CA2001831C

CA2001831C - Apparatus for blending particulate material

Info

Publication number: CA2001831C
Application number: CA002001831A
Authority: CA
Inventors: Paul D. Kermit
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-11-04
Filing date: 1989-10-31
Publication date: 1996-09-24
Anticipated expiration: 2009-10-31
Also published as: CA2001831A1; JPH02273529A; JPH0579370B2

Abstract

A blending apparatus for particulate material such as plastic pellets which may be assembled from an existing vertically oriented conical bottom silo. The invention includes inserting a inner cone member with a downwardly extending cylindrical member into the inside of the existing conical bottom silo. A vertically oriented lift pipe extends from below this cylindrical member upwardly through the conical insert to the upper reaches of the vessel. An inlet for gaseous fluid under pressure is provided to blending air to the bottom of the vessel for circulating material from the bottom of the vessel up through the lift pipe to the top of the vessel. A seal leg is established between the vertical lift pipe and the inner cone/hollow cylindrical extension to substantially prevent the blending air from by-passing the lift pipe to aerate material in the vessel. Secondary seal legs are provided around the periphery of the inner cone and extend into the material zone formed between the inner cone and the conical bottom of the silo. An auxiliary gas source may be connected to the area between the inner cone and the bottom of the silo.

Description

20~1831 APPARArlJ.C POR PT,RI~)TNr. p-ARTIrTTT~Al~E MAl'RRl'AT, RArT t'.'ROTlNT- ()l;' 'I'TTT~ v~ N
.~
The present invention relatea to blending apparatus for particulate material such as plaatic pellets and utilizes the blending concepts of withdrawing material from a plurality of points within the vessel thr-ough vertical dow~ and an ' internal recirculation system utilizing gas under pressure to recirculate the thus withdrawn materi~l back to the top of the vessel through a central lift pipe. In particular, the present 10 invention is an i .u~. over my copending U.5. Patent No.
4, 978, 227 .

More particularly, the present invention relates to an ~ nnm;l-~l use of eYi~ating vertically oriented storage silos for particulate material and converting those e~Yisting silos into blending aT~paratus.
The blender design disclosed in my prior above referenced U. S . patent includes a conical bottom vessel with tubular AY~ #i nn on the bottom. A vertical lift pipe ls centrally mounted in the vessel and eYtends from the upper part of the 20 ves~el into the tubular ~Y~n=~nn, Blending air ls supplied to the bottom o the vesael for entralning material to be blended and conveying it up the center lift pipe for circulating material through the vessel. The tubular extension and lift pipe are dimensioned to define a seal leg to prevent blending air from bypassing the vertical lift pipe and flowing directly into the vessel. This arrangement improvea circulation of material through the vessel.

~ 2001831.
This lower protrusion or tubular eYtension is a design and installation inconvenience when an exi3ting conical bottom tank or vessel is being retrofitted to be used as a blender. When there i6 insufficient clearance between the bottom of the vessel and ground level to accommodate the tubular extension and associated equipment, the entire tank must be raised by as much as six to eight feet. This is not only eYeensive but not always possible, particularly if these are height limitations such as when the tank i8 located inside. An alternate is to raise the bottom of the silo but this option is not always acceptabLe as it would result in a signif icant reduction in silo capacity. A third alternate is to provide a pit below the existing silo to accommodate the tubula~ extension but this is usually not satisfactory as it causes a problem with existing foundations and results in an area whece water may accumulate.

It would be adYantageous to provide a design which is capable of utilizing the advantages of my prior invention with existing vessels to eliminate the requirement for either elevating the existing silo or digging a pit to accommodate the necessary seal leg and accompanying material handling equipment. At the same time the useable capacity of the existing silo should be maintained to the extent possible.

SU~S~RY

It is therefore the object of this invention to provide an apparatus for blending particulate material which is capable of economically utilizing an existing conical bottom storage silo .

2Q01831.

In general, the foregoing and other ob jects will be carried out by providing an apparatus fo~ blending particulate mate~ial comprising a vertically oriented Gilo having an upper end and a lower end; a hollow open ended inverted frustum of a cone mounted in the vessel so that it3 large diameter end i6 secured to the inside of the ve6sel and its small diametel end i5 positioned below the large diamete{ end: a hollow, open ended cylindrical member is secured to and eYtends downwardly from the small diameter end of the frustum toward the lower end of the silo: a vertical lift column is mounted in the vessel and eYtends from below the cylindrical member upwardly from the lower end of the vessel through the cylindrical member and the frustum toward the upper end of the silo: said frustum having a plurality of circumferentially spaced apart openings thereir~
near its large end ad jacent the silo: a plurality of conduits, each f low connected to one of the openings in the f rustum extends downwardly therefrom toward the lower end of the silo:
a plurality of vertically oriented downcomers are mounted in said vessel and terminate above said frustum, each of said downcomers having at least one opening therein for receiving material from the upper part of said silo and transporting the material by gravity toward the lower part of the silo above the frustum: means for supplying gaseous fluid under pressure to the bottom of the silo for entraining material in the region between the frustum and the lowe~ part of the silo and conveying it up through the lift column to the upper part of the vessel for blending the material.

;

The present invention provide~ for the mounting of a hollow, open-ended frustum of a cone inside an existing vessel spaced from the conical bottom of the existing vessel. A

c?ool831 cyLindeLcal member is attached to the lower end of thls Lnternal cone. A ve~tical lift pipo eYtends f~om near the bottom o the eYisting conical bottom or external cone of the vessel up into the upper pa~t of the vessel. The open-ended cylinder and vertical lit pipe aLe dlmensloned to fo~m a prlmary seal leg around the llft pipe by formlng a concenteic f low annulus . The apparatus includes an inlet for blending air in the bottom of the vessel for ent~ainlnq mate~lal in the veGsel and conveying it up the llf t plpe fo~ dlscharge lnto the top of the vessel. The concentric annulus 18 dlmensioned to form a prlmary seal leg to substantially prevent blending alr from bypassing the verticdl lift pipe and aerating or fluidizing material in the vessel.

Vertlcal downcomers are mounted in the vessel above the internal cone terminatlng above openlngs ln the inner cone. A
plurallty of secondary seal legs eYtend from openings ln the internal cone down towaeds the external cone. These aee aligned with the outlets of vertically oriented downcomers posltion~d wlthln the vessel above the lnteenal cone. The secondary seal leg3 are appeoximatelY the same length as the peimary leg formed by the concentcical annulus.

The inner cone serves a multiplicity o~ ~unctions includlng:

1. It deflnes wlth the vectlcal li~t pipe ~ p~imary seal leg to ensu~e material ci~culation through the vertical lift pipe and i~proves blendln~ without the need to raise the existing 8110 o~ reduce the capacity of the existinq silo.

2. The primary seaL leg is supported without the need of any spoke or splde~ leg steuctural members positioned in the f low steeam of bulk solids .

28625/bie~s ~4-

3. It 6uppo~t~ all of the seconda~y seal leqs.

4. It p~ovides a region whe~e the lowe~ inte~nal suppo~t Lo~ the lift pipe can be placed without bpanning the enti~e distance between the lif t pipe and the tank shell.

BR~EF DESCRIPTION OF THE DRAWING

The inventioQ will be desc~ibed in connection with the annexed drawing wherein:

Fig. 1 is a diagramatic view of the blende~ according to the present invention:

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1.

Fig. 3 is a fragmentary view of a modification of the present invention: and Fig. 4 is a ragmentary view of a further modif ication of the present invention.

DESCRIPTION OF THE t'K~ !;KKlSL) EMBODIMENT

Preferring to Fig. 1, a vertically oriented silo is gene~ally indicated at 1 which includes a conical bottom 2.
With the p~esent invention the vessel 1 will normally be an existing conical bottom vessel which may have been used for sto~age of pa~ticulate mate~ial. An outlet 3 for mate~ial within the silo o~ vessel 1 is p~ovided at the bottom of the cone 2. A conduit s is connected to outlet 3 fo~ withd~awing mate~ial f~om the vessel 1. A conduit 6 is connected to -2~0f 831 conduit 5 for supplying gas under pressure from a source (not shown) to the bottom of the vessel 1. A valve 7 controls gas flow through conduit 6. Valves 8 and 9 may be provided in conduit 5 for controlling the supply of gas under pressure from the source through conduit 6 and conduit 5 to the outlet 3 which also serves as the inlet for gaseous fluid under pressure. The valves 8 and 9 also control the withdrawal of material from the vessel. In a known manner, when it is desired to supply gas under pressure to the vessel 1, the valves 7 and 8 are opened 10 and the valve 9 is closed. When it is desired to withdraw material from the vessel the valve 7 is closed and the valves 8 and 9 are opened. The conduit 6 may be a supply for not only gas under pressure to the vessel, but also fresh feed of particulate material to be blended as disclosed in my prior above mentioned U. S . Patent No . 4, 978, 227 as well as in U. S .
Patent ~os. 4,569,596 and 4,573,800.

According to the present invention, an inner cone 10 is defined by a hollow frustum of a cone mounted within the existing vessel l as by welding. The inner cone 10 has an open 20 upper large diameter end 12 secured to the vessel walls and an open lower small diameter end 13. A hollow open-ended cylindrical member 15 is attached to the open end 13 of the inner member 10 and extends toward the outlet 3. A reservoir of material or material zone 17 is formed between the inner cone 10 ---and the conical bottom 2 of vessel 1. The upper end 12 of the cone 10 is provided with a plurality of circumferentially spaced apart openings 11.

A vertically oriented lift pipe 20 having a lower inlet 25 and an upper outlet 26 is centrally mounted within the vessel 1 2~01831 extending from below the cylindrical member 15, upwardly throuqh the cylindrical member and the cone member 10 into the vessel.
~ web or spider 21 may be utilized ior centering the r,olumn 20 within the vessel 1 an cone 10 in a known manner. The internal cone 10 enabLes the spider 21 to be short so that it need not span the entire distance between the lift ~ipe 20 and the Rhell of the silo 1~ Additional braclng may be provided for the lift pipe 20 in the upper levels of the vessel.
The cylindrical member 15 defines with the outside of the 10 liit pipe 20 an annular area on rr~nri~ntr~ r flow annulus 24 which is dimensioned to form a material seal as will be described hereinafter. The cylindrical member 15 and, rrnRerl~Pntly the primary seal leg of the blender is supported by cone 10 so that ~rlSitirni/l spoke or structural meDibers extending to the cone 2 or lift pipe 20 which may interfere with material flow are not required .
The inside of the ves~iel 1 is provided with a plurality of circumferentially spaced apart vertically oriented ~o~ 30 each having a plurality of vertically spaced apart inlet 20 openings 31. These downcomers are mounted on the periphery of the silo walls. As described in my af~,L, .t;rn~ U.S. Patent No. 4,978,227 the openings 31 may be provided with inwardly r1rtf~nd;nrJ baffle elements 33 to allow msterial to enter the downcomers at various levels; see also U.6. Patent Nos.
4,560,285 and 3,216,629. The flr~ may be supported at 34.
Each o~ these rlrT.r ~ has a lower outlet 32 spaced above the inner cone member 10 and each sligned with an opening 11 in cone 10. Material exiting the downcomers 30 will flow both into openings 11 and fall downwardly along cone 10 with the bul~
30 material in the silo 1.

. ~ 2001831 The invention includes a plurality of circumferentially ~paced apaet conduit members 35 each connected to an opening 11 in the cone member lo a~ ~hown in Fig. 1. Each of the conduits 35 extends downwardly into the zone L7 a distance approximately equal to the length of the cylindrical member 15 and form secondary seal legs. The inner cone 10 serves to support the aecondary seal legs or conduits 35. The conduits 35 receive material from not only the downcomer 30 immediately above ad jacent opening 11, but also directly from the inside of the vessel 1 immediately above the cone 10 at the opening 11. This is accomplished by having the inlet to the seal leg 35 larger in cross-sectional area than the outlet 32 of downcomer 30.
This ensures that the material entering the material zone 17 from tne vessel 1 above inner cone 10 is from both the upper levels of the vessel through openings 31 and downcomers 30 and from the vicinity of the openings 11.

Fig. 3 showr~ a modif ication of the pcesent invention wherein the conduit 35 has a horizontal upper end extending th~ouqh opening 11 into the vessel above cone 10. The conduit inlet is shown at lla and is larger in cross section than outlet 32 . In Fig. 4, a further modif ication is shown in that the conduit 35 extends a substantial di~tance into the upper part of the vessel. If desired, the design shown in Figs. 1, 3 and ~ could be mixed 80 that at some of the locations, the conduit 35 eYtends above cone 10 fu~ther than at other locations around the periphery of the cone. In each instance the conduit 35 should be long enough to establish a seal of material, and preferably the diameter of conduit inlet lla is larger than the diameter o~ outlet 32.

~ _9 During operation of the appa~atus, assuming that the vessel 1 is filled with matecial, the valvea 7 and 8 is open to allow gas unde~ p~essu~e to be supplied th~ough conduit 6 and conduit

5 through opening 3. ValYe 9 is closed to prevent mateeial discharge from the vessel. As can be seen in Fig. 1, the inlet 3 fo~ gas under pressu~e is aligned with the ve~tical lift pipe 20. The gas under pressu~e ent~ains material from the material zone 17, ad jacent the inlet 25 and lifts it up through vertical lift pipe 20 to be discharged through the outlet 26 in a geyse~-like manner into the upper end of the vessel. Gas under p~essu~e may be vented from the vessel 1 through vent pipe 27. Material already in the vessel will enter the openings 31 of downcomers 30, be conveyed by gravity through downcomers 30 to outlets 32. As material is withd~awn from the zone L7 to be conveyed up column 20, it will be replaced by material flowing by gravity th~ough secondary seal legs or conduits 35. This source of material in the conduits will be both downcome~s 30 and area immediately above cone 10.
In addition, mate~ial will fall by g~avity th~ough annulus 24 from above the cone 10 to the a~ea 17. P.s a ~esult, mate~ial moves f~om the upee~ eart of the vessel to the zone 17 and back up to the toe of the vessel. This mate~ial movement ~esults in a blending or mixing of material in the vessel. When it is desired to withdraw blended material from the vessel the valve 7 is closed and valves 8 and 9 a~e oeened to allow mate~ial to f low by g~avity th~ough outlet 3 and conduit 5 .

The length and diamete~ of the cylind~ical membe~ 15 and the diamete~ of the lift pipe 20 a~e selected 80 that the concent~ic annulus 24 is dimensioned to allow mate~ial to f low f ~om the above the cone 10 downwa~dly th~ough the annulus and _ _ _ _ _ _ _ _ _ , . _ . , _ . _ ....

l~ 20~1831 at the same time orm a seal of material to substantially prevent gas under pressure from by-passing the lift pipe 20 and fluidizing the material in the annuIus 24. This ensures the circulation of material from above cone 10 into zone 17 and fro zone 17 up through the pipe 20 to the top of the vessel. The length and diameter of the conduits 35 establish secondary seal legs which allow material v~ t by gravity from the vessel above cone 10 into ~one 17 without fluidization of material in the conduits 35 and without short circuiting of air from the 10 inlet 3 through conduits 35 to the upper part of vessel 1. This is the case whether the configuration of conduit 35 is as shown in Fig. 1, 3 or 4 or a ~ '-;n~t;r~n thereof.

If desired, a small air flow may be supplied through pipe 40 controlled by a valve means 41 for improving the circulation of material through the vessel by increasing the pounds of material to pounds of air loading in the lift column 20. This additional gas under pressure is not the same as that disclosed in U.S. Patent 4,569,596 in that it is not directed towards the bottom of the lift column and thus will not tend to fluidize 20 material within the annulus 24 and secondary seal legs 35 which fluidization would result in reduced circulation of material from above the cone 10, down through cylindrical member 15 to the inlet 25 and lift pipe 20.

From the foregoing it should be apparent that the objects of the invention have been carried out. ~n economical arrangement has been provided for converting an existing silo to a blender for particulate material. If the seal leg shown in my ~< prior U.~. Patent No. 4,978,227 is added to an existing silo, it 2031~31 would reQUire a substantial extension on the bottom of the cone 2 in order to accommodate the seal leg. This would necessitate raising the silo by an amount sufficient to accommodate that seal leg. Alternately, a oit could be provided for the seal leg. A third possibility would be tQ reduce the vessel capacity by raising the cone bottom an amount sufficient to accommodate the tubular extension thereby reducing the volume inside the silo. With the present invention, the internal cone member 10 and cylindrical member together with the vertical lift pipe 20 form the tubular extension and seal leg necessary to assure circulation of material through the vessel. By the use of the secondary seal legs 35, the usable volume of the existing silo is substantially retained in that only the space 18 above the zone 17 is lot to usable capacity. The advantages of my prior invention of receiving material from various levels in the vessel through the openings 31 to the downcomers 30 is retained.
The placement of the lower end of the primary seal leg 24 in relation to the lower cone 2 of the existing vessel 1 establishes the proportion of the total ~uantity of material recycled ~RT) through lift pipe 20 which originates from the downcomers 30 (RD~ compared with the Quantity of recycled material which originates from the bottom of the inner cone (Rc) through annulus 24, RT=RD+RC. Other designs of blenders such as that shown in my prior U. S. Patent No. 4, 978, 227 are limited by geometrical constraints such that F~D is usually eQual to or less than 1. 2 times RC . The present arrangement allows the designer X to achieve RD f 20 time~ RC or higher , --if desired. As illustrated in the drawing. the bottom 16 of cylind~ical member LS can be spaced a substantial distance from the outer cone 2. This distance can be ad justed by changing the length of cylindrical member lS (within the limits of maintaining the seal of material within annulus 24) and by ad justing the eosition of the inner cone lO in ~elation to the outer cone 2. The lower end of lift pipe 20 should be positioned sufficiently close to gas inlet/mate~ial outlet 3 to assure gas and entrained material flow up through the pipe 20.

Blender performance is related directly to the amount of ~ecirculation to which the contents have been subjected. Air flow through the lift column 20 is the transport media for material recirculation. Prior to the present invention, the material loading in the lift column has been limited to a ratio of between 12 to l and 15 to l pounds of material per pound of air. It i5 believed that by introducing a small quantity of air f low into the space 17 between the two cones as by conduit , 40, this material loading limit may be increased resulting in a more efficient and effective blender design. Commercially, this can translate into a lower cost blender while still achieving the same blender performance.

It is intended that the foregoing description be that of a preferred embodiment and that the invention be limited solely by that which is within the scope of the amended claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for blending particulate material such as plastic pellets comprising a vertically oriented silo having a conical bottom and an upper end. an inner cone defined by a hollow frustum of a cone mounted inside said silo and spaced from the conical bottom of the silo to define a material zone therebetween: said inner cone having an open upper, large diameter end and an open lower small diameter end: a hollow open ended cylindrical member attached to the open lower, small diameter end of the inner cone: a vertical lift pipe centrally mounted within the silo extending from below the cylindrical member upwardly through the cylindrical member and the inner cone into the upper end of the silo: said vertical lift pipe having an inlet in the material zone and an outlet in the upper end of the silo: a plurality of vertically oriented downcomers mounted inside said silo at circumferentially spaced apart positions around the periphery of the silo for supplying material from inside the silo to the material zone: said conical bottom having an opening therein aligned with and spaced from the vertical lift pipe and adapted to be connected to a source of gaseous fluid under pressure whereby gaseous fluid under pressure is supplied to the inlet of vertical lift pipe for lifting material from the material zone through the lift pipe to the outlet of the lift pipe for blending the material: said opening defining an outlet for blended material.

2. apparatus for blending particulate material according to claim 1 wherein said downcomers terminate inside the silo above the inner cone and further comprising a plurality of circumferentially spaced apart openings in the inner cone near its large diameter end, a plurality of circumferentially spaced apart conduits, each flow connected to one of the openings in the cone member and extending downwardly into the material zone.

3. Apparatus for blending particulate material according to claim 1, said inner cone having a plurality of circumferentially spaced apart openings therein near its large diameter end adjacent the walls of the silo; a plurality of conduits, each flow connected to one of the openings in the inner cone and extending downwardly therefrom into the material zone; each of said downcomers terminates above the inner cone and has at least one opening therein for receiving material from the upper part of said silo and an outlet above the inner cone .

4. Apparatus for blending particulate material according to claim 3 wherein said hollow cylindrical member has a length less than the distance between the small diameter end of the inner cone and the bottom of the vessel and sufficiently long to substantially prevent gaseous fluid under pressure from by-passing around said vertical lift pipe into the vessel above the inner cone,

5, Apparatus for blending particulate material according to claim 4 wherein said conduits have a length sufficient to establish a seal of material between the material zone and the area within the silo above the inner cone.

6. Apparatus for blending particulate material according to claim 4 wherein said conduits have a length substantially equal to the length of said cylindrical member.

7. Apparatus for blending particulate material according to claim 6 further comprising support means extending from said inner cone to said lift pipe for securing said lift pipe in said silo.

3. Apparatus for blending particulate material according to claim 6 further comprising means for supplying additional gas under pressure directly to the material zone for increasing the material loading in said lift pipe.

9. Apparatus for blending particulate material according to claim 3 wherein said hollow cylindrical member and said vertical lift pipe have diameters and heights in relationship to each other to establish a seal of material therebetween for substantially preventing gaseous fluid under pressure which is supplied to the bottom of the silo through said inlet from bypassing said lift pipe.