US2887341A

US2887341A - Pneumatic lift disengager

Info

Publication number: US2887341A
Application number: US641085A
Authority: US
Inventors: Jr Willis Jolleff Cross
Original assignee: Houdry Process Corp
Current assignee: Houdry Process Corp
Priority date: 1957-02-19
Filing date: 1957-02-19
Publication date: 1959-05-19
Anticipated expiration: 1976-05-19

Description

May 19, '1959 Filed Feb. 19, 1957 y w. J. cRoss, JR 2,887,341

PNEUMATIC LIFT DISENGAGER 2 Sheets-Sheet 1 a '64s III! aanfr M7- @fsf/vanaf@ TZUR ZVEY May 19, 1959 w. J. cRoss, JR 2,887,341

PNEUMATIC LIFT DISENGAGER Filed Feb. '19, 1957 2 sheets-sheet 2 IN V EN TOR.

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United States Patent O PNEUMATIC LIFT DISENGAGER Willis Jolleif Cross, Jr., Media, Pa., assignor to Houiiry Process Corporation, Wilmington, Del., a corporation of Delaware Application February 19, 1957, Serial No. 641,085

6 Claims. (Cl. 302-59) This invention relates to improvements in the disengager of a pneumatic lift for transporting granular material by means of lift gas, and has particular application to the type of gas lift commonly employed in catalytic hydrocarbon conversion systems for the purpose of circulating granular contact material. Such disengagers commonly comprise an elongated cylindrical vessel surrounding the upper end portion of one or more upright lift pipes disposed alongside, or distributed circumferentially around the processing unit or vessel. The disengaging vessel, or disengager, generally extends some distance above the discharge level of the lift pipe or pipes so as to permit substantially complete gravitational deceleration of the discharged stream of Solids, with accompanying free fall thereof to the bottom region of the disengager where they are directly withdrawn from the bottom of the vessel or are deposited onto the surface of a compact moving bed of previously disengaged solids maintained within said bottom region as a surge supply. Disengagement of the solids from the gaseous material occurs by reason of the `fact that the disengager is of greater cross-sectional ilow area than the one or more lift pipes, so that there is a substantial reduction in the velocity of the discharging stream or streams of lift gas. While it is a common practice to have the lift gas discharged into the disengager at substantially less than the supporting velocity of the solid particles, the solids nevertheless continue their upward movement for quite a distance as a result of their momentum.

ln the type of disengager to which the present invention is particularly directed the disengaged solids are collected at the bottom of the vessel and are discharged by gravity ilow therefrom through suitable conduit means, while the gaseous conveying medium is discharged from the Vessel through suitable conduit means communieating with the top region of the disengaging vessel. `Such gas conducting means may have its discharge outlet at the top, sides or bottom of the disengager.

Regardless of the number of lift pipes extending upwardly into the lower region of the disengager, and regardless of whether the lift pipe or pipes are near the vertical `axis of the vessel or are located in the peripheral region thereof,` the practical limitations with respect to the size of the disengager are such that occasional larger- `size particles of the granular contact material discharging from the lift pipes rebound from contact with the vessel walls or from contact with other particles and eventually reach a position so close to the mouth `of the gas outlet conduit that they are readily carried into such conduit means and out of the vessel by reason of the substantial increase in the velocity of the withdrawn gas in the region immediately adjacent to the gas outlet.

One way to minimize such loss of random or stray particles through the gas outlet is to provide some form of baille or dellector in the region adjacent to the gas outlet and in the path of the rising stream or streams of solids, so that the higher-rising portion of the discharged stream of particles will be intercepted by the baille and ICC deflected downwardly toward the sides or bottom of the disengaging vessel.

In order to overcome the aforementioned diillculties, it has been a practice in some commercial installations to provide near the upper end of the disengager a transverse baille which extends almost entirely across the vessel, leaving only a peripheral annular space for passage of `the lift gas around and over the top oi the baille to the gas outlet. Such baille, for example, may be in the form of a shallow concave disk supported below the gas outlet with its concave surface facing downward and conforming somewhat generally to the curvature of the dished head which normally closes the upper end of the vessel.

Although the cross-sectional area of the annular gas passage formed between the perimeter of the circular baille and the side walls of the vessel is such as not to greatly increase the velocity of the outgoing gas as it enters the passage, it is obvious that as the gas ilows above the baille toward the mouth of the outlet conduit its velocity gradually increases to a magnitude sufficient to entrain any solid particles which happen4 to Work their way into the region of such high gas velocity.

As stated, it is a common practice to operate gas lifts of the type referred to herein at such conditions that the gas leaving the lift pipes has already been decelerated to a velocity below the supporting velocity of the substantial major portion of the solids. Since the gas is further `decelerated within the larger area of the disengaging vessel there is no serious problem with respect to `entrainment of the solids by the gas stream tlowing into the annular passage. Nevertheless, by reason of the continual impact between rising and falling solids and with the wall surfaces of the disengager, some particles rebound into the annular passage and bounce into the region above the baille where the gas velocity is suilicient to influence their further movement toward and into the gas outlet.

It is therefore an object of the present invention to provide `an improved baille arrangement whereby lift gas may be collected in the upper peripheral region of a disengager and be conveyed out of contact with the main body of rising and falling solids to a gas outlet conduit communicating with the disengaging vessel in the region `shielded by the baille, the arrangement in its broadest concept comprising a primary baille means, extending horizontally across the major portion of the disengager and terminating short of the side walls a distance suilicient to provide a peripheral gas passage, and an annular secondary baille means, below the peripheral gas passage and in relatively close proximity thereto, so as to provide a circuitous path for gas flow between the disengaging zone and the mouth of the gas outlet conduit through which the separated lift gas is discharged from the vessel. The arrangement is such that the secondary baille provides a circumferential shelf or trough along the side wall of the vessel, extending inwardly into the path of the rising and expanding stream or streams of solids so as to intercept and deilect the substantial major portion of such solids which either directly or indirectly have been impelled toward the annular passage surrounding the pri,- mary baille; such few particles as happen to be projected onto the shelf or into the trough may be returned to the bottom of the disengager either by spill-off orby drainage through suitable openings provided in the bottom of the secondary baille.` With optimum arrangement and proportioning of the structural elements, and under optimum operating conditions, it is not deemed necessary to make any special provision for drainage from the secondary baille.

In a preferred embodiment of the invention, as applied to an upright, elongated cylindrical disengager having the entrance to its gas outlet conduit located centrally at its upper end, and having solids withdrawal means at its lower end, there is provided a primary baille in the form of a shallow concave disk rigidly supported axially below the gas outlet, which primary baille extends horizontally across all but a narrow peripheral area in the upper end region of the vessel, thereby providing an annular vertical outlet for the gas around the upper internal perimeter of the vessel. of a frusto-conical ring is placed below the primary baille with its lowermost and larger perimeter rigidly secured to the side walls of the vessel, and its uppermost and smaller perimeter located a distance vertically below, or even slightly inward of the downwardly projected perimeter of the primary baille. The annular gap or passageway between the vertically-spaced outer perimeter of the primary baille and inner perimeter of the secondary baille is substantially equal in ilow area to the annular gap or passageway between the horizontally-spaced outer perimeter of the primary baille and the sides of the vessel, so that the deilected gas in ilowing iirst outwardly between the two bailles and then upwardly and inwardly over the perimeter of the primary baffle will not undergo any substantial increase in velocity. The spacing of the bailles with respect to each other, and the spacing of the uppermost central baille with respect to the side walls of the vessel are preferably such as to maintain within the peripheral passages of the vessel a gas velocity in the range of about 7-20 t./sec., and preferably in the orderof about 10-15 ft./scc. The frusto-conical ring comprising the secondary baille forms with the side walls of the vessel an annular V-shaped trough into which stray deilected particles projected through the first-mentioned gap or passageway may be deposited. While it is not expected that there will normally be any substantial diversion of solids into such V-shaped trough, such solids as do accumulate in the trough may be permitted to remain there until eventually the trough becomes iilled to overilowing, after which additional diverted particles spill over the edge of the trough. Alternatively, outlet holes may be provided in the bottom of the trough to drain the solids therefrom.

If desired, conduits may communicate with the openings along the bottom of the trough, that is, immediately adjacent the vessel wall, to convey such accumulation of granular material downwardly through the main disengaging region of the vessel to a lower level which is below the discharge level of the lift pipes. Catalyst drains and drainpipes, however, are not to be considered essential, or necessarily even desirable except where other considerations dictate their use.

A fuller understanding of the invention may be had by reference to the following description and claims taken in connection with the accompanying drawing forming a part of this application, in which:

Fig. 1 diagrammatically illustrates a hydrocarbon conversion system of known design, to which the present invention has especial, though not exclusive, application;

Fig. 2 is an enlarged sectional elevation of the disengaging vessel shown at the upper end of Fig. l; and

Fig. 3 is a horizontal section taken along the line 3--3 of Fig. 2.

In the drawing, the hydrocarbon conversion system of Fig. 1 comprises superimposed reactor and regenerator vessels 11 and 12, respectively, connected by an elongated conduit or seal leg 13. Within each of vessels 11 and 12 the granular contact material, such as catalyst, ilows as a compact moving bed, and the granular material is continuously conveyed between such compact moving beds as a compact moving stream descending through thevseal leg 13.

Continuous circulation of the granular material through the reactor andthe regenerator is maintained by passing the contact material from the bottom of regenerator 12 as a plurality of compact moving streams through drawoil conduits 14 which discharge the granular material into A secondary baille in the form r lift engagers 15 of a pneumatic lift, generally indicated by the numeral 16. Although the invention is not limited to a multiple lift, for purposes of illustration, the pneumatic lift comprises a plurality of lift pipes 17 distributed about the vessels 11 and 12 and extending upwardly from individual lift engagers 15 to a common disengager 18 located above the upper end of the reactor 11. Near their upper ends, lift pipes 17 are bent slightly so as to curve inwardly over the top of reactor vessel 11. The converging ends of the lift pipes, of which there are four in the illustrated embodiment, enter through the conical bottom of the disengager, shown in Fig. 2.

Within the common disengager 18 the solids are disengaged from the gaseous material, the latter being discharged at the top of the disengager through overhead gas outlet 19, and the disengaged solids being discharged at the bottom of the disengager through a single draw-oil conduit 21 which conveys the disengaged solids back to the reactor 11. Since the invention is primarily concerned with improvements relating entirely to the disengager 18, a further detailed description of the hydrocarbon conversion unit as a whole is not considered necessary for an understanding of the invention, and will therefore be omitted.

Disengager 18 is of generally cylindrical shape, having a dished head and conical bottom section which collects the disengaged solids and directs them into the draw-off conduit 21. The four lift pipes 17 extend upwardly into the disengager through the sloping side walls of the conical bottom section and terminate at a common intermediate discharge level therein, suillcient vertical distance being provided between the discharge level of the lift pipes and the top of the disengager within which to disengage the substantial major portion of the solid particles from the lift gas.

The invention is also not limited to a multiple lift system in which the plurality of lift pipes are located around the treating vessels, as shown, but may have equal application to a multiple lift system in which the lift pipes are grouped to one side of the treating vessels. Or, the lift may comprise one or more lift pipes extending centrally upward into the disengager.

The stream of solid particles discharging with the gaseous material from the upper ends of the plurality of the lift pipes 17 will have a discharge pattern approximately as shown by the dotted lines diverging outwardly from the discharge ends of the lift pipes. 4

A primary baille 22 in the form of a shallow concave disk is horizontally supported, as by vertical rods 23, axially below the gas outlet 19. The diameter of baille 22 is smaller than that of the cylindrical vessel 18, so that an annular passageway 24 is provided between the perimeter of baille 22 and the side Walls of the vessel 18 through which gas may flow rst upwardly and then radially inwardly over the top of baille 22 toward the gas outlet 19.

A secondary baille 25, in the form of a frusto-conical ring, is supported concentrically below the primary baille 22 and is spaced vertically therefrom a distance substantially equal to the width of annular passageway 24, thereby forming between the primary and secondary bailles a horizontal passageway 26. The inner diameter of frustoconical baille ring 25 is not greater than the diameter of the baille disk 22, and may advantageously be slightly less than the latter diameter, so that the upper perimeter of baille ring 25 will be located below and slightly inwardly of the perimeter of baille disk 22.

rl`he frusto-conical baille 25 is sloped at an angle of about 35 or more to the horizontal. The matter of angularity is not too critical, although the angle should not be too small.

The lower perimeter of baille ring 25 is attached, as by welding, to the side walls of the vessel 18. A plurality of openings 27 are provided along the lower edge portion of baille 25 to serve as drains for solids accumulating in the annular hopper-like trough 28 formed between the baille 25 and the side walls of the vessel 18. Vertical conduits 29 are provided about the inner walls of the vessel 18 to convey disengaged solids from the outlets 27 to the lower region of the vessel 18 where they are deposited onto the surface of a compact moving bed 31 of disengaged solids continuously maintained in the bottom region of the disengager. The number of pipes 29 required will depend upon the size of the trough 28, the pipe size and spacing preferably being such as will preclude any spill-over of solids from the trough.

As the solid particles discharging from the lift pipes 17 rise to the upper region of the disengager it is expected that most of the solids will have become disengaged before they reach the level of the

bailles

22 and 25. The remaining, higher-rising portions of the solids streams will be deilected downwardly and inwardly by both the under surface of frusto-conical baille ring 25 and the concave under side of baille disk 22. Normally, it is not expected that any substantial portion of the solids rising above the principal zone for disengagement will fail to be deilected downwardly by the two bailles. However, since the course which particles will take after hitting the internal structural surfaces and after particle-to-particle impact is unpredictable, it is inevitable that some portion of ythe particles will be projected through the horizontal passageway 26 between the bailles 22 and 25. Since there is no region in the annular space within and above the trough 28 where the velocity of the ilowing gas will be increased, and since such velocity is in the range of 7-20 ft./sec., that is, below the supporting velocity of the larger-size particles, the latter become disengaged from the gas stream within such annular space and fall into the trough 28, from which they are eventually returned to the catalyst stream at the bottom of the vessel.

The conduits or downcomers 29 convey the solids from the trough 28 to a level in the bottom region of the disengaging zone where they may be deposited by free fall upon the surface of the bed 31 which provides catalyst supply for the system. If, as in some systems, a separate supply or storage hopper is provided below the disengager and above the reaction chamber, the conduits 29 may extend downwardly to a level near the sloping bottom walls of the vessel 18, so that the particles will not suffer severe impact upon reaching the surface on which they are deposited. In any case, the particles so returned should not come into contact with the high-velocity streams of solids discharging from the lift pipes 17.

Although the illustrated embodiment of the invention discloses a lift gas outlet located centrally in the upper head or end closure of the vessel, it is to be understood that the invention contemplates other outlet arrangements. The gas outlet may be at one side of the head, or several such outlets may be provided. Or the disengaged gas may be received into a conduit whose inlet end is located above the primary baille and whose outlet end is in the bottom or in some other part of the vessel.

While the invention has been shown in but one form, and has been described it will be obvious to those skilled in the art that it is susceptible to various changes and modifications without departing from the spirit of the invention, and it is desired therefore that there shall not be placed thereon any limitations other than those set forth in the appended claims.

What is claimed is:

1. In a pneumatic lift disengager comprising an upright vessel having at least one lift pipe discharging upwardly therein, a lift gas outlet at the upper end of said vessel, a solids outlet at the bottom of said vessel, and a horizontal baille disposed adjacently below said gas outlet and extending almost entirely across said vessel to pro` vide with the side walls thereof an annular opening for passage of lift gas upwardly and inwardly over the top of said baille to said gas outlet, said baflle being at such V,distance above the discharge level of said lift pipes as to -deilect the highest-rising particles of decelerating solids, the combination therewith of a secondary baille comprising an annular plate extending inwardly from the wall of said vessel to within the vertical downward extension of the perimeter of the primary baille, the vertical distance between the perimeter of said primary baille and the inner perimeter of said secondary baille being substantially equal to the width of said annular opening between said primary baille and the side walls of said vessel whereby lift gas rising through the upper region of said vessel is tirst deilected outwardly between said bailles to the peripheral region of said vessel and then upwardly and inwardly over the perimeter of said primary baille toward said gas outlet.

2. Apparatus as in claim l, in which the annular plate forming said secondary baille extends both inwardly and upwardly so as to form a continuous horizontal trough along the inner wall of said vessel.

3. Apparatus as in claim 2, including means for draining solids from the bottom of said trough.

4. Apparatus as in claim 3 in which said drainage means comprises conduits extending downwardly along the inner walls of said vessel to locations in the bottom region thereof which are outside the cones of solids discharge from said lift pipes.

5. Apparatus as in claim 2 in which said disengaging vessel is cylindrical, said primary baille is in the form of an inverted concave disk, and said :secondary baille is in the form of a frusto-conical ring.

6. Apparatus as in claim 1 in which said vertical distance between the perimeters of said bailles and said width of said annular opening between the perimeter of said primary baille and the side walls of said chamber are predetermined in accordance with the contemplated rate of gas ilow so that the velocity of the disengaged gas ilowing ilrst outwardly between said bailles and then upwardly and inwardly over the perimeter of said primary baille is maintained lower substantially than the supporting velocity of the substantial major portion of said granular material, whereby any heavier particles of said granular material which happened to be deflected through the opening between said bailles will be deposited upon said secondary batllle instead of being carried over the top of said primary baille to said gas outlet.

References Cited in the le of this patent UNITED STATES PATENTS 2,656,920 Kollgaard Oct. 27, 1953 2,672,374 Norris Mar. 16, 1954 2,689,153 McClure Sept. 14, 1954 2,708,142 Donovan May 10, 1955