US2091381A - Conversion of hydrocarbon oils - Google Patents

Description

Aug. 3l, 1937. K. swARTwooD 2,091,381

` CONVERSION oF HYDROCARBON oILs Filed March 26, 1936 Patented Aug. 31, 1937 UNiTED STATES PATENT FFICE CONVERSION F HYDRCARBON OILS Application March 26,

Claims.

This invention particularly refers to an improved process for the fractional distillation of hydrocarbon oils accompanied by selective pyrolytic conversion of intermediate fractions of the 5 charging stock andintermediate liquid conversion products of the process and further conversion of the residual liquid products from the distilling and cracking operations to produce either good quality fuel oil or coke.

One specific embodiment of the invention comprises subjecting relatively heavy intermediate liquid conversion products of the process to conversion conditions of cracking temperature and superatmospheric pressure in a heating coil and communicating enlarged reaction chamber,

separating the resulting vaporous and liquid conversion products, subjecting the latter to further vaporization in a Zone of substantially reduced pressure relative to that employed in the reac- 30 tion chamber, subjecting the vaporous conversion products to fractionation whereby their insufciently converted components are condensed as reflux condensate and separated into selected relatively low-boiling and high-boiling frac- 25 tions, supplying the latter to the heating coil for said conversion, subjecting fractionated vapors of the desired end-boiling point to condensation, recovering the resulting distillate, subjecting said 10W-boiling fractions of the reflux gq condensate to independently controlled conversion conditions of cracking temperature and superatrnospheric pressure in a separate heating coil, introducing the heated products from said separate heating coil into a separate Vaporizing 35 and fractionating Zone, supplying hydrocarbon oil charging stock for the process to said separate vaporizing and fractionating zone wherein it commingles with the heated products from said separate heating coil and is subjected to im vaporization and fractionation, returning selected intermediate fractions of the materials supplied to said separate vaporizing and fractionating zone to said separate heating coil for further conversion, subjecting fractionated va- 45 pors of the desired end-boiling point from said separate vaporizing and fractionating Zone to condensation, recovering the resulting distillate, subjecting residual liquid products from said reduced pressure vaporizing Zone and from said .so separate vaporizing and fractionating Zone to further conversion in another separate heating coil, separating the resulting vaporous and nonvaporous products and supplying the former to said reduced pressure vaporizing Zone.

By this method of operation the excess heat 1936, Serial No. 70,927

(C1. iBS- 49) in the products from the relatively light oil cracking coil is utilized for the useful purpose of effecting distillation of the charging stock, the charging stock in turn serving to cool the heated products sufficiently to prevent excessive further conversion thereof. Any desirable lowboiling fractions of the charging stock, such as materials within the boiling range of motor fuel and of satisfactory antiknock value, are recovered from the distillation step together with the motor fuel product of the relatively light oil cracking operation while other selected low-boiling or intermediate fractions of the charging stock are subjected to conversion together with selected relatively low-boiling intermediate fractions of the conversion products from both the light oil and heavy oil cracking operations. Any high-boiling fractions of the charging stock unsuitable for conversion with the selected intermediate fractions from the distilling and light oil cracking step are subjected, together with residual liquid from both the light oil and heavy oil cracking operations, to conversion under relatively rnild cracking conditions in a separate heating coil wherein conditions of operation may be regulated to produce from the residual liquid either relatively dry coke or a liquid residue of improved characteristics suitable for sale as fuel oil.

The accompanying diagrammatic drawing illustrates one specific form of apparatus embodying the features of the invention.

Referring to the drawing, heating coil I to which relatively heavy intermediate liquid conversion products of the process are supplied, in the manner to be later described, is located within a furnace 2 which supplies the required heat to the oil passing through the heating coil to subject the same to the desired conversion temperature, preferably at a substantial superatmospheric pressure. Hot conversion products fom heating coil i are discharged through line 3 and valve 4 into reaction chamber 5.

Chamber 5 is also preferably maintained at a substantial superatmospheric pressure and, although not indicated in the drawing, is preferably insulated in order that conversion of the heated products supplied to this Zone, and particularly their vaporous components, may continue therein. In the particular case here illustrated, both vaporous and residual liquid products are discharged in commingled state from the lower portion of chamber 5 through line 6 i the invention, when desired, to separately remove vaporous and liquid conversion products from chamber 5, in which case the liquid products are directed to chamber 8, in the manner described, while vaporous products separately removed from the chamber at any desired point therein may be directed by well known means, not illustrated, either to chamber 8 or to fractionator l2 or, in part, to both zones.

Chamber 8 is preferably maintained at a substantially reduced pressure relative to that employed in the reaction chamber by means of which appreciable further vaporization of the liquid conversion products supplied to this Zone is accomplished. Separation of vapors and nonvaporous residual liquid is accomplished in chamber 3, the latter being removed from the lower portion of this zone through line 9 and directed therefrom to cooling and storage or to further treatment, as will be later described, while vaporous products are withdrawn from the upper portion of chamber 8 and directed through line I3 and Valve II to fractionation in fractionator I2.

The vaporous products supplied to fractionator I2, boiling above the range of the desired light distillate product of this stage of the sys-tem are condensed in the fractionator as reflux condensate which may, when desired, be withdrawn from the lower portion of this zone through line I3 and valve lil topump- I5 by mea-ns of which it is returned through line I6 and valve Il to conversion, as previously described, in heating coil i. Preferably, however, the reflux condensate formed in fractionator I2 is separated into selected relatively low-boiling and high-boiling fractions, in which case only the high-boiling fractions are returned from the lower portion of the fractionator, as described, to conversion in heating coil I while the low-boiling fractions are removed from one or a plurality of suitable intermediate points in the fractionator and directed to separate further conversion. In the case here illustrated, a yselected low-boiling fraction of the reilux condensate is removed from fractionator l2 through line I8 and valve I3 to pump 2l! by means of which it is supplied through line 2| and valve 2 to conversion in heating coil 23, as will be later more fully described.

Fractionated vapors of the desired end-boiling point are withdrawn, together with uncondensable gas, from the upper portion of fractionator l2 through line 2l and valve 23 and are subjected to condensation and cooling in condenser 23. The resulting distillate and gas passes through line 33 and valve 3l to collection and separation in receiver 32. Uncondensed gases are released from the receiver through line 33 and valve 33. Distillate is withdrawn from receiver 32 through line 35 and valve 33 to storage or to any desired further treatment. When desired, regulated quantitles of the distillate collected in receiver 32 may be recirculated by well known means, not illustrated in the drawing, to the upper portion of fractionator l2 to serve as a refluxing and cooling medium in this zone for assisting fractionation of the vapors and to maintain the desired vapor outlet temperature therefrom.

The oil supplied to heating coil 23 from fracitonator I2, and/or other sources which will be later described, is subjected therein, by means of heat supplied from a furnace 24,to the desired conversion temperature, preferably at a substantial superatmospheric pressure, and the heated products are discharged from heating coil l23 through line 25 and valve 26 into the lower portion 3l of distilling and fractionating column 39. Preferably, the heated products are cooled, prior to their introduction into column 39, suiciently to prevent excessive further conversion thereof in this zone. This may be accomplished, at least in part, by substantially reducing the pressure imposed upon the stream of heated oil as it passes through valve 23 and, when desired, other means of cooling the stream of hot conversion products may be employed and one such means will be later described.

The lower portion 31 of column 39 comprises a vaporizing and separating chamber to which charging stock for the process, as well as the heated products from heating coil 33, are supplied, whereby the charging stock is subjected to vaporization by means of the excess heat in the hot conversion products discharged from the heating coil and the vaporous components thereof, subjected to subsequent fractionation, together with the vaporous products with which they are commingled. Charging stock is supplied through line 43' and valve 4I to pump l2 by means of which it is fed through line 43 and may bel introduced directly into chamber 3l by means of line 44 and valve 45 or it may be introduced, all or in part, through line 43 and valve lll into line 25, wherein it commingles with the stream of heated products from heating coil 23 and serves to cool the same, the commingled oils being introduced into chamber 3l'.

The components of the charging stock vaporized by contact with the heated products from heating coil 23 and the components of the conversion products which remain in vaporous state in chamber 3l are directed through a suitable partition d3 into the upper portion of column 33 which comprises a fractionating zone wherein the components of the vapors boiling above the endboiling point of the desired light distillate product of this stage of the process are condensed as reflux condensate. The reflux condensate formed in fractionator 3S is withdrawn therefrom through line le and valve 5@ to pump 5l by means of which it is fed through line 5.5?. and valve 53 into line 22 `and directed therefrom to heating coil 23 for conversion, either alone or together with the low-boiling reflux condensate from fraotionator I2.

Fractionated vapors of the desired end-boiling point are withdrawn, together with uncondensable gas, from the upper portion of fractionator 33, and directed through line 54 and valve 55 to condensation and cooling in condenser The resulting distillate and gas passes through line 5l and valve 58 to collection and separation in receiver 53. Uncondensed gases may be release from the receiver through line 53 and valve 3i. Distillate is withdrawn from receiver 53 through line 52 and valve 63 to storage or to any desired further treatment. When desired, regulated quantities of the distillate collected in, receiver 59 may be recirculated by well known means, not illustrated in the drawing, to the upper portion of fractionator 35.! to serve as a reiluxing and cooling medium in this zone for assisting fractionation of the vapors and to maintain the desired vapor outlet temperature therefrom.

The components of the conversion products, supplied to chamber 3l from heating coil 23, which remain unvaporized in chamber 3l and any high-boiling non-vaporous components of the charging stock are withdrawn from the lower portion of chamber 3l through line @il and valve 65 to pump t6 by means of which this residual liquid is directed through line 6l and valve 68 to conversion in heating coil 69.

Non-vaporous residual liquid withdrawn from chamber 8 through line 9, as. previously described, may be removed, all or in part, from the system through line l@ and valve 'H to cooling and storage or elsewhere, as desired, or it may be directed, all or in part, from line 9 through line 'i2 and Valve 'I3 into chamber (il, wherein it commingles with the liquid products in this zone to be directed therewith, in the manner previously described, to conversion in heating coil $9, or a portion or all of the residual liquid from chamber may be diverted from line 9 through line 'lli and valve 15 to pump 16 by means of which it is supplied through line "VI, valve 'I8 and line fil to further conversion in heating coil 69. In case chamber 3l is operated at a higher temperature or a lower pressure than that employed in chamber 8 introduction of the residual liquid from chamber 8 into this zone will serve to effect further vaporization of this material, prior to its introduction into heating coil 69.

The relatively high-boiling residual oils supplied, as d-escribed, to heating coil iii? are su jected therein to the desired temperature and pressure conditions by means of heat supplied from a furnace 79 and the heated products are discharged from the heating coil through line 8i! and valve 8l into chamber 82.

The conditions of operation employed in heating coil E59 and chamber t2 may be regulated to effect subsequent reduction of the residual oils to coke in chamber 82 or a milder type of conversion commonly termed viscosity breaking may be employed in heating coil @Ei so that the residual product recovered from chamber 82 is a liquid residue of improved characteristics, particularly with respect to viscosity and ash point. The conditions employed in heating coil 6g and chamber 82 may be selected to suit requirements, depending primarily upon the nature of the residual oil supplied to heating coil 59 and the desired type of residual product.

Vaporizing or coking chamber 32 is preferably operated at a substantially reduced pressure relative to that employed at the outlet from heating coil 59, although any desired pressure up to substantially the same as that at the outlet from the heating coil may be utilized in this zone, when desired. When coke is produced in chamber 82 it may be allowed to accumulate therein until the chamber is substantially filled or until its operation is completed for any other reason and, when desired, a plurality of similar coking chambers may be employed, although only one is illustrated in the drawing. When liquid residue is produced in chamber 82 it may be removed from the lower portion of this zone through line 83 and valve 84 to cooling and storage or elsewhere, as desired, and this line may also serve as a drain-line and, particularly when the chamber is operated as a coking zone, steam, water or any other suitable cooling material may be introduced into the coking chamber through line 83 and valve 84 to hasten cooling and facilitate the removal of coke from this zone after its operation has been completed and after it has been isolated from the rest of the system. Vaporous products are removed from the upper portion of chamber 32 and directed through line 85 and valve 8'5 to chamber 8 or they may, when desired, be supplied, by well known means not illustrated, either to chamber 31 or to fractionator l2.

The preferred range of operating conditions which the present process may employ to accomplish the desired results, in anapparatus such as illustrated and above described, may be approximately as follows: The heating coil to which the total reflux condensate from the fractionator of the first mentioned cracking stage or highboiling fractions of the reflux condensate from this state are supplied may utilize an outlet conversion temperature ranging for example, from 850 to 975 F., preferably with a superatmospheric pressure at this point in the system of from 100 to 500 pounds, or more, per square inch. The succeeding reaction chamber may employ a superatmospheric pressure substantially the same or lower than that utilized at the outlet from the heating coil. The vaporizing and separating chamber of this stage of the system preferably employs a substantially reduced pressure, relative to that utilized in the reaction chamber, ranging, for example, from a superatmospheric pressure of 100 pounds, or thereabouts, per square inch down to substantially atmospheric pressure and the pressure employed in this zone may be substantially equalized or reduced in the succeeding fractionating, condensing and collecting equipment. The heating coil to which reflux condensate from the distilling and fractionating column is supplied, either alone or together with light reflux condensate from the fractionator of the first mentioned cracking stage, preferably employs an outlet conversion temperature of the order of 900 to 1050 F. with any desired pressure from substantially atmospheric to a superatmospheric pressure of 800 pounds, or more, per square inch, relatively low superatmospheric pressure normally being employed when temperatures of the order of 1000 F,. or higher are utilized. The distilling and fractionating column to which the charging .stock and the conversion l pressure, although higher pressures up to substantially the same as that employed at the outlet from the communicating heating coil may be utilized in this zone, when desired. When the process is operated for the production of coke as the final residual product the temperature employed in the heating coil of the ccking stage may range, for example, from 9u() to 1050 F., preferably with a superatmospheric pressure in this zone of from 50 to 150 pounds or more per square inch and with a relatively short time factor in the heating coil in order to preclude any substantial formation and deposition of coke, prior to the introduction of the heated products into the coking chamber. When a viscosity breaking operation is employed in the heating coil to which the residual liquids are supplied the ternperature at the outlet therefrom may range, for example, from 775 to 875 F., preferably with a superatmospheric pressure at this point in the system of from 100 to 250 pounds, or thereabouts, per square inch. The vaporizing or coking chamber, as previously mentioned, may employ any desired pressure ranging from substantially the same as that employed at the outlet from the communicating heating coil down to subtantially atmospheric pressure.

The following is a specific example of the operation of the process as it may be accomplished in an apparatus such as illustrated and above described. The example, however, typifies only one embodiment of the invention and is not to be construed as limiting the various embodiments of the process disclosed. The charging .stock is a mixed base crude of approximately 37 A. P. I. gravity which contains approximately per cent of materials boiling up to 387 F. which are of satisfactory antiknock value for blending with the motor fuel products of the light oil cracking operation. A major portion of the charging stock is commingled with the. heated products from the light oil cracking coil, prior to their introduction into the distilling and fractionating column and the remainder is supplied directly to the lower portion of this Zone. High-boiling fractionsv of the reiiux condensate from the fractionator of the first cracking stage of the system are subjected in the heating coil to which this material is supplied to an outlet conversion temperature of approximately 930 F. at a superatmospheric pressure of about 300 pounds per square inch. This pressure is substantially equalized in the succeeding reaction chamber and is reduced in the vaporizing chamber, to which both liquid and vaporous conversion products from the reaction chamber are supplied, to a superatmospheric pressure of approximately pounds per square inch. This pressure is substantially equalized in the succeeding fractionating, condensing and collecting portions of the rst cracking stage'. Ar

motor fuel product of approximately 400 F. end- .boiling point is recovered from this stage of the system and low-boiling reflux condensate. from the fractionator of this stage, having a boiling range of approximately 380 to 525 F., is supplied, together with reflux condensate from the distilling and fractionating column, to the light oil cracking coil wherein those materials are subjected to an outlet conv-ersion temperature of approximately 950 F. at a superatmospheric pressure. of approximately 500 pounds per square inch. The distilling and fractionating column vis operated at a superatmospheric pressure of approximately 75 pounds per square inch and the conversion products supplied thereto from the light oil heating coil are cooled, prior to their introduction into this Zone, toapproximately 785 F. A motor fuel product comprising straightrun and cracked products having an end-boiling point of approximately 385 F. is recoveredas the overhead product from the distilling and fractionating column. Residual liquid from the distilling and fractionating column is supplied, together with residual liquid from the vaporizing chamber of the rst cracking stage, to a separate heating coil wherein it is quickly heated under non-coking conditions tc an outlet conversion temperature of approximately 980 F. at a superatmcspheric pressure of approximately 80 pounds per square inch and then introduced into the cok- V: ing zone which is operated at substantially the Same DI'GSSUIB.

An operation such as above described will prol duce, per barrel of charging stock, approximately '70 per cent of motor fuel of good antiknock quality and approximately 50 pounds of low Volatile pressure separating zone, the vapors subjected to fractionation for the formation of reflux condensate, fractionated vapors of the desired end-boiling point subjected to condensation, the resulting distillate recovered and reflux condensate formed by said fractionation subjected to said conversion, the improvement which comprises simultaneously introducing hydrocarbon oil charging stock for the process into a distilling and fractionating Zone wherein it is subjected to appreciable vaporization by direct contact with hot conversion products supplied to this Zone, as hereinafter set forth, and wherein the heavy nonvaporous components of the charging stock commingle with the residual liquid components of said conversion products while the vaporous components of the charging stock are subjected to fractionation in this zone together with the vaporous components of said conversion products, for the formation of reiiux condensate, subjecting fractionated vapors of the desired end-boiling point from the distilling and fractionating zone to condensation, recovering the resulting distillate, subjecting reflux condensate formed in the distilling and fractionating Zone to independently controlled conversion conditions in a separate cracking zone, introducing the resulting products into the distilling and fractionating zone, subjecting the commingled high-boiling components of the charging stock and residual liquid conversion products, together with residual liquid from the first mentioned cracking operation, to furtherv conversion in another separate cracking Zone, separating the resulting vaporous and non-vaporous products, and introducing said vaporous products to said reduced pressure separating Zone.

2. In a process for the pyrolytic conversion of hydrocarbon oils wherein selected intermediate liquid products of the process are subjected to conversion conditions of cracking temperature and superatmospheric pressure, the resulting vapors and residual liquid separated in a reduced pressure separating zone, the vapors subjected to fractionation for the formation of reflux condensate, fractionated vapors of the desired endboiling point subjected to condensation, the resulting distillate recovered and reflux condensate formed by said fractionation subjectedto said conversion, the improvement which comprises simultaneously introducing hydrocarbon oil charging stock for the process into a distilling and fractionating zone wherein it is subjected to appreciable vaporization by direct contact with hot conversion products supplied to this zone, as hereinafter set forth, and wherein the heavy non-vaporous components of the charging stock commingle with the residual liquid components of said conve-rsion products while the vaporous components of the charging stock are subjected to fractionation in this Zone, together with the vaporous components of said conversion products, for the formation of reflux condensate, subjecting fractionated vapors of the desired endboiling point from the distilling and fractionating zone to condensation, recovering the resulting distillate, subjecting reflux condensate formed in the distilling and fractionating zone to independently controlled conversion conditions in a separate cracking zone, introducing the resulting -products into the distilling and fractionating zone, subjecting the commingled high-boiling components of the charging stock and residual liquid conversion products, together with residual liquid from'the rst mentioned cracking operation, to further conversion in another separate cracking Zone, and fractionating resultant vapors in admixture With vapors separated in said reduced pressure separating zone.

3. A process such as claimed in claim l Wherein the reflux condensate formed by said fractionation of the vapors of the rst mentioned cracking operation is separated into selected relatively loW-boiling and high-boiling fractions, the high-boiling fractions subjected to the first mentioned cracking operation and the low-boiling fractions subjected to cracking together with said reflux condensate from the distilling and fractionating zone.

4. A process such as claimed in claim 2 wherein the reflux condensate formed by said fractionation of the vaporous conversion products of the rst mentioned cracking operation is separated into selected relatively low-boiling and highboiling fractions, the high-boiling fractions subjected to the first mentioned cracking operation and the 10W-boiling fractions subjected to cracking together With said reflux condensate from the distilling and fractionating Zone.

5. In a process for the pyrolytic conversion of hydrocarbon oils wherein selected intermediate liquid products of the process are subjected to conversion conditions of cracking temperature and superatmospheric pressure in a heating coil and communicating enlarged reaction chamber, the resulting vaporous and liquid conversion products separated, the vaporous conversion products subjected to fractionation for the formation of reflux condensate, fractionated vapors of the desired end-boiling point subjected to condensation, the resulting distillate recovered, said reflux condensate separated into selected relatively low-boiling and high-boiling fractions, the latter supplied for further cracking to said heating coil, said low-boiling fractions subjected to independently controlled conversion conditions of cracking temperature and superatmospheric pressure in a separate heating coil, the resulting heated products cooled to a temperature sufficient to prevent excessive further cracking thereof and introduced into a separate vaporizing and separating chamber, the improvement which comprises introducing hydrocarbon oil charging stock for the process into said separate vaporizing and separating chamber, subjecting the vaporous products therefrom, including vaporous components of the charging stock, to fractionation, subjecting fractionated vapors of the desired end-boiling point from the last mentioned fractionating step to condensation, recovering the resulting distillate, returning reflux condensate formed in the last mentioned fractionating step to cracking in said separate heating coil, removing residual liquid, including highboiling non-vaporous components of the charging stock and residual liquid conversion products formed in the last mentioned cracking operation, from said separate vaporizing and separating chamber, subjecting the same to independently controlled conversion conditions of cracking temperature and superatmospheric pressure in another separate heating coil, introducing the heated products into a separate chamber Wherein their vaporous and non-vaporous components are separated, and commingling the vaporous products from the last mentioned chamber with the first-mentioned vaporous conversion products of the process prior to fractionation of the latter.

6. A process such as claimed in claim 5 Wherein liquid conversion products of the first mentioned cracking operation are also supplied for further conversion to the last mentioned heating coil.

7. A process such as claimed in claim 5 Wherein charging stock for the process is commingled with the hot conversion products discharged from the second mentioned heating coil prior to their introduction into said separate vaporizing and separating chamber.

8. A process such as claimed in lclaim 5 Wherein the liquid conversion products of the rst mentioned cracking operation are introduced into said separate vaporizing and separating chamber.

9. A process such as claimed in claim 5 Wherein substantially dry coke is recovered in said separate chamber as the residual product of the last mentioned cracking operation.

l0. A process such as claimed in claim 5 Wherein the residual product recovered from the last mentioned cracking operation comprises liquid residue of improved characteristics relative to the residual liquids supplied to the last mentioned heating coil.

KENNETH SWARTWOOD.

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