US2142075A - Conversion of hydrocarbon oil - Google Patents

Description

L. C. RUBIN CONVERSION OF' HYDROCARBON OIL Filed Feb. '18, 195e Dec 27, 193s.

INVENTOR ATTORNEY QN m Patented Dec. 27, 1938 UNITED STATES PATENT oFFicE CONVERSION OF HYDROCARBON OIL Application February 18, 1936, Serial No. 64,446

6 Claims.

This invention relates to a method of processing hydrocarbon oil and pertains more particularly to a method of processing raw crude oil, partially reduced crude or other similar relatively heavy stock containing lighter and heavier constituents, to produce a maximum yield of high anti-knock gasoline on the one han-d and a fuel oil having a viscosity to meet the required specifications on the other.

In the treatment of raw crude oil or the like to produce gasoline it has been a practice heretofore to rst subject the crude oil to distillation to vaporize and separate lower-boiling constituents therefrom. These lower-boiling constituents usually include the natural gasoline present in the original crude and other constituents above the gasoline boiling range which areamenable to relatively high temperature cracking which Will produce desirably high anti-knock gasoline.

After these lower-boiling constituents have been removed from the crude oil, it has been a practice in some cases to subject the residual reduced crude to mild cracking treatment under low crack per pass conditions principally for the purpose of forming additional quantities of lighter hydrocarbons which in turn may be subjected to relatively high temperature, high crack per pass cracking treatment which will produce a further yield of high-grade gasoline.

Itis a desideratum of oil processes of this character to recover from the crude oil all of those Vconstituents which may be converted into gasoline. This includes all of the petroleum oil with the exception of the very heavy residue of an asphaltic and tarry nature. This heavy residual product from the process does not have a Wide market because it is too viscous to meet standard speciiications for liquid fuel. In View of this it has been a practice in some cases to convert this heavy residual product into a solid coke which can be employed in solid fuel burners. However, since liquid fuel is usually preferred to solid fuel it has been a practice in other cases te blend this heavy residual product with a lighter hydrocarbon cil to lower the viscosity thereof sufficient te meet the standard specifications for liquid iuel. In the latter cases lighter oils which are least suitable for conversion into gasoline are chosen as blending agents. Such lighter oils may inciude, for example, lighter recycle gas oils resulting from drastic cracking treatment, natural or solvent separated naphthenic oils, et cetera. While these cils are less suitable for the production of gasoline by common cracking processes, e5 they can be subjected to independent cracking Li l (Cl. ISG- 49) treatment by the more modern processes. The use of such oils, therefore, as blending agents for fuel oil reduces the yield of gasoline which can be obtained from natural petroleum resources.

One of the objects of my invention is to provide a method for completely processing crude, topped crude oil or the like to produce an improved yield of high-grade gasoline and a liquid residual fuel cil which will meet standard viscosity specifications Without blending with a lighter oil stock.

Another object of my invention is to provide a method of processing a heavy oil such as crude or topped crude oil wherein the individual steps of the process are carried out in such a relation to each other as to improve the over-all efiiciency of the process.

Another object of my invention is to provide a method for processing hydrocarbon oil wherein the heavy residual oil resulting from the distillation and mild cracking treatment of the original charge is converted into a fuel oil of desired viscosity.

Another object of my invention is to provide a method for completely processing petroleum oil which Will produce fuel oil as an ultimate residual product and an improved yield of gasoline over that produced by other processes of comparable nature.

Other and more specific objects of my invention will become apparent from the more detailed description hereinafter.

The above and other objects will be obtained by certain novel steps and combination of steps constituting my invention which will now be described.

In accordance With my invention a crude oil, or an oil stock containing a preponderance of virgin constituents, is initially distilled to remove the lower-boiling constituents therefrom. The reduced crude residue is subjected to a mild cracking treatment principally for producing an intermediate gas oil stock which is subsequently subjected to drastic cracking treatment. The products from this mild cracking treatment are hereafter introduced into a distilling chamber maintained under temperature and pressure conditions which will vaporize all distillable fractions therefrom and produce as a residual product a heavy semi-solid viscous residue. This heavy residual product is then subjected to a mild heat treatment to reduce the viscosity thereof sufcient to meet standard specifications.

Vapors formed as a result of the mild cracking and viscosity reducing treatment are subjected to fractionation to separate therefrom a heavy condensate fraction containing the highest boiling constituents thereof, an intermediate condensate fraction and a final distillate product. The heavy condensate fraction may be combined with the reduced crude residue and re-subjected to mild cracking treatment. The intermediate gas oil fraction is passed once through a hightemperature furnace coil wherein it is subjected to maximum conversion into gasoline. The products from the high-temperature coil are separated into vapors and residue without being permitted to commingle with products resulting from the mild cracking' and Viscosity reducing treatment.

The vapors so separated are then fractionated to condense and separate higher-boiling insuiiiciently cracked constituents as reflux condensate from the final gasoline distillate. The reflux condensate is then passed through a separate heating coil wherein it is subjected to independent cracking treatment under conditions best adapted for this type of charging stock.

The products from this last-mentioned heating coil are then combined with products from the high-temperature heating coil and subjected to further treatment therewith.

With the above general outline and the nature and objects in view my invention will now be described in more specific detail in which refer- 'ence is made to the accompanying drawing which is a diagrammatic and simplified illustration of an apparatus suitable for carrying the invention into effect.

Referring to the drawing, the apparatus may comprise in general the combinedy crude distilling and fractionating tower I0, a low-temperature cracking furnace I I, a combined low-pressure distilling and fractionating tower I2 connected thereto, a low-pressure fractionating tower I3, a high temperature furnace I4, a separating chamber I5 connected therewith, a high pressure fractionating tower I6 together with the necessary pipe lines, valves, controls, heat exchangers and other appurtenant equipment for carrying out the process as hereinafter described.

Fresh crude charging oil, after preliminary heating to a distilling temperature, for example, by indirect heat exchange with hot products resulting from the subsequent cracking step, or after having been heated in a directly fired coil, or both, is forced through charging line 20 by means of pump 2| to the bottom section of the combined crude-.distilling and iractionating tower I0, wherein lighter constituents thereof are liberated as vapors. These lighter constituents may include thoseboiling below 650 F., for example. Vapors liberated in the bottom portion of the combined crude-distilling and fractionating tower I0 pass upwardly through trapout tray 22 and are subjected to fractionation thereabove to separately condense higher-boiling constituents therefrom.

Vapors remaining uncondensed in the upper section of the tower I0 pass overhead therethrough through line 23 provided with a condenser 24 wherein the distillate is condensed to a receiving drum 25. Distillate is removed from drum 25 through line 2B and uncondensed gases through line 2'I as nal products of the process. The distillate recovered from the initial distillation of the crude may be a natural gasoline having an end point of 400 F. It is preferred, however, to condense the heavy naphtha constituents, boiling above 250 F., for example, in the upper section of the tower I0, in which case the distillate collected in drum 25 will be light naphtha.

Condensate formed in the upper section of the tower I 0, which preferably includes the heavy naphtha constituents of the crude oil, collects in trap-out tray 22 and is withdrawn therefrom through line 28 and is subjected to further treatment as hereinafter described.

Reduced crude, comprising the residue from this initial distillation, is withdrawn from the bottom of the combined distilling and fractionating chamber I0 through line 29. This reduced crude, combined with heavy gas oil formed as a result of the mild cracking treatment, as hereinafter described, is forced by means of pump 30, located in line 29, through coil 3| located in the low-temperature furnace I I.

The oil, during its passage through the heating coil 3|, is subjected to mild cracking treatment for the purpose of forming clean, intermediate condensate stock suitable for high-temperature,- vapor-phase cracking. Concurrently with the formation of the clean intermediate condensate stock above mentioned there will be formedy during the course of treatment in the heating coil 3| a relatively small percentage of gasoline, as compared with the yield of gasoline recovered from the higher temperature cracking operation hereinafter described. The extent of cracking of this heavy reduced crude is limited by the presence therein of constituents easily convertible into coke, and the cracking temperature and time of treatment in this stage of the process should be regulated to avoid the formation of vexcessive coke deposits and the fouling of the heating tubes thereby. When operating on a Mid-Continent reduced crude, for example, the temperature and time of treatment will usually be limited to form from about 20 to about 30 per cent of constituents boiling below the initial boiling point of the reduced crude of which less than half may be within the boiling range of gasoline.

Within practical limits of time and temperature feasible in commercial operations it is preferred to carry out the cracking of the reduced crude under the maximum temperature permissible so as to impart the highest possible heat to the products leaving the heating coil 3|.

The products from the heating coil 3| discharge through transfer line 32 provided with a reducing valve 33 into an intermediate section 34 of tower I2.

In lieu of carrying the desired conversion to completion within the heating coil 3|, the products therefrom may be passed from heating coil 3| through line 35 to a reaction chamber 36 wherein the desired conversion is completed. In such case the products from the reaction chamber 36 are withdrawn through line 31 and returned to the transfer line 32 in front of the reducing valve 33.

The converted products introduced into the intermediate section 34 of tower I2 are subjected to distillation to liberate distillable products therefrom and produce a heavy residue too viscous to meet standard fuel oil specifications. The distillation of the products may be aided by reducing the pressure thereon by means of reducing valve 33 or by introduction of a stripping medium such as steam or other light gas into section 34 of the tower I2 through line 39 or by both pressure reduction and gas stripping.

Vapors liberated in the intermediate section 34 of the tower I2, which include all distillable constituents of the products, pass upwardly through trap-out tray 4I and are subjected to preliminary fractionation inthe upper section 42 of the tower I2.

The heavy viscous residue resulting from the drastic distillation of the products from the cracking zone collects in trap-out tray 43 and is withdrawn therefrom through line 44 and is forced by pump 45 to heating coil 46 located in the upper section of the furnace II wherein it is subjected to mild heat treatment solely for the purpose of causing mild cracking adequate to lower the viscosity thereof sufficient to meet standard specifications. The heat treatment of this heavy viscous stock may be limited to avoid the formation of any appreciable amount of gasoline, for example, not over one or two per cent. If desired, a digestion chamber, not shown, may be provided in addition to the heating coil 46 for effecting this mild cracking treatment.

In event the character of the charging stock does not permit the desired distillation in section 64 of the tower I2, or if for any other reason it is found inexpedient to remove all distillable constituents from the residue in the tower I2 the withdrawn products may be subjected to further distillation by steam or under a partial vacuum. To this end the residue withdrawn from the trapout tray 43 of tower i2 through line 44, in lieu of passing directly to heating coil 46, may be diverted through line 41 to a Vacuum or steamdistilling chamber 48 wherein further distillation of the residue may be effected. Vapors liberated in the distilling chamber 48 pass overhead to a condenser 49 through line 50. Condensate formed in condenser 49 passes to a receiver I and may be forced by means of pump 52 through line 53 to the upper fractionating section 4Z of the tower I2. Pump 52 or a barometric condenser may be operated to maintain a partial vacuum within distilling chamber 48 or steam may be introduced into the chamber through line 55 to effect the final distillation. Unvaporized residue is withdrawn from the bottom of chamber 48 through line 54 which merges with line 44 and is forced by means of pump 45 located therein to heating coil 46.

The products from heating coil 46 discharge through transfer line 56 to the bottom section 51 of the low-pressure tower I2 where vapors formed during the heat treatment are liberated therefrom. Vapors so liberated pass upwardly through trap-out tray 43 and combine with vapors liberated during the drastic distillation of the products from the heating coil 3| or reaction chamber 36. The combined vapors then pass upwardly through trap-out tray 4I and are subjected to fractionation in the upper section 42.

Fuel oil of the desired viscosity comprising the unvaporized residue of the products from the heating coil 46 are withdrawn from the bottom of tower i2 through line 59.

Condensate formed as a result of initial fractionation in the upper section 42 of the tower I2 collects in trap-out tray 4I and is withdrawn therefrom through line 6I which merges with line 2Q carrying the reduced crude from distilling chamber i6 and is recycled to the heating coil 3l.

Vapors remaining uncondensed in the tower i2 pass overhead through line 62 to the fractionating tower I3 wherein they are subjected to further fractionation to condense higher-boiling constituents therefrom.

Vapors remaining uncondensed in the fractionating tower i3 pass overhead through line 63, provided with a condenser 64, wherein the gasoline constituents are condensed, to a receiving drum 65 wherein the liquid distillate collects. Gases remaining uncondensed in condenser 64 pass overhead from receiving drum 65 through line 66 and the distillate is withdrawn through line 61.

In event that steam is used in distillation of the cracked products the distillate, which includes the water, is passed through line 69 to a separating chamber 16 where the desired distillate is separated. Distillate is withdrawn from the top of chamber 1i! through line 1I and water through line 12. This distillate may be a normal end point gasoline or it may be a light naphtha fraction thereof.

Reflux condensate formed in the tower I3, which may include heavy naphtha constituents, is withdrawn from the bottom thereof through line 16 which merges with line 28 which contains condensate resulting from the distillation of the original crude in tower I6.

The combined stream of condensate continues through line 13 and is forced by means of pump 15 to a heating coil 16 located in high-temperature furnace I4 wherein it is subjected to hightemperature vapor-phase cracking under conditions which will eifect maximum conversion thereof into gasoline constituents during its passage through the heating furnace. Products from the heating coil 16 discharge through transfer line 11 into the separating chamber I5 wherein vapors separate from residue. In lieu of carrying the desired conversion of the condensate to completion in heating coil 16 the products may be passed through line 18 to a reaction chamber 19 and the desired conversion completed therein. In such case the converted products are withdrawn from reaction chamber 19 through line 86 which merges with transfer line 11.

Residue separated in chamber I5 is withdrawn from the bottom thereof through line BI and may be discharged from the system or subjected to further treatment as desired. Transfer line 11 may be provided with a reducing valve 82 for maintaining a differential pressure between the heating coil and separating chamber.

Vapors separated in chamber I5 pass overhead through line 83 to fractionating tower I6 wherein they undergo fractionation to condense insufciently cracked products as reflux condensate. Fractionating tower I6 is controlled to take overhead a gasoline of normal end point such as from 400 to 437 F., for example.

Vapors remaining uncondensed in the fractionating tower I6 pass overhead through line 84, provided with a condenser 65, wherein the final gasoline distillate condenses, to a receiving drum 86. Gasoline distillate is withdrawn from the bottom of the receiving drum 66 through line 81. Uncondensed gases are removed from receiving drum 86 through line 66.

Condensate formed as a result of fractionation of the vapors from the fractionating tower E6 is withdrawn from the bottom. thereof through line 89 and is passed by means of pump Si? to a separate heating coil 9i located in. the high temperature furnace i4 wherein it subjected to further cracking treatment. Products from the heating coil SI Vare Vthereafter discharged through transfer line 92 to the separating cha l-- ber I5 wherein vapors separate from residue and the products thereof com ine with the products resulting from the cracking treatment of the initial charging stock in coil 16. If desired, the

products from the heating coil 9|, instead of passing directly to the separating chamber I5 may be passed through a portion of line 92 and line 93 to a reaction chamber 94 and the desired conversion carried to completion therein. In such case the final products of conversion are withdrawn through line 96 and passed to separating chamber l5 through the continuation of line 92.

Having described the general steps, combination of steps and sequence thereof constituting my invention the following example of temperatures, pressures, conversions per pass and other conditions of operation may be helpful in carrying out my invention to obtain the greatest advantages therefrom, it being understood that the values given herein are illustrative rather than limitative.

For example, the original crude oil, which may be any of the common crude oils, such as Mid- Continent crude, is initially heated to a distilling temperature of from 600 to r700 F. or thereabouts before being discharged into the distilling and fractionating chamber I 0. Condensate collecting in the trap-out tray 22 of the chamber l may have an initial boiling point of from 250 F. to 400 F. and an end point of 650 F. or thereabouts. The distillate recovered from the initial distillation of the crude oil may have an end point of from 250 to 437 F. The crude distilling chamber I0 may be preferably operated at a relatively low pressure such as from atmospheric to 200 pounds per square inch.

The reduced crude Withdrawn from the bottom of the crude distilling chamber I0 may have an initial boiling point of about 650 F. and may be heated to an outlet temperature of from 875 to 900 F. or thereabouts during its passage through the heating coil 3| provided the time of treatment is limited to avoid excessive coke deposition. The temperature and time of treatment of the reduced clude in the heating coil 3| may be regulated with respect to each other to produce from 20 to 30 per cent of constituents boiling below the initial boiling point of the reduced crude of which from 8 to 15 per cent may be gasoline. The reduced crude, during its passage through the heating coil 3| is preferably maintained under a relatively high superatmospheric pressure such as in excess of 400 pounds per square inch.

The products from the heating coil 3| or reaction chamber 36, after being introduced into the section of the combined fractionating and distilling chamber 2 are subjected to distillation to remove all distillable fractions therefrom and form a residual product having a viscosity measurement of in excess of about 2000 seconds at 122 F. as measured on a Saybolt Furol viscosimeter. This heavy residue, during its passage through the second heating coil 46 located in the furnace may be cracked sufficiently to produce a fuel oil of desired viscosity specication, such as 300 seconds at 122 F. For example, the outlet temperature of the coil 46 may be from 800 to 850 F. providing the time is properly limited to avoid excessive coking. The amount of conversion into gasoline constituents during this heat treatment may be 1 or 2 per cent or thereabouts.

If desired, the residue withdrawn Vfrom the separator I may be blended with bottoms from the low pressure tower I2 to form a composite fuel oil, in which event the viscosity of the residue withdrawn from the bottom of tower l2 may be such that the blended fuel oil will have the required viscosity.

The combined distilling and fractionating tower 2 is preferably maintained under a relatively low pressure, such as atmospheric or somewhat above, e. g. from 100 to 200 pounds per square inch. The condensate collected in the trap-out tray 43 may have an initial boiling point of 650 F. or thereabouts and the condensate formed in the fractionating tower I3 may have an initial boiling point of from 250 to 400 F. depending. upon the desired end point of the desired distillate and an end point of 650 F. or thereabouts. The virgin condensate formed in the crude distilling chamber I0 and the condensate resulting from the mild cracking treatment formed in the fractionating tower |3 may be heated to a temperature falling within the range of 950 F. to 1050 F. or thereabouts. The time and temperature relationship in the heating coil I6 may be controlled to produce as high as 46 per cent gasoline or even more in event the condensate contains a relatively high proportion of heavy naphtha constituents present in the condensate from the charging oil during its passage through the heating coil. The pressure maintained in the heating coil 'I6 is preferably relatively high and may range from several atmospheres to 1000 or more pounds per square inch, but is most desirably about '700 pounds per square inch.

'Ihe separating chamber l5 may be maintained at substantially the same pressure as the heating coil 'I6 or a materially reduced pressure may be maintained within the separating chamber. The condensate formed in the fractionating tower I6 may have an initial boiling point of about 400 F. and an end point in the range of from 650 to 700 F. This condensate, during its passage through the heating coil 9| may be heated to a temperature of from 925 to 975 F. and preferably in the neighborhood of 950 to 960 F. The time and temperature relationship of the treatment of the oil in the heating coil 9| may be controlled to effect from to 25% conversion during its passage through the heating coil and preferably in the neighborhood of conversion into gasoline constituents. The pressure in the heating coil 9| is preferably somewhat lower than that maintained in heating coil 'I6 and may range from several atmospheres to 400 pounds per square inch for example.

Having described the preferred embodiment of my invention it will be understood that it embraces such other modifications and variations as come within the spirit and scope thereof, and that it is not my intention to limit the invention or to unnecessarily dedicate any novel features thereof except as necessary to distinguish from prior art.

I claim:

1. The method of treating petroleum oil to produce gasoline and fuel oil that comprises subjecting crude petroleum to distillation to form reduced crude and a distillate adapted for conversion into gasoline, subjecting the reduced crude to cracking in a primary cracking zone to effect conversion into a comparatively large yield of constituents lower boiling than the reduced crude treated but higher boiling than gasoline and a relatively small yield of constituents in the gasoline boiling range, directing the resultant products of said cracking into a rst separating zone wherein vaporization occurs to form a heavy viscous residue, withdrawing the heavy viscous residue from the primary separating zone and subjecting it to cracking in a secondary cracking zone to reduce the viscosity thereof, delivering the resultant viscosity broken products into a second separating zone wherein vaporization occurs to form a liquid residue adapted for fuel oil, withdrawing said liquid residue as a product of the process, subjecting resultant vapors from said first and second separating zones to fractionation in a common fractionating Zone to form a heavy condensate and a lighter condensate each adapted for conversion into gasoline, directing said heavy condensate to said primary cracking zone, directing said lighter condensate and aforesaid crude petroleum distillate to a cracking Zone and subjecting the oil therein to high cracking per pass conditions to effect conversion into high anti-knock gasoline constituents and separately fractionating the resultant products of the latter cracking to separate out a gasoline distillate as a product of the process.

2. The method of treating petroleum oil to produce internal combustion motor fuel and fuel oil that comprises subjecting reduced crude to cracking in a primary heating and cracking Zone under such conditions of temperature and reaction time as to effect conversion into a comparatively large yield of constituents lower boiling than the reduced crude treated but higher boiling than gasoline and a relatively small yield not exceeding about 10%-15% of constituents in the gasoline boiling range, directing the resultant products of said cracking into a first separating zone wherein separation of vapors from residue takes place while maintaining such conditions of vapor separation as to form a heavy semi-solid residue having a viscosity in excess of about 2080 at 122 F. Saybolt Furol, withdrawing said semisolid residue from the primary separating Zone and subjecting it to cracking in a secondary heating and cracking zone at a lower temperature than obtains in the primary cracking Zone under conditions such that any conversion into gasoline constituents does not exceed about 1-2% but with reduction in the viscosity of the semi-solid residue to such an extent as to produce a fuel oil product having a viscosity not exceeding about 360 at 122 F. Saybolt Furol, delivering the resultant viscosity broken products into a second separating Zone wherein vaporization occurs to form a liquid residue adapted for fuel oil, withdrawing said liquid residue as a product of the process, subjecting resultant vapors from said first and second separating Zones to fractionation in a common fractionating zone to form a heavy condensate and a lighter condensate each adapted for conversion in to gasoline, directing said heavy condensate to said primary cracking Zone, passing said lighter condensate to a cracking Zone and subjecting it to high cracking per pass conditions to effect conversion into high anti-knock gasoline constituents and separately fractionating the resultant products of the latter cracking to separate out a gasoline distillate as the motor fuel product of the process.

3. The method of treating petroleum oil to produce internal combustion motor fuel and a fuel oil as nnal products which comprises subjecting reduced crude to cracking in a primary heating and cracking Zone under such conditions of temperature and reaction time as to effect conversion into a comparatively large yield of constituents lower boiling than the reduced crude but higher boiling than gasoline and a relatively small yield not exceeding about of constituents in the gasoline boiling range, directing resultant cracked products into a first separating zone wherein separation of vapors from residue takes place while maintaining such conditions of vapor separation as to form a heavy semi-solid residue having a viscosity in excess of about 2000 at 122 F. Saybolt Furol, passing said semi-solid residue in a confined stream through a separate heating coil and subjecting it therein to a lower cracking temperature than obtains in the primary cracking zone under conditions such that any conversion into gasoline constituents does not exceed about 12% but with reduction in the viscosity of the semi-solid residue to such extent as to produce a fuel oil product having a viscosity not exceeding about 360 at 122 F, Saybolt Furol, separating vapors formed in the viscosity-breaking of the semisolid residue and withdrawing the resultant residue as the fuel oil product of the process, fractionating separated vapors from said first separating Zone to form a heavier condensate and a lighter condensate comprising constituents higher boiling than gasoline, directing the heavier condensate to the primary heating and cracking Zone for cracking with the reduced crude, passing the lighter condensate to a separate heating and cracking Zone and subjecting it therein to high cracking per pass conditions to effect conversion into high anti-knock gasoline constituents and separately fraotionating the resultant cracked products to form a distillate constituting the motor fuel product of the process.

4. The method of treating petroleum oil to produce internal combustion motor fuel and a fuel oil as final products which comprises subjecting crude petroleum to distillation to form reduced crude anda condensate adapted for ccnversion into gasoline, subjecting the reduced crude to cracking in a primary heating and cracking zone under such conditions of temperature and reaction time as to effect conn version into a comparatively large yield of constituents lower boiling than the reduced crude but higher boiling than gasoline and a relatively small yield not exceeding about 10%-l5% of con-- stituents in the gasoline boiling range, directing resultant cracked products into a first separating zone wherein separation of vapors from residue takes place separately from the distillation of the crude petroleum while maintaining such conditions of vapor separation as to form a heavy semi-solid residue having a viscosity in excess of about 200i) at 122 F. Saybolt Furcl, passing said semi-solid residue in a confined stream through a separate heating coil and subjecting it therein to cracking conditions more mild than obtain in the primary cracking zone to effect reduction in the viscosity of the semisolid residue and produce a fuel oil product having a viscosity adapted to meet specifications for fuel oil, separating vapors formed in the viscosity-breaking of the semi-solid residue and withdrawing the resultant residue as the fuel oil product of the process, fractionating separated vapors from said first separating Zone to form a heavier condensate and a lighter condensate comprising constituents higher boiling than gasoline, directing the heavier condensate to the primary heating and cracking Zone for cracking with the reduced crude, combining said lighter condensate with said condensate from the crude distillation and passing the mixture to a separate heating and cracking zone wherein it is subjected to high cracking per pass conditions to effect conversion into high anti-knock gasoline constituents and separately fractionating the resultant cracked products to form a distillate constituting the motor fuel product of the process.

5. The method of treating petroleum oil to produce internal combustion motor fuel and a fuel oil as final products which comprises subjecting crude petroleum to distillation to form reduced crude and a condensate adapted for conversion into gasoline, subjecting the reduced crude to cracking in a primary heating and cracking zone under such conditions of temperature and reaction time as to effect conversion into a comparatively large yield of constituents lower boiling than the reduced crude but higher boiling than gasoline and a relatively small yield not exceeding about ILO-15% of constituents in the gasoline boiling range, directing resultant cracked products into a first separating zone wherein separation of vapors from residue takes place separately from the distillation of the crude petroleum while maintaining such conditions of vapor separation as to form a heavy semi-solid residue having a viscosity in excess of about 2000 at 122 F. Saybolt Furol, passing said semi-solid residue in a conned stream through a separate heating coil and subjecting it therein to cracking conditions more mild than obtain in the primary cracking zone to effect reduction in the viscosity of the semisolid residue and produce a fuel oil product having a viscosity adapted to meet specifications for fuel oil, separating vapors formed in the viscosity-breaking of the semi-solid residue and withdrawing the resultant residue as the fuel oil product of the process, fractionating separated vapors from said rst separating zone to form a heavier condensate and a lighter condensate comprising constituents higher boiling than `gasoline, directing the heavier condensate to the primary heating and craclcing zone for cracking with the reduced crude, combining said lighter condensate with said condensate from the crude distillation and passing the mixture to a separate heating and cracking zone wherein it is subjected to high cracking per pass conditions to eect conversion into high anti-knock gasoline constituents, directing the resultant cracked products into a separate fractionating zone and fractionating them to form a distillate constituting the motor fuel product of the process and a reflux condensate, passing said reflux condensate to another separate heating and cracking zone wherein it is subjected to high cracking per pass conditions to effect conversion into high antiknock 'gasoline constituents and directing resultant cracked products into said separate fractionating zone.

6. The method of treating petroleum oil to produce internal combustion motor fuel and a fuel oil as final products which comprises subjecting reduced crude to cracking in a primary heating and cracking zone under such conditions of temperature and reaction time as to effect conversion into a comparatively large yield of constituents lower boiling than the reduced crude but higher boiling than gasoline and a relatively small yield not exceeding about l-l5% of constituents in the gasoline boiling range, directing resultant cracked products into a first separating zone wherein separation of vapors from residue takes place and passing the resultant residue into a secondary separating zone maintained under a Vacuum wherein further separation of vapors from residue occurs to form a heavy semi-solid residue having a viscosity in excess of about 2000 at 122 F. Saybolt Furol, passing said semi-solid residue in a confined stream through a separate heating coil and subjecting it therein to cracking conditions more mild than obtain in the primary cracking zone to eect reduction in the viscosity of the semi-solid residue and produce a fuel oil product having a viscosity adapted to meet specications for fuel oil, separating vapors formed in the viscosity-breaking of the semi-solid residue and withdrawing the resultant residue as the fuel oil product of the process, fractionating separated vapors from said rst separating zone in a fractionating zone to form a heavier condensate and a lighter condensate comprising constituents higher boiling than gasoline, introducing vaporized constituents separated in said secondary separating zone into said fractionating Zone, directing said heavier condensate to the primary heating and cracking Zone for cracking with the reduced crude, passing said lighter condensate to a separate heating and cracking zone and subjecting it therein to high cracking per pass conditions to effect conversion into high anti-knock gasoline constituents and separately fractionatinjg the resultant cracked products to form a distillate constituting the motor fuel product of the process.

LOUIS C. RUBIN,

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