| 摘要 |
Melamine is recovered from a hot gas mixture containing also ammonia and carbon dioxide (e.g. obtained in the catalytic reaction of ammonia with urea or a thermol decomposition product thereof at 300-450 DEG C.) by contacting the hot gas with a substantially constant volume of water in a cooling zone, the water becoming saturated with ammonia and carbon dioxide, discharging melamine from the cooling zone, separately discharging the remaining gas, containing at least 90% of the ammonia originally present; and making up water lost by evaporation or entrainment. The gas mixture may be cooled in two stages, first cocurrent with the coolant and then countercurrent. Ammonia separated from the gas mixture after recovery of melamine may be recycled to the melamine production zone. |
