Device and method for continuously producing methylhydrazine by hydrazine hydrate methanol method

Abstract

The invention discloses a device and method for continuously producing methylhydrazine through a hydrazine hydrate methanol method, and relates to the technical field of chemical processes and equipment.The device comprises a tubular reactor, a feeding port is connected with a hydrazine hydrochloride storage tank and a methanol storage tank, discharged materials of the tubular reactor enter a first distillation tower, and the tubular reactor comprises a tubular structure and a heat exchange structure; a gas-liquid redistributor and a heat exchange structure are respectively arranged inside and outside the pipe structure; the methanol return tank is connected with the first distillation tower, and a discharge port of the methanol return tank is connected with the first middle feed port; a feed port of the stirring kettle is connected with a discharge port of the first distillation tower, a discharge port of the stirring kettle is connected with the second distillation tower, a hydrazine hydrochloride outlet of the second distillation tower is connected with a hydrazine hydrochloride return tank, and a discharge port of the hydrazine hydrochloride return tank is connected with the second middle feed port; a feed port of the third rectifying tower is connected with a top discharge port of the second distillation tower, a discharge port of the third rectifying tower is connected with a methylhydrazine storage tank, and the third rectifying tower is further connected with a top feed pipe of the stirring kettle.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical processes and equipment, and more specifically, relates to a device and method for continuously producing methylhydrazine by a hydrazine hydrate methanol process. Background Art

[0002] Methylhydrazine is an important chemical propellant with high energy density and good chemical stability. It is widely used in aerospace and defense fields. In recent years, methylhydrazine has become an indispensable raw material for the synthesis of fine chemical products such as medicines and pesticides. Its application scope has been continuously expanded and it has gradually occupied an important position in many fields. In the existing methylhydrazine synthesis process, the alkylation reaction is violent and difficult to control.

[0003] The hydrazine hydrate methanol method is to react hydrazine hydrate hydrochloric acid solution with methanol to generate methylhydrazine hydrochloride, and then release methylhydrazine through water and hydrazine hydrate, and then obtain methylhydrazine product through dealcoholization, separation, refining and other processes. This method can effectively improve the reaction selectivity and reduce the production of by-products. The unreacted methanol and the produced hydrazine hydrochloride can be repeatedly involved in the alkylation reaction process. The preparation process is simple and the raw material utilization rate is high. Therefore, it is widely used in industry. The invention patent with application number 201720359031.5 provides a methylhydrazine autoclave reactor synthesis device, which makes the working chamber float up and down to improve the synthesis efficiency; but the floating up and down and stirring at the same time have high requirements on the sealing of the device, which is easy to increase the risk of damage and leakage of the device, and there are safety hazards; in addition, the autoclave reactor is prone to dead zone, the reaction rate is low, and the wall adhesion phenomenon is prone to occur during the reaction, which reduces the synthesis efficiency, resulting in poor reliability in use. Application No. 202210008727.9 provides a methylhydrazine continuous flow microchannel alkylation method, which can effectively improve the selectivity of the reaction and reduce the production of by-products. It also has a simple preparation process, mild reaction conditions, low energy consumption, and high safety. However, it is prone to clogging, has high equipment manufacturing costs, and has a small flux, making it difficult to adapt to large-scale production. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for continuously producing methylhydrazine by a hydrazine hydrate methanol process in view of the deficiencies in the prior art. The tubular reactor in the device for producing methylhydrazine can be composed of a plurality of groups of tube structures and heat exchange structures. The tube structures can be assembled and connected arbitrarily and can be easily enlarged, so that large-scale continuous production of methylhydrazine can be achieved. In addition, an intermediate feed port is added to the tube structure, and unreacted methanol and hydrazine hydrochloride aqueous solution are continuously returned to the tube structure to achieve recycling, thereby effectively improving the comprehensive conversion rate of the reactants.

[0005] In order to achieve the above object, the present invention provides a device for continuously producing methylhydrazine by hydrazine hydrate methanol method, comprising: A tubular reactor, wherein the feed port is connected to a hydrazine hydrochloride storage tank and a methanol storage tank, the discharge port of the tubular reactor is connected to the feed port of a first distillation tower, the tubular reactor comprises at least three groups of tube structures and heat exchange structures, each group of the tube structures comprises a vertical tube and a U-shaped elbow, the heat exchange structure is arranged outside the tube structure, and a gas-liquid redistributor is arranged inside the tube structure; A methanol return tank, wherein the feed port is connected to the methanol outlet of the first distillation tower, and the discharge port of the methanol return tank is connected to the first intermediate feed port provided on the U-shaped elbow; A stirring kettle, wherein the feed port is connected to the discharge port of the first distillation tower, the discharge port of the stirring kettle is connected to the feed port of the second distillation tower, the hydrazine hydrochloride outlet of the second distillation tower is connected to the feed port of the hydrazine hydrochloride return tank, the discharge port of the hydrazine hydrochloride return tank is connected to the second intermediate feed port provided on the U-shaped elbow, and a hydrazine hydrate feed pipe is also provided on the top of the stirring kettle; The feed port of the third distillation tower is connected to the top discharge port of the second distillation tower, the discharge port of the third distillation tower is connected to the methylhydrazine storage tank, and the bottom discharge port of the third distillation tower is connected to the top feed pipe of the stirring kettle.

[0006] Optionally, along the flow direction of the mixed liquid in the tubular reactor, the first intermediate feed port and the second intermediate feed port are sequentially arranged on different U-shaped elbows, and a pressure sensor and a temperature sensor are also arranged on the tube structure.

[0007] Optionally, the heat exchange structure includes a plurality of heat exchange sleeves, which are wrapped one-to-one with the vertical tubes, and adjacent heat exchange sleeves are connected by flanges. A temperature control medium inlet and a temperature control medium outlet are respectively provided on the heat exchange sleeves at the head and the tail.

[0008] Optionally, the inner diameter of the tube structure is 15-200 mm, the height of the vertical tube is 0.5-8 m, the inner diameter of the heat exchange sleeve is 30-300 mm, and the gas-liquid redistributor is arranged at intervals in the tube structure.

[0009] Optionally, the material of the tube structure is C276 Hastelloy, and the lining material of the tube structure is polytetrafluoroethylene or glass lining.

[0010] Optionally, the gas-liquid redistributor is one of an SV static mixer, an SX static mixer, an SH static mixer or an SK static mixer, and the material of the gas-liquid redistributor is one of polytetrafluoroethylene, ceramic or C276 Hastelloy.

[0011] The present invention also provides a method for continuously producing methylhydrazine by a hydrazine hydrate methanol method, using the above-mentioned device for continuously producing methylhydrazine by a hydrazine hydrate methanol method, the method steps comprising: Step 1: prepare a hydrazine hydrochloride aqueous solution by mixing hydrazine hydrate and hydrochloric acid in a molar ratio of 1: (1.15-1.5), and send the solution into the hydrazine hydrochloride storage tank, and add methanol with a purity exceeding 99.9% into the methanol storage tank; Step 2: delivering the hydrazine hydrochloride aqueous solution to the bottom inlet of the tube structure through a first pressure pump according to metering requirements, delivering methanol to the bottom inlet of the tube structure through a second pressure pump according to metering requirements, the hydrazine hydrochloride aqueous solution and the methanol flow and mix in the tube structure, and the heat exchange structure is preheated to the reaction temperature by delivering a heating medium; Step 3: In the tube structure, the hydrazine hydrochloride aqueous solution and methanol undergo an alkylation reaction to generate methylhydrazine hydrochloride, and the gas-liquid redistributor is used to achieve gas-liquid redistribution and sufficient mixing and contact of the solution; Step 4: sending the reaction mixture solution discharged from the top outlet of the tube structure to the first distillation tower through a cooler; Step 5: delivering the methanol solution coming out of the top of the first distillation tower to the first intermediate feed port through a third pressure pump according to metering requirements; Step 6: sending the liquid from the bottom of the first distillation tower to the stirring tank, and adding hydrazine hydrate into the stirring tank through the hydrazine hydrate feeding pipe according to the metering requirements; Step 7: sending the mixed liquid from the discharge port of the stirring tank to the second distillation tower, sending the hydrazine hydrochloride aqueous solution discharged from the second distillation tower to the second intermediate feed port through the fourth pressure pump according to the metering requirements, and sending the mixed liquid from the top discharge port of the second distillation tower to the third distillation tower; Step eight: sending the hydrazine hydrochloride solution discharged from the bottom discharge port of the third distillation tower to the stirring tank, and sending the methylhydrazine discharged from the discharge port of the third distillation tower to the methylhydrazine storage tank.

[0012] Optionally, in step 2, the molar ratio of the initial feed of methanol to the aqueous solution of hydrazine hydrochloride is 1.3 to 2.4; In step 5 and step 7, the molar ratio of methanol to hydrazine hydrochloride aqueous solution returned to the tubular reactor is 1.5 to 2.3.

[0013] Optionally, the reaction temperature in the tubular reactor is 90-130° C., and the reaction pressure is 1.1 MPa-1.5 MPa; The mixed liquid has an superficial liquid velocity of 0.002-0.02 m / s in the tube structure and a residence time of 0.2-2 h; The reaction temperature in the stirred tank is 50-80° C., and the residence time of the mixed liquid in the stirred tank is 0.3-1.0 h.

[0014] Optionally, the operating pressure of the first distillation tower is 0.01-0.05 MPa, the operating temperature is 62-93° C., the number of plates is 20-30, and the feed inlet is at the 7th-12th plate; The operating pressure of the second distillation tower is 0.005-0.015 MPa, the operating temperature is 60-190°C, the number of plates is 5-10, and the feed inlet is at the 3rd-4th plate; The operating pressure of the third distillation tower is 0.01-0.05 MPa, the operating temperature is 85-125° C., the number of plates is 25-37, and the feed inlet is at the 9th-15th plate.

[0015] The present invention provides a device and method for continuously producing methylhydrazine by a hydrazine hydrate methanol process, and the beneficial effects thereof are: 1. In the device for producing methylhydrazine, a heat exchange structure is sleeved on the outside of the tube structure, and methanol and hydrazine hydrochloride are fully mixed through the internal gas-liquid redistributor. In addition, the heat exchange structure transfers the heat of the heat exchange medium to the mixed liquid to achieve an alkylation reaction, which can effectively reduce the back mixing of the reaction materials, improve the selectivity of methylhydrazine, and effectively avoid the phenomenon of low product purity caused by excessive alkylation of methylhydrazine; 2. The tubular reactor of the device for producing methylhydrazine is characterized by connecting multiple groups of tubular structures end to end in sequence as needed. Methanol and hydrazine hydrochloride are mixed and passed through all tubular structures to ensure sufficient mixing and alkylation reaction. In addition, a feeding port is added to the U-shaped elbow on the adjacent tubular structure to facilitate the addition of return materials during the reaction. In this way, the structure of the tubular reactor is easy to scale up, and large-scale continuous production of methylhydrazine can be realized; 3. Two intermediate feed ports are arranged on the tubular reactor of the device for producing methylhydrazine, and unreacted methanol and hydrazine hydrochloride aqueous solution are continuously fed back to the tubular reactor to realize recycling and effectively improve the comprehensive conversion rate of the reactants.

[0016] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0018] Figure 1 A schematic structural diagram of a device for continuously producing methylhydrazine by a hydrazine hydrate methanol process according to an embodiment of the present invention is shown.

[0019] Figure 2 A schematic structural diagram of a tubular reactor according to an embodiment of the present invention is shown.

[0020] Description of reference numerals: 1. Hydrazine hydrochloride storage tank; 2. Methanol storage tank; 3. First booster pump; 4. Second booster pump; 5. Tubular reactor; 6. Cooler; 7. First distillation tower; 8. Methanol return tank; 9. Third booster pump; 10. First intermediate feed port; 11. Stirring kettle; 12. Second distillation tower; 13. Hydrazine hydrochloride return tank; 14. Fourth booster pump; 15. Second intermediate feed port; 16. Third distillation tower; 17. Methyl hydrazine storage tank; 18. U-shaped elbow; 19. Heat exchange sleeve; 20. Gas-liquid redistributor; 21. Pressure sensor; 22. Temperature sensor; 23. Flange; 24. Bottom inlet of pipe structure; 25. Top outlet of pipe structure; 26. Temperature control medium inlet; 27. Temperature control medium outlet. DETAILED DESCRIPTION

[0021] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0022] The present invention provides a device for continuously producing methylhydrazine by a hydrazine hydrate methanol process, comprising: A tubular reactor, wherein the feed port is connected to the hydrazine hydrochloride storage tank and the methanol storage tank, the discharge port of the tubular reactor is connected to the feed port of the first distillation tower, the tubular reactor comprises at least three groups of tube structures and heat exchange structures, each group of tube structures comprises a vertical tube and a U-shaped elbow, the heat exchange structure is arranged outside the tube structure, and a gas-liquid redistributor is arranged inside the tube structure; A methanol return tank, wherein the feed port is connected to the methanol outlet of the first distillation tower, and the discharge port of the methanol return tank is connected to the first intermediate feed port provided on the U-shaped elbow; A stirring kettle, wherein the feed port is connected to the discharge port of the first distillation tower, the discharge port of the stirring kettle is connected to the feed port of the second distillation tower, the hydrazine hydrochloride outlet of the second distillation tower is connected to the feed port of the hydrazine hydrochloride return tank, the discharge port of the hydrazine hydrochloride return tank is connected to the second intermediate feed port provided on the U-shaped elbow, and a hydrazine hydrate feed pipe is also provided on the top of the stirring kettle; The feed port of the third distillation tower is connected to the top discharge port of the second distillation tower, the discharge port of the third distillation tower is connected to the methylhydrazine storage tank, and the bottom discharge port of the third distillation tower is connected to the top feed pipe of the stirring kettle.

[0023] Specifically, the device pumps methanol and hydrazine hydrochloride into a tubular reactor in proportion, and through sufficient mixing in a gas-liquid redistributor and heating by a heat exchange structure, the resulting mixed liquid is cooled and sent to a first distillation tower; after the reaction in the first distillation tower, methanol is discharged from the top of the distillation tower and sent to a methanol return tank for storage, so that methanol is regularly fed into the tubular reactor through a first intermediate feed port, and the feed liquid discharged from the bottom of the distillation tower enters a stirring tank, and hydrazine hydrate is added to the stirring tank through a feed pipe, and the stirring tank is stirred. After the mixing kettle is stirred and mixed, the discharge from the mixing kettle is sent to the second distillation tower, and the hydrazine hydrochloride discharged from the bottom of the second distillation tower is sent to the hydrazine hydrochloride return tank for storage, so as to facilitate the regular feeding of hydrazine hydrochloride to the tubular reactor through the second intermediate feed port. The discharge from the top of the second distillation tower enters the third distillation tower. After being processed in the third distillation tower, the top liquid of the distillation tower is discharged into the methylhydrazine storage tank. In addition, the distillation tower also discharges light components such as dimethylhydrazine, and a hydrazine hydrochloride solution is discharged into the mixing kettle at the bottom of the distillation tower.

[0024] Optionally, along the flow direction of the mixed liquid in the tubular reactor, a first intermediate feed port and a second intermediate feed port are sequentially arranged on different U-shaped elbows, and a pressure sensor and a temperature sensor are also arranged on the tube structure.

[0025] Optionally, the heat exchange structure includes multiple heat exchange sleeves, which are wrapped around the vertical tubes one-to-one, and adjacent heat exchange sleeves are connected by flanges. The heat exchange sleeves at the head and the tail are respectively provided with a temperature control medium inlet and a temperature control medium outlet.

[0026] Specifically, in the tubular reactor, multiple rows of parallel vertical tubes are arranged, and adjacent vertical tubes are connected by a U-shaped elbow, so that a tube structure channel for unidirectional flow of the mixture can be formed in series, and a pressure sensor and a temperature sensor are also equipped to monitor the environmental pressure and temperature in the tube structure; a heat exchange sleeve is wrapped around the outer periphery of each vertical tube, and adjacent heat exchange sleeves are connected by flanges, so that the heating medium enters from the temperature control medium inlet of the heat exchange structure, flows in each heat exchange sleeve, and releases heat to each vertical tube, ensuring that the reaction temperature of the mixture reaches the set requirements, and finally is discharged from the temperature control medium outlet of the heat exchange structure.

[0027] In one embodiment, the tubular reactor is generally provided with 3 to 20 groups of tubular structures, and the number can be increased arbitrarily according to the production scale of methylhydrazine.

[0028] Optionally, the inner diameter of the tube structure is 15-200 mm, the height of the vertical tube is 0.5-8 m, the inner diameter of the heat exchange sleeve is 30-300 mm, and the gas-liquid redistributors are arranged at intervals in the tube structure.

[0029] Specifically, the interval between the gas-liquid redistributors is 5 to 20 times the inner diameter of the vertical pipe, and the gas-liquid redistributors can also fill the entire pipe structure.

[0030] Optionally, the material of the pipe structure is C276 Hastelloy, and the lining material of the pipe structure is polytetrafluoroethylene or glass lining.

[0031] Optionally, the gas-liquid redistributor is one of an SV type static mixer, an SX type static mixer, an SH type static mixer or an SK type static mixer, and the material of the gas-liquid redistributor is one of polytetrafluoroethylene, ceramic or C276 Hastelloy.

[0032] Optionally, the first distillation tower, the second distillation tower and the third rectification tower are structured packing towers, the structured packing is made of ceramic, C276 Hastelloy or polytetrafluoroethylene, the structure of the stirring kettle is a closed type, and the material of the stirring kettle is glass-lined.

[0033] The present invention also provides a method for continuously producing methylhydrazine by a hydrazine hydrate methanol method, using the above-mentioned device for continuously producing methylhydrazine by a hydrazine hydrate methanol method, the method steps comprising: Step 1: prepare a hydrazine hydrochloride aqueous solution by mixing hydrazine hydrate and hydrochloric acid in a molar ratio of 1:1.15-1.5, and send the solution into a hydrazine hydrochloride storage tank, and add methanol with a purity exceeding 99.9% into a methanol storage tank; Step 2: delivering the hydrazine hydrochloride aqueous solution to the bottom inlet of the tube structure through the first pressure pump according to the metering requirements, delivering methanol to the bottom inlet of the tube structure through the second pressure pump according to the metering requirements, the hydrazine hydrochloride aqueous solution and the methanol flow and mix in the tube structure, and the heat exchange structure is preheated to the reaction temperature by delivering the heating medium, so that the temperature in the tube structure can be heated to the reaction temperature; Step 3: In the tube structure, as the mixed liquid flows, the hydrazine hydrochloride aqueous solution and methanol undergo an alkylation reaction to generate methylhydrazine hydrochloride, and the gas-liquid redistribution and sufficient mixing contact of the solution are achieved through a gas-liquid redistributor, so that the reaction conversion rate can reach more than 50% and the selectivity of methylhydrazine hydrochloride can reach more than 90%; Step 4: sending the reaction mixture solution discharged from the top outlet of the tube structure to the first distillation tower through a cooler; Step 5: sending the methanol solution with a content greater than 95% coming out of the top of the first distillation tower into the methanol return tank, and then sending it to the first intermediate feed port according to the metering requirements through the third pressure pump; Step 6: sending the liquid from the bottom of the first distillation tower to a stirred tank, and adding hydrazine hydrate to the stirred tank through a hydrazine hydrate feed pipe according to the metering requirements, exchanging methylhydrazine hydrochloride with hydrazine hydrate in the stirred tank to obtain a mixed solution of hydrazine hydrochloride and methylhydrazine; Step 7: sending the mixed liquid from the discharge port of the stirred tank to the second distillation tower, performing a decompression operation in the second distillation tower, sending the hydrazine hydrochloride aqueous solution discharged from the second distillation tower into the hydrazine hydrochloride return tank, and then sending it to the second intermediate feed port according to the metering requirements through the fourth pressure pump, and sending the mixed liquid from the top discharge port of the second distillation tower to the third distillation tower; Step eight: sending the hydrazine hydrochloride solution discharged from the bottom discharge port of the third distillation tower to the stirring tank, and sending the methylhydrazine discharged from the discharge port of the third distillation tower to the methylhydrazine storage tank, wherein the product yield of the methylhydrazine reaches more than 90%.

[0034] Optionally, in step 2, the molar ratio of the initial feed of methanol to the aqueous solution of hydrazine hydrochloride is 1.3 to 2.4; In step 5 and step 7, the molar ratio of methanol to the hydrazine hydrochloride aqueous solution returned to the tubular reactor is 1.5 to 2.3.

[0035] Optionally, the reaction temperature in the tubular reactor is 90-130° C., and the reaction pressure is 1.1 MPa-1.5 MPa; The superficial liquid velocity of the mixed liquid in the tube structure is 0.002~0.02m / s, and the residence time is 0.2~2h; The reaction temperature in the stirred tank is 50~80°C, and the residence time of the mixed liquid in the stirred tank is 0.3~1.0h.

[0036] Optionally, the operating pressure of the first distillation tower is 0.01-0.05 MPa, the operating temperature is 62-93° C., the number of plates is 20-30, and the feed inlet is at the 7th-12th plate; The operating pressure of the second distillation tower is 0.005~0.015MPa, the operating temperature is 60~190℃, the number of plates is 5~10, and the feed port is at the 3rd~4th plate; The operating pressure of the third distillation tower is 0.01~0.05MPa, the operating temperature is 85~125℃, the number of plates is 25~37, and the feed inlet is at the 9th to 15th plates. Example 1

[0037] like Figure 1 to Figure 2As shown, in a device for continuous production of methylhydrazine by hydrazine hydrate methanol method of the present invention, the tubular reactor 5 is composed of 7 groups of pipe structures connected in sequence, using φ89×5mm C276 Hastelloy pipes, each group has a height of 4m; the heat exchange sleeve 19 is a φ159×4mm 304 stainless steel pipe, with a height of 3.5m; the gas-liquid redistributor 20 in the pipe structure is an SX type static mixer, made of C276 Hastelloy, and the static mixer is arranged in a group every 1.5m in the pipe, with a length of 300mm; the first distillation tower 7, the second distillation tower 12, and the third distillation tower 16 are all BX type structured packing towers, the structured packing material is ceramic, and the stirring tank 11 is a closed type, made of glass lining.

[0038] The production method of methyl hydrazine comprises the following steps: hydrazine hydrate and hydrochloric acid are configured into a hydrazine hydrochloride aqueous solution in a molar ratio of 1:1.2, and the solution is fed into a hydrazine hydrochloride storage tank 1; methanol with a purity exceeding 99.9% is added into a methanol storage tank 2; the hydrazine hydrochloride aqueous solution discharged from the hydrazine hydrochloride storage tank 1 is fed into a tubular reactor 5 through a first pressure pump 3 according to metering requirements; methanol discharged from the methanol storage tank 2 is fed into the tubular reactor 5 through a second pressure pump 4 according to metering requirements, and the molar ratio of methanol to hydrazine hydrochloride initial feed is 1:1.5; in the first group of pipe structures and the second group of pipe structures, the two streams are fed into the first group of pipe structures through a gas-liquid redistributor 20; The mixture is fully mixed and preheated to a reaction temperature of 110°C after heat exchange with the heating medium in the heat exchange sleeve 19. Subsequently, in the subsequent tube structure, hydrazine hydrochloride and methanol undergo an alkylation reaction to generate methylhydrazine hydrochloride. The pressure in the tubular reactor 5 needs to be maintained at 1.3 MPa, the temperature is controlled at 115-118°C, the empty tower liquid velocity of the reaction mixture is controlled at 0.005 m / s, the residence time is 1.5 h, the single-pass reaction conversion rate in the tubular reactor 5 is above 52%, and the selectivity of methylhydrazine hydrochloride is 94%.

[0039] The reaction mixed solution from the outlet of the tubular reactor 5 is decompressed after passing through the cooler 6 and enters the first distillation tower 7. The theoretical plate number of the first distillation tower 7 is set to 25, the height of the structured packing is 35 meters, the top pressure is a gauge pressure of 0.017 MPa, the top temperature is 64.7°C, the bottom temperature is 87.5°C, and the feed port is located at the packing height of 7 meters; the methanol solution from the top of the tower has a content of 98.5%, and the methanol is discharged into the methanol return tank 8 and fed into the first intermediate feed port 10 through the third booster pump 9 according to the metering requirements; the bottom liquid from the bottom of the first distillation tower 7 continuously enters the stirring tank 11, and hydrazine hydrate is continuously added through the hydrazine hydrate feed pipe according to the metering requirements; the reaction temperature of the stirring tank 11 is set to 75°C, and the average residence time of the mixed solution in the stirring tank 11 is 0.7h; in the stirring tank 11, methylhydrazine hydrochloride and hydrazine hydrate are exchanged for hydrochloride to obtain a mixed solution of hydrazine hydrochloride and methylhydrazine.

[0040] The mixed solution coming out from the bottom of the stirred tank 11 is distilled into the second distillation tower 12. The second distillation tower 12 has 9 theoretical plates, a structured packing height of 15 meters, a top operating pressure of 0.01 MPa absolute pressure, a top temperature of 68°C, a bottom temperature of 186°C, and a feed port located at a packing height of 5 meters; the hydrazine hydrochloride coming out from the top of the tower enters the hydrazine hydrochloride return tank 13, and then enters the tubular reactor 5 through the second intermediate feed port 15 according to the metering requirements through the fourth booster pump 14, and the molar ratio of the methanol to the hydrazine hydrochloride returning to the tubular reactor 5 is controlled at 1.8.

[0041] The bottom liquid coming out of the tower bottom enters the third distillation tower 16, the number of plates of the third distillation tower 16 is 29, the height of the structured packing is 40 meters, the operating pressure at the top of the tower is a gauge pressure of 0.023 MPa, the top temperature is 91°C, the bottom temperature is 123°C, and the feed inlet is located at the packing height of 18 meters; the hydrazine hydrochloride solution coming out of the top of the third distillation tower 16 is returned to the stirring tank 11, and the bottom liquid coming out of the top and bottom of the third distillation tower 16 is the methylhydrazine product, which is sent to the methylhydrazine storage tank 17, and the comprehensive yield of the obtained methylhydrazine product is 89%. Example 2

[0042] The equipment for producing methylhydrazine, the tubular reactor 5 is composed of 9 groups of pipe structures connected in sequence, using φ76×5mm polytetrafluoroethylene lined carbon steel pipes, each group is 3.5m high; the heat exchange sleeve 19 is a φ133×4mm carbon steel pipe, the height is 3.0m; the gas-liquid redistributor 20 in the vertical pipe is an SV type static mixer, the material is C276 Hastelloy alloy, the static mixer is arranged in a group every 1.0m in the pipe, and the length is 200mm; the first distillation tower 7, the second distillation tower 12, and the third distillation tower 16 are all BX type structured packing towers, the structured packing material is polytetrafluoroethylene; the stirring tank 11 is a closed type, made of glass-lined material.

[0043] The production method of methylhydrazine is as follows: hydrazine hydrate and hydrochloric acid are configured into a hydrazine hydrochloride aqueous solution in a molar ratio of 1:1.3, and the solution is fed into a hydrazine hydrochloride storage tank 1; methanol with a purity exceeding 99.9% is added into a methanol storage tank 2; the hydrazine hydrochloride aqueous solution discharged from the hydrazine hydrochloride storage tank 1 is fed into the inlet of a tubular reactor 5 through a first booster pump 3 according to metering requirements; methanol discharged from the methanol storage tank 2 is fed into the inlet of the tubular reactor 5 through a second booster pump 4 according to metering requirements, and the molar ratio of methanol to hydrazine hydrochloride initial feed is 1:1.8; in the first group of pipe structures and the second group of pipe structures, the two fluids are fully mixed through a gas-liquid redistributor 20, and are preheated to a reaction temperature of 100°C after heat exchange with a heating medium in a heat exchange sleeve 19, and then in the subsequent pipe structures, hydrazine hydrochloride and methanol undergo an alkylation reaction to generate methylhydrazine hydrochloride. The pressure in the tubular reactor 5 is 1.3 MPa, the temperature is 110-113° C., the empty tower liquid velocity of the reaction mixed solution is controlled at 0.007 m / s, the residence time is 1.3 h, the single-pass reaction conversion rate in the tubular reactor 5 is above 54%, and the selectivity of methylhydrazine hydrochloride is 95%.

[0044] The reaction mixed solution from the outlet of the tubular reactor 5 is decompressed after passing through the cooler and enters the first distillation tower 7; the theoretical plate number of the first distillation tower 7 is 27, the height of the structured packing is 28 meters, the top pressure is 0.025MPa, the top temperature is 66.2°C, the bottom temperature is 89.5°C, and the feed port is located at the packing height of 8 meters; the methanol solution content from the top of the tower is 98.5%, and the methanol is sent to the methanol return tank 8, and is sent to the first intermediate feed port 10 through the third pressure pump 9 according to the metering requirements. The bottom liquid from the bottom of the first distillation tower 7 continuously enters the stirring tank 11, and hydrazine hydrate is continuously added through the hydrazine hydrate feed pipe according to the metering requirements. The reaction temperature of the stirring tank 11 is 72°C, and the average residence time of the mixed solution in the stirring tank 11 is 0.8h. In the stirring tank 11, methylhydrazine hydrochloride and hydrazine hydrate are exchanged for hydrochloride to obtain a mixed solution of hydrazine hydrochloride and methylhydrazine.

[0045] The mixed solution from the bottom of the stirred tank 11 is distilled into the second distillation tower 12. The second distillation tower 12 has 10 theoretical plates, a structured packing height of 12 meters, an absolute pressure of 0.008 MPa at the top of the tower, a top temperature of 95°C, a bottom temperature of 175°C, and a feed port located at a packing height of 4 meters. The hydrazine hydrochloride from the top of the tower enters the hydrazine hydrochloride return tank 13, and then enters the tubular reactor 5 through the second intermediate feed port 15 according to the metering requirements through the fourth booster pump 14. The molar ratio of methanol to hydrazine hydrochloride returned to the tubular reactor 5 is controlled at 1.9.

[0046] The bottom liquid from the bottom of the tower enters the third distillation tower 16, the number of plates of the third distillation tower 16 is 31, the height of the structured packing is 30 meters, the operating pressure at the top of the tower is 0.03MPa, the top temperature is 74°C, the bottom temperature is 118°C, and the feed port is located at the packing height of 12 meters. The hydrazine hydrochloride solution from the top of the third distillation tower 16 is returned to the stirring tank 11, and the methylhydrazine product from the top and bottom of the third distillation tower 16 is sent to the methylhydrazine storage tank 17, and the comprehensive yield of the obtained methylhydrazine product is 91%. Example 3

[0047] In the equipment for producing methylhydrazine, the tubular reactor 5 is composed of 11 groups of tube structures connected in sequence. Each vertical tube is connected by 3 sections of φ108×6mm glass-lined tubes, each section is 1.5m high, and the total height is 4.5m. Each section of the glass-lined tube is covered with a heat exchange sleeve 19, which is a φ159×4mm carbon steel tube; the gas-liquid redistributor 20 in the vertical tube is an SH type static mixer made of C276 Hastelloy alloy, and each section of the glass-lined tube is provided with a group of static mixers with a length of 350mm; the first distillation tower 7, the second distillation tower 12, and the third distillation tower 16 are all BX type structured packing towers, and the structured packing is made of C276 Hastelloy alloy. The stirred tank 11 is a closed type and is made of glass-lined material.

[0048] The production method of methylhydrazine is as follows: hydrazine hydrate and hydrochloric acid are configured into a hydrazine hydrochloride aqueous solution in a molar ratio of 1:1.25, and the solution is fed into a hydrazine hydrochloride storage tank 1; methanol with a purity of more than 99.9% is added to a methanol storage tank 2; the hydrazine hydrochloride aqueous solution from the hydrazine hydrochloride storage tank 1 is added to the inlet of a tubular reactor 5 through a first booster pump 3 according to metering requirements; the methanol from the methanol storage tank 2 is added to the inlet of a tubular reactor 5 through a second booster pump 4 according to metering requirements, and the molar ratio of methanol to the initial feed of hydrazine hydrochloride is 1:2.0. In the first two groups of tube structures, the two streams are fully mixed through a gas-liquid redistributor 20, and are preheated to a reaction temperature of 105°C after heat exchange with a heating medium in a heat exchange sleeve 19, and then in the subsequent tube structure, hydrazine hydrochloride and methanol undergo an alkylation reaction to generate methylhydrazine hydrochloride. The pressure in the tubular reactor 5 is 1.25 MPa, the temperature is controlled at 115-120° C., the empty tower liquid velocity of the reaction mixed solution is controlled at 0.01 m / s, the residence time is 1.8 h, the single-pass reaction conversion rate in the tubular reactor 5 is above 58%, and the selectivity of methylhydrazine hydrochloride is 93%.

[0049] The reaction mixed solution from the outlet of the tubular reactor 5 is decompressed after passing through the cooler and enters the first distillation tower 7; the theoretical plate number of the first distillation tower 7 is 25, the height of the structured packing is 18 meters, the top pressure is 0.03MPa, the top temperature is 68.2℃, the bottom temperature is 91.5℃, and the feed port is located at the packing height of 6 meters. The methanol solution content from the top of the tower is 98.7%, and the methanol enters the methanol return tank 8 and is sent to the first intermediate feed port 10 through the third pressure pump 9 according to the metering requirements. The bottom liquid from the bottom of the first distillation tower 7 continuously enters the stirring tank 11, and hydrazine hydrate is continuously added through the hydrazine hydrate feed pipe according to the metering requirements. The reaction temperature of the stirring tank 11 is 70℃, and the average residence time of the mixed solution in the stirring tank 11 is 0.95h. In the stirring tank 11, methylhydrazine hydrochloride and hydrazine hydrate are exchanged for hydrochloride to obtain a mixed solution of hydrazine hydrochloride and methylhydrazine.

[0050] The mixed solution from the bottom of the stirred tank 11 is fed into the second distillation tower 12. The second distillation tower 12 has 9 theoretical plates, a structured packing height of 7 meters, a top operating pressure of 0.01 MPa absolute pressure, a top temperature of 100°C, a bottom temperature of 185°C, and a feed port located at a packing height of 3 meters. The hydrazine hydrochloride from the top of the tower is fed into the hydrazine hydrochloride return tank 13, and then enters the tubular reactor 5 through the second intermediate feed port 15 according to the metering requirements through the fourth booster pump 14. The molar ratio of methanol to hydrazine hydrochloride returned to the tubular reactor 5 is controlled at 2.1.

[0051] The bottom liquid from the bottom of the tower enters the third distillation tower 16. The number of plates of the third distillation tower 16 is 34, the height of the structured packing is 26 meters, the operating pressure at the top of the tower is 0.02MPa, the top temperature is 73°C, the bottom temperature is 120°C, and the feed port is located at the packing height of 10 meters. The hydrazine hydrochloride solution from the top of the third distillation tower 16 is returned to the stirring tank 11, and the methylhydrazine product from the top and bottom of the third distillation tower 16 is sent to the methylhydrazine storage tank 17. The comprehensive yield of the obtained methylhydrazine product is 92%. Example 4

[0052] In the equipment for producing methylhydrazine, the tubular reactor 5 is composed of 13 groups of tube structures connected in sequence, using φ76×5mm C276 Hastelloy tubes, and each group is 6m high. The heat exchange sleeve 19 is a φ159×4mm 304 stainless steel tube with a height of 5.5m; the gas-liquid redistributor 20 in the tube structure is a ridge-shaped component made of C276 Hastelloy, and the static mixer is set in a group every 1.5m in the tube, with a length of 300mm. The first distillation tower 7, the second distillation tower 12, and the third distillation tower 16 are all BX500 type structured packing towers, and the structured packing is made of C276 Hastelloy. The stirred tank 11 is a closed type, made of glass lining.

[0053] The production method of methylhydrazine is as follows: hydrazine hydrate and hydrochloric acid are configured into a hydrazine hydrochloride aqueous solution in a molar ratio of 1:1.4, and the solution is fed into a hydrazine hydrochloride storage tank 1; methanol with a purity exceeding 99.9% is added to a methanol storage tank 2. The hydrazine hydrochloride aqueous solution from the hydrazine hydrochloride storage tank 1 is added to the inlet of the tubular reactor 5 through a first booster pump 3 according to the metering requirements; the methanol from the methanol storage tank 2 is added to the inlet of the tubular reactor 5 through a second booster pump 4 according to the metering requirements, and the molar ratio of methanol to the initial feed of hydrazine hydrochloride is 1:1.8. In the first two groups of tube structures, the two streams are fully mixed by a gas-liquid redistributor 20, and are preheated to a reaction temperature of 108°C after heat exchange with the heating medium in the heat exchange sleeve 19, and then in the subsequent tube structure, hydrazine hydrochloride and methanol undergo an alkylation reaction to generate methylhydrazine hydrochloride. The pressure in the tubular reactor 5 is 1.3 MPa, the temperature is controlled at 113-116° C., the empty tower liquid velocity of the reaction mixture is controlled at 0.012 m / s, the residence time is 1.6 h, the single-pass reaction conversion rate in the tubular reactor 5 is above 56%, and the selectivity of methylhydrazine hydrochloride is 95.3%.

[0054] The reaction mixed solution from the outlet of the tubular reactor 5 is decompressed after passing through the cooler and enters the first distillation tower 7. The theoretical number of plates of the first distillation tower 7 is 28, the height of the structured packing is 15 meters, the top pressure is 0.027MPa, the top temperature is 67.3℃, the bottom temperature is 89.5℃, and the feed port is located at the packing height of 5 meters. The methanol solution content coming out of the top of the tower is 98.7%, and it is sent to the methanol return tank 8, and is sent to the first intermediate feed port 10 through the third booster pump 9 according to the metering requirements. The bottom liquid from the bottom of the first distillation tower 7 continuously enters the stirring tank 11, and hydrazine hydrate is continuously added through the hydrazine hydrate feed pipe according to the metering requirements. The reaction temperature of the stirring tank 11 is 80℃, and the average residence time of the mixed solution in the stirring tank 11 is 0.65h. In the stirring tank 11, methylhydrazine hydrochloride and hydrazine hydrate are exchanged for hydrochloride to obtain a mixed solution of hydrazine hydrochloride and methylhydrazine.

[0055] The mixed solution from the bottom of the stirred tank 11 is distilled into the second distillation tower 12. The second distillation tower 12 has 7 theoretical plates, a structured packing height of 4 meters, a top operating pressure of 0.008 MPa, a top temperature of 66°C, a bottom temperature of 167°C, and a feed port located at a packing height of 2 meters. The hydrazine hydrochloride from the top of the tower enters the hydrazine hydrochloride return tank 13, and then enters the tubular reactor 5 through the second intermediate feed port 15 according to the metering requirements through the fourth booster pump 14. The molar ratio of methanol to hydrazine hydrochloride returned to the tubular reactor 5 is controlled at 2.1.

[0056] The bottom liquid from the bottom of the tower enters the third distillation tower 16. The number of plates of the third distillation tower 16 is 30, the height of the structured packing is 20 meters, the operating pressure at the top of the tower is 0.023MPa, the top temperature is 92°C, the bottom temperature is 125°C, and the feed port is located at the packing height of 10 meters. The hydrazine hydrochloride solution from the top of the third distillation tower 16 is returned to the stirring tank 11, and the methylhydrazine product from the top and bottom of the third distillation tower 16 is sent to the methylhydrazine storage tank 17. The comprehensive yield of the obtained methylhydrazine product is 91.5%. Example 5

[0057] In the equipment for producing methylhydrazine, the tubular reactor 5 is composed of 13 groups of tube structures connected in sequence, using φ108×6mm C276 Hastelloy tubes, and each group is 5m high. The heat exchange sleeve 19 is a φ159×4mm 304 stainless steel tube with a height of 4.5m; the gas-liquid redistributor 20 in the tube structure is a BX300 type structured packing made of C276 Hastelloy, and the structured packing is arranged in a group every 1.0m in the tube, with a length of 800mm. The first distillation tower 7, the second distillation tower 12, and the third distillation tower 16 are BX300 type structured packing towers, and the structured packing is made of C276 Hastelloy. The stirred tank 11 is a closed type, made of glass lining.

[0058] The production method of methylhydrazine is as follows: hydrazine hydrate and hydrochloric acid are configured into a hydrazine hydrochloride aqueous solution in a molar ratio of 1:1.3, and the solution is fed into a hydrazine hydrochloride storage tank 1; methanol with a purity exceeding 99.9% is added to a methanol storage tank 2. The hydrazine hydrochloride aqueous solution from the hydrazine hydrochloride storage tank 1 is added to the inlet of the tubular reactor 5 through a first booster pump 3 according to the metering requirements; the methanol from the methanol storage tank 2 is added to the inlet of the tubular reactor 5 through a second booster pump 4 according to the metering requirements, and the molar ratio of methanol to the initial feed of hydrazine hydrochloride is 1:1.7. In the first two groups of pipe structures, the two streams are fully mixed by a gas-liquid redistributor, and are preheated to a reaction temperature of 105°C after heat exchange with the heating medium in the heat exchange sleeve 19, and then in the subsequent pipe structure, hydrazine hydrochloride and methanol undergo an alkylation reaction to generate methylhydrazine hydrochloride. The pressure in the tubular reactor 5 is 1.3 MPa, the temperature is controlled at 112-118° C., the empty tower liquid velocity of the reaction mixture is controlled at 0.010 m / s, the residence time is 1.7 h, the single-pass reaction conversion rate in the tubular reactor 5 is above 59%, and the selectivity of methylhydrazine hydrochloride is 96.2%.

[0059] The reaction mixed solution coming out of the outlet of the tubular reactor 5 is decompressed after passing through the cooler and enters the first distillation tower 7. The theoretical number of plates of the first distillation tower 7 is 27, the height of the structured packing is 24 meters, the top pressure is 0.025MPa, the top temperature is 66.5℃, the bottom temperature is 88.5℃, and the feed port is located at the packing height of 13 meters. The methanol solution content coming out of the top of the tower is 98.9%, and the methanol is sent to the methanol return tank 8, and is sent to the first intermediate feed port 10 through the third booster pump 9 according to the metering requirements. The bottom liquid coming out of the bottom of the first distillation tower 7 continuously enters the stirring tank 11, and hydrazine hydrate is continuously added through the hydrazine hydrate feed pipe according to the metering requirements. The reaction temperature of the stirring tank 11 is 73℃, and the average residence time of the mixed solution in the stirring tank 11 is 0.85h. In the stirring tank 11, methylhydrazine hydrochloride and hydrazine hydrate are exchanged for hydrochloride to obtain a mixed solution of hydrazine hydrochloride and methylhydrazine.

[0060] The mixed solution from the bottom of the stirred tank 11 is distilled into the second distillation tower 12. The second distillation tower 12 has 6 theoretical plates, a structured packing height of 6 meters, a top operating pressure of 0.009 MPa, a top temperature of 67°C, a bottom temperature of 169°C, and a feed port located at a packing height of 3 meters. The hydrazine hydrochloride from the top of the tower enters the hydrazine hydrochloride return tank 13, and then enters the tubular reactor 5 through the second intermediate feed port 15 according to the metering requirements through the fourth booster pump 14. The molar ratio of methanol to hydrazine hydrochloride returned to the tubular reactor 5 is controlled at 2.0.

[0061] The bottom liquid from the bottom of the tower enters the third distillation tower 16. The number of plates of the third distillation tower 16 is 32, the height of the structured packing is 30 meters, the operating pressure at the top of the tower is 0.023MPa, the top temperature is 92°C, the bottom temperature is 125°C, and the feed port is located at the packing height of 12 meters. The hydrazine hydrochloride solution from the top of the third distillation tower 16 is returned to the stirring tank 11, and the methylhydrazine product from the top and bottom of the third distillation tower 16 is sent to the methylhydrazine storage tank 17. The comprehensive yield of the obtained methylhydrazine product is 90.8%.

[0062] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A device for continuous production of methylhydrazine by hydrazine hydrate methanol method, characterized in that: include: A tubular reactor (5), wherein the feed port is connected to a hydrazine hydrochloride storage tank (1) and a methanol storage tank (2), and the discharge port of the tubular reactor (5) is connected to the feed port of a first distillation tower (7). The tubular reactor (5) comprises at least three groups of tube structures and heat exchange structures, each group of the tube structures comprises a vertical tube and a U-shaped elbow (18), the heat exchange structure is arranged outside the tube structure, and a gas-liquid redistributor (20) is arranged inside the tube structure; A methanol return tank (8), wherein the feed port is connected to the methanol outlet of the first distillation tower (7), and the discharge port of the methanol return tank (8) is connected to the first intermediate feed port (10) provided on the U-shaped elbow (18); A stirred tank (11), wherein the feed port is connected to the discharge port of the first distillation tower (7), the discharge port of the stirred tank (11) is connected to the feed port of the second distillation tower (12), the hydrazine hydrochloride outlet of the second distillation tower (12) is connected to the feed port of the hydrazine hydrochloride return tank (13), the discharge port of the hydrazine hydrochloride return tank (13) is connected to the second intermediate feed port (15) provided on the U-shaped elbow (18), and a hydrazine hydrate feed pipe is also provided on the top of the stirred tank (11); The third distillation tower (16) has a feed port connected to the top discharge port of the second distillation tower (12), the discharge port of the third distillation tower (16) is connected to the methylhydrazine storage tank (17), and the bottom discharge port of the third distillation tower (16) is connected to the top feed pipe of the stirring tank (11).

2. The device for continuous production of methylhydrazine by hydrazine hydrate methanol method according to claim 1, characterized in that: The first intermediate feed port (10) and the second intermediate feed port (15) are sequentially arranged on different U-shaped elbows (18) along the flow direction of the mixed liquid in the tubular reactor (5), and a pressure sensor (21) and a temperature sensor (22) are also arranged on the tube structure.

3. The device for continuous production of methylhydrazine by hydrazine hydrate methanol method according to claim 1, characterized in that: The heat exchange structure comprises a plurality of heat exchange sleeves (19), wherein the heat exchange sleeves (19) are arranged to wrap around the vertical tubes in a one-to-one manner, and adjacent heat exchange sleeves (19) are connected via flanges (23). A temperature control medium inlet (26) and a temperature control medium outlet (27) are respectively provided on the heat exchange sleeves (19) located at the head and the tail.

4. The device for continuous production of methylhydrazine by hydrazine hydrate methanol method according to claim 3, characterized in that: The inner diameter of the tube structure is 15-200 mm, the height of the vertical tube is 0.5-8 m, the inner diameter of the heat exchange sleeve (19) is 30-300 mm, and the gas-liquid redistributor (20) is arranged at intervals in the tube structure.

5. The device for continuous production of methylhydrazine by hydrazine hydrate methanol method according to claim 1, characterized in that: The material of the pipe structure is C276 Hastelloy, and the lining material of the pipe structure is polytetrafluoroethylene or glass lining.

6. The device for continuous production of methylhydrazine by hydrazine hydrate methanol method according to claim 1, characterized in that: The gas-liquid redistributor (20) is one of an SV type static mixer, an SX type static mixer, an SH type static mixer or an SK type static mixer, and the material of the gas-liquid redistributor (20) is one of polytetrafluoroethylene, ceramic or C276 Hastelloy.

7. A method for continuously producing methylhydrazine by hydrazine hydrate methanol method, using the device for continuously producing methylhydrazine by hydrazine hydrate methanol method according to any one of claims 1 to 6, characterized in that: The method steps include: Step 1: preparing a hydrazine hydrochloride aqueous solution by mixing hydrazine hydrate and hydrochloric acid in a molar ratio of 1:(1.15-1.5), and feeding the solution into the hydrazine hydrochloride storage tank (1), and adding methanol with a purity exceeding 99.9% into the methanol storage tank (2); Step 2: delivering the hydrazine hydrochloride aqueous solution to the bottom inlet (24) of the tube structure through the first pressure pump (3) according to the metering requirements, delivering methanol to the bottom inlet (24) of the tube structure through the second pressure pump (4) according to the metering requirements, the hydrazine hydrochloride aqueous solution and the methanol flow and mix in the tube structure, and the heat exchange structure is preheated to the reaction temperature by delivering the heating medium; Step 3: In the tube structure, the hydrazine hydrochloride aqueous solution and methanol undergo an alkylation reaction to generate methylhydrazine hydrochloride, and the gas-liquid redistributor (20) is used to achieve gas-liquid redistribution and sufficient mixing and contact of the solution; Step 4: sending the reaction mixture solution discharged from the top outlet (25) of the tube structure to the first distillation tower (7) through a cooler (6); Step 5: sending the methanol solution from the top of the first distillation tower (7) to the first intermediate feed port (10) through a third pressure pump (9) according to metering requirements; Step 6: sending the liquid from the bottom of the first distillation tower (7) to the stirring tank (11), and adding hydrazine hydrate into the stirring tank (11) through the hydrazine hydrate feeding pipe according to the metering requirements; Step 7: sending the mixed liquid discharged from the discharge port of the stirring tank (11) to the second distillation tower (12), sending the hydrazine hydrochloride aqueous solution discharged from the second distillation tower (12) to the second intermediate feed port (15) through a fourth pressure pump (14) according to metering requirements, and sending the mixed liquid at the top discharge port of the second distillation tower (12) to the third distillation tower (16); Step eight: sending the hydrazine hydrochloride solution discharged from the bottom outlet of the third distillation tower (16) to the stirred tank (11), and sending the methylhydrazine discharged from the outlet of the third distillation tower (16) to the methylhydrazine storage tank (17).

8. The method for continuous production of methylhydrazine by hydrazine hydrate methanol method according to claim 7, characterized in that: In step 2, the molar ratio of methanol to the initial feed of hydrazine hydrochloride aqueous solution is 1.3 to 2.4; In step 5 and step 7, the molar ratio of methanol to the hydrazine hydrochloride aqueous solution returned to the tubular reactor (5) is 1.5 to 2.

3.

9. The method for continuous production of methylhydrazine by hydrazine hydrate methanol method according to claim 7, characterized in that: The reaction temperature in the tubular reactor (5) is 90-130°C, and the reaction pressure is 1.1 MPa-1.5 MPa; The mixed liquid has an superficial liquid velocity of 0.002-0.02 m / s in the tube structure and a residence time of 0.2-2 h; The reaction temperature in the stirring tank (11) is 50-80°C, and the residence time of the mixed liquid in the stirring tank (11) is 0.3-1.0h.

10. The method for continuous production of methylhydrazine by hydrazine hydrate methanol method according to claim 7, characterized in that: The operating pressure of the first distillation tower (7) is 0.01-0.05 MPa, the operating temperature is 62-93°C, the number of plates is 20-30, and the feed inlet is at the 7th to 12th plates; The operating pressure of the second distillation tower (12) is 0.005-0.015 MPa, the operating temperature is 60-190°C, the number of plates is 5-10, and the feed inlet is at the 3rd-4th plate; The operating pressure of the third distillation tower (16) is a top gauge pressure of 0.01-0.05 MPa, the operating temperature is 85-125°C, the number of plates is 25-37, and the feed inlet is located at the 9th to 15th plates.

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