Vertical axial gas-liquid cyclone with high capacity

Abstract

The present invention relates to a cyclone for separating fluid from a gas-liquid-mixture comprising: a) a first hollow body, wherein the first hollow body comprises a peripheral wall, a lower end, an upper end and a swirl element, wherein the upper end as well as the lower end of the first hollow body are open, the peripheral wall comprises at least one perforation and the swirl element is provided in the first hollow body at or above its lower end, and b) a second hollow body, wherein the second hollow body comprises a peripheral wall, a lower end and an upper end, wherein the second hollow body partially surrounds the first hollow body so that one or more channels having each an upper end and a lower end are formed between the outer side of the peripheral wall of the first hollow body and the inner side of the peripheral wall of the second hollow body, wherein the lower end of the second hollow body is located in a vertical distance above the lower end of the first hollow body, wherein each upper end of the one or more channels is fluid tightly closed and each upper end of the one or more channels is partially closed so that one or more openings are formed therein, and wherein the vertical distance between the lower end of the first hollow body and the lower end of the second hollow body is 10 to 40% of the height of the first hollow body.

Description

[0001] Vertical axial gas-liquid cyclone with high capacity

[0002] The present invention relates to a cyclone for separating fluid from a gas-liquid- mixture, to a tray comprising a tray deck, at least one liquid drainage and a plurality of such cyclones as well as to a column comprising at least one such tray, such as in particular a gas-liquid scrubber.

[0003] The main goal of a gas-liquid scrubber is to remove liquid from a mixture comprising gas and liquid and in particular to remove liquid from a mixture comprising gas and comparable small liquid droplets being dispersed in the gas. For this purpose, gas-liquid scrubbers comprise at least one cyclone deck for removing liquid and in particular liquid droplets from the gas phase by centrifugal force. Since these cyclones do not satisfactorily work if the liquid droplets are too small, usually one or more coalescing devices, such as one or more demisters, for instance one or more mesh type demisters, are arranged upstream of the cyclone deck, in order to coalesce the small liquid droplets contained in the gas-liquid mixture to liquid droplets having a sufficiently large droplet size so that they are efficiently removed in the downstream cyclone deck. However, such meshes have the drawback of being prone to fouling, which limits their lifetime and / or require often maintenance. In view of this, coalescing devices comprising vane packs are often used as alternative to mesh type demisters. Also other demister types have been proposed. However, all these rely on a calescence of small liquid droplets to larger liquid droplets as preparation for the liquid removal in a cyclone deck instead of removing significant amounts of liquid from the gas-liquid mixture, and are limited concerning their capacity and efficiency. In view of this, the object underlying the present invention is to provide a cyclone for separating fluid from a gas-liquid-mixture, which is particularly suitable to be used instead of the aforementioned mesh type demisters and coalescing devices comprising vane packs in a gas-liquid scrubber or in a similar column, wherein the cyclone has a high capacity for efficiently removing liquid droplets and even small liquid droplets from the gas phase from a mixture of gas, in which the liquid droplets are dispersed, wherein the cyclone is cost-efficient.

[0004] In accordance with the present invention, this object is solved by providing a cyclone for separating fluid from a gas-liquid-mixture comprising: a) a first hollow body, wherein the first hollow body comprises a peripheral wall, a lower end, an upper end and a swirl element, wherein the upper end as well as the lower end of the first hollow body are open, the peripheral wall comprises at least one perforation and the swirl element is provided in the first hollow body at or above its lower end, and b) a second hollow body, wherein the second hollow body comprises a peripheral wall, a lower end and an upper end, wherein the second hollow body partially surrounds the first hollow body so that one or more channels having each an upper end and a lower end are formed between the outer side of the peripheral wall of the first hollow body and the inner side of the peripheral wall of the second hollow body, wherein the lower end of the second hollow body is located in a vertical distance above the lower end of the first hollow body, wherein each upper end of the one or more channels is fluid tightly closed and each lower end of the one or more channels is partially closed so that one or more openings are formed therein, and wherein the vertical distance between the lower end of the first hollow body and the lower end of the second hollow body is 10 to 40% of the height of the first hollow body. Surprisingly, such a cyclone comprising only one or very few mechanical parts as swirl element and thus being cost-efficient has a high capacity and allows to remove liquid and in particular comparable small liquid droplets having a droplet size, such as those having for example a droplet size of 1 pm to 5 mm from a gasliquid mixture with a particular high separation efficiency. This is mainly due to the fact that each lower end of the one or more channels being defined between the outer side of the peripheral wall of the first hollow body and the inner side of the peripheral wall of the second hollow body is partially closed so that one or more openings are formed therein. On account of the fact that each lower end of the one or more channels is partially closed, the total area of all openings is smaller than the total cross-sectional area of all channels. Thereby, the amount of gas flowing through the perforations provided in the peripheral wall of the first hollow body into the at least one channel and thus through the at least one opening of the at least one channel may be easily and precisely controlled so as to avoid a flooding of the cyclone. Namely, if too much gas flows through the at least one opening of the at least one channel, the liquid exiting the opening may not or at least not completely flow downwardly, as desired, but will be - at least partially - dragged vertically upwardly in the gas phase. Moreover, the at least one channel terminates the rotational or helical flow generated within the first hollow body by the swirl element, thus allowing the liquid exiting the at least one opening to flow in a controlled manner downwards, such as onto a tray deck and from there to a drainage opening being provided in the tray deck. Thus, the cyclone allows to efficiently separate liquid from the gas phase by feeding the gas-liquid mixture into the lower end of the first hollow body, by generating a helical upwardly flow of the gas-liquid mixture by the swirl element thereby guiding the liquid droplets by centrifugal force onto the inner side of the peripheral wall of the first hollow body so that liquid and a controlled amount of gas pass through the perforations into the at least one channel, in which the helical upwardly flow of the gas and liquid droplets is terminated and the gas and liquid droplets are deflected downwardly and exit the cyclone through the at least one opening, whereupon the gas rises vertically upward- ly, whereas the liquid droplets flow vertically downwards. Furthermore, it has been surprisingly found that a vertical distance between the lower end of the first hollow body and the lower end of the second hollow body of 10 to 40% and particularly of 15 to 35% leads to an optimal separation efficiency. While a vertical distance of 50% or more leads to an unexpected collapse of the vortex generated by the swirl element and hence to a decrease of the separation efficiency, even a low vertical distance of less than 10%, such as of about 5%, leads to an unexpected gas maldistribution, in particular a reversal of the gas flow in the upper section, along the perforations in the peripheral wall of the first hollow body and thus a decrease in separation efficiency. All in all, the cyclone in accordance with the present invention has a high capacity for efficiently removing liquid droplets and even small liquid droplets from the gas phase from a mixture of gas, in which the liquid droplets are dispersed, wherein the cyclone is cost-efficient. Another advantage of the cyclone in accordance with the present invention is that several cyclones may be easily installed and optionally connected with each other on a horizontal deck, such as a tray deck of a gas scrubber. Furthermore, the cyclone does not require a box around it. This allows an easy modularization. On account of these reasons the cyclone is particularly suitable to be used instead of the aforementioned mesh type demisters and coalescing devices comprising vane packs in a gas-liquid scrubber or in a similar column. The cyclone in accordance with the present invention may be used in the gas-liquid scrubber or in a similar column alone or in any arbitrary combination with one or more conventional cyclones.

[0005] In accordance with the present invention, the cyclone comprises a first hollow body. In principle, the present invention is not particularly limited concerning the cross-sectional form of the first hollow body. Thus, the first hollow body may have a circular, oval, elliptic, square, rectangular or polygonal cross-sectional form. However, good results are in particular obtained, when the first hollow body has a circular, oval or elliptic cross-sectional form. Yet more preferably, the first hollow body has a circular cross-sectional form, i.e. the peripheral wall of the first hollow body has a circular cross-section so that the first hollow body is a hollow cylindrical tube or a hollow truncated cone. Most preferably, the first hollow body is a hollow cylindrical tube.

[0006] In a further development of the idea of the present invention, it is suggested that the ratio of the length of the first hollow body divided by the longest distance of the cross-sectional area of the first hollow body is 2 to 7 and preferably 3 to 4. Thus, the first hollow body is preferably a vertical axial body. Length means the longest dimension of the first hollow body, which is - due to the vertical arrangement - in fact the height of the first hollow body. In the case that the first hollow body is a hollow cylindrical tube, the longest distance of the cross-sectional area of the first hollow body is its diameter so that the aforementioned numeric value ranges are the preferred ratio of the length of the first hollow body divided by the diameter of the first hollow body. In the case that the first hollow body is a hollow truncated cone, the longest distance of the cross-sectional area of the first hollow body is its average diameter seen over the length of the first hollow body so that the aforementioned numeric value ranges are the preferred ratio of the length of the first hollow body divided by the average diameter of the first hollow body.

[0007] In terms of absolute dimensions, it is preferred that the first hollow body has a longest distance of the cross-sectional area, or in case of a hollow cylindrical tube a diameter, or in case of a hollow truncated cone an average diameter, respectively, of 50 to 170 mm and preferably 70 to 120 mm. In addition, it is preferred that the height of the first hollow body is 200 to 700 mm and preferably 250 to 500 mm.

[0008] As set out above, the swirl element has the function to transform the mixture of gas and liquid droplets dispersed therein, which is fed into the cyclone via the lower end of the first hollow body as laminar or turbulent flow, within the first hollow body into a helical upwardly flow of a gas with liquid droplets being dispersed therein so that the liquid droplets are directed by centrifugal force onto the inner side of the peripheral wall of the first hollow body. Therefore, the swirl element is preferably arranged in the lowest longitudinal section of the first hollow body. In view of this, it is preferred that the swirl element is arranged so that it extends, seen in the vertical direction from the lower end to the upper end of the first hollow body, from a first point being located 0 to 20% and preferably 0 to 10% of the height of the first hollow body to a second point being located 1 to 10% and preferably 2 to 5% of the height of the first hollow body higher than the first point.

[0009] The present invention is not particularly restricted concerning the kind of swirl element being arranged in the first hollow body, as long as the swirl elements is able to generate within the first hollow body a helical upwardly flow of a gas with liquid droplets being dispersed therein. Good results are in particular obtained, when the swirl element comprises at least one, preferably at least two and more preferably 4 to 10 blades.

[0010] In order to allow the liquid droplets being dispersed in the gas phase to exit the first hollow body below its upper end, the peripheral wall of the first hollow body comprises at least one perforation, through which the liquid droplets being directed by centrifugal force onto the inner side of the peripheral wall flow through the peripheral wall of the first hollow body into the at least one channel being provided between the peripheral walls of the first and second hollow bodies, from which it exits the cyclone through the at least one opening. Perforation means in accordance with the present invention any opening in the peripheral wall, which allows liquid and gas to pass through the peripheral wall, irrespective of the form of the perforation. Thus, the at least one perforation may have any form, such as, seen in the length direction of the peripheral wall of the first hollow body, the form of a circle, a slit, an oval, an ellipse, a rectangle, a square or a polygon. Good results are in particular obtained, wherein the at least one perforation has, seen in the length direction of the peripheral wall of the first hollow body, the form of a slit, i.e. the perforation has a ratio of length divided by width of significantly higher than 1 , such as of at least 5:1 and more preferably of at least 10:1. Even more preferably, the at least one perforation has the form of a slit, which is sloped with regard to the vertical direction. Particularly preferably, the angle between the length direction of the at least one perforation in form of a slit and the vertical axis is 20 to 70°, more preferably 30 to 60°, even more preferably 40 to 50°, such as about 45°.

[0011] In view of the object of the at least one perforation in the peripheral wall of the first hollow body, it is particularly preferred that all of the at least one perforation are only arranged in the longitudinal section of the first hollow body, which is surrounded by the second hollow body and thus by a channel.

[0012] In order to fulfil the function, namely to let pass the liquid droplets being guided through centrifugal force - as a consequence of the helical upwardly flow having been generated by the swirl element - to the inner side of the peripheral wall through the peripheral wall of the first hollow body into the channels formed between the peripheral walls of the first and second hollow bodies, the peripheral wall of the first hollow body of the cyclone preferably comprises a plurality of perforations, such 2 to 100 and more preferably 4 to 16 perforations.

[0013] On account of the same reason, it is further preferred that the ratio of the total area of the perforations in the peripheral wall of the first hollow body divided by the total area of the longitudinal section of the peripheral wall of the first hollow body being surrounded by the second hollow body is 2 to 12% and preferably 3 to 7%. The total area of the peripheral wall is the total area of the wall including the total area of perforations.

[0014] In terms of absolute dimensions, it is preferred that each of the perforations in the peripheral wall of the first hollow body has, seen in the length direction of the peripheral wall of the first hollow body, an area 100 to 2,000 mm2 and more preferably 200 to 1 ,200 mm2. On account of the same reason, it is preferred that the total area of all perforations in the peripheral wall of the first hollow body is 2,000 to 8,000 mm2 and more preferably 3,000 to 6,000 mm2.

[0015] Also concerning the form of the second hollow body, the present invention is not particularly limited. For instance, the second hollow body may have, seen in its cross-section, the form of a circle, of an oval, of an ellipse, of a rectangle, of a square, of a polygon, of a rounded rectangle or of a rounded square. Preferably, the second hollow body has the form of a rounded rectangle.

[0016] In a further development of the idea of the present invention, it is proposed that the peripheral wall of the second hollow body of the cyclone touches the peripheral wall of the first hollow body at two or more different connection points thereby forming two or more channels. This has the advantage that the rotational or helical flow, respectively, of the gas-liquid mixture having been generated within the first hollow body by the swirl element is efficiently stopped within the channels, since a rotation or circulation, respectively, of the gas-liquid mixture along the outer side of the peripheral wall of the first hollow body is not possible, because it is terminated at the connection points, where the channels are interrupted. The number of connection points corresponds to the number of channels formed between the peripheral walls of the first and second hollow bodies. The number of connection points between the peripheral walls of the first and second hollow bodies depend on the forms of the first and second hollow bodies. In the case that the first hollow body has a circular cross-sectional form and that also the second hollow body has a circular cross-sectional form, no connection point is formed between both hollow bodies, if the second hollow body is concentrically arranged around the first hollow body, so that one channel is formed between the peripheral walls of the first and second hollow bodies. Or, at most one connection point is formed between both hollow bodies so that still one channel is formed between the peripheral walls of the first and second hollow bodies, if the second hollow body with a circular crosssection is not concentrically arranged around the first hollow body, but so that it touches the peripheral wall of the first hollow body at one point. However, in the case of a second hollow body having a square or rounded square cross-sectional form, the peripheral wall of the second hollow body may touch the peripheral wall of the first hollow body at two connection points so that two channels are formed between the peripheral walls of the first and second hollow bodies. In the case of a second hollow body having a rectangular or rounded rectangular cross-sectional form, the peripheral wall of the second hollow body may touch the peripheral wall of the first hollow body at four connection points so that four channels are formed between the peripheral walls of the first and second hollow bodies.

[0017] In accordance with the present invention, the lower end of the second hollow body is located in a vertical distance above the lower end of the first hollow body, wherein the vertical distance between the lower end of the first hollow body and the lower end of the second hollow body is 10 to 40%, in order to allow gas exiting the cyclone by flowing through the at least one opening of the at least one channel being formed between the peripheral walls of the first and second hollow bodies to change the flow direction after leaving the at least one opening from the downwardly to upwardly so as to ascend in the vertical direction, in order to prevent that the liquid droplets exiting the at least one opening downwardly splashes on the surface being arranged below the lower end of the cyclone, such as a tray deck, as well as in order to obtain an optimal separation efficiency. Good results are in particular obtained, when the vertical distance between the lower end of the first hollow body and the lower end of the second hollow body is 15 to 35% of the height of the first hollow body.

[0018] In terms of absolute dimensions, it is preferred that the vertical distance between the lower end of the first hollow body and the lower end of the second hollow body of the cyclone is 50 to 200 mm and more preferably 80 to 180 mm. In accordance with a further particularly preferred embodiment of the present invention, the ratio of the total cross-sectional area of all channels divided by the cross-sectional area of the first hollow body is 10 to 35% and preferably 15 to 30%. Thereby a good compromise is achieved between channel(s) being large enough so as to achieve a comparable large liquid-gas separation capacity of the cyclone, but small enough so as to avoid that the cyclone is flooded as consequence that the outside velocity becomes too high that the exiting gas drags liquid with it upwardly.

[0019] In view of this, it is particularly preferred that the largest gap width of the one or more channels is 5 to 30 mm and preferably 7 to 20 mm. Largest gap width means in this connection, seen in the cross-section of the cyclone, the largest distance between the outer side of the peripheral wall of the first inner hollow body and the inner side of the peripheral wall of the second inner hollow body of a line crossing the midpoint of the interior of the first hollow body.

[0020] In a further development of the idea of the present invention, it is suggested that the ratio of the total area of all openings of each channel divided by the cross- sectional area of the respective channel is 5 to 30% and preferably 12 to 20%. This allows to precisely control the amount of gas flowing through the channels and thus contributes to the avoidance that during the operation of the cyclone the cyclone is flooded as consequence that the outside velocity becomes too high that the exiting gas drags liquid with it upwardly as well as to the prevention that the liquid droplets exiting the openings downwardly splashes on the surface being below the lower end of the cyclone, such as a tray deck.

[0021] Preferably, the ratio of the total area of the perforations of the peripheral wall of the first hollow body divided by the total area of all openings of the channels of the second hollow body is 7 to 30 and preferably 12 to 22. This allows that a sufficient- ly high amount of liquid droplets may be removed via the perforations into the adjacent channel(s), thus leading to a high capacity of the cyclone.

[0022] In accordance with a further particularly preferred embodiment of the present invention, below each of the one or more openings of the one or more channels of the second hollow body a separation device for coalescing liquid droplets is arranged, wherein the separation device is preferably one or more of vanes, meshes or cyclonics. For instance, the cyclonic device may be a swirl element with blades leading to a rotation of the gas and thus helping to collect the liquid and drain it properly. A particular advantage of using a mesh with a specific porosity of for instance 90 to 99% is that the mesh allows to participate in the control the amount of gas exiting the cyclone via the openings, so that a flooding of the cyclone as consequence that the outside velocity of gas becomes too high that the exiting gas drags liquid with it upwardly, is avoided.

[0023] In accordance with a further aspect, the present invention relates to a tray comprising a tray deck and at least one above described cyclone, wherein the at least one cyclone is connected with its lower end of its first hollow body on the surface of the tray deck, and wherein the tray deck comprises at least one drainage opening. The at least one drainage opening allows that liquid which exited the at least one opening of the at least one channel of the cyclone and which is collected on the tray deck may flow to below the tray deck. A suitable example for a drainage opening is the opening of a downcomer.

[0024] Preferably, the tray comprises 30 to 200 and preferably 40 to 100 cyclones per square meter, all of which being arranged side by side, but spaced apart in distance to each other. In terms of absolute values, for instance the tray may comprise 10 to 100,000, more preferably 50 to 10,000 and most preferably 100 to 1 ,000 of the above described cyclones. The voids being formed between adjacent cyclones allow gas exiting the openings of the channels of the cyclones to ascend between the cyclones, instead of being forced to flow below the lower ends of the second hollow bodies of the cyclones. Good results are in particular obtained, when the horizontal distance between two adjacent cyclones is 90 to 180 mm and more preferably 100 to 150 mm.

[0025] In accordance with an alternative embodiment of the present invention, the tray comprises 10 to 100,000, preferably 50 to 10,000 and more preferably 100 to 1 ,000 of the above described cyclones, all of which being arranged side by side in touching connection to each other, wherein between adjacent cyclones at least one void is arranged through which gas may ascend between the adjacent cyclones upwardly.

[0026] Another aspect of the present invention is a column, which comprises two or more trays being arranged on top of each other, but spaced apart in distance to each other, wherein each of the trays comprises a tray deck with at least one drainage opening and at least one cyclone, wherein at least one of the trays comprises one or more of the above described cyclones.

[0027] The one or more other trays may comprise different cyclones.

[0028] In a further development of the idea of the present invention, it is proposed that the column is a separator or a mass transfer column, such as preferably a gas-liquid scrubber.

[0029] In accordance with a further aspect, the present invention relates to a method for separating fluid from a gas-liquid-mixture comprising the step of feeding a gasliquid-mixture into an above described cyclone through its lower end and of rotating the gas-liquid mixture through the swirl element so as to generate a helical upwardly flow of the gas-liquid-mixture. Again, gas-liquid-mixture means in particular a gaseous composition, in which liquid droplets are dispersed. Good results are in particular obtained, when the swirl angle of the helically upwardly flowing the gas-liquid-mixture, measured from the horizontal plane, is 20 to 60° and preferably 25 to 45°.

[0030] Specific embodiments in accordance with the present invention are subsequently described with reference to the appended drawings and by examples.

[0031] Fig. 1a is a longitudinal sectional view of a cyclone in accordance with one embodiment of the present invention.

[0032] Fig. 1 b is a perspective view of the cyclone shown in figure 1 a.

[0033] Fig. 1c is a top view of the cyclone shown in figure 1 a.

[0034] Fig. 2 is a schematic view of a tray in accordance with one embodiment of the present invention.

[0035] The cyclone 10 shown in figures 1a to 1c comprises a first hollow body 12 in form of a hollow cylindrical tube and a second hollow body 14, which partially surrounds the first hollow body 12. The first hollow body 12 comprises a peripheral wall 16, a lower end 18, an upper end 20 and a swirl element 22. While the upper end 20 as well as the lower end 18 of the first hollow body 12 are open, the peripheral wall 16 comprises a plurality of perforations 24, each of which having the form of a slit being sloped with its length axis with regard to the vertical direction or height axis of the cyclone 10, respectively, by about 45°. The swirl element 22 comprises several blades 28. The swirl element 22 extends from the lower end 18 of the first hollow body 12 along about 15% of the height of the first hollow body 12, i.e. along the vertical distance between the lower end 18 and the upper end 20 of the first hollow body 12. Also the second hollow body 14 comprises a peripheral wall 30, a lower end 32 and an upper end 34, wherein the second hollow body 14 partially surrounds the first hollow body 12, namely the upper longitudinal section of the first hollow body 12. More specifically, the second hollow body 14 extends with its lower end 32 from a position being located 30% of the height of the first hollow body 12 above the lower end 32 of the second hollow body 14 up to the upper end 20 of the first hollow body 12.

[0036] As shown in more detail in figure 1c, the second hollow body 14 has a rounded rectangular cross-sectional form so that its peripheral wall 30 touches the peripheral wall 16 of the first hollow body 12 at four connection points 36. Thereby, four channels 38, 38’, 38”, 38”’ are formed between the peripheral wall 30 of the second hollow body 14 and the peripheral wall 16 of the first hollow body 12, wherein each of the channels 38, 38’, 38”, 38’” has an upper end 40 and a lower end 42. The upper end 34 of the second hollow body 14 is closed by a top wall 44 so that neither gas nor liquid may pass through the upper end 40 of the channels 38, 38’, 38”, 38’”. In contrast thereto, the lower ends 42 of the channels 38, 38’, 38”, 38’” are partially closed by a bottom wall 46 so that one or more openings 48 are formed therein. Thus, the total area of the openings 48 in the bottom plate wall 46 is much smaller than the total cross-sectional area of all channels 38, 38’, 38”, 38’”. All of the perforations 24 are only arranged in the longitudinal section of the first hollow body 12, which is surrounded by the second hollow body 14 and thus by one of the channels 38, 38’, 38”, 38’”.

[0037] During the operation of the cyclone 10, a mixture of gas and liquid droplets dispersed therein is fed through the open lower end 18 into the first hollow body 12 and contacted with the swirl element 22, which generates a helical upwardly flow shown by the arrow 50. Thereby, the liquid droplets being heavier than the gaseous component are guided by centrifugal forces onto the inner side of the peripheral wall 16 of the first hollow body 12 and flow as indicated by the arrow 52 together with a minor portion of the gas as indicated by the arrow 54 through the perforations 24 into the channels 38, 38’, 38”, 38’”, whereas gas being essentially free of liquid droplets flows through the upper end 20 of the first hollow body 12 as indicated by the arrow 55. In the channels 38, 38’, 38”, 38’”, the helical upwardly flow is terminated, among others, because the upwardly flowing gas and liquid droplets are deflected at the top wall 44 and converted in a downwardly flow. The liquid droplets coalesce in the channels 38, 38’, 38”, 38”’ and flow out of the openings 48 and thereafter downwardly as indicated by the arrow 56, whereas the gas flows out of the openings 48 and thereafter upwardly as indicated by the arrow 58. The tray 60 shown in figure 2 comprises a tray deck 62 and a plurality of the above described cyclones 10, wherein all of the cyclones 10 are connected with their lower ends 18 of their first hollow bodies 12 with the surface of the tray deck 62. Furthermore, the tray deck 62 comprises several drainage openings 64. The cyclones 10 are arranged side by side, but spaced apart in distance to each other so that between adjacent cyclones enough space is present so as to allow gas exiting the channels (38, 38’, 38”, 38’”) to ascend upwardly.

[0038] Reference Numeral List

[0039] 10 Cyclone

[0040] 12 First hollow body

[0041] 14 Second hollow body

[0042] 16 Peripheral wall of the first hollow body

[0043] 18 Lower end of the first hollow body

[0044] 20 Upper end of the first hollow body

[0045] 22 Swirl element

[0046] 24 Perforations in peripheral wall of the first hollow body

[0047] 28 Blades of the swirl element

[0048] 30 Peripheral wall of the second hollow body

[0049] 32 Lower end of the second hollow body

[0050] 34 Upper end of the second hollow body

[0051] 36 Connection points between first and second hollow bodies

[0052] 38, 38’, 38”, 38’” Channel

[0053] 40 Upper end of a channel

[0054] 42 Lower end of a channel

[0055] 44 Top wall of a channel

[0056] 46 Bottom wall of a channel

[0057] 48 Opening in the bottom wall

[0058] 50 Arrow indicating a helical upwardly flow

[0059] 52 Arrow indicating the flow of liquid droplets through the perforations

[0060] 54 Arrow indicating the flow of gas through the perforations

[0061] 55 Arrow indicating the gas flow through the upper end of the first hollow body

[0062] 56 Arrow indicating the flow of liquid downwards of the openings Arrow indicating the flow of gas downwards of the openings Tray Tray deck Drainage openings on tray deck

Claims

Claims:1 . A cyclone (10) for separating fluid from a gas-liquid-mixture comprising: a) a first hollow body (12), wherein the first hollow body (12) comprises a peripheral wall (16), a lower end (18), an upper end (20) and a swirl element (22), wherein the upper end (20) as well as the lower end (18) of the first hollow body (12) are open, the peripheral wall (16) comprises at least one perforation (24) and the swirl element (22) is provided in the first hollow body (12) at or above its lower end (18), and b) a second hollow body (14), wherein the second hollow body (14) comprises a peripheral wall (30), a lower end (32) and an upper end (34), wherein the second hollow body (14) partially surrounds the first hollow body (12) so that one or more channels (38, 38’, 38”, 38”’) having each an upper end (40) and a lower end (42) are formed between the outer side of the peripheral wall (16) of the first hollow body (12) and the inner side of the peripheral wall (30) of the second hollow body (14), wherein the lower end (32) of the second hollow body (14) is located in a vertical distance above the lower end (18) of the first hollow body (12), wherein each upper end (40) of the one or more channels (38, 38’, 38”, 38’”) is fluid tightly closed and each lower end (42) of the one or more channels (38, 38’, 38”, 38’”) is partially closed so that one or more openings (48) are formed therein, and wherein the vertical distance between the lower end (18) of the first hollow body (12) and the lower end (32) of the second hollow body (14) is 10 to 40% of the height of the first hollow body (12).

2. The cyclone (10) in accordance with claim 1 , wherein the first hollow body (12) is a hollow cylindrical tube or a hollow truncated cone and is preferably a hollow cylindrical tube.

3. The cyclone (10) in accordance with claim 2, wherein the ratio of the length divided by the diameter of the first hollow body (12) is 2 to 7 and preferably 3 to 4.

4. The cyclone (10) in accordance with any of the preceding claims, wherein the swirl element (22) is arranged so that it extends, seen in the vertical direction from the lower end (18) to the upper end (20) of the first hollow body (12), from a first point being located 0 to 20% and preferably 0 to 10% of the height of the first hollow body (12) to a second point being located 1 to 10% and preferably 2 to 5% of the height of the first hollow body (12) higher than the first point.

5. The cyclone (10) in accordance with any of the preceding claims, wherein the swirl element (22) comprises at least one, preferably at least two and more preferably 4 to 10 blades (28).

6. The cyclone in accordance with any of the preceding claims, wherein the peripheral wall (16) of the first hollow body (12) comprises at least one perforation (24), wherein the at least one perforation (24) has, seen in the length direction of the peripheral wall (16) of the first hollow body (12), the form of a circle, a slit, an oval, an ellipse, a rectangle, a quadrat or a polygon.

7. The cyclone (10) in accordance with any of the preceding claims, wherein the ratio of the total area of the at least one perforation (24) divided by the total area of the longitudinal section of the peripheral wall (16) of the firsthollow body (12) being surrounded by the second hollow body (14) is 2 to 12% and preferably 3 to 7%.

8. The cyclone (10) in accordance with any of the preceding claims, wherein the peripheral wall (30) of the second hollow body (14) touches the peripheral wall (16) of the first hollow body (12) at two or more different connection points (36) thereby forming two or more channels (38, 38’, 38”, 38’”).

9. The cyclone (10) in accordance with any of the preceding claims, wherein the vertical distance between the lower end (18) of the first hollow body (12) and the lower end (32) of the second hollow body (14) is 15 to 35% of the height of the first hollow body (12).

10. The cyclone (10) in accordance with any of the preceding claims, wherein the ratio of the total cross-sectional area of all channels (38, 38’, 38”, 38’”) divided by the cross-sectional area of the first hollow body (12) is 10 to 35% and preferably 15 to 30%.11 . The cyclone (10) in accordance with any of the preceding claims, wherein the ratio of the total area of all openings (48) of each channel (38, 38’, 38”, 38’”) divided by the cross-sectional area of the respective channel (38, 38’, 38”, 38’”) is 5 to 30% and preferably 12 to 20%.

12. The cyclone (10) in accordance with any of the preceding claims, wherein below each of the one or more openings (48) of the one or more channels (38, 38’, 38”, 38’”) of the second hollow body (14) a separation device for coalescing liquid droplets is arranged, wherein the separation device is preferably one or more vanes, a mesh or cyclonic.

13. A tray (60) comprising a tray deck (62) and at least one cyclone (10) in accordance with any of the preceding claims, wherein the at least one cyclone (10) is connected with its lower end (18) of its first hollow body (12) with the surface of the tray deck (62), and wherein the tray deck (62) comprises at least one drainage opening (64).

14. A column comprising two or more trays (60) being arranged on top of each other, but spaced apart in distance to each other, wherein each of the trays (60) comprises a tray deck (62) with at least one drainage opening (64) and at least one cyclone (10), wherein at least one of the trays (60) comprises one or more cyclones (10) in accordance with any of claims 1 to 12.

15. A method for separating fluid from a gas-liquid-mixture comprising the step of feeding a gas-liquid-mixture into a cyclone (10) in accordance with any of claims 1 to 12 through its lower end (18) and of rotating the gas-liquid mixture through the swirl element (22) so as to generate a helical upwardly flow of the gas-liquid-mixture, wherein the swirl angle of the helically upwardly flowing the gas-liquid-mixture, measured from the horizontal plane, is 20 to 60° and preferably 25 to 45°.

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