CO_2 Sequestration by Carbonation of Minerals and Industrial By-Products in Finland

摘要

Sequestration of carbon dioxide as solid carbonate material appears to be Finland's only option for carbon sequestration. No locations exist for geological storage of CO_2 in, for example, underground aquifers, but vast resources of magnesium silicate minerals would allow for fixation of Finland's excess CO_2 emissions (with respect to the 1997 Kyoto protocol) as magnesium carbonate for hundreds of years. Serpentine-containing material is available as tailings from mining activities. Besides that, slag by-products from Finnish iron and steel industry provide a significant source of free calcium and the production of precipitated calcium carbonate for use in paper is being investigated as well. Here, the use of magnesium-based mineral for CO_2 sequestration and the bottleneck, i.e. the carbonation reaction kinetics, are discussed, for a staged gas/solid process for serpentine carbonation. Elevated pressures are shown to allow for higher temperatures, giving faster carbonation chemistry. Updated mapping shows vast suitable mineral resources across central Finland. Moreover, results on wet-chemical carbonation of serpentine or slag by-products from steelmaking industry are reported. It shows that magnesium and calcium may be rapidly and efficiently extracted by several solvents, but before carbonation an adjustment of solution acidity/alkalinity is needed. Nonetheless, quite pure (hydro-)carbonates could be produced.