Abstract This work presents an energy analysis and optimization of the hollow fiber membrane contactors for the recovery of dissolved methane (CH4) in effluents of anaerobic membrane bioreactor wastewater treatment processes. The obtained CH4 could be merged with biogas for further purification or used with a micro-turbine for electricity generation to achieve an energy self-sufficient wastewater treatment process. A mathematical model considering simultaneous CH4 and carbon dioxide (CO2) desorption was used to estimate the membrane area required to remove the dissolved CH4, as well as quality of the outlet gas from the membrane contactor. Energy balance between electrical energy obtained from the recovered CH4 and energies consumed by vacuum and liquid pumps for the operation of membrane contactor were investigated and reported as a Net Electricity obtained per m3 of effluent or simply Net E. Results revealed that a combination of a high strip gas flow rate and slightly low vacuum condition closed to the atmospheric pressure can provide the highest Net E at 0.178 MJ/m3. This value is 85.37% of the total electrical energy that can generated from a 90% recovery of dissolved CH4 using an effluent saturated with a 60 vol% CH4 biogas and flow rate at 2 m3/day. The calculation was made based on the assumptions that 1) the membrane contactor is operated in a non-wetting mode where membrane properties remain constant, 2) flux decline due to the membrane fouling is not considered and 3) the energy required for membrane cleaning and other relevant activities are not factored into the energy analysis. Based on our results, to obtain a high CH4 mole fraction at the gas outlet, a low strip gas flow rate is recommended, however, the operating gas pressure needs to be lowered by applying a vacuum condition to improve the Net E. In addition, it was found that the Net E could be improved by increasing the number of membrane fibers, and lowering the liquid flow rate. The CH4 recovery efficiency could also be optimized to obtain an optimal Net E.

中文翻译：

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中空纤维膜接触器回收厌氧膜生物反应器出水中溶解甲烷的能量分析与优化

摘要 这项工作提出了中空纤维膜接触器的能量分析和优化，用于回收厌氧膜生物反应器废水处理过程中的流出物中溶解的甲烷 (CH4)。获得的 CH4 可以与沼气合并进行进一步净化或与微型涡轮机一起发电，以实现能源自给的废水处理过程。考虑同时解吸 CH4 和二氧化碳 (CO2) 的数学模型用于估计去除溶解 CH4 所需的膜面积，以及来自膜接触器的出口气体的质量。研究了从回收的 CH4 获得的电能与真空泵和液体泵为膜接触器运行所消耗的能量之间的能量平衡，并将其报告为每 m3 流出物获得的净电能或简单的净 E。结果表明，高汽提气流速和接近大气压的略低真空条件可以提供最高的净 E，为 0.178 MJ/m3。该值是总电能的 85.37%，使用 60 vol% CH4 沼气饱和的流出物和 2 m3/天的流速可从 90% 的溶解 CH4 回收率中产生。计算基于以下假设：1) 膜接触器在非润湿模式下运行，其中膜特性保持恒定，2) 不考虑由于膜污染引起的通量下降和 3) 膜清洁和其他相关活动所需的能量未计入能量分析。根据我们的结果，为了在气体出口处获得高 CH4 摩尔分数，建议使用较低的汽提气流速，但是，需要通过施加真空条件来降低操作气体压力以提高净 E。此外，发现可以通过增加膜纤维的数量和降低液体流速来改善净 E。还可以优化 CH4 回收效率以获得最佳的 Net E。然而，需要通过施加真空条件来降低操作气体压力以改善净E。此外，发现可以通过增加膜纤维的数量和降低液体流速来改善净E。还可以优化 CH4 回收效率以获得最佳的 Net E。然而，需要通过施加真空条件来降低操作气体压力以改善净E。此外，发现可以通过增加膜纤维的数量和降低液体流速来改善净E。还可以优化 CH4 回收效率以获得最佳的 Net E。