Energy-saving and environment-friendly differential polyester glycol recovery device

Abstract

The utility model discloses an energy-saving and environment-friendly differential polyester glycol recovery device, which relates to the technical field of recovery devices, and comprises a crude EG tank, a low-boiling tower, a heater, a distillation kettle and a refined EG tank which are sequentially connected, and further comprises a settling tank arranged between the crude EG tank and the low-boiling tower, the crude EG tank, the settling tank, the low-boiling tower and the heater as well as the distillation kettle and the refined EG tank are sequentially connected through liquid delivery pumps; wherein the top of the settling tank is connected with a second liquid delivery pump, and the bottom of the settling tank is connected with a solid delivery pump; wherein the added special settling tank is only added on the basis of the original facility, and the settling tank equipment can use the old modified settling tank and the pipeline, so that the environment-friendly recovery of the crude ethylene glycol solution can be realized without increasing the equipment cost, the industrial universality is realized, and the method can be widely applied to the aspect of polyester industrial recovery and utilization. Polyester enterprises are assisted to realize green development.

Description

Technical Field

[0001] This utility model relates to the field of recycling equipment technology, specifically to an energy-saving and environmentally friendly differentiated polyester glycol recycling device. Background Technology

[0002] With the continuous growth of differentiated polyester industrial capacity, both domestic and international attention is increasingly focused on the treatment of crude ethylene glycol during polyester production. Ordinary polyethylene terephthalate (PET) is produced by esterification and polycondensation of terephthalic acid (PTA) and ethylene glycol (EG) using antimony-based or titanium-based catalysts to obtain polyester chips. In contrast, differentiated PET polyester is produced by adding modified monomers such as sodium isophthalate-5-sulfonate (SIPA), isophthalic acid (IPA), adipic acid, neopentyl glycol, and polyethylene glycol (PEG) of different molecular weights. In differentiated polyester polymerization, the addition of SIPA can significantly improve the water solubility and dyeing properties of PET polyester. However, it easily causes foaming in the reaction system during polymerization, and under high temperature, the foam entrainment phenomenon in the reaction system is severe. This leads to a large amount of oligomers, esters, unreacted or partially reacted PTA, IPA, SIPA, and other monomers entering the recovered crude EG. At the same time, since PEG of different molecular weights is not easily grafted into the main chain during polymerization, under negative pressure conditions, a large amount of PEG is extracted into the crude EG. In addition, low-boiling-point byproducts such as acetaldehyde, 2-methyl-1,3-dioxolane, and 1,4-dioxane, which occur during esterification and polycondensation, are also distilled out of the system. Therefore, the composition of the crude EG solution in the esterification and polycondensation process of differentiated polyester is more complex and more difficult to separate than that of glossy PET.

[0003] To reduce polyester production costs and balance EG production, polyester manufacturers need to recycle and utilize crude EG. For example, patent document CN203668271U discloses an EG recycling system for an esterification tower, in which recycled EG and fresh EG are partially mixed and connected to a high-temperature EG cooling pipeline, which is also connected to the high-temperature EG cooling pipeline before entering the EG in the boiling tower. Finally, the EG is recycled back to the esterification tower through a filtration device. Patent document CN105037095A discloses a high-efficiency and environmentally friendly EG recycling method, in which EG waste liquid is pressurized into an ultrafiltration system through a filter using a booster pump; then, it passes through two filters and two electrodialysis processes to obtain recycled EG. However, this method is prone to filter clogging and has limited processing capacity.

[0004] Currently, PET manufacturers primarily use a combination of low-boiling-point distillation and high-temperature distillation to recover crude EG. While this method is simple, it easily leads to oligomers carried over from the crude EG undergoing intermolecular polymerization and cross-linking during prolonged, negative-pressure, high-temperature distillation, forming a viscous, asphalt-like solid that cannot be reused, resulting in raw material waste. Furthermore, the viscous solid at the bottom of the distillation vessel needs to be incinerated, causing environmental problems and increased energy consumption. In addition, as the amount of viscous solid in the distillation vessel increases, high-temperature cooking is required before waste discharge to ensure it remains solid, further wasting significant energy and reducing the quality of the recovered EG. Utility Model Content

[0005] The purpose of this invention is to provide an energy-saving and environmentally friendly differentiated polyester glycol recovery device. Through a specially designed settling tank, the polymer separation in crude ethylene glycol is changed from post-treatment separation to pre-treatment separation. The polymer separated by this method does not undergo high-temperature treatment. Through process optimization, the recovered polymer can be reused in the product through depolymerization and other methods, becoming part of the product. This invention solves the following technical problems:

[0006] (1) How to reduce the viscous material at the bottom of the distillation vessel and reduce energy consumption during the crude EG recovery process.

[0007] (2) How to maximize the utilization of raw materials and minimize production costs while ensuring the quality of recycled EG.

[0008] The objective of this utility model can be achieved through the following technical solutions:

[0009] In a first aspect, this utility model discloses an energy-saving and environmentally friendly differentiated polyester ethylene glycol recovery device, comprising a crude EG tank, a low-boiling tower, a heater, a distillation kettle, and a refined EG tank connected in sequence, and a settling tank. The settling tank is located between the crude EG tank and the low-boiling tower. The crude EG tank, the settling tank, the low-boiling tower, the heater, and the distillation kettle and the refined EG tank are all connected in sequence by liquid transfer pumps. The top of the settling tank is connected to a second liquid transfer pump, and the bottom is connected to a solid transfer pump.

[0010] The settling tank includes a settling vessel, a top overflow baffle, a vertical plate for the settling liquid recycling area, a settling liquid recycling area, a feed hollow pipe, and a liquid distribution device. The top overflow baffle is located at the top of the settling vessel, the liquid distribution device is located below the top overflow baffle, the settling liquid recycling area is located between the liquid distribution device and the top overflow baffle, the vertical plate for the settling liquid recycling area is located below the top overflow baffle, and the feed hollow pipe passes through the top of the settling vessel, with its lower end connected to the liquid distribution device.

[0011] In a further embodiment of this invention: the crude EG tank is connected to the settling tank via a No. 1 liquid transfer pump; the settling tank is connected to the low-boiling tower via a No. 3 liquid transfer pump; the low-boiling tower is connected to the heater via a No. 4 liquid transfer pump; the heater is connected to the distillation kettle via a transfer pipeline; the distillation kettle is connected to the refined EG tank via a No. 5 liquid transfer pump; and the output end of the refined EG tank is also connected to a No. 6 liquid transfer pump.

[0012] In a further embodiment of this utility model: the diameter of the settling tank is 1000mm to 5000mm, the diameter-to-height ratio is 1:1 to 1:5, and the included angle c at the bottom of the settling tank ranges from 110° to 160°; the top overflow baffle is serrated, the angle of the top of the serration is 15° to 30°, the distance from the lowest point to the highest point of the serration is 20mm to 100mm, and the highest point of the serration is 50mm to 200mm lower than the outer perimeter of the settling tank; the height a of the vertical plate of the settling liquid reuse zone ranges from 100mm to 500mm; the settling liquid reuse zone occupies 10% to 40% of the cross-sectional area of ​​the settling tank 401; and the depth b of the feed hollow tube is 100-2000mm.

[0013] In a further embodiment of this utility model, the recycling method of the energy-saving and environmentally friendly differentiated polyester glycol recycling device includes the following steps:

[0014] S1. The crude EG in the crude EG tank is transferred to the settling tank by the No. 1 liquid transfer pump;

[0015] S2. The crude EG entering the settling tank undergoes solid-liquid separation by gravity. The upper part is liquid ethylene glycol separated from the settling liquid recycling zone, and the bottom part is the separated solid. Part of the ethylene glycol in the settling liquid recycling zone is sent to the pulping kettle or diester via the No. 2 liquid transfer pump, and the other part is sent to the low-boiling tower via the No. 3 liquid transfer pump. The solid at the bottom is removed by the solid transfer pump and sent to the diester for recycling.

[0016] S3. Ethylene glycol entering the low-boiling tower is fractionally distilled to remove water, acetaldehyde, 2-methyl-1,3-dioxolane, 1,4-dioxane and other low-boiling substances, and then sent to the distillation kettle by the No. 4 liquid transfer pump.

[0017] S4. Distill the ethylene glycol that enters the distillation kettle. The ethylene glycol distilled from the top of the distillation kettle is cooled by the condenser and then sent to the EG return tank for later use by the No. 5 liquid transfer pump. The viscous substance distilled from the bottom of the distillation kettle is discharged as waste after it meets the waste discharge standard.

[0018] In a further embodiment of this invention: in step S1, the crude EG is transported to the settling tank by a No. 1 liquid transfer pump at a flow rate of 0.5 to 7 T / h.

[0019] In a further embodiment of this invention: in step S2, when the crude EG enters the settling tank for solid-liquid separation, the temperature of the settling tank is 30-45℃.

[0020] In a further embodiment of this invention: in step S2, 0-40% of the ethylene glycol in the settling liquid recycling zone is fed into the pulping kettle or diester via a second liquid transfer pump, and the remaining ethylene glycol is fed into the low-boiling tower via a third liquid transfer pump.

[0021] In a further embodiment of this invention: in step S3, the temperature in the low-boiling tower is 110-140℃, the pressure is 9kPa-21kPa, and the temperature at the top of the column is 44℃-62℃.

[0022] In a further embodiment of this utility model: in step S4, the bottom temperature of the distillation vessel is 10℃-280℃, the pressure is 3.9kPa-20.0kPa, and the column top temperature is 110℃-155℃.

[0023] The beneficial effects of this utility model are:

[0024] (1) Compared with the traditional process technology of using PET to process crude ethylene glycol solution in the production of differentiated polyester, this utility model uses a sedimentation tank to environmentally recover oligomers from crude EG solution. The separated polymers have not undergone high temperature treatment. Through process optimization, the recovered polymers can be reused in the product through depolymerization and other methods and become part of the product.

[0025] (2) By adding a settling tank between the crude EG tank and the low-boiling tower, the crude EG can be separated into solid and liquid components to remove solid impurities. This improves the processing capacity and efficiency of the separated ethylene glycol when it enters the low-boiling tower and the distillation kettle, enhances the quality of ethylene glycol recovery, and reduces the amount of viscous material generated at the bottom of the distillation kettle, thereby reducing the energy consumption of the distillation kettle and achieving green treatment of the crude ethylene glycol solution.

[0026] (3) Compared with similar differentiated polyester enterprises, this utility model can reduce processing energy consumption by up to 20% and increase raw material utilization rate by up to 5%, thereby achieving full utilization of raw materials and reducing production costs.

[0027] (4) The special settling tank added in this utility model is simply an addition to the existing facilities. The settling tank equipment can use existing settling tanks and pipes that have been modified and reused. It can achieve environmentally friendly recycling of crude ethylene glycol solution without increasing equipment costs. It has industry universality and can be widely used in the recycling of polyester industry, helping polyester enterprises to achieve green development. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings.

[0029] Figure 1 This is a schematic diagram of the energy-saving and environmentally friendly differentiated polyester glycol recovery device in Embodiment 1 of this utility model;

[0030] Figure 2 yes Figure 1 A schematic diagram of the settling tank 4 in the diagram.

[0031] In the diagram: 1. Crude EG tank; 2. Liquid transfer pump No. 1; 3. Liquid transfer pump No. 2; 4. Settling tank; 401. Settling vessel; 402. Top overflow baffle; 403. Vertical plate of the settling liquid recycling area; 404. Settling liquid recycling area; 405. Feed hollow pipe; 406. Liquid inlet distribution device; 5. Solid transfer pump; 6. Liquid transfer pump No. 3; 7. Low boiling tower; 8. Liquid transfer pump No. 4; 9. Heater; 10. Distillation vessel; 11. Liquid transfer pump No. 5; 12. Refined EG tank; 13. Liquid transfer pump No. 6. Detailed Implementation

[0032] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0033] Example 1

[0034] Please see Figure 1 This embodiment discloses an energy-saving and environmentally friendly differentiated polyester glycol recovery device, including a crude EG tank 1, a settling tank 4, a low-boiling tower 7, a heater 9, a distillation kettle 10, and a refined EG tank 12 arranged in sequence. The crude EG tank 1 and the settling tank 4 are connected by a first liquid transfer pump 2. The settling tank 4 and the low-boiling tower 7 are connected by a third liquid transfer pump 6. The low-boiling tower 7 and the heater 9 are connected by a fourth liquid transfer pump 8. The heater 9 and the distillation kettle 10 are connected by a transfer pipeline. The distillation kettle 10 and the refined EG tank 12 are connected by a fifth liquid transfer pump 11. The output end of the refined EG tank 11 is also connected to a sixth liquid transfer pump 13.

[0035] Please see Figure 2The settling tank 4 includes a settling vessel 401, a top overflow baffle 402, a vertical plate 403 for the settling liquid recycling area, a settling liquid recycling area 404, a feed hollow pipe 405, and a liquid distribution device 406. A second liquid transfer pump 3 is connected to the top of the settling tank 4, and a solid transfer pump 5 is connected to the bottom. The top overflow baffle 402 is located at the top of the settling vessel 401, the liquid distribution device 406 is located below the top overflow baffle 402, the settling liquid recycling area 404 is located between the liquid distribution device 406 and the top overflow baffle 402, the vertical plate 403 for the settling liquid recycling area is located below the top overflow baffle 402, and the feed hollow pipe 405 passes through the top of the settling vessel 401, with its lower end connected to the liquid distribution device 406 in the settling vessel.

[0036] Specifically, the settling tank 401 has a diameter of 1000mm to 5000mm and a diameter-to-height ratio of 1:1 to 1:5. The included angle c at the bottom of the settling tank 401 ranges from 110° to 160°. The top overflow baffle 402 is serrated, with the angle at the top of the serrations ranging from 15° to 30°. The distance between the lowest and highest points of the serrations is 20mm to 100mm, and the highest point of the serrations is 50mm to 200mm lower than the outer perimeter of the settling tank 401. The height a of the vertical plate 403 in the settling liquid recycling zone ranges from 100mm to 500mm. The settling liquid recycling zone 404 occupies 10% to 40% of the cross-sectional area of ​​the settling tank 401. The depth b of the feed hollow pipe 405 is 100-2000mm.

[0037] Example 2

[0038] This embodiment discloses a recycling method for the energy-saving and environmentally friendly differentiated polyester glycol recycling device in Embodiment 1, including the following steps:

[0039] S1. The crude EG in the crude EG tank is transferred to the settling tank 4 by the No. 1 liquid transfer pump 2 at a flow rate of 0.5 to 3 T / h.

[0040] S2. The temperature of the settling tank 4 is controlled at 30-45℃. The liquid distribution device 404 is placed at a depth of 100-2000mm above the liquid surface. The coarse EG entering the settling tank 4 undergoes solid-liquid separation by gravity. The upper part is the separated liquid ethylene glycol, and the bottom part is the separated solid. Among the ethylene glycol in the upper part, 0-40% of the ethylene glycol is sent to the pulping kettle or diester via the second liquid transfer pump 3, and the remaining ethylene glycol is sent to the low-boiling tower 7 via the third liquid transfer pump 6. The solid at the bottom is removed by the solid transfer pump 5 and sent to the diester for recycling.

[0041] S3. The temperature inside the low-boiling column 7 is controlled at 110-140℃, the pressure at 9kPa-21kPa, and the column top temperature at 44℃-62℃. The ethylene glycol entering the low-boiling column 7 is fractionally distilled to remove water, acetaldehyde, 2-methyl-1,3-dioxocyclopentane, 1,4-dioxane and other low-boiling substances, and then sent to the distillation kettle 10 through the No. 4 liquid transfer pump 8.

[0042] S4. Control the bottom temperature of the distillation vessel 10 to 10℃-280℃, the pressure to 3.9kPa-20.0kPa, and the top temperature to 110℃-155℃. Distill the ethylene glycol entering the distillation vessel 10. The ethylene glycol distilled from the top of the distillation vessel 10 is cooled by the condenser and then sent to the return EG tank 12 for later use by the No. 5 liquid transfer pump 11. The viscous substance distilled from the bottom of the distillation vessel 10 is discharged after meeting the waste discharge standard.

[0043] Next, using the energy-saving and environmentally friendly differentiated polyester glycol recovery device disclosed in Example 1, the glycol recovery products generated in the production of water-soluble polyester were processed in Examples 3-6 using the recovery method disclosed in Example 2.

[0044] Example 3

[0045] In this embodiment, the parameters of the settling tank 4 are as follows: the diameter of the settling vessel 401 is 2000mm, the diameter-to-height ratio is 1:2, and the included angle c at the bottom of the settling vessel is 120°; the top overflow baffle 402 is serrated, the angle of the top of the serration is 15°, the distance from the lowest point to the highest point of the serration is 50mm, and the highest point of the serration is 50mm lower than the outer perimeter of the settling vessel 401; the height a of the vertical plate 403 in the settling liquid recycling area is 100mm; the settling liquid recycling area 404 occupies 15% of the cross-sectional area of ​​the settling vessel 401; and the depth b of the feed hollow pipe 405 is 700mm.

[0046] The crude EG recovered from the production line is fed into crude EG tank 1. The crude EG in tank 1 is then pumped to settling tank 4 at a flow rate of 1 T / h via liquid transfer pump 2. The temperature in settling tank 4 is maintained at 35℃. The crude EG in settling tank 4 undergoes solid-liquid separation. The upper portion is the separated liquid ethylene glycol, and the bottom portion is the separated solid. The upper portion of ethylene glycol is pumped into low-boiling tower 7 via liquid transfer pump 6, while the bottom solid is removed by pipette pump 3 and sent to the diester for further processing. The temperature in low-boiling tower 7 is controlled at 120℃. With a pressure of 14 kPa and a column top temperature of 53°C, ethylene glycol entering the low-boiling column 7 is fractionated to remove water and low-boiling substances, and then sent to the distillation kettle 10 via liquid transfer pump 8. The bottom temperature of the distillation kettle 10 is controlled at 250°C, the pressure at 11 kPa, and the column top temperature at 148°C to distill the ethylene glycol entering the distillation kettle 10. The ethylene glycol distilled from the top of the distillation kettle 10 is cooled by a condenser and then sent to the return EG tank 12 for later use via liquid transfer pump 11. The viscous substance distilled from the bottom of the distillation kettle 10 is discharged as waste after meeting the waste discharge standard.

[0047] Example 4

[0048] In this embodiment, the parameters of the settling tank 4 are as follows: the diameter of the settling vessel 401 is 2500mm, the diameter-to-height ratio is 1:2, the included angle c at the bottom of the settling vessel 401 is 120°; the top overflow baffle 402 is serrated, the angle of the top of the serration is 30°, the distance from the lowest point to the highest point of the serration is 40mm, and the highest point of the serration is 50mm lower than the outer perimeter of the settling vessel 401; the height a of the vertical plate 403 in the settling liquid recycling area is 100mm; the settling liquid recycling area 404 occupies 20% of the cross-sectional area of ​​the settling vessel 401; the depth b of the feed hollow pipe 405 is 900mm.

[0049] The crude EG recovered from the production line is sent to crude EG tank 1. The crude EG in crude EG tank 1 is then pumped to settling tank 4 at a flow rate of 1.5 T / h via liquid transfer pump 2. The temperature in settling tank 4 is maintained at 35℃. The crude EG entering settling tank 4 undergoes solid-liquid separation. The upper part is the separated liquid ethylene glycol, and the bottom part is the separated solid. The upper part of the ethylene glycol contains 20% ethylene glycol. 1% of ethylene glycol enters the pulping kettle system via liquid transfer pump 5 (number 2). The remaining ethylene glycol enters the low-boiling tower 7 via liquid transfer pump 6 (number 3). The solids at the bottom are removed by transfer pump 3 and sent to the diester for further processing. The temperature in the low-boiling tower 7 is controlled at 130°C, the pressure at 14 kPa, and the column top temperature at 53°C. The ethylene glycol entering the low-boiling tower 7 is fractionated to remove water and low-boiling substances, and then sent to the distillation kettle 10 via liquid transfer pump 8 (number 4). The bottom temperature of the distillation kettle 10 is controlled at 250°C, the pressure at 11 kPa, and the column top temperature at 148°C. The ethylene glycol entering the distillation kettle 10 is distilled. The ethylene glycol distilled from the top of the distillation kettle 10 is cooled by a condenser and then sent to the EG return tank 12 via liquid transfer pump 11 (number 5) for later use. The viscous material distilled from the bottom of the distillation kettle 10 is discharged as waste after meeting the discharge standards.

[0050] Example 5

[0051] In this embodiment, the parameters of the settling tank 4 are as follows: the diameter of the settling vessel 401 is 2500mm, the diameter-to-height ratio is 1:2, the included angle c at the bottom of the settling vessel 401 is 120°; the top overflow baffle 402 is serrated, the angle of the top of the serration is 30°, the distance from the lowest point to the highest point of the serration is 40mm, and the highest point of the serration is 50mm lower than the outer perimeter of the settling vessel 401; the height a of the vertical plate 403 in the settling liquid recycling area is 200mm; the settling liquid recycling area 404 occupies 30% of the cross-sectional area of ​​the settling vessel 401; the depth b of the feed hollow pipe 405 is 1200mm.

[0052] The crude EG recovered from the production line is sent to crude EG tank 1. The crude EG in crude EG tank 1 is then pumped to settling tank 4 at a flow rate of 2T / h via liquid transfer pump 2. The temperature in settling tank 4 is maintained at 40℃. The crude EG entering settling tank 4 undergoes solid-liquid separation. The upper part is the separated liquid ethylene glycol, and the bottom part is the separated solid. The upper part of the ethylene glycol contains 40% ethylene glycol. 1% of ethylene glycol enters the pulping kettle system via liquid transfer pump 5 (number 2). The remaining ethylene glycol enters the low-boiling tower 7 via liquid transfer pump 6 (number 3). The solids at the bottom are removed by transfer pump 3 and sent to the diester for further processing. The temperature in the low-boiling tower 7 is controlled at 140℃, the pressure at 12kPa, and the column top temperature at 49℃. The ethylene glycol entering the low-boiling tower 7 is fractionated to remove water and low-boiling substances, and then sent to the distillation kettle 10 via liquid transfer pump 8 (number 4). The bottom temperature of the distillation kettle 10 is controlled at 260℃, the pressure at 9.7kPa, and the column top temperature at 144℃. The ethylene glycol entering the distillation kettle 10 is distilled. The ethylene glycol distilled from the top of the distillation kettle 10 is cooled by a condenser and then sent to the EG return tank 12 via liquid transfer pump 11 (number 5) for later use. The viscous material distilled from the bottom of the distillation kettle 10 is discharged as waste after meeting the discharge standards.

[0053] Example 6

[0054] In this embodiment, the parameters of the settling tank 4 are as follows: the diameter of the settling vessel 401 is 3000mm, the diameter-to-height ratio is 1:2, the included angle c at the bottom of the settling vessel 401 is 120°; the top overflow baffle 402 is serrated, the angle of the top of the serration is 45°, the distance from the lowest point to the highest point of the serration is 50mm, and the highest point of the serration is 50mm lower than the outer perimeter of the settling vessel 401; the height a of the vertical plate 403 in the settling liquid recycling area is 300mm; the settling liquid recycling area 404 occupies 40% of the cross-sectional area of ​​the settling vessel 401; the depth b of the feed hollow pipe 405 is 1800mm.

[0055] The crude EG recovered from the production line is sent to crude EG tank 1. The crude EG in crude EG tank 1 is then pumped to settling tank 4 at a flow rate of 2T / h by liquid transfer pump 2. The temperature in settling tank 4 is maintained at 45℃, and the liquid inlet distribution device 404 is placed 900mm above the liquid surface. The crude EG entering settling tank 4 undergoes solid-liquid separation. The upper part is the separated liquid ethylene glycol, and the bottom part is the separated solid. The upper part of the ethylene glycol contains 50% volatile organic compounds (VOCs). 1% of ethylene glycol enters the pulping kettle system via liquid transfer pump 5 (number 2). The remaining ethylene glycol enters the low-boiling tower 7 via liquid transfer pump 6 (number 3). The solids at the bottom are removed by transfer pump 3 and sent to the diester for further processing. The temperature in the low-boiling tower 7 is controlled at 150°C, the pressure at 10 kPa, and the column top temperature at 46°C. The ethylene glycol entering the low-boiling tower 7 is fractionated to remove water and low-boiling substances, and then sent to the distillation kettle 10 via liquid transfer pump 8 (number 4). The bottom temperature of the distillation kettle 10 is controlled at 270°C, the pressure at 6.9 kPa, and the column top temperature at 138°C. The ethylene glycol entering the distillation kettle 10 is distilled. The ethylene glycol distilled from the top of the distillation kettle 10 is cooled by a condenser and then sent to the return EG tank 12 via liquid transfer pump 11 (number 5) for later use. The viscous material distilled from the bottom of the distillation kettle 10 is discharged as waste after meeting the discharge standards.

[0056] Comparative Example 1

[0057] Ethylene glycol is recovered using existing recycling devices. First, the energy-saving and environmentally friendly differentiated polyester ethylene glycol recovery device from Example 1 is modified by removing the settling tank 4 and the third liquid transfer pump 6, and directly connecting the output of the first liquid transfer pump 2 to the input of the low-boiling tower 7. Other structures remain unchanged, resulting in the existing recycling device. Then, ethylene glycol produced in the production of water-soluble polyester is recovered using the following method:

[0058] The crude EG recovered from the production line is sent to crude EG tank 1. The crude EG in crude EG tank 1 is then pumped to low-boiling tower 7 at a flow rate of 1T / h by liquid transfer pump 2. The temperature in low-boiling tower 7 is controlled at 120℃, the pressure at 14kPa, and the column top temperature at 53℃. The ethylene glycol entering low-boiling tower 7 is fractionated to remove water and low-boiling substances, and then sent to distillation kettle 10 by liquid transfer pump 8. The bottom temperature of distillation kettle 10 is controlled at 250℃, the pressure at 11kPa, and the column top temperature at 148℃. The ethylene glycol entering distillation kettle 10 is then distilled. The ethylene glycol distilled from the top of distillation kettle 10 is cooled by a condenser and then sent to refined EG tank 12 for later use by liquid transfer pump 11. The viscous substance distilled from the bottom of distillation kettle 10 is discharged as waste after meeting the waste discharge standards.

[0059] The effectiveness of the recycling methods in Examples 3-6 and Comparative Example 1 was tested, including sedimentation efficiency, raw material utilization improvement rate, energy consumption reduction rate, number of waste discharges, and cost reduction rate. The testing methods are as follows.

[0060] (1) Settling efficiency:

[0061] Where: C in The concentration of the inlet solution is g / L; C out The concentration of the solution at the outlet is in g / L.

[0062] (2) Improved raw material utilization rate:

[0063] Where: m1 is the slice mass after the solids in the settling tank are recycled into the system; m0 is the slice mass when the solids in the settling tank are not recycled.

[0064] (3) Energy consumption reduction rate:

[0065] Wherein: E0 represents the amount of natural gas used to process the same crude ethylene glycol without using a settling tank; E1 represents the amount of natural gas used to process the same crude ethylene glycol after using a settling tank.

[0066] (4) Number of waste discharges: based on actual production statistics.

[0067] The test results are listed in Table 1, as follows:

[0068] Table 1

[0069] Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Settling efficiency (%) 15 27 35 43 / Raw material utilization improvement rate (%) 1.0 2.3 3.4 5.0 0 Energy consumption reduction rate (%) 8 13 17 20 0 Waste discharge frequency (times / month) 4 4 3 2 5

[0070] Analysis of the data in Table 1 shows that, compared to Comparative Example 1, Examples 1-4 can settle solid impurities in crude EG, thereby reducing the problem of excessive viscous material at the bottom of the distillation vessel; the raw material utilization rate is improved, energy consumption is reduced, the number of waste discharges is reduced, and costs are lowered; therefore, the recycling device and method of this utility model can effectively improve the processing efficiency of crude EG and reduce energy consumption while ensuring the stability of product indicators and without increasing equipment costs, thereby increasing product profit margins, and is applicable to relevant polymerization recycling processes.

[0071] In the description of this utility model, it should be understood that the terms "upper," "lower," "left," and "right," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation or specific orientational structure and operation. Therefore, they should not be construed as limitations on this utility model. Furthermore, "first" and "second" are only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "multiple" means two or more.

[0072] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0073] The above description provides a detailed account of one embodiment of the present invention. However, this description is merely a preferred embodiment and should not be construed as limiting the scope of the present invention. All equivalent variations and improvements made within the scope of the claims of the present invention should still fall within the patent coverage of the present invention.

Claims

1. An energy-saving and environmentally friendly differentiated polyester glycol recovery device, comprising a crude EG tank (1), a low-boiling tower (7), a heater (9), a distillation kettle (10), and a refined EG tank (12) connected in sequence, characterized in that, It also includes a settling tank (4), which is located between the crude EG tank (1) and the low-boiling tower (7). The crude EG tank (1), the settling tank (4), the low-boiling tower (7), the heater (9), the distillation kettle (10), and the return EG tank (12) are all connected in sequence by liquid transfer pumps. The top of the settling tank (4) is connected to a second liquid transfer pump (3), and the bottom is connected to a solid transfer pump (5). The settling tank (4) includes a settling vessel (401), a top overflow baffle (402), a vertical plate (403) for the settling liquid recycling area, a settling liquid recycling area (404), a feed hollow pipe (405), and a liquid distribution device (406). The top overflow baffle (402) is located at the top of the settling vessel (401), the liquid distribution device (406) is located below the top overflow baffle (402), the settling liquid recycling area (404) is located between the liquid distribution device (406) and the top overflow baffle (402), the vertical plate (403) for the settling liquid recycling area is located below the top overflow baffle (402), and the feed hollow pipe (405) passes through the top of the settling vessel (401) and its lower end is connected to the liquid distribution device (406).

2. The energy-saving and environmentally friendly differentiated polyester glycol recovery device according to claim 1, characterized in that, The crude EG tank (1) is connected to the settling tank (4) by a No. 1 liquid transfer pump (2), the settling tank (4) is connected to the low-boiling tower (7) by a No. 3 liquid transfer pump (6), the low-boiling tower (7) is connected to the heater (9) by a No. 4 liquid transfer pump (8), the heater (9) is connected to the distillation kettle (10) by a transfer pipeline, the distillation kettle (10) is connected to the refined EG tank (12) by a No. 5 liquid transfer pump (11), and the output end of the refined EG tank (12) is also connected to a No. 6 liquid transfer pump (13).

3. The energy-saving and environmentally friendly differentiated polyester glycol recovery device according to claim 1, characterized in that, The settling tank (401) has a diameter of 1000mm~5000mm and a diameter-to-height ratio of 1:1~1:

5. The included angle c at the bottom of the settling tank (401) ranges from 110° to 160°. The top overflow baffle (402) is serrated with a serrated tip angle of 15°~30°. The distance from the lowest point to the highest point of the serration is 20mm~100mm. The highest point of the serration is 50mm~200mm lower than the outer perimeter of the settling tank (401). The height a of the vertical plate (403) of the settling liquid reuse area ranges from 100mm~500mm. The settling liquid reuse area (404) occupies 10%~40% of the cross-sectional area of ​​the settling tank (401).

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