Oxygen gas

When the air separation unit is in normal operation, the liquid flows down and can only flow on the tray and flow to the lower tray through the overflow bucket because the supporting force of the rising steam prevents the liquid from flowing down from the small hole of the tray. After shutdown, due to the interruption of rising gas flow, the liquid on the tray can flow from the overflow bucket to the lower tray, and also can flow through the small hole on the tray to the lower tray. This will cause the surface of liquid oxygen and liquid air rise, which may exceed the position of the expansion air outlet pipe, resulting in liquid carrying accident of the expander during restart. Therefore, pay attention to the liquid level position when stopping.

The amount of liquid nitrogen removed from the lower column of the air separation unit will affect the purity of the liquid nitrogen in the lower column and the oxygen enriched liquid air at the bottom of the column. When the liquid nitrogen removal amount of the lower column increases, the reflux liquid participating in the heat and mass exchange of the lower column will be reduced, the temperature rise of the rising steam on the column plate will be correspondingly reduced, the condensation of the rising steam will not be sufficient, the oxygen component will be condensed less, the purity of nitrogen at the column top will be reduced, and the purity of liquid nitrogen will be naturally reduced. At the same time, the temperature rise of the downflow liquid will increase, the liquid evaporation will be more sufficient, more nitrogen components will be evaporated to the top of the column, and the purity of the liquid air at the bottom of the column will be improved accordingly.