Esterification steam treatment system

Abstract

The utility model belongs to the technical field of chemical equipment, and particularly relates to an esterification steam treatment system which comprises an ethylene glycol separation tower, a stripping tower, a steam compressor and a first discharging pump, a steam inlet of the steam compressor is communicated with the top of the ethylene glycol separation tower, and a steam outlet of the steam compressor is communicated with the bottom of the stripping tower. And a liquid inlet of the first discharge pump is communicated with the bottom of the stripping tower. In the utility model, the esterification steam from which ethylene glycol is separated is pressurized and heated and then is directly fed into the bottom of the stripping tower to replace high-temperature steam to be in countercurrent contact with the esterification wastewater, so that on one hand, the heat of the esterification steam is utilized, and on the other hand, the high-temperature steam is not prepared for the stripping tower, thereby effectively reducing the energy consumption and the production cost; the production burden of enterprises is reduced.

Description

Technical Field

[0001] This utility model belongs to the field of chemical equipment technology, specifically relating to an esterification steam treatment system. Background Technology

[0002] In the production of polyester bottle chips, a large amount of esterification vapor containing ethylene glycol is generated in the esterification reaction section. The treatment method for this esterification vapor is typically as follows: ethylene glycol is separated from the esterification vapor in a process tower using their different boiling points. The ethylene glycol flows out from the bottom of the tower, while the high-temperature esterification vapor, after ethylene glycol removal, overflows from the top of the tower and is cooled and condensed into esterification wastewater by a cooling fan. This wastewater is then mixed with other esterification wastewater, such as esterification wastewater discharged from the bottom of the esterification reaction tower, and then processed through a stripping tower to recover organic compounds such as acetaldehyde and 2-methyl-1,3-dioxolane (2-MD). In the stripping tower, the esterification wastewater is sprayed from the top, while process steam is introduced from the bottom. The steam rises and carries away the acetaldehyde, 2-MD, and other organic compounds from the esterification wastewater, thus reducing the chemical oxygen demand (COD) content of the esterification wastewater flowing out from the bottom of the tower. While this treatment method can effectively separate organic compounds such as acetaldehyde and 2-MD, this esterification steam treatment method requires the preparation of high-temperature steam to continuously provide stripping conditions for the stripping tower, resulting in high energy consumption and placing a significant burden on enterprise production. Utility Model Content

[0003] The present invention aims to provide an esterification steam treatment system to solve the problems of high energy consumption and heavy production burden of traditional esterification steam treatment methods.

[0004] To achieve the above objectives, the present invention provides an esterification steam treatment system, comprising an ethylene glycol separation tower and a stripping tower, and further comprising a steam compressor and a first discharge pump. The steam inlet of the steam compressor is connected to the top of the ethylene glycol separation tower, the steam outlet of the steam compressor is connected to the bottom of the stripping tower, and the liquid inlet of the first discharge pump is connected to the bottom of the stripping tower.

[0005] The working principle and beneficial effects of this scheme are as follows: In this scheme, after the esterification steam separates ethylene glycol in the ethylene glycol separation tower, it is pressurized and heated by a steam compressor and directly sent to the bottom of the stripping tower. There, it comes into countercurrent contact with the spray water (esterification wastewater) sprayed from the top of the stripping tower. The heat of the esterification steam is transferred to the esterification wastewater, causing the low-boiling-point components (volatile components) in the wastewater, such as acetaldehyde and 2-MD, to turn into the gas phase, while the high-boiling-point components (non-volatile components) in the esterification steam turn into the liquid phase. The gas phase components containing acetaldehyde and 2-MD are discharged from the top of the stripping tower, and the liquid phase components are discharged from the bottom. The liquid phase is then transported to the wastewater treatment plant by the first discharge pump. In summary, in this scheme, the esterification steam is not cooled but pressurized and heated before entering the stripping tower, replacing the process steam. This utilizes the heat of the esterification steam and eliminates the need to prepare high-temperature steam for the stripping tower, thereby effectively reducing energy consumption, production costs, and the burden on the enterprise.

[0006] Optionally, it also includes an esterification wastewater collection tank, a second discharge pump, and a first heat exchanger. The inlet of the second discharge pump is connected to the esterification wastewater collection tank, and the outlets of the second discharge pump and the first discharge pump are respectively connected to the corresponding inlets on the first heat exchanger. The first heat exchanger is connected to the top of the stripping tower.

[0007] In this scheme, the esterification wastewater discharged from the bottom of the stripping tower has a relatively high temperature (70-90℃). Therefore, in order to avoid the esterification wastewater entering the top of the stripping tower being too cold, the esterification wastewater in the esterification wastewater collection tank and the esterification wastewater discharged from the bottom of the stripping tower are transported to the first heat exchanger to exchange heat, thereby increasing the temperature of the esterification wastewater entering the top of the stripping tower.

[0008] Optionally, it also includes a second heat exchanger, which is connected to the first heat exchanger.

[0009] In this scheme, a second heat exchanger is used to further cool the esterification wastewater, and the esterification wastewater is sent to the sewage treatment plant after secondary cooling.

[0010] Optionally, the second heat exchanger is connected to the esterification wastewater collection tank via a first branch pipe, and a second valve is installed on the first branch pipe.

[0011] In this scheme, part of the esterification wastewater discharged from the bottom of the stripping tower enters the esterification wastewater collection tank through the first branch pipe and is reused for spraying at the top of the stripping tower; the other part is transported to the wastewater treatment plant. Additionally, at the initial stage of system operation, the steam compressor is not working. Esterification steam enters the bottom of the stripping tower, cools into condensate inside the tower, and is then discharged from the bottom and enters the esterification wastewater collection tank. In this way, a cycle can be established solely using esterification steam for the entry of steam from the bottom of the stripping tower and the spraying of esterification wastewater from the stripping tower, thus achieving the treatment of the esterification steam.

[0012] Optionally, the first heat exchanger is connected to the esterification wastewater collection tank via a second branch pipe, and a fourth valve is installed on the second branch pipe.

[0013] In this scheme, the esterification wastewater discharged from the bottom of the stripping tower is cooled by the first heat exchanger and then enters the esterification wastewater collection tank through the second branch pipe. In this way, the water temperature in the esterification wastewater collection tank can be prevented from being too low in winter.

[0014] Optionally, the esterification wastewater collection tank is connected to an inlet pipe, and a first valve is installed on the inlet pipe.

[0015] In this scheme, the flow rate of the inlet pipe is controlled by the first valve, so that external esterification wastewater, such as esterification wastewater discharged from the bottom of the esterification reaction tower, vacuum drainage, and wastewater generated from the water washing process, can enter the esterification wastewater collection tank.

[0016] Optionally, the esterification wastewater collection tank is equipped with a liquid level sensor and a temperature sensor.

[0017] In this solution, a level sensor is used to monitor the liquid level in the esterification wastewater collection tank. When the liquid level exceeds the preset level, the second valve closes to prevent the esterification wastewater from overflowing. Simultaneously, a temperature sensor is used to monitor the water temperature in the esterification wastewater collection tank to prevent the wastewater temperature from becoming too high or too low. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an esterification steam treatment system according to Embodiment 1 of this utility model;

[0019] Figure 2 This is a schematic diagram of the structure of an esterification steam treatment system according to Embodiment 2 of this utility model;

[0020] Figure 3 This is a schematic diagram of the structure of an esterification steam treatment system according to Embodiment 3 of this utility model;

[0021] Figure 4 This is a schematic diagram of an esterification steam treatment system according to Embodiment 4 of this utility model. Detailed Implementation

[0022] The following detailed description illustrates the specific implementation method:

[0023] The markings in the accompanying drawings include: 1. Ethylene glycol separation tower; 2. Stripping tower; 3. Steam compressor; 4. First discharge pump; 5. Second discharge pump; 6. First heat exchanger; 7. Second heat exchanger; 8. Esterification wastewater collection tank; 9. Inlet pipe; 10. First valve; 11. First branch pipe; 12. Second valve; 13. Third valve; 14. Liquid level sensor; 15. Temperature sensor; 16. Second first branch pipe; 17. Fourth valve.

[0024] Example 1

[0025] This embodiment is basically as follows: Figure 1 The diagram shows an esterification steam treatment system, comprising an ethylene glycol separation tower 1, a stripping tower 2, a steam compressor 3, a first discharge pump 4, a second discharge pump 5, a first heat exchanger 6, a second heat exchanger 7, and an esterification wastewater collection tank 8. The steam inlet of the steam compressor 3 is connected to the top of the ethylene glycol separation tower 1 via a pipeline, and the steam outlet of the steam compressor 3 is connected to the bottom of the stripping tower 2 via a pipeline.

[0026] The inlet of the first discharge pump 4 is connected to the bottom of the stripping tower 2 via a pipeline. The outlet of the first discharge pump 4 is connected to the shell-side inlet of the first heat exchanger 6 via a pipeline. The shell-side outlet of the first heat exchanger 6 is connected to the tube-side inlet of the second heat exchanger 7 via a pipeline. The inlet of the second discharge pump 5 is connected to the esterification wastewater collection tank 8 via a pipeline. The outlet of the second discharge pump 5 is connected to the tube-side inlet of the first heat exchanger 6 via a pipeline. The tube-side outlet of the first heat exchanger 6 is connected to the top of the stripping tower 2 via a pipeline.

[0027] The esterification wastewater collection tank 8 is connected to an inlet pipe 9, and a first valve 10 is installed on the inlet pipe 9 to control the flow rate in the inlet pipe 9.

[0028] In practical use, esterification wastewater (including esterification wastewater discharged from the bottom of the esterification reaction tower, vacuum drainage, etc.) flows into the esterification wastewater collection tank 8 through the inlet pipe 9. Esterification vapor enters the ethylene glycol separation tower 1 from the bottom of the tower. Ethylene glycol in the esterification vapor is condensed in the tower and discharged from the bottom of the ethylene glycol separation tower 1. Esterification vapor after ethylene glycol removal is discharged from the top of the ethylene glycol separation tower 1, thus achieving the separation of ethylene glycol.

[0029] Subsequently, the esterification vapor discharged from the top of ethylene glycol separation tower 1 enters the steam compressor 3, where it is compressed and heated before being sent to the bottom of stripping tower 2, where it rises. Meanwhile, the esterification wastewater in the esterification wastewater collection tank 8 enters the tube side of the first heat exchanger 6 under the action of the second discharge pump 5, and then enters the top of stripping tower 2, where it is sprayed. Thus, the descending esterification wastewater and the rising esterification vapor come into countercurrent contact within the tower. Low-boiling-point components in the esterification wastewater, such as acetaldehyde and 2-MD, turn to the gas phase, while high-boiling-point components in the esterification vapor turn to the liquid phase. The top of stripping tower 2 discharges a gaseous component containing acetaldehyde and 2-MD, while the bottom of stripping tower 2 discharges the stripped esterification wastewater.

[0030] The esterification wastewater discharged from the bottom of stripping tower 2 has a high temperature, about 70-90℃. Under the action of the first discharge pump 4, the esterification wastewater discharged from the bottom of stripping tower 2 enters the shell side of the first heat exchanger 6 and exchanges heat with the esterification wastewater from the esterification wastewater collection tank 8 (located in the tube side of the first heat exchanger 6). This causes the temperature of the esterification wastewater entering the top of stripping tower 2 for spraying to rise, and also causes the temperature of the esterification wastewater discharged from the bottom of stripping tower 2 to drop to 40-60℃. The esterification wastewater then exchanges heat with the circulating cooling water in the second heat exchanger 7 before being sent to the wastewater treatment plant.

[0031] Thus, in this embodiment, the esterification steam, after separating ethylene glycol, is not cooled but is compressed and heated by the steam compressor 3 before entering the bottom of the stripping tower 2. Instead of high-temperature water vapor, it comes into countercurrent contact with the esterification wastewater inside the tower. Therefore, in this embodiment, not only can the heat of the esterification steam be utilized, but high-temperature water vapor is no longer required for the stripping tower 2, thereby effectively reducing energy consumption, production costs, and the production burden on enterprises.

[0032] Example 2

[0033] The difference between this embodiment and Embodiment 1 is that: Figure 2 As shown, in this embodiment, the esterification wastewater collection tank 8 is not connected to the inlet pipe 9, and the pipe connected to the outlet of the tube side of the second heat exchanger 7 is connected to the first branch pipe 11. The end of the first branch pipe 11 away from the second heat exchanger 7 is connected to the top of the esterification wastewater collection tank 8, and a second valve 12 is installed on the first branch pipe 11.

[0034] In this embodiment, at the initial stage of system operation, the steam compressor 3 is not working. Thus, the esterification vapor from the top of the ethylene glycol separation tower 1 enters the bottom of the stripping tower 2. After being partially cooled into condensate, it is pumped by the first discharge pump 4 through the first branch pipe 11 into the esterification wastewater collection tank 8 for storage. Once the liquid level in the esterification wastewater collection tank 8 reaches 50%–70%, the second discharge pump 5 starts, pumping the esterification wastewater from the collection tank 8 to the top of the stripping tower 2 for spraying. Simultaneously, the steam compressor 3 starts, compressing and heating the esterification vapor from the top of the ethylene glycol separation tower 1 before sending it into the stripping tower 2, thereby gradually establishing a normal process cycle. Furthermore, during the above process, the second valve 12 on the first branch pipe 11 can regulate the flow rate of the esterification wastewater entering the esterification wastewater collection tank 8, preventing the amount of esterification wastewater in the collection tank 8 from becoming too much or too little.

[0035] Example 3

[0036] The difference between this embodiment and Embodiment 1 is that: Figure 3As shown, in this embodiment, a first branch pipe 11 is connected to the pipe connected to the outlet of the tube side of the second heat exchanger 7. The end of the first branch pipe 11 away from the second heat exchanger 7 is connected to the top of the esterification wastewater collection tank 8. A second valve 12 is installed on the first branch pipe 11. Simultaneously, a third valve 13 is installed on the pipe connected to the outlet of the tube side of the second heat exchanger 7. Furthermore, a level sensor 14 and a temperature sensor 15 are installed inside the esterification wastewater collection tank 8. The level sensor 14 and the temperature sensor 15 transmit the detected signals to the control system, which controls the opening degrees of the first valve 10, the second valve 12, and the third valve 13.

[0037] In this embodiment, the source of esterification wastewater in the esterification wastewater collection tank 8 can be selected. That is, esterification wastewater discharged from the bottom of the esterification reaction tower, vacuum drainage, wastewater generated from the water washing process (external esterification wastewater), etc., can enter the esterification wastewater collection tank 8 through the water inlet pipe 9; while esterification wastewater discharged from the bottom of the stripping tower 2 can enter the esterification wastewater collection tank 8 through the first branch pipe 11. During system operation, the level sensor 14 monitors the liquid level in the esterification wastewater collection tank 8. When the liquid level exceeds the preset high level (the preset high level is 70% of the height of the esterification wastewater collection tank 8), the second valve 12 closes (the first valve 10 is normally closed), and the opening of the third valve 13 increases, so that all the esterification wastewater discharged from the bottom of the stripping tower 2 is sent to the sewage treatment plant. When the liquid level is lower than the preset low level (the preset low level is 50% of the height of the esterification wastewater collection tank 8), the first valve 10 opens, and external esterification wastewater enters the esterification wastewater collection tank 8 through the inlet pipe 9 until the liquid level rises to 70% and the first valve 10 closes.

[0038] In addition, during system operation, temperature sensor 15 monitors the water temperature in esterification wastewater collection tank 8. When the water temperature exceeds the preset high water temperature (the preset high water temperature is 40℃), the second valve 12 closes, the first valve 10 opens, and the opening of the third valve 13 increases. The esterification wastewater collection tank 8 receives external esterification wastewater, thereby reducing the water temperature. When the water temperature drops to the preset low water temperature (the preset low water temperature is 20℃), the first valve 10 closes, the second valve 12 opens, and the opening of the third valve 13 decreases, thereby achieving regulation of the water temperature in esterification wastewater collection tank 8.

[0039] In summary, this embodiment can regulate the liquid level and water temperature in the esterification wastewater collection tank 8 to ensure that the liquid level and water temperature in the esterification wastewater collection tank 8 are at a suitable level, thereby ensuring the normal operation of the system.

[0040] Example 4

[0041] The difference between this embodiment and Embodiment 3 is that: Figure 4As shown, in this embodiment, a second branch pipe 16 is connected to the pipe between the shell-side liquid outlet of the first heat exchanger 6 and the tube-side liquid inlet of the second heat exchanger 7. The end of the second branch pipe 16 away from the first heat exchanger 6 is connected to the top of the esterification wastewater collection tank 8. A fourth valve 17 is installed on the second branch pipe 16, and the fourth valve 17 is controlled by the control system.

[0042] In this embodiment, during winter, when the ambient temperature is low (ambient temperature < 20℃), the water temperature in the esterification wastewater collection tank 8 is easily lower than the preset low water temperature (the preset low water temperature is 20℃). Therefore, when the water temperature in the esterification wastewater collection tank 8 is lower than 20℃, the control system controls the fourth valve 17 to open and adjust its opening degree, so that part of the esterification wastewater at 40-60℃ flows into the esterification wastewater collection tank 8 through the second branch pipe 16, while another part of the esterification wastewater at 40-60℃ continues to enter the second heat exchanger 7 to exchange heat with the circulating cooling water and cool down to 20-40℃; the control system controls the opening degree of the second valve 12 and the third valve 13, so that part of the esterification wastewater at 20-40℃ flows into the esterification wastewater collection tank 8 through the first branch pipe 11, while another part of the esterification wastewater at 20-40℃ is transported to the sewage treatment plant. In this way, the water temperature in the esterification wastewater collection tank 8 can be automatically controlled, avoiding the water temperature of the esterification wastewater in the esterification wastewater collection tank 8 being too low in winter.

[0043] 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 esterification steam treatment system, comprising an ethylene glycol separation tower and a stripping tower, characterized in that: It also includes a steam compressor and a first discharge pump. The steam inlet of the steam compressor is connected to the top of the ethylene glycol separation tower, the steam outlet of the steam compressor is connected to the bottom of the stripping tower, and the liquid inlet of the first discharge pump is connected to the bottom of the stripping tower.

2. The esterification steam treatment system according to claim 1, characterized in that: It also includes an esterification wastewater collection tank, a second discharge pump, and a first heat exchanger. The inlet of the second discharge pump is connected to the esterification wastewater collection tank, and the outlets of the second discharge pump and the first discharge pump are respectively connected to the corresponding inlets on the first heat exchanger. The first heat exchanger is connected to the top of the stripping tower.

3. The esterification steam treatment system according to claim 2, characterized in that: It also includes a second heat exchanger, which is connected to the first heat exchanger.

4. The esterification steam treatment system according to claim 3, characterized in that: The second heat exchanger is connected to the esterification wastewater collection tank via a first branch pipe, on which a second valve is installed.

5. The esterification steam treatment system according to claim 4, characterized in that: The first heat exchanger is connected to the esterification wastewater collection tank via a second branch pipe, and a fourth valve is installed on the second branch pipe.

6. The esterification steam treatment system according to any one of claims 2-5, characterized in that: The esterification wastewater collection tank is connected to an inlet pipe, and a first valve is installed on the inlet pipe.

7. The esterification steam treatment system according to claim 6, characterized in that: The esterification wastewater collection tank is equipped with a liquid level sensor and a temperature sensor.

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