2011 Mennen Stamicarbon 7893298 Concentrating aqueous ammonia carbamate stream

The invention relates to a method for concentrating an aqueous ammonium carbamate stream, which has been formed in a process for the preparation of urea, has a pressure between 0.20 MPa and 0.9 MPa, a temperature between 35 °C and 95 °c., and contains at least 25 wt. % H20, comprising: a pressure increase step, in which the aqueous ammonium carbamate stream is increased in pressure to a pressure between 1.0 MPa and 7 MPa; a condensation step, in which the aqueous ammonium carbamate stream is contacted with a gas stream, which has been formed in a process for the preparation of melamine and which consists essentially of NH3, CO2 and optionally H20 and has a lower H20 content than the aqueous ammonium carbamate stream, the gas stream being absorbed in the aqueous ammonium carbamate stream in such a way that a concentrated annnonium carbamate stream is fonned that contains between 15 and 35 wt. % H20; a discharge step, in which the concentrated ammonium carbamate stream is separated and discharged.

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