US2127011A - Conversion of hydrocarbon oils - Google Patents

Description

Aug. 16, 1938. J. D. sEGUY CONVERSION OF HYDROCARBON OILS Original Filed May 25, 1952 'isha f Patented Aug. 16, 1938 UNITED STATES PATENT OFFICE CONVERSION OF HYDROCARBON OILS Application May 23, 1932, Serial No. 612,987 Renewed June 5, 1937 4 Claims.

This invention relates to the conversion of hydrocarbon oils and more particularly relates to an improved method and means of cracking hydrocarbon oils to produce high yields of desirable light products, such as motor fuel of high anti-knock value, accompanied by the reduction of the residual conversion products of the system to coke at reduced pressure.

In its primary concepts the invention comprises subjecting residual oil resulting from the conversion of hydrocarbon oil at superatmospheric pressure to coking at reduced pressure, aided by the introduction, into the coking zone, of highly heated relatively light oil. The light 5 oil, utilized as the heat carrying medium to assist the coking operation, should be an oil which may be heated to the high temperature required for coking of the residual oil without the formation of any substantial quantity of coke or caro bonaceous material in the heating coil. I have found that the ideal type of oil for this operation may be obtained from within the system and comprises secondary reflux condensate resulting from fractionation of the Vaporous products of 5 the system. Secondary reflux condensate fro-m the cracking operation or secondary reflux condensate from the coking operation or secondary reux condensate from both the cracking and coking operations may be utilized forv this purpose and in the preferred embodiment of the invention, fractionation is so controlled that the material thus utilized as the heat carrying medium for the coking operation contains, as its light components, some material boiling Within the boiling range of gasoline, for example, boiling above 300 F., and may include, as its heavy components, some or all of the products of the system commonly termed pressure distillate bottoms boiling, for example, up to 550 F., or there- :o abouts. The exact boiling range of the products utilized for this purpose will vary With different charging vstocks and with different operating conditions but we may mention, as a typical example, the materials boiling between 350 and L5 .450 F. This type of material not only has the desirable characteristics above mentioned, i. e. low coke-forming tendencies when heated to high temperatures but is amenable to reforming, under the conditions which may be employed during the reheating of this material, to produce increased yields of high anti-knock quality motor fuel.

A specific embodiment of the invention may comprise subjecting a hydrocarbon oil to conversion temperature at superatmospheric pressure in a heating coil, introducing the heated oil into an enlarged reaction chamber, also maintained at superatmospheric pressure, wherein Vaporous and residual liquid conversion products separate, subjecting the vapors to primary and secondary fractionation and separately collecting primary and secondary reflux condensate from said primary and secondary fractionating stages, introducing residual oil withdrawn from said reaction chamber to coking in a reduced pressure coking zone, subjecting said secondary reflux condensate to a higher conversion temperature in a separate heating coil and introducing the highly heated secondary reflux condensate into direct contact with the residual material in the coking Zone for the purpose of assisting the reduction of said residual material to coke.

Vaporous products from the coking o-peration preferably are separately subjected to primary fractionation for the purpose of removing therefrom their heaviest components, including tars, pitches and the like carried over with the vapors from the coking zone and as a special feature of the invention, this heavy reflux condensate resulting from primary fractionation of the vapors from the coking zone is introduced into the stream of material passing from the heating coil of the cracking system into the reaction chamber, being thereby subjected to further conversion under milder conversion conditions than those to which the raw oil charging stock for the system is subjected. Vapors resulting from primary fractionation of the vapors from the coking zone may be separately subjected to further fractionation and the reflux condensate from said secondary fractionating step may be utilized as a heat carrying medium to assist the coking operation or the vapors resulting from said primary fractionation may be subjected to further fractionation together with the Vaporous product from the reaction chamber.

Olne specific form of apparatus incorporating the features of the present invention is illustrated in the attached diagrammatic drawing and the operation of the process of the invention is more completely outlined in the following description of the drawing.

Raw oil charging stock for the system is supplied through line l and valve 2 to pump 3 from which it may be fed through line 4 and valve 5 to heating coil 6. When desired, a portion or all of the raw oil may be diverted from line 4 through line 'l and valve 8 to enter fractionator 9 wherein it may come into direct contact with the ascending vapors in this zone, assisting their fractionation, being thereby preheated and collecting, together with reflux condensate separated from the vapors by fractionation, in the lower portion of the fractionator. Reflux condensate from fractionator 9 or reflux condensate and preheated raw oil, as the case may be, is withdrawn through line I and valve I I to pump I2 from which it is fed through line i3 and valve I4 into line 4 and then to heating coil 6, for further conversion.

Heating coil 5 is located within a furnace I5 of any suitable form capable of heating the oil supplied thereto to the desired conversion temperature. The heated oil is discharged from heating coil S through line I6 and valve Il into reaction chamber I8, which is preferably maintained at substantial superatmospheric pressure and wherein vaporous and residual liquid conversion products are separated.

The vaporous conversion products pass from chamber I8 through line I9 and valve 20 into fractionator 9 wherein their heavy components are condensed as primary reflux condensate to be returned to heating coil 6, as already described, for further conversion. Vapors from fractionator 9 pass through line 2l and valve 22 to further fractionation in fractionator 23 wherein a secondary reflux condensate is formed, collecting in the lower portion of this Zone to be withdrawn therefrom to further treatment, as will be later described. Light Vaporous products of the desired end boiling point are removed from the upper portion of fractionator 23 through line 24 and valve 25, are subjected to condensation and cooling in condenser 26 from which distillate and uncondensable gas is withdrawn through line 2 and valve 28 to collection in receiver 29. Uncondensable gas may be released from the receiver through line 30 and valve 3|. Distillate is withdrawn from the receiver through line 32 and valve 33.

Residual liquid conversion products are withdrawn from reaction chamber I8 through line 34 and valve 35 and are introduced into the coking chambers 35 and 3'6 through lines 31 and 37', respectively, controlled by the respective valves 38 and 38. Chambers 36 and 36 are similar coking zones, preferably operated at reduced pressure relative to that employed in chamber I8. It will be understood that one or any number of a plurality of such chambers may be employed, a plurality being preferred, for the purpose of permitting prolonged operation of the process by providing additional space for the deposition oi' coke, and when two or more coking chambers are utilized they may be operated either alternately or simultaneously.

Secondary reux condensate is withdrawn from the lower portion of fractionator 23 through line 39 and valve 40 to pump 4I from which it is fed through line 42 and valve 43 to heating coil 44 wherein it is heated to a high temperature by means of heat supplied from a furnace 45 of any suitable form. Thev highly heated secondary reuX condensate is discharged from heating coil 44 through line 45, passing through line 4l and valve 48 into coking chamber 36 and through line 4'I' and valve 48 into coking chamber 36'. The highly heated secondary reflux condensate is thus directly contacted with the residual material in the coking Zone and, by virtue of the heat which it imparts to the residual material and its partial pressure effect, serves to assist reduction of said residual-material to substantially devolatilized petroleum coke.

Vapors are withdrawn from coking chamber 36 through line 49 and valve 50 and from coking chamber 3'6' through line 49 and valve 50', passing thence through line 5I to primary fractionation in fractionator 52 wherein their heaviest components including tar and pitch-like material carried over with the coking Zone are condensed, collecting in the lower portion of fractionator 52 from which they are withdrawn through line 53 and valve 54 to pump 55. Pump 55 supplies this heavy reflux condensate removed from the vapors from the coking Zone through linc 55 and valve 5l into line I6, wherein it commingles with the heated oil from heating coil 3, passing therewith to reaction chamber I8, for further treatment.

Vapors remaining uncondensed in fractionator 52 are removed from the upper portion of this zone through line 58 and may pass either through valve 59, in this line, to fractionator 9, for Ifurther fractionation together with the vaporous conversion products from chamber I8, or they may pass from line 58 through line 6I) and valve BI to separate further fractionation in fractionator 62.

In case the Vapors from fractionator 52 are directed to fractionator 9 they are subjected therein and insubsequent portions of the system to the same treatment already described as that 'afforded the vaporous conversion products from chamber I8.

When vapors lfrom fractionator 52 are subjected to further separate fractionation in fractionator E2, the secondary reflux condensate formed in this zone is withdrawn therefrom through line 53 and valve 64 to pump 65 from which this material is fed through line 66 and valve S'I into line 42 and thence to heating coil 4.4, to be there reheated and subsequently serve as a means of reducing the residual conversion products from chamber I8 to coke in chambers 36 and 36', as already described in connection with secondary reflux condensate from fractionator 23.

Vaporous products of the desired end boiling point are removed from the upper portion of fractionator 62 through line 63 and valve 69, are subjected to condensation and cooling `in condenser I0 from which distillate and uncondensable gas is withdrawn through line 'II` and valve 12 to be collected in receiver 73. Uncondensable gas may be released from receiver 13 through line 'I4 and valve '15. Distillate may be withdrawn from this receiver through line 'I6 and valve TI.

It will be understood that either secondary reflux condensate from fractionator 23 or secondary reflux condensate from fractionator 62, or a mixture of the two condensates may be employed as the heat carrying medium for the coking operation and in case only one or only a portion of these products is so used, the other product or the remaining portion of both products may be either withdrawn from the system to storage or ready indicated, vthe coking zone is preferably-75 `operated at substantially reduced pressure relative to that employed in the reaction chamber, said reduced pressure ranging, for example, from pounds per square inch down to substantially atmospheric pressure, or thereabouts. The fractionating, condensing and collecting stages through which vaporous products from the coking zone pass are operated at no greater pressure than that employed in the coking Zone. The temperature to which secondary reflux condensates from the system are reheated, prior to their introduction into the coking zone, may range from 950 to 1200 F., or thereabouts and pressure conditions to which they are subjected during this reheating may range from substantially atmospheric to 800 pounds, or more, per square inch.

As a specific example of the operation of the process of the present invention, a 22 A. P. I. gravity Mid-Continent fuel oil comprises the raw oil charging stock to be treated. This is subjected, together with reiiux condensate from the primary fractionator of the cracking portion of the system, to a temperature of approximately 915 F. at a superatmospheric pressure of about 250 pounds per square inch. Substantially this same pressure is utilized in the reaction chamber but is reduced in the succeeding fractionating, condensing and collecting portions of the system to a temperature of about 30 pounds per square inch, which is substantially the same as that employed in the coking zone. Heavy reflux condensate resulting from separate primary fractionation of the vapors from the coking zone is returned to commingle with the stream of heated oil passing from the primary heating coil to the reaction chamber, serving to lower the temperature of this stream somewhat below the temperature above given, prior to its introduction into the reaction chamber, so that said heavy reflux condensate is subjected to milder conversion conditions in the reaction chamber than those to which the raw oil charging stock and primary reux condensate are subjected in the heating coil. Vapors resulting from primary fractionation of the vapors from the coking zone are subjected to further fractionation, together with vaporous conversion products from the reaction chamber of the system. Secondary reflux condensate, comprising the components of the vaporous products from both the cracking and coking operations boiling between approximately 350 and 450 F., are subjected to further conversion to produce additional yields of desirable lighter products at a temperature of approximately 970 F., and a superatmospheric pressure of about 800 pounds per square inch. The highly heated secondary reux condensate is then introduced into direct contact with the residual material in the coking zone by means of which the latter is reduced to substantially dry coke. This operation may yield, per barrel of charging stock, about 68% of motor fuel having an anti-knock value equivalent to an octane number of approximately 78, about '75 pounds of coke having a volatile content of less than 5% and about 900 cubic feet of uncondensable gas.

I claim as my invention:

1. A hydrocarbon oil conversion process which comprises subjecting the charging oil to cracking conditions of temperature and pressure in a heating Zone and an enlarged reaction Zone, separating the same into vapors and unvaporized oil, subjecting the vapors to primary fractionation to condense and separate heavier fractions thereof and returning resultant reflux condensate to the cracking step, further fractionating the vapors and separating therefrom a light reflux condensate containing a substantial quantity of gasoline hydrocarbons, heating said light reflux condensate, independently of the charging'v oil, suiiiciently to increase the antiknock value of the gasoline hydrocarbons contained therein, contacting the thus heated light reflux condensate with said unvaporized oil and reducing the latter to coke in a coking Zone maintained under lower pressure than the reaction zone, subjecting the vapors evolved from the light reflux condensate and from the unvaporized oil to primary fractionation independently of the firstv 'mentioned-.'

vapors and supplying reiiux thus formed to the cracking step, combining at least a portion of these fractionated vapors with the cracked vapors undergoing said further fractionation, and finally condensing the vapors uncondensed by said further fractionation.

2. A hydrocarbon oil conversion process which comprises subjecting the charging oil to cracking conditions of temperature and pressure while flowing in a restricted stream through a heating zone and then discharging the same into an enlarged reaction Zone maintained under cracking conditions of temperature and pressure, effecting further cracking of the oil in the reaction Zone and separating the same into vapors and unvaporized oil, fractionating the vapors and returning resultant reflux condensate to the heating Zone, further fractionating the vapors and separating therefrom a light reiiux condensate containing a substantial quantity of gasoline hydrocarbons, heating said light reux condensate independently of the charging oil, suioiently toincrease the anti-knock value of the gasoline hydrocarbons contained therein, contacting the thus heated light reflux condensate with said unvaporized oil and reducing the latter to coke, subjecting the vapors from the coking step to primary fractionation independently of the firstmentioned vapors and introducing resultant reflux condensate directly to said reaction zone, then combining at least a portion of these fractionated vapors with the cracked vapors undergoing said further fractionation, and finally condensing the vapors uncondensed by the latter fractionation.

3. A combined cracking, coking and reforming process which comprises heating hydrocarbon oil to cracking temperature under pressure while flowing in a restricted stream through a heating zone, separating the heated oil into vapors and unvaporized oil in a separating Zone, distilling the latter to coke in a coking zone maintained under lower pressure than the heating zone, subjecting said vapors to primary fractionation and returning resultant primary reflux condensate to the heating zone, further fractionating the vapors and separating therefrom a light reflux condensate containing a substantial quantity of hydrocarbons boiling within the gasoline range, heating such light reux condensate in a second heating zone sufliciently to enhance the anti-knock value of the gasoline boiling hydrocarbons contained therein and then introducing the same into contact with the unvaporized oil in the coking zone to assist the reduction of the latter to coke, fractionating vapors evolved from the unvaporized oil and light reflux condensate in the coking zone independently of the rstnamed vapors and combining resultant reflux condensate with heated oil discharged from the first-mentioned heating-zone, and finally condensing the fractionated vapors.

4. A combined cracking, coking and reforming process which comprises heating hydrocarbon oil 4to cracking temperature lunder pressure While flowing in a restricted stream through a heating `zone, separating the heated oilinto vapors and unvaporized oil in a separating zone, distilling the latter to coke in a coking yzone maintained under llower pressure than the heating zone, subjecting heating Such light reflux condensate in a second heating zone su'iciently to enhance the antiknock value of the gasoline boiling hydrocarbons contained therein and then introducing the same into contact .with the unvaporized oil in the 4,

coking zone to` assist the reduction of the latter to.coke, subjecting the vapors evolved from the unvaporized oil and light reflux condensate in the coking zone to primary fractionation independently of the first-named vapors and combin- 10 ing resultant reflux condensate With heated oil discharged fromv the rst-mentioned heating zone, then subjecting these vapors to secondary fractionation and supplying lighter reflux condensate thus formed to said second heating zone 1;

JEAN DELATTRE SEGUY.

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