Device for reducing scaling of stripping tower in PTA (pure terephthalic acid) production process

Abstract

The invention discloses a device for reducing scaling of a stripping tower in a PTA (pure terephthalic acid) production process, which belongs to the technical field of chemical production and comprises the stripping tower, a deluge plate is arranged in the stripping tower, a low-pressure acetic acid solvent pipeline is arranged on the stripping tower and positioned on the upper side of the deluge plate, and a low-pressure steam pipeline is arranged on the stripping tower and positioned on the lower side of the deluge plate. One side of the stripping tower is provided with an electronic liquid level meter, one side of the stripping tower is provided with a scale inhibitor adding device, the other side of the stripping tower is provided with a slurry heating device, the bottom of the stripping tower is provided with a slurry pumping and discharging device, the slurry heating device is connected with the slurry pumping and discharging device through two pipelines, and the slurry pumping and discharging device is connected with the scale inhibitor adding device through a pipeline. According to the invention, the redundant scale inhibitor pumped and discharged from the stripping tower is re-extracted, and the concentration of the scale inhibitor input into the stripping tower is re-proportioned and increased, so that the lost and reduced scale inhibitor in the stripping tower is supplemented, and the scaling of the residue slurry in the stripping tower is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, in particular to a device for reducing scaling of a stripping tower in a PTA production process. Background Art

[0002] PTA stands for terephthalic acid. In the PTA production process, in order to ensure that the reaction by-products, p-xylene impurity derivatives and metal ions in the mother liquor of the oxidation unit are at acceptable concentrations, a maximum of 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 through a filter device and then enters a stripping tower for purification. About 90% of the low-pressure acetic acid solvent is evaporated into the methyl acetate stripping tower, and the remaining residue is left at the bottom of the stripping tower to form a residue slurry with a solid concentration of about 15-20% w / w. The residue slurry at the bottom of the stripping tower is extracted by a stripping tower delivery pump. Since this residue is easy to scale in the stripping tower, in order to reduce the scaling of the residue slurry, it is necessary to input a scale inhibitor into the stripping tower. However, since the amount of low-pressure acetic acid solvent entering the stripping tower upstream is unstable, the liquid level in the stripping tower increases, affecting the evaporation of the low-pressure acetic acid solvent. The prior art monitors the liquid level height in the stripping tower through an electronic liquid level gauge. When the liquid level height exceeds the standard, the residue slurry in the stripping tower is extracted by a material pump, heated by a reboiler, and then re-sent to the stripping tower. Since this heated part of the residue slurry As the material temperature rises, the evaporation of the low-pressure acetic acid solution therein accelerates, causing the liquid level in the stripping tower to drop back to below the set value. However, the heated residual slurry contains scale inhibitors, which will also evaporate after heating and enter the methyl acetate stripping tower together with the evaporated low-pressure acetic acid solvent, causing the purity of the purified low-pressure acetic acid solvent to decrease. Therefore, when the residual slurry is extracted for heating, the delivery of the scale inhibitor to the stripping tower must be stopped. However, this will lead to a decrease in the content of the scale inhibitor in the residual slurry in the stripping tower, making the residual slurry prone to scaling. The prior art ensures the balance of the scale inhibitor content in the stripping tower by adding additional scale inhibitors while resuming the delivery of the scale inhibitor to the stripping tower after the liquid level drops. However, the stripping tower is a large-scale equipment and is produced all year round. The additional addition of scale inhibitors is costly, which brings an economic burden to the production of the enterprise. Summary of the invention

[0003] In order to solve the technical problems mentioned in the above background technology, the present invention provides a device for reducing scaling of a stripping tower in a PTA production process, and the technical solution adopted is as follows:

[0004] It includes a stripping tower, which is provided with a shower plate inside the stripping tower, a low-pressure acetic acid solvent pipeline is provided on the upper side of the shower plate on the stripping tower, a low-pressure steam pipeline is provided on the lower side of the shower plate on the stripping tower, an electronic liquid level meter is provided on one side of the stripping tower, a scale inhibitor adding device is provided on one side of the stripping tower, a slurry heating device is provided on the other side of the stripping tower, a slurry pumping device is provided at the bottom of the stripping tower, the slurry heating device is connected to the slurry pumping device through two pipelines, and the slurry pumping device is connected to the scale inhibitor adding device through a pipeline.

[0005] Furthermore, the antiscalant adding device includes an antiscalant preparation tank, one side of which is provided with an antiscalant pipeline and a process water pipeline, the antiscalant preparation tank is connected to an antiscalant delivery pump through a pipeline, the antiscalant delivery pump is connected to the stripping tower through a pipeline and a gate valve a is provided on the pipeline.

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

[0007] Furthermore, the slurry extraction device includes a residue evaporator and an antiscalant recovery tower. The residue evaporator is connected to a stripping tower delivery pump through a pipeline. The stripping tower delivery pump is connected to the bottom of the stripping tower through a pipeline. The upper part of the residue evaporator is connected to the antiscalant recovery tower through a pipeline and a gate valve e is arranged on the pipeline. The bottom of the residue evaporator is provided with a pipeline and a gate valve f is arranged on the pipeline.

[0008] Furthermore, a branch pipeline is separated from the low-pressure steam pipeline on the stripping tower reboiler and connected to the residue evaporator, and a gate valve g is provided on the branch pipeline.

[0009] Furthermore, a branch pipeline is separated from the low-pressure steam pipeline on the stripping tower reboiler and connected to the residue evaporator, and a gate valve g is provided on the branch pipeline.

[0010] Furthermore, it is characterized in that the bottom of the antiscalant recovery tower is connected to a antiscalant circulation pump through a pipeline, and the antiscalant circulation pump is connected to the antiscalant preparation tank through a pipeline.

[0011] Furthermore, an ultrasonic vibrator is provided on the electronic liquid level meter.

[0012] The present invention has the following advantages: when the residual slurry liquid level at the bottom of the stripping tower is lower than the electronic liquid level meter, the scale inhibitor adding device transports the scale inhibitor into the stripping tower, the slurry heating device is in a parking state, and the slurry pumping device continuously pumps out and stores the residual slurry at the bottom of the stripping tower. When the residual slurry liquid level at the bottom of the stripping tower rises and is measured by the electronic liquid level meter, the scale inhibitor adding device stops adding the scale inhibitor, and the slurry heating device is started. The slurry heating device reheats the extracted part of the residual slurry, and then sends it back to the stripping tower to contact it with the low-pressure steam in the stripping tower again, so that it accelerates evaporation and purifies the low-pressure acetic acid solvent in the residual slurry, so that the residual slurry liquid level at the bottom of the stripping tower drops again, and the liquid level is lower than the electronic liquid level meter, and the slurry heating device is shut down. At this time, the low-pressure steam originally provided by the slurry heating device for heating passes through one of the pipelines. It is provided to the slurry pumping device to heat the residual slurry pumped out and stored by the slurry pumping device, and the scale inhibitor and a small part of the low-pressure acetic acid solvent carried in the residual slurry are evaporated, and the residue remains in the slurry pumping device. At the same time, the condensate after heat exchange and condensation of the slurry heating device enters the slurry pumping device through a pipeline, exchanges heat with the evaporated scale inhibitor and a small part of the low-pressure acetic acid solvent, so that the scale inhibitor and a small part of the low-pressure acetic acid solvent are condensed into liquid, and are pumped into the scale inhibitor adding device to increase the scale inhibitor concentration in the scale inhibitor adding device, and then sent to the stripping tower as a supplement for the reduced scale inhibitor concentration in the stripping tower. The present invention re-extracts the excess scale inhibitor pumped out of the stripping tower, re-proportions and increases the concentration of the scale inhibitor input into the stripping tower, so that the scale inhibitor that is missing and reduced in the stripping tower is supplemented, thereby ensuring that the residual slurry in the stripping tower reduces scaling. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a flow chart of the present invention.

[0014] Attached figures: 1 stripping tower, 2 shower plate, 3 electronic liquid level meter, 4 antiscalant preparation tank, 5 antiscalant delivery 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 antiscalant recovery tower, 14 stripping tower delivery pump, 15 gate valve e, 16 gate valve f, 17 gate valve g, 18 antiscalant circulation pump, 19 ultrasonic vibrator. DETAILED DESCRIPTION

[0015] 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.

[0016] Please refer to Figure 1The present invention provides a device for reducing scaling of a stripping tower in a PTA production process, comprising a stripping tower 1, a shower plate 2 is arranged in the stripping tower 1, a low-pressure acetic acid solvent falls in the form of rain through the shower plate 2, a low-pressure acetic acid solvent pipeline is arranged on the upper side of the shower plate 2 on the stripping tower 1, the low-pressure acetic acid solvent enters the stripping tower 1 through the low-pressure acetic acid solvent pipeline, a low-pressure steam pipeline is arranged on the lower side of the shower plate 2 on the stripping tower 1, the low-pressure steam enters the stripping tower 1 through the low-pressure steam pipeline, contacts with the low-pressure acetic acid solvent falling by rain, heats and evaporates the low-pressure acetic acid solvent, and realizes the stripping of the low-pressure acetic acid solvent, an electronic liquid level meter 3 is arranged on one side of the stripping tower 1, which is used to measure the stripping The concentration of the residual slurry at the bottom of tower 1, a scale inhibitor adding device is arranged on one side of the stripping tower 1, which is used to prepare the scale inhibitor and send the scale inhibitor into the stripping tower 1, a slurry heating device is arranged on the other side of the stripping tower 1, which is used to extract the residual slurry in the stripping tower and heat it, a slurry pumping device is arranged at the bottom of the stripping tower 1, which is used to pump out the residual slurry in the stripping tower 1, the slurry heating device is connected to the slurry pumping device through two pipelines, one of which provides low-pressure steam for the slurry pumping device, and the other provides low-pressure condensate for the slurry pumping device, the slurry pumping device is connected to the scale inhibitor adding device through a pipeline, and the scale inhibitor extracted from the slurry residue is sent into the scale inhibitor adding device through the slurry pumping device.

[0017] The scale inhibitor adding device comprises a scale inhibitor preparation tank 4, and a scale inhibitor pipeline and a process water pipeline are arranged 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 scale inhibitor of a certain concentration is prepared by the original scale inhibitor and the process water. The scale inhibitor preparation tank 4 is connected to the scale inhibitor delivery pump 5 through the pipeline, and the scale inhibitor in the scale inhibitor preparation tank 4 is delivered to the stripping tower 1 through the scale inhibitor delivery pump 5. The scale inhibitor delivery pump 5 is connected to the stripping tower 1 through the pipeline and a gate valve a6 is arranged on the pipeline. The gate valve a6 controls the switch of the pipeline.

[0018] The slurry heating device includes a stripping tower reboiler 7, which is connected to a stripping tower circulation pump 8 through a pipeline. The stripping tower circulation pump 8 is connected to the bottom of the stripping tower 1 through a pipeline and a gate valve b9 is provided on the pipeline. The gate valve b9 controls the switch of the pipeline. The stripping tower circulation pump 8 extracts the residual slurry on 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 through a pipeline. A low-pressure steam pipeline is provided on the upper part of the stripping tower reboiler 7 and a gate valve c10 is provided on the pipeline. The gate valve c10 controls the switch of the pipeline. A low-pressure condensate pipeline is provided at the bottom of 7 and a gate valve d11 is provided on the pipeline. The gate valve d11 controls the switch of the pipeline. The stripping tower reboiler 7 is a kind of heat exchanger. The low-pressure steam enters the stripping tower reboiler 7 as a heating source through the low-pressure steam pipeline. The low-pressure steam enters the shell side of the stripping tower reboiler 7, and the extracted residue slurry enters the tube side of the stripping tower reboiler 7. The residue slurry in the tube side realizes heat exchange with the low-pressure steam outside the tube side. The low-pressure steam condenses into low-pressure condensate after doing work in the shell side of the stripping tower reboiler 7 and is discharged through the low-pressure condensate pipeline.

[0019] The slurry pumping device includes a residue evaporator 12 and an antiscalant recovery tower 13. The residue evaporator 12 is connected to a stripping tower delivery pump 14 through a pipeline. The stripping tower delivery pump 14 is connected to the bottom of the stripping tower 1 through a pipeline. The residue slurry at the bottom of the stripping tower 1 is pumped into the residue evaporator 12 through the stripping tower delivery pump 14. The upper part of the residue evaporator 12 is connected to the antiscalant recovery tower 13 through a pipeline and a gate valve e15 is arranged on the pipeline. The gate valve e15 controls the switch of the pipeline. The bottom of the residue evaporator 12 is provided with a pipeline and a gate valve f16 is arranged on the pipeline. The gate valve f16 controls the switch of the pipeline. When the residue in the residue evaporator 12 accumulates to a certain extent, it is discharged by opening the gate valve f16.

[0020] A branch pipeline is separated from the low-pressure steam pipeline on the stripping tower reboiler 7 and connected to the residue evaporator 12 , and a gate valve g17 is provided on the branch pipeline. The gate valve g17 controls the switch of the pipeline. The low-pressure steam enters the residue evaporator 12 through the branch pipeline 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 antiscalant recovery tower 13, and the low-pressure condensate in the shell side of the stripping tower reboiler 7 is sent into the antiscalant recovery tower 13 through the low-pressure condensate pipeline at the bottom of the stripping tower reboiler 7. The bottom of the antiscalant recovery tower 13 is connected with an antiscalant circulation pump 18 through a pipeline. The antiscalant circulation pump 18 is connected to the antiscalant preparation tank 4 through a pipeline, and the antiscalant recovered in the antiscalant recovery tower is sent into the antiscalant preparation tank 4 through the antiscalant circulation pump 18. An ultrasonic vibrator 19 is provided on the electronic liquid level meter 3. The ultrasonic vibrator 19 vibrates the electronic liquid level meter 3 to avoid clogging the pipe mouth of the electronic liquid level meter 3 by residual slurry.

[0022] Working principle of the present invention:

[0023] Initially, the low-pressure acetic acid solvent enters the stripping tower 1 through the low-pressure acetic acid solvent pipeline, falls in the form of rain through the rain plate 2, and the low-pressure steam enters the stripping tower 1 through the low-pressure collection pipe line to contact the low-pressure acetic acid solvent falling in the rain. The gate valve b9 is closed to heat and evaporate the low-pressure acetic acid solvent and pass through the pipeline at the top of the stripping tower 1 to the methyl acetate stripping tower to make it stripped. The remaining residue slurry remains at the bottom of the stripping tower 1. The scale inhibitor and process water are respectively passed through the scale inhibitor pipeline and the process water. The process water pipeline enters the scale inhibitor preparation tank 4 to be configured into a certain concentration of scale inhibitor, open the gate valve a6, and send the scale inhibitor into the stripping tower 1 through the scale inhibitor delivery pump 5, and enter the residual slurry in the stripping tower 1 to reduce the structure of the residual slurry. The residual slurry in the stripping tower 1 is sent to the residual evaporator 12 for storage through the stripping tower delivery pump 14. The gate valve e15 and the gate valve f16 are both in the closed state. At this time, there is no heating source entering the residual evaporator 12, and it is only used as a storage device.

[0024] When the flow rate of the low-pressure acetic acid solvent in the low-pressure acetic acid solvent pipeline increases, so that the amount of low-pressure acetic acid solvent entering the stripping tower 1 exceeds the designed processing capacity of the low-pressure steam in the stripping tower 1, the low-pressure acetic acid solvent cannot evaporate efficiently, and too much liquid low-pressure acetic acid solvent falls into the stripping tower 1 and mixes with the residue slurry, causing the original residue slurry liquid level to rise. When the liquid level rises to a certain height and is measured by the electronic liquid level meter 3, the scale inhibitor delivery pump 5 and the gate valve a6 are closed, and the scale inhibitor is stopped from being delivered to the stripping tower 1. The gate valve b9, the stripping tower circulation pump 8 and the gate valve c10 are opened, and the upper layer of the residue slurry in the stripping tower 1 is pumped into the stripping tower reboiler 7 through the stripping tower circulation pump 8. The low-pressure steam enters the stripping tower reboiler 7 through the low-pressure steam pipeline, and exchanges heat with the residue slurry in the stripping tower reboiler 7 tube path to heat the extracted residue slurry. The heated residue slurry re-enters the stripping tower 1, and contacts with the low-pressure steam in the stripping tower 1 again, so that this part of the residue slurry is evaporated and stripped at high temperature and high efficiency, thereby reducing the liquid level of the residue slurry in the stripping tower 1. It is worth pointing out that in this process, the scale inhibitor entering the stripping tower 1 is turned off to avoid carrying more scale inhibitor in the extracted heated residue slurry, so that when it is heated and evaporated again, this part of the scale inhibitor will also evaporate, and more scale inhibitor will be stripped into the methyl acetate stripping tower.

[0025] When the liquid level is lower than the electronic liquid level gauge 3 again, open the antiscalant delivery pump 5 and the gate valve a6, close the gate valve b9, the stripping tower circulation pump 8, and the gate valve c10, and open the gate valve g17, the gate valve d11, the gate valve e15 and the antiscalant circulation pump 18. Since the stripping tower 1 stops delivering the antiscalant during the process of the stripping tower circulation pump 8 extracting the upper liquid of the residual slurry into the stripping tower reboiler 7, and the amount of the residual slurry continues to increase during this process, the amount of the antiscalant in the residual slurry in the stripping tower 1 is obviously insufficient. At this time, the low-pressure steam in the low-pressure steam pipeline enters the residual evaporator 12 through the branch pipeline of the gate valve g17, and the residual evaporator 12 starts to work. The low-pressure steam in the residual evaporator 12 contacts with the residual slurry pumped out by the stripping tower delivery pump 14, so that the residual slurry is heated, and the residual residue in the residual slurry is In the residue evaporator 12, the excess scale inhibitor in the residue slurry is heated and evaporated and enters the scale inhibitor recovery tower 13 through the pipeline on the gate valve e15, and the low-pressure steam originally heated and done in the stripping tower reboiler 7 is condensed and the low-pressure condensate remaining in the shell side of the stripping tower reboiler 7 enters the scale inhibitor recovery tower 13 through the low-pressure condensate pipeline on the gate valve d11, and contacts with the vapor state scale inhibitor, so that this part of the scale inhibitor is condensed into a liquid state. Among them, after the scale inhibitor vapor contacts with the condensate to form a liquid scale inhibitor, the scale inhibitor is mixed in the condensate, and the proportion of the condensate is very small, and then the scale inhibitor circulation pump 18 sends the scale inhibitor into the preparation tank 4, so that the scale inhibitor concentration in the scale inhibitor preparation tank 4 becomes larger, and then it is sent to the stripping tower 1 to make up for the amount of scale inhibitor missing in the stripping tower 1, thereby reducing the scaling of the residue slurry in the stripping tower 1.

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

Claims

1. A device for reducing scaling of a stripping tower in a PTA production process, comprising a stripping tower (1), wherein a shower plate (2) is arranged in the stripping tower (1), a low-pressure acetic acid solvent pipeline is arranged on the stripping tower (1) above the shower plate (2), and a low-pressure steam pipeline is arranged on the stripping tower (1) below the shower plate (2), characterized in that: An electronic liquid level meter (3) is arranged on one side of the stripping tower (1), an antiscalant adding device is arranged on one side of the stripping tower (1), a slurry heating device is arranged on the other side of the stripping tower (1), and a slurry pumping device is arranged at the bottom of the stripping tower (1). The slurry heating device is connected to the slurry pumping device through two pipelines, and the slurry pumping device is connected to the antiscalant adding device through pipelines.

2. A device for reducing scaling of a stripping tower in a PTA production process according to claim 1, characterized in that: The antiscalant adding device comprises an antiscalant preparation tank (4), one side of which is provided with an antiscalant pipeline and a process water pipeline, the antiscalant preparation tank (4) is connected to an antiscalant delivery pump (5) via a pipeline, the antiscalant delivery pump (5) is connected to a stripping tower (1) via a pipeline, and a gate valve a (6) is provided on the pipeline.

3. A device for reducing scaling of a stripping tower in a PTA production process according to claim 1, characterized in that: The slurry heating device comprises 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 b (9) is arranged on the pipeline, 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 arranged at the upper part of the stripping tower reboiler (7) and a gate valve c (10) is arranged on the pipeline, and a low-pressure condensate pipeline is arranged at the bottom of the stripping tower reboiler (7) and a gate valve d (11) is arranged on the pipeline.

4. A device for reducing scaling of a stripping tower in a PTA production process according to claim 1, characterized in that: The slurry pumping device comprises a residue evaporator (12) and an antiscalant 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 antiscalant recovery tower (13) via a pipeline and a gate valve e (15) is arranged on the pipeline; the bottom of the residue evaporator (12) is provided with a pipeline and a gate valve f (16) is arranged on the pipeline.

5. A device for reducing scaling of a stripping tower in a PTA production process according to claim 3 or 4, characterized in that: A branch pipeline is separated from the low-pressure steam pipeline on the stripping tower reboiler (7) and connected to the residue evaporator (12), and a gate valve g (17) is arranged on the branch pipeline.

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

7. A device for reducing scaling of a stripping tower in a PTA production process according to claim 4, characterized in that: The bottom of the antiscalant recovery tower (13) is connected to an antiscalant circulation pump (18) via a pipeline, and the antiscalant circulation pump (18) is connected to the antiscalant preparation tank (4) via a pipeline.

8. The device for reducing scaling of a stripping tower in a PTA production process according to claim 1, characterized in that: An ultrasonic vibrator (19) is provided on the electronic liquid level meter (3).

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