Patent Grant
8657930
The invention relates to a separation system comprising a swirl valve, a processing system comprising such a separation system, a method to separate a fluid flow, and a method for processing a fluid.
In the oil and gas industry control valves are used to control pressure, level, temperature and flow. In some cases these control valves operate at choked conditions, once sufficient pressure drop is created over the control valve. In processing natural gas this pressure reduction over a valve causes the temperature to drop without extracting heat or work from the gas. This so called isenthalpic expansion process is also known as Joule-Thompson (JT) cooling. The valve creating this pressure reduction is called a JT valve. The cooling effect over a JT valve is used to condense a part of the natural gas stream, such that the liquefied fraction can be separated in a vessel. For the majority of these separator vessels the driving force is either inertia or gravity forces or in other words the masses of the liquefied drops determine the efficiency of the separation. Such a Low Temperature Separator preceded by a JT valve is normally referred to as a JT-LTS system.
Even though the prime function of a JT valve is flow rate control, it is often forgotten that the second function is to create a separable liquid phase. In the gas processing industry the mean droplet size resulting from an isenthalpic expansion over a JT valve is unknown, hence the separation efficiency of downstream phase separators is to a large extent unknown. From time to time gas quality problems do occur due to a suboptimal separation efficiency. In those cases it is often the hydrocarbon dew point which remains too high, which indicates that especially hydrocarbon droplets tend to be too small.
According to the prior art, JT valves are known that can be used to control a flow rate, but which at the same is designed to create a liquid phase that can be separated relatively easy.
International patent application WO2006/070020A1 describes a throttling valve having a housing, a valve body which is movably arranged in the housing to control the flux of a fluid stream flowing from a fluid inlet channel into a fluid outlet channel of the valve such that the fluid stream is expanded and cooled. Also provided are swirl imparting means which impose a swirling motion to the fluid stream flowing through the fluid outlet channel. The swirl imparting means are oriented such that the fluid stream swirls about a longitudinal axis of the fluid outlet channel thereby inducing liquid droplets to swirl towards the outer periphery of the fluid outlet channel and to coalesce. By doing this, the size of the liquid droplets that flow through the fluid outlet channel are relatively large, enabling a more efficient separation process. A more detailed explanation of WO2006/07002A1 will be provided below with reference to
A similar valve is provided by WO2007/024138A1 filed in the name of Typhonix AS. WO2007/024138A1 describes a control valve which aims to maximize the liquid droplet size exiting the valve.
WO2006/070020A1 provides a swirl valve which enlarges the droplet size by providing a swirling motion to the flow as to improve the overall separation efficiency. The valve may also be referred to as a pressure let-down valve (such as used in JT-LTS systems).
Large and expensive phase separators may be required downstream of such a swirl valve to obtain sufficient separation.
Although the examples provided in this text are mainly about separation of liquid droplets from gas flows (droplet dispersion in gas flows), one can apply the provided embodiments to enlarge bubble dispersion in liquid flows or to enlarge the droplet dispersion in liquid flows. So, dispersed multiphase flows may include:
First an example of a swirl valve design, as already disclosed in WO2006/070020 is described in more detail.
Enlarging the Mean Diameter of the Dispersed Phase
Regarding pressure let-down valves (such as JT valves) droplets can be formed through 3 basic mechanisms:
For the first two mechanisms the interfacial tension is a dominant property. The lower the interfacial tension the smaller the droplets/bubbles resulting from a droplet or bubble formation process.
The third mechanism (coalescence) is proportional to the collision rate between droplets, which depends on: a) droplet number density, b) turbulence intensity, c) relative droplet speed.
a schematically depicts a traditional (non-swirl) 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
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. This is shown in
By displacing the piston 22 in the sleeve 23 in axial direction the flow area can be controlled.
This valve according to
The advantage of creating a swirling flow in the valve is twofold:
These advantages are explained in more detail below with reference to
Although any pressure let-down valve would be suitable to create a swirling flow, in the examples provided a cage-type valve as supplied by Mokveld is discussed.
According to an improved valve, the flow is throttled over a perforated cylinder (cage). In
The swirl valve shown in
b illustrates that in the swirl valve the perforated sleeve 3 comprises tilted or non-radial perforations 10, that are drilled in a selected partially tangential orientation relative to a central axis 11 of the fluid outlet channel 7 such that the longitudinal axis 12 of each of the perforations 10 crosses the central axis 11 at a distance D, which is between 0.2 and 1, preferably between 0.5 and 0.99 times the internal radius R of the sleeve 3.
The tilted perforations 10 create a swirling flow in the fluid stream flowing through the fluid outlet channel 7 as illustrated by arrow 14. The swirling motion may also be imposed by a specific geometry of the valve trim and/or valve stem. In the valve according to
Although any Joule-Thomson or other choke and/or throttling type valve could be suitable to create a swirling flow, the examples provided use a choke-type throttling valve as supplied by Mokveld Valves B.V. and disclosed in their International patent application WO2004083691.
According to
a and 3b schematically depict a flow pattern and a density distribution of droplets respectively, corresponding to the traditional valve as for instance shown in
The flow pattern in a cage valve with radial openings is highly disordered, as shown in
Furthermore, the swirling fluid flow as created in a swirl valve forces the droplets to move to the outer circumference of the flow area where they easily agglomerate to larger droplets. This is shown by
In general, valves in which a swirling motion is provided to the fluid flow flowing through there will be referred to as swirl valves. Downstream of such swirl valves further phase separators may be provided to separate the liquid droplets. In many cases a number of phase separators (separator trains) are required. This is disadvantageous, as it makes the prior art solutions relatively voluminous, heavy and thereby not very cost effective.
Such swirling valves and further phase separators may be used on fluid streams which evolve at high pressure such as well fluids from subterranean reservoirs (e.g. oil and gas). In more general terms the fluids under consideration mainly comprise hydrocarbon gases and liquids or mixtures whether or not diluted with an aqueous fluid (e.g. water). During the processing of said well fluids the pressure is reduced in a controlled way for instance to cool the fluid (gas) or to evaporate the volatile fluid components (oil). Especially for the latter process the pressure reduction goes down to atmospheric pressure to obtain a stabilized liquid, whereas for gas processing the pressure reduction is only partial in order to restore sufficient mass-density to economically transport the gas through a pipeline. After all these pressure reduction stages, phase separators may be applied to split:
It is an objective to provide a more compact separation system and processing system comprising a swirl valve.
According to an aspect there is provided a system comprising a flow inlet, wherein the separation system comprises a swirl valve, arranged to receive and control the flux of a fluid flow via the flow inlet and to generate a swirling flow, swirling about a central axis,
wherein the separation system further comprises a separation chamber positioned downstream with respect of the swirl valve to receive the swirling flow from the swirl valve, wherein the separation chamber comprises a first and second flow outlet, wherein the first flow outlet is positioned to receive an inner portion of the swirling flow and the second outlet is positioned to receive an outer portion of the swirling flow. Providing such a system allows establishing substantial cost savings especially on offshore platforms.
According to a further aspect there is provided a processing system, for processing a fluid, the processing system comprising at least one separation system according to the above.
According to a further aspect there is provided a method to separate a fluid flow, the method comprises:
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:
a, 1b, 2a and 2b schematically depict valves according to the prior art,
a, 3b, 4a and 4b schematically depict flow patterns and a density distributions of droplets according to the prior art,
a-5e schematically depict different embodiments,
a and 6b schematically depict further embodiments comprising an injection device,
a-c schematically depict embodiments of a gas processing system,
The embodiments described here provide an improved separation apparatus and separation process.
As shown in
The swirl valve 100 may be as shown in
By positioning the first and second flow outlets 41, 42 concentrically with respect to each other, the first flow outlet 41 receives a relatively light portion of the swirling flow, while the second flow outlet 42 receives a relatively heavy portion of the swirling flow, since the heavier portions will be forced to the outer periphery as a result of the swirling motion.
The first flow outlet 41 and the second flow outlet 42 may both be formed by a first duct 43 and a second duct 44 respectively, where the first duct 43 has a diameter smaller than the diameter of the second duct 44. Both the first and second tube 43, 44 may be positioned concentrically with respect to the central axis 11, thereby forming the first flow outlet 41 and the second flow outlet 42.
So, according to an embodiment, the first flow outlet 41 is positioned concentrically within the second flow outlet 42 with respect to the central axis 11.
It is noted that the separation chamber 40 is arranged to separate a two-phase fluid flow into a light and a heavy portion. The term two-phase is used to indicate a flow comprising at least two components having different densities, such that separation occurs in a swirling flow. The two phases may be liquid-liquid, gas-liquid, solid-liquid, or gas-solid. Also, as will be explained in more detail below, the two phases may be present in the fluid flow as received at the flow inlet 16, may be generated at or downstream of the swirl valve 100 or may be introduced by means of injection downstream of the swirl valve (as will be described in more detail further below) or a combination thereof. Generation of a new phase at or downstream of the swirl valve 100 may be the result of expansion and cooling of the fluid in the swirl valve 100 as a result of which liquid droplets may be formed by condensation. Of course, the term two-phase also covers flows comprising more than two components having different densities.
The heavy portion of the flow may comprise the hydrocarbon liquid when the light portion of the flow may be gas. Alternatively, the heavy portion of the flow may comprise water, when the light portion of the flow may be hydrocarbon liquid.
In case the separation involves removing liquids from gas (such as in JT-LTS systems) the light portion of the flow may be the product stream which needs no further treatment and the heavy portion of the flow may comprise liquids (such as water/glycol/hydrocarbons) and an entrained gas fraction, which require further treatment in a (reduced size) separator arrangement.
In case the separation process involves removing gases from a liquid (such as in oil stabilization trains) the heavy portion of the flow may be the product stream which needs no further treatment and the light portion of the flow may comprise gases (such as natural gas with liquid carry-over) which requires further treatment in a reduced separator arrangement. Alternatively, this may also be the other way around as described in the paragraph above.
In case the separation involves removing one liquid form another immiscible liquid (e.g. water from an oil) the light portion of the flow (i.e. oil) may be the product stream which needs no further treatment and the heavy portion of the flow may comprise the aqueous phase (e.g. water, glycol etc) and an entrained oil fraction, which requires further treatment in a reduced separator arrangement.
According to a further embodiment schematically depicted in
The settling chamber 30 may be provided to improve the separation efficiency by allowing the swirling motion to force the heavier components to the outer periphery and the lighter components to the centre.
The settling chamber 30 may be formed by a wall 31 that is axis symmetrical (with respect to the central axis 11) and may for instance be a conical shape or a cylinder shape.
The length L (as indicated in
Alternatively, when dealing with a bubbly flow said length L is chosen such that >99.5% of the bubble mass has reached a radial position equal to or smaller than inner radius R1 of the first duct 43 of the first flow outlet 41, such that they flow into the first duct 43 of the first flow outlet 41.
Depending on the feed conditions, the length L of the settling chamber 30 may be as small as 1 inlet diameter D-in of the settling chamber 30 up to 50 inlet diameters. The outlet diameter D-out of settling chamber 30 may vary typically from 1 times the inlet diameter D-in up to 4 times the inlet diameter D-in of settling chamber 30.
So, it will be understood that the settling chamber 30, although depicted in the drawings as a divergent settling chamber 30, may also be non-divergent/cylindrical.
The settling chamber 30 thereby generates a controlled deceleration of the swirling flow delivered by the swirl valve 100 and a vortex with a swirl factor that promotes growth and coalescence of condensed fluid droplets.
According to
It will be understood that the conical central body 15 may also be used in the embodiment shown in
The conical central body 15 may extend in a downstream direction into the settling chamber 30 or separation chamber 40. Instead of comprising a sharp extremity pointing in a downstream direction, as shown in
According to an embodiment, the swirl valve 100 is as described above with reference to
The heavier phase may be liquid droplets in a gaseous or liquid carrier or may be gas bubbles in a liquid carrier. The fluid flow received at the fluid inlet may be a two-phase fluid flow. Alternatively or in addition thereto, the two-phase character of the fluid flow may be the result of the expansion and cooling in the swirl valve.
In accordance with the above, there is provided a method to separate a fluid flow, the method comprises:
Injection Device
According to a further embodiment, the separation system comprises an injection device 60, 70 comprising an injection outlet 61, 71 positioned to inject a further inlet fluid into the swirling flow. The injection device 60, 70 may be connected to a further inlet fluid supply (not shown) and may be arranged to inject the further inlet fluid in the swirling flow, and may thus be positioned downstream with respect to the swirl valve 100.
The further inlet fluid is selected to selectively remove components from the fluid flow as received by the flow inlet 16. The further inlet fluid may either be a liquid—in case the component(s) to be removed are in the gas phase—or a gas—in case the component(s) to be removed are in the liquid phase. The first process is normally referred to as ‘absorption’, the second process is referred to as ‘stripping’. Two examples of such separation systems comprising injection devices are provided below with reference to
It will be understood that it is advantageously to create maximal interaction between the swirling flow and the further inlet fluid to maximize the separation efficiency. This can be done by injecting the further inlet fluid as a spray comprising a relatively high particle density. For instance, the injection device 60, 70 may be arranged to create a spray with a particle density of at least about 108/m3. Also, the injection device 60, 70 may be arranged to create spray particles with a size selected from one of a range from about 50 μm to about 0.2 μm, and a range from about 20 μm to about 1 μm. Maximal interaction between the swirling flow and the further inlet fluid may also be achieved by injection of the further inlet fluid in a direction having a substantially component in an upstream direction.
In order to obtain a maximum transfer of components from the swirling flow to the further inlet fluid the following design configurations are presented:
The first is discussed in more detail below with reference to
With reference to
The injection tube 62 may at least partially coincide with the central axis 11 and may have an injection outlet 61 at its extremity arranged to inject the further inlet fluid. To maximize the interaction between the flow and the further inlet fluid, the injection outlet 61 may further be arranged to inject the further inlet fluid in a (partially) upstream direction.
An advantage of using such a separation system in combination with an injection device 60 is that due to the large rotational motion (swirl), absorption liquids can be atomized in a micron size mist creating an enormous specific contact area for phase transfer, while still this absorption mist can be separated from the gaseous fluid exiting settling chamber 30.
A suitable droplet diameter of the atomized absorption liquid would be <20 micrometer, though preferably <10 micrometer. Suitable absorption liquids may include: Methanol, (Poly)Ethylene Glycol, Alcohols, DMEA, MEA, di-methyl ethers, ethane, propane, etc.
According to an example, the further inlet fluid may comprise at least one constituent for absorbing hydrogen sulphide or carbon dioxides. According to a further example, the further inlet fluid may comprise as constituent at least one of a Sulfolane and an ionic liquid. The ionic liquid may comprise at least one of a 1-butyl-3-methylimidazolium hexafluorophosphate and a 1-hexyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide.
With reference to
The injection ring 72 may be provided in the wall 31 of the settling chamber 30. The openings forming the injection outlet 71 may be provided on the inside of the injection ring 72. Again, to maximize the interaction between the flow and the further inlet fluid, the openings of the injection outlet 71 may further be arranged to inject the further inlet fluid in an upstream direction.
An advantage of such a separation system in combination with such an injection device 70 is that the large rotational motion (swirl) enables micron size bubbles to raise radial inwards through the rotating liquid film. A suitable bubble size of the dispersed stripping gas would be <50 micrometer thought preferably <20 micrometer.
Suitable stripping gases may include: Dew pointed natural gas, nitrogen etc.
The swirl valve as provided in the embodiments above, allows reducing the size of a separator train that is required downstream of the swirl valve to obtain sufficient separation. This allows for improved processing systems.
So there is provided a method as described above, comprising:
Processing Systems
The above embodiments can be used in process systems, examples of which are provided in
In general there is provided a processing system comprising at least one separation system SS1, SS2 according to the embodiments described above.
Gas Processing Systems
According to
a will now be described in more detail.
a shows a processing scheme wherein a high pressure natural gas flow 701 is received, which is pre-cooled in a pre-cooling unit PU. The pre-cooling unit PU may be a multi-stage pre-cooling unit. Of course, many different types of pre-cooling unit PU may be employed.
The pre-cooled gas flow 702 produced by the pre-cooling unit PU is connected to the flow inlet 16 of a first separation system SS1, wherein the separation system SS1 comprises a swirl valve 100, arranged to receive and control the flux of the fluid flow via the flow inlet 16 and to generate a swirling flow, swirling about a flow axis, and further comprising a separation chamber 40 and possibly a settling chamber 30 as described above.
The first output flow 703 via the first flow outlet 41 of the first separation system SS1, which is relatively cold, is fed back to the pre-cooling unit PU to cool the high pressure natural gas flow 701.
The second output flow 704 via the second flow outlet 42 of the first separation system SS1 is connected to a first separator vessel V1, HG.
The first separator vessel V1, HG produces a top flow 705 and a bottom flow 706. The separation process in the first separator vessel V1, HG may be gravitational driven.
The top flow 705 of the first separator vessel V1, HG is also connected to the pre-cooling unit PU to use the relatively cold gas obtained to cool the high pressure natural gas flow 701. The second output flow 704 via the second flow outlet 42 and the top flow 705 of the first separator vessel V1, HG are combined to form a cooling flow 708 for the pre-cooling unit PU.
The bottom flow 706 of the first separator vessel V1, HG, comprising a high pressure condensate, is connected to the flow inlet 16 of a second separation system SS2, wherein the second separation system SS2 comprises a swirl valve, arranged to receive and control the flux of the fluid flow via the flow inlet 16 and to generate a swirling flow, swirling about a flow axis, and further comprising a separation chamber 40 and possibly a settling chamber 30 as described above. The second separation system SS2 produces a further first output flow 713 via a further first flow outlet 41 and a further output flow 714 via a further second flow outlet 42.
With reference to
The hydrate-gas separator HG is of a mono-cyclone type as for instance published in EP1461134. The top section of the hydrate-gas separator HG removes the solid hydrates from the gas by inertia and gravitational settling. The settled hydrate solids entering the bottom section in which the hydrate solids are melted using internal heaters. The water evolving from the melting process can be separated from the non miscible hydrocarbon liquids which may also be present in this bottom section of the hydrate-gas separator HG. Due to gravitation, said two immiscible liquids will form a stratified liquid volume of a bottom layer of water, an intermediate layer of hydrates and a top layer of hydrocarbon liquids, in said bottom section of the hydrate-gas separator HG. The water and the hydrocarbon liquids may be separately drained from said bottom section.
According to a further embodiment, the processing system further comprises:
The further first output flow 713 of the second separation system SS2 is connected to an off gas compressor COM.
A top flow 715 of the second liquid-gas separator vessel V2 is also connected to the off gas compressor COM. The off gas compressor COM, which is driven by an engine M, produces a compressed outflow 718. This compressed outflow 718 is combined with the cooling flow 708 after having passed the pre-cooling unit PU and may comprise dew point natural gas.
Alternatively the remaining gas fraction evolving from second separation vessel V2 as top flow 715 or evolving from the discharge of the compressor 718, may be recycled and re-introduced in the second separation system SS2. In order to do this the second separation system SS2 may comprises a conical central body 15 which is substantially co-axial positioned along the central axis 11 in the swirl valve 100, having a gradually increasing cross-sectional area in an upstream direction. This was explained above with reference to
Instead of comprising a sharp extremity pointing in a downstream direction, as shown in
The further second output flow 714 of the second separation system SS2 may be connected to a second liquid-gas separator vessel V2. Said stream 714 is predominantly liquid though may contain small gas fractions. Also the liquids in 714 may contain both a hydrocarbon mixture as well as an aqueous mixture. The vessel V2 therefore may be designed as a 3 phase separator providing sufficient retention time for the minor gas fraction to rise to the liquid-gas interface where said gas is collected in the top dome of second separation vessel V2 and evacuated via outlet flow 715. Furthermore the second separation vessel V2 may contain internals to enhance the coalescence of the aqueous droplets present in the hydrocarbon liquid. These internals may comprise tilted plates, a porous medium or electrically charged plates. The aqueous liquids will be removed via outlet flow 716 and the hydrocarbon liquids via outlet flow 717.
Liquid Processing Systems
According to
The separation system SS may be in accordance with the embodiments described above. The combination of such a separation system SS and a further separation vessel V3, V4 provides an efficient and space-saving processing system. It will be understood that the separation vessels V3 and V4 may also be replaced by traditional inline or compact separators in order to further reduce the volume, weight and containment of the processing system. Such compact separators are disclosed in EP1600215 and WO2008020155.
a schematically depicts an embodiment, wherein the separation vessel V3 is arranged to receive the second output flow 804, and the top flow 805 of the separation vessel V3 is combined with the first output flow 803, the processing system further comprising a gas compressor COM arranged to receive the combined first output flow 803 and the top flow 805 of the separation vessel V3.
According to this embodiment, the separation vessel is a gas-liquid separation vessel V3 in which the separation is gravity driven. The bottom flow 806 of this separation vessel V3 is low pressure stabilized oil.
According to a further embodiment shown in
c schematically depicts an embodiment, wherein the separation vessel V4 is arranged to receive the first output flow 803, and the bottom flow 816 of the separation vessel V4 is combined with the second output flow 804, the processing system further comprising a gas compressor COM arranged to receive the top flow 815 of the separation vessel V4.
The compressor COM produces a compressed flow 820, that may be used in an advantageous way, it is to pre-heat the high pressure oil flow 802. So there is provided an embodiment, wherein the processing system further comprises a pre-heater unit PH and the gas compressor COM is arranged to produce a compressed flow 820, which is guided to the pre-heater unit PH to pre-heat the high pressure oil flow 802.
Examples of this are schematically depicted in
The horizontal separation vessels V3 are fed by the second flow outlet 804 of the separator system SS which, in use, outputs mainly oil/hydrocarbon liquid, and remove the remaining gas fraction from the oil/hydrocarbon liquid. These separation vessel V3 may be operated at elevated temperatures typically 10-50° C. above the feed temperature.
The vertical separation vessels V4 are fed by the first flow outlet 803 gas outlet of the separation system SS and removes the remaining liquid phase from the gas before entering the gas compressor COM.
The schemes from
Processing Methods
In accordance with the embodiments provided above with reference to
The method may be a gas processing method and comprises:
Further provided is a method, wherein the method is a liquid processing method and the method comprises:
The separation vessel V4 may be arranged to receive the first output flow 803, and the method may further comprise:
The gas compressor COM may be arranged to produce a compressed flow 820 and the method further comprises:
Hydrates
The embodiments described above with reference to
To avoid deposition of solids, according to the prior art, production chemicals are frequently used. The use of inhibition chemicals and/or heaters may be logistically complex and expensive and may incur a certain amount of risk to field personnel. Above all, results are far from optimal.
According to a further embodiment, a possibility is provided to process the gas without inhibiting chemicals.
For instance to avoid the accumulation of hydrate deposition, the internal surfaces of the apparatus can be coated with an icephobic coating. A suitable icephobic coating would be a fluorinated diamond like carbon (F-DLC). It is required that the surface roughness of said coating (and the underlying surface) is less than 0.05 micrometer in all directions though more preferably less than 0.02 micrometer in all directions. Any coating layer can be suitable as long as the static water contact angle on said surface is more than 90° or more preferably more than 110° while maintaining a difference between the advancing water contact angle and the receding water contact angle on said surface (i.e the hysteresis) of less than 25° but more preferably less than 15°.
All interior surfaces of the different parts of the embodiments provided above may be coated, such as tubes, pipes, valves, especially where cold fluids pass the tubes, or the heat-exchanger PU shown in
Further Remarks
Important aspect of the embodiments described above, is that the swirl valve, the separation system comprising such a swirl valve and the processing systems as described above all use the available free pressure in the fluid to create a swirling motion which in terms of angular momentum is an order of magnitude higher than conventional inline cyclonic separators.
A further advantage of the above embodiment is that in turn down mode the ratio of angular momentum/axial momentum slightly increases thereby restoring high separation efficiencies at lowered flow rates, unlike traditional inline cyclone separators where this ratio of angular/axial momentum decreases.
The swirl valve creates bigger droplets, increasing the separation efficiency. This is explained in more detail with reference to
Since most separators can be characterized by a typical separable diameter (i.e. cut-off diameter), the improvement of the swirl valve in conjunction with a separator, can be illustrated by the following graph. The meaning of the cut-off diameter is that droplets having a diameter that is above the cut-off diameter will be separated. The cut-off diameter may for instance be 20 μm.
The swirl valve increases the mean diameter, thereby increasing the separation efficiency. An example of this is shown in
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.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/NL2009/050181 | 4/7/2009 | WO | 00 | 12/8/2011 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2010/117259 | 10/14/2010 | WO | A |
| Number | Name | Date | Kind |
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| 6280502 | van Veen et al. | Aug 2001 | B1 |
| 6730236 | Kouba | May 2004 | B2 |
| 20030145724 | Betting et al. | Aug 2003 | A1 |
| 20090031756 | Betting et al. | Feb 2009 | A1 |
| Number | Date | Country |
|---|---|---|
| 1 974 790 | Oct 2008 | EP |
| 2006070020 | Jul 2006 | WO |
| 2006089948 | Aug 2006 | WO |
| 2009002174 | Dec 2008 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20120090467 A1 | Apr 2012 | US |
