| 摘要 |
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).
|
