A glycolide production system and method

Abstract

This application discloses a glycolide production system and method. The glycolide production system includes: a reaction unit configured to generate gaseous crude glycolide and solid residue by stepwise pyrolysis of polyglycolic acid oligomers; a dissolution and collection unit connected to the gaseous outlet of the reaction unit via a connecting pipeline; a condensation unit located on the connecting pipeline, configured to cool the gaseous crude glycolide into liquid crude glycolide and transport it to the dissolution and collection unit; and a residue collection unit connected to the reaction unit, configured to collect the solid residue and discharge it from the system. Thus, by employing a stepwise pyrolysis process, the conversion rate of oligomers is improved, the generation of solid residue is reduced, and the depolymerization process is omitted. The discharged solid residue is directly discharged from the system as a byproduct, thereby avoiding the impact of depolymerized and recovered materials on the operation of upstream units and improving the stability of system operation.

Description

Technical Field

[0001] This application relates to the field of glycolide production technology, and more particularly to a glycolide production system and method. Background Technology

[0002] PGA (Polyglycolideacid) is a fully biodegradable material with mild degradation conditions. Under the action of water and microorganisms, it can rapidly degrade carbon dioxide and water in the natural environment.

[0003] PGA also exhibits excellent degradation performance in seawater, and its degradation products are 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 unconventional underground 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 production. The conversion rate of oligomers in the process of producing glycolide through oligomer pyrolysis is low, resulting in a large amount of oligomer residue. Depolymerization is required to recover methyl formate from the material, but the depolymerization system is unstable, and the recovered material may cause instability in upstream systems.

[0004] Therefore, during the production of glycolide, a large amount of residue is generated during the depolymerization and recovery of materials, leading to instability in the production system. Summary of the Invention

[0005] In view of this, in order to solve at least one of the above-mentioned technical problems, this application provides a glycolide production system and method.

[0006] To achieve the above objectives, this application mainly provides the following technical solutions: A first aspect of this application provides a glycolide production system, comprising: The reaction apparatus is configured to produce gaseous crude glycolide and solid residue by stepwise pyrolysis of polyglycolic acid oligomers. A dissolution and collection device is connected to the gas phase outlet of the reaction device via a connecting pipeline. A condensing device is installed in the connecting pipeline and is configured to cool the gaseous crude glycolide into the liquid crude glycolide and transport it to the dissolution and collection device. A residue collection device is connected to the reaction device and is configured to collect solid residue and discharge it from the system.

[0007] For example, the reaction apparatus includes: The first reactor, whose inlet is connected to the polyglycolic acid oligomer feed pipe and the first catalyst feed pipe, is used to crack the polyglycolic acid oligomer to produce primary gas-phase crude glycolide and primary oligomer. The second reactor, whose inlet is connected to the first medium outlet and the second catalyst feed pipe of the first reactor, is used to crack the primary oligomers from the first reactor to produce secondary gas-phase crude glycolide and secondary oligomers. The third reactor, whose inlet is connected to the second medium outlet of the second reactor, is used to pyrolyze the secondary oligomers from the second reactor to produce tertiary gas-phase crude glycolide and solid residue. The residue collection device is connected to the third medium outlet of the third reactor.

[0008] For example, the reaction apparatus further includes: A first transfer pump, connected to the outlet of a first medium and the inlet of a second reactor, is configured to transfer primary oligomers from the first reactor to the second reactor. The second transfer pump, which is connected to the outlet of the second medium and the inlet of the third reactor, is configured to transfer the secondary oligomer from the second reactor to the third reactor; The third transfer pump, which is connected to the outlet of the third medium and the inlet of the residue collection device, is configured to transfer solid residue from the third reactor to the residue collection device.

[0009] For example, the connecting pipeline includes a first pipeline, a second pipeline, and a third pipeline that connect the dissolution and collection device to the gas phase outlet of the first reactor, the gas phase outlet of the second reactor, and the gas phase outlet of the third reactor, respectively. The condensation device includes a first condenser installed in a first pipeline, a second condenser installed in a second pipeline, and a third condenser installed in a third pipeline.

[0010] For example, the glycolide production system also includes: The vacuum-assisted system is connected to the condenser and reaction apparatus for controlling the condensation temperature of the condenser and the reaction pressure of the reaction apparatus.

[0011] For example, a first regulating valve is provided on the line between the vacuum assist system and the first condenser. The vacuum assist system regulates the pressure of the first condenser through the first regulating valve to regulate the reaction pressure of the first reactor. A second regulating valve is installed on the line between the vacuum assist system and the second condenser. The vacuum assist system regulates the pressure of the second condenser through the second regulating valve to regulate the reaction pressure of the second reactor. A third regulating valve is installed on the line between the vacuum-assisted system and the third condenser. The vacuum-assisted system regulates the pressure of the third condenser through the third regulating valve to regulate the reaction pressure of the third reactor.

[0012] For example, the inlet of the dissolution and collection device is also configured to be connected to the solvent feed pipe, through which the solvent enters the dissolution and collection device to dissolve the crude glycolide in liquid phase into a glycolide solution; The glycolide production system also includes a fourth transfer pump connected to the outlet of the dissolution and collection unit, the fourth transfer pump being configured to deliver the glycolide solution to downstream units.

[0013] A second aspect of this application provides a method for producing glycolide, used in any of the foregoing glycolide production systems, the method comprising: The reaction apparatus is used to pyrolyze polyglycolic acid oligomers in stages to produce crude glycolide in the gas phase and solid residue. The gaseous crude glycolate is cooled into liquid crude glycolate by a condenser and then transported to a dissolution and collection device, where it is dissolved into a glycolate solution. The solid residue is transported to the residue collection device for discharge.

[0014] For example, the step of using a reaction apparatus to progressively pyrolyze polyglycolic acid oligomers to produce gaseous crude glycolide and solid residue includes: The first reactor is used to pyrolyze polyglycolic acid oligomers to produce primary crude glycolide and primary oligomers. The primary oligomers are pyrolyzed using a second reactor to produce secondary crude glycolide and secondary oligomers; The secondary oligomers are pyrolyzed using a third reactor to produce tertiary crude glycolide and solid residue.

[0015] For example, the step of cooling the gaseous crude glycolide into liquid crude glycolide using a condenser and then conveying it to a dissolution and collection device to dissolve it into a glycolide solution includes: The primary gaseous crude glycolide is cooled into liquid crude glycolide by the first condenser and then transported to the dissolution and collection device. The secondary gaseous crude glycolide is cooled into liquid crude glycolide by the second condenser and then transported to the dissolution and collection device; After being cooled into liquid crude glycolate by the third condenser, the three-stage gas crude glycolate is transported to the dissolution and collection device. The solvent in the dissolution and collection device dissolves the crude glycolide in the liquid phase into a glycolide solution; The fourth transfer pump delivers the glycolide solution to the downstream unit; The steps of conveying solid residue to the residue collection device for discharge system include: The solid residue is transported from the third reactor to the residue collection device by the third transfer pump, and the residue collection device discharges the solid residue from the system by increasing or decreasing the pressure.

[0016] The glycolide production system and method provided in this application include a reaction device, a dissolution and collection device, a condensation device, and a residue collection device. The reaction device progressively pyrolyzes polyglycolic acid oligomers to produce gaseous crude glycolide and solid residue. The condensation device cools the gaseous crude glycolide produced in the reaction device into liquid crude glycolide, which is then transported to the dissolution and collection device to produce a glycolide solution. Therefore, the stepwise pyrolysis process improves the conversion rate of oligomers and reduces residue generation. Simultaneously, the residue collection device collects and discharges the solid residue produced in the reaction device, simplifying the material depolymerization and recovery process and avoiding the problem of depolymerized and recovered materials affecting the operational stability of upstream devices. This not only improves the conversion rate of oligomers and reduces residue generation, but also features a simple production process, stable system operation, and is suitable for widespread application.

[0017] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. Wherein: Figure 1 One of the schematic diagrams of a glycolide production system provided in an embodiment of this application is shown; Figure 2 One of the schematic flowcharts of the glycolide production method provided in the embodiments of this application is shown.

[0019] in, Figure 1 The correspondence between the reference numerals and component names in the attached drawings is as follows: 110 First reactor, 120 Second reactor, 130 Third reactor, 140 First transfer pump, 150 Second transfer pump, 160 Third transfer pump, 200 Dissolution and collection device, 300 Fourth transfer pump, 410 First condenser, 420 Second condenser, 430 Third condenser, 500 Residue collection device, 610 First regulating valve, 620 Second regulating valve, 630 Third regulating valve, 700 Vacuum-assisted system, 810 Polyglycolic acid oligomer feed pipe, 820 First catalyst feed pipe, 830 Second catalyst feed pipe, 840 Solvent feed pipe, 850 Nitrogen purging pipe. Detailed Implementation

[0020] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0021] like Figure 1 As shown in the embodiments of this application, a glycolide production system is provided, comprising: a reaction apparatus configured to generate gaseous crude glycolide and solid residue by stepwise pyrolysis of polyglycolic acid oligomers; a dissolution and collection device 200 connected to the gaseous outlet of the reaction apparatus via a connecting pipeline; a condensation device disposed on the connecting pipeline and configured to cool the gaseous crude glycolide into liquid crude glycolide and transport it to the dissolution and collection device 200; and a residue collection device 500 connected to the reaction apparatus and configured to collect the solid residue and discharge it from the system.

[0022] The glycolide production system provided in this application includes a reaction device, a dissolution and collection device 200, a condensation device, and a residue collection device 500. The reaction device progressively pyrolyzes polyglycolic acid oligomers to produce gaseous crude glycolide and solid residue. The condensation device cools the gaseous crude glycolide produced in the reaction device into liquid crude glycolide, which is then transported to the dissolution and collection device 200 to produce a glycolide solution. Therefore, this progressive pyrolysis process improves the conversion rate of oligomers and reduces residue generation. Simultaneously, the residue collection device 500 collects the solid residue produced in the reaction device and discharges it from the glycolide production system. Compared to related technologies that involve depolymerizing and recovering oligomer residues, this simplifies the material depolymerization and recovery process. This avoids the problem of depolymerized and recovered materials affecting the operational stability of upstream devices. It not only improves the conversion rate of oligomers and reduces residue generation, but also features a simple production process, stable system operation, and is suitable for widespread application.

[0023] The reaction apparatus may include multiple reactors connected in series to perform a staged pyrolysis operation on polyglycolic acid oligomers. It is understood that the reaction apparatus may include two, three, four, five, or other numbers of reactors. Each reactor further pyrolyzes the non-gaseous products generated by the previous reactor to produce gaseous crude glycolide and non-gaseous products again. The non-gaseous products can be at least one of liquid products, solid-liquid mixtures, and solid products. It is understood that the gaseous crude glycolide produced by each reactor is condensed by a condenser and then transported to a dissolution and collection device 200. Thus, by using multiple reactors to perform staged pyrolysis of polyglycolic acid oligomers, the conversion rate of the oligomers is improved, and the generation of solid residue is reduced.

[0024] It is understood that multiple reactors can be of the same type or different types, such as a reactor being at least one of tubular, batch, fixed bed, fluidized bed, tower, moving bed and trickle bed.

[0025] The residue collection device 500 is located downstream of the reaction device. After the solid residue is pressurized and depressurized in the residue collection device 500, it can be directly discharged from the system as a by-product. This avoids the material recovered from depolymerization from affecting the operation of the upstream device.

[0026] Specifically, the inlet of the residue collection device 500 is connected to a nitrogen purge pipe 850. Nitrogen is introduced into the residue collection device 500 through the nitrogen purge pipe 850 to regulate the internal pressure of the residue collection device 500, so that the solid residue is discharged directly from the system as a by-product after the pressure is increased and decreased within the residue collection device 500.

[0027] The dissolution and collection device 200 is located downstream of the condensation device. The condensation device cools the gaseous crude glycolide into liquid crude glycolide and transports it to the dissolution and collection device 200. The dissolution and collection device 200 can dissolve the liquid crude glycolide to obtain glycolide liquid.

[0028] like Figure 1 As shown, in some possible embodiments provided in this application, the reaction apparatus includes: a first reactor 110, the inlet of which is connected to a polyglycolic acid oligomer feed pipe 810 and a first catalyst feed pipe 820, respectively, for cracking polyglycolic acid oligomers to produce primary gas-phase crude glycolide and primary oligomers; a second reactor 120, the inlet of which is connected to a first medium outlet and a second catalyst feed pipe 830 of the first reactor 110, respectively, for cracking the primary oligomers from the first reactor 110 to produce secondary gas-phase crude glycolide and secondary oligomers; and a third reactor 130, the inlet of which is connected to a second medium outlet of the second reactor 120, for cracking the secondary oligomers from the second reactor 120 to produce tertiary gas-phase crude glycolide and solid residue.

[0029] The inlet of the first reactor 110 is connected to the polyglycolic acid oligomer feed pipe 810 and the first catalyst feed pipe 820 for the initial cracking of the polyglycolic acid oligomer. The catalyst can enter the first reactor 110 through the first catalyst feed pipe 820, meaning that a catalyst can be added to the first reactor 110, thus ensuring a good reaction effect. It is understood that the primary oligomer produced by the first reactor 110 can be a viscous oligomer.

[0030] The inlet of the second reactor 120 is connected to both the first medium outlet and the second catalyst feed pipe 830 of the first reactor 110 to further crack the primary oligomers from the first reactor 110. The catalyst can enter the second reactor 120 through the second catalyst feed pipe 830, meaning a catalyst can be added to the second reactor 120, thus ensuring a good reaction effect. It is understood that the secondary oligomers produced by the second reactor 120 can be near-solid oligomers.

[0031] The inlet of the third reactor 130 is connected to the second medium outlet of the second reactor 120 to further pyrolyze the secondary oligomers from the second reactor 120. It is understood that the pyrolysis in the third reactor 130 can produce solid oligomer residue, i.e., solid-phase residue.

[0032] In this embodiment, the first reactor 110, the second reactor 120, and the third reactor 130 are connected in series. The second reactor 120 is located downstream of the first reactor 110, and the third reactor 130 is located downstream of the second reactor 120. The process of connecting the three reactors in series achieves the gradual pyrolysis of polyglycolic acid oligomers. Finally, solid residue is obtained from the pyrolysis reaction in the third reactor 130, and is discharged from the system through the residue collection device 500, thereby achieving the purpose of improving the conversion rate of oligomers and reducing the generation of residue.

[0033] The first reactor 110, the second reactor 120, and the third reactor 130 can be of the same type or different types. For example, the first reactor 110 can be a coil reactor in a disc reactor, the second reactor 120 can be a stirred tank reactor, and the third reactor 130 can be a batch stirred tank reactor. It is understood that the first reactor 110, the second reactor 120, and the third reactor 130 can also be of other types.

[0034] It is understandable that the gaseous crude glycolide produced by the first reactor 110, the second reactor 120, and the third reactor 130 can be cooled into liquid crude glycolide by a condenser and then transported to the dissolution and collection device 200. It is also understandable that if the reaction in the third reactor 130 is poor, a catalyst can be added to the third reactor 130 to ensure the conversion effect of the final cracking reaction.

[0035] like Figure 1As shown, in some possible embodiments provided in this application, the reaction apparatus further includes: a first transfer pump 140, a second transfer pump 150, and a third transfer pump 160. The first transfer pump 140 is connected at both ends to the first medium outlet and the inlet of the second reactor 120, respectively. The first transfer pump 140 is configured to transport the primary oligomer from the first reactor 110 to the second reactor 120, thereby reducing the likelihood of primary oligomer clogging equipment and pipelines and improving the smoothness of primary oligomer transport from the first reactor 110 to the second reactor 120.

[0036] The second transfer pump 150 is connected to the outlet of the second medium and the inlet of the third reactor 130 at its two ends, respectively. The second transfer pump 150 is configured to transfer the secondary oligomer from the second reactor 120 to the third reactor 130, thereby reducing the possibility of the secondary oligomer clogging the equipment and pipelines and improving the smoothness of the transfer of the secondary oligomer from the second reactor 120 to the third reactor 130.

[0037] The third transfer pump 160 is connected at both ends to the third medium outlet of the third reactor 130 and the inlet of the residue collection device 500, respectively. The third transfer pump 160 is configured to transport solid residue from the third reactor 130 to the residue collection device 500. This reduces the likelihood of solid residue clogging equipment and pipelines, and improves the smoothness of solid residue transport from the third reactor 130 to the residue collection device 500.

[0038] In this embodiment, since primary oligomers, secondary oligomers, and solid residues may clog the equipment and pipelines during the three-stage pyrolysis reaction, the material is output by the first conveying pump 140, the second conveying pump 150, and the third conveying pump 160, which can avoid the situation of material retention and blockage and improve the reliability of the system.

[0039] The first delivery pump 140, the second delivery pump 150, and the third delivery pump 160 may have the same structure or different structures.

[0040] like Figure 1 As shown, in some possible embodiments provided in this application, the connecting pipeline includes a first pipeline, a second pipeline, and a third pipeline that connect the dissolution and collection device 200 to the gas phase outlets of the first reactor 110, the second reactor 120, and the third reactor 130, respectively. That is, the first pipeline connects the dissolution and collection device 200 and the gas phase outlet of the first reactor 110, the second pipeline connects the dissolution and collection device 200 and the gas phase outlet of the second reactor 120, and the third pipeline connects the dissolution and collection device 200 and the gas phase outlet of the third reactor 130.

[0041] like Figure 1As shown, the condensation device includes a first condenser 410, a second condenser 420, and a third condenser 430, all connected to a first pipeline, a second pipeline, and a third pipeline, respectively. The first reactor 110 is located on the first pipeline. The gas phase inlet of the first condenser 410 is connected to the gas phase outlet of the first reactor 110 via the first pipeline, and the liquid phase outlet of the first condenser 410 is connected to the dissolution and collection device 200 via the first pipeline. The first condenser 410 condenses the primary gaseous crude glycolide produced by the first reactor 110 to obtain liquid crude glycolide, which is then transported to the dissolution and collection device 200.

[0042] The second reactor 120 is installed on the second pipeline. The gas phase inlet of the second condenser 420 is connected to the gas phase outlet of the second reactor 120 through the second pipeline, and the liquid phase outlet of the second condenser 420 is connected to the dissolution and collection device 200 through the second pipeline. The second condenser 420 is used to condense the secondary gas phase crude glycolide produced by the second reactor 120 to obtain liquid phase crude glycolide, which is then transported to the dissolution and collection device 200.

[0043] The third condenser 430 is installed on the third pipeline. The gas phase inlet of the third condenser 430 is connected to the gas phase outlet of the third reactor 130 through the third pipeline, and the liquid phase outlet of the third condenser 430 is connected to the dissolution and collection device 200 through the third pipeline. The third condenser 430 is used to condense the three-stage gas-phase crude glycolide produced by the third reactor 130 to obtain liquid-phase crude glycolide, which is then transported to the dissolution and collection device 200.

[0044] Thus, gradual pyrolysis is achieved through the first reactor 110, the second reactor 120, and the third reactor 130, and gradual cooling is achieved through the first condenser 410, the second condenser 420, and the third condenser 430, thereby improving the conversion rate of the pyrolysis reaction.

[0045] The first condenser 410, the second condenser 420, and the third condenser 430 can have the same structure or different structures. For example... Figure 1 As shown, arrow a on the first condenser 410, the second condenser 420, and the third condenser 430 can represent hot water inlet, and arrow b on the first condenser 410, the second condenser 420, and the third condenser 430 can represent hot water return, thus representing the circulating water path of the condenser.

[0046] like Figure 1 As shown, in some possible embodiments provided in this application, the glycolide production system further includes: a vacuum auxiliary system 700, which is connected to the condensing device and the reaction device for controlling the condensing temperature of the condensing device and the reaction pressure of the reaction device.

[0047] In this embodiment, the condensation temperature of the condensing device and the reaction pressure of the reaction device are controlled by the vacuum-assisted system 700, which helps to ensure good reaction results. Furthermore, the vacuum-assisted system 700 can control both the condensing device and the reaction device, simplifying the structure compared to having two separate systems for each device.

[0048] Specifically, the vacuum assist system 700 can be a vacuum and washing system.

[0049] In some possible embodiments provided in this application, a first regulating valve 610 is provided on the line between the vacuum assist system 700 and the first condenser 410. The vacuum assist system 700 regulates the pressure of the first condenser 410 through the first regulating valve 610 to regulate the reaction pressure of the first reactor 110. A second regulating valve 620 is provided on the line between the vacuum assist system 700 and the second condenser 420. The vacuum assist system 700 regulates the pressure of the second condenser 420 through the second regulating valve 620 to regulate the reaction pressure of the second reactor 120. A third regulating valve 630 is provided on the line between the vacuum assist system 700 and the third condenser 430. The vacuum assist system 700 regulates the pressure of the third condenser 430 through the third regulating valve 630 to regulate the reaction pressure of the third reactor 130.

[0050] Therefore, the vacuum-assisted system 700 is used to adjust the pressures of the first condenser 410, the second condenser 420, and the third condenser 430 respectively via the first regulating valve 610, the second regulating valve 620, and the third regulating valve 630, thereby controlling the pressures of the first reactor 110, the second reactor 120, and the third reactor 130 respectively. Specifically, the pressure of the first reactor 110 is controlled and regulated by the vacuum-assisted system 700 controlling the opening of the first regulating valve 610; the pressure of the second reactor 120 is controlled and regulated by the vacuum-assisted system 700 controlling the opening of the second regulating valve 620; and the pressure of the third reactor 130 is controlled and regulated by the vacuum-assisted system 700 controlling the opening of the third regulating valve 630, thus achieving different pressure control according to the reaction degree of each reactor.

[0051] In one specific embodiment, the vacuum-assisted system 700 outputs different adjustment signals to the first regulating valve 610, the second regulating valve 620, and the third regulating valve 630 respectively, based on the reaction levels of the first reactor 110, the second reactor 120, and the third reactor 130, to control their opening or closing, thereby regulating the pressure. During this process, the temperatures of the first reactor 110, the second reactor 120, and the third reactor 130 can be controlled by the temperature of the heat transfer oil in the equipment jacket and the stirring shaft.

[0052] like Figure 1 As shown, in some possible embodiments provided in this application, the inlet of the dissolution and collection device 200 is also configured to be connected to the solvent feed pipe 840, and the solvent is configured to dissolve the crude glycolide in the liquid phase to obtain a glycolide solution; the glycolide production system also includes a fourth transfer pump 300 connected to the outlet of the dissolution and collection device 200, and the fourth transfer pump 300 is configured to transport the glycolide solution to downstream devices.

[0053] In this embodiment, after the condenser cools the gaseous crude glycolide into liquid crude glycolide and transports it to the dissolution and collection device 200, the first condenser 410, the second condenser 420, and the third condenser 430 respectively cool the primary gaseous crude glycolide produced by the first reactor 110, the secondary gaseous crude glycolide produced by the second reactor 120, and the tertiary gaseous crude glycolide produced by the third reactor 130 into liquid crude glycolide and transport it to the dissolution and collection device 200. The solvent is then fed into the dissolution and collection device 200 through the solvent feed pipe 840. Inside the dissolution and collection device 200, the solvent mixes with the liquid crude glycolide, and the solvent dissolves the liquid crude glycolide into a glycolide solution. Then, the glycolide solution is transported to the downstream device using the fourth transfer pump 300, thereby realizing the production and transportation of glycolide.

[0054] like Figure 2 As shown in the embodiments of this application, a method for producing glycolide is also provided, for use in any of the glycolide production systems described in the foregoing embodiments. The method includes: Step S1100: The polyglycolic acid oligomer is pyrolyzed in stages using a reaction apparatus to produce crude glycolide in the gas phase and solid residue in the solid phase. Step S1200: The gaseous crude glycolide is cooled into liquid crude glycolide by a condenser and then transported to a dissolution and collection device, where it is dissolved into a glycolide solution. Step S1300: The solid residue is conveyed to the residue collection device to be discharged.

[0055] The glycolide production method provided in this application utilizes a reaction device to progressively pyrolyze polyglycolic acid oligomers to produce gaseous crude glycolide and solid residue. A condensation device cools the gaseous crude glycolide produced in the reaction device into liquid crude glycolide, which is then transported to a dissolution and collection device 200 to produce a glycolide solution. Therefore, the progressive pyrolysis process improves the conversion rate of oligomers and reduces residue generation. Simultaneously, the residue collection device 500 collects the solid residue produced in the reaction device and discharges it from the glycolide production system. Compared with related technologies that depolymerize and recycle oligomer residues, this method simplifies the material depolymerization and recovery process. This avoids the problem of depolymerized and recovered materials affecting the operational stability of upstream devices. It not only improves the conversion rate of oligomers and reduces residue generation, but also features a simple production process, stable system operation, and is suitable for widespread application.

[0056] In some possible embodiments provided in this application, the step of using a reaction apparatus to progressively pyrolyze polyglycolic acid oligomers to produce crude glycolide in the gas phase and solid residue includes: The first reactor was used to pyrolyze polyglycolic acid oligomers for the first time, producing primary crude glycolide and primary oligomers.

[0057] Specifically, polyglycolic acid oligomers are added to the first reactor 110 through the polyglycolic acid oligomer feed pipe 810, and catalyst is added to the first reactor 110 through the first catalyst feed pipe 820. The first reactor 110 is used for the initial pyrolysis of the polyglycolic acid oligomers, and the added catalyst ensures the effectiveness of the initial pyrolysis reaction. Under the catalytic action of the catalyst, the first reactor 110 initially pyrolyzes the polyglycolic acid oligomers, producing primary gaseous crude glycolide and viscous primary oligomers. It can be understood that the primary oligomers can be considered as the polyglycolic acid oligomers remaining after the reaction in the first reactor 110, and these primary oligomers can be used as material for the secondary pyrolysis reaction.

[0058] The primary oligomers are pyrolyzed in a second reactor to produce secondary crude glycolide and secondary oligomers.

[0059] Specifically, the primary oligomers in the first reactor 110 are transported to the second reactor 120 using the first transfer pump 140. A catalyst is added to the second reactor 120 through the second catalyst feed pipe 830. The second reactor 120 is used to pyrolyze the primary oligomers, and the added catalyst ensures the conversion efficiency of the secondary pyrolysis reaction. Under the action of the catalyst, the second reactor 120 pyrolyzes the viscous primary oligomers, producing secondary gaseous crude glycolide and near-solid secondary oligomers. It can be understood that the secondary oligomers can be considered as a small amount of polyglycolic acid oligomers remaining after the reaction in the second reactor 120, and these secondary oligomers can serve as materials for the tertiary pyrolysis reaction.

[0060] The secondary oligomers are pyrolyzed again using a third reactor to produce tertiary crude glycolide and solid residue.

[0061] Specifically, the second reactor 120 uses stirring to forcibly transport near-solid secondary oligomers to the second transfer pump 150. The second transfer pump 150 then transports the secondary oligomers from the second reactor 120 to the third reactor 130. The third reactor 130 pyrolyzes the secondary oligomers, producing tertiary gaseous crude glycolide and solid residue. It is understood that if the reaction in the third reactor 130 is poor, a catalyst can be added to the third reactor 130 to ensure the conversion efficiency of the final pyrolysis reaction.

[0062] In this embodiment, a process of three reactors connected in series is used to gradually pyrolyze polyglycolic acid oligomers. The solid residue obtained from the pyrolysis reaction in the third reactor 130 is finally discharged from the system through the residue collection device 500, thereby achieving the purpose of improving the conversion rate of oligomers and reducing the generation of residue.

[0063] In some possible embodiments provided in this application, the step of cooling the gaseous crude glycolate into liquid crude glycolate by a condenser and then conveying it to a dissolution and collection device to dissolve it into a glycolate solution includes: The primary gaseous crude glycolide is cooled into liquid crude glycolide by the first condenser and then transported to the dissolution and collection device. The secondary gaseous crude glycolide is cooled into liquid crude glycolide by the second condenser and then transported to the dissolution and collection device; After being cooled into liquid crude glycolate by the third condenser, the three-stage gas crude glycolate is transported to the dissolution and collection device. The solvent in the dissolving and collecting device converts the crude glycolide in the liquid phase into a glycolide solution. The fourth transfer pump delivers the glycolide solution to the downstream unit.

[0064] In this embodiment, the first condenser 410, the second condenser 420, and the third condenser 430 respectively cool the primary gaseous crude glycolide produced by the first reactor 110, the secondary gaseous crude glycolide produced by the second reactor 120, and the tertiary gaseous crude glycolide produced by the third reactor 130 into liquid-phase crude glycolide, which is then transported to the dissolution and collection device 200. The solvent and liquid-phase crude glycolide in the dissolution and collection device 200 are mixed to dissolve the liquid-phase crude glycolide solution into a glycolide solution. The glycolide solution is then transported to the downstream device by the fourth transfer pump 300, thereby realizing the production and transportation of glycolide solution.

[0065] In some possible embodiments provided in this application, the step of conveying solid residue to a residue collection device for discharge includes: The solid residue is transported from the third reactor to the residue collection device by the third transfer pump, and the residue collection device discharges the solid residue from the system by increasing or decreasing the pressure.

[0066] In this embodiment, after the polyglycolic acid oligomer is successively cracked through the first reactor 110, the second reactor 120, and the third reactor 130, a small amount of solid residue is generated in the third reactor 130. The solid residue is transported from the third reactor 130 to the residue collection device 500 by the third transfer pump 160. The residue collection device 500 collects the solid residue and, under appropriate conditions, discharges the solid residue from the system by increasing or decreasing the pressure. Thus, there is no need to recover it through the depolymerization process, and the small amount of solid residue is discharged from the glycolide production system as a byproduct. This avoids the problem of the depolymerized material affecting the operational stability of the upstream equipment. It not only improves the conversion rate of oligomers and reduces the generation of residue, but also simplifies the production process and ensures stable system operation.

[0067] Specifically, the production process of glycolide provided in the embodiments of this application will be described in detail: Polyglycolic acid oligomers enter the first reactor 110 through the polyglycolic acid oligomer feed pipe 810. The catalyst required for cracking enters the first reactor 110 through the first catalyst feed pipe 820. In the first reactor 110, the polyglycolic acid oligomers undergo a cracking reaction under the action of the catalyst, producing primary gaseous crude glycolide and viscous primary oligomers. The primary gaseous crude glycolide is extracted in gaseous state to the first condenser 410, which cools the primary gaseous glycolide to liquid glycolide. The liquid glycolide flows by gravity into the dissolution and collection device 200. The viscous primary oligomers are sent to the second reactor 120 through the first transfer pump 140.

[0068] The catalyst required for cracking enters the second reactor 120 through the second catalyst feed pipe 830. The viscous primary oligomer undergoes further cracking in the second reactor 120, producing secondary gaseous crude glycolide and near-solid secondary oligomers. The secondary gaseous crude glycolide is extracted in gaseous state to the second condenser 420, which cools it to liquid glycolide. The liquid glycolide flows by gravity to the dissolution and collection device 200. The near-solid secondary oligomers are forcibly conveyed to the second transfer pump 150 by stirring, and then sent to the third reactor 130 by the second transfer pump 150.

[0069] A small amount of pyrolysis reaction also occurs in the third reactor 130, resulting in near-solid secondary oligomers that react to produce tertiary gaseous crude glycolide and solid residue. The tertiary gaseous crude glycolide is extracted in gaseous state to the third condenser 430, where it is cooled to liquid glycolide, which then flows by gravity to the dissolution and collection device 200. The solid residue is intermittently discharged to the residue collection device 500 via the third transfer pump 160. The material in the residue collection device 500 is controlled by valves, and the solid residue is intermittently discharged from the system by adjusting the pressure, serving directly as a byproduct outside the system.

[0070] The gaseous crude glycolide produced by the three pyrolysis reactions is cooled into liquid crude glycolide by a condenser and transported to a dissolution and collection device 200. In the dissolution and collection device 200, the liquid crude glycolide is mixed with a solvent to obtain a glycolide solution, which is then sent out of the system by a fourth transfer pump 300.

[0071] The vacuum-assisted system 700 controls the opening of the first regulating valve 610, the second regulating valve 620, and the third regulating valve 630 to adjust the different pressures of the first reactor 110, the second reactor 120, and the third reactor 130. The pressure control range is from 0.3 kPa(a) to 1.2 kPa(a). The temperature is controlled by the heat transfer oil in the jackets and stirring shafts of the first reactor 110, the second reactor 120, and the third reactor 130. The reactor temperature is controlled between 235°C and 250°C, which not only ensures the reaction effect but also improves the conversion rate of materials.

[0072] The glycolide production system and method provided in this embodiment greatly improve the single-pass conversion rate of polyglycolic acid oligomers, reduce the amount of oligomer solid residue discharged from the system, eliminate the need for a depolymerization system to recover methyl glycolate from the oligomers, and allow the small amount of solid residue remaining after the reaction to be discharged directly as a byproduct, significantly reducing clogging problems.

[0073] Therefore, the glycolide production system and method provided in this application only produce a small amount of solid residue that is directly discharged as a by-product. This not only reduces the risk of residue clogging equipment pipelines and causing instability in the production system, but also improves the single-pass conversion rate of polyglycolic acid oligomers and maintains the long-term stable operation of the upstream system.

[0074] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application. Those skilled in the art will understand that the modules in the apparatus of the embodiment can be distributed within the apparatus of the embodiment as described, or can be modified to be located in one or more apparatuses different from this embodiment. The modules of the above-described embodiment can be combined into one module, or further divided into multiple sub-modules.

[0075] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of any particular implementation scenario. The above disclosures are merely a few specific implementation scenarios of this application; however, this application is not limited thereto, and any variations conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A glycolide production system, characterized by, The system comprises: a reaction device configured to produce gas-phase crude glycolide and solid-phase residue by stepwise cracking of polyglycolic acid oligomers; a dissolving collection device in communication with a gas-phase outlet of the reaction device through a connecting pipeline; a condensing device provided in the connecting pipeline and configured to cool the gas-phase crude glycolide into liquid-phase crude glycolide and deliver it to the dissolving collection device; a residue collection device in communication with the reaction device and configured to receive and discharge the solid-phase residue from the system.

2. The glycolide production system according to claim 1, wherein, The reaction device comprises: a first reactor having an inlet connected with a polyglycolic acid oligomer feeding pipe and a first catalyst feeding pipe, respectively, for cracking the polyglycolic acid oligomers to produce first-stage gas-phase crude glycolide and first-stage oligomers; a second reactor having an inlet connected with a first medium outlet of the first reactor and a second catalyst feeding pipe, respectively, for cracking the first-stage oligomers from the first reactor to produce second-stage gas-phase crude glycolide and second-stage oligomers; a third reactor having an inlet connected with a second medium outlet of the second reactor, for cracking the second-stage oligomers from the second reactor to produce third-stage gas-phase crude glycolide and solid-phase residue, and a third medium outlet connected with the residue collection device.

3. The glycolide production system according to claim 2, wherein, The reaction device further comprises: a first delivery pump connected with the first medium outlet and the inlet of the second reactor, and configured to deliver the first-stage oligomers from the first reactor to the second reactor; a second delivery pump connected with the second medium outlet and the inlet of the third reactor, and configured to deliver the second-stage oligomers from the second reactor to the third reactor; a third delivery pump connected with the third medium outlet and the inlet of the residue collection device, and configured to deliver the solid-phase residue from the third reactor to the residue collection device.

4. The glycolide production system according to claim 2, wherein: the connecting pipeline comprises a first pipeline, a second pipeline and a third pipeline connecting the dissolving collection device with a gas-phase outlet of the first reactor, a gas-phase outlet of the second reactor and a gas-phase outlet of the third reactor, respectively; the condensing device comprises a first condenser provided in the first pipeline, a second condenser provided in the second pipeline and a third condenser provided in the third pipeline, respectively.

5. The glycolide production system according to claim 4, wherein Further comprising: a vacuum auxiliary system in control connection with the condensing device and the reaction device, for controlling the condensing temperature of the condensing device and the reaction pressure of the reaction device.

6. The glycolide production system according to claim 5, wherein: a first regulating valve is provided in a line between the vacuum auxiliary system and the first condenser, and the vacuum auxiliary system adjusts the pressure of the first condenser through the first regulating valve to adjust the reaction pressure of the first reactor. A second regulating valve is installed on the line between the vacuum assist system and the second condenser. The vacuum assist system regulates the pressure of the second condenser through the second regulating valve to regulate the reaction pressure of the second reactor. A third regulating valve is installed on the line between the vacuum assist system and the third condenser. The vacuum assist system regulates the pressure of the third condenser through the third regulating valve to regulate the reaction pressure of the third reactor.

7. The glycolide production system according to any one of claims 1 to 6, characterized in that, The inlet of the dissolution and collection device is also configured to be connected to a solvent feed pipe, through which the solvent enters the dissolution and collection device to dissolve the crude liquid-phase glycolide into a glycolide solution. The glycolide production system also includes a fourth delivery pump connected to the outlet of the dissolution and collection device, the fourth delivery pump being configured to deliver the glycolide solution to downstream devices.

8. A method for producing glycolide, characterized by, For a glycolide production system as described in any one of claims 1 to 7, the method comprises: The reaction apparatus is used to pyrolyze polyglycolic acid oligomers in stages to produce crude glycolide in the gas phase and solid residue. The gaseous crude glycolate is cooled into liquid crude glycolate by a condenser and then transported to a dissolution and collection device, where it is dissolved into a glycolate solution. The solid residue is transported to the residue collection device for discharge.

9. The glycolide production method according to claim 8, wherein The step of using a reaction device to progressively pyrolyze polyglycolic acid oligomers to produce crude glycolide in the gas phase and solid residue includes: The first reactor is used to pyrolyze polyglycolic acid oligomers to produce primary crude glycolide and primary oligomers. The primary oligomers are pyrolyzed using a second reactor to produce secondary crude glycolide and secondary oligomers; The secondary oligomers are pyrolyzed using a third reactor to produce tertiary crude glycolide and the solid residue.

10. The method for producing glycolide according to claim 9, characterized in that, The steps of cooling the gaseous crude glycolide into liquid crude glycolide using a condenser and then conveying it to a dissolution and collection device to dissolve it into a glycolide solution include: The primary gaseous crude glycolide is cooled into liquid-phase crude glycolide by the first condenser and then transported to the dissolution and collection device. The secondary gaseous crude glycolide is cooled into liquid crude glycolide by a second condenser and then transported to a dissolution and collection device. The crude glycolide from the third stage gaseous phase is cooled into crude glycolide in the liquid phase by the third condenser and then transported to the dissolution and collection device. The solvent in the dissolution and collection device dissolves the crude liquid-phase glycolide into a glycolide solution. The fourth transfer pump delivers the glycolide solution to the downstream unit; The step of conveying the solid residue to the residue collection device for discharge includes: The solid residue is transported from the third reactor to the residue collection device using a third transfer pump, and the residue collection device discharges the solid residue from the system by increasing or decreasing the pressure.

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