US2316334A - Cracking hydrocarbon oils - Google Patents

Description

'J. H. HIRSCH CRACKING HYDROCARBON OILS Filed March 25, 1941 JOEL H. l-llzscu NVENTOR ATTORNEY r v l l Hmmm mv..

April 13, 1943.

Patented Apr. 13, 1943 UNITED STATES PATENT OFFICE CRACKIN G HYDROCARBON OILS Joel H. Hirsch, Wichita, Kans., assigner to de Florez Engineering Co., Inc., Hartford, Conn., a corporation of Connecticut This invention relates to certain improvements in the cracking and coking of hydrocarbon oils.

The invention is concerned with a process in which raw charging stocks, or the residual constituents thereof, are subjected to coking, while lighter stocks, or the lighter components of the raw charging stocks, are subjected to cracking and the cracked residue is utilized for liquid fuel oil. A particular object of the invention is to provide for the distilling of the raw charging stocks in contact with the vapors from the coking and cracking operations in such manner as to produce a minimum quantity of residue for coking and the segregation of a maximum quantity of lighter or intermediate constituents for crack- 111g'.

The invention contemplates a particular association and interrelation of a pressure cracking operation, a flashing operation and a coking op'- eration. In accordance with the invention raw charging stock, such as crude petroleum or topped o1 reduced crude, is introduced into a dephlegrnator to dephlegmate vapors from both the coking and cracking operations whereby the charge is heated and subjected to vaporization and a resultant mixture of reflux condensate and unvaporized charging stock is possed into a dephlegmator of the ashing zone so that by reason of the contained heat of the mixture further vaporization and removal of lighter components may be accomplished to yield a higher boiling mixture of heavy condensate and residue and this mixture is combined with heated cycle condensate for coking in the coking zone. The vapors from the flash dephlegmator are further fractionated to produce a redux condensate which is cycled to the pressure cracking operation.

For the purpose of more fully disclosing the invention reference is had to the accompanying drawing which is a diagrammatic flow diagram illustrative of apparatus adapted for the practice of the invention.

The apparatus illustrated includes a furnaceheated coil A discharging into a reaction zone B, a flash tower C, a furnace-heated coil D discharging into a coking chamber E, a primary fractionating tower F and a secondary fractionating tower G. The raw charging stock, such as crude petroleum or topped or reduced crude, is introduced by a pump I through a charging line II in which line may be interposed heat exchange elements I2 and I3 and through which line the charging stock is introduced into the tower F to dephlegmate the vapors therein. The tower F receives vapors from the coking drum E through vapor line I4 and the tower is advantageously provided with a trapout tray I5 above the entrance of the line I4 so as to provide a primary dephlegmating zone I6 in which the vapors from the coking operation are initially dephlegmated to form a heavy tarry condensate removed through line Il. The dephlegmated vapors pass upwardly in the tower and are further dephlegmated with the charging stock to form a resultant mixture of reflux condensate and unvaporized charge which collects on tray I5. Vapors uncondensed in the tower F pass through vapor line I8 to the secondary tower G wherein further fractionation occurs to separate a reux condensate which is withdrawn by a pump I9 and directed through a line 20 to the heating coil D. Vapors uncondensed in the tower G pass through a condenser 2| thence to a distillate receiver or gas separator 22.

The mixture of reflux condensate and unvaporized residue collecting on tray I5 is conducted through a line 23, having a pressure reducing valve 24, to a dephlegmating section of the flash tower C. The Hash tower is provided with a primary separating section 25 which receives residue from the reaction chamber B through a line 26 and pressure reducing Valve 21 and wherein separation of vapors from liquid residue takes place. The liquid residue is withdrawn through a line 25a. The tower C is provided with trapout trays 28 and 29 producing an intermediate fractionating or dephlegmating section 30 and an upper fractionating or dephlegmating section 3|. The line 23 discharges the mixture of redux condensate and residue withdrawn from the tower F to the intermediate dephlegmating section 30 and due to the drop in pressure this mixture is subjected to stripping in section 30. The resultant stripped mixture of heavy reflux condensate and residue is withdrawn through a line 32 and directed by a pump 33 through line 34 to the transfer line from the heater D so as to combine the mixture with the heated products passing from the heater and accomplish conversion to coke in the coking drum E. The line I1 may be provided with a branch line 35 and pump 36 for conducting the heavy tarry condensate to the coking zones when it is desired to coke such condensate; it is normally preferable, however, to withdraw the tarry condensate and utilize it as fuel oil. Normally, a plurality of coking chambers E are ernployed so that while one or more of the chambers are on the line, others may be down for the re- "lcanti itesm moval of the coke and thus the continuity of the complete process maintained.

Vapors uncondensed in the dephlemating section 30 pass to the final fractionating section 3I wherein fractionation takes place to produce a reflux condensate collecting on the tray 29.

This condensate normally consists of constituents produced in the flashing operation and constituents produced in the revaporization of the mixture of condensate and residue introduced to the tower C from the tower F. This condensate is directed by a pump 31 through line 38 to the heater A wherein the oil is heated to a cracking temperature. The heated oil passes through a transfer line 39 to the reaction chamber B in which cracking conditions of temperature and pressure are maintained. Separation oi vapors from liquid residue takes place in the chamber B, a liquid residue passing through line 26 and pressure reducing valve 21 to the ash tower C, as stated, and the separated vapors being removed through a line 40 provided with a branch line 4I leading to the dephlegmating section I6 of tower F and with a branch line 42 entering the tower F at a point above the trapout tray I5. In some cases when both the vapors from the coking drum E and reaction chamber B are introduced to the dephlegmating section I6 there is a tendency toward coke formation therein due to the high concentration of high temperature vapors and it is accordingly advantageous to introduce the vapors from the react-ion chamber B above the tray I and to dephlegmate the coke still vapors prior to combining with the vapors from the reaction chamber.

It is advantageous to utilize a minimum of the products from the heating coil D for accomplishing coking and in accordance with the invention a portion of the stream from the heating coil D which is suiicient to accomplish the coking of the residual constituents is passed to the coking chamber E and the remainder of the stream is directed through a line 43 to the reaction zone B wherein the conditions are better suited for conversion into high antiknock gasoline than in the coking drum. In another modication of the invention a portion of the reilux condensate passing through line 20 is diverted through a line 44 to the heating coil A. This f feature of diverting a portion of the condensate from the tower G, either before heating or after heating in the coil D, to the coil A increases the flexibility of the process and enables the utilization of the minimum quantity of condensate necessary for coking while providing for the cracking of the portion not used for coking under conditions of higher cracking per pass.

Vapors uncondensed in the final fractionating section 3I of the flash tower C pass overhead through an exchanger 45 for cooling in contact with raw charging stock and the distillate is collected in a distillate receiver or gas separator 46. This distillate is normally withdrawn by a pump 41 and such portion as may be needed for cooling and refluxing in the tower C may be directed through a line 48, while the remainder is passed through a line 49 and directed into the tower G for refluxing and refractionation therein. Normally, the entire gasoline or naphtha distillate product of the complete process is collected in the receiving drum 22. A relatively small amount of reux condensate from the tower G may be conducted by a pump 50 to a cooling element 5| in heat exchange with element I3 and diiected thence through a line 52 to the dephlegmating section I6 of tower F to prevent coking therein.

In practicing the invention the oil is heated in the heater A to cracking temperatures of the order of 900 F. or 1000 F. and cracking is carried on in the reaction zone B under temperatures preferably in excess of 850 F. superatmospheric pressures of the order of 200 to 600 lbs. 'Ihe liquid residue should be rapidly withdrawn so as to prevent the accumulation of residue therein and enable the maintenance of high temperature conditions to high rates of cracking per pass and a resultant conversion into gasoline constituents of high antiknock quality. 'I'he oil stream in the heater Dis heated to temperatures of the order of 900 F. or 1000 F. and the coking chamber is maintained at a moderate superatmospheric pressure such as about 50 to 100 lbs. with temperatures of the order of 825 F. to 880 F. The residue from reaction chamber B is :dash distilled under a relatively low pressure such as 30 lbs. or even down to approximately atmospheric pressure. While the pressure in the tower F may be reduced somewhat from the pressure in the coking drum E it is desirable to maintain the pressure in the tower F considerably in excess of that of the ash tower C so that the charging stock may receive a high degree of heat in the tower F under a pressure materially higher than that of the ash tower with the result that upon the discharge of the mixture of reflux condensate and residue, withdrawn from tray I5 to the flash tower, the contained heat in the mixture will function to produce additional vaporization under the reduced pressure in the flash tower. In an example of the invention a topped crude is charged to the dephlegmator F and a portion of the gas oil components in the crude residue is distilled over to the tower G for recycling to the heating coil D together with gas oil constituents produced in the coking operation. 'I'he vapors from the coking drum pass to the dephlegmating section IE at a temperature of 880 F. The mixture of reflux condensate and residue collects on the tray I5 in the tower F at a temperature of 790 F. with lbs. pressure in the tower. This mixture is expanded into the flash dephlegmator 30 wherein a pressure of 30 lbs. is maintained and additional gas oil constituents are volatilized from the mixture. A resultant mixture of heavy reflux condensate and residue is withdrawn from the tray 28 at a temperature of '760 F. and combined with the stream leaving the heater D at a temperature of 1040 F. approximately 40% of the stream from heater D being diverted to the reaction chamber B. The oil in the heater A is heated to a temperature of 1020 F. and the reaction chamber B is maintained at a temperature of 920 F. under 400 lbs. pressure. Fuel oil products are withdrawn from the flash zone 25 and from the primary dephlegmating zone I6 and the naphtha distillate is collected in receiv- 4ing drum 22.

While I have described a particular embodiment of my invention for purposes of illustration, it should be understood that various modifications and adaptations thereof which will be obvious to one skilled in the art, may be made within the spirit of the invention as set forth in the appended claims.

I claim:

1.In the conversion of hydrocarbon oils the process that comprises passing condensate oil through a heating coil wherein the oil is heated to a cracking temperature, combining the heated oil with residual constituents of crude petroleum and subjecting the mixture to coking in a coking zone, passing condensate oil through a second heating coil wherein the oil is heated to a cracking temperature, delivering the resultant heated products into a reaction zone wherein cracking conditions of temperature and pressure are maintained and wherein separation of vapors from liquid residue takes place, combining resultant separated vapors with vapors evolved from the coking zone and subjecting the admixed vapors to dephlegmation in a dephlegmating zone, subjecting the dephlegmated vapors to fractionation to form a reux coni densate, directing resultant reflux condensate to the rst named heating coil, passing liquid residue from said reaction zone to a flashing Zone wherein vapors are separated from residue, passing the latter separated vapors to a primary dephlegmating zone, withdrawing a resultant reflux condensate from the aforesaid dephlegmating zone and directing it into said primary dephlegmating zone to subject it to vaporization, subjecting vapors from said primary dephlegmating zone to further fractionation to form a reflux condensate and directing the latter reflux condensate to the second heating coil.

2. In the conversion of hydrocarbon oils the process that comprises subjecting vapors evolved in a coking operation to dephlegmation in a dephlegmating zone with crude oil residual stock, subjecting the dephlegmated vapors to fractionation to form a reflux condensate, passing said reilux condensate to a heating coil wherein the oil is heated to a cracking temperature, passing a resultant mixture of reflux condensate and unvaporized resid-ual stock from said dephlegmating zone to a ash dephlegmating zone wherein the mixture is subjected to stripping, combining the resultant stripped mixture With heated products from said heating coil and subjecting the admixed products to coking in a coking zone, passing evolved vapors from the coking zone to the aforesaid dephlegmating zone, subjecting vapors frorn said flash dephlegmating zone to fractionation to form a reflux condensate, directing the latter reflux condensate to a cracking zone wherein the oil is subjected to cracking conditions of temperature and pressure, separating resultant cracked products into vapors and liquid residue, passing the separated vapors to said dephlegmating zone, flashing said liquid residue and passing resultant flashed vapors to said ash dephlegmating zone.

3. In the conversion of hydrocarbon oils the process that comprises subjecting admixed oils as hereinafter specified to coking in a coking zone, subjecting the evolved vapors to primary dephlegmation to form a tarry condensate, passing the dephlegmated vapors to a secondary dephlegmating zone, introducing crude oil residual stock into the secondary dephlegmating zone to dephlegmate the vapors therein, subjecting the dephlegmated vapors to further fractionation to form a reflux condensate, passing the reflux condensate to a heating coil wherein the oil is heated to a cracking temperature, passing a resultant mixture of reflux condensate and unvaporized residual stock from the secondary dephlegmating zone to a ash dephlegmating zone wherein the mixture is subjected to stripping under reduced pressure, combining the re- Search sultant stripped mixture with heated products from said heating coil and subjecting the admixed products to coking in said coking zone, passing evolved vapors from the coking zone to said primary dephlegmating zone, subjecting vapors from said flash dephlegmating zone to fractionation to form a reflux condensate, diresting the latter reflux condensate to a cracking zone wherein the oil is subjected to cracking conditions of temperature and pressure, separating resultant cracked products into vapors and liquid residue, passing the separated vapors to said secondary dephlegmating zone, flashing said liquid residue and passing resultant flashed vapors to said flash dephlegmating zone.

4. In the conversion of hydrocarbon oils the process that comprises subjecting vapors evolved in a coking operation to dephlegmation in Ya dephlegmating zone with crude oil residual stock, subjecting the dephlegmated vapors to fractionation to form a reflux condensate, passing said reux condensate to a heating coil wherein the oil is heated to a cracking temperatures, passing a resultant mixture of reflux condensate and unvaporized residual stock from said dephlegmati'ng zone to a flash dephlegmating zone wherein the mixture is subjected to stripping, combining the resultant stripped mixture from the ilash dephlegmating zone with a portion of the heated products from said heating coil sumcient in quantity to eiect conversion to a coke residue and effecting conversion to such coke residue in a coking zone, passing evolved vapors from the coking zone to the aforesaid dephlegmating zone, subjecting vapors from said flash dephlegmating zone to fractionation to form a reflux condensate, directing the latter reflux condensate to a heating coil wherein the oil is heated to a cracking temperature, combining the resultant heated products with the remaining portion of heated products from the rst named heating coil for cracking in a reaction zone maintained under cracking conditions of temperature and pressure, separating resultant cracked products into vapors and liquid residue, passing the separated vapors to said dephlegmating zone, flashing said liquid residue and passing resultant flashed vapors to said ash dephlegmating zone.

5. In the conversion of hydrocarbon oils the process that comprises subjecting vapors evolved in a coking operation to dephlegmation in a dephlegmating zone with crude oil residual stock, subjecting the dephlegmated vapors to fractionation in a fractionating zone to form a reflux condensate, passing reflux condensate from said fractionating zone to a heating coil wherein the oil is heated to a cracking temperature, passing a resultant mixture of reflux condensate and unvaporized residual stock from said dephlegmating zone to a flash dephlegmating zone wherein the niixture is subjected to stripping, combining the resultant stripped mixture with heated products from said heating coil and subjecting the admixed products to coking in a coking zone, passing evolved vapors from the coking zone to the aforesaid dephlegmating zone, passing reflux condensate from the aforesaid fractionating Zone to a cracking zone wherein the oil is subjected to cracking conditions of temperature and pressure, separating the resultant cracked products into vapors and liquid residue, passing the separated vapors to said dephlegmating zone, directing said liquid residue to a ashing zone, passing resultant flashed vapors to said iiash dephlegmating zone, subjecting vapors from said flash dephlegmating zone to further fraction to form a reflux condensate and directing the latter reux condensate to said cracking zone.

6. In the conversion of hydrocarbon oils the process that comprises subjecting vapors evolved in a coking operation to dephlegmation in a dephlegmating zone with crude oil residual stock, subjecting the dephlegmated vapors to fractionation to form a reux condensate, passing said reux condensate to a heating coil Wheren the oil is subjected to a cracking temperature, passing a. resultant mixture of reux conmixture from the stripping, combini g the resultant stripped ash dephlegmating zone with heated products from said heating coil and subjecting the admixed products to coking in a coking zone, passing evolved vapors from the coking zone to the aforesaid dephlegmating zone, subjecting vapors from said flash dephlegmating zone to fractionation to form a reux condensate, directing the latter reux condensate to a cracking zone wherein the oil is subjected to cracking conditions of temperature and pressure, subjecting residual constituents from the latter cracldng operation to flashing and passing resultant iiashed vapors to said ash densate and unvaporized residual stock from 15 dephlegmating zone.

said dephlegmating zone to a flash dephlegmating zone wherein the mixture is subjected to JOEL H. HIRSCH.

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