A device for recovering waste heat from the top steam of a low-temperature methanol washing and regeneration tower.

Abstract

This utility model discloses a device for recovering and utilizing waste heat from the overhead steam of a low-temperature methanol washing and regeneration tower, belonging to the field of energy-saving technology. The device includes a primary heat exchanger, a secondary heat exchanger, a primary flash tank, and a secondary flash tank, wherein the primary flash tank is installed on the primary heat exchanger, and the secondary flash tank is installed on the secondary heat exchanger. This utility model replaces the traditional steam heating method with heat pump distillation, utilizing the latent heat of the overhead steam and the compressor's electrical energy to power the low-temperature methanol tower, thus achieving a change in heating method, significantly reducing steam and cooling water consumption, and achieving the goal of energy saving and efficiency improvement.

Description

Technical Field

[0001] This utility model relates to an energy-saving device, specifically a device for recovering and utilizing waste heat from the top steam of a low-temperature methanol washing and regeneration tower, belonging to the field of energy-saving technology. Background Technology

[0002] The rectisol process is a widely used gas purification technology in chemical processes such as coal gasification, ammonia synthesis, and methanol synthesis. It is primarily used to remove acidic gases (such as carbon dioxide and hydrogen sulfide) from feedstock gases. In the rectisol process, the low-methanol regeneration tower (also known as the methanol regeneration tower or thermal regeneration tower) is a key piece of equipment used to recover and regenerate the methanol-rich solution after absorbing acidic gases. The main function of the low-methanol regeneration tower is to desorb acidic gases from the methanol-rich solution (methanol that has absorbed acidic gases such as carbon dioxide and hydrogen sulfide) through heating and depressurization, while simultaneously recovering pure methanol for recycling. During operation, the methanol-rich solution enters the low-methanol regeneration tower from the bottom of the absorption tower. Inside the tower, the methanol-rich solution is heated by a reboiler, raising its temperature and causing acidic gases (such as carbon dioxide and hydrogen sulfide) to desorb from the methanol. The desorbed acidic gases are discharged from the top of the tower and enter subsequent processing systems (such as sulfur recovery units or carbon dioxide compression systems). The desorbed lean methanol flows out from the bottom of the tower, is cooled, and returned to the absorption tower for reuse in gas purification.

[0003] The low-temperature methanol (LTM) column plays a crucial role in the low-temperature methanol washing process, but its high energy consumption and operational problems are the main factors restricting the process's economic efficiency and stability. The LTM column consumes a significant amount of energy during operation, primarily in reboiler heating, cooling, vacuum system energy consumption, and circulating methanol pump energy consumption. The reboiler heating and cooling processes in the LTM column are particularly energy-intensive, especially when handling high-concentration acidic gases, where energy consumption increases further. High energy consumption leads to increased operating costs, impacting the overall economics of the process. Summary of the Invention

[0004] Therefore, this utility model discloses a device for recovering and utilizing the waste heat of the top steam of a low-temperature methanol washing and regeneration tower. It replaces the traditional steam heating method with heat pump distillation, utilizing the latent heat of the top gas and the power of the compressor to power the low-temperature methanol tower, thereby realizing the transformation of the heating method, significantly reducing steam consumption and cooling water consumption, and achieving the goal of energy saving and efficiency improvement.

[0005] The technical solution adopted by this utility model to solve its technical problem is as follows:

[0006] A device for recovering waste heat from the top steam of a low-temperature methanol washing and regeneration tower consists of a methanol-rich gas-liquid separator, a secondary heat exchanger, a tower top gas pipeline, a secondary flash tank, a secondary pressure reducing valve, a primary heat exchanger, a primary pressure reducing valve, a primary flash tank, a primary gas-liquid separator, a primary spray regulating valve, a secondary gas buffer tank, and a secondary gas buffer tank drain valve.

[0007] A primary flash tank is installed on the primary heat exchanger, and a secondary flash tank is installed on the secondary heat exchanger.

[0008] The first-stage flash tank is equipped with a first-stage pressure reducing valve, and the second-stage flash tank is equipped with a second-stage pressure reducing valve.

[0009] A primary spray regulating valve is installed on the pipeline between the primary gas-liquid separator and the secondary flash tank.

[0010] The primary and secondary heat exchangers are plate heat exchangers or shell-and-tube falling film reboilers.

[0011] The beneficial effects of this invention are as follows: By employing this invention, a two-stage compressor is used. The first-stage compressor pressurizes the methanol flash vapor from the low-temperature, low-pressure section, and then introduces it together with the flash vapor from the high-temperature, high-pressure section into the second-stage compressor, achieving cascaded energy utilization. Compared to direct flash vaporization to the low-temperature compression section, this saves approximately 30% of compressor energy consumption. The compressor compresses the methanol flash vapor, resulting in a simpler medium characteristic and lower process risk. Partial condensation of the overhead vapor releases most of the heat, and the heat released by the overhead vapor and the electrical energy consumed by the compressor can essentially replace the steam consumption. The two-stage compressor connected in series has a compact structure, small size, and requires less space. Energy-saving retrofitting is easier, requires less engineering work, has high energy efficiency, and a short investment payback period. The higher the steam price and the lower the electricity price, the better the investment return. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the present invention.

[0013] The diagram shows the following components: 1. Methanol-rich gas-liquid separator; 2. Secondary heat exchanger; 3. Tower top gas pipeline; 4. Secondary flash tank; 5. Secondary pressure reducing valve; 6. Primary heat exchanger; 7. Primary pressure reducing valve; 8. Primary flash tank; 9. Primary gas-liquid separator; 10. Primary spray regulating valve; 11. Secondary gas buffer tank; and 12. Secondary gas buffer tank drain valve. Detailed Implementation

[0014] A device for recovering waste heat from the top steam of a low-temperature methanol washing and regeneration tower consists of a methanol-rich gas-liquid separator 1, a secondary heat exchanger 2, a tower top gas pipeline 3, a secondary flash tank 4, a secondary pressure reducing valve 5, a primary heat exchanger 6, a primary pressure reducing valve 7, a primary flash tank 8, a primary gas-liquid separator 9, a primary spray regulating valve 10, a secondary gas buffer tank 11, and a secondary gas buffer tank drain valve 12.

[0015] A primary flash tank 8 is installed on the primary heat exchanger 6, and a secondary flash tank 4 is installed on the secondary heat exchanger 2.

[0016] A primary pressure reducing valve 7 is installed on the primary flash tank 8, and a secondary pressure reducing valve 5 is installed on the secondary flash tank 4.

[0017] A primary spray regulating valve 10 is installed on the pipeline between the primary gas-liquid separator 9 and the secondary flash tank 4.

[0018] The primary heat exchanger 6 and the secondary heat exchanger 2 are plate heat exchangers or shell-and-tube falling film reboilers.

[0019] Detailed implementation process

[0020] The top vapor at a certain temperature enters the first-stage heat exchanger 6 and the second-stage heat exchanger 2 in stages. After the temperature drops to the set value and most of the heat is released, it enters the original condensation system and heats the bottom liquid of the tower in two stages.

[0021] The extracted bottom liquid is subjected to depressurization flash evaporation and endothermic vaporization, with temperatures dropping to 78.5℃ and 65.5℃ respectively. The vaporized methanol then enters a two-stage compressor. The first-stage compressor compresses the methanol from 65.5℃ to 78.5℃, and then combines it with the vaporized methanol flashed from 78.5℃ before entering the second-stage compressor. The second-stage compressor compresses the methanol gas to about 100℃, mixes it with the extracted bottom liquid, and returns it directly to the bottom of the tower, replacing the steam reboiler for heating the material.

Claims

1. A device for recovering waste heat from the top steam of a low-temperature methanol washing heat regeneration tower, comprising a methanol-rich gas-liquid separator (1), a secondary heat exchanger (2), a tower top gas pipeline (3), a secondary flash tank (4), a secondary pressure reducing valve (5), a primary heat exchanger (6), a primary pressure reducing valve (7), a primary flash tank (8), a primary gas-liquid separator (9), a primary spray regulating valve (10), a secondary gas buffer tank (11), and a secondary gas buffer tank drain valve (12), characterized in that: A primary flash tank (8) is installed on the primary heat exchanger (6), and a secondary flash tank (4) is installed on the secondary heat exchanger (2).

2. The device for recovering waste heat from the top steam of a low-temperature methanol washing and regeneration tower as described in claim 1, characterized in that: A primary pressure reducing valve (7) is installed on the primary flash tank (8), and a secondary pressure reducing valve (5) is installed on the secondary flash tank (4).

3. The device for recovering waste heat from the top steam of a low-temperature methanol washing and regeneration tower as described in claim 1, characterized in that: A primary spray regulating valve (10) is installed on the pipeline between the primary gas-liquid separator (9) and the secondary flash tank (4).

4. The device for recovering waste heat from the top steam of a low-temperature methanol washing and regeneration tower as described in claim 1, characterized in that: The primary heat exchanger (6) and the secondary heat exchanger (2) are plate heat exchangers or shell-and-tube falling film reboilers.

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