Method of processing discharge gas discharged from production process

Abstract

The present invention provides a method of processing discharge gas containing ammonia, hydrogen, nitrogen, and an organic metal compound discharged from the production process of a gallium nitride compound semiconductor. The discharge gas is brought into contact with a cleaning agent prepared by impregnating an alkali metal compound with a metal oxide to remove the organic metal compound from the discharge gas. The discharge gas from which an organic metal compound is removed is brought into contact with an ammonia decomposition catalyst on heating to decompose the ammonia into nitrogen and hydrogen. The discharge gas in which ammonia is decomposed is brought into contact with palladium alloy membrane on heating to recover hydrogen that has penetrated through the palladium alloy membrane. After an organic metal compound is removed to liquefy the ammonia contained in the discharge gas as described above, a pressurization process and a cooling process is conducted by a heat pump to pressurize and cool the discharge gas from which an organic metal compound is removed to liquefy the ammonia contained in the discharge gas and separate the liquefied ammonia from hydrogen and nitrogen so as to recover the liquefied ammonia. The recovered hydrogen and ammonia are supplied to and reused in the production process of a gallium nitride compound semiconductor.