Abstract Melamine is separated from a gaseous mixture containing melamine, ammonia and carbon dioxide by diverting and accelerating the gaseous mixture into a downwardly restricted flow path by means of a gas baffle which is at a temperature above 610 DEG F, and projecting an aqueous liquor transversely into the gaseous mixture below the downwardly restricted flow path, to form a slurry of solid melamine in the aqueous liquor. The gaseous mixture is usually at 650-800 DEG F. and is that obtained in the catalytic conversion of urea to melamine. It is preferred to use an aqueous liquor containing 1-10% by wt. solid melamine which has been used in a previous cooling cycle and which is at 150-170 DEG F. The rapid quenching gives a solid product which is free from the usual melamine contaminants. The process is illustrated by reference to drawings (not shown) of a suitable apparatus.ALSO:An apparatus, which may be used for condensing melamine from a gaseous mixture, comprises a vertical vessel provided with a gas baffle extending across the vessel and having a central aperture, a vertical passage extending downwards from said aperture to define a gas flow path and a projector positioned below said vertical passage to project aqueous liquor transverse to the gas flow path. In a preferred embodiment the vertical vessel is cylindrical, the gas baffle is horizontal and forms a disc with a round aperture, the vertical gas passage is cylindrical and the projector comprises a downwardly converging side wall terminating at a lower outlet disposed below the vertical gas passage, the lower outlet of said wall being defined by a horizontal projection lip. For use in the separation of melamine, the gas baffle is insulated and/or provided with heaters, e.g. electric resistor elements, to maintain the upper surface of the baffle at a temperature above 610 DEG F. The apparatus is described with reference to drawings (not shown).
IN THE PROCESS OF MELAMINE SYNTHESIS FROM UREA WHEREIN VAPORIZED UREA IS CATALYTICALLY CONVERTED AT ELEVATED TEMPERATURE TO FORM A GASEOUS MIXTURE OF MELAMINE, AMMONIA AND CARBON DIOXIDE, SAID GASEOUS MIXTURE IS COOLED BY CONTACT WITH A COLD AQUEOUS LIQUOR STREAM WHEREBY SOLID MELAMINE IS CONDENSED FROM THE GAS PHASE, RESIDUAL MIXED OFF-GAS COMPRISING AMMONIA AND CARBON DIOXIDE IS SEPARATED FROM THE LIQUID SLURRY COMPRISING SOLID MELAMINE IN WARMED AQUEOUS LIQUOR, SAID LIQUID SLURRY IS SEPARATED INTO PRODUCT SOLID MELAMINE AND WARMED AQUEOUS LIQUOR, AND SAID WARMED AQUEOUS LIQUOR IS COOLED AND RECYCLED TO SAID CONTACT WITH GASEOUS MIXTURE, THE IMPROVED METHOD OF QUENCH-COOLING SAID GASEOUS MIXTURE TO FORM PURE SOLID MELAMINE WHICH COMPRISES DIVERTING SAID GASEOUS MIXTURE INTO A DOWNWARDLY RESTRICTED FLOW PATH BY MEANS OF A GAS BAFFLE, THEREBY ACCELERATING SAID GASEOUS MIXTURE SAID GAS BAFFLE BEING AT A TEMPERATURE ABOVE 610*F. WHEREBY SAID GAS STREAM IS MAINTAINED AT A TEMPERATURE ABOVE 610*F. AND CONDENSATION OF SOLID MELAMINE IS PREVENTED, AND TENSVERSELY PROJECTING SAID COLD AQUEOUS LIQUOR STREAM INTO SAID GAWEOUS MIXTURE BELOW SAID GAS BAFFLE THEREBY CONDENSING ALL OF THE MELAMINE INTO THE LIQUID PHASE AS SOLID MELAMINE WITHOUT DEPOSITION OF SOLID MELAMINE ON SAID GAS BAFFLE.
Claim 2
Dependent Claim
200 words
IN THE PROCESS OF MELAMINE SYNTHESIS FROM UREA WHEREIN VAPORIZED UREA IS CATALYTICALLY CONVERTED AT ELEVATED TEMPERATURE TO FORM A GASEOUS MIXTURE OF MELAMINE, AMMONIA AND CARBON DIOXIDE, SAID GASEOUS MIXTURE IS COOLED BY CONTACT WITH A COLD AQUEOUS LIQUOR STREAM WHEREBY SOLID MELAMINE IS CONDENSED FROM THE GAS PHASE, RESIDUAL MIXED OFF-GAS COMPRISING AMMONIA AND CARBON DIOXIDE IS SEPARATED FROM THE LIQUID SLURRY COMPRISING SOLID MELAMINE IN WARMED AQUEOUS LIQUOR, SAID LIQUID SLURRY IS SEPARATED INTO PRODUCT SOLID MELAMINE AND WARMED AQUEOUS LIQUOR, AND SAID WARMED AQUEOUS LIQUOR IS COOLED AND RECYCLED TO SAID CONTACT WITH GASEOUS MIXTURE, THE IMPROVED METHOD OF QUENCH-COOLING SAID GASEOUS MIXTURE TO FORM PURE SOLID MELAMINE WHICH COMPRISES DIVERTING SAID GASEOUS MIXTURE INTO A DOWNWARDLY RESTRICTED FLOW PATH BY MEANS OF A GAS BAFFLE, THEREBY ACCELERATING SAID GASEOUS MIXTURE SAID GAS BAFFLE BEING AT A TEMPERATURE ABOVE 610*F. WHEREBY SAID GAS STREAM IS MAINTAINED AT A TEMPERATURE ABOVE 610*F. AND CONDENSATION OF SOLID MELAMINE IS PREVENTED, AND TENSVERSELY PROJECTING SAID COLD AQUEOUS LIQUOR STREAM INTO SAID GAWEOUS MIXTURE BELOW SAID GAS BAFFLE THEREBY CONDENSING ALL OF THE MELAMINE INTO THE LIQUID PHASE AS SOLID MELAMINE WITHOUT DEPOSITION OF SOLID MELAMINE ON SAID GAS BAFFLE.