Urea (NH2CONH2) is of great importance to the agriculture industry as a nitrogen-rich fertiliser.
Urea is made from ammonia and carbon dioxide. Ammonia is synthesised from hydrogen (from natural gas) and nitrogen (from the air). The ammonia and carbon dioxide are fed into the reactor at high pressure and temperature, and the urea is formed in a two step reaction:
2NH3 + CO2 <=>NH2COONH4 (ammonium carbamate)
NH2COONH4 <=> H2O + NH2CONH2 (urea)
The urea contains unreacted NH3 and CO2 and ammonium carbamate. As the pressure is reduced and heat applied the NH2COONH4 decomposes to NH3 and CO2. The ammonia and carbon dioxide are recycled.
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