NOVELTY - Metallic silicon (510) is reacted with gaseous chlorine (511) to obtain low-purity silicon tetrachloride (512), which is distilled (502) to obtain (501) highly purified silicon tetrachloride (513). Silicon-tetrachloride vapors are reacted with zinc vapors (515) to obtain (503) polycrystalline silicon (516). The component in exhaust gas (11) is separated (504) into zinc chloride/unreacted zinc mixture (519) and unreacted tetrachloride (514), which is sent for distillation. The zinc mixture is electrolyzed (506) to obtain zinc and gaseous chlorine.    USE - Manufacture of polycrystalline silicon for solar cells and semiconductors.    ADVANTAGE - The method enables economical manufacture of polycrystalline silicon with simple operational and device management, with high yield.    DETAILED DESCRIPTION - Raw-material metallic silicon is reacted with gaseous chlorine to obtain low-purity silicon tetrachloride. The low-purity silicon tetrachloride is distilled to obtain highly purified silicon tetrachloride. The vapors of highly purified silicon tetrachloride and zinc vapors are supplied from the upper portion of a reactor, and exhaust gas is discharged from the lower portion of the reactor. Silicon-tetrachloride vapors are reacted with zinc vapors within the reactor and the obtained polycrystalline silicon is deposited in the reactor. The component in exhaust gas is separated into a mixture of zinc chloride and unreacted zinc, and unreacted silicon tetrachloride. Zinc chloride and unreacted zinc mixture is electrolyzed to obtain zinc and gaseous chlorine. Unreacted silicon tetrachloride is transferred to distillation process and distilled with low-purity silicon tetrachloride. Gaseous chlorine obtained by electrolysis is used as gaseous chlorine in production of silicon tetrachloride. Zinc obtained by electrolysis is used as zinc in production of polycrystalline silicon.    DESCRIPTION OF DRAWING(S) - The drawing shows a flowchart of the manufacturing method of polycrystalline silicon.    Exhaust gas (11)    Silicon-tetrachloride manufacturing process (501)    Distillation (502)    Polycrystalline-silicon manufacturing process (503)    Separation process (504)    Electrolysis (506)    Raw-material metallic silicon (510)    Gaseous chlorine (511)    Low-purity silicon tetrachloride (512)    Highly purified silicon tetrachloride (513)    Unreacted silicon tetrachloride (514)    Zinc vapors (515)    Polycrystalline silicon (516)    Mixture of zinc chloride and unreacted zinc (519)