Authors
Preveniou, Athina; Ma, Yan; Pettersen, Johan Berg; Kladis, Anastasios; van der Eijk, Casper
Abstract
The environmental impact of the alumina produced via the Modified Pedersen Method (MPM) is analyzed and compared with the conventional Bayer method, using the life cycle assessment approach. Pedersen method was implemented in low-capacity industrial scale back in 1928 but ceased its operation in 1969 due to energy-related costs. The increasing demand of alumina and the high production rate per ton of product of the waste generated via Bayer method (the so-called bauxite residue) contribute to higher accumulation of this residue that impacts land availability, while the alkalinity of BR is an important barrier for its direct utilization in the building sector. In the Pedersen, high-alumina and high-iron containing source together with quicklime, are fed in a smelting-reduction step to produce pig iron and a leachable slag. If this input material is processed through Bayer, iron-compounds would drift to the bauxite residue stream. The second by-product of MPM is a high-calcium carbonate material (grey mud), which can be valorized in the building and agricultural sectors. Modifications of the original Pedersen method are studied in the scope of ENSUREAL project and aim to a more sustainable and circular way of alumina production in the following ways: complete utilization of high-iron bauxites and bauxite tailings, CO2 direct utilization and co-production of calcium carbonate material. The MPM does not only prevent BR generation but also targets to its valorization as alumina source. ENSUREAL team in parallel with several H2020 projects (RemovaL, ReActiv, HARARE and SisAl) targets to well-address the BR-related challenges. The performance of the MPM for four different alumina-containing input materials, different energy sources and potential valorization options for the grey mud is presented and analyzed. Keywords: Pedersen method, alumina production, bauxite, bauxite residue valorization, LCA