Process for preparing granular urea
AssigneeToyo Engineering Corporation
InventorsHidetsugu Fujii, Haruyuki Morikawa
Life of this patent
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Abstract
The present invention provides a process for preparing granular urea, which solves the problem of removing moisture in a prilling tower method and the problem of concentrating diluted formaldehyde in granulation by a fluidized, spouted bed method when urea is granulated in the presence of formaldehyde. That is, the present invention provides a process for preparing granular urea from liquid drops or sprayed drops of a urea solution, wherein the urea solution is divided into two portions of a urea solution A and a urea solution B, and a urea solution prepared by mixing an aqueous formaldehyde solution with the urea solution A, concentrating the above mixed solution and then mixing it with the urea solution B is used.
Claims11
A process for preparing granulates of urea from a solution or melt of urea, which comprises the steps of:
- providing a urea solution which is obtained directly from a urea production facility;
- dividing the urea solution into a first portion A and a second portion B;
- mixing the first portion A with ammonia and an aqueous formaldehyde solution to form a mixture A, the amount of formaldehyde being from 0.3 to 0.6% by weight based on the amount of urea fed to a means for granulating;
- feeding the mixture A to a means for concentrating the mixture A;
- concentrating the mixture A to form a concentrated mixture A;
- mixing the concentrated mixture A with a second portion B to form a resultant mixture;
- feeding the resultant mixture to the means for granulating;
- and
- granulating the resultant mixture.
A process for preparing granulates of urea from a solution or melt of urea, which comprises the steps of:
- providing a urea solution which is obtained directly from a urea production facility;
- dividing the urea solution into a first portion A and a second portion B;
- mixing the first portion A with ammonia and an aqueous formaldehyde solution to form a mixture A, the mole ratio of urea to formaldehyde being at least 0.5 and the amount of formaldehyde being from 0.3 to 0.6% by weight based on the amount of urea fed to a means for granulating;
- maintaining mixture A at a temperature of from 40 to 100.degree. C. and a pH of at least 6.5 during the mixing of the first portion A with the aqueous formaldehyde solution;
- feeding the mixture A to a means for concentrating the mixture A;
- concentrating the mixture A to form a concentrated mixture A;
- mixing the concentrated mixture A with the second portion B to form a resultant mixture;
- feeding the resultant mixture to a means for granulating;
- and
- granulating the resultant mixture.
Dependencies are inferred from the claim text.