US2010128A - Centrifugal separator - Google Patents

Description

1935- G. D. ARNOLD 2,010,128

CENTRIFUGAL SEPARATOR I Filed Sept. 17, 1931 2 Sheets-Sheet 1 INVENTOR ATTORNEYS Filed Sept. 17, 1931 2 Sheets-Sheet 2 ATTORNEYS Patented Aug. 6, 1935 s PATENT OFFICE CENTRIFUGAL SEPARATOR Gerald D. Arnold, Wanwatosa, Wis. Application September 17, 1931, Serial No. 563,339

11 Claims. (Cl. 209144) This invention relates to improvements in cenvortex through which lighter particles are drawn trifugal separators. from the material which should be discharged It has particular reference to the type of cenbelow. By destroying the rotative movement of trifugal separator known as a collector and used the air inthe course of its discharge, I break at the terminus of a pneumatic conveyor to sepaup the eddy which has heretofore interfered rate from the air stream the material carried with effective separation and at the same time thereby. I so far increase the effective capacity of the air Where the material conveyed has substantial discharge Op t I am able to handle much weight, the problem of separation is easy, but greater quantities of air at low velocity through when the material comprises ground feeds, dust, a smaller ope g than it has heretofore been or dehydrated particles of light weight, it is very possible to thus reducing h a l Size diflioult to achieve complete separation. of the collector and making it not merely more Attempts have been made to recirculate the compact but also more efllcient in its centrifugal air in an effort to free it of entrained dust-like action. particles, but obviously recirculation through a In the drawings: I piece of apparatus which has once failed to re- Figure 1 s a Vertical a a Section ou One move the dust can at best only be partially eflecembodiment of the Present inventiontive. Various other expedients have also been Fig r 2 i a fr n detail in p p v proposed, including a rapid taper or reduction of three of the component parts making up the in diameter of the separator in order that the collector assembly shown in Figure 1. centrifugal force may be increased by the re- F gu 3 is a p View the app Shown duced'radius while considerable kinetic energy in Figure l. still remains in the material undergoing separa- Figure 4 is a fragmentary detail partially in tion. There is a point, however, at which the side elevation and partially in vertical axial sec- -horizontal pull of centrifugal force acting tion showing a very compact multiple organizathrough the material against the inclined throat tion in which two collectors are assembled conof the separator develops an upright component centrically in a single unit. of force suificient to overcome the pull of gravita Figure 5 is a plan view of the apparatus shown tion so that the material accumulates, bridges in Figure 4. the separator throat, chokes the apparatus, and Like parts are identified by the same reference allows a considerable portion of its mass to es-, characters throughout the several views. cape upwardly in the eddy formed by the up- The general form of the collector is similar to wardly discharging air, which in the ordinary that of other devices in that the collector has a separator, maintains its whirling or cyclonic cylindrical chamber '6 at its top and a tapering motion. discharge throat 1 leading downwardly there- The present invention seeks to provide a comfrom to a spout 8 through which the solid matepact simplified centrifugal separator whereby rials pass in the operation of the device. The even the lightest of materials can successfully be air escapes through a central pipe 9 which is poremoved almost entirely from a supporting air sitioned in the upper or cylindrical portion of current. More specifically stated, I propose to the device and is preferably capped as shown at provide a separator in which the discharge throat to to exclude rain and to reduce the velocity of has a helical rib of such pitch as to mechanically escaping gases. feed dow wa d y a d ou wa d y the whirl ng The material to be separated, usually pneumatmass of material which might otherwise tend to ically conveyed dust, chaff, or feed, enters the bridge the throat and choke it. device through a tangential inlet passage at H. I further propose to provide the separator with For about ninety degrees about the axis of the baflle means for destroying a cyclonic eddy moseparator I prefer that passage II should remain tion of the discharged air; I have found that a closed conduit as shown at 12 in Figs. 1, 2, 3 in the ordinary separator, regardless of how big and 4. In this ninety degrees of movement about the air discharge opening may be, its cross secthe apparatus the material entering through the tion is not effectively utilized due to the rotative large opening at H has been concentrated by or eddy motion of the air which maintains praccentrifugal force to a thin stream following the tically all of the air mass within an annular space inner periphery of the chamber 6. only an inch or two in thickness around the pe- It is particularly to be noted that the conduit 55 riphery of the opening, the center comprising a I2 has ahelical top wall l3 which closes the upper UNITED STATE terial through the device in an axial direction,

but it is employed primarily because it ensures effective separation of solids from air or other gases at the entrance to the collector by eliminating the possibility that the smooth flow of the material and the effectiveness of its separation might be interfered with by previously introduced material making a second or third turn of the device. In the apparatus disclosed, the material follows a distinct path in each turn which it makes about the apparatus, and hence there is no interference such as might develop eddy currents to dissipate the lighter material into the separated air.

It being understood that Stratification of the solid matter of the air in annular layers is actually achieved in conduit I 2 and chamber 6, the problem of maintaining the separation during delivery of the air and solid matter to different ports, remains.

As above indicated, separation is most easily effected where the radius is small and the centrifugal force developed in the whirling material is correspondingly high with reference to its velocity. Where considerable volumes of air are to be handled it has heretofore been necessary to make the air escape opening of large diameter in order to reduce the air velocity to the point where little of the solid matter would be entrained. Yet an air escape port of large diameter has inherently required an increase in radius of the separator as a whole, thereby rendering separation less eifective. These two factors have seemed to prescribed limits making complete separation of light particles from large volumes of air impossible.

' I have discovered, however, that the observed discharge of light particles of solid matter with the air escaping from previously known separators has been attributable to the velocity of the air in its rotative movement about the escape pipe. Not only has its rotative speed been such as to enable it to entrain light particles of material, but a central vortex has existed which has sucked the material upwardly from the whirling mass in the throat of the separator. The difficulty in this regard is solved through the use of bailie means preventing the air from rotating during its escape through pipe 9.

I prefer to employ a cross-shaped baffle device l5 having four wings axially joined and tapered downwardly to an apex at l6 which is preferably well below the lower end of pipe 9. The projection of the bafiles downwardly into throat l of the device breaks up at its inception the eddy which tends to lift light particles toward the air outlet. The mass of the air being relatively small, the air is readily made to change its direction and to flow practically directly upwardly through pipe 9. Thus, I use the entire cross sectional area, of pipe 9 as an air escape means, whereas, if I omitted the baflle means, I would be delivering all of the air at relatively high velocity adjacent the periphery of the pipe, and the center would be unused. The bafile eliminates both the vortex and the high escape velocity of the air and prevents the discharge through the air pipe of any particles of solid matter which have once been effectively separated.

aoionzs The construction disclosed might have a tendency to increase the probability of bridging as above described, if it were not for the provision of a stationary rib or feed screw at $8 which passes about the interior of the tapering throat l with a pitch gradually increasing toward the discharge pipe 8. This screw may be made by 'welding a narrow strip of metal to the inner surface of the throat l, or it may be made by integrally forming the material whereof said throat is made.

The helical direction of the stationary feed screw 83 corresponds to the helical direction of the material as introduced through conduit i2. At its inception, at or near the point at which the material tends to bridge across the throat, the feed screw is substantially parallel to the normal flow of material through throat I, and the pitch increases so gradually as to change the direction of flow of the solid matter without any appreciable eddy currents such as might throw the finer particles into the path of air escape through pipe 9. I have found that collectors which were practically inoperative with certain materials because of their tendency to bridge and choke the collector, may be used eifectively by the addition of the feed screw herein disclosed. The feed screw should be spaced well below the bafile apex [6. It is used only in that portion of the throat in which mechanical feeding is required and in which the tendency of the material to bridge across the throat evidences the substantially completeelimination of the air or other fluid. If the screw is extended higher into the throat it will cause eddies due to the exposure of its surfaces to the air. As a result, much of the finer material will pass out with the air stream and the purposes of the invention will not be fully achieved.

Figs. 4 and 5 show an apparatus capable of handling the separation from air or the like, of dust or powdered material too fine to be separated by the ordinary large capacity apparatus. As above noted, fine materials can be perfectly separated only by reducing the radius of the collector for a given air stream. In accordance with this invention I am able actually to increase the capacity of the air escape duct while including therein an auxiliary collector fed from the first collector and so arranged as to receive only material, separation of which is difficult.

The cylindrically chambered portions of the outer collector are shown at 26, and of the inner collector are shown at 21. The outer collector has a'throat 28 and the inner collector a throat 29, these throats terminating in concentric discharge pipes as shown. From the inlet ll of the larger collector its conduit l2 preferably follows not merely a helical but a spiral path of gradually decreasing radius.

A gate is provided at 30 which subdivides conduit l2 and is adjustable to vary the relative capacities of the conduit portions on either side of the gate. Practically all the material passing through the conduit, both air and solid matter, will be compacted in a thin layer on the outer periphery of conduit l2 before gate 30 is reached. Gate 30 should be adjusted toskim from this layer merely the more rarefied air and the extremely light particles floating therein.

Thus, although the larger volume of the conduit is disposed on the inside of gate 39 the mass of the material deflected by the gate will be very much less than that of the material remaining in the channel of less cross section on the outside of the gate. The latter material is discharged into the cylindrical portion 26 of the larger separator, while the lighter material passes through the spiral branch conduit 3| of gradually decreasing cross section to the chamber 21 of the smaller separator.

Each of the concentric separating throats is provided with,a helical feed screw l8 as previously described.

Each of the concentric separators has baflles I in its air outlet pipe as previously described. The bafiles for the larger separator comprise webs which support the smaller separator. The air escape space for the larger separator comprises the area between its pipe 9 and the wall of the inner separator. Due to the reduced cross section of the feed flow space between pipe 9 and housing 26, the total area of the air escape openings from the concentric collectors is actually greater than that from a single collector of like dimensions and due to the use of baffles the total cross section is utilized to reduce air velocity more effectively than has heretofore been possible. The construction illustrated may be taken in a broad sense as merely an exemplification of multiple concentric separators arranged for successive handling of material.

I claim:

1. In a separator, the combination with a casing having a substantially tangential inlet and a substantially central discharge throat of gradually reducing diameter, of a helix applied peripherally to the interior of said throat in the path of material traversing said throat toward said outlet, the pitch of said helix being slight at the beginning thereof and increasing in a direction to lead such material to the outlet.

2. In a centrifugal separator, the combination with a casing having a helical inlet conduit discharging tangentially into the casing, and a tapering throat, of a helical feed screw positioned in said throat having an initial pitch corresponding substantially with the direction of flow of material entering said casing through said conduit and thence gradually increasing in pitch toward the smaller end of said throat.

3. A centrifugal separator comprising the combination with a casing having a tangential inlet, a tapering throat and acentral air outlet pipe, of bafile means in the air outlet and projecting into said casing adapted to break up the rotative movement of air in said outlet said outlet being otherwise substantially unobstructed, and means for mechanically feeding through said throat material separated from said air, said mechanical feeding means comprising a relatively stationary screw acted on by such material in the course of its rotative movement in said throat and having a pitch gradually increasing toward the smaller end of said throat.

4. A centrifugal separator comprising the combination with an annular separator having outer and inner walls and a tangential inlet. of a second separator positioned within said annular sep-. arator in spaced relation to said inner wall to provide an air outlet from said annular separator, said second separator having a tangential inlet and arcuately curved conduit leading to the tangential inlet of said annular separator, a gate concentrically subdividing said conduit, said conduit comprising means for deflecting material from the inside of said gate to said second separator, the conduit exteriorly of said gate being in communication with said annular separator.

5. Centrifugal separating equipment comprising the combination with a plurality of separating casings concentrically arranged, of a tube intervening between said casings and providing an opening between it and the innermost casing for the escape of air from the outer casing, a conduit communicating tangentially with the respective casings, and means for subdividing the material in said conduit for delivery to the respective casings, each of said casings having outlets for the delivery of portions of said material.

6. Centrifugal separatingequipment comprising the combination with an arcuate conduit, of a plurality of concentric casings to the outer of which said conduit leads directly, a branch conduit leading from the inner side of said first mentioned conduit to an inner casing and tangentially communicating therewith, an air escape pipe leading from said inner casing, and substantially concentric throats leading independently from both of said casings for the separate discharge of their respective contents.

7. Centrifugal separating equipment comprising the combination with an arcuate conduit, of a plurality of mutually spaced concentric casings each having inner and outer walls to the outer of which casings said conduit leads directly, a branch conduit leading from the inner side of said first mentioned conduit to an inner casing and tangentially communicating therewith, an air escape pipe leading from said inner casing, and substantially concentric throats leading from both of said casings, said conduit having a gate adjustable to vary the respective proportions of its contents delivered to the respective casings.

8. In a separator, the combination with a casing and means for effecting rotative movement of the material therein for centrifugal separation, of a pipe axially opening from said casing, and a baffle plate extending in a general axial direction with reference to said pipe and projecting from the end thereof toward the center of the casing with its outer margin converging toward said center, the opening to said pipe from said casing being otherwise substantially unobstructed, whereby to interrupt the circumferential movement of material adjacent the opening into said pipe and to permit such material to flow axially through the pipe.

9. A centrifugal separator comprising the com-, bination with a casing having a tangential inlet conduit, of an outlet pipe opening from said casing adjacent the center thereof, and bafiie means comprising plates disposed substantially radially with respect to said pipe and projecting beyond said pipe toward a common apex within said casing, the said plates having their convergent outer margins exposed to material moving in said casing in advance of the admission of such material to said pipe.

10. A centrifugal separator comprising the combination with a casing having a tangential inlet, a tapering throat, and a central air outlet pipe, of baflle means extending from the side of said pipe toward the center thereof and projecting axially of said pipe beyond the end thereof into said casing, the outer margin of said baffle means being convergent toward the projected axis of said pipe, whereby to be adapted to obstruct the whirling movement of gases in said casing in advance of the admission of such material to said pipe, the outlet pipe being otherwise substantially unobstructed, whereby to facilitate the free delivery of such gases axially therethrough, and means for mechanically feeding through said throat material separated from said gases.

11. Centrifugal separating equipment comprising the combination of a plurality of concentric separators having separate air discharge ports, the air discharge port of the larger separator comprising a tubular wall centrally disposed therewithin, the smaller separator comprising a casing located within said tubular wall and in spaced relation thereto, whereby to provide a passage between said' separators for the discharge of air from the outermost, and a closed conduit communicating through said wall with the outer separator and leading therefrom across said air discharge passage into the casing of the inner of said separators and comprising means for diverting material from the larger separator for feeding the smaller.

GERALD D. ARNOLD.

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