Eccentric head hydrocyclone

3,385,437

May 28, 1968

M. D. WOODRUFF

ECCENTRIC HEAD HYDROCYCLONE

Filed April 3, 1965

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ATTORNEYS

United States Patent Office

3,385,437

Patented May 28, 1368

3,385,437

ECCENTRIC HEAD HYDROCYCLONE Maurice D. Woodruff, Springfield, Ohio, assignor to The

Bauer Bros. Co., Springfield, Ohio, a corporation of Ohio

Filed Apr. 2,1965, Ser. No. 444,998 14 Claims. (Ci. 209—211)

This invention relates to the hydrocyclonic separation of a flowing slurry or the like into accepted and rejected fractions, and particularly to improvements therein achieving greater operating efficiency.

The invention has special, though not limited, reference to hydrocyclone separators, used in paper making processes to separate clean, usable fibrous material from a flowing slurry which, in addition to the usable material, contains unwanted heavier particles and dirt. A device of the kind described comprises means defining a separating chamber circular in cross section and open at its opposite ends to define outlets for the respective fractions. Through an inlet at the accepts end the flowing slurry is introduced tangentially into the separating chamber in a manner to progress from one end to the other in a swirling helical motion. The accepts end is located to receive and guide an inner vortex in which is comprised the accepted fraction, the rejected fraction discharging through the opposite or rejects end of the separating chamber. The described accepts and rejects ends of the separating chamber are considered as providing for overflow and underflow of respective slurry portions. These terms, however, do not denote attitude limitations since the hydrocyclone can be mounted in any position which is convenient from an installation standpoint, the speed of movement of the slurry through the separator making the device operationally independent of gravity.

The instant invention has in view the obtaining of a more thorough and precise separation between the acceptable and rejectable fractions in the separating chamber by creating a disturbing influence therein. The effect thereof is to reduce slurry consistency, particularly adjacent to the separator wall and to obviate the tendency of unwanted slurry particles to orbit within the separating chamber in conditions of equilibrium brought about by counteracting hydraulic and centrifugal forces.

An object of the invention is to present a generally new and simplified method of achieving more efficient separation in a hydrocyclone.

A further object of the invention is to present a method and apparatus in hydrocyclonic separators wherein means are provided exerting a disturbing influence within the separating chamber.

Still another object of the invention is to achieve objectives as in the foregoing through means inhering in the structure of the separator.

A still further object of the invention is to achieve operating efficiency as described in a separator especially characterized by simplicity of construction and by a useful life which is at least equal to that of standard hydrocylonic separators of the prior art.

A further object of the invention is to provide a hydrocyclonic separator possessing the advantageous structural features, the inherent meritorious characteristics and the mode of operation herein mentioned.

With the above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring to the accompanying drawing wherein is shown one but obviously not necessarily the only form of embodiment of the invention,

FIG. 1 is a view in longitudinal section of a hydrocyclonic separator in accordance with one illustrated etn5 bodiment of the invention;

FIG. 2 is a view in cross section, taken substantially along the line 2—2 of FIG. 1;

FIG. 3 is an enlarged detail view of a created ledge in the separator;

FIG. 4 is a view in cross section, taken substantially along the irregular line 4—4 of FIG. 1; and

FIG. 5 is a fragmentary view in longitudinal section showing another illustrated form of the invention.

Like parts are indicated by similar characters of ref15 efence throughout the several views.

In its illustrated embodiment, the invention is disclosed in a hydrocyclone separator as used especially in the pulp and paper industry to enable high standards of paper cleanliness. From a flowing pulp slurry containing not 20 only the light fibrous material desirable for paper making but also various undesirable materials, the unit operates to separate the slurry into acceptable and rejectable fractions, directing these to respectively different outlets. According to the objectives of the separator the highest pos25 sible percentage of bark specks, dirt solids, fibre aggregates, shives and the like is excluded from the accepts outlet and directed as a part of the main slurry to the rejects outlet. Within this concept the percentage of the pulp slurry reporting to the rejects outlet incorporates 30 minor amounts of usable fibres and hence is desirably low.

A hydrocyclonic separator according to the illustrated embodiment of the invention comprises a device of unitary construction, as by being made of a plurality of sections bolted or otherwise secured together. In FIG. 1 ³⁵ such a device 10 includes a body section 11 having the shape of a truncated cone, the interior of such body section being hollow to define a separating chamber 12 and the opposite ends of such chamber opening through the base and apex ends thereof. Further comprised in the ⁴ device 10 is a head section 13 mounted in generally superposed relation to the base end of section 11. The head section 13 comprises a cylindrical sleeve-iike portion 14. Through the cooperation of an internally threaded nut 15 the cylindrical portion 14 is drawn down ⁴⁵ to a seat on the base end of the section 11, the nut 15 reacting against an external flange 16 on section 11 near the base thereof.

The cylindrical portion 14 is formed with a longitudi₅₀ nal through bore 17. Received in the outer end of such bore is an expanded head portion 18 of a nozzle 19. A flange 21 on head portion 18 is drawn to a seat on the outer end of the cylindrical portion 14 by an internally threaded nut 22. The arrangement is one to hold 55 the assembly comprising cylindrical portion 14 and nozzle 19 in an assembled position relatively to one another and to the cone section 11. Further comprised in the nozzle 19 is an axial tube portion 23. Inwardly of the head portion 18 the tube 23 projects to a transverse plane ₆0 defined by the juncture of the base end of the body section 11 and the inner end of the cylindrical sleeve portion 14. On the other or outer end of the head portion 18 the tube 23 projects as an externally threaded connector 24 by which the device 10 is joined to outlet 55 conduit means. The tube 23 is open throughout its length and occupies a position in bore 17 spaced from the wall thereof and defining therewith an annular chamber 25. The chamber 25 overlies and communicates with the separating chamber 12 and may be considered a part 70 thereof.·

At its outer end the annular chamber 25 is closed by head portion 18 of the nozzle 19. Immediately within the

3,385.437 back wall of section 13, as defined by the head portion 18, is an inlet 26 communicating through a laterally projecting boss 27 with the exterior of the device 10, the boss 27 being adapted to be connected in a system to supply thereto a pulp slurry under pressure. The arrangement is one to introduce the pulp slurry into the cylindrical sleeve portion 14 tangentially of the wall of bore 17. The continued application of pressure at the inlet causes the pulp slurry to progress from the head section of the device through annular chamber 25 into the base end of section 11 and thence through separating chamber 12 to the apex end of section 11 in a swirling, helical motion inducing centrifugal forces.

As a result of these forces there is left in the axis of the device an area of low pressure creating what may be considered to be an inner vortex moving contra to the outer vortex, that is in a direction from the apex end to the base end. The nozzle 19 serves in this connection as a vortex finder, the inner end of its tube 23 extending to receive the inner vortex and to conduct it out of the separating device, the outer end of the nozzle being adapted, as noted, for connection in a suitable conduit to conduct the materials caught in the inner vortex to a subsequent process step. In accordance with the concept and mode of operation of the separator, relatively light and desirable fibres from the liquid pulp slurry are gathered up by the inner vortex and conducted out through the head section 13 by way of nozzle 19. This comprises the accepted fraction, the remainder of the slurry leaving the separator through the apex end of the section 11 as the rejected fraction.

Considering further the flow effects taking place in the separator, the velocity of flow of the slurry accelerates rapidly and uniformly as it encounters the decreasing diameter of conical body section 11. The centrifugal action forcing heavier particles outward toward the wall of the separating chamber is greatly multiplied. At the same time, however, a spiraling column, moving in the opposite direction, is formed in the central region of the separating chamber, at the axis of which is a liquid free core. In operation, the light desirable pulp particles transfer from the outer vortex to the inner vortex and are directed thereby to and through the accepts nozzle 19.

The device provides opposed components of flow directed respectively toward the base and apex ends of the separator chamber 12. A pressure differential from the outer chamber wall toward the center line or axis of the chamber 12 produces a movement of liquid in this direction, this being in conjunction with the downward component of liquid flow. Some “dirt” particles moving toward the outer wall under centrifugal influence may find themselves balanced by the involved forces. As a result, these particles assume a position of equilibrium and go into a more or less fixed orbit. Eventually these particles leave their orbits and appear, unpredictably, in the accepts or the rejects fractions. Also, when the slurry is introduced into the cleaner the pulp and dirt begin to move to the outside of the separator wall. The population of solids adjacent the chamber wall increases. As subsequent dirt particles attempt to join or move through this population collisions occur. Some dirt particles thus may not reach the outer wall but instead be caused to intersect the inner vortex and come under the influence of this stream. The increased consistency in the region of the separator wall thus has the effect of restricting outward motion of dirt particles, allowing some of these particles to be drawn into the center vortex along with acceptable material. Pulp material is separated or “cleaned” in stages and improvements in the efficiency of the hydrocyclone are desirable as reducing the number of required stages, as well as providing clean, conditioned pulp for the paper making process in as facile and economical a manner as possible.

In accordance with the instant invention improved ' . 4 efficiency is achieved by creating a controlled turbulence in the slurry flow in the separating chamber 12 in an area within or beyond the inner end of nozzle 19. The flow disturbance has the effect of reducing consistency at the 5 separator wall and of inhibiting orbiting by dirt particles.

In achieving this result, in the illustrated instance, the bore 17 in cylindrical sleeve portion 14 is formed eccentrically of the sleeve axis.

The annular chamber 25 and the separating chamber 10 12 proper accordingly are misaligned. The sleeve 14 is so positioned atop the base end of body section 11 as to align a segment of the wall of bore 17 with the wall of separating chamber 12. This occurs in the relatively thin wall portion of the sleeve 14 and the transfer of flowing 15 slurry at this location from the annular chamber 25 to the chamber 12 proper is a relatively smooth and uninterrupted motion. However, the relatively thicker section of sleeve 14 under this mounting condition overlaps the engaged part of the base end of section 11 in such 20 manner as to define in effect an arcuate, undercut or inverted ledge 28. The location of such ledge is in the aforementioned transverse plane at the juncture of sleeve portion 14 and the base end of conical body section 11. In consequence of the described construction, slurry 25 flowing helically through the annular chamber 25 encounters an abrupt drop-off at the location of ledge 28. The slurry accordingly reaches the underlying wall of chamber 12 with a diffused eccentric action. The result is to produce roiling turbulence in the region of the 30 separator wall beneath nozzle 19. By reason of the helical motion of the slurry, the region of turbulence is spread circumferentially of the separator wall and is projected as a continuing disturbance longitudinally thereof. This turbulence disturbs the equilibrium condi35 tions conducive to orbiting of dirt particles and accordingly inhibits such orbiting tendency. Also, in the turbulent area the tendency of pulp particles to assume dense, relatively impenetrable formations is inhibited. The consistency toward and in the region of the separator wall 40 is accordingly restrained from increasing or is relatively reduced as before described.

While the bore 17 is eccentrically disposed relative to the axis of conical body section 11, the nozzle 19 is concentric to such axis. This is accomplished by forming 45 in the outer end of the cylindrical sleeve portion 14 a counterbore 29 which is concentric with the axis of section 11 and which seats therein the head portion 18 of the nozzle 19. The bore 17 is eccentric troughout its length except for counterbore 29, and inlet 26 is posi50 tioned to be diametrically opposed to the portion of greater width of the ledge 28. Modifications of these arrangements are, of course, possible, particularly one placing the ledge 28 at any point along the length of the bore 17. Further, the arcuate distance of such ledge may 55 be varied or it may in fact be continuous around the circumference of the base end of section 11. The present arrangement, whereby a portion of the communicating passage between annular chamber 25 and separator chamber 12 is comprised of a smooth uninterrupted sur60 face is deemed desirable since it gives an opportunity for abrasive particles in the slurry to escape from beneath the ledge 28 and be directed along with other rejectable material to the apex outlet. Sand or other grit may become trapped beneath a continuous ledge 28, and, in 65 continuous rotation under centrifugal force, produce excessive wear on the separator wall. It is a feature of this invention that the desired, controlled turbulence is produced without means productive of unusual or excessive wear, the created turbulence being in the main comprised 70 of liquid movements resulting from transfer of the pulp slurry from the annular chamber 25 to the relatively misaligned separator chamber 12.

Another modification may find the ledge 28, rather than being downtumed or inverted relative to slurry 75 flow, facing upward or toward inlet 26. The results, in

3,385,437 the production of controlled turbulence are like those of the illustrated form. Slurry reaching such ledge has its flow pattern disturbed, tends to be turned back upon itself and proceeds into and through the separator chamber with incorporated areas of turbulence. This modifica- 5 tion may be achieved, perhaps most imply, by making bore 17 larger in diameter than it is at present in such manner that the formed ledge is provided by an arcuate portion of the base end of section 11.

In still another modification nozzle 19 and bore 17 ₁₀may be made concentric with one another while section 11 is made eccentric to both. This produces, selectively, either an upturned or down turned ledge corresponding to the ledge 28. The required degree of eccentricity is slight but if necessary more nearly to align the underflow 15 apex outlet with the overflow nozzle 23 the body section 11 may be caused to assume a slightly tilted position.

The means of the invention has been described as operating to improve the efficiency of a hydrocyclone by inhibiting particle orbiting therein and by reducing con- 20 sistency toward the separator wall. It is possible, however, that other operational factors are involved presently unknown. Thus no attempt is made exhaustively to analyze the effects produced by the invention in its various forms. It is known that efficiency improvements 25 result and it has been the object herein merely to state some of the likely or probable causes therefor without excluding others.

In terms of rejection rate, by which is meant the percentage of slurry discharged through the rejects outlet 30 under given conditions of pressure, stock consistency, temperature and the like, the instant invention affords distinct and substantial advantages.

As compared to a standard separator the rejection rate is significantly lower at elevated pulp temperatures. It 35 is well established that heretofore the higher the temperature of pulp in a pulp mill the greater will be the rejection rate. “In direct test comparisons, it has been shown that a standard separator has been adversely affected by increases in pulp temperature, the rejection rate 40 more than tripling under comparatively modest temperature rises as from 90° F. to 111° F. A separator of the instant invention, however, operating under the same conditions, has its reject rate relatively unaffected by the temperature rise.” Thus, from a practical standpoint, the 45 separator with the eccentric bore in the head has substantial advantages over a standard device. It is capable of operating to greater advantage over a wide range of temperatures. Also it is more efficient. The turbulence created in the upper part of the separator chamber pre- 50 vents matting of the fibers as they move down the inner wall of the cone section. Since the consistency of the layer near the well is lower with the eccentric head cleaner, there are fewer collisions between a dirt particle making its way to the wall and the fibres which lie 55 therebetween.

Further, increased separating efficiency is accomplished under conditions of reduced pressure drop, yielding advantages in lower power consumption. Thus the kind and degree of turbulence achieved is such as to facilitate 60 movement of liquid to the center vortex without, however, inhibiting access of acceptable solids thereto. As a result a given throughput in terms of gallons per minute may be achieved in a separator of the present invention at relatively low cost in pressure drop, the indicated ⁶⁵reduction over the prior art being in excess of twenty percent.

In referring herein to relatively eccentrically disposed cylinder and body portions it is not intended to exclude ₇θ constructions in which the eccentricity is obtained by insert means installed in the head section. Thus a separator with concentric head and body portions may be modified to perform in accordance with the present invention by mounting in the head section a crescent shaped 75 insert or the like producing a ledge corresponding to and functioning as the ledge 28. Such insert device, within concepts previously expressed, may be coextensive in length with the head section or occupy only a lower or upper part thereof. FIG. 5 hereof shows, in partly diagrammatic form, a separator body 31 comprising concentric head and cone sections 32 and 33. A crescent shaped segment 34 is installed in the head section 32 in a generally opposed relation to an inlet 35 and in a manner presenting a ledge 36 over which the slurry discharges in a part of the circumference of the head in passing into the cone section.

Further, it will be understood that the invention is applicable not only to separators having cylindrical head and conical body sections, but also to separators of single configuration. For example a form of separator in common use defines throughout its length a single section of a cone. The base end thereof serves as the “head” and may be constructed in accordance with any of the foregoing examples to achieve the instantly provided ledge. In substance therefore, the invention contemplates a fully conical separator, respective sections of which may be eccentrically offset to produce a flow disturbing ledge as provided by the present invention.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modifications in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific feaures shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.