However, direct use of oxygen, or enrichment of the air with oxygen, is necessary for some processes. 但是对于某些过程，直接使用氧或富氧空气是必要的。
Occasionally enriched air or supple mental oxygen is available and a greater ratio of secondary reforming to primary reforming is possible. 偶尔有富氧空气或补充氧的，因而二段转化对一段转化的大比例是可能的。
