| 摘要 |
The invention concerns a process for producing pure melamine in which liquid, ammonia-containing melamine is rapidly expanded from an ammonia partial pressure p1 of between 400 and 50 bar to an ammonia partial pressure p2 of between 200 bar and atmospheric pressure at a temperature which is between 0 and 60 DEG C above the fixed point of the melamine which is dependent on the prevailing ammonia partial pressure in each case, higher pressures permitting a greater margin of the temperature from the fixed point of the melamine than lower pressures, and p1 always being greater than p2. As a result thereof, pure melamine is deposited in solid form. Further expansion of the melamine to atmospheric pressure, if necessary, and cooling to room temperature are then carried out in any order and the pure melamine is isolated. |
