| 摘要 |
The present invention relates to a non-catalytic process for the preparation of melamine comprising: a) reacting molten urea in a reaction section at a pressure of 4.5 to 15 MPa to produce a reaction mixture containing molten melamine and reaction off-gases; b) vaporizing the molten melamine in said reaction mixture in a vaporization section to produce a gaseous mixture comprising the vaporized melamine and the reaction off-gases at a pressure of 4.5 to 15 MPa; c) quenching the gaseous mixture obtained from step b) by contact with an aqueous ammonium carbamate solution; and d) isolating melamine; and to a combined process for the preparation of urea and melamine, wherein melamine is prepared in accordance to the above method wherein at least part of the concentrated aqueous ammonium carbamate solution is transferred to an urea plant as at least part of the feed stock, urea is prepared utilizing said concentrated aqueous carbamate solution and urea obtained from said preparation step is supplied in molten form to the reacting step a).
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