Jet mill and circulating type milling system thereof

The jet mill comprises a lower cover body and an upper cover body, the outer side of the interior of the lower cover body is connected with a lower hollow gas injection ring, the lower hollow gas injection ring outwards communicates with a lower gas inlet pipe, and a plurality of lower gas injection nozzles inclining in the same direction are installed between the outer wall of the lower cover body and the lower hollow gas injection ring; the two ends of the lower air injection nozzle are communicated with the lower hollow air injection ring and the lower cover body respectively, and the lower cover body is outwards communicated with a lower feeding pipe below the lower air injection nozzle; an upper hollow gas injection ring is connected to the outer side in the upper cover body, the upper hollow gas injection ring is outwards communicated with an upper gas inlet pipe, a plurality of upper gas injection nozzles which are inclined opposite to the lower gas injection nozzles are installed between the outer wal