UAN


 * This article is about the chemical fertilizer solution. For the animal rescue organization, see United Animal Nations.

UAN is a solution of urea and ammonium nitrate in water used as a fertilizer. The combination of urea and ammonium nitrate has an extremely low critical relative humidity (18% at 30°C) and can therefore only be used in liquid fertilizers. The most commonly used grade of these fertilizer solutions is UAN 32.0.0 (32%N), which consists of 45% ammonium nitrate, 35% urea and only 20% water. Other grades are UAN 28, UAN 30 and UAN 18. The solutions are quite corrosive towards mild steel (up to 500 MPY on C1010 steel) and are therefore generally equipped with a corrosion inhibitor to protect tanks, pipelines, nozzles, etc.

Physical and Chemical Characteristics of Urea Ammonium Nitrate Solutions
The solutions contain a remarkably low amount of water and nevertheless have a low salt-out temperature: