Settling tray

Abstract

The utility model relates to a settling tower tray which comprises a liquid receiving area, a tower tray plate, an overflow weir, a downcomer and a riser, the riser is provided with a top end opening with an upward opening at the top end and a bottom end opening with a downward opening at the bottom end, and the whole wall of the riser between the top end opening and the bottom end opening is closed. An opening in the bottom end of the riser is communicated with the tower tray hole in the tower tray plate and is tightly connected or integrally formed with the tower tray plate on the whole circumference; the gas rising cap is designed to shield the whole area of the opening in the top end of the gas rising pipe on the upper portion, and a downward opening communicated with the interior of the gas rising pipe is jointly defined by the gas rising cap and the opening in the top end of the gas rising pipe on at least part of the perimeter of the lower edge of the gas rising cap; and the lower edge of the gas raising cap is not higher than the upper edge of the outlet weir.

Description

Technical Field

[0001] The utility model relates to a settling tray. Background Art

[0002] In many industries such as petrochemical, coal chemical, chlor-alkali industry, and fertilizer industry, when using a tower for separation, blockage problems are often encountered. Some are due to solid substances such as dust, sediment, coke powder, and catalyst in the gas or liquid material to be treated. Others will generate high-melting-point substances (such as inorganic salts, polymers, etc. in solid form) that are prone to fouling or coking during the mass transfer process due to reasons such as heating or chemical reactions.

[0003] When using a plate column, these solid substances will deposit on the tray plate, downcomer, or receiving area, preventing the passage of gas or liquid, blocking bubbling units such as sieve holes, floating valves, and fixed valves, and affecting the mass transfer efficiency and processing capacity of the tray. The fouling and solid particles in the material will partially or completely block the gas or liquid channels, reducing the separation efficiency of the tray. In severe cases, it will even completely lose the separation function, causing the tray to be unable to work and having to be frequently shut down for cleaning and then put back into use after treatment, which seriously affects normal production.

[0004] In the prior art, some technical solutions have been proposed to extend the available time of the tray by increasing the riser pipe and the height of the overflow weir.

[0005] Chinese Utility Model CN 201394374Y discloses a deep liquid layer anti-blocking tray. Rectangular or square tray holes are opened on the horizontal tray installed in the tower. Each tray hole corresponds to an anti-blocking spray hood. A separation plate for gas-liquid separation is installed at the top of the spray hood. Spray plates with spray holes are installed on the upper parts of both sides of the spray hood, and anti-blocking plates are installed on the lower parts of both sides of the spray hood. A liquid channel is provided between the spray plate and the anti-blocking plate of the spray hood. The liquid flowing down from the downcomer of the upper tray and higher than the liquid channel enters the spray hood from the channel, and the gas enters the rectangular tray hole from below each tray and then enters the spray hood. The gas entraining liquid in the spray hood sprays out from the spray holes on the spray plate, and mass transfer and heat transfer occur between the gas and the liquid. Then, the gas and the liquid are separated at the separation plate. The gas enters the upper tray, and the liquid falls back to the tray and flows to the lower tray through the downcomer. The space below the anti-blocking plate is used for settling the easily blocked substances contained in the liquid.

[0006] Chinese utility model CN ​​203971435 U discloses an anti-blocking type fixed valve tower plate, wherein a number of risers are evenly distributed on the tower plate, the risers are embedded in the tower plate and are higher than the tower plate by a certain height, and each riser is provided with a shielding structure, the shielding structure includes a horizontal top plate and at least two side plates, the horizontal top plate is located above the riser and has a gap with the upper end of the riser, the side plate is located on the outside of the riser and has a gap with the wall of the riser, the bottom end of the side plate is sealed with the tower plate, and the top end of the side plate is sealed with the horizontal top plate to support the horizontal top plate. Injection holes are provided on the side plates of the shielding structure. After sufficient contact between gas and liquid, the gas and liquid leave the shielding structure through the injection holes or the side of the shielding structure without side plates. Solid matter in the liquid settles in the area at the bottom of the riser without injection holes.

[0007] Chinese utility model CN ​​211755042 U discloses an anti-clogging spray tray, wherein a plurality of through holes are evenly arranged on the tray, and the through holes are fixedly connected to an inverted cap cover through a fixedly connected bracket, and a gap is formed between the lower edge of the cap cover and the tray, and a plurality of air outlets are arranged on the side wall of the cap cover. The bottom (gas) medium enters the cap cover after contraction through the through holes of the tray, and the upper (liquid) medium enters the cover from the gap between the tray and the cap cover, and the bottom medium pulls the upper medium entering the cap cover, and after film pulling, film breaking, and crushing, it hits the top of the cap cover, and after the collision, the gas or liquid returns and sprays out from the air outlet of the cap cover, and the liquid drops fall back to the tray, and the gaseous state rises and enters the upper tray.

[0008] Chinese utility model CN ​​212396755 U discloses an anti-blocking valve tray for tower equipment, wherein a plurality of tray holes are arranged on the tray plate, the tray holes are square or rectangular, and a tray hole shielding device is arranged on the tray plate at the tray holes. The tray hole shielding device comprises a top plate, two liquid blocking plates located at one opposite side of the tray hole, and two side plates located at the other opposite side of the tray hole, wherein the area of ​​the top plate is larger than the tray hole; the two liquid blocking plates are closing inclined plates inclined toward the tray hole, the height of the side plates is higher than the liquid blocking plates, and the heights of the two side plates are flush, the two side edges of the top plate are respectively connected to the two side plates, and the other two side edges of the top plate are respectively provided with baffles, wherein the baffles have an angle inclined downward from the lower edge of the connection of the top plate, and the contour of the lower edge of the baffles is serrated. The valve-fixed tray also comprises a cover plate covering all tray hole shielding devices.

[0009] Chinese utility model CN ​​215137010 U discloses a three-dimensional fixed valve tower plate, wherein the three-dimensional fixed valve is arranged above the tower plate and the bottom opening is connected to the corresponding opening. The three-dimensional fixed valve is multiple and at least two three-dimensional fixed valves have different heights. The three-dimensional fixed valve is provided with a spray hole.

[0010] A large-throughput anti-blocking tray is disclosed in Chinese Utility Model CN 218359288 U, which includes a tray plate. Plate holes are evenly formed in the tray plate. A riser pipe is provided on the plate hole. The top of the riser pipe is higher than the tray plate, and multiple layers of baffles are arranged in a staggered manner on the upper part of the riser pipe.

[0011] An umbrella-shaped structure cap is disclosed in Chinese Utility Model CN 219630645 U, which includes a cap body. Wings are provided at the top of the cap body and are inclined at a certain angle on both sides of the side baffle of the cap body and have a gap with the rectangular side baffle of the cap body. Wing holes are provided on the wings; side baffle holes are formed in the upper part of the rectangular side baffle. The gas passes through the wing holes to increase the turbulence degree of the liquid phase on the wings and prevent solid particles from depositing. The liquid on the tray enters the cap through the gap between the tray and the rectangular side baffle of the cap, mixes with the rising gas, and the gas-liquid mixture is ejected from the side baffle holes and then separated by the wings. The gas rises and the liquid falls back onto the tray plate.

[0012] In the above prior art, it is not possible to well prevent the sedimented solid substances from blocking the liquid passage. Summary of the Invention

[0013] In view of the above technical problems, the present utility model provides a sedimentation tray, which includes: a liquid receiving area for receiving liquid; a tray plate arranged side by side to form a tray plane for receiving the liquid from the liquid receiving area, and a plurality of tray holes penetrating the upper and lower surfaces are provided on the tray plate; an overflow weir arranged downstream of the tray plate in the liquid flow direction relative to the liquid receiving area for controlling the liquid level height on the tray plate; a downcomer arranged downstream of the overflow weir for enabling the liquid flowing out of the tray plate over the overflow weir to reach the liquid receiving area of the next layer of tray plane through the downcomer; wherein, the sedimentation tray further includes: a riser pipe having an upward-opening top opening at the top end and a downward-opening bottom opening at the bottom end, and the entire pipe wall of the riser pipe between the top opening and the bottom opening is closed. The bottom opening of the riser pipe is connected to the tray hole on the tray plate and is tightly connected or integrally formed with the tray plate over the entire circumference; a riser cap designed to shield the entire area of the top opening of the riser pipe above and jointly enclose a downward-opening communicating with the inside of the riser pipe at least partially along the circumference of the lower edge of the riser cap and the top opening of the riser pipe, and the lower edge of the riser cap is not higher than the upper edge of the overflow weir.

[0014] The gas flows downward through the annular space between the riser cap and the riser pipe to reach above the tray plate, mixes, transfers heat and mass with the liquid on the tray plate, then flows upward, separates from the liquid and enters the upper layer of the tray.

[0015] The riser and the riser cap together form a bubbling structure on the tray plate. The gas enters the riser from bottom to top through the tray hole. Since the bottom opening of the riser is tightly connected to the tray hole and preferably has a consistent shape, the gas can only continue to move upward until it is folded back by the riser cap. The riser cap and the riser together form a downward opening connected to the top opening of the riser on at least part of the circumference of the lower edge. This means that a gas channel is formed between the riser cap and the riser. The riser cap is suspended above the top opening of the riser, and the gas can be folded over the top opening of the riser and flow downward at least on at least part of the circumference of the riser cap. The liquid flows horizontally through the tray plate. Since the riser protrudes upward from the tray plate, and the liquid level is limited by the upper edge of the overflow weir, when the lower edge of the riser cap is not higher than the upper edge of the overflow weir, the gas sprayed downward from the riser through the riser cap is violently mixed with the liquid near the lower edge of the riser cap, forming turbulence there, and the gas and liquid achieve heat and mass transfer.

[0016] In the dirty blockage system, solid impurities are mainly deposited on the tower plate and the gas lift cap. When the sedimentation tower plate of the utility model is working, the gas reaches the gas lift cap and then turns back and flows downward to the tower plate on the outside of the gas lift pipe, and mixes violently with the liquid near the lower edge of the gas lift cap. This can effectively avoid the deposition of solid impurities in the gas channel. The solid impurities deposited on the tower plate have a sufficient height difference from the lower edge of the gas lift cap, so the deposited solid impurities will not block the gas channel, thereby greatly extending the operating cycle of the sedimentation tower plate.

[0017] In a scaling system with high alkalinity, scaling materials mainly grow along the rough surface, such as around the sieve hole or tongue hole, which will cause the sieve hole or tongue hole to become smaller and smaller, thus affecting the operation cycle. In this structure of the utility model, since the only rough surface in contact with the liquid is the lower edge of the gas lift cap, when scaling occurs, scaling materials usually occur on this rough surface and will not gather in the gas passage between the gas lift cap and the gas lift pipe. Therefore, the technical solution of the utility model greatly avoids the blockage of the gas passage of the settling tower plate with a simple structure, and also achieves the extension of the operation cycle.

[0018] According to a preferred embodiment of the settling tray of the utility model, the lower edge of the gas lift cap is at least flush with or lower than the height of the top opening of the gas lift pipe. In this way, when the gas reaches the gas lift cap and turns back and flows downward outside the gas lift pipe, the gas is better guided, mixed more intensely with the liquid near the lower edge of the gas lift cap, and the gas-liquid heat and mass transfer effect is better.

[0019] According to another preferred embodiment of the settling tray of the present utility model, the riser cap is supported on the riser pipe by a number of spaced-apart support members. There is a space through which gas can pass between the top opening of the riser pipe and the riser cap. For example, the above structure is achieved by struts. One end of the strut is supported on the top opening of the riser pipe or the inner wall of the pipe wall nearby, and the other end is supported on the inner wall of the bottom surface of the riser cap. Therefore, the gas in the riser pipe can smoothly pass through the gap between the support members and return to the outside of the pipe wall of the riser pipe.

[0020] However, according to another preferred embodiment of the settling tray of the present utility model, the riser cap can also be directly supported on the tray plate by a number of struts without acting on the riser pipe, as long as there is a space through which gas can pass between the riser cap and the top opening of the riser pipe.

[0021] According to a preferred embodiment of the settling tray of the present utility model, the riser cap has an inclined top and a side portion bent downward from the top, and the end of the side portion forms the lower edge of the riser cap. As an alternative or supplement, in another preferred embodiment of the settling tray of the present utility model, the riser cap has a flat top and a side portion bent downward from the top, and the end of the side portion forms the lower edge of the riser cap. It should be understood that the function of the riser cap is to shield the riser pipe from above to prevent the gas in the riser pipe from directly escaping upward without turning back, because if this happens, the gas cannot be fully mixed with the liquid on the tray plate to achieve heat transfer and mass transfer. Therefore, as long as the riser cap can leave enough space for gas to pass through, the shape of the top is not limited to the above-mentioned sloping top or flat top, but can be set into any shape.

[0022] According to a preferred embodiment of the settling tray of the present utility model, the riser pipe always has the same cross-sectional area in the extending direction. As an alternative embodiment, the riser pipe can also have a varying cross-sectional area in the extending direction. For example, the cross-sectional area of the riser pipe continuously narrows from bottom to top or first narrows and then increases. Preferably, the top opening of the riser pipe has a smaller cross-sectional area than the bottom opening of the riser pipe.

[0023] According to a preferred embodiment of the settling tray of the present utility model, the tray holes on the tray plate have a coincident horizontal projection with the lower edge of the riser cap on part of the perimeter. Optionally, the tray holes on the tray plate are surrounded at a distance by the lower edge of the riser cap on the entire perimeter.

[0024] The cross-section of the riser pipe is circular, elliptical, or polygonal (including triangle, square, rectangle, etc.). The riser cap can also have any shape that can cover the riser pipe.

[0025] Preferably, the lower edge of the gas-lifting cap is 0 to 50 mm lower than the top opening of the gas-lifting pipe. Preferably, the lower edge of the gas-lifting cap is 0 to 100 mm lower than the upper edge of the overflow weir. Preferably, the height of the gas-lifting pipe is 10 to 500 mm. Preferably, the width of the gas-lifting pipe is 25 to 300 mm, and the length is 50 to 1500 mm. When the cross-section of the gas-lifting pipe is circular, the diameter of the gas-lifting pipe is 25 to 300 mm. Description of the Drawings

[0026] The technical solution of the present utility model will be described below in conjunction with the drawings. In the drawings:

[0027] Figure 1 A schematic cross-sectional view of a sedimentation tray according to the present utility model installed in a container is shown;

[0028] Figure 2A A schematic top view of a sedimentation tray according to an embodiment of the present utility model is shown;

[0029] Figure 2B A schematic top view of a sedimentation tray according to an embodiment of the present utility model is shown;

[0030] Figure 2C A schematic top view of a sedimentation tray according to an embodiment of the present utility model is shown;

[0031] Figures 3A to 3C Schematic top views of a set of gas-lifting pipes and gas-lifting caps of a sedimentation tray according to an embodiment of the present utility model and two schematic cross-sectional views thereof are respectively shown;

[0032] Figures 4A to 4C Schematic top views of a set of gas-lifting pipes and gas-lifting caps of a sedimentation tray according to an embodiment of the present utility model and two schematic cross-sectional views thereof are respectively shown;

[0033] Figures 5A to 5C Schematic top views of a set of gas-lifting pipes and gas-lifting caps of a sedimentation tray according to an embodiment of the present utility model and two schematic cross-sectional views thereof are respectively shown; and

[0034] Figures 6A to 6C Schematic top views of a set of gas-lifting pipes and gas-lifting caps of a sedimentation tray according to an embodiment of the present utility model and two schematic cross-sectional views thereof are shown.

[0035] The drawings are only used to explain the present utility model and should not be construed as a limitation to the present utility model. The same reference numerals represent the same technical features, and they are schematic rather than restrictive. Detailed Embodiments

[0036] Figure 1The sectional schematic view of the sedimentation tray according to the present utility model installed in a container is shown. The sedimentation tray 1 is arranged in the container in a multi-layer form. In a typical container for gas-liquid heat transfer and mass transfer, gas is provided from the lower part of the container and flows upward. Liquid is provided from above the container and flows downward. The sedimentation tray 1 of the same layer includes a liquid receiving area 10, a tray plate 20, an overflow weir 30 and a downcomer 40. The liquid receiving area 10 receives the liquid falling from above. According to the size of the container, there may be multiple tray plates 20, which are arranged side by side to form a tray plane for receiving the liquid from the liquid receiving area 10. The tray plate 20 has a number of tray holes 210 penetrating the upper and lower surfaces. The overflow weir 30 is arranged relative to the liquid receiving area 10 downstream of the tray plate 20 in the liquid flow direction for controlling the liquid level height on the tray plate 20. The downcomer 40 is arranged downstream of the overflow weir 30 in the liquid flow direction. The liquid flowing out of the tray plate 20 and overflowing the overflow weir 30 reaches the liquid receiving area 10 of the next lower tray plane through the downcomer 40.

[0037] Each tray hole 210 of the tray plate 20 corresponds to a riser pipe 50. The riser pipe 50 has a top opening 510 with an upward opening at the top end and a bottom opening 520 with a downward opening at the bottom end. The entire pipe wall of the riser pipe 50 between the top opening 510 and the bottom opening 520 is closed. The bottom opening 520 of the riser pipe 50 is communicated with the tray hole 210 on the tray plate 20 and is tightly connected or integrally formed with the tray plate 20 over the entire circumference. In this way, the liquid on the tray plate 20 has no passage to enter the interior of the riser pipe.

[0038] On the contrary, the riser cap 60 is designed to cover the entire area of the top opening of the riser pipe 50 from above and jointly enclose a downward opening communicating with the interior of the riser pipe 50 with the top opening 510 of the riser pipe 50 at least on part of the circumference of the lower edge 610 of the riser cap 60. The lower edge 610 of the riser cap 60 is not higher than the height of the upper edge of the overflow weir 30. Thus, the gaseous substance entering the interior of the riser pipe 50 from the lower layer through the tray hole 210 can only turn back and cross the pipe wall of the riser pipe 50 after encountering the riser cap and leave the riser cap downward through the downward opening jointly formed by the upper edge of the riser pipe 50 and the lower edge 620 of the riser cap. At this position of leaving the riser cap, intense heat transfer and mass transfer occur between the gas and the liquid. Different from the prior art, the riser pipe has no side wall through holes, and the gas in the riser pipe does not leave the riser cap laterally but downward. In this structure, the rough surface (such as the cutting surface during processing) in contact with the liquid is only the lower edge 610 of the riser cap 60, but the lower edge 610 is not in the gas passage, and even if fouling occurs on it, it will not block the gas passage.

[0039] When the gas lift cap 60 is designed so that its lower edge 610 is at least flush with or lower than the height of the top opening 510 of the gas lift pipe 50, the gas can be better guided when it reaches the gas lift cap and turns back and flows downward on the outside of the gas lift pipe, and mixes more intensely with the liquid near the lower edge of the gas lift cap, thereby achieving better heat and mass transfer effects between gas and liquid.

[0040] The riser 50 can be surrounded by the riser cap 60 at intervals over the entire circumference. This, for example, forms an annular gas passage around the upper edge of the riser 50. In fact, it is only necessary to arrange a number of support rods connecting the inner bottom surface of the riser cap 60 and the riser 50 at several points on or near the upper edge of the riser 50. These support rods occupy a very small proportion of the gas passage and are not shown in the figure. However, it is obvious that according to a variant implementation, part of the circumference of the riser 50 can also be directly extended to the riser cap 60 to support the latter, while the remaining part of the circumference is open to the gas passage.

[0041] Of course, the gas lift cap may not be supported on the gas lift pipe, but may be directly supported on the tower plate, for example, by a number of support rods. To save space, this embodiment is not shown here as a preferred embodiment.

[0042] In terms of shape, the riser 50 and the riser cap 60 can be of any shape, as long as the former can be completely covered by the latter in horizontal projection and can properly support the latter and leave a gas passage, because this can play the role of returning the airflow in the riser 50 to flow downward.

[0043] The upper edge of the overflow weir 30 has a higher height than the air lift cap 60, such as Figure 1 As shown. The upper edge of the overflow weir 30 is used to control the liquid level on the tower plate 20, which means that the lower edge of the gas lift cap 60 will be completely inserted below the liquid surface. Combined with the design that the lower edge 610 of the gas lift cap 60 is at least flush with or lower than the upper edge of the gas lift pipe 50, this effectively ensures that the gas is ejected downward from the bubbling device composed of the gas lift pipe 50 and the gas lift cap 60, while avoiding the possibility of liquid backflow into the gas lift pipe 50.

[0044] Figures 2A to 2C Schematic top views of settling tower plates according to different embodiments of the present invention are shown respectively. Figures 2A to 2C In the embodiment shown, after the liquid falls into the liquid receiving area 10 on the left side of the figure, it flows to the right through all the bubbling devices on the tower plate 20, that is, the combination of the air riser 50 and the air riser cap 60, and then crosses the overflow weir 30 and falls from the downcomer 40 to the liquid receiving area of ​​the lower layer. Figure 2AThe top views of the riser pipe 50 and the riser cap 60 are both rectangular. The riser cap 60 completely surrounds the riser pipe 50 in all perimeter directions with a gap left. The riser cap 60 can be, for example, in the shape of an arcuate vault and is supported on the riser pipe 50 by struts (not shown). Figure 2B Differing from Figure 2A is that the top-view rectangular shapes of the riser pipe 50 and the riser cap 60 have orthogonal rectangular orientations in Figure 2B and Figure 2A respectively. Figure 2C The circular riser cap 60 and riser pipe 50 are shown in

[0045] Correspondingly, Figures 3A to 6C Top-view schematic diagrams of four groups of riser pipes and riser caps of the settling tray according to the implementation forms of the present utility model and two sectional schematic diagrams of each of them are shown respectively. Differing from Figures 2A to 2C are that Figures 3A to 5C the three groups of riser pipes and riser caps shown are completely enclosed on two sides of the rectangle (preferably the short sides here) to form mutual support, while on the other two sides (preferably the long sides here) gas passages are formed. Figures 6A to 6C shows a group of rectangular riser pipes and riser caps that are separated with intervals both inside and outside on all four sides, that is, Figure 2A or Figure 2B the bubbling device in the shown implementation form. Figures 3A to 4C Two implementation forms with riser caps in the shape of a sloping top are shown, and their difference lies in the riser pipes with different cross-sectional shapes. Figures 3A to 3C In the implementation form shown in Figures 4A to 4C the riser pipe 50 tapers upward, while Figures 5A to 5C in the implementation form shown in

[0046] The preferred embodiments of the present utility model are described above, but the spirit and scope of the present utility model are not limited to the specific content disclosed here. Those skilled in the art can arbitrarily combine and expand the above embodiments according to the teachings of the present utility model and make more implementation modes and applications within the spirit and scope of the present utility model. The spirit and scope of the present utility model are not defined by the specific embodiments, but by the claims.

[0047] List of reference numerals

[0048] 1 Settling tray

[0049] 10 Liquid receiving area

[0050] 20 Trays

[0051] 210 Tray Holes

[0052] 30 Overflow Weir

[0053] 40 Downcomer

[0054] 50 Uplift Pipe

[0055] 510 Top Opening

[0056] 520 Bottom Opening

[0057] 60 Uplift Cap

[0058] 610 Lower Edge

Claims

1. A settling tray, comprising: A liquid receiving area, the liquid receiving area is used to receive liquid; A tray plate, the tray plates are arranged side by side to form a tray plane, for receiving the liquid from the liquid receiving area, and the tray plate has a plurality of tray holes penetrating the upper and lower surfaces; An overflow weir, which is arranged downstream of the tray in the liquid flow direction relative to the liquid receiving area and is used to control the liquid level height on the tray; A downcomer, which is arranged downstream of the overflow weir and is used to allow the liquid flowing on the tray plate and overflowing the overflow weir to reach the liquid receiving area on the plane of the next tray layer from the downcomer; Characterized in that the settling tower tray also includes: A riser, wherein the riser has a top opening opening upward at the top and a bottom opening opening downward at the bottom, the entire tube wall of the riser between the top opening and the bottom opening is closed, the bottom opening of the riser is connected to the tray hole on the tray plate and is tightly connected or integrally formed with the tray plate over the entire circumference; An air riser cap is designed to cover the entire area of ​​the top end opening of the air riser from above and to form together with the top end opening of the air riser on at least a portion of the circumference of the lower edge of the air riser cap a downward opening connected to the interior of the air riser, and the lower edge of the air riser cap is not higher than the height of the upper edge of the overflow weir.

2. The settling tray according to claim 1, characterized in that: The lower edge of the air riser cap is at least flush with or lower than the height of the top end opening of the air riser.

3. The settling tray according to claim 1, characterized in that: The air lifting cap has an inclined top and a side portion bent downward from the top, and a terminal end of the side portion forms a lower edge of the air lifting cap.

4. The settling tray according to claim 1, characterized in that: The air lifting cap has a flat top and a side portion bent downward from the top, and a terminal end of the side portion forms a lower edge of the air lifting cap.

5. The settling tray according to claim 1, characterized in that: The riser has the same cross-sectional area from bottom to top.

6. The settling tray according to claim 1, characterized in that: The riser has a cross-sectional area that changes from bottom to top.

7. The settling tray according to claim 1, characterized in that: The cross section of the riser is circular, elliptical or polygonal.

8. The settling tray according to claim 2, characterized in that: The lower edge of the air riser cap is 0 to 50 mm lower than the top end opening of the air riser.

9. The settling tray according to claim 1, characterized in that: The lower edge of the air lift cap is 0 to 100 mm lower than the upper edge of the overflow weir.

10. The settling tray according to claim 1, characterized in that: The height of the riser is 10 to 500 mm.

11. The settling tray according to claim 1, characterized in that: The riser has a width of 25 to 300 mm and a length of 50 to 1500 mm.

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