功率超声波强化产氢产甲烷梯度发酵机理

Hydrogen and methane gradient fermentation could produce both hydrogen and methane, and obtain higher theoretical energy yield and organic loading rate than traditional single phase anaerobic fermentation. However, due to the division of anaerobic fermentation stage in hydrogen and methane gradient fermentation, the hydrogen producing phase got hydrogen partial pressure increase and organic acids accumulation, which decreased the actual energy yield and fermentation stability. In present researches the hydrogen partial pressure were mainly decreased by mechanical stirring and gas stripping，and the accumulative organic acids were neutralized by the effluent recycle of methanogenic phase. However, mechanical stirring and gas stripping could only promote hydrogen bubble escaping from liquid, seldom promote hydrogen mass transfer inner microbial aggregates, and the effluent recycle cannot increase the organic acids degradation rate in methanogenic phase. To solve above problems, the project presented the technical scheme which integrate technologies of power ultrasound enhancement and solid and liquid cross recycle between hydrogen producing phase and methanogenic phase. Experiment and theoretical analysis will be applied to reveal the mechanism of power ultrasound enhancing hydrogen mass transfer inner microbial aggregates, clarify the influence of solid and liquid cross recycle on the gradient fermentation, and realize the efficient coupling of hydrogen producing phase and methanogenic phase. The project will be helpful to solving the bottleneck problem of hydrogen and methane gradient fermentation.

产氢产甲烷梯度发酵可同时获得氢和甲烷，比单相厌氧发酵具有更高理论能量产率和有机负荷率。但由于该过程分割了常规的厌氧发酵过程，使产氢相发生氢分压升高和有机酸积累，降低了系统实际能量产率和发酵稳定性。降低氢分压可采用机械搅拌和气体吹脱，平衡有机酸可采用发酵液回流。但搅拌和气体吹脱只能促进液相中氢气泡的逸出，对微生物聚集体内部的氢传质影响较小，回流只能中和产氢相有机酸，无法提高其在产甲烷相的降解率。为此提出了综合运用功率超声波强化和产氢相与产甲烷相固液交叉回流的技术方案。并通过试验和理论分析揭示功率超声波强化微生物聚集体内氢传质机理，阐明固液交叉回流对梯度发酵的影响规律，实现两相高效稳定匹配，从而解决产氢产甲烷梯度发酵面临的瓶颈问题。

产氢产甲烷梯度发酵可同时获得氢和甲烷，比单相厌氧发酵具有更高理论能量产率和有机负荷率。但由于该过程分割了常规的厌氧发酵过程，使产氢相发生氢分压升高和有机酸积累，降低了系统实际能量产率和发酵稳定性。本项目发现产氢颗粒污泥的形成经历污泥絮凝、絮状污泥形成、絮状污泥膨胀及颗粒污泥形成四个阶段；胞外聚合物的增加对颗粒污泥的形成、生长起到了重要的促进作用；产氢颗粒污泥为多孔隙结构，具有沉降速度快、渗透性好和抗剪切强度高等物理性质。通过功率超声波的空化作用，可以提高颗粒污泥所受的剪切力，改变颗粒污泥的粒径、浓度、沉降性能和强度等物理性质，提高颗粒污泥内传质效率，抑制耗氢菌。当占空比0.167%时，氢浓度和产氢率较高，分别为48%和1.81 mol H2/mol glucose，较未施加超声波组分别提高了60%和80%。在上升流速0.6 m/h条件下和有机负荷为80 gCOD/(L.d)时，颗粒污泥结构紧实，沉降性能良好，产氢率较高。本项目成果为解决产氢产甲烷梯度发酵面临的瓶颈问题，提供了参考。