H2O2预处理胜利褐煤镜质组的生物产气研究

Biogas production of vitrinite from Shengli lignite pretreated with H2O2

摘要:

【目的】研究H₂O₂处理对煤中镜质组生物产气的影响。【方法】选择内蒙古胜利褐煤作为研究对象，以实验室前期富集保存的产甲烷微生物作为出发菌群，首先通过浮选对煤炭进行显微组分分离(高镜质组GJ、中镜质组ZJ和低镜质组DJ)，并对煤的物化性质进行表征，然后在固液比1:15、H₂O₂浓度10%、预处理时间30 d条件下用H₂O₂处理不同镜质组含量的样品，再以处理前后的原煤及残煤进行生物产气实验。采用气相色谱、X射线衍射和傅里叶变换红外光谱等方法分析H₂O₂处理前后产气及煤的物化性质变化。【结果】经过H₂O₂预处理后，煤中镜质组的含量有所下降，挥发成分增加，固定碳减少，H₂O₂与高镜质组煤样反应更剧烈，氧含量增加，碳含量减少。未经过处理的煤在100 d时产甲烷量为GJ＞ZJ＞DJ，分别为174.24、164.31、135.52 μmol/g煤，而经过H₂O₂预处理的煤在20 d后停止产气，最终产甲烷量分别为39.63、39.61、41.55μmol/g煤，比原煤产气减少了77.26%、75.89%和69.34%。随着镜质组含量的增加，经过H₂O₂处理后的煤样芳香环层片的层间距d₀₀₂、单层层片的延展度L_a和层片的堆叠度L_c减小，而芳香层数N增加，表明晶核结构变小。经过H₂O₂处理后煤芳烃碳、芳香族、C=O基团和C=C基团所占比例增加，芳环缩合度增大，含氧官能团变多。【结论】利用H₂O₂长时间处理使煤基质中较易被微生物利用的有机质结构减少，从而降低了产气能力。

Abstract:

[Objective] To study the effect of hydrogen peroxide (H₂O₂) treatment on biogas production of vitrinite from coal. [Methods] Shengli lignite collected from Inner Mongolia was used in this study. The methanogenic microbial consortium previously enriched and preserved in our laboratory was used as the inoculum. Coal macerals were separated by floatation, which yielded three samples containing high vitrinite (GJ), medium vitrinite (ZJ), and low vitrinite (DJ). After being characterized, the samples were treated with 10% H₂O₂ for 30 days at a solid-to-liquid ratio of 1:15. Biogas production experiments were conducted with the coal samples before and after treatment. Gas chromatography was employed to analyze the gas composition, and X-ray diffractometry and Fourier transform infrared spectroscopy were employed to study the physical and chemical properties of the coal before and after treatment as well as after gas production.[Results] The coal samples after H₂O₂ treatment showcased reduced vitrinite content and carbon fixation and increased volatile matter. The reaction was more intense in the coal sample with high content of vitrinite, accompanied by increased oxygen content and reduced carbon. Methane yields from untreated coal samples on day 100 followed the order of GJ (174.24 μmol/g coal)＞ZJ (164.31 μmol/g coal)＞DJ (135.52 μmol/g coal). However, the coal samples pretreated with H₂O₂ ceased gas production after day 20, with the gas yields of 39.63, 39.61, and 41.55 μmol/g coal, respectively, representing reductions of 77.26%, 75.89%, and 69.34%, respectively, compared with those from the coal samples without treatment. Furthermore, as vitrinite content increased, the coal samples demonstrated decreased layer spacing (d₀₀₂) of the aromatic ring lamellae, ductility (L_a) of the single-layer lamellae, and stacking degree (L_c) of the lamellae and increased number of aromatic layers (N) after H₂O₂ treatment, which indicated that the crystal nuclei appeared smaller. In addition, H₂O₂ treatment led to increased proportions of aromatic carbons, aromatic moieties, C=O groups, and C=C groups, enhanced aromatic ring condensation, and increased number of oxygen-containing functional groups. [Conclusion] Long-term H₂O₂ treatment reduces organic matter that is readily bioavailable in coal matrix, thereby decreasing gas production.