US2873146A - Lift disengager - Google Patents

Description

Feb; 1o, 1959 W. J. CROSS, JR.. ET AL LIFT DISENGAGER 2 Sheets-.Sheet 2 Filed Deo. 19, 1957 f s. E Z mi Nima f WwH @W m M a 1 z WMM@ Z 5 4. a0 MM z 2;/ .f w, ANIM ,l C? 111111 United States Patent O iceN LIFT DISENGAGER Willis J. Cross, Jr., Media, and Albert Wesley Hoge,

Swarthmore, Pa., assignors to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware Application December 19, 1957, Serial No. 703,958

5 Claims. (Cl. 302--59) peripheral region of the disengaging zone.

Because of the frangible nature of the granular contact material generally employed in such hydrocarbon conversion systems, one of the principal problems involved inthe disengagement of the solids from the lift gas is that of minimizing forceful impact of the solids against the metal surfaces of the disengager vessel and its internal structural elements as well as against each other. Such particle-to-particle impact may result from collisions between ascending solids in the discharging lift stream and descending solids which have already become disengaged from the lift gas and are falling to the bottom of the disengager. Additionalforceful impact may occur when the falling disengaged particles bounce upon the bottom of the disengager vessel or upon earlier disengaged particles of solids which are retained upon or are moving across the bottom surface. Since the height of rise, that is, the disengaging height, of catalyst within a disengager is generally quite high, the disengaged particles may have ya considerable distance of free fall. Unless provision is made for arresting or minimizing such freefall, severe attrition of the solid particles may result.

It is a principal object of the present invention to provide a disengager adapted to receive in the peripheral region thereof a plurality of upwardly discharging streams of solids and lift gas, and to so direct or deflect the rising solids that forceful impingement of particles against the structural surfaces and forceful` particle-to-particle contact between the solids will be held `to a minimum, with resultant decrease in solids attrition.

l, In accordance withthe invention, the lift pipes enter through the lower end of the disengager at points distributed along and adjacent to the inner periphery of the vessel. The lift pipes may enter either vertically or at a slight inclination toward the axis of the vessel. The openings in the bottom of the disengager for receiving the lift pipes are ofgreater diameter than the lift pipes and are provided with short cylindrical guide sleeves into which the lift pipes extend. The lift pipes are free to move longitudinally within the sleeves to accommodate expansion or contraction of the pipes resulting from ternperature changes.

Each guide sleeve has a solids-deflecting hood attached to its upper end. The lower portion of the hood forms a vertical tubular extension of the guide sleeve and, by reason of the increased flow area, provides some additional decelerating effect for the solids which, preferably,

`2,873,146 Patented Feb. 10, 1959 have already been decelerated in the upper end region of the lift pipe. The remaining upper portion of the hood is half cut away on the side toward the axis of the vessel, the vertical sides of the half section being equally extended by flat parallel vanes toward `the central region of the vessel. Thus, the open portion of the hood surrounds the rising stream of solids on three sides, The hood extends upwardly to the highest practical level within the disengager, and the upper end of the hood is turned inwardly toward the axis of the vessel.

An inverted dished baille is supported horizontally above the circular row of hoods and outwardly overhangs the same. The baille is vertically spaced from a central lift gas outlet at the top of the vessel, so that the rising lift gas follows a tortuous path, rst flowing upwardly and inwardly from the hoods toward the axis of the vessel, and then in a double reversal of flow outwardly over the tops of the hoods and inwardly over the top of the dished bale to the gas outlet.

In the lower central region of the disengager vessel a dished receptacle or tray having a plurality of short drain pipes is rigidly positioned at a level just below the side discharge openings of the hoods. The disengaged solids fall onto the surface of the central dished head and drain freely through the short drain pipes, again falling freely to the bottom of the disengager vessel. Elongated draw- .oif pipes distributed about the bottom of the vessel conduct the disengaged solids by free fall to a surge chamber, not shown, which is located below the disengager vessel and from which the solids may be returned to the conversion system.

For a fuller understanding of the invention reference may be had to the accompanying drawings forming a part of this application, in which:

Fig. 1 is a sectional elevation of the lift disengager;

Fig.` 2 is a sectional plan View taken along the line of 2 2 of Fig. l;

Fig. 3 is a fragmentary section `of a group of hoods; and t Fig. 4 isa plan View of twoadjacent hoods.

Referring toFig. l of the drawings, the disengager is of the bottom portion of the lift has been omitted for the sake of clarity, since they form no part lof the presentinvention.

The disengager receives through its lower end theupper ends of a lcircular row of lift pipes 14. Ten lift pipes have been illustratedin the drawing, but fewer or more lift pipesmay be employed, as desired. The disengager is rigidly supported above the upper end of the `hydrocarbon unit, as shown, as by a lower extension 15 of the cylindrical shell 11, `or by other suitable structural elements.

In the illustrated embodiment the lift pipes 14, which may be assumed to be upright and straight over the substantial major portion of their length, have their upper endsinclined slightly inward toward the axis of `the disengager. At each point where a lift pipe enters the lower end ofthe disengager a guide sleeve 16 of larger diameter than the lift pipe is set in suitable openings inthe bottom of the head 13 to freely receive the upper end of the lift pipe. Radial spacers 17 are secured about the upper end of the lift pipe to freely guide `and to maintain concen` tricity of the lift pipeI `within the sleeve during longitudinal movement of the lift pipe as a result of expansion or contraction with changing temperature. The sleeve ast/3,146

guide 16is; set at( the same angle as the lift pipe 14 and has attached, as by butt welding, to its upper end a solids-deliecting hood, generally indicated by the numeral 18.

The hood 1d comprises a lower cylindrical portion 19- ofthe same diametery as guide sleeve 1'6. The semi-cylindrical portion of cylinder 19 located farthest from the axis of the disengager has a vertical extension 21 extending upwardly. toa level near the top of the cylindrical portion 11 and is cut ofi at an angle, as shown at 22.

Elongated V-shaped channel members 23, of the same length as vertical extension` 21, are set vertically between adjacent extensions 21, withy the base, of each channel pointing toward the axis of the disengager. The vertically-positioned edges of each V-channel are attached to the adjacent vertical edges of adjacent extensions 21. The arrangement is such that the sides of channels 23 forming a radial pair of Vanes for each extension 21 are Y substantiallyI parallel. Obviously, with a` lesser number of lift pipes itmay become impracticable tol employ V-channels to form the parallel vanes, in which case they may be fabricated at a U-channel or even asV separateplate elements.

An inclined baie plate 24 is attached near the upper en d of each hood 1S so as to deflect high-rising solid particles toward the axial region of the disengager. The top surface of the inclined baffle 24 together with they upper end portions of members'21 and 23 forms a catchbasin for stray particles. A drain hole. 25 in the side of extension 21 permits solids to drainA from the catch-basin and fall to the bottom of the vessel.

An inverted, dished baie 25 ispositioned in the upper central region of the vessel and overhangs the circular row of hoods 18, the batlie being supported from the upper ends of the hoods, as by vertical support membersl 27. Bailiel 26- is spaced from upper head 12 of the disengager vessel so that the lift gas, free of solids, may flow from the upper peripheral region of the disengager through annular gap 28 and then over the top of baffle 26 into and through the central outlet 29 at the top of the vessel. Depending from the central portion of the bafe 26 is an elongated pipe member 31 having a plurality of longitudinal ns 32 extending radially outward. The number of tins 32 corresponds to the number of hoods 18, the iins being directed toward the apexes of the V-channels 23.

A hanged, dished` head comprising a tray portion 33 and a vertical side or flange portion 34 is positioned in the lower central region of the disengager, inwardly of the lower cylindrical portions 19 of the hoods 18. A plurality of vertical spacers 35 are attached along one edge to the cylindrical. portions 19 and along the upper portion of their opposite edge to the vertical flange 34 of the receptacle 33 so as to unite the whole into a rigid unitary structure supported from the guide sleeves 16. rl`he bottomA of the receptacle formed by members 33 and 34 is provided with a plurality of short drain pipes 36, so that disengaged. solids falling upon the tray may be temporarily interrupted in their fall and then fall freely through the pipes 36 tothe bottom ofthe disengager vessel.

The bottom of thel disengager vessel is provided with elongated draw-olf pipes 37 through which solids collected at the bottom of the disengager on lower dished head 13l may fallV freely to a receiving vessel or chamber located below the disengager, but not shown in the drawing. Suchl lower receiving vessel may provide the storage or' surge for the solids circulating system.

In the operation of the invention, the streams of lift gasand solids discharging from liftpipes 14 and passing through guide sleeves 16 and` cylindrical portions 19 are deected slightly toward the axis of the disengager as they traverse the elongated open portions of the hoods provided by members 21 and 23. Such portion of the solids as may rise to the top ofthe hood is deflected by the inclined baiile 24 into the mass of solids moving inwardly and upwardly toward the axial region of the. disengager. Within such axial region the solid particles become disengaged from the lift gas and reverse their direction of flow so as to fall freely toward the bottom of the disengager. Some portion of the inwardly moving mass of deflected solids will have sucient energy to reach the finned tube 31 depending axially from the baiiie 26. The finned tube 31- arrests the further inward movement of the particles and they are caused to either rebound or fall downwardly toward the receptacle, or tray 33 located some distance below. It is expected that to a great extent the vertical side members 23 which channel the flow of solids` inwardly toward the axis of the disengager, together with the fins 32 of the depending member 31 will cause the solids discharging from the plurality of lift pipes to be distributed substantially uniformly throughout the actual region of disengagement, so that the disengaged solids will descend in a substantially uniform pattern upon the surface of tray 33.

Obviously, withv particles of solids traveling at high velocity and bombarding all exposed` portions of thestructural members as well as colliding with each other, it is inevitable that some of the particles Will be deliected over the tops of the hoods and move toward the annular space 28 through which the lift gas is rising to reach the central outlet 29. The velocity of the lift gas flowing over the region above the hoods is below supporting velocity for the solid particles, so that the stray particles readily disengage themselves from the lift gas` and fall either into the catch basins formed on top of the inclined baflles 2,4, or pass over the catch basins and fall tothe bottom of the disengager through the spaces between the vessel wall 11 and the outer surfaces of members 21, 19 and 2,3.

The receptacle or tray 33 arrests the free fall of the disengaged solids before they have attained any substantial gravitational acceleration. A portion of the dis engaged solids will collect on the bottom of tray 33 and form a stagnant layer surrounding the inlet ends of drain pipes 36. The surface of the layer of solids around each outlet will be inclined to the horizontal at the angle of repose for the particular solids. Thus, those disengaged solids which do not actually fall directly through the drain tubes 36 will land upon the layer of solids supported on the tray 33 and roll down the inclined surface areas of such layer into and through the drain tubes 36. Solids discharging from drain tubes 36 fall freely to the lower head 13 of the disengager and, in similar manner, are either retained in part as a stagnant layer at the bottom of. the vessel or roll down the inclinedsurfaces of thestagnant layer of solids into and through the draw-oi tubes 37. It is contemplated that the substantial major portion of the solids will become disengaged within the central region of the disengager and will descend to the bottom of the disengager as just described, and that only a relatively minor portion of the total disengaged solids will be deilected to the upper peripheral region of the disengager and be caused to` parallel` plate members extending from the vertical sides of the hood openings toward the central region of the vessel tends to avoid any substantial amount of particleto-particle impact'between the solids of adjacent streams. Without the physicalV barrier orl baffling provided by the present invention all the discharging streams of solids would spread and tend to merge as a broad moving mass of dispersed solids in the upper region of the disengager, with consequent substantial particle-to-particle contact with `the rising solids and the falling disengaged particles. With the present channeling and inward de flection of the separate streams the particles, after losing their momentum as a result of gravitational decelera tion, and after reversing their direction of flow, fall` freely downward within the upper central region of the vessel. Since the substantialmajor portion of the freefalling disengaged particles descend within the central region ofthe disengager, that is, within the area` surrounded by the envelope of upwardly discharging streams of solids, there is a minimum of collisions between upwardly moving and downwardly moving particles.

In the usual commercial practice lift pipes are tapered, at least along the upper end portion,` so as to decelerate the solids before their discharge into the disengaging zone, thereby lowering the heightrequirements of the disengager for effecting complete deceleration and disengagement from` the rising lift stream. As the solids discharge into the larger guide sleeve and pass through the hood the gas velocity quickly/"diminishes `to such eX- tent that further upward movement of the solids is almost entirely the effect of momentum.

Upon discharge into the wider path formed by the guide sleeve and the tubular portion of the hood the solids stream tends to diverge or spread. In passing through the open upper portion of the hood the solids are free to move gradually inward toward the axis of the disengager in response to the horizontal force component. At the opposite side of the solids stream, however, the solids soon strike the vertical wall of the hood and are deflected inwardly. The cumulative effect of the inward horizontal force components of the deflected solids as they collide repeatedly with solids nearer the center of the solids stream tends to force the stream out of its vertical path and produces a curved trajectory toward the axis of the disengager. To be timely effective, the rising stream of solids should engage the de fleeting surface of the hood along a lower portion thereof. On the other hand, the diameter of the hood should be sufficiently larger than the diameter of the lift pipe to effect a desired further reduction in gas velocity.

It is believed that, once the solids leave the top of the lift pipe and the accompanying lift gases are allowed to expand, first, withinthe enlarged flow path provided by members 16 and 19 and, then, within the larger disengager vessel, the ultimate path of flow which the solid particles thereafter take is substantially exclusively the result of collisions and impacts either between the solids and the structural surfaces within the vessel or between the solids. In other words, very shortly after the solids and gas leave the lift pipe the gas is decelerated to a velocity much too low to have any significant effect upon the direction of movement of the solid particles. It is partly for this reason that the channeling or baffling of the separate discharging streams of solids effectively reduces the amount of solids attrition.

In order to minimize impact attrition of the solid particles it is preferred that the sides of thehood which serves to deflect or channel the flow of solids toward the center of the vessel be designed and located in such manner that the widening stream of upwardly moving solids impacts the hood at a very shallow angle, prefer-V ably less than about With respect to the inclined baffle 24 forming the top of each hood, the angularity of impact may be somewhat greater, because the particles attaining such height will already have lost much of their momentum.

It is the purpose of the hood 18 to surround the rising stream of solids on three sides. The effective length of the deflector hood, that is, the portion formed by elements 21 and 23 should be as long as possible, within practical limits. The hood diameter, however, is prefer,

ably inthe range `of about 1.5 to 2.5 times the lift pipe diameter'.

A further restriction on hood size is recommended, however. Since the inward deflection of the solids stream as a whole commences only after the sides of the stream engage the inside wall of the hood, such engagement should commence at a low level along the opensided portion of the hood. If the diameter o f the sleeve extension 19, which also may be considered the diameter of the hood, is too great, so that there is a considerable horizontal spacing between the lift pipe and the sleeve, the solids will not strike the hood at a level low enough to effect the desired deflection. It is considered desirable, therefore, that the solids leaving the lift pipe strike the side ofthe hood at a level within the lowermost 25% of the overall distance between the top of the lift pipe and the top of the hood. This can best be expressed by the following equation:

Dmax: maximum/sleeve diameter, ft.

d==lift pipe diameter at top, ft.

L=blow height above top of lift, ft., blow height being the average vertical distance from the top of the lift to the turned in top portion of the hood.

In designing a hood for a particular application there is always the necessity of weighing the value of increased hood height, whereby there will be substantially no largersize solids hitting the top of the hood or the dished baffle above it, against the disadvantage of increasing the height or vertical distance through which the disengaged particles must fall to reach the bottom of the disengaging zone. Too great a distance of free fall can cause excessive fracture of the solids as they bounce upon the bottom of the vessel or upon the tray.

It is expected that the principal benefits in the way of reduced solids attrition will be effected by reason of the fact that there is a minimum of impacts between the falling solids and the rising solids. Once the solids fall below the zone or region where collision with rising solids is possible, much of the danger of severe impact is eliminated. The tray 33, which lets the falling solids down in easy stages, further reduces the danger of severe impact. However, in some cases it may be possible to eliminate the tray 33 and permit the disengaged solids to fall directly to the bottom of the disengager Without serious danger of impact attrition.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is susceptible to various modifications and improvements without imparting from the spirit thereof, and it is desired therefore that only such limitations shall be placed thereon as are specifically set forth in the appended claims.

What is claimed is:

l. A solids disengager for a multiple pneumatic lift having a plurality of lift pipes discharging at uniformly spaced locations in a horizontal circular row comprising: a disengager vessel adapted to encompass such discharge locations at its lower end; guide sleeves set in the bottom of said vessel so as to receive in sliding engagement the discharge ends of said lift pipes, said guide sleeves being of substantially greater diameter than said lift pipes; a plurality of solids-deflecting hoods individual to and secured to the upper ends of said guide sleeves, said hoods opening inwardly toward the axis of said vessel along the major upper portion of their length and i having parallel vertical plate members extending inwardly toward the axis of said Vessel from the vertical sides of saidopenings and an inclined upper end portion converging toward said axis, whereby solids discharging upwardly and inwardly from said hoods reverse their direction of flow and descend Wholly within the central regionl of said vessel and substantially out of contact with the rising streams of solids; a central lift gas outlet at the upper end of' said vessel; a horizontal baille spaced from the upper end of said vessel and overhanging the circular row of hoods, whereby lift gas discharging from said hoods and directed toward the upper central region of said vessel is first deflected outwardly by said baie to the peripheral region thereof and then caused to ow upwardly and inwardly over the top of said horizontal baille to said lift gas outlet; and a plurality of solids draw-olf tubes distributed about the lower end of said vessel adapted to drain the disengaged solids by free fall from said vessel.

2. Apparatus as in claim l including a horizontal tray located at an intermediate level within said vessel and below the hood openings, said tray being arranged to intercept substantially all the solids discharging from said hoods and descending by free fall within the central region of said vessel; and a plurality of drains in the bottom of said tray adapted to drain the intercepted solid particles by free fallfrom said tray to the bottom of said vessel.

3. Apparatus as in claim l including an elongated baffle depending axially from the center of said horizontal baille and comprising a cylindrical member having longitudinal ins extending, radially outward' therefrom and corresponding in number to the number of said lift pipesQsaid radial fins being directed equi-distantly between said lift plpes- .,o

4. Apparatus as in claim l in which the curved portions of said hoods form vertical extensions of the outer half of their associated guide sleeves, and in which the diameter of said guide sleeves is in the range of about 1.5v to 2.5 times the diameter of said lift pipes.

5. Apparatus as in claim l inV which the diameter. of the confined path formed by said guide sleeve and the lower portion of its associated hoodis expressed by the equation f DmBX= 1/z L tan 11"-l-d where i Dmax=maximum sleeve diameter, ft. d=lift pipe diameter at top, ft. L -blow height above lift, ft.

whereby the expanding stream of solids meets the side'

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