US2897965A - Continuous vortical classifier - Google Patents

Description

Aug. 4, 1959 N. GOODWIN CONTINUOUS VORTICAL CLASSIFIER 2 Sheets-Sheet 1 Filed Sept. 8, 1953 INVENTOR. '/VORRI.$ 60 0 WIN M /II-1fl A TTORIVEV Aug. 4, 1959 N. GOODWIN commuous VORTICAL CLASSIFIER 2 Sheets-Sheet 2 Filed Sept. 8, 1953 IN VENTOR. A o/m/s Goopwnv AZ'TUR/VEV United States Patent 2,897,965 CONTINUOUS VORTICAL CLASSIFIER Norris Goodwin, San Francisco, Calif., assignor to Norris Goodwin and G. G. Sanders, San Francisco, Calif., jointly as trustees, and doing business as Goodwin Classifier Company Application September 8, 1953, Serial No. 378,707

3 Claims. (Cl. 209-211) The present invention relates to classifiers, and more particularly to the form in which solids suspended in liquids may be continuously separated into two fractions with great accuracy at a desired particle size.

It is known that in present practice classification is accomplished by gravity settling with varying degrees of agitation, such as may be found in the Dorr rake-type classifier or the Akins screw-type classifier. Machines of these types are incapable of making a truly sharp cut. For example, if a cut at 30 mesh is desired, the coarser fraction will still contain entrained fines, and considerable material coarser than 30 mesh will be carried over by and with the fines.

Classifiers of the centrifugal type, utilizing a free vortex system, are quite successful in handling material finer than 100 mesh. The action of these machines depends upon the establishment of a vortex which requires relatively high angular velocities, under which conditions cuts can easily be made at mesh size finer than 100. When the angular velocity is slowed, however, a true vortex does not form and no separation is possible since all material flows out through the underflow outlet at the bottom of the cone.

It is to be noted that existing gravity-type classifiers are designed and built for a given service where the volume of flow is balanced against settling area. They are thus inflexible and serve within a narrow range.

It has been found that in the range of particle sizes from 100 mesh to 6 mesh present machines are not capable of economically attaining such cuts, and, further,- that below 6 mesh, it is not usually economical to screen the material to obtain the classified sizing.

In material of the range of operation of intermediate classification, it is generally desirable to keep the underflow at a very low Water content, and such a requirement is not possible of attainment in the required commercial scale with equipment presently available for classification.

Accordingly, it is among the obejcts of the present invention to provide a vessel of small size and large capacity which will accomplish classification in the intermediate range and which will accurately make cuts from 100 mesh to 6 mesh.

Another object of the present invention is to produce a machine where initial classification is accomplished in a relatively slow vortex and where the remainder is then reclassified with a relatively faster vortex.

Another object of the invention is to produce a unit which is highly flexible and easily adjusted so that the classifying out can be varied as desired in all increments, either by the original adjustment prior to operation, or adjustment while in service.

A further object of the present invention is to provide a unit for making intermediate classifications of wet materials not based upon gravity settling, but controlled by the centrifugal forces acting within a separated inner chamber and above its upper extremity.

2,897,965 Patented Aug. 4, 1959 A further object is to provide a unit for intermediate classification comprising two concentric cylinders in which material is fed to and settles in the outer annular cylinder and at the bottom thereof is subject to a sucking action induced within the inner cylinder whereby a change of direction ofthe liquid takes place causing the heavier solid particles to pass out of the bottom, and forcing the major portion of the liquid together with entrained fines to pass upward through the inner cylinder where it is subject to a vortex action which returns undesired coarse'particles to the outer annular cylinder and delivers liquid with solids of desired fineness upwardly and outwardly.

Further objects are to provide a construction of maximum simplicity, economy and ease of manufacture, and also such further objects, advantages and capabilities as will fully appear and as are inherently possessed by the device and the invention described herein.

The invention further resides in the combination, construction and arrangement of parts illustrated in the accompanying drawings, and while there is shown therein a preferred embodiment thereof, it is to be understood that the same is merely illustrative of the invention, and that the invention is capable of modification and change and comprehends other details of construction without departing from the spirit thereof, or the scope of the appended claims.

Referring to the drawings:

Figure 1 is a vertical section taken on the line I-I of Figure 2 and looking in the direction of the arrows. In addition, this view shows a section through the inlet pipe, which would not appear in the normal vertical section. Figure 2 is a top plan view of the assembled device. Figure 3 is a transverse section taken on the line III-III of Figure 1 and looking in the direction of the arrows.

Referring now more particularly to the drawings, in which like reference numerals indicate like parts in the several views, and with particular reference to Figure 1, the device comprises a cylindrical shell 10 which has a conical bottom 11, culminating in an underflow outlet 12 and pipe coupling 12a located axially of the shell 10. The top of the cylindrical shell 10 is. provided with a frusto-conical cover member 14- having a central aperture which is defined by the lip or edge 15.

Coaxially within the shell 10 and substantially of the same vertical dimension, is the inner sleeve cylinder 17, which is tubular in shape and open at both ends. This inner cylinder 17 is spaced from the inner surface of the shell 10 and secured thereto by fins or vanes 18, 19 and 20. The vanes 18, 19 and 20 are preferably not horizontal, but are arranged at a downward pitch with respect to the direction of flow. All of their leading edges are higher and are onthe same horizontal plane, while the trailing edges are lower and also on the same horizontal plane. Since the vanes or spacers 18, 19 and 20 do not function in the process but are merely supports for the inner sleeve cylinder 17, they may be described as independent. The pitch is to make their presence cause as littleturbulence or diversion as possible, so far as the treatment or process is concerned. The shell 10 is pierced with a tangential feed inlet 21 in such a manner that the feed is directed against the lower surface of vane 20, or any other vane, with the result that the incoming flow, which is clockwise with respect to Figure 3, is constantly being directed downwardly with little or no opportunity for the incoming feed to mix with the flow already within the shell above the plane of the vanes. If the fins or vanes are placed in a substantially horizontal position then the feed is likewise, delivered below them.

The central cylindrical member 17 at both top and bottom is provided with aninner cylindrical sleeve 22 and 23, respectively. Both of these sleeves areprovided with suitable meanslnot shown) for raising or lowering them to increase the effective lengthof'the tubularjrriem ber'17, either at the top or'th'e bottom, or bothl Surrounding the top portion of the shell and'comf pletely around the cover member 14 is a launder 24 with its chamber so shaped as to provide a gravity delivery to'an overflow outlet 25. The overflow from thetop 14 is over the lip 15. p i V Mounted axially within the central tube'17 is an axial flow impeller 26, which is driven by shaft 27, passing axially up throu'gh'the aperture defined by the lip 15 in the cover 14, and driven by a source of power which is not shown. v Impeller 26 is an axial flow impeller rotated in such a manner that the flow is upward, as indicated by p j the arrows 28. If greater control is desired the'imp'elle'r rejection of coarse material in a horizontal plane, partly due to the centrifugal action'in the relatively slow vortex of chamber 30, and partly due to the change in direction induced by the suction to the central chamber 31. As the particles near the lowerend of the cylinder 17, they come under the influenceof the suction and tend to change their downward path to'a' lateral and upward path, This change of direction causes the larger particles 'to be'rejected. Second, as the remaining liquid andtits 'suspendedimaterial is sucked up by the rotation of the axial flow impeller 26, a relatively faster vortex is created which is complex in its nature. Because of the rotation of the impeller 26, a horizontal spiral vortex is created which. moves upwardly. This produces a resorting of a middling fraction which is rejected to the outer chamber and mixed with the incoming feed. At the same time, because the rejected material is delivered in the, space between the top 14- and the upper edge of the cylinder 17 in an arc of 360 and the feed material comes around the bottom edge of the cylinder 17, or its respective extensions 22 and 23, in an arc of 360", there is a continuous vertical rotation in combination with the it: lateral spiral. It is apparent that the flow of liquid thereof in the chamber 30, which is defined by the inner surface of the shell 10 and the outer surface ofthe central tube member 17. The tangential inlet is not n'ecessary either to establish or insure the slow rotary motion of the material within the outer chamber 30, which motion will be induced by the axial flow impeller, elsewhere described, even with radial entry of feed. This slow rotary motion tends to throw the heavy and oversize material with entrained fines outwardly and downwardly; This oversized material will pass downwardly to the conicontrol 'the operation and particle size of the cut.

cal bottom 11, passing along the slope thereof and eventually out through the underflow pipe outlet 12. It is to be noted that while the feed to the unit may be led through the tangential orifice 21 to induce gentle rotation of the material being treated, no attempt is made to constrict this orifice for the purpose of contributing rotational energy, as is done in the more conventional cy clone separators. This not only eliminates a vulnerable point of wear and variation of operation, but allows full control of the energy contributed to the system through the axial flow impeller 26.

The downward travel of the material in the chamber 30 is subject to the sucking or pulling action iridu ced by the axial flow impeller 26 which is continuously being rotated within the inner sleeve 17 in chamber 31. This with its suspended, solids is continuously fed into the inlet pipe 21 and continually subjected to the relatively slow vortex in chamber 30, Where the initial classification is made. Third, the overflow of fines or classified material moves upward and over the lip 15 and is gathered in the launder 24 from whence it is delivered to the outlet 25.

It is apparent that there are several readily controllable features of this eq uipment, the regulation of which will One ofthese is the rate of rotation and/or pitch of the impeller 26. The faster the rotation, usually, the finer the cut and the drier the underflow, although this is not a hard and fast principle. In any event, the rate of rotation ofthe impeller 26 governs the activity of the clasvortex in'the cylinder 17.

suction'serves to lift the liquid, together with the fine solids, and also reduces the static head at the outlet 12. It is apparent that the vortex in the chamber 30 is relatively slow, while that in chamber 31, on the interior of the tubular member 17, is much higher. The true vortex created by the impeller 26 and established in chamber 31 passes upwardly. Here a secondary classification or sorting takes place. The larger or coarser entrained particles move to the wall of chamber 31 and as they reach the top of the cylinder 17 or its extension 22, are rejected back to the feed over the top edge 32 and are returned to the relatively slower vortex of the material within chamber 30. Their vortex is further slowed by the presence and resistance of the angled vanes 18, 19

and 20, which causes the larger particles to pass down-' wardly in chamber 30 and become comingled with the incoming feed for reclassification with the rejected paricles passing to the bottom and out through the underflow outlet 12. The liquid phase containing the classified cuts passes out and overflows over the lip 15 and is collected by the launder 24 and delivered to the liquid outlet 25. e v I It is apparent, from the operation of this device, that there are three active phases of classification. First, the

sification'in the sleeve cylinder 17. The axial flow impeller serves two functions, i.e., to'create a suction at the lower end of the machine, and to create and maintain a It has been found that by regulating the speed and/or pitch of the impeller, and hence the degree of suction, air can be drawn through the bottom outlet 12. When this condition is established the relatively dry coarse material slowly passes: out through the overflow outlet 25.

It is also apparent that the cut and the operation of the equipment may be regulated by controlling the rate of feed. It is, of course, true that by increasing or decreasing the rate of feed, the relatively slow vortex within chamber 30 may be in'creased'or decreased, as desired. While the'volume of primary feed controls the volume of overflow, it is to be particularly noted that it' does not control the particle size of the solids in the overflow since the separation is 'not'based on gravity settling, but is controlled by 'the centrifugal forces acting within the sleeve and above itsupper extremity.

' Another means for making this device thoroughly flexible is that the cut may be controlled by the relative movement in or out of the extension members 22 and 23.. For example, as the height of the member 22 is extended to increasethe height of the sleeve cylinder 17, the ,closerhit approachesto the top of the-member 17, making the overflow channel 33 increasingly narrower. Obviously, if'the member 22 is extended so that it contacts the top, closing the overflow aperture 33 entirely, then all of the material subject to reclassification will pass off through the launder 24 and out the overflow outlet 25. Widening or narrowing the opening or passage varies the time and opportunity for particles to pass 30. The width of the band passing over increases as the space is increased.

It seems clear fi'om a description of the operation that means has been provided for securing and controlling a cut of classifiable solid material suspended in a liquid, which can easily be controlled either at the time of the original setting for the operation, or during the operation if conditions change and warrant such regulation.

The present invention has its optimum operating characteristics in producing sharp cuts of a range of from 100 mesh to 6 mesh.

It should be pointed out, that, although the invention does not apply a vacuum and none can be obtained because of the opening in the top of the cover, neverthe less, the device may be operated without necessity of a valve at the outlet 12. By rotation of the axial flow impeller 26, a suflicient suction can be created which would relieve pressure on the outlet 12 at the bottom. While this can be done, it is preferable to use a valve on the outlet 12, which is not shown, which will permit the impeller to operate at slower rotational speeds than would be possible without it, While still controlling the percentage of water in underflow.

Because of the continuous nature of the feed and because of the special types of flows and vortexes set up within the container 10, a relatively small tank is required for the handling of tremendous volumes. While direct capacity comparisons are diflicult to establish, for example when operating on a slurry of 30% pulp density and making a 35 mesh cut, a device which is 18" in diameter and less than 3' from top to underflow coupling 12, is sufficient to handle in excess of 150 gallons of feed per minute. This capacity is greater than a 24" helical screw mounted in a tank 15 long.

Because of the suction created by the rotation of the impeller 26, the material reaching the underflow outlet 12 has a very low water content, which may be below 40% water by weight.

While the inletpipe or orifice 21 has been described as being tangential, this positioning is not essential and it may be radial. It is the impeller which establishes and maintains the vortexes in the classifier, even in chamber 30, and the movement is not dependent upon the method of introducing the feed.

I claim:

1. A wet classifier comprising in combination a cylindrical shell having a conical bottom and a top each tapering axially to a reduced diameter, a central underflow outlet in said bottom and a central overflow outlet in said top over the lip thereof, a cylindrical sleeve member of substantially the same diameter as said top outlet interior of said shell concentric therewith and projecting into said conical bottom and top but spaced axially therefrom, providing an annular chamber and an inner chamber, solid lateral spacer members in said annular chamber adjacent the top thereof securing said sleeve to said shell, an axial flow impeller mounted adjacent the lower end of said sleeve for rotation in a plane perpendicular to the wall of said sleeve and a feed inlet through said shell to said annular chamber below said spacer members.

2. A wet classifier comprising in combination a cylindrical shell of substantial height having a conical bottom and a top each tapering axially to a reduced diameter, a central underflow outlet in said bottom and a central overflow outlet in said top over the lip thereof, a cylindrical sleeve member interior of substantially the same diameter as said top outlet of said shell, concentric therewith and projecting into said conical bottom and top but spaced axially therefrom, providing an annular chamber and an inner chamber, solid lateral spacer members, each directed downwardly in the direction of flow, in said annular chamber adjacent the top thereof securing said sleeve to said shell, an axial flow impeller mounted adjacent the lower end of said sleeve for rotation in a plane perpendicular to the wall of said sleeve, and a tangential feed inlet through said shell to said annular chamber below said spacer members.

3. A wet classifier comprising in combination a cylindrical shell of substantial height having a conical bottom and a top each tapering axially to a reduced diameter, a central underflow outlet in said bottom and a central overflow outlet in said top over the lip thereof, a launder associated with said overflow outlet, a cylindrical sleeve member of substantially the same diameter as said top outlet interior of said shell, concentric therewith and pro jeoting into said conical bottom and top but spaced axially therefrom,'providing an annular chamber and an inner chamber, solid lateral spacer members, each directed downwardly in the direction of flow, in said annular chamber adjacent the top thereof securing said sleeve to said shell, an axial flow impeller mounted adjacent the lower end of said sleeve for rotation in a plane perpendicular to the wall of said sleeve, and a tangential feed inlet through said shell to said annular chamber below said spacer member.

References Cited in the file of this patent UNITED STATES PATENTS

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