US2776053A - Hydraulic separating apparatus and method - Google Patents

Description

Jan. 1, 1957 K. KREBS 2,776,053

HYDRAULIC SEPARATING APPARATUS AND METHOD Filed Jan. 28, 1954 2 Sheets-Sheet l INVENTOR. A///09 A lb5 BY HTTORNEYS Jan. 1, 1957 K. KREBS 2,776,053

HYDRAULIC SEPARATING APPARATUS AND METHOD Filed Jan. 28, 1954 2 Sheets-Sheet 2 PIE E INVENTOR. AJ/ogy yrs-b5 A TTORNE Y5 HYDRAULIC SEPARATING APPARATUS AND METHOD Kellogg Krebs, Palo Alto, Calif., assimior to Equipment Engineers, Inc., San Francisco, Calif., a corporation of California Application January 28, 1954, Serial No. 466,785

6 Claims. (Cl. 209-211) This invention relates generally to methods and apparatus for the treatment of liquid feed materials to effect a hydraulic separating or classifying operation.

It is well known that the principles of a vortex can be used for effecting hydraulic separating or classifying operations. Conventional apparatus for this purpose (see for example Bretney 453,105) confines all or a large part or the liquid body to conical form, with removal of overflow through a pipe opening into the central portion of the chamber, and removal of undertlow through a passage leading from the small lower end of the cone. Without confinement the vortex has a cylindrical dynamic pattern, and is of constant strength throughout its entire length. I have observed that confinement in a conical chamber imposes a modification upon the cylindrical dynamic pattern, and although it serves to density the underfiow, it introduces certain objectionable features. Particularly it contributes to turbulence within theseparating zone and this in turn tends to detract from sharpness of separation and over-all separating capacity and performance. In addition it is a contributing factor tending to cause tramp oversize material to find its way into the overflow.

In general it is an object of the present invention to provide a method and apparatus making use of the vortex principle, but which employs this principle in such a manner as to make possible better over-all separating performance, and particularly to obtain sharper separation and greater capacity for a specified separating operation.

Another object of the invention is to provide a method and apparatus of the above character which makes possible a densitying action, while at the same time avoiding the detrimental efiects of a conical shaped chamber such as is used in prior types of vortex separating equipment.

Another object of the invention is to provide a method and apparatus of the above character having improved means for introducing the feed material into the body of material undergoing centrifugal treatment.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure l is a side elevational view partly in section, illustrating apparatus incorporating the present invention.

Figure 2 is a plan view of the apparatus shown in Figure 1.

Figure 3 is a cross-sectional view taken along the line 3-3 of Figure 1.

Figure 4 is a cross-sectional view taken along the line 44 of Figure l.

The invention as illustrated in the drawings consists of primaiy and secondary separating and densifying devices A and B. Device A is constructed to effect a nited States Patent Patented Jan. 1, 1.957

separating operation by the use of a true vortex, while device B serves to density the underflow.

Device A consists of a housing 10 which is shaped to provide a cylindrical interior. To facilitate manufacture, the side walls of the housing can be made in the several separable sections 11a, 11b and 110. Assuming that the apparatus is used in upright position as shown in Figure l, which is generally the case, section 11a is formed for the introduction of feed material. Section 11b forms the main intermediate cylindrical part, while section forms the lower part and is provided with a passage for delivering material into the device B. The several housing sections are suitably bolted together and to the end plates 12 and 13. Thus cap screws 14 clamp the end plate 12 to a flange on the section 11a, and cap screws 15 connect adjacent flanges on sections 11a and 11b. Bolts 16 connect a flange on section 1111 with the end plate 13, thereby clamping these parts against the sides of section 110.

A conduit extension 17 serves to introduce feed material into the upper part of the housing chamber 18, and the passage 19 provided by this conduit is preferably shaped as illustrated in Figure 4. Note particularly that instead of having a linear inlet passage which communicates tangentially with the chamber, the center line of the passage is curved on a gradually decreasing radius. The purpose of this arrangement is to gradually increase angular velocity as the material flows through the conduit and until the angular velocity is increased to that existing within the chamber 18.

A pair of aligned pipes 21 and 22 extend coincident with the longitudinal axis of the chamber, and have their inner open ends 23 and 24 axially spaced. Suitable means such as the flanges 26 and 27 can be provided for mounting these pipes upon the end plates 12 and 13. The exterior ends of these pipes are connected to suitable means, such as a common conduit, for continuous removal of overflow material. For the vertical positioning of the apparatus illustrated in Figure 1, the end 23 of pipe 21 is at a level below the zone into which feed material is being introduced.

The ends 23 and 24 of the pipes 21 and 22 should be sufliciently far apart whereby flow into one pipe does not disturb flow into the other. In practice a spacing such as illustrated gives good results, or in other Words the spacing can be of the order of from 2 to 3 times the internal diameter of the pipes. It is desirable to line the side and end walls of the housing with layers 25 and 30 of natural or synthetic resilient rubber, to minimize erosion of the metal.

The hydraulic separating device A just described has a direct connection with the densifying device B. The densifying device preferably is of the cyclone type, or in other words a substantial part of its confining chamber 28 is conical shaped. The particular device illustrated consists of separable body sections 2% and 2%, which are secured together by suitable means such as bolts 31. The section 11c of the separating device 10 is provided with a lateral extension 11d, which is clamped by means of bolts 32 between the end plate 33 and the housing section 29a. A liner 34, which can be made of suitable material such as natural or synthetic rubber, is fitted within the housing and is shaped to provide the inner conical shaped portion 35, and the upper substantially cylindrical shaped portion 36, the latter portion being within the extension 11d. A flow passage 37 connects the two devices A and B, and can be formed substantially as illustrated in Figure 3. Thus it communicates tangentially with a peripheral portion of the main cylindrical chamber 18, and delivers material tangentially into the annular or cylindrical portion 36 of the device B. Note from Figure 3 that the arrangement is such that for clockwise rotation of material in chamber 18, the body of material in chamber 28 is caused to rotate counterclockwise.

The resilient rubber liner is provided with a lower opening 41 for the discharge of heavier separated material or underfiow. In order to control the size of this opening, it is formed in a resilient extension 42 of the liner, and this extension fits within a conical opening formed in the sleeve 43. This sleeve in turn is slidably fitted within the slotted housing section 2%, and is connected by pin 44 with the operating arm 46. One end of arm 46 has a pivotal connection 47 with the stationary housing section 2911, while its other movable end is adapted to be adjustably clamped to a slotted arm 48, the latter having a pivotal connection 4B to the housing.

Overflow is removed from the device B through the pipe 51, which extends concentric with the axis of the device and through the end wall 33. The inner open end 52 is located below the level of the Zone into which the passage 37 introduces material. Exterior pipe 53 delivers the overflow material to any place desired, and may be provided with an adjustable flow control valve.

Operation of the apparatus described above is as follows: A suitable pump, such as one of the centrifugal type, has its discharge side connected to the conduit 17 for introducing feed material. It will be assumed that the feed material is a slurry or pulp consisting of water together with coarse and fine solids, which are to be separated. Many metallurgical slurries or pulps are of this type, and consist of coarse particles like sand, together with finely divided slime solids. It is assumed that the pump delivers the feed material into the main cylindrical chamber 18 with considerable velocity, and at a substantial hydrostatic pressure. With the cylindrical chamber 18 filled with material undergoing treatment, kinetic energy is transferred to this body by virtue of the incoming stream of material to cause the body to be maintained in continuous rotation about the central vertical axis. At the lower end of the cylindrical chamber, that is at the end which is remote from the point of introduction, material discharges continuously through the passage 37 with substantial velocity, and is delivered into the interior of the device B. The body of material within the device B is likewise in continuous rotation about its central vertical axis, although the vertical action is modified by its conical shaping.

Within the cylindrical chamber 18 the material rotating about the central axis is subjected to centrifugal separating forces, with the result that the heavier material tends to progress outwardly towards the side walls of the chamber, to be discharged into the device B. A continuous overflow draw-off is established by way of the pipes 21 and 22, and this draw-off carries away the bulk of the lighter solids, such as the slime solids referred to above in metallurgical pulp. This draw-off is regulated as desired by suitable means such as valves (not shown). Within the device B the rotating body of material subjects the solids to separating forces with collection of the heavier solids into the lower conical portion of chamber 28, from which they can be withdrawn as a relatively dense underflow, through the opening 41. A continuous overflow is established through the pipes 51 and 53.

As described above in the primary hydraulic separating device A there is a relatively true vortex, whereby sharp separation can be maintained between the heavier and lighter solids. Sharp separation is aided by virtue of the fact that turbulence is not occasioned by imposing a conical shaping upon the rotating body of material, as in prior types of equipment. Likewise a minimum of turbulence is caused by introduction of the material into the rotating body, and this is established by virtue of the shaping of the inlet passage 19, which gradually subjects the material to increasing angular velocity. The

angular velocity of the material within the primary device A remains substantially the same throughout the entire length of the cylindrical chamber. Within the region of the discharge passage 37, the heavier separated solids are virtually taken oif the peripheral surface of the cylindrical chamber, for delivery into the treatment chamber of the secondary device B. Within the chamber of the device B the material rotates with angular velocity substantially greater than that within the cylindrical chamber. By virtue of such increased angular velocity, and also because of the conical shaping, the device B is well suited for dewatering the underflow from the device A, or in other words for densifying the underflow.

By way of example, in one particular instance a machine was constructed as illustrated in the drawing, and with dimensions as follows: The cylindrical chamber of device A had a diameter of 10 inches, and a length of 18 inches. Inlet passage 19 had a diameter of 2 /2 inches, and was connected to the discharge side of a centrifugal pump. Pipes 21 and 22 had an internal diameter of 2 inches, and the opposed ends 23 and 24 were 3 inches apart. Passage 37 had an effective cross sectional flow area of 0.7 square inch. The upper part 36 of the chamber in secondary device B had a diameter of 4 inches, and an axial length of 12 inches. The conical portion 35 of the chamber had a length of 10 inches, and large and small ends of 4 and 1 inches respectively. Passage 37 had an effective cross sectional flow area of 1 square inch. Pipe 51 had an internal diameter of 1% inches.

The above apparatus was operated on a metallurgical slurry containing solids ranging in size from 14 to 325 mesh. A centrifugal pump was arranged to deliver this feed at 142 gallons per minute (G. P. M.), at a static pressure of 20 p. s. i. Twenty eight (28) G. P. M. of recycled secondary overflow (i. e. overflow from pipe 53) were supplied to the inlet of the pump and delivered to the apparatus together with the 142 gallons, making a total feed of 170 gallons feed per minute The results obtained are tabulated as follows:

Feed Overflow Underflow G. P. M 142 120 10 Percent Solids... 27 17 74 Tons per Hour. t 0 5. 4

Percent Percent Wt. Wt

It is evident from the above data that a sharp separation was maintained for a relatively high operating capacity. No material coarser than 200 mesh was found in the overflow. For 325 mesh, only 2.5% was found in the overflow. For material finer than 325 mesh, 97.4% of the same passed out in the overflow. For the inlet pressure mentioned above of 20 p. s. i., the pressure into the secondary device B was 18 p. s. i., thus demonstrating that the primary separating device functions in accordance with a true vortex.

Back pressure in the cylindrical chamber of device A is maintained by virtue of the back pressure imposed by the device B, and such back pressure in turn is maintained by virtue of the greatly increased angular velocity of the material, and by controlling the opening 41 together with discharge through pipes 51 and 53.

It will be noted that the two devices A and B cooperate together in a particular manner to secure the desired results, while at the same time avoiding such interaction as might interfere with the desired separation. Particularly it will be noted that although cyclonic action in a conical chamber is employed in the densifying device B, this action does not in any way cause turbulence within the cylindrical chamber of device A, and therefore it does not in any way interfere with separation by virtue of true vortex action.

It should be noted that in the stream discharging through passage 37, there is a distribution of solid material corresponding generally to what exists within the lower part of the centrifugal chamber. In other words coarser and heavier material tends to remain on that side of the passage 37 corresponding to the outer peripheral surface of the cylindrical chamber. Because of the opposite direction of rotation in the secondary device B, the distribution of solids being introduced into the device B changes, whereby the coarser and heavier solids move outwardly under centrifugal force, with some remaining fine and lighter material passing out with the overflow through pipe 51. The action just described facilitates a further separation between lighter and heavier solids within the device B, and in particular tends to remove and separate the lighter solids which may have attached themselves to the coarser and heavier material.

I claim:

1. In a separating method for effecting a separation between solids of diflerent separating characteristics in a liquid feed, the steps of continuously supplying the feed to a body of the same, confining the body to substantially cylindrical form, causing the body to rotate with cylindrical symmetry to thereby form a substantially true vortex, removing an overflow from a region adjacent the axis of the rotating body, continuously removing an underflow stream from a peripheral portion of the body, said underflow stream containing heavier centrifugally separated solids, causing :said underflow stream to be introduced tangentially into a body of the same without substantial reduction in velocity, causing a substantial part of said last named body to be confined to conical form with swirling about the axis of the same, removing underflow solids from the smaller end of the last named body, and continuously removing -a liquid fraction from a region near the axis of the last named body.

2. A method as in claim 1 in which the last named body is of a diameter relatively small compared to the first named body.

3. In a hydraulic separating apparatus of the character described, means forming a substantially cylindrical treatment chamber, means for introducing feed material tangentially into a peripheral portion of said cylindrical chamber to rotate the body of material therein about the longitudinal axis of the chamber, said rotation serving to effect centrifugal separation between heavier and lighter solids in the feed, means for withdrawing overflow from a region near the longitudinal axis of the cylindrical chamber, a secondary densifying device, and means forming a flow passage for directly delivering material from a region near the periphery of the cylindrical chamber to said densifying device, said last named region being spaced from the region in which the feed material is introduced, the spacing being in a direction longitudinally of the chamber, said densifying device comprising means for 6 centrifugally separating a liquid fraction from the heavier separated solids.

4. Apparatus as in claim 3 in which said secondary device comprises means forming a cyclonic treatment chamber having a substantial conical portion, means for removing the heavier separated solids from the smaller end of the chamber, and means for removing liquid from a region near the axis of said chamber.

5. In hydraulic separating apparatus, means forming a substantially cylindrical treatment chamber, means for introducing feed material tangentially into a peripheral portion of said chamber whereby the body of material undergoing treatment within said chamber is caused to rotate about the chamber axis, a pair of pipes extending axially into said chamber through opposite ends of the same, the inner ends of said pipes being open and being spaced apart whereby centrifugally separated overflow may progress from the interior of the cylindrical chamber into said pipes, a secondary densifying device, means forming a flow passage establishing communication with another peripheral portion of said cylindrical chamber and serving to deliver material from said cylindrical chamber to said secondary device, said secondary device comprising a housing forming a centrifugal cyclonic treatment chamber, and means for withdrawing underflow solids and a liquid fraction from the last named chamber, said last named chamber being connected to said passage tangentially and being of a diameter substantially less than the diameter of the cylindrical chamber.

6. In a hydraulic separating apparatus, means forming a substantially cylindrical treatment chamber, means for introducing feed material in a general tangential direction into a peripheral portion of the chamber adjacent one end thereof, whereby the body of material undergoing treatment within the chamber is caused to rotate about the axis of the chamber, at least one pipe extending axially into the feed chamber, the inner end of said pipe being open whereby a separated overflow may progress from the interior of the chamber into said pipe, at secondary densifying device disposed adjacent said chamber, means forming a flow passage establishing direct communication between another peripheral portion of said cylindrical chamber and said densifying device and serving to deliver material from said cylindrical chamber to said secondary device, said last named peripheral portion being adjacent that end of the cylindrical chamber remote from said first named peripheral portion,

said secondary device comprising a housing forming a centrifugal cyclonic treatment chamber, said last named flow passage extending substantially tangentially to both said cylindrical chamber and said cyclonic treatment chamber, and means for withdrawing underflow solids and a liquid fraction from said cyclonic treatment chamber, said cyclonic treatment chamber being of a diameter substantially less than the diameter of the cyclonic chamber.

References Cited in the file of this patent UNITED STATES PATENTS 474,490 Walter May 10, 1892 762,866 Allen June 21, 1904 1,517,597 Stebbins Dec. 2, 1924 2,008,643 Lockett July 16, 1935 2,533,074 Weinig Dec. 5, 1950 FOREIGN PATENTS 502,453 Belgium Apr. 30, 1951

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