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Triboelectric charging and free-fall separation are attractive technologies for lunar mineral beneficiation. Here, an optimised tribocharger design was built and evaluated under terrestrial conditions. The charging behaviour of pure silica and ilmenite were tested using the optimised design, as were mixtures of silica and ilmenite, and samples of lunar regolith simulant JSC-1. Pure silica and ilmenite acquired negative and positive charge, respectively, through contact with the tribocharger. The tribocharger affected significantly the movement of the pure minerals in the electrostatic field. Results from the binary mixtures indicate that ilmenite recovery is independent of initial ilmenite concentration, and can be predicted from the mass distribution of pure ilmenite samples. For JSC-1, the tribocharger was found to increase the density of the material in certain collectors, indicating an upgrading of denser constituents. The optimised tribocharger design has a significant effect on the charging and separation performance.

Tribocharger design optimisations presented in the literature are based typically on experimental investigations. While this approach is useful and necessary to evaluate the performance of a design, experimental investigations are limited to studying a finite matrix of parameters. Computational approaches, such as the discrete element method (DEM), offer greater flexibility, however they have not been used previously for tribocharger design optimisation. This work presents a novel approach using the DEM to study the effect of different tribocharger designs on the charging process using particle–wall and particle–particle contact areas as proxies for charge transfer. The bulk sample charge output from the model are compared with bulk charges measured experimentally, showing good agreement. Furthermore, a method to predict approximately the charging behaviour of complex mixtures from linear combinations of the simulation outputs of single species, single size particle samples is presented, demonstrating good agreement.

Many discrete element method (DEM) tribocharging models presented in the literature rely on ill-defined or poorly quantified charging parameters. This work presents a straightforward experimental method to quantify key parameters, namely the charge transfer limit, Γ, and the charging efficiency, κc. These parameters are then used in both 2D and 3D DEM simulations to evaluate the applicability of faster 2D models to tribocharge modelling. Both the 2D and 3D models are found to perform well against the experimental data for single-contact and single-particle, multi-contact systems. However, the 2D model fails to produce good agreement with experimental data for multi-contact, multi-particle systems. This approach for determining experimentally the parameters for the DEM tribocharging model is found to be effective and produces good agreement between simulated and experimental data. This method will improve and simplify the DEM modelling of triboelectric charging in dry material handling processes.