Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
  • D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
  • D21D5/18—Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force
  • D21D5/24—Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force in cyclones
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04C—APPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
  • B04C5/00—Apparatus in which the axial direction of the vortex is reversed
  • B04C5/12—Construction of the overflow ducting, e.g. diffusing or spiral exits
  • B04C5/13—Construction of the overflow ducting, e.g. diffusing or spiral exits formed as a vortex finder and extending into the vortex chamber; Discharge from vortex finder otherwise than at the top of the cyclone; Devices for controlling the overflow

Definitions

• This invention relates to improvements in hydrocyclones, which includes centrifugal separators and centrifugal clean ⁇ ers. Its embodiment provides an improved construction for the overflow tube of a hydrocyclone which has unexpectedly resulted in the recovery of kinetic energy in the overflow as well as other significant benefits in the performance of the hydrocyclone. This is particularly evidenced in the application of the invention to the processing of pulp in a pulp refining operation. Accordingly, the invention will be described in this frame of reference, but only for pur ⁇ pose of illustration and not by way of limitation.
• a hydrocyclone is a device used for cleaning, separa ⁇ tion and/or classification of the contents of a relative fluid mass.
• the objective in its use is to extract and separate therefrom elements or particles of wood or other fibrous matter in the slurry best suited, and in a form best suited, for use in a par ⁇ ticular end product.
• the level.and amount of energy required for the operation of prior art hydrocyclones or hydrocyclone systems can be quite substantial.
• the extent of the pressure drop which occurs in the use of prior art hydrocyclones to process a pulp slurry limits the through ⁇ put of the slurry as well as its flow rate in moving through and from the hydrocyclone.
• the problems noted are and have been a matter of serious concern for a long period of time.
• the present invention not only overcomes the foregoing problems to a substantial degree but its application to any hydrocyclone of a given size provides it with an inherent mode of operation resulting in an increase in its feed flow rate as well as a significant improvement in its cleaning efficiency.
• the application of the invention enables more of the energy applied in use of a hydrocyclone to contribute, very effectively, to the spin of the flow of a slurry introduced to and moved within and longitudinally of the hydrocyclone separating chamber.
• the result of this last feature is a cleaner and more ef ⁇ fective separation of the contents of the slurry which is subjected to a separating procedure.
• Preferred embodiments of the present invention comprise a hydrocyclone the body of which defines therein a separating chamber having an overflow end and an underflow end, an inlet and at least two outlets, one to each of the opposite ends of the separating chamber. One of these outlets provides an underflow outlet and the other an overflow outlet.
• the inner wall of the hydrocyclone has a tubular configuration and the underflow and overflow outlets are in a substantially coaxial alignment.
• the inlet applies the slurry tangential to the inner wall surface of the hydrocyclone to develop within its separating chamber a vortex-type flow of the slurry producing counterflowing vortices thereof.
• the result of the counterflowing vortices is to induce, normally, a particularly desired portion of the contents of the slurry to move to an area within the separating chamber comprising its central longitudinally extending core from which such material is inherently in ⁇ quizd to flow to and through the overflow outlet of the hydrocyclone.
• another portion of the contents of the slurry within the separating chamber in ⁇ cluded in the outer of said counterflowing vortices is caused to move to and through the underflow outlet of the hydrocyclone.
• the over ⁇ flow outlet is defined by an overflow tube structure, here ⁇ inafter referred to as an overflow tube, the diameter of the inner surface of which is stepped along its length.
• the inner surface of the overflow tube de ⁇ fines an overflow passage one end of which communicates with the overflow end of the hydrocyclone separating chamber and the other end of which connects to a conduit or conduits for directing the discharge from the overflow tube to a desired place of storage or use.
• the inner surface of the overflow tube and the overflow passage which it defines are formed to produce therein a conversion of kinetic energy in flow therethrough from the hydrocyclone separating chamber to pressure energy. This produces inobvious and most ad ⁇ vantageous improvements in the performance of the hydrocyclone.
• what has been observed to occur in the use of an overflow tube having an overflow passage formed in accordance with the invention is a "hydraulic jump" phenomena.
• a preferred embodiment of the invention provides that the outflow passage defined by its overflow tube includes straight line segments of its length which are spaced by a relatively short coaxial segment which has the shape of a truncated cone.
• the upstream of these straight line segments will have a diameter corresponding to the small ⁇ est diameter of the relatively short segment which has the configuration of a truncated cone while the straight line segment of the outflow passage immediately downstream of this short segment will have a diameter which is relatively enlarged as compared to that of the upstream segment and corresponds with that of the downstream end of said short segment.
• the efficiency of the operation of a hydrocyclone of a given size is sub ⁇ stantially improved and there is a corresponding saving and added utilization of the available energy.
• a significant aspect of the invention is the economy possible in its em ⁇ bodiment.
• B UREA OMPI which are easy to fabricate and which render such devices more efficient and satisfactory in use, adaptable to a wide variety of applications and less likely to adversely function.
• Another object is to provide hydrocyclones with an outflow passage the construction of which creates hydraulic jump in the flow therethrough and consequent improvements in the hydrocyclone operating efficiency.
• a further object is to provide an overflow tube for a hydrocyclone the construction of which converts kinetic energy in flow therethrough to pressure energy, thereby to improve the operating and cleaning or separating ef ⁇ ficiency of the associated hydrocyclone.
• An additional object is to provide an outflow tube in connection with a hydrocyclone wherein immediately ad ⁇ jacent segments of the outflow passage which it defines are spaced and interconnected by a short segment of the length of the outflow passage which has the configuration of a truncated cone, producing a conical transition and ex ⁇ pansion of the cross section of the outflow passage from the smaller diameter of the passage segment immediately upstream to the larger diameter of the passage segment immediately downstream of said short segment.
• a further object is to provide a reduced pressure drop in the operation of a hydrocyclone cleaner of a given di ⁇ mension. Another object is to provide increased throughput or flow rate of a pulp slurry applied to a hydrocyclone for separation, cleaning or classification of its contents.
• An additional object of the invention is to provide an overflow tube and an assembly thereof with a hydrocyclone possessing the advantageous structural features, the in ⁇ herent meritorious characteristics and the means and mode of operation herein described.
• Figs. 1-4 each schematically exhibit the application of an overflow tube to a hydrocyclone having a form and con ⁇ struction and composition which is basically similar but somewhat different in each of the illustrations.
• the invention is herein illustrated and described with particular reference to its application to a hydrocyclone of the type advantageously used for the pro ⁇ cessing of the contents of a pulp slurry.
• Fig. 1 illustrates a hydrocyclone of this type the body or housing of which comprises an integral tubular shell-like peripheral wall structure 10 one longi ⁇ tudinally extending section 12 of the length of which is
• the diameter of the cross section of the section 12 is uniform the length thereof.
• the section 12 has one end thereof integrated with and longi ⁇ tudinally extended by a coaxial section 14 of the tubular wall structure 10.
• the section 14 which is thus a direct extension of the section 12 has the shape of a truncated cone which conically converges from the end of the section 12 with which it is integrally connected.
• the truncated apex end of the section 14 rims a small diameter opening 16 at this end of the tubular wall structure 10.
• annular plate 20 Connected with and in bridging relation to the end 18 of the section 12 which is remote from the section 14 is an annular plate 20.
• the outer limit of plate 20 is fixed in a sealed tight relation to the end 18 of section 12 and its inner limit is fixed about and in a sealed tight relation to the outer wall surface of a tubular overflow structure, hereinafter referred to as an overflow tube 22.
• a short tube 24 has one end thereof integrally connected to the section 12 immediately of the plate 20 to have what constitutes its discharge end rim an inlet opening 26 in the wall structure 10.
• the short tube 24 is so related to the opening 26 and the opening 26 so related to the inner sur ⁇ face of the wall structure 10 as to provide a tangential inlet to the separating chamber 28 which is defined by the plate 20 and the wall structure 10.
• the plate 20 defines the overflow end of the pulp pro ⁇ cessing art
• the overflow tube 22 defines an overflow passage " 30 leading f and communicating at its inlet end with the separating chambe As seen in Fig. 1, the overflow tube 22 is coaxially ali with the underflow outlet 16. Furthermore, the inner wall su of the overflow tube 22 is so constructed that the overflow p sage 30 has a central longitudinal axis the configuration of w is that of a straight line. As the overflow tube 22 is appli to the hydrocyclone in Fig.
• the segment 32 of the passage 3 has a uniform but relatively small diameter and is immediately followed by a segment 34 of the passage 30 which is very short in length.
• the portion of the inner wall surface of the tube 22 bounding the segment 34 has and provides the segment 34 wit a configuration corresponding to that of a truncated cone.
• Th cross sectional area exhibited by one end of this truncated cone has a diameter corresponding to that of the segment
• the overflow tube 22 has an inner wall surface which is stepped as to its diameter along the length thereof, thereby to provide an upstream segment 32 and a downstream segment 36 of the overflow passage spaced by the interposed conical segment 34.
• the thickness of the wall 40 of the overflow tube 22 is uniform except at its inlet end 42, where its outer surface expands to produce thereon a bell-shape immediately about the inlet to the overflow passage. Accordingly, except for the bell-shaped modification at its inlet end, the outer wall surface of the overflow tube has a configuration along its length which corresponds in all respects with the configuration of its inner wall sur ⁇ face which defines the overflow passage. Further noting Fig. 1, the overflow tube 22, as shown, has its enlarged diameter end projected outwardly of the plate 20 a limited extent and perpendicular thereto.
• Fig. 2 shows a hydrocyclone structure identical to that shown in and described with reference to Fig. 1 except for the construction and relative position of the illustrated overflow tube and the length of the section 12 of the wall • -n- structure 10 being somewhat shorter than that illustrated in Fig. 1.
• the overflow tube 52 of the hydrocyclone is distinguished by a uniformly cylindrical outer wall sur ⁇ face 50 the diameter of which is uniform from one end thereof to the other.
• the overflow tube 52 is so positioned in its perpendicular relation to the plate 20 that its re ⁇ spective ends are substantially equidistantly spaced from the adjacent surfaces of the plate 20 and its innermost ex ⁇ tremity is spaced longitudinally and outwardly from the plane transversely of and perpendicular to the longitudi ⁇ nal axis of the separating chamber 28 which intersects the connection between the sections 12 and 14 of the wall structure 10.
• the inner wall surface 58 defining the overflow or outflow passage 60 of the overflow tube 52 has the same general configuration as the inner wall sur ⁇ face of the overflow tube 22 but differs in that here the length of the smaller diameter upstream segment of the overflow passage which corresponds to the segment 32 of Fig. 1 is shorter and the length of its larger diameter downstream segment which corresponds to the segment 36 of Fig. 1 is longer than the respective lengths of the corresponding segments of the overflow passage 30 of the overflow tube 22.
• the hydrocyclone assembly of Fig. 3 is identical to that of Fig. 1 except for the following differences.
• Its overflow tube 22' which otherwise has a construction and configuration identical with that of the overflow tube 22 differs by reason of the elimination of the bell shape at the mouth of its inlet end.
• Another difference in the hydrocyclone assembly shown in Fig. 3 from that of Fig. 1 is that its overflow tube is so mounted with reference to the plate 20 to provide that the portion of the wall struc ⁇ ture of the overflow tube 22' bounding the segments 34 and 36 of its overflow passage are positioned exteriorly of the plate 20.
• the opening in the plate 20 is re ⁇ quizzed in diameter sufficient to accommodate and seal about the reduced external diameter portion of the wall of the overflow tube 22' bounding the upstream segment 32 of the overflow passage 30.
• the relative position of the overflow tube 22' provides, that the reduced diameter end of the conically configured segment 34 of its overflow passage lies in a plane corresponding to the plane of the outer surface of the plate 20.
• the axial length of the section 12 of the wall structure 10 is shortened in correspondence with the limited projection of the inlet end portion of the overflow tube with ref ⁇ erence to the inner surface of the plate 20.
• the con ⁇ figuration of the wall structure 10 provides that the sections 12 and 14 thereof are relatively elongated but otherwise similar to the corresponding sections in Fig. 1.
• a head plate such as the plate 20 incorporated in the embodiments of Figs. 1, 2 and 3
• the head 64 is configured to provide the overflow end of the hydrocyclone with an axial inlet 66 which is a blind bore parallel to the central longitudinal axis of its separating chamber 28.
• the inlet 66 opens later ⁇ ally to one end of a restricted helical flow passage 68 de ⁇ fined by the head with the inner wall surface;of the end of the wall structure 10 in which the head is plug fit.
• the flow passage 68 is extended and exits to a continuation of its helical form defined by the inner surface 62 of the head which defines the overflow end of the separating chamber 28.
• OMPI inwardly of the separating chamber from the surface 62 to have its innermost end terminate in a plane parallel to and in an adjacent spaced relation to and short of a plane transverse to the separating chamber 28 and perpendicular to its longi ⁇ tudinal axis which intersects the wall structure 10 at the connection between the sections 12 and 14 thereof.
• the tubular projection 70 defines part of the inlet segment 74 of an overflow passage 72 which is directed through the head from the separating chamber 28.
• the overflow passage 72 is composed of successive communicating segments a portion of which is angularly diverted and offset from the line of the segment 74 as the overflow passage extends through the head to have its outermost segments position parallel to the line of the inlet segment 74.
• the segment 76 of the overflow passage 72 immediately following the inlet segment 74 is angularly diverted from the line of segment 74 as it extends outwardly from the separating chamber and forms a continuation of the segment .74.
• the segments following the segment 76, in succession, which form a continuation thereof and each other, are re ⁇ spectively numbered in succession 78, 80 and 82.
• the seg ⁇ ments 78, 80 and 82 which have a coaxial alignment, are diverted, commonly, from the line of the segment 76 to extend in a line offset from and parallel to the line of the inlet segment 74.
• the diameter of the segments 74, 76 and 78 of the overflow passage are essentially the same and these segments are generally elongate, but in the case illustrated successively somewhat shorter in length.
• the segment 80 is very short in length and its cross section exhibits the shape of a conically expanding truncated cone. The smallest diameter of this cone is at its end im ⁇ mediately of the segment 78 and corresponds in dimension to the dimension of its diameter. The largest diameter end of the cone of the segment 80 opens to the segment 82 the di ⁇ ameter of which corresponds thereto.
• a slurry the contents of which are to be separated, cleaned and/or classified is in each case directed through the hydrocyclone inlet to the separating chamber 28 to move therein and the length thereof in a helical flow pattern producing counter- flowing vortices which inherently result in a portion of the slurry contents which have the form of fibers and fiber bundles which are light in weight and desirable in form being caused to move to the inner vortex portion of the slurry flow.
• the conically expanded segment 34, 80,of the overflow passage which is very short in length, has a "free expansion" cone angle expanding downstream in the direction of flow which can range from about 40° to about 80° as measured from the center line of the truncated conical segment to the conical surface defining its expansion and shape.
• the length of the segment of the overflow passage immediately upstream of the conically expanding segment should be equal to at least three times the dimension of the diameter of the inlet to the overflow passage. Furthermore, it is preferred and most desirable that the extension of the conical segment of the flow passage in the segment of this passage which is immediately downstream thereof should have a length equal to at least twice the dimension of the maximum diameter of the conical segment of the flow passage. For optimal results, the segments of the overflow passage immediately upstream and downstream of the conically expanding short segment thereof should have a coaxial relation.
• its diameter downstream of the con ⁇ ically expanded portion of the flow passage should be from about 1-1/2 to 2 times its diameter immediately upstreai. thereof. Smaller ratios could provide some benefit but would not achieve the practical gains so advantageous in the use of a hydrocyclone as herein described.
• OMPI dia eter for the inlet to the overflow tube than would nor ⁇ mally be provided and achieve therein better cleaning and separating efficiency with the same overall pressure drop as would be conventionally experienced using a prior art overflow tube.
• the invention application provides an ad ⁇ ditional benefit, namely an approximately 20% increase in the throughput of the hydrocyclone.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Cyclones (AREA)

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• 1982
  • 1982-05-07 EP EP19820902004 patent/EP0108058A4/de not_active Withdrawn
  • 1982-05-07 FI FI834886A patent/FI834886A0/fi not_active Application Discontinuation
  • 1982-05-07 WO PCT/US1982/000605 patent/WO1983003986A1/en not_active Ceased
• 1983
  • 1983-04-21 CA CA000426450A patent/CA1221659A/en not_active Expired

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