Simulation of CO2 Chemisorption Characteristics in Coal and Power Plant Flue Gas.

The injection of flue gas originating from coal-fired power plants into underground strata, wherein carbon dioxide (CO2) is adsorbed by coal, achieves multiple effects: inhibiting coal spontaneous combustion, displacing gas, and sequestering CO2. To study the chemisorption characteristics of CO2 on coal surfaces at a microscopic level, models such as the Tashan lignite three-dimensional model and graphene-doped functional group coal model were constructed. The adsorption behavior of coal and CO2 was simulated using methods such as Monte Carlo, molecular dynamics, and density functional theory. Results reveal that the average isosteric heat of adsorption is close to the critical threshold, with a maximum exceeding 13 kcal/mol, confirming chemical adsorption. Radial distribution functions indicate that CO2 is most likely to undergo chemisorption near carboxyl groups. The density of states of the four oxygen-containing functional group-graphene coal models increased around -7 and -4 eV before and after CO2 adsorption. Analysis of the partial density of states reveals resonance peaks in the P orbital between CO2 and carboxyl groups, indicative of electron accumulation and bond formation. These findings provide theoretical support for flue gas injection into coal seams to achieve carbon-stable sequestration.