WO2003002227A1

WO2003002227A1 - High viscosity hydrocyclone for air removal

Info

Publication number: WO2003002227A1
Application number: PCT/US2002/020496
Authority: WO
Inventors: John A. Taylor
Original assignee: Black Clawson Company, Inc.
Priority date: 2001-06-29
Filing date: 2002-06-28
Publication date: 2003-01-09

Abstract

A preferred cyclonic separator (10) comprises a body (11) and a cutoff core (32). The body (11) has an inlet opening (12) for conducting a mixture of a liquid ad a gas into the body (11) and one or more passageways (14, 25) extending along an axis (17). Most preferably, the mixture is induced to rotate as it flows through the passageways (14, 25) and the initial pressure of the mixture is sufficient that the pressure reaches a sub-atmospheric level near the axis (17) as the mixture flows through the passageways (14, 25). The cutoff core (32) defines an axial conduit (45) and an outwardly inclined cutoff surface (36) for separating the mixture into first and second components. The preferred body (11) and the preferred cutoff core (35) define one or more expansion chambers (40, 50) which expand the first and second components before the components exit the separator (10).

Description

HIGH VISCOSITY HYDROCYCLONE FOR AIR REMOVAL

FIELD OF THE INVENTION [0001] This invention relates to the field of gas separation and more particularly, to a cyclonic separation apparatus and method for removing air bubbles, and some dissolved air, from highly viscous, pumpable liquid materials.

BACKGROUND OF THE INVENTION [0002] Taylor et al. U.S. Patent No. 5,149,341 discloses a cyclone vortex separator especially adapted for the removal of entrained gas from highly viscous fluids, such as paper coatings. The coating enters the inlet end of a vortex tube, and is forced to spiral by a vortex generator in the form of a helical or spiral baffle. The centrifugal force of the swirling creates a pressure gradient that decreases toward the center of the tube. A plot of this pressure gradient is nearly constant over the length of the tube. Since a bubble of entrained gas occupies a space in the pressure gradient, it has a higher pressure on one side that the other, and since it cannot maintain an internal pressure difference, it moves toward the tube center forming a gas reject column. A gas reject phase pickup conduit is centered in the opposite outlet end, and extracts the bubbles along with some of the coating, thereby leaving an annulus of essentially bubble-free material. The hydrocyclone disclosed and claimed in Taylor et al. has proved to be particularly effective in the removal of air bubbles from liquid coatings and similar materials at about 450 cps at 200/sec. [0003] Long U.S. Patent No. 3,201,919 proposes a drilling mud degasser in which the mud is introduced into a closed vacuum tank tangentially so a to impart a whirling movement to the fluid, and preferably withdraw gas removed from the mud by means of a perforated tube extending axially through the center of the tank. The drilling mud or fluid to be degassed is tangentially fed at a high velocity from the borehole return mud supply into a cylindrical chamber to cause the mud to travel along a helical path within the chamber. Forces created by the resulting centrifugal action move the lighter gas-cut or gas-laden fluid inwardly toward the axis of the chamber while the heavier uncut portion tends to flow toward the periphery of the chamber. By subjecting the axial region of the chamber to a sub-atmospheric pressure (as by means of a vacuum pump), the gas bubbles are broken and removed to the atmosphere outside of the chamber. The heavy degassed fluid then is discharged from the chamber, through a fluid seal, to the mud pump suction tank, to be recirculated in the drilling rig mud system, and a portion recirculated through the degasser.

[0004] Matsui et al. U.S. Patent No. 4,390,351 proposes a gas/liquid separator having a concentrically and upwardly coiled channel which is defined by a concentrically and upwardly coiled pipe and a plurality of spaced apart bubble trapping or separating openings formed through the inner side wall of the uppermost coil. Each bubble trapping opening is connected to a header or the like through a bubble riser with a valve. In operation, a liquid with entrained bubbles is charged through an inlet into the coiled pipe at a high velocity and flows out from a discharge or outlet port. When the liquid flows through the coiled pipe, it experiences a centrifugal force. The bubbles entrained in the liquid have a specific gravity smaller than that of the liquid so that they are forced to flow along the radially inward wall of the coiled pipe and enter the bubble trapping holes of the uppermost coil. [0005] Rojey et al. U.S. Patent No. 5,252,229 proposes a method and device for separating a continuous phase, such as a liquid phase, from at least one dispersed phase, such as a gaseous phase, with each phase having a different density. This method is characterized in that the mixture of the phases to be separated is supplied into a device formed by at least one approximately cylindrically-shaped chamber and at least one helically-shaped internal piece whose at least one face has one helicoidal surface, the piece delimiting at least one helicoidal passage. The internal piece is adapted in such away so that the maximum path of one particle of the dispersed phase along the radial direction before colliding is less than one quarter of the peripheral diameter of the internal piece. The helicoidal surface has, as a projection on a phase perpendicular to the axis of the chamber, a surface equal to at least half of the total internal right section of the cylindrical chamber. [0006] The flow of the mixture of the phases and along the passage provokes a rotational movement around the axis of the chamber, resulting in the lighter phase moving towards the axis and the heavier phase moving towards the periphery of the chamber during which the dispersed phase coalesces, at least partially on the walls of the passage, and then forms a continuous phase separated from the continuous phase by an interface, the lighter and heavier phases being bled on both sides of the interface. [0007] Sassi U.S. Patent No. 5,585,000 proposes a cyclone separator of the type utilized in the food processing industry for separating water vapor from a liquid foodstuff, such as tomato juice. The separator comprises a vertical chamber compassed by a wall composed of a top section that converges gently upwards at a predetermined taper, and extending down from the top section, in sequence, a first frustoconical section, a cylindrical section and a further frustoconical section. A tangential inlet is associated with the top section, through which the product to be separated is directed into the chamber. The chamber is provided further with a coaxially disposed bottom outlet through which the heavier part or liquid phase of the separated product is discharged. A duct comprising a vertical stretch extends internally of, and coaxially through, the chamber. The topmost end of the vertical stretch occupies a level above the level of the tangential inlet and affords an inlet port into which vapors are gathered. Sassi teaches that the particular geometry of the tapered wall of the top section enhances the centrifugal force by which the liquid and vapor phases are separated. [0008] Christiansen U.S. Patent No. 6,190,543 proposes a cyclonic separator for separating fluids of different densities comprising a separator vessel which includes a main gas/liquid separation chamber having a mixture inlet port and a liquid outlet port; and a second stage gas/liquid separation chamber or scrubber having a gas outlet port and a liquid drainage port. The main chamber is located within the second chamber. A vortex finder is coaxially located within the main chamber and is held in place by supports connected to curved vanes. The vortex finder has a frusto-conical first end portion which tapers outwardly towards the gas outlet port; a tapered second end portion which tapers inwardly towards the liquid outlet port; and a central cylindrical portion. A tapered core member is coaxially located within the vortex finder by a first generally helical vane so as to define an annular helical channel therebetween. [0009] When in use, a hydrocarbon fluid mixture, for example, an oil/gas mixture, is introduced at high pressure through the inlet port and gains a rotational velocity component. A vortex is therefore formed within the main chamber by the mixture, causing the constituents of the mixture, in this case gas and oil, to separate, the higher density fluid, in this case oil, residing at the periphery of the vortex and the lower density fluid, in this case gas, residing in the core of the vortex. A back pressure generated within the main gas/liquid separation chamber urges the gas and a residual quantity of oil to pass into the vortex finder until the first generally helical vane is reached. The passage of the residual mixture around the first generally helical vane translates the majority of the axial velocity component of the residual mixture into a rotational velocity component, causing the oil component of the residual mixture to be projected outwardly due to centrifugal forces. The residual oil passes down through the second chamber, along the inner wall of the separator vessel, and leaves the separator via the liquid drainage port , whilst the gas leaves the separator via the gas outlet port.

[0010] Despite these proposals, there remains a need in the art for a cyclone separator and a separation process capable of efficiently removing entrained air bubbles from pumpable liquid materials having viscosities substantially in excess of 450 cps (at 200/sec) without the use of an external vacuum source. For example, there is a need to provide air-free coatings used in some reverse roll coaters and die slot coaters that wipe on a high viscosity coating in excess of that which can effectively be handled by the apparatus as shown in Taylor. In addition, there remains a need in the food processing industry for high viscosity air removal devices and methods for materials, such as tomato paste, having viscosities as high as 1800 cps.

SUMMARY OF THE INVENTION [0011] A preferred cyclonic separator in accordance with this invention imparts a high degree of rotational momentum to the material, in a confined space, to create an intense pressure gradient through the thickness of a thin, annular classification layer. The intense pressure gradient produces, on the axis of the preferred cyclonic separator, a sub-atmospheric pressure as low as, or substantially lower than, the vapor pressure of the liquid being processed. This sub-atmospheric pressure or substantial vacuum is created entirely within the cyclonic separator using no external vacuum source. This process has succeeded in removing all air bubbles and some of the dissolved air in viscous materials that approach soft solids, including yogurt and cold gravy.

[0012] The preferred method requires a substantially high input pressure and subjecting the fluid to an inlet spiral to impart rotational momentum, in which the pressure is stored by the rotational momentum. The centrifugal force of the material rotating at high speed in a classification passageway, followed by controlled expansion into an expansion chamber at the exit end of the narrower classification passageway creates a sub-atmospheric pressure in the material near the axis of the classification passageway. This lower pressure near the axis of the classification passageway expands bubbles in the material and increases the relative buoyancy of the bubbles. This increased buoyancy allows classification at the relatively high viscosities and causes some fluids to boil at room temperatures. The extremely low pressure in the annulus expands the already existing air bubbles and helps to remove them from the fluid. [0013] In addition, this low pressure causes the release of some of the dissolved gasses so that the deaerated fluid has some ability to absorb bubbles after deaeration, to make a substantially bubble-free fluid. This is achieved without the use of a vacuum pump since the relatively high supply pressure is converted from static to kinetic energy while rotating at high speed within the restricted confines of a cylindrical classification chamber, resulting in the sub-atmospheric static pressure along the axis of the annulus while the energy is stored as rotational momentum. [0014] In accordance with a preferred embodiment for separating a mixture of a liquid and a gas, apparatus in accordance with the invention comprises a body and a cutoff core. The preferred body has a first outlet for conducting a first, preferably gas-rich, component from the body; a second outlet for conducting a second, preferably liquid-rich or deaerated, component from the body; and an inlet opening for conducting the mixture into the body along an inlet opening flow direction. In addition, the preferred body defines one or more communicating passageways extending along an axis transverse to the inlet opening flow direction, including a first passageway which communicates with the inlet opening for receiving the mixture. [0015] The preferred cutoff core extends within the body downstream of the one or more passageways. It defines an axial conduit for receiving the second component and an outwardly inclined cutoff surface for directing the first component away from the second component. [0016] In practice, the mixture is pressurized to an initial pressure; induced to flow along an axis of the body; and induced to rotate about the axis through the one or more passageways. Most preferably, the initial pressure is sufficient to create a sub-atmospheric pressure near the axis while the mixture rotates about the axis. The mixture is separated by the preferred cutoff core the first component and the second component. The preferred body and the preferred cutoff core define one or more expansion chambers communicating with at least one of the first and second outlets so as to expand the first and second components before the components exit the apparatus.

[0017] Most preferably, an insert having one or more spiral grooves (most preferably from one to three grooves) is positioned in one of the passageways to define one or more spiral channels. The preferred spiral channels have lead angles of less than 45° to promote the rotation of the mixture in the passageways. Alternatively, the mixture can be induced to rotate in the passageways solely by introducing the mixture into the passageways tangentially through the inlet opening without the intervention of an insert defining spiral channels; or by the combined effects of tangential introduction and the spiral channels of the preferred insert. [0018] In accordance with an especially preferred embodiment, the one or more passageways include the first passageway which communicates with the inlet opening and a second or classification passageway downstream of the first passageway which communicates with the one or more expansion chambers. The preferred second passageway has a cross-sectional area smaller or narrower than the preferred first passageway such that the two passageways are joined by an inwardly inclined wall. This inwardly inclined wall acts as a flow restriction which serves to speed up the rotation of the fluid and convert more of the static pressure into rotational momentum.

[0019] The insert with the spiral channels preferably fits into the first passageway. Most preferably, the insert is supported in the first passageway by means of a mandrel which extends beyond the insert. The preferred mandrel is so constructed and arranged as to cooperate with the first passageway to define a section having a constant cross-section. This section of constant cross-section serves to improve the performance of the apparatus. [0020] The preferred apparatus defines two expansion chambers, one for each of the separated components. Most preferably, the body defines a outwardly inclined first inner wall and the cutoff core is received within the first inner wall such that the cutoff surface is axially aligned with the first inner wall. The preferred first inner wall and the preferred cutoff surface diverge so as to define the first expansion chamber. In addition, the cutoff core defines an outwardly inclined second inner wall. A second core, which defines an outwardly inclined second core surface, is received within the second inner wall such that the second core surface is axially aligned with the second inner wall. The second inner wall and the second core surface diverge so as to define the second expansion chamber. The first expansion chamber communicates with the first outlet and the second expansion chamber communicates with the second outlet so as to conduct the first and second components from the apparatus.

[0021] Most preferably, the one or more passageways are substantially circular or cylindrical in cross-section; and the cutoff core and the second core are each substantially conical in shape. This promotes rotational or vortex movement of fluids within the cyclonic separator. Nevertheless, the shapes of the passageways and the cores are not critical to the invention and alternative configuration will be apparent to those of ordinary skill in the art. [0022] In accordance with an especially preferred embodiment, the gap between the second or classification passageway and the cutoff core is adjustable. This gap preferably is adjustable to control the split between the accepts and rejects components output from the separator. Alternatively, the gap is adjustable in response to pressure measurements taken upstream of the cutoff core. More specifically, the diversion of the flow through and about the cutoff core into the first and second expansion chambers tends to generate a back pressure against the flow through the classification passageway. Adjusting the gap between the classification passageway and the cutoff core provides control over this pressure. Most preferably, the apparatus includes a transducer for measuring pressure upstream of the cutoff core, as at the inwardly inclined wall connecting the preferred first passageway with the second or classification passageway or in the classification passageway near the inwardly inclined wall. The' gap between the classification passageway and the cutoff core then is adjusted so as to equalize the measured pressure with a desired value so as to maintain the desired pressure gradient within the classification passageway. [0023] It has been found unexpectedly that the pressure drop across the spiral channels correlates with the momentum of the mixture in the preferred cyclonic separator. For example, in one embodiment of the invention, it was found that the pressure drop "Δp" across the spiral channels, where the bulk of the pressure drop occurs, is proportional to "pQ²", where "p" is the density of the particular material and "Q" is the volume flow. It is believed that, in the particular embodiment studied, the torque T" in the inlet spiral is primary attributable to the pressure drop:

T = « tfR_s ²R_taΔpcos(Θ) ,

where "Rg" is the outer radius of the inlet spiral; "R,." is the radius of a solid core of the spiral; "R^" is the log mean radius of the inlet spiral; "Θ" is the spiral lead angle; and Rg » R,. by design. The angular velocity "ω" of steady flow through the spiral is:

Qcos(Θ) a

A„R lm

where "A,," is the area of the spiral channel and. Treating the mass flowing through the spiral channels as the mathematical equivalent of a solid cylinder, it is possible to express the torque in terms of the rate of change of angular momentum: _ ,Y Q COS(©)^ _ />Q²R² cos(@) r = iø = ,-pQ*.^,

A_sR_ta J 2A R lm

where "I" is the moment of inertia of the mass of material and "p" is the density of the material. Equating the two expressions for the torque: pQ²R² _s cos(Θ)

^R_s ²R_lmΔp cos(Θ) =

2A.R_ta

or

It was verified experimentally that the pressure predicted by this expression equalled 99.7% of the observed pressure drop in the inlet spiral of the preferred cyclonic separator, with a square deviation of 87% at least partially attributable to inherent variations in the flow rate measurements.

[0024] Conversely, one embodiment of the invention is characterizable by such proportionality between the pressure drop across the spiral channels and the quantity "pQ²." This is believed to be a significant departure from the results described in the literature on cyclonic separators, probably because the behavior of cyclonic separators at these high flow intensities has not been studied in the past. [0025] Movement of the mixture from the classification passageway into the expansion chambers slows down the rotational speed of the separated components and converts the momenta of the components back to static pressure to push the components out of the cyclonic separator through the accepts and rejects outlets. The pressure gradient across the radial thickness of the annular layer of mixture rotating at high speed extends from a negative pressure at the center of the annulus to a high positive pressure on the outside. The accepts and the rejects are split by the sharp circular edge of an annular cutoff surface that is adjustably positioned in the explosion chamber to define radially expanding first and second expansion chambers. In both of these chambers, the angular rotation of the components decreases with motion along the axis of the separator, converting rotational energy into positive pressure by providing pressure both for removal through the accepts outlet and for removal through the rejects outlet.

[0026] It is accordingly an important object of this invention to provide a cyclonic separator capable of separating a light or air-laden fraction in or from highly viscous pumpable materials, for example, 4500 cps at 200/sec, or, stated in terms of the yield point, from fluids measuring 0.011 psi (1.6 x 10^"3 mPa) yield point or higher.

[0027] A further object of the invention is the provision of a cyclonic separator for pumpable viscous materials in which one or more spiral channels accelerate the material to an initial angular velocity; an annular section of constant cross-section allows the velocity distribution in the flow to become uniform; a flow restriction accelerates the rotation of the flow to bring the mixture to a final high angular velocity as the mixture enters a classification passageway of relatively small, constant diameter; a first expansion chambers positioned on the axis of the classification passageway receives a first component having reduced air or entirely free of air content; and a second expansion chamber concentric with the first expansion chamber receives an air-containing rejects component. [0028] A still further object of the invention is the provision of a cyclonic separator, as defined, in which an outlet of the classification passageway faces an accepts cutoff core having an axial conduit in axial alignment with the classification passageway for receiving the rejects component and being adjustable with respect to the exit end of the classification chamber for the purpose of controlling a fluid flow split between the accepts and rejects. [0029] A further important object of the invention is the provision of a process or method by which highly viscous pumpable materials containing entrained air may be deaerated by the steps of accelerating the angular velocity, causing the angularly rotated material to pass a flow restriction into a second or classification passageway having a cross-sectional area substantially smaller than that of first passageway which supplies the mixture to the flow restriction and the classification passageway for greatly accelerating the rotational velocity of the material in the classification chamber; causing a substantial pressure gradient from the central axis to the walls of the classification chamber; and creating a region of sub-atmospheric pressure at and along such central axis, thereby creating an air-rich portion along the central axis and an air-free annular portion along the walls of the classification passageway, followed by separating the air-free component in an expansion chamber formed as an axial extension of the classification passageway and removing the air- laden component along the central axis.

[0030] Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Fig. 1 is a side sectional view of a cyclonic separator in accordance with the invention; and

[0032] Fig. 2 is a schematic view of one preferred system employing the cyclonic separator of Fig. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0033] Referring to Fig. 1, a through-flow type hydrocyclone is shown generally at 10 as having an elongated body 11. A side inlet opening 12 defining an inlet opening axis 13 is formed in one end of the body 11 through which high viscosity pumpable mixture (not shown) is applied for deaeration.

[0034] The inlet end of the body 11 is formed with a cylindrical opening or first passageway 14 that is formed on the axis 17 of the body 11, The first passageway 14 intercepts the inlet opening 12 in such a manner that the inlet opening axis 13 is transverse (that is, perpendicular or oblique), to the direction of the axis 17. Most preferably, the inlet opening 12 opens tangentially into the first passageway 14. [0035] A dual-lead spiral insert 15 is mounted on a generally cylindrical support mandrel 16 and is removably received within the first passageway 14 of the body 11. The insert 15 is positioned immediately downstream of the opening 12. The preferred insert 15 may be mounted on the mandrel 16, or may be integrally formed with the mandrel, and has an outer diameter that forms a close, fluid-tight fit with the cylindrical surface of the first passageway 14. [0036] The preferred insert 15 is formed, at its outer cylindrical periphery, with steeply inclined peripheral grooves or channels 20 that are, in effect, the rectangular spaces between spiral threads 19 that lead circumferentially and axially of the body 11. The channels 20 define spirals that provide a high intensity circumferential movement to the mixture (not shown) applied under pressure at the inlet 12. The insert 15 may be provided with as few as one or as many as three such channels 20, but two such channels are preferred. As shown, the channels 20 have a lead angle to a radius which is quite shallow and substantially less than 45°, to impart a high component of rotational velocity to the mixture (not shown). [0037] During use, the mixture (not shown) exits the channels 20 into a downstream section 21 of the first passageway 14 surrounding the outer surface of the mandrel 16. This section 21, for a short distance, remains of constant dimensions. The section 21 expands radially inwardly by reason of the formation of a conical nose 22 on the mandrel 16 and an axially-spaced inwardly inclined wall 24 formed in the body 11. The effective cross-sectional area then decreases substantially within the inwardly inclined wall 24 to an inlet end of a relatively constant diameter second or classification passageway 25 so as to increase the speed of rotation of the mixture (not shown) as the mixture enters into the second passageway 25. A pressure transducer 26 is mounted axially of the mandrel 16, and leads 27 are brought out to a pressure gauge 28 for the purpose of monitoring pressure at the inlet to the classification chamber 25.

[0038] The second passageway 25 opens at its downstream end into a diverging region in the body 11 forming one or more expansion or explosion chambers. The conical diverging region is defined in part by a first outwardly inclined (preferably conical) inner wall 30 formed by the body 11. A first or cutoff core 32 is preferably received within an outlet end of the body 11 so that a sharp- nosed, preferably conical exterior cutoff or first core surface 36 of the first core 23 extends within the first inner wall 30 to define a first or accepts expansion chamber 40 which communicates with a first or accepts outlet 42. Most preferably, an axial conduit 45 extends through the cutoff core 32.

[0039] The cutoff core 32 is hollow, forming a second outwardly inclined (preferably conical) inner wall 52 within which a second core 35 is received. Most preferably, the second core 35 is received within an outlet end of the cutoff core 32 and defines a sharp-nosed, preferably conical exterior second core surface which extends within the second inner wall 52 to define a second or rejects expansion chamber 50 which communicates with a second or rejects outlet 56.

[0040] The preferred cutoff core 32 is formed with a sharp, annular nose 60 at the inlet end of the axial conduit 45. The nose 60 is accurately positioned with respect to the outlet end of the second passageway 25 to form an accurately defined cutoff gap 61 with the wall 36. The cutoff gap 61 directs a first or accepts component (not shown) of the mixture (not shown) into the first expansion chamber 40 toward the first outlet 42 and directs a second or rejects component (not shown) of the mixture (not shown) through the axial conduit 45 and the second expansion chamber 50 toward the second or rejects outlet 56. Too large a gap 61 between the nose 60 and the second passageway 25 allows air to be sucked in with the accepts, while too small a gap reduces production and unnecessarily increases the rate of rejects flow.

[0041] The preferred cutoff core 32 is positioned within the body 11 by means of threaded engagement between the cutoff core 32 and the outlet end of the body 11. This arrangement facilitates adjustment of the gap 61 so as to control the split of the mixture exiting the second passageway 25 between the first component entering the first expansion chamber 40 and the second component entering the second expansion chamber 50. Alternatively, the arrangement facilitates adjustment of the gap 61 in response to pressure measured at the transducer 28 so as to control back pressure imposed by the flow past the cutoff core 32 on the flow through the second passageway 25.

[0042] Most preferably, the second or rejects component (not shown) passing through the second expansion chamber 50 ejects chamber 50 flows through three equally spaced axial holes 55 leading to the second outlet 56. The output of the second outlet 56 preferably is positioned over a recirculation tank 100 (Fig. 2). [0043] The first outlet 42 may be fitted with a short length of pipe 12 (Fig. 2).

It is preferred that any such extension or length of pipe (not shown) be kept short and its diameter large to minimize back pressure. In the example below, a one-inch (3 cm) diameter pipe, three inches (8 cm) long, has been found to be acceptable. [0044] The operation of a preferred cyclonic separator 10 in accordance with the invention will be described in connection with the dimensions of a preferred embodiment. This example is intended only to illustrate one preferred mode of operation of the invention and is not intended as a limitation on the scope of the invention as set forth in the appended claim.

[0045] Thus, by way of example, an especially preferred insert 15 includes channels 20 providing two openings, each 0.010 inch x 0.010 inch (0.25 mm x 0.25 mm) with a lead angle to a radius of 8 ° . The preferred threads 20 revolve through one 360° turn. Downstream of the insert 15, the mandrel 16 extends another inch (2.5 cm) within the body 11 creating the annular, constant-cross-section, cylinder- shaped section 21. In this section 21, the rotating flow becomes more uniform, and this space 21 provides an area where the mixture (not shown) acts as a fly wheel to even out any flow pulsations (not shown) in the liquid exiting the channels 20. In this manner, the section 21 improves the performance of the cyclonic separator 10. [0046] The rate of rotation of the mixture (not shown) increases as the diameter decreases at the tapered walls 24. This increase in the rate of rotation and decrease in diameter tends to convert static pressure into dynamic pressure as the centrifugal force of the mixture (not shown) against the inwardly inclined wall 24 and the surface bounding the second passageway 25 increases. For example, the pressure may be 350 psi (50 mPa) at the exit of the channels 20 and only 25 psi (3.6 mPa) at the downstream end of the second passageway 25. Optionally, the transducer 26 may be moved axially a short distance so that it extends into the interior of the second passageway 25 for the purpose of measuring this pressure and adjusting the size of the cutoff gap 61 to maintain a desired static pressure within the second passageway 25.

[0047] The combination of the pitch spiral; the pitch diameter; the extent of the channels 20 into the section 21; and the relatively narrow diameter of the second passageway 25 create a high intensity rotation. In the example, the contraction of the rotating fluid is from a diameter of 0.625 inch (15.9 mm) in the first passageway 14 , -\5-

immediately downstream of the insert 15 to a diameter of 0.125 inch (3.18 mm) in the second passageway. This contraction creates a significant drop in static pressure. [0048] In the example, the second passageway 25 has a length of four inches

(10 cm) and a diameter of 0.125 inch (3.18 mm), as mentioned previously. This induces the mixture (not shown) in the second passageway 25 to act as a rotating fluid annulus with an intense pressure gradient along the direction extending from the surface bounding the second passageway 25 to the axis 17 of the body 11. In the case where the pressure on the cylinder wall is 250 psi (36 mPa) , the pressure at the center of the tube with a 0.001 inch (0.03 mm) thick film of fluid is at the boiling point of the fluid. In the case of water at 90°F, the pressure at the center of rotation would be 0.7 psi (0.1 mPa), thereby creating a pressure gradient from the center to the wall in the order of 35,000 psi/inch (2.0 10³ mPa/cm). [0049] The low pressure at and near the axis of the classification chamber expands bubbles of air or other gas (not shown) in the mixture (not shown) and increases the buoyancy of the bubbles (not shown). The increased buoyancy allows separation of such air or other gas (not shown) from liquids (not shown) having higher viscosities than known previously. It also allows some liquids (not shown) to boil at room temperature, and the boiling expands the bubbles of the air or other gas (not shown) so as to help to separate the air or gas from the liquid (not shown). Also, boiling removes some gases (not shown) dissolved in the liquid (not shown), so that the deaerated liquid component (not shown) output from the cyclonic separator 10 has some ability to absorb bubbles (not shown) after deaeration, thereby providing a substantially totally bubble free liquid component (not shown). This is accomplished without the need for a vacuum pump. [0050] Thus, in a preferred method in accordance with the invention, the mixture (not shown) flowing through second passageway 25 has a sub-atmospheric static pressure near the axis 17 while energy is stored as rotational momentum. When first and second components of the mixture (not shown) are separated and exit the second passageway 25 into the explosion chambers 40, 50, the rotational speeds of the components slow and the momenta of the components convert back to static pressure to push the components out of the cyclonic separator 10 through the outlets 42, 56. Thus, the sub-atmospheric pressure preferably achieved within the second passageway 25 is retained wholly within the body 11.

[0051] Flow rates of five gallons per minute (3 x 10² cπrVsec) have been achieved through a 0.125 inch (3.18 mm) diameter chamber 25, with cut off cones set to form a gap 61 with the classification chamber of between 0.107 and 0.270 inch (2.72 and 6.85 mm).

[0052] The inlet pressure at the inlet opening 12 must be sufficiently high so that the flow of the mixture (not shown) is sufficient to create sub-atmospheric pressure near the axis 17 in the second passageway 25. Thus, five gallons can be pushed through a 0.125 inch (3.18 mm) diameter classification chamber with pressures up to 600 psi (90 mPa) at the inlet. However, if the flow is allowed to drop in this example down to only 1.5 gallons per minute (95 cπrVsec), it has been found that there is an insufficient force to create a desirable radial pressure gradient and obtain satisfactory separation. Further, one has to be careful to avoid supersonic flow since supersonic flow will tend to create back pressure on the second passageway 25. It is relatively easy to detect supersonic conditions as such conditions will cause the separator 10 to squeal.

[0053] With reference to Fig. 2, one preferred system employing a preferred cyclonic separator 10 in accordance with the invention includes a recirculation tank 100 for receiving a fluid, such as a high viscosity mixture containing a liquid and a gas, from a source 102 located beneath a fluid level in the recirculation tank 100. The fluid level in the tank is controlled by any suitable arrangement, such as by means of a valve 103. [0054] The system further includes a variable speed, high pressure pump 110 for extracting the fluid from the tank 100. A preferred pump 110 is capable of delivering fluid at 350 psi and preferably higher, up to or in excess of 600 psi. The ability to adjust the speed of the preferred pump 110 is valuable since different applications may have different process production flow rate requirements, and pumping more liquid than necessary only heats the fluid. A pressure relief valve 112 prevents the system from over pressurizing during adjustments.

[0055] Fluid extracted from the recirculation tank 100 is conducted under pressure to the cyclonic separator 10. A stream 114 of an air-laden rejects component preferably exits from the conduit 56 and falls back into the tank 100, allowing the air (not shown) to breath out of the fluid. The low density air (not shown) is allowed to rest near the top of the tank 100 for further bubble collapsing and degassing. A stream of a deaerated accepts component exits the cyclonic separator 10 through a short outlet pipe 116 connected to the outlet 42 into a receiving chamber 120, where the accepts component can overflow back into the recirculation tank 100 or be drawn off for use through a pipe 122. [0056] A desirable feature of the system shown in Fig. 2 is the fact that the cyclonic separator 10 is positioned over the recirculation tank 100 to permit the rejects component to fall freely back into the tank 100. This assures a minimum back pressure at the rejects outlet 56 so as to promote the formation a sub-atmospheric pressure along the axis 17 (Fig. 1) in the second passageway 25 (Fig. 1). [0057] Thus, one significant advantage of the preferred cyclonic separator 10 in accordance with the invention is that it serves to classify liquid mixtures having viscosities higher than those susceptible to classification by conventional means. The preferred cyclonic separator 10 imparts high speed vortex or spiral motion to a mixture of a liquid and a gas and injects the mixture into a relatively narrow passageway 25. The high speed rotation of the fluid creates a pressure gradient which produces low, preferably sub-atmospheric, pressures near the axis 17. These low pressures serve to increase the size and buoyancy of gas bubbles in the mixture and promotes the aggregation of these gas bubbles near the axis 17. This permits the mixture to be classified into a gas-rich component near the axis 17 and a liquid-rich, deaerated component farther from the axis 17. After being classified in this manner, the two components are expanded in expansion chambers 40, 50 to return the components approximately to ambient pressure without exerting undue back pressure on the passageway 25. No external vacuum source is required. [0058] While the form of apparatus herein described constitutes a preferred embodiment of this invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims. [0059] What is claimed is:

Claims

1. Apparatus for separating a mixture of a liquid and a gas into a first component and a second component comprising: a body having a first outlet for conducting the first component from said body, a second outlet for conducting the second component from said body, and an inlet opening for conducting the mixture into said body along an inlet opening flow direction; said body defining one or more communicating passageways extending along an axis transverse to said inlet opening flow direction, a first passageway of said one or more passageways communicating with said inlet opening for receiving said mixture; a cutoff core extending within said body downstream of said one or more passageways, said cutoff core defining an axial conduit for receiving said second component and an outwardly inclined cutoff surface for directing said first component away from said second component; and said body and said cutoff core defining one or more expansion chambers communicating with at least one of said first and second outlets.

2. The apparatus as recited in claim 1 including an insert having one or more spiral grooves cooperating with said body to define one or more spiral channels in a passageway of said one or more passageways.

3. The apparatus as recited in claim 1 including an insert having one or more spiral grooves cooperating with said body to define one or more spiral channels in a passageway of said one or more passageways, said one or more spiral grooves each having a lead angle less than 45° .

4. The apparatus as recited in claim 1 including an insert having one or more spiral grooves cooperating with said body to define one or more spiral channels in a passageway of said one or more passageways; and a mandrel extending beyond said insert, said mandrel being so constructed and arranged as to define a section within said one passageway having a substantially constant cross-section.

5. The apparatus as recited in claim 1 wherein said inlet opening communicates tangentially into a first passageway of said one or more passageways.

6. The apparatus as recited in claim 1 wherein said one or more passageways includes a first passageway having a substantially constant first cross- sectional area, said inlet opening communicating with said first passageway; a second passageway having a substantially constant second cross-sectional area smaller than said first cross-sectional area, said second passageway communicating with said one or more expansion chambers; and an inwardly inclined wall connecting the first and second passageways.

7. The apparatus as recited in claim 1 including an insert having one or more spiral grooves; and wherein said one or more passageways includes a first passageway having a first cross-sectional area, said inlet opening communicating with said first . passageway; a second passageway having a substantially constant second cross- sectional area smaller than said first cross-sectional area, said second passageway communicating with said one or more expansion chambers; and an inwardly inclined wall connecting the first and second passageways; said insert being positioned in said first passageway and cooperating with said first passageway to define one or more spiral channels.

8. The apparatus as recited in claim 1 including an insert having one or more spiral grooves and a mandrel extending beyond said insert; and wherein said one or more passageways includes a first passageway having a first cross-sectional area, said inlet opening communicating with said first passageway; a second passageway having a substantially constant second cross- sectional area smaller than said first cross-sectional area, said second passageway communicating with said one or more expansion chambers; and an inwardly inclined wall connecting the first and second passageways; said insert and said mandrel being positioned in said first passageway; said insert cooperating with said first passageway to define one or more spiral channels; and said mandrel being so constructed and arranged as to define a section within said first passageway having a substantially constant cross-section upstream of said inwardly inclined wall.

9. The apparatus as recited in claim 1 wherein said body defines a outwardly inclined inner wall downstream from said one or more passageways; said cutoff core is received within said inner wall; said cutoff surface is axially aligned with said inner wall; and said inner wall and said cutoff surface diverge so as to define an expansion chamber of said one or more expansion chambers.

10. The apparatus as recited in claim 1 including a second core, wherein said body defines a outwardly inclined first inner wall receiving said cutoff core downstream of said one or more passageways; said first inner wall and said cutoff surface diverge so as to define a first expansion chamber of said one or more expansion chambers in communication with said first outlet; said first core defines an outwardly inclined second inner wall; said second core is received within said second inner wall; said second core defines an outwardly inclined second core surface; said second inner wall and said second core surface diverge so as to define a second expansion chamber of said one or more expansion chambers in communication with said second outlet; and said axial conduit communicates axially between said first and second expansion chambers.

11. Apparatus for separating a mixture of a liquid and a gas into a first component and a second component comprising: a body having a first outlet for conducting the first component from said body, a second outlet for conducting the second component from said body, and an inlet opening for conducting the mixture into said body; said body defining a first passageway having a substantially constant first cross-sectional area, said inlet opening communicating with said first passageway; said body defining a second passageway having a substantially constant second cross-sectional area smaller than said first cross-sectional area; said body defining an inwardly inclined wall connecting the first and second passageways; said body defining a outwardly inclined first inner wall downstream of said second passageway; an insert positioned in said first section, said insert having one or more spiral grooves cooperating with said first elongated passageway to define one or more spiral channels for imparting rotation to said mixture; a cutoff core received within said first inner wall, said cutoff core defining an outwardly inclined cutoff surface axially aligned with said first inner wall, an outwardly inclined second inner wall within said cutoff surface, and an axial conduit extending between said cutoff surface and said second inner wall; said first inner wall and said cutoff surface diverging so as to define a first expansion chamber in communication with said first outlet; a second core received within said second inner wall, said second core defining an outwardly inclined second core surface axially aligned with said second inner wall; and said second inner wall and said second core surface diverging so as to define a second expansion chamber in communication with said second outlet.

12. A method for separating a mixture of a liquid and a gas into a first component and a second component, said method comprising: a) pressurizing the mixture to an initial pressure; b) inducing the mixture to flow along an axis and to rotate about the axis through a passageway, said initial pressure being sufficient to create a sub- atmospheric pressure near said axis; and c) separating said mixture into a first component spaced from said axis and a second component proximate the axis; and d) expanding at least one of the first and second components.

13. The method as recited in claim 12 wherein said step b) includes inducing the mixture to flow through one or more spiral channels.

14. The method as recited in claim 12 wherein said step b) includes inducing the mixture to flow through one or more spiral channels and then inducing the mixture to flow through a section of a passageway having a substantially constant cross-section.

15. The method as recited in claim 12 wherein said step b) includes inducing the mixture to flow past a flow restriction defined by an inwardly inclined wall.

16. The method as recited in claim 12 wherein said step d) includes inducing the first component to flow into a first expansion chamber and inducing the second component to flow into a second expansion chamber.

17. The method as recited in claim 12 wherein said step d) includes inducing the first component to flow into a first expansion chamber and inducing the second component to flow into a second expansion chamber located within the first expansion chamber.

18. The method as recited in claim 12 wherein: said step b) includes inducing the mixture to flow along the axis and to rotate about the axis through the passageway; said step c) includes positioning a cutoff core defining an axial conduit for receiving the second component and an outwardly inclined cutoff surface proximate the passageway for directing the first component away from the second component, the axial conduit being separated from the passageway by a cutoff gap; and said method includes the additional step of adjusting the cutoff gap.

19. The method as recited in claim 12 wherein: said step b) includes inducing the mixture to flow along the axis and to rotate about the axis through the passageway; said step c) includes positioning a cutoff core defining an axial conduit for receiving the second component and an outwardly inclined cutoff surface proximate the passageway for directing the first component away from the second component, the axial conduit being separated from the passageway by a cutoff gap; and said method includes the additional steps of measuring a pressure in the mixture upstream of the cutoff core and adjusting the cutoff gap so as to equalize the pressure in the mixture upstream of the cutoff core with a desired pressure.