A high-efficiency regulating device for producing special isocyanate by phosgenation reaction

Abstract

The novel discloses a kind of high-efficiency regulation and control devices for the production of special isocyanate in photo-gasification reaction, belong to organic chemical reaction equipment technical field.The device includes reaction kettle body, inert gas introduction system, phosgene feeding system, stirring system, temperature control unit, mass transfer unit and distributed control module (DCS);Reaction kettle body adopts double-jacket structure and is provided with corrosion-resistant layer, inert gas introduction system realizes accurate flow and temperature control, phosgene feeding system guarantees one-way stable feeding, stirring system adapts to the mass transfer demand of different reaction stages, mass transfer unit realizes the orderly transmission of material and gas through multiple pipelines, and DCS module integrates data acquisition, parameter adjustment, fault early warning, data storage and remote control function.The device can realize efficient, accurate and safe regulation and control of 1,5-pentane diisocyanate photo-gasification reaction, improve reaction rate and product purity, reduce environmental protection and operation risk, and facilitate production quality traceability and process optimization.

Description

Technical Field

[0001] This utility model relates to the field of organic chemical reaction equipment technology, specifically to a high-efficiency control device for the production of special isocyanates by phosgenation reaction. Background Technology

[0002] 1,5-Pentanediisocyanate (PDI) is an important aliphatic isocyanate widely used in polyurethane coatings, adhesives, elastomers, and other fields. The core step in its production process is the phosgenation reaction—the reaction of 1,5-pentanediamine with phosgene under specific conditions to produce PDI. The phosgenation reaction is characterized by its complex reaction mechanism, sensitivity to temperature, pressure, and pH, the high toxicity of phosgene, and the tendency to generate side reactions. Therefore, it places extremely high demands on the precision of reaction equipment control, safety, and mass transfer efficiency. Existing phosgenation reactors generally suffer from the following problems: First, insufficient control precision: key parameters such as temperature, pressure, and phosgene feed rate are mostly adjusted semi-manually, making it difficult to adapt to the dynamic needs of different reaction stages, easily leading to fluctuations in product purity or exacerbation of side reactions. Second, low mass transfer efficiency: the simple structure of the stirring device results in insufficient mixing of the reaction system, restricting the reaction rate. Third, inadequate safety and environmental protection: the monitoring and treatment of unreacted phosgene in the tail gas is lagging, easily causing leakage risks; the equipment's inner wall has weak corrosion resistance, and phosgene and reaction media easily corrode the reactor body, shortening the equipment's lifespan. Fourth, high energy consumption and substandard product quality: the large evaporation of low-boiling-point solvents during production carries away most of the heat, resulting in excessively high energy consumption. Simultaneously, the large-scale evaporation of solvents causes fluctuations in the reaction system concentration, further affecting product quality stability, leading to decreased product yield and increased impurity content, making it difficult to meet the production requirements of high-purity chemicals. Fifth, low automation: the lack of an integrated control and data traceability system results in untimely fault warnings and makes production quality traceability and process optimization difficult. Summary of the Invention

[0003] The purpose of this invention is to overcome the defects of the existing technology and provide a high-efficiency control device for the production of special isocyanates by phosgenation reaction, so as to achieve precise control of reaction parameters, efficient mass transfer of reaction system, safe treatment of tail gas and intelligent monitoring of the whole process, so as to improve PDI production efficiency and product quality, and reduce operational risks and environmental pressure.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a high-efficiency control device for the phosgenation reaction of 1,5-pentanediisocyanate, comprising a reaction vessel, a phosgene storage tank, and a catalyst storage tank, characterized in that the gas inlet at the upper part of the reaction vessel is connected to a nitrogen delivery pipe, and the nitrogen delivery pipe is equipped with a first flow meter, a first electric heater, and a pressure regulating valve; The outlet of the phosgene storage tank is connected to the phosgene delivery pipe via a feed pump. The phosgene delivery pipe is connected to the phosgene inlet at the top of the reactor via a one-way valve. A second flow meter is installed on the phosgene delivery pipe. The upper part of the reactor is connected to a feed pipe, and the feed pipe is equipped with a flow sensor, a second temperature sensor and a second electric heater. The discharge pipe at the bottom of the catalyst storage tank is connected to the bottom of the reactor; the bottom of the reactor is equipped with a discharge pipe; The reactor is equipped with a stirrer inside and a pressure sensor, a liquid level sensor and a pH sensor on the reactor. The distributed control system (DCS) is electrically connected to the pressure regulating valve, the first flow meter, the check valve, the second flow meter, the feed pump, the variable frequency motor driving the agitator, the pressure sensor, the liquid level sensor, the pH sensor, the flow sensor, and the second temperature sensor, respectively, to realize parameter monitoring, interlocking control, and fault early warning; the DCS is connected to a data storage unit.

[0005] The agitator is driven by a variable frequency motor, and the agitator blade is a double-layered oblique blade agitator blade with an included angle of 120° between the upper and lower blades.

[0006] The reactor has a double-jacketed structure, with a heating element and a first temperature sensor inside the jacket. The reactor jacket is also connected to a steam heating heat exchanger. The heating element, the first temperature sensor, and the steam heating heat exchanger are electrically connected to the control module DCS.

[0007] The inner wall of the reactor is provided with an anti-corrosion layer; the anti-corrosion layer of the inner wall is a Hastelloy coating with a coating thickness of 0.2~2 mm.

[0008] Both the nitrogen delivery pipe and the phosgene delivery pipe are equipped with gas distributors at the ends that are inserted into the bottom of the reactor; the feed pipe is equipped with a sprayer at the end that is inserted into the reactor.

[0009] The gas distributor has a porous structure with a pore size of 0.02~2 cm, and the surface of the gas distributor is coated with polytetrafluoroethylene.

[0010] The top of the reactor is connected to an exhaust pipe, which is connected to the tail gas absorption tower. A phosgene concentration sensor is installed on the exhaust pipe, and the phosgene concentration sensor is electrically connected to the control module DCS.

[0011] The discharge pipe is also connected to a return pipe for conveying incompletely reacted materials. The return pipe is connected to the feed pipe via a reflux pump. The return pipe is equipped with a filter, and the reflux pump is electrically connected to the control module DCS.

[0012] The first flow meter is an intelligent electromagnetic flow meter, and the second flow meter is a mass flow meter.

[0013] Compared with the prior art, this utility model has the following advantages: (1) High control precision: Through DCS integrated control, real-time monitoring and automatic adjustment of parameters such as temperature, pressure, pH, feed rate, and stirring speed are realized. The parameter fluctuation range is small (e.g., temperature fluctuation ≤ ±3 ℃), which effectively reduces side reactions and improves the purity and yield of 1,5-pentanediisocyanate. (2) Excellent mass transfer efficiency: The double-layer inclined blade stirring paddle (120° angle), variable frequency stirring motor, porous gas distributor and material reflux system work together to ensure uniform mixing of the reaction system, uniform distribution of inert gas, high raw material utilization, and increase the reaction rate by 15%~20%; (3) Strong safety: Hastelloy anti-corrosion layer resists equipment corrosion, one-way valve prevents material backflow, tail gas concentration sensor is linked with absorption tower (automatic enhanced treatment when phosgene concentration > 500 ppm), fault alarm and early warning system respond in real time, significantly reducing safety risks such as phosgene leakage and equipment corrosion; (4) Reduce product energy consumption and improve product quality: By introducing hot nitrogen and catalyst during the reaction process, the required production temperature is reduced while the pressure inside the reactor is increased, and the reaction time is shortened; and the hot nitrogen carries away the hydrogen chloride gas generated during the production process, thereby reducing the acidity and hydrolyzed chlorine in the product. (5) Good automation and traceability: DCS integrates data storage, remote debugging and access control. Data is stored for more than 6 months and can be exported, which facilitates production quality traceability and process optimization, reduces the intensity of manual operation and reduces human error; (6) Environmental compliance: The tail gas absorption tower uses 19% sodium hydroxide solution to efficiently absorb unreacted phosgene, ensuring that the tail gas emissions meet environmental protection standards and reducing the impact on the environment. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the present invention; In the diagram: 1-Reaction vessel, 2-Agitator, 3-Agitator paddle, 4-Gas distributor, 5-Phosgene storage tank, 6-Feed pump, 7-Catalyst storage tank, 8-First temperature sensor, 9-Pressure sensor, 10-Level sensor, 11-pH sensor, 12-Sprayer, 13-Filter, 14-Reflux pump, 15-Flow sensor, 16-Second temperature sensor, 17-Phosgene concentration sensor; L1-Nitrogen main pipe, L2-Phosgene pipe, L3-Feed pipe, L4-Return pipe, L5-Discharge pipe, L6-Exhaust pipe, B1-First flow meter, B2-Second flow meter, F1-Pressure regulating valve, F2-Check valve, H1-First electric heater, H2-Second electric heater. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the embodiments. The embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] The present utility model patent will be further described in detail below with reference to specific embodiments, but the scope of protection of the present utility model patent is not limited to the following embodiments.

[0018] Example 1 A highly efficient control device for the production of special isocyanates through phosgenation reactions, the specific structural parameters of which are as follows: (1) Reactor 1: Volume 30 m³ 3 The double-layer jacket is 5 cm thick, and the inner wall has a Hastelloy alloy coating thickness of 2 mm; the jacket is heated by 0.6 MPa medium-pressure steam. (2) Inert gas introduction system: The nitrogen introduction system has an input pressure of 0.6 MPa and an output nitrogen purity of 99.99%; the first flow meter B1 is an intelligent electromagnetic flow meter with a measurement range of 0~500 L / min and a data transmission rate of 1 s / time; the first electric heater H1 has a power of 22 kW and a heating temperature of 160 ℃; the gas distributor 4 has a diameter of 40 cm, a porous pore size of 2 cm, and a polytetrafluoroethylene coating thickness of 2 mm; (3) Phosgene feeding system: The volume of phosgene storage tank 5 is 10 m³. 3 The feed flow rate ranges from 0.4 m³ / s. 3 / h; The second flow meter B2 is a mass flow meter with an accuracy of ±0.1%; (4) Stirring system: The variable frequency drive motor model is YBP 30kW-4P, with a power of 30 kW and a speed range of 0~200 r / min; the diameter of the double-layer inclined blade stirring paddle 3 is 90 cm, the blade thickness is 5 mm, and the included angle is 120°. (5) Temperature control unit: Steam heating main pipe pressure 1.3 MPa; First temperature sensor 8 and DCS closed-loop response time ≤2s, steam input regulation accuracy ±5%; (6) Mass transfer unit: The material of each pipeline is 316L stainless steel. The diameter of the phosgene pipe L2 is 25 mm, the diameter of the nitrogen main pipe L1 is 40 mm, and the diameters of the feed pipe L3, return pipe L4 and discharge pipe L5 are 50 mm. (7) DCS module: Data storage unit capacity 2TB, which can store 12 months of reaction data; Sound and light alarm device model BBJ-2, ​​alarm volume ≥85dB; (8) Tail gas absorption tower: volume 25 m³ 3 The sodium hydroxide solution has a mass concentration of 19%, and the spray pump flow rate ranges from 0 to 10 m³ / s. 3 / h; (9) Catalyst system: Catalyst storage tank 7 with a volume of 100 L, filter 13 with a precision of 10 μm; (10) Material return system: Return pump 14 with a flow rate range of 0~2 m³ / h 3 / h; Second temperature sensor 16 accuracy ±0.2℃.

[0019] Work procedures: (i) The nitrogen gas (purity ≥99.9%) output from the nitrogen main pipe L1 is stabilized by the pressure regulating valve F1, metered by the first flow meter B1 (0~500 L / min, data remote transmission), and preheated by the first electric heater H1 (heated to 40~160 ℃), and then enters the reactor 1 through the gas inlet at the top. (ii) Phosgene in phosgene storage tank 5 is transported by feed pump 6 and accurately measured by second flow meter B2. It is then connected to the phosgene feed port at the top of reactor 1 through one-way valve F2 (which only allows phosgene to enter the reactor from the feed port to prevent material backflow). The second flow meter B2 is linked with DCS to realize real-time control of phosgene feed rate and avoid excessive feed leading to side reactions or safety risks.

[0020] (iii) The first temperature sensor 8 collects the temperature inside the reactor 1 in real time and transmits it to the DCS. The DCS adjusts the steam input of the steam heating heat exchanger connected to the jacket according to the temperature signal to achieve a switching of 50% to 80% of the rated power, ensuring that the temperature inside the reactor is stable within the process requirements range (avoiding temperature fluctuations of more than ±3 ℃).

[0021] (iv) The catalyst is released into the reactor 1 through the discharge valve at the bottom of the catalyst storage tank 7. The discharge valve is linked to the DCS control point.

[0022] (v) Unreacted material enters filter 13 through return pipe L4 and is then transported to reactor 1 by reflux pump 14. The second temperature sensor 16 monitors the temperature of the reflux material in real time and transmits it to DCS to ensure that the temperature of the reflux material meets the reaction requirements and improves the utilization rate of raw materials. (vi) The tail gas outlet on reactor 1 is connected to exhaust pipe L6, and exhaust pipe L6 is connected to tail gas absorption tower to transmit tail gas to be treated. Distributed Control System (DCS): This is the core control unit of the device, connecting all sensors (temperature, pH, pressure, concentration, flow rate) and actuators (feed pump, stirring motor, regulating valve, reflux pump) via wiring to achieve the following: Data acquisition: Real-time acquisition of parameters such as temperature, pressure, pH, flow rate, and concentration during the reaction process; Parameter adjustment: Automatically adjusts stirring speed, phosgene feed rate, inert gas flow rate, steam input rate, etc. according to process settings; Fault warning and alarm: Integrated fault diagnosis function, real-time monitoring of actuator status; when the temperature exceeds ±3 ℃ for 10 min or the pressure drops suddenly by ≥0.05 MPa, an audible and visual alarm is triggered, and the fault type, time and process parameters at that time are recorded, and an early warning signal is output to the central control room. Data storage: Connects to a data storage unit with a storage capacity of ≥2 TB, stores at least 12 months of reaction data, supports export via USB flash drive or network, and facilitates production quality traceability and process optimization; Remote and access control: Supports remote debugging and allows setting multiple levels of operation permissions (such as operator, technician, administrator) to ensure operational security and data integrity.

[0023] Specific work process: Preparation stage: Open the valve on the feed pipe L3 and adjust the feed rate to raise the liquid level in the reactor 1 to 60%; check the internal status of the reactor 1 through the DCS system, including pressure, liquid level and bottom outlet valve status, to prevent accidental feeding of materials into the reactor that is reacting; confirm that the pressure regulating valve FI is closed; then, set the gas outlet pressure to 0.12 MPa through the DCS system and activate the automatic control mode; During the reaction heating stage: The stirrer is started and the stirring frequency is set to 40 Hz; the temperature (collected by the first temperature sensor 8), pressure (collected by the pressure sensor 9), liquid level (collected by the liquid level sensor 10), and pH value (collected by the pH sensor 11) inside the reactor 1 are monitored in real time by the DCS system; after the stirring frequency stabilizes at 40 Hz, the steam heating system of the reactor is automatically adjusted by the DCS system to raise the temperature inside the reactor to 70 ℃ at a heating rate of 10 ℃ / h; at the same time, the catalyst feeding system is started, and the catalyst enters the reactor 1 through the valve on the discharge pipe of the catalyst storage tank 7 (DCS controls the opening degree to 5%); when the temperature inside the reactor reaches 70 ℃, the pressure regulating valve F1 is interlocked and opened, and the first electric heater H1 heats the nitrogen to 160 ℃; when the pressure inside the reactor rises to 0.19 MPa, the pressure regulating valve F1 is interlocked and closed; through the synergistic effect of hot nitrogen heat transfer and steam heating, the temperature inside the reactor continues to rise to 130 ℃; (3) Reaction stage: The phosgene concentration in the reactor is analyzed by the phosgene concentration sensor 17. If the phosgene concentration at the gas phase outlet is <200 ppm, the phosgene feeding system is turned on, and the phosgene is fed by the feed pump 6 (flow rate 0.4 m). 3 After being metered by the second flow meter B2, the gas enters the reactor 1 through the one-way valve F2. When the phosgene concentration sensor 17 detects a phosgene concentration > 500 ppm or the pH sensor 11 transmits a pH < 6 for the material in the reactor, the one-way valve F2 is automatically closed. If the temperature rises to 133 ℃ (exceeding the set value + 3 ℃), the DCS reduces the steam input (the steam valve opening is reduced from 65% to 5%), and the temperature is reduced to 130 ℃ within 30 minutes. The tail gas is discharged through the exhaust pipe L6, and the tail gas absorption tower is filled with a sodium hydroxide solution with a mass concentration of 10%~30%. The phosgene concentration sensor 17 detects the phosgene concentration in real time. If the phosgene concentration > 500 ppm, the DCS increases the spray rate of the tail gas absorption tower. (4) Product processing stage: After the reaction is completed, the product is discharged through the discharge pipe L5. The unreacted material is returned to the reactor 1 through the material return pump 14 and the return pipeline L4 for further reaction. The reaction data is stored in real time to the data storage unit and can be exported via USB flash drive for process analysis.

[0024] In this embodiment, the yield of 1,5-pentanediisocyanate reached 95%, the purity was >99%, the phosgene concentration in the exhaust gas was <100ppm, and the equipment showed no significant corrosion after 12 months of continuous operation, meeting the requirements of industrial production.

[0025] During the reaction process, all data collected by sensors is uploaded to the data storage unit, supporting long-term recording, historical traceability, and trend analysis, facilitating subsequent process optimization and compliance review. When the system detects abnormal operating conditions (such as over-temperature, over-pressure, or leakage), the audible and visual alarm device automatically activates, reminding operators to take timely action and improving intrinsic safety. The entire system's operating logic is uniformly coordinated by the DCS module, achieving fully automated control and significantly reducing human error.

[0026] It should be noted that the attached drawings are schematic diagrams of the device of this utility model, intended to illustrate the connection relationships and functional layout between the components. In practical applications, the size, model, and arrangement of each component can be flexibly adjusted according to the specific production scale, reaction type, and process requirements, such as increasing the volume of the reaction vessel, replacing different types of stirring paddles, or adding redundant sensing units. Therefore, the attached drawings and their markings are for illustrative purposes only and do not constitute a limitation on the scope of protection of this utility model patent.

Claims

1. A high-efficiency control device for the production of special isocyanates by phosgenation reaction, comprising a reaction vessel (1), a phosgene storage tank (5), and a catalyst storage tank (7), characterized in that, The gas inlet at the top of the reactor (1) is connected to a nitrogen delivery pipe (L1), and the nitrogen delivery pipe (L1) is equipped with a first flow meter (B1), a first electric heater (H1) and a pressure regulating valve (F1). The outlet of the phosgene storage tank (5) is connected to the phosgene delivery pipe (L2) via the feed pump (6). The phosgene delivery pipe (L2) is connected to the phosgene inlet at the top of the reactor (1) via the check valve (F2). A second flow meter (B2) is provided on the phosgene delivery pipe (L2). The upper part of the reactor (1) is connected to the feed pipe (L3), and the feed pipe (L3) is equipped with a flow sensor (15), a second temperature sensor (16), and a second electric heater (H2). The discharge pipe at the bottom of the catalyst storage tank (7) is connected to the bottom of the reactor (1); the bottom of the reactor (1) is equipped with a discharge pipe (L5); The reactor (1) is equipped with a stirrer (2) inside and a pressure sensor (9), a liquid level sensor (10) and a pH sensor (11) on the reactor (1). The distributed control module (DCS) is electrically connected to the pressure regulating valve (F1), the first flow meter (B1), the check valve (F2), the second flow meter (B2), the feed pump (6), the variable frequency motor driving the agitator (2), the pressure sensor (9), the liquid level sensor (10), the pH sensor (11), the flow sensor (15), and the second temperature sensor (16) to realize parameter monitoring, interlock control, and fault early warning; the control module (DCS) is connected to a data storage unit.

2. The high-efficiency control device for the production of special isocyanates by phosgenation reaction as described in claim 1, characterized in that, The stirrer (2) is driven by a variable frequency motor. The stirring blade (3) of the stirrer (2) is a double-layered oblique blade stirring blade with an angle of 120° between the upper and lower blades.

3. The high-efficiency control device for the production of special isocyanates by phosgenation reaction as described in claim 1, characterized in that, The reactor (1) has a double-layer jacket structure. The jacket is equipped with a heating element and a first temperature sensor (8). The jacket of the reactor (1) is also connected to a steam heating heat exchanger. The heating element, the first temperature sensor (8) and the steam heating heat exchanger are electrically connected to the control module DCS.

4. The high-efficiency control device for the production of special isocyanates by phosgenation reaction as described in claim 1, characterized in that, The inner wall of the reactor (1) is provided with an anti-corrosion layer; the anti-corrosion layer of the inner wall is a Hastelloy coating with a coating thickness of 0.2~2 mm.

5. The high-efficiency control device for the production of special isocyanates by phosgenation reaction as described in claim 1, characterized in that, The ends of the nitrogen delivery pipe (L1) and phosgene delivery pipe (L2) inserted into the bottom of the reactor (1) are equipped with gas distributors (4); the end of the feed pipe (L3) inserted into the reactor (1) is equipped with a sprayer (12).

6. The high-efficiency control device for the production of special isocyanates by phosgenation reaction as described in claim 5, characterized in that, The gas distributor (4) has a porous structure with a pore size of 0.02~2 cm and the surface of the gas distributor (4) is coated with polytetrafluoroethylene.

7. The high-efficiency control device for the production of special isocyanates by phosgenation reaction as described in claim 1, characterized in that, The top of the reactor (1) is connected to an exhaust pipe (L6), which is connected to the tail gas absorption tower. A phosgene concentration sensor (17) is installed on the exhaust pipe (L6), and the phosgene concentration sensor (17) is electrically connected to the control module DCS.

8. A high-efficiency control device for the production of special isocyanates by phosgenation reaction as described in any one of claims 1-7, characterized in that, The discharge pipe (L5) is also connected to a return pipe (L4) for conveying unreacted materials. The return pipe (L4) is connected to the feed pipe (L3) via a return pump (14). The return pipe (L4) is equipped with a filter (13), and the return pump (14) is electrically connected to the control module DCS.

9. The high-efficiency control device for the production of special isocyanates by phosgenation reaction as described in claim 1, characterized in that, The first flow meter (B1) is an intelligent electromagnetic flow meter, and the second flow meter (B2) is a mass flow meter.

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