化工学报 ›› 2019, Vol. 70 ›› Issue (8): 3094-3103.DOI: 10.11949/0438-1157.20190310

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不同温度下煤灰熔渣的结构演变规律

王浩男(),玄伟伟(),夏德宏   

  1. 北京科技大学能源与环境工程学院,北京 100083
  • 收稿日期:2019-04-01 修回日期:2019-05-09 出版日期:2019-08-05 发布日期:2019-08-05
  • 通讯作者: 玄伟伟
  • 作者简介:王浩男(1994—),男,硕士研究生,<email>s20170164@xs.ustb.edu.cn</email>
  • 基金资助:
    国家自然科学基金项目(51606009);中央高校基本业务费项目(FRF-TP-18-017A2)

Structural evolution of coal ash slag at different temperatures

Haonan WANG(),Weiwei XUAN(),Dehong XIA   

  1. School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China
  • Received:2019-04-01 Revised:2019-05-09 Online:2019-08-05 Published:2019-08-05
  • Contact: Weiwei XUAN

摘要:

采用热力学计算和分子动力学模拟方法研究了高铁煤灰熔体的结构特征以及结构随温度的变化规律,计算了不同温度下Fe3+和Fe2+的含量,分析了径向分布函数、配位数、键角、桥氧与非桥氧、Q n 结构单元等结构特征。热力学计算的结果显示温度升高有利于Fe3+转变成Fe2+,据此得到了Fe3+/Fe2+随温度的变化规律。在采用BMH势函数的基础上,分子动力学模拟显示熔体具有短程有序,长程无序的结构特征。随着温度升高,各离子对的径向分布函数曲线的高度和尖锐度下降,各离子的较高配位状态减少,较低配位状态增加,键角曲线的高度和锐度降低并向较小的方向移动,预示着离子的聚集程度减弱,熔体内部的无序化程度增强。氧的配位状态和Q n 的变化是熔体聚合度变化的直观反映,温度升高导致三配位氧和桥氧含量降低,非桥氧和自由氧含量增加,并最终导致较高聚合度的Q4结构单元解体生成较低聚合度的Q3、Q2、Q1和Q0结构单元。

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

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