US2125086A - Pneumatic classifier - Google Patents

Description

July 26, 1938. l R. K'. oURKE 125,086

` PNEUMATIC cLAs'sIFIER Filed Jan. 29, 1935 2 Sheets-Sheet l 31 Wenko/r,

n r klima/ud I July 2 6, 1938. R. K. .ROURKE PNEUMATIG CLASSIFIER Filed Jan. 29, 1935 2 Sheets-Sheet 2 www Wag 550w/@ Patentedjuly 26, i938 AUNITED s'rAri-:s

.Y u 2.125.086 PNEUMATIO CLASSIFIER Rupert K. Rourke, Lompoc, Calif.

Application January z .19 claims.

, 'I'his Ainvention relates to methods and means wherebyl disintegrated. p ulverulent or comminuted materials such as the non-metallic minerals. clays, decoiorizing carbons, etc., may be treated for the removal of impurities and/or particles which are arger than or heavier than remaining portions of such disintegrated material. In the manufacture of disintegrated or com- `minutedmaterials such as diatomaceous filteraids (in natural uncaicined form and/or in calcined or chemically treated form), bleaching clays or decolorizing material and numerous 'other substances used in a finely divided condition, it is highly desirable to remove impurities.

'I'he reasons for such removal need not .be explained in detail but it may be stated for purilxs poses of illustration that in the manufacture ofl diatomaceous nlter-aids the. removal of coarse particles is desirable as such coarse particles do not function as' effective components of the filteraid. vVery often theY impurities, although within the desired particle size (by linear or volumetric measurement), are of ahigher specific gravity than the main biidy of material and such heavy particles should also'be removed. g l

In prior methods of classification, separatorsv of the cyclone type have been extensively used but in such vseparators there is a tendency for .the`

finer particles to adhere to larger particles and 'to be carried with such larger or coarse particles out of the system` whereas it is highly desirable that such finer particles be removed from. the coarse, thereby increasing the output of the more finely divided product. In the lnormal and usual separators of the cyclone type, only a minor proportion of 'the material introduced (generally less than 20%) is separately discharged as fines, whereas the method of this invention contemplates the separation of the liner particles frommore of the total feed.

The method of this invention distinguishes from .prior methods 7in that a iiuid bearing a heterogeneous mixture of large and small parinto, a classification or separation zone and, a body of such fluid rotating in a substantially horizontal plane is formed. Fluid bearing the smaller and lighter particles is continuously withdrawn axially fromthe central and lower portions of such body of fluid. The fluid introduced .into the classification zone is introduced at a velocity sufcient to impart a'decided outward velocity' component to the larger and heavier particles, which particles-assume a downwardly inclined,` spiral path toward the outer and lower portions of the classification and separation zone. In order to more eiectively vseparate the lighter. and smaller particles from the larger particles; additional or secondary fluid is tanthe same feed material to the extentof 40% or` ticles in-V suspension is vcontinuously introduced s, r193s, serial No. 3,895 (ol. eos-144i genuauy in'trtdud into the lower portion of lthe classiiication and separation zone and in the direction'of rotation of the aforesaid bodyl of fluid. This secondary fluid may be preferably introduced at substantially the same velocity as the primary fiuidfbearing the disintegrated maponent to some extent andvblows adhering fine particles from the larger and heavier particles.

Eventually, the now cleansed larger and heavier particles of material areseparately discharged from points along the lowerv edge of the classification or separation zone.

It is to be noted that in the usual cyclone type of separator; the nes 4are removed upwardly (against the action of gravity) while the coarser particles move downwardly. In the method and apparatus'of this invention, both fines and coarse move-downwardly but alongdiiferent paths, the

separation thereby taking place without relying upon gravity to the extent characterizing prior methods. Y

Although the method of this invention may be carried out in various forms of apparatus, the present invention -s also directed to a preferred form and arrangement whereby the method of this invention-may be canied out very effectively. lIhe invention also contemplates a combined milling and classification system in which the hereinabove described method may-form an integral part.v

It is an object o! this invention, therefore, to disclose and provide a method of classifying disintegrated. comminuted and/or pulverulent materials.

Another object is to disclose 'and provide a method of classifying and/or separating disintegrated materialsfor the purpose of removing therefrom larger and heavier particles.

A further object of the invention is to disclose 'A sun further bject or uns .invention 'is to disclose and provide an arrangement of means,i whereby the classification and separation .of disly and accurately obtained.

These and other objects, uses and advantages of the invention will become apparent to those skilled in the art from Ihe following detailed description of a milling system, classification means and classifying-method of operation. It

is to be understood that the subsequently de- Y scribed specificforms and conditions of opera- Fig. 4 is a horizontal section taken alongthe f plane IV-'IV of Fig. 2 c

Fig. 5 is a vertical section taken along the plane V-V of Fig'. 4.

Fig. 6 is a vertical section taken along the plane VI-VI of Fig. 4.

In Fig.` 1, the feeder bin is represented at I, this bin containing disintegrated material vsupplied thereto from a preliminary or primary milling system, not shown. The material from the bin I may be discharged in controlled .quantities by means of an automatic feeder 2 into the inlet line 3 of the systemthrough a rotaryseal mechanism 4. The gases passing through the line 3 are picked up by a blower, such as a paddle type fan 5, and discharged through a line or conduit 6 into the outer end of a classifying unit IU. In this. unit (subsequently Vdescribed in greater detail) the disintegrated material is classified, the larger and heavier particles being retained within the lowerhousing II for discharge through the valved outlet I2 whereas the smaller and lighter particles are discharged through the conduit I3.`rl

The conduit I3 leads tol a separator 1 in which the particles are more or less perfectly separated from the conveying fiuid or gas, the particles settling in the lower portion of the separator from which they may be removed through the valved outlet 8, whereas the gas or fluid is discharged through conduit 9.

,When operating under substantially closed cir. rcuit conditions, the outlet conduit 9 may connect with the inlet conduit 3, as indicated. Furthermore, the discharge conduit 9 may be provided with abranch line I4 leading to a fan or blower I5 which then supplies secondary air or gas to the classier I0 through the line I6. Dampers may be lprovided in the conduits 6 and I6' as indicated at I1 and I8 respectively.

Although in the above described form of apparatus air is constantly recirculated, it is "obyious that` the blower 5 may draw in atmospheric air or gas from any suitable source, such `as for example, preheated gas or air. The discharge line 9 may furthermore be connected with? bag house or other suitable separating device for the removal .of finest particles therefrom. The

III. functions for the removal of 'larger and heavier .'of the classifler.

fmunicates with the discharge. line I3-which may y extend through the housing II, one end of the ,l 2,125,086 integrated materials may' be rapidly, economical-fparticles from the suspension of disintegrated material supplied thereto by the feed conduit `6. This feed will hereinafter-be referred to as the primary feed and for purposes of illustration it will be assumed that air is the medium used in conveying the disintegrated material through the apparatus..

The classifier, more specifically shown in Figs. 2 to 6 inclusive, consists of a classifier 20 which,-

internally, is substantially cylindrical with substantially cylindrical walls. The interior of such classification zone is indicated at 2|. Such classification zone is provided with a closure member or cover plate 22 and may well be divided into an upper andlower section, said sections being separated by a plate or member 23. In the preferred -embodiment shown in the drawings the height above the bottom edge of the classifier 20 and spaced from the walls thereof. The edge of the funnel member' 24 is provided with an outwardly and downwardly extending apron 25 directed toward-the housing II, said apron 25 being spaced from the lower edges of the interior surface 2| The funnel member 24 comline I3 being sealed as by plate 26.

The diameter of the upper edge of the funnel classifier, the upper'edge f the funnel member,

under such conditions, being placed slightly below the lower edges of the surface 2I of the classifier. It is to be understood that the diameter of the classier at, the secondary inlet por'- tion may exceed the .diameter of-the primary air inlet prtionfalthoughthe form shown is more readily constructed. I

'I'he upper portion of theA classifier 2li, that is, the portion between the closuremember-22 and the horizontally disposed partition plate 23, may be provided with a plurality of tangentially directed passageways indicated at 21; 2l, 29, etc. By identifying the passageways 2.1, 28, 29, etc., as tangential, it is to be' understood that they may be' tangential to the inner wall 2I, or to the outlet funnel 24, or to some circle between these two elements. These passageways preferably termi-- V nate inl openings which are larger in height than inwldth and which become reduced in cross sectional' area as they approach the inner wall 2I of qtheclassiiier, thereby causing an increase in the velocity of gases passed therethrough. The shape of these .openings is not critical and may be varied greatly,"nor is it necessary that the passageways vary in cross sectional area. l

The closure nreinber 22 is provided `with aplurality of ports communicating with passageways. Conduits, such as the conduits .31,

member 24 bears an important relation to the.

38 and 39, connect the ports in the closureplate 22 witha conical'head 30 connected with the in.

take conduit 6.' Axially positioned within the cone 30- is a distributor corie 3l whichassistsin f to the tangentially succosa plied to the classifier I0 by thefintake conduit 6 is distributed through the. conduits 31, 38, 39, etc., directed passageways 21, 28, 29, etc. i'

A vortex is thus formed within the classiiier 20, the only voutlet therefrom being through the funnel-like member 24 and dischargev line I3. The port of the funnel-like member 24 is' located in a plane not materially below the edge of the section 20 and preferablyin a planev virtually coincidental with the plane of the lower edges of the secondary air inlet ports. Outwardly directed components I`are thus caused to exist in a direction opposite to the inwardly directed compots .due to the movement and discharge of gases from such vortex. The tangential yor outwardly directed component will vary with the velocity of the fluid discharged into the classication zone; 'the radial, inwardly directed component will vary with the volume of uid supplied. When the. volume of airused is maintained constant, the tangential velocity may be increased or decreased by changing the area of the inlet ports, and it may be :noted thatianJ in` crease of velocity will decrease the average particle size of the productl discharged as lines.

As a result, the lighteriand smaller v.particles pass with the gas through the funnel-like member 24 into the discharge line I3 while the larger and, heavier particles tend to move toward the inner wall 2i of the classifier zone 20, along which wall they move helically downward.

In order to classify the disintegrated material with extraordinary accuracy, secondary air is admitted through the conduit I6 into a manifold Il from whence it is distributed by a plurality of conduits, such as the conduits l2, 43, etc.,

through suitably arranged ports in thecover plateA 22 to passageways or channels I4, 45, and the like, formed in the lower portion of the classiiier zone 20. 'I'hese passageways M, I5; etc., discharge tangentially into the classifier at a plurality of circumferentially spaced points. 'I'he l velocity of the gases discharged through `.and

' duits-and eight secondary conduits. 510 cubic feet of primary air was supplied per minute and 275 cubic feet of secondary air per minute. Diatomaceous earth, previously disintegrated, was introduced with the primaryair at the rate of 16 pounds per minute. The milled diatomaceous earth so introduced into the classiiercontained 3.2% of 150 mesh and'9. 9% by weight of particles larger than 20 microns (in sedimentation characteristics) in the form of large and heavyparticles through the valved outlet I2; 60.3% of the feed was carried over as iinal product. 'I'he coarse product contained 6.0% by weight larger than 150 mesh and 24.3% by weight larger than 20 microns. The final product discharged through the conduit I3 contained only 0.8% larger than 150 mesh and 3.8%v larger than 20 microns.` l

Afterseparation, it was foundA that 39.7% of the material fed was discharged- The velocity of gasesl introduced into the classifler may range from abouti 1,000 to 12,000 feet 1 per minute and in the experimental device described hereinabove the velocity was about 2,000 feet per minute. The velocity used will, oi course, depend upon the specific gravity ofA the materials treated and the degree" of classicatio'n required.

I claim: i e l. In a classifying and separating apparatus, the combination of a substantially cylindrical classier provided with substantially vertical walls; a closure for the top of said classiner; a plurality of tangentially arranged inlet conduits communicating with the upper portion of said classier; means for supplying a uid suspensin of disintegrated material to said inlet conduits; a plurality of tangentially arranged secondary inlet conduits' communicating with the lower portion of the classiier; conduit means for supform a vortex in said classifier; a downwardlyl and inwardly directed-funnel member provided with an outwardly and downwardly extending lip positioned below said classier with theglip spaced from the lower edges of said classier; a' housing `.tor said funnel member, and a discharge conduit extending into said housing and terminating at the lower end of said funnel member.

2. In a classifying and separating apparatus, the combination ofzfa substantially'cylindrical classifier provided with a top closure and a downwardly extending housing of larger internal cross sectional area, at a plane immediately below said classier, than the internal cross sectional area of said classiiier; means for introducing uid bearing disintegrated material in suspension tangentally into the upper portion of said classifier; ,means for tangentially introducing secondary uid into the lower portion of the classifier whereby a vortex is formed in said classiier, the bottom of said vortex being open; and a discharge conduit extending into said housing and communicating with the lower and central portion of said. classifier whereby the central and lower portions of the vortex and suspension of liner particles in fluid comprising the same may be separately drawn oii. l

3. In a classifyingy and separating apparatus,

the combination of: a substantially cylindrical portion of said classier; and means carried by the upperlend of said discharge conduit and spaced from the lower edge'of the classier for directing larger and heavier particlesoutwardly into said housing. l

4. In a classifying and separating apparatus.

the` combination of: a substantially' cylindrical classiier provided with a top closure and a downwardly extending housing of larger internal cross sectional area, at a plane immediately below said classifier, than the internal cross sectional area of' said classifier; means for introducing fiuid bearing disintegrated material in suspension tangentially into the upper portion of said classiiier; 76

means for ltangentially introducing secondary fluid into the lower portion of the classier;v a discharge conduit extending into said housing and communicating with the lower and central portion oi said classier; and means carried by the upper end of said discharge conduit and spaced from the lower edge of the classifier for directing largerand heavier particles outwardly into said housing, said means having a diameter at their upper edge of not less than 1/2 the internal diameter of the lower portion of said classifier.

5. In a classifying and separating apparatus particularly adapted to eiiiciently separate lighter .and nner-particles from a heterogeneous mixture containing such particles, the combination of a cylindrical ,chamber provided with a closed topl and an open bottom, a plurality of circumferentially arranged/'ports in the walls of said cylindrical chamber, means for introducing fluid bearing disintegratedmateriai in suspension tangentially into the upper portion of said classier chamber through certain of said' ports to form a vortex within said chamber, means for tangentially introducing secondary iiuid into the lower portion of said cylindrical chamber through other of said ports, two concentricoutlets at the bottom of said "cylindrical chamber, and a hopper surrounding said outlets, the outer annular outlet being adapted to discharge heavier and larger particles into the hopper, the inner outlet communicating with an outlet conduit.

-said ports, a downwardly extending hopper connected to the bottom of said cylindrical classiiier,

and an outlet conduit extending Vinto said hop? per and terminating in a plane passing through the bottom of the ports in the walls of said classier. said outlet conduit Abeing concentrically positioned with respect to said cylindrical classier, `the upper edges of said conduit being slightly spaced from the lower edges of said cylindrical classifier to`form an annular port through which heavier particles may be discharged from? said kclassifier into said hopper.

7.v In a classifying and separating apparatus.

the combination of:A a substantially cylindrical4 classiner provided with a closed top, a housing below said classifier. a conduit, for supplying a gas bearing disintegrated material in suspension to said classifier, 'a plurality of circumferentially spaced and tangentially directed inlet ports in the upper section-of said classier. a plurality ofv conduits connecting said ,ports with vsaid vsupply conduit, means for distributing iiuld bearing disintegrated material in suspension from said supply conduit to said plurality of conduits. means mr tangentially' introducing secondary nuid man the lower portion of the classifier', and a discharge conduit provided with an'intake port positioned axially o! said classifier, said intake port lying in a plane not materially below said means for tangentially introducing secondary fluid.

8. In a l classiiyingand separating apparatus. the combination of: a substantially cylindrical classiiier provided with a closed top', the internal l diameter of said classiiier being greater than the height thereof, a housing below said classiiier, said housing having a larger internal cross-sectional area at a plane immediately below said vclassifier than the internal cross-sectional area Y of said classifier, a plurality of tangentially directed circumferentially spaced inlet ports in the upper portion of said classifier, means for supplying i'iuid bearing disintegrated material in suspension to said ports, a plurality oi tangentially directed secondary iiuid inlet ports in the lower part of said classifier, means for supplying secondary fluid to said secondary ports, and a discharge conduit provided with an intake port axiallypositioned with respect to said classinensaid intake port in said discharge conduit lying in a plane virtually coincidental with the plane of the lower edges of said secondary iiuid inlet ports.

9. In a classifying. and separating apparatus, the combination of: a substantially cylindrical classifier provided with a closed top, Ethe internal diameter of said classier being greater than the height thereof, a housing below said classifier, said housing having a larger internal crosssectional area at a plane immediately below said classifier than the internal cross-sectional area of said classier, a plurality of tangentially directed cir.

cumferentially spaced inlet ports in the upper portion of said classier, means for supplying fluid bearing disintegrated materialv in suspension to said ports, a plurality of tangentially directed secondary fluid inlet ports in the lower part of said classiiler, means for supplying secondary iluid to said secondary ports, a downwardly andinwardly directed funnel member positioned axially with respect to said classifier, the upper edge of said funnel member lying in a plane virtually coincidental with the lower edge of said classiiler,

la downwardly and outwardly extending apron i carried by theupper edge of said funnel member int beneath the lower edge a discharge conduit exand extending to a of said classier; an

tending through said housing'and communicating with the lower edge of said funnel'mem'ber where- 'by fluid may be discharged from said classiiier.

10,)In a classifying and separating apparatus,

vthe combination of:4 a substantially cylindrical classifier provided with a closed top, a housing below said classiiier, said housing having a larger internal cross-sectional area at a plane immediately below said classiiler than the internal cross-sectional area of said classifier, a plurality of tangentially directed and circumferentially spaced ports 4in the upper portion of the ciassiiler,

means for distributing iluid from a supply conduit intoa plurality of conduits. a plurality o f conduits connecting said plurality of ports with said distributing means, .`a supply conduit, adapted g to supply iluid bearing disintegrated material in suspension to said distributing means, a plurality .00

Yot circumfcrentially spaced and tangentially* ldirected secondary fluid ports in the lower por- Ltion of said classifier, means for mpplying `secondary iluid to said ports, a downwardly and inwardly directed funnel member positiaaeda'x-l ially with respect to said classiiier. the upper edge of saidfunnel member lying in 'a plane virtually coincidental with the lower edge of said ci r',

and a discharge conduit extending through. d

housing and communicating with the lower edge of said funnel member whereby iluid may be discharged from said classiiier. y n

RUPERT K. Ronan.

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