GB509987A - Process for the treatment of mixtures of urea, water, carbon dioxide and ammonia, produced in the course of the manufacture of urea - Google Patents

Abstract

509,987. Drying gaseous mixtures. COMPAGNIE DE PRODUITS CHIMIQUES ET ELECTROMETALLURGIQUES, ALAIS, FROGES, ET CAMARGUE. Dec. 2, 1938, No. 35167. Convention date, Jan. 6. [Class 34 (i)] [Also in Group IV] Mixtures of urea,.water, carbon dioxide, and ammonia produced in the manufacture of urea in an autoclave, are treated under pressure in a rectifying column to reduce their water content as far as possible, part of the concentrated urea solution flowing from the bottom of that column being lifted to the top thereof by pumps or, if desired, by utilizing an injector or mixing cone, actuated by the reaction mixture flowing under pressure from the urea synthesis autoclave. In this way blockage of the column or the formation of deposits therein is minimized, and, especially when using a column fitted with rings, better contact is obtained between gases and liquid so that the water concentration of the gases leaving the rectifying column approaches closer to theoretical figures. Carbon dioxide and ammonia from other sources may be absorbed in water and the resulting solution redistilled in an auxiliary column under a pressure equal to or greater than that of the rectifying column, the wet gases from the auxiliary column then being introduced at the bottom-of the rectifying column to be dehydrated together with the gases from the urea synthesis. In this way fresh carbon dioxide and ammonia may be introduced into the urea circuit to replace that converted into urea. The gas mixture dehydrated according to the invention may be used to prepare a suspension of carbamate or carbonate of ammonia in an inert liquid, the suspension then being heated to 160-200‹ C. and pumped back into the autoclave at 100- 250 atmospheres pressure.