WO2011005077A1

WO2011005077A1 - Flareless condensate stabilization in combination with gas conditioning

Info

Publication number: WO2011005077A1
Application number: PCT/NL2009/050419
Authority: WO
Inventors: Dirk Gijs De Kuyper; Cornelis Antonie Tjeenk Willink; Marco Betting; Jacob Arie Cornelis Langerak
Original assignee: Twister B.V.
Priority date: 2009-07-10
Filing date: 2009-07-10
Publication date: 2011-01-13
Also published as: EA201270157A1; IN2012DN00229A; EA025118B1

Abstract

The invention relates to a processing scheme for gas conditioning, comprising an expansion-coolingbased separation stage (200) and a stabilisation stage (300). The expansion-coolingbased separation stage (200) comprises an expander (EXP), a separator (SEP) and a compressor (COM), and is arranged to receive an input stream (I2). The stabilisation stage (300) comprises a fractionation column (FC), and is arranged to receive an intermediate input stream (I3) from the expansion-coolingbased separation stage (200). The processing scheme further comprises a jet pump (JP), arranged to receive at least part of a fractionation top stream (FT) and a portion of the input stream (I2') taken upstream of the expander (EXP), to combine these into a feedback stream (FS) which is re-introduced in the expansion-coolingbased separation stage (200) at a feedback position.

Description

Flareless condensate stabilization in combination with gas conditioning

TECHNICAL FIELD

The invention relates to a method and processing scheme for gas conditioning.

STATE OF THE ART

Dew pointing and condensate stabilization are common practice in the oil and gas industry. Water and hydrocarbons are extracted from the gas in order to meet pipeline specification, specifications related to a national distribution system, or to create an additional revenue stream. These drivers together with the available technology have led to an enormous variety in gas conditioning process schemes and condensate stabilization process schemes for the gas processing companies. Hydrocarbon dewpointing schemes can be based on the following technologies:

- adsorption and/or

- refrigerant cooling, and/or

- expansion cooling.

Adsorption is mostly applied for simultaneous removal of water and

hydrocarbons for lean high pressure gas streams

Refrigerant cooling is mostly applied at lower pressures. A coolant is used to cool the gas and thus condensing the hydrocarbons.

Most commonly used expansion cooling is applying a Joule-Thomson (JT) control valve. JT cooling is a less efficient isenthalpic cooling thereby destroying the available pressure, hence no recompression takes place.

For a more efficient cooling isentropic expansion may be used, such as in a turbo expander or a cyclonic separator, such as described in WO03/029739A2. Both include a gas expansion and recompression phase.

The resulting produced condensate from all mentioned technologies above can subsequently be stabilized or exported as live condensate. For stabilization of the condensate the light hydrocarbons which are dissolved in the condensate need to be removed. This can either be achieved by reducing the pressure to atmosphere and thereby flashing off the liquids in several stages, or by stripping the gas from the liquids making use of a stabilization column. A stabilization column works at somewhat higher pressures than in a flash vessel but requires heat input to remove the light hydrocarbons from the liquid.

The removed light hydrocarbons can either be flared or re-combined with the main gas process stream. Flaring will result in loss of valuable product and the emission OfCO₂. Most countries have a non- flaring policy in place.

To recombine the light hydrocarbons with the main process stream the off-gas needs to be recompressed by an off-gas compression unit as the flash vessels or stabilization columns normally operate at relatively low pressures . SHORT DESCRIPTION

It is an object to provide a process scheme that does not involve flaring nor additional recompression units or the like. This object is achieved by a processing scheme for gas conditioning, comprising an expansion-cooling based separation stage and a stabilisation stage,

the expansion-cooling based separation stage comprises an expander and a separator, and is arranged to receive an input stream,

the stabilisation stage comprises a fractionation column, and being arranged to receive an intermediate input stream from the expansion-cooling based separation stage,

wherein the processing scheme further comprises a jet pump, arranged to receive at least part of a fractionation top stream and a portion of the input stream taken upstream of the expander, to combine these into a feedback stream which is reintroduced in the expansion-cooling based separation stage at a feedback position.

According to a further aspect there is provided a method for gas conditioning, the method comprising:

- feeding an input stream to an expansion-cooling based separation stage, the expansion-cooling based separation stage forming an intermediate input stream,

- feeding the intermediate input stream to an stabilisation stage, the stabilisation stage comprising a fractionation column,

- the fractionation column creating a fractionation top stream and a fractionation bottom stream,

- feeding at least part of the fractionation top stream and a portion of the input stream taken upstream of the expander to a jet pump, to combine these into a feedback stream, - re-introducing the feedback stream in the expansion-cooling based separation stage at a feedback position.

Further embodiments are described in the dependent claims. SHORT DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figure 1 schematically depicts a processing scheme according an embodiment, , - Figures 2a - 2d schematically depict expansion-cooling based devices,

Figures 3 - 6 schematically depict processing schemes according to embodiments.

DETAILED DESCRIPTION

The embodiments presented comprise an expansion-cooling based separation stage 200. This expansion-cooling based separation stage 200 may be preceded by a pre-separation stage 100 and may have a stabilisation stage 300 downstream thereof. Fig. 1 shows a schematic drawing of such a separation system, which will be described in more detail below.

The working principle of such an expansion-cooling based separation stage 200 is based on rapid expansion of a fluid, accompanied with a reduction of pressure, thereby cooling the fluid and causing initially gaseous components to condense, creating liquid droplets. The liquid droplets can be separated from the rest of the fluid. After expansion, the fluid may be re-compressed.

Such an expansion-cooling based separation stage 200 may comprise an expander EXP, a separator SEP and possibly a compressor COM. In general, the expansion- cooling based separation stage 200 is arranged to:

- receive an input stream of a gaseous fluid,

- expand and thereby adiabatically cool the input stream in the expander, such that at least some initially gaseous components become supersaturated and condense creating liquid droplets in the gaseous fluid,

- receive at least part of the expanded stream in the separator, the separator comprising at least a separation vessel arranged to produce a top stream and a bottom stream, - recompress at least part of the received input stream after expansion in the

compressor,

The separation vessel may be a liquid degassing vessel, such as for instance a gravitational drive separation vessel, a separation vessel with a filter or a centrifugal separation vessel or any other suitable type of separation vessel.

The expansion-cooling based separation stage 200 may comprises further separators, such as a separation vessels and the like. The expander EXP, the separator SEP and the compressor COM may be embodied in different ways, a few examples of which will be provided below with reference to

Fig.'s 2a - 2d, respectively showing a cyclonic fluid separator, an alternative cyclonic fluid separator, a turbo-expander compressor, and a pressure reduction valve or Joule-Thompson valve.

Cyclonic fluid separator TW

Extraction of natural gas liquids (NGL) from natural gas is "common practice" in the oil and gas industry. NGL 's are extracted to generate additional value or because of certain specifications that should be met. Fig. 2a schematically depicts a cyclonic fluid separator TW as may be used in an expansion-cooling based separation stage 200.

WO03/029739A2 describes a cyclonic separator comprising a tubular throat portion in which the fluid stream is accelerated to a possibly supersonic speed and rapidly cooled down as a result of adiabatic expansion. The rapid cooling will cause condensation and/or solidification of condensable vapours in the fluid stream into small droplets or particles. If the fluid stream is a natural gas stream emerging from a natural gas production well then the condensable vapours may comprise water, hydrocarbons, carbon dioxide, hydrogen sulphide and mercury. These separators furthermore comprise an assembly of swirl imparting vanes in an inlet portion upstream of the throat portion, which vane or vanes are tilted or form a helix relative to a central axis of the throat portion to create a swirling motion of the fluid stream within the separator. The centrifugal forces exerted by the swirling motion on the fluid mixture will induce the relatively high density condensed and/or solidified components to swirl to the outer periphery of the interior of the throat portion and of a diverging outlet section whereas relatively low density gaseous components are concentrated near the central axis of the separator. The gaseous components are subsequently discharged from the cyclonic separator through a primary central outlet conduit, whereas the condensates enriched fluid stream is discharged from the cyclonic separator through a secondary outlet which is located at the outer circumference of the diverging outlet section. A more detailed description of a cyclonic separator is provided below.

As an example, Fig. 2a depicts a longitudinal sectional view of a fluid separator, which may also be referred to as a cyclonic separator, a cyclonic inertia separator, a cyclonic fluid separator.

Referring to Fig. 2a, there is shown a cyclonic inertia separator which comprises a swirl inlet device comprising a pear-shaped central body 1 on which a series of swirl imparting vanes 2 is mounted and which is arranged coaxial to a central axis I of the cyclonic separator and inside the cyclonic separator such that an annular flow path 3 is created between the central body 1 and separator housing 20.

The width of the annulus 3 is designed such that the cross-sectional area of the annulus gradually decreases downstream of the swirl imparting vanes 2 such that in use the fluid velocity in the annulus gradually increases and reaches a supersonic speed at a location downstream of the swirl imparting vanes 2.

The cyclonic fluid separator further comprises a tubular throat portion 4 from which, in use, the swirling fluid stream is discharged into a diverging fluid separation chamber 5 which is equipped with a central primary outlet conduit 7 for gaseous components and with an outer secondary outlet conduit 6 for condensables enriched fluid components. The central body 1 has a substantially cylindrical elongated tail section 8 on which an assembly of flow straightening blades 19 is mounted. The central body 1 has a largest outer width or diameter 2R_{0 max} which is larger than the smallest inner width or diameter 2R_{n min} of the tubular throat portion 4.

The tubular throat portion 4 comprises the part of the annulus 3 having the smallest cross-sectional area. The maximum diameter of the central body 1 is larger than the minimum diameter of the tubular throat portion 4.

The various components of the cyclonic separator as shown in Fig. 2a are described below.

The swirl imparting vanes 2 which are oriented at an angle (α) relative to the central axis I create a circulation in the fluid stream. The angle α may be between 20° and 60°. The fluid stream is subsequently induced to flow into the annular flow area 3. The cross-sectional surface of this area is defined as:

-Aannulus Tt (.i^outer " ^Miiner )

The latter two being the outer radius and inner radius of the annulus at a selected location. The mean radius of the annulus at that location is defined as:

Rmean ⁼ V[/4( Router + Rinner )]•

At the maximum value of the mean annulus radius R_mean, max the fluid stream is flowing between the assembly of swirl imparting vanes 2 at a velocity (U), which vanes deflect the flow direction of the fluid stream proportional to the deflection angle (α) and so obtaining a tangential velocity component which equals U_φ = U. sin (α) and an axial velocity component U_x =U. cos (α).

In the annular space 3 downstream of the swirl imparting vanes 2 the swirling fluid stream is expanded to high velocities, wherein the mean annulus radius is gradually decreasing from R_mean, max to R_mean, mm- It is considered that during this annular expansion two processes occur:

(1) The heat or enthalpy (h) in the flow decreases with the amount Δh = - 1/2 U², thereby condensing those flow constituents which first reach phase equilibrium. This results in a swirling mist flow containing small liquid or solid particles.

(2) The tangential velocity component U_φ increases inversely with the mean annulus radius substantially in accordance with the equation

Uφ,final Uφ, initial * (

^mean, miiy-

This results in a strong increase of the centrifugal acceleration of the fluid particles (a_c), which will finally be in the order of:

miiy- In the tubular throat portion 4 the fluid stream may be induced to further expand to higher velocity or be kept at a substantially constant speed. In the first case condensation is ongoing and particles will gain mass. In the latter case condensation is about to stop after a defined relaxation time. In both cases the centrifugal action causes the particles to drift to the outer circumference of the flow area adjacent to the inner wall of the separator housing 20, which is called the separation area. The time period for the particles to drift to this outer circumference of the flow area determines the length of the tubular throat portion 4. It is understood that particles may include solid or solidified particles. Downstream of the tubular throat portion 4 the condensables enriched 'wet' fluid components tend to concentrate adjacent to the inner surface of the diverging fluid separation chamber 5 and the 'dry' gaseous fluid components are concentrated at or near the central axis I, whereupon the wet condensables enriched 'wet' fluid

components are discharged into an outer secondary fluid outlet 6 via one slot or a series of slots, (micro) porous portions whereas the 'dry' gaseous components are discharged into the central primary fluid outlet conduit 7.

In the diverging primary fluid outlet conduit 7 the fluid stream is further decelerated so that the remaining kinetic energy is transformed into potential energy.

The diverging primary outlet conduit may be equipped with an assembly of flow straightening means, such as flow straightening vanes 19 to recover the circulation energy.

The term fluid as used here refers to the liquid, the gaseous phase, as well as a combination of liquid and gaseous phases. Fluids as defined here could also be laden with solid particles.

The swirl imparting vanes 2 may be replaced with other suitable swirl imparting devices. For instance, the swirl imparting vanes 2 may be formed by providing a tangential inflow of the fluid.

The flow straightening vanes 19 may be replaced with other suitable flow straightening devices.

As will be understood, the cyclonic fluid separator is substantially rotational symmetrical with respect to the central axis I.

It is emphasized that the above described cyclonic separator is just an example and the embodiments described below may also be applied in other type of cyclonic separators, such as the one discussed with reference to WO0023757.

The cyclonic fluid separator TW as described and shown in Fig. 2a may be used for high-pressure flows, i.e. the pressure just upstream of the central body may typically be 100 bar.

The cyclonic fluid separator as shown in Fig. 2a may be used in the expansion- cooling based separation stage 200.

The expander EXP may be formed by the annular space 3 downstream of the swirl imparting vanes 2 until the diverging fluid separation chamber 5, including the tubular throat portion 4. The separator SEP may be formed by the fluid separation chamber 5. The compressor COM may be formed by the outer secondary fluid outlet 6 and the central primary fluid outlet conduit 7. These parts are schematically depicted in Fig. 2a. Cyclonic fluid separator with an additional central flow TW

Fig. 2b schematically depicts an alternative cyclonic fluid separator TW as may be used in an expansion-cooling based separation stage 200.

Fig. 2b shows a cross sectional view of a fluid separator according to an embodiment. Same reference numbers are used to denote same items as above. Again, a pear-shaped central body 10 on which a series of swirl imparting vanes 2 are mounted is provided. The central body 10 is arranged coaxial to a central axis I of the fluid separator and inside the separator such that an annular flow path 3 is created between the central body 10 and separator. The fluid flow entering the fluid separator through this annular flow path will be referred to as the main flow. The fluid separator further comprises a tubular throat portion 4, a diverging fluid separation chamber 5 which is equipped with a central primary outlet conduit 7 for gaseous components and with an outer secondary outlet conduit 6 for condensables enriched fluid components.

According to this embodiment, the central body 10 does not comprise an elongated tail section 8 substantially cylindrical elongated tail section 8 as in Fig. 2a. Instead thereof, the central body 10 comprises a central outlet 13. The central outlet 13 is positioned on the downstream side of the central body 10, directed towards the throat portion 4. The position and direction of the central outlet 13 substantially coincides with the central axis I. The central outlet 13 is arranged to add a central flow to the cyclonic fluid separator 1.

So, according to this embodiment, there is provided a fluid separator comprising:

- a throat portion 4 which is arranged between a converging fluid inlet section and a diverging fluid outlet section, the diverging fluid outlet section comprising an inner primary outlet 7 for condensables depleted fluid components and an outer secondary outlet for condensables enriched fluid components 6; and

- a central body 10 provided upstream of the throat portion 4 in the fluid inlet section, the central body 10 being arranged substantially coaxial to a central axis I of the fluid separator, the fluid separator being arranged to facilitate a main flow through the converging fluid inlet section, the throat portion 4 towards the diverging fluid outlet section, wherein the central body 10 comprises a central outlet 13, directed towards the tubular throat portion 4 and arranged to add a central flow towards the throat portion 4. The central outlet 13 is provided upstream with respect to the throat portion 4.

A duct 12 may be provided to provide the central outlet 13 with a fluid flow. In use, the central flow substantially coincides with the central axis I and is surrounded by the main flow. The central flow may be a swirling flow.

The central fluid flow provided by the central outlet 13 ensures that the main flow remains stable throughout the fluid separator TW. The central flow plays a role similar to the substantially cylindrical elongate tail section 8 as described above with reference to Fig. 2a in that the central flow prevents vortex breakdown at the central axis of main flow.

Since the central flow is not a rigid object (as tail section 8) and moves in the same direction as the main flow, friction between the central flow and the main flow is relatively low. This contributes to the throughput of the fluid separator.

According to an embodiment, the fluid separator comprises a swirl imparting device 2 for creating a swirling motion of the main flow within at least part of the fluid separator TW. An example of such a swirl imparting device are swirl imparting vanes 2 as shown in Fig. 2b and already discussed above with reference to Fig. 2a.

The central body 1 may have a substantially circular shape in a cross-axial direction and comprises upstream of the swirl imparting device 2 a nose section of which the diameter gradually increases such that the degree of diameter increase gradually decreases in downstream direction, and the central body 10 further comprises downstream of the swirl imparting device a section of which the diameter gradually decreases in downstream direction. This is shown in Fig. 2b, showing a substantially pear-shaped central body 10.

The fluid separator TW may comprise a housing 20 in which the central body 10 is arranged such that an annulus 3 is present between an inner surface of the housing 20 and an outer surface of the central body 10.

The fluid separator TW may comprise a central outlet 13 which comprises a swirl imparting device for creating a swirling motion of the central flow within at least part of the fluid separator (not shown). The swirl provided to the central flow may be lower than the swirl of the main flow (i.e. less rotations per second or less rotations per traveled distance in the direction of the central axis I, such that no vortex breakdown of the central flow occurs). By adding a swirl to the central flow, the velocity gradient in the tangential direction between the central flow and the main flow is reduced.

For instance, the entrance velocity in axial (i.e. longitudinal) direction of the central flow is relatively low, typically 20 m/s and 0 - 20 m/s in tangential direction, whilst at that point the main flow velocity is high though possibly still subsonic, for instance 250 m/s axial and 100 m/s tangential. However, the main flow may already be supersonic at this point.

Hence, the central flow momentum will be propelled by the outer main flow in both axial and tangential direction (like the working principle of a jet pump / gas ejector). Now, the function of the prior art elongated tail end 8 (i.e. to prevent further tangential acceleration causing vortex breakdown) is replaced by the gaseous central flow. Instead of factional dissipation of momentum at the boundary of the elongated tail end 8, part of the main flow momentum is used (i.e. transferred) to propel the central gas flow.

A number of spokes 21 may be provided between the housing 20 and the central body 10, to mount the central body 10. The spokes 21 may be provided upstream of the swirl imparting means 2, such that the spokes 21 have less effect on the main flow. According to an alternative, the swirl imparting means 2 and the spokes 21 are integrated into a single part. Also, one or more of the spokes 21 may be hollow and connected to the duct 12 as to guide the flow to central outlet 13.

In Fig. 2b three pressure symbols are depicted: PO, Pl and P2. PO represents the pressure upstream of the central body 10 and may typically be in the order of 100 bar. Pl represents the pressure at the position of the central outlet 13 and may typically be 50% - 70% lower than PO. P2 represents the pressure at the position of the secondary outlet conduit 6 and may typically be 25% - 50% lower than the inlet pressure PO. It will be understood that the values of the pressures PO, Pl, P2 may vary depending on the pressure supplied to the fluid separator TW and the actual shape of the fluid separator TW and central body 10. However, typically the following relation applies: PO > P2 > P1.

So, in use, the central outlet 13 is at a first pressure Pl (i.e. the space to which the central outlet 13 supplies the central flow is at the first pressure Pl) and the secondary outlet conduit 6 is at a second pressure P2, the first pressure Pl being lower than the second pressure P2. The fluid added via the central outlet 13 typically has a pressure higher than the first pressure Pl to ensure a smooth flow.

As described with reference to Fig. 2a, according to the state of the art, flow straightening blades 19 were provided on the elongated tail end 8. However, in the embodiments described here, no elongated tail section 8 is present. Therefore, a flow straightening device 19', such as flow straightening blades, may be provided that is mounted to the diffuser casing 14 or a diffuser body 18 (as shown in Fig. 2b). A more detailed description is provided in patent application PCT/NL2008/050172.

So, accordingly, there is provided a method of separating a fluid mixture using a fluid separator as described above. The method may comprise

providing a first fluid to form the main flow,

providing a second fluid to form the central flow.

The cyclonic fluid separator TW as described with reference to Fig. 2b may be used in the expansion-cooling based separation stage 200.

The expander EXP may be formed by the annular space 3 downstream of the swirl imparting vanes 2 until the diverging fluid separation chamber 5, including the tubular throat portion 4. The separator SEP may be formed by the fluid separation chamber 5. The compressor COM may be formed by the outer secondary fluid outlet 6 and the central primary fluid outlet conduit 7.

Of course it will be understood that the cyclonic fluid separator with an additional central flow TW as described here with reference to Fig. 2b is just an example and that other similar device may be used as well to function as a cyclonic fluid separator with an additional central flow, such as the device described in International Patent application WO2009/028987.

Turbo-expander-compressor TEC

Fig. 2c schematically depicts a turbo-expander-compressor TEC as may be used in an expansion-cooling based separation stage 200, as an alternative to the cyclonic fluid separators TW described above.

The turbo-expander-compressor TEC may comprise a turbo expander TE arranged to receive an input stream 61. The turbo expander TE may be a radial or axial flow through which the high pressure input stream 61 is expanded to produce work, producing an expanded stream 62. The turbo-expander TE may comprise a turbine wheel that is driven by the expanding input stream 61. The produced work may be transferred to the compressor TC to drive the compressor TC as will be explained below.

Because work is extracted from the expanding input stream 61 and the expansion is an isentropic process (i.e., a near constant entropy process), the expanded stream 62, which is at a lower pressure than the input stream 61 is also at a lower temperature than the input stream 61, for instance -50 ⁰C or less. This causes condensation and formation of liquid droplets.

The expanded stream 62 is transferred to a separation vessel V4, for instance a

Low Temperature Separation (LTS) vessel V4. The liquid droplets that are formed will mainly be extracted at the bottom of the separation vessel V4 and form a liquid enriched output stream 64. The other components will form a gas enriched output stream 63 which is extracted at the top part of the separation vessel V4.

This gas enriched output stream 63 is fed to the compressor TC. It will be understood that many types of compressors may be used.

The compressor TC is arranged to increase the pressure of the gas enriched output stream 63 to form a re-pressurized output stream 65. Again, the following relation applies: PO'>P2'>P1 ', where PO' is the pressure of input stream 61, Pl ' is the pressure of the expanded stream 62 and P2' is the pressure of the output stream 65, as indicated in Fig. 2c.

According to the example provided in Fig. 2c, the compressor TC is in connection with the turbo expander TE via a shaft SH. The shaft SH is used to drive the compressor TC using work extracted from the input stream 61 by the turbo expander TE. In use, the shaft SH may rotate. Of course, the transfer of energy may be achieved in any suitable way, possibly without a shaft SH. The transfer of energy may be achieved in an electrical way.

The turbo-expander-compressor TEC as shown in Fig. 2c may be used in the expansion-cooling based separation stage 200.

The expander EXP may be formed by the turbo-expander TE. The separator SEP may be formed by the separation vessel V4. The compressor COM may be formed by the compressor TC. These parts are schematically depicted in Fig. 2c.

Joule-Thomson Valve (JT) Fig. 2d schematically depicts a Joule-Thompson valve JT as may be used in an expansion-cooling based separation stage 200. Many different Joule-Thompson valves JT are known to the skilled person. An example of a Joule-Thompson valve JT is provided in Fig. 2d, schematically depicting a traditional cage- valve for flow control service as supplied by Mokveld Valves B. V. in which the flux of fluid is throttled over a perforated sleeve or cage 23, which is connected to a piston-type valve body 22.

The conventional Mokveld throttling valve shown in Fig. 2d comprises a valve housing 21 in which a piston- type valve body 22 is slideably arranged in the associated perforated sleeve 23 such that by rotation of a gear wheel 24 at a valve shaft 25 a teethed piston rod 26 pushes the piston type valve body 22 up and down into a fluid outlet channel 27 as illustrated by arrow 28. The valve has an fluid inlet channel 29 which has an annular downstream section 29A that may surround the piston 22 and/or perforated sleeve 23 and the flux of fluid which is permitted to flow from the fluid inlet channel 29 into the fluid outlet channel 27 is controlled by the axial position of the piston-type valve body 22 in relation to the associated perforated sleeve 23.

The conventional sleeve 23 comprises perforations 30 - slots or holes - that have a radial orientation i.e. rectangular to the cylindrical surface of the sleeve 23. By displacing the piston 22 in the sleeve 23 in axial direction the flow area can be controlled.

Variations to such this valve are conceivable, for instance, the available free pressure for isenthalpic expansion may be used to create a swirling flow imposed by a specific geometry of the valve trim and/or valve stem. The kinetic energy is then mainly dissipated through dampening of the vortex along an extended pipe length downstream the valve. The swirling flow may be created by providing perforations 30 that have a tangential component with respect to a central body axis of the sleeve 23.

Downstream of the fluid outlet channel 27 a separator SEP may be provided, for instance formed by a separation vessel V3, such as a Low Temperature Separator or a Hydrate Separator

Of course, other types of Joule-Thompson valves JT may be used as well.

In general, the Joule -Thompson valve JT comprises an expander EXP (formed by perforations 30 in Fig. 2d) which may be followed by a separator SEP (e.g. formed by a separation vessel V3). EMBODIMENTS

The embodiments presented below with reference to Fig.'s 1, 3 and 4, provide a process scheme for hydrocarbon dew pointing based on expansion-cooling technology, thus using an expansion-cooling based separation stage 200, e.g. using a turbo- expander-compressor TEC, Joule-Thompson valve JT, or a cyclonic separator TW, TW as described above, with reference to Fig.'s 2a - 2d.

The embodiments describe a scheme for hydrocarbon dewpointing, comprising an expansion-cooling based separation stage 200 and a stabilisation stage 300.

Upstream of the expansion-cooling based separation stage 200 may be provided a pre- separation stage 100, an example of which will be described first.

The embodiments use an expansion-cooling based separation stage, possibly including a recompression step. In some embodiments, the recompression step may be absent, as in the case where the process scheme for hydrocarbon dew pointing is based on expansion technology only by using a JT valve. The recompression step may also be intrinsically be built in, for instance in case a cyclonic separator TW, TW' as described above is used.

Pre-separation stage 100

A pre-separation stage 100 may be provided, comprising a first separation vessel Vl, a heat exchanger HEl and a second separation vessel V2. The pre-separation stage 100 is arranged to receive a pre-separation input stream II, which may be an incoming gas stream, comprising hydrocarbons. Examples of such a pre-separation stage 100 are schematically depicted in Fig.'s 3, 4, 5 and 6 and in a more schematic way in Fig. 1.

In general, the pre-separation stage 100 may be arranged to receive an incoming gas stream, also referred to as a pre-separation input stream II, which is cooled, for instance using the first heat exchanger HEl. The first heat exchanger HEl may be a Gas-Gas heat exchanger which uses relatively cold export gas for cooling. Other cooling devices or combinations of cooling devices can be used as well e.g., air cooler, propane chiller, gas liquid heat exchanger.

The pre-separation input stream Il is connected to the first separation vessel Vl, which may be a gravitational driven separator or any other suitable type of separation vessel. The first separation vessel Vl thus produces a first liquid enriched output stream Ll and a first gas enriched output stream Gl. The first separation vessel Vl is mainly used for separating free liquids.

The first gas enriched output stream Gl is guided through the heat exchanger HEl and is introduced in the second separation vessel V2, which may be a gravitational driven separator or any other suitable type of separation vessel. The second separation vessel V2 thus produces a second liquid enriched output stream L2 and a second gas enriched output stream G2. The second liquid enriched output stream L2 may be combined with the first liquid enriched output stream Ll within or outside the pre- separation stage 100, and may form input for the stabilisation stage 300.

The second gas enriched output stream G2 is used as second input stream 12 for the expansion-cooling based separation stage 200.

Expansion-cooling based separation stage 200

An expansion-cooling based separation stage 200 is provided which is arranged to receive an input stream 12 and a feedback stream FS from the stabilisation stage 300.

The input stream 12 may for instance originate from the pre-separation stage 100. In that case the input stream 12 may be formed by the second gas enriched output stream G2.

The pressure of the input stream 12 may be relatively high, for instance in the order of 100 bar and may have a temperature of typically 298K. The pressure is reduced by expansion in an expander EXP, such as provided by a cyclonic fluid separator TW, TW as described above with reference to Fig.'s 2a and 2b, in a turbo- expander-compressor TEC as described above with reference to Fig. 2c, or in a JT valve JT as described above with reference to Fig. 2d.

Due to expansion the temperature of the input stream 12 is significantly reduced which will result in the formation of liquid hydrocarbons, though the outlet temperature in case of the Joule-Thompson valves JT may be higher than for the others due to its isenthalpic cooling.

In case a cyclonic fluid separator TW, TW' is used, the formed liquids are at least partially separated within the cyclonic fluid separator TW, TW'. The cyclonic fluid separator TW, TW' produces a condensables enriched stream CE via the outer secondary outlet conduit 6 and a gaseous enriched stream GE via the central primary outlet conduit 7. The condensables enriched stream CE may contain some slip gas, typically 30-35%.

In case a cyclonic fluid separator TW according to Fig. 2a is used, the feedback stream FS stream may be supplied directly to separator vessel V3, hence without extracting condensables from the feedback stream FS. In case of a cyclonic fluid separator with an additional central flow TW according to Fig. 2b, the feedback stream FS is injected halfway during the expansion process, i.e. via central outlet 13, and hence condensables from FS will also be produced with the extra condensables enriched stream CE. This is schematically shown in Fig. 4.

The condensables enriched stream CE is therefore supplied to a separator vessel

V3, to remove the slip gas.

The separator vessel V3 could be a Hydrate Separator or a Low Temperature Separator. The Hydrate Separator uses heat input to control hydrate formation while the Low Temperature Separator requires upstream dehydration of the expansion-cooling based separation stage 200 or hydrate suppression by chemical inhibition. Separator V3 may be a liquid degassing vessel, the separator V3 thus produces a top stream TS, mainly comprising the slip gas, and a bottom stream BS. An example of a hydrate separator is provided in WO2006/070019.

The gaseous enriched stream GE from the cyclonic fluid separator TW, TW' and the top stream TS of the hydrate separator V3 may be combined and used to cool the pre-separation input stream Il in the pre-separation stage 100, after which the gas will be exported.

In case a turbo-expander-compressor TEC as shown in Fig. 2c is used in the expansion-cooling based separation stage 200 as an alternative to the cyclonic fluid separator TW, TW', the input stream 12 (compare input stream 61 shown in Fig. 2c) is expanded in the turbo expander TE, producing an expanded stream ES (compare expanded stream 62 in Fig. 2c). An example of this is shown in Fig. 5.

The expanded stream ES, which comprises condensed liquids, is applied to a Low Temperature Separator V4. Upstream of the Low Temperature Separator V4 dehydration or hydrate suppressing by chemical inhibition is required.

The Low Temperature Separator V4 also produces a top stream TS (compare gas enriched output stream 63 of Fig. 2c) and a bottom stream BS (compare liquid enriched output stream 64 in Fig. 2c). Again, the relatively cold top stream TS may be used to cool the pre-separation input stream Il in the pre-separation stage 100. After this, the top stream TS may be fed to the compressor TC. The compressor TC is arranged to increase the pressure of the top stream TS to form a re-pressurized output stream. Many types of compressors may be used.

The bottom stream BS may be further processed in a stabilisation stage 300. In case a Joule-Thompson valve JT is used, the expanded stream ES created downstream of the Joule-Thompson valve (compare reference 27 in Fig. 2d), which comprises condensed liquids, is applied to a separation vessel V3, which may for instance be a Low Temperature Separator or a Hydrate Separator.

The expansion-cooling stage 200 whereby the feedback stream FS from stage 300 is combined with the intermediate Separation SEP is based on the cyclonic fluid separator with central outlet TW and turbo-expander-compressor (TEC), i.e. before compression. Alternatively the cyclonic fluid separator TW and Joule Thompson valve JT configuration apply. In the latter case the feedback stream FS may be combined either with the separator vessel V3 at a higher pressure and hence also a higher flow than in the earlier expander-compression scheme, or a separate off-gas compression unit is to be added to combine with the first gas enriched output stream Gl .

Stabilisation stage 300

Downstream of the expansion-cooling based separation stage 200 a further (separation) stage is provided, referred to as a stabilisation stage 300, which comprises a heat based separator, such as a fractionation column FC. The functioning of fractionation columns FC and peripheral devices will be understood by the skilled person. An example of a stabilisation stage 300 is provided in Fig.'s 3 - 6.

The fractionation column FC may comprise a re-boiler RB at the bottom and a reflux circuit RF, comprising an air-cooler AC at the top. The fractionation column FC produces a fractionation bottom stream FB that is partially re-introduced into the fractionation column FC via the re-boiler RB. The remaining part is used to pre-heat the input stream of the fractionation column FC as will be explained in more detail below. The fractionation column FC also produces a fractionation top stream FT that is supplied to the air-cooler AC, after which it is partially re-introduced into the fractionation column FC. The stabilisation stage 300 uses the bottom stream BS of separation vessels V3,

V4 as input, possibly in combination with first and second liquid enriched output stream Ll, L2. This is referred to as the intermediate input stream 13.

Before entering the fractionation column FC, the intermediate input stream 13 may be fed to a static coalescer (known by the skilled person) CO to remove free water from the condensate. The bottom stream (water) of the coalescer BC is being disposed of. The coalescer CO will increase the droplet size of the free water so that it can be separated from the condensate.

When combining the first and second liquid enriched output stream Ll, L2 with the bottom stream BS, the first and second liquid enriched output streams Ll, L2 may flash, creating three phases (gas, condensate and water). The coalescer CO may not be able to handle these three phases. Therefore, additional devices may be introduced to solve this problem:

- instead of one coalescer CO, two different coalescers (not shown) may be provided, a first coalescer for the first and second liquid enriched output stream Ll, L2 and a second coalescer for the bottom stream BS, the first coalescer working on a relatively high pressure, the second coalescer working on a relatively low pressure. The outputs of the first and second coalescers may be combined,

- increasing the pressure of the bottom stream BS before combining it with the first and second liquid enriched output streams Ll, L2 to a pressure level that is substantially equal to the pressure level of the first and second liquid enriched output streams Ll, L2 and then removing the free water in a single coalescer.

The top stream of the coalescer TCO, i.e. the cold condensate feed, is pre-heated in a second heat exchanger HE2, i.e. a liquid-liquid heat exchanger, making use of the relatively hot stabilized condensate that is present in the fractionation bottom stream FB. After the second heat exchanger HE2, the top stream of the coalescer CO is applied as input to the fractionation column FC. The use of a fractionation column FC allows the flash gas and condensate to remain at a higher than atmospheric pressure, as a fractionation column can be operated between 15-30 bar.

As mentioned, the fractionation top stream FT which comprises relatively light hydrocarbon gas, is partially re-introduced into the fractionation column FC. However, another part, for instance obtained from the air cooler AC is re-introduced in the expansion-cooling based separation stage 200, by means of a jet pump JP.

Jet pump JP

According to the embodiments, a jet pump JP is provided that is arranged to receive part of the fractionating top stream FT as input, also referred to as intermediate feedback stream 14. Examples of the jet pump JP are provided in Fig.'s 1 and 3 - 6. The intermediate feedback stream 14 comprises relatively light hydrocarbon gas, and is typically at a pressure of 15 - 30 bar.

The intermediate feedback stream 14 is then sent to a jet pump JP. Jet pumps are known to the skilled person and are also often referred to as 'injector' or 'ejector'.

The pressure of the intermediate feedback stream 14 is increased by making use of the high pressure of the input stream 12. The pressure of the intermediate feedback stream 14 is typically 15 - 30 bar, the pressure of the input stream 12 is typically 100 bar. By mixing these by means of a jet pump JP, the feedback stream FS can be created with a pressure of for instance 50 bar or the like. So, the pressure of the feedback stream FS is a higher pressure than the pressure at which the fractionation column FC is operating, though lower than the pressure of input stream 12. The pressure of the intermediate feedback stream 14 may thus be increased such that it is higher than the pressure prior to recompression of the main process stream in the compressor COM or higher than the pressure in the separation vessels V3, V4.

In case a cyclonic fluid separator with an additional central flow TW is used, the pressure of the feedback stream FS may be above the pressure Pl representing the pressure at the position of the central outlet 13. In case a turbo-expander-compressor TEC is used, the pressure of the feedback stream FS may be above the pressure of the low temperature separator V4 and in case a cyclonic fluid separator TW according to Fig. 2a is used or a Joule Thompson valve JT according to Fig. 2d is used, the pressure of the feedback stream or FS may be above the pressure of the separation vessel V3 (e.g. being a low temperature separator or a hydrate separator).

The feedback stream FS is then re-introduced into the expansion-cooling based separation stage 200. The position wherein the feedback stream FS is re-introduced may vary for different embodiments. It may be downstream or halfway the expander EXP, and upstream of the compressor COM, if a compressor COM is present.

Optionally, the feedback position may be upstream with respect to the expander EXP, as will be explained in more detail below. In case the feedback position is upstream of the expander EXP, an additional separate off-gas compression unit (not shown) is needed to boost the feedback stream FS to pressure PO. However, this additional off-gas compression unit may be relatively small as the pressure is already increased to some extent by the jet pump JP.

Alternatively, the feedback stream FS may be fed back to the separation vessel V3, in which case no additional gas compression unit is required.

Fig. 1 shows a more schematic processing scheme, which is based on the embodiments described with reference to Fig.'s 1, 3 - 6.

So, according to an embodiment there is provided a processing scheme for gas conditioning, comprising an expansion-cooling based separation stage 200 and a stabilisation stage 300, the expansion-cooling based separation stage 200 comprises an expander EXP and a separator SEP , and is arranged to receive an input stream 12, the stabilisation stage 300 comprises a fractionation column FC, and being arranged to receive an intermediate input stream 13 from the expansion-cooling based separation stage 200, wherein the processing scheme further comprises a jet pump JP, arranged to receive at least part of a fractionation top stream FT and a portion of the input stream 12' taken upstream of the expander EXP, to combine these into a feedback stream FS which is re-introduced in the expansion-cooling based separation stage 200 at a feedback position.

As described, the expansion-cooling based separation stage 200 is arranged to - receive the input stream 12 of a gaseous fluid,

- expand and thereby adiabatically cool the input stream 12 in the expander EXP, such that at least some initially gaseous components become supersaturated and condense creating liquid droplets in the gaseous fluid, - receive at least part of the expanded stream in the separator SEP, the separator SEP comprising at least a separation vessel V3, V4 arranged to produce a top stream TS and a bottom stream BS, and optionally

- recompress at least part of the received input stream 12 after expansion in the compressor COM. The intermediate input stream 13 from the expansion-cooling based separation stage 200 comprises the bottom stream BS.

According to an embodiment, the stabilisation stage 300 may further comprise a coalescer CO and a second heat exchanger HE2, where the coalescer CO is arranged to receive the intermediate input stream 13, the coalescer CO producing a top stream TCO which is heated by the second heat exchanger HE2 before being provided to the fractionation column FC. The top stream TCO may also be referred to as a dehydrated condensate top stream TCO.

The fractionation column FC is arranged to

- separate at least part of the intermediate input stream 13 in the fractionation column FC, the fractionation column FC being arranged to produce a fractionation top stream

FT and a fractionation bottom stream FB.

The pressure of the feedback stream FS is in between the pressure of the fractionation top stream FT and the input stream 12, and is equal to or higher than the pressure at the feedback position. In some occasions a further compressor may be needed. However, such a compressor can be much smaller due to the increase in pressure created by the jet pump JP.

As described, according to an embodiment, the expansion-cooling based separation stage 200 comprises a cyclonic fluid separator TW, TW or a Joule- Thompson valve (JT) and comprises a separation vessel V3, embodying the expander EXP and the separator SEP. The separation vessel V3 may be a Low Temperature Separator LTS or a Hydrate Separator.

The processing scheme may further comprise a pre-separation stage 100 comprising at least one separation vessel Vl, V2 and a first heat-exchanger HEl,

the pre-separation stage 100 being arranged to receive an incoming gas stream II, which is cooled by the first heat-exchanger HEl and to separate the incoming gas stream by the at least one separation vessel Vl, V2, producing a gas enriched output stream G2 and a liquid enriched output stream Ll, L2, the gas enriched output stream G2 forming input stream 12. The pre-separation stage 100 is in fact also a separation stage, but is mainly used to prepare the fluids for the expansion-cooling based separation stage (200).

Further provided is a method for gas conditioning, the method comprising:

- feeding an input stream 12 to an expansion-cooling based separation stage 200, the expansion-cooling based separation stage forming an intermediate input stream 13,

- feeding the intermediate input stream 13 to an stabilisation stage 300, the stabilisation stage 300 comprising a fractionation column FC,

- the fractionation column FC creating a fractionation top stream FT and a fractionation bottom stream FB,

- feeding at least part of the fractionation top stream FT and a portion of the input stream 12' taken upstream of the expander EXP to a jet pump JP, to combine these into a feedback stream FS,

- re-introducing the feedback stream FS in the expansion-cooling based separation stage 200 at a feedback position.

Upstream expander EXP

According to an embodiment, the feedback stream FS is re-introduced upstream of the expander EXP, i.e. upstream of the cyclonic fluid separator TW, the cyclonic fluid separator with an additional central flow TW , the turbo-expander-compressor TEC, or the Joule-Thompson- valve JT, where it could be combined with the input stream 12. Alternatively, the feedback stream FS may be re-introduced in the pre- separation stage 100, for instance in the first gas enriched output stream Gl.

However, it will be understood that since the pressure of the feedback stream FS is below the pressure of the input stream 12, additional measures are required, such as an additional compressor to increase the pressure of the feedback stream FS.

Therefore, according to an embodiment, the processing scheme further comprises a compressor to increase the pressure of the feedback stream FS, and wherein the feedback position is upstream of the expander EXP. In this case, a relatively small additional off gas compressor unit may be needed to increase the pressure of the feedback stream FS to at least match the pressure to the pressure PO which is the pressure upstream of the expansion-cooling based separation stage 200 , which may typically in the order of 100 bar. Since the pressure of the feedback stream FS is relatively high as a result of the jet pump JP a relatively small and cost-efficient compressor is needed.

Halfway expander EXP

According to an embodiment, the feedback stream FS is re-introduced during expansion in the expander EXP, the feedback position thus being halfway the expander EXP. The feedback stream FS is for instance re-introduced using central outlet 13 as discussed above with reference to Fig. 2b. Central outlet 13 is positioned on the downstream side of the central body 10, directed towards the throat portion 4. The position and direction of the central outlet 13 substantially coincides with the central axis I. The central outlet 13 is arranged to add a central flow to the cyclonic fluid separator TW.

The cyclonic fluid separator with an additional central flow TW has a central outlet 13 which thus can be used to introduce flash gas as central flow. The required inlet pressure is significantly lower than the required inlet pressure of the primary inlet, i.e. the pressure upstream of the pear-shaped central body 10. The secondary inlet gas is comingled with the primary stream after expansion and recompressed together, after which it is used to pre cool the feed gas.

The fluid introduced via the central outlet 13 may be a fluid with a pressure higher than the pressure Pl (discussed above with reference to Fig. 2b), but with a pressure lower than pressure PO.

Although not shown in the drawings, the cyclonic fluid separator with an additional central flow TW may be provided with a duct 12 to provide the central outlet 13 with a fluid flow. According to an example, one or more of the spokes 21 may be hollow and connected to the duct 12 as to guide the flow to central outlet 13.

Downstream expander EXP

According to an embodiment, the feedback stream FS is re-introduced

downstream of the expander EXP, .

For instance, in case the expansion-cooling based separation stage 200 comprises a turbo-expander TE embodying the expander EXP, a separation vessel V4 embodying the separator SEP, and a compressor TC embodying the compressor COM, the feedback position may be provided as in inlet to the separation vessel V4, as for instance a Low Temperature Separation (LTS) vessel V4, described above with reference to Fig. 2c.

According to an alternative, the feedback stream FS is for instance re-introduced at a feedback position, which is upstream of the compressor TC, but downstream of the low temperature separation vessel V4.

This may be done when the feedback stream FS is an undersatured vapor. If the feedback stream FS is a saturated vapor, liquids may form when expanding to Pl' and the feedback stream FS may therefore be re-introduced in vessel V4.

So, for a turbo-expander-compressor TEC the boosted gas is combined with the main process stream at the Low Temperature Separator V4 or at the inlet of the turbo- compressor TC after which the total stream is used to pre-cool the first gas enriched output stream Gl after which it is re-compressed by the compressor TC driven by the turbo expander TE, and subsequently exported.

In case the cyclonic fluid separator TW, TW is used, without or with an additional central flow, the feedback stream FS may be re-introduced after

compression, i.e. into hydrate separator V3. So, the feedback position may be at the separation vessel V3, V4.

Furthermore it is noted that in the embodiments described above with reference to Fig.'s 4 and 5 (i.e. the cyclonic fluid separator TW with additional central flow and the turbo-expander-compressor TEC) the feedback stream FS is mixed with the

isentropically expanded flow in cyclonic fluid separator TW or with the isentropically expanded flow in separation vessel V4 of the turbo-expander-compressor TEC. So the feedback stream FS is being 'dew pointed' by the cold gas/ liquid, before the compression stage. Wherein in the embodiments described with reference to Fig.'s 3 and 6 (i.e. the cyclonic fluid separator TW and the Joule-Thompson valve JT) the feedback stream FS is mixed with the isenthalpically expanded flow in vessel V3. Hence for these latter two embodiments , a larger driving flow 12' is needed to get a higher pressure to meet the higher V3 pressure thus increasing the (untreated) feedback stream FS flow and hence contaminating the export gas. Alternatively an additional compressor unit needs to be added to feed FS into 12.

Advantages The embodiments provided above provide several advantages compared to hydrocarbon dewpointing and stabilization schemes according to the prior art, with for instance condensate stabilization by flashing the condensate to atmosphere.

The above embodiments provide relatively simple process schemes provided in which the gas is conditioned and the condensates are stabilized without flaring. As no flaring is necessary a significant reduction in CO₂ emissions and the like can be obtained, which is advantageous from an environmental point of view.

The embodiments comprising a cyclonic fluid separator TW, TW or a turbo- expander-compressor TEC or a Joule-Thompson valve JT also have the advantage that no or less additional off gas compressor units are required, as the off gas does not need off gas compression. As a result the power consumption and consequently the CO₂ emissions and the like are also being reduced.

In general, the process complexity is reduced as no off gas compressors are installed. This results in reduced capital expenditures as a jet pump JP is a relatively simple technology. Also, the operating expenditures are reduced as no off-gas compressor is required.

The embodiments allow for stabilizing and storing condensate at remote locations where no condensate or oil export pipeline is in place and where (live) condensate export is not preferred.

Additionally, in a processing scheme comprising a cyclonic fluid separator TW,

TW' no rotating equipment is used, reducing the maintenance and subsequently the operating expenditures and increasing the uptime, compared with a turbo-expander- compressor TEC based scheme.

The cyclonic fluid separator TW, TW' is capable of conditioning the gas in a single unit, thus water dewpointing in combination with hydrocarbon dewpointing. It does not require additional dehydration or chemical inhibition as does the turbo- expander-compressor TEC based processing scheme.

Further remarks

The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

1. Processing scheme for gas conditioning, comprising an expansion-cooling based separation stage (200) and a stabilisation stage (300),

the expansion-cooling based separation stage (200) comprises an expander (EXP) and a separator (SEP) , and is arranged to receive an input stream (12),

the stabilisation stage (300) comprises a fractionation column (FC), and being arranged to receive an intermediate input stream (13) from the expansion-cooling based separation stage (200),

wherein the processing scheme further comprises a jet pump (JP), arranged to receive at least part of a fractionation top stream (FT) and a portion of the input stream (12') taken upstream of the expander (EXP), to combine these into a feedback stream (FS) which is re-introduced in the expansion-cooling based separation stage (200) at a feedback position.

2. Processing scheme according to claim 1, wherein the expansion-cooling based separation stage (200) is arranged to

- receive the input stream (12) of a gaseous fluid,

- expand and thereby adiabatically cool the input stream (12) in the expander (EXP), such that at least some initially gaseous components become supersaturated and condense creating liquid droplets in the gaseous fluid,

- receive at least part of the expanded stream in the separator (SEP), the separator (SEP) comprising at least a separation vessel (V3, V4) arranged to produce a top stream (TS) and a bottom stream (BS).

3. Processing scheme according to claim 2, wherein the intermediate input stream (13) from the expansion-cooling based separation stage (200) comprises the bottom stream (BS).

4. Processing scheme according to any one of the preceding claims, wherein the stabilisation stage (300) further comprises a coalescer (CO) and a second heat exchanger (HE2), where the coalescer (CO) is arranged to receive the intermediate input stream (13), the coalescer (CO) producing a top stream (TCO) which is heated by the second heat exchanger (HE2) before being provided to the fractionation column (FC).

5. Processing scheme according to any one of the preceding claims, wherein the fractionation column (FC) is arranged to

- separate at least part of the intermediate input stream (13) in the fractionation column (FC), the fractionation column (FC) being arranged to produce a fractionation top stream (FT) and a fractionation bottom stream (FB).

6. Processing scheme according to any one of the preceding claims, wherein the pressure of the feedback stream (FS) is in between the pressure of the fractionation top stream (FT) and the input stream (12), and is equal to or higher than the pressure at the feedback position.

7. Processing scheme according to any one of the preceding claims, wherein the expansion-cooling based separation stage (200) comprises a cyclonic fluid separator (TW, TW) or a Joule-Thompson valve (JT) and comprises a separation vessel (V3), embodying the expander (EXP) and the separator (SEP).

8. Processing scheme according to claim 7, further comprising a compressor to increase the pressure of the feedback stream (FS), and wherein the feedback position is upstream of the expander (EXP).

9. Processing scheme according to claim 7, wherein the feedback position is halfway the expander (EXP).

10. Processing scheme according to claim 9, wherein the expansion-cooling based separation stage (200) comprises a cyclonic fluid separator (TW), the cyclonic fluid separator (TW) comprising a housing (20) in which a central body (10) is arranged such that an annulus (3) is present between an inner surface of the housing (20) and an outer surface of the central body (10), creating a converging fluid inlet section, the cyclonic fluid separator (TW) arranged to facilitate a main flow through the converging inlet section, the central body (10) comprising a central outlet (13) arranged to add a central flow to the main flow,

wherein the feedback position is formed by the central outlet 13.

11. Processing scheme according to claim 7, wherein the feedback position is at the separation vessel (V3, V4).

12. Processing scheme according to any one of the claims 1 - 8, wherein the expansion-cooling based separation stage (200) comprises a turbo-expander (TE) embodying the expander (EXP), a separation vessel (V4) embodying the separator (SEP), and a compressor (TC) embodying the compressor (COM).

13. Processing scheme according to claim 12, wherein the feedback position is provided as an inlet to the separation vessel (V4).

14. Processing scheme according to claim 12, wherein the feedback position is downstream of the separation vessel (V4) and upstream of the compressor (TC).

15. Processing scheme according to any one of the preceding claims, further comprising a pre-separation stage (100) comprising at least one separation vessel (Vl,

V2) and a first heat-exchanger (HEl),

the pre-separation stage (100) being arranged to receive an incoming gas stream

(II), which is cooled by the first heat-exchanger (HEl) and to separate the incoming gas stream by the at least one separation vessel (Vl, V2), producing a gas enriched output stream (G2) and a liquid enriched output stream (Ll, L2), the gas enriched output stream (G2) forming input stream (12).

16. Method for gas conditioning, the method comprising:

- feeding an input stream (12) to an expansion-cooling based separation stage (200), the expansion-cooling based separation stage forming an intermediate input stream (13),

- feeding the intermediate input stream (13) to an stabilisation stage (300), the stabilisation stage (300) comprising a fractionation column (FC), - the fractionation column (FC) creating a fractionation top stream (FT) and a fractionation bottom stream (FB),

- feeding at least part of the fractionation top stream (FT) and a portion of the input stream (12') taken upstream of the expander (EXP) to a jet pump (JP), to combine these into a feedback stream (FS),

- re-introducing the feedback stream (FS) in the expansion-cooling based separation stage (200) at a feedback position.