An apparatus for reducing fouling in a stripping column in a pta production process

Abstract

The application discloses a device for reducing the scaling of a stripping tower in a PTA production process and belongs to the technical field of chemical production. The device comprises a stripping tower, a sprinkler plate arranged in the stripping tower, a low-pressure acetic acid solvent pipeline arranged on the upper side of the sprinkler plate on the stripping tower, a low-pressure steam pipeline arranged on the lower side of the sprinkler plate on the stripping tower, an electronic liquid level meter arranged on one side of the stripping tower, a scale inhibitor adding device arranged on the other side of the stripping tower, a slurry heating device arranged on the other side of the stripping tower, a slurry pumping and discharging device arranged at the bottom of the stripping tower, the slurry heating device being connected with the slurry pumping and discharging device through two pipelines, and the slurry pumping and discharging device being connected with the scale inhibitor adding device through a pipeline. The device can extract the excessive scale inhibitor pumped and discharged from the stripping tower, readjust the concentration of the scale inhibitor input into the stripping tower, supplement the reduced scale inhibitor in the stripping tower, and thus ensure that the residual slurry in the stripping tower is reduced to scale.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, specifically to a device for reducing scaling in stripping towers during PTA production processes. Background Technology

[0002] PTA, or terephthalic acid, is used in the PTA production process. To ensure that the reaction byproducts, paraxylene impurity derivatives, and metal ions in the mother liquor of the oxidation unit are at acceptable concentrations, up to 14% of the mother liquor is extracted from the process mother liquor for purification. The extracted mother liquor (low-pressure acetic acid solvent) is filtered and then enters the stripping tower for purification. Approximately 90% of the low-pressure acetic acid solvent is evaporated into the methyl acetate stripping tower, leaving residue at the bottom, forming a slurry with a solid concentration of about 15-20% w / w. This slurry is pumped out from the bottom of the stripping tower. Because this residue is prone to scaling in the stripping tower, a scale inhibitor needs to be introduced to reduce scaling. However, the unstable amount of low-pressure acetic acid solvent entering the stripping tower upstream causes the liquid level to rise, affecting the evaporation of the low-pressure acetic acid solvent. Current technology monitors the liquid level in the stripping tower using an electronic level gauge. When the liquid level exceeds the limit, the slurry is pumped out, heated in a reboiler, and then reintroduced into the stripping tower. This heated portion of the slurry... As the material temperature rises, the low-pressure acetic acid solution evaporates more rapidly, causing the liquid level in the stripping tower to drop back below the set value. However, the heated residue slurry contains scale inhibitors, which also evaporate upon heating, entering the methyl acetate stripping tower along with the evaporating low-pressure acetic acid solvent. This further reduces the purity of the purified low-pressure acetic acid solvent. Therefore, when heating the residue slurry, the supply of scale inhibitors to the stripping tower must be stopped. However, this leads to a decrease in the scale inhibitor content in the residue slurry, making it prone to scaling. Existing technology restores the supply of scale inhibitors to the stripping tower after the liquid level drops by adding additional scale inhibitors to maintain a balance in the scale inhibitor content. However, stripping towers are large-scale equipment and are in continuous production, making the additional scale inhibitors very costly and placing an economic burden on enterprises. Summary of the Invention

[0003] To address the technical problems mentioned in the background section, this invention provides a device for reducing scaling in PTA stripping towers during the PTA production process, employing the following technical solution:

[0004] The system includes a stripping tower, which is equipped with a rain shower plate. A low-pressure acetic acid solvent pipeline is installed on the upper side of the rain shower plate, and a low-pressure steam pipeline is installed on the lower side of the rain shower plate. An electronic level gauge and a scale inhibitor addition device are installed on one side of the stripping tower, and a slurry heating device is installed on the other side. A slurry extraction device is installed at the bottom of the stripping tower. The slurry heating device is connected to the slurry extraction device through two pipelines, and the slurry extraction device is connected to the scale inhibitor addition device through a pipeline.

[0005] Furthermore, the scale inhibitor addition device includes a scale inhibitor preparation tank, on one side of which are scale inhibitor pipelines and process water pipelines. The scale inhibitor preparation tank is connected to a scale inhibitor delivery pump via pipelines, and the scale inhibitor delivery pump is connected to a stripping tower via pipelines, with a gate valve a installed on the pipelines.

[0006] Furthermore, the slurry heating device includes a stripping tower reboiler, which is connected to a stripping tower circulation pump via a pipeline. The stripping tower circulation pump is connected to the bottom of the stripping tower via a pipeline, and a gate valve b is installed on the pipeline. The stripping tower reboiler is connected to the upper part of the stripping tower via a pipeline. A low-pressure steam pipeline is installed on the upper part of the stripping tower reboiler, and a gate valve c is installed on the pipeline. A low-pressure condensate pipeline is installed at the bottom of the stripping tower reboiler, and a gate valve d is installed on the pipeline.

[0007] Furthermore, the slurry extraction device includes a residue evaporator and a scale inhibitor recovery tower. The residue evaporator is connected to a stripping tower conveying pump via a pipeline. The stripping tower conveying pump is connected to the bottom of the stripping tower via a pipeline. The upper part of the residue evaporator is connected to the scale inhibitor recovery tower via a pipeline, and a gate valve e is installed on the pipeline. A pipeline is installed at the bottom of the residue evaporator, and a gate valve f is installed on the pipeline.

[0008] Furthermore, a branch line of the low-pressure steam line on the stripping tower reboiler is connected to the residue evaporator, and a gate valve g is installed on the branch line.

[0009] Furthermore, a branch line of the low-pressure steam line on the stripping tower reboiler is connected to the residue evaporator, and a gate valve g is installed on the branch line.

[0010] Furthermore, the feature is that a scale inhibitor circulation pump is connected to the bottom of the scale inhibitor recovery tower via a pipeline, and the scale inhibitor circulation pump is connected to the scale inhibitor preparation tank via a pipeline.

[0011] Furthermore, the electronic level gauge is equipped with an ultrasonic vibrator.

[0012] This invention has the following advantages: When the residual slurry level at the bottom of the stripping tower is lower than the electronic level gauge, the scale inhibitor adding device supplies scale inhibitor into the stripping tower, the slurry heating device is stopped, and the slurry pumping device continuously pumps out and stores the residual slurry at the bottom of the stripping tower. When the residual slurry level at the bottom of the stripping tower rises and is detected by the electronic level gauge, the scale inhibitor adding device stops adding scale inhibitor, and the slurry heating device starts. The slurry heating device reheats the portion of the residual slurry that has been pumped out and then sends it back into the stripping tower to re-contact with the low-pressure steam in the stripping tower, thereby accelerating the evaporation and purification of the low-pressure acetic acid solvent in the residual slurry. This causes the residual slurry level at the bottom of the stripping tower to drop again. When the level is lower than the electronic level gauge, the slurry heating device is shut down. At this time, the low-pressure steam originally supplied by the slurry heating device is supplied through one of the pipelines. The slurry is supplied to a slurry extraction device, which heats the residual slurry that is extracted and stored. The scale inhibitor and a small amount of low-pressure acetic acid solvent carried in the residual slurry are evaporated, while the residue remains in the slurry extraction device. Simultaneously, the condensate after heat exchange and condensation in the slurry heating device enters the slurry extraction device through a pipeline, where it exchanges heat with the evaporated scale inhibitor and a small amount of low-pressure acetic acid solvent, causing the scale inhibitor and a small amount of low-pressure acetic acid solvent to condense into a liquid state. This liquid is then pumped into a scale inhibitor addition device, increasing the scale inhibitor concentration in the addition device. The liquid is then sent to a stripping tower to replenish the scale inhibitor concentration that has decreased in the stripping tower. This invention replenishes the scale inhibitor that has been extracted from the stripping tower, re-proportioned, and increased in concentration, thereby ensuring that the residual slurry in the stripping tower exhibits reduced scaling. Attached Figure Description

[0013] Figure 1 This is a flowchart of the present invention.

[0014] Attached Figures: 1. Stripping Tower, 2. Shower Plate, 3. Electronic Level Gauge, 4. Scale Inhibitor Preparation Tank, 5. Scale Inhibitor Transfer Pump, 6. Gate Valve a, 7. Stripping Tower Reboiler, 8. Stripping Tower Circulation Pump, 9. Gate Valve b, 10. Gate Valve c, 11. Gate Valve d, 12. Residue Evaporator, 13. Scale Inhibitor Recovery Tower, 14. Stripping Tower Transfer Pump, 15. Gate Valve e, 16. Gate Valve f, 17. Gate Valve g, 18. Scale Inhibitor Circulation Pump, 19. Ultrasonic Vibrator. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Please refer to Figure 1This invention provides a device for reducing scaling in a stripping tower during PTA production. The device includes a stripping tower 1 with a rain shower 2 inside. Low-pressure acetic acid solvent falls through the rain shower 2 in a rain-like manner. A low-pressure acetic acid solvent pipeline is located above the rain shower 2 on the stripping tower 1, through which the low-pressure acetic acid solvent enters the stripping tower 1. A low-pressure steam pipeline is located below the rain shower 2 on the stripping tower 1, through which low-pressure steam enters the stripping tower 1 and comes into contact with the rain-falling low-pressure acetic acid solvent, heating and evaporating the solvent to achieve stripping. An electronic level gauge 3 is installed on one side of the stripping tower 1 for measuring the stripping temperature. The concentration of the residual slurry at the bottom of stripping tower 1 is as follows: A scale inhibitor addition device is installed on one side of stripping tower 1 to prepare the scale inhibitor and send it into stripping tower 1; a slurry heating device is installed on the other side of stripping tower 1 to extract and heat the residual slurry in the stripping tower; a slurry extraction device is installed at the bottom of stripping tower 1 to extract the residual slurry in stripping tower 1; the slurry heating device is connected to the slurry extraction device through two pipelines, one of which provides low-pressure steam to the slurry extraction device, and the other of which provides low-pressure condensate to the slurry extraction device; the slurry extraction device is connected to the scale inhibitor addition device through a pipeline, and the scale inhibitor extracted from the slurry residue is sent into the scale inhibitor addition device through the slurry extraction device.

[0017] The scale inhibitor addition device includes a scale inhibitor preparation tank 4. A scale inhibitor pipeline and a process water pipeline are installed on one side of the scale inhibitor preparation tank 4. The scale inhibitor enters the scale inhibitor preparation tank 4 through the scale inhibitor pipeline, and the process water enters the scale inhibitor preparation tank 4 through the process water pipeline. The original scale inhibitor and process water are mixed to form a scale inhibitor of a certain concentration. The scale inhibitor preparation tank 4 is connected to a scale inhibitor delivery pump 5 through a pipeline. The scale inhibitor delivery pump 5 delivers the scale inhibitor from the scale inhibitor preparation tank 4 into the stripping tower 1. The scale inhibitor delivery pump 5 is connected to the stripping tower 1 through a pipeline, and a gate valve a6 is installed on the pipeline. The gate valve a6 controls the opening and closing of the pipeline.

[0018] The slurry heating device includes a stripping tower reboiler 7. The stripping tower reboiler 7 is connected to a stripping tower circulation pump 8 via a pipeline. The stripping tower circulation pump 8 is connected to the bottom of the stripping tower 1 via a pipeline, and a gate valve b9 is installed on the pipeline. The gate valve b9 controls the opening and closing of this pipeline. The stripping tower circulation pump 8 draws the residual slurry from the upper layer of the stripping tower 1 into the stripping tower reboiler 7. The stripping tower reboiler 7 is connected to the upper part of the stripping tower 1 via a pipeline. A low-pressure steam pipeline is installed on the upper part of the stripping tower reboiler 7, and a gate valve c10 is installed on this pipeline. The gate valve c10 controls the opening and closing of this pipeline. 7. A low-pressure condensate pipeline is installed at the bottom, and a gate valve d11 is installed on the pipeline. The gate valve d11 controls the opening and closing of the pipeline. The stripping tower reboiler 7 is a type of heat exchanger. Low-pressure steam enters the stripping tower reboiler 7 through the low-pressure steam pipeline as a heating source. The low-pressure steam enters the shell side of the stripping tower reboiler 7, while the extracted residue slurry enters the tube side of the stripping tower reboiler 7. The residue slurry in the tube side exchanges heat with the low-pressure steam outside the tube side. After the low-pressure steam completes its work in the shell side of the stripping tower reboiler 7, it condenses into low-pressure condensate and is discharged through the low-pressure condensate pipeline.

[0019] The slurry extraction device includes a residue evaporator 12 and a scale inhibitor recovery tower 13. The residue evaporator 12 is connected to a stripping tower transfer pump 14 via a pipeline. The stripping tower transfer pump 14 is connected to the bottom of the stripping tower 1 via a pipeline. The stripping tower transfer pump 14 pumps the residue slurry from the bottom of the stripping tower 1 into the residue evaporator 12. The upper part of the residue evaporator 12 is connected to the scale inhibitor recovery tower 13 via a pipeline, and a gate valve e15 is installed on the pipeline. The gate valve e15 controls the opening and closing of the pipeline. A pipeline is installed at the bottom of the residue evaporator 12, and a gate valve f16 is installed on the pipeline. The gate valve f16 controls the opening and closing of the pipeline. When the residue in the residue evaporator 12 accumulates to a certain level, it is discharged by opening the gate valve f16.

[0020] A branch line of the low-pressure steam pipeline on the stripping tower reboiler 7 is connected to the residue evaporator 12, and a gate valve g17 is installed on the branch line. The gate valve g17 controls the opening and closing of the pipeline. Low-pressure steam enters the residue evaporator 12 through the branch line to provide a heating source for the residue evaporator 12.

[0021] The low-pressure condensate pipeline at the bottom of the stripping tower reboiler 7 is connected to the upper part of the scale inhibitor recovery tower 13. The low-pressure condensate in the shell side of the stripping tower reboiler 7 is sent into the scale inhibitor recovery tower 13 through the low-pressure condensate pipeline at the bottom of the stripping tower reboiler 7. The scale inhibitor recovery tower 13 is connected to the bottom of the scale inhibitor recovery tower 13 through a pipeline. The scale inhibitor circulation pump 18 is connected to the scale inhibitor preparation tank 4 through a pipeline. The scale inhibitor recovered in the scale inhibitor recovery tower is sent into the scale inhibitor preparation tank 4 through the scale inhibitor circulation pump 18. An ultrasonic vibrator 19 is installed on the electronic level gauge 3. The vibration of the electronic level gauge 3 by the ultrasonic vibrator 19 avoids the clogging of the electronic level gauge 3 pipe opening by the residual slurry.

[0022] Working principle of the invention:

[0023] Initially, low-pressure acetic acid solvent enters stripping tower 1 through the low-pressure acetic acid solvent pipeline and falls in the form of rain through the deluge plate 2. Low-pressure steam enters stripping tower 1 through the low-pressure steam pipe and comes into contact with the rained-down low-pressure acetic acid solvent. Gate valve b9 is closed, causing the low-pressure acetic acid solvent to be heated and evaporated, and then passes through the pipeline at the top of stripping tower 1 to the methyl acetate stripping tower for stripping. The remaining residue slurry remains at the bottom of stripping tower 1. Scale inhibitor and process water flow through the scale inhibitor pipeline and process water pipeline, respectively. The process water pipeline enters the scale inhibitor preparation tank 4 to prepare a scale inhibitor of a certain concentration. The gate valve a6 is opened, and the scale inhibitor is sent to the stripping tower 1 through the scale inhibitor delivery pump 5. The scale inhibitor enters the residue slurry in the stripping tower 1 to reduce the structure of the residue slurry. The residue slurry in the stripping tower 1 is sent to the residue evaporator 12 for storage through the stripping tower delivery pump 14. Gate valves e15 and f16 are both closed. At this time, no heat source enters the residue evaporator 12, and it is only used as a storage device.

[0024] When the flow rate of low-pressure acetic acid solvent in the low-pressure acetic acid solvent pipeline increases, causing the amount of low-pressure acetic acid solvent entering stripping tower 1 to exceed the design processing capacity of low-pressure steam in stripping tower 1, the low-pressure acetic acid solvent cannot evaporate efficiently, resulting in excessive liquid low-pressure acetic acid solvent falling into stripping tower 1 and mixing with the residue slurry. This causes the original residue slurry level to rise. When the level rises to a certain height and is measured by electronic level gauge 3, scale inhibitor delivery pump 5 and gate valve a6 are shut off, stopping the supply of scale inhibitor to stripping tower 1. Gate valve b9, stripping tower circulation pump 8, and gate valve c10 are opened, and the upper layer of residue slurry in stripping tower 1 is pumped into stripping tower reboiler 7 through stripping tower circulation pump 8. Low-pressure steam enters the reboiler 7 of the stripping tower through the low-pressure steam pipeline, where it exchanges heat with the residual slurry in the tube side of the reboiler 7, thus heating the extracted residual slurry. The heated residual slurry then re-enters the stripping tower 1, where it comes into contact with the low-pressure steam again. This results in high-temperature, high-efficiency evaporation and stripping of this portion of the residual slurry, causing the liquid level of the residual slurry in the stripping tower 1 to drop. It is worth noting that in this process, the scale inhibitor entering the stripping tower 1 is shut off to prevent the extracted heated residual slurry from carrying more scale inhibitor, which would cause it to evaporate during reheating. This would also result in more scale inhibitor being stripped into the methyl acetate stripping tower.

[0025] When the liquid level falls below the electronic level gauge 3 again, open the scale inhibitor delivery pump 5 and gate valve a6, close gate valve b9, stripper circulation pump 8 and gate valve c10, and open gate valve g17, gate valve d11, gate valve e15 and scale inhibitor circulation pump 18. Because the stripper circulation pump 8 draws the upper layer of the residue slurry into the stripper reboiler 7, the scale inhibitor delivery to stripper 1 stops, while the amount of residue slurry continues to increase. Therefore, the amount of scale inhibitor in the residue slurry in stripper 1 is significantly insufficient. At this time, the low-pressure steam in the low-pressure steam pipeline enters the residue evaporator 12 through the branch pipeline of gate valve g17, and the residue evaporator 12 starts working. The low-pressure steam in the residue evaporator 12 comes into contact with the residue slurry pumped out by the stripper delivery pump 14, heating the residue slurry. The residue in the residue slurry remains... The excess scale inhibitor in the residue evaporator 12 is heated and evaporated, and enters the scale inhibitor recovery tower 13 through the pipeline on the gate valve e15. The low-pressure steam that was originally heated and completed its work in the stripper reboiler 7 is condensed and remains in the shell side of the stripper reboiler 7, and enters the scale inhibitor recovery tower 13 through the low-pressure condensate pipeline on the gate valve d11. It comes into contact with the vaporized scale inhibitor, causing this part of the scale inhibitor to condense into a liquid state. After the scale inhibitor vapor and condensate come into contact to form liquid scale inhibitor, the scale inhibitor is mixed in the condensate, but the proportion of condensate is very small. Then the scale inhibitor circulation pump 18 sends the scale inhibitor to the preparation tank 4, so that the scale inhibitor concentration in the preparation tank 4 increases, and then sends it to the stripper 1 to fill the amount of scale inhibitor missing in the stripper 1, thereby reducing the scaling of the residue slurry in the stripper 1.

[0026] This invention is simple to operate, convenient to use, and suitable for widespread promotion and application. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An apparatus for reducing scaling in a stripping tower during PTA production, comprising a stripping tower (1), a rain shower plate (2) disposed inside the stripping tower (1), a low-pressure acetic acid solvent pipeline disposed on the upper side of the rain shower plate (2) on the stripping tower (1), and a low-pressure steam pipeline disposed on the lower side of the rain shower plate (2) on the stripping tower (1), characterized in that, An electronic level gauge (3) is installed on one side of the stripping tower (1), a scale inhibitor addition device is installed on one side of the stripping tower (1), a slurry heating device is installed on the other side of the stripping tower (1), and a slurry extraction device is installed at the bottom of the stripping tower (1). The slurry heating device is connected to the slurry extraction device through two pipelines, and the slurry extraction device is connected to the scale inhibitor addition device through a pipeline. The slurry pumping device includes a residue evaporator (12) and a scale inhibitor recovery tower (13). The residue evaporator (12) is connected to a stripping tower delivery pump (14) via a pipeline. The stripping tower delivery pump (14) is connected to the bottom of the stripping tower (1) via a pipeline. The upper part of the residue evaporator (12) is connected to the scale inhibitor recovery tower (13) via a pipeline, and a gate valve e (15) is installed on the pipeline. The bottom of the scale inhibitor recovery tower (13) is connected to a scale inhibitor circulation pump (18) via a pipeline, and the scale inhibitor circulation pump (18) is connected to the scale inhibitor preparation tank (4) via a pipeline.

2. A device for reducing fouling in a stripping column in a PTA production process according to claim 1, characterized in that, The scale inhibitor addition device includes a scale inhibitor preparation tank (4), a scale inhibitor pipeline and a process water pipeline are provided on one side of the scale inhibitor preparation tank (4), the scale inhibitor preparation tank (4) is connected to a scale inhibitor delivery pump (5) through the pipeline, the scale inhibitor delivery pump (5) is connected to the stripping tower (1) through the pipeline and a gate valve a (6) is provided on the pipeline.

3. A device for reducing fouling in a stripping column in a PTA production process as claimed in claim 1, wherein, The slurry heating device includes a stripper reboiler (7), which is connected to a stripper circulation pump (8) via a pipeline. The stripper circulation pump (8) is connected to the bottom of the stripper (1) via a pipeline and a gate valve b (9) is installed on the pipeline. The stripper reboiler (7) is connected to the top of the stripper (1) via a pipeline. A low-pressure steam pipeline is installed on the top of the stripper reboiler (7) and a gate valve c (10) is installed on the pipeline. A low-pressure condensate pipeline is installed at the bottom of the stripper reboiler (7) and a gate valve d (11) is installed on the pipeline.

4. A device for reducing fouling in a stripping column in a PTA production process as claimed in claim 1, wherein, The bottom of the residue evaporator (12) is equipped with a pipeline and a gate valve f (16) is installed on the pipeline.

5. The apparatus for reducing fouling in a stripping column in a PTA production process according to claim 3 or 4, wherein, A branch line of the low-pressure steam line on the stripping tower reboiler (7) is connected to the residue evaporator (12), and a gate valve g (17) is installed on the branch line.

6. A device for reducing fouling in a stripping column in a PTA production process according to claim 3 or 4, characterized in that, The low-pressure condensate pipeline at the bottom of the stripper reboiler (7) is connected to the upper part of the scale inhibitor recovery tower (13).

7. A device for reducing fouling in a stripping column in a PTA production process according to claim 1, characterized in that, An ultrasonic vibrator (19) is installed on the electronic level gauge (3).

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