Recycling system for methanol in acid desorption flare gas
By using a system of combined water washing towers and other equipment to treat the flare gas of the low-temperature methanol washing unit, the problem of incomplete methanol combustion during start-up and shutdown was solved, achieving efficient methanol recovery and environmental protection, while reducing equipment investment and steam consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2026-03-31
AI Technical Summary
During start-up and shutdown of the low-temperature methanol washing unit, incomplete combustion of methanol in the flare exhaust gas leads to waste and environmental pollution, and the methanol content in the purified feed gas exceeds the standard, endangering safety.
The system consists of a water washing tower, a main absorption tower, a CO2 desorption tower, a tail gas water washing tower, a methanol distillation tower, and a gas-liquid separator. It purifies the raw gas by washing with deoxygenated water at room temperature, recovers methanol, and reduces the methanol content in the flare gas emissions.
This achieves efficient methanol recovery, reduces the safety risks of flare gas emissions, reduces equipment investment and steam consumption, and ensures environmental protection benefits.
Smart Images
Figure CN224057047U_ABST
Abstract
Description
Technical Field
[0001] This application relates to a system for recycling methanol in acid removal flare gas, belonging to the field of chemical technology for low-temperature methanol washing devices. Background Technology
[0002] During start-up and shutdown of the cryogenic methanol washing unit, substandard purified feed gas needs to be discharged into the flare for combustion before being released into the atmosphere. However, since the flare exhaust contains a large amount of methanol, direct combustion of this methanol not only wastes feed gas but also, if combustion at the flare head is incomplete, can easily lead to excessive methanol content in the exhaust gas, polluting the environment. Furthermore, residual methanol from incomplete combustion can diffuse to the ground with the flare gas, posing a health hazard to personnel.
[0003] At 25°C, methanol and water are completely miscible, meaning the solubility of methanol in water is infinite. The temperature of the purified feed gas in the low-temperature methanol washing unit is precisely around 25°C. Using water to wash methanol can effectively address the methanol treatment issue after the purified feed gas is emitted through the flare, reduce the methanol content in the gas phase of the flare system, meet the requirements for methanol recovery, and simultaneously achieve good safety and environmental protection results. Utility Model Content
[0004] To address the safety and environmental issues related to flare gas emissions in existing technologies for flare gas emissions during the start-up and shutdown of low-temperature methanol washing units, this application provides a system solution for recovering methanol from the purified flare gas emitted from the low-temperature methanol washing unit. By further treating the purified raw material gas and the emitted flare gas, both efficient methanol recovery and the safety and environmental issues of flare gas emissions are ensured.
[0005] The technical solution adopted in this application is as follows:
[0006] According to one aspect of this application, a system for recycling methanol in acid removal flare gas is provided, comprising: a water washing tower, a main absorption tower, a CO2 desorption tower, a tail gas water washing tower, a methanol distillation tower, a feed gas cooler, and a gas-liquid separator connected to each other.
[0007] A raw material gas feed pipeline is provided at the middle side of the gas-liquid separator, and the upper end of the gas-liquid separator is connected to the lower side of the main absorption tower through the material pipeline.
[0008] The upper end of the main absorption tower is used to discharge the logistics pipeline of low-temperature purified raw gas, the upper end of the CO2 desorption tower is used to discharge the logistics pipeline of low-temperature CO2, the upper end of the tail gas washing tower is used to discharge the logistics pipeline of low-temperature tail gas, and the raw gas feed pipeline passes in parallel through the raw gas cooler for heat exchange to cool the raw gas.
[0009] The lower end of the gas-liquid separator is connected to the middle side of the methanol distillation column.
[0010] Optionally, the upper end of the methanol distillation column is sequentially connected to the methanol-containing wastewater heater, the pressurization pump, and the lower end of the water washing tower via a logistics pipeline.
[0011] Optionally, a logistics pipeline branch connected to the middle side of the water washing tower is provided on the pipeline between the pressurization pump and the methanol-containing wastewater heater.
[0012] Optionally, the upper side of the water washing tower is provided with a logistics pipeline for introducing room temperature deoxygenated water.
[0013] Optionally, the upper end of the water washing tower is provided with a logistics pipeline for discharging purified raw material gas to the flare.
[0014] Optionally, the logistics pipeline for discharging low-temperature purified raw gas after passing through the raw gas cooler is provided with a logistics pipeline branch for connecting to the lower side end of the water washing tower.
[0015] Optionally, a methanol / water heater is provided on the logistics pipeline connecting the lower end of the gas-liquid separator and the middle side of the methanol distillation column.
[0016] The beneficial effects that this application can produce include:
[0017] The methanol recycling system for acid stripping flare gas provided in this application ensures efficient recovery of methanol from the purified feed gas containing H2 and CO by further treating the emitted flare gas, while also solving the safety and environmental protection issues of flare gas emissions. The system uses ambient temperature deoxygenated water as the absorbent, and the circulating washing reduces the consumption of ambient temperature deoxygenated water. The methanol content in the purified feed gas after washing is significantly reduced, effectively recovering methanol and reducing methanol consumption during the start-up and shutdown of the low-temperature methanol washing unit. The recovered methanol-containing wastewater is directly sent to the original unit for distillation treatment, saving equipment investment and steam consumption. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the methanol recycling system in the acid removal flare gas of this application.
[0019] Attached Figure Labels
[0020] 1. T-110 is a water washing tower; 2. T-101 is the main absorption tower; 3. T-102 is a CO2 desorption tower; 4. T-103 is a tail gas water washing tower; 5. T-105 is a methanol distillation tower; 6. E-101 is a feed gas cooler; 7. E-116 is a methanol / water heater; 8. E-130 is a methanol-containing wastewater heater; 9. V-101 is a gas-liquid separator; 10. P-110 is a booster pump. Detailed Implementation
[0021] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0022] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0023] The purified feed gas contains a large amount of toxic, harmful, flammable, and explosive gases such as H2 and CO. Under normal circumstances, during the start-up and shutdown of the cryogenic methanol washing unit, the purified feed gas is discharged to the flare for treatment. Because the operating temperature of the T-101 tower is higher than the normal operating temperature during the start-up and shutdown of the cryogenic methanol washing unit, the purified feed gas exiting the T-101 tower carries excessive methanol vapor, and may even contain methanol droplets. After being discharged to the flare, the methanol in the purified feed gas can easily accumulate inside the flare. In severe cases, it can even cause fire rain from the flare, endangering the safety of the surrounding environment.
[0024] Example 1
[0025] A system for recycling methanol in acid removal flare gas, such as... Figure 1 As shown, the system comprises an interconnected water washing tower, a main absorption tower, a CO2 desorption tower, a tail gas washing tower, a methanol distillation tower, a feed gas cooler, and a gas-liquid separator. A feed gas inlet pipeline is located at the middle side of the gas-liquid separator, and the upper end of the gas-liquid separator is connected to the lower side of the main absorption tower via a feed pipeline. The upper end of the main absorption tower, the upper end of the CO2 desorption tower, and the upper end of the tail gas washing tower are used to discharge low-temperature purified feed gas via a feed pipeline; the feed gas inlet pipeline also passes parallel to the feed gas cooler for heat exchange to cool the feed gas. The lower end of the gas-liquid separator is connected to the middle side of the methanol distillation tower. The upper side of the methanol distillation tower is sequentially connected to a methanol-containing wastewater heater, a booster pump, and the lower end of the water washing tower via feed pipelines. A branch pipeline connecting to the middle end of the water washing tower is installed on the pipeline between the pressurization pump and the methanol-containing wastewater heater. A pipeline for introducing room-temperature deoxygenated water is installed on the upper end of the water washing tower. A pipeline for discharging purified raw material gas to the flare is installed at the upper end of the water washing tower. A branch pipeline connecting to the lower end of the water washing tower is installed on the pipeline for discharging low-temperature purified raw material gas after the raw material gas cooler. A methanol / water heater is installed on the pipeline connecting the lower end of the gas-liquid separator and the middle end of the methanol distillation tower.
[0026] Based on the methanol recycling system for acid removal flare gas in Example 1, the ambient temperature feed gas from the conversion process is wetted with sprayed methanol. Then, it is cooled by heat exchange in E-101 with low-temperature CO2 gas from T-102, low-temperature tail gas from T-103, and low-temperature purified feed gas from T-101. After separation in V-101, the feed gas enters T-101 for desulfurization and decarbonization. The purified feed gas is drawn from the top of T-101 and reheated to ambient temperature in E-101 before being sent to downstream units. The methanol / water separated in V-101 is reheated in E-116 and sent to subsequent C-105 for methanol recovery. The low-temperature purified feed gas from T-101 is reheated to ambient temperature in E-101, and then depressurized before entering T-110 for methanol removal. Considering the presence of flammable and explosive gases such as H2 and CO in the purified feed gas, ambient temperature deoxygenated water was used as the absorbent. Washing and separation were performed in absorber T-110. The recovered methanol-containing wastewater was pressurized by pump P-110 and divided into two streams. One stream was returned to T-110 for recirculation and washing of the purified feed gas, while the other stream was heated by E-130 and sent to T-105 for distillation and recovery. The purified feed gas after alcohol removal was discharged to the flare.
[0027] 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 cyclic recovery and utilization system of methanol in acid-depleted flare gas, characterized in that, The application relates to a methanol production system. The system comprises a water washing tower, a main absorption tower, a CO2 desorption tower, a tail gas water washing tower, a methanol rectifying tower, a raw material gas cooler and a gas-liquid separator. A raw material gas feeding material pipeline is arranged at the middle side end of the gas-liquid separator, and the upper end of the gas-liquid separator is connected with the lower side end of the main absorption tower through a material pipeline. A raw material gas feeding material pipeline is arranged at the middle side end of the gas-liquid separator, and the upper end of the gas-liquid separator is connected with the lower side end of the main absorption tower through a material pipeline. The upper side end of the main absorption tower is provided with a stream pipeline for discharging low-temperature purified raw material gas, the upper end of the CO2 desorption tower is provided with a stream pipeline for discharging low-temperature CO2, the upper end of the tail gas water washing tower is provided with a stream pipeline for discharging low-temperature tail gas, and the raw material gas feeding material pipeline passes through the raw material gas cooler in parallel for heat exchange to cool the raw material gas.
2. The system for cyclic recovery and utilization of methanol from acid-depleted flare gas of claim 1, wherein, The lower end of the gas-liquid separator is connected with the middle side end of the methanol rectifying tower.
3. The system for cyclic recovery and utilization of methanol from acid-depleted flare gas of claim 2, wherein, The upper side end of the methanol rectifying tower is connected with a methanol-containing waste water heater, a pressurizing pump and the lower end of the water washing tower through stream pipelines in sequence.
4. The system for cyclic recovery and utilization of methanol from acid-depleted flare gas of claim 1, wherein, A stream pipeline branch connected with the middle side end of the water washing tower is arranged on the pipeline between the pressurizing pump and the methanol-containing waste water heater.
5. The system for cyclic recovery and utilization of methanol from acid-depleted flare gas of claim 1, wherein, A stream pipeline for feeding normal-temperature deoxygenated water is arranged at the upper side end of the water washing tower.
6. The system for cyclic recovery and utilization of methanol from acid-depleted flare gas of claim 1, wherein, A stream pipeline for discharging purified raw material gas to a flare is arranged at the upper end of the water washing tower.
7. The system for cyclic recovery and utilization of methanol from acid-depleted flare gas of claim 1, wherein, A stream pipeline branch for connecting with the lower side end of the water washing tower is arranged on the stream pipeline for discharging low-temperature purified raw material gas after passing through the raw material gas cooler. A methanol / water heater is arranged on the stream pipeline connecting the lower end of the gas-liquid separator with the middle side end of the methanol rectifying tower.