A system and method for continuous production of p-nitroaniline

Abstract

The application belongs to the technical field of chemical synthesis, and particularly relates to a system and method for continuously producing p-nitroaniline. The system for continuously producing p-nitroaniline comprises a first mixing unit, a second mixing unit, a third pipeline mixer, a flash tank and a liquid cyclone separator arranged in sequence. The third pipeline mixer is provided with a third mixed material inlet and a third mixed material outlet. The middle part of the flash tank is provided with a flash material inlet, the bottom part of the flash tank is provided with a flash liquid phase outlet, and the upper part of the flash tank is provided with a flash gas phase outlet. The liquid cyclone separator comprises a separator and a first material cylinder. The upper part of the first material cylinder is provided with a first material cylinder inlet, the top part of the first material cylinder is provided with a first liquid outlet, and the bottom part of the first material cylinder is provided with a first material cylinder outlet. The application effectively improves the reaction rate, reduces the reaction time, changes the reaction from an intermittent reaction to a continuous reaction, improves the production rate, and reduces the production cost.

Description

Technical Field

[0001] This invention relates to a system and method for the continuous production of p-nitroaniline, belonging to the field of chemical synthesis technology. Background Technology

[0002] p-Nitroaniline is a yellow needle-like crystal, highly toxic, easily sublimed, slightly soluble in cold water, and soluble in boiling water, ethanol, ether, benzene, and acid solutions. It is an important chemical raw material that can be directly used to synthesize various dyes and pigments. It can also be used as a raw material for the synthesis of p-phenylenediamine, o-chloro-p-nitroaniline, 2,6-dichloro-4-nitroaniline, 5-nitro-2-chlorophenol, etc. It can also be used to synthesize the pesticide chloronitramine and the pharmaceutical carbaryl. At the same time, it is also a raw material for antioxidants, light stabilizers, and developers.

[0003] The existing production facilities for p-nitroaniline use a 6000L or 11000L high-pressure amination reactor, with p-nitrochlorobenzene and concentrated ammonia as raw materials, and carry out ammonolysis reaction at 175–180℃ and 5.0–5.5 MPaG. After the reaction, the material is cooled to room temperature in a separation device and then pumped to a solid-liquid separation system for separation and washing. The separated solid p-nitroaniline is packaged and sold; the mother liquor is pumped to a wastewater treatment system. This process produces p-nitroaniline with the following drawbacks: low equipment utilization and long reaction time; cumbersome automation control and low process safety; the need to add process water during separation increases the amount of p-nitroaniline dissolved in the wastewater, resulting in short crystallization time, uneven product particle size, and low product yield; the high energy consumption per unit product due to the cooling, solid-liquid separation, and subsequent heating for deammoniation of the reacted material; and the increased unit treatment cost of wastewater because p-nitroaniline is highly toxic. Summary of the Invention

[0004] To address the aforementioned deficiencies in the prior art, this invention provides a system and method for the continuous production of p-nitroaniline.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] One objective of this invention is to provide a system for the continuous production of p-nitroaniline, comprising a primary mixing unit, a secondary mixing unit, a tertiary pipeline mixer, a flash tank, and a hydrocyclone separator arranged sequentially. The primary mixing unit is used for mixing and heating materials with steam; the secondary mixing unit is used for mixing and reacting materials; the tertiary pipeline mixer is used for reacting and condensing materials, and is equipped with a tertiary mixture inlet and a tertiary mixture outlet; the flash tank has a flash material inlet in its middle section, which is connected to the tertiary mixture outlet; the bottom of the flash tank has a flash liquid phase outlet; and the upper part of the flash tank... The device includes a flash vapor phase outlet connected to an ammonia absorption unit; the hydrocyclone separator comprises a primary feed cylinder and a separator; the primary feed cylinder has a primary feed cylinder inlet at its upper part, a primary liquid outlet at its top, and a primary feed cylinder outlet at its bottom; the separator has a separated gas phase outlet at its top, and a separated first discharge port and a separated second discharge port at its bottom; the flash vapor phase outlet is connected to the primary feed cylinder inlet, the primary feed cylinder outlet is connected to the separator, the separated first discharge port is connected to an ammonium chloride post-treatment device, and the separated second discharge port is connected to a p-nitroaniline crystallization unit.

[0007] The beneficial effects of the continuous production system for p-nitroaniline of the present invention are as follows: The system of the present invention adopts a jet feeding method, and the reaction is carried out in a pipeline mixer, making the reaction a continuous reaction, accelerating the reaction time and increasing the reaction rate, so that the reaction can proceed rapidly in a short time; The present invention uses a hydrocyclone separator to separate ammonium chloride solution and p-nitroaniline, eliminating the need to add pure water for washing, saving the dehydration step, and allowing direct crystallization, thus saving production costs.

[0008] Based on the above technical solution, the present invention can also be improved as follows:

[0009] Furthermore, the hydrocyclone separator also includes at least one secondary material cylinder, the upper part of which is provided with a secondary material cylinder inlet, the top of which is provided with a secondary liquid outlet, and the bottom of which is provided with a secondary material cylinder outlet. The secondary material cylinder outlet is connected to the separator, the primary liquid outlet is connected to the secondary material cylinder inlet, and the secondary liquid outlet is connected to the ammonium chloride post-treatment equipment.

[0010] The beneficial effect of adopting the above-mentioned further technical solution is that the hydrocyclone separator is used to separate p-nitroaniline and ammonium chloride solution. The structure of the hydrocyclone separator of the present invention can separate p-nitroaniline and ammonium chloride solution more efficiently. Since the density difference between p-nitroaniline and ammonium chloride solution is large, the material can complete the separation process within 2 to 3 seconds without stirring, thereby improving production capacity and production efficiency.

[0011] Furthermore, the separator is provided with a material discharge zone and a separation discharge zone, which are separated by a sintering plate. The primary material cylinder outlet and the secondary material cylinder outlet extend into the material discharge zone, and the separation gas phase outlet, the separation first discharge port, and the separation second discharge port are located in the separation discharge zone.

[0012] The beneficial effects of adopting the above-mentioned further technical solution are that the killed plate is in the form of a corrugated packing plate, and there are tortuous channels on the corrugated plate that allow fluid to flow back and forth, causing the dispersed droplets to aggregate to different degrees. The dispersed phase aggregates from small droplets into large liquid clusters on the surface of the packing. When the liquid clusters reach a sufficiently large size, they will float up to the upper surface of the liquid along the packing, thereby achieving the purpose of two-phase separation, improving the separation efficiency of the two phases in the separator, and the killed plate is not easily damaged and has a long service life.

[0013] Furthermore, the flash tank is provided with at least two trays corresponding to the flash material inlet, with a packing layer below the bottom tray and a feed distributor above the bottom tray.

[0014] The beneficial effects of adopting the above-mentioned further technical solutions are that the interior of the flash tank is equipped with trays and packing, and a feed distributor is installed above the trays. After the material enters the flash tank from the flash material inlet, it is distributed and fed through the feed distributor. The structure of the packing is not limited, and the packing can be ordinary packing. This reduces mist entrainment and allows the material to flash more thoroughly.

[0015] Furthermore, the flash tank is provided with a flash vapor inlet at its lower part.

[0016] Furthermore, a nozzle is provided inside the flash tank corresponding to the flash vapor phase inlet, and the nozzle is connected to the flash vapor phase inlet.

[0017] The beneficial effect of adopting the above-mentioned further technical solution is that a nozzle is added at the flash vapor inlet at the bottom of the flash tank, which can make the gas phase and liquid phase fully mixed before flash separation, thereby improving the efficiency and separation effect of flash separation.

[0018] Furthermore, the primary mixing unit includes a primary steam ejector and a primary pipeline mixer. The primary steam ejector is provided with a primary steam inlet, a primary ejector inlet, and a primary ejected material outlet. The primary pipeline mixer is provided with a primary mixed material inlet and a primary mixed material outlet. The primary ejected material outlet is connected to the primary mixed material inlet.

[0019] Furthermore, the secondary mixing unit includes a secondary steam ejector and a secondary pipeline mixer. The secondary steam ejector is provided with a secondary injection material inlet, a secondary ejector inlet, and a secondary injection material outlet. The secondary injection material inlet is connected to the primary mixture outlet. The secondary pipeline mixer is provided with a secondary mixture inlet and a secondary mixture outlet. The secondary injection material outlet is connected to the secondary mixture inlet, and the secondary mixture outlet is connected to the tertiary mixture inlet.

[0020] Furthermore, the secondary pipeline mixer and the tertiary pipeline mixer are provided with jackets on their exteriors, and the jackets contain heat-conducting media.

[0021] The beneficial effect of adopting the above-mentioned further technical solution is that the pipeline mixer used is equipped with a jacket, which can better keep the material warm.

[0022] The second objective of this invention is to provide a method for the continuous production of p-nitroaniline, which employs the system for the continuous production of p-nitroaniline as described above, specifically including the following steps:

[0023] (1) Liquid ammonia is mixed and vaporized with saturated steam at a pressure of 2.0 MPaG in the first-stage steam ejector, and then fed into the first-stage pipeline mixer by injection. The liquid ammonia is heated to 180℃~185℃ by saturated steam to bring the system to the temperature required for the reaction.

[0024] (2) The material enters the secondary steam ejector from the primary pipeline mixer, mixes with the p-nitrochlorobenzene that enters the secondary steam ejector, and then enters the secondary pipeline mixer from the secondary steam ejector by injection to mix and react.

[0025] (3) The reacted material enters a three-stage pipeline mixer. In the three-stage pipeline mixer, the reacted material is mixed with demineralized water (as condensate) at a pressure of 1.0 MPaG and a temperature of 80-95°C. The temperature and pressure are reduced, and the reaction produces p-nitroaniline and ammonium chloride.

[0026] (4) After the above mixing reaction is completed, the material enters the flash tank from the three-stage pipeline mixer. At 135℃~145℃, the flash tank is used to flash evaporate to remove the ammonia and some water generated in the mixing reaction. The discharged ammonia and water are absorbed by the ammonia absorption device.

[0027] (5) The solid-liquid mixture obtained after flash evaporation (i.e., p-nitroaniline and ammonium chloride solution) enters the hydrocyclone separator. The hydrocyclone separator separates the reaction product p-nitroaniline and ammonium chloride. After separation, the p-nitroaniline enters the p-nitroaniline crystallization device for crystallization and packaging. The ammonium chloride solution obtained after separation enters the ammonium chloride post-processing equipment for continuous deammoniation, extraction and crystallization.

[0028] The beneficial effects of this invention are as follows: In the ammonolysis reaction, this invention uses a jet feeding method and a pipeline mixer for mixing, which allows the reaction to proceed rapidly in a short time, effectively increasing the reaction rate, reducing reaction time, and improving reaction stability. This also increases the yield of p-nitroaniline (greater than 98%), transforming the reaction from a batch reaction to a continuous reaction, improving productivity, and reducing production costs. Furthermore, the product obtained after the reaction is separated using a hydrocyclone separator, achieving a separation rate of 99.99%. No pure water is needed for washing and separation, and no separate dehydration step is required afterward. Therefore, the entire preparation process of p-nitroaniline produces no excess wastewater, achieving a certain degree of green technology and clean production. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the system for the continuous production of p-nitroaniline according to the present invention;

[0030] Figure 2 This is a schematic diagram of the internal structure of the two-stage pipeline mixer of the present invention;

[0031] Figure 3 This is a schematic diagram of the internal structure of the flash tank of the present invention;

[0032] Figure 4 This is a schematic diagram of the hydrocyclone separation device of the present invention.

[0033] The attached diagrams are labeled as follows: 1. Primary steam ejector; 2. Primary pipeline mixer; 3. Secondary steam ejector; 4. Secondary pipeline mixer; 5. Tertiary pipeline mixer; 6. Flash tank; 7. Packing; 8. Nozzle; 9. Tray; 10. Feed distributor; 11. Flash vapor phase outlet; 12. Flash liquid phase outlet; 13. Flash vapor phase inlet; 14. Flash material inlet; 15. Hydrocyclone separator; 16. Primary feed cylinder; 17. Secondary feed cylinder; 18. Separator; 19. Killer plate; 20. First discharge port of separation; 21. Second discharge port of separation; 22. Gas phase outlet of separation; 23. Guide plate; 24. Microreactor. Detailed Implementation

[0034] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0035] Example

[0036] See Figures 1-4 A system for the continuous production of p-nitroaniline includes, in sequence, a primary mixing unit, a secondary mixing unit, a tertiary pipeline mixer, a flash tank, and a hydrocyclone separator. The primary mixing unit is used for mixing and heating materials with steam. The secondary mixing unit is used for mixing and reacting materials. The tertiary pipeline mixer is used for reacting and condensing materials, and has a tertiary mixture inlet and an outlet. The flash tank has a flash material inlet in its middle section, which is connected to the tertiary mixture outlet. The flash tank has a flash liquid phase outlet at its bottom and a flash vapor phase outlet at its top, which is connected to an ammonia absorption device. (See also...) Figure 4 The hydrocyclone separator includes a primary feed cylinder and a separator. The primary feed cylinder has a primary feed cylinder inlet at its upper part, a primary liquid outlet at its top, and a primary feed cylinder outlet at its bottom. The separator has a gas phase outlet at its top for separating nitroaniline and water, and can also reduce the pressure inside the separator. The separator has a first separation outlet and a second separation outlet at its bottom. The flash liquid phase outlet is connected to the primary feed cylinder inlet, the primary feed cylinder outlet is connected to the separator, the first separation outlet is connected to an ammonium chloride post-treatment device, and the second separation outlet is connected to a p-nitroaniline crystallization device.

[0037] The hydrocyclone separator further includes at least one secondary material cylinder. The upper part of the secondary material cylinder is provided with a secondary material cylinder inlet, the top of the secondary material cylinder is provided with a secondary liquid outlet, and the bottom of the secondary material cylinder is provided with a secondary material cylinder outlet. The secondary material cylinder outlet is connected to the separator, the primary liquid outlet is connected to the secondary material cylinder inlet, and the secondary liquid outlet is connected to the ammonium chloride post-treatment equipment.

[0038] The separator is provided with a material discharge zone and a separation discharge zone, which are separated by a sintered plate. The sintered plate of the present invention is in the form of a corrugated packing plate with tortuous channels for fluid to flow back and forth, causing the dispersed droplets to aggregate to different degrees. The dispersed phase aggregates from small droplets into large liquid clusters on the surface of the packing. When the liquid clusters reach a sufficiently large size, they float to the upper surface of the liquid along the packing, thereby achieving the purpose of two-phase separation and improving the separation efficiency of the two phases in the separator. In this embodiment, the liquid clusters float when they aggregate to a diameter between 50μm and 65μm.

[0039] The primary and secondary material cylinder outlets extend into the material discharge area. The bottom of the primary material cylinder is equipped with an anti-impact plate, which is a conical circular plate with dimensions matching the bottom dimensions of the primary material cylinder. The thickness of the anti-impact plate is 60mm, and the upper and lower conical sections are welded to the primary material cylinder using reinforcing ribs. The bottom of the secondary material cylinder is equipped with a wing valve, which is installed on the secondary material cylinder by welding. The valve plate is movable and vertically downward. The separation gas phase outlet, the first separation outlet, and the second separation outlet are located in the separation discharge area. The material separated by the primary and secondary material cylinders is further separated in the separation discharge area before being discharged.

[0040] See Figure 3 The flash tank is provided with at least two trays corresponding to the flash material inlet. In this embodiment, the trays are provided with three layers, with a tray spacing of 65 cm. A packing layer is provided below the bottom tray, with the packing position 65 cm away from the bottom tray and 30 cm away from the flash liquid phase outlet. A feed distributor is provided above the bottom tray, and the feed distributor is located in the middle between the bottom tray and the adjacent upper tray.

[0041] The flash tank is provided with a flash vapor inlet at the bottom, through which 1.0 MPa saturated steam is introduced for stripping and stirring.

[0042] The flash tank is equipped with a nozzle corresponding to the flash vapor phase inlet, and the nozzle is connected to the flash vapor phase inlet.

[0043] The primary mixing unit includes a primary steam ejector and a primary pipeline mixer. The primary steam ejector is provided with a primary steam inlet, a primary ejector inlet, and a primary ejected material outlet. The primary pipeline mixer is provided with a primary mixed material inlet and a primary mixed material outlet. The primary ejected material outlet is connected to the primary mixed material inlet.

[0044] The secondary mixing unit includes a secondary steam ejector and a secondary pipeline mixer. The secondary steam ejector is provided with a secondary injection material inlet, a secondary ejector inlet, and a secondary injection material outlet. The secondary injection material inlet is connected to the primary mixture outlet. The secondary pipeline mixer is provided with a secondary mixture inlet and a secondary mixture outlet. The secondary injection material outlet is connected to the secondary mixture inlet, and the secondary mixture outlet is connected to the tertiary mixture inlet.

[0045] This embodiment does not limit the primary pipeline mixer; any common pipeline mixer can be used. The secondary and tertiary pipeline mixers in this embodiment are pipeline mixing reactors designed according to the materials. The secondary pipeline mixing reactor in this embodiment is three meters long, and the tertiary pipeline mixing reactor is five meters long. Setting the length of the tertiary pipeline mixing reactor to five meters allows for thorough mixing and reaction of the materials, and also increases the reaction time, resulting in a more complete reaction. (See [link to relevant documentation]). Figure 2 The inlet of the secondary and / or tertiary pipeline mixers is equipped with guide plates, which allow the feed material to rotate and enter the pipeline mixer. Inside the secondary and / or tertiary pipeline mixers are three sets of mixing microreactors. These microreactors are designed with finned structures to facilitate heat transfer. The interiors of the microreactors are all plate-type mixing plates, and the gaps between the mixing plates allow for more thorough material contact, resulting in better mixing and reaction effects, achieving energy savings and reduced consumption. The secondary and tertiary pipeline mixers are externally equipped with jackets containing a heat-conducting medium, specifically heat-conducting oil, to ensure the reaction temperature remains within a controllable range.

[0046] The method for continuous production of p-nitroaniline using the above system in this embodiment specifically includes the following steps:

[0047] Step 1: The raw materials are p-nitrochlorobenzene and liquid ammonia (60% concentration). First, 2.0 MPaG saturated steam is introduced from the primary steam inlet, and liquid ammonia is fed from the primary ejector inlet. The feed rate of liquid ammonia is 60 kg / h, and the steam rate is 110.4 kg / h. After the liquid ammonia and 2.0 MPaG saturated steam are mixed in the steam ejector, they are injected into the primary pipeline mixer from the primary mixture inlet. The liquid ammonia is heated to 180°C using 2.0 MPaG saturated steam to achieve the required reaction temperature.

[0048] Step 2: 180°C liquid ammonia from the primary pipeline mixer enters the secondary steam ejector through the secondary injection material inlet, and p-nitrochlorobenzene enters the secondary steam ejector through the secondary ejector inlet. The p-nitrochlorobenzene feed rate is 62 kg / h. After the materials are mixed in the secondary steam ejector, they are injected into the secondary pipeline mixer for mixing and reaction. The reaction begins when the materials are mixed in the secondary steam ejector. Due to the injection feeding method, p-nitrochlorobenzene and liquid ammonia will react rapidly in the secondary pipeline mixer to produce p-nitroaniline and ammonium chloride.

[0049] Step 3: Introduce a water inlet, i.e., the tertiary condensate inlet, into the tertiary pipeline mixer. In this embodiment, the condensate is 1.0 MPaG, 80-95℃ demineralized water. The reactants from the secondary pipeline mixer enter the tertiary pipeline mixer through the tertiary mixture inlet. After feeding, they are mixed and reacted with the condensate. After mixing, they enter the flash tank to cool the reactants, reducing the material temperature to 145℃-140℃ and the pressure to 0.4 MPaG.

[0050] Step 4: The material is flash-evaporated in a flash tank to separate unreacted ammonia and some water, as well as a mixed solution of fully reacted p-nitroaniline and ammonium chloride. The unreacted ammonia and some water enter the ammonia absorption unit through the flash vapor phase outlet for ammonia absorption and recycling. The mixed solution of p-nitroaniline and ammonium chloride enters the hydrocyclone separator through the flash liquid phase outlet for separation of p-nitroaniline and ammonium chloride.

[0051] Step 5: The materials are separated in the hydrocyclone separator. The lighter ammonium chloride solution enters the ammonium chloride post-treatment equipment from the secondary liquid outlet and the first discharge port of the separator for continuous deammoniation, extraction and crystallization. The heavier p-nitroaniline solution exits from the second discharge port of the separator and enters the p-nitroaniline crystallization device for crystallization and packaging.

[0052] This embodiment improves the automation level of the equipment and achieves high efficiency in separation. The calculated product yield reaches 98.5%, which is a significant improvement compared to the traditional batch deammoniation and batch crystallization operation with a total yield of 97.6%.

[0053] Calculation process for p-nitroaniline yield:

[0054] Ammonia replenishment amount: 60 kg / g;

[0055] p-Nitrochlorobenzene feed rate: 62 kg / h;

[0056] p-Nitroaniline product output: 55.53 kg / h;

[0057] Main reaction:

[0058] C6H4C l NO2+2NH3→C6H6N2O2+NH4C l

[0059] Molar mass:

[0060] p-Nitrochlorobenzene: 157.556 g / mol, p-Nitroaniline: 138.124 g / mol.

[0061] From the main reaction formula, we know that 1 mol of p-nitrochlorobenzene produces 1 mol of p-nitroaniline, and the feed rate of p-nitrochlorobenzene is 62 kg / h, that is, the feed rate per hour is 62000 g.

[0062] The theoretical yield of p-nitroaniline per hour is:

[0063] 62000 / 157.556*138.124=54353.3g, which means the theoretical product yield of p-nitroaniline is 54.3533Kg / h. Therefore, the product yield can be calculated.

[0064] Yield = 53.53 / 54.3533 ≈ 98.5%

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for the continuous production of p-nitroaniline, characterized in that, The system includes, in sequence, a primary mixing unit, a secondary mixing unit, a tertiary pipeline mixer, a flash tank, and a hydrocyclone separator. The primary mixing unit is used for mixing and heating materials with steam. The secondary mixing unit is used for mixing and reacting materials. The tertiary pipeline mixer is used for reacting and condensing materials, and it has a tertiary mixture inlet and an outlet. The flash tank has a flash material inlet in its middle section, which is connected to the tertiary mixture outlet. The bottom of the flash tank has a flash liquid phase outlet, and the top of the flash tank has a flash vapor phase outlet. The gas phase outlet is connected to the ammonia absorption device; the hydrocyclone separator includes a primary material cylinder and a separator. The upper part of the primary material cylinder is provided with a primary material cylinder inlet, the top of the primary material cylinder is provided with a primary liquid outlet, and the bottom of the primary material cylinder is provided with a primary material cylinder outlet. The top of the separator is provided with a separated gas phase outlet, and the bottom of the separator is provided with a separated first discharge port and a separated second discharge port. The flash liquid phase outlet is connected to the primary material cylinder inlet, the primary material cylinder outlet is connected to the separator, the separated first discharge port is connected to the ammonium chloride post-treatment equipment, and the separated second discharge port is connected to the p-nitroaniline crystallization device. The primary mixing unit includes a primary steam ejector and a primary pipeline mixer. The primary steam ejector is provided with a primary steam inlet, a primary ejector inlet, and a primary ejected material outlet. The primary pipeline mixer is provided with a primary mixed material inlet and a primary mixed material outlet. The primary ejected material outlet is connected to the primary mixed material inlet. The secondary mixing unit includes a secondary steam ejector and a secondary pipeline mixer. The secondary steam ejector is provided with a secondary injection material inlet, a secondary ejector inlet, and a secondary injection material outlet. The secondary injection material inlet is connected to the primary mixture outlet. The secondary pipeline mixer is provided with a secondary mixture inlet and a secondary mixture outlet. The secondary injection material outlet is connected to the secondary mixture inlet, and the secondary mixture outlet is connected to the tertiary mixture inlet.

2. The system for continuous production of p-nitroaniline according to claim 1, characterized in that, The hydrocyclone separator further includes at least one secondary material cylinder. The upper part of the secondary material cylinder is provided with a secondary material cylinder inlet, the top of the secondary material cylinder is provided with a secondary liquid outlet, and the bottom of the secondary material cylinder is provided with a secondary material cylinder outlet. The secondary material cylinder outlet is connected to the separator, the primary liquid outlet is connected to the secondary material cylinder inlet, and the secondary liquid outlet is connected to the ammonium chloride post-treatment equipment.

3. The system for continuous production of p-nitroaniline according to claim 2, characterized in that, The separator is provided with a material discharge zone and a separation discharge zone, which are separated by a sintering plate. The primary material cylinder outlet and the secondary material cylinder outlet extend into the material discharge zone. The separation gas phase outlet, the separation first discharge port, and the separation second discharge port are located in the separation discharge zone.

4. The system for continuous production of p-nitroaniline according to claim 1, 2, or 3, characterized in that, The flash tank is provided with at least two trays corresponding to the flash material inlet. A packing layer is provided below the bottom tray, and a feed distributor is provided above the bottom tray.

5. The system for continuous production of p-nitroaniline according to claim 1, 2, or 3, characterized in that, The flash tank is provided with a flash vapor phase inlet at the bottom, and a nozzle is provided inside the flash tank corresponding to the flash vapor phase inlet, and the nozzle is connected to the flash vapor phase inlet.

6. The system for continuous production of p-nitroaniline according to claim 1, characterized in that, The secondary and tertiary pipeline mixers are externally equipped with jackets, and the jackets contain heat-conducting media.

7. A method for continuous production of p-nitroaniline, characterized in that, The system for continuous production of p-nitroaniline as described in any one of claims 1 to 6 is used.

8. The method for continuous production of p-nitroaniline according to claim 7, characterized in that, Specifically, the following steps are included: (1) Liquid ammonia is mixed with saturated steam and vaporized in the first-stage steam ejector, and then fed into the first-stage pipeline mixer by injection. The liquid ammonia is heated to 180℃~185℃ by saturated steam to bring the system to the temperature required for the reaction. (2) The material enters the secondary steam ejector from the primary pipeline mixer, mixes with the p-nitrochlorobenzene that enters the secondary steam ejector, and then enters the secondary pipeline mixer from the secondary steam ejector by injection to mix and react; (3) The reacted material enters the three-stage pipeline mixer, where it is mixed with the condensate to cool and depressurize. (4) After the above mixing reaction is completed, the material enters the flash tank from the three-stage pipeline mixer. At 135℃~145℃, the flash tank is used to flash the ammonia and some water to remove the ammonia and water. The discharged ammonia and water are absorbed by the ammonia absorption device. (5) The solid-liquid mixture obtained after flash evaporation enters the hydrocyclone separator. The hydrocyclone separator is used to separate the reaction product p-nitroaniline and ammonium chloride. After separation, the p-nitroaniline enters the p-nitroaniline crystallization device for crystallization and packaging. The ammonium chloride solution obtained after separation enters the ammonium chloride post-treatment equipment for continuous deammoniation, extraction and crystallization.

Images