NOVELTY - The device comprises a reactor column body (6), a gas distributor (8), a gas lead-in tube for gas to enter from a top of the reactor column body, a gas outlet (3), a feeding opening (4), a discharging opening, a gas circulating inlet (7), and valves (2, 5, 10, 11, 13). The gas distributor is arranged on a lower part of the reactor column body, and comprises a rounded plate having venting holes. The gas lead-in tube is arranged in the reactor column body. An outlet of the gas lead-in tube is extended downwards, and passes through the gas distributor.    USE - The device is useful for fermenting biomass synthesis gas to produce ethanol.    ADVANTAGE - The device is capable of effectively and economically fermenting the biomass synthesis gas with high efficiency and reduced energy consumption, and has simple structure.    DETAILED DESCRIPTION - The device comprises a reactor column body (6), a gas distributor (8), a gas lead-in tube for gas to enter from a top of the reactor column body, a gas outlet (3), a feeding opening (4), a discharging opening, a gas circulating inlet (7), and valves (2, 5, 10, 11, 13). The gas distributor is arranged on a lower part of the reactor column body, and comprises a rounded plate having venting holes. The gas lead-in tube is arranged in the reactor column body. An outlet of the gas lead-in tube is extended downwards, and passes through the gas distributor. The gas outlet and the feeding opening are arranged at the top of the reactor column body and on two sides of the gas lead-in tube. The discharging opening and the gas circulating inlet are arranged at a bottom of the reactor column body. The gas circulation inlet is communicated with the gas outlet at top of the reactor column body through a pipe. The valves are arranged on the gas outlet, the feeding opening, the discharging opening and the gas circulating inlet. An inlet of the gas lead-in tube is connected with a gas outlet of a gas storage tank. A decompression valve is arranged on the gas outlet of the gas storage tank. The reactor column bodies are arranged and connected in series. The gas outlets of the reactor column bodies are connected with the gas lead-in tubes of the next group of the reactor columns.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a device for fermenting biomass synthesis gas to produce ethanol.    Valves (2, 5, 10, 11, 13)    Gas outlet (3)    Feeding opening (4)    Reactor column body (6)    Gas circulating inlet (7)    Gas distributor. (8)