FIELD: production of inorganic compounds. SUBSTANCE: ammonia and carbon dioxide interact in two in-parallel installed reactors to yield purified urea solution and vapors of unreacted ammonia and carbon dioxide. Urea solution from the first reactor is fed into the first urea-isolation unit, while simultaneously condensing unreacted reactants in carbamate condenser. First carbamate decomposition operation is performed in the second reaction mixture obtained in the second reaction space operated at essentially the same pressure as that in carbamate condenser. As a result, additional primary stream of unreacted ammonia and carbon dioxide is separated and recycled into carbamate condenser. Second operation of decomposing carbamate contained in urea stream after the first decomposition operation is performed to give secondary stream of unreacted ammonia and carbon dioxide, which is condensed and recycled into carbamate condenser. Installation comprises: first urea synthesis reactor in the first reaction zone; carbamate condenser installed before urea synthesis reactor; carbon dioxide stripper; first reaction mixture- supply pipeline for carbon dioxide stripper; first urea isolation section; and second urea synthesis reactor installed in parallel to the first one. Installation additionally is provided with second unit for separation of the second reaction mixture produced in the second synthesis reactor, which includes at least first and second in-series installed carbamate decomposition apparatuses. Equipment for unreacted ammonia and carbon dioxide condensation and that for recycling condensate into carbamate condenser is also available. The second urea synthesis reactor is a high-performance periodic-type reactor with partial reaction heat removal. EFFECT: increased yield and quality of product. 21 cl, 3 dwg, 2 ex
