Dephlegmator
A dephlegmator (refluxing condenser) includes a feed gas passage and a refrigerant passage. A feed gas introduced into the feed gas passage from the bottom is in indirect heat-exchange with a refrigerant passing through the refrigerant passage. Components having low boiling points are withdrawn as rectified gases from the top, and high boiling point components are discharged as condensates from the bottom. The refrigerant passage is divided into a first, upper section and a second, lower section. In the first section, a liquid or gas-liquid two-phase refrigerant is introduced to flow co-currently with the feed gas. In the second section, a gas fraction of the refrigerant flows. The flow in this second section is preferably counter-current. The dephlegmator is preferably formed as a plate and fin type exchanger.