Sieve plate distillation column for hydrazine hydrate purification

Abstract

This application provides a sieve tray distillation column for hydrazine hydrate purification, comprising a column body, a reboiler, a condenser, and a multi-layer tray assembly arranged in parallel within the column body. The tray assembly includes an upper tray and a lower tray arranged in parallel. The upper tray has several upper overflow holes, and the lower tray has several lower overflow holes directly opposite the upper overflow holes. Each lower overflow hole has a cap, and the sidewall of the cap has vent holes. This sieve tray distillation column for hydrazine hydrate purification uses a tray assembly instead of a traditional single tray. The liquid phase falls from the upper overflow holes of the upper tray onto the caps of the lower tray, forming a liquid film. The gas phase passes through the caps from the lower overflow holes of the lower tray and comes into full contact with the liquid film. The contact time and area between the liquid and gas phases are significantly greater than the contact area between the liquid and gas phases in existing sieve tray distillation columns, thereby improving purification efficiency.

Description

Technical Field

[0001] This application relates to the technical field of hydrazine hydrate production equipment, and in particular to a sieve plate distillation column for hydrazine hydrate purification. Background Technology

[0002] Distillation columns are classified into packed distillation columns and tray distillation columns according to their internal structure. Tray distillation columns are further divided into sieve tray distillation columns, valve tray distillation columns, and bubble cap distillation columns based on the type of tray. Currently, the purification process of hydrazine hydrate generally uses bubble cap distillation columns. The working principle of a bubble cap distillation column is that the gas phase rises from the riser and disperses into bubbles through the gaps in the bubble cap, entering the liquid phase and forming a bubble layer for mass transfer. When using a bubble cap distillation column to purify crude hydrazine hydrate solution, the high salt content easily leads to salt buildup and blockage of the trays. Simultaneously, the production load flexibility is low, and steam consumption is high. The working principle of a sieve tray distillation column is that the rising gas phase disperses into bubbles through the sieve holes, contacting the liquid phase on the tray for mass transfer; the liquid phase flows to the lower tray through the downcomer. The advantages of sieve tray distillation columns are that they are less prone to blockage and have lower steam consumption. However, it is prone to problems such as leakage and flooding. In the purification process of hydrazine hydrate, its efficiency is significantly lower than that of bubble cap distillation column. At the same time, in order to reduce the problems of leakage and flooding, the production load flexibility is also relatively small. Summary of the Invention

[0003] In view of this, this application proposes a sieve plate distillation column for the purification of hydrazine hydrate, which can improve purification efficiency and increase production load flexibility.

[0004] A sieve tray distillation column for the purification of hydrazine hydrate includes a column body, a reboiler, a condenser, and a multi-layer tray assembly arranged in parallel within the column body. The tray assembly includes an upper tray and a lower tray arranged in parallel. The upper tray is provided with a plurality of upper overflow holes, and the lower tray is provided with a plurality of lower overflow holes directly opposite the upper overflow holes. The lower overflow holes are provided with umbrella caps, and the sidewalls of the umbrella caps are provided with vent holes.

[0005] Preferably, the umbrella cap is detachably connected to the lower tower plate.

[0006] Preferably, the umbrella cap includes a column and a cap body, the lower end of the column is connected to the lower tower plate, the upper end of the column is connected to the cap body, and the side wall of the column is provided with air holes.

[0007] Preferably, the column is provided with external threads, the cap is provided with internal threads, and the column and the cap are threadedly connected.

[0008] Preferably, the upper tray is provided with a baffle, the height of which is greater than the height of the upper overflow hole protrusion.

[0009] Preferably, the diameter of the overflow hole is 2 to 4 centimeters.

[0010] Preferably, the lower tower plate is provided with an overflow plate along its edge, and a liquid discharge channel is formed between the overflow plate and the tower body. The height of the overflow plate is greater than the height of the bottommost pore on the sidewall of the column.

[0011] Preferably, the tower body is provided with 6 to 8 layers of tower plate assemblies, and the downcomer channels between adjacent tower body assemblies are staggered.

[0012] Preferably, the top side wall of the tower body is provided with an azeotropic agent inlet, which is located above the uppermost tower body component and is positioned away from the downcomer channel opening; the middle part of the tower body is provided with a hydrazine hydrate inlet, which is located in the middle part of the tower body and is positioned away from the downcomer channel opening.

[0013] The technical advantages of this application are as follows: The sieve tray distillation column for hydrazine hydrate purification uses tray assemblies instead of traditional single trays. The liquid phase falls from the upper overflow hole of the upper tray onto the cap of the lower tray, forming a liquid film. The gas phase passes through the cap from the lower overflow hole of the lower tray and comes into full contact with the liquid film. Furthermore, the liquid and gas phases also intersect during the liquid phase's descent, and the liquid phase on the lower tray also intersects with the gas phase passing through the cap. The contact time and area between the liquid and gas phases are significantly greater than the contact area between the liquid and gas phases in existing sieve tray distillation columns, thereby improving purification efficiency. Simultaneously, the increased contact time and area between the liquid and gas phases also enhances the flexibility of production load. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the sieve plate distillation column for the purification of hydrazine hydrate according to this application;

[0015] Figure 2 This is a partial cross-sectional view of the sieve plate distillation column for the purification of hydrazine hydrate according to this application;

[0016] Figure 3 for Figure 2 A partial structural diagram.

[0017] Explanation of reference numerals in the attached diagram: 1. Tower body; 11. Azeotropic agent inlet; 12. Hydrazine hydrate inlet; 2. Reboiler; 3. Condenser; 4. Tray assembly; 41. Upper tray; 411. Upper overflow hole; 412. Baffle; 42. Lower tray; 421. Lower overflow hole; 422. Umbrella cap; 4221. Vent; 4222. Column; 4222. Cap; 5. Downcomer channel. Detailed Implementation

[0018] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0019] Please refer to Figures 1 to 3A sieve plate distillation column for the purification of hydrazine hydrate includes a column body 1, a reboiler 2, a condenser 3, and a multi-layer tray assembly 4 arranged in parallel within the column body 1. The tray assembly 4 includes an upper tray 41 and a lower tray 42 arranged in parallel. The upper tray 41 is provided with a plurality of upper overflow holes 411, and the lower tray 42 is provided with a plurality of lower overflow holes 421 opposite to the upper overflow holes 411. The lower overflow holes 421 are provided with umbrella caps 422, and the sidewalls of the umbrella caps 422 are provided with vent holes 4221.

[0020] The structure of the column body 1, reboiler 2, and condenser 3 in this application is the same as that of the distillation column currently used for hydrazine hydrate purification. The difference lies in the tray assembly 4 in this application. In the prior art, trays are generally single trays. After the liquid and gas phases come into contact at a single tray, the liquid phase flows downwards, and the gas phase flows upwards. During the downward flow of the liquid phase, the concentration of hydrazine hydrate increases with each single tray. Correspondingly, during the upward flow of the gas phase, the concentration of hydrazine hydrate in the gas phase decreases with each single tray. In this way, hydrazine hydrate is purified. The more sufficient the contact between the liquid and gas phases, the higher the purification efficiency.

[0021] The tray assembly 4 in this application adopts a double-tray structure. The upper tray 41 is mainly used to disperse the liquid phase, allowing it to fall more evenly onto the cap 422 of the lower tray 42. Simultaneously, the upper tray 41 also reduces the flow velocity of the liquid phase, extending the contact time between the liquid and gas phases. The lower tray 42 is mainly used for sufficient contact between the liquid and gas phases. The liquid phase falls from the upper overflow hole 411 onto the cap 422 to form a liquid film, while the gas phase exiting from the lower overflow hole 421 must pass through the liquid film to continue flowing upwards. Therefore, the liquid and gas phases can achieve sufficient contact. Furthermore, the hydraulic pressure formed by the liquid film is much lower than that of the liquid phase on the bubble cap tray. Therefore, this application has lower requirements for steam flow rate and volume, reducing steam consumption compared to bubble cap trays. The area of ​​the liquid film formed by liquid phase diffusion is significantly larger than the area of ​​the upper overflow hole 411. Therefore, compared with sieve trays, this application can improve purification efficiency and increase the flexibility of production load.

[0022] The umbrella cap 422 of this application has a downward slope, such as a cone shape, a hemispherical shape, or an inverted teardrop shape. In this way, it is easier for the liquid phase to form a liquid film after dispersion.

[0023] In a preferred embodiment, the umbrella cap 422 is detachably connected to the lower tower plate 42, more preferably by a threaded connection. That is, the lower end of the umbrella cap 422 is provided with an external thread, and the lower overflow hole 421 of the lower tower plate 42 is provided with a matching internal thread.

[0024] In another preferred embodiment, the umbrella cap 422 is welded to the lower tower plate 42.

[0025] In a preferred embodiment, the umbrella cap 422 includes a column 4222 and a cap 4223. The lower end of the column 4222 is connected to the lower tower plate 42, and the upper end of the column 4222 is connected to the cap 4223. The side wall of the column 4222 is provided with an air hole 4221.

[0026] The column 4222 in this application is mainly used to support the umbrella cap 422, while allowing the liquid phase sufficient space and time to form a liquid film. If the column 4222 is too low, it may fall into the liquid phase on the surface of the lower tray 42 before a liquid film is formed.

[0027] The cap body 4223 of this application is mainly used for liquid phase diffusion into a liquid film. The sloping portion of the cap body 4223 can be obtained by extrusion. The brim portion of the cap body 4223 can be obtained by machining iron sheets or the like using a machine tool, or it can be integrally formed with the column body 4222. A ring of vent holes 4221 can be provided in the brim portion to facilitate the passage of gas phase.

[0028] In a preferred embodiment, the column 4222 is provided with external threads, the cap 4223 is provided with internal threads, and the column 4222 and the cap 4223 are threadedly connected.

[0029] In a preferred embodiment, the upper tray 41 is provided with a baffle 412, the height of which is greater than the height of the upper overflow hole 411. When the liquid phase flows down from the upper tray assembly 4, it first falls onto the upper tray 41. Due to the presence of the baffle 412, the upper tray 41 can retain liquid phase at the same height as the overflow hole 411 on the liquid surface. Thus, the liquid phase overflows at the same height at all points on the upper tray 41, and the liquid phase can flow relatively evenly onto the cap 422 of the lower tray 42. During the downward overflow process, the liquid phase can also form a liquid film under suitable flow rate conditions, and the gas phase can fully contact the liquid phase as it rises to the upper tray 41.

[0030] In a preferred embodiment, the diameter of the upper overflow hole 411 is 2 to 4 centimeters.

[0031] In a preferred embodiment, an overflow plate is provided along the edge of the lower tray 42, forming a downcomer channel 5 between the overflow plate and the tower body 1. The height of the overflow plate is greater than the height of the bottommost vent 4221 on the sidewall of the column 4222. The lower tray 42 and the column 4222 of the umbrella cap 422 in this application constitute a conventional sieve tray. By providing the overflow plate, some liquid phase will flow downward along the vent 4221, thereby providing sufficient phase interface area and contact time for mass transfer.

[0032] In a preferred embodiment, the tower body 1 is provided with 6 to 8 layers of tower plate assemblies 4, and the downcomer channels 5 between adjacent tower body assemblies 1 are staggered.

[0033] The sieve plate distillation column of this application can be used with an azeotropic agent to reduce the steam temperature and thus reduce energy consumption. Adding the azeotropic agent lowers the boiling point of the liquid phase, making it easier for the liquid phase to evaporate after heating. After evaporation, some of the hydrazine hydrate in the gas phase is carried upwards by the liquid phase, while some water in the liquid phase is carried away by the upward-flowing steam. Thus, the concentration of hydrazine hydrate in the downward-flowing liquid phase gradually increases, while the concentration of hydrazine hydrate in the upward-flowing gas phase gradually decreases, thereby achieving the purpose of hydrazine hydrate purification. The azeotropic agent and water enter the condenser 3 from the top of the distillation column in gas phase form for further separation, separating the water and the azeotropic agent. Part of the liquid phase at the bottom of the distillation column is transferred away, while the other part enters the reboiler 2 and becomes steam to provide heat for the distillation column.

[0034] In a preferred embodiment, the top sidewall of the column body 1 is provided with an azeotropic agent inlet 11, which is located above the uppermost column body 1 assembly and is positioned away from the downcomer channel 5. A hydrazine hydrate inlet 12 is provided in the middle of the column body 1, also positioned away from the downcomer channel 5. In this way, the liquid phase flows in a serpentine manner within the distillation column, facilitating sufficient contact between the gas and liquid phases.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A sieve tray rectification column for purification of hydrazine hydrate, characterized by: The tower includes a tower body (1), a reboiler (2), a condenser (3), and a multi-layer tray assembly (4) arranged in parallel within the tower body (1). The tray assembly (4) includes an upper tray (41) and a lower tray (42) arranged in parallel. The upper tray (41) is provided with a plurality of upper overflow holes (411), and the lower tray (42) is provided with a plurality of lower overflow holes (421) that are directly opposite to the upper overflow holes (411). The lower overflow holes (421) are provided with umbrella caps (422), and the sidewalls of the umbrella caps (422) are provided with vent holes (4221).

2. The sieve tray rectification column for purification of hydrazine hydrate according to claim 1, characterized in that: The umbrella cap (422) is detachably connected to the lower tower plate (42).

3. The sieve tray rectification column for purification of hydrazine hydrate according to claim 1, characterized in that: The umbrella cap (422) includes a column (4222) and a cap (4223). The lower end of the column (4222) is connected to the lower tower plate (42), and the upper end of the column (4222) is connected to the cap (4223). The side wall of the column (4222) is provided with air holes (4221).

4. The sieve plate distillation column for hydrazine hydrate purification as described in claim 3, characterized in that: The column (4222) is provided with external threads, and the cap (4223) is provided with internal threads. The column (4222) and the cap (4223) are threaded together.

5. The sieve tray rectification column for purification of hydrazine hydrate as claimed in claim 1 wherein: The upper tower plate (41) is provided with a baffle (412), the height of which is greater than the height of the upper overflow hole (411).

6. The sieve tray rectification column for purification of hydrazine hydrate as claimed in claim 1 wherein: The diameter of the upper overflow hole (411) is 2-4 cm.

7. The sieve plate distillation column for hydrazine hydrate purification as described in claim 3, characterized in that: An overflow plate is provided on the edge of the lower tower plate (42), and a liquid discharge channel (5) is formed between the overflow plate and the tower body (1). The height of the overflow plate is greater than the height of the bottom pore (4221) on the side wall of the column (4222).

8. The sieve tray rectification column for purification of hydrazine hydrate according to claim 7, characterized in that: The tower body (1) is provided with 6 to 8 layers of tower plate assemblies, and the downcomer channels (5) between two adjacent tower plate assemblies (4) are staggered.

9. The sieve tray rectification column for purification of hydrazine hydrate according to claim 7, characterized in that: The top side wall of the tower body (1) is provided with an azeotropic agent inlet (11), which is located above the uppermost tower body (1) assembly and is positioned away from the outlet of the downcomer channel (5); the middle part of the tower body (1) is provided with a hydrazine hydrate inlet (12), which is located in the middle part of the tower body (1) and is positioned away from the outlet of the downcomer channel (5).

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