Transversal Submerged Membrane Contactor for Simultaneous Absorption and Desorption of CO₂ during Natural Gas Sweetening Process

In this work, a unique transversal submerged membrane contactor is used for CO₂ removal. The developed configuration is aimed to provide the possibility to perform simultaneous absorption and desorption of carbon dioxide in a single module. In addition, this configuration is expected to reduce the solvent circulation which is the major obstacle encountered in separated absorption-desorption unit. The module contains a number of polypropylene hollow fiber membranes arranged perpendicularly to the longitudinal axis in which the fibers are submerged into a solvent. Pure water which is placed in the shell of the module is used as the solvent. The effects of operating parameters such as gas flow rate (40-80 ml/min) and operating time on membrane performance are investigated. In addition, the simultaneous absorption-desorption process is compared to the separated ones. Results revealed that CO₂ removal is significantly affected by the gas flow rate. The optimum gas flow rate is 60 ml/min (vacuum pressure of 60.5 kPa) with >80% CO₂ absorption and desorption efficiencies. During a long-term operation, the separation efficiencies are decreased after 200 minutes of operation which may be associated with membrane wetting phenomenon. The simultaneous absorption-desorption process shows a higher separation efficiency rather than the separated process.