Glycolide condensing system and method for condensing glycolide gas phase material

Abstract

The application provides a glycolide condensing system and a method for condensing glycolide gas-phase materials. The glycolide condensing system can condense glycolide in the glycolide gas-phase materials and avoid the blockage of heat exchangers. The glycolide condensing system comprises a glycolide condenser for multi-stage spray condensation of glycolide gas-phase materials with methyl glycolate; a tail gas conveying pipe for conveying tail gas in the glycolide condenser to the outside and spraying methyl glycolate in the process of tail gas flow; a tail gas washing tank for receiving the tail gas and spraying methyl glycolate to the tail gas to obtain washed tail gas and washing liquid; a tail gas separation device for cooling and gas-liquid separation of the washed tail gas to obtain non-condensable gas and separation liquid containing methyl glycolate; and a slurry separation device for solid-liquid separation of glycolide slurry to obtain glycolide solid-phase materials and liquid-phase materials containing methyl glycolate.

Description

Technical Field

[0001] This invention relates to the field of condensation and cooling technology for glycolide gaseous materials, specifically to a glycolide condensation system and a method for condensing glycolide gaseous materials. Background Technology

[0002] Polyglycolic acid (PGA), as a fully biodegradable material, degrades under mild conditions, rapidly breaking down into carbon dioxide and water in the natural environment under the action of water and microorganisms. PGA also exhibits excellent degradation performance in seawater, with degradation products harmless to humans and the environment. PGA can be used to make disposable household items such as toothbrushes, spoons, cutlery, and plastic bags, and is widely used in the food, beverage, and packaging industries. When used in combination with other biodegradable materials, the degradation performance of the resulting products is even better. Furthermore, PGA possesses good biocompatibility and extremely high mechanical strength, making it widely applicable in high-end fields such as medical applications and underground unconventional oil and gas extraction. PGA is synthesized from glycolide through ring-opening polymerization under the action of a catalyst. Therefore, glycolide is a key raw material for PGA preparation, and the quality of glycolide (purity, water and acid content, etc.) has a significant impact on the quality of PGA products. Substandard glycolide cannot produce qualified PGA products, let alone meet the requirements for polymerization. Therefore, the primary task in producing glycolide products is to purify glycolide. The raw material used for purifying glycolide is crude glycolide. In the process of preparing crude glycolide, the gaseous glycolide produced in the previous stage needs to be heat-exchanged and then heat-exchanged with hot water to become liquid. The liquid glycolide is gradually obtained by solvent dissolution, crystallization, solid-liquid separation and sedimentation separation in the purification system. The solvent is recovered through auxiliary process equipment for reuse.

[0003] Before crude glycolate is dissolved and washed by solvent in the equipment, its gaseous state needs to undergo heat exchange in a heat exchanger. Specifically, the gaseous glycolate enters the heat exchanger and becomes liquid-phase crude glycolate after exchanging heat with hot water. However, the polymer entrained in the crude glycolate will condense into a solid in the heat exchanger, causing blockage of the heat exchanger tubes. This prevents the equipment from operating normally and requires shutdown for maintenance and cleaning of the blockage. Consequently, it affects the long-term, high-load operation of the equipment, making it difficult to guarantee continuous long-term operation, greatly increasing the company's production costs, and seriously affecting the smooth progress of the company's annual production plan. Summary of the Invention

[0004] This invention provides a glycolide condensation system and a method for condensing glycolide gaseous materials. The glycolide condensation system of this invention can condense glycolide in glycolide gaseous materials and helps to avoid heat exchanger blockage.

[0005] To achieve its objective, the present invention provides the following technical solution:

[0006] This invention provides a glycolide condensation system, the glycolide condensation system comprising:

[0007] A glycolide condenser is used to condense glycolide gaseous material through multi-stage spraying with methyl glycolate to obtain glycolide slurry and tail gas.

[0008] The exhaust gas delivery pipe is used to output the exhaust gas from the glycolide condenser to the outside and to spray methyl glycolate during the flow of the exhaust gas.

[0009] An exhaust gas scrubbing tank, connected to the exhaust gas delivery pipe, is used to receive the exhaust gas output from the exhaust gas delivery pipe and spray methyl glycolate onto the exhaust gas to obtain scrubbed exhaust gas and scrubbing liquid.

[0010] An exhaust gas separation device is used to cool and separate the washed exhaust gas output from the exhaust gas scrubbing tank to obtain non-condensable gas and a separation liquid containing methyl glycolate.

[0011] A slurry separation device is used to perform solid-liquid separation on the glycolide slurry obtained from the glycolide condenser to obtain glycolide solid material and liquid material containing methyl glycolate.

[0012] Preferably, it also includes a washing liquid recycling device for recycling the washing liquid obtained from the exhaust gas scrubbing tank to the exhaust gas scrubbing tank, the exhaust gas delivery pipe and / or the glycolide condenser for use in the spraying;

[0013] It also includes a liquid phase material recycling device for recycling the methyl glycolate-containing liquid phase material obtained from the slurry separation device to the glycolide condenser for use in the spraying.

[0014] Specifically, the glycolide condenser is provided with a first sprayer and a second sprayer for spraying methyl glycolate onto the glycolide gas phase material, and the first sprayer and the second sprayer are arranged at different heights and are located above the tail gas outlet of the glycolide condenser.

[0015] Preferably, the exhaust gas delivery pipe is provided with a third sprayer for spraying the methyl glycolate into the exhaust gas flowing into the exhaust gas delivery pipe.

[0016] The exhaust gas delivery pipe is arranged to allow the liquid stream inside the exhaust gas delivery pipe to flow to the glycolide condenser.

[0017] Preferably, the nozzle of the third sprayer is directed toward the exhaust gas outlet of the glycolide condenser.

[0018] Preferably, the exhaust gas scrubbing tank is provided with a fourth sprayer for spraying methyl glycolate onto the exhaust gas entering the exhaust gas scrubbing tank; preferably, the fourth sprayer is located above the exhaust gas inlet of the exhaust gas scrubbing tank.

[0019] In some embodiments, the washing liquid recycling device includes a washing liquid pump and a washing liquid cooler;

[0020] The washing liquid pump is located between the washing liquid cooler and the exhaust gas washing tank, and is used to output the washing liquid in the exhaust gas washing tank to the washing liquid cooler;

[0021] The washing liquid cooler is used to cool and lower the temperature of the washing liquid.

[0022] The washing liquid outlet of the washing liquid cooler is connected to the third sprayer and the fourth sprayer respectively; preferably, the washing liquid outlet of the washing liquid cooler is also connected to the first sprayer or the second sprayer.

[0023] Preferably, the connecting line between the washing liquid pump and the washing liquid cooler is also connected to the methyl glycolate input line.

[0024] In some embodiments, the liquid material recycling device includes a circulating liquid pump and a spray cooler;

[0025] The circulating liquid pump is located between the slurry separation device and the spray cooler, and is used to output the liquid phase material containing methyl glycolate obtained in the slurry separation device to the spray cooler;

[0026] The spray cooler is used to cool and lower the temperature of the liquid material containing methyl glycolate.

[0027] The liquid material outlet of the spray cooler is connected to at least one of the first sprayer and the second sprayer;

[0028] Preferably, the connecting pipeline between the spray cooler and the circulating liquid pump is also connected to the methyl glycolate input pipeline.

[0029] In some embodiments, the slurry separation device includes a separator, a solution pump, a solid-liquid separation device, and a liquid phase material storage tank;

[0030] The separator is connected to the glycolide slurry outlet of the glycolide condenser, and the separator is equipped with a stirrer.

[0031] The inlet of the solution pump is connected to the outlet of the separator;

[0032] The feed inlet of the solid-liquid separation device is connected to the outlet of the solution pump, and is used to perform solid-liquid separation on the glycolide slurry input by the solution pump to obtain glycolide solid material and liquid material containing methyl glycolate.

[0033] The liquid material storage tank is connected to the solid-liquid separation equipment and is used to store the liquid material containing methyl glycolate.

[0034] In some embodiments, the exhaust gas separation device includes an exhaust gas cooler and a separator;

[0035] The exhaust gas cooler is connected to the exhaust gas scrubbing tank and is used to cool the scrubbed exhaust gas output from the exhaust gas scrubbing tank to obtain the non-condensable gas and condensate.

[0036] The separator is used to process the condensate obtained from the exhaust gas cooler to separate the residual non-condensable gas and obtain the separated liquid containing methyl glycolate.

[0037] Preferably, the separator and the exhaust gas scrubbing tank are connected by a separator delivery pipeline, and the separator delivery pipeline is equipped with a separator delivery pump and a separator cooler.

[0038] The present invention also provides a method for condensing glycolide gaseous material using the glycolide condensation system described above, the method comprising the following steps:

[0039] The glycolide gaseous material is fed into the glycolide condenser, and the glycolide gaseous material is sprayed with methyl glycolate in multiple stages to condense the glycolide, thereby obtaining glycolide slurry and tail gas.

[0040] The exhaust gas is fed into the exhaust gas scrubbing tank through the exhaust gas delivery pipe. Methyl glycolate is sprayed onto the exhaust gas as it flows through the exhaust gas delivery pipe. After the exhaust gas flows into the exhaust gas scrubbing tank, methyl glycolate is sprayed onto the exhaust gas to condense the residual glycolide in the exhaust gas, thus obtaining scrubbed exhaust gas and scrubbing liquid.

[0041] The washed exhaust gas is sent to the exhaust gas separation device for cooling and gas-liquid separation to obtain non-condensable gas and a separation liquid containing methyl glycolate.

[0042] The glycolide slurry is fed into a slurry separation device for solid-liquid separation to obtain glycolide solid material and methyl glycolate liquid material.

[0043] Preferably, the liquid phase material in the exhaust gas delivery pipe is returned to the glycolide condenser;

[0044] Preferably, the washing liquid is recycled to the tail gas washing tank, the tail gas conveying pipe and / or the glycolide condenser through a washing liquid recycling device for continued use in the spraying; the liquid phase material containing methyl glycolate is recycled to the glycolide condenser through a liquid phase material recycling device for continued use in the spraying.

[0045] The technical solution provided by this invention has the following beneficial effects:

[0046] The glycolide condensation system of this invention involves multi-stage spraying of glycolide gaseous material with methyl glycolate in a glycolide condenser, and spraying of the tail gas with methyl glycolate as it flows through the tail gas delivery pipe. After the tail gas enters the tail gas scrubbing tank, it continues to be sprayed with methyl glycolate. Through direct contact heat exchange between methyl glycolate and the material, and through multi-stage spray cooling, the glycolide in the gaseous material is condensed and separated more thoroughly. At the same time, the heat carried by the gaseous glycolide is also indirectly carried away with the methyl glycolate coolant, which helps to avoid the blockage of the inner tubes in the downstream heat exchanger caused by glycolide entering the downstream heat exchanger, and helps to ensure the long-term operation of the system. Attached Figure Description

[0047] Figure 1 The diagram shows a schematic of a glycolide condensation system in one embodiment. Detailed Implementation

[0048] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" as used herein may include any and all combinations of one or more of the associated listed items. Where specific experimental steps or conditions are not specified in the examples, they can be performed according to the corresponding conventional experimental procedures or conditions in this art. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0050] The directional terms such as "upper," "lower," "front," "back," "top," and "bottom," mentioned or potentially used in this specification, are defined relative to the structures shown in the accompanying drawings. These are relative concepts and may therefore vary depending on their location and usage. The terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0051] This invention provides a glycolide condensation system, see [link to documentation]. Figure 1 The system mainly includes a glycolide condenser 2, a tail gas delivery pipe 24, a tail gas scrubbing tank 4, a tail gas separation device 26, and a slurry separation device 25.

[0052] Among them, the glycolide condenser 2 is connected to the upstream glycolide production unit and is used to receive the glycolide gaseous material generated in the upstream production unit. It is then sprayed and condensed in multiple stages with methyl glycolate, so that most of the glycolide in the glycolide gaseous material is condensed, thereby obtaining glycolide slurry and tail gas.

[0053] The exhaust gas delivery pipe 24 has its inlet connected to the exhaust gas outlet of the glycolide condenser 2. It is used to output the exhaust gas in the glycolide condenser 2 to the outside. During the flow of the exhaust gas through the exhaust gas delivery pipe 24, methyl glycolate can be sprayed onto the exhaust gas, so that the glycolide remaining in the exhaust gas can be further condensed.

[0054] The exhaust gas scrubbing tank 4 has its inlet connected to the outlet of the exhaust gas delivery pipe 24. It is used to receive the exhaust gas output from the exhaust gas delivery pipe 24 and spray methyl glycolate into the exhaust gas entering the exhaust gas scrubbing tank 4, so that the glycolide that may remain in the exhaust gas can be further condensed, thereby obtaining the scrubbed exhaust gas and scrubbing liquid, which mainly contains methyl glycolate.

[0055] The exhaust gas separation device 26 is connected to the exhaust gas scrubbing tank 4 and is used to cool and separate the scrubbed exhaust gas output from the exhaust gas scrubbing tank 4 to obtain non-condensable gas and a separation liquid containing methyl glycolate.

[0056] The slurry separation device 25 is connected to the glycolide condenser 2 and is used to perform solid-liquid separation on the glycolide slurry obtained from the glycolide condenser 2, thereby obtaining glycolide solid material and liquid material containing methyl glycolate. The glycolide solid material is crude glycolide, which can be sent to the downstream glycolide purification unit for further processing.

[0057] The glycolide condensation system of this invention involves multi-stage spraying of glycolide gaseous material with methyl glycolate in the glycolide condenser 2, and spraying of the tail gas with methyl glycolate as it flows through the tail gas delivery pipe 24. After the tail gas enters the tail gas scrubbing tank 4, it continues to be sprayed with methyl glycolate. Through direct contact heat exchange between methyl glycolate and the material, and through multi-stage spray cooling, the glycolide in the gaseous material is completely condensed and separated. At the same time, the heat carried by the gaseous glycolide is also indirectly carried away with the methyl glycolate coolant, preventing the glycolide from entering the downstream heat exchanger and causing blockage of the inner tubes. This helps ensure the long-term operation of the system, reduces enterprise production costs, and improves production efficiency.

[0058] Furthermore, the glycolide condensation system of the present invention also includes a washing liquid recycling device for circulating the washing liquid obtained from the tail gas scrubbing tank 4 to the tail gas scrubbing tank 4, the tail gas delivery pipe 24, and / or the glycolide condenser 2 for spraying. The glycolide condensation system of the present invention also includes a liquid phase material recycling device for circulating the methyl glycolate-containing liquid phase material obtained from the slurry separation device 25 to the glycolide condenser 2 for spraying. The system of the present invention can recycle the washing liquid obtained from the tail gas scrubbing tank 4 and the methyl glycolate-containing liquid phase material separated from the slurry separation device 25, which can significantly reduce the amount of fresh methyl glycolate coolant used and lower process costs.

[0059] Preferably, the glycolide condenser 2 is provided with a first sprayer 21 and a second sprayer 22 for spraying methyl glycolate onto the glycolide gaseous material. The first sprayer 21 and the second sprayer 22 are arranged at different heights and are spaced apart. Both the first sprayer 21 and the second sprayer 22 are located above the exhaust gas outlet of the glycolide condenser 2. By arranging the first and second sprayers in this manner, the glycolide gaseous material can be sufficiently condensed, reducing the exhaust gas volume. In some embodiments, the first sprayer 21 and the second sprayer 22 each specifically include multiple spray elements arranged circumferentially along the inner cavity of the glycolide condenser 2.

[0060] Specifically, the exhaust gas delivery pipe 24 is equipped with a third sprayer 23 for spraying methyl glycolate into the exhaust gas flowing into the exhaust gas delivery pipe 24; the exhaust gas delivery pipe 24 is arranged to allow the liquid stream within the exhaust gas delivery pipe 24 to flow towards the glycolide condenser 2, so as to... Figure 1 For example, the exhaust gas delivery pipe 24 is arranged at an upward inclination relative to the glycolide condenser 2, allowing the liquid stream within the exhaust gas delivery pipe 24 to flow naturally into the glycolide condenser 2. Specifically, the third sprayer 23 can be positioned near the exhaust gas outlet of the glycolide condenser 2. Preferably, the nozzle of the third sprayer 23 faces the exhaust gas outlet of the glycolide condenser 2, thereby facilitating counter-current contact between the sprayed methyl glycolate and the exhaust gas, improving the condensation effect. In some embodiments, the third sprayer 23 specifically includes multiple spray elements arranged circumferentially along the inner cavity of the exhaust gas delivery pipe 24.

[0061] Specifically, the exhaust gas scrubbing tank 4 is equipped with a fourth sprayer 41, which sprays methyl glycolate onto the exhaust gas entering the exhaust gas scrubbing tank 4, allowing any residual glycolide in the exhaust gas to be further condensed. Preferably, the fourth sprayer 41 is located above the exhaust gas inlet of the exhaust gas scrubbing tank 4. In some embodiments, the fourth sprayer 41 specifically includes a plurality of spray elements arranged circumferentially along the inner cavity of the exhaust gas scrubbing tank 4.

[0062] Specifically, the washing liquid recycling device includes a washing liquid pump 10 and a washing liquid cooler 3. The washing liquid pump 10 is located between the washing liquid cooler 3 and the exhaust gas scrubbing tank 4, and pumps the washing liquid from the exhaust gas scrubbing tank 4 to the washing liquid cooler 3. The washing liquid cooler 3 is used to cool the washing liquid. The washing liquid outlet of the washing liquid cooler 3 is connected to the third sprayer 23 and the fourth sprayer 41, respectively; in some embodiments, the washing liquid outlet of the washing liquid cooler 3 is also connected to the first or second sprayer. Preferably, the connecting pipeline between the washing liquid pump 10 and the washing liquid cooler 3 is also connected to the methyl glycolate input pipeline 19, through which fresh methyl glycolate can be introduced. Methyl glycolate can be replenished into the system as needed, and replenishing fresh methyl glycolate as needed helps to further prevent the washing liquid cooler 3 from becoming clogged. The washing liquid recycling device described above can cool and reuse washing liquid rich in methyl glycolate, continuing to be used as a coolant for spraying, which can save the consumption of fresh methyl glycolate and reduce costs.

[0063] Specifically, the liquid material recycling device includes a circulating liquid pump 13 and a spray cooler 1. The circulating liquid pump 13 is located between the slurry separation device 25 and the spray cooler 1, and is used to output the liquid material containing methyl glycolate obtained from the slurry separation device 25 to the spray cooler 1. The spray cooler 1 is used to cool and reduce the temperature of the liquid material containing methyl glycolate; the liquid material outlet of the spray cooler 1 is connected to at least one of the first sprayer 21 and the second sprayer 22. Preferably, the connecting pipeline between the spray cooler 1 and the circulating liquid pump 13 is also connected to the methyl glycolate input pipeline 18, through which fresh methyl glycolate can be introduced. Methyl glycolate can be replenished into the system as needed, and replenishing fresh methyl glycolate as needed helps to further prevent the spray cooler 1 from becoming clogged. The liquid material recycling device described above can cool and reuse liquid materials rich in methyl glycolate, continuing to be used as coolant for spraying, thus saving the consumption of fresh methyl glycolate and reducing costs.

[0064] Preferably, the slurry separation device 25 specifically includes a separator 17, a solution pump 14, a solid-liquid separation device 11, and a liquid phase material storage tank 12. The separator 17 is connected to the lactide slurry outlet of the lactide condenser 2. The separator 17 is equipped with a stirrer 15, which receives the lactide slurry obtained from the lactide condenser 2 and uses the stirrer 15 to prevent solid-liquid separation, maintaining good fluidity. The inlet of the solution pump 14 is connected to the outlet of the separator 17, and the outlet of the solution pump 14 is connected to the inlet of the solid-liquid separation device 11, conveying the lactide slurry to the solid-liquid separation device 11. The solid-liquid separation device 11 is used to separate the lactide slurry input by the solution pump 14 into solid and liquid phases, thereby obtaining a lactide solid phase and a liquid phase containing methyl glycolate. The solid-liquid separation device can be, for example, a centrifuge or a filter press (e.g., a rotary drum filter press). The liquid material storage tank 12 is connected to the solid-liquid separation equipment 11 and is used to store liquid materials containing methyl glycolate. Specifically, the liquid material storage tank 12 is connected to the circulating liquid pump 13 of the liquid material recycling device.

[0065] Specifically, the exhaust gas separation device 26 includes an exhaust gas cooler 5 and a separator 8. The exhaust gas cooler 5 is connected to the exhaust gas scrubbing tank 4 and is used to cool the scrubbed exhaust gas output from the scrubbing tank 4, thereby condensing any methyl glycolate that may be entrained in the scrubbed exhaust gas, resulting in non-condensable gas and condensate. The separator 8 is used to perform gas-liquid separation on the condensate obtained from the exhaust gas cooler 5, thereby separating the residual non-condensable gas and obtaining a separated liquid containing methyl glycolate. Preferably, the separator 8 is connected to the exhaust gas scrubbing tank 4 via a separated liquid delivery pipeline. The separated liquid delivery pipeline is equipped with a separated liquid delivery pump 9 and a separated liquid cooler 6, so that the separated liquid containing methyl glycolate is cooled and circulated back to the exhaust gas scrubbing tank 4, and can be reused as the coolant required for spraying via a scrubbing liquid recycling device. Specifically, the non-condensable gas outlets of both the exhaust gas cooler 5 and the separator 8 are connected to a vacuum pump 7 via pipelines, and the non-condensable gas is extracted outside the system by the vacuum pump 7.

[0066] In some embodiments, the outlets of the washing liquid pump 10 and the circulating liquid pump 13 are also connected to the drain line 20, so that a portion of the washing liquid output by the washing liquid pump 10 and a portion of the liquid phase material output by the circulating liquid pump 13 can be discharged out of the system as needed. At the same time, fresh methyl glycolate can be added in conjunction with the methyl glycolate input lines 18 and 19, so that the coolant required for spraying in the system can be updated according to process needs.

[0067] For some specific implementation methods, see Figure 1The second sprayer 22 is located at a position with a larger inner diameter than the glycolide condenser 2. The amount of methyl glycolate required for spraying by the second sprayer 22 is greater than the amount of methyl glycolate required by the first sprayer 21. The liquid material outlet of the spray cooler 1 can be connected to the second sprayer 22. The washing liquid outlet of the washing liquid cooler 3 can be connected to the first sprayer 21, the third sprayer 23 and the fourth sprayer 41.

[0068] In some embodiments, the first sprayer 21 is located on top of the glycolide condenser 2, the second sprayer 22 is located above the glycolide condenser 2 and below the first sprayer 21, and the fourth sprayer 41 is located on top of the exhaust gas scrubbing tank 4.

[0069] In some specific embodiments, the separator 17 is also connected to the middle of the glycolide condenser 2 via a balance line 16. The balance line 16 serves to equalize the pressure difference between the separator 17 and the glycolide condenser 2, which helps to ensure that the glycolide slurry flows from the glycolide condenser 2 into the separator 17 under vacuum.

[0070] This invention also provides a method for condensing glycolide gaseous materials based on the glycolide condensation system described above. Specific details regarding the glycolide condensation system are provided above and will not be repeated here. For any aspects of the method not specifically described, please refer to the corresponding content in the description of the glycolide condensation system above; they will not be repeated here. In this invention, methyl glycolate is used as the coolant required for spraying. The method specifically includes the following steps:

[0071] The gaseous material of glycolide is fed into glycolide condenser 2, and the glycolide gaseous material is sprayed in multiple stages with methyl glycolate to condense the glycolide, so as to obtain glycolide slurry and tail gas.

[0072] The exhaust gas is sent into the exhaust gas scrubbing tank 4 through the exhaust gas delivery pipe 24. Methyl glycolate is sprayed onto the exhaust gas as it flows through the exhaust gas delivery pipe 24. After the exhaust gas flows into the exhaust gas scrubbing tank 4, methyl glycolate is sprayed onto the exhaust gas to condense the residual glycolide in the exhaust gas, so as to obtain the scrubbed exhaust gas and the scrubbing liquid rich in methyl glycolate.

[0073] The washed exhaust gas is sent to the exhaust gas separation device 26 for cooling and gas-liquid separation to obtain a separation liquid containing methyl glycolate and non-condensable gas.

[0074] The glycolide slurry is fed into the slurry separation device 25 for solid-liquid separation to obtain glycolide solid material and methyl glycolate liquid material.

[0075] Preferably, the liquid material in the exhaust gas delivery pipe 24 is returned to the glycolide condenser 2.

[0076] Preferably, the washing liquid is recycled through a washing liquid recycling device to the tail gas scrubbing tank 4, tail gas delivery pipe 24, and / or glycolide condenser 2 for continued use in the spraying process; the liquid phase material containing methyl glycolate is recycled through a liquid phase material recycling device to the glycolide condenser 2 for continued use in the spraying process. For specific details regarding the washing liquid recycling device and the liquid phase material recycling device, please refer to the preceding description. Specifically, the washing liquid is pumped by the washing liquid pump 10 in the washing liquid recycling device to the washing liquid cooler 3 for cooling, and then pumped by the washing liquid cooler 3 to the tail gas scrubbing tank 4, tail gas delivery pipe 24, and / or glycolide condenser 2 for spraying, specifically, for example, to the first sprayer 21, the third sprayer 23, and the fourth sprayer 41. Specifically, the liquid phase material is pumped by the circulating liquid pump 13 of the liquid phase material recycling device to the spray cooler 1 for cooling, and then pumped by the spray cooler 1 to the glycolide condenser 2 for spraying, specifically, for example, to the second sprayer 22.

[0077] The following example illustrates the process of condensing glycolide gaseous materials using the system and method of the present invention:

[0078] See the system used. Figure 1 The gaseous material of glycolide (temperature 190-230℃) from the upstream reaction system enters from the top of glycolide condenser 2. After being cooled by methyl glycolate sprayed by the first sprayer 21 and the second sprayer 22, the glycolide in the condenser is cooled into solid particles and then enters the lower part of glycolide condenser 2. It mixes with methyl glycolate to form glycolide slurry (temperature 60-65℃) and flows into separator 17 by gravity. The pressure difference is balanced by the balance pipeline 16. The condensed glycolide is fully mixed with methyl glycolate by the stirrer 15 in separator 17. Then it is sent to solid-liquid separation equipment 11 by solution pump 14. After solid-liquid separation, crude glycolide is removed from the liquid phase methyl glycolate. The crude glycolide enters the downstream purification unit. The separated liquid methyl glycolate (with a glycolide content of 3-10%) carries away the heat from the glycolide, passes through the liquid material storage tank 12 and the circulating liquid pump 13, and then enters the spray cooler 1 for cooling (temperature 10-20℃) before returning to the glycolide condenser 2. This process prevents glycolide from clogging the tubes in the heat exchanger of the downstream purification unit. Simultaneously, to further prevent glycolide precipitation and blockage in the spray cooler 1, a small amount of fresh methyl glycolate can be added before the spray cooler 1 through the methyl glycolate inlet pipe 18.

[0079] Uncondensed and unseparated lactide inside the lactide condenser 2 is carried by the tail gas into the tail gas delivery pipe 24. The third sprayer 23 in the tail gas delivery pipe 24 sprays methyl glycolate to further cool the lactide, reducing the amount of crude lactide entrained in the tail gas. The liquid material in the tail gas delivery pipe 24 flows into the lactide condenser 2, and the tail gas output from the tail gas delivery pipe 24 enters the tail gas scrubbing tank 4. After being scrubbed and washed by the fourth sprayer 41 at the top of the tail gas scrubbing tank 4, almost all of the uncondensed lactide is removed. The remaining tail gas (which may contain trace amounts of methyl glycolate and glycolate, with glycolate content <1%) enters the tail gas cooler 5. After cooling, the resulting non-condensable gas is extracted by the vacuum pump 7. The condensate obtained from the tail gas cooler 5 enters the separator 8 for further gas-liquid separation. After being pressurized by the separator liquid transfer pump 9 and cooled by the separator liquid cooler 6 (temperature is 10-20℃), it returns to the tail gas scrubbing tank 4. The non-condensable gas coming out from the top of the separator 8 is extracted by the vacuum pump 7.

[0080] The washing liquid (with a glycolide content of 3-5%) in the exhaust gas scrubbing tank 4 is pressurized and output by the washing liquid pump 10, and then cooled by the washing liquid cooler 3 (temperature of 10-20℃) before being transported to the first sprayer 21, the third sprayer 23 and the fourth sprayer 41 to continue to be used as the cooling liquid required for spraying. Similarly, in order to better avoid glycolide precipitation in the washing liquid cooler 3 and blockage, a small amount of fresh glycolate is added before the washing liquid cooler 3 through the methyl glycolate inlet pipeline 19.

[0081] Using the system and method of the present invention, the glycolide gaseous material and methyl glycolate coolant are directly contacted and exchanged for heat through multi-stage spray cooling. The glycolide slurry undergoes solid-liquid separation in the slurry separation device 25, allowing the crude glycolide, which has cooled and solidified into a solid phase, to be separated from methyl glycolate. The separated liquid phase material rich in methyl glycolate, along with the washing liquid obtained in the tail gas scrubbing tank 4, is recycled for spraying. The separated crude glycolide is then sent to a downstream purification unit for further purification operations.

[0082] The system and method of this invention not only enable more thorough condensation and separation of glycolide in the gaseous material, but also indirectly remove the heat carried by the gaseous glycolide along with the methyl glycolate coolant. This helps prevent glycolide from entering the downstream heat exchanger and causing blockage of the tubes inside the heat exchanger, thus eliminating obstacles to ensure long-term operation of the equipment, significantly reducing production costs, and ensuring the smooth progress of the company's production plan. This invention achieves heat exchange through direct contact between methyl glycolate and the material, reducing the inlet resistance of the subsequent vacuum pump 7 and ensuring that the vacuum level at the gas inlet meets requirements. Since the coolers are all located in the coolant flow path, blockage can be effectively avoided. In some embodiments, backup coolers can be installed at the spray cooler 1, the washing liquid cooler 3, and the circulating cooler, facilitating cooler switching for maintenance when necessary.

[0083] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A glycolide condensation system, characterized in that, The glycolide condensation system includes: A glycolide condenser is used to condense glycolide gaseous material with methyl glycolate through multi-stage spraying to obtain glycolide slurry and tail gas; the glycolide condenser is provided with a first sprayer and a second sprayer for spraying methyl glycolate onto the glycolide gaseous material, and the first sprayer and the second sprayer are arranged at intervals at different heights. The exhaust gas delivery pipe is used to output the exhaust gas from the glycolide condenser and spray methyl glycolate during the flow of the exhaust gas; the exhaust gas delivery pipe is provided with a third sprayer for spraying methyl glycolate into the exhaust gas flowing into the exhaust gas delivery pipe, and the exhaust gas delivery pipe is arranged at an upward inclination relative to the glycolide condenser. An exhaust gas scrubbing tank, connected to the exhaust gas delivery pipe, is used to receive the exhaust gas output from the exhaust gas delivery pipe and spray methyl glycolate onto the exhaust gas to obtain scrubbed exhaust gas and scrubbing liquid; the exhaust gas scrubbing tank is equipped with a fourth sprayer for spraying methyl glycolate onto the exhaust gas entering the exhaust gas scrubbing tank. An exhaust gas separation device is used to cool and separate the washed exhaust gas output from the exhaust gas scrubbing tank to obtain non-condensable gas and a separation liquid containing methyl glycolate. The exhaust gas separation device includes an exhaust gas cooler and a separating tank. The exhaust gas cooler is connected to the exhaust gas scrubbing tank and is used to cool the washed exhaust gas output from the exhaust gas scrubbing tank to obtain the non-condensable gas and condensate. The separating tank is used to process the condensate obtained from the exhaust gas cooler to separate the residual non-condensable gas and obtain the separation liquid containing methyl glycolate. The separating tank is connected to the exhaust gas scrubbing tank through a separating liquid delivery pipeline, and the separating liquid delivery pipeline is equipped with a separating liquid delivery pump and a separating liquid cooler. A slurry separation device is used to perform solid-liquid separation on the glycolide slurry obtained from the glycolide condenser to obtain glycolide solid material and liquid material containing methyl glycolate. A washing liquid recycling device is used to circulate the washing liquid obtained from the exhaust gas washing tank to the exhaust gas washing tank, the exhaust gas delivery pipe, and / or the glycolide condenser for use in the spraying process; the washing liquid recycling device includes a washing liquid pump and a washing liquid cooler for cooling the washing liquid, the washing liquid pump being located between the washing liquid cooler and the exhaust gas washing tank, for outputting the washing liquid in the exhaust gas washing tank to the washing liquid cooler; the washing liquid outlet of the washing liquid cooler is connected to the third sprayer and the fourth sprayer respectively. A liquid phase material recycling device is used to circulate the methyl glycolate-containing liquid phase material obtained from the slurry separation device to the glycolide condenser for use in the spraying process; the liquid phase material recycling device includes a circulating liquid pump and a spray cooler; the circulating liquid pump is located between the slurry separation device and the spray cooler, and is used to output the methyl glycolate-containing liquid phase material obtained from the slurry separation device to the spray cooler; the spray cooler is used to cool and reduce the temperature of the methyl glycolate-containing liquid phase material, and the liquid phase material outlet of the spray cooler is connected to at least one of the first sprayer and the second sprayer.

2. The glycolide condensation system according to claim 1, characterized in that, Both the first sprayer and the second sprayer are located above the exhaust gas outlet of the glycolide condenser.

3. The glycolide condensation system according to claim 2, characterized in that, The exhaust gas delivery pipe is arranged to allow the liquid stream within the exhaust gas delivery pipe to flow to the glycolide condenser.

4. The glycolide condensation system according to claim 3, characterized in that, The nozzle of the third sprayer is directed toward the exhaust gas outlet of the glycolide condenser.

5. The glycolide condensation system according to claim 3, characterized in that, The fourth sprayer is located above the exhaust gas inlet of the exhaust gas scrubbing tank.

6. The glycolide condensation system according to claim 5, characterized in that, The washing liquid outlet of the washing liquid cooler is also connected to the first sprayer or the second sprayer.

7. The glycolide condensation system according to claim 6, characterized in that, The connecting line between the washing liquid pump and the washing liquid cooler is also connected to the methyl glycolate input line.

8. The glycolide condensation system according to claim 1, characterized in that, The connecting pipeline between the spray cooler and the circulating liquid pump is also connected to the methyl glycolate input pipeline.

9. The glycolide condensation system according to any one of claims 1-8, characterized in that, The slurry separation device includes a separator, a solution pump, a solid-liquid separation device, and a liquid phase material storage tank; The separator is connected to the glycolide slurry outlet of the glycolide condenser, and the separator is equipped with a stirrer. The inlet of the solution pump is connected to the outlet of the separator; The feed inlet of the solid-liquid separation device is connected to the outlet of the solution pump, and is used to perform solid-liquid separation on the glycolide slurry input by the solution pump to obtain glycolide solid material and liquid material containing methyl glycolate. The liquid material storage tank is connected to the solid-liquid separation equipment and is used to store the liquid material containing methyl glycolate.

10. A method for condensing glycolide gaseous material using the glycolide condensation system according to any one of claims 1-9, characterized in that, The method includes the following steps: The glycolide gaseous material is fed into the glycolide condenser, and the glycolide gaseous material is sprayed with methyl glycolate in multiple stages to condense the glycolide, thereby obtaining glycolide slurry and tail gas. The exhaust gas is fed into the exhaust gas scrubbing tank through the exhaust gas delivery pipe. Methyl glycolate is sprayed onto the exhaust gas as it flows through the exhaust gas delivery pipe. After the exhaust gas flows into the exhaust gas scrubbing tank, methyl glycolate is sprayed onto the exhaust gas to condense the residual glycolide in the exhaust gas, thus obtaining scrubbed exhaust gas and scrubbing liquid. The washed exhaust gas is sent to the exhaust gas separation device for cooling and gas-liquid separation to obtain non-condensable gas and a separation liquid containing methyl glycolate. The glycolide slurry is fed into a slurry separation device for solid-liquid separation to obtain glycolide solid material and methyl glycolate liquid material. The liquid phase material in the exhaust gas delivery pipe is returned to the glycolide condenser; The washing liquid is recycled through a washing liquid recycling device to the tail gas washing tank, the tail gas delivery pipe and / or the glycolide condenser for continued use in the spraying; the liquid phase material containing methyl glycolate is recycled through a liquid phase material recycling device to the glycolide condenser for continued use in the spraying.

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