戚绪尧,王涛,张兰君,等. 低共熔溶剂抑制煤自燃的机理[J]. 煤炭学报,2024,49(4):1917−1930. DOI: 10.13225/j.cnki.jccs.XR23.1551
引用本文: 戚绪尧,王涛,张兰君,等. 低共熔溶剂抑制煤自燃的机理[J]. 煤炭学报,2024,49(4):1917−1930. DOI: 10.13225/j.cnki.jccs.XR23.1551
QI Xuyao,WANG Tao,ZHANG Lanjun,et al. Mechanism of deep eutectic solvent on coal spontaneous combustion[J]. Journal of China Coal Society,2024,49(4):1917−1930. DOI: 10.13225/j.cnki.jccs.XR23.1551
Citation: QI Xuyao,WANG Tao,ZHANG Lanjun,et al. Mechanism of deep eutectic solvent on coal spontaneous combustion[J]. Journal of China Coal Society,2024,49(4):1917−1930. DOI: 10.13225/j.cnki.jccs.XR23.1551

低共熔溶剂抑制煤自燃的机理

Mechanism of deep eutectic solvent on coal spontaneous combustion

  • 摘要: 化学阻化是防治煤自燃的重要手段之一,提出了一种基于低共熔溶剂(DES)的类离子液体阻化方法。首先,采用加热法制备并筛选了7种室温低共熔溶剂,分析了不同DES处理后煤样的官能团及热力学特性变化规律,在此基础上采用密度泛函理论分析了DES中氢键强度对煤理化性质的改性差异,推导了低共熔溶剂的阻化机制及其最佳氢键强度。研究结果表明:DES处理后煤中氢键网络被破坏重排,脂肪烃与芳香烃相对丰度增加了10%~37%,脂肪族支链结构参数降低了9.38%~20.65%,含氧官能团(C=O和C—O)相对丰度下降了22.88%~56.94%,游离的小分子化合物和矿物质被溶出。DES处理后煤的蒸发脱附阶段质量损失和吸氧增重阶段的吸氧量减小,低温氧化阶段和热分解阶段放热量降低,减小幅度分别为8.94%~77.51%和5.40%~26.20%。氢键受体(HBD)作用点位电负性越强,与氢键供体(HBA)形成的DES团簇氢键强度越大。DES中氢键强度与煤中氢键网络破坏程度呈正相关关系,与吸氧增重阶段的吸氧量和低温氧化放热量及矿物质脱除率呈局部相关性。DES通过溶解煤中活性成分削弱煤的低温氧化强度。并通过促进氢键重排,将低热稳定性氢键转换为热稳定性更高的环状氢键四聚体和OH—N氢键,以此提高煤的断键吸热量。但过高的氢键强度将会抑制活性侧链的脱除和溶解,因此抑制煤自燃的低共熔溶剂的最佳氢键强度应控制在69.45~160.00 kJ/mol。

     

    Abstract: Chemical inhibition is one of the important measures for the prevention and control of coal spontaneous combustion. This paper proposed a quasi-ionic liquid inhibition method based on deep eutectic solvents (DES). First, seven kinds of room temperature deep eutectic solvents were prepared and screened using a heating method. The changes in the functional groups and thermodynamic characteristics of different DES-treated coal samples were analyzed. On this basis, the density functional theory was utilized to analyze the differences in the modification of coal's physicochemical properties by the hydrogen bond strength in the DES, and the inhibition mechanism of deep eutectic solvents and their optimal hydrogen bond strength were deduced. The results showed that after the DES treatment, the hydrogen bond network in coal was disrupted and rearranged. The relative abundance of aliphatic and aromatic hydrocarbons increased by 10%−37%, the content of aliphatic side chains decreased by 9.38%−20.65%, the relative abundance of oxygen-containing functional groups (C=O and C—O) decreased by 22.88%−56.94%, and free low-molecular compound and minerals were leached out. After the DES treatment, the mass loss during the evaporation and desorption stage of coal and the oxygen uptake during the oxygen absorption stage decreased. The heat release during the low temperature oxidation stage and the thermal decomposition stage was reduced by 8.94%−77.51% and 5.40%−26.20%, respectively. The stronger the electronegativity of the hydrogen bond acceptor site in the HBA, the greater the hydrogen bond strength formed between HBA and HBD. The hydrogen bond strength in the DES was positively correlated with the degree of destruction of the hydrogen bond network in coal, and was locally correlated with the oxygen uptake during the oxygen absorption stage, the heat release during low temperature oxidation, and the mineral removal rate. The DES weakened the low-temperature oxidation reactivity of coal by dissolving its active components, and increased the bond dissociation enthalpy of coal by promoting the rearrangement of hydrogen bonds into more thermally stable OH4 and OH—N hydrogen bonds. However, the excessive strong hydrogen bond strength would inhibit the removal and dissolution of active side chains. Therefore, the hydrogen bond strength of deep eutectic solvents used to inhibit coal spontaneous combustion should be controlled between 69.45 kJ/mol and 160.00 kJ/mol.

     

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