Urea synthesis with recycle of condensate - from carbamate decomposition to a separate reaction zone in thermal contact with main synthesis zone

摘要

In the prepn. of urea (I) from NH3 and CO2 with recycle of condensate from carbamate decomposition to the reactor with excess NH3, the synthesis gas with excess recycled NH3 is introduced into a first reaction zone, while the condensate with excess NH3 is introduced into a second zone. Both zones are sepd. by a heat-exchanger surface. Pref. the NH3:CO2 mole ratio is 2.5-5 in the first zone and 3.5-8 in the second. Both zones can operate at the same pressure, pref. 100-250 atm., or the first is at a pressure up to 200 atm. higher. Better yields and improved heat economy, even when using relatively low temp. and pressure, are obtd.