Ammonia (NH3, or R-717) in CNTP is a colorless, lighter gas than air (only 9 gases in the atmosphere are lighter than air, with Ammonia being the 5th) and has a very strong odor, which serves as a warning indicating its presence even in very small concentrations (from 5 ppm). Ammonia is a naturally occurring gas in the biological process and is an important part of the
nitrogen on the ground. The volume of ammonia produced by man is equivalent to only 3% of the total amount present in nature (4). In addition, ammonia is highly soluble in water forming a solution known as ammonium hydroxide, or ammonia in Brazil, (NH4OH), commonly used in household cleaning.
Ammonia does not destroy the ozone layer, and because it has a short lifetime in the atmosphere (maximum 15 days), it also does not contribute to the greenhouse effect. Still, due to its excellent thermodynamic properties, ammonia requires less primary energy to produce a certain cooling capacity than almost all other refrigerants, so that the indirect effect of global warming (TEWI) due to the use of energy from the Coal mills (mainly in northern countries) is also one of the lowest available.
Commercially the ammonia is produced from the combination of free nitrogen with hydrogen at high pressure and temperature in the presence of a catalyst. The most used process is the one that uses the Haber-Bosch method, developed in 1913. Anhydrous ammonia is the liquid obtained from pure ammonia gas (99.95%), technically without moisture, and this is the fluid used in the refrigeration cycles.
