US2151827A - Conversion of hydrocarbon oils - Google Patents

Description

lllll C. H. ANGELL Filed Dec.

- CONVERSION OF HYDROCARBON OILS March 28, 1939.

INVENTOR CHARLES H. ANGELL Patented Mar. 28, 1939 PATENT OFFICE 2,151,s2v CONVERSION or HYDROOARBON OILS Charles H. Angell, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application December 30, 1935, Serial No. 56,592

4 Claims.

This inventionjparticularly refers to an improved process for the selective conversion of relatively low boiling and high boiling hydrocarbon oils accompanied by reduction of the 5 residual liquid conversion products to coke in a relatively high pressure coking chamber of the system and wherein the vaporous conversion products from the coking chamber are subjected to continued conversion at substantial superatl mospheric pressure in a chamber separate from that wherein the coke is produced.

It is well recognized that cracking operations wherein coke is produced to the exclusion of residual liquid give higher yields of desirable 15 light liquid products, such as motor fuel, than those operated forthe production of residual liquid, due to the fact that a large proportion of the volatile components of the residual liquid, which are recovered from the residue when it is 20 subjected to coking, are suitable for further conversion within the system to produce additional yields of desirable light distillate. However, when coking of the heavy liquid conversion products is accomplished at substantially atmospheric or relatively low superatmospheric pressure the evolved vapors normally contain an appreciable quantity of undesirable high boiling components, including entrained tars and pitch-like material which are unsuitable for further conversion in 30 the heating coil of the system if the excessive 35 range of motor fuel are ordinarily of inferior anti-knock value as compared to those resulting from the pyrolytic conversion of the same oil under similar conditions but without coking of the residual liquid products. This is particularly 40 true when selective conversion of relatively low boiling and high boiling oils is employed, since in such operations the motor fuel resulting from relatively severe conversion of the relatively low boiling oils is normally of better anti-knock value 45 than that resulting from lower temperature conversion of the relatively high boiling oils, or of both oils in commingled state, regardless of whether or not coking is employed.

The present invention embodies a selective 50 cracking system, wherein coke is produced as the final product of the process, which avoids all of the disadvantages of ordinary coking operations.

One of the features of the invention resides in the use of relatively high superatmospheric 55 pressure in the coking zone and in introducing the vaporous products therefrom into a reaction chamber, also maintained at a substantial superatmospheric pressure, wherein undesirable high boiling components of the vapors are separated from their lower boiling components, the latter subjected to appreciable continue-d conversion in this zone, whereby the anti-knock value of their motor fuel components is materially improved, while the high boiling materials. separated from the vaporous products in the reaction chamber are returned to the coking chamber for further treatment and reduction to coke.

As another feature of the invention which is correlated with the feature above outline, selected a low boiling fractions of the intermediate liquid conversion products of the process resulting from fractionation of the vaporous products from the reaction chamber are subjected to independently controlled more severe conversion conditions than those to which the higher boiling fractions of the intermediate liquid conversion products are subjected, and the resulting highly heated conversion products may be introduced into the reaction chamber or into the coking chamber, or in part to both. When introduced into the coking chamher they serve to supply additional heat to the materials undergoing coking therein and assist their reduction to coke. When supplied to the reaction chamber they commingle therein with the vaporous products from the coking chamber, supplying additional heat thereto, to assist their further conversion in this zone.

In one embodiment, the invention comprises subjecting a hydrocarbon oil of relatively high boiling characteristics to cracking temperature and superatmospheric pressure in a heating coil, introducing the heated products into an enlarged coking chamber also maintained at substantial superatmospheric pressure, wherein their high boiling components are reduced to coke, remov- 40 ing vaporous products from the coking chamber and introduc'mg the same into a reaction chamber also maintained at substantial superatmospheric pressure, wherein high boiling liquid products are separated therefrom and their lower boiling components which remain vaporized in this zone are subjected to appreciable further conversion, removing said high boiling liquid products from the reaction chamber and returning the same to the coking chamber for further treatment, separately removing the vaporous conversion products from the reaction chamber after being subjected to said continued conversion therein, subjecting the same to fractionation whereby their components boiling above the range of the desired final motor fuel product of the process are condensed as reflux condensate, subjecting fractionated vapors of the desired end boiling point to condensation, recovering the resulting distillate, separating the reflux condensate formed by said fractionation into selected relatively low boiling and high boiling fractions, returning the latter to said heating coil for further conversion, subjecting said selected low boiling fractions of the reflux condensate to independently controlled more severe conversion conditions of cracking temperature and superatmospheric pressure in a separate heating coil, introducing a regulated portion of the highly heated products from said separate heating coil into the coking chamber to commingle therein with the materials undergoing coking and assist the coking operation, and introducing another regulated portion thereof into the reaction chamber to commingle therein with the vaporous conversion products and assist their continued conversion in this zone.

Hydrocarbon oil charging stock for the process may be supplied, depending upon its characteristics, to either heating coil of this system, or, all or in part, to the fractionator as will be later more fully explained.

The accompanying diagrammatic drawing illustrates one specific form of apparatus employing the features and advantages of the present invention and in which the process of the invention may be accomplished.

Referring to the drawing, heating coil I is located within any suitable furnace 2, whereby the oil supplied to the heating coil in a manner to be later more fully described is subjected during its passage therethrough to the desired conversion temperature, preferably at a substantial superatmospheric pressure. The resulting hot conversion products are discharged in a continuous stream from the heating coil through line 3 and valve 4 into coking chamber 5.

Chamber 5 is also preferably maintained at a substantial superatmospheric pressure, which may be substantially the same or somewhat lower than the pressure employed at the outlet from heating coil I, and the high boiling components of the heated products supplied to this zone are reduced therein to substantially dry coke. The coke may be allowed to accumulate within chamber 5, to be removed therefrom in anywell known manner (not shown), after the chamber is substantially filled or after its operation has been completed for any other reason. When desired, a plurality of coking chambers may be employed, although only one is illustrated in the drawing, in which case they may be simultaneously operated but preferably are alternately operated, cleaned and prepared for further operation, so that the duration of the operating cycle of the process is independent of the capacity of the coking zone. Chamber 5. is provided with a suitable drain line 6, controlled by valve I, and this line may also serve as, a means of introducing steam, water or any other suitable cooling material into the chamher after its operation has been completed and preferably after it has been isolated from the rest of the system, in order to hasten cooling and facilitate removal of the coke.

Vaporous products are withdrawn from the upper portion of the coking chamber and directed through line 8 and valve 9 into reaction chamber II), which is also preferably operated at a substantial superatmospheric pressure. The pressure maintained in the reaction chamber is nor-.

mally somewhat lower than that employed in the coking chamber in order that the hot vaporous products from the coking chamber may be transferred to the reaction chamber without the use of a pump or compressor. It is, however, entirely within the scope of the invention to employ a suitable pump or compressor for this purpose, in

which case chamber I may, when desired, be operated at a substantially higher pressure than that employed in the coking zone. Although not indicated in the drawing, the reaction chamber and the coking chamber are preferably well insulated in order to conserve heat and appreciable further conversion of the heated products supplied to the reaction chamber, and particularly their low boiling components which remain vaporized in this zone, is accomplished therein. The high boiling liquids formed in the reaction chamber or supplied thereto, including any entrained or dissolved tars and pitch-like material in the vaporous products from the coking chamber and also including any residual conversion products and high boiling polymers supplied to this zone with the heated products from the high temperature cracking coil of the system, in a manner to be later more fully described, momentarily collect in the lower portion of the reaction chamber, from which they are withdrawn through line II and valve I2 to pump I3, by means of which they are introduced through line I4 and valve I into the coking chamber for further treatment and reduction to coke in this zone. The vaporous products which pass throughthe reaction chamber and undergo appreciable continued conversion in this zone are withdrawn, in the case here illustrated, from the upper portion thereof and directed through line I6 and valve I'I into fractionator I8.

It is, of course, entirely within the scope of the invention, although not here illustrated, to supply the vaporous products from the coking chamber to the upper instead of to the lower portion of the reaction chamber, in which case vaporous and liquid conversion products may be separately withdrawn from the lower portion of this zone, the latter being returned, in the manner illustrated, to the coking chamber, while the vaporous products are supplied, by well known means (not shown), to the fractionator.

The components of the vaporous conversion products supplied to fractionator I8 boiling above the range of the desired final motor fuel product of the process are condensed in this zone as reflux condensate which is separated by fractional condensation into selected relatively low boiling and high boiling fractions, to be subjected to further conversion as will be later more fully described. Fractionated vapors of the desired end boiling point are withdrawn, together with uncondensable gas produced within the system, from the upper portion of fractionator I8 and directed through line I9 and valve 20 to condensation and cooling in condenser 2I. The resulting distillate and gas pass through line 22 and valve 23 to collection and separation in receiver 24. Gas may be released from the receiver through line 25 and valve 26.. The distillate collected in receiver 24 may be withdrawn therefrom through line 21 and valve 28 to storage or to any desired further treatment. When desired, regulated quantities of the distillate collected in receiver 24 may be recirculated, by well known means not illustrated in the drawing, to the upper portion of fractionator I8 to serve as a cooling and refluxing medium in this zone for assisting fractionation of the vapors and to maintain the desired outlet temperature'from the fractionator.

The high boiling fractions of the reflux condensate formed in fractionator I8 are withdrawn from the lower portion of this zone through line 29 and valve 30 to pump 3|, by means of which they are returned through line 32 and valve 33 to conversion, as previously described, in heating coil I.

The selected relatively low boiling fractions of the reflux condensate formed in fractionator l8 may be withdrawn from one or a plurality of suitable intermediate points in this zone, provision being made in the case here illustrated for withdrawing the same from the fractionator through line 34, wherefrom they are directed through valve 35 in this line to pump 36. Pump 36 supplies the relatively low boiling reflux condensate through line 31, valve'38 and line 39 to further conversion in heating coil 40, wherein they are subjected to independently controlled conversion conditions more severe than those to which the relatively high boiling oils are subjected in heating coil l.

A furnace 4! of suitable form supplies the required heat to the oil passing through heating coil 40 to subject it to the desired relatively high conversion temperature, preferably at a substantial superatmospheric pressure. The resulting highly heated products are discharged from heating coil 40 through line 42 and may thence pass, all or in part, through valve 43 in this line into reaction chamber Ill, or they may be supplied, all or in part, through line 44 and valve 45 into coking chamber 5. I

The invention specifically contemplates the introduction of regulated portions of the highly heated products from heating coil 40 into both the coking chamber and the reaction chamber. Any heated products supplied from heating coil 40 to the coking chamber preferably are directly commingled with the heavy liquid conversion products undergoing coking in this zone and serve to assist their reduction to coke. Any highly heated products from heating coil 40 supplied'to the reaction chamber commingled in this zone with the vaporous products from the coking chamber, supplied thereto as previously described, serving to supply additional heat thereto and assist'their continued conversion in the reaction chamber.

Charging stock for the process, which may comprise'any desired type of hydrocarbon oil, is supplied, in the case here illustrated, through line 46 and Valve ll to pump 48, wherefrom it is fed through line 49 and may be directed, all or in part, through line 50 and valve 5! into fractionator 18, through line 39 and valve 52, to conversion in heating coil 40, or through line 53,

valve 54 and line 32, to conversion in heating coil I. The manner in'which the charging stock is supplied to the system will depend primarily upon its characteristics. When it does not contain any appreciable quantity of high boiling materials unsuitable for conversion in heating coil 5, or any appreciable quantity of materials within the boiling range of the overhead motor fuel product, which are of poor anti-knock value or would otherwise tend to contaminate the cracked motor fuel product, the charging stock may be supplied, regardless of its other characteristics, to the fractionator, and it is preferably supplied to this zone when it comprises an oil of relatively wide boiling range, including materials corresponding in boiling range to both the low boiling and high boiling fractions of the reflux condensate. When the charging stock comprises an oil of relatively high boiling characteristics it may be supplied to heating coil I, and, on the other hand, when it comprises an oil-of relatively low boiling characteristics it may be supplied to heating coil 40, or it may, in either case, be supplied, all or in part, to fractionator i8.

The preferred range of operating conditions which may be employed to accomplish the objects of the invention in an apparatus such as illustrated and above described may be approximately as follows:

The relatively heavy oil heating coil may utilize an outlet conversion temperature ranging, for example, from 850 to 950 F., preferably with a superatmospheric pressure at this point in the system of from 100 to 500 pounds or more per square inch. The relatively light oil heating coil preferably employs an outlet conversion temperature of from 900 to 1050 F., or thereabouts, with a superatmospheric pressure measured at this point in the system of from 200 to 800 pounds, or more, per square inch. The coking chamber preferably employs a 'superatmospheric pressure of the order of 100 to 500 pounds, or thereabouts, per square inch, which may be substantially the same or somewhat lower than the pressure employed in the communicating heating coil utilizing the lowest pressure. The reaction chamber may employ a superatmospheric pressure of from 100 to .500 pounds, or thereabouts, per square inch, which, as previously mentioned, is preferably somewhat lower than the pressure employed in the coking chamber, but may when desired be operated at a substantially higher pressure than the coking chamber. The fractionating stage of the system is preferably operated at a substantially lower pressure than that employed in the reaction chamber, ranging for example from 1-50 pounds, or thereabouts, per square inch down to substantially atmospheric pressure, although higher pressures up to substantially the same as that employed in the reaction chamber may be utilized in this zone when desired. The pressures employed in the condensing and collecting portions of the system may be substantially equalized or somewhat reduced relative to the pressure employed in the fractionator.

As a specific example of an operation of the process of the invention as it may be accomplished in an apparatus such as illustrated and above described, the charging stock, which comprises a California reduced crude of about 24 A. P. I. gravity, is supplied to the heavy oil cracking coil, wherein it is subjected to a conversion temperature, measured at the outlet therefrom, of approximately 930 F. at a superatmospheric pressure of approximately 350 pounds per square inch. The coking chamber to which the resulting heated products are supplied is maintained at substantially the same pressure. Vaporous products from the coking chamber are supplied to the reaction chamber, which is maintained at a superatmospheric pressure of about 340 pounds per square inch, and liquid conversion products from this zone are returned, without additional heating, to the coking chamber. The fractionator to which vaporous products from the reaction chamber are supplied is maintained at a superatmospheric pressure of approximately 100 pounds per square inch, and the reflux condensate formed in this zone is separated into components boiling above and below approximately 640 F. The high boiling fractions of the reflux condensate are returned to the heavy oil heating coil for conversion together with the charging stock. The low boiling fractions of the reflux condensate are subjected, in a separate heating coil, to an outlet conversion temperature of approximately 950 F, at a superatmospheric pressure of about 400 pounds per square inch. Approximately 50% of the highly heated products from the light oil heating coil are introduced into the lower portion of the coking chamber and the remaining 50%, or thereabouts, is introduced into the reaction chamber. This operation will produce, per barrel of charging stock, approximately 62% of M10 F. end point motor fuel having an octane number of approximately 70 by the motor meth d and approximately 92 pounds of relatively low volatile petroleumcoke of uniform quality and good structural strength, the remainder being chargeable principally to uncondensable gas.

I claim as my invention:

1. A process for the conversion of hydrocarbon oils, which comprises subjecting an oil of relatively high boiling characteristics to conversion conditions of cracking temperature and superatmospheric pressure in a heating zone, reducing the high boiling components of the resulting heated products to coke in a coking zone, introducing the heated vaporous products, including those resulting from the coking operation, into a separate reaction zone wherein they are subjected to appreciable continued conversion, withdrawing resultant high boiling liquid products from the reaction zone and returning the same, without additional heating, to the coking zone, separately withdrawing vaporous conversion products from said reaction zone and subjecting the same to fractionation, subjecting fractionated vapors of the desired end boiling point to condensation, recovering the resulting distillate, returning high boiling fractions of reflux conden sate formed by said fractionation to conversion in the heating zone, separately subjecting selected low boiling fractions of the reflux condensate to independently controlled conversion conditions at higher cracking temperature in a separate heating zone, and introducing regulated quantities of the resulting highly heated products into the reaction zone wherein they commingle with the vaporous products from the coking zone and assist their further conversion.

2. A process for the conversion of hydrocarbon oils, which comprises subjecting an oil of relatively high boiling characteristics to conversion conditions of cracking temperature and superatmospheric pressure in a heating zone, reducing the high boiling components of the resulting heated products tov coke in a coking zone, introducing the heated vaporous products, including those resulting from the coking operation, into a separate reaction zone wherein they are subjected to appreciable continued conversion, withdrawing resultant high boiling liquid products from the reaction zone and returning the same, without,

additional heating, to the coking zone, separately withdrawing vaporous conversion products from said reaction zone and subjecting the same to fractionation, subjecting fractionated vapors of the desired end boiling point to condensation, recovering the resulting distillate, returning high boiling fractions of reflux condensate formed by said fractionation to conversion in the heating zone, separately subjecting selected low boiling fractions of the reflux condensate to independently controlled conversion conditions at higher cracking temperature in a separate heating zone, introducing regulated quantities of the resulting highly heated products into the coking zone to commingle with the materials undergoing coking therein and assist their reduction to coke, and introducing another regulated portion of said highly heated products into the reaction zone to commingle therein with the vaporous products from the coking zone and assist their further conversion,

3. In a process for the conversion of hydrocarbon oils, wherein an oil of relatively low boiling characteristics is subjected to cracking temperature at superatmospheric pressure in a heating coil, the resulting heated products introduced into an enlarged reaction chamber, also maintained at a substantial superatmospheric pressure, wherein separation of vaporous and liquid conversion products is accomplished and the latter are subjected to appreciable continued conversion, vaporous and liquid conversion products separately withdrawn from the reaction chamber, the latter supplied, without additional heating, to a coking chamber, the vaporous products subjected to fractionation, fractionated vapors of the desired end boiling point subjected to condensation and the resulting distillate recovered, the improvement which comprises returning selected low boiling fractions of reflux condensate formed by said fractionation to said heating coil for further conversion, subjecting selected high boiling fractions of the reflux condensate to independently controlled conversion conditions of cracking temperature and superatmospherlc pressure in a separate heating coil, introducing the heated products from said separate heating coil into the coking chamber, which is also maintained at a substantial superatmospheric pressure, withdrawing vaporous products from the coking chamber, and introducing the same into the reaction chamber wherein they commingle with the heated products from the first mentioned heating coil and are subjected to further con- ,version therewith.

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