Influence of membrane characteristics and operating parameters on transport properties of dissolved methane in a hollow fiber membrane contactor for biogas recovery from anaerobic effluents

Abstract

Several factors affect the performance of membrane-contacting systems for recovering dissolved methane (CH4) from anaerobic effluents, from membrane- to operations-related parameters. However, the conditions necessary to achieve high-efficiency CH4 recovery remain unclear. To improve our understanding of these dynamics, we systematically investigated the effects of membranes' physicochemical characteristics and operating parameters in a membrane-contacting system. We not only explored theoretical approaches to weigh the influence of diverse parameters but also evaluated the performance of four types of membranes with distinct morphological and chemical characteristics at various liquid velocities. According to our theoretical calculations, enlarging the mass transfer area (AM) decreases CH4 flux while a higher liquid flow rate (L) results in a reduction in CH4 recovery. Meanwhile, increasing the membrane's inner diameter (di) has a negative influence on both CH4 flux and recovery. However, a larger AM and a higher L are required to achieve higher recovery and flux, respectively. Our experimental results demonstrate that the capillary pressure imposed by the module inlet, pore wetting, and membrane resistance can also significantly affect the overall mass transfer resistance, thereby having a profound effect on CH4 flux. We clarify the underlying mechanisms to explain how each parameter influences CH4 flux and recovery, which leads to a system optimization to achieve the greatest CH4 recovery efficiency.