Process for the manufacture of urea

摘要

335,421. Naamlooze Vennootschap de Bataafsche Petroleum Maatschappij, (formerly De Bataafsche Petroleum Maatschappij). Nov. 13, 1928, [Convention date]. Manures.-In obtaining urea a suitable ammonia-carbon dioxide compound is mixed with an indifferent high-boiling viscous liquid such as transformer oil and brought under pressure at an elevated temperature with or without the presence of a catalyst. According to an example, carbon dioxide and ammonia are conducted into the viscous oil until a paste is formed containing ammonium carbamate and 50 per cent of oil. The paste is forced into a chamber where a temperature of 150-200‹ C. and a pressure of 100 atmospheres is maintained. The resulting mass of urea, water, unconverted ammonium carbamate and oil is transferred to a distilling apparatus provided with a reflux condenser wherein the unconverted ammonium carbamate is removed as ammonia and carbon dioxide, the heat remaining in the indifferent high-boiling liquid after conversion being utilized. The aqueous solution of urea is then separated from the layer of viscous oil. Alternatively ammonium carbonate or carbamate may be mixed in a paste with the viscous oil and treated as above. Fertilizers can be made by adding additional substances at different stages in the course of the process, for example during the preparation of the paste.