Energy-saving and anti-blocking vacuum system for polyester production

Abstract

The utility model belongs to the technical field of polyester production equipment, and particularly relates to an energy-saving and anti-blocking vacuum system for polyester production, which comprises a three-stage steam jet pump, a liquid ring pump, a first ethylene glycol liquid seal tank, a second ethylene glycol liquid seal tank, a heat exchanger and an ethylene glycol recycling tank, the third-stage steam jet pump comprises a first-stage spray tower, a second-stage spray tower and a third-stage spray tower which are communicated in sequence, the first-stage spray tower and the second-stage spray tower are both communicated with the first ethylene glycol liquid seal tank, the third-stage spray tower is communicated with the second ethylene glycol liquid seal tank, ethylene glycol in the second ethylene glycol liquid seal tank enters the ethylene glycol recycling tank, and the second-stage spray tower is communicated with the third-stage spray tower. Part of ethylene glycol in the first ethylene glycol liquid seal tank enters the ethylene glycol recycling tank, part of ethylene glycol enters the heat exchanger, and ethylene glycol cooled by the heat exchanger returns to the third-stage steam-jet pump; and the pipeline between the heat exchanger and the third-stage steam-jet pump is communicated with a flushing pipeline. The vacuum system for polyester production can solve the problems that an existing vacuum system for polyester production wastes heat and is easy to block.

Description

Technical Field

[0001] This utility model belongs to the technical field of polyester production equipment, specifically relating to an energy-saving and anti-clogging vacuum system for polyester production. Background Technology

[0002] Polyesters are a general term for polymers obtained by the condensation polymerization of polyols and polyacids, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polybutylene succinate (PBS). These are all high-performance and widely used engineering plastics. In polyester polycondensation reactions, vacuum is one of the important reaction conditions. A suitable vacuum can lower the reaction temperature, reduce the thermal degradation of polyester, and improve the color of the product. Currently, polyester polycondensation reactions commonly use a three-stage steam jet pump + liquid ring pump as the vacuum power source. During operation, motive steam and circulating cooling ethylene glycol are used as the working fluid. Furthermore, the motive steam and the gaseous medium extracted from the polyester polycondensation reaction need to be cooled by the circulating ethylene glycol within the three-stage steam jet pump. Thus, some materials and small molecules from the polyester polycondensation reaction carried in the gaseous medium can easily enter the circulating ethylene glycol, leading to increased impurities in the circulating ethylene glycol and potential clogging of the circulating ethylene glycol nozzle.

[0003] Furthermore, the circulating ethylene glycol from the three spray towers of the three-stage steam jet pump enters the same ethylene glycol liquid seal tank. A portion of the ethylene glycol flowing from the liquid seal tank enters the ethylene glycol recycling tank and the ethylene glycol evaporator, while the remaining portion, after cooling, returns to the spray towers of the three-stage steam jet pump for spraying, thus completing the ethylene glycol cycle. However, in reality, the temperature of the circulating ethylene glycol from the three spray towers of the three-stage steam jet pump is not the same. After mixing in the ethylene glycol liquid seal tank, its temperature is too high for the circulating spraying temperature, requiring a large amount of industrial circulating water for cooling. For the ethylene glycol that does not participate in the spraying, whether used in the ethylene glycol evaporator or in raw material preparation, there is a waste of heat. Utility Model Content

[0004] The present invention aims to provide an energy-saving and anti-clogging vacuum system for polyester production, in order to solve the problems of heat waste and easy clogging in the existing three-stage steam jet pump + liquid ring pump vacuum system.

[0005] To achieve the above objectives, the present invention provides an energy-saving and anti-clogging vacuum system for polyester production, comprising a three-stage steam jet pump, a liquid ring pump, a first ethylene glycol liquid seal tank, a heat exchanger, and an ethylene glycol recycling tank. The three-stage steam jet pump includes a first-stage spray tower, a second-stage spray tower, and a third-stage spray tower connected in sequence. The vacuum system also includes a second ethylene glycol liquid seal tank. The first-stage and second-stage spray towers are connected to the first ethylene glycol liquid seal tank, and the third-stage spray tower is connected to the second ethylene glycol liquid seal tank. Ethylene glycol in the second ethylene glycol liquid seal tank is transported to the ethylene glycol recycling tank by an ethylene glycol transfer pump. Ethylene glycol in the first ethylene glycol liquid seal tank is partially transported to the ethylene glycol recycling tank by an ethylene glycol circulation pump, and the other part is transported to the heat exchanger. The ethylene glycol cooled by the heat exchanger returns to the three-stage steam jet pump. A flushing pipeline connects the heat exchanger and the three-stage steam jet pump.

[0006] The working principle and beneficial effects of this scheme are as follows: In this scheme, the three-stage spray tower of the three-stage steam jet pump is rerouted to connect with the newly added second ethylene glycol liquid seal tank. Thus, the high-temperature ethylene glycol at the bottom of the three-stage spray tower enters the second ethylene glycol liquid seal tank, while the ethylene glycol at the bottom of the first and second stage spray towers flows into the first ethylene glycol liquid seal tank. Compared to a scheme where the first, second, and third stage spray towers are all connected to the first ethylene glycol liquid seal tank, this scheme allows for a lower temperature in the first ethylene glycol liquid seal tank, thereby reducing the cooling load on the heat exchanger. Simultaneously, this scheme increases the temperature of the ethylene glycol in the ethylene glycol recycling tank, thereby increasing the temperature of the PTA slurry. This reduces the heat required to raise the PTA slurry to the reaction temperature in the esterification reaction section during production, achieving heat utilization of the high-temperature ethylene glycol and reducing heat waste.

[0007] Furthermore, this solution adds a flushing pipeline to the pipe between the heat exchanger and the three-stage steam jet pump. The flushing pipeline is used to flush the ethylene glycol nozzles in the first, second, and third-stage spray towers to prevent the ethylene glycol nozzles from clogging, thereby preventing the vacuum system from becoming blocked.

[0008] Optionally, the flushing pipeline includes a main flushing pipe and three flushing branch pipes connected to the main flushing pipe. The pipes between the primary spray tower, the secondary spray tower, the tertiary spray tower, and the heat exchanger are respectively connected to the three flushing branch pipes, and a first valve is installed on the flushing branch pipe.

[0009] In this scheme, the flushing process of the ethylene glycol nozzle is controlled by controlling the opening and closing of the flushing branch pipe through the first valve.

[0010] Optionally, the flushing main pipe is connected to a hot ethylene glycol pipe and an ethylene glycol vapor pipe, and a second valve is installed on both the hot ethylene glycol pipe and the ethylene glycol vapor pipe.

[0011] In this scheme, hot ethylene glycol or ethylene glycol vapor is used as the rinsing medium to avoid contaminating the reaction system with other media during rinsing.

[0012] Optionally, both the first valve and the second valve are control valves, the first valve is electrically connected to a first selector switch, the second valve is electrically connected to a second selector switch, and both the first selector switch and the second selector switch are electrically connected to a controller.

[0013] In this solution, the selection of the flushing point is controlled by a controller and a first selection switch, and the selection of the flushing medium is controlled by a controller and a second selection switch. This eliminates the need for workers to manually open and close the first and second valves, thus improving the automation level of the vacuum system.

[0014] Optionally, both the first and second ethylene glycol liquid seal tanks are provided with partition plates, which divide the space inside the tanks into two connected storage cavities.

[0015] In this design, the partition plate divides the space inside the tank into interconnected storage chambers. In this way, one storage chamber is connected to the three-stage steam jet pump, and the other storage chamber is designed with an ethylene glycol discharge port, thereby ensuring that the storage chamber connected to the three-stage steam jet pump will not be affected by the discharge and cause the liquid level to be too low.

[0016] Optionally, a heat insulation layer is provided on the outer peripheral wall of the second ethylene glycol liquid seal tank.

[0017] In this design, the insulation layer reduces the amount of heat exchange between the second ethylene glycol liquid seal tank and the outside environment, thus achieving a heat preservation effect.

[0018] Optionally, the vacuum system further includes an ethylene glycol evaporator, wherein ethylene glycol in the first ethylene glycol liquid seal tank is partially transported to the ethylene glycol recycling tank and the ethylene glycol evaporator via an ethylene glycol circulation pump.

[0019] In this scheme, a portion of the ethylene glycol in the first ethylene glycol liquid seal tank can be diverted to the ethylene glycol evaporator as a raw material for ethylene glycol vapor.

[0020] Optionally, the first ethylene glycol liquid seal tank is connected to a fresh ethylene glycol replenishment pipe.

[0021] In this scheme, fresh ethylene glycol is added to the first ethylene glycol liquid seal tank through a fresh ethylene glycol replenishment pipe, thereby replenishing the entire circulation system with fresh ethylene glycol.

[0022] Optionally, flow meters are installed on the pipes between the primary spray tower, the secondary spray tower, the tertiary spray tower, and the heat exchanger.

[0023] In this scheme, flow meters are used to detect the spray flow rate of ethylene glycol in the primary, secondary, and tertiary spray towers.

[0024] Optionally, the second ethylene glycol liquid seal tank is connected to a tail gas pipe, a tail gas condenser is installed on the tail gas pipe, and the condensate outlet of the tail gas condenser is connected to a condensate recovery pipe.

[0025] In this design, to prevent severe liquid entrainment in the tail gas of the second ethylene glycol liquid seal tank, a tail gas condenser is added to reduce the amount of ethylene glycol carried into the tail gas system, thereby preventing liquid accumulation and fluctuations in the tail gas system. Simultaneously, the condensed ethylene glycol is recovered and reused via a condensate recovery pipe, preventing direct return to the second ethylene glycol liquid seal tank and reducing temperature loss in the tank. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of an energy-saving and anti-clogging vacuum system for polyester production according to Embodiment 1 of this utility model;

[0027] Figure 2 This is a schematic diagram of the structure of a vacuum system for polyester production in the prior art;

[0028] Figure 3 This is a schematic diagram of the structure of an energy-saving and anti-clogging vacuum system for polyester production according to Embodiment 2 of this utility model;

[0029] Figure 4 This is a schematic diagram of the structure of an energy-saving and anti-clogging vacuum system for polyester production according to Embodiment 3 of this utility model. Detailed Implementation

[0030] The following detailed description illustrates the specific implementation method:

[0031] The markings in the accompanying drawings include: 1. Three-stage steam jet pump; 101. First-stage spray tower; 102. Second-stage spray tower; 103. Third-stage spray tower; 2. Liquid ring pump; 3. First ethylene glycol liquid seal tank; 4. Second ethylene glycol liquid seal tank; 5. Heat exchanger; 6. Ethylene glycol recycling tank; 7. Ethylene glycol evaporator; 8. Divider plate; 9. Insulation layer; 10. Ethylene glycol transfer pump; 11. Ethylene glycol circulation pump; 12. Flow meter; 13. Main flushing pipe; 14. Branch flushing pipe; 15. First valve; 16. Hot ethylene glycol pipe; 17. Ethylene glycol steam pipe; 18. Second valve; 19. First selector switch; 20. Second selector switch; 21. Controller; 22. Tail gas pipe; 23. Tail gas condenser; 24. Condensate recovery pipe.

[0032] Example 1

[0033] This embodiment is basically as follows: Figure 1The diagram shows an energy-saving, anti-clogging vacuum system for polyester production, comprising a three-stage steam jet pump 1, a liquid ring pump 2, a first ethylene glycol liquid seal tank 3, a second ethylene glycol liquid seal tank 4, a heat exchanger 5, an ethylene glycol recycling tank 6, and an ethylene glycol evaporator 7. The three-stage steam jet pump 1 includes a first-stage spray tower 101, a second-stage spray tower 102, and a third-stage spray tower 103 connected in sequence. Both the first ethylene glycol liquid seal tank 3 and the second ethylene glycol liquid seal tank 4 are equipped with partition plates 8, which divide the tank space into a connected storage chamber I and a storage chamber II. Storage chamber II of the first ethylene glycol liquid seal tank 3 is connected to a fresh ethylene glycol replenishment pipe. An insulation layer 9 is adhered to the outer peripheral wall of the second ethylene glycol liquid seal tank 4 to reduce the rate of heat loss within the tank.

[0034] The bottoms of the primary spray tower 101 and the secondary spray tower 102 are connected to the storage chamber I of the first ethylene glycol liquid seal tank 3 via pipelines, and the bottom of the tertiary spray tower 103 is connected to the storage chamber I of the second ethylene glycol liquid seal tank 4 via pipelines. Ethylene glycol in the storage chamber II of the second ethylene glycol liquid seal tank 4 is transported to the ethylene glycol recycling tank 6 by the ethylene glycol transfer pump 10. Ethylene glycol in the storage chamber II of the first ethylene glycol is partially transported to the ethylene glycol recycling tank 6 and the ethylene glycol evaporator 7 by the ethylene glycol circulation pump 11, and the remaining portion is transported to the heat exchanger 5. After being cooled by the heat exchanger 5, part of the ethylene glycol returns to the tertiary steam jet pump 1, and the remaining portion enters the liquid ring pump 2. Flow meters 12 are installed on the pipelines between the heat exchanger 5 and the primary spray tower 101, the secondary spray tower 102, and the tertiary spray tower 103.

[0035] A flushing pipeline is connected between the heat exchanger 5 and the three-stage steam jet pump 1. The flushing pipeline includes a main flushing pipe 13 and three flushing branch pipes 14 connected to the main flushing pipe 13. The pipelines between the first-stage spray tower 101, the second-stage spray tower 102, and the third-stage spray tower 103 and the heat exchanger 5 are respectively connected to the three flushing branch pipes 14, and the connection point is located on the side of the flow meter 12 away from the three-stage steam jet pump 1. A first valve 15 is installed on the flushing branch pipe 14. The main flushing pipe 13 is connected to a hot ethylene glycol pipe 16 and an ethylene glycol vapor pipe 17. A second valve 18 is installed on both the hot ethylene glycol pipe 16 and the ethylene glycol vapor pipe 17.

[0036] In practical use, the ethylene glycol sprayed in the primary spray tower 101 and the secondary spray tower 102 flows from the bottom of the tower into the storage chamber I of the first ethylene glycol liquid seal tank 3. The ethylene glycol level in storage chamber I gradually rises. When the level exceeds the top of the partition plate 8, the ethylene glycol in storage chamber I enters storage chamber II. Under the pumping of the ethylene glycol circulation pump 11, part of the ethylene glycol in storage chamber II enters the ethylene glycol evaporator 7 and the ethylene glycol recycling tank 6, and the other part enters the heat exchanger 5 to exchange heat with the cooling water. After cooling, part of the ethylene glycol returns to the tertiary steam jet pump 1, thus realizing the circulation of ethylene glycol, and the other part enters the liquid ring pump 2. Simultaneously, the ethylene glycol sprayed in the three-stage spray tower 103 flows from the bottom of the tower into storage chamber I of the second ethylene glycol liquid seal tank 4. The ethylene glycol level in storage chamber I gradually rises, and when the level exceeds the top of the partition plate 8, the ethylene glycol in storage chamber I enters storage chamber II. The ethylene glycol in storage chamber II is then pumped into the ethylene glycol recycling tank 6 by the ethylene glycol transfer pump 10. The amount of ethylene glycol entering the ethylene glycol recycling tank 6, the ethylene glycol evaporator 7, the liquid ring pump 2, and the three-stage steam jet pump 1 can be controlled by valves (not shown in the figure) designed on the corresponding pipelines.

[0037] During vacuum system operation, workers can choose to flush the ethylene glycol nozzles in the three-stage steam jet pump 1 with hot ethylene glycol or ethylene glycol vapor, depending on the working conditions. Specifically, if the second valve 18 on the hot ethylene glycol pipe 16 is kept closed and the second valve 18 on the ethylene glycol vapor pipe 17 is opened, while the first valve 15 on the flushing branch pipe 14 is also opened, ethylene glycol vapor can be used to flush the ethylene glycol nozzles to prevent clogging. If the second valve 18 on the ethylene glycol vapor pipe 17 is kept closed and the second valve 18 on the hot ethylene glycol pipe 16 is opened, while the first valve 15 on the flushing branch pipe 14 is also opened, hot ethylene glycol can be used to flush the ethylene glycol nozzles to prevent clogging.

[0038] In the prior art, vacuum systems used in polyester production (such as...) Figure 2 In the example shown, the temperature of ethylene glycol in the first ethylene glycol liquid seal tank 3 is approximately 65°C. However, in this embodiment, the temperature of ethylene glycol in the first ethylene glycol liquid seal tank 3 is approximately 43°C, effectively reducing the temperature of the first ethylene glycol liquid seal tank 3 and thus reducing the cooling capacity of the heat exchanger 5. Simultaneously, in this embodiment, the temperature of ethylene glycol in the ethylene glycol recycling tank 6 is lower than... Figure 2 The temperature of the ethylene glycol in the ethylene glycol recycling tank 6 increased by approximately 20°C, thereby increasing the temperature of the PTA slurry in the polyester polycondensation reactor by 8–17°C. Therefore, in this embodiment, rerouting the three-stage spray tower 103 to connect it to the newly added second ethylene glycol liquid seal tank 4 effectively reduces the cooling load of the heat exchanger 5 and increases the ethylene glycol recycling temperature, effectively utilizing the heat from the high-temperature ethylene glycol and reducing heat waste. Furthermore, the added flushing pipeline in this embodiment prevents clogging of the ethylene glycol nozzles, thus preventing blockage of the vacuum system.

[0039] Example 2

[0040] The only difference between this embodiment and Embodiment 1 is that: Figure 3 As shown, in this embodiment, both the first valve 15 and the second valve 18 are control valves. The first valve 15 is electrically connected to a first selector switch 19, and the second valve 18 is electrically connected to a second selector switch 20. Both the first selector switch 19 and the second selector switch 20 are electrically connected to a controller 21.

[0041] Thus, in this embodiment, the controller 21 and the first selection switch 19 are used to control whether the primary spray tower 101, the secondary spray tower 102 and the tertiary spray tower 103 perform ethylene glycol nozzle flushing. The controller 21 and the second selection switch 20 are used to control the selection of the flushing medium (flushing medium refers to hot ethylene glycol and ethylene glycol vapor). Workers can remotely operate the flushing of the ethylene glycol nozzles and the selection of the flushing medium, reducing the workload of workers and improving the automation level of the vacuum system.

[0042] Example 3

[0043] The only difference between this embodiment and Embodiment 1 is that: Figure 4 As shown, the second ethylene glycol liquid seal tank 4 is connected to the tail gas pipe 22, the tail gas pipe 22 is equipped with a tail gas condenser 23, and the condensate outlet of the tail gas condenser 23 is connected to a condensate recovery pipe 24.

[0044] In this embodiment, to prevent severe liquid entrainment in the tail gas of the second ethylene glycol liquid seal tank 4, a tail gas condenser 23 is added to reduce the amount of ethylene glycol carried into the tail gas system, thereby preventing liquid accumulation in the tail gas system and causing fluctuations. Simultaneously, the ethylene glycol condensed by the tail gas condenser 23 is recycled and reused via the condensate recovery pipe 24, and does not flow directly back to the second ethylene glycol liquid seal tank 4, reducing temperature loss in the second ethylene glycol liquid seal tank 4.

[0045] The above descriptions are merely embodiments of this utility model, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of this utility model, and these should also be considered within the scope of protection of this utility model. These modifications will not affect the effectiveness or practicality of this utility model. The specific embodiments described in the specification can be used to interpret the claims.

Claims

1. An energy-saving and anti-clogging vacuum system for polyester production, comprising a three-stage steam jet pump, a liquid ring pump, a first ethylene glycol liquid seal tank, a heat exchanger, and an ethylene glycol recycling tank, wherein the three-stage steam jet pump comprises a first-stage spray tower, a second-stage spray tower, and a third-stage spray tower connected in sequence, characterized in that: The vacuum system also includes a second ethylene glycol liquid seal tank. The first-stage and second-stage spray towers are both connected to the first ethylene glycol liquid seal tank, and the third-stage spray tower is connected to the second ethylene glycol liquid seal tank. Ethylene glycol in the second ethylene glycol liquid seal tank is transported to the ethylene glycol recycling tank by an ethylene glycol transfer pump. Ethylene glycol in the first ethylene glycol liquid seal tank is partially transported to the ethylene glycol recycling tank by an ethylene glycol circulation pump, and the other part is transported to a heat exchanger. The ethylene glycol cooled by the heat exchanger returns to the third-stage steam jet pump. A flushing pipeline connects the heat exchanger and the third-stage steam jet pump.

2. The energy-saving and anti-clogging vacuum system for polyester production according to claim 1, characterized in that: The flushing pipeline includes a main flushing pipe and three flushing branch pipes connected to the main flushing pipe. The pipes between the primary spray tower, the secondary spray tower, the tertiary spray tower, and the heat exchanger are respectively connected to the three flushing branch pipes, and a first valve is installed on the flushing branch pipe.

3. The energy-saving and anti-clogging vacuum system for polyester production according to claim 2, characterized in that: The main flushing pipe is connected to a hot ethylene glycol pipe and an ethylene glycol vapor pipe, and a second valve is installed on both the hot ethylene glycol pipe and the ethylene glycol vapor pipe.

4. The energy-saving and anti-clogging vacuum system for polyester production according to claim 3, characterized in that: Both the first valve and the second valve are control valves. The first valve is electrically connected to a first selector switch, and the second valve is electrically connected to a second selector switch. Both the first selector switch and the second selector switch are electrically connected to a controller.

5. The energy-saving and anti-clogging vacuum system for polyester production according to claim 1, characterized in that: Both the first and second ethylene glycol liquid seal tanks are equipped with partition plates, which divide the space inside the tanks into two interconnected storage cavities.

6. The energy-saving and anti-clogging vacuum system for polyester production according to claim 1, characterized in that: The outer peripheral wall of the second ethylene glycol liquid seal tank is provided with a heat insulation layer.

7. The energy-saving and anti-clogging vacuum system for polyester production according to claim 1, characterized in that: The vacuum system also includes an ethylene glycol evaporator, and the ethylene glycol in the first ethylene glycol liquid seal tank is partially transported to the ethylene glycol recycling tank and the ethylene glycol evaporator via an ethylene glycol circulation pump.

8. The energy-saving and anti-clogging vacuum system for polyester production according to claim 1, characterized in that: The first ethylene glycol liquid seal tank is connected to a fresh ethylene glycol replenishment pipe.

9. The energy-saving and anti-clogging vacuum system for polyester production according to claim 1, characterized in that: Flow meters are installed on the pipes connecting the primary, secondary, and tertiary spray towers and the heat exchanger.

10. The energy-saving and anti-clogging vacuum system for polyester production according to claim 1, characterized in that: The second ethylene glycol liquid seal tank is connected to a tail gas pipe, and a tail gas condenser is installed on the tail gas pipe. The condensate outlet of the tail gas condenser is connected to a condensate recovery pipe.

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