Process for combined production of ammonia and urea

Abstract

A process for the combined production of ammonia and urea of the type comprising an ammonia synthesis reactor ( ), a urea synthesis reactor ( ) and a urea recovery section ( ) stands out for the fact of submitting at least a part of a flow comprising carbamate in aqueous solution coming from the urea recovery section ( ) to a partial decomposition treatment, to obtain a flow comprising ammonia and carbon dioxide in vapor phase and a flow comprising diluted carbamate in aqueous solution, which is fed together with a gas flow comprising hydrogen, nitrogen and carbon dioxide, preferably obtained by hydrocarbons steam reforming, and a flow comprising ammonia coming from the ammonia synthesis reactor ( ) to a carbamate synthesis section ( ), where ammonia and carbon dioxide are caused to react, to obtain a flow comprising carbamate in aqueous solution and a gas flow comprising hydrogen and nitrogen. The flow comprising carbamate in aqueous solution is then sent to the urea synthesis reactor ( ), while the gas flow comprising hydrogen and nitrogen is sent to the ammonia synthesis reactor ( ).