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Fertilizer (Ammonium Nitrate) Plant Explosion - Iowa

An ammonium nitrate plant exploded in December 1994 outside of Sioux City, Iowa. There were four deaths and many injuries. The explosion originated in the neutralizer where nitric acid and ammonia gas were mixed to form ammonium nitrate. A main issue in this case was whether or not a titanium sparger for the nitric acid catalyzed the explosion inside the sparger. Research showed that this was not the case and that the general conditions inside the neutralizer were ripe for explosion. 

Cut Cross Section of Neutralizer

Conditions contributing to the explosion were impurities known to sensitize ammonium nitrate (such as chlorides and organics), the use of high temperature steam (200 psig), and the lack of standard operating procedures. The plant automated control system records showed that a macroscopic event began at least 2 minutes prior to the explosion which was inconsistent with a sudden detonation originating inside the sparger.  Evidence also showed that the explosion originated below the sparger as opposed to inside it.

Dr. Fox is a nationally recognized metallurgy expert, corrosion expert and failure analysis expert who has published numerous peer-reviewed, scientific papers in these fields. He worked for years as a bench scientist and a research manager in the fields of corrosion, metallurgy and failure analysis of materials in nuclear reactors.