煤层后生生物H2S原位抑制机制试验研究

Experimental study on in-situ inhibition mechanism of epigenetic biogenic H2S in coal seam

  • 摘要: 在煤层气排采过程中,无论是高硫煤还是高硫酸盐煤层水,均易产生后生生物成因H2S:高硫煤中的有机硫经微生物降解转化为硫酸盐后,再被硫酸盐还原菌(SRB)还原为H2S;高硫酸盐煤层水中的硫酸盐则直接被SRB还原。二者机理同源,仅底物来源不同。针对这一共性问题,以晋城太原组15号高硫煤及本源菌为体系,比较钨酸钠与钼酸钠的梯度添加对H2S的抑制效果。结果表明:钼酸钠虽能抑制H2S,但在质量浓度为1.0 g/L时几乎同时抑制CH4生成(H2S累计产量为0.03 mL/g,CH4累计产量为0.08 mL/g);钨酸钠对CH4生成影响较小,其中在质量浓度为0.8 g/L时抑制效果最优。在此添加量下,气相H2S体积分数峰值由对照组第12天的240×10−6降至试验组第3天的27×10−6,峰值降低约88.8%并显著提前;H2S累计产量由5.72 mL/g降至1.88 mL/g,降低67.1%;CH4累计产量由4.25 mL/g升至4.50 mL/g,增加5.9%,且产气高峰提前3 d,说明钨酸钠的添加不抑制,甚至轻微促进产CH4。在添加钨酸钠的系统中,钨酸盐经TupABC/ModABC系统转运进入细胞后,竞争ATP硫化酶形成不稳定APW(5'−腺苷酸钨酸盐),阻断\mathrmSO_4^2- 到APS(5'−腺苷酸磷酸硫酸盐)的起始激活,表现为整个发酵过程中\mathrmSO_4^2- 含量不降反升。宏基因组和菌群测试表明,水解菌Macellibacteroides相对丰度下降,上游有机硫向硫酸盐的供给减缓;硫酸盐还原菌Desulfitibacter及关键基因sat/aprAB/dsrAB相对丰度下降,而钨酸盐转运基因tupABC/modABC相对丰度上升;乙酸营养型产甲烷菌 Methanosaeta相对丰度较对照组提高了55.51%,底物(VFA)更多流向产甲烷途径;亦识别到细菌Wolinella以亚硫酸盐为受体产H2S及与甲基营养型产甲烷菌共生产H2S,但SRB路径仍是主要且可控靶点。研究为压裂与排采阶段后生生物H2S的原位抑制提供了一种有效的技术,可避免煤层气产出后的被动脱硫,不仅经济效益显著,而且有利于抽采管路的维护。

     

    Abstract: During coalbed methane (CBM) drainage and production processes, both high-sulfur coal and high-sulfate coal seam water are prone to generate epigenetic biogenic H2S. The organic sulfur in high-sulfur coal is converted into sulfate by microbial degradation, and then reduced to H2S by sulfate-reducing bacteria (SRB). Sulfate in high sulfate coal seam water is directly reduced by SRB. These two pathways share the same mechanism but differ in substrate sources. In this common issue, the Jincheng Taiyuan Formation No.15 high-sulfur coal and indigenous bacteria were employed as the experimental system, and the H2S inhibition effects of gradient additions of sodium tungstate and sodium molybdate were compared.The results demonstrated that while sodium molybdate could inhibit H2S production, it almost simultaneously suppressed CH4 generation at 1.0 g/L concentration (cumulative H2S production H2S is 0.03 mL/g, cumulative CH4 production is 0.08 mL/g). Sodium tungstate showed minimal impact on CH4 production, with 0.8 g/L identified as the optimal concentration. Under optimal conditions, the peak gas-phase H2S concentration decreased from 240×10−6 on day 12 in the control group to 27×10−6 on day 3, representing an approximately 88.8% reduction with significantly earlier peak occurrence. The cumulative H2S production decreased from 5.72 mL/g to 1.88 mL/g (67.1% reduction), while cumulative CH4 production increased from 4.25 mL/g to 4.50 mL/g (a decrease of 5.9%), with the gas production peak advancing by 3 days. These findings indicate that sodium tungstate addition does not inhibit and may even slightly promote CH4 production. In systems supplemented with sodium tungstate, tungstate is transported into cells via TupABC/ModABC transporters, where it competes with ATP sulfurylase to form unstable APW (adenosine 5'-phosphotungstate), blocking the initial activation from \mathrmSO_4^2- to APS (adenosine 5'-phosphosulfate). This manifests as an increase rather than decrease in \mathrmSO_4^2- concentration throughout the fermentation process. Metagenomic and microbial community analyses revealed a decrease in the relative abundance of hydrolytic bacteria Macellibacteroides, slowing the upstream supply of organic sulfur to sulfate. The abundance of SRB (Desulfitibacter) and key genes (sat/aprAB/dsrAB) decreased, while tungstate transporter genes (tupABC/modABC) increased. The relative abundance of acetoclastic methanogen Methanosaeta increased by 55.51% compared to the control, with more substrate (Volatile Fatty Acids, VFA) directed toward methanogenic pathways. Additionally, H2S production by Wolinella using sulfite as an electron acceptor and symbiotic H2S production by methylotrophic methanogens were identified. However, the SRB pathway remains the primary and controllable target. This study provides an effective technology for in-situ inhibition of epigenetic biogenic H2S in fracturing and drainage stages, which can avoid passive desulfurization after coalbed methane production. It not only has significant economic benefits, but also is conducive to the maintenance of extraction pipelines.

     

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