Patent ID: 7214795

Claim:
Process for preparing melamine, comprising the steps of: (a) cooling in a first cooling step a melamine synthesis gas to form a melamine slurry and a gaseous mixture containing NH 3 , CO 2 and H 2 O; (b) feeding the gaseous mixture and a flow of liquid NH 3 to an absorption section; (c) contacting the mixture and the flow of liquid NH 3 in the absorption section with each other to form therein gaseous NH 3 and an ammonium carbamate solution; (d) separately discharging a stream of the gaseous NH 3 and a stream of the ammonium carbamate solution from the absorption section, (e) returning one part of the discharged stream of ammonium carbamate solution to the first cooling step; (f) removing from the process a second part of the discharged stream of ammonium carbamate solution, wherein the removed second part of the discharged stream of ammonium carbamate solution comprises CO 2 which is thereby removed from the process; (g) liquefying in a second cooling step a part of the stream of gaseous NH 3 which is discharged from the absorption section according to step (d); and (h) returning to the absorption section the liquefied NH 3 obtained in the second cooling step according to step (g), wherein the quantity by weight of the gaseous NH 3 which is discharged from the absorption section according to step (d) and is liquefied in the second cooling step according to step (g) divided by the quantity by weight of the CO 2 removed from the process by the second part of the discharged ammonium carbamate solution according to step (f) is between 0.01 and 5.