| 摘要 |
[Problems] Attempts have already been made to effectively utilize the by-produced hydrogen chloride in the exhaust gas discharged from the step of producing polysilicon. Hydrogen in the exhaust gas, too, has been partly utilized without using but discarding, however, the purge hydrogen that is used for desorbing the hydrogen chloride adsorbed in the above step. The invention recovers highly pure hydrogen from the exhaust purge gas and reuses it as a hydrogen source in other production steps contributing to greatly reducing the disposal cost and the cost of producing polysilicon. [Means for Solution] The hydrogen chloride contained in the exhaust gas discharged from the step of depositing polysilicon by using trichlorosilane, is adsorbed by active carbon. The active carbon layer is then purged with the hydrogen gas, and the adsorbed hydrogen chloride is desorbed. Next, the exhaust purge gas is brought into contact with a hydrogen chloride-absorbing solution such as an aqueous solution of sodium hydroxide to remove the hydrogen chloride from the exhaust purge gas and to separate and recover the highly pure hydrogen gas. The recovered hydrogen gas is compressed and is fed as a hydrogen source to other steps of producing, for example, fumed silica. |
