Method for recovering CO2 in the Rectisol process and recovery system

A method for recovering CO2 in the Rectisol process, comprising:

• performing reduced-pressure flash distillation treatment on a CO2-rich methanol liquid, and outputting CO2 desorbed gas obtained after the reduced-pressure flash distillation treatment as a product gas, wherein the CO2-rich methanol liquid comprises a sulfur-free methanol liquid and a sulfur-containing methanol liquid;
• performing heat exchange flash distillation treatment on a first methanol liquid obtained after the reduced-pressure flash distillation treatment, and outputting CO2 desorbed gas obtained after the heat exchange flash distillation treatment as a product gas;
• and
• performing vacuum flash distillation treatment on a second methanol liquid obtained after the heat exchange flash distillation treatment, and outputting CO2 desorbed gas obtained after the vacuum flash distillation treatment as a product gas;
• wherein a recovery system for implementing the method for recovering CO2 in the Rectisol process is provided, the recovery system comprising:
• a CO2 desorber used for performing the reduced-pressure flash distillation treatment on the CO2-rich methanol liquid;
• a first heat exchanger communicated with the CO2 desorber for performing the heat exchange flash distillation treatment on the first methanol liquid obtained after the reduced-pressure flash distillation treatment;
• and
• a vacuum desorption tank communicated with the CO2 desorber for performing the vacuum flash distillation treatment on the second methanol liquid obtained after the heat exchange flash distillation treatment;
• wherein the CO2 desorber comprises an upper section, a middle section and a lower section;
• the upper section of the CO2 desorber is used for performing the reduced-pressure flash distillation treatment on the sulfur-free methanol liquid in the CO2-rich methanol liquid;
• the middle section of the CO2 desorber is used for performing the reduced-pressure flash distillation treatment on the sulfur-containing methanol liquid in the CO2-rich methanol liquid;
• and
• a liquid inlet end of the first heat exchanger is communicated with the lower part of the middle section of the CO2 desorber, and a liquid outlet end of the first heat exchanger is communicated with the upper part of the lower section of the CO2 desorber.