This is the rather famous patent of Kaasenbrood, Stamicarbon which describes the CO2 stripper. Urea reactor effluent is treated counter currently with carbon dioxide or any other inert gas in a stripper at high pressure in order to dissociate carbamate and at the same time enable easy condensation without adding water. Preferably this is done at the same pressure as the reactor is operating thus avoiding the necessity of a pump, 150 atm is mentioned as the preferred pressure. A further benefit which is mentioned is that the condensation of strip gasses will produce steam leading to significant reduction is steam consumption to produce urea.
The patent also mentions that stripping with ammonia is possible but not advisable as the ammonia content in the stripped urea solution will be higher and more equipment stages will be needed in the recirculation section.