Low-energy-consumption process for the production of high-purity melamine, through the pyrolysis of urea and relative equipment

摘要

A process for the production of high-purity melamine comprising: a) separating a biphasic liquid-gas effluent product in a pyrolysis reaction of urea in a liquid stream of raw melamine (3) and a first stream of anhydrous off-gas (15); b) putting said liquid stream (3) in contact with a stream of gaseous anhydrous NH 3 (13) and forming a liquid stream of raw melamine impoverished in CO2 (4) and a second stream of anhydrous off-gas (16); c) putting said first and second anhydrous off-gas streams (15,16) in contact with at least one aqueous washing stream (32) and forming an aqueous stream (20) and a stream of damp off-gas (19); d) removing from said aqueous stream (20) at least a part of the CO 2 contained therein, and forming a stream (22) comprising the CO 2 removed and an aqueous stream (21) comprising melamine and impoverished in CO 2 ; e) recovering the melamine contained in said liquid stream (4) and the melamine contained in said aqueous stream (21) through crystallization by cooling, with the formation of a stream (10) of crystallized melamine and a stream (23) of mother liquor. The present invention also relates to the equipment for effecting the above process. img id="iaf01" file="imgaf001.tif" wi="247" he="132" img-content="drawing" img-format="tif"/