Industrial Accidents Involving Chemical Reactors
A person from one of the major U.S. chemical industries
approached AristaTek and asked whether the PEAC tool could help in the
assessment of run-away chemical reactions or reactor failure in the synthesis of
chemicals. We responded that the PEAC tool was designed primarily for
responders to a chemical accident to give information on protective action
distances in the case of an accidental release, cleanup, protection of
responders and the public, and other safety information, but the PEAC tool is
not designed to address the root causes of the chemical accident (failure due
to runaway temperature or pressure of a chemical reactor).
This question prompted AristaTek to review industrial
accidents investigated by the U.S. Chemical Safety and Hazard Investigation
Board and posted on the Internet. Real-world case studies are often the best
teacher. Several case studies are examined in this newsletter and matched
with PEAC tool information.
U.S. Chemical Safety and Hazard Investigation
The U.S. Chemical Safety and Hazard
Investigation Board (CSB) is an independent federal agency charged with
investigating industrial chemical accidents at fixed facilities. The agency
does not issue fines or citations but does make recommendations to the industry
involved and to regulatory agencies and labor groups. It is designed to
conduct scientific investigations as to the root cause of chemical accidents
and is not an enforcement or regulatory body. Most of the Board members and
staff have degrees in chemical or mechanical or other engineering disciplines,
have PE licenses, have chemical process industry experience, or are health or
safety professionals. Congress in establishing CSB
specifically stated (see 42
U.S.C. section 7412(r )(6)(G)): “No part of the conclusions, findings, or
recommendations of CSB relating to any chemical incident may be admitted as
evidence or used in any action or suit for damages arising out of any matter
mentioned in an investigation report”.
CSB was authorized by the Clean Air Act Amendments of 1990,
but did not become operational until 1998. More on the mission statement and
history can be found at
In 2002, CSB issued a study identifying 167 serious reactive
chemical accidents in the United States between 1980 and 2001 that involved
more than 100 fatalities collectively. Since 2001, CSB has tracked another two
dozen reactive chemical accidents.
A thorough CSB investigation of an industrial accident can
take several months, even sometimes over a year because of the complexity of
the situation. First responders coming on scene of an accident only have
limited information as to what is happening.
Example: April 2004 Toxic Allyl Alcohol Release Dalton Georgia
Information from several CSB
On 12 April 2004, MFG Chemical, Inc., at their facility in Dalton, Georgia, begin their first-ever production batch of triallyl cyanurate (TAC) in a
2000-gallon chemical reactor. Triallyl cyanurate is an intermediate chemical
used in the production of resins, plastics, coatings, and adhesives. The major
starting chemical used in the reactor is allyl alcohol. Allyl alcohol reacts
with cyanuric chloride in the presence of a catalyst generating TAC and
hydrogen chloride. Tests on TAC production had been carried out in the
laboratory and small batch reactors, but this was the first time in a large
production reactor. The reaction for TAC production generates considerable
heat; if the heat is not removed quickly enough from the reactor, the reaction
can self-accelerate or “run away”. This happened with the production reactor at
9:30PM; operators did not take into account that the heat could not be removed
as quickly from the 2000-gallon reactor compared with the small batch reactor.
The reactor pressure built up bursting 20 inch diameter manway gasket followed
quickly by failure of a rupture disk at 75 psig. The result was allyl alcohol
and possibly some hydrogen chloride released as a vapor cloud to the
atmosphere. No TAC or cyanuric chloride was released. The MFG crew evacuated
and called 911 within minutes. At 14 minutes into the event, residents called
in complaining of the odor. After 9 hours into the event, MFG successfully
knocked down the escaping vapor cloud using an overhead water spray. At 16.5
hours, the reactor was sealed.
More than 100 families and businesses were evacuated because
of the toxic allyl alcohol vapor cloud. Some 154 people were decontaminated
and evaluated at a local hospital. Contaminated water runoff from the
facility killed fish and other aquatic life in two creeks. Vegetation was chemically
burned up to 0.5 miles downwind of the facility.
CSB Chairman Carolyn Merritt said, “ This is yet another
serious industrial accident that endangered the public and resulted from an
uncontrolled chemical reaction. It is vital that chemical operators properly
assess the hazards of reactive processes and put appropriate safeguards and
emergency plans in place”. CSB investigators also noted that the MFG
emergency plan for the 31,000 pounds of allyl chloride stored at the site
addressed only flammability and not toxicity. Fire and police departments
responding to the scene lacked appropriate protective equipment, and 13 police
officers were affected by vapors. Another four ambulance crew workers were
sickened from exposure forcing withdrawal and inability to treat injured
The following slides were presented by CSB at a public
community meeting held on 16 November 2004 in Dalton, Georgia: The entire slide presentation is available at
Figure 1, top left: 2000 gallon reactor, with roof and
Top, right: rupture disk and manway gasket location as seen
from mezzanine floor
Bottom: Projected allyl vapor cloud 14 minutes after
release based on resident complaints of odor; emergency responders quickly came
to the site but drove through the vapor cloud to get there
What can the PEAC tool do?
The PEAC tool is
designed for emergency responders. The PEAC tool does not contain information
on run-away chemical reactions which might potentially happen during
synthesis. It is still the job of industry to inform emergency responders
what chemicals are stored or used on the facilities and provide an off-site
consequence analysis of accidents which may potentially happen, and do this
ahead of time. Under allyl alcohol, the PEAC tool displays the image shown
at the left, below. The user can also model the downwind plume cloud; the
PEAC tool asks the user information on the meteorology and amount or container
size released and a level of concern, and the PEAC tool calculates a downwind
protective action distance (example, below right).
The information contained in the 2004 Emergency Response
Guidebook (ERG) is also in the PEAC tool. The ERG is intended for use in
transportation accidents and not runaway chemical reactions which might occur
during synthesis. Nevertheless, there is still some useful information in the
ERG. The information under Guide 131 is displayed below.
displayed for sake of briefness; words in color can be selected to get
definitions or additional information)
One thing jumps out. The NFPA Hazmat diamond gives allyl
alcohol a “4” rating for a health hazard… deadly
. Some reference sources
might give allyl alcohol a “3” rating instead of a “4” rating. Toxic effects
of allyl alcohol include severe eye and respiratory irritation. There may be
lung, liver, and kidney complications for prolonged exposure. The toxic
effects of allyl alcohol are in the public domain at the government Toxicology
Data Network (Hazardous Substance Data Base) , available on the Internet at
The Immediately Dangerous to Life and Health (IDLH)
concentration in air is 20 parts per million (ppm). This is the Level of
Concern used in the PEAC tool example displayed, but the user can use other
levels of concern. Allyl alcohol has an irritating odor somewhat like
mustard. The map drawn by CSB was based on resident complaints and interviews
of residents after the event. The limits of odor detection varies between
individuals, but the Hazardous Substance Data Base list the limit of odor
detection as 0.78 ppm. The boundaries drawn in the CSB diagram for the toxic
cloud probably are closer to 10 or 20 ppm (based on the complaints) rather than
the limit of odor detection.
The normal boiling point of allyl alcohol is 208o
The rupture disk failed at 75 psig. This means that the temperature inside
the reactor at the time of rupture must have been considerably greater than the
normal boiling point. When the pressure is released, the allyl alcohol would
escape to the air as vapor and form a vapor cloud. There would be an
instantaneous release of vapor followed by a continuous and declining release
of more vapor. The vapor density is 2, which suggests that the vapor cloud
should tend to hug the ground at least away from the reactor after it cools.
The other components used in the reactor can be pulled up in
the PEAC tool and can be seen to have much higher boiling points (except
hydrogen chloride). CSB concluded that the other chemicals were not released
in any significant quantity based on the higher boiling points.
Vapor clouds from transportation accidents do not consider
fixed chemical reactors. In the case of allyl alcohol, the assumption is made
that a storage tank or drum is spilled, forms a liquid pool of chemical, and
this evaporates forming a toxic cloud. Therefore the protective action distance
(PAD) for a given amount of chemical would be less than if it were released all
as once as a vapor.
Fortunately, in the case of this accident there was no vapor
cloud explosion or fire. The lower explosive limit for allyl chloride is 2.5%
The best way of modeling the reactor release is to assume a
reasonable mass and treat as if it were released instantaneously. This
requires information that an emergency responder would not know but is better
answered by the industry operating the reactor, with various scenarios worked
out in advance.
Example: Phenol-Formaldehyde Runaway Reactions
Information from “How to
Prevent Runaway Reactions. Case Study: Phenol-Formaldehyde Reaction Hazards”.
EPA document 550-F99-004. August 1999. available from
The U.S. Environmental Protection Agency (EPA) examined
seven phenol-formaldehyde runaway reaction incidents resulting in explosions or
chemical releases at different industrial facilities between 1989 and 1997.
An example is an 8000-gallon reactor explosion at the Georgia-Pacific Resins,
Inc. facility in Columbus, Ohio, at 10:42 AM on 10 September 1997. The
accident was investigated jointly by EPA and the Occupational Safety and Health
Administration (OSHA) under a 1997 Memorandum of Understanding [CSB did not
become operational until 1998].
The phenol and formaldehyde chemicals are mixed in a reactor
in the presence of a catalyst to form a phenolic resin product. Phenolic
resins are used in adhesives, coatings, and molding products. There may be
variations in the starting chemicals and catalyst used by industry to make
these resin products; for example a substituted phenol or a different aldehyde
than formaldehyde might be used to get a different resin, or methanol might be
used. All of these reactions are exothermic, that is, they give off heat. Not
only do they give off heat, but the heat increases the rate of reaction which
in turn generates more heat. If there is no intervention, a very large amount
of heat will be generated within a short time. The heat generated evaporates
the liquid causing pressure to build up in the reactor. The excess heat is
normally removed by a combination of a reactor cooling jacket and by removing
the vapor/gases produced, condensing them in an external condenser, and
returning the liquid to the reactor (reflux cooling). Typically, the reactor
also contains rupture disc(s) for emergency relief. If the procedure is not
carried out properly, too much heat will be generated in a short time resulting
in a sudden build up of pressure. The result may be either a reactor tank
explosion or a release of toxic chemicals from the reactor, and possible vapor
cloud explosion and fire.
The reactor explosion at the Georgia-Pacific Resin facility
on 10 September 1997 in Columbus, Ohio, killed one worker and injured four
others. The blast was reported in the local paper (Dispatch
11, 1997) to be felt at least 2 miles away and heard possibly 7 miles away.
The explosion extensively damaged the plant. The reactor rupture also
resulted in the release of a large quantity of liquid resin, phenol, and
formaldehyde requiring the evacuation from homes, businesses, and a vocational
school within a ¾ mile radius. Three fire fighters were injured and treated
for first-degree chemical burns.
The EPA-OSHA investigation revealed that contrary to
Standard Operating Procedure (SOP) the operator charged the raw chemicals to
the reactor at once and turned on the steam to initiate the reaction. A high
temperature alarm sounded and the operator turned off the steam. Shortly
after, the top of the reactor blew and the sides of the reactor split killing
the operator and injuring four other workers. The top landed 400 feet away.
The reactor had heated up too fast resulting in a sudden increase in pressure
overwhelming the safety release devices and the reflux cooling system.
The EPA publication did not publish the SOP used at
Georgia-Pacific Resins, Inc., but stated that the information is in the public
domain [see Kirt-Othmer Encyclopedia of Chemical Technology, Phenolic Resins,
(1966), page 614]. Molten phenol is first placed into the reactor followed by
a precise amount of acid catalyst. The formaldehyde is added slowly either
continuously or as small incremental steps. It is not added all at once as
what was apparently done on September 10.
The EPA report emphasized the need to have clear, easy to
understand SOP and employee safety training. The EPA report also discussed
reactor safety features including implementation of interlocks to eliminate
opportunities of human error in critical manual operations. Also discussed
was the design of emergency relief systems to handle an appropriate worst case
scenario. Also recommended was an evaluation of measures such as a rapid
water or chemical quench for inhibiting a runaway reaction.
What Can the PEAC Tool Do?
Again, the PEAC tool is designed for emergency responders.
The PEAC tool does not contain information on run-away chemical reactions which
might potentially happen during synthesis. It does not contain SOPs for
chemical synthesis. It is still the job of industry to instruct workers on
safety and inform emergency responders what chemicals are stored or used on the
facilities and provide an off-site consequence analysis of accidents which may
potentially happen, and do this ahead of time.
The PEAC tool does provide information on chemicals. The
PEAC tool can help industry provide a consequence analysis in case of a
hazardous release of chemicals [in this case, formaldehyde] to the air. It
can also predict consequences in case of a vapor cloud explosion and
fireball. The PEAC tool is set up to run through different scenarios
rapidly. The PEAC tool can be a valuable instrument in employee safety
training in examining the consequence of accident scenarios involving chemicals
Industrial Accident Investigations and Reports
Investigative Reports on industrial chemical accidents by
the U.S. Chemical Safety and Hazard Investigation Board can be obtained through
Investigative reports from other agencies including that
conducted by foreign governments and by industry can be obtained through the
These reports are in the public domain. The root causes of
accidents are varied. They may include running a fork lift into a chemical
storage tank, overfilling of tanks or process equipment, an unstable explosive
byproduct produced, as well as runaway reactions in reactors, or a fire caused
by an unrelated incident. Each report is interesting and provides valuable
information for prevention and response to accidents.
Industry is required by law to prevent and mitigate
accidental releases of hazardous substances and provide worker training.
Clean Air Act Amendments of 1990, Section 112 ( r): Facilities
have a general duty to prevent and mitigate accidental releases of extremely
Risk Management Program, 40 CFR 68, EPA requirement: Facilities
with listed substances in quantities greater than the threshold planning
quantity must develop a hazard assessment, a prevention program, and an
emergency response program.
Process Safety Management Standard 29 CFR part 1910.119, OSHA
requirement: Facilities with listed substances at or above the threshold
planning quantity are subject to a number of requirements for management of
hazards, including performing a process hazards analysis and maintaining
mechanical integrity of equipment.
The PEAC tool provides (1) information on many chemicals,
(2) aids industry in doing a consequence analysis rapidly for many accidents
which may potentially occur, (3) provide information on personal protective
equipment in case of a chemical release, and (4) cleanup of spills. There is
also capacity in the PEAC tool to add specific information relative to the
chemicals used at a particular facility.