Technical Manual - Section 3 (Safety Hazards)

needed to prevent HCl from entering sewers and drains.
Health
Because this is a closed process, exposures are expected to be
minimal during normal operating conditions. There is a
potential for exposure to hydrogen gas, hydrochloric acid,
and hydrogen chloride and to dust when solid catalyst is used.
Safe work practices and/or appropriate personal protective
equipment may be needed for exposures to chemicals and
other hazards such as heat and noise, and during process
sampling, inspection, maintenance, and turnaround activities.
POLYMERIZATION
Polymerization in the petroleum industry is the process of
converting light olefin gases including ethylene, propylene,
and butylene into hydrocarbons of higher molecular weight
and higher octane number that can be used as gasoline
blending stocks. Polymerization combines two or more
identical olefin molecules to form a single molecule with the
same elements in the same proportions as the original
molecules. Polymerization may be accomplished thermally
or in the presence of a catalyst at lower temperatures.
The olefin feedstock is pretreated to remove sulfur and other
undesirable compounds. In the catalytic process the
feedstock is either passed over a solid phosphoric acid
catalyst or comes in contact with liquid phosphoric acid,
where an exothermic polymeric reaction occurs. This reaction
requires cooling water and the injection of cold feedstock into
the reactor to control
temperatures between 300º and 450º F at pressures from 200
psi to 1,200 psi. The reaction products leaving the reactor are
sent to stabilization and/or fractionator systems to separate
saturated and unreacted gases from the polymer gasoline
product.
NOTE: In the petroleum industry, polymerization is used to
indicate the production of gasoline components, hence the
term "polymer" gasoline. Furthermore, it is not essential that
only one type of monomer be involved. If unlike olefin
molecules are combined, the process is referred to as
"copolymerization." Polymerization in the true sense of the
word is normally prevented, and all attempts are made to
terminate the reaction at the dimer or trimer (three monomers
joined together) stage. However, in the petrochemical section
of a refinery, polymerization, which results in the production
of, for instance, polyethylene, is allowed to proceed until
materials of the required high molecular weight have been
produced.
SAFETY AND HEALTH CONSIDERATIONS
Fire Prevention and Protection
Polymerization is a closed process where the potential for a
fire could occur due to leaks or releases reaching a source of
ignition.
Safety
The potential for an uncontrolled exothermic reaction exists
should loss of cooling water occur. Severe corrosion leading
to equipment failure will occur should water make contact
with the phosphoric acid, such as during water washing at
shutdowns. Corrosion may also occur in piping manifolds,
Table III:2-16 POLYMERIZATION PROCESS
Feedstocks From Process Typical products................ To
Olefins Cracking Unification High octane naphtha...........Gasoline blending
processes
Petrochem. feedstocks.........Petrochemical
Liquefied petro. gas............Storage
III:2-37