Casale Sa

Simone Gamba

Enrico Rizzi

Andrea Scotto

Gabriele Di Carlo

A process for the synthesis of melamine including the purification of the offgas released by the synthesis of melamine by means of a first purification stage followed by a second purification stage (); in the first purification stage () the offgas () is contacted with urea melt from the second stage () and with a recirculated urea melt () containing ammonia and melamine precursors (); in the second purification stage () the offgas from the first stage is contacted with fresh urea melt (); said recirculated urea melt is withdrawn from bottom of the first stage and cooled in a shell and tube heat exchanger () to a temperature of not less than 165° C. preferably in the range 165° C. to 245° C. prior to reintroduction in said first stage.

Melamine process with a two-stage purification of melamine offgas

A process for the synthesis of melamine from urea, preferably of the high-pressure type, wherein offgas quenching is performed in a quenching vessel wherein in the upper part of the vessel, a rising flow of offgas is contacted in counter-current with liquid ammonia to obtain precipitation of melamine contained in the offgas and melamine-free anhydrous washed offgas; in the lower part of the vessel, the solid melamine is contacted with a liquid solvent to form a solution of melamine or a melamine slurry.

Process for quenching offgas of melamine synthesis

A process for the purification of a melamine melt () containing melamine and by-products, comprising the steps of: (a1) In quenching of said melamine melt; (a2) decomposition of by-products with alkali, providing an alkaline aqueous solution of melamine (); (b) stripping of said alkaline aqueous solution of melamine (); (c) crystallization of melamine with a first alkali-containing solution () and separation of solid melamine () from a mother liquor (); (d) treatment of said mother liquor, providing a waste water stream () containing carbonates; (e) decomposition of at least part of the carbonates contained in said waste water stream () into carbon dioxide and alkali, providing a second alkali-containing aqueous solution (); (f) recycle of at least part of said alkali-containing aqueous solution () to at least one of said steps (a1), (a2) and (c).

Process for melamine purification

A process for the purification of a melamine melt () containing melamine and by-products, comprising the steps of: (a1) quenching of said melamine melt; (a2) decomposition of by-products with alkali, providing an alkaline aqueous solution of melamine (); (b) stripping of said alkaline aqueous solution of melamine (); (c) crystallization of melamine with a first alkali-containing solution () and separation of solid melamine () from a mother liquor (); (d) treatment of said mother liquor, providing a waste water stream () containing carbonates; (e) decomposition of at least part of the carbonates contained in said waste water stream () into carbon dioxide and alkali, providing a second alkali-containing aqueous solution (); (f) recycle of at least part of said alkali-containing aqueous solution () to at least one of said steps (a1), (a2) and (c).

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Pagazzano, Italy

Simone Gamba