US2085939A - Conversion and coking of hydrocarbon oils - Google Patents

Description

July 6, 1937.

J. G. ALTHER 2,085,939

CONVERSION AND COKING OF HYDROCARBON OILS Filed Sept. 24, 1934 FRACTIONATOR INVENTOR JOSEPH G. ALTHER Patent ed July 6, 1931 CONVERSION AND COKING OF HYDRO- CARBON OILS Joseph G. Alther, Chicago, Ill., assignor to Universal,0il Products Company, Chicago, 111., a corporation of Delaware Application September 24, 1934, Serial No. 745,256 2 Claims. (01. 196-48) This invention particularly refers to an improved process for the conversion and coking of hydrocarbon oils wherein high-boiling fractions of the charging stock and high-boiling intermediate conversion products of the process are subjected to relatively mild conversion and the resulting residue reduced to coke'at relatively low pressure while lower boiling fractions of the charging stock and low-boiling intermediate conversion products of the process are subjected .to more severe conversion conditions within the same system at relatively high pressure, the resulting liquid' conversion products subjected to further vaporization at substantially reduced pressure and the resulting residual liquid either withdrawn from the system or subjected to coking, together with the residue from the first mentioned cracking operation. I a

The present invention differs from previously proposed processes for the simultaneous conversion and coking of hydrocarbon oils in that it provides for introduction of the products resulting from relatively mild conversion of high-boiling fractions of the charging stock and high-.

' severe conversion conditions than those employed for the treatment of the high-boiling intermediate conversion products and high-boiling fraction of the charging stock. Aside from the obvi-' ous advantages resulting from the elimination of a high-pressure reaction chamber for the highboiling oils this practice also permits the use of somewhat higher conversion temperatures or in' general-more severe conversion conditions in the cracking coil to which the high-boiling oils are ployed. This is due to the fact that continued conversion to the point of appreciable coke formation in a high-pressure reaction chamber is decidedly undesirable when the process is operated for the production of high yields of good quality motor fuel and minor yields of coke of uniform quality and low volatility, whereas, in the present invention the production of coke of relatively uniform quality and low volatility and the production 5 of high yields of low-boilingber, wherein reduction of the residue to coke may be accomplished without the addition of heat, While the production of high yields of good quality motor fuel is accomplished by subjecting any low-boiling fractions of the charging stock together with low-boiling intermediate conversion products of the process, including the relatively high yields of products from the coking operation of an intermediate character (boiling below the range of the desired motor fuel and above the range of the high-boiling fractions subjected to coking) 'to independently controlled more se- Vere-conversion conditions of elevated temperature and superatmospherie pressure in a separate heating coil and communicating high-pressure reaction chamber of the same system.

The present invention further provides for subjecting the liquid products resulting from conversion of the low-boiling oils to further vaporization at substantially reduced pressure for the production of a liquid residue which may be either withdrawn from the system as a final product of the process ormay be supplied, all or in part, to the coking zone and subjected therein to coking together with the residual products resulting from conversion of the high-boiling oils. In this manner they process may be operated for the production of good quality coke as the only residual product of the process or, when desired, both coke and good quality liquid residue may be produced simultaneously.

ing and relatively high-boiling fractions, subject-.

ing the low-boiling fractions of the charging stock, boiling above the range of any desired motor fuel components thereof, to conversion conditions of elevated temperature and superatmospheric pressure in the heating coil and communicating reaction chamber, subjecting the resulting liquid conversion products to further vaporization at substantially reduced pressure, introducing the resulting non-vaporous residual liquid into a low-pressure coking zone or withdrawing the same, all or in part, from the system, subjecting the vaporous products of the process, including the vaporous conversion products, the vapors resulting from said further vaporization of the liquid conversion products and the vaporous products from the coking zone, to fractionation whereby their components, boiling above the range of the desired light distillate 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 into selected low-boiling and high-boiling fractions, returning said low-boiling fractions to the heating coil for further conversion, together with the low-boiling fractions of the charging stock, subjecting said high-boiling fractions of the reflux condensate, together with high-boiling fractions of the charging stock, to independently controlled relatively mild conversion conditions of elevated temperature and superatmospheric pressure in a separate heating coil and introducing the heated products from said separate heating coil directly into said lowpressure coking zone.

The accompanying diagrammatic drawing illustrates one( specific form of apparatus for carrying out the invention. Raw oil charging stock for the process, which may comprise any desired hydrocarbon oil, although an oil of relatively wide boiling range such as crude petroleum, topped crude or the like is preferred, is supplied through line I and valve 2 to pump 3 by means of which it is fed through line 4 and may pass, all or in part, through valve 5 and line 9 into fractionator H or it may pass, all or in part, from line 4 through line 6, valve 1, heat exchanger 8, line 9 and valve ill into fractionator ll being preheated in heat exchanger 8 by indirect contact with hot vaporous products of the process, as will be later more fully described. It

will be understood that, when desired, any other suitable means of. preheating the charging stock,

prior to its introduction into the fractionator, 40

drawing. It is also within the scope of the invention, in case a charging stock of low-boiling characteristics is employed, to supply the same ,direct to heating coil 33, together with low-boiling fractions of the reflux condensate from the fractionator or, in case a charging stock of highboiling characteristics is employed it may be supplied to heating coil 53, together with highboiling fractions of the reflux condensate from the fractionator. Means for accomplishing-the two last mentioned methods of operation are well known in the art and for the sake of simplicity are not shown in the drawing.

-The charging stock supplied to fractionator II is commingled, in the case illustrated, with hot vaporous products of the process which are supplied to this zone as will be later more fully described, whereby it is subjected to vaporization and to fractionation therewith. The charging stock is separated in fractionator H, together with the intermediate conversion products (reflux condensate) boiling above the range of the desired light distillate product of the process into selected low-boiling and high-boiling fractions, each of which are subjected to further conversion within the system under independently controlled conversion conditions, as will be later more fully described.

Fractionated vapors of the desired end-boiling point, including motor fuel conversion products of the process and any corresponding motor fuel components of'the charging stock, as well as uncondensable gas produced by the process, pass from the upper portion of fractionator H 'through line l2 and valve l3 to be subjected to may be employed although not illustrated in the condensation and cooling in condenser I4. The resulting distillate and gas passes through line I5 and valve I6 to collection and separating in receiver I'I. Uncondensable gas may be released from the receiver through line l8 and valve 19. Distillate is withdrawn from receiver ll through line 20 and valve '2! to. storage or to any desired further treatment. When desired, a regulated portion of the distillate collected in receiver I! may be returned, by well known means, not illustrated, to the upper portion of. fractionator l I to serve as a refluxing and cooling medium to assist fractionation of the vapors and to maintain the desired vapor outlet temperature from the fractionator.

The selected low-boiling fractions of the reflux condensate and raw oil charging stock may be withdrawn as one or a plurality of side streams from any suitable intermediate point or points in fractionator ll, forexample, through line 22 and .valve 23 to column 24 wherein they may be reboiled to substantially free the same of entrained gas and any low-boiling fractions within the range of the desired overhead product of the process by means of circulating a suitable heating medium such as steam, hot oil'or the like through a heating coil 25 within the lower portion of column 24. The vapors evolved in column 24 may be returned to the fractionator by means of line 26 and valve 21. The reboiled low-boiling oils are withdrawn from the lower portion of column 24 through line 28 and valve 29 to pump 30 by means of which they are fed through line 3| and valve 32 to heating coil 33. It will be understood that column 24 is not an essential feature of the invention and may be eliminated, when desired, in which case other well known means, not illustrated, for reboiling the oil supplied to heating coil 33 may be employed or such reboiling may, when desired, be entirely eliminated.

A furnace 34, of any suitable form, supplies the required heat to the oil passing through heating coil 33 to bring the same to the desired conversion temperature, preferably at substantial superatmospheric pressure and the heated products are discharged through line 35 and valve 36 into reaction chamber 31.

Chamber 31 is also preferably maintained at a substantial superatmospheric pressure and, although not indicated in the drawing, is preferably well insulated in order to conserve heat, so

that conversion of the heated products from heating coil 33, and particularly their vaporous components, may continue in this zone. In the case here illustrated both vaporous and liquid conversion products are withdrawn in commingled state from the lower portion of chamber 31 through line 38 and valve 39 and are introduced into vaporizing chamber 40/ It is, of course, also within the scope of the invention, although not illustrated in'the drawing, instead of withdrawing the total conversion products fromthe lower portion of reaction chamber 31 to separately withdraw liquid and vaporous conversion products from this zone, introducing the liquid products, either alone or together with a regulated portion of the vapors, into chamber 40 and either separately supplying the vaporous products, all or, in part, to chamber or to heat exchanger 8 or direct to fractionator ll.

Chamber 40 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 to this zone is accomplished, The vapors evolved in chamber 40 pass, in the case illustrated,- together with the vaporous conversion products from chamber 31, through line 4| and valve 42 into heat exchanger.

8 wherein theyare partially cooled by indirect contact with a suitable cooling medium such as, for e'xample,-raw oil charging stock for the process, as previously indicated, whereby residual liquid entrained within the vapors and any similar high-boiling components are condensed and separated therefrom. The condensate is withdrawn from heat exchanger 8 through line 44 and may be returned through valve 45 in this line to chamber 40 or may be removed, all or in part, from the system, by well known means, not illustrated, or otherwise disposed of as desired, for example, by supplying the same by well known means, not shown, to the coking zone of. the system (chambers 58 and 58'). The vaporous products remaining uncondensed in heat exchanger 8 may pass therefrom through line 46 and valve 41 to fractionation in fractionator II. It will be understood that heat exchanger 8 may, when desired, be eliminated and that other well known means, not illustrated, for accomplishing the same or similar results may be employed, when desired.

The vaporous products supplied to fractionator H are subjected to fractionation whereby their components boiling within the range of the desired light distillate product of the process are removed as the overhead vaporous product from the fractionator, as previously described, while their higher boiling components are condensed as reflux condensate and separated into selected lowboiling and high-boiling fractions, the low-boiling fractions being returned, as previously described, to heating coil 33 for further conversion.

High-boiling fractions of the reflux condensate and raw oil charging stock are withdrawn, in the case illustrated, from the lower portion of fractionator H through line 48 and valve 49 to pump 50 by means of which they are fed through line 5| and valve 52 to conversion in heating coil 53. This material is subjected, in

heating coil 53, to independently controlled relatively mild conversion conditions of elevated temperature, preferably at substantial superatmospheric pressure by means of heat supplied from a furnace 54 of any suitable form and the resulting heated products are discharged through line 55 and may pass through line 53 and valve 51 into coking chamber 58 and through line 53 and valve 51' into coking chamber 58.

Chambers 58 and 58' are similar coking zones, preferably operated at substantially atmospheric or relatively low superatmospheric pressure, wherein the liquid conversion products from heating coil 53 are subjected to further vaporization and the resulting non-vaporous residue reduced to substantially dry coke. It will be understood that although two coking chambers are illustrated in the. drawing only one or any desired number of a plurality of such zones may be employed, a plurality being preferred and preferably being alternately operated, cleaned and prepared for further operation, in order that the coking stage of the system may be continuous. The coke may be allowed to accumulate within each chamber until it is substantially filled or until its operation is completed for any other reason, following which the coke may be removed therefrom in any well known manner, not illustrated, and the chamber cleaned and prepared for further operation. Chambers 58 and 58' are provided with suitable drain lines 59 and 59', respectively, controlled by the respective valves 60 and 60' which may also serve as a means of introducing steam, water or other suitable cooling medium into the chambers after their operation is completed in order to hasten cooling and facilitate cleaning of the same.

Vaporous products pass from chambers '58 and 58' through the respective lines GI and GI controlled, respectively, by valves 62 and- 32' and preferably pass through line 63 into vaporizing chamber 40 or may be directed, by well known means, not illustrated, to heat exchanger 8 or vor a regulated portion or all of this material may pass through valve 61 in line 54, to pump 68, by means of which it is supplied to the coking zone entering chamber 58, in the case illustrated, through line 56 and valve 51 and entering chamber 58' through line 56' and valve 51' together with the heated products from heating coil 53. It will, be understood, of course, that the residual liquid from chamber 40 and the heated prod-' 1 ucts from heating coil 53 may be separately introduced into the coking chamber, when desired, and that any desired point or plurality of points of introduction for either or both of these products may be employed, although not illustrated 1 in the drawing.

It is specifically within the scope of the present invention instead of subjecting the charging stock and the total vaporous conversion products to fractionation in the same fractionator to employ a separate fractionator for the charging stock or for the vaporous products from the coking zone or for the vaporous products from the light oil cracking cycle of the process or for each of these materials, although well known means whereby this method of operation may be accomplished are not illustrated in the drawing. A separate fractionator for the charging stock is particularly desirable in case the charging stock contains motor fuel or motor fuel fractions of inferior anti-knock value, in which case instead of collecting the same together with the motor fuel conversion products of the process they may be separately recovered and may, when desired, be returned, by well known means, not

. fuel which are of inferior antiknock value.

In a process of the character illustrated and above described, the preferred range of operating conditions may'be approximately as follows:

The heating coil to which the low-boiling oils are supplied may utilize an outlet conversion temperature ranging, for example, from 900 to 1050 F., or thereabouts, preferably with a superatmospheric pressure at this point in the system of from 200 to 800 pounds, or more, per square inch. This pressure may be either substantially equalized or somewhat reduced in the succeeding reaction chamber and a substantially reduced pressure relative to that employed in the reaction chamber ranging, for example, from 100 pounds, or thereabouts, per square inch, to substantially atmospheric is preferred in the vaporizing chamber. The pressures employed in the fractionating, condensing and collecting portions of the system may be either substantially equalized or somewhat reduced relative to the pressure employed in the vaporizing chamber. The heating coil to which the high-boiling oils are supplied may utilize an outlet conversion temperature within the range of 850 to 950 F., for example, and a substantial superatmospheric pressure of the order of 100 to 500 pounds, or thereabouts, per square inch, is preferred at this point in the system. Substantially atmospheric or a relatively low superatmospheric pressure up to 100 pounds, or thereabouts, per square inch, may

be employed in the coking zone.

As a specific example of an operation of the process of the present invention as it may be accomplished in an apparatus such as illustrated and above described, the charging stock, which is a Mid-Continent topped crude of about 30 A. P. I. gravity is heated by indirect contact with hot Vaporous products of the process and is supplied to the fractionator wherein it is separated, together with the reflux condensate into fractions boiling above and below approximately 600 F. The low-boiling fractions 'of the reflux condensate and charging stock are subjected in the heating coil to which they are supplied to an outlet conversion temperature of approximately 970 F., at a 'superatmospheric pressure of approximately 600 pounds per square inch. Sub- 40 stantially the same pressure is maintained in the succeeding reaction chamber but is reduced in the vaporizing chamber to a pressure of approximately 50 pounds per square inch. The highboiling fractions of the charging stock and re- 45 flux condensate are subjected in separate heating coils to an outlet conversion temperature of v approximately 950 F., at a superatmospheric pressure of about 300 pounds per square inch and the heated products are introduced into alter- 50 nately operated coking chambers maintained at chamber is returned to the coking chambers.

This operation will produce, per barrel of charging stock, approximately 62 percent of motor fuel having an antiknock value equivalent to an octane number of approximately '72 and about 85 pounds of good quality coke of relatively low volatility, the remainder being chargeable principally to uncondensable gas.

I claim as my invention: 1. A hydrocarbon oil conversion process which comprises fractionating the charging oil and separating therefrom a relatively light fraction and a heavier fraction, heating the light fraction to cracking temperature under pressure while flowing in a restricted stream through a heating coil and subsequently-separating the same into vapors and residual products in an enlarged separating zone, fractionating the vapors to separate relatively light and heavy reflux condensates therefrom, supplying the light reflux condensate to the heating coil for further treatment therein in admixture with the light fraction of the charging oil, passing the heavy reflux condensate and said heavier fraction of the charging oil through a second heating coil and subjecting the same therein to milder cracking conditions than the hydrocarbons in the first-named coil, discharging resultant heated products directly from said second coil into an enlarged coking zone and distilling the same to coke therein, introducing residual products from the separating zone into the coking zone for reduction to coke therein, and fractionating and condensing the vapors evolved in the coking zone. a

2. A hydrocarbon oil conversion process which comprises fractionating the charging oil in contact with cracked vapors, formed as hereinafter set forth, in a fractionating zone, separating from the contacting charging oil and vapors a relatively light reflux condensate and a heavier liquid fraction, heating said light reflux condensate to cracking temperatureunder pressure while flowing in a restricted stream through a heating coil and subsequently separating the same into vapors and residual products in an enlarged separating zone, supplying the Vaporous products to the fractionating zone as said cracked vapors, passing said heavier liquid fraction through a second heating coil and subjecting the same therein to milder cracking conditions than the light reflux condensate in the first-named

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