A lactide depolymerization substrate recycling process and equipment

Abstract

The present invention provides a lactide depolymerization substrate recycling process and equipment that can efficiently transfer mass and heat and be recycled. In order to solve the above technical problems, the present invention provides the following technical solutions, including a material evaporation cylinder, the material evaporation cylinder is filled with evaporation auxiliary plates, the evaporation auxiliary plates are respectively located at the upper and lower ends of the material evaporation cylinder, the evaporation auxiliary plates are divided into an upper evaporation auxiliary plate and a lower evaporation auxiliary plate, steam nozzles are respectively provided at the upper end of the upper evaporation auxiliary plate and the lower end of the lower evaporation auxiliary plate, liquid distributors are respectively provided at the upper end of the upper evaporation auxiliary plate and the upper end of the lower evaporation auxiliary plate, and a liquid collector is provided at the lower end of the upper evaporation auxiliary plate, a liquid storage chamber is provided at the lower end of the material evaporation cylinder, a steam collection port for collecting steam is opened on the side of the middle part of the material evaporation cylinder, a liquid circulation pump is connected to the lower end of the liquid storage chamber, and the liquid circulation pump is respectively connected to each liquid distributor through a conveying pipeline.

Description

Technical Field

[0001] The present invention relates to the technical field of lactide, and more specifically to a lactide depolymerization substrate recycling process and equipment. Background Art

[0002] The depolymerization reaction of lactide includes a main reaction of substrate cracking to generate lactide and a side reaction of substrate polymerization to generate a high molecular weight substrate. The side reaction leads to a decrease in the depolymerization catalytic activity and an increase in substrate viscosity. Lactide is difficult to escape from the reaction system, and the viscous substrate leads to a decrease in heat transfer efficiency, which is the essential problem causing mass transfer and heat transfer. The decrease in reaction efficiency leads to an increase in the residence time of the substrate, and long-term high temperature is the main cause of racemization. Therefore, controlling the molecular weight and viscosity of the depolymerized substrate at a low level is an effective way to solve mass transfer, heat transfer and racemization.

[0003] The process data such as different circulation volumes, different mixing intensities of the two melts, reaction conditions, etc. are optimized and combined for analysis to improve the mass transfer and heat transfer rates of the reaction system, thereby exploring the optimal closed-loop process parameters. The difficulty lies in the control of the molecular weight and flow rate of the depolymerization substrate returned from the synthesis step to the oligomer storage tank. If the molecular weight and flow rate are too large, it will be difficult for the depolymerization substrate to be decomposed into small molecular oligomers in the oligomer, and the viscosity reduction effect will not meet expectations, and the mass transfer and heat transfer problems cannot be alleviated.

[0004] The molecular weight and flow rate of the depolymerized substrate affect the yield of lactide, system viscosity and molecular weight. When the molecular weight of the depolymerized substrate is 12000Da, it is returned to the oligomer storage tank at a medium flow rate to mix with the oligomers, and then re-enters the synthesis process for depolymerization and cyclization reaction. At this time, the yield reaches 89%, and the system viscosity and molecular weight are at an intermediate level, which ensures the formation rate of lactide without affecting the distillation of lactide. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide a lactide depolymerization substrate recycling process and equipment that can efficiently transfer mass and heat and be recycled.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A lactide depolymerization substrate recycling process and equipment, including a material evaporation cylinder, the material evaporation cylinder is filled with evaporation auxiliary plates, the evaporation auxiliary plates are respectively located at the upper and lower ends of the material evaporation cylinder, the evaporation auxiliary plates are divided into an upper evaporation auxiliary plate and a lower evaporation auxiliary plate, steam nozzles are respectively provided at the upper end of the upper evaporation auxiliary plate and the lower end of the lower evaporation auxiliary plate, liquid distributors are respectively provided at the upper end of the upper evaporation auxiliary plate and the upper end of the lower evaporation auxiliary plate, and a liquid collector is provided at the lower end of the upper evaporation auxiliary plate, a liquid storage chamber is provided at the lower end of the material evaporation cylinder, a steam collection port for collecting steam is opened on the side of the middle part of the material evaporation cylinder, a liquid circulation pump is connected to the lower end of the liquid storage chamber, and the liquid circulation pump is respectively connected to each liquid distributor through a conveying pipeline.

[0008] Preferably, there are a plurality of evaporation auxiliary plates which are evenly spaced vertically, and the evaporation auxiliary plates include transverse plates and longitudinal plates which are staggered, and adjacent evaporation auxiliary plates are in contact with each other.

[0009] Preferably, a rotating shaft is rotatably connected in the liquid storage chamber, and scrapers are evenly distributed on the circumference of the rotating shaft. The scrapers are arc-shaped and fit against the inner wall of the liquid storage chamber. The lower end of the rotating shaft extends downward from the liquid storage chamber and is connected to a driving motor.

[0010] Preferably, the liquid distributor comprises a storage tank, a water pump is arranged in the storage tank, a liquid storage cavity is connected to a water inlet of the storage tank, and a water outlet of the storage tank is connected to each liquid distributor respectively.

[0011] Preferably, the liquid collector comprises a water collecting circle, in which two layers of water guiding grooves evenly spaced apart are provided, and adjacent water guiding grooves are staggered, with both ends of the water guiding grooves respectively connected to the water collecting circle.

[0012] Preferably, a water-guiding blade is provided on the inner side of the scraper, and the water-guiding blade is arranged obliquely and extends toward the inner side of the liquid storage chamber.

[0013] Preferably, a water outlet is provided at the lower end of the liquid storage cavity, and an opening and closing plate for covering the water outlet is provided inside the liquid storage cavity. A support rod extends downward from the lower end of the opening and closing plate, and the lower end of the support rod extends out of the liquid storage cavity and is connected to a lifting control rod.

[0014] Preferably, the steam nozzles are respectively located at the upper end of the upper evaporation auxiliary plate and the lower end of the lower evaporation auxiliary plate, and the steam nozzles include a pair of nozzles, and the nozzles are evenly distributed on the circumference of the steam nozzles.

[0015] Preferably, a steam collecting port is provided in the middle of the material evaporation cylinder, and an extended end of the steam collecting port extends obliquely upward toward the outside and is connected to a collecting device.

[0016] Preferably, a water pump is connected to the outside of the water collecting circle, and the water pump outputs the liquid in the water collecting circle to the outside, and the water outlet of the water pump is connected to the liquid distributor.

[0017] The technical solution of the present invention achieves the following beneficial technical effects:

[0018] 1. Able to circulate the liquid to be evaporated stably and efficiently;

[0019] 2. Able to evaporate stably and maintain a stable temperature during the circulation process;

[0020] 3. Evaporation auxiliary plates are respectively provided at the upper and lower ends of the material evaporation cylinder, which form a cycle by simultaneously conveying steam at the upper and lower ends of the material evaporation cylinder and collecting the steam through the middle of the material evaporation cylinder;

[0021] 4. The lactide is evaporated in sections in the material evaporator to avoid uneven heating;

[0022] 5. A liquid storage chamber is provided at the lower end of the material evaporation cylinder for storing circulating liquid, and a scraper is rotatably connected in the liquid storage chamber for scraping the inner wall of the liquid storage chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0024] Figure 2 It is a cross-sectional view of the overall structure of the present invention;

[0025] Figure 3 It is a schematic diagram of the internal structure of the present invention;

[0026] Figure 4 It is an overall cross-sectional view of the present invention;

[0027] Figure 5 This is a structural diagram of the liquid storage chamber of the present invention;

[0028] Figure 6 It is a structural diagram of the liquid distributor of the present invention;

[0029] Figure 7 This is a structural diagram of the evaporation auxiliary plate of the present invention;

[0030] Figure 8 This is a structural diagram of the liquid collector of the present invention;

[0031] Fig. 9 It is a cross-sectional view of the liquid collector of the present invention.

[0032] The reference numerals in the figure are as follows: 1. material evaporation cylinder; 2. upper evaporation auxiliary plate; 3. lower evaporation auxiliary plate; 4. steam nozzle; 5. liquid distributor; 6. liquid collector; 7. liquid storage chamber; 8. steam collecting port; 9. liquid circulation pump; 10. conveying pipeline; 11. rotating shaft; 12. scraper; 13. water collecting circle; 14. water guide groove; 15. water guide fan blade; 16. opening and closing plate; 17. support rod; 18. lifting control rod. DETAILED DESCRIPTION

[0033] This embodiment is described in detail with reference to the accompanying drawings.

[0034] In view of the fact that the viscosity of the system in the lactide reaction device makes it difficult to separate the lactide generated by the reaction and the heat transfer effect is poor, it is necessary to develop an internal enhanced interface synthesis reaction device with high mass transfer and a falling film reboiler with high heat transfer. The components in the material evaporation tube are used to fully crush the material and the vaporized material to form micron-level bubbles that are dispersed into the system to form an enhanced interface reaction system, thereby increasing the mass transfer area of ​​the vapor-liquid two phases. During the reaction process, the inner wall structure, the uniformity of material distribution, and the degree of dry wall need to be processed, and liquid is transported through a liquid redistribution element to ensure that the material flows evenly in the inner wall of the falling film tube, increase the evaporation rate, and eliminate the dry wall and material coking phenomenon. The combination of the two can shorten the reaction time, improve the reaction efficiency, inhibit the occurrence of side reactions, reduce the degree of racemization, and realize the controllable production of lactide.

[0035] When in use, the material evaporation cylinder 1 is filled with an evaporation auxiliary plate, and a steam nozzle 4 is provided at the upper end of the evaporation auxiliary plate. The liquid to be evaporated is stored in the material evaporation cylinder 1, and the lower end of the material evaporation cylinder 1 is a liquid storage chamber 7. The liquid to be evaporated is stored in the liquid storage chamber 7, and then the liquid circulation pump 9 connected to the lower end of the liquid storage chamber 7 is used to extract the liquid to be evaporated, and then the viscosity of the currently transported liquid is detected, and a certain amount of unused liquid is injected into the pipeline during the transportation process according to the viscosity to replenish it, and then the liquid is mixed and continued to be transported after passing through the circulation pump, and then transported to the steam nozzle 4 for circulation, so that the viscosity of the liquid is reduced and the subsequent steaming operation is convenient, so as to facilitate efficient steaming during the steaming operation.

[0036] During the steaming process, evaporation auxiliary plates are respectively arranged at the upper and lower ends of the material evaporation cylinder 1. The evaporation auxiliary plates are located at the upper and lower ends of the material evaporation cylinder 1. At the same time, the evaporation auxiliary plates are divided into an upper evaporation auxiliary plate 2 and a lower evaporation auxiliary plate 3. Steam nozzles 4 are respectively arranged at the upper end of the upper evaporation auxiliary plate 2 and the lower end of the lower evaporation auxiliary plate 3. The heated steam is sprayed out through the steam nozzles 4 to evaporate the reactants. A steam collecting port 8 is arranged in the middle of the material evaporation cylinder 1. The steam in the material evaporation barrel is collected through the steam collecting port 8, so that the circulation path of the steam is to enter the material evaporation cylinder 1 from the upper and lower ends of the material evaporation cylinder 1. The steam path passes through the evaporation auxiliary plate area, and then the liquid located on the evaporation auxiliary plate is heated, so that the lactide is evaporated when the liquid is heated, so that after the vaporization, The lactide flows out of the material evaporation cylinder 1 along with the steam, and then the evaporated lactide is collected. During the evaporation process, the viscosity of the lactide in the liquid will increase because a part of it is evaporated. In order to increase the evaporation efficiency, the liquid is collected at the lower end of the material evaporation cylinder 1, and then output outward after collection. After the liquid is output, the viscosity of the liquid is detected, and then after the monitoring is completed, the liquid that has not been evaporated is supplemented according to the viscosity, so that the liquid is diluted and the viscosity of the liquid is always kept within the set range. The diluted liquid is then transported to each liquid distributor 5, and then output from the corresponding liquid distributor 5, and then re-sprayed on the upper ends of the upper evaporation auxiliary plate 2 and the lower evaporation auxiliary plate 3, so that the liquid circulates and the lactide is continuously evaporated during the circulation process.

[0037] In order to prevent the evaporated liquid from existing at the lower end of the material evaporation cylinder 1 for too long and to prevent the liquid from always sticking to the inner wall of the material evaporation cylinder 1 and causing accumulation on the inner wall, a rotating shaft 11 is rotatably connected in the liquid storage chamber 7, and a plurality of scrapers 12 are fixedly connected to the rotating shaft 11. The circumference of each scraper 12 is evenly distributed on the rotating shaft 11, and the outer sides of each scraper 12 are respectively in contact with the inner wall of the liquid storage chamber 7, so that the scraper 12 scrapes the inner wall of the liquid storage chamber 7 as the rotating shaft 11 rotates, thereby preventing the liquid from becoming viscous and causing accumulation on the inner wall of the liquid storage chamber 7, and the scraper 12 is arc-shaped, and a water-guiding blade 15 is fixedly connected to the inner wall of the scraper 12, so that the water-guiding blade 15 guides the liquid as the rotating shaft 11 rotates, thereby stirring and mixing the liquid, avoiding uneven liquid flow and thus uneven liquid viscosity, and preventing uneven liquid flow and thus uneven liquid viscosity. The lower end of the cavity 7 is a water outlet, and a liftable opening and closing plate 16 is provided at the upper end of the water outlet. The opening and closing plate 16 covers the water outlet and is supported by a support rod 17 extending downward from the opening and closing plate 16. A lifting control rod 18 is connected to the liquid storage cavity 7 extending downward from the lower end of the support rod 17. The opening size of the opening and closing plate 16 is controlled by lifting and lowering the lifting control rod 18, and then the output amount of the liquid after use is controlled by the opening size of the opening and closing plate 16. The flow rate and viscosity of the newly added liquid after mixing are kept constant, and the viscosity of the circulating liquid is maintained by controlling the injection amount of the liquid after steaming, so as to make steaming better. A liquid holding port is provided at the upper end of the side of the liquid storage cavity 7. After a certain amount of liquid is stored in the liquid storage cavity 7, the excess liquid will overflow from the liquid holding port, thereby preventing the liquid height in the liquid storage cavity 7 from always being kept at a certain height.

[0038] A liquid collector 6 for receiving the liquid in the upper evaporation auxiliary plate 2 is provided at the lower end of the upper evaporation auxiliary plate 2. The liquid collector 6 includes an annular water collecting ring 13. The outer ring of the water collecting ring 13 is attached to the inner wall of the material evaporation cylinder 1 and opens upward. Two layers of water guide grooves 14 are provided in the water collecting ring 13. Adjacent water guide grooves 14 are arranged alternately. At the same time, the water guide grooves 14 are semicircular and open upward. Both ends of the water guide grooves 14 are connected to the water collecting ring 13, so that the liquid dripping in the water guide groove 14 flows into the water collecting ring 13, and then the water collecting ring 13 is connected to the drainage pump outward, and then the collection is completed. The collected liquid is circulated again, and the liquid collector 6 can only collect a part of the liquid, and the excess liquid will not have a great influence on the evaporation effect even if it drips down on the lower evaporation auxiliary plate 3 in time. The evaporation auxiliary plate is divided into an upper evaporation auxiliary plate 2 and a lower evaporation auxiliary plate 3, which can not only avoid the problem of incomplete evaporation and uneven heating caused by the height of the evaporation auxiliary plate being too high, but also be divided into a multi-stage structure, and steam is transported to the multi-stage structure respectively at the same time, so that the temperature of the evaporation part can always be maintained within the set range, avoiding the problem of uneven temperature caused by heat consumption during the evaporation process.

[0039] The evaporation auxiliary plates include transverse plates and longitudinal plates, which are arranged alternately and the outer sides of the evaporation auxiliary plates are in contact with the inner sides of the material evaporation cylinder 1 respectively. The lower ends of the transverse plates and the longitudinal plates are corrugated structures, so that the multiple layers of evaporation auxiliary plates are always in contact with each other during the contact process. The liquid on the upper evaporation auxiliary plates will fully contact with the lower evaporation auxiliary plates during the downward flow, and the liquid on the transverse plates and the longitudinal plates is flattened on the evaporation auxiliary plates to accelerate the evaporation process, thereby improving the evaporation efficiency of lactide.

[0040] The steam nozzle 4 includes an upper end of the upper evaporation auxiliary plate 2 and a lower end of the lower evaporation auxiliary plate 3, and a plurality of nozzles are evenly distributed on the circumference of the steam nozzle 4, through which the heated steam is ejected, and the evaporation efficiency of the evaporation auxiliary plate is maintained by the ejected heated steam, and the heat is maintained at the temperature in the material evaporation cylinder 1. Since the heat will rise and be maintained at the upper end of the material evaporation cylinder 1, although the evaporation efficiency in the lower evaporation auxiliary plate 3 is not as good as that in the upper evaporation auxiliary plate 2, it can assist in raising the temperature of the liquid in the material evaporation cylinder 1, and then the heated liquid drips back into the liquid storage chamber 7, and the liquid in the liquid storage chamber 7 is re-circulated, thereby avoiding the large temperature difference of the liquid during the circulation process, which causes the liquid to cool down after being ejected from the liquid distributor 5, thereby improving the evaporation efficiency.

[0041] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A lactide depolymerization substrate recycling process and equipment, characterized in that: The invention comprises a material evaporation cylinder (1), wherein the material evaporation cylinder (1) is filled with evaporation auxiliary plates, the evaporation auxiliary plates are respectively located at the upper and lower ends of the material evaporation cylinder (1), the evaporation auxiliary plates are divided into an upper evaporation auxiliary plate (2) and a lower evaporation auxiliary plate (3), a steam nozzle (4) is respectively provided at the upper end of the upper evaporation auxiliary plate (2) and the lower end of the lower evaporation auxiliary plate (3), a liquid distributor (5) is respectively provided at the upper end of the upper evaporation auxiliary plate (2) and the upper end of the lower evaporation auxiliary plate (3), and a liquid collector (6) is provided at the lower end of the upper evaporation auxiliary plate (2), a liquid storage chamber (7) is provided at the lower end of the material evaporation cylinder (1), a steam collection port (8) for collecting steam is provided on the side of the middle part of the material evaporation cylinder (1), a liquid circulation pump (9) is connected to the lower end of the liquid storage chamber (7), and the liquid circulation pump (9) is respectively connected to each liquid distributor (5) through a conveying pipeline (10).

2. A lactide depolymerization substrate recycling process and equipment according to claim 1, characterized in that: The evaporation auxiliary plates are multiple and are evenly spaced vertically. The evaporation auxiliary plates include transverse plates and longitudinal plates that are staggered, and adjacent evaporation auxiliary plates are in contact with each other.

3. The process and equipment for recycling lactide depolymerization substrate according to claim 1, characterized in that: A rotating shaft (11) is rotatably connected in the liquid storage chamber (7), and scrapers (12) are evenly distributed on the circumference of the rotating shaft (11). The scrapers (12) are arc-shaped structures and fit against the inner wall of the liquid storage chamber (7). The lower end of the rotating shaft (11) extends downwardly out of the liquid storage chamber (7) and is connected to a driving motor.

4. The process and equipment for recycling lactide depolymerization substrate according to claim 1, characterized in that: The liquid distributor (5) comprises a storage tank, in which a water pump is arranged, a liquid storage cavity (7) is connected to a water inlet of the storage tank, and a water outlet of the storage tank is connected to each liquid distributor (5) respectively.

5. A lactide depolymerization substrate recycling process and equipment according to claim 4, characterized in that: The liquid collector (6) comprises a water collecting circle (13), in which two layers of water guide grooves (14) are evenly spaced and arranged, and adjacent water guide grooves (14) are arranged in a staggered manner, and both ends of the water guide grooves (14) are respectively connected to the water collecting circle (13).

6. A lactide depolymerization substrate recycling process and equipment according to claim 3, characterized in that: A water guide blade (15) is provided on the inner side of the scraper (12), and the water guide blade (15) is arranged obliquely and extends toward the inner side of the liquid storage chamber (7).

7. A lactide depolymerization substrate recycling process and equipment according to claim 6, characterized in that: A water outlet is provided at the lower end of the liquid storage chamber (7), and an opening and closing plate (16) for covering the water outlet is provided inside the liquid storage chamber (7). A support rod (17) extends downward from the lower end of the opening and closing plate (16), and the lower end of the support rod (17) extends out of the liquid storage chamber (7) and is connected to a lifting control rod (18).

8. The process and equipment for recycling lactide depolymerization substrate according to claim 1, characterized in that: The steam nozzles (4) are respectively located at the upper end of the upper evaporation auxiliary plate (2) and the lower end of the lower evaporation auxiliary plate (3); the steam nozzles (4) include a pair of nozzles, and the nozzles are evenly distributed on the circumference of the steam nozzles (4).

9. A lactide depolymerization substrate recycling process and equipment according to claim 8, characterized in that: A steam collecting port (8) is provided in the middle of the material evaporation cylinder (1), and an extended end of the steam collecting port (8) extends obliquely upward toward the outside and is connected to a collecting device.

10. A lactide depolymerization substrate recycling process and equipment according to claim 5, characterized in that: The outside of the water collecting circle (13) is connected to a water delivery pump, which delivers the liquid in the water collecting circle (13) to the outside, and the water outlet of the water delivery pump is connected to the liquid distributor (5).

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