil is introduced into said evaporating zone below the point of withdrawing said heavy reflux condensate and directly in contact with hot products from said cracking zones whereby said portion is preheated and partially evaporated and said hot cracking products are quenched, thereby preventing undesirable formation or coke in said evaporating zone.

7. In the process of converting heavy hydrocarbon oils to antiknock motor fuels wherein a heavy distillate oil and a light distillate oil are subjected to cracking in separate conversion zones and a residual oil is subjected to viscosity breaking in a third conversion heating zone and the resulting cracked vapors are combined in' an evaporating zone, the improvement comprising substantially cooling the vapors released in said evaporating zone and condensing therefrom all coke-forming constituents, subsequently subjecting said vapors tree from coke-forming constituents to a fractionating operation and separating them into gasoline and a clean distillate recycle stock, charging said recycle stock to said light distillate conversion zone and subjecting it to a high conversion temperature between 925 and 10 50 F. whereby a motor fuel of high knock rating is produced, withdrawing from said evapcrating zone condensate containing coke forming constituents, cooling said condensate and subjecting it to the selective solvent action of a liquefied normally gaseous hydrocarbon whereby heavy hydrocarbons substantially free from cokei'orming constituents are selectively dissolved therein, heating the solution of said heavy hydrocarbons and liquefied gas to a temperature in the vicinity oi the critical temperature of said gas, whereby said solution is separated into a heavy fraction and a light fraction, returning said heavy fraction to said residual oil conversion zone and returning said light traction to said MAURICE H. ARVESON.

CERTIFICATE OF CORRECTION.

June 6, 1959.

MAURICE H. ARVESON.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, first column, line 32, claim h, for the word "propane" read solvent; and-that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 18th day of July, o. 19 9.

(Seal) Henry Van Arsdale, Acting Commissioner of Patents.

perature of about 850 to 925 F. and discharging the hot products into an evaporating zone, heating said heavy gas oil to a temperature of about 900 to 950 1''. and conducting the hot products to said evaporating zone, heating the said light gas oil to a temperature oi about 925 to 1050' F. and conducting the hot products to said evaporating zone, separating an unvaporized traction from the vaporized products in said evaporating zo'ne, condensing a portion oi said vaporized products as heavy reflux condensate therein and in troducing said heavy reflux condensate into said heavy gas oil cracking zone, Iractionating said remaining vapors in a tractionating zone to pro duce a gasoline distillate and a reflux condensate, introducing said reflux condensate into said light gas oil cracking zone, withdrawing and cooling said unvaporized fraction from said evaporating zone and extracting it with a liquefied normally gaseous hydrocarbon solvent selected from the class consisting of propane and butane, removing solvent from the insoluble portion and discarding the high boiling insoluble portion as a high melting asphalt, conducting the extract to a separating zone maintained at a higher temperature in the vicinity of the critical temperature of the said solvent whereby separation into two phases occurs and separating said extract into a light recycle oil phase and a heavy recycle oil phase, removing solvent from said light recycle oil phase and introducing the oil into the said heavy gas oil cracking zone, removing propane from said heavy recycle oil phase and introducing the oil into said viscosity breaking zone.

5. The process of claim 4 wherein solvent removed from said insoluble fraction and said light and heavy recycle all phases is condensed and returned to said extraction zone.

6. The process of claim 4- where in a portion of said heavy residual incompletely vaporizable oil is introduced into said evaporating zone below the point of withdrawing said heavy reflux condensate and directly in contact with hot products from said cracking zones whereby said portion is preheated and partially evaporated and said hot cracking products are quenched, thereby preventing undesirable formation or coke in said evaporating zone.

7. In the process of converting heavy hydrocarbon oils to antiknock motor fuels wherein a heavy distillate oil and a light distillate oil are subjected to cracking in separate conversion zones and a residual oil is subjected to viscosity breaking in a third conversion heating zone and the resulting cracked vapors are combined in' an evaporating zone, the improvement comprising substantially cooling the vapors released in said evaporating zone and condensing therefrom all coke-forming constituents, subsequently subjecting said vapors tree from coke-forming constituents to a fractionating operation and separating them into gasoline and a clean distillate recycle stock, charging said recycle stock to said light distillate conversion zone and subjecting it to a high conversion temperature between 925 and 10 50 F. whereby a motor fuel of high knock rating is produced, withdrawing from said evapcrating zone condensate containing coke forming constituents, cooling said condensate and subjecting it to the selective solvent action of a liquefied normally gaseous hydrocarbon whereby heavy hydrocarbons substantially free from cokei'orming constituents are selectively dissolved therein, heating the solution of said heavy hydrocarbons and liquefied gas to a temperature in the vicinity oi the critical temperature of said gas, whereby said solution is separated into a heavy fraction and a light fraction, returning said heavy fraction to said residual oil conversion zone and returning said light traction to said MAURICE H. ARVESON.

CERTIFICATE OF CORRECTION.

June 6, 1959.

MAURICE H. ARVESON.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, first column, line 32, claim h, for the word "propane" read solvent; and-that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 18th day of July, o. 19 9.

(Seal) Henry Van Arsdale, Acting Commissioner of Patents.

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