Treatment of urea synthesis effluent liquor

Claim 1

IN THE METHOD FOR TREATING UREA SYNTHESIS EFFLUENT LIQUOR FORMED IN A UREA SYNTHESIS FROM NH3 AND CO2 USED IN THE MOL RATIO OF 1 MOL OF CO2 FOR 2-6 MOLS OF NH2, AND CONTAINING UREA AND WATER, TO RECOVER FROM THE EFFLUENT LIQUOR UREA AS PRODUCT AND NH3 AND CO2 VALUES FOR REUSE IN THE SYNTHESIS, THE STEPS COMPRISING (A) SUBJECTING SAID UREA SYNTHESIS LIQUOR TO HIGH PRESSURE RECTIFICATION UNDER 10-30 KG./CM.2 IN ORDER TO DISTILOFF A MAJOR PORTION OF THE EXCESS NH3; (B) WASHING NH3 DISCHARGED FROM THE RECTIFICATION STEP TO REMOVE CO2 WITH MOTHER LIQUOR OF THE UREA SYTNTHESIS PRODUCT AND LIQUEFYING THE NH3 THUS FEED FROM CO2 FOR REUSE IN THE UREA SYNTHESIS IN THE FORM OF LIQUID NH3; (C) TREATING THE UREA SYNTHESIS LIQUOR OBTAINED IN STEP (A) IN A CONCENTRATION STEP AT ELEVATED TEMPERATURE AND SUPERATMOSPHERIC PRESSURE WITH A CARRIER GAS SELECTED FROM THE GROUP CONSISTING OF NH3, MIXTURE OF NH3 PLUS CO2, AND CO2, IN ORDER TO REMOVE WATER FROM THIS SYNTHESIS LIQUOR WITHOUT SUBSTANTIAL REMOVAL OF NH3 AND CO2 PRESENT IN SAID LIQUOR; (D) TREATING SAID CARRIER GAS AND WATER RESULTING FROM STEP (C) BY DEHUMIDIFICATION IN ORDER TO REMOVE THEREFROM SUBSTANTIALLY WATER ONLY AND REUSING SAID DEHUMIDIFIED GAS IN STEP (C); (E) COOLING THE SOLUTION RESULTING FROM STEP (C) IN ORDER TO SEPARATE UREA THEREFROM BY CRYSTALLIZATION, WITH SIMULTANEOUS FORMATION OF MOTHER LIQUOR; AND (F) PASSING THE MOTHER LIQUOR THUS OBTAINED TO THE UREA SYNTHESIS, AFTER USING IF FOR ABSORPTION OF CO2 FROM EXCESS NH3 OBTAINED BY SAID HIGH PRESSURE RECTIFICATION.