Process for the production of high-purity melamine from the pyrolysis of urea, with optimization of the deammoniation step of the mother liquors
AssigneeEurotecnica Contractors & Engineers S.p.A.
InventorsAlberto DE AMICIS, Giuseppe DI RUOCCO, Roberto SANTUCCI, Alberto Carlo SERRAFERO, Francesca PETRILLO, Matteo RABAIOLI
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Abstract
A process for the production of high-purity melamine from the pyrolysis of urea, with optimization of the deammoniation step of the mother liquors.
Claims5
A process for the production of high-purity melamine with high yields by the pyrolysis of urea carried out at a temperature ranging from 360 to 450° C. and at a pressure higher than 7.0 MPa, comprising recovering ammonia from a stream of mother liquor coming from a liquid/solid separation step of an ammonia aqueous stream containing melamine crystals, wherein said mother liquor stream is treated in a deammoniation section by distilling said stream of mother liquor to obtain:
- a stream comprising NH3 and water, which is recycled to the quench-ammonolysis section (QAL);
- a stream comprising water, CO2 and NH3 which is sent to an off-gas treatment step or recycled directly to a urea plant for the recovery of NH3 and CO2;
- a stream comprising water, OATs and a quantity of NH3 that ranges from 0.1 to 2% by weight with respect to the weight of stream, which is sent to the subsequent section (OE) for the elimination of the OATs,
- said distilling step being carried out in a distillation column with a temperature at the bottom of the column not exceeding 185° C.
An apparatus for recovering ammonia in a melamine production process, said ammonia recovery being carried out on a stream of mother liquor containing melamine crystals coming from a liquid/solid separation step of an aqueous ammonia stream, said apparatus comprising:
- i) a deammoniation section suitable for treating, by means of a distillation column having a temperature at the bottom of the column not exceeding 185° C., a part of the mother liquors coming from the melamine liquid/solid separation section, said deammoniation section being connected to said liquid/solid separation section from which it receives the stream of mother liquor containing melamine crystals and to a quench-ammonolysis section to which it sends a stream containing water and ammonia;
- ii) said deammoniation section also being connected to an OATs elimination section to which it sends a stream containing water, OATs, and a quantity of NH3 which is such as to avoid the precipitation of OATs, said OATs elimination section also being connected to the quench-ammonolysis section to which it sends a liquid phase substantially comprising water.
Dependencies are inferred from the claim text.