Abstract: One approach to improving storage stability, particularly that attribute characterized by reduction in the tendency for caking during storage of freshly prepared urea particles such as granules, is to treat the surface areas of the freshly prepared particles/granules with appropriate amounts and kinds of conditioning agents. This approach does not address the problem of increasing the hardness of the particles to impart improved high-strength characteristics thereto. A second approach to this problem of improving storage stability of urea granules is to admix and/or react certain anticaking and hardness improving additives into or with the urea melt prior to the solidification of urea particulates therefrom. The instant invention is directed to this second approach of imparting to the ultimately prepared urea particles both improved anticaking and hardness (as opposed to being easily crushed, i.e., friable) characteristics by means of addition to the urea melt of certain additives.

Abstract: The apparatus provides a homogeneous (with respect to particle size), dense, mass of sized particles in random motion so that highly uniform coatings of the same or of different solids can be applied to each particle by conventional spray-coating with the liquified coating material(s). The apparatus is a horizontal rotary drum containing lifting flights. A novel deflector pan is fixed in space inside the upper section of the drum which deflects particles falling from the lifting flights to the side of the drum where they form a narrow, dense falling cascade. The coating material is sprayed onto the cascading particles, preferably as they free-fall after leaving the lower edge of the pan. However, if desired, some or most of the coating material may be directed onto the top edge of the moving bed including the juncture of the cascade therewith.