Patent ID: 7402190

Claim:
A method for making a nitrogenous and complex fertilizer, for slowly releasing nitrogen in granule form, said method comprising the steps of preparing an aqueous urea-formaldehyde resin dispersion or mixture, wherein said resin dispersion is prepared by a reaction and a heating and cooling system, at atmospheric pressure and room temperature, formaldehyde, urea and water, with a formaldehyde/urea first ratio from substantially 0.8:1 to 2:1, thereby providing said aqueous dispersion, heating and reacting said aqueous dispersion to a temperature from substantially 80° C. to 110° C., controlling the pH from 4 to 7, monitoring at even time periods a viscosity of said dispersion and further adding to said aqueous dispersion a reaction stopping agent to achieve, upon stopping said reaction, a substantially pH neutrality condition, supplying the mixture in a liquid form to a storing tank, conveying said mixture from said storing tank to a drying and granulating device for simultaneously reactively drying and granulating said mixture to provide a solid support and spraying on said solid support said mixture to provide urea/formaldehyde substantially perfectly spherical homogenous fertilizer granules having a density in a range from 0.5 to 1 g/cm 3 , preferably from 0.8 to 0.9 g/cm 3 , a total nitrogen contents from 36 to 42%, preferably from 38 to 40% by weight, an ureic nitrogen contents less than 5% by weight, a nitric nitrogen content less than 10% by weight, preferably from 2 to 5% by weight, an ammoniacal nitrogen contents less than 15% by weight, preferably from 3 to 8% by weight, and a diameter from 0.5 to 5 mm.