Crude glycolide collection system and collection method

Abstract

The invention relates to a crude glycolide collecting system. Comprising a glycolide condenser for condensing gas-phase glycolide to obtain glycolide condensate, a crude glycolide buffer tank for receiving and storing the glycolide condensate, a crude glycolide collecting tank for receiving the glycolide condensate in the crude glycolide buffer tank, and a secondary condenser for receiving non-condensable gas output by the glycolide condenser, the vacuum device is connected with a gas phase outlet of the secondary condenser; an overflow pipe is arranged on the side surface of the upper part of the crude glycolide buffer tank, and the crude glycolide buffer tank is connected with the crude glycolide collecting tank through the overflow pipe; a filter screen is also arranged in the crude glycolide buffer tank. Compared with the prior art, the upper part of the crude glycolide buffer tank is connected with the crude glycolide collecting tank through the overflow pipe, so that glycolide condensate condensed by the glycolide condenser flows into the crude glycolide collecting tank in an overflow manner, and mixed solid impurities slowly settle in the crude glycolide buffer tank; and blockage caused by entering a downstream pipeline is avoided.

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 collection method. Background Art

[0002] Polyglycolic acid, also known as polyglycolide (PGA for short), is a biodegradable aliphatic polymer, which can be hydrolyzed under the catalysis of microorganisms or enzymes or acids and alkalis in organisms, and finally forms carbon dioxide and water, and 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] The production of glycolide uses glycolic acid or glycolic acid esters as reaction materials, prepares glycolic acid oligomers through polycondensation, then depolymerizes and cyclizes the glycolic acid oligomers, and the generated gaseous glycolide is evaporated from the ring-forming reactor under high temperature and high vacuum, and is transported to the refining unit for subsequent purification after condensation to obtain refined glycolide.

[0004] However, in actual production, gaseous glycolide is easily entrained by gas-liquid when evaporated from the ring-forming reactor, and solid small particles enter the glycolide gas, and then enter the conveying pipeline along with the glycolide condensate, affecting the conveying. After the glycolide condenser operates continuously for a period of time, some solid impurities will adhere to the wall of the condenser tube, and these solid impurities will also be washed out along with the glycolide condensate and enter the conveying pipeline, affecting the conveying. Summary of the Invention

[0005] The purpose of the present invention is to provide a crude glycolide collection system and a collection method, which are used to solve the problem that the solid impurities contained in the gas-phase glycolide discharged from the ring-forming reactor enter the conveying pipeline and affect the conveying.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The first aspect of the present invention provides a crude glycolide collection system, including:

[0008] A glycolide condenser, which is used to condense gaseous glycolide to obtain glycolide condensate. The glycolide condenser includes a condenser body and a heat exchange tube group arranged in the condenser body, and the heat exchange tube group is connected to an external circulation heat exchange unit;

[0009] The crude glycolide buffer tank is connected to the glycolide condenser and is used to receive and store the glycolide condensate. An overflow pipe is provided on the upper side of the crude glycolide buffer tank, and a discharge port is provided 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 outlet of the pipeline is located below the orifice of the overflow pipe. A filter screen is provided between the outlet of the pipeline and the bottom discharge port.

[0010] The crude glycolide collection tank is connected to the overflow pipe and is also connected to the bottom discharge port of the crude glycolide buffer tank through a collection tank feed valve, and is used to receive the glycolide condensate in the crude glycolide buffer tank.

[0011] The secondary condenser is connected to the gas-phase outlet at the top of the glycolide condenser and is used to receive the non-condensable gas output by the glycolide condenser.

[0012] The vacuum device is connected to the gas-phase outlet of the secondary condenser.

[0013] In some specific embodiments, both the crude glycolide buffer tank and the crude glycolide collection tank are provided with heat-insulating interlayers, which are used to keep the temperature inside the crude glycolide buffer tank and the crude glycolide collection tank at a set temperature.

[0014] In some specific embodiments, the length of the pipeline connecting the liquid-phase outlet of the glycolide condenser and the feed port of the crude glycolide buffer tank is more than 10 m.

[0015] In some specific embodiments, a liquid collection area is provided below the heat exchange tube group of the condenser body, the gas-phase inlet of the condenser body is 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.

[0016] The crude glycolide buffer tank is equipped 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 buffer tank body 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.

[0017] In some specific embodiments, the power member is a piston rod cylinder.

[0018] In some specific embodiments, the collection system further includes a solvent supply assembly for outputting a solvent to the crude glycolide buffer tank and the crude glycolide collection tank. The solvent supply assembly includes a main solvent pipe communicating with a solvent source, a buffer branch pipe communicating the main solvent pipe with the top of the crude glycolide buffer tank, a collection branch pipe communicating the main solvent pipe with the top of the crude glycolide collection tank, a buffer branch valve provided on the buffer branch pipe, and a collection branch valve provided on the collection branch pipe.

[0019] In some specific embodiments, a stirring crusher is provided inside the crude glycolide collection tank.

[0020] In some specific embodiments, a spray pipe is further provided inside the condenser body. The spray pipe is located between the heat exchange tube group and the liquid collection area, and the injection port of the spray pipe faces the bottom of the condenser body.

[0021] The collection system further includes a steam spraying device connected to the spray pipe for periodically outputting a spraying medium to perform steam spraying and cleaning on the inside of the glycolide condenser.

[0022] In some specific embodiments, the collection system further includes:

[0023] A liquid storage tank connected to the liquid phase outlet at the bottom of the secondary condenser for receiving and storing the spraying medium mixture.

[0024] A gas-liquid separator connected to the liquid storage tank and the steam spraying device respectively for vaporizing the spraying medium mixture, and the vaporized spraying medium enters the steam spraying device.

[0025] 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.

[0026] The second aspect of the present invention provides a method for collecting crude glycolide based on the above system, including the following steps:

[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, disconnect the connection between the bottom discharge port of the crude glycolide buffer tank and the crude glycolide collection tank, and the glycolide condensate enters the crude glycolide buffer tank for accumulation and storage.

[0029] After the liquid level of the crude glycolide buffer tank reaches the pipe orifice of the overflow pipe, the glycolide condensate flows into the crude glycolide collection tank through the overflow pipe.

[0030] 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, so that the remaining condensate in the crude glycolide buffer tank enters the crude glycolide collection tank through the bottom discharge port;

[0031] 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 mesh in the crude glycolide buffer tank.

[0032] In some specific embodiments, after slag cleaning is completed, a solvent is output to the crude glycolide buffer tank to clean the inside of the crude glycolide buffer tank, and the cleaning liquid enters the crude glycolide collection tank or is discharged externally through the bottom discharge port; after 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.

[0033] In some specific embodiments, after the material in the crude glycolide collection tank is discharged, 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, and a solvent is output to the crude glycolide collection tank to clean the inside of the crude glycolide collection tank;

[0034] After cleaning is completed, the glycolide condenser is reconnected to the crude glycolide buffer tank.

[0035] In some specific embodiments, during the condensation of gaseous glycolide, a spraying medium is periodically output through a steam spraying device to perform steam spraying and cleaning on the inside of the glycolide condenser, and the spraying medium steam enters the secondary condenser from the top of the glycolide condenser, and is condensed in the secondary condenser to obtain a spraying medium mixture;

[0036] The spraying 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 is a saturated liquid or steam of the spraying medium.

[0037] In some specific embodiments, the spraying period is once every 2 to 6 hours, or spraying is performed when the pressure difference between the top and bottom of the glycolide condenser exceeds 150 to 200 Pa;

[0038] The dosage of each spraying is 1 / 20 to 1 / 5 of the hourly output of the glycolide condensate; the spraying time is 5 seconds to 5 minutes.

[0039] In some specific embodiments, the collection method further includes: flowing the spray medium mixture into a liquid storage tank, transporting the spray medium mixture in the liquid storage tank to a gas-liquid separator, vaporizing the spray medium by heating, and allowing the vaporized spray medium to enter the steam spray device.

[0040] Compared with the prior art, the present invention has the following characteristics:

[0041] 1. Connect the upper part of the crude glycolide buffer tank and the crude glycolide collection tank through an overflow pipe, so that the glycolide condensate condensed by the glycolide condenser flows into the crude glycolide collection tank by overflow, and the entrained solid impurities slowly settle in the crude glycolide buffer tank, avoiding entering the crude glycolide collection tank and causing blockage of the downstream pipeline;

[0042] 2. A filter screen and a slag discharge port are arranged at the bottom of the crude glycolide buffer tank to separate and collect the solid impurities in the glycolide condensate. The effective filtering effect can be maintained by regularly clearing the slag, and the inside of the crude glycolide buffer tank and the crude glycolide collection tank can be cleaned regularly to avoid the deposition of solid blocks;

[0043] 3. By regularly performing on-line steam spray cleaning on the glycolide condenser, it does not affect the production and collection of glycolide, and there is no need to set two groups of glycolide condensers to be used alternately. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a process flow chart of a crude glycolide condensation and collection system in the present invention;

[0045] Figure 2 is a process flow chart of a crude glycolide condensation and collection system in the present invention;

[0046] DESCRIPTION OF THE REFERENCE NUMERALS:

[0047] 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 crusher, 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 pipeline, 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 DESCRIPTION OF THE EMBODIMENTS

[0048] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] The glycolide in the present invention is crude glycolide, which contains substances such as pure glycolide, linear PGA oligomer, glycolic acid, etc.

[0050] 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 secondary condenser 19 and a vacuum device 17.

[0051] The glycolide condenser 2 is used to condense gaseous glycolide to obtain glycolide condensate. Preferably, it is 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 gaseous 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 gaseous discharge; the heat exchange tube group 15 is connected to an 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.

[0052] The crude glycolide buffer tank 3 is connected to the glycolide condenser 2 and is used to receive and store glycolide condensate. An overflow pipe 6 is arranged on the upper side of the crude glycolide buffer tank 3, and a discharge port is arranged 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 orifice of the overflow pipe 6. A filter screen 5 is arranged between the pipeline outlet of the pipeline and the bottom discharge port. The crude glycolide buffer tank 3 is provided with a heat preservation interlayer for keeping 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 to 100°C.

[0053] The crude glycolide collection tank 4 is connected to the overflow pipe 6 and is also connected to the bottom discharge port of 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 for keeping 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 by 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 to 80°C. When the glycolide collected by the crude glycolide collection tank 4 is glycolide condensate, the temperature inside the crude glycolide collection tank 4 can be set at 80°C to 100°C.

[0054] 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 non-condensable gas output from the glycolide condenser 2. The structure of the secondary condenser 19 can be the same as that of the glycolide condenser 2, which is also a shell-and-tube condenser with an external circulation heat exchange unit; alternatively, the secondary condenser 19 can also be a spray tower. The non-condensable gas output from the glycolide condenser 2 is condensed by the secondary condenser 19. It is only necessary that the inlet temperature of the cooling medium in the secondary condenser 19 is lower than that in the glycolide condenser 2, preferably 30 °C or lower, so as to effectively condense the non-condensable gas output from the glycolide condenser 2 and prevent it from entering the vacuum device.

[0055] The vacuum device 17 is connected to the secondary condenser 19 and is used to provide a negative pressure environment for the system.

[0056] In view of the problem that when the gaseous glycolide evaporates 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 arranged 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, so as to prevent solid impurities from entering the crude glycolide collection tank 4 and causing blockage of the downstream pipeline.

[0057] Furthermore, the length of the pipeline 9 connecting the liquid-phase outlet of the glycolide condenser 2 and the feed inlet 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.

[0058] As a further improvement, a liquid collection area 16 is arranged below the heat exchange tube group 15 of the condenser body, the gas-phase inlet of the condenser body is located between the heat exchange tube group 15 and the liquid collection area 16, and a buffer tank feed valve 23 is arranged 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 scraper 7 to move, and a slag discharge port 8 opened on the buffer tank body and located at the end point of the scraper movement. 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. The power member can be selected as a piston rod cylinder, for example.

[0059] Specifically, when slag cleaning is required, the feed valve 23 of the buffer tank is closed, and the feed valve 24 of the collection tank is opened. First, the crude glycolide is discharged from the bottom discharge port of the crude glycolide buffer tank 3 to the crude glycolide collection tank 4, and solid impurities are further filtered out through the filter screen 5. The slag cleaning device removes the slag on the filter screen 5, specifically including: pushing the scraper 7 to move on the filter screen 5 through the power component, pushing the solid impurities deposited by filtration 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.

[0060] As a further improvement, the collection system further includes a solvent supply component for outputting a solvent to the crude glycolide buffer tank 3 and the crude glycolide collection tank 4. The solvent supply component includes a solvent main pipe communicating with the 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.

[0061] Specifically, when the inside of the crude glycolide buffer tank 3 needs to be cleaned, the buffer branch pipe valve 12 is opened to supply the solvent to the crude glycolide buffer tank 3; when the inside of the crude glycolide collection tank 4 needs to be cleaned, the collection branch pipe valve 14 is opened to supply the solvent to the crude glycolide collection tank 4; when the solvent needs to be introduced into the crude glycolide collection tank 4 to dissolve the glycolide, the collection branch pipe valve 14 can also be opened to supply the solvent to the crude glycolide collection tank 4.

[0062] 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, 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 can be a stirring paddle.

[0063] 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 is that: a spray pipe 18 is further provided inside the condenser body. The spray pipe 18 is located between the heat exchange tube group 15 and the liquid collection area 16, and the spray port of the spray pipe 18 faces the bottom of the condenser body; the collection system further includes a steam spray device 22. The steam spray device 22 selects a storage tank with a temperature control function and is connected to the spray pipe 18 for periodically outputting a spray medium to perform steam spray cleaning on the inside of the glycolide condenser 2.

[0064] 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 and 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 gas 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, thereby solving the problem of easy blockage inside the condenser.

[0065] The secondary condenser 19 is connected to the gas-phase outlet at the top of the glycolide condenser 2, can receive the spraying medium steam output by the glycolide condenser 2, and condenses the spraying medium steam to obtain a mixed liquid of the spraying medium and a small amount of glycolide entrained by the spraying steam. This mixed liquid 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.

[0066] 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.

[0067] In the secondary condenser 19, the spraying medium steam and a small amount of glycolide entrained 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 spraying pipe, and the heavy component, that is, glycolide, is periodically discharged through the liquid-phase outlet of the gas-liquid separator.

[0068] The present invention also provides a collection method for the above-mentioned crude glycolide collection system, including:

[0069] Condensing the gaseous glycolide through the glycolide condenser 2 to obtain glycolide condensate. The absolute pressure of the glycolide condenser 2 is 100 - 5000 Pa, the inlet temperature of the cooling medium introduced into the cooling medium inlet of 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;

[0070] During the condensation of gaseous glycolide, the buffer tank feed valve 23 is opened, and the collection tank feed valve 24 is closed to disconnect the bottom discharge port of the crude glycolide buffer tank 3 from the crude glycolide collection tank 4. The glycolide condensate enters the crude glycolide buffer tank 3 and accumulates therein. After the liquid level reaches the pipe orifice of the overflow pipe 6, the glycolide condensate flows into the crude glycolide collection tank 4 through the overflow pipe 6.

[0071] During the accumulation and storage of the glycolide condensate in the crude glycolide buffer tank 3, solid impurities are deposited on the filter screen 5. Further, the collection method further includes periodically cleaning the residue in the crude glycolide buffer tank 3, specifically including:

[0072] S1: After operating for a certain period of time, start cleaning the residue: close the buffer tank feed valve 23 to disconnect the glycolide condenser 2 from the crude glycolide buffer tank 3, temporarily store the glycolide condensate in the liquid collection area 16 of the glycolide condenser 2, open the collection tank feed valve 24 to connect the bottom discharge port of the crude glycolide buffer tank 3 with the crude glycolide collection tank 4, so that 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 collection tank feed valve 24, and the filter screen 5 filters the flowing glycolide condensate;

[0073] S2: After the glycolide condensate is discharged, open the slag discharge port 8 of the crude glycolide buffer tank 3, 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;

[0074] S3: After the slag cleaning is completed, close the slag discharge port 8, close the collection tank feed valve 24, open the buffer tank feed valve 23, and the crude glycolide buffer tank 3 resumes collecting the glycolide condensate.

[0075] In some specific applications, the solid slag at the bottom of the crude glycolide buffer tank 3 is cleaned regularly, preferably once every 3 to 8 hours. It is also possible to determine whether slag cleaning is required according to 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 required.

[0076] Further, the collection method further includes cleaning the inside of the crude glycolide buffer tank 3, specifically including:

[0077] After slag cleaning is completed, close the slag discharge port 8, then open the buffer branch pipe valve 12 on the buffer branch pipe 11, and supply solvent to the crude glycolide buffer tank 3 through the solvent supply assembly for solvent flushing. The cleaning liquid enters the crude glycolide collection tank 4 or is discharged to the cleaning liquid collection tank through the bottom discharge port of the crude glycolide buffer tank 3 and the collection tank feed valve 24 (the collection tank feed valve 24 is a three-way valve). After the cleaning is completed, close the collection tank feed valve 24 and open the buffer tank feed valve 23.

[0078] Furthermore, the collection method further includes cleaning the inside of the crude glycolide collection tank 4, specifically including:

[0079] After the glycolide condensate or glycolide solution in the crude glycolide collection tank 4 is pumped and transported to the subsequent refining unit, for example, when the collection amount 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 and transported to the subsequent refining unit, then close the buffer tank feed valve 23 to disconnect the connection between the glycolide condenser 2 and the crude glycolide buffer tank 3, open the collection branch pipe valve 14 on the collection branch pipe 13, and supply solvent to the crude glycolide collection tank 4 through the solvent supply assembly for solvent flushing. If there is solid block deposition, simultaneously start the stirring crusher 10 to break the solid block deposition and wash and discharge the residual impurities to the next process; after the cleaning is completed, open the buffer tank feed valve 23 again.

[0080] 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. The temperature of the solvent can be from 20°C (room temperature) to the saturated boiling point temperature, and the solvent supply assembly further includes a heater for heating the solvent.

[0081] As a further improvement, the collection method further includes periodically spray cleaning the glycolide condenser 2, specifically including:

[0082] During the condensation of gaseous glycolide, the steam spray device 22 periodically outputs a spray medium to perform steam spray cleaning on the inside 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 mixture.

[0083] The spray medium mixture flows into the liquid storage tank 20, and the spray medium mixture in the liquid storage tank 20 is transported to the gas-liquid separator 21. The spray medium is vaporized by heating, and the vaporized spray medium enters the steam spray device 22 and is reused for steam spray cleaning.

[0084] In some specific applications, the following process parameters can be adopted for each device:

[0085] Cyclization Reactor 1: The raw material is glycolic acid or a glycolic acid ester oligomer, preferably having a weight average molecular weight of 10,000 to 50,000; the catalyst is selected from at least one of stannous 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.

[0086] 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.

[0087] 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 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 and does not remain in the glycolide condensate.

[0088] The spraying medium can be any organic solvent that is gaseous under the pressure and temperature inside the glycolide condenser 2, for example, saturated liquids and vapors (saturated vapors, superheated vapors) of methyl glycolate, ethyl glycolate, ethanol, isopropanol, methyl acetate, ethyl acetate, butyl acetate, cyclohexane, cyclohexanone, etc. It is preferably a good solvent for glycolide and preferably the same medium as the solvent in the solvent supply component; 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 thermal deterioration of glycolide. The preferred temperature range is 80 to 200 °C.

[0089] 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 and cleaning according to the pressure difference between the upper and lower parts inside the glycolide condenser 2. When the pressure difference between the upper and lower parts inside the glycolide condenser 2 exceeds a threshold value, for example, 200 Pa, start the steam spraying and 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 a pressure difference between the upper and lower parts 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 and cleaning can be started according to the pressure difference between the upper and lower parts inside the glycolide condenser 2, and cleaning should not be carried out when the pressure difference is too large to avoid an unsatisfactory effect of the steam spraying and cleaning.

[0090] In a single spraying, the dosage 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.

[0091] Secondary condenser 19: It can be a shell-and-tube heat exchanger or a spray 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 spray tower, the spray cycle is started while the steam spraying and cleaning are carried out to keep the temperature inside the secondary condenser at -5 to 5 °C, and the spraying liquid and the spraying steam are the same medium.

[0092] This embodiment is implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0093] 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.

[0094] In the following embodiments, unless otherwise specified for raw material reagents or treatment techniques, it means that they are all conventional commercially available products or conventional treatment techniques in the art.

[0095] Example 1

[0096] As Figure 1A crude glycolide collection system is shown as follows: 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 cyclization 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 82 - 83 °C. The internal pressure of the glycolide condenser 2 is close to the internal pressure of the ring-forming reactor 1. The output of the glycolide condensate is about 30 kg / hr. At this stage, the buffer tank feed valve 23 is opened, and the collection tank feed valve 24, the buffer branch pipe 11, and the collection branch pipe valve 14 are closed.

[0097] The glycolide condensate enters the crude glycolide buffer tank 3, and the temperature inside the crude glycolide buffer tank 3 is maintained at 85 °C; after the glycolide condensate in the crude glycolide buffer tank 3 reaches the orifice of the overflow pipe 6, it flows into the crude glycolide collection tank 4 through the overflow pipe 6. 50% (volume fraction, the same below) of ethyl acetate is pre-stored in the crude glycolide collection tank 4, and the temperature inside the crude glycolide collection tank 4 is maintained at 60 °C.

[0098] The slag is removed every 6 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 pipe valve 12 is opened, and ethyl acetate at 40 °C is introduced for cleaning with a flow rate of 100 kg / hr and a cleaning time of 3 min. 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;

[0099] After the collection amount in the crude glycolide collection tank 4 reaches 70% 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 pipe valve 14 is opened, and ethyl acetate at 40 °C is introduced for cleaning. Stirring is started with a flow rate of 100 kg / hr and a cleaning time of 5 min. After the cleaning is completed, the transfer pump is closed, the collection branch pipe valve 14 is closed, and the buffer tank feed valve 23 is opened to continue collecting the glycolide condensate.

[0100] Example 2

[0101] A crude glycolide collection system, compared with Example 1, is different in that: the depolymerization cyclization reaction is carried out at about 260 °C and about 1000 Pa absolute pressure. The inlet temperature of the cooling medium of the glycolide condenser 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 / h; the slag is removed every 10 hours, and after the slag removal is completed, ethyl acetate at 50 °C is introduced to clean the crude glycolide buffer tank.

[0102] After the glycolide solution in the crude glycolide collection tank 4 is pumped out, similarly, ethyl acetate at 50°C is introduced to clean the crude glycolide collection tank 4.

[0103] Example 3

[0104] As Figure 2 A crude glycolide collection system as shown: 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 about 1000 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 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, with the inlet temperature of the cooling medium being 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.

[0105] 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 orifice of the overflow pipe 6, it flows into the crude glycolide collection tank 4 through the overflow pipe 6, and 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.

[0106] Spray cleaning is carried out 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, and the spray duration is controlled within 1 - 2 minutes. During the spray cleaning process, the flow rate of the cooling medium of the secondary condenser 19 is adjusted to control its cooling medium outlet temperature 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, 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 70°C. The ethyl acetate obtained by distillation is returned to the steam spray device 22 through a pipeline.

[0107] Discharge the residue every 4 hours. When discharging the residue, close the feed valve 23 of the buffer tank and open the feed valve 24 of the collection tank. After the glycolide condensate stored in the crude glycolide buffer tank 3 is discharged, open the slag discharge port 8, start the slag discharge device, move the scraper in the direction of the slag discharge port 8, move back and forth twice, and then close the slag discharge port 8; then open the buffer branch valve 12, introduce ethyl acetate at 50°C for cleaning, with a flow rate of 100 kg / hr and a cleaning time of 3 min. Discharge the cleaning solution into the crude glycolide collection tank 4. After the cleaning is completed, close the feed valve 24 of the collection tank and open the feed valve 23 of the buffer tank to continue collecting the glycolide condensate.

[0108] After the collection volume 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 feed valve 23 of the buffer tank, open the collection branch valve 14, introduce ethyl acetate at 50°C for cleaning, start stirring, with a flow rate of 100 kg / hr and a cleaning time of 5 min. After the cleaning is completed, turn off the transfer pump, close the collection branch valve 14, and open the feed valve 23 of the buffer tank to continue collecting the glycolide condensate.

[0109] Example 4

[0110] As Figure 2 shown, a crude glycolide collection system: 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 carry out a depolymerization cyclization reaction at about 280°C and about 1000 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 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) circulation of the spray tower is turned on, 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.

[0111] Open the feed valve 23 of the buffer tank and close the feed valve 24 of the collection tank. 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. Use a crude glycolide collection tank 4 with a stirring function of 2.0 m 3 Pre-store 50% of methyl glycolate in the crude glycolide collection tank 4; keep the temperature in the crude glycolide buffer tank 3 at 85°C and the temperature in the crude glycolide collection tank 4 at 80°C.

[0112] Spray and clean once every 4 hours. The spray medium is methyl glycolate at about 150°C. The total consumption of methyl glycolate is about 4 kg / hr. The spray duration is controlled between 30 seconds and 1 minute. 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 3 - 5°C. The methyl glycolate logistics sprayed down flows into the storage tank 20. After the spray ends, the system can resume the stable production state after 1 minute. After 4 times of spray cleaning, transfer 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 140°C. The methyl glycolate obtained by distillation returns to the steam spray device 22 through a pipeline.

[0113] Remove the slag once every 4 hours. When removing the 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 methyl glycolate at 70°C for cleaning with a flow rate of 150 kg / hr and a cleaning time of 2 minutes. 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 the glycolide condensate.

[0114] 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 methyl glycolate at 70°C for cleaning, start the stirring, with a flow rate of 130 kg / hr and a cleaning time of 3 minutes. After the cleaning is completed, turn off the transfer pump, close the collection branch valve 14, and open the buffer tank feed valve 23 to continue collecting the glycolide condensate.

[0115] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. 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 as disclosed should be within the protection scope of the present invention.

Claims

1. A crude glycolide collection system, characterized in that, Comprising: 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 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 (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 outlet of the pipeline is located below the orifice of the overflow pipe (6). A filter screen (5) is provided between the outlet of the pipeline and the bottom 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); A secondary condenser (19) connected to the gas phase outlet at the top of the glycolide condenser (2) for receiving the non-condensable gas output by the glycolide condenser (2); A vacuum device (17) connected to the gas phase outlet of the secondary condenser (19).

2. The crude glycolide collection system according to claim 1, wherein A liquid collection area (16) is provided below the heat exchange tube group (15) in the condenser body. The gas phase inlet of the condenser body is 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 configured 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 disposed 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 scraper movement. When the slag cleaning device operates, the buffer tank inlet valve (23) remains closed, and the glycolide condensate is stored in the liquid collection area (16).

3. The crude glycolide collection system according to claim 2, characterized in that, The collection system further includes: A solvent supply assembly for outputting 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).

4. The crude glycolide collection system according to claim 3, characterized in that, A stirring crusher (10) is provided inside the crude glycolide collection tank (4).

5. The crude glycolide collection system according to any one of claims 2 to 4, characterized in that, Inside the condenser body, a spray pipe (18) is further provided. The spray pipe (18) is located between the heat exchange tube group (15) and the liquid collection area (16), and the injection port of the spray pipe (18) faces the bottom of the condenser body; The collection system further includes a steam spraying device (22). The steam spraying device (22) is connected to the spray pipe (18) and is used to periodically output a spraying medium to perform steam spraying and cleaning on the inside of the glycolide condenser (2).

6. A method for collecting crude glycolide based on the system according to any one of claims 1 to 5, characterized in that, It includes the following steps: The gaseous 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, and the inlet temperature of the cooling medium introduced into the heat exchange tube group (15) is 60 - 120 °C; 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, and the glycolide condensate enters the crude glycolide buffer tank (3) for accumulation and storage; After the liquid level of the crude glycolide buffer tank (3) reaches the pipe orifice of the overflow pipe (6), the glycolide condensate flows into the crude glycolide collection tank (4) through the overflow pipe (6).

7. The crude glycolide collection method according to claim 6, characterized in that, When slag cleaning is required, the connection between the glycolide condenser (2) and the crude glycolide buffer tank (3) is disconnected. The glycolide condensate is temporarily stored in the liquid collection area (16) of the glycolide condenser (2). The bottom discharge port of the crude glycolide buffer tank (3) is connected to the crude glycolide collection tank (4), so that the remaining condensate in the crude glycolide buffer tank (3) enters the crude glycolide collection tank (4) through the bottom discharge port; After the remaining condensate in the crude glycolide buffer tank (3) enters the crude glycolide collection tank (4) through the bottom discharge port, the slag cleaning device is started to clean and discharge the solid slag on the filter net (5) inside the crude glycolide buffer tank (3).

8. The crude glycolide collection method according to claim 7, wherein After the slag cleaning is completed, a solvent is output to the crude glycolide buffer tank (3) to perform solvent cleaning on the inside of the crude glycolide buffer tank (3). The cleaning liquid enters the crude glycolide collection tank (4) through the bottom discharge port or is discharged externally; After the cleaning is completed, the connection between the bottom discharge port of the crude glycolide buffer tank (3) and the crude glycolide collection tank (4) is disconnected, and the glycolide condenser (2) and the crude glycolide buffer tank (3) are reconnected.

9. The crude glycolide collection method according to claim 8, wherein After the material in the crude glycolide collection tank (4) is discharged, the connection between the glycolide condenser (2) and the crude glycolide buffer tank (3) is disconnected. The glycolide condensate is temporarily stored in the liquid collection area (16) of the glycolide condenser (2). A solvent is output to the crude glycolide collection tank (4) to perform solvent cleaning on the inside of the crude glycolide collection tank (4); After the cleaning is completed, the glycolide condenser (2) and the crude glycolide buffer tank (3) are reconnected.

10. The method for collecting crude glycolide according to any one of claims 6 - 9, characterized in that During the condensation of gaseous glycolide, the inside of the glycolide condenser (2) is periodically cleaned by steam spraying with a spraying medium output by a steam spraying device (22). The spraying medium steam enters the secondary condenser (19) from the top of the glycolide condenser (2), and a spraying medium mixed liquid is obtained by condensation in the secondary condenser (19). The spraying 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.

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