Dissertation/Thesis Abstract

Mineral carbon dioxide sequestration: Enhancing process kinetics and a resource base assessment for minerals suitable for use in enhanced carbonation processes
by Krevor, Samuel C., Ph.D., Columbia University, 2009, 144; 3348434
Abstract (Summary)

Mineral carbon dioxide sequestration binds CO2 by reacting it with calcium or magnesium silicate minerals to form solid magnesium or calcium carbonate products that are ready for disposal. The development of a cost effective process would provide a powerful tool in carbon management.

Research on mineral sequestration has focused on enhancing process kinetics in aqueous processing schemes. High costs of these processes are associated with mineral processing, such as ultrafine grinding steps, or the consumption of acids and bases, required to speed up silicate mineral dissolution kinetics.

Through experimental work neutral organic salts such as sodium oxalate, and sodium citrate, are identified as potential catalysts for use in enhancing dissolution kinetics without being consumed in the reaction. Neutral salts NaCl, NH4Cl, and sodium acetate are shown to be ineffective. The dissolution rate of antigorite serpentine is shown to have concentration dependence of order 0.52 and activation energy of dissolution of 38.3 kJ/mol in the presence of the citrate ion under weakly acidic conditions. Rates are shown to be several orders of magnitude higher in the presence of citrate than in the weakly acidic solution alone.

The 2005 Intergovernmental Panel on Climate Change report on Carbon Dioxide Capture and Storage suggested that a major gap in mineral CO2 sequestration is locating the magnesium-silicate bedrock available to sequester the carbon dioxide. Researchers at Columbia University and the U.S. Geological Survey have developed a digital geologic database of ultramafic rocks in the conterminous United States. Data were compiled from varied-scale geologic maps of magnesium-silicate ultramafic rocks. The focus of our national-scale map is entirely on ultramafic rock types, which typically consist primarily of olivine- and serpentine-rich rocks. These rock types are potentially suitable as source material for mineral CO2 sequestration.

Simple estimates are made on the potential for CO2 storage capacity. Using simplifying assumptions on the depth of mines, the efficiency of conversion, and the magnesium concentration of the rock, it is shown that a conservative surface area specific sequestration capacity range for ultramafic rocks is 50-80 Mt CO2 per km2 of ultramafic rock exposure. There is over 16,000 km2 of ultramafic rock exposure in the conterminous United States, about 4,000 km2 of which lies in urban areas and federal lands such as national parks that exclude the possibility of mining. Thus the sequestration capacity of ultramafic rocks in the conterminous United States can reasonably believed to be at least 600-960 Gt CO2.

Indexing (document details)
Advisor: Lackner, Klaus S.
School: Columbia University
School Location: United States -- New York
Source: DAI-B 70/02, Dissertation Abstracts International
Subjects: Environmental science, Environmental engineering
Keywords: Carbon sequestration, Mineral sequestration, Serpentine, Silicate dissolution, Ultramafic rocks
Publication Number: 3348434
ISBN: 978-1-109-04144-6
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