US2381954A - Classifying system for pulverized materials - Google Patents

Description

Aug. 14; 1945. H. HARDINGE CLASSIFYING SYSTEM FOR PULVERIZED MATERIALS 3 Sheets-Sheet 2 Filed Aug. 3, 1940 FINES 8 fl/z 70 cause 10:

Hie: on): fined/AME W W m w M L M wmm mm W5 .Aug. 1945- H. HARDINGE CLASSIFYING SYSTEM FOR PULVERIZED MATERIALS Filed Aug. 3, 1940 3 Sheets-Sheet 3 PatentdAug'. 14,1945

CLASSIFYING SYSTEM roa rULvEmzEn:

MATERIALS Harlowe Hardinge, York, Pa. Application August 3, 1940, Serial No. 350,737

16 Claims.

The present invention relates to classifiers and more particularly to classifiers such as are.

used in the classification and extraction of coarse material and fine material from a body of material-laden air or 'other buoyant or elastic fluid capable of carrying particles in suspension.

' Whilemy inventive concept finds especial applian improved system of classifying in connection with grinding mills wherein a simplified method of classifying oversize from the fines discharged from the mill is employed and whereby the oversize may be returned either to the feed end or discharge end of the mill.

Another object of the present invention is to utilize the principle of centrifugal force in classification, which force can be varied without changing the quantity of air employed by means of splitting the air current into two or more components and re-combining so that one component opposes the other.

Yet another object of the present invention is l .to provide a method of classification whereby centrifugal force is used to effect a separation of the oversize from the fines in which some of the fines going with the oversize are re-classified by means of the hindered settling principle 'of classification. v v

A further object is to provide a method of classification whereby the centrifugal force utilized to efiect the classification is varied by the quantity of air supplied. I

.And yet another object isto provide'a classification device which is simple in construction,

which can be cheaply and easily manufactured and which is economical to maintain.

With these and other objects in-view, which may be incident to my improvements, the invention consists in the parts and combinations to be hereinafter set forth and claimed, with the understanding that the several necessary elements comprising my invention may' be varied in construction, proportions and arrangements. without departing from the spirit and scope of the appended claims.

In the drawings in which like numerals indicate the same or similar parts:

Figure 1 is an elevational view partly broken away illustrating the operative relation of the classifier with a grinding mill.

Figure 2 is a transverse sectional view of the classifier. I

Figure 3 is a transverse sectional view of the classifier showing the damper moved to the position whereby it splits the material-laden airstream.

Figure 4'is a sectional view taken along the line 44 of Figure 2.

Referring to the drawings, and .more specifically to Figure 1, I have shown a classifier l which is directly connected through a suitable conduit to discharge end 2 of a mill 3, from which a continual flow of material-laden air is withdrawn into a pipe 4. The mill 3, while shown here as the well knownconical mill, may also be of any conventional design such as a cylindrical mill, rod mill, hammer mill, etc. a

The coarse material-is fed into the mill by.a feeder 6 through a chute 1. Air is delivered to the mill through a conduit 8 by means of a blower 9 and enters the mill in an annular space [0 between a large portion II of the conduit 8 and I the central outlet pipe or conduit II. To improve the grlnding action of the mill 3, an extraI quantity of air is introduced more or less to collector l3 wherein the fine solids are separated from the air. The solids are discharged from the system through an air lock H of conventionaldesign whereby the pressure of the material in the collector opens the valve of the look as the load builds up in the bottom of the collector. However, as the bottom of the air lock is loaded :with material, air will not pass up at this point and the system' is kept virtually free of infiltration of outside air. The airfrom the product collector is returned to the blower 9 throu h; conduit II for re-circulation through the system.

' The oversize from the classifier I is returned either to the feed end of the mill 3 by a pipe IO' 1 or to thee point througha pipe l1. If

desired, part of the oversize is delivered to the pipe l6 and part to the pipe I! by means of a suitable dividing vane indicated generally at l8.

A conduit 19 functions as a bypass whereby part of the air from the blower 9 may be delivcred directly to the classifier I rather than through the mill 3. The air will enter the classifier either at a point joining the material-laden air as indicated at 20, or at the bottom of the classifier through .a conduit 2|, as clearly shown in Figure 2. The advantages of the by-passed air entering the classifier through the conduits 20 and 2| will later be more completely set forth.

To compensate for the infiltration of air in the vacuum side of the system where leaks might possibly occur and also at the feed end of the mill where a Slight indraft is desirable, a vent 22 is provided. The vent 22 is located on the pressure side of the blower 9 and has a'damper 23 which is adjustable for regulating the amount of air and water vapor, if any is present, that is discharged from the system In addition, a damper 24 which is located in the main conduit 8 regulates the quantity of air entering the mill 3, and in conjunction with dampers 25 and 28 (Figure 2) in the bypass pipes 2| and 28, respectively, regulate the total volume of air circulating in the 7 system.

splitting damper 28 that is movable across the upcoming stream to a position indicated by the numeral 28A of Figure 3, or backward to a position shown by the numeral 283 in Figure 2. On the other side of the classifier i a pivoted defleeting plate 29 which may be moved forward to the position indicated by the designation 29A or adjacent to the side of the classifier as at 29B (Figure 2). The deflector plate 29 may be solid, or as shown in the drawings, it may be a perforated plate.

Below the deflecting plate 29 is a hopper 38 for the oversize and an inner hopper 3| having a restricted outlet 3| is also provided. In the bottom of the hopper 38 is an air lock 32 which may be of the same type as the air lock M in the product collector I3, but the lock 32 is employed to handle the oversize material delivered from the classifier. 7

An inner wall segment of a circle extending across the face of the classifier is shown by the numeral 33. An outlet from the classifier for the fines and air'is indicated by the opening 34 which is in the form of a sleeve that extends slightly into the classifier as indicated at 34' in Figure 4.

Assuming that the splitting damper 28 is in the 'full line position shown in Figure 2, the materialladen air in passing between the periphery of the classifier I and the circular segment 33 tends to throw out the coarser particles at the periphery rotate rapidly inside of the segment 33 before it passes out of the opening 34, thus further separating the solids from the air. The solids will slide along the segment 33 and will be thrown out at the end in a downward motion eventually dropping out of the circuit and into the hopper 30.

The velocity of the material-laden air is controlled in a number of ways. In the first place, the volume of air throughout the entire system can be effected by the damper 24 (Figure l) on the pressure side of the blower 9. Inthe second place, the bypass air enterin through the pipes I9 and 20, and controlled by the damper 26, will augment the supply of air and increase the velocity of travel in the classifier I. In the third place, the splitting damper 28, when moved to the position 28B (Figure 2) will permit part of the air already rotating in the classifier to recirculate in the annular space between the segment 33 and periphery 2'1, thus increasing the velocity and centrifugal force in the classifier i.

In order to obtain a coarser product discharged from the classifier through the outlet 33, the vane 28 may be moved to the position shown at 28A, and the material-laden air will be split, part going up and around the space between the periphery 21 and the circular segment 33, and part being short-circuited directly toward the center of the classifier, thus opposing the direction of air flow. The effect of 'this action is to slow down the circular movement of the air-in the classifier both in the annular portion between the periphery 21 and the segment 33 and also in the center adjacent to the outlet pipe 34. The result of this arrangement is that there is a lesser tendency to throw out the solids from the air and as a result, the air discharged from the outlet, will contain more solids and coarser particles. By moving the. vane 28 to different positions it is obvious that different degrees of centrifugal force may be attained and different fineness of products secured.

It is also possible to vary the fineness by opening the bypass damper 25 in the pipe 2! which enters the space between the outer wall of the hopper 38 and the inner hopper 3!. The air .passes up through the opening 3| in the hopper 3i counter to the fiow of oversize being discharged by gravity. The effect of this action is to clean the oversize of fines that may be thrown down with the coarser particles and thus grade the oversize. The buoying effect of the air passing upwards through the hopper 3! tends to return to the upper section of the classifier particles somewhat coarser than would ordinarily be discharged through the pipe 33 since the more air that passes up through the opening 3i the more will be the buoying effect of the particles of intermediate size, and if they are not allowed to pass through the opening 31 by this action they will eventually go out through the opening 34.

Instead of using relatively clean air from the by-pass pipe 2| and its damper 25, another source of air for the hopper 30 and opening 3! may be derived by by-passing a portion of the material-laden air in the pipe 4 to the hopper 30 through the pipe 2|, which air is controlled by damper 25, Figure 2. Such an arrangement may not be as effective in securing oversize relatively free of fines, but the arrangement is sim-. pler, in that the long by-pass pipes l9 and 2E may, under certain conditions, be entirely eliminated, thus reducing the cost of the classifier unit.

tweeir'the periphery and the outletpyifi the so-called down side of the classifier quently when thi plate is in the post at "B, the .c -ifugal force in th somewhat redl' Q and bee-nines distur product is not -flne as when the pin position-I9. A189, in this latter positi deflecting plate" divides into two zones the tion where the centrifugal action occurs and the portion where the oversize settles into the hopper by/hindered settling.

As afurther aid, in the case of certain materials and under certain conditions, the deflector 29 may be perforated as indicated at 35, and a second baiile 38, also perforated if desired, may be used to aid in the gradation of the products produced by permitting the air entering through pipe 2| to pass up in such volume through the opening ii that it spreads out into the hopper beneath the plate 29 and up through the perforations 36 so as to flow back toward the center of the classifier with an appreciable buoying force. In this manner a further hindered set- I tling eflect is secured which permits a definite they passthrough the opening II and out of the air lock 32.

While I have shown and described the preferred embodiment of my invention, I wish it to be understood that I do not conflne myself to the precise details of construction herein set forth by way of illustration, as it is apparent that many changes and variations may be made therein, by those skilled in the art, without departing from the spirit of the invention, or exceeding the scope of the appended claims.

I claim:

1. A method of classifying coarse materials and line materials comprising establishing a stream of an elastic fluid carrying coarse and fine materials, splitting said material-laden stream and imparting to one portion thereofa cyclonic motion to throw the coarse material to the periphery of the cyclonic path, reintroducing the other portion to the cyclonic portion adjacent the P riphery and intermediate the length of the cyclonic portion to oppose thereby the cyclonic motion, controlling the intensity of the cyclonic motion by varying the quantity ofmaterial-laden fluid so reintroduced, removing the coarse material from'the-cyclonic zone, and'removing the fluid freed otthe coarse material axially of the cyclonic path.

3 iiid from which oversize has been removed, means establish a cyclonic action of the fluid within he container thereby to throw out the oversize,

,means to withdraw a portion of the incoming material-laden fluid and to reintroduce it to the material-laden cyclonic fluid thereby 'to vary the cyclonic action, such withdrawn fluid being reintroduced adjacent the periphery of the materialladen cyclonic fluid, and means to discharge the removed oversize from the container. I

5. An apparatus as defined in claim 4 in which the axis of cyclonic action is substantially horizontal and in which the oversize is discharged from the container radially oi the axis, of the cyclone.

6. An apparatus as defined in claim4 in which the point of reintroduction of the withdrawn air is in the periphery of and intermediate the length of the cyclonic body of fluid and in a direction substantially opposite to the direction of the fluid in such cyclonic path.

7. A device as defined in claim 4 in which the axis of cyclonic action is substantially horizontal and in which the outlet for the fluid consists of a duct extending into the container axially of the cyclone. I

8. An apparatus as deflned in claim 4 in which the point of reintroduction of the withdrawn incoming fluid to the fluid in the cyclonic path is in substantially the same plane radially of the axis of the cyclone as the point of introduction of the main body of fluid to said path.

, 9. An apparatus as defined in claim 3 in which means are provided for introducing material-free fluid to the incoming material-laden fluid.

10. In an apparatus for classifying coarse and fine materials in an elastic fluid medium, a container, an inlet for the material-laden fluid, a damper adjacent the inlet for splitting the incoming fluid, baiile means to curve one of the split portions of fluid and to thereafter establish a cyclonic path for the fluid, the damper being so p0- sitioned that theother split portion recombines 2. A method as described in claim '1, in which the cyclonic path is established about a substantially horizontal axis, and in which the coarse material is removed from the cyclonic zone ra dially thereof. I v

3. Amethod as described in claim 1 wherein the coarse material thrownout of the stream falls from the cyclonic zone and in which additional fluid is passed counter-current to the movement of said coarse material in'a substantially hindered settling fluid columns 4. In an apparatus for sizing materials in an elastic fluid medium, a container having an inlet for material-laden fluid and an outlet for the with the first portion moving in the cyclonic path to vary the intensity of the cyclonic action, an outlet for-the fluid located axially of the cyclonic path, means located radially of the cyclonic axis to receive the oversize material removed from the fluid, a restricted discharge opening in the receiver for the oversize, and means-to pass a cleaning fluid through said opening in a direction counter to the oversize passing therethrough.

11. In an apparatus for classifying coarse and fine materials in an elastic fluidmedium, a container having an arcuate wall, an inlet duct, an

arcuate bailie concentrically located with respect to the arcuate wall, an outlet. duct spaced inwardly and concentrically with respect to said tion to split the incoming fluid and thereby decrease the cyclonic action of fluid within the container and to be moved to another position topermit recirculation of fluid intermediate the arcuate wall and baiiie, and a hopper member to "receive coarse material thrown outof the fluid.

12. In an apparatus for classifying coarse and flnematerials, a container, means for moving a body of materialladen elastic fluid in a cyclonic path therein to separate the coarse material from the fines by centrifugal action, a screen-like member forming a portion of the container and adapted to receive such separated coarse mate- I rial, and means for directing a stream of cleaning fluid through the screen-like member from the side opposite to that on which said coarse material is deposited and thence into the cyclonic path of fluid thereby to remove fines entrapped with the deposited coarse material and return such fines and cleaning fluid into said cyclonic path.

13. An apparatus such as described in claim 12 in which a hopper communicates with the container and in which the screen-like member is adjustably positioned with respect to the discharge opening from the container into the hopper to vary the size of such discharge opening.

14. An apparatus as described in claim 12 in which the screen-like member is adjustable with respect to the walls of the container to vary the volume of material-laden fluid moving in the cyclonic path.

15. A method of classifying coarse and fine rial, dividing the material-laden stream, impartingj'ft one of the divided portions a cyclonic motion separate the coarse from fine material, discharging the coarse material zfrom the zone of cyclonic motion, directing the other portion of the divided Stream to a region removed from the cyclonic path and into the path of the discharging coarse material to remove fine material entrained therewith, and thence into the cyclonic path to commingle with the fluid in said cyclonic path and discharging the fluid freed from coarse material axially of the cyclonic path.

16. A method according to claim 15 in which the separated coarse material is discharged from the cyclonic zone by gravity and in which the last-named divided portion of the stream is directed to the cyclonic path in a rising substantially hindered settlingfluid column.

HARLOWE HABDINGE.

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