Catalytic Reactions of the Carbon Dioxide Emissions and the Solid Residues of Clean Coal Combustion to Beneficiate the Residues for Construction Applications

Statement of the Problem / Situation: The clean coal (selective catalytic, fluidized bed, etc.) combustion technologies adopted by power plants largely emphasize control of sulfur and nitrogen oxide emissions. These technologies tend to increase the quantity of the solid residues of coal combustion, and compromise the quality of these residues in existing applications of coal ash. There is thus a need for improved management of the solid residues of clean coal combustion. There is also a growing need for control of the CO2 emissions of coal-burning power plants. The Approach: Cost-effective, energy-efficient and environmentally friendly methods will be developed for in-situ sequestration of carbon dioxide emissions through reactions with the solid residues of clean coal combustion. These carbonation reactions would beneficiate the clean coal combustion residues for value-added use in a sustainable class of concrete (geopolymer concrete). Catalytic mechanochemistry will be used to significantly raise the carbon uptake of residues at ambient temperature and room pressure, and to resolve the chemical and toxicity barriers against value-added use of the clean coal combustion residues. Exploratory studies of the proposing team have indicated that : (i) mechanochemical carbonation adds significant value to the fluidized bed combustion fly ash as a source of aluminosilicats for geopolymerization; and (ii) the carbon uptake of solid residues far exceeds the carbon emissions of the mechanochemical process, yielding geopolymer concrete materials with negative carbon footprint. The proposed Phase I project will: (1) develop optimum conditions for catalytic mechanochemical carbonation of selected clean coal combustion residues; (2) formulate geopolymer binders which supplement carbonated clean coal combustion residues with minerals and activators to meet the relevant chemical requirements; (3) quantify the value rendered by carbonation of clean coal ash towards sequestration of carbon dioxide and development of high-performance geopolymer concrete materials; and (4) verify the life-cycle environmental benefits and the commercial merits of the approach. Commercial Applications and Other Benefits: The proposed approach will enable coal-burning power plants reduce their CO2 emissions and add value to the solid residues of clean coal combustion. Significant environmental and economic benefits can be realized by the power plants adopting the technology at limited capital cost. Value-added use of carbonated ash in geopolymer concrete would also help the construction industry with significant reduction of the carbon footprint and energy content of the concrete-based infrastructure. The improved durability characteristics of the resulting geopolymer concrete would also benefit the life-cycle economy and sustainability of the concrete-based infrastructure, which would be of value to the government and private owners of infrastructure systems. Key Words: clean coal combustion, solid residues, carbon dioxide sequestration, carbonation, mechanochemistry, catalysts, geopolymer concrete, sustainable construction. Summary for Members of Congress: The clean coal combustion technologies which are increasingly adopted by power plants for control of sulfur and nitrogen oxide emissions still emit significant quantities of carbon dioxide to the atmosphere, and yield growing quantities of landfill-bound ash. The technology will make value-added use of carbon dioxide emissions to beneficiate the ash for construction applications.