5. Figures 2-53 thru 2-59 are examples of chemical processing industries on aerial
imagery along with specific identification features of the industry.
Figure 2-53. Petroleum Refinery.
NOTE: Petroleum heated in pipe furnaces is flashed to vapor in the base of these
tall cylindrical fractionating towers.
The vapor rises in the towers with
different fractions condensing and collecting on perforated trays or plates.
From various levels in the towers, different fractions are withdrawn to be
stored in tanks.
Fractionating towers may operate as separate units or be
associated with thermal cracking units or catalytic cracking units.
NOTE: The box-like elements on the top of the units are the lids of cases filled
with a catalyst.
Water gas from the scrubbers or one of the gasholders
passes through these cases where the sulfur is removed. A crane removes the
square tops so the catalyst can be replaced. The cases may be round.