Concurrent Sequestration of Carbon Dioxide and Beneficiation of Impounded Coal Ash

Economically viable and market-driven methods are needed for value-added and large-volume use of the CO2 content of coal combustion emissions in industrial processes. At the same time, there are growing concerns with the environmental and health impacts of billions of tons of the coal combustion ashes that have been impounded and landfilled in the vicinity of coal-burning power plants over the past decades. A new method is proposed and partially verified for selective and large-volume incorporation of the carbon dioxide content of flue gas into impounded/landfilled coal ash without resorting to energy- intensive and costly high-temperature and high-pressure mineralization methods. The new process employs mechanochemical techniques which occur at ambient temperature and atmospheric pressure. This approach selectively captures the carbon dioxide content of flue gas, and incorporates it into impounded/landfilled coal ash as disordered carbonates. Concurrent incorporation of CO2 into and mechanical activation of ash yields a hydraulic binder with strong capabilities for stabilization/solidification of hazardous and radioactivewaste via formation of integrated carbonates and zeolitic structures. These structures permanently bind carbon dioxide as crystalline carbonates. The preliminary study undertaken to partially verify the proposed concepts demonstrated the potential for incorporation of carbon dioxide into coal ash particles at room temperature via mechanical activation in a dilute CO2 environment. This study also demonstrated the potential for concurrent CO2 incorporation into and mechanical activation of coal ash for production of a high-performance and sustainable hydraulic binder. Finally, the preliminary study confirmed that the CO2 incorporated into the coal ash particles at relatively large volumes yields beneficial effects by carbonation reactions supplementing the formation of zeolitic structures during the hydration process. The proposed Phase I project will: (i) develop models and devise theoretically viable formulations and processing conditions for concurrent CO2 incorporation into and mechanical activation of impounded/landfilled coal ash; (ii) experimentally verify the governing mechanisms and the beneficial effects of CO2 beneficiation of coal ashes subjected to mechanical activation for use in stabilization/solidification of hazardous and radioactive wastes; and (iii) verify and quantify the net CO2 consumption in the process, and the value rendered by CO2 to improve the competitive performance, cost and sustainability advantages of activated ash as a commercially viable inorganic binder for stabilization/solidification applications. Commercially viable methods will be developed for value-added and large-volume use of the CO2 emissions from coal-burning power plants to beneficiate the landfilled coal ash for environmental applications. Commercial Applications and Other Benefits: Value-added use of the CO2 emissions of coal-burning power plants to beneficiate the tremendous volumes of coal ash impounded and landfilled in the vicinity of power plants can transforms large volumes of carbon dioxide and the problematic solid residues of coal combustion into marketable products for large-volume use in stabilization/solidification of hazardous and radioactive wastes. The resulting inorganic binder offers distinct advantages in stabilization/solidification applications due to the parallel formation of integrated zeolitic structures and crystalline carbonates. The novel and simple processing techniques employed in the project enable cost-effective processing of CO2 into commercially viable end products which create market-driven opportunities for value-added and large- volume use of CO2 in environmental applications.