(69a) Anhydrous Ammonia—Understand What Fire and Explosion Scenarios Are Most Credible and Manage Those Risks

Anhydrous ammonia is one of the largest tonnage chemical commodities produced globally with current production on the order of 175 million mt/yr and growing.

Ammonia’s inherent hazardous characteristics include toxicity, reactivity, corrosivity and flammability.

While ammonia is classified by producers as a flammable gas (GHS Hazard Statement H221: Flammable gas), ammonia fire and explosion incidents have in fact been very rare. Ammonia does not generally represent anywhere near the same magnitude of risk for fires and explosions as is the situation for numerous other flammable commodities. However, there are credible fire and explosion risk scenarios across the production/ transport storage/use chain that need to be managed.

The presentation will include:

• examples of the more credible risk scenarios—those involving ammonia vapor cloud flash fires and vapor cloud explosions (VCEs) in contained or semi-contained spaces,
• some ammonia fire and explosion incident examples and common practices and safeguards to prevent them,
• a discussion of certain types of ammonia fires (e.g., jet fires, pool fires for refrigerated liquid) and explosions (unconfined VCEs) that are NOT generally considered to be credible or likely scenarios, and
• a brief semi-quantitative discussion of certain physical/thermodynamic properties and burning characteristics of ammonia compared with other flammables that help explain the reasons certain scenarios are less credible or not credible.