English to Russian Tech/Engineering Engineering: Industrial

Здравствуйте, скажите, пожалуйста, здесь reflux - это типа флегмы или орошение?

The cold, partly liquefied air is fed to the bottom of the so-called 'pressure column' (T3211) which is operated at a pressure of approx. 5,5 bar. In this column, the process air is separated by rectification into pure gaseous nitrogen at the top and oxygen enriched liquid at the bottom. The latter is fed through the subcooler (E3316) to the low pressure column (T3212), where it serves as reflux.

Спасибо