Urea production process and plant and method for modernizing a urea production plant

摘要

The invention relates to processes and plants for producing urea from ammonia and carbon dioxide and can be used in the chemical industry and in the production of fertilizers. The process of producing urea by synthesizing same from carbon dioxide and ammonia at high temperatures and pressures with the two stage distillation of the synthesis products (at 1.5-2.5 and 0.2-0.5 MPa) and the recirculation of unreacted ammonia and carbon dioxide in the form of an aqueous solution of carbon ammounium salts (CAS) additionally includes a stage for the adiabatic separation of the synthesis products at a pressure of 8-12 MPa followed by distillation at the same pressure in a stream of carbon dioxide representing 40 60% of the total amount thereof introduced into the process; the corresponding plant is additionally provided with the equipment necessary to carry out this stage. The gases isolated during this distillation stage together with a portion of the adiabatic separation gases are subjected to absorption condensation at the same pressure of 8-12 MPa and are returned in the form of a CAS solution for synthesis. The technical result achieved by using the proposed process and plant and by the modernization of a plant for the implementation of the proposed process is an increase in the degree of conversion of the initial reagents in the synthesis zone.