HYBRID DOUBLE HYDROCYCLONE-GRAVITY GAS/LIQUID SEPARATOR

DISPOSITIF HYBRIDE DOUBLE A HYDROCYCLONE ET DEBIT EN CHUTE POUR LA SEPARATION DE GAZ ET LIQUIDE

English Abstract

ABSTRACT OF THE DISCLOSURE
An apparatus and method is disclosed for
separating multiphasic mixtures of such things as gas and
oil, from liquids, such as petroleum production fluids.
It includes a centrifugal gas/liquid separator having a
generally conical inner surface, a gas/liquid inlet
located on this inner surface, an area for retaining the
liquid and for allowing further gravity separation of the
gas/liquid phase, an enclosure for the above mentioned
elements, a gas outlet, and a liquid outlet.
The device functions by initially separating the
gas from the oil by centrifugation in the conical separa-
tor, then by allowing the remaining liquid to further
separate by gravity in the retention area.

Claims

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THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An apparatus for separation of a gas from a
liquid in a multiphasic mixture, comprising:
an enclosing chamber;
an outlet for allowing gas to leave the enclosing
chamber;
an outlet for allowing liquid to leave the enclosing
chamber;
means to control the liquid outflow;
a generally smaller chamber within the enclosing
chamber, constructed so that a space may be formed between
both chambers, the smaller chamber having an inner surface
the shape of two cones which are joined at their bases;
an inflow line for pressurized well production fluid,
the inflow line having an outlet located on the involute
inner surface of the smaller chamber where the bases of
the cones are joined;
a blade means for splitting the flow of production
fluid into a stream for each conical section, the blade
means being located at the inflow outlet;
two liquid outlets for the smaller chamber, the out-
lets being located at the point of each cone and directed
downwards to the bottom of the enclosing chamber; and
a gas outlet for the smaller chamber;
so that pressurized well production may enter the smaller
chamber through the inflow line and spin on the inner
surface of the smaller chamber to initially separate a gas
fraction from a substantially liquid fraction, whereby the
residual, substantially liquid phase may have the majority
of the remaining gas separated by gravity while in the
space between the smaller chamber and the enclosing cham-
ber.
2. The apparatus for separating a gas from a liquid
in a multiphasic mixture as recited in Claim 1, further
including a primary demister means located downstream from
the gas outlet for the smaller chamber.

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3. The apparatus for separating a gas from a liquid
in a multiphasic mixture as recited in Claim 2, further
including a secondary demister means located upstream from
the gas outlet for the enclosing chamber.
4. The apparatus for separating a gas from a liquid
in a multiphasic mixture as recited in Claim 3, further
including gas turbulence generator means located on the
inner surface of the enclosing chamber and the outer sur-
face of the smaller chamber to help coalesce the airborne
liquid droplets.
5. The apparatus for separating a gas from a liquid
in a multiphasic mixture as recited in Claim 2, further
including a liquid retention area located at the outflow
of the smaller chamber, the retention area being defined
by baffles.
6. The apparatus for separating a gas from a liquid
in a multiphasic mixture as recited in Claim 3 further
including a particulate trap and a means for removing
accumulated particulates located within the liquid reten-
tion area.
7. The apparatus for separating a gas from a liquid
in a multiphasic mixture as recited in Claim 4, where the
means for removing accumulated particulates is an auto-
matic driving valve.
8. An apparatus for separation of a gas from a
liquid in a multiphasic mixture, comprising:
an enclosing chamber;
an outlet for allowing gas to leave the enclosing
chamber;
an outlet for allowing liquid to leave the enclosing
chamber;
means to control the liquid outflow;

9 61936-1707
a generally smaller chamber within the enclosing chamber,
constructed so that a space may be formed between both
chambers, the smaller chamber having an inner surface the shape
of two cones which are joined at their bases;
an inflow line for pressurized well production fluid, the
inflow line having an outlet located on the! involute inner
surface of the smaller chamber where the bases of the cones are
joined;
a blade means for splitting the flow of production fluid
into a stream for each conical section, the blade means being
located at the inflow outlet;
two liquid outlets for the smaller chamber, the outlets
being located at the point of each cone and directed downwards
to the bottom of the enclosing chamber;
a gas outlet for the smaller chamber; and
a liquid retention area located at the outflow of the
smaller chamber, the retention area being defined by baffles.
9. A method of separating a gas from a liquid in a
biphasic mixture comprising:
flowing a pressurized stream of biphasic mixture into a
primary separator;
spinning the biphasic mixture on the generally conical
inner surface of a primary separator to partially separate gas
from liquid by centrifugal force;
retaining the residual liquid in an enclosed space for a
period of time to separate more gas from the liquid by
gravitational force;
removing the gas fraction from the enclosed space;
removing the liquid fraction from the enclosed space.
10. The method for separating a biphasic mixture as
recited in Claim 9 where the primary separator has an inner
surface in the shape of two cones, joined at the base, and the
biphasic mixture is caused to flow in both conical sections of
the separator by a blade that splits the initial stream into
two smaller streams.

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11. The method for separating a biphasic mixture as
recited in Claim 10 further including reducing the
turbulence at the point where the residual liquid flows
out of the primary separator and into the enclosed space.
12. The method for separating a biphasic mixture as
recited in Claim 11 further including trapping and remov-
ing particulates that are present in the biphasic mixture.
13. The method for separating a biphasic mixture as
recited in Claim 9 further including removing aerosolized
liquid.
14. The method for separating a biphasic mixture as
recited in Claim 13 further including retaining the
separated gas in the enclosed space and removing the aero-
solized liquid with a primary demister means, located at
the point where the gas leaves the primary separator and
enters the enclosed space, and a secondary demister means,
located at the point the gas leaves the enclosed space to
be withdrawn.
15. A method for the separation of a gas from a
liquid in a gas/liquid mixture of well production fluid,
comprising;
flowing a pressurized stream of well production fluid
that contains both gas and oil through an inflow line and
then onto the inner, involute surface of a first chamber
having the shape of dual cones joined at the bases, the
conically shaped sections of the chamber being located
inside a larger enclosing chamber;
splitting the stream of pressurized fluid, at the
point the fluid meets the inner surface of the dual
conical section into two streams, one for each cone
section;
spinning the pressurized well fluid on the inside
surface of the conical sections;

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separating a portion of the gas that is contained in
the well production fluid from the liquid by the centri-
fugal force that is generated as the well production fluid
spins on the inner surfaces of the conically shaped
sections;
flowing the residual liquid portion of the well pro-
duction fluid out of a liquid outflow located at the top
of each conical section of the first chamber into an
enclosed space described by the larger enclosing chamber;
reducing the liquid turbulence at the liquid outflow
for each conical section;
trapping and removing particulates associated with
the liquid portion of the well production fluid;
retaining the residual liquid portion in the enclosed
space long enough so that more gas may separate from the
liquid portion;
flowing the separated gas fraction out of the first
chamber into the enclosed space described by the larger
enclosing chamber;
condensing aerosolized liquid from the gas with a
primary demister as it passes from the first chamber to
the enclosed space;
generating gas turbulence within the enclosed space
to assist in coalescing aerosolized liquid droplets;
further condensing aerosolized liquid droplets with a
secondary demister just before removing the gas from the
enclosed space;
removing the accumulated gas from the enclosed space;
and
removing the accumulated liquid from the enclosed
space when triggered by a liquid control device;
so that pressurized well production fluid, containing gas
and liquid, may be separated into liquid and gas fractions
by utilizing the pressure in the fluid itself to initially
spin most of the gas out of the liquid and then to allow
gravity to substantially complete the separation by allow-
ing the centrifuged liquid to remain in the device for a
sufficient period of time.

Description

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01 --1--
HYBRID DOUBLE HYDROCYCLONE-GRAVITY
GAS/LIQUID SEPARATOR
FIELD OF THE INVENTION
This invention relates to a separatory appara-
tus. More speciEically, to an apparatus designed to
separate a liquid and a gas.
BACKGROUND OF THE INVENTION
In .__
Devices that separate gases, liquids, and solids
work on a variety of principles, two of which are gravity
and centrifugal force. Conventional gravity type separa-
tors have been widely used to separate a gas from a liquid
- (or vice versa) on land-based crude oil and gas process
-15 plants. These separators are generally quite large and
heavy because the separation takes place over à~longer
period of time and to do so efficiently you need a larger
volume of space. Examples of this type of separator
are: Kotzebue, U.S. Patent No. 1,782,783; Pittman, U.S.
;~0
Patent No. 1,994,110; Orrell, U.S. Patent No. 2,767,802;
and Ray, U.S. Patent No. 2,887,174.
Other separators work by centrifugal force.
Generally they accelerate the division of gas and liquid
by increasing the separatory centrifugal forces.- ~hen a
liquid/gas mixture is spun, the heavier object, i.e., the
oil, makes its way through the mixture to the outermost
- point and the lighter gas migrates inward. Examples of
liquid/gas centrifugal force separators are: Moore, U.S.
Patent No. 3,713,279; Kartinen, U.S. Patent No. 3,810,347;
Reed et al., U.S. Patent No. 4,035,171; Beattie, U.S.
Patent No. 4,070,168 and Hodgson, U.S. Patent No.
4,187,089. Examples of sand centriEugal separators are:
Stavenger, U.S. Patent No. 3,259,246; Hill, U.S. Patent
Nos. 2,539,019, 2,566,662 and 1,919,653; Hruby, Jr., U.S.
Patent No. 3,067,876; and Hume, U.S. Patent No. 3,045,828.
Conventional gravity type separators have been
widely used to separate gas from liquid (or vice versa) on
land-based crude oil and gas process plants. The same
equipment has also been employed on offshore production
:, ~
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12~62~
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platfor~s in spite of significant associated installationcosts due to its large space and weight requirements. It
05 requires a large pressure vessel to provide a long enough
retention time in order to separate and settle, by
gravity, small liquid part.icles in the gas/liquid mixture.
Similarly, the centrifugal force oil/gas separators have
not been perfected for offshore use either.
Furthermore, the floating production platform,
such as a tension leg platform, floating barge, or a semi-
submersible, will experience significant motions due to
constant wave, current, and wind forces. The separation
performance of a gravity separator will be hampered sig-
nificantly due to the turbulence generated by sloshing
wave motions of the liquid caused by the vessel motions.
To correct this problem even larger and heavier pressure
vessels will be required to cope with this problem and
consequently further costs will be increased further for
the equipment and the structure supporting it.
One solution to the problem is to incorporate a
set of double hydrocyclones inside a conventional horizon-
tal (or vertical) gravity separator. This design takes
advantage of both the centrifugal force of the hydro-
cyclone and gravity as in a conventional separator. Mostof the basic separation will be done by the hydrocyclone
so that the size of the pressure vessel will be greatly
reduced. The result is a compact, lightweight separator
at a significantly reduced equipment weight. Because the
installation space requirement and the total associated
costs are low, this system is suitable for offshore
production platforms, in particular, for a floating
production platform application.
As a result, it is the principal object oE this
invention to create a device for gas/liquid separation.
It is a further object of this invention to create a
device that is lighter, smallerr and cheaper than current
gas/liquid separators.

i~8623Z
Ol ~3~
SUMMARY OF THE INVENTION
- The present invention involves an apparatus and
05 method for the separation of a gas and a liquid from a
well production fluid.
Components of the apparatus include an enclosing
chamber, one outlet to allow gas and one to allow liquid
to leave the enclosing chamber, and a device to control
the liquid outflow. Within the enclosing chamber is a
smaller chamber having an inner surface in the shape of
two cones joined at the base and is constructed so that a
retention space may be formed between-both chambers.
There is an inflow line for a stream of pressurized well
production fluid with an outlet located on the involute
inner surface of the smaller chamber. At this point a
blade splits the fluid flow into a stream for each conical
section. Lastly, there are two liquids outlets (at the
points of the cones) and a gas outlet for the smaller
2U chamber.
The apparatus separates the liquid/gas mixture
into its component parts by directing flowing well fluid
into the double hydrocyclone where it is split into two
streams, one stream per hydrocyclone. The fluid is spun
by its own velocity on the inner, conical surface of the
hydrocyclone where a primary centrifugal separation takes
place. Thereafter, the remaining liquid is directed to an
area where it is retained for further separation by
gravity. The gas that has been separated through the
initial process travels through a primary demister, then
out into the enclosed space oE the total chamber where it
mixes with gas that has evaporated from the liquid held in
the retention area. From here the gas goes through a
secondary demister and it leaves the system. The liquid
leaves through an outlet valve which is controlled by an
automatic float control or liquid level control.
BRIEF DESCRIPTION OF THE DRAWING
FIG. l represents a cutaway view of the double
` hydrocyclone/gravity separator.
''
.

232
4 61936-1707
DETAILED DESCRIPTION OF THE_EMBODIMENT
The present separator combines the cyclone concept
~i.e., the use of centrifugal force to separate elements of
different weights that occur in a mixture) with the advantages
of the conventional gravity separator. In referring to the
drawings, FIG. 1 discloses the double hydrocyclone/gravity
separator 1 encapsulated by a containment vessel 30. The
separator 1 has a dual hydrocyclone 12 (shaped like two cones
joined at their bases, having a common base and lying along a
common axis, the axis of the cones ~eing parallel to the axis
of the containment vessel~ to which is attached a well stream
inflow 2 at an involute double hydrocyclone inlet 6 located at
approximately the center of the axis of the containment vessel
30 ~the inlet may be tangential or involute). At the inlet 6 a
flow splitter 4 is positioned to separate the gas/liquid
mixture of well fluid into a stream for each cone section 13 of
the dual hydrocyclone 12. A set of baffles 18 and a sand trap
with an automatic dump valve 16 are also included in the bottom
of the separator 1. A cylindrical vortex finder 8 within the
dual hydrocyclone 12 leads to a set of primary demisters 10
that treat the initially vaporized gas fraction of the
gas/liquid mixture and remove aerosolized oil droplets.
Turbulence generators 14 on the outer surfaces of the dual
hydrocyclone 12 and the inner surface of the containment vessel
30 for the separator 1 help to coalesce liguid droplets from
the gas flow. A pair of secondary demisters 20 appear upstream
of a gas outlet pipe 22. A liquid outlet pipe 24 is provided
for the accumulated, retained liguids and liquid control valve
32 is opened by liquid control 26 once the surface of the
liquid 28 gets to a predetermined level ~or any other level
control device such as electronic control). A second liquid
outlet may be provided if stagnation occurs.
The dual hydrocyclone/gravity device 1 wor~s as
follows. In the separator 1 a set of lightweight, dual
hydrocyclones 12 is installed at the center of the separator 1
to perform a primary separation function as a pressurized,
flowing gas/liquid mixture of well fluid enters through a well
stream inflow i'. The primary separation is effected by the
centrifugal force generated
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Z32
01 --5--
`
in a cone section 13 of the cyclone 12. The well fluid
enters the cyclone involutely and is split by a flow
05 splitter 33 (acting as a blade) into a stream for each
cone section 13 of the cyclone 12. The gas/liquid mixture
is spun by its own velocity on the inner surface of the
cone section 13 of the hydrocyclone 12 and an initial
separation takes place (the heavier liquid is spun on the
inner surface of the cones while the lighter gas migrates
inward). Any gas that is initially separated goes through
the vortex finder 8, through a pair of primary demisters
10, and then into the open area of the separator 1. The
liquid portion of the gas/liquid mixture is spun out
lS through an aperture 17 in each cone section 13 of double
hydrocyclone 12. The liquid is deposited in a compartment
19 which may be equipped with submerged baffles 18 so that
the inflow of fluid will not create an excessive amount of
turbulence for the entire liquid system. (The liquid is
- ~0 allowed to migrate throughout the bottom of the separator
~ 1 and is retained to further separate the liquid and gas
- by gravity force.) If too much turbulence is created in
the retained liquid the separation due to gravity would be
hampered. These baffles 18 may be horizontal or vertical
and are also incorporated to attenuate liquid sloshing
motions when the separator 1 is installed on an offshore
floatin~ platform. The chamber 19 also may incorporate a
sand trap 16 and an automatic dump valve (not shown) which
are provided to remove accumulated sandsjsilts under the
underflow of the cyclone aperture 17.
The liquid surface 28 may extend into other
areas of the separator 1 and undergo further separation of
the gas/liquid mixture due to gravity and evaporation.
Any gas that evaporates during this time (and its accom-
panying aerosolized liquid) may encounter turbulencegenerating strips 14 to help coalesce the liquid droplets
from the gas flow. In the separator 1 a larger gas/liquid
interEace area is incorporated in order to provide a
.

01 -6-
larger evaporation surface compared to an ordinary hydro-
cyclone separator.
05 Once evaporation has taken place, the gas may be
effec-tively separated from the liquid by passing it
through a secondary pair of demisters 20 and then through
a gas outlet 22. These secondary demisters 20, like the
primary demisters 10, further remove airborne liquid
droplets by taking advantage of the well kno~n separation
methods of impingement, change of flow direction, and flow
velocity. These airborne liquid droplets are removed and
then returned to the larger liquid body by gravity flow to
the base of the containment vessel.
The removal of the separated liquid may be
accomplished by an automatic control 26 (either a float or
an electronic probe). Once the liquid level reaches a
predetermined level, the liquid control opens the liquid
outlet valve 32 and the separated liquid can be withdrawn
~0 from the separator 1 through the liquid outlet 24.
Additional functions of the separator 1 could be
provided by adding further weirs for water-oil separation
to provide a three-phase separator (i.e., gas/water/oil).
Furthermore, lightweight construction material for inter-
nals may be used since they are not subjected to any sig-
nificant loading.
Since many modifications and variations of the
present invention are possible within the spirit of this
disclosure, it is intended that the embodiment disclosed
is only illustrative and not restrictive. For that
reason, reference is made to the following claims rather
than to the specific description to indicate the scope of
this invention.

Representative Drawing