US2656920A

US2656920A - Elutriator for hydrocarbon conversion systems

Info

Publication number: US2656920A
Application number: US285269A
Authority: US
Inventors: Kollgaard Reyner
Original assignee: Houdry Process Corp
Current assignee: Houdry Process Corp
Priority date: 1952-04-30
Filing date: 1952-04-30
Publication date: 1953-10-27
Anticipated expiration: 1970-10-27

Description

R. KOLLGAARD 2,656,920

ELUTRIATOR FOR HYDROCARBON CONVERSION SYSTEMS 3 Sheets-Sheet 1 Oct. 27, 1953 Filed April 50, 1952 INVENTOR REYNER KULLEAARD ATTORNEY Oct. 27, 1953 R. KOLLGAARD 2,656,920

I ELUTRIATOR FOR HYDROCARBON CONVERSION SYSTEMS Filed April 30, 1952 3 Sheets-Sheet 2 INVENTOR REYNER KULLBAARD Oct. 27, 1953 R. KOLLGAARD ELUTRIATOR FOR HYDROCARBON CONVERSION SYSTEMS Filed April 50, 1952 'xxmu-mamumwmm .315

3 Sheets-Sheet 3 INVENTO'R REYNER KULLBAARD ATTORNEY Patented Oct. 27, 1953 ELUTRIATOR FOR HYDROCARBON CONVERSION SYSTEMS Reyncr Kollgaard, Media, Pa., assigno'r to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware Application April 30, 1952, Serial No. 285,269

12 Claims. I

This invention relates to a method and apparatus for elutriating granular contact material for the removal of small-size particles, particularly as applied to the circulatory system of a catalytic hydrocarbon conversion unit.

The invention is particularly adapted for use in a hydrocarbon conversion system involving the continuous circulation of granular contact material having a particle-size in the order of about 1-15, and preferably 2-8, millimeters in diameter, which circulatory system includes a down-flow path through which the contact material gravitates as a compact moving mass, and an up-fio'w path through which the contact material is pneumatically elevated for return to the upper end of the down-flow path.

A typical system to which the present invention may be applied is disclosed in an article entitled Houdrifiow: New Design in Catalytic Cracking, appearing at page 78 of the January 13, 1949, issue of the Oil and Gas Journal. The pneumatic lift disclosed in the article comprises an elongated vertical lift pipe having its lower inlet end. portion extending into a lower li ft hopper or engager, wherein contact material withdrawn from the lowermost contact zone of the down-flow path is engaged by one or more streams of lift gas and conveyed into and then upwardly through the lift pipe to an upper lift hopper or disengager containing the upper end portion of the lift pipe. Within the disengager vessel, the contact 'material discharged from the upper endof the lift pipe is separated from the accompanyinglift gas by gravitational deceleration and free fall of the particles of contact material. The disengaged contact material gravitates to the lower region of the lift disengager, from which regionitis continuously withdrawn and returned to the upper end of the down-flow path. The lift g'as, substantially free of contact material, is separately removed and is passed to conventional means, such as a cyclone separator, for the usual removal of entrained fines, i

It is a common practice in such systems to continuously by-pass a portion or the circulating contact material to an elutriator iorthe' purpose oi removing fines from the system, the fines being considered those particles which are about 14 mesh or smaller in size. The larger-size particles, which are suitable for reuse, are then returned to the circulatory system at any oneof several points in the circulatory path suitable for thereintr'oduction of'the contactniaterial.

Heretofore, it has been apractice to withdraw the elutriator feed stream from the circulatory system at some convenient location along its path of travel between the disengager and the point of introduction of the contact material 'into the hydrocarbon conversion unit. After the removal of undesired small-size particles, the contact material is returned to the circulatory system at some convenient lower level, such as directly into the lift engager.

In accordance with the present invention, the stream of contact material discharging upwardly into the lift disengager is intercepted during its free fall by tray-like members deposited at a plurality of levels withinthe disengager vessel. The contact material collected on the trays is passed stagewise downwardly from tray to tray in a plurality of separate circumferentiallyspaced streams adjacent to the inner wall of the ndisengager, each having a relatively short distance of free fall. From the lowermost tray, the contact material gravitates freely to the lower region of the disengager vessel, from which region it is continuously withdrawn and passed downwardly to the uppermost zone along the down-flow path of the hydrocarbon conversion unit A portion of the disengaged contact material is withdrawn from a location on one or more of the trays of the disengager at which there is a relatively high concentration of the smaller-size particles of disengaged contact material and is passed by gravity flow to an elutriator for the removal of undesirable small-size particles.

In a preferred embodiment of the invention the elutriator is so located that the separated large-size particles may be passed by gravity flow to the continuous compact moving mass of contact material gravitating through the down-flow path of the conversion unit. A portion of the lift gas separated from the contact material within the disengager is passed into the elutriator to effect in known manner therein the desired separation of fines from the large-size particles of contact material. The remaining portion of the disengager' gas and the gas discharge stream from the elutriator are both passed to a common cyclone separator which removes the fines from the lift gas and the elutriator gas streams before passing the same to the stack. I

In a multiple lift system employing a plurality of separate disengagers, each serving one passed to a second upper kiln, as disclosed in my application, Serial No. 285,270, filed April 30, 1952, the elutriator vessel and the common cyclone serving the elutriator and the disengagers may conveniently be located one above the other axially over the upper kiln.

For a fuller understanding of the invention reference may be had to the following descripticn and claims taken in connection with the accompanying drawings forming a part of this ap plication, in which:

Figure 1 is a sectional view, in elevation, showing one embodiment of the invention as applied to a multiple lift system;

Figure 2 is a fragmentary sectional view, in elevation, showing the elongated downcomers at one side of the disengager vessel;

Figure 3 is a horizontal section taken along the line 3-3 of Fig. 1;

Figure 4 is a horizontal section taken along the line i 1 of Fig. 1;

Figure 5. is a horizontal section taken along the line 5--5 of Fig. 1;

Figure 6 is a horizontal section taken along the line B-6 of Fig. 1;

Figure '7 is an elevational view of the disengager vessel, with a portion broken away'to show an embodiment of the invention wherein the elutriator is located internally of the disengager vessel;

Figure 8 is a horizontal section taken along the line ii8 of Fig. 7;

Figure 9 is a horizontal section taken along the line 9-9 of Fig. 7; and

Figure 10 is an elevational view showing the elutriator applied to a disengager which does not have a storage or surge capacity in its lower region, the elutriator being positioned axially above and in open communication with the uppermost zone containing the downwardly moving compact column of contact material.

Referring to the embodiment of theinvention illustrated in Figs. 1-6, the numeral H refers to thedisengager vessel of a multiple pneumatic lift. The disengager is supported at the upper end of a pair of parallel lift pipes l2, and comprises an upper cylindrical portion 13 and a lower conical portion. l4 eccentrically attached along its base to the lower perimeter of the cythrough the sloping side of the eccentric conical.

portion Hi and terminate approximately at the level of the juncture between portions l3 and It. The height of the conical portion and the discharge level of the lift pipes are such as to provide sufficient space in the bottom of the disengager for maintaining a compact moving bed it of disengaged contact material as surge capacity for the circulatory system. The axes of the lift pipes l2 areparallel to the axis of cylindrical portion; 13, and are equally spaced therefrom onacommondiameter. 7

At the lower end of the disengager, the apex of the conical portion M is connected to an inclined conduit it through which disengaged contact material from bed #5 may be continuously passed in the form of a compact moving column to the uppermost contact zone along the down flow path of the conversion unit, such as the reactor, not shown. 7

Within the disengager II the streams of contact materialand lift gas discharging from the streams to tray segment 18 next below.

The trays are located outside the approximate envelope of the rising streams of contact material, and are arranged to intercept the freely falling particles and to pass them stagewise from tray to tray until they reach the surface of the bed I5 in the lower region of the disengager.

The first, or uppermost, pair of tray segments I! and I1, shown in Figs. 1, 2 and 3, are located in the upper region of the disengager at a level which is attained, for the most part, only by the smaller-size particles in the rising streams of contact material. As the completely decelerated particles become disengaged from the lift gas and gravitate toward the bottom of the disengager, those particles which are in the pe ripheral region of the vessel above the first tray segments are deposited thereon, while the centrally located particles pass downward between the first tray segments to be deposited at a lower level.

Tray H is provided with an arcuate dam or weir 2| which serves to retain on the surface of the tray a static accumulation of the particles deposited thereon. Additional particles slide downwardly over the surface of the static mass and pass over the dam into the arcuate space between the dam and the wall of the vessel, from which space the particles drain through openings 22 and fall freely to the peripheral region of the tray segment [8 next below.

Tray I1 is similar to tray ll, with the exception of the provision for drain. Instead of drain openings, such as 22, tray I1 is provided with a plurality of parallel downcomers 23, two being illus trated, which convey the particles as confined The discharge ends of downcomers 23 are preferably located a short distance above the receiving tray.

The next lower pair of tray segments l 8 and 18' are of similar shape, as shown in Figs. 1, 2 and 4, but extend inwardly a greater distance toward the central region of the disengager. ally, however, both tray segments have a plurality of parallel dams 24 forming spaced chords of the arcuate dams 2i. Openings 22 in tray l8 permit the contact material to fall freely to tray i9 next below. Tray I8 is provided with a plurality of downcomers 25, two being shown, whose upper ends are disposed directly below the discharge ends of downcomers 23, and which converge so that their lower ends areat a single receiving [9, shown in Figs. 1, 2 and 5, have irregular inner edges, the edges being extendedcentrally to meet in a relatively narrow region'at the center of the vessel, thus forming openings 26 of 'sufiicient size to permit free passage of the separate rising streams of contact material.

lift pipes i2 expand and merge in the upper re- 'jgion of the disengagerf The approximate enalso are provided with arcuate dams 2 I 'and with straight parallel dams 24. Openings 22 are provided along the entire peripheral annularspace oftray l9, and at each end portion ofthe peripheral annular space of tray I 9'. Trayle' is provided with a single vertical downcomer ,2!

Addition- 7 Trays l9 andlil' whose? inlet end? is located immediately Beneath hie-aforementioned single receivin Trays 211' and showni Figs; E and 6;- are tireiowermost trays: 'Fh'ey p'rojeot a mamas short distance inwardly from the vessel wall but extend circumferentialiy along the wall of the vessel a greater distance than any of the traps above. Trays 20* and 21'!" receive all tlie contact material failingiree-ly through the: openings: 21' of trays l9 and l9.

The slope" and sizeof all the-trays and tlietotal flow area of the drains on" each tray are such as to" preclude; or at least minimize, any spill over of contact rrlaterial from the inner edges of the trays. Where the slope of the trays for" any reason is not suflicient to assure fieedom from spill-over, additional dams may-locprowlded al'ong the innermost edges'of each tray-1 Byrea'son of the fact that t'l'ie smaller particles tendto'require-a greater disengaging heigliiithan the larger particles, theccmcentra-tiion of smalls'ize particles increases or; in other words; the average particle size' decreases upwardly through the new system: I v

Dow'nco'mers 23 therefore convey streams of contact material which havethe highest'concentration of small-size particles: Since the in-l'et ends" of" downcomers 25 are adjacent to and directly below' the" discharge endsof down'comers 23, theformer will preferentially withdraw from the material on tray is" that which has eeenreceived from tray I1". Similarly; downcom'erfl preferentially withdraws from trayl9" that material which has been deposited thereon from downcomer's' 25'.

Downco'mer 21 is closed at its lower end, but has a side outlet adjacent theretoi From the lower end of the downcomer the contact material is assed into" a conduit 2'8- through whichthe material is conveyed by gravity flow outwardly throughthe wall of the' disengager toanelutriator, generall'yindicated by the numeral 29 Gonduit 28 has a short vertical run 30 provided with an orifice plate 3 l" to control the flow of contact material to be elut'riated. w

The elutriator' 29 comprises a hollow cylindrical member 32 havingitslower portion depending concentrically within a closed cylindrical chamber 33 of substantially greater diameter. The

lower end of conduit 28' extends into the upper region of cylindrical member 3? and is arranged to discharge the contact material axially downward therein. A distributor plate" 3 4 is supported axially below the end of conduit 23 to intercept and distribute outwardly" the falling stream of particles. 3

Elutriator gas is provided by withdrawing a portion of the disengaged lift gas from the di' engager fl through conduit 35. The inlet end of conduit 35 is located within the disengager at a point approximately level with the lowermost tray segment 20, and between the tray and the rising streams of contact material dischargin from the lift pipes ll} such location being selected because the gas. withdrawal does not interfere with the rise or fall of the contact material. To prevent the admission of stray particles of contact material into the conduit 35, the inlet end may be turned downward, as shown. The discharge end offconduit 35 isconn'ected into the side wall of chamber 33 at a level substantially above the open lower end of cylincirical member 32', so that the elutriat'or gas will first travel downwardly within the annular passage formed Between the concentric walls of members 3! and 6'. w and themupmdltr into andthrmiglnthe lattes; tn the falling; or! comnctmateriali.

The: remaining: portion: (It. the;- liit'. gas is. dice charged. from disengager lilz throughi overhead conduit? 29;. which; iSl provided in: known manner 1 with? a suitable: dampen;.. not shown; for the punpose of obtaining the desiredipropontioni of; gas flbwto:=the:el'ut1'laton29!'..

elutniator separates;- the?- smahi-size particles; from; the: large-size: particles of, contact. material; the. latter gravitating; to the surface-.- OIL a moving. beds. 35 of: the same maintained at the bottom of chamber 337; the former? lacing,- car.- ried upwardly out ofi. therelutriator through: condull: 3 by entrainment in thecountercurrcntly flowing gasstream;

The separated: largc sizea particles are continuously withdrawn: tram: the bottom oil bed; 356 through: conduit iiiijlprovidedi with an orifice plate 35, and'returned'; torthe: disengager Ill. Conduit 38 introdiicesi the: elutriator stream: at particles into the conical portion. I14: at a low point within thecompact moving bed Hi.

In order. to constantly maintain. the; compact moving bed; 3:6 at the: bottom at the: elutriator, a bypass conduit withdraws a portion of. the contact material flowing. in, the upper portion of vertical run so of conduit 28 at a. point above. the orifice 31 and) passes the same; downwardly to the surface of the'bed 36. The-discharge: end. of. conduit is belowthe-lower. end of cylindricalmemher 32, and determines thelevel-of bed 35.

To assure that conduit Ad will. by-pass a, mini- I mum of the: small-size particles the. juncture of conduit 40" with. vertical run. it is preferably at the side directly oppositeztothe side at-whichthe contact material enters the vertical runfrom the upper sloping portion of conduit 28; Thusthere is a minimum: withdrawal of particles from that portion of the stream flowing through conduit 28- which contains thegreatest concentration of fines. It is known that, by reason of. the. classification: of particles which: inherently occurs. during flow along'an. inclined path, such as the upper sloping portion of conduit 28%;, the small-size particles will flow in the vertical run along the wall portionwhichis nearest-the direction of lateral admission.

Disengager gas ontlet-condint 29- andelutriator gas outlet conduit 31' are preferably hotlr connected to a common cyclone separator; not shown,

for the removal of fine particles carried overhead from the disengager I l and rejected fine particles discharged overhead from the elutriator 2.9-.

Referring to the modification; of the invention illustrated in Figs. 7', 8' and 9,. the disengager vessel H of Fig. I, with slight modificationof the internal tray structure, is provided, with an internal elutriator, generally indicated by the numeral ment l9 adjacent to the wall of the cylindrical portion [3. The lower end. of cylinder 52 is open, and the upper end closed by a horizontal end plate 53. End plate 53 has a central opening to receive the lower end of a gas outlet conduit 54. Aportionof the separated lift gas within the disengage:- cnters the lower end of cylinder 52 and is discharged from the upper end through condult 54. End plate 53 also has four uniformly distributed openings, as shown in Fig. 8, to receive the lower endsoif two pairs or downcomers 5i and $8. The pair-of conduits 55 which have their discharge ends located nearest the axis of the disengager have their inlet ends set in the tray segment I1, and. the pair of conduits 56 whose discharge ends are farthest from the axis of the disengager have their inlet ends set in the tray segment l8. The usual distributor plates 51 are placed below the discharge ends of the downcomers, as shown.

All the contact material drained from tray ll is passed through conduits 55 to the elutriator, and all the contact material drained from tray [8' is conveyed to the elutriator through downcomers 56. If desired, however, one or more openings 22 may additionally be provided in tray segment IS in either of the embodiments of Figs. 1 and '7.

From the

downcomers

55 and 56 the contact material gravitates freely through cylinder 52, countercurrently to the stream of lift gas moving toward the discharge conduit 54. The small-size particles of contact material are carried out of the vessel by entrainment in the discharging gas stream, and the large size particles descend by free fall to the surface of tray segment 55; Tray segment 58, shown in Fig. 9, is substituted for tray segment 20' of Fig. 1, and extends inwardly toward the axis of the disengager sufficiently to intercept all the contact material discharging from the lower end of cylinder 52. Tray 58 also is provided with openings 22 through which the contact material drains to the surface of the bed maintained in the'lower end of the disengager. A drain conduit 59, controlled by valve 53 is provided at the lower level of tray 58 in order that samples may be withdrawn, as desired.

In the present modification, the gas flowing through the elutriator is controlled in the same manner as it is controlled in the embodiment Fig. 1. Gas discharge conduits 29 and 54 are connected to a common cyclone separator, not shown,

for the removal of fines and other rejected par a ticles.

Fig. shows the application of the invention to a system in which surge capacity, in the form of a compact moving bed, is not provided within the disengager vessel, and the contact, material slides freely through a disengager draw-01f conduit to a compact moving bed located at a lower level along the down-flow path. Examples of such arrangement may be found in systems employing a separate surge hopper at the upper end r of the conversion unit, and in a split kiln arrangement wherein the reactor is placed between upper and lower kilns, as shown in my companion application, Serial No. 285,270 filed April 30, 1952.

In Fig. 10, the elutriator 6! is located externally of the disengager 52, A tray structure, diagrammatically shown in broken lines, is provided within the d sengager 62, and the elutriator feed stream of contact material is withdrawn from a tray having a high concentration of small-size particles, such as the upper or the middle trays. l"h elutriator feed stream is conveyed through conduit 53, provided with an orifice 64, into the elutriator 6 l.

The elutriator is located axially above a vessel 65 which may be a reactor storage hopper or may be the upper kiln of a split-kiln system such as that disclosed in my aforementioned companion case. Axially above the elutriator is a cyclone separator 66 which receives the lift gas discharge from the disengager through conduit 61, as well as the lutriator gas discharge through conduit.

- The gas feed to. the elutriator Bl through con 5 duit 69 may be supplied from any suitable source,

8 such as the lift engager or the kiln. With a split.- kiln system, as above-defined, the elutriatorgas stream may be conveniently supplied directly from the upper kiln, a portion of such gas being by-passed to the elutriator for this purpose.

With the axial alignment of equipment, as shown, the elutriator conveniently discharges the returnable contact material vertically downward into the down-flow path of the circulatory system.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

What is claimed is:

I 1. In a circulatory system for conveying granular contact material wherein said material flows compactly downward through at least one contact zone and is thereafter pneumatically elevated through one or more lift paths for recirculation, with consequent production of fines by attrition of said granular material, the method which comprise discharging said pneumatically elevated granular material upwardly within an elongated disengaging zone, said zone being of sufficient height 'to effect the disengagement of said granular material from the lift gas by gravitational deceleration and free fall of the gran ular material, intercepting the freely falling material at one or more levels within said disengaging zone located laterally of the discharged stream of granular material and lift gas, passing a portion of said intercepted granular material by free fall stagewis through said levels to the lower region or" said disengaging zone, passing the remaining portion of said intercepted granular material along at least one confined path downwardly from at least one of said levels to an elutriating zone, said remaining portion having a relatively high concentration of said fines, separating the fines from the large-size particles of granular material within said elutriating zone' by countercurrent engagement with a stream of gas, removing said fines from said circulatory system, and returning said large-size particles to said granular material flowing compactly downward.

2, The method as defined in claim 1 characterized in that said gas introduced into said elutriatmg zone comprises gas disengaged from said granular material within said disengaging zone, and said large-size particles of granular material discharged from said elutriating zone are returned to said compactly flowing material within the lower region of said disengaging zone.

3. The method as defined in claim 2 further characterized in that said small-size particles are removed from said elutriating zone by said stream .of gas, and in that the remaining portion of the disengaged lift gas and said streamof gas from said elutriating zone are conveyed to a common separator for removing all the small-size particles of granular material from said gas.

4. A method as defined in claim 1' in which said disengaged granular material is intercepted within said disengaging zone at a plurality of vertically-spaced levels arranged to intercept material of different average particle size, decreasing progressively upward, and in which a portion'of the granular material intercepted at one or more uppermost levels is conveyed stagewise along separate confined paths from level to level and subsequently withdrawn as a confined stream'from said disengaging zone at a lower 9 level, said separate confined paths being arranged so that the discharge of granular material from the confined paths at one level is directly above the inlet to the confined paths at the next lower level.

5. A method as defined in claim 1 in which said elutriating zone comprises a confined zone within said disengaging zone and in open communication therewith only at the lower end of said elutriating zone, and wherein granular material is intercepted at one or more levels above said elutriating zone, said intercepted material being conveyed from each of said one or more levels along separate confined paths and discharged directly into the upper region of said elutriating zone, the disengaged gas being passed, in part, from the lower region of said disengaging zone upwardly into the open lower end of said elutriating zone and, in part, being discharged from th upper region of said disengaging zone, the gas and entrained solids being discharged from the upper end of said elutriating zone and passed with said lift gas discharged from the upper region of said disengaging zone to a common separator for removal from the combined gas stream of substantially all the small-size particles of granular material.

6. In a circulatory system for conveying granular contact material wherein said material fiows compactly downward through at least one contact zone and is thereafter pneumatically elevated through one or more lift paths for recirculation, with consequent production of fines by attrition of said granular material, the method which comprises discharging said pneumatically elevated granular material upwardly within an elongated disengaging zone, said zone being of sufiicient height to effect the disengagement of said granular material from the lift gas by gravitational deceleration and free fall of the granular material, intercepting the freely falling material at one or more levels within said disengaging zone located laterally of the discharged stream of granular material and lift gas, at least one of said levels being located in a region of said disengaging zone wherein the disengaged material predominantly comprises said fines, passing a portion of said intercepted material by free fall stagewise through said levels to the lower region of said disengaging zone and thence to the surface of said compactly flowing material, passing the remaining portion of said intercepted material, predominantly comprising fines, to an elutriating zone, separating the fines from the large-size particles of granular material within said elutriating zone, and retaining said largesize particles to said compactly flowing granular material.

'7. In a circulatory system for granular material wherein said material gravitates as a compact moving column along a down-flow path and is thereafter elevated by means of lift gas through one or more lift pipes, with consequent attrition of said granular material such as to require removal from said system of small-size attrited particles, the combination of a disengaging chamber containing the upper end portion of at least one of said lift pipes, said disengaging chamber extending above the discharge end of said lift pipe 9, distance sufiicient to permit substantially complete gravitational deceleration of granular material discharged from said lift pipe, and having an upper outlet for disengazed lift gas and a lower outlet for disengaged 10 granular material, one or more trays attached to the side of said disengaging chamber above said discharge end of said lift pipe and adapted to intercept freely falling granular material, at least one of said trays being located in the upper region of disengagement to thereby intercept a portion of the disengaged granular material having a relatively high concentration of small-size particles, an elutriating chamber having contact material and elutriating gas inlets, and having an outlet for large-size particles of granular material and an outlet for said elutriating gas and entrained small-size particles of granular material, and means for passing said portion of intercepted granular material having a relatively high concentration of small-size particles to said elutriating chamber.

8. Apparatus as defined in claim 7 including a cyclone separator, and means for conveying thereto both the disengaged lift gas from said disengaging zone and the mixture of elutriating gas and entrained small-size particles from said elutriating zone.

9. Apparatus as defined in claim '7 in which said trays are four in number and are attached to the sides of said disengaging chamber at longitudinally spaced levels above said discharge end of said lift pipe, and including downcomers in at least the two uppermost trays for conveying the concentrate of small-size particles from said uppermost trays to said elutriating chamber.

10. Apparatus as defined in claim 9 in which the third tray from the top extends transversely across the disengaging zone and has one or more openings adapted to freely pass the streams of contact material discharging upwardly from said one or more lift pipes, said third tray having set therein a withdrawal conduit which, together with said downcomers comprises said means for passing said small-size particles to said elutriating chamber.

11. Apparatus as defined in claim 10 in which each of said trays comprises a pair of diametrically opposite inclined segments whose inner edges are just outside the stream profile of said discharging stream of granular material, and in which the segments of said third tray are joined along a portion of their inner edges.

12. Apparatus as defined in claim 7 in which said trays are four in number and are attached to the sides of said disengaging chamber at longitudinally spaced levels above said discharge end of said lift pipe, and in which said elutriating chamber comprises a hollow cylindrical vessel set in the third tray from the top, said elutriator being closed at its top and open at its bottom, and including at least one downcomer set in each of the first and second trays and extending downwardly into said elutriator.

REYNER KOLLGAARD.

Germany Oct. 6, 1914 Great Britain May 16, 1929 Number Number