Posted on 04/20/2013 6:59:56 AM PDT by Sir Napsalot
(snip) What makes ammonium nitrate explosive?
Ammonium nitrate, a common fertiliser additive, is a white crystalline solid at room temperature.
It is stable except when it is contaminated with organic (carbon-based) material.
In practice, it is commonly mixed with fuel oil to form an industrial explosive (called ammonium nitrate/fuel oil, or ANFO) and is widely used in the mining industry.
In the case of the explosion in West, something had to heat the ammonium nitrate in the fertiliser factory to a critical temperature of 300C for it to auto-ignite.
This would need to be either organic contaminants reacting with the ammonium nitrate or a completely separate fire that spread to the ammonium nitrate storage area.
Video evidence confirms a major high temperature fire was burning for some time before the detonation occurred.
At high temperatures, ammonium and nitrogen dioxide are formed when ammonium nitrate breaks down, and can react together to produce massive amounts of heat.
If the heat isn’t dissipated and the reaction rate is allowed to escalate, the reaction will eventually cause detonation.
In West, it would appear all the damage done was caused by the pressure wave generated by the blast rather than toxic gases, though this has not yet been confirmed.
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