US2119401A - Process for the treatment of hydrocarbon oil - Google Patents

Description

May 31., 1938. 2,119,401

PROCESS FOR THE TREATMENT OF HYDROCARBON OIL H. PRICE ET AL Filed Feb. 25, 1935 NQSSwSk QSkuRQU 3.3% $55 tad? kmmtwtb 8 mmm 1 TH.V N m WHE PV my w R0 '1 N w Qv 3 I! M om .5 M I fi I wus kl m win 65 +m ATTORNEY Patented May 3l,

UNITED; STATES PATENT OFFICE PROCESS FOR THE TREATMENT OF HYDROOARBON OIL of Indiana Application February 23, 1935, Serial No. 7,688

7 Claims.

This invention relates to processes for the a treatment of hydrocarbon oil and pertains more particularly to processes whereby very heavy hydrocarbon oils may be converted into lighter products in the gasoline boiling range.

It is an object of our invention to provide an integral process for the simultaneous treatment of relatively light hydrocarbon fractions including normally gaseous fractions, and relatively 10 heavy liquid hydrocarbons, in order to cause the formation therefrom of desirable products in the gasoline boiling range. a A-further object of our invention is to provide an improved process whereby relatively heavy charging stockin the nature of crude petroleum, topped crude,.o"r the like, may be subjected to relatively drastic cracking in a single pass operation with the resulting'formation of relatively large quantities of products in the gasoline boil- 4 ing range, and clean cracking stock without deleterious coking of the apparatus.

More specifically it an object of our invention to establish 'a process whereby relatively light hydrocarbons, including fractions which are normally incondensible, and relatively heavy hydrocarbons, such as crude petroleum or the heavier ends thereof, or the like, may be subjectedto conversion into products in' the gasoline boiling range by a single unitary process whereby at least a portion of the heat necessary to conduct the cracking of the heavy hydrocarbons is supplied by contact thereof with the lighter hydrocarbons, which have previously been heatedto ahigh temperature to cause pyrolysis thereof and the gasoline boiling range.

According to our invention fresh gas to be treated, i. e. normally incondensable gas' plus vapors ordinarily considered too light for inc1u' 40 sion in gasoline, is passed througha gas cracking zone wherein it is raised to a relatively high conversion ,temperaturesuflicient to cause the formation. therefrom of benzol and other frac tions in the gasoline boiling range, and the resulting highly heated 'gasesand vapors including benzoland products of conversion, are directly contacted and intimately intermingled with the a attendant formation of low boiling products in wherein it is raised to a cracking temperature" and subjected to a moderate amount of cracking,

but need not necessarily be so preheated. In

,in an enlarged reaction zone wherein cracking of the heavy hydrocarbons takes place and deposition of coke will not be detrimental, and 15 from which the lighter products including gasoline constituents and intermediate boiling oil suitable for clean cracking stock may be quickly and continuously removed without being subjected to undesirably great amounts of crack- 20 ing. The hot gases and heavy liquid hydrocarbons may be introduced into the enlarged zone so as to commingle immediately on entrance or may be caused to flow countercurrent to one another in the said zone, or if desired the hot gases 5 and heavy liquid hydrocarbons may be com mingled in a common pipe line prior to entrance into the enlarged zone.

The cracked vapors from the enlarged reaction zone are then preferablyfractionated to 30 separate gases, gasoline distillate, and gas oil condensate, the former being passed to the gas cracking zone, either directly or after previous removal of any gasoline constituents or nonreactive gases, or both. The gas oil condensate 5 is then passed through a separate cracking zone wherein it is subjected to a cracking temperature to cause the formation of additional gasoline constituents and gas oil cycle stock, which 1 may be returned to the cracking zone already 40 mentioned, or may 'o'e'subjected to a separate cracking operation.

The hydrocarbon gas charged to the gas cracking zone preferably consists of or contains large amounts of ethane, propane, or butane, and may ,45 be derived from natural sources or from the cracking of liquid hydrocarbons, or any other source. Alternatively in place of utilizing cracked gas as a source of heat for the cracking of heavy liquid charging stock, or in addition-to the use of such hot gases, hot reformed naphtha vapors,

or hot vapors or other stock boiling below the gas oil boiling range, may be utilized. In this case the na'phtha or other stock heated to the high temperature may be derived from an exoil, reduced crude, or the like, is preferably first passed through a coil heating zone wherein it is raised to a moderate cracking temperature of, for example, around 850, F., with the attendant formation of the relatively small percentage of gasoline which can be formed without serious coking trouble, and is then passed into the mixing zone into contact with the highly heated cracked gas or reformed naphtha, or other stock, and is therein raised to a considerably higher temperature of, for example, 925 F. to 950 F., or even higher, with the resulting formation of additional quantities of gasoline constituents, and clean cracking stock for treatment as already specified.

By proceeding as described hereinbefore it is possible to quench the hot products from the gas cracking reaction so as to check undesirable further conversion, while at the same time raising the liquid quenching oil to a relatively high oil cracking or viscosity breaking temperature, with accompanying conversion of the heavy oil into gasoline and lighter products including intermediate boiling products suitable for use as clean cracking stock. Therefore even if a heavy liquid hydrocarbon in the nature of crude, oil, topped crude or the like is used for the quenching operation, it is assured that no virgin constituents thereof will pass oifwith the tar resulting from the gas cracking operation, in a subsequent separating .step, which would be the result if the temperature of the resulting mixture of hot cracked gases and quenching oil were not maintained at an oil cracking value for a suflicient period of time to eflect'the cracking of the liquid .011.

Another important advantage of the process, from another point of view, is that by using such relatively light material as normally incondensable gases or reformed naphtha or other stock boiling below the gas oil range, as the source of heat the intermediate boiling oil.

for carrying out the cracking or viscosity breaking step by direct contact, it is assured that the intermediate boiling oil obtained by the cracking or viscosity breaking of the heavier liquid hydrocarbon will be substantially free of cracked constituents resulting from any cracking process other than that in which the heavy liquid hydrocarbon oil was cracked, since the constituents of the highly heated gases, benzol, or reformed naphtha mixed with the heavy liquid hydrocarbon to cause the cracking thereof, are mainly of so lowboiling point as to fall within the gasoline boiling range or a lower boiling range, whereby they will be vaporized and passed oil. overhead with the final desired gasoline distillate. 'I'arry constituents resulting from the gas cracking or naphtha reforming steps are so high boiling as to pass off with the liquid residue instead of with If reformed naphtha is the source of heat,-the above-mentioned result is particularly assured by .selecting the naphtha to be reformed, so that substantially all of it boils at not over 450 F; a

This process provides that the intermediate boiling oil,.-or clean cracking stock, so obtained will be substantially homogeneous and will include only once-cracked constituents instead of a mixture of once-cracked and twice-cracked constituents, whereby the future cracking operation carried out on the clean cracking stock may be conducted under conditions more beheflcial to the treatment of once-cracked oil.

streams of hydrocarbons.

A further advantage is that by this procedure relatively high conversion of the heavy liquid hydrocarbons to lighter products can be accomplished in a single once-through cracking operation without recycling, whereby the expense and deleterious coking effects of a recycling operation carried out on the heavy liquid hydrocarbons may be avoided, while still securing even higher conversion thereof into gasoline and intermediate boiling oils suitable for use as clean cracking stock.

The co-pending application of Ralph H. Price, Serial No. 630,256, pertaining to the Production of motor fuel, describes and claims a somewhat related process according to which highly heated gases from a gas cracking process are quenched by scrubbing with a heavier liquid hydrocarbon.

The above-mentioned and further objects and advantages of our invention and the manner of attaining them will be more fully explained in the following description taken in conjunction with the accompanying drawing. I In the drawing Fig. 1 illustrates diagrammatically an oil cracking system embodying our 'invention and Fig. 2 illustrates in side elevation and partly in section, a mixing nozzle for use in carrying out our invention.

Referring more particularly to the drawing, reference numeral I indicates the charging line through which fresh relatively heavy charging stock, such as crude petroleum oil, topped crude or the like, is introduced. This charging oil is forced by pump 2 through indirect heat exchanger 3 and into the intermediate section 4 of combination tower 5, after having been also heated, if desired, either before or after passage through the indirect heat exchanger 3, by indirect heat exchange with other hot products of the operation, or by passage through an independent directly flred heating coil. In the section I, which serves as a flash drum, the introconversion to products in the gasoline boiling range with the. accompanying production of quantities of gas oil and other intermediate boiling products suitable for use as clean cracking stock. The heated products pass from the viscosity breaking furnace through line H and into the reaction chamber l2, preferably being di-- rected against a plate I I located above the liquid level therein, with such force as to break up the entering stream of oil into a spray of small droplets or particles.

In til; reaction chamber I! the stream of introduced heated heavy products is contacted and thoroughly intermixed with a more highly heated stream of, relatively light gases' and vapors introduced through line I4 and preferably also directed against the plate l3 so as to assure intimate contact between the two introduced The temperature of the gases and-vapors so introduced may be from 1000 to 1700 F. or more, while the temperature of the resulting mixture is most suitably in the range of 925 to 950 F., although it may have a somewhat higher temperature provided the time the mixture is maintained at the high temperature is kept suificiently short to prevent serious deposition of coke in the drum. In order to control the time of contact so that the desired cracking effect may be obtained, liquid residue is withdrawn from the base of the reaction chamber l2 by way of line I5, having control valve I6, at a rate sufficiently rapid to permit the desired cracking to take place; the faster the liquid residue is drawn off the shorter the time at which it is maintained at cracking temperature in the reaction chamber I2, and consequently the lesser the amount of cracking that takes place in that chamber. The withdrawn highly heated residue passes through the line I and control valve I6 into tar flasher section H of combination tower 5, preferably with a reduction in pressure, and therein separates into vapors and liquid residue, the former passing upwardly through the lower portion of crude flash section 4 wherein the rising vapors serve as a source of heat to aid in the stripping of lighter constituents from the introduced heavy oil, and are themselves at the same time subjected to fractional condensation, heavier constituents being condensed in the trap-out tray 6 in mixture with unvaporized portions of the introduced charging stock and being passed through the viscosity breaking heater III therewith. The unvaporized residual tar in the base of the tar flasher I! is withdrawn from the process through draw-off line I9, as fuel oil or for any desired use.

The lighter constituents separated as vapors in the reaction chamber I2 pass off through the vapor line 20 and are preferably directed through pipe 23, and line I in combination with the fresh charge, into the fractionator 5. Alternatively the vapors may be introduced into the fractionator 5 at a higher level.

The vapors in the tower 5 undergo fractional condensation, condensate of the nature of gas oil suitable for use as a clean cracking stock collecting on trap-out tray 29. Condensate so collected is withdrawn through line 32, and is preferably forced by pump 33 through the heating coils of cracking furnace 34, wherein it is raised to a cracking temperature and subjected to conversion, preferably in the so-called vapor phase, to cause formation of additional products in the gasoline boiling range. The resulting highly heated products are then preferably passed through the line 35, having control valve 36, into the base of tar flasher section II of combination tower 5, but may instead, if desired, be passed through branch line 37 having control valve 38, into a separate evaporating tower 39 wherein the cracked products are separated into vapors and liquid residue, the former passing through conduit 40 into the crude stripping section 4 of combination tower 5 while the liquid residue or tar is withdrawn from the process through pipe 4|.

, This alternative method of handling the cracked products from the furnace 34 has the advantage that the cracked tar may be separately withdrawn through line 4| while the tar derived from the fresh charging stock is withdrawn through line I9 from tar flasher I'I. Still further separation of the products may be assured by closing valve 42 in line 40 and passing the vapors from evaporator 39 through valved line 43 into an entirely separate fractionating system, not shown, wherein light constituents in the gasoline boiling range are separated as vapors from heavier constituents as liquids, the former being removed and separately condensed while the latter may be recycled through the cracking furnace or may be passed to an entirely separate cracking unit, not shown, wherein it is subjected to conversion into products in the gasoline boiling range, under optimum cracking conditions..-

The lighter constituents of the vapors separated in the various sections of the combination tower '5 pass off from the top section thereof through conduit 44 and cooler 45 into a receiver 46, which is preferably maintained under a high pressure. In this receiver, or high pressure gas separator, relatively dry gases separate from liquefied hydrocarbons and are preferably withdrawn from the process through line 41. The liquid constituents collected in the receiver pass through conduit 48 having pressure control valve 49 into a low pressure receiver or separator 50, wherein a further separation takes place, the undesirably light constituents passing off as vapors through conduit 5| while the liquid constituents are removed as a; desired distillate, e. g. gasoline, through drawoff line 52, forming a desired product of the process. Gasoline so obtained will be of relatively high anti-knock value, since it includes a percentage of benzol as well as vapor phase cracked gasoline constituents.

The highly heated gases and vapors contacted with the heavy oils introduced into reaction chamber I 2 are preferably obtained by the cracking of hydrocarbon gases for the production of benzol, these hydrocarbon gases being either fresh gas from a natural source, refinery gases, cracked gases from the unit itself, or a mixture of some or all of these.

In carrying out this phase of the invention fresh gas from line 53 and/or recycled gases from low pressure separator 50 are passed through gas cracking furnace 54, under pressure generated by compressorsv 55 and 51', and in passing through the cracking furnace are raised to a gas cracking temperature preferably in the range of 1000 to 1700 F. and under a pressure of from atmospheric to 500 pounds per squareinch or more, the conditions preferably being a temperature of from 1350 to 1700 F., anda pressure of from atmospheric to 100 pounds per square inch. With the higher pressures mentioned the lower temperatures may be used. The gases passing then pass through the line I4 to the reaction chamber I2 in contact with the heavy oil. Reference numerals 58 and 59 indicate valves whereby the necessary control of .the gas flow may be obtained.

In place of, or in addition to the cracked gas from cracking furnace 54, heat may be supplied to the heavy oil in the reaction chamber H by reforming naphtha or gasoline having an undesirably low anti-knock value to form higher anti-knock gasoline constituents and introducing the'highly heated reformed gasoline vapors into the reaction chamber l2. To accomplish this, fresh naphtha of relatively low anti-knock value formation of relatively high anti-knock gasoline g constituents. Naphtha for this purpose may suitfor that particular stock. As in the ably be a virgin fraction from crude oil with a boiling range in the neighborhood of from 200' to 450 F. The highly heated reformed products pass through line 63 having control valve 64, and into the line l4 from which they pass inside the reaction chamber l2 in contact with the heavy oil introduced thereinto through line i I. Instead of, or in addition to the naphtha from the external source 60, naphtha from the fractionating section 1 of combination tower 5 may be used, this naphtha comprising both virgin and cracked constituents. In this case the naphtha may be withdrawn from tray 65 in the fractionating section 1,-by way of pipe '66 and be forced by pump Slinto the coils of the reforming furnace 62. The reforming of the naphtha may be carried out at any well known pressure for that operation, but the outlet pressure on the reforming furnace is preferably in the neighborhood of 600 pounds per square inch, more or less.

According to an alternative method of operation. the vapors removed from the reaction chamber l2 through line 23, instead of being passed directly tothe tower 5 are passed through conduit 22 into a separate fractionator 25, wherein fractional condensation occurs with the result that constituents in the gas oil boiling range are condensed as reflux condensate, while lighter constituents comprising gas -and gasoline pass overhead through vapor line 30 into the tower 5, for further fractionation with the vapors passing through the last-mentioned tower. The reflux condensate collecting in the base of the fractionator 25 may then be withdrawn through line 21 and forced by pump 21' through the coils of cracking furnace 23 wherein the condensate is raised to a cracking temperature and subjected to conversion under conditions of temperature, pressure and time best suited for the desired conversion thereof. This procedure would leave any virgin constituents of the charging stock for passage through the cracking furnace 34 by way of line 32, after withdrawal from trap-out tray 23. In this connection it should be noted that the amount of volatile constituents released from the tar in chamber l1 and collecting on the trap-out tray 39 will be relatively small. As a result the cracking conditions in the furnace 34 could then be adjusted to give the optimum cracking effect case of the cracked products from furnace 34. the cracked products from furnace 28 may be passed through a separate evaporator and/or fractionator, not shown, to provide for the separate withdrawal of tar and the separate fractionation of the cracked vapors. Where the additional evaporator alone is used, the vapors may be directed from that evaporator to the tower 5, while the cracked tar is separately drawn off from the process.

Valve 10 is provided for controlling the outlet pressure on the coils of furnace 23, while valves H and 12 control the flow of vapors from the reaction chamber l2 to either tower 5 or fractionator 25.

The pressure maintained in the reaction chamber l2 may be varied considerably depending upon the operating conditions maintained in other portions of the apparatus, but where hot products of a gas cracking operation are introduced into this reaction chamber the pressure therein must be lower than that maintained at the outlet of the gas cracking furnace so as to permit of the flow of the hot cracked gases into the reaction chamber. In general where a gas cracking furnace is used as a source of supply of heat the-pressure in the reaction chamber may be maintained in the range of 50 to 100 pounds per square inch, while if the heat is derived from a reforming furnace only, the pressure irf the reaotio n chamber may be considerably higher,

for example in the neighborhood of 200 pounds per square inch, more or less.

The cracking conditions maintained in the out vapor phase crackingat a substantial rate,

for example, the oil may be raised to a cracking temperature in the neighborhood of 950 to 975 F., under a pressure in the neighborhood of a few hundred pounds per square inch, e. g., 200 pounds per square inch. Under these conditions the conversion to gasoline per pass may fall in the range of 15%v to 25%, ordinarily. about 20% per'pass, but in case the cracked products from the heater 34 are separately fractionated by being passed through line 31 to evaporator 38 and from vapor line 43 to a separate fractionating zone, not shown, wherein reflux condensate formed by fractionating the vapors is separately collected or I the heater 34 may be-carried considerably higher since the stock passing therethrough will then be mainly only once-cracked stock of less marked coke-forming tendencies. stances the temperature may be considerably higher and the conversion to gasoline per pass may be raised to 35% or more, particularly where higher pressures are used, e. g., 500 to 700 pounds per square inch or more. If the heater 28 is used the cracking conditions therein may be about the same as those of the heater 34.

In order to prevent undesirably great accumulation of gases in the apparatus it may be desirable'to bleed oif gases from the process from time to time through line 69, as well as from 41. A preferable method would be to separate hydrogen and methane from the recycled gases before passing them through the gas cracking furnace 54 and this may be done by any well known process such as low temperature fractionation or by scrubbing the gases with a selective solvent, such as light naphtha, which will tend to absorb the aseous fractions which it is desired to recrack while leaving the hydrogen and methane in vapor form to be drawn oil from the process. The absorbed gases should then be liberated from the solvent liquid by heating so that it will not be necessary to pass the solvent itself through the gas cracking zone. The apparatus for carrying out the separation of hydrogen and other undesirably light gases from the gases and vapors to be passed through the gas cracking furnace has not been shown on the drawing but may be constructed in accordance with the teachings'of the prior art.

The viscosity breaking furnace I0 is preferably employed for a preliminary heating of the reduced crude with an attendant moderate amount of cracking of a viscosity breaking nature, but if desired this furnace'may be bypassed by way of line 10', this being accomplished by proper ma- Urider these circumnipulation of the control valves 1| and 12'. The

cooling coils, which have not been indicated by reference numerals, cooling liquids may be pumped directly into the various chambers for refluxing purposes. When the indirect heat exchange coils are provided they may be used to preheat the fresh charging stock for the process if desired. Instead of passing the .highly heated gases and the cooler heavy liquid hydrocarbons into the reaction chamber I2 separately they may be mingled in a common conduit outside the reaction chamber so as to be introduced as a mixture. In this case some additional cracking may take place in the conduit. Alternatively the heavy liquid oil may be introduced into the reaction chamber at a higher level than the hot gases so as to cause countercurrent contact to take place.

A particularly effective type of arrangement for mixing the heavy liquid oil to be cracked with the highly heated gases and vapors from the gas cracking zone, with a minimum of deleterious carbon deposition is illustrated in Fig. 2. In this figure reference numeral I 2' indicates the wall of the reaction chamber and H and M the pipes through which the liquidoil and hot gases respectively, are introduced. Thirteen (i3) is the plate against which the introduced liquids and gases impinge. The end of the pipe i I is tapered to a nozzle 13 through which the oil is ejected at high pressure against theplate l3,while the end of the conduit l4 through which the hot gases are introduced is flared outwardly, funnel fashion, as indicated at 14, so that the gases are ejected at an angle to the surface of the plate, whereby any liquid oil particles which would tend to collect on the plate and deposit coke are quickly swept away into the body of the reaction chamber, from which any carbonaceous material may be removed with the liquid drawn off through line I5. With this arrangement intimate mixture of the liquid oil and hot gases is assured upon passage thereof through the restricted opening between the end of the pipe l4 and the plate l3.

By introducing the liquid oil at high velocity against a rigid splash plate the oil is broken up into a fog which is swept away by the stream of hot gases discharged at an angle to the plate around the periphery of the funnel-shaped enlargement of the gas inletline. The splashing of the oil against the plate keeps it relatively cool and free from coke and any coke formed by heating of the oil droplets constituting the fog, through contact with the hot gases, is mostly formed within the droplet while suspended in mid-air and as a result will tend to be carried in finely divided form out into the main body of the drum or reaction vessel. As already stated this carbonaceous material may settle in the bottom of the drum and be carried out with the liquid oil,- or some of it may pass overhead with the vapors through the vapor line 20.

While we have described a particular embodiment of our invention for the purposes of illustration, it should be understood that various modifications and adaptations thereof may be made within the spiritof the invention as set forth in the appended claims.

We claim:

1. The process of treating hydrocarbon oil which comprises heating relatively light hydrocarbons, substantially allof which boil at a temperature of not over 450' F., to a relatively high cracking temperature to cause conversion thereof into hot vapors in the gasoline boiling range,

introducing the resulting highly heated vapors and gases into a reaction zone and therein contacting them with relatively heavyJiquid hydrocarbon oil introduced at a lower temperature from a separate source, the relative quantities and temperatures of the highly heated gases and vapors and of the heavy oil being such that the temperature of the resulting mixture is considerably higher than that of the heavy oil at the time of its introduction, said temperature of the resulting mixture being such as to cause vapors therein, removing unvaporized portions of said charging stock in mixture with relatively heavy condensate and introducing the mixture into said reaction zone as said heavy liquid hydrocarbon oil, and removing unvaporized constituents from said reaction zone and introducing them into said separating zone with an accompanying reduction in pressure, to cause flashing thereof.

2. The process of treating hydrocarbon oil which comprises heating relatively light hydrocarbons, substantially all of which boil at a temperature of not over 450 F., to a relatively high cracking temperature to cause conversion thereof into hot vapors in the gasoline boiling range, introducing the resulting highly heated vapors and gases ,into a reaction zone and therein contacting them with relatively heavy liquid hydrocarbon oil introduced at a lower temperature from a separate source, the relative quantities and temperatures of the highly heated gases and vapors and of the heavy oil being such that the temperature of the resulting mixture is considerably higher thanthat of the heavy oil at the time of its introduction, said temperature of the resulting mixture being such as to cause cracking of said heavy oil, removing the resulting vapors from said reaction" zone and fractionating them in a fractionating zone to separate gasoline constituents and an intermediate boiling condensate, passing intermediate boiling condensate so obtained through a separate crackheavy liquid hydrocarbon oil, removing liquid residue from said reaction zone andintroducing it into a flashing zone under reduced pressure, passing vapors from said flashing zone into said fractionating zone, and utilizing gases derived from said fractionating zone, and of a lower boiling point than said gasoline distillate, as a source 01' said light hydrocarbons first-mentioned.

3. A process in accordance with claim 2 wherein the cracked intermediate condensate is introduced into said flashing zone for separation into vapors and liquids.

4. A process in accordance with claim 2 wherein a fraction falling in the boiling range of about 200 to 450 F. is removed from said fractionating zone, passed through a separate heating zone in a stream of restricted cross-sectional area wherein it is raised to a reforming temperature, and resulting reformed products are introduced into said reaction zone.

5. A process in accordance with claim 2 wherein said mixture of unvaporized fresh charge and heavy condensate is passed through a separate heating zone wherein it is raised to a cracking temperature prior to the introduction thereof into said reaction zone.

6. A process of forming gasoline which comprises passing hydrocarbon gases through a gas,

cracking zone in a stream of restricted crosssectional area wherein it is raised to a gas cracking temperature and subjected to conversion,

tities that the temperature of the mixture in said zone is at avalue sufliciently high to insure the cracking of said heavy oil but insuflicient to continue said gas cracking operation, removing resulting gases and vapors from said reaction zone and fractionating them to form a desired gasoline distillate and a reflux condensate, passing reflux condensate so obtained through'a separate heating zone in a stream of restricted crosssectional. area wherein it is raisedv to cracking temperature andsubjected to conversion, separating vapors from the resulting crackedproducts and fractionating them with said gases and vapors firstmentioned, removing residue from saidreaction zone and directing it into a flashing zone under reduced pressure, introducing resultant cracked reflux condensate into said flashing zone, removing vapors from said flashing zone and fractionating them with said gases and vapors first-mentioned.

7. The process of treating Hydrocarbon oil which comprises subjecting hydrocarbon gases to a cracking operation to form highly heated gases and vapors including benzol, introducing the resulting highly heated gases and vapors into a reaction zone, simultaneously introducing into said reaction zone a stream of heavy hydrocarbon oil at a cracking temperature considerably lower than that of said highly heated gases and vapors and thoroughly intermingling said gases and vapors with said heavy hydrocarbon oil whereby the gas cracking operation is terminated and the temperature of the mixture attains an oil cracking value materially-higher than that of the introduced heavy hydrocarbon oil, so as to cause rapid conversion of said heavy hydrocarbon oil into lighter products including gasoline constituents and intermediate boiling oil suitable for use as clean cracking stock, quickly removing lighter gaseous and vaporous constituents substantially as rapidly as they are formed in said reaction zone, and subjecting gaseous and vaporous constituents so removed to fractionation to separate gases in mixture with gasoline, benzol range of the final desired product, as vapors from gas oil and other relatively heavy constituents as' liquid, separately removing said gases and vapors and said liquid, separately subjecting liqand other light-products falling in the boiling uid so obtained to cracking temperature to cause lighter constituents, so as to cause partial vapori zation. of said charging stock, subjecting vapors so obtained to partial fractionation to segregate gasoline constituents from intermediate boiling oils in the nature of clean cracking stock, combining said intermediate boiling oils with the liquids derived from said fractionating step for cracking and introducing unvaporized portions of said charging stock into said reaction zone as l the heavy hydrocarbon oil to be cracked.

RALPH H. PRICE. VANDERVEER VOORHEES.

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