Segregation During Fertiliser Handling: Occurrence, Assessment and Control

Keywords: Segregation, Fertiliser handling, De-blending, Silo, Hopper, Feeders.

Summary:

The performance of many fertilisers is affected by the homogeneity of particle sizes or blend component population throughout the bulk. In the context of industrial practice the bulk form can be considered as quantities of particulates ranging from ship cargoes, wagon loads, silos, hoppers, big bags or sacks. A loss of blend homogeneity or drift in particle size range at any step from receipt of raw materials to processing or to end user application will exaggerate the segregation effect in subsequent handling / spreading operations.

The implications of a loss of consistency in the bulk particulate can range in impact from financial loss (as a result of the need for reject or rework of batches at plant level or at application level as the need for reapplication) to increased environmental impact (caused by localised concentrations of phosphates after application that can be more susceptible to run off into water ways) in addition losses can also be derived from poor crop yield.

For either type of impact there is clearly much to be gained from minimising the propensity of mono type materials or blends to segregate.

This paper will consider the process steps that are most likely to result in segregation of fertiliser. Techniques for the assessment of the propensity of fertilisers to segregate will also be discussed.

Having determined the likelihood for a given material to segregate and having identified process steps that are most likely to exaggerate this tendency, the paper will develop to discuss strategies for the implementation counter-measures to minimise variability in particle size distribution consistency that can be attributed to plant and equipment design.

Richard J Farnish MPhil CEng MIMechE and Prof. Mike S A Bradley, The Wolfson Centre for Bulk Solids Handling Technology, University of Greenwich, Chatham Maritime, Kent ME4 4TB, UK

28 pages, 30 figures, 9 references.