US2003137A - Treatment of hydrocarbon oils - Google Patents

Description

May 28, 1935. L... DE FLOREZ TREATMENT OF HYDROCARBON OILS Filed Feb. 2, 1931 INVEN TOR.

ATTORNEY.

Patented May 28, 1935 UNITED STATES TREATMENT OF HYDRO CARBON OILS Luis dc Flore z, Pomfret, (lonnqasslgnor to The Texas Company, New' York, N. Y., a corporation of Delaware mutations... 2, 1931, 'SerialNo. 512,855 a 10 Claims; (01.196-49 This invention relates to certain novel im- "provements'in the cracking of hydrocarbon oils for the production of gasoline and the'like.

The invention contemplates a method in'whi'ch 5 oil is subjected to cracking under relativelyhigh pressure conditions and a condensate derived from such cracking operation is then subjected to cracking under a relatively lower pressure. Thus, in accordance'with the invention, the oil may be subjected to cracking and vaporization, the evolved vapors dephlegmated to form a reflux condensate and this condensate directed into a lower pressure cracking system without the intervention of a pump, the pressure differential betweenthe two cracking elements being relied upon to force the condensate through the lower pressure cracking system.

In one method of operation contemplated by the inventionoil in a primary cracking opera,- tion is subjected to cracking under given temperature and pressure conditions and a condensate derived from this operation is subjected .to

cracking in a secondary cracking operation at higher temperatures but under lower pressures than those obtaining in the primary cracking zone.

When a cracking stock is subjected to a cracking operation there is a limitto the amount of cracking which can be carried on largely on account of the decomposition of polymers or high carbon-forming hydrocarbons'which are formed in the cracking reaction and which, as the reaction is continued, are converted to coke. In accordance with my invention, an original charging stock may be subjected to a given amount of cracking in a primary cracking zone under conditions avoiding any excessive production of coke,

evolved vapors subjected to fractionation and a clean condensate fraction thus obtained which rived from the secondary or lower pressure cracking system is conducted to the primary cracking zone or introduced into contact with vapors evolved in the primary cracking zone.

In order to more fully disclose the invention, reference will now be had to the accompanying drawing which is a diagrammatic sectional elevation of the apparatus constructed in accordance with the invention and constituting an embodiment thereof. s I

In the apparatus cracking apparatus is shown which includes a heating coil l and a cracking still I I. The heating coil is-shown mounted in a furnace I2 hav-' ing a burner indicated at l3 and the still II is provided with suitable-Eheatingi means. or with heat insulating means. Liquid or residue is with-. drawn from the still I I through a line H and the evolved vapors are dephlegmatedor fractionated in a tower IS. The overhead vaporfraction is removed from the towerthrough a line l6 to a condenser l1 and the distillate is collected in a receiver l8. .A line. 19 is shown extending from the tower l to a hot oil pump 20 provided with a discharge line 2| sothat. reflux condensate formed-in the tower may be cyclically conducted,

to the coil I0.

A secondary cracking apparatus is shown which includes a heating coil 22 and a cracking still 23. The coil 22 is shown mounted in a furnace 24 with a burner indicated at 25 and the still thus illustrated 'a primary 23 is provided with suitable heating means or with heat insulating means;

A transfer line 26 serves to vintroduce the charging stock to the secondary cracking apparatus and is shown provided with a: branch line 21 extending to an intermediate point in the tower l5 and another branch line 28 communicating with the line l9. Thus by appropriate manipulation of the'valves in these lines reflux condensates formed .in the tower 15 may be handled in various ways. Thus, for example, all of the heavier condensate which collects in the bottom of the tower may be removed by the line l9 and cycled back to the primary cracking zone by the hot oil pump 20, while an intermediate cut may be withdrawn from an intermediate point in the tower and directed by the lines 21 and 26 to the lower pressure cracking zone; or, if desired, a portion of the heavier condensate fraction may be combined with the intermediate cut passing to the lower pressurecracking zone. .In one alternative method-of operation'all of 'thecondensate collected in the tower l5 may be withdrawn through lines l9 and 28 and passed through line 26 to the lower pressure cracking zone. The disposition of the various condensates formed in the tower may be varied in any suitable manner, but in general it is preferable to employ the heavier or higher boiling condensate as cycle stock for returning to the primary cracking zone while using a lighter or lower boiling condensate for 34 extending to a hot oil pump 35, provided with a discharge line 38. The discharge line is shown,

extending to the intake line 18 of the pump 20 and as provided with a branch line 33A extending to the coil 22. It is generally preferable to cycle the condensate from the tower back thru the branch line 36A and coil 22, altho,

at times a portion or all of this condensate may be routed to the coil III. A by-pass line 31 is indicated for by-passing the pump 35 but as arule it is preferable to employ the pump; when the condensate is cycled to the coil 22 the hot oil pump or analogous pumping means is required and even in case the condensate is conducted to the 0011' I0 it is desirableto employ the pump 31 tothus take some of the load-off the pump 2ll.- a v The receiving drum 33 is shown provided with a liquid draw-oil linev 33 with which communicates'a line 33 extending to a distillate pump 4ll.

The discharge line 4| of'the pump 40 has a branch line 42 which is shown in communication with the still ll by'means of branch lines 42a,

42b and 420. Another branch line 43 is'provided which extends to the fractionating tower I5. Thus a portion or all of the distillate collected in the receiver 33 may, be passed into either the high pressure cracking still II or the high pressure fractionating tower I! or into both the cracking still and the tower. 1

In some cases it may be desirable to introduce a portion or all of the fresh charging stock into the lower pressure portion of the apparatus, and to accomplish this end-a charging pump 43 may be provided having a discharge line 43 with a branch line extending to the still and another branch line 5| extending to the fractions ating tower 30. Thus a charging stock containing light constituents may be stripped in either the still 23 or towerjll. The introduction of charging stock through the line 50 into the still 23 has the advantage that a dirty stock such, for example, ascrude or crude residuum may be thus introduced into the still 23, the residual products formed in the cracking and vaporization withdrawn through the line 23 and the evolved vapors consisting of cracked products from the coil 22 as well as vaporized charging stock that has been introduced through the line ill may be subjected to fractionation in the tower 30 to thus form the gasoline distillate fraction, which is withdrawn through the vapor line 3|, and a clean reflux condensate which is withdrawn through the line 34 and which may be passedthrough the line 36 tothe hot oil pump 20, to thus constitute charging stock for the high pressure cracking system embodyingthe coil l0 and still I I. In this way the-heat made available by reason of the high temperature applied in the coil 22 may be utilized in the preparation of a' clean charging stock for the high pressure cracking system and at the same time the introduction of the fresh charging stock into the cracking still 23 produces a digesting effect therein promoting increased yields of gasoline with-' ,to the maximum temperature.

out a corresponding increase in gas production.

In one method contemplated by the invention diflerent types of charging stock may be introduced by the respective charging pumps 44 and 48, the least refractory charging stock being introduced by the pump 44 and the more refractory charging stock being introduced by the pump 48. Thus for example, a virgin stock may be charged by the pump 44 and a cycle stock (that a stock which has previously been subjected to a cracking reaction) may be introduced by the pump 48. When operating in this manner it is preferable to conduct the reflux condensate producedin the tower 30, or at least the major portion of it, to the coil 22, which is subjected When introducing a relatively clean stock by the pump 43 it is advantageous to introduce a portion or all of the stockthrough the branch line 5| directly to the tower 30, although if desired the charge maybe distributed between the still 23 and fractionating tower 30. It is desired to have cracking as well as vaporization take place in the still 23 so that it is not advisable to introduce a sufllcient quantity of charging stock. through the line 53 as to unduly'reduce the cracking rate in that still. It may be pointed out however that while the charging stock introduced to the; still 23 through the line 50-may be subjected to some cracking in the still 23, that so far as this fresh charging stock is concerned the effect on it will ordinarily be largely one of vaporization withonly a limited cracking, so that constituents which are vaporized from the charging stock introduced by the line 50 and which are collected as a condensate in the bottom of the tower 30 may be subjected to amore complete cracking in the coil 22 or in some cases in the higher pressure lc'racking system composed of coil I 0 and still The original charging stock to the system may be introduced by a pump 44 through a charging line directly to the coil ID. If desired a bypass line 41 may be provided so that the charge introduced by the pump 44 may, instead of being routed through the heating coil 10, be passed directly to the still ll. One advantageous method of operation is to interpose a heating coil in the line 4'! heated by'hot products obtained in the process, such as the residue withdrawn from the still through the line l4, or such coil may be heated in an economizer section of the furnace l2 to thus utilize waste flue gases that have been employed in heating the coil III. Thus in using the line 41 the charge introduced by the pump 44 may be heated to a certain degree, which may not be a cracking temperature, before being introduced into the still ll.

When fresh charging stock is being introduced by the pump 44 to the coil l0 it is desirable to admit the cycle stock being handled by the pump 20 to an intermediate point in the coil Hi, the branch line 53 being provided for this purpose. It is generally preferable to admit the condensate from the line 2| to the coil III at a point therein wherein the temperature of the stream of oil with which the condensate is combined approximates that of such condensate.

The fractionating towers I 5 and 30 may be of any suitable type, being equipped with suitable bubble trays or other elements adapted for when charging into. still 22 liquid or the vapor phase,

"the invention cracking is carriedon in the still and for this purpose trays or contact elements 50 are shown for these stills. Thus, for example, it is advantageous to have bailles or trays to receive the charge and similarly when introducing distillate from the receiver 33 to the upper or intermediate'portions of the still II the baflles or trays are of advantage. A cooling reflux may be supplied to the tower 15 in additiomtcrthat furnished. by'the' distillate from the receiver 33. Thus a portion of the final distillate collected in the receiver I! may be refluxed to the top of the tower l5. Similarly distillate from the receiver 33 may be used 'as reflux for the tower 30.

The invention contemplates that any suitable range of temperature and pressure conditions may obtain, respectively, in-the high pressure and low pressure cracking zones, but preferably with a differential in pressure sufllcient to insure the delivery of condensate from the high pressure tower I! to the heating. coil 22 and to maintain a sufliciently high velocity through the coil ,22 to insure satisfactory results. By way of example, it may be stated that with 400-600 lbs. pressure in the fractionating tower [5, the still 23 may be held under about 100-200 lbs. pressure.

If desired, the cracking inthe high pressure still it may be carried on substantially in the liquid phase, as by maintaining a relatively high level of liquid inthe still, to thus maintain a body of oil undergoing cracking and vaporization. If desired,however, the liquid precipitating in the still H may be rapidly withdrawn through the line H so that a large body of vapor is maintained in the still H and cracking carried on. in the vapor phase. Similarly, cracking conditions in the still 23 may preferably, however, under vapor phase conditions.

In one method ofoperation contemplated by H under relatively high pressures and underv essentially liquid phase conditions, under, for

example, '400 lbs. pressure at temperatures of the order of 800. F., while cracking is carried on in' the still'23 under essentially vapor phase conditions under pressures of the order of 100 lbs. and at temperatures of the order of 900 to 1000' F.

The distillate as collected in the receiver I8 is of the boiling point desired for the final gasoline or other light distillate it is intended to pro duce, and the distillate collected in the receiver 33 may be of the same endpoint as that of the distillate'collected in the receiver It. When, however, the distillate from the receiver 32 is returned to the higher pressure cracking zone or dephlegmator, this distillate may advantageously be collected at a somewhat higher endpoint than that V, I8. By taking the receiver the receiver 33, which isdeof the distillate in this distillate from rived from .a relatively low, pressure-cracking operation, and by conducting this distillate to the high pressure tower l5, serves as a cooling reflux medium for the tower [-5, but this dephlegmation and redistillation in .the higher pressure tower, may be subjected to a polymerizing action in the tower, tending to produce its stabilization. If the distillate be admitted to the cracking still II, it may be subjected not merely to polymerization, cracking heat'its anti-knock value may be increased. I

Although the methods of heating the oil, as in the coils l0 and 22, may be varied, one method be maintained under either,

the distillate not onlydistillate by being subjected to but by being treated to further of operation contemplated is to pass the charging stock introduced to the coil llxthrough the coil substantially in countercurrent to the flow of the furnace gases so that the oil is progressively raised in temperature in transit through the coil and reaches the maximum temperature approximately at the end ofthe coil, while the oil passed throughthecoilfl may flowgsubstantially concurrent with the furnace gases so that the maximum temperature is reached at an intermediate point inthe coil, after which thetemperatureof the oil is substantially maintained at a desired cracking temperature- The stock introduced to the coil 22 will in ordinary practice he a-cleaner stock than that admitted to the coil l0, and consequently the oil passing through the coil 22 may advantageously be subjected to soaking with cracking carried on to a considerable'extent before oil is discharged into the still 23. This soak-' ing effect may be accomplished in'a known manner by properly regulating the furnace tempera! ture and the timeof passage of the oil through the coil. Y a

Certain aspects of the. complete process described herein are claimed in the copending application of W.'M-. Stratford, Serial No; 515,189, filed February 12, 1931.

In one method of operation 'contemplated by the invention residue may be withdrawn, as thru lower pressure cracking still may be operated as a pressure coke still running to a coke residue.

' Obviously many modifications and variations of the invention, as hereinbefore set forth, may bemade withoutdeparting from the spirit and scope thereof, 'andtherefore only such limitations should be imposed as are indicated in the appended claims.

I'claim:

1. The process of treating hydrocarbon oil which comprises passing relatively heavy o l in a stream of restricted cross section through a heating zone wherein said oilis raised to a cracking temperature, transferring the heated-oil into an enlarged zone of substantially constant temperature wherein conversion of said oil occurs and vapors are separated, fractionating said vapors in a first fractionating zone to separate therefrom a final light distillate, a relatively heavy reflux condensate and a relatively light reflux condensate, introducing said heavy con-. densate into'said stream first mentioned. passing said lightercondensate through a second zone of restricted cross section wherein the said lighter condensate attains a cracking temperature in excess of that first mentioned, introducing the resulting heated condensate into a second enlarged zone of substantially constant, temperature, wherein conversion .of the condensate occurs and vapors are separated, passing said vapors through a second fractionating zone wherein separation thereof into relatively light vapors and a refiux condensate occurs, condensing said light vapors and introducing the resulting condensate, free from said reflux condensate last mentioned into said enlarged zone first mentioned.

2. A process in accordance with claim 1 wherein a cracked charging stock is introducedinto said enlarged zone second mentioned, in quantities so small that the temperature of the said zone is not reduced below a cracking value.

3. A process in accordance-with claim 1 wherein said reflux condensate last mentioned is introduced into said stream first mentioned for additional cracking.

v 4. A process in accordance with claim lwherein a cracked charging stock is introduced into said fractionating zone last mentioned and reflux condensate formed in this fractionating zone and unvaporized portions of said cracked charging stock are introduced into said stream first mentioned for additional cracking.

5. In the conversion of higher boiling hydrocarbons into lower boiling ones, the process that comprises subjecting fresh relatively heavy hydrocarbon oil to cracking and vaporization in a primary cracking zone at relatively high superatmospheric pressure, subjecting evolved vapors to fractionation in a first fractionating zone to form overhead gasoline vapors and a reflux condensate. free from cracked residue, removing and condensing said overhead vapors as a desired product, passing said reflux condensate to a secondary cracking zone maintainedunder a lower pressure than that of the primary cracking zone, subjecting the condensate to cracking and vaporization in the secondary cracking zone, subjecting vapors evolved in the secondary cracking zone to fractionation in a second fractionating zone to segregate gasoline constituents therefrom, and'returning said gasoline constituents to a point in said primary cracking zone maintained at a cracking temperature, to thereby subject said gasoline constituents to heat at a pressure higher than that of their pyrogenesis.

6. In the conversion of higher boiling hydro-v carbons into lower boiling ones, the process that comprises subjecting fresh relatively heavy hydrocarbon oil to cracking and vaporization in a primary cracking zone at relatively high superatmospheric pressure, subjectingevolved vapors to fractionation in a first fractionating zone to form overhead gasoline vapors and a reflux condensate, free from cracked residue, removing and condensing said overhead vapors as a desired product, passing a cleancracking stock through a secondary cracking'zone maintained under a lower pressure than that of the primary cracking zone, subjecting the clean cracking stock to cracking and vaporization in the secondary cracking zone, subjecting vapors evolved in the secondary cracking zone to fractionation in a second fractionating zone to segregate gasoline constituents therefrom, and introducing gasoline constituents so segregated into a point in said primary cracking zone maintained at a cracking temperature, to subject said gasoline constitucuts to a pressure higher than that of their pyrogenesis and thereby polymerize unstable color and gum-forming constituents thereof.

7. In the conversion of higher boiling hydrocarbons into lower boiling ones, the process that comprises passing hydrocarbon oil through a heating zone in a stream of restricted cross sectional area wherein said oil is raised to a cracking temperature under relatively high superatmospheric pressure, passing the resulting heated oil into an enlarged reaction zone maintained under a substantially constant cracking pressure wherein said oil is subjected to conversion, subjecting resulting cracked vapors to fractionation in a first fractionating zone to form a desired gasoline distillate, subjecting hydrocarbon oil in another cracking zone to cracking and vaporization under a pressure lower than that of said cracking zone first mentioned, subjecting vapors evolved in the lower pressure cracking zone to fractionation in a second fractionating zone to form an overhead vapor fraction comprising mainly products in the gasoline boiling range and a reflux condensate, condensing said'overhead vapor fraction and introducing the resulting condensate into said enlarged reaction zone to thereby subject said resulting condensate to heat under a pressure higher than that of its pyrogenesis, whereby beneficial polymerization thereof occurs.

8. The process of treating hydrocarbon oil which comprises passing said oil in a stream of restricted cross section through a heating zone wherein said oil attains a cracking temperature, introducing the resulting heated oil directly into a reaction zone-maintained at a substantially constant cracking temperature of the order of 800 F. under a relatively high superatmospheric pressure, wherein additional conversion occurs, passing resulting vapors through a fractionating zone wherein'constituents heavier than those desired in the final product are condensed, removing the fractionated vapors and condensing them as a desired product, and introducing directly into said enlarged reaction zone a distillate oil comprising essentially gasoline constituents produced as a result of a cracking operation maintained under a pressure materially below that maintained in said reaction zone, whereby beneficial polymerization-of said gasoline constituents takes place.

9. In the conversion of higher boiling hydrocarbons into lower boiling ones, the process that comprises heating a confined stream of hydrocarbon oil to cracking temperature, thereafter passing said heated oil into a separate zone maintained at substantially constant cracking temperature and at relatively high superatmospheric pressure wherein conversion of said oil into lower boiling hydrocarbons is effected, separating said converted products into vapors and residual products, subjecting evolved vapors to fractionation in a first fractionating zone to form overhead gasoline vapors and a reflux condensate free 'from cracked residue, removing and condensing said overhead vapors as a desired product, passing said reflux condensate to a secondary cracking zone maintained under a lower pressure than that maintained in said first-mentioned cracking zone, subjecting the condensate to cracking and vaporization in the second-mentioned cracking zone in the absence of uncracked oil, subjecting vapors evolved in the secondary cracking zone to fractionation in a second fractionating zone to form an overhead vapor fraction and a reflux condensate, condensing said vapor fraction and conducting it free fromsaid reflux condensate last-mentioned to a point in said separate zone to thereby subject the condensed vapor fraction to heat at a pressure higher than that of its pyrogenesis,

10. The process of treating hydrocarbon oils which comprises subjecting heavy hydrocarbon oil to cracking temperature in a substantially liquid phase cracking zone, under relatively high pressure, separating the resulting vapors, and

withdrawing unvaporized residue from the process, simultaneously subjecting a lighter hydrocarbon oil to cracking temperature in a substantially vapor phase cracking zone, under relatively low pressure, separating resulting cracked products into 'vapors and a liquid residue, withdrawing said residue from the process, fractionating the resulting vapors from the liquid phase cracking operation and resulting low boiling products from the vaporphase cracking operation in a high pressure fractionating zone, under a pressure substantially equal to that of said liquid phase cracking zone, whereby said low boiling products from said vapor phase cracking operation are subjected to beneficial polymerization, and a vapor fraction,

cracking operation and charging saidheavier condensate. to said liquid phase cracking operation.

LUIS n: FLOREZ.

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