US2198557A - Cracking hydrocarbon oils - Google Patents

Description

April 23, 1940 l.. DE FLoRL-:z ET AL CRACKING HYDROCARBON OILS Filed ASepc. l5, 1956 E. QRS @SLC G Patented Apr. 23, 1940 UNITED s'rA'rss n N massi 2,198,557 CRACKING HYDRCARBON OILS Luis de Florez, Pornfret, Conn., Frank L. Herle, Warren, Pa., and Joel H. Hirsch, New York, N. Y.,assignors to De Flcrez Engineering Co., Inc., .Hartford, Conn., a corporation of Connecticut Application september 13, 1938, serial No. 229,662 4 claims. o1`.i9c-49) 'Ihis invention relates to a method' of treatingv hydrocarbon oils for the production of low boiling products, such as gasoline or motor fuel, and contemplates a process in which a lighter condensate is` subjected to cracking in a cracking zone and a portion of the resultant cracked products directed into a separating zone for separation into vapors and liquid residue, in which the separated vapors are fractionated to separate the desired gasoline or motor fuel distillate from higher boiling constituents, with the cycling of a'lighter fraction of such constituents tothe cracking zone mentioned and the passage of a heavier fraction thereof to a separate cracking zone, in which the products from the second cracking zone are separated 'into' vapors `and liquid residue in a second separating zone, in

which the liquid residue from both separating' zones is subjected to auto-distillation underrejected to coking by being passed into a coking zone and reduced to coke by means of a portion of the hot cracked products produced in the cracking of the lighter condensate.

The invention further contemplates a process in which lighter and heavier stocks are subjected to cracking in separate cracking zones and resultant cracked products separately distilled and in which heavier reiiux condensate obtained 'in fractionating the vapors from the lightoil cracking operation is directed into the fractionating zone of the vapors from the heavy oil cracking operation While a lighter fraction obtained in the fractionation of the vapors from thev heavy oil cracking operation is directed into the fractionating zone of the vapors from the light oil cracking operation. Thus the vvapors separated from the light oil cracking operation may be fractionated to form a heavy condensate, an inter mediate condensate and a gasoline or motor fuel distillate product, the intermediate condensate cycled to the light oil cracking zone, the heavy condensate directed into -the fractionating zone for the vapors of the heavy oil` cracking zone for vaporization and fractionation therein, the vapors `fractionated in the second fractionating zone to form a heavycondensate which is cycled to the second or heavy oil cracking zone anda' lighter fraction, which may include intermediate constituents adapted for cracking as Well as gasoline constituents, and this lighter fraction is directed to the first fractionating zone for fractionation therein so that constituents thereof may Y constituents may enter into the gasoline distillate taken off the rst fractionating zone. The

invention further contemplates that the vapors ink the second fractionating Zone may be fractionated to form a heavy or primary condensate which is cycled to the second cracking zone,l an intermediate fraction Which is directed into the iirst fractionating zone Vfor vaporization and fractionation therein and a lighter product comprising the desired gasoline or motor fuel 'distillate which is separately collected.

An important feature of the invention involves the introduction of a heavy charging stock, such rasv crude petroleum or topped or reduced crude, into the separator which receives cracked products of the light oil or higher temperature cracking Zone so that constituents adapted for cracking may bevaporized from the crude orresidue and the crude residual stock combined with residual material formed in the cracking, the flashing of thecombined crude residuum stock and cracked residue'to remove such portion of volatilizable materials as may be removed bythe auto-distillation andthe coking of the resultant iiashed residue which is accomplished by diverting into the coking Zone a portion of the cracked products from the light oil fraction cracking coil. By introducing the crude oil stock initially into a high temperature evaporator a large portion of vaporizable constituents may be removed therefrom by the heat ofthe cracked products and passed over into the` fractionating l zone in which fractions are lcollected for cracking and the resultant crude residuum produced may be removed before the residual constituents have been subjected to extensive cracking. The efviect of the operation is to dilute the cracked rescracking operations on cycle stocks, yields on coking relatively large proportions of gas as compared to gasoline and crackable stock, While a virgin residualfstock gives on coking a much rlower yield oi gas per volume of gasoline and c'rackable stock producedand furthermore the gas oil produced incoking virgin stocks is much less refractory than that'produced in the coking of highly cracked tarsr. The invention thus provides an advantageous method of ob-taining maximum yields of good i. crackable stock from an original crude petroleum or crude residuum charging stock in 'an operation in which the cracked residual constituents are also ultimately reduced to coke.

from the light oil cracking coil. The crackable fractions obtained inthe ashing and coking operations are combined with the other stocks being cracked so that the original charge of crude oil or crude residuum may b-e processed to ultimate yields.

For the lpurpose of more fully disclosing ythe invention, reference will now be had to the accompanying drawing which isa flow diagram representing a typical operation contemplated by the invention.

Referring ,tothe drawing, the lighter stock is subjected tov cracking in. the cracking coil Il] mounted in'a furnace II adapted for supplying the necessary heat. A transfer line I2 serves to conduct cracked products to a separator I3 provided with a fractionating section l from which uncondensed vapors pass through vapor line I5 to a fractionating tower IG provided with suitable bubble trays Vor the like for efficient fractionation.

The overhead vapors from tower I6 passto a condenser I 'l and the distillate is collected in a receiving drum or gas separator IB. Reflux condensate from tower It is directed by pump I9 through discharge line 2i! to the cracking coil III.'

The heavier vstock is subjected to crackingin a heating coil 2i mounted in a furnace 22 adapted for supplying the necessary'heat and the cracked products are discharged into a separator 23 for separation into vapors and'liquid residue. The separator tower 23 is preferably provided with a section 2d having bafflesv or trays to provide for liquid-vapor contact. The overhead vapors from tower 23 pass through vapor line 25 to a fractionating tower25 provided with suitable bubble trays'or thelike for eicient fractionation and formed with a trapout tray 26a for the collection of an intermediate condensate. The overhead vapors from tower 2S pass to a condenser coil 2I which discharges-into'a distillate receiver or gas separator 2t.. Reiiux condensate from the bottom of tower 2t is conducted by pump 29 through line 353 to the cracking coil 2|.

' Primary or heavy condensate produced in fractionating section I of tower I3 which collects on a trapout tray 3l', is withdrawn through line 32 and directed by pump '33 through line 3N having branches 35 and 35 by which the condensate may be directedtoeither or both of the vtowers 23 and 23, respectively. The lighter or intermediate condensate collected on trapout tray 26a of tower 26 is' directed by the pump 3'I through line 33 to the tower I6.

Residue from separator I 3 is conducted I through line 39 and residue. from separator 23- is conducted through line lic. 'Ihe lines 3S and til extend to a common tar line 4l by which the residues are discharged into a flash .drum 42 whereinl the residues are flashed under reduced pressure into vapors and liquid residue. l

The resultant flashed residue passes through line G73 to a coking drum 44. A line -45 extends from the transfer line I2 to the coke drum 44, or to the transfer line 43, for introducing a portion of the hot stream from the cracking coil I0 into the coking drum 44 to accomplishthe coking of the flashed residue introduced thereinto.

A common fractionating tower 5 receives vapors through vapor line 'I from the flash drum and vapors through vapor line 48 from the coking drum. Refiux condensate is drawn from tower i6 by pump 49 and directed through line 53 to line 3@ for passage through either or bothy yof lines 35 and 36 into towers 23 and 25, respectively. The overhead vapors from tower pass through a cooling coil 5I in heat exchange with a heat exchange element 52 thence to a second cooling and condensing coil 53 discharging into a dis tillate receiver or'gas separator 54. p

Charging stock for the process is introduced by a pump 55 through a line 56 to heat exchange element 52 and thence through line 5'! into separator tower I3. The charging stock is introduced into the tower .below trapout tray 3l and preferably flows over baies or trays 58 counter-curvrent to the separated vapors rising therein.'

In practicing the invention with the apparat-us illustrated, a charging stock, such as crude petroleum. or topped or reduced crude,is introduced by pump 55 and after being, preheated in the eX- changer 52, and additionally. preheated if desired, is directed into the evaporator i3 in which itis subjected to extensive vaporization by being contacted with hot products of cracking from the heating coil IG. Moderate superatmospheric pressures of the Aorder of 100 to 200 pounds are maintained in the evaporator i3.- The separated vapors including vaporized constituents of the charging stock and of the cracked products from cracking coil I0 are subjected to fractionation tc form a primary or heavy condensate at 3l, an

' condensate should be a substantially vaporizable stock having an endpoint of the order of 650 F. so lthat it may be well adapted for vapor phase cracking at relatively high cracking temperatures and with high rates of cracking per pass in the coil `II? so as to not only effect conversion into gasoline constituents of high anti-knock quality but also to provide a high degree of heat which is utilized both for the initial distilling of the charging stock in evaporator I3 and also to accomplish the coking in the lfinal coking step of the process. The heavier or primary condensate from trapout tray 3l and-the reflux condensate condensed in tower 46 fromy the vapors ofthe The oil in coil 2l ordinarily subjected coking operation, heavy constituents lof a tarry or coke-like nature may be carried over with the 'vapors and consequently it is advisable to re-dis- If desired,r I

orator I3 consisting of unvaporized constituents of the charging stock and residual constituents from the cracked products introduced iromcoil IIJ may, in accordance with the invention, be withdrawn from the evaporator at such a rate as to prevent the accumulation of liquid residue therein or so as to maintain only a low level of liquid therein, to thereby prevent the residual constituents of the charging stock from extensive cracking. This composite residue and the cracked residue from tower 23 are introduced into the fi'ash drum 42 wherein the pressure is reduced to a degree approaching or approximating atmospheric pressure and the residue ash distilled, with the aid of steam` or other carrier gas if desired. The resultant flashed residue is directed through line 43 into the coking drum 44 wherein the pressure may be further reduced, if desired. A portion of the cracked stream from the light oil or high temperature cracking coil I0 is diverted through line 45 into the flashed residue from the flashing drum to thereby raise the temperature of the iiashed residue and effect conversion of the coke. Usually about 20%-40% of the stream. from the cracking coil is adequate to accomplish the coking of the ashed residue.

ln a typical example of' the invention, a fuel oil (crude residuum) of 20 A. P. I. gravity is charged at the rate of 100 barrels per hour through heat exchanger 52 thence into the evaporator I3 which is maintained at 110 pounds pressure with a bottom temperature of 800 F., with a temperature of '725 F. adjacent the tray 3| and with a temperature of 700 F. at the top of the tower. The tower I6 is maintained at 100 pounds pressure with a temperature of 600 F. at the bottom. Cycle condensate at the rate of 200 barrels per hour from tower I6 is directed to heating coil I0 which is maintained under 500 pounds pressure with 1000 F. outlet temperature. The cracked stream from the cracking coil is split with 130 barrels per hour going to the evaporator I3 and '70 barrels per hour going to the coking drum 44. Cycle condensate at the rate of 100 barrels per hour is drawn from tower 26 and subjected to cracking in heating coil ZI'under 500 pounds pressure with an outlet temperature of 900 F. The tower 23 is held at 110 pounds pressure with a bottom temperature of 800 F. and a top temperature of 125 F. The tower 26 is maintained at 100 pounds pressure with a bottom temperature of 650 F. Reflux condensate from tower 46 and'reux condensate from tray 3l of tower I3 is refiuxed in the fractionating section 24 of tower 23. The fi'ash drum has a bottom temperature of 700 F. under 30 pounds pressure. The flashed residue is passed from the flash drum to the coking drum into which, as stated, cracked products from coil I0 are delivered at the rate of 70 barrels per hour which operate to raise the flashed residue to a temperature approximating 900 F. and eifect the coking thereof. The distillate collecting in receiving drum 54 is reiiuxed in the tower I6. Gasoline distillates are collected in receiving drums I8 and 28 amounting to a total yield of 59 barrels per hour.

While we have described a particular embodiment of our invention for the purpose of illustration, it should be understood that various modincations and adaptations thereof, occurring to one skilled in the art, may be made within the spirit of the invention as set forth in the appended claims.

We claim:

1. In a process for cracking hydrocarbon oil,

the method that comprises subjecting cycle condensate to cracking conditions of temperature and pressure in a cracking Zone to effect conversion into lower boiling hydrocarbons, removing the resultant cracked products from the cracking Zone in a stream, splitting the stream and def livering a portion thereof into a separating zone maintained under superatmospheric pressure wherein separation of vapors from liquid residue takes place, fractionating the separated vapors in a fractionating zone to form heavy reflux condensate, an intermediate reiiux condensate and a lighter condensate, directing resultant intermediate condensate to said crackingl zone as the cycle condensate subjected to cracking therein, directing resultant heavy reux condensate into a second ractionating zone wherein it is subjected to vaporization and fractionation, subjecting the vapors in said second fractionating zone to fractionation to form a heavy reflux condensate and a lighter reflux condensate, cycling resultant heavy reflux condensate to a second cracking zone wherein it is subjected to cracking conditions of temperature and pressure to effect conversion into lower boiling hydrocarbons, passing the resultant cracked products into a second separating Zone maintained under superatmospheric pressure wherein separation of vapors from liquid residue takes place, passing resultant separated vapors to the second fractionating zone', directing lighter reflux condensate from the second fractionating zone into the iirst fractionating Zone for vaporization and fractionation therein, withdrawing residue fromv the first andr second separating zones and subjecting the residue to hash distillation under reduced pressure to form a flashed residue, passing resultant flashed residue into a coking zone, and introducing the other portion of the stream of cracked products from the first cracking zone into said coking Zone to raise the temperature of the flashed residue introduced thereinto and effect a reduction of the ashed residue to coke.

. 2. The process of cracking hydrocarbon oil that comprises subjecting cycle condensate to cracking conditions of temperature and pressure in a cracking zone to effect conversion into lower boiling hydrocarbons, removing the resultant cracked products from the cracking zone in a stream, splitting the stream and delivering a portion thereof into a separating Zone maintained under superatmospheric pressure wherein separation of vapors from liquid residue takes place, introducing charging stock into said separating zone wherein it is subjected to vaporization to separate it into vapors and residue, passing the separated vapors from said separating zone to a fractionating zone wherein the vapors are fractionated to form a heavy reflux condensate, an intermediate reflux condensate and a lighter condensate, directing resultant intermediate condensate to said cracking Zone as the cycle condensate subjected to cracking therein, directing resultant heavy reflux condensate into a second fractionating Zone wherein it is subjected to vaporization and fractionation, subjecting the vapors in said second fractionating zone to fractionation to form a heavy reflux condensate and a lighter reiiux condensate, cycling resultant heavy reflux condensate to a second cracking Zone wherein it is subjected to cracking conditions of temperature and pressure to effect conversion into lower boiling hydrocarbons, passing the resultant cracked products into a second separating zone maintained under superatmospheric pressure wherein separation of vapors from liquid residue takes place, passing resultant separated vapors to the vsecond fractionating zone, directing lighter reflux condensate from the second fractionating Zone into the rst fractionating zone for vapori- Zation and fractionation therein, withdrawing residue from the rst separating zone comprising residual constituents of the charging stock and cracked products and withdrawing residue from the second separating zone, subjecting the residues thus Withdrawn to flash distillation under reduced pressure to form a ashed residue, passing resultant flashed residue into a coking Zone, and introducing the other portion of the stream of cracked products from the iirst cracking Zone into said coking zone to raise the temperature of the flashed residue introduced thereinto and eliect a reduction of the flashed residue to coke.

3. lThe process of cracking hydrocarbon oil that comprises sub-jecting cycle condensate to cracking conditions of temperature and pressure in a cracking zone to effect conversion into lower boiling hydrocarbons, removing the resultant cracked products from the cracking zone in a stream, splitting the stream and delivering a portion thereof into a separating Zone maintained under superatmospheric pressure wherein separation of vapors from liquid residue takes place, introducing charging stock into said separating Zone wherein itis subjected to vaporization to separate it into vapors and residue, passing the separated vapors from said separating Zone to a fractionating zone wherein the vaporsare fractionated to forma heavy reux condensate, an intermediate relux condensate and a lighter condensate, directing resultant intermediate condensate to said cracking zone as the cycle condensate subjected to cracking therein, directing resultant heavy refluxA condensate into a second fractionatingzone wherein it is subjected to vaporization and fractionation, subjecting the vapors in said second fractionating zone to fractionation to form a heavy reflux condensate and a lighter reux condensate, cycling resultant heavy reflux condensate to a second cracking zone wherein it is subjected to cracking conditions of temperature andpressure to eiect conversion into lower boiling hydrocarbons, passing the resultant cracked products into a second separating Zone maintained under superatmospheric pressure wherein separation of vapors from liquid residue takes place, passing resultant separated vapors to the second fractionating Zone, directing lighter reuX condensate from the second fractionating Zone into the rst fractionating zone for vaporization and fractionation therein, withdrawing residue from the first separating zone comprising residual constituents of the charging stock and cracked products and withdrawing residue from` the second separating zone, subjecting the residues thus withdrawn to ashing under reduced pressure to form dashed residue and separated vapors, passing resultant ashed residue into a coking zone, introducing the other portion of the stream' of cracked products from the rst cracking zone into said coking Zone to raise the temperature of the flashed residue intr'oduced thereinto and eiect a reduction of the flashed residue to coke, subjecting the resultant vapors from the flashing and coking steps to condensation to form a condensate and introducing said condensate into said second fractionating Zone.

4. The process of cracking hydrocarbon oil that comprises subjecting cycle condensate to cracking-conditions of temperature and pressure in a cracking zone to effect conversion into lower boiling hydrocarbons, removing the resultant cracked products from the cracking zone in a stream, splitting the stream and delivering a portion thereof into a separating zone maintained under superatmospheric pressure wherein separation of vapors from liquid residue takes place, introducing charging stock into said separating zone wherein it is subjected to vaporization to separate it into vapors and residue, passing the separated vapors from said separating zone to a fractionating zone wherein the vapors are fractionated to. form, a heavy reux condensate, an intermediate reliux condensate and a lighter condensate, directing resultant intermediate condensate to said cracking Zone as the cycle condensate subjected to cracking therein, directing resultant heavy reflux condensate into a second fractionating zone wherein it is subjected to vaporization and fractionation, subjecting the vapors in said second fractionating zone to fractionation to form a heavy reflux condensate and a lighter reux condensate, cycling resultant heavy reflux condensate to a second cracking zone wherein it is subjected to cracking conditions of temperature andv pressure to eiect conversion into lower boiling hydrocarbons, passing the resultant cracked products into a second separating zone maintained under superatmospheric pressure wherein separation of vapors from liquid residue; takes place, passing resultant separated vapors to the second fractionating zone, directing lighter reflux condensate from the second fractionating Zone into the rst fractionating zone for vaporization and fractionation therein, withdrawing residue from the first separating zone comprising residual constituents o1' the charging stock and cracked products and withdrawing residue from the second separating zone, subjecting the residues thus withdrawn to flashing under reduced pressure to form` flashed residue and separated vapors, passing resultant ilashed residue into a coking zone, introducing the other portion of the stream of cracked prod,- ucts fromthe rst cracking zone into said coking Zone to raise the temperature of the iiashed residue introduced thereinto and elect a reduction of the flashed residue to coke, passing the evolved vapors from the coking and flashing Zones into a third fractionating zone, subjecting the vapors to fractionation therein to form a reflux condensate and a lighter distillate and directing said reilux condensate into said second fractionating zone wherein it is subjected to vaporization and fractionation'.

LUIS DE FLOREZ. FRANK L. HERLE. JOEL H. HIRSCH.

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