CO2 fixation using magnesium silicate minerals part 1: Process description and performance

This paper describes a staged carbonation process for magnesium silicate mineral carbonation. This carbon dioxide capture and storage (CCS) alternative involves the production of magnesium hydroxide, followed by its carbonation in a pressurised fluidised bed (PFB) reactor. The goal is to utilise the heat of the carbonation reaction to drive the Mg(OH)2 production step. The results show that Mg(OH)2 can be produced successfully (up to 78% Mg extraction extent achieved so far) and efficiently from different serpentinite minerals from locations worldwide (Finland, Lithuania, Australia, Portugal…). From the extraction step, ammonium sulphate is recovered while iron oxides (from the mineral) are obtained as by-products. The carbonation step, while still being developed, resulted in >50%-wt conversion in 10 min (500°C, 20 bar) for > 300 μm serpentinite-derived Mg(OH)2 particles. Thus the reaction rate achieved so far is much faster than what is currently being considered fast in the field of mineral carbonation.