A glycolide purification system and purification method

Abstract

The present invention belongs to the technical field of glycolide, and relates to a glycolide purification system and a purification method, wherein the glycolide purification system comprises a first stirring kettle, a second stirring kettle, a feed component, a discharge component, a solvent adding component and a central control platform; the feed component, the discharge component and the solvent adding component are all connected to the first stirring kettle and the second stirring kettle; the central control platform is used to control the working states of the feed component, the discharge component and the solvent adding component; the mass ratio of the solvent to the crude glycolide is 1:(1.2-1.4); in the present invention, when the feed amount of the crude glycolide reaches a preset value, the central control platform automatically adjusts the states of relevant components, switches the conveying process of the crude glycolide to another stirring kettle, and automatically adds solvent to the corresponding stirring kettle, thereby realizing the automated control of the crude glycolide and solvent ratio process, ensuring the accuracy of the mass ratio between the crude glycolide and the solvent, and preventing the problem of unqualified product quality due to ratio deviation.

Description

Technical Field

[0001] The present invention relates to the technical field of glycolide, and in particular to a glycolide purification system and a purification method. Background Art

[0002] In the production process of polyglycolic acid from dimethyl oxalate, the purification of glycolide is a key link. The glycolide purification unit usually relies on various solvent dissolution and activated carbon adsorption to remove impurities in crude glycolide; specifically, glycolide is purified through a series of operations such as pulping, crystallization, filtration and drying. The operating accuracy of the glycolide purification unit, especially the accurate ratio of crude glycolide to solvent, is crucial to the quality and stability of the final product.

[0003] There is some research on the purification method of crude glycolide in the prior art. Referring to the patent document with application number 202410736782.9, a method for purifying crude glycolide is disclosed, which comprises the following steps: (1) adding liquid crude glycolide to a crystal forming kettle under stirring and containing a washing solvent to form a crystal solution, and cooling the crystal solution to 0°C to 40°C; (2) introducing the crystal solution into a three-in-one stirred kettle, and then filtering to remove the rich solvent, and the rich solvent is removed to a solvent recovery unit; (3) adding a lean solvent to the three-in-one stirred kettle, washing the crystals and filtering them; (4) repeating step (3) once or multiple times; (5) drying the crystals in the three-in-one stirred kettle to obtain purified glycolide. It can be seen that by mixing crude glycolide with a washing solvent, impurities in the crude glycolide are dissolved in the solvent to form a mixed liquid; then, the mixed liquid is cooled to promote the precipitation of impurities and the formation of crystals, the crystal solution is introduced into a three-in-one stirring tank for filtration to remove the solvent rich in impurities, a lean solvent is added to the stirring tank to wash and filter the crystals multiple times to further remove impurities, and finally the washed crystals are dried in the stirring tank to finally complete the purification of glycolide.

[0004] However, during the proportioning and feeding process of crude glycolide and solvent, the operator needs to remotely observe the liquid level changes in the stirring tank on the screen and manually control the corresponding feed valves of crude glycolide and solvent. Due to the error of liquid level observation and the delay of manual operation, the mass ratio between crude glycolide and solvent often deviates. The accurate proportion of crude glycolide and solvent is the key to ensuring product quality. Inaccurate proportion will directly affect the quality and stability of the product, resulting in unqualified product quality, which in turn affects the efficiency and benefits of the entire production line. Summary of the invention

[0005] In order to solve the technical problem in the background technology that the operator remotely observes the liquid level changes in the stirring tank on the screen and manually controls the corresponding feed valves of crude glycolide and the solvent, which leads to a deviation in the mass ratio between the crude glycolide and the solvent, the present invention provides a glycolide purification system and a purification method.

[0006] The glycolide purification system and purification method of the present invention realizes the automatic control of the process of proportioning crude glycolide and solvent by setting the connection between the central control platform and the feeding component, the discharging component and the solvent adding component; specifically, when the feeding amount of crude glycolide in the first stirring tank or the second stirring tank reaches the preset value, the central control platform automatically adjusts the state of the relevant components, switches the conveying process of crude glycolide from the current stirring tank to another stirring tank, and automatically adds solvent to the corresponding stirring tank according to the preset mass ratio. This automated control process effectively avoids the errors and delays caused by the operator's remote observation of liquid level changes and manual operation, ensures the accuracy of the mass ratio between crude glycolide and solvent, improves the quality and stability of the product, prevents the problem of unqualified product quality due to ratio deviation, and thus improves the efficiency and benefits of the entire production line.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A glycolide purification system and purification method, comprising a first stirring kettle, a second stirring kettle, a feeding assembly, a discharging assembly, a solvent adding assembly and a central control platform; the first stirring kettle and the second stirring kettle are both reaction containers for crude glycolide and solvent; the feeding assembly is connected to both the first stirring kettle and the second stirring kettle for conveying crude glycolide; the discharging assembly is connected to both the first stirring kettle and the second stirring kettle for discharging a mixed liquid of solvent and crude glycolide; the solvent adding assembly is connected to both the first stirring kettle and the second stirring kettle for conveying solvent; the central control platform is used to control the working states of the feeding assembly, the discharging assembly and the solvent adding assembly; wherein the mass ratio range of the crude glycolide in the first stirring kettle and the second stirring kettle to the solvent added by the solvent adding assembly is both 1:(1.2-1.4).

[0009] In a specific implementation scheme, the feed assembly includes a first main pipe, a first feed valve, a second feed valve and a first flow meter; the first main pipe is provided with a first branch pipe branching to a first stirring kettle and a second branch pipe branching to a second stirring kettle; the first feed valve is installed on the first branch pipe, the second feed valve is installed on the second branch pipe, and the first flow meter is installed on the first main pipe; wherein the first feed valve, the second feed valve and the first flow meter are all connected to the central control platform.

[0010] In a specific possible implementation scheme, the feed assembly includes a first main pipe, a first feed valve, a second feed valve and two first flow meters; the first main pipe is provided with a first branch pipe branching to a first stirring kettle and a second branch pipe branching to a second stirring kettle; the first feed valve is installed on the first branch pipe, the second feed valve is installed on the second branch pipe, and the two first flow meters are respectively installed on the first branch pipe and the second branch pipe; wherein the first feed valve, the second feed valve and the two first flow meters are all connected to the central control platform.

[0011] In a specific implementation scheme, the solvent addition component includes a second main pipe, a first solvent feed valve, a second solvent feed valve and a second flow meter; the second main pipe is provided with a third branch pipe branching to the first stirring kettle and a fourth branch pipe branching to the second stirring kettle; the first solvent feed valve is installed on the third branch pipe, the second solvent feed valve is installed on the fourth branch pipe, and the second flow meter is installed on the second main pipe; wherein the first solvent feed valve, the second solvent feed valve and the second flow meter are all connected to the central control platform.

[0012] In a specific implementation scheme, the solvent addition component includes a second main pipe, a first solvent feed valve, a second solvent feed valve and two second flow meters; the second main pipe is provided with a third branch pipe branching to the first stirring kettle and a fourth branch pipe branching to the second stirring kettle; the first solvent feed valve is installed on the third branch pipe, the second solvent feed valve is installed on the fourth branch pipe, and the two second flow meters are respectively installed on the third branch pipe and the fourth branch pipe; wherein the first solvent feed valve, the second solvent feed valve and the two second flow meters are all connected to the central control platform.

[0013] In a specific feasible implementation scheme, the discharge assembly includes a first discharge pipe, a second discharge pipe, a first discharge valve and a second discharge valve; the first discharge pipe is connected to the first stirring kettle, and the second discharge pipe is connected to the second stirring kettle; the first discharge valve is installed on the first discharge pipe, and the second discharge valve is installed on the second discharge pipe, and the first discharge valve and the second discharge valve are both connected to the central control platform.

[0014] In a specific implementation scheme, the inner walls of the first stirring tank and the second stirring tank are both connected to temperature sensors; the temperature sensors are connected to the central control platform and are used to measure the temperatures in the first stirring tank and the second stirring tank in real time.

[0015] In a specific implementation manner, the inner walls of the first stirring tank and the second stirring tank are both connected with time sensors; the time sensors are connected to the central control platform and are used to measure the reaction time of the crude glycolide and the solvent in the first stirring tank and the second stirring tank.

[0016] In a specific feasible implementation, the glycolide purification system further includes a drying kettle; the drying kettle is communicated with both the first discharge pipeline and the second discharge pipeline, and is used for further processing the mixed liquid conveyed out by the first discharge pipeline and / or the second discharge pipeline.

[0017] A glycolide purification method includes the following steps:

[0018] S1. Initial preparation:

[0019] According to the mass ratio of crude glycolide to the solvent, set the amount of crude glycolide M1, the amount of solvent N1 entering the first stirring kettle, the temperature value T1 in the first stirring kettle, and the reaction time H1 of crude glycolide and the solvent. The central control platform monitors the real-time temperature t1 in the first stirring kettle.

[0020] According to the mass ratio of crude glycolide to the solvent, set the amount of crude glycolide M2, the amount of solvent N2 entering the second stirring kettle, the temperature value T2 in the second stirring kettle, and the reaction time H2 of crude glycolide and the solvent. The central control platform monitors the real-time temperature t2 in the second stirring kettle.

[0021] S2. Alternate feeding of crude glycolide:

[0022] S2.1. Start feeding the first stirring kettle;

[0023] S2.1.1. Check whether the first discharge valve, the second feed valve, and the first solvent valve are all in the closed state;

[0024] If so, enter step S2.1.2;

[0025] If not, wait;

[0026] S2.1.2. The central control platform monitors the real-time flow rate m1 of the first flowmeter;

[0027] S2.1.3. The central control platform controls the first feed valve to open, and the crude glycolide flows through the first flowmeter and the first feed valve in sequence and enters the first stirring kettle;

[0028] S2.1.4. The central control platform compares the real-time flow rate m1 of the first flowmeter with the set amount of crude glycolide M1.

[0029] When m1 < M1, execute step S2.1.3.

[0030] When m1 = M1, execute step S2.1.5;

[0031] S2.1.5. The central control platform controls the first feed valve to close, clears the real-time flow rate m1 of the first flowmeter, and simultaneously executes step S2.2 and step S3.1;

[0032] S2.2. Start the feeding of the second stirring kettle;

[0033] S2.2.1. Check whether the second discharge valve, the first feed valve, and the second solvent valve are all in the closed state;

[0034] If so, proceed to step S2.2.2;

[0035] If not, wait;

[0036] S2.2.2. The central control platform monitors the real-time flow rate m2 of the first flowmeter;

[0037] S2.2.3. The central control platform controls the opening of the second feed valve, and the crude glycolide flows through the first flowmeter and the second feed valve in sequence and enters the second stirring kettle;

[0038] S2.2.4. The central control platform compares the real-time flow rate m2 of the first flowmeter with the set amount M2 of the crude glycolide.

[0039] When m2 < M2, execute step S2.2.3;

[0040] When m2 = M2, execute step S2.2.5;

[0041] S2.2.5. The central control platform controls the closing of the second feed valve, clears the real-time flow rate m2 of the first flowmeter, and simultaneously executes step S2.1 and step S3.2;

[0042] S3. Solvent addition:

[0043] S3.1. Add solvent to the first stirring kettle:

[0044] S3.1.1. The central control platform monitors the real-time flow rate n1 of the second flowmeter;

[0045] S3.1.2. The central control platform controls the opening of the first solvent valve, and the solvent flows through the second flowmeter and the first solvent valve in sequence and enters the first stirring kettle to form a mixed solution;

[0046] S3.1.3. The central control platform compares the real-time flow rate n1 of the second flowmeter with the set amount N1 of the solvent.

[0047] When n1 < N1, execute step S3.1.2;

[0048] When n1 = N1, execute step S3.1.4;

[0049] S3.1.4. The central control platform controls the closing of the first solvent valve, clears the real-time flow rate n1 of the second flowmeter, controls the time sensor in the second stirring kettle to start timing h1, and synchronously executes step S3.2 and step S4.1;

[0050] S3.2. Add solvent to the second stirring kettle:

[0051] S3.2.1. The central control platform monitors the real-time flow rate n2 of the second flowmeter;

[0052] S3.2.2. The central control platform controls the second solvent valve to open, and the solvent flows through the second flowmeter and the second solvent valve in sequence and enters the second stirring kettle to form a mixed solution;

[0053] S3.2.3. The central control platform compares the real-time flow rate n2 of the second flowmeter with the set solvent amount N2.

[0054] When n2 < N2, step S3.2.2 is executed.

[0055] When n2 = N2, step S3.2.4 is executed;

[0056] S3.2.4. The central control platform controls the second solvent valve to close, clears the real-time flow rate n2 of the second flowmeter, and controls the time sensor in the second stirring kettle to start timing h2, and executes step S4.2;

[0057] S4. Reaction timing and temperature monitoring:

[0058] S4.1. Monitor the reaction time and temperature of the first stirring kettle:

[0059] The central control platform compares the measured real-time temperature t1 with the set temperature value T1, and compares the reaction time h1 of crude glycolide and the solvent with the set reaction time H1.

[0060] When t1 < T1 or h1 < H1, step S4.1 is continued to be executed.

[0061] When t1 ≥ T1 and h1 ≥ H1, step S5.1 is executed;

[0062] S4.2. Monitor the reaction time and temperature of the second stirring kettle:

[0063] The central control platform compares the measured real-time temperature t2 with the set temperature value T2, and compares the reaction time h2 of crude glycolide and the solvent with the set reaction time H2.

[0064] When t2 < T2 or h2 < H2, step S4.2 is continued to be executed.

[0065] When t2 ≥ T2 and h2 ≥ H2, step S5.2 is executed;

[0066] S5. Drainage:

[0067] S5.1. Empty the first stirring kettle:

[0068] S5.1.1. The central control platform clears the h1 measured by the time sensor in the first stirring tank, controls the first discharge valve to open, and the mixed liquid in the first stirring tank flows through the first discharge valve and is discharged into the drying tank;

[0069] S5.1.2. The central control platform controls the first discharge valve to close;

[0070] S5.2. Empty the second stirred tank:

[0071] S5.2.1. The central control platform clears the h2 measured by the time sensor in the second stirring kettle, controls the second discharge valve to open, and the mixed liquid in the second stirring kettle flows through the second discharge valve and is discharged into the drying kettle;

[0072] S5.2.2. The central control platform controls the second discharge valve to close.

[0073] S6. Separation of glycolide and solvent:

[0074] The mixed liquid in the drying kettle is heated, the solvent evaporates, and glycolide is separated from the mixed liquid, thereby achieving the purification of glycolide.

[0075] In summary, the present invention includes the following beneficial technical effects:

[0076] 1. The glycolide purification system and purification method of the present invention realizes the automatic control of the crude glycolide and solvent ratio process by setting the connection between the central control platform and the feed component, the discharge component and the solvent addition component; specifically, when the feed amount of crude glycolide in the first stirring tank or the second stirring tank reaches the preset value, the central control platform automatically adjusts the state of the relevant components, switches the crude glycolide conveying process from the current stirring tank to another stirring tank, and automatically adds solvent to the corresponding stirring tank according to the preset mass ratio. This automated control process effectively avoids the errors and delays caused by the operator's remote observation of liquid level changes and manual operation, ensures the accuracy of the mass ratio between crude glycolide and solvent, improves the quality and stability of the product, and prevents the problem of unqualified product quality due to ratio deviation, thereby improving the efficiency and benefits of the entire production line.

[0077] 2. The glycolide purification system and purification method of the present invention are provided with a temperature sensor and a time sensor that cooperate with each other. The temperature sensor detects the temperature in the first stirring tank and the second stirring tank in real time. At the same time, when the solvent is added and the corresponding first solvent valve or second solvent valve is closed, the time sensor starts timing; once the temperature and reaction time reach the preset value, the central control platform automatically controls the corresponding first discharge valve and the second discharge valve to open and discharge the mixed liquid. Through the dual precise control of the temperature sensor and the time sensor, it is ensured that the impurities in the crude glycolide are fully dissolved in the solvent, the purification accuracy of the crude glycolide is improved, and then the quality and stability of the product are improved. At the same time, through the automated control process, it is avoided to waste unnecessary time, and the efficiency of the entire production line is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 It is a schematic diagram of the overall structure of the glycolide purification system of the present invention.

[0079] Explanation of the accompanying drawings: 1. first stirring kettle; 11. first feed valve; 12. first discharge valve; 13. first solvent valve; 2. second stirring kettle; 21. second feed valve; 22. second discharge valve; 23. second solvent valve; 3. first flow meter; 4. second flow meter. DETAILED DESCRIPTION

[0080] The technical solution of the present invention is further explained below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the implementation modes described below.

[0081] In the production process of polyglycolic acid from dimethyl oxalate, the purification of glycolide is a key link. In normal production operation, two sets of devices are used to purify crude glycolide with a purity of 70-80%. By injecting solvent into crude glycolide, impurities in crude glycolide are dissolved in the solvent, while glycolide is insoluble in the solvent, thereby achieving a preliminary separation of impurities and glycolide, and then the mixed solution of solvent and crude glycolide is transported to a drying kettle, and glycolide is separated by heating and / or reduced pressure distillation, and finally glycolide with a purity of 95% is obtained, thereby achieving the purification of glycolide.

[0082] Reference Figure 1, a glycolide purification system, comprising: a first stirring tank 1, a second stirring tank 2, a feeding component, a discharging component, a solvent adding component and a central control platform. The first stirring tank 1 and the second stirring tank 2 are both reaction vessels for crude glycolide and solvent; the feeding assembly is connected to the first stirring tank 1 and the second stirring tank 2 for conveying crude glycolide; the discharging assembly is connected to the first stirring tank 1 and the second stirring tank 2 for discharging the mixed liquid of solvent and crude glycolide; the solvent adding assembly is connected to the first stirring tank 1 and the second stirring tank 2 for conveying solvent; the central control platform is used to control the working status of the feeding assembly, the discharging assembly and the solvent adding assembly; wherein, the mass ratio of crude glycolide in the first stirring tank 1 and the second stirring tank 2 to the solvent added by the solvent adding assembly is both in the range of 1:(1.2-1.4), when the mass ratio of crude glycolide in the first stirring tank 1 or the second stirring tank 2 to the solvent added by the solvent adding assembly is in the range of 1:(1.2-1.4), the solubility of impurities in the crude glycolide in the solvent is the largest, thereby improving the purity of glycolide.

[0083] Specifically, the central control platform in the present invention is a term well known to those skilled in the art, and refers to a platform for centrally controlling and managing various links such as production equipment and production logistics during the factory production process.

[0084] Specifically, the impurities contained in the crude glycolide include methanol, water, oligomers, methyl glycolate, dimethyl oxalate, and methyl methoxyglycolate. The solvent in the present invention is dichloromethane.

[0085] Specifically, the mass ratio of crude glycolide to solvent can be 1:1.2, 1:1.3, or 1:1.4. A suitable mass ratio can be set according to production requirements to achieve the expected glycolide purity. Such settings are all acceptable. Preferably, the mass ratio of crude glycolide to solvent is 1:1.3, the amount of crude glycolide entering the first stirred tank and the second stirred tank is 1.3T, and the amount of solvent entering the first stirred tank and the second stirred tank is 1.69T, that is, M1=M2=1.3T, N1=N2=1.69T.

[0086] Reference Figure 1 The feed assembly includes a first main pipe, a first feed valve 11, a second feed valve 21 and a first flow meter 3. The first main pipe is provided with a first branch pipe branching to the first stirring tank 1 and a second branch pipe branching to the second stirring tank 2; the first feed valve 11 is installed on the first branch pipe, the second feed valve 21 is installed on the second branch pipe, and the first flow meter 3 is installed on the first main pipe; wherein the first feed valve 11, the second feed valve 21 and the first flow meter 3 are all connected to the central control platform.

[0087] Reference Figure 1The solvent addition assembly includes a second main pipe, a first solvent feed valve, a second solvent feed valve and a second flow meter 4. The second main pipe is provided with a third branch pipe branching to the first stirring kettle 1 and a fourth branch pipe branching to the second stirring kettle 2; the first solvent feed valve is installed on the third branch pipe, the second solvent feed valve is installed on the fourth branch pipe, and the second flow meter 4 is installed on the second main pipe; wherein the first solvent feed valve, the second solvent feed valve and the second flow meter 4 are all connected to the central control platform.

[0088] Reference Figure 1 The discharge assembly includes a first discharge pipe, a second discharge pipe, a first discharge valve 12 and a second discharge valve 22. The first discharge pipe is connected to the first stirring tank 1, and the second discharge pipe is connected to the second stirring tank 2; the first discharge valve 12 is installed on the first discharge pipe, and the second discharge valve 22 is installed on the second discharge pipe, and the first discharge valve 12 and the second discharge valve 22 are both connected to the central control platform.

[0089] Reference Figure 1 The inner walls of the first stirring tank 1 and the second stirring tank 2 are both connected with temperature sensors; the temperature sensors are connected to the central control platform and are used to measure the temperatures in the first stirring tank 1 and the second stirring tank 2 in real time.

[0090] Specifically, according to the slurry temperature in the stirring tank, when the temperature value in the first stirring tank 1 and the second stirring tank 2 is set to 30°C, the temperature requirement for the discharge of the mixed liquid is met; that is, T1 = T2 = 30°C.

[0091] In the present invention, the temperature sensor detects the temperature in the first stirring tank 1 and the second stirring tank 2 in real time, and is used in conjunction with the time sensor. Once the temperature and the reaction time reach the preset value, the central control platform automatically controls the corresponding first discharge valve 12 and the second discharge valve 22 to open and discharge the mixed liquid. This automatic process of dual temperature and time control significantly improves production efficiency and ensures the stability and consistency of product quality.

[0092] Reference Figure 1 , the inner walls of the first stirring tank 1 and the second stirring tank 2 are both connected with time sensors; the time sensors are connected to the central control platform, and are used to measure the reaction time of the crude glycolide and the solvent in the first stirring tank 1 and the second stirring tank 2. Among them, when the first solvent valve or the second solvent valve is closed, the central control platform automatically triggers the pulping and washing operation of the crude glycolide and the solvent, and the timing starting point of the time sensor is the moment when the crude glycolide and the solvent in the first stirring tank 1 or the second stirring tank 2 start pulping and washing; by pulping and washing the crude glycolide and the solvent, the impurities in the crude glycolide are promoted to dissolve in the solvent, and the purity of the glycolide is further improved. The pulping and washing operation is an operation well known to those skilled in the art, and will not be elaborated here.

[0093] Specifically, according to the pulping and washing time in the stirring tank, after the solvent is added and the corresponding first solvent valve 13 or second solvent valve 23 is closed, the time sensor counts to 1 hour, which meets the reaction time requirement for the discharge of the mixed liquid; that is, H1=H2=1 hour.

[0094] In the present invention, when the solvent is added and the corresponding first solvent valve 13 or second solvent valve 23 is closed, the time sensor starts timing and is used in conjunction with the temperature sensor. Once the temperature and reaction time reach the preset values, the central control platform automatically controls the corresponding first discharge valve 12 and second discharge valve 22 to open and discharge the mixed liquid. This automatic process of dual temperature and time control significantly improves production efficiency and ensures the stability and consistency of product quality.

[0095] Reference Figure 1 The glycolide purification system further comprises a drying kettle which is connected to the first discharge pipe and the second discharge pipe and is used for further processing the mixed liquid transported by the first discharge pipe and / or the second discharge pipe.

[0096] Specifically, after the mixed liquid delivered by the first discharge pipe and / or the second discharge pipe is delivered to the drying kettle, it will be heated and distilled under reduced pressure. These operations are conventional processes in the art. The solvent (such as dichloromethane) is evaporated by heating, and the glycolide is further purified by reduced pressure distillation technology to remove residual trace impurities. After the drying kettle treatment, glycolide with a purity of 95% is obtained.

[0097] A method for purifying glycolide comprises the following steps:

[0098] S1. Initial preparation:

[0099] According to the mass ratio of crude glycolide to solvent, the amount of crude glycolide M1 and the amount of solvent N1 entering the first stirring tank 1, the temperature value T1 in the first stirring tank 1, and the reaction time H1 of the crude glycolide and the solvent are set, and the central control platform monitors the real-time temperature t1 in the first stirring tank 1;

[0100] According to the mass ratio of crude glycolide to solvent, the amount of crude glycolide M2 ​​and the amount of solvent N2 entering the second stirring tank 2, the temperature value T2 in the second stirring tank 2, and the reaction time H2 of crude glycolide and solvent are set, and the central control platform monitors the real-time temperature t2 in the second stirring tank 2;

[0101] S2, crude glycolide alternate feeding:

[0102] S2.1, start feeding the first stirred tank 1;

[0103] S2.1.1, check whether the first discharge valve 12, the second feed valve 21 and the first solvent valve 13 are all in a closed state;

[0104] If so, go to step S2.1.2;

[0105] If not, wait;

[0106] S2.1.2. The central control platform monitors the real-time flow rate m1 of the first flowmeter 3;

[0107] S2.1.3. The central control platform controls the first feed valve 11 to open, and the crude glycolide flows through the first flowmeter 3 and the first feed valve 11 into the first stirring kettle 1 in sequence;

[0108] S2.1.4. The central control platform compares the real-time flow rate m1 of the first flowmeter 3 with the set amount M1 of crude glycolide,

[0109] When m1 < M1, execute step S2.1.3,

[0110] When m1 = M1, execute step S2.1.5;

[0111] S2.1.5. The central control platform controls the first feed valve 11 to close, clears the real-time flow rate m1 of the first flowmeter 3, and simultaneously executes step S2.2 and step S3.1;

[0112] S2.2. Start the feeding of the second stirring kettle 2;

[0113] S2.2.1. Check whether the second discharge valve 22, the first feed valve 11, and the second solvent valve 23 are all in the closed state;

[0114] If so, go to step S2.2.2;

[0115] If not, wait;

[0116] S2.2.2. The central control platform monitors the real-time flow rate m2 of the first flowmeter 3;

[0117] S2.2.3. The central control platform controls the second feed valve 21 to open, and the crude glycolide flows through the first flowmeter 3 and the second feed valve 21 into the second stirring kettle 2 in sequence;

[0118] S2.2.4. The central control platform compares the real-time flow rate m2 of the first flowmeter 3 with the set amount M2 of crude glycolide,

[0119] When m2 < M2, execute step S2.2.3,

[0120] When m2 = M2, execute step S2.2.5;

[0121] S2.2.5. The central control platform controls the second feed valve 21 to close, clears the real-time flow rate m2 of the first flowmeter 3, and simultaneously executes steps S2.1 and S3.2;

[0122] S3. Solvent addition:

[0123] S3.1. Add solvent to the first stirring kettle 1:

[0124] S3.1.1. The central control platform monitors the real-time flow rate n1 of the second flowmeter 4;

[0125] S3.1.2. The central control platform controls the first solvent valve 13 to open, and the solvent flows through the second flowmeter 4 and the first solvent valve 13 in sequence and enters the first stirring kettle 1 to form a mixed solution;

[0126] S3.1.3. The central control platform compares the real-time flow rate n1 of the second flowmeter 4 with the set solvent amount N1.

[0127] When n1 < N1, step S3.1.2 is executed.

[0128] When n1 = N1, step S3.1.4 is executed;

[0129] S3.1.4. The central control platform controls the first solvent valve 13 to close, clears the real-time flow rate n1 of the second flowmeter 4, controls the time sensor in the second stirring kettle 2 to start timing h1, and simultaneously executes steps S3.2 and S4.1;

[0130] S3.2. Add solvent to the second stirring kettle 2:

[0131] S3.2.1. The central control platform monitors the real-time flow rate n2 of the second flowmeter 4;

[0132] S3.2.2. The central control platform controls the second solvent valve 23 to open, and the solvent flows through the second flowmeter 4 and the second solvent valve 23 in sequence and enters the second stirring kettle 2 to form a mixed solution;

[0133] S3.2.3. The central control platform compares the real-time flow rate n2 of the second flowmeter 4 with the set solvent amount N2.

[0134] When n2 < N2, step S3.2.2 is executed.

[0135] When n2 = N2, step S3.2.4 is executed;

[0136] S3.2.4. The central control platform controls the second solvent valve 23 to close, clears the real-time flow rate n2 of the second flowmeter 4, controls the time sensor in the second stirring kettle 2 to start timing h2, and executes step S4.2;

[0137] S4. Reaction timing and temperature monitoring:

[0138] S4.1. Monitor the reaction time and temperature of the first stirring kettle 1:

[0139] The central control platform compares the measured real-time temperature t1 with the set temperature value T1, and compares the reaction time h1 of crude glycolide and the solvent with the set reaction time H1.

[0140] When t1 < T1 or h1 < H1, step S4.1 is continued.

[0141] When t1 ≥ T1 and h1 ≥ H1, step S5.1 is executed;

[0142] S4.2. Monitor the reaction time and temperature of the second stirring kettle 2:

[0143] The central control platform compares the measured real-time temperature t2 with the set temperature value T2, and compares the reaction time h2 of crude glycolide and the solvent with the set reaction time H2.

[0144] When t2 < T2 or h2 < H2, step S4.2 is continued.

[0145] When t2 ≥ T2 and h2 ≥ H2, step S5.2 is executed;

[0146] S5. Drainage:

[0147] S5.1. Empty the first stirring kettle 1:

[0148] S5.1.1. The central control platform clears h1 measured by the time sensor in the first stirring kettle 1, controls the first discharge valve 12 to open, and the mixed liquid in the first stirring kettle 1 flows through the first discharge valve 12 and is discharged into the drying kettle;

[0149] S5.1.2. The central control platform controls the first discharge valve 12 to close;

[0150] S5.2. Empty the second stirring kettle 2:

[0151] S5.2.1. The central control platform clears h2 measured by the time sensor in the second stirring kettle 2, controls the second discharge valve 22 to open, and the mixed liquid in the second stirring kettle 2 flows through the second discharge valve 22 and is discharged into the drying kettle;

[0152] S5.2.2. The central control platform controls the second discharge valve 22 to close;

[0153] S6. Separation of glycolide and solvent:

[0154] The mixed liquid in the drying kettle is heated to evaporate the solvent containing impurities, and glycolide is separated from the mixed liquid to obtain glycolide with a purity of 95%, thereby achieving the purification of glycolide.

[0155] Embodiment 1:

[0156] Reference Figure 1 In the glycolide purification system of this embodiment, the feed assembly includes a first main pipe, a first feed valve 11, a second feed valve 21 and two first flow meters 3. The first main pipe is provided with a first branch pipe branching to the first stirring tank 1 and a second branch pipe branching to the second stirring tank 2; the first feed valve 11 is installed on the first branch pipe, the second feed valve 21 is installed on the second branch pipe, and the two first flow meters 3 are installed on the first branch pipe and the second branch pipe respectively; wherein the first feed valve 11, the second feed valve 21 and the two first flow meters 3 are all connected to the central control platform.

[0157] Specifically, the two first flow meters 3 are respectively installed on the first branch pipe and the second branch pipe. When the feeding starts, the central control platform monitors the real-time flow of the first flow meter 3 on the first branch pipe and the second branch pipe respectively; when the real-time flow of the first flow meter 3 on the first branch pipe reaches the set crude glycolide amount M1, the central control platform controls the first feed valve 11 to close and clears the real-time flow of the first flow meter 3 on the first branch pipe; when the real-time flow of the first flow meter 3 on the second branch pipe reaches the set crude glycolide amount M2, the central control platform controls the second feed valve 21 to close and clears the real-time flow of the first flow meter 3 on the second branch pipe.

[0158] In this embodiment, a first flow meter 3 is provided on each of the first branch pipe and the second branch pipe, so that the central control platform can monitor the flow of the solvent in the first branch pipe and the second branch pipe in real time. When the real-time flow of the first flow meter 3 on any branch pipe reaches the preset crude glycolide amount (M1 or M2), the central control platform can immediately control the corresponding feed valve (first feed valve 11 or second feed valve 21) to close, and clear the real-time flow of the first flow meter 3 on the corresponding branch pipe. This real-time monitoring and precise control method can accurately control the amount of crude glycolide added to each stirring tank, and can avoid unnecessary downtime, thereby further improving the operating efficiency of the entire glycolide purification system.

[0159] Embodiment 2:

[0160] Reference Figure 1In the glycolide purification system of this embodiment, the solvent addition assembly includes a second main pipe, a first solvent feed valve, a second solvent feed valve and two second flow meters 4. The second main pipe is provided with a third branch pipe branching to the first stirring kettle 1 and a fourth branch pipe branching to the second stirring kettle 2; the first solvent feed valve is installed on the third branch pipe, the second solvent feed valve is installed on the fourth branch pipe, and the two second flow meters 4 are installed on the third branch pipe and the fourth branch pipe respectively; wherein, the first solvent feed valve, the second solvent feed valve and the two second flow meters 4 are all connected to the central control platform.

[0161] Specifically, the two second flow meters 4 are respectively installed on the third branch and the fourth branch. When the solvent is started to be added, the central control platform monitors the real-time flow of the second flow meters 4 on the third branch and the fourth branch respectively; when the real-time flow of the second flow meter 4 on the third branch reaches the set solvent amount N1, the central control platform controls the first solvent valve 13 to close, and clears the real-time flow of the second flow meter 4 on the third branch; when the real-time flow of the second flow meter 4 on the fourth branch reaches the set solvent amount N2, the central control platform controls the second solvent valve 23 to close, and clears the real-time flow of the second flow meter 4 on the fourth branch.

[0162] In this embodiment, a second flow meter 4 is provided on each of the third branch pipe and the fourth branch pipe, so that the central control platform can monitor the flow of the solvent in the third branch pipe and the fourth branch pipe in real time. When the real-time flow of the second flow meter 4 on any branch pipe reaches the preset solvent amount (N1 or N2), the central control platform can immediately control the corresponding solvent valve (the first solvent valve 13 or the second solvent valve 23) to close, and clear the real-time flow of the second flow meter 4 on the corresponding branch pipe. This real-time monitoring and precise control method can accurately control the amount of solvent added to each stirring tank, and can avoid unnecessary downtime, thereby further improving the operating efficiency of the entire glycolide purification system.

[0163] The preferred embodiments of the present invention are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A glycolide purification system, comprising: A first stirring kettle (1), a second stirring kettle (2), a feeding assembly, a discharging assembly, a solvent adding assembly and a central control platform; The first stirred tank (1) and the second stirred tank (2) are both reaction vessels for crude glycolide and solvent; The feed assembly is connected to both the first stirring tank (1) and the second stirring tank (2) and is used to transport the crude glycolide; The discharging assembly is connected to both the first stirring tank (1) and the second stirring tank (2) and is used to discharge a mixed solution of the solvent and the crude glycolide; The solvent adding component is connected to both the first stirring tank (1) and the second stirring tank (2) for conveying the solvent; The central control platform is used to control the working status of the feeding component, the discharging component and the solvent adding component; The mass ratio of the crude glycolide in the first stirred tank (1) and the second stirred tank (2) to the solvent added via the solvent adding assembly is both in the range of 1:(1.2-1.4).

2. The glycolide purification system according to claim 1, characterized in that: The feed assembly comprises a first main pipe, a first feed valve (11), a second feed valve (21) and a first flow meter (3); The first main pipe is provided with a first branch pipe branching to the first stirring tank (1) and a second branch pipe branching to the second stirring tank (2); The first feed valve (11) is installed on the first branch pipe, the second feed valve (21) is installed on the second branch pipe, and the first flow meter (3) is installed on the first main pipe; Wherein, the first feed valve (11), the second feed valve (21) and the first flow meter (3) are all connected to the central control platform.

3. The glycolide purification system according to claim 1, characterized in that: The feed assembly comprises a first main pipe, a first feed valve (11), a second feed valve (21) and two first flow meters (3); The first main pipe is provided with a first branch pipe branching to the first stirring tank (1) and a second branch pipe branching to the second stirring tank (2); The first feed valve (11) is installed on the first branch pipe, the second feed valve (21) is installed on the second branch pipe, and the two first flow meters (3) are installed on the first branch pipe and the second branch pipe respectively; Wherein, the first feed valve (11), the second feed valve (21) and the two first flow meters (3) are all connected to the central control platform.

4. The glycolide purification system according to claim 2, characterized in that: The solvent addition assembly comprises a second main pipe, a first solvent feed valve, a second solvent feed valve and a second flow meter (4); The second main pipe is provided with a third branch pipe branching to the first stirring tank (1) and a fourth branch pipe branching to the second stirring tank (2); The first solvent feed valve is installed on the third branch pipe, the second solvent feed valve is installed on the fourth branch pipe, and the second flow meter (4) is installed on the second main pipe; Wherein, the first solvent feed valve, the second solvent feed valve and the second flow meter (4) are all connected to the central control platform.

5. The glycolide purification system according to claim 2, characterized in that: The solvent addition assembly comprises a second main pipe, a first solvent feed valve, a second solvent feed valve and two second flow meters (4); The second main pipe is provided with a third branch pipe branching to the first stirring tank (1) and a fourth branch pipe branching to the second stirring tank (2); The first solvent feed valve is installed on the third branch pipe, the second solvent feed valve is installed on the fourth branch pipe, and the two second flow meters (4) are respectively installed on the third branch pipe and the fourth branch pipe; Among them, the first solvent feed valve, the second solvent feed valve, and the two second flow meters (4) are all connected to the central control platform.

6. The glycolide purification system according to claim 4, characterized in that: The discharge assembly includes a first discharge pipe, a second discharge pipe, a first discharge valve (12), and a second discharge valve (22); The first discharge pipe is communicated with the first stirring kettle (1), and the second discharge pipe is communicated with the second stirring kettle (2); The first discharge valve (12) is installed on the first discharge pipe, the second discharge valve (22) is installed on the second discharge pipe, and the first discharge valve (12) and the second discharge valve (22) are both connected to the central control platform.

7. The glycolide purification system according to claim 6, characterized in that: Temperature sensors are connected to the inner walls of the first stirring kettle (1) and the second stirring kettle (2); The temperature sensors are connected to the central control platform and are used to measure the temperatures in the first stirring kettle (1) and the second stirring kettle (2) in real time.

8. The glycolide purification system according to claim 7, characterized in that: Time sensors are connected to the inner walls of the first stirring kettle (1) and the second stirring kettle (2); The time sensors are connected to the central control platform and are used to measure the reaction time of the crude glycolide and the solvent in the first stirring kettle (1) and the second stirring kettle (2).

9. The glycolide purification system according to claim 6, characterized in that: The glycolide purification system further includes a drying kettle; The drying kettle is communicated with both the first discharge pipe and the second discharge pipe and is used to further process the mixed liquid conveyed by the first discharge pipe and / or the second discharge pipe.

10. A method for purifying glycolide, characterized in that: It includes the following steps: S1. Initial preparation: According to the mass ratio of crude glycolide to solvent, set the amount of crude glycolide M1, the amount of solvent N1, the temperature value T1 in the first stirring kettle (1), and the reaction time H1 of crude glycolide and solvent entering the first stirring kettle (1). The central control platform monitors the real-time temperature t1 in the first stirring kettle (1); According to the mass ratio of crude glycolide to solvent, set the amount of crude glycolide M2, the amount of solvent N2, the temperature value T2 in the second stirring kettle (2), and the reaction time H2 of crude glycolide and solvent entering the second stirring kettle (2). The central control platform monitors the real-time temperature t2 in the second stirring kettle (2); S2. Alternate feeding of crude glycolide: S2.

1. Start the feeding of the first stirring kettle (1); S2.1.

1. Check whether the first discharge valve (12), the second feed valve (21), and the first solvent valve (13) are all in the closed state; If so, enter step S2.1.2; If not, wait; S2.1.

2. The central control platform monitors the real-time flow rate m1 of the first flow meter (3); S2.1.

3. The central control platform controls the first feed valve (11) to open, and the crude glycolide flows through the first flow meter (3) and the first feed valve (11) in sequence and enters the first stirring kettle (1); S2.1.

4. The central control platform compares the real-time flow rate m1 of the first flow meter (3) with the set amount of crude glycolide M1, When m1 < M1, step S2.1.3 is executed, When m1 = M1, step S2.1.5 is executed; S2.1.

5. The central control platform controls the first feed valve (11) to close, clears the real-time flow rate m1 of the first flowmeter (3), and simultaneously executes step S2.2 and step S3.1; S2.

2. Start the feeding of the second stirring kettle (2); S2.2.

1. Check whether the second discharge valve (22), the first feed valve (11), and the second solvent valve (23) are all in the closed state; If so, proceed to step S2.2.2; If not, wait; S2.2.

2. The central control platform monitors the real-time flow rate m2 of the first flowmeter (3); S2.2.

3. The central control platform controls the second feed valve (21) to open, and the crude glycolide flows through the first flowmeter (3) and the second feed valve (21) in sequence and enters the second stirring kettle (2); S2.2.

4. The central control platform compares the real-time flow rate m2 of the first flowmeter (3) with the set amount M2 of the crude glycolide, When m2 < M2, step S2.2.3 is executed, When m2 = M2, step S2.2.5 is executed; S2.2.

5. The central control platform controls the second feed valve (21) to close, clears the real-time flow rate m2 of the first flowmeter (3), and simultaneously executes step S2.1 and step S3.2; S3. Solvent addition: S3.

1. Add solvent to the first stirring kettle (1): S3.1.

1. The central control platform monitors the real-time flow rate n1 of the second flowmeter (4); S3.1.

2. The central control platform controls the first solvent valve (13) to open, and the solvent flows through the second flowmeter (4) and the first solvent valve (13) in sequence and enters the first stirring kettle (1) to form a mixed solution; S3.1.

3. The central control platform compares the real-time flow rate n1 of the second flowmeter (4) with the set amount N1 of the solvent, When n1 < N1, step S3.1.2 is executed, When n1 = N1, step S3.1.4 is executed; S3.1.

4. The central control platform controls the first solvent valve (13) to close, clears the real-time flow rate n1 of the second flowmeter (4), controls the time sensor in the second stirring kettle (2) to start timing h1, and synchronously executes step S3.2 and step S4.1; S3.

2. Add solvent to the second stirring kettle (2): S3.2.

1. The central control platform monitors the real-time flow rate n2 of the second flowmeter (4); S3.2.

2. The central control platform controls the second solvent valve (23) to open, and the solvent flows through the second flowmeter (4) and the second solvent valve (23) in sequence and enters the second stirring kettle (2) to form a mixed solution; S3.2.

3. The central control platform compares the real-time flow rate n2 of the second flowmeter (4) with the set amount N2 of the solvent, When n2 < N2, step S3.2.2 is executed, When n2 = N2, step S3.2.4 is executed; S3.2.

4. The central control platform controls the second solvent valve (23) to close, clears the real-time flow rate n2 of the second flowmeter (4), controls the time sensor in the second stirring kettle (2) to start timing h2, and executes step S4.2; S4. Reaction timing and temperature monitoring: S4.

1. Monitor the reaction time and temperature of the first stirring kettle (1): The central control platform compares the measured real-time temperature t1 with the set temperature value T1, and compares the reaction time h1 of crude glycolide and the solvent with the set reaction time H1. When t1 < T1 or h1 < H1, step S4.1 is continued. When t1 ≥ T1 and h1 ≥ H1, step S5.1 is executed. S4.

2. Monitor the reaction time and temperature of the second stirring kettle (2): The central control platform compares the measured real-time temperature t2 with the set temperature value T2, and compares the reaction time h2 of crude glycolide and the solvent with the set reaction time H2. When t2 < T2 or h2 < H2, step S4.2 is continued. When t2 ≥ T2 and h2 ≥ H2, step S5.2 is executed. S5. Drainage: S5.

1. Empty the first stirring kettle (1): S5.1.

1. The central control platform clears h1 measured by the time sensor in the first stirring kettle (1), controls the first discharge valve (12) to open, and the mixed liquid in the first stirring kettle (1) flows through the first discharge valve (12) and is discharged into the drying kettle. S5.1.

2. The central control platform controls the first discharge valve (12) to close. S5.

2. Empty the second stirring kettle (2): S5.2.

1. The central control platform clears h2 measured by the time sensor in the second stirring kettle (2), controls the second discharge valve (22) to open, and the mixed liquid in the second stirring kettle (2) flows through the second discharge valve (22) and is discharged into the drying kettle. S5.2.

2. The central control platform controls the second discharge valve (22) to close. S6. Separation of glycolide and solvent: Heat the mixed liquid in the drying kettle, the solvent evaporates, and glycolide is separated from the mixed liquid to achieve the purification of glycolide.

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