A vacuum distillation column

Abstract

This application relates to distillation separation equipment, and discloses a vacuum distillation column. The vacuum distillation column structure may include: a column body, a plurality of first sieve trays, and a plurality of second sieve trays. The first sieve trays may include a first tray, with a square downcomer at the center of the first tray. Both the first tray and the square downcomer have overflow weirs. The second sieve trays may include a second tray, with a vertical baffle near the column body. The vertical baffle and the column body form a D-shaped downcomer. Both the second tray and the D-shaped downcomer have overflow weirs. The plurality of first and second sieve trays are arranged at intervals from top to bottom inside the column body. The height of the overflow weirs on the square downcomers is between 25 mm and 30 mm. By reasonably setting the height of the overflow weirs, the liquid layer thickness can be precisely controlled, ensuring that the liquid provides sufficient contact area for gas-liquid mass transfer while reducing the probability of excessive liquid layer hindering gas rise.

Description

Technical Field

[0001] This application relates to distillation separation equipment, and in particular to a vacuum distillation column. Background Technology

[0002] Currently, distillation towers are crucial equipment in the ammonia-soda process for soda ash production. In recent years, vacuum sieve plate distillation towers have become increasingly widely used in the industry due to their significant advantages. Compared to traditional vacuum bubble cap distillation towers, they can process more mother liquor, consume less steam, and recover heat through multi-stage flash evaporation, effectively reducing production costs and improving production efficiency.

[0003] However, vacuum sieve plate distillation columns have a serious problem in actual operation—the "gas top" phenomenon. In existing vacuum distillation columns, a certain thickness of liquid remains on the sieve plates, causing a significant pressure difference between the distillation section and the heating section. Furthermore, the liquid channel between the downcomer wall plate and the overflow weir tends to narrow, which exacerbates the problem of liquid accumulation on the trays and ultimately leads to the "gas top" phenomenon.

[0004] Once a "gas cap" occurs, a large amount of liquid will accumulate on a particular tray, causing a significant increase in the liquid thickness on the sieve plate. This obstructs gas flow and drastically increases resistance. At this point, key process parameters of the distillation column, such as temperature, vacuum, and pressure, will deviate significantly from normal ranges, and the column condition will deteriorate rapidly. In severe cases, the column must be shut down, which not only seriously affects production continuity but also causes substantial economic losses.

[0005] Therefore, effectively solving the "gas top" phenomenon in vacuum sieve plate distillation towers has become a key technical challenge that urgently needs to be overcome in the current ammonia-soda process for soda ash production. Utility Model Content

[0006] The technical problem to be solved by this application is: how to alleviate the "gas cap" phenomenon in a vacuum sieve plate distillation column.

[0007] To address the aforementioned technical problems, this application provides a vacuum distillation column. The vacuum distillation column structure includes: a column body; a plurality of first sieve trays, each first sieve tray including a first tray, with a square downcomer at the center of the first tray, and overflow weirs on both the first tray and the square downcomer; and a plurality of second sieve trays, each second sieve tray including a second tray, with a vertical baffle near the column body, the vertical baffle and the column body forming a D-shaped downcomer, and overflow weirs on both the second tray and the D-shaped downcomer; wherein the plurality of first sieve trays and the plurality of second sieve trays are arranged alternately from top to bottom inside the column body, and the height of the overflow weirs on the square downcomer is between 25 mm and 30 mm.

[0008] In one embodiment, the vacuum distillation column further includes several snap-fit ​​rings, which are fixed between the D-shaped downcomer and the overflow weir of the first tray.

[0009] In one embodiment, the snap ring is welded and fixed to the D-shaped downcomer.

[0010] In one embodiment, the snap ring is made of a corrosion-resistant material, wherein the mass percentage of chromium in the corrosion-resistant material is not less than 18% and the mass percentage of nickel is not less than 8%.

[0011] In one embodiment, there are a total of 34 layers of first and second sieve trays; wherein, the upper 15 layers of first and second sieve trays in the column body constitute the distillation section, and the lower 19 layers of first and second sieve trays in the column body constitute the heating section.

[0012] In one embodiment, the vacuum distillation column further includes a water collector installed at the bottom of the heating section, the water collector being connected to the pre-ash tank and the heater.

[0013] In one embodiment, the first tray and the second tray are provided with regular hexagonal sieve holes.

[0014] In one embodiment, an insulation layer is provided on the inner wall of the tower.

[0015] In one embodiment, both the square downcomer and the D-shaped downcomer have guide grooves on their inner walls, and the guide grooves are distributed in a spiral shape.

[0016] In one embodiment, an anti-fogging device is provided at the top of the tower body, and the anti-fogging device includes several layers of staggered baffles.

[0017] Compared with the prior art, the vacuum distillation column of this application has the following advantages:

[0018] This application sets the overflow weir height on the square downcomer between 25 mm and 30 mm, significantly reducing the weir height. This design allows for precise control of the liquid layer thickness on the sieve tray. In existing technologies, an unreasonable overflow weir height can lead to excessive liquid thickness on the sieve tray, increasing resistance to gas rise and causing a "gas top" phenomenon. This application, by controlling the overflow weir height within a suitable range, ensures that the liquid on the sieve tray provides sufficient contact area for gas-liquid mass transfer without obstructing gas rise due to excessive liquid thickness, thus effectively reducing the probability of "gas top" occurrence. The design combining square and D-shaped downcomers, with different shapes rationally distributed on different numbered trays, optimizes the liquid flow path, enabling more uniform and stable liquid flow between trays and reducing the probability of "gas top" occurrence. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a vacuum distillation column as illustrated in an embodiment of this application.

[0020] Figure 2 This is a schematic diagram of a partial cross-sectional view of a vacuum distillation column, as exemplarily shown in an embodiment of this application.

[0021] Figure 3 This is a schematic diagram of the structure of a vacuum distillation column as illustrated in an embodiment of this application, showing a top cross-sectional view.

[0022] Figure label:

[0023] 1. Vacuum distillation column; 11. Column body; 12. First sieve tray; 121. First tray; 122. Square downcomer; 123. Overflow weir; 13. Second sieve tray; 131. Second tray; 132. Vertical baffle; 133. D-shaped downcomer; 14. Snap ring. Detailed Implementation

[0024] The specific embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but are not intended to limit the scope of this application.

[0025] In the description of this application, it should be understood that the terms "first," "second," etc., in the specification, claims, and accompanying drawings are intended to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate so that embodiments of this application can be implemented using notation methods other than those shown or described. Furthermore, "comprising," "having," and any variations thereof are intended to cover non-exclusive inclusion. For example, a system, product, or device comprising a series of components or units is not necessarily limited to those explicitly listed components or units, but may also include other components or units not explicitly listed but inherent to these products or devices.

[0026] Currently, distillation towers are crucial in the ammonia-soda process for soda ash production. In recent years, vacuum sieve plate distillation towers have become increasingly widely used in the industry due to their significant advantages. Compared with traditional vacuum bubble cap distillation towers, they can process more mother liquor, consume less steam, and recover heat through multi-stage flash evaporation, effectively reducing production costs and improving production efficiency.

[0027] However, vacuum sieve plate distillation columns have a serious problem in actual operation—the "gas top" phenomenon. In existing vacuum distillation columns, a certain thickness of liquid remains on the sieve plates, causing a significant pressure difference between the distillation section and the heating section. Furthermore, the liquid channel between the downcomer wall plate and the overflow weir tends to narrow, exacerbating the problem of liquid accumulation on the trays and ultimately leading to the "gas top" phenomenon.

[0028] Once a "gas cap" occurs, a large amount of liquid will accumulate on a particular tray, causing a significant increase in the liquid thickness on the sieve plate. This obstructs gas flow and drastically increases resistance. At this point, key process parameters of the distillation column, such as temperature, vacuum, and pressure, will deviate significantly from normal ranges, and the column condition will deteriorate rapidly. In severe cases, the column must be shut down, which not only seriously affects production continuity but also causes substantial economic losses.

[0029] Therefore, effectively solving the "gas top" phenomenon in vacuum sieve plate distillation towers has become a key technical challenge that urgently needs to be overcome in the current ammonia-soda process for soda ash production.

[0030] The inventors discovered that "gas top" is mainly caused by liquid accumulating on a certain tray, increasing the liquid thickness on the sieve plate surface, which hinders the gas from rising and increases resistance. In the existing technology, if the overflow weir height is not reasonable, it will lead to excessive liquid thickness on the sieve plate, which is the main factor that increases the resistance to gas rising.

[0031] In view of this, such as Figure 1 As shown in the preferred embodiment of this application, a vacuum distillation column 1 may include: a column body 11, a plurality of first sieve trays 12 and a plurality of second sieve trays 13.

[0032] The first sieve tray 12 may include a first tray 121, with a square downcomer 122 at the center of the first tray 121. Both the first tray 121 and the square downcomer 122 are provided with overflow weirs 123. The second sieve tray 13 may include a second tray 131, with a vertical baffle 132 near the tower body 11. The vertical baffle 132 and the tower body 11 form a D-shaped downcomer 133. Both the second tray 131 and the D-shaped downcomer 133 are provided with overflow weirs 123.

[0033] Among them, a number of first sieve trays 12 and a number of second sieve trays 13 are arranged at intervals from top to bottom inside the tower body 11, and the height of the overflow weir 123 on the square downcomer 122 is between 25 mm and 30 mm.

[0034] In view of this, such as Figure 1-3 As shown in the preferred embodiment of this application, a vacuum distillation column 1 may include: a column body 11, a plurality of first sieve trays 12 and a plurality of second sieve trays 13.

[0035] The first sieve tray 12 may include a first tray 121, with a square downcomer 122 at the center of the first tray 121. Both the first tray 121 and the square downcomer 122 are provided with overflow weirs 123. The second sieve tray 13 may include a second tray 131, with a vertical baffle 132 near the tower body 11. The vertical baffle 132 and the tower body 11 form a D-shaped downcomer 133. Both the second tray 131 and the D-shaped downcomer 133 are provided with overflow weirs 123.

[0036] Among them, a number of first sieve trays 12 and a number of second sieve trays 13 are arranged at intervals from top to bottom inside the tower body 11, and the height of the overflow weir 123 on the square downcomer 122 is between 25 mm and 30 mm.

[0037] By rationally setting the height of the overflow weir 123 on the square downcomer 122, the thickness of the liquid layer on the sieve plate can be precisely controlled. This ensures that the liquid provides sufficient contact area for gas-liquid mass transfer without obstructing gas rise due to excessive liquid layer thickness, effectively reducing the probability of "gas top" phenomenon. Simultaneously, the distribution of downcomers of different shapes on different trays optimizes the liquid flow path, avoids localized liquid accumulation, and ensures smooth gas rise.

[0038] In this application, when a pressure difference is caused by an "air cap phenomenon," the overflow weir 123 of the D-shaped downcomer 133 may exhibit the following characteristics: Figure 2 The deformation shown. Therefore, in one embodiment, the vacuum distillation column 1 may further include a plurality of snap-fit ​​rings 14, which are fixed between the D-shaped downcomer 133 and the overflow weir 123 of the first tray 121.

[0039] The snap ring 14 enhances the connection stability between the D-shaped downcomer 133 and the overflow weir 123 of the first tray 121, preventing the downcomer from shifting or shaking under the impact of gas and liquid phases, thereby ensuring the stability of liquid flow in the downcomer and reducing the obstruction of liquid flow and "gas top" phenomenon caused by the instability of the downcomer.

[0040] In one embodiment, the snap ring 14 is welded and fixed to the D-shaped downcomer 133.

[0041] The welding fixing method forms a firm connection between the snap ring 14 and the D-shaped downcomer 133, which can withstand the continuous impact and vibration of the gas and liquid phases, maintain the stability of the structure for a long time, avoid the deformation of the downcomer and abnormal liquid flow caused by loose connection, and further alleviate the "gas top" phenomenon.

[0042] In one embodiment, the snap ring 14 is made of a corrosion-resistant material, wherein the mass percentage of chromium is not less than 18% and the mass percentage of nickel is not less than 8%.

[0043] The snap ring 14, made of this corrosion-resistant material, can be used for a long time in the high-temperature and highly corrosive working environment of the vacuum distillation tower 1 without being corroded or damaged. This ensures the durability of the snap ring 14's reinforcement effect on the downcomer structure, maintains the normal working condition of the downcomer, and prevents downcomer failure and "air capping" phenomenon caused by corrosion damage to the snap ring 14.

[0044] In one embodiment, the first sieve tray 12 and the second sieve tray 13 have a total of 34 layers; wherein, the first sieve tray 12 and the second sieve tray 13 in the upper 15 layers of the column body 11 constitute the distillation section, and the first sieve tray 12 and the second sieve tray 13 in the lower 19 layers of the column body 11 constitute the heating section.

[0045] The clearly defined layered design and functional zoning ensure a more orderly gas-liquid mass transfer and heating process during distillation. The optimal ratio of distillation and heating sections better meets the material separation requirements, improves distillation efficiency, and avoids poor gas flow and "gas top" phenomena caused by improper tray distribution.

[0046] In one embodiment, the vacuum distillation column 1 may further include a water collector installed at the bottom of the heating section, the water collector being connected to the pre-ash bucket and the heater.

[0047] The water collector can collect condensate and other liquids generated at the bottom of the heating section, preventing liquid from accumulating at the bottom of the column and affecting the distillation process. Connected to the pre-ash tank and heater, it enables liquid recycling, improving resource utilization while ensuring stable operation of the distillation system and reducing the "gas head" phenomenon caused by improper liquid handling.

[0048] In one embodiment, the first tray 121 and the second tray 131 are provided with regular hexagonal sieve holes.

[0049] The hexagonal sieve openings make the gas-liquid contact more uniform. Compared with the traditional sieve opening arrangement, it can improve the gas-liquid mass transfer efficiency, allowing the gas to pass through the liquid layer more smoothly and reducing the accumulation of gas in local areas, thereby effectively alleviating the "gas top" phenomenon.

[0050] In one embodiment, an insulation layer is provided on the inner wall of the tower body 11.

[0051] The insulation layer can reduce heat loss within the tower and maintain a stable temperature inside the tower. A stable temperature environment helps to ensure the physical properties and flow state of the gas and liquid, avoiding changes in gas volume and liquid viscosity caused by temperature fluctuations, thereby reducing the occurrence of the "gas top" phenomenon.

[0052] In one embodiment, the inner walls of both the square downcomer 122 and the D-shaped downcomer 133 are provided with guide grooves, which are distributed in a spiral shape.

[0053] The spiral guide channel can guide the liquid to descend in a spiral shape, enhance the stability and uniformity of the liquid flow, reduce the residence time of the liquid in the downcomer, reduce the possibility of liquid backmixing, and allow the liquid to flow more smoothly from the upper tray to the lower tray, avoiding the accumulation of liquid in the downcomer and causing the "gas head" phenomenon.

[0054] In one embodiment, an anti-fogging device is provided at the top of the tower body 11, and the anti-fogging device may include several layers of staggered baffles.

[0055] The baffles in the anti-fogging device effectively intercept mist in the rising steam, causing droplets in the mist to collide with the baffles and collect, flowing down into the tower and reducing mist entrainment. This helps improve the purity of the product at the top of the tower, while preventing mist from accumulating at the top of the tower and affecting gas discharge, thus alleviating the "gas top" phenomenon.

[0056] The vacuum distillation column 1 proposed in this application aims to improve distillation efficiency and alleviate the "gas cap" phenomenon. Its core structure includes a column body 11, several first sieve trays 12 and second sieve trays 13, which are arranged alternately. The first sieve trays 12 have square downcomers 122 with overflow weirs 123, and the second sieve trays 13 form D-shaped downcomers with overflow weirs 123 with the column body 11 through partitions. The height of the overflow weirs 123 of the square downcomers 122 is between 25 mm and 30 mm, which precisely controls the liquid layer thickness.

[0057] The design also incorporates several optimizations. The snap-fit ​​ring 14 is welded and fixed between the D-shaped downcomer and the overflow weir 123, using corrosion-resistant materials to ensure structural stability; the 34-layer tray is rationally divided into distillation and heating sections; the bottom water collector of the heating section is connected to the pre-ash tank and heater to achieve liquid circulation; the hexagonal sieve ensures more uniform gas-liquid contact; the insulation layer on the inner wall of the tower body 11 maintains temperature stability; the spiral guide groove on the inner wall of the downcomer enhances liquid flow stability; and the anti-fogging device at the top of the tower intercepts mist. These designs work together to effectively improve distillation efficiency and reduce the occurrence of "gas top" phenomena.

[0058] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application.

Claims

1. A vacuum distillation column, characterized in that, The vacuum distillation column (1) includes: Tower body (11); A plurality of first sieve trays (12), each first sieve tray (12) includes a first tray (121), a square downcomer (122) is provided at the center of the first tray (121), and an overflow weir (123) is provided on both the first tray (121) and the square downcomer (122). A plurality of second sieve trays (13) are provided, each second sieve tray (13) including a second tray (131). The second tray (131) is provided with a vertical baffle (132) near the tower body (11). The vertical baffle (132) and the tower body (11) form a D-shaped downcomer (133). Both the second tray (131) and the D-shaped downcomer (133) are provided with overflow weirs (123). Among them, a number of first sieve trays (12) and a number of second sieve trays (13) are arranged at intervals from top to bottom inside the tower body (11), and the height of the overflow weir (123) on the square downcomer (122) is between 25 mm and 30 mm.

2. The vacuum distillation column according to claim 1, characterized in that, The vacuum distillation column (1) also includes several snap rings (14), which are fixed between the D-shaped downcomer (133) and the overflow weir (123) of the first tray (121).

3. The vacuum distillation column according to claim 2, characterized in that, The buckle ring (14) is welded and fixed to the D-shaped downcomer (133).

4. The vacuum distillation column according to claim 3, characterized in that, The buckle ring (14) is made of corrosion-resistant material, wherein the mass percentage of chromium is not less than 18% and the mass percentage of nickel is not less than 8%.

5. The vacuum distillation column according to claim 1, characterized in that, The first sieve tray (12) and the second sieve tray (13) have a total of 34 layers; The first sieve tray (12) and the second sieve tray (13) in the upper 15 layers of the tower body (11) constitute the distillation section, and the first sieve tray (12) and the second sieve tray (13) in the lower 19 layers of the tower body (11) constitute the heating section.

6. The vacuum distillation column according to claim 5, characterized in that, The vacuum distillation column (1) also includes a water collector installed at the bottom of the heating section, which is connected to the pre-ash bucket and the heater.

7. The vacuum distillation column according to claim 1, characterized in that, The first tray (121) and the second tray (131) are provided with regular hexagonal sieve holes.

8. The vacuum distillation column according to claim 1, characterized in that, The inner wall of the tower body (11) is provided with a heat insulation layer.

9. The vacuum distillation column according to claim 1, characterized in that, The inner walls of both the square downcomer (122) and the D-shaped downcomer (133) are provided with guide grooves, which are distributed in a spiral shape.

10. The vacuum distillation column according to claim 1, characterized in that, The top of the tower body (11) is provided with an anti-fog device, which includes several layers of staggered baffles.

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