120 Refining Used Lubricating Oils
precipitators, bag lters, and high-energy venturi scrubbers), tall dispersive chim-
neys, and their location (often away from high population density areas).
5.3.1 fuels
The terms used oil (as applied to use in a combustor), recovered fuel oil, or pro-
cessed fuel oil are often used interchangeably. Processing typically involves basic
cleanup such as dewatering and processes such as ltering, settling, or centrifuging
to remove solid contaminants.
Used fuel oil has been in use for many years as a fuel for combustors, and
various commercial specications apply, with limits on elements such as (but not
limited to) sulfur, halogens, nickel, vanadium, and sodium. More recently, envi-
ronmental concerns have led to ...