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Concept
Ammonia production
Résumé
Ammonia production takes place worldwide, mostly in large-scale manufacturing plants that produce 235 million tonnes of ammonia (2021) annually. Leading producers are China (31.9%), Russia (8.7%), India (7.5%), and the United States (7.1%). 80% or more of ammonia is used as fertilizer. Ammonia is also used for the production of plastics, fibres, explosives, nitric acid (via the Ostwald process), and intermediates for dyes and pharmaceuticals. The industry contributes 1% to 2% of global CO2.
Before the start of World War I, most ammonia was obtained by the dry distillation of nitrogenous vegetable and animal products; by the reduction of nitrous acid and nitrites with hydrogen; and also by the decomposition of ammonium salts by alkaline hydroxides or by quicklime, the salt most generally used being the chloride (sal-ammoniac).
Frank-Caro process
Adolph Frank and Nikodem Caro found that Nitrogen could be fixed by using the same calcium carbide produced to make acetylene to form calcium-cyanamide, which could then be divided with water to form ammonia.
The method was developed between 1895 and 1899.
CaO + 3C CaC2 + CO
CaC2 + N2 CaCN2 + C
CaCN2 + 3H2O CaCO3 + 2NH3
Birkeland–Eyde process
While not strictly speaking a method of producing ammonia, nitrogen can be fixed by passing it (with oxygen) through an electric spark.
Heating metals such as magnesium in an atmosphere of pure nitrogen produces the nitride, which when combined with water produce the metal hydroxide and ammonia.
Ammonia production depends on plentiful supplies of energy. Sustainable production is possible by using non-polluting methane pyrolysis or generating hydrogen by water electrolysis with renewable energy sources. Thyssenkrupp Uhde Chlorine Engineers expanded its annual production capacity for alkaline water electrolysis to 1 gigawatt of electrolyzer capacity for this purpose.
In a hydrogen economy some hydrogen production could be diverted to feedstock use.
Source officielle
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