Simulation Of The Interaction Between Water And Carbon Particles In Fly Ash From Coal Combustion

Since the carbonaceous particles have a significant impact on human health, climate, environment. Water vapor heterogeneous condensation is considered to be one of the effective methods of removing fine particulate matter, and therefore to study the interaction of the carbonaceous fine particles and water molecules is of great significance. The carbonaceous particles in fly ash from coal combustion mainly exist in the form of amorphous structure and graphite type structure, this article mainly from the molecular level theory to study the interaction between amorphous carbon particles and water molecules, also the interaction between the graphite carbon particles in the coal fly ash and water molecules.Firstly the quenched molecular dynamics method was used to get the structure model of amorphous carbon particle in fly ash from coal combustion. Then grand canonical monte carlo method was adopted to simulate the adsorption of water molecules in the amorphous carbon particles. The radial distribution function and Pore size distribution function of amorphous carbon particles of different initial density were analyzed. The effects of the physical structure factors such as initial density and pore size on the adsorption of water molecules were studied. Also the influence of temperature on the adsorption of water molecules in the amorphous carbon particles was discussed. The results show that: for the same atomic number of amorphous carbon particles, with the increase of initial density, the probability of the occurrence of a larger internal aperture is smaller. And the greater the initial density, the less the number of adsorption of water molecules in the amorphous carbon particles. With the increase of temperature, the adsorption quantity of water molecules in the amorphous carbon particles is declining. And the higher the temperature, the less the ability of carbon particles firstly adsorb water molecules.Secondly the model of graphite type carbon particles was constructed. Then the adsorption of water molecules in graphite carbon particles was studied from the molecular level theory. The effect of aperture size of graphite type carbon particles on the adsorption of water molecules in graphite carbon particles was investigated. The influence of temperature on the adsorption of water molecule in graphite carbon particles was explored. The results show that: for graphite type carbon particle with pore size 6nm, the number of adsorbed water molecules will increase with the increase of relative pressure. Eventually there will be a capillary condensation phenomenon. But the adsorption amount of water in carbon particles with pore size 2nm will be approaching the equilibrium value. The peak of energy distribution curves of interaction between graphite type carbonaceous particles of different pore size and water molecule is not identical. The higher the temperature, the slower the speed of carbonaceous particles adsorb water molecules.Finally, we constructed the carbonaceous particles model whose surface containing carboxyl and hydroxyl functional groups, and then we studied the effects of two of their surficial oxygen-containing functional groups on the adsorption of water molecules in the carbonaceous particles model. The results show that : for the two types of carbonaceous particles, the carboxyl functional groups on the carbonaceous particles' surface can enhance its adsorption ability of water molecules, and the surface hydroxyl groups can also enhance its adsorption ability of water molecules, but its enhancement effect is less than the surface carboxyl functional groups. And the carboxyl functional groups on the carbonaceous particles surface form hydrogen bonds with water molecules.