Technical Manual - Section 3 (Safety Hazards)

Table III:2-14 HYDRODESULFURIZATION PROCESS
Feedstocks From Process Typical products......................To
Naphthas, distillates Atmospheric & Treating, Naphtha....................................Catalytic reformer
Sour gas oil, vacuum tower hydrogenation Hydrogen..................................Recycle
Residuals Catalytic & Distillates..................................Blending
thermal cracker
H 2 S, ammonia...........................Sulfur plant, treater
Gas.............................................Gas plant
Safety
Many processes require hydrogen generation to provide for
a continuous supply. Because of the operating temperatures
and presence of hydrogen, the hydrogen sulfide content of the
feedstock must be strictly controlled to a minimum to reduce
corrosion. Hydrogen chloride may form and condense as
hydrochloric acid in the lower-temperature parts of the unit.
Ammonium hydrosulfide may form in high-temperature,
high-pressure units. Excessive contact time and/or
temperature will create coking. Precautions need to be taken
when unloading coked catalyst from the unit to prevent iron
sulfide fires. The coked catalyst should be cooled to below
120 o F before removal,
or dumped into nitrogen-inerted bins where it can be cooled
before further handling. Special antifoam additives may be
used to prevent catalyst poisoning from silicone carryover in
the coker feedstock.
Health
Because this is a closed process, exposures are expected to be
minimal under normal operating conditions. There is a
potential for exposure to hydrogen sulfide or hydrogen gas in
the event of a release, or to ammonia should a sour-water leak
or spill occur. Phenol also may be present if high
boiling-point feedstocks are processed. Safe work practices
and/or appropriate personal protective equipment may be
needed for exposures to
Figure III:2-17 Distillate Hydrodesulffurization
III:2-34