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.