Crude glycolide collecting system and cleaning method thereof

Abstract

The invention relates to a crude glycolide collecting system and a cleaning method thereof. The collecting system comprises a glycolide condenser, a steam spraying device, a secondary condenser and a vacuum device, the glycolide condenser is used for condensing gas-phase glycolide to obtain glycolide condensate, a gas-phase inlet and a spraying pipe are arranged at the lower part of the glycolide condenser, and a spraying opening of the spraying pipe faces the bottom; the steam spraying device is connected with the spraying pipe and is used for regularly outputting a spraying medium through the spraying pipe so as to carry out steam spraying cleaning; the secondary condenser is connected with a gas phase outlet in the top of the glycolide condenser, and is used for receiving the spraying medium steam output by the glycolide condenser and condensing the spraying medium steam to obtain a spraying medium mixed solution. Compared with the prior art, the device has the advantages that the glycolide condenser is intermittently sprayed and cleaned on line, glycolide and oligomers thereof solidified on the surface of the pipe wall of the condenser can be flushed down in time, the production of the glycolide is not influenced in the cleaning process, and the continuity of the production of the glycolide is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of glycolide production, and relates to a crude glycolide collection system and a cleaning method thereof. Background Art

[0002] Polyglycolic acid, also known as polyglycolide (abbreviated as PGA), is a biodegradable aliphatic polymer. It can be hydrolyzed under the catalysis of microorganisms, enzymes, acids or alkalis in vivo, and finally form carbon dioxide and water. It is a degradable material with great development potential. Glycolide is the cyclic dimer of glycolic acid. Ring-opening polymerization of glycolide is a relatively mature method for preparing polyglycolic acid, and this method can obtain polyglycolic acid with a relatively high molecular weight.

[0003] In the production of glycolide, glycolic acid or glycolic acid esters are used as reaction materials. Glycolic acid oligomers are prepared by polycondensation, and then the glycolic acid oligomers are depolymerized and cyclized. Vapor-phase glycolide is evaporated from the ring-forming reactor under high temperature and high vacuum, condensed by a condenser, and then transported to a refining unit for subsequent purification to obtain refined glycolide. In the existing production process, after the glycolide condenser operates continuously for a period of time, it will gradually become blocked, resulting in an increase in the internal pressure difference. Glycolide no longer vaporizes, and production cannot continue. It is necessary to stop the machine for cleaning, which affects production. Summary of the Invention

[0004] The purpose of the present invention is to provide a crude glycolide collection system and a cleaning method thereof, which are used to solve the problem that the glycolide liquid film retained in the condenser tube wall will gradually self-polymerize and solidify on the surface of the condenser tube wall over time, resulting in blockage inside the condenser. The present invention performs online steam spraying cleaning on the glycolide condenser intermittently, and can wash down the glycolide and its oligomers solidified on the surface of the condenser tube wall in time. The cleaning process does not affect the output of glycolide and ensures the continuity of glycolide production.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The first aspect of the present invention provides a crude glycolide collection system, including:

[0007] A glycolide condenser for condensing vapor-phase glycolide to obtain glycolide condensate. The glycolide condenser includes a condenser body and a heat exchange tube group arranged in the condenser body. The heat exchange tube group is connected to an external circulation heat exchange unit. A gas phase inlet and a spray pipe are arranged at the lower part of the condenser body, and the injection port of the spray pipe faces the bottom of the condenser body;

[0008] A steam spraying device connected to the spray pipe for periodically outputting a spraying medium through the spray pipe to perform steam spraying cleaning on the inside of the glycolide condenser;

[0009] A secondary condenser, connected to the gas-phase outlet at the top of the glycolide condenser, is used to receive the spray medium steam output by the glycolide condenser and condense the spray medium steam to obtain a spray medium mixture;

[0010] A vacuum device is connected to the secondary condenser.

[0011] In some specific embodiments, the collection system further includes:

[0012] A liquid storage tank, connected to the liquid-phase outlet at the bottom of the secondary condenser, is used to receive and store the spray medium mixture;

[0013] A gas-liquid separator, respectively connected to the liquid storage tank and the steam spray device, is used to vaporize the spray medium mixture, and the vaporized spray medium enters the steam spray device;

[0014] The secondary condenser, the liquid storage tank, and the gas-liquid separator are arranged with a height difference, and the installation heights decrease in sequence.

[0015] In some specific embodiments, the collection system further includes:

[0016] A crude glycolide buffer tank, connected to the glycolide condenser, is used to receive and store the glycolide condensate. An overflow pipe is arranged on the upper side of the crude glycolide buffer tank, and a discharge port is arranged at the bottom of the crude glycolide buffer tank. The pipeline connecting the glycolide condenser and the crude glycolide buffer tank extends into the interior of the crude glycolide buffer tank, and the pipeline outlet of the pipeline is located below the pipe orifice of the overflow pipe. A filter screen is arranged between the pipeline outlet of the pipeline and the discharge port;

[0017] A crude glycolide collection tank, connected to the overflow pipe and connected to the bottom discharge port of the crude glycolide buffer tank through a collection tank feed valve, is used to receive the glycolide condensate in the crude glycolide buffer tank.

[0018] In some specific embodiments, both the crude glycolide buffer tank and the crude glycolide collection tank are provided with heat preservation interlayers to keep the temperature inside the crude glycolide buffer tank and the crude glycolide collection tank at a set temperature.

[0019] In some specific embodiments, the length of the pipeline connecting the glycolide condenser and the crude glycolide buffer tank is more than 10 m.

[0020] In some specific embodiments, a liquid collection area is provided below the heat exchange tube group of the condenser body, the gas phase inlet and the spray pipe are located between the heat exchange tube group and the liquid collection area, and a buffer tank feed valve is provided on the pipeline connecting the glycolide condenser and the crude glycolide buffer tank;

[0021] The crude glycolide buffer tank is configured with a slag cleaning device for cleaning and discharging the solid slag on the filter screen. The slag cleaning device includes a scraper movably arranged on the filter screen, a power member for driving the scraper to move, and a slag discharge port opened on the crude glycolide buffer tank and located at the end point of the scraper movement. When the slag cleaning device operates, the buffer tank feed valve remains closed, and the glycolide condensate is stored in the liquid collection area.

[0022] In some specific embodiments, the power member is a piston rod cylinder.

[0023] In some specific embodiments, the collection system further includes:

[0024] A solvent supply assembly for supplying solvents to the crude glycolide buffer tank and the crude glycolide collection tank. The solvent supply assembly includes a solvent main pipe communicating with a solvent source, a buffer branch pipe communicating the solvent main pipe with the top of the crude glycolide buffer tank, a collection branch pipe communicating the solvent main pipe with the top of the crude glycolide collection tank, a buffer branch pipe valve provided on the buffer branch pipe, and a collection branch pipe valve provided on the collection branch pipe.

[0025] In some specific embodiments, a stirring crusher is provided inside the crude glycolide collection tank.

[0026] A second aspect of the present invention provides a cleaning method based on the above-mentioned collection system, including:

[0027] Condensing the gaseous glycolide through the glycolide condenser to obtain a glycolide condensate. The absolute pressure of the glycolide condenser is 100 - 5000 Pa, and the inlet temperature of the cooling medium introduced into the heat exchange tube group is 60 - 120 °C;

[0028] During the condensation of the gaseous glycolide, regularly output a spray medium through the steam spray device to perform steam spray cleaning on the inside of the glycolide condenser. The spray medium steam enters the secondary condenser from the top of the glycolide condenser, and is condensed in the secondary condenser to obtain a spray medium mixture.

[0029] In some specific embodiments, the spray medium is selected from one of methyl glycolate, ethyl glycolate, ethanol, isopropanol, methyl acetate, ethyl acetate, butyl acetate, cyclohexane or cyclohexanone;

[0030] The spraying medium output by the steam spraying device is the saturated liquid or steam of the spraying medium.

[0031] In some specific embodiments, the spraying cycle is once every 2 to 6 hours, or spraying is carried out when the pressure difference between the top and bottom of the glycolide condenser exceeds 150 to 200 Pa;

[0032] The dosage for each spraying is 1 / 20 to 1 / 5 of the hourly output of glycolide condensate; the spraying time is 5 seconds to 5 minutes.

[0033] In some specific embodiments, the cleaning method further includes: making the spraying medium mixture flow into the liquid storage tank, transporting the spraying medium mixture in the liquid storage tank to the gas-liquid separator, vaporizing the spraying medium by heating, and the vaporized spraying medium enters the steam spraying device.

[0034] In some specific embodiments, during the condensation of gaseous glycolide, the connection between the bottom discharge port of the crude glycolide buffer tank and the crude glycolide collection tank is disconnected, so that the glycolide condensate in the crude glycolide buffer tank flows into the crude glycolide collection tank through the overflow pipe.

[0035] In some specific embodiments, when slag cleaning is required, the connection between the glycolide condenser and the crude glycolide buffer tank is disconnected, and the glycolide condensate is temporarily stored in the liquid collection area of the glycolide condenser; the bottom discharge port of the crude glycolide buffer tank is connected to the crude glycolide collection tank, and after the remaining condensate in the crude glycolide buffer tank enters the crude glycolide collection tank through the bottom discharge port, the slag cleaning device is started to clean and discharge the solid slag on the filter screen in the crude glycolide buffer tank.

[0036] In some specific embodiments, after the slag cleaning is completed, a solvent is supplied to the crude glycolide buffer tank through the solvent supply assembly for solvent flushing, and the cleaning liquid enters the crude glycolide collection tank or is discharged externally through the bottom discharge port; after the cleaning is completed, the connection between the bottom discharge port of the crude glycolide buffer tank and the crude glycolide collection tank is disconnected, and the glycolide condenser is reconnected to the crude glycolide buffer tank.

[0037] In some specific embodiments, after the glycolide in the crude glycolide collection tank is pumped and transported to the subsequent refining unit, the connection between the glycolide condenser and the crude glycolide buffer tank is disconnected, and the glycolide condensate is temporarily stored in the liquid collection area of the glycolide condenser; a solvent is supplied to the crude glycolide collection tank through the solvent supply assembly for solvent flushing, and optionally, the stirring crusher is started to break up the deposited solid blocks and wash out the residual impurities to the next process.

[0038] Compared with the prior art, the present invention has the following characteristics:

[0039] 1. By intermittently performing steam spray flushing on the glycolide condenser, and utilizing the flushing effect of the spray medium steam on the tube wall of the condenser, the attached glycolide liquid film can be promptly detached, avoiding the problem that the retained glycolide liquid film will gradually self-polymerize and solidify on the surface of the condenser tube wall over time, resulting in blockage inside the condenser.

[0040] 2. By adopting on-line cleaning, it does not affect the output of glycolide, ensuring the continuity of glycolide production; and there is no need to stop the machine, nor to set up two groups of glycolide condensers for alternating use, reducing equipment costs.

[0041] 3. Further, by setting up a crude glycolide buffer tank with an overflow pipe, the glycolide condensate condensed by the glycolide condenser flows into the crude glycolide collection tank in an overflow manner, avoiding pipeline blockage; a filter screen and slag cleaning port are provided at the bottom of the crude glycolide buffer tank, and slag is cleaned regularly, and the inside of the crude glycolide buffer tank and the crude glycolide collection tank are cleaned regularly. Description of the Drawings

[0042] Figure 1 is the process flow diagram of a glycolide condensation and collection system in the present invention;

[0043] Figure 2 is the process flow diagram of a glycolide condensation and collection system in the present invention;

[0044] Description of the Reference Numerals:

[0045] 1 - Ring-Forming Reactor, 2 - Glycolide Condenser, 3 - Crude Glycolide Buffer Tank, 4 - Crude Glycolide Collection Tank, 5 - Filter Screen, 6 - Overflow Pipe, 7 - Scraper, 8 - Slag Discharge Port, 9 - Pipeline, 10 - Stirring and Crushing Device, 11 - Buffer Branch Pipe, 12 - Buffer Branch Pipe Valve, 13 - Collection Branch Pipe, 14 - Collection Branch Pipe Valve, 15 - Heat Exchange Tube Group, 16 - Liquid Collection Area, 17 - Vacuum Device, 18 - Spray Pipe, 19 - Secondary Condenser, 20 - Liquid Storage Tank, 21 - Gas-Liquid Separator, 22 - Steam Spray Device, 23 - Buffer Tank Feed Valve, 24 - Collection Tank Feed Valve. Detailed Embodiments

[0046] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0047] The glycolide in the present invention is crude glycolide, which contains substances such as pure glycolide, linear PGA oligomer, glycolic acid, etc.

[0048] A crude glycolide collection system provided by an embodiment of the present invention, as Figure 1 shown, includes a glycolide condenser 2, a crude glycolide buffer tank 3, a crude glycolide collection tank 4, a steam spray device 22, a secondary condenser 19, and a vacuum device 17.

[0049] The glycolide condenser 2 is used to condense gaseous glycolide to obtain glycolide condensate, preferably a shell-and-tube condenser, which includes a condenser body and a heat exchange tube group 15 arranged inside the condenser body, that is, it includes a shell side and a tube side. The gas-phase discharge and the heat exchange medium flow through the shell side and the tube side respectively for wall heat exchange to achieve the condensation effect of the gas-phase discharge; the heat exchange tube group 15 is connected to the external circulation heat exchange unit. The external circulation heat exchange unit includes a circulating discharge port and a circulating feed port connected to the tube side of the shell-and-tube condenser, a circulating pipeline connected between the circulating discharge port and the circulating feed port, and a circulating cooler and a circulating pump arranged on the circulating pipeline; a gas-phase inlet and a spray pipe 18 are provided at the lower part of the condenser body, and the spray port of the spray pipe 18 faces the bottom of the condenser body.

[0050] The crude glycolide buffer tank 3 is connected to the glycolide condenser 2 through a pipeline 9 and is used to receive and store the glycolide condensate. The crude glycolide buffer tank 3 is provided with a heat preservation interlayer to keep the temperature inside the crude glycolide buffer tank at a set temperature. In practical applications, the freezing point of crude glycolide is generally about 60°C, and the temperature inside the crude glycolide buffer tank 3 can be set at 80°C - 100°C.

[0051] The crude glycolide collection tank 4 is connected to the crude glycolide buffer tank 3 through a collection tank feed valve 24 and is used to receive the glycolide condensate in the crude glycolide buffer tank 3. Similarly, the crude glycolide collection tank 4 is provided with a heat preservation interlayer to keep the temperature inside the crude glycolide collection tank 4 at a set temperature. In practical applications, when the crude glycolide collection tank 4 pre-stores a solvent or a solvent is input simultaneously, that is, when the glycolide collected in the crude glycolide collection tank 4 is a glycolide solution, the temperature inside the crude glycolide collection tank 4 can be set at 60°C - 80°C. When the glycolide collected in the crude glycolide collection tank 4 is glycolide condensate, the temperature inside the crude glycolide collection tank 4 can be set at 80°C - 100°C.

[0052] The steam spray device 22 selects a storage tank with a temperature control function and is connected to the spray pipe 18, preferably connected by a delivery pump, and is used to periodically output a spray medium through the spray pipe 18 to perform steam spray cleaning on the inside of the glycolide condenser 2.

[0053] The secondary condenser 19 is connected to the gas-phase outlet at the top of the glycolide condenser 2 and is used to receive the spray medium steam output by the glycolide condenser 2 and condense the spray medium steam to obtain a spray medium mixture. The structure of the secondary condenser 19 can be the same as that of the glycolide condenser 2, also a shell-and-tube condenser, with an external circulation heat exchange unit connected; or, the secondary condenser 19 can also adopt a spray tower.

[0054] The vacuum device 17 is connected to the secondary condenser 19 and is used to provide a negative pressure environment for the system.

[0055] Since glycolide is prone to self-polymerization in the presence of acidic impurities and under heated conditions, as the condensation time of the gaseous glycolide generated by the depolymerization cyclization reaction in the ring-forming reactor 1 accumulates, the glycolide liquid film retained on the wall surface of the heat exchange tube group 15 will gradually self-polymerize and solidify, and it is difficult to be washed out by the glycolide condensate. In this embodiment, the glycolide condenser 2 is periodically cleaned by steam spraying. When cleaning, a large stream of air generated after the spraying medium enters the glycolide condenser 2 is used to wash down the solid impurities retained on the wall surface of the glycolide condenser 2 together with the glycolide liquid film. The spraying medium steam is sucked into the secondary condenser 19 by the vacuum device 17, condensed by the secondary condenser 19 and then collected, thus solving the problem of easy blockage inside the condenser. The spray port of the spray pipe 18 faces the bottom of the condenser body, which can prevent the spray port from being blocked by the solid impurities washed down.

[0056] The glycolide liquid with a certain liquid level is kept in the crude glycolide buffer tank 3, and during the production process of glycolide, the liquid level remains relatively stable. Thus, the spraying steam will not enter the crude glycolide buffer tank 3 from the liquid phase outlet at the bottom, but enter the secondary condenser 19 from the gas phase outlet at the top.

[0057] The liquid flowing out from the liquid phase outlet of the secondary condenser 19 is a mixed liquid of the spraying medium and a small amount of glycolide entrained by the spraying steam, which can be returned to the steam spraying device 22 after being pressurized by a pump. After the steam spraying device 22 is heated to the set temperature, it is used for spraying again.

[0058] As a further improvement, the collection system further includes a liquid storage tank 20 and a gas-liquid separator 21; the liquid storage tank 20 is connected to the liquid phase outlet at the bottom of the secondary condenser 19 for receiving and storing the spraying medium mixed liquid; the gas-liquid separator 21 is respectively connected to the liquid storage tank 20 and the steam spraying device 22 for vaporizing the spraying medium mixed liquid, and the vaporized spraying medium enters the steam spraying device 22; the secondary condenser 19, the liquid storage tank 20, and the gas-liquid separator 21 are arranged with a height difference, and the installation heights decrease in sequence.

[0059] In the secondary condenser 19, the spraying medium steam and a small amount of entrained glycolide are condensed to form a mixed liquid. This mixed liquid flows into the liquid storage tank 20, can be stored in the liquid storage tank 20 first, and then enters the gas-liquid separator 21. After being separated by evaporation or rectification in the gas-liquid separator 21, the light component, that is, the spraying medium, is returned to the steam spraying device and sprayed again through the spray pipe, and the heavy component, that is, glycolide, is regularly discharged through the liquid phase outlet of the gas-liquid separator.

[0060] The embodiment of the present invention also provides a crude glycolide collection system, as Figure 2 shown, compared with the system as Figure 1 shown, the difference lies in that: the structures of the crude glycolide buffer tank 3 and the crude glycolide collection tank 4 are different.

[0061] An overflow pipe 6 is provided on the upper side of the crude glycolide buffer tank 3, and a discharge port is provided at the bottom of the crude glycolide buffer tank 3. The pipeline 9 connecting the glycolide condenser 2 and the crude glycolide buffer tank 3 extends into the interior of the crude glycolide buffer tank 3, and the pipeline outlet of the pipeline 9 is located below the nozzle of the overflow pipe 6. A filter screen 5 is provided between the pipeline outlet of the pipeline 9 and the discharge port; the crude glycolide collection tank 4 is connected to the overflow pipe 6 and is connected to the bottom discharge port of the crude glycolide buffer tank 3 through a collection tank feed valve 24.

[0062] In view of the problem that when the gaseous glycolide is evaporated from the ring-forming reactor 1, gas-liquid entrainment is likely to occur, and solid impurities enter the conveying pipeline and cause blockage, affecting the conveying, in this embodiment, an overflow pipe 6 is provided on the upper side of the crude glycolide buffer tank 3, and the solid impurities in the glycolide condensate are deposited on the filter screen 5 by gravity sedimentation to obtain supernatant liquid, which is discharged into the crude glycolide collection tank 4 through the overflow pipe 6 at the top of the crude glycolide buffer tank 3.

[0063] Furthermore, the length of the pipeline 9 connecting the liquid phase outlet of the glycolide condenser 2 and the feed port of the crude glycolide buffer tank 3 is more than 10 m, which is used to effectively balance the pressure inside and outside the crude glycolide buffer tank 3 and realize the overflow of the glycolide condensate in the crude glycolide buffer tank 3.

[0064] Furthermore, a liquid collection area 16 is provided below the heat exchange tube group 15 of the condenser body. The gas phase inlet and the spray pipe 18 are located between the heat exchange tube group 15 and the liquid collection area 16. A buffer tank feed valve 23 is provided on the pipeline connecting the glycolide condenser 2 and the crude glycolide buffer tank 3; the crude glycolide buffer tank 3 is equipped with a slag cleaning device for cleaning and discharging the solid slag on the filter screen 5. The slag cleaning device includes a scraper 7 movably arranged on the filter screen 5, a power member for driving the movement of the scraper 7, and a slag discharge port 8 opened on the buffer tank body and located at the end point of the movement of the scraper 7. When the slag cleaning device operates, the buffer tank feed valve 23 remains closed, and the glycolide condensate is stored in the liquid collection area 16.

[0065] Specifically, when slag cleaning is required, the buffer tank feed valve 23 is closed, and the collection tank feed valve 24 is opened. First, the crude glycolide collection tank 4 is fed through the discharge port at the bottom of the crude glycolide buffer tank 3, and solid impurities are further filtered through the filter screen 5. The slag cleaning device removes the filter residue on the filter screen 5, specifically including: pushing the scraper 7 to move on the filter screen 5 through the power member, pushing the deposited solid impurities to the slag discharge port 8, and discharging them out of the tank through the slag discharge port 8, so as to clean the slag in time and ensure the filtering effect of the filter screen 5. Exemplarily, the power member is a piston rod cylinder.

[0066] As a further improvement, the collection system further includes a solvent supply assembly for delivering a solvent to the crude glycolide buffer tank 3 and the crude glycolide collection tank 4. The solvent supply assembly includes a solvent main pipe communicating with a solvent source, a buffer branch pipe 11 communicating the solvent main pipe with the top of the crude glycolide buffer tank 3, a collection branch pipe 13 communicating the solvent main pipe with the top of the crude glycolide collection tank 4, a buffer branch pipe valve 12 provided on the buffer branch pipe 11, and a collection branch pipe valve 14 provided on the collection branch pipe 13.

[0067] Specifically, when it is necessary to clean the inside of the crude glycolide buffer tank 3, the solvent is delivered to the crude glycolide buffer tank 3 through the solvent supply assembly; when it is necessary to clean the inside of the crude glycolide collection tank 4, the solvent is delivered to the crude glycolide collection tank 4 through the solvent supply assembly; when it is necessary to introduce a solvent into the crude glycolide collection tank 4 to dissolve the glycolide, the solvent can also be delivered to the crude glycolide collection tank 4 through the solvent supply assembly.

[0068] As a further improvement, a stirring crusher 10 is provided inside the crude glycolide collection tank 4; for the solid impurities that cannot be filtered out, after entering the crude glycolide collection tank 4, they are further refined and crushed under the action of the stirring crusher 10 to remove the solid impurities that may cause pipeline blockage and ensure the smoothness of the conveying process. Among them, the stirring crusher 10 can be a stirring paddle.

[0069] The present invention also provides a cleaning method for the above-mentioned crude glycolide collection system, including:

[0070] The gas-phase glycolide is condensed by the glycolide condenser 2 to obtain a glycolide condensate. The absolute pressure of the glycolide condenser 2 is 100 - 5000 Pa, the inlet temperature of the cooling medium introduced into the heat exchange tube group 15 is 60 - 120 °C, and the outlet temperature of the cooling medium is controlled to be 0.1 °C - 5 °C higher than the inlet temperature;

[0071] During the condensation of the gas-phase glycolide, the steam spraying device 22 periodically outputs a spraying medium to perform steam spraying cleaning on the inside of the glycolide condenser 2. The spraying medium steam enters the secondary condenser 19 from the top of the glycolide condenser 2 and is condensed in the secondary condenser 19 to obtain a spraying medium mixture;

[0072] Furthermore, the spraying medium mixture flows into the liquid storage tank 20, the spraying medium mixture in the liquid storage tank 20 is delivered to the gas-liquid separator 21, the spraying medium is vaporized by heating, and the vaporized spraying medium enters the steam spraying device 22 and is reused for steam spraying cleaning.

[0073] In some specific applications, the following process parameters can be adopted for each device:

[0074] Cyclization Reactor 1: The raw material is glycolic acid or a glycolate oligomer, preferably having a weight average molecular weight of 10,000 to 50,000; the catalyst is selected from at least one of tin compounds, antimony compounds or zinc compounds, for example, stannous octoate, stannous chloride, stannous lactate, antimony trioxide, diethylzinc or zinc acetate dihydrate, etc. The amount of the catalyst is 0.1 to 3 wt% of the mass of polyglycolic acid or its ester; the pressure in the cyclization reactor 1 is the same as the pressure in the glycolide condenser 2, preferably below 2000 Pa, and the temperature is 230 to 300 °C.

[0075] Glycolide Condenser 2: The inlet temperature of the cooling medium is 60 to 120 °C, preferably 80 to 100 °C. The inlet temperature of the cooling medium cannot be too low to avoid the solidification of glycolide. The outlet temperature of the cooling medium is controlled to be 0.1 to 5 °C higher than its inlet temperature. The cooling medium enters from the bottom and exits from the top in the glycolide condenser 2.

[0076] Steam Spraying Device 22: The spraying medium provided is preferably a saturated liquid or steam of an organic solvent, or can also be a low-temperature liquid, which is heated by using the heat in the glycolide condenser (mainly the heat of the crude glycolide steam), or the low-temperature liquid generates steam under negative pressure after entering the glycolide condenser. When the spraying medium needs to be heated by using the heat in the glycolide condenser 2 to generate steam, it is necessary to confirm that the glycolide condenser 2 can completely heat the spraying medium within a short time (for example, within 3 seconds) so that the spraying medium is completely vaporized without remaining in the glycolide condensate.

[0077] Any organic solvent that is gaseous at the pressure and temperature inside the glycolide condenser 2 can be used as the spraying medium, for example, saturated liquids, vapors (saturated vapor, superheated vapor) of methyl glycolate, ethyl glycolate, ethanol, isopropanol, methyl acetate, ethyl acetate, butyl acetate, cyclohexane, cyclohexanone, etc., preferably a good solvent for glycolide; the temperature of the spraying medium needs to be controlled within a certain range, not lower than the melting point of glycolide to prevent the solidification of glycolide, not higher than the temperature of the cyclization reactor, and preferably not higher than the saturated vapor temperature of glycolide to prevent the deterioration of glycolide due to heat. The preferred temperature range is 80 to 200 °C.

[0078] The spraying period is preferably once every 2 to 6 hours, and more preferably once every 2 to 4 hours. It is also possible to start the steam spraying cleaning according to the upper and lower pressure differences inside the glycolide condenser 2. When the upper and lower pressure differences inside the glycolide condenser 2 exceed the threshold value, for example, 200 Pa, start the steam spraying cleaning. In actual production, under the vacuum of the vacuum device 17, the pressures inside the ring-forming reactor 1, the glycolide condenser 2, and the secondary condenser 19 are basically close. When there is an upper and lower pressure difference inside the glycolide condenser 2, it indicates that a paste has formed on the surface of the condenser tube wall, affecting the gas flux. Therefore, the steam spraying cleaning can be started according to the upper and lower pressure differences inside the glycolide condenser 2, and the cleaning should not be carried out when the pressure difference is too large to avoid an unsatisfactory effect of the steam spraying cleaning.

[0079] In a single spraying, the amount of the spraying medium is 1 / 20 to 1 / 5 of the hourly output of the glycolide condensate. For example, when the output of the glycolide condensate is 2 tons per hour, the amount of the spraying medium for one spraying is between 100 kg and 400 kg. The spraying duration is 5 seconds to 5 minutes, preferably 5 seconds to 3 minutes, and more preferably 10 seconds to 60 seconds. After the spraying ends, the system returns to the stable production state after 1 to 2 minutes.

[0080] Secondary condenser 19: It can be a shell-and-tube heat exchanger or a spraying tower. When it is a shell-and-tube heat exchanger, the inlet temperature of the cooling medium is -5 to 5°C, and the outlet temperature of the cooling medium is controlled to be 0.1 to 5°C higher than its inlet temperature; when it is a spraying tower, the spraying cycle is started while the steam spraying cleaning is carried out, and the temperature inside the secondary condenser is maintained at -5 to 5°C. The spraying liquid and the spraying steam are the same medium.

[0081] As a further improvement, the cleaning method also includes regularly removing slag from the crude glycolide buffer tank 3, specifically including:

[0082] S1: During the condensation of gaseous glycolide, open the buffer tank feed valve 23 and close the collection tank feed valve 24 to disconnect the bottom discharge port of the crude glycolide buffer tank 3 from the crude glycolide collection tank 4. The gaseous glycolide evaporates from the ring-forming reactor 1 and enters the glycolide condenser 2 for condensation. After the glycolide condensate enters the crude glycolide buffer tank 3 and accumulates, when the liquid level reaches the nozzle of the overflow pipe 6, the glycolide condensate flows into the crude glycolide collection tank 4 through the overflow pipe 6; during the accumulation and storage process, solid impurities are deposited on the filter screen 5;

[0083] S2: After running for a certain period of time, slag cleaning starts: close the feed valve 23 of the buffer tank to disconnect the connection between the glycolide condenser 2 and the crude glycolide buffer tank 3. The glycolide condensate is temporarily stored in the liquid collection area 16 at the bottom of the glycolide condenser 2. Open the feed valve 24 of the collection tank to connect the bottom discharge port of the crude glycolide buffer tank 3 with the crude glycolide collection tank 4. The remaining glycolide condensate in the crude glycolide buffer tank 3 flows into the crude glycolide collection tank 4 through the bottom discharge port and the feed valve 24 of the collection tank, and the filter screen 5 filters the flowing glycolide condensate. After the glycolide condensate is discharged, open the slag discharge port 8 of the crude glycolide buffer tank 3 and start the slag cleaning device to clean the solid slag. Specifically, the power component drives the scraper 7 to move on the filter screen 5 to push the filter residue deposited on the filter screen 5 to the slag discharge port 8 and be discharged.

[0084] S3: After the slag cleaning is completed, close the slag discharge port 8, close the feed valve 24 of the collection tank, and open the feed valve 23 of the buffer tank. The crude glycolide buffer tank 3 resumes collecting the glycolide condensate.

[0085] In some specific applications, the solid slag at the bottom of the crude glycolide buffer tank 3 is regularly cleaned, preferably once every 3 - 8 hours. It is also possible to determine whether slag cleaning is required based on the change in the flow rate of the glycolide condensate entering the crude glycolide buffer tank 3. When the material intercepted by the filter screen 5 is relatively large and accumulates at the outlet of the pipeline 9, resulting in a sharp decrease in the flow rate of the glycolide condensate entering the crude glycolide buffer tank 3, it indicates that slag cleaning is needed.

[0086] Furthermore, the cleaning method also includes internal cleaning of the crude glycolide buffer tank 3, specifically including:

[0087] After the slag cleaning is completed, close the slag discharge port 8, then open the buffer branch valve 12 on the buffer branch pipe 11, and supply solvent to the crude glycolide buffer tank 3 through the solvent supply component for solvent flushing. The cleaning liquid enters the crude glycolide collection tank 4 through the bottom discharge port of the crude glycolide buffer tank 3 and the feed valve 24 of the collection tank or is discharged to the cleaning liquid collection tank. After the cleaning is completed, close the feed valve 24 of the collection tank and open the feed valve 23 of the buffer tank.

[0088] Furthermore, the cleaning method also includes internal cleaning of the crude glycolide collection tank 4, specifically including:

[0089] After the glycolide condensate or glycolide solution in the crude glycolide collection tank 4 is pumped to the subsequent refining unit, for example, when the collection volume in the crude glycolide collection tank 4 reaches a certain amount (for example, reaches 70% of the tank volume), the glycolide condensate or glycolide solution in the crude glycolide collection tank 4 is pumped to the subsequent refining unit, then the buffer tank feed valve 23 is closed to disconnect the connection between the glycolide condenser 2 and the crude glycolide buffer tank 3, the collection branch valve 14 on the collection branch pipe 13 is opened, and a solvent is supplied to the crude glycolide collection tank 4 through the solvent supply assembly for solvent flushing. If there is solid block deposition, the stirring breaker 10 is simultaneously turned on to break the solid block deposition and wash out the residual impurities to the next process; after the cleaning is completed, the buffer tank feed valve 23 is opened again.

[0090] In the above embodiment, the solvent in the solvent supply assembly is a good solvent for glycolide, and the solvent type is at least one of lower alcohols, ethers, esters, etc. For example, methyl glycolate, ethyl glycolate, ethanol, isopropanol, methyl acetate, ethyl acetate, butyl acetate, etc. Preferably, the solvent in the solvent supply assembly and the spraying medium are the same medium. The temperature of the solvent can be room temperature of 20°C - saturated boiling point temperature, and the solvent supply assembly further includes a heater for heating the solvent.

[0091] This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0092] The following are more detailed implementation cases to further illustrate the technical solution of the present invention and the technical effects that can be obtained through the following implementation cases.

[0093] In the following embodiments, if there is no special description of raw material reagents or treatment techniques, it means that they are all conventional commercially available products or conventional treatment techniques in the art.

[0094] Example 1

[0095] As Figure 1 shown in a crude glycolide collection system: A mixed material of polyglycolic acid with a weight average molecular weight of about 34,000 and stannous octoate (mass fraction 0.5%) is introduced into the ring-forming reactor 1 in batches, and a ring-opening reaction is carried out at about 240°C and about 200 Pa absolute pressure. The generated glycolide vapor is introduced into the glycolide condenser 2. The inlet temperature of the cooling medium of the glycolide condenser 2 is 80°C, and the outlet temperature of the cooling medium is controlled at 82 - 83°C. The output of the glycolide condensate is about 30 kg / hr; the secondary condenser 19 is a shell-and-tube heat exchanger, and the cooling medium circulation of the shell-and-tube heat exchanger is turned on, and the inlet temperature of the cooling medium is 1°C; the internal pressures of the glycolide condenser 2 and the secondary condenser 19 are close to the internal pressure of the ring-forming reactor 1.

[0096] The collection tank feed valve 24 is closed. After the glycolide condensate in the crude glycolide buffer tank 3 reaches a certain liquid level, the collection tank feed valve 24 is opened, and the valve opening is adjusted to allow the glycolide condensate in the crude glycolide buffer tank 3 to flow into the crude glycolide collection tank 4, while keeping the liquid level in the crude glycolide buffer tank 3 relatively stable; the temperature in the crude glycolide buffer tank 3 is maintained at 85 °C, and the crude glycolide collection tank 4 is pre-stored with 50% (volume fraction, the same below) of ethyl acetate, and the temperature in the crude glycolide collection tank 4 is maintained at 65 °C.

[0097] Spray cleaning is carried out once every 6 hours. The spray medium is ethyl acetate at about 80 °C. The total consumption of ethyl acetate is about 3 kg / hr, and the spray duration is controlled within 10 - 30 seconds. During the spray cleaning process, the flow rate of the cooling medium of the secondary condenser 19 is adjusted to control the outlet temperature of its cooling medium at 2 - 5 °C. The liquid-phase material condensed by the secondary condenser 19 flows into the liquid storage tank 20. After the spray ends, the system can resume the stable production state after 1 minute.

[0098] After 5 times of spray cleaning, the liquid stored in the liquid storage tank 20 is introduced into the distillation tower, that is, the gas-liquid separator 21, and vacuum distillation is carried out at an absolute pressure of 80 kPa and 70 °C. The ethyl acetate obtained by distillation returns to the steam spray device 22 through the pipeline.

[0099] Example 2

[0100] As Figure 1 shown, a crude glycolide collection system: A mixed material of polyglycolic acid with a weight average molecular weight of about 34,000 and stannous octoate (mass fraction 0.5%) is introduced into the ring-forming reactor 1 in batches, and a depolymerization and cyclization reaction is carried out at about 260 °C and an absolute pressure of about 1000 Pa. The generated glycolide vapor is introduced into the glycolide condenser 2. The inlet temperature of the cooling medium of the glycolide condenser 2 is 85 °C, and the outlet temperature of the cooling medium is 86 - 88 °C. The output of the glycolide condensate is about 25 kg / hr; the secondary condenser 19 is a spray tower, and the cooling medium (methyl glycolate) of the spray tower is circulated and opened, and the inlet temperature of the cooling medium is about 5 °C; the internal pressures of the glycolide condenser 2 and the secondary condenser 19 are close to the internal pressure of the ring-forming reactor 1.

[0101] The collection tank feed valve 24 is closed. After the glycolide condensate in the crude glycolide buffer tank 3 reaches a certain liquid level, the collection tank feed valve 24 is opened, and the valve opening is adjusted to allow the glycolide condensate in the crude glycolide buffer tank 3 to flow into the crude glycolide collection tank 4, while keeping the liquid level in the crude glycolide buffer tank 3 relatively stable; the temperature in the crude glycolide buffer tank 3 is maintained at 85 °C, and the crude glycolide collection tank 4 is pre-stored with 50% (volume fraction, the same below) of methyl glycolate, and the temperature in the crude glycolide collection tank 4 is maintained at 70 °C.

[0102] Spray cleaning is carried out once every 8 hours. The spray medium is methyl glycolate at about 130 °C. The total consumption of methyl glycolate is about 5 kg / hr. After methyl glycolate enters the glycolide condenser 2, it flashes into steam under negative pressure. The spray duration is controlled within 2 - 3 minutes. During the spray cleaning process, adjust the flow rate of the cooling medium in the spray tower to control the outlet temperature of the cooling medium at 7 - 9 °C. Methyl glycolate flows into the storage tank 20. After the spray is over, the system can resume the stable production state after 1 minute.

[0103] After 4 times of spray cleaning, the liquid stored in the storage tank 20 is introduced into the distillation tower, i.e., the gas-liquid separator 21, and vacuum distillation is carried out at an absolute pressure of 80 kPa and 140 °C. The isopropanol obtained by distillation returns to the steam spray device 22 through the pipeline.

[0104] Example 3

[0105] As Figure 2 shown, a crude glycolide collection system: A mixed material of polyglycolic acid with a weight-average molecular weight of about 16,000 and stannous lactate (mass fraction 0.3%) is introduced into the ring-forming reactor 1 in batches, and a depolymerization cyclization reaction is carried out at about 260 °C and an absolute pressure of about 1000 Pa. The generated glycolide steam is introduced into the glycolide condenser 2. The inlet temperature of the cooling medium of the glycolide condenser 2 is 95 °C, and the outlet temperature of the cooling medium is 97 - 99 °C. The output of the glycolide condensate is about 40 kg / hr; The secondary condenser 19 is a shell-and-tube heat exchanger, and the cooling medium circulation of the shell-and-tube heat exchanger is turned on, and the inlet temperature of the cooling medium is 2 °C; The internal pressures of the glycolide condenser 2 and the secondary condenser 19 are close to the internal pressure of the ring-forming reactor 1.

[0106] The buffer tank feed valve 23 is opened, and the collection tank feed valve 24 is closed. After the glycolide condensate in the crude glycolide buffer tank 3 reaches the nozzle of the overflow pipe 6, it flows into the crude glycolide collection tank 4 through the overflow pipe 6. A crude glycolide collection tank 4 with a stirring function of 2.0 m 3 is used. 50% ethyl acetate is pre-stored in the crude glycolide collection tank 4; The temperature in the crude glycolide buffer tank 3 is maintained at 85 °C, and the temperature in the crude glycolide collection tank 4 is maintained at 65 °C.

[0107] Spray and clean once every 3 hours. The spray medium is ethyl acetate at about 130°C. The total consumption of ethyl acetate is about 5 kg / hr. The spray duration is controlled within 1 - 2 minutes. During the spray cleaning process, adjust the flow rate of the cooling medium of the secondary condenser 19 to control the outlet temperature of its cooling medium at 3 - 5°C. The liquid-phase material condensed by the secondary condenser 19 flows into the storage tank 20. After the spray ends, the system can resume the stable production state after 1 minute. After 3 times of spray cleaning, introduce the liquid stored in the storage tank 20 into the distillation tower, i.e., the gas-liquid separator 21, and conduct vacuum distillation at an absolute pressure of 80 kPa and 70°C. The ethyl acetate obtained by distillation returns to the steam spray device 22 through a pipeline.

[0108] Remove slag once every 4 hours. When removing slag, close the buffer tank feed valve 23 and open the collection tank feed valve 24. After the glycolide condensate stored in the crude glycolide buffer tank 3 is discharged, open the slag discharge port 8 and start the slag removal device to move the scraper in the direction of the slag discharge port 8. After moving back and forth 2 times, close the slag discharge port 8. Then open the buffer branch valve 12 and introduce ethyl acetate at 50°C for cleaning at a flow rate of 100 kg / hr and a cleaning time of 3 min. The cleaning liquid is discharged into the crude glycolide collection tank 4. After the cleaning is completed, close the collection tank feed valve 24 and open the buffer tank feed valve 23 to continue collecting glycolide condensate.

[0109] After the collection amount in the crude glycolide collection tank 4 reaches 80% of the tank volume, start the transfer pump to output the glycolide solution to the subsequent recrystallization unit. After the glycolide solution is pumped out, close the buffer tank feed valve 23, open the collection branch valve 14, introduce ethyl acetate at 50°C for cleaning, start stirring, at a flow rate of 100 kg / hr and a cleaning time of 5 min. After the cleaning is completed, close the transfer pump, close the collection branch valve 14, and open the buffer tank feed valve 23 to continue collecting glycolide condensate.

[0110] Example 4

[0111] As Figure 2 A crude glycolide collection system as shown: Batch-introduce a mixed material of polyglycolic acid with a weight-average molecular weight of about 40,000 and stannous lactate (mass fraction 1%) into the ring-forming reactor 1, and conduct a depolymerization and cyclization reaction at about 280°C and an absolute pressure of about 1000 Pa. The generated glycolide vapor is introduced into the glycolide condenser 2. The inlet temperature of the cooling medium of the glycolide condenser 2 is 100°C, and the outlet temperature of the cooling medium is 102 - 104°C. The output of the glycolide condensate is about 40 kg / hr. The secondary condenser 19 is a spray tower, and the cooling medium (methyl glycolate) of the spray tower is circulated and turned on. The inlet temperature of the cooling medium is about 5°C. The internal pressures of the glycolide condenser 2 and the secondary condenser 19 are close to the internal pressure of the ring-forming reactor 1.

[0112] The buffer tank feed valve 23 is opened, and the collection tank feed valve 24 is closed. After the glycolide condensate in the crude glycolide buffer tank 3 reaches the nozzle of the overflow pipe 6, it flows into the crude glycolide collection tank 4 through the overflow pipe 6, with a height of 2.0 m 3 The crude glycolide collection tank 4 with a stirring function pre-stores 50% methyl glycolate; the temperature in the crude glycolide buffer tank 3 is maintained at 85 °C, and the temperature in the crude glycolide collection tank 4 is maintained at 80 °C.

[0113] It is sprayed and cleaned once every 4 hours. The spraying medium is methyl glycolate at about 150 °C. The total consumption of methyl glycolate is about 4 kg / hr, and the spraying duration is controlled within 30 seconds to 1 minute. During the spraying and cleaning process, the flow rate of the cooling medium in the spray tower is adjusted to control the outlet temperature of the cooling medium at 3 - 5 °C. The methyl glycolate flowing down from the spray flows into the liquid storage tank 20. After the spraying is completed, the system can resume the stable production state after 1 minute; after 4 times of spraying and cleaning, the liquid stored in the liquid storage tank 20 is introduced into the distillation tower, that is, the gas-liquid separator 21, and vacuum distillation is carried out at an absolute pressure of 80 kPa and 140 °C. The methyl glycolate obtained by distillation returns to the steam spraying device 22 through the pipeline;

[0114] The slag is removed once every 4 hours. When removing the slag, the buffer tank feed valve 23 is closed, and the collection tank feed valve 24 is opened. After the glycolide condensate stored in the crude glycolide buffer tank 3 is discharged, the slag discharge port 8 is opened, and the slag removal device is started to move the scraper in the direction of the slag discharge port 8. After moving back and forth 2 times, the slag discharge port 8 is closed; then the buffer branch valve 12 is opened to introduce methyl glycolate at 70 °C for cleaning, with a flow rate of 150 kg / hr and a cleaning time of 2 min. The cleaning liquid is discharged into the crude glycolide collection tank 4. After the cleaning is completed, the collection tank feed valve 24 is closed, and the buffer tank feed valve 23 is opened to continue collecting the glycolide condensate;

[0115] After the collection amount in the crude glycolide collection tank 4 reaches 80% of the tank volume, the transfer pump is started to output the glycolide solution to the subsequent recrystallization unit. After the glycolide solution is pumped out, the buffer tank feed valve 23 is closed, the collection branch valve 14 is opened to introduce methyl glycolate at 70 °C for cleaning, the stirring is started, with a flow rate of 130 kg / hr and a cleaning time of 3 min. After the cleaning is completed, the transfer pump is closed, the collection branch valve 14 is closed, and the buffer tank feed valve 23 is opened to continue collecting the glycolide condensate.

[0116] The crude glycolide collection system in this Example 1 - 4 greatly reduces the problem of blockage inside the condenser. This system can operate continuously and stably for more than 30 days. If the online steam spraying and cleaning of the glycolide condenser 2 is not carried out, when the system runs for 72 hours, the inside of the glycolide condenser 2 has been blocked, and the gaseous glycolide no longer evaporates.

[0117] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. Obviously, those who are familiar with the technology in this field can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A crude glycolide collection system, characterized in that, The collection system includes: A glycolide condenser (2) for condensing gaseous glycolide to obtain a glycolide condensate. The glycolide condenser (2) includes a condenser body and a heat exchange tube group (15) disposed inside the condenser body. The heat exchange tube group (15) is connected to an external circulation heat exchange unit. A gas phase inlet and a spray pipe (18) are provided at the lower part of the condenser body, and the spray port of the spray pipe (18) faces the bottom of the condenser body; A steam spraying device (22) connected to the spray pipe (18) for periodically outputting a spraying medium through the spray pipe (18) to perform steam spraying cleaning on the inside of the glycolide condenser (2); A secondary condenser (19) connected to the gas phase outlet at the top of the glycolide condenser (2) for receiving the spraying medium steam output by the glycolide condenser (2) and condensing the spraying medium steam to obtain a spraying medium mixture; A vacuum device (17) connected to the secondary condenser (19).

2. The crude glycolide collection system according to claim 1, wherein The collection system further includes: A liquid storage tank (20) connected to the liquid phase outlet at the bottom of the secondary condenser (19) for receiving and storing the spraying medium mixture; A gas-liquid separator (21) connected to the liquid storage tank (20) and the steam spraying device (22) respectively for vaporizing the spraying medium mixture, and the vaporized spraying medium enters the steam spraying device (22); The secondary condenser (19), the liquid storage tank (20), and the gas-liquid separator (21) are arranged with a height difference, and the installation heights decrease in sequence.

3. The crude glycolide collection system according to claim 1 or 2, characterized in that, The collection system further includes: A crude glycolide buffer tank (3) connected to the glycolide condenser (2) for receiving and storing the glycolide condensate. An overflow pipe (6) is provided on the upper side of the crude glycolide buffer tank (3), and a discharge port is provided at the bottom of the crude glycolide buffer tank (3). The pipeline connecting the glycolide condenser (2) and the crude glycolide buffer tank (3) extends into the inside of the crude glycolide buffer tank (3), and the pipeline outlet of the pipeline is located below the pipe orifice of the overflow pipe (6). A filter screen (5) is provided between the pipeline outlet of the pipeline and the discharge port; A crude glycolide collection tank (4) connected to the overflow pipe (6) and connected to the bottom discharge port of the crude glycolide buffer tank (3) through a collection tank inlet valve (24) for receiving the glycolide condensate in the crude glycolide buffer tank (3).

4. The crude glycolide collection system according to claim 3, characterized in that, A liquid collection area (16) is provided below the heat exchange tube group (15) in the condenser body. The gas phase inlet and the spray pipe (18) are located between the heat exchange tube group (15) and the liquid collection area (16). A buffer tank inlet valve (23) is provided on the pipeline connecting the glycolide condenser (2) and the crude glycolide buffer tank (3); The crude glycolide buffer tank (3) is provided with a slag cleaning device for cleaning and discharging the solid slag on the filter screen (5). The slag cleaning device comprises a scraper (7) arranged on the filter screen (5) for moving, a power member for driving the scraper (7) to move, and a slag discharge port (8) provided on the crude glycolide buffer tank (3) and located at the end point of the scraper movement. When the slag cleaning device is in operation, the buffer tank feed valve (23) remains closed, and the glycolide condensate is stored in the liquid collection area (16).

5. The crude glycolide collection system according to claim 4, characterized in that, The collection system also includes: a solvent supply assembly, used for conveying solvent to the crude glycolide buffer tank (3) and the crude glycolide collecting tank (4), the solvent supply assembly comprising a solvent main pipe connected to a solvent source, a buffer branch pipe (11) connected to the solvent main pipe and the top of the crude glycolide buffer tank (3), a collecting branch pipe (13) connected to the solvent main pipe and the top of the crude glycolide collecting tank (4), a buffer branch pipe valve (12) arranged on the buffer branch pipe (11), and a collecting branch pipe valve (14) arranged on the collecting branch pipe (13); And / or, the crude glycolide collecting tank (4) is provided with a stirring and breaking device (10).

6. A cleaning method based on the crude glycolide collection system according to any one of claims 1 to 5, characterized in that, include: The glycolide condenser (2) is used to condense the gaseous glycolide to obtain glycolide condensate, wherein the absolute pressure of the glycolide condenser (2) is 100 to 5000 Pa, and the inlet temperature of the cooling medium entering the heat exchange tube group (15) is 60 to 120° C.; During the condensation of the gaseous glycolide, a spray medium is periodically output through a steam spray device (22) to steam spray and clean the interior of the glycolide condenser (2). The spray medium steam enters the secondary condenser (19) from the top of the glycolide condenser (2) and is condensed in the secondary condenser (19) to obtain a spray medium mixed liquid.

7. The cleaning method according to claim 6, characterized in that, The spray medium is selected from one of methyl glycolate, ethyl glycolate, ethanol, isopropanol, methyl acetate, ethyl acetate, butyl acetate, cyclohexane or cyclohexanone; And / or, the spraying medium output by the steam spraying device (22) is a saturated liquid or steam of the spraying medium.

8. The cleaning method according to claim 7, characterized in that The spraying cycle is once every 2 to 6 hours, or spraying is performed when the pressure difference between the top and the bottom of the glycolide condenser (2) exceeds a pressure difference threshold; The amount of the spraying medium each time is 1 / 20 to 1 / 5 of the hourly output of glycolide condensate; the spraying time is 5 seconds to 5 minutes.

9. The cleaning method according to claim 6, wherein The cleaning method further comprises: The spray medium mixed liquid is made to flow into a liquid storage tank (20), the spray medium mixed liquid in the liquid storage tank (20) is transported to a gas-liquid separator (21), the spray medium is vaporized by heating, and the vaporized spray medium enters the steam spray device (22).

10. The cleaning method according to any one of claims 6 to 9, characterized in that During the condensation of the gaseous glycolide, the connection between the bottom discharge port of the crude glycolide buffer tank (3) and the crude glycolide collection tank (4) is disconnected, so that the glycolide condensate in the crude glycolide buffer tank (3) flows into the crude glycolide collection tank (4) through the overflow pipe (6); When slag cleaning is required, disconnect the connection between the glycolide condenser (2) and the crude glycolide buffer tank (3), and temporarily store the glycolide condensate in the liquid collection area (16) of the glycolide condenser (2); connect the bottom discharge port of the crude glycolide buffer tank (3) to the crude glycolide collection tank (4). After the remaining condensate in the crude glycolide buffer tank (3) enters the crude glycolide collection tank (4) through the bottom discharge port, start the slag cleaning device to clean and discharge the solid slag on the filter screen (5) in the crude glycolide buffer tank (3).

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