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US 10,894,764 B2Granted
Method for granulating urea
AssigneeToyo Engineering Corporation
InventorsShuhei Nakamura, Akiko Sugiura, Keigo Sasaki
Life of this patent
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Abstract
Precipitation of an ammonium salt is prevented while suppressing an increase in water content of the aqueous urea solution which is to be supplied to a urea granulation step, when recovering and using urea and NH3 in a gas which contains urea dust and NH3 and which arises from a urea granulation step.
Claims8
A method for continuously granulating urea, comprising
- a granulation step of producing granular solid urea from a feed aqueous urea solution by using air, and discharging air containing urea dust and ammonia,
- a recovery step of recovering urea dust and ammonia from air containing urea dust and ammonia discharged from the granulation step, by use of an aqueous solution containing an acid, so as to obtain an aqueous recovered-urea solution which is an aqueous solution containing urea and an ammonium salt;
- an ammonium salt concentration adjustment step of mixing the aqueous recovered-urea solution which is obtained from the recovery step with an aqueous urea solution having a lower ammonium salt concentration as compared to that of the aqueous recovered-urea solution, so as to adjust the ammonium salt concentration of the aqueous recovered-urea solution;
- a concentration step of concentrating the aqueous recovered-urea solution which is obtained from the ammonium salt concentration adjustment step by vaporizing water which is contained in the aqueous recovered-urea solution which is obtained from the ammonium salt concentration adjustment step, so as to obtain a concentrated aqueous recovered-urea solution;
- and
- a mix step of mixing the concentrated aqueous recovered-urea solution with the feed aqueous urea solution before the feed aqueous urea solution is fed to the granulation step,
- wherein the ammonium salt concentration of the concentrated aqueous recovered-urea solution is 7 mass % or less.
4 more elements
Dependencies are inferred from the claim text.