Vortex devices with maximum efficiency nozzle

Abstract

In accordance with an embodiment of the invention, the apparatuses such as a vortex hydroseparator, a vortex vapor generator and a vortex catalytic generator are presented with the nozzle that serves as the exit port of a light liquid component separated from liquid mixture such as oil and water.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This is a continuation of a U.S. patent application Ser. No. 09/746,337 filed on Dec. 20, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates generally to the field of separation of liquids with different densities, and more specifically, it is directed to vortex devices, including a high efficiency separator utilizing a separation chamber having a cylindrical form, and a specially shaped nozzle for light liquid outflow. This invention is also directed to a vortex vapor generator and a vortex catalytic generator as described in our U.S. patent application Ser. No. 09/746,337.

[0004] 2. Description of the Prior Art

[0005] Cyclones, and their modification hydrocyclones have been known for over two hundred years. Hydrocyclones began utilized comparatively recently, since 1950's. There is a vast literature of articles, books, and patents on hydrocyclones. The most significant review publications on generally accepted hydrocyclone technology include a book “Solid-Liquid Separation” by L. Svarovsky (editor) in Chapter 6 “Hydrocyclones” (L. Svarovsky, editor), Butterworth-Heineman, Oxford (2000) beginning on page 191, a review “Solid-Liquid Separation” in Chapter 5 “The Theory and Applications of the Hydrocyclone” by D. F. Kelsall (J. B. Poole and D. Doyle, eds.), Chemical Publishing Company, Inc., New York (1968) beginning on page 68, U.S. Pat. No. 5,667,686 M. F. Schubert, and U.S. Pat. No. 6,238,579 B1—B. K. Paxton, et al.

[0006] The majority of modem hydrocyclones are made according to existing technology: development of devices similar to gas cyclones designed for gas purification from heavy solid particles and droplet phase. The main elements of the design of such cyclones are a vortex chamber with a tangential introduction of gases having a mixture of heavy fractions (particles), and with transition of its cylindrical part into a converging duct utilized for increase of a gas velocity.

[0007] A separation of heavy particles takes place due to action on them a centrifugal force f=MV&phgr;2/r, where M is a particle mass, V100 is a particle's azimuthal, or tangential velocity, and r is a radial distance of a particle from a vortex chamber axis. Heavy particles are pressed to a vortex chamber wall and they either fall down to its bottom, or stick to a wall. A large difference in density of heavy particles and gas molecules does not prevent the outflow of gas from a cyclone through an exit hole with partial entrainment of especially small solid particles and a liquid's droplet phase. In such devices particles with a size of several microns and less flow out of cyclones together with gases through an overflow pipe.

[0008] It was found that in hydrocyclones a separation of two liquids is more difficult than a separation of gas and heavy particles in cyclones. This is explained by the fact that droplets of one liquid dispersed in another liquid are very fragile due to a presence of a high shear stress in hydrocyclones. High shear stress produced by a change in different components of flow velocities, especially in a conical region of a hydrocyclone, breaks large droplets into smaller particles that are very hard to separate because a centrifugal force applied to small diameter liquid particles decreases with diameter of these particles. Another factor preventing efficient separation of liquids is a relatively small density difference between separated liquids in comparison with solids and gases that have quite a large density difference.

[0009] There have been works with an attempt to use hydrocyclone curved walls as described in U.S. Pat. No. 5,032,275 by Thew that helped to enhance a separation efficiency by reducing shear and flow stagnation. The optimal shape of a separation chamber is described by an exponential equation. It is claimed that such a shape allows a reduction of a flow turbilization in a cross section of a separation chamber of a hydrocyclone.

[0010] In U.S. Pat. No. 5,071,556 by Kalnins et al. it is claimed that the highest efficiency of liquid separation is provided by smaller diameter hydrocyclones due to increased acceleration of liquid after the inlet part followed by a longer separation part of a hydrocyclone. It is claimed that a hydrocyclone's smaller diameter gives a better separation efficiency due to a higher centrifugal force caused by shorter distances particles must travel in such hydrocyclones.

[0011] In order to achieve high separation efficiency there were various complex geometrical shapes, multiple taper and curved parts described in many past hydrocyclone inventions. However, various hydrocyclone shapes require exact measurements and they are quite expensive to manufacture making them economically unattractive. Complex shapes, transitions and conical part of a hydrocyclone produce several important problems such as:

[0012] a) A transition between various angles and constant changing angle, i.e. a transition into conical shape produces instability of a flow field and an increase of a flow energy loss;

[0013] b) A development of a locus of zero vertical velocities (LZVV), well-described in above mentioned work by D. F. Kelsall, “The Theory and Applications of the Hydrocyclone”, following a profile of the hydrocyclone creates a back flow near a gas vortex vicinity;

[0014] c) Liquids in LZVV area are a subject of strong turbulent flows due to a high differential velocity between liquid layers, drastically reducing the separation efficiency.

[0015] B. K. Paxton et al in U.S. Pat. No. 6,238,579 B1 presents a “device for separating solid particles in a fluid stream” which is a flat-bottom type of a hydrocyclone, predominantly cylindrical in shape, designed for separation of solid materials and liquid having different physical characteristics (densities, mass). The inlet of this separator is from one side (top) and an outlet for heavy particles, solids, is on the other side of the cylindrical hydrocyclone (bottom). A central outlet tube is used for light liquid, or light particles. This device, in similarity with hydrocyclones having cylindrical shape, still has a central tube as outlet for light components. Since this hydrocyclone is designed for separation of solid particles from a liquid, it is made with dimensions of inlets and outlets comparable with the hydrocyclone's diameter. Such designs with large dimensions of inlets and outlets and comparatively high mass flows of a liquid and solid particles require the use of high velocities of a supplied mixture of liquid and solid particles.

[0016] Our invention shows that a high velocity of a mixture leads to a high radial velocity of a light component, and causes substantial perturbations in a flow and decreases a separation efficiency. In a Paxton et. al. patent, there are no analytical relationships between dimensions of a separation chamber and inlet and outlet tubes which could regulate an applied speed of a separated mixture of heavy and light components, and there is no method for optimization of this process.

[0017] In our invention, it is also shown that outlet tubes of cylindrical, or conical shape utilized in hydrocyclones, or as in a Paxton et. al. patent, ignite a liquid shock in an exit flow which causes reverse waves leading to a turbulence in a hydrocyclone flow which drastically reduces a separation efficiency.

SUMMARY OF THE INVENTION

[0018] In light of the foregoing, it is an object of the invention to introduce an apparatus and a method for separation of immiscible liquids in vortex devices such as a hydroseparator, a vortex vapor generator that separates liquid's fractions with different boiling temperatures, and a vortex catalytic generator operating in similar way as a vortex vapor generator but having catalytic particles for breaking liquid heavy fractions (all these devices are presented in our U.S. patent application Ser. No. 09/746,337 filed on Dec. 20, 2000). However, for simplicity, and because the vortex devices in a liquid outflow perform in similar way, almost all discussions here refer to a vortex hydroseparator, and when it is necessary, corresponding devices are addressed separately.

[0019] Another object of the present invention is to provide a very high efficiency separation of a heavy liquid component (such as water) from a light liquid (such as oil) component contained in a liquid mixture applied into a hydroseparator.

[0020] Still another object of the present invention is to provide an analytical theory of processes in the separation chamber with special type of an outflow nozzle.

[0021] A further object of the present invention is a reduction of energy losses in a vortex separation device and other vortex devices such as a vortex vapor generator and a vortex catalytic generator.

[0022] Yet a further object of the present invention is to provide an apparatus design that eliminates any taper transitions, overflow pipe, or vortex finder which are inherent to regular hydrocyclones.

[0023] Still a further object of the present invention is the provision of an apparatus that utilizes a maximum flow capacity due to optimization provided by a nozzle in a separation model described by a presented theory and supported by experiments of this invention.

[0024] A further object of the present invention is the provision of an apparatus and method that reduces shear forces due to elimination of a change of a separation chamber diameter leading to liquid droplet breakup.

[0025] An invented vortex hydroseparator for immiscible liquids with different densities, or a vortex vapor generator, or a vortex catalytic generator represent itself a cylindrical chamber with a liquid's tangential introduction through one, or several opening inlets in one side of a separation chamber. For the exit of a heavy liquid component a regular cylindrical port can be used. This cylindrical port's diameter is close to an inlet diameter size.

[0026] In accordance with an embodiment of the present invention, a separator nozzle located on the separator's chamber axis provides an outflow of satellite gases, or vapors of a vaporized fraction, or fractions, or both satellite gases and vapors of a vaporized fraction, or fractions and a light liquid passing through this nozzle in a thin layer over a nozzle's wall providing a light liquid outflow with maximum efficiency. A nozzle has a shape (similar to a Laval nozzle utilized for gases) having a critical cross section and a variable liquid's depth; in this critical cross section a transition of a liquid flow velocity through its critical value from a slow to a fast flow is realized, or, in similarity with a gas flow, a transition from a subsonic to a supersonic flow takes place.

BRIEF DESCRIPTION OF DRAWINGS

[0027] Features of the present invention which are believed to be patentable are set forth with particularity in the appended claims. The organization and operation manner of the invention, together with further objectives and advantages thereof, may be understood by reference to the following descriptions of specific embodiments taken in connection with accompanying drawings, in the several figures of which like reference numerals identify similar elements and in which:

[0028] FIG. 1a, b are embodiments of the present invention with FIG. 1a showing a cross-sectional view of a vortex hydroseparator of gases (vapors), immiscible liquids, or fractions of different densities; FIG. 1b is an end elevational view of a hydroseparator showing main important radii of separating chamber such as a separation chamber radius Rch, a radius of entrance port for liquid's mixture rin, a radius of exit port for heavy liquid rout, a nozzle radius for gases (vapors) and a light liquid rn, a gas (vapors) vortex radius rv; FIG. 1b also shows a pressure distribution in a vortex hydroseparator;

[0029] FIG. 2a, b are the diagrams for a liquid's long waves propagation velocity C&lgr; and a liquid's axial velocity Vx as a function of a liquid thickness h (FIG. 2a) in a nozzle and a function of a geometrical parameter A (FIG. 2b);

[0030] FIG. 3 shows a schematic drawing of a liquid flow in a vortex hydroseparator nozzle in a “shallow water” approximation;

[0031] FIG. 4a, b shows two types of exit nozzles that can be used for hydrocyclones and for a vortex hydroseparator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Referring to FIG. 1, there is shown an invented hydroseparator for separation of liquids (or fractions of the same liquid, like oil, or similar liquids) with different densities and light gases or vapors of fractions. A hydroseparator represents itself a cylindrical vortex separation chamber with introduction of initial liquid, or a mixture of liquids through a port, or a series of ports tangentially into one side of a vortex chamber. For exit flow of a purified light liquid (lesser density) from a heavy liquid (higher density) on a cylinder axis there is a port (nozzle) located at the opposite side of a vortex device entrance port. For exit flow of a heavy liquid there is a port on a vortex chamber side where a nozzle is located.

[0033] As it was above noted, a hydroseparator is discussed here in details, but since other vortex devices (such as a vortex vapor generator, a vortex catalytic generator described in our U.S. patent application Ser. No. 09/746,336 filed on Dec. 20, 2000) have similar operating features, all described analytical solutions for relationships between vortex devices dimensional parameters (a chamber radius Rch, an,entering port radius rin, a nozzle's radius, of a nozzle's most narrow cross section rn, a gas/vapor vortex radius rv, an exit port radius for a heavy liquid rout) can be applied to the other vortex devices.

[0034] Principal schematics of such a vortex hydroseparator with one entrance port into a chamber, one exit port for a heavy,liquid and one nozzle is shown in FIG. 1a and FIG. 1b. This hydroseparator of immiscible liquids is comprised of the following main parts:

[0035] 1. A vortex separation chamber made of a metal cylinder 11 and flanges 21, 22, 23, 24, 25 with an entering port 13 for an inflow of a mixture of heavy and light liquids like water and oil, or other immiscible liquids.

[0036] 2. An exit port 12 that represents an axially-symmetrical nozzle with a smooth contracting-expanding profile similar to a Laval nozzle utilized for gases; a light liquid, vapors and satellite gases move through this nozzle 12.

[0037] 3. A collector 17 for a collection of a deposited heavy liquid (water, or oil heavy fraction) from a light liquid (or fraction) with holes 18 and with a port for an exit flow of a heavy liquid 14.

[0038] 4. A collector 15 for a collection of a light liquid (oil from water, or oil light fraction in a vortex vapor generator, or a vortex vapor catalytic generator) with a port for an exit flow 20.

[0039] 5. A port for exit of satellite gases and vapors of light fractions 16 through a flange 25.

[0040] A collector for a heavy liquid 17 can be made in a form of a sector occupying a part of a circumference, or a completely whole circumference of a vortex separation chamber. A droplet phase of a heavy liquid deposited under impact of centrifugal forces enters into a collector 17 through a system of holes 18 in a separator's cylindrical part and in an end-side wall opposite to an entering port 13. A pressure difference between an entering port plane (shown in FIG. 1a and FIG. 1b) and holes 18 for extraction of a deposited heavy liquid into a collector 17 assists movement of a near-wall flow of heavy liquid from the left side to the right side (however, the whole hydroseparator can be placed vertically, and, then a liquid will be moving from the top to the bottom) of the separation chamber for the direction of a heavy liquid flow into a collector 17.

[0041] A character of flow motions of light and heavy liquids is shown in FIG. 1a and FIG. 1b by light and dark arrows corresponding to a light liquid or oil and a heavy liquid or water with arrows directed into opposite directions. On FIG. 1b one can see some designations for the dimensions of a vortex chamber utilized for analytical description of main parameters such as rin which is a radius of an entering port 13 of a liquid mixture, rout which is a radius of an exit port 14 for a heavy liquid, Rch which is a vortex chamber radius, Rin which is an entering radius of a vortex chamber 11, and Rin=Rch+rin. For Rch>>rin, which is a general case in this invention, and for simplicity, it is assumed that Rin≈Rch≈Ro. In the text of this patent application, all these values are used. A nozzle's 12 radius is rn and a vortex 26 radius is rv. A pressure distribution in a vortex separation chamber is also shown in FIG. 1b.

[0042] A hydroseparator's principle of operation shown in FIG. 1 is clear from this drawing. Using the law of conservation of momentum, one can write that &rgr;V&phgr;r=const, or V&phgr;r=const at &rgr;=const, where &rgr; is a liquid's density, V&phgr; is a liquid's tangential, or azimuthal velocity, r is a current radius in any point inside of a vortex separation chamber between a chamber axis and walls, its effective value for liquid's velocity is between a gas (vapor) vortex rv and a separation chamber radius Rch. An increase of a tangential velocity V&phgr; with a decrease of radius r leads to a decrease of pressure P in correspondence with the Bernoulli integral P+&rgr;V&phgr;2/2=const. Due to this decrease in pressure near a vortex separation chamber axis, a gas (vapor) vortex is developed with a radius rv≦rn, with pressure in a gas vortex corresponding to pressure of the medium, where gases (or vapors of light fractions) contained in a liquid, flow out of a chamber. Heavier liquid.(water, or heavy fraction) droplets under influence of a centrifugal force move along a radius to a peripheral part of a vortex separation chamber. A lighter liquid (oil, or its light fraction) moves through a nozzle 12 into a collector 15. This lighter liquid makes a flow with an opened surface that occupies a small part of a nozzle, typically about 6-10% of a nozzle's area.

[0043] It is necessary to establish the main differences in motion of gases with solid mixtures in gas cyclones and in motion of a liquid with an opened surface developed by a gas vortex in a hydroseparator. Geometry of a gas vortex in a separation chamber 11, having form of a cylinder, or a contraction cone, or a diffuser is independent of the geometry of a vortex separation chamber. It remains cylindrical in a separation chamber, changing its shape at the exit of the nozzle 12 in correspondence with the nozzle shape; and, as it will be shown below, the exit shape plays very important role for the separation efficiency.

[0044] The process of liquid separation (deposition of droplets of heavy liquid) takes place in a chamber's main cylindrical part. Let us assume that a liquid consisting of a mixture of liquids with different densities is applied through a port 13 into a cylindrical chamber 11 with an exit flow of light liquid through a nozzle 12 placed on a chamber's axis. A heavy liquid is extracted through an exit port 14.

[0045] Differences in motion between two liquids distinguished by their relative densities in rotating liquid are determined by the difference between forces applied on elements of a volume (particles). Every particle, or element of a volume is a subject of inertial centrifugal force f=&rgr;V&phgr;2/r. The difference between forces f1 and f2 applied on elements of volume with different densities &rgr;1 and &rgr;2 (different particles) is

f1−f2=(&rgr;1−&rgr;2)V&phgr;2/r.   (1)

[0046] Action of these forces on liquid particles of the same size but with different densities results in different velocities of motion in the direction of the radius from an axis to the peripheral part of the chamber:

&Dgr;f=&Dgr;&rgr;V&phgr;2/r.   (2)

[0047] Multiplying expression (2) by a particle's volume U one can obtain the difference between forces applied to similar particles of different liquids located at the same radius of a vortex chamber r with the same tangential velocity V&phgr;:

&Dgr;F=&Dgr;U&Dgr;&rgr;V&phgr;2/r=&Dgr;MV&phgr;2/r.   (3)

[0048] The force F=MdVr/dt, applied in the direction of the radius develops a corresponding acceleration of a particle:

&Dgr;F=&Dgr;MdVr/dt=&Dgr;MVr∂Vr/∂r, (∂Vr/∂t=0).   (4)

[0049] From equations (3) and (4) it follows that at ∂Vr/∂r=dVr/dr one can have:

VrdVr/dr=V&phgr;2/r,

[0050] or

d(Vr2/2)=(V&phgr;2/r)dr.   (5)

[0051] Taking into account the preservation of momentum: V&phgr;r=const, from which it follows that

V&phgr;2=V&phgr;o2Ro2/r2,

[0052] where Ro, and V&phgr;o are the separation chamber radius, and the initial liquid tangential velocity at an entering port of a hydroseparator correspondingly.

[0053] Using this relationship, a value of a radial component Vrh of a heavy particle motion can be expressed as an integral of equation (5):

Vr2/2=∫(V&phgr;o2/r)dr=V&phgr;o2Ro2∫rRodr/r3.

[0054] After integration one can obtain:

Vrh=V&phgr;o(Ro2/r2−1)½.   (6)

[0055] Such behavior of a heavy droplet radial velocity (a deposition velocity) Vrh in a rotating flow of a lighter liquid is valid assuming the following conditions:

[0056] 1. the dimensions of a heavy liquid droplet volume do not change during its movement from chamber's center to a periphery;

[0057] 2. a light liquid velocity is absent;

[0058] 3. droplet dimensions of a heavy liquid are the same in a whole volume of a moving liquid mixture; and

[0059] 4. the friction of liquid about separating chamber walls and an intermolecular friction are small.

[0060] Despite of the fact that in real conditions the above written assumptions are not observed, the solution (6) permits a series of conclusions about influence of different factors on the deposition velocity of a heavy liquid. These conclusions are:

[0061] 1. the deposition velocity of heavy droplets increases with increasing a liquid flow tangential velocity;

[0062] 2. the deposition velocity of a heavy liquid from a central region is higher than from a peripheral region, i.e. the heavy liquid deposition velocity increases as the separation chamber radius increases and, the heavy liquid deposition velocity decreases as the ratio r/Ro increases.

[0063] In real conditions, deposition of heavy liquid droplets is influenced by the light liquid radial motion towards the separation chamber center with further exit flow through a nozzle. This velocity Vrl is determined by a light liquid mass flow m:

Vrl={dot over (m)}/(&rgr;2&pgr;RoL),   (7)

[0064] where L is a separation chamber length. As one can see the light liquid deposition velocity Vrl is a function of a light liquid mass flow {dot over (m)} and the main parameters of the vortex chamber Ro and L.

[0065] It is clear that for effective separation of heavy liquid droplets, the radial velocity of a heavy liquid Vrh must be significantly higher than the radial velocity of a light liquid Vrl. In other words, from equation (7) it follows that in order to increase the deposition efficiency of heavy liquid droplets, it is necessary to increase the separation chamber radius Ro and its length L. Also, a larger radius enhances a coagulation effect of heavy droplets. The coagulation efficiency is, in a first approximation, proportional to the current radius r.

[0066] It is assumed that a droplet size grows proportional to a propagation distance l˜2&pgr;r˜r. A proportionality coefficient can be determined more exactly if a heavy droplet trajectory (a current line) is known. This current line is determined by the relationship Vr/V&phgr;=dr/rd&phgr;. However, this relationship is also a first approximation because coagulation intensity of droplets in turbulent flow is unknown.

[0067] The theoretical basis for this invention is based on application of the theory of “shallow water” and the gas-hydraulic analogy, which is utilized for development of vortex devices with a new type of exit nozzle for a light liquid. The concept of a “shallow water” was introduced by N. E. Zhukovski in “Analogy between motion of liquid in a narrow channel and gas motion in a tube with a high speed” published in a “Collection of N. E. Zhukovski Works”, v. 7, by All-Union Scientific-Technical Publishing, Moscow (1937) beginning on page 364. A short version of a “shallow water” theory can be found in Theoretical Physics, v. VI, HYDRODYNAMICS by L. D. Landau and E. M. Lifshits, “Nauka”, Publishing House of Physical-Mathematical Literature, Moscow (1986), beginning on page 569.

[0068] An analogy to a behavior of a compressible gas represents a motion of incompressible liquid with a free surface in a gravity field, if a depth of a liquid's layer is sufficiently small. The liquid depth must be small in comparison with the characteristic dimensions of a problem, for example, in comparison with dimensions of uneven parts of a reservoir bottom. In such a case, a transversal component of a liquid velocity can be neglected in comparison with a longitudinal component, and a longitudinal velocity can be considered as a constant value along a layer's thickness. In this so-called hydraulic approximation, a liquid can be considered as a “two-dimensional” medium possessing in every point a definite velocity V, and also can be characterized by a layer's thickness h.

[0069] Euler's general equations of motion provide a solution for the long gravitation waves that represent small disturbances of motion for a considered system. The results (that can be found in a mentioned book by L. D. Landau and E. M. Livshitch, page 570) show that such disturbances propagate relative to a liquid with a thickness layer h with a finite velocity C that equal to

C=(gh)½,   (8)

[0070] where g is a gravity constant.

[0071] This velocity C plays a role of a velocity of sound in gasdynamics. It is necessary to note that, if liquid moves with velocities V<C (quiet flow), the influence of disturbances propagates to the entire flow, down and up of a flow. If liquid moves with a velocity V>C (fast flow), then the influence of disturbances propagates only on certain regions down a flow.

[0072] In this invention, the theory of “shallow water” and the gas-hydraulic analogy utilized for the description of behavior of a liquid in channels of a constant depth in a gravitational field, is modified for the case of a fast rotating liquid in a nozzle with an outflow of light liquid in a vortex hydroseparator and other devices, such as a vortex vapor generator, and a vortex vapor catalytic generator as it was described in our U.S. patent application Ser. No. 09/746,337 of Dec. 20, 2000. The behavior and velocity of long waves propagating on the surface of a rotating liquid applied to a liquid flow in a nozzle of a vortex hydroseparator, a vortex vapor generator, or a vortex catalytic generator is presented below.

[0073] Shallow liquid flow in channels with open surfaces is similar to a gas flow in a tube of a variable cross section. The N. E. Zhukovski's analogy can be used because such flows take place in the potential fields.

[0074] For example, the change in kinetic energy (velocity) of a liquid in an open channel flow in a gravitation field is a function of a difference in the initial and final potential energies of the liquid as described by the equation:

Vliq=[2g(ho−h1)]½,   (9)

[0075] where ho and h1 represent the liquid's initial and final heights respectively.

[0076] A change of kinetic energy (velocity) of a gas in a tube is determined by the difference in thermal potential that is an enthalpy:

Vg=[2(io=i1)]½,   (10)

[0077] where io and i1 are enthalpies of gas initial and final states.

[0078] From (9) and (10) follows that a liquid's depth serves as an analogue of enthalpy in gas. Since a hydrostatic pressure in a liquid is determined by a liquid's height h, by P=&rgr;gh, and if &rgr;=const, then a pressure difference is equivalent to a difference of enthalpies.

[0079] The characteristic feature of such flows is a change of flow velocity in a channel with a variable geometry with a transition through a velocity of propagation of disturbances in a flow. For open channel flows of a liquid, this is a velocity for propagation of long waves on a surface of a liquid C. In the field of gravitation forces this velocity is determined by the formula (8).

[0080] From the equation of a constant mass flow for a liquid moving in any arbitrary channel follows that liquid's flow velocity Vx can be determined as:

Vx={dot over (m)}/(&rgr;hL),   (11)

[0081] where h is a liquid's depth, L is a channel's width, {dot over (m)} is a mass flow per unit volume, per second, h is a liquid depth, and &rgr; is a liquid density.

[0082] From equations (8) and (11) it is possible to determine a liquid depth h for which a liquid's flow velocity is equal to a velocity of long waves propagation on a liquid's surface, or Vx=C:

h=[{dot over (m)}2/(&rgr;2gL2)]⅓.   (12)

[0083] As a liquid depth h decreases, a liquid's flow velocity Vx increases and a velocity C decreases. That is why for any specific values of {dot over (m)} and L, there is always a cross section in a channel where both velocities Vx and C are equal (FIG. 2a) that can be called a critical flow regime. In analogy with the gasdynamics flows, this cross section is the critical cross section Scr, and hcr is the critical depth. Also from here it follows that as flow velocity Vx further increases with the decreasing depth h and channel expansion L, this leads to a transition through the characteristic velocity C, i.e. to the supercritical flow regime with Vx>C, or, in analogy to gas flows, to the supersonic flow.

[0084] Since pressure in a liquid P=&rgr;gh, then the equation (12) can be transformed into equation:

hcr={dot over (m)}2g/(P2L2).   (13)

[0085] In the field of inertia forces of rotating liquid with the development of a gas vortex on a channel's axis, the propagation velocity of long waves C&lgr; on a liquid's surface, correspondingly, is equal:

C&lgr;=(jh)½,   (14)

[0086] where

j=V&phgr;v2/rv   (15)

[0087] is the tangential acceleration of rotating liquid on a vortex surface, V&phgr;v is the tangential liquid velocity on a vortex surface, rv is the radius of a gas vortex. Thus, the velocity of long wave propagation on the surface of a gas vortex in a nozzle of a vortex hydroseparator C&lgr; depends on the liquid depth h in a nozzle and the value j of a centrifugal acceleration (15) and serves as analogue of a sound velocity.

[0088] Here are main assumptions in the theory of “shallow water” that are illustrated by FIG. 3 that shows a liquid flow in a hydroseparator's nozzle:

[0089] 1. The transverse liquid velocity component Vz of a liquid flow in a vortex's device nozzle is small in comparison with a longitudinal velocity (along a liquid's layer) Vv.

[0090] 2. The longitudinal liquid velocity component Vx is constant across a liquid layer (a gas-hydraulic approximation). Thus, a liquid in a vortex device nozzle can be characterized as a medium with a certain velocity Vx and a depth h in every point of a nozzle flow.

[0091] 3. A liquid depth h in a vortex device nozzle is small in comparison with the nozzle radius rn, i.e. h<<rn.

[0092] 4. The wave amplitude is not assumed small, as it is normally accepted in the theory of long waves.

[0093] The channel depth h in a nozzle taking into account that the liquid thickness is small (a “shallow water” approximation) can be determined by combining the relationships: S=2&pgr;rvh and S=&pgr;(rn2−rv2) and solving for h:

h=(rn2−rv2)/2rv.   (16)

[0094] From the law of conservation of the momentum Vr=VinRin one can determine the tangential velocity on a gas vortex surface V&phgr;v:

V&phgr;v=VinRin/rv   (17)

[0095] and

j=Vin2Rin/rv3.   (18)

[0096] After substitution of h from (16) and j from (18) into (14) one can obtain a formula for the propagation velocity of long waves on a liquid surface in a vortex hydroseparator nozzle:

C&lgr;=(VinRin/rv2)[(rn2−rv2)/2]½,   (19)

[0097] The axial (longitudinal) liquid velocity component in a nozzle is:

Vx={dot over (m)}/(&rgr;2&pgr;rnh),   (20)

[0098] And the liquid mass flow can be expressed in terms of a radius of an entering port rin and liquid velocity at the entering port of a vortex chamber Vin:

{dot over (m)}=&rgr;Vin&pgr;rin2.   (21)

[0099] At the condition that the mass flow of the heavy liquid component is much less than the total mass flow, i.e. {dot over (m)}h<<{dot over (m)}, the axial liquid velocity in the nozzle Vx and the liquid velocity in the vortex chamber entering port Vin can be easily connected

Vx=Vinrin2/(2rnh).   (22)

[0100] The condition Vx=C&lgr; (a critical flow regime) determines a critical depth hcr of a liquid rotating in a nozzle as a function of geometrical dimensions of a vortex chamber:

rin2/(2rnhcr)=(Rin/rv2)[(rn2−rv2)/2]½.   (23)

[0101] Taking into account (15), after simple transformations using (21) one can obtain the dependence of the critical liquid depth in a nozzle as a function of the geometrical parameter A:

hcr=rv/(2A)⅔,   (24)

[0102] where

A=Rinrn/nrin2.   (25)

[0103] The value A is the geometrical characteristic of a chamber of a vortex hydroseparator, a vortex vapor generator, or a vortex catalytic generator, n is a number of entering ports.

[0104] For non-circular vortex chambers with mixture mass flows entering from ports along the chamber axis, the geometrical characteristic of the vortex chamber A is expressed as:

A=Rinrn&pgr;cos &thgr;/nSin,   (26)

[0105] where n is the number of entering ports, Sin is the surface area of an entering port (assuming all ports have equal area), &thgr; is the angle between a normal vector to the vortex chamber the axis. For simplicity here and in further estimations n is taken equal to 1.

[0106] The geometrical characteristic A is the similarity criterion for the devices with rotating liquid and with development of a gas vortex in an ideal liquid. For different dimensions of Rin, rn, and rin liquid flows are similar at equal values of A. Also, for different values of the geometrical characteristic A from equations (16) and (24) one can determine the radius of a gas vortex rv and at Vx≧C&lgr;, and A≧2 corresponding to the critical regime:

rvcr2=rn2[1−(½A)⅔].   (27)

[0107] For a practical case, the following parameters of the vortex device were utilized in experiments: Rin=116.5 mm, rin=5.0 mm, rn=5.0 mm, A=23.3, Vin=10 m/s, rv=4.85 mm, h=0.15 mm, Vx=169.5 m/s, C&lgr;=42.6 m/s, M*=4. The mass flows for liquid mixtures {dot over (m)}in varied from 1 kg/s to 5 kg/s. This device that was utilized as a vortex hydroseparator, a vortex vapor generator (in this case, liquid mixture was heated to temperature close to one of liquid fractions) and a vortex catalytic generator (in this case, small catalytic particles with the radius about 1 mm could be observed in stable position rotating at a certain distance from a gas vortex) was made of clear Plexiglas parts to permit visual observation of transparent liquid flows with gas vortex and catalytic particles.

[0108] It is necessary to note that in a definition of the geometrical parameter A there is no dimension of an exit port rout for a heavy liquid component. A dimension of a heavy liquid component exit port rout is determined by a heavy liquid mass flow (and has no influence on the geometrical parameter A):

{dot over (m)}hliq=&rgr;hliqVhliqS,   (28)

[0109] where {dot over (m)}hliq is the heavy liquid component mass flow, &rgr;hliq and Vliq are the density and velocity of heavy liquid component leaving an exit port with area S that for the simplest case of a circular port is equal to &pgr;rout2. For a mixture with {dot over (m)}in=5 kg/s, {dot over (m)}hliq=0.5 kg/s (10% of total mass flow) and for rout=20 mm the exit speed for a heavy component is 0.4 m/s. For mixtures with high percentage of a heavy component (over 15-20%) in a liquid mixture it is necessary to include a correction factor into the geometrical parameter A.

[0110] From equations (24) and (25) it also follows that for each vortex chamber geometrical characteristic A there is a certain value of a critical cross section of a liquid flow (a critical depth hcr) at which the transition to a supercritical regime of flow is realized. From the nozzle theory, it is known that the critical and supercritical flows correspond to the maximum liquid mass flow through a nozzle (Theoretical Physics, v. VI, HYDRODYNAMICS by L. D. Landau and E. M. Lifshits, “Nauka”, Publishing House of Physical-Mathematical Literature, Moscow (1986), beginning on page 504). For a liquid flow through a nozzle, as with a gas flow in a Laval nozzle, a nozzle profile must have a changing geometry along its axis. A significant influence of centrifugal forces, due to the sticking and wetting nature of liquids (with exception of mercury), allows a liquid flow in a chamber's nozzle to turn at a high angle and avoid an atomizing spray effect. Instead, for a nozzle with a changing geometry it is possible to create a smooth liquid flow from a nozzle with very high velocities (for most practical cases, Vin is 10-20 m/s, Vx is over 100 m/s).

[0111] A ratio Vx/C&lgr;=M*=1, where M* is an analogue of the Mach number M in gas, in a rotating liquid is achieved at A=2 (FIG. 2b). Just as the M number serves as a similarity criterion for gas flows, the M* is an analogous similarity criterion for liquid flows of a small depth. However, if a flow has a constant depth, then M*≦1. During a motion of a liquid with a variable depth this relationship doesn't take place. In this case, the value M* depends on the ratio of the area in an arbitrary cross section to the area in a narrow (critical) cross section.

[0112] The regime of a critical and supercritical flow in a nozzle is realized for the geometrical characteristic A≧2 (M*≧1). It requires observance of definite conditions for liquid extraction from a vortex chamber of a hydroseparator utilized for a purification of a liquid from liquid and solid admixtures. Exit flow of a liquid purified from heavy or light admixtures from hydrocyclones through long cylindrical or converging conical channels (nozzles) leads to development pressure waves in such channels. This phenomenon is similar to appearance of shock waves that occur when gases are expelled from a nozzle of a liquid-propellant rocket. Transitions from supercritical to undercritical regime of flow in long channels are caused by a flow discontinuities arising from friction (FIG. 4a).

[0113] Intense turbulization of a liquid flow with additives causes a development of large-scale waves (liquid jumps) and leads to the decrease of a liquid's separation efficiency and to the increase of energy losses. Efforts for the increase of the time for action of centrifugal forces in a liquid by the increase of a hydrocyclone channel length or the decrease of its diameter do not produce a necessary effect.

[0114] Extraction of the heavy droplet phase from a liquid should be carried out through a port on a peripheral part of a vortex chamber, and a purified light liquid must be removed through a profiled nozzle with an expanding radius (FIG. 1a and FIG. 4b).

[0115] Increasing separation efficiency of both heavy and light liquid fractions is achieved by increasing a separator vortex chamber length and radius. In this case, an appearance of shock waves (discontinuities) in a profiled nozzle with a high degree of expansion and small amplitude of a liquid layer in a nozzle (h<<rn) and the geometrical characteristics A≧2 does not adversely influence separation efficiency of a liquid from additives.

[0116] The severity of liquid discontinuities from shock waves while removing a purified liquid to a collector 15 can be significantly reduced or eliminated by enlarging the exit port 20 (FIG. 1a and FIG. 4b), which also decreases the need for intensive pumping at high mass flow rates.

[0117] Continuing the analogy with a gas flow, it is essential to note that the number M* depends not only on the ratios of areas but it depends also on the ratio of pressures and densities in a nozzle. In order to observe a critical flow regime in a nozzle it is necessary to have a certain pressure difference between a volume from where a flow is coming out and a pressure of the surrounding media to where a flow is coming in. This relationship has the form:

Po/Pcr=[(&kgr;+1)/2]&kgr;/(&kgr;−1),   (29)

[0118] where k=Cp/Cv is a ratio of specific heats, or an adiabatic coefficient. With this condition, a flow velocity is equal to a local velocity of sound, or, which is the same for a liquid moving in a thin layer of a nozzle, an axial component of flow velocity Vx is equal to a local velocity for propagation of long waves over its surface C&lgr;, or Vx=C&lgr;.

[0119] The decrease of pressure Po, or the increase of the critical pressure Pcr, leads to the decrease of exit velocity that is less than the local velocity of sound (M*<1). The increase of pressure in a volume doesn't lead to the increase of the M* number, it only increases pressure at nozzle exit. Exit flow velocity can increase only with a corresponding increase in the sound velocity. For the case of a liquid flow, this corresponds to a requirement for an increase of the propagation velocity of long waves. This is achieved by increasing either through a liquid depth h, or a centrifugal acceleration j.

[0120] Unlike gas under excess pressure at a nozzle exit, liquid cannot expand without losing continuity when leaving a nozzle. Instead, the extra pressure must be completely transformed to kinetic energy within a nozzle, as the liquid exits. This process takes place in a nozzle. A transformation of extra centrifugal pressure into a dynamic pressure occupies a certain length of a nozzle. If one can assume that potential energy makes a transition into kinetic energy without a discontinuity (rarefaction discontinuities exist only at special conditions), it follows that with the increase of pressure difference at a nozzle a critical cross section moves inside of a nozzle.

[0121] Thus, a critical cross section is determined by the value M*=1. This cross section also can be determined through pressure. For this purpose, one can substitute in equation (29) an adiabatic coefficient &kgr;=2:

Po*/Pcr*=(3/2)2=2.25,

[0122] or

Pcr*=0.445Po*.   (30)

[0123] Detailed analysis shows that for the existence of the critical and supercritical regime of flow in a nozzle of a vortex hydroseparator, (a vortex vapor generator, and a vortex catalytic generator) it is necessary and sufficient that an average pressure on a hydroseparator &Dgr;Pav is higher, or equal to 1.5 of an average extra pressure in a nozzle's critical cross section &Dgr;Pcr.av:

&Dgr;Pav≧1.5&Dgr;Pcr.av.   (31)

[0124] The maximum mass flow principle is satisfied for this condition (31). At &Dgr;Pav<1.5Pcr.av one can have a subcritical flow condition for which the principle of the maximum flow in a nozzle doesn't take place.

[0125] In conclusion, a nozzle with a shape converging—expanding areas (similar to Laval's nozzle) permits to have critical, or supercritical liquid flow in a thin layer providing maximum liquid mass flow without disturbances in the main separation chamber. Vortex devices utilizing such a nozzle provide very efficient and optimal separation of immiscible liquids, or fractions, so a nozzle serves for liquid motion in a thin layer and, at the same time, for gases, or vapors propagating in the central part of a nozzle unoccupied with a liquid.

Alternate Embodiments

[0126] When examined closely, several specific embodiments are possible for the subject invention. At its simplest level, a hydrocyclone-separator with several inlet holes and with several exit holes for heavy density liquid can be used.

[0127] Practically, most of hydrocyclones can be designed with the separation chamber radius Rin, with the entering port radius rin, and the exit port in the form of a nozzle with changing area and with the radius rn that the non-dimensional geometrical parameter A is within the range A≧2 and therefore hydrocyclones using the aforementioned “supersonic” flow principles will be substantially more efficient due to dramatically reduced flow turbulization.

Claims

1. A method for separation heavy and light components of a liquid mixture, comprising the steps of:

(a) providing a vortex device comprising a cylindrical volume having a tangentially located input port and an exit port, wherein said vortex device further comprises a nozzle having a radius less than the radius of said cylindrical volume, wherein said nozzle is coaxial with the central axis of said cylindrical volume;

wherein said nozzle has a contracting-expanding shape;

(b) introducing said liquid mixture into said cylindrical volume through said input port at a velocity and pressure sufficient to create a stable vortex of said liquid mixture in said cylindrical volume; and

(c) removing said light component through said nozzle; and

(d) removing said heavy component through said exit port.

2. A method in accordance with claim 1, wherein said vortex device comprises multiple tangential input ports.

3. A method in accordance with claim 1, wherein said nozzle provides critical and supercritical flow for said light component.

4. A method in accordance with claim 1, wherein said nozzle provides for liquid flow of said light component without reflections and also provides for exit of satellite gases or vapors of light fraction or fractions.

5. Vortex devices with geometrical dimensions and an exit nozzle for light liquid component, that for a maximum efficiency utilize the non-dimensional geometrical parameter A=Rorn/(nrin2). where Ro is the vortex device radius, rn is the nozzle radius, rin is the radius of entering port, n is the number of entrance ports; for providing a maximum liquid flow without liquid shocks a parameter A≧2; and for most practical and efficient operations A should be in the range 10≦A≦30.