US2114515A - Conversion of hydrocarbon oils - Google Patents

Description

April 19, 1938. J. G. ALTHER CONVERSION OF HYDROGARBON 01L;

Filed June 12, 1935 FRACTIONIATOR e9 a 1 s a1 INVENTOR JOSEPH G. ALTHER FIG.

FURNACE 25 ATTORNEY Patented Apr. 19, 1938 UNITED STATES CONVERSION OF HYDROCARBON OILS Joseph G. Alther, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application June 12,

9 Claims.

This invention refers to an improved. process for the selective conversionof relatively lowboiling and high-boiling hydrocarbon oils to produce high. yields. of desirable light distillate such as motor fuel of good antiknock value.

I! am awarev that many processes have been proposed for the selective conversion. of. relatively low-boiling and high-boiling hydrocarbon oils, many of which employ separate heating coils for the differentoils. and which, in many cases, employ a reaction chamber to which the heated products from both. heating coils are supplied and wherein said heated products are subjected to continued conversion- The object of employ- 15. ing separate heating coils for the relatively lowboiling and relatively high-boiling oil is to permit the use of independently controlled conversion conditions of temperature, pressure and time.

for the different oil components. However, it is common practice in such selective cracking operations employing a single reaction chamber common to both heating coils to commingle the two streams of heated products from both heating coils either before or immediately after their inv troduction intothe reaction chamber. This practice may be satisfactory in case it is desirable to retard conversion of the low-boiling. oils (which.

is usuallyv the highest temperature stream) and to increase conversion. of the high-boiling oils in the reaction chamber. This. in turn necessitates controlling the conversion conditions in the light oil heating coil so that substantially all of the conversion to which the light oil is subjected occurs in this zone and. controlling the conversion conditions in the heavy oil heating coil so that a, substantial degree of continued conversion of the heavy oil may occur in the reaction chamber. Obviously this necessitates careful correlation of the conditions in the two heating coils with each other and with the conditions maintained in the reaction chamber.

It is the object of the present invention to prevent comm-ingling of the two streams of heated.

introducing each of the streams of heated products into the reaction chamber at a remote point in this zone relative to the point of introduction of the other stream.

In the preferred embodiment of the present from the other stream. This is accomplished by 1935, Serial No. 26,189

invention the reaction zone to which the two streams of heated products from the light oil and heavy oil heating coils are supplied comprises an elongated vertical reaction chamber. The stream of heated products from either the lowv boiling or the high-boiling oil heating coil may be supplied to the upper portion of the reaction chamber, depending upon which stream it is desired, to subject to independent continued conversion in this zone, and the stream of heated products'from the other heating coil may be introduced at any desired lower point in the reaction chamber, the commingled streams being withdrawn from the lower portion of the chamber. On the other hand, one stream of heated products may be introduced into the lower portion. of the chamber, the other introduced at any desired higherpoint in this zone and the commingled vaporous components of both streams withdrawn from the upper portion of the cham- 20 ber. In accordance with another modification of the invention the stream of heated products from one heating coil may be introduced into the upper portion of the chamber, the stream of heated products from the other heating coil in- 25 troduced into the lower portion of the chamber and the vaporous components of two streams commingled and withdrawn at the desired intermediate point in this zone. In case the first described method of operation is employed, both vaporous and liquid conversion products may be withdrawn in commingled state from the lower portion of the reaction chamber or separation thereof may be accomplished therein and the vaporous and liquid products separately withdrawn. In case either of the two last described methods of operation, is employed, separation of vaporous and liquid conversion products may be accomplished in the reaction chamber, the liquid conversion products being withdrawn from the lower' portion of this zone and the vaporous products being removed, as the case may be, from the upper portion or from an intermediate point in this zone.

In one embodiment, the invention comprises subjecting a stream of hydrocarbon oil of relatively low-boiling characteristics and a separate stream of hydrocarbon oil of relatively high-boiling characteristics each to independently controlled conversion conditions of elevated temperature, super-atmospheric pressure and conversion time in a separate heating coil, introducing the stream of heated low-boiling oil into the upper portion of an enlarged vertical reaction chamber maintained at a substantial superatmospheric pressure, introducing the stream of heated relatively high-boiling oil into the lower portion of the same reaction chamber, withdrawing nonvaporous liquid conversion products from the lower portion of the reaction chamber, commingling vaporous components of both streams of heated products at an intermediate point in the reaction chamber and withdrawing the commingled materials therefrom, subjecting the vaporous conversion products to fractionation and condensing and collecting fractionated vapors of the desired end-boiling point as the final light distillate product of the process.

The accompanying diagrammatic drawing illustrates one specific form of apparatus in which the process of the invention may be accomplished as well as two alternative arrangements for connecting the reaction chamber with the rest of the system.

Figure 1 of the drawing is a side elevation of the cracking plant;

Figure 2 illustrates a reaction chamber similar to that shown in Figure 1 with a different arrangement of connected lines; and

Figure 3 illustrates another modification of the method of connecting the reaction chamber to the rest of the system which is also within the scope of the invention.

Referring particularly to Figure l of the drawing, hydrocarbon oil charging stock for the process is supplied through line I and valve 2 to pump 3 by means of which it is fed through line 4 and may be directed, all or in part, through line 5 and valve 6 into fractionator l or it may be supplied, depending upon its characteristics, through line 3, valve 3 and line l3 to light oil heating coil [5 or from line 8 through line l6, valve l1 and line 23 to heavy oil heating coil 24. The other oils which may be supplied to the light oil and heavy oil heating coils will be later more fully described.

Heating coil 15 is located within a furnace 25 of any suitable form and the relatively low-boiling oil supplied to this zone is heated therein to the desired conversion temperature, preferably at a substantial superatmospheric pressure and, in the particular case here illustrated, the resulting products are discharged in a continuous stream from heating coil 15 through line 26 and valve 2! into the upper portion of reaction chamber 3|.

Relatively high-boiling hydrocarbon oil is supplied, as will be later more fully described, to heating coil 24 wherein it is heated by means of heat supplied from a furnace 28 of any suitable form to the desired conversion temperature, preferably at a substantial superatmospheric pressure and the heated products are discharged in a continuous stream from this zone through line 29 and valve 30 and, in the case here illustrated, enter the lower portion of reaction chamber 3|.

Chamber 31, in the case here illustrated, is. an elongated, vertical chamber of materially increased cross-sectional area relative to the tubes of heating coils l5 and 24 and this zone is pref erably operated at a substantial superatmospheric pressure, which may be substantially the same or somewhat lower than the pressure employed in the preceding heating coil employing the lowest pressure, in case diiferent pressures are utilized in the two heating coils. When the two streams of heated products from heating coils i5 and 24 enter the reaction chamber in the manner illustrated in Figure 1, liquid components of the stream of heated products from the heavy oil heating coil will separate from vaporous. components of the same stream in the lower portion of the reaction chamber to be withdrawn therefrom, as will be later more fully described, while its vaporous components pass upward through the chamber and commingle at an intermediate point in this zone, with the vaporous components of the stream of heated products from heating coil l5, commingled materials being withdrawn from said intermediate portion of the chamber through line 32 to subsequent portions of the cracking system, as will be later more fully described. The stream of heated products supplied to the upper portion of chamber 3| may, when desired, be directed against the inner surface of the wallsof the chamber by means of a suitable spreader flange or spray arrangement such as indicated, for example, at 33 whereby their liquid components which are thus brought in contact with the walls of the chamber may flow downward thereover to the lower portion of the chamber to be withdrawn therefrom together with the liquid components of the stream of heated products supplied to the lower portion of the chamber. lected in the lower portion of chamber 3| may be quickly removed from this zone through line 34 and valve 35 to cooling and storage or elsewhere, as desired, or they may be directed, all or in part, through line 36 and valve 31 into vaporizing chamber 38, wherein they are subjected to further vaporization in order to increase their viscosity and flash point and to recover desirable low-boiling components thereof by vaporization, due to the substantially reduced pressure maintained in chamber 38 relative to that employed in the reaction chamber. The vaporous conversion products separately withdrawn, as previously indicated, from a suitable intermediate point in chamber 3| through line 32 may be directed, all or'in part, through valve 39 in this line into chamber 38 or they may be supplied, all or in part, through line 40, valve 4| and line 42 to fractionator I.

In case chamber 38 is employed it is, as previously indicated, preferably operated at a substantially reduced pressure relative to that employed in the reaction chamber by means of which further vaporization of the liquid conversion products supplied to this zone is accomplished. Final separation of vaporous and residual liquid conversion products is also accomplished in chamber 38, the latter being removed from the lower portion of this zone through line 43 and valve 44 to cooling and storage or elsewhere, as desired, while the vaporous conversion products are directed from the upper portion of chamber 38 through line 45, valve 46 and line 42 to fractionation in fractionator I.

The components. of the vaporous conversion products supplied to fractionator l, as previously described, boiling above the. range of the desired final light distillate product of the process are condensed in this zone as reflux condensate. The total reflux condensate may be collected within the lower portion of the fractionator to be removed therefrom through line H! and valve Hi to pump 20 by means of which it is fed through line 2| and may be directed through valve 22 in this line and through line l3 to further conversion in heating coil l5 or it may be directed from line 2| through line 41, valve 48 and line 23 to further conversion in heating coil 24. Reflux condensate may, on the other hand, be separated by fractional distillation in fractionator I, when so desired, into selected relatively low-boiling and The liquid conversion products thus colhigh-boiling fractions, in which case only the relatively high-boiling fractions are withdrawn, as described, from the lower portion of fractionator 7, this material being directed from pump 29 through line 2i, line 41, valve 48 and line 23 to further conversion in heating coil 24. When this method of operation is employed the relatively low-boiling fractions of the reflux condensate are withdrawn from one or a plurality of suitable intermediate points in this zone, provision being made in the case here illustrated for directing the relatively low-boiling oil through line It and valve I! to pump l2 by means of which it is fed through line [3 and valve M to heating coil I5 for further conversion.

When the charging stock for the process comprises an oil of relatively wide boiling range, containing an appreciable quantity of both relatively low-boiling and high-boiling fractions, it may be supplied, in the manner previously described, to fractionator l and separated in this zone, together with the reflux condensate, into selected relatively low-boiling and high-boiling fractions for selective conversion in the respective heating coils l5 and 2d.

Fractionated vapors of the desired end-boiling point are withdrawn, together with uncondensable gas produced by the process, from the upper portion of fractionator I and are directed through line 49 and valve 50 to condensation and cooling in condenser 5!. Tne resulting distillate and gas passes through line 52 and valve 53 to collection and separation in receiver 54. Uncondensable gas may be released from the receiver through line 55 and valve 56. Distillate may be withdrawn from receiver 54 through line 57 and valve 58 to storage or to any desired further treatment. When desired, a regulated portion of the distillate collected in receiver 5 1 may be recirculated by well known means, not illustrated, to the upper portion of fractionator 1 to serve as a cooling and refluxing medium in this zone for assisting fractionation of the vapors and to maintain the desired vapor outlet temperature.

Referring now particularly to Figure 2 of the drawing, which illustrates a different method of connecting reaction chamber 3! with the other portions of the system: The highly heated products from the heavy oil heating coil 24 are directed through line 59 and valve 60 into the upper portion of the chamber and may, when desired, be directed against the interior surface of the walls of the chamber by means of a suitable spreader flange or spray arrangement indicated as before at 33 whereby the heavy liquid components are contacted with the walls of the chamber and caused to flow rapidly downward thereover while the vaporous components pass downward through the vapor space in the chamber. The stream of highly heated products from the light oil heating coil l5 are directed through line SI and valve 62 into the chamber at a suitable intermediate point which, in the case here illustrated, is near its central portion. The vaporous products from the heavy oil heating coil are thereby commingled at a point in the chamber adjacent line 6| with the highly heated products from the light oil heating coil l5 and the commingled materials pass downward through the remaining or lower portion of the chamber to be withdrawn, in commingled state and together with the heavy liquids which flow downward over the walls of the chamber and momentarily accumulate in its lower portion, through line 53 and valve 35%, preferably being introduced therefrom into reduced pressure vaporizing chamber 38. A suitable spreader flange or spray arrangement such as indicated at 33 may also be employed, when desired, to direct the liquid components of the stream of heated oil from light oil heating coil I5 against the walls of chamber 3 I ,although this provision is not illustrated in Figure 2. Also, when desired, vaporous and liquid conversion products may be separately removed from the reaction chamber, the liquid products being withdrawn therefrom, either alone or together with a regulated portion of the vapors, through line 63 and valve 64, while the total or remaining vaporous products are separately removed from a suitable higher point in the chamber through line 13 and valve l4.

Referring now particularly to Figure 3 which illustrates another method of connecting reaction chamber 3| which is entirely within the scope of the present invention, the stream of highly heated products from heavy oil heating coil 24 are directed through line 65 and valve 66 into the lower portion of the reaction chamber wherein their non-vaporous heavy liquid components separate from their vaporous components, the latter passing upward through the reaction chamber While the liquid products are withdrawn from the lower portion thereof through line B! and valve 68 to chamber 38 or to cooling and storage or elsewhere, as desired. The stream of heated products from light oil heating coil l5 are introduced into chamber 3| at a suitable intermediate point through line 69 and valve ll commingling adjacent their point of introduction with the vaporous components of the heated products supplied to the lower portion of this zone through line 65 and valve 66. A suitable spreader flange or spray arrangement 33 may also be employed, when desired, to direct the liquid components of the products supplied to chamber 3i through line 69 and valve 76 against the walls of the chamber so that they will flow downward thereover and be removed from the lower portion of the chamber together with the liquid components of the products supplied thereto through line and valve 66. The commingled vaporous products continue in their upward path through chamber SI and are withdrawn from the upper portion thereof through line ll and valve #2 to be directed either to chamber 38 or to fractionator l, or in part to both zones in a manner similar to that indicated in Figure 1.

It will be understood, of course, that other modified forms of apparatus embodying the features and advantages of the present invention will be apparent to those skilled in the art and the present invention is therefore not limited to the specific forms of apparatus illustrated and described. In each of the three cases illustrated and above described the point of introduction of the heated streams of low-boiling and high-boiling oils may be reversed. It will also be understood that the various modified forms are not to be considered equivalent but rather serve to render the-process of the invention more flexible and may be selected to suit requirements.

The preferred range of operating conditions which may be employed to accomplish the objects of the present invention in a process of the general character illustrated and above described may be approximately as follows: A temperature of the order of 800 to 950 F. may be employed at the outlet from the heavy oil preferably with a superatmospheric pressure at this point in the system of from to 500 pounds, or more, per square inch. The temperature employed at the outlet from the light oil heating coil may range, for example, from 900 to 1050 F. and the pressure employed at this point in the system is preferably of the order of 200 to 800 pounds, or more, per square inch. Any desired substantial superatmospheric pressure up to approximately the same as that employed at the outlet from the communicating heating coil employing the lowest pressure may be utilized in the reaction chamber. When a vaporizing or flash distilling chamber is employed it is preferably operated at a substantially reduced pressure relative to that employed in the reaction chamber ranging, for example, from 100 pounds, or thereabouts, per square inch down to substantially atmospheric pressure. The fractionating, condensing and collecting portions of the system may utilize pressures substantially the same or somewhat lower ran the pressure employed in the preceding stage or" the system.

As a specific example of one of the many possible operations of the invention as it may be accomplished in an apparatus such as illustrated and above described, charging stock which comprises a Mid-continent topped crude of about 30 A. P. I. gravity is supplied to the fractionator of the system and there separated, together with the reflux condensate formed in this zone, into selected relatively low-boiling and high-boiling fractions. The low-boiling fractions of the charging stock and reflux condensate, per cent or thereabouts of which boil within the range of approximately 400 to 600 F. are subjected in the light oil heating coil to an outlet coversion temperature of approximately 950 F. at a superatmospheric pressure of about 500 pounds per square inch and the highly heated products are introduced into the upper portion of the chamber in the manner illustrated in Figure 1 of the drawing. The highboiling fractions of the charging stock and reflux condensate are subjected in the heavy oil heating coil to an outlet conversion temperature of approximately 920 F. at a superatmospheric pressure of about 350 pounds per square inch and the highly heated products from this zone are introduced into the lower portion of the reaction chamber. The reaction chamber is maintained at a superatmospheric pressure of approximately 350 pounds per square inch. The non-vaporous liquid conversion products which momentarily collect within the lower porton of the reaction chamber are quickly removed therefrom and introduced into a reduced pressure vaporizing chamber operated at approximately 50 pounds per square inch superatmospheric pressure. Vaporous conversion products from the light oil and heavy oil heating coils are commingled near the central portion of the reaction chamber, withdrawn therefrom and also introduced into the reduced pressure vaporizing chamber. Residual liquid remaining unvaporized in the vaporizing chamber is withdrawn therefrom to cooling and storage as the final residual liquid product of the process. The vaporous products from the vaporizing chamber are subjected to fractionation for the formation of said reflux condensate and the fractionated vapors have an end boiling point of approximately 400 F. are subjected to condensation and the resulting distillate recovered. This operation will produce, per barrel of charging stock, about 62 per cent of motor fuel having an octane number of approximately '70 and approximately 26 per cent of good quality residual liquid suitable for sale as premium fuel oil, the remainder being chargeable, principally, to uncondensable gas.

I claim as my invention:

1. In a process for the pyrolytic conversion of hydrocarbon oils wherein relatively low-boiling and high-boiling hydrocarbon oils are each subjected to independently controlled conversion conditions of cracking temperature, superatmospheric pressure and conversion time'while passing in a restricted stream through a heating coil, the low-boiling oil being heated to higher cracking temperature than the high-boiling oil, the separate streams or heated relatively low-boiling and high-boiling oils introduced into an enlarged vertical reaction chamber also maintained at substantial superatmospheric pressure, resulting vaporous conversion products separated from liquid conversion products in the reaction chamber and the former subjected to fractionation for the recovery of desirable light distillate bycondensation of the fractionated vapors, the improvement which comprises introducing the stream of heated relatively low-boiling oil into said reaction chamber at a point a substantial distance remote from the point of introduction thereto of the stream of heated high-boiling oil, removing the separated vaporous conversion products from the chamber at a point intermediate the points of introduction of said streams thereto, and separately removing the liquid conversion products from the lower portion of the chamber.

2. In a process for the pyrolytic conversion of hydrocarbon oils wherein relatively low-boiling and high-boiling hydrocarbon oils are each subjected to independently controlled conversion conditions of cracking temperature, superatmospheric pressure and conversion time while passing in a restricted stream through a heating coil, the low-boiling oil being heated to higher cracking temperature than the high-boiling oil, the separate streams of heated relatively low-boiling and high-boiling oils introduced into an enlarged vertical reaction chamber also maintained at substantial superatmospheric pressure and wherein substantial further conversion is effected, the resulting vaporous and liquid conversion products separated and the former subjected to fractionation for the recovery of desirable light distillate by condensation of the fractionated vapors, the improvement which comprises introducing the heated stream of relatively low-boiling oil into the upper portion of the reaction chamber, introducing the stream of relatively high-boiling oil into the lower portion of the reaction chamber, withdrawing liquid conversion products from the lower portion of the reaction chamber and separately removing vaporous components of both streams from a point in the reaction chamber intermediate the points of introduction of said low-boiling and high-boiling oils.

3. In a process for the pyrolytic conversion of hydrocarbon oils wherein relatively low-boiling and high-boiling hydrocarbon oils are each subjected to independently controlled conversion conditions of cracln'ng temperature, superatmospheric pressure and conversion time while passing in a restricted stream through a heating coil, the low-boiling oil being heated to higher cracking temperature than the high-boiling oil, the separate streams of heated relatively low-boiling and high-boiling oils introduced into an enlarged vertical reaction chamber also maintained at substantial superatmospheric pressure and wherein substantial further conversion is effected, the resulting vaporous and liquid conversion prod- 'llCfiS separated and the former subjected to fracstream-through a heating coil, simultaneously tionation for the recovery of desirable light distill'ateby. condensation of the fractionated vapors, the improvement which comprises introducing the stream of heated relativelylow-boiling oil into the upper portion of the reaction chamber, causing the liquid components thereof, to flow downward over the interior surfacev of the walls of the chamber to its lower portion, causing the vaporous components .thereof to pass separately downward in the reaction chamber, introducing the heated stream of relatively high-boiling oil into the lower portion of the reaction chamber, separating vaporous and liquid components thereof in this zone, causing the vaporous components thereof to pass upward in the reaction chamber, commingling the vaporous components of both streams intermediate their points of introduction into the reaction chamber, removing the commingled vaporous products from the chamber and separately removing liquid components of both of said streams from the lower portion of the reaction chamber.

4. In a process for the pyrolytic conversion of hydrocarbon oils wherein relatively low-boiling and high-boiling hydrocarbon oils are each subj ected to independently controlled conversion conditions of cracking temperature, superatmospheric pressure and conversion time while passing in a restricted stream through a heating coil, the lowboiling oil being heated to higher cracking temperature than the high-boiling oil, the separate streams of heated relatively low-boiling and highboiling oils introduced into an enlarged vertical reaction chamber also maintained at substantial superatmospheric pressure, the resulting vapor- V ous and liquid conversion products separated and the former subjected to fractionation for the recovery of desirable light distillate by condensation of the fractionated vapors, the improvement which comprises introducing the heated stream of relatively high-boiling oil into the upper portion of the reaction chamber, introducing the stream of relatively low-boiling oil into the lower portion of the reaction chamber, withdrawing liquid conversion products from the lower portion of the reaction chamber and separately removing vaporous components of both streams from a point in the reaction chamber intermediate the points of introduction of said low-boiling and high-boiling oils.

5. A process for the conversion of relatively heavy and light hydrocarbon oils which comprises heating the heavier oil to cracking temperature under pressure while flowing in a restricted stream through a heating coil, simultaneously heating a stream of the lighter oil to higher cracking temperature under pressure in a second heating coil, introducing the heated oil streams into an enlarged vertical reaction chamber maintained under superatmospheric pressure, the heated light oil stream being introduced to the chamber at a point a substantial distance remote from the point of introduction of the heated heavy oil stream, separating vaporous from liquid conversion products in the chamber, removing the separated vaporous products from the chamber at a point intermediate the points of introduction of said streams thereto and separately removing the liquid conversion products from the lower portion of the chamber.

6. A process for the conversion of relatively heavy and light hydrocarbon oils which comprises heating the heavier oil to cracking temperature under pressure While flowing in a restricted heating a stream of the lighter oil to higher cracking, temperature under pressure in a second heating coil, introducing the heated light oil the chamber, separating vaporous from liquid jCOllVBISiGII products in the chamber, removing the separated vaporous products from the chamber at a point intermediate the points of introduction of said streams thereto, and separately removing the liquid conversion products from the lower portion of the chamber.

'7. The process as defined in claim 6 further characterized in that the heated heavy oil stream is introduced to the upper portion of the chamber while the heated light oil stream is introduced at a substantially lower point in the chamber.

8. In a process for the pyrolytic conversion of hydrocarbon oils wherein relatively low-boiling and high-boiling hydrocarbon oils are each subjected to independently controlled conversion conditions of cracking temperature, superatmospheric pressure and conversion time while passing in a restricted stream through a heating coil, the low-boiling oil being heated to higher cracking temperature than the high-boiling oil, the separate streams of heated relatively low-boiling and high-boiling oils introduced into an enlarged vertical reaction chamber also maintained at substantial superatmospheric pressure and wherein substantial further conversion is effected, the resulting vaporous and liquid conversion products separated and the former subjected to fractionation for the recovery of desirable light distillate by condensation of the fractionated va-- pors, the improvement which comprises introducing the heated stream of relatively low-boiling oil into the upper portion of the reaction chamber and passing the liquid and vaporous components thereof downward in the chamber, introducing the heated stream of relatively high-boiling oil into the lower portion of the reaction chamber, separating vaporous and liquid components thereof in this zone, causing the vaporous components thereof to pass upward in the reaction chamber, commingling the vaporous components of both streams intermediate their points of introduction into the reaction chamber, removing the commingled vaporous products from the chamber intermediate the points of introduction of the heated streams to the chamber, and separately removing liquid components of both of said streams from the lower portion of the reaction chamber.

9. In a process for the pyrolytic conversion of hydrocarbon oils wherein relatively low-boiling and high-boiling hydrocarbon oils are each subjected to independently controlled conversion conditions of cracking temperature, superatmospheric pressure and conversion time while passing in a restricted stream through a heating coil, the low-boiling oil being heated to higher cracking temperature than the high-boiling oil, the separate streams of heated relatively low-boiling and high-boiling oils introduced into an enlarged vertical reaction chamber also maintained at substantial superatmospheric pressure and wherein substantially further conversion is effected, the resulting vaporous and liquid conversion products separated and the former subjected to fractionation for the recovery of desirable light distillate by condensation of the fractionated vapors, the improvement which comprises introducing one of the heated streams into the upper portion of the reaction chamber and passing the liquid and vaporous components thereof downward in the chamber, introducing the other heated oil stream into the lower portion of the reaction chamber, separating vaporous and liquid components thereof in this zone, causing the vaporous com- 10 ponents thereof to pass upward in the reaction

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