Experimental investigation of breakage and energy consumption characteristics of mixtures of different components in vertical spindle pulverizer

- Heterogeneous grinding of binary-mineral mixture is conducted in Hardgrove machine.
- Analyses of breakage behavior of the mixture and each component.
- Hardness index is modeled into the breakage model.
- Analyses of energy split based on the modified model and energy-size data.

Complex interactions among components in the heterogeneous grinding have an influence on breakage and energy consumption characteristics of components in mixtures if compared with the single breakage. In this paper, a modified Hardgrove mill, with the addition of a power meter, is used to simulate the grinding process of vertical spindle pulverizer. Binary-component mixtures of coal and pyrite, or coal and calcite, in the size of −2.8 + 2 mm, are prepared to study the heterogeneous breakage. For the mixture A of coal and pyrite, the fineness of pyrite progeny is higher than that from single-breakage. Instead, the coal in mixture A shows the opposite trend. Because of the relatively less difference in hardness between coal and calcite, size distributions of components are environment-independent. Breakage of mixture follows the first-order kinetics, as well as each component in mixtures. In order to describe the energy-size reduction of mixture, a modified model in the form t10=A(1-e-b·ECS/Hw), has been derived from modeling the mass weighted hardness index of mixture, and its predictions are highly fitted with experimental and supplemental data. In addition, energy split phenomena of components are discussed qualitatively using the modified model. Specific energies that need to yield the same product t10 of one component both in the single and mixture breakage are compared, and the interaction of one component on the breakage of another one in mixture grinding also has been analyzed. Size distributions of ground products using t10 are well predicted, which are critical to conduct the computation of size distribution of progenies at given specific energies.