1965 Biekart Stamicarbon 3171770 Process for substantially anhydrous and biuret free urea

We claim:

1. A process for »the production of substantially anhydrous urea in the form of solid globules having a moisture content of less than 0.5% by Weight which comprises concentrating an aqueous urea solution to a concentration of about 87 to 96% by weight of urea in a vacuum at a pressure in excess of 200 mm. of Hg and thereafter subjecting said concentrated solution While at a temperature not less than about 104 degC. to about 125 degC. to a second evaporation .in a second stage under a vacuum less than 100 mm. of Hg while removing the water vapor therefrom so as to provide a slurry of solid urea in a urea solution, converting said slurry of urea into a melt and removing said melt while continuously supplying heat thereto, controlling said supply of heat so that the exit temperature of said melt is maintained below 145 degC., dividing the melt into globules and converting said globules into urea prills by cooling said globules.

2. The process of claim 1 wherein said urea solution is concentrated in said first stage to a concentration of from about 90 to 94.5% by Weight and the pressure in said second stage is maintained at from about 50 to 80 mm. of Hg.

3. The process of claim 1 wherein a gas is introduced countercurrent to the discharge of said urea melt.

4. The process of claim 3 wherein said gas is ammonia.

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