Preparation of (NH4)2SO4 Spherical Particles with Functions of Sustained-Release and Anticaking by an Organic Solvent-Free Process

Ammonium sulfate is a widely used nitrogen fertilizer, with a significant market share in agricultural production. However, its poor powder characteristics and excessively fast release rate greatly hinder its development. This study investigates the effects of the abrasion and dissolution processes on the morphology of ammonium sulfate crystals. Furthermore, through a study of the cooling rate, stirring rate, and heating methods, a technique was developed to produce spherical ammonium sulfate particles through a single heating step without the use of organic solvents. The resulting spherical ammonium sulfate product exhibits excellent powder properties, good sphericity, and high flowability. More importantly, compared to cubic particles, the dissolution rate of the spherical product decreases by approximately 20%, and the caking ratio decreases by about 30% at the same humidity, demonstrating its anticaking and sustained-release performance.