Hydrogen can be produced through different pathways, i.e., natural gas reforming, gasification of coal, and electrolysis of water. A more sustainable pathway is through bio-H₂, which can be produced by bio-photolysis of water and photo-fermentation and dark fermentation of organic matters (OM). However, these routes are still limited by their specific energy requirement, process slowness, and microorganism sensitivity. These limitations can be mitigated by producing bio-H₂ via steam reforming of biogas sources such as landfill or anaerobic digester. In this study, the influence of the methane concentration in the biogas stream on reforming metrics was investigated. Two levels of modeling were pursued here: equilibrium and high fidelity numerical simulations. The former considers several reaction constants, elemental mass conservation, and energy balance. The latter model is based on the reactive Navier-Stokes of non-isothermal and multiple species flow in a cylindrical reactor. Process metrics such as species concentrations and conversion percentages as well as thermal process efficiencies were delineated and evaluated. Results showed that methane concentration has a pronounced influence on the resulting hydrogen concentration and the overall reforming efficiency. The anaerobic CH₄ source resulted in a mole fraction of near 0.3 for H₂ and a reforming efficiency of 36%. These values are much lower than those evaluated for natural gas (mole fraction of 0.5 for H₂ and reforming efficiency of 75%). Although this work illustrates the technical feasibility of biogas reforming, it highlights the low attained process efficiency that can be improved to achieve sustainable bio-H₂ production.

Graphical abstract

氢气可以通过不同的途径产生，例如天然气重整，煤的气化和水的电解。一种更可持续的途径是通过生物H ₂，其可以通过水的生物光解，光发酵和有机物质的黑暗发酵（OM）产生。但是，这些路线仍然受其特定能量需求，加工慢度和微生物敏感性的限制。这些限制可以通过生产bio-H ₂来缓解通过沼气源的蒸汽重整，例如垃圾填埋场或厌氧消化池。在这项研究中，研究了沼气中甲烷浓度对重整指标的影响。这里追求两个层次的建模：平衡和高保真数值模拟。前者考虑了几个反应常数，元素质量守恒和能量平衡。后一种模型基于非等温和多种物质在圆柱反应器中的反应性Navier-Stokes反应。描述并评估了过程指标，例如物种浓度和转化百分比以及热过程效率。结果表明，甲烷浓度对所得的氢浓度和整体重整效率具有显着影响。厌氧CH ₄离子源导致H ₂的摩尔分数接近0.3，重整效率为36％。这些值远低于天然气评估的值（H _2的摩尔分数为0.5 ，重整效率为75％）。尽管这项工作说明了沼气重整的技术可行性，但它强调了可以提高的工艺效率，可以实现可持续的生物H ₂生产。

图形概要