The issue of producing crude argon and purified argon
Thread Content
Why is the crude argon column used for oxygen-argon separation, while the refined argon column is used for nitrogen-argon separation? Isn’t it because the boiling points of oxygen and argon are close to each other that they are difficult to separate? How is process design taken into account?
The boiling point of oxygen-argon is close to that of nitrogen-argon. Precisely because their boiling points are similar, more theoretical plates are required for argon separation using full rectification.
It is because the boiling points of oxygen and argon are close to each other that, after supercooling, liquid nitrogen is used as a cooling source to completely condense oxygen; most of the argon also gets condensed. The temperature after heat exchange should be around -185 degrees, which is the saturation temperature of argon. Nitrogen, along with a small amount of argon that has not been condensed, is used for argon purification; the cooling source is supercooled liquid nitrogen, whose temperature after heat exchange is around -190 degrees Celsius, allowing the nitrogen to be completely vaporized while the argon is completely condensed. The new process uses full low pressure and does not require hydrogenation to produce argon. Old equipment, due to its outdated design and tray structure, has a limited height for the argon column; as a result, the hydrogenation, deoxygenation, and drainage processes are quite complicated. The new process doesn’t even have helium-neon emissions.
In learning*, then why not use liquid nitrogen as a cooling source?