A 2-phenylimidazoline production device

Abstract

A 2-phenylimidazoline production apparatus includes a reaction vessel, a primary heat exchanger for the reaction vessel, a secondary heat exchanger for the reaction vessel, a vacuum pump, a first ammonia water spray tower, a second ammonia water spray tower, a third ammonia water spray tower, a heat exchanger for the first ammonia water spray tower, a heat exchanger for the second ammonia water spray tower, and a cooling water storage tank. This apparatus, through a carefully designed heat exchange process, actively collects and utilizes the waste heat released during the production process to maintain the temperature of the cooling water within a suitable and stable process range. This provides stable and controllable cooling conditions for the entire reaction and separation process, ensuring efficient removal of ethylenediamine during the solvent removal process and completely solving the problems of product yellowing and high residue in winter.

Description

Technical Field

[0001] This utility model relates to a 2-phenylimidazoline production apparatus. Background Technology

[0002] 2-Phenylidene imidazoline, also known as 2-phenyl-2-imidazoline, has the molecular formula C9H. 10 N2 can be used as a curing agent for epoxy resin powder coatings, a pharmaceutical raw material, or in organic synthesis. Its chemical structure contains tertiary nitrogen atoms and active hydrogen, enabling the polymerization of epoxy groups at relatively low temperatures. The cured product exhibits excellent mechanical and physical properties and chemical stability. It appears as white or pale yellow crystals, with a melting point of 101℃, comparable to common solid epoxy resins (such as domestic E-12, American DOW663U, and Japanese YD-013). It also possesses good compatibility and processability, meeting the requirements of epoxy resin-based powder coatings. Therefore, it has been developed as a low-temperature rapid curing agent and curing accelerator for epoxy powder coatings.

[0003] In the synthesis of 2-phenylimidazoline using ethylenediamine and benzonitrile as main raw materials, reaction temperature control is crucial for product quality control. During winter production, due to minimal system heat release, the circulating water cannot meet process control requirements under low-load conditions, resulting in high levels of residual solvent and ethylenediamine. This causes the normally white 2-phenylimidazoline to appear yellow, leading to substandard purity analysis. To address the difficulty in controlling refrigerant temperature during winter production and remove excessive solvent from 2-phenylimidazoline, it is necessary to research and explore effective and low-cost refrigerant control methods to meet industrial production needs, improve the purity and color of 2-phenylimidazoline to a superior grade, and restore it to a high-quality product recognized by the market, thereby increasing product profitability.

[0004] 2-Phenylidene imidazoline, also known as 2-phenyl-2-imidazoline, has the molecular formula C9H. 10 Nitrogen (N2) can be used as a curing agent for epoxy resin powder coatings, a pharmaceutical raw material, or in organic synthesis. Its chemical structure contains tertiary nitrogen atoms and active hydrogen, enabling the polymerization of epoxy groups at relatively low temperatures. The cured product exhibits excellent mechanical and physical properties and chemical stability. It appears as white or pale yellow crystals, with a melting point of 101℃, comparable to common solid epoxy resins (such as domestic E-12, American DOW663U, and Japanese YD-013), and possesses good compatibility and processability. Meeting the requirements of epoxy resin-based powder coatings, it has been developed as a low-temperature rapid curing agent and curing accelerator for epoxy powder coatings.

[0005] The main industrial synthesis method for 2-phenylimidazoline currently employs benzonitrile and ethylenediamine as substrates. This method involves using benzonitrile and ethylenediamine as raw materials, and thioacetamide (anhydrous magnesium sulfate, N-bromosuccinimide, zirconium oxychloride, silicotungstic acid, and p-toluenesulfonic acid) as a catalyst, stirring under vacuum to generate 2-phenylimidazoline, while simultaneously releasing gaseous ammonia as a byproduct. This method offers advantages such as readily available raw materials, mature technology, and low cost, making it the mainstream synthesis method currently available.

[0006] There are few patent studies on the production of 2-phenylimidazoline. In the paper "Discussion on the Synthesis Mechanism of 2-phenylimidazoline", Bao Xinhao et al. of Ningbo Weikai Chemical Co., Ltd. explored the synthesis mechanism of 2-phenylimidazoline using benzonitrile and ethylenediamine as raw materials. The paper pointed out that the substances that may affect the purity of 2-phenylimidazoline by this synthesis route are benzoyl ethylenediamine, thiobenzoyl ethylenediamine, dimethylimidazoline, and raw material residues.

[0007] CN119707820A describes a process for producing 2-phenylimidazoline. Benzonitrile, ethylenediamine, and a catalyst are added to a reactor. Under an inert gas atmosphere, the reactor is raised to the reaction temperature to initiate the reaction. Once the temperature reaches 155-180℃, preferably 160-170℃, it stops rising. Timing begins at 80℃, and the reaction time is 4-12 hours, preferably about 5-10 hours. After the reaction, the reactor is vacuum distilled, and the product is obtained from the bottom of the reactor. The material ratio is: benzonitrile / ethylenediamine molar ratio of 1:1.03-1.20, and the catalyst addition to the ethylenediamine molar ratio of 0.004-0.01:1. This invention achieves near-complete benzonitrile conversion, with a conversion rate greater than 99.9%, and the residual benzonitrile content in the product is less than 0.01%, which is far superior to existing production processes.

[0008] In the production of 2-phenylimidazoline, this method uses circulating water as the primary heat exchanger and chilled water as the secondary heat exchanger.

[0009] The existing production process for 2-phenylimidazoline uses benzonitrile, ethylenediamine, and a catalyst as raw materials in a batch reactor. Ammonia, a byproduct of the reaction, is absorbed by a tail gas scrubbing tower and sent as ammonia water. During the reaction, as the temperature rises, the ethylenediamine acts as a solvent, serving as a heat exchanger. Partial vaporization of the ethylenediamine enters the system condenser, where it is condensed in a first-stage vertical jacketed heat exchanger and returned to the reactor for further reaction. Unreacted ethylenediamine is cooled in a second-stage horizontal jacketed condenser and returned to the reactor via a reflux line. After the reaction, the unreacted ethylenediamine, acting as a solvent, is removed from the 2-phenylimidazoline product under vacuum heating. After condensation, it enters a condensate tank for reuse as raw material in the next batch of reactions. The operating temperature of the first-stage condenser is 35-40℃, and the operating temperature of the second-stage condenser is 15-25℃.

[0010] The temperature control of the circulating water synthesized by this method depends on the ambient temperature. Under low-temperature conditions in winter (especially when the ambient temperature is consistently below 10°C), this cooling scheme reveals serious problems: 1) The refrigerant temperature is too low and uncontrollable. The ambient temperature causes the circulating water supply temperature to be too low (often below 10°C), making it difficult to maintain the operating temperature of the primary condenser (designed for 35-40°C), often dropping below 15°C; 2) Product quality is severely degraded. The supercooled ethylenediamine reflux liquid (which can be below 10°C) returns to the high-temperature reactor (155-180°C), causing severe localized cooling and temperature fluctuations, affecting the reaction rate, selectivity, and benzonitrile conversion rate; 3) At extremely low temperatures, ethylenediamine (melting point approximately 9.5°C) may solidify in the heat exchanger or pipelines, causing pipeline blockage, leading to increased reactor pressure and posing a safety risk. 4) During vacuum distillation to remove excess ethylenediamine, excessively low condenser temperatures can lead to excessively high condensation efficiency of ethylenediamine vapor, hindering complete removal of ethylenediamine from the product and resulting in excessive ethylenediamine residue. These factors collectively cause a decrease in product purity, and the residual ethylenediamine darkens the product color during subsequent storage, causing the color (L value) to fail to meet standards, changing from the expected white or pale yellow crystals to yellow. This negatively impacts the product's appearance and market acceptance. Therefore, to ensure product quality during winter production, the 2-phenylimidazoline production process needs to be optimized to stabilize refrigerant parameters.

[0011] Currently, common refrigerant control solutions include: fan-based temperature control and heating methods. Fan-based temperature control is suitable for summer production where the circulating water temperature is high; using a cooling tower fan can effectively lower the circulating water temperature and ensure process parameters. However, this method is not suitable for this system when the circulating water temperature is too low (below 10℃) in winter. Heating methods directly introduce hot water / condensate or steam into the circulating water tank to raise the circulating water temperature. This method has excessively high heating costs, and the circulating water station is exposed to the atmosphere without insulation under low-temperature conditions, making it unsuitable for industrial use. Therefore, existing technologies face several challenges in dealing with low-temperature winter environments, including difficulty in guaranteeing product quality, high energy consumption, and unstable operation, which urgently need to be addressed. Utility Model Content

[0012] This invention aims to overcome the aforementioned deficiencies of existing technologies by providing a 2-phenylimidazoline production system and its temperature control method. It specifically addresses the quality problems of high solvent (ethylenediamine) residue and poor color in the product caused by excessively low external refrigerant temperature during operation in low-temperature environments (such as winter); excessive energy consumption; and unstable process operation and potential safety hazards. In winter production, an independent, small-capacity, closed-loop cooling water circulation system is created. This system, through a carefully designed heat exchange process, actively collects and utilizes waste heat released during the production process (including heat released during product curing and slicing, heat absorbed by the ammonia spray tower, and heat condensation of the reaction gas phase) to maintain the cooling water temperature within a suitable and stable process range (20-25℃), thus providing stable and controllable cooling conditions for the entire reaction and separation process. This ensures product quality (product color L94 or higher, yield 99.4%) and reduces daily power consumption by more than 70%.

[0013] In this invention, research revealed that the system exhibits significant heat release from ethylenediamine condensation, ammonia spray absorption, and product curing / slicing. Specifically, the enthalpy of ethylenediamine vaporization is 40.5 kJ / mol, and the heat of ammonia absorption is 34.748 kJ / mol. Estimating the heat release for a single batch (3 tons / cycle), the total heat released throughout the entire production cycle is approximately 6.5 × 10⁻⁶ kJ / mol. 6 kJ.

[0014] During winter production, an independent, small-capacity, closed-loop cooling water circulation system is created. This system actively collects and utilizes the waste heat released during the production process (including heat released during product solidification and slicing, heat absorbed by the ammonia spray tower, and heat of condensation in the reaction gas phase) through a carefully designed heat exchange process to maintain the cooling water temperature within a suitable and stable process range (20-25℃), thereby providing stable and controllable cooling conditions for the entire reaction and separation process.

[0015] The 2-phenylimidazoline production apparatus of this invention includes a reaction vessel, a primary heat exchanger for the reaction vessel, a secondary heat exchanger for the reaction vessel, a vacuum pump, a first ammonia water spray tower, a second ammonia water spray tower, a third ammonia water spray tower, a heat exchanger for the first ammonia water spray tower, a heat exchanger for the second ammonia water spray tower, and a cooling water storage tank. The product outlet at the bottom of the reactor (e.g., via a pipeline) is connected to the inlet of the slicer. The outlet at the top of the reactor is connected to the material inlet (tube side or shell side) of the primary heat exchanger. The material outlet of the primary heat exchanger is connected to the material inlet (tube side or shell side) of the secondary heat exchanger. The material outlet of the secondary heat exchanger is divided into two paths: one path connects to the inlet of the reflux tank, and the other path returns to the reactor via the reflux line to continue the reaction. Valves are installed on both paths to switch between the reflux tank inlet and the reactor interior. The gas phase opening of the reflux tank is connected to the inlet of the vacuum pump via a pipeline. The outlet of the vacuum pump is connected to the feed inlet of the first ammonia spray tower via a pipeline. The gas outlet of the first ammonia spray tower is connected to the feed inlet of the second ammonia spray tower. The gas outlet of the second ammonia spray tower is connected to the feed inlet of the third ammonia spray tower. The bottom outlet of the third ammonia spray tower returns to the upper or top of the third ammonia spray tower via a pump. The gas outlet of the third ammonia spray tower is the tail gas outlet, which is discharged after treatment. The bottom outlet of the first ammonia spray tower is connected to the inlet of the heat exchanger of the first ammonia spray tower via a pump, and the outlet of the heat exchanger of the first ammonia spray tower returns to the upper or top of the first ammonia spray tower. The bottom outlet of the second ammonia spray tower is connected to the inlet of the heat exchanger of the second ammonia spray tower via a pump, and the outlet of the heat exchanger of the second ammonia spray tower returns to the upper or top of the second ammonia spray tower. The cooling water storage tank is connected to the cooling water jacket inlet of the slicer via a pump and a pipeline. The cooling water jacket outlet is connected to the heat exchange medium inlet of the first ammonia spray tower heat exchanger via a pipeline. The heat exchange medium outlet of the first ammonia spray tower heat exchanger is connected to the heat exchange medium inlet of the second ammonia spray tower heat exchanger via a pipeline. The heat exchange medium outlet of the second ammonia spray tower heat exchanger is connected to the heat exchange medium inlet (shell side or tube side) of the secondary heat exchanger of the reactor via a pipeline. The heat exchange medium outlet of the secondary heat exchanger of the reactor is connected to the heat exchange medium inlet of the primary heat exchanger of the reactor, and the heat exchange medium outlet of the primary heat exchanger of the reactor returns to the cooling water storage tank.

[0016] Optionally, the cooling water jacket outlet of the slicer is divided into two paths, which are respectively connected to the heat exchange medium inlets of the first ammonia spray tower heat exchanger and the second ammonia spray tower heat exchanger. The heat exchange medium outlets of the first ammonia spray tower heat exchanger and the second ammonia spray tower heat exchanger are both connected to the heat exchange medium inlet (shell side or tube side) of the secondary heat exchanger of the reactor via pipelines.

[0017] Preferably, the primary heat exchanger of the reactor is a vertical gas-phase heat exchanger, and the secondary heat exchanger of the reactor is a horizontal gas-phase heat exchanger.

[0018] The device of this invention includes an independent cooling water circulation system, which comprises a cooling water storage tank, a cooling water circulation pump, and a heat exchange pipeline network connecting the pump outlet to multiple devices requiring cooling. The key feature of the heat exchange pipeline network is its series-flow design. After being pumped from the tank, the cooling water flows sequentially through multiple heat exchange devices in a specific, thermodynamically optimized order, absorbing heat and increasing in temperature before finally returning to the storage tank. The flow sequence is: cooling water storage tank → cooling water pump → slicer cooling jacket → (first and second) ammonia spray tower heat exchangers → reactor secondary heat exchanger → reactor primary heat exchanger → return to cooling water storage tank. When the system has a three-stage spray absorption tower, the gas phase from the reactor enters the reflux tank after two-stage condensation. The gas phase from the reflux tank is connected to the vacuum pump inlet. The vacuum pump has a bypass process. During the atmospheric pressure reaction stage, the vacuum pump inlet and outlet are closed and bypass is used. During the depressurization and solvent removal stage, the vacuum pump is started, the bypass is closed, and the tail gas enters the spray tower, sequentially entering the first ammonia water spray tower, the second ammonia water spray tower, and the third ammonia water spray tower. After three-stage spray absorption, the ammonia gas is discharged through the tail gas chimney. The branches flowing to the ammonia water cooling heat exchangers of these two towers can be connected in series (first ammonia water spray tower, then the second ammonia water spray tower) or in parallel (entering both heat exchangers simultaneously and then merging). The parallel design can increase the cooling water volume of the ammonia water system and enhance the heat exchange effect.

[0019] According to a second aspect of this utility model, a process for producing 2-phenylimidazoline is provided, comprising the following steps: (1) Feeding and reaction: Benzonitrile, ethylenediamine and catalyst are fed into the reactor. Under an inert gas atmosphere, the reactor is raised to the reaction temperature (the temperature at which benzonitrile and ethylenediamine begin to react, for example, 80°C) to start the reaction. When the temperature rises to the maximum reaction temperature of 155-180°C, preferably 160-170°C, it stops rising. When the system stops releasing heat, the temperature of the reactor begins to drop. The atmospheric pressure reaction ends. The reactor is then vacuum distilled to obtain the product from the bottom of the reactor. (2) Condensation and reflux and solvent removal: The vacuum distillation process includes a reduced pressure reaction stage and a solvent removal stage. During the reduced pressure reaction stage, the pressure is gradually reduced. During the reaction, ammonia gas is continuously released. Ethylenediamine in the gas enters the reflux tank after primary and secondary condensation. During the atmospheric pressure reaction and reduced pressure reaction stages, all the condensate from the condenser is refluxed back to the reactor. The gas that is not condensed returns to the reflux tank (this can be achieved by setting a downward branch pipe leading to the reactor in the pipeline from the condenser to the reflux tank. With the reflux valve inlet to the reactor open, all the condensed reflux liquid enters the reactor to ensure that there is excess ethylenediamine in the system and that benzonitrile can react fully). After a period of reduced pressure reaction (e.g., usually 2 to 4 hours, preferably about 2.5 to 3.5 hours, more preferably about 3 hours, gradually reducing the pressure to -80 to -100 kPa, for example, -95 kPa vacuum), The solvent removal stage begins (which lasts for 4-10 hours under this vacuum). The condensate return process to the reactor is shut off, and all liquid and gas from the condenser enter the reflux tank. (The main reaction is completed under atmospheric pressure. After the atmospheric pressure reaction ends, the vacuum pump is started to evacuate the reaction system. The purpose is to remove ammonia from the reaction liquid to ensure a complete reaction. The pressure is gradually increased to -80 to -100 kPa, for example, above -95 kPa.) Uncondensed ammonia gas passes through the reflux tank in gas phase and then through the vacuum pump (the temperature of the ammonia gas from the vacuum pump is approximately 20-30°C). Finally, it enters the first ammonia water spray tower, the second ammonia water spray tower, and the third ammonia water spray tower in sequence, producing ammonia water as a byproduct. During the reaction, excess ethylenediamine is returned to the reactor through the primary heat exchanger and the secondary heat exchanger to continue the reaction. (3) Product molding: After the reaction is completed and excess ethylenediamine is removed by vacuum distillation, the molten product is put into a slicer to solidify and slice out (after being discharged, it can be stored in a silo, and the product in the silo is packaged in a packaging machine, and finally palletized and put into storage). The cooling water heat exchange process includes: During the reaction, the production cooling water (initial temperature is generally 10-15℃, gradually rising and stabilizing at 20-30℃ after operation) is sent by the first pump 7 to the cooling water jacket outside the slicer 9. Since slicing has not yet been performed, there is no heat exchange in the cooling water jacket outside the slicer. The water directly passes through the first ammonia spray tower heat exchanger, exchanging heat with the ammonia water (usually 20-30℃, preferably 25-30℃) sent from the first ammonia spray tower, fully absorbing the heat released by the dissolved ammonia gas in the spray water of the first ammonia spray tower (after heat exchange with the ammonia water from the first ammonia spray tower, the cooling water temperature reaches 20℃-22℃); then it passes through the second ammonia spray tower heat exchanger, exchanging heat with the ammonia water (usually 20-30℃, preferably 25-30℃) sent from the second ammonia spray tower, fully absorbing the heat released by the spray water of the second ammonia spray tower. The heat released after the ammonia gas is dissolved by the water (after heat exchange with the ammonia water from the second ammonia water spray tower, the cooling water temperature reaches 22℃~24℃) is used to further introduce the ammonia gas from the second ammonia water spray tower 12 into the third ammonia water spray tower. The ammonia water (usually at ambient temperature) drawn from the bottom of the third ammonia water spray tower is sprayed from the top of the tower to further absorb the ammonia gas in the gas. The gas is discharged from the top of the third ammonia water spray tower. The cooling water drawn from the heat exchangers of the first and second ammonia water spray towers enters the secondary heat exchanger and the primary heat exchanger of the reactor in sequence, where it exchanges heat with the gaseous ethylenediamine and the ammonia gas released from the reaction in the reactor to cool the solvent and ammonia gas. After exiting the primary heat exchanger of the reactor, the cooling water returns to the water tank. The cooled condensate is sent to the reflux tank and returned to the reactor. The ammonia gas enters the tail gas spray tower through the pipeline and is absorbed into ammonia water. When the reaction is complete and the product is sliced, the production cooling water exchanges heat with the slicer to absorb the heat released during the product slicing process. The initial temperature of the product is generally 160-170℃, and the temperature after cooling into a solid is 30-50℃. The temperature of the cooling water coming out of the slicer is 32-35℃ (during the reaction stage, ammonia gas is generated in the reaction vessel; from the desolventizing stage onwards, only the product and unreacted ethylenediamine are present in the reaction vessel, and no ammonia gas is generated).

[0020] This allows the cooling water temperature to gradually rise from the initial temperature (10-15℃) and stabilize within the ideal process window of 20-30℃ during a batch production cycle. This temperature ensures the effective operation of each stage of the condenser (38-40℃ at the outlet of the first-stage condenser and 20-25℃ at the outlet of the second-stage condenser), avoids overcooling of the reflux liquid, and creates favorable conditions for vacuum solvent removal.

[0021] The material ratio is as follows: the molar ratio of benzonitrile to ethylenediamine is 1:1.03-1.20, preferably 1:1.08-1.20, and even more preferably 1:1.10-1.17; the molar ratio of catalyst addition to ethylenediamine is 0.004-0.01:1, preferably 0.006-0.008:1.

[0022] The catalyst may be selected from one or more of thioacetamide, anhydrous magnesium sulfate, N-bromosuccinimide, zirconium oxychloride, silicotungstic acid, and p-toluenesulfonic acid.

[0023] This invention modifies the cooling water system to create an independent, small-capacity, closed-loop cooling water circulation system for winter production. It has the following advantages: 1. Solving Product Quality Issues in Winter: This system, through a carefully designed heat exchange process, actively collects and utilizes waste heat released during the production process (including heat released during product curing and slicing, heat absorbed by the ammonia spray tower, and heat of condensation in the reaction gas phase) to maintain the cooling water temperature within a suitable and stable process range (20-25℃), thus providing stable and controllable cooling conditions for the entire reaction and separation process. It ensures efficient removal of ethylenediamine during the solvent removal process. Examples show that benzonitrile residue in the product is below 0.07%, ethylenediamine residue is below 0.002%, and the L-value of color is consistently above 96, meeting the superior grade standard and completely solving the problems of yellowing and high residue in winter products.

[0024] 2. Achieve energy conservation and consumption reduction: Due to the optimized cooling process, energy-intensive circulating water pumps, chilled water pumps, and refrigeration units are shut down, requiring only a small-power (3-3.5kW) centrifugal pump to drive a small-capacity cooling water circulation. Example data shows that approximately 2000 kWh of electricity can be saved daily, with an energy saving rate exceeding 70%, significantly reducing production costs.

[0025] 3. Improved process stability and safety: Eliminates risks such as reaction temperature fluctuations and ethylenediamine solidification blockage caused by excessively low external water temperature, enabling the unit to achieve stable, safe, and continuous production throughout the year in a low-temperature environment, reducing the difficulty and intensity of operation.

[0026] 4. Achieve internal energy recycling and efficient utilization: Creatively regard the "waste heat" of each link in the production process as a "resource" to maintain the thermal balance of the system, and realize the internal recycling of heat through integrated design, which is a green and sustainable process improvement solution.

[0027] 5. The system is highly adaptable and easy to modify: This solution mainly involves adding a small independent circulating water system to the existing equipment and optimizing the pipeline connection. The modification investment is small, the effect is quick, and it is easy to implement and promote. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the 2-phenylimidazoline production apparatus of this utility model.

[0029] Figure 2 This is a schematic diagram of the 2-phenylimidazoline production apparatus of Comparative Example 1.

[0030] In the diagram: 1-Reaction vessel; 2-First-stage heat exchanger of the reaction vessel; 3-Second-stage heat exchanger of the reaction vessel; 4-First ammonia spray tower heat exchanger; 5-Second ammonia spray tower heat exchanger; 7-First pump (cooling water pump); 8-Cooling water storage tank; 9-Slicer; 10-First ammonia spray tower; 11-Second pump; 12-Second ammonia spray tower; 13-Third pump; 14-Vacuum pump; 15-Reflux tank; 16-Third ammonia spray tower; 17-Fourth pump. Detailed Implementation

[0031] The present application will be described in detail below with reference to the accompanying drawings.

[0032] like Figure 1 As shown, a 2-phenylimidazoline production apparatus includes a reactor 1, a primary heat exchanger 2 (i.e., a vertical gas-phase heat exchanger), a secondary heat exchanger 3 (i.e., a horizontal gas-phase heat exchanger), a vacuum pump 14, a first ammonia spray tower 10, a second ammonia spray tower 12, a third ammonia spray tower 16, a heat exchanger 4 for the first ammonia spray tower, a heat exchanger 5 for the second ammonia spray tower, and a cooling water storage tank 8. The bottom product outlet of reactor 1 (e.g., via a pipeline) is connected to the inlet of slicer 9. The top outlet of reactor 1 is connected to the material inlet of primary heat exchanger 2 (tube side or shell side). The material outlet of primary heat exchanger 2 is connected to the material inlet of secondary heat exchanger 3 (tube side or shell side). The material outlet of secondary heat exchanger 3 is connected to the inlet of reflux tank 15. The gas phase opening of reflux tank 15 is connected to vacuum pump 14 via a pipeline. The outlet of vacuum pump 14 is connected to the feed inlet of first ammonia spray tower 10 via a pipeline. The gas outlet of first ammonia spray tower is connected to the feed inlet of second ammonia spray tower 12. The gas outlet of second ammonia spray tower is connected to the feed inlet of third ammonia spray tower 16. The bottom outlet of third ammonia spray tower returns to the upper or top of third ammonia spray tower via fourth pump 17. The gas outlet of third ammonia spray tower is the tail gas outlet, which is directly discharged after treatment.

[0033] The bottom outlet of the first ammonia spray tower 10 is connected to the inlet of the first ammonia spray tower heat exchanger 4 via the second pump 11, and the outlet of the first ammonia spray tower heat exchanger 4 returns to the upper part or top of the first ammonia spray tower 10. The bottom outlet of the second ammonia spray tower 12 is connected to the inlet of the second ammonia spray tower heat exchanger 5 via the third pump 13, and the outlet of the second ammonia spray tower heat exchanger 5 returns to the upper part or top of the second ammonia spray tower 12. The cooling water storage tank 8 is connected to the cooling water jacket inlet of the slicer via a pipeline from the first pump (cooling water pump) 7. The cooling water jacket outlet is connected to the heat exchange medium inlet of the first ammonia spray tower heat exchanger 4 via a pipeline. The heat exchange medium outlet of the first ammonia spray tower heat exchanger 4 is connected to the heat exchange medium inlet of the second ammonia spray tower heat exchanger 5 via a pipeline. The heat exchange medium outlet of the second ammonia spray tower heat exchanger 5 is connected to the heat exchange medium inlet (shell side or tube side) of the secondary heat exchanger 3 of the reactor via a pipeline. The heat exchange medium outlet of the secondary heat exchanger 3 of the reactor is connected to the heat exchange medium inlet of the primary heat exchanger 2 of the reactor, and the heat exchange medium outlet of the primary heat exchanger 2 of the reactor returns to the cooling water storage tank 8.

[0034] Alternatively, the cooling water jacket outlet can be divided into two paths, which are respectively connected to the heat exchange medium inlets of the first ammonia spray tower heat exchanger 4 and the second ammonia spray tower heat exchanger 5. The heat exchange medium outlets of the first ammonia spray tower heat exchanger 4 and the second ammonia spray tower heat exchanger 5 are both connected to the heat exchange medium inlet (shell side or tube side) of the secondary heat exchanger 3 of the reactor via pipelines.

[0035] Heat exchanger function description: (1) Cooling water storage tank 8: A 5 cubic meter storage tank is used as an intermediate cooling water tank. The storage tank can be heated by steam. The water is heated by inserting a steam line into the storage tank to ensure that the water temperature is within the process index range (15-24℃). The outlet of the cooling water pump is connected to the heat exchange plate for heat exchange (the outlet of the cooling water pump enters the plate heat exchanger, and the other side uses circulating water to exchange heat with the plate heat exchanger. The cooling water is cooled as needed). The refrigerant temperature can be precisely controlled as required by the process.

[0036] (2) Heat exchange of slicer 9: The heat exchange of slicer is completed after the production process, and the water temperature requirement is as low as possible. Therefore, the cooling water enters slicer 9 as the first step.

[0037] (3) Heat exchanger 4 of the first ammonia spray tower: Cooling water enters the heat exchanger 4 of the first ammonia spray tower from the outlet of the slicer 9 to exchange heat with the ammonia water at the outlet of the second pump 11. Cooling water and ammonia water enter the heat exchanger in a counter-current manner for efficient heat exchange, ensuring that the temperature of the ammonia water in the first ammonia spray tower 10 is below 30°C when absorbing a large amount of ammonia gas in the early stage of the reaction, thus ensuring the absorption effect of the spray tower.

[0038] (4) Second ammonia spray tower heat exchanger 5 / Second ammonia spray tower heat exchange: Cooling water enters the second ammonia spray tower heat exchanger 5 from the outlet of the first ammonia spray tower heat exchanger 4. The cooling water and the ammonia water at the outlet of the third pump 13 exchange heat efficiently in a countercurrent manner, ensuring that the second ammonia spray tower completes the absorption of ammonia gas in the later stage of the system reaction after the first ammonia spray tower is saturated in the middle and late stages of the reaction.

[0039] (5) Heat exchange of the secondary heat exchanger 3 / secondary condenser of the reactor: Cooling water enters the secondary heat exchanger 3 of the reactor from the outlet of the second ammonia spray tower heat exchanger 5 to exchange heat with the reaction gas phase. The cooling water exchanges heat with the gaseous ethylenediamine / ammonia in the shell side and tube side. After the ethylenediamine is condensed by the cooling water, it returns to the reactor to continue to participate in the reaction. After passing through the slicer and the heat exchange of the ammonia spray tower, the temperature of the cooling water is controlled within the process parameters to ensure that the ethylenediamine can be cooled and recovered to avoid loss.

[0040] (6) Heat exchange of the primary heat exchanger 2 / primary condenser of the reactor: Cooling water enters the primary heat exchanger 2 of the reactor through the outlet of the secondary heat exchanger 3. The cooling water exchanges heat with the gaseous ethylenediamine / ammonia in the tube side in the shell side in a co-current manner, and exchanges heat with the reaction gas phase to ensure that ethylenediamine can be condensed and recovered from the gas phase during the reaction stage to avoid loss.

[0041] The cooling water passes through the slicer, two spray towers, and two heat exchangers, absorbing the heat of system reaction, the heat absorbed by ammonia, and a large amount of heat generated by the product slicing. In low-temperature weather, the cooling water temperature can be stably controlled at 20-25℃, ensuring the quality of the 2-phenylimidazoline product. Example 1

[0042] Using this utility model Figure 1 The system shown. The cooling water flow strictly follows the following direction: Cooling water storage tank 8 → First pump 7 → Slicer 9 cooling jacket → First ammonia spray tower heat exchanger 4 → Second ammonia spray tower heat exchanger 5 → Reactor secondary heat exchanger (condenser) 3 → Reactor primary heat exchanger (condenser) 2 → Return to cooling water storage tank 8.

[0043] At the start of the reaction, the production cooling water (initially 10-15℃, gradually rising and stabilizing at 20-30℃) is sent via the first pump 7 to the cooling water jacket outside the slicer 9. Since slicing has not yet begun, there is no heat exchange in the cooling water jacket outside the slicer. The water directly passes through the first ammonia spray tower heat exchanger 4 and the second pump 1 of the first ammonia spray tower 10 (the ammonia gas entering the first ammonia spray tower 10 and the second ammonia spray tower 12 comes from the tail gas of the reactor, and the temperature of the ammonia gas from the vacuum pump is about 20-30℃; the three spray towers are connected in series to absorb ammonia gas). 1. Ammonia water (generally 20-30℃) is pumped out for heat exchange, fully absorbing the heat released after the ammonia gas dissolves in the spray water of the first ammonia water spray tower 10. The temperature of the ammonia water in the first ammonia water spray tower 1 should be controlled to not exceed 30℃ (too high a temperature will affect the ammonia absorption effect). Then, it passes through the heat exchanger 5 of the second ammonia water spray tower, and exchanges heat with the ammonia water pumped out by the third pump 13 of the second ammonia water spray tower 2, fully absorbing the heat released after the ammonia gas dissolves in the spray water of the second ammonia water spray tower 12. The temperature of the ammonia water in the second ammonia water spray tower 12 should be controlled to not exceed 30℃ (too high a temperature will affect the absorption effect). (Ammonia absorption effect); Cooling water then enters the secondary heat exchanger 3 heat exchange channel of the reactor, where it exchanges heat with the gaseous ethylenediamine and the ammonia released from the reaction, cooling the solvent and ammonia. After cooling, the solvent returns to the reactor as condensate. The gas phase temperature after heat exchange is approximately 20°C. The ammonia from the second ammonia spray tower 12 is further introduced into the third ammonia spray tower. Ammonia water (at room temperature, as ammonia absorption mainly occurs in the first-stage spray tower) is sprayed from the top of the third ammonia spray tower, further absorbing the ammonia in the gas. The top of the third ammonia spray tower... The gas is discharged from the reactor. The cooling water then passes through the primary heat exchanger 2 of the reactor to exchange heat with the gas phase of ethylenediamine and ammonia in the reactor (the temperature of ammonia is generally 100~170℃). (Because the secondary heat exchanger 3 of the reactor requires a lower temperature, the cooling water first enters the secondary heat exchanger 3 of the reactor, and after the temperature increases, it enters the primary heat exchanger 2 of the reactor to exchange heat with the hot material coming out of the reactor, which is more effective for process control). After the heat exchange, the ethylenediamine falls directly back into the reactor through condensate. The gas phase temperature after the heat exchange is about 38℃ (the temperature of the cooling water coming out of the primary heat exchanger 2 of the reactor is generally 30~50℃).

[0044] When the reaction is complete and the product is sliced, the cooling water is sent from the cooling water storage tank 8 to the cooling water jacket set outside the slicer 9 via the first pump 7 to exchange heat with the slicer 9 and absorb the heat released during the product slicing process. The initial temperature of the product is about 165°C, and the temperature after cooling into a solid is about 45°C. After absorbing the heat generated by slicing, the cooling water generally rises to 32~35°C.

[0045] The outlet pressure of the first pump 7 is 0.3 MPa, the cooling water temperature before the reaction is 15℃, and the ambient temperature is 8℃ (in winter). 2000 kg of benzonitrile, 1260 kg of ethylenediamine, and 15 kg of catalyst are added to the reactor under an inert protective gas atmosphere. After thorough mixing, steam heating is initiated. The product at the top of the reactor, after atmospheric pressure reaction, reaches a temperature of approximately 38℃ in the first-stage condenser and approximately 20℃ in the second-stage condenser (the ethylenediamine condensed at the top of the reactor returns directly to the reactor during the reaction stage). During both atmospheric and reduced pressure reactions, all reflux liquid from the condensers returns to the reactor, while the uncondensed gas phase enters the reflux tank 15 and is pumped to the first ammonia spray tower 10 by vacuum pump 14.

[0046] After the atmospheric pressure reaction is completed, vacuum pump 14 is started to gradually and slowly reduce the pressure for a depressurization reaction. After about 3 hours, a vacuum of approximately -95 kPa is reached. At this point, the valve returning from the secondary heat exchanger 3 to the reactor is closed, and the cooling water in the primary heat exchanger 2 is shut off. This vacuum level is maintained for about 6 hours. Unreacted ethylenediamine in the reactor is vaporized, cooled by the secondary condenser, and then enters the reflux tank 15 as raw material for the next reactor reaction. The product is discharged from the reactor to the slicer for slicing. The sliced ​​product is then discharged from the slicer and stored in a silo. The product in the silo is then packaged by the packaging machine, and finally palletized and stored. During the slicing process, dust and exhaust gases generated by the slicer, silo, and packaging machine are absorbed by a blower in the exhaust gas spray tower. After slicing production is completed, the cooling water temperature is 32℃, the temperature of the first ammonia spray tower 10 is approximately 25℃, and the temperature of the second ammonia spray tower 12 is approximately 28℃.

[0047] After the product was sliced, samples were taken for analysis. The residual amounts of benzonitrile and ethylenediamine in the product were analyzed using the internal standard method. The residual amount of benzonitrile was 0.062%, and that of ethylenediamine was 0.0015%. The product's color L value was 96, and the yield of 2-phenylimidazoline was 99.33%.

[0048] During the reaction, the temperature of the cooling water in the cooling water storage tank 8 is controlled at 22℃ after fully absorbing the heat released by the system. Under these process parameters, the product yield, benzonitrile ethylenediamine residue, and product color all reach ideal values.

[0049] The cooling water pump uses a small-flow centrifugal pump (rated power 3kw), which saves 2000kwh of energy per day compared with the original design parameters of the cooling tower pump (rated power 45kw), chilled water pump (rated power 45kw) and refrigeration unit (rated power 500kw), resulting in a significant advantage in production cost. Example 2

[0050] The production cooling water (initial temperature 10-15℃, gradually rising and stabilizing at 20-30℃ after operation) flows from water tank 8 to slicer 9 via pump 7. The process is as follows: slicer 9 → first ammonia spray tower heat exchanger 4 / second ammonia spray tower heat exchanger 5 → reactor secondary heat exchanger (condenser) 3 → reactor primary heat exchanger (condenser) 2. The difference from Example 1 is that the cooling water from slicer 9 is divided into two parallel streams flowing through the first ammonia spray tower heat exchanger 4 and the second ammonia spray tower heat exchanger 5, converging before entering the reactor secondary heat exchanger 3.

[0051] At the start of the reaction, cooling water enters the first ammonia spray tower heat exchanger 4 and the second ammonia spray tower heat exchanger 5 in parallel, exchanging heat with the ammonia water pumped out by the second / third pumps 11 / 13 of the first ammonia spray tower 10 / second ammonia spray tower 12. This fully absorbs the heat released after the ammonia gas is dissolved in the spray water of the ammonia spray towers, and the temperature of the two ammonia spray towers (i.e., the temperature of the ammonia water after the ammonia gas is dissolved) is controlled at 30℃. Then, through the secondary heat exchanger 3 of the reactor, it exchanges heat with the gaseous ethylenediamine and the ammonia gas released from the reaction, thus improving the heat exchange between the solvent and the ammonia water. Ammonia gas is cooled down, and the solvent returns to the reactor via condensate after cooling. The gas phase temperature after heat exchange is 20°C. Cooling water then exchanges heat with the gas phases of ethylenediamine and ammonia in the reactor via the primary heat exchanger 2. After heat exchange, ethylenediamine falls directly back to the reactor via condensate (in the atmospheric pressure and reduced pressure reaction stages, all the condensate from the condenser returns to the reactor, and the uncondensed gas returns to the reflux tank. In the solvent removal stage, the condensate return process to the reactor is closed, and all of it enters the reflux tank). The gas phase temperature after heat exchange is approximately 38°C.

[0052] When the product is sliced ​​after the reaction is complete, the production cooling water first exchanges heat with the slicer 9 to absorb the heat released during the product slicing process. The initial temperature of the product is 167℃, and the temperature after cooling into a solid is 45℃.

[0053] The outlet pressure of cooling water pump 7 is 0.3 MPa. The temperature of cooling water in water tank 8 before the reaction is 15℃, and the ambient temperature is 8℃. Benzonitrile 2000 kg, ethylenediamine 1260 kg, and catalyst 15 kg are added to reactor 1 under an inert protective gas atmosphere. After thorough mixing of the reactants, steam heating is started. After the system undergoes atmospheric pressure reaction, the temperature of the primary heat exchanger 2 in the reactor is 37℃, and the temperature of the secondary heat exchanger 3 in the reactor is 21℃.

[0054] After vacuum desolventizing to remove excess ethylenediamine from the system, the product is used as raw material for the next reactor reaction. The product is discharged from the reactor to a slicer for slicing. After exiting the slicer, the sliced ​​product enters a storage silo. The product in the silo then enters a packaging machine for packaging, and finally, it is palletized and stored. During the slicing process, dust and exhaust gases generated by the slicer, silo, and packaging machine are absorbed by exhaust gas spray towers via fans. After slicing production is completed, the cooling water temperature is 32.5℃, the temperature of the first ammonia water spray tower is 25℃, and the temperature of the second ammonia water spray tower is 26℃.

[0055] After the product was sliced, samples were taken for analysis. The residual amounts of benzonitrile and ethylenediamine in the product were analyzed using the internal standard method. The residual amount of benzonitrile was 0.0586%, and that of ethylenediamine was 0.0010%. The product's color L value was 96.5, and the yield of 2-phenylimidazoline was 99.42%.

[0056] During the reaction, the cooling water temperature is controlled between 20-25℃ while fully absorbing the exothermic reaction of the system. Under these process parameters, the product yield, benzonitrile ethylenediamine residue, and product color all reach ideal values.

[0057] Compared to Example 1, the plate heat exchangers in the first and second ammonia spray towers are connected in parallel, resulting in a larger cooling water volume and better heat exchange effect. Consequently, the water temperature in the second ammonia spray tower decreases significantly. Although the temperature of the secondary heat exchanger in the reaction stage increases slightly, it remains within control limits. The larger cooling water volume ensures less loss of ethylenediamine during the reaction, and the higher water temperature improves the solvent removal effect. Therefore, under these conditions, the product quality is good, the residue is low, and the yield is higher.

[0058] The analysis results of Examples 1 and 2 show that, in winter production, using a small-capacity water tank with a small water pump as a heat exchanger for a batch reactor can, on the one hand, stabilize the cooling water process parameters, improve product quality and yield, ensure a product color of L94 or higher and a yield of 99.4%, achieving the highest product quality in the industry; on the other hand, it can significantly reduce production energy consumption, increase product profits, and reduce daily power consumption by 2000 kWh during production operation. Comparative Example 1

[0059] The traditional process before the modification is adopted. The plant's circulating water (with an initial water temperature of 5℃) is supplied in parallel to the primary heat exchanger (condenser) 2 of the reactor, the ammonia water spray tower heat exchangers 4 and 5, and the slicer 9. An independent chilled water system (with an initial water temperature of 5℃) supplies the secondary heat exchanger (condenser) 3 of the reactor.

[0060] During the reaction, the gaseous ethylenediamine in the reactor undergoes heat exchange through the circulating water in the primary heat exchanger 2. After heat exchange, the ethylenediamine at a temperature of 15°C flows directly back to reactor 1 from the vertical heat exchanger 2. The uncondensed gaseous ethylenediamine is condensed to 10°C by the chilled water in heat exchanger 3 and returns to reactor 1 via the reflux line. The ammonia gas produced in the reaction is cooled by heat exchangers 2 and 3 and then passes through the reflux tank and the vacuum pump branch line into the first ammonia spray tower 10, the second ammonia spray tower 12, and the third ammonia spray tower 16 for absorption. The ammonia water from the spray towers enters the first ammonia spray tower heat exchanger 4 and the second ammonia spray tower heat exchanger 5 from the outlets of the second pump 11 and the third pump 13, respectively, for heat exchange. The cooling water temperature is 5°C, and the ammonia spray tower temperature is 8°C (the ammonia spray tower temperature is controlled at around 8°C when the cooling water temperature is 5°C).

[0061] After the atmospheric pressure reaction is completed, vacuum pump 14 is started to gradually and slowly reduce the pressure for a reduced pressure reaction. After about 3 hours, a vacuum of approximately -95 kPa is reached. At this point, the valve returning from the secondary heat exchanger 3 to the reactor is closed, and the cooling water in the primary heat exchanger 2 is shut off. This vacuum level is maintained for about 6 hours. After vacuum desolventizing, excess ethylenediamine solvent is removed from the system and used as raw material for the next reactor reaction. The product is discharged from the reactor to a slicer for slicing. The sliced ​​product is then discharged from the slicer and stored in a silo. The product in the silo is then packaged in a packaging machine, and finally palletized and stored. During the slicing process, dust and exhaust gases generated by the slicer, silo, and packaging machine are absorbed by a blower in an exhaust gas spray tower. After slicing production is completed, the circulating water temperature is 5.5℃, the chilled water temperature is 8℃, the temperature of the first ammonia spray tower is 8℃, and the temperature of the second ammonia spray tower is 8℃.

[0062] After the product was sliced, samples were taken for analysis. The residual amounts of benzonitrile and ethylenediamine in the product were analyzed using the internal standard method. The residual amount of benzonitrile was 0.1208% and that of ethylenediamine was 0.0610%, indicating a significant increase in residues. The product's color L value was 90.5, which was obviously yellow and unqualified. The yield of 2-phenylimidazoline in the product was 99.04%.

[0063] During the reaction, under conditions of low cooling water, the reflux ethylenediamine temperature in reactor 1 was low, the reaction time was prolonged, and the conversion rate of benzonitrile decreased. Furthermore, the condenser temperature was too low during solvent removal, resulting in incomplete removal of ethylenediamine from reactor 1 and causing excessive ethylenediamine residue. The final product failed to meet standards for solvent residue and color. During production, the large circulating water pump, chilled water pump, and refrigeration unit were all in operation, resulting in energy consumption per ton of product that was 2.3 times that of Example 1.

[0064] Comparing Examples 1 and 2 with Comparative Example 1, it is clear that the system and method provided by this utility model can stably control the temperature of the cooling medium within an ideal range in low-temperature winter environments without relying on high external heat energy consumption, thereby simultaneously achieving high product quality (high purity, excellent color) and low production energy consumption, demonstrating outstanding technical effects.

[0065] In the above examples and comparative examples, the residual amounts of benzonitrile and ethylenediamine were analyzed using the following methods: The residual amounts of benzonitrile and ethylenediamine in the product were analyzed using the internal standard method. Preparation of the standard solution: Weigh approximately 1 g of the sample (accurate to 0.1 mg), dissolve and dilute with 20 g of DMF (accurate to 0.1 mg) in a sample preparation bottle, and shake well before use. Inject 0.4 μL of the prepared sample into a gas chromatograph, record the chromatogram, and then calculate the content of the analyte compound in the sample according to formula (1).

[0066] ···········(1) In the formula: w1 :--The content of the tested compound i in the sample, in milligrams per kilogram (mg / kg); A1 -- Peak area of ​​compound i in the sample; A -- Peak area of ​​calibration compound s in the standard working solution; W -- The content of calibration compound s in the standard working solution, in milligrams per kilogram (mg / kg); m 1 , -- The mass of the diluent r, in grams (g); m 2 , -- The mass of the sample, in grams (g).

[0067] In this embodiment, the product's colorimetric L value is determined using the following method: The colorimetry of the samples was analyzed using the PS2010 "Fat Girl" spectrophotometer produced by Guangdong Sanenshi Intelligent Technology Co., Ltd., where L value is the black and white value, which ranges from 0 to 100. A value closer to 100 indicates a whiter product, while a value closer to 0 indicates a darker product.

Claims

1. An apparatus for producing 2-phenylimidazoline, characterized by comprising: It includes a reactor (1), a primary heat exchanger (2), a secondary heat exchanger (3), a vacuum pump (14), a first ammonia spray tower (10), a second ammonia spray tower (12), a third ammonia spray tower (16), a heat exchanger for the first ammonia spray tower (4), a heat exchanger for the second ammonia spray tower (5), and a cooling water storage tank (8). The bottom product outlet of the reactor (1) is connected to the inlet of the slicer (9), and the top outlet of the reactor is connected to the material inlet of the primary heat exchanger (2). The material outlet of the primary heat exchanger (2) is connected to the material inlet of the secondary heat exchanger (3). The material outlet of the secondary heat exchanger (3) can be switched between the inlet of the reflux tank (15) and the interior of the reactor. The gas phase opening of the reflux tank (15) is connected to the feed inlet of the first ammonia spray tower (10) via a pipeline through a vacuum pump (14). The gas outlet of the first ammonia spray tower (10) is connected to the feed inlet of the second ammonia spray tower (12). The gas outlet of the second ammonia spray tower (12) is connected to the feed inlet of the third ammonia spray tower (16). The bottom outlet of the third ammonia spray tower (16) is returned to the upper or top of the third ammonia spray tower via a fourth pump (17). The gas outlet of the third ammonia spray tower (16) is the tail gas outlet. The bottom outlet of the first ammonia spray tower (10) is connected to the inlet of the first ammonia spray tower heat exchanger (4) via the second pump (11), and the outlet of the first ammonia spray tower heat exchanger (4) returns to the upper or top part of the first ammonia spray tower (10). The bottom outlet of the second ammonia spray tower (12) is connected to the inlet of the second ammonia spray tower heat exchanger (5) via the third pump (13), and the outlet of the second ammonia spray tower heat exchanger (5) returns to the upper or top part of the second ammonia spray tower (12). The cooling water storage tank (8) is connected to the cooling water jacket inlet of the slicer (9) via a pipeline through the first pump (7). The cooling water jacket outlet is connected to the heat exchange medium inlet of the first ammonia spray tower heat exchanger (4) via a pipeline. The heat exchange medium outlet of the first ammonia spray tower heat exchanger (4) is connected to the heat exchange medium inlet of the second ammonia spray tower heat exchanger (5) via a pipeline. The heat exchange medium outlet of the second ammonia spray tower heat exchanger (5) is connected to the heat exchange medium inlet of the secondary heat exchanger (3) of the reactor via a pipeline. The heat exchange medium outlet of the secondary heat exchanger (3) of the reactor is connected to the heat exchange medium inlet of the primary heat exchanger (2) of the reactor, and the heat exchange medium outlet of the primary heat exchanger (2) of the reactor returns to the cooling water storage tank (8).

2. The 2-phenylimidazoline production device according to claim 1, characterized by The cooling water jacket outlet of the slicer (9) is divided into two paths, which are respectively connected to the heat exchange medium inlet of the first ammonia spray tower heat exchanger (4) and the second ammonia spray tower heat exchanger (5). The heat exchange medium outlets of the first ammonia spray tower heat exchanger (4) and the second ammonia spray tower heat exchanger (5) are both connected to the heat exchange medium inlet of the secondary heat exchanger (3) of the reactor via pipelines.

3. The 2-phenylimidazoline production apparatus according to claim 1, characterized in that, The primary heat exchanger of the reactor is a vertical gas-phase heat exchanger, and the secondary heat exchanger of the reactor is a horizontal gas-phase heat exchanger.

4. The 2-phenylimidazoline production apparatus according to claim 1, characterized by It includes an independent cooling water circulation system, which includes a cooling water storage tank, a cooling water pump, and a heat exchange pipeline network connecting the pump outlet to multiple devices that need to be cooled. The heat exchange pipeline network is designed in series, and the cooling water flow sequence is: cooling water storage tank → cooling water pump → slicer cooling jacket → ammonia spray tower heat exchanger → reactor secondary heat exchanger → reactor primary heat exchanger → return to cooling water storage tank.

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