prills

A prill is a small, roughly spherical particle produced by a prilling process, in which a molten or liquid formulation is sprayed to form droplets that solidify into beads as they cool in air. Prills are designed to be uniform in size and shape, typically ranging from about 0.5 to 3 millimeters in diameter, though other sizes are produced for specific applications. This form reduces dust, eases handling, and improves flow and storage compared with finer powders.

Common uses are in agriculture and agrochemistry. Fertilizer prills include urea, ammonium nitrate, and various phosphate-based fertilizers. Some prills are coated or encapsulated to provide slow or controlled release of nutrients or to protect active components from moisture. Pesticide and micronutrient formulations are also made as prills to enable uniform distribution and reduce drift.

Production of prills can occur in prilling towers, rotary discs, or nozzle-based systems, with molten or slurry formulations atomized into cool air where droplets solidify into spheres. Key factors affecting prill characteristics include melt viscosity, feed temperature, droplet size, air flow, and residence time.

Prills offer advantages such as consistent particle size, lower dust generation, better flowability, and improved packaging and handling. They also require appropriate storage to prevent caking or moisture uptake. In some cases, the prilling process enables specialized formulations, such as nutrient-coated granules or moisture-resistant coatings for agrochemicals.