Heat recovery in urea synthesis process

Claim 1

IN THE PROCESS OF PRODUCING UREA COMPRISING REACTING AMMONIA WITH CARBON DIOXIDE IN AT LEAST THE MOL RATIO OF 2:1 AT PRESSURES IN THE RANGE OF 2000-4500 P.S.I.G. AND AT TEMPERATURES IN THE RANGE OF 320*F.-392%F. TO FORM A SOLUTION CONTAINING UREA, AMMONIUM CARBANATE, AMMONIA AND WATER, PASSING SAID SOLUTION TO A HIGHER PRESSURE CARBANATE DECOMPOSITION BEING OPERATED AT PRESSURES IN THE RANGE OF 200 TO 400 P.S.I.G., AND TEMPERATURES IN THE RANGE OF 240*-300*F., WHEREIN A PORTION OF THE AMMONIUM CARBONATE IS DECOMPOSED TO YIELD A GAS PHASE COMPRISING CARBON DIOXIDE AND AMMONIA AND A LIQUID PHASE, SEPARATING A GAS PHASE FROM THE LIQUID PHASE, PASSING SAID SOLUTION TO A SECOND CARBANATE DECOMPOSITION STEP BEING OPERATED AT PRESSURES BELOW 50 P.S.I.G. AND TEMPERATURE IN THE RANGE OF 150*-230*F., WHEREIN SUBSTANTIALLY ALL THE REMAINING AMMONIUM CARBANATE IS DECOMPOSED TO CARBON DIOXIDE AND AMMONIA, THEREAFTER SEPARATELY RECOVERING THE THUS PURIFIED UREA SOLUTION; THE IMPROVEMENT IN COMBINATION THEREWITH WHICH COMPRISES ABSORBING THE GAS MIXTURE DERIVED FROM THE HIGH PRESSURE DECOMPOSITION OF AMMONIUM CARBAMATE IN AN AQUEOUS ABSORBENT SOLUTION WHILE IN INDIRECT HEAT EXCHANGE RELATIONSHIP WITH THE AMMONIUM CARBAMATE BEING DECOMPOSED AT A PRESSURE BELOW 5.S.I.G., THEREBY PRODUCING SUFFICIENT HEAT TO DECOMPOSE THE AMMONIUM CARBAMATE AT THE LOWER PRESSURE.