Neutralization of bauxite residues by gas purging

Abstract

The utilization of industrial byproducts, IBPs, for creating huge infrastructure projects (viz., land reclamation, rehabilitation of low-lying areas, backfilling of mines and construction of embankments, etc.), is being hypothesized to address the issues related with the sustainability. One of such IBPs are the bauxite residues, BRs, which get generated at alumina refineries; either in the slurry form or cakes coming out of the filter press, has been stacked at industrial premises, in the form of heaps or dumps. Ideally, the BRs can be utilized for the above-mentioned projects, provided they are suitably 'neutralized' to bring down their pH. Though, at this stage, it appears to be a 'distant dream', successful demonstration of such a philosophy would be a game-changer for the alumina refineries and the infrastructure sector, in general. In lieu of this, different techniques for neutralizing the BRs by using various chemicals, (sea)water, and bacteria have been adopted in the past. However, another interesting strategy to neutralize the magnanimous quantity of BRs stacked could be through purging CO2 that needs to be investigated in detail. With this in view, and to investigate the technical feasibility of CO2 purging in the BRs in their semi-solid state, a setup NeGaPur (connoting to the Neutralization by Gas Purging) that simulates BRs-gas interaction in the laboratory conditions has been adopted and its details are presented in this paper.