Patent ID: 6579980
Filing Date: 2003-06-17
Classification: C07D

Abstract:
A method for preparing melamine having high purity from a melamine melt, said method comprising:introducing melamine melt at a temperature of from the melting point of melamine to 450Â° C. into an injection vessel; introducing a quantity of ammonia into the injection vessel in an amount which is in excess of the equilibrium saturation amount relative to the molten melamine to thereby form a two-phase gas/liquid mixture wherein ammonia is present in the mixture dissolved in the melamine melt and in the form of gas bubbles, the gas/liquid mixture having a gas/liquid mass ratio of from 0.01 to 1.0, and spraying the two-phase gas/liquid mixture into an expansion vessel having an ammonia atmosphere at a lower pressure than the pressure in the injection vessel but above atmospheric pressure, whereby directly causing the gaseous ammonia in the mixture to expand and evaporate and thereby cooling and solidifying the liquid melamine without requiring additional or external cooling.