Energy-saving azeotropic distillation device for producing hydrazine hydrate by urea method

Abstract

The application provides an energy-saving azeotropic distillation device for producing hydrazine hydrate by a urea method, which comprises a distillation tower body, wherein the distillation tower body comprises a distillation section, a stripping section, a hydrazine hydrate inlet arranged between the distillation section and the stripping section, and an azeotropic agent inlet arranged at the upper end of the distillation section; a spraying mechanism for spraying the azeotropic agent, wherein the spraying mechanism is provided with a spraying pipeline which is arranged in the distillation tower body through the azeotropic agent inlet; a uniform distribution plate for uniformly distributing the azeotropic agent, wherein the uniform distribution plate is arranged below the spraying pipeline and connected with the inner wall of the distillation tower body; a filler layer for fully contacting the azeotropic agent and the rising steam; and a plurality of tower plates for accelerating the evaporation of the hydrazine hydrate solution. Compared with the prior art, the contact area of the hydrazine hydrate solution and the azeotropic agent can be significantly increased, and the separation efficiency of water and hydrazine hydrate can be improved.

Description

Technical Field

[0001] This application relates to the field of hydrazine hydrate production technology, and in particular to an energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process. Background Technology

[0002] Hydrazine hydrate is an important fine chemical raw material with wide applications in pharmaceuticals, pesticides, dyes, foaming agents, and many other fields. The urea process is one of the traditional processes for producing hydrazine hydrate, offering advantages such as readily available raw materials and low cost. The urea process involves the reaction of urea, sodium hypochlorite, and sodium hydroxide to produce hydrazine hydrate, sodium chloride, and sodium carbonate. The initial concentration of hydrazine hydrate is very low, only 5%–8%. Further purification to 40%–80%, or even higher, is required. In this field, preliminary distillation is often performed first, gradually concentrating the hydrazine hydrate solution at the bottom of the column. After removing impurities, further separation of hydrazine hydrate and water is achieved through vacuum distillation. In the preliminary distillation, the distillation column is divided into a stripping section and a rectification section from bottom to top, with the inlet located between the two sections. The stripping section removes sodium chloride, while the rectification section separates hydrazine hydrate and water. The initial hydrazine hydrate solution enters the distillation column through the inlet, flowing downwards into the stripping section and upwards to evaporate into the rectification section. Water has a lower boiling point than hydrazine hydrate. As the initial hydrazine hydrate solution flows downwards, its concentration gradually increases, and sodium chloride is removed by precipitation in the stripping section. Because the boiling points of water and hydrazine hydrate are relatively close, a small amount of hydrazine hydrate is also released during the upward evaporation of water. Furthermore, when hydrazine hydrate is concentrated to a certain degree, it forms an azeotrope with water; the higher the concentration of hydrazine hydrate, the more hydrazine hydrate is lost during evaporation. Thus, a high concentration of hydrazine hydrate cannot be obtained.

[0003] The invention patent application with application number 201510786973.7, entitled "A Method for Preparing High-Concentration Hydrazine Hydrate," employs a method of mixing a 60-80% hydrazine hydrate solution with an azeotropic agent, followed by distillation in a distillation column. A mixture of the azeotropic agent and water is obtained at the top of the column, while concentrated hydrazine hydrate is obtained at the bottom. Mixing the azeotropic agent with the hydrazine hydrate allows for azeotropic distillation at atmospheric pressure and relatively low temperature, removing water from the hydrazine hydrate and increasing its concentration. The azeotropic agent includes toluene, ethylbenzene, m-xylene, or aniline, preferably toluene or aniline.

[0004] The working principle of azeotropic agents is to disrupt the azeotropic properties of hydrazine hydrate and water, and then form a new azeotrope with water itself, carrying away the water and achieving separation of hydrazine hydrate and water. However, these organic azeotropic agents are immiscible with water and are difficult to mix evenly. Once in the distillation column, the azeotropic agent has difficulty making sufficient contact with water and generating an azeotropic effect. Therefore, a large amount of azeotropic agent is required for mixing, and the separation effect of water and hydrazine hydrate is poor. Utility Model Content

[0005] In view of this, this application proposes an energy-saving azeotropic distillation apparatus for the production of hydrazine hydrate using the urea process, which reduces the consumption of azeotropic agents while improving the separation efficiency of water and hydrazine hydrate.

[0006] An energy-saving azeotropic distillation unit for producing hydrazine hydrate using the urea process includes: A distillation column body, comprising a rectification section, a stripping section, a hydrazine hydrate inlet located between the rectification section and the stripping section, and an azeotropic agent inlet located at the upper end of the rectification section; A spraying mechanism for spraying azeotropic agents, wherein the spraying mechanism is provided with a spraying pipe that passes through the azeotropic agent inlet and is installed in the distillation column body; A uniform distribution plate for evenly distributing the azeotropic agent, the uniform distribution plate being located below the spray pipe and connected to the inner wall of the distillation column; A packing layer used to ensure sufficient contact between the azeotropic agent and the rising steam; Several trays used for accelerated evaporation of hydrazine hydrate solution.

[0007] To further recover the azeotropic agent, preferably, the energy-saving azeotropic distillation unit for producing hydrazine hydrate using the urea process also includes: A condenser for cooling azeotrope, wherein the condenser’s inlet is connected to the top of the distillation column via a pipe; An oil-water separator for separating water and azeotropic agents, wherein the inlet of the oil-water separator is connected to the outlet of the condenser via a pipe; A reflux tank for temporarily storing azeotropic agents, wherein the inlet of the reflux tank is connected to the oil outlet of an oil-water separator via a pipe, and the outlet of the reflux tank is connected to a spraying mechanism via a pipe.

[0008] To ensure sufficient contact between the azeotropic agent and the azeotrope formed by water and hydrazine hydrate, the filler layer is a corrugated filler layer.

[0009] The hydrazine hydrate solution contains a small amount of corrosive gases, such as chlorine and hydrogen chloride. To prevent these gases from corroding the corrugated packing, the corrugated packing layer is further made of ceramic.

[0010] Furthermore, the specific surface area of ​​the corrugated packing is 350–500 m² / m³, and the corrugation angle is 30–45 degrees.

[0011] Hydrazine hydrate is a heat-sensitive substance that is prone to decomposition at high temperatures. In order to allow the water in the hydrazine hydrate solution to evaporate at a lower temperature and reduce the decomposition of hydrazine hydrate, the tray is preferably a sieve tray.

[0012] To prevent high-concentration hydrazine hydrate droplets from being carried into the rectification section by steam, thus requiring the azeotropic agent to process more hydrazine hydrate and increasing the separation load, the energy-saving azeotropic distillation unit for producing hydrazine hydrate via the urea process preferably includes a baffle demister located between the stripping section and the hydrazine hydrate inlet, with an inclination angle of 30–45 degrees. The baffle demister guides the droplets back to the lower tray, improving the concentration efficiency of the stripping section.

[0013] To facilitate the separation of water and azeotropic agent, the liquid sprayed from the spray pipe is toluene.

[0014] The technical advantages of this application are as follows: In the rectification section, the azeotropic agent is uniformly dispersed through a uniformly distributed plate and fully contacts the evaporated water and hydrazine hydrate azeotrope through the packing layer. Water and the azeotropic agent form a new azeotrope, which is carried away by evaporation, while the hydrazine hydrate returns to a liquid state and falls. Compared with existing technologies, this significantly increases the contact area between the hydrazine hydrate solution and the azeotropic agent, improving the separation efficiency of water and hydrazine hydrate. Simultaneously, the concentration of the hydrazine hydrate solution increases during its descent. Hydrazine hydrate is a heat-sensitive substance; the use of tray distillation in the stripping section results in a smaller pressure drop and lower pressure required at the bottom of the column. This means a lower boiling point, which is beneficial for water evaporation, reduces the decomposition of hydrazine hydrate, and helps improve the concentration and yield of hydrazine hydrate. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process according to this application. Explanation of reference numerals in the attached drawings: 1. Distillation column body; 11. Rectifying section; 12. Stripping section; 2. Spraying mechanism; 3. Distribution plate; 4. Packing layer; 5. Tray; 6. Condenser; 7. Oil-water separator; 8. Reflux tank; 9. Preheating tank; 10. Baffle demister. Detailed Implementation

[0016] 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.

[0017] Please refer to Figure 1 An energy-saving azeotropic distillation unit for producing hydrazine hydrate using the urea process includes: The distillation column body 1 includes a rectification section 11, a stripping section 12, a hydrazine hydrate inlet located between the rectification section 11 and the stripping section 12, and an azeotropic agent inlet located at the upper end of the rectification section 11. After the initial solution of hydrazine hydrate enters through the hydrazine hydrate inlet, it is heated by the steam at the bottom of the tower. The gas phase in the initial solution rises with the steam, while the liquid phase falls due to gravity.

[0018] The rising vapors come into contact with the azeotropic agent in the rectification section 11, where water and the azeotropic agent form a new azeotrope and continue to rise. Some of the hydrazine hydrate re-liquidizes and accumulates downwards, thereby increasing the yield of hydrazine hydrate.

[0019] As the descending liquid phase falls, it is heated by the rising steam. The rising steam carries the gradually enriched hydrazine hydrate as it continues to descend. Simultaneously, as the concentrations of hydrazine hydrate and sodium chloride increase, sodium chloride precipitates out, and the hydrazine hydrate is gradually purified.

[0020] A spraying mechanism 2 for spraying azeotropic agents, wherein the spraying mechanism 2 is provided with a spraying pipe, which passes through the azeotropic agent inlet and is installed in the distillation column body 1; The azeotropic agent in the spray pipe comes from two sources: one is the azeotropic agent recovered by condensation, and the other is transported through external pipelines. The spray pipe sprays the azeotropic agent onto the uniform distribution plate 3, which then distributes the azeotropic agent evenly.

[0021] A uniform distribution plate 3 is used to evenly distribute the azeotropic agent. The uniform distribution plate 3 is located below the spray pipe and is connected to the inner wall of the distillation column body 1. Packing layer 4 is used to ensure sufficient contact between the azeotropic agent and the rising steam; After the azeotropic agent is evenly distributed on the uniform distribution plate 3, it falls onto the packing layer 4 and comes into full contact with the rising steam. The azeotropic agent carries away the moisture in the steam, and the remaining hydrazine hydrate, due to the decrease in boiling point caused by no longer azeotropically, becomes liquid and falls onto the tray 5.

[0022] Several trays 5 are used for accelerated evaporation of hydrazine hydrate solution.

[0023] The unevaporated hydrazine hydrate solution and the hydrazine hydrate falling from packing layer 4 reach tray 5. Hot steam passing through tray 5 from bottom to top heats the hydrazine hydrate solution. Due to the low boiling point of water, some of the water and a small amount of hydrazine hydrate in the solution turn into steam and rise, while the concentrated hydrazine hydrate solution continues to fall until it reaches the bottom of the column. If the concentration of the hydrazine hydrate solution at the bottom of the column is still low, it needs to be heated in a reboiler to turn into steam for further concentration.

[0024] After the azeotrope formed by the azeotropic agent and water exits from the top of the column, the azeotropic agent needs to be recovered; otherwise, the cost would be very high. Generally, oil-based azeotropic agents are used, allowing for stratified recovery after condensation.

[0025] Azeotropic agents, such as toluene, can be recovered using the methods described above. In a preferred embodiment, the energy-saving azeotropic distillation unit for producing hydrazine hydrate using the urea process further includes: A condenser 6 is used to cool the azeotrope, and the inlet of the condenser 6 is connected to the top of the distillation column 1 via a pipe. The azeotrope formed by toluene and water has a boiling point of 85 degrees Celsius. Condenser 6 cools the azeotrope to below 85 degrees Celsius. The refrigerant, after being heated, can be used to preheat the initial hydrazine hydrate solution, thus reducing energy consumption.

[0026] Therefore, in a preferred embodiment, the energy-saving azeotropic distillation apparatus for producing hydrazine hydrate by the urea process further includes a preheating tank 9, which is provided with a jacket and connected to the refrigerant inlet and refrigerant outlet of the condenser 6 through a pipeline, and the refrigerant circulates between the condenser 6 and the preheating tank 9.

[0027] An oil-water separator 7 is used to separate water and azeotropic agents, wherein the inlet of the oil-water separator 7 is connected to the outlet of the condenser 6 via a pipe. After the azeotrope enters the oil-water separator 7, it undergoes settling and stratification. The water layer is discharged for the preparation of hydrazine hydrate. The oil layer enters the reflux tank 8 for buffering.

[0028] A reflux tank 8 is used to temporarily store the azeotropic agent. The inlet of the reflux tank 8 is connected to the oil outlet of the oil-water separator 7 via a pipe, and the outlet of the reflux tank 8 is connected to the spray mechanism 2 via a pipe. The reflux tank 8 provides a stable flow of azeotropic agent to the spray mechanism 2, ensuring that hydrazine hydrate in the steam is fully separated.

[0029] In order to ensure that the azeotropic agent is in full contact with the azeotrope formed by water and hydrazine hydrate, the filler layer 4 is a corrugated filler layer 4.

[0030] The corrugated packing layer 4 has a low pressure drop, which reduces the decomposition of hydrazine hydrate. It also has a large specific surface area, allowing for more thorough gas-liquid contact.

[0031] The hydrazine hydrate solution contains a small amount of corrosive gases, such as chlorine and hydrogen chloride. To prevent these gases from corroding the corrugated packing, the corrugated packing layer 4 is further made of ceramic.

[0032] Furthermore, the specific surface area of ​​the corrugated packing is 350–500 m² / m³, and the corrugation angle is 30–45 degrees.

[0033] Hydrazine hydrate is a heat-sensitive substance that is prone to decomposition at high temperatures. In order to allow the water in the hydrazine hydrate solution to evaporate at a lower temperature and reduce the decomposition of hydrazine hydrate, preferably, the tray 5 is a sieve tray 5.

[0034] To prevent high-concentration hydrazine hydrate droplets from being carried into the rectification section 11 by steam, which would require the azeotropic agent to process more hydrazine hydrate and increase the separation load, in a preferred embodiment, the energy-saving azeotropic distillation unit for producing hydrazine hydrate using the urea process further includes a baffle demister 10. The baffle demister 10 is located between the stripping section 12 and the hydrazine hydrate inlet, and its inclination angle is 30–45 degrees. The baffle demister 10 guides the droplets back to the lower tray 5, improving the concentration efficiency of the stripping section 12.

[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. An energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process, characterized in that, include: The distillation column body (1) includes a rectification section (11), a stripping section (12), a hydrazine hydrate inlet located between the rectification section (11) and the stripping section (12), and an azeotropic agent inlet located at the upper end of the rectification section (11). A spraying mechanism (2) for spraying azeotropic agents, wherein the spraying mechanism (2) is provided with a spraying pipe, which passes through the azeotropic agent inlet and is located in the distillation column body (1); A uniform distribution plate (3) for uniformly distributing the azeotropic agent is located below the spray pipe and is connected to the inner wall of the distillation column body (1). (4) A packing layer used to ensure sufficient contact between the azeotropic agent and the rising steam; Several trays (5) used for accelerated evaporation of hydrazine hydrate solution.

2. The energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process as described in claim 1, characterized in that... Also includes: A condenser (6) for cooling azeotropic materials, wherein the inlet of the condenser (6) is connected to the top of the distillation column (1) via a pipe. An oil-water separator (7) for separating water and azeotropic agents, wherein the inlet of the oil-water separator (7) is connected to the outlet of the condenser (6) via a pipe. A reflux tank (8) for temporarily storing azeotropic agents is provided. The inlet of the reflux tank (8) is connected to the outlet of the oil-water separator (7) via a pipe, and the outlet of the reflux tank (8) is connected to the spraying mechanism (2) via a pipe.

3. The energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process as described in claim 1, characterized in that... Also includes: The preheating tank (9) is provided with a jacket and is connected to the refrigerant inlet and refrigerant outlet of the condenser (6) through a pipeline. The refrigerant circulates between the condenser (6) and the preheating tank (9).

4. The energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process as described in claim 1, characterized in that: The packing layer (4) is a corrugated packing layer.

5. The energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process as described in claim 4, characterized in that, The corrugated packing layer is made of ceramic.

6. The energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process as described in claim 4, characterized in that: The specific surface area of ​​the corrugated packing layer is 350–500 m². 2 / m 3 The corrugation angle is 30 to 45 degrees.

7. The energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process as described in claim 1, characterized in that: The tray (5) is a sieve tray.

8. The energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process as described in claim 1, characterized in that... It also includes a baffle demister (10), which is located between the stripping section (12) and the hydrazine hydrate inlet. The baffle demister (10) has an inclination angle of 30 to 45 degrees. The baffle demister (10) guides the droplets back to the lower tray (5) to improve the concentration efficiency of the stripping section (12).

9. The energy-saving azeotropic distillation apparatus for producing hydrazine hydrate using the urea process as described in claim 1, characterized in that: The liquid sprayed from the spray pipe is toluene.

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