Here's what we know so
far. In the early morning hours of
Thursday, May 7, workers at a petrochemical plant in the southeastern India coastal
city of Visakhapatnam were trying to restart the plant, which had been shut
down earlier due to lockdown restrictions imposed in connection with the
COVID-19 pandemic. Around 3:30 AM, a gas
leak occurred and spread rapidly throughout the densely-populated area
surrounding the plant. At least 200
people wound up hospitalized, and as of May 8, 13 had died from the effects of
the leak.
The plant is presently owned
by the South Korean firm LG Chem, but was founded in 1961 and has passed
through several changes of ownership since then. Its main output is polystyrene plastic, and
to make polystyrene requires styrene, a benzene-like molecule that is liquid at
room temperature. About 2,000 metric
tons of the monomer were stored onsite in tanks.
A Chevron safety sheet on the
styrene "monomer" (what the molecule is called before it is
polymerized into a chain) emphasizes the main danger from storing it: runaway polymerization. Most polymers have to be forced into
polymerizing, but evidently styrene is an exception: it will polymerize if given half a chance,
and especially at temperatures above about 68 F (20 C). When it polymerizes, it gives off heat, which
makes it polymerize faster, and the resultant heat and pressure buildup can
cause an explosion.
This is why storage tanks of
styrene are normally refrigerated to keep them cooler than 20 C, so that
spontaneous polymerization doesn't happen.
While the exact sequence of events is not yet clear, it appears that a
computer glitch or other problem interfered with the refrigeration of the
styrene tanks. Once the temperature rose
much above 20 C, polymerization in the tanks would have raised the temperature
and pressure, and eventually a safety valve somewhere must have opened, or else
a rupture in the tank or piping occurred.
At any rate, a large amount
of styrene monomer escaped the limits of the plant and must have traveled
hundreds of meters, affecting several villages that have sprung up around the
plant in the sixty or so years since its founding. Styrene, being heavier than air, sticks to
the ground, and in sufficient density it will suffocate you. But lower concentrations than that will still
cause intense respiratory problems and death, as it did for 13 people that
night. Eventually, authorities evacuated
a 3-km-radius area around the plant, but by that time most of the damage had
been done.
While this accident pales in
comparison to the well-known Bhopal tragedy of 1984 in which about half a
million people were exposed to a toxic chemical and thousands died, even one
death of a resident near a chemical plant is unnecessary. What lessons can be learned so far from the
LG Chem plant accident?
A common thread that shows
up in many chemical-plant accidents is that they tend to occur when a plant is
being started up after a shutdown. There
are several reasons why starting up is a dangerous time. Conditions in the system have to be brought
from a low-pressure, low-temperature state to operating pressures and
temperatures without straying into combinations that can be dangerous to
equipment or personnel. This requires
more than typical vigilance from operating personnel, who may not have
experienced that many shutdowns and restarts in their careers. The procedures for starting up a plant can be
much more complex than those required to keep it running, and more mistakes can
be made in a complicated, time-sensitive process than simply one in which your
job is to make sure everything stays the way it is and runs smoothly. Last but not necessarily least, it seems that
a favorite time for doing a startup is after the beginning of the midnight
shift. Whether the implied secrecy of
early morning is appealing in case anything goes wrong, or whether it is simply
a more convenient time with regard to plant schedules, I don't know. But from the viewpoint of sounding an alarm
to the general public if anything goes wrong, the period from late evening to early
morning is the worst possible time to do something that might cause problems to
people outside the plant, who will all be asleep and hard to evacuate in an emergency.
Another factor in this
accident is the presence of densely-populated villages just outside the plant
boundaries. According to one news
report, in 1961 the region where the plant was erected was rural, but with the
subsequent population growth of cities such as Visakhapatnam, that
changed. The permit status of the plant
is reportedly in a legal gray area, which might result from the fact that if
the plant were to be built from scratch today in the same location, it might
not be allowed at all, or at a minimum a large buffer zone would be required
between the active plant and the surrounding populated areas. As is true in most parts of the world, the land
surrounding chemical plants is where you find some of the lowest-priced
housing, and the kind of people who live in low-priced housing are generally
poor people. While they are not happy to
be taking an unknown risk of sudden death or long-term illness by living within
the sights, sounds, and smells of a chemical plant, they may not have much of a
choice.
At last report, an
investigative team from LG Chem's South Korean headquarters was onsite trying
to determine the accident's cause. But
that is little comfort for those who lost loved ones or the hundreds who were
injured in this accident.
Absolute safety in
industrial processes is virtually impossible without exiling plants to an uninhabited
island operated entirely by robots. And
in any case, such an operation would be undercut in cost by operations such as
LG Chem that runs with human beings and in proximity to people who may not know
they are taking a chance every day of their lives just by living close by. In a sovereign nation, the only force that
can generally make sure powerful manufacturing interests don't hurt or kill too
many people is the various branches of government, with perhaps private
insurance companies coming in a distant second.
I hope that this accident teaches all concerned—corporations operating
in India, the government officials responsible for regulation, and the Indian
people—how to do things better next time, and to make it a long time before the
next such accident occurs.
Sources: I relied on
the Wikipedia article " Visakhapatnam gas leak," as well as reports on
the website thehindu.com at https://www.thehindu.com/news/national/andhra-pradesh/visakhapatnam-gas-leak-lg-chem-dispatches-technical-team-from-seoul-for-investigation-rehabilitation-works/article31573936.ece
and https://www.thehindu.com/news/cities/Visakhapatnam/visakhapatnam-lg-polimers-chemical-plant-gas-leak-updates-may-7-2020/article31523178.ece?homepage=true. I also referred to a Chevron safety sheet on
styrene at http://www.cpchem.com/bl/aromatics/en-us/Documents/Safe_Handling_and_Storage_of_Styrene_Monomer.pdf.
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