Effects of coal swelling on modeling of CO₂ sorption on the coal and correction approaches

Volumetric errors that occurred in the isothermal sorption experiment were quantitatively modified in both Langmuir model and Dubinin-Astakhov model with a volumetric deviation. Furthermore, the experimental data of CO₂ isothermal sorption under 25 and 40°C conditions were refitted by the modified models. Modeling results indicate that the modified refitting results agree with experimental data much more satisfactorily than the fitting without model modification. The correlation coefficient of modified refitting curves with experimental data of 25 and 40°C is up to 0.998 and 1.000 respectively. Comparing to the tested adsorption capacity of coal with volume errors of coal swelling, the corrected adsorption capacities of coal towards CO₂, as predicted by the modified Langmuir and Dubinin-Astakhov models, increase by 1.8% to 29.3% and 1.1% to 8.2% respectively. Dubinin-Astakhov model generally works better than Langmuir model in the modeling of CO₂ sorption.