The noble gases are argon, neon, helium, krypton and xenon. Because of their different boiling points, the concentrations in air are very different, so the components are collected in different parts of the rectification column.
Krypton and xenon have the highest boiling points (at standard atmospheric pressure, the boiling point of krypton is -152.9 degrees Celsius, the boiling point of xenon is -108.1 degrees Celsius), and after the process air enters the lower tower, krypton and xenon are condensed into liquid air in the lower tower. The liquid air then enters the upper tower through the throttle valve and collects one by one in the liquid oxygen and gaseous oxygen at the bottom of the upper tower. Therefore, if you want to extract krypton and xenon from the air separation unit, it is common practice to introduce product oxygen into the krypton tower and use rectification to obtain poor krypton and xenon raw gas.
The boiling point of neon (-245.9 degrees Celsius) and helium (-268.9 degrees Celsius) is much lower than that of the helium component. Therefore, the neon and helium components in the process air are combined with the nitrogen components at the boiling point of the low gas network. After the process air enters the lower tower, the neon and helium components rise with the nitrogen components to the nitrogen side of the main condensing evaporator and the nitrogen gas is condensed, while the neon and helium cannot be condensed due to their low boiling point and become “non-condensable gases” in the main refrigeration. Therefore it can be taken from the top of the main cold nitroge
The boiling point of argon is -185.7 degrees Celsius, between the boiling points of oxygen and nitrogen and close to that of oxygen. Most of the argon in the air of the lower column enters the upper column with liquid air, and a small proportion enters the upper column with liquid nitrogen. There are rich areas of argon components in the rectification and distillation sections of the upper column. The upper part of the rectification section is mainly nitrogen and argon separation. The lower part of the distillation section is mainly oxygen and argon separation.
Post time: Jan-06-2025