6.06 million pounds in a pile can create it's own reaction over time.
As ammonium nitrate is a salt, both the cation, NH4+, and the anion, NO3-, may take part in chemical reactions.
Solid ammonium nitrate decomposes on heating. At temperatures below ca. 300 C the decomposition is mainly to nitrous oxide and water:
NH4NO3 → N2O + 2H2O
At higher temperatures, the following reaction predominates:
2NH4NO3 → 2N2 + O2 + 4H2O
Both decomposition reactions are exothermic. Consequently, when the mass of ammonium nitrate is greater than the critical mass the decomposition is explosive. Many ammonium nitrate disasters, with loss of lives, have occurred. The brown, red and/or orange colour in an explosion cloud is due to nitrogen dioxide, a secondary reaction product.
so that's really interesting. What would be more devious is if a bad actor planned to have their cargo seized, stored in this facility and for that breakdown to occur in hopes of destroying the Port of Beirut for some future attack we have yet to see.
