CA1048233A - Fluids solids contacting - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Contacting apparatus chamber having a grid structure positioned therein, characterized by downwardly projecting frustoconic shaped nozzles, which extend below the lower face of the plate defining "dead spaces" in between the nozzles.
The nozzle walls diverge at an angle no greater than 30° and preferably at an angle of about 3° to about 6°, measured from the vertical axis of the nozzle.
This grid structure permits smooth flow of materials through the grid thereby avoiding fouling of the grid.

Description

This invention relate~ to new and improved mech-

2 anical contacting devices for lessening the formation of

3 deposits ~nd for improving the g~s-~olids contacting c~r-

4 acteristics in fluldized beds" especially in the bed~ of iron ore reduction proce~ses~
6 In fluidized solld~ apparatus g a porous or per-7 forated mem~er is gener~lly horizontally disposed or ex-tended acro~s the path o~ f'low, or flow area9 in a ves~el 9 ~or supporting the ~olids . Such members 9 generally re- ~:
ferred to as gridsg form a boundary between a gas or a ~:
11 dilute solids phase and a den~a solids or emul~ion phase 12 constituting a fluidized ~olids bed. Fluids9 e Og~ 9 gases 13 are injected through the grid ~rom below to ~luidized bed `:~
14 at the upper æide of the grid~
Frequently baffles are used in ~luidized solids 16 apparatus for mech~nic~l distribution of the fluids within ~ :
17 the reactor. For example9 baffle~ are often u~ed within 18 the bed of fluidized solids to redistribute the fluid6 19 within ~he bsd thereby e~ecting better ~luid solids con-20 tact~ Most often9 however~ the ba~le~ are located within 21 the plenum chamber below the grid to distribute the fluids 22 within the chamber as they enterO
23 Thus~ grid3 are employed primarily to support the 24 fluidized bed while ba~fles are employed primarily to effect .; . , a mechanlcal distribution of fluids within the reactorO
26 Grids and baffle~ are further distinguished in that the .
27 pressure drop across grids is generally high wherea~ the 28 pressure drop acros a b~ffle is generally low.
29 In any event 9 many proce~ses are described in the .:
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30 art wherein grid and baffles are employedO These include, ~ -''' , ~
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1 e.g.~ high and low temparature ~luid coking oper~tions9 2 fluid hydroforming operation~ 3 various catalytic cracking 3 operations~ and the like~
4 A fluidized proce~s o~ considerable importance is that relating to the dlrect reduction of iron ores. In 6 a typical process9 iron oxide~ ~re progressively reduced in ~ .
7 a single vertical reactor having a ~eries o~ reduction 8 stage~9 each ~tage containing a sep~rate fluidized bed Or 9 particulate oxidic iron ore at di~erent levels of oxida-10 tionO A prepared particulate ore is fed into the top ~tage, 11 the ore flowing continuou~ly from one bed to the next bed 12 or stage of the ~eries9 ~ounter-current to a flow of a~-13 cending hot reducing gas which consist~ generally of carbon 14 monoxide or hydrogen9 or mixtures thereofO
The individual beds are operated at the ~ame or 16 di~ferent elev~ted temperature~ ranging generally from about ~`.
17 900F~ to about 1800Fog or more generally ~rom about 1200Fo 18 to about 1500Fo In the fir~t 8tageg or ~tages~ the oxide6 9 are preheated and reduced ~neralIy ~rom the ~erric oxide 2 state to magnetic oxide or iron; in ~ ~ubsequent stage9 or21 stages9 ~rom magnetic oxide ~ iron to ~errous oxide; and 22 finally~ in a further stage, or stages9 from ferrous oxide 23 to suhstanti~lly metallic ironO The reduced iron productg 24 ranging generally from about fifty to ~bou~ ninety-~ive 25 percent met~llization9 is withdrawn ~rom the final stage of 26 the series, and i8 usu~lly agglomer~ted or briquetted in a 27 pressO In some instancesJ a direct melt~ng ~tep is provided.
2B The problem o~ preventing grid follling or plugging 29 differs considerably ~rom one type of fluidized proce~s to .:
anotherg and often the problem i~ more difficult to overcomc ~IIL¢~4~:~33 in one proc0ss ~3 opposed to anoth~rO Th1" i.8 particularly 2 so a~ regards the problems encountered in the reduction of 3 iron ores as contrAsted with certain other fluidized pro-4 cesses. In fluidized iron ore reduction proces~es9 such

5 problems are especially acuteO In factg the problem di~fer~

6 drastically from one o~ the several stages of the fluidized

7 iron ore reduction oper~tion a~ compared with another.

8 Ma~or difficulties are a~sociated with the ferrou~ reduction

9 stage~ or ~t~ges, ~ Oe - ~ that where~n the oxides are reduced, :
or partially reduced9 ~rom ~errous oxide to metallic iron 11 The problem is particularly acute where the ferrou~ reduc-12 tion proceeds over a plurality of stages9 and oddly enough, 13 is most severe in the stage~ preceding the final reduction 14 stageO
It has been postulated that l'grid-hole plugging"
16 or ~ouling is associated with adherence of the more finely 17 divided metallic particles, i~eO9 9'fine~9 1I to the surfaces 18 surrounding the grid holesO The fine~9 ranging generally 19 in ~ize from about 325 mesh (Taylor serie~) and smaller, are blown into the openingæ ~nd stick to the surfaces surround-21 ing the grid holes or opening~3 gradually building up and 22 forming deposit~ which obætruct further passage of ga~O
23 This, inter aliag results in high pressure drops acro~ the 24 grids and ultimately there is a nec2ssity of complete ~hut-down to effect grid ~leaningO
26 There are ~180 other forces at work which, to 27 some extent 9 tend to cau~e ~ines to percolate downwardly 28 through the grid opening~ or perforationæO The fluidizing ~9 medium, ~fter passage through the grid ~nd while within the bed, segregates from the solid~ a~ bubbles3 iOeO, areas of ~:
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~)4~;~33 1 dilute solids phase concentr~tion ~urrounded by solids 2 partlcle~ ln emulsion or dense phase concentration~ One 3 reason for this is that the fluidizing gas has a tendency, 4 in its ascent through the reactor~ to seek and follow a path lying at the center of the bed 7 and there the finer 6 bubbles coalesce into larger bubblesO This gives rise to 7 a "boiling" or pulsating actlon, and solids particles tend 8 to reflux downwardly along -the walls o~ the reactor toward 9 the grid openingsO The net e4~ect o~ these phenomena i8 lo that it is very difficult9 particul~rly in certain stages of 11 the direct iron ore reduction processes, to pr~vent grid 12 fouling 13 According to the present invention there is pro-14 vided a novel apparatus contemplating ~ plate or grid of .
special construction for horizont~l loc~tion across a flow 16 areaO The plate is provided with an array or plurality of 17 apertures or openings upon which are ~ligned downwardly di-18 verging nozzles which ex~end beyond the lower face of the 19 plate, the individual nozzles being æpaced suf.ficiently far apart as to leave void or "dead spaces" on the lower or un-21 der side of the plate above the entry portions of the nozzlesO
22 The nozzle walls diverge at an angle no greater 23 than 30, for example between 2 to 30 3 as measured from the 24 vertical axis of the nozzleO Preferably3 the nozzle walls diverge ~t an angle o~ from 2 to 15 and more preferably 26 from about 3 to abou~ 6 as measured from the vertic~l axi~
27 of the nozzle. The ef~ect of the diverging nozzle walls is 28 to provide a smooth ~low p~th that sweeps solids away from ~ :
29 the nozzle walls preventing their sticking to the grid thereby fouling it. For example9 the gases with entrained ~olids 1 which are heading generally upwardly i.nto the dead space~
2 between the nozzle openings ~re affected as follows The 3 ga~ is forced to alter its original d~rection of flow so as 4 to enter the nozzlesO The entra:ined solids, on the other hand~ have sufficient momentum or inertia to continue on 1n 6 their initial direction and enter the dead ~paces between 7 the nozzlesO The solids tend to strike or appro~ch the grid 8 plate, but ultim~tely are forced to descend, and eventu~lly enter the nozzles or descend to become disentrainedO
The sh~rp turn~ ~ormed by the walls at the nozzle 11 entrances will alter the normal solids flow profiles Due 12 to the change in direction of the solids which enter the 13 nozzles9most of the solids will ~low upwardly n0ar the ver-14 tical axis o~ the nozzle bu~ will not ascend at locations ne~r the nozzle wallsO Thus, near the nozzle wall~ there i8 16 produced a centrifugal acceleration which causes disentrain-17 ment of the solids~ 'rhese disentrained particles do not im-18 pinge on nor stick to the walls~ On the other h~nd~ the 19 p~rticles which move through the centers of the nozzles have no chance of sticking by contacting the walls of the nozzles~
21 In one embodiment of the present inven~ion there 22 i~ contemplated the use of baffles in combination with the 23 novel grid disclosed and claimed hereinO The baffles gener- -24 ally will have the con~igurations of discs, doughnuts or combinations o~ both~
26 Further~ in another embodiment, ~ recovsry deck or 27 plat~orm is provided by means of which disentrained solids 28 can be continuously removed. The gas-solids flow can also ~9 be directed. For example, in normal operation, wherein a 30 recovery deck is provided, gas ~ith entrained solids ~ets-:1~4~33 1 upwardly through the holes on the recovery deck toward the 2 dead spaces of the plateG At the bottom of the plate, near 3 the entrance to the nozzles, solids are thrown outwardly and 4 are reentrained to move upwardly through the center of the grid holes or are di entrained In this manner the tendency 6 toward plugging is eliminated or drastically ~uppressed.
7 In yet another embodiment, the entrances to the 8 nozzles are provided with vortex breakers, or structure~
9 having a series of separate channels through which the gases a enter. These provide structures having a honeycomb-like 11 appearance which further smooths out flow through the nozzles.
12 Preferably, the vvrtex breakers are constructed of a ~eries 13 o~ parallel plates or baffles spaced apart Qnd vertically 14 aligned upon the central axis of a nozzle, or aligned gener-ally in the direction o~ flow through the nozzlesO Preferably, 16 also, this series of plates is intersected at regularly spaced 17 intervals by another series of vertically-a~igned plates~ thu~
18 creating a plurality of independent flow channels at the en-19 trance to a nozzleO The length: diameter (L/D) ratio of the individual honeyeomb openings or channels ranges from about 21 lO to about 30J ~nd preferably ~rom about 15 to about 250 22 The diameter or cross-section of an individual opening through 23 the honeycomb structure is preferably as large as, or larger 24 than the minimum grid opening of the nozzles to which it is attached In addition, preferably the forward portion of the 26 nozzle containing the vortex breaker is constituted of a 27 straight run section, or ~ections, the walls of which neither 28 converge nor divergeg to provide a minimu~ wall area for im-29 pact of solidsO Downstream of the vortex breaker is provided gradually converging walls forming ~ tr~næition zone which ,,' ~

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1 produce a gradually increa~lng rQte of flow of gase3 2 through the nozzle~.
3 These and other features of the invention will be 4 better understood by reference to the following detailed descriptlon9 and to the attached drawings to which referenc~
6 ls m~de in the descriptionO
7 Figure 1 is a schematic elevation view depicting a .
8 reactor containing a multiple number o~ ~luidized beds, each 9 bed being separated3 one rrom another, by a grid structure o~ a type defined by the present invention; and also showing 11 ba~fle means in con~unction therewith3 12 Figure 2 is a plane vlew taken along Section 2-2 13 of Figure 1 ~howing9 from the bottom, one of the grid struc-tures of the character generally described;
Figure 3 i8 a schematic diagr~m ~howing a nozzle :
16 of the grid structure described herein and the divergence o~
17 the nozzle walls from the vertical axis of the nozzle;
18 Figure 4 is an elevation view o~ a segment of a 19 plate and recovery deck showing in detail the characteri~tics of the downwardly-diverging nozzles which are dispersed or 21 arrayed across the dlameter of the plate and the positi.oning 22 of the recovery deck;
23 Figures 5 and 69 reBpectively show elevation and 24 plan views of a further refin~* nozzle provided with a vor-tex breaker at the gas entrance; and 26 Figures 7 and 8 respectively, show ~c.~matic side 27 views of a section of a fluid bed reactor having copvex and 28 conc~ve grid structures o~ ~ type de~ned b~ t-he pr.e~ent 29 invention~
While the invention will be de~cribed with parti-~4~Z33 1 cular re~erence to a multi-b0d reactor, the invention i~
2 equally applicable to ~ plurality of ~in~le~bed reactors 3 as well.
4 Referrlng now ~pecifically to Figure 1 there is S shown a vertical reactor 10 o~ the type employed in the 6 direct reduction of iron oresO P~rticul~te iron ore ~olids 7 are fed into the inltial st~ge (~tage 1) ~nd the reduced 8 iron ore i8 removed from the bottom or ~inal ~tage (~t~ge 9 5) of the re~ctor lOo Hot reducing ga~ is fed into the bottom of re~ctor 10 vi~ line 19 to fluidize the solid~ and 11 spent reduclng ga~ is removed from the top of the reactor 12 10 via line 16~
13 The re~ctor 10 i~ divided into a series of ~tage~ --1~ ViZ ~ J 1 through 5 - each of which cont~in~ a ~luidized bed of oxidic iron ore. Each of the ~t~ges are separated, one 16 from another~ by me~ns of grids 113 12, 13, 143 15 through 17 which àscends a hot stream of reducing gaB which fluidizes :~
18 the particulate iron oxide ~olids which are supported ab~
9 said grids~ While the grid is placed substantially horlzo~-tally across the enclosing wall~ of the re~ctor the grid 21 plate need not be perfectly ~lat but may, for reasons of 22 strength~ be convex or concave in shape such ~s is shown in 23 Figure~ 7 and 8 respectivelyO
24 In reactor 10 baffle me~ns, shown as disc 20 and ~ ~`
doughnut 21, are located in the plenum chamber below grid 15 26 to distribute thP flow of gasesO If inter~t~ge cyclone~ are 27 employed above e~ch bed, baffl~s m~y be used below any or all 28 of th~ grid~ to distribute the fiow of gases and entrained 29 solidsO Similarly baffles may be used below the grid~ where individual reactor~ are used in lieu of a multiple bed re-1 actor system.
2 As indicated previouslyJ in one embodiment per-3 forated or recovery decks (not shown in Figure 1) are pro-vided below each of the grids 11, 12~ 13~ 14~ 15, re~pec-S tively, for removal o~ disentrained solid~ particle~. The~e b particles can be bled out through openirlgs (not ~hown) in the walls of the reactor lOo 8 Iron ore i~ charged into the top o~ reactor 10, 9 ~nd into ~tage 1 which, mo~t often9 is a low temperature lo prehe~t zone where little or no reduction t~kes placeO The 11 preheat ore from stage 1 i~ flowed downwardly via ~ ~tand-~, 12 pipe 6 to zone 2 which is operated at a temperature 3U~
, 13 cient to reduce ~erric oxide to substantially magnetic oxlde 14 of iron, or a mixture approximating the ~ormula Fe3Q4, -~e-The partially reduced ~olid~ are overflowed from stage 2 via 16 a standpipe 7 to stage 3 wherein the magnetic oxide o~ iron 17 is converted to qubstantially ~errous oxide~ Ferrous oxide 18 ~rom stage 3 i~ overflowed via standpipe 8 to ~tage 4, and 19 from ~tage 4 via standpipe 9 to stage 59 the final ~tage of the serie~.
21 Stage 4, the stage wherein relatively highly re-22 duced iron particles contact the grid, is the stage wherein 23 grid ~ouling is mo~t acute because metallized p~rticles are 24 blow~ upw~rdly from stage 5 below into grid 14, the~e par-ticles tending to aggravate the problem o~ pluggage, For 26 the ~ame,reason there is al80 con~iderable tendency for the 27 grid 13 to become plugge~0 Thusg relatively simple grids 28 might be employed in the very upper stage~y if de~ired, ~ince the very la~t stage~ of the ~erie~ are most readily and acutely disturbed by grid pluggage and foullngO Grid~
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l ll, 12 can thu~ be o~ more ~imple constructionJ or grids 2 13, 14~ 15 can also be used ~t the~e location~
3 The reducing ga8, which is a re~ctant as well as a 4 fluidizing medium, fed into reactor 10 via line 19 can be a fresh reducing gas consisting e~senti~lly of a mixture of b carbon monoxide ~nd hydrogen such as ~ormed by partial oxi-7 dation o~ hydrocarbons or by the ~team reform~tion of hydro-carbons, or a reducing gas from an entirely dl~ferent ~ourceO
9 Reducing g~s from the top o~ reactor 109 which exits there-from via line 16J can be regenerated by removal of oxidized ll components, if desired, and reintrodllc0d via line 17 with 12 ~resh ma~e-up ga~ whlch enters the reactor lO via lines 18~
13 l9 from a reducing gas "generator" ~not shown)O The reducing 14 gas can be regenerated by generally conventional means, e.g., by ~crubbing with an adsorbent to remove th0 carbon dioxide 16 or by refrigerat~on to remove w~ter~ or bothO
17 As can be seen from Figures l and 2 the grid plate 18 is provided with a plurality of openings, preferably symmetri~
19 cally distributed across the plate~ to best control and regu-late gas and solid~ flow. Each of the openings ~s provided 21 with downwardly diverging nozzles 260 The sides of the no~-22 zles form enclosing walls which converge into an aperture to 23 form a ~ructo-conic opening 27 which face~ downwardly when 24 the plate i8 in place in reactor lOo As can be seen from Figure 3, the side w~ll o~ each nozzle diverges at an angle 26 O, as measured from the vertical a~ls of the nozzle, which 27 angle is no greater than 30, preferably bet~een 2 and 15, 28 and more prefer~bly between abou~ 3 and about 6 Option-29 ally7 the nozzles can have smooth downwardly diverging w~lls thereby term~nating in a horn or bell sh~pe . . .

1 In general, the openlngs to the cones under the 2 grid represent greater th~n about 5% of the total area of 3 the grid. Indeed, the usu~l range of open area .i5 from 4 about 5 to about 30~ with 10 to 20~ open area being pre-ferred.
6 In normal operation the flow of gases and solids 7 is upwardly through the central portion o~ the nozzlcO Be-8 tween the nozæles 26, in ~pace~ 28, b010w the plate 14 for 9 exam~leJ are located "dead spaces" wherein the ri~ing gas lo is blocked and forced to descend ~round the walls of nozzle~
11 26 to enter openings 270 The ~harp turn causes some of the 12 solids to be deentrained due to the centrifugal acceleration 13 of the gases but the solids which are re-entrained rise up-14 wardly through the center of the openings without contact with the walls of nozzles 26.
16 In one embodiment of this invention~ as shown in 17 segment in Figure 49 a perforated platform or recovery deck 18 is loc~ted below the grid and conveys di~engaged solids par-19 ticles to the side of the raactor 10 from where they can be disch~rged via ope~in~ (not shown)~ The perforations 241 21 permit passage of gas, with entrained solidsO The perfor~-22 tions 241 are preferably located directly below the dead 23 sp~ces 80 that entrained solids wilI not impinge directly 24 upon the in~ide waIls of the nozzles 26~ Fluids le~ving orifices or nozzles do not diverge ve:ry rapidly~ Solids 26 contained In auch gases, on the other h~nd, hardly diverge 27 at allO Thus, the ~olids will tend to continue in the ~ :
28 upward direction toward the flat part of the grid plate 29 between the grid nozzlesg whereas the gase3 will tend to ent~r directly into the grid nozzle~, although some of the ~ . .

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~4~3~

gQ3es will approach the ~lat portion of the grid plate.
2 The angle of slope o~ a platform 24 i8 sufficlent-3 ly great to permit free flow o~ solids particles down the 4 walls~ The angle of the platform 24 must be greater, or st~eper, than the angle o~ repose, iOe~ the angle required :
6 to overcome the internal friction of the solids. For iron 7 oxides, the angle must be at le~st about 60G, ~nd prefer~bly 8 ranges ~rom about 60 to ~bout ~0, me~ured from horizontal.
9 The size o~ the openings 241 for upward passage of gase~ is determined by the throughput of g~se~ to be h~ndled in the 11 reactor 10, but preferably are oversized to les~en any undue 12 pressure drop withi~ the reactor 10 o Low pr~ssure drops, 13 and thus relatively low velocities ~less than about 15 to 14 about 25 feet per second) 9 eliminate fouling of these holes 4 Thus, for a reactor operating at gas velocities of about 4 16 feet per second, these perforations 241 constitute about 10 to 25 percent o~ the cross ~ection of the vesselO Operating 18 with the~e perforat~d plat~orms permits con~iderably higher 19 ~ntrance velocities into the nozzlesO These latter velocities ~ can appro~ch 59 feet per ~econd but preferably the entrance 21 velocity at the nozzle inlet is 1e~8 than 30 feet per second.
22 In Figure 4 the walls of the nozzle are shown 23 curving downwardly and outwardly from wall 29 terminating in 24 a bell or ho m shape and thereby providing ~ streamlined en-tr~nce æhape that minimizes fluid flow distortionsO
26 In conventional grid hol0 openings the vena contr~cta D i~ within the grid plate itselfO The gas flo~ coming from be-28 low the grid plate passes the bottom rim of the grid hole, 29 separates from tne grid hole wall (vena contracta) and fans outward again a~ter the vena contracta to reat~ach to ~he ~4BZ33 1 wall of the grid hole. Small particle~ follow the gas 2 around the vena contrac~aO Due to their lnertia, these 3 particles cannot "reattach" to the walls as the g~ doe3 4 and therefors impinge against the upper part of the grid hole ~orming a ~aucer-shaped depositO Further, particle~
6 falling downwardly from the bed above o~ten enter into this 7 low velocity zone and tend to contact the periphery of the 8 openings to stick and produce p~ugging~ The nozzle~ used 9 according to the be~t practice of thls invention, howevQr, are provided with walls upwardly converging and optionally 11 curving converging walls which provide a definite rate of 12 change of gas velocity per unit of lengthO
13 The gas velocity profile will be near~y normalJ
14 but the solids velocity profile will be relatively higher at the center of the nozzles th2n normally encountered at 16 the entrancesO The concentration of soli.ds due to the cen-`: 17 trifugal ~ction of making the turn will be higher at axis of 1~ the no~zle but lower near the walls than nor~lly encountered 19 ~or conv~ntional gas entr~ncesO The velccity profile of an upwardly converging nozzle will be somewhat higher at the 21 walls than for a straight tube~or the gases but the solids 22 velocity will be considerably hlgher at the center line due 23 to initial entrance effects. The net effect i5 that solids 24 particles are either disengaged so that they will not con-tact ~olids sur~aces or are thrown into the fa3ter moving ~ /~M ~J o~
26 stream at the center of the nozzleO Thi~ 4~4~4-i3 de-27 picted with p~rticular reference to the embodiment represen-- 28 ted in segment in Figure 40 29 The nozzle deQign, illu3tr~ted by specific re~er-; 30 ence to Figure~ 5 and 6 (3ection 6-6 o~ Figure 5), is e~-- 14 - ~

~41~Z3~

1 peci~lly useful .~n imp~rting better flow characterl~tics to 2 ga~esO The design i9 some~hat ~imllar to tha-t shown by 3 reference to the preceding figures except that, primarily, nO~
the ~ e includes an optlonal, ~nd de~irable, ~traight 5 run portion sr entry portion within whlch is provided a vor-6 tex breaker. Thus, the nozzle ~tructllre 40 ~nclude~ a vortex bre~ker, ~n the shape of a honeycomb structure 41, 8 located within the inside wall 42~ The angle of entry into 9 the ~rustoconical portion is limited to less th~n a maximum of 30 with 'che vertical axis o~ the nozzle so as to mini-11 mize imp~ct efrects of the entrained solids. In other word~, 12 the frusto-conical portion has the same relative dimensions 13 of the nozzle without the straight run or entry portion.
14 The honeycomb is constituted of two series of parallel spaced, vertically-aligned plates located within 16 the wall 42 of the nozzleO The plates are fitted or meshed 17 together to provide ~ plurality of individual channels or 1~'.
18 cross-sectional openingsJ in th~t instance square openings 19 or channel~, which have a flow area as great ~SJ or greater than~ an opening through the gridO The lengthodiameter (L/D) 21 ratio of the individual honeysomb openings ranges from about 2? 10 to about 30~:~nd pre~erably from about 15 to about 25.
The cross-sectional area of an individu~l opening through 24 the honeycomb structure is preferably as large~ or largerg than the opening D which approximates th~t of the grid open-26 ing to which the nozzle is ~ttached~ The honeycomb 41 re-27 duces or destroys large turbulent eddies and ~orces the 28 gases to enter in~o ~he nozzle in a more vertical direction~
29 ~nd also reduces angular momentum and ~wirling.

Down~re~m of the honeycomb 41 is located a transi-. I ~

~L~)4~3~33 1 tion zone 43 wherein entr~ined solids particles are oriented 2 and directed in a straighter *low path for smooth entry into 3 the acceleration zone 44~ The walls 42 of the transition 4 zone 43 are inclined to provide a desired and definite rate o~ change of velocity per unit of length. The rate of change 6 i.9 set to minimize the ef~`ects o~ ~olids impa~tionO
7 The transition zone 43 is shaped to give a smooth 8 entry into the modlfied frusto-conical nozzle ~nd should 9 have a minimum length o~ 8iX times the diameter of the tube outlet. Thi~ transltion length should not be greater than ~ O timeæ the diameter and preferably ~hould range between : 12 about lO to about 15 times the di~meter D.
13 In accordance with this invention the gas and 14 solids acceler~tion pattern is the critical feature to be lS incorporated to prevent solids sticking again~t the w~ll o~
16 the nozzleO The gases and solids should enter the vortex 17 b~reaker at relatively low velocitie~O This portion of the 18 a~paratus smooths out and minimiæes the eddies of solids and 19 ga3es entering the nozzleO The transition zone is shaped so as to result in ~inimum distortion of the smooth flow es-21 tablished by the vortex breaker, yet designed to prevent ex-22 cessive solid impingement on the walls o~ the transition zone.
23 Having established smooth entrance conditions to 24 the nozzle by use of the vorte~ breaker and transition zone9 the design of the nozzle itself i9 the most critical portion 26 of the present invention~ The nozzle is so designed as to 27 give the solids contained in the gases suf~icient time to ;~
28 accelerate and approach the velocity of the gases at the 29 point where the gaSQ5 and solids leave the nozzleO Thus, the maximum rate of change of gas velocity with length of .
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1 traval down the nozzle is not greater than a constant and 2 is preferably ~ decreasing ~mooth function of the di~tance 3 from the nozzle entrance.
4 It is apparent that certain modifications and changes can be made in the present invention without de-6 parting its spirit and scopeO

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Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An apparatus for use in a fluidized solid system comprising:
a vessel defining a flow path for said fluidized solids;
means for introducing and means for removing said solids;
means for introducing and means for removing fluidizing gases;
a plate horizontally located across the enclosing walls of said vessel thereby forming a boundary for a fluidized solids bed, said plate containing a plurality of apertures therethrough; further characterized by nozzles for each aperture in said plate having an outlet on the upper surface of said plate, formed from walls surrounding said apertures, said nozzles extending downwardly below the lower face of said plate, said downwardly extending nozzles having walls diverging at an angle of between 2° and 30°
as measured from the vertical axis of said nozzle whereby a smooth flow path is provided so that most of the solids will flow upwardly near the vertical axis of said nozzles and thereby avoid sticking and fouling of the grid.

2. The apparatus of claim 1 wherein a plurality of said plates are located in said vessel, one above the other, in spaced relation, thereby forming boundaries for a plurality of fluidized solid beds and including means for passing said solids downwardly from bed to bed.

3. The apparatus of claim 1 wherein said walls diverge at an angle between 2° and 15° as measured from the vertical axis of said nozzles.

4. The apparatus of claim 1 wherein said walls diverge at an angle between about 3° and about 6° as meas-ured from the vertical axis of said nozzles.

5. The apparatus of claim 1 wherein said nozzles are provided with straight wall entry portions within which is included a series of individual channels formed by honey-combed structures which reorient and smooth out the flow of gases of the fluid solid systems through the nozzles.

6. The apparatus of claim 5 wherein the indivi-dual channels through the honeycombed structure provide a length: diameter ratio ranging from about 10 to about 30 and wherein the cross-sectional diameter of an individual channel is at least as great as an individual aperture through the plate.

7. The apparatus of claim 6 wherein the length:
diameter ranges from about 15 to about 25.

8. The apparatus of claim 1 including means for directing the upward flow of entrained solids essentially completely toward said plate to an area between said nozzles.

9. The apparatus of claim 1 including baffle means located below said plate for distributing the flow of fluid in said vessel.

10. The apparatus of claim 1 wherein said plate is convex in shape.

11. The apparatus of claim 1 wherein said plate is concave in shape.

12. The apparatus of claim 1 including means for directing the upward flow of entrained solids essentially completely toward said dead spaces whereby the normal solids flow profile is altered so that most of the solids will flow upwardly near the vertical axis of said nozzles.

13. The apparatus of claim 12 wherein the means for directing upward flow of entrained solids is a recovery deck provided with a plurality of apertures, said apertures being aligned with the dead spaces between the individual nozzles whereby the entrained solids flow upwardly through the apertures essentially completely toward the dead spaces of said plate.

14. The apparatus of claim 1 wherein said nozzles are provided with straight wall entry portions within which is included a series of individual channels formed by honey-combed structures which reorient and smooth out the flow of gases of the fluidized solids systems through the nozzles.

15. The apparatus of claim 14 wherein the indivi-dual channels in the honeycombed structure provide a length:
diameter ratio ranging from about 10 to about 30 and wherein the cross-sectional diameter of the individual channel is at least as great as an individual aperture through the plate.