Little Bits of History

Oppau Explosion

Posted in History by patriciahysell on September 21, 2015
Oppau explosion

Oppau explosion

September 21, 1921: The Oppau explosion takes place. Oppau today is part of Ludwigshafen, Germany. It is located along the Rhine River in southwestern Germany and remains home of BASF. They are the largest chemical producer in the world and had been founded in 1865. One of their storage silos was the site of the explosion on this day.  Prior to 1911, the plant produced ammonium sulfate as fertilizer. But during World War I, Germany was unable to obtain sulfur due to both war conditions and embargos. So the plant began producing ammonium nitrate as well, possible because the Haber process did not need overseas resources. The Haber or Haber-Bosch process remains in use as an artificial fixation process for producing ammonia.

Ammonium nitrate is far more hygroscopic (attracting water from the environment and holding it) than is ammonium sulfate. The two products mixed together and under the pressure of its own weight, formed on solid mass of plaster-like stuff. The 65 foot high silo was packed solid and the only way to get it out was to use pickaxes. However, if anyone dared enter the silo, they were threatened by being buried in collapsing fertilizer. It was understood at the time that the substance was volatile, but even so, it was decided that small charges of dynamite would be safe. The process had been used safely during World War I.

Tests done in 1919 concluded that the mix, if it was less than 60% nitrate, was unlikely to explode. Tests indicated that mixtures at 50/50, it was stable enough to store in 50,000 tonne lots which was ten times more than the amount involved the explosion. So dynamite was used. There had been an estimated 20,000 firings in an attempt to clear the silo and they were done safely. Since everyone involved in the explosion was killed, it is not clear what went wrong. More recent testing has shown that the theory of less than 60% nitrate is safe is simply wrong. When nitrate is less than 50%, explosions are confined to a small space, but the higher the concentration, the more likely an explosion will take place. Nearby nitrates can be ignited by small explosions and detonate and expand.

BASF had changed the process for making nitrates and the humidity level of the mixture was lowered by nearly half, which lowered the apparent density. Both of these factors increased the explosive potential. The charge fired on this day caused the entire silo to explode. The sound was heard in Munich, almost 200 miles away. Windows were shattered in Heidelberg, 18 miles away, stopping traffic. About 80% of the buildings in Oppau were destroyed and 6,500 people were homeless. About 500-600 were killed and thousands more were injured. Where the silo once stood was a crater 300 x 400 feet and 60 feet deep. There were 450 tonnes of fertilizer in the silo (and 4,500 tonnes in the warehouse). The damages were listed as 321 million Marks at the time, but inflation in Germany was bizarre and it is not possible to convert that to a meaningful number in today’s economy.

If people will bring dynamite into a powder factory, they must expect explosions. – Dorothy L. Sayers

Fertilizer does no good in a heap, but a little spread around works miracles all over. – Percy Ross

Decay is quiet but ghastly, explosion is dramatic and dreadful. There’s not much to choose between the two of them in reality, and most of our lives have sufficient of both. – Anne Roiphe

Two out of every five people on Earth today owe their lives to the higher crop outputs that fertilizer has made possible. – Bill Gates

Also on this day: Yes, Virginia – In 1897, Virginia found out there was a Santa Clause.
Got Milk? – In 1995, the Miracle of the Milk began in India.
Monday Night Changes – In 1970, Monday Night Football premiered.
Ablaze – In 1776, New York City was on fire.
Dead Poet’s Society – In 19 BC, Virgil died.


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