(738c) Layer-Wise Agglomeration of Urea Granules

Urea has been widely used as a nitrogen fertilizer due to its high nitrogen content. However, because of its high water-solubility, the nitrate content is lost as surface runoff. In this study, different binders were used to alter the internal structure of the urea granule to control the dissolution behavior and reduce the rate of dissolution. Urea, with binders, was granulated in layers. The core of the granule was manufactured by granulating technical urea powder in a drum granulator, with corn starch as the binder. A second layer was added, by drum granulation, to the core in order to obtain a nutrient release pattern that matches the crop nitrate demand. Corn starch, PEG 4000, and corn starch hydrogel were used as binders for the second layer. The density, thermal properties, fracture pressure, internal porosity, and dissolution rate of the two-layer granules were measured using standard methods. Dissolution rate of the double layer granules were slower than the market urea granules. The mechanical fracture pressure of the double layer granules with hydrogel binder was the highest among these three types of double layer granules. Among these three types of granules, the dissolution behavior of the granule with starch hydrogel on the second layer was identical to the crop nitrate demand curve. Overall, the double layer granule with corn starch binder in the core and hydrogel as the binder in the second layer had a better physical and dissolution properties. Though the pattern of dissolution of double layer granule was similar to the crop nitrate demand curve, but, a soil based study is needed to verify the nitrate release characteristics in the future.