Hydrocyclone

Abstract

A hydrocyclone comprises: an inlet chamber including a generally cylindrical body and a feed inlet generally tangential thereto; a separation chamber extending downwards from the inlet chamber; an underflow discharge leading from the separation chamber; an air removal chamber extending upwards from the inlet chamber; and a vortex finder. The vortex finder comprises an insert portion extending through the air removal chamber and into the inlet chamber such that an annular swirl volume is defined within the inlet and air removal chambers and around the insert portion. The air removal chamber further comprises an air vent discharge in fluid communication with the annular swirl volume. During operation, air entrained in the slurry rises up the annular swirl volume and exits via the air vent discharge.

Description

[0001] HYDROCYCLONE

[0002] FIELD OF INVENTION

[0003] This invention relates to separation apparatus. More particularly, it relates to a hydrocyclone and to a method of operating the hydrocyclone.

[0004] BACKGROUND OF THE INVENTION

[0005] Hydrocyclones typically comprise a hollow body that includes an upper, generally cylindrical, section and a lower, frusto-conical section. The upper section includes a generally tangential feed inlet and receives and imparts swirling flow to a feed as it enters therein. The lower section extends downwards from the upper section and defines a separation chamber.

[0006] A spigot is coupled to a lower part of the separation chamber and forms a discharge outlet or underflow discharge through which heavier particles are discharged.

[0007] A tubular member, usually referred to as a vortex finder extends through an upper end of the upper section and has an inlet end which is positioned in the cavity defined by the body and an outlet end which forms an outlet or overflow through which lighter particles and / or water is discharged.

[0008] In use, fluid is fed into the body through the feed inlet such that a vortex or swirling flow is created within the body. As it enters the lower section, the spiralling fluid initially moves downwardly in the form of an outer vortex and then at least a portion of the spiralling fluid, referred to herein as an overflow stream, moves upwardly in the form of an inner vortex (or air core) through the centre of the separator and out through the vortex finder as overflow. By virtue of the configuration of the body, the fluid and the particles entrained therein are subjected inter alia to centripetal and gravitational forces. This causes a separation of the particles based on particle size, weight and / or specific gravity, such that larger, heavier more dense particles move radially outwardly in the outer vortex and are discharged through the underflow discharge and smaller, lighter, less dense particles remain entrained in the portion of the fluid forming the inner vortex or overflow stream which passes through the vortex finder and out through the overflow discharge.

[0009] This arrangement provides a cost-effective manner of separating the particles into two groups, i.e. a coarse fraction containing larger, heavier and / or more dense particles which are discharged from the underflow discharge opening defined by a spigot and a fine fraction or overflow stream containing smaller, lighter and less dense particles which are discharged from the vortex finder through the overflow.

[0010] One potential application for cyclones is in separating a slurry containing a high percentage of air in addition to particles suspended in liquid. The presence of air typically has an adverse effect on cyclone operation.

[0011] It is an object of embodiments of this invention to provide means that alleviate or remove this problem or other problems in the prior art, or provide a useful alternative.

[0012] SUMMARY

[0013] This summary is provided to introduce a selection of concepts that are further described in the detailed description below. This summary is not intended to identify indispensable features of the claimed subject matter, nor is it intended for use as an aid in limiting the scope of the claimed subject matter.

[0014] According to a first aspect, there is provided a hydrocyclone for separating aerated slurry into three discharge streams, the hydrocyclone comprising: an inlet chamber including a generally cylindrical body and a feed inlet generally tangential thereto; a separation chamber extending downwards from the inlet chamber; an underflow discharge leading from the separation chamber; an air removal chamber extending upwards from the inlet chamber; and a vortex finder comprising (i) an insert portion extending through the air removal chamber and into the inlet chamber such that an annular swirl volume is defined within the inlet and air removal chambers and around the insert portion, and (ii) a protruding portion extending above the air removal chamber and defining an overflow discharge; the air removal chamber further comprising an air vent discharge in fluid communication with the annular swirl volume such that, during operation, air entrained in the slurry as it enters the inlet chamber rises up the annular swirl volume and exits via the air vent discharge without passing into the separation chamber.

[0015] Optionally, the separation chamber has a frusto-conical shape.

[0016] Preferably, the inlet chamber is generally cylindrical on an outer surface and includes a partial helix on an inside surface thereof to impart a swirling motion to slurry fed therein. Preferably, the insert portion is co-axial with the protruding portion. The insert portion and the protruding portion of the vortex finder may have the same internal diameter.

[0017] Preferably, the underflow discharge is defined by an end of a spigot coupled to the frusto-conical separation chamber. The spigot may include a tapering portion (e.g. where the spigot couples to the separation chamber) and a cylindrical portion (e.g. defining the underflow discharge). The tapering portion may taper axially inwards as it extends away from the separation chamber.

[0018] Optionally, a distal end of the insert portion may extend into the separation chamber. Alternatively, the distal end of the insert portion may terminate axially above the separation chamber.

[0019] Optionally, the air vent comprises an outlet extending generally tangentially to the cylindrical body.

[0020] Optionally, the outlet may comprise a pressurised chamber.

[0021] Optionally, the air vent discharge is located above the feed inlet.

[0022] Optionally, the air vent discharge is located at a side of a generally cylindrical body of the air removal chamber. Alternatively, the air vent discharge is located on a top of the air removal chamber.

[0023] Optionally, the air vent discharge may comprise a pressure relief valve.

[0024] Optionally, the inlet chamber and the air removal chamber are portions of a unitary upper chamber.

[0025] By virtue of this aspect, an aerated slurry may be fed into the hydrocyclone and separated into a coarse fraction, a light fraction including liquid, and air. This is advantageous where it is desired to remove air from an aerated slurry in addition to separating the slurry into a coarse (or heavy) stream and a fine (or light) stream.

[0026] According to a second aspect, there is provided a method of separating aerated slurry into three discharge streams using a hydrocyclone, the method comprising receiving an aerated slurry; directing a heavy particle stream to an underflow discharge; directing a lighter particle stream to an overflow discharge; and directing an air stream to an air vent discharge instead of into the separation chamber.

[0027] The hydrocyclone may comprise a hydrocyclone according to the first aspect. According to a third aspect, there is provided an upper chamber for use with a separation chamber and a vortex finder of a hydrocyclone, the upper chamber defining an internal volume surrounding a pipe of the vortex finder leading to an overflow discharge, the upper chamber, and the upper chamber comprising: (i) an inlet chamber comprising: (a) a cylindrical body, and (b) a feed inlet generally tangential to the cylindrical body; and (ii) an air removal chamber comprising an air vent discharge in fluid communication with the internal volume such that, during operation, air entrained in the slurry rises up the internal volume and exits via the air vent discharge without passing into the separation chamber.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] These and other aspects will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

[0030] Figure 1 is a simplified, schematic perspective view of a hydrocyclone in accordance with one embodiment of the invention;

[0031] Figure 2 is an exploded perspective view of the hydrocyclone of Figure 1 ;

[0032] Figure 3 is a simplified, pictorial perspective view of illustrating an aerated slurry being separated in the hydrocyclone of Figure 1 ;

[0033] Figure 4 is a simplified perspective view of a hydrocyclone in accordance with another embodiment;

[0034] Figure 5 is a simplified top view of the hydrocyclone of Figure 4;

[0035] Figure 6 is a simplified, longitudinal sectional view of the hydrocyclone of Figure 4;

[0036] Figure 7 is a simplified perspective view of a hydrocyclone in accordance with yet another embodiment;

[0037] Figure 8 is a simplified top view of the hydrocyclone of Figure 7; and

[0038] Figure 9 is a simplified, longitudinal sectional view of the hydrocyclone of Figure 7.

[0039] DETAILED DESCRIPTION OF EMBODIMENTS

[0040] Reference is now made to the drawings, and particularly to Figure 1 , which is a simplified, schematic, perspective view of a hydrocyclone 10 in accordance with one embodiment of the invention. The hydrocyclone 10 defines an axis 11 , which in this embodiment is an upright axis, but in other embodiments the hydrocyclone 10 may be used at an incline, in which embodiments the axis 11 would be at a (nonzero) angle to the vertical.

[0041] In this embodiment, the hydrocyclone 10 comprises: an upper chamber 12 and a frusto-conical separation chamber 16 extending from a lower part of the upper chamber 12 and narrowing as it extends downwards (i.e. tapering inwards). The hydrocyclone 10 further comprises: a spigot 18 coupled to a lower portion of the separation chamber 16 and defining an underflow discharge 20 at an end opposite the separation chamber 16, and a vortex finder 22.

[0042] The upper chamber 12 comprises an inlet chamber 26 at a lower part thereof, and an air removal chamber 28 at an upper part thereof. The inlet chamber 26 and the air removal chamber 28 are mutually coupled in this embodiment, but in other embodiments they may be a unitary construction.

[0043] The inlet chamber 26 includes a generally cylindrical body 30 (best seen in Figure 2) and a feed inlet 32. The feed inlet 32 includes an external opening 34 into which aerated slurry may be fed from a pipe, spool or other connection. An inner side of the feed inlet 32 defines an extended slot, matching a corresponding entrance aperture in a sidewall 36 of the cylindrical body 30, so that slurry entering the feed inlet external opening 34 passes through the feed inlet 32 and swirls as it enters an internal volume of the upper chamber 12. The feed inlet 32 is generally tangential to the cylindrical body 30.

[0044] The air removal chamber 28 includes a generally cylindrical body 40 (best seen in Figure 2) having a sidewall 42 in registration, and coaxial, with the inlet chamber body sidewall 36. However, in other embodiments, the upper chamber sidewall 42 and the inlet chamber sidewall 36 may be unitary, such that the inlet chamber 26 and the air removal chamber 28 are non-separable portions of a single upper chamber.

[0045] The air removal chamber 28 further comprises an air vent discharge 44 located axially above the feed inlet opening 34 and extending from the air removal chamber sidewall 42. The air vent discharge 44 defines an exit aperture 46 at a distal end from the sidewall 42. The air vent discharge 44 is generally tangential to the generally cylindrical body 40.

[0046] The vortex finder 22 comprises a pipe 50 having an insert portion 52 at a lower part thereof. The insert portion 52 extends through the air removal chamber 28 and into the inlet chamber 26 such that an annular swirl volume 54 (having a donut shape) is defined within the upper chamber 12 and around the insert portion 52. The pipe 50 also has a protruding portion 56 extending above a top (or cap) 58 of the air removal chamber 28 and defining an overflow discharge 60.

[0047] The top (or cap) 58 of the air removal chamber 28 defines an aperture 62 (best seen in Figure 2) through which the pipe 50 is inserted.

[0048] Although the pipe 50 is a unitary component in this embodiment, in other embodiments multiple coupled components may be used; e.g. two tubular cylinders may be used, having the same (or a different) internal diameter and being axially aligned.

[0049] Reference is now also made to Figure 3, which is a simplified, pictorial perspective view of the hydrocyclone 10, (with the hydrocyclone 10 having transparent walls) illustrating an aerated slurry being separated in the hydrocyclone 10. The air bubbles are illustrated by lines 70, and the slurry is illustrated by lines 72.

[0050] The air vent discharge 44 is in fluid communication with the annular swirl volume 54 such that, during operation, when a slurry / air mixture (i.e. air entrained in a slurry) is fed into the hydrocyclone 10 under pressure via the opening 34 of the feed inlet 32, there is a natural segregation of the air and slurry, with air bubbles generally rising to the top due to the density difference. This means that the air bubbles mainly occupy an upper layer of the slurry / air input stream.

[0051] When this slurry mixture enters into the upper chamber 12, the lighter (aerated) slurry and froth circulate in the annular swirl volume 54 around the insert portion 52 of pipe 50 thereby releasing air into the upper part of the upper chamber 12, i.e. into the air removal chamber 28. The positive pressure within the hydrocyclone 10 causes the released air to exit from the air removal chamber 28. Thus, air entrained in the slurry rises up the internal volume and exits via the air vent discharge 44 without (instead of) passing into the separation chamber 16. Removing air entrained in the slurry as it enters the hydrocyclone 10 and before it reaches the separation chamber 16 has a number of advantages. The vortex finder 22 creates a pressure drop in the separation chamber 16, which is influenced by the velocity of the fluid in the vortex finder 22. By removing air from the fluid as it enters the vortex finder 22, the fluid occupies less volume so the pressure drop is reduced. This improves the capacity of the hydrocyclone 10. In addition, air bubbles (formed by the entrained air) create turbulence in the separation chamber 16, removing air bubbles prior to the separation chamber 16 should result in a higher classification efficiency because of the reduced turbulence.

[0052] The de-aerated slurry moves downwards from the upper chamber 12 to the separation chamber 16, where hydroclassification occurs in a conventional manner such that the de-aerated slurry is separated into a fine particle steam (exiting via the vortex finder 22) and a coarse particle stream (exiting via the spigot 18).

[0053] By virtue of the configuration of the separation chamber 16, particles contained within the fluid are separated with the larger, heavier, more dense particles being discharged through the underflow discharge 20 defined by the spigot 18. An overflow stream containing the lighter particles, and some of the liquid in which they are suspended, passes upwardly through the vortex finder 22 and out through the overflow discharge 60. Air entrained in the slurry rises upwards into the annular swirl volume 54, from where it exits the hydrocyclone 10 via the air vent discharge 44. Thus, the hydrocyclone 10 generates three exit streams - overflow, underflow and air.

[0054] Reference is now made to a second embodiment, shown in Figures 4 to 6. In Figures 4 to 6, corresponding parts to the first embodiment have 100 added to the reference numerals. In this embodiment, a hydrocyclone 110 includes a unitary upper chamber 112.

[0055] The hydrocyclone 110 defines an upright axis 111. In this embodiment, the hydrocyclone 110 comprises: a unitary upper chamber 112 and a frusto-conical separation chamber 116 extending from a lower part of the upper chamber 112 and narrowing as it extends downwards. The hydrocyclone 110 further comprises: a spigot 118 coupled to a lower portion of the separation chamber 116 and defining an underflow discharge 120 at an end opposite the separation chamber 116, and a vortex finder 122. The separation chamber 116 comprises a plurality of mutually coupled frusto-conical sections, together defining a continuously-tapered sidewall. In Figure 4, two frusto-conical sections 124a,b are shown.

[0056] The upper chamber 112 comprises an inlet chamber 126 at a lower part thereof, and an air removal chamber 128 at an upper part thereof. The inlet chamber 126 and the air removal chamber 128 are formed as a unitary component having a generally cylindrical body 131 (Figure 5) having an outer sidewall 137.

[0057] The inlet chamber 126 includes a feed inlet 132 having a generally volute shape extending circumferentially around an upper portion of the generally cylindrical body 130 (best seen in Figure 5). The feed inlet 132 includes an opening 134 into which aerated slurry may be fed. An inner side of the feed inlet 132 defines an extended slot, matching a corresponding opening 139 (Figure 6) of the upper chamber body outer sidewall 137 (the part that is in registration with the feed inlet 132), so that slurry entering the feed inlet opening 134 swirls as it passes through the feed inlet 132 and enters an internal volume of the upper chamber 112. The feed inlet 132 is generally tangential to the cylindrical body 130.

[0058] The air removal chamber 128 further comprises an air vent discharge 144 located axially above the feed inlet opening 134 and extending partially around the upper chamber cylindrical body 131. The air vent discharge 144 defines an exit aperture 146 at a distal end from the sidewall 137. The air vent discharge 144 is generally tangential to the generally cylindrical body 131. The air removal chamber 128 defines a pressure relief exit 148 in registration with the air vent discharge 144. A pressurised pipe may be coupled to the exit aperture 146 in some embodiments.

[0059] The vortex finder 122 comprises a pipe 150 having an insert portion 152 at a lower part thereof. The insert portion 152 extends through the air removal chamber 128 and into the inlet chamber 126 such that an annular swirl volume 154 (having a donut shape) is defined within the upper chamber 112 and around the insert portion 152. The pipe 150 also has a protruding portion 156 extending above a top (or cap) 158 of the air removal chamber 128 and defining an overflow discharge 160.

[0060] The top (or cap) 158 of the air removal chamber 128 defines an aperture 162 (best seen in Figure 2) through which the pipe 150 is inserted.

[0061] Although the pipe 150 is a unitary component in this embodiment, in other embodiments multiple coupled components may be used; e.g. two tubular cylinders may be used, having the same (or a different) internal diameter and being axially aligned.

[0062] The operation of the hydrocyclone 110 is similar to that of hydrocyclone 10 in that the hydrocyclone 110 generates three exit streams - overflow, underflow and air. Reference is now made to a third embodiment, shown in Figures 7 to 9. The third embodiment is very similar to the second embodiment, except that the air vent discharge 244 and the exit aperture 246 in the third embodiment are on the opposite side of the cylindrical body to the air vent discharge 144 and the exit aperture 146 in the second embodiment. The air vent discharge 244 and the exit aperture 246 also face the opposite way to the air vent discharge 144 and the exit aperture 146.

[0063] In Figures 7 to 9, corresponding parts to the second embodiment have 100 added to the reference numerals, and identical parts have the same reference numeral. In this embodiment, a hydrocyclone 210 includes a unitary upper chamber 212.

[0064] The hydrocyclone 210 defines an upright axis 211. In this embodiment, the hydrocyclone 210 comprises: a unitary upper chamber 212 and a frusto-conical separation chamber 116 extending from a lower part of the upper chamber 212 and narrowing as it extends downwards. The hydrocyclone 210 further comprises: a spigot 118 coupled to a lower portion of the separation chamber 116 and defining an underflow discharge 120 at an end opposite the separation chamber 116, and a vortex finder 122.

[0065] The upper chamber 212 comprises an inlet chamber 226 at a lower part thereof, and an air removal chamber 228 at an upper part thereof. The inlet chamber 226 and the air removal chamber 228 are formed as a unitary component having a generally cylindrical body 231 (Figure 8) having an outer sidewall 237.

[0066] The inlet chamber 226 includes a feed inlet 132 having a generally volute shape extending circumferentially around an upper portion of the generally cylindrical body 230 (best seen in Figure 8).

[0067] The air removal chamber 228 further comprises an air vent discharge 244 located axially above the feed inlet opening 134 and on an opposite side of the cylindrical body 231 thereto. The air vent discharge 244 extends partially around the upper chamber cylindrical body 231. The air vent discharge 244 defines an exit aperture 246 generally tangential to the generally cylindrical body 231. The air removal chamber 228 defines a pressure relief exit 248 in registration with the air vent discharge 244. A pressurised pipe may be coupled to the exit aperture 246 in some embodiments. The operation of the hydrocyclone 210 is similar to that of hydrocyclones 110 and 10 in that the hydrocyclone 210 generates three exit streams - overflow, underflow and air.

[0068] It should now be appreciated that these embodiments have the advantage that air entrained in a slurry can be selectively removed by the hydrocyclone 10, 110, 210 during normal operation such that three discharge streams are provided.

[0069] Various modifications may be made to the above described embodiments within the scope of the present invention. In other embodiments, the air vent discharge 44, 144, 244 may be located in a different position, for example, in the top 58, 158 of the upper chamber 12, 112, 212 to one side of the pipe 50, 150 of vortex finder 22, 122. In other embodiments, the separation chamber may have a different shape, for example, cylindrical instead of frusto-conical.

[0070] In other embodiments, an extension portion may be provided between the inlet chamber and the separation chamber. The extension portion may be generally cylindrical.

[0071] In the above embodiments, the feed inlet imparts a clockwise (as viewed from above) rotation because the feed inlet is located on the left-hand side of the hydrocyclone; but in other embodiments, the feed inlet may impart an anti-clockwise rotation (as viewed from above), for example if the feed inlet is located on the righthand side of the hydrocyclone.

[0072] Reference Numerals hydrocyclone (hydrocyclone) 10, 110, 210 hydrocyclone axis 11 , 111 , 211 upper chamber 12, 112, 212 separation chamber 16, 116 spigot 18, 118 underflow discharge 20, 120 vortex finder 22, 122 inlet chamber 26, 126, 226 air removal chamber 28, 128, 228 cylindrical body (of inlet chamber) 30, 130, 230 feed inlet (of inlet chamber) 32, 132 opening (of feed inlet) 34, 134 sidewall (of inlet chamber body) 36, 136 cylindrical body (of air removal chamber) 40 sidewall (of air removal chamber) 42 air vent discharge 44, 144 exit aperture (of air vent discharge) 46, 146 pipe (of vortex finder) 50, 150 insert portion (of pipe) 52, 152 annular swirl volume 54, 154 protruding portion (of pipe) 56, 156 top or cap (of inlet chamber) 58, 158 overflow discharge 60, 160 cap aperture 62, 162 frusto-conical sections 124a,b cylindrical body (of unitary upper chamber) 131 , 231 outer sidewall (of unitary upper chamber) 137, 237 opening (of upper chamber body sidewall) 139 pressure relief exit 148, 248

Claims

CLAIMS1 . A hydrocyclone for separating aerated slurry into three discharge streams, the hydrocyclone comprising: an inlet chamber including a generally cylindrical body and a feed inlet generally tangential thereto; a separation chamber extending downwards from the inlet chamber; an underflow discharge leading from the separation chamber; an air removal chamber extending upwards from the inlet chamber; and a vortex finder comprising (i) an insert portion extending through the air removal chamber and into the inlet chamber such that an annular swirl volume is defined within the inlet and air removal chambers and around the insert portion and (ii) a protruding portion extending above the air removal chamber and defining an overflow discharge; wherein the air removal chamber further comprises an air vent discharge in fluid communication with the annular swirl volume such that, during operation, air entrained in the slurry as it enters the inlet chamber rises up the annular swirl volume and exits via the air vent discharge without passing into the separation chamber.

2. A hydrocyclone as claimed in claim 1 , wherein the inlet chamber is generally cylindrical on an outer surface and includes a partial helix on an inside surface thereof to impart a swirling motion to slurry fed therein.

3. A hydrocyclone as claimed in claim 1 or 2, wherein the insert portion is coaxial with the protruding portion and they have the same internal diameter.

4. A hydrocyclone as claimed in claim 3, wherein a distal end of the insert portion extends into the separation chamber.

5. A hydrocyclone as claimed in any preceding claim, wherein the air vent discharge comprises an outlet extending generally tangentially to the cylindrical body.

6. A hydrocyclone as claimed in claim 5, wherein the outlet comprises a pressurised chamber.

7. A hydrocyclone as claimed in any preceding claim, wherein the air vent discharge is located at a side of a generally cylindrical body of the air removal chamber above the feed inlet.

8. A hydrocyclone as claimed in any one of claims 1 to 6, wherein the air vent discharge is located on a top of the generally cylindrical body of the inlet chamber.

9. A hydrocyclone as claimed in any preceding claim, wherein the inlet chamber and the air removal chamber are portions of a unitary upper chamber.

10. A hydrocyclone as claimed in any preceding claim, wherein the hydrocyclone further comprises a cylindrical extension portion located between the inlet chamber and the separation chamber.

11. A hydrocyclone as claimed in any preceding claim, wherein the separation chamber has a generally frusto-conical shape.

12. A hydrocyclone as claimed in any preceding claim, wherein the air vent discharge is located on an opposite side to the feed inlet.

13. A hydrocyclone as claimed in any preceding claim, wherein the feed inlet imparts a clockwise spin to medium fed therein.

14. A method of separating aerated slurry into three discharge streams using a hydrocyclone according to any of claims 1 to 13, the method comprising:(i) receiving an aerated slurry;(ii) directing a heavy particle stream to an underflow discharge;(iii) directing a lighter particle stream to an overflow discharge; and(iv) directing an air stream to an air vent discharge instead of into the separation chamber.

15. An upper chamber for use with a separation chamber and a vortex finder of a hydrocyclone, the upper chamber defining an internal volume surrounding a pipe of the vortex finder leading to an overflow discharge, the upper chamber comprising:(i) an inlet chamber comprising: (a) a cylindrical body, and (b) a feed inlet generally tangential to the cylindrical body; and(ii) an air removal chamber comprising an air vent discharge in fluid communication with the internal volume such that, during operation, air entrained in the slurry rises up the internal volume and exits via the air vent discharge without passing into the separation chamber.

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