US1984662A - Conversion of hydrocarbon oils - Google Patents

Description

Dec. 18, 1934. K. swARTwooD CONVERSION OF HYDROCARBON OILS Filed March 2, 1953 NNSGMQ hw NN ATTORNEY.

Patented Dec. 18, 1934 UNITED STAT when@ n CONVERSION OF HYDROCARBON OILS Application March 2,

6 Claims.

This invention particularly refers to an improved process and apparatus for the conversion of hydrocarbon Voils to produce high yields of good quality motor fuel and is more specifically directed to an improved method and means of controlling both the quality of the motor fuel product of the process, particularly with respect to its antiknock value, and the quality of residual product.

A specific embodiment of the invention cornprises subjecting a hydrocarbon oil to conversion temperature at superatmospheric pressure in a heating coil, introducing heated oil into an Venlarged reaction chamber, also maintained at vsubstantial superatmospheric pressure, wherein continued conversionof the heated oil, and particularly its vaporous components, is accomplished, continuously withdrawing a portion of the vaporous conversion products from a point in the reaction chamber remote from the point of their introduction thereto, passing the same through a separate heating coil wherein they are subjected to further conversion at elevated temperature and superatmospheric pressure, continuously returning the reheated vapors to the reaction chamber at a point adjacent the 'point of introduction of the heated oil from the first heating coil, simultaneously withdrawing both vaporous and liquid conversion products from the reaction chamber and introducing them into a reduced pressure vaporizing cham- .ber wherein the liquid products are subjected to .further vaporization and the vapors separated from the remaining unvaporized residue, subjecting the vaporous products from the reduced pressure vaporizing chamber to fractionation whereby theirjinsuiiciently converted components boiling above -the end-boiling point of the desired final light product of the process are v40 condensed as reflux condensate, returning the reux condensate to the first mentioned heating coil for further conversion, together with the charging stock, subjecting fractionated vapors of the desired `end-boiling point to condensation and collecting the resulting distillate and gas.

rEhe feature of the present invention which comprises continuous reheating and local circue lation of the vaporous products undergoing conversion in the reaction chamberaccomplishes 50 prolonged conversion time and when desired, permits subjectingl the vaporous products to a higher conversion temperature and/or pressure than that to which the oil supplied to the first heating coil is subjected, `thereby accomplishing the degree of conversion required for the low- 1933, Serial No. 659,249

the process separated from the vaporous prodf ucts, the feature of the present invention which provides for local circulation and reheating, of the vaporous products in the reaction chamber also provides an additional means of controlling the degree of vaporization to which the liquid conversion products are subjected in the Vaporizing chamber, thereby controlling the quality of the residual product of the process as well as controlling the quality of the motor fuel product.

I am aware that it has previously been proposed to locally recirculate and reheat vaporous conversion products from a distillatory type of reaction chamber wherein the residual liquid is allowed to accumulate and iinal separation of vaporous and residual conversion products is accomplished. I wish to distinctly differentiate between this practice and the salient feature of the present invention which provides for local circulation and reheating of the vaporous conversion products in a high pressure reaction chamber in conjunction with continuous and rapid removal of the liquid conversion products from the reaction zone, together with vaporous conversion products from the same Zone and followed by a reduction in pressure and .Y

further vaporization of the residual conversion products assisted by the distilling action and partial pressure effect of the highly heated vapors withdrawn from the reaction chamber with the residual liquid as well as by the reduction in pressure. Witha distillatory type of reaction chamber wherein the residual liquid is allowed to accumulate, recirculation and reheating of the vapors, so far as the residual conversion product of the process is concerned, simply serves to further heat and produce further conversion of the residual liquid without materially increasing its vaporization, said continued conversion tending toward the production of large quantities of coke and pitchy material in the residue, materially decreasing its commercial value. in the present invention the liquid conversion products are removed from the reaction chamber substantially as fast as they accumulate therein and their further conversion is arrested by a substantial reduction in pressure. The latent heat liberated by the reduction in pressure and the partial pressure effect produced upon the liquid conversion products by the removal of vaporous conversion products from the reaction chamber therewith and their simultaneous flash distillation at reduced pressure serves to effect further vaporization of the liquid conversion products, thereby materially lowering the boiling point of the residual liquid product of the process, without permitting conversion thereof to the point where any appreciable quantity of coke is formed. In the present case the heat added to the vaporous conversion products in the reaction chamber by their circulation through a separate heating coil serves to effect further vaporization of the liquid conversion products in the vaporizing chamber rather than producing any appreciable further conversion of the residual liquid since the liquid conversion products are not allowed to accumulate or remain in the high pressure reaction chamber for any appreciable length of time.

The accompanying diagrammatic drawing illustrates one specic form of apparatus in which the features of the present invention are incorporated and in which the process of the invention may be practiced.

Referring to the drawing, raw oil charging stock for the process is supplied through line 1 and valve 2 to pump 3 by means of which it is fed through line 4, from which it may pass either through line 5 and valve 6 direct to heating coil 7 or all or yany desired portion of the charging stock may be directed through line 8 and valve 9 into `fractionator 10. The raw oil supplied to fractionator 10 may be preheated by either direct or indirect contact with the vapors undergoing fractionation, prior to its introduction into heating coil 7. In the case illustrated the charging stock is introduced into direct contact with the vaporous conversion products in the fractionator, serving to assist their fractionation and collecting in the lower portion of the fractionator, together with the reflux condensate produced in this Zone. The reflux condensate or reflux condensate and preheated raw oil, as the case may be, is withdrawn from the lower portion of fractionator 10 through line 11 and valve 12 to pump 13 by means of which it is fed through line 14 and valve 15 into line 5, commingling therein with that portion, if any, of the charging stock supplied through line 5, as described, and passing therewith to heating coil 7. Y

A furnace 16 of any suitable form supplied the heat required to bring the oil passing through heating coil 7 to thedesired conversion temperature, preferably at a substantial superatmospheric pressure and the heated oil is discharged through line 17 and valve 18 into reaction chamber 19 entering, in the case illustrated, into the upper portion of the reaction chamber.

Chamber 19 is also preferably maintained at a substantial superatrnospheric pressure and, although not illustrated in the drawing, is preferably well insulated to prevent the excessive loss of heat therefrom by radiation so that conversion of the oil supplied to this zone, and particularly its vaporous components, may continue in the reaction chamber. The liquid conversion products from heating coil 7 pass only once through reaction chamber 19 and are quickly removed from the lower portion of this zone, together with vaporous. conversion' products,

through line 20 and valve 21. A regulated portion of the vaporous conversion products are withdrawn from the reaction chamber at a point remote from the point of introduction of the heated oil thereto from heating coil 7, for example, through line 22, from which they may pass through Valve 23 and line 24 to pump or compressor 25,` by means of whichthey are fed through line 26 and valve 27 to heating coil 28, passing therefrom through line 29 and valve 30 back into reaction chamber 19, entering this Zone at a point remote from the point of their removal therefrom and which point of introduction, incidentally, is adjacent the point of introduction of the heated oil from heating coil 7.

In order to avoid pumping of the highly heated vaporous conversion products from reaction chamber 19 to heating coil 28 the vapors may, when desired, be directed from line 22 through line 31 and valve 32 to cooler and condenser 33, from which the resulting distillate and uncondensable gas passesto the receiver or reservoir 34. Uncondensable gas is released from this zone through line 35 and valve 36 While the distillate is Withdrawn therefrom through line f 37 andvalve 38 and through line 24 to pump 25 which, in case this type of operation is practiced, may be designed to operate at ordinary temperatures, supplying the condensate through to their circulation may be subjected to a prolonged conversion time at this temperature or, when desired, vthe temperature of theV vapors may be substantially increased during their pas- 'sage through heating coil 28 so that a higher conversion temperature is maintained in chamber 19 than would be the case if heating coil 28 and the recirculating means were not employed. Also, when desired, a higher pressure may be employed in heating coil 28 than that utilized in the reaction chamber, thereby accomplishing still further conversion of the recirculated vapors. In any case more prolonged vapor conversion time is accomplished by recirculation and reheating such as described.

The vaporous and liquid conversion products withdrawn from the lower portion of chamber 19 through line 20 and valve 21 are introduced into vaporizing chamber 40, which is maintained at a substantially reduced pressure relative to that employed in chamber 19. Further vapori- Zation ofthe liquid conversion products introduced into chamber 40 is accomplished by means of the latent heat liberated by the pressure reduction and the partial pressure effect of the vaporous conversion products upon the heavier liquid products and vaporization of the liquid `conversion lproducts may be increased to any desired degree, in the present case, over that accomplished under otherwise similar conditions in a process not utilizing the features of the present invention, due to the increased temperat'ure at which the vapors are withdrawn from chamber 19 to chamber 40. Residual liquid remaining `unvaporized in chamber 40 may be vvithizlravvntherefrom through line 41 `and valve 4'2 tol cooling andestorage orto 4'any desired l:fur-

through line .43 and 'valve '44 to fractionation in rractionator 40.

kAs already indicated, the insuiciently convertedv components of the vaporous products supplied to fractionator l0, boiling .above the endboiling point of the desired iinal light product o'f the process, are condensed by fractionation in this zone and collect as reflux condensate kin the lower portion of the fractionator from. which v'they are returned, as already described, to -heating `coil .7 for further conversion, together with the raw oil charging stock.

Fractionated vapors of the desired end-boiling point are withdrawn, together with uncondensable gas produced by the process, from the upper portion of fractionator through line 45 and valve 46, are subjected to condensation and cooling in condenser 47 from which the resulting distillate and uncondensable gas passes through line 48 and valve 49 to collection and separation in receiver 50. Uncondensable gas may be released from the receiver through line 51 and valve 52. The distillate may be Withdrawn from this zone through line 53 and valve 54 to storage or to any desired further treatment. When required, to assist fractionation of the vaporous conversion products in fractionator 10, a portion of the distillate collecting in receiver 50 may be recirculated to the upper portion of the fractionator, by Well known means not shown in the drawing, thereby controlling the vapor outlet temperature from this zone and the end-boiling point of the light distillate product of the process.

The heating coil to which the raw oil charging stock and reflux condensate from the fractionator of the system are supplied preferably utilizes and outlet conversion temperature within the range of 850 to 950 F. and preferably a superatmospheric pressure of the order of 100 to 500 pounds, or thereabouts, per sq. in. is employed at the outlet from this Zone. Any desired pressure Within substantially this same range, but not greater than that employed at the outlet from the heating coil, may be employed in the reaction chamber. The heating coil through which a continuous circulation of vapors to and from the reaction chamber is maintained may heat the vapors to any desired conversion temperature within the range of 900 to 1050 F. and the pressure maintained at the outlet from this Zone may range, for example, from 200 to 800 pounds, or more, per sq. in.; the pressure, of course, being reduced, prior to the introduction of the reheated vapors into the reaction chamber, in case a higher pressure is maintained at the outlet from the vapor heating coil than that at which the heated oil from the other heating coil of the process enters the reaction chamber. A substantially reduced pressure relative to that employed in the reaction chamber ranging, for example, from 100 pounds, or thereabouts, per sq. in. down to substantially atmospheric pressure may be employed in the vaporizing chamber and this pressure may be substantially equalized or somewhat reduced in the succeeding fractionating, condensing and collecting portions of the system.

As a specific example of the operation of the process of the present invention as it may be practiced in an apparatus such as illustrated and above described, `thecharging-1stock is a Pennsylvania naptha-fuel-oillblendof about 43 A. P. I. lgravity containing about 36 percent of material lboiling* upv to437 F., the charging stock is sub- Aje'cted together with reflux condensate from the 'racti'onator' of "the system to a conversion temperature 4of approximately 925 F. at a superatmospheric pressure of about 350 pounds per sq. in. in the first heating `coil and the heated oil vis introduce-d Vinto a 'reaction chamber maintained.atabout :the `same pressure. A portion of the `vaporous products are continuously Withdrawn from-the reaction chamber, reheatedto a conversion temperature of approximately 970F. at a superatmospheric kpressure of about 500 pounds per sq. in. and .returned to the reaction chamber. The vap'orizing chamber is maintained at a pressure of about 50 pounds per sq. in., which pressure is substantially equalized in the succeeding fractionating, condensing and collecting portions of the system.

An operation of the character above described may yield, per barrel of charging stock, about 74 percent of motor fuel having an antiknock value equivalent to an octane number of approximately '78, and about 10 percent of residual oil of loW gravity but containing a loW percentage of B. S. & W. The remaining 16 percent, or thereabouts, based on the charging stock, is chargeable principally to gas and loss.

I claim as my invention:

l. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure while flowing in a restricted stream through a heating zone, discharging the heated oil into the upper portion of an enlarged vertical reaction Zone maintained under cracking conditions of temperature and pressure, and passing both vapors and unvaporized oil downwardly therethrough, removing the unvaporized oil together with a portion of the vapors as a mixture from the bottom of the reaction zone, separately removing another portion of the vapors from the lower portion of t'he reaction Zone, heating these separately Withdrawn hydrocarbons to cracking temperature in a second heating zone and thence introducing the same to the upper portion of the reaction zone, separating said mixture Withdrawn from the bottom of the reaction zone into vapors and residue, and fractionating and condensing the last named vapors.

2. A conversion process Which comprises heating hydrocarbon oil to cracking temperature under pressure While flowing in a restricted stream through a heating zone, discharging the heated oil into the upper portion of an enlarged vertical reaction zone maintained under cracking conditions of temperature and pressure, and passing both vapors and unvaporized oil downwardly therethrough, removing the unvaporized oil together with a portion of the vapors as a mixture from the bottom of the reaction zone, separately removing another portion of the vapors from the lower portion of the reaction zone, heating the separately withdrawn vapors to cracking temperature in a second heating zone and thence introducing the same to the upper portion of the reaction zone, separating said mixture Withdrawn from the bottom of the reaction zone into vapors and residue, and fractionating and condensing the last named vapors.

3. A conversion process Which comprises heating hydrocarbon oil to cracking temperature under pressure while owing in a restricted stream through a heating zone, discharging the cracking conditions of temperature and presv sure, and passingboth vapors and unvaporized cil downwardly therethrough, removing the unvaporized oil together with a portion of the vaporsas a mixture from the bottom of the reaction. zone, separately removing another portion of the vapors from theflovver portion of the reaction zone and condensing the same, heating resultant condensate vto cracking temperature in a second heating zone and thence introducing the same to the upper portion of the reaction zone, separating said mixture Withdrawn from the bottom of the reaction zone into Vvapors and residue, and fractionating and coni densing the last-named vapors.

4. The process as dened in claim 1 further characterized in that said separately withdrawn in the second heating zone than the oil in the rst mentioned heating zone.

5. The process as defined in claim 2 further characterized in that said separately withdrawn vapors are heated to higher temperature in the second heating zone than the oil in the first mentioned heating zone.

6. The process as dened in claim 3 further characterized in that said condensate is heated to higher temperature in the second heating zone than the oil in the first mentioned heating zone.

, KENNETH SWAR'I'WOOD.V

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