3. Reaction kinetics

3.1 General

Knowledge of the factors on which the speed of a chemical reaction depends, and of the mechanisms that control it, is fundamental to mastering an extraction process. In pyro-metallurgy, reactions are generally heterogeneous, as they originate and develop at the interface of two phases; homogeneous reactions are rare and limited.

The kinetics of heterogeneous reactions depend on the speed with which a reactant is transported to the reactive sites at the interface. In a fluid, transport takes place by convection, which is all the more difficult to achieve when the fluid is viscous and immobile. Convective transfer must therefore be ensured by mechanical, electromagnetic or pneumatic agitation, so that the fluid layer associated with the surface, known...