Solid-liquid separation device and hydrazine hydrate recovery method

Abstract

The application belongs to the technical field of producing methylhydrazine, and particularly relates to a solid-liquid separation device and a hydrazine hydrate recovery method. The solid-liquid separation device comprises a storage cylinder, the storage cylinder is arranged obliquely, a rotating shaft is arranged through the storage cylinder, a plurality of liquid inlets are arranged on the rotating shaft, a mechanical seal A is connected to one end of the rotating shaft, a liquid suction pipe is connected to the mechanical seal A, a vacuum pump is connected to the liquid suction pipe, a liquid receiving tank is connected to the vacuum pump, a driving motor is connected to the other end of the rotating shaft, and an auger spiral piece is fixed on the rotating shaft. The application not only realizes the purpose of quickly discharging solid waste, but also realizes the purpose of recycling hydrazine hydrate to make it become mother liquor for continuous application. The application solves the problem of oxidation and yellowing of hydrazine hydrate waste liquid caused by contact with air, and ensures the quality of hydrazine hydrate mother liquor application.

Description

Technical Field

[0001] This invention belongs to the technical field of methylhydrazine production, specifically relating to a solid-liquid separation device and a method for recovering hydrazine hydrate. Background Technology

[0002] Methylhydrazine is produced from hydrazine hydrate and benzaldehyde through condensation and methylation reactions. The production of methylhydrazine generates highly toxic hydrazine hydrate waste liquid, which is easily oxidized upon contact with air and poses a risk of combustion and explosion. To prevent the discharge of hydrazine hydrate waste liquid and environmental pollution, it is recycled. When recovering excess hydrazine monohydrochloride during the production of methylhydrazine, an aqueous solution of sodium hydroxide is added for free distillation to recover the hydrazine hydrate. During the reaction of hydrazine monohydrochloride with sodium hydroxide, solid sodium chloride precipitates. The chemical reaction process is as follows: Sodium chloride solid is separated from hydrazine hydrate waste liquid for solid waste treatment, while the liquid hydrazine hydrate waste liquid is recovered by distillation for reuse. Currently, centrifuges are used to separate hydrazine hydrate waste liquid and sodium chloride solid, and then solid waste is treated by manually digging up waste salt. This method causes the recycled hydrazine hydrate waste liquid to be oxidized by air and turn yellow, thus affecting the quality of hydrazine hydrate recovery and posing a safety hazard of combustion and explosion. At the same time, workers are exposed to hydrazine vapor in the waste salt during long-term digging, endangering their health.

[0003] Existing technologies include research on the health risks of manually handling solid waste during solid-liquid separation, such as the solid-liquid separation device in patent application CN109383066A. This device achieves solid-liquid separation through a screw, filter tank, and discharge outlet, solving the health and safety issues associated with manual solid waste handling. However, existing solid-liquid separation devices can only separate solids and liquids and discharge the solids. For recovering highly toxic hydrazine hydrate, a recycling and treatment device is required to recover the hydrazine hydrate waste liquid into a mother liquor for reuse. Current technologies struggle to balance the recovery of hydrazine hydrate and the treatment of sodium chloride solid waste, and the quality of the recovered hydrazine hydrate is difficult to control. Therefore, a new technical solution is needed to address these problems. Summary of the Invention

[0004] The purpose of this invention is to provide a solid-liquid separation device and a method for recovering hydrazine hydrate, in order to solve the problems mentioned in the background art. At present, solid-liquid separation devices need to be added for the recovery and treatment of highly toxic hydrazine hydrate in order to realize the recovery of hydrazine hydrate waste liquid into mother liquor for continued reuse. Furthermore, the existing technology has difficulty in balancing the recovery of hydrazine hydrate and the solid waste treatment of sodium chloride solid, and it is also difficult to control the quality of the recovered hydrazine hydrate.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a solid-liquid separation device, comprising a storage cylinder, wherein the storage cylinder is inclined and a rotating shaft is rotatably inserted inside it, the rotating shaft has a plurality of liquid inlets opened in the axial direction, one end of which is connected to a mechanical seal A which is stationary relative to the rotating shaft, and a liquid extraction pipe connected to the liquid inlets is connected through the mechanical seal A, a vacuum pump is connected to the liquid extraction pipe, and a liquid collection tank is connected through the vacuum pump, the other end of the rotating shaft is connected to a drive motor, and an auger spiral blade is fixed in the axial direction thereon, the auger spiral blade rotates inside the storage cylinder by the drive motor and the rotating shaft.

[0006] Furthermore, each of the liquid inlets is fixed with a filter screen and connected to a liquid collection chamber. The liquid collection chamber is located inside the rotating shaft and is connected to a liquid extraction pipe through a mechanical seal A. The liquid extraction pipe is connected to a liquid collection tank under negative pressure through a vacuum pump. A recovery pipe is connected to the liquid collection tank, and a transfer pump is installed on the recovery pipe and connected to a distillation kettle through the transfer pump.

[0007] Furthermore, the auger spiral blade is fixed in a spiral shape along the axial direction of the rotating shaft, and its spiral amplitude is smaller than the diameter of the storage cylinder. Each end of the storage cylinder is connected to a mechanical seal B, and the mechanical seal B is stationary relative to the rotating shaft. The mechanical seal B has a shaft hole and is connected to the rotating shaft through the shaft hole.

[0008] Furthermore, the storage cylinder is connected to an inlet pipe, a nitrogen delivery pipe, and a solid discharge pipe. The solid discharge pipe and the nitrogen delivery pipe are connected to the same side of the storage cylinder, the inlet pipe is connected to the other side of the storage cylinder, an inlet pump is installed on the inlet pipe and connected to a free vessel through the inlet pump, a nitrogen valve is installed on the nitrogen delivery pipe and connected to a nitrogen storage tank through the nitrogen valve, and the solid discharge pipe is connected to a solid waste collection box.

[0009] Furthermore, the free vessel is connected to the distillation vessel in sequence via a feed pipe, a liquid inlet, a filter screen, a liquid collection chamber, a liquid extraction pipe, and a liquid collection tank. The free vessel is also connected to the solid waste collection box in sequence via a feed pipe, an auger spiral blade, and a solid discharge pipe.

[0010] The specific steps for recovering hydrazine hydrate using the solid-liquid separation device described above are as follows:

[0011] First, the hydrazine hydrate waste liquid generated in the free reactor is pumped into the storage cylinder through the feed pipe and feed pump. Second, nitrogen gas from the nitrogen storage tank is pumped into the storage cylinder through the nitrogen delivery pipe and nitrogen valve. Then, under the protection of nitrogen, sodium chloride solid will precipitate from the hydrazine hydrate waste liquid. The sodium chloride solid will be discharged into the solid waste collection box through the solid discharge pipe under the rotation of the rotating shaft and auger blade driven by the drive motor. At the same time, the liquid hydrazine hydrate waste liquid will be drawn back to the collection tank through the liquid inlet, filter screen, liquid collection chamber and liquid extraction pipe under the negative pressure of the vacuum pump. Finally, it is pumped into the distillation kettle through the recovery pipe and delivery pump for distillation to recover hydrazine hydrate.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] 1. This invention utilizes a through-type rotating arrangement of a storage cylinder and a rotating shaft, giving the solid-liquid separation device a simple structure and convenient operation. This allows the device to not only quickly discharge solid waste but also simultaneously recover hydrazine hydrate, turning it into a mother liquor for reuse, eliminating the need for a separate recovery and utilization device. This effectively reduces the production cost of methylhydrazine. The inclined storage cylinder allows the hydrazine hydrate waste liquid entering the cylinder to collect downwards, effectively avoiding the problem of vacuum pump cavitation. The rotating shaft, which runs through the storage cylinder, allows the sodium chloride solid precipitated from the hydrazine hydrate waste liquid to be driven by a motor, rotating the shaft and driving the auger. The spiral blades rotate and automatically discharge the waste salt from the storage cylinder, eliminating the need for manual waste salt removal and effectively avoiding health risks associated with manual waste salt removal. This also effectively improves the efficiency and effectiveness of solid waste treatment. By setting several liquid inlets along the axial direction of the rotating shaft, the hydrazine hydrate waste liquid can be quickly drawn back from the storage cylinder to the collection tank under the negative pressure of the vacuum pump through the liquid inlets and the extraction pipe, effectively improving the efficiency of hydrazine hydrate recovery. The use of mechanical seal A effectively prevents the hydrazine hydrate waste liquid entering the rotating shaft from oxidizing and turning yellow upon contact with air, thus effectively controlling the quality of hydrazine hydrate recovery and ensuring the quality of hydrazine hydrate mother liquor reuse.

[0014] 2. This invention effectively avoids the problem of solid-liquid separation being affected by sodium chloride solid entering the collection chamber due to the fixed filter screen at the liquid inlet. By connecting the collection tank to the distillation kettle through the recovery pipe and the transfer pump, the hydrazine hydrate waste liquid can quickly enter the distillation kettle for distillation and recovery of hydrazine hydrate, thereby achieving the purpose of recovering hydrazine hydrate waste liquid into mother liquor for reuse, effectively improving the efficiency of hydrazine hydrate recovery. By connecting a mechanical seal B to each end of the storage cylinder, the problem of hydrazine hydrate waste liquid entering the storage cylinder oxidizing and turning yellow due to contact with air is effectively avoided, thus effectively controlling the quality of hydrazine hydrate recovery and ensuring the quality of hydrazine hydrate mother liquor reuse.

[0015] 3. This invention improves the safety of hydrazine hydrate recovery by installing a nitrogen delivery pipe on the storage cylinder, allowing the hydrazine hydrate waste liquid entering the storage cylinder to avoid reaction with air under the protection of nitrogen. This effectively controls the quality of hydrazine hydrate recovery and ensures the quality of hydrazine hydrate mother liquor reuse. By connecting the storage cylinder to the free reactor through the feed pump and feed pipe, the hydrazine hydrate waste liquid and the precipitated sodium chloride solid can be continuously separated into solid and liquid, ensuring the continuity of hydrazine hydrate recovery and mother liquor reuse. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0017] Figure 2 for Figure 1 Schematic diagram of the structure of sodium chloride solid in its separated state;

[0018] Figure 3 for Figure 1 A schematic diagram of the structure of the mother liquor of hydrazine hydrochloride in the separation state;

[0019] Figure 4 for Figure 1 Schematic diagram of a solid-liquid separation device;

[0020] Figure 5 for Figure 4 A schematic diagram of the structure of the central storage cylinder (including the feed pipe, nitrogen delivery pipe, and solid discharge pipe);

[0021] Figure 6 for Figure 4 A schematic diagram of the structure of the central rotating shaft (including the drive motor and the auger spiral blades).

[0022] The components are as follows: 1. Storage cylinder; 2. Rotating shaft; 201. Mechanical seal A; 3. Liquid inlet; 4. Liquid extraction pipe; 5. Vacuum pump; 6. Liquid collection tank; 7. Drive motor; 8. Screwdriver blade; 9. Mechanical seal B; 10. Shaft hole; 11. Feed pipe; 12. Nitrogen delivery pipe; 13. Solid discharge pipe; 14. Feed pump; 15. Free vessel; 16. Nitrogen valve; 17. Nitrogen storage tank; 18. Solid waste collection box; 19. Filter screen; 20. Liquid collection chamber; 21. Recovery pipe; 22. Transfer pump; 23. Distillation vessel. Detailed Implementation

[0023] The following examples are used to further illustrate the content of the present invention and do not limit the application of the present invention.

[0024] Please see Figures 1-6A solid-liquid separation device includes a storage cylinder 1 for storing hydrazine hydrate mother liquor generated in a free reactor. The storage cylinder 1 is inclined and has a semi-hollow rotating shaft 2 for solid-liquid separation rotatably running through its interior. The hollow structure of the rotating shaft 2 has several inlets 3 for separating out the hydrazine hydrate mother liquor along its axial direction. One end of the rotating shaft 2 is connected to a mechanical seal A201, which is stationary relative to the rotating shaft 2 and is used to seal the internal space of the rotating shaft 2. The mechanical seal A201 is connected to a pump for drawing back the hydrazine hydrate mother liquor. The liquid pipe 4 and the liquid extraction pipe 4 are connected to the liquid inlet 3. The liquid extraction pipe 4 is connected to a vacuum pump 5 for negative pressure extraction of hydrazine hydrate mother liquor. The vacuum pump 5 is connected to a liquid collection tank 6 for collecting hydrazine hydrate mother liquor. The other end of the solid structure of the rotating shaft 2 is connected to a drive motor 7 for driving the rotating shaft 2 to rotate. The hollow structure of the rotating shaft 2 is also fixed with a screw conveyor 8 for separating sodium chloride solid precipitated from the hydrazine hydrate mother liquor. The screw conveyor 8 rotates in the storage cylinder 1 through the drive motor 7 and the rotating shaft 2.

[0025] Please see Figures 1-6 The screw conveyor blade 8 is fixed in a spiral shape on the axial direction of the hollow structure of the rotating shaft 2, and its spiral amplitude is smaller than the diameter of the storage cylinder 1. Each end of the storage cylinder 1 is connected to a mechanical seal B9 for sealing the internal space of the storage cylinder 1, and the mechanical seal B9 is stationary relative to the rotating shaft 2. The mechanical seal B9 has a shaft hole 10 for the rotating shaft 2 to pass through, and is connected to the rotating shaft 2 through the shaft hole 10.

[0026] The storage cylinder 1 is connected to an inlet pipe 11 for the entry of hydrazine hydrate mother liquor, a nitrogen conveying pipe 12 for the entry of nitrogen gas, and a solid discharge pipe 13 for the discharge of sodium chloride solid. The solid discharge pipe 13 and the nitrogen conveying pipe 12 are connected to the same side of the storage cylinder 1. The inlet pipe 11 is connected to the other side of the storage cylinder 1. The inlet pipe 11 is equipped with a feed pump 14 and is connected to a free vessel 15 for discharging hydrazine hydrate mother liquor. The nitrogen conveying pipe 12 is equipped with a nitrogen valve 16 and is connected to a nitrogen storage tank 17. The solid discharge pipe 13 is connected to a solid waste collection box 18 for collecting sodium chloride solid for centralized treatment.

[0027] Please see Figures 1-4 and Figure 6 Each of the three inlets is equipped with a filter screen 19 to prevent sodium chloride solid from entering. The filter screen 19 is connected to a collection chamber 20 for buffering the extraction of hydrazine hydrate mother liquor. The collection chamber 20 is located inside the rotating shaft 2. The collection chamber 20 is connected to the extraction pipe 4 through a mechanical seal A201. The extraction pipe 4 is connected to the receiving tank 6 under negative pressure through a vacuum pump 5. The receiving tank 6 is connected to a recovery pipe 21. A transfer pump 22 is installed on the recovery pipe 21 and is connected to a distillation kettle 23 for distilling and recovering hydrazine hydrate.

[0028] Please see Figures 1-3 The free vessel 15 is connected to the distillation vessel 23 via the feed pipe 11, liquid inlet 3, filter screen 19, liquid collection chamber 20, liquid extraction pipe 4, and liquid collection tank 6 in sequence. This is the liquid separation route. Figure 3 As shown; the free vessel 15 is connected to the solid waste collection box 18 via the feed pipe 11, the auger spiral blade 8, and the solid discharge pipe 13 in sequence. This is the solid separation route. Figure 2 As shown.

[0029] When hydrazine hydrate is produced during the production of methylhydrazine, operators can use the solid-liquid separation device described above to recover the hydrazine hydrate, allowing the hydrazine hydrate mother liquor to be reused. This solves the problem of hydrazine hydrate being released into the air and polluting the environment, while also effectively reducing the cost of methylhydrazine production.

[0030] When hydrazine hydrate needs to be recovered, since vacuum pump 5, drive motor 7, feed pump 14, nitrogen valve 16, and transfer pump 22 are all controlled by a control box or controller (the functions and structures of conventional equipment such as control boxes or controllers are well known in the art, and their connection settings are also common knowledge, so they will not be described in detail here, nor are they shown in the attached drawings), the operator first operates the control box or controller to control feed pump 14. The feed pump 14 opens, allowing the hydrazine hydrate waste liquid (a mixture of hydrazine hydrate, sodium hydroxide, and sodium chloride, and a mixture of hydrazine hydrate and water, generated after the addition of caustic soda) in the free reactor 15 to be pumped into the storage tank 1 via the feed pipe 11. Then, the control box or controller opens the nitrogen valve 16, allowing nitrogen from the nitrogen storage tank to be supplied to the storage tank 1 via the nitrogen delivery pipe 12, filling the storage tank 1 with nitrogen and creating a protective atmosphere. This effectively prevents the hydrazine hydrate waste liquid from reacting with air, improving solid-liquid separation. For safety reasons, the control box or controller then turns on the drive motor 7 and vacuum pump 5. At this time, under the protection of nitrogen, some sodium chloride in the hydrazine hydrate waste liquid will dissolve, and some will precipitate as solid sodium chloride (since the solubility of sodium chloride is lower than that of sodium hydroxide, some solid will precipitate first). The precipitated solid sodium chloride will be driven by the drive motor 7 to rotate the rotating shaft 2, which in turn drives the auger spiral blades 8 to rotate. The solid sodium chloride will then spiral upwards towards the solid discharge pipe 13, and then automatically discharged into the solid waste collection box 18 via the solid discharge pipe 13 (the separation route for solid sodium chloride is as follows). Figure 2 As shown by the arrow in the diagram), solid waste is treated. Simultaneously, the liquid hydrazine hydrate waste containing dissolved sodium chloride is drawn into the collection chamber 20 through the inlet 3 and filter screen 19 under the operation of vacuum pump 5. It is then drawn back into the collection tank 6 through the collection chamber 20 and extraction pipe 4 (the separation route for the liquid hydrazine hydrate waste containing dissolved sodium chloride is shown in the diagram). Figure 3As indicated by the arrow in the diagram), solid-liquid separation is achieved. Finally, the control box or controller activates the transfer pump 22. At this time, the hydrazine hydrate waste liquid in the receiving tank 6 is pumped into the distillation kettle 23 via the recovery pipe 21 under the operation of the transfer pump 22. The hydrazine hydrate waste liquid is then recovered through distillation in the distillation kettle 23 (the hydrazine hydrate recovery route is shown in the diagram). Figure 3 (As indicated by the arrow), the recovered hydrazine hydrate will be reused as the mother liquor for the production of methylhydrazine; after the hydrazine hydrate recovery is completed, the operator needs to shut down the feed pump 14, vacuum pump 5, drive motor 7, nitrogen valve 16 and transfer pump 22 in sequence through the control box or controller.

Claims

1. A solid-liquid separation device, comprising a storage cylinder, characterized in that, The storage cylinder is inclined and has a rotating shaft running through it. Several liquid inlets are opened along the axial direction of the rotating shaft, and one end of the shaft is connected to a mechanical seal A, which is stationary relative to the rotating shaft. A suction pipe connected to the liquid inlet is connected to the mechanical seal A, and a liquid collection tank is connected to the suction pipe. A drive motor is connected to the other end of the rotating shaft, and an auger blade is fixed along its axial direction. The auger blade rotates within the storage cylinder via the drive motor and the rotating shaft. A filter screen is fixed at each liquid inlet and connected to a collection chamber, which is located inside the rotating shaft. The liquid chamber is connected to the extraction pipe via a mechanical seal A. The extraction pipe is connected to the liquid receiving tank under negative pressure via a vacuum pump. The liquid receiving tank is connected to a recovery pipe, and a transfer pump is installed on the recovery pipe, which is connected to a distillation kettle. The storage cylinder is connected to an inlet pipe, a nitrogen delivery pipe, and a solid discharge pipe. The solid discharge pipe and the nitrogen delivery pipe are connected to the same side of the storage cylinder, and the inlet pipe is connected to the other side of the storage cylinder. A feed pump is installed on the inlet pipe, which is connected to a free vessel. A nitrogen valve is installed on the nitrogen delivery pipe, which is connected to a nitrogen storage tank. The solid discharge pipe is connected to a solid waste collection box.

2. The solid-liquid separation device according to claim 1, characterized in that, The auger spiral blades are fixed in a spiral shape along the axial direction of the rotating shaft, and the spiral amplitude of its rotation is smaller than the diameter of the storage cylinder.

3. The solid-liquid separation device according to claim 2, characterized in that, The storage cylinder is connected to a mechanical seal B at each end, and the mechanical seal B is stationary relative to the rotating shaft. The mechanical seal B has a shaft hole and is connected to the rotating shaft through the shaft hole.

4. A solid-liquid separation device according to claim 3, characterized in that, The free vessel is connected to the distillation vessel in sequence through a feed pipe, a liquid inlet, a filter screen, a liquid collection chamber, a liquid extraction pipe, and a liquid collection tank. The free vessel is connected to the solid waste collection box in sequence through a feed pipe, an auger spiral blade, and a solid discharge pipe.

5. A method for recovering hydrazine hydrate, characterized in that, The solid-liquid separation device according to claim 4 is used to recover hydrazine hydrate. The specific recovery steps are as follows: First, the hydrazine hydrate waste liquid generated in the free vessel is pumped into the storage cylinder through the feed pipe and feed pump; second, nitrogen gas from the nitrogen storage tank is pumped into the storage cylinder through the nitrogen delivery pipe and nitrogen valve; then, under the protection of nitrogen gas, sodium chloride solid will precipitate out of the hydrazine hydrate waste liquid. The sodium chloride solid will be discharged into the solid waste collection box through the solid discharge pipe under the rotation of the rotating shaft and the auger spiral blade driven by the drive motor. At the same time, the liquid hydrazine hydrate waste liquid will be drawn back to the collection tank through the liquid inlet, filter screen, liquid collection chamber and liquid extraction pipe under the negative pressure of the vacuum pump; finally, it is pumped into the distillation kettle through the recovery pipe and delivery pump for distillation to recover hydrazine hydrate.

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