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

Abstract

The invention discloses an energy-saving and environment-friendly differential polyester glycol recovery device and a recovery method thereof, and relates to the technical field of recovery devices.The recovery device comprises a crude EG tank, a low-boiling tower, a heater, a distillation still and a refined EG tank which are sequentially connected, and further comprises a settling tank which is 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] The invention relates to the technical field of recovery devices, and in particular to an energy-saving and environmentally friendly differentiated polyester glycol recovery device and a recovery method thereof. Background Art

[0002] With the continuous growth of the production capacity of the differentiated polyester industry, both at home and abroad, more and more attention has been paid to the treatment of crude ethylene glycol in the polyester production process. Ordinary polyethylene terephthalate (PET) uses terephthalic acid (PTA) and ethylene glycol (EG) as raw materials, antimony catalysts or titanium catalysts as catalysts, and polyester chips are obtained through esterification and polycondensation. Differentiated PET polyester is obtained by adding modified monomers such as sodium 5-sulfonate isophthalic acid (SIPA), isophthalic acid (IPA), adipic acid, neopentyl glycol, and polyethylene glycol (PEG) of different molecular weights. In the polymerization of differentiated polyester, the addition of S IPA can significantly improve the water solubility and dyeing functions of PET polyester, but it is easy to cause foaming in the reaction system during polymerization, and under high temperature, the foam entrainment phenomenon in the reaction system is serious, resulting in a large amount of oligomers, esterification products, unreacted or partially reacted PTA, IPA, S IPA and other monomers in the system entering the recovered crude EG; at the same time, given that PEG of different molecular weights is not easy to graft into the main chain during polymerization, under negative pressure conditions, a large amount of PEG is extracted into the crude EG. In addition, the side reaction products of acetaldehyde, 2-methyl-1,3-dioxolane, 1,4-dioxane and other low-boiling point by-products in the esterification and polycondensation process also evaporate out of the system. Therefore, the composition of the crude EG solution of differentiated polyester in the esterification and polycondensation process is more complex and more difficult to separate than that of the large light PET.

[0003] In order to reduce the production cost of polyester and balance the production of EG, polyester manufacturers need to recycle and utilize crude EG. For example, the patent document with publication number CN203668271U provides a boiling tower EG recycling system for an esterification tower, in which the recycled EG and fresh EG are partially mixed and connected to the high-temperature EG cooling pipeline, and at the same time connected to the high-temperature EG cooling pipeline to enter the boiling tower EG, and finally the EG is recycled to the esterification tower through a filtering device; the patent document with publication number CN105037095A discloses a high-efficiency and environmentally friendly EG recycling method, in which the EG waste liquid is pressed into the ultrafiltration system through a booster pump through a filter; and then it passes through two filters and two electrodialysis in sequence to obtain the recycled EG. This method is prone to filter blockage and limited processing capacity.

[0004] At present, PET manufacturers mainly use a combination of low-boiling towers and high-temperature distillation to recover crude EG. This method is simple, but it is easy to cause the oligomers in the crude EG to undergo intermolecular polymerization and cross-linking during the long-term, negative pressure and high-temperature distillation process to form a "asphalt"-like viscous solid that cannot be reused, resulting in a waste of raw materials. At the same time, the viscous solids at the bottom of the distillation kettle need to be incinerated, causing environmental problems and increased energy consumption. In addition, with the increase of viscous solids in the distillation kettle, in order to be solid when discharged, high-temperature cooking is required before discharge, which further leads to a large amount of energy waste in the system and a reduction in the quality of the refined EG. Summary of the invention

[0005] The purpose of the present invention is to provide an energy-saving and environmentally friendly differentiated polyester glycol recovery device and a recovery method thereof. Through the special sedimentation tank equipment designed by the present invention, the polymer in the crude glycol is changed from post-treatment separation to pre-treatment separation; the polymer separated by this method is not subjected to high-temperature treatment. Through the optimization of the process, the recovered polymer can be reused in the product by depolymerization and other methods and become a part of the product; the following technical problems can be solved:

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

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

[0008] The purpose of the present invention can be achieved through the following technical solutions:

[0009] In the first aspect, the present invention 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 refining EG tank which are sequentially connected, and a settling tank, wherein the settling tank is arranged between the crude EG tank and the low-boiling tower, and the crude EG tank, the settling tank, the low-boiling tower, the heater, and the distillation kettle and the refining EG tank are sequentially connected through a liquid delivery pump; wherein the top of the settling tank is connected to a No. 2 liquid delivery pump, and the bottom is connected to a solid delivery pump;

[0010] The settling tank includes a settling kettle, a top overflow baffle, a standing liquid reuse zone vertical plate, a standing liquid reuse zone, a feed hollow pipe, and a liquid inlet distribution device; the top overflow baffle is arranged at the inner top of the settling kettle, the liquid inlet distribution device is arranged below the top overflow baffle, the standing liquid reuse zone is arranged between the liquid inlet distribution device and the top overflow baffle, the standing liquid reuse zone vertical plate is arranged on the lower side of the top overflow baffle, the feed hollow pipe is passed through the top of the settling kettle, and the lower end is connected to the liquid inlet distribution device.

[0011] In a further embodiment of the present invention: the crude EG tank is connected to the sedimentation tank by a No. 1 liquid delivery pump, the sedimentation tank is connected to the low boiling tower by a No. 3 liquid delivery pump, the low boiling tower is connected to the heater by a No. 4 liquid delivery pump, the heater is connected to the distillation kettle by a delivery pipeline, the distillation kettle is connected to the refining EG tank by a No. 5 liquid delivery pump, and the output end of the refining EG tank is also connected to a No. 6 liquid delivery pump.

[0012] In a further embodiment of the present invention: the diameter of the settling kettle is 1000mm-5000mm, the diameter-to-height ratio is 1:1-1:5, and the bottom angle c of the settling kettle is in the range of 110°-160°; the top overflow baffle is arranged in a sawtooth shape, the angle of the sawtooth top is 15°-30°, the distance from the lowest point to the highest point of the sawtooth is 20mm-100mm, and the highest point of the sawtooth is 50mm-200mm lower than the outer height of the settling kettle; the height a of the vertical plate of the standing liquid recycling zone is in the range of 100mm-500mm; the standing liquid recycling zone occupies 10%-40% of the diameter cross-sectional area of ​​the settling kettle 401; the depth b of the feed hollow tube is 100-2000mm.

[0013] In a second aspect, the present invention further discloses a recycling method of the energy-saving and environmentally friendly differentiated polyester glycol recycling device as described above, comprising the following steps:

[0014] S1, transport the crude EG in the crude EG tank to the sedimentation tank through the No. 1 liquid delivery pump;

[0015] S2. The crude EG entering the sedimentation tank is separated into solid and liquid by gravity. The upper part is the liquid ethylene glycol separated in the standing liquid recycling zone, and the bottom is the separated solid. Part of the ethylene glycol in the standing liquid recycling zone enters the pulping kettle or the diesterification kettle through the No. 2 liquid delivery pump, and the other part enters the low boiling tower through the No. 3 liquid delivery pump; the solid at the bottom is removed by the solid delivery pump and sent to the diesterification kettle for recycling;

[0016] S3, the ethylene glycol entering the low-boiling tower is fractionated to remove water and low-boiling substances such as acetaldehyde, 2-methyl-1,3-dioxolane, and 1,4-dioxane, and then sent to the distillation kettle through a No. 4 liquid delivery pump;

[0017] S4. The ethylene glycol entering the distillation kettle is distilled. The ethylene glycol distilled from the top of the distillation kettle is cooled by the condenser and then sent to the EG tank for standby use through the No. 5 liquid delivery pump. The viscous material distilled from the bottom of the distillation kettle is discharged after reaching the waste discharge standard.

[0018] In a further embodiment of the present invention: in step S1, the crude EG is delivered to the sedimentation tank by the No. 1 liquid delivery pump at a flow rate of 0.5-7 T / h.

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

[0020] In a further embodiment of the present invention: in step S2, 0-40 vol% of the ethylene glycol in the static liquid recycling zone enters the pulping kettle or the diesterification kettle through the No. 2 liquid delivery pump, and the remaining ethylene glycol enters the low boiling tower through the No. 3 liquid delivery pump.

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

[0022] In a further embodiment of the present invention: in step S4, the bottom temperature of the distillation kettle is 10°C-280°C, the pressure is 3.9 kPa-20.0 kPa, and the column top temperature is controlled at 110°C-155°C.

[0023] Beneficial effects of the present invention:

[0024] (1) Compared with the conventional process technology of treating the crude ethylene glycol solution in the production process of differentiated polyester by the PET method, the present invention adopts a sedimentation tank to recover the oligomers in the crude EG solution in an environmentally friendly manner, and the separated polymers are not subjected to high-temperature treatment. By optimizing the process, the recovered polymers can be reused in the product by depolymerization and become part of the product.

[0025] (2) The present invention can perform solid-liquid separation on the crude EG by adding a settling tank between the crude EG tank and the low-boiling tower to remove solid impurities therein, thereby improving the processing capacity and efficiency of the separated ethylene glycol when it enters the low-boiling tower and the distillation kettle, thereby improving the recovery quality of ethylene glycol. At the same time, it also reduces the amount of viscous matter generated at the bottom of the distillation kettle, reduces the energy consumption of the distillation kettle, and realizes green treatment of the crude ethylene glycol solution.

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

[0027] (4) The special sedimentation tank added in the present invention is only added on the basis of the original facilities, and the sedimentation tank equipment can use the sedimentation tank and pipeline that have been renovated and reused, and environmentally friendly recovery of crude ethylene glycol solution can be achieved without increasing the equipment cost. It has industry universality and can be widely used in polyester industrial recycling and utilization, helping polyester enterprises to achieve green development. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 1 It is a schematic structural diagram of an energy-saving and environmentally friendly differentiated polyester glycol recovery device in Example 1 of the present invention;

[0030] Figure 2 yes Figure 1 Schematic diagram of the structure of the sedimentation tank 4.

[0031] In the figure: 1. Crude EG tank; 2. No. 1 liquid delivery pump; 3. No. 2 liquid delivery pump; 4. Sedimentation tank; 401. Sedimentation kettle; 402. Top overflow baffle; 403. Vertical plate of standing liquid recycling area; 404. Standing liquid recycling area; 405. Feed hollow pipe; 406. Liquid inlet distribution device; 5. Solid delivery pump; 6. No. 3 liquid delivery pump; 7. Low boiling tower; 8. No. 4 liquid delivery pump; 9. Heater; 10. Distillation kettle; 11. No. 5 liquid delivery pump; 12. Refinement EG tank; 13. No. 6 liquid delivery pump. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] See also Figure 1 The present embodiment discloses an energy-saving and environmentally friendly differentiated polyester ethylene glycol recovery device, comprising 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 which are arranged in sequence. The crude EG tank 1 is connected to the settling tank 4 through a No. 1 liquid delivery pump 2, the settling tank 4 is connected to the low boiling tower 7 through a No. 3 liquid delivery pump 6, the low boiling tower 7 is connected to the heater 9 through a No. 4 liquid delivery pump 8, the heater 9 is connected to the distillation kettle 10 through a delivery pipeline, the distillation kettle 10 is connected to the refined EG tank 12 through a No. 5 liquid delivery pump 11, and the output end of the refined EG tank 11 is also connected to a No. 6 liquid delivery pump 13.

[0035] See also Figure 2The settling tank 4 includes a settling tank 401, a top overflow baffle 402, a standing liquid reuse area vertical plate 403, a standing liquid reuse area 404, a feed hollow pipe 405, and a liquid inlet distribution device 406; the top of the settling tank 4 is connected to a No. 2 liquid delivery pump 3, and the bottom is connected to a solid delivery pump 5; the top overflow baffle 402 is arranged at the inner top of the settling tank 401, the liquid inlet distribution device 406 is arranged below the top overflow baffle 402, the standing liquid reuse area 404 is arranged between the liquid inlet distribution device 406 and the top overflow baffle 402, the standing liquid reuse area vertical plate 403 is arranged on the lower side of the top overflow baffle 402, the feed hollow pipe 405 is penetrated through the top of the settling tank 401, and the lower end is connected to the liquid inlet distribution device 406 in the settling tank.

[0036] Specifically, the diameter of the settling kettle 401 is 1000mm~5000mm, the diameter-to-height ratio is 1:1~1:5, the bottom angle c of the settling kettle 401 ranges from 110° to 160°; the top overflow baffle 402 is set to be sawtooth-shaped, the angle of the sawtooth top is 15°~30°, the distance from the lowest point to the highest point of the sawtooth is 20mm~100mm, and the highest point of the sawtooth is 50mm~200mm lower than the outer height of the settling kettle 401; the height a of the vertical plate 403 in the standing liquid recycling area ranges from 100mm to 500mm; the standing liquid recycling area 404 occupies 10%~40% of the diameter cross-sectional area of ​​the settling kettle 401; the depth b of the feed hollow tube 405 is 100-2000mm.

[0037] Example 2

[0038] This embodiment discloses a recovery method of the energy-saving and environmentally friendly differentiated polyester glycol recovery device in Example 1, comprising the following steps:

[0039] S1, the crude EG in the crude EG tank is transported to the sedimentation tank 4 through the No. 1 liquid delivery pump 2 at a flow rate of 0.5-3T / h;

[0040] S2, control the temperature of the sedimentation tank 4 to 30-45°C, place the liquid inlet distribution device 404 at 100-2000mm from the liquid surface, and separate the crude EG entering the sedimentation tank 4 into solid and liquid by gravity, the upper part is the separated liquid ethylene glycol, and the bottom is the separated solid, wherein, in the ethylene glycol of the upper part, 0-40vol% of the ethylene glycol enters the pulping kettle or the diesterification kettle through the No. 2 liquid delivery pump 3, and the remaining ethylene glycol enters the low boiling tower 7 through the No. 3 liquid delivery pump 6; the solid at the bottom is removed by the solid delivery pump 5 and sent to the diesterification kettle for recycling;

[0041] S3, controlling the temperature in the low boiling tower 7 to 110-140°C, the pressure to 9kPa-21kPa, and the column top temperature to 44°C-62°C, and the ethylene glycol entering the low boiling tower 7 is fractionally distilled to remove water and low boiling substances such as acetaldehyde, 2-methyl-1,3-dioxolane, and 1,4-dioxane, and then sent to the distillation kettle 10 through the No. 4 liquid delivery pump 8;

[0042] S4. Control the bottom temperature of the still 10 to be 10°C-280°C, the pressure to be 3.9kPa-20.0kPa, and the top temperature to be 110°C-155°C, and distill the ethylene glycol entering the still 10. The ethylene glycol distilled from the top of the still 10 is cooled by the condenser and then sent to the refining EG tank 12 through the No. 5 liquid delivery pump 11 for standby use. The viscous material distilled from the bottom of the still 10 is discharged after reaching the waste discharge standard.

[0043] Next, the energy-saving and environmentally friendly differentiated polyester ethylene glycol recovery device disclosed in Example 1 was used to carry out Examples 3-6 on the ethylene glycol recovery product generated in the production of water-soluble polyester using the recovery method disclosed in Example 2.

[0044] Example 3

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

[0046] The crude EG recovered from the production line is sent to the crude EG tank 1, and the crude EG in the crude EG tank 1 is transported to the sedimentation tank 4 at a flow rate of 1T / h through the No. 1 liquid delivery pump 2, and the temperature in the sedimentation tank 4 is maintained at 35°C; the crude EG entering the sedimentation tank 4 is subjected to solid-liquid separation, and the upper part is the separated liquid ethylene glycol, and the bottom is the separated solid, wherein the upper part of the ethylene glycol enters the low boiling tower 7 through the No. 3 liquid delivery pump 6, and the solid at the bottom is removed by the transfer pump 3 and sent to the diesterification kettle for treatment and use; the temperature in the low boiling tower 7 is controlled to be 120°C, and the pressure is The pressure is 14kPa, and the column top temperature is 53°C. The ethylene glycol entering the low-boiling tower 7 is fractionated to remove water and low-boiling substances therein, and then is sent to the distillation kettle 10 through the No. 4 liquid delivery pump 8; the bottom temperature of the distillation kettle 10 is controlled to be 250°C, the pressure is 11kPa, and the column top temperature is controlled to be 148°C. The ethylene glycol distilled from the top of the distillation kettle 10 is distilled, and the ethylene glycol distilled from the top of the distillation kettle 10 is cooled by the condenser and then sent to the refining EG tank 12 for standby use through the No. 5 liquid delivery pump 11. The viscous material distilled from the bottom of the distillation kettle 10 is discharged after reaching the waste discharge standard.

[0047] Example 4

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

[0049] The crude EG recovered from the production line is sent to the crude EG tank 1, and the crude EG in the crude EG tank 1 is transported to the sedimentation tank 4 at a flow rate of 1.5T / h by the No. 1 liquid delivery pump 2. The temperature in the sedimentation tank 4 is maintained at 35°C; the crude EG entering the sedimentation tank 4 is subjected to solid-liquid separation, the upper part is the separated liquid ethylene glycol, and the bottom is the separated solid. Among them, 20vo 1% of ethylene glycol enters the pulping kettle system through the No. 2 liquid delivery pump 5, and the remaining ethylene glycol enters the low boiling tower 7 through the No. 3 liquid delivery pump 6, and the solid at the bottom is removed by the pipetting pump 3 and sent to the diesterification kettle for treatment and use; the temperature in the low boiling tower 7 is controlled to be 130°C, the pressure is 14kPa, and the column top temperature is 53°C. The ethylene glycol entering the low boiling tower 7 is fractionally distilled to remove water and low boiling substances, and then sent to the distillation kettle 10 through the No. 4 liquid delivery pump 8; the bottom temperature of the distillation kettle 10 is controlled to be 250°C, the pressure is 11kPa, and the column top temperature is controlled to be 148°C, and 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 the condenser and sent to the EG tank 12 for standby use through the No. 5 liquid delivery pump 11. The viscous material distilled from the bottom of the distillation kettle 10 is discharged after reaching the waste discharge standard.

[0050] Example 5

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

[0052] The crude EG recovered from the production line is sent to the crude EG tank 1, and the crude EG in the crude EG tank 1 is transported to the sedimentation tank 4 at a flow rate of 2T / h through the No. 1 liquid delivery pump 2, and the temperature in the sedimentation tank 4 is maintained at 40°C; the crude EG entering the sedimentation tank 4 is subjected to solid-liquid separation, the upper part is the separated liquid ethylene glycol, and the bottom is the separated solid, wherein the ethylene glycol in the upper part has 40vo 1% of ethylene glycol enters the pulping kettle system through the No. 2 liquid delivery pump 5, and the remaining ethylene glycol enters the low boiling tower 7 through the No. 3 liquid delivery pump 6, and the solid at the bottom is removed by the pipetting pump 3 and sent to the diesterification kettle for treatment and use; the temperature in the low boiling tower 7 is controlled to be 140°C, the pressure is 12kPa, and the column top temperature is 49°C. The ethylene glycol entering the low boiling tower 7 is fractionated to remove water and low boiling substances therein, and then sent to the distillation kettle 10 through the No. 4 liquid delivery pump 8; the bottom temperature of the distillation kettle 10 is controlled to be 260°C, the pressure is 9.7kPa, and the column top temperature is controlled to be 144°C, and 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 the condenser and sent to the EG tank 12 for standby use through the No. 5 liquid delivery pump 11. The viscous material distilled from the bottom of the distillation kettle 10 is discharged after reaching the waste discharge standard.

[0053] Example 6

[0054] In this embodiment, the parameters of the sedimentation tank 4 are as follows: the diameter of the sedimentation tank 401 is 3000mm, the diameter-to-height ratio is 1:2, the range of the bottom angle c of the sedimentation tank 401 is 120°; the top overflow baffle 402 is set to be sawtooth-shaped, the angle of the sawtooth top is 45°, the distance from the lowest point to the highest point of the sawtooth is 50mm, and the highest point of the sawtooth is 50mm lower than the outer height of the sedimentation tank 401; the range of the height a of the vertical plate 403 in the standing liquid recycling area is 300mm; the standing liquid recycling area 404 accounts for 40% of the diameter cross-sectional area of ​​the sedimentation tank 401; the depth b of the feed hollow tube 405 is 1800mm;

[0055] The crude EG recovered from the production line is sent to the crude EG tank 1, and the crude EG in the crude EG tank 1 is transported to the sedimentation tank 4 at a flow rate of 2T / h through the No. 1 liquid delivery pump 2. The temperature in the sedimentation tank 4 is maintained at 45°C, and the liquid inlet distribution device 404 is placed at 900mm above the liquid surface; the crude EG entering the sedimentation tank 4 is subjected to solid-liquid separation, the upper part is the separated liquid ethylene glycol, and the bottom is the separated solid, wherein, in the upper part of the ethylene glycol, 50vo 1% of ethylene glycol enters the pulping kettle system through the No. 2 liquid delivery pump 5, and the remaining ethylene glycol enters the low boiling tower 7 through the No. 3 liquid delivery pump 6, and the solid at the bottom is removed by the pipetting pump 3 and sent to the diesterification kettle for treatment and use; the temperature in the low boiling tower 7 is controlled to be 150°C, the pressure is 10kPa, and the column top temperature is 46°C. The ethylene glycol entering the low boiling tower 7 is fractionally distilled to remove water and low boiling substances therein, and then sent to the distillation kettle 10 through the No. 4 liquid delivery pump 8; the bottom temperature of the distillation kettle 10 is controlled to be 270°C, the pressure is 6.9kPa, and the column top temperature is controlled to be 138°C, and 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 the condenser and sent to the EG tank 12 for standby use through the No. 5 liquid delivery pump 11. The viscous material distilled from the bottom of the distillation kettle 10 is discharged after reaching the waste discharge standard.

[0056] Comparative Example 1

[0057] The recovery device in the prior art is used to recover ethylene glycol. First, the energy-saving and environmentally friendly differentiated polyester ethylene glycol recovery device in Example 1 is modified, the sedimentation tank 4 and the third liquid delivery pump 6 are removed, and the output end of the first liquid delivery pump 2 is directly connected to the input end of the low boiling tower 7. The other structures remain unchanged to obtain the recovery device in the prior art, and then the ethylene glycol generated in the production of water-soluble polyester is recovered. The specific method is as follows:

[0058] The crude EG recovered from the production line is sent to the crude EG tank 1, and the crude EG in the crude EG tank 1 is transported to the low boiling tower 7 at a flow rate of 1T / h through the No. 1 liquid delivery pump 2. The temperature in the low boiling tower 7 is controlled to be 120°C, the pressure is 14kPa, and the column top temperature is 53°C. The ethylene glycol entering the low boiling tower 7 is fractionated to remove water and low boiling substances therein, and then sent to the distillation kettle 10 through the No. 4 liquid delivery pump 8; the bottom temperature of the distillation kettle 10 is controlled to be 250°C, the pressure is 11kPa, and the column top temperature is controlled to be 148°C, and 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 the condenser and then sent to the refined EG tank 12 for standby use through the No. 5 liquid delivery pump 11. The viscous material distilled from the bottom of the distillation kettle 10 is discharged after reaching the waste discharge standard.

[0059] The effects of the recovery methods of Examples 3-6 and Comparative Example 1 were tested, including sedimentation efficiency, raw material utilization improvement rate, energy consumption reduction rate, waste discharge times and cost reduction rate. The testing method is as follows;

[0060] (1) Sedimentation efficiency:

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

[0062] (2) Improvement of raw material utilization rate:

[0063] Among them: m1 is the mass of slices after the solids in the sedimentation tank are recycled into the system; m0 is the mass of slices when the solids in the sedimentation tank are not recycled.

[0064] (3)Energy consumption reduction rate:

[0065] Among them: E0 is the amount of natural gas used to process the same crude ethylene glycol without using a settling tank; E1 is 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. Table 1 is as follows:

[0068] Table 1

[0069] Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Sedimentation 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] By analyzing the data in Table 1, it can be learned that, compared with Comparative Example 1, Examples 1-4 can settle the solid impurities in the crude EG, thereby reducing the problem of a lot of viscous matter at the bottom of the distillation kettle; the raw material utilization rate is improved, the energy consumption is reduced, the number of waste discharges is reduced, and the cost is reduced; therefore, the recovery device and method of the present invention can effectively improve the processing efficiency of crude EG and reduce energy consumption on the basis of ensuring the stability of product indicators and not increasing equipment costs, thereby increasing product profit margins, and is suitable for related polymerization recovery processes.

[0071] In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction and a specific direction structure and operation, and therefore, cannot be understood as a limitation on the present invention. In addition, "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0072] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0073] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. An energy-saving and environmentally friendly differentiated polyester ethylene 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) which are sequentially connected, characterized in that: It also includes a sedimentation tank (4), which is arranged between the crude EG tank (1) and the low boiling tower (7), and the crude EG tank (1), the sedimentation tank (4), the low boiling tower (7), the heater (9), and the distillation kettle (10) and the regeneration EG tank (12) are all connected in sequence through a liquid delivery pump; wherein the top of the sedimentation tank (4) is connected to a No. 2 liquid delivery pump (3), and the bottom is connected to a solid delivery pump (5); The settling tank (4) comprises a settling tank (401), a top overflow baffle (402), a standing liquid recycling zone vertical plate (403), a standing liquid recycling zone (404), a feed hollow pipe (405), and a liquid inlet distribution device (406); the top overflow baffle (402) is arranged at the inner top of the settling tank (401), the liquid inlet distribution device (406) is arranged below the top overflow baffle (402), the standing liquid recycling zone (404) is arranged between the liquid inlet distribution device (406) and the top overflow baffle (402), the standing liquid recycling zone vertical plate (403) is arranged on the lower side of the top overflow baffle (402), and the feed hollow pipe (405) is passed through the top of the settling tank (401), and the lower end is connected to the liquid inlet distribution device (406).

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

3. The energy-saving and environmentally friendly differentiated polyester glycol recovery device according to claim 1 is characterized in that: The diameter of the settling kettle (401) is 1000 mm to 5000 mm, the diameter-to-height ratio is 1:1 to 1:5, and the included angle c of the bottom (401) of the settling kettle is in the range of 110° to 160°; the top overflow baffle (402) is arranged in a sawtooth shape, the angle of the sawtooth top is 15° to 30°, the distance from the lowest point to the highest point of the sawtooth is 20 mm to 100 mm, and the highest point of the sawtooth is 50 mm to 200 mm lower than the outer height of the settling kettle (401); the height a of the vertical plate (403) of the standing liquid recycling zone is in the range of 100 mm to 500 mm; the standing liquid recycling zone (404) occupies 10% to 40% of the diameter cross-sectional area of ​​the settling kettle (401); the depth b of the feeding hollow tube (405) is 100-2000 mm.

4. A recycling method of an energy-saving and environmentally friendly differentiated polyester glycol recycling device according to any one of claims 1 to 3, characterized in that: The steps include: S1, the crude EG in the crude EG tank is transported to the sedimentation tank (4) through the No. 1 liquid delivery pump (2); S2, the crude EG entering the sedimentation tank (4) is separated into solid and liquid by gravity, the upper part is the liquid ethylene glycol separated in the static liquid recycling zone (404), and the bottom is the separated solid, wherein a part of the ethylene glycol in the static liquid recycling zone (404) enters the pulping kettle or the diesterification kettle through the No. 2 liquid delivery pump (3), and the other part enters the low boiling tower (7) through the No. 3 liquid delivery pump (6); the solid at the bottom is removed by the solid delivery pump (5) and sent to the diesterification kettle for recycling; S3, the ethylene glycol entering the low-boiling tower (7) is fractionally distilled to remove water and low-boiling substances therein, and then is sent to the distillation kettle (10) through the No. 4 liquid delivery pump (8); S4. 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 recovery tank (12) through a No. 5 liquid delivery pump (11) for standby use. The viscous material distilled from the bottom of the distillation kettle (10) is discharged after reaching the waste discharge standard.

5. The energy-saving and environmentally friendly recovery method of the differentiated polyester glycol recovery device according to claim 4 is characterized in that: In step S1, the crude EG is delivered to the sedimentation tank (4) by the first liquid delivery pump (2) at a flow rate of 0.5 to 7 T / h.

6. The energy-saving and environmentally friendly recovery method of the differentiated polyester glycol recovery device according to claim 4, characterized in that: In step S2, when the crude EG enters the sedimentation tank for solid-liquid separation, the temperature of the sedimentation tank (4) is 30-45°C.

7. The energy-saving and environmentally friendly recovery method of the differentiated polyester glycol recovery device according to claim 4, characterized in that: In step S2, 0-40 vol% of the ethylene glycol in the stationary liquid recycling zone (404) enters the pulping kettle or the diesterification kettle through the No. 2 liquid delivery pump (3), and the remaining ethylene glycol enters the low boiling tower (7) through the No. 3 liquid delivery pump (6).

8. The energy-saving and environmentally friendly recovery method of the differentiated polyester glycol recovery device according to claim 4, characterized in that: In step S3, the temperature in the low boiling tower (7) is 110-140°C, the pressure is 9 kPa-21 kPa, and the column top temperature is 44°C-62°C.

9. The energy-saving and environmentally friendly recovery method of the differentiated polyester glycol recovery device according to claim 4, characterized in that: In step S4, the bottom temperature of the distillation kettle (10) is 10°C-280°C, the pressure is 3.9 kPa-20.0 kPa, and the column top temperature is controlled at 110°C-155°C.

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