Process for the production of melamine

Claim 1

IN A CONTINUOUS PROCESS FOR THE PRODUCTION OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF MELAMINE AND GUANIDINE SULPHAMATE BY REACTING UREA, AMMONIA AND SULPHUR DIOXIDE IN A SYNTHESIS REACTION VESSEL AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 260*C. TO ABOUT 360*C. AND UNDER A SUPERATMOSPHERIC PRESSURE OF AMMONIA, THE IMPROVEMENT WHICH COMPRISES THE STEPS OF CONTINUOUSLY HEATING THE REACTANTS UREA, AMMONIA AND SULPHUR DIOXIDE IN A PRELIMINARY MIXING VESSEL AT A TEMPERATURE BETWEEN 200*C. AND 280*C. FOR A PERIOD OF TIME SUFFICIENT TO REACT SULPHUR DIOXIDE AND AMMONIA AND FORM A FLUID, PRELIMINARY REACTION MIXTURE WHICH COMPRISES UREA, AMMONIA AND AMMONIA-SULPHUR DIOXIDE REACTION COMPOUNDS BUT WHICH IS SUBSTANTIALLY FREE FROM SULPHUR DIOXIDE, CONTINUOUSLY PASSING SAID FLUID PRELIMINARY REACTION MIXTURE FROM SAID PRELIMINARY MIXING VESSEL TO A SYNTHESIS REACTION VESSEL, REACTING SAID FLUID PRELIMINARY REACTION MIXTURE IN SAID SYNTHESIS REACTION VESSEL AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 260*C. TO ABOUT 360*C. AND UNDER A SUPERATMOSPHERIC PRESSURE OF AMMONIA TO PRODUCE A REACTION PRODUCT WHICH CONTAINS A RECOVERABLE AMOUNT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF MELAMINE AND GUANIDINE SULPHAMATE, CONTINUOUSLY DISCHARGING REACTION PRODUCT FROM SAID SYNTHESIS REACTION VESSEL, AND RECOVERING A COMPOUND SELECTED FROM THE GROUP CONSISTING OF MELAMINE AND GUANIDINE SULPHAMATE FROM SAID REACTION PORDUCT.