Ammonia
Authors: Czuppon T. A. , Knez S. A. , Rovner J. M. 
Published: August 2004

Abstract

Ammonia, NH
3
, a colorless alkaline gas, is lighter than air and possesses a unique, penetrating odor. The synthesis of ammonia directly from hydrogen and nitrogen on a commercial scale was pioneered by Haber and Bosch. Further developments in economical, large‐scale ammonia production for fertilizers have made a significant impact on increases in the world's food supply. The flammable limits of ammonia in air are 16 to 25% by volume; in oxygen the range is 15 to 79%. Such mixtures can explode, although ammonia–air mixtures are quite difficult to ignite. Ammonia is readily absorbed in water to make ammonia liquor. Additional thermodynamic properties may be found in the literature. Considerable heat is evolved during the solution of ammonia in water. Ammonia is an excellent solvent for salts, and has an exceptional capacity to ionize electrolytes. Many organic compounds such as amines, nitro compounds, and aromatic sulfonic acids also dissolve in liquid ammonia. Ammonia is comparatively stable at ordinary temperatures, but decomposes into hydrogen and nitrogen at elevated temperatures. Ammonia reacts readily with a large variety of substances. Oxidation at a high temperature is one of the more important reactions, giving nitrogen and water. The reaction of ammonia and carbon dioxide, giving ammonium carbamate, CH
6
N
2
O
2
, which then decomposes to urea and water, is of major industrial importance. Ammonia is synthesized by the reversible reaction of hydrogen and nitrogen. The energy‐intensive nature of ammonia production and the worldwide energy crisis in the 1970s led to the proposal of new concepts for synthesis gas generation that do not require hydrocarbon feedstock. In the 1980s, however, the prices of oil and natural gas reversed their upward trends. Natural gas discoveries and oil discoveries contributed more feedstock potential for ammonia production. Based on these developments, the foreseeable future sources of ammonia synthesis gas are expected to be mainly from steam‐reforming of natural gas. At the start of the 1990s, almost 70% of the world's ammonia production was based on this source. Ammonia production
per se
is relatively clean compared to other chemical process industries. Synthesis gas generation is the principal area requiring environmental controls. Coal feedstocks present the most serious environmental problems. Reforming of natural gas or naphtha, respectively, constitutes the cleanest synthesis gas generation operations. All fired equipment, whether it be a process furnace or a utility boiler, is also subject to regulation, usually in the form of sulfur and nitrous oxide limitations. Anhydrous ammonia is ordinarily stored in refrigerated tanks at the plant site at

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and atmospheric pressure. Distribution of anhydrous ammonia in the United States is facilitated by pipeline, by water, by rail, and by truck. Ammonia production has worldwide significance; about 85% of the ammonia produced is used for nitrogen fertilizers. As the primary source of fertilizer nitrogen, it is key to solving world food production requirements. The remaining 15% goes into various industrial products such as fibers, animal feeds, explosives, refrigerant, etc. Ammonia is a strong local irritant which also has a corrosive effect on the eyes and the membranes of the pulmonary system. Respiratory protection should be provided for workers exposed to ammonia. Protective clothing such as rubber aprons, boots, gloves, and goggles should be worn when handling ammonia. The search for a high yield alternative energy route to ammonia, in an effort to meet fertilizer demands and conserve natural gas reserve, is a continuing one. Alternate energy sources are being explored in the laboratory for fixing nitrogen as ammonia.