Problem No. 1: Foaming in purification and concentration section

The heart of any urea plant is the high pressure synthesis section where the two feeds, ammonia and carbon dioxide, are converted to urea with water as a byproduct. As this conversion reaction is an equilibrium reaction, a purification/recirculation section is needed to separate urea (and water) from the more volatile non converted feeds. Downstream of the recirculation section, urea and water are separated in a concentration/evaporation section (see picture). Under vacuum conditions water is evaporated and the urea melt is concentrated to about 96 or 99.6 wt-% depending on the type of finishing section present.