Abstract A multi-field model is proposed to study methane oxidation in landfill covers, especially its temporal and spatial variability. The proposed model consists of water-gas two-phase flow, multi-component gas flow, heat transfer, and biochemical reaction modules, and is solved using OpenFOAM based on the finite volume method. Applying this model, the coupled effect of gas diffusion, temperature and oxidation rate is studied, and the influence of water content on oxidation efficiency and capacity is quantified. The temporal variability of oxidation efficiency and capacity in landfill covers is illustrated by modelling a long-term field test. It is found that the CH4 removal rate can reach 40 g d−1 m−2 in the summers and drop to less than 10 g d−1 m−2 in the winters. A 3-D landfill cover cell with a cracked zone is applied to illustrate the spatial variability of oxidation, and a significant preferential flow can be observed when the cracked zone depth of a 1 m thick soil cover exceeds 0.8 m. The above studies demonstrate that the proposed model is able to predict temporal and spatial distributions of methane oxidation efficiency and capacity, and some results contribute to a better understanding of methane oxidation in landfill covers.

中文翻译：

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垃圾填埋场甲烷氧化时空变化的有限体积数值模型

摘要 提出了一个多场模型来研究垃圾填埋场覆盖物中的甲烷氧化，特别是其时空变异性。所提出的模型由水气两相流、多组分气流、传热和生化反应模块组成，并使用基于有限体积法的OpenFOAM求解。应用该模型，研究了气体扩散、温度和氧化速率的耦合效应，量化了含水量对氧化效率和氧化能力的影响。通过对长期现场测试建模，说明了垃圾填埋场覆盖层中氧化效率和容量的时间变化。结果表明，CH4 去除率在夏季可达 40 g d-1 m-2，在冬季降至 10 g d-1 m-2 以下。应用带有裂缝区的 3-D 垃圾填埋场覆盖单元来说明氧化的空间变异性，当 1 m 厚的土壤覆盖层的裂缝区深度超过 0.8 m 时，可以观察到显着的优先流。上述研究表明，所提出的模型能够预测甲烷氧化效率和能力的时空分布，一些结果有助于更好地了解垃圾填埋场覆盖物中的甲烷氧化。