Control system for preparing dimethyl phosphite

Abstract

The utility model discloses a control system for preparing dimethyl phosphite. The control system comprises a DCS (Distributed Control System) controller, a phosphorus trichloride flowmeter and a phosphorus trichloride regulating valve which are arranged on a phosphorus trichloride inlet pipe, a water flowmeter and a water regulating valve which are arranged on a water inlet pipe, a methanol flowmeter and a methanol regulating valve which are arranged on a methanol inlet pipe, and a liquid level meter and a pressure transmitter which are arranged on a gas-liquid separator; the pressure regulating valve is arranged on the gas phase outlet pipe, the lower liquid regulating valve is arranged on the lower liquid pipe I, the motor is connected with the distributor, and the temperature sensor II is arranged on the jacket; the phosphorus trichloride flow meter, the phosphorus trichloride adjusting valve, the water flow meter, the water adjusting valve, the methanol flow meter, the methanol adjusting valve, the liquid level meter, the liquid discharging adjusting valve, the pressure transmitter, the pressure adjusting valve, the motor and the temperature sensor II are all connected with the DCS controller. The automation of the dimethyl phosphite preparation process is realized, and the stability, controllability and traceability of the dimethyl phosphite preparation process are ensured.

Description

Technical Field

[0001] The utility model relates to a control system for preparing dimethyl phosphite, belonging to the technical field of dimethyl phosphite synthesis. Background Art

[0002] The primary use of dimethyl phosphite is in the synthesis of glyphosate. Currently, the industrial synthesis method for dimethyl phosphite involves the continuous quantitative addition of phosphorus trichloride and methanol as raw materials, followed by reaction under negative pressure while simultaneously removing the generated hydrogen chloride. Finally, dimethyl phosphite undergoes deep deacidification and distillation. The reaction mechanism involves the reaction of methanol with phosphorus trichloride to form trimethyl phosphite and hydrogen chloride; trimethyl phosphite then rapidly reacts with one molecule of hydrogen chloride to form dimethyl phosphite and one molecule of methyl chloride. The overall reaction equation is as follows:

[0003] PCl3+3CH3OH =H(O)P(OCH3)2+2 HCl↑+CH3Cl↑

[0004] The reaction mechanism includes:

[0005] PCl3+3CH3OH=P(OCH3)3+3HCl

[0006] P(OCH3)3+HCl=H(O)P(OCH3)2+CH3Cl

[0007] One molecule of phosphorus trichloride consumes three molecules of methanol to produce one molecule of dimethyl phosphite, two molecules of hydrogen chloride, and one molecule of methyl chloride. The hydrogen chloride is absorbed with water to form hydrochloric acid, which can be used in the subsequent hydrolysis step of glyphosate synthesis. The methyl chloride, on the other hand, requires purification and disposal before being sold as a byproduct. Furthermore, the product dimethyl phosphite contains only two methoxy groups. For every three molecules of methanol consumed, one molecule of methanol is ultimately converted into methyl chloride, resulting in low methanol molecule utilization. Furthermore, the byproduct of methyl chloride requires additional purification and storage, which in turn increases risks and environmental pressures.

[0008] Although the prior art discloses “a novel method for synthesizing dimethyl phosphite” in CN107488193A, “a method for producing dimethyl phosphite” in CN101870712A, “a process for efficiently synthesizing dimethyl phosphite” in CN114605469A, “a method for continuously preparing dimethyl phosphite and its application” in CN114920772A, and “a method for continuously synthesizing dialkyl phosphite in a continuous flow reactor” in CN108840884A, the following problems still exist: there is still a lack of corresponding automation control technology. Summary of the Invention

[0009] To address the low atomic utilization rate of existing raw material methanol, high byproduct production of methyl chloride, and the near-absence of automated control in the production system, this utility model proposes a control system for the production of dimethyl phosphite. This technical solution not only automates the dimethyl phosphite production process, effectively reducing labor intensity while ensuring the stability, controllability, and traceability of the dimethyl phosphite production process, but also enables systematic control and management to complement the dimethyl phosphite production process.

[0010] In order to achieve the above technical objectives, the following technical solutions are proposed:

[0011] A control system for preparing dimethyl phosphite is provided in a dimethyl phosphite preparation system, wherein the dimethyl phosphite preparation system comprises a continuous flow reactor I, a continuous flow reactor II, a gas-liquid separator, a deacidification kettle, a packed tower and a tail gas treatment system, wherein the tail gas treatment system comprises a normal pressure tail gas treatment system and a vacuum tail gas treatment system; the continuous flow reactor I is connected to a phosphorus trichloride storage tank via a phosphorus trichloride inlet pipe, the continuous flow reactor I is connected to a water storage tank via a water inlet pipe, the continuous flow reactor I is connected to the continuous flow reactor II; the continuous flow reactor II is connected to a continuous flow reactor II via a methanol inlet pipe The methanol storage tank and the continuous flow reactor II are connected to the gas-liquid separator; the liquid outlet of the gas-liquid separator is connected to the deacidification kettle through a downpipe I, the outside of the deacidification kettle is provided with a jacket, a distributor is provided in the deacidification kettle, the distributor is connected to the downpipe I, the gas outlet of the deacidification kettle is connected to the packing tower through a gas phase outlet pipe, and the packing tower is connected to the vacuum tail gas treatment system; the gas outlet of the gas-liquid separator is connected to the heat exchanger I through a gas phase outlet pipe, and a pressure regulating valve is provided on the gas phase outlet pipe. The condensate outlet of the heat exchanger I is connected to the gas-liquid separator through a condensate pipeline, and the gas outlet of the heat exchanger I is connected to the atmospheric pressure tail gas treatment system;

[0012] The control system includes a DCS controller, a phosphorus trichloride flowmeter and a phosphorus trichloride regulating valve provided on the phosphorus trichloride inlet pipe, a water flowmeter and a water regulating valve provided on the water inlet pipe, a methanol flowmeter and a methanol regulating valve provided on the methanol inlet pipe, a liquid level gauge and a pressure transmitter provided on the gas-liquid separator, a pressure regulating valve provided on the gas phase outlet pipe, a lower liquid regulating valve provided on the lower liquid pipe I, a motor connected to the distributor, and a temperature sensor II provided on the jacket;

[0013] The phosphorus trichloride flowmeter, phosphorus trichloride regulating valve, water flowmeter, water regulating valve, methanol flowmeter, methanol regulating valve, liquid level gauge, lower liquid regulating valve, pressure transmitter, pressure regulating valve, motor and temperature sensor II are all connected to the DCS controller;

[0014] Among them, a control loop is formed between the phosphorus trichloride flowmeter, DCS controller and phosphorus trichloride regulating valve through electrical signals;

[0015] A control loop is formed between the water flow meter, DCS controller and water regulating valve through electrical signals;

[0016] A control loop is formed between the methanol flow meter, DCS controller and methanol regulating valve through electrical signals;

[0017] A control loop is formed between the liquid level meter, DCS controller and lower liquid regulating valve through electrical signals;

[0018] A control loop is formed between the pressure transmitter, DCS controller and the pressure regulating valve through electrical signals;

[0019] A control loop is formed among the phosphorus trichloride flowmeter, the water flowmeter, the methanol flowmeter, the DCS controller and the phosphorus trichloride regulating valve through electrical signals.

[0020] Furthermore, the phosphorus trichloride inlet pipe, the water inlet pipe and the methanol inlet pipe are all provided with a pressure sensor and a temperature sensor I, and the pressure sensor and the temperature sensor I are both connected to the DCS controller.

[0021] Furthermore, a phosphorus trichloride delivery pump is provided on the phosphorus trichloride inlet pipe, and the phosphorus trichloride delivery pump is connected to a DCS controller.

[0022] Furthermore, a water delivery pump is provided on the water inlet pipe, and the water delivery pump is connected to the DCS controller.

[0023] Furthermore, a methanol delivery pump is provided on the methanol inlet pipe, and the methanol delivery pump is connected to a DCS controller.

[0024] The positional relationships involved in this technical solution, such as "middle", "between", "above", "inside", and "outside", are defined according to the actual usage conditions. They are conventional terms in this technical field and are also conventional terms used by technical personnel in this field in actual use.

[0025] In the description of this technical solution, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0026] The beneficial technical effects brought about by adopting this technical solution are:

[0027] The utility model is provided in a dimethyl phosphite preparation system, and can better cooperate with the dimethyl phosphite preparation process (the reaction of phosphorus trichloride with water and methanol is an exothermic reaction, and the reaction is violent. If it is not accurately controlled, side reactions are very likely to occur). It ensures a high degree of automation control on the dimethyl phosphite preparation production line, low labor intensity, and can effectively control manpower and other costs. At the same time, it ensures the stability, controllability and traceability of the dimethyl phosphite preparation process.

[0028] In addition, the utility model can better realize systematic control and management to fill the gap in the automation control technology in the dimethyl phosphite preparation process and meet the requirements of industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the control principle diagram involved in the utility model;

[0030] Figure 2 This is a diagram of the equipment connections in the preparation system involved in the present utility model;

[0031] Figure 3 This is a process flow chart of the preparation process involved in this utility model;

[0032] Among them, in the figure: 1, continuous flow reactor I, 2, continuous flow reactor II, 3, gas-liquid separator, 4, deacidification kettle, 5, packed tower, 6, atmospheric tail gas treatment system, 7, phosphorus trichloride inlet pipe, 8, phosphorus trichloride storage tank, 9, phosphorus trichloride delivery pump, 10, phosphorus trichloride flow meter, 11, phosphorus trichloride regulating valve, 12, water inlet pipe, 13, water storage tank, 14, water delivery pump, 15, water flow meter, 16, water regulating valve, 17, methanol inlet pipe, 18, methanol storage tank, 19, methanol delivery pump, 20, methanol flow meter, 21, methanol regulating Valve, 22. Liquid level gauge, 23. Pressure transmitter, 24. Downpipe I, 25. Downpipe regulating valve, 26. Gas phase outlet pipe, 27. Heat exchanger I, 28. Pressure regulating valve, 29. Condensate pipeline, 31. Distributor, 32. Exhaust pipe, 33. Reflux pipe, 34. Heat exchanger II, 35. Receiving tank, 36. Vacuum unit, 37. Dimethyl phosphite crude product temporary storage tank, 38. Downpipe II, 39. Pressure sensor, 40. Temperature sensor I, 42. Temperature sensor II, 43. Motor, 44. Jacket, 45. Vacuum tail gas treatment system. DETAILED DESCRIPTION

[0033] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. It is obvious that the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Example 1

[0035] This embodiment provides: a control system for preparing dimethyl phosphite, such as Figure 1-2 As shown, it is set in a dimethyl phosphite preparation system, which includes a continuous flow reactor I1, a continuous flow reactor II2 and a gas-liquid separator 3. The continuous flow reactor I1 is connected to a phosphorus trichloride storage tank 8 through a phosphorus trichloride inlet pipe 7, and the continuous flow reactor I1 is connected to a water storage tank 13 through a water inlet pipe 12. The continuous flow reactor I1 is connected to the continuous flow reactor II2; the continuous flow reactor II2 is connected to a methanol storage tank 18 through a methanol inlet pipe 17, and the continuous flow reactor II2 is connected to the gas-liquid separator 3; the liquid outlet of the gas-liquid separator 3 is connected to a dimethyl phosphite crude product temporary storage tank 37 through a lower liquid pipe I 24, and the gas outlet of the gas-liquid separator 3 is connected to a normal pressure tail gas treatment system 6 through a gas phase outlet pipe 26;

[0036] The control system includes a DCS controller, a phosphorus trichloride flowmeter 10 and a phosphorus trichloride regulating valve 11 provided on the phosphorus trichloride inlet pipe 7, a water flowmeter 15 and a water regulating valve 16 provided on the water inlet pipe 12, a methanol flowmeter 20 and a methanol regulating valve 21 provided on the methanol inlet pipe 17, a liquid level gauge 22 and a pressure transmitter 23 provided on the gas-liquid separator 3, a lower liquid regulating valve 25 provided on the lower liquid pipe I 24, and a pressure regulating valve 28 provided on the gas phase outlet pipe 26;

[0037] The phosphorus trichloride flowmeter 10, the phosphorus trichloride regulating valve 11, the water flowmeter 15, the water regulating valve 16, the methanol flowmeter 20, the methanol regulating valve 21, the liquid level gauge 22, the pressure transmitter 23, the lower liquid regulating valve 25 and the pressure regulating valve 28 are all connected to the DCS controller;

[0038] Among them, a control loop is formed between the phosphorus trichloride flowmeter 10, the DCS controller and the phosphorus trichloride regulating valve 11 through electrical signals;

[0039] A control loop is formed between the water flow meter 15, the DCS controller and the water regulating valve 16 through electrical signals;

[0040] A control loop is formed between the methanol flow meter 20, the DCS controller and the methanol regulating valve 21 through electrical signals;

[0041] A control loop is formed between the liquid level meter 22, the DCS controller and the lower liquid regulating valve 25 through electrical signals;

[0042] A control loop is formed between the pressure transmitter 23, the DCS controller and the pressure regulating valve 28 through electrical signals;

[0043] A control loop is formed by electrical signals between the phosphorus trichloride flowmeter 10, the water flowmeter 15, the methanol flowmeter 20, the DCS controller, and the phosphorus trichloride regulating valve 11. The control loop regulates and ensures that the molar flow rate of phosphorus trichloride is less than 1 / 3 of the total molar flow rate of methanol and water. At the same time, the control loop regulates and ensures that the molar flow rate of phosphorus trichloride is not less than the molar flow rate of water.

[0044] Example 2

[0045] On the basis of Example 1, in order to better feed and ensure further accurate control of the reaction process after the raw materials are put in, this example defines:

[0046] The phosphorus trichloride inlet pipe 7, the water inlet pipe 12 and the methanol inlet pipe 17 are all provided with a pressure sensor 39 and a temperature sensor I 40, and the pressure sensor 39 and the temperature sensor I 40 are both connected to the DCS controller.

[0047] Wherein, a phosphorus trichloride delivery pump 9 is provided on the phosphorus trichloride inlet pipe 7, and the phosphorus trichloride delivery pump 9 is connected to the DCS controller.

[0048] A water delivery pump 14 is provided on the water inlet pipe 12 and is connected to the DCS controller.

[0049] A methanol delivery pump 19 is provided on the methanol inlet pipe 17 and is connected to the DCS controller.

[0050] Example 3

[0051] On the basis of Examples 1-2, this example further defines the following in order to increase the yield of the target product dimethyl phosphite, recover the unreacted raw materials, collect the by-product chloromethane, and ensure environmentally friendly production:

[0052] A deacidification kettle 4 is provided between the upper liquid outlet of the gas-liquid separator 3 and the temporary storage tank 37 for crude dimethyl phosphite. A jacket 44 is provided on the outer side of the deacidification kettle 4, and a temperature sensor II 42 is provided on the jacket 44. A distributor 31 is provided in the deacidification kettle 4, and the distributor 31 is connected to the downpipe I 24, and the distributor 31 is connected to a motor 43. The upper gas outlet of the deacidification kettle 4 is connected to a packing tower 5 through an exhaust pipe 32, and the packing tower 5 is connected to a vacuum tail gas treatment system 45. The motor 43 and the temperature sensor II 42 are both connected to a DCS controller.

[0053] A heat exchanger I 27 is provided between the gas outlet of the gas-liquid separator 3 and the atmospheric tail gas treatment system 6 . The condensate outlet of the heat exchanger I 27 is connected to the gas-liquid separator 3 through a condensate pipeline 29 , and the gas outlet of the heat exchanger I 27 is connected to the atmospheric tail gas treatment system 6 .

[0054] Example 4

[0055] Based on Examples 1-3, this embodiment provides: a system for efficiently preparing dimethyl phosphite, comprising a continuous flow reactor I 1, a continuous flow reactor II 2, a gas-liquid separator 3, a deacidification kettle 4, a packed tower 5, and an exhaust gas treatment system (including an atmospheric exhaust gas treatment system 6 and a vacuum exhaust gas treatment system 45);

[0056] Continuous flow reactor I1: connected to a phosphorus trichloride storage tank 8 via a phosphorus trichloride inlet pipe 7, on which a phosphorus trichloride delivery pump 9, a phosphorus trichloride flowmeter 10, and a phosphorus trichloride regulating valve 11 are provided. The upper discharge port of the continuous flow reactor I1 is connected to the continuous flow reactor II2; the continuous flow reactor I1 is also connected to a water storage tank 13 via a water inlet pipe 12, on which a water delivery pump 14, a water flowmeter 15, and a water regulating valve 16 are provided.

[0057] Continuous flow reactor II 2: Located at the rear of the station of continuous flow reactor I 1, continuous flow reactor II 2 is connected to a methanol storage tank 18 via a methanol inlet pipe 17. The methanol inlet pipe 17 is provided with a methanol delivery pump 19, a methanol flow meter 20, and a methanol regulating valve 21. The upper discharge port of continuous flow reactor II 2 is connected to a gas-liquid separator 3;

[0058] Gas-liquid separator 3: located at the rear side of the continuous flow reactor II 2. A liquid level gauge 22 and a pressure transmitter 23 are provided on the gas-liquid separator 3. The liquid outlet of the gas-liquid separator 3 is connected to the deacidification kettle 4 via a liquid downpipe I 24. A liquid downpipe I 24 is provided with a liquid downpipe regulating valve 25.

[0059] In addition, the gas outlet of the gas-liquid separator 3 is connected to the heat exchanger I 27 via a gas phase outlet pipe 26. The gas phase outlet pipe 26 is provided with a pressure regulating valve 28. The condensate outlet of the heat exchanger I 27 is connected to the gas-liquid separator 3 via a condensate pipeline 29. The heat exchanger I 27 is disposed at a higher position relative to the gas-liquid separator 3. The gas outlet of the heat exchanger is connected to the atmospheric pressure tail gas treatment system 6, which includes a scrubber. A continuous passage for condensation and reflux of methanol and dimethyl phosphite in the gas I is formed between the gas outlet of the gas-liquid separator 3, the gas phase outlet pipe 26, the heat exchanger I 27, the condensate outlet of the heat exchanger I 27, and the condensate pipeline 29.

[0060] Deacidification kettle 4: It is located at the rear side of the station of gas-liquid separator 3. A distributor 31 is provided in the deacidification kettle 4, which is connected to the downpipe I 24. The upper gas outlet of the deacidification kettle 4 is connected to the middle or lower part of the packing tower 5 through the exhaust pipe 32. The bottom of the packing tower 5 is connected to the deacidification kettle 4 through the reflux pipe 33. A continuous passage for condensation and reflux of the heavy components in the gas II is formed between the upper gas outlet of the deacidification kettle 4, the exhaust pipe 32, the packing tower 5 and the reflux pipe 33. The upper part of the packing tower 5 is connected to the heat exchanger II 34, and the heat exchanger II 34 is connected to the receiving tank 35. The gas outlet on the receiving tank 35 is connected to the vacuum tail gas treatment system 45; the vacuum tail gas treatment system 45 is connected to the vacuum unit 36 ​​to ensure that the gas-liquid separator 3 and the deacidification kettle 4 operate under negative pressure conditions; the liquid outlet on the receiving tank 35 is connected to the packing tower 5, and the liquid outlet on the receiving tank 35 is connected to the methanol storage tank 18; a dimethyl phosphite crude product temporary storage tank 37 is provided at the rear side of the station of the deacidification kettle 4, and the lower liquid pipe II 38 of the deacidification kettle 4 extends to the middle or bottom of the dimethyl phosphite crude product temporary storage tank 37 to ensure the formation of a liquid seal. Preferably, the height difference between the bottom end of the deacidification kettle 4 and the bottom of the dimethyl phosphite crude product temporary storage tank 37 is controlled to be 10 to 15 meters to ensure that the deacidification kettle 4 can operate continuously under negative pressure, thereby realizing continuous operation of the entire system.

[0061] In addition, the phosphorus trichloride inlet pipe 7, the water inlet pipe 12 and the methanol inlet pipe 17 are all provided with a pressure sensor 39 and a temperature sensor I 40.

[0062] Among them, the distributor 31 includes a cylindrical distribution trough, and the distributor 31 is connected to the motor 43 through a rotating shaft, that is, the motor 43 drives the distribution trough to perform centrifugal motion; the lower liquid pipe Ⅰ24 extends into the deacidification kettle 4 to the top of the distribution trough, and passes the separation liquid into the distribution trough. Under the action of centrifugal force, the separation liquid moves outward along the surface of the distribution trough, and then flies out of the distribution trough, evenly adheres to the inner wall of the deacidification kettle 4, and flows downward. It is heated during the flow process, and the low-boiling substances are vaporized, and finally the material separation is completed efficiently and with high quality.

[0063] Example 5

[0064] Based on Examples 1-4, this embodiment provides: a process for efficiently preparing dimethyl phosphite, such as Figure 3 As shown, the specific steps include:

[0065] 1) First reaction: Phosphorus trichloride and water are introduced into a continuous flow reactor I at a molar ratio of phosphorus trichloride to water of 1:0-1, and the temperature and pressure in the continuous flow reactor I are controlled at 30-80°C and -0.1-0.1 MPa to obtain an intermediate product;

[0066] 2) Second Reaction: With a molar ratio of phosphorus trichloride to methanol of 1:2-4, methanol and the intermediate product obtained in step S1 are introduced into a continuous flow reactor II, and the temperature and pressure in the continuous flow reactor II are controlled to be 20-70° C. and -0.1-0.1 MPa, to obtain a reaction solution;

[0067] During the entire reaction process of step 1) and step 2), the molar ratio of the total amount of water and methanol introduced to the amount of phosphorus trichloride introduced is controlled to be 3.1 to 4:1; the raw material - water can specifically be "deionized water";

[0068] 3) Gas-liquid separation: The reaction liquid obtained in step 2) is passed into a gas-liquid separator, and the temperature and pressure in the gas-liquid separator are controlled at 20-70° C. and -0.1-0.1 MPa to perform gas-liquid separation, thereby obtaining gas I (a large amount of gas, which is hydrogen chloride gas containing a small amount of methyl chloride, methanol, and vaporized dimethyl phosphite) and a separated liquid;

[0069] After condensation, Gas I is passed into the atmospheric tail gas treatment system for water washing, producing a large amount of by-product hydrochloric acid and a small amount of water-unabsorbed gas (primarily methyl chloride). This small amount of water-unabsorbed gas is discharged into the methyl chloride recovery system. Gas I is first condensed to reduce the amount of phosphorus-containing substances entering the atmospheric tail gas treatment system, effectively reducing the phosphorus content of the by-product hydrochloric acid and improving the quality of the hydrochloric acid.

[0070] 4) Deacidification and separation: The separated liquid obtained in step 3) is passed into a deacidification kettle, and the distributor speed in the deacidification kettle is controlled to be 30-120 r / min, the temperature to be 30-80° C., and the pressure to be -0.1-0.5 MPa to perform separation to obtain Gas II (a small amount of gas, mainly including vaporized dimethyl phosphite, methanol, hydrogen chloride gas, and a very small amount of chloromethane) and crude dimethyl phosphite;

[0071] Gas II is passed through a packed tower, where it is separated to obtain heavy components (mainly dimethyl phosphite) and light components (methanol containing a small amount of hydrogen chloride). The heavy components are refluxed into the deacidification kettle; the light components are recovered (condensed) and then used in the synthesis of dimethyl phosphite; the small amount of non-condensable gas (mainly hydrogen chloride and chloromethane) formed is passed through a vacuum tail gas treatment system for water washing to obtain a small amount of by-product hydrochloric acid and a very small amount of water-unabsorbed gas (mainly chloromethane), which is discharged into a chloromethane recovery system. Gas II is passed through a packed tower, and a condensation reflux system is set up at the top of the packed tower to avoid the entrainment of heavy components in the gas phase, effectively reducing the phosphorus content of the by-product hydrochloric acid in the subsequent vacuum tail gas treatment system and improving the quality of the hydrochloric acid. At the same time, a high content of anhydrous methanol can be obtained after recovery and directly reused in the synthesis process of dimethyl phosphite, thereby achieving the purpose of reducing methanol consumption. In other words, without increasing energy consumption, methanol consumption is reduced and the quality of by-product hydrochloric acid is improved.

[0072] 5) Post-treatment: The crude dimethyl phosphite obtained in step 4) is post-treated to obtain dimethyl phosphite as a transparent liquid.

[0073] This preparation process, on the one hand, uses both water and methanol as raw materials, reducing methanol usage and significantly reducing the byproduct of chloromethane. Furthermore, by employing a continuous flow reactor and a gas-liquid separator, and by appropriately treating and recycling the resulting tail gases (Gas I and Gas II), this process eliminates the need for large amounts of non-condensable gases to be processed by a vacuum unit before being discharged to the chloromethane recovery system, as is the case with traditional processes. The load on the vacuum unit is reduced exponentially, significantly reducing equipment investment and energy consumption. Furthermore, in this preparation process, the reaction temperature is controlled by a cooling system integrated with the continuous flow reactor, and the reaction pressure is controlled by a pressure regulating valve on the gas phase outlet pipe of the gas-liquid separator.

[0074] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention falls within the scope of protection of the present invention.

Claims

1. A control system for the preparation of dimethyl phosphite, characterized in that: The invention is provided in a dimethyl phosphite preparation system, wherein the dimethyl phosphite preparation system comprises a continuous flow reactor I (1), a continuous flow reactor II (2) and a gas-liquid separator (3); the continuous flow reactor I (1) is connected to a phosphorus trichloride storage tank (8) via a phosphorus trichloride inlet pipe (7); the continuous flow reactor I (1) is connected to a water storage tank (13) via a water inlet pipe (12); the continuous flow reactor I (1) is connected to the continuous flow reactor II (2); the continuous flow reactor II (2) is connected to a methanol storage tank (18) via a methanol inlet pipe (17); the continuous flow reactor II (2) is connected to the gas-liquid separator (3); the liquid outlet of the gas-liquid separator (3) is connected to a dimethyl phosphite crude product temporary storage tank (37) via a lower liquid pipe I (24); the gas outlet of the gas-liquid separator (3) is connected to a normal pressure tail gas treatment system (6) via a gas phase outlet pipe (26); The control system includes a DCS controller, a phosphorus trichloride flowmeter (10) and a phosphorus trichloride regulating valve (11) provided on a phosphorus trichloride inlet pipe (7), a water flowmeter (15) and a water regulating valve (16) provided on a water inlet pipe (12), a methanol flowmeter (20) and a methanol regulating valve (21) provided on a methanol inlet pipe (17), a liquid level meter (22) and a pressure transmitter (23) provided on a gas-liquid separator (3), a lower liquid regulating valve (25) provided on a lower liquid pipe I (24), and a pressure regulating valve (28) provided on a gas phase outlet pipe (26); The phosphorus trichloride flow meter (10), the phosphorus trichloride regulating valve (11), the water flow meter (15), the water regulating valve (16), the methanol flow meter (20), the methanol regulating valve (21), the liquid level meter (22), the pressure transmitter (23), the lower liquid regulating valve (25) and the pressure regulating valve (28) are all connected to the DCS controller; A control loop is formed between the phosphorus trichloride flow meter (10), the DCS controller and the phosphorus trichloride regulating valve (11) through electrical signals; A control loop is formed between the water flow meter (15), the DCS controller and the water regulating valve (16) through electrical signals; A control loop is formed between the methanol flow meter (20), the DCS controller and the methanol regulating valve (21) through electrical signals; A control loop is formed between the liquid level meter (22), the DCS controller and the lower liquid regulating valve (25) through electrical signals; A control loop is formed between the pressure transmitter (23), the DCS controller and the pressure regulating valve (28) through electrical signals; A control loop is formed between the phosphorus trichloride flow meter (10), the water flow meter (15), the methanol flow meter (20), the DCS controller and the phosphorus trichloride regulating valve (11) through electrical signals.

2. The control system for preparing dimethyl phosphite according to claim 1, wherein The phosphorus trichloride inlet pipe (7), the water inlet pipe (12) and the methanol inlet pipe (17) are all provided with a pressure sensor (39) and a temperature sensor I (40), and the pressure sensor (39) and the temperature sensor I (40) are both connected to the DCS controller.

3. The control system for preparing dimethyl phosphite according to claim 1, wherein: The phosphorus trichloride inlet pipe (7) is provided with a phosphorus trichloride delivery pump (9), and the phosphorus trichloride delivery pump (9) is connected to a DCS controller.

4. The control system for preparing dimethyl phosphite according to claim 1, wherein A water delivery pump (14) is provided on the water inlet pipe (12), and the water delivery pump (14) is connected to a DCS controller.

5. The control system for preparing dimethyl phosphite according to claim 1, characterized in that: A methanol delivery pump (19) is provided on the methanol inlet pipe (17), and the methanol delivery pump (19) is connected to a DCS controller.

6. The control system for preparing dimethyl phosphite according to any one of claims 1 to 5, characterized in that: A deacidification kettle (4) is provided between the liquid outlet of the gas-liquid separator (3) and the temporary storage tank (37) for crude dimethyl phosphite. A jacket (44) is provided on the outside of the deacidification kettle (4), and a temperature sensor II (42) is provided on the jacket (44). A distributor (31) is provided in the deacidification kettle (4), and the distributor (31) is connected to the lower liquid pipe I (24), and the distributor (31) is connected to a motor (43). The upper gas outlet of the deacidification kettle (4) is connected to a packing tower (5) through an exhaust pipe (32), and the packing tower (5) is connected to a vacuum tail gas treatment system (45). The motor (43) and the temperature sensor II (42) are both connected to the DCS controller.

7. The control system for preparing dimethyl phosphite according to any one of claims 1 to 5, characterized in that: A heat exchanger I (27) is provided between the gas outlet of the gas-liquid separator (3) and the atmospheric tail gas treatment system (6). The condensate outlet of the heat exchanger is connected to the gas-liquid separator (3) via a condensate pipeline (29), and the gas outlet of the heat exchanger is connected to the atmospheric tail gas treatment system (6).

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