US1895873A - Process for cracking hydrocarbon oils - Google Patents

Description

Jan. 31, 1933. J. G. AL'rHER PROCESS FOR CRACKING HYDROCARBON OILS Filed Aug. 23.

Patented Jan. 31, 1933 UNITED STATES PATENT OFFICE JOSEPH G. ALTHER, OF CHICAGO, ILLINOIS, ASSIGNORTD UNIVERSAL OIL PRODUCTS COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF SOUTH DAKOTA PROCESS FOR CRACKING HYDROCARBON OILS Application led August 23, 1926. Serial No. 131,025.

This invention contemplates the provision of an improved process for the conversion of high boiling point hydrocarbon oils into hydrocarbon oils of lower boiling point and itis a specific object of the invention to provide a process for the continuous conversion of hydrocarbon oils with a minimum of coke formation.

One of the great diiculties which has materially reduced `,the eiiiciency of cracking processes has been the excessive formation of carbon during the cracking reaction. There have been various attempts made yto develop efficient cracking processes, many of which are commercially successful, but in these processes provision has been made for taking care of excessive accumulations of coke rather than for the Vreduction of coke formation during the cracking reaction. It has been almost universally the custom in what are known as lcontinuous processes to provide an enlarged chamber in which the carbon and coke like accumulations resulting from the reaction of the oil collect. My process specifically contemplates an improvement in a continuous process of this general character. In such processes the accumulations of so-called coke contain a high percentage of oils which it is desirable to recover. Various methods have been devised for treating the coke like residue 'from a cracking process but these methods are directed to the treatment of the residue subsequentIto the cracking operation. My invention contemplates the treatment of the coke like residue as a step in the continuous cracking process. I have found that substantial quantities of the materials other than carbon contained in the coke like residue can be dissolved therefrom by the employment of a. suitable solvent oil. Accordingly in my process I introduce into the accumulating mass of coke like residue quantities of reiux condensate separated from the vapors in the cracking process,'such reflux condensate functioning as a solvent oil for dissolving the materials other than carbon in the coke like residue.

My invention will be more clearly understood from the following description which,

of the charging oil can be passed through the line 7 and conveyed through the closed conduit 9 in heat interchange relation with vapors undergoing dephlegmation in the primary dephlegmator D, the oil thence flowing through the line 10 to the heating coil A. The charging oil is given its cracking heat While flowing through the heating coil A and is thence delivered by Way of the line 11 controlled by the valve 12 to the reactionL and mixing chamber B. 'It is to be noted that no vapors .are taken off from the reaction and mixing chamber B for dephelgmation. The oil is adapted to pass from the chamber B through any one of the lines 13 controlled by the valves 14 into the separating chamber C. The vaporized constituents of the oil leave the chamber C through the line 15 controlled by the valve 16 and are conveyed to the primary dephlegmator D wherein portions of the insuliiciently cracked vapors are condensed forming reflux condensate. The vapors uncondensed in the primary dephlegmator D pass to the secondary dephlegmatorE through the line 17 controlled by the valve 18. It is to be understood that the several valves l2, 13, 16 and 18 may all be employed for the purpose of regulating the pressure conditions maintained in the several elements of the apparatus.l The dephlegmated vapors issuing from the secondary dephlegmator E pass through the line 19 controlled by the valve 20 to a suitable condenser F from which the condensatellows throughV the line 21 controlled by the valve 22 into the receiver G which is 4of conventional form being provided with the valve controlled distillate draw-olf line 23 and like'residue. Accordingly I return this re- -the reflux condensate separated from the lvapors in. thedephlegmator D may be returned through the line 25, valve 26, pump 27 and valve`28 to the raw oil charging line 3. or by suitably regulating the valves 26, 28 and 29. This refiux condensate may b`e permitted to flow by gravity through the bypass vv30 into the charging line 3 to be fed 'with the charging oil through the heating coil for further cracking.-

The less refractory reflux condensate collecting in the dephlegmator D constitutes a very good solvent oil for treating the coke flux condensate from the dephlegmator D through the line 31, valve 32, pump 33, valve 34 and line 37 into the reaction and mixing chamber B, wherein the coke like residue accumulates, through any one of the lines 38 controlled by the valves 39 depending upon the uantity of material in the chamber B. The y-pass on the line 36 in which is positioned a valve 35 is provided for by-passing the pump 33. In order that the reflux condensate returned to the body of material in the reaction chamber B will not retard cracking by lowering the temperature of material therein, I- provide for heating the reflux condensate from the dephlegmator D prior to its introduction to the chamber B. To this end a line 43 controlled by a valve 42 communicates with the line 37 and may be employed for conveying the reflux condensate to the reflux heating coil H positioned in the cracking'furnaoe from which the heated reflux condensate is conveyed through the line 44 controlled by the valve 41 back to the yline 37. It is to be noted that by suitably controlling the valves 40, 41 and42 the reflux condensate can be either passed through the heating coil H or introduced directly into the chamber B.

The hot relux condensate introduced to the chamber B functions to dissolve substantial quantities'of thecoke like precipitate colleeted in this chamberand the dissolved constituent/s of the oil together with the reflux condensate pass to the separating chamber C leaving only a small volume of a substantially carbon'like residue in the chamber B. Substantial vaporization takes place in thek chamber C and vapors are taken off from this chamber for dephlegmation, as above described. The unvaporized oil collecting in the chamber C is of a very different character than the liquid residue accumulating in the reaction zone of the usual continuous cracking process in that' it contains substantially no carbon. This residue can therefore` be successfully retreated in the heating zone of @5 the cracking process. I therefore provide for from the vapors to the oil passing drawingof unvaporized oil from the chamber C through any one of the lines 45 controlled by the valves 46, and this unvaporized oil may be returned to the heating coil by way of the line 47, pump 48, and valves 49 and 50. In some operations or inthe treatment of exceedingly refractory oils it may not be desirable to return this oil to the heating zone in which event the same can be passed to anyv suitable storage through the line 51 controlled by the valve 52.

The process is exceedingly flexible and capable of various modifications. I have, however, found that good results can 'be obtained primary dephlegmator D at a temperaturev of substantially 550 F. while taking oE/only end point gasoline, i. e. 437 F. from the top of the secondary dephlegmator E, and during the operation maintaining a uniform pressure of substantially 135 pounds per square inch. It must be appreciated that I do not limit myself to these particular conditions of operation since they may vary widely in the treatment of various oils. It furthermore may be advantageous to maintain lower pressures on the dephlegmators than is maintained inthe heating coil A and fr chambers B and C. It may also be desirable in some operations to lower the pressure in the chamber C somewhat lower than the pres-l sure maintained in the chamber B. By properly controlling the various lvalves shown such conditions can be maintained.

Since the rate of coke formation is largely dependent upon' the oil treated,I no specific data is here given as tothe quantity of coke.

formation. It has, however, been found that by employing a solvent oil in-treating the coke like residue in the processV the coke production can be lowered to form 1/2 to 1,41

the normal production. From the foregoing it will be seen that my process contem lates the inclusion vin the continuous crac ing process of steps which materially reduce the coke formation and which thereby increase the efliciency of the cracking process.

Having thus described my invention, what I claim is:

1. A process 60xcracking hydrocarbon oil comprising initially subjecting the oil to a crac ing temperature, thence passing the oil through a reaction zone wherein a time period of reaction is allowed without increase in temperature of the oil, in passing the oil from the reaction zone to a separating chamber maintained under a lower pressure than the pressure in the reaction zone, takingof vapors from said separating chamber, subjecting such vapors to reiux condensation and in returning reflux condensate se aratel the reaction chamber without previously commingling with the oil being treated in the process, controlling the temperature of the reflux condensate returned to the oil in the reaction zone by separately heating predetermined portions of the returned reflux condensate prior to introduction thereof to the reaction zone.

2. A process for converting high boiling point hydrocarbon oils into lower boiling point hydrocarbons comprising initially subjecting the oil to a cracking temperature,v

thereafter maintaining the oil under cracking conditions in a reaction zone, passing the oil from the reaction zone to a separating zone maintained under a lower pressure than the pressure in said reaction zone Wherein substantial vaporization occurs, subjecting the vapors to reiux condensation, uniting the less refractory portion of the reflux condensate with the oil in said reaction zone, and controlling the temperature of the reflux condensate returned to the oil in the reaction zone by separately heating predetermined portions of the returned reflux condensate prior to introduction thereof to the reaction zone.

3. A hydrocarbon oil cracking process which comprises subjecting the oil to cracking conditions of temperature and pressure While passing thru a heating zone, discharging the heated oil into a reaction zone maintained under conversion conditions and effecting a separation of vapors from unvaporized oil, subjecting the separated vapors to primary and secondary dephlegmation, introducing charging oil for the process into direct contact with the vapors undergoing secondary dephlegmation, passing another portion of charging oil for the process in indirect lieat exchange relation with the vapors undergoing primary dephlegmation, passing the commingled chargin oil'and reiux condensate from the secondary dephlegmation to said heating zone to be subjected to cracking conditions of temperature and pressure therein, independently heating reflux condensate produced by said primary dephlegmation and introducing the sametosaid reaction zone, and condensing the vapors uncondensed by said secondary dephlegmation.

JOSEPH G. ALTHER.

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