(122g) Enabling Sustainable Fossil Fuel Energy Conversion Systems: Co2 and So2 Mineral Sequestration and Utilization of Solid Byproducts

CO2 is a greenhouse gas, and its reduction and control has been the subject of much research effort. Mineral sequestration mimics natural chemical transformations of CO2, such as the weathering of rocks, to form calcium or magnesium carbonates. Since CO2 is chemically immobilized and incorporated into the mineral matrix, there is no possibility of an accidental release of CO2 from the disposal site. Therefore, mineral sequestration offers a safe and permanent method of CO2 disposal. In this study, a pH swing process that utilizes both chemical and physical activation of Mg-bearing minerals is developed to provide an economically feasible CO2 and SO2 abatement method, which will allow for sustainable electricity generation.

Screening of mineral samples for their application in the CO2 mineral sequestration scheme has identified both olivine and serpentine to be viable candidates. From the investigation of serpentine dissolution in various solvents, the chelating agent that promotes the dissolution of Mg-bearing minerals, while not interfering with the precipitation of both iron oxide and magnesium carbonate, are identified. Next, the dissolution of Mg-bearing minerals is physically activated and, moreover, CO2 is sequestered using a pH swing process that has recently been patented. Both in-situ physical activation and utilization of the pH swing process drastically improved the mineral carbonation compared to techniques previously demonstrated.

In addition, by controlling the pH of the system, three solid products were generated: SiO2-rich solids, iron oxide, and MgCO3·3H2O. Since the iron oxide and magnesium carbonate produced were highly pure, these value-added products could eventually reduce the overall cost of the carbon sequestration process. In addition, it was found that the Mg-rich solution prepared during the pH swing process was also effective at removing SO2 from flue gas. Consequently, there is a potential application of this process as a multi-pollutant control system. Based on the Life Cycle Analysis results, the proposed carbon sequestration process is confirmed to be a net consumer of CO2.