Method for recovering reduction system tail gas in polycrystalline silicon production

The invention relates to a method for recovering reduction system tail gas in polycrystalline silicon production. The method comprises the following steps: reduction system tail gas is directly fed into a cold hydrogenation system, hydrogen is injected into the cold hydrogenation system, and the volume of injected hydrogen is 15%-21% of the total gas volume of the cold hydrogenation system; the reduction system tail gas and hydrogen are heated by the cold hydrogenation system at the temperature of 540-560 DEG C; the heated reduction system tail gas and hydrogen are input into a cold hydrogenation reactor for hydrogenation, silicon tetrachloride in the reduction system tail gas is enabled to have a reaction with hydrogen and is directly converted into trichlorosilane, and dichlorosilane in the reduction system tail gas is converted into trichlorosilane through a purifying device in the cold hydrogenation reactor. According to the method, the tail gas exhausted from a reduction furnace is directly subjected to hydrogenation as a raw material without cooling, separation or desorption, so that the process can be shortened, and the purposes of energy saving and consumption reduction can be achieved.