The recycling process of the primary aluminium waste to obtain secondary aluminium alloys produces more than 1 million tonnes of salt slags in Europe. This hazardous waste is enhanced through a complex 5-stage process, which allows the recovery of three by-products that return to the market: aluminium concentrates, melting salts and secondary aluminium oxide: Paval. The Life Bauxal II project is focused on the enhancement of this secondary aluminium oxide, ensuring the closed cycle and boosting circular economy. The physical and chemical characteristics of the secondary oxide are very similar to bauxite, suggesting that it can be considered as a secondary bauxite, with 10% by weight of magnesium oxide, mainly in spinel form and some impurities such as halogens and salts. The undesired elements can be removed through further refining, resulting in a new raw material: Refinal, which will be able to compete against mineral bauxites with more demanding requirements. The roadmap provides for a step dedicated to the optimisation of densification conditions of this material until it is transformed into a new product: Bauxal (alternative to calcined bauxites, commercially available on the market). Finally, the validation of this alternative raw material into mineral resources in the refractory market will be done in the smelting furnaces of aluminium wastes.
- Hydrometallurgical refining: this step consists of reducing the unwanted compounds to acceptable values, thus obtaining a new raw material, Refinal. The construction of a pre-industrial treatment facility with a capacity of 500 tpy for hydrometallurgical treatment will be carried out. - Optimisation of the densification conditions: evaluation of physical milling or agglomerating process and their subsequent thermal treatment at high temperatures of the Refinal to produce the new product: Bauxal. - Demonstration of the new Bauxal-based refractories. The transformed refractory aggregate will be refined in grain size for the manufacture of new refractory bricks and then they will be demonstrated in the aluminium smelting furnaces.