US3094828A - Centrifugal dust separator - Google Patents

Description

R. E. PAYNE ETAL CENTRIFUGAL DUST SEPARATOR June 25, 1963 Filed Aug. 11, 1958 s Sheets-Sheet 1 Fig. l

INVENTORS.

ROBERT E. PAYNE FRED P. GOOCH ATTORNEY J1me 1963 R. E. PAYNE ETAL GENTRIFUGAL. DUST SEPARATGR 3 Sheets-Sheet 2 Filed Aug. 11,

INVENTORS. ROBERT E. PAYNE FRED P. GOOCH ATTORNEY June 25, 1963" R. E. PAYNE ETAL CENTRIFUGAL DUST SEPARATOR Z5 Sheets-Sheet 3 Sad O Filed Aug. 11, 1958 .s Y E m TH R. w w m. P m EE R O R to persons skilled in the art as United States Patent corporation of Delaware Filed Aug. 11, 1958, Ser.No. 754,334 Claims. (Cl. 55-407) This invention pertains generally to centrifugal dust separators, and more particularly to dust separatorsof this type which are adapted to separate from a gas, such as air, particles down to submicron size. This invention also pertains to the concentration in a gaseous medium of such particles.

Although the invention is adapted to many uses, as will become evident to persons skilled in the art upon becoming familiar herewith, it is particularly useful in the samplingof at various altitudes to determine the relative proportion of suspended dust particles therein, including those of radioactive properties.

The importance of a device capable of separating extremely fine dust particles for analysis, whether 'at or near or below the earths surface, or at altitudes up to those capable of being reached by airplanes or by balloon or rocket flights, cannot be overemphasized, particularly in view of present concern with respect to radioactive fallout resulting from the testing of nuclear weapons, or, should it so transpire, their practical use.

The separation from a gas, such as air, of particles capable of being seen by the naked eye presents no problem, for many devices are available for the purpose for both industrial and household use. However, in the case of particles having average dimensions of microscopic or sub-microscopic size, including those approaching the average size of viri,'pr0blems become involved which have put the practical application of the intelligence of mankind to the acid test, as will be readily recognized.

The application of centrifugal force quite naturally suggests itself as a means to a solution of the problem, but this tool standing by itself heretofore has proved to be inadequate for the purpose, although highly effective in the case of particles of larger size. The past shows clearly that not only is it necessary to apply centrifugal force under conditions of highest efficiency, but also that some joint-acting cooperative force'is essential to a realization of the desired results.

The present invention is based upon the foregoing incontrovertible premise, and provides an apparatus for the separation from a gas of extremely fine-solid particles, by the-combined action of centrifugal forceand the forces of Coriolis, at times with that of the drag forces of the gaseous medium, to produce a result which is not only surprising, but which is unique in and of itself.

' Further features of the invention will become apparent the description proceeds, particularly with reference to the drawings in which:

FIGURE 1 is an elevation, largely in section, of an embodiment of the invention;

FIGURE 2 'is :asection on line 2-2 of FIGURE 1;

FIGURE 3 is a section on line 3-3 of FIGURE 1;

FIGURE 4 is a perspective view, partly diagrammatic, of the impeller;

FIGURE 5 is a sectional elevation of another embodiment of the invention;

FIGURE 6 is .a section on line and FIGURE 7 is a flow sheet of acascade system for concentrarting dust particles.

Referring now more particularly to FIGURE 1 to 4, at 10 is shown a casing which serves as a collecting chamber, designated as 20, for relatively larger particles, and

66 of FIGURE 5;

progressively decreasing 1111161 secured in position by which is comprised of "a cylindrically shaped wall 11, and a slanting flat wall 12. Supe' posed upon casing 10 is a more or less frusto-conical shaped dome 13 which terminates in a scroll 14 for the exit of gas such as air, virtually denuded of solid particles. Adjoining casing 10 and 'dome'13 is a tubular collecting chamber 15 for relatively smaller particles. It will be evident that if fractionation between relatively larger and smaller particles is not a factor in the separation, which frequently is the case, casing 10 and tubular chamber 15 may be combined in a unitary collecting-chamber, or that chamber 15 may exhaust into chamber 10. In any case, any other suitable structure may be substituted.

Projecting upwardly through Wall 12 is housing 16 in which is journaled, as by bearings 17 andn18, shaft 21 to which is connected, at its upper end, impeller 22. Shaft 21 is driven in any desired manner, such as by pulley 23, belts 24, and pulley 25.

Surround-ing impeller 22 and projecting upwardly therefrom is a more or less double bell-shaped member 26 which, at its upper bell-shaped end, serves as an inlet for gas, such as air, and which, at its lower bell-shaped end, serves as a bell-shaped housing for impeller 22. Member 26 may be supported in any desired manner such as on scroll 14.

The body portion 27 of impeller 22 increases in diameter .from its tip to its base, being generally b'el-l shaped, e.g. having an outward shape or surface conforming to a surface of revolution generated by a concave line. This line or curve, if desired, may conform to a mathematical formula, such, :for instance, as a hyperbola, in which case impeller 22 would conform to a hyperboloid. In any case, body portion 27 is provided with a plurality of longitudinally arranged primary vanes 28 circumferentially'spaced about its periphery, each vane 28 being inclinedin the direction of rotation as clearly seen in FIG- URES 3 and 4. The upper or inlet ends 31 of vanes 28 are shown curved inwardly in the direction of rotation, as illustrated in FIGURE 4, which is highly preferred.

Vanes 28 are preferably spaced closely about body portion 27, and generally uniformly about its tip and about its base, which, in view of the greater diameter of its base, results in a gradually increasing distance between vanes 28 from tip to base. To compensate for the progressive increase in the distance between primary vanes 28, secondary vanes 32 are preferably provided between adjacent primary vanes 28, starting adjacent the outer ends of the latter, as illustrated in FIGURE 4. Vanes 32 may have any desired length, such-as between /3 and the length of vanes 28, eg /2 such length, and preferably are tapered from their outer ends toward their inner ends, terminating at their inner ends'in a more or less sharp or roundededge or line to facilitate smooth flow of, or reduced turbulence in,-- gas entering the channels on "each side of each such secondary vane.

The lower bell-shaped end of housing 26 conforms to the outer contour of vanes 28 and 32, and is arranged in close proximity thereto.

Annulus 33 is positioned around the lower periphery of impeller 22 in a manner to provide an annular opening 34 therebetween, preferably of restricted width, such asbetween and and annulus 33 is preferably provided with an inner tapered edge 35, for purposes to be hereinafter more particularly-described.

Positioned within the space between dome 1B and the lower bell-shaped portion of member 26 and transversely thereof, are a plurality of spaced annuli 36 preferably of diameter upwardly, or, in from opening 34, said annuli 36 being any suitable means, such as a plurali-ty-of circumferentially spaced rods 37 to which said other words, away annuli may be attached, e.g. 37 may be attached to the surrounding framework by any suitable means, e.g. by bolting, welding, or otherwise. It will be noted that the inner periphery of each annulus 36 is spaced from the outer periphery of member 26 to provide a circumferential path, chamber or free space 38, and that dome 13 serves as a second housing about the lower end of the housing 26.

As illustrated, dome '13 is provided with a lower cylindrical portion or wall 41 having a tangential opening 42 (see FIGURE 3) which leads LlD'tO tubular collecting chamber 15.

Gas recycle tubes 43 and 44 lead from collecting chambers 15 and 20, respectively, to the gas inlet end 45 of member 26, the flow of recycle gas being controlled by valves 46 and 47, respectively. Also collecting chambers 15 and are shown provided with solid particle withdrawal valves, e.g. star valves, their lower ends.

The operation of the dust separator illustrated in FIG- URES 1 to, 4 is as follows:

When the separation of particles of sub-microscopic size is involved, impeller 22 is driven at high speed by virtue of shaft 21, pulley 23, belts 24, and pulley 25, e.g. between 100,000 and 200,000 r.p.m. Rotation is counterclockwise as seen in FIGURE 3. Gas laden with finely divided solid particles, e.g. atmospheric air, enters inlet 45, and is brought into high speed rotation by vanes 28 on impeller 22, inwardly curved ends 31, when employed, assisting in the process, particularly in the reduction of turbulence, and in initiating the application of coriolis effect. By virtue of the forward inclination of vanes 28, and of the secondary vanes 32 when employed, solid particles suspended in the gas are subjected to the separating influences, not only of high centrifugal force but also of the phenomena of coriolis, whereby they are deposited on the vanes and are caused to slide thereon outwardly toward annular opening or solid particle outlet 34, through which they are ejected or pass downwardly into collecting chamber 20. The gas, whirling at high speed, on the other hand, passes outwardly into space 38, and upwardly into scroll 14 from which it is discharged through outlet 51. On ascending through space 38, the gas is brought inwardly toward the axis of rotation, outlet 50 from chamber 38 into scroll 14 being of substantially lesser diameter than the diameter of the outlet end of housing 26, and, by virtue of conservation of angular momentum, the gas is caused to increase in tangential velocity with resulting marked increase in centrifugal force, increase in tangential velocity being, of course, accompanied by increase in angular velocity. Thus any solid particles, such as finer solid particles, which have failed to pass through annular opening 34 into collecting chamber 20, are subjected to a substantially higher centrifugal force for their separation from the gas. These particles are thrown outwardly into the spaces between annular rings 36, and pass downwardly into collecting chamber 15. Final separation of particles from the gas in space or chamber 38 is greatly assisted by the progressive decrease in inner diameter of annuli 36, which are preferably flat as illustrated, for as the gas sweeps upwardly past the inner edges of such annuli, particles thrown outwardly by centrifugal force are caused to strike the under surfaces of annuli 36, thus being released from the propelling or dragging force of the upwardly flowing gas. By reason of their high tangential velocity, particles thus separated or released from the upwardly propelling force of the gas, fly outwardly into the space 52, striking, for the most part at least, the inner surface of dome 1-3 'on which they slide, both circumferentially and downwardly, due to their momentum, and the continued action of the rotating air, and finally pass through opening 42 into collecting chamber 15.

It will be noted that annuli 36 are spaced radially inwardly from the inner surface of dome 13, thus affording by welding. Likewise, rods not only the free circumferential flow of gas in chamber 52, but also the free flow of particles through the spaces between annuli 36, which avoids large reduction in tangential velocities of the particles and consequent clogging. The free rotation of air in space or chamber 52 even though confined, is a significant factor in the avoidance of clogging, and in the delivery of solid particles to tangential outlet 42.

Experience has shown that extremely finely divided particles, particularly of certain types, sometimes have a tendency to agglomenate or build up or pack at points or areas somewhat analogous to snow in a blizzard, making it necessary to eventually shut down for cleaning punposes 48 and 49 respectively, at 7 to maintain a high level of efiiciency. The period between suoh shut downs may be markedly prolonged or eliminated by permitting a small percentage of gas, e.g. air, to escape along with separated particles into the collecting chamber or chambers.

It will be noted that in the rator particularly described, the gas pressure in the respective collecting chambers 15 and 20 is higher than at the inlet 45, due to the conversion of velocity into pressure. Thus to cause a small percentage of gas to pass through tangential opening 42 or through annular opening 34, to clear the respective openings or to maintain such openings clear of accumulations of particles, it is merely necessary to open, or partially open, valves 46 and 47 respectively, thereby reducing the pressure in the respective chambers. In order to avoid the loss of any particle-s which might be carreid along with the released gas and/ or to assure a diiferential in pressure, the released gas is preferably recycled into inlet 45 in member 26. Any other means to accomplish the stated purpose obviously may be substituted.

Although it has been convenient, in the particular description of the embodiment of the invention shown in GURES l to 4, to consider the dust separator as operating while in a Vertical position, including the fall by gravity of particles discharged into collecting chambers 15 and 20, it will be understood that, by modification of the configurations of the respective collecting chambers, operation is made possible about any axis vertical, horizontal or inclined, e.g. irrespective of any angle between the axis of rotation and the earths surface. In this connection it should be kept in mind that the centrifugal forces employed are such a large multiple of the force of gravity as to nullify the effect of the latter virtually altogether. As a result particles separating while under centrifugal force may be guided for collection completely independently of the force of gravity or the position in space of the axis of rotation.

Annulus 33 is preferably made adjustable axially relative to terminal edge 53 of body portion 27 of impeller 22, so that, if desired, it may be made to occupy a selected position radially outwardly from the space between edge 53 and terminal edge 54 on member 26. It will be underthe solid particles to operation of the dust sepaby the deflecting or skimming action of edge 35.

The dust separator of the invention may be made to any suitable dimensions, although it is preferred, when employing a very high speed of rotation, such as in the separation of particles of sub-microscopic size, to hold the largest diameter of impeller 22 to between 1'' and 3", and to employ, in the fabrication thereof, high tensile strength material, such as high tensile strength alloy steel. It will be noted that impeller 22 lends itself readily to machining operations.

Another embodiment of the invention is illustrated in FIGURES 5 and 6.

At 61 is shown a shaft having an enlarged portion 62.

Shaft 61 is 'journaled in bearings 63 and 64, and is provided with pulley 65 for driving purposes. Rotation of shaft 61 is counterclockwise when viewed from the left as seen in FIGURE 5.

Surrounding shaft 61 and spaced therefrom is housing 66 having a central enlarged portion 67, and ends of reduced diameter 68 and 69. Gas inlet conduit 71 is connected to inlet end 68 ofhousing 66.

Aflixed to shaft 61 and extending through housing 66 from inlet end 68 to outlet end 69, are a plurality of circumferentially spaced radial vanes 72 positioned in a manner to act as gas impeller elements to cause the flow of gas through housing 66 from left to right as seen in FIGURE 5, as well as to impart a whirling motion thereto. Vanes 72 are shown arranged with tips'73 advanced in the direction of rotation. Also tips 73 are preferably curved in the direction of rotation as illustrated at 75. In addition, vanes 72 may be inclined in the direction of rotation in a manner similar to that described in connection with vanes 28 and 32 of FIGURES 1 to 4, although this is not anessential, and in certain instances may not be preferred.

Tips 74 on vanes 72 within outlet end 69 of housing 66 are shown positioned and shaped somewhat similarly to -tips 73'within inlet end 68 but reversed in direction, that is advanced in a direction opposite to the direction of rotation, for reasons to be hereinafter more pa-rticuLarly described.

Positioned within enlarged portion 67 of housing 66 are a plurality of spaced annuli 78, supported as by rods 81. It is to be understood that whereas annuli 78 are shown with equal inner diameters, they may be provided with progressively decreasing inner diameters from inlet to outlet of housing portion 67 similarly to the case of annuli 36 in FIGURES 1 to 4. It will be understood, of course, that the diagrammatic illustration is intended to indicate spaced annuli 78 extending throughout housing portion 67 from left to right as seen in FIGURE 5.

Gas recycle conduit 82 provided with valve 83 leads from the inner periphery of housing portion 67 preferably adjacent end 68 (this being the higher pressure end in housing portion 67) to inlet 71. Recycle gas flow, however, may be caused or facilitated by the use of a pump, or other device, if desired, such as a centrifugal pump. The same applies to the recycle of gas through conduit 43 and/ or conduit 44 in FIGURE 1. By the use of these features gas is recycled from a locus downstream of gas flow to a locus upstream thereof for purposes already described in' connection with FIGURES 1 to 4.

Housing 66 is provided with tangential outlet 84, the exit of which is controlled by valve 85, eg. a star valve.

.In operation gas laden with finely divided solid particles, e.g. air, enters through inlet conduit 71, and is brought up to speed by vanes 72. Separation of finely divided solid particles takes place, the particles collecting on the vanes 72 and sliding outwardly along the same into the enlarged portion 67 of housing 66, being thrown tangentially outwardly against the inner periphery thereof and removed through tangential outlet 84. The gas, revolving at the high rate of speed imparted to it by the vanes 72, continues through housing 66 for the separation of residual particles contained therein, spaced annuli 78 assisting in this connection, for particles thrown outwardly, upon their impingement on a face of an annulus 78, are released from the dragging influence of the gas, and travel outwardly against and around the inner periphery of enlarged portion 67, due to their tangential velocity, and are removed through outlet 84.

The spacing of annuli 78 from the inner periphery of enlarged portion 67 of housing 66 to form the cylindrical chamber or free space 77 affords not only the free circumferential rotation of gas in chamber 77, but also the free flow of particles outwardly through the spaces between annuli 78, which, the same as in FIGURES 1 to 4, avoids large reduction in tangential velocity of the particles which reduction is not desired trom the standpoint of blogging. The free rotational flow of air in space 77, even though such air may be confined therein, is a significant factor in the avoidance of clogging, and the delivery of solid particles to outlet 84. Gas may be recycled to inlet 71 through conduit 82, which as shown is connected to the higher pressure end of chamber 77 the same as conduit 43 is in communication with the higher pressure end of chamber 520i FIGURE 1.

The use of tips 74 on vanes 72 is preferred, although not essential. The function of tips 74 is to recover power from the exhausting gas which leaves housing 66 through end-69.

At the beginning of this specification it was brought out that this invention also pertains to the concentration in a gaseous medium of finely divided solid particles, e.g. of sub-micron size. This is illustrated in the flow sheet of FIGURE 7, in which P indicates particles entrained in the air stream.

Referring now more particularly to FIGURE 7, at 91 is indicated a dust separator, e.g. similar to that described in connection with FIGURES 5 and 6. Dust separator '91 may be of a 'size capable of handling, for example, 100,000 cubic feet per minute of particle laden air, exhausting along with the separated particles 3000 cubic feet per minute of air, through valve 85, and 97,000 cubic -fe'etzper minute of particle free air through outlet end 69.

The particles or powder concentrated in the air exhausted from separator 91 may be subjected to analysis as such, or if further concentration is desired, the mixture, so concentrated in powder or particles, may be fed to a second dust separator indicated at 92, e.g. a dust separator similar to that described in connection with FIGURES 5 and 6, and capable of handling, for example, 3000 cubic feet per minute of air with particles concentrated therein.

Dust separator 92 could be set to exhaust cubic feet per minute of air along with the solid particles,

through valve 85, and 2900 cubic feet per minute of particle free air.

At this point, the particles concentrated in air exhausted therewith from dust separator 92 might be utilized as such. On the other hand, if further concentrationis desired, the mixture can be fed into a third dust separator indicated at 93, e.g. a dust separator similar to that described in connection with FIGURES l to 4 and capable of handling, for example, the 100 cubic feet per minute of dust laden air from separator 92, and exhausting air free of particles at the rate of 100 cubic feet per minute, and the particles free from suspending air.

From the foregoing description it will be noted that the embodiment of the invention shown in FIGURES 5 and 6 is more particularly adapted to the concentration of particles in a gaseous medium, whereas the embodiment shown in FIGURES 1 to 4 is particularly adapted, not only to concentration of particles in a gaseous medium, e.g. involving drawing off of gas with suspended particles through lines 43 and/ or 44- without recycle, and/ or through scroll 14, but also to the complete separation from a gaseous medium of solid particles. Also that the various embodiments are adapted to the separation from a gaseous medium of particles of any size up to and including those visible to the naked eye. Moreover, the various embodiments may be built to any desired size to handle any desired cubic feet per minute of particleladen gas, rotational speed being limited only by the strength of the materials employed. Thus it is contemplated that the rotors may be made with relatively large diameters in large capacity machines, e.g. with diameters up to ten feet or more, which adapts the invention to various industrial uses, such as the removal of ash from flue gas. The cascade system described in connection with FIGURE 7 is particularly adapted to the continuous rapid processing and analysis of large volumes of air, e.g. in an enclosure or room containing equipment capable of nuclear radiation, such as a nuclear reactor, or labora- 7 tory or test equipment as will be obvious upon becoming familiar herewith. Other uses for the invention will become apparent to persons skilled in the art.

In the various embodiment of the invention particularly described it will be noted that recycle gas is preferably taken from the higher pressure end of the respective chambers or spaces surrounding the spaced annuli, e.g. chamber 52 in FIGURES 1 to 4 and chamber 77 in FIGURES 5 and 6. This represents an outstanding feature of the invention, in that whereas the free rapid circumferential flow of gas is desired in the respective chambers for the reasons particularly described, the drawing off of recycle gas from the higher pressure end reduces or eliminates any tendency for gas to short circuit or pass around the main separating chambers through such spaces.

From the foregoing particular description which is by way of illustration, it will be seen that the invention is adapted to wide versatility, and that changes, omissions, additions, substitutions and/or other modifications may be made Without departing from the spirit thereof. Accordingly it is intended that the patent shall cover, by suitable expression in the claims, the various features of patentable novelty that reside in the invention.

We claim:

1. Apparatus comprising a rotor, said rotor being bellshaped, vanes on the outer surfaces of said rotor arranged generally longitudinally thereof, means for rotating said rotor, said vanes being inclined toward the direction of rotation of said rotor, a bell-shaped housing surrounding said vanes, said housing having an inlet and an outlet, an annular outlet for particles around the outlet for said housing and positioned in the path of separated particles ejected by said rotor, a second housing downstream from and surrounding said first housing for the flow therethrough of said gas, a plurality of spaced stationary generally flat annuli arranged longitudinally of and around the path of flow of gas through said second housing, said annuli progressively decreasing in inner diameter in the direction of flow of said gas, and an outlet for said second housing for the exit of said gas, said last-mentioned outlet being of lesser diameter than the outlet for said first housing.

2. Apparatus comprising a bell-shaped rotor, vanes on the outer surface of said rotor arranged generally longitudinally thereof, means for rotating said rotor, said vanes being inclined toward the direction of rotation of said rotor, a bell-shaped housing surrounding said vanes, said housing having an inlet at the narrow end of its bellshape and an outlet at the wider end of its bell-shape, an annular outlet for particles around the outlet for said housing and positioned in the path of separated particles ejected by said rotor, a second housing downstream from and surrounding said first housing for the flow therethrough of said gas, a plurality of spaced stationary generally flat annuli arranged longitudinally of and around the path of flow of gas through said second housing, said annuli progressively decreasing an inner diameter in the direction of flow of said gas, an outlet for said second housing for the exit of said gas, said last-mentioned outlet being of substantially lesser diameter than the outlet for said first housing to cause gas flowing through said second housing to move toward its axis of rotation, and a scroll connected to the outlet for said second housing for the exit of gas from said dust separator.

3. Apparatus for separating particles from gas comprising .a rotor, vanes on the rotor, means for rotating the rotor, a housing for said rotor having an inlet and an annular exhaust opening about the periphery of the rotor, an enclosure surrounding at least the exhaust opening and outward from the rotor for leading at least a portion of the exhaust from the rotor in a direction generally axially with respect to the rotor, the enclosure being substantially coaxial of the rotor and having an axial discharge opening of diameter less than the diameter of the annular exhaust opening, a plurality of spaced stationary annuli in the enclosure positioned around and transversely of the flow from the rotor, said spaced annuli progressively decreasing in inner diameter in the direction of flow from the rotor, and the enclosure having means outward from the annuli for receiving particles.

4. The apparatus of claim 3 wherein the peripheral wall of said enclosure gradually converges toward said discharge opening.

5. The apparatus of claim 3 wherein an annulus is positioned about the annular exhaust opening from the rotor housing to deflect heavier particles in a direction opposite the flow of exhaust into the enclosure.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. APPARATUS COMPRISING A ROTOR, SAID ROTOR BEING BELLSHAPED, VANES ON THE OUTER SURFACES OF SAID ROTOR ARRANGED GENERALLY LONGITUDINALLY THEREOF, MEANS FOR ROTATING SAID ROTOR, SAID VANES BEING INCLINED TOWARD THE DIRECTION OF ROTATION OF SAID ROTOR, A BELL-SHAPED HOUSING SURROUNDING SAID VANES, SAID HOUSING HAVING AN INLET AND AN OUTLET, AN ANNULAR OUTLET FOR PARTICLES AROUND THE OUTLET FOR SAID HOUSING AND POSITIONED IN THE PATH OF SEPARATED PARTICLES EJECTED BY SAID ROTOR, A SECOND HOUSING DOWNSTREAM FROM AND SURROUNDING SAID FIRST HOUSING FOR THE FLOW THERETHROUGH OF SAID GAS, A PLURALITY OF SPACED STATIONARY GENERALLY FLAT ANNULI ARRANGED LONGITUDINALLY OF AND AROUND THE PATH OF FLOW OF GAS THROUGH SAID SECOND HOUSING, SAID ANNULI PROGRESSIVELY DECREASING IN INNER

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