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Customized process scheme accoding to the specific melamine technology.
Efficient integration to minimize the water recycled to Urea reactor.

A melamine plant is normally integrated with a urea plant for two reasons:

  • urea is the feedstock to make melamine
  • the off gas from melamine synthesis, containing ammonia, CO2 and water cannot be discharge to atmosphere and must to be recycled back to the urea plant

The presents two problems. First, the synthesis loop needs to handle the higher production due to the additional CO2 and ammonia of the melamine off-gases.

The second problem stems from the fact that the melamine off-gases are normally available at a lower pressure than the urea synthesis, so they have to be condensed and pumped up to the synthesis loop pressure. Off-gas condensation requires a given amount of water to keep the ammonia and carbon dioxide in a liquid phase, strictly depending on the off-gas pressure and composition, which in turn varies according to the specific melamine technology. This additional water is thus inevitably recycled to the synthesis loop, reducing the efficiency of the urea synthesis.

The key to any successful melamine integration is to make the most efficient use of the water already present in the urea process so as to minimize the need for additional water for off-gas condensation.

Casale, thanks to its unique experience both as a urea and melamine licensor, can design and supply off-gas condensation and recycle units which are specifically tailored to the actual combination of urea and melamine plant technologies, minimizing the impact on the existing urea plant.

Figure: New MP section dedicated to condensation of off-gases from Eurotecnica melamine plant New MP section dedicated to condensation of off-gases from Eurotecnica melamine plant
Figure: Block diagram of the integration of Lurgi melamine process with a CO2 stripping urea process Block diagram of the integration of Lurgi melamine process with a CO2 stripping urea process