Refining system for circulating 1, 3-propanediol in continuous production of poly(trimethylene terephthalate)

The invention relates to a refining system for circulating 1, 3-propanediol (PDO) in continuous production of poly(trimethylene terephthalate) (PTT). The refining system comprises a treating tower and a refined PDO cooler connected to the treating tower, an overhead steam condenser, a tower bottom circulating pump and a vacuum pump. The treating tower can be a plate-type or plate-type/packed tower. The mixed material inlet and the refined PDO outlet of the treating tower are respectively connected to a PDO mixture outlet of the PTT continuous production system and the inlet of a device for storing or applying the refined PDO. The tower bottom circulating pump is positioned between an outlet for tower bottoms of the treating tower and a material inlet of a treating tower reboiler. The refined PDO from the refining system of the invention has high PDO purity and low water content, satisfies the quality requirement for PDO raw materials in PTT production, and can be recycled in PTT continuous production. In addition, the system provided in the invention can realize continuous refining and is suitable for continuous PTT production.