Acetic acid manufacturing method

A method of manufacturing acetic acid by carbonylating a raw material comprising one or more compounds selected from methanol, dimethyl ether, or methyl acetate with carbon monoxide, the method comprising:

• a reaction step of reacting the raw material with carbon monoxide in the presence of a catalyst inside a reactor to thereby form a reaction mixture containing acetic acid;
• and a purification step of purifying the reaction mixture formed in the reaction step to thereby obtain product acetic acid, wherein
• the purification step includes
• a flash evaporation step of introducing the reaction mixture into a flasher vessel and vaporizing a part thereof to thereby separate the reaction mixture into a vapor-phase mixture containing acetic acid and low-boiling point components lower in boiling point than acetic acid, and a liquid-phase mixture containing acetic acid and a high-boiling point component higher in boiling point than acetic acid,
• a first distillation step of introducing the vapor-phase mixture into a light ends column consisting of at least one column and distilling the vapor-phase mixture to thereby separate and remove at least a part of the low-boiling point components from the vapor-phase mixture and obtain crude acetic acid, and
• a second distillation step of introducing the crude acetic acid into a heavy ends column and distilling the crude acetic acid to thereby further purify the crude acetic acid and obtain product acetic acid, and
• in the second distillation step, the low-boiling point components remaining in the crude acetic acid are drawn out from a column top of the heavy ends column, the product acetic acid is drawn out from an intermediate drawing stage of the heavy ends column, and a bottoms liquid surface level in the heavy ends column is controlled by adjusting an amount to be drawn out from the intermediate drawing stage.