US3061098A - Centrifugal classifier and stock cleaner - Google Patents

Description

Oct. 30, 1962 J. P. BREZINSKI CENTRIFUGAL CLASSIFIER AND STOCK CLEANER 2 Sheets-Sheet 1 Filed July 18, 1960 1962 J. P. BREZlNSKl 3,061,098

CENTRIFUGAL CLASSIFIER AND STOCK CLEANER Filed July 18, 1960 2 Sheets-Sheet 2 [27 Z Efi fayde ram e firezlnsl/ United States Patent Ofiice 3,061,098 Patented Oct. 30, 1962 3,061,098 CENTRIFUGAL CLASSIFIER AND STOUK CLEANER Jerome P. Brezinski, Beloit, Wis., assignor to Beloit Iron Works, Beloit, Wis., a corporation of Wisconsin Filed July 18, 1960, Ser. No. 43,524 Claims. (Cl. 209211) This invention relates generally to classifying and separating methods and to new and improved apparatus for carrying out such methods, and is more particularly directed to separating solid particles by size and weight from fluids and fluid suspensions.

It has been customary in the art to employ various methods and apparatuses utilizing the centrifugal principle for classifying or removing suspended solids from hydrous slurries. In these devices the slurry is introduced tangentially into a stationary chamber from a pump or like pressure source, whereby the entire body of liquid within the chamber rotates about the axis of the chamber to thereby develop the centrifugal separating forces dependent upon the differences in weight (or density) of the fractions present. An outlet is provided for removal of the overweight particles usually at the opposite end of the chamber.

Prior methods for the separation of particles on the basis of their size commonly employ screens, drilled plates, or other like perforated or porous septums in which the size of the pores or apertures is chosen for restricting the passage of particles of some desired size, but to permit the passage of smaller particles. The particles which do not pass through the perforated septum tend to plug the apertures thereby reducing the capacity and/or performance of the screening device. It is essential in most applications that such oversize material be removed from the screen and it has been necessary to employ scrapers, vibrators, or rotating devices to assist in the removal of oversize particles from the screening surface.

I have discovered that effective cleaning of the screen may be accomplished by exposing the screening surface to intense fluid turbulence. It is thereby possible to generate such turbulent activity by innumerable methods which involve moving parts and the mechanical input of power. It is most desirable, however, to generate the desired degree of turbulence by using the energy available in the fluid which was supplied initially to the fluid by means of a pump. It has also been discovered that the generation and maintenance of an intense turbulent condition in the fluid slurry at the screening septum is beneficial in the screening of oversize material from fiber slur'ries, where the fibers must pass through the screening apertures. Fibers in aqueous suspension exhibit strong tendencies to agglomerate into network-like structures rather than to remain suspended individually. These fiber networks are too large to pass readily through the apertures of the screening member and will either plug the apertures or be rejected from the system with other oversize material. The creation of turbulence in the fluid suspension aids in minimizing the formation of fiber networks and tends to destroy networks which do already exist, thereby presenting a better dispersed slurry to the screen. My invention, by combining a screening member mounted axially within the central core of fluid of the centrifugal separating device, permits the practice of two screening methodssize and weight within the same apparatus withoutt mechanical moving parts while at the same time taking full advantage of turbulent flow. I am enabled to achieve separation of particles both on the basis of weight and of size.

It is therefore an object of this invention to provide apparatus for the separation of oversize and overweight fractions from liquids or liquid suspensions.

It is also an object of this invention to provide a uni tary stock cleaner device combining the features of centrifugal force separation and stock screening in a single chamber.

A funther object of the present invention is to provide a method for separating solids from hydrous slurries by size and weight.

These and other objects, features and advantages of the present invention will become apparent upon a careful consideration of the following detailed description, when taken in conjunction with the accompanying drawing, illustrating preferred embodiments of my invention, wherein like reference characters refe to like or corresponding parts throughout the several views.

On the drawing:

FIGURE 1 is a view in partial cross-section showing the details of apparatus constructed in accordance with the principles of my invention.

FlGURE 2 is a view in cross-section taken along lines IIII of FIGURE 1.

FIGURE 3 is a view in partial cross-section illustrating a preferred embodiment of the present invention.

-FlGURE 4 is a view in cross-section taken along lines IV-IV of FIGURE 3.

As shown on the drawing:

Referring to FIGURE 1, the separating apparatus comprises a housing 10 defining a chamber 11 which is annular in section and which-is disposed with its central. axis in a vertical position, as shown. The upper end of. the chamber 11 is provided with an inlet 13 which in turn is detachably connected to slurry feed means by any suitable means including if desired, flanges as at 14. The inlet 13. is positioned to inject the stock to undergo treatment generally tangentially into the chamber from a converging acceleration chamber 15 in a manner to cause a helical flow of the liquid suspension downwardly along the inside walls of the chamber 11 to the region at or adjacent the lower end thereof; At the lower end thereof housing 10 is .centrally apertured to receive a stock outlet pipe 16 extending into the interior of the chamber 11 for removal of .the cleaned stock therefrom. The bottom wall 17' of housing 10 is also apertured to provide aninlet adapted to receive a conduit 18 of reduced diameter for removal of the particles. .Conduit 18 may be provided, with conventional means for controlling or regulating the rated discharge therefrom, such as valve 19.

- Means for separating suspended particles in accordance to their relative size arepositioned in'the chamber 11 and, in the preferred arrangement shown in FIGURE 1, take the form of a hollow truncated come 20 of suitable material having vva plurality of apertures formed therein ofa size to prevent passage of oversize particles there'- throu-gh. This foraminous member is positioned in the chamber 11 so as to be centrally located within the core of the vortex of the liquid suspension or liquid in the chamber while in operation. The foraminous member 20 may be for-med of a screen constructed-of.woven wire mesh, perforated plate formed in frusto-conical shape, or a frusto-conical porous ceramic member or. the like. If it is necessary to perforate the member, the apertures may be either round or elongated. Experience has also indicated that the angle of taper of the member 20 will vary from approximately 4 to a maximum of about 25, preferably about 6 to about 7 if the device is to be utilized for paper making purposes.

The strength requirements of the foraminous member are determined by the differential pressure created in the event of stoppage of flow through the screening member.

With slurries used in papermaking, these requirements would normally range up to 5 atmospheres to the output of the pump being used. It will be appreciated that the differential pressure will depend upon the pore sizes chosen for the formainous member and upon the liquid suspension undergoing treatment. In papermaking this is preferred to be as low as possible and normally not exceeding one-half atmosphere. As applied in other slurries these requirements will be readily determined by one versed in the art.

The hollow member 20 is provided with an annular collar 21 or ohter suitable means for securing the lower end of the member to the stock outlet pipe 16.

The pipe 16 extends inwardly of the bottom wall 17 of the chamber 11 and with the chamber defines an annular collecting zone for oversize and/ or overweight particles from the slurry. This annular zone is of sufficient length l to dampen out the turbulent flow action caused by centrifugal filtering and permit collection of such particles. Depending upon the particular type suspension or liquid undergoing treatment, the length l of the dampening and collecting zone may be adjusted to perform the dampening function efficiently.

The upper portion of the member 20, that of reduced diameter, has a collar 22 which is connected to a mounting member 23 suitably secured to the upper end wall of the housing 10. Preferably the mounting member is approximately of cylindrical shape and the eflicient length thereof is determined by the particular application for which the device is to be utilized. The minimum requirements therefor, determined by experience, are that the mounting member 23 should be of sufiicient length to establish centrifugal whirl of the slurry thereabout from the tangential stock inlet, and that the length of the mounting member should not be less than the axial dimension of the inlet.

The length of the cylindrical mounting or core member 23 should be of sufficient length to establish the centrifugal whirl or helix of the slurry fed to the chamber 11. Thus the entire slurry mass flow will be stabilized since the core, being of sufficient length, will provide the time period required to permit a particle of contaminant to traverse the annular thickness of the stream. Consider, by way of example, an overweight particle entering the chamber at the inward side of the inlet 13. In order for effective separation of this particle to occur, this particle being under a slight ditference in centrifugal force due to its mass difference must travel through the entire thickness of the helical annular stream in order to be separated from the flow mass. Dimensioning the length of the core 23 assists in separation under these circumstances. Thus in general, the length of the core 23 should be of a length of from about one and one-half to about several times that of the vertical dimension of the inlet 13.

Thus, the chamber 11 may be considered as being divided into three zones, an upper slurry inlet and centrifugal whirl starting zone, an intermediate particle size separating zone and a lower flow dampening and collecting zone.

In operation, the liquid or liquid suspension containing the various size and weight particles is introduced tangentially from the acceleration chamber into the whirl zone of the chamber 11 at relatively high flow rates, the rate depending upon the particular type suspension or liquid involved. The heavier particles are centrifuged toward the walls of the chamber 11 and are urged downwardly by the mass flow. Particles of desired size pass through the perforations in the hollow truncated member 20 and, from the interior thereof, pass through the clean stock outlet to the next stage in the overall operation. The oversized particles and overweight particles are urged downwardly to the bottom dampening and collecting zone by the helical mass flow for subsequent discharge through the conduit for subsequent use, reprocessing or disposal. The perforations in the conical member are provided in sufficient number so that the fluid fiow therethrough from the slurry is sufiicient to maintain enough of the perforations clear for effective screening. Experience has indicated that the change in flow behavior resulting from the plugging of a number of holes in the conical member by oversized particles results in only a small pressure rise, and that the effects thereof on the screening efiiciency is negligible.

It will be appreciated that the pressure existing across the perforate septum will be a function of flow rate, consistency, and particle or pore size. If one of these factors is changed due to some upstream condition there is a possibility that plugging may occur. For example, both quantity and size of particle material borne in the suspension appears to have a marked effect upon turbulence, therefore, means should be provided preferably to give control of the consistency of the slurry to the separating unit. Thus, if either the pressure drop across the septum or the flow rate of accepted stock is changed significantly the quantity of water or other medium introduced may be changed in order to maintain stability.

Although fluid flow does not appear to impose critical requirements it will be appreciated that each and every application will have a particular flow range.

It will be seen from the foregoing that both the overweight and oversized particles discharge from the collecting and dampening zone through the discharge conduit and are effectively filtered and separated from the desired size and weight particles which flow through the stock outlet to the next stage in the overall operation.

In FIGURE 3, an improved and preferred embodiment of the present invention is illustrated wherein the housing 30 is of general conical shape communicating at one end with the slurry inlet zone of generally cylindrical config- F uration and at the other end tapering in communication with the annular damping and collecting zone I.

In the embodiment shown in FIGURE 3, the end wall 17 communicates the dampening and collecting zone with the conduit 18 for discharge of oversize and overweight particles.

The taper of the body 30 provides means for continuing acceleration of the fluid slurry during its annular downward travel. In normal operation therefore, a lesser pressure drop is required than in the apparatus of FIGURE 1 and more eificient operation obtained in the gallons of slurry passing through the apparatus per H'P. In this modification, the outlet for accepted stock particles is positioned at the top of the assembly and is generally designated by the numeral 16.

As aforementioned with respect to the length of the member 23 of the embodiment of FIGURE 1, the outlet 16 is of generally cylindrical configuration presenting a solid surface to the slurry being tangentially introduced into the chamber 11 through the inlet 13. The cylindrical member 16 should be of sufiicient length to establish the centrifugal whirl or helix of the slurry fed to the chamber 11.

The member 16 has attached thereto as by a collar 24, the tapered foraminous member 20, similar in construction and operation to the foraminous member 20 of the embodiment shown in FIGURE 1.

The mounting collar 21 of the smaller end of the member 20 is preferably flexible in order to permit vibration of the foraminous member 20 generated by the turbulence of the slurry thereby providing a reasonable amplitude both to assist in the screening operation and to prevent damage to the member 20. 'Ihe smaller end of the member 20 adjacent collar 21 is closed as by an end plate. (not shown).

For this purpose, a plurality of link members 21a may be pivotally connected to the housing 30 and to the collar 21. If desired, the member 20 and the outlet 16 may be vibrated by means of a source of mechanical vibration, such as an electromagnetic vibrator, shown in diagrammatic form and indicated generally by the numeral 34.

The vibration link arm 35 of the vibrator 34 is connected to a link member 36 which extends'through a suitable 'slot formed in the housing 31!. The link member 36 may be connected at the other end thereof to the collar 21 for inducing vibrations longitudinally in the foraminous member and attached outlet 16. A bellows sleeve 37 may be provided to prevent leakage through the slot.

To permit such vibrations, the upper end of the housing 30 may be provided with an outwardly extending and centrally located sleeve 30a providing a seat for a seal 33 of conventional construction. The member 16 may extend through the bore of the sleeve 30a in spaced relation thereto and may be provided with an annular flange 31 in engagement with a plurality of annularly spaced springs 32 bottomed on housing 30* for permitting longitudinal vibration of the screen and outlet assembly.

Thus, in operation, the contaminant-containing slurry will be introduced tangentially into the chamber 11 in the centrifugal or helix swirl establishing zone at the upper end of the assembly. The electro-magnetic vibrator 34 will cause vibration of the screen 20' and attached outlet 16 against the force exerted by the springs 32 acting on the collar or flange 31. The oversize and overweight particles will be forced towards the walls of the housing 30 while the particles of predetermined size and weight will pass through the apertures of the screen 20.

The helical vortex of the centrifuging fluid mass tends to force the fluid flow within the screen 20 up through the discharge outlet 16. The remainder of the fluid, that containing the oversize and overweight particles, collects in the collecting zone for subsequent discharge through the conduit 18.

Thus it will be appreciated that by employment of my invention, I provide a new and improved device for effectively separating both overweight and oversize particles from a liquid or liquid suspension in a unitary device.

Although various minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such embodiments as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. Apparatus for separating solid particles by size and weight from a liquid comprising: a stationary housing having a cylindrical chamber; means for tangentially introducing a solids-containing liquid under pressure into the upper portion of the chamber; cylindrical liquid vor tex establishing means in the upper portion of the chamber defining an annular liquid vortex forming zone; conduit means extending into the lower portion of the cylindrical chamber defining with the chamber wall an annular liquid vortex damping and particle collecting zone; an outlet formed in the lower portion of the housing for discharging overweight and oversize particles from the damping and collecting zone, and frusto-conical apertured means in the chamber having its larger diameter end communicating with the conduit means and defining an intermediate particle size screening zone between the forming and collecting zones, said annular collecting zone being of a sufiicient length to dampen out turbulent flow action caused by centrifugal screening and permit collection of overweight and oversize particles, the longitudinal axis of the apertured means being substantially in alignment with the longitudinal axes of the liquid vortex establishing means and the conduit means whereby centrifugal flow action imparted to a solids-containing liquid in the chamber thereby separates solid particles by weight and size, overweight and oversize particles flowing into the vortex damping and particle collecting zone for discharge through the outlet and solid particles of predetermined size and weight flowing through the apertured means for discharge through the conduit means in communication therewith.

2. Apparatus for separating solid particles by size and weight from a liquid comprising: a housing having an upper cylindrical section and a lower cylindrical section of relatively lesser diameter, a downwardly tapering ,frusto-conical section connecting the upper and lower chamber sections; a downwardly tapered frusto-conical screening member concentric with the tapering chamber section in the chamber and having a plurality of apertures of a predetermined size to pass particles of predetermined size to the interior thereof from a liquid centrifuging in the chamber; an irnperforate cylindrical conduit communicating with the screening member at the upper end thereof, and the lower end of said screen member being closed, said imperforate conduit being concentrically aligned with the upper cylindrical section of the housing, and extending into the housing for discharging acceptable solid particles that pass through said screen member, means communicating the lower cylindrical section of the housing with a discharge conduit for oversize and overweight particles; means communicating the upper cylindrical chamber section with a conduit for introducing a solids-containing liquid under pressure tangentially into the chamber whereby the centrifugal flow of the liquid is established around the imperforate conduit communicating with the screening member, and means for longitudinally vibrating the screening member.

3. Apparatus adapted for separating solid particles by size and weight from liquid slurries and the like comprising: a housing defining a cylindrical chamber, an inlet to the chamber located for tangentially introducing a slurry under pressure into the upper portion of said chamber, a hollow and substantially rigid first member centrally located in the chamber, said first member defining a plurality of apertures of a predeterminad dimension therein for permitting passage therethrough of solid particles of a predetermined size from a centrifuging slurry, said apertures being provided in an amount suificient to minimize pressure differential across the member, a particle separation zone defined by the first member and the cylindrical chamber wall, a second imperforate member in the clindrical chamber adjacent the inlet axially aligned with the first member and of a length sufiicient to establish centrifugal whirl of the slurry fed through the inlet before introduction of the slurry to the particle separation zone, a turbulence damping chamber within said cylindrical chamber communicating with the particle separation zone for receiving oversized and overweight particles, an outlet for removal of overweight and oversized particles from the damping chamber, and an outlet communicating with the first member for removal of the centrifuged and substantially particle-free slurry therefrom.

4. Apparatus adapted for separating separate particles by size and weight from liquid slurries and the like comprising: a housing defining a cylindrical chamber, an inlet to the chamber located for tangentially introducing a slurry under pressure into the upper portion of said chamber, a hollow and substantially rigid frustoconical first member centrally located in the chamber, said first member defining a plurality of apertures of a predetermined dimension in the first member sized for permitting passage therethrough of solid particles of a predetermined size from the slurry centrifuging adjacent thereto, said apertures being provided in an amount sufiicient to minimize pressure increase across the member, a particle separation zone defined by the first member and the cylindrical chamber wall, a second cylindrical imperforate member in the cylindrical chamber adjacent the inlet in axial alignment with the first member and of a length sufiicient to establish centrifugal whirl of the slurry fed into the chamber through the inlet before introduction of the slurry to the particle separation zone, an outlet conduit communicating with an end of said first member opposite said second imperforate member for discharge of centrifuged slurry from the housing, a

particle collecting and centrifuge damping zone formed by the cylindrical chamber wall and said outlet conduit, and an outlet for discharge of overweight and oversize particles from the particle collecting and centrifuge damping zone.

5. Apparatus for separating solid particles by size and weight from a liquid comprising: a housing having an upper cylindrical section and a lower cylindrical section of lesser diameter relative to the upper section, a downwardly tapering frusto-conical chamber section conmeeting the upper and lower chamber sections, a downwardly tapered frusto-conical screening member in the said frusto-conical chamber section and concentric therewith, the apertures of said screening member being of a size to pass particles of predetermined size to the interior thereof from a liquid centrifuging in the fnistoconical chamber and being in an amount sufiicient to minimize pressure differential across the member, a cylindrical imperforate discharge conduit extending into the upper cylindrical section and axially aligned with the interior of the screening member to receive centrifugal liquid therefrom, said conduit being of a length sufficient to establish centrifugal whirl in a liquid introduced under pressure tangentially into the upper cylindrical section, said frusto-conical screen being closed at its lower end, said lower cylindrical section providing a damping and particle collection zone, and an outlet communicating with said lower section for discharge of overweight and oversize particles.

References Cited in the file of this patent UNITED STATES PATENTS 601,355 Paterson Mar. 29, 1898 603,285 Porbeck May 3, 1898 971,013 Smith Sept. 20, 1910 1,757,834 Haegler May 6, 1930 1,797,812 Waring Mar. 24, 1931 2,514,159 Jonsson July 4, 1950 2,782,927 Derrick Feb. 26, 1957

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