电化学强化无烟煤吸水性的实验研究

Experimental study on electrochemical enhancement of water absorption of anthracite

  • 摘要: 煤层注水是一种常见的降低工作面粉尘、防止瓦斯突出的方法,但无烟煤的疏水性强,煤层注水效果欠佳,电化学方法可以显著提高无烟煤表面润湿性和孔裂隙发育程度,达到强化煤层注水的目的。采用0.05 mol/L的Na2SO4电解液对山西晋城寺河煤矿无烟煤进行电化学改性实验,并对改性前后煤样的吸水性能、表面特性和孔隙特征进行测试和分析。研究结果表明:电化学改性后煤样的含水率较原煤的增幅随吸水时间呈现先增大后减小,最后逐渐趋于稳定的趋势,与无烟煤自然煤样相比,电化学改性后阳极、中间和阴极区域煤样自然吸水率分别提高了72.57%,87.14%和102.29%;电化学改性阳极区域发生氧化反应,使煤样中的芳烃和脂肪烃氧化为含氧官能基团,表面润湿性得到增强,煤-水动态接触角较改性前降低了25.96°,煤表面ζ电位为21.38 mV,中间和阴极区域均发生还原反应,使煤样中的烷基支链脱落,芳环发生裂解,氧的相对含量增加,煤-水动态接触角较改性前分别降低了20.40°和15.21°,煤表面ζ电位分别为-68.47,-80.01 mV;在电化学过程中产生的H+和电泳的作用下,无烟煤孔隙内充填的部分碳酸盐类矿物被溶蚀并发生运移,最终脱离煤体,改性后无烟煤中部分微孔产生“扩孔效应”,阳极、中间和阴极区域的平均孔径分别增大了3.77倍,3.67倍和5.02倍,增强了水的渗透性。

     

    Abstract: Coal seam water injection is a common method to reduce dust in coal working face and prevent gas outburst.However,the anthracite is highly hydrophobic and the coal seam water injection effect is limited. For the purpose of water injection in coal seam,the electrochemical method can significantly improve the surface wetta-bility and development of pore and fracture of anthracite. Anthracite in Sihe Coal Mine of Jincheng,China was electrochemically modified with 0. 05 mol / L Na2SO4 electrolyte,and the water absorption,surface properties and pore characteristics before and after modification were tested and analyzed. The results show that after the elec-trochemical modification, the changed water content of the coal sample increased first and then decreased,and finally gradually tended to be stable with time. Compared with the unmodified anthracite sample,the natural water absorption of the coal samples in the anode,middle and cathode regions increased by 72. 57% ,87. 14% and 102. 29% respectively. The oxidation reaction occurred in the electrochemically modified anode region,the aro-matic hydrocarbons and aliphatic hydrocarbons in the coal sample were oxidized to oxygen-containing functional groups,the wettability was enhanced,and the dynamic contact angle of coal-water was reduced by 25. 96°,the zeta potential was 21. 38 mV. The reduction reaction occurred in both the middle and cathode regions,so that the alkyl branch was detached,the aromatic ring was cracked,and the relative content of oxygen was increased,the coal-water dynamic contact angle was decreased by 20. 40° and 15. 21° respectively,the zeta potential was -68. 47 mV and -80. 01 mV respectively. Under the action of H+and electrophoresis generated in the electrochemical process,some carbonate minerals filled in the anthracite pores were dissolved and transported,and finally left the coal,thus,some micro-pores produced the “reaming effect”,and the average pore diameters of the anode,middle and cathode regions increased by 3. 77 times,3. 67 times and 5. 02 times respectively,and the permeability of water was improved. The research results in this paper provide a basis for the electrochemical modification of anthracite coal seam water injection.

     

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