Amorphous Structure Modeling And Adsorption Mechanism Study Of Unburned Carbon In Fly Ash

The unburned carbon is tiny carbon particle which remained due to coal incomplete combustion. After the high-temperature combustion process, it is rendered inside the amorphous and porous structure. It can replace the activated carbon used as a cheap catalyst carrier and the gas phase adsorbent, which plays an important role in many aspects of the production and life. There is still no clear understanding about the physical as well as chemical structure and the adsorption mechanism of the unburned carbon in current researches, thereby limiting the reuse of their resources to be maximized. It is necessary to introduce computer simulation methods to have a better understanding of the microporous carbon adsorption mechanism and the effects of different pore size distribution and surface characteristics on the adsorption.The quenched molecular dynamics method was used to get the amorphous structure model of unburned carbon through controlling different reaction conditions. This study had investigated the influence of different initial densities and quench rate on the amorphous structure and analyzed the distribution functions of the radial distribution and pore size distribution. The impact of the initial conditions on the resulting structure was obtained.Amorphous carbon samples were prepared by thermal depolymerization of the furfuryl alcohol. And its structure and adsorption performance were characterized, and thereby experimental verification of the model was conducted. The radial distribution function, the true density and pore size distribution were employed to verify the accuracy of the model and the force field.The N2and CO2adsorption properties of the established model were simulated using the grand canonical Monte Carlo method, and the comparisons of the experimental results and simulation results were obtained with the same conditions. The adsorption behavior of mixed component with equimolar ratio of CO2/N2in microporous amorphous carbon had been simulated. The effect of different pore size distribution on N2and CO2adsorption performance had been studied. The results show that:the microporous amorphous carbon has a high selectivity on mixed component with the equimolar ratio CO2/N2and the selectivity decreased with the increase of temperature, pressure and the average pore size. Finally, the surface modification of amorphous carbon was simulated in CO2gas with the use of molecular dynamics reactive force fields. To explore the effect of surface functional groups on CO2and N2adsorption, that were simulated using the grand canonical Monte Carlo method after the model modification when a variety of oxygen-containing functional groups were added on the amorphous carbon surface. The results show that:after the surface modification, the amount of CO2adsorption and the selectivity on the mixed component with equimolar ratio of CO2/N2increased while the amount of N2adsorbed decreased.