Dsm N.v.

Julius G Van Wijck

Jozef Hubert Meessen

Cornelis G Van De Moesdijk

Johan J Thoelen

In the present process for the preparation of urea, an off-gas stream released during the synthesis of melamine in a high-pressure melamine process which consists predominantly of ammonia and carbon dioxide, is introduced into at least one high-pressure section of a urea stripping plant and is used in the synthesis of urea. The off-gas stream can be used directly without any further treatment.

Process for the preparation of urea

Process for the preparation of urea, in which the gas stream which is released during the synthesis of melamine and is composed essentially of ammonia and carbon dioxide is used to synthesize urea, in which process the gas stream which originates from a high-pressure melamine process and is composed essentially of ammonia and carbon dioxide is condensed at a pressure virtually equal to the pressure in the melamine reactor, in which process substantially anhydrous ammonium carbamate is formed, after which said ammonium carbamate is fed to a high-pressure section of a urea stripping plant.

Process for preparing urea

Disclosed is an improved method for separating impurities from a hot synthesis gas mixture which is obtained in the preparation of melamine and urea. The improved separation is achieved by use of filters made of sintered, essentially pure chromium, molybdenum, tungsten, or a mixture of any of these elements.

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Maastricht, Netherlands

Julius G Van Wijck