Gas sparged hydrocyclone

Abstract: A hydrocyclone (10) establishes a first vortex (15) of fluent material at one end (e.g. in a top portion 4), and a second vortex at the other end (e.g. in a bottom portion 24). The first vortex is established within a porous surface of revolution (18) to which gas or other fluid is supplied, passing through the porous surface into the first vortex. The second vortex is established by a conical end section (24) extending outwardly from (e.g. below) the porous surface, and with an axial (e.g. bottom 23) discharge for fluent material. Some fluent material -- for example having heavy particles -- is removed tangentially from the conical end section at a portion (35) near the porous surface of revolution. A conical shroud (25) having a circumferential periphery is mounted by a number of spaced legs (28) connected between the shroud and the conical bottom section so that fluent material may pass (thru 32) between the circumferential periphery of the shroud and the porous surface of revolution. An axial gas passage (27) is provided in the shroud to allow gas to escape from the second vortex into the first vortex, and ultimately out the first end (e.g. top) of the hydrocyclone (Figure 1).

Description: BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates to a hydrocyclone, comprising: a substantially hollow body having first and second ends, and having a wall disposed about an axis and axially elongated; inlet means for introducing a liquid or liquid suspension into the hollow body at the first end thereof, so that the liquid or liquid suspension flows in a vortex within said hollow body; first withdrawing means for withdrawing fluid from adjacent the axis at said first end of said body; a porous surface of revolution disposed within said hollow body wall generally symmetrical with said axis; means defining a plenum between said body wall and said porous surface of revolution; means for introducing fluid into said plenum to pass through said porous surface of revolution into said vortex; and second withdrawing means for withdrawing the liquid or liquid suspension from said hollow body at said second end thereof. The present invention also relates to a method of separating components of a liquid slurry utilizing a hydrocyclone. There are many emerging uses for gas sparged hydrocyclones in the treating of fluent materials in general, particularly liquid slurries and liquids. In a gas sparged hydrocyclone, such as shown in US-A-4,279,743, 4,399,027, and 4,838,434, the fluent material is introduced into a hollow body to establish a vortex, and gas is sparged through a porous surrounding wall into the vortex. Gas, and elements carried thereby, are withdrawn from the center top portion of the vortex, while the fluent material is withdrawn from a bottom portion of the vortex. While the hydrocyclones illustrated in the above-identified patents are used solely for flotation, it has recently been established that the hydrocyclones are useful for many other processes, including effecting chemical treatment of solids in a slurry with a chemically reactive gas, scrubbing flue gases, chemically reacting a liquid with a gas stripping a strippable component from a liquid utilizing a stripping gas, and absorbing a gas within an absorbable component in an absorbent liquid. The aim of the present invention is to create a device, of the type mentioned initially, and a method treating a liquid or liquid suspension utilizing a hydrocyclone to improve the versatility of existing gas sparged hydrocyclones, and in some circumstances the efficiency thereof. The achieve this aim the hydrocyclone according to the invention is characterized by means for establishing further vortex action in a volume between said porous surface of revolution and said second withdrawing means to effect separation of gases from the liquid or liquid suspension adjacent said second withdrawing means, a conical solid wall end section of said hollow body extending from said porous surface of revolution to said second withdrawing means. Preferred embodiments of the hydrocyclone according to the invention are described within the scope of what is expressed in the subclaims. Preferably, a shroud -- such as a conical shroud -- having a circumferential periphery is disposed above the conical solid wall end section, and intensifies the second vortex action. A plurality of legs, or like mounting means, mount the shroud so that the liquid or liquid suspension may pass between the circumferential periphery of the shroud and the porous surface of revolution, but the mounting means does not disrupt flow patterns. A central axially extending gas passage is formed in the shroud allowing passage of gas separated in the conical solid wall end section to flow to the gas withdrawal means at the top of the first vortex. Preferably said shroud is conical, with a larger diameter adjacent said conical solid wall end section than further from said conical solid wall end section. Further the hydrocyclone is provided with means for establishing a conical interior passage in said conical shroud, said passage having a larger diameter adjacent said conical solid wall end section than further from said conical solid wall end section. It is advantageous if said means for establishing further vortex action comprises a conical solid wall end section of said hollow body extending from said porous surface of revolution to said second withdrawing means. Some fluent material -- particularly a heavier particle fractions of a slurry -- may be tangentially withdrawn from the conical solid wall end section, perferably by a tangential outlet nozzle, at a part thereof adjacent the porous surface of revolution. According to another aspect of the present invention as described in claim 7, a hydrocyclone is provided having -- in addition to other components -- wall means for dividing said plenum into at least first and second axially spaced portions; and means for introducing fluid into each of said first and second portions of said plenum, said porous surface of revolution being liquid porous at least at the first plenum portion. Preferably said porous surface of revolution is not liquid porous at said second portion, and said introducing means introduces gas into said second portion and liquid into said first portion. A liquid may be introduced into one of the plenum portions, and the gas into the other, the liquid being introduced so that it has a pressure drop across the plenum so that gas therein (the liquid may be saturated with gas) will be released in small bubble form. The method according to the invention, of separating components of a liquid slurry, comprises the steps of: (a) introducing the liquid slurry into a first vortex at a first end thereof; (b) introducing fluid (thru an inlet) from exteriorly of the vortex into contact with the liquid slurry in the vortex; (c) removing some fluid from (thru the first withdrawing means) the first end of said first vortex; and is characterized by (d) after step (b), subjecting the liquid slurry to a first end of a second vortex action; (e) removing a liquid or liquid suspension from the second end of the axis of the second vortex; and (f) removing a portion of the slurry with heavy particles therein tangentially (thru the tangential outlet nozzle) from the first end of the second vortex. There may be the still-further step (g) of shrouding the central axis of the second vortex while allowing axial (e.g upward) passage of gas from the central vortex to be withdrawn as fluid in step (c). Utilizing the apparatus and processes as set forth above, a wider variety of treatments can be given to a liquid or a liquid suspension, and/or the efficiency of existing treatments (such as flotation) may be enhanced. It is the primary object of the present invention to provide hydrocyclones and procedures with improved versatility and/or efficiency compared to conventional gas sparged hydrocyclones and utilizing the same. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a side schematic cross-sectional view of an exemplary hydrocyclone according to the present invention; FIGURE 2 is a perspective view, with portions cut away for clarity of illustration, of the conical shroud of the hydrocyclone of FIGURE 1; and FIGURE 3 is a side view, partly in cross-section and partly in elevation, of a second embodiment of hydrocyclone according to the present invention. DETAILED DESCRIPTION OF THE DRAWINGS An exemplary hydrocyclone according to one embodiment of the present invention is illustrated generally by reference numeral 10 in FIGURE 1. The conventional components of the hydrocyclone include: A top portion 11 of a hollow body including a liquid or liquid suspension inlet 12, and a top surface 13 with a conduit 14 therein comprising a first means for withdrawing fluid (gas, froth, or foam) from the hydrocyclone 10. A main hollow body portion 16 is connected to the top portion 11, and includes an inlet 17 for the introduction of sparging fluid, such as gas, into the vortex 15 established within the body 16. Mounted within the wall 16 is a porous surface of revolution, for example a porous cylinder (as actually illustrated in FIGURE 1), cone, or the like, having a top portion 19 adjacent the bottom 20 of the gas withdrawal conduit 14, and a bottom portion 21. A plenum 22 is defined between the hollow body wall 16 and the porous surface of revolution 18. The material of the porous surface of revolution 18 may be porous ceramic or plastic, sintered metal, or other material such as suggested in US-A-4,279,743, 4,399,027, and 4,838,434. A second withdrawing means, outlet 23, is provided at the second end 21 of the porous surface of revolution 18, "treated" liquid or liquid suspension passing therethrough. Normally the body 16, surface 18, and the like are symmetrical about a substantially vertical axis A-A, while the inlet 12 is tangential to impart the vortex action 15 to the liquid or liquid suspension. However the invention is in no way restricted to vertical axis vortices, and the terms "top" and "bottom" are to be understood as merely relative. What has heretofore been described are basically conventional components of the gas sparged hydrocyclone. According to the present invention additional components are provided for increasing the versatility and/or efficiency of the hydrocyclone 10. One of the features of the hydrocyclone 10 according to the invention is means for establishing a further vortex action in a volume between the bottom (second end) 21 of the porous surface of revolution 18, and the second withdrawal means or outlet 23, to effect separation of some or substantially all of the remaining gases in the liquid or liquid suspension when it reaches the bottom 21 of the porous surface of revolution 18. Such means preferably comprise the conical solid wall end (second end) section 24 (e.g. sharply tapered). A shroud means 25 is mounted in a particular association with the porous surface of revolution 18 and the conical solid wall end section 24. The shroud 25, which may comprise a conical body 26 having a central axially extending passage 27 therein, is mounted by legs 28 or like mounting means so that the porous surface of revolution 18 bottom (second end) surface 21 is just below (past) the circumferential periphery 31 of the shroud 25, and so an annular passage 32 is provided between the circumferential periphery of the shroud 25 and the porous surface of revolution 18. The legs 28 are designed so that they do not interfere with the flow of slurry or like liquid or liquid suspension from the first vortex 15 to the conical solid wall end section 24, and so that the conical body 26 shields the outlet 23 from the liquid or liquid suspension and intensifies the vortex action of the liquid or liquid suspension within the conical solid wall end section 24. Note that the conical body 26 top (first end) has a smaller diameter at the top (first end) than the bottom (second end) thereof, gradually increasing toward the conical solid wall end section 24. Most desirably a conical interior passage 30 is provided within the shroud 26, also increasing in diameter as it approaches the conical solid wall end section 24, for collecting gas and channeling it through the central axial passage 27. Preferably a solid cylindrical section 34 is provided as an extension of porous member 18. The hydrocyclone 10 can be used for a wide variety of methods of acting upon fluent particularly slurries. The invention is particularly useful for minimizing foam carryover with the accepted slurry stream, very efficiently separates the gas, and allows some simultaneous separation of heavy weight particles in the slurry, for example separation of sand from comminuted cellulosic fibrous material (paper) pulp. Suction can be applied to conduit 14 if desired, or the device 10 can be pressurized (e.g. at above atmospheric pressure). A pipe with holes drilled in it may sometimes be used as the porous surface of revolution 18. The slurry or other liquid or liquid suspension is introduced tangentially into the top (first end) 11 via the inlet 12, and moves in a vortex 15, in a spiral (e.g. downwardly) within the body 11, 16. Fluid, particularly gas, is introduced through conduit 17 into plenum 22 and passes through the porous surface of revolution 18 into the slurry in the vortex 15. The gas acts upon the slurry -- in the case of flotation applications causing the hydrophobic particles to move upwardly in a foam to be discharged in gas/froth/foam withdrawal conduit 14 -- while the accepted slurry flows downwardly toward the outlet 23. As the slurry approaches the shroud 25, the shroud facilitates separation of the foam in the center portion of the vortex 15 from the slurry surrounding it, and intensifies the vortex action as the slurry flows through the annular passage 32 into the conical solid wall end section 24, where it is subjected to further vortex action. The further vortex action in the conical solid wall end section 24 causes remaining gas to escape and move to the central axis A, collecting in the conical passage 30 and then passing through gas passage 27 axially (e.g. upwardly) into the main body 16, and ultimately out the conduit 14. The high density and larger particles, when subjected to the further vortex action in the conical solid wall end section 24, move toward the wall where they are extracted through a generally tangential outlet nozzle 35. Approximately 5-25% of the slurry flow passes through the nozzle 35, while the balance exits the outlet 23. FIGURE 3 illustrates another exemplary hydrocyclone according to the invention, having features which may be used in conjunction with the hydrocyclone 10 of FIGURES 1 and 2. In the FIGURE 3 embodiment components functionally comparable to those in the FIGURE 1 embodiment are illustrated by the same reference numeral only preceded by a "1". In the FIGURE 3 embodiment, the main distinguishing hydrocyclone 110 from a conventional gas sparged hydrocyclone are the separation of the annular plenum into two different portions. A bottom portion 122 of the plenum is disposed between the bottom portions of wall 116 and porous surface of revolution 118, while the top portion 40 of the plenum is separated from the bottom portion 122 by an annular solid wall 41 extending generally perpendicular to the axis of the vortex (e. g. horizontally). The porous surface of revolution 118 can be constructed so that it is both gas and liquid pervious, or it may be constructed so that the portion thereof below the wall 41 is only gas pervious (e.g. has relatively small pores), while the surface 118 above the wall 41 is both gas and liquid porous (e. g. has relatively large pores). One fluid is introduced into inlet 117 to plenum 122, while a second fluid is introduced in inlet 42 to the plenum 40. In the specific example illustrated in FIGURE 3, gas is introduced into the inlet 117, while liquid -- or liquid partially or completely saturated with dissolved gas, or a liquid above its boiling point -- is introduced in inlet 42. When liquid is introduced into a plenum -- such as through inlet 42 into plenum 40 -- it is introduced at a temperature and pressure such that it undergoes a pressure drop as it passes through the porous surface of revolution 118. When it undergoes this pressure drop, gas in the form of small bubbles is released into the vortex within the body 116, formed by the liquid or liquid suspension being acted upon, and eventually moves toward the gas outlet 114. Utilizing this approach it is possible to produce smaller bubbles than would otherwise be possible. The production of smaller bubbles increases chemical reaction rates, absorption rates, or causes smaller particulate materials to float from the incoming liquid or slurry. Also porous media plugging problems, experienced in some applications, may be overcome. If desired, a conventional pedestal 44, which is not part of the invention -- such as disclosed in US-A-4,838,434 -- may be provided extending into the vortex from adjacent the bottom outlet 123 of the liquid or slurry. While the hydrocyclone 110 has been described with two different plenums 40, 122, and with the liquid introduced at one end (the top) at 42 and gas introduced at the other end (e.g. bottom) at 117, it is to be understood that a plurality of different plenums may be provided with annular dividing walls 41 between each, the liquid could be introduced in the second end (bottom) and the gas at the first end (top), or just liquid or just gas could be introduced into all of the plenums (different liquids or gases would be introduced into the different plenums). Also the liquids or gases introduced into the different plenums could be chemically the same, but at different pressures and/or temperatures. The hydrocyclone 110 has a wide variety of uses. In addition to being utilizable for separation (particularly it could be combined with the features of the hydrocyclone 10 in FIGURE 1), it can be used for many other uses, including effecting chemical treatment of solids in a slurry with a gas chemically reactive with the slurry solids, scrubbing flue gases, chemically reacting a liquid with a gas, stripping a strippable component from a liquid utilizing a stripping gas or liquid, and absorbing a gas with an absorbable component in an absorbent liquid. Also it can be used for chemically reacting one liquid with another. It will thus be seen that according to the present invention the versatility and/or efficiency of gas sparged hydrocyclones and related procedures have been enhanced.

Claims: A hydrocyclone (10), comprising: a substantially hollow body having first and second ends, and having a wall (16) disposed about an axis and axially elongated; inlet means (12) for introducing a liquid or liquid suspension into the hollow body at the first end thereof, so that the liquid or liquid suspension flows in a vortex within said hollow body; first withdrawing means (14) for withdrawing fluid from adjacent the axis at said first end of said body; a porous surface of revolution (18) disposed within said hollow body wall generally symmetrical with said axis; means defining a plenum (22, 40, 122) between said body wall and said porous surface of revolution; means (17, 42, 117) for introducing fluid into said plenum to pass through said porous surface of revolution into said vortex; and second withdrawing means (23) for withdrawing the liquid or liquid suspension from said hollow body at said second end thereof; characterized by means (24,25) for establishing further vortex action in a volume between said porous surface of revolution and said second withdrawing means to effect separation of gases from the liquid or liquid suspension adjacent said second withdrawing means, a conical solid wall end section (24) of said hollow body extending from said porous surface of revolution to said second withdrawing means. A hydrocyclone as recited in claim 1 further characterized in that said means for establishing further vortex action further comprises a shroud (25) having a circumferential periphery and disposed above said conical solid wall end section; means (28) for mounting said shroud so that the liquid or liquid suspension may pass between the circumferential periphery of said shroud and said porous surface of revolution; and means defining a central axially extending gas passage (27) in said shroud allowing passage of gas separated in said conical solid wall end section to flow to said first withdrawal means. A hydrocyclone as recited in claim 2 further characterized in that said means for mounting said shroud comprises a plurality of spaced legs (28) connected between said shroud and said conical solid wall end section. A hydrocyclone as recited in claim 2 or 3 further characterized in that said shroud is conical, with a larger diameter adjacent said conical solid wall end section (31) than further from said conical solid wall end section. A hydrocyclone as recited in any of the claims 1 to 4 wherein said means for establishing further vortex action comprises a conical solid wall end section of said hollow body extending from said porous surface of revolution to said second withdrawing means. A hydrocyclone as recited in claim 4 characterized by means for establishing a conical interior passage in said conical shroud, said passage having a larger diameter adjacent said conical solid wall end section than further from said conical solid wall end section. A hydrocyclone as recited in any of the claims 1 to 6 further characterized by wall means (41) for dividing said plenum into at least first and second axially spaced portions (40, 122); and means for introducing fluid into each of said first and second portions of said plenum, said porous surface of revolution being liquid porous at least at the first plenum portion. A hydrocyclone as recited in any of the claims 1 to 7 further characterized in that said porous surface of revolution is not liquid porous at said second portion, said introducing means (117) for introducing gas into said second portion, and liquid (42) into said first portion. A hydrocylone as recited in any claims 1 to 8 further characterized by a tangential outlet nozzle (35) for removing heavy particles from said conical solid wall end section (24). A method of separating components of a liquid slurry, comprising the steps of: (a) introducing the liquid slurry into a first vortex (15) at a first end thereof; (b) introducing fluid (thru 17) from exteriorly of the vortex into contact with the liquid slurry in the vortex; and (c) removing some fluid from (thru 14) the first end of said first vortex; characterized by: (d) after step (b), subjecting the liquid slurry to a first end of a second vortex action (in 24); (e) removing a liquid or liquid suspension from the second end of the axis of the second vortex; and (f) removing a portion of the slurry with heavy particles therein tangentially (thru 35) from the first end of the second vortex.

Inventors: TORREGROSSA LOUIS O, TORREGROSSA LOUIS O.
Applicants: KAMYR INC, KAMYR, INC.
Application year: 1991
Main classification: B03D1
IPC codes: B04C5, D21D5, B03D1