| 摘要 |
1. A process for the purification of melamine, deriving from urea according to a high pressure non-catalytic process, by means of polycondensates and other by-products transformation, which by-products derive from the melamine synthesis, comprising the following steps: -dissolving in water, the raw liquid melamine coming out of the synthesis reactor and containing polycondensates and other melamine synthesis by-products, -subjecting such solution to a treatment capable to remove dissolved CO2, reducing its concentration to a value lower than 0.5%wt, -submitting such raw melamine solution, to the action of ammonia, in an amount of 5 to 25%wt, at a temperature of 100 to 250 degree C and leaving the mixture to react for some minutes, -recovering a solution having polycondensates concentration lower than 1000 ppm, typically less than 100 ppm, characterised in that the reduction of CO2 is obtained by solution stripping with an inert gas, preferably steam. 2. A process for the purification of melamine, deriving from urea, by means of polycondensates and other by-products transformation, which by-products derive from the melamine synthesis according to claim 1, characterised in that CO2 concentration in the solution is reduced to a value lower than 0.2%wt. 3. A process for the purification of melamine, deriving from urea, by means of polycondensates and other by-products transformation, which by-products derive from the melamine synthesis according to claim 1and/or 2, characterised in that NH3 amount utilised in the solution treatment is comprised from 12 to 15% and the treatment temperature is in the range 160 to 180 degree C. 4. A process for the purification of melamine, deriving from urea, by means of polycondensates and other by-products transformation, which by-products derive from the melamine synthesis according to preceding claims, characterised in that the raw melamine solution is obtained by water quenching of the reaction mixture.
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