Method and device for producing long-chain fatty alcohol through continuous low-pressure rectification of biological waste oil hydrogenated alcohol

The invention discloses a method for producing long-chain fatty alcohol by low-pressure continuous rectification of biological waste oil hydrogenated alcohol. The method comprises the following steps: introducing the biological waste oil hydrogenated alcohol into a de-ashing distillation tower, and separating refined biological waste oil hydrogenated alcohol from the tower bottom; the refined biological waste oil hydrogenated alcohol is introduced into a first-stage rectifying tower, a first light component is separated from the tower top, and a first heavy component is separated from the tower bottom; the first heavy component is introduced into a second-stage rectifying tower, cetanol is separated from the tower top, and octadecanol is separated from the tower bottom; the first light component is introduced into a third-stage rectifying tower, a second light component is separated from the tower top, and tetradecanol is separated from the tower bottom; the second light component is introduced into a fourth-