CONTACT TRAY HAVING A Baffle WALL FOR CONCENTRATING LOW-FLOW LIQUID FLOW AND

Abstract

The present invention provides a contact tray for a mass transfer or heat exchange column and having a plurality of baffle walls that cause a liquid flowing on an upper surface of a tray plate tray to change its flow direction when the liquid flows from an inlet region on the tray plate to an outlet, and the width of the flow path is reduced and the length of the flow path is increased. By reducing the flow path, the volumetric flow rate of the liquid at any portion of the plate is increased, and the opportunity that the liquid entrains vapor at low liquid flow rates is reduced. A downcomer extends downwardly from the outlet to receive liquid as it enters the outlet and then deliver it downwardly to a discharge outlet at a lower end of the downcomer.

Description

[0001] This application is a divisional application of Chinese invention patent application No. 201880005714.8 (entry date into the Chinese national phase: July 1, 2019; invention title: contact tray having baffle walls for concentrating low-velocity liquid flow and a method thereof). Background Technology

[0002] The present invention relates generally to towers in which mass transfer and heat exchange occur, and more specifically to contact trays for use in such towers to facilitate interaction between fluid flows flowing into the tower, and methods for using the contact trays for mass transfer and / or heat exchange.

[0003] Mass transfer columns are configured to contact at least two inflowing fluid flows in order to provide a product stream with a specific composition and / or temperature. As used herein, the term "mass transfer column" is intended to encompass columns in which mass and / or heat transfer is the primary objective. Some mass transfer columns, such as those for multicomponent distillation and absorption applications, contact a vapor stream with a liquid stream, while others, such as extraction columns, may be designed to facilitate contact between two liquid phases of different densities. Typically, mass transfer columns are configured to contact an upward vapor or liquid stream with a downward liquid stream, usually along multiple trays or other mass transfer surfaces disposed within the column.

[0004] Various types of trays are commonly used in mass transfer columns to facilitate the required contact and mass transfer between upward and downward fluid flows. Each tray typically extends horizontally across substantially the entire horizontal cross-section of the column and is supported around its perimeter by a support ring welded to the inner surface of a circular column wall or shell. Multiple trays are positioned in this manner with uniform vertical spacing between adjacent trays. The tray may be positioned only in a portion of the column to perform part of a multi-step process utilizing the column. Alternatively, the tray may be positioned along substantially the entire vertical height of the column.

[0005] The aforementioned type of tray includes one or more downcomers positioned at the outlet opening in the tray to provide a passage for liquid to descend from one tray to an adjacent lower tray. Before entering the downcomer, the liquid on the tray interacts with rising vapor through orifices provided in selected sections of the tray, then flows over the outlet weir into the outlet opening in the tray. Those areas of the tray containing the vapor orifices are often referred to as the "active" areas because vapor mixing and foaming occur above those areas of the tray.

[0006] At low liquid flow rates, such as less than 25 US gallons per minute (25 gpm per foot of flow path width), most of the liquid flowing through the active zone of the tray can be entrained as droplets in the rising vapor and carried by the vapor to the upper tray. Smaller entrained droplets can be carried by the vapor through the vapor orifices in the upper tray, while larger droplets can impact the lower surface of the upper tray and form a film thereon. A portion of this film can then be carried by the vapor through the vapor orifices in the upper tray. When this entrained liquid is carried by the vapor through the vapor orifices, it restricts the cross-sectional area available for vapor flow and increases the pressure drop across the entire tray. The entrained liquid also bypasses the necessary interaction with the vapor on the lower tray, leading to reduced operating efficiency.

[0007] Therefore, there is a need for improved trays that can reduce liquid entrainment in rising vapor during periods of low liquid flow rate. Summary of the Invention

[0008] In one aspect, the present invention relates to trays for use in mass transfer towers to facilitate the interaction between fluids as they flow within the tower. The tray includes a tray plate having an upper surface; an inlet region on the tray plate for receiving liquid flowing downward onto the upper surface of the tray plate; a plurality of orifices distributed across the area of ​​the tray plate and extending through the tray plate to allow fluid to flow upward through the tray plate, for interacting with the liquid after it leaves the inlet region and flows across and above the area of ​​the tray plate with orifices distributed thereon; an outlet located away from the inlet region on the tray plate for allowing liquid to be removed from the upper surface of the tray plate after the liquid flows out from the inlet region and interacts with the fluid flowing upward through the orifices in the area of ​​the tray plate; a plurality of baffle walls extending upward from the upper surface of the tray plate and positioned to narrow the width of the liquid flow path as the liquid flows from the inlet region to the outlet and to force the liquid to change its flow direction at least twice, thereby lengthening the flow path; and a downcomer extending downward from the outlet, which receives the liquid as it enters the outlet and then conveys the liquid downward to a discharge outlet located at the lower end of the downcomer. The downcomer includes an inclined or horizontal section that positions the discharge outlet below and vertically aligned with the inlet area on the tray plate.

[0009] In another aspect, the present invention relates to a mass transfer tower comprising a shell, an open interior region within the shell, and a plurality of trays positioned in a vertically spaced relationship within a cross section of the open interior region and extending across the cross section of the open interior region.

[0010] In another aspect, the present invention relates to a method for causing fluids to interact above and above the upper surface of trays in a vertically spaced relationship within a mass transfer column and extending across a cross-section of an open interior region formed by the outer shell of the mass transfer column. The method includes the steps of: delivering liquid to the inlet region of the tray plate on each tray in the trays and allowing it to flow along and above the upper surface of the tray plate along a serpentine flow path, the serpentine flow path being partially defined by a plurality of baffle walls extending upward from the upper surface of each tray plate in the trays, wherein the liquid flows along and above the upper surface of the tray plate along the serpentine flow path at a rate less than 25 gpm per foot of flow path width; causing vapor to rise through a plurality of orifices in the tray plate to interact with the liquid as it flows along its serpentine flow path; removing the liquid from the tray plate at the end of its serpentine flow path by guiding the liquid through an outlet in the tray plate and into a downcomer; and then discharging the liquid from the downcomer onto the inlet region of the adjacent lower tray in the trays. Attached Figure Description

[0011] In the accompanying drawings, which form part of this specification and use similar reference numerals in various views to indicate similar parts:

[0012] Figure 1 This is a partial perspective view of a tower in which mass transfer and / or heat exchange are expected to occur, and in which a portion of the tower's outer shell is stripped away to illustrate one embodiment of the tray of the present invention.

[0013] Figure 2 for Figure 1 The enlarged partial view of a portion of the tower shown is taken from the left-hand perspective;

[0014] Figure 3 For similar Figure 2 A magnified partial view, but taken from the right-hand perspective;

[0015] Figure 4 A top plan view of the tower, showing... Figures 1-3 One of the trays shown;

[0016] Figure 5 For similar Figure 1 A partial perspective view of the tower, but showing a second embodiment of the tower tray of the present invention;

[0017] Figure 6 for Figure 5 The views of the tower shown are from different perspectives; and

[0018] Figure 7 A top plan view of the tower, showing... Figure 5 and Figure 6 One of the trays shown. Detailed Implementation

[0019] Now turn to the more detailed attached images and first go to... Figure 1 Mass transfer towers suitable for use in mass transfer or heat exchange processes are typically designated with the numeral 10. Although other configurations, including polygons, are possible and within the scope of this invention, the tower 10 includes a vertical outer shell 12, which may be of a generally cylindrical configuration. The shell 12 may have any suitable diameter and height and may be constructed of one or more rigid materials that are advantageously inert to or otherwise compatible with the fluids and conditions present during the operation of the tower 10.

[0020] The tower 10 is of the type used to process fluid flows (typically liquid and vapor flows) to obtain fractionation products or otherwise induce mass transfer or heat exchange between fluid flows. For example, the tower 10 may be a tower in which crude oil is subjected to atmospheric pressure, lubricating oil vacuum, crude oil vacuum, fluid or thermal cracking fractionation, coking or viscous cracking furnace fractionation, coke washing, reactor exhaust gas washing, gas quenching, edible oil deodorization, pollution control scrubbing, or other processes.

[0021] The outer shell 12 of tower 10 defines an open interior region 14 in which the desired mass transfer or heat exchange occurs between fluid flows. In one embodiment, the fluid flows may include one or more rising vapor flows and one or more falling liquid flows. In other embodiments, the fluid flows may include substantially any combination of rising or falling liquid flows or rising or falling vapor flows.

[0022] One or more fluid flows can be directed into column 10 via any number of feed lines 16 (such as lower feed line 16a or upper feed line 16b) positioned at appropriate locations along the height of column 10. In one embodiment, the vapor flow may be generated within column 10 rather than being introduced into column 10 via feed lines 16a, 16b. One or more fluid flows can be directed out of column 10 via any number of discharge lines 18 (such as lower discharge line 18a and upper discharge line 18b). In one embodiment, liquid may be introduced via upper feed line 16b, descend through column 10, and be removed via lower discharge line 18a, while vapor may be introduced via lower feed line 16a, rise through column 10, and be removed via upper discharge line 18b.

[0023] Other commonly found tower components, such as reflux feed lines, reboilers, condensers, vaporhorns, liquid distributors, etc., are not shown in the accompanying drawings because they are essentially conventional and illustrations of these components are not believed to be necessary for understanding the invention.

[0024] Alternatively, go to Figures 2-4 Multiple contact trays 20 are positioned vertically spaced within the open interior region 14 of the tower 10 to facilitate the interaction of fluids flowing within the open interior region 14. The trays 20 generally have the same or similar construction and extend substantially horizontally across the entire horizontal cross-section of the tower 10. In the illustrated embodiment, adjacent trays 20 are rotated 180 degrees relative to each other about a central vertical axis.

[0025] Each tray 20 has a generally planar tray plate 22 with an upper surface 24 along which fluid flows, as described in more detail below. The tray plate 22 is typically formed of interconnected tray panels, each sized to pass through a manhole (not shown) in the housing 12. An inlet region 26 is positioned on the tray plate to receive liquid flowing downwards onto the upper surface 24 of the tray plate 22, such as from the upper tray 20 or from a liquid distributor (not shown). A plurality of orifices 28 are distributed on a region of the tray plate 22 referred to as the active region. The orifices 28 extend fully through the tray plate 22 to allow fluid to flow upwards through the tray plate 22 for interaction with the liquid after it leaves the inlet region 26 and flows across and above the active region on which the orifices 28 are distributed. The orifices 28 may be simple sieves, or they may form part of a fixed or movable valve. In the illustrated embodiment, and as shown in Figure 4 As can be best seen, orifice 28 forms part of valve 30, which has valve cover 32 that is capable of floating up and down in response to the force exerted by fluid (such as steam) flowing upward through orifice 28. Figure 4 In this embodiment, one of the valve covers 32 is removed to reveal the hole 28 associated with the valve 30. In another embodiment, the valve cover may be fixed to the tray plate so that it cannot float up and down.

[0026] Each tray 20 also includes an outlet 34 located in the tray plate 22 away from the inlet region 26, for allowing liquid to be removed from the upper surface 24 of the tray plate 22 after the liquid flows out of the inlet region 26 and interacts with the fluid through the orifices 28 in the active region of the tray plate 22. The interaction between the vapor rising through the orifices 28 or valve 30 and the liquid flowing along the upper surface 24 of the tray plate 22 typically produces foam or spray above the tray plate 22. Each tray 20 also includes a downcomer 34 extending downward from the outlet 36 to receive the liquid as it enters the outlet 34. The downcomer 36 then conveys the liquid downward for discharge onto the inlet region 26 of the adjacent lower tray 20, or, in the case of the lowest tray 20, to a liquid collector (not shown) or other internal device.

[0027] As in Figure 4 As best seen in one embodiment, inlet region 26 and outlet 34 are diagonally positioned opposite each other at opposite ends of tray 22. The dimensions of inlet region 26 and outlet 34 are each set to accommodate the design volumetric flow rate of the liquid on tray 20. In the illustrated embodiment, inlet region 26 and outlet 34 each occupy only small segments of the chordal region at opposite ends of tray 22. In other embodiments, inlet region 26 and outlet 34 may each occupy large segments (inclusive) of the chordal region at opposite ends of tray 22.

[0028] Each tray 20 includes a plurality of baffle walls 38 extending upward from the upper surface 24 of the tray plate 22 and positioned to reduce the width of the liquid flow path as liquid flows from the inlet region 26 to the outlet 34 above and above the tray plate 22, and to force the liquid to change its flow direction at least twice, such as by reversing its flow direction twice, thereby lengthening its flow path. By constructing the flow path in this way, the baffle walls 38 concentrate the liquid flow and increase the volumetric flow rate of the liquid and head present above and above any portion of the active region of the tray plate 22. This increase in liquid volumetric flow rate reduces the chance of liquid entrainment in vapor rising through the orifices 28 in the tray plate 22 and improves the efficiency of the tray 20 under low liquid flux or flow conditions, especially liquid flow rates below 25 gpm per foot of flow path width or 10 gpm per foot of flow path width.

[0029] In one implementation scheme, such as Figures 1-4As shown, the first and second baffle walls 38 are used and positioned in a spaced-apart relationship. In the illustrated embodiment, the first and second baffle walls 38 are positioned parallel to each other and divide the tray 22 into three sections of substantially equal area. One end of the first baffle wall 38 is adjacent to one side of the housing 12, and the opposite end of the first baffle wall 38 is spaced from the opposite side of the housing 12 by a preselected distance. The preselected distance is typically chosen such that the width of the flow path on the tray 22 when liquid flows around the end of the first baffle wall 38 is substantially the same as the width of the flow path on either side of the first baffle wall 38. The second baffle wall 38 is positioned opposite the first baffle wall 38. That is, one end of the second baffle wall 38 is spaced from the side of the housing 12 by a preselected distance, with the first baffle wall 38 adjacent to this side, and the opposite end of the second baffle wall 38 is adjacent to the opposite side of the housing 12, with the first baffle wall 38 spaced from this opposite side by a preselected distance. By placing the baffle wall 38 in this manner, a serpentine flow path is created for the liquid as it flows from the inlet region 26 to the outlet 34 on the tray 22. In the case of retrofitting an existing tray 20 with a side-chord downcomer, the baffle wall 38 can be installed in a section of the wall (not shown) or a portion of the orifice plate (not shown) to prevent liquid from entering the downcomer, except at the desired end of the liquid flow path.

[0030] Each baffle wall 38 has a height sufficient to guide most of the liquid foam and spray flowing above and above the tray plate 22 along one side of each baffle wall 38, and to cause the liquid (including any foam and spray) to reverse direction and flow along the opposite side of the baffle wall 38 when it reaches the end of the baffle wall 38. As an example, the height of the baffle wall 38 may be at least 50% of the vertical distance between the upper surface 24 of the tray plate 22 it occupies and the lower surface of the adjacent upper tray plate 22. As another example, the height of the baffle wall 38 may be at least 75% of such vertical distance between the tray plates 22. As a further example, the height of the baffle wall 38 may be 100% of the vertical distance, such that the baffle wall 38 extends upward to the lower surface of the adjacent upper tray plate 22. In this example, the baffle wall 38 may be attached to the upper tray plate 22 to maintain the desired spacing between adjacent tray plates 22 and to provide a more rigid tray assembly 20.

[0031] It should be understood that additional baffle walls 38 can be used to further extend the liquid flow path on tray 22 and reduce the width of the flow path. This narrowing of the flow path increases the volumetric flow rate of the liquid at any point in the active region of tray 22. For example, as Figures 5-7As shown, the third baffle wall in baffle wall 38 can be positioned in a spaced-apart relationship with the first and second baffle walls in baffle wall 38, so that the liquid changes its direction three times as it flows from inlet region 26 to outlet 34. The use of a third baffle wall 38 and any odd number of baffle walls 38 is particularly advantageous because it allows inlet region 26 and outlet 34 to be located at the same end of tray 22, with inlet region 26 vertically aligned on tray 20 and outlet 34 also vertically aligned on tray 20. When inlet region 26 and outlet 34 are vertically aligned in this manner, the serpentine flow of the liquid can occur in the same direction on each tray, rather than in... Figures 1-4 In the tray implementation shown, the flow path is reversed, creating a spiral flow path as the liquid continuously descends from one tray 20 to the next. Since this serpentine flow is in the same direction on each successive tray 20, increased tray 20 efficiency is achieved.

[0032] To deliver liquid from outlet 34 on one tray 20 to inlet region 26 on the next lower tray 20, a downcomer 40 (such as formed by a pipe segment) extends downward from outlet 34 and includes an inclined or horizontal portion 42 such that the outlet 44 of the downcomer 40 is positioned vertically aligned with the inlet region 26 on the tray plate 22 of the lower tray 20. The downcomer 40 may need to extend through one or more of the baffle walls 38 on the lower tray plate 22 to achieve this common directional or helical flow.

[0033] The invention also relates to a method for causing fluid to interact above and over the upper surface 24 of the tray plate 22 of the tray 20 when the tray 20 is positioned in a vertically spaced relationship within a mass transfer column 10 and extends across the cross-section of an open internal region 14 formed by the outer shell 12 of the mass transfer column 10. The method includes the steps of: delivering liquid to the inlet region 26 of each tray in the tray 20, allowing it to flow along a flow path oriented in one direction on one side of a first baffle wall 38, then in another direction on the opposite side of the first baffle wall, and then terminating at an outlet 34, along and above the upper surface 24 of the tray plate. Vapor is caused to rise through orifices 28 or valves 30 (if present) in the tray plate 22 to interact with the liquid as it flows along its flow path. The liquid is removed from the tray plate 22 at the end of its flow path by guiding it through the outlet 34 and into a downcomer 36 or 40. The liquid is then discharged from the downcomer 36 or 40 to…

[0034] On the inlet region 26 of an adjacent lower tray in tray 20. In one embodiment, the amount of liquid delivered to the inlet region 26 of each tray in tray 20 is such that it flows along the liquid flow path along and above the upper surface 24 of tray plate 22 at a flow rate less than 25 gpm per foot of flow path width. In another embodiment, the liquid flow rate is less than 10 gpm per foot of flow path width.

[0035] The method further includes causing the liquid to flow around an additional baffle wall 38, which extends upward from the upper surface 24 of the tray 22 and is positioned such that the liquid flow path is a serpentine flow path. In one embodiment, the liquid flows in the opposite direction along the serpentine flow path on adjacent trays of tray 20. In another embodiment, the liquid flows in the same direction along the serpentine flow path on tray 20.

[0036] As can be seen from the above, the present invention is well suited to achieve all the purposes and objectives set forth above, and has other advantages inherent in its structure.

[0037] It should be understood that certain features and sub-combinations are practical and can be adopted without reference to other features and sub-combinations. This is contemplated by the present invention and is within the scope of the present invention.

[0038] Since various feasible embodiments can be made according to the invention without departing from the scope of the invention, it should be understood that all content set forth herein or shown in the accompanying drawings is to be understood as exemplary rather than restrictive.

Claims

1. A tray for use in a mass transfer column to facilitate interaction between fluids as they flow within the mass transfer column, the tray comprising: A tray, the tray having an upper surface; An inlet region located on the tray plate, the inlet region being used to receive liquid flowing downward onto the upper surface of the tray plate; Multiple orifices are distributed across a region of the tray plate and extend through the tray plate to allow fluid to flow upward through the tray plate, for interacting with the liquid after it leaves the inlet region and flows over the region where the orifices are distributed and over the region. An outlet located away from the inlet region on the tray plate, the outlet being used to allow liquid to be removed from the upper surface of the tray plate after liquid flows out of the inlet region and interacts with the fluid flowing upward through the orifice in the region, the inlet region and the outlet being located at the same end of the tray plate; Multiple parallel, spaced-apart baffle walls extend upward from the upper surface of the tray and are positioned to reduce the width of the liquid flow path as the liquid flows from the inlet region to the outlet, and force the liquid to reverse its flow direction at least three times, thereby lengthening the flow path. and Among them, three or more odd-numbered spaced baffle walls are located between the inlet region and the outlet on the tray plate, wherein one end of the nth baffle wall in a direction perpendicular to the baffle wall abuts against the side of the shell of the mass transfer column where the inlet region and the outlet are located, and the opposite end of the nth baffle wall is spaced apart from the opposite side of the shell by a predetermined distance, where n is an odd number; A downcomer extends downward from the outlet to receive liquid as it enters the outlet and then deliver the liquid downward to a discharge outlet located at the lower end of the downcomer, wherein the downcomer includes an inclined or horizontal portion such that the discharge outlet is positioned below and vertically aligned with the inlet area on the tray plate.

2. The tray according to claim 1, wherein the plurality of spaced-apart baffle walls include three of the baffle walls.

3. The tray according to claim 2, wherein the flow path is a serpentine flow path.

4. The tray of claim 3, comprising a valve partially formed by the orifice.

5. The tray of claim 4, wherein the valve includes a valve cover capable of floating up and down in response to a force exerted by fluid flowing upward through the orifice.

6. The tray according to claim 1, wherein the downcomer is formed from a pipe section.

7. The tray of claim 6, wherein the downcomer extends through one or more of the plurality of spaced-apart baffle walls.

8. A mass transfer tower comprising a shell, an open interior region within the shell, and a plurality of trays according to claim 1, the plurality of trays being positioned vertically spaced apart within a cross section of the open interior region and extending across the cross section of the open interior region, wherein the inlet regions of the trays are vertically aligned, the outlets of the trays are also vertically aligned, and the flow path is a serpentine flow path in the same direction on each of the trays.

9. The mass transfer tower according to claim 8, wherein the plurality of spaced-apart baffle walls include three of the baffle walls.

10. The mass transfer tower of claim 9, wherein each of the baffle walls has an end adjacent to one side of the outer shell and an opposite end spaced apart from the opposite side of the outer shell by a preselected distance.

11. The mass transfer tower of claim 9, comprising a valve partially formed by the orifice.

12. The mass transfer tower of claim 11, wherein the valve includes a valve cover capable of floating up and down in response to a force exerted by fluid flowing upward through the orifice.

13. The mass transfer tower according to claim 8, wherein the downcomer is formed of a pipe section.

14. The mass transfer tower of claim 13, wherein the baffle wall extends upward to the lower surface of the adjacent upper tray.

15. A method for causing fluid to interact on and above the upper surface of a tray according to claim 1, the tray being positioned vertically spaced within a mass transfer column and extending across a cross-section of an open interior region formed by the outer shell of the mass transfer column, the method comprising the steps of: Liquid is delivered to the inlet area of ​​the tray plate on each of the trays and allowed to flow along a serpentine flow path along and above the upper surface of the tray plate, the serpentine flow path being partially defined by a plurality of baffle walls extending upward from the upper surface of each of the tray plates, the liquid flowing along the serpentine flow path along and above the upper surface of the tray plate at a rate less than 25 gpm per foot of flow path width; The vapor is allowed to rise through multiple holes in the tray to interact with the liquid as it flows along its serpentine flow path. The liquid is removed from the tray at the end of its serpentine flow path by guiding it through an outlet in the tray and into a downcomer. as well as The liquid is then discharged from the downcomer to the inlet area of ​​the adjacent lower tray in the tray.

16. The method of claim 15, wherein the liquid flows along the flow path along the upper surface of the tray and above the upper surface of the tray at a rate less than 10 gpm per foot of flow path width.

17. The method of claim 15, comprising: The liquid is made to flow in the same direction along the serpentine flow path above adjacent trays in the tray.

18. The method of claim 17, comprising: The liquid is allowed to flow around three of the baffle walls on the upper surface of each tray.

19. The method of claim 15, comprising: The spacing between adjacent trays in the trays is maintained by extending the baffle wall upward to the lower surface of the adjacent upper tray and attaching the baffle wall to the adjacent upper tray.

20. The method of claim 19, wherein the liquid flows along the flow path along the upper surface of the tray and above the upper surface of the tray at a rate less than 10 gpm per foot of flow path width.

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