Urea synthesis

Claim 1

IN THE PROCESS OF SYNTHESIZING UREA FROM REACTION OF AMMONIA WITH GASEOUS CARBON DIOXIDE UNDER PRESSURE IN THE RANGE OF 100 TO 300 ATMOSPHERES, AT A TEMPERATURE IN THE RANGE OF 140* TO 200*C. AND AT A RESISDENCE TIME OF 5 TO 60 MINUTES TO FORM A UREA MELT WHICH CONTAINS THE UREA, WATER AND AMMONIUM CARBAMATE IN A UREA SYNTHESIS REACTION ZONE AND SUBSEQUENTLY DECOMPOSING SAID AMMONIUM CARBAMATE IN A DECOMPOSING AND STRIPPING ZONE, THE IMPROVEMENT STEPS WHICH COMPRISE: (A) FLOWING THE UREA MELT FROM THE SYNTHESIS REACTION ZONE DOWN THROUGH SAID DECOMPOSING AND STRIPPING ZONE; (B) TRANSFERRING MOST OF THE HEAT RVOLVED IN THE SYNTHESIS REACTION ZONE TO THE UREA MELT FLOWING DOWN THROUGH THE DECOMPOSING AND STRIPPING ZONE, THEREBY CONTROLLING THE TEMPERATURE IN SAID SYNTHESIS REACTION ZONE; (C) CONTACTING THE UREA MELT WITH A COUNTERCURRENT STREAM OF GASEOUS CO2 TO CAUSE DECOMPOSITION OF THE CARBAMATE AND TO STRIP CO2 AND NH3 GAS RELEASED BY DECOMPOSITION OF THE CARBAMATE; (D) PASSING THE COUNTERCURRENT STREAM OF CARBON DIOXIDE CARRYING AMMONIA AND WATER VAPOR FROM THE DECOMPOSITION AND STRIPPING ZONE INTO THE UREA SYNTHESIS REACTION ZONE WHEREIN THE CARBON DIOXIDE REACTS AND CONSUMES AMONIA FEED TO FRM ADDITIONAL UREA MELT; AND (E) MAINTAINING THE DECOMPOSITION AND STRIPPING ZONE AT ESSENTIALLY THE SAME PRESSURE AS THE PRESSURE IN THE SYNTHESIS REACTION ZONE.