(Our initial story on the West plant explosion and its
aftermath can be read by clicking here.)
By GAUTAM NAIK
Experts are still trying to pin down the chain of events
that triggered the mammoth explosion at a Texas fertilizer
plant on Wednesday night, but such explosions are unusual
because of the high temperatures required to ignite them.
facility, run by West Fertilizer Co., appears to be a place
where agricultural fertilizer was likely stored, rather than
manufactured. One of the main chemicals at the facility likely
was ammonia -- a colorless, pungent gas that's stored in liquid
form under high pressure in steel containers.
But because ammonia is relatively stable and only
ignites at a temperature of 1562 degrees Fahrenheit, such
events are rare.
"This is pretty new to us," said Kathy Mathers, spokeswoman
for The Fertilizer Institute, or TFI, a US trade association
for the fertilizer industry. "It's not something we are
familiar with in our business."
While nitrogen is found widely in the environment, many plants aren't
especially efficient at using it for growth. Fertilizer
provides nitrogen in a form that's easier for plants to take
Mined minerals such as potash and phosphates are a type of
fertilizer that can be spread. Another fertilizer is ammonia
gas, a combination of nitrogen and hydrogen. In the US, ammonia
gas is often directly injected into the soil.
Nitrogen fertilizers are often made with a century-old
technique known as the Haber-Bosch process. The process takes
nitrogen out of the air and combines it with hydrogen obtained
from natural gas.
When ammonia is heated, it expands. "Traditionally, that's
our concern," said Ford West, president of TFI. "That's why
tanks [that store ammonia] have safety release valves" that get triggered if the
pressure inside rises past a certain point.
It's not clear what occurred at the Texas facility. The fire
which preceded the blast could have heated up the storage tanks
and set off the explosion. For now, though, "that is still
speculation," said Mr. West.
Another fertilizer is ammonium nitrate, which is easy to
spread and often used for specialty crops, fruits and
vegetables. The product is highly combustible but requires a
fuel booster before it can ignite. Ammonium nitrate is also to
make explosive and was the material used in the deadly Oklahoma
City bombing of April 19, 1995.
It is not known if ammonium nitrate was stored at the Texas
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