PROCESS FOR PREPARING SLOWLY-SOLUBLE GRANULAR FERTILIZERS BASED ON UREA, AS A NITROGEN SOURCE, AND SECONDARY SULPHUR PRODUCTS

摘要

The invention relates to a process for preparing slowly-soluble fertilizers based on urea, with addition of inorganic substances with soluble sulphur. According to the invention, the process comprises the on-plate granulation of the solid phase consisting of a homogeneous mixture of crystallized urea, the fine fraction recycled after grinding and a sulphur-containing by-product with concentrated urea melt, at temperatures of 90...99°C in the mass of material on the granulation plate, to result in mixed fertilizer granules containing nitrogen and soluble sulphur having sizes in the range of 1...4 mm as useful fraction which, after being cooled and classified, are packaged and the coarse fraction and fine fraction which result from grinding are recycled in the granulation stage.