US2081342A - Conversion of hydrocarbon oils - Google Patents

Description

May 25, 1937. K. swARTwooD CONVERSION OF HYDROCARBON OILS Filed May 29, 1955 Tracfl'onaof INVENTOR. jfwzzzetiz .jy'zz/oocl, BY gi ATTORNEY.

AIIIHHH H||||||||| Tu Wha Ce Patented May 25, 1937 UNITED STATES PATENT OFFICE CONVERSION F HYDROCARBON OILS Application May 29, 1933, Serial No. 673,332

2 Claims.

This invention `particularly refers to an improved process and apparatus for the simultaneous conversion of hydrocarbon oils of different characteristics, the different oils each being subjected to treatment under independently controlled conversion conditions most suitable to secure high yields of the desired products.

In one specific embodiment, the invention comprises subjecting a relatively low-boiling hydrocarbon oil,.such as motor fuel of inferior antiknock value, naphtha, kerosene orvkeros'ene distillate, pressure distillate bottoms, or the like, or fractions or mixtures of such materials, to the desired conversion conditions of elevated temperature and superatmospheric pressure in a heating coil, discharging the stream of heated oil from the heating coil, and commingling therei with a stream of cooler high-boiling hydrocarbon oilsuch as crude petroleum, topped crude, fuel oil, gas oil or the like for the purpose of cooling the lower boiling oils and retarding or arresting their conversion, subjecting the commingled oils to vaporization at substantially reduced pressure relative to that employed in the heating coil, separating the resulting vapors Vand residual liquid conversion products, subjecting the vapors to fractionation whereby their insufficiently converted components are condensed as reflux condensate, subjecting fractionated vapors of the desired end-boiling point to condensation, co1- lecting and separating the resulting distillate and gas, subjecting said reflux condensate resulting from .fractionation of the vaporous conversion products of theV process to independently controlled less severe conversion conditions of elevated temperature and superatmospheric pressure in a separate heating coil and communicating reaction chamber, separating the resulting vaporous and residual liquid conversion products preferably at substantially reduced pressure relative to that employed in the reaction chamber and subjecting the vapors to fractionation, together With the vapors resulting from the rst mentioned cracking and vaporizing operations.

Several alternative flows are possible within the scope ofthe present invention, some of which depart in detail from the specific embodiment above described. The accompanying diagrammatic drawing, which illustrates one specific form of ap-` paratus embodying the essential features of the` present` invention, and the following description of the drawing, will serve to more clearly illustrate the` operation of the invention as well as several of the many possible alternate flows and operating conditions, which alternatives, however, are not to be considered equivalent.

Referring to the drawing, a relatively light hydrocarbon oil charging stock of the nature heretofore indicated is supplied through line I and valve 2 to pump 3 by means of which it is fed, in the case illustrated, through line 4 and valve 5 to heating coil E. It will be understood that this charging stock may, when desired, be preheated in any well known manner, prior to its introduclo tion into the heating coil, although provisions for accomplishing such preheating are not illustrated in the drawing.

A furnace 'l of any suitable form encloses heating coil '6 and supplies the required heat to bring 15 the oil passing through the heating coil to the desired conversion temperature, preferably at a substantially superatmospheric pressure and the heated oil is preferably maintained at a conversion temperature near the maximum attained in the heating coil for a suicient length of time to substantially complete the desired degree of conversion in this zone. The highly heated low-boiling oil is discharged from heating coil 6 through line 8 and valve 9 and may pass through valve I0 in this line into vaporizing chamber I I.

Simultaneously another oil of higher average boiling point than that supplied to heating coil 6 and of the nature heretofore indicated is supplied through line I2 and valve I3 to pump I4 from which it is discharged through line I5 and may pasls, all or in part, through valve I6 in this line into line 8. The high-boiling charging stock may be preheated, when desired, to any desired temperature below that at which its appreciable conversion will occur, prior to its introduction into line B. This may be accomplished in any well known manner and as one approved method of accomplishing this all or any regulated portion of the heavy charging stock may be diverted from line I5 through line Il and valve I8 into heat exchanger I9 wherein it is preheated by indirect contact with vaporous conversion products of the process, as will be later more fully described, the preheated charging stock passing from heat eX- changer I9 through line 2li and valve 2I back into line I5 and thence into line 8, together with that portion, if any, of the heavy charging stock not passed through the heat exchanger. The re1- atively high-boiling charging stock commingled in line `8 with the highly heated lower boiling oil from heating coil 6 serves to cool the latter to the desired degree which is regulated by the temperature and the volume of higher boiling oil supplied to line 8, the cooling preferably being of sufficient extent to substantially retard or arrest further conversion of the low-boiling oils from the heating coil so that the conversion time as well as the temperature and pressure conditions to which the low-boiling oils are subjected is under positive control. An appreciable reduction in the pressure imposed upon the stream of highly heated low-boiling oils discharged from heating coil 5 is accomplished, as desired, either prior or subsequent to the introduction of the cooling oil into line S, Valves 9 and I being provided for this purpose. The reduction in pressure serves to assist cooling of the heated oil and also assists vaporization of the commingled high-boiling and low-boiling oils in vaporizing chamber II.

Chamber II, as already indicated, is preferably operated at a substantially reduced pressure relative to that employed in heating coil 6, the pressure employed in this zone being regulated to secure vaporization of substantially all of the commingled oils supplied to this zone with the exception of any high-boiling components of a heavy residual nature unsuitable for conversion, together with the reflux condensate, which operation will be later more fully described. Residual liquid remaining unvaporized in chamber I I may be withdrawn therefrom through line 22 and valve 23 to cooling and storage or to any desired further treatment. Vaporous products pass from chamber I i through line 24, valve 25 and line 26, in the case illustrated, into heat exchanger I9 wherein they may serve to 'preheat high-boiling charging stock supplied to this zone, as previously indicated, the vaporous products passing from the heat exchanger through line 2l and valve 28 tc fractionation in fractionator 29. It will be understood that heat exchanger I9 may be bypassed, when desired, by all or a portion of the vaporous products from chamber I I, although the well known means for accomplishing this are not shown in the drawing. Any condensate removed from the vapors passing through heat exchanger I9 may be withdrawn therefrom through line 62 and valve 63 and may, for example, be returned by well known means, not illustrated in the drawing, either to vaporizing chamber II or to fractionator 29.

As an alternate method of operation whereby vaporizing chamber II may be eliminated and which may be utilized when the nature of the charging stocks and the conversion conditions employed in heating coil 6 are such that the stream of commingled high-boiling and low-boiling oils in line 8 contains no appreciable quantity of deleterious residual materials, the commingled stream of heated oils instead of passing to vaporizing chamber II may be diverted from line 8 through line 26 and Valve 2 to heat exchanger I9 and thence to fractionator 29. When this method of operation is employed it may be desirable to utilize a heat exchanger in place of heat exchanger I9 of a somewhat different type than that illustrated in the drawing or, when desired, the heat exchanger may be eliminated.

The vaporous products supplied to fractionator 29 are subjected therein to fractionation by any well known means whereby their insufficiently converted components boiling above the desired end-point of the final light distillate product of the process are condensed as reflux condensate which collects in the lower portion of the fractionator, together with any oil supplied to this zone in unvaporized state and passing therefrom through line 39 and valve 3I to pump 32 by means cf which the reflux condensate is supplied through line 33 and valve 34 to further conversion in heating coil 35, as will be later described.

Fractionated vapors of the desired end-boiling point are withdrawn, together with uncondensable gas produced in the process, from the upper portion of fractionator 29 through line 36 and valve 31 and are subjected to condensation and cooling in condenser 39. The resulting distillate and uncondensable gas passes through line 39 and Valve 45 to collection and separation in receiver 4I. Uncondensable gas may be released from the receiver through line 42 and valve 43. Distillate is withdrawn from this Zone through line 44 and valve 45 to storage or to any desired further treatment. When desired, a regulated portion of the distillate collected in receiver 4I may be withdrawn therefrom through line 46 and valve 4l to pump 48 by means of which it is returned through line 49 and valve 59 to the upper portion of fractionator 29, serving the purpose of a cooling and refluxing medium to assist fractionation of the vapors and maintain the desired vapor outlet temperature from the fractionator, thus controlling the end-boiling point of the nal light distillate product withdrawn from receiver 4I.

Heating coil 35 is located in a furnace 5I of any suitable form by means of which sufficient heat is supplied to the oil passing through the heating coil to subject it to the desired conversion ternperature, preferably at a substantial superatmospheric pressure and the heated oil is discharged through line 52 and valve 53, in the case illustrated, into reaction chamber 54, which is preferably also maintained at a substantial superatmospheric pressure and, although not illust'rated in the drawing, is preferably well insulated against the excessive loss of heat by radiation so that conversion of the heated oil from heating coil 35 and particularly its vaporous components may continue in this zone.

Both vaporous and liquid conversion products are withdrawn from the lower portion of chamber 54, in the case illustrated, through line 55 and valve 56 and introduced into vaporizing chamber 5l', which is preferably operated at a substantially reduced pressure relative to that employed in the reaction chamber by means of which further vaporization of the liquid conversion products supplied thereto is accomplished. Residual liquid remaining unvaporized in chamber 51 may be withdrawn therefrom through line 58 and valve 59 to cooling and storage or to any desired further treatment. The vaporous conversion products pass from chamber 5'I through line 6U, valve 6I and line 21 to fractionation in fractionator 29, together with the other material supplied to this zone, as previously described.

As another somewhat different method of operation which, although not illustrated in the drawing, may be utilized within the scope of the present invention, when chamber II is employed, the stream of vaporous and liquid conversion products from chamber 54 may be supplied to chamber Il instead of to chamber 57, thus eliminating the latter. Also, when desired, reaction chamber 54 may be eliminated by supplying the heated oil from heating coil 35 to chamber II by well known means, not shown in the drawing. This latter alternative is preferably employed only when the nature of the oil supplied for conversion to heating coil 35 is such that its desired degree of conversion may be substantially completed with the heating coil without the necessity of separating heavy liquid conversion products therefrom lin order to avoid excessive coke formation and deposition in heating coil and/or the excessive production of gas.

'Ihe conversion temperature employed at the outlet from the heating coil to which the lowboiling charging stock is supplied may range, for example, from 950 to 1050 F., preferably with a substantial superatmospheric pressure, measured at this point, within the range of 300 to 800 pounds, or more, per square inch. The substantially reduced pressure employed in the succeeding vaporizing chamber, when such a zone is utilized, may range, for example, from 100 pounds, or thereabouts, per square inch, superatmospheric pressure down to substantially atmospheric pressure and this same range of pressures may be utilized in the succeeding fractionating, condensing and collecting portions of the system. The heating coil to which the reux condensate from the fractionator is supplied for further conversion may utilize an outlet temperature ranging, for example, from 850 to 925 F., preferably with a substantial superatmospheric pressure, measured at the outlet from the heating coil, of from 100 to 500 pounds, or thereabouts, per square inch. 'Ihe reaction chamber, when such a zone is employed, may utilize a superatmospheric pressure of from 100 to 500 pounds, or thereabouts, per square inch and a substantially reduced pressure ranging from 100 pounds, or thereabouts, to substantially atmospheric pressure is preferred in the succeeding vap'orizing chamber.

As a specic example of the operation of the process of the present invention, as it Vmay be practiced in an apparatus such as illustrated and above described, the low-boiling charging stock is a Pennsylvania distillate of about 52 A. P. I. gravity which is subjected in the heating coil to a conversion temperature of approximately 980 F. at a superatmospheric pressure of about 500 pounds per square inch and is then cooled to a temperature of approximately '720 F., by pressure reduction and by commingling therewith the high-boiling charging stock, and the commingled oils are introduced into the vaporizing chamber, which is operated at a pressure of approximately 50 pounds per square inch. The high-boiling charging stock, in this case, is a Mid-continent topped crude of about 30 A. P. I. gravity and about equal quantities of low-boiling and highboiling charging stocks are supplied to the system. The pressure employed in the vaporizing chamber is substantially equalized in the fractionating, condensing and collecting portions of the system. Reilux condensate from the fractionator is subjected in the separate heating coil to which it is supplied, to an outlet temperature of approximately 910 F. with a superatmospheric pressure 60 of approximately 300 pounds per square inch and the heated products are passed through a reaction chamber operated at about the same pressure, the vaporous and residual liquid conversion products being subsequently separated at reduced pressure and the vapors subjected to fractionation, together with the vapors from the preceding portion of the system.

An operation such as above described may yield, per barrel of total charging stock, approximately 67 percent of motor fuel having an antiknock value equivalent to an octane number of approximately 76 and about 22 percent of residual oil of low B. S. content, the remaining 13 percent, or thereabouts, based on the charging stock being chargeable principally to gas and unaccountable loss.r

I claim as myl invention:

1. A process for the simultaneous reforming of light hydrocarbon oil containing gasoline fractions of inferior anti-knock value and for the conversion of hydrocarbon oil heavier than gasoline into gasoline, which comprises subjecting the light oil while flowing in a restricted stream through a heating coil to cracking conditions of temperature and pressure adequate to enhance the anti-knock value of said gasoline fractions contained therein, cooling the thus heated light oil promptly upon discharge from the coil to below cracking temperature by commingling therewith said heavier oil while at below cracking Ytemperature and by pressure reduction thereon,

thereby heating the heavier oil to distillation temperature, separating the commingled oils into vapors and residue and fractionating the former to condense heavier fractions thereof, heating resultant reux condensate, while flowing in a restricted stream through a second heating coil,4

to a lower cracking temperature than the light oil in the first-mentioned heating coil and then passing the same through a reaction Zone maintained under cracking conditions and effecting further conversion therein, fractionating resultant vapors in admixture with the rst-named vapors whereby insuniciently cracked fractions thereof are returned to the second heating coil in said reflux condensate, and nally condensingI the fractionated vapors.

2. A hydrocarbon Voil conversion process which comprises passing a relatively light oil through a heating coil and subjecting the same therein to cracking conditions of temperature and pressure, commingling a relatively cool and heavy oil with the cracked light oil promptly upon discharge of the latter from the coil and cooling the heated light oil to below cracking temperature, separating the resultant mixture into vapors and residue and fractionating the former to condense heavier fractions thereof, passing resultant reflux condensate through a second heating coil and subjecting the same therein to milder cracking than the light oil in the first-named coil, then passing the heated reflux condensate through a reaction zone maintained under cracking conditions of temperature and pressure and continuing the cracking of the reux condensate in this zone, discharging the cracked products from the reaction zone into a reduced pressure separating Zone and therein separating the vaporous from unvaporized products, fractionating the vaporous products in admixture with the first-named vapors, and nally condensing and collecting the fractionated vapors.

KENNETH SWARTWOOD.

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