Segregation of the bulk blend fertilizers

Bulk blend fertilizers are a mixture of different kinds of fertilizers in order to obtain a predicted N-P-K chemical composition. Although this production method has some advantages, segregation appears at different stages, from the production to the final spreading on the field. An experiment has been implemented to predict and quantify the influence of some physical properties on the occurrence of segregation. The principle was to blend two fertilizers having identical physical properties except for one, such as size, shape or density and to measure the segregation of the blend following various operations, such as filling or emptying a container. Results show that the spread of the fragment size distribution has a big influence on the segregation of the generated heap. In order to reduce this phenomenon, the granulometric spread index (GSI) [(d(84)-d(16))/2d(50)] must be smaller than 10. Other properties don't seem to have an influence. The granulometric segregation can lead to a chemical heterogeneity. The absolute sum of the difference between d(16) and d(84) must be limited around 0.5 mm. Above this value, the chemical segregation begins to be excessive. It seems also that if there is a limited difference in size for the components, the chemical segregation is amplified if the density of the fertilizer with the biggest particles is lower. It is not the case for the difference in shape. (C) 2004 Elsevier B.V. All rights reserved.