Technical Manual - Section 3 (Safety Hazards)

HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
Alkylation units are closed processes; however, the potential
exists for fire should a leak or release occur that allows
product or vapor to reach a source of ignition.
Safety
Sulfuric acid and hydrofluoric acid are potentially hazardous
chemicals. Loss of coolant water, which is needed to
maintain process temperatures, could result in an upset.
Precautions are necessary to ensure that equipment and
materials that have been in contact with acid are handled
carefully and are thoroughly cleaned before they leave the
process area or refinery. Immersion wash vats are often
provided for neutralization of equipment that has come into
contact with hydrofluoric acid. Hydrofluoric acid units should
be thoroughly drained and chemically cleaned prior to
turnarounds and entry to remove all traces of iron fluoride
and hydro-fluoric acid. Following shutdown, where water has
been used the unit should be thoroughly dried before
hydrofluoric acid is introduced.
Leaks, spills, or releases involving hydrofluoric acid or
hydrocarbons containing hydrofluoric acid can be extremely
hazardous. Care during delivery and unloading of acid is
essential. Process unit containment by curbs and drainage and
isolation so that effluent can be neutralized before release to
the sewer system should be considered. Vents can be routed
to soda-ash scrubbers to neutralize hydrogen fluoride gas or
hydrofluoric acid vapors before release. Pressure on the
cooling water and steam side of exchangers should be kept
below the minimum pressure on the acid service side to
prevent water contamination.
Some corrosion and fouling in sulfuric acid units may occur
from the breakdown of sulfuric acid esters or where caustic is
added for neutralization. These esters can be removed by
fresh acid treating and hot-water washing. To prevent
corrosion from
hydrofluoric acid, the acid concentration inside the process
unit should be maintained above 65% and moisture below
4%.
Health
Because this is a closed process, exposures are expected to be
minimal during normal operations. There is a potential for
exposure should leaks, spills, or releases occur. Sulfuric acid
and (particularly) hydrofluoric acid are potentially hazardous
chemicals. Special precautionary emergency preparedness
measures and protection appropriate to the potential hazard
and areas possibly affected need to be provided. Safe work
practices and appropriate skin and respiratory personal
protective equipment are needed for potential exposures to
hydro-fluoric and sulfuric acids during normal operations
such as reading gauges, inspecting, and process sampling, as
well as during emergency response, maintenance, and
turnaround activities. Procedures should be in place to ensure
that protective equipment and clothing worn in hydrofluoric
acid activities are decontaminated and inspected before
reissue. Appropriate personal protection for exposure to heat
and noise also may be required.
SWEETENING AND TREATING
PROCESSES
Treating is a means by which contaminants such as organic
compounds containing sulfur, nitrogen, and oxygen;
dissolved metals and inorganic salts; and soluble salts
dissolved in emulsified water are removed from petroleum
fractions or streams. Petroleum refiners have a choice of
several different treating processes, but the primary purpose
of the majority of them is the elimination of unwanted sulfur
compounds. A variety of intermediate and finished products,
including middle distillates, gasoline, kerosene, jet fuel and
sour gases are dried and sweetened. Sweetening, a major
refinery treatment of gasoline, treats sulfur compounds
(hydrogen sulfide, thiophene and mercaptan) to improve
color, odor and oxidation stability. Sweetening also reduces
concentrations of carbon dioxide.
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