Melamine Chemicals, Inc.

Dsm N.v.

David E Best

Tjay Tjien Tjioe

Amit Gupta

Roger E Thomas

Process for the preparation of melamine from urea via a high-pressure process in which dry melamine powder is obtained by transferring the melamine melt leaving the reactor to a vessel in which the melamine melt is cooled by means of ammonia characterized in that the melamine melt is sprayed into a cooling vessel and cooled by droplets of evaporating liquid ammonia which is sprayed into the same cooling vessel at a pressure above 0.1 MPa and a temperature between 50&deg; C. and the melting point of the melamine in the cooling vessel.

Process for the preparation of melamine

A high-pressure, non-catalytic process for producing melamine from urea wherein the melamine is recovered directly as a dry powder without washing or recrystallization is described. In the process, liquid melamine is fed to a cooling unit where it is quenched with a liquid medium, preferably liquid ammonia. By increasing the pressure within the cooling unit to a pressure in excess of 600 psi and preferably to 1200 to 1400 psi provides melamine having a purity in excess of 99%.

Melamine of improved purity produced by high-pressure, non-catalytic

This high-pressure, high-temperature anhydrous process prepares melamine from urea. It is a primary object of the present invention to provide a highly energy-efficient and improved continuous process for the production of melamine from urea which utilizes a simplified process to produce and recover a high-grade (96 to 99.5% purity) melamine as a dry powder directly from liquid melamine melt. Molten urea is supplied to a reactor maintained at high temperature (700.degree. to 800.degree. F.) and high pressure (1700 to 2200 psig) whereby melamine, CO.sub.2, and NH.sub.3 are formed. The reactor effluent stream containing liquid melamine, CO.sub.2, and NH.sub.3 is transferred to a gas separator where CO.sub.2 and NH.sub.3 containing melamine are separated and cycled to a scrubber unit for scrubbing with molten urea reactant to remove the melamine before transfer of the CO.sub.2 and NH.sub.3 gases at high pressure to an adjacent urea plant for utilization in producing urea. The melamine liquid product is transferred from the gas separator to a collecting tank maintained at a pressure of less than about 615 psig and from about 120.degree. to 260.degree. F. where the liquid melamine is immediately contacted with, or quenched with a liquid, preferably liquid ammonia. The melamine separates as a dry powder which requires no further processing, having a purity in the range of 96 to 99.5%, useful in applications including fertilizer and resin manufacture. This process is highly cost efficient.

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Prairieville, LA, United States of America

David E Best