US2361758A - Separator - Google Patents

Description

Oct. 3l, 1944.

w. DE FLIGUE sEPMToR Filed June 11, 1937 3 Sheets-Sheet l JWN om., 3l, 1944. w, DE FLlGUE` 2,361,758

SEPARATQR Filed June 11, 1937 3 Sheets-Sheet 2 /fw y a? Afro/.WISY

` Oct, s1, 1944. w. 'DE FUGUE 2,361,758

sEPARAToR Filed June 114, 1937` 3 Sheets-Sheet I5 Ulu" the ratio of quired by forces in the known separator provide an apparatus v,the above type while `etmaal on, si, i944 snrsasroa Wladimir de Fligllrarls, France; vested Alien Property Custodian Application June 11, 1937*, Selial No. 147,610

(Cl. 209-144)v 6 Claims.

This invention relates to a separator and. speciiically, a separator for iinely divided solid materials. ,y

Various industries require solid materials in ax finely divided state. if not in a colloidal4 state. Certain materials exist naturally'in this state, while others may be brought to it by grinding, condensation ofl vapors or the like. In all processes used'to finely divide solid material, as well as in cases oinatural occurrence of nely divided materlals, it is necessary to separate the particles which aresuillciently'iine from those which are not. Furthermore. it may be desirable to separate different substances if the original material worked in is not homogeneous. The classication in such case may be by density. One of the known processes of separation of powdered materialsds based.l on the tact that the mass of a body is proportional ito the cube of its lineal dimensions, and its' cross-section is pro` portional to the square oi such lineal dimensions.

In one process of which has a valuedependent upon the crossf sectionoi' the body and the other dependent upon its mass. The result is that a more or'less imperfect selection is eitected 'due to the i'act that mass in section is.' for a homogeneous material, dependent on the dimensions oi the particles. It will be obvious. also. that particles of diderent densities but the same dimensions may be separated'since, while the sections will be the same, the masses will be different. f

Among the a. centrifugal force. It it is desired to select materials of successively smaller particle sizes. the mass of the Iparticles will decrease faster than their section. The decrease in mass is prof Vportional tothe cube of the lineal dimensions and the decrease certain industries, the centriiugai become too small and the forces due to the air iiowtoo large to obtain an veffective separation. i

It is the object of the present invention to for eii'ecting separation of avoiding the diiilculties inherent vin the types oi apparatusheretoiore used. Partitmlarlxrv high controllable centrifugal forces maybeobtained,thei'orcesinthetwocaael forces which can bel thus'opposed to realize selection of the above type, one may bel the action of a stream oi air. theother being being controllable at willand opposed in an eiiective fashion. Brieiiy stated, the apparatus comprises a rotor selector, built according to principles described below. used in conjunction with an exhauster or aspirator connected in om position to the rotor selector and having an eiect predominating over that vof the rotor selector in its action as an impeller sc that an air current is caused to iiow Vradially inward through the selector.

vIn accordance with the invention. the selector is oi an improved form to avoid the existence of critical points in the selector passages. which will determine by the position oi the particle relative to them whether ornot the particle will be passed or rejected by the selector. Speciii-` cally, it is an object of the present invention to separation of powdered mate; i i rials it is sought 'to oppose' two forces. one of provide aselector -in which throughout a. substantial radial path the relation between the op-V posing forces acting on a particle ot vgivensize will be substantially constant. The above and other objects of the invention, relating particularly to details of construction will be apparent `from the following description read in conjunction with the accompanying. drawings in which:

Figure 1 is a vertical section through the improved separator-taken on the plane indicated at i--I inFigure 2;

Figure 2 is a vertical vsection taken on thev plane indicated at I-I inv Figure l:

Figure 3 is an enlarged tional view illustrating the design ot a separator rotor:

'Figure e is an explanatory .diagram illustrating the mode oi' operation off the improved selectordas compared with that of the previous types; an

' Figure fox-moi separator constructed in accordance with the mVentlOn.

in section to the square -ot the same. The result is that for the minute sizes re- Inthe.. illustrated apparatus, the powdered materiallto be separated is fed from a supply,

:conventionally shown as a hopper 2. through an adjustable valve I which regulates the iiow into a conduit C, intoA which air i s admitted through a nozzle I. While air may-be ioreed 'through the nozzle. there may be provided only an induced i' iioated particles now of air by means of an impeller hereafter described. The nasale in the latter case will be open tothe atmosphere and in either case is used only to'secure the necessaryvelocity to neat the particles in an air stream. The conduit l delivers through aserics 0i' tangentially arranged. openinll il, i! and Il into the housing Il ofthe selector proper. `'.'ilie conduits are B is'a diagrammatic viewof a modiiied the air carrying'the so arranged, as well as the tangential nozzles, so

that the velocity of flow throughout the intro- A 'The plate 28 carries impeller vanes 32 having slight clearances 34 with theconduit 30 and having radial lengths substantially greater than those of the passages 26, with the result that the impeller formed by these vanes will provide greater suction than that resulting from the passage forming elements 24. As a consequence,

- there will be a slight circulation of air outwardly between the'passages defined by the vanes 82, as indicatedby the arrowsin Figure 2. This automatically provides a sealing effect preventing any passage of air carrying unseparated particles between the plate 28 and an. adjacent wall of the housing i6. as labyrinthine packing'maybe used.

In order to control the ow through conduit 30, there is provided a valve 36. The material passing through the conduit 30 from the 4center Other sealing means such of the selector rotor enters the intake of a second impeller 38 driven through a shaft 40 and discharging at 42. through theselectorrotor and are discharged at 42 may be precipitated and separated in any suitable fashion, for example, by electrical precipitation, filtration or the like. The iiow may be controlled also by variation of velocity of impeller 38.

The heavier` material which will not pass inwardly through the passages 26 will separate out in the annular passage i 8 and may be collected in a receiver comprising an upper chamber 44,

The light particles which pass an intermediate chamber 60 and a discharge 52. y

Valves indicated at 46 and 48 may be provided so that with 48 closed the material collecting in 44 may be discharged into 50 by opening the valve 46, and' then with 46 closed 48 may be opened to provide for discharge of chamber 68 without affecting the pressure within the housing I6, or diverting any of the air within the housing.

In the arrangement illustrated, the impeller 38 is used to produce a radially inward flow of air through the passages 26 despite the tendency of'the selector rotor to act as an impeller. In other words, there are two impellers acting in opposition, and theimpeller 38 prevails in its eiect. The air emerging from the nozzle 8 ex-y pands just at the point wherethepowdered material is fed into the conduit 6 and, by reason of the expansion, aggregation of the particles after their separation and suspension by the jet is prevented. As has been pointed out above, the c feeding conduit is so arranged as to maintain the air velocity sufliciently high to prevent any settling, before the air carrying .the powdered material in vsuspension enters the `'rotor chamber.

' asomss -homogeneous but consists of particles of more or less the same size, will be substantially the same for al1 the particles in thel mixture being separated; and in which s is the maximum section of the particle in a plane perpendicular to the air stream in relation to the particle and v is the relative velocity of the air stream and particle.

It will vbe noted that the average velocity of the particle in a radial direction at the entrance to one of the passages 26 will be substantially l zero and, under conditions such as are here involved, the radial velocity will be quite low throughout the entire passage 28 as compared with the actual velocity of the air stream. Consequently, v may be regarded as the velocity-of the air stream neglecting the radial velocity of the particle.-

' The opposition of-the forces thus obtained .permits a-selection either according to the sizeor according to the density of the particles.

In order to secureeiective separation, it is obviously desirable that the two forces should act upon any particle for a maximum length of time in such fashion as to secure the same separating effect throughout that entire time. Since, in the present apparatus, the separation ltakes place only in the passage 26, the time of actionof these forces is measured by the time it takes for .the particle to pass (if it is to pass) through a passage 26. Consequently, it follows that the design should be such 4that if a particleis to pass through a passage 26 the forces should be such at all points of that passage as tocause it to do so; and if a particle is not to pass through the passage 26 then the forces should be such as to prevent its doing so, even though it may have .entered part way into the passage. It is to he understood, of course, that the' separation involves statistical considerations. In other words, particles of any given size will have a range of entering velocities (due to turbulence. etc.) extending above and below some Ymean velocity and consequentlyy separation effected by any such apparatus cannot be absolutely perfect. However, with attention to considerations such as those indicated above, any particle will be subjected to conditions tending to either pass it or reject it over a maximum .time with consequent improved selection. Considering a particle which is of a size such that particles of larger size should be rejected and particles of smaller sizes passed, the two opposing forces for that particular particle should be balanced throughout the ,radial extent of each passage 26, or, in other words, Vthrough the passage mwr should be equal to ksvz. Since m, w, k and s are constant, b should be proportional to V17.. This v means that the air velocity between'the impellers of the selector should be proportional to Vr? or,

In the passages 26 any particle is subjected tof/70 two forces.

of therotor itself, it will be subjected to a cen- Since it will b e takingm-part in .a' .rotary motion substantially identicalwith that which m is the mass of the particle, a is the 76 in other words, the decreasey of the centrifugal force from the outside to the center of the selector should be balanced by an equivalent decrease in ing to the selector impeliers sucha section that 'f substantially achieved by having a inlets symmetrically located a's at' Il.Ik arid providing asuiilclent space betw the cross-section o f the passage will be inversely proportional to Vr.

In-Pigure 3 the dotted lines indicated at il indicate the tlfeoretical walls for a passage I6.

In order to illustrate .the nature oi' the curves ll, they are produced inwardly to indicate that they are ultimately tangential to a circle which is of considerably less radius than the innermost radius *ilow. etc., the theoretical curved surfaces may be replaced by plane surfaces of the type provided The foregoing design, it will be noticed. assumes the axial width of each passage 26 is Y constant. Ii that-is not the case, the cross-sectional design must be mde to correspond so as to remain inversely proportional to Vr.

The walls of the passages should be polished to prevent sticking ot any of the solid material, particularly when the material has a natural tendency tostick or become aggregated. It is to be noted that with increased accuracy or sharpness oi v separation, the tendency of the powder to deposit on the wall would be increased, since the end to be desiredis a separation such that certain particles are in equilibrium in the passages with theoretically a zero velocity. In general, of course. such zero velocity would not tend to occur the friction with a wall. was quite high, because smooth ilow would not be attained and turbulence would .maintain the particles in suspension unless they were of a sticky or aggregative nature. It is further desirable to polish the vsurfaces because offtlie Coriolis acceleration which shows that a particle between two rotating impellers and moving from the outside toward the center will have a tendency. to eventually hit the preceding impeller. The setting of the impellers at an angle to the radius will not avoid this because the phenomenon is dependent upon the velocity of the particle between the impellersand, therefore, is dependent upon its size. The particles composing a powdered material are, of course, different in-size, so that a design avoiding the Coriolis phenomenon for one particle would not hold for another. d

It will be noticed from a'consideratlon of the radii drawn in. .-ciistmction4 lines and indicated at Il that, if the inner radius of the selector rotor passages is made of substantial size, the centrifugai forcewill, to a high degree of approximation, be constant across the cross-section of any passage 2i, not ditleringby any more than the cosine ci half the angles formed at the center by the inner ends of walls 26.

In the above, it is also assumed that the pres- I.' sure diterentialbetwe'en the outside and center ofthe selector is constant throughout its rotation. For this to betrue it is necessary that the pressure be the same at all points of the periphery o! the'selector rotor-because it canbe'assumed that the inlet pressure at the exhaustor will not be disturbed bythe existence of an unsymmetrical origin. The feeding of theair and the powf dereemari'al should tneoreticaily'be made' uni-ly 'rhisgeireci will be formalljaround the rotor.

ality ot lector rotor and its -casing, as well'as by'fsubeta'nway, the'inuenceoi the diilerences of velocity between the inilowing iluid and that entrained by the selector rotor will be negligible. Complete separation of the particles is, of course,vneces sary, and this may be best obtained by producing. expansion of air at the point of feed of the solid material, as indicated above. Itis also necessary to prevent bypassing of the selector rotor by means of a labyrinth type oi Joint or, as in thepresent case, by use of an auxiliary impeller arrangement 32 to provide a slight circulation opposing any bypass.

Reference to Figure 4 will illustrate sonie of the characteristics of operation of the improved device as compared with anarrangement having radially extending varies so that the passages increase in size radlallyoutwards. A' comparison will now bemade showing the characteristics of the improved `separator as comparedwiththe characteristics of' this other type-whichl comparison will serve to illustrate the characteristics of the improved separator as compared with various other types not in accordance with the invention. In Figure 4, the centrifugal and centripetal forces are plotted against the radlalposition of a particle. The values Ri and R.: of the radius are assumed to be the radial limits of a passage such as 28.

For a given angularvelocity oi the separator rotor and a given air ilow condition representing, for example, some definite velocity of flow at the radius Rz, let. is be `assumed that the mass and cross-sectional area of a particle in equilibrium are ma and so respectively. According to the design principles indicated `above, it follows that the straight line OA will represent the variations of both manif and lksnv2 with the radius. Of course, theseare opposite in sign so that the -particle is in equilibrium throughout this entire straight line, and, a fortiori, between the radius limits Ri and Rz. v

Now.- consider a particle having a mass mi greater than the mass mo, but having the same cross-section so,i. e., particles of thel same size but higher density. 'I'he curve representing the values of mwr will be a straight line OB. This,

throughout its entire extent, will lie above the curve OA, which will still represent the value ksovi. Consequently, the forces will be such as to reject this new particle throughout the entire passage 2B. Attention must again be .called to the fact that the distribution will be of a'statlsti-V cal nature, so that a particle such as the one last mentionedl might well enter part way into the passage 28. However, since it will be subjected to an expelling force through the entire radial extent of the passage 2l, it is extremely likely that, despite its entrance'into the passage, its direction of movement will be reversed and it will be ultimately rejected. The reiection is the more certain, of course, as the mass mi differs from the equilibrium mass mo.

y Again let us consider a particle having the same sectionlss as the equilibrium particle, but having asmaller mass mi i. e., a 'lower density.

The curve Ol" will represent the centrifugal force acting on this particle, while OA will still representthe force due to air `flow. The curve /OF lies nwholly". below the curve 0A and accordingly,

throughout the extent of the 'passage 26. there will be a tendency toward passage of the particle inwardly beyond theradius Ri.

l, A l 4 A Y Let us now consider a particle of the same l tially tangential; feed of the air and particles in' 7i;` densityas the particle im, so but of larger size, i

the direction of rotation of the selector. In this OA and OF- A particle OA and OC--A particle mls If the function mwr is represented bythe line- O B, the function lcsiv2 will be represented by a line OC, which, according to the above. will lie f between OA, -and OB. Accordingly, a particle m1,s1 of the same density but'of larger size introduced between the impellers will be subjected throughout the entirelength of the passage to an-ejecting force.

Similar reasoning will show that aparticle of mass m2 and section sa of the vsame density as the particle maso, but of smaller size, will be represented by the curves OE and OF, respec- -tively, so that a particle of such type willfbe section so'but a larger mass mi, so that asheforeyziwr will be represented by the line B. 0B intersects MN at Q at a radial distance within thelimits of the passage. Outwardly of Q the centrifugal force exceeds the centripetal force on such a particle. while inwardly of Q the reverse is true. In other words, ii.' the initial enter'- ing velocity of this type of particle will not carry it inwardly of the point Q. it will be rejected. On the other hand, if it passes the point Q. it will be very strongly urged inwardly and will pass the separator rotor. y tion of this particle is concerned, therefore,"the separator passage has an effective length only that represented by the diiference of the radii of the points Q and Ra. Not only is. thevradial distance between R1 and Q ineiIective to reject the particle, but 'rather itis very effective to pass the particle.

carried inwards by the prevailing centripetal force throughout the radial extent of the impellers. .s 1

summarizing, the variuus'curves inFigure 4 'represent the following in comparison-with the particlemaso, which isin equilibriumand represented by the curve OA:

OA and OB-A particle ofthe same size and higher density.

ofy the same size' but lowerfdensity;

of the same mass and lower density.

OA and OEL-LA particle of the same mass and higher density.

If we consider a particle of section so and mass ma, i. e., material of the same size as maso but of lower density, the curve MN will still represent the force ksoi. Line OF will represent the centrifugalforce mmr, and it can be seen that such a particle will be passed through the selector.

A particle of the same density as maso but of .larger size, for example, musi, will have the curves OB and Mi,N1 as its characteristic curves.

OB and OC-A particle of the samedensity but l larger size. OE and OF-A particle of the same density but smaller size.

As contrasted with the' :emits obtained by the' use of the improved separator :described above,

consideration may be given to the action of the These curves intersect at a point Q', and it can be seen that between Q and Ra the particle will be expelled, while betwen R and Q' it -will be forced inwardly.v Thereforeponly the part of the passage between Q.' and Rr willsbe eifective for the removal of undesired particles.

A particle ofthe same density but of smallerA dimensions will be subject to forces represented by the curves OF and Mn,N2, with the result that the centrifugal force is always smaller than the centripetal force, so that such a particle will be passed throughout the passage.

It is obvious from the above demonstration that the improved selector is far more efilcient in rejecting undesirable material of either large size or high density than a selector in which the impellers have a constant thickness, with the resultl that the separation is much more sharply dened. In 'the improved selector the nature of type having ordinary radially extending vanes and, consequently, outwardly diverging passages. Consider the same equilibrium particle mesureferred. to above. I

In this case, assuming radial vanes,th e crosssection of the passage is proportional to the radius and 'the velocity is inversely proportional to the radius, so that a curve ksav is a second degree'curve such as indicated at'MN. It will now be necessary to specify where the'p'article i is at equilibrium,y and let it be assumed that the equilibrium occurs at the -radius Ra, namely, at the entrance end of a passage. Thecurve OA Awill still represent the value of moar, but if equilibrium is to occur at radius Re, th'ecurve 'whichmeans that the centripetal force will er:-`

ceed the centrifugal force. yIn other words, if the particle under consideration once enters within Y the radius R2, it will bepulled by a continuous increasing force. within the separator.

.i ,Now consider a particle having the same crossthe predominating force acting on a particle will be constantindependently of the radius. In the radial vane selector, on the other hand, the selection is only eifective'at or near the inlet of the passages limited by the vanes.

'I'he conditions of separation may be lvaried in diiferent ways, for example, by changing the velocities of the selector and impeller rotors, by throttling ilow through conduit Il or 42, by con-` trolling or introducing air through nomle 8, etc.

In Figure 5 there is indicated another embodiment of the invention involving the'provision of a substantially closed system which is capable of somewhat more eifective control of the .iiow and consequently of the separation. In this gure,

the separator proper is the same as that heretoforedescribed. The conduit- 30, however, provides iiow into a iilter chamber, indicated at, provided with a support .l for illter material i2. The particles which pass the selector separate in the chamber 58 and may be removed through the conduit 8l connects the nlter chamber with a valved exit 8l. An admission port for air is provided at Il and serves to permit the replacement of any air,lost with the powdered material. A

compressor driven through a shaft 12, which compressor delivers air through conduit 10 from Bo far as rejecassures the Jet. 8, which serves for the entrainment of the V ilowoi air through the passage 6I.

What I claim and desire to protect by Letters Patent isz,`

1t A separator for ne particles comprising a casing,l a rotor Within said casing, means for introducing particles in gaseous suspension into the casing adjacent the periphery of the rotor, and a tubular means providing an erdt from4 the center of the rotor, said tubular means opening at a location approximately midway of the axial extent of said rotor. i

2. A device for separating nely divided solids according to size comprising a casing, a rotor within said casing. walls on said rotor forming passages extending inwardly from the periphery.

oi the rotor a majors portion of the distance to the center thereof, means providing an exit from ,the center oi said rotor. means for rotating said rotor, means for producing a. current of -air inwardly through said passages and out through said exit, and means for introducing finely divided solid material into said current of air, said walls being unbroken from their outer to their inner edges and .so formed as to coniine continuously the current-of air in each passage during its passage from the periphery. to the exit, and being so shaped that the cross-sectional area of said passages increases from the periphery to the center thereof Iat such a rate that the resultant of the centrifugal force and the force of the inwardly flowing current of air will tend to move any given particle only inward throughout the radial extent of said passages or only outwardly throughout the radiaisextent oi' said passages, de- Pending on the size and mass oi said particle.

3. A device for separating `finely divided solids according to size comprising a casing, a rotor within said casing, walls, on said rotor forming passages tending inwardly lfrom the periphery oi' the ro a maior portion of the distance to the center thereof, means providing an exit from the center ot said rotor, means for rotating said rotor, means for lproducing a current of air in- Ywardly through said passagesand out.through said exit, 'and means for introducing finely di f vided solid material into said current oi air, said walls comprising walls approximately conforming to planes parallel to the axis of rotation and arranged' in pairs forming sides of each passage. the walls of each pair diverg'ing from each other in a radially inward direction, and comprising other walls approximately conforming to planes perpendicular to the axis of rotation, said walls air will tend to move any givenparticle only inward throughout the radialextent of said passages or only outwardly throughout the radial extent of saidpassages, depending on the size and mass of said particle.

4. A separator for ilne particles comprising a casing, a rotor within said casing, means for ro- ,i 'tilting said rotor, means for introducing particles in gaseous suspension into the casing adjacent the periphery of the rotor, and means providing an exit `from the center of the rotor, said rotor having passages ot substantial radial extent for inward flow of said gaseous suspension having crosssections decreasing with increase of radius and related thereto to effect on any particle, asth e result'of 'centrifugal force and the force of the inwardly ilowing-current of air, the imposition of a resultant force tending to move it only inward throughout -the radial extent of each passage or tending to move it only outward throughout the radial-extent of each passage, depending upon its size and mass, eachof said passages being bounded from its outer to its inner end by continuous unbroken walls. i

5. A separator for line particles comprising a casing, a rotor within said casing, means' for rok tating said rotor, means -for introducing particles in gaseous suspension intoV the casing adjacent the periphery of the rotor, and means providing an exit from the center of the rotor, said rotor having passages of substantial radial extent for inward ow of said gaseous suspension having cross-sectionsy decreasing with increase of radius and related thereto to effect on any particle, as the result of centrifugal force and the force of the inwardly owing current of aix", the imposition of a resultant force tending to move it only inward throughout the radial extent of eachv pasi sage or tending to move it only outward throughconforming to planes parallel to the axis of rotabeing so formed as to confine the current of air z during itspas'ge from the periphery to the exit and being so shaped that thel cross-sectional areai of said es increases from the periphery of y said rotor for a maior portion of the distance' from the periphery to the center thereof at' such a rate that the resultant of the centrifugal force and the force of the inwardly'tiowing current of 65 tion and arranged in pairs diverging from each other in a radially inward direction, and by walls approximately conforming to planes perpendicular to the axis of rotation.-

6. A separator for iine particles comprising a casing, a rotor within said casing having inwardly; directedpassages for particlesin gaseous suspension, means for driving said rotor, a plurallty of guide passages opening tangentially into the region about' the periphery o'f the rotor and o' adiacent thereto in the vdirection of rotationV of the rotor at a plurality of uniformly spaced locations. means for introducing into said guide passages particles in gaseous suspension from a common source, said guide passages and said rotor passages .being so constructed and arranged as to secure substantially uniform loading of the rotor 'with said suspension, and means providing an exit` from the center of the rotor.

n: mGUE.

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