Interactions of nitric oxide with various rank coals: Implications for oxy-coal combustion flue gas sequestration in deep coal seams with enhanced coalbed methane recovery

Oxy-coal combustion is a promising option for capturing CO2 emitted from coal-fired power plant. Meanwhile, CO2 sequestration in deep coal seams with enhanced coal-bed methane (CH4) recovery (CO2-ECBM) can store the captured CO2 in geologic period. Thus, if the oxy-coal combustion flue gas directly sequestrated in deep coal seams is successfully implemented, the emissions of greenhouse gas (CO2) and the main gaseous pollutants (NOx, SO2) contained in flue gas will be simultaneously mitigated and CH4 as a by-product can also be recovered. It is acknowledged that the fluid sequestration in the deep coal seams is mainly attributed to the strong adsorption performance of coal matrix, thus the interactions of NO with various rank coals including adsorption behaviors and the possible interaction mechanism were primarily addressed in this work. Adsorption equilibrium study shows that the Sips isotherm model can well describe NO adsorption behavior on various rank coals, which is probably related to the high heterogeneity of coals. The Elovich equation can fit NO adsorption kinetics on coals successfully, indicating that the chemisorption probably plays a dominant role between NO and coals. Both Fourier Transform Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) characterization results further confirm that the interactions with NO can change the nitrogen speciation compositions of all the test coals, and chemisorption is the main interaction mechanism between NO and coals. The chemisorption mechanism between NO and coals will contribute to the steady storage of NO in the target coal seams.