Prilling is the solidification of a melt (liquid droplets) into prills. The solidification is done in a tower by counter-current cold air.
Prilling is the solidification of a melt (liquid droplets) into prills (very round particles) inside a tower.
Falling by gravity from the top of the tower, the melt has the tendency to form very round droplets due to its surface tension. The air injected at the bottom of the prilling tower crosses the melt flow and crystallized the droplets into prills.