WINSTON-SALEM, N.C. (WGHP) — If you want to know why fire officials are worried about the raging blaze at a fertilizer plant in Winston-Salem, where ammonium nitrate is stored, you have to look no further than what happened in Beirut, Lebanon, in 2020. Or in Tianjin, China, in 2015. Or in West, Texas, in 2013. Or Oklahoma City in 1995.
You may recall the massive explosion two years ago that killed 218 people near the seaport in Beirut. Some 7,000 were injured, and another 300,000 were displaced from their homes, which is a little more than half the population of Winston-Salem.
That blast on Aug. 5, 2020, was generated by more than 2,700 tons of ammonium nitrate, a chemical compound that officials said was stored improperly. The blast registered as magnitude 3.3 on the Richter scale, and the damage was likened to an earthquake.
In Tianjin, a blast involving 800 tons of ammonium nitrate killed 173 and caused an estimated $1 billion in loss. It occurred when an ammonium nitrate-enhanced blaze escalated and ignited nail polish. About
Timothy McVeigh used 2 tons of ammonium nitrate mixed with fuel oil to blow up a federal building in Oklahoma City in April 1995, killing 168, including 19 children, and injuring 500.
That’s why officials are being so careful with evacuations and school closings in Winston-Salem while the fire rages at Weaver Fertilizer on Cherry Street. They fear such accelerated explosions.
Winston-Salem Fire Chief Trey Mayo addressed questions comparing the situation to what happened in West, where a fertilizer plant containing about 270 tons of ammonium nitrate and 55 tons of anhydrous ammonia, according to a filing the year before, exploded, leaving 5 people dead and hundreds hurt.
According to the Winston-Salem fire chief, there were roughly 500 tons of ammonium nitrate in the Weaver fertilizer plant building and an additional 100 tons in an adjacent rail car, bringing it to 600 tons of the product at the scene of the fire.
Mayo, in answering questions about comparisons to West, said, “We’ve got about a 36-hour window for an explosion to happen. And we’re about 14 hours in. Things just haven’t been quite right yet.”
The blast in West left a crater 90 feet wide and 10 feet deep. Regulators said careless storage of explosive materials contributed to the blast. They said there was bad ventilation and combustible materials nearby. They later said the fire was set by an arsonist. Emergency workers were among those killed, and a nearby school was destroyed.
But nearly 70 years before that, in 1947, Texas City, near the Galveston Bay, also was the site of a massive explosion that was so powerful it was heard 250 miles away. The death count from that explosion has not been detailed, but it’s in the hundreds, many of them had come to the docks to watch the raging blast.
The cause of that explosion? A French freighter had arrived in port with a massive load of ammonium nitrate fertilizer. A small fire had broken out inside the ship, and efforts to extinguish the blaze attracted the onlookers who became victims. The explosion ignited nearby oil storage tanks and a chemical plant.
Ammonium nitrate is used as a fertilizer, an explosive (common in mining) and an oxidizing agent. You would find it in common products marketed by Miracle-Gro or Spectrum or Sunniland.
Scientists say that ammonium nitrate doesn’t burn on its own, that it acts as a source of oxygen that can accelerate the burning of materials around it. Scientific American says that ammonium nitrate provides a more concentrated supply of oxygen than natural air.
At high enough temperatures, however, ammonium nitrate can violently decompose on its own. This process creates gases, including nitrogen oxides and water vapor, and it is the rapid release of gases that causes an explosion.
Its melting point is 338 degrees, and once its temperature has been accelerated to that level by a nearby fire, its decomposition causes its combustibility, wrote Scott G. Davis, the principal engineer for Gexcon, a company that investigates such explosions.
Scientists suggest that smaller amounts can just burn out, but there are about 500 tons of ammonium nitrate in Winston-Salem.