1964 Otsuka Toyo 3146263 Urea synthesis effluent treatment
This invention is valid for a Total recycle urea plant. It describes an improved recirculation section.
After a rectifying step where pure ammonia and carbamate liquid is recycled to the reactor the urea solution still contains some ammonia and carbon dioxide. This invention suggests to further concentrate the urea solution by means of a carrier gas, which can be ammonia/carbon dioxide mixture of pure carbon dioxide gas. After this concentrator the urea solution is cooled and urea crystals are formed.