The diclosure is directed to methods of gas separation wherein controlled flow vortex tube expansion principles are employed in liquefaction and cold producing processes; a multi-stage low pressure and a multi-stage high pressure process being involved. The vortex tube is introduced in the parent application as being employed in cases with more efficiency than the expansion turbine. Herein, by addition, support figures are supplied for these cases, and also vortex tube separation processes are shown capable of replacing rectification column processes; liquefaction and separation processes using controlled flow vortex tubes with double purpose being submitted herein as new.