Internal and external double-circular current fermentation can

This invention is a new ventilating fermentation tank of the chemical machinery domain. It introduces the effective functions of static mixer and Venturi tube on the basis of gas-lift fermentation tank, internal circulation of fluid is formed between ascending and descending tubes, and external circulation of fluid is formed from material suction tube through circulating pump and Venturi tube, passing mixed fluid distributor injecting into static mixer. The fermentating liquid by use of this invention is suniformly mixed, has fine bubbles and high-level dissolved oxygen, promotes conduction circulation, has stable fermentation process, and capability of high output with excellent quality.