A nitrogen protection pipeline anti-corrosion system for the gas phase system of a PTA dehydration tower

Abstract

The present invention provides a nitrogen protection pipeline anti-corrosion system for a PTA dehydration tower gas phase system. The present invention includes a liquid collection well arranged between a nitrogen protection system one-way valve and a solvent dehydration tower cooler, and also includes a continuous nitrogen purge pipeline, wherein the continuous nitrogen purge pipeline includes a first valve, a second valve, and a rotor flowmeter and a nitrogen purge pipeline one-way valve arranged therebetween, and the output end of the second valve is arranged above the liquid collection well. The present invention simultaneously applies nitrogen purge and liquid collection well collection and drainage, thereby effectively ensuring that the gas phase liquid in the dehydration tower is reduced in condensation, and the problem of being unable to be completely discharged after condensation is solved.

Description

Technical Field

[0001] The invention relates to the technical field of terephthalic acid production, in particular to a nitrogen protection pipeline anti-corrosion system for a PTA dehydration tower gas phase system. Background Art

[0002] Purified Terephthalic Acid (PTA) is an important chemical raw material, widely used in polyester and other chemical production. The production of PTA generally uses paraxylene (PX) as raw material and acetic acid (HAC) as solvent to catalytically oxidize at a certain temperature and pressure to produce crude terephthalic acid (TA), which is then refined into high-purity purified terephthalic acid.

[0003] In the PTA device, a solvent dehydration tower is generally used to separate and recover acetic acid. The existing dehydration tower gas phase system is equipped with a nitrogen protection system to prevent system negative pressure. Specifically, the nitrogen pipeline is made of carbon steel and is connected to the dehydration tower gas phase system with two stainless steel one-way valves. Since the gas phase gas in the dehydration tower will condense in the pipeline, liquid will accumulate at the one-way valve. Once the one-way valve is opened, a small amount of acetic acid liquid will flow into the carbon steel pipeline, causing pipeline corrosion and leakage. Summary of the invention

[0004] According to the technical problems raised above, a nitrogen protection pipeline anti-corrosion system for a PTA dehydration tower gas phase system is provided. The technical means adopted by the present invention are as follows:

[0005] A nitrogen protection pipeline anti-corrosion system for a PTA dehydration tower gas phase system, wherein a nitrogen protection system for preventing system negative pressure is connected to a solvent dehydration tower cooler, a nitrogen protection system one-way valve is arranged therebetween, a liquid collecting well is arranged between the nitrogen protection system one-way valve and the solvent dehydration tower cooler, and a continuous nitrogen purge pipeline is also provided, wherein the continuous nitrogen purge pipeline comprises a first valve, a second valve, a rotor flowmeter and a nitrogen purge pipeline one-way valve arranged therebetween, and an output end of the second valve is arranged above the liquid collecting well.

[0006] Furthermore, there is a preset height difference between the liquid collecting well and the inlet end of the solvent dehydration tower cooler, and the condensed liquid droplets collected by the liquid collecting well flow to the downstream process under the action of gravity and pressure difference of the bottom pipeline.

[0007] Furthermore, a liquid collecting well outlet valve is provided between the liquid collecting well and the inlet end of the solvent dehydration tower cooler.

[0008] Furthermore, in the working state, the first valve or the second valve is fully opened, and the opening of the other valve matches the rotor flowmeter to a specified flow rate.

[0009] The present invention simultaneously applies nitrogen purging and liquid collection in a liquid collecting well to effectively prevent condensation of gas phase liquid in a dehydration tower and the problem of being unable to be completely discharged after condensation, thereby avoiding corrosion and leakage of nitrogen pipelines, ensuring the safety of the pipeline, and ensuring that the negative pressure protection nitrogen in the dehydration tower system can be put into normal use. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0011] Figure 1 This is the overall piping diagram of the corrosion-resistant PTA dehydration tower gas phase system of the present invention.

[0012] In the figure: 1. nitrogen purge pipeline; 2. solvent dehydration tower pipeline; 3. nitrogen protection pipeline; 4. desalted water pipeline; 5. low-pressure alkali solution pipeline; 6. solvent dehydration tower cooler; 11. first valve; 12. rotor flowmeter; 13. nitrogen purge pipeline one-way valve; 14. second valve; 15. liquid collection well outlet valve; 16. liquid collection well. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0014] The existing dehydration tower gas phase system includes several pipelines connected to the solvent dehydration tower cooler 6, including the solvent dehydration tower pipeline 2, the nitrogen protection pipeline 3, the desalted water pipeline 4 and the low-pressure alkali solution pipeline 5. Because the nitrogen protection gas is only turned on under special working conditions and there is no flow during normal operation, the dehydration tower gas phase will be partially condensed into liquid in this pipeline. When the nitrogen protection pipeline, the one-way valve is opened, the liquid enters the nitrogen pipeline, and the gravity of the liquid causes corrosion of the pipeline.

[0015] For this reason, Figure 1As shown, this embodiment discloses a nitrogen protection pipeline anti-corrosion system for a PTA dehydration tower gas phase system, wherein the nitrogen protection system for preventing system negative pressure is connected to the solvent dehydration tower cooler, and a nitrogen protection system one-way valve is provided therebetween, and also includes a liquid collecting well 16 arranged between the nitrogen protection system one-way valve and the solvent dehydration tower cooler, and also includes a continuous nitrogen purge pipeline 1, wherein the continuous nitrogen purge pipeline includes a first valve 11, a second valve 14, and a rotor flowmeter 12 and a nitrogen purge pipeline one-way valve 13 arranged therebetween, and the output end of the second valve is arranged above the liquid collecting well. The specification of the nitrogen purge pipeline is 1”, and the liquid collecting well is located below the pipeline, and the size is 1 / 2 of the 16” pipeline is 8”, and a 1” is connected to discharge to the back-end process to ensure that the liquid collecting well will not be filled.

[0016] There is a preset height difference between the liquid collecting well and the inlet end of the solvent dehydration tower cooler, and the condensed liquid droplets collected by the liquid collecting well flow to the downstream process under the action of gravity and pressure difference of the bottom pipeline.

[0017] In the working state, the first valve or the second valve is fully opened, and the opening of the other valve matches the specified flow rate of the rotor flowmeter. A liquid collecting well outlet valve 15 is provided between the liquid collecting well and the inlet end of the solvent dehydration tower cooler. The valve is opened slightly, and once the liquid level accumulates, it can be transported to the back-end process.

[0018] The corrosion-resistant PTA dehydration tower gas phase system provided in this embodiment can ensure that low-grade material pipelines are not corroded by corrosive media. At the connection between two different material pipeline materials, the high-grade material has corrosive gas, and the pipeline has a horizontal and vertical pipe section. A small flow nitrogen protection is arranged above the horizontal pipe section pipeline, and a liquid collection well is arranged below the horizontal pipe section pipeline, thereby preventing the corrosive medium from condensing into the low-grade pipeline and causing pipeline corrosion.

[0019] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A nitrogen protection pipeline anti-corrosion system for a PTA dehydration tower gas phase system, wherein: A nitrogen protection system for preventing negative pressure in the gas phase system of the dehydration tower is connected to the solvent dehydration tower cooler, and a nitrogen protection system one-way valve is provided therebetween, characterized in that the anti-corrosion system comprises a liquid collecting well arranged between the nitrogen protection system one-way valve and the solvent dehydration tower cooler, and also comprises a continuous nitrogen purge pipeline, the continuous nitrogen purge pipeline comprises a first valve, a second valve, and a rotor flowmeter and a nitrogen purge pipeline one-way valve arranged therebetween, and the output end of the second valve is arranged above the liquid collecting well; The nitrogen protection pipeline of the nitrogen protection system has a horizontal section and a vertical section; There is a preset height difference between the liquid collecting well and the inlet end of the solvent dehydration tower cooler, and the condensed liquid droplets collected by the liquid collecting well flow to the upstream process under the action of gravity and pressure difference of the bottom pipeline; A liquid collecting well outlet valve is provided between the liquid collecting well and the inlet end of the solvent dehydration tower cooler; In the working state, the first valve or the second valve is fully open, and the opening of the other valve matches the rotor flowmeter to a specified flow rate.

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