Hydrogen gas recovery system and hydrogen gas separation and recovery method

摘要

The reaction exhaust gas from which chlorosilanes and hydrogen chloride have been removed in a hydrogen chloride absorption unit (30) is introduced to an adsorption unit (50) to recover a purified hydrogen (S105). Activated carbon is packed in the adsorption unit (50), the gas, which is mainly composed of hydrogen, is passed through the activated carbon-packed layer during which unseparated chlorosilanes, hydrogen chloride, nitrogen, carbon monoxide, methane, and monosilane contained in the gas are adsorbed on the activated carbon and removed from the gas, and thereby the purified hydrogen is obtained. Nitrogen, carbon monoxide, methane and monosilane are a compressed gas in the state of adsorption, whereas hydrogen chloride and chlorosilanes are a liquid in the state of adsorption, and require a vaporization heat during desorption. Using these properties, the separation of hydrogen chloride and chlorosilanes from other impurity components is possible merely by separating the pathways for the desorbed gas.

主权项

1. A hydrogen gas recovery system comprising:
a condensation separation unit, which condenses and separates chlorosilanes from a hydrogen-comprising reaction exhaust gas discharged from a polycrystalline silicon production apparatus; a compression unit, which compresses hydrogen-comprising reaction exhaust gas discharged from the condensation separation unit; an absorption unit, which absorbs and separates hydrogen chloride by contacting the hydrogen-comprising reaction exhaust gas discharged from the compression unit with an absorption liquid; and an adsorption unit comprising a plurality of activated carbon-packed columns, which adsorptively remove methane, hydrogen chloride, and chlorosilanes from the hydrogen-comprising reaction exhaust gas discharged from the absorption unit; wherein each of the activated carbon-packed columns has a first line used as a discharge line, which discharges a hydrogen gas as a carrier that regenerates activated carbon in an activated carbon-packed column outside the system and a second line that circulates the hydrogen gas once discharged from the adsorption unit into the adsorption unit; and each column is configured such that the hydrogen gas can selectively be sent to any of the first and second lines, and the second line has a condensation separation part for chlorosilanes, a gas compression part and an absorption separation part for hydrogen chloride in this order.