US2080118A - Process for cracking petroleum oil - Google Patents

Description

. nw @WJ m May 1l, 1937. C.' P. @USBS PROCESS FOR CRACKING PETROLEUM OIL original Filed July 31, 19'22 SSI Patented May il, i937 stares attain PROCESS FOR CRACKING PETROLEUM Om Carbon P. Dubbs, Wilmette, lll., assigner, by mesne assignments, to Universal Oil Products Company, Chicago, Ill., a corporation of Deia- Wal'e Application July 31, 1922, Seria-l No. 578,705

Renewed July 11, i936 12 Claims.

This invention relates to improvements in a process and apparatus for cracking petroleum oil and refers more particularly to the conversion of higher into lower boiling point products.

Among the salient objects of the invention are to provide a process in which the oil vapors generated in an expansion or vaporizing chamber are relieved of their higher boiling point fractions in a dephlegmating zone so constructed to reduce the superheat of the vapors and separate out the higher boiling point products, and further controlling the temperatures of dephlegmation `so that a more uniform and better quality distillate passes over to the final condensing stage.

The single iigure is a diagrammatic side elevational View of the apparatus. Referring in detail to the drawing, the oil to be treated vvis introduced through the line I which has separate connections 2, 3, and 4 controlled by valves 5, 6, and E respectively, to manifolds 8, 9, and I0. The manifolds 9 and IIJ are connected to circular roses or sprays Ii and i2, While the discharge end of the manifold 8 extends through the T connection I3 and into the vapor line I4 in the through the lower manifold and into the vaporline through the perforated pipe I5 where rit is charged near the` bottom of the dephlegmator directly into the vapor line.

The oil combined with what condensate itmay separate from the vapors in the dephlegmating stage, will collect in the dephlegmator 'leg ll from which it is drawn off through the line i8 controlled by the valve I9, and directed to the heating coils 20' mounted in the furnace 2I. A

connecting pipe 22 controlled by valve 23 furnishes a means for supplying additional raw oil to the charging line, if desired. After passing through the continuous coil 20 in the furnace. the temperature of the oil has been raised to a cracking heat, and in this condition it is introduced in a fluid state to the vaporizing chamber 24. In this enlarged chamber the oil is permitted to collect, the vapors evolved passing off 0 through the vapor line I4 and the liquid unvaporized products being drawn off through the line 25 which is regulated by the valve 26. The vapors passing through the dephlegmator I6 are subjected to the reiiuxing action of the raw oil or' returned condensate which is introduced to the dephlegmator through the manifolds 8, 9 and I0 as explained. In the dephlegmating or refiuxing zone there isseparated from the oil vapors the higher boiling point fractions undesirable to the production of a low boiling point distillate.

At thebottom of the dephlegmatorleg in addition to the draw-01T line I8 is a second drawoff line 21 which is controlled by valve 28 through which a portion of the condensates separated out;` in the dephlegmator together with quantities of raw oil which it may contain, may be drawn from the dephlegmator. This oil directed through the line 2l may be passed through a cooler 29, thence through a line 30 regulated by a valve 3l to a charging pump 32 from which it is pumped through the line 33 to any one or all of the manifolds 8, 9 and III which are connected to the line 33 by secondary connections 34, 35 and 36. The amount of condensate returned in this manner to the separate manifolds may' be regulated by the valves 31,38 and 39 interposed in the secondary connections. Thus, it is obvious that in addition to the introduction of raw oil to the manifold, the condensate may be also returned and introduced in regulated quantities with the raw oil so that an accurate control may be had over the temperature conditions maintained in the dephlegmating column at all times.

The vapors which remain uncondensed in the dephlegmator pass over -through the line 40 in which is interposed a valve 4I, to the water condenser coil 42 mounted in the condenser box 43. The discharge end of the condenser coil is connected by a line- 44, regulated by a valve 45 to a distillate receiving tank 46. The tank is equipped with pressure relief valve 41, pressure gauge 48, liquid level gauge 49. A liquid drawo line 50 connected to the bottom of the tank is controlled by a valve 5I, and is connected to the suction side of a pump 52 by means of which the distillate may be charged back through the line 53 to any ofthe manifolds il, 9, or I0 through the dephlegmating or proper reuxing of the vapors so that the dephlegmator cannot eicientiy separate or sift out the higher boiling point fractions. Thus owing to the superheat or excess heat of the vapors from the reacting or Vaporizing chamber, a greater part o thel dephlegmator is used for extracting this excess heat before a substantial amount of reflux condensation can take place. For this reason, the superheat of the incoming vapors must be reduced, and this absorption of heat by the refiuxing column exhausts to a great extent the cooling capacity of the dephlegmator, thereby reducing to that extent the effectiveness of the apparatus in separating out the higher boiling point vapors. By cooling the vapors sumciently before orjust after they enter the dephlegmator a much more satisfactory separation of the higher boiling point fractions may be obtained.

It has been found that by controlling the capacity of the dephlegmating stage through the introduction of cool oil in different parts of the dephlegmator, a more satisfactory separation is obtained than when an apparatus, dependent upon a radiating surface exposed to the air, for controlling the capacity of the dephlegmating stage is used.

It will be noted that by the pipe arrangement shown, it is possible to cool or extract the superheat from the vapors in the vapor line prior to their entering the dephlegmator or into the lower part of the dephlegmator. In doing this the cool oil is introduced through the perforated pipe i5, this oil consisting of the raw oil or combined feed or raw oil, returned condensate, or a combination of the raw oil, refiux condensate and pressure distillate from the receiving tank.

Further dephlegmation is obtained by introducing regulated combinations of the oils mentioned to different heights in the dephlegmator.

AIt is understood of course, that oils diier in respect to their treatment, and the control of the dephlegmation will likewise necessarily be altered with the dierent types of oil treated. By proportioning the amount of cooling in the different parts of the reuxing stage, a more satisfactory and complete control for sifting of the vapors can be obtained, and allows the capacity of a given size dephlegmator to be substantially varied, for example-assume that the vapors in the vapor line have a temperature of from 800 to 820 F., these vapors may be cooled by the introduction of a cooling oil near the bottom of the dephlegmator to temperatures ranging from 600 to 700 F., which will condense a large part of the vapors having high boiling point fractions, while the remaining vapors having high boiling point cuts are condensed and thus separated out in the dephlegmator proper by regulated amounts of cool oil supplied through the upper manifold. It will be recognized that the temperatures of the vapors entering the dephlegmator can be maintained at practically any desired degree regardless of how much higher in temperature they may be as they leave the expansion chamber.

The particular design of the. apparatus may be varied in numerous ways without departing from the principles involved.

I claim as my invention:

1. In the art of cracking hydrocarbons, the process which comprises conducting a stream of hydrocarbons through acracking zone and then into .a separating chamber, conducting vapors from said separating chamber to a reflux condenser, continually feeding charging stock aoeaiie through a portion of said reux condenser-to preheat the charging stock and cool the vapors, mixing the charging stock with the reflux condensate, transmitting the mixture through said cracking zone and then into said separating chamber, maintaining the contents of said separating chamber at a temperature high enough to crack said charging stock, and preventing material cracking of the mixture of reflux condensate and charging stock in said reflux condenser by cooling the vapors passing from said separatirm chamber to said reflux condenser.

2. A process for cracking petroleum oil consisting in raising the oil to a cracking temperature in a heating zone, vaporizing the oil in an expansion zone, passing the evolved vapors through dephlegmating and condensing zones, subjecting the vapors in their travel from the vaporizing zone to the dephlegmating zone to a cooling action by intimate contact with a cooling oil medium, comprising regulated quantities of a mixture of charging oil and distillate from the condensing zone, permitting oil and condensate to accumulate in the dephlegmating zone and returning portions of the oil and condensate from the dephlegmating zone to the heating zone for retreatment, cooling other portions of the oil and condensate andrecycling them to the dephlegmating zone, and maintaining regulated pressure on the system during treatment.

3. In the art of cracking hydrocarbons, the

' process which comprises conducting a stream of hydrocarbons through a crackingl zone and then into a separating chamber, conducting vapors from said separating chamber to a reux condenser, continually feeding charging stock through'a portion of said reflux condenser to preheat the charging stock and cool the vapors, mixing the charging stock with the reflux condensate, transmitting the mixture through said cracking zone and then into said separating chamber, maintaining the contents of said separating chamber at a temperature high enough to crack said charging stock, and preventing material cracking of the mixture of reux condensate and charging stock in said reflux condenser by cooling the vapors passing from said separating chamber to said reflux condenser, by introducing a cooling medium into direct contact with the vapors moving from the separating chamber to the reflux condenser. r

4. In the art of crackingl hydrocarbons, the process which comprises conducting a stream of hydrocarbons once only through a cracking zone and then into a separating chamber, conducting 4 vapors from said separating chamber to a reflux condenser, continually feeding charging stock through a portion of said reflux condenser to preheat the charging stock and cool the vapors, mixing the charging stock with the reflux condensate, transmitting the mixture through said cracking zone and then into said separating chamber, maintaining the contents of said sepaarating chamber at a temperature high enough t0 crack said charging stock, and preventing material cracking of the mixture of reux condensate and charging stock in said reux condenser by cooling the vapors passing from said separating chamber to said reflux condenser by introducing a cooling medium into direct contact with the vapors moving from the separating chamber to the reux condenser.

5. In a process of cracking oils which comprises subjecting oil to cracking conditions of temtemperature and pressure in a owing restricted stream, separating the vaporous products of the reaction stream from the liquid products thereof in a separating zone, and passing all of the vaporous products of the reaction stream simultaneously into a fractionating zone, therein to produce a fractionator condensate liquid at the temperature existing in the bottom of the said fractionator and a fractionator overhead comprising substantially the desired products of the reaction, that step which consists of removing a portion of the fractionator condensate, cooling it sufficiently to remove a substantial portion of its sensible heat, preventing the direct return of heat so removed to the fractionator, and introducing said cooled condensate into physical admixture with the vaporous products of the reaction zone between said separator and said fractionator, thereby to cool said vapors before they are subjected to fractionation, whereby the relative volume of vapors passing upward through the equilibrium zones of said ractionator is decreased, and a fractionator of fixed vapor volume capacity is enabled to handle a relatively increased amount of desired reaction zone product.

6. The process of producing relatively low boiling point hydrocarbons from relatively high boiling point hydrocarbons which comprises passing relatively high boiling point hydrocarbons through a `heating zone and heating the same while in the heating zone to a temperature adequate to effect cracking of a substantial portion of the hydrocarbons, passing the hydrocarbons from the heating zone into a separating zone and therein eecting separation of the same into vapors constituting all of the vapors produced by the heat applied to said hydrocarbons in the heating zone and a liquid residual oil, passing the said vapors from the separating zone and into a fractionating zone as a continuously owing stream and effecting in the fractionating zone initial fractionation of the total 'vapors passed from the separating zone and the condensation of higher boiling point portions thereof to form a fractionator'condensate having a boiling point above the temperature existing at the bottom of the fractionation zone while the lower boiling point portions of said vapors are permitted to pass through and out of said fractionating zone uncondensed substantially continuously withdrawing and cooling a portion of the said fractionator condensate having its boiling point above the temperature existing at the bottom of the fractionating zone to remove therefrom a substantial quantity of sensible heat while preventing the direct return of the heat thus removed to the fractionating zone, introducing fractionator condensate thus cooled into admixture with the vapors from the separating zone before they are subjected to fractionation in said fractionating zone to effect the cooling of the said vapors, whereupon the previously cooled vcondensate is again collected in the fractionating zone together with additional condensate having.

alboiling point above the temperature existing at the bottom of the fractionating zone, the cooling of the vapors thereby reducing the relative amount of cooling which must be effected in said fractionating operation, and reducing substantially the relative volume of vapors existent within the fractionating operation, whereby the said fractionating zone is capable of handling a substantially increased production of lowI boiling point hydrocarbons from the heating and separating zones.

'7. The process of producing low boiling point hydrocarbons from relatively high boiling point hydrocarbons which comprises passing relatively high boiling point hydrocarbons in a stream through a heating zone and therein heating the same to a temperature adequate to effect cracking of a substantial portion of the same, passing the stream of hydrocarbons from the heating zone into a separating zone and effecting separation of the same into vapors and a liquid residual oil, passing said vapors from the separating zone as a continuously owing stream into a fractionating zone for effecting initial fractionation of the vapors and condensation of higher boiling point portions thereof to form a fractionator condensate having a boiling point above the temperature existing at the bottom of the fractionating zone while the lower boiling point portions of said vapors are permitted to pass through and out of said fractionating zone uncondensed, condensing and collecting the said lower boiling point portions of the vapors, withdrawing from said fractionating zone fractionator condensate having itsboiling point above the temperature existing at the bottom of said zone, subjecting fractionator condensate thus withdrawn to heat treatment in the said heating zone with a fresh charge of relatively high boiling point liquid hydrocarbons which have not previouslybeen passed through the heating zone, substantially continuously withdrawing a furtherportion of the fractionator condensate and cooling same to remove therefrom a substantial quantity of sensible heat while avoiding any direct return of the heat thus removed to the fractionating zone, introducing fractionator condensate thus cooled into admixture into the vapors of the stream between the separating zone and the fractionating zone to effect the cooling of the stream prior to its passage into the fractionating zone whereupon the previously cooled condensate is again collected in the fractionating zone with additional condensate having a boiling point above the temperature existing at the bottom of the fractionating zone, the cooling of the stream thereby reducing the relative amount of cooling which must be effected in the-said fractionating operation, and reducing substantially the relative volume of vapors existent within the fractionating operation, whereby the said fractionating zone is capable of handling a substantially increased production of low boiling point hydrocarbons `from the heating and separating zones.

8. In the art of cracking hydrocarbons, the process which comprises conducting a stream of hydrocarbons through a cracking zone and then into a separating chamber, conducting vapors from said separating chamber to a reflux condenser, separately removing residue from the chamber, continually feeding relatively cool oil through a portion of said reux condenser to cool the vapors, transmitting reiiux condensate from the reflux condenser through said cracking zone and then into said separating chamber, maintaining the contents of said separating chamber at a cracking temperature, and extracting a substantial amount of heat from the vapors prior to their refiux condensation in said reux condenser by cooling the vapors passing from said separating chamber to said reux condenser.

9. The process as defined in claim 8 further characterized in that said relatively cool oil comprises condensate formed by condensation of the vapors issuing from said reflux condenser.

10. The process as defined in claim 8 further .m

spaans characterzed in that said relativey cool oil com pris reux condensate formed in the reux condenser. separating chamber to the reux condenser sie 11. The process as defined in claim 8 further cooed by Contact with charging oil for the proccharacterized in that the vapors passing from the ess.

sepamting chamber to the reux condenser are cooled by Contact: with a cooling liquid.

12. The process as dened in claim 8 mrthcz CARBON P. DUBBS.

characterized in that the vapors passing from the

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