Abstract (EN)

The phosphate extraction process of at the Ben Guerir deposit feeds 14 ore stocks of different chemical characteristics. The production decisions impact the replenishment of these stocks, which can be strongly delayed in time. The ore demand to be met for the export or production of phosphoric acids does not concern these primary ores but blended ore grades matching certain chemical characteristics. The cost of this transformation is not very sensitive to required grade and many possible blending “recipes” lead to the same end product (blended ore grade). The structure of this grade demand fluctuates over time and orders are known only a few weeks in advance. The stock replenishments of extracted ores are strongly irregular. This paper shows that degrees of freedom in blend structure, unfortunately often ignored, are available: 1) to meet demand while limiting recourse to emergency procedures to offset ore shortages; 2) to limit temporary storage of quantities of certain produced ores due to insufficient storage space in the blending zone. Mathematical programming can be used to define tailored blends based on available ores to meet grade demands within a few weeks, and so avoiding or limiting costs induced by use of a standard blend of extracted ores. This is illustrated by a number of examples1. The parameterization used in the formulation of the problem enables instantaneous adjustment to any change in the characteristics of the extracted ores and required grades