CO2 storage in solid form: a study of direct mineral carbonation

Direct mineral carbonation by an ex-situ process in an aqueous system has been investigated over the past two years. The process utilizes a slurry of water mixed with a magnesium silicate mineral, such as olivine [forsterite end member (Mg2SiO4)], or serpentine [Mg3Si2O5(OH)4]. This slurry is reacte...

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Bibliographic Details
Main Authors: O'Connor, William K., Dahlin, David C., Nilsen, David N., Rush, G.E., Walters, Richard P., Turner, Paul C.
Language:unknown
Published: 2008
Subjects:
36 MATERIALS SCIENCE
58 GEOSCIENCES
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACID CARBONATES
AMBIENT TEMPERATURE
CARBON DIOXIDE
CARBONATES
CARBONIC ACID
CATIONS
GREENHOUSE GASES
KINETICS
MAGNESIUM SILICATES
OLIVINE
PARTIAL PRESSURE
REACTION KINETICS
SERPENTINE
STIRRING
STORAGE
Carbonic acid
Online Access:http://www.osti.gov/servlets/purl/896225
https://www.osti.gov/biblio/896225
Description
Summary:Direct mineral carbonation by an ex-situ process in an aqueous system has been investigated over the past two years. The process utilizes a slurry of water mixed with a magnesium silicate mineral, such as olivine [forsterite end member (Mg2SiO4)], or serpentine [Mg3Si2O5(OH)4]. This slurry is reacted with sub- or supercritical carbon dioxide (CO2) to produce magnesite (MgCO3). The CO2 is dissolved in water to form carbonic acid (H2CO3), which dissociates to H+ and HCO3-. The H+ ion hydrolyzes the mineral, liberating Mg2+ cations which react with the bicarbonate to form the solid carbonate. Results of the baseline tests, conducted on ground products of the natural minerals, have demonstrated that the kinetics of the reaction are slow at ambient temperature (22 C) and subcritical CO2 pressures (below 73 atm). However, at elevated temperature and pressure, coupled with continuous stirring of the slurry and gas dispersion within the water column, significant conversion to the carbonate occurs. Extent of reaction is roughly 90% within 24 hours, at 185 C and partial pressure of CO2 (PCO2) of 115 atm. Heat pretreatment of the serpentine, coupled with bicarbonate and salt additions to the solution, improve reaction kinetics, resulting in an extent of reaction of roughly 80% within 0.5 hours, at 155 C and PCO2 of 185 atm. Subsequent tests are intended to examine various pretreatment options, the carbonation solution characteristics, as well as other mineral groups.

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