US2072378A - Conversion and coking of hydrocarbon oils - Google Patents

Description

March 2, 1937. E. F. NELSON 2,072,378

CONVERSION AND COKING OF HYDROCARBQN OILS 'Ffi.=led'March so, 1952 RECEIVER FURNACE I NVENTOR EDWIN F. NELSON wazz ATTORN Patented Mar. 2, 1937 UNITED STATES CONVERSION AND COKING OF HYDROCAR- BON OILS Edwin F. Nelson, Chicago, Ill., assignor, by mesne assignments, to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application March 30,

3 Claims.

This invention relates to the conversion and coking of hydrocarbon oils and more particularly refers to an improved process and apparatus for the conversion of hydrocarbon oil and coking of 5 the residual oil produced thereby, said coking being assisted by direct contact between the residual oil and highly heated raw oil charging stock to be cracked.

In one of its specific embodiments, the inven- 110 tion comprises an improvement of the type of cracking operation wherein hydrocarbon oil is subjected to conversion in a'heating coil, the heated oil, is passed through an enlarged reaction zone maintained at superatmospheric pressure .15 wherein conversion, particularly of the vaporous products, may continue, vaporous and non-vaporous products are withdrawn simultaneously from the reaction chamber and introduced into a reduced pressure vaporizing chamber, vapors from the vaporizing chamber are subjected to fractionation, their heavier components, which are condensed by fractionation, being returned to the heating coil for further conversion while the light vaporous overhead product is withdrawn from the fractionator, subjected to condensation and the resulting distillate and gas collected, said improvement comprising withdrawing from said vaporizing chamber residual oil remaining unvaporized therein and introducing it into a coking zone, heating raw oil charging stock for the system to a high temperature and introducing it into direct contact with the residual oil in said coking zone, for the purpose of supplying heat thereto and. assisting reduction of the residual oil to coke, and returning vapors from said coking zone to said reduced pressure vaporizing chamber.

The raw oil charging stock, prior to its introduction into the coking zone, is heated to a temperature suificient to eiTect reduction of the residual oil therein to coke. This temperature may be'of the order of 900 to 950 F. or thereabouts but the time to which the raw oil is subjected to this high temperature is regulated, dependent upon the type of raw oil charging stock utilized, so that no substantial formation and deposition of coke occurs in the heating coil through which the raw oil charging stock is passed. As time is one of the factors governing the degree of conversion, it is possible to subject the raw oil charging stock to very little or to extensive conversion, as desired, and particularly with heavy charging stocks such as residual oils, fuel oils.

L55 heavy crudes and the like, coking of some of the 1932, Serial No. 602,014

heavier components of the raw oil may also be the cracking system together with lighter relatively clean reflux condensate. This advantage will be immediately recognized by those familiar with the cracking art and does not require extensive explanation. However, it permits, among other things, the use of a wide variety of charging stocks without the necessity of short operating periods, due to excessive deposition of coke in thecracking coil, and permits, even with relatively heavy charging stocks, the use of higher conversion temperatures than would otherwise be possible without excessive gas formation and coking in the heating coil. Also, when appreciable conversion of the raw oil is accomplished by the treatment to which it is subjected in the coking operation, further conversion of the resulting intermediate conversion products, which is accomplished in the main cracking system, results in the production of substantial yields of motor fuel high in anti-knock value.

One specific form of apparatus in which the process of the present invention may be practiced is illustrated in the attached diagrammatic drawing. A heating coil l receives hydrocarbon oils to be cracked from sources which will be later more fully described and, by means of heat supplied from a furnace 2 of any suitable form, the oil is heated to the desired conversion temperature and is discharged through line 3 and valve 4 into reaction chamber 5. Chamber 5, like heating coil l, is preierably maintained at substantial superatmospheric pressure and the vaporousproducts from the heating coil, which pass through the reaction zone at a slower rate than the heavier liquid conversion products, are subjected to continued conversion in the reaction zone for a greater length of time than said heavier liquids. Both vaporous and non-vaporous conversion products are withdrawn from reaction chamber 5 through line B and valve 1 and are introduced into vaporizing chamber 8,

which is preferably maintained at substantially reduced pressure relative to that employed in chamber 5.

Vaporous conversion products and residual liquid separate in chamber 8, the vapors pass through line 9 and Valve H] to fractionation in fractionator II.

The relatively heavy components of the vapors are condensed in the fractionator and are withdrawn as reflux condensate from its lower portion through line l2 and valve l3 to pump l4 which supplies this oil through line I5 and valve IE to heating coil I for conversion.

vaporous products remaining uncondensed in fractionator H are removed from its upper portion through line H and valve l8, are subjected to condensation and cooling in condenser I9 and the resulting distillate and gas passes through line 20 and valve 2! to be collected in receiver 22. Uncondensable gas may be released from the receiver through line 23 controlled by valve 24. Distillate may be withdrawn from the receiver through line 25 and valve 26. A portion of the distillate from receiver 22 may, when desired, be recirculated by means of line 21, valve 28, pump 29, line and valve 3| to the upper portion of fractionator H to assist fractionation in this zone and to control the vapor outlet temperature.

Residual oil remaining unvaporized in chamher 8 is withdrawn through line 32 and valve 33 to pump 34 from which it is fed through line 35 either into coking chamber 36 through line 3! and valve 38 or into coking chamber 36' through line 31' and valve 38'. Coking chambers 36 and 36 are alternate coking zones wherein the cracked residual oil is reduced to substantially dry carbonaceous residue. It is, of course, within the scope of the invention to employ a single coking chamber or, when desired, more than the two illustrated in the drawing. The object of employing more than one coking zone is to permit one to be cleaned and prepared for operation while the other is being operated and thus prolong the operating cycle of the process. Raw oil charging stock for the system supplied through line 39 and valve 40 to pump 4| is fed through line 42 and valve 43 to heating coil 44. The raw oil may, of course, be preheated in any well known manner not illustrated in the drawing, prior to its introduction into heating coil 44, for example, by indirect contact with relatively hot liquid and/or vaporous conversion products of the process. The raw oil is heated in heating coil 44, by means of heat supplied from a furnace 45 of any suitable form, to a temperature suificient to subsequently effect coking of the cracked residual oil by direct contact therewith. The heated raw oil charging stock is discharged from heating coil 44 through line '46 and may pass to coking chamber 36, through valve 41 in this line, or into coking chamber 36', through line 46' and valve 41'. Direct contact is obtained in the coking zone between the highly heated raw oil charging stock and the residual oil from vaporizing chamber 8 and the heat thus imparted to the residual oil effects its reduction to coke. In case the raw oil charging stock is a relatively heavy oil, some of its heavier components may also be reduced to coke in chambers 36 and 36'. However, conditions are so controlled in heating coil 44, as has previously been explained, that no appreciable coke deposition occurs in the heating coil.

Vapors are withdrawn from coking chamber 36 through line 48 and valve 49 while vapors are withdrawn from coking chamber 36 through line 48' and valve 49', vapors from either or both chambers passing thence through line 50 into vaporizing chamber 8, where they commingle with the conversion products supplied to this zone from reaction chamber 5, are separated into vaporous products and non-vaporous residual liquid and are subsequently subjected to the same treatment as that afforded the vaporous and residual liquid products from chamber 5.

The cracking coil wherein reflux condensate from the fractionator of the system is subjected to conversion may employ a conversion temperature ranging, for example, from 850 to 1050 F., with superatmospheric pressures ranging from 100 to 500 pounds, or thereabouts, per square inch. A substantial superatmospheric pressure substantially equalized with that in the cracking coil is preferably employed in the reaction chamber although somewhat reduced pressure may be employed in this zone, when desired. The vaporizing chamber, as well as the succeeding fractionating, condensing and collecting portions of the system, preferably utilizes a substan tially reduced pressure relative to that employed in the reaction chamber, said reduced pressure ranging, for example, from 100 pounds, or thereabouts, down to substantially atmospheric pressure. A pressure substantially equalized with or lower than that in the vaporizing chamber is preferred in the coking chambers although higher pressures up to several hundred pounds per square inch, may be employed in the coking zone, when desired, particularly when it is desirable to subject the raw oil charging stock to extensive conversion in the coking portion of the system. The raw oil charging stock may be heated, prior to its introduction into the coking zone, to a temperature of the order of 900 to 950 F. or more, and the pressure employed in this heating coil may range, for example, from substantially atn'lilospheric to 500 pounds, or more, per square inc 7 As a specific example of the operation of the process of the present invention, the raw oil charging stock is a 40 A. P. I. gravity Mid-Continent crude containing about 40% of material boiling up to 437 F. This material is subjected in the raw oil heating coil to a temperature of approximately 950 F. at a superatmospheric pressure of about 350 pounds per square inch and is introduced into direct contact with the residual oil in the coking zone at a reduced pressure of approximately 50 pounds per square inch. Vapors from the coking zone are supplied to the vaporizing chamber of the cracking system and reflux condensate from the succeeding fractionator of the cracking system is subjected to a temperature of approximately 930 F., in a cracking coil at a superatmospheric pressure of about 400 pounds per square inch. The reaction chamber is maintained at substantially this same pressure but the pressure is reduced to approximately 50 pounds per square inch, in the vaporizing chamber. This operation may yield, per barrel of raw oil charging stock, about 70% of 400 end point motor fuel having an octane number of approximately 70,-about 70 pounds of coke and approximately 550 cubic feet of uncondensable gas.

I claim as my invention:

1. A cracking process which comprises subjecting hydrocarbon oil to cracking conditions of temperature and pressure in a cracking zone, 7

continuously removing reaction products from said zone and flash distilling the same in a flashing zone by pressure reduction, thereby forming vapors and unvaporized oil, removing the latter from the flashing zone and introducing the same to a coking zone, simultaneously passing additional hydrocarbon oil through a second heating zone and heating the same therein to the coking temperature of said unvaporized oil, discharging the thus heated additional oil into the coking zone and into contact With the unvaporized oil therein and distilling the latter substantially to coke by the heat of said additional oil, introducing the vapors evolved in the coking zone into contact with the oil being flash distilled in the flashing zone, removing the admixed vapors from the flashing zone and fractionating the same to condense heavier fractions thereof, supplying resultant reflux condensate to said cracking zone and finally condensing the fractionated vapors.

2. A cracking process which comprises heating relatively clean hydrocarbon stock, formed as hereinafter set forth, to cracking temperature under pressure while flowing in a restricted stream through a heating zone, introducing the heated oil to a reaction zone maintained under cracking conditions of temperature and pressure, continuously removing reaction products from the reaction zone and flash distilling the same in a flashing zone by pressure reduction thereby forming vapors and unvaporized oil, removing the latter from the flashing zone and introducing the same to a coking zone, simultaneously passing additional hydrocarbon oil through a second heating zone and heating the same therein to the coking temperature of said unvaporized oil, discharging the thus heated additional oil into the coking zone and into contact with the unvaporized oil therein and distilling the latter substantially to coke by the heat of said additional oil, combining vapors evolved in the coking zone with vapors evolved in the flashing zone and fractionating the admixed vapors to condense heavier fractions thereof, supplying resultant reflux condensate to the first-mentioned heating zone as said relatively clean stock, and finally condensing the fractionated vapors.

3. A cracking process which comprises heating relatively clean hydrocarbon stock, formed as hereinafter set forth, to cracking temperature under pressure while flowing in a restricted stream through a heating zone, introducing the heated oil to a reaction zone maintained under cracking conditions of temperature and pressure, continuously removing reaction products from the reaction zone, flash distilling the same in a flashing zone by pressure reduction, thereby forming vapors and unvaporized oil, removing the latter from the flashing zone and introducing the same to a coking zone, simultaneously passing additional hydrocarbon oil through a second heating zone and heating the same therein to the coking temperature of said unvaporized oil, discharging the thus heated additional oil into the coking zone and into contact with the unvaporized oil therein and distilling the latter substantially to coke by the heat of said additional oil, introducing the vapors evolved in the coking zone into contact with the oil being'flash distilled in the flashing zone, removing the admixed vapors from the flashing zone and fractionating the same to condense heavier fractions thereof, supplying resultant reflux condensate to the first-mentioned heating zone as said relatively clean stock, and

finally condensing the fractionated vapors.

EDWIN F. NELSON.

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