Effect of recycle ratio on the cost of natural gas processing in countercurrent hollow fiber membrane system

• Hollow fiber membrane model for countercurrent multi-component separation.
• Implemented in Aspen HYSYS process simulator.
• Validated with published experimental results.
• Study of effect of recycle ratio to the process economics.
• Parameter sensitivities of typical conditions adapted in industrial application.

The separation of the countercurrent hollow fiber membrane module has been characterized adapting a “Multi-component Progressive Cell Balance” approach and incorporated within the Aspen HYSYS process simulator. The simulated data is found to exhibit good accordance with published experimental result. The study of the double staged membrane module with permeate recycle system, which was proposed to be the optimum configuration in previous works, has been extended by altering the recycle ratio of the permeate stream to study the process economics. Parameter sensitivities of typical membrane selectivity and CO2 feed concentration adapted in industrial application have been conducted. The study of high CO2 content is highlighted since it represents the future expansion of natural gas extraction considering that most of the remaining fields contain high concentration. It is observed that the recycle ratio is an important parameter to be considered in the industrial design process since it affects the gas processing cost significantly. Increasing the recycle ratio is proposed to increase the membrane area and compressor power while improving the hydrocarbon recovery, with substantial impact observed at low selectivity membrane and high CO2 feed concentration. A tradeoff must be determined among these parameters for determination of the optimal recycle ratio configuration.