关键词: 高铁煤灰熔渣, 显微结构, 分子模拟, 计算机模拟, 热力学计算, 聚合度

Abstract:

The structural characteristics of high iron coal ash melt and the variation of structure with temperature were studied by thermodynamic calculation and molecular dynamics simulation. The contents of Fe³⁺ and Fe²⁺ at different temperatures were calculated, and the radial distribution function, coordination number, bond angle, coordination state of oxygen and Q ⁿ structural units were analyzed. The results of thermodynamic calculations show that the increase of temperature is beneficial to the conversion of Fe³⁺ to Fe²⁺, and the change of Fe³⁺/Fe²⁺ with temperature is obtained. Based on the BMH potential function, molecular dynamics simulations show that the melt has short-range order and long-range disordered structural features. As the temperature increases, the height and sharpness of the radial distribution function curve of each ion pair decrease, the higher coordination state of each ion decreases and the lower coordination state increases, the height and sharpness of the bond angle curve decrease and the first peak moves in a smaller direction. These phenomena all indicate that the degree of aggregation of ions is weakened, and the degree of disorder inside the melt is enhanced. The coordination state of oxygen and the change of Q ⁿ are a direct reflection of the change of melt polymerization degree. The increase of temperature leads to the decrease of tri-coordinate oxygen and bridge oxygen, and the increase of non-bridge oxygen and free oxygen. Q⁴ structural unit disintegrated to generate Q³, Q², Q¹ and Q⁰ structural units with lower degree of polymerization.

Key words: high iron coal ash slag, microstructure, molecular simulation, computer simulation, thermodynamic calculation, degree of polymerization