CA1279760C - Mixing device for vertical flow fluid-solid contacting - Google Patents

Abstract

"MIXING DEVICE FOR VERTICAL FLOW FLUID-SOLID CONTACTING"

ABSTRACT
A fluid mixing apparatus which is used in a vertical flow-solid contacting column having a fluid inlet and a fluid outlet at opposite ends, two or more distinct beds of particulate material, and which is operated with single or dual phase fluid flow. The mixing apparatus comprises a vertical flow barrier, positioned intermediate two adjacent beds of particulate material, having a substantially imper-forate outer area and at least one central opening for passing fluid between beds and a fluid impingement compartment located at the center of the barrier. The impingement compartment has vertical sides contain-ing at least two similarly sized inlet openings in communication with the upstream side of the barrier for receiving the fluid flow detained by the barrier into the compartment with the sides and inlet openings being arranged so that the projection of all inlet axial centerlines lie in a common horizontal plane and intersect at a point selected so that fluid entering the compartment will converge at a centerpoint equidistant from all inlet openings. Mixing is promoted by sizing the inlet openings to produce fluid jets having a length at least equal to the distance between the inlet openings and the centerpoint so that the fluid streams impact turbulently. Fluid leaves the impingement compartment through a fluid outlet comprising the central opening of the barrier, which is in communication with the downstream side of the barrier and provides a balanced flow out of the impingement compartment.

Description

t)~l 7~

"MIXING DEVICE FOR VERTICAL FLOW FLUID-SOLID CONT~CTIN6"
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FIELD OF THE INVE~TION
This invention relates g2nerally to the field of fluid-solid con-tacting. More specifically, this inventicn deals with ~he mixin~ of fluids between beds of particulate material. Included within the scope of this in-vention is the mixing of single phase or tw~ phase ~luids.
BACKGP~OUND OF THE INVENTION
Fluid-solid contacting devices haYe a wide variety oiE applicatio~ Such devices find common application in processes ~Eor hydrocarbon comers;ion and adsorption columns for separation oi fluid components. ~hen the fhlid-solid contacting device is an adsorption column the particula~e material will com~rise an adsorbent through which the fluid passes. In the case of hydrocarbon conversion the fluid-solid contàc~ing apparatus is typically a reactor containing catalys~. Typical hydrocarbon conversion reactions that may be carried out are l~ydrogena~ion, hydro~reating, hydrocracklng, hydrodealkyala~ion, etc.
Fluid-solid contacting devices to which thk invention apply are ~sranged as an elongated cylinder having a ~ertical orientation through which an essentially vertical flow oi fluid is maintained. JParticulate ma~erial contained in this ~ssel is arran~ed in a seri~s of vertically spaced beds. Fluid enters the vessel t~ugh at~east vne inlet and outlet located at opposing ends. The fluid can Ilo~r throu~h ~e reac~or ln a upflow or downflow fashion. I~ is also commonly kno~4n ~ add or ?O wi~h~raw fluid from between ~he particulate beds. This is comm~ly done in a~dsorp~ion schemes where the oomposition of the fluid passin~ between particle ~ds is changing or in hydrocarbon conversion processes wh~re a quench sys$em is ~ied to cool ~luid as it passes between beds.
Changes in the compcsition or properties of the fluid passin~ lthrough the 2~ particular zone present little problem provided these changes occur uniformly. In adsorp~ion systems these changes are the resul~ of reter-tion or displacanent o~fluids within the adsDrbent. For reaction systems changes in temperature as ~ell as composition of the fluid are caused by the particulate catalyst material cor~ined in ~he bcds.
Nonur)iform Ilow oiE fluid throu~h these beds can be caused l~y pcor initial rnixing of the fluid entering the bed or varia~ions in flow resistance across the " '.'~-7~ 3 particula~e bed. Variations in the flow resistar!ce across the bed can vary contact time of the fluid within the par~icles thereby resulting in uneven reactions or adsorption of the fluid stream passing through the bed. In extreme instances $his is referred to as channelin~ wherein fluid o~e~ a limited portion of the bed is allowed to move in a narrow open area with virtually no resistance to flow. When channeling occurs a portion of the fluid passing throu~h the bed will have minimal contact with the particulate matter of the bed. If the process is one of adsorption the fluidpassing through the channel area will not be absorbed, thereby altering the composition of this fluid with respect to fluid passing through other portions of the absorbent bed. For a catalytic reaction the reduction in catalyst contact time will also alter the product composition of fluid as it leaves different portions of the catalyst bed.
ln addition to problems of fluid composition, irregularities in the particulate bed can also affect the density and temperature of ~he fluid passingthrou~h the bed. For many separation processes retained and displaced componentsof the fluid have different densities which tend to disrupt the flow profile through the bed. Nonuniform contacting with the adsorbent particles will exacerbate ~he problem by introducing more variation in thæ density of the fluid across the bed ~hereby further disrupting the flow profile of the fluid as it passes ~hrouKh the particle bed.
In reaction zones ~emperature variations are most often associated with nonuni~orm catalyst contact due to the endothermic or exothermic nature of such systems. Nonuniforrn contact with the catalyst will adversely affec~ the reac~ion taking place by overheatin~ or overcooling the reactants. This problem is most ~5 severe in exothermic reactions where the hi8her temperature can cause further reaction of feed stock or other fluid components into undesirable products or can introduce local hot spots that will cause dama~e to the catalyst and/or mechanical components.
Therefore, in order to minimi~e 11le problems that are associated with variations in fluid flow through beds of particulate material, methods of remlxing fluid between beds o catalyst or adsorbents haYe been incorporated into a number of processes. Devices for collecting and remixing a portion of the fluid moving through a series o~ particle beds are shown in U.S. patents 3,6S2,~50 and 4 ,087 ,252 .
In these references, the remixing of the fluid is done in conjunction with the addition o$ a second fluid into the mixing zone between beds. In both of these reEerences~ mix;ng of ~he fluid passing between beds and the added fluid is performed in a number oî discreet mixin~ chambers located in or between ~he lower boundary of the upper bed and the upper boundary of the lower bed.
U.S. Patent 3,824,080 by Smith reveals an in~ernal reactor con~iguration for rnixing fluid passing between beds independent of a second added fluid in that zone. The Smith deYice collects a mixed phase fluid flow in a region between particle beds having a horizontal baffle containing a central openin~ for passlng the fluid between beds. This central opening has a flow diverter device which direc~s all vapor flow through the top of the chamber and all liquid flow in through the sides.
In the Srnith invention, vapor and liquid irnpinge upon each other a~ right angles thereby effecting remixing. After the remixed vapor and liquid passes through the opening in the baffle it contacts another horizontal series of baffles ~or providing an even flow of fluid over the downstream particle bed.
U.$. Pa~ent 3,598,541 by ~ennemuth et al teaches the remixing of fluid passin~ between beds of particulate rnaterial by direct impin~ement with a quench fluid added to the mixing zone. Mixin~ occurs in a centralized space through which all fluid passes. The centralized space contains an annular area defined by two vertically oriented cylinders. Fluid passing between beds enters via horizontally projec$ing holes in the outer cylinder, while the quench fluid enters ~hrough horizontally projecting holes in the inner cylinder. The lower end of the annular rnixing zone communicates with the downstream particle zone to allow passage o the mixed flui~.
An objec~ of the invention disclosed herein is to improve the mixing of fluids passing between beds of particulant material. It is a further object of this invention to achieve mixing of the fluid passing between beds independent of theaddition of a second fluid into the zone between particle beds. A further object OI
this inventlon is to provide a simpli~ied device for achieving mixin~ of fluid between beds which is easily incorporated into a minimal space between particle beds.

SUMMARY OF THE INVENTION
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Therefore, in one embodiment this invention comprises a fluid mixing chamber for use in a vertical flow fluid-solid con~acting vessel having fluid inlet and ~luid autlet at opposite ends, and ~wo or more vertically spaced discrete beds of I~articulate material.

7~ 3 In a m~e specific embodimen~, the ~luid mixing charnber eomprises a vertical flow barrier positioned intermediate two particle beds hav;ng a substan-tially imper~orate ou~er area and a~ least one central opening for passing fluidbetween zones; a fluid impingement compartmen~ located at the center of said 5 barrier having vertical sides containing at kas~ ~wo iden~ical inlet openin~s restricted in size ~o produce a fluid jet, ~vhich are in communication with ~he upstream side of said barrier for receiving fluid de~airled by ~he barrier wi~h ~he vertical sides being arranged such that the projection of all inlet axial centerlines lie in a common horizontal plane and intersect at a point selected lC to cause fluid entering ~he compartment ~o converge at a center point equidistant from inlet openings and alithin the projection nf ~he fluid jets; at least one fluid outlet frorn tl~e in pingemen~ compar~ment with an open area grea~er than that of the iniet openings which is in commurlication with the downstream dde ofthe barrier and provides a balanced flow to ~he area downstream of the barrier;
15 means on the upstream side of said barrier for conveying an eslual amount of fluid iErom tl~ periphery of the barrier to each inlet opening; and means for redistrlbuting ~luid ~rom the outlet of the impingement compartment over the downs~ream particle bed.
More limited embodiments of ~is inven~ion inv~lve different means for 20 ~dding, distribut;ng, collecting or wi~hdr~wing ~luid ghat enters or exi~s the impingement compartment and par~icular arrangemen~s or configurations of she fluid collec~ion barrier between particle beds and t~ innpingement compartment.
There~ore, ln its broadest sense, this invention is directed ~o a centrally located mixing ~cction for receivin~ ~ubs~an9ially the entire flow o~ fluid passing into a downstream bed. This mixing section acts to thoroughly mix the fluid and passes it to the downstrea~ particle bed in a balanced fashion to f~cili~ateredistribution of the fluid~ The mixing of the fluid is essentially derived by the configuration of the mixing zone. In this zone equal jets of fluid are directed into each other thereby producing turbulence which will promote vigor-ous mixing within the mixing zone and proY~de the fluid effluent with a uni-form composition~ Thus an important element of this invention is ~he provi-sion of means for directing equal je~s of fluid into each other in order to maximize turbulence tn mixing~ With this basic concept in mind, other objects, t~ r~

~nbodiments and advantages of the inventi~n ~nll b.ecome ~eadily apparent to those skilled in the art from the more detailed Jlescripti~n th~t f~ w~
BRIEF DESCRIPTION OF THE ~ GS
Fi~ure 1 sho~vs ~ partially cutaway elevation ~riew of ~ vertica~l flow 5 con~cting column having multipl~ s of catalyst and mixing devices located between particle beds in accordance with this invention.
Figure 2 is an isome~ric YieW o~ ~he mixing device from figure 1 removed from the rest of the column internals.
Figure 3 is a partial ~levation view of a downflow reactor with a 10 cutaway proportion showing a more limited embodiment o~ the mixing chamber having a series of parallel channels for collecting fluid which passes ~rough a rectangular mixing zone.
Figure ~ is a plan view of ~e channel collection system for the mi~ing zone of Figure 3.
Fi~ùre 5 is an isometric view depicting thP mixing zone of Fiqures 3 an~l wi~hin a portion o~ the channel.

DETAILFD DESCRIPTION OF THE INV~NTION

As previously mentioned, this invention relates to a rneans ~! mixing fluid between particulate beds in a fluid-solid c~ntacting device. The basic eJen ents of thls invention consist of a containment vessel, one or more beds ofparticulant material ~hat are disposed in vertically spaced zones and ~ mixing chamber positioned between beds sf particlllate material. The inven~ion itself resides in the particular arrangement of the mixlng chamber and the componen~s loca~ed therein. A more complete understanding of the interrelation ~tween the ~5 ~arious elements within the mixin~ chamber and the vertical flow column ~n be obtained from the figures provided.
~/ith specific reference to Figure 1 the cutaway elevatiorl view shows the column 1 wi~h a fluid inlet no~zle located at its top and a fluid outlet bcated at its bottom. l,ocated within this vessel are horizontal zones of catalyst 2t 12 and 14.
E~ach particle b~ is composed of solid particles which can be in the form of pills, sphere cylinders or other extruded shapes~ The actual proper~ies of the par~icles will depend upon the pr~ess which is carried out in the con~ainment vessel. Ger~rally~ lthis means that the particles will consist of an adsorbent or a catalyst. Above each p~r~icle bed is a layer of s~or~ material 3, which serves to hold down the particles and enhance flow distrlbu~ion over the bed. This material which is of~en ernployed, but not essential9 will ~dally cQnsist of ceramic balls or other inert compositions having a regular shape. Support material ~ is also often S provided beneath the particle bed to prevent migration of the catalyst particles throughaperforatedplateprofileorscreenelement 5 that is used to de~ine the lower boundary o~ the particle bed. Support ~ater;al at the bottom of the catalyst bed is similar in shape and composition to that used above the bed Located l~tween beds is the fluid collection and mixing region.
Immediately below the particle retention plate S is l~cated a fluid collection area 6.
This collec~lon area allows the transfer o~ ~luid across barrier pla~e 8 to the impingernent compartment 7. As shown in Figure 1, the collection area can consist of an empty space that allows fluid flow in a ~rizontal direction. However, as discussed in more de~ail in conjunction with Figures 3, 4 and 5 the collection space may be integral with the barrier 8 so that the ekments restric~ing fluid can also direct the fluid to the impingement compar~ment. Therefore, means for collectingfluid is no~ meant to be limi~ed to any sne confi~ura~ion but coneemplates any means for passing fluid ~o the impin~ement compartment. In its simplist iEorm, the ~low barrier 8 will consist o~ a plate attached and ~aled at the column wall andhaving an open center over which impingement co~p~rtment 7 is located. 1 loweYer, the barrier can take on any ~orm provided it substantially prevents ~luid ~low at any location except through the impingement compartment openin~s. The limitation o~
~he barrier or baffle ~o substan~ially prevenit fiuid flow recognizes that particulate material from the various beds is often unload~ from ~e bottom o~ the vessel ~hrough ~he overlying l~eds. In order to accomplish this unloading, verticaJ conduits are commonly prbYided in the grids between the beds to allow the passage of the - particulant rma~erial from one bed to the next for vvithdrawal from the contacting column. 1~ is wi~hin ~he contemplation of this invenlion ~hat the barrier will contain several S~ll conduits. These conduits are U5Uall)' left open but packed with thepreYiously described inert support material. These~ore, resis~ance to fluid $10wthrough ~ese conduit~ is much ~reater than that of the herein described impinge-ment compartment and collection system. Conse~ntly ~he amount o~ fluid pa~sing through ~ese conduits should be less than S% o~ ~e total flow of fluid between bc~s~
The impin~ement compartment, whidl ~ hereinafter described in more detail, receives fluicl from the coliection space 6 and, after thorough mixin~, allows it to pass throu~h the barrier 8. Below ~he barrier 8 is ano~her space 10 that alls~ws redistribution of the fluid. Once again in its simplest form this redistribution area is simply a space between the outlet of the impingement compartment and the top of the downstream catalyst bed. Nevertheless, it is possible to include other devices such as baffle plates, flow diverters or vapor-liquid trays to fur~her aid in the redistribution of flow over the top of the downstream catalys~ bed. ~ithin the redistribution area 10 is shown a nozzle and a pipe system 9 for adding fluid orwithdrawin~ fluid from the contacting column. In the case of separation processes ~his nozzle can be used to add or withdraw selected component streams. The specific application of this nozzle for downflow reactors is the addition of a quench medium to cool the reaction medium entering the next catalyst bed. While the nozzle and pipe system in Figure 1 has been shown below barrier 8, it is a!lso wiShin the contemplation of this invention that the nozzle and pipe system be located above barrier `8 and possibly in the uppermost por~ion of the downstrearn catalyst bed or the lowermost portion of the upstream catalyst bed. The mixed ~uid ~tlen enters the next bed of particulant material from which it rnay continue ~hrough subsequent remixin~ zones and particulate beds before leaving the column through a suitable outlet.
Figure 2 depicts one embodiment of the impingement compartmen~.
This particular irnpingement compartment is composed of two sides having inlet openings 16 and 17; a wire screen outlet 2û on the bottom; an lmperforate top plate 13 and imperforate sides 18 and 19. The impingement compartmer~t is not restricted to any par~icular shape. For example the impingement compartment 23 could consist of a vertically oriented cylinder with side inlets and a bottom outle~.
Nevertheless, there are some general dimensional limi~ations which are her~inafter discussed in more detail. The basic function of the impingement compartment is to provide intimate mixing of the fluid passing between beds of particulant material.
Such mixing is achieved throu~h the orientation and sizing of inlet opening 16 and 17. These openings are sized such that a jet or concentrated stream of fluid enters through each openin~. The inlets are positioned such that the fluid jets impact upon each other in opposing fashion at a central point of the impingement compartment.
In Figure 2 only ~wo inlet openings are shown, however it is possible to have more than two inlet openings provided the openings are located in a symmetrical ~ashion which balances the irnpin~ement of the jets in all directions. Also importan~ to this 7~

invention is the vertical orientation of the inlet openings. All inlets should be located at the same elevation. Thls equal elevation is necessary to pro~.ride equal velocity impingement with no unbalanced componen~ Lastlyg in terms of shape, there is no necessity that the inlet openings be round. The only essentia requirement of the inlet opening shape is the restric~ion o~ i~s cross sectional area such that the necessary fluid je~ is formed.
Obviously, the size and number of the openings will determine the length of the flu}d jet ~or any given pressure drop through the impingement compar~rnent.
However, since it is usually desirable to minimlze pressure drop in the vertical flow column practical conslderations will restrict the length of the jet. As is well known by those skilled in the art, the pressure drop is a f~ion of f~uid Yelocity and average fluid density. Methods of calculating jet lengths and pressure drops over an opening or series of openings are well known by ~hose skllled in the ar~. Por most fluids to which this invention will be applied, the openings are sized for a velocity in the range of 4.6 to 15.2 m/s. The mixing compar~nent must be sized to insure that the jets of fluid will impact with sufficient velocity to thoroughly mix the fluid. Therefore the distance between any inlet o~ning and the cen~er point of ~he impingement compartment mus~ not exceed 6û96 o~ the je~s calculated length.
~hus the pressure drop and jet length consideratios~s will dictate the len~th ordiameter of the irnpingemen~ compartment.
Although any shape of lmpingement compartment can be used, a square or rectangular implngement compartment having only two inlet openings is particularly preferred because of its simplicity and adaptability to the channelcollection device hereinafter described. Where there are only two circular openings in the impingement compartment, the maximum distance between openings should not exceed six times the diameter of the inlet openines and preIerably will be less than three inlet opening diameters. The reduced sp~cin~ between inlets tends to increase turbulence and promote better mixin~. Of course some distance between inlet openings must be maintained. The minimum dis1ance is required to allow sufficient outlet opening area and stlll maintain the required length to width ratio for the impingement compartment.
Furthermore, in order to maxirnize turbu5ence or mixing, the overall height of the mixing compartments should not exceed four times the vertical dimension o~ the inlet opening. Likewise, in order to prevent stagnant areas in rectan~ular con~igurations, the width of the irnpingement compartment should also .7~3~7~3 be restricted to four times ~he hori20ntal dimension of the inlet openings. In the case of a circular cross xctit~n impingement compartment composed of a vertically ori~nted cyllnder~ ei~her ~he restrictions on inlet openings, spacing or maximumwidth limitations may govern the diameter of the compartrnent.
Referring ag~in to Figure 2, the impingement eompartrnent contains at least one outl~t opening 20. Th~ most important res~riction on ~he outlet opening is that its open cross sectional area exceed that o~ the to~al cross sectional area of the inlet openings. This is of course necessary to allow jets of fluid to form at the inlets to the compartment. In terms of velocity, it is usually desirable to design the outlet so that the velocity does not exceed 4.6 m/s and is preferably less than 3 m/2. Although it is not necessary to provide any form of restriction over the outle~, the opening may include profile wire as shown in Figure 2, or perfora~ed plate or wire screen.
These outlet restrictions are often used to impro~re flow dis~ribution, ~rap particulate material or minimize the foaming that can occur as a result of the turbulen~ mixin~ of certain fluids. In addition the location of the outlet o~ning is not restricted to any particwlar side of the compartment and the outlet opening may in fact be multiple openings. The ou~let opening or openin~s may be located In any side of the impingement cornpartment ~rhich is in communication with the dswnstream portion of the mixing chamber as iong as the opening or openings are symmetrical wi~h the center line of the impingement compartment. The only limitation on she outlet opening or openings is that the lccation be symmetrical with respect to the downs~ream bed so that a balanced flow of fluid out of 2he impingernent chamber is delivered to the downstream particulate bed. In this way~ redis~rlbution of ~he fluid over ~he bed of particulan~ matter is facilita~ed.
Although Figure 1 generally depicts an arrangement for a downflow reactor, this invcntion is not limi~ed ~o a single flow directiGn through the column.
In the case of an Lpflow reactor, the inlets must be in cornmunic~tion with the lower particle bed and the impingement chamber reversed so that the outlet of the impingement compartn en~ opens into an upper redistribution zone. Thus the mixing chamber of this invention is equally applicable to upflow ~r downflow con-figurations.
As noted in the prior art, many of the intermediate mixing devices use addition oiE an external fluid as an integral part of the mixing operation. Con-~ersely, this apparatus do2s not require any external fluid addition to effect mixing of the fiuid passing between beds oiE particulant material. Thus thls invention has ~`t~

the advantage of provicling ~ood mixing o~ fluid passin~ between beds independent of the addition or withdrawal of fluid. Another advantage of this invention is the overall simplicity and compactness of the impinge~~ent compartment. These features make it possible to incorporate the mixing chamber of this invention into the existing space between a series of particulate beds without extensive modifi-cation of the contacting 70ne internals.
Apart from the impingement compartment, other components o~ the mixing chamber consist of the previously mentioned di~ributors, support materials, baffles and pipe grids. The design of these components depenclson a number of 10 ~actors. Among these factors are the allowable pressure drops for the equipment, the composition of the fluid passing between partWe beds and the operating conditions within the contacting zone. In addition, far mixed phase systems, ~hequantity of vapor or liquid passin~ between beds will largely dicta~e the type of baffles required, the size of inlet and outlet openings ~hrough the barrier and the 15 appropriate re~istribution means. Other consideratior~s that will affect the overall sizing and configuratlon of ~he mixing chamber is ~he addition of a quench. The placement and operation of the quench distribution system will require additional space within the mixin~ zone. Of coursel the factors mentioned here by no means exhaust the list of mechanical and process considerations that will go int~ designing 20 the mixing chamber. However, such considerations are vell know by those skilled in the art and do not require fs~rther elabora~ion.
The mixing device of the invention is es~æcially sui~ed for use in a downflow reactor in combination with a barrier or baffle plate composed of a seties of channels. Such a reactor is advan~ageously employed ~o carry out hydrogena~ion7 25 hydrotreating, hydrocracking and hydrodealkylation re~ctions. ~hen performin~exothermic reactions, such as hydrotreating and hydr~:racking, a quench stream is usually added between catalyst beds to control the t~perature of the reactants.
Operation of the mixing zone independent of ~he quench stream as offered by thisinvention is of particular advantage for these exothennic reactions. As catalyst30 deactivates with continued operation of the reac~on zone, the amount or temperature of the quench, which usually consis~s of hydrogen, must be reduced.
The reduction of cooling requirements for the quench poses problems in remixing zones that employ the quench as part of the mixing op~ion. In such schemes, it is often necessary ~o vary the ternperature o~ the quenc~ in order to achieve reduced 35 cooling while still maintaining an adequate liquid volume addition of quench medium to the mixing zone. Since the quench in my invention is added independent of ~heimpin~ ment compartmen~, varying the amount of quench will have little efiEect on th~ mixing of reactants.
Nevertheless it is also important to obtain good mixing of the quench stream and the reactants. Thus while it may be possible to obtain adequate mixing of the quench by a pipe distribution system located downstream of the impingement compartment"ocating the quench distribu~ion system upstream of the impingement compartment is particularly advantageous. With the quench stream located ahead of the impingement compartment there are two opportunities for the quenching medium to mix with the reactants. First mixing of the quench medium occurs at the initial dis$ribution point of the quench into the reactants and a~ain when the quench and reactants flow through the impingement compartment.
Attention is now drawn to ~i~ures 3, 4 and 5 wherein a specific combination of a quench system9 vertical flow barrier and impin~ement compartment `are incorpora~ed beneficially into a down~low reactor. in this embodiment, an overall flow scheme in accordance with Figure 1 is employed. Thus reactants enter a vertically elongated reactor and flow through a series of catalyst beds and intermediate mixing charnbers. Looking now at Figure 3, additional details of the intermediate mixing portion are shownO
In this arrangement reactants flow downwardly through catalyst bed 22 while a quench medium is added at nozzle ~3 and distributed over a lower cross section of the catalys~ bed by pipe distribution system 24. The reactants con~inue ~hrough support material 25 which rests on a wke mesll screen 21. IJpon passing through ~he screen reactants and quench mediurn are collected in a series of parallel channels 27, 61 and 62, which run in a horizvntal direction and are open to the upper catalyst bed. Fluid is conveyed Erom the outer channels 27 through the interrnediate channels 61 to the center channel 62 by means of conduits ~8 and 29 which allow fluid flow between channelsO The center channel is divided into two parts by theimpingement compartment 30 as shown in Figure 4. In order to provide equal amounts of fluid to each side of the impingement compartment, four conduits 29 are used to provide an equal flow of fluid on each side of the compartment. Fluid leaving the ~tlet of the compartment enters redistri~ution zone 40 where vapor and liquid are redistributed over the entire area of the lower catalyst bed. In order to prornote bet~er dis~ribu~ion of the mixed vapor and liquid stream, a vapor liquid redistributor tray 51 is located at the top of the lower catalyst bed. These types of 7 ~ i 3 trays are well known ~o those skilled in the art and consist o horizontal tray portion 51 and vertical conduits 50 loca~ed therein having a co~ered top, V-notch opening in an upper portion for receiving vapor and perforated side por~ions adjacent the upper tray surface for allowing the passage of liquid. Following passa~e through the vapor liquid redistributor tray the fluid enters another open region 52 where further redistribution may take place. Fluid then passes through a layer of support material 53 and continues on through the next catalyst bed 54.
A more complete understanding of the ~rrangement of the collection channels and impingement compartments can be obtained from Figure ~ which shows a plan view of these internals. The ends of the channels have closures that match the outline of the containment vessel. Outer collection s~aces 27 may be connected to the next inward channels by means of a single conduit 28. The conduits connecting channels are designed for minimum pressure drop. The maximum fluid velocity through conduits 28 and 29 shall not exceed 4.6 m/s and is preferably less than 3 m/s. Fluid collected in inte~mediate channel 61 along with fluid from outer channels 27 passes throuE h central channel 62 whichcontains impingement compartment 30. Fluid is directed into the central channelsin a sylTmetrical fashion to provide an equal volum~ of fluid to either side oF the compartment. Figure 4 also shows vertical concluits 55 ~hich are used in unloading catalyst from the reactor as previously discussed.
Figure 5 shows the impingement compartmellt which ~s located in central channel 62. As can be appreciated from the drawin~, the impingement compar~ment is integral with the channel on three sides 56, S7 and S8. These sides contain aperforated sectlon in the area of ~he impingement cornpartment which serves as an outlet for the mixed fluid. In this particular embodiment the opposing sides 59 and 63 contain inlet openings 60 in the form of circular ori~ices and are Df a lesser height than the depth of the channel. This reduced hei~h~ allows additional fluid passa~e over the top of the impingement compartment 59 which serves to equalize any imbalance in fluid flow to the inlets. However, it is also possible to have the end plates containing the inlet openings completely block the cross sectional area of the channel.
This embodiment is not meant to limit ~he ~ay in which a channel may be integrated wi~h the impingement chamber. The impingement chamber and channels of this invention may be combined in any number of arrangements. Other possibilities include having the inle~ streams to the impingement compartment flow in a direction perpendicular to ~he major axis of the channels or usin~s an e~ven number of channels with the impingement compartmen~ located between two center channels.
Those familiar with the design of reactor internals can readily appre-ciate the economy in the arrangement of internals depicted in Figure 3. First the fluid collection channel which also forrr~the bar~ier or baffle for the vertical flow of flow are compact and require little vertical space wi~hin the reactor. In addition, these channels are easily Eabricated with a support flange portion 42 to fi~ upon a series of parallel support beams 26 which are frequently used to hold up the catalyst bed. Moreover no additional space is required for the impingement compartment which can be conveniently located in the central channel. The location s)f the channel collection system is also advanta~eous in that it does not interfere with the location of the quench distribution system on the upper portion oE the support beams. Thus whether incorporated in a downflow reac~os or more generally in any vertical flow fluid solid contacting column the collection channel and impingement compartment offer unique benefits to an intermediate mixing zoneD

Claims (8)

1. A fluid mixing apparatus for use in a vertical flow fluid-solid contacting column having at least one fluid inlet and a fluid outlet at opposite ends, two or more vertically spaced discrete beds of particulate material, said mixing chamber comprising:
a) a flow barrier, for substantially preventing the vertical flow of fluid positioned intermediate any two adjacent beds, said flow barrier having a substantially imperforate outer area and at least one central opening for passing fluid between beds;
b) A fluid impingement compartment located at the center of said barrier having vertical sides containing at least two substantially identical inlet openings in communication with the upstream side of said barrier for receiving the fluid flow detained by said barrier into the compartment, said sides and inlet openings being arranged such that the projection of all inlet axial centerlines lie in a common horizontal plane and intersect at a point selected so that fluid entering the compartment will converge at a centerpoint equidistant from all inlet openings, said inlet openings being restricted in size to produce a fluid jet having a length at least equal to the distance between said inlet openings and the centerpoint and at least one fluid outlet comprising the central opening of said barrier having an open area greater than the combined area of all inlet openings which is in communication with the downstream side of said barrier and provides a balanced flow to the area downstream of said barrier;
c) means on the upstream side of said barrier for conveying an equal amount of fluid from the periphery of said barrier to each inlet opening;
d) means for redistributing fluid from the outlet of said compartment over the downstream particle bed.

2. The apparatus of claim 1 wherein the impingement compart-ment outlet consists of perforated plate, profile wire, or screen material.

3. The apparatus of claim 1 wherein the impingement compartment is substantially rectangular in shape having circular inlet openings in two opposed vertical sides and outlet openings in any of the remaining sides.

4. The apparatus of claim 1 wherein said conveying and redis-tribution means consists of free zones between the carrier and the lower and upper boundary of the particle zones.

5. The apparatus of claim 1 wherein the inlet openings of said impingement compartment are sized for a velocity in the range of 4.6 to 15.2 m/s and the outlet openings of said impingement compartment are sized for a maximum velocity of less than 4.6 m/s.

6. The apparatus of claim 3 wherein the distance between opposing inlet openings does not exceed six inlet opening diameters.

7. The apparatus of claim 6 wherein the maximum dimension of the impingement compartment perpendicular to the inlet opening centerlines does not exceed three inlet opening diameters.

8. The apparatus of claim 1 wherein said barrier comprises a series of open parallel channels concave to the upstream particle zone and connected by conduits such that fluid is collected in said channels and conveyed to the impingement compartment.