Process for the production of high purity melamine from urea

摘要

The present invention concerns process for obtaining melamine at high purity characterized by comprising the steps of:—quenching a melamine melt, deprived of off-gases of the melamine synthesis and containing melamine impurities such as ammeline, ammelide and polycondensates, with an aqueous solution comprising ammonia under conditions such to substantially convert polycondensates into melamine, obtaining a melamine solution substantially free of polycondensates, recovering melamine from said melamine solution by melamine crystallization, obtaining melamine crystals and a melamine crystallization mother liquor,—treating said crystallization melamine mother liquor under conditions such to convert at least a portion of its ammeline content into ammelide and melammine, obtaining a treated mother liquid having at least a reduced ammeline content. The invention also concerns a high-pressure non-catalytic plant for the production of high-purity melamine implementing the above process and apparatuses suitable to be used in this plant.

主权项

1. A process for obtaining melamine at high purity comprising the steps of:
quenching a melamine melt, deprived of off-gases of the melamine synthesis and containing melamine impurities such as ammeline, ammelide and polycondensates, by mixing said melamine melt with an aqueous solution comprising ammonia under conditions such to substantially convert polycondensates into melamine, obtaining a melamine solution substantially free of polycondensates, recovering melamine from said melamine solution by melamine crystallisation, obtaining melamine crystals and a melamine crystallization mother liquor, thermally treating said crystallization melamine mother liquor by converting at least a portion of the ammeline contained in said melamine crystallization mother liquor into ammelide and melammine, obtaining a treated mother liquid having an ammeline content less than that of said melamine crystallization mother liquor.