Syngas biomethanation using trickle bed reactor, impact of external hydrogen addition at high loading rate.xlsx

Syngas is a mixture of CO, CO₂, and H₂ produced from gasification carbon-containing feedstocks. Syngas can be biologically converted into methane (CH₄) using microbial consortia at lower energy input compared to conventional catalytic processes called syngas biomethanation. However, challenges such as H₂ limitation, poor gas solubility, and cell damage from mechanical agitation impact conversion efficiency. Trickle bed reactors (TBRs) offer a promising solution to these challenges by enhancing gas-liquid transfer through biofilm formation on packing material while minimizing shear stress, thus improving CH₄ productivity. Accordingly, this study investigated the effect of external hydrogen (H₂) injection on syngas biomethanation using two thermophilic TBRs at 51 ˚C. One TBR (TBR Control) was fed with syngas containing 15% CO, while the other received additional H₂(TBR Test). Both TBRs effectively converted syngas to CH₄, but TBR Test achieved higher performance, with over 90% CH₄ conversion efficiency at a gas loading rate of 15 m³/m³·d and a peak CH₄ production rate of 4.5 mmol/L_bed·h at 20 m³/m³·d. Volatile fatty acid concentrations remained low. 16S rRNA sequencing analysis showed dominance of <i>Methanobacterium</i>, indicating methanogenesis-driven activity. Overall, the study highlights the benefit of H₂ injection during syngas biomethanation and suggests future work should focus on optimizing reactor control to further enhance capacity.

合成气（Syngas）是由含碳原料经气化制备的一氧化碳（CO）、二氧化碳（CO₂）与氢气（H₂）的混合气体。相较于传统催化工艺，合成气可通过微生物菌群（microbial consortia）实现生物转化以生成甲烷（CH₄），该转化过程即合成气生物甲烷化（syngas biomethanation），且其能量输入更低。然而，氢气限制、气体溶解性不佳以及机械搅拌引发的细胞损伤等问题，会对转化效率产生不利影响。滴流床反应器（Trickle Bed Reactors, TBRs）可为上述挑战提供颇具前景的解决方案：其通过在填料表面形成生物膜强化气液传质，同时可有效降低剪切应力，进而提升甲烷产率。据此，本研究在51℃条件下，采用两台嗜热型滴流床反应器，探究了外源氢气（H₂）补加对合成气生物甲烷化的影响。其中一台反应器（对照组TBR）以含15%一氧化碳的合成气为进料，另一台实验组TBR则额外补加氢气。两台反应器均成功将合成气转化为甲烷，但实验组TBR的性能更优：在气体负荷为15 m³/(m³·d)时，甲烷转化效率超过90%；在20 m³/(m³·d)的负荷下，甲烷产率峰值可达4.5 mmol/(L_床·h)。体系内挥发性脂肪酸浓度始终维持在较低水平。16S核糖体RNA（16S rRNA）测序分析结果显示，产甲烷杆菌属（Methanobacterium）为菌群优势菌属，表明体系的核心代谢活性为产甲烷途径。综上，本研究证实了合成气生物甲烷化过程中补加氢气的积极作用，并建议未来研究应聚焦于反应器调控优化，以进一步提升系统产能。