反应详情

The fertilizer coatings may be applied in batch mode by loading a targeted weight of urea prills or granules to a drum roller, roller mill, or other rolling-cylinder configuration, sprayed with between 1.0 and 1.75 percent water by weight, and rolled for about one minute to permit the urea surface to soften. Powdered calcium sulfate dihydrate (gypsum) is then added to the drum roller to provide a final ammonium sulfate to urea ratio of 1 to 3 (i.e., 25 percent ammonium sulfate by dry weight). Rolling of the urea and gypsum is continued for 2 minutes at which time, a polyurethane coating is applied at between 0.1 and 0.5 percent by weight by spraying with separate streams of isocyanate and polyol to improve the coating integrity.