US2067730A - Process for the treatment of hydrocarbon oil - Google Patents

Description

Jan. 12, 1937. R. H. PRICE Er AL 2,067,730

, PROCESS FOR THE TREATMENT OF HYDROCARBON OIL Filed May 23, 1934 CH4/FGE HEATER INVENTORS RALPH H. PRICE ATTORN EY Patented Jan. 12 1937 PATENT OFFICE PROCESS FOR THE TREATMENT OF HYDROCARBON OIL Ralph H. Price, Galveston, Tex., and Rodney V.

Shankl and, Hammond, Ind., assignors to Standard Oil Company (Indiana), Chicago, 111., a corporation of Indiana I Application May 23, 1934, Serial No. 727,046

6 Claims. (Cl. 196-49) This invention relates to processes and apparatus for the treatment of hydrocarbon oil and more particularly to the production of lowerboiling point oil from higher boiling point oil. 7

It is an object of our invention to provide an improved three stage cracking process for producing gasoline of high anti-knock value from heavier hydrocarbon oil, whereby the heavy oil to be treated is first subjected to a preliminary 1o cracking operation of a viscosity breaking nature, wherein light clean gas oil is produced; the light gas oil is subsequently separated and subjected to a single pass cracking step wherein a relatively large amount of conversion takes place rapidly is under relatively high temperature and high pressure conditions; the resulting cracked products are separated into a light final distillate and an intermediate condensate stock; and this intermediate condensate stock is thereafter cyclically go cracked to completion in a separate low pressure high temperature cracking operation, at lower conversion per pass.

In accordance with our invention the heavy oil to be treated is first subjected to a preliminary g5 cracking operation of a viscosity breaking nature, such as to produce light clean gas oil relatively free from coke forming tendencies, with only a relatively small accompanying production of products in the gasoline boiling range, 6. g.,

30 8%20% per pass. The resulting lightly cracked products are separated into heavy tar-like residue, light clean gas oil and gasoline; a heavier gas oil may also be separated if desired, and be recycled to the viscosity breaking cracking operation.

35 The light clean gas oil is then subjected to a drastic cracking operation by being passed once through a primary crackingzone at a relatively high temperature and under a relatively high pressure, whereby a large amount of conversion takes place 40 quickly, for example, such as to produce from 35% toj55% of 420 E. P. gasoline. The cracked products'from this once-through operation are thereafter passed to an evaporator tower wherein the lighter products are separated from a 4 tar-like residue,rthese lighter products being sub sequently fractionated in a bubble tower or similar device to produce an intermediate condensate stock suitable for further cracking, preferably under low pressure in the vapor phase, and a final distillate. The condensate stock so produced is subsequently cyclically cracked to completion in the vapor phase in a secondary zone at a relatively high temperature and at relatively low pressure, the amount of cracking per pass being considerably lower than that taking place in the primary cracking zone. The vapor phase cracked products are either fractionated to produce a final distillate and condensate for further recycling through the vapor phase cracking zone, or are combined with the primary or 5 high pressure stage cracked products for fractionation therewith. In the event that the vapor phase or low pressure cracked products are separately fractionated the final distillate may be combine-d with that produced by the fractionation 10 of the high pressure cracked products resulting from the once-through cracking operation, or with the gasoline dfrived from the viscosity breaking cracking op ration, or if desired other blends of the light final distillates may be made to produce a final product of desired characteristics. Heavy naphtha separated in the process may be reformed if desired and resulting high anti-knock gasoline may be blended with the other distillates to increase the anti-knock value of the final gasoline distillate.

An important condition of this invention is that the temperatures and pressures of the primary and secondary cracking zones and time of passage of the oil therethrough should be selected to produce high cracking per pass in the primary single pass zone and relatively low conversion in the secondary recycling zone. The values depend upon the characteristics of the charging stock, the temperature of the primary zone being, for example, from 850 to 985 F. or even higher where a very clean stock, e. g., a redistilled low end point stock, is used, and the pressure being from 500 to 2000 pounds per square inch, or more. The secondary zone may operate undera temperature of from 875 to 1100 F. and a pressure of from 50 to 400 pounds per square inch. The preliminary or viscosity breaking cracking zone is operated under such conditions of temperature, pressure and time as to cause the cracking of the relatively heavy charging stock to produce relatively large quantities of clean lightgas oil cracking stock suitable for high cracking per pass in the primary cracking zone. For example, the temperature may be from 840 to 880 F., preferably about 875 F. and the pressure is most suitably in the range of from 150 pounds per square inch to 300 pounds per square inch, preferably about 230 pounds per square inch, these conditions corresponding to cracking of about 8% to 10% per pass. Higher temperatures, such as 875-890 F., and/or longer times of contact at the elevated temperature, will be necessary to secure cracking per pass at a value as high as 20%. In the heating steps the times of passage of the oil through the heating coils are preferably such that little or no coke will be deposited therein.

The preliminary or viscosity breaking cracking operation servesto form a relatively large percentage of light clean gas oil, having an end point of about 650 to 700 F. for example, which is suitable as charging stock for high cracking per pass in the succeeding primary cracking step. This gas oil, and also any gasoline formed, are removed from the crackedproducts directly upon the discharge of the cracked products from the preliminary cracking Zone, so that in event recycling is carried out, only heavy gas oil is returned for further cracking in the preliminary zone. As a result of the drastic cracking of this light clean gas oil charging stock in the primary single pass zone, under high temperature and high pressure, a final distillate gasoline is produced having a high anti-knock value, And. the intermediate condensate stock when cycically cracked to completion in the secondary zone, under high temperature and low pressure, produces a final distillate gasoline also of high anti-knock value, which may be blended with the distillate first mentioned. The anti-knock value of the final product can be increased still more by reforming virgin heavy naphtha. viscosity breaker naphtha, or both, and blending resulting gasoline distillate with the other distillates mentioned.

The above mentioned and further objects and. advantages of our invention will be made clear inthe following description taken in conjunction with the accompanying drawing.

In the drawing, the single figure is a diagrammatic view of an oil cracking system embodying our invention.

Referring more particularly to the drawing, reference numeral indicates a charging line through which fresh charge, such as Mid-Continent heavy gas oil, reduced crude, or the like, is forced by pump 2 through the heating coils of preliminary or viscosity breaking heater 3. In

'this heater the fresh charge is subjected to cracking of a viscosity breaking nature, such for example as to cause a conversion to products in the gasoline boiling range, of 8% to 20% per pass. The temperature of the oil emerging from the heater is preferably about 875 F. and the pressure thereon preferably about 230 pounds per square inch. The hot cracked products pass through line 4 and control valve 5 into evaporator 6, which may be equipped with fractionating elements, such as bafiies l and bubble trays 8, the necessary reflux being supplied by means of a. cooling coil 9, or in any other well-known manner. In this vessel, which may be held at the same or a lower presure than the coils of heater 3, the hot cracked products separate into vapors, which pass off overhead, and a liquid residue. This residue is removed through line H] having reducing valve ll, drum I2, which is held under considerably lower pressure, for example, substantially atmospheric pressure. Partial vaporization of the residue takes place in drum |2 as a result of the reduced pressure, and the vapors move upwardly past baffle plates l3, reflux being supplied by suitable means, such as cooling coil M, in the usual manner. A heavy gas oil condensate is collected on trap-out tray l5 and preferably recycled, by way of line l6, through heater 3, for further cracking.

The lighter vapors remaining uncondensed pass off through vapor line I! into condenser l8, the condensate collecting in receiver l9. This condensate is preferably then pumped, wholly or and introduced into flash in part, through line 20 into the fractionator tower 2|, in which it may serve as reflux, if desired. Vapors from the top of evaporator 6 pass by way of pipe 22 into fractionator 2|, and are therein subjected to fractionation, vapors of the desired end point, e. g., gasoline vapors, being withdrawn from the top of the fractionator by way of pipe 23, and condensed in condenser 24. The resulting distillate is collected in receiver 25. Reference numeral 26 indicates fractionating elements, such as bubble trays or the like, and 2'! indicates a conventional cooling coil.

Reflux condensate is withdrawn from the base of fractionator 2| and constitutes the charge for the primary high pressure stage, to which it is conducted through conduit 28 having pump 29. This reflux condensate is a light clean gas oil relatively free from coke forming tendencies and having, for example, an end point. of 650 to 700 F. or thereabouts.

This light gas oil passes through the coils of heater 30, leaving them preferably ata temperature of about 950 F., and a pressure approximating 750 pounds per square inch, and traveling through pipe 3|, into reaction chamber 32. After being soaked in the reaction chamber, the resulting cracked products pass through a conduit 33 into the base of evaporator 34 wherein separation of the cracked products takes place with the result that lighter vapors pass overhead through a vapor line 35 into fractionator 36, and tar residuum is conducted through line 31 having reducing valve 38 into tar flasher 39. The evaporator 34 may be supplied with baflie plates or similar devices 40 which serve to prevent entrainment of tar in the evolved vapors. A few bubble trays 4| may also be furnished if desired, to effect additional fractionation of the vapors. Reference numeral 42 indicates a cooling coil for supplying reflux in the usual manner; other suitable conventional refluxing means may be used if desired. This evaporator is operated at a pressure lower than that of the reaction chamber 32, for example, 125 pounds per square inch, the reduction in pressure being insured by pressure reducing valve 43 located in the conduit 33 connecting the evaporator and reaction chamber. If desired the reaction chamber may be bypassed byproper manipulation of valves 43, 44 and 45, in which event a higher temperature and/or pressure will berequired in transfer line 3| in order to obtain the same extent of crackmg.

In the fractionator 36 the vapors are separated into a light vaporous portion, e. g., gasoline vapors, which passes overhead through vapor line 46 and condenser 4'! into receiver 48, and an intermediate condensate stock which is drawn off from the bottom of the tower through a conduit 49 for treatment in the secondary cracking zone.

In the tar flasher 39 the introduced residue is partially vaporized as a result of the reduction in pressure, the vapors rising past baflle plates or other similar devices 50, reflux being supplied by means of cooling coil 5|, in the conventional manner, although direct introduction of cooling liquid may be employed if desired. The vapors remaining uncondensed, being of the nature of light clean gas oil, pass off through vaporline 52 and condenser 53, the resulting condensate being collected in receiver 54. This condensate is preferably forced through line 55, by pump 56, into fractionator 36 where it may serve as a refluxing medium.

The intermediate condensate from the bottom of fractionator 36 passes through pipe 49 and is forced by pump 51 through the coils of secondary or vapor phase heater 58, emerging therefrom at a vapor phasecracking temperature of preferably more than 900 F., for example, 950 F., under a relatively low pressure such as 175 pounds per square inch, and is passed through transfer line 59 into reaction chamber or digester 60, preferably under substantially the same pressure. The amount of cracking per pass through the vapor phase cracking zone is preferably relatively low; most suitably around 18%, although it may range from 15% to 25%. Partor all of this cracking may take place in the heater 58 itself, the digester 60 being bypassed if desired, by operation of valves GI, 62 and I02. The digested products pass from the reaction chamber through vapor line 63 and reducing valve 64 into evaporator 65. The evaporator is preferably maintained at a pressure considerably lower than that of the reaction chamber, for example 50 pounds per square inch. This evaporator may also have bafile plates 66 and a cooling coil 61 similar to evaporator 34. Light vapors pass ofi from the top of the evaporator through vapor line 68, which introduces them into the base of fractionator 69, whilethe liquid tar residue collecting in the bottom of the evaporator is transferred through conduit I0, having reducing valve ll, into tar flasher I2, the latter being held at approximately atmospheric pressure. The reduction in pressure on the tar residuum causes the lighter portions to be driven off through vapor line 13 and condenser It, the resulting condensate being collected in receiver 75, from which it may be drawn off through pipe 82 or returned to fractionator 69 through valved line I20 having pump I2I.

Heavy tar may be separately withdrawn from each of tar flashers I2, 39 and 12, through drawofi lines 16, TI and I8, respectively, or any or all of these tar residues may be blended together by means of line I9, for final drawing off through pipe 88. The residue so drawn off may be cut back with distillate withdrawn from receiver I5 through line 8|, or with reflux condensate from base of fractionator 69 through line I22. Part or all of the distillate from receiver 15 may be diverted through pipe 82. The pipe arrangement shown also makes possible the blending of any two or more of the tar residues with one another, or the blendingof any one or combination of residues with the flashed distillate from receiver 15 or with reflux condensate from base of fractionator 69.

In the fractionator 69 the vapors are separated into a light fraction of the desired end point, which passes through the vapor line 83 and condenser 84, the resulting condensate being collected in receiver 85, and a reflux condensate that collects in the base of the fractionator. Distillate deposited in the receiver '85 having the desired end point may either be used separately or be blended with the distillate from the receivers 25 and/or 48, the lines 86 and 81 being provided for thisv purpose. Reflux condensate is withdrawn from the base of the fractionator through conduit 88, and is forced by pump 89 through the coils of the secondary heater 58, along with the charge introduced through line '49, this recycling of the reflux condensate serv-- ing to cause additional cracking thereof.

Reference numerals 90, 9| and 92 indicate valved draw-off lines whereby any desired quantitles of condensate, collected in fractionators 2|, 36 and 69 respectively, may be diverted from the process in order to establish any selected balance of conditions. Similar draw-off lines 93 and 94 are provided whereby any desired quantity of flash distillate may be diverted from receivers I9 and 54 respectively. The light gasoline distillates collected in receivers 25, 48 and 85 may be drawn oif individually through valved draw-off lines 95, 96 and 91 respectively. In place of the cooling coils in the various towers or in cooperation with the coils direct cooling may be employed by pumping back distillate or other cooling mediums in the customary manner.

Instead of utilizing two different fractionators for the primary high pressure and the secondary vapor phase portions of the system, a single fractionator alone may be used, cross-over line 98 being provided so that vapors from evaporator 65 can be directed into fractionator 36. When this manner of operation is desired valve 99 is closed and valve I00 is opened. When operating in this manner the final distillates from both the primary high pressure system and secondary vapor phase system are collected together in receiver 48. Even more apparatus may be eliminated if separate tar draw-off lines are not desired, by introducing the digested products from reaction chamber 60 directly into evaporator 34, this operation being effected by means of cross-over line WI and valves 64 and I03. Upon closure of valve 64 and opening of valve I03 the vapor phase digested products are diverted into the evaporator 34. This manner of operation causes the diversion to the flash drum 39 of a single residue resulting from cracking both at high pressure in the heater 30, and at low pressure in the heater 58.

Additional light clean gas oil forcracking in the primary high pressure heater 30 may be supplied through charging line I04, this oil being, for example, a light virgin gas oil separated from crude by distillation, for example, by means of heat picked up in the system. Fresh charge for the entire process may consist of a crude oil which is passed through some or all of the heat exchange coils 9 and 21 and the corresponding coils in other parts of the system, the resulting heated crude being introduced into a stripping tower I05 through line I06. Any gasoline present may be taken off from the top of the tower in the usual manner through vapor line I08 and condensed in condenser I99, the condensate being collected in receiver I I0. The

light clean gas oil may be taken off from a trapout tray III and conducted through pipe H2 into pipe I04 while the'heavy reduced crude is taken off through draw-off line H3 and directed into charging line I.

In order to obtain increased anti-knock value of the final gasoline distillate of the process, a cut of heavy virgin naphtha may be removed from the stripper I05, after having been collccted on trap-out tray I23, and passed by way of valved line I24 through a separate reforming coil located in the secondary vapor phase heater 58, in which it is subjected to a conventional reforming operation, for example, one carried out at a temperature in excess of 950 F. and a pressure of, for example, 700 lbs. per square inch, or more. The resulting reformed products may be passed into the soaking drum 80 or evaporator 65 through line I25 having branch lines I26 and I 21, each supplied with pressure control valves as shown. If desired vis-breakernaphtha may be collected on a trap-out tray I28 in the fractionator 2|, and passed through line I24 into the reformer coil in the furnace 58, either alone, or in mixture with heavy virgin naphtha collected on the trap-out tray 23 of the stripper I115. The illustrative temperatures and pressures given for the reforming operation are not intended to be taken as invariable, since different conditions of temperature and pressure may be used for producing different degrees of reformation. The reforming coil might also be located in either of the furnaces 3 or 30, or in a separate furnace if desired, the only requisite being that the necessary temperature be attained. Alternatively the reforming coil might discharge into one of the other evaporators of the system.

Operation In operation heavy charging stock such as heavy gas oil or reduced crude of about 22 A. P. I. gravity, from line passes through vis cosity breaking heater 3 wherein it is cracked :ufflciently to produce from 8% to 20%, e. g., 8% to 10% of products in the gasoline boiling range, and the resulting cracked products are introduced into the evaporator 6. The cracking conditions in the heater 3 may be a temperature of from 840 to 880 F., preferably about 875 F., and a pressure of from 150 pounds to 300 pounds per square inch, preferably about 230 pounds per square inch. In the evaporator, which may be held at the same or a lower pressure than that of the heater, the products separate into vapors and a liquid residue, the former passing upwardly through the tower and being partially fractionated therein, while the latter is withdrawn from the bottom thereof and transferred to the flash drum I2. The partially fractionated vapors pass through the vapor line 22 into fractionator 2|, wherein they are completely fractionated in the usual manner, the fractionated vapors passing off from the top thereof and ming collected in receiver 25 as a gasoline distillate suitable for blending to produce a final desired product. The residue introduced into tar flasher |2 undergoes partial vaporization therein and these vapors are partially fractionated in the upper part of the vessel with the resulting formation of a heavy condensate which is collected on trap-out tray l5, and light gas oil vapors which pass overhead and are condensed and collected in receiver 9. The distillate so collected is pumped into the fractionator 2|, wherein it may be again partly vaporized,the heavy ends thereof being commingled with the reflux condensate in the base of the tower and the lighter ends passing off with the fractionated vapors. not be introduced so as to serve as a reflux medium. The heavy condensate collected on trap-'out tray I5 is preferably recycled through the viscosity breaking heater 3 for further conversion.

The reflux condensate withdrawn from the base of fractionator 2| is a light clean gas oil, preferably one having an end point of from 650 to 700 F. This condensate is then passed through primary high pressure heater 30 which operates on a once-through basis without recycling. In this heater the oil is subjected to a high temperature, preferably in excess of 900 F., e. g., 950 F., under a high pressure such as 750 pounds per square inch, and the heated products are then transferred to the reaction chamber 32 wherein additional conversion takes place, the conditions of temperature and pressure already This distillate may or may;

mentioned being regulated to cause cracking to an extent of from 35% to 55% or more per pass through the heater, for example 45% or 50%. After leaving the reaction chamber the cracked products pass to the evaporator 34, the pressure in the evaporator being held at a lower value, which may approximate pounds per square inch, by action of valve 43 in the transfer pipe 33, through which the pro-ducts travel from the reaction chamber to the evaporator. In the evaporator the introduced products. being under lower pressure and at a suitable temperature such as 800 to 825 F., separate into a vapor portion which passes overhead through vapor line 35 into fractionator 36, and a liquid residue portion which is introduced into the tar flasher 39 through pipe 31. The pressure on the residuum is reduced by valve 38, the tar flasher preferably being operated at substantially atmospheric pressure. The fractionator 36 is provided with bubble plates and caps or similar fractionating devices,

and serves in the well-known manner to separate the vapors into an intermediate reflux condensate suitable for further cracking which collects in the base of the fractionator, and a light vapor portion having the desired boiling characteristics, which passes over head and is then condensed and collected in receiver 48.

The intermediate condensate oil is drawn off through the conduit 49 and passed through secondary vapor phase heater 58 wherein it is raised to a temperature preferably in excess of 900 F.. for example 950'" F. under a relatively low pressure such as 1'75 pounds per square inch. the same as that prevailing in the digester 50 into which which is maintained at a still lower pressure. 3

such as 50 pounds per square inch, by action of the reducing valve 64. Alternatively digester 60 may be by-passed by opening valve 62 and closing valves GI and H12. Light vapors travel from the evaporator through vapor line 68, which introduces them into the bottom of fractionator 69, while the liquid tar residue collecting in the base of the evaporator is transferred through conduit 10 and reducing valve II, into tar flasher 12, the

latter being held, preferably, at approximately atmospheric pressure. The reduction in pressure on the tar residuum causes the lighter portions to -be driven off as vapors through vapor line 13 and condenser 14, the condensate being collected in receiver 15, either for blending with one or all of the tars from tar flashers I2, 39 and 12, for withdrawal from the process separately or for return to fractionator 69.

In the fractionator 69 the vapors are separated into a light fraction of the desired boiling characteristics, which passes off from the top thereof and is collected as a distillate of desired end point, or of desired blending characteristics, in receiver 85, and a reflux condensate that collects in the base of the fractionator. This reflux condensate is preferably recycled through line 88 for further cracking in the heater 58.

In the preceding description of the operation it has been assumed that only a heavy charging stock in the nature of heavy gas oil or reduced crude is to be treated. In the event that it is desired to charge crude or other heavy oil containing lighter constituents, this oil is preheated, for example by passage through some or all of heat exchange coils 9 and 21 and other corresponding heat exchange coils in the system, or in any other manner desired, and is subjected to a conventional stripping opration, for example, .in a tower such as I05, with the resulting segregation of. the crude into reduced crude which is introduced into the charging line I, a light clean gas oil condensate, preferably having an end point of from 675 to 725 F.,,which may be introduced directly into the primary high pressure heater 30, as shown on the drawing, by way of lines H2 and I04, and a light distillate of lower boiling characteristics than desired for treatment in the high pressure heater. This light distillate, which is collected in receiver I.I0, would fall in the gasoline boiling range. Additional virgin gas oil may be introduced through the line I04 from an external source if desired.

Instead of using separate evaporators and fractionators for the primary high pressure stage and secondary vapor phase stage as assumed in the preceding description of the operation, valve 64 may be closed and valve I03 opened, thereby directing all of the products into evaporator 34. In this event all of the gasoline distillate from both of these stages would be collected in receiver 48. When so operating, a portionof the flash distillate from receiver 54 or reflux condensate from fractionator 36 may be used for diluting the tar from tar flashers I2 and 39, if desired. Instead of using a single evaporator the secondary vapor phase products may be permitted to pass into evaporator 65 and the vapors therefrom be diverted into the fractionator 36 by closing of valve 99 and opening of valve I00. This latter method of operation would eliminate one fractionator and its accessories, while permitting separate tar drawoff from each stage.

The tar drawn oif from the several tar flashers through draw-off lines I6, 11 and I8, may be cut back with condensate stock withdrawn through any of draw-off lines 90, 9| and 92, if desired,

the condensate withdrawn through line 92 from naphtha from trap-out tray I28 of fractionator 2| may be subjected to reformation either individually, or in mixture, by passing through the reformer coil located in the furnace 58 or in one of the other furnaces shown, or in a separate furnace if desired. In passing through this reform-' ing coil the naphtha is'raised to a suitable reforming temperature, for example, a temperature of from 950 F. to 1050 F. under a pressure of, for example, 500 pounds to 1000 pounds per square inch, more or less, the resulting reformed products being introduced into the soaking drum 60 or evaporator 65, after having been reduced in pressure if desired by action of one of the control valves located in the branch lines I26 and I21. Alternatively the reformed products might be introduced into oneof the other evaporators.

Our invention as described hereinbefore permits the production from relatively heavy initial charging stock having coke forming tendencies, of a relatively large quantity of high anti-knock gasoline, the preliminary viscosity breaking stage serving to produce a very clean cracking stock suitable for very high cracking per pass in the primary high pressure stage wherein, since the cracking is carried out under high pressure and high temperature, ,gas production is minimized as a result. Likewise, as the cracking is done rapidly tar does not have much chance to form. In the subsequent cracking of the intermediate condensate from the high pressure stage, in the following secondary vapor phase stage, tar formation is still further retarded and since a large part of the lighter products produced has already been removed in the high pressure operation the total loss of desired distillate clue to the secondary cracking is smaller, being essentially only that which occurs in the low pressure cracking operation.

The expression cracking per pass used throughout this specification refers to the percent conversion to end point gasoline of the stock passed into the conversion zone in a single pass therethrough.

This specification describes certain specific embodiments of our invention but the scope of the invention is not intended to be limited thereto except as set forth in the accompanying claims. Thus, we may obtain higher cracking per pass in the primary stage than that set forth, particularly when using higher pressures, as pressures of 1500-2000 pounds per square inch. These high degrees of conversion are a distinctive feature of our invention and to them we ascribe in large measure the success of the process.

We claim:

1. The process of treating hydrocarbon oil which comprises passing relatively heavy charging oil, not suitable for use as clean cracking stock, through a viscosity breaking cracking zone wherein it is raised to a cracking temperature and subjected to conversion, separating the resulting cracked products into vapors and a liquid residue in a first separating zone, fractionating vapors so obtained in a first fractionating zone to form a final desired light distillate, a heavy naphtha condensate, and a clean gas oil condensate, combining fresh virgin gas oil with said gas oil condensate and passing the resulting mixture through a primary, high-pressure, cracking zone wherein it is raised to a. cracking temperature and subjected to conversion, separating resulting cracked products into vapors and a liquid residue in a second separating zone, fractionating resulting vapors in a second fractionating zone to form a quantity of final desired distillate and a clean gas oil condensate, passing said clean gas oil condensate through a secondary cracking zone wherein it is raised to a vapor phase cracking temperature and subjected to conversion, separating the resulting cracked products into vapors and a liquid residue in a third separating zone, fractionating the separated vapors to form an additional quantity of final desired distillate, simultaneously passing said heavy naphtha condensate through a separate reforming zone wherein it is raised to a cracking temperature and subjected to reformation and introducing the resulting reformed products into said third separating zone.

2. The process of treating hydrocarbon oil which comprises separating crude charging oil, in a stripping zone, into a heavy naphtha condensate, a clean gas oil condensate and a liquid residue, passing said liquid residue through a vis-- in a first fractionating zone to form a final desired light distillate, a heavy naphtha condensate and a clean gas oil condensate, combining said gas oil condensate from said stripping zone with said gas oil condensate last-mentioned and passing the resulting mixture through a primary high-pressure cracking zone wherein it is raised to a cracking temperature and subjected to conversion, separating resulting cracked products into vapors and a liquid residue in a second separating zone, fractionating resulting vapors in a second fractionating zone to form a quantity of final desired distillate and a clean gas oil condensate, passing said clean gas oil condensate through a secondary cracking zone wherein it is raised to a vapor phase cracking temperature and subjected to conversion, separating the resulting cracked products into vapors and a liquid residue in a third separating zone, fractionating the separated vapors to form an additional quantity of final desired distillate, simultaneously passing said heavy naphtha condensate through a separate reforming zone wherein it is raised to a cracking temperature and subjected to reformation and introducing the resulting reformed products into said third separating zone.

3. A process in accordance with claim 2 Wherein the vapors from said third separating zone are fractionated in a third fractionating zone. I

p 4. A process in accordance with claim 2 wherein the vapors from said third separating zone are fractionated in said second fractionating zone.

5. The process of treating hydrocarbon oil which comprises subjecting crude petroleum to vaporization leaving liquid reduced crude, fractionating resulting vapors to form light condensate in the gasoline boiling range and a gas oil condensate, passing reduced crude thus produced through a first heating zone wherein it is subjected to a cracking temperature for a period of time sufficient to cause cracking thereof into lighter products, only a relatively small proportion of which are so light as to fall in the gasoline boiling range, separating resulting hot cracked products into vapors and a liquid residue, fractionating said vapors to separate therefrom a light gas oil condensate, removing remaining fractionated vapors, passing ligh't gas oil condensate so produced together with gas oil condensate from the crude petroleum once through a second, separate, heating zone wherein it is subjected to a cracking temperature of at least 850 F. under a pressure of at least 500 pounds per square inch for a period of time sufficient to cause a relatively high degree ofcracking thereof, with attendant production of at least 35% of products in the gasoline boiling range, separating resulting h'ot cracked products into vapors and a liquid residue, fractionating said vapors to separate therefrom a reflux condensate, leaving uncondensed vapors in the gasoline boiling range, removing and condensing as a desired product said vapors last mentioned, passing said reflux condensate through a third, separate, heating zone wherein it is subjected to cracking temperature for a period of time, suflicient to cause a moderate amount of conversion to products in the gasoline boiling range, separating resulting cracked products into vapors and a liquid residue, fractionating said vapors to separate therefrom as reflux condensate products heavier than gasoline, leaving uncondensed vapors in the gasoline boiling range, removing and condensing the last mentioned vapors as a desired product, and recycling said reflux condensate to said third heating zone for further cracking.

6. The process of treating hydrocarbon oil which comprises passing a relatively heavy oil of the nature of reduced crude through a heating zone wherein it is subjected to a cracking temperature of from 840 to 880 F. and a pressure of from to 300 pounds per square inch for a period of time sufficient to cause cracking thereof of a viscosity breaking nature, with the attendant production of about 8 to 10% of products in the gasoline boiling range per pass, separating resulting hot cracked products into vapors and a liquid residue, fractionating said vapors to separate therefrom a light gas oil condensate having an end point of about 650 to 700 F., removing and condensing remaining fractionated vapors, passing light gas oil condensate so produced once through a second, separate, heating zone wherein it is subjected to a cracking temperature of at least 850 F., under a pressure of at least 500 pounds per square inch, for a period of time sufficient to cause a relatively high degree of crack ing thereof, with the attendant production of at least 35% of products in the gasoline boiling range per pass, separating the resulting hot cracked products into vapors and a liquid residue, fractionating said vapors to separate therefrom a reflux condensate, leaving uncondensed vapors 1 in the gasoline boiling range, removing and condensing as a desired product said vapors lastmentioned, passing said reflux condensate through a third, separate, heating zone wherein it is subjected to cracking temperature, under a pressure of around pounds per square inch, for a period of' time sufficient to cause a moderate amount of conversion to products in the gasoline boiling range, separating resulting cracked products into vapors and a liquid residue, fractionating said vapors to separate therefrom as reflux condensate products heavier than gasoline, leaving uncondensed vapors in the gasoline boiling range, removing and condensing the last-mentioned vapors, as a desired product, and'rec'ycling said reflux condensate to said third heating zone for further cracking.-

RALPH H. PRICE.

RODNEY V. SHANKLAND.

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