A THERMALLY INTEGRATED METHOD FOR THE PREPARATION OF AMMONIA AND UREA

A thermally integrated ammonia production plant and urea production plant in which the waste process heat in the crude ammonia synthesis gas discharged from the low temperature CO shift converter is fed to heat-using apparatus portions of the urea synthesis plant when the urea synthesis plant is operating under steady state operating conditions, and when the urea synthesis plant is shutdown or is operating under non-steady state operating conditions said crude ammonia synthesis gas is fed to a different heat- using apparatus. Thereafter, the crude ammonia synthesis gas is fed from whichever heat-using apparatus is employed into the CO2-removing apparatus in the ammonia production plant.