| 摘要 |
Method for preparing melamine from urea via a high-pressure process in which solid melamine is obtained by transferring the melamine melt coming from the reactor to a vessel where the melamine melt is cooled with an evaporating cooling medium. The melamine melt comes from the melamine reactor at a temperature between the melting point of melamine and 450 degree C and is sprayed into a cooling vessel, via spraying means, and cooled by means of an evaporating cooling medium to form melamine powder. The cooling vessel has an ammonia environment with an increased ammonia pressure. The melamine melt is thereby converted into melamine powder having a temperature of between 200 degree C and the solidification point of melamine. The melamine powder is then cooled to a temperature below 200 degree C with the powder mechanically agitated and being cooled directly or indirectly, after which the ammonia pressure is released and, if necessary, the melamine powder is cooled further. |
