A PTA plant alkali solution recovery and reuse device

Abstract

This invention discloses a PTA plant alkali solution recovery and reuse device, belonging to the technical field of alkali solution recovery and reuse devices. It includes an alkali tank and a filter unit connected to the alkali tank via pipelines. The bottom of the filter unit is connected to the top of the solution tank via pipelines. A tank circulation pump is connected to the bottom of the solution tank via pipelines. The tank circulation pump is connected to a primary evaporator via pipelines, and a gate valve a is connected to the pipeline. A secondary evaporator is connected to the bottom of the primary evaporator via pipelines. The bottom of the secondary evaporator is connected to the solution tank via pipelines. This invention sends the alkali washing solution in the solution tank into the primary evaporator to evaporate a portion of the water, obtaining an alkali washing solution with a higher alkali concentration suitable for the filter unit. This solution then enters the secondary evaporator for further evaporation and is then sent back to the solution tank. This achieves both an increase in the concentration of the alkali washing solution to meet usage standards and the recovery of the alkali washing solution, improving the resource recycling rate.

Description

Technical Field

[0001] This invention relates to the field of alkaline solution recovery and reuse devices, specifically to an alkaline solution recovery and reuse device for a PTA plant. Background Technology

[0002] PTA (purified terephthalic acid) is an important chemical raw material widely used in industries such as textiles and plastics. The mainstream PTA production process consists of an oxidation section and a refining section. In the oxidation section, p-xylene, the raw material, reacts with oxygen in the air in a cobalt-manganese catalyst-acetic acid environment to produce crude terephthalic acid and byproduct impurities. The main byproduct impurities are p-carboxybenzaldehyde and small amounts of benzoic acid and other colored impurities. The refining section uses a hydrogenation reaction to convert p-carboxybenzaldehyde into p-methylbenzoic acid and colorless impurities. Due to the process characteristics of the product, the product and its byproducts are prone to crystallization and scaling in the filtration equipment at the end of the oxidation section and inside the filtration equipment in the refining section, clogging the filters and affecting separation efficiency.

[0003] Currently, it is known that over 95% of PTA plants in China require daily alkaline flushing of oxidation and refining filtration units, with each unit undergoing extensive alkaline washing to ensure equipment performance. The daily alkaline washing consumption for each filtration unit is approximately 40 tons (5% sodium hydroxide solution). The solution after alkaline washing is directly discharged into the wastewater. Considering the actual reaction ratio between the crystallizing and scaling materials and the alkaline solution, the actual alkaline solution consumption is relatively low. The direct discharge of large amounts of alkaline solution results in waste. Although existing technologies recover the alkaline washing solution, the concentration of alkali in the solution is insufficient, and the dilution is severe. Direct recycling does not meet the alkaline washing standards for the filtration units, leading to poor alkaline washing performance. Summary of the Invention

[0004] To address the technical problems mentioned in the background section, the present invention provides a device for recovering and reusing alkaline solutions from a PTA plant, employing the following technical solution:

[0005] It includes an alkali tank and a filter unit connected to the alkali tank via a pipeline, and also includes a solution tank. The bottom of the filter unit is connected to the top of the solution tank via a pipeline. The bottom of the solution tank is connected to a tank circulation pump via a pipeline. The tank circulation pump is connected to a primary evaporator via a pipeline and a gate valve a is connected to the pipeline. The bottom of the primary evaporator is connected to a secondary evaporator via a pipeline. The bottom of the secondary evaporator is connected to the solution tank via a pipeline.

[0006] Furthermore, the pipeline where the tank circulation pump is located is connected to a detector and a branch pipeline, and the branch pipeline is connected to a filter unit. A gate valve b is connected to the branch pipeline. A bypass pipeline is also connected to the pipeline where the tank circulation pump is located. A gate valve c is connected to the bypass pipeline. Both gate valve b and gate valve c are electrically connected to the detector.

[0007] Furthermore, the bottom of the primary evaporator is connected to the top of the secondary evaporator via pipelines.

[0008] Furthermore, a primary gas-liquid separator is connected to the top of the primary evaporator via a pipeline, and a secondary gas-liquid separator is connected to the bottom of the secondary evaporator via a pipeline.

[0009] Furthermore, the bottom of the primary gas-liquid separator is connected to the upper part of the primary evaporator via a pipeline, and the bottom of the secondary gas-liquid separator is connected to the upper part of the secondary evaporator via a pipeline.

[0010] Furthermore, the tops of the primary gas-liquid separator and the secondary gas-liquid separator are respectively connected to venting condensing scrubbing towers via pipelines. A connected cooler is installed on the upper part of the venting condensing scrubbing tower, and a connected packed scrubbing tower is installed on the upper part of the cooler. A chimney is connected to the upper part of the packed scrubbing tower.

[0011] Furthermore, a circulation pump is connected to the bottom of the venting condensation scrubbing tower via pipelines. Two pipelines are connected to the outlet of the circulation pump: one connects to the alkali tank, and the other to the solution tank. Each pipeline at the outlet of the circulation pump is equipped with a regulating valve to precisely control the delivery ratio of alkali and solution. Both the alkali and solution tanks are equipped with level sensors, which are linked to the central control system to achieve automatic replenishment and concentration regulation. The packed scrubbing tower is filled with high-efficiency, structured packing material to ensure that residual organic matter and acidic gases in the exhaust gas are fully absorbed. An online monitoring instrument is installed at the top of the chimney to provide real-time feedback on whether emission indicators meet environmental standards.

[0012] The present invention has the following advantages: by sending the alkaline washing solution in the solution tank into the first-stage evaporator to evaporate part of the water in the alkaline washing solution, a high alkaline concentration suitable for the filtration unit is obtained. Then, it enters the second-stage evaporator for further evaporation and is sent back to the solution tank. This not only increases the concentration of the alkaline washing solution to meet the usage standards, but also realizes the recovery of the alkaline washing solution, thereby improving the resource recycling rate. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the process of the present invention.

[0014] Attached Figures: 1. Solution Tank, 2. Tank Circulation Pump, 3. Primary Evaporator, 4. Gate Valve a, 5. Secondary Evaporator, 6. Detector, 7. Gate Valve b, 8. Gate Valve c, 9. Primary Gas-Liquid Separator, 10. Secondary Gas-Liquid Separator, 11. Venting Condensation Scrubber, 12. Cooler, 13. Packed Scrubber, 14. Chimney, 15. Circulation Pump. 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 1 This invention provides a PTA plant alkali solution recovery and reuse device, including an alkali tank and a filter unit connected to the alkali tank via a pipeline. After use, the alkali tank needs to be rinsed with alkali solution. The rinsed alkali solution enters the filter unit for filtration to remove impurities. The device also includes a solution tank 1. The bottom of the filter unit is connected to the top of the solution tank 1 via a pipeline. The alkali solution, after impurities are removed by the filter unit, enters the solution tank 1 via the pipeline. The bottom of the solution tank 1 is connected to a tank circulation pump 2 via a pipeline. The tank circulation pump 2 is connected to a primary evaporator 3 via a pipeline, and a gate valve a4 is connected to the pipeline. Opening the gate valve a4 allows... The tank circulation pump 2 sends the alkaline washing solution in the solution tank 1 into the primary evaporator 3 for heating, causing some of the water in the alkaline washing solution to evaporate. The evaporated steam is discharged through the pipeline at the top of the primary evaporator 3, resulting in a high-concentration alkaline washing solution in the primary evaporator 3. The bottom of the primary evaporator 3 is connected to the secondary evaporator 5 through a pipeline, and the bottom of the secondary evaporator 5 is connected to the solution tank 1 through a pipeline. The alkaline washing solution in the primary evaporator 3 enters the secondary evaporator 5 through the pipeline for further evaporation. The evaporated steam is discharged through the pipeline at the top of the secondary evaporator 5, resulting in an alkaline washing solution of the required concentration, which is then sent back to the solution tank 1 through the pipeline for recovery.

[0017] Both the primary evaporator 3 and the secondary evaporator 5 are heat exchange tube evaporators. The heating source for the primary evaporator 3 is by-product steam from other process units. This by-product steam enters the shell side of the primary evaporator 3, and the alkaline washing solution enters the heat exchange tubes inside the primary evaporator 3. The by-product steam heats the alkaline washing solution in the heat exchange tubes. The bottom of the primary evaporator 3 is connected to the top of the secondary evaporator 5 through a pipeline. The by-product steam from the shell side of the primary evaporator 3 enters the shell side of the secondary evaporator 5 through the pipeline, heating the alkaline washing solution in the heat exchange tubes inside the secondary evaporator 5.

[0018] The pipeline containing the tank circulation pump 2 is connected to a detector 6 and a branch pipeline, which is connected to a filter unit. A gate valve b7 is connected to this branch pipeline, which controls the opening and closing of the branch pipeline. A bypass pipeline is also connected to the pipeline containing the tank circulation pump 2, and a gate valve c8 is connected to this bypass pipeline, which controls the opening and closing of the bypass pipeline. Both gate valves b7 and c8 are electrically connected to the detector 6. The detector 6 can detect the concentration of the alkaline washing solution. The detector 6 has a built-in controller, which controls the opening and closing of gate valves b7 and c8.

[0019] The top of the primary evaporator 3 is connected to a primary gas-liquid separator 9 via a pipeline. The steam generated by the primary evaporator 3 enters the primary gas-liquid separator 9 through the pipeline for gas-liquid separation. The bottom of the secondary evaporator 5 is connected to a secondary gas-liquid separator 10 via a pipeline. The steam generated by the secondary evaporator 5 enters the secondary gas-liquid separator 10 through the pipeline for gas-liquid separation. The gas-liquid separation aims to obtain drier steam as much as possible, reducing the amount of alkaline liquid carried in the steam and reducing the pollution to the atmosphere caused by external discharge.

[0020] The bottom of the primary gas-liquid separator 9 is connected to the upper part of the primary evaporator 3 via a pipeline, and the bottom of the secondary gas-liquid separator 10 is connected to the upper part of the secondary evaporator 5 via a pipeline. The alkaline solution separated in the primary gas-liquid separator 9 and the secondary gas-liquid separator 10 is sent back to the primary evaporator 3 and the secondary evaporator 5 via pipelines for circulation evaporation, so as to separate and retain the alkaline components in the alkaline solution to the maximum extent possible in the primary evaporator 3 and the secondary evaporator 5.

[0021] The tops of the primary gas-liquid separator 9 and the secondary gas-liquid separator 10 are respectively connected to a venting condensing scrubbing tower 11 via pipelines. A connected cooler 12 is installed on the upper part of the venting condensing scrubbing tower 11. The cooler is a heat exchange tube type cooler. The cooling enters the shell side of the cooler 12, cools the heat exchange tubes in the shell side, and exits through the other end of the shell side. A connected packed scrubbing tower 13 is installed on the upper part of the cooler 12. The packed scrubbing tower 13 is filled with packing. When the demineralized water enters the packed scrubbing tower 13, it falls in the form of rain as it passes through the packing, which can fully contact the steam. A chimney 14 is connected to the upper part of the packed scrubbing tower 13.

[0022] The bottom of the venting condensing and washing tower 11 is connected to a circulation pump 15 via a pipeline. Two pipelines are connected to the outlet of the circulation pump 15, one of which is connected to the alkali tank and the other is connected to the solution tank 1. Part of the liquid condensed and washed in the venting condensing and washing tower 11 is transported to the alkali tank by the circulation pump 15 for use in alkali preparation, and the other part is recovered to the solution tank 1 to adjust the alkali concentration.

[0023] Working principle of the invention:

[0024] Close gate valves b7 and c8, open gate valve a4, and the alkaline washing solution in solution tank 1 is sent into the primary evaporator 3 through tank circulation pump 2. After evaporation in the primary evaporator 3, some of the water in the alkaline washing solution becomes steam and is discharged through the pipeline at the top of the evaporator 3. The alkaline solution remaining has a higher alkali concentration and enters the secondary evaporator 5 through the pipeline for further evaporation to further remove water from the alkaline washing solution. The generated steam is discharged through the pipeline at the top of the secondary evaporator 5. The alkaline washing solution with a higher concentration obtained in the secondary evaporator 5 is sent back to solution tank 1 through the pipeline to achieve recycling.

[0025] After the recycling is completed, gate valve a4 is closed, and detector 6 detects the alkaline washing solution in the pipeline (which is connected to solution tank 1) after the concentration has increased. If the concentration of the alkaline washing solution meets the standard, detector 6 controls gate valve b7 to open, so that the alkaline washing solution recovered from alkaline tank 1 is sent to the filtration unit through the pipeline and used as alkaline washing solution for the filtration unit, which increases the utilization value of the recovered alkaline washing solution.

[0026] Steam generated in the primary evaporator 3 and the secondary evaporator 5 enters the primary gas-liquid separator 9 and the secondary gas-liquid separator 10 through pipelines to achieve gas-liquid separation, separating out a portion of the alkaline solution in the steam, making the steam as dry as possible, reducing the alkaline solution content, and avoiding external discharge that could pollute the atmosphere. Steam generated in the primary gas-liquid separator 9 and the secondary gas-liquid separator 10 enters the venting condensing scrubbing tower 11 through pipelines and moves upwards, entering the heat exchange tubes of the cooler 12 to be cooled, further cooling the alkaline washing solution in the steam and causing it to fall into the venting condensing scrubbing tower 11. The remaining steam continues to move upwards, and the demineralized water falls downwards through the packing material in the packed scrubbing tower 13 in the form of rain, making full contact with the upward-moving steam, further washing away the alkaline components and some organic impurities carried in the steam. Then the steam passes through the chimney 14 and is discharged upwards through the chimney 14.

[0027] 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. A PTA plant alkali solution recovery and reuse device, comprising an alkali tank and a filter unit connected to the alkali tank via a pipeline, characterized in that, It also includes a solution tank (1), the bottom of the filter unit is connected to the top of the solution tank (1) via a pipeline, the bottom of the solution tank (1) is connected to a tank circulation pump (2) via a pipeline, the tank circulation pump (2) is connected to a primary evaporator (3) via a pipeline and a gate valve a (4) is connected to the pipeline, the bottom of the primary evaporator (3) is connected to a secondary evaporator (5) via a pipeline, and the bottom of the secondary evaporator (5) is connected to the solution tank (1) via a pipeline.

2. The PTA plant alkali solution recovery and reuse device according to claim 1, characterized in that, The pipeline where the tank circulation pump (2) is located is connected to the detector (6) and a branch pipeline, and the branch pipeline is connected to the filter unit. The branch pipeline is connected to the gate valve b (7). The pipeline where the tank circulation pump (2) is located is also connected to a bypass pipeline, and the bypass pipeline is connected to the gate valve c (8). Both the gate valve b (7) and the gate valve c (8) are electrically connected to the detector (6).

3. The PTA plant alkali solution recovery and reuse device according to claim 1, characterized in that, The bottom of the primary evaporator (3) is connected to the top of the secondary evaporator (5) via a pipeline.

4. The PTA plant alkali solution recovery and reuse device according to claim 1, characterized in that, The top of the primary evaporator (3) is connected to a primary gas-liquid separator (9) via a pipeline, and the bottom of the secondary evaporator (5) is connected to a secondary gas-liquid separator (10) via a pipeline.

5. The PTA plant alkali solution recovery and reuse device according to claim 4, characterized in that, The bottom of the primary gas-liquid separator (9) is connected to the upper part of the primary evaporator (3) via a pipeline, and the bottom of the secondary gas-liquid separator (10) is connected to the upper part of the secondary evaporator (5) via a pipeline.

6. The PTA plant alkali solution recovery and reuse device according to claim 4, characterized in that, The top of the primary gas-liquid separator (9) and the secondary gas-liquid separator (10) are respectively connected to the venting condensing scrubbing tower (11) via pipelines. The upper part of the venting condensing scrubbing tower (11) is equipped with a connected cooler (12). The upper part of the cooler (12) is equipped with a connected packed scrubbing tower (13). The upper part of the packed scrubbing tower (13) is connected to a chimney (14).

7. The PTA plant alkali solution recovery and reuse device according to claim 6, characterized in that, The bottom of the venting condenser washing tower (11) is connected to a circulating pump (15) via a pipeline. Two pipelines are connected to the outlet of the circulating pump (15), one of which is connected to the alkali tank and the other is connected to the solution tank (1).

Images