
265Refining Processes for Used Oil Recycling to Base Oils or Fuels
resins and asphalts from the bottom of the tower. The overhead stream from these
extraction towers then proceeds to a propane recovery section which recovers the
propane for recycling and includes a gas-stripping section to remove residual pro-
pane and water. The oil stream then passes to a multi-unit vacuum distillation system
which removes light ends and the base oil fractions continue to a hydroning section
where the stream is mixed with hydrogen using an in-line static mixer and passes
through multiple units which contain suitable catalysts and operating conditions to
remo ...