Abstract: The present invention relates to a method for recycling water in a melamine production process comprising—a wet process comprising the steps of aqueous treatment of a melamine melt from a melamine synthesis plant with an aqueous alkali containing solution and crystallization for producing solid melamine and a triazine containing alkaline mother liquor,—a wastewater treatment process comprising the steps of thermal treatment of said triazine containing alkaline motor liquor, and—a recycling process, whereby at least parts of the thermally treated alkaline mother liquor are being recycled to the wet process.

Abstract: The invention relates to a method for purifying wastewaters of melamine systems. The method is characterized in that triazine-containing wastewater is subjected to a thermal pretreatment stage, whereupon the vapors are condensed from the gas phase of the thermal pretreatment stage, and the liquid phase of the thermal pretreatment stage is subjected to a thermal hydrolysis stage while NH3 is isolated from the obtained liquid phase containing H2O, CO2, and NH3. The inventive method makes it possible to compensate varying wastewater qualities, thus allowing the melamine system and wastewater station to be operated in a constant and safe fashion. Furthermore, the strain on the subsequent thermal hydrolysis stage is relieved with the aid of the thermal pretreatment stage of the inventive method.

Abstract: The present invention relates to a method for recycling water in a melamine production process comprising—a wet process comprising the steps of aqueous treatment of a melamine melt from a melamine synthesis plant with an aqueous alkali containing solution and crystallization for producing solid melamine and a triazine containing alkaline mother liquor,—a wastewater treatment process comprising the steps of thermal treatment of said triazine containing alkaline motor liquor, and—a recycling process, whereby at least parts of the thermally treated alkaline mother liquor are being recycled to the wet process.

Abstract: The invention relates to a method for purifying wastewaters of melamine systems. The method is characterized in that triazine-containing wastewater is subjected to a thermal pretreatment stage, whereupon the vapors are condensed from the gas phase of the thermal pretreatment stage, and the liquid phase of the thermal pretreatment stage is subjected to a thermal hydrolysis stage while NH3 is isolated from the obtained liquid phase containing H2O, CO2, and NH3. The inventive method makes it possible to compensate varying wastewater qualities, thus allowing the melamine system and wastewater station to be operated in a constant and safe fashion. Furthermore, the strain on the subsequent thermal hydrolysis stage is relieved with the aid of the thermal pretreatment stage of the inventive method.

Abstract: The invention relates to a device for thermally purifying waste water, comprising a tank through which waste water can flow. The inventive device is characterized by having at least one flow guiding means for guiding the waste water inside the tank in an essentially meandering manner, and by having at least one heating means inside the tank for regulating a predetermined temperature.

Abstract: A two-stage process is provided for purifying off-gases from a high-pressure melamine plant. In the first stage, the off-gases are contacted with a recirculated urea melt containing melamine precursors and NH3. In the second stage, the off-gases are contacted with a fresh urea melt.

Abstract: The invention relates to a method for producing melem-free melamine by means of aqueous processing of a melted mass of melamine which is obtained using a high-pressure method. According to the inventive method, the melted mass of melamine is quenched by means of an aqueous solution containing alkalis, following the isolation of the off-gases, and is directly transferred into an aqueous alkaline melamine solution, out of which the melamine is then crystallized. The invention thus enables melamine to be obtained, with a melam content of less than 1000 ppm and a melem content of less than 50 ppm. The invention also relates to a quenching agent.