Flexible integration of the production of ammonia and urea

Abstract

The process of the present invention which produces the flexible integration for the production of ammonia and urea uses adiabatic reforming of the carbonaceous feedstock such as natural gas. With adiabatic reforming of natural gas, a surplus of carbon dioxide is produced. With adiabatic reforming, substantially pure oxygen and nitrogen may be used which does not involve inert gases such as argon in the system. More importantly, adibatic reforming allows operation at much higher pressure than standard primary reforming, namely, between 700 and 3000 psig. When these pressures are used, the process includes a recycle of the methane and hydrogen from the ammonia synthesis loop to the adiabatic reformer. The process of the present invention uniquely removes the carbon dioxide which is produced by the reforming of the carbonaceous feedstock and treatment by the watergas shift reaction in two independent stages. After the watergas shift, treatment of the ammonia synthesis gases is carried out preferably with a physical solvent, which removes at low cost most of the carbon dioxide. The remaining carbon dioxide is removed by reaction with ammonia, either hot or cold, respectfully leading to the production of ammonium carbamate, or ammonium carbonate. The process of the present invention, further, is characterized by making a significant change in operation upon obtaining the message that the urea plant has to be turned down or shut down for a short period of time.