An empirical thermodynamic model for the ammonia—water—carbon dioxide system at urea synthesis conditions

Abstract

Abstract An empirical thermodynamic model for the NH 3 –H 2 OCO 2 system at equilibrium at urea synthesis conditions (140 ≤ T ≤ 200 °C, 50 ≤ P ≤ 250 atm, 2.4 ≤ NH 3 /CO 2 ≤ 6, H 2 O/CO 2 ≤ 0.5) is presented. This model can quantitatively or semi‐quantitatively describe a number of important phenomena in the urea synthesis, such as the bubble‐point and gas—liquid equilibrium conditions and the effect of excess ammonia and water on the conversion to urea in the liquid phase. The model also sheds light on the problem of the conversion to urea at high temperatures ( T > 190–200 °C).