US2102525A - Separation of solid particles from fluids - Google Patents

Description

H. FREEMAN Dec. 14, 1937.

SEPARATION OF SOLIlj PARTICLES FROM FLUIDS ATTORNEYS m RM 0 6 T 6 NE F V m e w w H JI/M /M Original Filed March 13, 1936 Patented Dec. 14, 1937 SEPARATION OF SOLID PARTICLES FROM FLUIDS 1 Horace Freeman, Three Rivers, Quebec, Canada, assignor to Nichols Engineering & Research Corporation, New York, N. 1L, a corporation of Delaware Continuation of applications Serial No. 68,667,

March 13, 1936, and Serial No. 111,578, November 19, 1936. This application August 24, 1937, Serial No. 160,578. In'Canada March 11, 1936 18 Claims. (Cl. 92-28) This invention relates to the separation of solid or heavier particles, such for example as impurities from liquids, the classifying of fluid suspensions, and apparatus for such purposes.

' This application comprises a continuation of my applications Ser. No. 68,667, filed March 13, 1936, and Ser. No. 111,578, filed November 19, 1936.

Among other uses, for the separation of fluid suspensions, the invention is particularly adapted for the separation of impurities from suspensions of paper-making stock or other fibers in water. Such impurities usually include particles very close in specific gravity to both the fiber and the water itself, and hence the problem of thoroughly removing such particles to the extent necessary for making satisfactory paper, is generally diflicult and expensive. For example, such impurities may include ground particles of the knotty portions of wood and the like. Other impurities generally only slightly less difficult to adequately remove, comprise fine grit as from the pulp grinders, sand, silt, scale, sawdust, and compacted lumps of pulp, pitch or rosin.

Some paper pulp suspensions may also embody China clay, the removal of which with the impurities is to be avoided. The present invention is particularly adapted for the removal of impurities from suspensions of China clay, and also from such suspensions with pulp, without danger of removing the desiredfine China clay, while at the same time any oversize particles of the clay, which would be as troublesome as impurities, are readily removed. The invention is also well adapted for the refining or classifying of a large variety of materials similar to China clay suspensions.

Heretofore in preparing pulp for paper manufacture, the removal of impurities and oversize particles such as above referred to, has generally involved more or less elaborate apparatus, expensive and sometimes troublesome to maintain and operate. Yet if particles of sand or the like are not quite thoroughly removed from the papermaking stock, substantial percentages of the paper product will be marred by imperfections and has to be discarded. Also the rollers of the papermaking machines as well as the lithographing andprinting plates, etc., will be scarred or-subjected to excessive wear. One of the objects of the present invention is to eliminate substantially all of these troublesome impurities from paper-making stock with a method and apparatus which is uniformly dependable, and inexpensive in operation.

It has previously been the practice in paper mills to effect the partial separation of such impurities by causing the suspension to flow at reduced speeds into settling troughs provided with riflies, but the separation in these devices is far from complete. It has also sometimes been the practice to use centrifugal force to increase the inertial reaction and for this purpose the sus-" pensions have been passed into rapidly rotating mechanical devices which of necessity are of complicated construction, expensive to erect and maintain in operation. The present invention on the other hand, while utilizing centrifugal force, does not require any moving mechanical parts other than a pump to impart pressure to the stream of the suspension being treated. Accordvortices. While it has heretofore been proposed to remove relatively heavy particles, such as sand, from water supplies by the establishing of a vortex in the water, such problem has not involved the difiiculty of retaining material such as paper pulp and China clay in the suspension, nor the problem of such complete removal of the particles of impurities as is required for uniformly satisfactory paper stock. It has also been proposed to remove particles of heavy impurities, from paper pulp by establishing a vortex in a stream of the stock,'but prior to this invention such attempts have been unsuccessful in removing the impurities to a degree such as to make possible a perfected paper product-unless supplemental apparatus is provided for removing the finer and lighter impurities.

While for the above reasons the invention is particularly useful for paper pulp cleaning, important features of the invention are useful for treating various other forms of fluid suspensions for the purpose of classifying the suspended materials or removing undesired portions thereof.

Various further and more specific objects, features and advantages will more clearly appear from the detailed description given below, taken in connection with the accompanying drawing which form a part of this specification and illustrate merely by way of example certain preferred forms of the apparatus of the invention.

The invention consists in such novel features, arrangements and combinations of parts as may be shown and described in connection with the apparatus hereindisclosed. and .also such novel methodsas are disclosed and described hereinafter.

In the drawing Fig. 1 comprises a vertical sectional view of one unit-of the apparatus embodying the invention and in which the method of the invention maybe carried out;

Fig. 2 is an enlarged vertical sectional view of a portion of the apparatus of Fig. 1 and illustrating somewhat schematically the form of. the vortices established within the device;

Fig. 3 is a plan view illustrating the manner of connecting a plurality of the units of the apparatus;

Fig. 4 is a vertical sectional view of a portion of the apparatus in a modifled form; and

Fig. 5 is a vertical sectional view of an alternative embodiment of the apparatus.

The apparatus of Fig. 1 may includea head piece Ill comprising ior example a-casting provided with an inlet connection as at II in the form 01' a somewhat tapered nozzle discharging tangentially into an annular, space 12, of somewhat spiral form and surrounding an outlet connection as at It. The.outlet connection may comprise a-trumpet-shaped pipe located axially of the head piece with its lower and more restricted end as at ll extending substantially below the inlet connection.

The main body of the device may comprise an upper cylindrical section or chamber as at II and a lower chamber as at ll preferably similar to the upper chamber, although not necessarily so. An apertured disc as at I! may be interposed transversely between the chambers I! and i6.

This disc is preferably formed of a pliable sheet This disc may initially be flat, as indicated by" of rubber or other flexible or suitable material.

the dotted lines, or if desired it may be made normally somewhat conical as shown in full lines.

The conical form of the disc is shown somewhat is generally preferably made somewhat less than i "the diameter of the restricted outlet I4 and in the neighborhood of three-eighths of the diameter of the chamber Ii.

While the disc n if desired may be made of relatively rigid hard metallic sheet material, it

- has been found that if the material being treated embodies much sand or grit, such a metallic disc will be rapidly worn away, whereas a rubber or yieldable disc or partition member will withstand the highly abrasive action of the sand for very long periods without noticeable wear. The use of a rubber or other pliable disc is also of an advantage in that it tends to automatically assume such a conical shape or sagging position under the pressures of the vortices hereinafter described, as will result in very eflective action in permitting proper downward movement and separation of the impurities from the liquid within and around the zone of the disc, and causing the impurities to be entrapped below the disc and prevented from rising to the outlet i4.

At the lower end of the chamber it another transverse apertured disc or partition as at is may be provided, which also may be of rubber neath the disc I! and preferably, although not necessarily, this chamber is in the form of an inverted cone as shown.

The various chamber portions of the device as above described may be secured together and to the head piece as by flanged connections as shown, the flanges being suitably bolted or otherwise secured together in any desired well-known manner.

The lower end of the conical chamber 22 may be connected through a normally open valve as at 23 to a waste pipe 24 including if desired a length of transparent tubing which forms a "sight glass" in which the waste material may be viewed as it settles through the clear quiescent liquid at this point. The lower end at the waste pipe 24 may be connected to a waste receiver or reservoir as at 25 which may be made of metal or may comprise a glass bottle. This chamber which is kept sealed during the normal-operation of the equipment, is initially fllled with clear liquid such as water, to provide a collecting chamber for the waste material which gradually displaces the water. The waste receiver or chamber 25 may be provided with an air discharge cook 26 and with a water pipe connection as at 21. If desired, the lower end of the receiver 25 may be provided with a valved outlet as at 20.

The operation oi the device of Fig. 1 will be The prepared pulp suspension or other fluid suspension to be treated may be conducted into the inlet ll under a substantial pressure created by a suitable pump for example. Since the suspension is discharged from the inlet ll tangentially into the'annular space l2, it will be forced downwardly in a spiral path-i. e. more speciflcally a substantially helical path, forming an annular body of the suspension as at 3|. It will 'be noted that the outer surface of the downwardly rotating body, of the suspension 30 is substantially cylindrical all the way from the head piece nearly down to the disc or partition I1, and this body will occupy all of the space within the chamber I 5 except for a central or core section occupied by an upwardly moving vortex 3i hereinafter described. The outer vortex or body of suspension 10 is so restricted and subject to pressure conditions such that the angular velocity therein about the central vertical axis of the device will be quite rapid, with the result that the centrifugal force causes the solid and heavier particles of impurities to be thrown outwardly toward the walls of the chamber l5. Since the vertical dimension of the body 30 is relatively great as compared with its diameter, for example atleast in the neighborhood of from four to flve times as great, this centrifugal action on the particles of impurities will be quite prolonged. This will insure that the heavier particles in all portions of the downwardly moving body of the fluid suspension will have opportunity to move close to the walls of the chamber, notwithstanding that from time to time portions of pulp for example, may momentarily tend to obstruct this desired movement of the heavier particles. Then as the fluid in the vortex 3'0 approaches the disc ll, it will be forced inwardly toward the axis of the device,

, and at the same time the heavier particles will be drawn-downwardly and along the inside surfaces of the chamber l5 and then radially inwardly along the upper surface of the disc I! toward. the central aperture l8. As the fluid thus comes into the neighborhood of the aperture l8,a small inner portion thereof (practically free of impurities) may be deflected upwardly into the central vortex 3!, but the greater part of the fluid will be passed as an annular downwardly moving helix or vortex through the aperture l8. As a result of the restriction interposed by the aperture IS, the angular velocity of this downwardly moving helix will be greatly increased, thus insuring that substantially all of the particles of impurities therein, together with particles previously expelled to the outer surfaces of the helix, will be passed through the aperture l8 at the very periphery thereof. Once these particles have passed through the aperture 1 8, the disc I! serves to entrap them against their returning up into the chamber l5.

7 The orifice I8 is such as to offer only a momentary restriction to the flow, allowing the vortices to almost immediately expand again andadapt themselves to the contour of the chamber.

Below the aperture ill the helical downwardly moving body or vortex will expand in diameter as indicated at 30' and continue in the form of another hollow substantially cylindrical body rotating downwardly to a point near the zone of the lower disc IS. The outer vortex within the chamber I6 will still retain suflicientcentrifugal effect to maintain the particles of impurities near the walls of the chamber I 6 as they settle or are carried toward the disc I91 disc l9 centrally and upwardly to form an inner upwardly moving helix or vortex 3|.

The particles carried through the aperture or apertures 21 will settle to the bottom of the conical chamber 22 and the relatively small amount of fluid passing down through the apertures 2| will find a return passage upwardly through the central aperture 20. This fluid in passing up through aperture 20 may impinge upon the lower ends of the vortices 30' and 3| with an umbrella efl'ect protecting the disc l9 against the abrasive action of any sand particles which might otherwise rapidly wear the disc at the areas of deflection of the downward vortex into the upward vortex.

In some cases if desired it may be found feasible to omit the disc IS, in which event the lower reversal of the vortices may occur within or near the conical chamber 22.

The upwardly rotating central core or vortex 3! being of a diameter and cross section somewhat less than the vortex 30', will have an increased angular velocity as compared with vortex 30'. Accordingly any of the impurities which are more difficult of removal or which may have been swept upwardly in this central vortex, are now subjected to a further intense centrifugal action forcing such particles out of the central vortex and into the downwardly moving vortex 30'. This action may be made quite prolonged and effective, inasmuch as the vortex 3| as shown is of a height many times greater than its diameter.

Yet despite the action of the device as thus far described, some of the particles of impurities more difllcult of removal may be still re-' ticles of impurities remaining within the innerupwardly moving vortex at the aperture l8 need only travel radially outwardly a very short distance before they will be enveloped in the downwardly moving annular vortex at the outer edges of this aperture. This fact .together with the great angular velocity within the aperture, insures that the inner vortex as it emerges upwardly from the aperture l8, will be substantially wholly free of the undesired particles. And as this inner vortex continues on upwardly as indicated at 3|, its angular and linear velocity will be sufllcient (and greater than occurs in vortex so as to prevent any of the undesired particles from being reintroduced into vortex 3i.

Finally the treated suspension is withdrawn of the device. The lower end of the outlet I4 is located suiflciently below the point of discharge of the incoming stream into the device so that the outer downwardly moving vortex will be firmly established before it passes the outlet i4. Thus the direct passage of any of the incoming fluid into the outlet will be prevented. It will be further noted that the inner lower end of the outlet I4 is relatively restricted as compared with the cross section of the inlet, and so as to conform to or be no greater than the cross sectional area of the upwardly flowing vortex 3!, This further insures that none but the treated fluid will be allowed to escape through the outlet. At

higher points the outlet conduit may be expanded in cross sectional area so as to not create any excessive back pressure in the apparatus.

Liquid suspensions are preferably introduced into the device in such .manner as to avoid introduction of any substantial amounts of air or gas therewith which might interfere with the above described formation of the vortices. However, the centrifugal action of the vortices will ordinarily be so intense as to cause a small substantially evacuated space to be established along the entire vertical axis of the chambers I5 and I 6 as indicated by the wavy central lines 32.

The impurities settling in the chamber 22 will further slowly settle through the normally open valve 23, sight glass 24 and into the receptacle 25, these parts being filled with a quiescent body of liquid such as water introduced before the apparatus is placed in operation. As the receptacle 25 becomes filled with the impurities, they will serve to gradually displace the liquid and except for this very slow gradual upward movement of the displaced liquid, the liquid below the conical chamber 22 will be free of motion. Thus the apparatus not only provides re-'; peated and prolonged opportunity for the par-' ticles of impurities to be centriiugaily removed from the vortices of the pulp suspension, but the apertured disc arrangements at i! and. serve .to entrap these particles against any possibility of their return toward the pulp outlet. And the portions below the disc I! serves to maintain a quiescent body of liquid into which the particies of impurities may settle without possibility of their being again agitated and entrained in the vortices.

From time to time, for example once a day, as the receptacle 2! may become filled with impurities, the valve 23' may be closed for a moment while the receptacle 25 is emptied through its valved outlet 28 and then refilled with fresh water through the supply pipe 21. Then upon closing valve 28, the valve 23 may be opened again. During the short interval of cleaning the receptacle 2!, the impurities being removed may accumulate in the conical chamber 22 without difliculty. Accordingly, the device may be maintained in continuous operation during the cleaning of the receptacle 25. I

If desired, the walls of the chambers l5 and Ii may be made of transparent material so that the action or the vortices may be readily observed, but this is unnecessary once a typical unit has been placed in proper operation for a particular purpose.

.In controlling the vortices in the manner above described, the dimensions of the various parts may become of substantial importance. .In the particular example shown in Fig. 1 as used in purifying paper pulp stock, pumped into the apparatus at 25 pounds of pressure, for example, the preferred dimensions are as follows:-The' length of the cylinder comprising chambers I5 and i6, is about 42 inches and has a diameter oi. 4 inches. The inlet pipe Ii has a diameter of 3 inches, and the restricted lower end of the outlet H, a diameter of 2 inches. The aperture in the disc ll has a diameter of 1% inches. The central aperture in the disc l9 has a diameter of inch, and the aperture 2| a diameter of inch, although the latter may be varied depending on whether one or more of such apertures 2| are provided. The height of the conical chamber 22 is 6 inches and may be provided with an outlet pipe 1 inch in diameter, although the dimensions and shape of the chamber 22 and of the waste outlet therehom are not of such importance as other factors above mentioned A single unit as above described has a capacity of about 150 imperial gallons of liquid per minute. Assuming a stock consistency of about 0.5%, each of these units can be used to treat in the neighborhood of 5 to 6 tons of paper stock (dry basis) per day, if supplied with stock at a pressure of about 25 pounds per square inch. With this supply pressure, the pressure difference between the inlet and outlet may be maintained at about 15 pounds per square inch, or more. With the particular device as above specified, it has been found important to maintain a pressure drop therein, at least as great as 15 pounds per square inch, and the inlet and outlet pressures are of less importance so long as such pressure drop is maintained. It is of substantial importance that the diameter of the chambers I5 and I6 be maintained small in comparison with the height. Most effective results may be obtained material enlargement of the cross sectional area of the annular space through which this stream must pass in forming the prolonged downwardly If the diameter is increased, .the eiii-.

flowing annular body. This relationship appears to be of very substantial'importance in securing ,the most effective separating action in the device.

Such relationship insures that the fluid in the downwardly flowing vortex will have sufiicient force, at all points to rather sharply distinguish this vortex from the inner upwardly moving core of fluid, thereby preventing intermingling of the treated and untreated fluid, despite the prolonged extent of bothvortices. Furthermore, a downward vortex of a cross sectional area about the same as that of the incoming stream, insures that the inner, upward vortex will be properly confined by the outer vortex so that the inner vortex' will be of smaller cross section and hence have a higher angular velocity, assisting in the final effective removal of the particles and preventing redeflection of removed particles into the inner core before it is withdrawn. Thisrelationship of the cross sectional areas of the vortices further makes it possible to use an outlet conduit of such size as to be filled by the upwardly flowing inner core to the exclusion of adjacent downwardly flowing untreated liquid, while the outlet .conduit may still be of a diameter sufiicient to avoid undue back pressures in the device.

The interior surfaces of the chambers l5 and l6 should be made quite smooth so as to prevent the formation of irregular eddy currents interfering with the action of the vortices, as above described. The extended cylindrical form of these chambers greatly contributes to the substantial uniform maintenance of the rather sharply defined and extended concentric downwardly and upwardly moving vortices, once the vortices have been normally established.

with the device used as above disclosed, it has been determined that under actual operating conditions in paper mills over a considerable period, at least 94% of the totalimpurities (oversize particles and particles heavier than the pulp fiber) maybe removed from the liquid suspension, and the particles thus removed constitute substantially all of those which would otherwise cause noticeable imperfections in the paper. The pulp stock treated with this device and without further treatment, has been found to be more free of the troublesome impurities than is the case with pulp stock heretofore treated with other devices even including very expensive centrifugal equipment with mechanically rotating parts.

Fig. 3 illustrates the manner in which several of the above described units of the device may be interconnected with a single pump for treating a greater volume of liquid. In Fig. 3 a common feed manifold is indicated at to which inlet pipes as at H are connected. A common outlet manifold for the treated liquid is indicated at 4|, connected to the outlets i 3 of the several units. The manifold-40 is shown as connected to a suitable pump as at 42 for supplying the necessary pressure to the incoming liquid.

Fig. 4 illustrates an alternative construction which maybe used in lieu of the conical chamber 22 above described. That is, in Fig. 4 a lower or conical chamber 43 may have its inner surfaces formed with a plurality of vertically and inwardly extending fins as at 44, for diminishing the turbulence within this chamber and thereby affording greater opportunity for the particles of impurities to promptly settle, and preventing any abrasive action of such particles tending to wear away the walls of the chamber. This form of conical chamber is particularly useful in the event the disc f9 is omitted.

In Fig. 5 an alternative embodiment of the apparatus is shown which may be similar to that of Fig. 1 except for the features hereinafter described. The main body of the device of Fig. 5 may comprise a single and vertically elongated cylindrical chamber 35 corresponding in general as to function to the chamber l5 above described, although of suflicient length to accomplish in part the functions of chamber I6 also. An apertured disc 36 corresponds in general to the disc I! above described. And the action of the vortices 3'! and 38 as restricted in passing through the disc 36, will be similar to the action of the vortices within the aperture of the disc I! above described. The functions of the chambers l6 and 22 explained in connection with Fig. 1, are in Fig. 5 combined to some extent within a single conical chamber 39, although of course the vortices within this chamber will be greatly restricted in length as compared with those occurring in chamber l 6. With the disc or partition 36 arranged as in Fig. 5, to provide a single passage of the fluid through a confining aperture and trap for the impurities or heavier particles, this construction has been found to operate successfully and efficiently in normal commercial use.

It will be apparent that this invention provides a simple form of construction adapted for a wide variety of uses in classifying materials conducted in a stream of. fluid. And the construction has no moving parts or other parts subject to any appreciable wear. No great expense for power is required in operating the device. The space required for an installation isv small and the units when used for paper pulp cleaning may be located close to the paper machines using generally the existing pipe lines, valves, etc., and frequently the same pump previously used for supplying the pulp stock to the machines.

While the invention has been described with respect to certain particular preferred examples which give satisfactory results, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended, therefore, in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent is:

1. In apparatus for separating relatively heavy particles from fluid, a disc of rubber or the like flexible material supported at its periphery and having a central aperture, a chamber above said disc, means for establishing a downwardly and helically flowing annular body of the fluid in said chamber impinging against said disc around said aperture and deflecting the areas of the disc substantially downwardly with said helically flowing body'extending in restricted form through said aperture, means including an enclosed chamber below said disc for causing said fluid to return from below said disc upwardly through the center of said aperture while still flowing in a helical path, and an enclosed quiescent body of fluid below said last named chamber and normally in communication therewith for receiving said particles. 2. Apparatus for separating relatively hea particles from fluid, comprising an upstanding cylinder of a height at least several times its diameter, a partition with a central aperture and extending transversely across the lower end of said cylinder, a chamber below said partition, a closure for the top of said cylinder, means for introducing tangentially at said top a stream of the fluid under sumcient pressure for establishing a downward helically flowing annular body of fluid fllling'the peripheral zones of the cylinder and extending in restricted form through said aperture and thence in expanded form into said chamber, the cross sectional area of said introduced "stream approximating that of said helically flowing body in the cylinder, and an outlet conduit with a restricted mouth positioned in the space within the upper end of said cylinder, and extending upwardly, the parts being of such proportions and shape that the fluid after entering said chamber returns upwardly within said annular body, forming a helical core of high angular velocity, confined within and by said downwardly flowing body and filling said outlet to the exclusion of adjacent downwardly flowing fluid.

3. Apparatus for separating relatively heavy particles from fluid, comprising an upstanding substantially cylindrical chamber, a closure for the top thereof, means for forcing a stream of the fluid of such dimensions and pressure into chamber, said. partition having a central apery ture whereby said vortices are greatly restricted in passing concentrically therethrough, a second partition extending across said chamber in the neighborhood of the lower end thereof and being apertured to permit a relatively gentle current of fluid to carry particles from said downward vortex to a point below said second partition, and permitting such current to return to the upward vortex, and means normally enclosing the space below said second partition against other escape of fluid therefrom.

4. Apparatus for separating relatively heavy particles from fluid, comprising an upstanding substantially cylindrical chamber, a closure for the top thereof, means for forcing a stream of g the fluid of such dimensions and pressure into the upper end of said chamber as to establish a downwardly flowing outer vortex occupying the peripheral zones thereof, the fluid of said vortex returning as an upwardly flowing inner vortex confined within and by the downward vortex, an outlet for withdrawing the fluid of said upward vortex upwardly from within the upper end of said outer vortex, a partition extending across said chamber at a point spaced substantially from both the upper and lower ends or said cylindrical chamber. said partition having a central aperture whereby said vortices are greatly restricted in passing concentrically therethrough, an enclosed quiescent body of fluid below the lower ends of said vortices, and means normally providing a restricted communication between such body and said lower ends.

5. In apparatus for separating relatively heavy particles from paper pulp water suspensions, a disc supported at its periphery and having a central aperture, a chamber above said disc means including an inlet at the top oi said chamber for establishing a downwardly and helically flowing annular body 01' the water suspension in said chamber impinging against said disc with said helically flowing body extending in restricted form through said aperture and expanding again below said aperture, means including an enclosed chamber below said disc for then causing such water suspension to return upwardly through the center of said aperture while still flowing helically, a discharge conduit for said suspension, said conduit having its mouth within the upper portion oi said first named chamber but below said inlet and within said annular body for withdrawing irom the apparatus such upward helical flow exclusively of the adjacent downward flow, and an enclosed quiescent body of water beneath and spaced from said helical flows for receiving said particles.

6. The method of separating relatively hea particles from fluid, which comprises establishing a downwardly flowing vortex oi the fluid confined under substantial pressure and in the shape of a vertically extending substantially cylindrical body oi a height at least several times greater than its diameter, deflecting the fluid at the lower end of said vortex upwardly and centrally of said vortex whereby a second and upwardly flowing vortex is formed within and confined by said first named vortex, said second vortex also being of a vertically extended substantially cylindrical shape and having a higher angular velocity than the first, withdrawing the fluid comprised in the second vortex, axially and upwardly from within the upper end 01' the first vortex, without directly withdrawing any substantial amount of the fluid oi the first vortex, and greatly restricting the diameter of said first vortex and thereby causing restriction of the second vortex therein at a point spaced substantially below the upper ends oi the vortices whereby the angular velocities of the vortices are increased at such restriction, and providing, a quiescent fluid body beneath and normally communicatingwith the zone or said deflecting, whereby said heavy particles in the upward vortex are thrown by centrifugal force into the downward vortex, and with increased eiiectiveness at said restriction, and such particles in the downward vortex are thrown to the periphery thereof and carried down to said quiescent particles from liquid suspensions of fibrous lighter material, which comprises so introducing a stream oi said suspension into a chamber as to establish a downwardly flowing vortex of the liquid suspension confined in said chamber under substantial pressure and in the shape of a vertically extended substantially cylindrical body or a height at least several times greater than its diameter, deflecting the liquid suspension at the lower end or said vortex upwardly and centrally of said vortex aroasac whereby a second and upwardly flowing vortex is formed within and confined by said first named vortex, said second vortex also being 01 a vertically extended substantially cylindrical shape and having a higher angular velocity than the first, withdrawing the desired liquid suspension comprised in the second vortex, axially and upwardly-from within the upper end 01' the first vortex, without directly withdrawing any substantial amount of the liquid of the first vortex, the stream of the suspension as withdrawn being substantially restricted as compared with the cross section of the introduced stream, and providing a normally enclosed quiescent body of liquid beneath the zone where said deflecting occurs and in restricted communication with such zone, whereby said heavy particles in the upward vortex are thrown by centrifugal force into the downward vortex and such particles in the latter vortex are thrown to the periphery thereof and carried down to said quiescent liquid.

8. The method of separating relatively heavy particles from liquid suspensions 01' lighter or finer material, which comprises establishing a downwardly flowing vortex oi the liquid confined under substantial pressure and in the shape of a vertically extended substantially cylindrical body of a height at least several times greater than its diameter, deflecting the liquid at the lower end of said vortex upwardly and centrally of said vortex whereby a second and upwardly flowing vortex is formed within and confined by said first named vortex, said second vortex also being of a vertically extended substantially cylindrical shape and having a higher angular velocity than the first, withdrawing the desired liquid suspension comprised in the second vortex, axially and upwardly from within the upper end of the first vortex, without directly withdrawing any substantial amount of the liquid of the first vortex, and greatly restricting the diameter of said first vortex and thereby causing restriction of the second vortex therein at a point intermediate the upper and lower ends or the vortices whereby the angular velocities of the vortices are increased at such restriction, and providing a quiescent body of liquid beneath the zone 01' said deflecting, and with restricted communication with said zone, whereby said heavy particles are thrown by centrifugal force to the periphery oi the downward vortex and are carried down to said quiescent liquid.

9. The method of separating relatively heavy or solid particles of an abrasive character from fluid, which comprises establishing a downwardly and helically flowing annular body oi the fluid, providing an annular obstruction having a passage therethrough surrounded with downwardly yielding areas, said obstructions being in the path of such flow for directing the same as a more restricted helically flowing annular body through such passage, then returning said fluid while still flowing helically, upwardly, axially 0i and within said annular body of fluid to a point of withdrawal, whereby said particles are thrown by centrifugal force to,-and carried down in the peripheral zones in the downwardly flowing fluid and prevented by the action of said obstruction from rising to said point of withdrawal.

10. The method of separating relatively heavy particles from liquid fibrous pulp suspensions, which comprises tangentially introducing a stream of the liquid suspension under substantial pressure into a space so restricted as to establish a downward helically flowing annular body oi stantially distinct core of higher angular and linear velocity within and confined by said annular body, withdrawing the liquid suspension of such core only, upwardly from within the upper end of said annular body, and providing an enclosed quiescent body of liquid below the lower end of said annular body for receiving said particles.

11. The method of separating relatively heavy particles from liquid, which comprises establishing a downwardly and helically flowing annular body of the liquid, providing an annular obstruction in the path of such flow for directing the same as a more restricted helically flowing annular body through the center of such obstruction, then causing such helical flow to expand and continue downwardly beneath the obstruction, then returning said liquid while still flowing helically, upwardly, axially of and within said annular body of liquid to a point of withdrawal, whereby said particles are thrown by centrifugal force to, and carried down in the peripheral zones in the downwardly flowing liquid and prevented by the action of said obstruction from rising to said point of withdrawal, and maintaining .a distinct substantially quiescent body of liquid below the zones of such helical flows for-receiving said particles.

12. Apparatus for separating solids from fluid suspensions comprising a closed vertical stationary chamber having a cylindrical portion long in relation to its diameter, means for admitting the fluid suspension tangentially under pressure to the chamber adjacent the top of the cylindrical portion, a disc extending transversely across the space within said cylindrical portion and having therein a central openin-gaxially disposed of said chamber, means for. discharging fluid upwardly from a point axially located adjacent the top but below the inlet to said chamber, a lower discharge outlet for said solids located substantially axially of the chamber below said disc, and a chamber having its side walls extending downwardly to said outlet from points on said disc spaced from said opening.

13. Apparatus for purifying fluid paper-making stock and the like which comprises a plurality of units as defined in claim 12 in combination with a common feed manifold for all said units and a pump for exerting a constant pressure on stock flowing through said manifold to said units.

14. Apparatus for purifying paper stock comprising a closed and stationary cylinder long in realtion to its diameter, a tangential inlet adjacent the top, a top discharge outlet pipe projecting into the cylinder to a point below said inlet,

a substantially plane disc having an opening therein, said disc extending transversely across 15. Apparatus for purifying flbrouspulp stock comprising a closed-cylinder long in relation to its diameter and subdivided into three superposed separating chambers, a disc with a central opening therein constituting the lower wall of each of the two uppermost chambers, said discs extending over the greater part of their areas in a general direction at right angles'to the axis of said cylinder, a discharge opening at the base of the other of said chambers, a tangential inlet adjacent the top of said cylinder and an-axially disposed outlet pipe also adjacent-the top of said; I

therein at least two superposed unobstructed cy- 1 lindrical portions, long in relation to their diameter, and a base portion all with a common i vertical axis, a disc with a central opening therein constituting the lower wall of each of said cylindrical portions, a discharge opening in said base portion at a point removed from the lower of said discs, the cylindrical portions constituting at least the major part of said chamber, another discharge opening extending axially and upwardly from within the upper cylindrical portion, and an inlet extending substantially tangentially into the space surrounding said last named discharge opening.

1'7. Apparatus of the character described comprising a closed chamber having therein two superposed unobstructed, cylindrical, axially disposed portions, long in relation to their diameter, a disc with a central opening therein at the base of each portion and anchored in the walls thereof, a settling portion below the lower disc with a discharge outlet at a point removed from said lower disc, another discharge opening extending axially and upwardly from within the upper cylindrical portion, and an inletextending substantially tangentially into the space surrounding said last named discharge opening.

18. Apparatus for separating relatively heavy particles from a fluid, comprising an upstanding cylinder of a height at least several times its diameter, a partition with a central aperture and extending transversely across said cylinderjat a substantial distance from its upper end, a chamber below said partition, a closure for the top of said cylinder, inlet means for introducing tangentially at said top a stream of the fluid of such dimensions and pressure as to establish a downward helically flowing annular body of the fluid occupying the peripheral zones of the cylinder and extending in restricted form through said aperture and thence into saidchamber, an outlet conduit having its mouth positioned in the space within the upper end of said cylinder but below said inlet means, said conduit extending upwardly, the parts being of such proportions andshape that the fluid after entering said chamber returns upwardly within said annular body, forming a helical core of high angular velocity, confined within and by said downwardly flowing body and filling said outlet to the exclusion of adjacent downwardly flowing fluid, and a receptacle containing a quiescent body of fluid, normally communicating with the bottom of said chamber for receiving said particles.

HORACE FREEMAN.

patent No. 2,102, 525.

CERTIFICATE OF CORRECTION. I I I December 1h, 1937. HORACE FREEMAN. x I It is hereby certified that error appears in Printed p cification of the above numbered Patent requiring correction as follows: Page 1, second column, line 50, for the word "for-m" read forms; line 50-51 for "illustrate" read illustrates; page 5, first column, line 11 claim 1, stril ce out the words around said aperture" and insert the sameafter "disc", line 75, same claim: and that the said Letters Patent should be read with these corrections therein that the same may conform, to the record of the case in the Patent Office.

Signed and sealed this 1st day of March, A. D. 195

Henry Van Arsdale,

(Seal).

' Acting Commissioner of Patents.

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