Contaminant removal from natural gas using dual hollow fiber membrane contactors

Hollow fiber membrane contactors are advantageous in natural gas processing where the required equipment foot-print is small. Hollow fiber membrane contactors used for gas-liquid have typically had separate absorption and regeneration system, which may not be practical for offshore gas treating due to limited space. Based on our previous work, one membrane hollow fiber modules with two sets of membranes for absorption and regeneration are proposed which combines the absorber and stripper into one unit operation. In this design, the gas flows through the porous membrane hollow fibers immersed in a solvent and the solvent strips the gas of the contaminant. Nonporous membrane hollow fibers with a low pressure inside are in the same shell. They partially regenerate the solvent by stripping the contaminant out. The proposed modules and an ordinary single hollow fiber membrane contactor were modeled using partial differential equations based on a single component absorption scheme. A numerical model based on mass balance was developed to predict the performance of the dual contactor modules and also concentration change in both gas and liquid phase in the modules. The predictions of the developed numerical model were found to be in good agreement with the previous experimental results presented by Dindore et al. Simulation results show that the nonporous membranes in the dual hollow fiber membrane contactor can partially regenerate the solvent during the absorption and result in a better gas removal efficiency than the ordinary module. In addition, the baffles increased the mass transfer by minimizing shell-side bypass and increasing liquid velocity. (C) 2011 Elsevier B.V. All rights reserved.