Urea granular

Urea processes provide an aqueous solution containing 70—87% urea. This solution can be used directiy for nitrogen-fertilizer suspensions or solutions such as urea—ammonium nitrate solution, which has grown ia popularity recentiy (18). Urea solution can be concentrated by evaporation or crystallization for the preparation of granular compound fertilizers and other products. Concentrated urea is sohdified ia essentially pure form as prills, granules, flakes, or crystals. SoHd urea can be shipped, stored, distributed, and used mote economically than ia solution. Furthermore, ia the soHd form, urea is more stable and biuret formation less likely. 

Fig. 2. Fertilizers in the prilled or granular form (a), prilled ammonium nitrate (b), prilled urea (c), granular urea (d), granular diammonium phosphate ...

Fig. 18. TVA-type cogranulation process with preneutralizer, as used for production of granular mixed fertilizers. Feed materials such as ammonium sulfate, ammonium nitrate, urea, superphosphates, sulfuric acid, and potash are used.

Gra.nula.r Compositions. Granular compositions of UF reaction products are divided into three classes, each based on their degree of water solubihty as affected by their polymer distributions, ie, ureaform, the least water-soluble class methylene ureas and methylene diurea/dimethylene triurea (MDU/DMTU) compositions, the shortest-chain MU oligomers and the most water-soluble. 

The nitrogen content of granular urea—formaldehyde reaction products typicahy ranges from 35 to 42% depending on the methylene urea polymer distribution. 

These compounds are stable only under basic conditions and must be held at high pH if stored for considerable periods of time. In Step 2, these methylolureas further react under acidic conditions with urea to form the various methylene urea oligomers. Water generated from the condensation reaction is removed by evaporation when producing granular UE products. 

Eiroa, M., Kennes, C., and Veiga, M.C., Formaldehyde and urea removal in a denitrifying granular sludge blanket reactor, Water Res., 38, 3495-3502, 2004. 

Renal Effects. Blood urea nitrogen and serum electrolyte levels were normal in several individuals overcome by unknown concentrations of hydrogen sulfide gas in a pelt room (Audeau et al. 1985). One of these four patients had protein and blood in the urine initially, which was not detected upon later testing. Albumin and some granular casts were noted in the urine in another patient, but these findings were transient (Audeau et al. 1985). 

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