US2304398A

US2304398A - Catalytic cracking

Info

Publication number: US2304398A
Application number: US317930A
Authority: US
Inventors: Oliver F Campbell
Original assignee: Sinclair Refining Co
Current assignee: Sinclair Refining Co
Priority date: 1940-02-08
Filing date: 1940-02-08
Publication date: 1942-12-08
Anticipated expiration: 1959-12-08

Description

D c. 8, o. F. CAMPBELL 2,304,398

CATALYTIC CRACKING Filed Feb. 8, 1940 5 Sheets-Sheet "l INVENTOR OZz'ver F Campbell ATTORNEYS Dec. 8, 1942. C o. F. CAMPBVELL 2,304,398 CATALYTIC CRACKING Filed Feb. a, 1940 s Sheets-Sheet 2 ATTORNEYS 9 o. F. CAMPBELL CATALYTIC CRACKING 5 She ets-Sheet 3 Filed Feb. 8, 1940 INVENTOR aZzVer ff'fampie]! ATTORNEYS Dec. 8, 1942. o CAMPBELL 2,304,398

CATALYT IC CRACKING 5 Sheets-Sheet 5 O. F. CAMPBELL CATALYTIC CRACKING Filed Fgb. 8, 1940 Dec. 8, 1942.

' a... bead, m 2,304,398

UNITED" STATES PATENT OFFICE -1- m-my i smsa aer m Application February a, 1940, serial No. 317,930-

operations, in which higher-boiling hydrocarbons are cracked to provide more valuable lowerboiling hydrocarbons in the presence of a catalyst. This application is a continuation-in-part of my copending application .Serial No. 290,398,

filed August 16, 1939.

In heretofore customary operations, the catalytic treatment of the hydrocarbons has been conducted in an intermittent manner. The hy-.

drocarbons to be cracked, for example a petroleum stock, are vaporized by heating under a low pressure, usually in the presence of steam to promote vaporization. The temperature of the resulting vaporous mixture of hydrocarbons, and any steam, may range from TOO-800 F. to about l000-l100 F.; the pressure may range from subatmcspheric to as high as 100 pounds per square inch or more. Depending upon the nature of the stock to be cracked, the temperature and pressure, and the proportion of steam employed, all or only a portion of the stock may be vaporized. When unvaporized hydrocarbons remain these are usually separated andremoved prior to catalyst contact. In any event, the vaporized hydrocarbons are sent. to the cracking operation. There, in a reaction zone, a stream of the hydrocarbon vapors is passed in 7 contact with a solid and usually porous or granular catalytic mass, such, for example, as fuller's I earth or kieselguhr alone, or admixed with various metals or metal salts. Lower-boiling hydrocarbons and carbon" result from the ensuing cracking. The lower-boiling hydrocarbons and some of the carbon are removed from the reaction zone as formed, but a substantial portion of the carbon adheres to the catalyst and coats its surfaces and chokes its pores as it accumulates. As the carbon accumulates and fouls the catalyst, the activity of the latter decreases. When the economic limit of catalyst activity has been reached, the stream of hydrocarbon vapors to be cracked is diverted to another reaction zone containing a reactivated or regenerated catalyst mass, and the fouled mass is subjected to regeneration. This is usually accomplished by passing a hot oxidizing gas in contact with the catalyst so as to burn off the carbon accumulated on the surfaces and in the pores thereof and thus clean the catalyst for further service. Once. the catalyst has been reactivated or regenerated by such treatment, the stream of vapors to be cracked is ultimately diverted back .5Clalms. (c1. ms-'52) v regenerated catalyst mass and the operation thus proceeds.

The economic limit of'catalyst activity may be reached in a very short time, even in a few sec-.

fonds, and in certain catalytic cracking operafouled catalytic-mass to a regenerated one. Such control mechanisms not only increase plant investment and maintenance costs, but are sub- .iect to operating diiiiculties. The-regular production of superior cracked products requires uniform operating conditions.

, The heat of the cracking reaction is composed ofthe heat of decomposition and the'heat oi Decomposition is enchemical condensation. dothermic and condensation is exothermic, and whether or not the reaction as a whole is heatreleasing or heat-consuming depends upon whether the heat of chemical condensation or the heat of decomposition is greater. When the cracking in-the region of catalyst contact is an endothermic reaction (as is often the case), it consumes considerable heat which may be supplied from the stock itself, or froman exterior source as by conduction through the walls of the chamber in which; the catalyst is confined. On the 'other'hand, regeneration involving as it does combustion of carbon, is exothermic, and its successful accomplishment requires dissipation of heat. This situation is one in which heat exchange between the cracking zone and the zone of regeneration is desirable, but such exchange has heretofore been accomplished only at the expense of additional and cumbersome equipment.

In my copending applications Serial Nos. 290,398 and 290,399, filed August 16, 1939 (the latter application having become U. S. Patent 2,246,345), I have described and claimed apparatus and methods for the catalytic cracking of. hydrocarbons, involving continuous cracking of a stream of hydrocarbon stock without diverting this stream periodically as the catalyst requires regeneration. Such an operation permits a substantial gain in thermal eificiency through improved heat exchange between the cracking and regeneration phases of the cycle and also afiords advantages with respect to control in that it permits elimination of heretofore necessary but cumbersome automatic controls (with consequent savings in costs for plant, op-

to a reaction zone containing the reactivated or 5-: oration and maintenance), greater ease of operation and improvement in product. These results are achieved in a catalytic cracking process by rotating segments of a catalytic mass successively and cyclically through four zones. To the first zone vaporized hydrocarbons to be cracked mass in the first or cracking zone are removed and in the fourth zone gaseous products entrained in the third or regenerative zone are removed.

The cycle time for such an operation may vary over wide limits, but is in general short, say of the order of 1 to 10 minutes. I have discovered that when the cycle time is short purging must be more eificient than in conventional apparatus with longer cycle times, in order to minimize loss of valuable hydrocarbons which pass into and are burned in the regenerative zone. The hydrocarbons to be purged comprise "fixed gas, gasoline, gas oil and relatively non-volatile hydrocarbons. These latter are the most difficult to purge because of their high boiling point or because-they are strongly adsorbed by the catalytic surfaces or because they penetrate deeply into. the pores of the mass and are not reached by purging fluids such as steam. In any event, I have found that the operation is greatly improved if the purging, at least in the second zone and a regenerative section by radially extending bafiies. These sections are sealed from each other, but enclose a concentrically mounted wheel 11-- vided into a plurality of segments in each of which is disposed a catalyst. The wheel is rotatable with respect to the various sections which enclose it, so that its catalyst segments may be passed continuously through the series of sections and thus be alternately employed to crack hydrocarbons passing continuously through the cracking section and be regenerated by hot oxidizing gases in the regenerative section. More specifically, the invention of my copending application provides, in apparatus for the catalytic cracking of hydrocarbons, the combination which comprises a hollow and preferably annular head divided around its periphery into a plurality of segmental chambers, said head having a, flat bearing plate with ports therein communicating, respectively, with each of said chambers, a second hollow head (preferably a mirror image of the first) disposed-concentrically to the first head where hydrocarbons are removed from the catapurging the catalyst, at least in the second zone.

by means of vacuum. Hence, in accordance with the present invention the second zone (or a portion thereof) and in some instances both the are maintained under a reduced pressure (as compared with that of the cracking and regencrating zones) and preferably under pressure less than atmospheric, by means of electors, pumps,

I second and fourth zones (or. portions thereof) or other vacuum-producing apparatus connected to the exhaust sides of the purging zones.

In my presently preferred method of operation, the second zone is divided into two-portions a? the direction of rotation of the catalyst. In the first portion, immediately adiacent the cracking zone, vacuum purging is practiced, and this is followed by purging with a fluid, such as steam, passed through the catalyst from an exterior source in the second portion of the second zone. The fourth zone may. likewise be divided into a vacuum purging portion followed by a steam purging portion, but 'the advantages of vacuum purging are not so pronounced in the fourth zone, and it may be advantageous to employ only steam purging therein.

The above-described method may be carried on in a variety of apparatus, but is advantageously performed in apparatus of the type de-,

and having segmental chambers matching those in the first head with a fiat bearing plate having ports therein corresponding to those in the first head, said bearing plates being disposed concentricaliy and parallel facing each other and spaced apart a fixed distance, a catalyst carrier in the form of a wheel disposed between the two bearing plates with its axis coinciding with that of the two heads and rotatable relative to the heads, said carrier being divided into a plurality of segments or compartments by radial vanes extending substantially from one bearing plate to the other, a catalytic mass disposed in the compartments of the catalyst carrier, means for forcing vaporized hydrocarbons from a chamber of one head to a corresponding chamber of the other head in contact with the catalytic mass in a compartment, means for simultaneously forcing a. hot oxidizing gas from a second chamber of one head to a corresponding second chamber of the other head in contact with the catalytic mass in another compartment, and means for simultaneously rotating the wheel relative to the heads.

In the preferredform of the above-described apparatus, the heads are annular; the catalyst carrier is rigidly mounted on a shaft disposed on the common axis of the two heads and passing therethrough; means are provided for rotating the shaft; means are provided for preventing leakage of vapor between the various sections of the apparatus, and the catalyst carrier is sur- -rounded by an annular jacket for a hot diluent gas such as steam. The Jacket space is enclosed by a drum fastened to the two heads so as to enclose the carrier, and means are provided for a casing divided into at least a cracking section supplying the diluent gas (say steam) to the jacket at a pressure in excess of that prevailing in any of the chambers so that leakage of gas.

if any, will take place into the carrier compartments rather than out, thereby preventing leakage to the outside and undesirable admixture of hydrocarbons and oxidizing gases within the apparatus.

There may be two or more chambers in each of the heads. For practice of the instant invention with purging by suction, there are conveniently at least five compartments, corresponding respectively to (along the direction of rotation of the carrier wheel) a zone for hydrocarbons, a second (subdivided into two sections) for purging out the products of the first zone by vacuum and steam, in that order, a succeeding regenerating zone for the oxidizing gas and a final zone for purging the products of oxidation by steam or other purging gas.

The number of compartments or segments in the catalyst carrier may be two or more, but preferably a large number (such as eighteen or twenty) is provided. In any case, the segments should be of such dimensions relative to the distance between the ports in the bearing plates that no one catalyst segment is in contact with the ports of different chambers in the same head at the same time; that is to say a segment should be out of contact with the port supplying hydrocarbon before it comes in contact with the port which supplies purging gas, or through which evacuation occurs under reduced pressure. This may be assured by making the radial space between ports, 1. e., the distance between them in the path of rotation, greater than the radial space or angle devoted to a single segment.

Apparatus of this general type adapted to carry out the process of my present invention is illustrated in the accompanying drawings and my invention will be .more clearly understood in the light of the following detailed description in connection therewith.

In drawings:

Fig. l is a plan view of one form of apparatus adapted to carry out the process of my invention and having means for rotating a catalyst successively through a cracking zone, a purging zone divided into first and second sections, a regenerative zone, and a second purging zone.

Fig. 2 is a vertical taken through the apparatus of Fig. 1 along the section line 2-4;

Fig. 3 is a horizontal section taken through the apparatus of Figs. 1 and 2 along the section line 3-3 of Fig. 2;

Fig. 4 is another horizontal section taken through said apparatus along the line 4-4 of' Fig. 2;

Fig. 5 is a developed vertical diagrammatic view of the apparatus illustrated in Figs. 1 and 2, this being a form of apparatus embodying means for applying vacuum purging only to a portion of the first purging zone;

Fig. 6 is a section of a portion of the apparatus taken along the line 6-4 of Fig. 2 and showing a type of wiper seal for sealing the various zones of the apparatus from each other;

Fig. '7 is a diagrammatic flow sheet showing the disposition of the rotating catalyst apparatus of Figs. 1 to 6 in a system for the catalytic cracking of hydrocarbons; and

Fig. 8 is a developed vertical diagrammatic view of a modified form of apparatus including means for applying vacuum purging to portions of both the first and second purging zones.

Referring now to the drawings and particularly to Figs. 1, 2 and 3, it will be observed that in general the apparatus comprises a vertical shaft assembly Iii upon which is rigidly mounted a substantially cylindrical catalyst carrier wheel H. The outer portion of the carrier wheel is enclosed by an annular casihg I2 which is circular in plan and comprises a center cylindrical drum portion or jacket I! to which is fastened at the top andbottom, respectively, a pair of hollow annular heads l4 and IS. The inner wall of each head is formed by flat annular bearing plates l6 and H. The heads are mirror images of each other and each is divided into five sections by radially extending baffles. These sections correspond toa cracking zone I8, a first purging zone I! having a first vacuum purging section 75 ISA and a first steam purging section i913, a regenerative zone 20 and a final steam purging zone 2i (Figs. 3 and.5).

The carrier wheel is adapted to rotate successively through these zones, carrying "catalyst segments mounted thereon in contact with the hydrocarbons to be cracked, thence in succession into the first and second sections of the first purging zone for purgingrespectively by means of suction and superheated steam or other purging gas, thence into contact with an oxidizing gas in the regenerative zone and finally into the final; purging zone for purging with an extraneous gas stream.

To consider the apparatus in greater detail, the

'yertical shaft assembly is connected at its upper end through a variable speed reducer 22, or other means of varying the speed of rotation, to a motor (not shown). The shaft assembly is hollow topermit water cooling. It is supported adjacent' its lower end 23 by a thrust bearing 26 through which it passes. The shaft assembly and its mid-portion within the carrier wheel is enlarged and enclosed by a cylindrical wall 15. to form a cooling water chamber 28. A water inlet pipe 21 projects upwardly from the base of i the shaft to a point adjacent its closed upper end This pipe is stationary. Water forced into it through an inlet 28 enters the'cooling water chamber and flows downwardly through the lower hollow portion 30 of the shaft into a water outlet gland 3| disposed below the thrust bearing and concentrically around the water inlet pipe. The lower portion of the shaft is rotatably mounted on this gland, this forming a sealed system. Water forced through the inlet pipe cools the interior of the shaft, flows downwardly through a rotatable coupling 32 disposed below the thrust bearing and out through the gland.

The carrier wheel I! is rigidly fastened to the shaft adjacent its enlarged portion. Immediately adjacent the shaft, the carrier wheel has an ,annular chamber 33 enclosed by a cylindrical sheath-34 and upper and lower

annular walls

35 and 38. This chamber is filled with non-infiammable heat insulating material 31 such as Sil- O-Cel.

The outer vertical wall of the carrier wheel is a cylindrical shell 38 that is separated from the sheath, by a considerable annular space. At the top and bottom of the shell 38 are fastened. respectively, outwardly projecting peripheral labyrinth seal members 39 and 40. These members are disposed adjacent the plates I6 and II that form the walls of the upper and lower heads, respectively. Each seal member has a series of concentric circular grooves 4i, 42, 43 and 44, 45,

rality of segmental compartments A; 55B, 55C,

et seq. to "R by vertical radial bafiies or vanes 56A to 56R, inclusive (Fig. 4). Any desired number of compartments may be provided but it is desirable to have a relatively large number of them, and in the instant case eighteen com partments are provided. The vertical baille plates extend substantially completely from top to bottom of the carrier wheel and have straight V horizontal I known,

"direction r the peripheral.

' catalyst bed. -With temperature within the apparatus,

unperand lower edges 51 and as to and-parallel with thefinner surfaces of the bearing plates of the two -heads.- In the lower 1 portion oteach compartment a horizontal ioraminous plate I! or other catalyst support is fastened. A'porous or loose granular catalytic is disposed in'eachhof the. lsegmass 60 or bed mental'compartments' of the plates. It may be composed of any 01f the conventional solid cata- .lysts suitable for catalyzing. the cracking of hy-' -'drocarbons.- A number of such materials are kieselguhr or fullers among thembeing 'earth.. The catalyst bed'substantially fills the f segmental compartments to a point just below the upper edge oi the vanes. Thecatalyst bed end 90, and these chambers are disposed, respec-' purging zone by b'aflies 81, states, as and tively. in the crackingzone l8, in the vacuum section of the first purging zone ISA, in the steam purging section of the first purging zone "B, in the regenerative zone 20, and in the second' purging zone 2!. Likewise, the interior 82 of the lower head is divided into five corresponding segmental chambers 9|, 92A, 92B, 93 and 84 should be porous or otherwise designed to permit the passage'of gases.

It will be observed that around the catalyst carrier wheel between its outer shell and the drum portion I3 01 the chamber 6!. space is enclosed at its upper leak through the annular. space also maintaining a'proper steam is admitted into the annular chamber through a pipe such by-passing and 62, the pressure of the steam being in excess-oi.

therethrou'gh in a vertical casing there is an annular This annular chamber or jacket 1 and lower ends by seal members.- However, unless these seals are perfect there is a tendency for gas under pressure to g from one head to the otherand thus by-pass the a view toward preventing by bellies 9!, 98A, 86B, 91 and 98 (see Fig. and these chambers are disposed, respectively, in the cracking zone, in the vacuum section of the first purging zone,'in the steam section of the-first purging zone, ln the regenerative zone and in the second purging zone. In short; in the preferred form of apparatus (Fig. 5), the first purging zone is divided into two portions, r sections in the first of which vacuum purg g occurs,

with steam purging in the second.

The rotation of the carrier wheel is counter clockwise, as viewed from above, thus, as the wheel is rotated, any segment of the catalyst bed passes successively between chambers 83, 9i '(i. e., the hydrocarbon chambers of the upper and lower heads), between

thechambers

84A and 92A (i. e., the vacuum chambers of the first purging zone), between chambers 84B and 92B that maintained within the apparatus as a whole i so that any leakage which occurs will be of steam from the annular chamber into the space occupied by", the carrier wheel and the upper and 1 lower heads. a

. The inner pair of peripheral labyrinth has a: and 6d are provided, respectively, at the top and the-bottom of the carrier disk adjacent the space filled with insulating material. In this instance,

a series of concentrically disposed rings GSA, 65B, 65C and 68A, 66B and 660, are fastened respectively to the upper and lower surfaces 0! the carrier

wheel o'nthe plates

35, 36 and peripheralconcentric grooves 61A, 61B, 61C and project into formed. in a pair of upper and I1, 18 through which the shaft sea. tan; sac lowerbearings passes. Thelabyrinth seals 63, 64, or other seal-- ing device oi'like form, are necessary to prevent leakage of gases from the space above and below the catalyst bed outwardly to the atmosphere. If desired, packing material'may be placed in. the

f seals.

To consider the construction of the upper and lower-l'wdsllland I! of the casing,'reierence should made particularly to Figs. 2 and 3. The upper and lower heads are substantially mirror images 01 each othe'rand are annular in iorm, being concentrically disposed in parallel planes. The outer portions of the heads, 1. e.,

the portions remote from the carrier wheel are. formed or grooved plates 19 and 80. These are welded to the inner fiat annular bearing plates lland l1. Each of the annular chambers 81 and 82 thus lnclosed is divided into at least five segmental chambers by vertical radially extends ing baflles. I

Thus, as shown in Figs. 3 and 5, the chamber 8! of the upper head preferably is divided into a series of chambers which include, reading from right to left in Fig. 5, a hydrocarbon chamber 83, a vacuum chamber 84A anda steam chamber Bot the first purging zone, an oxidizing gas (i. e., the steam purging chambers of the first purging zone). between the chambers 85 and 93 (i. -e., the oxidizing gas chambers) and between

chambers

86 and 94 or the second steam chambers.

The upper a branch of. line 84 so that, if desired, steam or other purging gas may be admitted to the vacuum purging section. The lower vacuum chamber 92A has a port INA in its upper wall through which hydrocarbon gases, etc., are sucked from .the catalyst passing through the vacuum purging section from the cracking section.

As illustrated in Fig. 5, the hydrocarbon chambers occupy about ths of the respective heads. Hydrocarbon vapors to be cracked enter the upper hydrocarbon chamber 83 through a feed pipe 89 of relativelylarge diameter, pass from this chamber through a port lilo that corresponds in radial space to about six catalyst segments, through these catalyst segments and a matching outlet port Illl into the lower hydrocarbon chamber 9|. The resulting lower boiling hydrocarbons are removed from this chamber 9| through an outlet pipe 102 of relatively large diameter.

Adjacent the hydrocarbon chambers 88, SI, of

the respective heads are the

vacuum'chambers

84A, 92A which occupy gfi ths o! the respective heads. Steam may be admitted into-the upper chamber 84A through a branch of pipe 84, and passed into contact with a rotating catalyst carrier through the small port NBA in its bottom or bearing plate. This port is equal radially to about 1 catalyst segment and is disposed in the approximate center of the section of the plate included between baflies 88A and 883. -The steam port BA is separated from the hydrocarbon port Hill by a radial distance greater than that of one catalyst segment so that such a segment must pass out of contact with the hydrocarbons before steam is admitted thereto. There is a corresponding port IIMA, in the plate of the chamber 85, and a steam chamber 88 of the secv matching lower vacuum chamber 92A. Steam admitted into the upper chamber 84A through the pipe 84 is sucked from the lower chamber 92A through a port IMA which is maintained under I vacuum chamber 84A is provided 1 with a port NBA and a gas inlet valve "SA on reduced pressure by means of a vacuum pump "SA, a steam-fed ejector or other vacuum producing apparatus disposed in pipe IOBB. Ordinarily, however, the valve I29A is maintained in a closed position, and the suction on the pipe IBBB serves to create a vacuum within the catalyst segments passing through the vacuum purging section and to withdraw from the segments hydrocarbons entrapped therein in the cracking section prior to the passage of steam throughthe segments in the second section or steam purging section of the first purging zone.

Following the vacuum section of the first purging zone is the steam purging portion of the first purging zone. It comprises an upper chamber 64B supplied with steam through a branch of pipe 84 containing valve I293 and a matching lower chamber 92B. These chambers are equivalent to about two catalyst segments and are provided, respectively, with ports 10313, "MB, through which steam enters and leaves the catalyst segments.

Next around the periphery of the apparatus is the regenerative section in which are disposed oxidizing

gas chambers

85, 93. These chambers occupy approximately 9 ths of the respective upper and lower heads. They are provided with'a pair of. segmental ports I01 and I08, respectively, in the upper and lower bearing plates through which hot oxidizing gases pass for contact with the catalyst segments to be regenerated. The ports in the regenerative section of the apparatus approximate in cross section somewhat less than six catalyst segments and are spaced from adjacent ports-by a distance equal to more than one of the segments of the catalyst wheel, for reasons hereinbei'ore explained. Hot air or other oxidizing gas for burning carbon from the catalyst segments is admitted in the upper chamber 85 through a pipe I09, passes downwardly through the rotating catalyst segments into the corresponding lower chamber 93 of the lower head and is withdrawn therefrom through an outlet pipe H0.

The balance of the apparatus is occupied by the second purging section. This second purging section corresponds radially to two of the catalyst segments. It contains the

second steam chambers

86, 94, in the upper and lower heads, respectively. Steam for purging may be admitted into the upper chamber through an inlet pipe ill and passed through the adjacent catalyst segment to the steam chamber 94 in the lower head from whence any steam admitted and the products purged out are withdrawn' through an outlet pipe H2 connected therewith.

Both upper and lower chambers of the second purging zone are provided with small pie-shaped ports H3, H4, (equal to about one catalyst segment) through which steam may pass into and out of the catalyst segment.

Purging in the second zone (following regeneration) may be accomplished by steam alone or by steam and vacuum employed separately but simultaneously. Generally speaking, purging in the second purging zone by steam alone is satisfactory, but vacuum may be employed to evacuate pores in the catalyst segments, and thereby accelerate catalytic action when the rotating catalyst is reintroduced into the cracking zone. The apparatus illustrated in Fig. 5 is adapted only to the use of steam purging in the second purging zone.

To employ steam for purging in the second purging zone in the apparatus of Fig. 5, the valve 128 on the steam line III is opened to admit steam into the apparatus and steam is withgenerative zone through line H0.

If it is desired to employ bothsteam and vacuum for purging in the second purging zone the latter. must be divided into two independent portions, as in the first purging zone of Fig. 5. Such an arrangement is illustrated in Fig. 8. The arrangement shown in Fig. 8 is similar to that shown in Fig. 5 except that the cracking and regenerating sections are reduced in width and the second purging zone is divided into a vacuum purging section 2 IA anda steam purging section 2 IB similar in all respects to the vacuum purging section ISA and the steam purging section I9B, respectively. In this arrangement the portions of the annular chambers included between

baflles

81 and 90A in the upper head and baflles 95 and 98A in the lower head are divided into chambers 85A, 86B and 94A, ME by baflles 90B and 9813, respectively. In this modified arrangement steam may be supplied to chambers 86A and 863 through branch pipes IA and I] I3 containing valves |28A and i283, and this steam may pass from the chambers to the catalyst segments through ports 3A and 3B. Gases evacuated through port I A and vacuum chamber 94A are discharged through line 213 by the vacuum created by means of vacuum pump 2A. Similarly, steam and purged products passing through port H413 and chamber 943 Steam and vacuum should not be employed together in purging due to the fact that vacuum tends to draw in oxygen-containing gases which, in admixture with purged hydrocarbons, are explosive- Vacuum and steam applied to a single purging zone also tend to increase hydrocarbon loss. I

To prevent leakage between the various sections of the apparatus, the upper and lower edges of each of the vanes on the catalyst carrier wheel are provided with wiper seals which bear against the inner plates of the upper and lower heads. Such a seal-is shown in detail in Fig. 6 and comprises a flexible brush H5 fastened to the vane and bearing against the inside plate of the head. Seals of different construction may, of course, be provided, but that illustrated is simple and eifectiveli' The upper head is provided with four thermocouples IIS, 1, H8 and H9 disposed, respectively, in wells I20, l2l, I22, I23, in each of the several chambers to which fluids normally are supplied to, enable proper temperature control of the system. Like thermocouples in similar wells are (provided in the several chambers of the lower A better idea of the operation of the apparatus described hereinbefore may be obtained by reference to Fig. 5 which is a developed diagram of the presently preferred form of my apparatus.

Referring now to this diagram, it will be obhave oil vapor flow may also becontrolled on I to a conventional-heater, (not shown) interposed the purging sections.

ments'oi the carrier), through these four segments and the corresponding lower hydrocarbon port into the lower hydrocarbon, chamber from whence it is withdrawn.

At the same time, a catalyst segment contaminated with products,such' as hydrocarbons, entrained by it in the cracking zone, is being cleaned in the vacuum section of, the first purging zone prior to its passage into the steam purging section of this zone. As indicated 'hereinbeiore, the vacuum purging section is maintained under a reduced pressure by means of the vacuum pump or ejector, which withdraws the entrained products employed, and'tends to free the catalyst'segments of impurities otherthan solids, such as carbon. Simultaneously steam is.

admitted into the steam section of thefirst purgmg zone, and this steam plus such substances as I been purged from the catalyst (principally entrained hydrocarbons) is withdrawn from the chamber in the lower head either independently or together with the cracked oil vapor from the cracking section.

Simultaneously, hot air plus steam or inert gas is introduced into the regenerating section which corresponds in this case to about five or six catalyst segments. The mixture oi steam or inert gas with hot airenters the oxidizing gas chamber of the upper head, passes through a port therein corresponding to about four catalyst segments and through these catalyst segments and a corresponding lower port into the oxidizing gas compartment of the lower head." The excess oxidizing gas'and the products of carbon combustion are then withdrawn and sent to 'waste or to a heat recoverysystem.

At the same time that certain oi the catalyst segments are being subjected to contact with bilvaporsjothers to purging in the first purging section and still others to contact with hot oxidizing gas in the regenerative section, the balance 01 the catalyst segments are being treated in the second purging section. Treatment in the second purging section preferably issimilar to that in the steam section or the first purging zone, and involves driving out of the catalyst segments gaseous products of combustion entrained by the segments in the regenerative zone plus the steam introduced for purging purposes.

As shown in Fig. 5, a control valve I20 maybe provided on the-inlet line 09 for regulating the passage oi oil vapor to the cracking section. The the inlet in the line 99. A pair-of valves I26, I21 are provided in branch pipes .for regulating the propertions of air and steam or inert gas supplied to .the regenerative section through the pipe I09.

Likewise, control valves I28, IISA and iiajB'ai-e provided for regulating the supply of steam to I Valves I30, I 3I and 1132, I33 are also provided, respectively, on the outlets irom the steam purging section of theflrstzone and of the second zone so that steamplus other gases therefrom may be passed through by pass lines I,

' certain stocks when the heat of condensation exceeds the heat of decomposition. Hence, in most instances, it is necessary to add heat to the cracking zone, but with certain stocks and under certain conditions it may be necessary to extract heat. In either case, the apparatus and method hereindescribed provide onvenient means for regulating the heat supplied to the cracking zone or removed therefrom, by varying the amount of heat contained in the rotatin catalyst segments.

If, for example, the particular cracking reaction being carried out is strongly endothermic, it

is necessary to supply to the cracking zone a relatively large amount of heat. In accordance withmy invention, this heat is supplied by the rotating catalytic segments which serve a dual purpose in that they act as a heat exchanger in addition to acting as catalysts. By proper control of the speed of rotation and of the heat supplying media in the purging and regenerative sections of the apparatus, an amount of heat can be stored in the rotating catalytic segments which will be just suflicient to supply that nec-.

essary for the cracking reaction. In the event that the cracking reaction is exo- ',thermic, the rotating catalyst segments are I35 and mixed, i1 desired,.with

the products oithe cracking and regenerative sections, respectively, or else handled separately.

f'lhus, the valves I30, I3I on the outlet of the steam purging sectionof the first purging zone permit exhaust gases therefrom to be mixed with the product of the cracking section or handled independently. Likewise, the valves I32, I33 on I as upq'n thermal several zones and the catalyst segments passing cooled in the zones other than the cracking zone, and are returned to the letter at a temperature below that prevailing in the cracking zone, so that they act to extract heat.

The heat supplied and extracted trom the rotating catalytic segments in the various zones will, of course, depend upon the specific heat, 1. e.,

'the heat containing capacity of a given mass of the catalyst per degree of temperature, as. well gradients existing between the therethrough. Consequently, the catalytic mass should have a relatively high specific heat and the mass itself should be large enough to assure ample heat carrying capacity. I

Assuming that the catalyst segments are such as to carry an adequate amount of heat to or from the cracking zone, the regulation oi the amount of heat so carried can be controlled in various ways. If gases'or constant specific heat,

temperature and volume are passing through the purging and regenerative sections, the amount of heat supplied to the cracking zone may be altered by varying the speed of rotation of the catalyst carrier. On the other hand, the amount of heat introduced into the catalyst carrier and supplied to the cracking zone may be varied by varying the temperature of the purginggases,

or by varying the temperature or the oxidizing gases passed in contact with the catalyst in the regenerative zone. Since the great bulk of the heat supplied to the catalyst'is supplied in the the outlet of the second purging zone permit exits regenerative zone, this isa satisfactory point at which to regulate the amount of heat supplied. This regulation may be brought about by changing the temperature or the specific heat or both.

'dition having been attained, and assuming the posited thereon. Thus, if desired, all or the I be supplied in the reactivation zone either from v the heat of combustion, orfrom the sensible heat and quantity of preheated steam orv other purgthrough the regenerative section.

1 in the cracking zone.

of the gases passed through the regenerative zone. However, this regulationof heat in the regenerative zone cannot be regulated without regard tothe oxidizing characteristics or capacities of the gases passingtherethrough. Conse- 5 quently, it is convenient to provide, as illustrated in Fig. 5,-a source 01' hot oxidizing gas and or a hot diluent or inert gas, which may be inert carbonaceous gaseous products of combustion or steam or both. By regulating the temperature and proportions of these ingredients, it is possible to obtain a gas mixture which has the correct oxidizing characteristics concurrently with the proper specific heat and temperature. This conoptimum activity or the catalyst for the particular hydrocarbon stock undergoing cracking. Once the desired speed of rotation for a given stock has been established, thecharacter; and amount of oxidizing gas employed in reactivation may be controlled soas to burn from the catalyst the desired proportion oithe carbon content decarbon may be burned out of the catalyst. However, it is preferable to burn substantially only thesuriace carbon from the catalyst, leaving 7 some deposit oi carbon within the pores of the mass. Operations so conducted result in an increased yield of more valuable hydrocarbons with a minimum degradation or conversion 0! hydrocarbons to elemental carbon.

. In the event that the heat or reaction cannot of gases introducedtherein while maintaining an optimum catalyst eiilciency, the apparatus may be divided into five sections rather than four, the additional section being used for raising or lowering the temperature or the catalyst bed by means of steam, inert gas, or by passing the gaseous products of reactivation through the mass. Moreover, by varying the temperature mg gas passed through the purging sections, the

amount or heat picked up by-the rotating catalyst may be varied tosome degree.

As indicated hereinbetore, the sealing steam introduced into the. jacket space between the catalyst wheel and the drum of the casing tends to leak into the oil'vapor being cracked as well as into the inert gas or steam-air mixture passed For this reason, the steam employed for sealing should be maintained at a temperature sufliciently high that leakage thereof into the apparatus will not reduce the temperature of the vapor and gas streams, especially the stream of hydrocarbons. Hence, it is necessary to superheat the steam employed for sealing to a temperature slightly. in excess of that of the oil vapors being treated Superheating the steam oiIers a further advantage by serving to reduce the amount of steam required for sealing.

asoasas In order to minimize steam consumptlonlin the apparatus and especially steam consumption 7 due to leakage, it is desirable to maintain the pressure oi'the gases employed in reactivation substantially the same as the pressure or the oil vapor entering the cracking zone. v

To minimize leakage from zone to zone at the bottom of the carrier wheel a back pressure should be maintained on the products from the reactivation zone substantially equal to the back pressure on the oil vapors leaving the cracking zone.

In order to maintain the desired pressure in the reactivation'zone while varying the supply of oxygen thereto, the amount of steam or additional inert gas introduced into the reactivation zone may be .varied inversely to the air supply so as to maintain a substantially constant volume flowing through the catalyst. This will permit the maintenance or a pressure drop through the reactivation zone equivalent to the pressure drop 01 the oil vapors passingthrough the cracking zone. The valves provided in the apparatus, as

illustrated in Fig. 5, permit such variations.

Generally speaking, the portion of the apparatus employed as a regenerative zone should be approximately the same in size as that employed in cracking and both should occupy several times as much space as the'purging sections. However, when it is'necessary to supply a very large amount of heat to the cracking zone, it maybe desirable to reducethe size of the crackingzone as compared to the regenerative zone thereby increasing the heat transfer therebetween. "It should also be observed that sumcient plate must be leftbetween' the ports of both upper and lower heads to prevent any catalyst carrier segment of the carrier wheel from coming in contact with two zones at the same time.

reduce operating costs greatly, the advantages oi" vacuum purging increasing as cycle time 01' the catalytic cracking operation is decreased. In other words, economies due to the use of vacuum purging are greater as cycle times are decreased, principally due to a saving in hydrocarbons. For some reason not clearly understood, steam or other gases introduced from an exterior source require a considerable time in contact with a catalyst segment to purge it efflciently of hydrocarbons, unless the' purging gas is assisted first bya reduced pressure.

Generally speaking, the degree or the amount of suction to be maintained upon the purging sections will depend upon several factors, including; (1) the introduction of steam or other purging gas from anextericr sourceinto the purging zones, whichtends to reduce the suction or, conversely, to increase the pressure in the purging zones; (2) the degree of-a pressure maintained in the cracking zone and regenera 'tive zone. Thegreater thepressure in these zones, the greater is the tendency for leakage through the seals into adjacent purging zones, if a high degree of vacuum ismaintained in these zones.

To take a specific example, in an operation in which the pressure in the cracking zone and regenerative zone is maintained at about 10 lbs. per sq. in. (gauge), eiiective operation is at- Thus, any individual segment of. the catalyst carrier must pass completely out tained'if a vacuum of about 29 inches Hg is maintained in the vacuum section of the first purging zone.

Employment of vacuum to maintain reduced pressure in the purging zones not only brings about a saving of hydrocarbons but also some are shortened; there is a marked improvement of character of product and in cracking emciency. Thus, the yield of gasoline per unit of catalyst is increased substantiallyqand there is also a minor tendency for an increase in the octane rating of the product. A further advantage of vacuum purging resides in the fact that it lengthens catalyst life, by reducing the quantity of steam in contact with the catalyst which tends to have'a. slow but positive deleterious effect.

The apparatus of Figs. l'to 6 may be incorporated into a variety of hydrocarbon cracking systems, and utilized in conjunction with a variety of equipment for recovering and separating the cracked hydrocarbons. One means of utilizing the apparatus is illustrated in Fig. '1

which is a flow sheet of a. catalytic cracking system including the rotating catalyst apparatus hereinbefore described. troleum stock I50 to be cracked is mixed with an appropriate amount of steam' II and the mixture is passed to a heater I52 which vaporizes the oil substantially completely. From the heater a mixture i53 of oil vapor and steam (say in 'equimolecular proportions) passes 'to a cracking apparatus I54, constructed as described in detail hereinbefore and indicated diagrammatically on Fig. '1. The oil vapor and steam In this system, a pethe regenerator section of the cracking apparatus. To produce the hot compressed air, atmospheric air is first compressed in a compressor I'62, passed through a heater I63 and thence into the line I6I. The inert gases for diluting the air and thus impeding the combustion of the carbon on the catalyst segments passing through the regenerative section may be produced by burning carbonaceous fuel I64 in hot compressed air delivered to an inert gas generator I65 through a pipe line I66. 'From the inert gas generator the inert gas, in which the oxygen has been substantially all consumed is sent into the pipe line I6 I.

superheated steam may be admitted to the second purging section through a conduit I61, and

after passing through the rotating catalyst segments be withdrawn. from the lower head and passed to waste either independently or mixed with the exhaust gases from the regenerative section through a stack I68.

When the petroleum stock to be cracked is a relatively light oil which can be completely vaporized under prevailing temperature and pressure conditions, say a temperature ranging from 800 to 1000" F. and a pressure ranging from sub-atmospheric to in excess of 100 lbs. per sq. in., it is not necessary to remove u'nvaporized hydrocarbons prior to introduction of the mixture of oil and steam into the cracking apparatus. Otherwise, a flash chamber (not shown) should be disposed between the heater and the inlet for the oil vapors into the cracking apparatus.

If desired, one or more of the cracking apparatus or units may be connected in parallel or in series. In any event, the outlet from the crack ing sections of the apparatus augmented by seal- I ing steam and any purging steam mployed (all at a temperature of about 750-11OQ F. and preferably between 800-1000 F.) is sent to the flash tower I60A without release of pressure.

The flash tower temperature may be controlled either by recirculation of condensed tar or by inmixture passes through the cracking section of the apparatus as the catalyst carrier thereof is rotated (at a speed of, say, two revolutions per minute) and the oil is cracked and withdrawn in a mixture I of steam and vapors of lower boiling hydrocarbons at the lower portion of the apparatus.

A supply of steam I56 for operating the purging sections of the crackirm apparatus, for admixture with hot air for the regenerative section and for sealing purposes is passed through a superheater I51, and there heated to a temperature in excess of that of the oil entering the cracking section. Part of this superheated steam is passed through a line I58 into the 7 space between the catalyst wheel and the drum of the casing, from which it may leak through the labyrinthian seals into any of the sections of the apparatus but in so doing prevents leakage outwardly from these sections. Another part of the superheated steam may pass through a line I59 into the first purging section of the apparatus and there aid in sweeping out of the catalyst segments that rotate therethrough residual oil vapors. The steam from the first purging section may be permitted to intermingle with the cracked hydrocarbons exhausted from the cracking apparatus to form the mixture I55 and through a pipe line I60 the mixture is sent to a flash tower IBIIA. V

A third portion of the steam from the superheater may be mixed with hot compressed air and inert gases in a pipe line I6I and passed through troductlon of fractionating column bottoms to give a desired tar gravity preferably less than 10 A. P. I. Both types of control are provided for in the apparatus illustrated in Fig. '1. Thus, tar may be withdrawn from the bottom of the flash tower through a line I69 and part of the tar forced through a pump I10 back into the flash tower with or without cooling in a cooler I1 I.

The flash tower overhead I12 passes to a fractionating tower I13. Here two gas oil cuts may be taken oiI-one as a side stream I14 and one as a bottom out I15. Either or both of these streams may be recycled through the system for further processing and may be returned to the tower system either hot or cold, as desired. In the apparatus illustrated in Fig. 7, provision is made only for recirculation of the bottom .cut through a pump I16 and optionally either through a cooling coil I11 or directly in the hot condition.

In the apparatus illustrated in Fig. 7 the side stream cut is passed through the cooler I18 and thence is withdrawn from the system for further processing.

I82 and a line i8; for controlling'the tempera-C ture of the top of this column.

The apparatus of Fig. 7 is designed for low' pressure operation, in which case a gaseous overhead product I84 of the receiver i8! (i. e., the portion. of the fractionating column overhead which remains uncondensed) is withdrawn from separated under a pressure of approximately 250 lbs. per sq. in. Such separation gives a gaseous end product which is relatively free from hydrocarbons that should be included in' the liquid product or distillate.

The distillate I88 from the highpressure receiver, i. e., the bottoms product or liquid, resulting from the separation under high pressure, is sent to a conventional stabilizer I89 from which a distillate I90 of the desired vapor pressure is drawn 011? as a bottoms product. Overhead gas "I from the stabilizer normally is diverted together with the overhead I92 from the high pressure receiver to a polymerization plant for conversion of these gases to higher olefin for polymer asoline.

It will be understood, of course, that the advantages of vacuum purging apply whether or not it is practiced in the second zone following cracking, or in the fourth zone following regeneration, or in both the second and fourth zones. Thus, in accordance with my invention vacuum and steam purging may be practiced in the second zone with steam purging in the fourth zone, or vice versa. Moreover, it may be advantageous in certain operations to practice a steam and vacuum ipurging in both the second and fourth zones.

i I claim: i

1. In the catalytic cracking of hydrocarbons involving the contact of a catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and the subsequent treatment of the mass in an oxidizing atmosphere to burn the carbon and regenerate the mass for further contact with the hydrocarbons, the improvement which comprises rotating the catalytic mass successively and substantially continuously relative to and through a first zone to which the vaporized hydrocarbons are supplied substantially continuously and from which the resulting cracked hydrocarbons are substantially continuously withdrawn, a second zone having a first portion maintained under a pressure substantially less than that in the first zone and from which vapors entrained by the rotating catalytic mass are sucked substantially continuously and a second portion through which a purging gas is passed from an extraneous source, a succeeding regenerative zone through which a hot oxidizing gas is passed substantially continuously and in which the carbon on the mass is oxidized, the resulting carbonaceous gases being withdrawn substantiaily. continuously from said regenerative zone and a final purging zone from which entrained gaseous products-of the carbon combustion in the regenerative zone are removed substantially continuously.

2. In the catalytic cracking of hydrocarbons involving the contact of a catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and the subsequent treatment of the mass in an oxidizing atmosphere to burn the carbon andregenerate the mass for further contact with the hydrocarbons, the improvement Which comprises rotating the catalytic mass successively and substantially continuously relative to and through a first zone to which the vaporized hydrocarbons are supplied substantially continuously and from which the resulting cracked hydrocarbons are substantially continuously withdrawn, a second zone having a first portion maintained at a pressure substantially less than that in the first zone and from which vapors entrained by the rotating mass are sucked substantially continuously, a second portion of the second zone through which a hot purging gas is passed substantially continuously, the hot purging gastogetherwith gaseous products removed from the catalytic mass inthe second portion being removed from said portion, a succeeding regenerative zone into which a hot oxidizing gas is passed substantially continuously and in which the carbon on the massis oxidized, the resulting carbonaceous gases being with-' drawn substantially continuously from said regenerative zone, and a final purging zone in which the rotating catalytic mass is purged of the gaseous products of the carbon combustion entrained in the regenerative zone by passing a hot purging gas therethrough prior to reintroduction of the mass into the first zone.

3. In the catalytic cracking of hydrocarbons involving the contact of a catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and the subsequent treatment of the mass in an oxidizing atmosphere to burn the carbon and regenerate the mass for further contact with the hydrocarbons, the improvement which comprises rotating the catalytic mass successively and substantially continuously relative to and through a first zone to which the vaporized hydrocarbons are supplied substantially continuously and from which the resulting cracked hydrocarbons are substantially continuously withdrawn, a second zone the first portion of which is maintained under a pressure substantially less than that prevailing in the first zone and from which hydrocarbon gases are sucked substantially continuously and the second portion of which is treated with a hot purginggas that is passed substantially continuously therethrough,- the hot purging gas together with gaseous products entrained by the mass in the second portion being withdrawn therefrom substantially continuously, a succeedingregenerative zone through which a hot oxidizing gas is passed substantially continuously and in which the carbon on the mass is oxidized, the resulting carbonaceous gas being withdrawn substantially continuously from said regenerative zone, and a final purging zone regenerative zone being withdrawn from the final purging zone and the resulting purged catalytic ,mass being reintroduced into the first zone.

4.'In the catalytic cracking of hydrocarbons involving the contact of a catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and the subsequent treatment of the mass in an oxidizing atmosphere to burn' the carbon and regenerate the mass for further contact with the hydrocarbons, the improvement which comprises rotating the catalytic mass successively and substantially continuously relative to and through a first zone to which the vaporized hydrocarbons are supplied substantially continuously and from which the resulting cracked hydrocarbons are substantially continuously withdrawn, a second zone divided into two portions, the first of which is maintained at a pressure substantially less than that of the first zone and from which hydrocarbons entrained in the first zone are sucked substantially continuously and the second of which is purged by means of a hot gas passed therethrough, a succeeding regenerative zone through which a hot oxidizing gas is passed substantially continuously and in which the carbon on the mass is oxidized, the resulting carbonaceous gases being withdrawn substantially continuously from said regenerative zone, and a final purging zone into which superheated steam is introduced substantially continuously and from which the resulting mixture of supe heated steam and carbonaceous gases is withdrawn substantially continuously, the catalytic mass being reintroduced into the first zone.

5. In the catalytic cracking of hydrocarbons involving the contact of a catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and the subsequent treatment of the mass in an oxidizing atmosphere to 'burn the carbon and regenerate the mass for further contact with the hydrocarbons, the improvement which comprises rotating the catalytic mass successively and substantially continuously relative to and through a first zone to which the vaporized hydrocarbons are supplied substantially continuously and from which the resulting cracked hydrocarbons are substantially continuously withdrawn, a second zone from which vapors entrained by the rotating catalytic mass in the first zone are purged substantially continuously, a'

succeeding regenerative zone through which a hot oxidizing gas is passed substantially continuously and in which the carbon on the mass is oxidized, the resulting carbonaceous gases being withdrawn substantially continuously from said regenerative zone, and a final purging zone having OLIVER F. CAMPBELL.

CERTIFICATE OF CORRECTION. Patent No. 2,50l4 598. December 8, 911.2.

OLIVER F. CAMPBELL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 51+, after the word "vertical" insert --section-; and in the drawings, Sheets 1 and 5, Figures landh. should read as shown below instead of as in the patent :nd that the said Letters Patent should be read with this correction theren that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 50th day of March, A. D. 1915.

Henry Van Arsdale, (Seal) Acting Gorgmissioner of Patent