Thermophysical Modeling: Why was UREA modified for the MSE model?

The Background

Circa 2009 OLI Systems was asked by one of its customers to model the decomposition of Urea in aqueous solutions. OLI undertook this modeling and created a model. The basic chemistry of urea decomposition is as follows:

Urea: (NH₂)₂CO

Water: H₂O

Ammonium Carbamate: NH₂COONH₂

Ammonia: NH₃

Carbon Dioxide: CO₂

(NH₂)₂CO + H₂O = NH₂COONH₂

NH₂COONH₂ = NH₃ + CO₂

There are several side reactions which OLI attempted to model as well. Two molecules of urea can combine to form a species called biuret with a loss of an ammonia molecule.

Biuret: (CONH₂)₂

The reaction is:

2(NH₂)₂CO = (CONH₂)₂ + NH₃

In addtion, another side reaction is the formation of ammonium cyanate from urea.

Ammonium Cyanate: NH₄OCN

(NH₂)₂CO = NH₄OCN

Finally Ammonia Cyanate decomposes to isocyanic acid and ammonia

Isocyanic Acid: HOCN

NH₄OCN = HOCN + NH₃