Ammonia flammability limits

Preeautions also have to be instituted to proteet against the inherent properties of the eylinder eontents, e.g. toxie, eorrosive, flammable (refer to Table 9.1). Most gases are denser than air eommon exeeptions inelude aeetylene, ammonia, helium, hydrogen and methane. Even these may on eseape be mueh eooler than ambient air and therefore slump initially. Eventually the gas will rise and aeeumulate at high levels unless ventilated. Hydrogen and aeetylene, whieh both have very wide flammable limits (Table 6.1), ean form explosive atmospheres in this way. 

Moist ammonia attacks copper, tin, zinc and their alloys. Ammonia is also flammable with flammability limits of 15-28%. 

Fire Hazards - Flash Point Not pertinent Flammable Limits in Air (%) Not pertinent Fire Extinguishing Agents Water Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards of Combustion Products Toxic ammonia gas will form in fires Behavior in Fire Decomposes, but reaction is not explosive. Ammonia gas is formed Ignition Temperature Not pertinent Electrical Hazard Not pertinent Burning Rate Not pertinent. 

Ammonia bums in air with difficulty, the flammable limits being 16-25 vol%. Normal combustion yields nitrogen but, in the presence of a Pt or Pt/Rh catalyst at 750-900°C, the reaction proceeds further to give the thermodynamically less-favoured products NO and NO2 ... 

Checkel, M. D. et al., J. Loss Prevention, 1995, 8(4), 215 Flammability limits of mixtures of nitric oxide and ammonia were studied. The limits are 15-70% ammonia tenfold pressure rise and explosion are possible. Introduction of oxygen into flammable compositions will produce autoignition, via nitrogen dioxide formation, contamination with air might. 

The data presented in Table El are for fuel gases and vapors and are taken almost exclusively from Zabetakis. [IJS Bur. Mines Bull. 627 (1965)]. The conditions are for the fuel-air mixture at 25°C and 1 atm unless otherwise specified. As noted in the text, most fuels have a rich limit at approximately = 3.3 and a lean limit at approximately = 0.5. The fuels which vary most from the rich limit are those that are either very tightly bound as ammonia is or which can decompose as hydrazine or any monopropellant does. Additional sources of flammability limit data can be found in the Ignition Handbook by Babrauskas (Fire Science Publishers, Issaquah, WA, 2003) and from Kuchta [1/5 Bur. Mines Bull. 680 (1985)]. 

Ammonia, Anhydrous — Fire Hazards Flash Point (deg. F) Not flammable under condition likely to be encountered Flammable Limits in Air (%) 15.50 - 27.00 Fire Extinguishing Agents ... 

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