Flexibility of dynamic blending with alternative routings combined with security stocks: a new approach in a mining supply chain

In the OCP phosphate supply chain, source ores (SOs) are extracted according to a tactical extraction programme, constrained by geological conditions that constantly limit and modify the variety of available SOs. Then SOs are blended to get merchantable ores (MOs) respecting composition constraints and ordered by internal (phosphoric acid plant) or external (export) customers. The blending process is performed in a dry blending plant, possibly followed by treatments in a washing plant which modifies the SOs weights and compositions. The choice of alternative routings and blends depends on orders book and SOs availability in the dry blending area or present on mine. To improve the performance in meeting a rolling 4-weeks orders book, a quadratic model was created and implemented. It optimises jointly: (i) for each order, the routing and the SOs quantities used in the dry blending plant; (ii) the SOs quantities transferred from the mine; (iii) security stocks to face some unforeseen change in the MO book order, and the slight instability of the SO chemical composition that triggers a SO multiplication to be contained. The performance of the linearised model has led the relevant OCP site to develop and use an extended version of this model.