This is part of a continuing series of blog posts discussing
President Obama’s recently signed executive order on “Improving
Chemical Facility Safety and Security” (EO 13650). The other posts in the
series are:
Section 6(c) of the EO requires the EPA and
OSHA to look at adding ‘additional regulated substances and types of hazards’
to their respective chemical safety programs. First and foremost (this is a
response to the West Fertilizer incident after all) would be adding ammonium
nitrate to the list of covered chemicals. Additionally, the Chemical Safety
Board has long advocated the addition of ‘reactive chemical hazards’ to the
coverage of these programs. In this post I’ll look at some of the types of
hazards that this might include.
Reactive
Chemical Hazards
There are a huge variety of known and
potential chemical reactions. Under the wrong circumstances any one of these
reactions could be considered hazardous, either in the products consumed or
produced or the energies consumed or produced. No one advocates expanding the
either the RMP or PSM programs to cover all of these reactions. Only those
reactions that are sufficiently dangerous in their consequences that they pose
an imminent danger to life, limb or property should be considered.
As a general rule the EPA Risk Management
Plan (RMP) program would be best suited to the management of chemical processes
that would have significant off-site consequences if the reactions got out of
control. The OSHA Process Safety Management (PSM) program would address those
that would potentially affect the health and safety of on-site personnel if
they were not properly controlled. Since it is hard to imagine a process that
could have significant off-site consequences without affecting facility
personnel, it seems obvious that the PSM program should cover more chemical
reactions than the RMP program.
I’ll leave for a separate discussion whether
or not these reactions (or some sub-set of the reactions) should be considered
for coverage under the CFATS program.
Defining
the Reactions
One of the reasons that both EPA and OSHA
have been dragging their feet on implementing the CSB recommendation to include
reactive chemical hazards in the RMP and PSM safety programs is the difficulty
in defining exactly what chemical processes or reactions would be covered. Both
programs currently rely on a printed list of chemicals to determine what is
covered and what isn’t. Things won’t be that easy with reactive chemical
hazards.
To see why let’s look at a common class of reactive
chemicals, monomers, and look at how we might determine which ones would be
regulated and which wouldn’t. First, monomers are molecules that react with
similar molecules to form long chains called polymers. Polymers can be made out
of chains of one type monomer or multiple types.
Most polymerization reactions produce heat as
a byproduct of the reaction. With most reactions the higher the temperature the
reaction takes place at, the faster the reaction takes place. Thus, normally
the heat of polymerization increases the rate of polymerization. For all
practical purposes the polymerization reaction continues until all of the
available monomer is consumed in the reaction.
In a commercial polymerization process the
ratio of reactants and solvents, initiators (chemicals that start the polymerization
process) and inhibitors (chemicals that impede the polymerization process) and
reaction conditions of temperature and pressure are all tightly controlled to
produce a specific desired polymer.
Polymerization
Hazard
In an improperly controlled process a number
of things can go wrong to make bad things happen. Most of those ‘bad’ things
are bad in the business sense; off-spec material is produced that must undergo
additional handling and possibly costly disposal. Those consequences are of no
real concern to the PSM or RMP programs.
In some cases, however, dangerous bad things
can happen. For example, when polymerization takes place in a volatile solvent
the improperly controlled heat of reaction can heat the solvent to the boiling
point greatly increasing the pressure in the reaction vessel. If that vessel is
not properly vented, the pressure can increase to the point where the vessel
catastrophically fails in an incident that closely resembles an explosion. If
the solvent is above its flashpoint and there is an ignition source available
near the vessel failure there may be a fire or even an actual explosion that
results. That type of reaction could certainly be of concern to an EPA or OSHA
regulator.
The regulatory definition problem here is
that it is the combination of the monomer and solvent that is dangerous. With a
different solvent, no solvent, or more solvent there might be no way the
reaction could produce enough heat to reach the boiling point. If the boiling
point cannot be reached there is nothing of interest for the EPA or OSHA to
regulate.
Now, you could define a regulatable (made-up
word) polymerization process as any combination of solvent and monomer in a
single container that the heat of polymerization of the available monomer is
sufficient to raise the available solvent to its boiling point. Those are
values that can be reasonably calculated from publicly available data for most
monomers and solvents. Where the information is not publicly available any competent
chemist or chemical engineer or laboratory technician can measure the appropriate
data in a reasonably equipped laboratory.
Other
Reactions
A polymerization reaction is the easiest of
the potentially dangerous chemical reactions to define and it is probably one
of the least violent. To be really dangerous on a catastrophic scale you have
to turn to reactions that not only produce heat but also evolve gasses. A good
example of this type of reaction is the self-accelerating decomposition
reaction (SADR). These reactions typically involve chemical intermediates and
are much more difficult to describe in a concise manner. To see a good
discussion of the hazards involved in this type of reaction see the Chemical
Safety Board’s investigation of the T2
Laboratories explosion.
Establishing a regulatory definition for
these types of reactions will be much more difficult. Relying on a list of
reactions will be of very little use. People using known SADR reactions will
typically be taking appropriate precautions. The newly discovered reactions of
this type are most often described in accident literature.
Expected
Working Group Actions
I will be very surprised if the Working Group
is able to do much more by the November 5th deadline for
the §6(c) requirement to look at reactive chemistries than recommend that
ammonium nitrate be added to the current list PSM and RMP chemicals. Actions beyond
that will be rely on reaction descriptions that will be too controversial to be
able to resolve through just a standard rule making process. They will require
legislative action on a complex technical issue that there is currently no
political consensus to support.
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