| 摘要 |
<p>A process for preparing granules, containing urea as the main component, from an aqueous urea solution having a urea concentration of at least 70 weight percent, the solution containing a crystallization retarder for the urea in solution. The process comprising: spraying the solution, in the form of droplets having an average diameter of from 20 to 120 microns, onto a fluidized bed of nuclei at a temperature at which water from the sprayed solution is evaporated and granules are formed on the nuclei. The process being characterized in that the crystallization retarder consists of a water-soluble, inorganic aluminum salt used in a quantity equivalent to at least 0.1 weight percent, calculated as Al2O3, relative to the solid content of the solution. In a preferred aspect the solution contains at least one other fertilizer in solution and/or suspension. The other fertilizer can be ammonium sulphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate or mixtures thereof.</p> |
