Production device and production method for synthesizing acetic acid through methanol low-pressure carbonylation

The invention discloses a production device and a production method for synthesizing acetic acid through methanol low-pressure carbonylation. The production device comprises a reaction kettle, a flash tower, a dehydrating tower and a finished product tower, the reaction kettle is used for feeding CO and methanol into the reaction kettle and extracting a material flow containing acetic acid and a catalyst from the reaction kettle; the pipeline of the material flow containing the acetic acid and the catalyst is connected with the flash tower, so that the material flow containing the acetic acid and the catalyst is separated in the flash tower, and a material flow containing an acetic acid crude product is extracted from the flash tower; the pipeline of the material flow containing the acetic acid crude product is connected with the dehydrating tower so as to be used for further separating the material flow containing the acetic acid crude product, and a material flow containing acetic acid and propionic acid is