
210 Refining Used Lubricating Oils
and expanded through a valve into a container that separates the solvent gas for
recycle from the residue stream.
The uid phase leaving the top of the rst separation column is taken to a second
separation column, again operating within the limits earlier discussed, but in any
case at a higher temperature or lower pressure (or both) than the rst separation col-
umn. The stream leaving the bottom of the rst separation column is again expanded
through a valve into a vessel that allows separation of the solvent gas for recycle and
a heavy base oil component.
Again, the uid leaving the top of the second separat ...