To produce urea from ammonia (NH3) and carbon dioxide (CO2). The process is based on applying Casale’s highly efficient equipment, including:
• Casale full condenser
• Casale-Dente high-efficiency trays
• Casale high efficiency hydrolyzer used in the process condensate treatment unit.
This process is called the Casale split flow loop process, and is an improved CO2 stripping process.
Urea is formed from CO2 (18) and NH3 (19) in the HP loop (1) in a reactor (2) fitted with Casale-Dente high-efficiency trays. The urea solution (3) from the reactor (2), which still contains unreacted NH3 and CO2, is first treated in a stripper (4), operating at the same pressure as the reactor, heated with steam and using CO2 (18) as stripping agents to recover most of the unreacted NH3 and CO2.
The vapor stream (5) (NH3, CO2 and H2O) generated in the stripper, containing all inerts, is split after leaving the high-pressure (HP) stripper (4). One portion of the vapor stream is sent to the HP carbamate condenser (6) (Casale full condenser), while the rest of the vapors bypass the condenser and go directly to the reactor (2).
The Casale full condenser (6) is practically a submerged condenser and the carbamate flow obtained in this equipment is sent to the reactor. From the stripper (4), the urea solution, still containing unreacted NH3 and CO2, is sent to a low-pressure (LP) single decomposition/condensation stage (7a+7b) where practically all of the remaining unreacted NH3 and CO2 is recovered in the form of a carbamate solution (8). The urea-water solution (9), containing only small quantities of NH3 and CO2, is further treated in a vacuum evaporation section (10) to obtain a urea melt (11) for the prilling tower or the granulator.
The process condensate, obtained from the vacuum condensers (12) is purified with two columns and one hydrolyzer (13) to eliminate all NH3, CO2 and urea, thus obtaining the purified water (14). The carbamate solution (15) obtained in the LP section is sent first to the HP scrubber (16), where the inerts (17) leaving the HP loop are washed, and then sent through the Casale full condenser (6) to the reactor (2).
Licensor: Urea Casale SA, Switzerland
