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Appendix C: Unit Operations
in a Re-Refinery
C.1 TYPICAL UNIT OPERATIONS
There are a number of chemical engineering unit operations that originate from the
rening industry (Speight and Ozum 2002; Hsu and Robinson 2006; Gary et al.
2007; Speight 2014); these are applied in the re-rening of used oil and will be
briey reviewed here. The various processes developed by different operators will
combine some of these unit operations in a number of different ways, ranging from
the simpler processes, which are usually cheaper and result in a less valuable prod-
uct, to the more complicated and expensive processes, which give a range of high-
gra