A recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction
By adding a stripping flash section to the H2S concentration tower and using a high-temperature methanol-rich solution for stripping, the problem of high nitrogen consumption in small-scale plants was solved, resulting in a significant reduction in nitrogen consumption and an increase in CO2 product gas volume.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- DALIAN JIACHUN GAS PURIFICATION TECH DEV
- Filing Date
- 2025-03-31
- Publication Date
- 2026-05-26
AI Technical Summary
In small-scale or low-load coal chemical plants, the existing low-temperature methanol washing process consumes a lot of nitrogen, has low gas stripping efficiency, affects the purity of CO2 product gas and increases energy consumption, and poses a risk of low-temperature embrittlement of equipment.
Adding a stripping flash section (N section) to the H2S concentration tower allows for stripping using a high-temperature methanol-rich solution, improving the stripping effect and reducing nitrogen consumption.
It effectively reduces nitrogen consumption by more than 20%, lowers operating costs, increases CO2 product output, and avoids the risk of equipment embrittlement at low temperatures.
Smart Images
Figure CN224270686U_ABST
Abstract
Description
Technical Field
[0001] This application relates to a recovery system for reducing the amount of nitrogen used in low-temperature methanol washing gas extraction, belonging to the field of gas purification technology for coal chemical plants. Background Technology
[0002] Low-temperature methanol washing, as a core technology in the field of gas purification, is widely used in coal chemical industry, natural gas processing, and syngas refining. Its core process chain typically includes three stages: a medium-pressure flash distillation tower, a CO2 desorption tower, and an H2S concentration tower. The H2S concentration tower uses nitrogen stripping to reduce the partial pressure of acidic gases, achieving H2S enrichment and deep CO2 removal, ultimately ensuring the purified gas meets sulfur content requirements.
[0003] In existing technologies, H2S concentration towers generally employ a constant nitrogen flux stripping mode, designed based on material balance requirements in large-scale continuous production scenarios. However, in plants with lower CO2 product gas demand (such as intermittent production units, small distributed plants, or low-load operation), conventional stripping processes have significant drawbacks: excessive nitrogen injection not only leads to low stripping efficiency (insufficient contact time between nitrogen and methanol liquid) but also increases the processing load of downstream sulfur recovery units (dilution effect leads to increased energy consumption in Claus units), while significantly increasing the proportion of nitrogen consumption to operating costs. Furthermore, excessive nitrogen mixed into the tail gas system may affect the purity of CO2 product gas and even trigger the risk of low-temperature embrittlement of equipment.
[0004] Although there is a general demand in the industry to reduce nitrogen consumption, existing technological improvements are mostly focused on optimizing the structure of the stripping tower (such as increasing the number of trays) or fine-tuning operating parameters (such as temperature / pressure gradient control). These improvements have failed to fundamentally solve the problem of mismatch between nitrogen utilization efficiency and process requirements in small-scale plants, and there is a lack of targeted control solutions for low CO2 production conditions. Utility Model Content
[0005] To address the problem that existing low-temperature methanol washing processes involve large nitrogen consumption and are unsuitable for devices requiring smaller CO2 product gas volumes, this application provides a recovery system solution for reducing nitrogen consumption during low-temperature methanol washing. By enhancing heat exchange to increase the temperature of methanol-rich gases, the system achieves higher temperatures and better gas stripping performance, thus saving on the amount of nitrogen used in the gas stripping stage.
[0006] According to one aspect of this application, a recovery system for reducing the amount of nitrogen used in low-temperature methanol washing gas extraction is provided, characterized in that it includes a medium-pressure flash distillation tower, a CO2 desorption tower, and an H2S concentration tower connected to each other.
[0007] The medium-pressure flash evaporator comprises, from bottom to top, section A and section B;
[0008] The CO2 desorption tower comprises, from bottom to top, sections A, B, and C.
[0009] The H2S concentration tower comprises, from bottom to top, sections A, N, and B;
[0010] The flash tower has a No. 1 logistics pipeline for introducing sulfur-containing rich methanol solution at the side end of section A, and a No. 2 logistics pipeline for introducing sulfur-free rich methanol solution at the upper side end of section B. The upper side end of section A and the upper end of section B of the flash tower are provided with logistics pipeline branches for discharging steam from the medium-pressure flash tower and collecting it into the No. 3 logistics pipeline.
[0011] The upper end of section C of the CO2 desorption tower is equipped with a No. 5 logistics pipeline for discharging CO2 gas.
[0012] The upper end of section B of the H2S concentration tower is equipped with a No. 4 logistics pipeline for discharging exhaust gas.
[0013] The lower end of section N of the H2S concentration tower is connected to the upper end of section A of the H2S concentration tower via a No. 11 logistics pipeline, which is equipped with a No. 2 methanol-rich pump and a No. 5 methanol-rich pump.
[0014] Optionally, the lower end of section B of the flash tower is connected to the upper side of section B and the upper side of section C of the CO2 desorption tower via logistics pipeline No. 6 and two logistics pipeline branches of logistics pipeline No. 6, respectively.
[0015] Optionally, the lower end of section A of the flash tower is connected to the lower side of section B of the CO2 desorption tower via pipeline No. 8.
[0016] Optionally, the lower end of section A of the CO2 desorption tower is connected to the side end of section N of the H2S concentration tower via pipeline No. 11.
[0017] Optionally, the lower end of section B of the CO2 desorption tower is connected to the lower end of section B of the H2S concentration tower via a No. 10 logistics pipeline.
[0018] Optionally, the lower end of section C of the CO2 desorption tower is connected to the upper end of section B of the H2S concentration tower via pipeline No. 9.
[0019] Optionally, the A-section side of the H2S concentration tower is provided with a No. 12 logistics pipeline for introducing nitrogen gas.
[0020] Optionally, the lower end of section A of the H2S concentration tower is provided with a No. 7 flow pipeline for discharging sulfur-containing methanol-rich solution;
[0021] The No. 7 pipeline is equipped with a No. 3 methanol-rich pump.
[0022] Optionally, the lower end of section B of the H2S concentration tower is connected to the upper end of section A of the CO2 desorption tower via pipeline No. 13.
[0023] Optionally, the No. 13 logistics pipeline is equipped with a No. 1 methanol-rich pump and a No. 4 methanol-rich pump.
[0024] The beneficial effects that this application can produce include:
[0025] The recovery system provided in this application for reducing nitrogen consumption during low-temperature methanol washing stripping involves adding a stripping flash section (N-section) in the middle of the original H2S concentration tower. In this section, gas from the bottom of the H2S concentration tower is used for stripping. The solution from the N-section is heated by heat exchange with the methanol-rich solution from the absorption tower to a maximum temperature. This higher-temperature solution is then stripped again in the lower section of the H2S concentration tower, resulting in a lower temperature of the methanol-rich solution reaching the E-102 heat exchanger and a greater heat exchange, thus reducing the amount of nitrogen used for stripping. The higher-temperature solution is easier to strip, and nitrogen consumption can be significantly reduced, by more than 20%. For devices requiring a smaller CO2 product gas volume, this can reduce the amount of nitrogen used for stripping and lower operating costs. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the recovery system used to reduce the amount of nitrogen extracted from low-temperature methanol washing gas in Embodiment 1 of this application;
[0027] Figure 2 This is a schematic diagram of the methanol washing process in the prior art of Embodiment 1 of this application.
[0028] Attached Figure Labels
[0029] T-101 is a medium-pressure flash distillation tower; T-102 is a CO2 desorption tower; T-103 is an H2S concentration tower; P-101 is a methanol-rich pump #1; P-102 is a methanol-rich pump #2; P-103 is a methanol-rich pump #3; E-101 is a methanol-rich pump #4; E-102 is a methanol-rich pump #5.
[0030] A, B, C, and D represent the working sections in the tower;
[0031] 1-14 represent logistics pipelines 1-14 respectively. Detailed Implementation
[0032] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0033] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0034] Example 1
[0035] Recovery systems used to reduce nitrogen extraction from low-temperature methanol washing gas, such as Figure 1 As shown, it consists of a medium-pressure flash distillation tower T-101, a CO2 desorption tower T-102, and an H2S concentration tower T-103 that are interconnected.
[0036] The medium-pressure flash evaporator T-101 includes section A and section B from bottom to top;
[0037] The CO2 desorption tower T-102 comprises, from bottom to top, sections A, B, and C.
[0038] The H2S concentration tower T-103 comprises, from bottom to top, sections A, N, and B;
[0039] The flash tower has a No. 1 logistics pipeline for introducing sulfur-containing rich methanol solution at the side end of section A, and a No. 2 logistics pipeline for introducing sulfur-free rich methanol solution at the upper side end of section B. The upper side end of section A and the upper end of section B of the flash tower are provided with logistics pipeline branches for discharging steam from the medium-pressure flash tower and collecting it into the No. 3 logistics pipeline.
[0040] The upper end of section C of the CO2 desorption tower T-102 is equipped with a No. 5 logistics pipeline for discharging CO2 gas.
[0041] The upper end of section B of the H2S concentration tower T-103 is equipped with a No. 4 logistics pipeline for discharging exhaust gas.
[0042] The lower end of section N of the H2S concentration tower T-103 is connected to the upper end of section A of the H2S concentration tower T-103 via logistics pipeline No. 11. Logistics pipeline No. 11 is equipped with methanol-rich pump P-102 (No. 2) and methanol-rich pump E-102 (No. 5).
[0043] The lower end of section B of the flash tower is connected to the upper side of section B and the upper side of section C of the CO2 desorption tower T-102 via logistics pipeline No. 6 and two branches of logistics pipeline No. 6, respectively.
[0044] The lower end of section A of the flash tower is connected to the lower side of section B of the CO2 desorption tower T-102 via logistics pipeline No. 8.
[0045] The lower end of section A of the CO2 desorption tower T-102 is connected to the side end of section N of the H2S concentration tower T-103 via logistics pipeline No. 11.
[0046] The lower end of section B of the CO2 desorption tower T-102 is connected to the lower end of section B of the H2S concentration tower T-103 via the No. 10 logistics pipeline.
[0047] The lower end of section C of the CO2 desorption tower T-102 is connected to the upper end of section B of the H2S concentration tower T-103 via pipeline No. 9.
[0048] The A section of the H2S concentration tower T-103 is equipped with a No. 12 logistics pipeline for introducing nitrogen.
[0049] The lower end of section A of the H2S concentration tower T-103 is equipped with a No. 7 logistics pipeline for discharging sulfur-containing methanol-rich solution.
[0050] The No. 7 pipeline is equipped with a No. 3 methanol-rich pump P-103.
[0051] The lower end of section B of the H2S concentration tower T-103 is connected to the upper end of section A of the CO2 desorption tower T-102 via logistics pipeline No. 13.
[0052] The No. 13 logistics pipeline is equipped with a No. 1 methanol-rich pump P-101 and a No. 4 methanol-rich pump E-101.
[0053] Comparative Example 1
[0054] Existing low-temperature methanol washing gas recovery systems, such as Figure 2 As shown, it consists of a medium-pressure flash distillation tower T-101, a CO2 desorption tower T-102, and an H2S concentration tower T-103 that are interconnected.
[0055] The medium-pressure flash evaporator T-101 includes section A and section B from bottom to top;
[0056] The CO2 desorption tower T-102 comprises, from bottom to top, sections A, B, C, and D.
[0057] The H2S concentration tower T-103 includes section A and section B from bottom to top;
[0058] The flash tower has a No. 1 logistics pipeline for introducing sulfur-containing rich methanol solution at the side end of section A, and a No. 2 logistics pipeline for introducing sulfur-free rich methanol solution at the upper side end of section B. The upper side end of section A and the upper end of section B of the flash tower are provided with logistics pipeline branches for discharging steam from the medium-pressure flash tower and collecting it into the No. 3 logistics pipeline.
[0059] The upper part of section D of the CO2 desorption tower T-102 is equipped with a No. 5 logistics pipeline for discharging CO2 gas.
[0060] The upper end of section B of the H2S concentration tower T-103 is equipped with a No. 4 logistics pipeline for discharging exhaust gas, and the No. 4 logistics pipeline is controllably connected to the No. 5 logistics pipeline.
[0061] The lower end of section A of the H2S concentration tower T-103 is equipped with a No. 14 logistics pipeline for introducing nitrogen gas, and the lower end of section A of the H2S concentration tower T-103 is equipped with a No. 7 logistics pipeline for discharging sulfur-rich methanol. The No. 7 logistics pipeline is equipped with a No. 3 methanol-rich pump P-103.
[0062] The lower end of section B of the flash tower is connected to the upper end of section C and the upper end of section D of the CO2 desorption tower T-102 via logistics pipeline No. 6 and two branches of logistics pipeline No. 6, respectively.
[0063] The lower end of section A of the flash tower is connected to the lower side of section C of the CO2 desorption tower T-102 via logistics pipeline No. 8.
[0064] The lower end of section A of the CO2 desorption tower T-102 is connected to the upper side of section B of the CO2 desorption tower T-102 through the No. 12 logistics pipeline. The No. 12 logistics pipeline is equipped with a No. 2 methanol-rich pump and a No. 5 methanol-rich pump.
[0065] The lower end of section B of the CO2 desorption tower T-102 is connected to the upper end of section A of the H2S concentration tower T-103 via logistics pipeline No. 11.
[0066] The lower end of section C of the CO2 desorption tower T-102 is connected to the middle end of section B of the H2S concentration tower T-103 via the No. 10 logistics pipeline.
[0067] The lower end of section D of the CO2 desorption tower T-102 is connected to the upper end of section B of the H2S concentration tower T-103 via logistics pipeline No. 9.
[0068] The lower end of section B of the H2S concentration tower T-103 is connected to the upper end of section A of the CO2 desorption tower T-102 via logistics pipeline No. 13.
[0069] The No. 13 logistics pipeline is equipped with a No. 1 methanol-rich pump P-101 and a No. 4 methanol-rich pump E-101.
[0070] In the system of Comparative Example 1, T-102 has 4 stages and T-103 has 2 stages. The advantage of this process is that the CO2 production is slightly higher, but the CO2 production itself is already surplus. Without a plan for extensive use of the CO2, the excess CO2 will be vented to the tail gas through a branch. The methanol-rich material, after heat exchange in E-101, is directly flash-distilled in stage A of T-102. Due to the high pressure in T-102, the temperature of the 12 streams after flash-distillation is around -35°C. The heat exchange effect in E-102 is poor, resulting in incomplete flash-distillation in stage B of T-102. Therefore, more nitrogen is required for stripping in stage A of T-103.
[0071] In the system of Example 1, tower T-102 has three sections, and tower T-103 has three sections. After heat exchange in E-101, the methanol-rich methanol is flash-evaporated in section A of tower T-102 and then sent to section N of tower T-103. After low-pressure flash evaporation and stripping, the temperature is approximately -50°C. Due to the even lower cold end temperature, the heat exchange load in E-102 increases significantly, and CO2 in the methanol-rich methanol is fully desorbed. At this point, it is sent to section A of tower T-103 for stripping, which can save 20% of nitrogen consumption.
[0072] Furthermore, to address the elevation difference issue in the flow of methanol from tower T-102 to tower T-103, towers T-101 and T-102 are arranged in an overlapping manner, with tower T-102 placed above tower T-101.
[0073] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction, characterized in that, This includes interconnected medium-pressure flash distillation tower, CO2 desorption tower, and H2S concentration tower; The medium-pressure flash evaporator comprises, from bottom to top, section A and section B; The CO2 desorption tower comprises, from bottom to top, sections A, B, and C. The H2S concentration tower comprises, from bottom to top, sections A, N, and B; The flash tower has a No. 1 logistics pipeline for introducing sulfur-containing rich methanol solution at the side end of section A, and a No. 2 logistics pipeline for introducing sulfur-free rich methanol solution at the upper side end of section B. The upper side end of section A and the upper end of section B of the flash tower are provided with logistics pipeline branches for discharging steam from the medium-pressure flash tower and collecting it into the No. 3 logistics pipeline. The upper end of section C of the CO2 desorption tower is equipped with a No. 5 logistics pipeline for discharging CO2 gas. The upper end of section B of the H2S concentration tower is equipped with a No. 4 logistics pipeline for discharging exhaust gas. The lower end of section N of the H2S concentration tower is connected to the upper end of section A of the H2S concentration tower via a No. 11 logistics pipeline, which is equipped with a No. 2 methanol-rich pump and a No. 5 methanol-rich pump.
2. The recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction according to claim 1, characterized in that, The lower end of section B of the flash tower is connected to the upper side of section B and the upper side of section C of the CO2 desorption tower via logistics pipeline No. 6 and two branches of logistics pipeline No. 6, respectively.
3. The recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction according to claim 1, characterized in that, The lower end of section A of the flash tower is connected to the lower side of section B of the CO2 desorption tower via logistics pipeline No.
8.
4. The recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction according to claim 1, characterized in that, The lower end of section A of the CO2 desorption tower is connected to the side end of section N of the H2S concentration tower via pipeline No.
11.
5. The recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction according to claim 4, characterized in that, The lower end of section B of the CO2 desorption tower is connected to the lower end of section B of the H2S concentration tower via pipeline No.
10.
6. The recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction according to claim 1, characterized in that, The lower end of section C of the CO2 desorption tower is connected to the upper end of section B of the H2S concentration tower via pipeline No.
9.
7. The recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction according to claim 1, characterized in that, The A-section side of the H2S concentration tower is equipped with a No. 12 logistics pipeline for introducing nitrogen gas.
8. The recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction according to claim 7, characterized in that, The lower end of section A of the H2S concentration tower is equipped with a No. 7 logistics pipeline for discharging sulfur-containing methanol-rich solution. A methanol-rich pump #3 is installed on pipeline #7.
9. The recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction according to claim 1, characterized in that, The lower end of section B of the H2S concentration tower is connected to the upper end of section A of the CO2 desorption tower via pipeline No.
13.
10. The recovery system for reducing nitrogen consumption during low-temperature methanol washing gas extraction according to claim 9, characterized in that, The No. 13 logistics pipeline is equipped with a No. 1 methanol-rich pump and a No. 4 methanol-rich pump.