Abstract: A process for separating two close-boiling chemical compounds by fractionation wherein a vapor stream removed from the overhead receiver is superheated by indirect heat exchange and is then further heated by compression. The thus-heated high pressure stream is cooled by heat exchange against the overhead vapor and split into at least two portions. One portion of the high pressure stream is passed through a reboiler at an intermediate point in a fractionation column. Preferably, both portions of the high pressure stream are subcooled and returned to the overhead receiver except for the overhead product drawn off.

Abstract: A hydrocarbon conversion apparatus is dried as a preliminary step of a startup procedure by the circulation of a superheated vapor stream which is formed in one of two reboilers attached to a fractionation column used in the process. Preferably this vapor stream is formed on the tube side of the reboiler, with normal on-stream operation comprising the generation of the vapors fed to the column on the shell side of the reboiler.