中低阶煤官能团对煤润湿性影响试验研究

Experimental study on the influence of middle and low rank coal functional groups on coal wettability

煤层注水可有效抑制煤矿开采过程中瓦斯大量涌出,其抑制效果主要取决于煤层的润湿特性。煤的化学结构是影响煤体润湿性的重要因素之一,为研究中低阶煤体官能团与其润湿性之间关系,对典型中低阶煤样进行煤质特征分析,采用Nicolet iN10傅里叶变换显微红外光谱仪得到煤样官能团参数。以去离子水在煤表面固−液−气交界处接触角的大小来表征煤体润湿性强弱,采用JC2000D接触角测量仪得到煤样接触角大小;Zeta电位可反映煤样润湿性和煤表面官能团电离程度,以此建立煤样亲水性官能团(羟基官能团、其他含氧官能团)与接触角、Zeta电位的关系。试验结果表明:随着煤变质程度增加,煤样亲水性官能团强度逐渐减小,中阶煤亲水性官能团峰高较低阶煤降低0.13,吸收峰面积减小58.91;亲水性官能团与煤样接触角为负相关关系,即随着亲水性官能团吸收峰强度增大其接触角逐渐减小,从中阶煤艾维尔沟煤样到低阶煤屯堡煤样,接触角减小8.27°;亲水性官能团与煤样Zeta电位呈一阶指数衰减函数关系,其相关系数高达0.95以上,即随着亲水性官能团吸收峰面积增大其Zeta电位绝对值逐渐增大,煤样表面负电性强,煤体亲水性好。其中,羟基官能团对煤润湿性影响较大,自缔合羟基形成的氢键是主要影响煤体润湿的因素;其他含氧官能团中的羧基、醚键等亲水性官能团在分子间作用力下与水分子结合,表现出较强的活力,提高了煤体亲水性。

Coal seam water injection can effectively inhibit gas gushing in the process of coal mining,and its inhibition effect mainly depends on the wetting characteristics of coal seam.The chemical structure of coal is one of the important factors affecting the wettability of coal.In order to study the relationship between the functional groups of medium and low rank coal and its wettability,the coal quality characteristics of typical medium and low rank coal samples were analyzed,and the parameters of different coal samples were obtained by Nicolet iN10 Fourier Transform microscopic infrared spectrometer.In this paper,the size of the contact Angle of deionized water at the solid-liquid-gas junction on the coal surface is used to characterize the wettability of coal.JC2000D contact Angle measuring instrument is used to obtain the contact Angle of different coal samples.Zeta potential can reflect wettability and ionization degree of coal surface functional groups,so as to establish the relationship between hydrophilic functional groups(hydroxyl functional groups,other oxygen-containing functional groups),contact Angle and Zeta potential of coal samples.The experimental results show that with the deepening of coal metamorphism,the strength of hydrophilic functional groups of coal samples decreases gradually,the peak height of hydrophilic functional groups of middle rank coal decreases by 0.13 compared with that of low rank coal,and the absorption peak area decreases by 58.91.The hydrophilic functional groups are negatively correlated with the contact Angle of coal samples,that is,the contact Angle decreases gradually with the increase of absorption peak intensity of hydrophilic functional groups,and the contact Angle decreases by 8.27°from middle rank coal samples to low rank coal samples.The relationship between hydrophilic functional groups and Zeta potential of coal samples shows a first-order exponential decay function,and the correlation coefficient is as high as 0.95.That is to say,the absolute value of Zeta potential increases gradually with the increase of absorption peak area of hydrophilic functional groups.The surface electronicity of coal samples is strong,and the hydrophilicity of coal is good.Among them,the hydroxyl functional group has a great influence on the wettability of coal,and the hydrogen bond formed by self-associating hydroxyl group is the main factor affecting the wettability of coal.Other oxygen-containing functional groups,such as carboxyl and ether bond hydrophilic functional groups,combine with water molecules under intermolecular force,showing strong vitality and improving the hydrophilicity of coal.