Technical Manual - Section 3 (Safety Hazards)

Figure III:2-23 Molecular Sieve Drying and Sweetening
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
The potential exists for fire from a leak or release of feedstock
or product. Sweetening processes use air or oxygen. If excess
oxygen enters these processes, it is possible for a fire to occur
in the settler due to the generation of static electricity, which
acts as the ignition source.
Health
Because these are closed processes, exposures are expected
to be minimal under normal operating conditions. There is a
potential for exposure to hydrogen sulfide, caustic (sodium
hydroxide), spent caustic, spent catalyst (Merox), catalyst
dust and sweetening agents (sodium carbonate and sodium
bicarbonate). Safe work practices and/or appropriate personal
protective equipment may be needed for exposures to
chemicals
and other hazards such as noise and heat, and during process
sampling, inspection, maintenance, and turnaround activities.
UNSATURATED GAS PLANTS
Unsaturated (unsat) gas plants recover light hydrocarbons (C 3
and C 4 olefins) from wet gas streams from the FCC, TCC, and
delayed coker overhead accumulators or fractionation
receivers. In a typical unsat gas plant, the gases are
compressed and treated with amine to remove hydrogen
sulfide either before or after they are sent to a fractionating
absorber where they are mixed into a concurrent flow of
debutanized gasoline. The light fractions are separated by
heat in a reboiler, the offgas is sent to a sponge absorber, and
the bottoms are sent to a debutanizer. A portion of the
debutanized hydrocarbon is recycled, with the balance sent to
the splitter for separation. The overhead gases go to a
depropanizer for use as alkylation unit feedstock.
III:2-43