A continuous nitration synthesis device for 2,4-dichloro-3-fluoronitrobenzene

Abstract

The present application relates to a kind of 2,4-dichloro-3-fluorine nitrobenzene continuous nitration synthesis device, belong to chemical reaction technical field, the device includes tubular reactor, micro medium exhaust component, monitoring component and distributor, tubular reactor is equipped with inner tube and jacket cooling cavity, micro medium exhaust component is set in inner tube top, including angle plate, embedded in the liquid- repellent gas permeable membrane of angle plate and protective cover, protective cover and angle plate between form micro gas accumulation cavity, protective cover top end is equipped with exhaust pipe, for the micro-bubble generated by reaction is discharged and avoids material leakage, monitoring component includes the sleeve of being set in the outer portion of inner tube, vacuum monitoring interlayer is formed between sleeve and inner tube, and monitoring head is connected by communicating pipeline, for real-time early warning inner tube pitting penetration, distributor is connected in discharge end, its inner is equipped with according to the baffle of fluid temperature swing, the present application can realize in situ exhaust in continuous nitration process, corrosion early warning and self-adapting shunt.

Description

Technical Field

[0001] This invention belongs to the field of chemical reaction technology and relates to a continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene. Background Technology

[0002] 2,4-Dichloro-3-fluoronitrobenzene is an important class of fluorine-containing fine chemical intermediates, widely used in the synthesis and processing of high-end pharmaceuticals, pesticides, and special fluorine-containing materials. The mainstream preparation process in the industry uses a low-temperature nitration reaction of 2,6-dichlorofluorobenzene with a mixed acid system. Compared with batch reaction processes, tubular continuous nitration processes have the advantages of strong reaction controllability, stable production capacity, and high degree of automation, and have gradually become the mainstream industrial production method.

[0003] Nitrification is a typical gas-generating and exothermic reaction. During the reaction, trace amounts of nitrogen oxide microbubbles are continuously released. Traditional reactors do not have a targeted micro-venting structure, so microbubbles easily adhere to the inner wall of the reaction pipe or mix in the material flow channel. Long-term accumulation will form local gas resistance, which will disrupt the uniformity of material flow. At the same time, it will cause local heat exchange obstruction on the pipe wall, heat accumulation and temperature rise, which will easily induce side reactions such as multiple substitution and decomposition, reduce the purity of the finished product and the reaction conversion rate, and result in poor batch stability of the product.

[0004] The mixed acid medium used in the nitration process has extremely strong corrosive properties. The material conveying pipelines inside the reactor are in long-term contact with the strong acid medium, which makes them prone to slow pitting, wear, perforation and other failures. Traditional tubular reactors only have simple reaction and cooling functions and lack a pre-corrosion monitoring and early warning structure. Piping and perforation of the pipelines cannot be detected in the early stages. Once damage occurs, the pressurized strong acid material inside will leak directly, which not only causes raw material waste and environmental pollution, but also poses major safety hazards such as combustion, corrosion and explosive boiling. Moreover, equipment failure can only be diagnosed by shutting down and disassembling the machine for inspection, resulting in high operation and maintenance costs and poor production continuity.

[0005] In addition, during the non-steady-state operation of continuous tubular reactors during start-up preheating and shutdown, the reaction temperature inside the pipeline cannot quickly reach the process standard. Insufficient material reaction temperature and mismatched reaction residence time will produce a large amount of unqualified waste material with incomplete reaction and excessive impurities. In existing production scenarios, most rely on manual monitoring and observation of temperature instruments to manually switch diversion valves. Manual operation has problems such as judgment bias, action lag, and oversight, which can easily lead to unqualified materials being mixed into the finished product storage tank. Some production lines use PLC combined with solenoid valves for electrically controlled diversion systems, but the chemical conditions of strong acid, low temperature, and high humidity can cause sensor corrosion failure, signal drift, and transmission lag. The electrically controlled valves frequently malfunction and jam, and hidden mixing failures occur frequently, which can easily cause the entire batch of finished products to be scrapped, resulting in large production losses and difficulty in ensuring product yield. Summary of the Invention

[0006] This invention addresses the problems encountered in the continuous nitration production of 2,4-dichloro-3-fluoronitrobenzene, including micro-bubble gas resistance and heat accumulation, high risk of pipeline leakage due to highly corrosive media, and easy failure of electronically controlled flow diversion under strong acid conditions. During the research and development process, it was found that existing technologies lack a targeted micro-venting structure, leading to long-term accumulation of nitrogen oxide microbubbles generated by the reaction, which creates localized gas resistance, disrupts flow field uniformity, causes localized heat accumulation on the pipe wall, induces side reactions, and exacerbates equipment corrosion. Ultrasonic corrosion monitoring is prone to failure under strong acid media and cannot provide early warning of pitting corrosion, resulting in frequent pipeline leaks. The electronically controlled flow diversion scheme, using temperature sensors and solenoid valves, is prone to corrosion and malfunction under strong acid and high humidity conditions, leading to signal drift and the introduction of substandard materials into the finished product, causing the entire batch to be scrapped.

[0007] This invention designs an in-situ micro-medium exhaust component, utilizing the unidirectional permeability of PTFE liquid-phobic and breathable membrane to continuously discharge micro-bubbles without material leakage, thereby stabilizing the reaction flow field and temperature field; it develops a vacuum jacket visualization corrosion early warning system, using the pressure of the leaking material itself to drive the bellows to expand, achieving a visual early warning of the initial pitting corrosion; and it adopts an adaptive distributor driven by the thermal expansion and contraction of paraffin wax to automatically separate unqualified waste materials from qualified finished products according to the material temperature, providing a continuous nitration synthesis device for 2,4-dichloro-3-fluoronitrobenzene.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene, comprising: A tubular reactor, comprising a pressure-bearing outer cylinder, end caps fixed to both ends of the pressure-bearing outer cylinder, a pipe joint located at the outer end of the end caps, an inner tube located within the pressure-bearing outer cylinder, and a jacketed cooling cavity formed between the inner tube and the pressure-bearing outer cylinder, wherein both ends of the inner tube are respectively connected to the pipe joint. The micro-media exhaust assembly is installed on the inner tube and includes a corner plate covering the gas collection port at the top of the inner tube, a liquid-repellent and breathable membrane embedded in the top of the corner plate, and a protective cover fixed to the outer wall of the inner tube. The corner plate is located inside the protective cover, and a micro-gas collection cavity is formed between the protective cover and the corner plate. The top of the protective cover is provided with an exhaust pipe that penetrates the pressure-bearing outer cylinder. The monitoring component is mounted on the inner tube and includes a sleeve fitted over the outside of the inner tube. A vacuum monitoring interlayer is formed between the sleeve and the inner tube. A monitoring head is connected to the top of the sleeve through a connecting pipe II. The distributor, connected to the discharge end of the tubular reactor, includes a pipeline extension section, a connecting box, and a tee pipe connected in sequence. The connecting box is equipped with a baffle that swings according to the fluid temperature to selectively guide the material to the waste tank or the qualified product channel.

[0009] As a further improvement to the above technical solution: The top of the inner tube is provided with a rectangular air collection port, and the corner plate is fixed inside the rectangular air collection port, with both ends of the corner plate sealed.

[0010] The monitoring head includes a connecting cylinder fixedly sleeved on the outer wall of the connecting pipe II, a corrugated pipe disposed on the top of the connecting pipe II, a sealing cap fixed on the top of the corrugated pipe, and a visible transparent cover fixed on the top of the connecting cylinder. When pitting and perforation occur in the inner tube, the liquid inside the inner tube enters the vacuum monitoring interlayer and drives the bellows to expand upward, exposing the sealing cap to the visible transparent cover.

[0011] A flow channel partition plate is fixedly installed inside the three-way pipe, which divides one end of the three-way pipe into two channels. A rotating shaft is rotatably installed at the top of the three-way pipe, and a baffle is fixed to the outer wall of the rotating shaft. A groove adapted to the rotating shaft is opened at one end of the flow channel partition plate, and a sealing gasket is installed in the groove.

[0012] A storage cylinder is fixedly installed inside the connecting box. An extension tube is fixedly installed through the top of the connecting box. The bottom end of the extension tube is connected to the storage cylinder. A piston rod is slidably installed at the other end of the extension tube. A spring is sleeved on the outer wall of the piston rod. The two ends of the spring abut against one side of the piston rod and one side of the inner wall of the extension tube, respectively. A limiting ring for limiting the piston rod is fixed inside the extension tube. The piston rod is connected to the rotating shaft for transmission.

[0013] The top of the connecting box is fixedly provided with a drive box, the top of the rotating shaft is rotatably disposed inside the drive box, the outer wall of the rotating shaft is fixedly sleeved with a gear located inside the drive box, a rack is slidably disposed inside the drive box, and the outer end of the piston rod is slidably disposed inside the drive box and fixedly connected to one end of the rack.

[0014] The storage cylinder contains a paraffin temperature measuring medium. When the fluid temperature is lower than the set value, the paraffin contracts, and the spring pulls the piston rod back. This causes the rotating shaft to rotate through the rack and gear, blocking the finished product channel and opening the waste channel. When the fluid temperature reaches the set value, the paraffin expands, pushing the piston rod out and causing the baffle to rotate in the opposite direction, blocking the waste channel and opening the finished product channel.

[0015] Multiple tubular reactors are provided, and adjacent tubular reactors are connected end-to-end by a connecting pipe I.

[0016] The jacketed cooling chamber is formed by an annular space between the outer wall of the inner tube and the inner wall of the pressure-bearing outer cylinder, which is used to introduce a heat exchange medium to remove the heat released by the nitration reaction.

[0017] The liquid-repellent and breathable membrane is a PTFE microporous breathable membrane, used to allow gas to pass through unidirectionally and to block the leakage of liquid materials.

[0018] The beneficial effects of this invention are as follows: 1. The 2,4-dichloro-3-fluoronitrobenzene continuous nitration synthesis device disclosed in this invention, by adding a micro-media exhaust component, can continuously collect and discharge trace amounts of nitrogen oxide bubbles precipitated during the continuous reaction of materials. Through the one-way permeability of the liquid-phobic and gas-permeable membrane, gas-liquid separation is achieved under the premise of completely eliminating material leakage, avoiding the problems of gas resistance and uneven heat exchange caused by microbubbles adhering to the pipe wall, stabilizing the internal flow field and temperature field of the pipeline, solving the defects of unstable reaction and increased by-products caused by gas accumulation in traditional equipment, and improving the consistency of products produced in batches. 2. The 2,4-dichloro-3-fluoronitrobenzene continuous nitration synthesis apparatus disclosed in this invention utilizes a vacuum monitoring interlayer between the inner tube and the outer casing, combined with a visual monitoring head structure, to monitor pitting corrosion damage to the inner tube in real time. When the inner tube is corroded and perforated by a strong acid medium, the material seeps into the interlayer, driving the corrugated pipe to deform and exposing the sealing cap. This provides early warning of equipment corrosion failures, allowing for troubleshooting without shutdown and disassembly. It effectively avoids safety accidents caused by strong acid material leakage, reduces equipment maintenance costs, and enhances the inherent safety and production continuity of the entire apparatus. 3. The 2,4-dichloro-3-fluoronitrobenzene continuous nitration synthesis device disclosed in this invention utilizes the purely physical properties of thermal expansion and contraction of paraffin medium in conjunction with a gear and rack transmission structure to achieve adaptive material diversion under working conditions. During the low-temperature unsteady-state stage of the device's start-up, the waste channel is automatically opened and the finished product channel is blocked. During the steady-state production stage, the finished product channel is automatically switched. This solves the problems of waste mixing caused by lag in manual operation, corrosion failure of electrical control sensors, and signal drift, thereby improving the yield of finished products and reducing material loss during production.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a three-dimensional structural schematic diagram of a continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to the present invention; Figure 2 This is a schematic diagram of the installation structure of the micro-media exhaust component and monitoring component of a continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to the present invention; Figure 3This is a side cross-sectional view of the micro-medium exhaust component and monitoring component of a continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to the present invention. Figure 4 This is a schematic cross-sectional view of the monitoring head of a continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to the present invention. Figure 5 This is a schematic diagram of the exploded structure of the feeder of a continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to the present invention; Figure 6 This is a schematic diagram of the flow channel partition plate and rotating shaft structure of a continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to the present invention; Figure 7 This is a cross-sectional schematic diagram of the storage cylinder, extension tube, and drive box of a continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to the present invention.

[0021] Reference numerals: 1. Tubular reactor; 11. Pressure-bearing outer cylinder; 12. End cap; 13. Pipe joint; 14. Inner pipe; 15. Jacketed cooling chamber; 2. Connecting pipe I; 3. Distributor; 31. Pipe extension section; 32. Connecting box; 33. Baffle; 34. T-joint; 35. Extension pipe; 36. Drive box; 37. Flow channel partition plate; 38. Rotating shaft; 39. Storage cylinder; 310. Piston rod; 311. Spring; 312. 1. Limiting ring; 313. Rack; 314. Gear; 4. Micro-medium exhaust assembly; 41. Rectangular gas collection port; 42. Angle plate; 43. Liquid-repellent and breathable membrane; 44. Protective cover; 45. Micro-gas collection cavity; 46. Exhaust pipe; 5. Monitoring assembly; 51. Sleeve; 52. Vacuum monitoring interlayer; 53. Connecting pipe II; 54. Monitoring head; 541. Connecting cylinder; 542. Corrugated pipe; 543. Sealing cover; 544. Visible transparent cover. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0024] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0025] Example 1 like Figures 1-7As shown, a continuous nitration synthesis device for 2,4-dichloro-3-fluoronitrobenzene is provided. The entire set of equipment is equipped with multiple sets of tubular reactors 1. Adjacent sets of tubular reactors 1 are connected end-to-end by a connecting pipe I2. The two ends of the connecting pipe I2 are fixedly assembled to the ports of the tubular reactors 1 by flange sealing, forming a closed and continuous material reaction channel. The number of tubular reactors 1 connected in series can be flexibly increased or decreased according to the actual production capacity to adapt to different scales of continuous production operation scenarios. The tubular reactor 1 includes a pressure-bearing outer cylinder 11, which is made of high-strength corrosion-resistant alloy seamless steel pipe or welded, possessing excellent structural strength and deformation resistance, and can be stably operated under high-pressure corrosion conditions in chemical industry for a long time. The two ends of the pressure-bearing outer cylinder 11 are fixedly assembled with end caps 12 by bolts. The end caps 12 are sealed to the ports of the pressure-bearing outer cylinder 11 to eliminate the risk of media leakage. The outer end of the end cap 12 is integrally formed with a pipe connector 13. The pipe connector 13 adopts a standardized chemical pipe connection structure, and the whole is integrated with the end cap 12. The structure has strong integrity and stable sealing performance, which can realize quick and accurate docking and assembly, ensuring the overall airtightness of the entire pipeline system. The inner tube 14 is coaxially arranged inside the pressure-bearing outer cylinder 11. The inner tube 14 is made of a high corrosion-resistant special alloy material, which has extremely strong resistance to the corrosive media of mixed acid in the nitration process and can resist the erosion and wear of concentrated sulfuric acid and concentrated nitric acid mixed media for a long time. The two ends of the inner tube 14 are precisely connected to the inner ports of the pipe connectors 13 on both sides, ensuring smooth flow of materials throughout the process, while ensuring good sealing performance. The closed cavity between the outer wall of the inner tube 14 and the inner wall of the pressure-bearing outer cylinder 11 forms a jacketed cooling cavity 15. The jacketed cooling cavity 15 is a closed annular heat exchange cavity, which can be circulated with a low-temperature heat exchange medium to complete the heat exchange and cooling operation, continuously remove the heat released by the nitration reaction, maintain the stability of the reaction conditions inside the tube, avoid side reaction problems caused by local heat accumulation, and ensure the stability of the nitration reaction and the purity of the finished product.

[0026] A micro-media exhaust assembly 4 is fixedly installed on the inner tube 14 to continuously discharge microbubbles of nitrogen oxides released during the nitration reaction, thereby avoiding production problems such as gas resistance, local heat accumulation, and uneven mass transfer within the tube. A through-type rectangular gas collecting port 41 is provided on the top wall of the inner tube 14. The rectangular gas collecting port 41 has a regular rectangular channel structure, serving as a concentrating flow channel for the extraction of microbubbles from the tube. An angle plate 42 is fixedly installed at the end of the rectangular gas collecting port 41. This angle plate 42 is inverted V-shaped, and its external dimensions are larger than the opening size of the rectangular gas collecting port 41. The bottom surface of the angle plate 42 is flush with the outer wall of the inner tube 14 and fixed to the top outer wall of the inner tube 14 by welding or corrosion-resistant adhesive, completely covering the rectangular gas collecting port 41. The corner plate 42 is sealed to the outer wall of the inner tube 14 at its four edges. A rectangular opening is provided in the middle of the corner plate 42 to fix the liquefactive and breathable membrane 43. The liquefactive and breathable membrane 43 is made of PTFE microporous breathable material, which has excellent liquefactive and breathable properties, allowing for one-way gas penetration and complete blocking of liquid materials. It can continuously exhaust tiny bubbles from the tube without leaking reactants. The outer wall of the inner tube 14 is fitted with a protective cover 44 by welding. The protective cover 44 is made of corrosion-resistant metal and has a hollow cover structure. The corner plate 42 is housed in the internal cavity of the protective cover 44. The inner wall of the protective cover 44 and the outer surface of the corner plate 42 form a sealed micro-gas accumulation cavity 45. The micro-bubbles that precipitate in the tube can be concentrated and collected in the micro-gas accumulation cavity 45, avoiding scattered bubbles adhering to the tube wall and causing local heat exchange abnormalities and flow field turbulence. The exhaust pipe 46 is fixedly installed through the top plate of the protective cover 44. The exhaust pipe 46 is made of corrosion-resistant tubular material and is seamlessly welded and sealed to the top of the protective cover 44. The top tube of the exhaust pipe 46 extends upward and penetrates the outside of the pressure-bearing outer cylinder 11. The bottom end is connected to the micro-gas collection chamber 45. The collected micro-reaction gas can be uniformly discharged and processed through the exhaust pipe 46 to continuously maintain the smooth flow of the inner tube 14 and the stable reaction conditions.

[0027] The entire device has a distributor 3 fixedly installed at the discharge end of the tubular reactor 1 at the bottom. This distributor is used to distinguish the reaction materials under non-steady-state conditions during start-up and shutdown from those under continuous steady-state conditions, achieving fully automatic physical separation of unqualified waste and qualified finished products, eliminating mixing problems caused by manual operation and electrical control failure. The distributor 3 consists of a pipeline extension section 31, a connecting box 32, and a tee pipe 34, which are sequentially sealed and connected. All three are fixedly connected by welding seals, resulting in a strong overall airtight structure with no risk of material leakage or cross-flow. The pipeline extension section 31 adopts a corrosion-resistant tubular structure, with its top precisely aligned with the discharge port of the tubular reactor 1, ensuring a smooth introduction of the reaction materials into the distributor 3. The connecting box 32 is a hollow, sealed box structure with movable baffles 33 inside. The baffles 33 are made of corrosion-resistant hard plate material, with a flat and sealed surface, and can autonomously swing and change direction according to changes in material temperature. During the preheating phase of the equipment, the overall operating conditions of the equipment have not reached the steady-state standard. The material reaction is insufficient, the content of by-products and impurities is high, and the output material is unqualified waste. The baffle 33 maintains a fixed deflection angle to guide the material into the waste tank. When the equipment preheating is completed, the equipment enters a continuous steady-state production state. The material reaction is sufficient, the product purity meets the standard, and the baffle 33 automatically completes the angle switching to guide the qualified material to the qualified product output channel. The entire process relies on the adaptive operation of the mechanical structure and does not effectively avoid the problems of waste mixing and finished product scrapping caused by the lag of manual operation and the failure of electrical control components.

[0028] The internal cavity of the three-way pipe 34 is fitted with a flow channel partition plate 37, which is made of corrosion-resistant rigid plate and is vertically arranged inside the three-way pipe 34 by welding. The plate structure divides the outlet end of the three-way pipe 34 into two independent flow paths: a waste channel and a finished product channel. The two flow paths are regular and independent, with no dead corners for material stagnation, and can be matched with the stable flow of continuously nitrated materials. The top wall of the three-way pipe 34 has a through-hole circular assembly hole, inside which a rotating shaft 38 is mounted via a bearing. The rotating shaft 38 is made of high-strength corrosion-resistant metal and rotates flexibly without jamming. The side plate of the baffle 33 is fixed to the outer wall of the rotating shaft 38 by bolts. The baffle 33 and the rotating shaft 38 rotate synchronously, with precise and error-free angular linkage. The flow channel partition plate 37 has an arc-shaped groove at the end near the rotating shaft 38 that matches the outer diameter of the rotating shaft 38. A fixed elastic sealing gasket is embedded in the groove. The sealing gasket is always in close contact with the outer wall of the rotating shaft 38, which can completely seal the assembly gap between the rotating shaft 38 and the flow channel partition plate 37, effectively preventing the cross-flow of materials in different flow paths and ensuring the uniqueness and accuracy of material diversion. The sealing gasket is made of polytetrafluoroethylene (PTFE) or perfluoroether rubber (FFKM) with strong acid resistance and low coefficient of friction to reduce the rotational resistance of the rotating shaft 38 while ensuring the sealing effect. During the operation of this device, the sealing gasket can be checked or replaced regularly according to the working conditions to maintain long-term sealing reliability.

[0029] A storage cylinder 39 is fixedly mounted inside the internal cavity of the connecting box 32. The storage cylinder 39 is a sealed cylindrical structure made of a material resistant to low temperatures and strong acid corrosion. It contains an inert paraffin temperature-measuring medium, utilizing the purely physical property of thermal expansion and contraction of the paraffin medium to provide stable mechanical power for the reversing swing of the baffle 33. An extension tube 35 is fixedly mounted through the top plate of the connecting box 32. The extension tube 35 is a corrosion-resistant tubular structure, with its bottom end seamlessly connected to the internal cavity of the storage cylinder 39, allowing the paraffin medium inside the storage cylinder 39 to freely enter and exit the internal cavity of the extension tube 35. A piston rod 310 is slidably mounted inside the upper end of the extension tube 35. The piston rod 310 has a smooth, corrosion-resistant rod structure, with a reasonable gap matching between the rod and the inner wall of the extension tube 35, allowing it to smoothly complete reciprocating sliding motion along the axial direction of the extension tube 35. A spring 311 is fitted onto the outer wall of the piston rod 310. The spring 311 is made of corrosion-resistant alloy spring steel, ensuring stable elasticity. Both ends of the spring 311 abut against the lateral stepped surface of the piston rod 310 and the inner limiting end face of the extension tube 35, respectively. Under low-temperature, unsteady-state operating conditions, the spring 311 remains in a pre-compressed state, providing a stable restoring force for the piston rod 310. A limiting ring 312 is fixedly installed inside the extension tube 35. The limiting ring 312 adopts a ring-shaped limiting structure and is fixed to the inner wall of the extension tube 35 by a snap-fit ​​method. The positioning of the limiting ring 312 corresponds to the sliding stroke range of the piston rod 310, mechanically limiting the sliding displacement of the piston rod 310 to prevent over-slipping of the piston rod 310, which could cause structural jamming and component wear damage. The outer end structure of the piston rod 310 forms a stable mechanical transmission relationship with the rotating shaft 38. The extension and retraction of the piston rod 310 can drive the rotating shaft 38 to accurately complete the rotational reversal action.

[0030] A drive box 36 is fixedly mounted on the top plate of the connecting box 32. The drive box 36 is a sealed, corrosion-resistant protective shell, fixed to the top of the connecting box 32 by bolts, effectively isolating it from external corrosive media, dust, and moisture, providing all-around protection for the internal transmission structure and ensuring its long-term stable operation. The top shaft of the rotating shaft 38 extends upward through the connecting box 32 and is rotatably mounted on the inner top plate of the drive box 36, ensuring smooth and unobstructed rotation. A gear 314 is fixedly mounted on the shaft section of the rotating shaft 38 inside the drive box 36. The gear 314 is fixedly connected to the rotating shaft 38 by a key, allowing it to rotate synchronously with the shaft. A rack 313 is horizontally slidably mounted in the internal cavity of the drive box 36. The rack 313 engages with the inner wall of the drive box 36 through a sliding limit structure, allowing only horizontal linear reciprocating sliding. The teeth of the rack 313 precisely mesh with the teeth of the gear 314, ensuring a tight and gapless transmission. The outer end of the piston rod 310 slides through and into the drive box 36, and the end of the piston rod 310 is welded to one end face of the rack 313, resulting in high transmission synchronization. When the material temperature changes, the paraffin medium inside the extension tube 35 expands or contracts with the temperature change, thereby pushing the piston rod 310 to slide along the axial direction of the extension tube 35. The piston rod 310 synchronously drives the rack 313 to move horizontally reciprocating inside the drive box 36. Through the precise meshing of the rack 313 and the gear 314, the rotating shaft 38 is driven to rotate at a precise angle, ultimately achieving stable reversing oscillation of the baffle 33.

[0031] Example 2 Reference Figures 2-4This invention provides a novel technical solution: a continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene. A monitoring component 5 is fixedly installed on the outer wall of the inner tube 14 to monitor in real time for pitting and perforation faults that may occur after long-term corrosion and wear of the inner tube 14. This allows for early warning of potential equipment safety hazards and avoids the risk of strong acid leakage. The monitoring component 5 includes a sleeve 51 made of corrosion-resistant rigid tubing, which is coaxially fitted onto the outside of the inner tube 14. The sleeve 51 and the inner tube 14 are evenly spaced, and both inner walls are welded to the outer wall of the inner tube 14. The closed cavity between them forms a vacuum monitoring interlayer 52. The vacuum monitoring interlayer 52 is a sealed vacuum cavity structure, which is vacuum-sealed before leaving the factory and can maintain a long-term vacuum-sealed state, unaffected by fluctuations in conventional process conditions. The top wall of the sleeve 51 penetrates and is fixedly connected to the connecting pipe II 53. The connecting pipe II 53 is made of corrosion-resistant metal and is seamlessly welded and sealed to the wall of the sleeve 51. The top end of the connecting pipe II 53 penetrates the pressure-bearing outer cylinder 11 and is fixedly mounted with a monitoring head 54. The monitoring head 54 provides a direct view of the internal condition of the vacuum monitoring jacket 52, allowing for assessment of corrosion and damage to the inner pipe 14. The monitoring head 54 includes a connecting cylinder 541, a corrugated pipe 542, a sealing cap 543, and a transparent cover 544. The connecting cylinder 541 is a hollow cylindrical structure, fixedly fitted onto the outer wall of the connecting pipe II 53 using welding, ensuring a secure and stable assembly. The corrugated pipe 542 is fixedly installed at the top end of the connecting pipe II 53. The corrugated pipe 542 is made of flexible, corrosion-resistant metal and possesses excellent expansion and contraction properties. The corrugated pipe 542 is entirely housed within the internal cavity of the connecting cylinder 541. A sealing cap 543 is fixedly fitted to the top end face of the bellows 542. The sealing cap 543 is a rigid, corrosion-resistant circular cover plate structure that is sealed and fixed to the top end of the bellows 542 and can complete the lifting and deformation movements synchronously with the bellows 542. A visible transparent cover 544 is fixedly fitted to the top port of the connecting cylinder 541. The visible transparent cover 544 is made of high light transmittance and corrosion resistant glass material and is sealed and snapped to the port of the connecting cylinder 541. It will not fog or corrode during long-term use and can maintain a clear visual observation state. The top of the transparent enclosure 544 is equipped with a vent that communicates with the atmosphere. When the inner tube 14 is in long-term contact with a highly corrosive mixed acid medium and develops pitting and perforation defects, the reactant material inside the inner tube 14 will seep into the vacuum monitoring jacket 52 through the perforation, breaking the vacuum state of the jacket. The material fluid will continuously act on the bottom of the bellows 542 through the connecting pipe II 53, pushing the bellows 542 to stretch and expand upward, and simultaneously causing the sealing cap 543 at the top to move upward. This compresses the air inside the transparent enclosure 544 and discharges it through the vent, exposing the sealing cap 543, which was originally in a concealed state, to the visible range of the transparent enclosure 544. Operators can directly determine the corrosion and perforation fault of the inner tube 14 by visual inspection, and stop the machine in time to carry out maintenance work, effectively avoiding safety accidents and production losses caused by a large amount of strong acid material leakage.

[0032] The overall workflow is as follows: During formal operation, 2,6-dichlorofluorobenzene raw material and mixed acid medium are continuously fed into the inner tube 14 of the tubular reactor 1 according to the process ratio. Multiple tubular reactors 1 are connected in series through connecting pipe I2 to form a continuous reaction channel. The material flows continuously forward along the inner tube 14 and undergoes a low-temperature nitration synthesis reaction. During the reaction, a low-temperature heat exchange medium is continuously introduced into the jacketed cooling chamber 15 to remove the heat released by the nitration reaction in real time, maintain a stable reaction temperature inside the inner tube 14, avoid side reactions caused by local heat accumulation, and ensure that the reaction proceeds continuously and smoothly. During the material reaction, trace amounts of nitrogen oxide bubbles will be released. When these scattered bubbles flow with the material to the rectangular gas collection port 41, they will gather upwards to the corner plate 42. Through the one-way permeability of the liquid-phobic and breathable membrane 43, they will penetrate the membrane and enter the micro-gas collection cavity 45 formed by the protective cover 44 and the corner plate 42, where they will be concentrated. Finally, they will be discharged outwards through the exhaust pipe 46 at the top, continuously discharging the micro-gas inside the pipe throughout the process. This eliminates problems such as gas blockage, heat accumulation, and uneven mass transfer, ensuring smooth flow and stable reaction conditions.

[0033] During long-term operation of the equipment, the monitoring component 5 continuously monitors the corrosion status of the equipment in real time. When the inner tube 14 is in normal and intact condition, the vacuum monitoring jacket 52 is kept in a sealed vacuum state, the bellows 542 is in a contracted and retracted state, and the sealing cover 543 is hidden inside the connecting cylinder 541. When the inner tube 14 is corroded by strong acid medium and pitting perforation occurs, the material inside the tube seeps into the vacuum monitoring jacket 52, changes the jacket pressure state, pushes the bellows 542 to expand and deform upward, and causes the sealing cover 543 to move upward and be exposed in the visible transparent cover 544. The staff can intuitively discover the equipment failure, carry out maintenance work in a timely manner, and avoid strong acid leakage safety accidents.

[0034] During the non-steady-state preheating stage of the equipment, the overall temperature of the equipment has not reached the steady-state standard of the process. The material reaction is incomplete and the impurity content is high. At this time, the paraffin medium inside the storage cylinder 39 is in a contracted state. The spring 311 is kept in a pre-tightened reset state, pulling the piston rod 310 back. Through the meshing transmission of the rack 313 and the gear 314, the rotating shaft 38 is driven to rotate, causing the baffle 33 to deflect and block the finished product channel and open the waste channel. All unqualified materials are sent to the waste tank for storage. After the equipment preheating is completed, the equipment enters the continuous steady-state production condition. The material temperature reaches the process standard. The paraffin medium expands due to heat, pushing the piston rod 310 to slide outward, driving the rack 313 to move horizontally and driving the gear 314 and the rotating shaft 38 to rotate in opposite directions. This realizes the reversal of the baffle 33, blocking the waste channel and opening the finished product channel. The qualified material that has reacted completely and meets the purity standard flows smoothly into the qualified product output channel, completing the continuous discharge operation. When the equipment stops and cools down after production, the material temperature drops, the paraffin medium contracts and releases pressure, the spring 311 pulls the structure to automatically reset, and the baffle 33 switches back to the waste material conduction state, completing the adaptive cycle operation of the whole set of working conditions.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene, characterized in that, include: A tubular reactor (1) includes a pressure-bearing outer cylinder (11), end caps (12) fixed at both ends of the pressure-bearing outer cylinder (11), a pipe joint (13) located at the outer end of the end caps (12), an inner tube (14) located inside the pressure-bearing outer cylinder (11), and a jacketed cooling cavity (15) formed between the inner tube (14) and the pressure-bearing outer cylinder (11). The two ends of the inner tube (14) are respectively connected to the pipe joint (13). The micro-media exhaust assembly (4) is disposed on the inner tube (14) and includes a corner plate (42) covering the gas collection port at the top of the inner tube (14), a liquid-repellent and breathable membrane (43) embedded in the top of the corner plate (42), and a protective cover (44) fixed to the outer wall of the inner tube (14). The corner plate (42) is located inside the protective cover (44), and a micro-gas collection cavity (45) is formed between the protective cover (44) and the corner plate (42). The top of the protective cover (44) is provided with an exhaust pipe (46) that penetrates the pressure-bearing outer cylinder (11). The monitoring component (5) is installed on the inner tube (14) and includes a sleeve (51) sleeved outside the inner tube (14). A vacuum monitoring interlayer (52) is formed between the sleeve (51) and the inner tube (14). The top of the sleeve (51) is connected to a monitoring head (54) through a connecting pipe II (53). The distributor (3) is connected to the discharge end of the tubular reactor (1) and includes a pipeline extension section (31), a connecting box (32) and a three-way pipe (34) connected in sequence. The connecting box (32) is provided with a baffle (33) that swings according to the fluid temperature, which is used to selectively guide the material to the waste tank or the qualified product channel.

2. The continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to claim 1, characterized in that, The top of the inner tube (14) is provided with a rectangular air collection port (41), and the corner plate (42) is fixed inside the rectangular air collection port (41), and both ends of the corner plate (42) are sealed.

3. The continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to claim 1, characterized in that, The monitoring head (54) includes a connecting cylinder (541) fixedly sleeved on the outer wall of the connecting pipe II (53), a corrugated pipe (542) set on the top of the connecting pipe II (53), a sealing cap (543) fixed on the top of the corrugated pipe (542), and a visible transparent cover (544) fixed on the top of the connecting cylinder (541). When pitting perforation occurs in the inner tube (14), the liquid inside the inner tube (14) enters the vacuum monitoring interlayer (52) and drives the bellows (542) to expand upward, exposing the sealing cap (543) inside the visible transparent cover (544).

4. The continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to claim 1, characterized in that, The three-way pipe (34) is fixedly provided with a flow channel partition plate (37), which divides one end of the three-way pipe (34) into two channels. The top of the three-way pipe (34) is rotatably provided with a rotating shaft (38), and the baffle (33) is fixed to the outer wall of the rotating shaft (38). One end of the flow channel partition plate (37) is provided with a groove that matches the rotating shaft (38), and a sealing gasket is provided in the groove.

5. The continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to claim 4, characterized in that, The connecting box (32) is fixedly provided with a storage cylinder (39). An extension tube (35) is fixedly provided through the top of the connecting box (32). The bottom end of the extension tube (35) is connected to the storage cylinder (39). A piston rod (310) is slidably provided at the other end of the extension tube (35). A spring (311) is sleeved on the outer wall of the piston rod (310). The two ends of the spring (311) abut against one side of the piston rod (310) and one side of the inner wall of the extension tube (35), respectively. A limiting ring (312) for limiting the piston rod (310) is fixedly provided inside the extension tube (35). The piston rod (310) is connected to the rotating shaft (38) for transmission.

6. The continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to claim 5, characterized in that, The top of the connecting box (32) is fixedly provided with a drive box (36), the top of the rotating shaft (38) is rotatably disposed inside the drive box (36), the outer wall of the rotating shaft (38) is fixedly sleeved with a gear (314) located inside the drive box (36), a rack (313) is slidably disposed inside the drive box (36), and the outer end of the piston rod (310) is slidably disposed inside the drive box (36) and fixedly connected to one end of the rack (313).

7. A continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to claim 6, characterized in that, The storage cylinder (39) contains a paraffin temperature measuring medium. When the fluid temperature is lower than the set value, the paraffin contracts, and the spring (311) pulls the piston rod (310) back. The rotating shaft (38) is driven to rotate through the rack (313) and gear (314), so that the baffle (33) blocks the finished product channel and opens the waste channel. When the fluid temperature reaches the set value, the paraffin expands, pushes the piston rod (310) to extend, and makes the baffle (33) rotate in the opposite direction, blocking the waste channel and opening the finished product channel.

8. The continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to claim 1, characterized in that, Multiple tubular reactors (1) are provided, and adjacent tubular reactors (1) are connected end-to-end by a connecting pipe I (2).

9. The continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to claim 1, characterized in that, The jacketed cooling chamber (15) is formed by an annular space between the outer wall of the inner tube (14) and the inner wall of the pressure-bearing outer cylinder (11), and is used to introduce heat exchange medium to remove the heat released by the nitration reaction.

10. A continuous nitration synthesis apparatus for 2,4-dichloro-3-fluoronitrobenzene according to claim 1, characterized in that, The liquid-repellent and breathable membrane (43) is a PTFE microporous breathable membrane used to allow gas to pass through unidirectionally and to block the leakage of liquid materials.

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