Combustion characteristics review of ammonia-air mixtures
Ammonia as a refrigerant presents both combustion safety concerns and interest regarding disposal in a flare under controlled combustion conditions. These two aspects involve the combustion characteristics of ammonia. The literature was reviewed with the objective of identifying the technical information pertinent to combustion safety and performance as a fuel. Ammonia's flammability limits in air at standard atmospheric conditions are 14.8% (lower flammability limit, LFL) and 33.5% (upper flammability limit, UFL) concentration of ammonia by volume in air. Lower pressures tend to narrow the flammability limits and, as temperature increases, the LFL is decreased. The presence of water vapor was noted to narrow the flammability limits. Ignition energy requirements, burning velocity, and explosion hazards are also reviewed. More information is required to ascertain the effect of ammonia liquid droplets and lubricating oil, both possible components of a release at a refrigeration plant, on the combustion characteristics of ammonia.
Fenton, D. L., Khan, A. S., Kelley, R. D., & Chapman, K. S. (1995). Combustion characteristics review of ammonia-air mixtures. ASHRAE Transactions 101: 476-485.