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Title:
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Carbon dioxide sequestration by mineral carbonation: Literature Review
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Author(s):
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Published by:
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Publication date:
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ECN
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1-2-2003
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ECN report number:
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Document type:
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ECN-C--03-016
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ECN publication
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Number of pages:
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Full text:
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52
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Download PDF
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Abstract:
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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