Amination reactor and amination reaction system for preparing paranitroaniline

Abstract

The utility model relates to the technical field of chemical raw material synthesis, in particular to an amination reactor and an amination reaction system for preparing paranitroaniline. The amination reactor comprises a reactor shell, at least one nozzle assembly is arranged in the reactor shell, each nozzle assembly comprises a plurality of annularly-distributed Venturi nozzles, the Venturi nozzles are located at the bottom and the side wall of the reactor shell, each Venturi nozzle comprises a nozzle opening, and each nozzle opening is communicated with the corresponding Venturi nozzle. And the nozzle opening points to the interior of the reactor shell. Through the design of the three-stage series amination reactors and the gravity flow, the continuous conveying of materials is realized, the limitation of the traditional intermittent process is broken through, the reaction period is shortened, the productivity is obviously improved, and the conversion rate of reactants is improved by increasing the reaction temperature and optimizing the reaction conditions step by step; a jet feeding mode is adopted, high-strength turbulent flow is formed by multiple stages of Venturi nozzles, the gas-liquid mass transfer efficiency is improved, the product purity is improved, and side reactions are reduced; the operation process is safe, simple and convenient.

Description

Technical Field

[0001] This utility model relates to the field of chemical raw material synthesis technology, and in particular to an amination reactor and amination reaction system for preparing p-nitroaniline. Background Technology

[0002] p-Nitroaniline appears as pale yellow needle-like crystals and is easily sublimated. It is an important intermediate in the dye industry, and can be directly used to synthesize azo dye intermediates (such as Direct Fast Black G, Direct Green B, Disperse Red P-4G, Cationic Deep Yellow 2RL, and Fur Black D); it can be used to synthesize the pesticide chloronitrate; it is a raw material for the production of antioxidants, light stabilizers, and developers; and through reduction, it can yield p-phenylenediamine, which is an important intermediate between dyes and high-strength polymers.

[0003] There are generally two methods for synthesizing p-nitroaniline: one is ammonolysis, where p-nitrochlorobenzene and concentrated ammonia are reacted in an autoclave at 140–175°C and 4.0–5.5 MPa for 15–20 hours to produce p-nitroaniline, which is then crystallized and filtered to obtain the final product; the other is nitration-hydrolysis, where n-acetaniline is nitrated with mixed acid to obtain p-nitro-n-acetaniline, which is then hydrolyzed to obtain the final product. Domestic manufacturers generally use the first method, but the intermittent ammonolysis process suffers from unstable product quality, long reaction cycles, high energy consumption, and the generation of large amounts of saline wastewater. With increasingly stringent environmental protection requirements in China, there is an urgent need to develop a new, environmentally friendly, low-energy-consumption, and stable p-nitroaniline synthesis process. Utility Model Content

[0004] In view of the shortcomings of the prior art, the purpose of this utility model is to provide an amination reactor and amination reaction system for preparing p-nitroaniline.

[0005] To achieve the above objectives, the technical solution adopted is:

[0006] One of the objectives of this invention is to provide an amination reactor for preparing p-nitroaniline, comprising a reactor shell, wherein at least one set of nozzle assemblies is provided inside the reactor shell, the nozzle assembly comprising a plurality of venturi nozzles arranged in a ring, the venturi nozzles being located at the bottom and sidewalls of the reactor shell, and the venturi nozzles including nozzle orifices pointing toward the interior of the reactor shell.

[0007] The beneficial effects of adopting the above technical solution are as follows: The Venturi effect enables efficient mixing and transport of fluids. During the fluid's passage through the nozzle, changes in flow velocity and pressure reduction allow for rapid and uniform mixing of different fluids, thereby improving mixing efficiency and reducing energy consumption. Compared to traditional agitators or mixers, Venturi nozzles offer higher mixing efficiency and lower energy consumption. Secondly, the compact design of Venturi nozzles allows for easy installation in various equipment and pipelines without requiring large-scale modifications to existing systems. Operation and maintenance are also relatively simple, reducing operational complexity and maintenance costs. Furthermore, the materials and manufacturing processes of Venturi nozzles are carefully selected and optimized to ensure long-term stable operation under harsh conditions. In terms of environmental protection, Venturi nozzles reduce fluid waste and emissions during processing, minimizing environmental pollution. Their materials and manufacturing processes also meet environmental protection requirements, ensuring the product's green attributes. The nozzles can form a high-flow-rate circulation and feature anti-clogging injection orifices. When high-speed liquid passes through the nozzle, it carries the surrounding liquid into the jet to form a circulation. This part of the liquid mixes with the pumped solution, thereby increasing the total amount of circulating solution. The nozzle can produce a flow rate ratio of 4:1, so small pumps equipped with mixing nozzles can be used for large-capacity fluid circulation while saving energy in all aspects. The annular arrangement has a higher mixing efficiency than the single arrangement.

[0008] Preferably, each nozzle assembly includes a horizontally arranged transverse tube, on which a vertically arranged third Venturi nozzle with its nozzle opening facing upwards is provided. Two vertical tubes, a first vertical tube and a second vertical tube, are connected above the transverse tube. A first Venturi nozzle is provided on the side of the first vertical tube closer to the second vertical tube, and a second Venturi nozzle is provided on the side of the second vertical tube closer to the first vertical tube. The first Venturi nozzle and the second Venturi nozzle are arranged alternately and opposite to each other, and preferably horizontally.

[0009] The beneficial effects of adopting the above technical solution are as follows: by forming turbulence through horizontal and vertical multi-angle injection, the gas-liquid mixing efficiency is enhanced, the reaction rate of p-nitroaniline is increased, side reactions caused by excessive local concentration are avoided, and the purity of the product is improved; the staggered and opposite arrangement of the Venturi nozzles can generate opposing jets, enhance material collision and diffusion, and significantly improve mass transfer efficiency.

[0010] Preferably, the reactor shell is provided with two sets of nozzle assemblies arranged vertically, with two first Venturi nozzles on the first vertical tube and three second Venturi nozzles on the second vertical tube.

[0011] The beneficial effects of adopting the above technical solution are as follows: the nozzle assembly is set to two layers, which enhances mass transfer, and the number of Venturi nozzles should not be too large, otherwise the material flow ejected from each nozzle may interfere with each other, forming a complex and disordered flow state, resulting in mixed flow.

[0012] The second objective of this invention is to provide an amination reaction system for preparing p-nitroaniline, comprising a primary amination reactor, a secondary amination reactor, and a tertiary amination reactor connected in series with decreasing installation heights. The structures of the primary and secondary amination reactors are as described above. The tertiary amination reactor includes a reactor shell, a fourth Venturi nozzle is provided at the bottom of the reactor shell, and packing is provided above the fourth Venturi nozzle.

[0013] The beneficial effects of adopting the above technical solution are as follows: the three amination reactors have a height difference, and the material flow is driven by gravitational potential energy, so that the reactors can form a circulation through overflow and pump transportation, thereby reducing energy consumption.

[0014] Preferably, the fourth Venturi nozzle is horizontally positioned.

[0015] The beneficial effects of adopting the above technical solution are as follows: the horizontal setting of the fourth Venturi nozzle is conducive to increasing the flow effect of materials in the reactor.

[0016] Preferably, the bottom of the primary amination reactor is connected to the middle of the primary amination reactor via a primary amination circulation pump and pipeline, that is, the primary amination reactor is connected to a circulation loop with bottom outlet and middle inlet, and a primary amination circulation heat exchanger is provided on the circulation loop.

[0017] Preferably, a material inlet pipe is provided on the circulation loop, and the material inlet pipe is located between the primary amination circulation heat exchanger and the primary amination circulation pump.

[0018] Preferably, the top of the primary amination reactor is connected to the middle of the secondary amination reactor via a pipeline, and the bottom of the secondary amination reactor is provided with a circulation loop, on which a secondary amination circulation pump and a secondary amination circulation heat exchanger are sequentially provided.

[0019] The beneficial effects of adopting the above technical solution are as follows: the outlet pipes of the primary amination circulation pump and the secondary amination circulation pump are connected to the bottom of the amination reactor to provide the driving force for circulation and the linear velocity of the nozzle outlet.

[0020] More preferably, the top material outlet of the secondary amination reactor is divided into two branches. One branch is connected to a second material transfer port via a tertiary amination circulation pump. The material enters the deammoniation tower directly through the second material transfer port for subsequent deammoniation treatment. The other branch is connected to the bottom of the tertiary amination reactor. The middle of the tertiary amination reactor is connected to a first material transfer port. The material enters the deammoniation tower for subsequent deammoniation treatment after gas-phase heat exchange with the flash tank through the first material transfer port.

[0021] Preferably, the primary amination circulating heat exchanger and the secondary amination circulating heat exchanger are connected to a heat source or a cold source, and preferably connected to an amination steam drum that produces by-product steam, so as to heat or cool the materials in the primary amination reactor and the secondary amination reactor. In the early stage of the reaction, steam is required to provide heat to reach the reaction temperature. After the reaction conditions are reached, 4S steam can be produced as a by-product for heat recovery, while preventing the reaction from overheating.

[0022] Preferably, the top of the primary amination reactor, the secondary amination reactor, and the tertiary amination reactor are connected to an ammonia outlet via pipelines, and the ammonia outlet is connected to an ammonia absorption device.

[0023] Preferably, the flow rate of each venturi nozzle is 200 m³ / s. 3 / h, maximum pressure drop less than or equal to 0.15Mpa, material is S22053 stainless steel.

[0024] The beneficial effects of adopting the above technical solution are as follows: after the material is sprayed from the nozzle, it can effectively penetrate the entire cross-section of the reactor, driving the liquid inside the reactor to form macroscopic convection. When the nozzle spray speed is 20-25m / s, it can penetrate the material inside the reactor and be evenly dispersed into the main material after passing through the nozzle of the lower reactor. Under the action of the nozzle jet, the material in the amination reactor forms a relatively strong macroscopic convection flow and eddies. The pressure drop through a single nozzle is preferably 0.135Mpa, and the total pressure drop through the entire amination reactor is 0.269Mpa. The optimized fluid dynamics design ensures that the pressure loss is controllable under high flow rate and reduces the load on the circulating pump.

[0025] Preferably, the venturi nozzle is connected to the horizontal or vertical pipe via a flange for easy disassembly.

[0026] Compared with existing technologies, the advantages of this invention are as follows: This invention achieves continuous material transport through a three-stage series amination reactor and gravity flow design, breaking through the limitations of traditional batch processes, shortening the reaction cycle, and significantly increasing production capacity. The series reactors can progressively increase the reaction temperature and optimize the reaction conditions, with each reactor undertaking different reaction steps or stages. By progressively scaling up the reaction conditions, the overall reaction efficiency and product yield can be effectively improved, as well as the conversion rate of reactants. By adopting a jet feeding method, multi-stage Venturi nozzles (annular arrangement + staggered upper and lower jets) form high-intensity turbulence, improving gas-liquid mass transfer efficiency, increasing product purity, and reducing side reactions. The circulating heat exchange system integrates by-product steam recovery, combined with low-resistance nozzles, reducing overall energy consumption and improving ammonia recovery rate. The operation process is safe, simple, and convenient. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the primary amination reactor or the secondary amination reactor of this utility model;

[0028] Figure 2 This is a schematic diagram of the nozzle assembly of this utility model;

[0029] Figure 3 This is a schematic diagram of the structure of the Venturi nozzle of this utility model;

[0030] Figure 4 This is a flowchart of the amination reaction system for preparing p-nitroaniline according to this invention;

[0031] Figure 5 This is a schematic diagram of the three-stage amination reactor of this utility model;

[0032] Reference numerals: 1. Primary amination reactor; 2. Primary amination circulating heat exchanger; 3. Primary amination circulating pump; 4. Secondary amination reactor; 5. Secondary amination circulating heat exchanger; 6. Secondary amination circulating pump; 7. Tertiary amination reactor; 8. Tertiary amination circulating pump; 901. First Venturi nozzle; 902. Second Venturi nozzle; 903. Third Venturi nozzle; 904. Fourth Venturi nozzle; 91. Packing material; 905. Horizontal tube; 906. First vertical tube; 907. Second vertical tube. Detailed Implementation

[0033] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. Although the description of this utility model will be presented in conjunction with preferred embodiments, this does not mean that the features of this utility model are limited to this embodiment. On the contrary, the purpose of describing the utility model in conjunction with the embodiments is to cover other options or modifications that may be derived based on the claims of this utility model. To provide a deep understanding of this utility model, many specific details will be included in the following description. This utility model may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this utility model, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this utility model can be combined with each other.

[0034] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0035] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0036] See Figures 1-5This invention provides an amination reactor for preparing p-nitroaniline, comprising a reactor shell, wherein at least one set of nozzle assemblies is provided within the reactor shell, and the nozzle assembly includes a plurality of annularly arranged Venturi nozzles, the Venturi nozzle structure being as follows: Figure 3 As shown, the Venturi nozzle is located at the bottom and side wall of the reactor shell, and the Venturi nozzle includes a nozzle orifice that points into the interior of the reactor shell.

[0037] In a preferred embodiment, each nozzle assembly includes a horizontally arranged horizontal tube 905, on which a vertically arranged third Venturi nozzle 903 with its nozzle orifice facing upwards is provided. Two vertical tubes, a first vertical tube 906 and a second vertical tube 907, are connected above the horizontal tube 905. A first Venturi nozzle 901 is provided on the side of the first vertical tube 906 near the second vertical tube 907, and a second Venturi nozzle 902 is provided on the side of the second vertical tube 907 near the first vertical tube 906. The first Venturi nozzle 901 and the second Venturi nozzle 902 are arranged alternately and opposite each other, and preferably horizontally.

[0038] In this embodiment, the reactor shell is provided with two sets of nozzle assemblies arranged vertically. The first vertical pipe 906 is provided with two first Venturi nozzles 901, and the second vertical pipe 907 is provided with three second Venturi nozzles 902. Specifically, as shown... Figures 1-2 As shown, both the primary amination reactor 1 and the secondary amination reactor 4 are divided into upper and lower layers, with 6 nozzles arranged in each layer. One Venturi nozzle is arranged on the horizontal tube 905, and five Venturi nozzles are arranged on the two vertical tubes. A total of 12 nozzles are arranged in a single reactor shell.

[0039] This invention also provides an amination reaction system for preparing p-nitroaniline, such as... Figure 4 As shown, the reactor comprises a primary amination reactor 1, a secondary amination reactor 4, and a tertiary amination reactor 7, which are connected in series and installed at progressively decreasing heights. The structures of the primary amination reactor 1 and the secondary amination reactor 4 are as described above. The tertiary amination reactor 7 includes a reactor shell, with a fourth Venturi nozzle 904 located at the bottom of the reactor shell. A packing material 91 is located above the fourth Venturi nozzle 904. The structure is as follows. Figure 5 As shown.

[0040] In a preferred embodiment, the fourth venturi nozzle 904 is horizontally positioned.

[0041] In an optional embodiment, the bottom of the primary amination reactor 1 is connected to the middle of the primary amination reactor 1 via a primary amination circulation pump 3 and a pipeline, that is, the primary amination reactor 1 is connected to a circulation loop with bottom outlet and middle inlet.

[0042] In an optional embodiment, the circulation loop is provided with a primary amination circulation heat exchanger 2.

[0043] In this embodiment, a material inlet pipe is provided on the circulation loop, and the material inlet pipe is located between the primary amination circulation heat exchanger 2 and the primary amination circulation pump 3.

[0044] In an optional embodiment, the top of the primary amination reactor 1 is connected to the middle of the secondary amination reactor 4 via a pipeline. The bottom of the secondary amination reactor 4 is provided with a circulation loop. The circulation loop is provided with a secondary amination circulation pump 6 and a secondary amination circulation heat exchanger 5 in sequence. That is, the secondary amination reactor 4 is connected to a circulation loop with bottom outlet and middle inlet.

[0045] In an optional embodiment, the top material outlet of the secondary amination reactor 4 is divided into two branches. One branch is connected to a second material transfer port via a tertiary amination circulation pump 8, through which the material directly enters the deammoniation tower for subsequent deammoniation treatment. The other branch is connected to the bottom of the tertiary amination reactor 7, which is connected to a first material transfer port in the middle. The material enters the deammoniation tower for subsequent deammoniation treatment after gas-phase heat exchange with the flash tank through the first material transfer port.

[0046] In an optional embodiment, the primary amination circulating heat exchanger 2 and the secondary amination circulating heat exchanger 5 are connected to a heat source or a cold source, preferably connected to an amination steam drum that produces by-product steam, to heat or cool the materials in the primary amination reactor 1 and the secondary amination reactor 4. In the early stage of the reaction, steam is required to provide heat to reach the reaction temperature. After the reaction conditions are met, by-product steam can be used for heat recovery, while preventing the reaction from overheating.

[0047] In an optional embodiment, the tops of the primary amination reactor 1, the secondary amination reactor 4, and the tertiary amination reactor 7 are connected to ammonia outlets via pipelines. The ammonia outlets are connected to ammonia absorption devices, such as a flash tank for cooling and depressurization, followed by a deammoniation tower from the flash tank, and finally absorption in the ammonia absorption tower.

[0048] In this embodiment, the flow rate of each venturi nozzle is 200 m³ / h. 3 / h, maximum pressure drop less than or equal to 0.15Mpa, material is S22053 stainless steel.

[0049] The reactor is equipped with nozzles to enhance reaction, mass transfer, and heat transfer. The reaction requires a residence time of 8 to 10 hours at 5.0–5.5 MPa and 175–180°C. The designed residence time is 1.2 times that of the industrial-scale experiment, and continuous discharge is achieved.

[0050] The amination reaction employs a high circulation flow rate, with a reaction depth exceeding 90% in the circulating flow. The system circulation volume reaches 30-40 times the feed volume. Even in the event of a power outage, circulation pump failure, or cooling failure, the feed can be effectively shut off via interlocking. The maximum temperature rise of the reaction system does not exceed 20°C, meaning the reaction temperature will not exceed 200°C. The decomposition temperature of p-nitrophenol is 279°C, that of p-nitroaniline is 297°C, and that of p-nitrochlorobenzene is 300°C. Therefore, even under special circumstances such as power outages, the highest temperature of the reaction system is far below the decomposition temperature of the materials. The ratio of p-nitrochlorobenzene to ammonia is adjusted to prevent excessively high material concentrations, which could lead to an excessively rapid reaction rate and subsequent overheating.

[0051] Optionally, to prevent overheating, the reactor temperature is linked to the steam regulating valve in the steam drum. When the reaction temperature exceeds the set temperature, the opening of the steam outlet regulating valve increases, increasing the gas production and the heat exchange for cooling the reaction. This removes more heat of reaction per unit time, thereby controlling the temperature of the amination reaction. When the reaction temperature falls below the set temperature, the opening of the steam outlet regulating valve decreases, increasing the pressure inside the steam drum. This reduces the gas production and the heat removed per unit time, causing the reaction temperature to rise to the set value, thus controlling the reaction temperature within the set range.

[0052] Optionally, the primary and secondary amination steam drums are equipped with liquid level regulation and low liquid level alarm. When the liquid level is low, the boiler water supply valve is opened wide to prevent the reaction from overheating due to liquid level loss.

[0053] In this embodiment, the venturi nozzle is connected to the horizontal pipe 905 or the vertical pipe via a flange.

[0054] The specific production process of this reaction system is as follows: p-nitrochlorobenzene from the tank farm is mixed with ammonia water in a certain proportion, with the ammonia water in excess. The mixture enters the primary amination reactor 1 through the material inlet pipe, where an amination reaction is carried out under high temperature and high pressure to produce p-nitroaniline and ammonium chloride. The heat of reaction is removed through an external primary amination circulating heat exchanger 2, and 0.4 MPa saturated steam is generated by the heat of reaction. The unreacted material overflows sequentially into the secondary amination reactor 4 and the tertiary amination reactor 7, and continues to react until the p-nitrochlorobenzene is completely reacted. After deammoniation, extraction, crystallization and other operations from the first material outlet and the second material outlet, the p-nitroaniline product is obtained.

[0055] Although the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the present invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the present invention to these descriptions. Those skilled in the art can make various changes in form and detail, including some simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. An amination reactor for the production of p-nitroaniline, characterized in that The reactor shell is provided with at least one set of nozzle assembly, which comprises several annularly arranged Venturi nozzles located at the bottom and sidewall of the reactor shell, and the Venturi nozzles comprise nozzle ports pointing to the interior of the reactor shell.

2. The amination reactor for producing p-nitroaniline according to claim 1, characterized by, Each set of nozzle assembly comprises a horizontally arranged cross pipe provided with upwardly vertically arranged third Venturi nozzles on the pipe line of the cross pipe, and two vertical pipes, i.e. first vertical pipe and second vertical pipe, are respectively connected above the cross pipe, the first vertical pipe is provided with first Venturi nozzles on the side close to the second vertical pipe, and the second vertical pipe is provided with second Venturi nozzles on the side close to the first vertical pipe, and the first Venturi nozzles and the second Venturi nozzles are arranged in staggered relation.

3. The amination reactor for producing p-nitroaniline according to claim 2, characterized by, The reactor shell is provided with two sets of nozzle assembly arranged in up-down relation, the first vertical pipe is provided with two first Venturi nozzles, and the second vertical pipe is provided with three second Venturi nozzles.

4. An amination reaction system for the production of p-nitroaniline, characterized by, The tertiary amine reactor comprises a reactor shell, and the bottom of the reactor shell is provided with fourth Venturi nozzles, and the upper portion of the fourth Venturi nozzles is provided with fillers.

5. The amination reaction system for producing p-nitroaniline according to claim 4, wherein The fourth Venturi nozzles are horizontally arranged.

6. The amination reaction system for preparing p-nitroaniline according to claim 4, characterized by, The bottom of the primary amine reactor is connected to the middle portion of the primary amine reactor through a primary amine circulating pump and a pipe line, i.e. the primary amine reactor is connected with a circulating loop with bottom outlet and middle inlet, and the circulating loop is provided with a primary amine circulating heat exchanger.

7. The amination reaction system for producing p-nitroaniline according to claim 6, characterized by, The circulating loop is provided with a material feeding pipe, which is located between the primary amine circulating heat exchanger and the primary amine circulating pump.

8. The amination reaction system for producing p-nitroaniline according to claim 6, wherein The top portion of the primary amine reactor is connected to the middle portion of the secondary amine reactor through a pipe line, the bottom portion of the secondary amine reactor is provided with a circulating loop, and the circulating loop is provided with a secondary amine circulating pump and a secondary amine circulating heat exchanger in sequence.

9. The amination reaction system for producing p-nitroaniline according to claim 8, characterized by, The top portion material outlet of the secondary amine reactor is divided into two branches, one branch is connected with a second material conveying port through a tertiary amine circulating pump, and the other branch is connected to the bottom portion of the tertiary amine reactor, and the middle portion of the tertiary amine reactor is connected with a first material conveying port.

10. The amination reaction system for the production of p-nitroaniline according to any one of claims 4 to 9, characterized in that, The top portion of the primary amine reactor, the secondary amine reactor and the tertiary amine reactor are connected with an ammonia gas outlet through a pipe line.

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