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Principle of methanol production: In the gas used in the methanol synthesis process, CO and CO2 react with H2, under the action of copper-based catalysts, to primarily form methanol; various side reactions also occur simultaneously. Main reaction: Catalyst + CO + 2H2 → CH3OH + Q; Catalyst + CO2 + 3H2 → CH3OH + H2O + Q. Major side reactions: 2CO + 4H2 → CH3OCH3 + H2O; 4CO + 8H2 → C4H9OH + 3H2O; CO + 3H2 → CH4 + H2O; 2CO + 2H2 → CH4 + CO2. 2.2 Brief description of the process flow: The syngas, with a pressure of 5.9 MPa and a temperature of 80°C, passes through the shell side of the gas-gas heat exchangers (C40001A, B), where it is preheated to 225°C by hot gas from the methanol synthesis tower. After that, it enters the top of the methanol synthesis tower (D40001). The methanol synthesis tower (D40001) is a shell-and-tube reactor equipped with a C307 copper-based catalyst inside the tubes. When syngas enters the catalyst layer, H2 reacts with CO and CO2 to produce methanol and water; simultaneously, trace amounts of other impurities are also formed. The outside of the tube is filled with boiler water, which absorbs the heat released by the reaction; simultaneously, steam at 3.9 Mpa and 249°C is generated, and after being cooled and depressurized to around 0.5 Mpa and 160°C, it is sent to the low-pressure steam network. The mixed gas exiting the tube side of the gas-to-gas heat exchanger enters the water cooler (C40002), where it is cooled to ≤40°C; methanol is condensed into a liquid, which then enters the methanol separator (F40003) to separate out crude methanol. The gas from which crude methanol has been separated, with a pressure of 5.45 MPa and a temperature of 40°C, is returned to the circulation section of the syngas compressor (J63001), where it is pressurized and reused. To prevent the accumulation of inert gases in the synthesis system, it is necessary to continuously discharge a portion of the recycle gas. After methanol is washed in the alcohol washing tower (E40001), this gas is sent to the fuel gas network as vent gas. The crude methanol obtained is depressurized to 0.5 Mpa and sent to the flash tank (F40002), where the vaporized gas is sent to the fuel gas network as fuel. The crude methanol in the flash tank and the dilute methanol stream from the bottom of the alcohol washing tower are sent to the methanol distillation section. The boiler water from the conversion unit, with a pressure of 4.1 MPa and a temperature of 190°C, is sent to the drum (F40004). Through connecting pipes, it forms a natural circulation boiler with the methanol synthesis tower, producing medium-pressure saturated steam at 3.9 MPa and 245°C; this steam is then cooled and depressurized before being sent to the low-pressure steam network. To ensure the quality of the boiler water, a 5% (wt) phosphate solution is continuously injected via the phosphate pumps (J40002A, B) ； Continuous blowdown is provided at both the drum (F40004) and the lower part of the synthesis tower (D40001); the wastewater is sent to biological treatment after passing through the blowdown expander (F40006). The desalinated water from the desalination water network is sent to the dilute alcohol water tank (F40001), and then pumped into the alcohol washing tower by the dilute alcohol pumps (J40001A, B) where it comes into countercurrent contact with the vent gas. Part of the dilute alcohol solution containing methanol is sent to the distillation section, while the rest is sent back to the dilute alcohol water tank for reuse. There are also two pipelines on the outlet pipeline of the syngas compressor; one is a nitrogen pipeline from the air separation unit, which is used for heating the catalyst or displacing the syngas. The other one is the instrument air line from air separation, which can also be used for catalyst deactivation.