Removal of carbon dioxide from pressurized CO₂-CH₄ gas mixture using hollow fiber membrane contactors

Hollow fiber membrane (HFM) contactors have seen considerable attention in the past few years as an effective tool for numerous gas separation applications. However, most of the previously reported HFM modules (either commercial or custom fabricated), were only appropriate for low-pressure operation and hence most experimental studies focused on such low-pressure applications, making them less useful for important industrial processes such as the sweetening of natural gas. To address such deficiency, this study evaluates the CO₂ removal from a binary gas mixture (9.5% CO₂ in CH₄) pressurized up to 50 bar using both physical and chemical absorption. A novel design of HFM modules suitable for high-pressure operations and the detailed experimental considerations are presented. The modules were fabricated from stainless steel body and equipped with expanded polytetrafluoroethylene (ePTFE) hollow fibers. The CO₂ absorption rates in distilled water, aqueous sodium hydroxide and amine solutions, were investigated and compared. The experimental results indicated that CO₂ flux was enhanced by increasing the gas pressure for both physical and chemical absorption. However, the increase of CO₂ flux in the case of physical absorption was more pronounced than that obtained with chemical absorption.