US2185200A - Cracking of hydrocarbon oils - Google Patents

Description

IML 2, 194@ P. c. KEITH, JR., ET A1. 2,185,200

CRACKING OF HYDROCARBON OILS Original Filed Feb. ll, 1937 2 Sheets-Sheet l ORS ATTORNEY Nm. MQ

M1- 2, 1940- P. c. KEITH. JR., ET A1. 2,185,200

CRACKING OF HYDROCRBON OILS Original Filed Feb. ll, 1937 2 Sheets-Sheet 2 c or non i z Percival G. heith, Jr., Peapack, N. i., and Joseph h, herts, iilossmoor, Ml., assignors of onehali' to Standard @il Company, Chicago, lill., a coration of llndana, and one-half to Gasoline Products Uompany, line.,

.liersey mty,

N. li., a cor-ation of Delaware @i mi application February 1l., 1937, Serial 125,204. Divided and this application liliecemher 2t, 1938, Serial No. 246,774

i application is a division of our pending iiication, Serial No. 125,204, filed February 11,

This invention relates to processes for the treatment of hydrocarbon oil and pertains more particularly to processes adapted for the production of gasoline or other light distillate from heavy oil such as crude petroleum, partially reduced crude or the like.

it is an object of our invention to provide a combination cracking unit or process wherein the crude petroleum is 'subjected to a distilling operation to separate virgin gasoline, heavy naphtha, kerosene, gas oil and reduced crude oil, and to provide for the separate treatment of these several iractions.

A feature oi our invention resides in the oncethrough cracking of the heavy reduced crude and the introduction thereof into a vapor separating and fractionating system, from Whicha heavy gas oil condensate is Withdrawn: separately cracked, and returned to the evaporating and fractionating system, this latter operation being conducted on a recycling basis.

.another feature resides in the removal of the kerosene fraction from the process and the separate cracking or reforming of a mixture of the virgin heavy naphtha and virgin gas oil and the passage of the resulting cracked products to an evaporating and fractionating system.

i further feature resides in a particular method of connecting together the two separate evaporating and iractionating systems whereby economy of operation is attained.

The invention contemplates a combination cracking process in which-a crude petroleum stock is subjected to fractionation to form a residue and a lighter fraction, in which the residue is passed to a primary cracking or viscositybreaking Zone wherein the residue is subjected to cracking temperature under conditions to eect the formation of a high yield of gas oil constituents, adapted for conversion into gasoline, the resultant viscosity-broken products separated into vapors and residue and the vapors fractionated to form a heavy reflux condensate and a lighter fraction comprising such intermediate constituents, in which the heavy reflux condensate is pressed to a secondary viscosity-breaking or heavy gas oil cracking zone wherein the heavy condensate is subjected to'cracking temperature under conditions to eect the formation of an additional yield of gas oil constituents adapted ior conversion into gasoline, the resultant cracked products separated into vapors and resi,

(ci. isc-i9) due and the separated vapors fractionated together with the vapors separated from the cracked products of the primary viscosity-breaking operation so as to combine gas oil constituents formed in the two cracking or viscosityt breaking operations, in which such lighter fractions from the crude fractionating operation and from the cracking or viscosity-breaking operations mentioned are combined and the mixture subjected to cracking in a third cracking zone ll@ under high cracking temperature and under conditions of high' cracking per pass'to eect conversion into gasoline of high anti-knock quality and the cracked products separately fractionated to recover the desired gasoline product.

In accordance with the invention the cracked products from the third or high cracking per pass. cracking zone are separated into vapors and residue and the vapors fractionated to form a reflux condensate which is subjected to cracking in a recycling cracking zone while the admixed fractions from the crude fractionating step and from the viscosity-breaking operations are subjected to cracking in a single-pass cracking zone.

The invention further contemplates the vacuurn-flashing of residual material separated out from the viscosity-broken products from the viscosity-breakng operations to form heavy residue and vacuum-flashed distillate, and the combining of vacuum-flashed distillate constituents with the heavy reflux condensate passing to the secondary viscosity-breaking or heavy gas oil cracking zone. In accordance with the invention the vacuum-flashed distillate is introduced into the fractionating zone in which the vapors from both of the viscosity-breaking zones are fractionated so that any portion of the vacnum-flashed distillate remaining unvaporized after contact with the vapors undergoing fractionation therein Will be charged to the secondary viscosity-breaking or heavy gas oil cracking zone with the heavy reflux condensate being directed thereto.

In accordance with our invention the fresh heavy charging oil such as crude oil, partially reduced crude or the like, is preheated by any suitable method such as indirect heat exchange or direct heating in a iired coil, or both, and then introduced into a crude flash tower, from which a gasoline fraction, heavy naphtha fraction,

vkerosene fraction, gas oil fraction and reduced crude are withdrawn. The reduced crude is passed once through a cracking heater wherein it is raised to a cracking temperature and subjected to conversion and the cracked oil ls then passed to an evaporating zone, the vapors from which are subjected to fractional condensation with the resulting formation of a heavy gas oil condensate and an overhead light distillate coprising gasoline and light gas oil, but which may comprise substantially only gasoline. The heavy condensate is removed, passed through a separate cracking zone and returned to the evaporating zone while the overhead light distillate is combined with the virgin heavy naphtha and gas oil and the mixture is passed through a third cracking zone wherein cracking and reformation occurs, the products of conversion then being introduced into a high pressure evaporator wherein separation of vapors from residue takes place. The separated vapors are subjected to fractionation in a separate relatively high pressure fractionator to form a reflux condensate which is directed to a recycling cracking coil, lthe cracked products from which are discharged into the high pressure evaporator. 'I'he fractionated vapors from the high pressure fractionator are removed and condensed as a desired product.

Liquid residue from the high-pressure evaporator is preferably flashed in a flash tower under reduced pressure, the ilashed vapors being conducted to the low-pressure fractionating system. At the same time residue from the low-pressure evaporator is preferably Withdrawn and flashed in a separate flash drum under vacuum, the overhead distillate obtained being returned to the lowpressure evaporating and fractionating system, most suitably in such manner that unvaporized portions thereof are passed through the second cracking zone with the heavy condensate.

Where different types of crude oil are charged different quantities of heat must be supplied thereto for effecting distillation and, to accomplish this most eillciently, an auxiliary furnace is provided through which the crude charging oil may be passed in one direction prior to introduction into the crude ilash tower. Provision is also made for passing recycle stock from the highpressure fractionator in the opposite direction through this auxiliary furnace when that furnace is not being used for preheating crude oil.

The above-mentioned and further objects and advantages of .our invention and the manner of attaining them will be more fully set forth in the following description taken in conjunction with the accompanying drawings.

Figure 1 illustrates diagrammatically in side elevation apparatus adapted to carry out the process of the invention.

Figure 2 is a simplified flow diagram of the invention.

Referring more particularly to the drawings, heavy charging .oil such as crude oil, partially reduced crude or the like is introduced through line I and forced by pump 2 into crude flash tower 3, after having passed through suitable preheating means such as heat exchangers 4 and 5 wherein the oil is raised to a distillation temperature, and by-pass line 6. Alternatively the oil may travel through heating coil 1 of furnace 8 to pick up suillcient heat for distillation purposes, valves 9, I0, and II providing the necessary control.

In tower 3 the crude oil is fractionally distilled to form an overhead distillate of light naphtha, i. e., the light ends of gasoline, which is removed via vapor line I2 and condenser I3 and collected in receiver I4, and naphtha, kerosene, and gas oil condensates, which are collected on trap-out trays I5, I6, and I1 respectively, and

reduced crude which is collected at the base of the tower. These several condensates are conducted through valved lines I8, I9, and 20 into strippers 2l, 22 and 23 respectively, wherein they are stripped of lighter ends by aid of steam or gas introduced through connections |50. The kerosene is preferably withdrawn from the process through valved line 24 as a desired product while the heavy naphtha comprising heavy ends of gasoline, and gas oil condensate are introduced into accumulator 25 by way of valved connections 26 and 21. The latter connection includes heat exchanger 28 which may be by-passed by means of valved line 29. Kerosene when not withdrawn from the process may likewise be passed to accumulator 25 through valved pipe I5I. Vapors from the several strippers and from the accumulator are returned to the tower 3 by means of vapor pipes 30, 3|, 32 and 33.

Reduced crude is withdrawn from the base of tower 3 through pipe 34 and forced by pump 35 through heating coil 36 located in furnace 31, wherein it is subjected to mild cracking conditions to effect viscosity-breaking. The cracked products pass through transfer line 38 having control valve 39, into the evaporator portion 40 of combination tower 4I, wherein vapors separate from liquid residue. The vapors travel upwardly through the tower around baille plates .or other contact elements 42, then through fractionator section 43 of the tower having bubble trays or other fractionating elements 44. The fractionated vapors of desired boiling characteristics, e. g., gasoline, pass through vapor pipe 45, are cooled in heat exchanger 46A and 41, and condensed in condenser 48, and the distillate is collected in receiver 49 which is equipped with the usual gas vent line 50 and liquid withdrawal line 5I.

Heavy gas oil condensate is collected on trapout tray 52 from which it is withdrawn through conduit 53 and forced by pump 54 through heating coil 55 in furnace 31. In this coil the oil is raised to a moderate cracking temperature, preferably somewhat higher than that to which the oil is raised in coil 36, and is subjected to a moderate degree of conversion. The resulting cracked products pass through transfer line 56 having control valve 51 into the evaporator section 40 of tower 4 I.

Liquid residue is directed from the base of tower 4I through pipe 58 having reducing valve 59, into vacuum flash tower 60 wherein lighter constituents thereof are distilled by their contained heat, leaving a heavy tar residue which is drawn o from the process through valved line 6I having pump 62, for use alone or in mixture with other tar or distillate from the process. The vacum flash tower may operate under an absolute pressure of, for example, about '70 millimeters of mercury. The flashed vapors are removed through vapor pipe 63, heat exchanger 63A and condenser 64 and the distillate is collected in receiver 65, from which part is returned via line 66 under pressure of pump 61, to the flash tower as a reiluxing medium while the remainder is conducted by conduit 68 into fractionator section 43 through branch connection 69 and heat exchanger 63A or through branch connections 'I0 and 1I into evaporator section 40. Each of these connections is furnished with a control valve as shown. Gas oil may be circulated from tray 52 through conduit 12 having pump 13 and cooler 14 into any or all of the branch connections mentioned for use as a refluxing or cooling medium. Reference numeral 46 indicates an exhausting aieaaoo device such as a. pump or barometric condenser for producing a vacuum in the ash tower.

'I'he mixture of virgin heavy naphtha and gas oil is removed from accumulator 25 by way of pipe 15 and is forced by pump 16 through heating coil 11 located in furnace 96 wherein it is raised to a high cracking temperaturesufiicient to form high anti-knock gasolinefractions, and the cracked products are conducted into the lower portion of evaporator 18 through pipe 19 having control valve 80. In the evaporator vapors separate from liquid residue, the latter being drawn off through pipe 8| having reducing valve 82, into flash drum 83 wherein lighter constituents are vaporized by their contained heat leaving ashed liquid residue which is withdrawn from the procprocess.

Vthe radiant section llll.

ess via line 84 as fuel oil. If desired this flashed residue may be blended with tar removed from vacuum ash tower 60 or with bottoms from tower 81 or both. The flashed vapors flow .through vapor pipe 85 into fractionator section 43 Vapors from evaporator 18 travel through vapor line 86 into fractionator 81 and are therein fractionated in the usual way to give overhead vapors of the desired boiling characteristics, e. g.. gasoline, which are removed by way of vapor pipe 88 and condensed in condenser 89, the distillate being collected in receiver 99 as a product of the in the base of the fractionator, is withdrawn by way of line 9| and forced by pump 92 through heating coil 93 in furnace 96 and is therein raised to an active cracking temperature which may be somewhat less than that attained by the oil traversing coil 11 but in excess of that to which the reduced crude and heavy gas oil condensate are raised in their respective heating coils. The cracked products so derived are conducted through transfer line 98 having control valve 95 into the base of evaporator 18.

Alternatively part or all of the reux condensate from the base of fractionator 81 may be forced through pipe 91 and heating coil 1 of furnace 8 when this heating coil is not being used for heating fresh charging oil. In this heating coil the oil is raised to a cracking temperature such as that attained in the coil 93 and is then conducted through transfer line 98 having control valve 99 into the evaporator tower 18. In this manner of operation the gas oil passes through the heating coil 1 by entering the convection section |08 of the coil and leaving through When this coil is used for preheating crude oil the flow is in the opposite direction, the crude oil entering the radiant section 185| and leaving through the convection section |89. Valves |82 and |03 are provided for controlling the flow of gas oil conducted from the tower 81 to the heating furnaces.

Cooling at the top of the fractionator tower 81 is provided by withdrawing a side stream of reflux condensate through line |08 and passing it through heat exchanger and auxiliary cooler |05 into the top of the tower, the necessary pressure being provided by pump |85. Cooling for the top of fractionator section 83 of combination tower 8| is effected by pumping back to the top of the tower through pipe |01 under pressure generated by pump |88, a portion of the gasoline i control.

collected in receiver 89. Another portion of this same gasoline distillate may be directed through connection |09 into the top of fuel oil flash tower 38, valves H and furnishing the necessary Cooling for the top of crude ash tower Clean gas oil reux condensate collects Y 3 is provided in a like manner, a portion of the gasoline collected in receiver i4 being forced through pipe H2 and pump H3 into the top of that tower, the necessary control being brought about through valve H4. Reflux condensate is withdrawn from trap-out tray H5 in tower 81 and directed by pressure of pump H1 through conduit H6 and heat exchanger 5 in indirect heat exchange relation with the crude oil charging stock, thence through auxiliary cooler H9 and pipe to an intermediate point in the tower 81. A line I2| is provided to return a portion of this cooled reux condensate to different levels in the evaporator tower 18 by way of valved pipes |22 and |23. A by-pass control line |28 is arranged across the terminals of auxiliary cooling coil H9 for control purposes. A connection is furnished for leading oil to the base of the fractionator through valved pipe |26 and to the transfer lines 19 and 98 by way Eof valved terminal lines |21 and |28. Pump |29 gives the necessary pres Sure. By means of this line last-mentioned uxing oil is injected into the transfer line to prevent coking diiculties. Surplus oil returns to fractionator 81 through the pipe |26.

Distillate collected in receiver |39 may be diverted from the process through draw-ofi line 5|, but preferably this distillate is passed through pipe |3|, heat exchanger 28, pipe |32, heat exchanger 81, and pipe |33, into an intermediate level in fractionator tower 81. By-pass valve H8 is provided so that part or all of this distillate may be directed to conduit 15 for passage with the Virgin stock through heating coil 11. In this case the distillate would desirably be mainly gasoline which itis desired to reform. Valved pipe |5| is provided to by-pass heat exchanger 28.

By returning distillate from the receiver 49 to either the fractionator 81 or the evaporator 18 or to both the fractionator 81 and evaporator 18. refractionation thereof takes place with the desirably light constituents passing 01T overhead through vapor line 88 to be collected with the nal desired gasoline distillate in receiver 90. Since refractionation takes place the end point of the distillate collected in receiver 49 need not be exactly that of the final desired product but it may be somewhat heavier including even light gas oil. In most instances it will be found desirable to pass the light gas oil into the receiver 49 so that it can be introduced into the fractionator tower 81 and find its way through connection 9| to heating coil 93 for further cracking at fairly high cracking temperatures,

Reference numeral |35 indicates a reduced pressure stripper tower into which an intermediate reflux condensate cut in the boiling range of light gas oil or furnace or tractor oil, for example, is directed by way of draw-off line |36 which is connected to a trap-out tray |31 in the fractionator 81. 'I'his oil, after undergoing stripping in the tower |35, is withdrawn from the process as a desired product, e. g., furnace oil, through valved draw-ofi line |38 while the overhead vapors rom this stripper tower travel through pipe |39 into vapor line 45 for passage through condenser 88. A refluxmg line for passing distillate from pipe |33 to the top of the stripper tower |35 is referred to by numeral |40.

In actual operation the temperature of the oil leaving the, initial viscosity-breaking coil 36 is preferably in the neighborhood of 870900 F. and the pressure desirably being about 150-200 pounds per square inch. The temperature may, however, range fromA 850 to 950 F., more or less, and the pressure may be higher or lower than that indicated as preferable, extending, for example, from 75 pounds to 400 pounds per squareinch, more or less. The heavy gas oil upon emerging from heating coil 55 preferably has a temperature of about 950 F., the pressure being desirably about 400 pounds per -square inch. These values are preferred but the temperature may vary considerably ranging, for example, from 900 to 1000 F., and the pressure ranging from a few pounds per square inch to as high as 1000 pounds per square inch or more.

The mixture of virgin heavy naphtha and gas oil passing through the heating coil 'Il is raised to a higher cracking temperature of, for example, about 1000 F.1020 F. under a pressure of, for example, about 750 pounds per square inch although the temperature may range from 950 to 1150 F. and the pressure may also vary considerably, for example from 200, pounds to 1000 pounds per square inch. The reflux condensate from the base of fractionating column 81 is heated in the coil 93 or in the coil 1, if that be used, under substantially the saine conditions of temperature and pressure as mentioned for oil leaving coil 17, although a somewhat higher temperature and lower pressure may be used in some instances. The pressure maintained in the two evaporating zones 'I8 and 40 will depend upon the pressures used in the heating coils, necessarily being lower than the outlet pressure of any heating coil discharging thereinto. However, the pressure in evaporator 'I8 will be higher than that held in evaporator section 40, the pressure in the former being, for example, about D-300 pounds per square inch and that in the latter about 50 pounds per square inch, more or less.

With this type of operation a suitable boiling range for the kerosene fraction removed from the crude ash tower and diverted from the process is about 450 to 550 F. This is merely illustrative as the boiling ran-ge may be somewhat higher or lower. The heavy naphtha and .the gas oil which are mixed in accumulator for cracking together in coil 'I'I may have boiling ranges of from 250 to 450 F., and 550 to 750 F., respectively, for example. The boiling range of the naphtha will depend upon the anti-knock value desired for the final gasoline distillate, the

-higher the anti-knock value necessary the greater the quantity of naphtha which must be reformed and accordingly the lower the initial boiling point of the naphtha passed through coil Tl. The conversion to products in the gasoline boiling range per pass in the heating coils 36, 55, 11, and 93, may be about 10%, 15%, 60% and 20% respectively. But these values are merely illustrative and may be varied to suit different charging stocks and different desired products. Obviously the lighter and cleaner the stock the higher the rate of conversion may be. Referring to the coil 'l1 high conversions per pass will follow from high initial gasoline content. Reaction chambers may be used with any or all of the cracking coils to provide for additional cracking.

In an alternative method of handling a crude oil charging stock, the crude charge introduced by pump 2, after preheating in heat exchangers, such as 4 and 5, instead of being passed directly to the crude flash tower 3, is introduced into a pre-flash drum for the release of light vapors which are passed into the lower part of the crude flash tower 3, and the residue from the pre-flash drum is passed through heating coil 1 and the heated crude directed through line 6 into the flash tower 3.

While we have described a particular embodiment of our invention for purposes of illustration, it should be understood that various modiiications and adaptations thereof which will be obvious to one skilled in the art, may be made within the spirit of the invention as set forth in the appended claims.

We claim:

1. In the cracking of hydrocarbon oils the process that comprises subjecting crude petroleum in a primary fractionating zone to fractionation to form a residue and a lighter fraction, passing said residue to a primary viscosity-breaking zone wherein the residue is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the viscosity-broken products into a separate evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zone and subjecting the vapors therein to fractionation to form a heavy reflux condensate and a lighter fraction, passing resultant heavy reflux condensate to a secondary viscosity-breaking zone wherein the heavy condensate is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, separating the latter viscosity-broken products into vapors and residue and passing the separated vapors into said separate fractionating zone, combining said lighter fractions obtained from the viscosity-broken products and from the crude petroleum fractionation and subjecting the combined fractions to cracking in a separate cracking zone under high cracking temperature and under conditions of high cracking per pass to effect conversion to gasoline of high antiknock quality and directing the resultant products of the latter cracking into a separate fractionating zone to recover the desired gasoline product.

2. In the cracking of hydrocarbon oils the process that comprises subjecting crude petroleum in a primary fractionating zone to fractionation to form a residue and a lighter fraction, passing said residue to a primary Viscosity-breaking zone wherein the residue is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the viscositybroken products into a separate evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zone and subjecting the vapors therein to fractionation to form a heavy reux condensate and a lighter condensate comprising such gas oil constituents, passing resultant heavy reux condensate to a secondary viscositybreaking zone wherein the heavy condensate is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, separating the latter viscosity-broken products into vapors and residue and passing the separated vapors into said separate fractionating zone, combining said lighter fractions obtained from the viscosity-broken products and from the crude petroleum fractionation and subjecting the combined fractions to cracking in a separate cracking zone under high cracking temperature lili dit

and under conditions of high cracking per pass to eect conversion to gasoline of high anti-knock quality, directing the resultant products of the latter cracking into another evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zone wherein the vapors are fractionated to form a reiiux condensate and a nal distillate product, passing resultant reflux condensate to a fourth cracking zone wherein it is subjected to cracking temperature to elfect conversion into gasoline constituents and directing the resultant products of conversion into said latter separating zone.

3. In the cracking of hydrocarbon oils the process that comprises primarily subjecting crude petroleum to a stripping operation to separate it into vapors and residue and fr actionating the vapors to form a condensate, passing said residue to a primary viscosity-breaking zone wherein the residue is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the viscosity-broken products into a separate evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zone and subjecting the vapors therein to fractionation to form a heavy reux condensate and a lighter condensate comprising such gas oil constituents, passing resultant heavy reux condensate to a secondary viscosity-breaking zone wherein the heavy condensate is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the latter viscosity-broken products into said separate evaporating zone, combining said lighter condensate obtained from the viscositybroken products with said condensate obtained from the stripping of the crude petroleum and subjecting the combined condensates to cracking in a separate cracking zone under high temperature and conditions of high cracking per pass to eect conversion into gasoline of high anti-knock quality, directing the resultant products of the latter cracking into another evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zone wherein the vapors are fractionated to form a reux condensate and a nal distillate product, passing resultant reflux condensate to a fourth cracking zone wherein it is subjected to cracking temperature to effect conversion into gasoline constituents and directing the resultant products of conversion into said latter separating zone. p

i. In the cracking of hydrocarbon oils the process that comprises-subjecting crude petroleum in a. primary fractionating zone to fractionation to form a residue and a lighter fraction, passing said residue to a primary viscosity-breaking zone wherein the residue is subjected to cracking temperature under conditions to eifect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the'viscositybroken products into a separate evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zone and subjecting the vapors therein to fractionation to form a heavy reux condensate and a lighter condensate comprising such gas oil constituents, passing resultant heavy reflux condensate to a secondary viscositybreaking zone wherein the heavy condensate is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the latter viscosity-broken products into said separate evaporating zone, withdrawing residue from the latter evaporating zone and subjecting it to vacuum distillation in a flashing zone held under sub-atmospheric pressure to form heavy residue and vacuum-'flashed distillate and combining resultant Vacuum-flashed distillate constituents with the heavy reiiux condensate passing to the secondary viscosity-breaking zone, combining said lighter fractions obtained from the viscosity-broken products and from the crude petroleum fractionation and subjecting the combined fractions to cracking in a separate cracking zone under high cracking temperature and under conditions of high cracking per pass to effect conversion to gasoline of high anti-knock quality and directing the resultant products of the latter cracking into a separate fractionating zone to recover the desired gasoline product.

5. In the cracking of hydrocarbon oils the process that comprises subjecting crude petroleum in a primary fractionating zone to fractionation to form a residue and a lighter fraction, passing said residue to a primary Viscosity-breaking zone wherein the residue is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the viscosity-broken products into a separate evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zone and subjecting the vapors therein to fractionation to form a heavy reflux condensate and a lighter condensate comprising such gas oil constituents, passing resultant heavy `reflux condensate to a secondary viscosity-breaking zone wherein the heavy condensate is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, separating the latter viscositybroken products into vapors and residue and passing the separated vapors into said separate fractionating zone, passing residual material separated out from the viscosity-broken products from both of said viscosity-breaking zones to a vacuum flashing zone wherein the residual material is subjected to ash distillation under sub-atmosphericv pressure to form heavy residue and vacnum-flashed distillate, combining resultant vacnum-flashed distillate constituents with the heavy reflux condensate passing to the secondary viscosity-breaking zone, combining said lighter fractions obtained from the viscosity-broken products and from the crude petroleum fractionation and subjecting the combined fractions to cracking in a separate cracking zone under high cracking temperature and under conditions of high cracking per pass to effect conversion to gasoline of high anti-knock quality and directing the resultant products of the lattercracking into a separate fractionating zone to recover the desired gasoline product.

6. In the cracking of hydrocarbon oils the process that comprises subjecting crude petroleum in a primary fractionating zone to fractionation to form a residue and a lighter fraction, passing said residue to a, primary viscosity-breaking zone wherein the residue is subjected to cracking temperature under conditions to eiect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the viscosity-broken products into a separate evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zone and subjecting the vapors therein to fractionation to form a heavy reflux condensate and a lighter condensate comprising such gas oil constituents, passing resultant heavy reflux condensate to a secondary viscositybreaking zone wherein the heavy condensate is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the latter viscosity-broken products into said separate evaporating zone, withdrawing residue from the latter evaporating zone and subjecting it to vacuum distillation in a ashing zone held under sub-atmospheric pressure to form heavy residue and vacuum-ashed distillate and introducing resultant vacuumashed distillate into the aforesaid separate fractionating zone so that any portion of the vacuum-flashed distillate remaining unvaporized after contact with the vapors undergoing fractionation therein will be charged to said secondary viscosity-breaking zone with said heavy reiiux condensate, combining said lighter fractions obtained from the viscosity-broken products and from the crude petroleum fractionation and subjecting the combined fractions to cracking in a separate cracking zone under high cracking temperature and under conditions of high cracking per pass to effect conversion to gasoline of high anti-knock quality and directing the resultant'products of the latter cracking into a separate fractionating zone to recover the desired gasoline product.

7. In the cracking of hydrocarbon oils the process that comprises subjecting crude petroleum in a primary fractionating zone to fractionation to form a residue and a lighter fraction,passing said residue to a primary viscosity-breaking zone wherein the residue is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the viscosity-broken products into a separate evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zone and subjecting the vapors therein to fractionation to form a heavy reux condensate and a lighter condensate comprising such gas oil constituents, passing resultant heavy reux condensate to a secondary viscosity-breaking zone wherein the heavy condensate is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, separating the latter viscositybroken products into vapors and residue and passing the separated vapors into said separate fractionating zone, passing residual material separated out from the viscosity-broken products from both of said viscosity-breaking zones to a vacuum flashing zone wherein the residual material is subjected to flash distillation under subatmospheric pressure to form heavy residue and vacuum-ashed distillate, introducing resultant vacuum-flashed distillate into the aforesaid separate fractionating zone so that any portion of the vacuum-ashed distillate remaining unvaporized after contact with the vapors undergoing fractionation therein will be charged to said secondary viscosity-breaking zone with said heavy reflux condensate, combining said lighter fractions obtained from the viscosity-broken products and from the crude petroleum fractionation and subjecting the combined fractions to cracking in a separate cracking zone under high cracking temperature and under conditions of high cracking per pass to eifect conversion to gasoline of high anti-knock quality and directing the resultant products of the latter cracking into a separate fractionating zone to recoverthe desired gasoline product.

8. In the cracking of hydrocarbon oils the process that comprises subjecting crude petroleum in a primary fractionating zone to fractionation to form a residue and a lighter fraction, passing said residue to a primary viscositybreaking zone wherein the residue is subjected to cracking temperature under conditions to eect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the viscosity-broken products intoa separate evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zone and subjecting the vapors therein to fractionation to form a heavy reux condensate and a lighter condensate comprising such gas oil constituents, passing resultant heavy reux condensate to a secondary viscosity-breaking zone wherein the heavy condensate is subjected to cracking temperature under conditions to effect the formation of a high yield .of gas oil constituents adapted for conversion into gasoline, separating the latter viscosity-broken products into vapors and residue and passing the separated vapors into said separate fractionating zone, passing residual material separated out from the viscosity-broken products from both of said viscosity-breaking zones to a vacuum flashing zone wherein the residual material is subjected to ash distillation under sub-atmospheric pressure to form heavy residue and vacuumfiashed distillate, combining resultant vacuumashed distillate constituents with the heavy reflux condensate passing to the secondary viscosity-breaking zone, combining said lighter fractions obtained from the viscosity-broken products and from the crude petroleum fractionation and subjecting the combined fractions to cracking in a separate cracking zone under high cracking temperature and under conditions of high cracking per pass to eilg'ect conversion to gasoline of high anti-knock quality, directing the resultant products of the latter cracking into another evaporating zone wherein separation of vapors from residue takes place, passing the-sep arated vapors into a separate fractionating zone wherein the vapors are fractionated to form a reflux condensate and a i'lnal distillate product, passing resultant reflux condensate to a fourth cracking zone wherein it is subjected to cracking temperature to effect conversion into gasoline constituents and directing the resultant products of conversion into said latter separating zone.

9. In the cracking of hydrocarbon oils the process that comprises primarily subjecting crude petroleum to a stripping operation to separate it into vapors and residue and fractionating the vapors to form a condensate, passing said residue to a primary viscosity-breaking zone wherein the residue is subjected to cracking temperature under conditions to effect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the viscositybroken products into a separate evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate ractionating zone and subjecting the vapors therein to fractionation to form a heavy reflux condensate and a lighter condensate, comprising such gas oil constituents, passing resultant heavy reflux condensate to a secondary viscosit 1- breaking zone wherein the heavy condensate is subjected to cracking temperature under conditions to eiect the formation of a high yield of gas oil constituents adapted for conversion into gasoline, directing the latter viscosity-broken products into said separate evaporating zone, withdrawing residue from the latter evaporating zone and subjecting it to vacuum distillation in a ashing zone held under sub-atmospheric pressure to form heavy residue and vacuum-flashed distillate and introducing resultant vacuumlashed distillate into the aforesaid separate fractionating Zone so that any portion of the vacnum-flashed distillate remaining unvaporized after contact with the vapors undergoing fractionation therein wil be charged to said secondary viscosity-breaking zone with said heavy reux condensate, combining said dighter condensate obtained from the viscosity-broken products with said condensate obtained from the stripping of the crude petroleum and subjecting the combined condensates to cracking in a separate cracking zone under high temperature and conditions of high cracking per pass to eiect conversion into gasoline of high anti-knock quality, directing the resultant products of the latter cracking into another evaporating zone wherein separation of vapors from residue takes place, passing the separated vapors into a separate fractionating zon'e wherein the vapors are fractionated to form a reflux condensate and a nal distillate product, passing resultant reux condensate to a fourth cracking zone wherein it is subjected to cracking temperature to eiect conversion into gasoline constituents and directing the resultant products of conversion into said latter separating zone.

PERCIVAL C. KEITH, JR. JOSEPH K. ROBERTS.

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