| 摘要 |
Ammonia synthesis gas containing hydrogen, nitrogen and carbon dioxide is freed from the latter constituent before entering the ammonia synthesis reactor by washing with an aqueous absorbent solution containing ammonia and carbon dioxide at a pressure of at least 150 kg./cm.2 to absorb substantially all of the carbon dioxide, the mol. ratio of ammonia to carbon dioxide in the absorbent being adjusted (e.g. by introduction of ammonia) to give a ratio of between 2 and 3.6 in the absorbate, which is maintained at a urea-synthesizing temperature to form urea. Reference has been directed by the Comptroller to Specification 981,265.ALSO:Urea synthesis in which a raw material gas containing hydrogen, nitrogen and carbon dioxide suitable for use in the synthesis of ammonia is washed with an aqueous absorbent solution containing ammonia and carbon dioxide at a pressure of at least 150 kg./cm.2 to absorb substantially all of the carbon dioxide contained in the said raw material gas, the mol. ratio of ammonia to carbon dioxide in the absorbent being adjusted (e.g. by introduction of ammonia) to give a ratio of between 2 and 3.6 in the absorbate, which is maintained at a urea-synthesizing temperature to form urea. The above absorbent solution may initially contain a minor amount of urea. After urea synthesis unreacted ammonia and carbon dioxide may be distilled from the resulting urea solution and recycled to form fresh absorbent. The raw material gas free from carbon dioxide may be passed to an ammonia synthesis reactor. Reference has been directed by the Comptroller to Specification 981,265. |
