Dados da Submissão

Título

GEOCHEMICAL MODELING OF SHARED STORAGE FACILITIES CONTAINING IRON ORE DRAINED TAILINGS AND WASTE ROCK USING PHREEQC

Texto do resumo

The failure of two iron ore tailings dams, carried out in 2015 and 2019, in Brazil, has led to increased scrutiny of the storage and disposal of tailings and waste rock in mining operations. As a result, the construction of storage facilities containing drained tailings and waste rock has become an alternative. With the construction of these structures, the mining industry has faced new challenges regarding the characteristics of the resulting or future effluents. Regarding iron ore tailings, chemical mobilization of its components was widely considered as insignificant since its oxidized materials tend to be stable under atmospheric conditions. However, the construction of these mixed structures poses new geochemical conditions on materials that must be thoroughly investigated. Taking into account this context, issues have been faced, such as: (i) influence of the gaseous diffusion in variable saturation especially partial pressures of O2 and CO2 in the unsaturated zone; (ii) Interaction of aqueous phases percolated by tailings and waste rock; (iii) hydrodynamic characteristics related to the different materials and under distinct saturation; and (iv) potential for chemical drain clogging. Thereby, a geochemical modelling protocol was developed to answer these questions. The protocol begins by developing a conceptual model that considers the geotechnical design of the structure, the material disposal, the three-phase flow, and respective interactions between them. Numerical simulation was carried out using the software PHREEQC, an application designed for geochemical calculations in a saturated medium. In the developed protocol, it was possible to bypass this limitation by considering the hydrodynamic characteristics of the flow, implemented through TRANSPORT datablock, and interaction with the interstitial aqueous phase. Additionally, a gas diffusion model is prescript in the protocol to assess the depth of the swift of redox conditions from an oxidizing to a reductor environment and support the conditions of the geochemical model. The redox conditions at the drain outlet were also considered, as the water level in the structure can affect the potential for dissolved iron precipitation, which can lead to chemical drain clogging.Through the use of this developed modelling protocol, it was possible to simulate different scenarios as well as predict the hydrochemical composition of the effluents, as well as identify the conditions under which chemical clogging may compromise the structure.

Palavras Chave

PHREEQC; geochemical modeling; Mining facilities; kinetics