Role of Comminution as a Pretreatment of Physical Concentration in Resources Recycling

This paper demonstrates the importance of comminution for achieving compositional liberation in order to establish an effective solid-solid separation process, in especial, in the field of mineral processing and resources recycling. We have developed a unique liberation model in comminution process by introducing an index of “preferential breakage probability”, e₁, at phase boundary to the Wiegel model, which is well known in the field of mineral processing. From the results, we easily understood that the degree of liberation gradually increased with increasing the e₁ and it could be demonstrated that the energy required for obtaining a certain degree of liberation dramatically decreased with increasing the e₁. This calculation indicated the importance of preferential breakage at phase boundary in comminution with lower energy consumption, which could contribute better separation efficiency in the following solid-solid separation. In other words, the e₁ must become a good index for the DfR (Design for Recycling) as an “EcoDesign” from the viewpoint of compositional separation. The paper also describes several recent approaches to obtain a good liberation of structural components in comminution, such as (semi)-autogenous grinding, surface grinding, blasting in water, microwave pretreatment, and electrical disintegration.