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Document Type and Number:
WIPO Patent Application WO/2018/168573
Kind Code:
When recovering and utilizing the urea and NH3 contained in a gas that contains urea dust and NH3 and has been discharged from a urea granulation step, an aqueous urea solution to be fed to the urea granulation step is prevented from suffering the precipitation of an ammonium salt while inhibiting the solution from increasing in water content. The method for granulating urea comprises: a granulation step in which granular solid urea is produced from a feed aqueous urea solution using air, a recovery step in which urea dust and NH3 are recovered, using an acid-containing aqueous solution, from the air discharged from the granulation step, thereby obtaining a recovery liquid containing urea and an ammonium salt, a salt concentration regulation step in which an aqueous urea solution having a lower ammonium salt concentration than the recovery liquid is mixed with the recovery liquid to regulate the ammonium salt concentration in the recovery liquid, a concentration step in which water contained in the liquid obtained in the salt concentration regulation step is vaporized to concentrate the liquid obtained in the salt concentration regulation step, thereby obtaining a concentrated recovery liquid, and a mixing step in which the concentrated recovery liquid is mixed with the feed aqueous urea solution, the concentrated recovery liquid being regulated so as to have an ammonium salt concentration of 7 mass% or less.

NAKAMURA Shuhei (8-1 Akanehama 2-chome, Narashino-sh, Chiba 24, 〒2750024, JP)
USHIFUSA Akiko (8-1 Akanehama 2-chome, Narashino-sh, Chiba 24, 〒2750024, JP)
SASAKI Keigo (8-1 Akanehama 2-chome, Narashino-sh, Chiba 24, 〒2750024, JP)
Application Number:
Publication Date:
September 20, 2018
Filing Date:
March 06, 2018
Export Citation:
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TOYO ENGINEERING CORPORATION (5-1 Marunouchi 1-chome, Chiyoda-ku Tokyo, 11, 〒1006511, JP)
International Classes:
C07C273/16; C07C275/00
Domestic Patent References:
Foreign References:
Attorney, Agent or Firm:
MIYAZAKI Teruo et al. (3F Tamachi Square, 26-24 Shiba 5-chome, Minato-k, Tokyo 14, 〒1080014, JP)
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