US2095952A - Conversion of hydrocarbon oils - Google Patents

Description

Oct. 19, 1937. c. H. ANGELL 2,095,952

CONVERSION OF HYDROCARBON OILS Filed Feb. 27, 1955 FURNACE TOPPING COLUMN INVENTOR CHARLES; H. ANGELL Patented Oct. 19, 1937 UNITED STATES CONVERSION OF HYDROCARBON OILS Charles H. Angell, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of'Delaware Application February 27, 1933, Serial No. 658,707

2 Claims.

' 15 tions obtained therein which are selected as most desirable for the further treatment of said intermediate conversion products.

It is within the scope of the present invention either to subject the total reflux condensate 20 formed by fractionation of the vaporous conversion products of the process to the same treatment as that afforded the high boiling components of the charging stock or to separate the reflux condensate and, when desired, the topped 25 charging stock, into low boiling and high boiling fractions, returning said low boiling fractions to conversion together with the low boiling fractions of the charging stock separated therefrom by the topping operation and subjecting said 30 high boiling fractions to independently controlled less severe conversion conditions in a separate heating coil. The features and advantages of the present invention will be apparent to those familiar with the prior art from the foregoing brief 35 description of the process and from the following more detailed description of the accompanying diagrammatic drawing. The drawing illustrates one specific form of apparatus embodying the features of the present invention and in which 40 the process of the invention may be practiced.

Referring to the drawing, raw oil charging stock for the process, which may comprise, for example, crude petroleum or other hydrocarbon oil containing a substantial proportion of motor 45 fuel or motor fuel fractions as well as higher boiling components and including, when desired, such materials as pressure distillate containing motor fuel resulting from cracking but of poor antiknock value, is supplied in heated state 50 through line I and valve 2 to topping column 3,

comprising, in the case illustrated, a fractionator of any suitable form whereby the gasoline components of the changing stock, which enter the column in vaporous form, are separated from 55 its higher boiling components, which either enter the column as liquid or' are condensed by fractional condensation in this zone, It will be understood that the raw oil is introduced into column 3 at a temperature somewhat in excess of the end-boiling point of the light product which it is desired to separate from the higher boiling fractions of the charging stock, although specific means for accomplishing heating and total or partial vaporization of the charging stock are not shown. The temperature to which the oil is heated, prior to its introduction into column 3 may range, for example, from 400 to 600 F., or more, and the pressure employed in column 3 may range from substantially atmospheric or a slight subatmospheric pressure to a superatmospheric pressure of 100 pounds per sq. in., substantially atmospheric pressure being preferred. Heating of the oil may be accomplished in a suitable heating coil disposed in any well known form of furnace (not shown), which will be independently fired or supplied with flue gases from the cracking furnace of the process, or the required heat may be recovered by indirectly contacting the charging stock with any suitable hot vaporous or liquid products of the process by means of suitable heat exchangers of any well. known form, not shown in the drawing, or any combination of the methods mentioned may be utilized for heating the charging stock to the temperature required for the topping operation.

Low-boiling fractions of the charging stock, of the desired end-boiling point, separated from its higher boiling components in column 3 are with drawn in vaporous form, together with any gas resulting from the topping operation, from the upper portion of the topping column through line 4 and valve 5 to be subjected to condensation in condenser 6, from which the resulting distillate and gas passes through line I and valve 8 to collection and separation in receiver 9.

While the distillate thus collected in receiver 9 preferably contains all of the gasoline components of the charging stock boiling up to 400 F., 7

which may be regulated to suit requirements by any well known method, not shown, of controlling the vapor outlet temperature from the upper portion of column 3. It is also within the scope of the invention, although not shown in the drawing, when the charging stock contains certain predetermined motor fuel fractions of sufiiciently good antiknock value to warrant no reforming treatment, to separately recover such selected fractions from topping column 3 by well known means, not shown, subjecting the remaining portion of the motor fuel of inferior antiknock value to reforming, as will be presently more fully described, while the selected fractions of good antiknock value are preferably blended with the final motor fuel products of the process.

Uncondensable gas is released from receiver 9 through line l and valve A portion of the distillate collected in receiver 9 may, when desired, be withdrawn to storage or to any desired further treatment through line l2 and valve l3. However, at least a portion of the distillate collected in receiver 9 is withdrawn therefrom through line 4 and valve |5 to pump |6 by means of which it is fed through line l1 and valve l8 to heating coil I9 for further treatment.

Heating coil I9 is located Within a furnace 20 of any suitable form by means of which heat is supplied to the oil passing through the heating coil to bring it to the desired temperature, preferably at a substantial superatmospheric pressure, the conditions in heating coil l9 being regulated to effect a markedirnprovement in the motor fuel characteristics of the oil supplied to this zone,

particularly with respect to its antiknock value, without excessively altering its boiling range. The heated oil may be discharged from heating coil I9 through line 2| and valve 22 into reaction chamber 23.

Chamber 23 is also preferably maintained at a substantial superatmospheric pressure and, although not shown in the drawing, this zone is preferably well insulated to prevent excessive loss of heat by radiation so that conversion of the oils introduced into the reaction chamber, and particularly their vaporous components. may continue therein. Both vaporous and liquid conversion products are withdrawn from the lower portion of chamber 23 and are introduced through line 24 and valve 25 into vaporizing chamber 26.

Chamber 26 is preferably maintained at a substantially reduced pressure relative to that employed in chamber 23, by means of which further vaporization of the liquid conversion products is accomplished and the vapors are separated from the final residual products of the process. The residual liquid remaining unvaporized in chamber 26, when desired as the final residual product of the process, is withdrawn therefrom through line 21 and valve 28 to cooling and storage or to any desired further treatment. Means will be later more fully described for securing the production of coke in chamber 26 as the final residual product of the process. The vaporous products of the process pass from chamber 26 through line 25 and valve 30 to fractionation in fractionator 3|.

Simultaneous with the operation above described the high-boiling components of the charging stock, withdrawn as bottoms from the topping and fractionating operation in column 3 through line 32 and valve 33 to pump 34, are supplied therefrom through line 35 and valve 36 to fractionator 3|, to commingle therein with the hot vaporous conversion products of the process Sup,

plied to this zone from chamber 26, as described, being thereby subjected to vaporization and the same fractionation as that afforded the vaporous conversion products of the process in this zone and, at the same time, assisting fractionation of the vapors. When desired, a portion or all of the topped charging stock, instead of passing to fractionator 3| may be diverted from line 35 through line 52 and valve 53 into line 50, passing therewith together with the total reflux condensate or with the high-boiling components of the reflux condensate from fractionator 3|, as will be later more fully described, to conversion in heating coil 54.

Fractionated vapors of the desired end-boiling point, preferably comprising materials within the boiling range of motor fuel and of good antiknock value, are withdrawn, together with uncondensable gas produced by the cracking operation, from the upper portion of fractionator 3| through line 31 and valve 38 and are subjected to condensation and cooling in condenser 39, from which the resulting distillate and gas passes through line 40 and valve 4| to collection and separation in receiver 42. Uncondensable gas may be released from receiver 42 through line 43 and valve 44. The distillate collected in receiver 42, comprising the final motor fuel conversion product of the process, may be withdrawn through line 45 and valve 46 to storage or to any desired further treatment. A portion of the distillate collected in receiver 42 may, when desired, be returned, by well known means not shown in the drawing, to the upper portion of fractionator 3|,

to assist fractionation of the vapors in this zone and to maintain the desired vapor outlet temperature, thus controlling the end-boiling point of the final light distillate conversion product of the process.

The vaporous products of the process, together with any topped charging stock supplied to fractionator 3|, as described, are subjected to fractionation in this zone whereby their components boiling above the end-boiling point of the desired overhead vaporous product are condensed or remain unvaporized in this zone, collecting therein as reflux condensate. All or, when desired, as will be later more fully described, only high-boiling components of the reflux condensate collect within the lower portion of fractionator 3| from which they are withdrawn through line 41 and valve 48 to pump 49, by. means of which this oil is supplied through line 50 and valve 5| to heating coil 54 commingling in line 50, as already described, with the topped charging stock or that portion, if any, of this material supplied through line 52, valve 53 and line 50 to heating coil 54.

The oil supplied to heating coil 54 is subjected therein, by means of heat supplied from a furnace 55 of any suitable form, to the described conversion temperature, which is preferably somewhat lower than that employed in heating coil l9, and preferably at substantial superatmospheric pressure. The heated oil is discharged from heating coil 54 through line 56 and valve 51 into reaction chamber 23. It will be understood that the heated oils from heating coils l9 and 54 may be commingled, as shown in the drawing, prior to their introduction into chamber 23, or that the two streams may be separately introduced into the reaction chamber entering this zone at any desired point therein, by well known is particularly desirable when the nature of the charging stock and the other operating conditions of the process are such that a substantial proportion of the reflux condensate formed in fractionator 3| comprises relatively low-boiling oils which may be advantageously subjected to the same treatment in heating coil l9 as that afforded the distillate from receiver 9, such lowboiling fractions of the reflux condensate, including any fractions of the topped charging stock supplied to the fractionator of similar boiling range and cracking characteristics, may be withdrawn as a side-stream from one or any number of suitable points in fractionator 3|, for example, through line 58 and valve 59 to pump 60 by means of which these selected low-boiling fractions are fed through line GI and valve 52 into line H, commingling therein with the distillate from receiver 9 and passing therewith to further conversion in heating coil l9. 1

As another optional feature of the invention which is especially advantageous when it is desirable to produce a heavy asphaltic or pitchy residue or to entirely eliminate the production of liquid residue, producing only substantially dry coke as the residual product of the.pr ocess, all or any desired portion of the highly heated oil from heating coil l9 may be diverted from line 2| through line 63 and valve 64 into chamber 26, entering this zone at any desired point by preferably below the level of residual material therein; whereby additional heat is imparted to the residual oil suiiicient to reduce it to coke or to the desired intermediate asphaltic or pitchy stage. When the process is operated for the production of coke or semi-solid residue in chamber 26 a plu rality of such zones may be employed, when de sired, although only a single chamber is shown in the drawing. When a plurality of coking chambers are utilized they may be operated simultaneously or, preferably, are alternately operated, cleaned and prepared for further operation so that the duration of the operating cycle will not be limited by the capacity of the coking zone.

As already stated, the temperature of the charging stock entering the topping column may range, for example, from 400 to 600 F., or more, and substantially atmospheric pressure is preferably employed in the topping portion of the system, although subatmospheric pressure or superatmospheric pressures up to pounds, or more, per sq. in., may be employed, when desired. A conversion temperature ranging, for example, from 950 to 1050 F. and a superatmospheric pressure of from 200 to 800 pounds, or more, per sq. in. is preferably employed at the outlet from the heating coil to which the low-boiling fractions of the charging stock from the topping operation are supplied. The other heatingcoil of the system to which are or high-boiling fractions of the reflux condensate and topped charging stock are supplied preferably employs an outlet temperature ranging, for example, from 875 to 975 F., with a superatmospheric pressure measured at the outlet from the heating coil of from 100 to -500 pounds, or thereabouts, per square inch. A super-atmospheric pressure within the range of 100 tov 500 pounds, or thereabouts, may

be maintained in the reaction chamber. A substantially reduced pressure ranging, for example, from 100 pounds or thereabouts per square inch down to substantially atmospheric pressure is preferred in the vaporizing or coking chamber and this pressure may be either substantially equalized or somewhat reduced in the succeeding fractionating, condensing and collecting portions of the cracking system.

As a specific example of one of the many possible operations of the process of the present invention, the charging stock is a 32 A. P. I. gravity crude containing approximately 27 percent. of 40.0" F. end point gasoline of low antiknock value, fractions of the charging stock boiling up to approximately 500 F., are recovered by the topping operation and the topped crude is subjected, together with reflux condensate from the fractionator of the cracking system to a conversion temperature of approximately 940 F., at a superatmospheric pressure of about 350 pounds per square inch at the outlet from the heating coil to which this material is supplied. A pressure of about 350 pounds per sq. in. is maintained in the reaction chamber. A reduced pressure of approximately 60 pounds per sq. in. is maintained in the vaporizing chamber and is substantially equalized in the succeeding portions of the cracking system. The distillate from the topping operation is subjected in a separate heating coil to a conversion temperature of approximately 970 F. at a superatmospheric pressure of about 600 pounds per sq. in. and the heated oils from the two heating coils are commingled, prior to their introduction into the reaction chamber. This operation may yield, per barrel of charging stock, about 76 percent of 400 end-point motor fuel having an antiknock value equivalent to an octane number of approximately 76, the additional products of the operation being about 14 percent of good quality residual oil and about 460 cubic feet of uncondensable gas.

In a somewhat different type of operation similar to that above described except that the temperature in the first mentioned heating coil is increased to about 950 F. and the highly heated oil from the reforming coil is introduced into direct contact with the residual material in the reduced pressure chamber, coke is produced in this zone as the residual product of the process and the yields from this operation are approximately as follows: 78 percent of 400 end-point motor fuel having an antiknock value equivalent to an octane number of approximately 75, about 47 pounds of coke and about 550 cubic feet of uncondensable gas, per barrel, of charging stock.

In either of the operations above described by withdrawing a selecting low-boiling fraction of the reflux condensate from the fractionator of the cracking system, having an end-boiling point approximately corresponding to or somewhat higher than that of the distillate from the topping operation, and returning this material to reforming with said distillate, the antiknock value of the motor fuel produced may be somewhat increased at the expense of a somewhat lower yield of motor fuel and a slightly increased yield of gas.

I claim as my invention:

1. A conversion process which comprises fractionating a gasoline-containing oil and separating therefrom a light fraction containing gasoline hydrocarbons and a heavier fraction composed of hydrocarbons boiling above the gasoline range, simultaneously fractionating cracked vapors in a fractionating zone to form primary reflux condensate and a lighter secondary reflux condensate, combining the primary reflux condensate. with said heavier fraction and heating the resultant mixture to cracking temperature under pressure while flowing in a restricted stream through a heating zone, introducing the heated mixture into an enlarged reaction zone maintained under cracking conditions of temperature and pressure and effecting further conversion therein, removing vaporous and liquid reaction products in commingled state from the reaction zone and discharging the same into a separating zone maintained under lower pressure than the reaction zone, combining the secondary reflux condensate with said light fraction and heating the resultant mixture, in an independent heating zone maintained at higher temperature than the first-named heating zone, to a. temperature adequate to improve the antiknock value of the gasoline hydrocarbons contained in the light fraction, discharging heated products directly from said independent zone into the reduced pressure separating zone and separating the oils therein into vapors and residue, supplying the separated vapors to the fractionating zone as said cracked vapors, and finally condensing the fractionated vapors.

2. A conversion process which comprises topping and fractionating crude petroleum in a topping zone and separating therefrom a light fraction containing gasoline hydrocarbons and a heavier fraction composed of hydrocarbons boiling above the gasoline range, simultaneously fractionating cracked vapors in a fractionating zone apart from said topping zone to form primary reflux condensate and a lighter secondary reflux condensate, combining the primary reflux condensate with said heavier fraction and cracking the resultant mixture under pressure in a conversion zone, discharging the cracked mixture into a separating zone maintained under lower pressure than the conversion zone, combining the secondary reflux condensate with said light fraction and heating the resultant mixture, in an independent heating zone maintained at higher temperature than said conversion zone, to a temperature adequate to improve the anti-knock value of the gasoline hydrocarbons contained in the light fraction, discharging heated products directly from said independent zone into the reduced pressure separating zone and separating the oils therein into vapors and residue, supplying the separated vapors to the fractionating zone as said cracked vapors, and finally condensing the fractionated vapors.

CHARLES H. ANGELL.

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