Comparative studies of the equilibrium adsorption of CO2 onto coal ash zeolites Na-X and Na-Ca-X

Coal-fired Thermal Power Plants (TPPs) are the main source of greenhouse gas emissions in the atmosphere, but they also generate huge amounts of solid by-products, including fly ash (FA). A modern strategy for sustainable energy production is to improve the ecology of the TPPs by developing technological solutions for zero-emission plants. However, this concept is still far from a practical realization and requires intensive research efforts. Thanks to its aluminosilicate nature, FA is investigated to be converted into zeolites for applications in gas cleaning systems. The development of technologies for CO2 capture by fly ash zeolites (FAZ) will provide a join solution for the two main ecological problems concerning coal supplied TPPs, namely utilization of solid residues and implementation of carbon capture technologies. In the present study, the comparative studies were performed on the adsorption of CO2 onto FAZ obtained from FA referred to classes F and C according to the standard specification of coal fly ash (ASTM 618). FA-derived zeolites of Na-X and Ca-Na-X types were studied with respect to their specific surface and porosity by model studies of their nitrogen adsorption/desorption isotherms at cryogenic temperatures. The adsorption isotherms of CO2 were measured in the relative pressure range p/p0=0.001-0.03 at 0 oC and mathematically analyzed. Acknowledgements: The financial support of Bulgarian National Science Fund (BNSF) under the project DN 17/18 (12.12.2017) is highly appreciated.