摘要 |
An oxidizing gas containing water vapor generated by hydrogen combustion is introduced from an external gas burner via gas supply pipes into the upper space of a process tube surrounded by a heater, and exhausted from the lower part of the process tube. Until the flame of hydrogen burnt in the external gas burner becomes stable, a dilute gas such as N2 is introduced into the upper space of the process tube via other gas supply pipes so as to suppress the initial oxidation. Suppressing the initial oxidation may also be performed by bypassing an oxidizing gas from the external gas burner to an exhaust system while introducing a non-oxidizing gas such as N2 into the upper space of the process tube.
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