US2176320A - Conversion of hydrocarbon oils - Google Patents

Description

CONVERSION OF HYDROCARBON OILS Filed NOV. 23, 1936 F RACTIONATOR HEAT DISTILLING AND EXCHANGER FRACTIONATING COLUMN FURNACE 5 RECEIVER INVE NTOR CHARLES H. ANGELL ATTORNEY tillate and the like.

Patented Oct. 17,

PATENT OFFICE".

CONVERSION OF HYDROCARBON OILS Charles H. Angell, Chicago, Ill., assignor to Universal Oil Products Company,'Chicago, 111., a corporation of Delaware Application November 23, 1936, Serial No. 112,200

3 Claims.

This invention relates to a process and apparatus for the pyrolytic conversion of hydrocarbon oils to produce therefrom high yields of good quality gasoline and refers more particularly to a combination topping, cracking and reforming system wherein various stages of the operation are interdependent and cooperate to produce the desired beneficial results.

In this process the charging stock may comprise crude petroleum or any other hydrocarbon oil of relatively wide boiling range which contains a substantial quantity of low-boiling materials, such. as gasoline or gasoline fractions of inferior antiknockvalue, naphtha, kerosene, kerosene dis- At least a substantial portion. of the heat required for topping the charging stock is recovered from heated products of the reforming operation by indirect heat exchange therewith and the materials supplied to the reforming coil comprise selected low-boiling fractions of the charging stock recovered as the overhead product of the topping stage and may, when desired, also include selected relatively lowboiling products resulting from the pyrolytic conversion of the topped crude such as, for example, high-boiling gasoline fractions, naphtha, kerosene, kerosene distillate, pressure distillate, pressure distillate bottoms, and the like. The high-boiling fractions of the charging stock, comprising the bottoms from the topping operation, are subjected to further vaporization in the vaporizing chamber of the cracking stage of the system and the vaporous products from this zone are subjected to fractionation for recovery of the desired gasoline product and the formation of reflux condensate. All or the high-boiling fractions of said reflux condensate are supplied to the heavy oil cracking coil of the system and, when. desired, selected low-boiling fractions r thereof are supplied to the reforming coil.

The invention also provides, when desired, for commingling the high-boiling fractions of the charging stock, comprising the bottoms from the topping operation, with the relatively hot products discharged from the reforming coil, preferably following indirect heat exchange between the latterand the charging stock, the comrningled materials being supplied to the vaporizing chamber of the cracking system. This serves the twofold purpose of cooling the reformed products sufficiently to prevent any excessive further cracking thereof and heating the high-boiling fractions of the charging stock sufficiently to effect their appreciable further vaporization.

It will be apparent from the foregoing that the various stages of the process are combined in a cooperative and inter-dependent manner to give a relatively simple but highly efficient topping, cracking and reforming operation for the production of high yields of good quality gasoline.

The accompanying diagrammatic drawing illustrates one specific form of apparatus in which the process of the invention may be conducted, but it will, of course, be understood that the invention is not limited to the specific form of apparatus illustrated since many modifications thereof may be employed to utilize some or all of the novel features of the invention.

Referring to the drawing, heating coil l, to I which reflux condensate formed within the system and high-boiling or intermediate fractions of the charging stock are supplied, as will be later described, for cracking, is disposed in a suitable furnace 2, by means of which the oil passing through the heating coil is heated to the desired cracking temperature preferably at a substantial superatmospheric pressure. The heated products are discharged from heating coil I through line 3 and valve 4 into reaction chamber 5.

Chamber 5 is also preferably maintained at a substantial superatmospheric pressure and, although not indicated in the drawing, this zone is preferably well insulated to conserve heat and the heated products thus supplied to the reaction chamber are subjected to appreciable continued conversion therein. In the particular case here illustrated both vaporous and liquid conversion products are withdrawn from the lower portion of chamber 5 and directed through line 6 and valve 1 into vaporizing and separating chamber 8. It is, however, also within the scope of the invention to separately remove vaporous and liquid products from chamber 5 by well known means, not illustrated, supplying the latter to chamber 8, as illustrated, and supplying the vaporous products separately removed from the reaction chamber either to chamber 8 at any desired point or plurality of points in this zone or direct to fractionation l3 or, in part to each, by well known 7 means not illustrated. a 5

It is also entirely within the scope of the invention, when desired, to eliminate the high-pressure reaction chamber 5 and to supply the heated products from coil I to chamber 8 without prior separation of their vaporous and liquid components.

Chamber 8 is preferably maintained at a substantially reduced pressure relative to that employed in the reaction chamber or, in case the reaction chamber is not used, relative to the pressure employed in heating coil I. By means of the reduced pressure appreciable vaporization of the liquid products supplied to chamber 8 is accomplished therein. Residual liquid remaining unvaporized in chamber 8 may be withdrawn from the lower portion thereof through line 9 and valve Hi to cooling and storage or elsewhere, as desired, or, when desired, this chamber may be operated as a coking zone wherein, by control of the operating conditions maintained, the residual products may be reduced to coke. When desired, a plurality of such coking chambers may be employed, although only one is illustrated, in which case they may be simultaneously operated or, preferably, two or more chambers are alternately operated, cleaned and prepared for further operation in order that the operating cycle of the process will not be limited by the capacity of the coking zone. When chamber 8 is operated as a coking zone the coke accumulated therein may be removed in any well known manner after the operation of the chamber is completed and preferably after it has been isolated from the rest of the system;

Vaporous productsare directed from the upper portion of chamber 8 through line H and valve I2 to fractionation in fractionator l3 wherein their insuificiently converted components are condensed as; reflux condensate.

Fractionated vapors of the desired end-boiling point comprising, materials within the boiling range of gasoline of the desired quality, are directed from the upper portion of fractionator l3 through line [4 and valve IE to condensation and cooling in condenser IS. The resulting distillate and uncondensed gases pass through line I! and valve [8 to collection and separation in receiver l9. The gaseous products may be released from the receiver through line 20 and valve 2| and distillate may be withdrawn from the receiver through line 22 and valve 23 to storage or to any desired further treatment. When desired, regulated quantities of the distillate collected in receiver l9 may be recirculated, by well known means, not illustrated in the drawing, to the upper portion of fractionator I3 to serve as a refluxing and cooling medium in this zone for assisting fractionation of the vapors and to maintain the desired vapor outlet temperature therefrom.

The total reflux condensate formed in fractionator 13 may, when desired, be withdrawn from the lower portion of this zone through line 24 and valve 25 to pump 26 by means of which it is returned through line 2'! and valve 28 to further cracking in heating coil I.

On the other hand selected low-boiling fractions of the reflux condensate formed in fractionator I3, which may comprise such material ashigh-boiling gasoline fractions of inferior antiknock value, naphtha, kerosene, kerosene distillate and the like may be separately removed from one or a plurality of suitable intermediate points in the fractionator and directed through line 29 and valve 30' to pump 3| by means of which they are supplied through line 32, valve 33 and line 54 to further treatment in heating coil 56. In such cases only the remaining higher [boiling fractions of the reflux condensate are supplied in the manner previously described to further treatment in heating coil I.

Crude petroleum or other wideboiling range hydrocarbon oils of the nature previously indicated is supplied through line 34 and valve 35 to pump 36 by means of which it is fed through line 31, heat exchanger 38, line '39 and valve 40 into distilling and fractionating column 4! wherein it is separated by fractional distillation into selected relatively low-boiling and high-boiling fractions.

The charging stock recovers a substantial portion at least of the heat required for distillation thereof by indirect heat exchange in heat exchanger 38 with the highly heated products from the light oil cracking or reforming stage of the process. However, additional heat may, when desired, be supplied to the charging stock in any well known manner, not illustrated, either prior or subsequent to its passage through heat exchanger 38.

Selected low-boiling fractions of the charging stock, which may comprise, for example, gasoline or gasoline fractions of poor antiknock value, naphtha, kerosene or kerosene distillate and the like or any desired mixture of such materials, are withdrawn as fractionated vapors from the upper portion of column A! and directed through line 42 and valve 43 to condensation and cooling in condenser 44 wherefrom the resulting distillate and any uncondensed gases are directed through line 46 and valve 4'! to collection and separation in receiver 38. Uncondensed gases may be released from the receiver through line 49 and valve 59 and the distillate collected therein is directed through line i and valve 52 to pump 53 by means of which it is supplied through line 54 and valve 55 to heating coil 56. When desired, regulated quantities of the distillate collected in receiver 38 may be recirculated, by well known means, not illustrated in the drawing, to the upper portion of column M to serve as a refluxing and cooling medium in this zone for assisting fractionation of the vapors and to maintain the desired vapor outlet temperature therefrom.

Heating coil 56 is disposed within a suitable furnace 51 by means of which the relatively lowboiling oil passing through the heating coil is heated to reforming conditions of cracking temperature at a substantial superatmospherio pressure. The conditions of temperature, pressure and cracking time are so controlled in heating coil 57 as to materially improve the antiknock value of any gasoline or gasoline fractions supplied to this zone and to crack any higher boiling oils supplied thereto for the production therefrom of high yields of good quality gasoline. The highly heated products are directed from heating coil 56 through line 58 and valve 59 to heat exchanger 33 wherein they are partially cooled by indirect heat exchange with the charging stock. The partially cooled products may then be supplied through line 60 and valve 6i into vaporizing and separating chamber 8, entering this zone at any desired point or plurality of points therein or, when desired, they may be additionally cooled, prior to their introduction into chamber 8, by commingling in line 6% with high-boiling fractions of the charging stock from column 4|, as will be later described.

When the charging stock contains any lowboiling, intermediate or high-boiling fraction which it is desired to recover without subjecting the same to cracking, such as, for example, gasoline or low-boiling gasoline fractions of good antiknock value, Diesel fuel, lubricating oil, asphalt or the like, such materials may be recovered by well known means, not illustrated, from suitable points in column 4!. However, at least a portion of the intermediate or high-boiling fractions of the charging stock, or both, is subjected to cracking in heating coil l and the communicating reaction 76/ chamber. This is accomplished, in the case here illustrated, by withdrawing the selected highboiling fractions of the charging stock from the lower portion of column 4| through line 62 and valve 63 to pump 64 by means of which they are fed through line 65 and may be directed through Valves 66 and 61 in this line into fractionator l3 or from line 65, line 68 and valve 69 into chamber 8, or this material may be supplied, in part, to chamber 8 and, in part, to fractionator [3.

When desired, and particularly in case chamber 8 is not operated as a coking zone, all or a regulated portion of the high-boiling and/or intermediate fraction of the charging stock may be utilized as a cooling medium for reducing the temperature of the reformed products discharged from heating coil 56 prior to the introduction of the latter into chamber 8. This may be accomplished by directing the topped charging stock from line 65 through line 10 and valve ll into line 60 or, when desired, the topped charging stock may be cooled, prior to its introduction into line 60, by passing the same through a suitable cooling coil 12 having communicating lines 13 and I4, controlled, respectively, by valves 75 and 16.

Although not illustrated in the drawing, the invention also contemplates, when desired, commingling the high-boiling fractions of the charging stock from the lower portion of column 4! with the stream of more highly heated products passing from the lower portion of chamber 5 to chamber 8 or, in case chamber 5 is not utilized, with the stream of heated products passing from heating coil I to chamber 8, whereby to partially cool the conversion products and heat the highboiling fractions of the charging stock to a higher temperature.

When the highly heated products discharged from heating coil 56 are cooled both by indirect heat exchange with the charging stock and by directly commingling the same with the topped charging stock, the two methods of heat exchange may be reversed to that illustrated in the drawing; in other words the hot conversion products discharged from heating coil 56 may be first commingled with the high-boiling fractions of the charging stock and the commingled materials then passed in indirect heat exchange with a portion or all of the total charging stock.

When the topped charging stock is supplied to fractionator l3 all or a substantial portion thereof will remain unvaporized or will be vaporized and recondensed in fractionator 13, passing therefrom to conversion in heating coil I, in the manner previously described, while any fractions of the topped charging stock within the boiling range of the intermediate liquid conversion products supplied from fractionator l3 to heating coil 56 will be directed therewith to heating coil 56. When the topped charging stock contains any substantial quantity of high-boiling residual products undesirable as cracking stock for heating coil i it is preferably supplied to chamber 8, wherein said heavy residual fractions will commingle with the non-vaporous residual conversion products supplied to this zone from heating coil 56 or chamber 5, the commingled materials being withdrawn from chamber 8 as liquid residue or reduced therein to coke, as previously explained, while the lower boiling fractions of the topped charging stock pass, together with the vaporous conversion products from chamber 8, into'fractionator 13.

The preferred range of operating conditions which may be employed in conducting the process of the invention in an apparatus such as illustrated and above described may be approximately as follows: The cracking coil to which reflux condensate and high-boiling or intermediate fractions of the charging stock are supplied may utilize an outlet conversion temperature ranging, for example, from 850 to 950 F., or thereabouts, preferably with a superatmospheric pressure, measured at the outlet from the heating coil, ranging from to 500 pounds or more per square inch. A superatmospheric pressure substantially the same or somewhat lower than that employed in the communicating heating coil is utilized in the reaction chamber and the succeeding vaporizing or coking zone preferably employs a substantially reduced pressure relative to that in the reaction chamber which may range, for example, from substantially atmospheric pressure to a superatmospheric pressure of pounds, or thereabouts, per square inch. The fractionating, condensing and collecting portions of the cracking stage of the system may utilize pressures substantially the same or somewhat lower than the pressure employed in the vaporizing or coking zone. The topping operation is preferably accomplished at substantially atmospheric pressure although subat- M mospheric or relatively low superatmospheric pressures up to 150 pounds, or thereabouts, per square inch may be employed in this zone, when desired. The light oil cracking or reforming coil preferably employs an outlet temperature of the order of 950 to 1100 F., preferably with a superatmospheric pressure measured at the outlet from this zone of from 300 to 1000 pounds, or thereabouts, per square inch although lower pressures down to substantially atmospheric may be employed in this zone, when desired, although in the latter case a temperature of the order of 1000 F., or higher, is preferably utilized. The degree to which the heated products from the reforming coil are cooled prior to their introduction into the vaporizing or coking zone will depend primarily upon the nature of the oils undergoing treatment and the type of operation desired. When the process is operated for the production of coke as the residual product, the materials from the reforming coil preferably enter the coking zone at a temperature of the order of 850 F., or more, but when the process is operated for the production of liquid residue this temperature may be reduced to as low as 650 F., or thereabouts.

As a specific example of an operation of the process, the charging stock is a California crude of about 30 A. P. I. gravity containing approximately 5 per cent of material boiling up to 232 F. and slightly more than 25 per cent boiling up to 400 F. The charging stock is passed in indirect heat exchange with the hot products from the reforming coil of the system and heated to a temperature of approximately 600 F. for topping. The topping column is operated at substantially atmospheric pressure and the overhead distillate product from this stage, comprising approximately 35 per cent of the charging stock and having an end-boiling point of approximately 500 F., is supplied to the reforming coil wherein it is heated to an outlet conversion temperature of approximately 980 F. at a superatmospheric pressure of about 800 pounds per square inch. The higher boiling fractions of the charging stock are commingled with the products from the reforming coil after the latter have passed in indirect heat exchange with the charging stock and the commingled materials are introduced into the vaporizing chamber of the cracking system which is operated at a superatmospheric pressure of approximately pounds per square inch. Liquid residue is recovered from the vaporizing chamber and the vaporous products from this zone are subjected to fractionation for the formation of reflux condensate. Selected low-boiling fractions of the reflux condensate, having an initial boiling point of approximately 390" F. and an end-boiling point of approximately 500 F. are supplied to the reforming coil. The higher boiling fractions of the reflux condensate are supplied to the heating coil of the cracking system wherein they are subjected to an outlet conversion temperature of approximately 950 F. at a superatmospheric pressure of about 350 pounds per square inch. The heated products from this coil are supplied to a reaction chamber maintained at substantially the same pressure and both vaporous and liquid conversion products from the reaction chamber are supplied to the vaporizing chamber. This operation will yield, per barrel of charging stock, approximately 68 per cent of 400 F. endpoint gasoline having an octane number of approximately 70 by the motor method and approximately 20 per cent of premium fuel oil, the remainder being chargeable, principally, to uncondensable gas.

I claim as my invention:

1. A conversion process which comprises topping crude petroleum to form topped crude and a distillate containing the low anti-knock straight-run gasoline components of the crude, subjecting the distillate in a heating coil to cracking conditions adequate to enhance the anti-knock value of said gasoline components, introducing the resultant products into a reduced pressure vaporizer, passing the major portion at least of the topped crude, Without prior cracking thereof, directly from the topping step into said reduced pressure vaporizer and therein vaporizing a substantial portion thereof, separating vapors from residue in the vaporizer and fractionating the vapors to separate relatively heavy and light reflux condensates therefrom, subjecting such heavier reflux condensate, unadmixed with residual portions of the crude, in a second heating coil to independently controlled cracking conditions of temperature and pressure and subsequently discharging the same into the reduced pressure vaporizer, supplying lighter reflux condensate formed by the fractionation to the first-mentioned coil for retreatment therein together With the straight-run distillate, and finally condensing the fractionated vapors.

2. The process as defined in claim 1 further characterized in that the topped crude is introduced to the vaporizer by being commingled with the heated products in transit from the firstmentioned coil to the vaporizer.

3. The process as defined in claim 1 further characterized in that the crude petroleum, prior to the topping thereof, is passed in indirect heat exchange relation with the heated products in transit from the first-mentioned coil to the vaporizer to cool said products and to preheat the crude for the topping operation.

CHARLES H. ANGELL.

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