Treatment of Flue Gas using Graphene Sponge: A Simulation Study

Grand canonical Monte Carlo simulations are conducted to investigate the adsorption ability of a 3-D graphene sponge (GS) to separate acidic gases from flue gas stream. To assess the adsorption capacity of GS, first, adsorption of pure component flue gas is studied at a temperature of 303 K and varying pressure up to 2.5 bar. Subsequently, the adsorption capacity and selectivity of GS are investigated for a ternary mixture (CO2/SO2/N-2) of flue gas under the same conditions. This study shows that the maximum adsorption capacity of GS for pure component flue gas is observed for SO2 followed by CO2 and N-2. The adsorption uptake decreases with an increase in pore size of GS. At 1 bar, the amount of adsorption of SO2 and CO2 are similar to 13 mmol/g and, similar to 2.6 mmol/g, respectively. Upon increasing the average pore size to 20 A, the excess amount decreases 56% and 58% for SO2 and CO2, respectively. The adsorption capacities of GS for CO2 and SO2 are better than other carbon based adsorbents except for CNT bundles. In the case of a ternary mixture of N-2, CO2, and SO2 in the mole ratios of 0.8, 0.15, and 0.05, we found that the adsorption behavior follows the same order as in the pure component flue gas adsorption. However, the adsorption amount decreases significantly from that of pure component adsorption amount in GS. The adsorption amount of SO2 and CO2 at postcombustion conditions decreases to 1.3 mmol/g and 0.5 mmol/g, respectively, which further decreases upon increasing the average pore size. Selectivity analysis of adsorption shows that the adsorption selectivity of SO2 over N-2 is the maximum followed by the selectivity of CO2 over N-2 and SO2 over CO2. Both selectivity and uptake capacity decreases with increase in average pore size of GS.