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Titel:
Carbon dioxide sequestration by mineral carbonation: Literature Review
 
Auteur(s):
 
Gepubliceerd door: Publicatie datum:
ECN SF 1-2-2003
 
ECN publicatienummer: Publicatie type:
ECN-C--03-016 ECN rapport
 
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Samenvatting:
In order to prevent CO2 concentrations in the atmosphere rising to unacceptablelevels, carbon dioxide can be separated from the flue gas of, for example, a power plant and subsequently sequestrated. Various technologies for carbon dioxide sequestration have been proposed, such as storage in depleted gas fields, oceans and aquifers. An alternative sequestration route is the so-called "mineral CO2 sequestration" route in which CO2 is chemically stored in solid carbonates by the carbonation of minerals. As mineral feedstock, rocks that are rich in alkaline earth silicates can be used. Examples are olivine (MgSiO4) and wollastonite (CaSiO3). Mineral CO2 sequestration has some fundamental advantages compared to other sequestration routes. The formed products are thermodynamically stable and therefore the sequestration of CO2 is permanent and safe. Furthermore, the sequestration capacity is large because large suitable feedstock deposits are available worldwide. Finally, the carbonation reactions are exothermic and occur spontaneously in nature. The reaction rates of the process at atmospheric conditions, however, are much too slow for an industrial process. Therefore, research focuses on increasing the reaction rate in order to obtain an industrial viable process.

Optimisation of the process conditions is constrained by the thermodynamics of the process. Increasing the temperature and CO2 pressure accelerates the reaction rate, but gaseous CO2 is favoured over mineral carbonates at high temperatures. Using water or another solvent to extract the reactive component from the matrix accelerates the process. Pre-treatment of the mineral by size reduction and thermal or mechanical activation and optimisation of the solution chemistry result in major improvements of the reaction rate. During recent years, laboratory-scale experiments have shown major improvements of the conversion rates by developing various process routes and optimising process conditions. The most promising route available seems to be the direct aqueous route, for which reasonable reaction rates at feasible process conditions have been shown.

Important aspects of mineral CO2 sequestration are the transport of the materials involved and the fate of the products. Transport costs can be minimised by transporting the carbon dioxide towards a mineral sequestration plant situated near the feedstock mine. The carbonated products can be used for mine reclamation and construction applications. Unfortunately, only few rough cost estimates have been published and detailed cost analyses of the most promising process routes are absent in the literature. Therefore, at present, there is insufficient knowledge to conclude whether a cost-effective and energetically acceptable process will be feasible. Mineral carbon sequestration is a longer-term option compared to other sequestration routes, but its fundamental advantages justify further research. Major issues that need to be resolved in order to enable large-scale implementation are the energy consumption of the process, the reaction rates and the environmental impact of mineral CO2 sequestration. Finally, the use of alkaline solid wastes as an alternative feedstock for calcium or magnesium is acknowledged and warrants further research.


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