US2008502A - Cracking hydrocarbon oils - Google Patents

Description

July 16, 1935. J. B. HElD 2,008,502

CRACKING HYDROCARBON OILS Filed Dec. 26, 1930 FRACTIONATOR FURNACE INVENTOR JACOB BENJAMEN HEID ATTORNEY Patented July 16, 1935 PATENT OFFICE CRACKING HYDROCARBON OILS Jacob Benjamin Held, Chicago, 111., assignor to Universal Oil Products Company, Chicago, 111.,

a corporation of South Dakota Application December 26, 1930, serial No. 504,853

' 2 Claims. 01. 196-48) This invention relates to the cracking of hydrocarbon oils, and refers more particularly to an improved process and apparatus for the conversion of relatively heavy oils into lighter and more "5 valuable products.

Primarily, the invention comprises dividing a stream of combined feed (raw oil charging stock and'reflux condensate from a cracking system), supplying separate portions of said stream to separate heating elements wherein each of the separated portions may be subjected tounlike conditions of treatment, subsequently uniting said separated portions, and simultaneously subjecting them to further treatment in-the balance of the system. By uniting the, two streams after their passage through said heating elements, the cooler-stream serves to cool the hotter stream, thus checking or dampening the reaction so as to control the reaction andthe nature of the re.- 20 sultant products thereof. v v r The treatment to which one portion of the combined feed may be subjected in a heating element towhich it may be passed-may be within the range of any desired conversion conditions, or may be of a higher or lower order. For ex ample, the conversion conditions to which the oil may be subjected in one heating element may be of a less severe nature and of suchextent as to merely bring the temperature. of the oil up to about a relatively mild cracking temperature, while the remaining portion of the combined feed of oil may be subjected in a separate heating element to a relatively high conversion temperature, sometimes termed vapor-phase? conversion conditions, in order to obtain a product of improved anti-knock quality. r

The treatment to which the oil may be subjected in one heating element into which a portion of the combined feed may be introduced, is 40 always milder than the conditions to whichthe remaining portion thereof may be subjected, and, as a result, the more severe conditions will be sufiicient to effect substantial conversion of the oil, obtaining an improved product from the standpoint of anti-knock quality.

Referring to the attached diagrammatic drawing illustrating one form of apparatus in which the invention may be carried out, raw oil charging stock may be supplied through a line I, controlled by a valve 2 to a pump 3 and line 4, and may pass via a line 5, controlled by valve 6 to a fractionator I where it may be preheated by contact with the relatively hot vapors being treated therein, serving to assist in their fractionation. 5 After passing through said fractionator, the preheated raw oil, together with relatively heavy insufiicientlyconverted fractions of thevapors condensed in said fractionator may be withdrawn therefrom through a line 8, controlled by a valve 9, to said line 4, combining therein with that portion, if any, of the raw oil'being fed directly to said line through control valve lll' interposed therein. It will be understood, however, that any desired portion or all of the raw oil may be passed directly overhead to fractionator l', or directly through said'line 4 and valve It]. In all cases, however, reflux condensate from fractionator 'l and raw oil are combined in that portion of line 4 beyond the juncture of line 8 therewith. The combined feed from said line 4 may be passed, in part, through-a line H, controlled by valve 12, a pump l3 disposed in said line, and a line 14, controlled by valve I5 to a heating element l6, and,

in part,through a line ll, controlled by valve l8, a pump l6, and a line 2!], controlled by valve 2!, to a heating element 22. g

Heating elementslfi and 22 may be disposed within combustion zones 23 and .24, respectively, ina suitable furnace 25, or, if desired, separate furnaces may be employed. In all cases, how

, through which heated products from heating element 22 may pass. Line 38 is suitably controlled byvalve 3|, and the recombined and commingled products from heating elements It and 22 may pass through said line 30, controlled by valve 32, to. a-reaction chamber 33 wherein separation of vaporized and unvaporized materials may occur. Unvaporized residual oil from said chamber 33 may be withdrawn therefrom through a line td controlled by valve 35, and the vaporized products from said chamber may pass through a line 36, controlled by a valve 3?, to a iractionator where their heavy, insufiiciently converted portions may be condensed, withdrawn and subsequently subjected to retreatment, together with raw oil charging'stock, as described. The lighter portions of the fractionated vapors of the desired composition may pass from said iractionator through a line 33, controlled by valve 39 and be subjected to condensation and cooling in a condenser 40. Condensed distillate and incondensable gas from said condenser may pass through a line 4|, controlled by valve 42 to a receiver 43. Distillate may be removed from said receiver through a line 44, controlled by valve 45, and incondensable gas may be released therefrom through a line 46, controlled by valve 41. Any desired amount of the distillate from receiver 43 may be withdrawn through a line 48 controlled by valve 49 and recirculated by means of a pump 50, via line 5|, controlled by valve 52 to'fractionator I, to further assist in fractionation of the vapors therein.

Pressures employed within the system may range from subatmospheric to superatmospheric pressures of the order of 2000 pounds or more per square inch. Substantially equalized or differential pressures may be employed throughout the system, or between anyor all of the various elements thereof. Conversion temperatures employed may range from 750 to 1200 F., more or less.

As one specific example of an operation in which the principles of the invention may be practiced, a heavy fuel oil of about 22 A. P. I. gravity was 'fed, together with reflux condensate from a fractionator of a system, in part to each of two heating elements. That portion supplied to the relatively low temperature heating element was subjected, at a pressure of about 175 pounds per square inch, to a temperature of about 850 F. Thatportion supplied to the relatively high temperature heating element was subjected to a conversion temperature of about 930 F.,- at a superatmospheric pressure of approximately 250 pounds per square inch. The quantity of oil fed to each heating element was so regulated that the temperature of the stream of the recombined material after heating entering the reaction chamber was about 875 F. The reaction chamher and succeeding portions of the system were maintained under a substantially equalized pressure of approximately 30 pounds per square inch. A yield of about 53% of good quality motor fuel, about 15% of pressure distillate bottoms, and approximately 24% of residual oil suitable for sale as fuel, all based on the raw oil charged to the system, was obtained. The remaining 8% or thereabouts was chargeable to gas and coke.

In addition to the above example, another specific operation, in which a 36-38" A. P. I. gravity gas oil was employed as a charging stock was carried out. That portion of the combined feed supplied to the relatively low temperature heating element was subjected to a conversion temperature of about 850 F., under a superatmospheric pressure of about 300pounds per square inch, and that portion of the combined feed supplied to the relatively high temperature heating element was subjected to a temperature of approximately 1000 F., under a superatmospheric pressure of about pounds per square inch. The temperature of the recombined stream of material after heating entering the reaction chamber in this operation, was approximately 930 F. The reaction chamber and succeeding portions of the system were maintained under a superatniospheric pressure of about 100 pounds per square inch. A yield of about 60% or more of motor fuel, having an anti-knock value equivalent to a blend of approximately 60% benzol and 40% Pennsylvania straight-run gasoline, was obtained, and the lower boiling components of the distillate which may amount to about 15%, more or less, based on the raw oil charged, were highly desirable as vapor-phase charging stock, and the 15% or thereabouts of residual oil produced met specification requirements for marketable fuel oil.

I claim as my invention:--- 7 1. A hydrocarbon oil cracking process which comprises removing vapors from a vapor separating zone of a cracking system, dephlegmating the vapors in direct contact with charging oil amenable to vapor phase cracking thereby forming a mixture of preheated charging oil and reflux condensate, dividing said mixture into a plurality of portions of similar boiling point and gravity, passing one of said portions in a restricted stream through a heating zone and heating the same therein to vapor phase cracking temperature under relatively low pressure, passing another of said portions through a second heating zone and heating the same therein to lower cracking temperature under higher pressure than the first-mentioned portion whereby the oil in said second heating zone is maintained substantially in liquid phase, discharging the 9 thus heated portions from said heating zones into said separating zone and separating the commingled portions therein into vapors and residue, and condensing as a product of the process the Vapors uncondensed by the dephlegmation.

2. A hydrocarbon oil cracking process which comprises combining with a charging'oil amenable to vapor phase cracking a reflux condensate formed as hereinafter set forth, dividing the resultant mixture into separate streams of similar boiling point and gravity, heating one of said streams to vapor phase cracking temperature under relatively low pressure, separately heating another of said streams to a lower cracking temperature and under a higher pressure than the first-mentioned stream whereby it is maintained substantially in liquid phase during the heating, then commingling the thus heated streams and separating the mixture in vapors and residue, dephlegmating the separated vapors to condense insufiiciently cracked fractions thereof, utilizing such condensed fractions as said reflux condensate, and finally condensing th dephlegmated vapors.

JACOB BENJAMIN HEID.

Images