US2149860A - Conversion of hydrocarbon oils - Google Patents

Description

March 7, 1939. J. C, MORRELL' l 2,149,869

' CONVERSON OF HYDROCARBON OILS .FiledvJ'une 27, 195e Kripo@ @mmf/NG @No @EHU/0N CMMBEE Patented Mar. 7, 1939 UNITED STATES PATENT FFICE coNvEasIoN or HyDitocAao-N ons Application June 27,

6 Claims.

This invention refers to an improved process for the fractional distillation of hydrocarbon oils accompanied by the selective pyrolytic conversion of low-boiling and high-boiling fractions of the 5. charging stock, together withV selected intermediate liquid products of the process.

The process is particularly well adapted to the treatment of charging stocks of relatively Wide boiling range, such as crude petroleum, and more l particularly those containing a substantial quantity of relatively low-boiling components, such as gasoline or gasoline fractions of inferior antiknock value. It is not limited to this type of charging stock since it may be advantageously employed for the treatment of any hydrocarbon oil of relatively wide boiling range.

`In the preferred embodiment of the invention a substantial portion or all of the heat required for fractional distillation of the charging stock is recovered from hot conversion products of the process and comprises heat Which Would other- Wise be normally Wasted. Also, by this method of operation, excess'heat is extracted from the hot conversion products by their indirect heat -exchange with the charging stock as Well as, when desired, by directly commingling the hot conversion products with high-boiling fractions of the charging stock recovered from the initial distilling or topping operation. 30m The invention retains, in one specific embodiment thereof, the Well established advantageous feature of selectively cracking relatively loW- boiling and high-boiling fractions of the intermediate liquid conversion products of the process under independently controlled cracking conditions. It further provides for continued cracking or reforming of the vaporous products of said selected cracking steps, together with selected 10W-boiling fractions of the charging stock. The 40 latter specifically comprise any gasoline or gasoline fractions contained in the charging stock which are of unsatisfactory antiknock value or they may consist of or include somewhat higher boiling fractions of the charging stock such as 45 naphtha, kerosene or kerosene distillate, light gas oil and the like.

The high-boiling fractions of the charging stock recovered from the fractional distillation step of the process may be supplied directly to sc the same cracking zone to which the total or `high-boiling fractions of the intermediate liquid conversion products of the process are supplied or they may be commingled, all or in part, with heated products from the final cracking or re- 5a forming stage of the process and supplied there- 1936, vSerial No. 87,650

With to a separating chamber, wherefrom highboiling liquid components of the commingled materials, undesirable as cracking stock for the system, are recovered and Wherefrom the vaporous components of the commingled materials pass 'to fractionation for the removal therefrom, as reflux condensate, of said selected intermediate liquid products of the process supplied to a single or to said selected cracking steps.

In one specific embodiment, the invention comprises subjecting a hydrocarbon oil charging stock of relatively wide boiling range to fractional distillation, Whereby it is separated into selected relatively low-boiling and high-boiling fractions, subjecting selected high-boiling fractions of the charging stockto cracking tempera- Y ture at superatmospheric pressure in a heating coil and communicating enlarged reaction chamber, withdrawing vaporous conversion products from the reaction chamber, commingling the same with selected 10W-boiling fractions of -the charging stock, passing the commingled materials through a separate heating coil wherein they are subjected to pyrolytic conversion, discharging the resulting heated products from said separate heating coil, passing the same in indirect heat exchange with the charging stock, whereby to supply heat tov the latter for said fractional distillation thereof and whereby to partially cool said conversion products, introducing the partially cooled products into a separating chamber wherein their vaporous'and high-boiling non- Y vaporous components separate, subjecting the former to fractionation whereby their components boiling above the range of the desired rnal motor fuel product are condensed as reflux condensate, subjecting fractionated vapors of the desired end-boiling point to condensation, collecting and separating the resulting distillate and gas, separating the reflux condensate formed by said fractionation into selected relatively lowboiling and high-boiling fractions, supplying the high-boiling fractions of said reflux condensate to further cracking in the first mentioned heating coil, subjecting selected 10W-boiling fractions of the reflux condensate to independently controlled cracking conditions in a separate heating coil and introducing the resulting heated products into said reaction chamber.

Various modications of the process above outlined which, however, are not to be considered equivalent and various features of the invention not previously mentioned are described in conjunction With the following description of the accompanying diagrammatic drawing. The

drawing illustrates diagrammatically one specific form of apparatus embodying the various features of the invention and in which the process may be accomplished.

Referring to the drawing, the total or relatively high-boiling intermediate liquid conversion products of the process, as desired, and selected high-boiling fractions of the charging stock are supplied, as will be later described, to heating coil I. Heat is supplied to this coil from. a furnace 2 and the oil passing therethrough is heated to the desired cracking temperature, preferably at a substantial superatmospheric pressure. The heated products are discharged from coil I through line 3 and valve 4 and are directed through line 5 to reaction chamber 6.

Simultaneously with this operation, selected lower boiling intermediate liquid products of the process may be supplied, when desired and as will be later described, to heating coil l. The oil passing through heating coil l is preferably subjected to a higher cracking temperature than that employed in coil I, preferably at a substantial superatmospheric pressure. Heat for the cracking reaction is supplied from a furnace 8.

The heated products are discharged from heating coil 'I and directed through line 5 and valve 9 into reaction chamber 5.

Although the heated products from coils I and l are supplied to chamber 6, in the case yhere illustrated, in commingled state they may,

when desired, be separately introduced into this zone at any desired point or plurality of points therein.

Chamber 6 is also preferably maintained at a substantial superatmospheric pressure and the heated products supplied thereto are subjected to continued cracking in this zone at the temperature and pressure conditions prevailing therein. Preferably, although not illustrated, chamber 6 is insulated to conserve heat. Vaporous and liquid conversion products are separated in chamber 6. The latter are withdrawn from the lower portion of this zone through line I6 and may, when desired, be directed, all or in part, through valve II in this line to cooling and storage or to any desired further treatment, including, when desired, reduction to coke in a separate coking zone, not illustrated, or the liquid products may be supplied, all or in part, to further treatment within the system, as will be later described. Vaporous conversion products are removed from any desired point or plurality of points: in chamber 6, being withdrawn, in the case here illustrated, from the upper portion of this zone wherefrom they are directed through line I2 and valve I3 to heating coil Ill.Y

Selected low-boiling fractions of the charging stock are also supplied, as will be later described, to heating coil It and the commingled materials passing therethrough are subjected to the desired cracking conditions by means of heat supplied from a furnace I5. The cracking conditions maintained in heating coil I4 are regulated to effect a substantial improvement in the motor fuel characteristics (particularly the antiknock value) of any components of the oils supplied thereto boiling within the range of gasoline without excessively altering their boiling characteristics and to simultaneously accomplish additional cracking of any higher boiling oils supplied to this zone for the production of additional yields of high antiknock gasoline.

The heated products are discharged from heating coil I4 through line I6 and valve Il and preferably pass through heat exchanger I8 wherein they are cooled by indirect heat exchange with the charging stock The partially cooled conversion products pass from heat exchanger I8 through line I9 and valve 20 into separating chamber 2I and, when desired, additional cooling of these materials may be accomplished prior to their introduction into the separating chamber by means of commingling the heated products with relatively cool oils recovered from within the system, as will belater more fully explained.

Preferably, the heated products discharged from heating coil Ill are cooled, by their direct commingling with cooler oils and/or by indirect heat exchange with the charging stock, suiciently to prevent any substantial further cracking thereof. The partially cooled products from heating coil Iii, or the commingled materials, as the case may be, supplied toy chamber 2| are separated in this zone into Vaporous and residual liquid components. The latter are removed from the lower portion of the separating chamber through line 22 and valve 23 to cooling and storage or to any desired further treatment and these materials may, when desired, be supplied to a separate coking zone, not illustrated, wherein they are reduced to substantially dry coke and wherefrom Vaporous products, preferably pass to reaction chamber 6 or to distilling column 54.

Vaporous components of the materials: supplied to chamber 2| are directed therefrom through line 24 and valve 25 to fractionation in fractionator 26, wherein their components boiling above the range of the desired nal motor fuel product of the process are condensed as reux condensate. Fractionated vapors of the desired end-boiling point, preferably comprising good quality gasoline, are removed, together withpgaseous products of the process, from the upper portion of fractionator 26 and directed through line 27 and valve 28 to condensation and cooling in condense-r 29. The resulting distillate and uncondensed gases pass through line 30 and valve 3l to collection and separation in receiver 32. Uncondensed gases may be released from receiver 32 through line 33 and valve 34. Distillate is withdrawn from receiver 32 through line 35 and valve 35 to storage or to any desired further treatment. When desired, regulated quantitiesl of the distillate collected in receiver 32 may be reciroulated by well known means, not illustrated in the drawing, to the upper portion of fractionator 26 to serve as a reuxing and cooling medium in this zone for assisting fractionation of the vapors and to malntain the desired vapor outlet temperature'therefrom.

The total reflux condensate formed in fractionator 26 may, when desired, be withdrawn from the lower portion of this zone through line 37 and valve 38 to pump 39 by means of which it is supplied through line 40 and valve 4I to further cracking in heating coil I, in the manner previously described. Preferably, however, the reflux condensate formed in fractionator 26 is separated in this zone into selected relatively low-boiling and high-boiling fractions. In the latter case only the high-boiling fractions are directed from the lower portion of fractionator 26, as described, to heating coil I, while the selected lower boiling fractions are removed from any desired intermediate point or plurality of points in fractionator 26 and directed therefrom to cracking in heating coil 1. Provision is made, in the case here illustrated, for removing selected from fractionator 26-through line 42 and valve 43 to pump 44 by means of which they are supplied through line 45 and valve 46 to cracking in heating coil 1, in the manner previously described.

Charging stock for the process which, as previously mentioned, preferably comprises a hydrocarbon oil of relatively wide boiling range, specifically including crude oils and more particularly crudes containing gasoline or gasoline fractions of inferior antiknock value, is supplied through line 41 and valve 43 to pump 49 by means of which it is fed through line 50 and valve 5I to heat exchanger I8. The charging stock passes through heat exchanger I8 in indirect heat exchange with the heated products from I heating coil I4 and is directed therefrom through line 52 and valve 53lto distilling column 54.

Additional heat for effecting distillation of the charging stock may, when required, be supplied thereto in any well known manner not illustrated, but in the preferred embodiment of the invention at least a substantial portion of the heat required is recovered by indirect heat exchange between the charging stock and relatively hot conversion products of the process, preferably those from heating coil I4.

The extent of vaporization to which the charging stock is subjected in column 54 is controlled by the temperature to which it is heated and the pressure conditions maintained in this zone. In the preferred embodiment of the invention only suicient vaporization of the charging stock lneed be effected in column 54 to accomplish separation from the charging stock of substantially all of its low-boiling components desirable as cracking stock in heating coil I4. In the case here illustrated, the desired low-boiling fractions of the charging stock are withdrawn in vaporous state from the upper portion of column 54 and directed therefrom through line 55,.valve 55 and line I2 to cracking in heating coil I4, together with the vaporous products from chamber B. Preferably a sucient pressure is maintained in column 54 to permit supplying the selected lowboiling fractions of the charging stock from this zone to heating coil I4 without the use of a pump or compressor and to permit maintaining the ydesired pressure conditions in heating coil I4.

It is, however, entirely within the scope of the invention to utilize a pump or compressor in line i 55, although this is not illustrated, or to subject the desired low-boiling components of the charging stock to condensation, by well known means,

not illustrated, either within chamber 54 or in an exterior condenser. In either of the latter cases the resulting condensate may be supplied by means of a pump, not illustrated, to heating coil I4 and, when desired, a substantially higher pressure may be maintained in coil I4 than in chamber 54.

It is also within the scope of the invention, in case the charging stock contains desirable lowboiling components such as gasoline or low-boiling gasoline fractions of satisfactory quality, to separately recover the same from chamber 54 by condensation of the overhead vaporous products from this zone in any well known manner, not

Aillustrated. In such cases somewhat higher boiling components of the charging stock, such as, for example, high-boiling gasoline fractions, naphtha, kerosene or kerosene distillate, light gas oil and the like, may be separately recovered from .chamber 54 as an intermediate condensate and supplied by well known means, not illustrated, to heating coil I4.

The high-boiling components of the charging stock which remain unvaporized in chamber 54 are withdrawn from the lower portion of this Zone through line 5l valve 5 8 to pump 59 by means of which they are fed through line 60 and may, when desired, pass all or in part through valve 6I in this line into line 40 and thence to cracking in heating coil I together with the reflux condensate or high-boiling fractions of the reflux condensate, as the case may be, from fractionator 25. .l

Provision is also made in the case hereV illustrated for directing a regulated portion or all of the high-boiling fractions of the charging stock from line 65 through line @2 and valve 63 into line I9, wherein they commingle with the conversion products from heating coil I4 passing to chamber 2l and serve to partially cool the latter. By this method of operation lthe highboiling fractions of the charging stock thus supplied to chamber 2l are subjected to further vaporization in this zone, whereby any highboiling fractions of the charging stock undesirable as cracking stock for the system may be recovered or subjected to further treatment together with the residual liquid from chamber 2 I, while its lower boiling fractions which are vaporized in this zone pass therefrom, together with the vaporous conversion products, to fractionation in fractionator 26.

The invention also contemplates, when desired,

supplying all or a regulated portion of the liquid conversion products withdrawn, as previously described, from chamber 6 to chamber 2I, wherein further vaporization of the liquid products to separate desirable low-boiling materials therefrom may be accomplished either by maintaining a higher temperature in chamber 2I than that of the liquid products withdrawn from chamber 5 or by maintaining a lower pressure in chamber 2l than that maintained in chamber 6 or by both methods. In such cases the liquid products supplied from chamber 6 to chamber 2| may be utilized, when desired, as a means of partially cooling the products discharged from heating coil I4 and provision is made, in the case here illustrated, for directing liquid products removed from chamber 5 from line Il) through line 64 and valve 55 into line I9, wherein they commingle with the products in heating coil I4 and pass therewith to chamber 2|. Although, in the apparatus illustrated in the drawing, provision is made for introducing cooling oil into theA stream of products discharged from heating coil I4 only after their indirect heat exchange with the charging stock it is, of course, within the scope of the invention to reverse this procedure and commingle cooling oil with the stream of heated products discharged from heating coil I4 prior to their introduction into heat exchanger I8. The latter method is particularly desirable, in case sufficient heat can readily be recovered from the products discharged from heating coil I4 to accomplish vaporization of the charging stock to the desired extent after the products from heating coil I4 have been partially cooled.

The preferred range of operating conditions which may be employed, in an apparatus such as illustrated and above described, to accomplish the desired results is approximately as follows: The heating coil to which the total reflux condensate selected high-boiling fractions of Vthe charging stock are supplied may employ an outlet conversion temperature ranging, for example, from 875 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. When a separate heating coil is employed for the conversion of selected low-boiling fractions ofthe reflux condensate the temperature employed at the outlet therefrom may range, for example, from 900 to 1000 F., or thereabouts, preferably with a superatmospheric pressure measured at the outlet from this zone of from 200 to 800 pounds, or more, per square inch. A superatmospheric pressure of from 100 to 500 pounds, or more, per square inch, is preferred in the reaction chamber but the pressure maintained in VVthis zone is no greater and may, when desired, be somewhat lower than that maintained at the outlet from the preceding heating coil utilizing the lowest pressure, in case two preceding heating coils are employed. Preferably, ra pressure of from substantially atmospheric to 300 pounds, or thereabouts, per square inch, superatmospheric, and a temperature of from 950 to 1100 F., or thereabouts, is employed in the heating coil succeeding the reaction chamber to which vaporous products from the reaction chamber and selected low-boiling fractions of the charging stock are supplied although, when desired, any pressure up to substantially the same as that employed in the reaction chamber maybe utilized in this heating coil. Any desired pressure ranging from substantially atmospheric to superatmospheric pressure of 500 pounds per square inch, or thereabouts, may be employed in the distilling stage of the system to which the charging stock is supplied and, as previously mentioned, this zone is ordinarily operated at substantially the same or somewhat higher pressure than that Amaintained at the outlet from the heating coil to which selected low-boiling fractions of the charging stock are supplied. The separating chamber may be operated at any desired pressure ranging from substantially atmospheric up to substantially the same pressure as that maintained at the outlet from the communicating heating coil and when liquid products from the reaction chamber are supplied to the separating chamber it is preferably operated at a substantially reduced pressure` relative to that in the reaction chamber. The pressures employed in the fractionating, condensing and collecting portions of the system may be substantially the same or somewhat lower than that employed in the separating chamber.

As a specific example of one of the many possible operations of the process as it may be accomplished in an apparatus such as illustrated and above described, the charging stock comprises a crude petroleum of about 29-30 A. P. I. gravity containing approximately 5 per cent of material boiling up to 206 F. and containing approximately 27 per cent of 400 F. end-point gasoline of inferior antiknock value. The charging stock is passed in indirect heat exchange with the heated products from the vapor heating coil of the system and is introduced into the distilling zone at a temperature of approximately ponents of the commingled materials are withdrawn as residual liquid fromV the separating chamber and the vaporous products from this zone are subjected to fractionation for the recovery therefrom of motor fuel of about 400 F. end-boiling point and the formation of light and heavy reux condensates. The heavy reux condensate is subjected in a heating coil to a cracking temperature ofl approximately 900 F. at a superatmospheric pressure of about 300 pounds per square inch. The light reflux condensate is subjected in a separate heating coil to a cracking temperature of approximately 950 F. at a superatmospheric pressure of approximately 350 pounds per square inch. The heated products from both the light and heavy reflux heating coils are supplied to the reaction chamber which is maintained at a superatmospheric pressure of approximately 300 pounds per square inch. Liquid products from the reaction chamber are supplied, as previously mentioned, to the separating chamber which latter zone is maintained at a superatmospheric pressure of approximately 45 pounds per square inch. Vaporous products from the reaction chamber and said low-boiling fractions of the charging stock, which latter have an end-boiling point of approximately 500 F., are subjected in the vapor heating coil to a cracking temperature of approximately 1000 F., the pressure in this zone being substantially equalized with that maintained in the reaction chamber.` This operation will produce, per barrel of charging stock, approximately 70 per cent of 400 F, end-point gasoline having an octane number by the motor method of approximately 72 and approximately 15 per cent of good quality liquid residue suitable for sale as premium fuel oil, the remainder being chargeable, principally, to uncondensable gas which is rich in polymerizable olens and is highly desirable, after separating low`boiling xed gases therefrom, as charging stock for a well known catalytic polymerization process to produce additional yields of gasoline of exceptionally high antiknock value.

I claim as my invention:

l. In a process for the treatment of hydrocarbon oils wherein an oil of relatively high-boiling characteristics, recovered from within the system, is subjected to cracking temperature at superatmospheric pressure in a heating coil, the heated products introduced into an enlarged chamber also maintained at substantial superatmospheric pressure wherein separationv of their vaporous and residual liquid components is accomplished and the vaporous products passed through a separate cracking coil wherein they are subjected to additional cracking, the improvement which comprises passing v charging stock for the process, comprising a, hydrocarbon oil of relatively wide boiling range, in indirect heat exchange with relatively hot products discharged from the last mentioned cracking coil, introducing the heated `charging stock into a distilling column wherein a substantial portion thereof is vaporized,` supplying vapors from said column to the last mentioned cracking coil, commingling unvaporized portions of the charging stock from said column with heated products discharged from the last mentioned cracking coil, introducing the commingled materials and residual liquid withdrawn from said enlarged charnber into a separating chamber maintained Yat a substantially reduced pressure relative to that employed in said enlarged chamber, removing the resulting non-vaporous residue from the separating chamber, subjecting vaporous products from the separating chamber to fractionation for the formation of reflux condensate, subjecting fractionated vapors of the desired end-boiling point to condensation, recovering the resulting distillate, supplying selected relatively high-boiling fractions of the reflux condensate formed by said fractionation to the first mentioned cracking coil, subjecting selected lower boiling fractions of the reflux condensate formed by said fractionation to an independently controlled cracking temperature at substantial superatmospheric pressure in another separate heating coil, and introducing the heated products from said separate heating coil into ,said enlarged chamber.

2. In a process for the treatment of hydrocarbon oils wherein a charging stock of relatively Wide boiling range is subjected to partial vaporization and unvapolrized portions thereof, subjected to cracking temperature at substantial superatmospheric pressure and the resulting vaporous and liquid conversion products separated, the improvement which comprises commingling said vaporous products with vaporized portions of the charging stock from the partial vaporization step, heating the commingled materials to a higher cracking temperature in a separate cracking zone, passing heated products discharged from the last mentioned cracking zone in indirect heat exchange with the charging stock whereby to partially cool said heated products and supply to the charging stock at least a substantial portion of the heat required for said partial vaporization thereof, introducing the partially cooled materials into a separating zone wherein their vaporous and residual liquid components are separated, subjecting the vapors from said separating zone to fractionation and separating their insurliciently converted components into relatively light and heavy reilux condensates, subjecting fractionated vapors of the desired end-boiling point from the fractlonating step to condensation, recovering the resulting distillate, returning the heavy reux condensate formed by said fractionation to the first mentioned cracking step, further cracking the light reilux condensate in another independently controlled cracking Zone, and commingling heated products from the firstmentioned and last-mentioned cracking steps prior to the separation of their vaporous and liquid components.

3. A process such as defined in claim 2 wherein at least a portion of said liquid products separated from the vaporous products of the first mentioned cracking step are subjected to appreciable further vaporization by introducing the same into the same separating zone to which said partially cooled products from the second mentioned cracking step are supplied.

4. A conversion process which comprises subjecting hydrocarbon oil to cracking conditions of temperature and pressure in a heating zone, passing the resultant heated products in indirect heat exchange with relatively cool charging oil for the process to partially cool said products and to preheat the charging oil, subjecting the preheated charging oil to partial vaporization under noncracking conditions, supplying vaporized portions of the charging oil to said heating Zone, commingling unvaporized portions of the charging oil without prior cracking thereof and while at below cracking temperatures with the partially cooled products from the heat exchange step to further cool said products, separating the resultant mixture into vapors and residue, and fractionating and condensing the vapors.

5. A conversion process which comprises subjecting hydrocarbon oil to cracking conditions of temperature and pressure in a heating zone, passing the resultant heated products in indirect heat exchange with relatively cool charging oil for the process to partially cool said products and to preheat the charging oil, subjecting the preheated charging oil to partial vaporization under non-cracking conditions, supplying resultant vapors to said heating zone, commingling unvaporized portions of the charging oil, without prior cracking thereof and while at below cracking temperatures, with the partially cooled products from the heat exchange step, separating the resultant mixture into vapors and residue, fractionating the last-named vapors and subjecting resultant reilux condensate to independently controlled cracking conditions of temperature and pressure in a second heating zone, and supplying vaporous products of this cracking operation to the rst-rnentioned heating zone.

6. A hydrocarbon oil conversion process which comprises subjecting the charging oil to partial vaporization under non-cracking conditions, heating resultant vapors to cracking temperature in a heating zone, commingling unvaporized portions of the charging oil, without prior cracking thereof and while at below cracking temperatures, with the heated vapors from the heating zone, separating the resultant mixture into vaporous and residual products, fractionatlng the vaporous products to form relatively heavy and light reflux condensates, subjecting these reflux condensates to independently controlled cracking conditions of temperature and pressure, each in a separate heating Zone apart from the rstmentioned heating zone, commingling the products from said separate heating zones and separating the same into vapors and residue, and supplying at least a portion of the last-named vapors to the rst-mentioned heating zone.

JACQUE C. MORRELL.

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