283417 Evaluating the Viability of CO2 Mineralization Via Reaction of Caustic Waste Materials

Tuesday, October 30, 2012: 2:10 PM
301 (Convention Center )
Robert Dilmore1, D. Allen2, S. W. Hedges1 and Yee Soong1, (1)National Energy Technology Laboratory, U.S. Department of Energy, Pittsburgh, PA, (2)Geological Sciences, Salem State College, Salem, MA

Consensus in the scientific community is that anthropogenic greenhouse gas (GHG) emissions are a dominant factor contributing to global climate change.  While CO2 is not the strongest greenhouse gas with respect to radiative forcing, it is, by far, the largest volume GHG, and is recognized by most researchers to be the greatest contributor to observed increases in mean atmospheric temperatures.  As such, separation of anthropogenic CO2 from coal fired power plants and other large industrial sources, and storage of that CO2 out of the atmosphere has been proposed as a means to slow the rise of, and possibly stabilize atmospheric concentrations of CO2.  Proposed sinks for anthropogenic CO2 include storage in geologic formations (saline formations, coal seams, depleted oil- and gas-bearing formations, basalts, and organic-rich shales), uptake of CO2 into plants with terrestrial storage in soil and biomass, and reaction of CO2 ex situ with naturally occurring minerals or byproduct streams from industrial processes.   

Reacting CO2 with caustic industrial byproduct streams (solids, slurries, or solutions) has been proposed by many as a possible viable approach for ex situ CO2 sequestration.  Cited advantages of this paradigm include proximity (often co-location) of CO2-bearing industrial byproduct gas streams to caustic byproduct materials, possibility of reacting whole flue gas streams with caustic byproduct – thereby obviating CO2 separation from mixed byproduct gas streams, concomitant neutralization of caustic waste materials that would otherwise need to be neutralized with acidic reagents, ability to realize significant reaction efficiency at very modest reaction conditions, storage of anthropogenic CO2 in a stable mineralized form, and potential to generate a saleable coproduct mineral carbonate stream.  Acknowledged disadvantages of this CO2 storage paradigm include:  relatively low CO2 storage capacity of global caustic industrial byproduct streams as compared to global anthropogenic CO2 emissions, need to handle large volumes of reactant and product materials, potential to mobilize heavy metals and other trace constituents of concern, and potential for mineralized CO2 to react and release stored CO2 under certain environmental conditions.  Taken together, these suggest that CO2 mineralization using caustic byproduct materials may be a viable approach to partially offset CO2 emissions for select industries and at specific facilities, but may not make a significant contribution toward stabilizing atmospheric CO2 concentrations.

Given this context, select proposed approaches for CO2 mineralization with caustic materials will be considered.  Discussion will include summary of experimental efforts to evaluate reactivity of CO2 with coal utilization byproducts and bauxite residue materials, consideration of the applicability of geochemical equilibrium modeling to estimate CO2 mineralization potential, and discussion of possible implications for viability of this CO2 storage paradigm.

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