Production of high-strength, storage-stable particulate urea

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. The additives discovered and now disclosed as a principal feature of the instant invention are from the class of compounds known as lignosulfonates and are added in such minute quantites that although they impart the improved desired characteristics to the particles formed from said melt, they neither add nor detract substantially from other properties thereof.

Dependencies are inferred from the claim text.