CO2 Sequestration by Direct Dry Gas-Solid Contact of Serpentinite Mining Residues: A Solution for Industrial CO2 Emission

Abstract

Direct dry gas-solid carbonation is a simple approach towards mineral carbon dioxide sequestration. The route theoretically implies the direct reaction of CO₂ with silicates of Calcium and Magnesium in dry condition to form stable, insoluble metal carbonates. The mining regions of southern Quebec have a large deposit of serpentinite residues. The current study examines the suitability of serpentinite mining residues to use as the feedstock material for mineral carbonation. The focus of the present work is to assess the CO₂ removal efficiency of the residue from a simulated flue gas mixture of a typical cement plant (18 Vol% CO₂). This approach avoids the requirement of separate CO₂ capture and pre-concentration prior to mineral carbonation. The reaction parameters considered are temperature, pressure and time. The optimization of parameters is carried out for the maximum CO₂ removal efficiency (%) from the feed gas. Operating condition for CO₂ removal is optimized at 258 °C, 5.6 barg (pCO₂ ≈ 1) for 310 minutes with a removal efficiency of 37%. Preliminary analysis of reacted solid indicates carbonation is null at optimum condition, nevertheless, CO₂ is depleted from the feed gas might be due to a reversible adsorption. The study also checks the importance of pre-treatment options such as grinding, magnetic separation and heat treatment on CO₂ removal. A separate optimization study is carried out for magnetic separation of serpentinite residue and the separation parameters are optimized at an initial pulp density of 40% and magnetic intensity of 7.5*10⁻³ T with about 70% of iron oxide removal from the initial feed.