| 摘要 |
Method for preparing melamine from urea via a high-pressure process in which solid melamine is obtained by transferring the melamine melt to an expansion vessel where the melamine melt is cooled by incorporated ammonia. Excess ammonia gas is added to the melamine melt to produce a gas/liquid mixture having a mass ratio of at least 0.01. This two-phase mixture is then sprayed via a spraying means into an expansion vessel, the expansion vessel having a n ammonia environment with a reduced ammonia pressure. The melamine melt is cooled and solidified by the expansion and evaporation of the incorporated ammonia to form melamine powder. The melamine melt is thereby directly converted into a melamine powder after which the melamine powder is cooled further and the ammonia pressure is released.
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