Note: Descriptions are shown in the official language in which they were submitted.
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A SYSTEM FOR SEPARATING AN ENTRAINED LIQUID
COMPONENT FROM A GAS STREAM
Background of the Invention
This disclosure is to an improved vortex tube for use in separating an
immiscible
liquid component from a gas stream and more particularly, for a system and a
method of
15 operating a system for separating liquid components from a gas.stream. An
example of
an application of the invention is for separating entrained water from a
natural gas
stream.
The subject of the invention generally relates to gasfliquid separators or
gas/Iiquid/solid separators. Separators of this type are typically process
vessels thatmay
20 be at atmospheric or above atmospheric pressures. The main function of the
separator
system is to segregate immiscible phases of the process stream such as when
the process
stream is the form of a gas, such as natural gas that carries with it an
immiscible liquid
component. The function of the separator of this invention is to separate out
the liquid
component to provide at the output of the separator a gas stream that is
relatively free
25 from entrained liquids.
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Separators for separating liquid components from a gas stream are commonly
utilized in the oil and gas industry, specifically in oil and gas productiony
oil refining and
gas processing. While very commonly utilized in the oil and gas industry,
separators of
this type are also used in the mining industry, chemical plants, water
treatment facilities,
pulp and paper plants and phannaceutical manufacturing facilities. Separators
can be
designed to separate a two-phase stream - that is, a vapor/liquid stream or a
three-phase
stream - that is, a vapor/organic liquid/aqueous stream or a four-phase stream
- that is, a
vapor/organic liquid/aqueous liquid/solids stream.
Separation of immiscible components of the stream usually and ultimately
depend
on the force of gravity. Gravity can be either natural gravity - that is, the
pull of objects
towards the center of the earth or created gravitational forces such as
represented by,
centrifugal separators. Natural gravity is usually used by flowing a stream
having
immiscible components into a vessel which provides a quiescent zone - that is,
a
relatively undisturbed environment that allows gravity to act on heavier
components of
the stream and move them into a downward part of the vessel. This movement has
the
counteraction of the lighter components of the stream migrating to an upward
part of the
vessel. In this way, the heavier components - that is, liquids, can be
withdrawn from the
lower part of the vessel and the lighter components - that is, gases,
withdrawn from an
upper part of the vessel.
Another type of gravitational separator utilizes artificial gravity attained
by
centrifugal force. One way of generating artificial gravity is by the use of a
vortex tube.
A vortex tube is typically an elongated tube having a cylindrical interior
wall that is
preferably vertically mounted or at lease mounted with a vertically downward
tangent.
Adjacent an upper end of the vessel is an inlet opening into the vortex tube,
the inlet
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being arranged so that fluids flowing therein tangentially intersect the
interior wall of the
vortex tube and flow around the interior wall thereby creating centrifugal
force that is
applied to the components, the centrifugal force serving to move the heavier
component -
that is, the liquid component, towards the wall of the vortex tube while the
lighter
component is forced towards the interior of the vortex tube. In a typical
vortex tube the
gas is withdrawn from an upper central vortex opening while the liquid
component is
withdrawn from a liquid outlet in the bottom portion of the vortex tube. The
invention
herein pertains to improvements to vortex tubes and to methods of using the
improved
vortex tubes for separation of immiscible components of a gas stream.
For background information relating to the general subject matter of this
invention reference may be had to the following previously issued United
States patents:
PATENT NO. INVENTOR TITLE.
1,836,004 Becker pparatus for Treating Gas
2,808,897 Reinsch et al pparatus for Contacting
iquid and Vaporous
aterials
3,296,774 Hoogendorn et al Gas-Liquid Contactor with
Wall Obstructions and
Contacting Method
3,498,028 Trouw pparatus for Contacting
iquids and Gases
3,581,467 Donnelly ethod and Apparatus for
ortical Liquid-Gas
ovement
3,605,388 Zuiderweg et al pparatus for Contacting
i uids and Gases
3,662,521 Behar et al evice for Reaction Between
iquid Phase and Gaseous
hase
3,930,816 Miczek Structure for a Gas and
iquid Contacting Chamber
in a Gas Effluent Processing
System
4,128,406 Spevack Contact Apparatus for
ultiphase Processing
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4,486,203 Rooker Inlet Momentum Absorber
or Fluid Separation
4,838,906 Kiselev Contact-and-Separating
lement
4,880,451 Konijn Gas/Liquid Contacting
Apparatus
5,145,612 Reay et al pparatus for Mixing Vapor
in a Countercurrent Column
5,683,629 Konijn orizontal Tray and Column
or Contacting Gas and
iquid
5,714,068 Brown nlet Device for Large Oil
ield Separator
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Brief Summary of the Invention
Separators are process vessels, commonly pressurized, which segregate
immiscible phases of a process stream. They are commonly used in oil and gas
production, oil refining, gas processing, mining, chemical plants, waste water
treatment,
pulp and paper, and pharmaceutical plants. They separate two-phase streams
(vapor/liquid), three-phase streams (vapor/organic liquid/aqueous liquid) or
four-phase
streams (vapor/organic liquid/aqueous liquid/solids). Separators commonly have
an inlet
momentum absorber or deflector intended to utilize or reduce fluid incoming
momentum,
and distribute liquid and gas. This energy reduction initiates phase
separation inside the
separator vessel. These inlet devices are then followed by various types of de-
misting,
de-foaming, and/or liquid coalescing apparatus.
These inlet devices are then followed by various types of de-misting, de-
foaming,
and/or liquid coalescing apparatus. The most common separator inlet device is
a "splash
plate" -- that is, a flat, curved or dished impingement plate that intercepts
the incoming
flow stream. Fluids are allowed to rebound in a direction considered least
destructive to
the quiescence of the bulk phases residing in the vessel. Splash plates are
characterized
by relatively high rebound turbulence. A diffusion inlet is another generic
type of inlet
device. It typically divides the flow stream into multiple smaller streams and
reduces
momentum by gradual enlargement of the flow areas of each stream.
The invention herein relates to a "vortex tube" that is frequently utilized in
a
"vortex tube cluster". A vortex tube can be used as a momentum dissipating
inlet device
and can eliminate other phase separation elements as well. A vortex tube has
an inlet
through which fluids enter tangentially creating rotational flow. Centrifugal
force
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separates phases within the tube, which then exit, gas from the top through a
central gas
orifice and liquids from the bottom through peripheral openings. A vortex is
formed
inside the tube. In a preferred embodiment, the bottom of each tube is
submerged below
the liquid surface to a depth that prevents the gas vortex from blowing out
the bottom.
An essential characteristic of a vortex tube is that it uses flow energy
constructively to separate phases whereas in impingement and diffusion devices
flow
energy is counterproductive to separation, and so they seek to dissipate flow
energy as
non-destructively as is practical. ("Destructive" refers to the tendency of
hydraulic
agitation to mix, rather than to separate phases). This invention herein
includes. an
improved vortex tube that is usually employed in a vortex tube cluster.
The disclosure herein covers a vortex tube system, which produces optimum
performance for a variety of process circumstances and conditions.
One improvement described herein minimizes fluid shear by shielding the
axially
flowing gas stream leaving the top of the tube from the feed stream as it
enters the tube
tangentially. It consists of a 'vortex finder', which shields the vortex tube
outlet stream
from disturbance by the inlet stream. It is comprised of a vertical tube the
same size as
the gas orifice and concentric with the vertical vortex tube and protrudes
from the orifice
plate on top downward to below the lowest point of the vortex tube entry..
This
improvement also includes a method of diverting the fluid already rotating
circumferentially about the tube as it completes its first rotation from the
entering stream.
This is done by directing the inlet stream downward using a deflector at such
an angle as
to miss the tube inlet after one revolution. The deflector diverts the
incoming fluid
stream downward at the necessary angle. A benefit of using this method is that
a smaller
amount of liquid mist is carried out of the tube with the gas stream.
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Occasionally the gas flow velocity inside a vortex tube may exceed the ideal
design limits, either continuously or intermittently due to slugging. This
excessive
velocity re-entrains liquid mist, and causes the gas stream to spit coarse
mist droplets out
of the gas orifice. Uncontained, these droplets can result in separator liquid
carryover. A
second improvement described herein is a method for diverting the gas outlet
from the
vortex tube downward so that any entrained liquid is directed toward the
standing liquid
phase. A curved outlet tube is installed on top of the gas orifice to catch
these large
droplets and direct them harmlessly downward towards the standing liquid. The
deflecting tube must arch down sufficiently to create this downward velocity
component
but does not need to point directly down. If space limits the curve oÃthe
tube, it can be
modified as shown in Figure 9. The benefit of this device is that it allows a
smaller tube
cluster, making the unit more competitive and giving a greater flow turndown
to the
device without carryover.
In the operation of a vortex tube it is important to control the flow of
liquid as it is.
discharged from the tube bottom. This is done by changing flow direction -
that is, to
direct the liquid discharge from the tube upward instead of outward by using a
tube-on-tube device. This is important if there is any gas carryunder from the
tube. Gas
exiting the bottom of the tube, if allowed to radiate outward, can propel gas-
laden liquid
towards the liquid outlet, resulting in carryunder of gas from the separator
vessel. The
tube-on-tube design projects this flow upward so that gas more quickly reaches
the
gas-liquid surface. This tends to keep the gas entrainment localized, allowing
a quiet
zone in the separator to be more gas-free. The benefit of the tube-on-tube
design results
in more gas-free liquid leaving the separator.
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The liquid release point for a typical vortex tube is located well beneath the
liquid
surface. However, in low level situations or at start-up, the bottom of the
tube may not
be submerged. The tube-on-tube arrangement establishes tube-bottom submergence
as
soon as any liquid is produced. A resulting benefit of incorporating the tube-
on-tube
system is that during separator startup, or during low liquid level
excursions, the vortex
tube liquid discharge will remain submerged and will therefore function
normally.
Another benefit of the tube-on-tube system is that it keeps disturbance of the
oil-water interface more localized around the tube. In three-phase separators
the top of
the outer tube is typically located below the oil-water interface. An
improvement to the
tube-on-tube system is the deflector ring. If the liquid release of a tube-on-
tube system is
near the liquid or interface surface, the deflector ring deflects the upward
momentum into
a horizontal direction. By the time this deflection occurs, gas has been
released and
velocity has slowed by natural diffusion. This reduces surface disturbance and
phase
re-entrainment. The benefit is a reduction in cross-contamination between
liquid phases
leaving the separator.
To diffuse liquid discharged from a cluster of vortex tubes, a liquid energy
absorber may be used that is in the form of a box that surrounds the entire
bottom portion
of a tube cluster. The box has sides, a top and a bottom, some or all of which
are of
perforated plate. A liquid energy absorber system reduces turbulent spots in
separator
liquid residence sections by diffusing vortex tube exit velocities and reduces
channeling
by improving fluid distribution.
In vertical separators or in large diameter horizontal separators the vertical
height
of vortex tubes can be significant. When this occurs, liquid separated within
the tubes
must fall a long distance down the tube wall. As it plunges, gravity
accelerates its
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velocity such that when it finally impinges on the standing liquid, its high
momentum
re-entrains gas into the liquid phases. Concurrently, in tall vortex tubes,
wall friction
slows down rotational liquid velocity causing a loss of centrifugal separation
as the liquid
progresses down the tube. Tlius at the bottom of the tube, the liquid velocity
direction is
nearly vertically downward. To alleviate this probl.em, a system employing
free-fall
preventers is used. The benefit of the free-fall preventer system is that gas
re-entrainment
and foatni.ng are greatly rninin,ized or eliminated, and a. higher average g-
force is
maintained in the vortex tubes to improve phase separation within the tubes.
The claims and the.,specification describe the invention presented and the
terms
that are employed in the claims draw their meaning from the use of such
tertrzs in the
specification. The same. terms employed in the,prior art may be broader in
meaning than
specifically employed herein. Whenever there is a question between the broader
definition of such terms used in the prior art and the more specific use of
the terms
herein, the more, spe.cific;meaning is meant.
While the invention has been.described with a certain degree of particularity,
it is
manifest that many changes may be made in the details of construction and the
arrangement of components without departi.ng. from the spirit and scope of
this
disclosure. It is understood that the invention is not lirnited to the
embodiments set forth
herein for purposes of eaemplification, but is to be li_mited only by the
scope of the
attached claim or claims, including the full range of equivalency to which
each element
thereof is entitled..
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In one broad aspect, there is provided a system
for separating an entrained immiscible liquid component from
a wet gas stream comprising: a vessel having an interior in
communication with a wet gas inlet, a dry gas outlet and a
liquid outlet; at least one vortex tube supported within
said vessel interior, the vortex tube having an internal
wall surface, a first end, an outlet end and a wet gas inlet
in and tangential to said internal wall surface, the
tangential wet gas inlet being spaced from said first end
and arranged so that wet gas entering therein rotates within
said vortex tube to cause at least some of the liquid
components thereof to be separated from said wet gas stream
as it is forced against said internal wall surface by
centrifugal action; and at least one free-fall preventer
within said vortex tube positioned below said tangential wet
gas inlet and above said vortex tube outlet end, the free-
fall preventer having a plurality of spaced apart radially
arranged flow diverting vanes positioned in a plane
perpendicular to a longitudinal axis of said vortex tube and
configured to impose minimal restriction to flow within said
vortex tube while augmenting the rotation of separated
liquid component as it traverses downwardly in said vortex
tube.
In another broad aspect, there is provided
apparatus for separating an entrained immiscible liquid
component from a wet gas stream comprising: a vortex tube
having an internal wall surface, a first end, an outlet end
and a wet gas inlet in and tangential to said internal wall
surface, the tangential wet gas inlet being spaced from said
first end and arranged so that wet gas entering therein
rotates within said vortex tube to cause at least some of
the liquid components thereof to be separated from said wet
gas stream and to be forced against said internal wall
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surface by centrifugal action; and at least one free-fall
preventer within said vortex tube positioned below said
tangential wet gas inlet and above said vortex tube outlet
end, the free-fall preventer having a plurality of spaced
apart radially arranged flow diverting vanes positioned in a
plane perpendicular to a longitudinal axis of said vortex
tube configured to impose minimal restriction to flow within
said vortex tube while augmenting the rotation of separated
liquid component as it traverses downwardly in said vortex
tube.
A better understanding of the invention will be
obtained from the following detailed description of the
preferred embodiments taken in conjunction with the attached
drawings.
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Description of the Drawings
Figure 1 shows a cluster of vortex tubes or a vortex tube assembly positioned
within a separator vessel. The separator vessel is shown very diagrammatically
to show a
fluid inlet, a gas outlet and a liquid outlet to show very generally the
environment in
which the vortex tube assembly of Figure 1 is employed.
Figure 2 is a horizontal cross-sectional view taken along the line 2-2 of
Figure 1
and showing the manner in which wet gas is introduced from the horizontal
inlet tube
into the vertically arranged vortex tubes.
Figure 3 is an elevational cross-sectional view of one of the vortex tubes as
taken
along the line 3-3 of Figure 3.
Figure 4 is a fragmentary cross-sectional view of the upper portion of a
vortex
tube as shown enlarged.
Figure 5 is a cross-sectional view of the upper portion of a vortex tube
showing
one improvement of the invention herein that includes a short length vertical
tubular
vortex finder that serves to separate the incoming fluid stream from the gas
outlet stream.
Figure 6 is an isometric view of the upper portion of a vortex tube having a
short
length vortex finder as shown in Figure 5 and further, having a downward flow
diverter
so that gas tangentially entering the vortex tube is immediately directed in a
downward
spiral tangent.
Figure 7 is an isometric view of a vortex tube showing a gas flow diverter
that is
in communication with the vortex tube gas outlet on the top of the vortex
tube, and that
serves to direct the outlet gas in a downward tangent.
Figure 8 is a side view of a gas flow diverter extending from the upper end of
a
vortex tube and showing a more U-shaped flow diverter to provide an increased
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downward tangent for gas passing out of the vortex tube. This is the normal
configuration.
Figure 9 is a view similar to Figure 8 except it shows the wall of a
cylindrical
vessel in which the vortex tube is positioned and showing the vortex tube
adjacent the
wall and specifically, the gas flow diverter as being positioned adjacent the
vessel
cylindrical wall and shows the use of a shield to direct exhaust gas away from
the vessel
sidewall. This configuration is used instead of that in Figure 8 when
available space does
not permit the Figure 8 design.
Figure 10 shows in cross-section the bottom end portion of a vortex tube, the
vortex tube extending below a liquid level established within a vessel. A
portion of the
vessel is shown. Spaced from the lower end of the vortex tube is a bottom
diverter plate
that serves to spread the flow of liquid exiting from the vortex tube. The
bottom diverter
plate also serves to decrease the possibility that the gas vortex formed
within the diverter
tube can elongate to extend out the lower end of the vortex tube.
Figure 11 is a view of the bottom portion of a vortex tube as in Figure 10 but
showing the use of a tube-on-tube attachment that provides a short length
annular space
at the lower end of the vortex tube through which liquids passing out of the
vortex tube
travels. The tube-on-tube arrangement of Figure 11 decreases the turbulence of
the fluid
flowing from the vortex tube and further decreases the possibility that the
gas vortex
formed within the tube can extend out the lower end thereof.
Figure 12 is like Figures 10 and 11 in that it shows the lower end portion of
a
vortex tube. In these figures, the liquid accumulation within the bottom of
the separator
vessel is shown as being a two-phase arrangement - that is, with a lower
heavier phase,
such as water and an upper lighter liquid phase such as oil with gas in the
vessel being
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above the lighter liquid or oil phase. In Figure 11, the upper end of the tube-
on-tube
attachment discharges into the denser liquid phase whereas in the arrangement
of Figure
12, the length of the tube-on-tube attachment is such that the upper end is
above the
liquid level of the lightest liquid phase so that liquid passing therethrough
is distributed
on top of the upper liquid phase.
Figure 13 is a cross-sectional view of a lower portion of a vortex tube,
having a
"tube-on-tube" flow diverter as in Figure 11 with the addition of a horizontal
deflector
ring. Figure 13 sliows a flat diverter ring on the left side of the vortex
tube - that is, a
diverter ring in a horizontal plane, and on the right side of the vortex tube
a curved
deflector ring.
Figure 14 is an isometric view of a cluster of vertically oriented vortex
tubes fed
by an inlet manifold tube and showing the lower end portions of each of the
vortex tubes
making up the cluster as encompassed within a liquid energy absorber. The
liquid energy
absorber is formed of an enclosure that can be rectangular as illustrated and
that is highly
perforated to let fluid freely flow out but in a way to diffuse the fluid flow
and thereby
minimize turbulence.
Figure 15 is an elevational view of a vertically-oriented vortex tube fed by
an
inlet conduit and showing the employment of spaced apart free-fall
preventerswithin the
vortex tube. In Figure 15 two free-fall preventers are illustrated.
Figure 16 is an isometric view of a free-fall preventer of the type positioned
within the vortex tube as illustrated in Figure 15.
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Detailed Description of the Preferred Embodiments
Referring to Figure 1, a system for separating entrained liquid components
from a
gas stream is diagrammatically illustrated. Generally speaking, the system of
this
invention employs one or more vortex tubes and the invention is specifically
concerned
with the construction of vortex tubes. Figure 1 is more or less representative
of the state
of the prior art to which the principles of this invention apply with the
intent of providing
vortex tube systems to attain more effective separation of entrained
immiscible liquid
components from a gas stream. Figure 1 illustrates diagrammatically a vessel
10 which
can be, as an example, a horizontal cylindrical vessel or a vertical
cylindrical vessel or
any other type of vessel that provides a quiescent internal zone 12, a wet gas
inlet 14, a
liquid outlet 16 and a gas outlet 18. In the typical operation of a separator
as shown in.
Figure 1, a liquid level 20 is established within a lower portion of the
vessel, the liquid
being drawn off at a rate to approximately maintain the liquid level 20 while
gas is
removed from an upper portion of the vessel through an upper gas outlet 18. In
the
typical operation of the system of Figure I, a liquid level control means (not
shown) is
used to control the rate of liquid discharge so as to maintain a liquid level
20.
Figure 2 is a horizontal cross-sectional view of Figure 1 showing a fluid
injection
conduit 22 that receives the wet gas from wet gas inlet 14 of the vessel of
Figure 1, and
showing a plurality of vertically positioned vortex tubes 24. Each vortex tube
has a wet
gas inlet 26 in the vertical sidewall thereof. Wet gas under pressure flows
through an
opening 26 in each of the vortex tubes and enters the vortex tube tangentially
- that is, at
a tangent to the interior sidewall 28 of each of the vortex tubes. Figure 3 is
a
cross-sectional view of a single vortex tube 24 that is representative of the
other vortex
tubes shown in the cluster. The upper end of each vortex tube is closed with
atop plate
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30 having a concentric gas outlet opening 32 therein. As seen in Figure 3, the
bottom end
34 of each vortex tube 24 is open to admit the free-flow of liquid out of the
lower bottom
end. A horizontally positioned bottom diverter plate is supported to the
vortex tube
sidewall 24 and spaced from the bottom 34 of the vortex tube to allow a
circumferential
liquid outlet passageway 3 8. Bottom diverter plate is typically supported to
vortex tube
24 by spaced apart stand-offs that are not shown but can be in the form of
short-length
metal rods welded to the interior or exterior surface of the cylindrical wall
of the vortex
tube.
A vortex tube functions to separate an immiscible liquid component from a wet
gas stream by utilizing artificially created gravity - that is, centrifugal
force. Inlet fluids
enter the fluids injection tube 22 and flows through opening, 26 into the
interior of the
vortex tube tangentially so that the fluids swirl at a rapid rate within the
vortex tube as
illustrated by the dotted lines in Figure 3. The swirling gas causes entrained
liquids to be
expelled and to encounter the vortex tube internal cylindrical wall 28 where
the liquids
accumulate and fall downwardly by gravity to ultimately flow out of the vortex
tube
through the liquid outlet passageway 38. The swirling gas component ofthe
fluid stream
having substantially less density than the entrained liquid component migrates
to the
axial center of each vortex tube 24 and flows out through the upper concentric
gas outlet
26. The swirling gas is in the form of a gas vortex that takes the geometrical
pattern as
shown by the vortex boundary 48.
Thus Figures 1, 2 and 3 are representative of the state of the art to which
this
disclosure applies to provide the improvements to obtain more effective
separation of an
entrained immiscible liquid component from a wet gas stream. Systems can
operate with
one vortex tube which is typically oriented vertically but that can operate as
long as it has
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a vertical downward tangent however, a vertical operation is preferred. A
vessel can
include a single vortex tube or a cluster of vortex tubes as shown in Figure 1
or a
plurality of clusters of vortex tubes depending on the volume of wet gas being
treated and
the arrangement of the vessel 10. The length of vortex tubes can vary in
length; where
long length vortex tubes are employed a vertically oriented vessel may be
preferred but
where shorter length vortex tubes are employed typically a horizontal vessel
offers the
most economic housing for the separation system.
The improvements of the invention are illustrated in Figures 5 through 16 as
will
now be described.
Figure 5 illustrates an improvement of the basic concept of a vortex tube
separator
in the form of a tubular vortex fmder 42 having an upper end connected with
top plate 30
and an internal tubular wall 44 that communicates with concentric gas outlet
32. Vortex
finder 42 minimizes fluid shear by shielding the axially flowing gas stream
that leaves
the top of the vortex tube from the feed stream as it enters the vortex tube
through
tangential inlet opening 26. Stated another way, vortex finder 42 shields the
vortex tube
outlet stream from disturbance by the inlet stream. The lower end 46 of vortex
finder 42
should preferably extend below the lowest point of the vortex tube entry -
that is, below
the lowest point of tangential inlet opening 26.
Figure 6 is an isometric view of a portion of a vortex tube 24 that includes
the
improvements of Figure 5 - that is, a short length tubular vortex finder 42
but in addition
includes a sloped deflector 48. Deflector 48 fits in the annular area 50
exterior of vortex
finder 42 and within vortex tube internal cylindrical sidewall 28 and is
spirally sloped
downwardly so that the incoming gas stream that enters the vortex tube through
opening
26 (seen in Figure 5 but not seen in Figure 6) is spirally deflected
downwardly by the
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sloped deflector 48. The sloped deflector diverts the incbming wet gas stream
downward
at the necessary angle. A benefit of using the sloped deflector 48 is that it
minimizes
liquid droplet break-up caused by shearing as the rotating stream intersects
the incomng
stream. As a result of a smaller amount of liquid mist is carried out of the
tube with the
gas stream that passes upwardly through vortex finder 42.
Occasionally the gas flow velocity inside a voittex tiibe may exceed the ideal
design limits either continuously, or intermittently due to slugging. Excess
flow velocity
of gas re-entrains liquid mist and causes the gas stream to spit course mist
droplets out of
the gas orifice, that is out of the orifice 32 as in Figure 4 or out of the
vortex finder 42 in
the embodiment 'of Figure 5 and 6. Uncontained, these droplets can result in
separator
liqu'id carry-over - that is, the liquid that is contained in the rapidly
discharged'gas is
carried upwardly into the -vessel into the compartment where gas is intended
to
accumulate instead of downwardly into the area where the liquid should
accumulate. To
overcome this problem, a method of diverting the gas outlet from the vortex
tube
downwardly so that any entrained liquid is directed towardthe standing liquid
phase is
illustrated in Figures 7, 8 and 9. Figure 7 shows the vortex tube 24 withtop
plate 30, the
vortex tube'extending fromand receiving the inlet of gas from wet gas injector
conduit
22. Affixed to top plate 30 is a gas flow diverter 52 that is a bent tubular
member having
an inlet end 54 connected to the concentric dry gas outlet in a top plate 30,
the two being
curved so that its outlet end 56 is directed in a downward tangent that is,
gas flow
through gas flow diverter 52 makes a transition of more than 90 . By the
downward
diversion of the gas passing out of the vortex tube, any entrained droplets
are directed
downwardly toward the liquid that collects in the bottom of the vessel, such
as the liquid
shown in the bottom of vessel 10 that has a liquid level 20.
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Figure 8 is an elevational view of the top portion only of the vortex tube 24
showing the tubular dry gas flow diverter in which the outlet end 46 has a
more
downward inclination. It can be seen that, if desired, the tubular gas flow
diverter 52
could include a bend of 180 so that the gas is directed vertically downwardly
if desired
however, any downward direction imparted to droplets that pass out with the
gas is very
beneficial in preventing re-entrainment of the liquid with the exiting gas
stream.
Figure 9 shows a special application of the gas diverter of Figures 7 and 8
where
the outlet end 56 of the tubular gas diverter is closely spaced to the
internal wall surface
58 of a vessel 10 in an arrangement that does not permit sufficient space to
provide a
fully arcuate downwardly directed bent tubular gas flow diverter 52 as shown
in Figure 8.
In this predicament, downward diversion of any fluid droplets carried by the
gas stream
exiting vortex tube 24 can be deflected by use of an angular diversion shield
60 welded
or otherwise attached to tubular gas diverter 52.
In the operation of a vortex tube it is important to control the flow of
liquid being
discharged from the lower end of the tube and to prevent the gas vortex formed
inside the
tube from extending beyond the lower end of the tube and thereby into the
liquid
chamber in the bottom of the separator vessel. For this purpose, a bottom
diverter plate
has been used such as shown in Figure 10 and that has previously been
described with
reference to Figure 1, the bottom diverter plate 36 having been described with
reference
to Figures 1 and 3.
An improved method of controlling the fluid flow out the bottom end 34 of a
vortex tube 24 is shown in Figures 11, 12 and 13. Each of these figures show
the lower
end portion of the vortex tube 24 positioned within a vessel having a vessel
wall 10 with
the vortex tube lower end 46 being below the level of liquid 20. In Figures 10
through
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13, liquid level 20 is shown wherein the separated liquid is oftwo-phase. For
instance, in
separating liquid from a gas stream in the petroleum industry it is common
that the
separated liquid be co-mingled water and oil and preferably these liquids are
separately
removed from the interior of the separator vessel -- that is, a separator can
be operated
where all the separated liquids are discharged in a common stream but in many
applications it is desirable that if the liquid is of two-phases, the two
phases be separately
discharged. As shown in Figures 10 through 13, the liquid is in two-phase
providing a
water phase 20 having a liquid leve120A and on top of the water level an oil
phase that
has the top liquid level 20. In any event, in Figures 10 through 11, the lower
end 38
extends into the bottom liquid phase - that is, below the intermediate liquid
level 20A. If
there is any possibility that a high liquid flow rate from vortex tube 24 can
cause
entrained gas to flow out the lower end 46, of vortex tube 24, if allowed to
radiate
outwardly, can propel gas-laden liquid toward the liquid outlet, resulting in
a carryunder
of gas from the separator vessel. To prevent this, a tube-on-tube arrangement
is
exceedingly useful, such as shown in Figures 11 through 13. This system
requires a short
length exterior tubular member 62 that has an internal wa1164 of a diameter
greater than
the external diameter of vortex tube 24 providing an annular area 66
therebetween. The
lower end of tubular member 62 is closed with a bottom plate 68 so that all
fluids exiting
the lower end of the vortex tube pass upwardly through the annular area 66 and
are
dispersed around the exterior of vortex tube 24. In Figure 11, the top end 70
of tubular
members 62 is below the intermediate liquid leve120A. In the embodiment in
Figure 12,
the top end 70 is above liquid leve120 so that fluid flows out on top of the
level of liquid
and is spread over the liquid contained in the bottom of the vessel. It can be
seen that the
length of tubular member 62 could be varied according to design requirements
and, as an
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example, could be of an intermediate length between that
shown in Figures 11 and 12 so that the top end 70 is above
the intermediate liquid level 20A but below the top liquid
level 20.
Figure 13 shows an alternate arrangement wherein
there is provided, in addition to the tube-on-tube method a
horizontal distributor plate 72 that is positioned above the
top end 70 of tubular member 62. This planar horizontal
distributor plate 72 extends radially around vortex tube 24
for a full 360 in the practice of the invention. Instead
of the circumferential distributor plate being horizontal as
shown in element 62, the circumferential distributor plate
can be arcuate as shown in the right side of vortex tube of
Figure 13, the arcuate circumferential distributor plate
being indicated by the numeral 74. Whether a horizontal
circumferential distributor plate or an arcuate
circumferential distributor plate 74, any disturbance of the
oil/water interface caused by liquid exiting the lower end
of the vortex tube 24 is more localized around the tube. If
the liquid release of the tube-on-tube system is near the
liquid interface surface, the deflector ring either 70 or 72
deflects the upper momentum of the flowing liquid into a
horizontal direction. This reduces the surface disturbance
either the surface 20A or the top liquid surface 20 to
thereby reduce phase re-entrainment. The benefit of the
system of Figure 13 is a reduction in cross-contamination
between liquid phases leaving the separator.
Figure 14 shows a cluster of vortex tubes as seen
in Figure 1 with the installation of a liquid energy
absorber 76 which also may be referred to as a liquid energy
diffuser. The energy absorber or diffuser is generally
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indicated by the numeral 76 and is in the form of a
container having a top 78 and four sidewalls 80, only two of
which are seen in Figure 14 and a bottom 82. The sidewalls
are perforated at 84. If desired the top 78 and/or bottom
82 could, in like manner, be perforated. Liquid energy
absorber 76 reduces
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turbulent spots in the liquid collected in the bottom of the separator by
diffusing the exits
from the vortex tube and reduces channeling of fluid flow by improved fluid
distribution.
While in Figure 14, the liquid energy absorber is shown as a box enclosure
that is, in a
horizontal plane rectangular, the enclosure could be circular, spherical or
any other shape
the only requirement being that the liquid energy absorber provide a closed
area
encompassing the lower ends of each vortex tube making up a cluster of vortex
tubes to
diffuse and break up fluid channel flow paths that might otherwise be created
within the
fluid collected in the bottom of a separator vessel.
Figure 15 shows an alternate embodiment of a vortex tube separator system in
which there is positioned within the vortex tube one or more free-fall
preventers, the
free-fall preventers being generally indicated by the numeral 86. Figure 16 is
an
isometric view of a free-fall preventer that is preferably formed of a short
length center
tube 88 with an open tubular passageway 90 therethrough. Radially extending
around the
external circumference of center tube 88 are a plurality of vanes 92. These
vanes extend
out to contact the internal cylindrical wall of vortex tube 24.
In vertical separators or in large diameter horizontal separators, the
vertical height
of vortex tube 24 can be significant. When this occurs, liquid separated
within the tubes
must fall a long distance down the tube wall. As the liquid plunges, gravity
accelerates
this velocity such that when it finally impinges on the standing liquid that
would be
approximately at the height of liquid level 20, its high momentum tends to re-
entrain gas
into the liquid phase. Concurrently, in such tall vortex tubes wall friction
slows down the
rotational liquid velocity causing a loss of centrifugal separation as the
liquid progresses
down the tube. Thus, at the bottom of the tube the liquid velocity direction
is nearly
vertically downward. To alleviate this problem the free-fall preventers 86 can
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employed. The benefit of the use of free-fall preventers 86 is that gas re-
entrainment and
foaming are greatly minimized or eliminated and a higher average centrifugal
force is
maintained in the liquids swirling within the vortex tube. Note that swirling
gas that has
not yet migrated to the center of the tube passes downwardly through the vanes
and as it
passes downwardly, additional swirling action is imparted. Gas that migrates
toward the
center of the vortex passes freely upwardly through the open passageway 90 in
center
tube 88 of each of the free-fall preventers and thus the gas can flow
outwardly through
the concentric gas outlet opening 32 and the top of each of the vortex tubes.
Figure 15 shows use of two spaced apart free-fall preventers but only one may
have been employed or more than two may be employed according to the length of
the
vortex tube 24.
The improved separator system of this invention can be practiced employing
various combinations of the improved vortex tube features as has been
described herein
according to design perameters dictated by the particular entrained liquid
verses volume
of gas in the wet gas stream, by the nature of the entrainment - that is,
whether in
relatively small or relatively large droplets, the nature of the liquid
whether heavy such as
water or relatively light such hydrocarbon condensate, and many other
parameters.
The claims and the specification describe the invention presented and the
terms
that are employed in the claims draw their meaning from the use of such terms
in the
specification. The same terms employed in the prior art may be broader in
meaning than
specifically employed herein. Whenever there is a question between the broader
definition of such terms used in the prior art and the more specific use of
the terms
herein, the more specific meaning is meant.
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While the invention has been described with a certain degree ofparticularity,
it is
manifest that many changes may be made in the details of construction and the
arrangement of components without departing from the spirit and scope of this
disclosure. It is understood that the invention is not limited to the
embodiments set forth
herein for purposes of exemplification, but is to be limited only by the scope
of the
attached claim or claims, including the full range of equivalency to which
each element
thereof is entitled.
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