基于硅酸盐熔体结构演变的煤灰黏温特性调控机制

The regulation and prediction of ash viscosity-temperature characteristics (AVT) has been a key for the development of coal entrained-flow gasification technology. The composition and structure of silicate melts are important factors to determine coal AVT. In view of the slag problems related to adhering and discharge during the process of coal entrained-flow gasification, the aim of this project is to explore the AVT regulation mechanism of coal from the perspective of structure evolution of silicate melts and crystal precipitation, and to build the prediction model of AVT. Through the analyses of the transformation behaviors of typical aluminum mineral in coal at high temperature and its thermodynamic constants, and the discussions of the AVT and structure characteristics of silicate melts for different silicon-aluminum (SiO2 + Al2O3) content coals, the influences of aluminum mineral content on AVT and the structure of silicate melts are to be investigated. Based on the exploration of the influences of ash composition on the AVT and silicate melt structure, the evolution mechanism of composition on silicate melts structure and crystal precipitation mechanism from silicate melts are to be explored from the views of mineral reaction tendency and molecular reaction route, and the influences of silicate melts structure variation and crystal precipitation on the AVT are to be clarified by the chemical bond theory. After that, the co-relationship between AVT and the structural parameters of ash silicate melts, and the AVT prediction model will be constructed through the least square support vector machine technology. Finally, the mode will be verified by the experiments of coal blending or additive. This result will provide basic data and guidance to regualte the AVT and determine the operating parameters during coal entrained-flow gasification.

煤灰黏温特性调控和预测是气流床气化技术发展的关键环节。硅酸盐熔体组成和结构是决定煤灰黏温特性的重要因素。针对煤气流床气化中挂渣和排渣等问题，从硅酸盐熔体结构演变和晶体析出角度探索煤灰粘温特性的调控机制，建立煤灰黏温特性预测模型。通过分析煤中含铝矿物质高温转化行为和热力学常数，表征不同硅铝含量煤灰的黏温特性和硅酸盐熔体结构特征，揭示含铝矿物质对煤灰黏温特性和硅酸盐熔体结构的影响；探索组成变化对煤灰熔融黏温特性和硅酸盐熔体结构的影响规律，从煤灰矿物质反应趋向性和分子反应路径角度探索组成变化引起硅酸盐熔体结构演变和熔体冷却晶体析出机理，发现组成改变导致煤灰熔融黏温特性变化的价键结构基础；采用最小二乘支持向量机模型构建煤灰黏温特性与硅酸盐结构参数的关联，建立煤灰黏温特性预测模型。通过配煤或添加剂试验完善预测模型，为煤气流床气化灰黏温特性的调控和操作参数的优化提供基础数据和理论依据。

灰黏温特性调控和预测是煤气流床气化发展的关键。针对煤气流床气化中结渣问题，在从硅酸盐熔体结构演变角度探索灰黏温特性调控机制的基础上，建立灰融温度预测模型。（1）Na2O, Fe2O3和CaO增加阻止了莫来石生成，促进了低熔点钠长石、铁尖晶石生成，导致灰熔点降低；磷能够逐渐取代硅酸盐或硅铝酸盐中的硅生成不同熔点的磷酸盐，P2O5添加促使沙咀子煤灰中低熔点磷铝矿石生成和莫来石的减少从而引起灰熔点降低，而准东煤和义马煤灰中高熔点磷酸钙的生成导致灰熔点的提高。（2）对襄阳煤，随晋城无烟煤增加，钙长石含量明显增加导致灰熔点提高；随孙家壕煤或沙咀子煤的添加高熔点莫来石和刚玉的形成引起灰熔点升高；（3）随着Na2O, Fe2O3和CaO含量的增加，网状稳定结构的桥氧键被金属离子(如：Fe2+，Ca2+和Na+) 破坏，形成大量非桥氧键使硅酸盐网络结构松弛，导致灰熔融温度下降和黏度降低。随着高硅铝煤灰质量比的增加，高钙高铁煤灰样品中的R（R =（Q3 + Q2）/（Q1 + Q0））逐渐增加和非桥氧键与桥氧键的比值降低，引起Si-O和Si-O-Al向高频区域移动，形成更稳定的硅酸盐网络结构，促使灰熔融温度和黏度的提高。(4) 发现煤灰流动温度（FT）与FactSage计算的90%液相质量分数对应温度（T90）的关联：FT=245.837+0.765T90（相关系数0.91），找到了FT与FactSage计算的矿物因子（MF）的相关性：FT=0.64MF+1332（相关系数0.94）；发现不同液相含量段（0–20%, 20–85%和85–100%）随温度变化趋势与煤灰特征温度的关系，提出根据三段变化趋势交点对应温度预测灰变形温度和流动温度的方法。该成果丰富了灰的硅酸盐熔体结构理论，通过对灰黏温特性的调控能有效避免煤等含碳物质气流床煤气化因排渣不畅而引起的停车，具有重要的理论和实践意义。