Abstract: A process is described, having a low-energy consumption and reduced ammonia consumption for the production of high-purity melamine, through the pyrolysis of urea, and the relative plant.

Abstract: The present invention relates to a tank for the containment of a liquid, preferably a molten salt, said tank being associable to an aspiration pump of said liquid, wherein said tank comprises a bottom from which a lateral wall raises and wherein said aspiration pump requires a minimum level of liquid in said tank for operating, characterized in that it comprises at least an element occupying a volume and placeable inside said tank with at least a portion of said volume arranged at a height, with respect to said bottom, which is lower than said minimum level. The improved tanks of the present invention are suitable as storage tanks for liquids at elevated temperature such as molten salts to be used in heat storage systems in connection with solar power plants.

Abstract: It is described the use of urea containing formaldehyde in a process for the production of melamine by the pyrolysis of urea, which can be applied both to a high-pressure process and to a low-pressure process.

Abstract: The present invention relates to an improved process for the purification of melamine obtained by synthesis from urea which comprises the following steps: a) bringing raw melamine containing impurities of polycondensates and other by-products of the synthesis reaction, into solution, obtaining a solution/suspension in which the insoluble products are dispersed; b) subjecting the solution/suspension thus obtained to treatment to remove the CO2 dissolved, reducing its concentration to values lower than 0.5% by weight; c) treating the solution/suspension obtained in step b), having a content of CO2 lower than 0.5% by weight, with ammonia in a quantity ranging from 1 to 15%, preferably from 3 to 9% by weight, at a temperature ranging from 110 to 180° C., preferably from 130 to 140° C.; d) putting the solution leaving step c) in contact with a solid catalyst, under the same conditions as step c). The present invention also relates to the equipment for effecting said process.

Abstract: A low-energy-consumption process is described for the production of high-purity melamine, through the pyrolysis of urea, by the collection and purification of the melamine in aqueous solution produced in the pyrolysis reactor, and its separation by crystallization. The present invention also relates to the equipment for effecting the above process.

Abstract: The present invention relates to a tank for the containment of a liquid, preferably a molten salt, said tank being associable to an aspiration pump of said liquid, wherein said tank comprises a bottom from which a lateral wall raises and wherein said aspiration pump requires a minimum level of liquid in said tank for operating, characterized in that it comprises at least an element occupying a volume and placeable inside said tank with at least a portion of said volume arranged at a height, with respect to said bottom, which is lower than said minimum level. The improved tanks of the present invention are suitable as storage tanks for liquids at elevated temperature such as molten salts to be used in heat storage systems in connection with solar power plants.

Abstract: The present invention relates to an improved process for the purification of melamine obtained by synthesis from urea which comprises the following steps: a) bringing raw melamine containing impurities of polycondensates and other by-products of the synthesis reaction, into solution, obtaining a solution/suspension in which the insoluble products are dispersed; b) subjecting the solution/suspension thus obtained to treatment to remove the CO2 dissolved, reducing its concentration to values lower than 0.5% by weight; c) treating the solution/suspension obtained in step b), having a content of CO2 lower than 0.5% by weight, with ammonia in a quantity ranging from 1 to 15%, preferably from 3 to 9% by weight, at a temperature ranging from 110 to 180° C., preferably from 130 to 140° C.; d) putting the solution leaving step c) in contact with a solid catalyst, under the same conditions as step c). The present invention also relates to the equipment for effecting said process.

Abstract: A process for the production of high-purity melamine by pyrolysis of urea at high pressure, wherein the liquid phase output from the pyrolysis reactor is sent to a downstream post-reactor, and wherein the anhydrous gaseous phase from the pyrolysis reactor and from the post-reactor are subjected to washing with molten urea for the recovery of the melamine. The purified liquid exiting the post-reactor is treated in a quenching column, in order to eliminate polycondensates, while the quenching column output is cooled. A high purity melamine is then separated by crystallization from a mother liquor, the greater part of which is recycled to the quenching column, thereby enabling a costless recovery of ammonia and melamine. The remaining mother liquor is treated for the separation of oxidized products of pyrolysis and is then sent back to the quenching column, thereby realizing the complete recovery of the melamine.